Bimodal trigger intelligent diaphragm, battery, preparation method and application

Abstract

The invention relates to a bimodal trigger intelligent diaphragm, a battery, a preparation method and application. The bimodal trigger intelligent diaphragm comprises a base film, and a thermal response layer and an electric response layer which are respectively positioned on two sides of the base film, the thermal response layer is prepared from the following raw materials in percentage by weight: 30 to 50 percent of capsule, 10 to 15 percent of PVDF-HFP and the balance of solvent; the capsule comprises a Wood alloy and a capsule wall wrapping the Wood alloy, the material of the capsule wall is polymethyl methacrylate, and the composition of the Wood alloy is Bi < 50 > Pb < 2. 7 > Sn < 1. 3 > Se < 0.5 > Cd10. The electric response layer is prepared from the following raw material components: 0.2 to 0.5 M of N-(4-sulfonyl butyryl) aniline, 0.6 to 1.5 M of sulfuric acid and 0.05 to 0.2 M of benzene sulfonate; according to the invention, dual protection is realized through thermal response and electrical response, the sensitivity, stability and response speed of thermal protection are effectively improved, and the protection effect is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion battery separators, and particularly relates to a bimodal trigger intelligent separator, a battery, a preparation method and an application. BACKGROUND

[0002] As a core power carrier in the new energy era, the safety of lithium ion batteries is directly related to the reliability of major infrastructures such as electric vehicles and energy storage power stations. However, as the energy density continues to rise, the risk of thermal runaway has become a key bottleneck restricting the development of the industry. According to the statistical data of UL 1642 safety standards, 62% of thermal runaway accidents are caused by lithium precipitation at the negative electrode and positive electrode structure collapse due to overcharging, 28% are caused by local thermal abuse, and mechanical abuse accounts for only 10%.

[0003] The existing safety protection system has significant defects: the traditional PP / PE separator melts off at 160℃ or above, and the response lag is as high as 30 seconds or more; and the intelligent separator with a single mechanism can only solve local problems, such as Al2O3 / PVDF-HFP thermal shutdown film cannot respond to voltage mutation, and polyaniline coating film can inhibit dendrites but lacks thermal protection function. The current commercialized separator has three major core defects when dealing with multiple failure scenarios, as follows: 1) Single response mode: More than 90% of intelligent separators focus on thermal trigger mechanism, but lack effective blocking of the chain reaction caused by overcharging. When the battery voltage exceeds 4.35V, the ion conductivity of the traditional separator does not change significantly, and it cannot build an ion lock mechanism.

[0004] 2) Material synergy failure: the physical mixed composite functional layer has the problem of interface phase separation.

[0005] 3) Insufficient trigger precision: in the GB / T 36276-2023 adiabatic temperature rise test, the thermal runaway starting temperature of the traditional separator has a high dispersion of ±8℃. SUMMARY

[0006] The technical problem to be solved by the application is to provide a bimodal trigger intelligent separator, a battery, a preparation method and an application, which realizes double protection through thermal response and electrical response, effectively improves the sensitivity, stability and response speed of thermal protection, and improves the protection effect.

[0007] The embodiment of the application provides a bimodal trigger intelligent separator, which comprises a base film and a thermal response layer and an electrical response layer located on both sides of the base film respectively; the base film comprises a PE film or a PP film on which the thermal response layer is deposited, and a conductive film on which the electrical response layer is deposited; The raw material of the thermally responsive layer comprises the following components by weight percentage: capsules 30-50%, PVDF-HFP 10-15%, and the balance being solvent; the capsules comprise Wood's alloy and a capsule wall encapsulating the Wood's alloy, the capsule wall being made of polymethyl methacrylate, and the Wood's alloy being Bi alloy encapsulated with Se. 50 Pb 26.7 Sn 13.3 Cd 10 ; The raw materials of the electroresponsive layer include the following components: 0.2-0.5 M N-(4-sulfonylbutyroyl)aniline, 0.6-1.5 M sulfuric acid, and 0.05-0.2 M benzenesulfonate.

