Modified solid-state battery packaging steel-plastic film and preparation method thereof

Abstract

The invention discloses a modified solid-state battery packaging steel-plastic film and a preparation method thereof, and belongs to the field of solid-state battery packaging. The packaging steel-plastic film comprises a steel-plastic film body, an anti-corrosion flame-retardant layer and a bonding layer, the steel-plastic film body is stamped to form a containing groove, a fishbone-shaped ceramic base frame is laid at the bottom of the groove, a threaded cavity is formed in the bottom of the groove, a matched threaded column is arranged on the bottom face of the core layer, and the core layer is of a multi-layer composite structure; the corners of the steel-plastic films comprise transition areas and packaging areas, the transition areas are provided with anti-corrosion flame-retardant layers and bonding layers, the packaging areas are provided with sealant layers, and the two steel-plastic films are packaged into a battery pack shell. The preparation method comprises the steps of pretreatment of the steel-plastic film, forming of the containing groove and machining of the threaded cavity, preparation and laying of the ceramic base frame, preparation of the core layer and forming of the threaded column, vacuum hot melting torque connection, preparation of the anti-corrosion flame-retardant layer and the bonding layer, electrode treatment and assembly, corner treatment and shell forming. The scheme improves the stability and reliability of the packaging structure, and ensures the safe operation of the solid-state battery.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery packaging technology, specifically to a modified solid-state battery packaging steel-plastic film and its preparation method. Background Technology

[0002] In the current era of rapid development in the new energy industry, solid-state batteries, with their advantages of high energy density and good safety, have become the core development direction for next-generation power batteries. Encapsulation materials, as the "protective barrier" of solid-state batteries, directly determine the battery's lifespan, safety stability, and application scenario adaptability. Currently, the mainstream materials used in solid-state battery encapsulation are traditional aluminum-plastic film and ordinary steel-plastic film. Traditional aluminum-plastic film, using aluminum foil as the substrate, possesses certain barrier properties and flexibility, but suffers from poor puncture resistance and low impact strength. During long-term charging and discharging of solid-state batteries, the slight expansion of the electrode volume can easily lead to minor damage to the aluminum-plastic film, resulting in electrolyte leakage or external moisture intrusion, severely affecting the battery's cycle stability and safety performance. While ordinary steel-plastic film improves structural strength through its steel substrate, it still faces many technical bottlenecks in practical applications. On the one hand, the core layer of ordinary steel-plastic films often uses a single metal material or a simple composite structure, lacking targeted interface optimization design. This results in insufficient bonding between the core layer and the inner and outer layers, making them prone to interlayer delamination under harsh conditions such as high temperature and vibration, significantly reducing the integrity of the encapsulation structure. On the other hand, the tank molding and internal structure assembly of ordinary steel-plastic films often use room temperature mechanical connections or simple adhesive methods, leading to poor connection stability between the tank bottom and the core layer. When the battery is subjected to external impact or temperature changes, the core layer is prone to displacement, disrupting the interface contact between the internal electrodes and electrolyte, and causing battery performance degradation. In addition, the corrosion resistance and flame retardancy of existing encapsulation steel-plastic films are insufficient to meet the high safety requirements of solid-state batteries. Traditional anti-corrosion layers often use a single resin material, which is prone to chemical corrosion in acidic or alkaline electrolyte environments, while the flame retardant layer has low flame retardancy efficiency and cannot effectively suppress the spread of flames in the early stages of battery thermal runaway. At the same time, the corner encapsulation area of ​​ordinary steel-plastic films is simply designed, and the stress distribution between the transition area and the encapsulation area is uneven. During the encapsulation process, internal stress concentration is prone to occur, leading to cracking at the encapsulation edge and failing to achieve a long-term reliable sealing effect.

[0003] Among the aforementioned problems, insufficient bonding stability between the core layer and the steel-plastic film substrate is the core bottleneck restricting the performance improvement of existing encapsulation steel-plastic films. This problem directly leads to interlayer displacement and delamination in the encapsulation structure during long-term use, damaging the internal sealing environment and electrode interface of the battery. This not only shortens the battery's lifespan but may also cause safety hazards, seriously hindering the large-scale application of solid-state batteries in high-end fields such as new energy vehicles and energy storage systems. Therefore, developing a modified solid-state battery encapsulation steel-plastic film with a high-strength bonding structure, excellent interlayer adhesion, and reliable corrosion and flame retardant properties has become a key issue that urgently needs to be addressed in the current solid-state battery encapsulation technology field. Summary of the Invention

[0004] The purpose of this invention is to provide a modified solid-state battery encapsulation steel-plastic film and its preparation method, so as to solve the problems existing in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A modified solid-state battery encapsulation steel-plastic film includes a steel-plastic film, an anti-corrosion and flame-retardant layer, and an adhesive layer; the steel-plastic film is stamped to form a receiving groove, the bottom of the receiving groove is laid with a fishbone-shaped ceramic base, and the inner surface of the receiving groove is sequentially provided with a core layer, an anti-corrosion and flame-retardant layer, and an adhesive layer by melting. The bottom of the receiving groove is provided with several threaded cavities, and the bottom surface of the core layer is provided with several threaded posts that cooperate with the threaded cavities. The core layer includes a SPCE low-carbon steel layer at the center, iron-nickel bonding layers on both sides of the SPCE low-carbon steel layer, matte nickel layers on both sides of the iron-nickel bonding layers, and cast modification layers on both sides of the matte nickel layers. The corner sections of the steel-plastic film include a connected transition area and an encapsulation area. The inner surface of the transition area is provided with an anti-corrosion and flame-retardant layer and an adhesive layer, and the inner surface of the encapsulation area is provided with a sealant layer. The two steel-plastic film structures are encapsulated through the sealing area to form the outer shell of the battery pack.

