Aluminum-based silicon carbide composite battery casing and its preparation method, battery and electronic equipment

Abstract

This invention discloses an aluminum-based silicon carbide composite battery casing, its preparation method, battery, and electronic device, relating to the field of battery casing technology. By setting aluminum-based silicon carbide composite intermediate layers with different silicon carbide contents and particle sizes, wherein the central layer has a relatively high silicon carbide content and a larger particle size, it can provide sufficient strength support for the battery; the sub-layer uses silicon carbide with a relatively small particle size and a smaller amount, which can effectively improve the interfacial bonding density of the material, reduce stress concentration, and improve the strain compatibility of the aluminum-based silicon carbide composite intermediate layer during plastic deformation, thereby significantly improving the ductility and crack propagation resistance of the material. The battery casing provided by this invention ensures the overall strength of the material while achieving lightweight construction. Simultaneously, the surface layer uses a high-aluminum-content aluminum alloy to ensure good corrosion resistance and weldability of the battery casing. After forming, laser welding can achieve weld sealing.

Description

Technical Field

[0001] This invention relates to the field of battery casing technology, and more specifically, to an aluminum-based silicon carbide composite battery casing, its preparation method, battery, and electronic device. Background Technology

[0002] Currently, the main materials used for battery casings fall into two categories: stainless steel and aluminum-plastic pouch batteries. Stainless steel boasts excellent mechanical strength and pressure resistance, with a high modulus of elasticity, effectively resisting drop impacts and mechanical stress during user assembly and disassembly, thus meeting the rigidity requirements for detachable structures stipulated in the EU's new Battery Regulation. However, stainless steel has a density of 7.9 g / cm³. 3 This results in a significant increase in the overall weight of equipment using this material. Furthermore, stainless steel has a thermal conductivity of only 16 W / m·K. Under high-rate charge and discharge conditions, the thermal resistance effect leads to a large temperature difference between the battery cell and the casing, easily triggering the system's frequency reduction protection. More importantly, its high-strength material properties can become a safety hazard in the event of thermal runaway. Because the casing is not prone to directional fracture, energy accumulation could cause instantaneous explosion, resulting in high initial velocities of the fragments and increasing the safety risk.

[0003] Aluminum-plastic flexible packaging materials exhibit a completely different combination of properties, with a density of only 2.7 g / cm³. 3 Combined with an aluminum foil composite layer, this material achieves a weight reduction of over 40% compared to a stainless steel casing. Furthermore, its thermal conductivity exceeds 150 W / m·K, enabling rapid heat dissipation during charging and discharging. However, the multi-layered composite structure of the aluminum-plastic soft-pack material results in insufficient tensile strength, making it prone to puncture damage during drop tests. This leads to a high breakage rate during user replacement, making it difficult to meet the regulatory requirement of 50 cycles of disassembly and reassembly. Additionally, the large volume expansion rate of the aluminum-plastic soft-pack material during charge-discharge cycles can easily lead to stress concentration at casing seams and a risk of decreased product airtightness after multiple cycles.

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

[0005] The purpose of this invention is to provide an aluminum-based silicon carbide composite battery casing, its preparation method, battery, and electronic device.

[0006] This invention is implemented as follows:

[0007] In a first aspect, the present invention provides an aluminum-based silicon carbide composite battery casing, comprising an aluminum alloy outer layer and an aluminum-based silicon carbide composite intermediate layer, wherein the aluminum-based silicon carbide composite intermediate layer is located between the two aluminum alloy outer layers.

[0008] The aluminum-based silicon carbide composite intermediate layer includes a central layer and a sub-surface layer; the central layer is located between the two sub-surface layers, and the sub-surface layers are connected to the aluminum alloy surface layer.

[0009] The materials of the aluminum-based silicon carbide composite intermediate layer include aluminum alloy raw materials and silicon carbide raw materials; in the intermediate layer, the volume fraction of silicon carbide raw materials is 20~30%; in the sub-layer, the volume fraction of silicon carbide raw materials is 6~15%; and the particle size of silicon carbide raw materials in the sub-layer is smaller than that of silicon carbide raw materials in the intermediate layer.

[0010] Secondly, the present invention provides a method for preparing an aluminum-based silicon carbide composite battery casing as described in any of the foregoing embodiments, comprising laying an aluminum-based silicon carbide composite intermediate layer material between two aluminum alloy surface layers, then rolling it after vacuum hot pressing sintering, annealing the obtained rolled part, and then blow molding thermoforming.

[0011] Thirdly, the present invention provides a battery comprising a battery body and an aluminum-based silicon carbide composite battery casing as described in any of the foregoing embodiments or an aluminum-based silicon carbide composite battery casing prepared by any of the foregoing embodiments.

[0012] Fourthly, the present invention provides an electronic device including a battery as described in the foregoing embodiments.

[0013] The present invention has the following beneficial effects:

[0014] This invention provides an aluminum-based silicon carbide composite battery casing, its preparation method, battery, and electronic device. By setting aluminum-based silicon carbide composite intermediate layers with different silicon carbide contents and particle sizes, the central layer has a relatively high silicon carbide content and a larger particle size, providing sufficient strength support for the battery. This results in a battery casing with higher strength compared to aluminum-plastic battery casings. Furthermore, the sub-surface layer uses relatively small silicon carbide particles and a smaller amount, effectively improving the interfacial bonding density, reducing stress concentration, and improving the strain compatibility of the aluminum-based silicon carbide composite intermediate layer during plastic deformation, thereby significantly improving the material's ductility and crack propagation resistance. The battery casing provided by this invention achieves lightweight while ensuring the overall strength and related mechanical properties of the material. Simultaneously, the surface layer uses a high-aluminum-content aluminum alloy to ensure good corrosion resistance and weldability. Laser welding after molding achieves a weld seal. Attached Figure Description

[0015] 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.

[0016] Figure 1 This is a schematic diagram of the structure of the aluminum-based silicon carbide composite battery casing provided in an embodiment of the present invention;

[0017] Figure 2 A process flow diagram of the method for preparing an aluminum-based silicon carbide composite battery casing provided in an embodiment of the present invention;

[0018] Figure 3 This is a schematic diagram of the blow molding thermoforming process provided in an embodiment of the present invention. Detailed Implementation

[0019] 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.

