A carbon-compatible binder for silicon-carbon anodes of lithium-ion batteries and its preparation method and application

Abstract

The application belongs to the technical field of lithium ion batteries, and discloses a carbon-compatible binder for a silicon-carbon negative electrode of a lithium ion battery, a preparation method and application thereof, wherein the carbon-compatible binder is abbreviated as CMC-Py, sodium carboxymethyl cellulose is dissolved in a phosphate buffer solution, then N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl) carbodiimide are added to activate the carboxyl group of the sodium carboxymethyl cellulose, finally, 1-pyrenemethylamine hydrochloride is added, and the reaction is carried out under stirring and N2 at room temperature to obtain the binder. The binder is prepared by the amidation reaction of sodium carboxymethyl cellulose as a main chain and 1-pyrenemethylamine hydrochloride, the pyrene group introduced can form a pi-pi conjugated system with graphite in the silicon-carbon material, the interface compatibility of the binder and the silicon-carbon material can be effectively improved, the dispersibility and the adhesion of the silicon-carbon material can be enhanced, and the electrochemical performance of the silicon-carbon negative electrode of the lithium ion battery is significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a carbon-compatible binder for silicon-carbon anodes of lithium-ion batteries, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries, due to their advantages such as high energy density, high operating voltage, low self-discharge rate, and no memory effect, are now widely used in commercial products, such as mobile phones, laptops, digital cameras, and new energy vehicles. In the application of lithium-ion battery anode materials, silicon is favored due to its very high theoretical specific capacity (4200 mAh g⁻¹). -1 This is far higher than the theoretical specific capacity of commercial graphite (372 mAh g⁻¹). -1 Silicon-carbon (SiC) is considered the most promising next-generation anode material. However, silicon undergoes significant volume changes during lithium insertion / extraction, severely hindering its commercialization. Compared to silicon, SiC offers better cycle performance and higher coulombic efficiency, making it a hot topic in the commercialization of silicon-based materials. However, SiC still suffers from substantial volume changes, resulting in poor cycle stability and rate performance of batteries.

[0003] Currently, the main methods to address the volume change problem of silicon-carbon anodes include nano-sizing, composite manufacturing, and structuring. However, these methods involve complex synthesis steps and are costly, making commercialization difficult. In contrast, improving the performance of silicon-carbon anodes by modifying binders is more economical and effective. Although binders account for a small proportion of electrode materials, typically less than 10%, they are an extremely important component in the structure of lithium-ion battery electrodes, significantly impacting battery performance. Commonly used anode binders such as PAA and CMC / SBR struggle to uniformly disperse silicon-carbon materials during slurry preparation. This is primarily because silicon-carbon materials have a relatively complex structure and contain a significant amount of carbon, while these conventional binders lack carbophilic groups, leading to interfacial incompatibility with carbon and causing electrode powder shedding. Therefore, conventional binders are currently unsuitable for silicon-carbon anodes. Summary of the Invention

[0004] In view of the problems existing in the above-mentioned background technology, the present invention provides a carbon compatible binder for silicon-carbon anodes of lithium-ion batteries.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned carbon-compatible binder for silicon-carbon anodes of lithium-ion batteries.

[0006] Another object of the present invention is to provide the application of the above-mentioned carbon-compatible binder.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A carbon-compatible binder for silicon-carbon anodes in lithium-ion batteries, abbreviated as CMC-Py, is prepared by dissolving sodium carboxymethyl cellulose in a phosphate buffer solution, then adding N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide to activate the carboxyl groups of sodium carboxymethyl cellulose, and finally adding 1-pyrene methylamine hydrochloride, followed by stirring with N2 at room temperature.

[0009] Preferably, the molar ratio of 1-pyrene methylamine hydrochloride in the sodium carboxymethyl cellulose and 1-pyrene methylamine hydrochloride solution is (2-4):1; the concentration of the 1-pyrene methylamine hydrochloride solution is 0.01-0.04 g / mL; the sodium carboxymethyl cellulose is 1-2 wt% of the phosphate buffer solution; and the molar ratio of the sodium carboxymethyl cellulose to the total molar ratio of N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide is (1-2):1.

[0010] Preferably, the pH of the phosphate buffer solution is 5-6, and the reaction time is 6-12 hours.

