A lithium ion battery pole piece, a lithium ion battery, a battery module and a power utilization equipment

Abstract

This invention discloses a lithium-ion battery electrode, a lithium-ion battery, a battery module, and electrical devices, belonging to the field of battery technology. The lithium-ion battery electrode includes a current collector and an electrode layer covering the surface of the current collector; the electrode layer, from the current collector outwards, includes a thermally conductive functional coating and an active material layer; the thermally conductive functional coating includes a thermally conductive component and a binder; the thermally conductive component includes at least one of boron nitride nanosheets, graphene microsheets, alumina nanowires, aluminum nitride nanowires, silicon carbide nanowires, conductive graphite, and carbon black; the mass fraction of the thermally conductive component in the thermally conductive functional coating is 40%~85%; the density of the thermally conductive functional coating is 0.8 g / cm³. 3 ~2.2g / cm 3 This invention establishes an effective heat conduction channel through a thermally conductive coating, which facilitates the rapid dissipation of heat generated during the reaction to the current collector and further to the battery casing, thereby reducing the internal temperature difference of the electrode and suppressing local hot spots.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to a lithium-ion battery electrode, a lithium-ion battery, a battery module, and electrical equipment. Background Technology

[0002] With the rapid growth in demand for fast charging performance from electric vehicles, the thermal management of lithium-ion batteries under high-rate (≥3C) charge-discharge conditions is becoming increasingly prominent. Currently, when cylindrical and prismatic batteries operate at high rates, the Joule heat and polarization heat inside the electrodes are highly concentrated within the active material layers on both the positive and negative electrode sides. Because the electrode materials themselves are electronic conductors but have relatively low thermal conductivity, and the porous structure inside the electrodes further obstructs heat conduction paths, significant localized hot spots form within the electrodes.

[0003] In the prior art, heat is mainly diffused slowly to the tab in the in-plane direction, with a long path and high thermal resistance. When discharging at 5C rate, the temperature at the center of the cell can be 15℃~20℃ higher than that at the tab, which can easily lead to: (1) uneven local current density distribution and excessively high reaction rate in hot spot areas; (2) unstable thickening of local SEI film and rapid capacity decay.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a lithium-ion battery electrode, a lithium-ion battery, a battery module, and an electrical device to solve or improve the above-mentioned technical problems.

[0006] This invention can be implemented as follows: In a first aspect, the present invention provides a lithium-ion battery electrode, comprising a current collector and an electrode layer covering the surface of the current collector; The electrode layer, from the current collector outwards, includes a thermally conductive functional coating and an active material layer; the thermally conductive functional coating includes a thermally conductive component and a binder; the thermally conductive component includes at least one of boron nitride nanosheets, graphene microsheets, alumina nanowires, aluminum nitride nanowires, silicon carbide nanowires, conductive graphite, and carbon black. The thermally conductive component constitutes 40%–85% of the thermally conductive functional coating by mass; the density of the thermally conductive functional coating is 0.8 g / cm³. 3 ~2.2g / cm 3 .

[0007] In an optional embodiment, the thermally conductive coating has at least one of the following characteristics: Feature 1: The thickness of the thermally conductive coating is 3μm~15μm, preferably 5μm~10μm; Feature 2: The thermally conductive components are oriented in a direction parallel to the surface of the current collector; Feature 3: The binder includes at least one of polyimide, polyvinylidene fluoride, polytetrafluoroethylene and sodium carboxymethyl cellulose.

[0008] In an optional embodiment, the thermally conductive functional coating includes a first thermally conductive sublayer and a second thermally conductive sublayer stacked sequentially, wherein the first thermally conductive sublayer is disposed close to the current collector; the thermally conductive component content in the first thermally conductive sublayer is lower than the thermally conductive component content in the second thermally conductive sublayer.

[0009] In an optional embodiment, the electrode layer with the thermally conductive coating further has at least one of the following characteristics: Feature 4: The active material layer includes a positive electrode active material or a negative electrode active material. The positive electrode active material includes at least one of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and high-nickel single crystal nickel cobalt manganese. The negative electrode active material includes at least one of artificial graphite, natural graphite, silicon-carbon composite material, and silicon-oxygen composite material. Feature 5: The area of ​​the electrode layer is 100 cm². 2 ~5000cm 2 ; Feature 6: The thickness of the active material layer is 60μm~150μm.

[0010] In an optional embodiment, the current collector with a thermally conductive coating has at least one of the following characteristics: Feature 7: The surface of the current collector is provided with microstructures, including at least one of micropore arrays, microgrooves, and micro-uneven structures; Feature 8: The surface roughness of the current collector is 0.5μm~2.0μm; Feature 9: The thickness of the current collector is 8μm~20μm.

[0011] In an optional embodiment, the electrode layer has a longitudinal heat conduction channel, which is composed of a plurality of sequentially arranged heat conduction bodies. One end of each heat conduction body is thermally connected to the current collector, and the other end extends to the surface or near-surface region of the electrode layer. The heat conduction body includes one of carbon nanotube fibers, boron nitride nanotubes, zinc oxide nanowires, and silicon carbide nanowires.

[0012] In an optional implementation, the heat-conducting body includes at least one of the following features: Feature 10: The diameter or side length of the heat-conducting body is 10nm~50μm, preferably 100nm~5μm; Feature 11: The volume fraction of the heat-conducting bulk material in the electrode layer is 0.5%~8%, preferably 1%~4%; Feature 12: The surface of the current collector has an active material layer, and the depth of the heat-conducting body extending from the current collector into the active material layer is 80%~100% of the total thickness of the electrode layer; Feature 13: The spacing between two adjacent longitudinal heat conduction channels is 50μm~500μm.