[0020] In a first aspect, the present invention provides an aluminum-based silicon carbide composite battery casing, comprising an aluminum alloy outer layer and an aluminum-based silicon carbide composite intermediate layer, wherein the aluminum-based silicon carbide composite intermediate layer is located between the two aluminum alloy outer layers.

[0021] The aluminum-based silicon carbide composite intermediate layer includes a central layer and a sub-surface layer; the central layer is located between the two sub-surface layers, and the sub-surface layers are connected to the aluminum alloy surface layer.

[0022] That is, the aluminum-based silicon carbide composite battery casing provided by this invention has a cross-sectional structure consisting of five layers: an aluminum alloy surface layer, a sub-surface layer, a central layer, a sub-surface layer, and an aluminum alloy surface layer. Figure 1 As shown.

[0023] In some preferred embodiments, the aluminum alloy surface layer is made of pure aluminum alloy material, and the mass percentage of aluminum is ≥99.5%; more preferably, the aluminum alloy surface layer is a 1-series aluminum alloy plate, such as grades 1050 and 1060.

[0024] The materials of the aluminum-based silicon carbide composite intermediate layer include aluminum alloy raw materials and silicon carbide raw materials; in the intermediate layer, the volume fraction of silicon carbide raw materials is 20~30%; in the sub-layer, the volume fraction of silicon carbide raw materials is 6~15%; and the particle size of silicon carbide raw materials in the sub-layer is smaller than that of silicon carbide raw materials in the intermediate layer.

[0025] The core layer has a relatively high silicon carbide content and a large particle size, which can provide sufficient strength support for the battery, making the battery casing provided by this invention stronger than the traditional aluminum-plastic battery casing. In addition, the secondary layer uses silicon carbide with a relatively small particle size and a small amount added, which can effectively improve the interfacial bonding density of the material, reduce stress concentration, and improve the strain compatibility of the aluminum-based silicon carbide composite intermediate layer during plastic deformation, thereby significantly improving the ductility and crack propagation resistance of the material.

[0026] The battery casing provided by this invention ensures the overall strength and related mechanical properties of the material while achieving lightweight. At the same time, the surface layer uses an aluminum alloy with high aluminum content to ensure that the battery casing has good corrosion resistance and weldability. After forming, laser welding can be used to achieve weld sealing.

[0027] In an optional embodiment, the volume ratio of aluminum alloy raw material to silicon carbide raw material in the central layer is 70:30~80:20; and the volume ratio of aluminum alloy raw material to silicon carbide raw material in the sub-surface layer is 85:15~94:6.

[0028] In an optional embodiment, in the central layer, the silicon carbide raw material has a particle size distribution of 7~20μm and D50=8~12μm; the aluminum alloy raw material has a particle size distribution of 20~50μm and D50=28~32μm; in the subsurface layer, the silicon carbide raw material has a particle size distribution of 2~5μm and D50=3~4μm; the aluminum alloy raw material has a particle size distribution of 10~15μm and D50=12~13μm.

[0029] In an optional embodiment, both the aluminum alloy raw material and the silicon carbide raw material in the aluminum-based silicon carbide composite interlayer are spherical powders, and the sphericity of the silicon carbide raw material is ≥0.80. Spherical particles help improve powder flowability, mixing uniformity, and sintering density, and avoid sharp edges from causing crack initiation.

[0030] By controlling the raw materials of the aluminum-based silicon carbide composite intermediate layer to meet the above requirements, the addition amount, shape and particle size distribution of the raw materials are synergistic, which is beneficial to improving the overall performance of the battery casing.

[0031] Firstly, regarding the central layer, its core function is to provide a high-strength, high-modulus, and high-thermal-conductivity framework support. This invention significantly improves the overall stiffness and strength of the battery casing by increasing the volume fraction of SiC in the central layer. However, excessive SiC addition will lead to a sharp decrease in the material's plasticity, while excessive SiC addition will affect the strength of the battery casing. Therefore, controlling the volume ratio of aluminum alloy raw materials to silicon carbide raw materials in the central layer within the range of 70:30 to 80:20 is beneficial to achieving a balance between the stiffness and toughness of the material.

[0032] In addition, the use of large-sized spherical SiC particles of 7~20μm in the central layer is beneficial to reducing the interfacial density of the material and reducing stress concentration points. At the same time, the thermal conduction path of large-particle SiC is more continuous, which is beneficial to improving the densification ability and thermal conductivity of the material. Large-particle SiC also has the advantage of lower cost, making it suitable for industrial applications.

[0033] Secondly, regarding the sub-surface layer, its function is to serve as a gradient transition zone between the aluminum alloy surface layer and the central layer. If there is a deviation in the material design of this area, it will seriously affect the interface bonding quality, easily leading to crack propagation and local cracking during the fabrication of the shell.

[0034] The subsurface layer, by employing fine SiC particles (2~5μm), can achieve more uniform stress transfer, reduce residual stress caused by thermal expansion mismatch, and promote sintering diffusion. Fine particles can also refine the matrix grains, providing dispersion strengthening without significantly sacrificing the material's ductility. Therefore, controlling the particle size of the subsurface layer within the aforementioned range is one of the keys to achieving a synergistic effect of high strength and high plasticity in the overall battery casing.

[0035] In addition, the volume fraction of silicon carbide raw material in the sub-surface layer is relatively low. The purpose is to retain sufficient continuity of the aluminum alloy matrix to maintain the plasticity of the material, while also providing a certain reinforcing effect, playing the role of connection, buffering and partial strength support.

[0036] Preferably, the aluminum alloy raw materials for the sub-surface layer and the central layer include at least one of Al-Mn, Al-Si, and Al-Mg aluminum alloys.

[0037] By designing a battery casing with the above-mentioned five-layer structure and controlling the raw material composition of each layer, the present invention can realize the production of ultra-thin battery casings. For example, in some embodiments of the present invention, the total thickness of the battery casing is ≤10mm.

