Pole piece slurry of high-rate lithium battery and coating process of pole piece slurry

Abstract

The invention discloses pole piece slurry of a high-rate lithium battery and a coating process of the pole piece slurry, and belongs to the technical field of lithium batteries. The preparation method comprises the following steps: by taking chitosan as a carbon source, compounding a modified titanium carbide nanosheet and nickel-cobalt doped silicon spheres through glutaraldehyde crosslinking, performing high-temperature carbonization to form carbon coating, mixing the carbon-coated composite porous microspheres with nano copper powder, conductive carbon black and a sodium carboxymethyl cellulose solution, and performing gradient stirring to obtain the pole piece slurry of the high-rate lithium battery. The metal-doped porous silicon spheres and the modified titanium carbide nanosheets cooperate with carbon coating to construct a conductive network, so that metal ions are uniformly anchored on the surfaces of the silicon spheres and in pores, the conductivity of the silicon-based material is improved, particle pulverization caused by silicon volume expansion is relieved, a core-shell structure is formed by carbon coating, and the conductivity of the silicon-based material is improved. And high conductivity and high magnification of the pole piece slurry are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium batteries, and in particular relates to a pole piece slurry for a high-rate lithium battery and a coating process thereof. Background Art

[0002] As an important source of clean power, new energy batteries have achieved remarkable success in applications such as electric vehicles, energy storage, electronics, and electric ships. Lithium-ion batteries, with their high energy density and reliable electrochemical performance, have become an indispensable component of the new energy industry. With the development of the new energy industry, the demand for lithium-ion batteries continues to increase, placing higher demands on the battery manufacturing industry. Starting from the battery production process, it is imperative to optimize production process parameters to improve battery performance.

[0003] Electrode slurry is a solid-liquid mixture formed by dispersing electrode active materials and a conductive agent in an electrolyte. It includes the electrode active materials, conductive agent, binder, solvent, and softening agent. During electrode preparation, a softening agent can be added to the electrode slurry or applied to the surface of an already prepared electrode, resulting in a low-hardness and brittle electrode. This significantly reduces the probability of electrode breakage during processing and use, improving the processing yield and safety of lithium-ion batteries. It also overcomes the problem of negative electrode powder shedding during charge and discharge, extending the battery's service life.

[0004] The electrode slurry for high-rate lithium-ion batteries is a special conductive colloid, primarily composed of a mixture of active material particles, a conductive agent, and a binder (carbon colloid phase), along with pores. It balances power and energy density while extending life. As demand for fast charging in electrical products increases, slurry technology will continue to evolve towards low resistance, high adhesion, and nano-crystallization.

[0005] Chinese invention patent application publication number CN113336276A discloses a method for preparing an electrode material, an electrode material, and a capacitor. The electrode material is obtained by first preparing a spherical cobalt-nickel complex and heating it with potassium hydroxide. 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 expansion of the cobalt nickel hydroxide electrode material. If the electrode material structure is not stable enough, it is easy to cause particle rupture or structural collapse, thereby affecting the cycle life. Cobalt nickel hydroxide itself has a layered structure, but the layered structure is prone to phase change under high voltage or rapid charge and discharge, resulting in capacity attenuation.

[0007] A Chinese invention patent application with publication number 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 the silicon-carbon particles along the parallel direction of the current collector, thereby reducing the volume expansion of the silicon-carbon particles; however, due to the insufficient conductivity of the silicon element, the conductivity will decrease after drilling, resulting in a decrease in charging rate and capacity. Summary of the Invention

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

[0009] The present invention constructs a conductive network through the synergistic action of metal-doped porous silicon spheres and modified titanium carbide nanosheets in conjunction with carbon coating, so that metal ions are evenly anchored on the surface and in the pores of the silicon spheres, thereby improving the conductivity of the silicon-based material and alleviating the particle pulverization caused by the volume expansion of silicon. The carbon coating forms a "core-shell" structure, which suppresses volume expansion while achieving high conductivity and high rate.

