Pressure-temperature dual-response intelligent diaphragm material and preparation method and application thereof

Abstract

The application discloses a pressure-temperature dual-response intelligent diaphragm material and a preparation method and application thereof, and belongs to the technical field of electrochemical energy storage device materials. The intelligent diaphragm comprises a porous base film and at least one functional sensing layer integrated with the porous base film; the functional sensing layer is a conductive network structure with ion transmission pores, and the components of the functional sensing layer comprise pressure-sensitive nanomaterials and temperature-sensitive nanomaterials. The application constructs a functional layer containing two different response mechanism nanomaterials on a traditional diaphragm, so that the diaphragm has the ability to perceive internal stress changes (piezoresistive effect) and temperature fluctuations (thermosensitive effect) while maintaining the core ion transmission function. The configuration design does not need to additionally increase a sensor component in the battery, solves the pain points of increasing the thickness of the battery and hindering ion transmission of the existing in-situ monitoring technology, and realizes the lossless and real-time monitoring of the multi-dimensional physical field of the core region of the energy storage device.

Description

Technical Field

[0001] This invention relates to the field of materials technology for electrochemical energy storage devices, specifically to a pressure-temperature dual-response smart diaphragm material, its preparation method, and its application. Background Technology

[0002] With the global energy structure shifting towards cleaner and lower-carbon energy, the new energy vehicle and large-scale energy storage industries are developing rapidly. The safety and reliability of electrochemical energy storage devices have become a core challenge for the industry. Internal pressure changes and temperature fluctuations are key physical parameters reflecting the battery's operating state: the expansion and contraction of electrode materials during charging and discharging generate internal pressure changes (breathing effect), and abnormal local pressure accumulation is a significant precursor to lithium plating and internal short circuits; while the uneven distribution of the internal temperature field is directly related to the battery's thermal runaway safety boundary. Therefore, real-time, accurate, in-situ monitoring of the battery's internal pressure and temperature is crucial.

[0003] Current in-situ monitoring technologies for batteries primarily rely on inserting independent sensors, such as thin-film pressure sensors and miniature thermocouples, between the electrodes or on the surface of the separator inside the battery. However, this technology has significant drawbacks: First, the additional sensor layer increases the physical thickness and volume of the cell, reducing the battery's volumetric energy density and contradicting the development requirements for high energy density in energy storage devices. Second, most commercially available sensors are based on non-porous films such as PET and PI, which, when inserted into the battery, block local lithium-ion transport channels, leading to increased battery polarization and severely affecting electrochemical performance. Third, the long-term chemical compatibility between the external sensor materials and the battery electrolyte is questionable, easily triggering side reactions at the interface and reducing the battery's cycle life. Fourth, sensors are mostly placed in non-core areas of the battery, making it difficult for monitoring data to reflect the true physical field distribution inside the battery.

[0004] To address these issues, existing research has attempted to directly integrate sensing functions into the battery separator. For example, Chinese patent application CN119253198A discloses a separator that monitors temperature and pressure by embedding independent thermistors and pressure sensors within a porous thin film. However, in this approach, the sensors are physically encapsulated within the separator as discrete components, resulting in complex fabrication processes, significant sensor thickness, and independent responses to pressure and temperature by different devices, making it difficult to achieve integrated dual-parameter sensing within a single ultrathin functional layer. Another example is a flexible integrated sensor based on piezoresistive and thermistor effects, constructed using CNTs and Ni to create a pressure-sensitive layer with a near-zero temperature coefficient of resistance, and additionally featuring independent temperature-sensitive points to achieve dual-parameter sensing and decoupling. While this approach achieves sensor flexibility, it still requires separate fabrication of pressure and temperature-sensitive units, resulting in a complex overall sensor structure. Furthermore, these sensors are typically attached to the outside of the battery or inside the module, making integrated integration with the separator body impossible and failing to meet the requirements for in-situ, ultrathin, and high-sensitivity monitoring.

[0005] Therefore, developing a technology that does not require additional battery components, does not hinder ion transport, and can utilize existing core battery components to achieve dual in-situ sensing of pressure and temperature has become a key breakthrough in solving the safety monitoring problem of electrochemical energy storage devices, and is of great significance to promoting the high-quality development of the new energy storage industry. Summary of the Invention

[0006] The purpose of this invention is to provide a pressure-temperature dual-response smart separator material and its preparation method, which integrates sensing functions into the core component of the battery—the separator. This enables the separator to maintain the core function of ion transport while achieving non-destructive, real-time, and in-situ monitoring of internal pressure and temperature of the battery, thereby solving the problems of increased battery thickness, impeded ion transport, and poor interface compatibility in existing technologies.

