Pressure-sensitive microcapsule hydrogel lithium battery thermal management material, preparation method and application thereof
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHONGQING UNIV
- Filing Date
- 2026-04-14
- Publication Date
- 2026-06-02
Smart Images
Figure CN122136565A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrochemical energy storage safety technology, specifically relating to a pressure-sensitive microcapsule hydrogel lithium battery thermal management material, its preparation method, and its application. Background Technology
[0002] As the core energy storage unit in key application scenarios such as new energy vehicles and energy storage power stations, the thermal safety of lithium batteries has become a major bottleneck restricting the development of related industries. The frequent thermal runaway accidents and the continuously narrowing thermal management time window in recent years indicate that there is a critical "expansion-valve-jet" stage before thermal runaway of lithium batteries. This stage is accompanied by obvious synergistic evolution of mechanical and thermal signals, which is the core window period for achieving effective thermal safety early warning and intervention.
[0003] During abnormal heat generation in lithium batteries, the initial heat generation rate is relatively slow, and temperature changes are not significant, making it difficult to effectively capture by a single temperature sensor. However, due to factors such as side reaction gas production and changes in crystal structure, the expansion stress inside the battery accumulates continuously during this stage, and after reaching a certain critical threshold, it increases rapidly and non-linearly. This change in mechanical signal precedes the change in temperature signal, serving as an earlier and more sensitive warning signal for thermal runaway. However, existing active thermal management technologies generally suffer from problems such as response lag, system complexity, and high cost. Passive thermal management technologies are limited by their susceptibility to failure or their ability to respond to only a single signal.
[0004] The common drawback of these technologies is their inability to simultaneously sense both force and heat signals, and their lack of ability to buffer internal battery pressure to delay valve release. Therefore, there is an urgent need to develop a new passive thermal management technology that can coordinate the response to force and heat signals to effectively protect against battery thermal runaway. Summary of the Invention
[0005] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the main objective of this invention is to provide a pressure-sensitive microcapsule hydrogel lithium battery thermal management material capable of synergistically responding to force and thermal signals, and a method for preparing the same.
[0006] The present invention also provides the application of the pressure-sensitive microcapsule hydrogel lithium battery thermal management material in lithium battery thermal safety management.
[0007] The objective of this invention is achieved through the following technical solution: A pressure-sensitive microcapsule hydrogel lithium battery thermal management material includes a hydrogel and pressure-sensitive microcapsules contained within the hydrogel that can synergistically change in response to externally applied pressure and changes in ambient temperature.
[0008] In some specific embodiments, the pressure-sensitive microcapsule is internally encapsulated with an oil-phase filler, and the rupture pressure threshold of the pressure-sensitive microcapsule is ≥ 0.6 MPa.
[0009] The oil phase filler is one or more of dichloromethane, perfluorohexane, acetone, methoxynonafluorobutane, and perfluoropolyether.
[0010] In some specific embodiments, the pressure-sensitive microcapsules are obtained by the following preparation method: 1) Dissolve sodium alginate and surfactant in deionized water and stir until homogeneous to obtain the outer gelling solution; 2) Use oil-phase filler as oil-phase core material; use an aqueous solution containing calcium chloride and sodium carboxymethyl cellulose as the receiving phase solution; 3) Using a coaxial dripping device, the oil phase filler in step 2) is used as the inner layer fluid, and the outer layer gelling solution in step 1) is used as the outer layer fluid. Core-shell droplets are formed by co-extrusion through a coaxial needle and directly dripped into the receiving phase solution in step 2) to form microcapsules with an initial shell. 4) Remove the microcapsules with the initial shell from the gel bath, rinse with deionized water to remove residual ions on the surface, and obtain pressure-sensitive microcapsules.
[0011] In some specific embodiments, in the gelling solution described in step 1), the concentration of sodium alginate is 10-20 g / L, and the concentration of surfactant is 10-50 g / L.