[0013] In an optional embodiment, an interfacial bonding layer is provided between the heat-conducting body and the active material layer.

[0014] In an optional embodiment, the interfacial bonding layer includes at least one of an alumina layer, a silicon dioxide layer, and a carbon layer.

[0015] In an optional implementation, the thickness of the interfacial adhesive layer is 1 nm to 100 nm.

[0016] In an optional embodiment, the current collector is provided with micropores, and one end of the heat-conducting body is embedded in or passes through the micropores.

[0017] In an optional implementation, the diameter of the micropores is 10 nm to 50 μm.

[0018] In an optional implementation, the spacing between two adjacent micropores is 50 μm to 500 μm.

[0019] In an optional embodiment, the micropore density in the current collector is 100 pores / cm². 2 ~100,000 pieces / cm 2 .

[0020] In an optional embodiment, the thickness of the current collector is 8 μm to 25 μm.

[0021] Secondly, the present invention provides a lithium-ion battery, including the lithium-ion battery electrode of any of the foregoing embodiments.

[0022] In an optional implementation, under 5C discharge conditions, the temperature difference between the center temperature of the electrode and the temperature at the tab is ≤5℃.

[0023] In an optional implementation, the capacity retention is not less than 91.5% after 500 1C / 1C cycles.

[0024] Thirdly, the present invention provides a battery module comprising a plurality of lithium-ion batteries according to the aforementioned embodiments.

[0025] Fourthly, the present invention provides an electrical device comprising a lithium-ion battery according to any of the foregoing embodiments, or a battery module comprising any of the foregoing embodiments.

[0026] The beneficial effects of this invention include: In the solution provided by this invention, an independent thermally conductive coating is set between the active material layer and the current collector, and a planar or sheet-like thermally conductive filler with a high thermal conductivity can be used to form an interlayer thermally conductive channel. The establishment of this thermally conductive channel is beneficial for quickly dissipating the heat generated during the reaction to the current collector and further transferring it to the battery casing, thereby reducing the internal temperature difference of the electrode and suppressing local hot spots. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A schematic diagram of a first cross-sectional structure of a lithium-ion battery electrode provided by the present invention; Figure 2 This is a schematic diagram of a second cross-sectional structure of a lithium-ion battery electrode provided by the present invention; Figure 3 The results show the comparison of the center-tab temperature difference of the electrodes in Comparative Examples 1, 2, and 6 during 5C discharge.

[0029] Icons: 10-Current collector; 21-Thermal conductive coating; 22-Thermal conductive body; 30-Active material layer; 40-Micropores. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0031] The following is a detailed description of the lithium-ion battery electrode, lithium-ion battery, battery module, and electrical equipment provided by the present invention.

[0032] The present invention provides a lithium-ion battery electrode, including a current collector 10 and an electrode layer covering the surface of the current collector 10.

[0033] like Figure 1 As shown, the electrode layer includes a thermally conductive coating 21 and an active material layer 30 sequentially from the current collector 10 outwards.

[0034] In some alternative embodiments, the thermally conductive coating 21 includes a thermally conductive component and a binder.

[0035] The thermally conductive component may, by way of example but not by way of limitation, include at least one of boron nitride nanosheets, graphene microsheets, alumina nanowires, aluminum nitride nanowires, silicon carbide nanowires, conductive graphite, and carbon black.

[0036] The adhesive may, by way of example but not by way of limitation, include at least one of polyimide (PI), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and sodium carboxymethyl cellulose (CMC).

[0037] In some alternative embodiments, the mass fraction of the thermally conductive component in the thermally conductive functional coating 21 can be 40% to 85%, such as 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80% or 85%, or other values ​​within the range of 40% to 85%.

[0038] If the mass fraction of the thermally conductive component in the thermally conductive functional coating 21 is less than 40%, it is not conducive to the formation of a continuous and effective thermal conduction path between the thermally conductive fillers. The thermal conductivity in the coating surface is low, and it is impossible to quickly conduct and dissipate the heat inside the active material layer 30 laterally. If the mass fraction of the thermally conductive functional coating 21 is higher than 85%, it is easy to result in an excessively low binder content, which leads to insufficient interfacial bonding between the coating and the current collector 10 and the active material layer 30, and it is easy to cause coating peeling, powdering, or deterioration of coating processing performance.

[0039] In some alternative embodiments, the density of the thermally conductive coating 21 can be 0.8 g / cm³. 3 ~2.2g / cm 3 For example, 0.8g / cm 3 1g / cm 3 1.5g / cm 3 1.8g / cm 3 2g / cm 3 Or 2.2g / cm 3 The value can also be 0.8 g / cm³. 3 ~2.2g / cm 3 Other values ​​within the range.

[0040] If the density of the thermally conductive coating 21 is too low, it will not be conducive to effective contact between the thermally conductive particles, resulting in a decrease in the overall thermal conductivity of the coating and insufficient mechanical strength. If the density of the thermally conductive coating 21 is too high, it will not be conducive to electrolyte wetting and the diffusion and transport of lithium ions in the coating, and the coating flexibility will decrease, making it prone to cracking during rolling or long-term cycling.

[0041] In some preferred embodiments, the thermally conductive functional coating 21 includes a first thermally conductive sublayer and a second thermally conductive sublayer stacked sequentially, wherein the first thermally conductive sublayer is disposed close to the current collector 10; the thermally conductive component content in the first thermally conductive sublayer is lower than the thermally conductive component content in the second thermally conductive sublayer.

