Preparation method and application of high-safety current collector

Abstract

The invention discloses a preparation method and application of a high-safety current collector. The preparation method comprises the following steps: (1) preparing microcapsules; (2) coating; (3) preparing safe coating slurry; and (4) preparing a safe current collector: obtaining the high-safety current collector. The high-safety current collector is used for a secondary battery. The preparation and application of the high-safety current collector are realized by researching the conditions of the phase change material, the flame retardant, the conductive agent, the mass ratio of the phase change material to the flame retardant, the thickness of the safety coating and the like, and the contradiction among wide temperature range adaptability, high safety and long-acting cycle stability can be synergistically solved; according to the invention, rapid response and inhibition of thermal runaway risk can be realized under a high-temperature condition, and integrity of a coating structure and a conductive function can be maintained under a low-temperature environment so as to ensure that a battery can still work safely and stably under extreme conditions.

Description

Technical Field

[0001] This invention relates to the field of batteries, and more particularly to a method for preparing a high-safety current collector and its application. Background Technology

[0002] Batteries (especially lithium-ion batteries), as highly efficient energy storage and conversion devices, are widely used in electric vehicles, portable electronic devices, aerospace, and energy storage power stations. Their working principle primarily relies on the reversible insertion and extraction of lithium ions between the positive and negative electrodes to achieve the storage and release of electrochemical energy. Current collectors, as a key component of the battery, play a crucial role in collecting current and supporting the active materials; common current collectors include copper foil and aluminum foil. With the continuous expansion of application scenarios, the performance requirements for batteries are also increasing, especially safety and electrochemical stability under extreme environments, which have become key factors restricting their further development.

[0003] In practical applications, lithium-ion batteries face severe challenges in adapting to high and low temperatures. At low temperatures, such as below -20°C, the ionic conductivity of the electrolyte decreases significantly, the lithium-ion diffusion rate of the electrode materials slows down, and the interfacial contact resistance between the active material and the current collector increases, leading to a sharp rise in internal resistance and a significant decrease in discharge capacity, sometimes even preventing normal startup. At high temperatures, such as above 60°C, internal side reactions intensify, and the solid electrolyte interfacial film may decompose, potentially triggering thermal runaway and causing safety accidents such as smoke, fire, or explosion. Therefore, developing a battery technology that can maintain high safety and high electrochemical performance over a wide temperature range is of significant practical importance.

[0004] To address battery safety concerns, existing technologies have proposed various solutions. One mainstream approach involves directly adding flame-retardant components to the electrode materials or electrolyte. For example, this involves mixing phosphate ester flame retardants into the positive electrode slurry or dissolving phosphorus- or fluorine-containing flame-retardant additives in the electrolyte. While this method is simple and requires no additional preparation steps, the flame retardant may interact with the electrode active materials or electrolyte components, affecting lithium-ion transport kinetics and leading to increased battery internal resistance and shortened cycle life. Furthermore, during long-term cycling, the flame retardant may gradually decompose or migrate, weakening its flame-retardant effect and making it difficult to continuously ensure battery safety.

[0005] Another technical approach involves modifying the current collector itself and coating its surface with a safety-functional coating. These coatings typically consist of conductive agents and binders, designed to improve the bonding between the current collector and the active material, and to some extent, improve the uniformity of current distribution. However, existing safety coating technologies largely focus on thermal blocking in single high-temperature scenarios, such as using ceramicization of the coating at high temperatures to form an insulating layer, but fail to effectively address the performance maintenance issues of the battery in low-temperature environments. Under low-temperature conditions, the coating material may crack due to increased brittleness, disrupting the conductive network, leading to increased interfacial contact resistance and a sharp decline in battery discharge capacity. Furthermore, some coating structures exhibit poor compatibility with electrolytes or electrode materials, and are prone to interfacial degradation after long-term cycling, affecting the overall lifespan and reliability of the battery.