[0008] Preferably, the PE or PP film is treated with Ar plasma. The conductive film is made of stainless steel, preferably a stainless steel mesh. The Wood's alloy of the present invention is Bi coated with Se. 50 Pb 26.7 Sn 13.3 Cd 10 , Se and Bi 50 Pb 26.7 Sn 13.3 Cd 10 The weight ratio is 0.5:99.5, meaning that the weight of Se is 0.5% of the total weight of Wood alloy.

[0009] Preferably, the solvent is an aqueous solution of acetone, and the volume ratio of acetone to water is 6-8:2-4. The raw material of the thermal response layer also includes 0.3-0.8% wetting agent.

[0010] Preferably, the raw material of the thermal response layer comprises the following components by weight percentage: 40% capsule, 12% PVDF-HFP, 0.5% wetting agent, and the balance being solvent.

[0011] Preferably, the raw material of the electroresponsive layer comprises the following components: 0.3M N-(4-sulfonylbutyroyl)aniline, 1M sulfuric acid, and 0.1M benzenesulfonate; The thickness of the thermally responsive layer is 2-4 μm, and the thickness of the electrically responsive layer is 1-3 μm.

[0012] The thickness of the PE or PP film is 5-30 μm. Preferably, when the base film is a PE base film, the thickness is 5-20 μm, and when the base film is a PP base film, the thickness is 8-30 μm.

[0013] This invention provides a battery including the dual-mode triggered smart separator, wherein the thermal response layer contacts the positive electrode side and the electrical response layer contacts the negative electrode side.

[0014] This invention provides a method for preparing the dual-modal triggered smart diaphragm, comprising the following steps: 1) Molten Wood's alloy is injected into the aqueous phase channel of the microfluidic chip, and the oil phase is an MMA / chloroform solution to generate emulsion droplets; 2) The emulsion droplets and cross-linking agent are mixed to initiate cross-linking, resulting in capsules; 3) Mix and disperse the capsules, PVDF-HFP and solvent, then coat them onto a PE or PP base film and dry them to obtain a base film coated with a thermally responsive layer; 4) The base film coated with the thermal response layer is immersed in an electrolyte to carry out an electropolymerization reaction. The electrolyte is 0.2-0.5 M N-(4-sulfonylbutyroyl)aniline, 0.6-1.5 M sulfuric acid and 0.05-0.2 M benzenesulfonate to obtain a dual-mode triggered smart diaphragm.

[0015] Preferably, the crosslinking agent is dicumyl peroxide, and the crosslinking reaction temperature is 65°C.

[0016] Preferably, after electropolymerization, the membrane is immersed in a 1 M LiTFSI / EC-DMC solution and polarized at -1 V to obtain a dual-mode triggered smart membrane.

[0017] This invention provides an application of the dual-mode triggered smart separator, which is used to prepare lithium-ion battery separators.

[0018] The beneficial effects of this invention are that it pioneers a self-doped potential-sensitive system, using N-(4-sulfonylbutyroyl)aniline monomer to achieve stable conductivity over a wide pH range (0~10), responds to lithium plating risk within 0.5 seconds, improves lithium plating during 6C fast charging, and when the negative electrode potential is detected to be <0V (vs. Li⁺ / Li), the porosity increases from 40% to 60% within 0.5 seconds, increasing the response speed by 240 times, and forced current equalization avoids lithium plating.

