A modified solid-state battery packaging steel plastic film and a preparation method thereof

Abstract

The application 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, an anticorrosion and flame-retardant layer and an adhesive layer, the steel-plastic film is punched to form a containing groove, the groove bottom is paved with a fish-bone-shaped ceramic base frame and a threaded cavity is formed, a matching threaded column is arranged on the bottom surface of the core layer, and the core layer is a multilayer composite structure; the edges and corners of the steel-plastic film contain a transition zone and a packaging zone, the transition zone is provided with the anticorrosion and flame-retardant layer and the adhesive layer, the packaging zone is provided with a sealing glue layer, and two steel-plastic films are packaged to form a battery pack shell. The preparation method comprises the following steps of steel-plastic film pretreatment, containing groove forming and threaded cavity processing, ceramic base frame preparation and paving, core layer preparation and threaded column forming, vacuum hot melting torque connection, anticorrosion and flame-retardant layer and adhesive layer preparation, electrode treatment and assembly, edge and corner treatment and shell forming. The scheme improves the stability and reliability of the packaging structure and guarantees the safe operation of the solid-state battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid-state battery packaging, in particular to a modified solid-state battery packaging steel-plastic film and a preparation method thereof. BACKGROUND

[0002] At present, the mainstream material used in the field of solid-state battery packaging is traditional aluminum-plastic film and ordinary steel-plastic film. The traditional aluminum-plastic film uses aluminum foil as the base material, has certain barrier property and flexibility, but has poor puncture resistance and low impact strength. In the long-term charging and discharging process of solid-state batteries, the slight expansion of the electrode volume can easily cause the aluminum-plastic film to be slightly damaged, thereby causing electrolyte leakage or external water vapor intrusion, which seriously affects the cycle stability and safety performance of the battery. The core layer of the ordinary steel-plastic film is mostly made of single metal material or simple composite structure, which lacks targeted interface optimization design, resulting in insufficient bonding force between the core layer and the inner and outer layers. In harsh working conditions such as high temperature and vibration, interlayer peeling phenomenon easily occurs, which greatly reduces the integrity of the packaging structure. On the other hand, the groove forming and internal structure assembly of the ordinary steel-plastic film mostly use normal temperature mechanical connection or simple adhesive method, and the connection stability of the groove bottom and the core layer is poor. When the battery is subjected to external force impact or temperature change, the core layer is easily displaced, which destroys the interface contact between the battery internal electrode and the electrolyte, and causes the battery performance to decay. In addition, the corrosion and flame retardant performance of the existing packaging steel-plastic film cannot meet the high safety requirements of solid-state batteries. The traditional corrosion layer mostly uses single resin material, which is easily chemically corroded in acidic or alkaline electrolyte environment, and the flame retardant efficiency of the flame retardant layer is low, which cannot effectively inhibit the flame spread in the initial stage of battery thermal runaway. At the same time, the edge packaging area of the ordinary steel-plastic film is designed simply, and the stress distribution of the transition zone and the packaging zone is uneven, which easily causes internal stress concentration during the packaging process, resulting in cracking at the edge of the packaging, and cannot realize long-term reliable sealing effect.

[0003] Among the above problems, the insufficient connection stability of the core layer and the steel-plastic film substrate is the core bottleneck restricting the performance improvement of the existing packaging steel-plastic film. This problem directly leads to the easy occurrence of interlayer displacement and peeling of the packaging structure during long-term use, which destroys the sealing environment and electrode interface inside the battery, not only shortens the service life of the battery, but also may cause safety hazards, and seriously hinders 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 packaging steel-plastic film with high-strength connection structure, excellent interlayer adhesion and reliable corrosion-resistant and flame-retardant performance has become a key problem to be solved in the current solid-state battery packaging technology field. SUMMARY

[0004] The purpose of the present application is to provide a modified solid-state battery packaging steel-plastic film and a preparation method thereof to solve the problems in the above background art.

[0005] To achieve the above purpose, the present application provides the following technical solutions:

[0006] A modified solid-state battery packaging steel-plastic film, comprising a steel-plastic film, a corrosion-resistant and flame-retardant layer, and an adhesive layer; the steel-plastic film is formed by stamping to form a containing groove, the groove bottom of the containing groove is paved with a fishbone-shaped ceramic base, and the inner surface of the containing groove is sequentially provided with a core layer, a corrosion-resistant and flame-retardant layer, and an adhesive layer by a melting method;

[0007] The groove bottom of the containing groove is provided with a plurality of threaded cavities, and the bottom surface of the core layer is provided with a plurality of threaded columns matched with the threaded cavities;

[0008] The core layer comprises a SPCE low-carbon steel layer at the center, iron-nickel bonding layers on both sides of the SPCE low-carbon steel layer, dumb dark nickel layers on both outer sides of the iron-nickel bonding layers, and flow-modified layers on both outer sides of the dumb dark nickel layers;

[0009] The edge corner section of the steel-plastic film comprises a transition zone and a packaging zone connected in series, the inner surface of the transition zone is provided with a corrosion-resistant and flame-retardant layer and an adhesive layer, the inner surface of the packaging zone is provided with a sealant layer, and two steel-plastic film structures are packaged to form an outer shell of a battery pack through a sealing area.

[0010] The preparation method of the modified solid-state battery packaging steel-plastic film is as follows:

[0011] Step 1: Pretreatment of steel-plastic film substrate

[0012] The cold-rolled steel plate with a thickness of 0.15-0.2 mm is selected as the base material of the steel-plastic film. First, the surface of the base material is cleaned by an ultrasonic cleaning device. The cleaning liquid is a mixture of deionized water and ethanol in a volume ratio of 3:1. The cleaning temperature is controlled at 50-60°C, and the cleaning time is 15-20 min to remove oil stains, dust and other impurities on the surface of the base material. After cleaning, the base material is placed in a vacuum drying oven and dried at 80-90°C under a vacuum degree of ≤1 Pa for 30-40 min to ensure that there is no water residue on the surface of the base material. Then, the surface of the base material is activated by a plasma treatment device. The plasma gas is a mixture of argon and oxygen in a volume ratio of 5:1. The treatment power is 300-350 W, and the treatment time is 5-8 min to improve the roughness and surface energy of the base material surface and enhance the bonding force with other layers.

[0013] Step 2: Containing groove stamping and thread cavity processing

[0014] The pretreated steel-plastic film base material is fixed on the mold of the numerical control punching machine. According to the size requirements of the solid-state battery, the punching pressure is set to 8-10 MPa, and the punching temperature is set to 120-150°C. The containing groove is formed on the base material by a gradual punching process. Cooling water is used to cool the mold during the punching process to ensure that the mold temperature is stable at 50-60°C, avoiding deformation of the base material due to high temperature. After the containing groove is formed, a laser processing device is used to process several thread cavities on the groove bottom. The diameter of the thread cavity is 2-3 mm, the depth is 1-1.5 mm, the distance between adjacent thread cavities is 5-8 mm, the laser processing power is controlled at 200-250 W, and the processing speed is 5-8 mm / s. After processing, compressed air is used to blow the groove bottom to remove metal debris generated during processing.

[0015] Step 3: Fishbone-shaped ceramic base preparation and laying

[0016] The ceramic raw material is selected by mixing alumina and zirconia in a mass ratio of 7:3, a polyvinyl alcohol binder with a mass fraction of 5% is added, and the ceramic slurry is prepared after stirring uniformly; the ceramic slurry is poured into a fishbone-shaped mold, dried at 150-180°C for 2-3h, and a ceramic green body is formed; then the ceramic green body is placed in a high-temperature sintering furnace and sintered at 1200-1300°C for 4-5h, to obtain a fishbone-shaped ceramic base, the porosity of the base after sintering is controlled at 10-15%, ensuring that it has certain buffering performance; the prepared fishbone-shaped ceramic base is laid on the bottom of the containing groove, and the position of the base is ensured to be accurate by using a positioning tool, and then the steel plastic film base material is transferred to a vacuum hot pressing equipment, and hot pressing is performed under the conditions of a vacuum degree ≤1Pa, a temperature of 200-220°C, and a pressure of 3-5MPa for 10-15min, so that the fishbone-shaped ceramic base is tightly combined with the bottom of the containing groove;

