Modified current collector and electrochemical device and electronic equipment comprising same

Abstract

The invention discloses a modified current collector and an electrochemical device and electronic equipment comprising the same. The modified current collector comprises a current collector substrate and a functional layer arranged on at least one surface of the current collector substrate, the functional layer comprises a carbon material, and the carbon material meets the conditions that the heat conductivity coefficient is 500-1090 W / (m.K), and the electric conductivity coefficient is 570-870 S / m. The modified current collector has high thermal conductivity and excellent electrical conductivity, and an electrochemical device (especially a lithium ion battery) obtained by applying the modified current collector to a pole piece has excellent high-temperature cycle performance and uniform heat distribution.

Description

Technical Field

[0001] This invention provides a modified current collector and an electrochemical device and electronic device containing the same. Background Technology

[0002] As energy storage cells become larger and larger, they generate more heat and become more unevenly distributed inside, leading to uneven lithium-ion concentration and lithium plating. This results in poor cycle performance, especially at high temperatures, which can cause safety issues and hinders the application of lithium manganese iron phosphate materials in the market. Summary of the Invention

[0003] The technical problem this invention aims to solve is to overcome the shortcomings of poor high-temperature cycle performance in existing batteries, and to provide a modified current collector and electrochemical and electronic devices containing it. The modified current collector of this invention has high thermal conductivity and high electrical conductivity. Electrochemical devices (especially lithium-ion batteries) using this modified current collector in electrodes exhibit excellent high-temperature cycle performance and uniform heat distribution.

[0004] The present invention solves the above-mentioned technical problems through the following technical solution:

[0005] A first aspect of the present invention provides a modified current collector comprising a current collector matrix and a functional layer disposed on at least one surface of the current collector matrix; the functional layer comprises a carbon material having the following properties: thermal conductivity of 500~1090 W / (m·K) and electrical conductivity of 570~870 S / m.

[0006] A second aspect of the present invention provides an electrochemical device comprising an electrode comprising a modified current collector as described above.

[0007] A third aspect of the present invention provides an electronic device comprising the electrochemical device described above.

[0008] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0009] The reagents and raw materials used in this invention are all commercially available.

[0010] The positive and progressive effects of this invention are as follows:

[0011] In this invention, a modified current collector is obtained by setting a functional layer on the surface of the current collector substrate. The carbon material in the functional layer satisfies the following conditions: thermal conductivity of 500~1090 W / (m·K) and electrical conductivity of 570~870 S / m. The resulting modified current collector has high thermal conductivity and excellent electrical conductivity. Electrochemical devices (especially lithium-ion batteries) using this modified current collector in electrodes have excellent high-temperature cycle performance and uniform heat distribution. Attached Figure Description

[0012] Figure 1 The image shows the SEM image of the carbon material in Example 1 at a magnification of 10K.

[0013] Figure 2 This is a TEM image of the carbon material in Example 1 obtained at a magnification of 400K.

[0014] Figure 3 The image shows the heat distribution of a lithium-ion battery prepared using the modified current collector from Comparative Example 1.

[0015] Figure 4 This is a heat distribution diagram of a lithium-ion battery prepared using the modified current collector in Example 1.

[0016] Figure 5 The graph shows a comparison of the cycle performance of lithium-ion batteries prepared using the modified current collectors in Example 1 (dashed line) and Comparative Example 1 (solid line), respectively. Detailed Implementation

[0017] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0018] A first aspect of the present invention provides a modified current collector comprising a current collector matrix and a functional layer disposed on at least one surface of the current collector matrix; the functional layer comprises a carbon material having the following properties: thermal conductivity of 500~1090 W / (m·K) and electrical conductivity of 570~870 S / m.

[0019] In some embodiments of the present invention, the thermal conductivity of the carbon material is 800~1090 W / (m·K).

[0020] In some specific embodiments of the present invention, the thermal conductivity of the carbon material is 500 W / (m·K), 800 W / (m·K), 900 W / (m·K), 950 W / (m·K), 980 W / (m·K), 1000 W / (m·K), 1010 W / (m·K), 1040 W / (m·K), 1030 W / (m·K), or 1090 W / (m·K).

[0021] In this invention, the bulk conductivity of the carbon material is used as the conductivity coefficient of the carbon material.

[0022] In some embodiments of the present invention, the conductivity of the carbon material is 600~870 S / m.

[0023] In some specific embodiments of the present invention, the conductivity of the carbon material is 550 S / m, 585 S / m, 570 S / m, 590 S / m, 680 S / m, 640 S / m, 630 S / m, 610 S / m, 620 S / m, 720 S / m or 870 S / m.

[0024] In a specific embodiment of the present invention, the carbon material satisfies the following conditions: thermal conductivity of 1000 W / (m·K) and electrical conductivity of 590 S / m.

[0025] In a specific embodiment of the present invention, the carbon material satisfies the following conditions: thermal conductivity of 800 W / (m·K) and electrical conductivity of 680 S / m.

[0026] In a specific embodiment of the present invention, the carbon material satisfies the following conditions: thermal conductivity of 500 W / (m·K) and electrical conductivity of 870 S / m.

[0027] In one specific embodiment of the present invention, the carbon material satisfies the following conditions: thermal conductivity of 900 W / (m·K) and electrical conductivity of 640 S / m.

[0028] In a specific embodiment of the present invention, the carbon material satisfies the following conditions: thermal conductivity of 1010 W / (m·K) and electrical conductivity of 550 S / m.

[0029] In a specific embodiment of the present invention, the carbon material satisfies the following conditions: thermal conductivity of 1040 W / (m·K) and electrical conductivity of 630 S / m.

