A battery, an electric device

Abstract

The application discloses a battery and a power utilization device, and belongs to the technical field of batteries. The battery provided by the application comprises a battery shell assembly. A first coating layer is introduced on at least part of the surface of the shell, and a second coating layer is introduced on at least part of the surface of the first coating layer. Meanwhile, the first coating layer is defined as having different elastic modulus ranges at a first temperature and a second temperature, and the porosity and volume resistivity of the second coating layer at 85 DEG C are within a certain range. The two coating layers have excellent synergistic effect, can realize stress dissipation and reduce the crack length of the coating layer, and can improve the insulation reliability and the functional stability in a wide temperature range.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a battery and an electrical device. Background Technology

[0002] Traditional secondary battery casing insulation coatings often use a single material or a simple layered structure, which has the following problems: First, the sudden change in the modulus between polymer and ceramic can easily cause stress concentration at the interface, and cracks can penetrate the coating after long-term cycling; Second, the flexible layer and the rigid layer have independent functions, making it difficult to balance "buffering" and "protection"; Third, a single material cannot simultaneously cope with low-temperature brittleness and high-temperature softening, and performance degradation is significant at extreme temperatures. Summary of the Invention

[0003] The purpose of this application is to solve the technical problems in the prior art where secondary battery casings are prone to stress cracking, making it difficult to achieve good buffering and protection capabilities at the same time, and having poor environmental adaptability at different temperatures. The application proposes a battery casing assembly and battery that can achieve stress dissipation and reduce the length of coating cracks, and has excellent insulation and wide temperature range adaptability.

[0004] To achieve the above objectives, a first aspect of this application provides a battery including a battery housing assembly, the battery housing assembly including a housing, a first coating disposed on at least a portion of the surface of the housing, and a second coating disposed on at least a portion of the surface of the first coating; The elastic modulus of the first coating at a first temperature is 30 MPa to 50 MPa, and at a second temperature it is 80 MPa to 120 MPa. The first temperature is t1℃, where t1 = T1℃ - 20℃, and T1℃ is the endothermic transformation initiation temperature of the first coating in differential scanning calorimetry testing. The second temperature is t2℃, and the second temperature t2 = T2℃ + 20℃, where T2℃ is the end-temperature temperature of the endothermic transformation of the first coating in the differential scanning calorimetry test. The porosity of the second coating is ≤1%, and the volume resistivity of the second coating at 85°C is >1×10⁻⁶. 14 Ω·cm.

[0005] As some embodiments of this application, the first coating has an elongation at break of 200% to 250% at a first temperature and an elongation at break of 100% to 250% at a second temperature.

[0006] As some embodiments of this application, the glass transition temperature of the first coating is 20°C to 40°C.

[0007] As some embodiments of this application, the first coating includes a polymer matrix, a temperature-responsive material, and additives.

[0008] As some embodiments of this application, in the first coating, the polymer matrix has a mass percentage of 90-95%.

[0009] As some embodiments of this application, in the first coating, the mass percentage of the temperature-responsive material is 5% to 10%.

[0010] As some embodiments of this application, the polymer matrix is ​​selected from at least one of thermoplastic polyurethane, silicone rubber, and thermoplastic elastomer.

[0011] As some embodiments of this application, the temperature-responsive material is selected from at least one of poly(N-isopropylacrylamide), poly(N-vinylpyrrolidone), and polyacrylic acid.

[0012] As some embodiments of this application, the additive is selected from at least one of dispersants and coupling agents.

[0013] As some embodiments of this application, the second coating includes ceramic, surface treatment agent, and dispersion promoter.

[0014] As some embodiments of this application, in the second coating, the mass percentage of the ceramic is 95% to 98%.

[0015] In some embodiments of this application, the surface treatment agent in the second coating has a mass percentage of 2% to 5%.

[0016] As some embodiments of this application, the ceramic is selected from at least one of alumina, silicon carbide, boron nitride, and a composite of alumina and titanium oxide.

[0017] As some embodiments of this application, the surface treatment agent is selected from at least one of silane coupling agents, titanate coupling agents, aluminate coupling agents, and sulfuric acid-oxalic acid mixtures.

[0018] As some embodiments of this application, the thickness of the first coating is 50 μm to 100 μm.

[0019] As some embodiments of this application, the thickness of the second coating is 5 μm to 20 μm.

[0020] A second aspect of this application provides a battery including the battery housing assembly described in this application.

[0021] Compared with the prior art, the beneficial effects of this application are: The battery provided in this application includes a battery housing assembly. By introducing a first coating on at least a portion of the surface of the housing and a second coating on at least a portion of the surface of the first coating, the first coating is defined to have different elastic modulus ranges at a first temperature and a second temperature, and the porosity and volume resistivity of the second coating at 85°C are within a certain range. The two coatings have excellent synergistic effects, which can achieve stress dissipation and reduce the length of coating cracks, and can also improve insulation reliability and functional stability over a wider temperature range. Attached Figure Description

[0022] Figure 1 Here is a schematic diagram of the battery casing assembly in Example 1: 101 - Housing, 102 - First coating, 103 - Second coating. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0025] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0026] In one embodiment of this application, a battery is provided, the battery including a battery housing assembly, the battery housing assembly including a housing, a first coating disposed on at least a portion of the surface of the housing, and a second coating disposed on at least a portion of the surface of the first coating; The elastic modulus of the first coating at the first temperature is 30 MPa to 50 MPa, and the elastic modulus at the second temperature is 80 MPa to 120 MPa. The first temperature is t1℃, and the first temperature t1 = T1℃ - 20℃. T1℃ is the temperature at which the first coating begins to absorb heat during differential scanning calorimetry testing. The second temperature is t2℃, and the second temperature t2 = T2℃ + 20℃. T2℃ is the end point temperature of the endothermic transformation of the first coating in the differential scanning calorimetry test. The porosity of the second coating is ≤1%, and the volume resistivity of the second coating at 85℃ is >1×10⁻⁶. 14 Ω·cm.

[0027] The battery housing assembly provided in this application introduces a first coating on at least a portion of the housing surface and a second coating on at least a portion of the first coating surface. The first coating is defined to have different elastic modulus ranges at a first temperature and a second temperature, and the porosity and volume resistivity of the second coating at 85°C are within a certain range. The two coatings have excellent synergistic effects, which can achieve stress dissipation and reduce the length of coating cracks, and can also improve insulation reliability and functional stability over a wider temperature range.

[0028] Specifically, when the battery heats up (e.g., to 85°C), the first coating absorbs heat, and the mobility of the polymer chain segments is activated (transitioning from a glassy state to a highly elastic state). At this point, the modulus drops to 30MPa~50MPa, and the first coating exhibits characteristics similar to a "thermally softened gel." Within this specific low modulus range, the first coating can convert the thermal expansion stress transmitted from the outside into internal frictional heat of the molecular chains (i.e., viscoelastic loss) through the relative slippage and rearrangement of the polymer chain segments, thereby efficiently "absorbing" and relaxing most of the thermal stress.

[0029] When the temperature drops (e.g., -20°C), the molecular chain segment movement is frozen, and the modulus recovers to 80MPa~120MPa. This modulus ensures that the first coating does not lose its mechanical strength due to excessive softening at low temperatures, while also providing appropriate rigidity to reduce the risk of coating collapse caused by battery swelling.

[0030] Furthermore, the porosity of the second coating is ≤1%, which helps to conduct heat from the shell to the first coating. Understandably, if the porosity of the second coating is too large, it is prone to local expansion or structural distortion when heated, consuming a large amount of energy within itself, making it difficult to effectively transfer thermal stress downwards.

[0031] By controlling the porosity of the second coating within a small, reasonable range, the second coating forms a rigid, thermally expandable continuous phase. When drastic changes in ambient temperature generate thermal stress, the second coating acts like a smooth bridge, efficiently and effectively transferring the stress to the first coating (i.e., the stress dissipation center), ensuring that the first coating can promptly exert its "viscoelastic relaxation" ability.

