CN114242990B - A polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon negative electrode water-based binder and its preparation method and application - Google Patents

Abstract

The invention discloses a polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon negative electrode water-based adhesive, and a preparation method and application thereof. The adhesive is prepared by hydrogen bond crosslinking of polyvinyl alcohol and an acrylic acid-acrylamide- (2-acrylamide-2-methylpropanesulfonic acid) terpolymer. The adhesive has an interpenetrating network structure, excellent bonding strength and good capability of promoting lithium ion transmission. The adhesive is applied to a liquid lithium ion battery, so that the rate capability can be effectively improved, and the cycle service life of the battery can be prolonged. According to the invention, the adhesive with an interpenetrating network structure is obtained by forming hydrogen bond crosslinking through the free radical copolymerization of acrylic acid, acrylamide and 2-acrylamide-2-methylpropanesulfonic acid monomers in a polyvinyl alcohol aqueous solution. The adhesive prepared by the method has a plurality of functional groups which endow the adhesive with strong adhesive capacity and lithium ion affinity.

Description

A polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode water-based binder Preparation methods and applications thereof

Technical field

The invention relates to the technical field of liquid lithium ion batteries, and specifically relates to a polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode water-based binder and its preparation method and application.

Background technique

Lithium-ion batteries have rapidly occupied a dominant position in the fields of mobile electronic devices and electric vehicles due to their many advantages such as high discharge voltage, high energy density, long cycle life, green and pollution-free. As the demand for batteries for portable electronic devices and electric vehicles continues to grow, the pursuit of electrodes with high energy density and long cycle life has never stopped. Currently commonly used lithium-ion batteries mainly use graphite material as the negative electrode, but the theoretical specific capacity of the graphite electrode is only 372mAh/g, which limits its further application in the high-energy-density battery industry.

Silicon has become a hot spot in current research because of its high specific capacity (4200mAh/g), abundant reserves in the earth's crust, and low cost. Although silicon-based materials have many excellent properties, a series of problems still need to be solved in the practical application of lithium-ion batteries. Silicon has a significant volume change (about 400%) during the process of intercalation and deintercalation with lithium ions, which can easily cause the electrode material to crack and be exposed to the active surface, causing the electrolyte to continuously decompose. In addition, mechanical fracture of the internal frame of the electrode and loss of active materials will accelerate the decay of the capacity of the electrode material, resulting in a reduction in the battery cycle life. This shortcoming of silicon anode makes its commercialization difficult. Effectively mixing silicon and graphite to form a silicon-carbon composite material can increase the specific capacity while reducing the problems caused by volume expansion, and has become a hot spot in commercial exploration.

As a key part of lithium-ion batteries, polymer binders can effectively connect active materials, conductive agents and current collectors, provide interconnected structures and mechanical strength for electrodes, and maintain electron/ion transfer during battery cycling. . Traditional binders, such as PVDF, have poor performance for high energy density lithium-ion batteries due to their relatively low adhesion and weak mechanical strength. Although the CMC/SBR binder can provide good cycling capability and mechanical stability to the electrode, the distribution of the binder is uneven, and SBR tends to migrate with the solvent during the drying process. In order to effectively improve the impact of volume changes on battery performance caused by silicon carbon anode materials during charge and discharge, it is urgent to design and modify the binder. In order to meet the current requirements for green, efficient, and high-performance battery electrodes, it is urgent to develop aqueous binders for lithium-ion battery negative electrodes with high bonding strength and elasticity.

There are literatures using acrylic acid (AA), lithium acrylate (LiAA) and hydroxyethyl acrylate (HEA) as monomers to perform free radical graft polymerization on polyvinyl alcohol (PVA) to synthesize a partially lithiated ternary graft copolymer. Material with good flexibility, elasticity and bonding strength. (Liu S, Zhang L. Partially lithiated ternary graft copolymer with enhanced elasticity as aqueous binder for Si anode[J]. Journal of Applied Polymer Science, 2021, 138.) However, the molecular weight of the graft copolymer is limited by the polymer (polyvinyl alcohol) The molecular weight of the polymer makes it impossible to synthesize higher molecular weight polymers, and it is difficult to form a dense network structure. In comparison, direct free radical copolymerization in a polymer aqueous solution is not only simple and easy to operate, but also produces a high molecular weight polymer with an interpenetrating network structure, further improving the bonding strength and elasticity.

Contents of the invention

The purpose of the present invention is to provide a polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode water-based bonding in order to solve the problems of poor bonding performance of existing silicon carbon negative electrode binders and difficulty in suppressing the volume expansion of active materials. Agents and preparation methods thereof.

The second object of the present invention is to provide the application of this polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode aqueous binder, which can be used to prepare silicon carbon negative electrodes for liquid lithium ion batteries.

The adhesive provided by the invention contains a large number of polar groups. The hydrogen bond cross-linking between the molecular chains of polyvinyl alcohol and allyl copolymer makes the adhesive have an interpenetrating network structure and can provide strong adhesive force. , tightly bonding the silicon-carbon composite to the current collector.

The invention provides a polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode water-based binder, whose raw material composition includes polyvinyl alcohol, acrylic acid, acrylamide and 2-acrylamide-2-methylpropanesulfonate. acid.

The invention provides a polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode water-based binder prepared by hydrogen bond cross-linking between molecular chains.

The object of the present invention is achieved by at least one of the following technical solutions.

The invention provides a method for preparing a polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode aqueous binder, which includes the following steps:

(1) Add polyvinyl alcohol (PVA) to water, heat and stir until completely dissolved, and cool to room temperature to obtain a PVA aqueous solution;

(2) Add the alkaline substance to water, dissolve it completely with ultrasound, put it in an ice water bath and cool it to room temperature, then slowly add acrylic acid (AA), stir evenly, and when the solution temperature is lower than room temperature again, add acrylamide (AM), 2-Acrylamide-2-methylpropanesulfonic acid (AMPS), ultrasonic until completely dissolved, to obtain a comonomer mixed aqueous solution; the comonomer includes alkaline substances, acrylic acid (AA), acrylamide (AM) and 2 -Acrylamide-2-methylpropanesulfonic acid (AMPS);

(3) Add ammonium persulfate (APS) to water and dissolve it completely with ultrasound to obtain an APS aqueous solution; add sodium bisulfite (NaHSO ₃ ) to water and dissolve it completely with ultrasound to obtain a NaHSO ₃ aqueous solution;

(4) Mix the PVA aqueous solution described in step (1), the comonomer mixed aqueous solution described in step (2), the APS aqueous solution and NaHSO ₃ aqueous solution described in step (3) evenly to obtain a reaction aqueous solution;

(5) After fully replacing the air with argon, the reaction aqueous solution in step (4) is magnetically stirred under heating conditions to obtain a product solution;

(6) Freeze-dry the product solution described in step (5), grind it into fine powder, wash with absolute ethanol, filter and dry under vacuum to obtain the polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode Water-based adhesive.

Further, the polyvinyl alcohol in step (1) is PVA1788 type or PVA1797 type; the concentration of the PVA aqueous solution in step (1) is 5 to 10 wt%; and the heating temperature in step (1) is 80 to 90°C.

Further, the alkaline substance in step (2) is sodium hydroxide (NaOH), potassium hydroxide (KOH) or lithium hydroxide monohydrate (LiOH·H ₂ O); the comonomers in step (2) are mixed The concentration of the aqueous solution is 20wt% ~ 30wt%; the molar ratio of the alkaline substance and acrylic acid described in step (2) is 80 ~ 90:100 (mol:mol); acrylic acid, acrylamide, 2-propene described in step (2) The molar ratio of amide-2-methylpropanesulfonic acid is 1 to 5:1:1 (mol:mol:mol).

