An amphiphilic binder for silicon-carbon anodes in lithium-ion batteries, its preparation method and application.

Abstract

This invention belongs to the field of lithium battery technology and discloses an amphiphilic binder for silicon-carbon anodes in lithium-ion batteries, its preparation method, and its application. The amphiphilic binder, abbreviated as PDB, is prepared by dissolving levodopa in water, adding polyacrylic acid powder, 1-pyrene methylamino hydrochloride, and a catalyst, reacting at 50-80°C, and then dialyzing. This binder uses polyacrylic acid as the main chain and undergoes an amidation reaction with levodopa and 1-pyrene methylamino hydrochloride to synthesize an amphiphilic binder. This amphiphilic binder has advantages such as easy solubility in water, good dispersibility to silicon-carbon materials, and strong adhesion. The binder can effectively protect the active materials from the influence of the electrolyte and reduce the formation of a large amount of SEI film. The binder prepared by this method significantly improves the electrochemical performance of silicon-carbon anodes in lithium-ion batteries. Furthermore, the preparation process of this binder is simple, low-cost, and easy to apply.

Description

Technical Field

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

[0002] Lithium-ion batteries possess advantages such as high capacity, no memory effect, rapid reversible charge and discharge, and high coulombic efficiency. They are currently widely used in commercial products such as mobile phones, laptops, digital cameras, and new energy vehicles. In the application of anode materials for lithium-ion batteries, silicon is considered the most promising next-generation anode material, with a theoretical capacity as high as 4200 mAh / g, far exceeding the 372 mAh / g capacity of commercial graphite. However, the huge volume change (approximately 300%) and low initial coulombic efficiency of silicon-based anode materials severely hinder their commercialization. Silicon-carbon materials, with better cycle performance and higher coulombic efficiency, are currently the focus of silicon-based material commercialization; however, silicon-carbon materials still suffer from some volume expansion, resulting in poor long-cycle stability and rate performance.

[0003] Currently, the main methods to address the volume expansion problem of silicon-carbon anodes include nano-sizing and structuring. However, these methods are difficult to commercialize due to their complex synthesis processes, cumbersome steps, and high costs. Research indicates that optimizing binders is one of the most economical and effective methods to solve the volume expansion problem of silicon-carbon anodes. The main functions of anode binders are: to bond the anode material and the current collector, thereby stabilizing the structure; and to act as a dispersant during the preparation of the anode slurry, reducing material agglomeration. Due to the complexity of silicon-carbon materials, commonly used anode binders (CMC and SBR) are difficult to disperse during the slurry preparation process. Furthermore, their poor affinity results in weak adhesion between the material and the copper foil, leading to easy powder shedding. Therefore, currently commercially available binders are not suitable for silicon-carbon anodes. In recent years, researchers have made significant efforts in designing and preparing silicon-carbon binders, synthesizing high-performance composite binders to improve the electrochemical performance of silicon-carbon anodes. Summary of the Invention

[0004] In order to overcome the shortcomings and disadvantages of the prior art, the primary objective of this invention is to provide an amphiphilic binder for silicon-carbon anodes in lithium-ion batteries.

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

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

[0008] An amphiphilic binder for silicon-carbon anodes in lithium-ion batteries, abbreviated as PDB, is prepared by dissolving levodopamine in water, adding polyacrylic acid powder, 1-pyrene methylamino hydrochloride and a catalyst, reacting at 50-80°C, and then dialyzing.

[0009] Preferably, the mass ratio of L-dopamine, 1-pyrene methylhydrochloride and polyacrylic acid is 1:(0.5-1):(8-10); and the mass ratio of L-dopamine and water is 1:(180-190).

[0010] Preferably, the polyacrylic acid powder has a molecular weight of 240,000 to 5,000,000.

[0011] Preferably, the reaction time is 6 to 36 hours; the dialysis time is 12 to 36 hours.

[0012] Preferably, the catalyst is 1-ethyl-(3-dimethylaminopropyl)carbodiimide.

[0013] The method for preparing the amphiphilic binder for silicon-carbon anodes in lithium-ion batteries includes the following steps:

[0014] S1. Dissolve levodopa in water, then add polyacrylic acid powder and 1-pyrene methylamino hydrochloride to obtain a mixed solution;

[0015] S2. Add a catalyst to the mixed solution and react at 50-80℃. After the reaction is complete, dialyze the solution with a dialysis bag to obtain the amphiphilic binder.

[0016] A negative electrode is prepared by mixing an active material silicon carbon, a conductive agent and an amphiphilic binder as described in any one of claims 1-5, adding deionized water and stirring to obtain a uniformly dispersed electrode slurry, coating the electrode slurry onto a copper foil and drying it under vacuum.

[0017] Preferably, the conductive agent is 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 amphiphilic binder is (7-8):(1-2):1; the stirring time is 6-8 hours; the vacuum drying temperature is 70-80°C; and the vacuum drying time is 12-36 hours.

