KR102816302B1 - Oxyhalide and its preparation method and all-solid-state lithium battery - Google Patents

Abstract

The present invention provides an oxyhalide, a method for producing the same, and an all-solid-state lithium battery. The method comprises the steps of: (1) crushing and pressing a mixture of a lithium source and a boron source weighed according to a stoichiometric ratio, placing the mixture into a reaction tube, vacuuming and sealing the reaction tube, and performing a first calcination, wherein the temperature of the first calcination is 300 to 450°C, and the time of the first calcination is 4 to 20 h; and (2) cooling to room temperature after the first calcination, taking out an intermediate product in the reaction tube, crushing and pressing it again, placing the mixture into a reaction tube, vacuuming and sealing the reaction tube, performing a second calcination, and cooling to room temperature. The method of the present invention is simple, has high raw material utilization, no by-products, and is advantageous for industrial production; the produced oxyhalide has high ionic conductivity and stability, and has excellent interfacial stability with lithium metal; and the produced all-solid-state lithium battery has excellent electrochemical performance.

Description

Oxyhalide and its preparation method and all-solid-state lithium battery

The present invention relates to an oxyhalide, a method for producing the same, and an all-solid-state lithium battery.

All-solid-state lithium batteries have attracted much attention because of their simple structure, high safety, and high energy density. All-solid-state lithium batteries use solid electrolytes instead of electrolytes and separators, which makes the battery thinner and smaller in volume, thus improving the energy density of the battery and enhancing the safety of the battery. Therefore, the research and development of all-solid-state lithium batteries that can replace traditional lithium-ion batteries are of great significance. However, all-solid-state lithium batteries have the following problems: (1) How to solve the transport of positive and negative electrodes and electrolyte ions at the electrode level; (2) During the cycling process, the positive and negative electrodes cannot maintain very good contact like liquids; (3) Metallic lithium is prone to lithium dendrites during the charge and discharge process, which will reduce the electrochemical performance of all-solid-state lithium batteries and are not conducive to practical application and development.

The core of all-solid-state lithium batteries lies in the compound as a solid electrolyte. At present, both organic compounds and inorganic compounds have been reported as high-quality electrolytes, and inorganic solid electrolytes have higher ionic conductivity and stability than organic solid electrolytes. Up to now, the materials of inorganic solid electrolytes can be divided into sulfides, oxides and halides. Sulfide solid electrolytes have high ionic conductivity (>10 ^-3 S cm ^-1 ), but they are easily affected by moisture in the surrounding atmosphere, which causes harmful hydrolysis reactions and greatly reduces ionic conductivity; in addition, the poor oxidation stability of sulfides greatly limits their direct use as high-voltage negative electrode materials. Oxide solid electrolytes have high air stability and thermal stability, low manufacturing cost, and are easy to be mass-produced, but their mechanical rigidity makes the interfacial contact with electrode materials poor, and high-temperature processes or liquid electrolyte introduction are required to assemble the battery. Halide solid electrolytes have very high ionic conductivity (>10 ^-3 S cm ^-1 ) at room temperature, but they still have the problems of easy decomposition and low stability.

In oxyhalide materials, the strong binding energy of oxygen as well as the polarity of halogen are maintained due to the bonding of divalent oxygen ion and halogen ion, which provides more possibilities for exploring new electrolyte materials in the future. In addition, it has been reported that Li ₄ B ₇ O ₁₂ Cl has high ionic conductivity at 300 °C. However, previous reports have shown that a series of by-products, such as Li ₂ B ₄ O ₇ , were generated during the synthesis of Li ₄ B ₇ O ₁₂ Cl, which reduced the conductivity and electrochemical performance of Li ₄ B ₇ O ₁₂ Cl to some extent.

Therefore, research and development of pure oxyhalide materials with excellent conductivity and electrochemical performance are of great significance in the battery field.

The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art that it is difficult to produce a pure oxyhalide having excellent conductivity and electrochemical performance, and to provide an oxyhalide, a method for producing the same, and an all-solid-state lithium battery. The production method of the present invention is simple, has a high utilization rate of raw materials, produces no by-products, and is advantageous for industrial production; the produced oxyhalide has high ionic conductivity and stability, and excellent interfacial stability with lithium metal; and the produced all-solid-state lithium battery has excellent electrochemical performance.

In order to manufacture the pure oxyhalide, the inventor uses a solid-phase reaction method to manufacture, and crushes and presses the raw materials during the manufacturing process to make the contact between each raw material closer and reduce the occurrence of side reactions between the raw materials and the reaction tube; calcines in a vacuum environment to further avoid the occurrence of side reactions; and uses a calcination method combining low-temperature pre-calcination and high-temperature calcination to make the mixing between each raw material component more uniform and more fully react, and prevent the production of by-products to the greatest extent. Through the synergy effect between each technical feature, the pure oxyhalide was finally manufactured.

The present invention solves the above technical problem through the following technical solutions.

The present invention provides a method for producing an oxyhalide, wherein the chemical formula of the oxyhalide is

Li ₃ B ₇ O ₁₂ ·(LiX) _a , X is Cl and/or Br, 0＜a≤1, and the method comprises:

(1) A step of crushing and pressing a mixture of lithium source and boron source weighed according to a stoichiometric ratio, placing it in a reaction tube, vacuuming and sealing the reaction tube, and performing a first calcination, wherein the temperature of the first calcination is 300 to 450°C, and the time of the first calcination is 4 to 20 h; and

(2) a step of cooling to room temperature after the first calcination, taking out the intermediate product in the reaction tube, crushing and pressing it, placing it in the reaction tube, vacuuming and sealing the reaction tube, performing a second calcination, and cooling to room temperature to obtain the oxyhalide;

When the lithium source is lithium halide and lithium oxide and the boron source is boron oxide, the temperature of the second calcination is 810 to 860°C, and the time of the second calcination is 12 to 30 h;

When the lithium source is lithium halide and lithium borate and the boron source is boron oxide, the temperature of the second calcination is 450 to 800°C, and the time of the second calcination is 12 to 30 h.

