Preparation method of high-rate lithium battery pole piece slurry and coating process thereof

Abstract

This invention discloses a method for preparing electrode slurry for high-rate lithium batteries and its coating process, belonging to the field of lithium battery technology. Using chitosan as a carbon source, modified titanium carbide nanosheets are composited with nickel-cobalt-doped silicon spheres via glutaraldehyde crosslinking. High-temperature carbonization forms a carbon coating. The carbon-coated composite porous microspheres are then mixed with nano-copper powder, conductive carbon black, and sodium carboxymethyl cellulose solution, and subjected to gradient stirring to obtain the electrode slurry for high-rate lithium batteries. This invention utilizes the synergistic effect of metal-doped porous silicon spheres and modified titanium carbide nanosheets with carbon coating to construct a conductive network, allowing metal ions to be uniformly anchored on the surface and within the pores of the silicon spheres. This improves the conductivity of the silicon-based material and alleviates particle pulverization caused by silicon volume expansion. The carbon coating forms a "core-shell" structure, achieving high conductivity and high rate capability in the electrode slurry.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to a method for preparing electrode slurry for high-rate lithium batteries and its coating process. Background Technology

[0002] Lithium-ion batteries, with their high energy density and reliable electrochemical performance, have become an indispensable part of the new energy industry. With the development of the new energy industry, the demand for lithium-ion batteries continues to increase, thus placing higher demands on the battery manufacturing industry. Therefore, optimizing production process parameters to improve battery performance is imperative, starting with the battery manufacturing process itself.

[0003] Electrode slurry is a solid-liquid mixture system formed by dispersing electrode active materials and conductive agents in an electrolyte. It includes electrode active materials, conductive agents, binders, solvents, and flexible agents. During electrode preparation, a flexible agent can be incorporated into the electrode slurry to form the electrode, or a flexible agent can be coated onto the surface of a pre-made electrode, thereby obtaining an electrode with low hardness and brittleness. Such electrodes have a significantly reduced probability of breakage during processing and use, improving the processing yield and safety of lithium-ion batteries, overcoming the problem of powder shedding from the negative electrode during charging and discharging, and extending the lifespan of lithium-ion batteries.

[0004] High-rate lithium-ion battery electrode slurry is a special conductive colloid, mainly composed of a mixture of active material particles, conductive agents, and binders (carbon colloid phase) and pores. It plays a role in balancing power, energy density, and extending battery life. With the increasing demand for fast charging in electrical products, slurry technology will need to continue to develop towards lower resistance, higher adhesion, and nano-scale applications.

[0005] Chinese invention patent application CN113336276A discloses a method for preparing an electrode material, the electrode material, and a capacitor. The method involves first preparing a spherical cobalt-nickel complex and reacting it with potassium hydroxide by heating to obtain the electrode material. By preparing a spherical shell structure, the specific surface area is increased, the volume effect during charging and discharging is reduced, and a capacitor with stability and large specific capacitance is obtained.

[0006] However, under high-rate charge and discharge conditions, the rapid insertion and extraction of lithium ions will cause the volume of the cobalt-nickel hydroxide electrode material to expand. If the electrode material structure is not stable enough, it is easy to cause particle breakage or structural collapse, which will affect the cycle life. Cobalt-nickel hydroxide itself has a layered structure, but the layered structure is prone to phase transition under high voltage or rapid charge and discharge, resulting in capacity decay.

[0007] Chinese invention patent application CN104091921A discloses a porous silicon-carbon hybrid anode electrode and a lithium-ion secondary battery containing the electrode. By preparing a porous anode current collector and two coating layers coated on the porous current collector, the porous structure absorbs the tension of silicon-carbon particles along the parallel direction of the current collector, reducing the volume expansion of silicon-carbon particles. However, due to the insufficient conductivity of silicon, drilling holes will lead to a decrease in conductivity, resulting in a decrease in charging rate and capacity. Summary of the Invention

[0008] The purpose of this invention is to solve the problems of large volume expansion rate of silicon and insufficient conductivity in high-rate lithium batteries, and to provide a method for preparing electrode slurry for high-rate lithium batteries.

