Membrane and its preparation method and secondary battery

Abstract

This application provides a separator, its preparation method, and a secondary battery. The first aspect of this application proposes a separator comprising a three-dimensional network structure formed by polymer fibers. The polymer fibers include a polymer matrix and metal halide oxides dispersed within and on the surface of the polymer matrix. The polymer fiber matrix and the metal halide oxide particles dispersed within and on the surface of the polymer fiber matrix form a "fiber-nanoparticle" composite structure, effectively enhancing the thermal stability and ion transport performance of the separator. This three-dimensional network structure has a uniformly distributed small-scale pore structure, which facilitates rapid ion migration while inhibiting excessive electrolyte permeation, thus improving the separator's barrier performance. Furthermore, the introduction of metal halide oxides constructs abundant active sites on the separator surface, including halogen vacancies and metal centers, which can serve as ion migration channels, reducing the ion transport energy barrier and improving the battery's rate performance.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy storage technology, and in particular to separators and their preparation methods and secondary batteries. Background Technology

[0002] With the increasing demands for battery performance, issues related to battery safety, thermal stability, and electrochemical efficiency have become increasingly prominent. As a key component of batteries, the separator not only serves the physical function of isolating the positive and negative electrodes to prevent short circuits, but also needs to possess good ion transport capabilities, thermal stability, and interfacial compatibility with electrode materials. However, traditional separator materials, represented by polyolefins, still have significant limitations in practical applications, including insufficient thermal stability and limited lithium-ion migration rates.

[0003] To address this, existing research has focused on improving thermal stability through inorganic nanomaterials (such as Al2O3 and TiO2) or composite materials (such as polymer / inorganic composite membranes), or enhancing ion transport performance through surface functionalization. However, there is often a challenge in achieving a balance between thermal stability and ion transport performance, resulting in a lack of systematic improvements to the overall performance of membranes. Summary of the Invention

[0004] The main objective of this application is to propose a separator, its preparation method, and a secondary battery that can balance thermal stability and ion transport performance, thereby achieving a systematic improvement in the overall performance of the separator.

[0005] To achieve the above objectives, a first aspect of this application provides a diaphragm comprising a three-dimensional network structure formed of polymer fibers, wherein the polymer fibers comprise a polymer matrix and metal halide oxides dispersed within and on the surface of the polymer matrix.

[0006] In some embodiments, the polymer matrix comprises a polymer containing polar groups. The halogen groups (such as CI, Br) on the surface of the metal halide oxide and the polar groups (such as C=O, CN) in the polymer molecular chain form strong interfacial interactions through hydrogen bonding or coordination, which enhances interfacial compatibility and reduces interfacial defects, thereby improving the cycle performance of the cell.

[0007] In some embodiments, the polymer matrix includes at least one selected from polyacrylonitrile, polyvinylidene fluoride, polyimide, polybenzimidazole, polyethylene terephthalate, polybutylene terephthalate, polyamide, polyacetal, polycarbonate, polyetherketone, polyethersulfone, polyphenylene ether, polyphenylene sulfide, polyethylene naphthalate, polytetrafluoroethylene, polyvinyl chloride, poly(p-phenylenebenzodiazole), and polyarylate.

[0008] In some embodiments, the metal element of the metal halide oxide includes at least one selected from iron, cobalt, nickel, titanium, lanthanum, cerium, and gadolinium, and / or the halogen of the metal halide oxide includes at least one selected from chlorine, bromine, and iodine.

[0009] In some embodiments, the general formula for metal halide oxides is A. a O b X c Where A is at least one of Fe, Co, Ni, Ti, La, Ce, and Gd, and X is at least one of Cl, Br, and I. a, b, and c satisfy ai a +bi b +ci c =0, i a i b i c These represent the valence states of A, O, and X, respectively. The valence state of A can be any of the following, such as +1, +2, or +3, depending on the element. The valence state of O is usually -1 or -2, and the valence state of X is usually -1.

[0010] In some embodiments, the metal halide oxide includes at least one of FeOCl, CoOCl, NiOCl, TiOCl, LaOCl, CeOCl, GdOCl, FeOBr, CoOBr, NiOBr, TiOBr, LaOBr, CeOBr, GdOBr, FeOI, CoOI, NiOI, TiOI, LaOI, CeOI, and GdOI.