[0042] Furthermore, the thermally conductive functional coating 21 may also provide a third or more thermally conductive sublayers on the outside of the second thermally conductive sublayer, with the content of thermally conductive components in each thermally conductive sublayer increasing sequentially from the inside to the outside.

[0043] By setting the thermally conductive components in the manner described above, which increases sequentially from the inside out, it is beneficial to gradually improve the thermal conductivity of the outer side of the coating while ensuring that the bottom layer has good adhesion and flexibility of the current collector 10. This maximizes the heat transfer efficiency from the active material layer 30 to the current collector 10 without sacrificing the mechanical strength and interface compatibility of the coating.

[0044] In some optional embodiments, the thickness of the thermally conductive coating 21 can be 3μm to 15μm, such as 3μm, 5μm, 8μm, 10μm, 12μm or 15μm, or other values ​​within that range. In some more typical embodiments, the thickness of the thermally conductive coating 21 can be 5μm to 10μm.

[0045] If the thermally conductive coating 21 is too thin, it is not conducive to forming a complete and continuous thermally conductive layer, making it difficult to fully cover the surface of the current collector 10 to establish a uniform heat conduction path, and its effect on reducing interfacial thermal resistance is limited; if the thermally conductive coating 21 is too thick, it is not conducive to improving the volumetric energy density of the battery, and may increase interfacial resistance and ion transport resistance.

[0046] In some alternative embodiments, the thermally conductive components are oriented in a direction parallel to the surface of the current collector 10. More specifically, particles with planar or sheet-like structures in the thermally conductive components may be oriented in a direction parallel to the surface of the current collector 10. For example, the c-axis normal of boron nitride nanosheets or the in-plane direction of graphene microsheets may be aligned perpendicular to the electrode surface direction, forming a thermally conductive channel perpendicular to the surface of the current collector 10.

[0047] In some optional embodiments, the active material layer 30 includes a positive electrode active material or a negative electrode active material. The positive electrode active material may, by way of example but not limitation, include at least one of lithium iron phosphate (LFP), lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), and high-nickel single-crystal nickel cobalt manganese (such as NCM811). The negative electrode active material may, by way of example but not limitation, include at least one of artificial graphite, natural graphite, silicon-carbon composite materials, and silicon-oxygen composite materials.

[0048] In some optional embodiments, the thickness of the active material layer 30 can be 60μm to 150μm, such as 60μm, 80μm, 100μm, 120μm or 150μm, or other values ​​in the range of 60μm to 150μm.

[0049] In some alternative implementations, the area of ​​the electrode layer can be 100 cm². 2 ~5000cm 2 , such as 100cm 2 500cm 2 1000cm 2 1500cm 2 2000cm 2 2500cm 2 3000cm 2 3500cm 2 4000cm 2 4500cm 2 Or 5000cm 2 etc., can also be 100cm 2 ~5000cm 2 Other values ​​within the range.

[0050] In some alternative embodiments, the surface of the current collector 10 is provided with microstructures, which may include, but are not limited to, at least one of an array of micropores 40, microgrooves, and micro-uneven structures. By providing microstructures on the surface of the current collector 10, the actual contact area between the current collector 10 and the thermally conductive coating 21 (or the active material layer 30) is increased, reducing interfacial contact thermal resistance and contact resistance. At the same time, the coating adhesion is improved through mechanical interlocking effect, reducing the risk of interfacial peeling.

[0051] The roughness of the current collector 10 can be 0.5μm to 2.0μm, such as 0.5μm, 1μm, 1.5μm or 2μm, or other values ​​within the range of 0.5μm to 2.0μm.

[0052] The thickness of the current collector 10 can be 8μm to 20μm, such as 8μm, 10μm, 12μm, 15μm, 18μm or 20μm, or other values ​​within the range of 8μm to 20μm. The current collector 10 can be aluminum foil or copper foil.

[0053] In some optional embodiments, the method for preparing the above-mentioned electrode may include the following steps: S1: Preparation of thermally conductive functional coating 21 slurry: Disperse the thermally conductive components and binder in the solvent and stir.

[0054] In some alternative embodiments, the solvent can be deionized water or N-methylpyrrolidone (NMP), etc. The stirring speed can be 2000 rpm to 5000 rpm, and the stirring time can be 1 h to 4 h.

[0055] For example, the viscosity of the thermally conductive coating 21 slurry can be 2000 mPa·s to 6000 mPa·s.

[0056] S2: Apply the thermally conductive functional coating 21 slurry to the surface of the current collector 10, and after drying, form a thermally conductive functional coating 21 with a thickness of 3μm~15μm.

[0057] In some alternative embodiments, the surface of the current collector 10 may be pretreated before coating to give it a roughness of 0.5 μm to 2.0 μm.

[0058] In some optional embodiments, the drying temperature can be 60℃~120℃, and the drying time can be 30min~2h.

[0059] S3: Prepare an active substance slurry and coat it onto the surface of the thermally conductive coating 21, then dry and roll it.

[0060] In some alternative embodiments, the compaction density of the positive electrode active material layer 30 after rolling can be 2.0 g / cm³. 3 ~3.6g / cm 3 The compaction density of the negative electrode active material layer 30 can be 1.4 g / cm³. 3 ~1.8g / cm 3 .

[0061] Continuing from the above, by setting an independent thermally conductive functional coating 21 between the active material layer 30 and the current collector 10, an interlayer thermally conductive channel is formed using planar or sheet-like thermally conductive fillers with high thermal conductivity.