[0010] The purpose of the present invention can be achieved through the following technical solutions:

[0011] A high-rate lithium battery electrode slurry comprises the following steps:

[0012] Step 1: Add acetic acid solution, deionized water and chitosan into a reactor, stir evenly at 80-90°C, add modified titanium carbide nanosheets and nickel-cobalt doped porous silicon spheres and stir evenly, then add glutaraldehyde crosslinker and stir evenly, vacuum dry, transfer to a tube furnace, and 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 1.5wt% sodium carboxymethyl cellulose solution into a reactor and stir evenly, then add 18wt% styrene-butadiene rubber solution and stir evenly to obtain a high-rate lithium battery electrode slurry.

[0014] 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.

[0015] Furthermore, the usage ratio of acetic acid solution, deionized water, chitosan, modified titanium carbide nanosheets, nickel-cobalt doped porous silicon spheres, and glutaraldehyde crosslinking agent is 18-20 mL: 800-1000 mL: 18-20 g: 8-10 g: 25-30 g: 15-20 mL.

[0016] Furthermore, nickel-cobalt doped porous silicon spheres are prepared by the following steps:

[0017] Ammonium fluoride, cobalt sulfate and nickel sulfate were dissolved in deionized water, and the pH value was adjusted to 8 with ammonia water and added to the reactor. Then, porous silicon ball powder was added and stirred for 1-2 hours. The mixture was centrifuged and filtered to collect the precipitate. The filter cake was washed alternately with deionized water and ethanol and dried to obtain nickel-cobalt doped porous silicon balls.

[0018] Furthermore, the usage ratio of ammonium fluoride, cobalt sulfate, nickel sulfate, deionized water, and porous silicon ball powder is 18-20 g: 0.15-0.2 g: 0.15-0.2 g: 1-1.2 L: 1-3 g.

[0019] Furthermore, porous silicon sphere powder is prepared by the following steps:

[0020] Add ferrosilicon powder and 1.0 mol / L hydrochloric acid solution into a reactor, perform ultrasonic dispersion for 20-30 minutes, react at room temperature for 20-24 hours, collect the precipitate by centrifugal filtration, wash the filter cake with deionized water and dry it to obtain porous silicon ball powder.

[0021] Furthermore, the usage ratio of ferrosilicon powder and hydrochloric acid solution is 80-100 g:10-12 L.

[0022] Furthermore, the modified titanium carbide nanosheets are prepared by the following steps:

[0023] Titanium carbide nanosheets, aminobenzenesulfonic acid and tert-butyl nitrite are added into a reaction kettle in sequence, vacuumed for 3-5 times, and reacted at 80-100° C. for 8-10 hours to obtain modified titanium carbide nanosheets.

[0024] Furthermore, the ratio of titanium carbide nanosheets, aminobenzenesulfonic acid, and tert-butyl nitrite is 1:7:7.

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

[0026] Lithium fluoride and 9 mol / L dilute hydrochloric acid are added to a reaction kettle and stirred for 20-30 minutes. Titanium aluminum carbide powder is then added and reacted at 500-800 rpm and 40-50° C. for 48-50 hours. The mixture is washed, centrifuged, and freeze-dried to obtain titanium carbide nanosheets.

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

[0028] Furthermore, a coating process for a high-rate lithium battery electrode slurry includes the following steps: dipping the high-rate lithium battery electrode slurry on the surface of the current collector and evenly coating it with a scraper, drying it, and completing the coating process for the high-rate lithium battery electrode slurry.

[0029] Beneficial effects of the present invention:

[0030] 1. The present invention constructs a conductive network through the synergistic action of metal-doped porous silicon spheres and modified titanium carbide nanosheets in conjunction with carbon coating; nickel and cobalt elements are evenly anchored on the surface and pores of the silicon spheres, thereby improving the conductivity of the silicon-based material and alleviating particle pulverization caused by silicon volume expansion. 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. Carbon-coated composite microspheres are used as active materials to provide high specific capacity and cycle stability, suppressing volume expansion while achieving high conductivity and high rate.

