Functional current collector capable of reducing temperature rise, preparation method thereof, pole piece and battery

Abstract

The invention discloses a functional current collector capable of reducing temperature rise, a preparation method of the functional current collector, a pole piece and a battery. The functional current collector comprises a base membrane modified layer and metal functional layers on two sides of the base membrane modified layer, a modified filler is uniformly dispersed in the base membrane modified layer, and the modified filler is a composite system formed by PCM microcapsules and BN nanosheets of which the surfaces are grafted with PEG; the surface of the metal functional layer is provided with a micron-sized groove structure, and directionally arranged BN nanowires are embedded in the micron-sized groove structure. Through structural improvement and material compounding, the heat dissipation performance of the current collector of the battery is remarkably improved, and effective control over the temperature rise of the battery is achieved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a functional current collector for reducing temperature rise, its preparation method, an electrode, and a battery. Background Technology

[0002] Currently, the excessive temperature rise of prismatic batteries under high-power charging and discharging scenarios has become a key issue restricting their performance improvement, leading to thermal management problems. With the continuous increase in battery energy density and charge / discharge rate, the heat dissipation capacity of traditional composite current collectors is no longer sufficient. Although these current collectors employ metal-polymer laminated structures (such as aluminum / copper composites with PET / PP / PI base films) to improve mechanical safety, the base film materials generally have low thermal conductivity, causing heat to accumulate inside the battery, affecting cycle life and safety.

[0003] To address the temperature rise issue, current industry technologies primarily attempt breakthroughs in two directions: First, by increasing the thickness of the metal coating on the composite current collector to improve thermal conductivity. For example, thickening the conventional metal coating enhances heat transfer. However, this method has significant limitations: an excessively thick metal layer significantly increases the weight of the current collector, reduces battery energy density, and may also cause interfacial stress problems, affecting long-term stability. Second, by optimizing the tab design to improve conductivity. Due to the unique structure of composite current collectors, traditional metal foil needs to be transferred at the tabs to achieve current collection. To reduce temperature rise, the contact area of ​​the tabs needs to be increased. However, this design often requires more space, leading to a decrease in battery volume utilization and a forced sacrifice in energy density. Neither of these solutions adequately addresses the balance between heat dissipation efficiency and battery performance. Summary of the Invention

[0004] The purpose of this invention is to provide a functional current collector that reduces temperature rise, its preparation method, electrode, and battery. Through structural improvements and material composites, the heat dissipation performance of the battery current collector is significantly improved, achieving effective control of battery temperature rise and ensuring battery performance.

[0005] To achieve the above objectives, the technical solution provided by the present invention is as follows: This invention is achieved through the following technical solution: The first aspect of this application provides a functional current collector for reducing temperature rise, comprising a base film modification layer and metal functional layers on both sides of the base film modification layer; The modified base film layer contains uniformly dispersed modified fillers, which are composite systems formed by PCM microcapsules and BN nanosheets grafted with PEG on the surface. The surface of the metal functional layer has a micron-scale trench structure, within which oriented BN nanowires are embedded.

[0006] Preferably, the modified filler content in the base film modified layer is 5-15% by mass.

[0007] The surface-grafted PEG BN nanosheets have a sheet thickness of 50~100nm and a lateral dimension of 2~5μm; the PCM microcapsules have a particle size of 1~3μm and a phase transition temperature range of 45~60℃.

[0008] The groove depth of the micron-scale trench structure is 2~5μm and the spacing is 10~20μm; the diameter of the BN nanowire is 50~100nm and the length is 5~10μm.

[0009] The second aspect of this application provides a method for preparing a functional current collector that reduces temperature rise, comprising the following steps: S1: Add BN nanosheets to a PEG aqueous solution and perform surface grafting by ultrasonic treatment to obtain PEG-BN nanosheets; use paraffin as the core material and perform in-situ polymerization of melamine-formaldehyde resin to obtain PCM microcapsules; S2: PEG-BN nanosheets and PCM microcapsules were added to a solvent, ultrasonically dispersed, and then mixed with a polyimide resin solution. After casting and drying, the modified polyimide-based film was obtained by heating and imidization. S3: A metal layer is magnetron sputtered on both sides of the modified polyimide-based film, and then a micron-scale trench structure is formed by electrochemical etching. BN nanowires are deposited in the micron-scale trench structure by electrophoresis.