[0030] In a specific embodiment of the present invention, the carbon material satisfies the following conditions: thermal conductivity of 980 W / (m·K) and electrical conductivity of 610 S / m.

[0031] In a specific embodiment of the present invention, the carbon material satisfies the following conditions: thermal conductivity of 980 W / (m·K) and electrical conductivity of 585 S / m.

[0032] In a specific embodiment of the present invention, the carbon material satisfies the following conditions: thermal conductivity of 1030 W / (m·K) and electrical conductivity of 610 S / m.

[0033] In one specific embodiment of the present invention, the carbon material satisfies the following conditions: thermal conductivity of 980 W / (m·K) and electrical conductivity of 570 S / m.

[0034] In a specific embodiment of the present invention, the carbon material satisfies the following conditions: thermal conductivity of 1090 W / (m·K) and electrical conductivity of 720 S / m.

[0035] In a specific embodiment of the present invention, the carbon material satisfies the following conditions: thermal conductivity of 950 W / (m·K) and electrical conductivity of 620 S / m.

[0036] In some embodiments of the present invention, the BET specific surface area of ​​the carbon material is 1600~2200 m². 2 / g, for example, 1700 m 2 / g、1750 m 2 / g、1650 m 2 / g、1680 m 2 / g、1660 m 2 / g、1640 m 2 / g or 1900 m 2 / g.

[0037] In some embodiments of the present invention, the tap density of the carbon material is 0.1~0.35 g / cm³. 3 For example, 0.12 g / cm³ 3 .

[0038] In some embodiments of the present invention, the ID / IG ratio of the carbon material is 0.51 to 0.81, for example, 0.58, 0.72, 0.55, 0.60, 0.65 or 0.75.

[0039] In some embodiments of the present invention, the carbon material is carbon microspheres, which are formed by the aggregation of carbon nanosheets, and the carbon nanosheets contain carbon nanocages. The carbon nanocages are prone to collapse, and the particle size of the carbon nanocages before collapse is 10-30 nm, with 1-4 cage wall layers.

[0040] In some preferred embodiments of the present invention, the particle size of the carbon microspheres is 2~10 μm, for example, 3 μm, 4 μm, 6 μm or 7 μm. In the present invention, the particle size of the carbon microspheres being 2~10 μm can be understood as the straight-line distance between any two points on the carbon microspheres in three-dimensional space being within the range of 2~10 μm.

[0041] In some embodiments of the present invention, the method for preparing the carbon material includes the following steps:

[0042] S1. A raw material composition containing an organic carbon source and a metal salt is reacted to obtain a carbon-coated metal oxide; wherein the reaction temperature is 750~1200℃.

[0043] S2. Remove the metal oxide to obtain the carbon material.

[0044] In some preferred embodiments of the present invention, in step S1, the reaction temperature is 800~1200℃, for example 850℃, 900℃, 1000℃, 1050℃, 1100℃ or 1150℃.

[0045] In some preferred embodiments of the present invention, in step S1, the amount of organic carbon source added relative to the metal salt is 25~110 mg / g, for example 26.4 mg / g, 32.0 mg / g, 42.6 mg / g, 53.3 mg / g or 74.6 mg / g.

[0046] In some preferred embodiments of the present invention, in step S1, the metal salt includes one or more of magnesium carbonate, zinc carbonate, and iron carbonate. The magnesium carbonate is, for example, basic magnesium carbonate; the zinc carbonate is, for example, basic zinc carbonate; and the iron carbonate is, for example, basic iron carbonate.

[0047] In some preferred embodiments of the present invention, in step S1, the organic carbon source includes one or more of benzene, thiophene, pyridine, xylene and pyrimidine, for example benzene or thiophene.

[0048] In some preferred embodiments of the present invention, in step S1, the reaction time is 2 to 4 hours, for example, 3 hours.

[0049] In some preferred embodiments of the present invention, step S2, the method for removing the metal oxide includes acid washing followed by drying.

[0050] In some embodiments of the present invention, the carbon material content in the functional layer is 40% to 50%, where the percentage is the mass percentage of the carbon material in the functional layer.

[0051] In some embodiments of the present invention, the functional layer further includes an adhesive.

[0052] In some preferred embodiments of the present invention, the content of the adhesive in the functional layer is 50% to 60%, and the percentage is the mass percentage of the adhesive in the functional layer.

[0053] In some preferred embodiments of the present invention, the mass ratio of the binder to the carbon material is (50~60):(40~50), for example, 55:45.

[0054] In some preferred embodiments of the present invention, the adhesive comprises one or more of PVDF, PAA and SBR, for example, PAA.

[0055] In some embodiments of the present invention, the thickness of one side of the functional layer is 0.75~1.5 μm, for example, 1 μm. The thickness of one side of the functional layer refers to the thickness of the functional layer disposed on the same surface of the current collector substrate.

[0056] In some embodiments of the present invention, the ratio of the single-sided thickness of the functional layer to the thickness of the current collector substrate is (0.75~1.5):(13~15), for example, 1:13.

[0057] In some embodiments, the modified current collector is a modified positive current collector, and the current collector matrix is ​​a positive current collector matrix.

[0058] In the modified positive current collector, the positive current collector substrate can be a conventional positive current collector substrate used for positive electrode sheets in the art.

[0059] In this invention, the positive electrode current collector substrate can be made of a material that does not cause chemical changes and has high conductivity, without limitation. For example, stainless steel, aluminum, nickel, or titanium are commonly used, or aluminum or stainless steel materials surface-treated with nickel, titanium, silver, etc. To enhance adhesion, micro-embossing can be formed on the surface of the positive electrode current collector substrate. The positive electrode current collector substrate can be used in various forms, such as a film, sheet, foil, mesh, or porous body. Generally, the positive electrode current collector substrate is aluminum foil.