[0031] 2. In the nickel-cobalt doped porous silicon spheres of the present invention, nickel and cobalt form a continuous metal conductive network on the surface of the porous silicon spheres through chemical bonding (Si-OM bond), and the electron transmission path is improved from the semiconductor properties of silicon to the metal-doped layer after metal doping, and the volume expansion during charging and discharging can also be suppressed; titanium carbide nanosheets have metal-like conductivity. After modification with aminobenzenesulfonic acid, sulfonic acid groups are introduced on their surface to enhance the lithium ion adsorption capacity while reducing the interface impedance. The two-dimensional layered structure of titanium carbide nanosheets can disperse the silicon expansion stress through interlayer slippage and support the silicon particle structure. The surface functional groups of the modified titanium carbide nanosheets form chemical bonds with the silicon particles, further anchoring the active substance and suppressing the formation of lithium dendrites.

[0032] 3. Nickel-cobalt doped porous silicon spheres provide a metal conductive network and titanium carbide nanosheets provide dual channels for ions and electrons, forming a three-dimensional interpenetrating conductive structure. The overall conductivity of the electrode is improved. The interlayer lithium ion transport of titanium carbide nanosheets complements the electron transport of nickel and cobalt, supporting high-rate charge and discharge. The porous silicon spheres can buffer the primary expansion of silicon, and the interlayer slip of titanium carbide nanosheets disperses the secondary stress to prevent the collapse of the overall structure of the electrode. The carbon layer after carbonization of chitosan further coats the silicon particles to form an elastic buffer layer, which makes the volume expansion rate change small and the electrode structure remains intact after cycling, inhibiting structural pulverization. The two work together to improve the capacity retention rate after 100 cycles, inhibit lithium dendrites and combine interface stability. DETAILED DESCRIPTION

[0033] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] Example 1: A high-rate lithium battery electrode slurry, comprising the following steps:

[0035] S1: 80 g of ferrosilicon powder and 10 L of 1.0 mol / L hydrochloric acid solution were added to a reactor, ultrasonically dispersed for 20 min, reacted at room temperature for 20 h, and centrifuged to collect the precipitate. The filter cake was washed three times with deionized water and dried at 70°C for 10 h 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; ultrasonic dispersion, reaction dissolution, washing to remove by-products, and drying to obtain porous silicon ball powder.

[0037] S2: Dissolve 18g of ammonium fluoride, 0.15g of cobalt sulfate and 0.15g of nickel sulfate in 1L of deionized water, adjust the pH value to 8 with ammonia water and add them into the reactor, then add 1g of porous silicon ball powder, stir for 1h, collect the precipitate by centrifugation, wash the filter cake alternately with deionized water and ethanol for 3 times, and dry it at 70℃ for 10h to obtain nickel-cobalt doped porous silicon balls.

[0038] By F - With Co 2+ 、Ni 2+ Forming a stable fluorine complex, inhibiting the formation of hydroxide precipitation, and ensuring that metal ions are evenly dispersed in the 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; adding ammonia water provides a weak alkaline environment, which promotes the deprotonation of hydroxyl groups on the surface of the silicon sphere and binds to 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 doping structure.

[0039] S3: Add 32g lithium fluoride and 400mL of 9mol / L dilute hydrochloric acid to the reactor, stir for 20min, then add 10g of titanium aluminum carbide powder, react at 500rpm and 40°C for 48h, transfer to a centrifuge, centrifuge and wash with 400mL of 2mol / L dilute hydrochloric acid at 3500rpm for 5min, then centrifuge and wash with deionized water at 3500rpm for 8min until the solution is neutral, let it stand for 12h, remove the upper solution and add 400mL of deionized water, stir evenly and transfer to the reactor, ultrasonicate under argon protection at 3500rpm for 2h, transfer the product to a centrifuge, centrifuge at 3500rpm for 45min, let it stand for 12h, collect the upper solution, and freeze-dry for 10h to obtain titanium carbide nanosheets.

[0040] Lithium fluoride reacts with hydrochloric acid to produce hydrofluoric acid and lithium chloride, which etch titanium aluminum carbide, a MAX phase material with functional groups such as -O, -F or -OH on the surface, in an acidic environment. The hydrofluoric acid etches away the aluminum layer to obtain titanium carbide nanosheets, which are then washed with dilute hydrochloric acid and deionized water to further purify the MXene nanosheets.