[0012] In some specific embodiments, the mass percentage of oil phase filler in the thermal management material is determined by the following heat balance equation: in: The mass of the packing material; The mass of the target battery; This refers to the temperature change of the battery from when it reaches the expansion threshold to when it is before the valve sprays. This represents the average specific heat capacity of the battery. The latent heat of phase change for the selected filler; This refers to the system's heat transfer efficiency.
[0013] The pressure-sensitive microcapsule hydrogel lithium battery thermal management material provided by this invention enables dynamic thermal management throughout the battery's entire lifecycle, and is designed based on the dynamic thermal conditions of the battery from normal operation to abnormal operating conditions. A1: When the battery is in its normal operating temperature range, the pressure-sensitive microcapsules in the hydrogel remain intact, and the hydrogel maintains the battery's normal temperature with preset thermal properties. A2: When a battery is abused and causes micro-short circuits or other hazards, gas is generated inside the battery and expands. The pressure generated by the expansion acts on the hydrogel, which can intelligently respond to changes in battery temperature and pressure. Experimental verification shows that before the pressure-sensitive microcapsule ruptures, the heat transfer coefficient of the hydrogel layer increases synchronously with the gradual increase in battery pressure. A3: When the extrusion pressure reaches the pressure-sensitive microcapsule rupture threshold, it causes the pressure-sensitive microcapsules in the hydrogel layer to rupture and release the encapsulated dichloromethane; the released dichloromethane evaporates rapidly at its low boiling point, and the evaporation process enhances heat transfer, thereby achieving efficient heat removal from the battery. As part of the same inventive concept, this invention also provides a method for preparing the pressure-sensitive microcapsule hydrogel lithium battery thermal management material, comprising the following steps: S1) Add crosslinking agent, initiator and accelerator to acrylamide solution, stir and mix evenly to obtain hydrogel matrix; S2) Add pressure-sensitive microcapsules to the hydrogel matrix, disperse them evenly, and then inject them into a mold to form a pressure-sensitive microcapsule hydrogel lithium battery thermal management material.
[0014] In some specific embodiments, the mass ratio of the acrylamide solution, crosslinking agent, initiator and accelerator in step S1) is 100:(0.05-0.15):(0.3-1.0):(0.1-0.3); wherein the crosslinking agent is methylenebisacrylamide, the initiator is ammonium persulfate, and the accelerator is (N,N,N',N'-tetramethylethylenediamine).
[0015] In some specific embodiments, the mass ratio of the pressure-sensitive microcapsule to the hydrogel matrix in step S2) is (20-30):100.
[0016] As part of the same inventive concept, this invention also provides an application of the pressure-sensitive microcapsule hydrogel lithium battery thermal management material in lithium battery thermal safety management.
[0017] In some specific embodiments, the application is the pressure-sensitive microcapsule hydrogel lithium battery thermal management material, which is attached to both sides of the battery body.
[0018] Compared with the prior art, the present invention has at least the following advantages: 1) The pressure-sensitive microcapsule hydrogel lithium battery thermal management material provided by the present invention includes a hydrogel and pressure-sensitive microcapsules contained within the hydrogel that can synergistically change in response to externally applied pressure and changes in ambient temperature. Based on the characteristic that battery pressure changes are sensitive to temperature changes, this thermal management material achieves dynamic self-response thermal management triggered by pressure, which not only significantly improves the reliability and adaptability of thermal management, but also saves the research, development, installation and maintenance costs of active control systems; thus, it realizes passive thermal management of the battery from normal operation to abnormal operating conditions without any additional active control devices.
[0019] 2) This invention also discloses the application of pressure-sensitive microcapsule hydrogel lithium battery thermal management materials in lithium battery thermal safety management. Specifically, the pressure-sensitive microcapsule hydrogel lithium battery thermal management material is tightly bonded to both sides of the battery to construct an intelligent responsive thermal management device covering the entire battery lifecycle. This design requires no complex auxiliary structures and can achieve precise temperature control of the battery solely through the properties of the hydrogel itself, thus constructing a full lifecycle thermal management solution that combines intelligent responsiveness, efficient heat transfer capability, and high safety. Attached Figure Description
[0020] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below.
