Composite current collector and manufacturing method therefor, electrode sheet, battery, and electrical device

Abstract

A composite current collector, comprising a current collector body and a coating, wherein the coating is arranged on the current collector body; the coating comprises a pyrolysis agent; when the pyrolysis agent is within a first temperature range, the internal resistance is increased, and within a second temperature range, the pyrolysis agent is decomposed and releases gases; the minimum value of the first temperature range is T1, and the maximum value of the first temperature range is T2; the minimum value of the second temperature range is T3, and the maximum value of the second temperature range is T4; T3 is greater than or equal to T1, and T4 is greater than or equal to T2.

Description

Composite current collector, method for manufacturing the same, electrode sheet, battery and electric device

[0001] The present application claims priority to the Chinese patent application No. 202410634506.1, filed on May 21, 2024, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present disclosure relates to the technical field of batteries, and in particular to a composite current collector, a method for manufacturing the same, an electrode sheet, a battery and an electric device. BACKGROUND

[0003] With the rapid development of electrochemical energy storage devices, high safety and high stability lithium ion energy storage systems such as lithium ion batteries are an inevitable choice for the development of the power industry. Lithium ion batteries are a kind of secondary batteries, which include electrode materials and mainly work by lithium ions in the electrode materials moving back and forth between the positive and negative electrodes.

[0004] SUMMARY

[0005] The present disclosure provides a composite current collector, a method for manufacturing the same, an electrode sheet, a battery and an electric device, which solves the problem of battery thermal runaway.

[0006] The present disclosure provides the following technical solutions:

[0007] In a first aspect, the present disclosure provides a composite current collector, comprising a current collector body and a coating, the coating is arranged on the current collector body, the coating comprises a pyrolysis agent, the pyrolysis agent increases the internal resistance in a first temperature range, and the pyrolysis agent decomposes and releases gas in a second temperature range; the minimum value of the first temperature range is T1, and the maximum value of the first temperature range is T2; the minimum value of the second temperature range is T3, and the maximum value of the second temperature range is T4; T3 is greater than or equal to T1, and T4 is greater than or equal to T2.

[0008] In some embodiments, the cleavage agent comprises at least one of an inorganic cleavage agent and an organic cleavage agent, the second temperature range comprises a first sub-temperature range and a second sub-temperature range; in the case that the cleavage agent comprises an inorganic cleavage agent, the inorganic cleavage agent decomposes and releases gas in the first sub-temperature range; in the case that the cleavage agent comprises an organic cleavage agent, the organic cleavage agent decomposes and releases gas in the second sub-temperature range; in the case that the cleavage agent comprises both an inorganic cleavage agent and an organic cleavage agent, the inorganic cleavage agent decomposes and releases gas in the first sub-temperature range, and the organic cleavage agent decomposes and releases gas in the second sub-temperature range; the minimum value of the first sub-temperature range is T3, and the maximum value of the first sub-temperature range is T31; the minimum value of the second sub-temperature range is T32, and the maximum value of the second sub-temperature range is T4; T32 is greater than or equal to T31.

[0009] In some embodiments, the organic cleavage agent comprises one or more of a combination of polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyacrylic acid, polymethyl methacrylate, polyvinyl alcohol, polyacrylamide, acrylonitrile-butadiene-styrene copolymer resin, and modified resin.

[0010] In some embodiments, the inorganic cleavage agent comprises one or more of a combination of ammonium salt, carbonate, bicarbonate, such as ammonium chloride, ammonium sulfate, ammonium bisulfate, ammonium nitrate, ammonium iodide, sodium bromide, ammonium bicarbonate, amine carbonate, sodium carbonate, sodium bicarbonate, silver carbonate, potassium carbonate, potassium bicarbonate.

[0011] In some embodiments, the first temperature range is 120-200℃, the first sub-temperature range is 150-300℃, and the second sub-temperature range is 300-500℃.