[0018] The application of the aforementioned amphiphilic binder in lithium-ion batteries.

[0019] Preferably, the negative electrode material of the lithium-ion battery is a silicon-carbon composite material.

[0020] This invention relates to polyacrylic acid, a synthetic polymer with acrylic acid as its monomer, having the molecular formula [C3H4O2]n (3000 < n < 50000). The polyacrylic acid material may be a homopolymer of acrylic acid itself, or a cross-linked polymer formed by cross-linking with allyl ethers of pentaerythritol, sucrose, or propylene. Polyacrylic acid has a linear structure and good adhesive properties. Based on this, this invention synthesizes an amphiphilic adhesive with a three-dimensional network structure by amidation reaction of polyacrylic acid with small molecule materials levodopa and 1-pyrene methylamine hydrochloride. The composite adhesive, modified with biomaterials, improves the mechanical strength of the adhesive, achieving cycle stability of the silicon-based anode.

[0021] This invention involves mixing active material silicon-carbon, conductive agent (conductive carbon black, carbon nanotubes, highly conductive carbon black, or conductive graphite), and binder at a mass ratio of (7-8):(1-2):1. After adding an appropriate amount of deionized water, the mixture is stirred for 6-8 hours to obtain a uniformly dispersed slurry. This slurry is then coated onto copper foil, vacuum dried at 80°C for 12 hours, and cut into circular electrode sheets with a diameter of 14 mm. The dried electrode sheets are transferred to an argon-filled glove box for battery assembly. The battery uses a lithium foil as the counter electrode, and the electrolyte is 1.2 mmol / L LiPF6 as the solute, with EC and DEC in a 1:1 volume ratio as the solvent. 10 wt% FEC and 1 wt% VC are used as additives. CR2032 coin cells are used for assembly.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The PDB amphiphilic binder of the present invention is an amphiphilic binder with good affinity for both graphite and silicon anode materials. It is prepared by amidation reaction of polyacrylic acid with levonorgestrel and 1-pyrene methylamine hydrochloride. It has good affinity for graphite, conductive carbon black and silicon materials. This is because polyacrylic acid has a large number of hydroxyl groups, which have good affinity for silicon. At the same time, levonorgestrel and 1-pyrene methylamine hydrochloride contain a large number of benzene ring functional groups, which are similar to the structure of graphite and will form π-π conjugation. The combination of the two is conducive to forming a coating layer on the surface of silicon carbon materials.

[0024] 2. The PDB amphiphilic binder prepared by this invention is an aqueous binder with strong adhesion, and has the advantages of being environmentally friendly and low in cost; at the same time, it has good mechanical properties and electrochemical stability, which is beneficial to the long-cycle stability of silicon-carbon anodes in lithium-ion batteries.

[0025] 3. This invention uses polyacrylic acid as the main chain and undergoes an amidation reaction with levodopa and 1-pyrene methylamino hydrochloride to synthesize a binder with amphiphilic properties. This binder exhibits advantages such as easy water solubility, good dispersibility in silicon-carbon materials, and strong adhesion. It can effectively protect active materials from the influence of the electrolyte, reduce the formation of a large amount of SEI film, and significantly improve the electrochemical performance of silicon-carbon anodes in lithium-ion batteries.

[0026] 4. The preparation process of this invention is simple, low in cost, and easy to apply. Attached Figure Description

[0027] Figure 1 Mechanical properties of films made of polyacrylic acid and amphiphilic binder (PDB).

[0028] Figure 2 The graph shows the cycle performance of the coin cell prepared in Example 1.

[0029] Figure 3 This is a comparison graph showing the cycle performance of the coin cells prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0030] 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.

[0031] Example 1

[0032] 1. Dissolve 0.05g of L-dopamine in 9.5g of water, add polyacrylic acid and 1-pyrene methylamino hydrochloride with a molecular weight of 24w, wherein the mass ratio of L-dopamine, 1-pyrene methylamino hydrochloride and polyacrylic acid is 1:1:9, and add 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC) as a catalyst. After the reaction is complete at 80℃, dialyze the solution through a dialysis bag. Heat and concentrate the dialyzed solution to a 5% mass fraction of amphiphilic binder solution (PDB).

[0033] 2. Mix the active material silicon carbon, conductive agent SuperP and 5% by mass of amphiphilic binder solution at a mass ratio of 8:1:1, add an appropriate amount of deionized water and stir in a degassing mixer to obtain a uniformly dispersed electrode slurry. Coat the electrode slurry onto copper foil and vacuum dry at 80℃ for 12 hours. Cut into circular negative electrode sheets with a diameter of 14 mm.