[0032] Specifically, in the first aspect, this application controls the elastic modulus of the first coating to be 30MPa~50MPa at a first temperature and 80MPa~120MPa at a second temperature, and specifies that the first temperature t1℃=T1℃-20℃, where T1℃ is the endothermic transition initiation temperature of the first coating in differential scanning calorimetry testing, and the second temperature t2=T2℃+20℃, where T2℃ is the endothermic transition termination temperature of the first coating in differential scanning calorimetry testing; this enables the first coating to have a suitable range of elastic modulus at different temperatures, thereby achieving good flexibility near the endothermic transition initiation temperature and achieving excellent buffering capacity; it also enables it to have a high modulus near the endothermic transition termination temperature and achieve suitable rigidity; at the same time, the elastic modulus of the first coating changes with temperature, which helps to achieve functional stability and structural stability of the battery casing assembly in a wide temperature range (-40℃ to 85℃).

[0033] Secondly, this application limits the porosity of the second coating to a certain range, which can reduce the generation of stress cracks and further improve structural stability and safety.

[0034] Thirdly, this application limits the volume resistivity of the second coating at 85°C to a certain range, which can synergize with the porosity to a certain extent to improve the insulation performance, especially the insulation performance at high temperatures, thereby improving the functional stability and structural stability of the battery casing assembly over a wider temperature range.

[0035] When the first coating is applied to the inner surface of the housing and the second coating is applied to at least a portion of the surface of the first coating, the first coating maintains flexibility while also resisting lithium dendrite penetration; the second coating has a good ability to block electrolyte, thereby slowing down corrosion and effectively blocking lithium dendrite penetration.

[0036] Specifically, from a mechanical perspective, due to the significant difference in elastic modulus and fracture toughness between the first and second coatings (mechanical mismatch), when a crack reaches the interface, it will deflect or pin, greatly consuming the energy for crack propagation. From an electrical perspective, in the event of thermal runaway or abnormal gas generation in the secondary battery causing casing deformation, the double-layer coating structure ensures that even under extreme deformation, the first coating maintains insulation on the bottom surface, and fragments of the second coating are difficult to peel off. From a thermodynamic perspective, when in a high-temperature environment, the first coating softens upon heating, and the internal polymer molecular chain segments move more rapidly, effectively relaxing the thermal stress caused by the mismatch in thermal expansion coefficients between the metal casing and the second coating. This makes it difficult for the second coating to warp or crack due to thermal expansion and contraction, thus ensuring that various performance indicators remain stable within a suitable range across a wide temperature range from extreme cold to extreme heat.

[0037] For example, the elastic modulus of the first coating at the first temperature can be any point value between 30MPa and 50MPa or a range between any two points, such as 30MPa, 32MPa, 35MPa, 38MPa, 40MPa, 42MPa, 45MPa, 48MPa, 50MPa, etc.

[0038] For example, the elastic modulus of the first coating at the second temperature can be any point value between 80MPa and 120MPa or a range between any two points, such as 80MPa, 85MPa, 90MPa, 95MPa, 100MPa, 105MPa, 110MPa, 115MPa, 120MPa, etc.

[0039] It should be noted that the reason for testing the elastic modulus of the first coating at the first temperature t1 = T1℃ - 20℃ and the second temperature t2 = T2℃ + 20℃ is to accurately capture the critical point of mechanical state switching when the first coating crosses the glass transition region. Using the endothermic transition start point T1 and end point T2 as thermodynamic anchoring benchmarks can eliminate test errors caused by heating rate and thermal history, ensuring the objectivity and reproducibility of the characterization. The test temperature of the elastic modulus of the first coating is offset by ±20℃ from the endothermic transition start point / end point to lock the peak modulus of the first coating in supporting the structure when leaving the glassy state (i.e., T1 - 20℃), and to capture the valley modulus of the first coating in achieving stress dissipation when entering the high elastic state (i.e., T2 + 20℃), thereby scientifically verifying the dynamic protection capability of this scheme in the entire temperature range.

[0040] It should be noted that the method for testing the elastic modulus of the first coating at a first temperature and at a second temperature includes the following steps: 1. Determining Temperature Points: First, disassemble the battery to obtain the battery casing assembly. Fix the battery casing assembly and use a high-speed drill bit with a diameter of 0.8 mm to control the drilling depth within the first coating layer. Collect the drilled powder as a test sample. Use differential scanning calorimetry (DSC) to obtain the endothermic transition onset temperature (Tonset, T1) and endothermic transition termination temperature (Toffset, T2) of the first coating material. Then calculate two characteristic test temperatures: first temperature t1 = T1℃ - 20℃, second temperature t2 = T2℃ + 20℃; 2. Measure the elastic modulus: Then, using a dynamic thermomechanical analyzer (DMA), the elastic modulus of the first coating (usually characterized by the storage modulus E') is directly tested at two isothermal points, the first temperature and the second temperature.

[0041] For example, the porosity of the second coating can be any point value of ≤1% or a range between any two points, such as 0.1% to 1%, or 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc.

[0042] In some embodiments, the porosity of the second coating is 0.5% to 0.8%. For example, it can be 0.5%, 0.52%, 0.55%, 0.58%, 0.6%, 0.62%, 0.65%, 0.68%, 0.7%, 0.72%, 0.75%, 0.78%, 0.8%, etc.

[0043] It should be noted that the test method for the porosity of the second coating is as follows: It is performed in accordance with the national standard GB / T 21650.1-2008 "Determination of Pore Size Distribution and Porosity of Solid Materials by Mercury Intrusion Porosimetry and Gas Adsorption Methods - Part 1: Mercury Intrusion Porosimetry"; specifically: 1. Sample Preparation: Disassemble the battery to obtain the battery casing assembly. Obtain test samples from the second coating of the battery casing assembly using non-destructive or minimal-destructive methods such as diamond wire cutting. The sample should be as representative as possible of the overall characteristics of the coating, typically requiring a regular block shape or the entire cross-section of the coating to ensure the test surface is the actual surface of the second coating. Before testing, the sample must be vacuum-dried at 120°C for 2 hours to thoroughly remove adsorbed moisture and volatile substances. 2. Testing process: 1) Instrument: A fully automatic mercury porosimeter is used; 2) Pretreatment: Weigh the dried sample and place it into a dedicated dilatometer sample tube; 3) Low-pressure analysis: In the low-pressure station, the sample chamber is evacuated to <10 μmHg to remove air from the pores. Then, initial mercury injection is performed under low pressure to fill the voids between sample particles. 4) High-pressure analysis: The sample is transferred to the high-pressure station, and pressure is gradually applied until the maximum value is reached. The instrument automatically records the volume of mercury injected into the pores at different pressure points; 5) Data Processing: After the test, the instrument software calculates the total pore volume of the sample from the pressure-mercury ingress curve using the Washburn equation. Porosity (P) is calculated using the following formula: P (%) = (Vp / (Vp + Vs)) × 100% where, Vp is the total pore volume. Vs is the skeleton volume calculated based on the sample mass and the theoretical density of the material.

[0044] For example, the volume resistivity of the second coating at 85°C can be >1×10⁻⁶. 14The value of Ω·cm at any point or within a range of any two points, for example, 1.1 × 10⁻⁶. 14 Ω·cm ~11×10 14 Ω·cm, or 1.1×10 14 Ω·cm, 1.5×10 14 Ω·cm, 2×10 14 Ω·cm, 5×10 14 Ω·cm, 8×10 14 Ω·cm, 1×10 15 Ω·cm, 1.1×10 15 Ω·cm, etc.

