Solid electrolytes, their preparation methods and applications, and lithium-ion batteries

Abstract

This invention provides a solid electrolyte, its preparation method, applications, and a lithium-ion battery. The electrolyte comprises alternating A and B layers, wherein the A and B layers are made of different materials, each containing a polymer and an alkali metal salt, and one of the A and B layers contains an inorganic filler. The solid electrolyte of this invention has advantages such as low impedance, high elongation at break, and high initial capacity of the assembled battery.

Description

Technical Field

[0001] This invention relates to solid electrolytes, their preparation methods and applications, and lithium-ion batteries. Background Technology

[0002] With growing commercial interest in power tools, hybrid electric vehicles, electric vehicles in the automotive industry, and portable devices in daily life, there is increasing focus on the development of high-performance lithium-ion batteries. As a key component, the electrolyte is crucial for the fabrication of long-life and high-performance lithium-ion batteries. In most commercially available batteries, the electrolyte used is generally an optimized liquid electrolyte, exhibiting high conductivity. However, liquid electrolytes present challenges such as flammable solvent leakage, fire, and explosion, leading to performance degradation and safety issues that hinder the large-scale commercialization of lithium-ion batteries. Therefore, researching safer and more reliable lithium-ion battery electrolytes is of paramount importance. Furthermore, a better understanding of the high demand for novel electrolytes is needed to improve the performance and energy density of lithium-ion batteries.

[0003] Polymer-based solid electrolytes (SPEs) have attracted widespread attention due to their excellent safety, mechanical properties, and flexibility. Ions can move freely within the space provided by the free volume of the polymer matrix, thus the conductivity may be higher than the polymer's glass transition temperature (Tg), at which polymer molecules can move freely. Current improvements mainly focus on two aspects: increasing the ionic conductivity of all-solid-state electrolytes and improving the interfacial contact between the electrolyte and the electrode sheet. Most current improvements addressing these two issues concentrate on the materials used and the manufacturing process, primarily falling into the following categories: 1) Adding inorganic fillers or plasticizers to improve ionic conductivity, controlling the type and distribution of inorganic fillers; 2) Modifying polymers: grafting, copolymerization, composites, etc.; 3) Optimizing the type of lithium salt, applying novel lithium salts or additives; 4) Improving film-forming processes, such as using hot pressing instead of traditional solution film formation, resulting in a green and pollution-free process. Summary of the Invention

[0004] As mentioned above, there are few reports in the prior art on improving the morphology and structure of the membrane to reduce impedance in order to address the shortcomings of electrolytes. In view of this, the present invention provides a solid electrolyte, its preparation method and application, and a lithium-ion battery.

[0005] According to a first aspect of the present invention, the present invention provides a solid electrolyte comprising alternating layers A and B, wherein the materials of layers A and B are different, each of the materials of layers A and B contains a polymer and an alkali metal salt, and one of the materials of layers A and B contains an inorganic filler.

[0006] According to a second aspect of the present invention, the present invention provides a method for preparing a solid electrolyte, wherein the method comprises:

[0007] a) Forming a slurry M from the polymer and alkali metal salt;

[0008] b) Forming a slurry N from polymers, alkali metal salts, and inorganic fillers;

[0009] c) Coat slurry M or slurry N into a film and heat until the solvent evaporates; coat another layer of different slurry at fixed points on the surface of the film, hold the slurry at the fixed point, scrape it flat, and heat until the solvent evaporates; optionally, repeat the fixed-point coating, holding and scraping and heating until the solvent evaporates of another layer of slurry as needed; so that the electrolyte includes an interleaved multilayer structure.

[0010] According to a third aspect of the present invention, the present invention provides the application of the solid electrolyte described herein or the solid electrolyte prepared by the method described herein in a battery.

[0011] According to a fourth aspect of the present invention, the present invention provides a lithium-ion battery assembled from a solid electrolyte, a positive electrode, and a lithium electrode, wherein the solid electrolyte is the solid electrolyte described in the present invention or a solid electrolyte prepared by the method described in the present invention.

[0012] The solid electrolyte of the present invention has advantages such as low impedance, high elongation at break, and high initial capacity of the assembled battery.