[0034] 3. Transfer the dried negative electrode sheet into an argon-filled glove box. Use a lithium sheet as the counter electrode. The electrolyte is 1.2 mmol / L LiPF6 as the solute and EC and DEC in a 1:1 volume ratio as the solvent, with 10 wt% FEC and 1 wt% VC as additives. Assemble using CR2032 coin cells and let the assembled coin cells stand for 8 hours. Perform constant current electrochemical performance tests on the cells in the Xinwei testing system after standing.

[0035] Figure 1 Mechanical property graphs of films made from polyacrylic acid and amphiphilic binder (PDB). From Figure 1 As can be seen, PDB binder has good elastic properties, which helps to alleviate the volume expansion of the negative electrode. Figure 2 The cycling performance diagram of the coin cell prepared in Example 1 is shown below. Figure 2 It can be seen that the silicon electrode composed of amphiphilic binder (PDB) has an initial discharge specific capacity of 1100 mAh g at a current density of 100 mA / g. -1 The initial coulombic efficiency was above 80%, and the capacity remained at 850 mAh / g after 100 cycles, demonstrating excellent cycling stability.

[0036] Comparative Example 1

[0037] 1. Add 0.5g of polyacrylic acid powder with a molecular weight of 24w to 9.5g of deionized water to obtain a 5% by mass binder.

[0038] 2. Mix the active material silicon carbon, conductive agent SuperP and 5% binder at a mass ratio of 8:1:1, add an appropriate amount of deionized water and stir for 6-8 hours to obtain a uniformly dispersed electrode slurry. Coat the electrode slurry onto copper foil, vacuum dry at 80℃ for 12 hours, and cut into circular electrode sheets with a diameter of 14 mm.

[0039] 3. Transfer the electrode sheets into an argon-filled glove box for battery assembly. The lithium electrode serves as the counter electrode. The electrolyte uses 1.2 mmol / L LiPF6 as the solute and ethylene carbonate (EC) and diethyl carbonate (DEC) in a 1:1 volume ratio as the solvent. 10 wt% fluoroethylene carbonate (FEC) and 1 wt% ethylene carbonate (VC) are used as additives. The battery is assembled using CR2032 coin cells.

[0040] The coin cells assembled in Example 1 and Comparative Example 1 were left to stand at 28°C for 10 hours before their electrochemical performance was tested using a constant current testing system. The test conditions were: current density 100 mA / g; voltage window 0.01-1.5 V. Figure 3 This is a comparison graph showing the cycle performance of the coin cells prepared in Example 1 and Comparative Example 1. Figure 3The results show that the coin cell prepared in Comparative Example 1, at a current density of 100 mA / g, experienced a capacity degradation to approximately 591 mAh / g after 100 cycles, while the coin cell prepared in Example 1 maintained a capacity of 850 mAh / g, exhibiting higher discharge capacity and better cycle stability. Figure 3 It is known that amphiphilic binders (PDB) can enable silicon-carbon anodes to exhibit good cycle stability.

[0041] 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. An amphiphilic binder for silicon-carbon anodes in lithium-ion batteries, characterized in that, The amphiphilic binder, abbreviated as PDB, is prepared by dissolving levodopamine in water, adding polyacrylic acid powder, 1-pyrene methylhydrochloride and a catalyst, reacting at 50-80°C, and then dialyzing. The mass ratio of levodopamine, 1-pyrene methylhydrochloride and polyacrylic acid is 1:(0.5-1):(8-10); the mass ratio of levodopamine to water is 1:(180-190); the molecular weight of the polyacrylic acid powder is 240,000 to 5,000,000; and the catalyst is 1-ethyl-(3-dimethylaminopropyl)carbodiimide.

2. The amphiphilic binder for silicon-carbon anodes in lithium-ion batteries according to claim 1, characterized in that, The reaction time is 6-36 hours; the dialysis time is 12-36 hours.

3. The method for preparing the amphiphilic binder for silicon-carbon anodes of lithium-ion batteries according to claim 1 or 2, characterized in that, Includes the following steps: S1. Dissolve levodopamine in water, then add polyacrylic acid powder and 1-pyrene methylhydrochloride to obtain a mixed solution; S2. Add a catalyst to the mixed solution and react at 50~80℃. After the reaction is complete, dialyze the solution through a dialysis bag to obtain the amphiphilic binder.

4. A negative electrode, characterized in that, The negative electrode is prepared by mixing active material silicon carbon, conductive agent and amphiphilic binder as described in claim 1 or 2, adding deionized water and stirring to obtain a uniformly dispersed electrode slurry, coating the electrode slurry onto copper foil and drying it under vacuum.

5. The negative electrode according to claim 4, characterized in that, The conductive agent is 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 amphiphilic binder is (7~8):(1~2):1; the stirring time is 6~8h; the vacuum drying temperature is 70~80℃; and the vacuum drying time is 12~36h.

6. The application of the amphiphilic binder according to claim 1 or 2 in lithium-ion batteries.

7. The application according to claim 6, characterized in that, The negative electrode material of the lithium-ion battery is a silicon-carbon composite material.

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