WO2018000578A1 - Multi-functional modified polyvinyl alcohol-based water-borne adhesive for lithium ion battery and application thereof in electrochemical energy storage device - Google Patents

Abstract

A multi-functional modified polyvinyl alcohol-based (PVA-based) water-borne adhesive for lithium-ion batteries; the adhesive is prepared and modified by means of the Michael addition reaction, wherein PVA is used as a substrate, and a hydrophilic monomer and a lipophilic monomer are used as functional modifying monomers; said adhesive has good water-solubility, elasticity and bonding properties, and may be used in the preparation process of a lithium-ion battery electrode sheet so as to improve the uniformity of an electrode paste, so that the electrode paste may uniformly and smoothly form a film on a current collector. Therefore, the electrode sheet does not shed materials, which may prevent a drop in capacity, and greatly improve the high-rate capacity and cycle stability of positive and negative materials of the lithium-ion battery, thereby effectively prolonging a service life of the battery.

Description

Multifunctionalized modified polyvinyl alcohol based lithium ion battery aqueous binder and its application in electrochemical energy storage devices Technical field:

The invention relates to a polymer lithium ion battery binder, in particular to a multi-functionalized modified polyvinyl alcohol-based lithium ion battery aqueous binder and application in an electrochemical energy storage device.

Background technique:

The binder is an important inactive component of the lithium ion battery in which the electrode active material and the conductive agent are adhered to the current collector, and the performance of the battery directly affects the electrochemical performance of the battery. In addition to requiring a good bonding between the electrode active material, the conductive agent and the current collector, the binder should have a sufficiently good dispersibility, thereby facilitating the conduction of electrons and ions during charging and discharging, and reducing The impedance between the current collector and the electrode material; in addition, the adhesive should have sufficient elasticity to prevent the active material particles from loosening and falling off due to their expansion and contraction during charging and discharging of the battery.

At present, in the large-scale production of the lithium ion battery industry, polyvinylidene fluoride (PVDF) dissolved in N-methylpyrrolidone (NMP) is mainly used as a binder. However, due to the shortcomings of PVDF, such as poor conductivity of electrons and ions, there is a certain swelling in the electrolyte, and an exothermic reaction occurs with metal lithium and LixC6 at a relatively high temperature, which has a large safety hazard. In addition, the Young's modulus of PVDF is relatively high, the flexibility of the pole piece is not good enough, the molecular weight decreases after water absorption, and the viscosity is deteriorated. Therefore, the humidity requirement for the environment is relatively high, the energy consumption is large, the PVDF is expensive, and the production cost is high. high. Therefore, the search for a new type of green binder that can replace PVDF has far-reaching significance and has gradually become an important development direction of lithium ion battery binder.

The development of water-based binders is an important direction in the development of lithium-ion battery binders. Styrene-butadiene rubber (SBR) / sodium carboxymethyl cellulose (CMC), polyacrylate water-based adhesives have been widely used in the market, but their adhesion and inhibition of the expansion of the pole pieces are limited, so the use thereof The scope is subject to certain restrictions. Polyvinyl alcohol (PVA) is a bulk product in the synthesis of water-soluble resins. Compared with natural products such as starch, dextrin and protein, the synthetic water-soluble polymer has the competitive advantage of stable and uniform product quality and good comprehensive performance. Modified PVA is also used as a binder for lithium ion batteries. Acetal modified PVA resin (CN105518914A) and PVA graft copolymerized polymer (CN105637686A) can be used as an oil binder for lithium ion batteries; Modified PVA composite polyacrylic acid can be used as an aqueous binder in silicon negative electrode lithium ion batteries (Journal of Power Sources 298 (2015) 8-13); PVA as emulsifier, styrene monomer and acrylate monomer Copolymerization (CN105261759A) can be used to prepare aqueous binders for lithium ion batteries, but polystyrene is disadvantageous in that it is brittle, low in impact strength, prone to stress cracking, and poor heat resistance. Research and development of new PVA-based lithium-ion battery water-based binder to improve its bonding performance, further improve battery performance and reduce production costs, especially for the development of corresponding aqueous binder for the positive electrode is the current hot spot.