[0007] To achieve the above objectives, the present invention provides a pressure-temperature dual-response smart membrane material, comprising a porous base membrane and a functional sensing layer integrally integrated on at least one surface of the porous base membrane. The functional sensing layer is a micro / nano structure layer with ion transport capability, which includes a polymer binder matrix and functional fillers dispersed in the polymer binder matrix to form a conductive network. The functional filler comprises a first component and a second component. The first component is a piezoresistive nanomaterial with a piezoresistive effect, and the second component is a thermosensitive nanomaterial with a thermistor effect. The first component forms a conductive network in the functional sensing layer that is near the percolation threshold; The composite resistance value of the functional sensing layer changes and is detected as a function of external pressure and temperature.

[0008] Preferably, the thickness of the functional sensing layer is less than 5 micrometers, and it has a through-pore structure with a porosity of 30%-60%, which ensures the realization of the sensing function without hindering the smooth transmission of lithium ions.

[0009] Preferably, the thickness of the functional sensing layer is 1-3 micrometers.

[0010] Preferably, the first component is one or more of carbon nanotubes, graphene, conductive carbon black, MXenes materials, metal nanowires or conductive polymer nanofibers. This component achieves pressure response through the piezoresistive effect, that is, when the pressure increases, the number of contact points between nanomaterials increases and the contact resistance decreases. The component accounts for 5%-50% of the mass of the functional sensing layer.

[0011] Preferably, the second component achieves temperature response through the thermistor effect, that is, the intrinsic resistivity changes significantly with temperature.

[0012] Preferably, the second component is a transition metal oxide nanoparticle with a negative temperature coefficient, which is either manganese nickel cobalt oxide or lithium iron phosphate.

[0013] Preferably, the second component is a conductive particle with a positive temperature coefficient, which is any one of conductive polymer composite particles, platinum nanoparticles, and gold nanoparticles, and the conductive polymer composite particles are any one of carbon black / polyethylene composite particles and acetylene black.

[0014] Preferably, the polymer binder matrix is ​​any one of PP, PE, and PVDF, and its mass percentage in the functional sensing layer is 1-10%.

[0015] Preferably, the composite resistance of the functional sensing layer is determined by both the piezoresistive effect and the thermistor effect. By using a decoupling algorithm to take advantage of the nonlinear differences in the effects of pressure and temperature on resistance, the real-time pressure and temperature values ​​can be separated from a single composite resistance signal.

[0016] Preferably, the porous base membrane is a PE, PP or ceramic coated base membrane with a thickness of 8μm-12μm to ensure the basic mechanical properties of the diaphragm and ion transport channels.

[0017] This invention also provides a method for preparing the above-mentioned pressure-temperature dual-response smart membrane material, wherein the functional sensing layer and the porous base membrane are integrated in one of the following ways: (1) Surface coating configuration: The functional sensing layer is attached to one or both sides of the porous base film through a coating process; (2) Multilayer co-extrusion configuration: The functional sensing layer and the porous base film are formed into a sandwich structure or a multilayer composite structure through a multilayer co-extrusion process, wherein the functional sensing layer is used as the middle layer or the surface layer. (3) In-situ growth configuration: The functional sensing layer is grown in situ on the surface of the porous base membrane through chemical vapor deposition or physical vapor deposition to form a nanofilm layer.

[0018] The intelligent diaphragm material provided by this invention is used in electrochemical energy storage devices. As a diaphragm material, it is placed between the positive electrode and the negative electrode. The edge of the functional sensing layer is provided with a flexible electrode lead-out terminal for connecting an external detection circuit to output a composite resistance signal reflecting pressure and temperature changes.

[0019] Therefore, the present invention, employing the aforementioned pressure-temperature dual-response smart diaphragm material, its preparation method, and its application, possesses the following beneficial effects: (1) Zero parasitic volume, high energy density is maintained: The sensing function is integrated into the original separator of the battery without adding any additional sensor components. The sensing is achieved by utilizing the space of the separator itself, without increasing the thickness and volume of the cell, ensuring that the volumetric energy density of the battery is not affected.