In the present invention, in the oxyhalide, LiX is distributed in the pore structure of the Li ₃ B ₇ O ₁₂ skeleton.

In the present invention, the lithium halide may be lithium chloride or lithium bromide.

When the above X is Cl, the lithium halide is lithium chloride.

When the above X is Br, the above lithium halide is lithium bromide.

In the present invention, in the chemical formula of the oxyhalide, preferably, 0＜a＜1 or a is 1, for example, 0.4, 0.5 or 0.9, and more preferably 0.8＜a＜0.98.

In step (2), when the lithium source is lithium chloride and lithium oxide and the boron source is boron oxide, the molar ratio of the lithium chloride, the lithium oxide and the boron oxide may be (0~2):3:7 and does not include 0:3:7, for example, 2:3:7, 1.8:3:7, 1:3:7 or 0.8:3:7, and preferably (1.6~1.96):3:7.

In step (2), when the lithium source is lithium chloride and lithium borate, the boron source is boron oxide, and the lithium borate is lithium metaborate, the molar ratio of the lithium chloride, the lithium borate, and the boron oxide may be (0~1):3:2 and does not include 0:3:2, for example, 0.4:3:2, 0.5:3:2, 0.9:3:2 or 1:3:2, and preferably is (0.8~0.98):3:2.

In the present invention, the lithium borate may be lithium metaborate (LiBO ₂ ), lithium tetraborate (Li ₂ B ₄ O ₇ ), or lithium pentaborate (LiB ₅ O ₈ ).

In step (1) and/or step (2), the operation and conditions of the crushing may be those common in the art and may be performed, for example, in a mortar.

In step (1) and/or step (2), the pressing device may be a common one in the art, for example, a press. The pressing pressure is preferably 5 to 15 MPa, for example, 10 MPa.

In step (1) and/or step (2), the reaction tube is preferably a quartz tube.

In step (1) and/or step (2), after the evacuation, the vacuum degree of the reaction tube is preferably 10 ^-3 Pa or less.

In step (1) and/or step (2), the sealing is generally performed by heating and melting both ends of the reaction tube.

In the present invention, the first firing and the second firing are generally performed in a muffle furnace.

In step (1), the heating rate to the temperature of the first firing may be 30 to 90°C/h, for example, 60°C/h.

In step (1), the temperature of the first firing is preferably 350 to 450°C, for example, 400°C.

In step (1), the time for the first firing is preferably 10 to 15 h, for example, 12 h.

In step (2), the cooling rate after the first firing may be 10°C/h to 80°C/h, for example, 50°C/h.

In step (2), the heating rate to the temperature of the secondary firing may be 30 to 90°C/h, for example, 60°C/h.

In step (2), the cooling rate after the secondary firing may be 10°C/h to 80°C/h, for example, 50°C/h.

In step (2), when the lithium source is lithium chloride and lithium oxide and the boron source is boron oxide, the temperature of the secondary calcination is, for example, 830°C, 840°C, 845°C or 850°C, preferably 835 to 855°C.

In step (2), when the lithium source is lithium chloride and lithium oxide and the boron source is boron oxide, the time of the secondary calcination is preferably 15 to 26 h, for example, 20 h or 24 h.

In step (2), when the lithium source is lithium chloride and lithium borate and the boron source is boron oxide, the temperature of the secondary calcination is, for example, 500°C, 600°C or 700°C, preferably 480 to 610°C.

In step (2), when the lithium source is lithium chloride and lithium borate and the boron source is boron oxide, the time of the secondary calcination is preferably 15 to 26 h, for example, 20 h or 24 h.

The present invention also provides an oxyhalide manufactured by the above-described manufacturing method, wherein the ionic conductivity of the oxyhalide at 25°C is 0.2 to 2 mS cm ^-1 .

In the present invention, the crystal particle size of the oxyhalide is preferably 0.6 to 5 μm, more preferably 0.8 to 1.5 μm, for example, 1 μm.

In the present invention, the ionic conductivity of the oxyhalide at 25°C is, for example, 0.25 mS cm ^-1 , 0.44 mS cm ^-1 , 0.52 mS cm ^-1 , 0.72 mS cm ^-1 , 0.81 mS cm ^-1 , 0.83 mS cm ^-1 , 0.92 mS cm ^-1 , 1.01 mS cm ^-1 or 1.12 mS cm ^-1 , preferably 0.4 to 2 mS cm ^-1 .

In the present invention, the electronic conductivity of the oxyhalide at 25°C is preferably 1×10 ^-8 to 1×10 ^-6 S cm ^-1 , for example, 3.18×10 ^-7 S cm ^-1 or 6.52×10 ^-7 S cm ^-1 , more preferably 2.5×10 ^-7 to 5×10 ^-7 S cm ^-1 .

In the present invention, the ionic conductivity of the oxyhalide at 30°C is preferably 0.4 to 5 mS cm ^-1 , for example, 1.23 mS cm ^-1 .