Summary of the invention:

The object of the present invention is to provide a multi-functionalized modified polyvinyl alcohol-based lithium ion battery aqueous binder, which has good water-soluble acrylic acid and its salts, good bonding properties and electrochemical properties of acrylonitrile, Or a well-flexible acrylamide monomer is bonded to the PVA molecule by a Michael addition reaction, and the prepared aqueous binder has good water solubility, and can improve the uniformity of the electrode slurry during the preparation of the lithium ion battery electrode sheet. Properties, so that the electrode slurry can form a film uniformly and flatly on the current collector; it can enhance the bonding strength between the electrode active material, the conductive agent and the current collector, and is favorable for the electron/ion in the charging and discharging process. Conduction reduces the electrochemical interface impedance of the pole piece, greatly improves the high rate performance of the positive and negative materials of the lithium battery, and the cycle stability performance, does not drop the material, and does not cause a decrease in capacity, thereby effectively extending the battery life. Compared with the polymer functional modified PVA binder, the Michael addition reaction can controllably introduce functional monomers into the PVA molecule, so that the prepared binder product has stable and uniform quality and good comprehensive performance.

The present invention is achieved by the following technical solutions:

A multi-functionalized modified polyvinyl alcohol-based lithium ion battery aqueous binder, which uses polyvinyl alcohol as a substrate, hydrophilic monomer and oleophilic monomer as functional modified monomers, via Michael The water-soluble gum solution prepared by addition reaction modification has a solid content of 2-50% and a viscosity of 10 to 20000 mPa·s; and the hydrophilic monomer is at least one of the following structural monomers: CH ₂ = CR ₁ R ₂ ; wherein R _{1 is} selected from -H, -CH ₃ , -CH ₂ CH ₃ ; R _{2 is} selected from -COOH, -COOLi, -COONa, -CONH ₂ ; the oleophilic monomer has the following At least one of the monomers of the structure: CH ₂ =CR ₃ R ₄ ; wherein R _{3 is} selected from -H, -CH ₃ , -CH ₂ CH ₃ , and R _{4 is} selected from -CN, -OCOCH ₃ , -CONHCH At least one of ₃ , -CON(CH ₃ ) ₂ , and -COOR ₅ , wherein R ₅ is at least one selected from the group consisting of C1 to C8 alkyl groups; the polyvinyl alcohol has a molecular weight of 10,000 to 250,000, and polyvinyl alcohol The molar ratio of the hydroxyl group-containing repeating polymerization unit, the hydrophilic monomer, and the lipophilic monomer is from 1:0.01 to 1:0 to 0.99.

The Michael addition reaction means that one or more of polyvinyl alcohol and one of a hydrophilic monomer and a lipophilic monomer are reacted by a basic catalyst at a temperature of from 0 to 90 °C.

The basic catalyst is preferably one or more of LiOH, NaOH, LiOH/urea, NaOH/urea; and the catalyst is used in an amount of 0.1 to 10% by weight based on the total mass of the monomers.

The invention also provides a preparation method of the multi-functionalized modified polyvinyl alcohol-based lithium ion battery aqueous binder, comprising the following steps:

1) Firstly dissolving polyvinyl alcohol in deionized water and stirring it under a protective atmosphere for 0.5 to 2.5 hours to drive off oxygen to obtain a uniform and dispersible solution;

2) adding a basic catalyst to the solution obtained in the step 1), stirring well to obtain a mixed solution; adding a hydrophilic monomer and a lipophilic monomer at 0 to 90 ° C and stirring the reaction for 1 to 9 hours to obtain a multi-functionalized modified a polyvinyl alcohol-based lithium ion battery aqueous binder; adjusting the solubility of the binder by adjusting the mass ratio of the hydrophilic monomer and the lipophilic monomer; The amount is 0.1 to 10% of the total mass of the monomer; the molecular weight of the polyvinyl alcohol is 10,000 to 250,000, and the molar ratio of the hydroxyl group-containing repeating polymerization unit, the hydrophilic monomer, and the lipophilic monomer of the polyvinyl alcohol is 1:0.01. ～1:0 to 0.99; the basic catalyst is used in an amount of 0.1 to 10% by weight based on the total mass of the monomers.