[0009] This invention constructs a conductive network through the synergistic effect of metal-doped porous silicon spheres and modified titanium carbide nanosheets with carbon coating. This allows metal ions to be uniformly anchored on the surface and within the pores of the silicon spheres, improving the conductivity of silicon-based materials and mitigating particle pulverization caused by silicon volume expansion. The carbon coating forms a "core-shell" structure, suppressing volume expansion while achieving high conductivity and high rate capability.

[0010] The objective of this invention can be achieved through the following technical solutions:

[0011] A method for preparing electrode slurry for high-rate lithium batteries includes the following steps:

[0012] Step 1: Add acetic acid solution, deionized water and chitosan to the reaction vessel, stir evenly at 80-90℃, add modified titanium carbide nanosheets and nickel-cobalt doped porous silicon spheres and stir evenly, then add glutaraldehyde crosslinking agent and stir evenly, vacuum dry, transfer to tube furnace, react under argon protection to obtain carbon-coated composite porous microspheres.

[0013] Step 2: Transfer nano-copper powder, conductive carbon black, carbon-coated composite porous microspheres and 1.5 wt% sodium carboxymethyl cellulose solution to a reaction vessel and stir evenly. Then add 18 wt% styrene-butadiene rubber solution and stir evenly to obtain the electrode slurry for high-rate lithium batteries.

[0014] Furthermore, the ratio of acetic acid solution, deionized water, chitosan, modified titanium carbide nanosheets, nickel-cobalt doped porous silicon spheres, and glutaraldehyde crosslinking agent is 18-20mL: 800-1000mL: 18-20g: 8-10g: 25-30g: 15-20mL.

[0015] Furthermore, the modified titanium carbide nanosheets are prepared through the following steps:

[0016] Titanium carbide nanosheets, aminobenzenesulfonic acid, and tert-butyl nitrite were sequentially added to a reaction vessel, and the vessel was evacuated 3-5 times. The reaction was carried out at 80-100℃ for 8-10 hours to obtain modified titanium carbide nanosheets.

[0017] Furthermore, the mass ratio of titanium carbide nanosheets, aminobenzenesulfonic acid, and tert-butyl nitrite is 1:7:7.

[0018] Furthermore, the mass ratio of nano-copper powder, conductive carbon black, carbon-coated composite porous microspheres, sodium carboxymethyl cellulose solution, and styrene-butadiene rubber solution is 70-80:18-20:18-20:210-240:18-20.

[0019] Furthermore, nickel-cobalt doped porous silicon spheres are prepared through the following steps:

[0020] Ammonium fluoride, cobalt sulfate, and nickel sulfate were dissolved in deionized water, and the pH was adjusted to 8 with ammonia water before being added to the reaction vessel. Porous silicon sphere powder was then added, and the mixture was stirred for 1-2 hours. After centrifugation and filtration, the precipitate was collected. The filter cake was washed alternately with deionized water and ethanol and then dried to obtain nickel-cobalt doped porous silicon spheres.

[0021] Furthermore, the ratio of ammonium fluoride, cobalt sulfate, nickel sulfate, deionized water, and porous silica sphere powder is 18-20g: 0.15-0.2g: 0.15-0.2g: 1-1.2L: 1-3g.

[0022] Furthermore, the porous silicon sphere powder is prepared through the following steps:

[0023] Add ferrosilicon powder and a 1.0 mol / L hydrochloric acid solution to a reaction vessel, ultrasonically disperse for 20-30 min, react at room temperature for 20-24 h, centrifuge and filter to collect the precipitate, wash the filter cake with deionized water and dry to obtain porous silica sphere powder.

[0024] Furthermore, the ratio of ferrosilicon powder to hydrochloric acid solution is 80-100g: 10-12L.