[0045] In some embodiments, the volume resistivity of the second coating at 85°C is 2 × 10⁻⁶. 14 Ω·cm~5×10 14 Ω·cm. For example, it could be 2 × 10⁻⁶. 14 Ω·cm, 2.2×10 14 Ω·cm, 2.5×10 14 Ω·cm, 2.8×10 14 Ω·cm, 3×10 14 Ω·cm, 3.2×10 14 Ω·cm, 3.5×10 14 Ω·cm, 3.8×10 14 Ω·cm, 4×10 14 Ω·cm, 4.2×10 14 Ω·cm, 4.5×10 14 Ω·cm, 4.8×10 14 Ω·cm, 5×10 14 Ω·cm, etc.

[0046] It should be noted that the test method for the volume resistivity of the second coating at 85°C includes the following steps: 1. Sample and Electrode Preparation: The battery is disassembled to obtain the battery casing assembly. Test samples are obtained from the second coating of the battery casing assembly using non-destructive or minimal-destructive methods such as diamond wire cutting. The sample should be as representative of the overall characteristics of the coating as possible, typically requiring a regular block shape or the entire cross-section of the coating to ensure the test surface is the actual surface of the second coating. Two parallel rectangular electrodes are prepared on the smooth surface of the coated sample by vacuum evaporation or by applying conductive silver paste. The electrode area is known, and the distance between the electrodes (i.e., in the coating thickness direction) can be accurately measured using a thickness gauge. 2. High temperature environment control: Place the prepared electrode sample in a high temperature test chamber with precise temperature control, set and stabilize the temperature at (85±1)℃, and keep it at the temperature for a certain period of time to make the overall temperature of the sample uniform. 3. Resistance measurement: Under constant temperature conditions of 85℃, use a high resistance meter to measure the insulation resistance (R) between the two electrodes at a specified DC test voltage (e.g., 500V). 4. Calculate the volume resistivity: Based on the measured insulation resistance (R), electrode area (A), and coating thickness (d), the volume resistivity is calculated using the formula ρ = R × (A / d), with the unit being Ω·cm.

[0047] In some embodiments, the first coating has an elongation at break of 200% to 250% at a first temperature and an elongation at break of 100% to 250% at a second temperature.

[0048] For example, the elongation at break of the first coating at the first temperature can be any point value between 200% and 250% or a range between any two points, such as 200%, 210%, 215%, 220%, 225%, 230%, 235%, 240%, 245%, 250%, etc.

[0049] For example, the elongation at break of the first coating at the second temperature can be any point value between 100% and 250% or a range between any two points, such as 100%, 120%, 140%, 150%, 160%, 180%, 200%, 220%, 230%, 250%, etc.

[0050] It should be noted that the test method for the elongation at break of the first coating at the first temperature and the second temperature includes the following steps: 1. Determine the test temperature: Obtain the first temperature (t1 ℃ = T1℃ - 20℃) and the second temperature (t2 = T2℃ + 20℃) by comparing the elastic modulus test process with that of the reference first coating. 2. Sample preparation: Cut the first coating into standard dumbbell-shaped specimens; 3. Temperature control and testing: Place the tensile testing machine in a high and low temperature environment chamber, or install the specimen on a fixture equipped with a temperature control device. Precisely control and stabilize the ambient temperature at the first temperature (t1) and the second temperature (t2). 4. Tensile Testing and Measurement: At each target temperature, the specimen is stretched at a constant tensile rate (e.g., 10 mm / min) until it breaks. The testing machine automatically records the displacement (ΔL) at the point of specimen fracture. 5. Calculate the elongation at break: Based on the original gauge length (L0) of the specimen and the elongation at break (ΔL), calculate the elongation at break using the formula: Elongation at break = (ΔL / L0) × 100%.

[0051] This application research found that by limiting the elongation at break of the first coating at a first temperature and at a second temperature to a certain range, the first coating can have a suitable range of elongation at break at different temperatures. This allows it to have high flexibility near the endothermic transition initiation temperature, achieving excellent buffering capacity and reducing crack formation; it also allows it to have suitable flexibility near the endothermic transition termination temperature. Furthermore, it can be combined with the elastic modulus to achieve flexible bonding and high ductility at relatively low temperatures, as well as rigidity and sufficient toughness at relatively high temperatures; thereby helping to achieve functional and structural stability of the battery casing assembly across the entire temperature range.

[0052] In some embodiments, the glass transition temperature of the first coating is 20°C to 40°C.

[0053] For example, the glass transition temperature of the first coating can be any point value between 20°C and 40°C or a range between any two points, such as 20°C, 22°C, 24°C, 25°C, 28°C, 30°C, 32°C, 35°C, 38°C, 40°C, etc.

[0054] It should be noted that the glass transition temperature of the first coating was tested using differential scanning calorimetry, specifically: 1. Testing Standards: Comply with ASTM D3418-22 or equivalent national standards; 2. Sample Preparation: Disassemble the battery to obtain the battery casing assembly, then scrape off an appropriate amount of sample (approximately 5 mg to 10 mg) from the first coating and place it in a sealed aluminum crucible specifically designed for the DSC instrument. Ensure the sample is flat and in good contact with the bottom of the crucible; 3. Test conditions: Under an inert atmosphere (such as nitrogen), a heating scan is performed at a constant rate of 10℃ / min. The typical temperature range is -50℃ to 150℃ to fully cover the phase transition process. 4. Data Interpretation: On the obtained heat flow-temperature curve, the glass transition exhibits a step-like endothermic abrupt change. This is determined according to standard methods. 1) Transformation onset temperature (Tg, onset): The temperature at which the tangent line at which the baseline begins to deviate from the baseline before the transformation intersects with the tangent line of the steep part of the curve; 2) Transition midpoint temperature (Tg, mid): Usually, the temperature corresponding to half of the heat flux change is taken. This is the most frequently reported glass transition temperature value. 3) Transition termination temperature (Tg, offset): The temperature at which the tangent line of the curve recovers to the new baseline intersects with the tangent line of the steep part.

[0055] This application research found that the glass transition temperature is the characteristic temperature window for the first coating to change from a glassy state to a rubbery state. By limiting the glass transition temperature of the first coating to the above range, the first coating can be in a glassy or transitional state below room temperature (25°C) and enter the rubbery state above room temperature (25°C), thereby better matching the actual working conditions of the battery and achieving functional and structural stability of the battery over a wider temperature range.

[0056] In some embodiments, the first coating comprises a polymer matrix, a temperature-responsive material, and additives.

[0057] In some embodiments, the polymer matrix in the first coating is 90% to 95% by mass.

[0058] For example, the mass percentage of the polymer matrix, based on the total mass of the first coating, can be any point value or a range between any two points between 90% and 95%, such as 90%, 91%, 92%, 93%, 94%, 95%, etc.

[0059] This application study found that selecting the mass percentage of the polymer matrix within the above-mentioned range can ensure that the parameters of the first coating are within a suitable range, thereby helping to dissipate stress in the battery housing assembly, reduce the length of coating cracks, and improve its adaptability across the entire temperature range.

[0060] In some embodiments, the mass percentage of the temperature-responsive material in the first coating is 5% to 10%.

[0061] For example, the mass percentage of the temperature-responsive material, based on the total mass of the first coating, can be any point value or a range between any two points between 5% and 10%, such as 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, etc.

[0062] This application research found that when the mass percentage of the temperature-responsive material is within the above-mentioned range, it can cooperate with the polymer matrix to achieve the parameters of the first coating within the corresponding range, thereby helping to dissipate stress in the battery casing assembly, reduce the length of coating cracks, and improve its adaptability over a wider temperature range.