Preferably, the protective gas of step 1) is nitrogen and/or argon;

Preferably, step 2); the stirring reaction temperature is 80 °C. ;

Preferably, the stirring reaction time of the step 2) is 8 hours; the basic catalyst is selected from one or more of LiOH, NaOH, LiOH/urea, NaOH/urea.

The invention also protects that the multi-functionalized modified polyvinyl alcohol-based lithium ion battery aqueous binder can be directly applied to the positive or negative electrode sheets of the lithium ion battery, and the binder can also be prepared with LiOH, Li ₂ CO. ₃ , NaOH and other alkalis are neutralized and then applied to the positive or negative electrode of lithium ion batteries.

The application of the multi-functionalized modified polyvinyl alcohol-based lithium ion battery aqueous binder in a positive electrode sheet of a lithium ion battery, wherein the positive electrode sheet of the lithium ion battery comprises a current collector and a positive electrode of a lithium ion battery supported on the current collector a slurry; the lithium ion battery positive electrode slurry includes a positive electrode active material, a conductive agent, the multi-functionalized modified polyvinyl alcohol-based lithium ion battery binder, and a solvent; the positive electrode active material, a conductive agent, and the The mass ratio of the multi-functionalized modified polyvinyl alcohol-based lithium ion battery binder is =70 to 95:1 to 20:4 to 10; the positive electrode active material is selected from lithium iron phosphate, lithium cobaltate, lithium manganate Or one or more of a ternary material (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , NMC); the conductive agent is acetylene black; the current collector is aluminum foil; the lithium ion battery positive electrode The solid content of the slurry is 30 to 75%, and the viscosity of the positive electrode slurry of the lithium ion battery is 3,000 to 8000 mPa·s.

The multi-functionalized modified polyvinyl alcohol-based lithium ion battery binder is used in a lithium ion battery negative electrode sheet, and the lithium ion battery negative electrode sheet comprises a current collector and a lithium ion battery negative electrode slurry supported on the current collector The lithium ion battery negative electrode slurry includes a negative electrode active material, a conductive agent, the multi-functionalized modified polyvinyl alcohol-based lithium ion battery binder, and a solvent; the negative electrode active material, the conductive agent, and the plurality of materials The mass ratio of the functionalized modified polyvinyl alcohol-based lithium ion battery binder is 70 to 95:1 to 20:4 to 10; the negative electrode active material is selected from one of silicon-based materials, lithium titanate or graphite. Two or more; the conductive agent is acetylene black; and the current collector is copper foil.

The binder is applied to other electrochemical energy storage devices such as other secondary batteries, supercapacitors, or solar cells.

The invention also provides a lithium ion battery comprising a battery case, a pole core and an electrolyte, the pole core and the electrolyte being sealed in the battery case, the pole core comprising the plurality of An electrode of a functionalized modified polyvinyl alcohol based lithium ion battery binder and a separator positioned between the electrodes.

The invention has the following beneficial effects:

1) The multi-functionalized modified polyvinyl alcohol-based lithium ion battery aqueous binder provided by the present invention is compared with the graft polymer functional modified PVA binder (CN105637686A, CN105261759A), and the invention is subjected to Michael addition reaction. The functional monomer can be controlled to be introduced into the PVA molecule, so that the prepared binder product has stable and uniform quality and good comprehensive performance.

2) The multi-functionalized modified polyvinyl alcohol-based lithium ion battery aqueous binder provided by the invention has good water solubility, elasticity and bonding property, and can be used for improving electrode paste in the preparation process of lithium ion battery electrode sheets. Uniformity, so that the electrode slurry can form a film uniformly and flatly on the current collector; therefore, the pole piece does not fall off, does not cause a decrease in capacity, and greatly improves the high magnification of the positive and negative materials of the lithium ion battery. Performance and cycle stability to extend battery life.

3) The multi-functionalized modified polyvinyl alcohol-based lithium ion battery aqueous binder provided by the invention is applied to the positive and negative electrodes of the lithium ion battery, and can enhance the bonding strength between the electrode active material, the conductive agent and the current collector, Conducive to the conduction of electrons/ions during charge and discharge, reduce the electrochemical interface impedance of the pole piece, and greatly improve the high rate performance and cycle stability of the positive and negative materials of the lithium battery.