[0021] Figure 1 This is a schematic diagram illustrating the application of the pressure-sensitive microcapsule hydrogel thermal management material provided in Embodiment 5 of the present invention in a battery; Figure 2 This is a schematic diagram simulating the rupture process of pressure-sensitive microcapsules in the pressure-sensitive microcapsule hydrogel thermal management material provided in Embodiment 4 of the present invention; Figure 3 A diagram showing the internal temperature changes of a battery with pressure-sensitive microcapsule hydrogel thermal management materials of varying thicknesses attached. Figure 4 A diagram showing the internal pressure changes of a battery containing pressure-sensitive microcapsule hydrogel thermal management materials of varying thicknesses. Figure 5 The graph shows the change in thermal conductivity of the pressure-sensitive microcapsule hydrogel thermal management material provided in Embodiment 4 of the present invention as a function of compression. Detailed Implementation
[0022] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are merely descriptive and not limiting, and should not be construed as limiting the scope of protection of the present invention.
[0023] When a quantity, concentration, or other value or parameter is described as a range, preferred range, or preferred upper and lower limits, it should be understood that it is equivalent to specifically disclosing any range by combining any pair of upper or preferred values with any lower or preferred values, regardless of whether the range is specifically disclosed. Unless otherwise stated, the numerical range values listed herein include the endpoints of the range and all integers and fractions within that range.
[0024] Unless otherwise stated, all percentages, parts, ratios, etc. in this document are by weight.
[0025] The materials, methods, and embodiments described herein are exemplary and should not be construed as limiting unless otherwise stated.
[0026] The test methods used in the following embodiments include: The performance of the hydrogel during different processes of battery valve spraying is demonstrated by testing the main performance of each test sample separately. The main performance tested in this application includes the average temperature of the hydrogel, the pressure on the hydrogel, and the thermal conductivity of the hydrogel.
[0027] 1) Hydrogel thermal conductivity test; Using equipment such as a steady-state thermal conductivity meter and a displacement sensor, the thermal conductivity of hydrogel samples was tested under different pressures using the steady-state heat flow method. 2) Average temperature test of hydrogel on battery outer surface: The average temperature of the hydrogel sample was measured using lithium battery charge and discharge testing equipment, K-type thermocouples, and other equipment through the Seebeck effect of the thermocouples. 3) Maximum stress test on the outer surface of the battery: The maximum stress value on the battery surface was measured using equipment such as a contact surface pressure sensor and a high-temperature resistant fixture. Example 1
[0028] This embodiment provides a method for preparing pressure-sensitive microcapsules, which includes the following steps: 1) Preparation of shell solution and gel bath: Dissolve 10 g sodium alginate and 15 g Tween 80 in 1 L deionized water and stir to form a homogeneous solution as the outer gelation solution; separately prepare an aqueous solution containing CaCl2 (concentration of 10 g / L) and sodium carboxymethyl cellulose (concentration of 10 g / L) as the receiving phase solution. 2) Set up a coaxial drip system: Use a coaxial nozzle (the inner tube orifice diameter is adapted according to the core material flow rate, and the outer tube outlet inner diameter is 0.5 mm), and connect two injection pumps respectively; use the oil phase core material dichloromethane as the inner layer fluid, and the outer layer gelling solution prepared in step 1) as the outer layer fluid; 3) Coaxial dripping and in-situ gelation: At room temperature, the injection pump is adjusted to co-extract the inner and outer layer fluids through a coaxial nozzle, forming a core-shell structured droplet. The vertical distance between the lower end of the nozzle and the surface of the receiving phase solution is controlled to be 3 cm, allowing the droplet to fall into the receiving phase solution. At this time, the sodium alginate and Ca in the outer layer fluid react... 2+ Ionic crosslinking occurs, and rapid solidification at the interface forms a continuous shell; the receiving phase solution is kept under gentle stirring (250 r / min) and gelled for 30 min to form microcapsules with the initial shell. 4) Post-processing and secondary enhancement: The microcapsules with the initial shell are taken out and washed with deionized water to obtain the pressure-sensitive microcapsules (the mass ratio of the oil phase core material dichloromethane to the shell in the pressure-sensitive microcapsules is 4.5:1). Example 2
