Battery casing, preparation method thereof, and secondary battery

Abstract

The present application relates to the field of battery technology, and in particular to a battery casing, a preparation method thereof, and a secondary battery. The battery casing includes a shell and a thermally conductive insulating coating covering the shell; the thermally conductive insulating coating includes the following raw materials in parts by weight: 40 to 60 parts of water-based epoxy resin, 10 to 30 parts of curing agent, 5.1 to 20.5 parts of modified filler, 0.2 to 2 parts of leveling agent, and 2 to 6 parts of flame retardant; the modified filler includes a thermally conductive filler and a silane coupling agent loaded on the thermally conductive filler; the mass ratio of the thermally conductive filler to the silane coupling agent is (5 to 20): (0.1 to 0.5). The present application covers the shell with a layer of thermally conductive insulating coating, which can effectively improve the insulation performance, heat dissipation performance, and high-temperature protection performance of the battery casing, thereby improving the safety of the battery and reducing the thermal management energy consumption of the battery.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery casing, a preparation method thereof, and a secondary battery. Background Art

[0002] The large-scale use of traditional fossil fuels has led to increasingly severe problems such as resource shortages and environmental pollution. Accelerating the transformation of the energy structure and developing clean, renewable energy sources are of great significance. Lithium-ion batteries, due to their high energy density, long cycle life, excellent rate performance, and low cost, are widely used in consumer electronics, energy storage systems, and power batteries.

[0003] Traditional lithium-ion batteries utilize conductive, easily charged aluminum metal casings for their cell housings. To ensure battery safety, the outer surface of the cell typically requires insulation protection. Currently, lithium-ion batteries commonly incorporate a blue film over the aluminum casing as a protective layer for insulation and wear protection. However, this film has drawbacks such as low thermal conductivity, poor heat resistance, and flammability, severely limiting the battery's heat dissipation and high-temperature performance. Summary of the Invention

[0004] Based on this, it is necessary to provide a battery housing, a preparation method thereof, and a secondary battery to solve the problem that the thermal conductivity of the blue film is low, which seriously hinders the heat dissipation of the lithium-ion battery.

[0005] The above-mentioned purpose of this application is achieved through the following technical solutions:

[0006] In a first aspect of the present application, a battery housing is provided, comprising a shell and a thermally conductive insulating coating covering the shell;

[0007] The thermally conductive insulating coating comprises the following raw materials in parts by weight:

[0008] 40~60 parts of waterborne epoxy resin,

[0009] 10~30 parts of curing agent,

[0010] 5.1 to 20.5 parts of modified filler,

[0011] 0.2 to 2 parts of leveling agent, and

[0012] 2 to 6 parts of flame retardant;

[0013] The modified filler includes a thermally conductive filler and a silane coupling agent loaded on the thermally conductive filler;

[0014] The mass ratio of the thermal conductive filler to the silane coupling agent is (5-20): (0.1-0.5).

[0015] In one embodiment, the thermally conductive filler includes one or more of aluminum nitride, boron nitride, silicon nitride, aluminum oxide, magnesium oxide, zinc oxide, beryllium oxide, and silicon oxide.

[0016] In one embodiment, the silane coupling agent includes one or more of 3-aminopropyltriethoxysilane, 3-(isomethylacryloyloxy)propyltrimethoxysilane, γ-aminopropyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane.

[0017] In one embodiment, the water-based epoxy resin includes one or more of bisphenol A epoxy resin, tetrabromobisphenol A epoxy resin, fluorinated epoxy resin, novolac epoxy resin and glycidylamine epoxy resin.

[0018] In one embodiment, the curing agent includes one or more of an amine curing agent, an acid anhydride curing agent, an imidazole curing agent, and a hydrazide curing agent.

[0019] In one embodiment, the leveling agent includes one or more of polyethylene glycol, polyethyleneimine, polydimethylsiloxane, polymethylphenylsiloxane, and polyacrylic acid fluoride.

[0020] In one embodiment, the flame retardant includes one or more of silicon dioxide, talc, aluminum hydroxide, ammonium phosphate, and tetrabromobisphenol A bis(dibromopropyl) ether.

[0021] In one embodiment, the thermally conductive insulating coating further includes 0.1 to 1 part of a pigment, wherein the pigment includes one or more of iron oxide red, iron oxide blue, phthalocyanine blue, phthalocyanine green, molybdenum chrome red, and chrome yellow.

[0022] In one embodiment, the thickness of the thermally conductive insulating coating is 100 μm to 300 μm;

[0023] A plurality of grooves are provided on a side of the shell facing the thermally conductive insulating coating. The depth of the grooves is less than the thickness of the shell, and the depth of the grooves is less than the thickness of the thermally conductive insulating coating.

[0024] In one embodiment, the depth of the groove is 2% to 30% of the thickness of the shell.

[0025] In a second aspect of the present application, a method for preparing the battery housing as described above is provided, comprising the following steps:

[0026] Provide water-based coatings containing water-based epoxy resin, curing agent, modified filler, leveling agent, flame retardant and pigment;

[0027] Covering the shell with the water-based paint to form a liquid film;

[0028] The liquid film is cured at 80° C. to 160° C. for 2 h to 4 h to form a thermally conductive insulating coating.

[0029] In one embodiment, the preparation method of the water-based coating comprises the following steps:

[0030] uniformly dispersing the modified filler in the waterborne epoxy resin to obtain a glue solution;

[0031] Mixing the glue, the curing agent, the leveling agent, the flame retardant, the pigment and the water to obtain the water-based paint;

[0032] The preparation method of the modified filler comprises the following steps:

[0033] mixing the thermally conductive filler, the silane coupling agent, and a solvent, and performing a modification reaction at 60° C. to 80° C. for 4 to 6 hours, so that the silane coupling agent is loaded on the thermally conductive filler, to obtain a mixture;

[0034] The mixture is subjected to purification, grinding and screening to obtain the modified filler.