[0025] Furthermore, titanium carbide nanosheets are prepared through the following steps:

[0026] Lithium fluoride and 9 mol / L dilute hydrochloric acid were added to a reaction vessel and stirred for 20-30 min. Then titanium aluminum carbide powder was added and reacted at 500-800 rpm and 40-50℃ for 48-50 h. After washing, centrifugation and freeze drying, titanium carbide nanosheets were obtained.

[0027] Furthermore, the ratio of lithium fluoride, dilute hydrochloric acid, and titanium aluminum carbide powder is 32-40g: 400-500mL: 10-15g.

[0028] Furthermore, a coating process for preparing electrode slurry for a high-rate lithium battery includes the following steps: applying the electrode slurry of the high-rate lithium battery onto the surface of the current collector and uniformly coating it, then drying it to complete the coating process of the electrode slurry for the high-rate lithium battery.

[0029] The beneficial effects of this invention are:

[0030] 1. This invention constructs a conductive network through the synergistic effect of metal-doped porous silicon spheres and modified titanium carbide nanosheets with carbon coating; nickel and cobalt elements are uniformly anchored on the surface and within the pores of the silicon spheres, improving the conductivity of silicon-based materials and alleviating particle pulverization caused by silicon volume expansion. The carbon coating forms a "core-shell" structure, and the addition of nano-copper powder and conductive carbon black constructs a three-dimensional conductive network, reducing the internal resistance of the electrode. Using carbon-coated composite microspheres as active materials provides high specific capacity and cycle stability, achieving high conductivity and high rate capability while suppressing volume expansion.

[0031] 2. In this invention, nickel and cobalt doped porous silicon spheres form a continuous metallic conductive network on the surface of the porous silicon spheres through chemical bonding (Si-OM bond). The electron transport path is improved from the semiconductor properties of silicon to the metal doped layer after metal doping, which can also suppress volume expansion during charging and discharging. Titanium carbide nanosheets have metal-like conductivity. After modification with aminobenzenesulfonic acid, sulfonic acid groups are introduced on their surface, which enhances the lithium ion adsorption capacity and reduces the interfacial impedance. The two-dimensional layered structure of titanium carbide nanosheets can disperse the silicon expansion stress through interlayer slip and support the silicon particle structure. The functional groups on the surface of the modified titanium carbide nanosheets form chemical bonds with the silicon particles, further anchoring the active material and inhibiting the formation of lithium dendrites.

[0032] 3. Nickel-cobalt doped porous silicon spheres provide a metallic conductive network, while titanium carbide nanosheets provide dual channels for ions and electrons, forming a three-dimensional interpenetrating conductive structure. This improves the overall conductivity of the electrode. The interlayer lithium-ion transport of titanium carbide nanosheets complements the electron transport of nickel-cobalt, supporting high-rate charge and discharge. The porous silicon spheres buffer the primary expansion of silicon, while the interlayer slip of titanium carbide nanosheets disperses secondary stress, preventing the overall electrode structure from collapsing. The carbon layer after chitosan carbonization further coats the silicon particles, forming an elastic buffer layer that minimizes changes in volume expansion and maintains the integrity of the electrode structure after cycling, inhibiting structural pulverization. The synergy of these two factors improves the capacity retention rate after 100 cycles, suppresses lithium dendrite formation, and combines interface stability. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments in the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1: A method for preparing electrode slurry for high-rate lithium batteries, comprising the following steps:

[0035] S1: Add 80g of ferrosilicon powder and 10L of 1.0mol / L hydrochloric acid solution to the reactor, sonicate for 20min, react at room temperature for 20h, centrifuge and filter to collect the precipitate, wash the filter cake three times with deionized water, and dry at 70℃ for 10h to obtain porous silicon sphere powder.

[0036] The iron in the ferrosilicon powder is corroded and dissolved by hydrochloric acid, leaving a porous silicon structure; it is then ultrasonically dispersed, reacted and dissolved, washed to remove byproducts, and dried to obtain porous silicon sphere powder.