[0060] In some embodiments, the modified current collector is a modified negative electrode current collector, and the current collector matrix is ​​a negative electrode current collector matrix.

[0061] In the modified negative electrode current collector, the negative electrode current collector substrate can be a conventional negative electrode current collector substrate used for negative electrode sheets in the art.

[0062] In this invention, the negative electrode current collector substrate is typically a metal foil with a thickness of 3-500 μm. There are no particular limitations on the material, as long as it has high conductivity and does not produce a chemical reaction in the secondary battery system. For example, it can be a foil formed by surface treatment of materials such as nickel, titanium, aluminum, silver, or stainless steel. The negative electrode current collector substrate is usually smooth, but fine textures can also be formed on its surface to improve the adhesion between the functional layer and the negative electrode current collector substrate. Besides foil, the negative electrode current collector substrate can also be any one or more combinations of various forms such as film, mesh, porous, foam, or non-woven fabric. Generally, the negative electrode current collector substrate is copper foil.

[0063] In some alternative embodiments, the thickness of the modified current collector can be 8 to 16 μm, for example 15 μm.

[0064] A second aspect of the present invention provides an electrochemical device comprising an electrode comprising a modified current collector as described above.

[0065] In this invention, the electrochemical device is preferably a battery.

[0066] In this invention, the electrochemical device is preferably a lithium-ion battery. The lithium-ion battery can be a liquid battery, a solid-state battery, or a semi-solid-state battery. For example, a liquid lithium-ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte; a solid lithium-ion battery includes a positive electrode, a negative electrode, and a solid electrolyte. The type of battery does not limit the scope of protection of this invention.

[0067] The following uses a liquid battery as a specific embodiment to illustrate the technical content of the present invention.

[0068] In one alternative embodiment, the electrochemical device is a lithium-ion battery; the lithium-ion battery includes a negative electrode, a positive electrode, an electrolyte, and a separator.

[0069] In some embodiments, the positive electrode includes a modified positive current collector as described above, and the negative electrode uses a negative current collector conventional in the art.

[0070] In some embodiments, the negative electrode includes a modified negative current collector as described above, and the positive electrode uses a positive current collector conventional in the art.

[0071] In some embodiments, the positive electrode includes the modified positive current collector as described above, and the negative electrode includes the modified negative current collector as described above.

[0072] Positive electrode film

[0073] In this invention, the positive electrode sheet may include a positive current collector and a positive electrode material layer, wherein the positive electrode material layer is disposed on at least one surface of the positive current collector; the positive electrode material layer includes a positive electrode material.

[0074] In some embodiments, the positive current collector is a modified positive current collector as described above.

[0075] In some embodiments, the positive electrode material in the positive electrode material layer may be a positive electrode material conventionally used in the art, preferably including one or more of lithium iron phosphate, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese iron phosphate, and lithium cobalt oxide, such as lithium iron phosphate.

[0076] In some embodiments, the positive electrode material layer further includes a conductive agent. The conductive agent is a reagent used to ensure that the electrode has good charge-discharge performance. It can be selected from graphite materials such as natural graphite and artificial graphite; carbon black materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal cracking black; conductive fibers such as carbon fibers and metal fibers; metal powders such as fluorinated carbon powder, aluminum powder, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; and conductive metal oxides or polyphenylene derivatives such as titanium dioxide, for example, carbon black.

[0077] In some embodiments, the positive electrode material layer further includes a binder. The binder may be a component that facilitates bonding between the positive electrode material and the conductive agent, and also facilitates bonding between the positive electrode material and the positive electrode current collector. It can typically be selected from polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers, such as PVDF.

[0078] In some embodiments, the cathode material layer further includes a dispersant. The dispersant may be a component that improves the dispersibility of the cathode material, conductive agent, and binder, thereby preventing particle agglomeration and improving uniformity and stability, such as hydrogenated nitrile butadiene rubber (HNBR).

[0079] In some implementations, the cathode material layer includes lithium iron phosphate, polyvinylidene fluoride, conductive carbon black, and hydrogenated nitrile rubber.

[0080] In some specific implementations, the mass ratio of lithium iron phosphate, polyvinylidene fluoride, conductive carbon black, and hydrogenated nitrile rubber is 97.5:1.5:0.7:0.3.

[0081] In this invention, the positive electrode sheet can be prepared using methods conventional in the art.

[0082] In some alternative embodiments, the method for preparing the positive electrode includes the following steps:

[0083] After mixing the raw material components of the positive electrode material layer, a solvent is added and mixed evenly to obtain a positive electrode slurry; then the positive electrode slurry is evenly coated on at least one surface of the positive electrode current collector; and then the positive electrode sheet is prepared by drying, rolling, slitting and other processes.

[0084] negative electrode sheet

[0085] In this invention, the negative electrode sheet may include a negative electrode current collector and a negative electrode material layer, wherein the negative electrode material layer is disposed on at least one surface of the negative electrode current collector, and the negative electrode material layer includes a negative electrode material.

[0086] In some embodiments, the negative electrode current collector is a conventional negative electrode current collector used in the art, typically a metal foil with a thickness of 3-500 μm. There are no particular limitations on the material, as long as it has high conductivity and does not produce a chemical reaction in the secondary battery system. For example, it can be a foil formed by surface treatment of materials such as nickel, titanium, aluminum, silver, or stainless steel. The negative electrode current collector typically has a smooth surface, but fine textures can also be formed on its surface to improve the adhesion between the negative electrode material layer and the negative electrode current collector. Besides foil, the negative electrode current collector can also be used in any one or more combinations of various forms such as film, mesh, porous, foam, or non-woven fabric. Generally, the negative electrode current collector is copper foil.