[0063] It should be noted that the mass percentage of the polymer matrix and temperature-responsive material in the first coating is determined by thermogravimetric analysis, specifically: 1. Testing Standards: Compliance with ISO 11358-1 or equivalent national standards; 2. Sample preparation: A sample of approximately 10 mg to 20 mg is precisely scraped or peeled off from the first coating and placed in a platinum or alumina crucible of the TGA instrument; 3. Test conditions: Under an inert atmosphere, the sample was heated from room temperature to 600℃ at a constant rate of 10℃ / min, and the mass change curve of the sample with temperature was recorded in real time. 4. Data Analysis: On the obtained thermogravimetric curves, the polymer matrix and temperature-responsive materials typically exhibit one or more distinct mass loss steps. By performing tangential analysis on each weight loss step using analysis software, the temperature range and mass loss ratio corresponding to the thermal decomposition of each component can be determined. 1) Calculation of temperature-responsive material content: If the temperature-responsive material has unique and stable thermal decomposition characteristics (such as a specific decomposition temperature range), its mass percentage can be directly determined by the mass loss percentage corresponding to the decomposition range of that characteristic.

[0064] 2) Calculation of polymer matrix content: Subtract the percentage of mass loss of temperature-responsive material from the total mass, and then subtract any inorganic fillers or ash (final high-temperature residual mass) to obtain the percentage of polymer matrix mass.

[0065] In some embodiments, the polymer matrix is ​​selected from at least one of thermoplastic polyurethane, silicone rubber, and thermoplastic elastomer.

[0066] This application does not specifically limit the type of thermoplastic polyurethane, and any thermoplastic polyurethane (TPU) conventionally used in the art can be used.

[0067] This application does not specifically limit the type of silicone rubber; any thermoplastic silicone rubber commonly used in the art can be used. For example, the silicone rubber may be methyl vinyl silicone rubber, phenyl silicone rubber, etc.

[0068] This application does not specifically limit the type of thermoplastic elastomer, and any thermoplastic elastomer conventionally used in the art can be used. For example, the thermoplastic elastomer may be a styrene-based thermoplastic elastomer (such as styrene-butadiene-styrene block copolymer (SBS) or hydrogenated styrene-ethylene / butene-styrene block copolymer (SEBS)), a polyolefin-based thermoplastic elastomer (such as ethylene-octene copolymer (POE) or dynamically vulcanized polypropylene / ethylene-propylene rubber blend (TPV)), etc.

[0069] This study found that selecting the above-mentioned type of polymer matrix can better improve the overall performance of the battery casing assembly.

[0070] In some embodiments, the temperature-responsive material is selected from at least one of poly(N-isopropylacrylamide) (PNIPAM), poly(N-vinylpyrrolidone) (PVP), and polyacrylic acid (PAA).

[0071] This study found that selecting the above-mentioned type of temperature-responsive material can better complement the polymer matrix and improve the overall performance of the battery casing assembly.

[0072] It should be noted that the present invention does not particularly limit the weight-average molecular weight of the temperature-responsive material. For example, the weight-average molecular weight of the temperature-responsive material can be 50,000 to 200,000.

[0073] In some embodiments, the adjuvant is selected from at least one of dispersants and coupling agents.

[0074] This application does not specifically limit the type of dispersant, and any dispersant commonly used in the art can be used. For example, the dispersant may be a polycarboxylate (such as sodium polyacrylate or ammonium polymethacrylate), a polymeric dispersant (such as polyacrylates (e.g., commercial models such as BYK-154, DISPERBYK-110, etc.), or a modified polyurethane (e.g., the BYK-2000 series)).

[0075] This application does not specifically limit the type of coupling agent, and any coupling agent conventionally used in the art can be used. For example, the coupling agent may be a silane coupling agent (such as γ-aminopropyltriethoxysilane (KH-550), γ-glycidyl etheroxypropyltrimethoxysilane (KH-560), etc.), a titanate coupling agent (such as isopropyltris(dioctylpyrophosphate)titanate (KR-38S), bis(dioctylpyrophosphate)oxyacetate titanium (KR-138S), etc.).

[0076] This study found that the addition of dispersants helps the system disperse better, improves system homogeneity, and thus enhances structural stability. The addition of coupling agents helps increase the binding force between substances, thereby improving structural stability.

[0077] In some embodiments, the second coating includes ceramic, a surface treatment agent, and a dispersion promoter.

[0078] In some embodiments, the ceramic mass percentage in the second coating is 95% to 98%.

[0079] For example, the mass percentage of ceramics, based on the total mass of the second coating, can be any point value or a range between any two points between 95% and 98%, such as 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, etc.

[0080] This study found that the mass percentage of ceramic in the second coating affects the parameters of the second coating. When the mass percentage of ceramic in the second coating is selected within the above range, the overall performance of the battery casing assembly can be better achieved.

[0081] In some embodiments, the surface treatment agent in the second coating is 2% to 5% by mass.

[0082] For example, the mass percentage of the surface treatment agent can be any point value or a range between any two points, based on the total mass of the surface treatment agent, such as 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0083] This study found that the amount of surface treatment agent added affects its dispersion effect with ceramics and the structural density of the second coating. It also affects the bonding force between the second coating and the first coating. When the mass percentage of the surface treatment agent is further selected within the above range, the overall performance of the battery casing assembly is better.

[0084] It should be noted that the test method for the mass percentage of ceramics and surface treatment agent in the second coating is thermogravimetric analysis, specifically: 1. Test Principles and Standards: The test shall be conducted in accordance with ISO 11358-1 or equivalent national standards. The test shall be performed in an inert atmosphere (such as nitrogen) to prevent oxidation interference. 2. Sample preparation: Precisely scrape or peel off approximately 10 mg to 20 mg of powder or flake sample from the cured second coating and place it in the crucible of the TGA instrument; 3. Test conditions: Under a nitrogen flow, the temperature was increased from room temperature to 800°C at a constant rate of 10°C / min; 4. Data Analysis: On the obtained thermogravimetric curves, surface treatment agents (organosilanes, titanates, etc.) undergo thermal decomposition within a specific temperature range (usually 300℃~500℃), exhibiting a clear mass loss step. Ceramic phases (such as Al2O3, SiC) maintain stable mass within this temperature range. 1) Calculation of ceramic mass percentage: The percentage of the final residual mass of the sample after heating to 800℃ and holding at that temperature for a while is the percentage of the ceramic phase in the second coating. 2) Calculation of surface treatment agent mass percentage: Subtract the mass percentage of the ceramic phase from 100% to obtain the mass percentage of the surface treatment agent in the second coating. This value directly corresponds to the percentage of total mass loss caused by the decomposition of the surface treatment agent.

[0085] In some embodiments, the ceramic is selected from at least one of alumina, silicon carbide, boron nitride, and a composite of alumina and titanium oxide.

[0086] This study found that the above-mentioned type of ceramic can better achieve the porosity range of the second coating and the volume resistivity range at 85°C, and can also help improve the stress buffering effect of the battery housing assembly, thereby improving the overall performance of the battery housing assembly.

[0087] In some embodiments, the surface treatment agent is selected from at least one of silane coupling agents, titanate coupling agents, aluminate coupling agents, and sulfuric acid-oxalic acid mixtures.

[0088] This study found that selecting the above-mentioned type of surface treatment agent can better improve the bonding force within and between coatings, thereby resulting in better overall performance of the battery casing assembly.

[0089] For example, the silane coupling agent can be KH550 or KH560; the titanate coupling agent can be KR-38S or KR-138S; the aluminate coupling agent can be distearyloxyisopropoxyaluminate (such as model DL-411) or octadecyl aluminate (such as model DL-451); in the sulfuric acid-oxalic acid mixture, the mass percentage of oxalic acid is 1% to 5%, the mass percentage of sulfuric acid is 5% to 20%, and the balance is deionized water.

[0090] In some embodiments, the thickness of the first coating is 50 μm to 100 μm.

[0091] For example, the thickness of the first coating can be any point value or a range between any two points between 50μm and 100μm, such as 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, 100μm, etc.