[0012] In some embodiments, the mass ratio of the inorganic cleavage agent to the organic cleavage agent is (0-80):(20-100).

[0013] In some embodiments, the mass percentage of the cleavage agent in the coating layer is 5%-60%.

[0014] In some embodiments, the coating layer further comprises a binder and a conductive agent, in terms of mass percentage; the mass percentage of the binder in the coating layer is 5%-60%, and the mass percentage of the conductive agent in the coating layer is 1%-50%.

[0015] In some embodiments, the thickness of the coating layer is 500 nm-10 μm.

[0016] In a second aspect, the present disclosure provides a method for manufacturing a composite current collector, comprising: mixing a splitting agent and a solvent to obtain a coating slurry; and coating the coating slurry on a current collector body to obtain the composite current collector after roller pressing and drying.

[0017] In a third aspect, the present disclosure provides an electrode sheet, comprising an active material layer and the composite current collector of the first aspect, the active material layer being arranged on at least one side surface of the composite current collector, and the active material layer being one of a positive electrode active material layer or a negative electrode active material layer.

[0018] In a fourth aspect, the present disclosure provides a battery, comprising a positive electrode sheet, a negative electrode sheet, and a separator arranged between the positive electrode sheet and the negative electrode sheet, at least one of the positive electrode sheet or the negative electrode sheet being the electrode sheet of the third aspect.

[0019] In a fifth aspect, the present disclosure provides an electrical device, comprising an electrical appliance and the battery of the fourth aspect.

[0020] The composite current collector provided by the present disclosure has a coating layer arranged on the current collector body, the splitting agent in the coating layer increases the internal resistance in a first temperature range, and decomposes and releases gas in a second temperature range, so that the internal resistance of the battery is increased to reduce the self-heat generation of the battery before the thermal runaway of the battery occurs, and then a large amount of gas is generated to make the battery open the valve in advance and release a large amount of organic or inorganic gas carrying a large amount of heat, so that the temperature of the battery body is significantly reduced, thereby realizing self-blocking of the thermal runaway of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and other drawings can be obtained by those skilled in the art without creative labor.

[0022] FIG. 1 is a schematic cross-sectional view of a composite current collector according to some embodiments;

[0023] FIG. 2 is a manufacturing flowchart of a composite current collector according to some embodiments;

[0024] FIG. 3 is a thermal runaway test result of Example 4;

[0025] FIG. 4 is a thermal runaway test result of Example 9. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present disclosure will be described clearly and completely in combination with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present disclosure.

[0027] Unless otherwise defined, all technical and scientific terms used in the present disclosure have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure belongs. The terms used in the specification of the present disclosure are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure. The term "and / or" used in the present disclosure includes any and all combinations of one or more related listed items.

[0028] With the rapid development of electrochemical energy storage devices, safety problems are increasingly prominent. A high-safety and high-stability lithium ion energy storage system is an inevitable choice for the development of the power industry. At present, the current collector in the battery may be damaged when the battery is overcharged, overdischarged or subjected to external impact, leading to internal short circuit of the battery and causing serious safety problems such as thermal runaway and explosion of the battery.

[0029] Therefore, it is crucial to provide a stable composite current collector to solve the problem of battery thermal runaway.

[0030] Some embodiments of the present disclosure will be described in detail below in combination with the drawings. The following embodiments and features in the embodiments can be combined with each other without conflict.

[0031] The terms appearing in the text are explained as follows:

[0032] PTC material: The resistance of a conductive composite material with a positive temperature coefficient (PTC) characteristic has a sharp response to temperature changes, which can be used as a material for current sensing elements, and has been widely used in overcurrent protection elements or circuit elements. The resistance of the PTC conductive composite material at normal temperature can be maintained at a very low value, so that the circuit or battery can operate normally. However, when overcurrent or overtemperature occurs in the circuit or battery, the resistance value will instantaneously increase to a high resistance state (i.e. tripping), thereby reversing the excess current and achieving protection of the battery or circuit element.