[0087] In some alternative embodiments, the thickness of the negative electrode current collector can be 4 to 16 μm, for example 5 μm.

[0088] In this invention, the negative electrode material in the negative electrode material layer can be a negative electrode material conventionally used in the art, such as graphite-based negative electrode material, silicon-oxygen-based negative electrode material, or silicon-carbon-based negative electrode material.

[0089] In some embodiments, the negative electrode material includes one or more of lithium titanate, graphite, soft carbon, hard carbon, mesophase carbon microspheres, silicon suboxide, and silicon carbide.

[0090] In some implementations, the negative electrode material layer further includes a conductive agent.

[0091] The conductive agent is not particularly limited, as long as it is conductive and does not cause chemical changes in the battery. For example, specific materials that can be used include: graphite, such as natural or artificial graphite; carbon-based materials, such as conductive carbon black (Super P, abbreviated as SP), carbon nanotubes (CNT), acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, or carbon fiber; metal powders or metal fibers, such as copper, nickel, aluminum, or silver; conductive whiskers, such as zinc oxide whiskers or potassium titanate whiskers; conductive metal oxides, such as titanium dioxide; or conductive polymers, such as polyphenylene derivatives.

[0092] In some specific implementations, the conductive agent in the negative electrode material layer is conductive carbon black SP.

[0093] In some implementations, the negative electrode material layer further includes a binder.

[0094] The type of adhesive is not particularly limited and can be selected from polyvinylidene fluoride, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid (PAA), ethylene-propylene-diene terpolymer and its sulfonates, styrene-butadiene rubber (SBR), fluororubber and various copolymers, such as SBR and PAA.

[0095] In some implementations, the negative electrode material layer also includes a thickener.

[0096] The addition of the thickener can increase the viscosity of the system of each component in the negative electrode slurry. It can be a thickener commonly used in the art to prepare negative electrode sheets, such as sodium carboxymethyl cellulose (CMC).

[0097] In some embodiments, the negative electrode material layer includes graphite, conductive carbon black, sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyacrylic acid.

[0098] In some specific embodiments, the mass ratio of graphite, conductive carbon black, sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyacrylic acid is 97.3:0.4:0.5:0.5:1.3.

[0099] In this invention, the negative electrode sheet can be prepared using methods conventional in the art.

[0100] In some embodiments, the method for preparing the negative electrode sheet includes the following steps: coating the negative electrode slurry obtained by thoroughly mixing the components of the negative electrode material layer in a solvent onto at least one surface of the negative electrode current collector, drying, cold pressing, and slitting to obtain the final product.

[0101] electrolyte

[0102] In some embodiments, the electrolyte may be a conventional electrolyte used in batteries, typically including non-aqueous solvents and lithium salts.

[0103] In this invention, the non-aqueous solvent can be a conventional non-aqueous solvent in the art.

[0104] In some embodiments, the non-aqueous solvent preferably comprises ester solvents and / or dimethyl sulfoxide (DMSO), more preferably carbonate solvents. The carbonate solvent may optionally be one or more of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), methyl ethyl carbonate (EMC), ethylene carbonate, propylene carbonate, and butyl carbonate (BC). The non-aqueous solvent may also include ethyl acetate.

[0105] In this invention, the lithium salt can be a conventional lithium salt in the art, preferably one or more of LiPF6, LiBF4, LiClO4, LiCF3SO3 and LiN(CF3SO2)2, for example, LiPF6.

[0106] In this invention, the electrolyte may include additives, which may be conventional additives in the art, such as fluoroethylene carbonate (FEC).

[0107] In some embodiments, the electrolyte includes LiPF6, ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0108] The volume ratio of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate is, for example, 1:2:1.

[0109] The concentration of the lithium salt is, for example, 1 mol / L.

[0110] In some embodiments, the electrolyte can be prepared by conventional methods in the art. Optionally, it can be prepared by the following method: mixing the various non-aqueous solvents and additives in proportion in an argon atmosphere glove box with a water content of <10 ppm, and then adding a fully dried lithium salt and mixing evenly to obtain the electrolyte.

[0111] diaphragm

[0112] In some alternative embodiments, the diaphragm may be a polypropylene membrane or a polyethylene membrane.

[0113] In one specific embodiment, the diaphragm is a polyethylene film; the thickness of the diaphragm is 10 μm.

[0114] In this invention, the method for preparing the lithium-ion battery can be a conventional method in the art. It can be that the positive electrode, separator, and negative electrode are wound in sequence to obtain the battery cell, which is then packaged in a packaging shell and injected with the electrolyte. Alternatively, the positive electrode, separator, and negative electrode are stacked in sequence to obtain the battery cell, which is then packaged in a packaging shell and injected with the electrolyte. After that, the lithium-ion battery is obtained through processes such as settling, hot and cold pressing, formation, clamping, and capacity testing.

[0115] A third aspect of the present invention provides an electronic device comprising the electrochemical device described above.

[0116] For example, the electronic devices described in this invention may be, but are not limited to, mobile devices (such as mobile phones, tablets, laptops, video recorders, portable printers / copiers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems and backup power supplies, etc.