4) The preparation method of the multi-functionalized modified polyvinyl alcohol-based lithium ion battery aqueous binder provided by the invention is simple, green, environmentally friendly, rich in resources, can significantly reduce the cost, and has broad market prospect; the lithium ion battery can be applied. Positive and negative electrodes can promote the technological progress of the lithium-ion battery industry, and even promote the development of strategic emerging industries such as electric vehicles.

5) The binder is applied to other electrochemical energy storage devices such as other secondary batteries, supercapacitors, or solar cells.

BRIEF DESCRIPTION OF THE DRAWINGS:

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an infrared contrast spectrum of an aqueous binder of a multi-functionalized modified polyvinyl alcohol-based lithium ion battery obtained in Example 1-3 of the present invention.

2 is a graph showing the peel strength of an aluminum alloy foil of an aqueous binder of a multi-functionalized modified polyvinyl alcohol-based lithium ion battery obtained in Example 1-3 of the present invention.

3 is a graph showing the peel strength of different aqueous materials of the multi-functionalized modified polyvinyl alcohol-based lithium ion battery aqueous binder obtained in Example 3 of the present invention.

4 is a comparison of voltage-specific capacity of the first discharge of the multi-functionalized modified polyvinyl alcohol-based lithium ion battery aqueous binder and the lithium iron phosphate LiFePO ₄ /Li battery with PVDF binder obtained in Example 3 of the present invention; Graph.

5 is a cyclic voltammetric comparison diagram of an aqueous binder of a multi-functionalized modified polyvinyl alcohol-based lithium ion battery obtained in Example 3 of the present invention and a lithium iron phosphate LiFePO ₄ /Li battery using a PVDF binder.

6 is a cycle performance of a lithium iron phosphate LiFePO ₄ /Li battery of an aqueous binder of a multi-functionalized modified polyvinyl alcohol-based lithium ion battery obtained in Example 3 of the present invention.

7 is a circuit impedance of a ternary LiNi _1/3 Co _1/3 Mn _1/3 O ₂ /Li battery of a multi-functionalized modified polyvinyl alcohol-based lithium ion battery aqueous binder obtained in Example 3 of the present invention; Figure.

8 is a graph showing the rate performance of a ternary LiNi _1/3 Co _1/3 Mn _1/3 O ₂ /Li battery of a multi-functionalized modified polyvinyl alcohol-based lithium ion battery aqueous binder obtained in Example 3 of the present invention. .

Fig. 9 is a graph showing the cycle performance of a silicon-based Si/Li battery of an aqueous binder of a multi-functionalized modified polyvinyl alcohol-based lithium ion battery obtained in Example 3 of the present invention.

Figure 10 is a comparison diagram of the flatness of the coating films of different electrode materials (positive electrode: LFP, NMC; negative electrode: Si, Graphite) according to Examples 1-3 of the present invention.

detailed description:

The following is a further description of the invention and is not to be construed as limiting.

Example 1:

(1) First, 3 g of polyvinyl alcohol is previously dissolved in 50 ml of deionized water (DI-Water), and stirred well under an argon atmosphere for 0.5 to 2.5 hours to obtain a uniform, dispersible solution;

(2) Weighing 0.1 g of NaOH catalyst in the reaction system in (1), stirring well to obtain a uniform system; adding 2.5 g of acrylic monomer, the molar ratio of the hydroxyl group-containing repeating polymerization unit of the polyvinyl alcohol to the acrylic monomer is 1 :0.51, adjust the reaction temperature to 80 ° C, keep stirring, constant temperature reaction for 8h, obtain transparent uniform glue, and then neutralize with LiOH to pH 6-7, which is a multi-functionalized modified polyvinyl alcohol-based lithium ion battery Aqueous binder

Example 2:

The binder preparation method in this embodiment is referred to in Example 1, except that the monomer to be added is a mixture: 2.5 g of acrylic acid and 0.84 g of acrylonitrile, a hydroxyl group-containing repeating polymerization unit of polyvinyl alcohol, an acrylic monomer, and The molar ratio of acrylonitrile monomer is 1:0.51:0.23, the reaction temperature is 80 ° C, and the white glue is obtained, and then neutralized to pH 6-7 with LiOH, which is a multifunctional functionalized modified polyvinyl alcohol-based lithium ion. Battery water-based binder;