[0011] In some embodiments, the metal halide oxide is a layered metal halide oxide. The layered crystal structure of the metal halide oxide and the coordination polymer network work synergistically with the polymer fiber matrix to form a "rigid-flexible" composite structure, which maintains the flexibility of the fiber and enhances the thermal barrier capability of the membrane through metal-oxygen-halogen bonds.

[0012] In some embodiments, the mass ratio of the polymer matrix to the metal halide oxide is 10:(0.2~5). With the mass of the polymer matrix as 10 parts by mass, the mass parts of the metal halide oxide can be any one of the following values, or any combination thereof: 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.4, 1.5, 1.6, 1.8, 2, 2.2, 2.4, 2.5, 2.6, 2.8, 3, 3.2, 3.4, 3.5, 3.6, 3.8, 4, 4.2, 4.4, 4.5, 4.6, 4.8, 5.

[0013] In some implementations, the porosity of the three-dimensional network structure is 36% to 40%, for example, it can be any value among 36%, 37%, 38%, 39%, 40%, or any value between two of them.

[0014] A second aspect of this application provides a method for preparing a diaphragm, comprising the following steps: The polymer matrix solution is mixed with a metal halide oxide to obtain a precursor solution; The precursor solution was used to obtain a diaphragm by electrospinning.

[0015] In some embodiments, metal halide oxides are prepared by a method comprising the following steps: Ammonium halide salts are mixed with metal hydroxy oxides and subjected to a hydrothermal reaction. The precipitate is collected, washed, and dried to obtain metal halide oxides.

[0016] In some embodiments, the ammonium halide salt includes at least one of ammonium chloride, ammonium bromide, and ammonium iodide.

[0017] In some embodiments, the metal hydroxyl oxide is prepared by a method comprising the following steps: A mixed solution is obtained by mixing a metal salt with deionized water and n-butanol; The mixed solution was mixed with urea and carboxylic acid ligands and subjected to a hydrothermal reaction. The precipitate was collected, washed, and dried to obtain metal hydroxy oxides.

[0018] In some embodiments, carboxylic acid ligands include carboxylate ligands.

[0019] In some embodiments, the carboxylic acid ligands include at least one of citric acid ligands, acetic acid ligands, succinic acid ligands, malonic acid ligands, glycine ligands, tartaric acid ligands, oxalic acid ligands, benzoic acid ligands, malic acid ligands, and phthalic acid ligands.

[0020] In some embodiments, the metal salt includes at least one of a metal nitrate and a metal sulfate.

[0021] In some implementations, the metal salt includes a hydrated metal salt.

[0022] In some embodiments, the metal salt includes one of cobalt nitrate hexahydrate, ferric nitrate nonahydrate, nickel nitrate hexahydrate, manganese nitrate hexahydrate, copper nitrate hexahydrate, zinc nitrate hexahydrate, magnesium nitrate hexahydrate, and related sulfates.

[0023] In some embodiments, the preparation parameters of the electrospinning method include a spinning voltage of 10~15 kV, for example, any value or a value between 10 kV, 11 kV, 12 kV, 13 kV, 14 kV, and 15 kV; and a curing distance of 5~20 cm, for example, any value or a value between 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, 10 cm, 11 cm, 12 cm, 13 cm, 14 cm, 15 cm, 16 cm, 17 cm, 18 cm, 19 cm, and 20 cm.

[0024] In some embodiments, the solvent for the polymer matrix solution includes an organic solvent. In some embodiments, the organic solvent includes at least one of the following: amide solvents (such as N,N-dimethylformamide, N,N-dimethylacetamide), halocarbon solvents (such as chloroform, dichloromethane), and ketone solvents (such as acetone). The specific type varies depending on the polymer material used.

[0025] In some embodiments, the polymer matrix solution and the metal halide oxide are mixed and then subjected to ball milling and magnetic stirring to obtain a precursor solution.

[0026] A third aspect of this application provides a secondary battery, the secondary battery including the separator of the first aspect.

[0027] In some implementations, the secondary battery is either a solid-state battery or a liquid-ion battery.

[0028] In some implementations, the secondary battery is any one of lithium battery, sodium battery, potassium battery, magnesium battery, calcium battery, and aluminum battery.

[0029] In some embodiments, the secondary battery is any one of solid-state lithium battery, solid-state sodium battery, solid-state potassium battery, solid-state magnesium battery, solid-state calcium battery, solid-state aluminum battery, lithium-ion battery, sodium-ion battery, potassium-ion battery, magnesium-ion battery, calcium-ion battery, and aluminum-ion battery.