[0010] Furthermore, in step S1, the mass-to-volume ratio of BN nanosheets to PEG aqueous solution is 1:18~20 g / ml; the mass concentration of PEG aqueous solution is 4~7%.

[0011] Furthermore, in step S2, the mass ratio of PEG-BN nanosheets to PCM microcapsules is 1~1.5:1~1.5; the ultrasonic power is 250~350W, and the duration is 45~70min.

[0012] A third aspect of this application provides an electrode comprising the aforementioned functional current collector for reducing temperature rise.

[0013] A fourth aspect of this application provides a battery comprising the aforementioned electrode.

[0014] The battery is a square stacked battery. The position of the tabs cut on each electrode sheet in the stacked battery is different. After the electrode sheets are stacked, each tab is connected to the terminal post through a connecting metal.

[0015] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a functional current collector for reducing temperature rise and its preparation method. The current collector consists of a modified base film layer and two metal functional layers on both sides. The modified base film layer contains a composite system of PCM microcapsules and BN nanosheets grafted with PEG, forming a three-dimensional thermally conductive network. The surface of the metal functional layers has a micron-scale trench structure, with oriented BN nanowires embedded within the trenches, constructing a metal-ceramic thermally conductive bridging structure. The preparation method involves first grafting PEG onto the surface of BN nanosheets through ultrasonic treatment, and then preparing paraffin-based PCM microcapsules through in-situ polymerization. Subsequently, the two are blended with polyimide resin, followed by casting, drying, and imidization treatment to form a modified base film layer. Finally, metal layers are magnetron sputtered on both sides of the base film, trenches are formed by electrochemical etching, and BN nanowires are oriented and filled into the trenches using electrophoretic deposition.

[0016] This invention combines a high thermal conductivity BN network with PCM phase change temperature control technology to form a dual-mechanism heat dissipation system of thermal conduction and phase change: the continuous thermal conduction path constructed by BN nanosheets and nanowires significantly improves the thermal conductivity of the base film, and the PCM microcapsules absorb heat at high temperatures to delay thermal runaway; at the same time, PEG grafting enhances the interfacial bonding force between BN and the metal layer, and the trench structure further optimizes the peel strength to avoid cyclic debonding.

[0017] In addition, the matching tab design improves conductivity by increasing the contact area without increasing the battery thickness, further enhancing battery performance, and is particularly suitable for prismatic batteries.

[0018] This invention is applicable to various systems such as ternary lithium, lithium iron phosphate and solid-state batteries, and has clear commercial potential. Attached Figure Description Figure 1 : A schematic diagram of stacked electrodes with different tab cutting positions according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the stacked electrode sheets of the present invention being transferred to a metal current collector by welding. Detailed Implementation

[0019] The present invention will be further described in detail below through specific embodiments, but it should not be construed as limiting the scope of the subject matter of the present invention to the following embodiments. All technologies implemented based on the above content of the present invention fall within the scope of the present invention.

[0020] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the reagents, methods and equipment used are conventional reagents, methods and equipment in this technical field.

[0021] In this invention, PCM is an abbreviation for Phase Change Material.

[0022] The present invention provides a functional current collector for reducing temperature rise, comprising a base film modified layer and metal functional layers on both sides of the base film modified layer; The modified filler is uniformly dispersed in the base film modified layer. The modified filler is a composite system formed by PCM microcapsules and BN nanosheets grafted with PEG on the surface. The surface of the metal functional layer has a micron-scale trench structure, within which oriented BN nanowires are embedded.

[0023] In some embodiments, the modified filler content in the base film modified layer is 5-15% by mass.

[0024] In some embodiments, the PEG-grafted BN nanosheets have a sheet thickness of 50-100 nm and a lateral dimension of 2-5 μm, forming a two-dimensional sheet structure; the PCM microcapsules have a particle size of 1-3 μm and a phase transition temperature range of 45-60 °C.

[0025] In some embodiments, the trenches of the micron-scale trench structure have a depth of 2-5 μm and a spacing of 10-20 μm; the BN nanowires have a diameter of 50-100 nm and a length of 5-10 μm, and are one-dimensional linear structures.