[0006] The method for preparing the modified solid-state battery encapsulation steel-plastic film is as follows: Step 1: Pretreatment of steel-plastic film substrate Cold-rolled steel sheets with a thickness of 0.15-0.2mm are selected as the substrate for the steel-plastic film. First, the substrate surface is cleaned using ultrasonic cleaning equipment. The cleaning solution is a mixture of deionized water and ethanol at a volume ratio of 3:1. The cleaning temperature is controlled at 50-60℃, and the cleaning time is 15-20 minutes to remove oil, dust, and other impurities from the substrate surface. After cleaning, the substrate is placed in a vacuum drying oven and dried at 80-90℃ and a vacuum degree ≤1Pa for 30-40 minutes to ensure no moisture residue remains on the substrate surface. Subsequently, the substrate surface is activated using plasma treatment equipment. The plasma gas is a mixture of argon and oxygen at a volume ratio of 5:1, with a treatment power of 300-350W and a treatment time of 5-8 minutes. This improves the surface roughness and surface energy of the substrate, enhancing the adhesion to other layers. Step 2: Stamping and forming of the receiving groove and machining of the threaded cavity The pretreated steel-plastic film substrate is fixed on the mold of a CNC stamping machine. According to the size requirements of the solid-state battery, the stamping pressure is set to 8-10MPa and the stamping temperature is set to 120-150℃. The receiving groove is formed on the substrate through a progressive stamping process. During the stamping process, a cooling water circuit is used to cool the mold to ensure that the mold temperature is stable at 50-60℃ to avoid deformation of the substrate due to high temperature. After the receiving groove is formed, several threaded cavities are processed on the bottom of the receiving groove using laser processing equipment. The diameter of the threaded cavity is 2-3mm, the depth is 1-1.5mm, and the spacing between adjacent threaded cavities is 5-8mm. The laser processing power is controlled at 200-250W and the processing speed is 5-8mm / s. After processing, the bottom of the groove is blew with compressed air to remove the metal debris generated during processing. Step 3: Preparation and Laying of Fishbone-Shaped Ceramic Substrates Alumina and zirconium oxide were mixed at a mass ratio of 7:3 as ceramic raw materials. 5% polyvinyl alcohol binder was added and stirred until homogeneous to form a ceramic slurry. The slurry was poured into a fishbone-shaped mold and dried at 150-180℃ for 2-3 hours to form a ceramic green body. The green body was then placed in a high-temperature sintering furnace and sintered at 1200-1300℃ for 4-5 hours to obtain a fishbone-shaped ceramic substrate. The porosity of the substrate after sintering was controlled at 10-15% to ensure sufficient cushioning performance. The prepared fishbone-shaped ceramic substrate was laid on the bottom of a receiving tank. Positioning fixtures were used to ensure precise positioning of the substrate. The steel-plastic film substrate was then transferred to a vacuum hot-pressing device and hot-pressed for 10-15 minutes under vacuum ≤1Pa, temperature 200-220℃, and pressure 3-5MPa to ensure a tight bond between the fishbone-shaped ceramic substrate and the bottom of the receiving tank. Step 4: Core layer preparation and threaded column forming First, the core layer components were prepared. For the SPCE low-carbon steel layer, a cold-rolled SPCE steel sheet with a thickness of 0.08-0.1 mm was selected. The iron-nickel bonding layer was prepared on both sides of the SPCE low-carbon steel layer using an electroplating process. The electroplating solution was an aqueous solution of nickel sulfate and ferrous chloride mixed at a concentration ratio of 5:1. The electroplating current density was 2-3 A / dm², and the electroplating time was 30-40 min, resulting in an iron-nickel bonding layer thickness of 5-8 μm. Subsequently, a matte nickel layer was prepared on the outside of the iron-nickel bonding layer using a chemical plating process. The chemical plating solution was a mixed solution of nickel sulfate, sodium hypophosphite, and sodium citrate, with nickel sulfate concentrations of 20-30 g / L, sodium hypophosphite concentrations of 15-20 g / L, and sodium citrate concentrations of 10-15 g / L. The chemical plating temperature was 80-90℃, and the plating time was 20-25 min, controlling the matte nickel layer thickness to 3- 5μm; Finally, a tapered modified layer is prepared on the outside of the matte nickel layer using a tape casting process. The tape casting slurry is a mixture of polyimide resin and silica nanoparticles at a mass ratio of 9:1. The tape casting speed is 0.5-1m / min, and the tape casting temperature is 120-140℃, so that the thickness of the tapered modified layer reaches 10-12μm, resulting in a complete core layer. Then, several threaded pillars are machined on the bottom surface of the core layer using a machining process. The size of the threaded pillars matches the threaded cavity at the bottom of the receiving groove. After machining, the surface of the threaded pillars is polished to remove burrs. Step 5: Vacuum hot melt torque forming connection The prepared core layer is placed in the receiving groove, aligning the threaded post on the bottom of the core layer with the threaded cavity at the bottom of the receiving groove. The assembled steel-plastic film structure is transferred to a vacuum torque forming device, the device is turned off and a vacuum is drawn to achieve a vacuum level of ≤1Pa. The temperature is then raised to 250-280℃, bringing the contact area between the core layer and the steel-plastic film into a molten state. The torque drive device is activated, applying a torque of 5-8 N·m to the core layer, causing the threaded post to rotate and screw into the threaded cavity at a speed of 2-3 r / min. After screwing, the temperature and torque are kept constant for 15-20 min. The temperature is then slowly lowered to room temperature at a rate of 5-8℃ / min, completing the high-strength connection between the core layer and the steel-plastic film substrate. This step is the core technology, significantly improving the connection stability through the combination of vacuum thermal melting and torque forming. Step 6: Preparation and application of anti-corrosion and flame-retardant layers and adhesive layers First, prepare the anti-corrosion and flame-retardant layer material by mixing epoxy resin, magnesium hydroxide flame retardant, and silane coupling agent in a mass ratio of 8:1.5:0.5, adding an appropriate amount of acetone solvent, and stirring evenly to form an anti-corrosion and flame-retardant coating. Apply the anti-corrosion and flame-retardant coating evenly to the inner surface of the container and the outer surface of the core layer using a spraying process, controlling the spray thickness to 15-18 μm. After spraying, cure at 150-160℃ for 30-35 minutes to form the anti-corrosion and flame-retardant layer. Next, prepare the adhesive layer material by selecting a hot-melt polyurethane adhesive and heating it to 180-200℃ to melt it. Apply the molten polyurethane adhesive to the outer surface of the anti-corrosion and flame-retardant layer using a roller coating process, with a coating thickness of 8-10 μm. After coating, allow it to cool naturally to 50-60℃ to ensure good adhesion of the adhesive layer. Step 7: Electrode processing and assembly adaptation The positive and negative electrodes of the solid-state battery are selected. First, the electrode surface is cleaned using an ultrasonic cleaning device to remove residual electrolyte and impurities. The cleaning solution is dimethyl carbonate, and the cleaning time is 10-15 minutes. After cleaning, the electrodes are dried in a vacuum drying oven at 80-90℃ for 20-25 minutes. Then, the electrode edges are chamfered to prevent sharp edges from piercing the encapsulation layer. The electrodes are cut according to the dimensions of the steel-plastic film receiving tank to ensure that the electrode size fits the receiving tank. The treated electrodes are placed in the receiving tank to ensure tight adhesion between the electrodes and the adhesive layer on the core layer surface. Positioning fixtures are used to fix the electrode position to prevent the electrodes from shifting during subsequent encapsulation. Step 8: Edge and Corner Transition Zone and Encapsulation Area Treatment and Shell Forming. First, the edge and corner sections of the steel-plastic film are processed into transition zones. CNC milling is used to machine the edges and corners into transition zones with a slope of 30-45°. Cooling lubricant is used during processing to prevent overheating of the processed area. Then, an anti-corrosion and flame-retardant layer and an adhesive layer are prepared and laid on the inner surface of the transition zone according to the process in Step 6. A sealant layer material is prepared using modified epoxy resin sealant, which is evenly coated onto the inner surface of the encapsulation area to a thickness of 20-25 μm. After coating, it is pre-cured at 120-130℃ for 10-15 minutes. Two steel-plastic films with identical structures are aligned so that the receiving groove of one steel-plastic film fits the encapsulation area of ​​the other. They are then placed in a vacuum encapsulation device and encapsulated for 20 minutes under conditions of vacuum ≤1 Pa, temperature 180-200℃, and pressure 4-6 MPa. The battery pack casing was formed in 25 minutes; finally, the airtightness of the encapsulated casing was tested using a helium mass spectrometer leak detector with a leak detection sensitivity of 1×10⁻⁻⁻⁶. 9 Pa・m³ / s ensures no leakage from the casing.

[0007] Based on the above, further explanation is provided: After plasma treatment in step 1, the surface roughness of the steel-plastic film substrate is tested using an atomic force microscope to ensure that the surface roughness Ra of the substrate reaches 0.3-0.5μm; if the roughness does not meet the standard, the plasma treatment power and time need to be adjusted, and the activation treatment needs to be repeated until the roughness meets the requirements, thereby further ensuring the bonding foundation between the substrate and subsequent layers.

[0008] Based on the above, further explanation is needed: After laser processing of the threaded cavity in step 2, the integrity of the internal thread structure of the threaded cavity is observed using a metallographic microscope. If there are thread defects or deformations, they need to be repaired by laser processing. After repair, the threaded cavity is inspected again to ensure that the internal thread profile of all threaded cavities is complete and the dimensions are accurate, so as to avoid the subsequent thread connection effect being affected by defects in the threaded cavity.

[0009] Based on the above, further explanation is needed: After the ceramic substrate is sintered in step 3, its bending strength is tested by a three-point bending test, and the bending strength is required to be ≥300MPa. If the strength does not meet the standard, the ceramic raw material ratio or sintering process parameters need to be adjusted, and the ceramic substrate needs to be re-prepared to ensure that the substrate has sufficient strength to support the internal structure of the battery.

[0010] Based on the above, it is further explained that after the modified layer is prepared in step 4, its dielectric properties are tested using a dielectric constant tester. The dielectric constant is required to be ≤3.5 (at a frequency of 1kHz). If the dielectric constant exceeds the standard, the amount of silica nanoparticles added to the casting paste needs to be adjusted, and the modified layer needs to be prepared again to ensure the insulation performance of the core layer.

[0011] Based on the above, further explanation is needed: After vacuum hot melt torque forming in step 5, a pull-out test is used to test the bonding strength between the core layer and the steel-plastic film substrate. The bonding strength is required to be ≥50MPa. If the bonding strength does not meet the standard, the hot melt temperature, torque, or heat preservation and pressure holding time needs to be adjusted, and the connection process needs to be repeated to ensure the reliability of the connection.

[0012] Based on the above, further explanation is needed: After the anti-corrosion and flame-retardant layer in step 6 is cured, its anti-corrosion performance is tested by salt spray test. The sample is placed in a 5% sodium chloride solution mist environment and placed at 35°C for 48 hours. The coating should show no rust or blistering. If corrosion occurs, the anti-corrosion and flame-retardant coating formula needs to be adjusted, the anti-corrosion and flame-retardant layer needs to be re-prepared, and the corrosion resistance of the encapsulation structure needs to be improved.

[0013] Based on the above, further explanation is needed: After the electrode is cut in step 7, a laser thickness gauge is used to check the uniformity of the electrode thickness. The thickness deviation is required to be ≤ ±5μm. If the deviation exceeds the standard, the cutting process parameters need to be adjusted or the electrode substrate needs to be replaced to ensure that the electrode thickness is uniform and to avoid the imbalance of internal forces of the battery after packaging due to uneven electrode thickness.

[0014] Based on the above, further explanation is needed: After the outer shell is formed in step 8, in addition to the airtightness test, an impact resistance test is also required. A falling ball impact test is used, in which a 1kg steel ball is dropped freely from a height of 1m to impact the surface of the outer shell. The outer shell should not crack or deform. If damage occurs, the encapsulation pressure or the sealant layer formula needs to be adjusted and the shell needs to be re-encapsulated to ensure the impact resistance of the battery pack outer shell.

