A method for preparing a lithium-ion battery cell

Abstract

This invention relates to the field of lithium battery technology, and in particular to a method for preparing a lithium-ion battery cell. The invention discloses a method for preparing a lithium-ion battery cell, comprising: first, preparing a positive electrode slurry containing modified titanium aluminum carbide, graphene oxide, etc., and a negative electrode slurry containing aminated carbon nanotubes, zinc aluminum spinel, etc., both processed according to specific proportions and processes; second, coating the positive and negative electrode slurries separately onto a current collector, and obtaining positive and negative electrode sheets through drying, coating with a coating agent, etc.; next, preparing a composite separator coated with a separator coating agent and curing it; finally, winding the separator in a positive-separator-negative-separator sequence, and obtaining a lithium-ion battery cell through drying, encapsulation, electrolyte injection, formation, etc.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to a method for preparing a lithium-ion battery cell. Background Technology

[0002] Lithium-ion batteries, as a highly efficient energy storage device, have become a core power source for consumer electronics, electric vehicles, and large-scale energy storage due to their advantages such as high energy density, long cycle life, and no memory effect. With the rapid development of the new energy industry, market demands for lithium-ion battery performance continue to rise: in the electric vehicle sector, higher energy density, longer cycle life, better safety, faster charging and discharging capabilities, and stronger high-temperature resistance are required; in the energy storage sector, the need to adapt to large-scale, long-term energy storage and dispatch places even more stringent demands on battery consistency, stability, high-temperature resistance, and cost control.

[0003] However, existing lithium-ion cell manufacturing technologies still have many bottlenecks, making it difficult to meet the above-mentioned high-performance requirements. These bottlenecks are mainly reflected in the performance of positive electrode materials, the interface and structure of negative electrodes, and the safety shortcomings and high-temperature resistance of separators and electrodes.

[0004] Chinese patent CN118970147A discloses a battery cell and its preparation method, as well as a lithium-ion battery. First, raw materials such as a first conductive agent are mixed in proportion to prepare a safety coating slurry, controlling the solid content and viscosity. Second, the slurry is coated onto the positive electrode current collector to obtain a current collector containing a safety coating. Next, a positive electrode active material layer is coated onto the current collector or the safety coating to obtain a positive electrode sheet. Then, raw materials are coated onto the negative electrode current collector to form a negative electrode sheet. Finally, the positive and negative electrode sheets are assembled to obtain a battery cell. The positive electrode active material in this patent includes high-nickel ternary materials such as NCM811. Although these materials have high energy density, they have inherent problems such as volume expansion and transition metal dissolution during charge-discharge cycles. Furthermore, they have not been optimized to address the characteristics of high-nickel materials being prone to decomposition and oxygen release at high temperatures, resulting in insufficient high-temperature resistance. During high-temperature cycling, not only does the capacity decay rate accelerate, but the risk of thermal runaway may also be exacerbated by material decomposition. Although these problems are mitigated by the first active material in the safety coating, the structural modification of the positive electrode active material itself is not addressed. Under long-term cycling, the capacity may still decay rapidly due to the collapse of the material's own structure. Moreover, there may be lattice mismatch or excessively high interfacial impedance between the first active material in the safety coating and the active material in the positive electrode active material layer. Although the coating parameters of the safety coating are specified, the ion conduction efficiency at the interface between the two is not clearly defined, which may lead to an increase in the overall impedance of the positive electrode and affect the rate performance.

[0005] Chinese patent CN115020793A discloses a lithium-ion battery core pack, a lithium-ion battery, and a method for preparing a lithium-ion battery. First, raw materials are mixed to form positive and negative electrode slurries. Second, the slurry is coated onto a current collector and dried to obtain electrode sheets. Next, the electrode sheets are punched and compacted, and then assembled with a separator and glued to form an electrode core. Finally, the electrode core is sealed with an aluminum-plastic film, and then liquid is injected, sealed, capacity tested, and qualified batteries are obtained. The negative electrode preparation in this patent only involves basic steps such as slurry coating, punching and compaction, without mentioning optimization measures for the negative electrode / electrolyte interface, nor addressing issues such as interlayer delamination and lithium dendrite growth that may occur in graphite and other negative electrode materials during cycling. Instability of the SEI film may lead to increased internal resistance and accelerated capacity decay, and if lithium dendrites puncture the separator, they may cause a short circuit. Furthermore, the high-temperature resistance of the electrode and separator is not enhanced. Under high-temperature conditions, conventional separators are prone to thermal shrinkage, leading to direct contact between the positive and negative electrodes. The active material of the electrode is also prone to falling off due to binder failure, further exacerbating the risk of thermal runaway. The enhancement of the mechanical strength of the electrode and the puncture resistance and high-temperature resistance of the separator is insufficient, making it difficult to effectively reduce the risk of thermal runaway.