[0026] The second aspect of this application provides a method for preparing a functional current collector that reduces temperature rise, comprising the following steps: S1: Add BN nanosheets to a PEG aqueous solution and perform surface grafting by ultrasonic treatment to obtain PEG-BN nanosheets; use paraffin as the core material and perform in-situ polymerization of melamine-formaldehyde resin to obtain PCM microcapsules; S2: PEG-BN nanosheets and PCM microcapsules were added to a solvent, ultrasonically dispersed, and then mixed with a polyimide resin solution. After casting and drying, the modified polyimide-based film was obtained by heating and imidization. S3: A metal layer is magnetron sputtered on both sides of the modified polyimide-based film, and then a micron-scale trench structure is formed by electrochemical etching. BN nanowires are deposited in the micron-scale trench structure by electrophoresis.

[0027] The composite system formed by the PCM microcapsules and BN nanosheets grafted with PEG in this invention forms a three-dimensional thermally conductive network in the modified polyimide film.

[0028] This invention deposits BN nanowires in a metal layer to form a metal-ceramic thermally conductive bridging structure.

[0029] In some embodiments, in step S1, the mass-to-volume ratio of BN nanosheets to PEG aqueous solution is 1:18~20 g / ml; the mass concentration of PEG aqueous solution is 4~7%.

[0030] In some embodiments, in step S2, the mass ratio of PEG-BN nanosheets to PCM microcapsules is 1~1.5:1~1.5; the ultrasonic power is 250~350W, and the duration is 45~70min.

[0031] The present invention also provides an electrode comprising the above-mentioned functional current collector for reducing temperature rise.

[0032] The present invention also provides a battery comprising the above-described electrode.

[0033] The battery is a square stacked cell. The position of the tabs cut on each electrode sheet in the stacked cell is different. After the electrodes are stacked, each tab is connected to the terminal post through a connecting metal.

[0034] This invention firstly forms a three-dimensional thermally conductive network in a polyimide-based film by grafting PEG-coated BN nanosheets and PCM microcapsules, which significantly improves the thermal conductivity of the base film and achieves efficient heat dissipation. The PCM microcapsules undergo a phase transition and absorb heat at high temperatures, which can delay the process of battery thermal runaway and buy time for safety protection. At the same time, the PEG grafting technology enhances the interfacial bonding force between the BN nanosheets and the metal layer, and together with the micron-level trench structure on the surface of the metal layer, it effectively improves the peel strength.

[0035] Specifically, this invention combines highly thermally conductive BN nanonetworks with PCM phase change temperature control technology to form a synergistic heat dissipation system of thermal conductivity and phase change, changing the traditional single heat dissipation mode; by directionally filling BN nanowires in metal trenches through electrophoretic deposition, a continuous metal-ceramic thermal conduction path is constructed, which significantly improves the longitudinal heat conduction efficiency; in addition, the corresponding optimized tab design improves conductivity by increasing the contact area while keeping the battery thickness unchanged, further reducing battery temperature rise and internal resistance.

[0036] The technical solution of the present invention will be further described in detail below with reference to specific embodiments: Example 1 (1) Add 5g of BN nanosheets to 100mL of 5% PEG aqueous solution and sonicate at 40℃ for 2h to obtain PEG-BN nanosheets with a sheet thickness of 60~70nm and a transverse dimension of 3~3.5μm; (2) Mix 10g of molten paraffin with emulsifier and disperse it in the aqueous phase under high-speed stirring at 2000 rpm to form an O / W emulsion. The pH of the aqueous phase is adjusted to 5.0 by hydrochloric acid or citric acid to avoid premature polymerization and uneven particle size. Melamine-formaldehyde resin prepolymer is slowly added to the emulsion system, and the reaction temperature is maintained at 55℃ with a stirring rate of 600 rpm. The reaction time is about 2 hours until the resin crosslinks on the surface of the paraffin droplets to form a dense wall material. After the reaction, the microcapsules are separated by centrifugation, washed with deionized water to remove unreacted monomers, and dried under vacuum below 40℃ to avoid melting of paraffin. Finally, PCM microcapsules with an average particle size of about 2μm and a phase transition temperature range of 50~55℃ are obtained. (3) 5g of PEG-BN nanosheets and 5g of PCM microcapsules were added to 200mL of NMP solvent, ultrasonically dispersed at 300W for 1h, and then mixed with 100g of PI resin solution with a solid content of 20%. After casting into a film, the film was dried at 150℃ for 2h and then imidized at 350℃ to obtain a 5μm thick modified PI base film. The mass fraction of the modified filler in the modified base film layer was 7.4%. (4) An 80 nm thick Al layer was magnetron sputtered onto the surface of the modified PI film at a magnetron sputtering power of 250 W and an argon flow rate of 18 sccm; trenches were formed by electrochemical etching with a 10% sulfuric acid solution at a current density of 8 mA / cm. 2 The process takes 45 seconds, and the trenches of the micron-scale trench structure have a depth of 3 μm and a spacing of 15 μm. Then, BN nanowires are deposited by electrophoresis at 12V. The diameter of the BN nanowires is 60~70 nm and the length is 7~8 μm. The composite aluminum foil is then vacuum dried at 80℃.