In the present invention, the ionic conductivity of the oxyhalide at 40°C is preferably 0.6 to 5 mS cm ^-1 , for example, 1.17 mS cm ^-1 .

In the present invention, the ionic conductivity of the oxyhalide at 50°C is preferably 1 to 5 mS cm ^-1 , for example, 2.03 mS cm ^-1 .

The present invention also provides an all-solid-state lithium battery, the all-solid-state lithium battery comprising a positive electrode, a solid electrolyte layer, a buffer layer and a negative electrode sequentially installed;

The positive electrode includes a positive electrode current collector and a positive electrode active material layer positioned on a surface of the positive electrode current collector, the positive electrode active material layer includes LiFePO ₄ and the above-described oxyhalide; the solid electrolyte layer includes the above-described oxyhalide, the buffer layer includes Li ₆ PS ₅ Cl, and the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on a surface of the negative electrode current collector.

In the present invention, for the positive electrode current collector, a material having high conductivity without causing chemical change can be used without limitation. For example, stainless steel, aluminum, nickel, titanium, carbon, or “aluminum or stainless steel material surface-treated with carbon, nickel, titanium, silver, etc.” can be used.

In the present invention, the thickness of the positive electrode collector may be a thickness common in the field, for example, 16 μm.

In the present invention, in the positive electrode active material layer, the mass ratio of LiFePO ₄ and the oxyhalide may be (2 to 5):1, for example, 3:1.

In the present invention, the thickness of the positive electrode active material layer may be 50 to 500 μm, for example, 100 μm.

In the present invention, the thickness of the solid electrolyte layer may be 100 to 1000 μm, for example, 400 μm.

In the present invention, the thickness of the buffer layer may be 100 to 1000 μm, for example, 420 μm.

In the present invention, for the negative electrode current collector, a material that does not cause a chemical change and is conductive can be used without limitation. For example, copper, stainless steel, aluminum, nickel, titanium, carbon, aluminum-cadmium alloy, or “copper, stainless steel material or aluminum-cadmium alloy surface-treated with carbon, nickel, titanium or silver, etc.” can be used.

In the present invention, the thickness of the negative electrode collector may be 4.5 to 10 μm, for example, 6 μm.

In the present invention, the negative electrode active material layer includes graphite and/or silicon carbon, for example, graphite.

In the present invention, the thickness of the negative electrode active material layer may be 50 to 500 μm, for example, 100 μm.

In the present invention, the all-solid-state lithium battery further includes a case, and the positive electrode, the solid electrolyte layer, the buffer layer, and the negative electrode are packaged in the case.

In the present invention, according to the convention in the field, the all-solid-state lithium battery means a lithium battery that does not contain any liquid.

The present invention also provides a method for manufacturing the aforementioned all-solid-state lithium battery, said method comprising:

A step of first compressing the material of the solid electrolyte layer to obtain the solid electrolyte layer;

A step of adding the material of the buffer layer to one side of the solid electrolyte layer and then performing secondary compression to obtain the buffer layer;

A step of adding a material of the positive electrode active material layer to the other side of the solid electrolyte layer and then performing a third compression to obtain the positive electrode active material layer; and

It includes a step of adding the material of the negative active material layer to one side of the buffer layer and then performing a fourth compression to obtain the all-solid-state lithium battery.

In the present invention, after the fourth pressing, preferably, the method further includes a step of arranging the positive electrode current collector on one side of the positive electrode active material layer, a step of arranging the negative electrode current collector on one side of the negative electrode active material layer, and a step of performing a fifth pressing.

In the present invention, the first pressing, the second pressing, the third pressing, the fourth pressing and the fifth pressing are generally performed in an all-solid-state battery mold.

In the present invention, the pressure of the first compression may be 300 to 500 MPa, for example, 380 MPa.

In the present invention, the pressure of the secondary pressing may be 200 to 400 MPa, for example, 250 MPa.

In the present invention, the pressure of the third compression may be 200 to 400 MPa, for example, 250 MPa.

In the present invention, the pressure of the fourth compression may be 200 to 400 MPa, for example, 250 MPa.

In the present invention, the pressure of the fifth pressing may be 60 to 180 MPa, for example, 100 MPa.

In the present invention, when the all-solid-state lithium battery further includes a case, the positive electrode, the solid electrolyte layer, the buffer layer, and the negative electrode are packaged in the case.

All raw materials and reagents used in the present invention are commercially available.

Based on common sense in this field, each preferable embodiment of the present invention can be obtained by arbitrarily combining each of the above preferable conditions.

All reagents and raw materials used in the present invention are commercially available.

The positive progressive effects of the present invention are as follows.

(1) The method according to the present invention has a simple synthesis process, high utilization rate of raw materials, no by-products, and is advantageous for industrial production;

(2) The manufactured oxyhalide has high ionic conductivity, air stability and thermal stability, and excellent interfacial stability with lithium metal;

(3) The manufactured all-solid-state lithium battery has excellent electrochemical performance.

Figure 1 is a SEM image of the oxyhalide Li ₄ B ₇ O ₁₂ Cl prepared in Example 1.
Figure 2 is an XRD pattern of the oxyhalides manufactured in Examples 1 to 2 and Comparative Examples 5 to 7.
Figure 3 is an XRD pattern of the oxyhalides manufactured in Examples 3 to 5 and Comparative Example 1.

The present invention is further described below by way of examples, but the present invention is not limited to the scope of the above examples. In the following examples, experimental methods that do not specify specific conditions should follow general methods and conditions or be selected according to the product description.

