Lithium ion battery diaphragm, preparation method thereof and battery

Abstract

The invention belongs to the technical field of battery diaphragms, and particularly relates to a lithium ion battery diaphragm, a preparation method thereof and a battery, the lithium ion battery diaphragm comprises a base membrane and a nano Sn-conductive aerogel composite coating at least attached to one side surface of the base membrane, and nano Sn is distributed in gaps of conductive aerogel particles. The conductive aerogel provides a three-dimensional porous conductive network and a high-elasticity buffer space, and nano Sn is loaded in pores in situ, so that the contact efficiency with Li < + > is ensured, and the expansion stress of the Li-Sn alloy is counteracted through pore compression of the aerogel.

Description

Technical Field

[0001] This invention belongs to the field of battery separator technology, specifically relating to a lithium-ion battery separator, its preparation method, and the battery. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] During the charging process of current lithium-ion batteries, factors such as high current during fast charging (due to insufficient fast charging performance of the negative electrode), poor low-temperature performance of the negative electrode, electrode defects, and overcharging can cause irregular dendritic lithium crystals, or lithium dendrites, to form on the surface of the negative electrode. These lithium dendrites can pierce the separator, leading to direct contact between the positive and negative electrodes inside the battery, causing short circuits, overheating, or even explosions. Simultaneously, lithium dendrites can damage the solid electrolyte interphase (SEI) film on the surface of the negative electrode, hindering lithium-ion transport, reducing rate performance and cycle life, and further accelerating capacity decay as dendrites break off during repeated charge and discharge cycles.

[0004] Currently, battery separators mainly resist the puncture damage of lithium dendrites by enhancing the mechanical strength of the separator. This can only delay the process of battery short circuit to a certain extent, but cannot stop the continuous growth of lithium dendrites. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a lithium-ion battery separator, its preparation method and battery.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a lithium-ion battery separator, comprising a base film and a nano-Sn-conductive aerogel composite coating at least attached to one side of the base film, wherein the nano-Sn is distributed in the gaps between the conductive aerogel particles.

[0007] During charging, when the charging potential approaches the lithium plating potential, Li + Prioritizes alloying with Sn, consuming free Li at the interface. + Reduce dendrite nucleation, remaining Li + Normal embedding into the negative electrode can effectively suppress the formation of lithium dendrites.

[0008] When lithium dendrites form due to abnormal conditions (such as overcharging or negative electrode defects), the lithium dendrites will come into contact with and react with the nano-Sn in the nano-Sn-conductive aerogel composite particles to form a Li-Sn alloy. At this time, Sn acts as a dendrite scavenger, consuming the already formed lithium dendrites through the alloying reaction and preventing them from piercing the separator.

[0009] By synergistically suppressing nucleation and eliminating existing lithium dendrites, battery safety can be effectively ensured.

[0010] When the lithium battery discharges again, the Li-Sn alloy will release Li again. + In the electrolyte (Li-Sn alloy formation / decomposition potential (0.05~0.4 V vs Li) + / Li) and the charge / discharge window of lithium batteries (2.5~4.2 V for ternary graphite cathode (vsLi) + / Li) & negative electrode 0.01~4.2 V (vs Li) + / Li), lithium iron phosphate graphite system 2.5~3.65V (vs Li + / Li) & negative electrode 0.01~4.2 V (vs Li) + / Li) is fully compatible with Li that is deintercalated from the negative electrode. + They participate in the reaction together, forming a dual-path lithium supply, without affecting the total battery capacity.

[0011] Conductive aerogels provide a three-dimensional porous conductive network and highly elastic buffer space, with nano-Sn loaded in situ within the pores, ensuring both adhesion to Li and... + The aerogel improves contact efficiency and counteracts the expansion stress of the Li-Sn alloy (volume expansion rate ≈300%) through pore compression. Simultaneously, the conductive aerogel components (MXene / CNT / PI), nano-Sn, and the coating are all electrochemically inactive within the battery's operating window, do not undergo side reactions with the electrolyte, and do not introduce additional impedance. Because it acts at the separator-anode interface, it can intervene in dendrite growth earlier, reducing the risk of short circuits.

[0012] In some embodiments, the base film is made of polyethylene, polypropylene, polyimide, or polyaramid.

[0013] Preferably, the thickness of the base film is 5~20μm.

[0014] In some embodiments, the nano-Sn-conducting aerogel composite coating further includes ceramic powder, and the mass ratio of ceramic powder to nano-Sn-conducting aerogel is 1:5~10.

[0015] Preferably, the ceramic powder is alumina, zirconium oxide, or boehmite.

[0016] Ceramic powders (such as alumina, zirconium oxide, and boehmite) possess high hardness and rigidity, and when combined with conductive aerogel, they can enhance the tensile strength and puncture resistance of the coating. This helps resist the volume expansion stress during the Li-Sn alloying process, preventing coating cracking, and further inhibiting lithium dendrites from piercing the separator.

[0017] Ceramic materials (such as alumina and boehmite) have excellent high-temperature resistance properties, which can reduce the risk of thermal shrinkage of the coating in the high-temperature environment of the battery.

[0018] The addition of ceramic powder can adjust the pore structure of the coating, improve electrolyte wettability, and promote Li + Diffusion. Simultaneously, the hydroxyl groups on the surface of the ceramic powder can enhance the interfacial adhesion with the base film, reducing the risk of coating peeling and improving cycle stability.

[0019] In some embodiments, the thickness of the nano-Sn-conductive aerogel composite coating is 1~3μm; the mass percentage of nano-Sn in the coating is 5~15%.

[0020] In some embodiments, the conductive aerogel is a polyimide-modified conductive aerogel.

[0021] The high volume expansion rate during Li-Sn alloying necessitates that conductive aerogels possess sufficient structural toughness to buffer stress. The rigid aromatic ring structure and strong hydrogen bonding in the PI molecular chain can significantly improve the tensile strength and elastic recovery rate of the aerogel.

[0022] PI exhibits excellent high-temperature resistance, and modification can reduce the risk of thermal shrinkage of aerogels in the high-temperature environment of batteries. The surface of PI is rich in polar groups, which can enhance the interfacial bonding with nano-Sn particles and ceramic powder, preventing the active material from falling off.

[0023] PI, as the matrix material, forms an interpenetrating network with conductive components such as MXene and CNTs, retaining a three-dimensional porous structure (pore size 0.2~1.5μm) to promote Li + Diffusion, on the other hand, can maintain the integrity of the conductive path through the rigid support of PI, thus ensuring the efficiency of electron transport.

[0024] Preferably, the matrix material of the conductive aerogel is at least one of MXene, graphene or multi-walled carbon nanotubes (MWCNTs), and carbon black (such as acetylene black or Ketjen black).