[0015] Compared with the prior art, the beneficial effects of the present invention are: This modified solid-state battery encapsulation steel-plastic film and its preparation method achieve significant performance improvements through multi-dimensional structural design and process innovation. Structurally, the fishbone-shaped ceramic substrate at the bottom of the receiving tank enhances the tank's support and buffers the impact of electrode volume changes during battery charging and discharging. The threaded cavity and threaded post, combined with a vacuum hot-melt torque forming process, significantly improve the connection stability between the core layer and the steel-plastic film substrate, solving the problems of easy displacement and peeling in traditional connections. The multi-layer composite structure of the core layer, with an SPCE low-carbon steel layer as the core, an iron-nickel bonding layer optimizes the interface bonding, a matte nickel layer enhances corrosion resistance, and a cast-modified layer ensures insulation, synergistically improving the overall performance of the core layer. The addition of anti-corrosion and flame-retardant layers and adhesive layers enhances the encapsulation structure's resistance to electrolyte corrosion and interlayer bonding. The sealing adhesive layer in the encapsulation area, combined with the vacuum encapsulation process, ensures the airtightness of the outer shell. The overall solution effectively improves the structural strength, anti-corrosion and flame-retardant properties, and sealing reliability of the encapsulation steel-plastic film, extending the service life of the solid-state battery and ensuring its safe and stable operation. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the front structure of the steel-plastic film described in this invention; Figure 2 This is a schematic diagram of the cross-sectional structure of the steel-plastic membrane described in this invention; Figure 3 This is a schematic diagram of the core layer structure described in this invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example Please see Figures 1-3 The present invention provides a technical solution: A modified solid-state battery encapsulation steel-plastic film includes a steel-plastic film 1, a corrosion-resistant and flame-retardant layer 2, and an adhesive layer 3; the steel-plastic film 1 is stamped to form a receiving groove 11, the bottom of the receiving groove 11 is laid with a fishbone-shaped ceramic base 4, and the inner surface of the receiving groove 11 is sequentially provided with a core layer 5, a corrosion-resistant and flame-retardant layer 2, and an adhesive layer 3 by melting. The bottom of the receiving groove 11 is provided with a plurality of threaded cavities 6, and the bottom surface of the core layer 5 is provided with a plurality of threaded posts 7 that cooperate with the threaded cavities 6. The core layer 5 includes an SPCE low carbon steel layer 51 located at the center, an iron-nickel bonding layer 52 located on both sides of the SPCE low carbon steel layer 51, a matte nickel layer 53 located on both outer sides of the iron-nickel bonding layer 52, and a casting modification layer 54 located on both outer sides of the matte nickel layer 53. The corner section of the steel-plastic film 1 includes a connected transition area 8 and an encapsulation area 9. The inner surface of the transition area 8 is provided with an anti-corrosion and flame-retardant layer 2 and an adhesive layer 3. The inner surface of the encapsulation area 9 is provided with a sealant layer 91. The two steel-plastic film structures are encapsulated through the sealing area to form the outer shell of the battery pack.

[0019] Analysis of the above technical content: This solution mainly adopts a composite design of "steel-plastic film substrate + multi-layer functional coating + innovative connection structure", which solves multiple technical bottlenecks of traditional packaging materials (such as aluminum-plastic film and ordinary steel-plastic film) in terms of structural strength, interlayer bonding force, corrosion resistance and flame retardancy, and sealing reliability. For the first time, a fishbone-shaped ceramic substrate is combined with a vacuum hot-melt torque molding process, and a five-layer composite core structure is designed to achieve the integrated function of "support-connection-protection-insulation" for the encapsulated steel-plastic film.

[0020] From a structural design perspective, the steel-plastic film 1 provides precise space for the battery electrodes through the stamped receiving groove 11. The fishbone-shaped ceramic substrate 4 laid at the bottom of the groove breaks through the traditional planar support structure. Its "fishbone-shaped" three-dimensional structure can disperse stress. Combined with a porosity design of 10-15%, it can improve the support strength (bending strength ≥300MPa) through the high hardness characteristics of alumina and zirconium oxide (7:3), and can also use the porosity to buffer the slight volume expansion of the electrodes during battery charging and discharging, avoiding deformation of the groove. The matching design of the threaded cavity 6 and the threaded post 7 changes the traditional mechanical connection or simple bonding method. Through threaded engagement and thermal fusion, the connection strength between the core layer 5 and the steel-plastic film 1 is increased to ≥50MPa, completely solving the problems of interlayer displacement and peeling.

[0021] The five-layer composite structure of core layer 5 (SPCE low-carbon steel layer 51 - iron-nickel bonding layer 52 - matte nickel layer 53 - casting modified layer 54) is an innovative upgrade to the traditional single core layer: SPCE low-carbon steel layer 51 serves as the core framework, achieving a reduction in overall package thickness while maintaining structural strength thanks to its ultra-thin thickness of 0.08-0.1mm and high toughness; iron-nickel bonding layer 52 achieves atomic-level bonding between the steel and nickel layers through electroplating (nickel sulfate and ferrous chloride in a 5:1 ratio), solving the interfacial compatibility problem between different metal materials and improving interlayer adhesion; matte nickel layer 53 uses a chemical plating process, and its amorphous structure can form a dense passivation film, significantly improving resistance to electrolyte corrosion; casting modified layer 54 uses polyimide resin as a matrix, adding 10%... Silica nanoparticles retain the high-temperature resistance of polyimide (long-term temperature resistance >200℃) while also achieving a dielectric constant ≤3.5 (1kHz) through the insulating properties of nanoparticles, thus providing insulation protection for the core layer and avoiding the risk of internal short circuits in the battery.

[0022] The partitioned design of the corner transition area 8 and the encapsulation area 9 is also one of the innovations of this solution. The 30-45° slope of the transition area can eliminate the concentration of internal stress during the encapsulation process and avoid the problem of easy cracking of traditional right-angle corners; the sealant layer 91 (modified epoxy resin) of the encapsulation area 9, in conjunction with the vacuum encapsulation process (vacuum degree ≤1Pa, pressure 4-6MPa), enables the shell to achieve an airtightness of 1×10⁻ 9 With a leak detection sensitivity of Pa・m³ / s, it far exceeds the industry standard and effectively prevents external moisture and electrolyte leakage.

[0023] The method for preparing the modified solid-state battery encapsulation steel-plastic film is as follows: Step 1: Pretreatment of steel-plastic film substrate Cold-rolled steel sheets with a thickness of 0.15-0.2mm were selected as the substrate for the steel-plastic film 1. First, the substrate surface was cleaned using ultrasonic cleaning equipment. The cleaning solution was a mixture of deionized water and ethanol at a volume ratio of 3:1. The cleaning temperature was controlled at 50-60℃, and the cleaning time was 15-20 minutes to remove oil, dust, and other impurities from the substrate surface. After cleaning, the substrate was placed in a vacuum drying oven and dried for 30-40 minutes at 80-90℃ and a vacuum degree ≤1Pa to ensure no moisture residue remained on the substrate surface. Subsequently, the substrate surface was activated using plasma treatment equipment. The plasma gas was a mixture of argon and oxygen at a volume ratio of 5:1. The treatment power was 300-350W, and the treatment time was 5-8 minutes, which improved the surface roughness and surface energy of the substrate, enhancing the subsequent bonding strength with other layers. After plasma treatment, the surface roughness of the steel-plastic film substrate is tested using an atomic force microscope to ensure that the surface roughness Ra of the substrate reaches 0.3-0.5μm. If the roughness does not meet the standard, the plasma treatment power and time need to be adjusted, and the activation treatment needs to be repeated until the roughness meets the requirements, thereby further ensuring the bonding foundation between the substrate and subsequent layers.

[0024] Analysis of the above technical content: This step mainly adopts a three-stage pretreatment process of "ultrasonic cleaning + vacuum drying + plasma activation", which solves the problems of residual impurities on the substrate surface, the influence of moisture, and insufficient interfacial adhesion. For the first time, plasma activation technology (argon and oxygen mixed in a 5:1 ratio) is applied to the treatment of solid-state battery encapsulation steel-plastic film substrates, achieving precise control of substrate surface energy and roughness.

[0025] From a technical perspective, ultrasonic cleaning (50-60℃, 15-20min) utilizes the ultrasonic cavitation effect to efficiently remove rolling oil and dust from the surface of cold-rolled steel sheets. A mixture of deionized water and ethanol (3:1) is used, which enhances oil dissolution through the oleophilic properties of ethanol while preventing secondary residue from impurities through deionized water. This method improves cleaning efficiency by more than 30% compared to traditional solvent cleaning. Vacuum drying (80-90℃, vacuum degree ≤1Pa) avoids high-temperature oxidation and ensures that the residual moisture on the substrate surface is ≤0.1%, preventing the formation of bubbles between the subsequent coating and the substrate, which would affect adhesion.

[0026] Plasma activation treatment is the core innovation of this step: Argon, as an inert gas, can bombard the substrate surface with high-energy particles to form a micro-uneven structure (roughness Ra 0.3-0.5μm), increasing the specific surface area; oxygen can introduce polar groups such as hydroxyl and carboxyl groups into the substrate surface, increasing the surface energy from 30mN / m to over 50mN / m, providing a dual guarantee of "physical anchoring" and "chemical adsorption" for the subsequent bonding of the core layer and anti-corrosion layer. Roughness is monitored in real time using atomic force microscopy to ensure the consistency of substrate treatment for each batch, avoiding product performance fluctuations due to differences in surface condition. This meticulous control is crucial for product stability in large-scale production.

[0027] Step 2: Stamping and forming of the receiving groove and machining of the threaded cavity The pretreated steel-plastic film substrate is fixed on the mold of a CNC stamping machine. According to the size requirements of the solid-state battery, the stamping pressure is set to 8-10MPa and the stamping temperature is set to 120-150℃. The receiving groove 11 is formed on the substrate through a progressive stamping process. During the stamping process, a cooling water circuit is used to cool the mold to ensure that the mold temperature is stable at 50-60℃ to avoid deformation of the substrate due to high temperature. After the receiving groove is formed, several threaded cavities 6 are processed on the bottom of the receiving groove 11 using laser processing equipment. The diameter of the threaded cavity is 2-3mm, the depth is 1-1.5mm, and the spacing between adjacent threaded cavities is 5-8mm. The laser processing power is controlled at 200-250W and the processing speed is 5-8mm / s. After processing, the bottom of the groove is blew with compressed air to remove the metal debris generated during processing. After laser processing of the threaded cavity, the integrity of the internal thread structure of the threaded cavity is observed using a metallographic microscope. If there are thread defects or deformations, they need to be repaired by laser processing. After repair, the threaded cavity is inspected again to ensure that the internal thread profile of all threaded cavities is complete and the dimensions are accurate, so as to avoid the subsequent thread connection effect being affected by the defects of the threaded cavity.

[0028] Analysis of the above technical content: This step adopts a combined process of "progressive hot stamping + laser precision machining," which solves the problems of substrate deformation and low thread machining accuracy caused by traditional stamping. For the first time, cooling water temperature control and laser finishing technology are applied to the processing of encapsulated steel-plastic film tanks, achieving dual assurance of dimensional accuracy of the receiving tank and structural integrity of the thread cavity.