[0092] This application research found that the thickness of the first coating affects the mechanical properties of the battery housing assembly, thereby affecting its buffering capacity and resistance to lithium dendrites; when the thickness of the first coating is selected within the above range, it helps the battery housing assembly to dissipate stress and reduce the length of coating cracks, and has better adaptability to the entire temperature range.

[0093] In some embodiments, the thickness of the second coating is 5 μm to 20 μm.

[0094] For example, the thickness of the second coating can be any point value or a range between any two points between 5μm and 20μm, such as 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 12μm, 14μm, 15μm, 16μm, 18μm, 20μm, etc.

[0095] This study found that the thickness of the second coating affects its insulation performance, as well as its physical barrier capability and strength. When the thickness of the second coating is further selected within the above range, it helps to dissipate stress in the battery casing assembly and reduce the length of coating cracks, resulting in better adaptability to a wider temperature range and superior insulation performance.

[0096] It should be noted that the thickness of the first and second coatings was measured using cross-sectional microscopy, specifically as follows: 1. Sample preparation Sampling: Take a small sample (approximately 5mm x 5mm) from the target area of ​​the battery casing assembly (such as the flat part in the middle of the casing) to ensure that it contains the complete three-layer structure of "casing-first coating-second coating"; Embedding and polishing: Embed the sample in epoxy resin or acrylic resin (for easy handling and observation), and grind it until the cross-section of the coating is exposed after curing; polish it in sequence with 800#, 1200#, and 2000# sandpaper, and then polish it to a mirror finish with diamond polishing paste (0.5μm particle size) to ensure that the interface between the coating and the substrate is clear and free of scratches; 2. Thickness Measurement Equipment selection: 1) First coating: Optical microscope (magnification 200-500x, with eyepiece and micrometer). 2) Second coating: Optical microscope (magnification 500-1000x).

[0097] Measurement operation: 1) Place the polished sample with the cross-section facing up on the microscope stage and focus until the interface is clear; 2) Randomly select at least 5 measurement points on the cross-section of the coating; 3) Use an eyepiece micrometer or image analysis software (such as ImageJ) to measure the vertical thickness of the coating at each point (i.e., the distance from the substrate surface to the outer surface of the coating). 4) Calculate the average thickness of each coating.

[0098] In some embodiments, the method for manufacturing the battery casing assembly includes the following steps: (1) Preparation of the first coating slurry: The polymer matrix, temperature-responsive material and additives are added to the first solvent and mixed evenly to obtain the first coating slurry; (2) Preparation of the second coating slurry: The ceramic and the surface treatment agent are added to the second solvent and mixed evenly to obtain the second coating slurry; (3) Preparation of battery housing assembly: The first coating slurry is applied to the surface of the housing, then pre-dried and cured for the first time to form the first coating; then the second coating slurry is applied to the surface of the first coating, then dried and cured for the second time to form the second coating, thus obtaining the battery housing assembly.

[0099] In some embodiments, in step (3), coating includes spraying or scraping.

[0100] In some embodiments, in step (3), the pre-drying temperature is 50°C to 70°C and the time is 8 min to 12 min.

[0101] In some embodiments, in step (3), the first curing can be infrared or ultraviolet curing. For infrared curing, the wavelength is 2μm to 5μm, the power is 500W to 700W, the temperature is 120℃ to 140℃, and the time is 6min to 10min; for ultraviolet curing, the wavelength is 365nm (or 395nm), the power density is 80 mW / cm² to 120 mW / cm², and the time is 4min to 7min.

[0102] In some embodiments, in step (3), the drying temperature is 70℃~90℃, the time is 1.5h~2.5h, and the vacuum degree is -0.09±0.02MPa.

[0103] In some embodiments, in step (3), the second curing is ultraviolet (UV) curing. The UV curing wavelength is 365 nm, and the power is 80 mW / cm². 2 ~120 mW / cm 2 The time is 4 to 7 minutes.

[0104] In some embodiments, the first solvent includes at least one of acetone, N-methylpyrrolidone (NMP), propylene glycol methyl ether (PMA), and isopropanol (IPA).

[0105] In some embodiments, the second solvent includes at least one of anhydrous ethanol, propylene glycol methyl ether (PMA), butanone (MEK), and ethylene glycol ethyl ether.

[0106] In some embodiments, the solid content of the first coating slurry is 30% to 40%.

[0107] In some embodiments, the solid content of the second coating slurry is 40% to 50%.

[0108] It is understandable that by adjusting the type of polymer matrix and its mass ratio with the temperature-responsive material, the range of glass transition temperature (Tg) can be further optimized, thereby enabling the control of the elastic modulus of the first coating at the first temperature and at the second temperature.

[0109] It is understandable that by adjusting the type of polymer matrix, the mass ratio of the polymer matrix to the temperature-responsive material, and the molecular weight of the temperature-responsive material, the elongation at break of the first coating at the first temperature and the elongation at break at the second temperature can be controlled.

[0110] In addition, the solid content of the first coating slurry can be set to 30wt%~40wt%. Within this solid content range, combined with a shear dispersion process, the particle size distribution range of the slurry can be controlled within 0.8~1.2, thereby ensuring the uniformity of the slurry and thus ensuring that the coating has stable ductility over a wide temperature range.

[0111] It is understandable that the glass transition temperature of the first coating can be changed by adjusting the type of polymer matrix, the type and content of temperature-responsive materials.

[0112] It is understandable that the porosity of the second coating can be changed by adjusting the dispersion of ceramic particles, the size and morphology of ceramic particles, and the second curing process.

[0113] It is understandable that the volume resistivity of the second coating at 85°C can be changed by adjusting the ceramic phase type, porosity, solid content of the slurry, and drying process parameters.

[0114] It is understandable that the thickness of the first coating can be changed by adjusting the coating process parameters.

[0115] It is understandable that the thickness of the second coating can be changed by adjusting the coating process parameters.

[0116] A second aspect of this application provides a battery, including the battery housing assembly of this application.

[0117] In some embodiments, the battery further includes a positive electrode, a negative electrode, an electrolyte, and a separator.

[0118] In some embodiments, the positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector; the positive active material layer includes a positive active material, a positive conductive agent, and a positive binder.

[0119] This application does not limit the positive electrode active material; any known positive electrode active material can be used. For example, the positive electrode active material may be at least one of lithium iron phosphate, lithium manganese iron phosphate, or ternary materials.

[0120] This application does not limit the positive electrode conductive agent; any known positive electrode conductive agent can be used. For example, the positive electrode conductive agent may be at least one of acetylene black, graphene, and carbon nanotubes (CNTs).

[0121] This application does not limit the positive electrode binder; any known positive electrode binder can be used. For example, the positive electrode binder may be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), sodium polyacrylate (PAANa), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR).

[0122] In some embodiments, the negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector; the negative active material layer includes a negative active material, a negative conductive agent, a negative binder, and a negative thickener.

[0123] This application does not limit the negative electrode active material; any known negative electrode active material can be used. For example, the negative electrode active material may be at least one of artificial graphite, natural graphite, silicon carbide, and silicon oxide.

[0124] This application does not limit the choice of negative electrode conductive agent; any known negative electrode conductive agent can be used. For example, the negative electrode conductive agent may be at least one of acetylene black, graphene, and carbon nanotubes (CNTs).

[0125] This application does not limit the negative electrode binder; any known negative electrode binder can be used. For example, the negative electrode binder may be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), sodium polyacrylate (PAANa), and styrene-butadiene rubber (SBR).

[0126] This application does not limit the negative electrode thickener; any known negative electrode thickener may be used. For example, the negative electrode thickener may be carboxymethyl cellulose (CMC).

[0127] In some embodiments, the electrolyte includes an organic solvent, a lithium salt, and additives.