[0038] In an optional embodiment, the thickness ratio of the aluminum-based silicon carbide composite intermediate layer to the single-layer aluminum alloy surface layer is 3:1 to 5:1, for example, it can be any one of 3:1, 4:1 or 5:1 or any two of these ratios.

[0039] In an optional implementation, the thickness ratio of the central layer to the single-layer surface layer is 1:1 to 3:1, for example, it can be any one of 1:1, 2:1 or 3:1 or any two of these ratios.

[0040] Secondly, the present invention provides a method for preparing an aluminum-based silicon carbide composite battery casing as described in any of the foregoing embodiments, comprising laying an aluminum-based silicon carbide composite intermediate layer material between two aluminum alloy surface layers, then rolling it after vacuum hot pressing sintering, annealing the obtained rolled part, and then blow molding thermoforming.

[0041] Currently, traditional stainless steel battery casings are mainly produced using a stamping process, where stainless steel sheets are stamped into casings. However, to ensure the structural stability of the stamped casing, the stainless steel sheet needs an elongation of approximately 22% to stretch the material to a thickness of 3-4 mm, which places high demands on the material's elongation. This invention, through a refined and targeted design of the multi-layered structure of the battery casing, allows the material obtained after rolling and annealing to be used for blow molding thermoforming of the battery casing. This reduces the high elongation requirement while ensuring high strength, low cracking rate, and excellent formability of the battery casing.

[0042] Please refer to Figure 2 In an optional embodiment, the method for preparing the aluminum-based silicon carbide composite battery casing provided by the present invention includes the following steps:

[0043] S01, Spreading powder

[0044] In an optional embodiment, materials for a sub-surface layer, a central layer, and another sub-surface layer are sequentially laid on the aluminum alloy surface layer, and then a second aluminum alloy surface layer is placed on the surface of the topmost sub-surface layer to form a blank to be processed.

[0045] In an optional implementation, the powder thickness of each surface layer is 1-5 mm; the powder thickness of each center layer is 5-9 mm.

[0046] In an optional embodiment, the preparation of the subsurface material includes: mixing aluminum alloy raw materials and silicon carbide raw materials in a mixer in proportion.

[0047] Preferably, the mixing parameters include: the powder loading is 60-70% of the effective volume of the mixer, the operating frequency of the mixer is 26-50Hz, the rotation speed is 16-25r / min, the mixing time is 10-12h, the mixing atmosphere is a non-reactive atmosphere, and the mixing environment humidity is 20-40%RH.

[0048] The preparation of the core layer material includes: mixing aluminum alloy raw materials and silicon carbide raw materials in a mixer according to a certain ratio. The mixing parameters selectable in the mixer are the same as those selectable in the sub-surface layer. However, in the actual mixing process, the mixing parameters of the core layer and the sub-surface layer do not need to be exactly the same, as long as they are within the range required above.

[0049] Preferably, before mixing the materials of the central layer and the sub-surface layer, the silicon carbide raw materials need to be baked at 500~650℃ for 1~3 hours to avoid excessive moisture content in the silicon carbide, which would affect the performance of the battery casing.

[0050] Preferably, in order to avoid powder displacement, after each layer of powder is laid, the powder is scraped flat and pre-compacted, and the pre-compacting pressure is 0.05~0.5MPa.

[0051] Preferably, before applying powder, the aluminum alloy surface layer is further subjected to cleaning and degreasing, followed by polishing with 200-500 mesh sandpaper, and then drying to form a roughened layer on the aluminum alloy surface layer, which facilitates the stable bonding of subsequent powder with the aluminum alloy surface layer.

[0052] S02, vacuum hot pressing sintering

[0053] In an optional embodiment, the parameters for vacuum hot pressing sintering include: vacuum degree ≤ 1 × 10⁻⁶. -2 Pa, sintering temperature is 480~540℃, heating rate is 5~10℃ / min, axial pressure in reaction chamber is 10~50MPa, holding time is 1~2h, and cooling is carried out with the furnace after sintering.

[0054] Preferably, to facilitate control of the parameters within the vacuum sintering chamber to meet the above-mentioned ranges, a vacuum degassing process can be performed after preloading a pressure of 0.5~2MPa until the vacuum degree is ≤1×10⁻⁶. -2 Pa.

[0055] By employing vacuum hot pressing sintering, densification and sintering can be achieved simultaneously, significantly improving the interfacial bonding strength between the surface, subsurface, and central layers of the aluminum alloy. Through precise control of the battery casing's structure and materials, coupled with sintering temperature and pressure parameters, low-temperature sintering is achieved, while simultaneously avoiding the formation of the brittle Al4C3 phase. The resulting sintered body achieves a density exceeding 99%, exhibiting excellent dimensional stability and mechanical properties.

[0056] S03, Rolling and Forming

[0057] The sintered body obtained in step S02 is rolled. The rolling process includes hot rolling of the sintered body followed by cold rolling finishing to obtain a plate-shaped rolled part, which is convenient for subsequent blow molding.

[0058] Preferably, the surface roughness Ra of the sintered body is ≤1.6μm to ensure the surface quality of the rolled piece during rolling.

[0059] Preferably, hot rolling involves heating the sintered body and then rolling it into a sheet.

[0060] Preferably, the heating adopts a gradient preheating process, which includes: a first stage of heating at 4~6℃ / min to 290~310℃ and holding for 8~12min; and a second stage of heating at 2~4℃ / min to 400~450℃, with the holding time calculated as 2min per millimeter of sintered body thickness.

[0061] Preferably, the hot rolling stages include primary rolling, intermediate rolling, and finishing rolling in sequence.

[0062] Preferably, the reduction per pass in the initial hot rolling stage is 5-20%, the rolling speed is 0.3-0.5 m / s, and the rolling force is 800-1200 kN.

[0063] Preferably, the reduction per pass in the hot rolling intermediate stage is 30-40%, and the rolling speed is 0.5-0.8 m / s.

[0064] Preferably, the reduction per pass in the hot rolling finishing stage is 10~15%, the rolling speed is 0.3~0.5m / s, and the final rolling temperature is ≥350℃.