[0020] (2) It does not hinder ion transport and has excellent electrochemical performance: The functional sensing layer is designed as a porous micro-nano structure with a thickness of less than 5μm and a porosity of 30%-60%. It has a through lithium ion transport channel and has almost no impact on the ion conduction and charge-discharge performance of the battery, thus solving the problem of blocking ion transport in traditional sensors.

[0021] (3) Core area monitoring, data is true and reliable: The separator is located between the positive and negative electrodes of the battery. It is the core and most sensitive area of ​​the battery's physical and chemical reactions. Pressure and temperature monitoring is carried out here, and the data obtained can truly reflect the actual state inside the battery. Compared with traditional non-core area monitoring, it has higher accuracy and representativeness.

[0022] (4) Dual pressure and temperature response for more efficient safety warning: Simultaneously realizes in-situ real-time monitoring of internal battery pressure and temperature, can capture abnormal pressure accumulation and local temperature rise signals before faults such as lithium plating and internal short circuit, realize dual safety warning, and compared with single parameter monitoring, can predict battery safety risks earlier and more accurately.

[0023] (5) Integrated configuration with excellent interface compatibility: The functional sensing layer and the porous base film are integrated through coating, co-extrusion or in-situ growth processes. There is no interface contact problem between the external sensor and the battery. It has good chemical compatibility with the electrolyte and will not cause interface side reactions, thus ensuring the cycle life of the battery.

[0024] (6) Mature preparation process, easy to scale up production: The preparation of the functional sensing layer adopts mature industry processes such as micro-gravure coating, co-extrusion blown film, CVD / PVD, which can be compatible with existing battery separator production lines without large-scale equipment modification, making it easy to industrial mass production and promotion.

[0025] (7) The sensing signal is easy to acquire and has strong adaptability: By setting an ultra-thin flexible electrode lead-out end at the edge of the diaphragm, the composite resistance signal can be directly exported and adapted to conventional resistance detection equipment. No special signal acquisition system is required, the detection cost is low, the operation is simple, and it can be flexibly applied to different types of electrochemical energy storage devices.

[0026] (8) Ultra-high pressure sensitivity: Unlike existing piezoresistive sensors that use conventional conductive networks, this invention controls the concentration of the first component near the percolation threshold, placing the conductive network of the functional sensing layer in a critical state of interconnection. In this state, the network resistance is mainly dominated by the contact resistance between particles, rather than the intrinsic resistance of the particles themselves. Even small changes in external pressure can cause significant changes in the number and quality of contact points, leading to a drastic change in the composite resistance value, thereby achieving a pressure detection sensitivity that is more than an order of magnitude higher than that of conventional piezoresistive sensors.

[0027] (9) Multi-information coupling: Unlike existing technologies where pressure and temperature are output as two independent signals by discrete devices, this invention co-converts pressure-sensitive and temperature-sensitive materials into the same functional layer, outputting a single composite resistance signal that is simultaneously modulated by pressure and temperature. Since the two physical effects contribute to resistance through different mechanisms, this composite signal is theoretically decoupled, and pressure and temperature information can be extracted separately by establishing a resistance-pressure-temperature calibration relationship.

[0028] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the smart membrane material of the present invention; Figure 2 This is a schematic diagram of the structure of the functional sensing layer of the present invention; Figure 3 This is a schematic diagram illustrating the application of the intelligent separator of the present invention inside a lithium-ion battery and its signal extraction. Figure 4 This is a schematic diagram of the 3D configuration of the battery core and the multi-dimensional test connection of the present invention; Figure 5 This is a comparison chart of the air permeability performance of the intelligent diaphragm of this invention and a conventional commercial diaphragm; Figure 6 This is a comparison chart of the mechanical tensile properties of the diaphragm of this invention and a commercially available conventional diaphragm; Figure 7 This is a stress distribution diagram for commercial PE diaphragm testing. Figure 8 This is a stress distribution diagram of the smart diaphragm prepared in Example 1 of the present invention. Figure Labels 1. Porous base membrane; 2. Functional sensing layer; 2-1. Polymer binder matrix; 2-2. First component; 2-3. Second component; 3. Electrode lead-out terminal; 4. Positive electrode; 5. Negative electrode; 6. Ultrafine wire; 7. Electrode tab; 8. Resistance detection equipment; 9. Electrochemical testing equipment; 10. Smart diaphragm. Detailed Implementation

[0030] This invention provides a pressure-temperature dual-response smart membrane material, the structure of which is as follows: Figure 1 As shown, it includes a porous base membrane 1 and a functional sensing layer 2 integrally integrated on at least one surface of the porous base membrane 1, and an electrode lead-out end 3 is provided at the edge of the membrane.