[0033] It should be noted that the decomposition temperature involved in the following text is obtained by thermal gravimetric analyzer (TGA) test, for example, the test method includes:

[0034] In an inert gas atmosphere, the test sample is raised from 25℃ to 500℃ at a temperature rise rate of 10℃ / min, and kept constant for 10min; then reduced from 500℃ to 25℃ at a temperature drop rate of 10℃ / min; cycle three times.

[0035] In an air atmosphere, the test sample is raised from 25℃ to 500℃ at a temperature rise rate of 10℃ / min, and kept constant for 10min; then reduced from 500℃ to 25℃ at a temperature drop rate of 10℃ / min.

[0036] Some embodiments of the present disclosure provide a composite current collector, referring to FIG. 1, the composite current collector includes a current collector body 10 and a coating layer 20, the coating layer 20 is arranged on the current collector body 10. For example, the coating layer 20 can be arranged on any surface of the current collector body 10 along the thickness direction. In FIG. 1, the coating layer 20 is mainly taken as an example arranged on the upper surface of the current collector body 10.

[0037] The coating layer 20 includes a decomposition agent, the decomposition agent increases the internal resistance in a first temperature range, and the decomposition agent decomposes and releases gas in a second temperature range. For example, the minimum value of the first temperature range is T1, and the maximum value of the first temperature range is T2; the minimum value of the second temperature range is T3, and the maximum value of the second temperature range is T4; T3 is greater than or equal to T1, and T4 is greater than or equal to T2; that is, the first temperature range belongs to [T1, T2], and the second temperature range belongs to [T3, T4]. In some embodiments, the current collector body can be an aluminum foil or a copper foil. The decomposition agent can be a PTC material, which can significantly increase the internal resistance of the battery cell in the first temperature range, reduce the self-heating of the battery cell, and thus achieve battery thermal runaway protection. As the temperature of the battery continues to rise, the decomposition agent can decompose in the second temperature range to produce CO2, CO, N2, NH3 and other gases, which can be used to reduce the temperature of the battery, thereby achieving double protection of thermal runaway.

[0038] For example, T1 is less than T2 and T3; T2 can be greater than or less than T3, of course, T2 can also be equal to T3; T2 can also be less than T4, and T3 can also be less than T4.

[0039] For example, the units of T1, T2, T3 and T4 are all ℃.

[0040] In some embodiments, the first temperature range and the second temperature range can intersect, for example, the first temperature range is 120℃-200℃, and the second temperature range is 150℃-500℃.

[0041] Some embodiments of the present disclosure provide a composite current collector, by setting a coating layer on the current collector body, the decomposition agent in the coating layer will increase the internal resistance of the battery in the first temperature range, and will decompose and release gas in the second temperature range, so as to increase the internal resistance of the battery before the thermal runaway of the battery, reduce the self-heat generation of the battery, and then generate a large amount of gas, so that the battery valve is opened in advance, and the organic gas or inorganic gas containing a large amount of heat is released, so that the battery body and the temperature are significantly reduced, thereby realizing the self-blocking of the battery thermal runaway; and realizing the double protection of the battery thermal runaway.

[0042] In some embodiments, the decomposition agent includes at least one of an inorganic decomposition agent and an organic decomposition agent, and the second temperature range includes a first sub-temperature range and a second sub-temperature range. For example, the minimum value of the first sub-temperature range is T3, and the maximum value of the first sub-temperature range is T31; the minimum value of the second sub-temperature range is T32, and the maximum value of the second sub-temperature range is T4; that is, the first temperature range belongs to [T3, T31], and the second temperature range belongs to [T32, T4]; T32 is greater than or equal to T31. The inorganic decomposition agent decomposes and releases gas in the first sub-temperature range, and the organic decomposition agent decomposes and releases gas in the second sub-temperature range.