Preferably, the alkaline substance in step (2) is lithium hydroxide monohydrate (LiOH·H ₂ O).

Further, the concentration of the APS aqueous solution in step (3) is 1 to 5 wt%; the concentration of the NaHSO ₃ aqueous solution in step (3) is 1 to 5 wt%.

Further, the molar ratio of APS and _NaHSO in step (4) is 1 to 2:1; the comonomer (alkaline substance, AA, AM and AMPS) in the mixed aqueous solution of APS and comonomer in step (4) The mass ratio is 0.1 to 0.5:100; the mass ratio of the comonomers (alkaline substances, AA, AM and AMPS) in the mixed aqueous solution of PVA and comonomer in step (4) is 5 to 20:100.

Further, the heating temperature in step (5) is 30-50°C; the reaction time in step (5) is 12-24 hours.

Further, the vacuum drying temperature in step (6) is 40-60°C, and the vacuum drying time is 10-12 hours.

In the above preparation method, the water used is ultrapure water, the resistivity is greater than 18.2MΩ·cm, and the magnetic stirring speed is 400rad/min.

The invention provides a polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode aqueous binder prepared by the above preparation method.

The invention provides the application of a polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode aqueous binder in the preparation of liquid lithium ion battery silicon carbon negative electrodes.

The liquid lithium ion battery silicon carbon negative electrode includes: a silicon carbon composite and a polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode water-based binder; the silicon carbon composite is a silicon carbon active material (SiC400 , SiC450, SiC500 or SiC550), a mixture of conductive agent (Super P) and carboxymethylcellulose aqueous solution (CMC).

The application of the polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode aqueous binder in the preparation of liquid lithium ion battery silicon carbon negative electrode includes the following steps:

(1) Add a certain mass of silicon carbon active material to the cryopreservation tube, then add conductive agent (Super P) and carboxymethyl cellulose aqueous solution (CMC) in proportion, and shake thoroughly on a small ball mill to obtain a mixture Uniform silicon-carbon composite;

(2) Add the polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode water-based binder to the silicon carbon composite obtained in step (1), and shake it thoroughly on a small ball mill to obtain a uniform silicon carbon negative electrode. slurry;

(3) Evenly apply the silicon carbon negative electrode slurry obtained in step (2) on the current collector copper foil to obtain the electrode piece to be baked. Put the electrode piece to be baked into the oven to dry thoroughly, and then cut it on the slicer. A disc of a certain size is the silicon-carbon negative electrode piece of liquid lithium-ion battery.

Further, the silicon carbon active material in step (1) is SiC400, SiC450, SiC500 or SiC550; the concentration of the carboxymethylcellulose aqueous solution (CMC) in step (1) is 1wt%; the silicon carbon in step (1) The solid content mass ratio of active material, conductive agent (Super P) and carboxymethylcellulose aqueous solution (CMC) is 94:1.5:0.75; the volume of the cryovial in step (1) is 2mL; The rotation speed of the ball mill is 3000-4000rad/min; the homogenization time in step (1) is 3-6 minutes.

Further, the solid content mass ratio of the silicon-carbon composite and the polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon anode aqueous binder described in step (2) is 96.25:3.75; the ball mill described in step (2) The rotation speed is 3000~4000rad/min; the homogenization time in step (2) is 9~15min.

Further, the drying temperature in the oven in step (3) is 60°C; the drying time in the oven in step (3) is 12 to 24 hours; the diameter of the disc in step (3) is 12 mm.

The silicon-carbon negative electrode sheet of the liquid lithium ion battery provided by the present invention can be used in the preparation of liquid lithium ion batteries. The liquid lithium ion battery includes: liquid lithium ion battery silicon carbon negative electrode sheet, polymer separator, electrolyte and metal lithium sheet.

The liquid lithium-ion battery prepared by the present invention using the polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon negative electrode water-based binder has a first charge specific capacity of 390.840mAh/ when the SiC400 load is 3.76mg/ ^cm2 . g, the first Coulombic efficiency is 92.604%. After 80 cycles at a current density of 0.2C, the charge specific capacity is still as high as 372.383mAh/g, and the capacity retention rate is 95.278%.

The third object of the present invention is to provide a liquid lithium ion battery, including a liquid lithium ion battery silicon carbon negative electrode sheet, a polymer separator, an electrolyte and a metal lithium sheet. The liquid lithium ion battery silicon carbon negative electrode sheet is The above-mentioned liquid lithium ion battery silicon carbon negative electrode sheet of the present invention.

Further, the polymer separator is one of polyethylene (PE) single-layer separator, polypropylene (PP) single-layer separator or PP/PE/PP three-layer separator, preferably polypropylene (PP) single-layer separator. .

Further, the electrolyte component is LiPF ₆ with a concentration of 1.0M dissolved in a mass ratio of ethylene carbonate (EC): diethyl carbonate (DEC): dimethyl carbonate (DMC) = 1:1:1 (wt %) mixed solvent, and add 10wt% fluoroethylene carbonate (FEC) and 2wt% vinylene carbonate (VC).

Compared with the existing technology, the present invention has the following advantages and beneficial effects:

(1) The preparation method provided by the invention uses polyvinyl alcohol, acrylic acid, acrylamide and 2-acrylamide-2-methylpropanesulfonic acid as basic raw materials, and uses free radical copolymerization of monomers in another polymer aqueous solution. , generating hydrogen bond cross-linking to obtain an interpenetrating network water-based adhesive. Compared with the existing monofunctional linear structure negative electrode binders on the market, this binder can firmly adhere the negative electrode active material silicon carbon material and conductive agent to the current collector during the charge and discharge process, ensuring effective electronic conduction.

(2) In the preparation method provided by the invention, the commercial polymer polyvinyl alcohol selected has high bonding strength. In addition, polyvinyl alcohol and acrylic acid-acrylamide-(2-acrylamide-2-methylpropanesulfonic acid ) The interpenetrating network structure between the copolymer molecular chains further improves the bonding strength of the binder, which can tightly bond the negative electrode active material silicon carbon material and conductive agent to the current collector during the charge and discharge process, effectively inhibiting the negative electrode activity. The material expands to prevent it from falling off. The polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon negative electrode water-based binder further extends the cycle life of the battery.

(3) In the preparation method provided by the present invention, the water-based binder contains a large number of polar functional groups (-COOH, -NH ₂ ), which improves the adhesion to silicon and copper foil, and at the same time it contains sulfonic acid groups ( -SO ₃ ) has a strong affinity with lithium ions, which is beneficial to the conduction of lithium ions. The polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode water-based binder can further improve the rate performance of the battery.

(4) The preparation method provided by the invention uses water as the solvent throughout the reaction process. Compared with traditional binders such as polyvinylidene fluoride, it avoids the use of toxic organic solvents. The method is environmentally friendly and efficient, and the equipment used is low in cost. And simple and easy to operate.