[0031] The functional sensing layer 2 is a micro / nano structure layer with ion transport capability, comprising a polymer binder matrix 2-1 and a functional filler dispersed in the polymer binder matrix 2-1 to form a conductive network. The functional filler comprises a first component 2-2 and a second component 2-3. The first component 2-2 is a piezoresistive nanomaterial with a piezoresistive effect, and the second component 2-3 is a thermosensitive nanomaterial with a thermistor effect. The first component 2-2 forms a conductive network in the functional sensing layer 2 near the percolation threshold. The composite resistance value of the functional sensing layer 2 changes with changes in external pressure and temperature, and is thus detected.

[0032] The functional sensing layer 2 has a thickness of less than 5 micrometers, preferably 1-3 micrometers, and has a through-pore structure with a porosity of 30%-60%, which ensures the realization of the sensing function without hindering the smooth transmission of lithium ions.

[0033] The first component 2-2 is one or more of carbon nanotubes, graphene, conductive carbon black, MXenes materials, metal nanowires or conductive polymer nanofibers. This component achieves pressure response through the piezoresistive effect, that is, when the pressure increases, the number of contact points between nanomaterials increases and the contact resistance decreases.

[0034] The second component 2-3 achieves temperature response through the thermistor effect, that is, the intrinsic resistivity changes significantly with temperature. The second component 2-3 is a transition metal oxide nanoparticle with negative temperature coefficient characteristics (such as manganese nickel cobalt oxide) or a conductive particle with positive temperature coefficient characteristics (such as any one of conductive polymer composite particles, platinum nanoparticles, and gold nanoparticles).

[0035] Taking the second component 2-3 as transition metal oxide nanoparticles with negative temperature coefficient characteristics as an example, the schematic diagram of the functional sensing layer 2 is as follows. Figure 2As shown, the polymer binder matrix 2-1 contains a pressure-sensitive first component 2-2 and a temperature-sensitive second component 2-3, which are particulate NTC powders. The first component 2-2 overlaps to form a conductive network, and the second component 2-3 is embedded in the network. The overall structure has a large number of nanoscale interconnected pores. The arrows indicate that the carbon nanotubes become more tightly connected under the action of pressure P, and the resistance of the NTC particles changes under the action of temperature T.

[0036] The polymer binder matrix 2-1 can be any one of the following. The porous base membrane 1 is a PE, PP or ceramic coated base membrane with a thickness of 8μm-12μm, ensuring the basic mechanical properties and ion transport channels of the diaphragm.

[0037] The core mechanism of this invention is to integrate the piezoresistive effect and thermistor effect into the functional sensing layer 2 of the battery separator, and achieve a dual pressure-temperature response through the synergistic effect of the composite conductive network. The specific mechanism is as follows: Piezoresistive response mechanism: Piezoresistive nanomaterials form a conductive network in the functional sensing layer 2 that is near the percolation threshold. When there is no external pressure, there are few contact points and high contact resistance between nanomaterials. When the internal pressure of the battery increases (such as the electrode expansion compressing the diaphragm), the functional sensing layer 2 is deformed by pressure, the number of contact points between nanomaterials increases, the contact area increases, and the contact resistance decreases nonlinearly, thus realizing the sensing and conversion of pressure signals.

[0038] Thermosensitive response mechanism: The intrinsic resistivity of thermosensitive nanomaterials is highly sensitive to temperature. The resistivity of NTC type materials decreases significantly with increasing temperature, while the resistivity of PTC type materials increases sharply with increasing temperature. Temperature changes directly change the resistance value of thermosensitive nanomaterials, thereby realizing the sensing and conversion of temperature signals.

[0039] Signal decoupling mechanism: The composite resistor of the functional sensing layer 2 is the result of the coupling between the piezoresistive network resistor and the thermosensitive material resistor. The influence of pressure and temperature on the resistor has different nonlinear characteristics and different contribution mechanisms. Through calibration and algorithms, pressure and temperature can be decoupled from a single resistor signal.