In the following examples and comparative examples, the manufacturers and purities of the raw materials used are as shown in Table 1 below.

raw material Manufacturer water LiCl MERCK Sigma-Aldrich 99.9% Li ₂ O MACKLIN 99.9% B ₂ O ₃ Aladdin 99.9% LiBO ₂ Aladdin 99.9% LiFePO ₄ Aladdin 99.9% Li ₆ PS ₅ Cl MACKLIN 99.9% black smoke MERCK Sigma-Aldrich 99.9%

Example 1 (1) 2 mmol of LiCl, 3 mmol of Li ₂ O and 7 mmol of B ₂ O ₃ are weighed according to the stoichiometric ratio, and then generally ground using a mortar, and then pressed into a thin sheet using a press at a pressure of 10 MPa, placed into a quartz tube, and the quartz tube is vacuumed and sealed (both ends of the quartz tube are sealed by heating and melting) (vacuum degree＜10 ^-3 Pa), and then transferred to a muffle furnace to perform the first firing, and the heating rate is 60°C/h, the temperature of the first firing is 400°C, and the time of the first firing is 12 h;

(2) After the first calcination, cool to room temperature, the cooling rate is 50°C/h, the intermediate product inside the quartz tube is taken out, crushed and pressed again (the conditions of crushing and pressing are the same as in step 1), placed into the quartz tube, the quartz tube is vacuumed and sealed, and then transferred to a muffle furnace to perform the second calcination, the heating rate is 60°C/h, the temperature of the second calcination is 845°C, the time of the second calcination is 22 h, cooled to room temperature, and the cooling rate is 50°C/h, thereby obtaining pure oxyhalide Li ₄ B ₇ O ₁₂ Cl.

Example 2

Compared with Example 1, the remaining operations and conditions are all the same as Example 1, except that the temperature of the secondary firing in step (2) was adjusted to 830°C.

Example 3

(1) Weigh 1 mmol LiCl, 3 mmol LiBO ₂ and 2 mmol B ₂ O ₃ according to the stoichiometric ratio, and use a mortar to generally grind them, and then use a press to press them into a thin sheet at a pressure of 10 MPa, put them into a quartz tube, vacuum and seal the quartz tube (both ends of the quartz tube are heat-melted and sealed) (vacuum degree＜10 ^-3 Pa), and then transfer to a muffle furnace to perform the first calcination, the heating rate is 60℃/h, the temperature of the first calcination is 400℃, and the time of the first calcination is 12h;

(2) After the first calcination, cool to room temperature, the cooling rate is 50°C/h, the intermediate product inside the quartz tube is taken out, crushed and pressed again (the conditions of crushing and pressing are the same as in step 1), placed into the quartz tube, the quartz tube is vacuumed and sealed, and then transferred to a muffle furnace to perform the second calcination, the heating rate is 60°C/h, the temperature of the second calcination is 500°C, the time of the second calcination is 24 h, cooled to room temperature, and the cooling rate is 50°C/h, thereby obtaining pure oxyhalide Li ₄ B ₇ O ₁₂ Cl.

Example 4

Compared with Example 3, the remaining operations and conditions are all the same as in Example 3, except that the temperature of the secondary firing in step (2) was adjusted to 600°C.

Example 5

Compared with Example 3, the remaining operations and conditions are all the same as in Example 3, except that the temperature of the secondary firing in step (2) was adjusted to 700°C.

Example 6

Compared with Example 4, the remaining operations and conditions were all the same as in Example 4, except that the amount of LiCl added in step (1) was adjusted to 0.9 mmol, thereby obtaining oxyhalide Li ₃ B ₇ O ₁₂ ·(LiCl) _0.9 .

Example 7

Compared with Example 4, except that LiCl in step (1) was replaced with LiBr, the remaining operations and conditions were all the same as in Example 4, thereby obtaining oxyhalide Li ₄ B ₇ O ₁₂ Br.

Example 8

Compared with Example 4, the remaining operations and conditions were all the same as in Example 4, except that the amount of LiCl added in step (1) was adjusted to 0.4 mmol, thereby obtaining oxyhalide Li ₃ B ₇ O ₁₂ ·(LiCl) _0.4 .

Example 9

Compared with Example 4, the remaining operations and conditions were all the same as in Example 4, except that 1 mmol of LiCl in step (1) was replaced with 0.25 mmol of LiCl and 0.25 mmol of LiBr, thereby obtaining oxyhalide Li ₃ B ₇ O ₁₂ ·(LiCl) _0.25 (LiBr) _0.25 .

Example 10

Manufacturing of all-solid-state lithium batteries

LiFePO ₄ and the manufactured oxyhalide were sanded with a sand mill for 20 minutes according to a mass ratio of 7.5:2.5 to obtain the material of the cathode active material layer; the cathode current collector is aluminum foil, and the thickness is 16 μm;

The manufactured oxyhalide is used as a solid electrolyte material; Li ₆ PS ₅ Cl is used as a buffer layer material; graphite is used as a material of the negative electrode active material layer; and the negative electrode current collector is a copper foil with a thickness of 6 μm.