[0037] S2: Dissolve 18g ammonium fluoride, 0.15g cobalt sulfate and 0.15g nickel sulfate in 1L of deionized water, adjust the pH to 8 with ammonia water and add them to the reaction vessel, then add 1g of porous silicon ball powder, stir for 1h, centrifuge and filter to collect the precipitate, wash the filter cake three times alternately with deionized water and ethanol, and dry at 70℃ for 10h to obtain nickel cobalt doped porous silicon balls.

[0038] Through F - With Co 2+ Ni 2+ It forms stable fluorine complexes, inhibits the formation of hydroxide precipitates, and ensures uniform dispersion of metal ions in solution; F - The silicon dioxide layer on the surface of the silicon sphere can be slightly etched to expose fresh Si-OH groups and enhance the metal adsorption sites; the addition of ammonia provides a weakly alkaline environment, which promotes the deprotonation of hydroxyl groups on the surface of the silicon sphere and binds metal cations through electrostatic attraction; the Si-OH on the surface of the silicon sphere undergoes ligand exchange with the metal complex to form Si-OM (M=Co,Ni) bonds, achieving chemical anchoring and forming a chemically bonded and stable doped structure.

[0039] S3: Add 32g of lithium fluoride and 400mL of 9mol / L dilute hydrochloric acid to a reaction vessel and stir for 20min. Then add 10g of titanium aluminum carbide powder and react at 500rpm and 40℃ for 48h. Transfer to a centrifuge and wash with 400mL of 2mol / L dilute hydrochloric acid at 3500rpm for 5min. Then wash with deionized water at 3500rpm for 8min until the solution is neutral. Let stand for 12h to remove the supernatant and add 400mL of deionized water. Stir well and transfer to a reaction vessel. Sonicate at 3500rpm for 2h under argon protection. Transfer the product to a centrifuge and centrifuge at 3500rpm for 45min. Let stand for 12h to collect the supernatant and freeze-dry for 10h to obtain titanium carbide nanosheets.

[0040] Lithium fluoride reacts with hydrochloric acid to produce hydrofluoric acid and lithium chloride. In an acidic environment, titanium aluminum carbide, a MAX phase material, is etched off. The surface of the material has functional groups such as -O, -F or -OH, which allow hydrofluoric acid to etch away the aluminum layer, yielding titanium carbide nanosheets. The nanosheets are then washed with dilute hydrochloric acid and deionized water to further purify them.

[0041] S4: 18g of titanium carbide nanosheets, 126g of aminobenzenesulfonic acid and 126g of tert-butyl nitrite were added to the reaction vessel in sequence, vacuumed 3 times, and reacted at 80℃ for 8h to obtain modified titanium carbide nanosheets.

[0042] Principle: The sulfonic acid group in aminobenzenesulfonic acid is introduced onto the surface of MXene. Tert-butyl nitrite decomposes under acidic conditions to produce nitrous acid, which then participates in the diazotization reaction. The amino group of aminobenzenesulfonic acid is diazotized to form a diazonium salt, which then undergoes a coupling reaction with the functional groups on the MXene surface, grafting the sulfonic acid group onto the MXene.

[0043] S5: Add 18 mL of acetic acid solution, 800 mL of deionized water and 18 g of chitosan to the reactor. Stir at 80 °C for 30 min, then add 8 g of modified titanium carbide nanosheets and 25 g of nickel-cobalt doped porous silicon spheres and stir for 30 min. Then add 15 mL of glutaraldehyde crosslinking agent and stir for 20 min. Vacuum dry, transfer to a tube furnace and react at 900 °C for 2 h under argon protection to obtain carbon-coated composite porous microspheres.

[0044] After carbonization, chitosan aerogel can coat the surface of silicon nanoparticles with a derived carbon layer and stably and firmly wrap the modified titanium carbide nanosheets. The two work together to buffer the stress generated by the volume expansion effect of silicon, prevent the silicon particles from cracking and pulverizing, improve cycle stability, and improve the conductivity of the electrode.

