Cooperative thermal management-based multifunctional integrated buffer layer and preparation method and application thereof

Abstract

The invention relates to a multifunctional integrated buffer layer based on collaborative thermal management and a preparation method and application thereof, and specifically, the multifunctional integrated buffer layer based on collaborative thermal management comprises a polymer matrix layer; the microencapsulated phase change material is dispersed in the polymer matrix layer; the functional electrolyte storage pipe penetrates through the polymer matrix layer; the outer side of the polymer matrix layer is coated with the flame-retardant shell layer. The device is compact in structure, achieves the function of synchronously regulating and controlling heat management, liquid retention amount and safety, and has remarkable industrial application value.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a multifunctional integrated buffer layer based on synergistic thermal management, its preparation method, and its application. Background Technology

[0002] Pouch lithium-ion batteries have been widely used in consumer electronics, new energy vehicles, and energy storage systems due to their advantages such as high energy density, light weight, and flexible shape design. However, as the market continues to demand higher energy density, cycle life, and safety performance from batteries, traditional pouch cells face a series of severe challenges in structural design and material systems.

[0003] Firstly, in terms of thermal management, traditional pouch cells mainly rely on external thermal management systems at the battery pack level (such as liquid cooling plates, air cooling systems, etc.) to maintain their operating temperature. This external system has a complex structure, significantly increasing the overall manufacturing cost, weight, and volume of the battery pack, and its operation and maintenance costs remain high. More importantly, external thermal management suffers from response delays and inaccurate temperature control, making it difficult to cope with the instantaneous heat generated inside the cell. This leads to uneven temperature distribution within the cell, accelerating performance degradation and creating potential safety hazards.

[0004] Secondly, regarding electrolyte retention and replenishment, in existing processes, the electrolyte is mainly stored in the pores of the separator and the micropores of the electrodes, resulting in a limited electrolyte retention capacity, typically only 8% to 12% of the cell weight. During long-term cycling, the electrolyte is irreversibly and continuously consumed, leading to a continuous thickening of the SEI film at the electrode-electrolyte interface, an increase in interfacial impedance, and accelerated capacity decay. To address this issue, existing technologies have attempted methods such as increasing the electrolyte injection volume and constructing porous coatings on the electrodes or separator (e.g., Chinese patent CN112259796A). However, increasing the electrolyte injection volume is limited by the packaging space of flexible packaging, and excessive electrolyte injection can easily lead to gas expansion or even leakage of the cell during cycling; while porous coating designs often come at the cost of sacrificing energy density.

[0005] Furthermore, regarding safety protection, especially thermal runaway protection, traditional fully filled electrolyte cells, under thermal abuse conditions, experience a large concentration of electrolyte participating in a violent reaction, which drastically increases the risk of combustion and explosion. Existing technologies have introduced solutions with built-in electrolyte replenishment or fire extinguishing modules (e.g., Chinese patent CN220121904U). This solution uses a pre-installed, three-layered metal-plastic film cavity filled with phase change material or fire extinguishing agent to achieve thermal management or safety protection functions. However, such solutions are relatively singular in function, typically focusing only on one of "liquid storage and replenishment," "thermal management," or "flame retardancy," failing to achieve deep synergy and integration of multiple functions. For example, the cavity structure of Chinese patent CN220121904U does not involve the collaborative working mechanism of the porous electrolyte storage structure and phase change material efficiently integrated with the side space of the electrode core; its functions are discrete rather than coupled.

[0006] In addition, in order to adapt to the gas generation during the formation process of pouch batteries, the traditional process requires lengthening the gas bag, which not only increases the cost of machine adjustment, but also causes waste of materials.

[0007] In summary, there is an urgent need in this field for an innovative solution that can integrate thermal management, dynamic electrolyte replenishment, and multi-level safety protection functions without significantly sacrificing energy density, thereby fundamentally and synergistically improving the cycle life, thermal stability, and safety performance of pouch cells. Summary of the Invention

[0008] Based on the aforementioned technical deficiencies, this invention adds additional fillers to one side, both sides, and inside the stacked battery cell. The fillers include a structure with an insulating coating such as ceramic that prevents thermal runaway of the battery cell, as well as a porous material with electrolyte storage function. This material pre-stores electrolyte for subsequent cycling and storage consumption. In addition, there is a phase change material layer, which absorbs heat during battery cell charging and discharging and slowly releases the heat, thereby stabilizing the battery cell temperature and reducing battery temperature rise.

[0009] The first inventive point of this invention is a multifunctional integrated buffer layer based on synergistic thermal management, comprising: A polymer matrix layer; a microencapsulated phase change material dispersed within the polymer matrix layer; a functional electrolyte reservoir penetrating the polymer matrix layer; and a flame-retardant shell layer covering the outside of the polymer matrix layer.

[0010] Furthermore, the thickness of the polymer matrix layer is 0.5 mm to 5 mm; the amount of the microencapsulated phase change material added is 5% to 80% of the polymer matrix; and the thickness of the flame-retardant shell layer is 0.005 mm to 0.5 mm.

[0011] Furthermore, the polymer matrix includes at least one of the following: polyvinylidene fluoride-hexafluoropropylene copolymer, modified polyimide aerogel, cross-linked polymethyl methacrylate / polyurethane, cross-linked nanocellulose / clay, cross-linked fluorinated nanosilica-polyurethane foam, cross-linked bacterial cellulose / boron nitride nanosheets, and cross-linked sodium alginate / epoxy resin.

