TWI551541B - Process for producing lvp/lfp/c composite material and use the same - Google Patents

Description

Method for preparing lithium phosphate vanadium/lithium lithium phosphate/carbon composite material and use thereof

The invention relates to a lithium phosphate vanadium/lithium iron phosphate/carbon composite material, in particular to a method for preparing a lithium phosphate vanadium/lithium iron phosphate/carbon composite material and a use thereof.

With the development of the 3C industry, many portable technology products are powered by lithium ion secondary batteries with high energy, long cycle life, low cost and environmental protection. The lithium ion secondary battery is mainly composed of an anode, a cathode, an electrolyte and a diaphragm. Among them, the cathode material occupies the most important position, and the quality of the cathode material directly determines the final performance of the secondary battery product, and the cathode material It also has the highest proportion of battery costs.

Cathode materials commonly used in lithium ion secondary batteries include: lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), lithium manganese oxide (LiMn ₂ O ₄ ), lithium iron phosphate (LiFePO ₄ ), and phosphoric acid. Lithium vanadium (Li ₃ V ₂ (PO ₄ ) ₃ ), etc.; however, these commonly used cathode materials have their disadvantages, for example, lithium cobalt oxide (LiCoO ₂ ) is expensive and environmentally friendly; lithium nickel oxide ( LiNiO ₂ ) has poor thermal stability; lithium manganese oxide (LiMn ₂ O ₄ ) has a low capacitance and manganese ions are easily dissolved in the electrolyte; in particular, lithium iron phosphate (LFP) and lithium phosphate (LVP) Both the electronic conductivity (σ _e ) and the lithium ion diffusion coefficient (Di) are low, resulting in limitations in the development of cathode materials for lithium ion secondary batteries.

In order to increase the electronic conductivity (σ _e ) of lithium phosphate vanadium (LVP) or lithium iron phosphate (LFP) materials, the following common techniques are available in the prior art:

1. Surface carbon coating of lithium phosphate vanadium (LVP) material or lithium iron phosphate (LFP) material, prepared lithium vanadium phosphate/carbon (hereinafter referred to as LVP/C) composite material or lithium iron phosphate / Carbon (hereinafter referred to as LFP / C) composite material, significantly improved electronic conductivity and electrochemical performance.

2. Using carbon as a reducing agent, synthesizing lithium phosphate vanadium (LVP) material or lithium iron phosphate (LFP) material at high temperature by carbon thermal reduction, and using the remaining carbon as a conductive agent to improve LVP material Or the electrical conductivity and electrochemical properties of LFP materials.

3. The LVP/C film or the LFP/C film is prepared by electrostatic sputtering deposition (ESD) to improve the electronic conductivity and discharge rate performance of the LVP/C film or the LFP/C film.

4. The doping metal ions are used to improve the electronic conductivity of the LVP material or the LFP material and the cycle stability at high rate discharge.

However, none of the above prior art mentions the addition of a high molecular carbon source to solve the problem of low electronic conductivity of a lithium phosphate vanadium (LVP) material or a lithium iron phosphate (LFP) material, and there is no mention of adding a conductive carbon material (for example, Super P). Or carbon sphere (CS) conductive carbon material) as a conductive agent for lithium vanadium phosphate (LVP) material or lithium iron phosphate (LFP) material, and even did not mention a lithium phosphate vanadium / lithium iron phosphate / carbon composite material at high magnification Excellent cycle stability during discharge.

In view of this, the main object of the present invention is to provide a lithium vanadium phosphate/lithium iron phosphate/carbon composite material, which is synthesized by hydrothermal method, solid state method, sol-gel method or spray drying method to obtain lithium vanadium phosphate and phosphoric acid. Lithium iron two different cathode materials, and the use of high molecular carbon source or conductive carbon material after calcination to become a carbon layer between lithium phosphate vanadium and lithium iron phosphate (or residual carbon content), can effectively improve the electrification of the composite itself The performance of the lithium phosphate/lithium phosphate/carbon composite material has a high voltage platform and high power performance, and also has a very excellent charge/discharge cycle life.

The lithium phosphate vanadium/lithium iron phosphate/carbon composite of the present invention comprises a residual carbon content of from 1 to 15% by weight, preferably from 5 to 10% by weight, most preferably from 3 to 8% by weight.

The lithium phosphate vanadium/lithium iron phosphate/carbon composite material of the present invention is prepared by a solid phase method comprising: a) preparing a lithium iron phosphate/carbon (LFP/C) cathode material; b) preparing lithium phosphate vanadium/carbon ( LVP/C) cathode material; c) preparation of lithium phosphate vanadium/lithium lithium phosphate/carbon cathode material by solid state method; lithium iron phosphate/carbon (LFP/C): lithium phosphate vanadium/carbon (LVP/C) Ratio is 1:1 or 3:1 or 5:1 One of them is to quantitatively select prefabricated lithium iron phosphate/carbon (LFP/C) cathode material and lithium phosphate vanadium/carbon (LVP/C) cathode material, and directly mix and grind the two materials directly by solid state method to obtain The lithium phosphate vanadium/lithium iron phosphate/carbon composite material.

The lithium phosphate vanadium/lithium iron phosphate/carbon composite material of the present invention is prepared by a hydrothermal method comprising: a) preparing a lithium iron phosphate/carbon (LFP/C) cathode material: b) based on lithium vanadium phosphate/lithium phosphate The weight of the iron/carbon composite is selected from 1 to 30% by weight of the carbon source; c) the hydrothermal method is used to prepare lithium phosphate vanadium/lithium lithium phosphate/carbon cathode material precursor; c1) lithium (Li): vanadium (V): the molar ratio of phosphoric acid (PO ₄ ) is 3:2:3, and the lithium source, the vanadium source and the phosphoric acid source are selected as raw materials, and the liquid phase is mixed into an aqueous lithium vanadium phosphate (LVP) solution; c2) lithium phosphate Iron/Carbon (LFP/C): Lithium phosphate vanadium/carbon (LVP/C) with a molar ratio of 1:1 or 3:1 or 5:1, quantitatively selected pre-formed lithium iron phosphate/carbon (LFP) /C) cathode material; c3) adding the selected lithium iron phosphate/carbon (LFP/C) cathode material and carbon source to the lithium phosphate vanadium (LVP) aqueous solution, and uniformly stirring into a lithium phosphate/phosphoric acid containing a carbon source Lithium iron (LVP/LFP) mixed aqueous solution; hydrothermal method is used to surround the surface of lithium iron phosphate/carbon (LFP/C) cathode material with a lithium phosphate vanadium/carbon (LVP/C) cathode material, and dried to obtain lithium phosphate Vanadium/lithium iron phosphate/carbon cathode material D) the lithium phosphate vanadium / lithium iron phosphate / carbon cathode material precursor is placed in a high temperature furnace for calcination to obtain a lithium carbonate lithium / lithium iron phosphate / carbon composite material with residual carbon content of 1 ~ 15wt% .

The lithium phosphate vanadium/lithium iron phosphate/carbon composite material of the present invention is prepared by a sol-gel method comprising: a) preparing a lithium iron phosphate/carbon (LFP/C) cathode material: b) based on lithium vanadium phosphate/ a lithium iron phosphate/carbon composite material having a weight selected from 1 to 30% by weight of a carbon source; c) a lithium phosphate vanadium/carbon (LVP/C) cathode material; d) a vanadium alkoxide sol; e) Preparation of a lithium phosphate lithium/lithium phosphate/carbon cathode material precursor using a sol-gel method; e1) lithium iron phosphate/carbon (LFP/C): lithium phosphate vanadium/carbon (LVP/C) moule The ratio is 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, 7:3, 8:2 or One of 9:1, quantitatively select prefabricated lithium iron phosphate/carbon (LFP/C) cathode material and lithium phosphate vanadium/carbon (LVP/C) cathode material; e2) selected lithium iron phosphate/carbon (LFP/ C) a cathode material, a lithium vanadium phosphate/carbon (LVP/C) cathode material and a carbon source are added to the vanadium alkoxide sol, and uniformly mixed into a gel at a temperature of 100 to 120 ° C to make lithium iron phosphate/carbon (LFP/ C) the surface of the cathode material is surrounded by a lithium vanadium phosphate/carbon (LVP/C) cathode material, which is dried to obtain a lithium vanadium phosphate/lithium lithium phosphate/carbon cathode material precursor; f) the lithium vanadium phosphate/lithium iron phosphate The carbon cathode material precursor is placed in a high temperature furnace for calcination to obtain a lithium phosphate lithium phosphate/lithium iron phosphate/carbon composite material having a residual carbon content of 1 to 15 wt%.

The lithium phosphate vanadium/lithium iron phosphate/carbon composite material of the present invention is prepared by spray drying, comprising: a) preparing a lithium iron phosphate/carbon (LFP/C) cathode material: b) based on lithium vanadium phosphate/lithium iron phosphate /carbon composite weight, choose to use 1~30wt% carbon source; c) prepare lithium phosphate vanadium/carbon (LVP/C) cathode material; d) use spray drying to prepare lithium phosphate vanadium / lithium iron phosphate / carbon Cathode material precursor; d1) lithium iron phosphate / carbon (LFP / C): lithium phosphate vanadium / carbon (LVP / C) molar ratio of 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, 7:3, 8:2 or 9:1, prefabricated lithium iron phosphate/carbon (LFP/ C) cathode material and lithium vanadium phosphate/carbon (LVP/C) cathode material; d2) selected lithium iron phosphate/carbon (LFP/C) cathode material, lithium phosphate vanadium/carbon (LVP/C) cathode material and carbon The source is mixed in a liquid phase to form an aqueous solution, and then spray-dried to form a lithium iron phosphate/carbon (LFP/C) cathode material. The surface is surrounded by a lithium phosphate vanadium/carbon (LVP/C) cathode material. Lithium iron/carbon cathode material precursor; f) lithium vanadium phosphate / lithium iron phosphate / The carbon cathode material precursor is placed in a high temperature furnace for calcination to obtain a lithium phosphate lithium phosphate/lithium iron phosphate/carbon composite material having a residual carbon content of 1 to 15 wt%.

The lithium phosphate vanadium/lithium iron phosphate/carbon composite material of the present invention, in the preparation process, the step of preparing a lithium iron phosphate/carbon (LFP/C) cathode material, comprising: a1) lithium (Li): iron (Fe) : The molar ratio of phosphoric acid (PO ₄ ) is 1:1:1, and the lithium source, iron source and phosphoric acid source are selected as raw materials; a2) based on the weight of lithium iron phosphate/carbon (LFP/C) cathode material, the amount of use is selected. a carbon source of 1 to 30 wt%; a3) using one of a solid phase method, a hydrothermal method, a sol-gel method, or a spray drying method to make the lithium source, the iron source, the phosphoric acid source, and the carbon source The raw material is synthesized as a lithium iron phosphate/carbon (LFP/C) cathode material precursor; a4) the lithium iron phosphate/carbon (LFP/C) cathode material precursor is placed in a high temperature furnace for calcination to obtain the Lithium iron phosphate/carbon (LFP/C) cathode material.

The lithium phosphate vanadium/lithium iron phosphate/carbon composite material of the invention, in the preparation process, the step of preparing a lithium vanadium phosphate/carbon (LVP/C) cathode material, comprising: b1) lithium (Li): vanadium (V) : The molar ratio of phosphoric acid (PO ₄ ) is 3:2:3, the lithium source, the vanadium source and the phosphoric acid source are selected as raw materials; b2) the weight is selected based on the weight of the lithium phosphate vanadium/carbon (LVP/C) cathode material. a carbon source of 1 to 30 wt%; b3) one of a solid phase method, a hydrothermal method, a sol-gel method, or a spray drying method, wherein the lithium source, the vanadium source, the phosphoric acid source, and the carbon source are The raw material is synthesized as a lithium phosphate vanadium/carbon (LVP/C) cathode material precursor; b4) the lithium vanadium phosphate/carbon (LVP/C) cathode material precursor is placed in a high temperature furnace for calcination to obtain the Lithium phosphate vanadium/carbon (LVP/C) cathode material.