[0029] This embodiment provides a method for preparing pressure-sensitive microcapsules, which includes the following steps: 1) Preparation of shell solution and gel bath: Dissolve 15 g sodium alginate and 30 g Tween 80 in 1 L deionized water and stir to form a homogeneous solution as the outer gelation solution; separately prepare an aqueous solution containing CaCl2 (concentration of 15 g / L) and sodium carboxymethyl cellulose (concentration of 15 g / L) as the receiving phase solution. 2) Set up a coaxial drip system: Use a coaxial nozzle (the inner tube orifice diameter is adapted according to the core material flow rate, and the outer tube outlet inner diameter is 1.0 mm), and connect two injection pumps respectively; use the oil phase core material dichloromethane as the inner layer fluid, and the outer layer gelling solution prepared in step 1) as the outer layer fluid; 3) Coaxial dripping and in-situ gelation: Under room temperature and ventilation conditions, the injection pump is adjusted to co-extrude the inner and outer layer fluids through a coaxial nozzle, forming stable core-shell structured droplets; the vertical distance between the lower end of the nozzle and the surface of the receiving phase solution is controlled to be 3 cm, allowing the droplets to fall into the receiving phase solution. At this time, the sodium alginate in the outer layer fluid reacts with Ca... 2+ Ionic cross-linking occurs and rapid solidification forms an initial shell; wherein the receiving phase solution is kept stirred (250 r / min), and the initial gelation time is 40 min, forming microcapsules with an initial shell; 4) Collection: The microcapsules with the initial shell are taken out and washed with deionized water to obtain the pressure-sensitive microcapsules (the mass ratio of the oil phase core material dichloromethane to the shell in the pressure-sensitive microcapsules is 6:1). Example 3
[0030] This embodiment provides a method for preparing pressure-sensitive microcapsules, which includes the following steps: 1) Preparation of shell solution and gel bath: Dissolve 20 g sodium alginate and 50 g Tween 80 in 1 L deionized water and stir to form a homogeneous solution as the outer gelation solution; separately prepare an aqueous solution containing CaCl2 (concentration of 20 g / L) and sodium carboxymethyl cellulose (concentration of 20 g / L) as the receiving phase solution. 2) Set up a coaxial drip system: Use a coaxial nozzle (outer tube outlet inner diameter is 1.5 mm) and connect it to two injection pumps respectively; use dichloromethane as the oil phase core material as the inner layer fluid and the outer layer gelling solution prepared in step 1) as the outer layer fluid; 3) Coaxial dripping and in-situ gelation: Under room temperature and ventilation conditions, the injection pump is adjusted to co-extrude the inner and outer layer fluids through a coaxial nozzle, forming stable core-shell structured droplets; the vertical distance between the lower end of the nozzle and the surface of the gel bath is controlled to be 3 cm, allowing the droplets to fall into the receiving phase solution. At this time, sodium alginate and Ca in the outer layer fluid react... 2+ Ionic cross-linking occurs and rapid solidification forms an initial shell; wherein the receiving phase solution is kept stirred (250 r / min) and the initial gelation time is 30 min, forming microcapsules with an initial shell; 4) Collection: The microcapsules with the initial shell are taken out, washed with deionized water, and the pressure-sensitive microcapsules are obtained (the mass ratio of the oil phase core material dichloromethane to the shell in the pressure-sensitive microcapsules is 8:1). Example 4
[0031] This embodiment provides a method for preparing a pressure-sensitive microcapsule hydrogel lithium battery thermal management material, which includes the following steps: S1. Preparation of hydrogel matrix mixture: Acrylamide powder was dissolved in deionized water to prepare a 10wt% acrylamide solution, and then crosslinking agent (methylenebisacrylamide), initiator (ammonium persulfate) and accelerator (N,N,N',N'-tetramethylethylenediamine) were added and stirred to obtain a hydrogel matrix mixture; Specifically, based on an acrylamide solution, the methylenebisacrylamide has a mass fraction of 0.1%, the ammonium persulfate has a mass fraction of 0.5%, and the N,N,N',N'-tetramethylethylenediamine has a mass fraction of 0.2%. S2. Composite molding: The pressure-sensitive microcapsules (taking Example 1 as an example) were added to the hydrogel matrix mixture at a ratio of 24.5% of the hydrogel mass. The mixture was placed on a magnetic stirrer and stirred at a speed of 600 r / min for 2 min. After being evenly dispersed, the mixture was injected into a mold and sealed with a Parafilm film. The mixture was left to stand for 45 min under undisturbed conditions to promote the solidification and molding of the PAM hydrogel, thus obtaining the pressure-sensitive microcapsule hydrogel lithium battery thermal management material.
