A cell cover assembly for preventing and suppressing thermal runaway and the cell thereof.

Abstract

This application discloses a cell cover assembly and its cell for preventing and suppressing thermal runaway. The cell cover assembly includes: a top cover (1) with an explosion-proof valve mounting position and an explosion-proof valve (2) installed thereon; a lower plastic (3) laminated to the lower surface of the top cover (1) and having a lower plastic venting area (4), wherein the lower plastic venting area (4) is a grid structure; a fixing layer (5) laminated to the surface of the grid structure in the form of hot melt adhesive to form an adhesive thin layer; and thermally latent microcapsules loaded on the surface of the fixing layer (5); wherein the thermally latent microcapsules are composed of at least two wall materials with different softening temperatures encapsulating fire extinguishing agent core materials; the melting point of the fixing layer (5) is lower than the softening temperature of the wall materials, and it is liquid after melting. This invention can overcome the shortcomings and deficiencies of battery pack-level response lag, inability to accurately act on thermally runaway cells, and inability to detect early heat accumulation in a timely manner, and achieves active suppression of thermal runaway at the cell level.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery cell technology, specifically to a battery cell cover assembly for preventing and suppressing thermal runaway and the battery cell thereof. Background Technology

[0002] In recent years, with the rapid popularization of new energy vehicles, energy storage power stations, and portable high-power devices, the energy density of lithium-ion power batteries has been continuously improving, the space utilization of battery packs has been continuously optimized, and the volumetric energy density of cells has been continuously broken through. However, the high energy density leads to a narrower side reaction window and a significant increase in the risk of thermal runaway. The promulgation of GB 38031-2025 "Safety Requirements for Power Batteries for Electric Vehicles" has put forward the hard indicators of "earlier, more accurate, and faster" thermal runaway warning. At present, the thermal runaway suppression solutions commonly used in the industry are mainly concentrated at the battery pack or module level. For example, CN222530518U provides external fire extinguishing devices triggered by fire detection tubes or temperature sensors; CN111420336A sets fire extinguishing agent containers on the top of the battery pack and releases fire extinguishing agents in conjunction with pressure relief valves; another example is arranging fusible structures between modules, which release fire extinguishing materials after melting and breaking through at high temperatures.

[0003] Existing technologies primarily focus on the battery pack level and still face the following problems: 1. Response lag: Fire extinguishing agent release can only be triggered after thermal runaway occurs or the pressure relief valve opens; the path is long and efficiency is low; 2. Fire extinguishing agent needs to be transferred from outside the pack or between modules to the thermally runaway cell, resulting in a long transmission path and limited suppression efficiency; 3. Inability to act precisely: The fire extinguishing agent has a wide coverage area, making it difficult to concentrate its effect on abnormal cells, easily leading to resource waste; 4. Ineffective against early heat accumulation: There are no effective intervention methods for early temperature rise inside the cell (e.g., 80~120℃). Furthermore, existing explosion-proof valve structures, such as CN107331821A, are mainly limited to pressure relief and explosion prevention, and cannot actively intervene in thermal runaway. Although some solutions attempt to integrate temperature or pressure sensors at the explosion-proof valve to monitor abnormal states, they still rely on external control systems for signal processing and judgment, failing to achieve autonomous response and rapid suppression within the cell. Therefore, there is an urgent need for a thermal suppression solution that is simple in structure, responds quickly, and is compatible with existing cover plates, so as to achieve active fire suppression intervention at the cell level in the early stage of thermal runaway, thereby improving the intrinsic safety level of individual cells. Summary of the Invention

[0004] In view of this, the main objective of the present invention is to provide a cell cover plate assembly and its cell for preventing and suppressing thermal runaway, which can overcome the shortcomings and deficiencies such as battery pack-level response lag, inability to accurately act on thermal runaway cells, and inability to detect early heat accumulation in a timely manner, and achieve active suppression of thermal runaway at the cell level.

[0005] To achieve the above-mentioned objectives, the first aspect of this application provides a cell cover assembly for preventing and suppressing thermal runaway, comprising:

[0006] The top cover plate 1 is provided with an explosion-proof valve mounting position and an explosion-proof valve 2 is installed thereon; The lower plastic 3 is laminated to the lower surface of the top cover plate 1 and is provided with a lower plastic venting area 4, which is a grid structure; The fixing layer 5 is bonded to the surface of the grid structure in the form of hot melt adhesive to form an adhesive thin layer; And, thermally induced latent microcapsules, loaded on the surface of the immobilization layer 5; The thermally induced latent microcapsule is composed of a fire extinguishing agent core material encapsulated by at least two wall materials with different softening temperatures; the melting point of the fixing layer 5 is lower than the softening temperature of the wall material, and it is liquid after melting.

[0007] Furthermore, the wall material of the thermotropic latent microcapsules is selected from one or more of polymethyl methacrylate (PMMA), polystyrene (PS), polylactic acid (PLA), or copolymers thereof, and different softening temperatures are obtained by adjusting the molecular weight or copolymerization ratio.