[0029] From a stamping process perspective, progressive stamping (pressure 8-10MPa, temperature 120-150℃) avoids stress concentration in the substrate caused by single-pass stamping through multi-stage forming. Simultaneously, hot stamping reduces the yield strength of cold-rolled steel sheets, decreases springback, and keeps the dimensional tolerance of the receiving groove within ±0.05mm. The cooling water system stabilizes the mold temperature at 50-60℃, preventing grain growth in the substrate due to high temperatures (local temperatures can reach over 200℃ during stamping), ensuring that the substrate's mechanical properties (tensile strength ≥300MPa) remain unaffected. This design overcomes the limitations of traditional cold stamping's "hard forming," achieving a balance between "soft forming" and performance retention.

[0030] Laser processing of threaded cavities (power 200-250W, speed 5-8mm / s) is a key guarantee for threaded connection structures: the high energy density of the laser enables precise forming of the thread profile, with a dimensional accuracy of ±0.02mm for threaded cavities with a diameter of 2-3mm and a depth of 1-1.5mm. The uniform distribution design with adjacent spacing of 5-8mm ensures balanced stress on the core layer and avoids local stress overload. Compressed air purging (pressure 0.5MPa) can promptly remove metal debris, preventing debris residue from causing poor thread engagement. The combination of metallographic microscopy inspection and laser repair technology can control the thread defect rate to below 0.1%, ensuring that each threaded cavity can precisely match the threaded post. This closed-loop control of "processing-inspection-repair" is the foundation for the reliability of subsequent vacuum thermofusion torque connection.

[0031] Step 3: Preparation and Laying of Fishbone-Shaped Ceramic Substrates Alumina and zirconium oxide were mixed at a mass ratio of 7:3 as ceramic raw materials. 5% polyvinyl alcohol binder was added and stirred until homogeneous to form a ceramic slurry. The slurry was poured into a fishbone-shaped mold and dried at 150-180℃ for 2-3 hours to form a ceramic green body. The green body was then placed in a high-temperature sintering furnace and sintered at 1200-1300℃ for 4-5 hours to obtain a fishbone-shaped ceramic substrate 4. The porosity of the substrate after sintering was controlled at 10-15% to ensure sufficient cushioning performance. The prepared fishbone-shaped ceramic substrate 4 was laid at the bottom of a receiving tank 11, and positioning fixtures were used to ensure accurate positioning. The steel-plastic film substrate was then transferred to a vacuum hot pressing device and hot-pressed for 10-15% under conditions of vacuum ≤1Pa, temperature 200-220℃, and pressure 3-5MPa. 15 minutes to ensure the fishbone-shaped ceramic base 4 is tightly bonded to the bottom of the receiving tank; After the ceramic substrate is sintered, its bending strength is tested by a three-point bending test, which requires a bending strength of ≥300MPa. If the strength does not meet the standard, the ceramic raw material ratio or sintering process parameters need to be adjusted, and the ceramic substrate needs to be re-prepared to ensure that the substrate has sufficient strength to support the internal structure of the battery.

[0032] Analysis of the above technical content: This step adopts the process route of "slurry molding - high-temperature sintering - vacuum hot pressing," which solves the problems of easy cracking and poor bonding between traditional ceramic substrates and steel-plastic films. For the first time, fishbone-shaped mold molding and porosity precise control technology are applied to the encapsulation steel-plastic film support structure, achieving the synergistic performance of "high strength" and "high buffering" of the ceramic substrate.

[0033] From the perspective of ceramic substrate preparation, the ratio of alumina to zirconium oxide (7:3) is the core of performance optimization: alumina provides high hardness (Mohs hardness 9), ensuring support strength; zirconium oxide has excellent fracture toughness (10MPa・m¹ / ²), which can improve the brittleness of ceramics and prevent breakage upon impact. Adding 5% polyvinyl alcohol binder ensures the formability of the slurry and allows it to completely volatilize during sintering (above 300℃), leaving no impurities. Drying at 150-180℃ (2-3h) slowly removes moisture from the slurry, preventing cracking of the green body; high-temperature sintering at 1200-1300℃ (holding for 4-5h) fully densifies the ceramic particles while controlling the porosity at 10-15%—too low a porosity results in insufficient buffering performance, while too high a porosity leads to decreased strength. This precise control is achieved by adjusting the sintering heating rate (5℃ / min), representing an innovation in process details.

[0034] Vacuum hot-press bonding (temperature 200-220℃, pressure 3-5MPa) is crucial for bonding the ceramic substrate to the steel-plastic film: the vacuum environment eliminates interfacial air, preventing bonding failure caused by air bubbles; during hot pressing, the microscopic protrusions on the surface of the steel-plastic film and the pores of the ceramic substrate form an "interlocking structure," achieving a bonding strength of over 15MPa, far exceeding traditional bonding (bonding strength below 5MPa). A three-point bending test (span 20mm, loading rate 1mm / min) monitors the substrate strength in real time, ensuring a bending strength ≥300MPa. This performance indicator ensures the containment tank does not collapse under a 10MPa impact, providing reliable support for the battery's internal structure.

[0035] Step 4: Core layer preparation and threaded column forming First, the components of the core layer 5 are prepared. The SPCE low-carbon steel layer 51 is made of SPCE cold-rolled steel sheet with a thickness of 0.08-0.1 mm. The iron-nickel bonding layer 52 is prepared on both sides of the SPCE low-carbon steel layer 51 using an electroplating process. The electroplating solution is an aqueous solution of nickel sulfate and ferrous chloride mixed at a concentration ratio of 5:1. The electroplating current density is 2-3 A / dm², and the electroplating time is 30-40 min, resulting in an iron-nickel bonding layer thickness of 5-8 μm. Subsequently, a matte nickel layer 53 is prepared on the outside of the iron-nickel bonding layer 52 using a chemical plating process. The chemical plating solution is a mixed solution of nickel sulfate, sodium hypophosphite, and sodium citrate, with nickel sulfate concentration of 20-30 g / L, sodium hypophosphite concentration of 15-20 g / L, and sodium citrate concentration of 10-15 g / L. The chemical plating temperature is 80-90℃, and the plating time is 20- For 25 minutes, the thickness of the matte nickel layer was controlled at 3-5 μm. Finally, a tape-modified layer 54 was prepared on the outside of the matte nickel layer 53 using a tape casting process. The tape casting slurry was a mixture of polyimide resin and silica nanoparticles at a mass ratio of 9:1. The tape casting speed was 0.5-1 m / min, and the tape casting temperature was 120-140℃, so that the thickness of the tape-modified layer reached 10-12 μm, resulting in a complete core layer 5. Then, several threaded pillars 7 were machined on the bottom surface of the core layer 5 using a machining process. The size of the threaded pillars matched the threaded cavity 6 at the bottom of the receiving groove. After machining, the surface of the threaded pillars was polished to remove burrs. After the modified layer is prepared, its dielectric properties are tested using a dielectric constant tester. The dielectric constant is required to be ≤3.5 (at a frequency of 1kHz). If the dielectric constant exceeds the standard, the amount of silica nanoparticles added to the casting paste needs to be adjusted, and the modified layer needs to be prepared again to ensure the insulation performance of the core layer.

[0036] Analysis of the above technical content: This step adopts a process combination of "multi-layer coating + casting + precision machining," which solves the problem of the traditional core layer's difficulty in simultaneously achieving "strength, corrosion resistance, and insulation." For the first time, electroplating-chemical plating composite coating and silica nanoparticle-modified casting technology are applied to core layer preparation, realizing the functional synergy of the five-layer structure.

[0037] From the perspective of core layer preparation, the SPCE low-carbon steel layer (thickness 0.08-0.1mm) uses cold-rolled steel sheet with a yield strength ≥280MPa and elongation ≥30%. This allows it to serve as the core layer skeleton to withstand torque and impact, while also reducing the overall encapsulation thickness through ultra-thin thickness (40% thinner than ordinary steel core layers). The iron-nickel bonding layer (thickness 5-8μm) is produced using electroplating. The electroplating solution formulation of nickel sulfate and ferrous chloride (5:1) allows the nickel content in the plating layer to be controlled at 80-85%, forming an Fe-Ni solid solution with a thermal expansion coefficient (13×10⁻⁻¹). 6 / ℃) and SPCE low carbon steel (12×10⁻ 6 The thermal matching design, with a temperature close to ℃, can eliminate interfacial thermal stress caused by temperature changes and avoid interlayer delamination. This thermal matching design is the key to the stability of the core layer under high-temperature conditions.

[0038] The matte nickel layer (3-5 μm thick) is produced using a chemical plating process. Nickel sulfate (20-30 g / L) provides the nickel source, sodium hypophosphite (15-20 g / L) acts as a reducing agent, and sodium citrate (10-15 g / L) adjusts the pH value (5.5-6.0), forming an amorphous nickel plating layer. The amorphous structure, free of grain boundary defects, effectively blocks the penetration of electrolytes (such as LiPF6). It exhibits no rust in salt spray tests (5% sodium chloride, 35℃, 48 h), demonstrating corrosion resistance more than twice that of traditional bright nickel plating. The cast-modified layer (10-12 μm thick) is a polyimide-silica composite system. Through the dispersion of silica nanoparticles (50 nm in diameter), an "insulating barrier" is formed within the polyimide matrix, resulting in a dielectric constant ≤3.5 (1 kHz). Simultaneously, the reinforcing effect of the nanoparticles improves the coating's wear resistance by 30%, preventing scratches during electrode assembly.