[0035] In one embodiment, before the step of covering the shell with the water-based paint, the following steps are also included:

[0036] A plurality of grooves are formed on a side of the housing facing the thermally conductive insulating coating layer by a press molding method.

[0037] In a third aspect of the present application, a secondary battery is provided, comprising the battery casing as described above, or comprising a battery casing manufactured using the method for manufacturing the battery casing as described above.

[0038] This application has at least the following beneficial effects:

[0039] The present application adopts a water-based epoxy resin with high resistivity, low dielectric loss, excellent mechanical properties, good chemical stability and high temperature resistance as a matrix, so that the thermally conductive insulating coating has good insulation, mechanical strength and high temperature resistance; a thermally conductive filler with high insulation and high thermal conductivity is adopted, and a silane coupling agent is loaded on its surface so that it can be evenly dispersed in the thermally conductive insulating coating, and a stable and complete thermal conductive network and insulation network are constructed so that the thermally conductive insulating coating has excellent insulation high voltage resistance and thermal conductivity; a curing agent is used to cure the water-washed epoxy resin, a flame retardant is used to enhance the flame retardant effect, and a leveling agent is used to form a smooth, uniform coating without bubbles. A thermally conductive insulating coating is made of raw materials such as a specific ratio of water-based epoxy resin, a curing agent, and a modified filler, and the thermally conductive insulating coating is covered on the shell, which can effectively improve the insulation performance, heat dissipation performance and high temperature protection performance of the battery shell, thereby improving the safety of the battery and reducing the thermal management energy consumption of the battery. In addition, the production process of the battery shell provided by the present application is simple, environmentally friendly, and low in preparation cost, making it very suitable for batch production. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present application and to more fully understand the present application and its beneficial effects, the following is a brief introduction to the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0041] Figure 1 Schematic diagram of the structure of a battery housing in one embodiment;

[0042] Figure 2 is a schematic cross-sectional view of a housing in one embodiment;

[0043] Figure 3 Schematic diagram of the structure of a shell in one embodiment.

[0044] Figure 4 Schematic diagram of a process for preparing a battery casing in one embodiment.

[0045] Reference numerals: housing 10, thermally conductive insulating coating 20, groove 11, thickness d of the housing 10 , the thickness d of the thermally conductive insulating coating 20 20 , the depth of the groove d 11 . DETAILED DESCRIPTION

[0046] To facilitate understanding of the present application, the present application will be further described in detail below with reference to specific embodiments. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of the present application.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0048] In this application, the meaning of "and / or" includes any and all combinations of one or more related listed items. "At least one" means more than one, such as one, two and more than two. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layer" means at least two layers, such as two layers, three layers, etc., unless otherwise clearly and specifically defined. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise clearly and specifically defined.

[0049] When a numerical range is disclosed in this application, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed in this application should be understood to include any and all subranges subsumed therein.

[0050] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0051] In this application, “above” or “below” includes the number itself. For example, “1 below” includes 1.

[0052] Unless otherwise specified, the temperature parameters in this application allow for both constant temperature treatment and temperature fluctuations within a certain temperature range. It should be understood that the constant temperature treatment allows for temperature fluctuations within the accuracy range of instrument control. Fluctuations within ranges such as ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are permitted.

[0053] In this application, room temperature refers to indoor temperature, normal temperature or general temperature. Generally speaking, the range of room temperature can be any one of the following temperature intervals: 23℃±2℃, 25℃±5℃ or 20℃±5℃.

[0054] In traditional lithium-ion batteries, the cell casing is mostly made of conductive, easily charged aluminum metal. To ensure battery safety, the outer surface of the cell typically requires insulation protection. Currently, lithium-ion batteries commonly use a layer of blue film applied to the aluminum metal casing as a protective film to provide insulation and wear protection. Blue film is a single-sided tape made of a polyethylene terephthalate (PET) substrate with a pressure-sensitive adhesive (PSA) on the back. This product is mostly dark blue, so it is often referred to as "blue film." Blue film has excellent insulation and tensile strength, providing insulation protection for the battery casing.

[0055] Thermal management design is crucial in battery packs. Good heat dissipation effectively protects battery life and enhances safety. However, PET blue film suffers from low thermal conductivity and high-temperature resistance. While the film's low thermal conductivity hinders heat dissipation, its high-temperature resistance and flammability prevent it from effectively protecting the battery at high temperatures. Furthermore, the process of wrapping the battery cell with the blue film can lead to issues such as folding and the formation of bubbles, further reducing the cell's heat dissipation.

[0056] To simplify battery cell production and reduce costs, some reports have proposed spraying insulating varnish on the outer surface of the battery casing to provide insulation protection. However, traditional insulating varnishes often use a polymer matrix with low thermal conductivity, which significantly hinders the battery's heat dissipation performance.

[0057] Based on this, the first aspect of the present application provides a battery housing to solve the problem that the thermal conductivity of the blue film is low, which seriously hinders the heat dissipation of the lithium-ion battery.

[0058] See also Figure 1 , which is a schematic diagram of the structure of the battery housing in one embodiment. Figure 1 As shown, the battery housing includes a shell 10 and a thermally conductive insulating coating 20 covering the shell 10;

[0059] The thermally conductive insulating coating 20 includes the following raw materials in parts by weight:

[0060] 40~60 parts of waterborne epoxy resin,

[0061] 10~30 parts of curing agent,

[0062] 5.1 to 20.5 parts of modified filler,

[0063] 0.2 to 2 parts of leveling agent, and

[0064] 2 to 6 parts of flame retardant;

[0065] The modified filler includes a thermally conductive filler and a silane coupling agent loaded on the thermally conductive filler;

[0066] The mass ratio of the thermal conductive filler to the silane coupling agent is (5~20): (0.1~0.5).