Description of the drawings

Figure 1 is a schematic diagram of the peeling force testing device used in the embodiments and comparative examples of the present invention;

Figure 2a is a graph showing peeling test data of silicon carbon negative electrodes prepared from the binders described in Example 4, Example 6, Comparative Example 1 and Comparative Example 2;

Figure 2b is a graph showing peeling test data of silicon carbon negative electrodes prepared from the binders described in Example 3, Example 5, Comparative Example 1 and Comparative Example 2;

Figure 2c is a data diagram showing the average peeling force of silicon carbon negative electrodes prepared from the binders described in Example 1, Example 2, Example 3, Example 6, Comparative Example 1 and Comparative Example 2;

Figure 3a shows the liquid lithium ion battery prepared using the binder described in Example 2, Example 3, Example 6, Comparative Example 1 and Comparative Example 2 after activation for 3 cycles at 0.05C, when the SOC is 50%. AC impedance diagram;

Figure 3b shows the liquid lithium ion battery prepared using the binder described in Example 2, Example 3, Example 6, Comparative Example 1 and Comparative Example 2 after activation at 0.05C for 3 cycles, when the SOC is 50%. Actual impedance value graph;

Figure 4 shows the liquid lithium ion battery prepared using the binder described in Example 1, Example 3, Example 4, Example 6, Comparative Example 1 and Comparative Example 2 after being activated for 3 cycles at 0.05C. Rate performance data chart of 10 cycles at 0.1C, 0.2C, 0.5C, 1C and 0.1C;

Figure 5 is a specific capacity-voltage diagram of a liquid lithium-ion battery prepared using the binder described in Example 2, Example 3 and Comparative Example 2 when charged and discharged under 1C conditions;

Figure 6 is the cycle curve of the liquid lithium ion battery prepared using the binder described in Example 2, Example 3, Example 4, Example 5, Example 6, Comparative Example 1 and Comparative Example 2 at 0.2C and Coulomb efficiency diagram.

Detailed ways

The present invention will be described in further detail below with reference to examples, but the implementation of the present invention is not limited thereto. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent substitutions and are included in the protection scope of the present invention.

Example 1

The preparation method of polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode water-based binder includes the following steps:

(1) Add 5g PVA1788 to 95g water, heat to 80°C, stir until completely dissolved, and cool to room temperature to obtain a PVA aqueous solution with a mass fraction of 5wt%;

(2) Add 3.3568g (0.08mol) lithium hydroxide monohydrate (LiOH·H ₂ O) to 153.5832g water, dissolve it completely with ultrasound, put it in an ice water bath and cool it to room temperature, then add 7.206g (0.1mol) acrylic acid ( AA), stir evenly, and after the solution temperature is lower than room temperature again, add 7.108g (0.1mol) acrylamide (AM) and 20.725g (0.1mol) 2-acrylamide-2-methylpropanesulfonic acid (AMPS). Ultrasonicate until completely dissolved to obtain a comonomer mixed aqueous solution with a mass fraction of 20wt%;

(3) Add 0.1g ammonium persulfate (APS) to 9.9g water and dissolve it completely with ultrasound to obtain a 1wt% APS aqueous solution; add 0.1g sodium bisulfite (NaHSO ₃ ) to 9.9g water and dissolve it completely with ultrasound to obtain 1wt% NaHSO ₃ aqueous solution;

(4) Mix the 153.5832g PVA aqueous solution described in step (1), the mixed aqueous solution of all comonomers described in step (2), the 3.8396g APS aqueous solution and 0.8754g NaHSO ₃ aqueous solution described in step (3) evenly to obtain a reaction aqueous solution;

(5) After fully replacing the air with argon, the reaction aqueous solution described in step (4) was magnetically stirred for 24 hours at 30°C to obtain a product solution;

(6) Freeze-dry the product solution described in step (5), grind it into fine powder, wash with absolute ethanol, filter and vacuum-dry at 60°C for 10 hours to obtain the polyvinyl alcohol/allyl copolymer. Through network silicon carbon negative electrode water-based binder.

A method of assembling a liquid lithium-ion battery using the polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon negative electrode aqueous binder prepared in Example 1 as a binder, including the following steps:

A. Add 0.5640g SiC400 active material, 0.0090g conductive agent (Super P) and 0.4500g 1wt% carboxymethylcellulose aqueous solution (CMC) into a 2mL cryopreservation tube in sequence, and shake in a small ball mill with a shaking speed of 3000rad/min for 3 minutes. , to obtain a uniformly mixed silicon-carbon composite;

B. According to the solid content mass ratio of the silicon-carbon composite and the polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon anode aqueous binder is 96.25:3.75, add 0.7500g into the 2mL cryovial A polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon anode aqueous binder with a mass fraction of 3wt% is shaken in a small ball mill with a shaking speed of 3000rad/min for 15 minutes to obtain a uniform silicon-carbon anode slurry;

C. Coat the silicon-carbon negative electrode slurry on the copper foil with a scraper, dry it in a 60°C oven for 12 hours, and then cut the liquid lithium-ion battery silicon-carbon negative electrode sheet with a diameter of 12 mm on a slicer;

D. Based on the above silicon carbon negative electrode sheet of the liquid lithium ion battery, lithium metal is used as the counter electrode, the separator is Celgard's polypropylene separator 2500, and the electrolyte component is LiPF ₆ with a concentration of 1.0M dissolved in a mass ratio of EC:DEC: In the mixed solvent of DMC=1:1:1 (wt%), 10wt% FEC and 2wt% VC are added. Assemble the CR2025 button battery according to the corresponding operations in a glove box that is water-free and filled with argon gas (H ₂ O <0.01ppm, O ₂ <0.01ppm) to obtain a liquid lithium-ion button battery.

The liquid lithium ion button battery prepared in this example was allowed to stand for 24 hours before being used for electrochemical testing. The Newwell CT2001A battery testing system was used to test the cycle and rate performance of the above-assembled liquid lithium-ion button battery at 30°C. The cycle test conditions were: the charge and discharge window was selected between 0.01 and 2V, and the test was performed at a current density of 0.2C. Carry out; the rate test conditions are: the charge and discharge window is selected between 0.01 and 2V, and the test is performed at 0.1C, 0.2C, 0.5C, 1C, and 0.1C current densities for 10 cycles each. The Solartron Analytical electrochemical workstation was used to perform EIS (electrochemical impedance spectroscopy) testing on the above-assembled liquid lithium-ion button battery before cycling. The frequency range during the test was 10 ⁶ HZ ~ 10 ^-2 HZ, and the amplitude was 5mV.

Example 2

The preparation method of polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode water-based binder includes the following steps:

(1) Add 10g PVA1797 to 90g water, heat to 90°C, stir until completely dissolved, and cool to room temperature to obtain a PVA aqueous solution with a mass fraction of 10wt%;

(2) Add 3.6g (0.09mol) of sodium hydroxide (NaOH) to 74.1675g of water, dissolve it completely with ultrasound, put it in an ice water bath to cool to room temperature, then add 7.206g (0.1mol) of acrylic acid (AA), and stir evenly , after the solution temperature is lower than room temperature again, add 3.554g (0.05mol) acrylamide (AM), 10.3625g (0.05mol) 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and sonicate until completely dissolved. Obtain a comonomer mixed aqueous solution with a mass fraction of 25wt%;

(3) Add 0.2g ammonium persulfate (APS) to 9.8g water and dissolve it completely with ultrasound to obtain a 2wt% APS aqueous solution; add 0.2g sodium bisulfite (NaHSO ₃ ) to 9.8g water and dissolve it completely with ultrasound to obtain 2wt% NaHSO ₃ aqueous solution;

(4) Mix the 37.0838g PVA aqueous solution described in step (1), the mixed aqueous solution of all comonomers described in step (2), the 2.4723g APS aqueous solution and 1.1273g NaHSO ₃ aqueous solution described in step (3) evenly to obtain a reaction aqueous solution ;

(5) After fully replacing the air with argon, the reaction aqueous solution described in step (4) was magnetically stirred for 18 hours at 40°C to obtain a product solution;

(6) Freeze-dry the product solution described in step (5), grind it into fine powder, wash with absolute ethanol, filter and vacuum-dry at 50°C for 12 hours to obtain the polyvinyl alcohol/allyl copolymer. Through network silicon carbon negative electrode water-based binder.