[0065] The sintered body is hot-rolled into a sheet. In order to ensure the surface quality and uniform thickness of the sheet, cold rolling finishing is also carried out after hot rolling.

[0066] Preferably, before cold rolling finishing, the hot-rolled sheet needs to be pickled to remove surface oxides and impurities.

[0067] Preferably, the cold rolling finishing stage has three rolling passes, with the first pass having a reduction of 9.5-10.5%, the second pass having a reduction of 7.5-8.5%, and the third pass having a reduction of 4-6%.

[0068] Preferably, the rolling force in the cold rolling finishing stage is 50~80kN, and the roll diameter is 180~220mm.

[0069] Preferably, in order to prepare an ultra-thin battery casing, the thickness of the sheet material obtained after cold rolling finishing is 0.4±0.05mm.

[0070] S04, Annealing

[0071] In an optional embodiment, the sheet material obtained in step S03 is further subjected to annealing treatment at a temperature of 350~420°C and a holding time of 0.3~1.0h, in order to completely or partially eliminate rolling stress and improve the plasticity of the material.

[0072] S05, Blow Molding Thermoforming

[0073] Please refer to Figure 3 In an optional embodiment, blow molding thermoforming includes placing the annealed rolled piece in a mold and performing multiple blow molding passes using blow molding gas to blow mold the sheet-like rolled piece into the shape of a battery case. Figure 3 In the image, the structure indicated in red is a plate-shaped rolled piece.

[0074] Preferably, multi-pass blow molding can be performed in two, three, four, five, or six passes, as long as the battery casing can be formed.

[0075] In optional embodiments, the blow molding mold has at least two forming cavities, meaning that the blow molding thermoforming process of the present invention is a multi-part process, and each mold can produce multiple battery cases in a single blow molding operation. For example, in some embodiments, the mold can be used to produce six, four, or eight battery cases at a time.

[0076] In an optional embodiment, the preheating temperature of the blow molding die is 350~450℃, which is near the recrystallization temperature of the aluminum alloy, facilitating the dynamic recovery of the material and reducing residual stress. During each blow molding pass, the die temperature must be maintained within this range to ensure the molding quality of the product.

[0077] In an optional implementation, during the blow molding process, the temperature of the rolled part is 300~400℃. During each blow molding pass, the temperature of the rolled part needs to be kept within this temperature range to ensure the molding quality of the product.

[0078] In an optional implementation, the blow molding gas includes either nitrogen or argon.

[0079] In an optional implementation, the stretching depth of each pass is increased by 0.1 to 1 mm compared to the previous pass to ensure the molding quality of the battery casing and avoid excessive stretching in a single pass, which could lead to product performance defects.

[0080] In an optional implementation, the preheating time for each pass is increased by 2 to 12 minutes compared to the preheating time of the previous pass. The preheating time for each pass is gradually extended to ensure uniform temperature in thick-walled or complex areas.

[0081] In an optional implementation, the pressure of the blow molding gas in each pass is increased by 0~0.4 MPa compared to the previous pass. This moderate increase in blow molding gas pressure matches the increasing deformation resistance of the material, preventing defects such as cracking.

[0082] In a preferred embodiment, the blow molding process consists of three blow passes, and the parameters for the three blow passes include:

[0083] The preheating time for the first blow molding is 1~5 min, the blow molding gas pressure is 0.3~0.8 MPa, and the blow molding stretching depth is 1~2 mm.

[0084] The preheating time for the second blow molding is 3~10 min, the blow molding gas pressure is 0.5~1.2 MPa, and the blow molding stretching depth is 2~3 mm.

[0085] The preheating time for the third blow molding is 5~15 minutes, the blow molding gas pressure is 0.5~1.2 MPa, and the blow molding stretching depth is 3~4 mm.

[0086] This invention employs a step-by-step, progressive blow molding process, stretching the material to a depth of only 1-4 mm in each pass. This disperses the overall deformation across multiple small steps, with each step involving only a small amount of plastic deformation. This effectively avoids localized stress concentration, enabling the material to achieve a molding depth of 3-4 mm with a relatively low elongation. This significantly improves the forming capability and yield of low-plasticity composite materials, and solves the technical bottleneck of difficulty in deep drawing or stretching caused by the high strength and low plasticity characteristics of aluminum-based silicon carbide composite materials.

[0087] In addition, the blow molding thermoforming process adopts a multi-part arrangement in one mold, using the sheet area between adjacent products as an auxiliary support and flow compensation zone. Under the pressure of blow molding, the sheet area in the middle can provide material flow and relieve the tensile stress in the edge area, which is equivalent to forming a virtual flange area. It plays a role similar to the blank allowance in traditional stamping, but without the need for additional trimming, thus significantly reducing the risk of corner cracking, improving material utilization, and supporting the stable molding of ultra-thin wall (0.3–0.6 mm) structures.

[0088] Furthermore, the outer layer of the battery casing is made of a high-plasticity, high-aluminum-content pure aluminum alloy, which undergoes plastic deformation first during the blow molding process, acting as a buffer layer to absorb some strain energy and inhibit the initiation and propagation of microcracks in the internal brittle SiC reinforcing phase layer. The resulting battery casing has a smooth, crack-free surface, ensuring the overall mechanical properties and sealing performance of the battery casing.

[0089] Through multi-stage parameter fine control, it is possible to prevent uneven deformation of materials due to temperature differences, avoid premature cracking or excessive rebound of the battery casing, and help ensure batch production consistency.

[0090] In an optional implementation, the battery casing obtained by blow molding can be further refined to ensure the shape of the battery casing.

[0091] Thirdly, the present invention provides a battery comprising a battery body and an aluminum-based silicon carbide composite battery casing as described in any of the foregoing embodiments or an aluminum-based silicon carbide composite battery casing prepared by any of the foregoing embodiments, wherein the battery casing is used to encapsulate the battery body.

[0092] Fourthly, the present invention provides an electronic device including a battery as described in the foregoing embodiments.

[0093] For example, electronic devices can be mobile phones, tablets, computers, or other electronic products.