[0043] For example, in the case that the decomposition agent includes an inorganic decomposition agent, the inorganic decomposition agent decomposes and releases gas in the first sub-temperature range; in the case that the decomposition agent includes an organic decomposition agent, the organic decomposition agent decomposes and releases gas in the second sub-temperature range; in the case that the decomposition agent includes an inorganic decomposition agent and an organic decomposition agent, the inorganic decomposition agent decomposes and releases gas in the first sub-temperature range, and the organic decomposition agent decomposes and releases gas in the second sub-temperature range.

[0044] For example, the decomposition agent can include at least one of an inorganic decomposition agent and an organic decomposition agent, and the inorganic decomposition agent and the organic decomposition agent decompose at different temperature ranges. The inorganic decomposition agent decomposes in the first sub-temperature range, and the organic decomposition agent decomposes in the second sub-temperature range.

[0045] For example, T3 is less than T31; T31 can be greater than or less than T32, of course, T31 can also be equal to T32; T31 is also less than T4, and T32 is also less than T4. For example, the units of T31 and T32 are both ℃.

[0046] In some embodiments, the first sub-temperature range and the second sub-temperature range can intersect, for example, the first sub-temperature range is 150℃-350℃, and the second sub-temperature range is 300℃-500℃.

[0047] In some embodiments, the organic cleavage agent includes one or more of a combination of polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyacrylic acid, polymethyl methacrylate, polyvinyl alcohol, polyacrylamide, acrylonitrile-butadiene-styrene copolymer resin, and modified resin.

[0048] It should be noted that the acrylonitrile-butadiene-styrene copolymer resin is ABS resin, which is a terpolymer of acrylonitrile (A), butadiene (B), and styrene (S). The relative content of the three monomers can be arbitrarily changed to produce various types of trees.

[0049] In some embodiments, the inorganic cleavage agent includes one or more of a combination of ammonium salt, carbonate, bicarbonate, such as ammonium chloride, ammonium sulfate, ammonium bisulfate, ammonium nitrate, ammonium iodide, sodium bromide, ammonium bicarbonate, amine carbonate, sodium carbonate, sodium bicarbonate, silver carbonate, potassium carbonate, and potassium bicarbonate.

[0050] In some embodiments, the first temperature range is 120-200℃, the first sub-temperature range is 150-300℃, and the second sub-temperature range is 300-500℃.

[0051] In the case of meeting the above temperature relationship, and when the inorganic cleavage agent and the organic cleavage agent are added at the same time in the composite current collector, the battery can continuously generate gas in the range of 150-500℃ to cope with thermal runaway.

[0052] In some embodiments of the present disclosure, the starting temperature of the gas production of the composite current collector is 150℃, and the maximum temperature is as high as 500℃. For example, between 150-300℃, the temperature is reduced mainly by the gas production of the inorganic cleavage agent, and above 300℃, the gas is produced by the organic cleavage agent.

[0053] In addition, in some embodiments of the present disclosure, T1 is 120℃, which is to cope with the heating process in the battery manufacturing process. In the related art, the temperature of the electrode sheet in the coating baking process is as high as 110℃, and generally, the decomposition temperature of the foaming agent is between 80-100℃. Therefore, the cleavage agent provided in some embodiments of the present disclosure is different from the common foaming agent. The response temperature of the organic cleavage agent and the inorganic cleavage agent is both 120℃, so that the failure in the manufacturing process of the electrode sheet can be avoided, and the effect is only in the thermal runaway stage of the battery. Without affecting the related process, the safety of the lithium ion battery is improved.

[0054] In some embodiments, the mass ratio of the inorganic cleavage agent to the organic cleavage agent is (0-80):(20-100).

[0055] For example, in the case of using both inorganic and organic pyrolysis agents at the same time, the ratio of the two can be 0:100, 5:95, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30, or 80:20.