[0013] The polymer-based solid electrolyte synthesized in this invention is assembled into a coin cell with lithium foil and lithium iron phosphate cathode. Impedance spectra at 30-70°C are tested to characterize the material's impedance and ion diffusion properties. Compared to a control sample with a conventional monolayer PEO-LiFSI-LLZTO film, the Re value characterizing the material's impedance decreases from 800 Ω to 367 Ω. Attached Figure Description

[0014] Figure 1 This is a SEM image of the porous sandwich structure all-solid electrolyte surface from Example 1.

[0015] Figure 2 This is a magnified SEM image of the surface pores of the porous sandwich structure all-solid electrolyte in Example 1;

[0016] Figure 3 This is a SEM image of the cross-section of the porous sandwich structure all-solid electrolyte in Example 1;

[0017] Figure 4 Impedance spectrum of lithium battery based on porous sandwich structure all-solid electrolyte in Example 1;

[0018] Figure 5 The image shows the SEM image of the surface of the monolayer all-solid electrolyte in Comparative Example 1. Detailed Implementation

[0019] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0020] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by one of ordinary skill in the art. In case of conflict, the definitions in this specification shall prevail.

[0021] In the context of this specification, any two or more aspects of the present invention may be combined arbitrarily, and the resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0022] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this specification are based on weight, unless being based on weight would not be in accordance with the common understanding of those skilled in the art.

[0023] According to the present invention, the following embodiments are relevant.

[0024] This invention provides a solid electrolyte comprising alternating A and B layers, wherein the A and B layers are made of different materials, each containing a polymer and an alkali metal salt, and one of the A and B layers contains an inorganic filler. The solid electrolyte of this invention exhibits advantages such as low impedance, high elongation at break, high initial capacity of the assembled battery, high ionic conductivity, and good flexibility.

[0025] According to a preferred embodiment of the present invention, preferably, the initial discharge capacity of the battery assembled from the solid electrolyte and lithium iron phosphate electrode sheet is 160 mAh g. -1 above.

[0026] According to a preferred embodiment of the present invention, the impedance Re of the solid electrolyte is below 500Ω; preferably, the impedance Re of the solid electrolyte at 60°C is 300-500Ω.

[0027] According to a preferred embodiment of the present invention, preferably, the tensile elongation at break of the solid electrolyte is 100% or more, preferably 100-150%.

[0028] In this invention, the thickness of the solid electrolyte can be selected from a wide range. According to a preferred embodiment of this invention, the thickness of the solid electrolyte is preferably 900-2000 μm.

[0029] According to a preferred embodiment of the present invention, preferably, the solid electrolyte has multiple pores, each pore existing independently and having an irregular shape, and the pores do not penetrate the layer structure of the electrolyte. The solid electrolyte having the aforementioned structure has the advantages of high ionic conductivity and good flexibility.

[0030] According to a preferred embodiment of the present invention, the aperture of the hole is preferably 1-20 μm.

[0031] According to a preferred embodiment of the present invention, preferably, filamentous morphology runs through the pores. Solid electrolytes having the aforementioned structure have the advantage of good mechanical properties.

[0032] According to a preferred embodiment of the present invention, the electrolyte preferably comprises N layers of alternating A and B layers, where N is 2-10 layers, preferably 3-5 layers. Solid electrolytes with the aforementioned structure have the advantages of good contact with electrodes and high conductivity.

[0033] According to a preferred embodiment of the present invention, preferably, layer A and layer B each contain a polymer and an alkali metal salt, and layer B contains an inorganic filler; the electrolyte is an AB layer arrangement structure, a BA layer arrangement structure, an ABA layer arrangement structure, a BAB layer arrangement structure, an ABAB layer arrangement structure, a BABA layer arrangement structure, an ABABA layer arrangement structure, a BABAB layer arrangement structure, an ABABAB layer arrangement structure, or a BABABA layer arrangement structure.

[0034] In this invention, a wide range of polymer types can be selected. According to a preferred embodiment of this invention, the polymer is selected from one or more of polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), and poly(vinylidene fluoride hexafluoropropylene). Preferably, the polymer is selected from one or more polyethylene oxide (PEO) with a molecular weight of 40W, 60W, 80W, and 100W. The aforementioned preferred embodiment has the advantages of good mechanical properties and high electrical conductivity.