[0012] Furthermore, the microencapsulated phase change material includes solid-liquid phase change materials and solid-solid phase change materials; The phase transition enthalpy of the microencapsulated phase change material is 50-300 kJ / kg; Preferably, the enthalpy change range of the solid-liquid phase change material is 150–250 kJ / kg, and the enthalpy change range of the solid-solid phase change material is 80–180 kJ / kg.

[0013] Preferably, the microencapsulated phase change material is encapsulated within a polymer shell; preferably, the polymer shell further comprises carbon nanotubes or graphene.

[0014] Furthermore, at least one end of the functional electrolyte storage tube is provided with a storage tube seal, and the storage tube seal is made of a polymer material with a melting point of T2, wherein 40℃ < T2 < 70℃.

[0015] Preferably, the functional electrolyte pre-filled in the functional electrolyte storage tube includes one or more of the following: lithium-replenishing electrolyte, flame-retardant electrolyte, high-concentration lithium salt electrolyte, pure solvent electrolyte, or battery cell native electrolyte. Preferably, the amount of the functional electrolyte is 1% to 30% of the conventional injection volume.

[0016] Furthermore, the flame-retardant shell layer includes a ceramic or aramid-coated PP or PE film, a zirconium oxide and polyvinylidene fluoride coating, cross-linked polyethylene, a polyolefin elastomer, or a polyvinylidene fluoride-hexafluoropropylene copolymer-based composite material.

[0017] The second inventive point of this invention is a method for preparing the aforementioned multifunctional integrated buffer layer, comprising the following steps: S1. Constructing a porous framework: Using polymer matrix materials, a three-dimensional framework with high porosity and interconnected channels is prepared through freeze-drying, supercritical drying or foaming technology; S2. Introducing microencapsulated phase change material: Mixing the microencapsulated phase change material with the low-viscosity polymer matrix material precursor described in step S1 to form a microencapsulated phase change material slurry; S3. Vacuum impregnation and curing: Under vacuum conditions, the slurry prepared in step S2 is impregnated into the three-dimensional porous skeleton prepared in step S1 to fill the pores inside the skeleton, and then cured by heating or ultraviolet light. S4. Coat the outer layer of the three-dimensional porous skeleton prepared in step S3 with a flame-retardant shell.

[0018] The third inventive point of this invention is a method for preparing the aforementioned multifunctional integrated buffer layer, comprising the following steps: I. Blending and Slurry Preparation: Microencapsulated phase change material, polymer matrix, pore-forming agent and solvent are mixed to form a homogeneous slurry with a solid content of 10%-30%; II. Casting and film formation: The slurry prepared in step I is coated and formed into a film using a casting machine; III. Phase Inversion and Extraction: The polymer matrix is ​​solidified by phase inversion, while the pore-forming agent is extracted, thereby forming interconnected micron-sized pores in the membrane; IV. Coat the outer layer of the polymer matrix prepared in step III with a flame-retardant shell.

[0019] Furthermore, the pore-forming agent accounts for 1% to 80% of the total substance, and the pore-forming agent includes at least one of soluble salts and paraffin microspheres; the solvent includes at least one of N-methylpyrrolidone, glycerol, toluene, ethanol, carboxymethyl cellulose, and polyvinylidene fluoride, and the solvent accounts for 30% to 85% of the total substance.

[0020] The fourth inventive point of this invention is: a battery comprising a stacked electrode core and the aforementioned multifunctional integrated buffer layer, wherein the multifunctional integrated buffer layer is disposed on one side, both sides, or inside the stacked electrode core.

[0021] Preferably, during the stacking process, the multifunctional integrated buffer layer is provided between each electrode unit.

[0022] Preferably, the thickness of the multifunctional integrated buffer layer accounts for 3% to 20% of the cell thickness.

[0023] The fifth inventive point of this invention is: a method for manufacturing a battery cell, comprising: After the hot pressing and shaping process of the electrode core, the multifunctional integrated buffer layer described above or the multifunctional integrated buffer layer prepared by the above preparation method is placed on one side of the stacked electrode core and bonded with adhesive tape that is compatible with electrolyte. Then, it is encapsulated through the top-side sealing process of the soft-pack battery cell.

[0024] The sixth inventive point of this invention is the application of the aforementioned multifunctional integrated buffer layer in the thermal management of pouch batteries, the application of the multifunctional integrated buffer layer in extending the cycle life of pouch batteries, and / or, the application of the multifunctional integrated buffer layer in improving the safety performance of pouch batteries.

[0025] Beneficial effects This invention achieves a breakthrough improvement in the overall performance of pouch cells through a triple synergistic mechanism of "thermal-liquid-safety". In terms of thermal management, microencapsulated phase change material (MCPCM) integrated into the polymer matrix constitutes a highly efficient built-in thermal buffer system, capable of rapidly absorbing pulse heat generated during charging and discharging. This reduces the maximum temperature rise of the cell at 2C rate by more than 18°C ​​compared to traditional cells, significantly improving the cell's thermal stability and operating temperature uniformity. Regarding cycle life, the unique through-type electrolyte storage tube structure and thermally responsive sealing design enable dynamic "on-demand" replenishment of the electrolyte. This mechanism precisely replenishes the electrolyte consumed during cycling, effectively mitigating interfacial side reactions, improving the cell's capacity retention rate, and greatly delaying capacity decay. In terms of safety performance, a four-level active protection system is constructed: "phase change heat absorption → dynamic electrolyte replenishment → thermal shrinkage and current limiting → melting and closure". The outer flame-retardant shell can rapidly melt and close the pores under thermal abuse conditions, physically isolating flammable materials and raising the thermal runaway trigger temperature threshold to over 120°C, successfully curbing the risk of combustion and explosion.