[0117] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0118] Example 1

[0119] 1. Preparation of carbon materials:

[0120] ① Place 5g of basic magnesium carbonate in a quartz tube in a vertical furnace, heat it to 1000℃ in 120 sccm argon gas at a rate of 10 ℃ / min, and inject 150 μL of thiophene (32.0 mg / g relative to the metal salt addition) through a syringe pump at a feed rate of 50 μL / min. Hold the temperature for 2 h, and then cool it naturally to room temperature in an Ar gas flow to obtain MgO@C (particle size from nanometer to micrometer).

[0121] ② Wash MgO@C with 6 mol / L HCl to remove MgO, wash repeatedly with ultrapure water until neutral, and dry at 80℃ for 24 h to obtain carbon material.

[0122] 2. Preparation of modified current collectors

[0123] ① Aluminum foil pretreatment: The aluminum foil (13μm thick) is cleaned and surface treated to enhance the adhesion of subsequent coatings;

[0124] ②Conductive paste preparation: Mix conductive carbon material (45%), water-based binder PAA (55%), and a small amount of deionized water to form a uniform paste;

[0125] ③ Coating process: The paste is evenly coated onto both surfaces of the aluminum foil using a gravure roller coating method;

[0126] ④ Curing treatment: The slurry is cured by drying in an oven (processing temperature is usually 70℃, processing time is 8 seconds, and production line speed is 150m / min). The slurry forms a functional layer (continuous conductive network structure), which is the modified current collector. The thickness of each side of the functional layer is 1μm, and the total thickness is 2μm.

[0127] Example 2

[0128] The difference between this embodiment and Embodiment 1 is that in the preparation of the carbon material, only the injection volume of thiophene is changed to 250 μL (relative to the addition amount of metal salt 53.3 mg / g), while the other conditions and steps are the same as in Embodiment 1.

[0129] Example 3

[0130] The difference between this embodiment and Embodiment 1 is that in the preparation of the carbon material, only the injection volume of thiophene is changed to 350 μL (relative to the addition of metal salt 74.6 mg / g), while the other conditions and steps are the same as in Embodiment 1.

[0131] Example 4

[0132] The difference between this embodiment and Embodiment 1 is that in the preparation of the carbon material, the temperature is raised to 800°C, while the other conditions and steps are the same as in Embodiment 1.

[0133] Example 5

[0134] The difference between this embodiment and Embodiment 1 is that in the preparation of the carbon material, the temperature is raised to 1200℃, while the other conditions and steps are the same as in Embodiment 1.

[0135] Example 6

[0136] The difference between this embodiment and Embodiment 1 is that the carbon material is kept at a constant temperature for 4 hours, while the other conditions and steps are the same as in Embodiment 1.

[0137] Example 7

[0138] The difference between this embodiment and Embodiment 1 is that benzene is used instead of thiophene in the preparation of the carbon material, while the other conditions and steps are the same as in Embodiment 1.

[0139] Example 8

[0140] The only difference between this embodiment and Embodiment 1 is that, in the preparation of the carbon material, basic zinc carbonate is used instead of basic magnesium carbonate; the remaining steps and conditions are the same as in Embodiment 1.

[0141] Example 9

[0142] The only difference between this embodiment and Embodiment 1 is that, in the preparation of the carbon material, basic iron carbonate is used instead of basic magnesium carbonate; the remaining steps and conditions are the same as in Embodiment 1.

[0143] Example 10

[0144] The only difference between this embodiment and Embodiment 1 is that the amount of carbon material used in the preparation of the modified current collector is 50%, while the remaining steps and conditions are the same as in Embodiment 1.

[0145] Example 11

[0146] The only difference between this embodiment and Embodiment 1 is that the amount of carbon material used in the preparation of the modified current collector is 40%, while the remaining steps and conditions are the same as in Embodiment 1.

[0147] Example 12

[0148] The only difference between this embodiment and Embodiment 1 is that, in the preparation of the modified current collector, the single-sided thickness of the functional layer is 1.5 μm, and the total thickness is 3 μm. The remaining steps and conditions are the same as in Embodiment 1.

[0149] Example 13

[0150] The only difference between this embodiment and Embodiment 1 is that the carbon material is prepared at 750°C; the other steps and conditions are the same as in Embodiment 1.

[0151] Comparative Example 1

[0152] The only difference between this comparative example and Example 1 is that acetylene black was used instead of carbon nanospheres in the preparation of the modified current collector. The remaining steps and conditions are the same as in Example 1.

[0153] Comparative Example 2

[0154] The only difference between this comparative example and Example 1 is that the carbon material is prepared at 600°C; the other steps and conditions are the same as in Example 1.

[0155] Table 1 shows some relevant parameters in the preparation process of carbon materials in Examples 1-13 and Comparative Examples 1-2, and Table 2 shows relevant parameters in the functional layer of the obtained modified current collector.

[0156] Example 1

[0157] The carbon materials prepared in Examples 1-13 and Comparative Examples 1-2 were subjected to BET specific surface area, tap density, electrical conductivity, thermal conductivity, ID / IG ratio, SEM, and TEM tests, respectively, as follows:

[0158] (1) BET specific surface area test

[0159] Specific surface area and porosity analyzer: The above carbon material samples were first degassed and activated at 300 °C for 6 h, and then the adsorption measurement was carried out at 77 K using the volumetric method with N2 as the adsorbate. The pore structure and specific surface area were measured on a specific surface area and pore size analyzer (manufactured by Thermo Fisher Scientific, model Surfer). The specific surface area was calculated by the BET (Brunauer - Emmett - Teller, 0.05 < p / p0 < 0.3) method, and the pore distribution was obtained by processing the adsorption isotherm data using the HK model (Horvath - Kawazoe, < 2 nm micropores) and the BJH model (Barrett - Joyner - Halenda, > 2 nm mesopores and macropores). The measurement results are shown in Table 1.