[0008] Furthermore, the thermally induced latent microcapsule comprises a trigger-phase microcapsule I and a runaway-phase microcapsule II, wherein the wall material softening temperature range of the trigger-phase microcapsule I is T. I =80-120℃, the softening temperature range of the wall material of microcapsule II during the runaway period is T II =150-180℃, with a temperature interval of ≥20℃ between the two; preferably, the masses of the two satisfy m I +m II =100wt%, and m I :m II ≥0.5: More preferably, m I +m II =100wt%, and m I :m II =0.55~0.85.

[0009] Furthermore, the thermally induced latent microcapsules comprise a trigger-phase microcapsule A, a development-phase microcapsule B, and a runaway-phase microcapsule C; wherein, the wall material softening temperature T of the trigger-phase microcapsule A is... A =90-120℃; Softening temperature T of microcapsule B wall material during the development period A =120-150℃; Softening temperature T of microcapsule C wall material during runaway period C =150-180℃; and satisfy T A <T B <T C Temperature interval ≥ 20℃; Preferably, the mass ratio of the trigger-phase microcapsule A, the development-phase microcapsule B, and the runaway-phase microcapsule C satisfies: m A : m B : m C = (5-15) : (20-35) : (50-75), where m A +m B +m C =100 wt%, and m C ≥50 wt%.

[0010] Furthermore, the fire extinguishing agent core material is one or both of perfluorohexanone and BTP (2-bromo-3,3,3-trifluoropropylene); preferably, when it is a mixture of the two, the mass ratio of perfluorohexanone to BTP is 1:9-9:1.

[0011] Furthermore, the extinguishing agent core material accounts for 60-90 wt% of the total mass of the microcapsule, and the wall material accounts for 10-40 wt%.

[0012] Furthermore, the fixing layer 5 is one or more of ethylene-vinyl acetate copolymer (EVA), polyamide hot melt adhesive (PA), or polyurethane hot melt adhesive (PUR), with a melting point of 70-100℃ and a peel strength of ≥5 N / cm at 180°.

[0013] Furthermore, the thickness of the fixing layer 5 is 5-50 μm.

[0014] Furthermore, the microcapsules are granular with a volume average particle size D50 of 10-80 μm and a loading of 10-100 mg / cm²; or, the microcapsules are bulk materials with a porosity of 30-60% and a thickness of 0.1-1 mm.

[0015] The second aspect of the present invention provides a lithium-ion battery cell whose chemical system is selected from lithium iron phosphate, ternary lithium, lithium manganese iron phosphate or sodium ion liquid / semi-solid system, and is suitable for square or blade battery cells manufactured by winding or stacking process, wherein the battery cell adopts the above-mentioned battery cell cover plate assembly.

[0016] Compared with the prior art, the present invention has the following advantages: The thermally induced latent microcapsules provided by this invention are loaded on the surface of the fixed layer 5. The microcapsules are composed of at least two wall materials with different softening temperatures encapsulating the extinguishing agent core material. The melting point of the fixed layer 5 is lower than the softening temperature of the microcapsule wall material, so that when thermal runaway occurs, the fixed layer 5 melts before all the microcapsules, causing the microcapsules to fall off to the surface of the battery cell core (JR) due to gravity or remain on the grid. They then rupture and release the extinguishing agent one by one as the temperature continues to rise. Both the molten fixed layer 5 and the ruptured microcapsule wall material are in a liquid state during the runaway period, without occupying the explosion-proof valve exhaust space.

[0017] The fixing layer 5 of this application is composited on the surface of the grid structure. This application uses the fixing layer to directly place microcapsules on the innermost part of the battery cell, the "lower plastic exhaust zone grid," at a distance of less than 1 mm from the electrode core. It senses the internal hot air convection and radiation temperature without requiring heat conduction through the shell. The fixing layer (EVA, etc.) has a melting point of 70–100℃ and softens before all microcapsules, causing the capsules to instantly fall or remain on top of the electrode assembly, achieving "second-level" proximity to the heat source. Once close, the softening temperature of the capsule wall material corresponds to the actual internal temperature, and it ruptures at 90℃, truly achieving "internal temperature sensing → internal fire extinguishing agent release," without relying on any external sensors, BMS, or shell temperature.

[0018] Therefore, this application can sense the temperature change inside the battery cell in real time without relying on the external pressure or temperature monitoring of the battery cell, and quickly activate the fire extinguishing program when the temperature rises abnormally, effectively reducing the concentration and temperature of combustible gas inside the battery cell, preventing the spread of fire, and improving the timeliness and effectiveness of suppressing thermal runaway of the battery cell.

[0019] Other features and advantages of this application will be described in detail in the following specific embodiments. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the upper surface structure of the cell cover plate assembly for preventing and suppressing thermal runaway provided in Embodiment 1 of the present invention. Figure 2 This is a schematic diagram of the lower surface structure of the cell cover assembly for preventing and suppressing thermal runaway provided in Embodiment 1 of the present invention. The reference numerals are as follows: 1-Top cover, 2-Explosion-proof valve, 3-Lower plastic, 4-Ventilation zone, 5-Fixing layer. Detailed Implementation

[0021] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0022] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "first position" and "second position" refer to two different positions.

[0023] Unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, they can refer to fixed connections or detachable connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and connections within two components or interactions between two components. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0024] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0025] The main objective of this invention is to provide a cell cover assembly and its cell at the cell level for preventing and suppressing thermal runaway. By means of one or more thermally latent microcapsules integrated in the plastic under the cell cover, the invention can overcome the shortcomings and deficiencies of battery pack level response lag, inability to accurately act on thermally runaway cells, and inability to detect early heat accumulation in a timely manner.