[0062] Furthermore, such as Figure 2 As shown, the electrode layer may have a longitudinal heat conduction channel, which is composed of multiple sequentially arranged heat conduction bodies 22. One end of each heat conduction body 22 is thermally connected to the current collector 10, and the other end extends to the surface or near-surface region of the electrode layer.

[0063] The thermally conductive body 22 may, by way of example but not by way of limitation, include one of carbon nanotube fibers, boron nitride nanotubes, zinc oxide nanowires and silicon carbide nanowires.

[0064] In some optional embodiments, the diameter or side length of the heat-conducting body 22 can be 10 nm to 50 μm, such as 10 nm, 50 nm, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, or 50 μm, or other values ​​within the range of 10 nm to 50 μm. In some more preferred embodiments, the diameter or side length of the heat-conducting body 22 can be 100 nm to 5 μm.

[0065] In some optional embodiments, the spacing between two adjacent longitudinal heat conduction channels can be 50μm to 500μm, such as 50μm, 100μm, 200μm, 300μm, 400μm, or 500μm, or other values ​​within the range of 50μm to 500μm. In some more typical embodiments, the spacing between two adjacent longitudinal heat conduction channels can be 100μm to 500μm.

[0066] If the spacing between two adjacent longitudinal heat conduction channels is too narrow, the proportion of the heat conduction body 22 will be too high, squeezing out the space of the active material, reducing the energy density of the battery, and may also lead to uneven slurry coating, local stress concentration or obstruction of ion transport. If the spacing between two adjacent longitudinal heat conduction channels is too wide, the density of longitudinal heat conduction channels will be insufficient, and a uniform and continuous heat conduction network cannot be formed in the electrode surface. The heat inside the electrode will be difficult to be effectively conducted to the current collector 10, and the risk of local hot spots will increase.

[0067] In some optional embodiments, the volume fraction of the heat-conducting body 22 in the electrode layer can be 0.5% to 8%, such as 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, or 8%, or other values ​​within the range of 0.5% to 8%. In some more typical embodiments, the volume fraction of the heat-conducting body 22 in the electrode layer is 0.6% to 4%. In some more preferred embodiments, the volume fraction of the heat-conducting body 22 in the electrode layer is 1% to 4%.

[0068] If the volume fraction of the heat-conducting main body 22 in the electrode layer is less than 0.5%, it is not conducive to building a continuous and effective longitudinal heat-conducting network in the electrode layer, and the longitudinal heat conduction efficiency from the electrode surface to the current collector 10 is low. If the volume fraction of the heat-conducting main body 22 in the electrode layer is greater than 8%, it is not conducive to improving the effective volume fraction of the active material and the energy density of the electrode, and may also affect the compaction performance, ionic conductivity and interface stability of the electrode.

[0069] In some optional embodiments, the surface of the current collector 10 has an active material layer 30, and the depth of the heat-conducting body 22 extending from the current collector 10 into the active material layer 30 is 80% to 100% of the total thickness of the electrode layer, such as 80%, 90%, or 100%, or other values ​​within the range of 80% to 100%. If the depth of the heat-conducting body 22 extending from the current collector 10 into the active material layer 30 is too small, it is not conducive to reducing the overall temperature difference inside the electrode, and there is still a risk of local hot spots under high-rate charge and discharge conditions. In some more typical embodiments, the depth of the heat-conducting body 22 extending from the current collector 10 into the active material layer 30 is 80% to 93% of the total thickness of the electrode layer.

[0070] In some optional embodiments, an interface bonding layer is further provided between the thermally conductive body 22 and the active material layer 30. The interface bonding layer may, by way of example but not limitation, include at least one of an alumina layer, a silicon dioxide layer, and a carbon layer. The thickness of the interface bonding layer can be 1 nm to 100 nm, such as 1 nm, 5 nm, 10 nm, 50 nm, or 100 nm, or other values ​​within the range of 1 nm to 100 nm.

[0071] In some alternative embodiments, the current collector 10 is provided with micropores 40, and one end of the heat-conducting body 22 is embedded in or passes through the micropores 40.

[0072] The diameter of the heat-conducting body 22 matches the diameter of the micropore 40. The diameter of the micropore 40 can be 10nm~50μm, such as 10nm, 50nm, 100nm, 500nm, 1μm, 5μm, 10μm, 20μm, 30μm, 40μm or 50μm, or other values ​​within the range of 10nm~50μm.

[0073] The spacing between two adjacent micropores 40 can be 50μm to 500μm, such as 50μm, 100μm, 200μm, 300μm, 400μm or 500μm, or other values ​​within the range of 50μm to 500μm.

[0074] The density of micropores 40 in current collector 10 can be 100 pores / cm³. 2 ~100,000 pieces / cm 2 For example, 100 pieces / cm 2 500 pieces / cm 2 1000 pieces / cm 2 5000 pieces / cm 2 10,000 pieces / cm 2 50,000 pieces / cm 2 Or 100,000 / cm 2 Etc., can also be 100 pieces / cm 2~100,000 pieces / cm 2 Other values ​​within the range.

[0075] In some alternative embodiments, the thickness of the current collector 10 can be 8μm to 25μm, such as 8μm, 10μm, 15μm, 20μm or 25μm, or other values ​​within the range of 8μm to 25μm.

[0076] The current collector 10 may include aluminum foil or copper foil.

[0077] In some optional embodiments, the method for preparing the above-mentioned electrode may include the following steps: S1: Fabricate a micropore array 40 on the current collector 10.