The lithium phosphate vanadium/lithium phosphate/carbon composite material of the invention has a lithium source selected from the group consisting of lithium carbonate, lithium hydrogencarbonate, lithium hydroxide, lithium nitrate, lithium acetate, lithium hydrogen phosphate or lithium phosphate in the preparation process. Or a mixture of the above; the iron source is selected from one or more of iron sulfate, ferrous oxalate, iron phosphate, iron oxide, iron acetate, iron nitrate or ferric chloride; the vanadium source is selected from the group consisting of vanadium pentoxide and ammonium metavanadate , one or more of vanadium pentoxide, vanadyl sulfate or sodium vanadate; the phosphoric acid source is selected from the group consisting of ammonium dihydrogen phosphate, ammonium phosphate, ammonium hydrogen phosphate, lithium phosphate, lithium hydrogen phosphate, ammonium phosphate One or more of lithium or sodium phosphate; the carbon source is selected from the group consisting of sucrose, vitamin C, citric acid, starch, glucose, furan resin, polyvinyl alcohol, phenolic resin, polyvinylpyrrolidone, polystyrene, nanopolyphenylene Ethylene ball, nano polymethyl methacrylate ball, SP conductive carbon material, CS conductive carbon material, carbon black conductive carbon material, graphene conductive carbon material, CNTs carbon material, artificial graphite, synthetic graphite, acetylene black, carbon fiber or One or more of the mesocarbon microbeads are mixed.

The lithium phosphate vanadium/lithium iron phosphate/carbon composite material of the invention is subjected to a first-stage pre-baking heat treatment in a high-temperature furnace during the calcination process in a high-temperature furnace, and then heated to 500-1000 ° C under the temperature of 300-500 ° C. The second-stage calcination heat treatment is carried out, and the reaction time of the calcination and calcination heat treatment is from 8 to 72 hours.

The lithium phosphate vanadium/lithium iron phosphate/carbon composite material of the invention is subjected to heat treatment under the conditions of introducing hydrogen gas and argon gas in the first stage pre-baking heat treatment and/or the second-stage calcination heat treatment process in a high temperature furnace. The composition of the mixed gas of hydrogen and argon is H ₂ : Ar = 10%: 90%, H ₂ : Ar = 5%: 95%, H ₂ : Ar = 3%: 97%, H ₂ : Ar = 2 %: 98% or H ₂ : Ar = 1%: 99% of one; wherein argon (Ar) may also be substituted with nitrogen (N ₂ ).

The lithium phosphate vanadium/lithium iron phosphate/carbon composite material of the invention has excellent electronic conductivity and is suitable for being used as a cathode electrode for a lithium ion secondary battery, a button type battery or a half battery, at a low temperature of -20 ° C and 50 ° C In high temperature environment, it also has very good high power characteristics and good charge and discharge cycle life.

10‧‧‧ button battery

20‧‧‧Upper cover

30‧‧‧Circular cathode electrode

40‧‧‧Separator

50‧‧‧Lithium metal

60‧‧‧Under the cover

1a is a schematic view showing the structure of an LVP/LFP/C composite prepared by a solid state method of the present invention.

Figure 1b is a schematic view showing the structure of a LVP/LFP/C composite prepared by a hydrothermal method of the present invention.

2a is a flow diagram of a lithium phosphate lithium phosphate/lithium iron phosphate/carbon (LVP/LFP/C) composite prepared by hydrothermal method.

Figure 2b is a flow diagram of a lithium silicate phosphate/lithium iron phosphate/carbon (LVP/LFP/C) composite prepared using the sol-gel process of the present invention.

Fig. 3a is a graph showing the results of SEM surface analysis of an LVP/LFP/C composite prepared by a solid state method (LFP: LVP molar ratio = 5:1).

Figure 3b is a hydrothermal preparation (LFP: LVP molar ratio = 5:1) of LVP/LFP/C SEM surface analysis results of composite materials.

Fig. 3c is a graph showing the results of SEM surface analysis of an LVP/LFP/C composite prepared by a sol-gel method (LFP: LVP molar ratio = 5:1).

Fig. 3d is a graph showing the results of SEM surface analysis of the LVP/LFP/C composite prepared by the spray drying method (LFP: LVP molar ratio = 5:1).

4a is an XRD analysis diagram of an LVP/LFP/C composite prepared by a solid state method (LFP: LVP molar ratio = 5:1).

Figure 4b is an XRD analysis of the LVP/LFP/C composite prepared by hydrothermal method (LFP: LVP molar ratio = 5:1).

Figure 4c is an XRD analysis of the LVP/LFP/C composite prepared by the sol-gel method (LFP: LVP molar ratio = 5:1).

Figure 4d is an XRD analysis of the LVP/LFP/C composite prepared by spray drying (LFP: LVP molar ratio = 5:1).

Figure 5a is a full-range micro-Raman spectrum of the LVP/LFP/C composite prepared by solid state or hydrothermal method (LFP: LVP Mo ratio = 5:1).

Figure 5b is a full-range micro-Raman spectrum of the LVP/LFP/C composite prepared by the sol-gel method (LFP: LVP molar ratio = 5:1).

Figure 5c is a full range micro-Raman spectrum of the LVP/LFP/C composite prepared by spray drying (LFP: LVP molar ratio = 5:1).

Figure 5d is a full-range micro-Raman spectrum of the LVP/LFP/C composite prepared by the spray drying method (LFP: LVP molar ratio = 7:3).

Fig. 6 is a flow chart showing the fabrication of a cathode electrode of a lithium ion secondary battery using the hydrothermally prepared LVP/LFP/C composite material of the present invention.

Fig. 7 is an exploded view of the components of a general button type battery.

8a is a CV analysis diagram of LVP/LFP/C composite sample A prepared by solid state method (LFP: LVP molar ratio = 5:1) and prepared by hydrothermal method (LFP: LVP Moir). CV analysis of LCP/LFP/C composite sample B with ratio = 5:1).

Figure 8b is a CV analysis diagram of a sample L of LVP/LFP/C composite prepared by hydrothermal method (LFP: LVP molar ratio = 3:1) according to Example 1 of the present invention.

Figure 8c is a CV analysis diagram of a sample L of LVP/LFP/C composite prepared by spray drying using the spray drying method (LFP: LVP molar ratio = 5:1).

FIG. 9 is a graph showing charge and discharge curves of a 2032 button type battery fabricated in Example 2 of the present invention at a 0.1 C rate charge/discharge voltage between 2.0 and 4.3 V. FIG.

FIG. 10 is a graph showing charge and discharge curves of a 2032 button type battery fabricated in Example 2 according to the present invention at a charge/discharge rate of 0.2 C to 10 C between 2.0 and 4.3 V.

FIG. 11 is a graph showing charge and discharge curves of a 2032 button type battery fabricated in Example 3 of the present invention at a charge/discharge rate of 0.2 C to 10 C between 2.0 and 4.8 V.

FIG. 12 is a graph showing charge and discharge curves of a 2032 button type battery fabricated in Example 4 of the present invention at a 0.1 C rate charge/discharge voltage between 2.0 and 4.3 V. FIG.

FIG. 13 is a graph showing charge and discharge curves of a 2032 button type battery fabricated in Example 4 of the present invention at a charge/discharge rate of 0.2 C to 10 C between 2.0 and 4.3 V.

14 is a graph showing charge and discharge curves of a 2032 button type battery fabricated in Example 5 of the present invention at a 0.1 C rate charge/discharge voltage between 2.0 and 4.8 V.

FIG. 15 is a graph showing charge and discharge curves of a 2032 button type battery fabricated in Example 5 of the present invention at a charge/discharge rate of 0.2 C to 10 C between 2.0 and 4.8 V.

16 is a graph showing charge and discharge curves of a 2032 button type battery fabricated in Example 6 of the present invention at a 0.1 C rate charge/discharge voltage between 2.0 and 4.3 V.

17 is a graph showing charge and discharge curves of a 2032 button type battery fabricated in Example 6 of the present invention at a charge/discharge rate of 0.2 C to 10 C between 2.0 and 4.3 V.

18 is a graph showing charge and discharge curves of a 2032 button type battery fabricated in Example 7 of the present invention at a 0.1 C rate charge/discharge voltage between 2.0 and 4.8 V.

19 is a graph showing charge and discharge curves of a 2032 button type battery fabricated in Example 7 of the present invention at a charge/discharge rate of 0.2 C to 10 C between 2.0 and 4.8 V.

20 is a cycle life test result of charging and discharging 80 times of a 2032 button type battery of Example 2 and Example 4 at a voltage of 2.0 to 4.3 V according to Embodiment 8 of the present invention.

Figure 21 is a graph showing charge and discharge curves of a 2032 button type battery fabricated in Example 9 of the present invention at a 0.1 C rate charge/discharge voltage between 2.0 and 4.8V.

Figure 22 is a 2032 button type battery made in Example 9 of the present invention at a voltage of 2.0 to 4.8V. Charge and discharge curves at a charge/discharge rate of 0.2C to 10C.

Figure 23 is a graph showing charge and discharge curves of a 2032 button type battery fabricated in Example 10 of the present invention at a 0.1 C rate charge/discharge voltage between 2.0 and 4.8V.

FIG. 24 is a graph showing charge and discharge curves of a 2032 button type battery fabricated in Example 10 according to the present invention at a charge/discharge rate of 0.2 C to 10 C between 2.0 and 4.8 V.

Figure 25 is a graph showing charge and discharge curves of a 2032 button type battery fabricated in Example 11 of the present invention at a 0.1 C rate charge/discharge voltage between 2.0 and 4.8V.

Figure 26 is a graph showing charge and discharge curves of a 2032 button type battery fabricated in Example 11 of the present invention at a charge/discharge rate of 0.2 C to 10 C between 2.0 and 4.8 V.

Fig. 27 is a graph showing the comparison of charge and discharge performance of 0.2C to 10C between 2.0 and 4.8V of the 2032 button type battery produced in Example 9, Example 10 and Example 11.

Fig. 28 is a graph showing a charge/discharge curve of 0.1/0.1 C at a voltage of 2.0 to 4.8 V in a 50 ° C environment of a button type battery made in Example 10.

Fig. 29 is a graph showing the charging and discharging curves of a 0.2C to 10C voltage between 2.0 and 4.8V in a 50 ° C environment of a button type battery made in Example 10.

Fig. 30 is a graph showing a charge/discharge curve of 0.1/0.1 C at a voltage of 2.0 to 4.8 V in a button type battery fabricated in Example 10 at -20 °C.

Figure 31 is a graph showing the charging and discharging curves of a 0.2C to 10C voltage between 2.0 and 4.8V in a button type battery made in Example 10 at -20 °C.

32 is a comparison diagram of charge-discharge performance of 0.2C to 10C at a voltage of 2.0 to 4.8 V in a button type battery made in Example 10 at different temperatures of -20 ° C, 25 ° C, and 50 ° C.

The preparation method of the lithium vanadium phosphate/lithium iron phosphate/carbon cathode material (or LVP/LFP/C composite material for short) of the invention comprises four preparation methods of hydrothermal method, solid state method, sol-gel method or spray drying method.

The preparation method of the LVP/LFP/C composite material of the present invention, when using the solid state method (or solid phase method) preparation method, comprises the following steps:

1. Preparation of lithium iron phosphate / carbon cathode material (or LFP / C material for short); The steps of preparing the LFP/C material include:

1) According to the ratio of lithium (Li): iron (Fe): phosphoric acid (PO ₄ ), the molar ratio is 1:1:1, and the lithium source, the iron source and the phosphoric acid source are selected as raw materials;

2) selecting a certain amount of carbon source based on the total weight of the LFP/C material; wherein the carbon source comprises an organic compound carbon source, a polymer compound carbon source or, if necessary, a conductive carbon material; The carbon source is used in an amount of from 1 to 30% by weight, preferably from 5 to 10% by weight, based on the total mass of the C material.

3) Using one of the solid phase method, the hydrothermal method, the sol-gel method or the spray drying method, the four raw materials of the pre-selected lithium source, iron source, phosphoric acid source and carbon source are synthesized into LFP/C materials. Precursor

4) The LFP/C material precursor is placed in a high temperature furnace for calcination, and the lithium iron phosphate (LFP) particles are coated and modified by a carbon source to obtain the lithium iron phosphate/carbon (LFP/C) cathode material.