[0035] In this invention, the range of alkali metal salts that can be selected is relatively wide. For this invention, the alkali metal salts include, but are not limited to, one or more of lithium salts, sodium salts, and potassium salts; for this invention, lithium salts are preferred; more preferably, the lithium salt is selected from one or more of lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoroformyl)imide (LiTFSI), and lithium perchlorate (LiClO4). Using the aforementioned preferred embodiments, there are advantages of good solubility and high ionic conductivity.

[0036] In this invention, the range of selectable inorganic fillers is relatively wide. For this invention, the preferred inorganic fillers include, but are not limited to, alumina (Al₂O₃), silicon dioxide (SiO₂), and Li₂. 6.4 La3Zr 1.4 Ta 0.6 O 12 One or more of (LLZTO). The aforementioned preferred embodiments have the advantages of high strength and high ionic conductivity.

[0037] Solid electrolytes possessing the aforementioned features of this invention can all achieve the objectives of this invention, and there are no special requirements for their preparation methods. In view of this invention, a method for preparing a solid electrolyte is provided, wherein the method includes:

[0038] a) Forming a slurry M from the polymer and alkali metal salt;

[0039] b) Forming a slurry N from polymers, alkali metal salts, and inorganic fillers;

[0040] c) Coat slurry M or slurry N into a film and heat until the solvent evaporates; coat another layer of different slurry at fixed points on the surface of the film, hold the slurry at the fixed point, scrape it flat, and heat until the solvent evaporates; optionally, repeat the fixed-point coating, holding and scraping and heating until the solvent evaporates of another layer of slurry as needed; so that the electrolyte includes an interleaved multilayer structure.

[0041] In this invention, the range of polymer types that can be selected is relatively wide. According to a preferred embodiment of this invention, in slurry M and slurry N, the polymer is selected from one or more of polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), and poly(vinylidene fluoride hexafluoropropylene); preferably, the polymer is selected from one or more of polyethylene oxide (PEO) with a molecular weight of 40W, 60W, 80W, and 100W.

[0042] In this invention, the range of types of alkali metal salts is relatively wide. For this invention, in slurry M and slurry N, the alkali metal salts include, but are not limited to, one or more of sodium salt, potassium salt and lithium salt; preferably lithium salt; more preferably, the lithium salt is selected from one or more of lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoroformyl)imide (LiTFSI) and lithium perchlorate (LiClO4).

[0043] In this invention, there are no special requirements for the solvent of the slurry. For this invention, preferably, the solvents of slurry M and slurry N are each selected from one or more of acetonitrile and N,N-dimethylacetamide.

[0044] In this invention, the range of selectable inorganic fillers is relatively wide. For this invention, the preferred inorganic fillers include, but are not limited to, alumina (Al₂O₃), silicon dioxide (SiO₂), and Li₂. 6.4 La3Zr 1.4 Ta 0.6 O 12 One or more of (LLZTO).

[0045] In this invention, the content of each substance in the slurry M can be selected within a wide range. Preferably, for this invention, the polymer content in the slurry M is 0.05-0.1 g / mL, and the alkali metal salt content is 0.03-0.05 g / mL. Using the aforementioned preferred embodiment has the advantages of good solubility and high ionic conductivity.

[0046] In this invention, the content of each substance in slurry N can be selected within a wide range. For this invention, preferably, the content of polymer in slurry N is 0.05-0.1 g / mL; the content of inorganic filler is 0.01-0.04 g / mL; and the content of alkali metal salt is 0.03-0.05 g / mL.

[0047] In this invention, there are no special requirements for the leveling method. For this invention, it is preferred that the thickness of the scraper used for leveling is 800-1200 μm. The aforementioned preferred embodiment has the advantages of suitable thickness and good mechanical properties.

[0048] In this invention, preferably, the holding time at the fixed point is 5-10 minutes. The aforementioned preferred embodiment has the advantage of uniform hole formation.

[0049] According to a preferred embodiment of the present invention, the spot coating method involves applying a layer of slurry with a thickness of 2-4 cm every 2-4 cm on the dry film. Using the aforementioned preferred embodiment offers the advantages of uniform film formation and uniform pore size distribution.