[0026] In a first aspect, the present invention provides a cell cover assembly for preventing and suppressing thermal runaway, such as... Figure 1 As shown, it includes: The top cover plate 1 is provided with an explosion-proof valve mounting position and an explosion-proof valve 2 is installed at the position; The lower plastic 3 is laminated to the lower surface of the top cover plate 1 and is provided with a lower plastic venting area 4, which is a grid structure; The fixing layer 5 is bonded to the surface of the grid structure in the form of hot melt adhesive to form an adhesive thin layer; And, thermally induced latent microcapsules, loaded on the surface of the immobilization layer 5; The thermally induced latent microcapsules are composed of at least two wall materials with different softening temperatures encapsulating a fire extinguishing agent core material. The melting point of the fixing layer 5 is lower than the softening temperature of the wall materials, so that during thermal runaway, the fixing layer 5 melts before all the microcapsules, causing the microcapsules to fall onto the surface of the battery cell core (JR) due to gravity or remain on the grid, and then rupture sequentially to release the fire extinguishing agent as the temperature continues to rise. Both the molten fixing layer 5 and the ruptured microcapsule wall materials are in a liquid state during the runaway period, without occupying the venting space of the explosion-proof valve. In this invention, the viscous thin layer plays a supporting role for the microcapsules at the normal temperature of the battery cell; when the battery cell temperature is in the early stage of thermal runaway, the microcapsules melt and fall into the main body area of ​​the battery cell due to gravity.

[0027] In some specific embodiments, the wall material of the thermotropic latent microcapsules is selected from one or more of polymethyl methacrylate (PMMA), polystyrene (PS), polylactic acid (PLA), or copolymers thereof, and different softening temperatures are obtained by adjusting the molecular weight or copolymerization ratio.

[0028] In some specific embodiments, the thermally induced latent microcapsules comprise a trigger-phase microcapsule I and a runaway-phase microcapsule II, wherein the wall material softening temperature range of the trigger-phase microcapsule I is T. I =80-120℃, the softening temperature range of the wall material of microcapsule II during the runaway period is T II =150-180℃, the temperature difference between the two is ≥20℃; the mass of both satisfies m I +m II =100wt%, and m I :m II ≥0.5: Preferably, m I +m II =100wt%, and m I :m II =0.55~0.85.

[0029] For example, based on the above two types of microcapsules, the order of action of the thermally induced latent microcapsules in the thermal runaway process of the present invention is as follows: a) When the temperature rises to the melting point of the fixed layer 5, the fixed layer 5 melts, and the microcapsules either fall or remain; b) At 80-120℃, the wall material of the microcapsule I softens and cracks during the triggering period, releasing the first extinguishing agent and inhibiting the early chain reaction; c) At 150-180℃, the wall material of the microcapsule II softens and cracks during the runaway period, releasing the second extinguishing agent, which rapidly absorbs heat and isolates oxygen; d) The molten fixed layer and the ruptured microcapsule wall material are discharged from the explosion-proof valve along with the high-pressure gas, without blocking the exhaust channel.

[0030] The wall material softening temperature T of the triggering period microcapsule I I The temperature range is set at 80-120℃, corresponding to the early temperature rise during the cell's self-heating stage. During this stage, the SEI film inside the cell begins to decompose, generating a small amount of combustible gas with relatively low heat generation. At this temperature, the wall material of microcapsule I softens during the triggering period, significantly reducing its mechanical strength. The internally encapsulated extinguishing agent core material breaks through the wall material under vapor pressure, releasing the extinguishing agent and triggering the first extinguishing agent injection. The released extinguishing agent rapidly vaporizes and absorbs heat, lowering the local temperature and diluting the concentration of combustible gas, thus blocking the initiation path of the chain reaction and achieving proactive intervention in early heat accumulation.

[0031] The wall material softening temperature T of the runaway microcapsule II IIThe temperature range of 150-180℃ corresponds to the thermal runaway triggering stage of the battery cell. During this stage, the diaphragm contracts or ruptures, creating a large-area internal short circuit between the positive and negative electrodes, resulting in a sharp increase in heat generation. At this temperature, the wall material of microcapsule II softens and ruptures during the runaway period, releasing a high concentration of extinguishing agent core material, forming a second extinguishing agent spray. Because the internal temperature of the battery cell has already significantly increased, the extinguishing agent rapidly vaporizes and absorbs a large amount of heat, while simultaneously isolating oxygen from contact with combustibles, inhibiting the violent development of thermal runaway, reducing the peak temperature, and preventing the battery cell from igniting or exploding.

[0032] The mass ratio of the trigger-phase microcapsule I to the runaway-phase microcapsule II is m I: m II The mass ratio is ≥0.5, preferably 0.55~0.85. This mass ratio is set based on the following mechanism: Triggering phase microcapsules I are mainly used for early heat accumulation intervention, with a mass ratio of not less than 50wt%, ensuring sufficient extinguishing agent release during the self-heating stage to form effective coverage and promptly block the initiation path of thermal runaway; Runaway phase microcapsules II are used for strong suppression during the thermal runaway outbreak stage, with a mass ratio set at 15wt%~45wt%, preserving the last line of defense during the violent development stage of thermal runaway and reserving sufficient extinguishing agent to cope with violent reactions. Through the above mass ratio, a synergistic effect of sufficient early intervention and strong later suppression is achieved, reducing the overall amount of extinguishing agent used while improving suppression efficiency.