[0067] The present application adopts a water-based epoxy resin with high resistivity, low dielectric loss, excellent mechanical properties, good chemical stability and high temperature resistance as a matrix, so that the thermally conductive insulating coating 20 has good insulation, mechanical strength and high temperature resistance; a thermally conductive filler with high insulation and high thermal conductivity is used, and a silane coupling agent is loaded on its surface so that it can be evenly dispersed in the thermally conductive insulating coating 20, and a stable and complete thermal conductive network and insulation network are constructed to form a thermally conductive insulating coating 20 with excellent insulation high voltage resistance and thermal conductivity; a curing agent is used to cure the water-washed epoxy resin, a flame retardant is used to enhance the flame retardant effect, and a leveling agent is used to form a smooth, uniform coating without bubbles. A thermally conductive insulating coating 20 is made of raw materials such as a specific ratio of water-based epoxy resin, a curing agent, and a modified filler, and the thermally conductive insulating coating 20 is covered on the shell 10, which can effectively improve the insulation performance, heat dissipation performance and high temperature protection performance of the battery shell, thereby improving the safety of the battery and reducing the thermal management energy consumption of the battery. In addition, the production process of the battery shell provided by the present application is simple, environmentally friendly, and has low preparation cost, making it very suitable for mass production.

[0068] As an example, in the thermally conductive insulating coating 20, the weight portions of the water-based epoxy resin include but are not limited to 40 parts, 42 parts, 44 parts, 46 parts, 48 ​​parts, 50 parts, 52 parts, 54 parts, 56 parts, 58 parts or 60 parts, and may further be selected from 40 to 50 parts; the weight portions of the curing agent include but are not limited to 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts, 28 parts or 30 parts, and may further be selected from 10 to 15 parts; the weight portions of the modified filler include but are not limited to 5.1 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts or 20.5 parts, and can further be selected from 6 parts to 16 parts; the weight portions of the leveling agent include but are not limited to 0.2 parts, 0.4 parts, 0.6 parts, 0.8 parts, 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts or 2 parts, and can further be selected from 1 part to 2 parts; the weight portions of the flame retardant include but are not limited to 2 parts, 2.2 parts, 2.5 parts, 2.8 parts, 3 parts, 3.2 parts, 3.5 parts, 3.8 parts, 4 parts, 4.2 parts, 4.5 parts, 4.8 parts, 5 parts, 5.2 parts, 5.5 parts, 5.8 parts or 6 parts, and can further be selected from 2 parts to 4 parts.

[0069] As an example, in the modified coating, the mass ratio of the thermally conductive filler to the silane coupling agent includes but is not limited to 5:0.1, 10:0.1, 15:0.1, 20:0.1, 5:0.2, 10:0.2, 15:0.2, 20:0.2, 5:0.3, 10:0.3, 15:0.3, 20:0.3, 5:0.4, 10:0.4, 15:0.4, 20:0.4, 5:0.5, 10:0.5, 15:0.5 or 20:0.5, and can be further selected as (6-15): (0.2-0.5), and further selected as (12-15): (0.4-0.5).

[0070] Optionally, the modified filler includes the following raw materials in parts by weight: 5 to 20 parts of thermal conductive filler and 0.1 to 0.5 parts of silane coupling agent.

[0071] As an example, the weight proportion of the thermally conductive filler includes but is not limited to 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts or 20 parts, and can be further selected from 6 parts to 15 parts, and further can be selected from 12 parts to 15 parts; the weight proportion of the silane coupling agent includes but is not limited to 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts or 0.5 parts, and can be further selected from 0.2 parts to 0.5 parts, and further can be selected from 0.4 parts to 0.5 parts.

[0072] Optionally, the thermally conductive filler includes one or more of aluminum nitride, boron nitride, silicon nitride, aluminum oxide, magnesium oxide, zinc oxide, beryllium oxide, and silicon oxide.

[0073] Optionally, the silane coupling agent includes one or more of 3-aminopropyltriethoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane, γ-aminopropyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane.

[0074] In this embodiment, the silane coupling agent can not only be loaded on the surface of the thermally conductive filler, so that the modified filler has good dispersion uniformity in the epoxy resin matrix, thereby constructing a complete and stable thermally conductive insulation network, but also significantly improve the bonding strength between the thermally conductive insulation coating 20 and the shell 10, thereby preventing the thermally conductive insulation coating 20 from falling off.

[0075] Optionally, the waterborne epoxy resin includes one or more of bisphenol A epoxy resin, tetrabromobisphenol A epoxy resin, fluorinated epoxy resin, novolac epoxy resin and glycidylamine epoxy resin.

[0076] Optionally, the curing agent includes one or more of an amine curing agent, an acid anhydride curing agent, an imidazole curing agent, and a hydrazide curing agent.

[0077] Optionally, the amine curing agent includes one or more of an aliphatic polyamine curing agent, an aromatic amine curing agent, and a dicyandiamide curing agent. For example, aliphatic polyamine curing agents include, but are not limited to, ethylenediamine (EDA), diethylenetriamine (DETA), and triethylenetetramine (TETA); aromatic amine curing agents include, but are not limited to, m-phenylenediamine (MPD), diaminodiphenylmethane (DDM), and diaminodiphenyl sulfone; and dicyandiamide curing agents include, but are not limited to, dicyandiamide, dicyandiamide-aliphatic polyamine adducts, dicyandiamide-epoxy resin adducts, dicyandiamide-carboxylic acid compound adducts, and dicyandiamide-imidazoline compound adducts.

[0078] Optionally, the anhydride curing agent includes one or more of phthalic anhydride (PA), methyltetrahydrophthalic anhydride (MeTHPA) and pyromellitic dianhydride (PMDA).

[0079] Optionally, the imidazole curing agent includes one or more of 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole and 2-phenyl-4-methylimidazole.