[0056] It can be understood that by making the mass ratio of the inorganic and organic pyrolysis agents within the above range, it can be ensured that the system of the pyrolysis agent can have the organic pyrolysis agent. The organic pyrolysis agent has adhesion, can improve the connection strength of the coating on the current collector body, and the organic pyrolysis agent is low in cost, and can also reduce the cost of the composite current collector.

[0057] In some embodiments, the mass ratio of the pyrolysis agent in the coating is 5% to 60%. For example, the mass ratio of the pyrolysis agent in the coating can be 5%, 10%, 20%, 30%, 40%, 50%, or 60%.

[0058] In some embodiments, the coating further comprises a binder and a conductive agent, the mass ratio of the binder in the coating is 5% to 60%, and the mass ratio of the conductive agent in the coating is 1% to 50%.

[0059] For example, the mass ratio of the binder can be 5%, 10%, 20%, 30%, 40%, 50%, or 60%. For example, the mass ratio of the conductive agent can be 1%, 5%, 10%, 20%, 30%, 40%, or 50%.

[0060] In some embodiments, the binder is one or more of a high molecular resin. The high molecular resin includes but is not limited to acrylic resin, modified acrylic resin, and amide resin, etc.

[0061] Some embodiments of the present disclosure provide that the composite current collector can also not add a binder, but the organic pyrolysis agent can also play the role of the binder, and by modifying the high molecular material through high molecular grafting aniline and proton acid doping, the high temperature pyrolysis and the bonding effect can be realized.

[0062] In some embodiments, the conductive agent is one or more of graphite, graphene, conductive carbon, carbon nanotubes (CNTs), etc.

[0063] In some embodiments, the thickness of the coating is 500 nm to 10 μm. For example, the thickness of the coating can be 500 nm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm.

[0064] In some embodiments, the coating is dissolved in a water-based solvent or an oil-based solvent. The water-based solvent can be water, ethanol, n-butanol, isobutanol, or the like; the oil-based solvent can be N-methylpyrrolidone (NMP), chloroform, acetone, ethyl acetate, dimethylamide, or the like.

[0065] Some embodiments of the present disclosure also provide a method for manufacturing a composite current collector, referring to FIG. 2, the method comprises steps S10 and S20.

[0066] In step S10, the lysing agent and the solvent are mixed to obtain a coating slurry.

[0067] In step S20, the coating slurry is coated on the current collector body, and after roller drying, a composite current collector is obtained.

[0068] For example, in step S10, the lysing agent is placed in the solvent to obtain the coating slurry, comprising: placing the lysing agent, the binder, and the conductive agent in the solvent, and mixing uniformly to obtain the coating slurry.

[0069] Some embodiments of the present disclosure also provide an electrode sheet, which comprises an active material layer and the above-mentioned composite current collector, the active material layer is arranged on at least one side surface of the composite current collector, and the active material layer is a positive active material layer or a negative active material layer.

[0070] It can be understood that the active material layer can be a positive active material layer or a negative active material layer, for example, the active material layer can be set according to the type of the electrode sheet to be manufactured.

[0071] Some embodiments of the present disclosure also provide a battery, which comprises a positive electrode sheet, a negative electrode sheet, and a separator, the separator is arranged between the positive electrode sheet and the negative electrode sheet, and at least one of the positive electrode sheet or the negative electrode sheet is the above-mentioned electrode sheet.

[0072] Some embodiments of the present disclosure also provide an electrical equipment, which comprises an electrical appliance and the above-mentioned battery.

[0073] The technical solutions of the present disclosure are described in detail through multiple embodiments as follows.

[0074] Embodiment 1

[0075] This embodiment provides a composite current collector, which comprises a current collector body (aluminum foil) and a coating (lysing agent (polyacrylamide), binder (polyvinylidene difluoride, PVDF), conductive agent (graphite)). The proportions of the lysing agent, the binder, and the conductive agent are 60%, 30%, and 10%, respectively.