A method of assembling a liquid lithium-ion battery using the polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon negative electrode aqueous binder prepared in Example 2 as a binder, including the following steps:

A. Add 0.5640g SiC400 active material, 0.0090g conductive agent (Super P) and 0.4500g 1wt% carboxymethyl cellulose aqueous solution (CMC) into a 2mL cryopreservation tube in sequence, and shake in a small ball mill with a shaking speed of 4000rad/min 3 minutes to obtain a uniformly mixed silicon-carbon composite;

B. According to the solid content mass ratio of the silicon-carbon composite and the polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon anode aqueous binder is 96.25:3.75, add 0.7500g into the 2mL cryovial A polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon anode aqueous binder with a mass fraction of 3wt% was shaken in a small ball mill with a shaking speed of 4000rad/min for 9 minutes to obtain a uniform silicon-carbon anode slurry;

C. Coat the silicon-carbon negative electrode slurry on the copper foil with a scraper, dry it in a 60°C oven for 18 hours, and then cut the liquid lithium-ion battery silicon-carbon negative electrode sheet with a diameter of 12 mm on a slicer;

D. Based on the above silicon carbon negative electrode sheet of the liquid lithium ion battery, lithium metal is used as the counter electrode, the separator is Celgard's polypropylene separator 2500, and the electrolyte component is LiPF ₆ with a concentration of 1.0M dissolved in a mass ratio of EC:DEC: In the mixed solvent of DMC=1:1:1 (wt%), 10wt% FEC and 2wt% VC were added. Assemble the CR2025 button battery according to the corresponding operations in a glove box that is water-free and filled with argon gas (H ₂ O <0.01ppm, O ₂ <0.01ppm) to obtain a liquid lithium-ion button battery.

The liquid lithium ion button battery prepared in this example was allowed to stand for 24 hours before being used for electrochemical testing. The Newwell CT2001A battery testing system was used to test the cycle and rate performance of the above-assembled liquid lithium-ion button battery at 30°C. The cycle test conditions were: the charge and discharge window was selected between 0.01 and 2V, and the test was performed at a current density of 0.2C. Carry out; the rate test conditions are: the charge and discharge window is selected between 0.01 and 2V, and the test is performed at 0.1C, 0.2C, 0.5C, 1C, and 0.1C current densities for 10 cycles each. The Solartron Analytical electrochemical workstation was used to perform EIS (electrochemical impedance spectroscopy) testing on the above-assembled liquid lithium-ion button battery before cycling. The frequency range during the test was 10 ⁶ HZ ~ 10 ^-2 HZ, and the amplitude was 5mV.

Example 3

The preparation method of polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode water-based binder includes the following steps:

(1) Add 10g PVA1788 to 90g water, heat to 80°C, stir until completely dissolved, and cool to room temperature to obtain a PVA aqueous solution with a mass fraction of 10wt%;

(2) Add 5.7228g (0.102mol) potassium hydroxide (KOH) to 59.5075g water, dissolve it completely with ultrasound, put it in an ice water bath to cool to room temperature, then add 8.6472g (0.12mol) acrylic acid (AA), and stir evenly , after the solution temperature is lower than room temperature again, add 2.8432g (0.04mol) acrylamide (AM), 8.29g (0.04mol) 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and sonicate until completely dissolved. Obtain a comonomer mixed aqueous solution with a mass fraction of 30wt%;

(3) Add 0.5g ammonium persulfate (APS) to 9.5g water and dissolve it completely with ultrasound to obtain a 5wt% APS aqueous solution; add 0.5g sodium bisulfite (NaHSO ₃ ) to 9.5g water and dissolve it completely with ultrasound to obtain 5wt% NaHSO ₃ aqueous solution;

(4) Mix evenly the 25.5032g PVA aqueous solution described in step (1), the mixed aqueous solution of all comonomers described in step (2), the 2.5503g APS aqueous solution described in step (3) and 0.5815g NaHSO ₃ aqueous solution to obtain a reaction aqueous solution ;

(5) After fully replacing the air with argon, the reaction aqueous solution described in step (4) is magnetically stirred for 12 hours at 50°C to obtain a product solution;

(6) Freeze-dry the product solution described in step (5), grind it into fine powder, wash with absolute ethanol, filter and vacuum-dry at 40°C for 11 hours to obtain the polyvinyl alcohol/allyl copolymer. Through network silicon carbon negative electrode water-based binder.

A method of assembling a liquid lithium-ion battery using the polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon negative electrode aqueous binder prepared in Example 3 as a binder, including the following steps:

A. Add 0.5640g SiC400 active material, 0.0090g conductive agent (Super P) and 0.4500g 1wt% carboxymethylcellulose aqueous solution (CMC) into a 2mL cryopreservation tube in sequence, and shake in a small ball mill with a shaking speed of 3600rad/min. 6 minutes to obtain a uniformly mixed silicon-carbon composite;

B. According to the solid content mass ratio of the silicon-carbon composite and the polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon anode aqueous binder is 96.25:3.75, add 0.7500g into the 2mL cryovial A polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon anode aqueous binder with a mass fraction of 3wt% is shaken in a small ball mill with a shaking speed of 3600rad/min for 12 minutes to obtain a uniform silicon-carbon anode slurry;

C. Coat the silicon-carbon negative electrode slurry on the copper foil with a scraper, dry it in a 60°C oven for 24 hours, and then cut the liquid lithium-ion battery silicon-carbon negative electrode sheet with a diameter of 12 mm on a slicer;

D. Based on the above silicon carbon negative electrode sheet of the liquid lithium ion battery, lithium metal is used as the counter electrode, the separator is Celgard's polypropylene separator 2500, and the electrolyte component is LiPF ₆ with a concentration of 1.0M dissolved in a mass ratio of EC:DEC: In the mixed solvent of DMC=1:1:1 (wt%), 10wt% FEC and 2wt% VC were added. Assemble the CR2025 button battery according to the corresponding operations in a glove box that is water-free and filled with argon gas (H ₂ O <0.01ppm, O ₂ <0.01ppm) to obtain a liquid lithium-ion button battery.

The liquid lithium ion button battery prepared in this example was allowed to stand for 24 hours before being used for electrochemical testing. The Newwell CT2001A battery testing system was used to test the cycle and rate performance of the above-assembled liquid lithium-ion button battery at 30°C. The cycle test conditions were: the charge and discharge window was selected between 0.01 and 2V, and the test was performed at a current density of 0.2C. Carry out; the rate test conditions are: the charge and discharge window is selected between 0.01 and 2V, and the test is performed at 0.1C, 0.2C, 0.5C, 1C, and 0.1C current densities for 10 cycles each. The Solartron Analytical electrochemical workstation was used to perform EIS (electrochemical impedance spectroscopy) testing on the above-assembled liquid lithium-ion button battery before cycling. The frequency range during the test was 10 ⁶ HZ ~ 10 ^-2 HZ, and the amplitude was 5mV.