[0094] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0095] Example 1

[0096] This embodiment provides an aluminum-based silicon carbide composite battery casing, including an aluminum alloy surface layer and an aluminum-based silicon carbide composite intermediate layer. The aluminum-based silicon carbide composite intermediate layer includes a central layer and a sub-surface layer. The cross-section of the aluminum-based silicon carbide composite battery casing provided in this embodiment is a five-layer stacked structure from top to bottom, consisting of an aluminum alloy surface layer, a sub-surface layer, a central layer, a sub-surface layer, and an aluminum alloy surface layer.

[0097] The battery casing provided in this embodiment has a thickness of 10mm, each aluminum alloy surface layer has a thickness of 2mm, and the aluminum-based silicon carbide composite intermediate layer has a thickness of 6mm. The ratio of the thickness of each surface layer to the thickness of the central layer in the aluminum-based silicon carbide composite intermediate layer is 1:3.

[0098] The aluminum alloy surface layer is made of grade 1050 sheet metal.

[0099] The central layer is a mixture of 5052Al and SiC in a volume ratio of 75:25; the particle size distribution of SiC is 7~20μm, D50=10μm, and sphericity ≥0.80; the particle size distribution of 5052Al is 20~50μm, and D50=30μm.

[0100] The subsurface layer is a mixture of 5052Al and SiC in a volume ratio of 87.5:12.5; the SiC has a particle size distribution of 2~5μm, D50=3.5μm, and sphericity ≥0.80; the 5052Al has a particle size distribution of 10~15μm and D50=12.5μm.

[0101] This embodiment also provides a method for preparing an aluminum-based silicon carbide composite battery casing, comprising the following steps:

[0102] S01, Spreading powder

[0103] The aluminum alloy surface is cleaned and degreased, and then sanded with 200-500 grit sandpaper to a thickness of 2mm. After cleaning, it is dried to form a roughened layer on the aluminum alloy surface, which facilitates the stable bonding of subsequent powder with the aluminum alloy surface.

[0104] A 3.4mm thick secondary layer, a 9.0mm thick central layer, and a 3.4mm thick secondary layer are sequentially laid on the aluminum alloy surface layer. Then, a second aluminum alloy surface layer is placed on the surface of the top secondary layer to form the blank to be processed.

[0105] To prevent powder displacement, after each layer of powder is laid, the powder is scraped flat and pre-compacted at a pressure of 0.5 MPa.

[0106] The materials for the sub-surface layer and the core layer are mixed in a mixer. Before mixing, SiC is baked at 600℃ for 2 hours. Then, SiC and 5052Al are mixed according to the material requirements of the sub-surface layer and the core layer, respectively. The mixing parameters include: powder loading of 70% of the effective volume of the mixer, working frequency of the mixer of 30Hz, rotation speed of 20r / min, mixing time of 12 hours, mixing atmosphere of non-reactive atmosphere, and mixing environment humidity of 25%RH.

[0107] S02, vacuum hot pressing sintering

[0108] The blank obtained in step S01 is placed in a vacuum sintering furnace for vacuum hot pressing sintering. The parameters for vacuum hot pressing sintering include: vacuum degree ≤ 1 × 10⁻⁶. -2 The sintering temperature was 520℃, the heating rate was 6℃ / min, the axial pressure in the reaction chamber was 20MPa, the holding time was 1.5h, and the furnace was cooled after sintering.

[0109] S03, Rolling and Forming

[0110] The sintered body obtained in step S02 is rolled, and the surface roughness Ra of the sintered body is ≤1.6μm.

[0111] Rolling involves hot rolling the sintered body followed by cold rolling finishing to obtain a plate-shaped rolled product.

[0112] The heating of hot rolling adopts a gradient preheating process, which includes: the first stage of heating to 300℃ at 5℃ / min and holding for 10min; the second stage of heating to 450℃ at 3℃ / min and holding for 2min equal to the thickness, such as 20min for heating a 10mm thick plate.

[0113] The hot rolling process consists of primary rolling, intermediate rolling, and finishing rolling.

[0114] The reduction per pass in the initial hot rolling stage is 8%, the rolling speed is 0.4 m / s, and the rolling force is 1000 kN.

[0115] The reduction per pass in the hot rolling intermediate stage is 30%, and the rolling speed is 0.6 m / s.

[0116] The reduction per pass in the hot rolling finishing stage is 12%, the rolling speed is 0.4 m / s, and the final rolling temperature is ≥350℃.

[0117] The hot-rolled sheet is pickled and then cold-rolled for finishing. The cold-rolling finishing stage consists of three rolling passes: the first pass has a reduction of 10%, the second pass has a reduction of 8%, and the third pass has a reduction of 5%. The rolling force is 80 kN and the roll diameter is 200 mm, resulting in a sheet with a thickness of 0.4 mm.

[0118] S04, Annealing

[0119] The sheet material obtained in step S03 was annealed by holding it at 360℃ for 0.3 hours.

[0120] S05, Blow Molding Thermoforming

[0121] The annealed rolled part is placed in a mold with six evenly distributed forming cavities. Nitrogen gas is used for three-pass blow molding to shape the sheet-like rolled part into the shape of a battery case.

[0122] The preheating temperature of the mold for the first blow molding pass is 360℃, the temperature of the rolled part is 360℃, the preheating time is 3 minutes, the blow molding gas pressure is 0.5MPa, and the blow molding stretching depth is 1.5mm.

[0123] The preheating temperature of the mold for the second blow molding is 360℃, the temperature of the rolled part is 360℃, the preheating time is 3 minutes, the blow molding gas pressure is 0.8MPa, and the blow molding stretching depth is 2.5mm.

[0124] The preheating temperature of the mold for the third blow molding is 380℃, the temperature of the rolled part is 400℃, the preheating time is 10min, the blow molding gas pressure is 1.2MPa, and the blow molding stretching depth is 4mm.

[0125] Example 2

[0126] This embodiment provides an aluminum-based silicon carbide composite battery casing, including an aluminum alloy surface layer and an aluminum-based silicon carbide composite intermediate layer. The aluminum-based silicon carbide composite intermediate layer includes a central layer and a sub-surface layer. The cross-section of the aluminum-based silicon carbide composite battery casing provided in this embodiment is a five-layer stacked structure from top to bottom, consisting of an aluminum alloy surface layer, a sub-surface layer, a central layer, a sub-surface layer, and an aluminum alloy surface layer.