[0033] The design with a temperature interval of ≥20℃ ensures that microcapsule I during the triggering phase and microcapsule II during the runaway phase respond independently in different temperature zones. This avoids the simultaneous rupture of the two types of microcapsules within the same temperature range, which would lead to overly concentrated release of the extinguishing agent, or the overlapping of responses due to an excessively narrow temperature interval. A temperature interval of ≥20℃ provides sufficient time for temperature transfer within the battery cell and for the diffusion of the extinguishing agent, resulting in a phased and continuous suppression effect.

[0034] In some specific embodiments, the thermo-induced latency microcapsules comprise a trigger-phase microcapsule A, a development-phase microcapsule B, and a runaway-phase microcapsule C, which is a mixture of the above three types of microcapsules; wherein, Triggering period microcapsule A wall material softening temperature T A =90-120℃; The softening temperature T of the wall material of microcapsule B during the development period B =120-150℃; The softening temperature T of the microcapsule wall material during the runaway period C =150-180℃; Furthermore, it satisfies Ta < Tb < Tc and a temperature interval ≥ 20℃ to achieve a phased response to thermal runaway.

[0035] In this invention, the main purpose of the mixed configuration of the three types of microcapsules is to achieve temperature suppression at different stages of the battery cell. Specifically, the trigger-phase microcapsule A is mainly used to suppress the temperature during the self-heating stage of the battery cell, at which time the heat generation is relatively small compared to the latter two stages; the trigger-phase microcapsule B and the runaway-phase microcapsule C respectively achieve the thermal runaway triggering stage and the thermal runaway termination stage, with the heat generation increasing sequentially. This configuration can achieve the benefits of early capsule intervention, multiple prevention and control, and an overall reduction in the amount of microcapsules used.

[0036] For example, based on the above-described configuration of the microcapsule, the sequence of action of the thermally induced latent microcapsule in the thermal runaway process of the present invention is as follows: a) When the temperature rises to the melting point, the fixed layer 5 melts, and the microcapsules either fall or remain. b) At 90-120℃, microcapsule A ruptures during the triggering period, releasing the first extinguishing agent and inhibiting the chain reaction; c) At 120-150℃, during the development period, microcapsule B ruptures, releasing a secondary extinguishing agent and reducing the concentration of combustible gas; d) At 150-180℃, during the runaway period, microcapsule C ruptures, releasing the third extinguishing agent, which rapidly absorbs heat and isolates oxygen; e) The molten fixed layer 5 and the liquid wall material are discharged from the explosion-proof valve along with the high-pressure gas, without blocking the exhaust channel.

[0037] In some specific embodiments, the mass ratio of the trigger-phase microcapsule A, the development-phase microcapsule B, and the runaway-phase microcapsule C satisfies: m A : m B : m C = (5-15) : (20-35) : (50-75), where m A +m B +m C =100wt%, and m C ≥50 wt%.

[0038] In some specific embodiments, the fire extinguishing agent core material is one or both of perfluorohexanone and BTP (2-bromo-3,3,3-trifluoropropylene); preferably, when it is a mixture of the two, the mass ratio of perfluorohexanone to BTP is 1:9-9:1.

[0039] In some specific implementations, the fire extinguishing agent core material accounts for 60-90 wt% of the total mass of the microcapsule, and the wall material accounts for 10-40 wt%, ensuring that the wall material meets the mass boundary of the core material while ensuring more sufficient effective components.

[0040] In some specific embodiments, the fixing layer 5 is one or more of ethylene-vinyl acetate copolymer (EVA), polyamide hot melt adhesive (PA), or polyurethane hot melt adhesive (PUR), with a melting point of 70-100℃ and a peel strength of ≥5 N / cm at 180°, ensuring that the microcapsules do not fall off at room temperature.

[0041] In some specific embodiments, the thickness of the fixing layer 5 is 5-50 μm.

[0042] In some specific embodiments, the microcapsules are granular with a volume average particle size D50 of 10-80 μm and a loading of 10-100 mg / cm²; or, in other specific embodiments, the microcapsules are pre-pressed into blocks with a porosity of 30-60% and then adhered to the fixing layer 5, with a block thickness of 0.1-1 mm.

[0043] The second aspect of the present invention provides a lithium-ion battery cell whose chemical system is selected from lithium iron phosphate, ternary lithium, lithium manganese iron phosphate or sodium ion liquid / semi-solid system, and is suitable for square or blade battery cells manufactured by winding or stacking process, wherein the battery cell adopts the above-mentioned battery cell cover plate assembly.

[0044] The present application will be further described below with reference to the embodiments. However, the present application is not limited to the listed embodiments, but should also include equivalent improvements and modifications of the technical solutions defined in the appended claims.

[0045] In the following examples and comparative examples: (1) Main raw materials Unless otherwise specified, all raw materials involved in the embodiments of this application can be obtained from commercially available channels.