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

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

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

[0044] After the chitosan aerogel is carbonized, a layer of derived carbon can be coated on the surface of the nano-silicon particles and stably and firmly wrapped on the surface of the modified titanium carbide nanosheets. The two can synergistically buffer the stress generated by the volume expansion effect of silicon, prevent the cracking and pulverization of silicon particles, improve the cycle stability, and at the same time 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 1.5% sodium carboxymethyl cellulose solution were transferred to a reactor and stirred at 600rpm for 6h. 18g of 18% styrene-butadiene rubber solution was added at 100rpm and stirred for 30min to obtain a high-rate lithium battery electrode slurry.

[0046] Example 2: A high-rate lithium battery electrode slurry, comprising the following steps:

[0047] S1: Add 90g of ferrosilicon powder and 11L of 1.0mol / L hydrochloric acid solution into a reactor, ultrasonically disperse for 25min, react at room temperature for 22h, collect the precipitate by centrifugation, wash the filter cake with deionized water four times, and dry it at 75°C for 11h to obtain porous silicon sphere powder.

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

[0049] S3: 36 g of lithium fluoride and 450 mL of 9 mol / L dilute hydrochloric acid were added to the reactor and stirred for 25 min. Then 12.5 g of titanium aluminum carbide powder was added and reacted at 650 rpm and 45 ° C for 49 h. The mixture was transferred to a centrifuge and centrifuged at 3750 rpm for 6.5 min with 450 mL of 2 mol / L dilute hydrochloric acid. The mixture was then centrifuged and washed at 3750 rpm for 9 min with deionized water until the solution was neutral. The mixture was allowed to stand for 13.5 h, the upper layer of solution was removed, and 450 mL of deionized water was added. After stirring evenly, the mixture was transferred to a reactor and ultrasonicated at 3750 rpm for 3 h under argon protection. The product was transferred to a centrifuge and centrifuged at 3750 rpm for 52.5 min. The upper layer of solution was collected after standing for 13.5 h and freeze-dried for 11 h to obtain titanium carbide nanosheets.

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

[0051] S5: 19 mL of acetic acid solution, 900 mL of deionized water and 19 g of chitosan were added to the reactor, stirred at 85 ° C for 35 minutes, then 9 g of modified titanium carbide nanosheets and 27.5 g of nickel-cobalt-doped porous silicon balls were added and stirred for 35 minutes, and then 17.5 mL of glutaraldehyde cross-linking agent was added and stirred for 25 minutes. The mixture was vacuum dried and transferred to a tube furnace. The reaction was carried out at 950 ° C for 2.5 hours under argon protection to obtain carbon-coated composite porous microspheres.

[0052] S6: Transfer 75g of nano-copper powder, 19g of conductive carbon black, 19g of carbon-coated composite porous microspheres and 225g of 1.5% sodium carboxymethyl cellulose solution into a reactor, stir at 700rpm for 7h, add 19g of 18% styrene-butadiene rubber solution at 110rpm, and stir for 35min to obtain the electrode slurry for high-rate lithium battery.

[0053] Example 3: A high-rate lithium battery electrode slurry, comprising the following steps:

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

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

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

[0057] S4: 20 g of titanium carbide nanosheets, 140 g of aminobenzenesulfonic acid, and 140 g of tert-butyl nitrite were added to a reaction kettle in sequence, vacuumed for 5 times, and reacted at 100° C. for 10 h 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 into the reactor, stir at 90 ° C for 40 minutes, then add 10 g of modified titanium carbide nanosheets and 30 g of nickel-cobalt-doped porous silicon balls and stir for 40 minutes, then add 20 mL of glutaraldehyde cross-linking agent and stir for 30 minutes, vacuum dry, transfer to a tube furnace, and react at 1000 ° C for 3 hours under argon protection to obtain carbon-coated composite porous microspheres.