[0050] In this invention, there are no special requirements for the method and steps of heating to the point of solvent evaporation. According to a preferred embodiment of this invention, the heating method for heating to the point of solvent evaporation is vacuum drying, the heating temperature is 40-60℃, and the heating time is 24-48h.

[0051] According to a preferred embodiment of the present invention, the method preferably includes the following steps:

[0052] A) Dissolve polyethylene oxide and lithium salt in an organic solvent and stir at room temperature until completely dissolved;

[0053] Preferably, the ethylene oxide has a molecular weight of 40-100W;

[0054] Preferably, the lithium salt is one or more selected from lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoroformyl)imide (LiTFSI), and lithium perchlorate (LiClO4);

[0055] Preferably, the organic solvent is one of acetonitrile and N,N-dimethylacetamide;

[0056] B) Dissolve polyethylene oxide and lithium salt in an organic solvent. After complete dissolution, add the inorganic filler and stir at room temperature until evenly dispersed.

[0057] Preferably, the ethylene oxide has a molecular weight of 40-100W;

[0058] Preferably, the inorganic filler is alumina (Al2O3), silicon dioxide (SiO2), and Li. 6.4 La3Zr 1.4 Ta 0.6 O 12 One or more of (LLZTO);

[0059] Preferably, the lithium salt is one or more selected from lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoroformyl)imide (LiTFSI), and lithium perchlorate (LiClO4);

[0060] Preferably, the organic solvent is one of acetonitrile and N,N-dimethylacetamide;

[0061] C) The solution described in A) is uniformly coated onto a tetrafluoroethylene plate and vacuum dried until completely dry to obtain the first dry film;

[0062] Preferably, the uniform coating is performed by scraping with a doctor blade with a thickness of 800-1200 μm;

[0063] Preferably, the vacuum drying temperature is 40-60℃ and the heating time is 24-48h;

[0064] D) On the dry film described in C), a layer of the solution described in B) is deposited at specific points, and vacuum dried until the solvent is completely dried. Then, a layer of the solution described in A) is deposited at specific points and vacuum dried until completely dried to obtain a porous sandwich structure solid electrolyte membrane.

[0065] Preferably, the fixed-point overcoating method is to coat a wet film with a thickness of 2-4 cm every 2-4 cm on the dry film, leave it for 5-10 minutes, and then scrape it flat with an 800-1200μm doctor blade.

[0066] The preferred vacuum drying temperature is 40-60℃, and the heating time is 24-48h;

[0067] E) Assemble the three-layer porous solid electrolyte membrane described in D) with lithium foil and lithium iron phosphate cathode to form a coin cell.

[0068] The aforementioned method for preparing a sandwich-structured all-solid electrolyte with a special morphology through a combination of dry and wet methods yields a solid electrolyte with an internal pore structure of 1-20 μm diameter, consisting of three layers: inner, middle, and outer. Each layer is 50-70 μm thick, and the layers are tightly bonded together. In cross-section, the pores exist independently and are not interconnected. In one embodiment, the components of the three layers, from top to bottom, are: PEO-lithium salt, PEO-lithium salt-inorganic filler, and PEO-lithium salt.

[0069] This invention provides the application of the solid electrolyte described in this invention or the solid electrolyte prepared by the method described in this invention in batteries.

[0070] This invention provides a lithium-ion battery, which is assembled from a solid electrolyte, a positive electrode, and a lithium sheet. The solid electrolyte is the solid electrolyte described in this invention or a solid electrolyte prepared by the method described in this invention.

[0071] According to the present invention, preferably, the positive electrode contains lithium iron phosphate, polyvinylidene fluoride and acetylene black in a mass ratio of 1-50:0.1-10:1, and the current collector is aluminum foil.

[0072] According to a preferred embodiment of the present invention, preferably, the initial discharge capacity of the lithium-ion battery is 160 mAh g. -1 above.

[0073] According to a preferred embodiment of the present invention, preferably, the impedance Re of the lithium-ion battery at 60°C is below 500Ω.

[0074] To facilitate understanding of the present invention, embodiments are provided below. However, those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as specific limitations on the invention. The endpoints of the ranges and any values ​​disclosed herein are not limited to those precise ranges or values; such ranges or values ​​should be understood to include values ​​close to them.