[0006] Chinese patent CN104882630B discloses a bare lithium-ion battery cell and a method for preparing a lithium-ion battery containing the bare cell. The specific steps are as follows: First, a porous lithium-rich layer is obtained by pretreating a lithium-rich material. This layer is then combined with a dried separator and pressurized to form a composite separator. Second, the composite separator is assembled with cathode and anode sheets to form a bare cell, which is then placed in a casing / bag, filled with electrolyte, and left to stand. Next, the impregnated cell undergoes a formation treatment. Finally, pressure is applied to bring the lithium-rich layer into contact with the anode to form an electron channel for lithium replenishment. After shaping and degassing, the finished cell is obtained. This patent achieves spontaneous lithium intercalation through the potential difference between the lithium-rich material layer and the anode, but this process is highly dependent on sufficient contact between the lithium-rich layer and the anode surface. If the porous structure of the composite separator is unevenly distributed, or if the surface pressure is not properly controlled during lithium intercalation, excessive local lithium intercalation can easily occur, leading to lithium plating and subsequently puncturing the separator and causing a short circuit. Furthermore, excessively high composite surface pressure can damage the porous structure of the separator, affecting ion conductivity and exacerbating local heat accumulation. Simultaneously, the overall high-temperature resistance system of the cell is not optimized—the lithium-rich layer is prone to structural degradation at high temperatures, resulting in a significant decrease in lithium replenishment efficiency. Moreover, during high-temperature storage or charging / discharging of the cell, side reactions at the electrolyte-electrode interface are significantly aggravated, leading to poor performance stability. In addition, this patent does not optimize the efficient construction of the positive and negative electrode conductive networks or the consistency control during mass production, making it difficult to meet the requirements for high-rate performance, high-temperature resistance, and battery stability in mass production scenarios.

[0007] In summary, existing lithium-ion battery cell fabrication technologies have significant shortcomings in areas such as high-nickel cathode stability, anode interface control, safety enhancement, high-temperature resistance, and process synergy. These limitations make it difficult to meet the demands of the new energy industry (especially electric vehicles and large-scale energy storage) for batteries with high energy density, long lifespan, high safety, high temperature resistance, and high consistency. Therefore, developing a cell fabrication method that can overcome these bottlenecks and achieve performance breakthroughs in key dimensions such as high-nickel cathode stability, anode interface control, safety enhancement, and high-temperature resistance through material design and process innovation has become an important research direction in the current lithium-ion battery field. Summary of the Invention

[0008] To address the aforementioned problems, the present invention aims to provide a method for preparing a lithium-ion battery cell, specifically comprising the following steps: S001, modified titanium aluminum carbide, graphene oxide and lithium phosphate nanoparticles are added to N-methylpyrrolidone solvent for ultrasonic dispersion treatment, and then NCM811, conductive carbon black and polyvinylidene fluoride are added in sequence and subjected to gradient stirring treatment to obtain positive electrode slurry. S002, Aminated carbon nanotubes and zinc aluminum spinel powder are added to ultrapure water for spherical dispersion treatment, and then graphite, sodium carboxymethyl cellulose and styrene-butadiene rubber are added in sequence and stirred to obtain the negative electrode slurry. S003, the positive electrode slurry is coated on the positive electrode current collector, and then the positive electrode sheet is obtained by sequentially performing gradient drying treatment, positive electrode coating agent coating, segmented reaction drying treatment, gradient hot rolling reaction treatment, welding of electrode tabs and cutting sheet. S004, the negative electrode slurry is coated on the negative electrode current collector, and then subjected to gradient drying, negative electrode coating agent coating, segmented freeze drying, cold pressing, welding of electrode tabs and cutting of sheet to obtain the negative electrode sheet. S005, the diaphragm coating agent is applied to the polypropylene / polyethylene composite membrane and cured to obtain the diaphragm. S006 is produced by winding the positive electrode sheet, separator, negative electrode sheet, and separator in sequence, followed by drying, packaging, baking, electrolyte injection, standing, formation, and aging to obtain a lithium-ion battery cell.

[0009] In step S001, the mass ratio of NCM811, conductive carbon black, polyvinylidene fluoride, modified titanium aluminum carbide, graphene oxide, and lithium phosphate nanoparticles is 90:3:5:1:0.3:0.5; the volume-mass ratio of N-methylpyrrolidone solvent to titanium aluminum carbide powder is 150:1; the ultrasonic dispersion treatment is performed by ultrasonication at 350 W for 25 min; the gradient stirring treatment is performed by stirring at 300 rpm for 10 min, then at 500 rpm for 15 min, then at 800 rpm for 15 min, and finally at 1200 rpm for 15 min.