[0006] Some existing technologies attempt to introduce phase change materials (PCMs) into battery systems, utilizing their phase change process to absorb or release heat to regulate battery operating temperature. However, PCMs alone often lack flame-retardant properties, and if their combination with conductive components is not carefully designed, it may lead to uneven conductivity of the coating or component separation during cycling, reducing functional reliability. Therefore, current technologies have not yet achieved an integrated solution that can rapidly activate safety protection mechanisms at high temperatures while maintaining structural stability and conductive network integrity at low temperatures.

[0007] Therefore, it is necessary to design a method for preparing a high-safety current collector and its application. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, a method for preparing a high-safety current collector and its application are provided.

[0009] This invention is achieved through the following scheme: A method for preparing a high-safety current collector, the method comprising the following steps: (a) Microcapsules: Phase change material and flame retardant are added to an organic solvent and heated to dissolve them, forming a mixture. The mixture is then centrifugally spray-dried in a centrifugal spray dryer, cooled, washed with anhydrous ethanol, and dried to obtain microcapsules of phase change material coated with flame retardant. (ii) Coating: After the microcapsules and conductive agent obtained in step (i) are mixed evenly, the first binder is added for dispersion and coating. After passing through the first drying and refining process, the coated material is obtained. (iii) Safety coating slurry: The second binder, solvent and the coating material obtained in step (ii) are mixed evenly to obtain the safety coating slurry; (iv) Safety current collector: The safety coating slurry obtained in step (iii) is applied to the surface of the current collector, and after a second drying, the safety coating of the current collector is obtained, which is the high safety current collector.

[0010] The phase change material is at least one of stearic acid, Fischer-Tropsch wax, palmitic acid, behenic acid, and linalic acid; The flame retardant is one or more of the following: high-fluorine carbonate, phosphate ester flame retardant, hexabenzoxanthionyl triphosphazene, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and phosphine ester flame retardant; The organic solvent is selected from one or more of acetone, toluene, diethyl ether, toluene, ethanol, dimethyl carbonate, tetrahydrofuran, and tetrahydronaphthalene. The microcapsule particle size is 1-10 μm.

[0011] The mass ratio of the phase change material to the flame retardant is 5-10:1.

[0012] The conductive agent is one or more of conductive carbon black, conductive graphite, graphene, or carbon nanotubes. The conductive agent has a particle size of 0.2-0.8 μm; The first adhesive is one or more of polyvinylidene fluoride, polyurethane, polyacrylate, polyvinylidene fluoride, polyacrylic acid, lithium polyacrylate, sodium polystyrene sulfonate, polyethyleneimine, sodium polyacrylate, sodium carboxymethyl cellulose and styrene-butadiene rubber.

[0013] The mass ratio of the microcapsule to the conductive agent is 1:5-10; the mass ratio of the microcapsule to the first binder is 5-50:1.

[0014] The first drying temperature is 60℃-120℃.

[0015] The second adhesive is one or more of the following: polyvinylidene fluoride, polyurethane, polyacrylate, polyvinylidene fluoride, polyacrylic acid, lithium polyacrylate, sodium polystyrene sulfonate, polyethyleneimine, sodium polyacrylate, sodium carboxymethyl cellulose, and styrene-butadiene rubber; The solvent is either water or NMP.

[0016] The mass ratio of the coating material to the second adhesive is 5-50:1.

[0017] The current collector is one or more of copper foil, aluminum foil, composite copper foil, and composite aluminum foil; the coating is performed using a coating machine; the thickness of the safety coating on the current collector is 1-10 μm; and the second drying temperature is 60℃-120℃.

[0018] This high-safety current collector is used in secondary batteries.

[0019] The beneficial effects of this invention are as follows: 1. This invention constructs an intelligent safety response mechanism within the battery by introducing a microcapsule structure in which a flame retardant is encapsulated in a phase change material. When the battery temperature rises abnormally, the phase change material undergoes a phase change, promptly releasing the flame retardant and effectively suppressing the thermal runaway chain reaction, thereby significantly improving the intrinsic safety of the battery.