[0032] The quality of the pressure-sensitive microcapsule hydrogel lithium battery thermal management material is based on the battery dimensions (101.3 mm × 148 mm × 98 mm), designed thickness (5 mm), and material density (1.013 g / cm³). 3 The mass is calculated using the formula: mass = volume × density, where the mass of the hydrogel is 75g. The hydrogel contains pressure-sensitive microcapsules, which encapsulate dichloromethane (CH2Cl2). The proportion of pressure-sensitive microcapsules is determined by the following heat balance equation: in: The mass of the packing material; The target battery mass is 0.94g. The temperature change of the battery from the point of reaching the expansion threshold to the point of valve injection (8K). The average specific heat capacity of the battery is 0.83 kJ / (kg*K). The latent heat of phase change of the selected filler is approximately 326 kJ / kg. The system's heat transfer efficiency is 0.85.
[0033] The calculated required mass of dichloromethane is 20g. The mass ratio of the shell to the core material dichloromethane in the pressure-sensitive microcapsule is approximately 1:4.5, meaning the mass of the microcapsule shell is approximately 4.4g. The proportion Y of the pressure-sensitive microcapsule mass to the total material mass is: Performance characterization: This application conducts performance tests on the pressure-sensitive microcapsule hydrogel lithium battery thermal management material prepared in Example 4, specifically as follows: 1) Temperature curve This test example describes the preparation of a 5mm pressure-sensitive microcapsule hydrogel lithium battery thermal management material obtained in Example 4. Simultaneously, 1mm, 2mm, 3mm, and 4mm pressure-sensitive microcapsule hydrogel lithium battery thermal management materials were prepared using the preparation method of Example 4. Then, a battery with pressure-sensitive microcapsule hydrogel lithium battery thermal management materials bonded to both sides was prepared using the application method of Example 5.
[0034] Then, the internal temperature change of the battery with pressure-sensitive microcapsule hydrogel lithium battery thermal management materials of different thicknesses bonded on both sides was tested in the early stage of battery thermal runaway (pre-valve spray stage). The specific test steps are as follows: Step 1) Sample preparation and sensor setup After charging the lithium-ion battery to 100% SOC at a constant current-constant voltage rate of 1C at 25℃, multiple K-type thermocouples were fixed to the battery surface using high-temperature adhesive; and pre-prepared thermal management materials of different thicknesses were uniformly and tightly adhered to the battery surface, and then multiple K-type thermocouples were arranged on the material surface; the initial temperature of all thermocouples and the voltage and current data of the battery were recorded. Step 2) Perform overcharge test and data monitoring The charging and discharging test equipment is set to continuously charge the battery with a constant current of 1C, and the acquisition system synchronously records the time, voltage, current, and the temperature of all thermocouples. When the battery experiences violent valve ejection and a sharp rise in temperature, the charging is manually terminated. After confirming that the test chamber is safe, ventilation and cleaning are carried out.
[0035] Step 3) Data Processing and Analysis Export all time-temperature data series and plot the curves of temperature change over time at different measuring points.