[0046] (2) Characterization and testing 1. Test equipment The adiabatic accelerated calorimeter (ARC) is configured as follows: Temperature acquisition system: K-type thermocouple, accuracy ±0.5℃, acquisition frequency ≥1 Hz; Pressure acquisition system: piezoelectric pressure sensor, range 0-5 MPa, accuracy ±0.5% FS, acquisition frequency ≥10Hz; Data recording system: synchronously records temperature-time and pressure-time curves.

[0047] 2. Experimental Procedure (1) Place the battery cell in the center of the ARC calorimetric chamber and arrange the thermocouple at the geometric center of the large surface of the battery cell; (2) Seal the cavity, evacuate it, and then fill it with high-purity nitrogen to atmospheric pressure; (3) Start the temperature program: starting temperature 25℃, heating rate 5℃·min -¹, Heat-Wait-Seek mode, detection sensitivity 0.02℃·min - ¹; (4) When the self-heating rate exceeds 0.2℃·min - ¹Then, switch to adiabatic tracking mode; (5) Test termination conditions: The temperature drops to 50°C below the peak value or there is no further reaction after continuous monitoring for 30 min.

[0048] 3. Data Collection and Evaluation Indicators (1) Initial response temperature (°C) (2) Initial response temperature rise rate (dT / dt) (3) Peak temperature (Tmax) (4) dP / dt (MPa·min) at the first response (5) Maximum pressure rise rate (MPa·min) - ¹) (6) Peak pressure (Pmax) (7) Whether thermal runaway is suppressed (8) Is there any flame? (9) Whether heat spreads.

[0049] Example 1 Battery type: NCM811 / graphite square shell 80 Ah Fixing layer material: Ethylene-vinyl acetate copolymer (EVA) hot melt adhesive, melting point 85℃, 180° peel strength 7.2 N·cm - ¹, thickness 18 µm.

[0050] 1. Microcapsule preparation 1.1 Triggering Phase Microcapsule A:M w =8.5×10 4 Polymethyl methacrylate (PMMA) is used as the wall material, and perfluorohexanone is used as the core material, with a core-to-wall mass ratio of 85:15. After spray drying, D 50 =28 µm, wall material softening temperature T A =105℃.

[0051] 1.2 Developmental stage microcapsule B:M w =1.2×10 5 Polystyrene (PS) is used as the wall material, with a core-to-wall ratio of 75:25. 50 =35 µm, T b =140℃.

[0052] 1.3 Microcapsules in the runaway phase C:M w =1.6×10 5PS-co-PMMA (5:5) is used as the wall material, with a core-to-wall ratio of 80:20. 50 =42 µm, T c =170℃.

[0053] 2. Cover plate integration 2.1 Melt the EVA hot melt adhesive at 110°C and apply it through a slit applicator at a rate of 5 m·min. - ¹ The coating is applied evenly to the surface of the lower plastic grid at a high speed to form an 18 µm thick fixing layer, which is then cooled to room temperature to obtain an adhesive interface.

[0054] 2.2 Press m A :m B :m C Weigh out 3.0 g of mixed microcapsules at a ratio of 10:25:65 to obtain powder, and place it in an inert chamber at 50℃ and <5%RH. Use an electrostatic spray gun at 30 kV to uniformly spray the powder onto the surface of the fixed layer, with a loading of 55 mg·cm³. - ².

[0055] 3. Heating-triggered thermal runaway test The aforementioned cover plate was assembled with the NCM811 / graphite core to form an 80 Ah square-shell battery cell, which was then placed in the chamber of an adiabatic accelerated calorimeter (ARC) and calorimeter was set at 5 °C / min. - ¹The temperature is increased from 25℃, and the temperature-pressure curve is recorded simultaneously.

[0056] 95℃: The fixing layer melts, and the microcapsules slide down to the core surface under gravity, keeping the particles intact.

[0057] 105℃: During the triggering period, the wall material of microcapsule A softens and ruptures, releasing perfluorohexanone for the first time, with a temperature rise rate of 0.75℃·s. - ¹, Pressure rise rate 0.018 MPa·min - ¹.

[0058] 140℃: During the development phase, microcapsule B ruptures, releasing perfluorohexanone.

[0059] 170℃: During the runaway period, microcapsule C ruptures, instantly absorbing heat, with the highest temperature suppressed at 198℃ and peak pressure at 1.85MPa. Molten EVA and ruptured wall material are discharged from the explosion-proof valve along with the high-pressure gas, ensuring smooth exhaust, with no solid residue at the valve port, and no thermal propagation occurs in the battery cell.

[0060] Example 2 Battery type: NCM811 / graphite square shell 80 Ah Fixing layer material: EVA hot melt adhesive, melting point 85℃, 180° peel strength 7.2 N·cm - ¹, thickness 20 µm.

[0061] 1. Microcapsule preparation 1.1 Triggering phase microcapsule A: PLA (Mw=6.0×10⁻⁶) 4 T g =98℃), core material perfluorohexanone / BTP=7:3, core-to-wall ratio 80:20, D 50 =50 µm, T A =108℃.

[0062] 1.2 Developmental stage microcapsule B: PLA (M w =9.5×10 4 T g =135℃), core-to-wall ratio 80:20, D 50 =50 µm, T B =135℃.