[0020] 2. We utilize a core-shell design of microcapsules to encapsulate the flame retardant within the phase change material, avoiding potential side effects from direct contact between the flame retardant and the electrolyte or electrode materials. This structure not only ensures the stability of the flame retardant under normal operating conditions but also enables rapid and targeted activation of its flame-retardant function under thermal abuse conditions.

[0021] 3. The safety-coated current collector prepared by this invention is formed by compounding microcapsules with conductive agents and binders to form a uniform coating material, which is then coated onto the surface of the current collector. This coating maintains excellent conductivity while providing the current collector with active safety protection capabilities, enabling it to maintain structural integrity and prevent the propagation of internal short circuits even under conditions of mechanical abuse such as needle penetration and extrusion.

[0022] 4. Phase change materials undergo solid-liquid phase transitions within a specific temperature range, absorbing or releasing a large amount of latent heat, thereby buffering temperature fluctuations during battery operation. This characteristic helps improve battery performance in high and low temperature environments, mitigates the negative impact of extreme temperatures on electrochemical reactions, and enhances the battery's wide temperature range applicability.

[0023] 5. The first and second binders used in this invention are selected from common polymer materials such as polyvinylidene fluoride, polyurethane, and styrene-butadiene rubber. These materials have good compatibility with other components inside the battery and will not introduce additional side reactions or impedance, which is beneficial to maintaining the long cycle life and reliability of the battery. Attached Figure Description

[0024] Figure 1. Comparison curves of high and low temperature discharge for different current collectors; Figure 2. High and low temperature discharge curves of the NCM system; Figure 3. High and low temperature discharge curves of the LFP system; Figure 4 High and low temperature discharge curves of the NCA system; Figure 5 High and low temperature discharge curves of the LOM system; Figure 6. High and low temperature discharge curves of the LCO system; Figure 7. Acupuncture test diagram, where (a) before acupuncture test and (b) after acupuncture test. Detailed Implementation

[0025] The present invention will be further described below with reference to specific embodiments: A method for preparing a high-safety current collector, the method comprising the following steps: (a) Microcapsules: Phase change material and flame retardant are added to an organic solvent and heated to dissolve them, forming a mixture. The mixture is then centrifugally spray-dried in a centrifugal spray dryer, cooled, washed with anhydrous ethanol, and dried to obtain microcapsules of phase change material coated with flame retardant. (ii) Coating: After the microcapsules and conductive agent obtained in step (i) are mixed evenly, the first binder is added for dispersion and coating. After passing through the first drying and refining process, the coated material is obtained. (iii) Safety coating slurry: The second binder, solvent and the coating material obtained in step (ii) are mixed evenly to obtain the safety coating slurry; (iv) Safety current collector: The safety coating slurry obtained in step (iii) is applied to the surface of the current collector, and after a second drying, the safety coating of the current collector is obtained, which is the high safety current collector.

[0026] The phase change material is at least one of stearic acid, Fischer-Tropsch wax, palmitic acid, behenic acid, and linalic acid; The flame retardant is one or more of the following: high-fluorine carbonate, phosphate ester flame retardant, hexabenzoxanthionyl triphosphazene, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and phosphine ester flame retardant; The organic solvent is selected from one or more of acetone, toluene, diethyl ether, toluene, ethanol, dimethyl carbonate, tetrahydrofuran, and tetrahydronaphthalene. The microcapsule particle size is 1-10 μm.

[0027] The mass ratio of the phase change material to the flame retardant is 5-10:1.

[0028] The conductive agent is one or more of conductive carbon black, conductive graphite, graphene, or carbon nanotubes. The conductive agent has a particle size of 0.2-0.8 μm; The first adhesive is one or more of polyvinylidene fluoride, polyurethane, polyacrylate, polyvinylidene fluoride, polyacrylic acid, lithium polyacrylate, sodium polystyrene sulfonate, polyethyleneimine, sodium polyacrylate, sodium carboxymethyl cellulose and styrene-butadiene rubber.