[0025] In some embodiments, the conductive aerogel particles have a particle size of 0.5~2.5μm, and the nano-Sn particles have a particle size of 10~30nm.

[0026] In some embodiments, the nano-Sn-conductive aerogel is modified by immersion in a perfluorosulfonic acid solution. The perfluorosulfonic acid molecule contains sulfonic acid groups (-SO3H), which enhances the hydrophilicity of the coating surface, improves the wetting efficiency of the electrolyte in the coating, and accelerates the Li... + The diffusion rate within the coating pores. Simultaneously, the sulfonic acid groups can react with Li in the electrolyte. + Weak interactions are formed, interfacial impedance is reduced, and ion transport dynamics are optimized.

[0027] Nano-Sn particles have high surface activity and are prone to aggregation or oxidation. Perfluorosulfonic acid molecules can coat the surface of nano-Sn particles through physical adsorption or hydrogen bonding, forming a protective layer that prevents the nano-Sn particles from falling off due to volume expansion during cycling. At the same time, it isolates the nano-Sn particles from active substances in the air and electrolyte, inhibiting their oxidative failure.

[0028] Experiments have shown that the sulfonic acid group (-SO3H) in perfluorosulfonic acid molecules can react with Li + The formation of weak coordination accelerates Li + The modified nano-Sn particles can effectively increase the migration rate to the Sn particle surface and reduce the interfacial impedance.

[0029] In some embodiments, the lithium-ion battery separator includes a base film, a nano-Sn-conductive aerogel composite coating attached to one side of the base film, and a ceramic coating attached to the other side of the base film. The ceramic coating provides rigid support, resists physical puncture by lithium dendrites using its high hardness characteristics, reduces the risk of the separator being punctured, and reduces the shrinkage rate of the separator during battery thermal runaway through its high-temperature resistance characteristics (melting point > 2700°C).

[0030] Preferably, the thickness of the ceramic coating is 1~3μm.

[0031] Preferably, the ceramic particles in the ceramic coating are zirconium oxide, alumina, or boehmite.

[0032] Secondly, the present invention provides a method for preparing the lithium-ion battery separator, comprising the following steps: Conductive aerogel particles were immersed in a mixture of Sn salt and sodium citrate salt, and a reducing agent was added to make Sn... 2+ In situ reduction to nano-Sn within aerogel particles yields nano-Sn-conductive aerogel particles. The nano-Sn-conductive aerogel particles are prepared into a slurry, coated on at least one side of the base film, and dried to obtain the final product.

[0033] Sn 2+ In aqueous solution, it readily hydrolyzes to form Sn(OH)₂ precipitate, while the carboxyl group (-COO) in sodium citrate... - ) can be used with Sn 2+ It forms a soluble complex, thus avoiding the formation of Sn(OH)2 precipitate.

[0034] In addition, the addition of sodium citrate can also promote Sn to a certain extent. 2+ It penetrates into the interior of the aerogel particles.

[0035] In some embodiments, the reducing agent is NaBH4 or KBH4.

[0036] In some embodiments, conductive aerogel particles are immersed in a mixture of Sn salt and sodium citrate salt, and then vacuum treated for 30-60 minutes to allow the Sn salt to react with the sodium citrate. 2+ It penetrates into the pores of the aerogel.

[0037] In some embodiments, Sn 2+ When the aerogel particles are reduced in situ to nano-Sn, microwave irradiation is used. The microwave irradiation power is 250~280 W, the temperature is 60~70℃, and the time is 8~20 min.

[0038] Microwave irradiation utilizes the dipole vibration of polar molecules in a high-frequency electromagnetic field to generate internal heat, enabling the reaction system to rapidly reach the reaction temperature at 60-70°C, thus significantly improving preparation efficiency.

[0039] The rapid heating characteristic of microwaves can avoid the agglomeration of nano-Sn particles caused by localized overheating, thus preventing Sn from becoming brittle. 2+ Uniform nucleation and growth within the pores of conductive aerogels produce nano-Sn particles with controllable particle size (10~30 nm).

[0040] In some embodiments, the method further includes washing the obtained nano-Sn-conducting aerogel particles with water, replacing them with ethanol, and then vacuum drying them.

[0041] Preferably, the vacuum drying temperature is 50~60℃ and the vacuum drying time is 2~3h.

[0042] Nano-sized Sn particles have extremely high surface activity and readily react with oxygen in the air to form a SnO2 oxide layer, causing them to lose their affinity for Li. + The activity of alloying. Vacuum drying effectively prevents the oxidation of nano-Sn by isolating oxygen. After ethanol replacement, a small amount of ethanol and water remain in the particles. The vacuum environment lowers the boiling point of the solvent, accelerates the evaporation of ethanol and water, and thus effectively improves the drying efficiency.

[0043] A further preferred embodiment includes a step of impregnating and modifying vacuum-dried nano-Sn-conductive aerogel particles in a perfluorosulfonic acid solution.

[0044] More preferably, the concentration of the perfluorosulfonic acid solution is 0.1~0.15wt%, and the impregnation modification time is 10~20min.

[0045] In some embodiments, the base film is pretreated by means of ultrasonic cleaning with ethanol, drying, and then Ar plasma treatment.

[0046] Preferably, the Ar plasma treatment power is 80~150W, the gas pressure is 0.08~0.12Pa, and the treatment time is 5~10min.

[0047] Ar plasma bombards the surface of a base film (such as polyethylene or polypropylene) with high-energy particles, which can introduce polar groups such as hydroxyl (-OH) and carboxyl (-COOH) groups on the surface, significantly improving the wettability and adhesion of the coating slurry on the base film surface and preventing the coating from falling off during the cycle.

[0048] Although the base film has been cleaned with ethanol ultrasonic cleaning to remove oil stains, Ar plasma treatment can further remove trace amounts of residual organic contaminants (such as release agents and dust) on the surface and etch microscopic protrusions on the surface to form a roughened interface, thereby enhancing the bonding strength between the coating and the base film through a mechanical anchoring effect.

[0049] In some embodiments, the slurry prepared from nano-Sn-conductive aerogel particles includes a solvent, nano-Sn-conductive aerogel particles, a binder, and a thickener, wherein the mass ratio of the solvent, nano-Sn-conductive aerogel particles, binder, and thickener is 250~300:80~100:10~20:3~5.

[0050] Nano-Sn conductive aerogel particles (0.5~2.5μm) are prone to sedimentation in slurries due to density differences. The three-dimensional network structure formed by the thickener can hinder particle movement, resulting in a sedimentation rate of less than 5% after the slurry has been left to stand for 24 hours. This ensures uniform coating composition during application and avoids fluctuations in dendrite suppression effect caused by excessively high or low local nano-Sn content.