[0063] 1.3 Microcapsules C: PLA (M) during the runaway period w =1.3×10 5 T g =162℃), core-to-wall ratio 80:20, D 50 =50 µm, T C =162℃.

[0064] 2. Cover plate integration 2.1 EVA was melted at 110°C and coated onto the lower plastic grid to form a 20 µm fixing layer.

[0065] 2.2 Press m A :m B :m C The ingredients are mixed in a ratio of 12:28:60, and 5 wt% fumed SiO2 is added to granulate the mixture. The granules are then molded into flexible fire extinguishing blocks with a porosity of 45% and a thickness of 0.5 mm. A 20 µm EVA film is then hot-pressed onto the back of the block to obtain a self-supporting "fire extinguishing block-EVA" composite.

[0066] 2.3 The composite material is hot-pressed with the grid fixing layer to achieve overall adhesion of the block, with a loading capacity equivalent to 65 mg / cm³ of microcapsules. - ².

[0067] 3. Heating-triggered thermal runaway test 95℃: The fixing layer melts, the extinguishing block retains its shape but sinks to the top of the core.

[0068] 108℃: After the block comes into contact with the core surface, the heat transfer efficiency increases, capsule A ruptures, and the temperature rise rate is 0.71℃·s. - ¹, Pressure rise rate 0.015 MPa·min -¹; The block form allows for concentrated release of the extinguishing agent, resulting in a higher local concentration compared to powder.

[0069] 135℃: Capsule B ruptures, releasing perfluorohexanone / / BTP.

[0070] 162℃: Capsule C ruptured, with the highest temperature suppressed at 196℃ and peak pressure at 1.75 MPa. Molten EVA and PLA wall material were discharged in liquid form from the explosion-proof valve with the airflow, ensuring smooth venting and leaving no solid residue. The block structure improved the utilization efficiency of the extinguishing agent, and the peak pressure was slightly lower than in Example 1.

[0071] Example 3 Battery type: NCM811 / Silicon-carbon square case 80 Ah Fixing layer material: EVA hot melt adhesive, melting point 85℃, 180° peel strength 7.2 N·cm - ¹, thickness 15 µm.

[0072] 1. Microcapsule preparation 1.1 Triggering phase microcapsule A: PMMA-co-PS (3:7, M w =7.2×10 4 T g =110℃), core material perfluorohexanone, core-to-wall ratio 90:10, D 50 =15 µm.

[0073] 1.2 Developmental stage microcapsule B: PS (M w =1.1×10 5 T g =145℃), core-to-wall ratio 75:25, D 50 =30 µm, T b =145℃.

[0074] 1.3 Microcapsules C:PS (M) during the runaway period w =1.5×10 5 T g =175℃), core-to-wall ratio 75:25, D 50 =30 µm, T c =175℃.

[0075] 2. Cover plate integration 2.1 The EVA hot melt adhesive is melted at 110°C and applied to the lower plastic grid through slits to form a 15 µm fixing layer.

[0076] 2.2 Press m A :m B :m C The ingredients were mixed in a ratio of 5:30:65 and vibratory ball milled until the specific surface area reached 2.4 m²·g. -¹, The powder was uniformly deposited onto the surface of the fixed layer by electrostatic spraying at 30 Kv and <5%RH, with a loading of 40 mg·cm³. - ².

[0077] 3. Heating-triggered thermal runaway test 88℃: The fixing layer melts, and the microcapsule powder sinks to the surface of the core.

[0078] 110℃: Capsule A ruptures, releasing the extinguishing agent; temperature rise rate is 0.84℃·s. - ¹, The rate of pressure rise decreased to 0.01 MPa·min - ¹; Small particle size microcapsules (D 50 The response (=15 µm) is sensitive, and the early inhibition effect is better than that of Example 1.

[0079] 145℃: Capsule B ruptures, releasing perfluorohexanone.

[0080] 175°C: Capsule C ruptured, with the highest temperature suppressed at 208°C and peak pressure at 1.90 MPa. Molten EVA and PS wall material were discharged in liquid form from the explosion-proof valve, with smooth venting and no solid residue. Although the total load was only 2.4 g (80% of that in Example 1), effective suppression was still achieved.

[0081] Example 4 Battery type: NCM811 / graphite square shell 80 Ah Fixing layer material: EVA hot melt adhesive, melting point 85℃, 180° peel strength 7.2 N·cm - ¹, thickness 20 µm.

[0082] 1. Microcapsule preparation 1.1 Triggering Phase Microcapsule I: PMMA (M w =7.5×10 4 The wall material is perfluorohexanone, and the core material is perfluorohexanone. The core-to-wall mass ratio is 82:18. After spray drying, the D50 is 32 µm, and the softening temperature of the wall material is T. I =95℃.

[0083] 1.2 Runaway Phase Microcapsule II: PS (M w =1.5×10 5 The wall material is perfluorohexanone / BTP = 6:4, the core material is 78:22, and the wall material is D. 50 =38 µm, T II =165℃.

[0084] 2. Cover plate integration 2.1 Melt the EVA hot melt adhesive at 110°C and apply it through a slit applicator at a rate of 5 m·min. -¹ The coating is applied evenly to the surface of the lower plastic grating at a uniform speed, forming a 20 µm thick fixing layer.