[0076] The method for manufacturing the composite current collector comprises:

[0077] 1) Put polyacrylamide-60%, PVDF-30% and graphite-10% into solvent NMP and mix uniformly through a stirrer, adjust the viscosity with NMP to obtain a coating slurry.

[0078] 2) Apply the coating slurry to the surface of the aluminum foil through a plate roller to form a 1um coating.

[0079] 3) Dry at 100℃ to remove NMP to obtain the composite current collector.

[0080] Example 2

[0081] The composite current collector provided in this example comprises a current collector body (aluminum foil) and a coating layer (splitting agent (polyacrylamide), binder (PVDF), conductive agent (graphite)). The proportions of the splitting agent, the binder and the conductive agent are 30%, 30% and 40% respectively.

[0082] The method for manufacturing the composite current collector provided in Example 2 is the same as that in Example 1.

[0083] Example 3

[0084] The composite current collector provided in this example comprises a current collector body (aluminum foil) and a coating layer (splitting agent (polyacrylamide), binder (PVDF), conductive agent (graphite)). The proportions of the splitting agent, the binder and the conductive agent are 5%, 45% and 50% respectively.

[0085] The method for manufacturing the composite current collector provided in Example 3 is the same as that in Example 1.

[0086] Example 4

[0087] The composite current collector provided in this example comprises a current collector body (aluminum foil) and a coating layer (splitting agent (ammonium bicarbonate NH4HCO3), binder (PVDF), conductive agent (graphite)). The proportions of the splitting agent, the binder and the conductive agent are 60%, 30% and 10% respectively.

[0088] The method for manufacturing the composite current collector provided in Example 4 is the same as that in Example 1.

[0089] Example 5

[0090] The composite current collector provided in this example comprises a current collector body (aluminum foil) and a coating layer (splitting agent (ammonium bicarbonate NH4HCO3), binder (PVDF), conductive agent (graphite)). The proportions of the splitting agent, the binder and the conductive agent are 30%, 30% and 40% respectively.

[0091] The method for manufacturing the composite current collector provided in Example 5 is the same as that in Example 1.

[0092] Example 6

[0093] This example provides a composite current collector, including a current collector body (aluminum foil), a coating layer (a splitting agent (ammonium bicarbonate NH4HCO3), a binder (PVDF), a conductive agent (graphite)). The proportions of ammonium bicarbonate NH4HCO3, and polyacrylamide, a binder, and a conductive agent are 5%, 45%, 50%, respectively.

[0094] The manufacturing method of the composite current collector provided in Example 6 is the same as that in Example 1.

[0095] Example 7

[0096] This example provides a composite current collector, including a current collector body (aluminum foil), a coating layer (a splitting agent A (ammonium bicarbonate NH4HCO3 and polyacrylamide), a binder (PVDF), a conductive agent (graphite)). The proportions of ammonium bicarbonate NH4HCO3, and polyacrylamide, a binder, and a conductive agent are 30%, 30%, 30%, 10%, respectively.

[0097] The manufacturing method of the composite current collector provided in Example 7 is the same as that in Example 1.

[0098] Example 8

[0099] This example provides a composite current collector, including a current collector body (aluminum foil), a coating layer (a splitting agent (ammonium bicarbonate NH4HCO3 and polyacrylamide), a binder (PVDF), a conductive agent (graphite)). The proportions of ammonium bicarbonate NH4HCO3, and polyacrylamide, a binder, and a conductive agent are 2.5%, 2.5%, 45%, 50%, respectively.

[0100] The manufacturing method of the composite current collector provided in Example 8 is the same as that in Example 1.

[0101] Example 9

[0102] This example provides a composite current collector, including a current collector body (aluminum foil), a coating layer (a splitting agent (ammonium bicarbonate NH4HCO3 and polyacrylamide), a binder (PVDF), a conductive agent (graphite)). The proportions of ammonium bicarbonate NH4HCO3, and polyacrylamide, a binder, and a conductive agent are 48%, 12%, 30%, 10%, respectively.