[0045] S6: 70g of nano copper powder, 18g of conductive carbon black, 18g of carbon-coated composite porous microspheres and 210g of sodium carboxymethyl cellulose solution with a mass fraction of 1.5% were transferred to a reaction vessel and stirred at 600 rpm for 6 hours. Then, 18g of styrene-butadiene rubber solution with a mass fraction of 18% was added at 100 rpm and stirred for 30 minutes to obtain the electrode slurry for high-rate lithium batteries.

[0046] Example 2: A method for preparing electrode slurry for high-rate lithium batteries, comprising the following steps:

[0047] S1: Add 90g of ferrosilicon powder and 11L of 1.0mol / L hydrochloric acid solution to the reactor, sonicate for 25min, react at room temperature for 22h, centrifuge and filter to collect the precipitate, wash the filter cake with deionized water 4 times, and dry at 75℃ for 11h to obtain porous silicon ball powder.

[0048] S2: Dissolve 19g ammonium fluoride, 0.175g cobalt sulfate and 0.175g nickel sulfate in 1.1L of deionized water, adjust the pH to 8 with ammonia water and add them to the reaction vessel, then add 2g of porous silicon ball powder, stir for 1.5h, centrifuge and filter to collect the precipitate, wash the filter cake with deionized water and ethanol alternately 4 times, and dry at 75℃ for 11h to obtain nickel cobalt doped porous silicon balls.

[0049] S3: Add 36g of lithium fluoride and 450mL of 9mol / L dilute hydrochloric acid to a reaction vessel and stir for 25min. Then add 12.5g of titanium aluminum carbide powder and react at 650rpm and 45℃ for 49h. Transfer to a centrifuge and wash with 450mL of 2mol / L dilute hydrochloric acid at 3750rpm for 6.5min. Then wash with deionized water at 3750rpm for 9min until the solution is neutral. Let stand for 13.5h to remove the supernatant and add 450mL of deionized water. Stir well and transfer to a reaction vessel. Sonicate at 3750rpm for 3h under argon protection. Transfer the product to a centrifuge and centrifuge at 3750rpm for 52.5min. Let stand for 13.5h to collect the supernatant and freeze-dry for 11h to obtain titanium carbide nanosheets.

[0050] S4: 19g of titanium carbide nanosheets, 133g of aminobenzenesulfonic acid and 133g of tert-butyl nitrite were added to the reaction vessel in sequence, vacuumed 4 times, and reacted at 90℃ for 9h to obtain modified titanium carbide nanosheets.

[0051] S5: Add 19 mL of acetic acid solution, 900 mL of deionized water and 19 g of chitosan to a reaction vessel. Stir at 85 °C for 35 min, then add 9 g of modified titanium carbide nanosheets and 27.5 g of nickel-cobalt doped porous silicon spheres and stir for 35 min. Then add 17.5 mL of glutaraldehyde crosslinking agent and stir for 25 min. Vacuum dry, transfer to a tube furnace and react at 950 °C for 2.5 h under argon protection to obtain carbon-coated composite porous microspheres.

[0052] S6: 75g of nano copper powder, 19g of conductive carbon black, 19g of carbon-coated composite porous microspheres and 225g of sodium carboxymethyl cellulose solution with a mass fraction of 1.5% were transferred to a reaction vessel and stirred at 700 rpm for 7 hours. Then, 19g of styrene-butadiene rubber solution with a mass fraction of 18% was added at 110 rpm and stirred for 35 minutes to obtain the electrode slurry for high-rate lithium batteries.

[0053] Example 3: A method for preparing electrode slurry for high-rate lithium batteries, comprising the following steps:

[0054] S1: Add 100g of ferrosilicon powder and 12L of 1.0mol / L hydrochloric acid solution to the reactor, sonicate for 30min, react at room temperature for 24h, centrifuge and filter to collect the precipitate, wash the filter cake 5 times with deionized water, and dry at 80℃ for 12h to obtain porous silicon sphere powder.