[0030] In some implementations, the secondary battery includes a positive electrode, a negative electrode, and an electrolyte.

[0031] In some embodiments, the electrolyte includes either a solid electrolyte or an electrolyte solution.

[0032] In some embodiments, the electrolyte includes an electrolyte salt and an organic solvent. In some embodiments, the electrolyte also includes additives, such as at least one of a positive electrode film-forming additive, a negative electrode film-forming additive, and a low-temperature additive.

[0033] In some embodiments, the positive and negative electrode sheets in the secondary battery are obtained by at least one method such as stacking or winding to form a cell, thereby producing the secondary battery.

[0034] In some embodiments, the positive electrode includes a positive current collector layer and a positive active material layer.

[0035] In some implementations, the positive current collector layer comprises aluminum material, such as aluminum foil.

[0036] In some embodiments, the positive electrode active material layer includes a positive electrode active material. In some embodiments, the positive electrode active material includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium nickel manganese aluminum oxide. In some embodiments, the positive electrode active material layer further includes at least one of a conductive agent, a binder, and a thickener. In some embodiments, the conductive agent includes at least one of conductive graphite (such as KS-6, KS-15, SFG-6, SFG-15, SO, etc.), conductive carbon black (such as Super P, Super S, 350G, acetylene black, Ketjen black, etc.), conductive carbon fiber (such as VGCF, CNT), and graphene. In some embodiments, the binder includes at least one of polyisobutylene (PIB), styrene-butadiene rubber (SBR), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), hydrogenated styrene-butadiene block copolymer (SEBS), ethyl cellulose (EC), polyurethane (PU), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB). In some embodiments, the thickener includes at least one of carboxymethyl cellulose (CMC), hydroxypropyl methyl cellulose (HPMC), and hydroxyethyl cellulose (HEC).

[0037] In some embodiments, the negative electrode sheet includes a negative electrode current collector layer and a negative electrode active material layer.

[0038] In some implementations, the negative current collector layer comprises copper material, such as copper foil.

[0039] In some embodiments, the negative electrode active material layer includes the positive electrode active material. In some embodiments, the negative electrode active material includes at least one of carbon-based materials, silicon-based materials, and carbon-silicon composite materials. In some embodiments, the negative electrode active material layer further includes at least one of a conductive agent, a binder, and a thickener. In some embodiments, the conductive agent includes at least one of conductive graphite (such as KS-6, KS-15, SFG-6, SFG-15, SO, etc.), conductive carbon black (such as Super P, Super S, 350G, acetylene black, Ketjen black, etc.), conductive carbon fiber (such as VGCF, CNT), and graphene. In some embodiments, the binder includes at least one of polyisobutylene (PIB), styrene-butadiene rubber (SBR), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), hydrogenated styrene-butadiene block copolymer (SEBS), ethyl cellulose (EC), polyurethane (PU), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB). In some embodiments, the thickener includes at least one of sodium carboxymethyl cellulose (CMC-Na), hydroxypropyl methyl cellulose (HPMC), and hydroxyethyl cellulose (HEC).

[0040] A fourth aspect of this application provides an electrical device that includes the secondary battery of the third aspect.

[0041] In some implementations, the electrical equipment includes mobile phones, smartphones, laptops, tablets, wearable devices, smartwatches, smart bracelets, smart glasses, power banks, televisions, game consoles, game controllers, digital cameras, smart speakers, headphones, keyboards, mice, monitors, drones, audio equipment, home appliances, toys, power tools, automobiles, motorcycles, electric bicycles, bicycles, robots, robot dogs, industrial robots, android robots, etc.

[0042] The beneficial effects of this application are: The polymer fiber matrix and the metal halide oxide particles dispersed within and on the surface of the polymer fiber matrix form a "fiber-nanoparticle" composite structure, effectively enhancing the thermal stability and ion transport performance of the separator. This three-dimensional network structure features a uniformly distributed small-scale pore structure, which facilitates rapid ion migration while inhibiting excessive electrolyte permeation, thus improving the separator's barrier properties. Furthermore, the introduction of metal halide oxides creates abundant active sites on the separator surface, including halogen vacancies and metal centers, which can serve as ion migration channels, lowering the ion transport energy barrier and improving battery rate performance. Attached Figure Description

[0043] Figure 1This is a scanning electron microscope (SEM) image of the CoOCl / PAN composite membrane prepared in Example 1 of this application. Here, a and b represent different magnifications.