[0040] When the intelligent monitoring battery separator described in this invention is applied to electrochemical energy storage devices, its assembly method is as follows: Figure 3 and Figure 4 As shown: like Figure 3 As shown, the battery core adopts a structure in which the positive electrode 4, the smart separator 10, and the negative electrode 5 are stacked in sequence. The edge of the smart separator 10 extends beyond the tab 7 area of ​​the positive electrode 4 and the negative electrode 5. At the edge of the smart separator 10, the ultra-thin flexible electrode lead-out end 3 of the functional sensing layer 2 is connected to the external resistance detection device 8 through two ultra-fine wires 6 (such as micro-enameled wire or other flexible conductive wires), thereby exporting the composite resistance signal of the functional sensing layer 2 in real time.

[0041] like Figure 4 As shown, in the assembled battery, the smart separator 10 is located between the positive electrode 4 and the negative electrode 5, and the electrode lead-out end 3 outputs the sensing signal, which does not participate in the electrochemical test circuit; the electrochemical test equipment 9 directly collects the signals from the positive and negative electrode tabs 7 of the battery to test: voltage, current, capacity, impedance, charge-discharge curves and other battery electrochemical performance. Thus, during the battery charge-discharge process, the following can be achieved simultaneously: (1) in-situ real-time monitoring of the internal pressure and temperature of the battery (by collecting and decoupling the composite resistance signal); (2) testing of the battery's electrochemical performance (such as voltage, current, capacity, etc.). This integrated test scheme provides an effective technical means for studying the internal thermo-mechanical-electrical coupling behavior of the battery.

[0042] Based on the above mechanism, the functional sensing layer adopts an ultra-thin porous micro-nano structure design and is integrated with the porous base film, without occupying additional internal space of the battery, thus ensuring smooth lithium-ion transport. The separator is located in the core area between the positive and negative electrodes of the battery, and the monitored pressure and temperature data can truly reflect the physical field distribution inside the battery, achieving accurate monitoring of the core area.

[0043] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0044] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. These other embodiments are also covered within the scope of protection of this invention.

[0045] Unless otherwise specified, the reagents, instruments, and equipment used in this invention are all commonly used by those skilled in the art.

[0046] Example 1 This embodiment provides a pressure-temperature dual-response smart membrane material. The functional sensing layer is integrated onto a porous base membrane by surface coating. The specific preparation method is as follows: (1) Preparation of functional sensing slurry The component parameters are as follows: Solvent: N-methylpyrrolidone (NMP), 10% by mass; Polymer binder: polyvinylidene fluoride (PVDF), accounting for 10% of the mass of the functional sensing layer; First component: Multi-walled carbon nanotubes (MWCNTs), with a diameter of 10-20 nm and a length of 5-15 μm, accounting for 5% of the mass, are used to form a sensitive conductive network near the percolation threshold; The second component (thermosensitive): nano-manganese nickel cobaltate NTC thermistor ceramic powder, with a particle size of about 100nm, accounting for 85% by mass; The above materials are mixed in proportion, dispersed by a high-speed disperser for 30 minutes, and then ground by a sand mill for 2 hours to produce a uniform functional sensing slurry with a viscosity of 5000-8000 mPa·s.

[0047] (2) Coating process Commercial wet-process microporous polyethylene (PE) base film with a thickness of 9μm was selected as the porous base film; a microgravure printing coating machine was used to uniformly coat the functional sensing paste on one side of the PE base film, and the coating speed was controlled at 5m / min and the drying temperature was 80℃. After drying at 80℃ until the solvent evaporates completely and the material is cured, a functional sensing layer with a thickness of about 2μm is formed. This layer naturally forms a porous structure due to solvent evaporation and phase separation of PVDF, with a porosity of 45% and good permeability.

[0048] (3) Electrode lead-out preparation The coated composite film is cut to the specified size, and a 5mm electrode lead-out area is reserved at the edge of the membrane. Conductive silver paste is printed on the lead-out area using screen printing technology to form two tiny electrode contact points with a spacing of 10mm. A 0.1mm diameter ultra-fine enameled wire is connected as the electrode lead-out end and dried and cured at 60℃ to ensure that the contact resistance between the silver paste and the enameled wire is <1Ω.