[0026] In summary, this invention, with its integrated and compact structure, simultaneously overcomes three major challenges: thermal management, liquid retention, and safety, achieving a technological leap from "passive response" to "proactive intelligent management," and has significant industrial application value. Attached Figure Description

[0027] Figure 1 Schematic diagram of multifunctional integrated buffer layer and stacked pole core; Figure 2 Top view of the multi-functional integrated buffer layer; Figure 3 Main view of the multi-functional integrated buffer layer; Reference numerals: 101-Stacked electrode core, 102-Multifunctional integrated buffer layer, 201-Seal of liquid storage tube, 202-Polymer matrix, 203-Microencapsulated phase change material, 204-Functional electrolyte storage tube, 205-Flame-retardant shell. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this application clearer, a more detailed description is provided below. However, it should be understood that the description herein is merely for explaining this application and is not intended to limit its scope.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. All reagents and instruments used herein are commercially available, and the characterization methods involved can be found in relevant descriptions in the prior art, and will not be repeated here.

[0030] To further understand this application, the following detailed description is provided in conjunction with the preferred embodiments.

[0031] Example 1 This embodiment provides a multifunctional integrated buffer layer (102) based on synergistic thermal management, comprising: a polymer matrix layer; a microencapsulated phase change material (203) dispersed within the polymer matrix layer; a functional electrolyte reservoir (204) penetrating the polymer matrix (202) layer; and a flame-retardant shell layer (205) covering the outside of the polymer matrix layer, such as Figure 1 , 2 As shown in Figure 3.

[0032] As a further preferred embodiment, the thickness of the polymer matrix layer is 0.5 mm to 5 mm; the amount of the microencapsulated phase change material added is 5% to 80% of the polymer matrix; and the thickness of the flame-retardant shell layer is 0.005 mm to 0.5 mm.

[0033] Polymer matrix: A substance with certain elastic deformation and structural strength, mainly composed of an organic copolymer matrix with small swelling (less than 5%) and high heat distortion temperature (greater than 120℃).

[0034] Preferably, the polymer matrix comprises at least one of the following: polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), modified polyimide (PI) aerogel, cross-linked polymethyl methacrylate / polyurethane (PMMA / PU), cross-linked nanocellulose / clay, cross-linked fluorinated nanosilica-polyurethane (SiO2-PU) foam, cross-linked bacterial cellulose / boron nitride nanosheets (BNNS), and cross-linked sodium alginate / epoxy resin.

[0035] Microencapsulated phase change materials: Their main function is to absorb a large amount of heat generated during the charging and discharging of the battery cell near the phase change temperature, thereby reducing the temperature rise and maintaining the stability of the battery temperature.

[0036] Preferably, the phase transition enthalpy of the microencapsulated phase change material is 50-300 kJ / kg; Preferably, the microencapsulated phase change material includes solid-liquid phase change materials and solid-solid phase change materials; Solid-liquid phase change materials (SCTs): Available materials include straight-chain alkanes and polyethylene waxes. The carbon chain length can be flexibly selected based on the actual operating temperature of the battery cell. To maximize heat dissipation area and prevent direct contact between the SCT and the battery, physical isolation is the safest strategy, despite the material's inertness. SCTs are characterized by high enthalpy change and low cost.

[0037] Preferably, the enthalpy change range of the solid-liquid phase change material is 150–250 kJ / kg.

[0038] Solid-solid phase change materials: Layered perovskite materials can be selected, which are a class of inorganic-organic hybrid materials with a typical layered structure, achieving heat storage through crystal transformation. Polyols such as neopentyl glycol (NPG), trimethylolethane (TME), and pentaerythritol (PE) can also be used, as these materials have good chemical stability.

[0039] Preferably, the enthalpy change range of the solid-solid phase change material is 80–180 kJ / kg. As a further preferred embodiment, the microencapsulated phase change material is encapsulated within a polymer shell; preferably, the polymer shell material further includes carbon nanotubes or graphene.

[0040] When microencapsulated phase change materials (MCPCMs) are required, encapsulating the phase change material within a polymer shell such as melamine resin, polymethyl methacrylate, or expanded graphite can completely solve leakage and contact problems. To enhance the thermal conductivity of the shell, highly thermally conductive materials such as carbon nanotubes and graphene can be added.

[0041] Functional electrolyte storage tube: a channel formed naturally through a pre-set shape.

[0042] As a further preferred embodiment, at least one end of the functional electrolyte storage tube is provided with a storage tube seal, and the storage tube seal is made of a polymer material with a melting point of T2, wherein 40℃ < T2 < 70℃.

[0043] Storage pipe sealing: A polymer material with a certain melting point (T2) dissolves and releases the functional electrolyte in the storage pipe after reaching the characteristic temperature of T2.

[0044] The multifunctional buffer layer in this invention has several characteristic temperatures, which correspond to the four levels of active safety protection. The characteristic temperatures can be flexibly selected according to the battery cell usage strategy. Normal operating condition: T1 (30℃ < T1 < 60℃) Accelerated decay: T2 (40℃ < T2 < 70℃) Early stage of heat abuse: T3 (60℃ < T3 < 85℃) Thermal runaway trigger period: T4 (75℃ < T4 < 120℃) Normal operating condition (<T1): The core phase change material normally absorbs the heat of charging and discharging. As the expansion force of the cell increases, the electrolyte in the channel is squeezed and slowly released into the electrode core through the porous material at the top and bottom to dynamically replenish the electrolyte.

[0045] Accelerated decay (<T2): After the phase change material reaches its maximum designed heat absorption, the cell temperature continues to rise. The porous material at the top and bottom of the channel melts, and a large amount of electrolyte enters the electrode core. Timely replenishment of electrolyte reduces the cell decay rate.