[0044] Figure 2 These are the elemental analysis results of the CoOCl / PAN composite membrane prepared in Example 1 of this application. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit the application. Those skilled in the art will recognize that, with the evolution of technology and the emergence of new application scenarios, the technical solutions provided in the embodiments of this application are equally applicable to similar technical problems.

[0046] Example 1: CoOCl / PAN composite membrane This embodiment provides a CoOCl / PAN composite separator, which includes a three-dimensional network structure of polyacrylonitrile (PAN) fibers. The polyacrylonitrile fibers include a polyacrylonitrile matrix and cobalt oxychloride (CoOCl) powder dispersed inside and on the surface of the matrix. The mass ratio of the polyacrylonitrile matrix to the CoOCl powder is 10:1.

[0047] The preparation process of this CoOCl / PAN composite membrane is as follows: (1) Dissolve 1.13 g of cobalt nitrate hexahydrate in 40 mL of deionized water and 40 mL of n-butanol, and stir magnetically for 30 min to ensure uniform dispersion, to obtain mixed solution A.

[0048] (2) Add 0.38 g of urea and 15 mg of trisodium citrate to mixed solution A, and continue to stir magnetically for 30 min to obtain mixed solution B.

[0049] (3) Transfer the mixed solution B to a polytetrafluoroethylene-lined reactor and place it in a 120 °C constant temperature oven for 12 h. Collect the precipitate by vacuum filtration, then wash it with deionized water and anhydrous ethanol in sequence, and dry it to obtain cobalt hydroxyoxide precursor powder.

[0050] (4) 0.92 g of cobalt hydroxyoxide powder was redispersed in distilled water, and ammonia was added dropwise under magnetic stirring to adjust the pH to 8, resulting in mixed solution C.

[0051] (5) Dissolve 0.53 g of ammonium chloride in 50 mL of deionized water to prepare solution D. Add solution D slowly to mixed solution C under magnetic stirring to obtain the final mixed solution.

[0052] (6) The final mixed solution was transferred to a polytetrafluoroethylene-lined reactor and reacted at 180 °C for 10 h. The precipitate was collected by vacuum filtration, washed with deionized water and anhydrous ethanol in sequence, and then dried in an oven at 60 °C to obtain cobalt oxychloride powder.

[0053] (7) 2 g of polyacrylonitrile (PAN) was magnetically stirred in N,N-dimethylformamide (DMF) at 70 °C for 2 h to fully dissolve it in order to prepare a PAN solution with a mass fraction of about 10.0%.

[0054] (8) At room temperature, 0.2 g of cobalt oxychloride powder was added to PAN solution and ball-milled for 3 h to obtain a mixture in which the powder was uniformly dispersed.

[0055] (9) After the mixture is continuously magnetically stirred for 4 hours, a viscous and uniform spinning precursor solution is formed. During this period, the mixture is allowed to stand to eliminate air bubbles.

[0056] (10) Inject the spinning precursor liquid into the electrospinning device, select aluminum foil as the receiving substrate, set the spinning voltage to 12 kV, control the curing distance to 15 cm, and carry out electrospinning operation under the condition of 30%~40% ambient humidity. Under the action of electric field force, the spinning liquid is sprayed in the form of fibers and deposited on the receiving substrate to obtain a fiber membrane.

[0057] (11) The fiber membrane was dried in a vacuum drying oven at 60 °C for 12~24 h to obtain the CoOCl / PAN composite membrane.

[0058] Electron micrographs of the prepared CoOCl / PAN composite separator at different magnifications are shown below. Figure 1 As shown in the figure, the composite membrane prepared in this embodiment forms a three-dimensional network structure of PAN fibers, wherein the diameter of the PAN fibers is generally between 1 and 3 micrometers. Elemental analysis results are as follows. Figure 2 As shown in the figure, CoOCl powder is uniformly distributed inside and on the surface of PAN fibers.

[0059] Example 2: FeOBr / PAN composite membrane This embodiment provides a FeOBr / PAN composite membrane, which includes a three-dimensional network structure of polyacrylonitrile (PAN) fibers. The polyacrylonitrile fibers include a polyacrylonitrile matrix and iron oxybromine (FeOBr) powder dispersed inside and on the surface of the matrix. The mass ratio of the polyacrylonitrile matrix to the FeOBr powder is 10:1.

[0060] The preparation process of this FeOBr / PAN composite membrane is as follows: (1) Dissolve 0.84 g of ferric nitrate hexahydrate in a mixed solution of 40 mL of deionized water and 40 mL of n-butanol, and stir magnetically for 30 min to ensure uniform dispersion, to obtain mixed solution A.