[0049] (4) Testing and verification The smart separator was assembled into a soft-pack lithium-ion battery (positive electrode NMC622, negative electrode graphite, electrolyte 1mol / L LiPF6 / EC+DMC). Pressure response test: The battery was subjected to pressures ranging from 0.1 MPa to 1.0 MPa using an external pressure testing machine. The resistance of the membrane functional layer was observed to decrease nonlinearly from 12.5 kΩ to 3.2 kΩ. The pressure response sensitivity was 9.3 kΩ / MPa, and the repeatability error was <5%.

[0050] Temperature response test: The battery was placed in a constant temperature chamber, and the temperature was increased from 25℃ to 60℃. The resistance value was observed to decrease significantly from 12.5kΩ to 5.8kΩ, with a temperature response sensitivity of 0.19kΩ / ℃ and a linear correlation coefficient R0. 2 =0.992.

[0051] Dual response test: Simultaneously change the pressure (0.1-1.0MPa) and temperature (25-60℃), record the change pattern of the composite resistance, and accurately separate the real-time values ​​of pressure and temperature through the decoupling algorithm, with a separation error of <3%.

[0052] Routine performance tests: The tensile strength of this smart diaphragm is 12.5MPa, the elongation at break is 85%, the air permeability is 135s / 100mL, and the thermal decomposition temperature is 360℃, which is comparable to that of commercial PE diaphragms, with no significant performance degradation. Electrochemical performance test: The assembled pouch cell retained 96.8% capacity after 100 cycles at 0.5C rate, which is close to that of the cell using commercial PE separator (97.2%), indicating that the smart separator has no significant impact on the electrochemical performance of the cell.

[0053] Example 2 This embodiment provides a pressure-temperature dual-response smart membrane material. The functional sensing layer is integrated onto a porous base membrane via multilayer co-extrusion. The specific preparation method is as follows: (1) Preparation of functional masterbatch Matrix resin: homopolymer polypropylene (PP), melt index 2.5 g / 10 min; First component (pressure-sensitive): conductive carbon black (CB), particle size 30nm, specific surface area 120m². 2 / g, accounting for 15% by mass; The second component (temperature sensitive): PTC conductive polymer composite particles (carbon black / polyethylene composite), with a particle size of 500nm and a mass percentage of 10%; PP resin, conductive carbon black, PTC particles and compatibilizer are mixed in a certain proportion and granulated by a twin-screw extruder to produce functional masterbatch at a granulation temperature of 180-200℃.

[0054] (2) Co-extrusion process The process employs a three-layer co-extrusion blown film process, with the outer two layers being conventional PP chips and the middle layer being a mixture of the aforementioned functional masterbatch and PP chips (the functional masterbatch accounts for 30%). Control the extrusion temperature: barrel 170-190℃, die 195℃, blow-up ratio 2.0, and traction speed 8m / min; After longitudinal and transverse stretching to create pores, a smart membrane with a three-layer structure of PP / functional sensing layer / PP was prepared with a total thickness of 16μm, of which the thickness of the middle functional sensing layer is about 3μm. All three layers have a connected pore structure, and the overall porosity is 40%.

[0055] (3) Electrode lead-out and post-processing The co-extruded smart diaphragm material is subjected to corona treatment to improve surface wettability; Copper electrode leads were fabricated at the edge of the diaphragm using a vacuum evaporation process. The electrode thickness was 50 nm and the width was 3 mm. The electrode leads are encapsulated to ensure compatibility with the electrolyte, and the contact resistance is stable at <2Ω.

[0056] (4) Testing and verification The pressure response range of this co-extruded smart diaphragm is 0.05-1.5MPa, and the resistance variation range is 15.8kΩ-2.1kΩ.

[0057] With a temperature response range of -20℃ to 80℃, it exhibits significant PTC characteristics, with a sharp increase in resistance when the temperature exceeds 60℃, enabling simultaneous temperature monitoring and over-temperature protection.

[0058] The membrane has a tensile strength of 15.2 MPa, an air permeability of 145 s / 100 mL, and a heat shrinkage rate (105℃, 1h) of 1.2%, which is superior to commercial PP membranes in terms of overall performance. After being assembled into a lithium metal battery, the capacity retention rate is 95.3% after 50 cycles, and there is no phenomenon of lithium dendrites piercing the separator, which significantly improves safety.