2. Preparation of lithium phosphate vanadium/carbon cathode material (or LVP/C material for short); steps for preparing LVP/C material, including:

1) According to the ratio of lithium (Li): vanadium (V): phosphoric acid (PO ₄ ) with a molar ratio of 3:2:3, a lithium source, a vanadium source and a phosphoric acid source are selected as raw materials;

2) selecting a certain amount of carbon source based on the total weight of the LVP/C material; wherein the carbon source comprises an organic compound carbon source, a polymer compound carbon source or a conductive carbon material added as needed; based on LVP/ The carbon source is used in an amount of 5 to 10% by weight, preferably 5 to 8% by weight based on the total weight of the C material.

3) Using one of the solid phase method, hydrothermal method, sol-gel method or spray drying method, the four raw materials of pre-selected lithium source, vanadium source, phosphoric acid source and carbon source are synthesized into LVP/C material. Precursor

4) The LVP/C material precursor is placed in a high temperature furnace for calcination to obtain a carbon source for the lithium phosphate vanadium (LVP) particles. The coating is modified to produce the lithium vanadium phosphate/carbon (LVP/C) cathode material.

3. Preparation of lithium phosphate vanadium/lithium iron phosphate/carbon (LVP/LFP/C) cathode material by solid state method; taking a certain proportion of LFP/C material and LVP/C material; directly mixing and grinding the two materials directly That is, the LVP/LFP/C composite material having the structure shown in Fig. 1a was obtained. Among them, lithium iron phosphate/carbon (LFP/C): lithium alginate/carbon (LVP/C) has a molar ratio of 1:1 or 3:1 or 5:1, preferably 5:1.

The LVP/LFP/C composite material preparation method of the present invention comprises the following steps when using another hydrothermal preparation method:

1. Preparation of LFP/C material; the preparation method and preparation conditions of the LFP/C material are the same as the first step 1 of preparing the LVP/LFP/C composite material by the solid state method.

2. Preparation of lithium phosphate vanadium/lithium iron phosphate/carbon (LVP/LFP/C) cathode material by hydrothermal method;

1) According to the ratio of lithium (Li): vanadium (V): phosphoric acid (PO ₄ ) with a molar ratio of 3:2:3, a lithium source, a vanadium source and a phosphoric acid source are selected as raw materials;

2) uniformly mixing the three raw materials of the lithium source, the vanadium source and the phosphoric acid source into a mixed aqueous solution of lithium phosphate vanadium (LVP);

3) For the pre-formed lithium phosphate vanadium (LVP) mixed aqueous solution, a certain amount of LFP/C material is added, and uniformly stirred and mixed into a lithium phosphate vanadium/lithium iron phosphate (LVP/LFP) mixed aqueous solution; wherein, lithium iron phosphate/ Carbon (LFP/C): The molar ratio of lithium phosphate vanadium (LVP) is 1:1 or 3:1 or 5:1, preferably 5:1.

4) For the pre-formed lithium phosphate vanadium phosphate/lithium iron phosphate (LVP/LFP) mixed aqueous solution, a certain amount of carbon source is added, and the LVP/C material is uniformly coated on the surface of the LFP/C material by hydrothermal synthesis. That is, a LVP/LFP/C composite precursor which has a shell-core structure as shown in FIG. 1b is formed;

5) The LVP/LFP/C composite precursor is placed in a high-temperature furnace for calcination, so that the lithium iron phosphate/carbon (LFP/C) particles are coated with lithium vanadium phosphate/carbon (LVP/C) and a carbon source. That is, a lithium vanadium phosphate/lithium iron phosphate/carbon (LVP/LFP/C) cathode material having a structure as shown in Fig. 1b was obtained.

The LVP/LFP/C composite material preparation method of the present invention comprises the following steps when using another sol-gel method preparation method:

1. Preparation of LFP/C material; the preparation method and preparation conditions of the LFP/C material are the same as the first step 1 of preparing the LVP/LFP/C composite material by the solid state method.

2. Preparation of a lithium phosphate vanadium/carbon (LVP/C) material using a sol-gel method;

3. Select a carbon source;

4. preparing a vanadium alkoxide sol;

5. Use a certain amount of LFP/C material, LVP/C material and carbon source into the prefabricated vanadium alkoxide sol, mix uniformly at a temperature of 100~120 °C, and convert it into a gel structure to make LVP/C material. Uniformly coated on the surface of the LFP/C material to form a LVP/LFP/C composite precursor with a shell-core structure as shown in Figure 1b; in the above process, lithium iron phosphate/carbon (LFP/C) : The molar ratio of lithium phosphate vanadium/carbon (LVP/C) is 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4: 1, 5:1, 7:3, 8:2 or 9:1. Preferably, the sol is converted to a gel at a temperature of 120 °C.

6. The LVP/LFP/C composite precursor is placed in a high-temperature furnace for calcination, so that the LFP/C particles are coated with the LVP/C material and the carbon source, thereby obtaining a lithium vanadium phosphate structure as shown in Fig. 1b. / Lithium iron phosphate / carbon (LVP / LFP / C) cathode material.

The LVP/LFP/C composite material preparation method of the present invention comprises the following steps when using another spray drying preparation method:

1. Preparation of LFP/C material; the preparation method and preparation conditions of the LFP/C material are the same as the first step 1 of preparing the LVP/LFP/C composite material by the solid state method.

2. Preparation of LVP/C material; the preparation method and preparation conditions of the LVP/C material are the same as the above step 2 of preparing the LVP/LFP/C composite material by the solid state method.

3. Select a carbon source;

4. Take a certain amount of LFP/C material, LVP/C material and carbon source for liquid phase mixing directly; in the above method, lithium iron phosphate/carbon (LFP/C): lithium phosphate vanadium/carbon (LVP/C) The molar ratio is 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, 7:3, 8 : 2 or 9:1 of one of them.

5. For pre-formed LFP/C material, LVP/C material and carbon source mixed aqueous solution, spray-drying to form a spherical structure LVP/LFP/C composite precursor of coated carbon source;

6. The LVP/LFP/C composite precursor is placed in a high-temperature furnace for calcination in a reducing environment, so that the LFP/C particles are coated with LVP/C material and carbon source, and the structure is as shown in Fig. 1b. A lithium vanadium phosphate/lithium iron phosphate/carbon (LVP/LFP/C) cathode material is shown.

In the LVP/LFP/C composite material of the present invention, when a chelating agent and a reducing agent are required in the preparation process, a chelating agent selected from the group consisting of oxalic acid, tartaric acid, citric acid, polyacrylic acid or succinic acid can be used.

When the LVP/LFP/C composite material of the invention is prepared by hydrothermal method, solid state method, sol-gel method or spray drying method, in the high temperature furnace calcination stage, two stages of temperature rise can be adopted, and the temperature rises in the high temperature furnace. Up to 300 to 500 ° C, preferably to 350 ° C to 400 ° C, most preferably to 350 ° C, after the first stage of calcination heat treatment, and then at a temperature increase rate of 2 to 10 ° C / min, preferably The heating rate of 10 ° C / min is heated to 550 ~ 1000 ° C in a high temperature furnace, preferably to 600 ~ 900 ° C, most preferably to 700 ~ 800 ° C, the second stage of calcination heat treatment. The reaction time of the calcination and calcination heat treatment is between 8 and 72 hours, and the optimum reaction time is between 12 and 20 hours.

For the LVP/LFP/C composite precursors placed in the high temperature furnace, the first stage of pre-firing heat treatment is to remove the moisture and small molecules of the LVP/LFP/C composite precursor and improve the LVP/ The crystallinity of the LFP/C composite precursor is less likely to cause other complexes during calcination; the calcination heat treatment time is between 1 and 20 hours, preferably between 10 and 12 hours.

Moreover, in the high-temperature furnace, the pre-firing and calcination heat treatment of the LVP/LFP/C composite precursor can be carried out in air, or in an argon or nitrogen reduction environment, or in the passage of hydrogen and argon. The sintering heat treatment is performed in a reducing environment, wherein the composition ratio of the mixed gas of hydrogen and argon is H ₂ : Ar = 10%: 90%, H ₂ : Ar = 5%: 95%, and H ₂ : Ar = 3%: 97%, H ₂ : Ar = 2%: 98% or H ₂ : Ar = 1%: 99%. Further, the argon (Ar) inert gas in the hydrogen gas and the argon gas mixture may be replaced by nitrogen gas (N ₂ ).

In the preparation method of the LVP/LFP/C composite material of the present invention, the definition of the lithium source refers to a source of lithium, which may be selected from lithium carbonate, lithium hydrogencarbonate, lithium hydroxide, lithium nitrate, lithium acetate, hydrogen phosphate. One or more of lithium or lithium phosphate is mixed.

The definition of the vanadium source refers to a source of vanadium, which may be selected from one or more of vanadium pentoxide, ammonium metavanadate, vanadium pentoxide, vanadyl sulfate or vanadate (such as sodium vanadate). .

The definition of the iron source refers to the source of iron, and one or more of iron sulfate, ferrous oxalate, iron phosphate, iron oxide, iron acetate, iron nitrate or ferric chloride may be mixed.

The source of the phosphoric acid source refers to a source of phosphoric acid, which may be selected from one or more of ammonium dihydrogen phosphate, ammonium phosphate, ammonium hydrogen phosphate, lithium phosphate, lithium hydrogen phosphate, lithium ammonium phosphate, phosphoric acid or sodium phosphate. .

The definition of the carbon source refers to a source of carbon, which may be selected from a low molecular weight carbon source, a high molecular weight carbon source, or a low molecular weight carbon source and a high molecular weight carbon source. As mentioned above, the following references to “carbon sources” also include sources of conductive carbon materials that need to be added as appropriate.

Wherein, the low molecular weight carbon source may be selected from one or more of sucrose, ascorbic acid, citric acid, starch or glucose; the high molecular weight carbon source may be It is selected from Furan resin, polyvinyl alcohol (PVA), phenolic resin, polyvinylpyrrolidone (PVP), polystyrene (PS), nanopolystyrene ball (hereinafter referred to as PS ball) or nano poly One or more of the propylene methacrylate balls (referred to as PMMA balls) are mixed.

The conductive carbon material may be selected from the group consisting of Super P conductive carbon materials (hereinafter referred to as SP conductive carbon materials), carbon ball conductive carbon materials (hereinafter referred to as CS conductive carbon materials), carbon black conductive carbon materials, graphene conductive carbon materials, and nai One of carbon steel tube carbon materials (hereinafter referred to as CNTs carbon material), artificial graphite, synthetic graphite, acetylene black, carbon fiber or mesocarbon microspheres (MCMB); different combinations of conductive carbon materials can also be used, for example, using SP A combination of a conductive carbon material and a CS conductive carbon material, or a combination of an SP conductive carbon material and a CNTs carbon material, or a combination of graphite and CNTs carbon materials; or a conductive carbon material of the same or different form may be used. Wherein, the CS conductive carbon material has a particle diameter of 200 to 500 nm .

In the LVP/LFP/C composite material of the present invention, the carbon source is added in an amount of 1 to 30 wt%, preferably 3 to 12 wt%, based on the total weight of the LVP/LFP/C composite material in the preparation process. , most preferably between 5 and 10 wt%; and, after calcination heat treatment in a high temperature furnace, the carbon source content (or residual carbon content) of the LVP/LFP/C composite material obtained is between 1 and 15 wt%, It is preferably from 5 to 10% by weight, most preferably from 3 to 8% by weight.

The LVP/LFP/C composite material of the invention has a specific preparation method for prefabricating lithium iron phosphate/carbon (LFP/C) cathode material in the preparation process, comprising the following steps: 1) Lithium (Li): iron (Fe) : The molar ratio of phosphoric acid (PO ₄ ) is 1:1:1, and the lithium source, iron source and phosphoric acid source are directly mixed and ground; 2) placed in a high temperature furnace for calcination at a sintering temperature of 600 to 950 ° C. After continuous heat treatment for 10 to 72 hours, lithium iron phosphate (LFP) is synthesized; 3) the lithium iron phosphate (LFP) obtained in the step 2) is added with a carbon source based on the total weight of the final product of 1 to 30 wt% for carbon coating modification; 4) further heat treatment, at a sintering temperature of 600 ~ 800 ° C, continuous heat treatment for 1 to 20 hours after the end, to be reduced to room temperature to obtain a lithium iron phosphate / carbon (LFP / C) cathode material.