[0061] (2) Add 0.38 g of urea and 15 mg of trisodium citrate to mixed solution A, and continue to stir magnetically for 30 min to obtain mixed solution B.

[0062] (3) Transfer the mixed solution B to a polytetrafluoroethylene-lined reactor and place it in a 120 °C constant temperature oven for 12 h. Collect the precipitate by vacuum filtration, then wash it with deionized water and anhydrous ethanol in sequence, and dry it to obtain hydroxyl iron oxide precursor powder.

[0063] (4) 0.89 g of ferric hydroxide powder was redispersed in distilled water, and ammonia was added dropwise under magnetic stirring to adjust the pH to 8, resulting in mixed solution C.

[0064] (5) Dissolve 0.98 g of ammonium bromide in 50 mL of deionized water to prepare solution D. Add solution D slowly to mixed solution C under magnetic stirring to obtain the final mixed solution.

[0065] (6) The final mixed solution was transferred to a polytetrafluoroethylene-lined reactor and reacted at 180 °C for 10 h. The precipitate was collected by vacuum filtration, washed with deionized water and anhydrous ethanol in sequence, and then dried in an oven at 60 °C to obtain iron bromine oxide powder.

[0066] (7) 2 g of polyacrylonitrile (PAN) was magnetically stirred in N,N-dimethylformamide (DMF) at 70 °C for 2 h to fully dissolve it in order to prepare a PAN solution with a mass fraction of about 10.0%.

[0067] (8) At room temperature, 0.2 g of iron bromine oxide powder was added to PAN solution and ball milled for 3 h to obtain a uniformly dispersed mixture.

[0068] (9) After the mixture is continuously magnetically stirred for 4 hours, a viscous and uniform spinning precursor solution is formed. During this period, the mixture is allowed to stand to eliminate air bubbles.

[0069] (10) Inject the spinning precursor liquid into the electrospinning device, select aluminum foil as the receiving substrate, set the spinning voltage to 15 kV, control the curing distance to 20 cm, and carry out electrospinning operation under the condition of 30%~40% ambient humidity. Under the action of electric field force, the spinning liquid is sprayed in the form of fibers and deposited on the receiving substrate to obtain a fiber membrane.

[0070] (11) The fiber membrane was dried in a vacuum drying oven at 60 °C for 12~24h to obtain the FeOBr / PAN composite membrane.

[0071] Examples 3-7 Examples 3-7 each provide a composite membrane, which differs from Example 1 in that the metal halide oxides dispersed in the interior and surface of the matrix are NiOCl, TiOBr, LaOCl, CeOI, and GdOI, respectively.

[0072] Examples 8-14 Examples 8-14 each provide a composite membrane, the difference from Example 1 being that the polyacrylonitrile fiber is replaced with polyvinylidene fluoride fiber, polyimide fiber, polybenzimidazole fiber, polyethylene terephthalate fiber, polybutylene terephthalate fiber, polyamide fiber, and polytetrafluoroethylene fiber.

[0073] Examples 15-16 Examples 15 and 16 respectively provide a composite membrane. The difference from Example 1 is that in step (8), 0.04 g and 1 g of cobalt oxychloride powder are respectively ball-milled with PAN solution to obtain a mixture.

[0074] Comparative Example 1: PAN composite membrane coated with CoOCl surface This comparative example provides a CoOCl-coated PAN composite separator, comprising a PAN separator layer and a CoOCl coating layer on the surface of the PAN separator layer. The preparation process of this CoOCl-coated PAN composite separator is as follows: (1) 2 g of polyacrylonitrile (PAN) was magnetically stirred in N,N-dimethylformamide (DMF) at 70 °C for 2 h to fully dissolve it and prepare a PAN solution with a mass fraction of approximately 10.0%. After continuous magnetic stirring for 4 h, a viscous and uniform spinning precursor solution was formed, during which time air bubbles were eliminated by allowing it to stand. The spinning precursor solution was injected into an electrospinning apparatus, aluminum foil was selected as the receiving substrate, the spinning voltage was set to 12 kV, the curing distance was controlled at 15 cm, and electrospinning was performed under an ambient humidity of 30%~40%. Under the action of the electric field, the spinning solution was sprayed in the form of fibers and deposited on the receiving substrate to obtain a pure PAN fiber membrane. The pure PAN fiber membrane was dried in a vacuum drying oven at 60 °C for 24 h to obtain a pure PAN separator.