Example 3:

The binder preparation method in this embodiment is referred to in Example 1, except that the monomer to be added is a mixture: 2.5 g of acrylic acid, 0.84 g of acrylonitrile, and 1 g of acrylamide, a hydroxyl group-containing repeating polymerization unit of polyvinyl alcohol, acrylic acid. The molar ratio of the monomer, the acrylonitrile monomer, and the acrylamide monomer is 1:0.51:0.23:0.21, the reaction temperature is 80 ° C, and the white gum is obtained, and then neutralized to pH 6-7 with LiOH. Multifunctionalized modified polyvinyl alcohol based lithium ion battery aqueous binder;

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an infrared contrast spectrum of an aqueous binder of a multi-functionalized modified polyvinyl alcohol lithium ion battery obtained in Example 1-3 of the present invention. As can be seen from Fig. 1, Example 1 has a significant stretching vibration signal of C=O in the carboxyl group at a wavenumber of 1668 cm ^-1 , whereas in Example 2 and Example 3, in addition to the stretching vibration signal of the carbonyl group, there is 2250 cm ^{- 1} wave number - CN vibration signal.

Table 1

*Acrylic is abbreviated as AA, acrylonitrile is abbreviated as AN, and acrylamide is abbreviated as AM.

Table 1 is a table showing the viscosity of the aqueous binder of the multi-functionalized modified polyvinyl alcohol-based lithium ion battery obtained in Example 1-3, the peeling force against the current collector aluminum foil, and the average peel strength. The average peel strength in the table is measured by first preparing a pure binder electrode sheet: directly coating 2 wt% of the binder on the Al foil, coating a thickness of 200 μm, and then testing the peel strength. Test method: intercepting a section The electrode sheets having a width of 15 mm were then tested by a peeling tester (Shenzhen, Kay Strong 180° peeling tester) (peeling speed was 20 mm/min), and finally summarized into a table. It can be seen from the average peel strength of the current collector aluminum foil from the multi-functionalized modified polyvinyl alcohol-based lithium ion battery aqueous binder that the peel strength can reach the order of 60-70 mN/mm through multi-functional modification. The peel strength is shown in Figure 2.

Example 4:

Using lithium iron phosphate as a positive electrode material, the white glue liquid synthesized in Example 3 was used as an aqueous binder.

First, the preparation of the test battery:

An embodiment of the positive electrode tab for a lithium ion battery according to the present invention, the positive electrode tab of the lithium ion battery includes a current collector and a lithium ion battery positive electrode slurry supported on the current collector; the lithium ion battery positive electrode slurry includes a positive electrode active material, a conductive agent, a binder, and a solvent; the binder is a white glue liquid synthesized in Example 3; and the mass ratio of the positive electrode active material, the conductive agent, and the binder is a positive electrode active material : Conductive agent: binder = 90:5:5, the solvent is water. The positive active material is lithium iron phosphate (LiFePO ₄ , LFP); the conductive agent is acetylene black; the current collector is aluminum foil current collector; the lithium ion battery positive electrode slurry has a solid content of 45%, lithium ion The viscosity of the battery positive electrode slurry was 3000 mPa·s.

The LFP and the conductive agent are mixed and stirred until uniformly dispersed; the glue liquid synthesized in Example 3 is added into the above system as an aqueous binder, stirred uniformly, and an appropriate amount of deionized water is added to adjust the viscosity to obtain an LFP electrode slurry; The obtained slurry was uniformly coated on an Al foil and dried under vacuum at 90 ° C to obtain an LFP positive electrode sheet. After vacuum-dried pole piece pieces were weighed, they were assembled in a 2025 battery case in a glove box, with lithium sheets as the counter electrode, polyethylene film as the separator, and 1M LiPF ₆ EC/DMC/DEC ( v/v/v=1/1) Cyclic voltammetry test and constant current charge and discharge test for electrolyte assembled batteries.