[0046] Early stage of thermal abuse (<T3): The core phase change material absorbs a large amount of heat, striving to mitigate the temperature rise and buy valuable buffer time for the system. The outer shell begins to soften and undergo lateral thermal contraction. This contraction produces two key effects: Physical isolation: Tightening the channel between the battery cell and the cell, thus restricting the exchange of matter.

[0047] Mechanical compression: The contraction force will slightly compress the core, which helps to "squeeze" the internally stored electrolyte towards the cell more quickly, making a final emergency replenishment and alleviating the impending local dryness.

[0048] Thermal runaway triggering period (<T4): The outer casing melts and closes the pores, completely isolating thermal runaway within the cell body.

[0049] Preferably, the functional electrolyte pre-filled in the functional electrolyte storage tube includes one or more of the following: lithium-replenishing electrolyte, flame-retardant electrolyte, high-concentration lithium salt electrolyte, pure solvent electrolyte, or original electrolyte of the battery cell.

[0050] Preferably, the amount of the functional electrolyte is 1% to 30% of the conventional injection volume.

[0051] Flame-retardant shell: A flame-retardant coating with thermal closed-cell effect.

[0052] Preferably, the flame-retardant shell layer comprises a ceramic or aramid-coated PP or PE film, a zirconium oxide and polyvinylidene fluoride (PVDF) coating, cross-linked polyethylene, a polyolefin elastomer, or a polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) based composite material.

[0053] Example 2 This example provides a method for preparing a multifunctional integrated buffer layer according to Embodiment 1, including the following steps: S1. Constructing a porous framework: Using polymer matrix materials, a three-dimensional framework with high porosity and interconnected channels is prepared through freeze-drying, supercritical drying or foaming technology; S2. Introducing microencapsulated phase change material: Mixing the microencapsulated phase change material with the low-viscosity polymer matrix material precursor described in step S1 to form a microencapsulated phase change material slurry; S3. Vacuum impregnation and curing: Under vacuum conditions, the slurry prepared in step S2 is impregnated into the three-dimensional porous skeleton prepared in step S1 to fill the pores inside the skeleton, and then cured by heating or ultraviolet light. S4. Coat the outer layer of the three-dimensional porous skeleton prepared in step S3 with a flame-retardant shell.

[0054] The core of this preparation method is to construct a preform that combines a high-porosity region with pre-reserved through-channels. The formation of these through-channels can be achieved by pre-setting a soluble or fusible mandrel before molding. After the framework solidifies, the mandrel is removed by dissolving or melting to obtain the desired liquid storage channels. This framework has two characteristics: one is its relatively high porosity for filling microencapsulated phase change materials, and the other is the through-channels used to form the liquid storage channels. The preparation of the through-channels is similar to first pre-fabricating a model of the channels, and then, when preparing the three-dimensional framework, the space occupied by the channel model will not be encroached upon. After the three-dimensional framework is fabricated, the channels are etched out through etching and extraction.

[0055] This embodiment also provides a method for preparing the multifunctional integrated buffer layer according to Embodiment 1, including the following steps: I. Blending and Slurry Preparation: Microencapsulated phase change material, polymer matrix, pore-forming agent and solvent are mixed to form a homogeneous slurry with a solid content of 10%-30%; II. Casting and film formation: The slurry prepared in step I is coated and formed into a film using a casting machine; III. Phase Inversion and Extraction: The polymer matrix is ​​solidified by phase inversion, while the pore-forming agent is extracted, thereby forming interconnected micron-sized pores in the membrane; IV. Coat the outer layer of the polymer matrix prepared in step III with a flame-retardant shell.

[0056] As a further preferred embodiment, the pore-forming agent accounts for 1% to 80% of the total substance, and the pore-forming agent includes at least one of soluble salts and paraffin microspheres; the solvent includes at least one of N-methylpyrrolidone (NMP), glycerol, toluene, ethanol, carboxymethyl cellulose, and polyvinylidene fluoride, and the solvent accounts for 30% to 85% of the total substance.

[0057] Example 3 This embodiment provides a battery including a stacked electrode core and a multifunctional integrated buffer layer as described in Embodiment 1. The multifunctional integrated buffer layer is disposed on one side of the stacked electrode core. Figure 1 As shown, on both sides or inside.

[0058] As a further preferred embodiment, during the stacking process, the multifunctional integrated buffer layer is provided between each electrode unit.

[0059] The laminated electrode core comprises alternating layers of positive electrode plates, negative electrode plates, and separators.

[0060] The multifunctional integrated buffer layer can be a sheet-like structure set on one or both sides of the electrode core, or it can be placed inside the electrode core. A more extreme solution is to separate each electrode unit with this "core-shell composite material" during the stacking process to achieve three-dimensional protection of the entire cell.

[0061] The core of this sheet-like structure is composed of two hybrid components. Macroscopic channels store and transport the electrolyte, with the upper and lower portions sealed using a porous material with a melting point of T2. Microencapsulated phase change material, acting as a core filler, is uniformly dispersed within the matrix, responsible for thermal management. These two structures are integrated together through a stable, thermodynamically compatible polymer matrix. The electrolyte-phase change binary composite material handles daily thermal management and electrolyte storage and replenishment. Outside this structure, a layer of thermally shrinkable and meltable closed-cell material completely encapsulates the composite. This layer, consisting of a ceramic layer or aramid nanofiber-coated PP film, a zirconium oxide and PVDF coating, or cross-linked polyethylene and polyolefin elastomers, acts as a melt seal to block and release channels in case of thermal runaway.