[0075] Example 1

[0076] 1. Synthesis of porous sandwich-structured solid electrolytes

[0077] 2g of polyethylene oxide with a molecular weight of 40W and 1g of lithium bis(fluorosulfonyl)imide (LiFSI) were dissolved in 20mL of acetonitrile and magnetically stirred at room temperature for 24h. This solution is denoted as solution A.

[0078] 2 g of 40 W polyethylene oxide and 1 g of lithium bis(fluorosulfonyl)imide (LiFSI) were dissolved in 20 mL of N,N-dimethylacetamide and magnetically stirred at room temperature for 24 h. Then 0.8 g of Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Stir magnetically at room temperature for 24 hours, and this solution is denoted as solution B.

[0079] Solution A was uniformly coated onto a polytetrafluoroethylene (PTFE) plate using a 1000 μm spatula and placed in a vacuum oven at 60 °C for 24 h. After drying, a 3 cm thick layer of solution B was coated every 3 cm on the dry film. After standing for 5 min, the coating was smoothed with a 1000 μm spatula and placed in a vacuum drying oven at 60 °C for 24 h. After drying, a 3 cm thick layer of solution A was coated every 3 cm on the dry film. After standing for 5 min, the coating was smoothed with a 1000 μm spatula and placed in a vacuum drying oven at 60 °C for 24 h to obtain a porous three-layer membrane. The microstructure of the prepared electrolyte membrane was observed using a scanning electron microscope. The pore size distribution was 1-20 μm, and the thickness of the electrolyte membrane was 1000 μm. The mechanical properties of the material were tested using a tensile tester at a tensile rate of 100 mm / min, and the elongation at break was as high as 150%.

[0080] 2. Assembly and testing of all-solid-state lithium-ion batteries

[0081] The synthesized porous electrolyte membrane was used as the electrolyte and assembled with lithium foil and lithium iron phosphate cathode (lithium iron phosphate: polyvinylidene fluoride: acetylene black = 8:1:1) to form a 2035 coin cell. The impedance spectrum of the resulting cell was measured at 60°C, with a frequency range of 10... 3 -10 6 Ω. The Re at 60℃ is 367Ω. At room temperature, with a charge-discharge rate of 0.1C, the initial discharge capacity is 165mAh g.-1 .

[0082] Comparative Example 1

[0083] 1. Synthesis of monolayer solid electrolytes

[0084] 2g of 40W polyethylene oxide and 1g of lithium bis(fluorosulfonyl)imide (LiFSI) were dissolved in 20mL of acetonitrile and magnetically stirred at room temperature for 24h. Then, 0.8g of Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The electrolyte was magnetically stirred at room temperature for 24 hours, then uniformly coated onto a polytetrafluoroethylene (PTFE) plate using a 1000 μm scraper. The plate was then placed in a vacuum oven and heated at 60 °C for 24 hours. After drying, a single-layer solid electrolyte was obtained. The microstructure of the prepared electrolyte membrane was observed using a scanning electron microscope (SEM), revealing a porous three-layer membrane. The prepared electrolyte membrane, observed under an SEM, showed no pores and had a thickness of 350 μm. The mechanical properties of the material were tested using a tensile testing machine at a tensile rate of 100 mm / min, yielding an elongation at break of only 80%.

[0085] 2. Assembly and testing of all-solid-state lithium-ion batteries

[0086] The synthesized porous electrolyte membrane was used as the electrolyte and assembled with lithium foil and lithium iron phosphate cathode (lithium iron phosphate: polyvinylidene fluoride: acetylene black = 8:1:1) to form a 2035 coin cell. The Re at 60°C was 800 Ω, and the initial discharge capacity was 152 mAh g at room temperature with a charge-discharge rate of 0.1C. -1

[0087] Figure 1 This is a SEM image of the surface of the porous sandwich structure all-solid electrolyte in Example 1. Figure 1 It can be seen that the material is composed of pores of varying sizes, which is beneficial for ionic conductivity;

[0088] Figure 2 This is a magnified SEM image of the surface pores of the porous sandwich structure all-solid electrolyte in Example 1. Figure 2 It can be seen that there are filaments connecting the holes, and the holes are not permeable, which can prevent dendrites from piercing through;