[0019] This invention utilizes an intramolecular sulfonic acid group (-SO3H) as a permanent proton source to maintain the stability of the quinone structure within a pH range of 0 to 10. Even if the HF in the electrolyte is depleted, the monomer still provides H+ through the dissociation of the sulfonic acid group. + To ensure that the conductivity remains stable at 10 -2 With a conductivity above S / cm, pH dependence is eliminated, preventing failure due to HF consumption during cycling. It exhibits wide pH adaptability, with a 10% increase in conductivity at high pH. 4This invention utilizes a butyryl chain (-C4H8O) as a bridge connecting the benzene ring and the sulfonic acid group, reducing the intramolecular rotational barrier. When the potential drops to 0V, the local current density decreases by 40%. This invention adds sodium benzenesulfonate as a morphology-directing agent to guide the three-dimensional interweaving of nanofibers during electropolymerization. The network generated at a constant potential of 1.2V has 100-300nm interconnected channels, resulting in a 3-fold increase in ion mobility compared to traditional PANI membranes.

[0020] This invention utilizes microfluidic technology to generate olive-shaped Wood's alloy microcapsules with an encapsulation efficiency >95%. This structure generates a stress concentration effect upon thermal triggering, achieving a rupture temperature accuracy of ±0.3℃ (compared to ±5℃ for traditional spherical capsules). This forces the conversion of electrical energy into Joule heat dissipation, thereby significantly improving diaphragm thermal shrinkage. The PVDF-HFP / Wood's alloy microcapsule coating, upon microcapsule rupture at 70.5℃, forms a conductive network, further converting electrical energy into Joule heat dissipation.

[0021] This invention generates W / O / W emulsion droplets by adjusting the two-phase flow rate ratio (oil phase:water phase = 3:1), and can control their deformation into an olive shape. This structure generates a stress concentration effect upon thermal triggering, achieving a rupture temperature accuracy of ±0.3℃ (compared to ±5℃ for traditional spherical capsules).

[0022] This invention adds 0.3 wt% dicumyl peroxide (DCP) to initiate PMMA crosslinking, forming a network structure at 65°C. Nanoindentation testing shows that the breaking strength is 200% higher than that of the traditional emulsification method at a wall thickness of 300 nm.

[0023] This invention is performed under nitrogen protection, where Wood's alloy is molten (80°C) and injected into the cross-linking curing process to ensure the alloy composition is Bi. 50 Pb 26.7 Sn 13.3 Cd 10 The addition of 0.5 wt% Se increases the phase transition enthalpy, resulting in an encapsulation efficiency of over 95%.

[0024] This invention employs a three-layer gradient structure enhanced by atomic layer deposition and plasma treatment, resulting in a thermal shrinkage rate of <5% (150℃) and a needle penetration temperature of <100℃, thereby improving thermal runaway performance.

[0025] The present invention provides a thermal response layer and an electrical response layer on both sides of the base film. After thermal cycling at 150°C, there is no delamination, the interlayer bonding is strong, and the overall structure is more stable. The thermal shutdown time is 0.8s, which is much shorter than that of the traditional structure.

[0026] This invention modifies the base film through thermal and electrical response layers, which not only significantly improves the thermal runaway threshold of lithium-ion batteries, but also provides a smart safety solution to suppress lithium plating from the source, achieving dual thermal and electrical protection, effectively improving the safety performance of the battery cell and enhancing the protection effect. Attached Figure Description

[0027] Figure 1 The image shows a scanning electron microscope (SEM) image (a) and a schematic diagram (b) of the dimensions of the olive-shaped Wood alloy microcapsules prepared in Example 1.

[0028] Figure 2 The results of the electrochemical response test are shown in (a) and (b). (a) is the SEM image of the negative electrode of the traditional membrane assembly and (b) is the SEM image of the negative electrode of the smart membrane assembly. Detailed Implementation

[0029] Example 1 A method for preparing a dual-modal triggered smart diaphragm includes the following steps: I. Preparation of Olive-Shaped Wood Alloy Microcapsules 1) Prepare Wood's alloy, wherein the Wood's alloy is Bi 50 Pb 26.7 Sn 13.3 Cd 10 The phase transition enthalpy was adjusted to 125 J / g by adding 0.5 wt% Se. The melting point is 70 ± 0.5 °C.