First, 40 mg of oxyhalide powder is placed into the mold, and a first pressing is performed at a pressure of 380 MPa using a press to obtain a solid electrolyte layer; 42 mg of Li ₆ PS ₅ Cl is added to one side of the solid electrolyte layer, and a second pressing is performed at a pressure of 250 MPa using a press to obtain a buffer layer; 10 mg of the material of the positive active material layer is added to the other side of the solid electrolyte layer, and a third pressing is performed at a pressure of 250 MPa using a press to obtain a positive active material layer; 10 mg of the material of the negative active material layer is added to one side of the buffer layer, and a fourth pressing is performed at a pressure of 250 MPa using a press to obtain a negative active material layer; Finally, a positive electrode collector is arranged on one side of the positive electrode active material layer, and a negative electrode collector is arranged on one side of the negative electrode active material layer, and then a fifth pressing is performed at a pressure of 100 MPa using a press to manufacture an all-solid-state lithium battery; wherein, in the all-solid-state lithium battery, the thickness of the solid electrolyte layer is 400 μm, the thickness of the buffer layer is 420 μm, the thickness of the positive electrode active material layer is 100 μm, and the thickness of the negative electrode active material layer is 100 μm.

Comparative Example 1

(1) Weigh 1 mmol LiCl, 3 mmol LiBO ₂ and 2 mmol B ₂ O ₃ according to the stoichiometric ratio, and use a mortar to generally crush them, then use a press to press them into a thin sheet at a pressure of 10 MPa, put them into a quartz tube (without performing vacuum and sealing operations), and transfer them to a muffle furnace to perform the first calcination, the heating rate is 60 ℃/h, the temperature of the first calcination is 400 ℃, and the time of the first calcination is 12 h;

(2) After the first calcination, cool to room temperature, the cooling rate is 50°C/h, the intermediate product inside the quartz tube is taken out, crushed and pressed again (the conditions of crushing and pressing are the same as in step 1), then placed into the quartz tube and transferred to a muffle furnace to perform the second calcination, the heating rate is 60°C/h, the temperature of the second calcination is 500°C, the time of the second calcination is 24 h, cool to room temperature, and the cooling rate is 50°C/h, thereby obtaining an oxyhalide containing impurities.

Comparative Example 2

(1) Weigh 2 mmol of LiCl, 3 mmol of Li ₂ O and 7 mmol of B ₂ O ₃ according to the stoichiometric ratio, grind them normally using a mortar, put them into a quartz tube, vacuum and seal the quartz tube (vacuum degree＜10 ^-3 Pa), and then transfer them to a muffle furnace to perform the first calcination, the heating rate is 60℃/h, the temperature of the first calcination is 400℃, and the time of the first calcination is 12h;

(2) After the first calcination, cool to room temperature, the cooling rate is 50°C/h, the intermediate product inside the quartz tube is taken out, crushed again, placed in the quartz tube, the quartz tube is vacuumized and sealed, and then moved to a muffle furnace to perform the second calcination, the heating rate is 60°C/h, the temperature of the second calcination is 845°C, the time of the second calcination is 22 h, cool to room temperature, the cooling rate is 50°C/h, and thus an oxyhalide containing impurities is obtained.

Comparative Example 3

According to the stoichiometric ratio, 2 mmol of LiCl, 3 mmol of Li ₂ O and 7 mmol of B ₂ O ₃ were weighed, generally ground using a mortar, and then pressed into a thin sheet at a pressure of 10 MPa using a press, placed into a quartz tube, and the quartz tube was evacuated and sealed (vacuum degree＜10 ^-3 Pa), then transferred to a muffle furnace for firing, at a heating rate of 60°C/h, a firing temperature of 845°C, a firing time of 22 h, and then cooled to room temperature, at a cooling rate of 50°C/h, thereby obtaining an oxyhalide containing impurities.

Comparative Example 4

Compared with Example 1, the remaining operations and conditions are all the same as in Example 1, except that the temperature of the first firing in step (1) was adjusted to 200°C.

Comparative Example 5

Compared with Example 1, the remaining operations and conditions are all the same as Example 1, except that the temperature of the secondary firing in step (2) was adjusted to 780°C.

Comparative Example 6

Compared with Example 1, the remaining operations and conditions are all the same as in Example 1, except that the temperature of the secondary firing in step (2) was adjusted to 870°C.

Comparative Example 7

Compared with Example 1, the remaining operations and conditions are all the same as in Example 1, except that the temperature of the secondary firing in step (2) was adjusted to 890°C.

Comparative Example 8

Compared with Example 3, the remaining operations and conditions are all the same as in Example 3, except that the temperature of the secondary firing in step (2) was adjusted to 400°C.

Comparative Example 9

Compared with Example 3, the remaining operations and conditions are all the same as in Example 3, except that the temperature of the secondary firing in step (2) was adjusted to 900°C.

Effectiveness Example

(1) Structural and morphological analysis

Figure 1 is a SEM image of the oxyhalide Li ₄ B ₇ O ₁₂ Cl prepared in Example 1. As can be seen from the figure, the crystal particle size of Li ₄ B ₇ O ₁₂ Cl is about 1 μm.

(2) XRD characterization

FIG. 2 and FIG. 3 are XRD patterns of the oxyhalides manufactured in the Examples and Comparative Examples, and Table 2 shows the peak situations of the XRD of the samples manufactured in the Examples and Comparative Examples. As can be seen from the test results, the oxyhalides manufactured in Examples 1 to 9 had no impurities detected, and there was no significant difference in the XRD patterns, while the oxyhalides manufactured in the Comparative Examples had an impurity peak of Li ₂ B ₄ O ₇ . As can be seen from the figure, the oxyhalides manufactured in Examples 1 to 9 showed a crystal structure similar to the cubic lithium borate structure (space group F43c), which matches well with PDF# 34-0742.