[0080] Optionally, the hydrazide curing agent includes one or more of adipic acid dihydrazide, sebacic acid dihydrazide and isophthalic acid dihydrazide.

[0081] Optionally, the leveling agent includes one or more of polyethylene glycol, polyethyleneimine, polydimethylsiloxane, polymethylphenylsiloxane and polyacrylic acid fluoride.

[0082] Optionally, the flame retardant includes one or more of silicon dioxide, talc, aluminum hydroxide, ammonium phosphate, and tetrabromobisphenol A bis(dibromopropyl) ether.

[0083] Optionally, the thermally conductive insulating coating 20 further includes 0.1 to 1 part of a pigment, wherein the pigment includes one or more of iron oxide red, iron oxide blue, phthalocyanine blue, phthalocyanine green, molybdenum chrome red, and chrome yellow.

[0084] As an example, in the thermally conductive insulating coating 20, the weight proportion of the pigment includes but is not limited to 0.1 part, 0.2 part, 0.3 part, 0.4 part, 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part or 1 part, and can be further optionally 0.5 part to 0.8 part.

[0085] like Figure 1 As shown, the thickness of the housing 10 is denoted as d 10 The thickness of the thermally conductive insulating coating 20 is denoted as d 20 .

[0086] Optionally, the thickness d of the thermally conductive insulating coating 20 is 20 100μm~300μm.

[0087] As an example, the thickness d of the thermally conductive insulating coating 20 is 20 Including but not limited to 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 200 μm, 220 μm, 240 μm, 260 μm, 280 μm or 300 μm.

[0088] Optionally, the thickness d of the housing 10 10 It is 0.2mm~1.2mm.

[0089] As an example, the thickness d of the housing 10 10 Including but not limited to 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm or 1.2mm.

[0090] Optionally, the housing 10 includes one or more of an aluminum shell, a steel shell, and an aluminum alloy shell, and can further be an aluminum shell.

[0091] See Figure 2 and Figure 3 , Figure 2 is a schematic cross-sectional view of a housing in one embodiment, Figure 3 FIG. 1 is a schematic structural diagram of a housing in one embodiment. Figure 2 As shown, the depth of the groove 11 is d 11 .

[0092] Optionally, a plurality of grooves 11 are provided on one side of the housing 10 facing the heat-conducting insulating coating 20, and the depth d of the grooves 11 is 11 Less than the thickness d of the housing 10 10 , the depth d of the groove 11 11 Less than the thickness d of the thermally conductive insulating coating 20 20 .

[0093] It can be understood that when the housing 10 is provided with a plurality of grooves 11 on the side facing the heat-conducting insulating coating 20, the thickness d of the heat-conducting insulating coating 20 is 20 The depth d of the groove 11 is the maximum thickness of the thermal insulation coating 20, that is, the vertical distance from the bottom wall of the groove 11 to the surface of the thermal insulation coating 20 away from the housing 10. 11 Less than the thickness d of the thermally conductive insulating coating 20 20 Therefore, the thermally conductive insulating coating 20 can completely fill the inside of the groove 11 and cover the groove 11, and the thermally conductive insulating coating 20 completely covers all surfaces of the shell 10 facing the thermally conductive insulating coating 20 and forms a continuous thermally conductive insulating sleeve.

[0094] During the battery charging and discharging process, the housing 10 may deform slightly. This deformation of the smooth, flat housing surface can easily cause the thermally conductive insulating coating 20 to fall off, resulting in insulation failure. In response to this observation, this embodiment provides multiple grooves 11 on the side of the housing 10 facing the thermally conductive insulating coating 20. This increases the contact area between the thermally conductive insulating coating 20 and the housing 10 surface, improving the adhesion of the thermally conductive insulating coating 20 and effectively preventing the thermally conductive insulating coating 20 from falling off and cracking.

[0095] Optionally, the shape of the groove 11 includes one or more of a bar, a square, a diamond, a circle, an ellipse and an irregular shape.

[0096] Optionally, the grooves 11 may be regularly distributed or irregularly distributed. In some specific examples, the grooves 11 are regularly distributed and form a mesh structure. The regular mesh structure can further prevent the thermally conductive insulating coating 20 from cracking.

[0097] Optionally, the depth d of the groove 11 11 It is 2% to 30% of the thickness of the housing 10 .

[0098] As an example, the depth d of the groove 11 11It may be 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28% or 30% of the thickness of the housing 10 .

[0099] Optionally, the depth d of the groove 11 11 20μm~300μm.

[0100] As an example, the depth d of the groove 11 11 Including but not limited to 20μm, 40μm, 60μm, 80μm, 100μm, 120μm, 140μm, 160μm, 180μm, 200μm, 220μm, 240μm, 260μm, 280μm or 300μm.

[0101] In a second aspect of the present application, a method for preparing a battery casing is provided, for preparing the battery casing as described above.

[0102] See Figure 4 , which is a schematic flow chart of a method for preparing a battery shell in one embodiment. Figure 4 As shown, the preparation method of the battery shell includes the following steps:

[0103] S100: Provides water-based coatings containing water-based epoxy resin, curing agent, modified filler, leveling agent, flame retardant and pigment;

[0104] S200: Covering the shell with water-based paint to form a liquid film;

[0105] S300: Curing treatment at 80℃~160℃ for 2h~4h to solidify the liquid film to form a thermally conductive insulating coating.

[0106] Optionally, the preparation method of the modified filler comprises the following steps:

[0107] S111: mixing a thermally conductive filler, a silane coupling agent, and a solvent, and performing a modification reaction at 60° C. to 80° C. for 4 to 6 hours to load the silane coupling agent on the thermally conductive filler, thereby obtaining a mixture;

[0108] S112: Purifying, grinding, and screening the mixture to obtain a modified filler.