[0103] The manufacturing method of the composite current collector provided in Example 9 is the same as that in Example 1.

[0104] Example 10

[0105] The present embodiment provides a composite current collector, including a current collector body (aluminum foil), a coating layer (splitting agent (ammonium bicarbonate NH4HCO3 and polyacrylamide), binder (PVDF), conductive agent (graphite)). The proportion of ammonium bicarbonate NH4HCO3, and polyacrylamide, binder and conductive agent is 4%, 1%, 45%, 50% respectively.

[0106] The manufacturing method of the composite current collector provided in embodiment 10 is the same as that in embodiment 1.

[0107] Comparative example 1

[0108] The present comparative example provides a current collector (aluminum foil).

[0109] The coating slurry obtained from comparative example 1 is subjected to viscosity test: GB / T17473 is used to test the viscosity of the coating slurry.

[0110] The composite current collector obtained from comparative example 1 is subjected to peeling force test: GB / T4815 is used to record the peeling force of the coating layer.

[0111] The composite current collector obtained from comparative example 1 is subjected to sheet resistance test: the current collector (composite current collector) is assembled into a positive sheet, and the positive sheet uses the same mass ratio of positive active material (lithium iron phosphate); a four-probe membrane resistance meter is used to measure the sheet diameter of 14 mm under a pressure of 19 MPa.

[0112] The composite current collector obtained from comparative example 1 is subjected to thermal runaway test: the assembled positive sheet is assembled into a battery cell, and the battery uses the same negative sheet. The positive sheet is the positive sheet subjected to the sheet resistance test described above (including the positive sheet obtained from comparative example 1), and the negative sheet includes a copper foil and a negative active material (graphite). The battery is stacked from bottom to top: negative, separator, positive in turn. After the battery cell is assembled and baked, it is filled with liquid and formed into a complete battery cell. Then, the thermal runaway temperature and sheet resistance of the battery cell obtained from comparative example 1 are tested according to the national standard GBT-36276-2023.

[0113] Table 1 is the result of the above test.

[0114] Table 1

[0115] As shown in Table 1, from the test results of the sheet resistance of comparative example 1-10 and comparative example 1, it can be seen that the sheet resistance of the positive sheet in comparative example 1 is weakly affected by temperature, while the sheet resistance of the positive sheet in comparative example 1-10 increases with temperature and has a strong effect on the change of sheet resistance.

[0116] For example, in Example 4, the resistivity of the positive electrode sheet increased about 4 times when the temperature increased to 120°C, and in Example 9, the resistivity of the positive electrode sheet increased about 20 times when the temperature increased to 120°C. It is confirmed that some embodiments of the present disclosure can achieve a significant PTC effect at 120°C, increasing the internal resistance of the battery cell.

[0117] FIG. 3 is the thermal runaway test result of Example 4, and FIG. 4 is the thermal runaway test result of Example 9. In Example 4, the maximum temperature of the thermal runaway large surface was 303°C, and there was a significant hysteresis effect between the maximum voltage and the maximum temperature. When the battery cell voltage reached the maximum voltage, the battery cell large surface temperature was about 100°C, and there was a significant effect of inhibiting thermal runaway. In Example 9, the maximum temperature of the thermal runaway large surface was only 198°C, and there was a significant hysteresis effect between the maximum voltage and the maximum temperature. When the battery cell voltage reached the maximum voltage, the battery cell large surface temperature was about 85°C.

[0118] The above disclosure is only a preferred embodiment of the present disclosure, and of course cannot limit the scope of the present disclosure. Those skilled in the art can understand that the above-mentioned processes can be implemented in whole or in part, and equivalent changes can be made according to the claims of the present disclosure, which still belong to the scope of the present disclosure.