[0078] S2: Attach the continuous thermally conductive body 22 to the micro-hole 40 array on the current collector 10, or grow / deposit the thermally conductive body 22 on the surface of the current collector 10, so that one end of the thermally conductive body 22 is connected to the current collector 10. For example, after the thermally conductive body 22 is attached to the micro-hole 40, it can be fixed to the current collector 10 by riveting, ultrasonic welding, or hot pressing. The axial direction of the aforementioned thermally conductive body 22 is substantially perpendicular to the surface of the current collector 10.

[0079] S3: Apply a slurry containing active substances, conductive agents and binders to the exposed end of the thermally conductive fiber.

[0080] S4: Drying, rolling, and die-cutting to obtain lithium-ion battery electrodes.

[0081] Continuing from the above, by embedding a continuous longitudinal heat-conducting body 22 (such as a fiber or tubular structure) inside the electrode, a "microscopic heat pipe" is formed that extends from the surface of the electrode directly to the current collector 10, thereby achieving directional heat conduction.

[0082] It should be noted that when the thermally conductive coating 21 and the longitudinally conductive body 22 are present simultaneously, they can form a composite thermal conductivity effect. Through these two complementary thermal conductivity methods, a vertical heat conduction channel is established from the inside of the electrode to the current collector 10, which quickly conducts the heat generated during the reaction to the current collector 10 and further to the battery casing, thereby reducing the temperature difference inside the electrode and suppressing local hot spots.

[0083] Accordingly, the present invention also provides a lithium-ion battery comprising the aforementioned lithium-ion battery electrode.

[0084] Furthermore, lithium-ion battery electrodes also include a separator, electrolyte, and casing.

[0085] In some alternative implementations, the lithium-ion battery may exemplary include at least one of cylindrical batteries, prismatic batteries, and pouch batteries.

[0086] In some alternative implementations, the diameter of the cylindrical battery is 40mm to 50mm.

[0087] In some alternative implementations, the side dimensions of the square battery are no greater than 50 mm.

[0088] In some optional embodiments, under 5C discharge conditions, the temperature difference between the electrode center temperature and the tab temperature is ≤5℃, such as 1.5℃~4.8℃. In some preferred embodiments, under 5C discharge conditions, the temperature difference between the electrode center temperature and the tab temperature is ≤3℃, such as 1.5℃~2.8℃.

[0089] In some optional implementations, after 500 1C / 1C cycles, the capacity retention rate is not less than 91.5%, such as 91.5% to 95.5%.

[0090] In addition, the present invention also provides a battery module comprising a plurality of the above-described lithium-ion batteries.

[0091] In addition, the present invention also provides an electrical device that includes the above-mentioned lithium-ion battery or the above-mentioned battery module.

[0092] In some alternative implementations, the electrical equipment may exemplary include pure electric vehicles, plug-in hybrid electric vehicles, electric buses, electric forklifts, or stationary energy storage systems.

[0093] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0094] Example 1 This embodiment provides a lithium-ion battery electrode sheet, which is prepared by the following method: S1: Preparation of thermally conductive functional coating 21 slurry: 6.7g of thermally conductive component and 10g of binder were dispersed in 46.3g of solvent and stirred and sheared at 3000rpm for 2h to obtain thermally conductive functional coating 21 slurry.

[0095] The thermally conductive component is boron nitride nanosheets (BNNS, particle size D). 50 =2μm, aspect ratio 50:1), the binder is sodium carboxymethyl cellulose (CMC), and the solvent is water.

[0096] S2: Apply the thermally conductive functional coating 21 slurry to the surface of the current collector 10 (aluminum foil, length × width 80cm × 80cm) with a thickness of 12μm, and dry at 80℃ for 1h to form the thermally conductive functional coating 21.

[0097] The thermally conductive coating 21 has a thickness of 5 μm and a density of 1.35 g / cm³. 3The thermally conductive component in the thermally conductive coating 21 comprises approximately 40% by mass.

[0098] S3: Prepare an active substance slurry and coat it onto the surface of the thermally conductive coating 21, then dry and roll it.

[0099] The active material slurry was prepared by mixing NCM811, Super-P, and PVDF in a mass ratio of 95:2.5:2.5 and dissolving them in NMP. The active material slurry was coated onto the surface of the thermally conductive coating 21, with an areal density of 210 mg / 12 cm³. 2 The material was then dried at 120℃ for 30 minutes; it was then rolled until the compacted density was 3.5 g / cm³. 3 A positive electrode with a thickness of approximately 75 μm was obtained.

[0100] Example 2 The difference between this embodiment and Embodiment 1 is that 15g of thermally conductive component and 10g of binder are dispersed in 69.4g of solvent, and the mass fraction of thermally conductive component in the thermally conductive functional coating 21 is 60%. The thickness of the thermally conductive functional coating 21 is 8μm.

[0101] Example 3 The difference between this embodiment and Embodiment 1 is that 40g of thermally conductive component and 10g of binder are dispersed in 138.8g of solvent, and the mass fraction of thermally conductive component in thermally conductive functional coating 21 is 80%. The thickness of thermally conductive functional coating 21 is 12μm.

[0102] Example 4 The difference between this embodiment and Embodiment 2 is that boron nitride nanosheets are replaced with graphene microsheets (with a specific surface area of ​​1000 m²). 2 / g, with a tablet diameter of 10μm).