[0127] The battery casing provided in this embodiment has a thickness of 5mm. The thickness ratio of each aluminum alloy surface layer to the aluminum-based silicon carbide composite intermediate layer is 1:3, and the thickness ratio of each surface layer to the center layer in the aluminum-based silicon carbide composite intermediate layer is 1:2.

[0128] The aluminum alloy surface layer is made of grade 1050 sheet metal.

[0129] The central layer is a mixture of 5083Al and SiC in a volume ratio of 80:20; the particle size distribution of SiC is 7~20μm, D50=10μm, and sphericity ≥0.80; the particle size distribution of 5083Al is 20~50μm, and D50=30μm.

[0130] The subsurface layer is a mixture of 5083Al and SiC in a volume ratio of 90:10; the SiC has a particle size distribution of 2~5μm, D50=3.5μm, and sphericity ≥0.80; the 5083Al has a particle size distribution of 10~15μm and D50=12.5μm.

[0131] This embodiment also provides a method for preparing an aluminum-based silicon carbide composite battery casing. The specific steps are similar to those in Embodiment 1, except that step S01 is slightly different, as follows:

[0132] S01, Spreading powder

[0133] The aluminum alloy surface is cleaned and degreased, then sanded with 200-500 grit sandpaper to a thickness of 1 mm. After cleaning, it is dried to form a roughened layer on the aluminum alloy surface, which facilitates the stable bonding of subsequent powder coatings to the aluminum alloy surface.

[0134] A second aluminum alloy layer is laid on the aluminum alloy surface layer in sequence, consisting of a 2.2mm sub-surface layer, a 3.8mm center layer, and a 2.2mm sub-surface layer. Then, a second aluminum alloy surface layer is placed on the surface of the topmost sub-surface layer to form the blank to be processed.

[0135] Comparative Example 1

[0136] This comparative example provides an aluminum-based silicon carbide composite battery casing, the preparation method of which is similar to that of Example 1, except that: the material of the central layer provided in Example 1 is directly used for powder spreading and vacuum hot pressing sintering.

[0137] That is, the battery casing cross-sectional material provided in this comparative example is the same, and all of them are the same material as the central layer provided in Example 1.

[0138] Comparative Example 2

[0139] This comparative example provides an aluminum-based silicon carbide composite battery casing, the preparation method of which is similar to that of Example 2, except that the material of the central layer provided in Example 2 is directly used for powder spreading and vacuum hot pressing sintering.

[0140] That is, the battery casing cross-sectional material provided in this comparative example is the same, and all of them are the same material as the central layer provided in Example 2.

[0141] Comparative Example 3

[0142] This comparative example provides a battery casing, the preparation method of which is similar to that of Example 1, the only difference being that the particle size distribution of the silicon carbide raw materials in the central layer and the subsurface layer is 7~20μm, D50=10μm, and sphericity ≥0.80.

[0143] That is, the battery casing provided in this comparative example adopts the SiC particle size distribution of the central layer in the sub-surface layer, compared to Example 1.

[0144] Comparative Example 4

[0145] This comparative example provides a battery casing with the same structure as Example 1, except that in the preparation method, both the central layer and the subsurface layer are composed of a mixture of 5052Al and SiC in a volume ratio of 75:25.

[0146] In other words, the battery casing provided in this comparative example, compared to Example 1, uses the same volume ratio of 5052Al and SiC as the central layer in the sub-surface layer. The only difference between the central layer and the sub-surface layer is the particle size distribution of SiC, but there is no SiC volume fraction gradient distribution.

[0147] Comparative Example 5

[0148] This comparative example provides an aluminum-based silicon carbide composite battery casing, the preparation method of which is similar to that of Example 2. This comparative example provides a battery casing comprising two aluminum alloy surface layers and a central layer located between the two aluminum alloy surface layers. The materials and structures of the aluminum alloy surface layers and the central layer are the same as in Example 2, the only difference being the preparation method, which includes: directly using the material of the central layer provided in Example 2 for powder spreading and vacuum hot pressing sintering of the surface layer.

[0149] That is, the battery casing provided in this comparative example has only 3 layers, which are the same materials as the central layer and aluminum alloy surface layer provided in Example 2.

[0150] Comparative Example 6

[0151] This comparative example provides a battery casing with a structure similar to that of Example 2, except that the thickness ratio of each aluminum alloy surface layer to the thickness of the aluminum-based silicon carbide composite intermediate layer is 1:4, and the thickness ratio of each surface layer to the center layer in the aluminum-based silicon carbide composite intermediate layer is 3:1.

[0152] That is, the battery casing provided in this comparative example still has 5 layers, which is an increase in the surface layer thickness ratio compared to Example 2.

[0153] Comparative Example 7

[0154] This comparative example provides a battery casing, the preparation method of which is similar to that of Example 1, except that the central layer is composed of 5052Al and SiC mixed in a volume ratio of 60:40.

[0155] That is, the SiC volume fraction in the central layer of the battery casing provided in this comparative example is increased to a medium-high volume fraction.

[0156] Comparative Example 8

[0157] This comparative example provides an aluminum-based silicon carbide composite battery casing, the preparation method of which is similar to that of Example 1, except that: in the molding process, room temperature blow molding is used for each pass.

[0158] Comparative Example 9

[0159] This comparative example provides an aluminum-based silicon carbide composite battery casing, the preparation method of which is similar to that of Example 1, except that the forming depth of a single blow molding thermoforming process is ≥5mm.

[0160] Experimental Example 1

[0161] The battery casings prepared in Examples 1-2 and Comparative Examples 1-7 were subjected to performance tests, and the results are shown in Table 1.

[0162] Density was measured according to GB / T 3850-2015; yield strength and elongation after fracture were tested according to GB / T 228-2021; thermal conductivity was tested according to GB / T 3651-2008; and elastic modulus was tested according to GB / T22315-2008.