Through the experimental results of the above examples and comparative examples, it can be seen that, in the process of manufacturing oxyhalides, if the sintering environment is not a vacuum, if the raw materials are not pressed, if the first low-temperature sintering is not performed, if the temperature of the first sintering is not in the range of 350 to 450°C, or if the temperature of the second sintering is not in the range of 810 to 860°C or 450 to 800°C, all of the manufactured oxyhalides are not pure and contain impurities.

The peak positions listed in Table 2 indicate that the peak intensity of the material at the corresponding position is higher than 100 particles/s; “/” indicates that the peak intensity of the material at the corresponding position is lower than 100 particles/s, i.e., no corresponding peak is considered at the corresponding position, where “particles/s” indicates the number of x-ray particles received by the detector per second.

2θ/° PDF# 34-0742 14.6 20.7 / 25.4 / 29.4 33.0 / / 42.1 44.1 Example 1 14.6 20.6 / 25.3 / 29.4 33.0 / / 42.0 44.1 Example 2 14.6 20.7 / 25.3 / 29.3 33.0 / / 42.1 44.1 Example 3 14.5 20.7 / 25.4 / 29.4 33.0 / / 42.2 44.1 Example 4 14.6 20.7 / 25.4 / 29.4 33.0 / / 42.1 44.1 Example 5 14.6 20.7 / 25.4 / 29.3 33.0 / / 42.1 44.0 Example 6 14.7 20.9 / 25.4 / 29.4 33.0 / / 42.3 44.2 Example 7 14.6 20.8 / 25.4 / 29.4 33.0 / / 42.1 44.0 Example 8 14.5 20.7 / 25.5 / 29.5 33.1 / / 42.1 44.0 Example 9 14.6 20.6 / 25.4 / 29.4 33.0 / / 42.1 44.1 Comparative Example 1 14.6 20.7 21.8 25.4 / 29.4 33.0 33.6 34.6 42.1 44.1 Comparative Example 2 14.6 20.7 21.8 25.4 27.6 29.4 33.0 33.6 34.6 42.1 44.1 Comparative Example 3 14.6 20.7 21.8 25.4 27.6 29.4 33.0 33.6 34.6 42.1 44.1 Comparative Example 4 14.6 20.7 21.8 25.4 27.6 29.4 33.0 33.6 34.6 42.1 44.1 Comparative Example 5 14.6 20.7 21.8 25.4 / 29.4 33.0 33.6 34.6 42.1 44.1 Comparative Example 6 14.6 20.7 21.8 25.4 27.6 29.4 33.0 / 34.6 42.1 44.1 Comparative Example 7 14.5 20.7 21.8 25.4 27.6 29.4 33.0 33.6 34.6 42.1 44.1 Comparative Example 8 14.6 20.7 21.8 25.4 27.6 29.4 33.0 33.6 34.6 42.1 44.1 Comparative Example 9 14.6 20.7 21.8 25.4 27.6 29.4 33.0 33.6 34.6 42.1 44.1

(3) Ionic conductivity test

At room temperature 25℃, 300 mg of the oxyhalide powders manufactured in Examples 1 to 9 and Comparative Examples 1 to 9 were pressed into thin sheets at a pressure of 380 MPa, placed in a sealed vacuum quartz tube, and calcined at 600℃ for 20 h. After calcination, the particles were transferred to a mold PEEK sleeve, and an electrochemical impedance test was performed using an electrochemical workstation (CHI, 650E), the applied voltage was set to 0.05 V, and the frequency range was 10 ^-1 Hz to 10 ⁶ Hz. The test results are shown in Table 3.

The calculation formula for lithium ion conductivity of oxyhalide solid electrolyte is ion conductivity ρ = L/RS, where L is 3 mm, S represents the area of a circle with a radius of 5 mm, and R is impedance.

Sample Ionic Conductivity
(mS cm ^-1 ) Sample Ionic Conductivity
(mS cm ^-1 ) Example 1 0.83 Comparative Example 3 0.041 Example 2 0.25 Comparative Example 4 0.000024 Example 3 0.92 Comparative Example 5 0.124 Example 4 1.01 Comparative Example 6 0.097 Example 5 0.72 Comparative Example 7 0.155 Comparative Example 1 0.0035 Comparative Example 8 0.054 Comparative Example 2 0.028 Comparative Example 9 0.47 Example 6 1.12 Example 7 0.52 Example 8 0.81 Example 9 0.44

The lithium ion conductivity of the oxyhalide solid electrolyte prepared in Example 1 at different temperatures is shown in Table 4.

Temperature (℃) Ionic conductivity (mS cm ^-1 ) 25 0.83 30 1.23 40 1.17 50 2.03

(4) Electronic conductivity test

At room temperature of 25℃, the oxyhalide solid electrolyte powders manufactured in Examples 1 to 2 and Comparative Examples 6 to 7 were placed in a PEEK sleeve, two ion blocking electrodes were arranged at both ends of the powder, and a pressure of 380 MPa was applied. DC polarization measurements were performed using an electrochemical workstation (CHI, 650E) to test the electronic conductivity at different polarization voltages. The calculation formula for the electronic conductivity is σ _e = LI / SE, where σ _e is the electronic conductivity, L is the thickness of the Li ₄ B ₇ O ₁₂ Cl electrolyte (0.3 cm), S is the area of the Li ₄ B ₇ O ₁₂ Cl electrolyte (0.785 cm ² ), E is the polarization voltage (1 V), and I is the steady current.

The test results are shown in Table 5.