Second, the preparation of the comparison battery:

A comparative battery was prepared in the same manner using PVDF as a binder and NMP as a solvent.

Third, electrochemical testing:

Electrochemical testing was performed on the charge and discharge performance of the test battery and the comparative battery.

Fourth, the results analysis:

4 and FIG. 5 are respectively a voltage-specific capacity curve of the test battery and the comparative battery at a charge and discharge current density of 0.2 C and a cyclic voltammetry curve at a scan rate of 0.2 mV/s. It can be seen from the figure that the LFP battery prepared by the multi-functionalized modified polyvinyl alcohol-based aqueous binder has a larger discharge capacity and a higher discharge platform, and the voltage interval between the redox peaks is relatively higher. Small, which means that it undergoes a smaller polarization process during discharge, demonstrating an improvement in the conductivity of the electrode system by the multi-functionalized modified polyvinyl alcohol-based aqueous binder.

6 is a cycle performance curve of the test battery under the charge current density of 0.2 C in the present embodiment. After 30 cycles, the discharge specific capacity of the battery can reach 158 mAh/g, and the capacity retention rate is as high as 99%.

Example 5:

The ternary material was used as the positive electrode material, and the white glue liquid synthesized in Example 3 was used as the aqueous binder.

First, the preparation of test electrodes:

An embodiment of the positive electrode tab for a lithium ion battery according to the present invention, the positive electrode tab of the lithium ion battery includes a current collector and a lithium ion battery positive electrode slurry supported on the current collector; the lithium ion battery positive electrode slurry includes a positive electrode active material, a conductive agent, a binder, and a solvent; the binder is a white glue liquid synthesized in Example 3; and the mass ratio of the positive electrode active material, the conductive agent, and the binder is a positive electrode active material : Conductive agent: binder = 85:9:6, the solvent is water. The positive active material is a ternary material (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , NMC); the conductive agent is acetylene black; the current collector is an aluminum foil current collector; and the lithium ion battery The solid content of the positive electrode slurry was 45 wt%, and the viscosity of the positive electrode slurry of the lithium ion battery was 3000 mPa·s.

Mixing NMC and conductive agent to uniformly disperse; then adding the glue liquid synthesized in Example 3 to the above system and stirring uniformly, adding appropriate amount of deionized water to adjust the viscosity to obtain NMC electrode slurry; The obtained slurry was uniformly coated on an Al foil and dried under vacuum at 90 ° C to obtain an NMC positive electrode sheet. After vacuum-dried pole piece pieces were weighed, they were assembled in a 2025 battery case in a glove box, with lithium sheets as the counter electrode, polyethylene film as the separator, and 1M LiPF ₆ EC/DMC/DEC ( v/v/v=1/1) Constant current charge and discharge test for electrolyte assembled batteries.

Second, electrochemical testing:

Perform impedance test and charge and discharge performance test on the test battery.

Third, the results analysis:

Fig. 7 is an impedance diagram of the test battery before the cycle of the embodiment. Fig. 8 is a graph showing the rate performance of the test battery of the present embodiment. It can be seen from the figure that the battery of the present embodiment has a small impedance characteristic, and the NMC battery prepared by using the multi-functionalized modified polyvinyl alcohol-based aqueous binder has good rate performance, and the battery is under the condition of 2C rate. The discharge specific capacity can still be as high as 112 mAh/g.

Example 6

The white emulsion synthesized in Example 3 was used as an aqueous binder using a Si-based material as a negative electrode material.

First, the preparation of test electrodes:

In an embodiment of the lithium ion battery negative electrode sheet of the present invention, the lithium ion battery negative electrode sheet comprises a current collector and a lithium ion battery negative electrode slurry supported on the current collector; the lithium ion battery negative electrode slurry comprises a negative electrode active material, a conductive agent, a white emulsion synthesized in Example 3 as a binder and a solvent; and a mass ratio of the negative electrode active material, the conductive agent and the binder of 70:20:10, the solvent is water . The negative active material is a Si-based material; the conductive agent is acetylene black; the current collector is a copper foil current collector; the lithium ion battery negative electrode slurry has a solid content of 45 wt%, and the lithium ion battery negative electrode slurry The viscosity was 3000 mPa·s.