The LVP/LFP/C composite material of the invention has a specific preparation method for preparing a lithium vanadium phosphate/carbon (LVP/C) cathode material in the preparation process, and comprises the following steps: 1) separately preparing carbonic acid having a volume molar concentration of 1M. An aqueous solution of lithium (Li ₂ CO ₃ ), an aqueous solution of vanadium pentoxide (V ₂ O ₅ ), an aqueous solution of ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ), and an aqueous solution of oxalic acid (H ₂ C ₂ O ₄ ); 2) a furan (Furan) polymer is dissolved in methanol (ethyl alcohol) or ethyl alcohol (ethyl alcohol) organic solvent to prepare a concentration of 2 ~ 10wt% furan solution; 3) take vanadium pentoxide (V ₂ O ₅ ) aqueous solution and The aqueous solution of oxalic acid (H ₂ C ₂ O ₄ ) is mixed at a ratio of 1:3 by volume, and uniformly mixed at a temperature of 50 to 90 ° C to reduce V ⁵⁺ to V ³⁺ to obtain vanadium pentoxide (V ₂ O). ₅ ) a mixed solution; wherein oxalic acid is used as a chelating agent and a reducing agent, and VOC ₂ O _{4 is} synthesized after the reaction. nH ₂ O intermediate; 4) taking an aqueous solution of lithium carbonate (Li ₂ CO ₃ ) and an aqueous solution of ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) uniformly mixed at a volume ratio of 1:2, and then adding vanadium pentoxide (V ₂ O ₅ ) mixing the solution to obtain a mixed aqueous solution of lithium vanadium phosphate (LVP); 5) slowly adding a 2 to 10 wt% furan solution to the mixed aqueous solution of lithium vanadium phosphate (LVP); or, for enhancing the active material Conductivity, optionally adding 0.1~30wt% conductive carbon material, preferably 1~10wt% conductive carbon material; 6) pouring the above solution into a 600mL PTFE container used in hydrothermal synthesis and placing it In the stainless steel tank, hydrothermal reaction treatment is carried out, and the reaction temperature is between 120 and 200 ° C for 10 to 20 hours; after the hydrothermal method is completed, the powder is dried at a temperature of 110 ° C and then placed in a calcination temperature of 700. The high temperature tubular furnace at ~850 °C is calcined to obtain LVP/C material.

The specific manufacturing method of the LVP/LFP/C composite material of the present invention is described by the following four specific manufacturing methods:

1. A method for preparing the LVP/LFP/C composite material of the present invention by using a hydrothermal method (referred to as hy), as shown in FIG. 2a, comprising the following steps:

1. Preparation of lithium iron phosphate / carbon (LFP / C);

2. Prepare an aqueous solution of lithium carbonate (Li ₂ CO ₃ ) with a molar concentration of 1 M, an aqueous solution of vanadium pentoxide (V ₂ O ₅ ), an aqueous solution of ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ), and oxalic acid (H). ₂ C ₂ O ₄ ) aqueous solution;

3. The furan (Furan) polymer is dissolved in an alcohol (alcohol) organic solvent to prepare a 5~10 wt% furan solution;

4. The aqueous solution of vanadium pentoxide (V ₂ O ₅ ) and the aqueous solution of oxalic acid (H ₂ C ₂ O ₄ ) are mixed at a ratio of 1:3 by volume, for example, 50 mL of an aqueous solution of vanadium pentoxide (V ₂ O ₅ ) is taken. It is mixed with 150mL aqueous solution of oxalic acid (H ₂ C ₂ O ₄ ) and uniformly mixed at a temperature of 50-90 ° C, preferably uniformly mixed at a temperature of 70 ° C, so that V ^{5+ is} reduced to V ³⁺ , and pentoxide is obtained. A mixed solution of vanadium (V ₂ O ₅ ); wherein oxalic acid is used as a chelating agent and a reducing agent, and VOC ₂ O _{4 is} synthesized after the reaction. nH ₂ O intermediate;

5. The aqueous solution of lithium carbonate (Li ₂ CO ₃ ) and the aqueous solution of ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) are uniformly mixed according to a ratio of 1:2 by volume; for example, 75 mL of an aqueous solution of lithium carbonate (Li ₂ CO ₃ ) is taken. After uniformly mixing with 150 mL of an aqueous solution of ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ), a mixed solution of vanadium pentoxide (V ₂ O ₅ ) is further added to obtain a mixed aqueous solution of lithium vanadium phosphate (LVP);

6. A suitable amount of LFP/C is slowly added to a mixed aqueous solution of lithium phosphate (LVP), and after stirring at room temperature for 2 hours, an aqueous solution of the mixed precursor of LVP/LFP is obtained; wherein, lithium iron phosphate/carbon (LFP/C): lithium phosphate The iron/carbon (LFP/C) molar ratio is one of 1:1 or 3:1 or 5:1.

7. Add 5~10wt% furan solution or slowly to the mixed aqueous solution of lithium vanadium phosphate/lithium iron phosphate (LVP/LFP); or, to increase the conductivity of the active material, optionally add 0.1~ 30wt% conductive carbon material, preferably 1~10wt% conductive carbon material;

8. The solution is poured into a 600 mL PTFE container used in hydrothermal synthesis and placed in a stainless steel tank for hydrothermal reaction. The reaction temperature is between 120 and 250 ° C, and the reaction time is between 10 and 20 hours. Preferably, the hydrothermal reaction is carried out at a reaction temperature of 170 to 200 ° C for 10 hours; after completion of the hydrothermal method, the powder is dried at a temperature of 110 ° C, and then placed in a high temperature tubular furnace for calcination at a calcination temperature of 800 to 1000 At °C, it is preferable to calcin for 10~16 hours at the calcination temperature of 800~850 °C; after the end, it is to be cooled to room temperature to obtain LVP/LFP/C composite material.

2. The preparation method of the LVP/LFP/C composite material of the present invention by using the solid state method (abbreviated as BM), comprising the following steps:

1. Prepare lithium iron phosphate/carbon (LFP/C) cathode materials and lithium phosphate vanadium/carbon (LVP/C) cathode materials separately; 2. According to LFP: LVP Mohr ratio is 1:1 or 3:1 or 5: a ratio of 1 to a quantitative lithium iron phosphate/carbon (LFP/C) cathode material and a lithium phosphate vanadium/carbon (LVP/C) cathode; 3. using a ball mill to directly mix the two materials in a wet grinding manner, The LVP/LFP/C composite material is obtained by grinding at a grinding speed of 200 to 600 rpm for 3 to 6 hours, preferably at a rotation speed of 300 rpm for 4 hours.

3. A method for preparing the LVP/LFP/C composite material of the present invention by using a sol-gel method (SJ for short), as shown in FIG. 2b, comprising the following steps:

1. Preparation of lithium iron phosphate/carbon (LFP/C) cathode material; 2. Preparation of aqueous solution of lithium carbonate (Li ₂ CO ₃ ) having a molar concentration of 1 M, aqueous solution of vanadium pentoxide (V ₂ O ₅ ), phosphoric acid An aqueous solution of ammonium dihydrogen (NH ₄ H ₂ PO ₄ ), an aqueous solution of oxalic acid (H ₂ C ₂ O ₄ ) and an aqueous solution of adipic acid; 3. a polymer of polyvinylpyrrolidone (PVP) as a carbon source at a water temperature of 70 ° C Stirring is formulated into a 5 wt% concentration of PVP carbon source aqueous solution; 4. taking vanadium pentoxide (V ₂ O ₅ ) aqueous solution and oxalic acid (H ₂ C ₂ O ₄ ) aqueous solution according to a volume ratio of 1:1.5 Mixing in proportion, uniformly mixing at a temperature of 50-90 ° C, preferably uniformly mixing at a temperature of 70 ° C, such that V ^{5+ is} reduced to V ³⁺ to obtain a mixed solution of vanadium pentoxide (V ₂ O ₅ ); Oxalic acid is used as a chelating agent and a reducing agent, and VOC ₂ O _{4 is} synthesized after the reaction. nH ₂ O intermediate; 5. Lithium (Li): vanadium (V): phosphoric acid (PO ₄ ) molar ratio of 3:2:3, lithium carbonate (Li ₂ CO ₃ ) aqueous solution, phosphoric acid An aqueous solution of ammonium dihydrogen (NH ₄ H ₂ PO ₄ ) and an aqueous solution of adipic acid are poured into a mixed solution of vanadium pentoxide (V ₂ O ₅ ) to prepare an aqueous solution of lithium vanadium phosphate (LVP) precursor; 6. PVP A carbon source aqueous solution, a lithium iron phosphate/carbon (LFP/C) cathode material is added to an aqueous solution of lithium vanadium phosphate (LVP) precursor, which is converted into a gel and dried to prepare a lithium silicate phosphate prepared by a sol-gel method. / Lithium iron phosphate / carbon (LVP / LFP / C) cathode material precursor; this precursor has a core-shell structure, the inner layer is LFP / C material, the outer shell is LVP / C material; 7. The dried lithium vanadium phosphate/lithium iron phosphate/carbon (LVP/LFP/C) cathode material precursor is placed in a quartz boat, and then placed in a high temperature furnace at a heating rate of 5 ° C / min. After the first-stage pre-firing heat treatment for 4 hours at 350 ° C, the second-stage calcination heat treatment was carried out for 10 hours at a temperature increase rate of 10 ° C / min in a high-temperature furnace to 800 ° C; Down to room temperature LVP / LFP / C composite.

4. A method for preparing the LVP/LFP/C composite material of the present invention by using a spray drying method (Sp for short), comprising the following steps:

1. Prepare lithium iron phosphate/carbon (LFP/C) cathode material and lithium phosphate vanadium/carbon (LVP/C) cathode material separately; 2. Measure quantitative LFP according to LFP: LVP molar ratio of 5:1. /C material and LVP/C material; 3. Take about 0.6g of glucose organic matter as the first carbon source; 4. Take about 10g of homemade nanopolystyrene ball (PS ball) as the second a carbon source; 5. using deionized water as a solvent, the LFP/C material and the LVP/C material and the selected glucose source are directly mixed in the liquid phase; after continuous stirring for 1 hour, the liquid is The mixed aqueous solution is placed in a high temperature oven and dried at a temperature of 120 ° C to obtain a precursor of LVP/LFP/C coated with the first carbon source, and then ground to form a fine powder; 6. using deionized water as a solvent, The ground LVP/LFP/C precursor powder and the selected nanopolystyrene sphere (PS sphere) are directly mixed in the liquid phase and continuously stirred for 2 hours; 7. The liquid phase mixed aqueous solution of the previous step is applied. Spray-drying granulation to obtain a precursor structure of a spherical structure LVP/LFP/C composite coated with two carbon sources; 8. placing the precursor of the LVP/LFP/C composite material in the previous step into a quartz boat, Put it in a high temperature furnace In high temperature furnace into hydrogen gas and argon gas _{(H 2: Ar = 5%} : 95%) under a reducing environment, and the temperature was raised to 600 ~ 700 ℃ under conditions of a heat treatment calcined 10 hours; After completion of the decrease down to room At the temperature, a LVP/LFP/C composite coated with two carbon sources was prepared.

In order to specifically describe the characteristics of the LVP/LFP/C composite material of the present invention, the material composition includes the use of furan (Furan) resin, glucose organic matter or/and nanopolystyrene sphere (PS sphere) as a carbon source. And a LVP/LFP/C composite using a lithium iron phosphate/carbon (LFP/C): lithium iron phosphate/carbon (LFP/C) molar ratio of 5:1 was used as a sample. According to the preparation method of the following Table 1, the LVP/LFP/C composite material prepared by the solid state method (BM) was taken as the sample A, and the LVP/LFP/C composite material prepared by the hydrothermal method (hy) was taken as the sample B. The LVP/LFP/C composite material prepared by the sol-gel method (SJ) is sample E, and the LVP/LFP/C composite material prepared by the spray drying method (Sp) is sample F, and then the electron is taken. The surface morphology of the microscope (SEM, Hitachi 2600S) was observed and analyzed. 1. The SEM surface analysis structure of sample A prepared by solid state method (BM) is shown in Fig. 3a; 2. Hydrothermal method (hy) The prepared SEM surface analysis structure of sample B is shown in Fig. 3b; 3. The SEM surface analysis structure of sample E prepared by sol-gel method (SJ) is shown in Fig. 3c; 4. Spray drying The SEM surface analysis structure of Sample F prepared by the method (Sp) is shown in Figure 3d.