[0109] Optionally, in step S111 , the mass ratio of the thermal conductive filler to the solvent is (5-20):100, and the solvent includes ethanol and water in a mass ratio of (85-95):(5-15).

[0110] As an example, the mass ratio of thermally conductive filler and solvent includes but is not limited to 5:100, 6:100, 7:100, 8:100, 9:100, 10:100, 11:100, 12:100, 13:100, 14:100, 15:100, 16:100, 17:100, 18:100, 19:100 or 20:100; the mass ratio of ethanol and water includes but is not limited to 85:5, 85:10, 85:15, 90:5, 90:10, 90:15, 95:5, 95:10 or 95:15.

[0111] As an example, in step S111, the reaction temperature of the modification reaction includes but is not limited to 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C or 80°C; the reaction time of the modification reaction includes but is not limited to 4h, 4.2h, 4.5h, 4.8h, 5h, 5.2h, 5.5h, 5.8h or 6h.

[0112] Optionally, in step S112, the purification of the mixture includes one or more of filtration, suction filtration, filter press, centrifugation, washing, and drying. In some specific examples, the purification of the mixture includes the following steps: filtering and washing the mixture, and drying at 60°C to 80°C for 12 hours to 24 hours; wherein the drying temperature of the drying process includes but is not limited to 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C, or 80°C; and the drying time of the drying process includes but is not limited to 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, or 24 hours.

[0113] Optionally, in step S112, the grinding process includes one or more of ball milling and sand milling, and the mesh size of the sieve used in the screening process is 100-400 mesh. The particle size of the modified filler corresponding to the 100-mesh sieve is ≤150 μm, and the particle size of the modified filler corresponding to the 400-mesh sieve is ≤37.5 μm.

[0114] Optionally, the preparation method of the water-based coating comprises the following steps:

[0115] S121: uniformly dispersing the modified filler in a waterborne epoxy resin to obtain a glue solution;

[0116] S122: Mixing glue, curing agent, leveling agent, flame retardant, pigment and water to obtain a water-based paint.

[0117] Optionally, in step S121, uniformly dispersing the modified filler in the waterborne epoxy resin comprises the following steps: adding the modified filler to the waterborne epoxy resin, stirring the mixture at 60°C to 80°C for 4 to 8 hours, and ultrasonically treating the mixture for 30 to 60 minutes. The stirring temperature for the stirring treatment includes, but is not limited to, 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C, or 80°C; the stirring time for the stirring treatment includes, but is not limited to, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, or 8 hours; and the ultrasonic treatment time includes, but is not limited to, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, or 60 minutes.

[0118] Optionally, the water-based coating comprises 30 to 60 parts of water, including but not limited to 30 parts, 32 parts, 35 parts, 38 parts, 40 parts, 42 parts, 45 parts, 48 ​​parts, 50 parts, 52 parts, 55 parts, 58 parts or 60 parts.

[0119] Optionally, before step S200, that is, before the step of covering the shell with the water-based paint, the following step is also included: forming a plurality of grooves on the side of the shell facing the thermal conductive insulating coating by a press molding method.

[0120] Optionally, the press forming method includes one or more of a stamping method and a roll forming method.

[0121] Optionally, after forming the groove, the method further includes the following steps: plasma cleaning the side of the housing having the groove. Plasma cleaning can improve the surface roughness and surface activity of the housing, thereby enhancing the adhesion between the housing and the thermally conductive insulating coating.

[0122] Optionally, in step S200, the method of covering the shell with the water-based paint includes one or more of a spraying method, a dipping method, a screen printing method, and an inkjet printing method.

[0123] As an example, in step S300, the curing temperature of the curing treatment includes but is not limited to 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C or 160°C, and the curing temperature of the curing treatment includes but is not limited to 2h, 2.5h, 3h, 3.5h or 4h.

[0124] In a third aspect of the present application, a secondary battery is provided, comprising the battery casing as described above, or comprising a battery casing manufactured using the method for manufacturing the battery casing as described above.

[0125] Optionally, the secondary battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. During the charge and discharge process of the secondary battery, active ions (such as Li + 、Na + ) moves back and forth between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes and allows the passage of active ions. The electrolyte, located between the positive and negative electrodes, primarily conducts active ions.

[0126] Optionally, the positive electrode sheet, the negative electrode sheet and the separator are made into an electrode assembly through a winding process or a lamination process.

[0127] Optionally, the secondary battery includes a battery housing as described above, which is used to encapsulate the electrode assembly and electrolyte. The outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft package, such as a pouch-type soft package. The soft package can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0128] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square, or any other shape. In some specific examples, the secondary battery is square.

[0129] The following is further described in conjunction with specific examples and comparative examples. Unless otherwise specified, the raw materials involved in the following specific examples and comparative examples can be sourced from commercial sources. The instruments used can be sourced from commercial sources unless otherwise specified. The processes involved can be selected conventionally by those skilled in the art unless otherwise specified.

[0130] Example 1

[0131] Referring to Table 1, this embodiment provides a battery casing for encapsulating a square lithium-ion battery, and the preparation method thereof is as follows:

[0132] (1) Preparation of modified fillers:

[0133] 90 parts of anhydrous ethanol and 10 parts of deionized water were evenly mixed, and 0.3 parts of a silane coupling agent (3-glycidyloxypropyltrimethoxysilane) and 9 parts of a thermal conductive filler (aluminum nitride powder) were added respectively. The mixture was modified and reacted at 60°C for 6 hours to obtain a mixture; the mixture was filtered and washed, and then dried at 60°C for 24 hours; the dried product was crushed and ground, and then sieved using a 200-mesh sieve to obtain a modified filler.