[0010] In step S002, the mass ratio of graphite, sodium carboxymethyl cellulose, styrene-butadiene rubber, aminated carbon nanotubes, and zinc aluminum spinel powder is 92:1.5:1:0.8:0.6; the volume-to-mass ratio of ultrapure water to aminated carbon nanotubes is 120:1; the conditions for spherical dispersion treatment are grinding at 400 rpm for 45 min; and the conditions for stirring treatment are stirring at 800 rpm for 30 min.

[0011] In step S003, the positive electrode current collector is aluminum foil; the coating is done using a micro-gravure coating method; the thickness of the positive electrode slurry coating is 90 μm to 100 μm; the gradient drying process involves drying at 60 ℃ for 30 min, then at 90 ℃ for 20 min, and finally at 110 ℃ for 15 min; the positive electrode coating agent is composed of alumina, lithium borate, and ethanol in a mass-to-volume ratio of 2:1:50; the thickness of the positive electrode coating agent is 1 μm to 2 μm; the segmented reaction drying process involves drying at 50 ℃ for 15 min, then reacting at 90 ℃ for 25 min, and finally reacting at 110 ℃ and -0.09 MPa for 30 min; the gradient hot rolling reaction process involves holding at 60 ℃ and 25 MPa for 10 min, then hot rolling at 70 ℃, 25 MPa, and 1.0 m / min for 20 min; the size of the cut sheet is 150 mm × 40 mm.

[0012] In step S004, the negative electrode current collector is copper foil; the coating is done by slot extrusion coating; the thickness of the negative electrode slurry coating is 100 μm to 120 μm; the gradient drying process involves drying at 50 ℃ for 25 min, followed by drying at 80 ℃ and -0.09 MPa for 30 min; the negative electrode coating agent is composed of silicon monoxide, graphite carbon, lithium fluoride, and N-methylpyrrolidone, with a mass-to-volume ratio of 3:1:0.6:40; the thickness of the negative electrode coating agent is 1 μm to 2 μm; the segmented freeze-drying process involves freezing at -40 ℃ for 20 min, followed by sublimation drying at -0.09 MPa for 40 min, and then drying at 30 ℃ for 15 min; the cold pressing process involves holding at -10 ℃ and 20 MPa for 15 min, followed by standing at 25 ℃ for 5 min; the dimensions of the cut sheet are 160 mm × 42 mm.

[0013] In step S005, the diaphragm coating agent is composed of titanium dioxide, lithium silicate, polyamic acid, and N-methylpyrrolidone, with a mass-to-volume ratio of 3:2:1:50; the coating is applied using a slot extrusion coating method; the coating thickness of the diaphragm coating agent is 2 μm to 3 μm; the curing treatment is UV curing for 5 min; the dimensions of the polypropylene / polyethylene composite membrane are 170 mm × 44 mm.

[0014] In step S006, the winding tension is 10 N, and the product is dried at 90 ℃ for 14 h; it is then encapsulated using an aluminum-plastic film; baked at 125 ℃ and -0.09 MPa for 5 h; the electrolyte consists of lithium hexafluorophosphate, ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, lithium thiosulfate, and aluminum trifluoromethanesulfonate in a mass ratio of 119:311:315:231:5:3; the settling condition is 45 ℃ for 60 min; the formation process involves first charging at a constant current of 0.1 C to 4.2 V, then charging at a constant voltage until the current drops to 0.05 C, followed by discharging at a constant current of 0.2 C to 2.8 V, which constitutes one cycle, and three cycles are performed; the aging process involves aging at 45 ℃ for 24 h.

[0015] Modified titanium aluminum carbide is produced by modifying titanium aluminum carbide with a titanate coupling agent, specifically including the following steps: S101, the titanium aluminum carbide is dried and ground to obtain the pretreated titanium aluminum carbide. S102, Isopropyl tris(dioctyl pyrophosphoryloxy) titanate is slowly added to anhydrous ethanol and stirred to obtain titanate coupling agent solution. S103 involves adding pretreated titanium aluminum carbide to anhydrous ethanol, performing ultrasonic dispersion, slowly adding titanate coupling agent solution, stirring, adjusting pH, and then performing modification reaction, separation, washing, drying, and grinding to obtain modified titanium aluminum carbide.

[0016] In step S101, the drying process is carried out at 60 ℃ for 5 h; the grinding process is carried out until the material passes through a 100-mesh sieve.

[0017] In step S102, the concentration of isopropyltris(dioctylpyrophosphoryloxy)titanate in the titanate coupling agent solution is 0.01 g / mL; the stirring treatment is 300 rpm for 20 min.