[0059] S6: 80g of nano-copper powder, 20g of conductive carbon black, 20g of carbon-coated composite porous microspheres and 240g of 1.5% sodium carboxymethyl cellulose solution were transferred to a reactor and stirred at 800rpm for 8h. 20g of 18% styrene-butadiene rubber solution was added at 120rpm and stirred for 40min to obtain a high-rate lithium battery electrode slurry.

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

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

[0062] All raw materials in Examples 1 to 3 are commercially available products.

[0063] Comparative Example 1: The difference from Example 1 is that step S2 is deleted, and porous silicon ball powder is used to replace nickel-cobalt doped porous silicon balls in step S5. The other steps remain unchanged to prepare electrode slurry for high-rate lithium batteries.

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

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

[0066] The electrode slurry of the high-rate lithium battery prepared in Examples 1 to 3 and Comparative Examples 1 to 3 was made into electrodes according to the coating process in Example 4. The obtained electrodes were cut into 14 mm small discs, 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 turn. After 35 μL of electrolyte was dripped into it using a pipette, and then the diaphragm was placed and 70 μL of electrolyte was dripped into it. The electrode was aligned with the lithium sheet with the coated surface facing down, and the gasket, shrapnel and positive electrode shell were placed in turn. Finally, the battery was packaged into a CR2032 button battery at a pressure of 140 kg and transferred out of the glove box. The residual electrolyte on the surface was wiped off with dust-free paper dipped in anhydrous ethanol, and the electrochemical test was performed after standing at room temperature for 12 hours.

[0067] Electrochemical testing: 0.5C charge-discharge cycle performance tests were conducted at 25°C in the voltage range of 0.01-1.5V. The battery conductivity, initial coulombic efficiency, volume change percentage, 100-cycle capacity retention rate, and lithium dendrite phenomenon were recorded. The results are shown in Table 1:

[0068] Table 1: Performance test results

[0069]

[0070] As can be seen from Table 1, the performance of the electrode slurries of the high-rate lithium batteries prepared in Examples 1 to 3 of the present invention is significantly better than that of the comparative example, with higher conductivity, first coulombic efficiency and 100-cycle capacity retention rate, lower volume change percentage and reduced lithium dendrite phenomenon.

[0071] In Comparative Example 1, the conductivity and 100-cycle capacity retention rate decreased significantly. After removing the metal doping, the conductivity of the porous silicon sphere itself was poor, which may lead to a decrease in the overall conductivity of the electrode. The volume change of silicon during the cycle cannot be effectively suppressed, resulting in particle breakage and repeated growth of the solid electrolyte interface film, consumption of electrolyte and lithium source, and a decrease in capacity retention rate. Nickel-cobalt doped porous silicon spheres can form a conductive network, enhance the electron transmission ability of the material, and may also stabilize the silicon sphere structure through chemical bonding, reducing the shedding of active substances.

[0072] The first coulombic efficiency in Comparative Example 2 is significantly reduced. This may be because the surface of the unmodified titanium carbide nanosheets contains a large number of oxygen-containing, fluorine-containing and other functional groups. These defect sites will catalyze the decomposition of the electrolyte to form a thick and unstable solid electrolyte interface film, resulting in irreversible loss of lithium ions and electrolyte during the first charge and discharge process. It may also undergo side reactions with lithium and consume a large amount of active lithium, resulting in a decrease in the first coulombic efficiency.

[0073] In Comparative Example 3, the percentage of volume change is significantly increased and the lithium dendrite phenomenon is obvious. This may be because the carbon nanotubes have a linear structure and cannot effectively buffer the violent expansion of silicon. The modified titanium carbide nanosheets have a layered structure, which can disperse the silicon expansion stress and provide physical support. The carbon nanotubes are in physical contact with the silicon particles and are easily separated from the silicon particles during the expansion process, resulting in microcracks on the electrode surface. Lithium ions preferentially deposit at the cracks to form dendrites. The easy agglomeration of carbon nanotubes may also accelerate the growth of lithium dendrites.