[0051] Thickeners can enhance the cohesiveness of slurries, forming a continuous, crack-free coating after coating and drying, and significantly reducing ion transport resistance caused by coating defects.

[0052] Preferably, the slurry prepared from nano-Sn-conductive aerogel particles also includes ceramic powder, and the mass ratio of ceramic powder to nano-Sn-conductive aerogel particles is 1:5~10.

[0053] Preferably, the thickener is sodium carboxymethyl cellulose or lithium carboxymethyl cellulose.

[0054] In some embodiments, the method further includes a step of coating one side of the base film with a ceramic slurry, wherein the thickness of the prepared ceramic coating is 1~3 μm.

[0055] Preferably, in the ceramic slurry, the mass ratio of ceramic powder, dispersant and binder is 5~10:10~50:1.

[0056] More preferably, the dispersant is NMP or acetone.

[0057] More preferably, the adhesive is PVDF, PMMA, or PAA.

[0058] Thirdly, the present invention provides a lithium-ion battery, comprising the battery separator, a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode material is lithium iron phosphate positive electrode material and the electrolyte is a lithium iron phosphate & carbonate system electrolyte.

[0059] Through experimentation, the inventors discovered that when the battery separator of this application is combined with lithium iron phosphate cathode material and a lithium iron phosphate & carbonate electrolyte system to prepare a battery, the battery performance is better. The Li-Sn alloying potential is compatible with the lithium iron phosphate system. The conductive aerogel, nano-Sn, and coating are electrochemically inactive within the working window of the lithium iron phosphate system, do not undergo side reactions with the carbonate electrolyte, and do not introduce additional impedance. The lithium iron phosphate & carbonate electrolyte system has a high dielectric constant and low viscosity, which can form good wetting with the three-dimensional porous structure of the nano-Sn-conductive aerogel coating. The perfluorosulfonic acid modified coating surface is rich in sulfonic acid groups, which can react with Li in the electrolyte. + The formation of weak interactions reduces interfacial impedance and accelerates Li + diffusion.

[0060] Lithium iron phosphate has a low volume expansion rate, which matches the buffering capacity of the separator and further improves cycle stability.

[0061] In some embodiments, the mass ratio of LFP:SP:CNT:PVDF in the lithium iron phosphate cathode material is 96-97:0.8-1.2:0.3-0.7:1.8-2.2; In the lithium iron phosphate & carbonate electrolyte system, the mass ratio of each component is: LiPF6:LiFSI:EC:DMC:EMC:VC:DTD=12-13:1.8-2.2:22-24:35-36:23-24:2.5-3:0.3-0.7.

[0062] Preferably, in the lithium iron phosphate cathode material, the mass ratio of LFP:SP:CNT:PVDF is 96.5:1.0:0.5:2.0; In the lithium iron phosphate & carbonate electrolyte system, the mass ratio of each component is: LiPF6:LiFSI:EC:DMC:EMC:VC:DTD=12.5:2.0:23:35.3:23.9:2.8:0.5.

[0063] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows: The formation / decomposition potential of the Li-Sn alloy is fully compatible with the charge / discharge window of the lithium battery. During charging, Li... + Prioritizes alloying with Sn, consuming free Li at the interface. + Reduce dendrite nucleation, remaining Li +Normal embedding into the negative electrode can effectively suppress the formation of lithium dendrites; during discharge, the Li-Sn alloy will release Li again. + It is added to the electrolyte. Therefore, it can both suppress the formation of lithium dendrites and maintain battery capacity; The high porosity and elastic recovery rate of conductive aerogel completely offset the high expansion of Li-Sn alloy, which is beneficial to improving battery cycle performance. The coating process for the separator is compatible with existing lithium battery separator production processes, requiring no large-scale equipment modifications and making it suitable for industrial scale-up. Attached Figure Description

[0064] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0065] Figure 1 This is a photograph of the lithium-free electrode sheet in Embodiment 1 of the present invention; Figure 2 This is a photograph of the slightly lithium-plated electrode sheet in Comparative Example 1 of the present invention. Detailed Implementation

[0066] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0067] The present invention will be further described below with reference to the embodiments.

[0068] Example 1 (1) Preparation of dispersion: Ti3C2T x MXene (1 mg / mL), MWCNT (0.5 mg / mL) and PI precursor (polyamic acid, 5 mg / mL) were mixed and ultrasonically dispersed for 50 min (ultrasonic power 300 W), and 0.1 wt% dopamine was added as a crosslinking agent.

[0069] (2) The dispersion prepared in step (1) was directionally frozen at -40℃ for 12 h to form a directional porous structure (pore size 0.2~1μm); dried at -80℃ and 10 Pa for 30 h; and then calcined at 350℃ and nitrogen atmosphere for 2 h to obtain a conductive aerogel.

[0070] (3) The prepared conductive aerogel is crushed into particles of 0.5~1.5μm in an air jet mill under nitrogen protection.

[0071] (4) The conductive aerogel particles were immersed in a mixture of 0.05 mol / L SnCl2·2H2O and 0.1 mol / L trisodium citrate, and vacuum adsorbed for 30 min (negative pressure ~0.08 MPa); 0.03 mol / L NaBH4 solution was added, and the particles were irradiated with microwave (power 250W, temperature 60℃, time 10 min) to remove Sn. 2+ In situ reduction to nano-Sn (particle size 10~20 nm) within the aerogel pores yields nano-Sn-conductive aerogel particles.

[0072] (5) The nano-Sn-conducting aerogel particles were washed three times with deionized water, then replaced with ethanol, and finally vacuum dried (50℃, 2h); the dried nano-Sn-conducting aerogel particles were soaked in 0.1wt% perfluorosulfonic acid solution for 10min to obtain modified composite particles.

[0073] (6) The membrane base is made of polyethylene with a thickness of 7μm. The membrane coating is divided into A side and B side, with A side facing the positive electrode and B side facing the negative electrode.

[0074] Pretreatment of the base film: ultrasonic cleaning with ethanol for 10 min (power 150 W), drying at 60℃ for 30 min; Ar plasma treatment for 10 min (power 100 W, pressure 0.1 Pa).

[0075] (7) Ceramic coating was applied to the pretreated surface A. Boehmite and N-methylpyrrolidone (NMP) were mixed at a mass ratio of 0.4:1 and stirred at 1200 r / min for 1 hour, followed by ultrasonic-assisted dispersion for 30 min. PVDF binder was added and stirred continuously for 30 min (the mass ratio of binder to boehmite was 1:5) to obtain a ceramic slurry. The ceramic slurry was then gravure coated at a speed of 1.5 m / min, with the ceramic coating thickness controlled at 2 μm.