[0160] (2)Tap density

[0161] ① Sample preparation: Weigh 20 mg of the powder sample (recorded as m), ensuring that the sample has no lumps or impurities.

[0162] ② Tap operation: Load the powder into a graduated cylinder, start the tap densimeter (manufacturer and model: Dandong BET BT - 310), and let the graduated cylinder vibrate with the device 1000 times (until the volume basically no longer changes).

[0163] ③ Volume reading: After the tapping is completed, read the final volume (V) of the powder, with the line of sight level with the scale line of the graduated cylinder.

[0164] ④ Calculation result: Tap density (ρ) = sample mass (m) / tapped volume (V). Repeat the test 3 times and take the average value.

[0165] The measurement results are shown in Table 1.

[0166] (3)Conductivity coefficient test

[0167] In this invention, the bulk conductivity of the carbon material measured by a four - probe resistivity tester (manufacturer and model: RICOWAY FT - 331) is used as the conductivity coefficient of the carbon material. The specific test method is as follows:

[0168] The bulk conductivity is measured using a source measurement unit by the four - wire method. First, load the powder sample into an insulating mold, compact the sample under a certain pressure (3 MPa), then measure the resistance of the material, and further calculate the bulk conductivity. The measurement results are shown in Table 1.

[0169] (4)Thermal conductivity test

[0170] The thermal conductivity of carbon materials was tested using the laser flare method (LFA) and a laser thermal conductivity meter (manufacturer and model: Netzsch LFA427, Germany). The specific steps included: fixing powder onto a low thermal conductivity substrate; spraying an ultrathin gold / graphite coating onto the heated surface of the sample for surface treatment before starting the test; placing the sample on the sample stage; activating the laser pulse to heat the upper surface of the sample; and simultaneously recording the surface temperature change over time (Tt curve) using an infrared detector. The test was repeated three times, and the average value was taken. The measurement results are shown in Table 1.

[0171] (5) ID / IG test

[0172] Raman spectroscopy was performed using a laser Raman spectrometer (Horiba Instruments LabRAM Soleil). A small sample was placed on a glass slide for testing, and the excitation wavelength was 514 nm. The Raman spectrum showed a peak at 1350 cm⁻¹. -1 The nearby broad peak, known as the D peak, appears at 1580 cm. -1 The sharp peak nearby is called the G peak, and the intensity ratio of these two peaks is ID / IG. The measurement results are shown in Table 1.

[0173] (6) SEM testing

[0174] The SEM image of the carbon material was obtained using a scanning electron microscope (SEM, Hitachi S4800) with an accelerating voltage of 5.0 kV. The SEM image of the carbon material in Example 1 at 10K magnification is shown below. Figure 1 As shown. By Figure 1 It can be seen that at this magnification, the carbon material exhibits the state of carbon microspheres, which are composed of multiple carbon nanosheets aggregated together.

[0175] Based on the SEM images of carbon materials, the particle size of the carbon microspheres in Examples 1-13 and Comparative Example 2 was measured, specifically:

[0176] SEM images of carbon materials were obtained at 500x magnification. In these images, several carbon microspheres were uniformly distributed with similar particle sizes. Further increasing the magnification to 10K yielded an SEM image showing a complete carbon microsphere. The particle size of each microsphere was measured (using the nanometer tool). The particle size of a carbon microsphere is defined as the distance between the two furthest points on its edge. Based on this, the particle sizes of any 10 carbon microspheres were statistically analyzed, and the average value was taken as the particle size of the carbon microsphere. The measurement results are shown in Table 1.

[0177] (7) TEM test

[0178] TEM images were obtained using a high-resolution transmission electron microscope (HRTEM, manufacturer and model: JOEL JEM-2100, Japan Electronics), with an accelerating voltage of 200 kV. The TEM image of the carbon material in Example 1 obtained at a magnification of 400 K is shown below. Figure 2 As shown. By Figure 2 It can be seen that at this magnification, the carbon material exhibits a state of several carbon nanocages. From... Figures 1-2 It is known that the carbon material obtained in Example 1 is a carbon microsphere, which is formed by the aggregation of carbon nanosheets, wherein the carbon nanosheets contain carbon nanocages.

[0179] Example 2

[0180] The modified current collectors from Examples 1-13 and Comparative Examples 1-2 were applied to the preparation of positive electrode sheets, and prismatic batteries (lithium-ion batteries) were prepared accordingly. Details are as follows:

[0181] Positive electrode sheet: First, 97.5% of the positive electrode material lithium iron phosphate (LFP, LiFePO4), 0.7% of conductive carbon black SP, 1.5% of polyvinylidene fluoride (PVDF), and 0.3% of dispersant (hydrogenated nitrile butadiene rubber, HNBR) are mixed (where the percentages are the mass percentages of each component in the solid components of the positive electrode slurry). Then, N-methylpyrrolidone (NMP) is gradually added while stirring at high speed to prepare a positive electrode slurry with a certain viscosity (solid content of 70%). The prepared positive electrode slurry is then uniformly coated on both surfaces of the modified current collector and dried in a forced-air drying oven at 120°C for 10 minutes. Finally, the dried electrode sheet is rolled and cut to form a positive electrode sheet (total thickness of 179 μm, length of 13.5 m, and width of 200 mm); the rolling pressure is 19 T.