[0062] Level 4 Active Safety Protection: It constructs a system of "phase change heat absorption (stabilization) → dynamic liquid replenishment (buffering) → thermal shrinkage and flow restriction (early warning) → melting and pore closure (blocking)" to upgrade from passive protection of fillers to multi-level active intelligent management.

[0063] As a further preferred embodiment, the thickness of the multifunctional integrated buffer layer accounts for 5% to 30% of the cell thickness.

[0064] Example 4 This embodiment also provides a method for manufacturing a battery cell, including: after the hot pressing and shaping process of the electrode core, placing the multifunctional integrated buffer layer described in Embodiment 1 or the multifunctional integrated buffer layer prepared by Embodiment 2 on one side of the stacked electrode core, and bonding it with an adhesive tape that is compatible with electrolyte, and then encapsulating it through the top-side sealing process of the soft-pack battery cell.

[0065] Example 5 This embodiment provides an application of the multifunctional integrated buffer layer described in Embodiment 1 in the thermal management of a pouch battery. After applying the multifunctional integrated buffer layer, during battery operation (charging and discharging), heat is transferred from the inside of the cell to the surface. When the temperature of the contact surface reaches T1℃, the microencapsulated phase change material in the buffer layer undergoes a phase change, absorbing and storing a large amount of heat, effectively delaying the rapid rise in the overall battery temperature and maintaining the battery's operating temperature plateau within a relatively safe range of T1℃. Battery packs using this buffer layer show a 20% reduction in peak temperature rise during cycle testing. Simultaneously, the porous matrix ensures the inherent compressibility and electrical insulation of the buffer layer, providing continuous mechanical protection for the cell. The thermal management effect of the microencapsulated phase change material improves the thermal stability of the cell.

[0066] This embodiment also provides an application of the multifunctional integrated buffer layer described in Embodiment 1 in extending the cycle life of a pouch cell. During battery cycling, the internal pressure of the cell fluctuates periodically. The three-dimensional porous structure and absorbent gel of this buffer layer act as an "electrolyte reservoir." When the internal pressure increases, some electrolyte is temporarily stored in the pores of the buffer layer. When local electrolyte depletion occurs due to side reactions or insufficient interface wetting, the cell thickness increases, the expansion force increases, and the buffer layer is compressed, dynamically and slowly replenishing the cell, thereby continuously maintaining a good wetting state at the electrode / electrolyte interface. As the temperature gradually rises to T2℃, the porous material at both ends of the pores dissolves, and all the electrolyte is released into the electrode core. Comparative tests show that the pouch cell using this buffer layer increases the cycle life from 1500 cycles to 3000 cycles under 5C / 10C and 25℃ conditions. The dynamic electrolyte replenishment mechanism of the multifunctional integrated buffer layer extends the cell cycle life.

[0067] This embodiment also provides an application of the multifunctional integrated buffer layer described in Embodiment 1 in improving the safety performance of pouch batteries. At the end of the battery's lifespan, the internal temperature rises significantly, reaching the characteristic temperature T3°C of early thermal abuse. The phase change material inside the buffer layer has reached its heat absorption limit, while the cell temperature continues to rise, reaching the outer pore temperature, thus physically isolating the buffer layer from the electrode core. Comparative tests show that battery packs using this buffer layer have a thermal runaway trigger time delayed by approximately 25% in simulated thermal abuse tests.

[0068] Example 6 Basic cell specifications: System: NCM622 / graphite pouch cell Nominal capacity: 5 Ah Dimensions: 100 mm × 60 mm × 8 mm Electrolyte solvent: 1 M LiPF6 in EC:EMC (3:7, v / v) Experimental Example 1 1. A multifunctional integrated buffer layer based on collaborative thermal management: 1) Key parameters: Multifunctional integrated buffer layer thickness: 10% of the cell thickness; The polymer matrix is ​​0.8 mm thick and is made of modified polyimide (PI) aerogel. MCPCM: Microencapsulated fossil wax (phase transition temperature 45℃, enthalpy 200 kJ / kg), wall material polymethyl methacrylate doped with 2 wt% carbon nanotubes; Liquid storage pipeline: The sealing material has a melting point of T2 = 60℃ and stores a lithium replenishment electrolyte containing 2% FEC + 3% VC + 1M LiPF6; Flame-retardant shell: aramid nanofiber coated PP film, closed-cell temperature T4 = 110℃; Cell electrolyte filling volume: 0.8 times the conventional electrolyte filling volume (i.e., reserving 20% ​​space for the built-in buffer layer); 2) The preparation method is as follows: Prepare 100g of multifunctional integrated buffer layer slurry (excluding subsequent electrolyte and external coating film) for casting film formation.

[0069] Step I. Blending and Pulping: ①Formulation calculation: The mass ratio of PI aerogel, microencapsulated paraffin wax coated with wall material, and pore-forming paraffin microspheres is 7:2.2:0.8. This is based on preparing 100g of slurry (15% solid content). Total solid mass: 15g, including 10.5g PI aerogel, 3.3g microencapsulated paraffin wax coated with wall material, and 1.2g paraffin microsphere pore-forming agent; NMP solvent mass: 85g; ② Dissolution / Dispersion: Add 85g of NMP to a beaker equipped with a stirrer, place it on a heated stirrer, and heat to 50℃. Slowly add 10.5g of modified PI aerogel powder, maintaining a speed of 400rpm, and continue stirring for 2 hours until a uniform, slightly viscous, pale yellow dispersion is formed. Cool the system to room temperature (25℃) to prevent heat damage to the microcapsules. Under gentle stirring at 200rpm, slowly add 3.3g of wall-coated paraffin wax and 1.2g of pore-forming paraffin microspheres. Continue stirring for 2 hours to ensure uniform dispersion of the microcapsules without visible agglomeration. Transfer the slurry to a vacuum degassing machine and degas at a vacuum of -0.095MPa for 30 minutes until no bubbles escape from the slurry. Obtain a uniform and stable final slurry.