[0076] (8) The pretreated B side is coated with conductive aerogel. The composition of the coating slurry is: nano Sn-conductive aerogel particles, PVDF, sodium carboxymethyl cellulose and NMP in a mass ratio of 100:10:3:300. After mixing the components in proportion, the mixture is stirred at high speed (3000 rpm, 60 min) and ultrasonically dispersed (200W, 20 min). Gravure coating is then performed at a coating speed of 1.5 m / min. The thickness of the nano Sn-conductive aerogel coating is controlled at 2 μm.

[0077] (9) The cathode material selected is lithium iron phosphate cathode (LFP:SP:CNT:PVDF) with a ratio of 96.5%:1.0%:0.5%:2.0% and a single-sided areal density of 180 g / m³. 2The negative electrode is a graphite negative electrode with a composition of Gr:SP:SBR:CMC = 96.0%:1.0%:1.8%:1.2% and a single-sided areal density of 85 g / m³. 2 .

[0078] The electrolyte is a conventional lithium iron phosphate & carbonate system electrolyte, with the specific composition being LiPF6:LiFSI:EC:DMC:EMC:VC:DTD=12.5%:2.0%:23%:35.3%:23.9%:2.8%:0.5%.

[0079] The separator prepared above is wound with positive and negative electrode sheets to produce a 5Ah soft-pack battery cell with a rated operating voltage of 2.5~3.65V.

[0080] Example 2 Steps (1)-(8) are the same as in Example 1, but the positive electrode material and electrolyte in step (9) are different from those in Example 1.

[0081] (1) Preparation of dispersion: Ti3C2T x MXene (1 mg / mL), MWCNT (0.5 mg / mL) and PI precursor (polyamic acid, 5 mg / mL) were mixed and ultrasonically dispersed for 50 min (ultrasonic power 300 W), and 0.1 wt% dopamine was added as a crosslinking agent.

[0082] (2) The dispersion prepared in step (1) was directionally frozen at -40℃ for 12 h to form a directional porous structure (pore size 0.2~1μm); dried at -80℃ and 10 Pa for 30 h; and then calcined at 350℃ and nitrogen atmosphere for 2 h to obtain a conductive aerogel.

[0083] (3) The prepared conductive aerogel is crushed into particles of 0.5~1.5μm in an air jet mill under nitrogen protection.

[0084] (4) The conductive aerogel particles were immersed in a mixture of 0.05 mol / L SnCl2·2H2O and 0.1 mol / L trisodium citrate, and vacuum adsorbed for 30 min (negative pressure ~0.08 MPa); 0.03 mol / L NaBH4 solution was added, and the particles were irradiated with microwave (power 250W, temperature 60℃, time 10 min) to remove Sn. 2+ In situ reduction to nano-Sn (particle size 10~20 nm) within the aerogel pores yields nano-Sn-conductive aerogel particles.

[0085] (5) The nano-Sn-conducting aerogel particles were washed three times with deionized water, then replaced with ethanol, and finally vacuum dried (50℃, 2h); the dried nano-Sn-conducting aerogel particles were soaked in 0.1wt% perfluorosulfonic acid solution for 10min to obtain modified composite particles.

[0086] (6) The membrane base is made of polyethylene with a thickness of 7μm. The membrane coating is divided into A side and B side, with A side facing the positive electrode and B side facing the negative electrode.

[0087] Pretreatment of the base film: ultrasonic cleaning with ethanol for 10 min (power 150 W), drying at 60℃ for 30 min; Ar plasma treatment for 10 min (power 100 W, pressure 0.1 Pa).

[0088] (7) Ceramic coating was applied to the pretreated surface A. Boehmite and N-methylpyrrolidone (NMP) were mixed at a mass ratio of 0.4:1 and stirred at 1200 r / min for 1 hour, followed by ultrasonic-assisted dispersion for 30 min. PVDF binder was added and stirred continuously for 30 min (the mass ratio of binder to boehmite was 1:5) to obtain a ceramic slurry. The ceramic slurry was then gravure coated at a speed of 1.5 m / min, with the ceramic coating thickness controlled at 2 μm.

[0089] (8) The pretreated B side is coated with conductive aerogel. The composition of the coating slurry is: nano Sn-conductive aerogel particles, PVDF, sodium carboxymethyl cellulose and NMP in a mass ratio of 100:10:3:300. After mixing the components in proportion, the mixture is stirred at high speed (3000 rpm, 60 min) and ultrasonically dispersed (200W, 20 min). Gravure coating is then performed at a coating speed of 1.5 m / min. The thickness of the nano Sn-conductive aerogel coating is controlled at 2 μm.

[0090] (9) The cathode material selected is a nickel-cobalt-manganese 622 ternary cathode with NCM:SP:CNT:PVDF=96.5%:1.0%:0.5%:2.0% and a single-sided areal density of 180g / m³. 2 The negative electrode is a graphite negative electrode with a composition of Gr:SP:SBR:CMC = 96.0%:1.0%:1.8%:1.2% and a single-sided areal density of 110 g / m³. 2 .

[0091] The electrolyte is a conventional ternary and carbonate system electrolyte, with the specific composition being LiPF6:LiFSI:EC:DMC:EMC:VC:DTD:PS=12.5%:2.0%:23%:33.5%:23.9%:2.8%:1.5%:0.8%.

[0092] The separator prepared above is wound with positive and negative electrode sheets to produce a 5Ah soft-pack battery cell with a rated operating voltage of 2.5~4.2V.

[0093] Example 3 Steps (1)-(8) are the same as in Example 1, but the positive electrode material and electrolyte in step (9) are different from those in Example 1.

[0094] (1) Preparation of dispersion: Ti3C2T x MXene (1 mg / mL), MWCNT (0.5 mg / mL) and PI precursor (polyamic acid, 5 mg / mL) were mixed and ultrasonically dispersed for 50 min (ultrasonic power 300 W), and 0.1 wt% dopamine was added as a crosslinking agent.

[0095] (2) The dispersion prepared in step (1) was directionally frozen at -40℃ for 12 h to form a directional porous structure (pore size 0.2~1μm); dried at -80℃ and 10 Pa for 30 h; and then calcined at 350℃ and nitrogen atmosphere for 2 h to obtain a conductive aerogel.

[0096] (3) The prepared conductive aerogel is crushed into particles of 0.5~1.5μm in an air jet mill under nitrogen protection.

[0097] (4) The conductive aerogel particles were immersed in a mixture of 0.05 mol / L SnCl2·2H2O and 0.1 mol / L trisodium citrate, and vacuum adsorbed for 30 min (negative pressure ~0.08 MPa); 0.03 mol / L NaBH4 solution was added, and the particles were irradiated with microwave (power 250W, temperature 60℃, time 10 min) to remove Sn. 2+ In situ reduction to nano-Sn (particle size 10~20 nm) within the aerogel pores yields nano-Sn-conductive aerogel particles.