[0128] This application does not limit the choice of organic solvent; any known organic solvent may be used. For example, the organic solvent may be at least one of ethylene carbonate, ethyl methyl carbonate, diethyl carbonate, and dimethyl carbonate.

[0129] This application does not limit the choice of lithium salt; any known lithium salt may be used. Exemplarily, the lithium salt may be at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide.

[0130] This application does not limit the choice of additives; any known additives may be used. For example, the additive may be at least one of vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0131] In some embodiments, a diaphragm is disposed between the positive electrode and the negative electrode.

[0132] Example 1 This application provides a battery casing assembly and a battery. The method for manufacturing the battery casing assembly and the battery includes the following steps: I. Raw material sources and specifications are shown in Table 1. Table 1 II. Detailed Preparation Steps (1) Preparation of the first coating slurry Ingredient ratio (mass ratio): Polymer matrix (TPU): Temperature responsive material (PNIPAM): Additive (KH-550) = 85:10:1 (i.e., 85g TPU + 10g PNIPAM + 1g KH-550, total solid mass 96g); The ratio of the mass of the first solvent (acetone) to the total solid mass is 4:96.

[0133] Mixing process: 1. Add TPU granules (85g) to acetone (4g) and stir magnetically (300r / min) at room temperature for 30min until the TPU is completely dissolved (forming a transparent viscous solution). 2. Add PNIPAM powder (10g) and continue stirring for 1 hour (500 rpm) to ensure uniform particle dispersion; 3. Finally, add KH-550 (1g) and stir for 30 minutes (300r / min) to obtain a uniform first coating slurry.

[0134] (2) Preparation of the second coating slurry Ingredient ratio (mass ratio): ceramic (nano Al2O3): surface treatment agent (KH-550) = 92:2 (i.e., 92g Al2O3 + 2g KH-550, total solid mass 94g); the ratio of the mass of the second solvent (anhydrous ethanol) to the total solid mass is 6:94.

[0135] Mixing process: 1. Add nano Al2O3 (92g) and KH-550 (2g) to anhydrous ethanol (6g) and place them in a planetary ball mill; 2. Ball milling parameters: agate balls (5mm in diameter, 200g in total weight), rotation speed 300r / min, ball milling time 6h (during which the machine is stopped and stirred for 5min every 1h to avoid sedimentation); 3. After ball milling, the slurry is filtered through a 0.45μm filter membrane to remove large particle agglomerates, resulting in a uniform second coating slurry.

[0136] (3) Preparation of battery casing assembly Shell pretreatment: 1. Wipe the aluminum alloy casing three times with anhydrous ethanol (analytical grade) to remove surface oil stains; 2. Lightly sand the surface in the same direction with 800# sandpaper (to remove the oxide layer and enhance adhesion), and blow away the dust with compressed air (0.3MPa); 3. Preheat in a 60℃ oven for 10 minutes (to prevent the slurry from bubbling due to temperature difference during coating).

[0137] First coating application and curing: 1. Coating: An automatic spraying line is used to uniformly spray the first coating slurry onto the surface of the housing (spray gun pressure 0.3MPa, nozzle distance from the surface 15cm, gun speed 0.5m / s), controlling the wet film thickness to be approximately 100μm; 2. Pre-drying: Immediately place the coated housing into a 60℃ forced-air drying oven for 10 minutes to pre-dry (to remove some acetone and prevent bubbling during curing); 3. Curing: Transfer to an infrared curing oven (wavelength 2μm ~ 5μm, power 600W) and cure at 130℃ for 8 minutes to form the first coating.

[0138] Second coating application and curing: 1. Coating: The second coating slurry is applied by spin coating, dropping it onto the surface of the first coating (dropping amount 0.1 mL / cm²). 2 Spin coat at 2000 r / min for 30 s; 2. Drying: Place in an 80℃ vacuum drying oven (vacuum degree -0.09MPa) and dry for 2 hours; 3. Curing: Use a UV curing machine (UV wavelength 365nm, power 100W / cm²). 2 Irradiate for 6 minutes (energy 500mJ / cm²) 2 This allows KH-550 to react with the hydroxyl groups on the Al2O3 surface and the -C=O of the first coating TPU, forming covalent bonds (-Si-O-Al-, -Si-OC-), thus forming the second coating.

[0139] A schematic diagram of the battery casing assembly is shown below. Figure 1 As shown, it includes a housing 101, and a first coating 102 and a second coating 103 disposed on the housing 101.

[0140] (4) Preparation of positive electrode sheet The positive electrode active material (LiNi) 0.8 Mn 0.1 Co 0.1 O2, NCM811), positive electrode conductive agent (Super P) and positive electrode binder (PVDF) are mixed in a mass ratio of 96:2:2, and N-methylpyrrolidone (NMP) is added and stirred to form a positive electrode slurry; the positive electrode slurry is uniformly coated on an aluminum foil current collector, and after drying, rolling and cutting, a positive electrode sheet is obtained.

[0141] (5) Preparation of negative electrode sheet The negative electrode active material (artificial graphite), negative electrode thickener (CMC) and negative electrode binder (SBR) are mixed in a mass ratio of 96:1.5:2.5, and deionized water is added and stirred to form a negative electrode slurry. The negative electrode slurry is uniformly coated on a copper foil current collector, and after drying, rolling and cutting, a negative electrode sheet is obtained.

[0142] (6) Preparation of electrolyte Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:5:2 to prepare a non-aqueous organic solvent. Lithium hexafluorophosphate (LiPF6) was added to the non-aqueous organic solvent to make its concentration 1.15 mol / L, and an appropriate amount of additive (VC, with a mass percentage of 1% based on the total mass of the electrolyte) was added. After mixing evenly, the electrolyte was obtained.

[0143] (7) Battery preparation The positive electrode, separator (polyethylene porous membrane) and negative electrode prepared above are stacked or wound in sequence to form a bare cell; the bare cell is placed into the battery casing assembly prepared in step (3) above, electrolyte is injected, and after encapsulation, formation and aging processes, a secondary battery is obtained.

[0144] Examples 2-4 This application provides a battery casing assembly and a battery. The difference between the battery casing assembly preparation method and that of Example 1 is that the glass transition temperature (Tg) range is adjusted to achieve the parameters in Tables 2-3. In Example 2, the glass transition temperature of the first coating was adjusted to 30°C. Specifically, this was achieved by using a polyether-type TPU (Desmopan® 9370 AU, Tg=28°C) + a temperature-responsive material PNIPAM (Aladdin P106788), and while maintaining the total solid mass, the amount of the temperature-responsive material was reduced to 8g, with the difference adjusted using the polymer matrix. The resulting Tg was 30°C. The achieved parameters were: first temperature modulus of elasticity 35MPa, second temperature modulus of elasticity 100MPa, first temperature elongation at break 230%, and second temperature elongation at break 180%. In Example 3, the glass transition temperature of the first coating was adjusted to 20°C. Specifically, this was achieved by using silicone rubber (VMQ, Tg = -10°C) + PNIPAM, and while maintaining the total solid mass, the temperature-responsive material was reduced to 5g, with the difference adjusted using the polymer matrix. The resulting Tg was 20°C. The achieved parameters were: first temperature modulus of elasticity 30MPa, second temperature modulus of elasticity 80MPa, first temperature elongation at break 200%, and second temperature elongation at break 100%. In Example 4, the glass transition temperature of the first coating was adjusted to 40°C. Specifically, this was achieved by using a polyester-based TPU (Desmopan® 786E, Tg=40°C) + PNIPAM, resulting in a Tg of 40°C. The achieved parameters were: first temperature modulus of elasticity 50 MPa, second temperature modulus of elasticity 120 MPa, first temperature elongation at break 250%, and second temperature elongation at break 250%.