[0055] S2: Dissolve 20g ammonium fluoride, 0.2g cobalt sulfate and 0.2g nickel sulfate in 1.2L deionized water, adjust the pH to 8 with ammonia water and add them to the reaction vessel, then add 3g porous silicon ball powder, stir for 2h, centrifuge and filter to collect the precipitate, wash the filter cake with deionized water and ethanol alternately 5 times, and dry at 80℃ for 12h to obtain nickel cobalt doped porous silicon balls.

[0056] S3: Add 40g of lithium fluoride and 500mL of 9mol / L dilute hydrochloric acid to a reaction vessel and stir for 30min. Then add 15g of titanium aluminum carbide powder and react at 800rpm and 50℃ for 50h. Transfer to a centrifuge and wash with 500mL of 2mol / L dilute hydrochloric acid at 4000rpm for 8min. Then wash with deionized water at 4000rpm for 10min until the solution is neutral. Let stand for 15h to remove the supernatant and add 500mL of deionized water. Stir well and transfer to a reaction vessel. Sonicate at 4000rpm for 4h under argon protection. Transfer the product to a centrifuge and centrifuge at 4000rpm for 60min. Let stand for 15h to collect the supernatant and freeze-dry for 12h to obtain titanium carbide nanosheets.

[0057] S4: 20g of titanium carbide nanosheets, 140g of aminobenzenesulfonic acid and 140g of tert-butyl nitrite were added to the reaction vessel in sequence, vacuumed 5 times, and reacted at 100℃ for 10h to obtain modified titanium carbide nanosheets.

[0058] S5: Add 20 mL of acetic acid solution, 1000 mL of deionized water and 20 g of chitosan to the reactor. Stir at 90 °C for 40 min, then add 10 g of modified titanium carbide nanosheets and 30 g of nickel-cobalt doped porous silicon spheres and stir for 40 min. Then add 20 mL of glutaraldehyde crosslinking agent and stir for 30 min. Vacuum dry, transfer to a tube furnace and react at 1000 °C for 3 h under argon protection to obtain carbon-coated composite porous microspheres.

[0059] S6: Transfer 80g of nano copper powder, 20g of conductive carbon black, 20g of carbon-coated composite porous microspheres and 240g of sodium carboxymethyl cellulose solution with a mass fraction of 1.5% to a reaction vessel, stir at 800rpm for 8h, add 20g of styrene-butadiene rubber solution with a mass fraction of 18% at 120rpm, stir for 40min to obtain the electrode slurry for high-rate lithium batteries.

[0060] Example 4: A coating process for electrode slurry of a high-rate lithium battery, comprising the following steps:

[0061] The copper foil was wiped dry with ethanol. The electrode slurry of the high-rate lithium battery in Example 3 was dipped onto the surface of the copper foil and coated evenly with a scraper. Then, it was placed in a forced-air drying oven and dried at 80°C for 40 minutes. The electrode was then transferred to a vacuum drying oven at 60°C and vacuum dried at 60°C for 12 hours to obtain a coating process for electrode slurry of a high-rate lithium battery.

[0062] All raw materials used in Examples 1-3 were commercially available products.

[0063] Comparative Example 1: The difference from Example 1 is that step S2 is deleted, and in step S5, the nickel-cobalt doped porous silicon spheres are replaced with porous silicon sphere powder. The remaining steps remain unchanged to prepare the electrode slurry for high-rate lithium batteries.

[0064] Comparative Example 2: The difference from Example 1 is that step S4 is deleted, and in step S5, the modified titanium carbide nanosheets are replaced with titanium carbide nanosheets. The remaining steps remain unchanged to prepare electrode slurry for high-rate lithium batteries.

[0065] Comparative Example 3: The difference from Example 1 is that steps S3 and S4 are deleted, and carbon nanotubes are used to replace modified titanium carbide nanosheets in step S5. The remaining steps remain unchanged to prepare electrode slurry for high-rate lithium batteries.