[0070] Step II. Casting Film Formation: Horizontally fix the clean, dry glass plate or polyester film onto the casting machine or coating platform. Set the squeegee gap (wet film thickness) to 2.5mm (calculated based on solids content; dry film thickness is 15% * wet film thickness). When using the casting machine, set the substrate movement speed to 0.5m / min. After one coat, place a tube shaped like a liquid reservoir onto the wet film, and then perform a second coat. When coating manually, maintain a uniform speed and scrape smoothly. Pour the degassed slurry onto the front end of the substrate, immediately start the casting machine, or use a squeegee to scrape evenly to form a smooth wet film.

[0071] Step III. Phase Inversion and Extraction: Deionized water and NMP are mixed at a volume ratio of 9:1 and placed in a constant-temperature water bath at 25°C. The substrate with the wet film cast is then steadily immersed in the coagulation bath for 10 minutes. During this process, the polymer (PI) undergoes solvent-induced phase separation and solidifies into a film, initially forming a porous structure. The pre-cured film is carefully peeled off from the substrate. The film is transferred to deionized water, with the water changed every 2 hours for 6 hours to fully extract any residual NMP solvent, finally yielding the polymer matrix layer. Step IV. Finally, fill the channel with 10% lithium electrolyte, seal the opening with a thin film of polycaprolactone, a porous material with a melting point of 60°C, and finally cover it with a PP film coated with aramid nanofibers.

[0072] 2. A battery cell, the preparation method of which is as follows: after the hot pressing and shaping process of the electrode core, the multifunctional integrated buffer layer prepared above is placed on one side of the stacked electrode core, 10% lithium electrolyte is pre-encapsulated in the channel, and adhesive tape with good compatibility with electrolyte is used for bonding, and then the soft-pack battery cell top side sealing process is performed for encapsulation.

[0073] Experimental Example 2 1. A multifunctional integrated buffer layer based on collaborative thermal management: 1) Key parameters: Multifunctional integrated buffer layer thickness: 5% of cell thickness Polymer matrix: Sodium alginate + epoxy resin composite matrix, with a thickness of 0.5 mm; MCPCM: Perovskite phase change material (phase change temperature 30℃, enthalpy 80 kJ / kg), wall material is polymethyl methacrylate doped with 5 wt% carbon nanotubes; Storage pipeline: The sealing material has a melting point of T2 = 40℃ and stores a high-concentration lithium salt electrolyte containing 2M LiPF6; Flame-retardant shell: ceramic-coated PE film, closed-cell temperature T4 = 130℃; Cell electrolyte filling volume: 0.9 times the conventional electrolyte filling volume; 2) The preparation method is as follows: Step S1: Prepare a 3-5 wt% sodium alginate aqueous solution and magnetically stir at 50°C for 4 hours until completely dissolved, forming a homogeneous, transparent, viscous liquid. Pour the solution into a mold (with a pre-installed reservoir tube shape), pre-freeze in a -20°C freezer for 6 hours, and then transfer to a -80°C ultra-low temperature freezer for 4 hours to ensure complete freezing. Quickly place the frozen sample into a freeze dryer and dry for 48-72 hours under conditions of cold trap temperature ≤ -50°C and vacuum degree ≤ 10 Pa. Remove the sample to obtain a three-dimensional sponge-like skeleton with high porosity (>90%) and interconnected ice crystal template pores.

[0074] Step S2: Weigh the epoxy resin and curing agent at a mass ratio of 100:35. Mix the two at room temperature (25℃) and stir at 500 rpm for 10 minutes to obtain a homogeneous, low-viscosity mixed precursor. Gradually add the perovskite phase change material to the above mixed precursor while gently stirring at 300 rpm. The amount of perovskite phase change material added is 50 wt% of the total mass of the precursor. Continue stirring for 30 minutes to ensure that the phase change material is evenly dispersed and free from severe sedimentation and agglomeration. Place the slurry in a vacuum drying oven and degas for 15 minutes under a vacuum of -0.095 MPa to remove air bubbles introduced by stirring, obtaining the slurry to be impregnated.

[0075] Step S3: Dry the porous framework prepared in Step S1 in a 60℃ oven for 2 hours to ensure no residual moisture inside the framework, then cool and set aside. Completely immerse the dried framework in the slurry prepared in Step S2. Place the entire framework in a vacuum drying oven and evacuate to -0.1MPa. Maintain the vacuum for 30-45 minutes, during which bubbles can be observed continuously escaping from the framework pores. Slowly release the vacuum, using atmospheric pressure to fully press the slurry into all the pores of the framework. Remove the impregnated sample and gently scrape off excess slurry from the surface with a scraper. Place it in a forced-air drying oven and perform stepwise temperature increases for curing according to the program of 80℃ / 2 hours + 120℃ / 2 hours. Place the sample under a UV curing machine and irradiate at a wavelength of 365nm and an intensity of 50mW / cm² for 5 minutes for initial curing, then cure at 60℃ for 1 hour to obtain the polymer matrix layer. Step S4: Finally, fill the channel with high-concentration lithium salt electrolyte, seal the opening with a porous material paraffin / PET composite film with a melting point of 40℃, and finally cover it with a PE film coated with ceramic alumina.