[0029] The mass ratio of the microcapsule to the conductive agent is 1:5-10; the mass ratio of the microcapsule to the first binder is 5-50:1.

[0030] The first drying temperature is 60℃-120℃.

[0031] The second adhesive is one or more of the following: polyvinylidene fluoride, polyurethane, polyacrylate, polyvinylidene fluoride, polyacrylic acid, lithium polyacrylate, sodium polystyrene sulfonate, polyethyleneimine, sodium polyacrylate, sodium carboxymethyl cellulose, and styrene-butadiene rubber; The solvent is either water or NMP.

[0032] It is worth noting that the two binders in this application exhibit polarity reversal in their dissolution behavior in the solvent. For example, the first binder is solvent-friendly and can be dispersed in the solvent, while the second binder is solvent-resistant, which prevents the coating material from dissolving during the process of uniformly mixing in step (iii) to obtain the safe coating slurry, and prevents the conductive agent from falling off.

[0033] The mass ratio of the coating material to the second adhesive is 5-50:1.

[0034] The current collector is one or more of copper foil, aluminum foil, composite copper foil, and composite aluminum foil; the coating is performed using a coating machine; the thickness of the safety coating on the current collector is 1-10 μm; and the second drying temperature is 60℃-120℃.

[0035] This high-safety current collector is used in secondary batteries.

[0036] This invention achieves rapid flame retardancy at high temperatures without affecting normal battery performance through the synergistic design of microencapsulated flame retardants and conductive networks. At low temperatures, the phase change material solidifies, enhancing the coating's mechanical strength and suppressing contact failure of the conductive network due to electrode shrinkage. This ensures the coating maintains conductivity and interfacial stability within a temperature range of -70℃ to 80℃. The microcapsules consist of a shell and a core. The core is selected from one or both organic and inorganic flame retardants, while the shell is a phase change material. After the microcapsules and conductive agent are uniformly dispersed, a current collector is coated onto them. At the battery's thermal runaway temperature, the phase change material absorbs heat, transforming from a solid to a liquid state and releasing the flame retardant into the electrolyte, effectively preventing the electrolyte from igniting while maintaining good conductivity.

[0037] The present invention will be further illustrated by the following examples.

[0038] Example 1 This embodiment provides a high-safety, wide-temperature-range battery technology, the preparation method of which includes the following steps: 1) Preparation of microcapsules: The raw materials were weighed according to the mass ratio of Fischer-Tropsch wax and tricresyl phosphate of 5:1, with 4000g of Fischer-Tropsch wax and 800g of tricresyl phosphate. The mixture was heated and stirred, and then mixed evenly in a toluene solution. The mixture was then centrifuged, sprayed, cooled, and dried to obtain microcapsules of tricresyl phosphate coated with Fischer-Tropsch wax.

[0039] 2) Take 4000g of the microcapsules obtained in step 1), 80g of polyvinylidene fluoride, and an appropriate amount of NMP solvent, stir for 1 hour, then add 20000g of conductive carbon black with a particle size of 0.2μm, continue stirring for 2 hours, and then spray dry and refine the mixture to obtain the coated material.

[0040] 3) Mix 4000g of the coating material obtained in step 2), 200g of styrene-butadiene rubber latex, and an appropriate amount of water evenly to obtain a coating slurry with a solid content of 35wt%. 4) The coating slurry described in step 3) is applied to both sides of the aluminum current collector with a thickness of 10 μm using a coating machine, and then dried at 60°C to obtain a current collector safety coating with a thickness of 2 μm.