[0017] Step 4: Core layer preparation and threaded column forming

[0018] First, the core layer materials are prepared, the SPCE low carbon steel layer is selected from SPCE cold rolled steel plate with a thickness of 0.08-0.1mm, the iron-nickel bonding layer is prepared on both sides of the SPCE low carbon steel layer by electroplating process, the electroplating solution is a water solution of nickel sulfate and ferrous chloride mixed in 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 dull nickel layer is prepared on the outside of the iron-nickel bonding layer by chemical plating process, the chemical plating solution is a mixed solution of nickel sulfate, sodium hypophosphite and sodium citrate, the concentration of nickel sulfate is 20-30g / L, the concentration of sodium hypophosphite is 15-20g / L, and the concentration of sodium citrate is 10-15g / L, the chemical plating temperature is 80-90°C, the plating time is 20-25min, and the thickness of the dull nickel layer is controlled at 3-5μm; finally, a flow casting modified layer is prepared on the outside of the dull nickel layer by flow casting process, the flow casting slurry is prepared by mixing polyimide resin and silicon dioxide nanoparticles in a mass ratio of 9:1, the flow casting speed is 0.5-1m / min, and the flow casting temperature is 120-140°C, so that the thickness of the flow casting modified layer reaches 10-12μm, and a complete core layer is obtained; then a plurality of threaded columns are machined on the bottom surface of the core layer by mechanical machining process, the size of the threaded columns matches the threaded cavity of the bottom of the containing groove, and the surface of the threaded columns is polished after machining to remove burrs;

[0019] Step 5: Vacuum hot melting torque forming connection

[0020] Put the prepared core layer in the containing groove, align the threaded column on the bottom surface of the core layer with the threaded cavity on the bottom of the containing groove; transfer the assembled steel-plastic film structure to the vacuum torque forming equipment, close the equipment and vacuumize, so that the vacuum degree in the equipment reaches ≤1Pa; then heat to 250-280℃, so that the contact area between the core layer and the steel-plastic film is in a hot molten state; start the torque driving device, apply a torque of 5-8 N·m to the core layer, drive the threaded column to rotate and screw into the threaded cavity, the screwing speed is 2-3 r / min, after screwing is completed, the temperature and torque are kept unchanged, and the temperature and pressure are kept for 15-20 min; then slowly cool to room temperature, the cooling rate is controlled at 5-8℃ / min, the high-strength connection of the core layer and the steel-plastic film base material is completed, which is the core technical point, through the combination of vacuum hot melting and torque forming, the connection stability is greatly improved;

[0021] Step 6: Preparation and laying of corrosion-resistant and flame-retardant layer and adhesive layer

[0022] First, prepare the corrosion-resistant and flame-retardant layer material, mix epoxy resin, magnesium hydroxide flame retardant and silane coupling agent according to the mass ratio of 8:1.5:0.5, add appropriate amount of acetone solvent and stir uniformly to prepare the corrosion-resistant and flame-retardant coating; use spraying process to uniformly coat the corrosion-resistant and flame-retardant coating on the inner surface of the containing groove and the outer surface of the core layer, the spraying thickness is controlled at 15-18μm, after spraying is completed, solidify at 150-160℃ for 30-35min to form the corrosion-resistant and flame-retardant layer; then prepare the adhesive layer material, select hot melt polyurethane adhesive, heat it to 180-200℃ to melt it; use roll coating process to coat the melted polyurethane adhesive on the outer surface of the corrosion-resistant and flame-retardant layer, the coating thickness is 8-10μm, after coating is completed, naturally cool to 50-60℃ to ensure that the adhesive layer has good adhesion;

[0023] Step 7: Electrode processing and assembly adaptation

[0024] Select the positive and negative electrodes of the solid-state battery, first use the ultrasonic cleaning equipment to clean the surface of the electrode, remove the residual electrolyte and impurities on the surface, the cleaning liquid is dimethyl carbonate, the cleaning time is 10-15min, after cleaning is completed, dry in the vacuum drying oven at 80-90℃ for 20-25min; then chamfer the edge of the electrode to avoid the sharp part of the electrode edge piercing the packaging layer; according to the size of the steel-plastic film containing groove, cut the electrode to ensure that the electrode size is adapted to the containing groove; put the treated electrode into the containing groove, so that the electrode is tightly attached to the adhesive layer on the surface of the core layer, use positioning clamps to fix the electrode position to prevent the electrode from shifting during the subsequent packaging process;

[0025] Step 8: Corner transition zone and packaging area processing and shell forming. First, the corner section of the steel-plastic film is processed in the transition zone. A numerical control milling is used to process the corner section into a transition zone with a slope of 30-45°. Cooling lubricant is used during the processing to avoid overheating of the processing area. Then, the inner surface of the transition zone is prepared and coated with the corrosion-resistant and flame-retardant layer and the adhesive layer according to the process of Step 6. The sealing glue material is prepared, and the modified epoxy resin sealing glue is uniformly coated on the inner surface of the packaging area with a coating thickness of 20-25μm. After coating, pre-curing is carried out at 120-130℃ for 10-15min. Two steel-plastic films with the same structure are aligned, and the receiving groove of one steel-plastic film is attached to the packaging area of the other steel-plastic film. The two steel-plastic films are placed in a vacuum packaging device and packaged at a vacuum degree of ≤1Pa, a temperature of 180-200℃, and a pressure of 4-6MPa for 20-25min to form the battery pack shell. Finally, the packaged shell is subjected to air tightness detection using a helium mass spectrometer with a leak detection sensitivity of 1×10⁻ 9 Pa・m³ / s to ensure that the shell has no leakage.

[0026] Based on the above, it is further explained that after the plasma treatment in Step 1, the surface roughness of the steel-plastic film substrate is detected 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 for reactivation treatment until the roughness meets the requirements, which further ensures the bonding basis of the substrate and subsequent layers.

[0027] Based on the above, it is further explained that after the laser processing of the thread cavity in Step 2, the integrity of the internal thread structure of the thread cavity is observed using a metallographic microscope. If there are thread defects or deformations, laser repair processing is used for repair. After repair, the thread cavity is detected again to ensure that all thread cavities have complete thread forms and accurate sizes to avoid affecting the subsequent thread connection effect due to thread cavity defects.

[0028] Based on the above, it is further explained that after the sintering of the ceramic base frame in Step 3, the bending strength of the ceramic base frame is detected using 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 to reprepare the ceramic base frame to ensure that the base frame has sufficient strength to support the internal structure of the battery.

[0029] Based on the above, it is further explained that after the preparation of the flow-modified layer in Step 4, the dielectric performance of the flow-modified layer is detected using a dielectric constant tester, and the dielectric constant is required to be ≤3.5 (at a frequency of 1kHz). If the dielectric constant exceeds the standard, the amount of silicon dioxide nanoparticles in the flow slurry needs to be adjusted to reprepare the flow-modified layer to ensure the insulation performance of the core layer.

[0030] Based on the above, further explained: in step 5, after vacuum hot melting torque forming, the bonding strength between the core layer and the steel plastic film substrate is detected by tensile test, and the bonding strength is required to be greater than or equal to 50MPa; if the bonding strength does not meet the standard, the hot melting temperature, torque size or holding time needs to be adjusted, and the connection process is re-performed to ensure the reliability of the connection.

[0031] Based on the above, further explained: in step 6, after the corrosion-resistant and flame-retardant layer is cured, the corrosion resistance is detected by salt spray test, the sample is placed in a 5% sodium chloride solution mist environment at 35℃ for 48h, and the coating is required to be free of rust and blistering; if corrosion occurs, the corrosion-resistant and flame-retardant coating formula needs to be adjusted, and the corrosion-resistant and flame-retardant layer is re-prepared to improve the corrosion resistance of the packaging structure.

[0032] Based on the above, further explained: in step 7, after the electrode is cut, the thickness uniformity of the electrode is detected by laser thickness gauge, and the thickness deviation is required to be less than or equal to ±5μm; if the deviation is out of standard, the cutting process parameters need to be adjusted or the electrode substrate needs to be replaced to ensure the uniformity of the electrode thickness and avoid the imbalance of the internal force of the battery after packaging due to the uneven thickness of the electrode.

[0033] Based on the above, further explained: in step 8, after the shell is formed, in addition to the air tightness detection, the impact resistance test is also needed, the drop ball impact test is used, a 1kg steel ball is dropped from 1m high to impact the shell surface, and the shell is required to be free of rupture and deformation; if damage occurs, the packaging pressure or the sealant layer formula needs to be adjusted, and the packaging is re-performed to ensure the impact resistance of the battery pack shell.

[0034] Compared with the prior art, the beneficial effects of the present application are:

[0035] The modified solid-state battery packaging steel plastic film and the preparation method, through multi-dimensional structure design and process innovation, realize significant performance improvement. On the structure, the fishbone-shaped ceramic base frame at the bottom of the accommodating groove can enhance the supporting force of the groove body, buffer the impact caused by the volume change of the electrode during battery charging and discharging; the threaded cavity cooperates with the threaded column, combined with the vacuum hot melting torque forming process, greatly improves the connection stability of the core layer and the steel plastic film substrate, solves the problem of displacement and peeling of traditional connection. The multi-layer composite structure of the core layer takes the SPCE low carbon steel layer as the core, optimizes the interface bonding of the iron-nickel combination layer, improves the corrosion resistance of the dumb dark nickel layer, and guarantees the insulation of the cast modified layer, thereby synergistically improving the comprehensive performance of the core layer. The setting of the corrosion-resistant and flame-retardant layer and the adhesive layer enhances the resistance of the packaging structure to electrolyte corrosion and the interlayer bonding force, and the sealant layer in the packaging area cooperates with the vacuum packaging process to ensure the air tightness of the shell. The overall scheme effectively improves the structural strength, corrosion resistance and sealing reliability of the packaging steel plastic film, prolongs the service life of the solid-state battery, and ensures its safe and stable operation. BRIEF DESCRIPTION OF DRAWINGS

[0036] Fig. 1 The steel plastic film front structure schematic diagram of the present application is shown in the figure.