From the observation and analysis of the SEM surface analysis structure diagrams of Figures 3a, 3b, 3c and 3d, the following conclusions are obtained:

1. The LVP/LFP/C composite of the present invention, whether the sample A is obtained by a solid state method, or the sample B is obtained by a hydrothermal method, or the sample E is obtained by a sol-gel method, or the sample F is obtained by a spray drying method, There is a relatively uneven carbon layer around the LVP/LFP/C particles;

2. Analyze and compare the SEM surface analysis structure diagrams of Fig. 3a (solid state method), Fig. 3b (hydrothermal method), Fig. 3c (sol-gel method) and Fig. 3d (spray drying method), samples prepared by hydrothermal method B material surface structure, particle size is uniform, and evenly dispersed, especially LVP material can evenly cover the surface of LFP, forming a shell-core structure material, there will be better structural stability, in the high charge Excellent stability and gram capacity when discharging.

The sample F obtained by the spray drying method is coated with a glucose carbon source to effectively adhere the LVP material and the PS ball to the surface of the LFP/C active material, and the dispersion is complete. The porous 3D sphere structure of many gaps helps to make the electrolyte deeper into the active material and makes the conduction of electrons easier, and has the best stability and capacity when performing high charge and discharge.

In contrast, the surface structure of the sample A prepared by the solid state method or the sample E prepared by the sol-gel method, the carbon source such as furan, glucose or PS sphere is relatively unevenly dispersed, and when charging/discharging is performed, the electrons are compared. It is not easy to get in and out of the sample itself, and the overall stability of the material is poor.

3. According to the conclusion of the preceding paragraph, the LVP/LFP/C composite material prepared by hydrothermal method or spray drying method can effectively coat the surface and surrounding of all LFP/C active materials with LVP materials and carbon sources; The cathode material commonly used in lithium ion secondary batteries can increase the cycle test stability and the gram capacity of the battery as a whole when charging and discharging at a high voltage (4.8 V vs. Li/Li+).

Sample A, sample B, sample E and sample F of the LVP/LFP/C composite material of the present invention were ground in a stainless steel mortar, and the materials were separately ground, filled in a stainless steel stage, and then placed in X-rays. The crystal structure was analyzed in a diffractometer (XRD, hardware device: Brucker D2 Phaser, Germany), and the X-ray diffraction pattern shown in Fig. 4a and Figs. 4b, 4c and 4d was obtained. By comparison, the X-ray diffraction pattern of the LVP/LFP/C composite of Figures 4a to 4d is the same as that of the X-ray diffraction pattern in the literature, and no other miscellaneous items are produced.

Take the LVP/LFP/C composite material sample A, sample B, sample E, sample F of the present invention and the LVP/LFP/C composite material sample G (LFP: obtained by spray drying method (Sp) with reference to Table 1 above. LVP=7:3) is the material, about 5mg for each scale, and then placed on the microscope test piece, and flattened with a spatula. The microscope test piece is placed on a Confocal micro-Renishaw microscope. The surface of the LVP/LFP/C composite prepared by different synthetic methods was analyzed by Raman spectroscopy, and the full-range microscopic Raman spectrum shown in Fig. 5a to Fig. 5d was obtained.

Analysis of the full range of Raman spectra of Figures 5a to 5d gives the following conclusions:

1. Even if prepared by different synthesis methods, the main positions of phosphate (PO ₄ ^3- ) of sample A, sample B, sample E, sample F and sample G are 940 cm ^-1 , 990 cm. ^-1 , 1060cm ^-1 ; and the Raman peak of the carbon source is mainly two peaks of D-band (I _D ) at 1320 cm ^-1 and G-band (I _G ) at around 1580 cm ^-1 ;

2. From the observation and analysis of the Raman spectrum of Sample B and Sample F, it was found that the degree of graphitization of the LVP/LFP/C composite of the present invention using the hydrothermal method or the spray drying method for carbon source coating modification is better. The reason is that the hydrothermal method or the spray drying method uniformly disperses the carbon source, can be more uniformly heated during calcination, and can effectively coat the LEP/LVP/C composite material.

In addition, Sample A and Sample B were analyzed by R ₁ value and R ₂ value as shown in Table 2.

Table 2

The data in Table 2, Sample _E, R ₁ average of 1.36, the sample G (LFP: LVP = 7: 3) R ₁ in the average value was 1.22, so prepared by spray drying LVP / LFP / C Composite (ie, sample G) has the lowest R ₁ value (R ₁ = 1.22), and the R ₁ value (R ₁ = 1.30) of the LVP/LFP/C composite prepared by hydrothermal method (ie, sample B) is low. Samples G and B have more graphite-like carbon in the carbon layer, which will favor the electronic conductivity of the LVP/LFP/C composite.

In addition, the LVP/LFP/C composite prepared by hydrothermal method (ie, sample B) has the highest R ₂ value (R ₂ =1.619), and the LVP/LFP/C composite prepared by spray drying (ie, sample F) The R ₂ value (R ₂ =1.01) is the second highest, and the higher the R ₂ value, the more the carbon content of the residual carbon coating on the LVP/C, indicating that the LVP/LFP/C composite of the present invention is hydrothermally or Prepared by spray drying, the advantages include: increased residual carbon content of the coated LVP/C material and better uniform dispersion.

3. From the observation and analysis of the Raman spectra of sample A, sample B, sample E and sample F, it was found that the LCP/LFP/C composite samples prepared by hydrothermal method or spray drying method have stronger detection intensity. This means that the LVP/LFP/C composite of the present invention is prepared by a hydrothermal method or by a spray drying method, which can effectively improve the overall crystallinity of the composite LVP/LFP/C cathode material and make the material structure more stable.

According to the preparation method of the following Table 3, the LVP/LFP/C composite material sample A, sample B, sample E, sample F and sample G of the invention are selected as materials, and pre-made phosphoric acid is selected. Lithium iron/carbon (LFP/C) cathode material (component of LFP+10wt% Furan) is sample H, lithium phosphate vanadium/carbon (LVP/C) cathode material (component of which is LVP+5wt% Furan) is sample I , lithium iron phosphate / carbon (LFP / C) cathode material (its composition is LFP + 10wt% Glucose + 10wt% PS ball) for sample J, lithium phosphate vanadium / carbon (LVP / C) cathode material (its composition is LVP + 10wt% Glucose + 10wt% PS ball) is sample K, according to the method of weighing about 1.5~2.5mg each time, weigh each time twice, then put them into aluminum pan and wrap them separately, then put them separately In the sample cell of the elemental analyzer (EA, hardware device: Perkin Elmer EA 2400), for LVP/LFP/C composite, lithium iron phosphate/carbon (LFP/C) cathode material and lithium vanadium phosphate/carbon (LVP/ C) Quantitative analysis of the total carbon content of the cathode material.

The results of the EA analysis are shown in Table 3.

According to the data in Table 3, the following conclusions are obtained: 1. The pre-made LFP/C and LVP/C composite materials of the present invention are prepared by different synthesis methods, and different polymer materials are selected as carbon sources or carbons of different amounts are added. The residual carbon amount of the sample after calcination is different, for example, the residual carbon amount of the sample E prepared by the solid state method is 5.74 wt%; the residual carbon amount of the sample F prepared by the hydrothermal method is 6.54 wt%; The residual carbon contents of Sample J and Sample K prepared by spray drying method were 5.24% by weight and 3.83wt%, respectively; 2. The LVP/LFP/C composite material of the present invention was prepared by different synthesis methods, and different Moer was selected and used. The ratio of LFP and LVP, and the addition of different carbon sources, the amount of residual carbon after calcination is different, for example, the residual carbon content of sample A prepared by solid state method (LFP: LVP molar ratio = 5:1) The residual carbon content of sample B prepared by hydrothermal method (LFP: LVP molar ratio = 5:1) was 6.54 wt%; prepared by sol-gel method or by spray drying method (LFP: The residual carbon content of sample E or sample F of LVP molar ratio = 5:1) was 4.71 wt%, and was prepared by spray drying (LFP: LVP molar ratio = 7: The residual carbon amount of the sample G of 3) was 5.37 wt%.

Accordingly, the method for producing the LVP/LFP/C composite material of the present invention can obtain different residual carbon amounts depending on the difference in the preparation method and the type of use of the carbon source or the amount of addition. Therefore, the residual carbon amount of the LVP/LFP/C composite material of the present invention can be controlled to an optimum of about 5.0% by weight.

Take the LVP/LFP/C composite material sample A and sample B in Table 1 above, and weigh about 1.0g, respectively, and then add 0.02g of polyvinylidene fluoride (PVDF) aqueous solution and mix them uniformly to form a slurry. Put the slurry into the snoring device, and then put the smashed finished product into the oven for drying. After drying, put the sputum into the two-pole film measuring fixture, and measure the AC resistance by AC impedance analyzer. The value (R _b ), the area (A), and the δ (electrode thickness) were calculated for the electronic conductivity (σ _e ), which is σ _e = δ / (A × R _b ).

The results of the electronic conductivity (σ _e ) analysis are shown in Table 4.

According to the data in Table 4, the following conclusions are obtained:

1. In the electron conductivity (σ _e) aspect, an electronic conductivity (σ _e) Sample A 1.893 × 10 ^-3 S cm ^-1, relative to the electronic conductivity of the sample B (σ _e) about 2.532 × 10 ^-3 S cm ^-1 , the LCP/LFP/C composite of sample B has excellent electronic conductivity (σ _e ).

Accordingly, it is shown that the LVP/LFP/C composite prepared by the hydrothermal method has a better carbon source coating uniformity, so that a higher electron conductivity (σ _e ) can be obtained.

2. The LVP/LFP/C composite material of the present invention, when a furan (Furan) resin is used as a carbon source, since the furan (Furan) resin belongs to a five-ring type polymer material, it is easy to make LVP/LFP/C after calcination. The composite material is coated with a residual carbon layer to increase the conduction velocity of electrons.

Therefore, the LVP/LFP/C composite material of the present invention is a carbon source added, and in addition to speeding up the electron transport speed, a higher electron conductivity (σ _e ) and a better high power discharge capability can be obtained.

According to the foregoing, the LVP/LFP/C composite material of the present invention is suitable for forming an electrode sheet and has a high discharge capacity; for example, a button type battery fabricated according to the following embodiment 1, at 2.0 V~ When charging/discharging between 4.3V, the gram capacity at 0.1C charge/discharge rate is between 133~135mAh/g; according to the button type battery made in the following Example 7, at 2.0V~4.8V When charging/discharging is performed, the gram capacity at a charge/discharge rate of 0.1 C is 151 to 155 mAh/g, and the gram capacity at a charge/discharge rate of 1 C is 127 to 129 mAh/g. Accordingly, the electrode sheet made of the LVP/LFP/C composite material of the present invention can be used as a cathode electrode of a lithium ion secondary battery in use.

As shown in FIG. 6, when preparing an electrode sheet of a cathode electrode of a lithium ion secondary battery, one of the LVP/LFP/C composite materials and polyvinylidene fluoride (PVDF) prepared by using different synthesis methods of the present invention is selected. Poly(vinylidene difluoride)/N-methylpyrrolidone (about 14% by weight) (NMP (14wt%)) adhesive, N-methylpyrrolidone solvent (NMP solvent, Barrick (Panreac) company) and Super P conductive carbon material (or carbon black conductive agent) as raw materials; blended according to LVP / LFP / C: PVDF: Super P = 80wt%: 10wt%: 10wt%, respectively weigh Take 3g of LVP/LFP/C composite material, 2.678g of PVDF/NMP (about 14wt%), 8g of NMP, 0.375g of Super P conductive carbon material; after mixing PVDF/NMP with NMP for 10min, Super P conductive carbon material is slowly added to 10.678g of PVDF/NMP and stirred by a mixer. After stirring evenly, the LVP/LFP/C composite material is slowly added to the slurry and continuously stirred. After being thoroughly stirred, it will be prepared. The slurry is coated on a treated aluminum foil with a doctor blade and made into a cathode electrode, and the prepared cathode electrode is placed in an oven to remove residual organic solvent, for example, at a temperature of 70 ° C. After drying for 2-3 hours, it is dried again at a temperature of 110 ° C for 2 hours; the dried cathode electrode is rolled and leveled by a roller press. Finally, the circular cathode electrode was cut using a 13 mm cutter. The solid-liquid ratio control during the preparation of the cathode electrode sheet is 1:3, and the average weight of the active material of the cathode electrode sheet is between 4 and 6 mg.