[0066] The electrode slurries of the high-rate lithium batteries prepared in Examples 1-3 and Comparative Examples 1-3 were used to make electrode sheets according to the coating process in Example 4. The obtained electrode sheets were cut into 14mm small round pieces, weighed and recorded, and then assembled in an argon-filled glove box. The negative electrode shell was placed on a tray, and the gasket and lithium sheet were placed in sequence. Then, 35μL of electrolyte was dropped in using a pipette. After that, the separator was placed in and another 70μL of electrolyte was dropped in. The electrode sheet was aligned with the lithium sheet with the coated side facing down, and the gasket, spring sheet and positive electrode shell were placed in sequence. Finally, the battery was packaged into a CR2032 button battery with a pressure of 140kg and transferred out of the glove box. The residual electrolyte on the surface was wiped off with lint-free paper dipped in anhydrous ethanol. After standing at room temperature for 12h, electrochemical tests were performed.

[0067] Electrochemical testing: The battery was tested at 25℃ and within a voltage range of 0.01-1.5V at 0.5C. The battery conductivity, initial coulombic efficiency, percentage volume change, capacity retention after 100 cycles, and lithium dendrite formation were recorded. The results are shown in Table 1.

[0068] Table 1: Performance Test Results

[0069] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Electrical conductivity (S / cm) 32.1 32.4 32.3 17.8 18.6 19.3 First-time Coulomb efficiency (%) 96.8 97.1 96.9 86.5 84.6 85.1 Percentage change in volume (%) 82 78 80 95 90 112 Capacity retention rate after 100 cycles (%) 94.6 95.2 94.8 81.8 82.4 83.1 Lithium dendrites present or absent No obvious No obvious No obvious less less More

[0070] As can be seen from Table 1, the electrode slurry of the high-rate lithium battery prepared in Examples 1-3 of this invention has significantly better performance than the comparative example, with higher conductivity, first coulombic efficiency, capacity retention after 100 cycles, lower volume change percentage, and reduced lithium dendrite formation.

[0071] In Comparative Example 1, the conductivity and capacity retention after 100 cycles decreased significantly. Removing the metal dopant resulted in poor conductivity of the porous silicon spheres, which may have led to a decrease in the overall conductivity of the electrode. The volume change of silicon during cycling could not be effectively suppressed, resulting in particle breakage and repeated growth of the solid electrolyte interface film, consuming electrolyte and lithium source, and reducing capacity retention. Nickel-cobalt doped porous silicon spheres can form a conductive network, enhance the electron transport capability of the material, and may also stabilize the silicon sphere structure through chemical bonding, reducing the shedding of active material.

[0072] The significant decrease in initial coulombic efficiency in Comparative Example 2 may be due to the presence of numerous oxygen- and fluorine-containing functional groups on the surface of the unmodified titanium carbide nanosheets. These defect sites catalyze the decomposition of the electrolyte, generating a thick and unstable solid electrolyte interface film. This leads to irreversible loss of lithium ions and electrolyte during the first charge and discharge process. Furthermore, they may undergo side reactions with lithium, consuming a large amount of active lithium, resulting in a decrease in initial coulombic efficiency.

[0073] The significantly increased percentage of volume change and the obvious lithium dendrite phenomenon in Comparative Example 3 may be due to the fact that carbon nanotubes, being linear structures, cannot effectively buffer the intense expansion of silicon, while modified titanium carbide nanosheets, with their layered structure, can disperse the expansion stress of silicon and provide physical support. The carbon nanotubes are in physical contact with the silicon particles, and during the expansion process, they are prone to separating from the silicon particles, resulting in microcracks on the electrode surface. Lithium ions preferentially deposit at the cracks, forming dendrites. The tendency of carbon nanotubes to agglomerate may also accelerate the growth of lithium dendrites.