The Si and the conductive agent are mixed and stirred until uniformly dispersed; the white emulsion synthesized in Example 3 is added to the above system as an aqueous binder, stirred uniformly, and an appropriate amount of deionized water is added to adjust the viscosity to obtain a Si electrode slurry; The obtained slurry was uniformly coated on a Cu foil and dried under vacuum at 60 ° C to obtain a Si-based negative electrode sheet. After vacuum-dried pole piece pieces were weighed, they were assembled in a 2025 battery case in a glove box, with lithium sheets as the counter electrode, polyethylene film as the separator, and 1M LiPF ₆ EC/DMC/DEC ( v/v/v=1/1) Constant current charge and discharge test for electrolyte assembled batteries.

Second, electrochemical testing:

Electrochemical tests were performed on the charge and discharge cycle stability of the test electrode and the comparison electrode.

Third, the results analysis:

9 is a cycle performance test curve of a test battery at a charge and discharge current density of 400 mA/g in the present embodiment, and it can be seen from the figure that a multi-functionalized modified polyvinyl alcohol-based lithium ion battery aqueous binder is used as a bond. The Si-based battery prepared by the agent has a first charge and discharge coulombic efficiency of 82%, and also initially exhibits good charge and discharge cycle performance.

Example 7

Using graphite as a negative electrode material, the white emulsion synthesized in Example 3 was used as an aqueous binder.

First, the preparation of test electrodes:

Referring to Example 6, the graphite electrode was prepared in a manner in which the mass ratio of the negative electrode active material (graphite), the conductive agent, and the binder was 90:5:5.

Table 2

Electrode sheet Binder Average peel strength (mN/mm) Example 4 Lithium iron phosphate PVA-AA-AN-AM 61 Example 5 Ternary material PVA-AA-AN-AM 35 Example 6 Nano silicon powder PVA-AA-AN-AM 40 Example 7 graphite PVA-AA-AN-AM 60

Table 2 shows the peel strength of the electrode sheets of Example 4-7, and the thickness parameters at the time of coating: 100 μm of the positive electrode-LiFePO _{4 ,} 100 μm of the ternary LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , and the negative electrode - Si was 80 μm and graphite was 50 μm. It can be seen from the experimental results that the multi-functionalized modified polyvinyl alcohol-based aqueous binder has a high peel strength, and the peel strength is enhanced compared to the polystyrene-containing binder system (CN 105261759A). One order of magnitude.

Example 8

PVA-AA, PVA-AA-AN or PVA-AA-AN synthesized by using the graphite, the Si-based as the negative electrode material, the lithium iron phosphate and the ternary material as the positive electrode materials, respectively, using the examples 1, 2 or 3. The -AM polymer lithium ion battery binder is used as a binder to form electrode sheets, and the flatness of the pole pieces is compared.

First, the preparation of test electrodes:

The preparation of the graphite electrode is referred to Example 7, except that the binder used is PVA-AA;

The preparation of the Si-based electrode is as in Reference Example 6, except that the binder used is PVA-AA-AN;

The formulation of the LFP based electrode is referred to Example 4.

The formulation of the NCM electrode is referred to Example 5.

Second, the pole piece flatness test:

The flatness of the test electrode sheets was observed and compared.

Fourth, the results analysis:

Fig. 10 is a comparison diagram of the flatness of the pole pieces of the different test electrode sheets of the present embodiment. It can be seen from the figure that graphite, Si negative electrode sheets prepared by multi-functionalized modified PVA-AA, PVA-AA-AN polymer lithium ion battery binder, and multi-functionalized modified PVA-AA- The lithium iron phosphate and ternary material positive electrode sheets prepared by AN-AM polymer lithium ion battery binder have excellent uniformity and flatness, no graininess or discontinuity, which is beneficial to improve the long cycle of the battery. Electrochemical stability, thereby improving the service life of the battery, has broad application prospects and development potential.