[0037] Fig. 2 The steel plastic film cross section structure schematic diagram of the present application is shown in the figure.

[0038] Fig. 3 The core layer structure schematic diagram of the present application is shown in the figure. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0040] EMBODIMENT

[0041] Please refer to Figs. 1-3 The present application provides a technical solution:

[0042] A modified solid-state battery packaging steel plastic film, comprising a steel plastic film 1, a corrosion-resistant flame-retardant layer 2 and an adhesive layer 3; the steel plastic film 1 is formed by stamping to form a containing groove 11, the groove bottom of the containing groove 11 is paved with a fishbone-shaped ceramic base 4, and the inner surface of the containing groove 11 is sequentially provided with a core layer 5, a corrosion-resistant flame-retardant layer 2 and an adhesive layer 3 by a melting method;

[0043] The groove bottom of the containing 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 columns 7 matched with the threaded cavities 6;

[0044] The core layer 5 comprises a SPCE low-carbon steel layer 51 located at the center, iron-nickel bonding layers 52 located on both sides of the SPCE low-carbon steel layer 51, dumb dark nickel layers 53 located on the outer sides of the iron-nickel bonding layers 52, and flow casting modified layers 54 located on the outer sides of the dumb dark nickel layers 53.

[0045] The edge corner section of the steel plastic film 1 comprises a transition zone 8 and a packaging zone 9 connected in series, the inner surface of the transition zone 8 is provided with the corrosion-resistant flame-retardant layer 2 and the adhesive layer 3, the inner surface of the packaging zone 9 is provided with a sealant layer 91, and the two steel plastic film structures are packaged to form the shell of the battery pack through the sealing area.

[0046] Technical content analysis: The scheme mainly adopts the composite design of "steel-plastic film base material + multi-layer functional coating + innovative connection structure", which solves the multiple technical bottlenecks of traditional packaging materials (such as aluminum-plastic film and ordinary steel-plastic film) in structural strength, interlayer bonding force, corrosion and flame retardance, and sealing reliability. For the first time, the fishbone-shaped ceramic base is combined with the vacuum hot melt torque forming process, and a five-layer composite core layer structure is designed, realizing the integration of the functions of "support - connection - protection - insulation" of the packaging steel-plastic film.

[0047] From the structural design, the accommodating groove 11 formed by stamping of the steel-plastic film 1 provides a precise accommodating space for the battery electrode, and the fishbone-shaped ceramic base 4 laid at the groove bottom breaks through the traditional plane support structure. Its "fishbone-shaped" three-dimensional structure can disperse stress, and with a porosity of 10-15%, it can not only improve the support strength (bending strength ≥ 300MPa) through the high hardness characteristics of aluminum oxide and zirconium oxide (7:3), but also can utilize the porosity to buffer the volume micro-expansion of the electrode during battery charging and discharging, avoiding deformation of the groove body. The cooperation design of the threaded cavity 6 and the threaded column 7 changes the traditional mechanical connection or simple bonding method, and through the combination of threaded engagement and hot melting, the connection strength of the core layer 5 and the steel-plastic film 1 is improved to ≥50MPa, completely solving the problem of interlayer displacement and peeling.

[0048] The five-layer composite structure (SPCE low-carbon steel layer 51 - iron-nickel combination layer 52 - dull dark nickel layer 53 - flow modification layer 54) of the core layer 5 is an innovative upgrade of the traditional single core layer: the SPCE low-carbon steel layer 51 as the core framework, with a thickness of 0.08-0.1mm and high toughness, it can reduce the overall packaging thickness while ensuring the structural strength; the iron-nickel combination layer 52 realizes atomic-level combination of steel layer and nickel layer through electroplating process (5:1 ratio of nickel sulfate and ferrous chloride), solving the interface compatibility problem of different metal materials and improving the interlayer adhesion; the dull dark nickel layer 53 adopts chemical plating process, its amorphous structure can form a dense passivation film, greatly improving the electrolyte corrosion resistance; the flow modification layer 54 takes polyimide resin as the matrix and adds 10% silicon dioxide nanoparticles, which not only retains the high temperature resistance of polyimide (long-term temperature resistance > 200℃), but also makes the dielectric constant ≤3.5 (1kHz) through the insulating properties of nanoparticles, realizing the insulation protection of the core layer and avoiding the risk of internal short circuit of the battery.

[0049] 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.

[0050] The method for preparing the modified solid-state battery encapsulation steel-plastic film is as follows:

[0051] Step 1: Pretreatment of steel-plastic film substrate

[0052] 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.

[0053] 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.

[0054] 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.

[0055] From the technical principle, ultrasonic cleaning (50-60℃, 15-20min) utilizes ultrasonic cavitation effect to efficiently remove rolling oil stains and dust on the surface of cold-rolled steel plate. The mixture of deionized water and ethanol (3:1) can not only enhance oil stain dissolution through the lipophilicity of ethanol, but also avoid secondary residue of impurities through deionized water. The cleaning efficiency is improved by more than 30% compared with traditional solvent cleaning. Vacuum drying (80-90℃, vacuum degree≤1Pa) can avoid high-temperature oxidation while ensuring that the residual amount of water on the substrate surface is ≤0.1%, preventing the formation of bubbles between the subsequent coating and the substrate, which affects the adhesion.

[0056] Plasma activation treatment is the core innovation of this step: argon as an inert gas can form a micro concave-convex structure (roughness Ra 0.3-0.5μm) on the substrate surface by high-energy particle bombardment, increasing the specific surface area; oxygen can introduce polar groups such as hydroxyl and carboxyl groups on the substrate surface, increasing the surface energy from 30mN / m to more than 50mN / m, providing a dual guarantee of “physical anchoring” and “chemical adsorption” for the combination of the subsequent core layer and corrosion-resistant layer. Real-time detection of roughness by atomic force microscopy ensures the consistency of each batch of substrate treatment, avoiding fluctuations in product performance due to differences in surface state. This detail control is the key to product stability in large-scale production.

[0057] Step 2: Containing groove stamping and thread cavity processing

[0058] The pretreated steel-plastic film substrate is fixed on the mold of the numerical control punching machine. According to the size requirements of the solid-state battery, the punching pressure is set to 8-10MPa and the punching temperature is set to 120-150℃. The containing groove 11 is formed on the substrate by gradual punching process. Cooling water is used to cool the mold during the punching process to ensure that the mold temperature is stable at 50-60℃, avoiding deformation of the substrate due to high temperature. After the containing groove is formed, a laser processing equipment is used to process several thread cavities 6 on the groove bottom of the containing groove 11. The diameter of the thread cavity is 2-3mm, the depth is 1-1.5mm, the distance between adjacent thread cavities is 5-8mm, the laser processing power is controlled at 200-250W, and the processing speed is 5-8mm / s. After processing, compressed air is used to blow the groove bottom to remove metal debris generated during processing;

[0059] After laser processing of the thread cavity, the internal thread structure integrity of the thread cavity is observed by metallographic microscope. If there are thread defects or deformation, laser repair is needed. After repair, it is detected again to ensure that the internal thread profile of all thread cavities is complete and the size is accurate, avoiding the influence of thread cavity defects on the subsequent thread connection effect.

[0060] Analysis of the above technical content: This step adopts the combined process of "progressive hot stamping + laser precision machining", which solves the problem of substrate deformation and low thread machining precision caused by traditional stamping. For the first time, cooling waterway temperature control and laser repair technology are applied to the processing of packaging steel plastic film tank body, realizing the dual protection of containment tank size precision and thread cavity structure integrity.

[0061] From the perspective of stamping process, progressive stamping (pressure 8-10 MPa, temperature 120-150℃) is formed by multiple steps to avoid stress concentration caused by one-time stamping, while hot stamping can reduce the yield strength of cold rolled steel sheet and reduce the amount of springback, so that the size tolerance of the containment tank can be controlled within ±0.05mm. The cooling waterway stabilizes the mold temperature at 50-60℃, which can prevent the grain growth of the substrate due to high temperature (the local temperature during stamping can reach more than 200℃), and ensure that the mechanical properties (tensile strength ≥300MPa) of the substrate are not affected. This design breaks through the limitations of traditional cold stamping "hard forming", and realizes the balance between "soft forming" and performance retention.