[0037] (5) The composite aluminum foil prepared in this embodiment is used as the positive current collector. A ternary positive electrode paste (manufacturer: Ruixiang Technology) is coated on the current collector to prepare an electrode sheet. Then, the electrode sheet is punched by die cutting. The tabs of each electrode sheet are arranged in different positions from left to right. After the electrode sheets are stacked, a traditional metal foil is transferred to the electrode sheet by ultrasonic welding to collect current to the electrode post and make a battery cell.

[0038] (6) The battery cell prepared in this embodiment was subjected to performance testing. The test items were: physical properties of composite current collector, peel strength between composite aluminum foil and positive electrode active material, cycle life and temperature rise, and rate charge and discharge performance and temperature rise.

[0039] Example 2 (1) Add 8g of BN nanosheets to 100mL of 8% PEG aqueous solution and sonicate at 40℃ for 2h to obtain PEG-BN nanosheets with a sheet thickness of 80~90nm and a transverse dimension of 4~4.5μm; (2) Mix 10g of molten paraffin with emulsifier and disperse it in the aqueous phase under high-speed stirring at 2000 rpm to form an O / W emulsion. The pH of the aqueous phase is adjusted to 5.0 by hydrochloric acid or citric acid to avoid premature polymerization and uneven particle size. Melamine-formaldehyde resin prepolymer is slowly added to the emulsion system, and the reaction temperature is maintained at 55℃ with a stirring rate of 600 rpm. The reaction time is about 2 hours until the resin crosslinks on the surface of the paraffin droplets to form a dense wall material. After the reaction, the microcapsules are separated by centrifugation, washed with deionized water to remove unreacted monomers, and dried under vacuum below 40℃ to avoid melting of paraffin. Finally, PCM microcapsules with an average particle size of about 2μm and a phase transition temperature range of 50~55℃ are obtained. (3) 5g of PEG-BN nanosheets and 4g of PCM microcapsules were added to 200mL of NMP solvent, ultrasonically dispersed at 300W for 1h, and then mixed with 100g of PI resin solution with a solid content of 20%. After casting into a film, the film was dried at 150℃ for 2h and then imidized at 350℃ to obtain a 4μm thick modified PI base film. The mass fraction of the modified filler in the modified base film layer was 6.8%. (4) A 100 nm thick Cu layer was magnetron sputtered onto the surface of the modified PI film at a magnetron sputtering power of 300 W and an argon flow rate of 20 sccm; trenches were formed by electrochemical etching with a 10% sulfuric acid solution at a current density of 8 mA / cm. 2 The time was 60s; then BN nanowires were deposited by electrophoresis at 15V. The diameter of the BN nanowires was 80~90nm and the length was 8~9μm. The composite copper foil was obtained by vacuum drying at 80℃.

[0040] (5) The composite copper foil prepared in this embodiment is used as the negative electrode current collector. The negative electrode slurry is coated on the current collector. Specifically, the negative electrode graphite + silicon carbon slurry (90% graphite + 10% silicon carbon) is used to prepare the electrode sheet. Then, the electrode sheet is punched by die cutting. The tabs of each electrode sheet are arranged in different positions from left to right. After the electrode sheets are stacked, a traditional metal foil is transferred to the electrode sheet by ultrasonic welding to collect current to the electrode post and make a battery cell.

[0041] (6) The battery cell prepared in this embodiment was subjected to performance testing. The test items were: physical properties of composite current collector, peel strength between composite copper foil and negative electrode active material, cycle life and temperature rise, and rate charge and discharge performance and temperature rise.

[0042] Example 3 The scheme in this embodiment is basically the same as that in embodiment 1, except that: in step (1), 100 mL of 5% PEG aqueous solution is replaced with 100 mL of 7% PEG aqueous solution.

[0043] Example 4 The scheme in this embodiment is basically the same as that in embodiment 2, except that step (3) 300W ultrasonic dispersion for 1h is replaced with 280W ultrasonic dispersion for 1h.