[0011] Preferably, the mass ratio of N-hydroxysuccinimide to 1-ethyl-(3-dimethylaminopropyl)carbodiimide is 1:1.

[0012] The method for preparing the carbon-compatible binder for silicon-carbon anodes in lithium-ion batteries includes the following steps:

[0013] S1. Dissolve sodium carboxymethyl cellulose in phosphate buffer solution, and then add N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide to activate the carboxyl group of sodium carboxymethyl cellulose;

[0014] S2. Then, 1-pyrene methylamine hydrochloride is added to step S1, and the mixture is stirred and reacted with N2 at room temperature to obtain a carbon-compatible binder.

[0015] One type of negative electrode is prepared by mixing active material silicon carbon, conductive agent and carbon compatible binder, dissolving in deionized water, coating the mixture evenly on copper foil, and then drying under vacuum.

[0016] Preferably, the conductive agent is one or more of conductive carbon black, carbon nanotubes, highly conductive carbon black, or conductive graphite; the mass ratio of the active material silicon carbon, the conductive agent, and the carbon-compatible binder is (7-8):(1-2):1; the vacuum drying temperature is 60-100℃, and the vacuum drying time is 10-16h.

[0017] The application of the negative electrode in lithium-ion batteries.

[0018] Preferably, the negative electrode material of the lithium-ion battery is a silicon-carbon composite material.

[0019] This invention utilizes sodium carboxymethyl cellulose as the main chain and undergoes an amidation reaction with 1-pyrene methylamine hydrochloride to synthesize a carbon-compatible binder. Sodium carboxymethyl cellulose is a carboxymethylated derivative of cellulose and is the most important ionic cellulose adhesive. Sodium carboxymethyl cellulose is typically an anionic polymer compound obtained by reacting natural cellulose with caustic alkali and monochloroacetic acid, with molecular weights ranging from several thousand to millions. Sodium carboxymethyl cellulose is a white fibrous or granular powder, odorless, tasteless, hygroscopic, and easily dispersed in water to form a transparent colloidal solution. The pyrene groups in this binder can form π-π conjugations with graphite in silicon-carbon materials, effectively improving the interfacial compatibility between the binder and silicon-carbon materials, enhancing the dispersibility and adhesion of the binder to silicon-carbon materials, thereby significantly improving the electrochemical performance of silicon-carbon anodes in lithium-ion batteries.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The carbon-compatible binder CMC-Py of the present invention is a binder with good interfacial compatibility between graphite and silicon anode materials. It is prepared by amidation reaction of sodium carboxymethyl cellulose as the main chain with 1-pyrene methylamine hydrochloride. It has good interfacial compatibility with graphite, conductive carbon black and silicon materials. This is because sodium carboxymethyl cellulose contains a large number of hydroxyl groups, which can form hydrogen bonds with oxygen-containing functional groups on the silicon surface. At the same time, the introduced pyrene group contains a large number of benzene ring functional groups, which are similar to the structure of graphite and can form π-π conjugation.

[0022] 2. The CMC-Py carbon compatible binder prepared in this invention is an aqueous binder, which has the advantages of being easily soluble in water, having good dispersibility and strong adhesion to silicon-carbon materials. It can effectively improve the interfacial compatibility between the binder and silicon-carbon materials, and enhance the dispersibility and adhesion to silicon-carbon materials. At the same time, it has electrochemical stability, which is beneficial to improving the long-cycle stability of silicon-carbon anodes in lithium-ion batteries, and significantly improving the electrochemical performance of silicon-carbon anodes in lithium-ion batteries.

[0023] 3. The present invention has the advantages of simple synthesis process, low cost and environmental friendliness, which makes it easy to apply. Attached Figure Description

[0024] Figure 1 Cycling performance of the CR2032 coin cell assembled for Example 1 at a current density of 0.3C.