[0062] Laser machining thread cavity (power 200-250W, speed 5-8mm / s) is the key guarantee of thread connection structure: the high energy density of laser can realize precise forming of thread profile, the size precision of thread cavity with diameter 2-3mm and depth 1-1.5mm can reach ±0.02mm, and the uniform distribution design with adjacent spacing 5-8mm can balance the stress of the core layer and avoid local stress overload. Compressed air blowing (pressure 0.5MPa) can remove metal debris in time to prevent debris from remaining and causing poor thread engagement; the combination of metallographic microscope detection and laser repair technology can control the thread defect rate to less than 0.1%, ensuring that each thread cavity can precisely cooperate with the thread column. This "machining-detection-repair" closed-loop control is the basis for the reliability of subsequent vacuum hot melt torque connection.

[0063] Step 3: Fishbone-shaped ceramic base preparation and laying

[0064] The ceramic raw material is prepared by mixing alumina and zirconia in a mass ratio of 7:3, adding 5% polyvinyl alcohol binder by mass fraction, and stirring uniformly to form a ceramic slurry; the ceramic slurry is poured into a fishbone-shaped mold, dried at 150-180°C for 2-3h to form a ceramic green body; then the ceramic green body is placed in a high-temperature sintering furnace and sintered at 1200-1300°C for 4-5h to obtain a fishbone-shaped ceramic base 4, the porosity of the base after sintering is controlled at 10-15% to ensure that it has certain buffering performance; the prepared fishbone-shaped ceramic base 4 is laid on the bottom of the containing groove 11, and the position of the base is accurately ensured by using a positioning tool, and then the steel-plastic film base material is transferred to a vacuum hot pressing equipment, and hot pressing is performed under the conditions of a vacuum degree ≤1Pa, a temperature of 200-220°C, and a pressure of 3-5MPa for 10-15min, so that the fishbone-shaped ceramic base 4 is tightly combined with the bottom of the containing groove.

[0065] After sintering of the ceramic base, the bending strength of the ceramic base is detected by 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 base is prepared again to ensure that the base has sufficient strength to support the internal structure of the battery.

[0066] Analysis of the above technical content: This step adopts the process route of “slurry forming - high-temperature sintering - vacuum hot pressing combination”, which solves the problems of brittle cracking of traditional ceramic bases and poor combination of ceramic bases with steel-plastic films. For the first time, the fishbone-shaped mold forming and porosity precise control technology are applied to the packaging steel-plastic film support structure, realizing the synergistic performance of “high strength” and “high buffering” of the ceramic base.

[0067] From the preparation of the ceramic base, the ratio of alumina to zirconia (7:3) is the core of performance optimization: alumina provides high hardness (Mohs hardness 9) to ensure support strength; zirconia has excellent fracture toughness (10MPa・m¹ / ²) to improve the brittleness of the ceramic and avoid cracking when impacted. Adding 5% polyvinyl alcohol binder can ensure the slurry forming property and completely volatilize (above 300°C) during sintering without leaving impurities. Drying at 150-180°C for 2-3h can slowly remove the water in the slurry to prevent the green body from cracking; high-temperature sintering at 1200-1300°C for 4-5h can fully densify the ceramic particles while controlling the porosity at 10-15% - too low porosity will result in insufficient buffering performance, and too high porosity will reduce the strength, and this precise control is achieved by adjusting the sintering heating rate (5°C / min), which is a process detail innovation.

[0068] Vacuum hot-pressing (temperature 200-220℃, pressure 3-5MPa) is the key to the combination of ceramic base frame and steel plastic film: the vacuum environment can exclude air at the interface, avoiding the combination failure caused by air bubbles; during the hot-pressing process, the micro protrusions on the surface of the steel plastic film form a "fitting structure" with the pores of the ceramic base frame, and the bonding strength can reach more than 15MPa, far exceeding the traditional bonding (bonding strength less than 5MPa). The three-point bending test (span 20mm, loading rate 1mm / min) monitors the strength of the base frame in real time to ensure that the bending strength is ≥300MPa, which can prevent the containment groove from collapsing when subjected to a 10MPa impact, providing reliable support for the internal structure of the battery.

[0069] Step 4: Core layer preparation and threaded column forming

[0070] First, prepare the core layer 5 component materials, the SPCE low carbon steel layer 51 is selected as a 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 process, the electroplating solution is a water 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, the matte nickel layer 53 is prepared on the outside of the iron-nickel bonding layer 52 by chemical plating process, 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, and the concentration of sodium citrate is 10-15g / L, the chemical plating temperature is 80-90℃, the plating time is 20-25min, and the thickness of the matte nickel layer is controlled at 3-5μm; finally, the cast modified layer 54 is prepared on the outside of the matte nickel layer 53 by cast forming process, the cast slurry is a mixture of polyimide resin and silicon dioxide nanoparticles at a mass ratio of 9:1, the casting speed is 0.5-1m / min, the casting temperature is 120-140℃, so that the thickness of the cast modified layer reaches 10-12μm, and a complete core layer 5 is obtained; then, a plurality of threaded columns 7 are machined on the bottom surface of the core layer 5 by mechanical machining process, the size of the threaded columns matches the threaded cavity 6 of the bottom of the containment groove, and the surface of the threaded columns is polished after machining to remove burrs;

[0071] Among them, after the preparation of the cast modified layer, a dielectric constant tester is used to detect its dielectric properties, and the dielectric constant is required to be ≤3.5 (at a frequency of 1kHz); if the dielectric constant is out of standard, the amount of silicon dioxide nanoparticles in the cast slurry needs to be adjusted, and the cast modified layer needs to be prepared again to ensure the insulation performance of the core layer.

[0072] Analysis of the above technical content: This step adopts the process combination of "multi-layer plating film + flow casting + mechanical precision machining", which solves the problem that the traditional core layer "strength - corrosion resistance - insulation" performance is difficult to balance. For the first time, electroplating - chemical plating composite plating film and silica nanoparticle modified flow casting technology are applied to the preparation of the core layer, realizing the functional synergy of the five-layer structure.

[0073] From the preparation of each layer of the core layer, the SPCE low carbon steel layer (thickness 0.08-0.1mm) selects cold rolled steel plate, whose yield strength is ≥280MPa and elongation is ≥30%, which can not only bear torque and impact as the core skeleton, but also reduce the overall thickness of the package through ultra-thin thickness (40% thinner than ordinary steel core layer). The iron-nickel bonding layer (thickness 5-8μm) adopts electroplating process, and the electroplating solution formula of nickel sulfate and ferrous chloride (5:1) can control the nickel content in the plating layer to 80-85%, forming a Fe-Ni solid solution, whose thermal expansion coefficient (13×10⁻ 6 / ℃) is close to that of SPCE low carbon steel (12×10⁻ 6 / ℃), which can eliminate the interfacial thermal stress caused by temperature change and avoid interlayer peeling. This thermal matching design is the key to the stability of the core layer under high temperature conditions.

[0074] The dull dark nickel layer (thickness 3-5μm) adopts chemical plating process, with nickel sulfate (20-30g / L) providing nickel source, sodium hypophosphite (15-20g / L) as reducing agent, and sodium citrate (10-15g / L) adjusting pH value (5.5-6.0), which can form amorphous nickel plating layer. The amorphous structure has no grain boundary defects, which can effectively block the penetration of electrolyte (such as LiPF6), and there is no rust in the salt spray test (5% sodium chloride, 35℃, 48h), and the corrosion resistance is more than 2 times higher than that of traditional bright nickel plating layer. The flow casting modified layer (thickness 10-12μm) of polyimide-silica composite system can form an "insulation barrier" in the polyimide matrix through the dispersion of silica nanoparticles (particle size 50nm), so that the dielectric constant is ≤3.5 (1kHz), and the wear resistance of the coating is improved by 30% due to the enhancement of nanoparticles, avoiding scratches during electrode assembly.

[0075] Mechanical processing (precision grade IT6) and polishing (surface roughness Ra 0.1μm) of the threaded column can ensure that the fitting clearance of the threaded column and the threaded cavity is ≤0.01mm, providing precise positioning for subsequent torque connection and avoiding the decrease of connection strength caused by fitting deviation.

[0076] Step 5: vacuum hot melting torque forming connection

[0077] The prepared core layer 5 is placed in the containing groove 11, so that the threaded column 7 at the bottom surface of the core layer is aligned with the threaded cavity 6 at the bottom of the containing groove; the assembled steel-plastic film structure is transferred to a vacuum torque forming equipment, the equipment is closed and vacuumized, so that the vacuum degree in the equipment is ≤1 Pa; then the temperature is raised to 250-280℃, so that the contact area between the core layer 5 and the steel-plastic film 1 is in a hot melting state; the torque driving device is started, a torque of 5-8 N·m is applied to the core layer 5, the threaded column 7 is rotated and screwed into the threaded cavity 6, the screwing speed is 2-3 r / min, after screwing is completed, the temperature and torque are kept unchanged, and the temperature and pressure are kept for 15-20 min; then the temperature is slowly lowered to room temperature at a rate of 5-8℃ / min, the high-strength connection between the core layer and the steel-plastic film base material is completed, and this step is a core technical point. Through the combination of vacuum hot melting and torque forming, the connection stability is greatly improved.