[0085] 2.2 Press m I :m II Weigh out 3.2 g of the mixed microcapsules (65:35 ratio) and place them in an inert chamber at 50℃ and <5%RH. Apply the powder evenly to the surface of the fixed layer using an electrostatic spray gun at 30 kV, with a loading of 58 mg·cm³. - ².

[0086] 3. Heating-triggered thermal runaway test 85℃: The fixing layer melts, and the microcapsules fall off onto the core surface as a whole, with the particles intact.

[0087] 95℃: During the triggering period, the wall material of microcapsule I softens and ruptures, releasing perfluorohexanone for the first time, with the temperature rise rate decreasing to 0.62℃·s. - ¹, Pressure rise rate 0.014 MPa·min - ¹; The quality of the trigger period accounted for 65%, indicating sufficient early intervention.

[0088] 120-160℃: No microcapsule response during the development phase, but the extinguishing agent released in the early stage continues to play a role, with the temperature rise rate maintained at 0.62-0.9℃·s. - ¹.

[0089] 165℃: During the runaway phase, microcapsule II ruptures, releasing a high concentration of composite extinguishing agent, which instantly absorbs heat, and the pressure rise rate drops to 0.038 MPa·min. - ¹; The highest temperature was suppressed at 201℃, and the peak pressure was 1.87 MPa, which were the lowest among all embodiments. Molten EVA and cracked wall material were discharged from the explosion-proof valve with high-pressure gas, the exhaust was smooth, there was no solid residue, and no thermal propagation occurred in the battery cell.

[0090] Comparative Example 1 Battery type: NCM811 / graphite square shell 80 Ah Fixing layer material: EVA hot melt adhesive, melting point 85℃, 180° peel strength 7.2 N·cm - ¹, thickness 18 µm.

[0091] 1. Microcapsule preparation Single wall material microcapsule B:PS (M w =1.2×10 5 ) is the wall material, with a core-to-wall ratio of 75:25, D 50 =35 µm, T b =140℃.

[0092] 2. Cover plate integration 2.1 Melt the EVA hot melt adhesive at 110°C and apply it to the surface of the lower plastic grid to form an 18 µm fixing layer.

[0093] 2.2 Weigh 3.0 g of microcapsules B and electrostatically spray them onto the surface of the fixing layer with a loading of 55 mg·cm³. - ².

[0094] 3. Heating-triggered thermal runaway test 95℃: The fixing layer melts, and the microcapsules fall off onto the core surface as a whole, with the particles intact.

[0095] 105-135℃: No capsule rupture, temperature rise rate continues to increase to 1.3℃·s - ¹(105℃) and 2.5℃·s - ¹ (135℃), a large amount of heat and combustible gas accumulate, and the pressure rises at a rate of 0.045 MPa·min. - ¹.

[0096] 140℃: Capsule B ruptures in one go, releasing all the extinguishing agent at once. After a brief temperature drop (ΔT≈8℃), the temperature rebounds rapidly. Due to the large amount of heat and pressure accumulated in the early stage, the temperature continues to rise.

[0097] 170℃: The battery cell enters a severe runaway state, with a maximum temperature of 245℃, a peak pressure of 3.2 MPa, and a maximum pressure rise rate of 0.35 MPa·min. - ¹. After the explosion-proof valve is opened, the exhaust is smooth and there is no solid blockage, but flames are emitted, heat spreads to adjacent electrode groups, and the battery cell is scrapped.

[0098] The parameters and performance data of each embodiment and comparative example are shown in Table 1 below: Table 1

[0099] A comparison of Examples 1-4 and Comparative Example 1 shows that the staged response microcapsule design of this invention, through the melting of the fixing layer, allows the microcapsules to detach onto the core surface and release the extinguishing agent sequentially at different temperature zones, effectively suppressing thermal runaway of the battery cell. The initial response temperatures of Examples 1-4 are all earlier than those of Comparative Example 1, with peak temperatures controlled at 196-208℃ and peak pressures controlled at 1.75-1.87 MPa. No thermal propagation occurred, and the explosion-proof valves provided unobstructed venting. In contrast, Comparative Example 1, using a single-wall-material microcapsule, lacked early intervention, leading to a continuous accumulation of heat and pressure, resulting in severe thermal runaway, with peak temperatures reaching 245℃ and peak pressures reaching 3.2 MPa, ultimately resulting in flame ejection and thermal propagation. This demonstrates that this invention, through staged response of microcapsules with at least two different softening temperatures, achieves active suppression of thermal runaway at the battery cell level, overcoming the shortcomings of delayed response at the battery pack level, inability to precisely target thermally runaway cells, and inability to promptly detect early heat accumulation.

[0100] A comparison of Examples 1-3 and Example 4 of this invention shows that Examples 1-3, by introducing development-stage microcapsules, achieve a third release of the extinguishing agent in the 120-150℃ range, forming a smoother three-stage inhibition curve, suitable for scenarios with high requirements for stable temperature rise throughout the process. Example 4, by increasing the mass ratio of the trigger-stage microcapsules to 65%, enhances early intervention capabilities. Although the development-stage microcapsules are omitted, the peak temperature is controlled at 201℃, comparable to Examples 1-3, thanks to sufficient early extinguishing agent release and the synergistic effect of the composite extinguishing agent. Furthermore, the system is simplified and costs are reduced, making it suitable for scenarios with higher requirements for early response speed. Both technical solutions are within the scope of protection of the claims of this invention and can be flexibly selected according to the cell chemistry system, cost constraints, and application scenarios.