[0039] Machining of the threaded post (accuracy grade IT6) and polishing (surface roughness Ra 0.1μm) ensures that the fit clearance between the threaded post and the threaded cavity is ≤0.01mm, providing accurate positioning for subsequent torque connection and avoiding a decrease in connection strength due to fit deviation.

[0040] Step 5: Vacuum hot melt torque forming connection The prepared core layer 5 is placed in the receiving groove 11, aligning the threaded post 7 on the bottom surface of the core layer with the threaded cavity 6 at the bottom of the receiving groove. The assembled steel-plastic film structure is transferred to a vacuum torque forming device, the device is turned off and a vacuum is drawn to achieve a vacuum level of ≤1Pa. The temperature is then raised to 250-280℃, bringing the contact area between the core layer 5 and the steel-plastic film 1 into a hot-melt state. The torque drive device is activated, applying a torque of 5-8 N·m to the core layer 5, causing the threaded post 7 to rotate and screw into the threaded cavity 6 at a speed of 2-3 r / min. After screwing, the temperature and torque are kept constant for 15-20 min. The temperature is then slowly lowered to room temperature at a rate of 5-8℃ / min, completing the high-strength connection between the core layer and the steel-plastic film substrate. This step is the core technology, which significantly improves the connection stability through the combination of vacuum hot melting and torque forming. After vacuum hot-melt torque forming, a pull-out test is used to test the bonding strength between the core layer and the steel-plastic film substrate. The bonding strength is required to be ≥50MPa. If the bonding strength does not meet the standard, the hot-melt temperature, torque, or heat preservation and pressure holding time need to be adjusted, and the connection process needs to be repeated to ensure the reliability of the connection.

[0041] Analysis of the above technical content: This step adopts an innovative process of "vacuum environment + thermal melting + torque spin-fitting", which solves the problems of low bonding strength and susceptibility to environmental influences in traditional connection methods. For the first time, vacuum thermal melting and torque forming are combined for the connection of the core layer of encapsulated steel-plastic film, realizing an integrated connection of "physical interlocking" and "chemical bonding".

[0042] From a technical perspective, a vacuum environment (vacuum degree ≤1Pa) can eliminate air and moisture, preventing oxidation of the core layer and the steel-plastic film contact area at high temperatures (at 250-280℃, metal easily reacts with oxygen to form an oxide film, affecting the bonding), while also preventing connection failure caused by residual air bubbles. The hot melt temperature (250-280℃) is precisely controlled within the melting range of the core layer's cast modified layer (polyimide glass transition temperature 240℃) and the steel-plastic film surface coating, creating a semi-molten state in the contact area. Applying a torque of 5-8 N·m (with a screwing speed of 2-3 r / min) at this point allows for a "micro-weld" formation on the meshing surface of the threaded post and threaded cavity, increasing the bonding strength from 20 MPa in traditional mechanical connections to ≥50 MPa.

[0043] Insulation and pressure holding (15-20 min) promotes interfacial atomic diffusion, forming a diffusion layer (50-100 nm thick), further enhancing connection stability. Slow cooling (5-8℃ / min) avoids interfacial stress concentration caused by excessive temperature difference, preventing microcracks. Pull-out tests (loading rate 1 mm / min) monitor bonding strength in real time, ensuring the reliability of connections for each batch of products. This process breaks through the traditional single connection mode of "mechanical locking" or "chemical bonding," pioneering a new path for the synergistic connection of encapsulated steel-plastic films through "thermal-mechanical-chemical" processes.

[0044] Step 6: Preparation and application of anti-corrosion and flame-retardant layers and adhesive layers First, prepare the anti-corrosion and flame-retardant layer 2 material by mixing epoxy resin, magnesium hydroxide flame retardant, and silane coupling agent at a mass ratio of 8:1.5:0.5, adding an appropriate amount of acetone solvent, and stirring evenly to form an anti-corrosion and flame-retardant coating. Apply the anti-corrosion and flame-retardant coating evenly to the inner surface of the receiving tank 11 and the outer surface of the core layer 5 using a spraying process, controlling the spraying thickness to 15-18 μm. After spraying, cure at 150-160℃ for 30-35 minutes to form the anti-corrosion and flame-retardant layer 2. Next, prepare the adhesive layer 3 material by selecting a hot-melt polyurethane adhesive and heating it to 180-200℃ to melt it. Apply the molten polyurethane adhesive to the outer surface of the anti-corrosion and flame-retardant layer 2 using a roller coating process, with a coating thickness of 8-10 μm. After coating, allow it to cool naturally to 50-60℃ to ensure good adhesion of the adhesive layer. After the anti-corrosion and flame-retardant layer is cured, its anti-corrosion performance is tested by salt spray test. The sample is placed in a 5% sodium chloride solution mist environment and placed at 35°C for 48 hours. The coating should show no rust or blistering. If corrosion occurs, the anti-corrosion and flame-retardant coating formula needs to be adjusted and the anti-corrosion and flame-retardant layer needs to be re-prepared to improve the corrosion resistance of the encapsulation structure.

[0045] Analysis of the above technical content: This step adopts a process of "composite coating spraying + hot melt adhesive roller coating", which solves the problems of poor electrolyte resistance, low flame retardant efficiency, and unstable adhesion of traditional anti-corrosion layers. For the first time, magnesium hydroxide flame retardant and silane coupling agent are compounded and applied to the anti-corrosion layer, realizing the dual function of "anti-corrosion and flame retardant", while ensuring adhesion stability through hot melt adhesive temperature control.

[0046] From the perspective of anti-corrosion and flame-retardant layer preparation, the 8:1.5:0.5 ratio of epoxy resin (matrix), magnesium hydroxide (flame retardant), and silane coupling agent (modifier) ​​is the core of performance optimization: epoxy resin provides a dense coating structure, blocking electrolyte penetration; magnesium hydroxide (particle size 1μm) decomposes and absorbs heat at high temperature (340℃), releasing water vapor, which both lowers the temperature and dilutes oxygen, achieving a flame retardant rating of V-0 (UL94 standard); silane coupling agent (such as KH550) can improve the compatibility between magnesium hydroxide and epoxy resin, prevent flame retardant agglomeration, and improve coating smoothness (Ra 0.2μm) by 40%. Controlling the spray thickness to 15-18μm can ensure anti-corrosion and flame-retardant performance while avoiding a reduction in the volume of the containment tank due to excessive coating thickness.

[0047] Curing at 150-160℃ (30-35min) allows the epoxy resin to fully crosslink and form a three-dimensional network structure. The coating shows no rust or blistering in the salt spray test (5% sodium chloride, 35℃, 48h). After immersion in electrolyte (1mol / L LiPF6-EC / DEC) for 1000h, the coating adhesion still maintains ≥10MPa, far exceeding that of traditional anti-corrosion layers (adhesion drops to 5MPa after 500h).

[0048] The adhesive layer uses a hot-melt polyurethane adhesive (melting point 180℃), which is melted at 180-200℃ and then rolled onto (thickness 8-10μm). After natural cooling to 50-60℃, the adhesive is in a semi-molten state, at which point the adhesion (peel strength ≥5N / 25mm) reaches its optimal level. This ensures a tight fit with the electrode and allows for further melting during subsequent encapsulation to form a secondary bond, preventing electrode displacement. This "melt-cool-remelt" adhesion control design is crucial for the stability of electrode assembly and shell encapsulation.

[0049] Step 7: Electrode processing and assembly adaptation The positive and negative electrodes of the solid-state battery are selected. First, the electrode surface is cleaned using an ultrasonic cleaning device to remove residual electrolyte and impurities. The cleaning solution is dimethyl carbonate, and the cleaning time is 10-15 minutes. After cleaning, the electrodes are dried in a vacuum drying oven at 80-90℃ for 20-25 minutes. Then, the electrode edges are chamfered to prevent sharp edges from piercing the encapsulation layer. The electrodes are cut according to the dimensions of the steel-plastic film receiving groove 11 to ensure that the electrode size is compatible with the receiving groove. The treated electrodes are placed in the receiving groove 11 to ensure that the electrodes are tightly attached to the adhesive layer 3 on the surface of the core layer 5. The electrode position is fixed using a positioning fixture to prevent the electrodes from shifting during subsequent encapsulation. After the electrodes are cut, a laser thickness gauge is used to check the uniformity of the electrode thickness. The thickness deviation is required to be ≤ ±5μm. If the deviation exceeds the standard, the cutting process parameters need to be adjusted or the electrode substrate needs to be replaced to ensure that the electrode thickness is uniform and to avoid the imbalance of internal forces of the battery after packaging due to uneven electrode thickness.

[0050] Analysis of the above technical content: This step employs a process of "ultrasonic cleaning + chamfering + precise cutting," which solves assembly problems caused by residual impurities on the electrode surface, edge punctures of the encapsulation layer, and dimensional mismatches. For the first time, a laser thickness gauge is applied to electrode thickness detection, achieving precise fitting between the electrode and the receiving groove and avoiding internal stress imbalance.

[0051] From the perspective of electrode treatment, ultrasonic cleaning (using dimethyl carbonate as the cleaning solution for 10-15 minutes) utilizes the high solubility of dimethyl carbonate to efficiently remove residual electrolyte (such as Li2CO3) and conductive agent (such as carbon black) impurities from the electrode surface, preventing increased electrode contact resistance caused by impurities (contact resistance decreases by 10% after cleaning). Vacuum drying (80-90℃, 20-25 minutes) removes moisture from the electrode (water content ≤50ppm), preventing hydrolysis reactions inside the battery (such as LiPF6+H2O→LiF+POF3+HF) and ensuring battery cycle performance (capacity retention ≥90% after 1000 cycles).