[0030] The method for preparing the Wood's alloy of this application involves melting Bi, Pb, and Sn under a protective atmosphere to form a pre-alloyed melt, then cooling the melt to 250°C and adding Cd and Se to obtain the molten Wood's alloy. More specifically: 1. Based on the target component Bi 50 Pb 26.7 Sn 13.3 Cd 10 Calculate the required mass of each metal, and additionally calculate and weigh 0.5 wt% of selenium (Se) powder.

[0031] 2. First, place the metals (Bi, Pb, Sn) other than cadmium (Cd) and selenium (Se) into the crucible (Cd is volatile and Se is easily oxidized; adding them later reduces losses). Place the crucible in the melting furnace and evacuate to 10°C. -2 Below Pa, then high-purity nitrogen (N2) is introduced to a slightly positive pressure. This purging process is repeated 2-3 times to completely remove oxygen.

[0032] 3. Under nitrogen protection, raise the furnace temperature to 300-350°C to completely melt Bi, Pb, and Sn. Then, mechanically stir for 10-20 minutes to form a homogeneous pre-alloyed melt. Next, lower the temperature to approximately 250°C (above the melting point of Wood's alloy but below the violent volatilization temperatures of Cd and Se), add cadmium (Cd) blocks and selenium (Se) powder, and stir quickly but gently to avoid excessive oxidation and volatilization. Maintain this temperature and stir for about 30 minutes until Se is completely dissolved and evenly distributed.

[0033] Se atoms are small in size and highly electronegative, making them more likely to be relocated to higher-energy surfaces to lower the system energy compared to the other four metallic elements. Therefore, Se is located on the surface of Wood's alloy.

[0034] 2) Microfluidic encapsulation: Under nitrogen protection, molten Wood's alloy (temperature 80℃) is injected into the aqueous phase channel of the microfluidic chip. The oil phase is an MMA / chloroform solution (MMA is methyl methacrylate; to prepare 100 mL of MMA / chloroform solution, 5-10 g of MMA is weighed, dissolved in chloroform, and the volume is adjusted to 100 mL, i.e., the mass-to-volume ratio of MMA to chloroform is 5-10 g / 100 mL, and in this example, it is 5 g / 100 mL). The flow rate ratio of the two phases is controlled at 3:1 to generate emulsion droplets with a droplet size of 6-10 μm.

[0035] 3) Interfacial polymerization: Emulsion droplets and dicumyl peroxide (added at 0.3 wt% of the total content) were mixed and cross-linked with methyl methacrylate at 65°C for 2 hours to obtain olive-shaped Wood alloy microcapsules.

[0036] This invention employs low-temperature curing; although 65℃ is lower than the Tg of PMMA (105℃), the free radical activity is sufficient to drive local crosslinking (local movement of molecular chain segments). The crosslinking network of this invention blocks the intermolecular gaps of PMMA, improving the capsule wall density (encapsulation efficiency >95%) and preventing oxygen diffusion to avoid oxidation of Wood's alloy. After crosslinking of methyl methacrylate initiated by dicumyl peroxide, the tensile strength is 360 MPa, and the oxygen permeability is extremely low. The olive-shaped Wood's alloy microcapsules prepared by this invention can ensure stress concentration fracture within the range of 70.5 ± 0.3℃, thereby improving thermally triggered stability.

[0037] The resulting microcapsules, such as Figure 1 As shown, the wall thickness is 300±50 nm, the maximum length of the microcapsule is 8.0±0.2 μm, the encapsulation efficiency is >95%, and the microcapsule structure is olive-shaped. This invention uses microfluidic technology to achieve precise encapsulation, which can improve the encapsulation efficiency by more than 15% compared with the traditional emulsification method.

[0038] II. Preparation of PVDF-HFP / Wood's alloy microcapsules 1) Mix 40wt% Wood alloy microcapsules, 12wt% PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene copolymer), 47.5wt% acetone-water (acetone and water volume ratio of 7:3) mixed solvent and 0.5wt% perfluoropolyether (PFPE) wetting agent.