As shown in FIG. 7, the structure of the general button type battery 10 includes an upper cover 20, a circular negative electrode 30, a separator 40, a lithium metal 50 and a lower cover 60. An electrode sheet made of one of the LVP/LFP/C composite materials prepared by the present invention using different synthesis methods can be used as the circular cathode electrode 30 of the button type battery 10.

[Examples]

The LVP/LFP/C composite samples A to D used in the following Examples 1-8 were made according to the ingredients listed in the following table:

Moreover, according to the results of the following measurement conditions, Examples 1-8 will specifically explain that the LVP/LFP/C composite material of the present invention is suitable for use in making a circular cathode electrode for a button type battery.

1. Cyclic voltammetry analysis:

Cyclic voltammetry (CV) is a method for determining whether a electrode has a reversible oxidation/reduction electrochemical reaction. The CV diagram of the LVP/LFP/C cathode electrode of the embodiment and its parameter values are obtained by cyclic voltammetry (CV), and it is judged and analyzed in which potential range the LVP/LFP/C cathode electrode is reversible. Sexual oxidation/reduction electrochemical reaction.

The basic principle is to use a change potential to obtain a redox reaction cycle potential map (or cyclic voltammetry map, referred to as CV map). From the peak height and symmetry of the oxidation wave and the reduction wave in the obtained CV diagram, the degree of reversibility of the reaction of the electroactive substance on the electrode surface can be judged. If the oxidation/reduction electrochemical reaction of the electrode is reversible, the curve in the CV diagram is vertically symmetrical, whereas if it is irreversible, the curve in the CV diagram is asymmetrical.

2. AC impedance analysis:

AC impedance is an important item for measuring battery electrode behavior and analyzing the electronic impedance of materials. An AC impedance analysis map (or Nyquist plot) is obtained by an AC impedance spectrometer to analyze the electrochemical reactions that may occur inside the lithium ion battery.

The basic principle is to put the test battery into the test fixture, use the potentiostat (Potentionstat Analyzer) to charge/discharge the test battery at a constant current rate, and then use the AC resistance spectrum analyzer to send a set AC signal, so that the original potentiostat The stable electric field supplied to the test tool generates amplitude signals of different frequencies, and the method can observe the response signal generated by the electrons of the test battery through the electrochemical reaction to different frequencies, and obtain the AC impedance analysis chart of the test battery.

From the AC impedance analysis chart, the surface reaction of each component of the test battery (for example, the cathode electrode) and the change of the number of alternating current (AC) impedance parameters such as the intrinsic impedance, the interface impedance, and the capacitance effect can be distinguished. For example, the change in the overall impedance value (Bulk Resistance, R _b ) and the AC impedance parameter value of the charge transfer resistance (R _ct ) on the electrode.

The charge transfer impedance (R _ct ) represents the charge transfer resistance on the electrode, that is, the resistance of the lithium ion to electron loss at the electrode. The value of the R _ct parameter value can be used to observe the ease of reaction on the electrode; if the R _ct parameter value is large, it means that the electrode reaction is quite slow, and if the R _ct value is small, it means that the electrical reaction is quite rapid.

3. Charge / discharge analysis

Measuring hardware: Model (Model BAT-750B) charge and discharge analyzer manufactured by Jiayou.

Measurement method: Place the button type battery without short circuit on the charge/discharge analyzer, set and adjust the parameters, set the voltage range from 3.0V to 4.8V, and perform different charge at constant current according to different set current values. /Discharge rate detection.

Qualification: After each charge and discharge, the rest interval is about 3 minutes, and then the next cycle test is continued.

After several consecutive charge/discharge tests, the computer records and obtains the discharge curve and capacitance data of voltage and time changes. After analysis and comparison, the actual discharge capacity of the test battery at different discharge rates is obtained.

Example 1

Using the LVP/LFP/C composite material sample A, the sample B, the sample F, and the sample C as materials, a circular cathode electrode for a button type battery was separately fabricated, and a button type battery was separately formed by sealing with a battery packer.

Cyclic voltammetry (CV) was used to obtain the reversible oxidation/reduction electrochemical reaction CV pattern of LVP/LFP/C cathode electrode prepared using sample A, sample B, sample C and sample F, as shown in Fig. 8a, Fig. 8b and Figure 8c, and obtain the relevant CV parameter values, as shown in Table 5.

After analyzing the CV diagrams of Fig. 8a, Fig. 8b and Fig. 8c, the prepared LVP/LFP/C cathode electrode has different oxidation/reduction peak pairs in the potential range of 2.0-4.3V, and has reversible oxidation/reduction electrification. Learn the reaction.

In the CV parameters of Table 5, the closer the values of R ₁ , R ₂ and R ₃ are to 1, the better the reversible oxidation/reduction electrochemical reaction of the prepared LVP/LFP/C cathode. The closer the values of ΔE ₁ , ΔE ₂ and ΔE ₃ are to 0, the easier the electrons are to conduct inside the LVP/LFP/C cathode electrode, which helps to improve the battery's ability to charge/discharge.

According to the CV parameter values of Table 5, R ₁ and R ₃ of the LVP/LFP/C cathode electrode prepared using Sample A are between 1.099 and 1.101; ΔE ₁ and ΔE _{2 are} between 0.083 and 0.336; The solid-state LVP/LFP/C composite cathode material has excellent reversible oxidation/reduction electrochemical reaction and also helps to improve the battery's ability to charge/discharge.

R ₁ and R ₃ of the LVP/LFP/C cathode electrode prepared using Sample B were between 1.181 and 1.245; ΔE ₁ and ΔE _{2 were} between 0.088 and 0.305; this indicates the LVP/produced by hydrothermal method. The LFP/C composite cathode material has a good reversible oxidation/reduction electrochemical reaction and also helps to improve the battery's ability to charge/discharge.

R ₁ and R ₃ of the LVP/LFP/C cathode electrode prepared using sample C are between 1.188 and 1.276; the ΔE ₁ and ΔE _{2 are} between 0.156 and 0.429, and also have good reversible oxidation/reduction electrochemistry. The reaction also helps to improve the battery's ability to charge/discharge.

R ₁ and R ₃ of the LVP/LFP/C cathode electrode prepared using sample F were between 1.079 and 1.247; ΔE ₁ and ΔE _{2 were} between 0.328 and 0.748, which indicates LVP/produced by spray drying. The LFP/C composite cathode material has very good oxidation/reduction reversibility, which improves the overall stability and charge and discharge capability of the battery.

In contrast, the LVP/LFP/C cathode electrode prepared using Sample B has a value of ΔE ₁ , ΔE ₂ and ΔE ₃ which is closer to 0, indicating that electrons are more easily conducted inside the LVP/LFP/C cathode electrode. It helps to improve the battery's ability to charge/discharge.

It was thus confirmed that the LVP/LFP/C composite of the present invention was prepared by hydrothermal method, had good oxidation/reduction reversibility and reduced potential polarization, and was applied to the LVP/LFP/C cathode electrode. The performance is even better, which helps to increase the stability of the button type battery and improve the charge and discharge capability.

Example 2

The LVP/LFP/C composite sample A prepared by the solid state method (BM) was used as a material, and an LVP/LFP/C cathode electrode for a 2032 button type battery was fabricated, and a 2032 button type battery was assembled.

Electrical detection of different charge/discharge rates at constant current was performed using a charge/discharge analyzer (manufactured by Jiayou, Model: BAT-750B) according to different current values. The voltage range is set between 2.0 and 4.3V. The battery is tested four times at 0.1C rate charge/discharge and three times at 0.2C~10C rate charge/discharge. After each charge and discharge, rest about 3 After the minute, continue to the next loop detection.

After the test, the charge and discharge curve of the battery at the 0.1C rate charge/discharge, as shown in Figure 9; the battery charge capacity at 0.2C~10C charge/discharge, the test results are shown in Table 6, the charge and discharge The curve is shown in Figure 10.

Table 6 shows the gram capacity between 2.0V and 4.3V at different charge/discharge rates of 0.2C~10C.

The coin-type battery of the present embodiment has a gram capacity between 2.0 and 4.3 V: 1. at a charge/discharge rate of 0.1 C, according to the charge and discharge curve of Fig. 9, up to 135 mAh/g; 2. at 0.2 C, 0.5. C, 1C, 3C, 5C and 10C rate charge / discharge, according to the gram capacity parameter values of Table 6, respectively, up to 130mAh / g, 125mAh / g, 121mAh / g, 96mAh / g, 76mAh / g and 20mAh / g .

It was confirmed that the LVP/LFP/C composite prepared by the solid state method is suitable for forming a circular cathode electrode of a button type battery, and the assembled button type battery has an excellent high rate charge between 2.0 and 4.3V. Ability and good electrical performance.

Example 3

Same as Embodiment 2, but the voltage range of the charge/discharge analyzer is set between 2.0 and 4.8V, and the power is set. The cell was tested for three discharges at a rate of 0.2 C to 10 C charge/discharge.

After the test, the battery has a gram capacity under charge/discharge at a rate of 0.2 C to 10 C. The test results are shown in Table 7, and the charge and discharge curves are shown in Fig. 11.

The button type battery of the present embodiment has a gram capacity between 2.0 and 4.8 V, and is charged/discharged at a rate of 0.2 C, 0.5 C, 1 C, 3 C, 5 C, and 10 C, according to the gram capacity (Q _{sp, Ch} ) Parameter values were 134 mAh/g, 135 mAh/g, 131 mAh/g, 113 mAh/g, 91 mAh/g and 30 mAh/g, respectively.

It was confirmed that the LVP/LFP/C composite prepared by the solid state method can raise the material discharge platform from 3.4V to 4.3V or 4.8V, which can improve the high power density (W/kg) capacity and high of the original LFP material. Energy density (Wh/kg) and suitable for round cathode electrodes made of button cells The assembled button-type battery has excellent high-rate charging and discharging performance and good electrical performance between 2.0 and 4.8V.

Example 4

The LVP/LFP/C composite sample B prepared by hydrothermal method (hy) was used as a material, and an LVP/LFP/C cathode electrode for a 2032 button type battery was fabricated, and a 2032 button type battery was assembled.

Using a charge/discharge analyzer with a voltage range between 2.0 and 4.3 V, the battery was tested four times at a charge/discharge of 0.1 C rate and three times at a charge/discharge rate of 0.2 C to 10 C.

After the test, the charge and discharge curve of the battery at the 0.1C rate charge/discharge, as shown in Figure 12; the battery charge capacity at 0.2C~10C charge/discharge, the test results are shown in Table 8, the charge and discharge The curve is shown in Figure 13.

The coin-type battery of the present embodiment has a gram capacity between 2.0 and 4.3 V: 1. at a charge/discharge rate of 0.1 C, according to the charge and discharge curve of Fig. 12, it also reaches 135 mAh/g; 2. at 0.2 C, 0.5C, 1C, 3C, 5C and 10C rate charge/discharge, according to the gram capacity parameter values of Table 8, respectively, up to about 132mAh / g, 129mAh / g, 126mAh / g, 111mAh / g, 93mAh / g and 77mAh /g.

Compared with the button type battery of the second embodiment, the coin battery of the present embodiment is more excellent in the gram capacity at the 5C and 10C rate charge and discharge.

It was confirmed that the LVP/LFP/C composite prepared by the hydrothermal method is more suitable for the round cathode electrode of the button type battery than the LCP/LFP/C composite material prepared by the solid state method, and the assembled button The battery has better high-rate charge and discharge capability and good electrical performance between 2.0 and 4.3V.