[0044] Comparative Example 1 (using conventional micron-sized Al2O3 particles to modify the current collector) Micron-sized Al2O3 particles were uniformly coated onto the surface of a PI-based film to form an Al2O3 modified layer; the coating was then dried at low temperature; and an 80 nm thick Al layer was magnetron sputtered onto the surface of the Al2O3 modified layer.

[0045] Comparative Example 2 (without PCM microcapsules) (1) Add 8g of BN nanosheets to 100mL of 8% PEG aqueous solution and sonicate at 40℃ for 2h to obtain PEG-BN nanosheets; (2) 5g of PEG-BN nanosheets were added to 200mL of NMP solvent, ultrasonically dispersed at 300W for 1h, and then mixed with 100g of PI resin solution with 20% solid content. After casting into a film, the film was dried at 150℃ for 2h and then imidized at 350℃ to obtain a 4μm thick modified PI film. The remaining steps are the same as (4), (5), and (6) of Example 1.

[0046] Comparative Example 3 (Grooveless Nanowire Structure) Steps (1) to (3), (5), and (6) of this comparative example are the same as those in Example 1. The difference in step (4) is as follows: (4) A 100 nm thick Cu layer was magnetron sputtered on the surface of the modified PI film with a magnetron sputtering power of 300 W and an argon flow rate of 20 sccm to obtain a composite copper foil.

[0047] Comparative Example 4 The scheme of this comparative example is basically the same as that of Example 1, except that in step (1), 100 mL of 5% PEG aqueous solution is replaced with 100 mL of 3% PEG aqueous solution.

[0048] Comparative Example 5 The scheme of this comparative example is basically the same as that of Example 1, except that: in step (1), 100 mL of 5% PEG aqueous solution is replaced with 100 mL of 10% PEG aqueous solution.

[0049] Comparative Example 6 The scheme of this comparative example is basically the same as that of Example 1, except that step (3) 300W ultrasonic dispersion for 1h is replaced with 200W ultrasonic dispersion for 1h.

[0050] Comparative Example 7 The scheme of this comparative example is basically the same as that of Example 1, except that step (3) 300W ultrasonic dispersion for 1h is replaced with 400W ultrasonic dispersion for 1h.

[0051] The results of the experiments conducted on each embodiment and comparative example are shown in Table 1: Table 1 Comparison of test results between each embodiment and the comparative example

[0052] Based on the comparative analysis of test data from the embodiments and comparative examples, the functional current collector of the present invention exhibits significant advantages in several key performance indicators.

[0053] In terms of mechanical properties and interfacial bonding, the tensile strengths of Examples 1 and 2 reached 125 MPa and 130 MPa, respectively, and the electrode peeling forces were 30 N / m and 33 N / m, respectively, which were significantly better than those of the comparative examples. This indicates that the composite filler of PEG-grafted BN nanosheets and PCM microcapsules effectively enhanced the mechanical properties of the base film. At the same time, the trench structure of the metal layer and the filling of BN nanowires greatly improved the bonding force between the current collector and the active material.

[0054] In terms of thermal management performance, the temperature rise control effect of the embodiments is particularly outstanding. The best embodiment 1 has a charge and discharge temperature rise of only 8°C and 10°C at 1C rate, and 14°C and 16°C at 2C rate, which is much lower than all comparative examples, verifying the effectiveness of the synergistic heat dissipation system of BN three-dimensional thermal conductive network and PCM phase change temperature control. The temperature rise data of comparative example 2 (without PCM microcapsule) and comparative example 3 (without trench-nanowire structure) are between the embodiments and the completely conventional scheme, indicating that the thermal conductive network and phase change temperature control are indispensable and must work together to achieve the best heat dissipation effect.

[0055] In terms of cycle life, each embodiment achieved more than 1100 cycles, which is significantly better than the comparative examples, demonstrating the stability of the design in long-term use.

[0056] The conventional Al2O3 modified current collector in Comparative Example 1 relies solely on the passive heat conduction of Al2O3 particles and lacks the phase change heat absorption capacity of PCM microcapsules, thus failing to effectively delay thermal runaway at high temperatures. The absence of PEG-grafted BN nanosheets results in insufficient bonding strength between the filler and the base film and metal layer, making it prone to debonding during cycling and exhibiting weak interfacial bonding. Furthermore, the micron-sized Al2O3 particles struggle to form an effective heat conduction network, and the metal layer lacks a groove-nanowire structure, leading to discontinuous heat conduction paths and low longitudinal heat transfer efficiency.