Sample Steady current (μA) Electronic conductivity (S cm ^-1 ) Example 1 0.832 3.18×10 ^-7 Example 2 0.71 6.52×10 ^-7 Comparative Example 6 2.28 8.73×10 ^-7 Comparative Example 7 1.67 6.37×10 ^-7

(5) Stability study of Li ₄ B ₇ O ₁₂ Cl

The oxyhalide Li ₄ B ₇ O ₁₂ Cl prepared in Example 1 was exposed to air for 6 months (room temperature) and sintered in a muffle furnace at 300°C for 12 hours in air, and then XRD characterization was performed. As can be seen from the test results, all peak values after exposure to air for 6 months or sintering in air are consistent with those of the initial sample, indicating that Li ₄ B ₇ O ₁₂ Cl has very high air stability and thermal stability.

(6) Study on the interfacial stability between Li ₄ B ₇ O ₁₂ Cl and lithium metal

The oxyhalide Li ₄ B ₇ O ₁₂ Cl prepared in Example 1 was used in the study.

Ion transport has a negative effect on concentration polarization during charge and discharge, which increases the power density of the battery and limits the movement of anions within the lithium salt.

Li | Li ₄ B ₇ O ₁₂ Cl | Li The lithium ion transport capacity of Li ₄ B ₇ O ₁₂ Cl was studied by assembling a symmetric half-cell, and the assembly process of the half-cell is as follows.

The lithium metal sheet was rolled into a thin sheet, and cut into circular sheets by using a circular cutter with a diameter of 1 mm; 40 mg of Li ₄ B ₇ O ₁₂ Cl powder was put into the mold, and pressed by using a press at a pressure of 380 MPa, and then the pre-cut circular sheets were placed on both sides of the Li ₄ B ₇ O ₁₂ Cl respectively, and pressed at a pressure of 100 MPa to obtain a Li | Li ₄ B ₇ O ₁₂ Cl | Li symmetrical half-cell.

Li | Li ₄ B ₇ O ₁₂ Cl | The Li ⁺ migration number (T _Li+ ) of Li ₄ B ₇ O ₁₂ Cl electrolyte was measured using Li | Li 4 B 7 O 12 Cl battery. The initial current and stable current were obtained by performing potentiostatic measurement under a DC polarization voltage of 0.05 V. The initial resistance (R ₀ ) before the potentiostatic test and the resistance after the measurement (R _s ) were obtained through AC impedance measurement, and the frequency is 10 ^-1 Hz to 10 ⁶ Hz. The migration number of the electrolyte is obtained by the following formula.

Here, ΔV (0.01 V) is the DC polarization voltage applied to the sample, I ₀ is the initial current, and I _s is the stable current.

According to the experimental results, the lithium ion migration number of Li ₄ B ₇ O ₁₂ Cl was calculated to be 0.74. The higher the lithium ion migration number, the lower the migration number of the corresponding anion and the smaller the concentration polarization, which hinders the growth of lithium dendrites and the occurrence of some side reactions.

To evaluate the electrochemical stability of the Li ₄ B ₇ O ₁₂ Cl solid electrolyte against metallic lithium, the assembled Li | Li ₄ B ₇ O ₁₂ Cl | Li symmetric half-cells were subjected to galvanostatic charge-discharge cycling at 50 °C and current densities of 0.01 mA cm ^-2 and 0.05 mA cm ^-2 using a multi-channel battery test system (LAND, CT3002A). The symmetric half-cells reached a polarization voltage of 5 V after 40 cycles (80 h) and 200 cycles (400 h) at current densities of 0.05 mA cm ^-2 and 0.01 mA cm ^-2 .

(7) Study on the electrochemical performance of all-solid-state lithium batteries (ASSLB)

Based on the Li ₄ B ₇ O ₁₂ Cl manufactured in Example 1, it was assembled into an ASSLB according to the above method and studied. The constant current charge/discharge characteristics of the LiFePO ₄ @ Li ₄ B ₇ O ₁₂ Cl | Li ₄ B ₇ O ₁₂ Cl | Li ₆ PS ₅ Cl | graphite ASSLB were tested at 50°C using a battery test system (LAND, CT3002A).

According to the test results, the initial discharge capacity and the 100th discharge capacity of the assembled all-solid-state lithium battery are 75 mAh·g ^-1 and 88 mAh·g ^-1 , respectively. The initial Coulombic efficiency of the ASSLB is 78%. The ASSLB has high cycle stability and reversible capacity. After 180 cycles, the discharge specific capacity is 83.6 mAh·g ^-1 and the Coulombic efficiency is 76%.

Although the above describes specific embodiments of the present invention, it should be understood by those skilled in the art that these are merely examples, and the scope of protection of the present invention is limited by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principle and substance of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims (10)