[0036] The results are as follows Figure 3 As shown in the figure, in the initial stage of the gradual increase in the internal heat generation rate of the battery, due to the initial thermal conductivity of the thermal management material and the fact that the pressure-sensitive microcapsules have not yet ruptured, the battery interface temperature shows a steady upward trend. When the valve is opened (800s), the maximum temperature difference is 7-10K. This indicates that when the battery valve is opened and the pressure-sensitive microcapsules begin to rupture and release dichloromethane, the mass of dichloromethane is sufficient to satisfy the phase change endothermic energy to reduce the battery temperature by 7-10K.
[0037] 2) Pressure curve This test example describes the preparation of a 5mm pressure-sensitive microcapsule hydrogel lithium battery thermal management material obtained in Example 4. Simultaneously, 1mm, 2mm, 3mm, and 4mm pressure-sensitive microcapsule hydrogel lithium battery thermal management materials were prepared using the preparation method of Example 4. Then, a battery with pressure-sensitive microcapsule hydrogel lithium battery thermal management materials bonded to both sides was prepared using the application method of Example 5.
[0038] Then, the stress changes of the battery material in the early stage of battery thermal runaway (pre-valve spray stage) were tested, with pressure-sensitive microcapsule hydrogel lithium battery thermal management materials of different thicknesses attached to both sides. The specific steps are as follows: Step 1) Sample preparation and sensor setup After charging the lithium-ion battery to 100% SOC at a constant current-constant voltage rate of 1C at 25°C, multiple flexible pressure sensors were fixed to the battery surface using high-temperature adhesive. Pre-prepared thermal management material was then uniformly and tightly adhered to the battery surface. After calibration under no-load (no pressure) and pre-load (light pressure with known weight) conditions, the initial values of all sensors and the battery's voltage and current data were recorded.
[0039] Step 2) Perform overcharge test and data monitoring The charge / discharge testing equipment was set to continuously charge the battery with a constant current of 1C, and the data acquisition system simultaneously recorded time, voltage, current, and all sensor data. Charging was manually terminated when the battery experienced severe valve ejection or a rapid temperature rise. Ventilation and cleaning were then carried out after confirming safety within the test chamber.
[0040] Step 3) Data Processing and Analysis Export all time-pressure data sequences, align the pressure, displacement, voltage, and temperature curves with the overcharge start time as the time zero point.
[0041] The results are as follows Figure 4 As shown in the figure, the pressure change exhibits a significant nonlinear characteristic. Before 400s, the pressure increases slowly. After 400s, due to the accelerated gas production from the side reactions inside the battery and the intensified volume expansion, the extrusion pressure acting on the hydrogel layer begins to rise sharply, and the slope of the curve increases dramatically. At the valve injection point (approximately 800s), the pressure reaches 0.6MPa, which is also the threshold point for the material to switch from the thermal conductivity enhancement mode to the phase change endothermic mode. This indicates that setting the rupture threshold of the pressure-sensitive microcapsule to 0.6MPa can meet the design requirements of the thermal management system.
[0042] 3) How thermal conductivity changes with compression This test example uses the 5mm pressure-sensitive microcapsule hydrogel lithium battery thermal management material prepared in step 4. The thermal conductivity of the thermal management material, with the material bonded to both sides, changes with compression during the initial stage of thermal runaway (before valve ejection). The specific steps are as follows: Step 1) Sample preparation and initial measurement Material samples were prepared according to the preparation method in Example 4, and their thickness was measured, recorded, and the initial volume was calculated.
[0043] Step 2) Installation and Pre-compression Place the thermal management material sample in the center of the hot plate of the testing instrument, lower the cold plate, and record the initial contact thickness. Fill the material sample with thermal insulation cotton to reduce heat loss.
[0044] Step 3) Set the compression amount and perform a steady-state test. Slowly press the cold plate down until the thermal management material sample is compressed to the preset value. After setting the temperatures of the hot and cold plates, start the system and continuously monitor the heat flux through the thermal management material sample and the temperatures of the upper and lower plates. When the system reaches steady state, record the heat flux density, hot plate temperature, and cold plate temperature at steady state.