[0163] Table 1 Performance of the battery casing

[0164]

[0165] As shown in Table 1, the aluminum-based silicon carbide composite battery casing provided in this embodiment of the invention has a low density, which can significantly reduce the weight of batteries and electronic products. At the same time, it has high yield strength and moderately high elastic modulus, resulting in strong resistance to deformation and effectively ensuring battery safety. It also has high thermal conductivity, thus providing excellent heat dissipation performance and effectively suppressing the risk of battery temperature rise. Furthermore, it has high elongation after fracture, indicating excellent plasticity of the battery casing, which supports complex molding and is not prone to cracking.

[0166] Comparative Examples 1 and 2 both used the material of the central layer to prepare the battery casing. The yield strength and elastic modulus increased significantly, and the strength of the material was improved. However, the elongation after fracture at room temperature decreased significantly. This indicates that the plates of Comparative Examples 1 and 2 are not suitable for battery casing molding processes with a high degree of stretching, which can easily lead to cracks or even cracking defects in the battery casing.

[0167] Comparative Example 3 uses SiC particles with the same particle size as the central layer but larger size in the subsurface layer, which weakens the toughening effect of fine particles on the matrix. Although the yield strength does not decrease significantly, the elongation after fracture at room temperature decreases significantly, making it prone to cracking or internal cracks during deep drawing.

[0168] In Comparative Example 4, although the SiC particle sizes in the central layer and the subsurface layer were the same as in Example 1, the volume fraction of SiC particles in the subsurface layer was increased to 25 vol.%, resulting in an increase in the yield strength and elastic modulus of the material. However, the excessive SiC particles hindered the deformation of the matrix during tensile testing, thus significantly reducing the elongation at room temperature. Comparative Example 5 used the central layer and surface layer from Example 2, with an increased proportion of the central layer, for the same reason.

[0169] Comparative Example 6 increased the layer-to-thickness ratio of the sub-surface layer, and in particular reduced the thickness of the central layer, which weakened the strength support effect of the central layer. As a result, the strength and elastic modulus of the material decreased, while the elongation at room temperature after fracture increased.

[0170] In Comparative Example 7, the central layer used SiC with a medium to high volume fraction. The central layer material had excessively high strength, and as the number of SiC particles increased, its dispersion within the aluminum alloy decreased, making the central layer highly susceptible to cracking during rolling. The deformation coordination between the central layer, the sub-layer, and the surface layer during the rolling process was poor. When the interlayer stress increased to a certain value, the surface layer cracked. Therefore, surface cracks appeared even before the sample was blow-molded.

[0171] Comparative Example 8 was formed by room temperature blow molding. The sample had high strength and stiffness, and the deformation pressure increased exponentially, so it was insufficient for molding. Comparative Example 9 was formed by single-pass deep drawing of the battery casing to a thickness of more than 5mm. The material deformation was large, especially at the right-angled edges where the bends were too large, making it prone to cracking and splitting.

[0172] This invention provides an aluminum-based silicon carbide composite battery casing, its preparation method, the battery, and an electronic device, which have at least the following advantages:

[0173] 1) Gradient Distribution Structure: Based on the different stress states during the forming process, this invention prepares a structure of aluminum-based silicon carbide composite material with a pure aluminum alloy surface and a gradient distribution of SiC inside. This gradient distribution is reflected in the size and volume fraction of SiC particles. The inner central layer provides high strength and high modulus, while the sub-surface layer and aluminum alloy surface layer provide good plasticity. Furthermore, the aluminum alloy surface layer effectively suppresses the generation of rolling crack initiation during the rolling process, resulting in superior overall performance of the material.

[0174] 2) Strong weldability: Due to its high aluminum content, the surface layer of aluminum alloy can be considered as a pure aluminum structure. Its weldability is significantly better than that of aluminum alloys with low aluminum content or aluminum-based silicon carbide composite materials. Laser welding can be used to provide better weld appearance and weld reliability, which is an important guarantee for high yield.

[0175] 3) High thermal conductivity: The main materials of this invention are aluminum-based silicon carbide composite material and high-aluminum-content aluminum alloy. The thermal conductivity of the aluminum alloy surface layer is 238 W / m·K. The aluminum-based silicon carbide composite intermediate layer, obtained by vacuum hot pressing, has a near-theoretical density and a thermal conductivity exceeding 160 W / m·K. During the vacuum hot pressing process, the powder forms a strong bond with the aluminum alloy surface layer under pressure. The interfacial bonding strength is much higher than that of solid-solid layered composites. The overall thermal conductivity after composite formation is ≥170 W / m·K, far exceeding that of stainless steel.

[0176] 4) Multi-pass blow thermoforming: This invention arranges the components according to the size or structural characteristics of the product and uses multi-pass blow thermoforming. By utilizing the material width between parts, the elongation of the material is reduced to 9-10%. The ultra-high plasticity aluminum alloy surface layer inhibits cracking of the aluminum-based silicon carbide composite material layer and reduces the difficulty of deep drawing.

[0177] 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. An aluminum-based silicon carbide composite battery case, characterized by, The aluminum alloy surface layer and the aluminum-based silicon carbide composite intermediate layer are located between two aluminum alloy surface layers. The aluminum-based silicon carbide composite intermediate layer includes a central layer and a subsurface layer; the central layer is located between two subsurface layers, and the subsurface layer is connected with the aluminum alloy surface layer. The material of the aluminum-based silicon carbide composite intermediate layer includes aluminum alloy raw materials and silicon carbide raw materials; in the central layer, the volume fraction of silicon carbide raw materials is 20-30%; in the subsurface layer, the volume fraction of silicon carbide raw materials is 6-15%; and the particle size of silicon carbide raw materials in the subsurface layer is smaller than that in the central layer.