[0018] In step S103, the mass-to-volume ratio of the pretreated titanium aluminum carbide, anhydrous ethanol, and titanate coupling agent solution is 1:15:5; ultrasonic dispersion is performed at 300 W for 30 min; stirring is performed at 600 rpm for 30 min; pH is adjusted to 4-5; modification reaction is performed at 60 ℃ and 600 rpm for 3 h; centrifugation is performed at 10000 r / min for 15 min, and the supernatant is discarded; washing is performed by first adding anhydrous ethanol, then centrifuging at 10000 r / min for 15 min, and then discarding the supernatant, which is one wash, and this is repeated 4 times; drying is performed at 70 ℃ and -0.09 MPa for 8 h; and grinding is performed until it passes through a 200-mesh sieve.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention extends battery cycle life and imparts excellent high-temperature resistance to the battery through the synergistic stabilizing effect of the interface complex and the regulation of the reactive SEI film. For the positive electrode, modified titanium aluminum carbide itself possesses excellent high-temperature structural stability. The ternary interface complex formed by the coordination of its surface titanate segments with the hydroxyl groups of graphene oxide and the phosphorus-oxygen bonds on the lithium phosphate surface maintains structural integrity even at high temperatures. Titanium aluminum carbide effectively suppresses excessive volume expansion and decomposition of NCM811 at high temperatures. The multidimensional conductive network of graphene oxide and conductive carbon black is not easily broken at high temperatures, ensuring stable electron transport efficiency. The lithium phosphate transition layer reduces the dissolution rate of transition metal ions at high temperatures, preventing the aggravation of high-temperature side reactions between the electrode and the electrolyte. For the negative electrode, the flexible conductive framework of the aminated carbon nanotube-zinc aluminum spinel interface complex resists thermally induced exfoliation between graphite layers during high-temperature cycling. The stable crystal structure of zinc aluminum spinel buffers the volume fluctuations of the negative electrode at high temperatures, reducing structural collapse caused by thermal stress. The inorganic-organic composite SEI membrane constructed from lithium thiosulfate and aluminum trifluoromethanesulfonate in the electrolyte exhibits significantly better high-temperature resistance than conventional SEI membranes: the inorganic layers of lithium sulfide and lithium sulfite can resist the damage to the membrane structure caused by high temperatures, while aluminum fluoride can inhibit the hydrolysis of the electrolyte to generate hydrogen fluoride at high temperatures, thus avoiding high-temperature corrosion failure of the SEI membrane. This reduces side reactions and capacity decay under high-temperature conditions and ensures cycle life stability. 2. This invention enhances battery safety and reduces the risk of thermal runaway by improving the mechanical strength and thermal stability of the electrode and strengthening the heat resistance and puncture resistance of the separator. The core of this invention lies in constructing a comprehensive high-temperature protection system. The alumina in the positive electrode coating not only possesses high hardness but also excellent high-temperature resistance, maintaining the rigidity of the electrode structure and reducing thermal deformation at high temperatures. The gradient hot rolling process improves the electrode density while promoting uniform distribution of the binder, preventing local binder failure at high temperatures that could lead to the shedding of active material. In the negative electrode coating, the lithium fluoride-modified SEI film does not decrease in mechanical strength at high temperatures and can effectively inhibit the abnormal growth of lithium dendrites at high temperatures. The stable composite layer formed by the reaction of silicon monoxide and lithium can prevent excessive reaction between the electrolyte and the negative electrode at high temperatures, further optimizing interfacial thermal stability. Regarding the separator, the polypropylene / polyethylene composite membrane combines the low-heat closed-cell properties of polyethylene with the high-temperature structural strength of polypropylene. After the coated separator coating agent is cured by ultraviolet light, titanium dioxide and lithium silicate form a high-temperature resistant inorganic skeleton, while the organic layer after polyamic acid curing enhances the puncture resistance. Even under high-temperature thermal shock, the separator can still maintain its integrity, avoiding direct contact between the positive and negative electrodes and causing short circuits, thus fundamentally reducing the risk of high-temperature thermal runaway. 3. This invention improves rate performance and optimizes charge / discharge efficiency by constructing a highly efficient conductive network, and this performance remains stable even at high temperatures. The multidimensional conductive pathway formed by the modified titanium aluminum carbide-graphene oxide-lithium phosphate composite in the positive electrode and the aminated carbon nanotube-zinc aluminum spinel composite in the negative electrode exhibits a much lower increase in electron transport impedance at high temperatures compared to conventional conductive networks. The NCM-composite lattice-matched phase induced by thermal rolling reduces interfacial impedance fluctuations within the electrode at high temperatures. The lithium-silicon-titanium oxide coherent phase generated by the separator coating reaction maintains a continuous lithium-ion channel structure at high temperatures, preventing channel breakage due to thermal vibration. Combined with the ion bridging effect of the alumina-lithium borate solid solution in the positive electrode, it accelerates the migration rate of lithium ions at high temperatures, avoiding the sharp drop in charge / discharge efficiency that occurs in conventional batteries under high-rate and high-temperature conditions, ensuring excellent rate performance even in high-temperature fast-charging scenarios. 4. This invention provides process support for improving battery consistency by controlling each stage of the production process, while ensuring the uniformity of the battery's high-temperature performance. The ultrasonic dispersion and gradient stirring of the positive electrode, and the spherical dispersion process of the negative electrode, not only ensure uniform mixing of the slurry but also allow for the uniform distribution of high-temperature resistant components such as modified titanium aluminum carbide and aminated carbon nanotubes in the slurry, avoiding high-temperature performance fluctuations caused by local differences in the concentration of high-temperature resistant components on the electrode sheet. High-precision control of micro-gravure coating and slot extrusion coating ensures consistent thickness of the electrode sheet and separator, resulting in uniform high-temperature coating thickness in different areas and reducing differences in high-temperature heat distribution across different parts of the cell after winding. Gradient drying and segmented reaction drying, through gradual heating and negative pressure, prevent internal stress caused by temperature differences in the coating during drying, ensuring that the coating is not prone to cracking or peeling at high temperatures. Segmented freeze-drying allows the negative electrode coating to form a uniform porous microstructure. This structure has consistent liquid absorption and retention capacity at high temperatures, reducing the deviation in high-temperature cycle performance between batches of cells, laying the foundation for battery consistency and mass production stability under high-temperature conditions from the source of the process. Detailed Implementation