[0039] 2) Disperse at high speed of 3000 rpm for 30 minutes, and then treat with high pressure microjet (150 MPa, 3 cycles) to ensure uniform dispersion of microcapsules and obtain PVDF-HFP / Wood alloy microcapsules.

[0040] The performance of the capsules obtained by the traditional emulsification method (i.e., direct mechanical stirring, which involves directly stirring 40 wt% Wood alloy microcapsules, 12 wt% PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene copolymer), 47.5 wt% acetone-water (acetone and water volume ratio of 7:3) mixed solvent and 0.5 wt% perfluoropolyether (PFPE) wetting agent at a temperature of 65℃, a rotation speed of 10000±2000 rpm, and a time of 45 min) is compared with that obtained by the traditional emulsification method. Table 1 shows the performance of the capsules obtained by the traditional emulsification method.

[0041] Table 1 Performance parameters of Wood alloy microcapsules

[0042] As shown in Table 1, the microcapsules prepared by the method of the present invention have a smaller average particle size, more uniform particle distribution, thinner and more uniform coating wall thickness, and better performance consistency.

[0043] III. Base Film Coating Microcapsules 1) Substrate Treatment: The 16 μm PE membrane is treated with Ar plasma (100 W, 15 m / min) to increase its surface energy for easier coating. The substrate consists of a PE membrane and a stainless steel mesh stacked together. The specific preparation method is as follows: The material is pressed through a pair of heated rollers (hot press rollers) at specific temperatures, pressures, and times.

[0044] The temperature will be controlled slightly below the melting point of the PE membrane (120-130℃ for PE membrane, melting point of PE membrane is about 135℃; for PP membrane, 140-150℃ for PP membrane, melting point of PP membrane is about 160℃). At this temperature, the membrane will not completely melt, but will soften and have extremely high plasticity.

[0045] Under pressure, the softened PE film is squeezed and flows into the mesh of the stainless steel mesh, and solidifies after cooling.

[0046] After cooling and solidification, the polyolefin acts like an "anchor" firmly locked in the holes of the stainless steel mesh, forming a three-dimensional, interwoven structure. This bonding method is very strong, with a strength far exceeding that of surface bonding. It can effectively resist the shear force generated by the expansion and contraction of the electrode volume during battery charging and discharging, preventing delamination.

[0047] 2) The PVDF-HFP / Wood alloy microcapsules were coated onto the treated PE membrane using a microgravure secondary transfer coating technology. The coating parameters were: coating speed 8 m / min, wet film thickness 15 μm; step drying (60-120℃) was used to obtain the coating with a thickness of 3.0±1.0 μm. The final product was a base film coated with a thermally responsive layer.

[0048] IV. Fabrication of the Electrically Response Layer 1) The base film coated with a thermally responsive layer is immersed in an electrolyte for electropolymerization (i.e., polymerization at a constant potential of 1.2 V (reference electrode: Ag / AgCl) for 300 seconds). The electrolyte consists of 0.2-0.5 M N-(4-sulfonylbutyroyl)aniline, 0.6-1.5 M sulfuric acid, and 0.05-0.2 M benzenesulfonate (solvent: water). A porous nanofiber network (fiber diameter 80±10 nm, pore size distribution 100-300 nm) is formed on the stainless steel mesh substrate. Both the thermally responsive layer coated on one side of the base film and the base film itself are excellent electronic insulators. When the entire composite membrane is immersed in the electrolyte and a potential is applied, the current can only flow through the conductive stainless steel mesh. The electrochemical reaction (monomer polymerization here) occurs strictly at the electrode surface through which the current flows, i.e., at the interface where the electronic conductor contacts the electrolyte. Therefore, the polymerization reaction only occurs on the conductive stainless steel mesh surface exposed to the electrolyte. Since no current flows through the insulating thermally responsive layer and the back of the PE base film, no monomer polymerization reaction occurs. Through this design, the growth of the electroresponsive layer is successfully and precisely confined to the stainless steel mesh substrate, which serves as the negative electrode side, perfectly avoiding its coverage and functional interference with the thermally responsive layer, and achieving spatial isolation of the dual functional layers.