Claims

1. A composite current collector, comprising: a current collector body; and a coating layer disposed on the current collector body, the coating layer comprising a pyrolysis agent, the pyrolysis agent increasing internal resistance in a first temperature range, the pyrolysis agent decomposing and releasing gas in a second temperature range; wherein a minimum value of the first temperature range is T1 and a maximum value of the first temperature range is T2; a minimum value of the second temperature range is T3 and a maximum value of the second temperature range is T4; T3 is greater than or equal to T1 and T4 is greater than or equal to T2. the pyrolysis agent comprises at least one of an inorganic pyrolysis agent and an organic pyrolysis agent; the second temperature range comprises a first sub-temperature range and a second sub-temperature range; 2. The composite current collector of claim 1, wherein, in the case that the pyrolysis agent comprises an inorganic pyrolysis agent, the inorganic pyrolysis agent decomposes and releases gas in the first sub-temperature range; in the case that the pyrolysis agent comprises an organic pyrolysis agent, the organic pyrolysis agent decomposes and releases gas in the second sub-temperature range; in the case that the pyrolysis agent comprises an inorganic pyrolysis agent and an organic pyrolysis agent, the inorganic pyrolysis agent decomposes and releases gas in the first sub-temperature range and the organic pyrolysis agent decomposes and releases gas in the second sub-temperature range; wherein a minimum value of the first sub-temperature range is T31 and a maximum value of the first sub-temperature range is T3; a minimum value of the second sub-temperature range is T32 and a maximum value of the second sub-temperature range is T4; T32 is greater than or equal to T31. the organic pyrolysis agent comprises one or more of a combination of polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyacrylic acid, polymethyl methacrylate, polyvinyl alcohol, polyacrylamide, acrylonitrile-butadiene-styrene copolymer resin, and modified resin.

3. The composite current collector of claim 2, wherein, the inorganic pyrolysis agent comprises one or more of a combination of ammonium salt, carbonate, bicarbonate, such as ammonium chloride, ammonium sulfate, ammonium bisulfate, ammonium nitrate, ammonium iodide, sodium bromide, ammonium bicarbonate, amine carbonate, sodium carbonate, sodium bicarbonate, silver carbonate, potassium carbonate, potassium bicarbonate.

4. The composite current collector of claim 2, wherein, the first temperature range is 120℃-200℃, the first sub-temperature range is 150℃-300℃, and the second sub-temperature range is 300℃-500℃.

5. The composite current collector of claim 2, wherein, a mass ratio of the inorganic pyrolysis agent to the organic pyrolysis agent is (0-80):(20-100).

6. The composite current collector of claim 2, wherein, a mass percentage of the pyrolysis agent in the coating layer is 5%-60%.

7. The composite current collector of any one of claims 1 to 6, wherein, the coating layer further comprises a binder and a conductive agent; a mass percentage of the binder in the coating layer is 5%-60%, and a mass percentage of the conductive agent in the coating layer is 1%-50%.

8. The composite current collector of any one of claims 1 to 7, wherein, a thickness of the coating layer is 500nm-10μm.

9. The composite current collector of any one of claims 1 to 8, wherein, 10.A method for manufacturing a composite current collector, comprising: mixing a pyrolysis agent and a solvent to obtain a coating layer slurry; coating the coating layer slurry on a current collector body, and drying by rolling to obtain a composite current collector. 11.An electrode sheet, comprising: an active material layer; and a current collector. ​ The composite current collector according to any one of claims 1 to 9, wherein the active material layer is provided on at least one side surface of the composite current collector, and the active material layer is one of a positive electrode active material layer or a negative electrode active material layer.

12. A battery comprising: a positive electrode sheet; a negative electrode sheet; and a separator provided between the positive electrode sheet and the negative electrode sheet; wherein at least one of the positive electrode sheet or the negative electrode sheet is the electrode sheet according to claim 11.

13. An electrical device comprising: an electrical consumer; and the battery according to claim 12.

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