[0076] 2. A battery cell, the preparation method of which is as follows: after the hot pressing and shaping process of the electrode core, the multifunctional integrated buffer layer prepared above is placed on one side of the stacked electrode core, 10% electrolyte is pre-encapsulated in the channel, and adhesive tape with good compatibility with electrolyte is used for bonding, and then the cell is encapsulated through the top side sealing process of the soft-pack battery cell.

[0077] Comparative Example 1 This comparative example provides a method for manufacturing a battery cell, including: after the core hot-pressing shaping process, without adding a multi-functional integrated buffer layer, the electrolyte filling volume is 100%, followed by a top-side sealing process for soft-pack battery cells, and subsequent normal processes such as formation, capacity testing, and aging. A conventional fully filled electrolyte battery cell has no built-in functional layers.

[0078] Comparative Example 2 This comparative example provides a method for manufacturing a battery cell, comprising: after the hot pressing and shaping process of the electrode core, placing a filler with only a through-channel liquid storage layer on one side of the stacked electrode core, wherein the through-channel liquid storage layer is the same as the liquid storage structure of Example 1, but without MCPCM and flame-retardant shell, 10% electrolyte is pre-encapsulated in the channel, and the filler is bonded with an adhesive tape that is highly compatible with the electrolyte, and then the cell is encapsulated through a top-side sealing process, followed by normal processes such as formation, capacity testing, and aging. Other materials and their preparation methods are the same as in Example 1.

[0079] Comparative Example 3 This comparative example provides a method for manufacturing a battery cell, including: after the hot pressing and shaping process of the electrode core, placing a filler containing only microcapsule phase change material, wherein the filler only has a microcapsule paraffin composite film and has no electrolyte storage channel or flame retardant layer, on one side of the stacked electrode core, and bonding it with an adhesive tape that is compatible with the electrolyte. Then, it is encapsulated through a top-side sealing process for a soft-pack battery cell, followed by normal processes such as formation, capacity testing, and aging. Other materials and their preparation methods are the same as in Example 1.

[0080] Comparative Example 4 This comparative example provides a method for manufacturing a battery cell, including: after the hot pressing and shaping process of the electrode core, placing an aramid / PP film with flame-retardant function (only the aramid / PP flame-retardant film is attached to the electrode core side (no electrolyte, no phase change material)) on one side of the stacked electrode core, and bonding it with an adhesive tape that is compatible with the electrolyte. Then, it is encapsulated through the top-side sealing process of the soft-pack battery cell, followed by normal processes such as formation, capacity testing, and aging. Other materials and their preparation methods are the same as in Example 1.

[0081] Example 7: Effect Example 1. Cycle Life Comparison Test: The battery cells prepared for each test case and the comparative example were subjected to cycle tests at an ambient temperature of 25°C and a charge / discharge rate of 1C. Each cycle included constant current and constant voltage charging to the cutoff voltage, followed by constant current discharging to the cutoff voltage after resting. The test was continued until the capacity retention rate of the battery cell decayed to 80% of the initial capacity, and the corresponding number of cycles was recorded. The specific results are shown in Table 1.

[0082] 2. High-rate temperature rise test: After fully charging the cells prepared for each test example and the comparative example at 25°C, constant current discharge was performed at an extremely high rate of 10°C. The temperature at the center of the cell surface was monitored in real time using thermocouples, and the highest temperature rise value (ΔT) from the start to the end of the discharge was recorded. The specific results are shown in Table 1.

[0083] 3. Thermal runaway safety test: A thermal chamber experiment was conducted. A fully charged cell was placed in the chamber and heated at a programmed rate of 5℃ / min, while monitoring the changes in cell voltage and temperature. When the cell temperature experienced a rapid jump (temperature rise rate ≥ 1℃ / s) accompanied by smoke, fire, or explosion, it was determined to be thermal runaway, and the phenomenon was recorded. Specific results are shown in Table 1.

[0084] Table 1 Performance test results of the battery cells prepared in the experimental examples and comparative examples of this application.

[0085] in conclusion: The experimental example 1 of this invention (containing lithium-ion electrolyte, phase transition temperature 45°C) showed the best performance, with a lifespan three times that of Comparative Example 1 (conventional cell). The performance of Comparative Example 2 (liquid storage only) and Comparative Example 3 (phase transition only) was far inferior to the integrated synergistic design of this invention, which demonstrates the significant synergistic gain effect produced by the synergistic integration of liquid storage, thermal management, and safety protection.

[0086] The temperature control effect of this invention is extremely outstanding. The temperature rise of Test Example 1 and Test Example 2 was only 15℃ and 18℃ respectively, significantly lower than the 30℃ of Comparative Example 1. Comparative Example 3 (phase change only) is inferior to this invention, indicating that the integrated thermal coupling design of the microencapsulated phase change material with the matrix and electrolyte channels in this invention results in higher heat transfer efficiency and faster response. Comparative Examples 2 (liquid storage only) and 4 (flame retardant only) have no active heat absorption function, and their temperature rise is close to that of traditional battery cells. This highlights the key role of the active heat absorption mechanism of the built-in microencapsulated phase change material (MCPCM) in this invention in suppressing instantaneous high heat.

[0087] Neither test examples 1 nor 2 of this invention experienced thermal runaway, proving the effectiveness of its constructed "thermal shrinkage and flow restriction - melting and pore closing" four-level safety protection system. All comparative examples (1-4) experienced thermal runaway, and the final failure thermal runaway safety test strongly proves the melting and pore closing mechanism of the outer flame-retardant shell of this invention. Combined with the internal thermal management buffer, it achieves an intrinsic safety improvement from delay to blockage, which cannot be achieved by a single functional module or simple combination.