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

Claims

1. A high-rate lithium battery electrode slurry, characterized in that: The steps include: Step 1: Add acetic acid solution, deionized water and chitosan to a reactor, stir evenly at 80-90°C, add modified titanium carbide nanosheets and nickel-cobalt doped porous silicon spheres and stir evenly, then add glutaraldehyde crosslinker and stir evenly, vacuum dry, transfer to a tube furnace, and react under argon protection to obtain carbon-coated composite porous microspheres; Step 2: Transfer nano copper powder, conductive carbon black, carbon-coated composite porous microspheres and 1.5wt% sodium carboxymethyl cellulose solution into a reactor and stir evenly, then add 18wt% styrene-butadiene rubber solution and stir evenly to obtain a high-rate lithium battery electrode slurry.

2. The electrode slurry for a high-rate lithium battery according to claim 1, characterized in that: The dosage ratio of the acetic acid solution, deionized water, chitosan, modified titanium carbide nanosheets, nickel-cobalt doped porous silicon spheres, and glutaraldehyde crosslinking agent in step 1 is 18-20 mL: 800-1000 mL: 18-20 g: 8-10 g: 25-30 g: 15-20 mL.

3. The electrode slurry for a high-rate lithium battery according to claim 1, characterized in that: The mass ratio of the nano copper powder, conductive carbon black, carbon-coated composite porous microspheres, sodium carboxymethyl cellulose solution, and styrene-butadiene rubber solution in step 2 is 70-80:18-20:18-20:210-240:18-20.

4. The electrode slurry for a high-rate lithium battery according to claim 1, characterized in that: The nickel-cobalt doped porous silicon spheres are prepared by the following steps: Ammonium fluoride, cobalt sulfate, and nickel sulfate were dissolved in deionized water, and the pH value was adjusted to 8 with ammonia water and added to the reactor. The porous silicon ball powder was then added and stirred for 1-2 hours. The precipitate was collected by centrifugation and the filter cake was washed alternately with deionized water and ethanol and dried to obtain nickel-cobalt doped porous silicon balls. The usage 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.

5. The electrode slurry for a high-rate lithium battery according to claim 4, characterized in that: The porous silicon sphere powder is prepared by the following steps: Add ferrosilicon powder and 1.0 mol / L hydrochloric acid solution into a reactor, perform ultrasonic dispersion for 20-30 min, react at room temperature for 20-24 h, collect the precipitate by centrifugation, wash the filter cake with deionized water and dry it to obtain porous silicon sphere powder; The usage ratio of the ferrosilicon powder and the hydrochloric acid solution is 80-100 g:10-12 L.

6. The electrode slurry for a high-rate lithium battery according to claim 1, characterized in that: The modified titanium carbide nanosheets are prepared by the following steps: Titanium carbide nanosheets, aminobenzenesulfonic acid and tert-butyl nitrite are added into a reaction kettle in sequence, vacuumed for 3-5 times, and reacted at 80-100° C. for 8-10 hours to obtain modified titanium carbide nanosheets.

7. The electrode slurry for a high-rate lithium battery according to claim 6, characterized in that: The ratio of the titanium carbide nanosheets, aminobenzenesulfonic acid and tert-butyl nitrite is 1:7:

7.

8. The electrode slurry for a high-rate lithium battery according to claim 7, characterized in that: The titanium carbide nanosheets are prepared by the following steps: Lithium fluoride and 9 mol / L dilute hydrochloric acid are added to a reaction kettle, stirred for 20-30 minutes, and then titanium aluminum carbide powder is added. The reaction is carried out at 500-800 rpm and 40-50° C. for 48-50 hours, washed, centrifuged, and freeze-dried to obtain titanium carbide nanosheets.

9. The electrode slurry for a high-rate lithium battery according to claim 8, characterized in that: The usage ratio of the lithium fluoride, dilute hydrochloric acid and titanium aluminum carbide powder is 32-40 g: 400-500 mL: 10-15 g.

10. The coating process of the electrode slurry for a high-rate lithium battery according to claim 1, characterized in that: The steps include: The high-rate lithium battery pole piece slurry is dipped into the current collector surface and evenly coated with a scraper, and then dried to complete the coating process of the high-rate lithium battery pole piece slurry.

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