A method for manufacturing an oxyhalide,
The chemical formula of the above oxyhalide is Li ₃ B ₇ O ₁₂ ·(LiX) _a , X is Cl and/or Br, 0＜a≤1, and the method comprises:
(1) A step of crushing and pressing a mixture of lithium source and boron source weighed according to a stoichiometric ratio, placing it in a reaction tube, vacuuming and sealing the reaction tube, and performing a first calcination, wherein the temperature of the first calcination is 300 to 450°C, and the time of the first calcination is 4 to 20 h; and
(2) a step of cooling to room temperature after the first calcination, taking out the intermediate product in the reaction tube, crushing and pressing it again, placing it in the reaction tube, vacuuming and sealing the reaction tube, performing a second calcination, and cooling to room temperature to obtain the oxyhalide;
When the lithium source is lithium halide and lithium oxide and the boron source is boron oxide, the temperature of the second calcination is 810 to 860°C, and the time of the second calcination is 12 to 30 h;
A method for producing an oxyhalide, characterized in that when the lithium source is lithium halide and lithium borate and the boron source is boron oxide, the temperature of the secondary calcination is 450 to 800°C and the time of the secondary calcination is 12 to 30 h. In the first paragraph,
The above manufacturing method is,
(1) In step (1) and/or step (2), the pressing pressure is 5 to 15 MPa;
(2) In step (1) and/or step (2), the reaction tube is a quartz tube;
(3) In step (1) and/or step (2), after the evacuation, the vacuum level of the reaction tube is 10 ^-3 Pa or less;
(4) The above lithium borate is lithium metaborate, lithium tetraborate or lithium pentaborate;
(5) The above lithium halide is lithium chloride or lithium bromide; and
(6) A method for producing an oxyhalide, characterized in that at least one of the conditions of 0.8＜a＜0.98 is satisfied in the chemical formula of the oxyhalide. In the first paragraph,
In step (1), the temperature of the first firing is 350 to 450°C;
And/or, a method for producing an oxyhalide, characterized in that in step (1), the time of the first calcination is 10 to 15 h. In the first paragraph,
In step (2), when the lithium source is lithium chloride and lithium oxide and the boron source is boron oxide, the temperature of the secondary calcination is 835 to 855°C;
And/or, in step (2), when the lithium source is lithium chloride and lithium oxide and the boron source is boron oxide, the time of the secondary calcination is 15 to 26 h;
And/or, in step (2), a method for producing an oxyhalide, characterized in that when the lithium source is lithium chloride and lithium oxide and the boron source is boron oxide, the molar ratio of the lithium chloride, the lithium oxide, and the boron oxide is (1.6 to 1.96):3:7. In the first paragraph,
In step (2), when the lithium source is lithium chloride and lithium borate and the boron source is boron oxide, the temperature of the secondary calcination is 480 to 610°C;
And/or, in step (2), when the lithium source is lithium chloride and lithium borate and the boron source is boron oxide, the time of the secondary calcination is 15 to 26 h;
And/or, in step (2), a method for producing an oxyhalide, characterized in that when the lithium source is lithium chloride and lithium borate, the boron source is boron oxide, and the lithium borate is lithium metaborate, the molar ratio of the lithium chloride, the lithium borate, and the boron oxide is (0.8 to 0.98):3:2. As an oxyhalide,
An oxyhalide manufactured according to a method for manufacturing an oxyhalide according to any one of claims 1 to 5, and characterized in that the oxyhalide has an ionic conductivity of 0.2 to 2 mS cm ^-1 at 25° C. As an all-solid-state lithium battery,
Comprising a positive electrode, a solid electrolyte layer, a buffer layer and a negative electrode installed sequentially;
An all-solid-state lithium battery, characterized in that the positive electrode comprises a positive electrode current collector and a positive electrode active material layer positioned on a surface of the positive electrode current collector, the positive electrode active material layer comprises LiFePO ₄ and an oxyhalide according to claim 6; the solid electrolyte layer comprises an oxyhalide according to claim 6, the buffer layer comprises Li ₆ PS ₅ Cl, and the negative electrode comprises a negative electrode current collector and a negative electrode active material layer positioned on a surface of the negative electrode current collector. In Article 7,
The above all-solid-state lithium battery,
(1) In the positive electrode active material layer, the mass ratio of LiFePO ₄ and the oxyhalide is (2 to 5): 1;
(2) The thickness of the positive electrode active material layer is 50 to 500 μm;
(3) The thickness of the solid electrolyte layer is 100 to 1000 μm;
(4) Conditions where the thickness of the buffer layer is 100 to 1000 μm; and
(5) An all-solid-state lithium battery characterized in that it satisfies at least one of the conditions that the thickness of the negative electrode active material layer is 50 to 500 μm. A method for manufacturing an all-solid-state lithium battery according to Article 7,
The above method,
A step of first compressing the material of the solid electrolyte layer of the above all-solid-state lithium battery to obtain the solid electrolyte layer;
A step of adding a material of a buffer layer of the above all-solid-state lithium battery to one side of the above solid electrolyte layer and then performing secondary compression to obtain the above buffer layer;
A step of adding a material of the positive electrode active material layer of the above all-solid-state lithium battery to the other side of the above solid electrolyte layer and then performing a third compression to obtain the positive electrode active material layer; and
A method for manufacturing an all-solid-state lithium battery, characterized in that it comprises a step of adding a material of a negative active material layer of the all-solid-state lithium battery to one side of the buffer layer and then performing a fourth compression to obtain the all-solid-state lithium battery. In Article 9,
The above manufacturing method is,
(1) A condition further including a step of arranging the positive electrode current collector on one side of the positive electrode active material layer after the fourth pressing, a step of arranging the negative electrode current collector on one side of the negative electrode active material layer, and a step of performing a fifth pressing;
(2) The pressure of the first compression is 300 to 500 MPa;
(3) The pressure of the above secondary pressing is 200 to 400 MPa;
(4) The pressure of the above third compression is 200 to 400 MPa;
(5) The pressure of the fourth compression is 200 to 400 MPa; and
(6) A method for manufacturing an all-solid-state lithium battery, characterized in that it satisfies at least one of the conditions that the pressure of the fifth pressing is 60 to 180 MPa.