[0020] The present invention will be further described below with reference to specific embodiments. Example

[0021] A method for preparing a lithium-ion battery cell specifically includes the following steps: 10 g of titanium aluminum carbide was dried at 60 ℃ for 5 h and then ground until it passed through a 100-mesh sieve to obtain pretreated titanium aluminum carbide. 0.5 g of isopropyltris(dioctylpyrophosphoryloxy)titanate was slowly added to 50 mL of anhydrous ethanol and stirred at 300 rpm for 20 min to obtain a titanate coupling agent solution. Pretreated titanium aluminum carbide was added to 150 mL of anhydrous ethanol, sonicated at 300 W for 30 min, titanate coupling agent solution was slowly added dropwise, stirred at 600 rpm for 30 min, pH was adjusted to 4-5, and reacted at 60 ℃ and 600 rpm for 3 h. After centrifugation at 10000 r / min for 15 min, the supernatant was discarded. Anhydrous ethanol was added first, and centrifugation at 10000 r / min for 15 min was performed again. The supernatant was then discarded, which was the first washing. The washing was repeated 4 times. The mixture was dried at 70 ℃ and -0.09 MPa for 8 h, and then ground until it passed through a 200-mesh sieve to obtain modified titanium aluminum carbide. 1 g of modified titanium aluminum carbide, 0.3 g of graphene oxide and 0.5 g of lithium phosphate nanoparticles were added to 150 mL of N-methylpyrrolidone solvent and sonicated at 350 W for 25 min. Then, 90 g of NCM811, 3 g of conductive carbon black and 5 g of polyvinylidene fluoride were added in sequence. The mixture was stirred at 300 rpm for 10 min, then at 500 rpm for 15 min, then at 800 rpm for 15 min, and finally at 1200 rpm for 15 min to obtain the positive electrode slurry. Add 0.8 g of aminated carbon nanotubes and 0.6 g of zinc aluminum spinel powder to 120 mL of ultrapure water and grind at 400 rpm for 45 min. Then add 92 g of graphite, 1.5 g of sodium carboxymethyl cellulose and 1 g of styrene-butadiene rubber in sequence and stir at 800 rpm for 30 min to obtain the negative electrode slurry. The positive electrode slurry is coated onto the aluminum foil positive electrode current collector and dried at 60 ℃ for 30 min, then at 90 ℃ for 20 min, and then at 110 ℃ for 15 min. The positive electrode coating agent is then coated and dried at 50 ℃ for 15 min, then reacted at 90 ℃ for 25 min, and then reacted at 110 ℃ and -0.09 MPa for 30 min. The electrode is then held at 60 ℃ and 25 MPa for 10 min, and then hot-rolled at 70 ℃, 25 MPa and 1.0 m / min for 20 min. The tabs and the cut sheet are then welded to obtain the positive electrode sheet. The negative electrode slurry is coated onto the copper foil negative electrode current collector, dried at 50 ℃ for 25 min, then dried at 80 ℃ and -0.09 MPa for 30 min. The negative electrode coating agent is then coated, first frozen at -40 ℃ for 20 min, then sublimated and dried at -0.09 MPa for 40 min, then dried at 30 ℃ for 15 min. It is then held at -10 ℃ and 20 MPa for 15 min, then allowed to stand at 25 ℃ for 5 min. The tabs and the cut sheet are then welded to obtain the negative electrode sheet. The diaphragm coating agent is applied to the polypropylene / polyethylene composite membrane and cured under ultraviolet light for 5 minutes to obtain the diaphragm. The positive electrode sheet, separator, negative electrode sheet, and separator were wound in that order, dried at 90 ℃ for 14 h, packaged, baked at 125 ℃ and -0.09 MPa for 5 h, injected with electrolyte, and allowed to stand at 45 ℃ for 60 min. The battery was first charged at a constant current of 0.1 C to 4.2 V, then charged at a constant voltage until the current dropped to 0.05 C, and then discharged at a constant current of 0.2 C to 2.8 V, which constitutes one cycle. After three cycles, the battery was aged at 45 ℃ for 24 h to obtain the lithium-ion battery cell, which is designated as test sample 1.