[0045] Step 4: Data Processing Substitute the data recorded for each compression level into the principle formula to calculate the effective thermal conductivity under that compression state.
[0046] The results are as follows Figure 5 As shown in the figure, the effective heat transfer coefficient of the thermal management material increases continuously as the battery pressure gradually increases, indicating that the pressure-sensitive microcapsule hydrogel lithium battery thermal management material provided in this application can adapt to the temperature rise of the battery and improve its heat dissipation capacity as the battery temperature rises. Example 5
[0047] This embodiment provides an application of pressure-sensitive microcapsule hydrogel lithium battery thermal management material in lithium battery thermal safety management. The specific application process is as follows: B1. Material pretreatment: Before use, the prepared pressure-sensitive microcapsule hydrogel thermal management material should be visually inspected to ensure that the material surface is free of damage, bubbles, and has uniform thickness. B2. Installation and Fitting: According to the size and specifications of the target battery, cut the thermal management material into a shape that matches the side of the battery. During the cutting process, avoid pulling too hard, which could cause premature rupture of the pressure-sensitive microcapsules. Evenly attach the cut material to both sides of the battery body (e.g., ...). Figure 1 As shown in the figure, this ensures that the material adheres tightly to the battery surface without any gaps.
[0048] After pressure-sensitive microcapsule hydrogel thermal management material is attached to both sides of the battery body, the actual use process mainly consists of three stages. A schematic diagram simulating the rupture process of the pressure-sensitive microcapsules is shown below. Figure 2 As shown: C1. Normal operation thermal management: When the battery is in normal operating condition (temperature 25-40℃, internal pressure of hydrogel ≤0.6MPa), the pressure-sensitive microcapsules in the thermal management material remain intact, and the hydrogel matrix achieves heat conduction by means of basic thermal properties, maintaining the temperature stability during battery charging and discharging. C2. Passive response to abnormal operating conditions: When the battery has a micro-short circuit risk due to overcharging, over-discharging, short circuit, cycle aging and other electrical abuse, gas is generated inside the battery and gradually expands. The surface pressure begins to rise slowly, and the thermal conductivity of the hydrogel also gradually increases due to the pressure of its own expansion, so as to dissipate heat more quickly. C3. When the internal pressure of the hydrogel rises to the pressure-sensitive microcapsule rupture threshold (0.6MPa), the pressure-sensitive microcapsule ruptures rapidly under pressure, releasing the internally encapsulated dichloromethane filler. The dichloromethane evaporates rapidly due to its own properties, dissipating battery heat and inhibiting the temperature from rising continuously.
[0049] In this process, the simulation diagram of the pressure-sensitive microcapsule rupture process is as follows: Figure 2As shown, the pressure-sensitive microcapsule hydrogel thermal management material provided in this application achieves dynamic thermal management throughout the battery's entire life cycle. The mechanism of action consists of three stages: First, the normal operation stage: When the battery operates within the normal temperature range (25℃-40℃) and working pressure (below the microcapsule rupture threshold), the pressure-sensitive microcapsules within the hydrogel maintain structural integrity. At this stage, the hydrogel primarily relies on its basic thermal properties (such as thermal conductivity) for heat conduction, maintaining the daily stability of the battery temperature. During this stage, the material exhibits good mechanical compatibility and will not damage the battery structure. Second, the abnormal expansion stage: Due to battery abuse such as cycle aging, overcharging, over-discharging, and short circuits, the battery expands in volume. When the internal pressure of the hydrogel is less than the threshold (0.6MPa), as the battery pressure gradually increases, the effective heat transfer coefficient of the hydrogel layer shows a continuous upward trend, intelligently adapting to the battery's temperature rise. Third, during the abnormal expansion stage, when the internal pressure of the hydrogel is greater than or equal to the threshold (0.6 MPa), the microcapsules inside are triggered to rupture, releasing the dichloromethane encapsulated inside. After release, the dichloromethane evaporates rapidly due to its phase change characteristics. This process absorbs a large amount of heat, thereby quickly dissipating the accumulated heat and effectively suppressing the risk of a sharp rise in battery temperature and thermal runaway.