[0134] (2) Preparation of water-based coatings:

[0135] 9.3 parts of modified filler were added to 60 parts of bisphenol A-based epoxy resin, stirred and dispersed at 60°C for 4 hours, and then ultrasonically treated for 30 minutes to obtain a glue solution; 20 parts of amine curing agent (ethylenediamine), 1 part of leveling agent (polydimethylsiloxane), 5 parts of flame retardant (silicon dioxide powder), 1 part of pigment (iron oxide red) and 40 parts of water were added to the glue solution, and stirring was continued at 60°C for 30 minutes to obtain a water-based coating.

[0136] (3) Pretreatment of the shell:

[0137] A 0.4mm thick aluminum shell is used as the shell. Multiple grooves are formed on one side of the shell by stamping. The depth of the grooves is 50μm. The grooves are formed in a diamond shape and distributed in a regular network. The side of the shell with the grooves is plasma cleaned to improve its surface roughness and surface activity.

[0138] (4) Formation of thermally conductive insulating coating:

[0139] The side of the shell with the groove is completely immersed in the water-based coating, taken out after dipping for 1 minute, and placed in an oven at 140°C for high-temperature curing for 2 hours to form a thermally conductive insulating coating with a thickness of 100 μm on the side of the shell with the groove, thereby obtaining a battery shell for encapsulating square lithium-ion batteries.

[0140] Example 2

[0141] Referring to Table 1, this embodiment provides a battery casing for encapsulating a square lithium-ion battery, and the preparation method thereof is as follows:

[0142] (1) Preparation of modified fillers:

[0143] 95 parts of anhydrous ethanol and 5 parts of deionized water were evenly mixed, and 0.5 parts of a silane coupling agent (3-aminopropyltriethoxysilane) and 15 parts of a thermal conductive filler (composed of alumina powder and magnesium oxide powder in a mass ratio of 1:1) were added respectively. The mixture was modified and reacted at 80°C for 4 hours to obtain a mixture; the mixture was filtered and washed, and then dried at 80°C for 12 hours; the dried product was crushed and ground, and then sieved using a 300-mesh sieve to obtain a modified filler.

[0144] (2) Preparation of water-based coatings:

[0145] 15.5 parts of modified filler were added to 50 parts of phenolic epoxy resin, stirred and dispersed at 80°C for 2 hours, and then ultrasonically treated for 60 minutes to obtain a glue solution; 15 parts of aromatic amine curing agent (m-phenylenediamine), 0.5 parts of leveling agent (polymethylphenylsiloxane), 2 parts of flame retardant (tetrabromobisphenol A bis(dibromopropyl) ether), 0.5 parts of pigment (phthalocyanine blue) and 60 parts of water were added to the glue solution, and stirring was continued at 70°C for 20 minutes to obtain a water-based coating.

[0146] (3) Pretreatment of the shell:

[0147] A 0.6mm-thick aluminum shell is used as the shell. Multiple grooves are formed on one side of the shell by stamping. The depth of the grooves is 100μm. The grooves are formed in a diamond shape and distributed in a regular network. The side of the shell with the grooves is plasma cleaned to improve its surface roughness and surface activity.

[0148] (4) Formation of thermally conductive insulating coating:

[0149] By spraying, the water-based paint is evenly and slowly sprayed on the side of the shell with the groove to ensure that the outer surface is completely covered with a uniform liquid film on one side. After spraying, it is placed in a blast drying oven at 80°C for constant temperature curing for 4 hours to form a thermally conductive insulating coating with a thickness of 140 μm on the side of the shell with the groove, thereby obtaining a battery shell for encapsulating square lithium-ion batteries.

[0150] Example 3

[0151] Referring to Table 1, this embodiment provides a battery casing for encapsulating a square lithium-ion battery, and the preparation method thereof is as follows:

[0152] (1) Preparation of modified fillers:

[0153] 95 parts of anhydrous ethanol and 5 parts of deionized water were evenly mixed, and 0.4 parts of a silane coupling agent (γ-aminopropyltrimethoxysilane) and 12 parts of a thermal conductive filler (composed of boron nitride powder and aluminum oxide powder in a mass ratio of 3:1) were added respectively. The mixture was modified and reacted at 70°C for 5 hours to obtain a mixture; the mixture was filtered and washed, and then dried at 70°C for 14 hours; the dried product was crushed and ground, and then sieved using a 150-mesh sieve to obtain a modified filler.

[0154] (2) Preparation of water-based coatings:

[0155] 12.4 parts of modified filler were added to 40 parts of fluorinated epoxy resin, stirred and dispersed at 70°C for 2 hours, and then ultrasonically treated for 45 minutes to obtain a glue solution; 10 parts of anhydride curing agent (hexahydrophthalic anhydride), 2 parts of leveling agent (polyethylene glycol), 3 parts of flame retardant (talc), 0.8 parts of pigment (molybdate chrome red) and 30 parts of water were added to the glue solution, and stirring was continued at 70°C for 45 minutes to obtain a water-based coating.

[0156] (3) Pretreatment of the shell:

[0157] An aluminum shell with a thickness of 0.8 mm is used as the shell. Multiple grooves are formed on one side of the shell by stamping. The depth of the grooves is 150 μm. The grooves are formed in a diamond shape and distributed in a regular network. The side of the shell with the grooves is plasma cleaned to improve its surface roughness and surface activity.

[0158] (4) Formation of thermally conductive insulating coating:

[0159] The side of the shell with the groove is completely immersed in the water-based coating, and after dipping for 0.5 minutes, it is taken out and placed in an oven at 120°C for high-temperature curing for 2 hours to form a thermally conductive insulating coating with a thickness of 180 μm on the side of the shell with the groove, thereby obtaining a battery shell for encapsulating square lithium-ion batteries.