[0049] 2) Then immerse it in 1 M LiTFSI / EC-DMC solution (LiTFSI is lithium bis(trifluoromethanesulfonyl)imide, and the solvent is EC-DMC, i.e. ethylene carbonate-dimethyl carbonate), and polarize it at -1 V to obtain a dual-mode triggered smart diaphragm.

[0050] The electroresponsive layer is a PANI derivative layer with a thickness of 2.0±0.2 μm and dynamically adjustable porosity (40%~60%).

[0051] The electroresponsive layer completely covers the surface of the conductive film, i.e., the stainless steel mesh, meaning the stainless steel mesh is entirely encapsulated by an insulating or semiconductorized polyaniline derivative layer. This PANI material is electronically insulating at normal battery operating potentials (although it is a conductive polymer, its conductivity is much lower than that of metals, and its electron conduction path is blocked upon contact with the electrolyte). Therefore, it effectively isolates the stainless steel mesh from the electrolyte and the negative electrode electronically. The PP or PE film is inherently an excellent electronic insulator; electrons from the positive electrode cannot pass through these two insulators to form a conductive circuit with the stainless steel mesh. In the organic electrolyte environment of a lithium-ion battery, a very thin and dense passivation film (usually LiF and other fluorides) spontaneously forms on the surface of the stainless steel mesh. This passivation film is an ionic conductor but also an electronic insulator. Therefore, the stainless steel mesh will not conduct electricity, preventing a short circuit in the battery.

[0052] Comparative Example 1 Comparative Example 1 is a traditional membrane, which is prepared using either a dry uniaxial stretching process (PP membrane) or a wet phase separation process (PE membrane). The dry process involves melt-extruding polypropylene into sheets, forming a microfiber structure through uniaxial stretching, and then heat-setting to generate a microporous membrane with a narrow and elongated pore structure and significant anisotropy.

[0053] The wet process involves blending polyolefins with plasticizers (such as paraffin oil) to form a film, followed by extraction to remove the plasticizer, resulting in a bidirectional, uniform microporous network. Membranes prepared using this method exhibit more uniform pore size distribution and better mechanical properties.

[0054] Both are made of polyolefin, which relies on its thermoplasticity to achieve a melt-closed-cell effect at around 160°C.

[0055] Example 2 1. Thermal trigger response test The thermal shrinkage rate of the conventional diaphragm and the smart diaphragm of Example 1 was tested at 150°C. The results showed that the thermal shrinkage of the conventional diaphragm exceeded 70%, while the thermal shrinkage of the smart diaphragm was less than 10%.

[0056] The intelligent diaphragm triggering mechanism is as follows: at 70±5℃, the olive-shaped microcapsules rupture, the Wood alloy melts and flows, forming a conductive network in the PVDF-HFP layer, the diaphragm resistance drops sharply, and the electrical energy is forcibly converted into Joule heat dissipation, thereby significantly improving the thermal shrinkage of the diaphragm.

[0057] 2. Electrochemical response test The lithium plating suppression verification employed a three-electrode system, comparing a conventional separator with the smart separator of Example 1. The three electrodes consisted of a graphite anode as the working electrode, a lithium metal sheet as the counter electrode, and a Li wire as the reference electrode. After fabrication, the three electrodes were constant-current charged to a graphite potential of 0.05 V (vs. Li⁺ / Li) by controlling the potential, thus forcibly simulating a high-risk lithium plating scenario at the end of fast charging for 1 hour.

[0058] Experimental results of the negative electrode of the traditional diaphragm assembly are as follows: Figure 2 As shown in (a), needle-like lithium dendrites (length > 20 μm) appear on the negative electrode of the smart separator. Figure 2 As shown in (b), the negative electrode surface is very smooth with a roughness of less than 0.1 μm and no lithium is deposited.