[0025] Figure 2 The cycle performance of the CR2032 coin cells assembled in Example 1 and Comparative Example 1 is shown. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments, but these should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0027] Example 1

[0028] 0.5 g of sodium carboxymethyl cellulose (CMC) was dissolved in 50 mL of phosphate buffer solution (PBS, pH 5.0), and then 0.0594 g of N-hydroxysuccinimide and 0.099 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide were added to activate the carboxyl group of sodium carboxymethyl cellulose. After 30 min, 1-pyrene methylamine hydrochloride solution (0.138 g of 1-pyrene methylamine hydrochloride dissolved in 10 mL of methanol) was added dropwise. The mixture was stirred under N2 at room temperature for 9 h, then washed with ethanol to precipitate the product. The precipitate was filtered and lyophilized for 12 h to obtain carboxymethyl cellulose grafted pyrene powder, abbreviated as CMC-Py.

[0029] 2. Dissolve CMC-Py powder in deionized water to prepare a 5wt% CMC-Py aqueous solution.

[0030] 3. The active material silicon carbon, the conductive agent SuperP and 5wt% CMC-Py aqueous solution are mixed at a mass ratio of 8:1:1. After adding 500μL of deionized water, the mixture is stirred in a degassing mixer to obtain a uniformly dispersed electrode slurry. The electrode slurry is coated onto copper foil and dried under vacuum at 80℃ for 12h. The slurry is then cut into circular negative electrode sheets with a diameter of 14mm.

[0031] 4. Transfer the dried negative electrode sheet into a glove box filled with argon gas, using a lithium sheet as the counter electrode, and the electrolyte solution at 1 mol / L. -1 Using LiPF6 as the solute, ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1 as solvents, and 10 wt% fluoroethylene carbonate (FEC) and 1 wt% ethylene carbonate (VC) as additives, a CR2032 coin cell, abbreviated as SiC950@CMC-Py, was assembled.

[0032] Figure 1 The cycling performance of the CR2032 coin cell prepared in Example 1 at a current density of 0.3C. From Figure 1 As can be seen from the data, the CR2032 coin cell composed of carbon-compatible binder CMC-Py has an initial discharge specific capacity of 1000 mAh g at a current density of 0.3C. -1 The initial coulombic efficiency is above 80%, and the capacity remains at 672 mAh g after 200 cycles. -1 It exhibits good cycle performance.

[0033] Example 2

[0034] 1. Dissolve 0.5 g of sodium carboxymethyl cellulose (CMC) in 50 mL of phosphate buffer solution (PBS, pH = 5.0), then add 0.0594 g of N-hydroxysuccinimide and 0.099 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide to activate the carboxyl group of sodium carboxymethyl cellulose. After 30 min, add dropwise 1-pyrene methylamine hydrochloride solution (0.276 g of 1-pyrene methylamine hydrochloride dissolved in 10 mL of methanol), stir under N2 at room temperature for 9 h, then wash with ethanol to precipitate the product, filter, and freeze-dry for 12 h to obtain carboxymethyl cellulose grafted pyrene powder, abbreviated as CMC-Py.

[0035] 2. Dissolve CMC-Py powder in deionized water to prepare a 5wt% CMC-Py aqueous solution.

[0036] 3. The active material silicon carbon, the conductive agent SuperP and 5wt% CMC-Py aqueous solution are mixed at a mass ratio of 8:1:1. After adding 500μL of deionized water, the mixture is stirred in a degassing mixer to obtain a uniformly dispersed electrode slurry. The electrode slurry is coated onto copper foil and dried under vacuum at 80℃ for 12h. The slurry is then cut into circular negative electrode sheets with a diameter of 14mm.

[0037] 4. Transfer the dried negative electrode sheet into a glove box filled with argon gas, using a lithium sheet as the counter electrode, and the electrolyte solution at 1 mol / L. -1 Using LiPF6 as the solute, ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1 as solvents, and 10 wt% fluoroethylene carbonate (FEC) and 1 wt% ethylene carbonate (VC) as additives, a CR2032 coin cell was assembled.

[0038] Comparative Example 1

[0039] 1. Dissolve sodium carboxymethyl cellulose powder in deionized water to prepare a 5 wt% sodium carboxymethyl cellulose aqueous solution.

[0040] 2. The active material silicon carbon, the conductive agent SuperP and 5wt% sodium carboxymethyl cellulose aqueous solution are mixed at a mass ratio of 8:1:1. After adding 500μL of deionized water, the mixture is stirred in a degassing mixer to obtain a uniformly dispersed electrode slurry. The electrode slurry is coated onto copper foil and dried under vacuum at 80℃ for 12h. The slurry is then cut into circular negative electrode sheets with a diameter of 14mm.