[0022] Comparative Example 1 A method for preparing a lithium-ion battery cell without modified titanium aluminum carbide specifically includes the following steps: The difference from Example 1 is that no modified titanium aluminum carbide is added when preparing the positive electrode slurry. The remaining steps are the same as in Example 1, thus obtaining control product 1.

[0023] Comparative Example 2 A method for preparing a lithium-ion battery cell with an electrolyte free of lithium thiosulfate and aluminum trifluoromethanesulfonate specifically includes the following steps: The difference from Example 1 is that an electrolyte without lithium thiosulfate and aluminum trifluoromethanesulfonate is added when preparing the lithium-ion battery cell. The remaining steps are the same as in Example 1, thus obtaining control product 2.

[0024] Comparative Example 3 A method for preparing a lithium-ion battery cell without a positive electrode coating agent specifically includes the following steps: The difference from Example 1 is that no positive electrode coating agent is applied when preparing the positive electrode sheet. The remaining steps are the same as in Example 1, thus obtaining control product 3.

[0025] Comparative Example 4 A method for preparing a lithium-ion battery cell using a negative electrode sheet with a conventional drying process specifically includes the following steps: The difference from Example 1 is that, in preparing the negative electrode sheet, the negative electrode slurry is coated on the copper foil negative electrode current collector and dried at 80 ℃ for 120 min, the negative electrode coating agent is coated and dried at 80 ℃ for 120 min, first pressure is maintained at -10 ℃ and 20 MPa for 15 min, then it is allowed to stand at 25 ℃ for 5 min, and the electrode tabs and cut sheets are welded to obtain the negative electrode sheet; The remaining steps are the same as in Example 1, thus obtaining control sample 4.

[0026] Experimental Example 1 This experimental example conducts high-temperature cycle life tests on Example 1 and Comparative Examples 1-4, specifically including the following steps: Five cells from each of Example 1 and Comparative Examples 1-4 were randomly selected and placed at 60 °C for 2 h. They were then charged at a constant current of 0.5 C to 4.2 V, charged at a constant voltage until the current dropped to 0.05 C, and then stopped. After being placed at a constant current of 0.5 C for 30 min, they were discharged at a constant current of 0.5 C to 2.8 V, and the initial discharge capacity was recorded. At 60 °C, charge at a constant current of 0.5 C to 4.2 V, charge at a constant voltage to a current of 0.05 C, let stand for 20 min, discharge at a constant current of 0.5 C to 2.8 V, let stand for 20 min, that is, one cycle, and record the discharge capacity after the cycle; The capacity retention rate was calculated by comparing the discharge capacity after cycling with the initial discharge capacity. When the capacity retention rate first dropped to 80%, the number of high-temperature cycle lifetimes was recorded and the average value was taken. The test results are shown in Table 1.

[0027] Table 1. High-Temperature Cyclic Life Test Results

[0028] As shown in Table 1, the high-temperature cycle life of Example 1 (1286±3 cycles) is higher than that of the comparative examples. Compared with Comparative Example 1 (without modified titanium aluminum carbide), the cycle life of Example 1 is increased by 2.1 times, indicating that the addition of modified titanium aluminum carbide can significantly improve the battery cycle life. Compared with Comparative Example 2 (electrolyte without lithium thiosulfate and aluminum trifluoromethanesulfonate), the cycle life of Example 1 is increased by 1.5 times, indicating that the electrolyte containing lithium thiosulfate and aluminum trifluoromethanesulfonate helps to enhance cycle stability. Compared with Comparative Example 3 (no positive electrode coating agent), the cycle life of Example 1 is increased by 2.5 times, indicating that the positive electrode coating agent is crucial to improving cycle life. Compared with Comparative Example 4 (negative electrode using conventional drying process), the cycle life of Example 1 is increased by 1.35 times, demonstrating that the segmented freeze-drying process used can effectively avoid thermal damage to the coating and improve cycle performance. In summary, Example 1 achieved a significant improvement in the high-temperature cycle life of lithium-ion cells through multiple measures, including the preparation and addition of modified titanium aluminum carbide, specific electrolyte composition, application of positive electrode coating agent, and optimized negative electrode drying process.