[0050] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.
Claims
1. A pressure-sensitive microcapsule hydrogel lithium battery thermal management material, characterized in that, This includes hydrogels, and pressure-sensitive microcapsules contained within the hydrogels that can synergistically change in response to externally applied pressure and changes in ambient temperature.
2. The pressure-sensitive microcapsule hydrogel lithium battery thermal management material according to claim 1, characterized in that, The pressure-sensitive microcapsule is internally encapsulated with an oil-phase filler, and the rupture pressure threshold of the pressure-sensitive microcapsule is ≥ 0.6 MPa.
3. The pressure-sensitive microcapsule hydrogel lithium battery thermal management material according to claim 1, characterized in that, The pressure-sensitive microcapsules are obtained by the following preparation method: 1) Dissolve sodium alginate and surfactant in deionized water and stir until homogeneous to obtain the outer gelling solution; 2) Use oil phase filler as oil phase core material and an aqueous solution containing calcium chloride and sodium carboxymethyl cellulose as receiving phase solution; 3) Using a coaxial dripping device, the oil phase filler in step 2) is used as the inner layer fluid, and the outer layer gelling solution in step 1) is used as the outer layer fluid. Core-shell droplets are formed by co-extrusion through a coaxial needle and directly dripped into the receiving phase solution in step 2). Sodium alginate and calcium ions gel at the interface to form microcapsules with an initial shell. 4) Remove the microcapsules with the initial shell from the gel bath and rinse them with deionized water to remove residual ions on the surface, thus obtaining pressure-sensitive microcapsules.
4. The pressure-sensitive microcapsule hydrogel lithium battery thermal management material according to claim 3, characterized in that, In the gelling solution described in step 1), the concentration of sodium alginate is 10-20 g / L, and the surfactant is Tween 80 with a concentration of 10-50 g / L.
5. The pressure-sensitive microcapsule hydrogel lithium battery thermal management material according to claim 2, characterized in that, The mass percentage of oil phase filler in the thermal management material is determined by the following heat balance equation: in: The mass of the packing material; The mass of the target battery; This refers to the temperature change of the battery from when it reaches the expansion threshold to when it is before the valve sprays. This represents the average specific heat capacity of the battery. The latent heat of phase change for the selected filler; This represents the system's heat transfer efficiency.
6. A method for preparing a pressure-sensitive microcapsule hydrogel lithium battery thermal management material according to any one of claims 1-5, characterized in that, Includes the following steps: S1) Add crosslinking agent, initiator and accelerator to acrylamide solution, stir and mix evenly to obtain hydrogel matrix; S2) Add pressure-sensitive microcapsules to the hydrogel matrix, disperse them evenly, and then inject them into a mold to form a pressure-sensitive microcapsule hydrogel lithium battery thermal management material.
7. The pressure-sensitive microcapsule hydrogel lithium battery thermal management material according to claim 6, characterized in that, In step S1), the mass ratio of acrylamide solution, crosslinking agent, initiator and accelerator is 100:(0.05-0.15):(0.3-1.0):(0.1-0.3); wherein the crosslinking agent is methylenebisacrylamide, the initiator is ammonium persulfate and the accelerator is (N,N,N',N'-tetramethylethylenediamine).
8. The pressure-sensitive microcapsule hydrogel lithium battery thermal management material according to claim 7, characterized in that, The mass ratio of the pressure-sensitive microcapsule to the hydrogel matrix in step S2) is (20-30):
100.
9. The application of a pressure-sensitive microcapsule hydrogel lithium battery thermal management material according to any one of claims 1-5 in the thermal safety management of lithium batteries.
10. The application according to claim 9, characterized in that, Specifically, the pressure-sensitive microcapsule hydrogel lithium battery thermal management material as described in any one of claims 1-5 is attached to both sides of the battery body.