[0059] Example 3 This embodiment provides a pressure-temperature dual-response smart membrane material, in which the functional sensing layer is integrated on a porous base membrane in an in-situ grown configuration. The specific preparation method is as follows: (1) Base film pretreatment A ceramic-coated PE base film with a thickness of 10 μm (the ceramic layer is Al2O3 with a thickness of 1 μm) was selected as the porous base film. The base film was subjected to plasma treatment at a power of 100W for 5 minutes to enhance the activity of the base film skeleton surface.

[0060] (2) In-situ growth process Graphene nanosheets (pressure-sensitive first component) were grown in situ on the surface of the base film framework using chemical vapor deposition (CVD) with acetylene as the carbon source. The growth temperature was 600℃ and the time was 30 min. The thickness of the graphene layer was about 50 nm. Using physical vapor deposition (PVD) with manganese nickel cobalt oxide target material as source, NTC nanoparticles (temperature-sensitive second component) were deposited in situ on the surface of graphene layer. The deposition power was 200W and the time was 20min. The NTC particle size was about 80nm. The functional sensing layer formed after in-situ growth is seamlessly integrated with the base film skeleton. The total thickness of the functional sensor layer is about 400 nm, and the porosity is 55%, which does not affect lithium-ion transmission.

[0061] (3) Electrode lead-out preparation Gold electrode leads were fabricated at the edge of the diaphragm using magnetron sputtering with a sputtering thickness of 100 nm to ensure good contact with the graphene layer. The electrode leads were encapsulated with polyimide tape to prevent electrolyte corrosion.

[0062] (4) Testing and verification The pressure response sensitivity of this in-situ grown smart diaphragm is 10.5 kΩ / MPa, and the linear correlation coefficient of its temperature response is R. 2 =0.995, response speed <100ms, exhibiting ultra-fast sensing response characteristics.

[0063] The in-situ grown smart membrane exhibits excellent thermal stability, with no significant thermal shrinkage below 250℃ and thermal decomposition beginning at 380℃.

[0064] After being assembled into a high-rate lithium-ion battery, it retains 94.5% of its capacity after 200 cycles at 5C, exhibiting both excellent sensing and electrochemical performance.

[0065] Example 4 The difference between this embodiment and Embodiment 1 is that a doctor blade coating process is used to simultaneously coat the functional sensing slurry onto both sides of the PE base film. The thickness of each functional sensing layer is 1 μm, the total thickness of the functional layer is 2 μm, and the porosity is 42%. Test verification shows that the pressure response sensitivity of this double-sided coated smart diaphragm is improved to 11.2 kΩ / MPa, and the temperature response uniformity is better, making it suitable for energy storage device scenarios with higher monitoring accuracy requirements.

[0066] To verify the comprehensive performance of the smart diaphragm of this invention, the smart diaphragms prepared in Examples 1-3 were compared with commercial conventional PE / PP diaphragms. The test items included conventional diaphragm performance (mechanical tensile strength, air permeability, thermal stability), sensing performance (pressure / temperature response sensitivity, linearity, repeatability), and electrochemical performance (capacity retention, cycle life). The air permeability results are as follows: Figure 5 As shown, the mechanical tensile properties are as follows: Figure 6 As shown, all the above results are summarized in Table 1: Table 1 Performance Test Results

[0067] The test results show that the conventional properties of the smart separator prepared by this invention, such as mechanical tensile strength, air permeability, and thermal stability, are basically equivalent to those of commercial conventional separators, with no significant attenuation, and fully meet the requirements for use as a battery separator.

[0068] The stress test distribution diagrams of the commercial PE film and the smart membrane of Example 1 are shown below. Figure 7 and Figure 8As shown, the results indicate that the stress values ​​of commercial PE membranes are generally low and unevenly distributed, with the highest stress being approximately 0.32 MPa. The stress concentration points are scattered and the gradient is large, reflecting the uneven stress distribution and insensitive stress response of traditional membranes. In contrast, the stress values ​​of the smart membrane are significantly higher, reaching a maximum of 0.67 MPa. The stress distribution is continuous and uniform with a gentle gradient, and the overall stress level and uniformity are far superior to those of commercial membranes. This demonstrates that the functional sensing layer can efficiently transmit and sense pressure signals, with a more sensitive pressure response and a more stable signal.

[0069] All three smart separators exhibit excellent dual pressure and temperature response characteristics, with high response sensitivity, good linearity, and excellent repeatability, enabling precise in-situ monitoring. The electrochemical performance of batteries assembled with smart separators is close to that of commercial separators, indicating that the introduction of the functional sensing layer did not have a significant negative impact on the battery's ion transport and cycle performance, thus combining sensing functionality and electrochemical performance.