[0029] Experiment Example 2 This experimental example conducts safety tests on Example 1 and Comparative Examples 1-4, specifically including the following steps: Thermal runaway temperature test: Three cells from each of Example 1 and Comparative Examples 1-4 were randomly selected, discharged to 2.8 V, fixed in the ARC sample chamber, sealed, and evacuated to -0.1 MPa, followed by argon gas filling to 0.1 MPa. A thermal runaway search mode was used with an initial heating rate of 5 °C / min. When the temperature suddenly increased to over 10 °C / min, the temperature at that point was recorded, and the average value was taken as the thermal runaway temperature. The test results are shown in Table 2.

[0030] Puncture test: Three cells from each of Example 1 and Comparative Examples 1-4 were randomly selected and charged to 4.2 V at a constant current of 0.5 C, followed by constant voltage charging until the current dropped to 0.05 C, and then left to stand at 25 ℃ for 1 h. The battery cell was fixed horizontally on the test platform. The steel needle was aimed at the center of the battery cell and pierced the battery cell vertically until it was completely penetrated. The results were observed and recorded to see if the battery cell showed signs of smoke, fire, or explosion. The most severe result of the three battery cells was taken as the puncture test result. The test results are shown in Table 2.

[0031] Table 2 Security Test Results

[0032] As shown in Table 2, the thermal runaway temperature of Example 1 was 215±3 ℃, which is higher than that of Comparative Examples 1-4, indicating that it has better thermal stability and is less likely to trigger thermal runaway. Example 1 showed no abnormalities in the puncture test; Comparative Example 1 caught fire, Comparative Example 2 emitted smoke, Comparative Example 3 exploded, and Comparative Example 4 emitted smoke. It is evident that Example 1 is far safer than the comparative examples when subjected to puncture. The comparative examples, due to changes in the preparation process such as the absence of modified titanium aluminum carbide, different electrolyte composition, lack of positive electrode coating agent, and conventional drying process for the negative electrode, experienced a significant decrease in puncture safety.

[0033] In summary, the battery cell prepared in Example 1 using modified titanium aluminum carbide and other materials and a special process exhibits superior performance in thermal runaway temperature and puncture tests, demonstrating significantly better thermal stability and puncture resistance than the comparative example. The comparative example, lacking the key material modified titanium aluminum carbide, altering the electrolyte composition, omitting the positive electrode coating agent, and employing a conventional negative electrode drying process, suffers from a higher risk of thermal runaway and poorer puncture safety. This highlights the effectiveness of the preparation method in Example 1 in improving the safety of lithium-ion battery cells.

[0034] Experimental Example 3 This experimental example conducts rate capability tests on Example 1 and Comparative Examples 1-4, specifically including the following steps: Three cells from each of Example 1 and Comparative Examples 1 to 4 were randomly selected and placed at 60°C for 3 hours. They were then charged at a constant current of 0.5 C to 4.2 V, charged at a constant voltage until the current dropped to 0.05 C, and then stopped. After being placed at a constant current of 0.5 C for 45 minutes, they were discharged at a constant current of 0.5 C to 2.8 V, and the initial discharge capacity was recorded. Charged at a constant current of 0.5 C to 4.2 V, then charged at a constant voltage until the current dropped to 0.05 C. After resting for 45 min, discharged at a constant current of 0.5 C to 2.8 V. After resting for 45 min, charged at a constant current of 0.5 C to 4.2 V, then charged at a constant voltage until the current dropped to 0.05 C. After resting for 45 min, discharged at a constant current of 1 C to 2.8 V. After resting for 45 min, charged at a constant current of 0.5 C to 4.2 V, then charged at a constant voltage until the current dropped to 0.05 C. After resting for 45 min, discharged at a constant current of 2 C to 2.8 V. After resting for 45 min, charged at a constant current of 0.5 C to 4.2 V, then charged at a constant voltage until the current dropped to 0.05 C. After resting for 45 min, discharged at a constant current of 5 C to 2.8 V. The discharge capacity after different discharge rates was recorded. The capacity ratio was calculated by comparing the discharge capacity after different discharge rates with the initial discharge capacity, and the average value was taken. The test results are shown in Table 3.