[0041] Active material NCM523, binder polyvinylidene fluoride (PVDF), conductive agent conductive carbon black (SP), and carbon nanotube conductive slurry were added to solvent N-methylpyrrolidone and mixed to obtain a positive electrode slurry. This positive electrode slurry was then coated onto a prepared positive electrode current collector and vacuum dried to obtain a positive electrode sheet. The mass ratio of active material NCM523, binder PVDF, conductive agent SP, and carbon nanotubes was 97%:1.8%:0.8%. 0.06%. Artificial graphite, polyvinylidene fluoride (PVDF) binder, conductive carbon black (SP) conductive agent, and carbon nanotube conductive paste are added to the solvent N-methylpyrrolidone and mixed to obtain a negative electrode slurry. This negative electrode slurry is then coated onto copper foil and vacuum dried to obtain a negative electrode sheet. The mass ratio of artificial graphite, PVDF binder, SP conductive agent, and carbon nanotubes is 96%:2.95%:0.5%:0.05%. The above-prepared positive electrode, negative electrode, and separator assembly are packaged in an aluminum-plastic film, and then an appropriate amount of electrolyte is injected. The electrolyte is a mixed solution of EC:DEC:LiFSI:LiDFOB:FEC:VC=15:15:15:5:3:3. The aluminum-plastic film is then hot-pressed to obtain a 50Ah lithium-ion battery.

[0042] Comparative Example 1 The comparative example uses the same battery manufacturing process as Example 1, except that the lithium battery current collector in Comparative Example 1 is a 14-micron carbon-coated aluminum foil. Comparative Example 2 The comparative example uses the same battery manufacturing process as Example 1, except that the lithium battery current collector in Comparative Example 2 is a 14-micron aluminum foil with no conductive coating on its surface. The battery cells of the above embodiments were subjected to 3C charge-discharge tests, high and low temperature discharge tests, and needle penetration tests under a voltage range of 2.5-4.2V. The test results are shown in Table 1 below.

[0043] Table 1 ; From Table 1 and Figure 1 It is known that using a safety-coated battery cell offers advantages in electrical performance: a higher low-temperature discharge platform (-0.1V) and a higher retention rate (-5%), with no impact on high-temperature performance. In Example 1, a high-temperature resistant steel needle with a φ8mm tip and a conical angle of 45°-60° was used to penetrate the battery cells at a speed of 25mm / s ± 5mm / s, perpendicular to the battery plates. This process was repeated for three individual cells, with the needle finally remaining inside the lithium-ion battery. After 1 hour of observation, the battery did not catch fire or explode. Figure 7 As shown.

[0044] Example 2 This embodiment provides a high-safety wide-temperature-range battery technology. Compared with the preparation method described in Embodiment 1, the only difference is that the tricresyl phosphate in step 1) is replaced with an equal mass of bisphenol A type polycarbonate.

[0045] Example 3 This embodiment provides a high-safety, wide-temperature-range battery technology, the preparation method of which includes the following steps: 1) Preparation of microcapsules: Weigh the raw materials according to the mass ratio of Fischer-Tropsch wax and perfluoropolyether carbonate of 5:1, with 5000g of Fischer-Tropsch wax and 1000g of perfluoropolyether carbonate. Heat and stir, mix evenly in hexafluoroisopropanol solution, and then centrifuge, spray, cool and dry to obtain microcapsules of perfluoropolyether carbonate coated with Fischer-Tropsch wax.

[0046] 2) Take 4000g of the microcapsules obtained in step 1), 80g of polyvinylidene fluoride, and an appropriate amount of NMP solvent, stir for 1 hour, then add 20000g of conductive carbon black with a particle size of 0.2μm, continue stirring for 2 hours, and then spray dry and refine the mixture to obtain the coated material.

[0047] 3) Mix 4000g of the coating material obtained in step 2), 200g of styrene-butadiene rubber latex, and an appropriate amount of water evenly to obtain a coating slurry with a solid content of 36wt%. 4) The coating slurry described in step 3) is applied to both sides of the aluminum current collector with a thickness of 9μm using a coating machine, and then dried at 60℃ to obtain a current collector safety coating with a thickness of 2μm.