[0075] (2) Weigh an appropriate amount of polyvinylidene fluoride (PVDF) powder, add it to N-methylpyrrolidone (NMP) and stir magnetically until completely dissolved. Then add the CoOCl powder prepared in Example 1 in batches and stir continuously for 90 min. Then disperse it with ultrasonic assistance for 25 min to ensure uniform dispersion and obtain a mixed slurry. The PVDF content in the mixed slurry is 5 wt% and the CoOCl content is 20 wt%.

[0076] (3) Use a coating machine to uniformly coat the above mixed slurry onto the surface of the pure PAN diaphragm prepared in step (1). The coating speed is set to 5 m / min, and the doctor blade gap is adjusted to 0.3 mm to control the coating thickness to 5-50 μm.

[0077] (4) The coated diaphragm is dried in stages in vacuum ovens at 60-80 ℃ and 100-120 ℃ to remove residual solvent, and finally the PAN composite diaphragm coated with CoOCl is obtained.

[0078] Comparative Example 2: Co3O4 / PAN Composite Separator This comparative example provides a Co3O4 / PAN composite membrane comprising a three-dimensional network structure of polyacrylonitrile (PAN) fibers, wherein the polyacrylonitrile fibers comprise a polyacrylonitrile matrix and alumina powder dispersed within and on the surface of the matrix, and the mass ratio of the polyacrylonitrile matrix to the Co3O4 powder is 10:1.

[0079] The preparation process of this Co3O4 / PAN composite membrane is as follows: (1) Dissolve 1.5 g of cobalt nitrate hexahydrate in 60 mL of deionized water and stir for 30 min until completely dissolved to obtain mixed solution A.

[0080] (2) Add 0.5 g of urea and 0.1 g of trisodium citrate to mixed solution A, and continue to stir magnetically for 30 min to obtain mixed solution B.

[0081] (3) Transfer the mixed solution B to a polytetrafluoroethylene-lined reactor and place it in a 180 °C constant temperature oven for 12 h. Collect the precipitate by vacuum filtration, then wash it with deionized water and anhydrous ethanol in sequence, and dry it to obtain cobalt hydroxyoxide precursor powder.

[0082] (4) 0.8 g of cobalt hydroxyoxide powder was redispersed in distilled water, and NaOH was added dropwise under magnetic stirring to adjust the pH to 10, resulting in mixed solution C.

[0083] (5) The mixed solution C was transferred to a polytetrafluoroethylene-lined reactor and reacted at 200 °C for 6 h. The precipitate was collected by vacuum filtration, washed with deionized water and anhydrous ethanol in sequence, and then dried in an oven at 80 °C to obtain alumina powder.

[0084] (6) 2 g of polyacrylonitrile (PAN) was magnetically stirred in N,N-dimethylformamide (DMF) at 70 °C for 2 h to fully dissolve it in order to prepare a PAN solution with a mass fraction of about 10.0%.

[0085] (7) 0.2 g of alumina powder was added to PAN solution at room temperature and ball milled for 3 h to obtain a uniformly dispersed mixture of powder.

[0086] (8) After the mixture is continuously magnetically stirred for 4 hours, a viscous and uniform spinning precursor solution is formed. During this period, the mixture is allowed to stand to eliminate air bubbles.

[0087] (9) Inject the spinning precursor liquid into the electrospinning device, select aluminum foil as the receiving substrate, set the spinning voltage to 15 kV, control the curing distance to 20 cm, and carry out electrospinning operation under the condition of 30%~40% ambient humidity. Under the action of electric field force, the spinning liquid is sprayed in the form of fibers and deposited on the receiving substrate to obtain a fiber membrane.

[0088] (10) The fiber membrane was dried in a vacuum drying oven at 60 °C for 12~24h to obtain a Co3O4 / PAN composite membrane.

[0089] Comparative Example 3: PAN diaphragm This comparative example provides a PAN separator, and the specific preparation process is as follows: (1) 2 g of polyacrylonitrile (PAN) was magnetically stirred in N,N-dimethylformamide (DMF) at 70 °C for 2 h to fully dissolve it in order to prepare a PAN solution with a mass fraction of about 10.0%.

[0090] (2) The PAN solution was continuously magnetically stirred at room temperature for 4 h to form a viscous and uniform spinning precursor solution. During this period, the solution was allowed to stand to eliminate air bubbles.