[0035] Table 3. Rate Performance Test Results

[0036] As shown in Table 3, Example 1 exhibits superior rate performance compared to the comparative examples. At low rates (0.5 C), the capacity ratios of all samples are close to 100%, indicating that the capacity can be fully released at low rates. At medium to high rates (1 C, 2 C, 5 C), the capacity ratios of Example 1 (96.2±0.3%, 93.5±0.1%, 90.1±0.2%) are significantly higher than those of the comparative examples, demonstrating excellent medium to high rate discharge capability. Compared to Comparative Example 1 (without modified titanium aluminum carbide), Example 1 shows approximately 13.7%, 18.2%, and 21.4% higher capacity ratios at 1 C, 2 C, and 5 C, respectively, indicating that the addition of modified titanium aluminum carbide can significantly improve battery rate performance, especially capacity retention at high rates. Compared to Comparative Example 2 (electrolyte without lithium thiosulfate and aluminum trifluoromethanesulfonate), Example 1 showed significantly higher capacity ratios at 1 C, 2 C, and 5 C, with increases of approximately 8.1%, 12.0%, and 13.9%, respectively, indicating that the electrolyte containing lithium thiosulfate and aluminum trifluoromethanesulfonate significantly enhances rate performance. Compared to Comparative Example 3 (no positive electrode coating), Example 1 showed significantly higher capacity ratios at 1 C, 2 C, and 5 C, with increases of approximately 16.9%, 21.4%, and 24.3%, respectively, demonstrating that the positive electrode coating is a key factor in ensuring rate performance. Compared to Comparative Example 4 (negative electrode using conventional drying process), Example 1 showed significantly higher capacity ratios at 1 C, 2 C, and 5 C, with increases of 17.7%, 22.3%, and 24.8%, respectively, showcasing that its optimized segmented freeze-drying process can form a uniform porous structure, ensuring efficient electron and ion transport and greatly improving rate performance. In summary, Example 1 achieved excellent capacity retention of lithium-ion cells across the entire rate range through the synergistic effect of measures such as the preparation and addition of modified titanium aluminum carbide, specific electrolyte composition, application of positive electrode coating agent, and optimized negative electrode drying process.

[0037] The above description is only used to illustrate the technical solution of the present invention and is not intended to limit it. Equal modifications and variations made by those skilled in the art to the technical solution of the present invention, as long as they do not depart from the overall concept of the present invention, shall still fall within the scope of the present invention.

Claims

1. A method for preparing a lithium-ion battery cell, characterized in that: Specifically, the following steps are included: S001, modified titanium aluminum carbide, graphene oxide and lithium phosphate nanoparticles are added to N-methylpyrrolidone solvent for ultrasonic dispersion treatment, and then NCM811, conductive carbon black and polyvinylidene fluoride are added in sequence and subjected to gradient stirring treatment to obtain positive electrode slurry. S002, Aminated carbon nanotubes and zinc aluminum spinel powder are added to ultrapure water for spherical dispersion treatment, and then graphite, sodium carboxymethyl cellulose and styrene-butadiene rubber are added in sequence and stirred to obtain negative electrode slurry; S003, the positive electrode slurry is coated on the positive electrode current collector, and then subjected to gradient drying treatment, positive electrode coating agent coating, segmented reaction drying treatment, gradient hot rolling reaction treatment, welding of electrode tabs and cutting of sheet to obtain positive electrode sheet. S004, the negative electrode slurry is coated on the negative electrode current collector, and then subjected to gradient drying, negative electrode coating agent coating, segmented freeze drying, cold pressing, welding of electrode tabs and cutting of sheet to obtain the negative electrode sheet. S005, the diaphragm coating agent is coated on the polypropylene / polyethylene composite membrane and cured to obtain the diaphragm; S006 is produced by winding the positive electrode sheet, separator, negative electrode sheet, and separator in sequence, followed by drying, packaging, baking, electrolyte injection, standing, formation, and aging treatments to obtain a lithium-ion battery cell.

2. The preparation method according to claim 1, characterized in that: In step S001, the mass ratio of NCM811, conductive carbon black, polyvinylidene fluoride, modified titanium aluminum carbide, graphene oxide, and lithium phosphate nanoparticles is 90:3:5:1:0.3:0.5; the volume mass ratio of N-methylpyrrolidone solvent to titanium aluminum carbide powder is 150:1; the modified titanium aluminum carbide is obtained by modifying titanium aluminum carbide with a titanate coupling agent.

3. The preparation method according to claim 1, characterized in that: In step S002, the mass ratio of graphite, sodium carboxymethyl cellulose, styrene-butadiene rubber, aminated carbon nanotubes, and zinc aluminum spinel powder is 92:1.5:1:0.8:0.6; the volume mass ratio of ultrapure water to aminated carbon nanotubes is 120:

1.

4. The preparation method according to claim 1, characterized in that: In step S003, the positive electrode current collector is aluminum foil; the positive electrode coating agent is composed of aluminum oxide, lithium borate and ethanol, with a mass-to-volume ratio of 2:1:

50.

5. The preparation method according to claim 1, characterized in that: In step S004, the negative electrode current collector is copper foil; the negative electrode coating agent is composed of silicon monoxide, graphite carbon, lithium fluoride, and N-methylpyrrolidone, with a mass-to-volume ratio of 3:1:0.6:

40.

6. The preparation method according to claim 1, characterized in that: In step S005, the diaphragm coating agent is composed of titanium dioxide, lithium silicate, polyamic acid, and N-methylpyrrolidone, with a mass-to-volume ratio of 3:2:1:

50.

7. The preparation method according to claim 1, characterized in that: In step S006, the electrolyte is composed of lithium hexafluorophosphate, ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, lithium thiosulfate, and aluminum trifluoromethanesulfonate in a mass ratio of 119:311:315:231:5:3.

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