[0048] Example 4 This embodiment provides a high-safety, wide-temperature-range battery technology, the preparation method of which includes the following steps: 1) Preparation of microcapsules: The raw materials were weighed according to the mass ratio of Fischer-Tropsch wax and hexaphenoxycyclotriphosphazene 5:1, with 5000g of Fischer-Tropsch wax and 1000g of hexaphenoxycyclotriphosphazene. The mixture was heated and stirred, and then mixed evenly in toluene solution. The mixture was then centrifuged, sprayed, cooled and dried to obtain microcapsules of hexaphenoxycyclotriphosphazene coated with Fischer-Tropsch wax.

[0049] 2) Take 4000g of the microcapsules obtained in step 1), 80g of polyvinylidene fluoride, and an appropriate amount of NMP solvent, stir for 1 hour, then add 20000g of conductive carbon black with a particle size of 0.2μm, continue stirring for 2 hours, and then spray dry and refine the mixture to obtain the coated material.

[0050] 3) Mix 4000g of the coating material obtained in step 2), 200g of styrene-butadiene rubber latex, and an appropriate amount of water evenly to obtain a coating slurry with a solid content of 36wt%. 4) The coating slurry described in step 3) is applied to both sides of the aluminum current collector with a thickness of 9μm using a coating machine, and then dried at 60℃ to obtain a current collector safety coating with a thickness of 2μm.

[0051] Example 5 This embodiment provides a high-safety, wide-temperature-range battery technology, the preparation method of which includes the following steps: 1) Preparation of microcapsules: The raw materials were weighed according to the mass ratio of Fischer-Tropsch wax and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide of 5:1. The mass of Fischer-Tropsch wax was 5000g and the mass of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide of 1000g. The mixture was heated and stirred, and then mixed evenly in toluene solution. The mixture was then subjected to centrifugation, spraying, cooling and drying to obtain microcapsules of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide coated with Fischer-Tropsch wax.

[0052] 2) Take 4000g of the microcapsules obtained in step 1), 80g of polyvinylidene fluoride, and an appropriate amount of NMP solvent, stir for 1 hour, then add 20000g of conductive carbon black with a particle size of 0.2μm, continue stirring for 2 hours, and then spray dry and refine the mixture to obtain the coated material.

[0053] 3) Mix 4000g of the coating material obtained in step 2), 200g of styrene-butadiene rubber latex, and an appropriate amount of water evenly to obtain a coating slurry with a solid content of 35wt%. 4) The coating slurry described in step 3) is applied to both sides of the aluminum current collector with a thickness of 9μm using a coating machine, and then dried at 60℃ to obtain a current collector safety coating with a thickness of 2μm.

[0054] Example 6 This embodiment provides a high-safety, wide-temperature-range battery technology, the preparation method of which includes the following steps: 1) Preparation of microcapsules: The raw materials were weighed according to the mass ratio of Fischer-Tropsch wax and dimethyl methylphosphonate 5:1, with 5000g of Fischer-Tropsch wax and 1000g of dimethyl methylphosphonate. The mixture was heated and stirred, and then mixed evenly in a methanol solution. The mixture was then centrifuged, sprayed, cooled, and dried to obtain microcapsules of dimethyl methylphosphonate coated with Fischer-Tropsch wax.

[0055] 2) Take 4000g of the microcapsules obtained in step 1), 80g of polyvinylidene fluoride, and an appropriate amount of NMP solvent, stir for 1 hour, then add 20000g of conductive carbon black with a particle size of 0.2μm, continue stirring for 2 hours, and then spray dry and refine the mixture to obtain the coated material.

[0056] 3) Mix 4000g of the coating material obtained in step 2), 200g of styrene-butadiene rubber latex, and an appropriate amount of water evenly to obtain a coating slurry with a solid content of 35wt%. 4) The coating slurry described in step 3) is applied to both sides of the aluminum current collector with a thickness of 10 μm using a coating machine, and then dried at 60°C to obtain a current collector safety coating with a thickness of 2 μm.

[0057] The lithium battery current collectors with conductive coatings prepared in Examples 2-6 were used to fabricate square pouch cells with a capacity of approximately 50 Ah.