Example 4

The preparation method of polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode water-based binder includes the following steps:

(1) Add 8g PVA1797 to 92g water, heat to 85°C, stir until completely dissolved, and cool to room temperature to obtain a PVA aqueous solution with a mass fraction of 8wt%;

(2) Add 4.0282g (0.096mol) lithium hydroxide monohydrate (LiOH·H ₂ O) to 84.1012g water, dissolve it completely with ultrasound, put it in an ice-water bath and cool it to room temperature, then add 8.6472g (0.12mol) acrylic acid (AA), stir evenly, and after the solution temperature is lower than room temperature again, add 2.1324g (0.03mol) acrylamide (AM) and 6.2175g (0.03mol) 2-acrylamide-2-methylpropanesulfonic acid (AMPS) , ultrasonic until completely dissolved, to obtain a comonomer mixed aqueous solution with a mass fraction of 20wt%;

(3) Add 0.1g ammonium persulfate (APS) to 9.9g water and dissolve it completely with ultrasound to obtain a 1wt% APS aqueous solution; add 0.1g sodium bisulfite (NaHSO ₃ ) to 9.9g water and dissolve it completely with ultrasound to obtain 1wt% NaHSO ₃ aqueous solution;

(4) Mix the 13.1408g PVA aqueous solution described in step (1), the mixed aqueous solution of all comonomers described in step (2), the 2.1025g APS aqueous solution and 0.9588g NaHSO ₃ aqueous solution described in step (3) evenly to obtain a reaction aqueous solution ;

(5) After fully replacing the air with argon, the reaction aqueous solution described in step (4) was magnetically stirred for 24 hours at 40°C to obtain a product solution;

(6) Freeze-dry the product solution described in step (5), grind it into fine powder, wash with absolute ethanol, filter and vacuum-dry at 50°C for 10 hours to obtain the polyvinyl alcohol/allyl copolymer. Through network silicon carbon negative electrode water-based binder.

A method of assembling a liquid lithium-ion battery using the polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon negative electrode aqueous binder prepared in Example 4 as a binder, including the following steps:

A. Add 0.5640g SiC400 active material, 0.0090g conductive agent (Super P) and 0.4500g 1wt% carboxymethyl cellulose aqueous solution (CMC) into a 2mL cryopreservation tube in sequence, and shake in a small ball mill with a shaking speed of 4000rad/min 3 minutes to obtain a uniformly mixed silicon-carbon composite;

B. According to the solid content mass ratio of the silicon-carbon composite and the polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon anode aqueous binder is 96.25:3.75, add 0.7500g into the 2mL cryovial A polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon anode aqueous binder with a mass fraction of 3wt% is shaken in a small ball mill with a shaking speed of 4000rad/min for 12 minutes to obtain a uniform silicon-carbon anode slurry;

C. Coat the silicon-carbon negative electrode slurry on the copper foil with a scraper, dry it in a 60°C oven for 18 hours, and then cut the liquid lithium-ion battery silicon-carbon negative electrode sheet with a diameter of 12 mm on a slicer;

D. Based on the above silicon carbon negative electrode sheet of the liquid lithium ion battery, lithium metal is used as the counter electrode, the separator is Celgard's polypropylene separator 2500, and the electrolyte component is LiPF ₆ with a concentration of 1.0M dissolved in a mass ratio of EC:DEC: In the mixed solvent of DMC=1:1:1 (wt%), 10wt% FEC and 2wt% VC were added. Assemble the CR2025 button battery according to the corresponding operations in a glove box that is water-free and filled with argon gas (H ₂ O <0.01ppm, O ₂ <0.01ppm) to obtain a liquid lithium-ion button battery.

The liquid lithium ion button battery prepared in this example was allowed to stand for 24 hours before being used for electrochemical testing. The Newwell CT2001A battery testing system was used to test the cycle and rate performance of the above-assembled liquid lithium-ion button battery at 30°C. The cycle test conditions were: the charge and discharge window was selected between 0.01 and 2V, and the test was performed at a current density of 0.2C. Carry out; the rate test conditions are: the charge and discharge window is selected between 0.01 and 2V, and the test is performed at 0.1C, 0.2C, 0.5C, 1C, and 0.1C current densities for 10 cycles each. The Solartron Analytical electrochemical workstation was used to perform EIS (electrochemical impedance spectroscopy) testing on the above-assembled liquid lithium-ion button battery before cycling. The frequency range during the test was 10 ⁶ HZ ~ 10 ^-2 HZ, and the amplitude was 5mV.

Example 5

The preparation method of polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode water-based binder includes the following steps:

(1) Add 10g PVA1788 to 90g water, heat to 80°C, stir until completely dissolved, and cool to room temperature to obtain a PVA aqueous solution with a mass fraction of 10wt%;

(2) Add 6.8g (0.17mol) sodium hydroxide (NaOH) to 97.0356g water, dissolve it completely with ultrasound, put it in an ice water bath and cool it to room temperature, then add 14.412g (0.2mol) acrylic acid (AA), and stir evenly , after the solution temperature is lower than room temperature again, add 2.8432g (0.04mol) acrylamide (AM), 8.29g (0.04mol) 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and sonicate until completely dissolved. Obtain a comonomer mixed aqueous solution with a mass fraction of 25wt%;

(3) Add 0.1g ammonium persulfate (APS) to 9.9g water and dissolve it completely with ultrasound to obtain a 1wt% APS aqueous solution; add 0.1g sodium bisulfite (NaHSO ₃ ) to 9.9g water and dissolve it completely with ultrasound to obtain 1wt% NaHSO ₃ aqueous solution;

(4) Mix the 32.3452g PVA aqueous solution described in step (1), the mixed aqueous solution of all comonomers described in step (2), the 6.4690g APS aqueous solution and 1.4749g NaHSO ₃ aqueous solution described in step (3) evenly to obtain a reaction aqueous solution ;

(5) After fully replacing the air with argon, the reaction aqueous solution described in step (4) was magnetically stirred for 18 hours at 40°C to obtain a product solution;

(6) Freeze-dry the product solution described in step (5), grind it into fine powder, wash with absolute ethanol, filter and vacuum-dry at 60°C for 11 hours to obtain the polyvinyl alcohol/allyl copolymer. Through network silicon carbon negative electrode water-based binder.

A method of assembling a liquid lithium-ion battery using the polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon negative electrode aqueous binder prepared in Example 5 as a binder, including the following steps:

A. Add 0.5640g SiC400 active material, 0.0090g conductive agent (Super P) and 0.4500g 1wt% carboxymethyl cellulose aqueous solution (CMC) into a 2mL cryopreservation tube in sequence, and shake in a small ball mill with a shaking speed of 3000rad/min 6 minutes to obtain a uniformly mixed silicon-carbon composite;

B. According to the solid content mass ratio of the silicon-carbon composite and the polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon anode aqueous binder is 96.25:3.75, add 0.7500g into the 2mL cryovial A polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon anode aqueous binder with a mass fraction of 3wt% is shaken in a small ball mill with a shaking speed of 3000rad/min for 15 minutes to obtain a uniform silicon-carbon anode slurry;

C. Coat the silicon-carbon negative electrode slurry on the copper foil with a scraper, dry it in a 60°C oven for 24 hours, and then cut the liquid lithium-ion battery silicon-carbon negative electrode sheet with a diameter of 12 mm on a slicer;

D. Based on the above silicon carbon negative electrode sheet of the liquid lithium ion battery, lithium metal is used as the counter electrode, the separator is Celgard's polypropylene separator 2500, and the electrolyte component is LiPF ₆ with a concentration of 1.0M dissolved in a mass ratio of EC:DEC: In the mixed solvent of DMC=1:1:1 (wt%), 10wt% FEC and 2wt% VC are added. Assemble the CR2025 button battery according to the corresponding operations in a glove box that is water-free and filled with argon gas (H ₂ O <0.01ppm, O ₂ <0.01ppm) to obtain a liquid lithium-ion button battery.

The liquid lithium ion button battery prepared in this example was allowed to stand for 24 hours before being used for electrochemical testing. The Newwell CT2001A battery testing system was used to test the cycle and rate performance of the above-assembled liquid lithium-ion button battery at 30°C. The cycle test conditions were: the charge and discharge window was selected between 0.01 and 2V, and the test was performed at a current density of 0.2C. Carry out; the rate test conditions are: the charge and discharge window is selected between 0.01 and 2V, and the test is performed at 0.1C, 0.2C, 0.5C, 1C, and 0.1C current densities for 10 cycles each. The Solartron Analytical electrochemical workstation was used to perform EIS (electrochemical impedance spectroscopy) testing on the above-assembled liquid lithium-ion button battery before cycling. The frequency range during the test was 10 ⁶ HZ ~ 10 ^-2 HZ, and the amplitude was 5mV.