[0057] Comparative Example 2 (without PCM microcapsules): Although BN nanosheets provide a thermally conductive network, they lack the phase change endothermic effect of PCM microcapsules. At high temperatures, they cannot delay the temperature rise through latent heat absorption, resulting in a shortened thermal runaway protection time.

[0058] Comparative Example 3 (Trenchless Nanowire Structure) did not form a trench structure through electrochemical etching and did not deposit BN nanowires. The internal heat conduction path of the metal layer was discontinuous, and heat could not be efficiently conducted longitudinally to the external heat dissipation system.

[0059] Furthermore, the parameter optimization comparison shows that there is an optimal range for process parameters such as PEG concentration and ultrasonic power. Although the performance of Examples 3 and 4 is slightly lower than that of the optimal Examples 1 and 2, it is still better than most comparative examples. However, comparative examples 4 to 7, which are outside the reasonable range, all showed a decline in performance. For example, excessively high PEG concentration can lead to uneven dispersion of BN nanosheets, and insufficient ultrasonic power can cause filler agglomeration, which weakens the thermal conductivity and interfacial bonding strength of the composite material.

[0060] In summary, the functional current collector of this invention, through innovative material composite and structural design, achieves efficient temperature rise control while maintaining good mechanical properties, providing a reliable technical solution for the application of high-power batteries.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent substitutions, and improvements made by those skilled in the art to the above embodiments without departing from the scope of the technical solution of the present invention, based on the technical essence of the present invention, shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A functional current collector for reducing temperature rise, characterized in that, It includes a base film modification layer and metal functional layers on both sides of the base film modification layer; The modified base film layer contains uniformly dispersed modified fillers, which are composite systems formed by PCM microcapsules and BN nanosheets grafted with PEG on the surface. The surface of the metal functional layer has a micron-scale trench structure, within which oriented BN nanowires are embedded.

2. The temperature-reducing current collector according to claim 1, characterized in that: In the modified base film layer, the mass fraction of the modified filler is 5-15%.

3. The temperature-reducing current collector according to claim 1, characterized in that: The PCM microcapsules have a particle size of 1~3μm and a phase transition temperature range of 45~60℃; the surface-grafted PEG BN nanosheets have a sheet thickness of 50~100nm and a lateral dimension of 2~5μm.

4. The temperature-reducing current collector according to claim 1, characterized in that: The groove depth of the micron-scale trench structure is 2~5μm and the spacing is 10~20μm; the diameter of the BN nanowire is 50~100nm and the length is 5~10μm.

5. The method for preparing the temperature-reducing current collector according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1: Add BN nanosheets to a PEG aqueous solution and perform surface grafting by ultrasonic treatment to obtain PEG-BN nanosheets; use paraffin as the core material and perform in-situ polymerization of melamine-formaldehyde resin to obtain PCM microcapsules; S2: PEG-BN nanosheets and PCM microcapsules were added to a solvent, ultrasonically dispersed, and then mixed with a polyimide resin solution. After casting and drying, the modified polyimide-based film was obtained by heating and imidization. S3: A metal layer is magnetron sputtered on both sides of the modified polyimide-based film, and then a micron-scale trench structure is formed by electrochemical etching. BN nanowires are deposited in the micron-scale trench structure by electrophoresis.

6. The method for preparing a temperature-reducing current collector according to claim 1, characterized in that: In step S1, the mass-to-volume ratio of BN nanosheets to PEG aqueous solution is 1:18~20 g / ml, and the mass concentration fraction of PEG aqueous solution is 4~7%.

7. The method for preparing a temperature-reducing current collector according to claim 1, characterized in that: In step S2, the mass ratio of PEG-BN nanosheets to PCM microcapsules is 1~1.5:1~1.5; the ultrasonic power is 250~350W, and the duration is 45~70min.

8. An electrode sheet, characterized in that: It includes the temperature-reducing current collector as described in claim 8.

9. A battery, characterized in that: It includes the electrode sheet as described in claim 9.

10. The battery according to claim 9, characterized in that: The battery is a square stacked battery. The position of the tabs cut on each electrode sheet in the stacked battery is different. After the electrode sheets are stacked, each tab is connected to the terminal post through a connecting metal.

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