[0160] Example 4

[0161] Referring to Table 1, this embodiment provides a battery casing for encapsulating a square lithium-ion battery, and the preparation method thereof is as follows:

[0162] (1) Preparation of modified fillers:

[0163] 85 parts of anhydrous ethanol and 15 parts of deionized water were evenly mixed, and 0.2 parts of a silane coupling agent (3-(isobutyleneoxy)propyltrimethoxysilane) and 6 parts of a thermal conductive filler (composed of alumina powder and aluminum nitride powder in a mass ratio of 1:2) were added respectively. The mixture was modified and reacted at 60°C for 6 hours to obtain a mixture; the mixture was filtered and washed, and then dried at 80°C for 20 hours; the dried product was crushed and ground, and then sieved using a 400-mesh sieve to obtain a modified filler.

[0164] (2) Preparation of water-based coatings:

[0165] 6.2 parts of modified filler were added to 45 parts of fluorinated epoxy resin, stirred and dispersed at 60°C for 4 hours, and then ultrasonically treated for 30 minutes to obtain a glue solution; 10 parts of aliphatic polyamine curing agent (diethylenetriamine), 0.4 parts of leveling agent (polymethylphenylsiloxane), 4 parts of flame retardant (composed of silica powder and ammonium phosphate powder in a mass ratio of 1:1), 0.2 parts of pigment (iron oxide red) and 55 parts of water were added to the glue solution, and stirring was continued at 70°C for 40 minutes to obtain a water-based coating.

[0166] (3) Pretreatment of the shell:

[0167] An aluminum shell with a thickness of 0.4 mm is used as the shell. Multiple grooves are formed on one side of the shell by stamping. The depth of the grooves is 100 μm. The grooves are formed in a diamond shape and distributed in a regular network. The side of the shell with the grooves is plasma cleaned to improve its surface roughness and surface activity.

[0168] (4) Formation of thermal conductive insulating coating:

[0169] By spraying, the water-based paint is evenly and slowly sprayed on the side of the shell with the groove to ensure that the outer surface is completely covered with a uniform liquid film on one side. After spraying, it is placed in a 100°C forced air drying oven for constant temperature curing for 2 hours to form a thermally conductive insulating coating with a thickness of 150 μm on the side of the shell with the groove, thereby obtaining a battery shell for encapsulating square lithium-ion batteries.

[0170] Example 5

[0171] This embodiment is basically the same as embodiment 1, except that in step (3), no groove is formed on one side of the shell, and only plasma cleaning is performed.

[0172] Comparative Example 1

[0173] Please refer to Table 1. This comparative example is basically the same as Example 1, except that the water-based coating includes 41.2 parts of modified filler and 5 parts of pigment (iron oxide red), and the modified filler is made of 40 parts of thermal conductive filler (aluminum nitride powder) and 1.2 parts of silane coupling agent (3-glycidyloxypropyltrimethoxysilane).

[0174] Comparative Example 2

[0175] Please refer to Table 1. This comparative example is basically the same as Example 1, except that the water-based paint includes 5 parts of thermal conductive filler (magnesium oxide powder) and 1 part of pigment (phthalocyanine blue).

[0176] Comparative Example 3

[0177] Please refer to Table 1. This comparative example is basically the same as Example 1, except that no thermal conductive filler is added to the water-based coating, and 0.3 parts of silane coupling agent (3-glycidyloxypropyltrimethoxysilane) is directly added to 60 parts of bisphenol A-based epoxy resin in step (2).

[0178] Comparative Example 4

[0179] Please refer to Table 1. This comparative example is basically the same as Example 1, except that no leveling agent and flame retardant are added to the water-based filler.

[0180] Comparative Example 5

[0181] This comparative example is basically the same as Example 1, except that: the silane coupling agent and the thermal conductive filler are not subjected to a modification reaction to prepare the modified filler, and in step (2), 0.3 parts of a silane coupling agent (3-glycidyloxypropyltrimethoxysilane) and 9 parts of a thermal conductive filler (aluminum nitride powder) are directly added to 60 parts of bisphenol A-based epoxy resin.

[0182] Test Case

[0183] Please refer to Table 2, the battery housings of each embodiment and each comparative example were tested as follows:

[0184] (1) Thickness of thermal insulation coating and depth of groove: Slice the battery shell and measure the groove depth by metallographic analysis; use a paint film thickness gauge to measure the thickness of the battery shell coating, and take the average value after 6 consecutive measurements at different positions.

[0185] (2) Thermal conductivity of thermally conductive insulating coatings: The thermal conductivity of thermally conductive insulating coatings is measured using a heat flow meter method. An aluminum sheet sample with thermally conductive insulating coatings is inserted between two flat plates, and a certain temperature gradient is set. A calibrated heat flow sensor is used to measure the heat flow through the sample. The sensor is in contact with the sample between the flat plates and the sample. The thermal conductivity of the sample can be calculated by measuring the sample thickness, the temperature gradient between the upper and lower plates, and the heat flow through the sample.

[0186] (3) High-voltage resistance: Take a battery case with a thermally conductive insulating coating and conduct a breakdown test at different locations on the battery case. The test conditions are: temperature 20°C to 45°C, frequency 50 Hz, steady voltage increase, and the electrode is copper or brass with a diameter of 10 mm. The arithmetic mean of the test results is then taken as the average breakdown voltage (kV).

[0187] (4) Weather resistance: High and low temperature shock cycles at -55℃~130℃ for 30 minutes each, for 6 consecutive times.

[0188] (5) Flame retardancy: The vertical burning test method is used. The battery shell with thermally conductive insulating coating is hung in a vertical position, its lower part is ignited, and the burning extension speed and time of the flame are measured to evaluate its flame retardancy.