[0074] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a slurry of electrode sheet for high rate lithium battery, characterized by, Comprising the following steps: Step one: acetic acid solution, deionized water and chitosan are added to the reaction kettle, 80-90℃ stirring uniform, adding modified titanium carbide nanosheet and nickel cobalt doped porous silicon ball stirring uniform, adding glutaraldehyde crosslinking agent stirring uniform, vacuum drying, transfer to the tube furnace, under argon protection reaction, carbon-coated composite porous microspheres are obtained; Step two: nano copper powder, conductive carbon black, carbon-coated composite porous microspheres and 1.5wt% carboxymethyl cellulose sodium solution are transferred to the reaction kettle and stirred uniformly, then 18wt% butadiene-styrene rubber solution is added and stirred uniformly to obtain the slurry of the pole piece of high rate lithium battery; The amount ratio of acetic acid solution, deionized water, chitosan, modified titanium carbide nanosheet, nickel cobalt doped porous silicon ball and glutaraldehyde crosslinking agent is 18-20mL:800-1000mL:18-20g:8-10g:25-30g:15-20mL; The modified titanium carbide nanosheet is prepared by the following steps: The titanium carbide nanosheet, aminobenzenesulfonic acid and tert-butyl nitrite are sequentially added to the reaction kettle, vacuumed for 3-5 times, and reacted at 80-100℃ for 8-10h to obtain the modified titanium carbide nanosheet. The mass ratio of the titanium carbide nanosheet, aminobenzenesulfonic acid and tert-butyl nitrite is 1:7:

7.

2. The method of claim 1, wherein the slurry is prepared by mixing the lithium metal oxide, the conductive agent, the binder, and the solvent. The mass ratio of the nano copper powder, conductive carbon black, carbon-coated composite porous microspheres, carboxymethyl cellulose sodium solution and butadiene-styrene rubber solution in step two is 70-80:18-20:18-20:210-240:18-20.

3. The method of claim 1, wherein the slurry is prepared by mixing the lithium metal oxide, the conductive agent, the binder, and the solvent. The nickel cobalt doped porous silicon ball is prepared by the following steps: Ammonium fluoride, cobalt sulfate and nickel sulfate are dissolved in deionized water, the pH value is adjusted to 8 with ammonia respectively, and then added to the reaction kettle. Then, porous silicon ball powder is added and stirred for 1-2h, centrifuged and filtered to collect the precipitate. The filter cake is washed with deionized water and ethanol alternately, and then dried to obtain the nickel cobalt doped porous silicon ball. The amount ratio of ammonium fluoride, cobalt sulfate, nickel sulfate, deionized water and porous silicon ball powder is 18-20g:0.15-0.2g:0.15-0.2g:1-1.2L:1-3g.

4. The method of claim 3, wherein the slurry is prepared by adding the binder to the solvent, and then adding the conductive material and the lithium metal oxide to the binder-solvent mixture. The porous silicon ball powder is prepared by the following steps: Silicon iron powder and hydrochloric acid solution with a concentration of 1.0mol / L are added to the reaction kettle, ultrasonic dispersion is performed for 20-30min, reaction is performed at room temperature for 20-24h, the precipitate is collected by centrifugal filtration, and the filter cake is washed with deionized water and dried to obtain the porous silicon ball powder. The amount ratio of silicon iron powder and hydrochloric acid solution is 80-100g:10-12L.

5. The method of claim 1, wherein the slurry is prepared by mixing the lithium metal oxide, the conductive agent, the binder, and the solvent. The titanium carbide nanosheet is prepared by the following steps: Lithium fluoride and dilute hydrochloric acid with a concentration of 9mol / L are added to the reaction kettle, stirred for 20-30min, then titanium aluminum carbide powder is added, and reaction is performed at 500-800rpm and 40-50℃ for 48-50h. After washing, centrifugal separation and freeze drying, the titanium carbide nanosheet is obtained.

6. The method of claim 5, wherein the slurry is prepared by mixing the lithium metal oxide, the conductive agent, the binder, and the solvent. The amount ratio of lithium fluoride, dilute hydrochloric acid and titanium aluminum carbide powder is 32-40g:400-500mL:10-15g.

7. The coating process of the slurry of the electrode sheet of the high rate lithium battery obtained by the production method according to claim 1, characterized by, Comprising the following steps: The high-rate lithium battery pole piece slurry is dipped on the surface of the current collector to be uniformly scraped, dried, and the coating process of the high-rate lithium battery pole piece slurry is completed.