[0059] The lithium plating suppression mechanism of the smart separator is as follows: when the negative electrode potential is <0 V (vs. Li⁺ / Li), the polyaniline derivative undergoes reduction shrinkage, and the quinone structure of the PANI main chain is reduced to the benzene structure. Characterized by in-situ EC-AFM (electrochemical atomic force microscopy), the pore size increases by ~50% in the reduced state, the porosity increases from 40% to 60%, and the local current density decreases by 40%, thereby suppressing lithium plating.

[0060] 3. Comprehensive testing of the electrochemical and safety performance of finished battery cells The positive electrode uses lithium iron phosphate, and the negative electrode uses graphite. Both are then fabricated into finished battery cells using conventional and smart separators respectively, employing a stacking process. Safety tests, including nail penetration, thermal runaway, and insulation tests, are performed on both types of cells.

[0061] As can be seen from the results in Table 2, Wood's alloy forms a metal isolation layer on the positive electrode, which blocks the redox reaction chain, and has significant advantages in safety performance tests such as needle penetration, thermal runaway, and insulation tests.

[0062] Table 2 Comparison Data of Safety Abuse Tests

[0063] Example 3 Example 3 compared the performance of Wood alloy with and without the addition of Se, and the experimental results are shown in Table 3.

[0064] Table 3 Comparison of the performance of Wood alloy with and without Se addition

[0065] The addition of 0.5 wt% Se significantly improved the melting point and uniformity of the alloy. Se formed a dense selenide protective film on the alloy surface, effectively blocking the oxidation of active components such as Bi and Sn during the preparation process, greatly improving the antioxidant properties and ensuring the long-term reliability of the microcapsules.

[0066] Example 4 Compared with Example 1, Comparative Example 2 differs in that: Comparative Example 2 directly replaces the PVDF-HFP / Wood alloy microcapsules in the base film coating microcapsules of Example 1 with olive-shaped Wood alloy microcapsules, that is, the olive-shaped Wood alloy microcapsules are coated on the treated substrate. Everything else is the same as in Example 1, and the membrane of Comparative Example 2 is prepared.

[0067] Example 4 compares the performance of the diaphragm of Comparative Example 2 and the smart diaphragm of Example 1. The performance indicators are shown in Table 4.

[0068] Table 4

[0069] Table 4 shows that the PVDF-HFP matrix is ​​not only a support for the microcapsules, but its more crucial role is to assist in the construction of an efficient three-dimensional conductive network after triggering, which transforms the phase change behavior of the microcapsules into a dramatic change in the macroscopic electrical properties of the membrane, thereby achieving rapid and efficient heat dissipation.

[0070] Example 5 Comparative Example 3 uses conventional PANI, i.e., polyaniline, to prepare a smart membrane. The difference between Comparative Example 3 and Example 1 is that aniline is used instead of N-(4-sulfonylbutyroyl)aniline. Otherwise, it is the same as Example 1, and the membrane of Comparative Example 3 is obtained.

[0071] Its performance was tested, as shown in Table 5.

[0072] Table 5

[0073] N-(4-sulfonylbutyryl)aniline completely solves the pH dependence problem of traditional PANI, achieving stable conductivity over a wide pH range in battery operating conditions. Furthermore, the flexible butyryl chain (-C4H8O-) gives the molecular chain greater flexibility, accelerating the conformational change during the reduction process and resulting in an order-of-magnitude improvement in response speed.

[0074] Example 6 Compared with Example 1, Comparative Example 4 differs in that sodium benzenesulfonate is removed, otherwise it is the same as Example 1.

[0075] The membrane performance of Comparative Example 4 and Example 1 was tested, and the results are shown in Table 6.

[0076] Table 6

[0077] Table 6 shows that sodium benzenesulfonate, due to its unique aromatic ring structure, exhibits a significant advantage in guiding the formation of high-flux ion channels. The porous structure it creates increases ion mobility several times, thereby enabling rapid ion transport during fast charging and greatly reducing the risk of lithium plating.