Example 5

The LVP/LFP/C composite sample C prepared by hydrothermal method (hy) was used as a material, and an LVP/LFP/C cathode electrode for a 2032 button type battery was fabricated, and a 2032 button type battery was assembled.

Using a charge/discharge analyzer with a voltage range of 2.0 to 4.8 V, the battery was tested four times at a charge/discharge of 0.1 C rate and three times at a charge/discharge rate of 0.2 C to 10 C.

After the test, the charge-discharge curve of the battery at the charge/discharge rate of 0.1C is shown in Figure 14; the charge capacity of the battery at the charge/discharge rate of 0.2C~10C, the test results are shown in Table 9, the charge and discharge The curve is shown in Figure 15.

The coin-type battery of the present embodiment has a gram capacity between 2.0 and 4.8 V: 1. at a charge and discharge rate of 0.1 C, according to the charge and discharge curve of Fig. 14, it also reaches 137 mAh/g; 2. at 0.2 C, 0.5. C, 1C, 3C, 5C and 10C rate charge / discharge, according to the gram capacity parameter values of Table 9, respectively, up to 121mAh / g, 110mAh / g, 99mAh / g, 67mAh / g, 45mAh / g, 8mAh / g

Compared with the button type battery of Example 3 (LFP: LVP molar ratio = 5:1), the electric capacity at the charge/discharge rate of 0.2 C and 0.5 C, this example (LFP: LVP molar ratio = The button battery of 3:1) is not inferior.

It was confirmed that when the LVP/LFP/C composite prepared by hydrothermal method can be used, a smaller amount of LFP can be used, and it is still suitable for the round cathode electrode of the button type battery, and assembled into a button type battery in 2.0. High-rate charge and discharge capability and good electrical performance are still available between ~4.8V.

Example 6

The LVP/LFP/C composite sample D prepared by hydrothermal method (hy) was used as a material and made LVP/LFP/C cathode electrode for 2032 button type battery, and assembled into 2032 button type battery.

Using a charge/discharge analyzer with a voltage range between 2.0 and 4.3 V, the battery was tested four times at a charge/discharge of 0.1 C rate and three times at a charge/discharge rate of 0.2 C to 10 C.

After the test, the charge and discharge curve of the battery under charge/discharge at 0.1C rate is shown in Figure 16; the gram capacity of the battery under charge/discharge at 0.2C~10C, the test results are shown in Table 10, and its charge and discharge The curve is shown in Figure 17.

The button type battery of the embodiment has a gram capacity of between 2.0 and 4.3 V: 1. at a charge/discharge rate of 0.1 C, according to the charge and discharge curve of FIG. 16, it also reaches 127 mAh/g; 2. Under the charge/discharge rate of 0.2C, 0.5C, 1C, 3C, 5C and 10C, according to the gram capacity parameter values of Table 10, respectively, 129mAh/g, 129mAh/g, 126mAh/g, 116mAh/g, 110 mAh/g and 72 mAh/g.

Compared with the button type battery of the fourth embodiment, the button type battery of the present embodiment is inferior to the gram capacity at the 5C and 10C rate charge and discharge.

It was confirmed that the different materials of furan (Furan) or polystyrene (PS) were used as the carbon source, and the LVP/LFP/C composite prepared by hydrothermal method was suitable for the round cathode of the button type battery. The electrode and the assembled button type battery have excellent high-rate charging and discharging performance and good electrical performance between 2.0 and 4.3V.

Example 7

Same as Embodiment 6, but the voltage range of the charge/discharge analyzer is set between 2.0 and 4.8 V, and the discharge amount of the battery is tested three times at a rate of 0.2 C to 10 C charge/discharge.

After the test, the charge and discharge curve of the battery at the 0.1C rate charge/discharge, as shown in Figure 18; the battery charge capacity at 0.2C~10C charge/discharge, the test results are shown in Table 11, the charge and discharge The curve is shown in Figure 19.

The coin-type battery of the present embodiment has a gram capacity between 2.0 and 4.8 V: 1. at a charge/discharge rate of 0.1 C, according to the charge and discharge curve of Fig. 18, reaching 151 to 155 mAh/g; 2. at 0.2 C. , 0.5C, 1C, 3C, 5C and 10C rate charge and discharge, according to the gram capacity (Q _{sp, ch} ) parameter values of Table 11, respectively, reached 143mAh / g, 140mAh / g, 129mAh / g, 97mAh / g, 78 mAh/g and 37 mAh/g.

It was confirmed that the LVP/LFP/C composite material prepared by using hydrothermal method using polystyrene (PS) as a carbon source is suitable for forming a circular cathode electrode of a button type battery, and the assembled button type battery is Excellent high-speed charge and discharge performance and good electrical performance (including overall energy capacity, high power density (W/kg) capacity and high energy density (Wh/kg)) between 2.0 and 4.8V.

Example 8

The button type batteries of Example 2 and Example 4 were taken as samples, and charged/discharged between 2.0 and 4.3 V, and subjected to a cycle life test of 80 times of charge and discharge at a charge/discharge rate of 0.2 C/1 C. As shown in Figure 20.

According to the cycle life test result of FIG. 20, regardless of the LVP/LFP/C composite material prepared by the solid state method (see Example 2) or the hydrothermal method (Example 4), the gram capacity after charging and discharging 80 times There is still 115mAh/g, which is suitable for the round cathode electrode of the button type battery.

Example 9

LVP/LFP/C composite sample E prepared by sol-gel method (SJ) (LFP: LVP molar ratio = 5:1) was used as a material, and LVP/LFP/ for 2032 button type battery was fabricated. C cathode electrode, And assembled into a 2032 button type battery.

Using a charge/discharge analyzer with a voltage range of 2.0 to 4.8 V, the battery was tested four times at a charge/discharge of 0.1 C rate and three times at a charge/discharge rate of 0.2 C to 10 C.

After the test, the battery's gram capacity at the 0.1C rate charge/discharge, the test results are shown in Table 12, its charge and discharge curve charge and discharge curve, as shown in Figure 21; battery at 0.2C ~ 10C rate charge / discharge The electrical capacity of the test is shown in Table 13, and the charge and discharge curves are shown in Fig. 22.

The coin-type battery of the present embodiment has a gram capacity between 2.0 and 4.8 V: 1. At a charge/discharge rate of 0.1 C, according to the gram capacity parameter value of Table 12, it also reaches 152 mAh/g; 2. at 0.2. C, 0.5C, 1C rate charge / discharge, according to the gram capacity parameter values of Table 13, respectively, reached 138, 135mAh / g, 126mAh / g.

Example 10

LVP/LFP/C composite sample F prepared by spray drying (Sp) (LFP: LVP molar ratio = 5:1) was used as the material, and LVP/LFP/C for 2032 button type battery was made. Electrodes, and assembled into 2032 button-type batteries.

Using a charge/discharge analyzer with a voltage range of 2.0 to 4.8 V, the battery was tested four times at a charge/discharge of 0.1 C rate and three times at a charge/discharge rate of 0.2 C to 10 C.

After the test, the battery is charged/discharged at a rate of 0.1 C. The test results are shown in Table 14. The charge and discharge curves of the charge and discharge curves are shown in Figure 23; the battery is charged/discharged at a rate of 0.2 C to 10 C. The electrical capacity of the test is shown in Table 15, and the charge and discharge curves are shown in Fig. 24.

Further, in the button type batteries of the ninth embodiment and the present embodiment, the electrical analysis results between 2.0 and 4.8 V were consolidated as shown in FIG.

The coin-type battery of the embodiment has a gram capacity between 2.0 and 4.8 V: 1. at a charge/discharge rate of 0.1 C, according to the gram capacity parameter value of Table 14, up to 160 mAh/g; 2. at 0.2 C, 0.5C, 1C, 3C, 5C and 10C rate charge / discharge, according to the gram capacity parameter values of Table 15, respectively, 149mAh / g, 146mAh / g, 135mAh / g, 115mAh / g, 103mAh / g, 82 mAh / g discharge capacity generation; 3. Referring to the electrical analysis results of Figure 27, the electrical performance of the LVP / LFP / C composite prepared by spray drying method (including the overall gram capacity, high power density ( W/kg) capacity and high energy density Degree (Wh/kg), etc. is superior to the LVP/LFP/C composite prepared by the sol-gel method.

Example 11

LVP/LFP/C composite sample F prepared by spray drying (Sp) (LFP: LVP molar ratio = 7:3) was used as a material, and LVP/LFP/C for 2032 button type battery was made. Electrodes, and assembled into 2032 button-type batteries.

Using a charge/discharge analyzer with a voltage range of 2.0 to 4.8 V, the battery was tested four times at a charge/discharge of 0.1 C rate and three times at a charge/discharge rate of 0.2 C to 10 C.

After the test, the battery is charged and discharged at a rate of 0.1 C. The test results are shown in Table 16. The charge and discharge curves of the charge and discharge curves are shown in Figure 25; the battery is charged/discharged at a rate of 0.2 C to 10 C. The electrical capacity of the test is shown in Table 17, and the charge and discharge curves are shown in Fig. 26.

Moreover, in the button type battery of the embodiment 10 and the embodiment, the electrical analysis result between 2.0 and 4.8 V is merged into a battery as shown in FIG.

The coin-type battery of the present embodiment has a gram capacity between 2.0 and 4.8 V: 1. at a charge/discharge rate of 0.1 C, according to the gram capacity parameter value of Table 16, up to 158 mAh/g; 2. at 0.2 C, 0.5C, 1C rate charge and discharge, according to the gram capacity parameter values of Table 17, respectively, the discharge gram capacity of about 150mAh / g, 142mAh / g, 132mAh / g; 3. Refer to the electrical properties of Figure 27. As a result of the analysis, the LVP/LFP/C composite prepared by spray drying (LFP: LVP molar ratio = 5:1) has electrical properties (including overall gram capacity, high power density (W/kg) capacity and High energy density (Wh/kg), etc. is superior to LVP/LFP/C composites prepared by spray drying (LFP: LVP molar ratio = 7:3).

Example 12

The button type battery of Example 10 was placed on a charge/discharge analyzer, and the voltage range was set between 2.0 and 4.8 V at a temperature of 50 ° C, at 0.1 C / 0.1 C, 0.2 C / 0.2 C, 0.2 C. /0.5C, 0.2C/1C, 0.2C/3C, 0.2C/5C and 0.2C/10C charge/discharge rate, three discharges were measured, the test results are shown in Table 18 and Table 19, charge and discharge curves As shown in Figures 28 and 29, respectively.

The button type battery of Example 10 was prepared by a spray drying method (LFP: LVP molar ratio = 5:1) of a LVP/LFP/C composite material as a circular cathode electrode:

1. At 50 ° C high temperature, the 0.1 C charge / discharge rate of gram capacity, according to the gram capacity parameter value of Table 18, up to 172 mAh / g;

2. At 50 ° C high temperature, 0.2 C / 0.2 C, 0.2 C / 0.5 C, 0.2 C / 1 C, 0.2 C / 3 C and 0.2 C / 5 C charge / discharge rate of the gram capacity, according to Table 19 The capacity parameter values were 167 mAh/g, 166 mAh/g, 156 mAh/g, 120 mAh/g, and 49 mAh/g, respectively.

3. Compared with the results of Table 14 and Table 15 tested at 25 ° C in the button type battery of Example 10, the charge and discharge gram capacity of the button type battery is also increased by about 10 mAh/g as the temperature is increased, and the display temperature is It is of great benefit to increase the charge and discharge capacity of the button type battery.

Based on the above results, it was confirmed that the button type battery of the present embodiment has an excellent and very stable high rate charge and discharge capability and a very excellent electrical performance in a high temperature environment of 50 °C.

result

1. The invention uses the solid state method to prepare the LVP/LFP/C composite material, and when used for assembling the circular cathode electrode of the button type battery, when charging/discharging between 2.0V and 4.3V, charging at 0.1C/ The gram capacity at discharge rate is between 133 and 135 mAh/g, and there is still 114 mAh/g after 80 cycles test at 0.1 C charge/discharge rate; the gram capacity at 1 C charge/discharge rate is 119-121 mAh/ g; the gram capacity at 5C charge/discharge rate can reach 72~76mAh/g.