[0070] Therefore, the intelligent separator material and its configuration design with dual pressure and temperature response functions of the present invention can be directly applied to electrochemical energy storage devices such as lithium-ion batteries, lithium metal batteries, and sodium-ion batteries, and are especially suitable for scenarios such as new energy vehicle power batteries and large-scale energy storage battery PACKs where safety requirements are high. This intelligent separator can be seamlessly integrated with existing battery manufacturing processes without changing the battery assembly process. Only a resistance detection module needs to be added to the outside of the battery to achieve in-situ pressure-temperature monitoring. The detection system is low-cost and easy to integrate.

[0071] Meanwhile, the intelligent separator of the present invention can be combined with the battery management system (BMS) to transmit the monitored pressure and temperature data to the BMS in real time, realize dynamic monitoring and safety warning of battery working status. When abnormal pressure or temperature is detected, the BMS can trigger the protection mechanism in time, effectively prevent battery thermal runaway and safety accidents, and improve the safety and reliability of electrochemical energy storage devices.

[0072] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and does not limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A pressure-temperature dual-response smart membrane material, comprising a porous base membrane, characterized in that, A functional sensing layer is integrally integrated on at least one surface of the porous base membrane; The functional sensing layer is a micro / nano structure layer with ion transport capability, which includes a polymer binder matrix and functional fillers dispersed in the polymer binder matrix to form a conductive network. The functional filler comprises a first component and a second component. The first component is a piezoresistive nanomaterial with a piezoresistive effect, and the second component is a thermosensitive nanomaterial with a thermistor effect. The first component forms a conductive network in the functional sensing layer that is near the percolation threshold; The composite resistance value of the functional sensing layer changes and is detected as a function of external pressure and temperature.

2. The pressure-temperature dual-response smart diaphragm material according to claim 1, characterized in that, The functional sensing layer is less than 5 micrometers thick and has a through-pore structure with a porosity of 30%-60%.

3. The pressure-temperature dual-response smart diaphragm material according to claim 1, characterized in that, The first component consists of one or more of the following: carbon nanotubes, graphene, conductive carbon black, MXenes materials, metal nanowires, or conductive polymer nanofibers, accounting for 5%–50% of the mass of the functional sensing layer.

4. The pressure-temperature dual-response smart diaphragm material according to claim 1, characterized in that, The second component consists of transition metal oxide nanoparticles with a negative temperature coefficient, which can be any one of manganese nickel cobalt oxide or lithium iron phosphate.

5. The pressure-temperature dual-response smart diaphragm material according to claim 1, characterized in that, The second component consists of conductive particles with a positive temperature coefficient, which can be any one of conductive polymer composite particles, platinum nanoparticles, or gold nanoparticles.

6. The pressure-temperature dual-response smart diaphragm material according to claim 1, characterized in that, The polymer binder matrix is ​​any one of PP, PE, or PVDF, and its mass percentage in the functional sensing layer is 1%–10%.

7. The pressure-temperature dual-response smart diaphragm material according to claim 1, characterized in that, The composite resistance value of the functional sensing layer is a single resistance signal that is simultaneously modulated by pressure and temperature.

8. A method for preparing a pressure-temperature dual-response smart diaphragm material as described in any one of claims 1-7, characterized in that, The functional sensing layer and the porous base membrane can be integrated in one of the following ways: (1) Surface coating configuration: The functional sensing layer is attached to one or both sides of the porous base film through a coating process; (2) Multilayer co-extrusion configuration: The functional sensing layer and the porous base film are formed into a sandwich structure or a multilayer composite structure through a multilayer co-extrusion process, wherein the functional sensing layer is used as the middle layer or the surface layer. (3) In-situ growth configuration: The functional sensing layer is grown in situ on the surface of the porous base membrane through chemical vapor deposition or physical vapor deposition to form a nanofilm layer.

9. An application of the pressure-temperature dual-response smart diaphragm material as described in any one of claims 1-7, characterized in that, The intelligent diaphragm material is used in electrochemical energy storage devices. As a diaphragm material, it is placed between the positive and negative electrode plates. The edge of the functional sensing layer is provided with a flexible electrode lead-out terminal for connecting to an external detection circuit to output a composite resistance signal reflecting pressure and temperature changes.

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