[0091] (3) Inject the spinning precursor liquid into the electrospinning device, select aluminum foil as the receiving substrate, set the spinning voltage to 10 kV, control the curing distance to 10 cm, and carry out electrospinning operation under the condition of 30%~40% ambient humidity. Under the action of electric field force, the spinning liquid is sprayed in the form of fibers and deposited on the receiving substrate to obtain a fiber membrane.

[0092] (4) The fiber membrane is dried in a vacuum drying oven at 60 ℃ for 12~24h to obtain PAN membrane.

[0093] Comparative Example 4 This comparative example uses commercially available Celgard 2400 PP / PE / PP separator.

[0094] Comparative test The physical and electrochemical properties of the membranes obtained in the examples and comparative examples were analyzed: Porosity: The true density of the sample skeleton was obtained by measuring the volume of the sample using a true density meter-TMY0008 through the gas expansion displacement method. The porosity was calculated by combining the apparent density (= mass / apparent volume) with the porosity = (apparent density - true density) / apparent density × 100%.

[0095] Puncture strength: The test was conducted using an electronic universal tensile testing machine - TMY0067, referring to the puncture strength test in section 6.5.3 of the standard for polyolefin separators for lithium-ion batteries (GB / T 36363-2018).

[0096] Melting point: The DSC curve was obtained using a differential scanning calorimeter-TMY0011, and the peak temperature Tp was taken as the melting point.

[0097] Ionic conductivity: The separator and stainless steel sheet (SS) were assembled into an SS / separator / SS symmetrical cell. After standing for 2 h, the electrochemical impedance spectroscopy was measured using an electrochemical workstation-CHI 760E. The focal intersection of the oblique line and the horizontal axis is the bulk impedance (Ω). The test frequency was 1~1×10⁻⁶. 6 Hz, voltage 10 mV. The calculated ionic conductivity (mS / cm) = diaphragm thickness / (body impedance × stainless steel sheet area).

[0098] The battery is then assembled, as follows: The positive electrode active material LiCoO2, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 97.6:1.1:1.3, and N-methylpyrrolidone (NMP) was added and mixed evenly to obtain a positive electrode slurry. The slurry was then uniformly coated onto aluminum foil, dried, cold-pressed, and cut to obtain a positive electrode sheet.

[0099] The negative electrode active material artificial graphite, conductive carbon black SP, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are mixed in a mass ratio of 96.5:1.1:1.2:1.2, and deionized water is added and mixed evenly to obtain a negative electrode slurry. The slurry is then uniformly coated onto copper foil, dried, cold-pressed, and cut to obtain a negative electrode sheet.

[0100] Propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) were mixed in a mass ratio of 1:1.2:4, and LiPF6 was added to dissolve and mix well to obtain an electrolyte with a LiPF6 concentration of 1 mol / L.

[0101] The positive electrode, separator, and negative electrode are stacked in sequence and wound to obtain an electrode assembly. The electrode assembly is placed in an aluminum-plastic film packaging bag, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, degassing, and edge trimming, a battery is obtained.

[0102] The battery's cycle performance and rate performance were tested as follows: Cyclic performance: The assembled battery was tested in a 25 ℃ environment using the Xinwei CT-8000 high-performance battery testing system. The test voltage range was 2.5~3.8 V, and charge-discharge cycles were performed at 0.2C. The discharge capacity of the first cycle and the 500th cycle were recorded. Cyclic capacity retention = (500-cycle discharge capacity / first-cycle discharge capacity) × 100%.

[0103] Rate performance: The assembled battery was tested in the Xinwei CT-8000 high-performance battery testing system under a test environment of 25 ℃. The test voltage range was 2.5~3.8 V. After the battery was fully charged at 0.5 C, the discharge capacity was tested at multiple rates such as n C (n=0.5, 1, 2, 3) to obtain the discharge capacity.

[0104] The results are shown in Tables 1-3: Table 1. Physicochemical performance test results

[0105] Table 2. Cyclic performance test results

[0106] Table 3. Ratio Performance Test Results

[0107] Based on the combined technical effects of Examples 1 and 2, this application successfully prepared a composite separator with excellent thermal stability, high ionic conductivity, and good mechanical strength (especially puncture strength) by incorporating metal halide oxides into the interior and surface of electrospun polymer fibers. The melting points of Examples 1 and 2 are significantly higher than those of Comparative Examples 4 and 3, greatly reducing the risk of fire. Simultaneously, the significantly better ionic conductivity and puncture strength compared to Comparative Examples 1 and 2 reduce the resistance to lithium ion passage within the separator, decrease the risk of internal short circuits, and enhance battery safety.