Claims (7)

A multi-functionalized modified polyvinyl alcohol-based lithium ion battery aqueous binder characterized in that it is based on polyvinyl alcohol as a substrate, and a hydrophilic monomer and a lipophilic monomer are used as functionalized modifying monomers. The water-soluble gum solution modified by the Michael addition reaction has a solid content of 2 to 50% and a viscosity of 10 to 20,000 mPa·s; and the hydrophilic monomer is at least one of the following structural monomers: CH ₂ =CR ₁ R ₂ ; wherein R _{1 is} selected from -H, -CH ₃ , -CH ₂ CH ₃ ; R _{2 is} selected from -COOH, -COOLi, -COONa, -CONH ₂ ; At least one of the monomers having the structure: CH ₂ =CR ₃ R ₄ ; wherein R _{3 is} selected from -H, -CH ₃ , -CH ₂ CH ₃ , and R _{4 is} selected from -CN, -OCOCH ₃ , At least one of -CONHCH ₃ , -CON(CH ₃ ) ₂ , and -COOR ₅ , wherein R ₅ is at least one selected from the group consisting of C1 to C8 alkyl groups; the polyvinyl alcohol has a molecular weight of 10,000 to 250,000, and is polymerized. The molar ratio of the hydroxyl group-containing repeating polymerization unit, the hydrophilic monomer, and the lipophilic monomer of the vinyl alcohol is from 1:0.01 to 1:0 to 0.99. The multi-functionalized modified polyvinyl alcohol-based lithium ion battery aqueous binder according to claim 1, wherein said Michael addition reaction means a polyvinyl alcohol and a hydrophilic monomer and a lipophilic monomer Or a plurality of reactions initiated by a basic catalyst at a temperature of from 0 to 90 ° C; the basic catalyst is used in an amount of from 0.1 to 10% by weight based on the total mass of the monomers. The multi-functionalized modified polyvinyl alcohol-based lithium ion battery aqueous binder according to claim 2, wherein the basic catalyst is selected from one of LiOH, NaOH, LiOH/urea, NaOH/urea or Two or more. The application of the multi-functionalized modified polyvinyl alcohol-based lithium ion battery aqueous binder in the positive electrode sheet of the lithium ion battery according to claim 1, wherein the positive electrode sheet of the lithium ion battery comprises a current collector and a load in the set a lithium ion battery positive electrode slurry on the fluid; the lithium ion battery positive electrode slurry comprising a positive electrode active material, a conductive agent, the multi-functionalized modified polyvinyl alcohol based lithium ion battery binder of claim 1 and a solvent; The mass ratio of the positive electrode active material, the conductive agent and the multi-functionalized modified polyvinyl alcohol-based lithium ion battery binder is =70 to 95:1 to 20:4 to 10; the positive electrode active material is selected from phosphoric acid One or more of iron lithium, lithium cobaltate, lithium manganate or a ternary material; the conductive agent is acetylene black; the current collector is aluminum foil; and the solid content of the lithium ion battery positive electrode slurry is 30 ～ 75%, the viscosity of the lithium ion battery positive electrode slurry is 3,000 to 8000 mPa·s. The multifunctional functionalized modified polyvinyl alcohol-based lithium ion battery binder of claim 1 in lithium ion The battery negative electrode sheet is characterized in that: the lithium ion battery negative electrode sheet comprises a current collector and a lithium ion battery negative electrode slurry supported on the current collector; and the lithium ion battery negative electrode slurry comprises a negative electrode active material and conductive The multi-functionalized modified polyvinyl alcohol-based lithium ion battery binder and the solvent according to claim 1; the negative electrode active material, the conductive agent and the multi-functionalized modified polyvinyl alcohol-based lithium ion battery are bonded The mass ratio of the agent is 70 to 95:1 to 20:4 to 10; the negative electrode active material is selected from one or more of a silicon-based material, lithium titanate or graphite; the conductive agent is acetylene black; The current collector is a copper foil. The multi-functionalized modified polyvinyl alcohol-based lithium ion battery binder of claim 1 is applied to an electrochemical energy storage device, characterized in that the electrochemical energy storage device is a supercapacitor or a solar cell. A lithium ion battery comprising a battery case, a pole core and an electrolyte, wherein the pole core and the electrolyte are sealed in the battery case, wherein the pole core comprises the claim 1 or 2 An electrode of the multi-functionalized modified polyvinyl alcohol-based lithium ion battery binder and a separator positioned between the electrodes.

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