[0088] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A multifunctional integrated buffer layer based on synergistic thermal management, characterized in that, include: Polymer matrix layer; Microencapsulated phase change material dispersed within the polymer matrix layer; A functional electrolyte storage tube penetrating the polymer matrix layer; And a flame-retardant shell layer covering the outside of the polymer matrix layer.

2. The multifunctional integrated buffer layer according to claim 1, characterized in that, The thickness of the polymer matrix layer is 0.5 mm to 5 mm; the amount of microencapsulated phase change material added is 5% to 80% of the polymer matrix; the thickness of the flame-retardant shell layer is 0.005 mm to 0.5 mm.

3. The multifunctional integrated buffer layer according to claim 1, characterized in that, The polymer matrix includes at least one of the following: polyvinylidene fluoride-hexafluoropropylene copolymer, modified polyimide aerogel, cross-linked polymethyl methacrylate / polyurethane, cross-linked nanocellulose / clay, cross-linked fluorinated nanosilica-polyurethane foam, cross-linked bacterial cellulose / boron nitride nanosheets, and cross-linked sodium alginate / epoxy resin.

4. The multifunctional integrated buffer layer according to claim 1, characterized in that, The microencapsulated phase change materials include solid-liquid phase change materials and solid-solid phase change materials; Preferably, the phase transition enthalpy of the microencapsulated phase change material is 50-300 kJ / kg; Preferably, the enthalpy change range of the solid-liquid phase change material is 150–250 kJ / kg, and the enthalpy change range of the solid-solid phase change material is 80–180 kJ / kg; Preferably, the microencapsulated phase change material is encapsulated within a polymer shell; Preferably, the material of the polymer shell further includes carbon nanotubes or graphene.

5. The multifunctional integrated buffer layer according to claim 1, characterized in that, At least one end of the functional electrolyte storage tube is provided with a storage tube seal, and the storage tube seal is made of a polymer material with a melting point of T2, wherein 40℃ < T2 < 70℃; Preferably, the functional electrolyte pre-filled in the functional electrolyte storage tube includes one or more of the following: lithium-replenishing electrolyte, flame-retardant electrolyte, high-concentration lithium salt electrolyte, pure solvent electrolyte, or battery cell native electrolyte. Preferably, the amount of the functional electrolyte is 1% to 30% of the conventional injection volume; Preferably, the flame-retardant shell layer comprises a ceramic or aramid-coated PP or PE film, a zirconium oxide and polyvinylidene fluoride coating, cross-linked polyethylene, a polyolefin elastomer, or a polyvinylidene fluoride-hexafluoropropylene copolymer-based composite material.

6. A method for preparing a multifunctional integrated buffer layer according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Constructing a porous framework: Using polymer matrix materials, a three-dimensional framework with high porosity and interconnected channels is prepared through freeze-drying, supercritical drying or foaming technology; S2. Introducing microencapsulated phase change material: Mixing the microencapsulated phase change material with the low-viscosity polymer matrix material precursor described in step S1 to form a microencapsulated phase change material slurry; S3. Vacuum impregnation and curing: Under vacuum conditions, the slurry prepared in step S2 is impregnated into the three-dimensional porous skeleton prepared in step S1 to fill the pores inside the skeleton, and then cured by heating or ultraviolet light. S4. Coat the outer layer of the three-dimensional porous skeleton prepared in step S3 with a flame-retardant shell.

7. A method for preparing a multifunctional integrated buffer layer according to any one of claims 1-5, characterized in that, Includes the following steps: I. Blending and Slurry Preparation: Microencapsulated phase change material, polymer matrix, pore-forming agent and solvent are mixed to form a homogeneous slurry with a solid content of 10%-30%; II. Casting and film formation: The slurry prepared in step I is coated and formed into a film using a casting machine; III. Phase Inversion and Extraction: The polymer matrix is ​​solidified by phase inversion, while the pore-forming agent is extracted, thereby forming interconnected micron-sized pores in the membrane; IV. Coat the outer layer of the polymer matrix prepared in step III with a flame-retardant shell. Preferably, the pore-forming agent accounts for 1% to 80% of the total substance, and the pore-forming agent includes at least one of soluble salts and paraffin microspheres; the solvent includes at least one of N-methylpyrrolidone, glycerol, toluene, ethanol, carboxymethyl cellulose, and polyvinylidene fluoride, and the solvent accounts for 30% to 85% of the total substance.

8. A battery comprising stacked electrode cores, characterized in that, It also includes a multifunctional integrated buffer layer as described in any one of claims 1-5, wherein the multifunctional integrated buffer layer is disposed on one side, both sides or inside the stacked electrode core; Preferably, during the stacking process, the multifunctional integrated buffer layer is provided between each electrode unit. Preferably, the thickness of the multifunctional integrated buffer layer accounts for 5% to 30% of the cell thickness.

9. A method for manufacturing a battery cell, characterized in that, include: After the hot pressing and shaping process of the electrode core, the multifunctional integrated buffer layer as described in any one of claims 1-5 or the multifunctional integrated buffer layer prepared by any one of claims 7-8 is placed on one side of the stacked electrode core and bonded with an adhesive tape that is compatible with electrolyte. Then, it is encapsulated by the top-side sealing process of the soft-pack battery cell.

10. The application of a multifunctional integrated buffer layer according to any one of claims 1-5 in the thermal management of a pouch battery, characterized in that, The application of the multifunctional integrated buffer layer in extending the cycle life of pouch batteries, and / or the application of the multifunctional integrated buffer layer in improving the safety performance of pouch batteries.

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