2. The aluminum-based silicon carbide composite battery can of claim 1, wherein The aluminum-based silicon carbide composite intermediate layer satisfies at least one of the following characteristics: Characteristic 1: In the central layer, the volume ratio of aluminum alloy raw materials to silicon carbide raw materials is 70:30-80:20; in the subsurface layer, the volume ratio of aluminum alloy raw materials to silicon carbide raw materials is 85:15-94:6; Characteristic 2: In the central layer, the particle size distribution of silicon carbide raw materials is 7-20 μm, and the particle size distribution of aluminum alloy raw materials is 20-50 μm; in the subsurface layer, the particle size distribution of silicon carbide raw materials is 2-5 μm, and the particle size distribution of aluminum alloy raw materials is 10-15 μm; Characteristic 3: The aluminum alloy raw materials and silicon carbide raw materials of the aluminum-based silicon carbide composite intermediate layer are spherical powders, and the sphericity of the silicon carbide raw materials is ≥0.

80.

3. The aluminum-based silicon carbide composite battery can of claim 1, wherein The thickness of the battery shell satisfies at least one of the following characteristics: Characteristic 4: The thickness ratio of the aluminum-based silicon carbide composite intermediate layer to a single aluminum alloy surface layer is 3:1-5:1; Characteristic 5: The thickness ratio of the central layer to a single subsurface layer is 1:1-3:1; Characteristic 6: The total thickness of the battery shell is ≤10 mm.

4. A method of producing an aluminum-based silicon carbide composite battery case as claimed in any one of claims 1 to 3, characterized by, The material of the aluminum-based silicon carbide composite intermediate layer is laid between two aluminum alloy surface layers, then vacuum hot-pressed and sintered, and then rolled into a shape, and the obtained rolling piece is annealed and blow-molded.

5. The preparation method according to claim 4, characterized in that, The blow-molding includes placing the annealed rolling piece in a mold and using a blow gas for multi-pass blow-molding; the mold has at least two forming cavities; The parameters of the blow-molding include at least one of the following characteristics: Characteristic 7: The preheating temperature of the mold is 350-450°C; Characteristic 8: The temperature of the rolling piece is 300-400°C; Characteristic 9: The blow gas includes any one of nitrogen and argon; Characteristic 10: The stretching depth of each pass is increased by 0.1-1 mm compared with that of the previous pass; Characteristic 11: The preheating time of each pass is increased by 2-12 min compared with that of the previous pass; Characteristic 12: The pressure of the blow gas of each pass is increased by 0-0.4 MPa compared with that of the previous pass.

6. The production method according to claim 5, wherein The blow-molding has three passes, and the parameters of the three passes are as follows: The preheating time of the first pass is 1-5 min, the blow gas pressure is 0.3-0.8 MPa, and the blow-molding stretching depth is 1-2 mm; The preheating time of the second pass is 3-10 min, the blow gas pressure is 0.5-1.2 MPa, and the blow-molding stretching depth is 2-3 mm; The preheating time of the third pass blow molding is 5-15 min, the blow molding gas pressure is 0.5-1.2 MPa, and the blow molding stretch depth is 3-4 mm.

7. The preparation method according to claim 4, characterized in that, The laying process of the aluminum-based silicon carbide composite intermediate layer comprises: laying the materials of the subsurface layer, the center layer and the subsurface layer on the aluminum alloy surface layer in sequence, and the parameters of the powder laying process meet at least one of the following characteristics: Characteristic 13: the powder laying thickness of each layer of the subsurface layer is 1-5 mm; the powder laying thickness of each layer of the center layer is 5-9 mm; Characteristic 14: after each layer of powder is laid, the powder is scraped and pre-compacted, and the pre-compaction pressure is 0.05-0.5 MPa; And / or, the mixing process of the aluminum-based silicon carbide composite intermediate layer comprises separately mixing the raw materials of the center layer and the subsurface layer, and the mixing parameters meet at least one of the following characteristics: Characteristic 15: the powder loading amount is 60-70% of the effective volume of the mixer, the working frequency of the mixer is 26-50 Hz, the rotating speed is 16-25 r / min, the mixing time is 10-12 h, the mixing atmosphere is a non-reactive atmosphere, and the mixing environment humidity is 20-40% RH; Characteristic 16: the silicon carbide raw material is baked at 500-650℃ for 1-3 h before mixing.

8. The preparation method according to claim 4, characterized in that, The parameters of the vacuum hot-press sintering include: vacuum degree ≤1×10 -2 Pa, sintering temperature 480-540 ℃, heating rate 5-10 ℃ / min, axial pressure in the reaction cavity 10-50 MPa, and holding time 1-2 h. And / or, the rolling comprises: after the sintered body obtained by sintering is subjected to hot rolling, cold rolling finishing is performed; and the rolling parameters comprise at least one of the following characteristics: Characteristic 17: the surface roughness Ra of the sintered body is ≤1.6 μm; Characteristic 18: the sintered body is heated by using a gradient preheating process before rolling, and the gradient preheating process comprises: in the first stage, the temperature is raised to 290-310℃ at a rate of 4-6℃ / min and is kept for 8-12 min; in the second stage, the temperature is raised to 400-450℃ at a rate of 2-4℃ / min, and the holding time is calculated according to 2 min per millimeter of the thickness of the sintered body; Characteristic 19: the pass reduction amount of the hot rolling initial rolling stage is 5-20%, the rolling speed is 0.3-0.5 m / s, and the rolling force is 800-1200 kN; Characteristic 20: the pass reduction amount of the hot rolling intermediate rolling stage is 30-40%, and the rolling speed is 0.5-0.8 m / s; Characteristic 21: the pass reduction amount of the hot rolling finishing rolling stage is 10-15%, the rolling speed is 0.3-0.5 m / s, and the final rolling temperature is ≥350℃; Characteristic 22: the rolling passes of the cold rolling finishing stage are three passes, the first pass reduction amount is 9.5-10.5%, the second pass reduction amount is 7.5-8.5%, and the third pass reduction amount is 4-6%; Characteristic 23: the rolling force of the cold rolling finishing stage is 50-80 kN, and the roller diameter is 180-220 mm; And / or, the annealing temperature is 350-420℃, and the holding time is 0.3-1.0 h.

9. A battery, characterized by The battery comprises a battery body and an aluminum-based silicon carbide composite battery shell as claimed in any one of claims 1-3 or prepared by the preparation method as claimed in any one of claims 4-8.

10. An electronic device, comprising: The battery comprises the battery as claimed in claim 9.

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