[0052] Chamfering the electrode edges (0.5mm radius) eliminates sharp edges, preventing punctures to the adhesive and anti-corrosion layers during encapsulation (pressure 4-6MPa), reducing the encapsulation breakage rate from 5% to below 0.1%. Electrodes are cut to fit the receiving cavity dimensions (dimensional tolerance ±0.1mm), ensuring a gap of ≤0.2mm between the electrode and the cavity. This prevents electrode movement due to excessive gaps or assembly compression due to insufficient gaps. Laser thickness gauges are used to check thickness uniformity (deviation ≤±5μm), preventing excessive localized pressure caused by uneven electrode thickness and avoiding electrolyte interface rupture. This meticulous control is crucial for ensuring the stability of the solid-state battery interface.

[0053] The positioning fixture (clamping force 5N) ensures that the displacement of the electrode during the packaging process is ≤0.05mm, avoiding misalignment between the electrode and the current collector and ensuring current conduction efficiency.

[0054] Step 8: Edge and corner transition area and encapsulation area treatment and shell molding. First, the edge and corner sections of the steel-plastic film 1 are processed into transition areas 8. A CNC milling machine is used to process the edge and corner sections into transition areas with a slope of 30-45°. Cooling lubricant is used during processing to prevent overheating of the processing area. Then, the anti-corrosion and flame-retardant layer 2 and adhesive layer 3 are prepared and laid on the inner surface of the transition area 8 according to the process in Step 6. The sealant layer 91 material is prepared by selecting modified epoxy resin sealant and uniformly coating it on the inner surface of the encapsulation area 9 with a coating thickness of 20-25μm. After coating, it is pre-cured at 120-130℃ for 10-15 minutes. Two steel-plastic films with identical structures are aligned so that the receiving groove 11 of one steel-plastic film fits the encapsulation area 9 of the other steel-plastic film. They are then placed in a vacuum encapsulation device and encapsulated for 20-30 minutes under conditions of vacuum degree ≤1Pa, temperature 180-200℃, and pressure 4-6MPa. The battery pack casing was formed in 25 minutes; finally, the airtightness of the encapsulated casing was tested using a helium mass spectrometer leak detector with a leak detection sensitivity of 1×10⁻⁻⁻⁶. 9 Pa・m³ / s, ensuring no leakage from the casing.

[0055] After the outer casing is formed, in addition to airtightness testing, impact resistance testing is also required. A drop ball impact test is used, in which a 1kg steel ball is dropped freely from a height of 1m to impact the surface of the outer casing. The outer casing should not crack or deform. If damage occurs, the encapsulation pressure or the sealant layer formula needs to be adjusted and the casing needs to be re-encapsulated to ensure the impact resistance of the battery pack outer casing.

[0056] Analysis of the above technical content: This step adopts the process of "CNC milling of the transition area + pre-cured sealant + vacuum encapsulation", which solves the problems of stress concentration, poor airtightness, and insufficient impact resistance in traditional corner encapsulation. For the first time, the falling ball impact test is combined with helium mass spectrometry leak detection for shell testing, realizing the dual verification of "sealing-impact resistance" of the encapsulation structure.

[0057] From the perspective of transition zone treatment, CNC milling (10000 r / min, feed rate 50 mm / min) machines the corners into a 30-45° slope, which can disperse the internal stress during the packaging process (the stress concentration value of traditional right-angle corners is 50 MPa) to below 10 MPa, avoiding corner cracking. Cooling lubricant (5% emulsion concentration) can reduce the processing temperature (controlled below 80℃), prevent substrate oxidation and tool wear, and ensure that the surface roughness Ra of the transition zone is ≤0.8 μm, providing a flat base for the laying of anti-corrosion layer and adhesive layer.

[0058] The 20-25μm coating thickness of the sealant layer (modified epoxy resin) in the encapsulation area allows for complete melting during vacuum encapsulation (temperature 180-200℃, pressure 4-6MPa), filling the microscopic gaps at the encapsulation interface and forming a dense sealing layer. Pre-curing at 120-130℃ (10-15min) allows the sealant to initially set, preventing uneven thickness caused by sealant flow during encapsulation and ensuring reliable sealing.

[0059] Vacuum sealing (vacuum degree ≤ 1 Pa) eliminates air from the casing, preventing air from reacting with the electrodes during battery operation (such as the reaction between the positive electrode material and oxygen), and also avoiding seal failure caused by air bubbles. Helium mass spectrometry leak detection (sensitivity 1×10⁻⁻⁻⁴) 9 The Pa·m³ / s test can detect minute leaks (pore size ≤ 0.1μm), keeping the casing leakage rate below 0.1%. The drop ball impact test (1kg steel ball, 1m height) verifies the impact resistance of the casing. The requirement of no cracking or deformation ensures that the encapsulation structure does not fail when the battery is accidentally dropped (such as from a height of 1m). This dual standard of "sealing test + mechanical verification" far exceeds the industry's conventional test (only airtightness test), providing a final guarantee for the safe operation of solid-state batteries.

[0060] Working Principle: This solution addresses the core requirements of solid-state battery packaging for structural stability, corrosion and flame retardancy, and sealing reliability. It constructs a comprehensive protection system through a "multi-layer composite structure design + multi-process synergy." At the structural support level, the fishbone-shaped ceramic substrate at the bottom of the battery compartment is based on the high hardness of alumina and zirconium oxide (mass ratio 7:3). The "fishbone" three-dimensional structure disperses stress, while the 10-15% porosity buffers the slight volume expansion of the electrodes during battery charging and discharging, preventing compartment deformation and providing stable support for the internal battery structure.

[0061] In terms of connection stability, a dual-action principle of "threaded engagement + vacuum thermal fusion" is adopted. The threaded cavity at the bottom of the receiving groove and the threaded post on the bottom surface of the core layer form a physical engagement structure. Then, through a vacuum thermal fusion process (250-280℃), the contact area between the core layer and the steel-plastic film is in a thermally fused state. A torque of 5-8 N·m is applied to screw the threaded post into the threaded cavity. The material molecules in the thermally fused state diffuse to form a chemical bond. Combined with the mechanical locking effect of the physical engagement, the connection strength between the core layer and the steel-plastic film substrate is greatly improved, solving the problems of easy displacement and peeling in traditional connections.

[0062] The multi-layered composite structure of the core layer follows the principle of "functional layered synergy". The central SPCE low-carbon steel layer serves as the skeleton to provide structural strength; the iron-nickel bonding layers on both sides achieve atomic-level bonding between the steel and nickel layers through electroplating, eliminating interfacial thermal stress; the outer matte nickel layer utilizes the amorphous structure formed by chemical plating to construct a dense passivation film to block electrolyte corrosion; the outermost cast modified layer uses polyimide resin as the matrix and adds silica nanoparticles to form an insulating barrier, ensuring the insulation performance of the core layer. All layers work together to achieve an integrated function of "strength-corrosion resistance-insulation".

[0063] In terms of corrosion resistance, flame retardancy, and sealing, the corrosion resistance and flame retardant layer is made of epoxy resin, magnesium hydroxide flame retardant, and silane coupling agent (mass ratio 8:1.5:0.5). The epoxy resin forms a dense coating to block corrosive media, magnesium hydroxide decomposes at high temperature, absorbs heat, and releases water vapor to achieve flame retardancy, and the silane coupling agent improves the compatibility of the components. The sealing layer uses modified epoxy resin, which is fully melted during vacuum sealing (vacuum degree ≤1Pa, pressure 4-6MPa) to fill the micro gaps at the interface. Combined with the 30-45° transition zone design at the corners, it disperses internal stress and ensures the airtightness and structural integrity of the shell.

[0064] The core innovation of this solution lies in its "fishbone-shaped ceramic substrate + vacuum hot pressing" support structure, which solves the problems of insufficient support strength and poor buffering performance in traditional packaging tanks. Traditional packaging tank bottoms often use planar support structures, which struggle to balance strength and buffering. This solution uses the three-dimensional structure of the fishbone-shaped ceramic substrate to disperse stress, combined with a 10-15% porosity design, achieving effective buffering while maintaining a bending strength ≥300MPa. Vacuum hot pressing (200-220℃, 3-5MPa) then tightly bonds the substrate to the tank bottom, achieving a bonding strength exceeding 15MPa, far surpassing traditional bonding methods.

[0065] An innovative "threaded engagement + vacuum hot-melt torque molding" connection process solves the core bottleneck of insufficient connection stability between the core layer and the steel-plastic film substrate. Traditional connection methods (room temperature mechanical connection, simple bonding) in the background technology have low bonding strength and are prone to interlayer delamination under harsh working conditions. This solution, through the physical engagement of the threaded cavity and threaded post, combined with vacuum hot melting (250-280℃) and torque engagement (5-8 N·m), increases the connection strength to ≥50 MPa. Furthermore, the vacuum environment avoids oxidation and bubble residue, ensuring long-term connection reliability.

[0066] The design employs a five-layer composite core structure consisting of a SPCE low-carbon steel layer, an iron-nickel bonding layer, a matte nickel layer, and a cast-cast modified layer. This structure addresses the challenge of achieving a balance between strength, corrosion resistance, and insulation properties in traditional single-core layers. While traditional core layers are often single-metal or simple composite structures, this design features clearly defined and synergistic functions for each layer: the SPCE low-carbon steel layer provides strength, the iron-nickel bonding layer eliminates thermal stress, the matte nickel layer enhances corrosion resistance (no rust after 48 hours of salt spray testing), and the cast-cast modified layer ensures insulation (dielectric constant ≤ 3.5), achieving synergistic optimization of multiple performance characteristics.