[0145] Examples 5-6 This application provides a battery housing assembly and a battery. The difference between the battery housing assembly preparation method and that of Embodiment 1 is that the thickness of the first coating is adjusted to achieve the parameters in Tables 2-3. In Example 5, the first coating was applied using a scraping process with a scraper gap of 50 μm, a slurry solid content of 30%, and a dry film thickness of 50 μm. In Example 6, when the first coating was applied, the doctor blade gap was set to 100 μm, the slurry solid content was 40%, and the dry film thickness was controlled to be 100 μm.

[0146] Examples 7-9 This application provides a battery housing assembly and a battery. The difference between the preparation method of the battery housing assembly and that of Embodiment 1 is that the porosity of the second coating is adjusted to achieve the parameters in Tables 2-3. In Example 7, the ball milling time of the second coating slurry was set to 8 hours, and while keeping the total solid mass constant, the surfactant KH-550 was changed to 3g, with the difference adjusted using ceramics. The particles were uniformly dispersed, and the porosity was 0.5%. In Example 8, the ball milling time was extended to 12 hours. When the ball milling was in progress for 6 hours, ultrasonic-assisted dispersion treatment was introduced for 30 minutes with the ultrasonic power set to 400W. Then, the remaining 6 hours of ball milling were completed. The particles were tightly packed with a porosity of 0.1%. In Example 9, the ball milling time was shortened to 4 hours, and while keeping the total solid mass unchanged, the surfactant KH-550 was changed to 1g, the difference was adjusted with ceramic, the particles agglomerated, and the porosity was 1%.

[0147] Examples 10-12 This application provides a battery casing assembly and a battery. The difference between the battery casing assembly preparation method and that of Embodiment 1 is that the volume resistivity of the second coating is adjusted to achieve the parameters in Tables 2-3. In Example 10, nano-Al2O3 (99.5% purity, Aladdin A104856) was used. While maintaining the total solid mass, the surfactant KH-550 was replaced with 3g, and the difference was adjusted using ceramic. The volume resistivity was 5 × 10⁻⁶. 14 Ω·cm; In Example 11, high-purity Al2O3 (99.9%) with a volume resistivity of 1×10⁻⁶ was used. 15 Ω·cm; In Example 12, SiC ceramic (semiconductor, resistivity 1×10⁻⁶) was used instead. 13 (Ω·cm), and while keeping the total solid mass constant, the surfactant KH-550 is changed to 5g, and the difference is adjusted with ceramics, resulting in a volume resistivity of 1.1×10⁻⁶. 14Ω·cm.

[0148] Examples 13-14 This application provides a battery housing assembly and a battery. The difference between the battery housing assembly preparation method and that of Embodiment 1 is that the thickness of the second coating is adjusted to achieve the parameters in Tables 2-3. In Example 13, the second coating was applied using a dip coating process, with the lifting speed increased to 10 mm / s and the dry film thickness to 5 μm. In Example 14, the second coating slurry was applied to the surface of the first coating using a precision spraying process. The spraying parameters were: atomization pressure 0.3 MPa, moving speed 200 mm / s, and wet film thickness controlled at 40 μm to 50 μm. After pre-curing at 80°C for 10 min and final curing at 150°C for 30 min, the dry film thickness was measured to be 20 μm.

[0149] Comparative Examples 1-2 This application provides a battery casing assembly and a battery as comparative examples. The difference between the preparation method of the battery casing assembly and Example 1 is that the elastic modulus at the first temperature is not within the range, thereby achieving the parameters in Tables 2-3. In Comparative Example 1, the mass of the additives remained unchanged, the mass of PNIPAM was 12g, the mass of TPU was 88g, the high elastic modulus was insufficient, and the elastic modulus was 25MPa. In Comparative Example 2, the mass of the additives remained unchanged, with PNIPAM at 5g and TPU at 95g. The high-elastic modulus increased, and the elastic modulus was 55MPa.

[0150] Comparative Examples 3-4 This application provides a battery casing assembly and a battery as comparative examples. The difference between the preparation method of the battery casing assembly and Example 1 is that the second temperature elastic modulus is not within the range, thereby achieving the parameters in Tables 2-3. In Comparative Example 3, silicone rubber (VMQ, Tg=-10℃) was used to replace TPU, resulting in a decrease in glass modulus and an elastic modulus of 70MPa. In Comparative Example 4, polyester-type TPU (Tg=50℃) was used to replace polyether-type TPU, resulting in an increased glass modulus and an elastic modulus of 130MPa.

[0151] Comparative Example 5 This application provides a battery housing assembly and a battery as comparative examples. The difference between the preparation method of the battery housing assembly and Example 1 is that the porosity of the second coating is not within the range, thereby achieving the parameters in Tables 2-3. In Comparative Example 5, the ball milling time of the second coating slurry was shortened to 4 hours. While keeping the total solid mass unchanged, the surfactant KH-550 was changed to 1g, and the difference was adjusted with ceramic. The particles agglomerated, and the porosity was 1.2% > 1%.

[0152] Comparative Example 6 This application provides a battery housing assembly and a battery as comparative examples. The difference between the preparation method of the battery housing assembly and Example 1 is that the volume resistivity of the second coating is not within the range, thereby achieving the parameters in Tables 2-3. In Comparative Example 6, the second coating was replaced with SiC ceramic (semiconductor, resistivity 1×10⁻⁶). 13 (Ω·cm), and while keeping the total solid mass constant, the surfactant KH-550 was changed to 5g, and the difference was adjusted with ceramic. The volume resistivity at 85℃ was 1×10 14 Ω·cm.

[0153] Comparative Example 7 This application provides a battery housing assembly and a battery as comparative examples. The difference between the preparation method of the battery housing assembly and Example 1 is that a second coating is not introduced, thereby achieving the parameters in Tables 2-3.

[0154] Comparative Example 8 This application provides a battery housing assembly and a battery as comparative examples. The difference between the preparation method of the battery housing assembly and Example 1 is that the first coating is not introduced, thereby achieving the parameters in Tables 2-3.

[0155] Comparative Example 9 This application provides a battery casing assembly and a battery as comparative examples. The difference between the preparation method of the battery casing assembly and Example 1 is that a second coating is introduced first, followed by a first coating, thereby achieving the parameters in Tables 2-3.

[0156] Comparative Example 10 This application provides a battery casing assembly and a battery as comparative examples. The difference between the preparation method of the battery casing assembly and Example 1 is that the test temperature offset of the first coating is set too small (t1=T1-10℃, t2=T2+10℃).

[0157] Comparative Example 11 This application provides a battery casing assembly and a battery as comparative examples. The difference between the preparation method of the battery casing assembly and Example 1 is that the test temperature offset of the first coating is set too large (t1=T1-30℃, t2=T2+30℃).

[0158] The glass transition temperature Tg of the first coating in the examples and comparative examples, the elastic modulus E1 of the first coating at a first temperature and the elastic modulus E2 of the first coating at a second temperature, the first temperature t1, the second temperature t2, the endothermic transition initiation temperature T1, the endothermic transition termination temperature T2, the elongation at break Eb1 of the first coating at the first temperature and the elongation at break Eb2 of the first coating at the second temperature, the mass percentage W1 of the polymer matrix in the first coating, the mass percentage W2 of the temperature-responsive material in the first coating, and the thickness of the first coating. h1, the porosity P of the second coating, the volume resistivity R of the second coating at 85°C, the mass percentage W3 of ceramic in the second coating, the mass percentage W4 of surface treatment agent in the second coating, and the thickness h2 of the second coating are shown in Tables 2-3; wherein, the embodiments and comparative examples 1 to 9 satisfy t1=T1°C-20°C, t2=T2°C+20°C; comparative example 10 satisfies t1=T1-10°C, t2=T2+10°C; and comparative example 11 satisfies t1=T1-30°C, t2=T2+30°C.