Example 6

The preparation method of polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode water-based binder includes the following steps:

(1) Add 10g PVA1788 to 90g water, heat to 80°C, stir until completely dissolved, and cool to room temperature to obtain a PVA aqueous solution with a mass fraction of 10wt%;

(2) Add 4.5317g (0.108mol) lithium hydroxide monohydrate (LiOH·H ₂ O) to 56.7282g water, dissolve it completely with ultrasound, put it in an ice-water bath and cool it to room temperature, then add 8.6472g (0.12mol) acrylic acid (AA), stir evenly, and after the solution temperature is lower than room temperature again, add 2.8432g (0.04mol) acrylamide (AM) and 8.29g (0.04mol) 2-acrylamide-2-methylpropanesulfonic acid (AMPS) , ultrasonic until completely dissolved, to obtain a comonomer mixed aqueous solution with a mass fraction of 30wt%;

(3) Add 0.5g ammonium persulfate (APS) to 9.5g water and dissolve it completely with ultrasound to obtain a 5wt% APS aqueous solution; add 0.5g sodium bisulfite (NaHSO ₃ ) to 9.5g water and dissolve it completely with ultrasound to obtain 5wt% NaHSO ₃ aqueous solution;

(4) Mix the 24.3121g PVA aqueous solution described in step (1), the mixed aqueous solution of all comonomers described in step (2), the 0.4862g APS aqueous solution and 0.1109g NaHSO ₃ aqueous solution described in step (3) evenly to obtain a reaction aqueous solution ;

(5) After fully replacing the air with argon, the reaction aqueous solution described in step (4) was magnetically stirred for 24 hours at 40°C to obtain a product solution;

(6) Freeze-dry the product solution described in step (5), grind it into fine powder, wash with absolute ethanol, filter and vacuum-dry at 60°C for 12 hours to obtain the polyvinyl alcohol/allyl copolymer. Through network silicon carbon negative electrode water-based binder.

A method of assembling a liquid lithium-ion battery using the polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon negative electrode aqueous binder prepared in Example 6 as a binder, including the following steps:

A. Add 0.5640g SiC400 active material, 0.0090g conductive agent (Super P) and 0.4500g 1wt% carboxymethylcellulose aqueous solution (CMC) into a 2mL cryopreservation tube in sequence, and shake in a small ball mill with a shaking speed of 3600rad/min. 3 minutes to obtain a uniformly mixed silicon-carbon composite;

B. According to the solid content mass ratio of the silicon-carbon composite and the polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon anode aqueous binder is 96.25:3.75, add 0.7500g into the 2mL cryovial A polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon anode aqueous binder with a mass fraction of 3wt% is shaken in a small ball mill with a shaking speed of 3600rad/min for 12 minutes to obtain a uniform silicon-carbon anode slurry;

C. Coat the silicon-carbon negative electrode slurry on the copper foil with a scraper, dry it in a 60°C oven for 18 hours, and then cut the liquid lithium-ion battery silicon-carbon negative electrode sheet with a diameter of 12 mm on a slicer;

D. Based on the above silicon carbon negative electrode sheet of the liquid lithium ion battery, lithium metal is used as the counter electrode, the separator is Celgard's polypropylene separator 2500, and the electrolyte component is LiPF ₆ with a concentration of 1.0M dissolved in a mass ratio of EC:DEC: In the mixed solvent of DMC=1:1:1 (wt%), 10wt% FEC and 2wt% VC are added. Assemble the CR2025 button battery according to the corresponding operations in a glove box that is water-free and filled with argon gas (H ₂ O <0.01ppm, O ₂ <0.01ppm) to obtain a liquid lithium-ion button battery.

The liquid lithium ion button battery prepared in this example was allowed to stand for 24 hours before being used for electrochemical testing. The Newwell CT2001A battery testing system was used to test the cycle and rate performance of the above-assembled liquid lithium-ion button battery at 30°C. The cycle test conditions were: the charge and discharge window was selected between 0.01 and 2V, and the test was performed at a current density of 0.2C. Carry out; the rate test conditions are: the charge and discharge window is selected between 0.01 and 2V, and the test is performed at 0.1C, 0.2C, 0.5C, 1C, and 0.1C current densities for 10 cycles each. The Solartron Analytical electrochemical workstation was used to perform EIS (electrochemical impedance spectroscopy) testing on the above-assembled liquid lithium-ion button battery before cycling. The frequency range during the test was 10 ⁶ HZ ~ 10 ^-2 HZ, and the amplitude was 5mV.

Comparative example 1

Preparation of liquid lithium-ion batteries using PVA1788 as binder:

(1) Add 10g PVA1788 to 90g water, heat to 80°C, stir until completely dissolved, and cool to room temperature to obtain a PVA aqueous solution with a mass fraction of 10wt%;

(2) Add 0.5640g SiC400 active material, 0.0090g conductive agent (Super P) and 0.4500g 1wt% carboxymethylcellulose aqueous solution (CMC) into a 2mL cryopreservation tube in sequence, and shake in a small ball mill with a shaking speed of 3600rad/min. Slurry for 3 minutes to obtain a uniformly mixed silicon-carbon composite;

(3) According to the solid content mass ratio of the silicon-carbon composite described in step (2) to the PVA aqueous solution described in step (1) is 96.25:3.75, add 0.2250g PVA aqueous solution into the 2mL cryopreservation tube, and shake at a speed of 3600rad/ min. Shake the slurry in a small ball mill for 12 minutes to obtain a uniform silicon carbon negative electrode slurry;

(4) Coat the silicon carbon negative electrode slurry on the copper foil with a scraper, dry it in a 60°C oven for 18 hours, and then cut it on a slicer to cut the liquid lithium ion battery silicon carbon negative electrode sheet with a diameter of 12 mm;

(5) Based on the above silicon carbon negative electrode sheet of the liquid lithium ion battery, lithium metal is used as the counter electrode, the separator is Celgard's polypropylene separator 2500, and the electrolyte component is LiPF ₆ with a concentration of 1.0M dissolved in a mass ratio of EC:DEC :DMC=1:1:1 (wt%) mixed solvent, and add 10wt% FEC and 2wt% VC. Assemble the CR2025 button battery according to the corresponding operations in a glove box that is water-free and filled with argon gas (H2O<0.01ppm, O2<0.01ppm) to obtain a liquid lithium-ion button battery.

The liquid lithium ion button battery prepared in this comparative example was allowed to stand for 24 hours before being used for electrochemical testing. The Newwell CT2001A battery testing system was used to test the cycle and rate performance of the above-assembled liquid lithium-ion button battery at 30°C. The cycle test conditions were: the charge and discharge window was selected between 0.01 and 2V, and the test was performed at a current density of 0.2C. Carry out; the rate test conditions are: the charge and discharge window is selected between 0.01 and 2V, and the test is performed at 0.1C, 0.2C, 0.5C, 1C, and 0.1C current densities for 10 cycles each. The Solartron Analytical electrochemical workstation was used to perform EIS (electrochemical impedance spectroscopy) testing on the above-assembled liquid lithium-ion button battery before cycling. The frequency range during the test was 10 ⁶ HZ ~ 10 ^-2 HZ, and the amplitude was 5mV.