[0182] Negative electrode sheet: 97.3% graphite, 0.4% conductive carbon black SP, 0.5% sodium carboxymethyl cellulose (CMC) solution, 0.5% styrene-butadiene rubber latex (SBR) and 1.3% polyacrylic acid (PAA) were mixed (where the percentages are the mass percentages of each component in the solid components of the negative electrode slurry), deionized water was added, and the mixture was stirred under vacuum until stable and homogeneous to obtain a negative electrode slurry; the negative electrode slurry was uniformly coated on both surfaces of a 5μm thick copper foil; after the copper foil was dried at room temperature, it was transferred to a 120℃ forced-air oven to dry for 1 hour, and then cold-pressed and slit to obtain a negative electrode sheet (total thickness 132μm, length 14m, width 204mm).

[0183] The diaphragm is made of polyethylene (PE) membrane with a thickness of 10μm.

[0184] The positive electrode, separator, and negative electrode are stacked and wound in the order of positive electrode, separator, and negative electrode to form a bare cell electrode group (JR). The positive electrode in a JR has 48 winding layers and the negative electrode has 50 winding layers. Four JRs are linked together to obtain a bare cell. Each JR is connected by an adapter. The dimensions of each JR are: length 17mm × width 270mm × height 200mm. After winding, electrolyte is added. The bare cell is placed in an aluminum shell to obtain a prismatic battery. An insulating and heat-insulating film, specifically polyethylene terephthalate film (PET film, purchased from Mylar), is placed between the bare cell and the aluminum shell.

[0185] The electrolyte was purchased from Guangzhou Tinci Advanced Materials Co., Ltd., and its model number is TC-E8087#.

[0186] The specific heat capacity, thermal conductivity, and cycle performance of the prepared prismatic batteries were tested. Simulations were performed based on the battery's specific heat capacity and thermal conductivity to obtain the battery's heat distribution diagram, as shown below:

[0187] (1) Specific heat capacity of the battery

[0188] By using an adiabatic accelerated calorimeter to provide an adiabatic environment, the specific heat capacity Cp of a battery can be determined.

[0189] Before each test, the specific heat capacity of the sample was corrected using a standard substance, namely aluminum alloy (mass specific heat capacity: 0.896 J / (g∙K)).

[0190] After correction, the specific heat capacity of the battery was measured using an adiabatic accelerated rate calorimeter (ARC, manufactured by THT UK, model EV+ARC). Specifically: First, two batteries were packaged into a "sample package," with a polyimide heating element sandwiched inside. The heating element provided a stable heating power P to the "sample package." The batteries were packaged with aluminum foil tape with good thermal conductivity. The "sample package" was placed in the middle of the adiabatic cavity, without contacting the cavity itself; that is, there was no direct heat exchange between the "sample package" and the calorimeter. The "sample package" was heated, and the temperature of the calorimeter and the temperature of the "sample package" remained consistent throughout. The temperature-time (T~t) curve was obtained, and the slope of the curve was [value missing]. Finally, weigh the cell to obtain its mass m, and then calculate the cell's specific heat capacity using formula (1). The calculation formula is as follows:

[0191]

[0192] (2) Thermal conductivity of the battery

[0193] The thermal conductivity of the battery was obtained by directly measuring heat transfer using the transient planar heat source method (TPS) and a thermal constant analyzer (Hot Disk TPS3500, Sweden). Specifically, at an ambient temperature of 25℃±2℃, the sample surface was kept flat, and a single-sided method was used, where one side of the test probe was in direct contact with the sample, while the other side of the test probe was thermally insulated. The sample was heated for 40 seconds at a power of 2.5W, and two batteries were tested twice in parallel to obtain the thermal conductivity of the battery.

[0194] (3) Simulation of the heat distribution diagram of the battery

[0195] Based on the measured specific heat capacity and thermal conductivity of the batteries, simulations were performed using Starccm software to obtain heat distribution diagrams of the lithium-ion batteries prepared with the modified current collectors in Examples 1-12 and Comparative Examples 1-3. The specific parameter settings in the Starccm software during the simulation were as follows:

[0196] The simulation conditions were set as follows: "0.5P charging - stationary - 0.5P discharging (P = battery capacity 587Ah × voltage plateau 3.2V)"; initial temperature was set to "25℃"; cooling power was set to "22W per cell"; coolant flow rate was set to "10L / min"; cooling water inlet temperature was set to "20℃"; cooling method was set to "100% cooling area on the bottom surface"; and convective heat transfer coefficient was set to "250W / (m^2·K) on the bottom surface".

[0197] The heat distribution diagram of the lithium-ion battery prepared by the modified current collector in Comparative Example 1 is shown below. Figure 3 As shown, the heat distribution diagram of the lithium-ion battery prepared by the modified current collector obtained in Example 1 is as follows. Figure 4 As shown. By Figure 3 and Figure 4 It can be seen that, compared with the lithium-ion battery prepared by the modified current collector with acetylene black as carbon material in Comparative Example 1, the difference between the highest and lowest temperatures in the heat distribution diagram of the lithium-ion battery prepared by the modified current collector with carbon microspheres as carbon material in Example 1 decreased from 7.9℃ to 3.6℃, ​​a decrease of 4.3℃, and the heat distribution was more uniform.

[0198] The difference between the highest and lowest temperatures in the heat distribution diagrams of the lithium-ion batteries prepared by the modified current collectors in Examples 1-13 and Comparative Examples 1-2 is shown in Table 3.