[0058] The battery cells of the above embodiments were subjected to 3C charge-discharge tests, high and low temperature discharge tests, and needle penetration tests under a voltage range of 2.5-4.2V. The test results are shown in Table 2 below.

[0059] Table 2 ; Examples 7-10 The only difference between Examples 7-10 and Example 1 is that the phase change material is different; all other experimental parameters are the same as those in Example 1.

[0060] The lithium battery current collectors with conductive coatings prepared in Examples 7-10 were used to fabricate square pouch cells with a capacity of approximately 50 Ah. The cells from the above embodiments were subjected to 3C charge-discharge tests, high and low temperature discharge tests, and nail penetration tests under a voltage range of 2.5-4.2V. The test results are shown in Table 3 below.

[0061] Table 3 ; Examples 11-16 The only difference between Examples 11-16 and Example 1 is that the conductive agent used in step 2) is different; all other experimental parameters are the same as those in Example 1.

[0062] The lithium battery current collectors with conductive coatings prepared in Examples 11-16 were used to fabricate square pouch batteries with a capacity of approximately 50 Ah. The battery cells from the above embodiments were subjected to 3C charge-discharge tests, high and low temperature discharge tests, and nail penetration tests under a voltage range of 2.5-4.2V. The test results are shown in Table 4 below.

[0063] Table 4 ; Examples 17-21 The only difference between Examples 17-21 and Example 1 is that the mass ratio of the phase change material and the flame retardant in step 1) is different; the other experimental parameters are the same as those in Example 1.

[0064] The lithium battery current collectors with conductive coatings prepared in Examples 17-21 were used to fabricate square pouch cells with a capacity of approximately 50 Ah. The cells from the above embodiments were subjected to 3C charge-discharge tests, high and low temperature discharge tests, and nail penetration tests under a voltage range of 2.5-4.2V. The test results are shown in Table 5 below.

[0065] Table 5 ; Examples 22-26 The only difference between Examples 22-26 and Example 1 is that the mass ratio of microcapsules to conductive agent in step 2) is different; all other experimental parameters are the same as those in Example 1.

[0066] The lithium battery current collectors with conductive coatings prepared in Examples 22-26 were used to fabricate square pouch cells with a capacity of approximately 50 Ah. The cells from the above embodiments were subjected to 3C charge-discharge tests, high and low temperature discharge tests, and nail penetration tests under a voltage range of 2.5-4.2V. The test results are shown in Table 6 below.

[0067] Table 6 ; Examples 27-30 The only difference between Examples 27-30 and Example 1 is that the thickness of the current collector safety coating in step 4) is different; all other experimental parameters are the same as those in Example 1.

[0068] The lithium battery current collectors with conductive coatings prepared in Examples 27-30 were used to fabricate square pouch cells with a capacity of approximately 50 Ah. The cells from the above embodiments were subjected to 3C charge-discharge tests, high and low temperature discharge tests, and nail penetration tests under a voltage range of 2.5-4.2V. The test results are shown in Table 7 below.

[0069] Table 7 ; Examples 31-34 The only difference between Examples 31-34 and Example 1 is that the cathode material is different; all other experimental parameters are the same as those in Example 1.

[0070] The battery cells of the above embodiments were subjected to 3C charge-discharge tests, high and low temperature discharge tests, and needle penetration tests under a voltage range of 2.5-4.2V (LFP 2.0-3.65V). The test results are shown in Table 8 below.

[0071] Table 8 ; From Table 8 and Figure 2-6 It can be seen that the safety coating current collector exhibits the same effect when applied to different positive electrodes: the discharge retention rate at 0.5C is -97% at 80℃, the discharge retention rate at 0.5C is >55% at -50℃, and the needle penetration pass rate is -90%.

[0072] This invention studies the conditions of phase change materials, flame retardants, conductive agents, the mass ratio of phase change materials and flame retardants, and the thickness of safety coatings to achieve the preparation and application of high-safety current collectors. It can synergistically solve the contradiction between wide temperature range adaptability, high safety and long-term cycle stability. This invention should be able to respond rapidly and suppress the risk of thermal runaway under high temperature conditions, while maintaining the integrity of the coating structure and conductive function under low temperature conditions, thereby ensuring that the battery can still work safely and stably under extreme conditions.