[0103] Example 5 The difference between this embodiment and Embodiment 1 is that the current collector 10 is pre-treated with plasma etching to form a micro-uneven structure with a roughness Ra=1.2μm. Based on this, a double-layer thermally conductive coating is applied to the surface of the current collector 10 from the inside out (the bottom layer is BNNS + binder, 3μm thick, BNNS content 50wt%; the top layer is BNNS + conductive carbon black + binder, 4μm thick, BNNS content 80wt%, conductive carbon black content 15%, binder content 5%), followed by an active material layer 30. The total thickness of the thermally conductive coating is 7μm, and the total BNNS content is approximately 70wt%.

[0104] Comparative Example 1 This comparative example provides a conventional electrode without a thermally conductive structure: NCM811 active material, Super-P conductive agent, and PVDF binder are mixed in a mass ratio of 95:2.5:2.5, and NMP is used as a solvent to stir into a slurry. The slurry is coated onto one side of a 12μm aluminum foil current collector 10, with a coating density of 210 mg / 12cm². 2 Dry and roll-press to a compacted density of 3.5 g / cm³. 3 This yields the positive electrode sheet.

[0105] Comparative Example 2 The difference between this comparative example and Example 2 is that the thermally conductive component is directly mixed with the active material slurry and then coated on the surface of the current collector 10 in one step, dried, and rolled (the final coating on the surface of the current collector 10 has a thermally conductive component mass percentage of 8wt%).

[0106] Comparative Example 3 The difference between this comparative example and Example 1 is that the mass fraction of the thermally conductive component in the thermally conductive functional coating 21 is 30 wt%.

[0107] S1: Preparation of thermally conductive functional coating 21 slurry: 12g of thermally conductive component (boron nitride nanosheets, BNNS) and 28g of binder (sodium carboxymethyl cellulose, CMC) were dispersed in an appropriate amount of deionized water and stirred and sheared at high speed at 3000rpm for 2h to obtain thermally conductive functional coating 21 slurry.

[0108] S2: The above slurry is coated onto the surface of the current collector 10 (aluminum foil) with a thickness of 12 μm, and dried at 80°C for 1 h to form a thermally conductive functional coating 21 with a thickness of 8 μm. The mass fraction of the thermally conductive component in the thermally conductive functional coating 21 is 30 wt%.

[0109] S3: Prepare an active material slurry and coat it onto the surface of the thermally conductive coating 21, then dry and roll-press it. The active material slurry formulation, coating density, and rolling to a compaction density of 3.5 g / cm³ are the same as in Example 1, resulting in a positive electrode sheet.

[0110] Comparative Example 4 The difference between this comparative example and Example 1 is that the mass fraction of the thermally conductive component in the thermally conductive functional coating 21 is 90 wt%.

[0111] S1: Preparation of thermally conductive functional coating 21 slurry: 36g of thermally conductive component (boron nitride nanosheets, BNNS) and 4g of binder (sodium carboxymethyl cellulose, CMC) were dispersed in an appropriate amount of deionized water and stirred and sheared at 3000rpm for 2h to obtain thermally conductive functional coating 21 slurry.

[0112] S2: The above slurry is coated onto the surface of the current collector 10 (aluminum foil) with a thickness of 12 μm, and dried at 80°C for 1 h to form a thermally conductive functional coating 21 with a thickness of 8 μm. The mass fraction of the thermally conductive component in the thermally conductive functional coating 21 is 90 wt%.

[0113] S3: Prepare an active substance slurry and coat it onto the surface of the thermally conductive coating 21, then dry and roll-press it. The active substance slurry formulation, coating surface density, and compaction density to a final density of 3.5 g / cm³ are specified. 3 Under the same conditions as in Example 1, a positive electrode sheet was obtained.

[0114] Example 6 This embodiment provides a lithium-ion battery electrode, which differs from Embodiment 1 in that the electrode layer also has a longitudinal heat conduction channel.

[0115] The lithium-ion battery electrode was prepared by the following method: S1: Fabricate a micropore array 40 on the current collector 10.

[0116] A laser-drilled array (without penetration) with a pore size of 6 μm and a pore spacing of 200 μm was pre-fabricated on a 12 μm aluminum foil current collector 10. The pore density was approximately 2500 pores / cm². 2 .

[0117] S2: A continuous thermally conductive body 22 (multi-walled carbon nanotube fiber bundle, MWCNT, with an outer diameter of about 5 μm, an aspect ratio of 1000~50000, and an axial thermal conductivity of 50 W / m·K~200 W / m·K) is attached to a micropore array 40 on the current collector 10.

[0118] S3: Preparation of thermally conductive functional coating 21 slurry: 6.7g of thermally conductive component and 10g of binder were dispersed in 46.3g of solvent and stirred and sheared at 3000rpm for 2h to obtain thermally conductive functional coating 21 slurry.

[0119] The thermally conductive component is boron nitride nanosheets (BNNS, particle size D). 50 =2μm, aspect ratio 50:1), the binder is sodium carboxymethyl cellulose (CMC), and the solvent is water.

[0120] S4: Apply the thermally conductive functional coating 21 slurry to the surface of the current collector 10 (aluminum foil, length × width 80cm × 80cm) with a thickness of 12μm, and dry at 80℃ for 1h to form the thermally conductive functional coating 21.

[0121] The thermally conductive coating 21 has a thickness of 5 μm and a density of 1.35 g / cm³. 3 The thermally conductive component in the thermally conductive coating 21 comprises approximately 40% by mass.

[0122] S5: The positive electrode active material slurry containing active material, conductive agent and binder is coated onto the exposed end of the thermally conductive fiber and the surface of the thermally conductive functional coating 21, and then dried and rolled.