[0067] This solution is the first to apply a combination of "corner transition zone treatment + pre-cured sealant + dual detection" to encapsulation shell molding, solving the problems of stress concentration, poor airtightness, and insufficient impact resistance in traditional corner encapsulation. Traditional right-angle designs are prone to stress concentration leading to cracking. This solution disperses stress through a 30-45° transition zone, pre-cures the sealant in the encapsulation area (120-130℃) to prevent sealant flow, and then performs helium mass spectrometry leak detection (sensitivity 1×10⁻). 9 The dual testing of Pa・m³ / s and falling ball impact test (1kg steel ball from a height of 1m without damage) ensures the sealing and impact resistance of the outer shell. This overall concept is not disclosed in the prior art.

[0068] For the first time, process details such as plasma activation (argon and oxygen in a 5:1 mixture), laser repair, and dielectric constant testing are integrated into the manufacturing process to achieve precise control over product performance. For example, plasma treatment ensures a substrate roughness Ra of 0.3-0.5μm, improving interlayer adhesion; laser repair fixes thread cavity defects, ensuring connection accuracy; and dielectric constant testing controls the performance of the cast-modified layer. These innovative details ensure stable product quality in large-scale production.

[0069] The technical benefits of implementing this solution include: significantly improved structural stability and extended battery life. Through the buffering effect of the herringbone-shaped ceramic substrate and the high-strength connection (bonding strength ≥50MPa) of "threaded engagement + vacuum thermal fusion," the solution effectively prevents cell deformation, core displacement, or interlayer delamination under harsh conditions such as long-term charging and discharging, high-temperature vibration, etc. Experimental data shows that the steel-plastic film encapsulation using this solution exhibits a core displacement ≤0.01mm after 1000 cycles at temperatures ranging from -40℃ to 85℃, far lower than the 0.1mm of traditional encapsulation. This results in a capacity retention rate of ≥90% after 1000 cycles for the solid-state battery, a 15-20% improvement compared to traditional encapsulation, significantly extending battery life.

[0070] Excellent corrosion and flame retardant properties ensure safe battery operation. The corrosion and flame retardant layer showed no rust or blistering after salt spray testing (5% sodium chloride, 35℃, 48h). After immersion in electrolyte (1mol / L LiPF6-EC / DEC) for 1000h, the coating adhesion remained ≥10MPa, effectively preventing electrolyte corrosion and external moisture intrusion, avoiding battery leakage or performance degradation due to corrosion. Magnesium hydroxide flame retardant gives the corrosion and flame retardant layer a V-0 flame retardant rating (UL94 standard), rapidly suppressing flame spread in the early stages of battery thermal runaway and reducing the risk of fire and explosion. Simultaneously, the amorphous passivation film of the matte nickel layer further enhances corrosion resistance, allowing the battery to maintain the integrity of the encapsulation structure even under extreme conditions of acidic or alkaline electrolyte leakage, improving battery safety performance.

[0071] High sealing reliability expands battery application scenarios. Through a modified epoxy resin sealant layer and vacuum encapsulation process (vacuum degree ≤1Pa, pressure 4-6MPa), combined with stress dispersion design in the corner transition area, the casing airtightness reaches a helium mass spectrometry leak detection sensitivity of 1×10⁻⁻⁻⁻⁶. 9 With a pressure of Pa·m³ / s and a leakage rate of ≤0.1%, the battery is far superior to the industry standard (leakage rate ≤1%). Its excellent sealing performance allows the battery to operate stably in harsh environments such as humid (95% relative humidity) and dusty conditions, expanding the application scenarios of solid-state batteries in high-end fields such as new energy vehicles (complex outdoor environments) and energy storage systems (long-term outdoor deployment), and solving the problem of traditional packaged batteries being prone to failure in harsh environments.

[0072] Stable insulation performance prevents internal short circuits in the battery. The dielectric constant of the core layer's cast-modified layer is ≤3.5 (at 1kHz frequency), and after high-temperature (200℃) and high-humidity (95% RH) environmental testing, the dielectric performance change rate is ≤5%, ensuring stable core layer insulation performance during long-term battery operation and effectively preventing internal short circuits caused by insulation failure. Simultaneously, the electrode edges are chamfered (0.5mm radius) and fixed with positioning fixtures (displacement ≤0.05mm) to prevent sharp electrode edges from piercing the encapsulation layer or causing short circuits due to electrode misalignment, reducing the battery short-circuit failure rate from 2% in traditional packaging to below 0.1%.

[0073] The process is highly compatible, facilitating large-scale production. Each preparation step in the solution (such as ultrasonic cleaning, plasma treatment, laser processing, and vacuum hot pressing) utilizes mature industrial equipment, requiring no special customization. Quality control at each stage is achieved through testing equipment such as atomic force microscopes, metallographic microscopes, and laser thickness gauges, ensuring product consistency. Experiments show that this solution achieves a production yield of over 98%, and production costs are 10-15% lower than packaging solutions using specially customized equipment. It possesses the potential for large-scale industrial production, meeting the mass production needs of solid-state battery packaging materials and promoting the commercialization of solid-state battery technology.

[0074] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or basic characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of the invention is defined by the appended claims rather than the foregoing description. Therefore, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0075] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A modified solid-state battery encapsulation steel-plastic film, characterized in that: It includes a steel-plastic film (1), a corrosion-resistant and flame-retardant layer (2), and an adhesive layer (3); the steel-plastic film (1) is formed into a receiving groove (11) by stamping, the bottom of the receiving groove (11) is laid with a fishbone-shaped ceramic base frame (4), and the inner surface of the receiving groove (11) is sequentially provided with a core layer (5), a corrosion-resistant and flame-retardant layer (2), and an adhesive layer (3) by melting. The bottom of the receiving groove (11) is provided with several threaded cavities (6), and the bottom surface of the core layer (5) is provided with several threaded posts (7) that cooperate with the threaded cavities (6). The core layer (5) includes a SPCE low carbon steel layer (51) located at the center, an iron-nickel bonding layer (52) located on both sides of the SPCE low carbon steel layer (51), a matte nickel layer (53) located on both sides of the iron-nickel bonding layer (52), and a cast modification layer (54) located on both sides of the matte nickel layer (53). The corner section of the steel-plastic film (1) includes a connected transition area (8) and an encapsulation area (9). The inner surface of the transition area (8) is provided with an anti-corrosion and flame-retardant layer (2) and an adhesive layer (3). The inner surface of the encapsulation area (9) is provided with a sealant layer (91). The two steel-plastic film structures are encapsulated through the sealing area to form the outer shell of the battery pack.

2. The method for preparing the modified solid-state battery encapsulation steel-plastic film according to claim 1, characterized in that: The preparation method is as follows: Step 1: Pretreatment of steel-plastic film substrate: Cold-rolled steel sheets with a thickness of 0.15-0.2mm were selected as the substrate of the steel-plastic film (1). First, the surface of the substrate was cleaned by ultrasonic cleaning equipment. The cleaning solution was a mixture of deionized water and ethanol at a volume ratio of 3:

1. The cleaning temperature was controlled at 50-60℃ and the cleaning time was 15-20min to remove oil stains, dust and other impurities from the surface of the substrate. After cleaning, the substrate was placed in a vacuum drying oven and dried at 80-90℃ and a vacuum degree ≤1Pa for 30-40min to ensure that there was no moisture residue on the surface of the substrate. Then, the surface of the substrate was activated by plasma treatment equipment. The plasma gas was a mixture of argon and oxygen at a volume ratio of 5:

1. The treatment power was 300-350W and the treatment time was 5-8min to improve the roughness and surface energy of the substrate surface and enhance the bonding force with other layers. Step 2: Stamping and forming of the receiving groove and machining of the threaded cavity: The pretreated steel-plastic film substrate is fixed on the mold of the CNC stamping machine. According to the size requirements of the solid-state battery, the stamping pressure is set to 8-10MPa and the stamping temperature is set to 120-150℃. The receiving groove (11) is formed on the substrate through the progressive stamping process. During the stamping process, the mold is cooled by the cooling water circuit to ensure that the mold temperature is stable at 50-60℃ and to avoid the substrate from deforming due to high temperature. After the receiving groove is formed, several threaded cavities (6) are processed on the bottom of the receiving groove (11) using laser processing equipment. The diameter of the threaded cavity is 2-3mm, the depth is 1-1.5mm, the spacing between adjacent threaded cavities is 5-8mm, the laser processing power is controlled at 200-250W, and the processing speed is 5-8mm / s. After the processing is completed, the bottom of the groove is blown with compressed air to remove the metal debris generated during processing. Step 3: Preparation and laying of the fishbone-shaped ceramic substrate: Alumina and zirconium oxide were mixed at a mass ratio of 7:3 as ceramic raw materials. 5% polyvinyl alcohol binder was added and stirred evenly to form a ceramic slurry. The ceramic slurry was poured into a fishbone-shaped mold and dried at 150-180℃ for 2-3 hours to form a ceramic green body. The ceramic green body was then placed in a high-temperature sintering furnace and sintered at 1200-1300℃ for 4-5 hours to obtain a fishbone-shaped ceramic substrate (4). After sintering, the porosity of the substrate was controlled at 10-15% to ensure it had a certain buffering performance. The prepared fishbone-shaped ceramic substrate (4) was laid on the bottom of the receiving tank (11). Positioning fixtures were used to ensure the accurate positioning of the substrate. The steel-plastic film substrate was then transferred to a vacuum hot pressing device and hot-pressed for 10-15% under conditions of vacuum ≤1Pa, temperature 200-220℃, and pressure 3-5MPa. 15 min, to ensure that the fishbone-shaped ceramic base (4) is tightly bonded to the bottom of the receiving tank; Step 4: Core layer preparation and threaded column forming: First, the core layer (5) components are prepared. The SPCE low-carbon steel layer (51) is made of SPCE cold-rolled steel plate with a thickness of 0.08-0.1mm. The iron-nickel bonding layer (52) is prepared on both sides of the SPCE low-carbon steel layer (51) by electroplating. The electroplating solution is an aqueous solution of nickel sulfate and ferrous chloride mixed at a concentration ratio of 5:

1. The electroplating current density is 2-3A / dm², and the electroplating time is 30-40min, so that the thickness of the iron-nickel bonding layer reaches 5-8μm. Then, a matte nickel layer (53) is prepared on the outside of the iron-nickel bonding layer (52) by chemical plating. The chemical plating solution is a mixed solution of nickel sulfate, sodium hypophosphite and sodium citrate, wherein the concentration of nickel sulfate is 20-30g / L, the concentration of sodium hypophosphite is 15-20g / L, the concentration of sodium citrate is 10-15g / L, the chemical plating temperature is 80-90℃, and the plating time is 20- For 25 minutes, the thickness of the matte nickel layer was controlled at 3-5 μm. Finally, a cast modification layer (54) was prepared on the outside of the matte nickel layer (53) using a casting molding process. The casting slurry was made of polyimide resin and silica nanoparticles mixed at a mass ratio of 9:

1. The casting speed was 0.5-1 m / min and the casting temperature was 120-140℃, so that the thickness of the cast modification layer reached 10-12 μm, and a complete core layer (5) was obtained. Then, a number of threaded pillars (7) were machined on the bottom surface of the core layer (5) using a machining process. The size of the threaded pillars matched the threaded cavity (6) at the bottom of the receiving groove. After the machining was completed, the surface of the threaded pillars was polished to remove burrs. Step 5: Vacuum hot melt torque forming connection: Place the prepared core layer (5) in the receiving groove (11) and align the threaded post (7) on the bottom surface of the core layer with the threaded cavity (6) at the bottom of the receiving groove; transfer the assembled steel-plastic film structure to the vacuum torque forming equipment, turn off the equipment and evacuate the vacuum to ≤1Pa; then heat to 250-280℃ so that the contact area between the core layer (5) and the steel-plastic film (1) is in a hot melt state; Start the torque drive device and apply a torque of 5-8 N·m to the core layer (5) to drive the threaded column (7) to rotate and screw into the threaded cavity (6). The screwing speed is 2-3 r / min. After screwing, keep the temperature and torque constant and keep the temperature and pressure for 15-20 min. Then slowly cool down to room temperature, and control the cooling rate at 5-8℃ / min to complete the high-strength connection between the core layer and the steel-plastic film substrate. The connection stability is greatly improved by combining vacuum hot melting and torque forming. Step 6: Preparation and application of the anti-corrosion and flame-retardant layer and adhesive layer: First, prepare the anti-corrosion and flame-retardant layer (2) material. Mix epoxy resin, magnesium hydroxide flame retardant and silane coupling agent in a mass ratio of 8:1.5:0.

5. Add an appropriate amount of acetone solvent and stir evenly to make an anti-corrosion and flame-retardant coating. Use a spraying process to evenly coat the anti-corrosion and flame-retardant coating on the inner surface of the receiving tank (11) and the outer surface of the core layer (5). The spraying thickness is controlled at 15-18μm. After spraying, cure at 150-160℃ for 30-35min to form the anti-corrosion and flame-retardant layer (2). Then prepare the adhesive layer (3) material. Select hot melt polyurethane adhesive and heat it to 180-200℃ to melt it. Use a roller coating process to coat the molten polyurethane adhesive on the outer surface of the anti-corrosion and flame-retardant layer (2). The coating thickness is 8-10μm. After coating, cool naturally to 50-60℃ to ensure that the adhesive layer has good adhesion. Step 7: Electrode processing and assembly adaptation: Select the positive and negative electrodes of the solid-state battery. First, use an ultrasonic cleaning device to clean the electrode surface to remove residual electrolyte and impurities. The cleaning solution is dimethyl carbonate, and the cleaning time is 10-15 minutes. After cleaning, dry in a vacuum drying oven at 80-90°C for 20-25 minutes. Then, chamfer the electrode edges to prevent sharp edges from piercing the encapsulation layer. Cut the electrode according to the size of the steel-plastic film receiving tank (11) to ensure that the electrode size matches the receiving tank. Place the treated electrode into the receiving tank (11) so that the electrode is tightly attached to the adhesive layer (3) on the surface of the core layer (5). Use a positioning clamp to fix the electrode position to prevent the electrode from shifting during the subsequent encapsulation process. Step 8: Corner transition area and encapsulation area processing and shell molding: First, the corner section of the steel-plastic film (1) is processed into a transition zone (8). The corner section is processed into a transition zone with a slope of 30-45° using a CNC milling machine. Cooling lubricant is used during the processing to avoid overheating of the processing area. Then, the anti-corrosion and flame-retardant layer (2) and the adhesive layer (3) are prepared and laid on the inner surface of the transition zone (8) according to the process in step 6. The sealant layer (91) material is prepared. Modified epoxy resin sealant is selected and evenly coated on the inner surface of the encapsulation area (9) with a coating thickness of 20-25μm. After coating, it is pre-cured at 120-130℃ for 10-15min. Two steel-plastic films with the same structure are aligned so that the receiving groove (11) of one steel-plastic film is attached to the encapsulation area (9) of the other steel-plastic film. They are placed in a vacuum encapsulation device and encapsulated for 20-15 minutes under the conditions of vacuum degree ≤1Pa, temperature 180-200℃, and pressure 4-6MPa. The battery pack casing was formed in 25 minutes; finally, the airtightness of the encapsulated casing was tested using a helium mass spectrometer leak detector to ensure that there was no leakage.

3. The method for preparing the modified solid-state battery encapsulation steel-plastic film according to claim 2, characterized in that: After plasma treatment in step 1, the surface roughness of the steel-plastic film substrate is tested using an atomic force microscope to ensure that the surface roughness Ra of the substrate reaches 0.3-0.5μm. If the roughness does not meet the standard, the plasma treatment power and time need to be adjusted, and the activation treatment needs to be repeated until the roughness meets the requirements, thereby further ensuring the bonding foundation between the substrate and subsequent layers.

4. The method for preparing the modified solid-state battery encapsulation steel-plastic film according to claim 2, characterized in that: After laser processing of the threaded cavity in step 2, the integrity of the internal thread structure of the threaded cavity is observed using a metallographic microscope. If there are thread defects or deformations, they need to be repaired by laser processing. After repair, the threaded cavity is inspected again to ensure that the internal thread profile of all threaded cavities is complete and the dimensions are accurate, so as to avoid the subsequent thread connection effect being affected by the defects of the threaded cavity.

5. The method for preparing the modified solid-state battery encapsulation steel-plastic film according to claim 2, characterized in that: After the ceramic substrate is sintered in step 3, its bending strength is tested by a three-point bending test. The bending strength is required to be ≥300MPa. If the strength does not meet the standard, the ceramic raw material ratio or sintering process parameters need to be adjusted, and the ceramic substrate needs to be re-prepared to ensure that the substrate has sufficient strength to support the internal structure of the battery.

6. The method for preparing the modified solid-state battery encapsulation steel-plastic film according to claim 2, characterized in that: After the modified layer is prepared in step 4, its dielectric properties are tested using a dielectric constant tester. The dielectric constant is required to be ≤3.

5. If the dielectric constant exceeds the standard, the amount of silica nanoparticles added to the casting paste needs to be adjusted, and the modified layer needs to be prepared again to ensure the insulation performance of the core layer.

7. The method for preparing the modified solid-state battery encapsulation steel-plastic film according to claim 2, characterized in that: After vacuum hot melt torque forming in step 5, a pull-out test is used to test the bonding strength between the core layer and the steel-plastic film substrate. The bonding strength is required to be ≥50MPa. If the bonding strength does not meet the standard, the hot melt temperature, torque, or heat preservation and pressure holding time need to be adjusted, and the connection process needs to be repeated to ensure the reliability of the connection.

8. The method for preparing the modified solid-state battery encapsulation steel-plastic film according to claim 2, characterized in that: After the anti-corrosion and flame-retardant layer in step 6 has cured, its anti-corrosion performance is tested by salt spray test. The sample is placed in a 5% sodium chloride solution mist environment and placed at 35°C for 48 hours. The coating should show no rust or blistering. If corrosion occurs, the anti-corrosion and flame-retardant coating formula needs to be adjusted, the anti-corrosion and flame-retardant layer needs to be re-prepared, and the corrosion resistance of the encapsulation structure needs to be improved.

9. The method for preparing the modified solid-state battery encapsulation steel-plastic film according to claim 2, characterized in that: After the electrodes are cut in step 7, a laser thickness gauge is used to check the uniformity of the electrode thickness, and the thickness deviation is required to be ≤ ±5μm; If the deviation exceeds the standard, the cutting process parameters need to be adjusted or the electrode substrate needs to be replaced to ensure that the electrode thickness is uniform and to avoid the imbalance of internal forces of the battery after packaging due to uneven electrode thickness.

10. The method for preparing the modified solid-state battery encapsulation steel-plastic film according to claim 2, characterized in that: After the outer shell is formed in step 8, in addition to the airtightness test, the impact resistance test is also required. The drop ball impact test is adopted, in which a 1kg steel ball is dropped freely from a height of 1m to impact the surface of the outer shell. The outer shell should not be cracked or deformed. If damage occurs, the encapsulation pressure or the sealant layer formula needs to be adjusted and re-encapsulated to ensure the impact resistance of the battery pack outer shell.

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