[0073] Although the technical solutions of the present invention have been described and enumerated in detail, it should be understood that modifications to the above embodiments or the adoption of equivalent alternatives are obvious to those skilled in the art. Such modifications or improvements made without departing from the spirit of the present invention are all within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a high-safety current collector, characterized in that, The method includes the following steps: (a) Microcapsules: Phase change material and flame retardant are added to an organic solvent, heated to dissolve them, forming a mixture. The mixture is then centrifuged and spray-dried, cooled, washed, and dried to obtain microcapsules of phase change material coated with flame retardant. (ii) Coating: After the microcapsules and conductive agent obtained in step (i) are mixed evenly, the first binder is added for dispersion and coating. After passing through the first drying and refining process, the coated material is obtained. (iii) Safety coating slurry: The second binder, solvent and the coating material obtained in step (ii) are mixed evenly to obtain the safety coating slurry; (iv) Safety current collector: The safety coating slurry obtained in step (iii) is applied to the surface of the current collector, and after a second drying, the safety coating of the current collector is obtained, which is the high safety current collector.

2. The method for preparing a high-safety current collector according to claim 1, characterized in that, The phase change material is at least one of stearic acid, Fischer-Tropsch wax, palmitic acid, behenic acid, and linalic acid; The flame retardant is one or more of the following: high-fluorine carbonate, phosphate ester flame retardant, hexabenzoxanthionyl triphosphazene, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and phosphine ester flame retardant; The organic solvent is selected from one or more of acetone, toluene, diethyl ether, toluene, ethanol, dimethyl carbonate, tetrahydrofuran, and tetrahydronaphthalene. The microcapsule particle size is 1-10 μm.

3. The method for preparing a high-safety current collector according to claim 1, characterized in that, The mass ratio of the phase change material to the flame retardant is 5-10:

1.

4. The method for preparing a high-safety current collector according to claim 1, characterized in that, The conductive agent is one or more of conductive carbon black, conductive graphite, graphene, or carbon nanotubes. The conductive agent has a particle size of 0.2-0.8 μm; The first adhesive is one or more of polyvinylidene fluoride, polyurethane, polyacrylate, polyvinylidene fluoride, polyacrylic acid, lithium polyacrylate, sodium polystyrene sulfonate, polyethyleneimine, sodium polyacrylate, sodium carboxymethyl cellulose and styrene-butadiene rubber.

5. The method for preparing a high-safety current collector according to claim 1, characterized in that, The mass ratio of the microcapsule to the conductive agent is 1:5-10; the mass ratio of the microcapsule to the first binder is 5-50:

1.

6. The method for preparing a high-safety current collector according to claim 1, characterized in that, The first drying temperature is 60℃-120℃.

7. The method for preparing a high-safety current collector according to claim 1, characterized in that, The second adhesive is one or more of the following: polyvinylidene fluoride, polyurethane, polyacrylate, polyvinylidene fluoride, polyacrylic acid, lithium polyacrylate, sodium polystyrene sulfonate, polyethyleneimine, sodium polyacrylate, sodium carboxymethyl cellulose, and styrene-butadiene rubber; The solvent is either water or NMP.

8. The method for preparing a high-safety current collector according to claim 1, characterized in that, The mass ratio of the coating material to the second adhesive is 5-50:

1.

9. The method for preparing a high-safety current collector according to claim 1, characterized in that, The current collector is one or more of copper foil, aluminum foil, composite copper foil, and composite aluminum foil; the coating is performed using a coating machine; the thickness of the safety coating on the current collector is 1-10 μm; and the second drying temperature is 60℃-120℃.

10. An application of a high-safety current collector prepared by any one of claims 1-9, characterized in that, This high-safety current collector is used in secondary batteries.

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