[0101] Therefore, by arranging thermally latent microcapsules within the battery cell, this invention can accurately and timely suppress thermal runaway, including the thermal runaway triggering period, the development period, and the runaway period. By arranging thermally latent microcapsules within the battery cell, this invention does not rely on external pressure or temperature sensors for sensing, thus improving the reliability of thermal suppression.

[0102] Obviously, the above embodiments of this application are merely examples for clearly illustrating this application, and are not intended to limit the implementation of this application. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of this application are within the scope of the spirit and scope of this application.

Claims

1. A cell cover assembly for preventing and suppressing thermal runaway, characterized in that, include: The top cover plate (1) is provided with an explosion-proof valve mounting position and an explosion-proof valve (2) is installed thereon; The lower plastic (3) is laminated to the lower surface of the top cover plate (1) and is provided with a lower plastic exhaust area (4), wherein the lower plastic exhaust area (4) is a grid structure; The fixing layer (5) is bonded to the surface of the grid structure in the form of hot melt adhesive to form an adhesive thin layer; And, thermally induced latent microcapsules, loaded on the surface of the immobilization layer (5); The thermally induced latent microcapsule is composed of a fire extinguishing agent core material encapsulated by at least two wall materials with different softening temperatures; the melting point of the fixing layer (5) is lower than the softening temperature of the wall material, and it is liquid after melting.

2. The cell cover assembly for preventing and suppressing thermal runaway according to claim 1, characterized in that, The wall material of the thermo-induced latent microcapsules is selected from one or more of polymethyl methacrylate, polystyrene, polylactic acid, or copolymers thereof, and different softening temperatures are obtained by adjusting the molecular weight or copolymerization ratio.

3. The cell cover assembly for preventing and suppressing thermal runaway according to claim 1 or 2, characterized in that, The thermally induced latent microcapsules comprise trigger-phase microcapsules I and runaway-phase microcapsules II. The wall material softening temperature range of trigger-phase microcapsules I is T. I =80-120℃, the softening temperature range of the wall material of microcapsule II during the runaway period is T II =150-180℃, with a temperature interval of ≥20℃ between the two; preferably, the masses of the two satisfy m I +m II =100wt%, and m I :m II ≥0.5: More preferably, m I +m II =100wt%, and m I :m II =0.55~0.

85.

4. The cell cover assembly for preventing and suppressing thermal runaway according to claim 1 or 2, characterized in that, The thermally induced latent microcapsules comprise a trigger-phase microcapsule A, a development-phase microcapsule B, and a runaway-phase microcapsule C; wherein, the wall material softening temperature T of the trigger-phase microcapsule A is... A =90-120℃; Softening temperature T of microcapsule B wall material during the development period A =120-150℃; Softening temperature T of microcapsule C wall material during runaway period C =150-180℃; and satisfy T A <T B <T C Temperature interval ≥ 20℃; Preferably, the mass ratio of the trigger-phase microcapsule A, the development-phase microcapsule B, and the runaway-phase microcapsule C satisfies: m A :m B : m C = (5-15) : (20-35) : (50-75), where m A +m B +m C =100 wt%, and m C ≥50 wt%.

5. The cell cover assembly for preventing and suppressing thermal runaway according to any one of claims 1-4, characterized in that, The fire extinguishing agent core material is one or both of perfluorohexanone and BTP (2-bromo-3,3,3-trifluoropropylene); preferably, when it is a mixture of the two, the mass ratio of perfluorohexanone to BTP is 1:9-9:

1.

6. The cell cover assembly for preventing and suppressing thermal runaway according to any one of claims 1-5, characterized in that, The extinguishing agent core material accounts for 60-90 wt% of the total mass of the microcapsule, and the wall material accounts for 10-40 wt%.

7. The cell cover assembly for preventing and suppressing thermal runaway according to claim 1, characterized in that, The fixing layer (5) is one or more of ethylene-vinyl acetate copolymer, polyamide hot melt adhesive or polyurethane hot melt adhesive. Preferably, the fixing adhesive (5) has a melting point of 70-100℃ and a peel strength of ≥5 N / cm at 180°.

8. The cell cover assembly for preventing and suppressing thermal runaway according to claim 1 or 7, characterized in that, The thickness of the fixing layer (5) is 5-50 μm.

9. The cell cover assembly for preventing and suppressing thermal runaway according to any one of claims 1-8, characterized in that, The microcapsules are granular with a volume average particle size D50 of 10-80 μm and a loading of 10-100 mg / cm²; or, the microcapsules are bulk materials with a porosity of 30-60% and a thickness of 0.1-1 mm.

10. A lithium-ion battery cell, the chemical system of which is selected from lithium iron phosphate, ternary lithium, lithium manganese iron phosphate or sodium ion liquid / semi-solid system, suitable for square or blade battery cells manufactured by winding or stacking process, wherein the battery cell adopts the battery cell cover plate assembly as described in any one of claims 1-9.

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