[0078] After vacuum hot melting torque forming, the bonding strength between the core layer and the steel-plastic film base material is detected by tensile test, and the bonding strength is required to be ≥50 MPa; if the bonding strength does not meet the standard, the hot melting temperature, torque size or holding time need to be adjusted, and the connection process is re-performed to ensure the connection reliability.

[0079] Analysis of the above technical content: This step adopts the innovative process of “vacuum environment + hot melting + torque screwing”, which solves the problems of low bonding strength and easy environmental influence of traditional connection methods. Vacuum hot melting and torque forming are first combined to be applied to the connection of the encapsulated steel-plastic film core layer, realizing the integrated connection of “physical engagement” and “chemical combination”.

[0080] From the technical principle, the vacuum environment (vacuum degree ≤1 Pa) can exclude air and water vapor, avoid oxidation of the contact area between the core layer and the steel-plastic film at high temperature (250-280℃, metal is easy to react with oxygen to form an oxide film, affecting the bonding), and prevent connection failure caused by air bubble residue. The hot melting temperature (250-280℃) is accurately controlled in the melting interval of the core layer cast modified layer (polyimide glass transition temperature 240℃) and the surface coating of the steel-plastic film, so that the contact area forms a semi-melting state. At this time, a torque of 5-8 N·m (screwing speed 2-3 r / min) is applied, which can form a “micro-welding” between the engagement surface of the threaded column and the threaded cavity, and the bonding strength is increased from 20 MPa of traditional mechanical connection to ≥50 MPa.

[0081] The heat preservation and pressure (15-20 min) can promote the diffusion of interface atoms, forming a diffusion layer (thickness 50-100 nm), further enhancing the connection stability; slow cooling (5-8 ℃ / min) can avoid the stress concentration caused by large temperature difference, prevent the occurrence of micro cracks. The tensile test (loading rate 1 mm / min) detects the bonding strength in real time, ensures the connection reliability of each batch of products, which breaks through the traditional "mechanical locking" or "chemical bonding" single connection mode, and creates a new path for the "heat-force-chemical" collaborative connection of the packaging steel plastic film.

[0082] Step 6: Preparation and laying of corrosion and flame retardant layer and adhesive layer

[0083] First, the corrosion and flame retardant layer 2 material is prepared, the epoxy resin, magnesium hydroxide flame retardant and silane coupling agent are mixed in a mass ratio of 8:1.5:0.5, and a proper amount of acetone solvent is added and stirred uniformly to prepare a corrosion and flame retardant coating; the corrosion and flame retardant coating is uniformly coated on the inner surface of the containing groove 11 and the outer surface of the core layer 5 by spraying process, and the spraying thickness is controlled at 15-18 μm; after spraying, it is cured at 150-160 ℃ for 30-35 min to form a corrosion and flame retardant layer 2; then the adhesive layer 3 material is prepared, and a hot melt polyurethane adhesive is selected, which is heated to 180-200 ℃ to melt; the melted polyurethane adhesive is coated on the outer surface of the corrosion and flame retardant layer 2 by roll coating process, and the coating thickness is 8-10 μm; after coating, it is naturally cooled to 50-60 ℃ to ensure that the adhesive layer has good adhesion;

[0084] Among them, after the corrosion and flame retardant layer is cured, the corrosion resistance is detected by salt spray test, the sample is placed in a 5% sodium chloride solution mist environment, and placed at 35 ℃ for 48 h, the coating is required to be free of rust and blistering; if corrosion occurs, the corrosion and flame retardant coating formula needs to be adjusted and the corrosion and flame retardant layer is prepared again to improve the corrosion resistance of the packaging structure.

[0085] Analysis of the above technical content: this step adopts the process of "composite coating spraying + hot melt glue roll coating", which solves the problems of poor electrolyte resistance, low flame retardant efficiency and unstable adhesion of the traditional corrosion layer. For the first time, magnesium hydroxide flame retardant and silane coupling agent are compounded and applied to the corrosion layer to realize the functions of "corrosion - flame retardant", and the adhesion stability is ensured by controlling the temperature of the hot melt glue.

[0086] From the preparation of the corrosion-resistant flame-retardant layer, the ratio of 8:1.5:0.5 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 to block the penetration of electrolyte; magnesium hydroxide (particle size 1 μm) decomposes and absorbs heat at high temperatures (340°C), releasing water vapor, which not only reduces the temperature but also dilutes oxygen, and the flame retardant level can reach V-0 level (UL94 standard); silane coupling agent (such as KH550) can improve the compatibility of magnesium hydroxide and epoxy resin, avoid the agglomeration of flame retardant, and make the flatness of the coating (Ra 0.2 μm) improve by 40%. Controlling the spraying thickness of 15-18 μm can ensure the corrosion-resistant flame-retardant performance while avoiding the reduction of the volume of the accommodation groove caused by the over-thickness of the coating.

[0087] Curing at 150-160°C (30-35min) can make the epoxy resin fully cross-linked to form a three-dimensional network structure. The salt spray test (5% NaCl, 35°C, 48h) has no rust and blistering, and the coating adhesion remains ≥10MPa after 1000h of electrolyte immersion (1mol / L LiPF6-EC / DEC), far exceeding the traditional corrosion-resistant layer (adhesion decreases to 5MPa after 500h).

[0088] The adhesive layer uses a hot melt polyurethane adhesive (melting point 180°C), which is melted at 180-200°C and then rolled (thickness 8-10 μm), and then naturally cooled to 50-60°C. At this time, the adhesive is in a semi-melted state, and the adhesion (peel strength ≥5N / 25mm) is optimal, which can ensure close fitting with the electrode and further melting in the subsequent packaging process to form secondary adhesion, avoiding electrode displacement. This "melting - cooling - remelting" adhesion control design is the key to the stability of electrode assembly and shell packaging.

[0089] Step 7: Electrode processing and assembly adaptation

[0090] Selecting the positive and negative electrodes of the solid-state battery, first clean the electrode surface with an ultrasonic cleaning device to remove residual electrolyte and impurities on the surface. The cleaning liquid is dimethyl carbonate, and the cleaning time is 10-15min. After cleaning, dry the electrode in a vacuum drying oven at 80-90°C for 20-25min. Then chamfer the electrode edges to avoid sharp parts of the electrode piercing the packaging layer. According to the size of the steel-plastic film accommodation groove 11, cut the electrode to ensure that the electrode size is adapted to the accommodation groove. Place the processed electrode into the accommodation groove 11 to make the electrode closely fit with the adhesive layer 3 on the surface of the core layer 5. Use a positioning clamp to fix the electrode position to prevent electrode displacement during the subsequent packaging process.

[0091] After the electrode is cut, the thickness uniformity of the electrode is detected by a laser thickness gauge, and the thickness deviation is required to be ≤±5 μm; if the deviation exceeds the standard, the cutting process parameters need to be adjusted or the electrode substrate needs to be replaced to ensure the thickness uniformity of the electrode and avoid the imbalance of internal stress of the battery after packaging due to uneven thickness of the electrode.

[0092] After analyzing the above technical content, it is found that the process of “ultrasonic cleaning + chamfering + precise cutting” is adopted to solve the assembly problems caused by impurities remaining on the electrode surface, edge piercing the packaging layer, and size mismatch. For the first time, a laser thickness gauge is applied to electrode thickness detection, realizing precise adaptation of the electrode to the containing groove and avoiding internal stress imbalance.

[0093] From the perspective of electrode processing, ultrasonic cleaning (cleaning liquid dimethyl carbonate, time 10-15 min) can efficiently remove residual electrolyte (such as Li2CO3) and conductive agent (such as carbon black) impurities on the electrode surface by utilizing the high solubility of dimethyl carbonate, avoiding the increase of electrode contact resistance caused by impurities (contact resistance reduced by 10% after cleaning). Vacuum drying (80-90℃, 20-25min) can remove water from the electrode (water content ≤50ppm), preventing hydrolysis reactions (such as LiPF6+H2O→LiF+POF3+HF) from occurring inside the battery, and ensuring the cycle performance of the battery (capacity retention rate ≥90% after 1000 cycles).

[0094] Edge chamfering of the electrode (chamfer radius 0.5mm) can eliminate sharp edges and avoid piercing the adhesive layer and corrosion-resistant layer during packaging (pressure 4-6MPa), reducing the packaging damage rate from 5% to below 0.1%. The electrode is cut according to the size of the containing groove (size tolerance ±0.1mm), ensuring that the gap between the electrode and the containing groove is ≤0.2mm, avoiding electrode shaking caused by excessive gap or assembly extrusion caused by too small gap. Laser thickness gauge detects thickness uniformity (deviation ≤±5 μm), which can prevent excessive local pressure caused by uneven electrode thickness and avoid electrolyte interface rupture. This detailed control is an important guarantee for the stability of the solid-state battery interface.