[0041] 3. Transfer the dried negative electrode sheet into a glove box filled with argon gas, using a lithium sheet as the counter electrode, and the electrolyte solution at 1 mol / L. -1Using LiPF6 as the solute, ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1 as solvents, and 10 wt% fluoroethylene carbonate (FEC) and 1 wt% ethylene carbonate (VC) as additives, a CR2032 coin cell, abbreviated as SiC950@CMC, was assembled.

[0042] The electrochemical performance of the CR2032 coin cells assembled in Example 1 and Comparative Example 1 after standing at 28°C for 10 hours was compared. The constant current charge-discharge test conditions in the Xinwei testing system were: current density 0.3C (1C = 950 mAg). -1 Voltage window: 0.1–1.5V. Figure 2 The cycle performance of the CR2032 coin cells assembled in Example 1 and Comparative Example 1 is shown. Figure 2 The data shows that the CR2032 coin cell assembled in Comparative Example 1 exhibits a capacity degradation to approximately 677 mAg after 100 cycles at a current density of 0.3C. -1 The CR2032 coin cell assembled in Example 1 still maintains a capacity of 744 mAg. -1 It exhibits higher discharge capacity and better cycle stability. Therefore, the carbon-compatible binder CMC-Py can enable silicon-carbon anodes to exhibit good cycle stability.

[0043] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A carbon-compatible binder for silicon-carbon anodes in lithium-ion batteries, characterized in that, The carbon-compatible binder, abbreviated as CMC-Py, is prepared by dissolving sodium carboxymethyl cellulose in a phosphate buffer solution, then adding N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide to activate the carboxyl groups of sodium carboxymethyl cellulose, and finally adding 1-pyrene methylamine hydrochloride solution, followed by stirring with N2 at room temperature.

2. The carbon-compatible binder for silicon-carbon anodes in lithium-ion batteries according to claim 1, characterized in that, The molar ratio of 1-pyrene methylamine hydrochloride in the sodium carboxymethyl cellulose and 1-pyrene methylamine hydrochloride solution is (2~4):1; the concentration of the 1-pyrene methylamine hydrochloride solution is 0.01~0.04 g / mL; the sodium carboxymethyl cellulose is 1~2 wt% of the phosphate buffer solution; the molar ratio of the sodium carboxymethyl cellulose to the total molar ratio of N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide is (1~2):

1.

3. The carbon-compatible binder for silicon-carbon anodes in lithium-ion batteries according to claim 1, characterized in that, The pH of the phosphate buffer solution is 5-6, and the reaction time is 6-12 h.

4. The carbon-compatible binder for silicon-carbon anodes in lithium-ion batteries according to claim 1, characterized in that, The mass ratio of N-hydroxysuccinimide to 1-ethyl-(3-dimethylaminopropyl)carbodiimide is 1:

1.

5. The method for preparing a carbon-compatible binder for a silicon-carbon anode in a lithium-ion battery according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Dissolve sodium carboxymethyl cellulose in phosphate buffer solution, and then add N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide to activate the carboxyl group of sodium carboxymethyl cellulose; S2. Then, 1-pyrene methylamine hydrochloride is added to step S1, and the mixture is stirred with N2 at room temperature to obtain a carbon-compatible binder.

6. A negative electrode, characterized in that, The negative electrode is prepared by mixing the active material silicon carbon, the conductive agent and the carbon compatible binder according to any one of claims 1-4, dissolving them in deionized water, coating the mixture evenly on a copper foil, and then drying it under vacuum.

7. The negative electrode according to claim 6, characterized in that, The conductive agent is one or more of conductive carbon black, carbon nanotubes, highly conductive carbon black, or conductive graphite; the mass ratio of the active material silicon carbon, the conductive agent, and the carbon-compatible binder is (7~8):(1~2):1; the vacuum drying temperature is 60~100 ℃, and the vacuum drying time is 10~16 h.

8. The application of the negative electrode according to claim 6 or 7 in a lithium-ion battery.

9. The application of the negative electrode according to claim 8 in a lithium-ion battery, characterized in that, The negative electrode material of the lithium-ion battery is a silicon-carbon composite material.

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