Comparative example 2

Preparation of liquid lithium-ion batteries using allyl copolymers as binders:

(1) Add 3.3568g (0.08mol) lithium hydroxide monohydrate (LiOH·H ₂ O) to 153.5832g water, dissolve it completely with ultrasound, put it in an ice-water bath and cool it to room temperature, then add 7.206g (0.1mol) acrylic acid (AA), stir evenly, and after the solution temperature is lower than room temperature again, add 7.108g (0.1mol) acrylamide (AM) and 20.725g (0.1mol) 2-acrylamide-2-methylpropanesulfonic acid (AMPS) , ultrasonic until completely dissolved, to obtain a comonomer mixed aqueous solution with a mass fraction of 20wt%;

(2) Add 0.1g ammonium persulfate (APS) to 9.9g water and dissolve it completely with ultrasound to obtain a 1wt% APS aqueous solution; add 0.1g sodium bisulfite (NaHSO ₃ ) to 9.9g water and dissolve it completely with ultrasound to obtain 1wt% NaHSO ₃ aqueous solution;

(3) Mix all comonomer mixed aqueous solutions described in step (1), 3.8396g APS aqueous solution and 0.8754g NaHSO ₃ aqueous solution described in step (2) evenly to obtain a reaction aqueous solution;

(4) After fully replacing the air with argon, the reaction aqueous solution described in step (3) was magnetically stirred for 24 hours at 40°C to obtain a product solution;

(5) Freeze-dry the product solution described in step (4), grind it into fine powder, wash with absolute ethanol, filter and vacuum-dry at 60°C for 12 hours to obtain the allyl copolymer binder.

The method of assembling a liquid lithium-ion battery using the allyl copolymer binder prepared in Comparative Example 2 as a binder includes the following steps:

A. Add 0.5640g SiC400 active material, 0.0090g conductive agent (Super P) and 0.4500g 1wt% carboxymethyl cellulose aqueous solution (CMC) into a 2mL cryopreservation tube in sequence, and shake in a small ball mill with a shaking speed of 3000rad/min 3 minutes to obtain a uniformly mixed silicon-carbon composite;

B. According to the solid content mass ratio of the silicon-carbon composite and the polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon anode aqueous binder is 96.25:3.75, add 0.7500g into the 2mL cryovial The allyl copolymer binder with a mass fraction of 3wt% is shaken in a small ball mill with a shaking speed of 3000rad/min for 15 minutes to obtain a uniform silicon carbon negative electrode slurry;

C. Coat the silicon-carbon negative electrode slurry on the copper foil with a scraper, dry it in a 60°C oven for 12 hours, and then cut the liquid lithium-ion battery silicon-carbon negative electrode sheet with a diameter of 12 mm on a slicer;

D. Based on the above silicon carbon negative electrode sheet of the liquid lithium ion battery, lithium metal is used as the counter electrode, the separator is Celgard's polypropylene separator 2500, and the electrolyte component is LiPF ₆ with a concentration of 1.0M dissolved in a mass ratio of EC:DEC: In the mixed solvent of DMC=1:1:1 (wt%), 10wt% FEC and 2wt% VC were added. Assemble the CR2025 button battery according to the corresponding operations in a glove box that is water-free and filled with argon gas (H ₂ O <0.01ppm, O ₂ <0.01ppm) to obtain a liquid lithium-ion button battery.

The liquid lithium ion button battery prepared in this comparative example was allowed to stand for 24 hours before being used for electrochemical testing. The Newwell CT2001A battery testing system was used to test the cycle and rate performance of the above-assembled liquid lithium-ion button battery at 30°C. The cycle test conditions were: the charge and discharge window was selected between 0.01 and 2V, and the test was performed at a current density of 0.2C. Carry out; the rate test conditions are: the charge and discharge window is selected between 0.01 and 2V, and the test is performed at 0.1C, 0.2C, 0.5C, 1C, and 0.1C current densities for 10 cycles each. The Solartron Analytical electrochemical workstation was used to perform EIS (electrochemical impedance spectroscopy) testing on the above-assembled liquid lithium-ion button battery before cycling. The frequency range during the test was 10 ⁶ HZ ~ 10 ^-2 HZ, and the amplitude was 5mV.

Effectiveness analysis

Use the peel force testing device as shown in Figure 1 to test the adhesives described in Examples 1, 2, 3, 4, 5, 6, Comparative Example 1 and Comparative Example 2 respectively. The prepared silicon carbon negative electrode piece was subjected to a 180° peeling test, and the effective width of the test was 1.9cm. The results are shown in Figure 2a, Figure 2b, and Figure 2c. It can be seen from Figure 2a and Figure 2b that the peeling strength of the silicon carbon negative electrode sheet using the binder (allyl copolymer) described in Comparative Example 2 is lower than that of the binder (PVA1788) described in Example 1. The peel strength of the silicon-carbon negative electrode sheet is because polyvinyl alcohol itself has very strong binding ability as a binder. The peeling force of the silicon carbon negative electrode sheet using the binder described in Examples 3, 4, 5 and 6 is higher than the peeling force of the silicon carbon negative electrode sheet using the binder described in the Comparative Example. . As can be seen from Figure 2c, the average peeling force of the silicon carbon negative electrode sheet using the binder described in Example 6 is 3.44N/cm, which is almost the same as that using the binder (allyl copolymer) described in Comparative Example 2. ) is 2 times the average peeling force (1.83N/cm) of the silicon-carbon negative electrode sheet, which shows that the polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon negative electrode water-based binder prepared in the example, due to the molecular chain The hydrogen bond cross-linking and the presence of numerous polar functional groups further improve its bonding ability. This enables the binder to tightly bond the active material and conductive agent to the current collector during the battery cycle, ensuring the stability of the electrode structure and improving the long-term cycle stability of the battery. The silicon-carbon negative electrode pieces made of the binders described in other embodiments also have strong peeling force, see Figure 2a, Figure 2b and Figure 2c.

Figure 3a shows the liquid lithium ion battery prepared using the binder described in Example 2, Example 3, Example 6, Comparative Example 1 and Comparative Example 2 after activation for 3 cycles at 0.05C, when the SOC is 50%. AC impedance diagram. The AC impedance curve consists of two semicircular arcs and an oblique straight line. The intersection of the first semicircular arc and the x-axis corresponds to the ohmic impedance (R _s ). The diameter of the first semicircle corresponds to the SEI film impedance (R _SEI ). The diameter of a semicircle corresponds to the charge transfer resistance (R _ct ). Figure 3b shows the liquid lithium ion battery prepared using the binder described in Example 2, Example 3, Example 6, Comparative Example 1 and Comparative Example 2 after activation at 0.05C for 3 cycles, when the SOC is 50%. Plot of actual impedance values. It can be seen from the figure that the SEI film resistance and charge transfer resistance of the liquid lithium ion battery prepared using the binder described in the Example are lower than that of the liquid lithium ion battery prepared using the binder described in the Comparative Example. This is It illustrates that the polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon anode aqueous binder in the embodiment can maintain the integrity of the silicon-carbon anode structure, interpenetrating network structure and sulfonic acid groups during battery cycling. (-SO ₃ ) contributes to the transport of lithium ions, reducing the impedance of the battery and thus speeding up the electrochemical reaction of the battery. The binders described in other embodiments can also maintain the integrity of the silicon-carbon negative electrode structure during battery cycling, and their structural characteristics contribute to the transport of lithium ions. For details, see Figure 3a and Figure 3b.

Figure 4 shows the liquid lithium ion battery prepared using the binder described in Example 1, Example 3, Example 4, Example 6, Comparative Example 1 and Comparative Example 2 after being activated for 3 cycles at 0.05C. Rate performance data chart of 10 cycles at 0.1C, 0.2C, 0.5C, 1C and 0.1C. It can be found from Figure 4 that the discharge specific capacity of the liquid lithium-ion battery prepared using the binder described in Example 1, Example 3, Example 4, and Example 6 is higher than that of Comparative Example 1 and Comparative Example 2. The discharge specific capacity of the liquid lithium ion battery made with the binder, especially the rate performance of the liquid lithium ion battery made with the binder described in the embodiment under high current density (0.5C, 1C) conditions The performance is excellent, which shows that the polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon anode aqueous binder in the embodiment can effectively reduce the impact of the silicon-carbon anode volume expansion problem on battery performance, thereby increasing the battery rate. performance. Liquid lithium-ion batteries made with the binders described in other embodiments also have excellent rate performance. Please refer to Figure 4 for details.