[0095] Positioning fixture fixation (clamping force 5N) can ensure that the displacement of the electrode during packaging is ≤0.05mm, avoiding misalignment of the electrode and the current collector, and ensuring the current conduction efficiency.

[0096] Step 8: Corner transition zone and packaging area processing and shell forming. First, the corner section of the steel-plastic film 1 is processed into a transition zone 8 with a slope of 30-45° using numerical control milling equipment. Cooling lubricant is used during processing to avoid overheating of the processing area. Then, the anticorrosive 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 of Step 6. The sealant layer 91 material is prepared, and modified epoxy sealant is selected and uniformly coated on the inner surface of the packaging area 9 with a coating thickness of 20-25μm. After coating, pre-curing is performed at 120-130℃ for 10-15min. Two steel-plastic films with the same structure are aligned, with the containment groove 11 of one steel-plastic film adhering to the packaging area 9 of the other steel-plastic film, and placed in a vacuum packaging device. The packaging is performed under the conditions of vacuum degree ≤1Pa, temperature 180-200℃, and pressure 4-6MPa for 20-25min to complete the formation of the battery pack shell. Finally, the packaged shell is subjected to air tightness testing using a helium mass spectrometer with a leak detection sensitivity of 1×10⁻ 9 Pa・m³ / s to ensure that the shell has no leakage.

[0097] After the shell is formed, in addition to air tightness testing, impact resistance testing is also required. The drop ball impact test is used, in which a 1kg steel ball is dropped from a height of 1m to impact the surface of the shell. The shell is required to have no cracking or deformation. If damage occurs, the packaging pressure or sealant layer formulation needs to be adjusted and the packaging needs to be re-performed to ensure the impact resistance of the battery pack shell.

[0098] Analysis of the above technical content: This step uses the process of "numerical control milling of transition zone + pre-curing of sealant + vacuum packaging" to solve the problems of stress concentration, poor air tightness, and insufficient impact resistance of traditional corner packaging. The drop ball impact test combined with helium mass spectrometer leak detection is applied to shell detection for the first time, achieving double verification of the "sealing - impact resistance" of the packaging structure.

[0099] From the transition zone processing, numerical control milling (rotation speed 10000r / min, feed speed 50mm / min) processes the corners into a 30-45° slope, which can disperse the internal stress (traditional right-angle corner stress concentration value 50MPa) during packaging to below 10MPa, avoiding corner cracking. Cooling lubricant (emulsion concentration 5%) can reduce the processing temperature (controlled below 80℃) to prevent oxidation of the base material and wear of the tool, ensuring that the surface roughness Ra of the transition zone is ≤0.8μm, providing a flat base for the laying of the anticorrosive layer and the adhesive layer.

[0100] The 20-25 μm coating thickness of the encapsulation zone sealant layer (modified epoxy resin) can be fully melted during vacuum packaging (temperature 180-200 ℃, pressure 4-6 MPa), filling the micro gaps of the packaging interface and forming a dense sealing layer. Pre-curing at 120-130 ℃ (10-15 min) can make the sealant preliminarily set, avoid uneven thickness caused by the flow of the sealant during packaging, and ensure the sealing reliability.

[0101] The vacuum packaging environment (vacuum degree ≤ 1 Pa) can exclude the air inside the shell, prevent the reaction between air and electrode during battery operation (such as the reaction between positive electrode material and oxygen), and avoid sealing failure caused by air bubbles. Helium mass spectrometry leak detection (sensitivity 1 × 10⁻ 9 Pa・m³ / s) can detect small leaks (pore size ≤ 0.1 μm), control the shell leakage rate to below 0.1%, and verify the impact resistance of the shell. The drop ball impact test (1 kg steel ball, 1 m height) can ensure that the battery packaging structure does not fail when accidentally dropped (such as 1 m drop), which is a "sealing detection + mechanical verification" double standard, far exceeding the industry's conventional detection (only air tightness detection), providing the last safeguard for the safe operation of solid-state batteries.

[0102] Working principle: This scheme focuses on the core requirements of structural stability, corrosion and flame retardance, and sealing reliability of solid-state battery packaging, and builds a comprehensive protection system through the principle of "multi-layer composite structure design + multi-process synergy". In terms of structural support, the fishbone-shaped ceramic base at the bottom of the containing groove is based on the high hardness characteristics of aluminum oxide and zirconium oxide (mass ratio 7:3), and uses the "fishbone-shaped" three-dimensional structure to disperse stress, while the 10-15% porosity can buffer the volume expansion of the electrode during battery charging and discharging, avoiding deformation of the groove body, and providing stable support for the internal structure of the battery.

[0103] In terms of connection stability, the "thread engagement + vacuum heat melting" dual action principle is adopted. The threaded cavity at the bottom of the containing groove and the threaded column on the bottom surface of the core layer form a physical engagement structure, and then the vacuum heat melting process (250-280 ℃) is used to make the contact area between the core layer and the steel plastic film in a heat melting state, and the threaded column is rotated into the threaded cavity by applying a torque of 5-8 N・m. The material molecules in the heat melting state diffuse to form a chemical bond, combined with the mechanical locking effect of physical engagement, greatly improving the connection strength of the core layer and the steel plastic film substrate, solving the problem of displacement and peeling of traditional connection.

[0104] The multi-layer composite structure of the core layer follows the principle of "functional layering synergy". The central SPCE low-carbon steel layer serves as a framework to provide structural strength. The iron-nickel bonding layer on both sides realizes atomic-level bonding between the steel layer and the nickel layer through electroplating process, eliminating interfacial thermal stress. The outer dumb dark nickel layer utilizes the amorphous structure formed by chemical plating to construct a dense passivation film to block electrolyte corrosion. The outermost flow-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, and each layer cooperates to realize the integration of "strength-corrosion resistance-insulation" functions.

[0105] In terms of corrosion resistance and flame retardation, the corrosion-resistant flame-retardant layer uses a compound 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, the magnesium hydroxide decomposes and releases water vapor at high temperatures to achieve flame retardation, and the silane coupling agent improves compatibility. The sealant layer uses modified epoxy resin, which fully melts during vacuum packaging (vacuum degree ≤1 Pa, pressure 4-6 MPa), fills the micro gaps at the interface, disperses internal stress in the 30-45° transition zone at the corners, and ensures the air tightness and structural integrity of the shell.

[0106] The core innovation of this scheme is the "fishbone-shaped ceramic base + vacuum hot pressing" support structure scheme, which solves the problem of insufficient support strength and poor cushioning performance of traditional packaging groove bodies. The traditional packaging groove bottom adopts a flat support structure, which is difficult to balance strength and cushioning. This scheme disperses stress through the three-dimensional structure of the fishbone-shaped ceramic base, with a porosity of 10-15%, achieving effective cushioning while maintaining a bending strength of ≥300MPa. The base and the groove bottom are tightly combined through vacuum hot pressing (200-220°C, 3-5MPa), with a bonding strength of ≥15MPa, far exceeding traditional adhesive methods.

[0107] The innovative "thread engagement + vacuum hot melting torque forming" connection process solves the core bottleneck of insufficient connection stability between the core layer and the steel-plastic film substrate. The traditional connection method (room temperature mechanical connection, simple adhesion) in the background technology has low bonding strength and is prone to interlayer peeling in harsh working conditions. This scheme uses physical engagement of the threaded cavity and threaded column, combined with vacuum hot melting (250-280°C) and torque twisting (5-8N·m), to increase the connection strength to ≥50MPa. The vacuum environment avoids oxidation and bubble residue, ensuring long-term connection reliability.

[0108] The five-layer composite core layer structure of "SPCE low-carbon steel layer-iron-nickel combined layer-dull dark nickel layer-flowing modified layer" is designed to solve the problem that the traditional single core layer "strength-corrosion-resistance-insulation" performance is difficult to balance. The traditional core layer is mostly single metal or simple composite structure, and each layer in this scheme has clear function and synergy: the SPCE low-carbon steel layer provides strength, the iron-nickel combined layer eliminates thermal stress, the dull dark nickel layer improves corrosion resistance (no rust after 48h salt spray test), and the flowing modified layer guarantees insulation (dielectric constant ≤3.5), realizing the synergistic optimization of multiple performances.

[0109] For the first time, "corner transition zone partition processing + pre-cured sealant + double detection" is applied to the forming of the packaging shell to solve the problems of stress concentration, poor air tightness and insufficient impact resistance of traditional corners. The traditional corner design is a right angle, which is easy to cause stress concentration and cracking. In this scheme, the stress is dispersed through a 30-45° transition zone, and the sealant in the packaging area is pre-cured (120-130℃) to avoid glue flow. Then, it is double detected by helium mass spectrometry leak detection (sensitivity 1×10⁻ 9 Pa・m³ / s) and drop ball impact test (1kg steel ball 1m height without damage) to ensure the sealing and impact resistance of the shell. This overall concept scheme is not disclosed in the prior art.