[0189] The thermal conductivity of the traditional PET blue film is 0.15W / (m·K)~0.24W / (m·K), which has low thermal conductivity and poor heat dissipation performance, hindering the heat dissipation of the battery cells in the battery pack. As shown in Table 2, the thermal conductivity of the thermally conductive insulating coating of Examples 1 to 5 reaches 2.4W / (m·K)~3.8W / (m·K), which is an order of magnitude higher than that of the PET blue film, and has excellent heat dissipation performance. The breakdown voltage of Examples 1 to 5 reaches 2000V, and the flame retardant grade is V-0, with excellent insulation protection effect and high temperature protection effect. At the same time, compared with Example 5 in which no groove is set on the surface of the shell, the thermally conductive insulating coating of Examples 1 to 4 has good weather resistance, and there is no cracking or falling off after multiple high and low temperature impact cycles, which proves that setting a groove on the side of the shell facing the coating can effectively enhance the adhesion of the coating, thereby inhibiting the shedding and cracking of the coating.

[0190] Comparative Example 1 used an excessive amount of modified filler. Although the thermal conductivity was significantly improved, the coating's weather resistance was poor, and cracking occurred during high- and low-temperature impact tests. Comparative Example 2 added 5 parts of thermally conductive filler but did not use a silane coupling agent for modification. The thermally conductive filler easily agglomerated, failing to form a complete thermally conductive network, resulting in a significant decrease in thermal conductivity. Comparative Example 3 did not add any thermally conductive filler, resulting in very low thermal conductivity. Comparative Example 4 did not add a leveling agent or flame retardant, resulting in bubbles in the resulting thermally conductive insulating coating, which affected its thermal conductivity. This significantly reduced thermal conductivity and significantly degraded flame retardancy. Comparative Example 5 did not use a silane coupling agent and thermally conductive filler to modify the filler. The thermally conductive filler had poor dispersibility and also exhibited the defect of easy agglomeration, significantly reducing the thermal conductivity of the coating and resulting in poor heat dissipation performance.

[0191] In summary, the battery casing provided by the present application is suitable for encapsulating various square lithium-ion batteries. The thermally conductive insulating coating has a thermally conductive insulating network constructed by modified fillers, which can achieve high thermal conductivity while ensuring high insulation. This allows the battery casing to have excellent insulation performance, heat dissipation performance, and high-temperature protection performance, effectively improving the heat dissipation effect of the battery cells in the battery pack, reducing the overall thermal management energy consumption of the battery pack, and having high safety in use. In addition, the present application uses a water-based coating to form a thermally conductive insulating coating on one side of the shell, which can simplify the production process of the battery casing (omitting the coating process), has no environmental pollution, has a low preparation cost, does not have problems such as bubbles and folding, and the coating is uniform and stable with good coating effect, making it very suitable for mass production.

[0192] Table 1. Formulation of water-based coatings (unit: parts by weight)

[0193]

[0194] Table 2. Battery housing properties

[0195]

[0196] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0197] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of protection of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and such modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A battery casing, characterized in that: It includes a shell and a heat-conducting insulating coating covering the shell; The thermally conductive insulating coating comprises the following raw materials in parts by weight: The waterborne epoxy resin is a fluorinated epoxy resin, and the curing agent is an acid anhydride curing agent; The modified filler includes a thermally conductive filler and a silane coupling agent loaded on the thermally conductive filler; The mass ratio of the thermal conductive filler to the silane coupling agent is 12:0.4; The thermal conductive filler is 9 parts of boron nitride and 3 parts of aluminum oxide, and the silane coupling agent is γ-aminopropyltrimethoxysilane.

2. The battery case according to claim 1, wherein The flame retardant includes one or more of silicon dioxide, talc, aluminum hydroxide, ammonium phosphate and tetrabromobisphenol A bis(dibromopropyl) ether.

3. The battery case according to claim 2, wherein: The leveling agent includes one or more of polyethylene glycol, polyethylene imine, polydimethylsiloxane, polymethylphenylsiloxane, and polyacrylic acid fluoride ester.

4. The battery case according to any one of claims 1 to 3, wherein The thermally conductive insulating coating further comprises 0.1 to 1 part of a pigment, wherein the pigment comprises one or more of iron oxide red, iron oxide blue, phthalocyanine blue, phthalocyanine green, molybdenum chrome red and chrome yellow.

5. The battery case according to claim 4, wherein: The thickness of the thermally conductive insulating coating is 100 μm to 300 μm; A plurality of grooves are provided on a side of the shell facing the thermally conductive insulating coating. The depth of the grooves is less than the thickness of the shell, and the depth of the grooves is less than the thickness of the thermally conductive insulating coating.

6. The battery case according to claim 5, wherein: The depth of the groove is 2% to 30% of the thickness of the shell.

7. A method for preparing a battery casing according to any one of claims 1 to 6, characterized in that: The following steps are involved: Provide water-based coatings containing water-based epoxy resin, curing agent, modified filler, leveling agent, flame retardant and pigment; Covering the shell with the water-based paint to form a liquid film; curing the liquid film at 80° C. to 160° C. for 2 to 4 hours to form a thermally conductive insulating coating; The preparation method of the water-based coating comprises the following steps: uniformly dispersing the modified filler in the waterborne epoxy resin to obtain a glue solution; The glue, the curing agent, the leveling agent, the flame retardant, the pigment and water are mixed to obtain the water-based paint.

8. The method for preparing a battery casing according to claim 7, wherein: The preparation method of the modified filler comprises the following steps: Mixing the thermally conductive filler, the silane coupling agent, and a solvent, and performing a modification reaction at 60° C. to 80° C. for 4 to 6 hours, so that the silane coupling agent is loaded on the thermally conductive filler, to obtain a mixture; The mixture is subjected to purification, grinding and screening to obtain the modified filler.

9. The method for preparing a battery casing according to claim 7, wherein: Before the step of covering the shell with the water-based paint, the method further includes the following steps: A plurality of grooves are formed on a side of the housing facing the thermally conductive insulating coating layer by a press forming method.

10. A secondary battery, characterized in that: The invention comprises a battery shell according to any one of claims 1 to 6, or a battery shell prepared by the preparation method of a battery shell according to any one of claims 7 to 9.

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