2. The invention uses the hydrothermal method to prepare the LVP/LFP/C composite material, and when used for assembling the circular cathode electrode of the button type battery, when charging/discharging between 2.0V and 4.3V, charging at 0.1C The gram capacity at the discharge rate is between 133 and 135 mAh/g, and still has 115 mAh/g after 80 cycles test at a charge/discharge rate of 0.1 C; the charge capacity at a charge/discharge rate of 1 C is 124 to 126 mAh. /g; The gram capacity at 5C charge/discharge rate can reach 90~93mAh/g.

When charging/discharging between 2.0V and 4.8V, the gram capacity at 0.1C charge/discharge rate can be increased to 151~155mAh/g; at 1C charge/discharge rate, the gram capacity is 127~129mAh. /g.

3. When comparing the advantages and disadvantages of using LCP/LFP/C composites prepared by solid state method and hydrothermal method, it is better to prepare LVP/LFP/C composite materials by hydrothermal method, which is used for assembling circular cathode electrodes of button type batteries. This will help to increase the overall capacity of the button-type battery and increase the operating voltage of charge and discharge.

4. The invention adopts the solid state method and the hydrothermal method to separately prepare the LVP/LFP/C composite materials, and is suitable for the round cathode electrode of the button type battery, and when assembled into a button type battery, the voltage is 2.0~4.3V. Even if the voltage is increased to between 2.0 and 4.8V, both have excellent high-speed charge and discharge capability and good Electrical performance.

5. The present invention uses the sol-gel method to prepare an LVP/LFP/C composite material, and when used for assembling a circular cathode electrode of a button type battery, when charging/discharging between 2.0V and 4.8V, at 0.1 The gram capacity at C charge/discharge rate is between 148 and 151 mAh/g; the gram capacity at 1 C charge/discharge rate is 126 mAh/g; the gram capacity at 5 C charge/discharge rate can reach 76~ 77mAh/g.

6. The invention adopts the spray drying method to prepare the LVP/LFP/C composite material, and when used for assembling the circular cathode electrode of the button type battery, when charging/discharging between 2.0V and 4.8V, charging at 0.1C The gram capacity at the discharge rate can be increased to between 156 and 160 mAh/g; the gram capacity at the 1 C charge/discharge rate is 148 to 150 mAh/g; and the gram capacity at the 5 C charge/discharge rate can be Up to 102 mAh / g; in 10C high rate discharge, the gram capacity can reach 82 ~ 83mAh / g.

7. Referring to Figure 27, the electrical performance of the LVP/LFP/C composite prepared in Comparative Example 9 to Example 11 was compared. As a result, Example 10 was prepared by spray drying (Sp) (LFP: LVP More). The LVP/LFP/C composite with ratio = 5:1) has a high average discharge capacity of about 160 mAh/g; the reason is that the added nano PS sphere carbon source is uniformly dispersed on LVP/LFP/C. Effectively improve the composite discharge capacity and improve the high power discharge capacity and stability.

8. The LVP/LFP/C composite prepared by the invention is suitable for the circular cathode electrode assembled into a button type battery, and has an excellent and very stable high rate in a low temperature environment of -20 ° C and a high temperature environment of 50 ° C. Charge and discharge performance and excellent electrical performance.

Claims (8)

A method for preparing a lithium vanadium phosphate/lithium iron phosphate/carbon composite material, comprising a prefabricated lithium iron phosphate/carbon (LFP/C) cathode material as a precursor, comprising the steps of: a) preparing lithium iron phosphate/carbon (LFP/C) cathode material: a1) Lithium (Li): iron (Fe): phosphoric acid (PO ₄ ) has a molar ratio of 1:1:1, and a lithium source, an iron source and a phosphoric acid source are selected as raw materials; a2 Depending on the weight of the lithium iron phosphate/carbon (LFP/C) cathode material, a carbon source of 1 to 30% by weight is selected; a3) using a solid phase method, hydrothermal method, sol-gel method or spray drying method. One of the synthesis methods, the lithium source, the iron source, the phosphoric acid source and the carbon source are synthesized into a lithium iron phosphate/carbon (LFP/C) cathode material precursor; a4) the lithium iron phosphate/carbon (LFP/C) cathode material precursor is placed in a high temperature furnace for calcination to produce the lithium iron phosphate/carbon (LFP/C) cathode material; b) based on the weight of the lithium phosphate vanadium/lithium iron phosphate/carbon composite, Select a carbon source of 1 to 30 wt%; c) prepare a lithium phosphate vanadium/lithium lithium phosphate/carbon cathode material precursor using hydrothermal method; c1) lithium (Li): vanadium (V): phosphoric acid (PO ₄ ) Moerby is 3:2:3, choose Source, vanadium source and phosphoric acid source are raw materials, and the liquid phase is mixed into lithium phosphate vanadium (LVP) aqueous solution; c2) lithium iron phosphate/carbon (LFP/C): lithium phosphate vanadium/carbon (LVP/C) molar a ratio of 1:1 or 3:1 or 5:1, quantitatively selected prefabricated lithium iron phosphate / carbon (LFP / C) cathode material; c3) selected lithium iron phosphate / carbon (LFP / C) cathode The material and the carbon source are added to the aqueous solution of lithium vanadium phosphate (LVP), and uniformly stirred into a mixed aqueous solution of lithium vanadium phosphate/lithium iron phosphate (LVP/LFP) containing a carbon source; and then lithium iron phosphate/carbon is hydrothermally used ( The surface of the LFP/C) cathode material is surrounded by a layer of lithium vanadium phosphate/carbon (LVP/C) cathode material, which is dried to obtain a lithium vanadium phosphate/lithium lithium phosphate/carbon cathode material precursor; d) the lithium vanadium phosphate/phosphoric acid The lithium iron/carbon cathode material precursor is placed in a high temperature furnace for calcination to obtain a lithium phosphate lithium phosphate/lithium iron phosphate/carbon composite material having a residual carbon content of 1 to 15 wt%. A method for preparing lithium phosphate vanadium/lithium iron phosphate/carbon composite material, comprising a prefabricated lithium iron phosphate/carbon (LFP/C) cathode material and a prefabricated lithium vanadium phosphate/carbon (LVP/C) cathode material as precursors thereof, The method comprises the following steps: a) preparing a lithium iron phosphate/carbon (LFP/C) cathode material: a1) lithium (Li): iron (Fe): phosphoric acid (PO ₄ ) has a molar ratio of 1:1: 1. Select a lithium source, an iron source, and a phosphoric acid source as raw materials; a2) select a carbon source of 1 to 30 wt% based on the weight of the lithium iron phosphate/carbon (LFP/C) cathode material; a3) use a solid phase method , one of the hydrothermal method, the sol-gel method or the spray drying method, the lithium source, the iron source, the phosphoric acid source and the carbon source are synthesized into a lithium iron phosphate/carbon (LFP/C) cathode Material precursor; a4) placing the lithium iron phosphate/carbon (LFP/C) cathode material precursor into a high temperature furnace for calcination to produce the lithium iron phosphate/carbon (LFP/C) cathode material; b) Based on the weight of lithium vanadium phosphate/lithium iron phosphate/carbon composite, a carbon source of 1 to 30 wt% is selected; c) a lithium vanadium phosphate/carbon (LVP/C) cathode material is prepared; b1) lithium (Li) : Vanadium (V): The molar ratio of phosphoric acid (PO4) is 3: 2:3, select lithium source, vanadium source and phosphoric acid source as raw materials; b2) based on the weight of lithium phosphate vanadium/carbon (LVP/C) cathode material, choose to use carbon source of 1~30wt%; b3) use solid One of the synthesis methods of phase method, hydrothermal method, sol-gel method or spray drying method, the lithium source, vanadium source, phosphoric acid source and carbon source are synthesized into lithium phosphate vanadium/carbon (LVP/C) a cathode material precursor; b4) placing the lithium vanadium phosphate/carbon (LVP/C) cathode material precursor into a high temperature furnace for calcination to produce the lithium phosphate vanadium/carbon (LVP/C) cathode material; d) Preparation of lithium phosphate vanadium / lithium iron phosphate / carbon cathode material precursor using spray drying; d1) lithium iron phosphate / carbon (LFP / C): lithium phosphate vanadium / carbon (LVP / C) molar ratio of 1 :6, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, 7:3 or 8:2, Prefabricated lithium iron phosphate/carbon (LFP/C) cathode material and lithium phosphate vanadium/carbon (LVP/C) cathode material are selected; d2) selected lithium iron phosphate/carbon (LFP/C) cathode material, lithium lithium phosphate /Carbon (LVP/C) cathode material and carbon source are mixed in liquid phase to form an aqueous solution, and then spray dried to form phosphorus a surface of a lithium iron/carbon (LFP/C) cathode material surrounded by a layer of lithium phosphate vanadium/carbon (LVP/C) cathode material having a spherical structure of lithium phosphate vanadium phosphate/lithium lithium phosphate/carbon cathode material precursor; f) said phosphoric acid The lithium vanadium/lithium phosphate/carbon cathode material precursor is placed in a high temperature furnace for calcination to obtain a lithium phosphate lithium phosphate/lithium iron phosphate/carbon composite material having a residual carbon content of 1 to 15 wt%. The method for preparing a lithium vanadium phosphate/lithium iron phosphate/carbon composite material according to claim 1 or 2, wherein the lithium source is selected from the group consisting of lithium carbonate, lithium hydrogencarbonate, lithium hydroxide, and nitric acid. One or more of lithium, lithium acetate, lithium hydrogen phosphate or lithium phosphate; the iron source is one selected from the group consisting of iron sulfate, ferrous oxalate, iron phosphate, iron oxide, iron acetate, iron nitrate or ferric chloride Or a mixture of the above; the vanadium source is one or more selected from the group consisting of vanadium pentoxide, ammonium metavanadate, vanadium trioxide, vanadyl sulfate or sodium vanadate; the source of the phosphoric acid is selected from the group consisting of dihydrogen phosphate Mixing one or more of ammonium, ammonium phosphate, ammonium hydrogen phosphate, lithium phosphate, lithium hydrogen phosphate, lithium ammonium phosphate or sodium phosphate; the carbon source is selected from the group consisting of sucrose, vitamin C, citric acid, starch, glucose, furan Resin, polyvinyl alcohol, phenolic resin, polyvinylpyrrolidone, polystyrene, nanopolystyrene sphere, nano polymethyl methacrylate ball, SP conductive carbon material, CS conductive carbon material, carbon black conductive carbon material, Graphene conductive carbon material, CNTs carbon material, artificial stone , Synthetic graphite, acetylene black, carbon fiber or mesophase carbon microbeads of one or more thereof. The method for preparing a lithium vanadium phosphate/lithium iron phosphate/carbon composite material according to claim 3, wherein the lithium vanadium phosphate/lithium lithium phosphate/carbon cathode material precursor is placed in a high temperature furnace for calcination. The first stage of pre-baking heat treatment is carried out in a high-temperature furnace at a temperature of 300 to 500 ° C, and then heated to 500 to 1000 ° C for the second stage of calcination heat treatment, and the reaction time of the calcination and calcination heat treatment is between 8 and 72 hours. A method for preparing a lithium vanadium phosphate/lithium iron phosphate/carbon composite material according to claim 4, wherein in the first stage of the calcination heat treatment and/or the second stage of the calcination heat treatment, the method is The heat treatment is carried out under the conditions of hydrogen and argon. The composition of the mixed gas of hydrogen and argon is H ₂ : Ar = 10%: 90%, H ₂ : Ar = 5%: 95%, H ₂ : Ar = 3%: 97%, H ₂ : Ar = 2%: 98% or H ₂ : Ar = 1%: 99% of one. A method for producing a lithium vanadium phosphate/lithium iron phosphate/carbon composite according to claim 5, wherein the argon (Ar) is substituted with nitrogen (N ₂ ). The method for preparing a lithium phosphate vanadium/lithium iron phosphate/carbon composite material according to the first or second aspect of the patent application, the residual carbon content of the calcined lithium vanadium phosphate/lithium iron phosphate/carbon composite material is between 5~10wt%. A cathode electrode of a lithium ion secondary battery, which is made of a lithium vanadium phosphate/lithium iron phosphate/carbon composite material according to the first or second aspect of the patent application.