[0123] The coating process on the exposed end of the thermally conductive fiber includes: immersing the prepared current collector 10 with thermally conductive channels into a positive electrode active material slurry (the active material slurry is obtained by dissolving NMP in a mixture of NCM811, Super-P, and PVDF in a mass ratio of 95:2.5:2.5), with a coating surface density of 10 mg / cm³. 2 .

[0124] The coating on the surface of the thermally conductive functional coating 21 includes: coating an active substance slurry onto the surface of the thermally conductive functional coating 21, with an areal density of 210 mg / 12 cm³. 2 .

[0125] The active substance slurry is obtained by mixing NCM811, Super-P and PVDF in a mass ratio of 95:2.5:2.5 and then dissolving them in NMP.

[0126] Drying was carried out at 120℃ for 30 minutes; then rolled until the compacted density was 3.5 g / cm³. 3 The electrode is die-cut to obtain a lithium-ion battery electrode with a thickness of approximately 75 μm. In the above electrode layer, the volume fraction of the thermally conductive body 22 is 2.5%. The thermally conductive body 22 extends from the current collector 10 to the active material layer 30 by approximately 70 μm, accounting for approximately 93% of the total thickness of the electrode layer.

[0127] Example 7 The difference between this embodiment and Embodiment 6 is that boron nitride nanotubes (BNNTs) with an outer diameter of approximately 200 nm and an axial thermal conductivity of approximately 60 W / m·K were grown using chemical vapor deposition (CVD). A micropore array with a pore size of 300 nm and a spacing of 100 μm was fabricated on a 15 μm aluminum foil using electron beam lithography, resulting in a density of approximately 10,000 pores / cm². 2 BNNT is passed through micropores 40 and fixed to the current collector 10 by hot pressing. An active material slurry is then coated to a thickness of 100 μm.

[0128] Example 8 The difference between this embodiment and Embodiment 6 is that the pore spacing is 500 μm and the pore density is approximately 400 pores / cm³. 2 .

[0129] Example 9 The difference between this embodiment and Embodiment 6 is that both the positive and negative electrode sheets are embedded with longitudinal channels of MWCNT fibers, with a fiber spacing of 200 μm. The thickness of the positive electrode layer is 75 μm, and the thickness of the negative electrode layer is 65 μm.

[0130] Comparative Example 5 The difference between this comparative example and Example 6 is that the MWCNT fibers are directly mixed with the active material slurry and then applied to the surface of the current collector 10.

[0131] Test methods The positive electrode sheets obtained in Examples 1-8 and Comparisons 1-5 were respectively compared with a graphite negative electrode sheet (length × width 82cm × 82cm, areal density 115mg / cm³). 2 A 3.0Ah pouch cell was assembled using Celgard 2400 separators. The positive and negative electrodes obtained in Example 9 were assembled with Celgard 2400 separators to form a 3.0Ah pouch cell. The electrolyte was a conventional EC / DMC / EMC = 1:1:1 (wt%) + 1mol / L LiPF6 + 2wt% VC additive, with an injection volume of 3.5g / Ah. Comparisons of electrode characteristics for each example and comparative example are shown in Tables 1 and 3. The resulting pouch cells were subjected to performance tests, and the results are shown in Tables 2 and 4. Figure 3 As shown.

[0132] Table 1 Comparison of Electrodes

[0133] Table 2 Performance Test Results

[0134] As can be seen from Table 2, compared with Comparative Example 1 without thermally conductive coating, Examples 1 to 5 all significantly reduced the temperature difference between the electrode center and the tab during 5C discharge.

[0135] Of Examples 1 to 5, Examples 2 and 5 have better overall performance.

[0136] Comparative Example 2, which incorporates BNNS into the active material layer 30, not only has a thermal conductivity comparable to Comparative Example 1, but also exhibits a lower initial coulombic efficiency. This indicates that the thermally conductive functional coating 21, when independent of the active material layer 30, is more effective than combining the thermally conductive functional coating 21 and the active material layer 30 into a unified layer.

[0137] Table 3 Comparison of Electrodes

[0138] Table 4 Performance Test Results

[0139] As shown in Table 4, in Example 6, compared to Comparative Example 1, the temperature difference at 5°C was significantly reduced while maintaining a basically unchanged capacity. In Example 7, although the thermally conductive fibers were finer, the excessively dense spacing increased the difficulty of electrode fabrication and resulted in a small number of fiber breaks affecting the capacity. In Example 8, increasing the spacing to 500 μm resulted in a temperature difference of 7.2°C, indicating that increased spacing led to discontinuous thermal conductivity. In Example 9, the double-sided embedding of both positive and negative electrodes showed the most significant effect.

[0140] Compared to Comparative Example 1 and Examples 6-9, Comparative Example 5 demonstrates that the traditional method of adding carbon nanotube conductive agents into the coating has almost zero improvement on longitudinal thermal conductivity, indicating that the presence of longitudinal thermal conduction channels has a significant impact on the increase of battery performance.

[0141] In summary, the solution provided by this invention has at least the following advantages compared to the prior art: (1) The temperature difference inside the electrode is greatly reduced: Under the 5C rate discharge condition, the temperature difference between the center of the electrode and the tab can be reduced from 15℃~20℃ in traditional batteries to less than 8℃, or even less than 5℃, which greatly improves the uniformity of the reaction.

[0142] (2) Improved cycle life: Under high-rate cycling conditions, the capacity retention rate is significantly improved.