Figure 5 is a specific capacity-voltage diagram of the liquid lithium ion battery prepared using the binder described in Example 2, Example 3 and Comparative Example 2 when charged and discharged under 1C conditions. As can be seen from Figure 5, the liquid lithium-ion batteries prepared using the binders described in Example 2 and Example 3 have discharge specific capacities of 216.45mAh/g and 260mAh/g respectively under 1C conditions, which are much higher than The discharge specific capacity of the liquid lithium-ion battery prepared using the binder described in Comparative Example 2 is 91.11 mAh/g, which illustrates that the polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode water-based binder in the example , under high current density, it can effectively suppress the expansion of the silicon-carbon negative electrode and maintain the integrity of the electrode structure, thereby maintaining a high specific capacity of the battery. Liquid lithium-ion batteries made with the binders described in other embodiments also have higher specific discharge capacity at 1C. Please refer to Figure 5 for details.

Figure 6 is the cycle curve of liquid lithium ion batteries prepared using the binders described in Example 2, Example 3, Example 4, Example 5, Example 6, Comparative Example 1 and Comparative Example 2 at 0.2C. and Coulomb efficiency plot. As can be seen from Figure 6, the first charge specific capacity of the liquid lithium-ion battery prepared with the binder described in Examples 2, 3, 4, 5, and 6 (respectively 400.1322mAh/g, 388.1998mAh /g, 395.7251mAh/g, 388.4452mAh/g, 390.8396mAh/g) are all higher than the first charge specific capacity of the liquid lithium-ion battery prepared by the binder described in Comparative Example 1 and Comparative Example 2 (respectively 380.7542mAh/g). g, 375.0647mAh/g). After 80 cycles at 0.2C, the liquid lithium-ion battery prepared with the binder described in Example 6 has a charge specific capacity of 372.3827mAh/g, a capacity retention rate of 95.28%, and a Coulombic efficiency of 99.7%, which further supports The polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode aqueous binder prepared in the example has strong adhesive force, can firmly bond the silicon carbon active material and the conductive agent to the current collector, and is very It can well adapt to the huge volume changes that occur in the active material, thus improving the cycle life of the battery.

In summary, the polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon anode aqueous binder prepared in the above examples has excellent bonding strength compared with the adhesive prepared in the comparative example. And its good ability to promote lithium ion transmission enables the binder to adapt well to the huge volume changes that occur in the active material, tightly bonding the silicon carbon active material and conductive agent to the current collector to prevent the slurry from falling off. Therefore, compared with the polyvinyl alcohol binder of Comparative Example 1 and the allyl copolymer binder of Comparative Example 2, the polyvinyl alcohol/allyl copolymer interpenetrating network based on the embodiments of the present invention The specific capacity, Coulombic efficiency, rate performance and long-term cycle stability of liquid lithium-ion batteries using silicon-carbon negative electrode aqueous binders have been greatly improved.

The above embodiments are only preferred embodiments of the present invention and are only used to explain the present invention rather than limit the present invention. Changes, substitutions, modifications, etc. made by those skilled in the art without departing from the spirit and essence of the present invention shall all belong to this invention. protection scope of the invention.

Claims (10)

1. A method for preparing a polyvinyl alcohol/allyl copolymer interpenetrating network silicon-carbon anode aqueous binder, which is characterized by comprising the following steps: (1) Add polyvinyl alcohol (PVA) to water, heat and stir until completely dissolved, and cool to room temperature to obtain a PVA aqueous solution; (2) Add the alkaline substance to water, dissolve it completely with ultrasound, put it in an ice-water bath and cool it to room temperature, then add acrylic acid, stir evenly, and when the solution temperature is lower than room temperature again, add acrylamide and 2-acrylamide-2- Methylpropanesulfonic acid, ultrasonic until completely dissolved, to obtain a comonomer mixed aqueous solution; the comonomer includes alkaline substances, acrylic acid, acrylamide and 2-acrylamide-2-methylpropanesulfonic acid; (3) Add ammonium persulfate (APS) to water and dissolve it completely with ultrasound to obtain an APS aqueous solution; add sodium bisulfite (NaHSO ₃ ) to water and dissolve it completely with ultrasound to obtain a NaHSO ₃ aqueous solution; (4) Mix the PVA aqueous solution described in step (1), the comonomer mixed aqueous solution described in step (2), the APS aqueous solution and NaHSO ₃ aqueous solution described in step (3) evenly to obtain a reaction aqueous solution; (5) After fully replacing the air with argon, the reaction aqueous solution in step (4) is magnetically stirred under heating conditions to obtain a product solution; (6) Freeze-dry the product solution described in step (5), grind it into fine powder, wash with absolute ethanol, filter and dry under vacuum to obtain the polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode Water-based adhesive. 2. The preparation method of polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode aqueous binder according to claim 1, characterized in that the polyvinyl alcohol in step (1) is PVA1788 type or PVA1797 type; the concentration of the PVA aqueous solution in step (1) is 5 to 10 wt%; the heating temperature in step (1) is 80 to 90°C. 3. The preparation method of polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode aqueous binder according to claim 1, characterized in that the alkaline substance in step (2) is sodium hydroxide, Potassium hydroxide or lithium hydroxide monohydrate; the concentration of the comonomer mixed aqueous solution in step (2) is 20wt%~30wt%; the molar ratio of the alkaline substance and acrylic acid in step (2) is 80~90:100 ; The molar ratio of acrylic acid, acrylamide, and 2-acrylamide-2-methylpropanesulfonic acid in step (2) is 1 to 5:1:1. 4. The preparation method of polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode aqueous binder according to claim 1, characterized in that the concentration of the APS aqueous solution in step (3) is 1 to 5wt %; the concentration of the NaHSO ₃ aqueous solution in step (3) is 1 to 5 wt%. 5. The preparation method of polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode aqueous binder according to claim 1, characterized in that the molar ratio of APS and _NaHSO in step (4) is 1 ~2:1; the mass ratio of the comonomer in the mixed aqueous solution of APS and comonomer in step (4) is 0.1~0.5:100; the mass ratio of the comonomer in the mixed aqueous solution of PVA and comonomer in step (4) The mass ratio is 5~20:100. 6. The method for preparing the polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode aqueous binder according to claim 1, characterized in that the heating temperature in step (5) is 30 to 50°C. ; The reaction time in step (5) is 12 to 24h. 7. The preparation method of polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode aqueous binder according to claim 1, characterized in that the vacuum drying temperature in step (6) is 40 to 60 ℃; the vacuum drying time in step (6) is 10 to 12 hours. 8. A polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode aqueous binder prepared by the preparation method according to any one of claims 1 to 7. 9. Application of the polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode aqueous binder according to claim 8 in the preparation of liquid lithium ion battery silicon carbon negative electrodes. 10. Application of the polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode aqueous binder according to claim 9 in the preparation of liquid lithium ion battery silicon carbon negative electrode, characterized in that the liquid lithium ion Battery silicon carbon negative electrode, including: silicon carbon composite and polyvinyl alcohol/allyl copolymer interpenetrating network silicon carbon negative electrode water-based binder; the silicon carbon composite is silicon carbon active material, conductive agent SuperP and carboxymethyl A mixture of cellulose aqueous solutions.