[0110] For the first time, plasma activation (argon and oxygen mixed at 5:1), laser repair processing, dielectric constant detection and other process details are integrated into the preparation process to realize precise control of product performance. For example, plasma treatment ensures that the substrate roughness Ra is 0.3-0.5μm, which improves the interlayer bonding force; laser repair processing repairs thread cavity defects to ensure connection accuracy; dielectric constant detection controls the performance of the flowing modified layer. These detailed innovations ensure stable product quality in mass production.

[0111] The technical effects of implementing this scheme are: the structural stability is significantly improved, and the battery life is prolonged. Through the buffering effect of the fishbone-shaped ceramic base support and the high-strength connection of "thread engagement + vacuum hot melting" (bonding strength ≥50MPa), the phenomenon of groove deformation, core layer displacement or interlayer peeling of the battery under harsh working conditions such as long-term charging and discharging, high temperature vibration is effectively avoided. Experimental data show that the packaging steel-plastic film using this scheme has a core layer displacement of ≤0.01mm after 1000 temperature cycles from -40℃ to 85℃, which is much lower than the 0.1mm of traditional packaging, making the capacity retention rate of solid-state battery after 1000 cycles ≥90%, which is 15-20% higher than that of traditional packaged batteries, greatly prolonging the battery life.

[0112] The corrosion and flame-retardant layer has excellent corrosion and flame-retardant performance, ensuring safe operation of the battery. The corrosion and flame-retardant layer has no rust and blister after salt spray test (5% sodium chloride, 35°C, 48h), and the coating adhesion is still ≥10MPa after 1000h of electrolyte immersion (1mol / L LiPF6-EC / DEC), effectively preventing electrolyte corrosion and external water vapor intrusion, and avoiding battery leakage or performance degradation caused by corrosion; the magnesium hydroxide flame retardant makes the corrosion and flame-retardant layer reach V-0 level (UL94 standard), which can quickly suppress flame spread at the initial stage of battery thermal runaway, reducing the risk of fire and explosion. At the same time, the amorphous passivation film of the dull nickel layer further enhances the corrosion resistance, so that the battery can maintain the integrity of the packaging structure in the extreme case of acid or alkaline electrolyte leakage, and improve the safety performance of the battery.

[0113] High sealing reliability, expanding battery application scenarios. Through the modified epoxy resin sealant layer and vacuum packaging process (vacuum degree ≤1Pa, pressure 4-6MPa), combined with the stress dispersion design of the corner transition area, the shell gas tightness reaches the helium mass spectrometry leak detection sensitivity of 1×10⁻ 9 Pa・m³ / s, and the leakage rate is ≤0.1%, which is much better than the industry standard (leakage rate ≤1%). Excellent sealing makes the battery work stably in harsh environments such as humidity (relative humidity 95%) and dust, expanding the application scenarios of solid-state batteries in high-end fields such as new energy vehicles (outdoor complex environment) and energy storage systems (long-term outdoor deployment), solving the problem of easy failure of traditional packaged batteries in harsh environments.

[0114] Stable insulation performance, avoiding internal short circuit of battery. The dielectric constant of the core layer flow cast modified layer is ≤3.5 (1kHz frequency), and the dielectric performance change rate is ≤5% after high temperature (200°C) and high humidity (95% RH) environment test, ensuring the stability of the core layer insulation performance during long-term operation, effectively avoiding internal short circuit of the battery caused by insulation failure. At the same time, the electrode edge chamfering treatment (chamfer radius 0.5mm) and positioning clamp fixing (displacement ≤0.05mm) prevent the sharp edge of the electrode from piercing the packaging layer or electrode misalignment causing short circuit, reducing the battery short circuit failure rate from 2% of traditional packaging to below 0.1%.

[0115] The process has strong compatibility and is suitable for large-scale production. Each preparation step (such as ultrasonic cleaning, plasma treatment, laser processing, vacuum hot pressing, etc.) in the scheme adopts mature industrial equipment, without the need for special customization, and the quality control of each link is carried out through atomic force microscope, metallographic microscope, laser thickness gauge and other detection equipment, to ensure product consistency. Experiments show that the production yield of this scheme can reach more than 98%, the production cost is reduced by 10-15% compared with the packaging scheme using special customized equipment, and it has the potential for large-scale industrial production, can meet the batch demand of solid-state battery industrialization for packaging materials, and promote the commercialization of solid-state battery technology.

[0116] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. It is obvious for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application; therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, the scope of the present application is defined by the appended claims rather than the above description, therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application, and any reference signs in the claims should not be regarded as limiting the claims.

[0117] Although embodiments of the present application 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 present application, the scope of the present application being defined by the appended claims and their equivalents.

Claims

1. A modified solid-state battery packaging steel plastic film, characterized by: It comprises a steel plastic film (1), an anti-corrosion and flame-retardant layer (2) and an adhesive layer (3); the steel plastic film (1) is formed by stamping to form a containing groove (11), the groove bottom of the containing groove (11) is paved with a fishbone-shaped ceramic base (4), and the inner surface of the containing groove (11) is sequentially provided with a core layer (5), the anti-corrosion and flame-retardant layer (2) and the adhesive layer (3) by a melting method; The groove bottom of the containing 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 columns (7) used in cooperation with the threaded cavities (6); The core layer (5) comprises a SPCE low-carbon steel layer (51) located at the center, iron-nickel combined layers (52) located on both sides of the SPCE low-carbon steel layer (51), dumb dark nickel layers (53) located on both outer sides of the iron-nickel combined layers (52), and flow casting modified layers (54) located on both outer sides of the dumb dark nickel layers (53); the flow casting slurry is a mixture of polyimide resin and silicon dioxide nanoparticles in a mass ratio of 9:1; The edge corner section of the steel plastic film (1) comprises a transition area (8) and an encapsulation area (9) connected in sequence, the inner surface of the transition area (8) is provided with the anti-corrosion and flame-retardant layer (2) and the adhesive layer (3), the inner surface of the encapsulation area (9) is provided with a sealing adhesive layer (91), and two steel plastic film structures are encapsulated to form an outer shell of a battery pack through a sealing area; The porosity of the fishbone-shaped ceramic base (4) is controlled to be 10-15%, so that it has certain buffering performance; The core layer (5) is placed in the containing groove (11), so that the threaded columns (7) on the bottom surface of the core layer are aligned with the threaded cavities (6) on the groove bottom of the containing groove; the assembled steel plastic film structure is transferred to a vacuum torque forming equipment, the equipment is closed and vacuumized; Then, the temperature is increased so that the contact area between the core layer (5) and the steel plastic film (1) is in a hot melting state; The torque driving device is started, the torque is applied to the core layer (5), the threaded columns (7) are rotated and screwed into the threaded cavities (6), after the screwing is completed, the temperature and the torque are kept unchanged, and after the temperature and pressure are kept, the temperature is slowly reduced to room temperature, the high-strength connection between the core layer (5) and the steel plastic film base material is completed, and the connection stability is greatly improved by combining vacuum hot melting and torque forming.

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: steel plastic film base material pretreatment: The cold-rolled steel plate with a thickness of 0.15-0.2 mm is selected as the base material of the steel-plastic film (1). First, the surface of the base material is cleaned by an ultrasonic cleaning device. The cleaning liquid is a mixture of deionized water and ethanol with a volume ratio of 3:

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

1. The treatment power is 300-350 W, and the treatment time is 5-8 min to improve the roughness and surface energy of the base material surface and enhance the subsequent bonding force with other layers. Step 2: Containing groove stamping and thread cavity processing: The pretreated steel-plastic film base material is fixed on the mold of the numerical control punching machine. According to the size requirements of the solid-state battery, the punching pressure is set to 8-10 MPa, and the punching temperature is set to 120-150°C. The containing groove (11) is formed on the base material by a gradual punching process. Cooling water is used to cool the mold during the punching process to ensure that the mold temperature is stable at 50-60°C, avoiding deformation of the base material due to high temperature. After the containing groove is formed, a laser processing device is used to process several thread cavities (6) on the groove bottom of the containing groove (11). The diameter of the thread cavity is 2-3 mm, the depth is 1-1.5 mm, and the distance between adjacent thread cavities is 5-8 mm. The laser processing power is controlled at 200-250 W, and the processing speed is 5-8 mm / s. After processing, compressed air is used to blow the groove bottom to remove metal debris generated during processing. Step 3: Fishbone-shaped ceramic base preparation and laying: Alumina and zirconia are mixed in a mass ratio of 7:3 as ceramic raw materials, and 5% polyvinyl alcohol binder is added. After stirring evenly, ceramic slurry is prepared. The ceramic slurry is poured into a fishbone-shaped mold and dried at 150-180°C for 2-3 h to form a ceramic green body. Then, the ceramic green body is placed in a high-temperature sintering furnace and sintered at 1200-1300°C for 4-5 h to obtain a fishbone-shaped ceramic base (4). The porosity of the base after sintering is controlled at 10-15% to ensure that it has certain buffering performance. The prepared fishbone-shaped ceramic base (4) is laid on the groove bottom of the containing groove (11) using a positioning tool to ensure accurate positioning. Then, the steel-plastic film base material is transferred to a vacuum hot pressing device and hot pressed at a vacuum degree of ≤1 Pa, a temperature of 200-220°C, and a pressure of 3-5 MPa for 10-15 min to tightly bond the fishbone-shaped ceramic base (4) with the groove bottom. Step 4: Core layer preparation and thread column forming: First, the core layer (5) of each component material is prepared, the SPCE low carbon steel layer (51) is selected from the 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 process, the electroplating solution is a water solution of nickel sulfate and ferrous chloride mixed according to the 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 the dull nickel layer (53) is prepared on the outside of the iron-nickel bonding layer (52) by chemical plating process, 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, and the concentration of sodium citrate is 10-15g / L, the chemical plating temperature is 80-90℃, the plating time is 20-25min, and the thickness of the dull nickel layer is controlled to be 3-5μm; finally, the flow casting process is used to prepare the flow casting modified layer (54) on the outside of the dull nickel layer (53), the flow casting slurry is prepared by mixing polyimide resin and silicon dioxide nanoparticles according to the mass ratio of 9:1, the flow casting speed is 0.5-1m / min, the flow casting temperature is 120-140℃, so that the thickness of the flow casting modified layer reaches 10-12μm, and a complete core layer (5) is obtained; then a plurality of threaded columns (7) are machined on the bottom surface of the core layer (5) by mechanical machining process, the size of the threaded column is matched with the threaded cavity (6) of the bottom of the accommodating groove, and the surface of the threaded column is polished after machining to remove burrs; Step 5: vacuum hot melting torque forming connection: Place the prepared core layer (5) in the accommodating groove (11), so that the threaded column (7) on the bottom surface of the core layer is aligned with the threaded cavity (6) at the bottom of the accommodating groove; transfer the assembled steel-plastic film structure to the vacuum torque forming equipment, close the equipment and vacuumize, so that the vacuum degree in the equipment reaches ≤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 melting state; Start the torque driving device, apply a torque of 5-8N·m to the core layer (5), drive the threaded column (7) to rotate and screw into the threaded cavity (6), the screwing speed is 2-3r / min, after screwing is completed, the temperature and torque are kept unchanged, and the temperature and pressure are kept for 15-20min; then slowly cool to room temperature at a cooling rate of 5-8℃ / min, complete the high-strength connection of the core layer and the steel-plastic film base material, and greatly improve the connection stability by combining vacuum hot melting and torque forming; Step 6: preparation and laying of corrosion-resistant and flame-retardant layers and adhesive layers: First, the anticorrosion flame-retardant layer (2) material is prepared, epoxy resin, magnesium hydroxide flame retardant and silane coupling agent are mixed in a mass ratio of 8:1.5:0.5, a proper amount of acetone solvent is added and stirred uniformly to prepare an anticorrosion flame-retardant coating; the anticorrosion flame-retardant coating is uniformly coated on the inner surface of the containing groove (11) and the outer surface of the core layer (5) by spraying process, the spraying thickness is controlled at 15-18μm, and after spraying, it is cured at 150-160℃ for 30-35min to form the anticorrosion flame-retardant layer (2); then the adhesive layer (3) material is prepared, a hot melt polyurethane adhesive is selected, and it is heated to 180-200℃ to melt; the melted polyurethane adhesive is coated on the outer surface of the anticorrosion flame-retardant layer (2) by roll coating process, the coating thickness is 8-10μm, and after coating, it is naturally cooled to 50-60℃ to ensure that the adhesive layer has good adhesion; Step 7: electrode processing and assembly adaptation: The positive and negative electrodes of the solid-state battery are selected, the surface of the electrode is first cleaned by ultrasonic cleaning equipment to remove the residual electrolyte and impurities on the surface, the cleaning liquid is dimethyl carbonate, the cleaning time is 10-15min, and after cleaning, it is dried in a vacuum drying oven at 80-90℃ for 20-25min; then the electrode edges are chamfered to avoid the sharp edges of the electrode piercing the packaging layer; according to the size of the steel-plastic film containing groove (11), the electrode is cut to ensure that the electrode size is adapted to the containing groove; the processed electrode is placed in the containing groove (11), the electrode is tightly attached to the adhesive layer (3) on the surface of the core layer (5), and a positioning clamp is used to fix the electrode position to prevent the electrode from shifting during the subsequent packaging process; Step 8: corner transition area and packaging area processing and shell forming: First, the corner segment of the steel-plastic film (1) is processed into a transition area (8) with a slope of 30-45° using a numerical control milling equipment, and a cooling lubricant is used during processing to prevent overheating of the processing area; then the anticorrosion flame-retardant layer (2) and the adhesive layer (3) are prepared and laid on the inner surface of the transition area (8) according to the process of step 6; a sealant layer (91) material is prepared, a modified epoxy resin sealant is selected and uniformly coated on the inner surface of the packaging area (9) with a coating thickness of 20-25μm, and after coating, it is pre-cured at 120-130℃ for 10-15min; two steel-plastic films with the same structure are aligned, the containing groove (11) of one steel-plastic film is attached to the packaging area (9) of the other steel-plastic film, and they are placed in a vacuum packaging device, and the shell of the battery pack is formed under the conditions of vacuum degree≤1Pa, temperature 180-200℃, and pressure 4-6MPa for 20-25min; finally, the sealed shell is subjected to air tightness test using a helium mass spectrometer to ensure that the shell is leak-free.

3. The method for preparing the modified solid-state battery encapsulation steel-plastic film according to claim 2, characterized in that: After the plasma treatment in Step 1, the surface roughness of the steel-plastic film substrate is detected using an atomic force microscope to ensure that the surface roughness Ra reaches 0.3-0.5μm. If the roughness does not meet the standard, the plasma treatment power and time need to be adjusted for reactivation treatment until the roughness meets the requirements, further ensuring the bonding basis of 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 thread cavity in Step 2, the integrity of the internal thread structure of the thread cavity is observed using a metallographic microscope. If there are thread defects or deformation, laser repair processing is used for repair. After repair, detection is performed again to ensure that all thread cavities have complete internal thread profiles and accurate sizes, avoiding the impact of thread cavity defects on subsequent thread connection effects.

5. The method for preparing the modified solid-state battery encapsulation steel-plastic film according to claim 2, characterized in that: After sintering of the ceramic base frame in Step 3, the bending strength is detected using a three-point bending test, with a requirement of bending strength ≥300MPa. If the strength does not meet the standard, the ceramic raw material ratio or sintering process parameters need to be adjusted to reprepare the ceramic base frame, ensuring that the base frame 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 preparation of the flow-modified layer in Step 4, the dielectric performance is detected using a dielectric constant tester, with a requirement of dielectric constant ≤3.

5. If the dielectric constant exceeds the standard, the addition amount of silicon dioxide nanoparticles in the flow slurry needs to be adjusted to reprepare the flow-modified layer, ensuring 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 melting torque forming in Step 5, the bonding strength of the core layer and the steel-plastic film substrate is detected using a tensile test, with a requirement of bonding strength ≥50MPa. If the bonding strength does not meet the standard, the hot melting temperature, torque size, or holding time needs to be adjusted for reconnection process to ensure connection reliability.

8. The method for preparing the modified solid-state battery encapsulation steel-plastic film according to claim 2, characterized in that: After curing of the corrosion-resistant and flame-retardant layer in Step 6, the corrosion-resistant performance is detected using a salt spray test. The sample is placed in a 5% sodium chloride solution mist environment at 35℃ for 48h, with a requirement of no rusting or blistering of the coating. If corrosion occurs, the corrosion-resistant and flame-retardant coating formula needs to be adjusted to reprepare the corrosion-resistant and flame-retardant layer, improving the corrosion resistance of the packaging structure.

9. The method of making a modified solid state battery packaging steel plastic film of claim 2, wherein: After electrode cutting in Step 7, the thickness uniformity of the electrode is detected using a laser thickness gauge, with a requirement of thickness deviation ≤±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 the uniformity of the electrode thickness, avoiding the imbalance of the internal stress of the packaged battery due to uneven electrode thickness. After the shell is formed in Step 8, in addition to the air tightness test, the impact resistance test is also required. The drop ball impact test is used, with a 1kg steel ball dropped from a height of 1m to impact the shell surface. The shell is required to have no cracking or deformation. If damage occurs, the packaging pressure or sealant formula needs to be adjusted for re-packaging to ensure the impact resistance of the battery pack shell.

10. The method for preparing the modified solid-state battery encapsulation steel-plastic film according to claim 2, characterized in that: ​

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