[0098] (5) The nano-Sn-conducting aerogel particles were washed three times with deionized water, then replaced with ethanol, and finally vacuum dried (50℃, 2h); the dried nano-Sn-conducting aerogel particles were soaked in 0.1wt% perfluorosulfonic acid solution for 10min to obtain modified composite particles.

[0099] (6) The membrane base is made of polyethylene with a thickness of 7μm. The membrane coating is divided into A side and B side, with A side facing the positive electrode and B side facing the negative electrode.

[0100] Pretreatment of the base film: ultrasonic cleaning with ethanol for 10 min (power 150 W), drying at 60℃ for 30 min; Ar plasma treatment for 10 min (power 100 W, pressure 0.1 Pa).

[0101] (7) Ceramic coating was applied to the pretreated surface A. Boehmite and N-methylpyrrolidone (NMP) were mixed at a mass ratio of 0.4:1 and stirred at 1200 r / min for 1 hour, followed by ultrasonic-assisted dispersion for 30 min. PVDF binder was added and stirred continuously for 30 min (the mass ratio of binder to boehmite was 1:5) to obtain a ceramic slurry. The ceramic slurry was then gravure coated at a speed of 1.5 m / min, with the ceramic coating thickness controlled at 2 μm.

[0102] (8) The pretreated B side is coated with conductive aerogel. The composition of the coating slurry is: nano Sn-conductive aerogel particles, PVDF, sodium carboxymethyl cellulose and NMP in a mass ratio of 100:10:3:300. After mixing the components in proportion, the mixture is stirred at high speed (3000 rpm, 60 min) and ultrasonically dispersed (200W, 20 min). Gravure coating is then performed at a coating speed of 1.5 m / min. The thickness of the nano Sn-conductive aerogel coating is controlled at 2 μm.

[0103] (9) The cathode material selected is a nickel-cobalt-manganese 811 ternary cathode with NCM:SP:CNT:PVDF=96.5%:1.0%:0.5%:2.0% and a single-sided areal density of 180g / m³. 2 The negative electrode is a graphite negative electrode with a composition of Gr:SP:SBR:CMC = 96.0%:1.0%:1.8%:1.2% and a single-sided areal density of 120 g / m³. 2 .

[0104] The electrolyte is a conventional ternary and carbonate system electrolyte, with the specific composition being LiPF6:LiFSI:EC:DMC:EMC:VC:DTD:PS=12.5%:2.0%:23%:33.5%:23.9%:2.8%:1.5%:0.8%.

[0105] The separator prepared above is wound with positive and negative electrode sheets to produce a 5Ah soft-pack battery cell with a rated operating voltage of 2.5~4.2V.

[0106] Example 4 Steps (1)-(7) and (9) are the same as in Example 1. In step (8), the thickness of the nano-Sn-conductive aerogel coating is controlled at 3 μm.

[0107] Specifically: (1) Preparation of dispersion: Ti3C2T x MXene (1 mg / mL), MWCNT (0.5 mg / mL) and PI precursor (polyamic acid, 5 mg / mL) were mixed and ultrasonically dispersed for 50 min (ultrasonic power 300 W), and 0.1 wt% dopamine was added as a crosslinking agent.

[0108] (2) The dispersion prepared in step (1) was directionally frozen at -40℃ for 12 h to form a directional porous structure (pore size 0.2~1μm); dried at -80℃ and 10 Pa for 30 h; and then calcined at 350℃ and nitrogen atmosphere for 2 h to obtain a conductive aerogel.

[0109] (3) The prepared conductive aerogel is crushed into particles of 0.5~1.5μm in an air jet mill under nitrogen protection.

[0110] (4) The conductive aerogel particles were immersed in a mixture of 0.05 mol / L SnCl2·2H2O and 0.1 mol / L trisodium citrate, and vacuum adsorbed for 30 min (negative pressure ~0.08 MPa); 0.03 mol / L NaBH4 solution was added, and the particles were irradiated with microwave (power 250W, temperature 60℃, time 10 min) to remove Sn. 2+ In situ reduction to nano-Sn (particle size 10~20 nm) within the aerogel pores yields nano-Sn-conductive aerogel particles.

[0111] (5) The nano-Sn-conducting aerogel particles were washed three times with deionized water, then replaced with ethanol, and finally vacuum dried (50℃, 2h); the dried nano-Sn-conducting aerogel particles were soaked in 0.1wt% perfluorosulfonic acid solution for 10min to obtain modified composite particles.

[0112] (6) The membrane base is made of polyethylene with a thickness of 7μm. The membrane coating is divided into A side and B side, with A side facing the positive electrode and B side facing the negative electrode.

[0113] Pretreatment of the base film: ultrasonic cleaning with ethanol for 10 min (power 150 W), drying at 60℃ for 30 min; Ar plasma treatment for 10 min (power 100 W, pressure 0.1 Pa).

[0114] (7) Ceramic coating was applied to the pretreated surface A. Boehmite and N-methylpyrrolidone (NMP) were mixed at a mass ratio of 0.4:1 and stirred at 1200 r / min for 1 hour, followed by ultrasonic-assisted dispersion for 30 min. PVDF binder was added and stirred continuously for 30 min (the mass ratio of binder to boehmite was 1:5) to obtain a ceramic slurry. The ceramic slurry was then gravure coated at a speed of 1.5 m / min, with the ceramic coating thickness controlled at 2 μm.

[0115] (8) The pretreated B side is coated with conductive aerogel. The composition of the coating slurry is: nano Sn-conductive aerogel particles, PVDF, sodium carboxymethyl cellulose and NMP in a mass ratio of 100:10:3:300. After mixing the components in proportion, the mixture is stirred at high speed (3000 rpm, 60 min) and ultrasonically dispersed (200W, 20 min). Gravure coating is then performed at a coating speed of 1.5 m / min. The thickness of the nano Sn-conductive aerogel coating is controlled at 3 μm.

[0116] (9) The cathode material selected is lithium iron phosphate cathode (LFP:SP:CNT:PVDF) with a ratio of 96.5%:1.0%:0.5%:2.0% and a single-sided areal density of 180 g / m³. 2 The negative electrode is a graphite negative electrode with a composition of Gr:SP:SBR:CMC = 96.0%:1.0%:1.8%:1.2% and a single-sided areal density of 85 g / m³. 2 .

[0117] The electrolyte is a conventional lithium iron phosphate & carbonate system electrolyte, with the specific composition being LiPF6:LiFSI:EC:DMC:EMC:VC:DTD=12.5%:2.0%:23%:35.3%:23.9%:2.8%:0.5%.

[0118] Example 5 Steps (1)-(7) and (9) are the same as in Example 1. In step (8), boehmite is added to the slurry.