[0159] Table 2 Table 3 The battery casing assemblies and batteries prepared in the examples and comparative examples were subjected to performance tests, including the following aspects: 1. Vickers hardness HV: Characterizes the hardness of the second coating surface. The higher the hardness, the stronger the physical barrier ability to resist lithium dendrite tip puncture. Specifically, it includes the following steps: applying a constant load to the surface of the battery housing assembly through a diamond pyramid indenter, measuring the diagonal length of the indentation, and calculating the ability of the battery housing assembly to resist plastic deformation. The calculation formula is HV=1.854×F / d^2, where F is the load (mN) and d is the average length of the indentation diagonal (μm). The specific testing process is as follows: Take a sample of the battery casing assembly, fix the sample on the stage, mark the uniform position on the coating surface with an optical microscope for positioning, and then use a 100g load indenter to press vertically into the positioning area and hold the pressure for 10s. Use a high-precision micro Vickers hardness tester to measure the lengths d1 and d2 of the two diagonals of the indentation, take the average value as d, and then substitute it into the formula to calculate the HV value.

[0160] 2. Crack length after 500 thermal cycles: This simulates the crack resistance of the coating in the battery casing assembly under real-world conditions (temperature change + charge / discharge stress). Longer cracks indicate poorer stress dissipation, making it easier to induce lithium dendrite penetration or leakage. The specific steps include: taking a finished secondary battery (fully charged) and placing it in a thermal cycling test chamber for temperature shock from -40℃ to 85℃ (heating / cooling rate 5℃ / min, holding for 10min), while simultaneously performing 0.5C charge / discharge cycles; after 500 cycles, disassembling the secondary battery in an inert atmosphere glove box and removing the battery casing assembly. Observing the coating surface using an optical microscope, the lengths of the three longest visible cracks are measured, and the average value is recorded.

[0161] 3. Electrolyte permeability (85℃): Characterizes the density of the coating during long-term contact with the electrolyte; the lower the permeability, the denser the insulating layer, the better it can prevent electrolyte corrosion of the casing leading to short circuits, and also prevent lithium dendrites from growing along the pores; specifically, it includes the following steps: cut a sample of the battery casing assembly, weigh the initial weight m0, then immerse it in the electrolyte with the coating facing down for 24 hours (constant temperature chamber 85℃), remove it, wipe off the electrolyte, weigh it again m1, and record the weight change Δm = m1 - m0, then substitute it into the permeability calculation formula: P = (Δm × 10^6) / (A × t), where P is the permeability, Δmt is the weight gain (g) in 24 hours, and A is the contact area between the coating and the electrolyte (m²). 2 ), t is the soaking time (h), and then take an uncoated shell substrate sheet of the same size as a blank control. P sample = P test - P blank to obtain the corrected permeability.

[0162] The test results are shown in Table 4. Table 4 As can be seen from Table 3, when the technical solution provided in this application is adopted, the resulting battery casing assembly has reduced coating crack length and good insulation properties, while exhibiting excellent barrier properties at high temperatures. Specifically, the obtained battery casing assembly has a Vickers hardness between 850 HV and 1280 HV, a crack length below 80 μm after 500 thermal cycles, and an electrolyte permeability (85°C) below 0.30%. As can be seen from Examples 1-14 and Comparative Examples 1-6, significant effects can be achieved when the parameters of the first coating and the second coating are within the range given in this application; as can be seen from Examples 1-14 and Comparative Examples 7-9, significant effects can be achieved by adopting the battery housing assembly structure of this application.

[0163] As shown in Tables 5 and 6 below, it can be seen from Examples 1, 10, and 11 that when the test temperature deviation of the first coating deviates from the set range of ±20℃, the standard deviation of the values ​​of the elastic modulus E1 of the first coating at the first temperature and the elastic modulus E2 at the second temperature obtained from multiple tests is smaller. This indicates that when the test temperature deviation of the first coating deviates from the set range of ±20℃, the test error caused by the heating rate and thermal history can be eliminated, ensuring the objective reproducibility of the characterization.

[0164] Table 5 Table 6 Example 1: At t1=2℃ and t2=62℃, the first coating was at a stable plateau in the late glassy state and the early elastic state, respectively. At this time, the motion state of the molecular chain segments was highly consistent, so the E1 and E2 values ​​of the 5 tests almost overlapped, and the standard deviation was small (E1 was 0.15, E2 was 0.26), which proved the high reproducibility of the data.

[0165] Comparative Example 10: At t1=12℃, the coating is in the rapid transition zone from the glassy state to the elastic state. At this time, even small temperature fluctuations or differences in thermal history will lead to different degrees of chain segment thawing, resulting in a modulus that fluctuates greatly (32.9~36.2) and a standard deviation that increases sharply to 1.25.

[0166] Comparative Example 11: At t2=82℃, the coating is in the dangerous zone of transition from a highly elastic state to a viscous flow state. At this point, the material is too soft and may flow, resulting in extremely unstable modulus test values ​​(138.2~142.0) with a standard deviation as high as 1.52.

[0167] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of this application and not to limit the scope of protection of this application. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the substance and scope of the technical solutions of this application.

Claims

1. A battery, comprising a battery casing assembly, characterized in that, The battery housing assembly includes a housing, a first coating disposed on at least a portion of the surface of the housing, and a second coating disposed on at least a portion of the surface of the first coating; The elastic modulus of the first coating at a first temperature is 30 MPa to 50 MPa, and at a second temperature it is 80 MPa to 120 MPa. The first temperature is t1℃, where t1 = T1℃ - 20℃, and T1℃ is the endothermic transformation initiation temperature of the first coating in differential scanning calorimetry testing. The second temperature is t2℃, and the second temperature t2 = T2℃ + 20℃, where T2℃ is the end-temperature temperature of the endothermic transformation of the first coating in the differential scanning calorimetry test. The porosity of the second coating is ≤1%, and the volume resistivity of the second coating at 85°C is >1×10⁻⁶. 14 Ω·cm.

2. The battery according to claim 1, characterized in that, The first coating has an elongation at break of 200% to 250% at a first temperature and an elongation at break of 100% to 250% at a second temperature.

3. The battery according to claim 1, characterized in that, The glass transition temperature of the first coating is 20℃~40℃.

4. The battery according to claim 1, characterized in that, The first coating comprises a polymer matrix, a temperature-responsive material, and additives.

5. The battery according to claim 4, characterized in that, In the first coating, the polymer matrix comprises 90% to 95% by mass. And / or, in the first coating, the mass percentage of the temperature-responsive material is 5% to 10%.

6. The battery according to claim 4, characterized in that, The battery satisfies at least one of the following: (1) The polymer matrix is ​​selected from at least one of thermoplastic polyurethane, silicone rubber, and thermoplastic elastomer; (2) The temperature-responsive material is selected from at least one of poly(N-isopropylacrylamide), poly(N-vinylpyrrolidone), and polyacrylic acid; (3) The additive is selected from at least one of dispersants and coupling agents.

7. The battery according to claim 1, characterized in that, The second coating includes ceramics, surface treatment agents, and dispersion promoters.

8. The battery according to claim 7, characterized in that, In the second coating, the ceramic mass percentage is 95%~98%; And / or, in the second coating, the surface treatment agent has a mass percentage of 2% to 5%.

9. The battery according to claim 7, characterized in that, The ceramic is selected from at least one of alumina, silicon carbide, boron nitride, and a composite of alumina and titanium oxide; And / or, the surface treatment agent is selected from at least one of silane coupling agents, titanate coupling agents, aluminate coupling agents, and sulfuric acid-oxalic acid mixtures.

10. The battery according to claim 1, characterized in that, The thickness of the first coating is 50μm~100μm; And / or, the thickness of the second coating is 5 μm to 20 μm.

11. An electrical appliance, characterized in that, Includes the battery as described in any one of claims 1 to 10.

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