[0108] Compared to Comparative Example 4, Comparative Example 1, while improving ionic conductivity, melting point, and puncture strength through surface coating with metal halide oxides, showed a significant decrease in porosity. In contrast to the surface coating of Comparative Example 1, Example 1 incorporated metal halide oxides into polymer fibers via electrospinning, resulting in a significant improvement in porosity, melting point, puncture strength, and ionic conductivity. This approach balanced thermal stability with ion transport performance, leading to superior rate performance and cycle life of the battery.

[0109] Compared to Comparative Example 3, Comparative Example 2 improved ionic conductivity, melting point, and puncture strength through the doping of metal oxide inorganic fillers, but its porosity decreased significantly. In contrast to the metal oxide inorganic filler in Comparative Example 2, Example 1 replaced it with metal halide oxides, avoiding the problem of clogging the pore structure and reducing porosity while improving the thermal stability of the separator. The battery's rate performance and cycle performance were also superior.

[0110] Meanwhile, the results of Examples 3-16 show that by using metal halide oxides obtained from other specific metal elements or halogens as a substitute for CoOCl, or by using other specific polymer matrix materials, or by appropriately adjusting the ratio of the two, the prepared separator can also have similar physicochemical properties and exhibit good rate performance and cycle performance in the battery.

[0111] As can be seen from the above embodiments, by combining the hydrothermal method with electrospinning technology, a multifunctional separator with high porosity, strong chemical adsorption capacity, excellent lithium-ion transport performance and good thermal stability can be prepared. This can effectively improve the stability and ion migration rate of the separator, improve battery safety and rate performance, and solve the bottleneck problems of traditional separators in terms of thermal runaway risk and ion transport efficiency, providing a new approach for the development of high-safety, high-energy-density lithium-ion batteries.

[0112] The above embodiments are preferred embodiments of this application, but the implementation of this application is not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of this application shall be considered equivalent substitutions and shall be included within the protection scope of this application.

Claims

1. A diaphragm, characterized in that The membrane comprises a three-dimensional network structure formed of polymer fibers, the polymer fibers comprising a polymer matrix and metal halide oxides dispersed within and on the surface of the polymer matrix.

2. The separator according to claim 1, characterized in that The polymer matrix includes at least one of polyacrylonitrile, polyvinylidene fluoride, polyimide, polybenzimidazole, polyethylene terephthalate, polybutylene terephthalate, polyamide, polyacetal, polycarbonate, polyetherketone, polyethersulfone, polyphenylene ether, polyphenylene sulfide, polyethylene naphthalate, polytetrafluoroethylene, polyvinyl chloride, poly(p-phenylenebenzodiazole), and polyarylate.

3. The separator of claim 1, wherein The metal halide oxide contains at least one of the following metal elements: iron, cobalt, nickel, titanium, lanthanum, cerium, and gadolinium, and / or the halogen of the metal halide oxide contains at least one of the following halogen elements: chlorine, bromine, and iodine.

4. The separator of claim 1, wherein The mass ratio of the polymer matrix to the metal halide oxide is 10:(0.2~5).

5. Process for the production of a separator according to any one of claims 1 to 4, characterized in that, Includes the following steps: The polymer matrix solution is mixed with a metal halide oxide to obtain a precursor solution; The diaphragm is obtained by electrospinning the precursor solution.

6. The production method according to claim 5, wherein The metal halide oxide is prepared by a method comprising the following steps: The ammonium halide salt is mixed with a metal hydroxyl oxide and subjected to a hydrothermal reaction. The precipitate is collected, washed, and dried to obtain the metal halide oxide.

7. The production method according to claim 6, characterized by, The metal hydroxy oxide is prepared by a method comprising the following steps: A mixed solution is obtained by mixing a metal salt with deionized water and n-butanol; The mixed solution is mixed with urea and carboxylic acid ligands for a hydrothermal reaction. The precipitated product is collected, washed, and dried to obtain the metal hydroxy oxide.

8. The production method according to claim 5, characterized by, The preparation parameters for the electrospinning method include a spinning voltage of 10~15 kV and a curing distance of 5~20 cm.

9. A secondary battery characterized by Includes the diaphragm as described in any one of claims 1 to 4.

10. An electrical device, characterized by Includes the secondary battery as described in claim 9.

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