[0119] Specifically: In step (8), conductive aerogel is applied to surface B. The mass ratio of nano-Sn-conductive aerogel particles, boehmite, PVDF, sodium carboxymethyl cellulose, and NMP in the coating slurry is 100:10:10:3:300.

[0120] After mixing the components in proportion, the mixture was stirred at high speed (3000 rpm, 60 min) and ultrasonically dispersed (200 W, 20 min). Then, gravure coating was performed at a coating speed of 1.5 m / min, and the thickness of the nano-Sn-conductive aerogel coating was controlled at 2 μm.

[0121] Example 6 Steps (2)-(9) are the same as in Example 1, except that in step (1), the concentration of the PI precursor polyamic acid is 10 mg / mL.

[0122] Specifically: (1) Preparation of dispersion: Ti3C2T xMXene (1 mg / mL), MWCNT (0.5 mg / mL) and PI precursor (polyamic acid, 10 mg / mL) were mixed and ultrasonically dispersed for 50 min (ultrasonic power 300 W), and 0.1 wt% dopamine was added as a crosslinking agent.

[0123] Example 7 Steps (1)-(7) and (9) are the same as in Example 1, except that the slurry in step (8) does not contain PVDF.

[0124] Specifically: In step (8), conductive aerogel is applied to surface B. The composition of the coating slurry is as follows: The mass ratio of nano-Sn-conductive aerogel particles, sodium carboxymethyl cellulose, and NMP is 80:3:300.

[0125] The components were mixed in proportion, stirred at high speed (3000 rpm, 60 min) and ultrasonically dispersed (200 W, 20 min), and then gravure coated at a speed of 1.5 m / min. The thickness of the nano-Sn-conductive aerogel coating was controlled at 2 μm.

[0126] Example 8 Steps (1)-(7) are the same as in Example 1, and step (9) is the same as in Example 2.

[0127] In step (8), the pretreated B side is coated with conductive aerogel. The composition of the coating slurry is: nano Sn-conductive aerogel particles, sodium carboxymethyl cellulose and NMP in a mass ratio of 110:3:300. The components were mixed in proportion, stirred at high speed (3000 rpm, 60 min) and ultrasonically dispersed (200 W, 20 min), and then gravure coated at a speed of 1.5 m / min. The thickness of the nano-Sn-conductive aerogel coating was controlled at 2 μm.

[0128] Example 9 Steps (1)-(7) and (9) are the same as in Example 1. In step (8), zirconium oxide is added to the slurry.

[0129] Specifically: In step (8), conductive aerogel is applied to surface B. The mass ratio of nano-Sn-conductive aerogel particles, zirconium oxide, PVDF, sodium carboxymethyl cellulose, and NMP in the coating slurry is 100:10:10:3:300.

[0130] After mixing the components in proportion, the mixture was stirred at high speed (3000 rpm, 60 min) and ultrasonically dispersed (200 W, 20 min). Then, gravure coating was performed at a coating speed of 1.5 m / min, and the thickness of the nano-Sn-conductive aerogel coating was controlled at 2 μm.

[0131] Example 10 Steps (1)-(7) and (9) are the same as in Example 1. In step (8), alumina is added to the slurry.

[0132] Specifically: In step (8), conductive aerogel is applied to surface B. The mass ratio of nano-Sn-conductive aerogel particles, alumina, PVDF, sodium carboxymethyl cellulose, and NMP in the coating slurry is 100:10:10:3:300.

[0133] After mixing the components in proportion, the mixture was stirred at high speed (3000 rpm, 60 min) and ultrasonically dispersed (200 W, 20 min). Then, gravure coating was performed at a coating speed of 1.5 m / min, and the thickness of the nano-Sn-conductive aerogel coating was controlled at 2 μm.

[0134] Example 11 Steps (1)-(5) and (7)-(9) are the same as in Example 1. The difference is that in step (6), when pretreating the base film, the Ar plasma treatment step is omitted.

[0135] Specifically: (6) The membrane base is made of polyethylene with a thickness of 7μm. The membrane coating is divided into A side and B side, with A side facing the positive electrode and B side facing the negative electrode.

[0136] Pretreatment method for the base film: ultrasonic cleaning with ethanol for 10 min (power 150W), and drying at 60℃ for 30 min.

[0137] Example 12 Steps (1)-(5) and (7)-(9) are the same as in Example 1. The difference is that in step (6), the base membrane material is polypropylene with a thickness of 7μm. The membrane coating is divided into A side and B side, with A side facing the positive electrode and B side facing the negative electrode.

[0138] Pretreatment of the base film: ultrasonic cleaning with ethanol for 10 min (power 150 W), drying at 60℃ for 30 min; Ar plasma treatment for 10 min (power 100 W, pressure 0.1 Pa).

[0139] Example 13 Steps (1)-(5) and (7)-(9) are the same as in Example 1. The difference is that in step (6), the base film material is polyimide with a thickness of 7 μm. The membrane coating is divided into A side and B side, with A side facing the positive electrode and B side facing the negative electrode.

[0140] Pretreatment of the base film: ultrasonic cleaning with ethanol for 10 min (power 150 W), drying at 60℃ for 30 min; Ar plasma treatment for 10 min (power 100 W, pressure 0.1 Pa).

[0141] Example 14 Steps (1)-(5) and (7)-(9) are the same as in Example 1. The difference is that in step (6), the base film material is polyarylamide with a thickness of 7 μm. The membrane coating is divided into A side and B side, with A side facing the positive electrode and B side facing the negative electrode.

[0142] Pretreatment of the base film: ultrasonic cleaning with ethanol for 10 min (power 150 W), drying at 60℃ for 30 min; Ar plasma treatment for 10 min (power 100 W, pressure 0.1 Pa).

[0143] Example 15 The difference from Example 1 is that some process parameters are different.

[0144] (1) Preparation of dispersion: Ti3C2T x MXene (1 mg / mL), MWCNT (1.5 mg / mL) and PI precursor (polyamic acid, 5 mg / mL) were mixed and ultrasonically dispersed for 30 min (ultrasonic power 300 W), and 0.1 wt% dopamine was added as a crosslinking agent.

[0145] (2) The dispersion prepared in step (1) was directionally frozen at -40℃ for 12 h to form a directional porous structure (pore size 0.2~1μm); dried at -80℃ and 10 Pa for 36 h; and then calcined at 400℃ and nitrogen atmosphere for 2 h to obtain a conductive aerogel.

[0146] (3) The prepared conductive aerogel is crushed into particles of 0.5~1.5μm in an air jet mill under nitrogen protection.

[0147] (4) The conductive aerogel particles were immersed in a mixture of 0.02 mol / L SnCl2·2H2O and 0.15 mol / L trisodium citrate and vacuum adsorbed for 50 min (negative pressure ~0.08 MPa); 0.03 mol / L NaBH4 solution was added, and the particles were irradiated with microwave (power 270W, temperature 65℃, time 15min) to remove Sn. 2+In situ reduction to nano-Sn within the pores of the aerogel yields nano-Sn-conductive aerogel particles.