[0199] (2) High-temperature cycling performance

[0200] A two-piece clamp with a clamping force of 5000N was used to test the high-temperature cyclic performance. Specifically:

[0201] At 25℃, the 0.1P battery was first activated by charging and discharging it once within the operating voltage range of 2.5V (discharge cutoff voltage) to 3.65V (charge cutoff voltage). Then, at 45℃, the activated lithium-ion battery was connected to a Blue Battery charge-discharge tester and subjected to one charge-discharge cycle at a rate of 0.5P. The discharge capacity of the first cycle was recorded, and the battery was cycled continuously within the operating voltage range (a total of 1000 cycles). The ratio of the discharge capacity of the 1000th cycle to that of the first cycle was defined as the capacity retention rate over 1000 cycles. Where P = battery capacity 587Ah × voltage plateau 3.2V.

[0202] The high-temperature cycle performance comparison diagram of the lithium-ion batteries obtained by the modified current collectors in Example 1 and Comparative Example 1 is shown in the figure below. Figure 5 As shown. The dashed line represents the cycle performance test curve of the lithium-ion battery obtained with the modified current collector in Example 1, and the solid line represents the cycle performance test curve of the lithium-ion battery obtained with the modified current collector in Comparative Example 1. Figure 5 It can be seen that the lithium-ion battery prepared using the modified current collector in Example 1 has a 2% higher capacity retention rate than the lithium-ion battery prepared using the modified current collector in Comparative Example 1 after 1000 cycles at 45°C.

[0203] The test results are shown in Table 3.

[0204] (3) Safety performance

[0205] Batteries obtained using the modified current collectors of Examples 1-13 and Comparative Examples 1-2 of this invention can all pass the thermal runaway test in the energy storage safety test GB36276-2023.

[0206]

[0207]

[0208]

[0209] According to Tables 1 and 3, the carbon material in the modified current collectors in Examples 1 to 13 of this invention meets the following requirements: thermal conductivity of 500~1090 W / (m·K) and electrical conductivity of 550~870 S / m. The difference between the highest and lowest temperatures of the lithium-ion batteries obtained by using the modified current collector in the positive electrode is less than 7°C, and the capacity retention rate after 1000 cycles at 45°C can reach more than 90%, demonstrating excellent high-temperature cycling performance and uniform heat distribution.

[0210] Compared with Example 1, the modified current collector in Comparative Example 1 uses acetylene black as the carbon material. The conductivity of the carbon material is only 200 S / m and the thermal conductivity is only 11 W / (m·K), both of which are too small. The difference between the highest and lowest temperatures of the lithium-ion battery prepared by using this modified current collector as the positive electrode is significantly larger, and the capacity retention rate after 1000 cycles at 45°C is worse.

[0211] Compared with Example 1, the heating temperature during the preparation of carbon material in Comparative Example 2 was 600℃. The resulting carbon material had a low electrical conductivity and a low thermal conductivity of only 420 S / m and 400 W / (m·K), both of which were too small. The difference between the highest and lowest temperatures of the lithium-ion battery obtained by using this modified current collector to prepare the positive electrode was significantly larger, and the capacity retention rate after 1000 cycles at 45℃ was poor.

[0212] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A modified current collector characterized by, It comprises a current collector substrate and a functional layer arranged on at least one surface of the current collector substrate; the functional layer comprises a carbon material, the carbon material satisfies: a thermal conductivity coefficient of 500-1090 W / (m·K), and an electrical conductivity coefficient of 570-870 S / m.

2. The modified current collector of claim 1, wherein The carbon material satisfies one or more of the following conditions a-c: a. the tap density of the carbon material is 0.10 to 0.35 g / cm 3 ; b. the BET specific surface area of the carbon material is 1600 to 2200 m 2 / g; c. The ID / IG of the carbon material is 0.51-0.

81.

3. The modified current collector of claim 1, wherein The carbon material is carbon microspheres, the carbon microspheres are aggregated from carbon nanosheets, and the carbon nanosheets contain carbon nanocages.

4. The modified current collector of claim 3, wherein The particle size of the carbon microspheres is 2-10 μm.

5. The modified current collector of claim 1, wherein The preparation method of the carbon material comprises the following steps: S1. Reacting a raw material composition comprising an organic carbon source and a metal salt to obtain a carbon-coated metal oxide; wherein the temperature of the reaction is 750-1200°C; S2. Removing the metal oxide to obtain the carbon material.

6. The modified current collector of claim 5, wherein The preparation method of the carbon material satisfies one or more of the following conditions a-e: a. In step S1, the addition amount of the organic carbon source relative to the metal salt is: 25-110 mg / g; b. In step S1, the metal salt comprises one or more of magnesium carbonate, zinc carbonate, and iron carbonate; c. In step S1, the organic carbon source comprises one or more of benzene, thiophene, pyridine, xylene, and pyrimidine; d. In step S1, the reaction time is 2-4 h; e. In step S2, the method for removing the metal oxide comprises acid washing followed by drying.

7. The modified current collector of claim 1, wherein The functional layer further comprises a binder; the binder satisfies one or both of the following conditions a-b: a. The mass ratio of the binder to the carbon material is (50-60):(40-50); b. The binder comprises one or more of PVDF, PAA, and SBR.

8. The modified current collector of claim 1, wherein The functional layer satisfies one or more of the following conditions a-c: a. The single-sided thickness of the functional layer is 0.75-1.5 μm; b. The ratio of the single-sided thickness of the functional layer to the thickness of the current collector substrate is (0.75-1.5):(13-15); c. In the functional layer, the content of the carbon material is 40%-50%, the percentage being the mass percentage of the carbon material in the functional layer.

9. An electrochemical device, characterized by, It comprises a pole piece, the pole piece comprising the modified current collector according to any one of claims 1-8.

10. An electronic device, comprising: It comprises the electrochemical device according to claim 9.

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