[0143] (3) Adapt to different application scenarios and performance requirements: The thermally conductive functional coating 21 scheme has a simple process and is easy to mass-produce; the longitudinal thermally conductive channel scheme has higher thermal conductivity and can realize the "micro heat pipe" effect; the two schemes can be implemented separately or in combination as needed.

[0144] (4) Almost no interference with electrochemical performance: The thermally conductive coating 21 is physically separated from the active material layer 30. The longitudinal thermally conductive channel occupies only 0.5%~8% of the electrode volume and does not occupy the ion transport space of the active material layer 30. The initial coulombic efficiency is comparable to that of traditional electrodes.

[0145] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A lithium-ion battery electrode, characterized in that, Includes a current collector and an electrode layer covering the surface of the current collector; The electrode layer comprises, from the current collector outwards, a thermally conductive functional coating and an active material layer; the thermally conductive functional coating comprises a thermally conductive component and a binder; the thermally conductive component comprises at least one of boron nitride nanosheets, graphene microsheets, alumina nanowires, aluminum nitride nanowires, silicon carbide nanowires, conductive graphite, and carbon black. The thermally conductive component in the thermally conductive functional coating has a mass fraction of 40% to 85%; the density of the thermally conductive functional coating is 0.8 g / cm³. 3 ~2.2g / cm 3 .

2. The lithium-ion battery electrode according to claim 1, characterized in that, The thermally conductive coating has at least one of the following characteristics: Feature 1: The thickness of the thermally conductive coating is 3μm~15μm, preferably 5μm~10μm; Feature 2: The thermally conductive components are oriented in a direction parallel to the surface of the current collector; Feature 3: The binder comprises at least one of polyimide, polyvinylidene fluoride, polytetrafluoroethylene, and sodium carboxymethyl cellulose; Preferably, the thermally conductive functional coating includes a first thermally conductive sublayer and a second thermally conductive sublayer stacked sequentially, wherein the first thermally conductive sublayer is disposed close to the current collector; The thermally conductive component content in the first thermally conductive sublayer is lower than that in the second thermally conductive sublayer.

3. The lithium-ion battery electrode according to claim 1, characterized in that, The electrode layer with the thermally conductive coating also has at least one of the following characteristics: Feature 4: The active material layer includes a positive electrode active material or a negative electrode active material, wherein the positive electrode active material includes at least one of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and high-nickel single crystal nickel cobalt manganese; and the negative electrode active material includes at least one of artificial graphite, natural graphite, silicon-carbon composite material, and silicon-oxygen composite material. Feature 5: The area of ​​the electrode layer is 100 cm². 2 ~5000cm 2 ; Feature 6: The thickness of the active material layer is 60μm~150μm.

4. The lithium-ion battery electrode according to claim 3, characterized in that, The current collector with a thermally conductive coating has at least one of the following characteristics: Feature 7: The surface of the current collector is provided with microstructures, the microstructures including at least one of micropore array, microgroove and micro-uneven structure; Feature 8: The surface roughness of the current collector is 0.5 μm to 2.0 μm; Feature 9: The thickness of the current collector is 8μm~20μm.

5. The lithium-ion battery electrode according to any one of claims 1 to 4, characterized in that, The electrode layer has a longitudinal heat conduction channel inside, which is composed of a plurality of sequentially arranged heat conduction bodies. One end of each heat conduction body is thermally connected to the current collector, and the other end extends to the surface or near-surface region of the electrode layer. The heat conduction body includes one of carbon nanotube fibers, boron nitride nanotubes, zinc oxide nanowires, and silicon carbide nanowires.

6. The lithium-ion battery electrode according to claim 5, characterized in that, The heat-conducting body includes at least one of the following features: Feature 10: The diameter or side length of the heat-conducting body is 10nm~50μm, preferably 100nm~5μm; Feature 11: The volume fraction of the thermally conductive body in the electrode layer is 0.5% to 8%, preferably 1% to 4%; Feature 12: The surface of the current collector has an active material layer, and the depth of the heat-conducting body extending from the current collector into the active material layer is 80% to 100% of the total thickness of the electrode layer; Feature 13: The spacing between two adjacent longitudinal heat conduction channels is 50μm~500μm; Preferably, an interfacial bonding layer is provided between the heat-conducting body and the active material layer; Preferably, the interfacial bonding layer comprises at least one of an alumina layer, a silicon dioxide layer, and a carbon layer; Preferably, the thickness of the interfacial adhesive layer is 1 nm to 100 nm.

7. The lithium-ion battery electrode according to claim 5, characterized in that, The current collector is provided with micropores, and one end of the heat-conducting body is embedded in or passes through the micropores; Preferably, the diameter of the micropores is 10 nm to 50 μm; Preferably, the spacing between two adjacent micropores is 50 μm to 500 μm; Preferably, the micropore density in the current collector is 100 pores / cm². 2 ~100,000 pieces / cm 2 ; Preferably, the thickness of the current collector is 8μm to 25μm.

8. A lithium-ion battery, characterized in that, Includes the lithium-ion battery electrode as described in any one of claims 1 to 7; Preferably, under 5C discharge conditions, the temperature difference between the center temperature of the electrode and the temperature at the tab is ≤5℃; Preferably, after 500 1C / 1C cycles, the capacity retention is not less than 91.5%.

9. A battery module, characterized in that, Includes the lithium-ion batteries described in several claims 8.

10. An electrical appliance, characterized in that, It includes the lithium-ion battery of claim 8, or the battery module of claim 9.

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