[0148] (5) The nano-Sn-conducting aerogel particles were washed three times with deionized water, then replaced with ethanol, and finally vacuum dried (55℃, 2h). The dried nano-Sn-conducting aerogel particles were soaked in 0.15wt% perfluorosulfonic acid solution for 15min to obtain modified composite particles.

[0149] (6) The membrane base is made of polyethylene with a thickness of 7μm. The membrane coating is divided into A side and B side, with A side facing the positive electrode and B side facing the negative electrode.

[0150] Pretreatment method of base film: ultrasonic cleaning with ethanol for 10 min (power 150 W), drying at 60℃ for 30 min; Ar plasma treatment for 10 min (power 150 W, pressure 0.12 Pa).

[0151] (7) Ceramic coating was applied to the pretreated surface A. Zirconia and N-methylpyrrolidone (NMP) were mixed at a mass ratio of 0.3:1 and stirred at 1200 r / min for 1 hour, followed by ultrasonic-assisted dispersion for 30 min. PVDF binder was added and stirred continuously for 30 min (the mass ratio of binder to zirconia was 1:5) to obtain a ceramic slurry. The ceramic slurry was then gravure coated at a speed of 1.5 m / min, with the ceramic coating thickness controlled at 2 μm.

[0152] (8) The pretreated B side is coated with conductive aerogel. The composition of the coating slurry is: nano Sn-conductive aerogel particles, PVDF, sodium carboxymethyl cellulose and NMP in a mass ratio of 90:15:5:260. After mixing the components in proportion, the mixture is stirred at high speed (3000 rpm, 60 min) and ultrasonically dispersed (200W, 20 min). Gravure coating is then performed at a coating speed of 1.5 m / min. The thickness of the nano Sn-conductive aerogel coating is controlled at 2 μm.

[0153] Step (9) is the same as in Example 1.

[0154] Example 16 The difference from Example 1 is that some process parameters are different.

[0155] (1) Preparation of dispersion: Ti3C2T x MXene (1 mg / mL), MWCNT (0.5 mg / mL) and PI precursor (polyamic acid, 5 mg / mL) were mixed and ultrasonically dispersed for 30 min (ultrasonic power 300 W), and 0.2 wt% dopamine was added as a crosslinking agent.

[0156] (2) The dispersion prepared in step (1) was directionally frozen at -40℃ for 12 h to form a directional porous structure (pore size 0.2~1μm); dried at -80℃ and 10 Pa for 24 h; and then calcined at 300℃ and nitrogen atmosphere for 3 h to obtain a conductive aerogel.

[0157] (3) The prepared conductive aerogel is crushed into particles of 0.5~1.5μm in an air jet mill under nitrogen protection.

[0158] (4) The conductive aerogel particles were immersed in a mixture of 0.05 mol / L SnCl2·2H2O and 0.1 mol / L trisodium citrate, and vacuum adsorbed for 30 min (negative pressure ~0.08 MPa); 0.03 mol / L NaBH4 solution was added, and the particles were irradiated with microwave (power 250W, temperature 60℃, time 10 min) to remove Sn. 2+ In situ reduction to nano-Sn (particle size 10~20 nm) within the aerogel pores yields nano-Sn-conductive aerogel particles.

[0159] (5) The nano-Sn-conducting aerogel particles were washed three times with deionized water, then replaced with ethanol, and finally vacuum dried (60℃, 2h). The dried nano-Sn-conducting aerogel particles were soaked in 0.13wt% perfluorosulfonic acid solution for 10min to obtain modified composite particles.

[0160] (6) The membrane base is made of polyethylene with a thickness of 7μm. The membrane coating is divided into A side and B side, with A side facing the positive electrode and B side facing the negative electrode.

[0161] Pretreatment of the base film: ultrasonic cleaning with ethanol for 10 min (power 150 W), drying at 60℃ for 30 min; Ar plasma treatment for 10 min (power 100 W, pressure 0.1 Pa).

[0162] (7) The pretreated surface A was coated with ceramic. Alumina and N-methylpyrrolidone (NMP) were mixed at a mass ratio of 0.2:1 and stirred at 1200 r / min for 1 hour, followed by ultrasonic-assisted dispersion for 30 min. PVDF binder was added and stirred for 30 minutes (the mass ratio of binder to alumina was 1:5) to obtain a ceramic slurry. The ceramic slurry was then gravure coated at a speed of 1.5 m / min, with the ceramic coating thickness controlled at 2 μm.

[0163] (8) The pretreated B side is coated with conductive aerogel. The composition of the coating slurry is: nano Sn-conductive aerogel particles, PVDF, sodium carboxymethyl cellulose and NMP in a mass ratio of 100:15:3:270. After mixing the components in proportion, the mixture is stirred at high speed (3000 rpm, 60 min) and ultrasonically dispersed (200W, 20 min). Gravure coating is then performed at a coating speed of 1.5 m / min. The thickness of the nano Sn-conductive aerogel coating is controlled at 2 μm.

[0164] Step (9) is the same as in Example 1.

[0165] Comparative Example 1 The difference from Example 1 is that a 2μm PVDF adhesive layer is coated in step (8), while the rest is the same as in Example 1.

[0166] Comparative Example 2 The difference from Example 2 is that a 2μm PVDF adhesive layer is coated in step (8), while everything else is the same as in Example 2.

[0167] Comparative Example 3 The difference from Example 3 is that a 2μm PVDF adhesive layer is coated in step (8), while the rest is the same as in Example 3.

[0168] Comparative Example 4 The difference from Example 4 is that a 3μm PVDF adhesive layer is coated in step (8), while the rest is the same as in Example 4.

[0169] Comparative Example 5 The difference from Example 1 is that a 2μm ceramic coating is applied in step (8), which is the same as step (7), while everything else is the same as in Example 1.

[0170] Comparative Example 6 The difference from Example 1 is that in step (5), the step of "soaking the dried nano-Sn-conductive aerogel particles in 0.1wt% perfluorosulfonic acid solution for 10 min" is omitted, while the rest is the same as in Example 1.

[0171] Specifically: (5) The nano Sn-conductive aerogel particles were washed three times with deionized water, then replaced with ethanol, and finally vacuum dried (50℃, 2h) to obtain modified composite particles.

[0172] Comparative Example 7 The difference from Example 1 is that in step (1), the dispersion does not contain the PI precursor polyamic acid, but everything else is the same as in Example 1.

[0173] Specifically: (1) Preparation of dispersion: Ti3C2T x After mixing MXene (1 mg / mL) and MWCNT (0.5 mg / mL), the mixture was ultrasonically dispersed for 50 min (ultrasonic power 300 W), and 0.1 wt% dopamine was added as a crosslinking agent.