[0078] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of protection of this application is limited to these examples; under the concept of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of one or more embodiments of this application as described above, which are not provided in detail for the sake of brevity.

[0079] One or more embodiments in this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments in this application should be included within the protection scope of this application.

Claims

1. A dual-modal triggered smart diaphragm, characterized in that, It includes a base film and a thermally responsive layer and an electrically responsive layer located on both sides of the base film, respectively; the base film includes a PE film or a PP film with a deposited thermally responsive layer and a conductive film with a deposited electrically responsive layer; The raw material of the thermally responsive layer comprises the following components by weight percentage: capsules 30-50%, PVDF-HFP 10-15%, and the balance being solvent; the capsules comprise Wood's alloy and a capsule wall encapsulating the Wood's alloy, the capsule wall being made of polymethyl methacrylate, and the Wood's alloy being Bi alloy encapsulated with Se. 50 Pb 26.7 Sn 13.3 Cd 10 ; The raw materials of the electroresponsive layer include the following components: 0.2-0.5 M N-(4-sulfonylbutyroyl)aniline, 0.6-1.5 M sulfuric acid and 0.05-0.2 M benzenesulfonate.

2. The dual-modal triggered smart diaphragm as described in claim 1, characterized in that, The PE or PP film is treated with Ar plasma.

3. The dual-modal triggered smart diaphragm as described in claim 1, characterized in that, The solvent is an aqueous solution of acetone, with a volume ratio of acetone to water of 6-8:2-4. The raw material of the thermally responsive layer also includes a wetting agent of 0.3-0.8%.

4. The dual-modal triggered smart diaphragm as described in claim 3, characterized in that, The raw materials of the thermal response layer include the following components by weight percentage: 40% capsules, 12% PVDF-HFP, 0.5% wetting agent, and the balance being solvent.

5. The dual-modal triggered smart diaphragm as described in claim 1, characterized in that, The raw materials for the electroresponsive layer include the following components: 0.3 M N-(4-sulfonylbutyroyl)aniline, 1 M sulfuric acid, and 0.1 M benzenesulfonate; The thickness of the thermally responsive layer is 2-4 μm, and the thickness of the electrically responsive layer is 1-3 μm.

6. A battery, characterized in that, Includes the dual-mode triggered smart diaphragm as described in any one of claims 1-5, wherein the thermal response layer contacts the positive electrode side and the electrical response layer contacts the negative electrode side.

7. A method for preparing a dual-modal triggered smart diaphragm as described in any one of claims 1-5, characterized in that, Includes the following steps: 1) Molten Wood's alloy is injected into the aqueous phase channel of the microfluidic chip, and the oil phase is an MMA / chloroform solution to generate emulsion droplets; 2) The emulsion droplets and cross-linking agent are mixed to initiate cross-linking, resulting in capsules; 3) Mix the capsules, PVDF-HFP and solvent, disperse them, then coat them onto a PE or PP film, and dry them to obtain a base film coated with a thermally responsive layer; 4) The base film coated with the thermal response layer is immersed in an electrolyte to carry out an electropolymerization reaction. The electrolyte is 0.2-0.5 M N-(4-sulfonylbutyroyl)aniline, 0.6-1.5 M sulfuric acid and 0.05-0.2 M benzenesulfonate to obtain a dual-mode triggered smart diaphragm.

8. The preparation method according to claim 7, characterized in that, The crosslinking agent is dicumyl peroxide, and the crosslinking reaction temperature is 65°C.

9. The preparation method according to claim 7, characterized in that, After electropolymerization, the membrane is immersed in 1 M LiTFSI / EC-DMC solution and polarized at -1 V to obtain a dual-mode triggered smart membrane.

10. The use of a dual-modal triggered smart diaphragm as described in any one of claims 1-5, characterized in that, The dual-mode triggered smart separator is used to prepare lithium-ion battery separators.

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