[0174] Comparative Example 8 The difference from Example 1 is that in step (4), microwave irradiation is replaced by ordinary water bath heating, the heating temperature is 60°C, the heating reaction time is 10 min, and everything else is the same as in Example 1.

[0175] Comparative Example 9 The difference from Example 1 is that steps (1)-(3) are omitted; In step (4), 0.03 mol / L NaBH4 solution was added to a mixture of 0.05 mol / L SnCl2·2H2O and 0.1 mol / L trisodium citrate, and the mixture was microwave irradiated (power 250W, temperature 60℃, time 10min). 2+ Reduced to nano-Sn.

[0176] The other steps are the same as in Example 1, except that the nano-Sn-conductive aerogel particles are replaced with nano-Sn.

[0177] Comparative Example 10 The difference from Example 1 is that in step (8), the sodium carboxymethyl cellulose thickener is omitted, while everything else is the same as in Example 1.

[0178] Table 1 Comparison of tests on pouch cells

[0179] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. 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 lithium-ion battery separator, characterized in that: It includes a base film and a nano-Sn-conductive aerogel composite coating attached to at least one side of the base film, wherein the nano-Sn is distributed in the gaps between the conductive aerogel particles.

2. The lithium-ion battery separator according to claim 1, characterized in that: The nano-Sn-conducting aerogel composite coating also includes ceramic powder, and the mass ratio of ceramic powder to nano-Sn-conducting aerogel is 1:5~10. Preferably, the ceramic powder is alumina, zirconium oxide, or boehmite; Preferably, the conductive aerogel is a polyimide-modified conductive aerogel; Preferably, the matrix material of the conductive aerogel is at least one of MXene, graphene, or multi-walled carbon nanotubes.

3. The lithium-ion battery separator according to claim 1, characterized in that: The thickness of the nano-Sn-conductive aerogel composite coating is 1~3μm; Preferably, the conductive aerogel particles have a particle size of 0.5~2.5μm, and the nano-Sn particles have a particle size of 10~30nm; Preferably, the nano-Sn-conductive aerogel is modified by soaking in a perfluorosulfonic acid solution.

4. The lithium-ion battery separator according to claim 1, characterized in that: The lithium-ion battery separator includes a base film, a nano-Sn-conductive aerogel composite coating attached to one side of the base film, and a ceramic coating attached to the other side of the base film. Preferably, the thickness of the ceramic coating is 1~3μm; Preferably, the ceramic particles in the ceramic coating are zirconium oxide, alumina, or boehmite.

5. The method for preparing the lithium-ion battery separator according to any one of claims 1-4, characterized in that: Includes the following steps: Conductive aerogel particles were immersed in a mixture of Sn salt and sodium citrate salt, and a reducing agent was added to make Sn... 2+ In situ reduction to nano-Sn within aerogel particles yields nano-Sn-conductive aerogel particles. The nano-Sn-conductive aerogel particles are prepared into a slurry, coated on at least one side of the base film, and dried to obtain the final product.

6. The method for preparing the lithium-ion battery separator according to claim 5, characterized in that: The reducing agent is NaBH4 or KBH4; Preferably, the conductive aerogel particles are immersed in a mixture of Sn salt and sodium citrate salt, and then vacuum treated for 30-60 minutes to allow the Sn salt to penetrate. 2+ It penetrates into the pores of the aerogel; Preferably, Sn 2+ When the aerogel particles are reduced in situ to nano-Sn, microwave irradiation is used. The microwave irradiation power is 250~280 W, the temperature is 60~70℃, and the time is 8~20 min.

7. The method for preparing the lithium-ion battery separator according to claim 5, characterized in that: It also includes the steps of washing the obtained nano-Sn-conductive aerogel particles with water, replacing them with ethanol, and then vacuum drying them. Preferably, the vacuum drying temperature is 50~60℃, and the vacuum drying time is 2~3 hours; Preferably, the method further includes the step of impregnating and modifying the vacuum-dried nano-Sn-conductive aerogel particles in a perfluorosulfonic acid solution; Preferably, the concentration of the perfluorosulfonic acid solution is 0.1~0.15wt%, and the impregnation modification time is 10~20min; Preferably, the base film is pretreated by means of ultrasonic cleaning with ethanol, drying and then Ar plasma treatment. Preferably, the Ar plasma treatment power is 80~150W, the gas pressure is 0.08~0.12Pa, and the treatment time is 5~10min.

8. The method for preparing the lithium-ion battery separator according to claim 5, characterized in that: The slurry prepared from nano-Sn-conductive aerogel particles includes a solvent, nano-Sn-conductive aerogel particles, a binder, and a thickener, wherein the mass ratio of the solvent, nano-Sn-conductive aerogel particles, binder, and thickener is 250~300:80~100:10~20:3~5. Preferably, the slurry prepared from nano-Sn-conductive aerogel particles also includes ceramic powder, and the mass ratio of ceramic powder to nano-Sn-conductive aerogel particles is 1:5~10. Preferably, the thickener is sodium carboxymethyl cellulose or lithium carboxymethyl cellulose.

9. The method for preparing a lithium-ion battery separator according to claim 5, characterized in that: It also includes the step of coating a ceramic slurry on one side of the base film, and the thickness of the prepared ceramic coating is 1~3μm; Preferably, in the ceramic slurry, the mass ratio of ceramic powder, dispersant, and binder is 5~10:10~50:1; Preferably, the dispersant is NMP or acetone; Preferably, the adhesive is PVDF, PMMA or PAA.

10. A lithium-ion battery, characterized in that: The battery includes a battery separator, a positive electrode, a negative electrode, and an electrolyte prepared by any of the preparation methods described in claims 1-4 or 5-9, wherein the positive electrode material is lithium iron phosphate positive electrode material, and the electrolyte is a lithium iron phosphate & carbonate system electrolyte. Preferably, in the lithium iron phosphate cathode material, the mass ratio of LFP:SP:CNT:PVDF is 96-97:0.8-1.2:0.3-0.7:1.8-2.2; In the lithium iron phosphate & carbonate electrolyte system, the mass ratio of each component is: LiPF6:LiFSI:EC:DMC:EMC:VC:DTD=12-13:1.8-2.2:22-24:35-36:23-24:2.5-3:0.3-0.7; Preferably, in the lithium iron phosphate cathode material, the mass ratio of LFP:SP:CNT:PVDF is 96.5:1.0:0.5:2.0; In the lithium iron phosphate & carbonate electrolyte system, the mass ratio of each component is: LiPF6:LiFSI:EC:DMC:EMC:VC:DTD=12.5:2.0:23:35.3:23.9:2.8:0.5.

Images