[0089] Figure 3 This is a SEM image of the cross-section of the porous sandwich-structured all-solid-state electrolyte of Example 1. Figure 3 It can be seen that the cross-section is also covered with non-penetrating pores;

[0090] Figure 4 The impedance spectrum of the lithium battery based on the porous sandwich structure all-solid-state electrolyte of Example 1 is shown below. Figure 4It can be seen that the Re of the battery assembled with this solid electrolyte decreases with increasing temperature, and is as low as 367Ω at 60℃;

[0091] Figure 5 The image shows a SEM image of the surface of a monolayer all-solid-state electrolyte in Comparative Example 1. Figure 5 It can be seen that the surface of the monolayer electrolyte is uniform and has no pores.

[0092] Example 2

[0093] 1. Synthesis of porous sandwich-structured solid electrolytes

[0094] 1.5 g of polyacrylonitrile with a molecular weight of 40 W and 1 g of lithium difluorosulfonyl imide (LiFSI) were dissolved in 20 mL of acetonitrile and magnetically stirred at room temperature for 24 h. This solution is denoted as solution A.

[0095] 1.5 g of polyacrylonitrile with a molecular weight of 40 W and 1 g of lithium difluorosulfonyl imide (LiFSI) were dissolved in 20 mL of acetonitrile and magnetically stirred at room temperature for 24 h. Then 0.8 g of Al2O3 was added and magnetically stirred at room temperature for 24 h. This solution is denoted as solution B.

[0096] Solution B was uniformly coated onto a polytetrafluoroethylene (PTFE) plate using a 1000 μm spatula and placed in a vacuum oven at 60 °C for 24 h. After drying, a 3 cm thick layer of solution A was coated every 2 cm on the dry film. After standing for 5 min, the coating was smoothed with a 1000 μm spatula and placed in a vacuum drying oven at 60 °C for 24 h. After drying, a 3 cm thick layer of solution B was coated every 2 cm on the dry film. After standing for 5 min, the coating was smoothed with a 1000 μm spatula and placed in a vacuum drying oven at 60 °C for 24 h to obtain a porous three-layer membrane. The microstructure of the prepared electrolyte membrane was observed using a scanning electron microscope (SEM). The pore size distribution was 1-20 μm, and the thickness of the electrolyte membrane was 650 μm. The mechanical properties of the material were tested using a tensile tester at a tensile rate of 100 mm / min, and the elongation at break was as high as 135%.

[0097] 2. Assembly and testing of all-solid-state lithium-ion batteries

[0098] The synthesized porous electrolyte membrane was used as the electrolyte and assembled with lithium foil and lithium iron phosphate cathode (lithium iron phosphate: polyvinylidene fluoride: acetylene black = 8:1:1) to form a 2035 coin cell. The impedance spectra of the resulting cells were measured at 30, 40, 50, 60, and 70°C, with a frequency range of 10... 3 -10 6 The Re value at 60°C is 412 Ω. At room temperature, a charge-discharge rate of 0.1C yields an initial discharge capacity of 161 mAh g⁻¹.-1 .

[0099] Example 3

[0100] 1. Synthesis of porous sandwich-structured solid electrolytes

[0101] 1.0 g of polyvinylidene fluoride with a molecular weight of 40 W and 1 g of lithium bis(fluorosulfonyl)imide (LiFSI) were dissolved in 20 mL of acetonitrile and magnetically stirred at room temperature for 24 h. This solution is denoted as solution A.

[0102] 1.0 g of polyvinylidene fluoride with a molecular weight of 40 W and 1 g of lithium bis(fluorosulfonyl)imide (LiFSI) were dissolved in 20 mL of acetonitrile and magnetically stirred at room temperature for 24 h. Then 0.7 g of SiO2 was added and magnetically stirred at room temperature for 24 h. This solution is denoted as solution B.

[0103] Solution A was uniformly coated onto a polytetrafluoroethylene (PTFE) plate using an 800 μm spatula and placed in a vacuum oven at 60 °C for 24 h. After drying, a 3 cm thick layer of solution B was coated every 3 cm on the dry film. After standing for 5 min, the coating was smoothed with an 800 μm spatula and placed in a vacuum oven at 60 °C for 24 h. This process was repeated to obtain a porous four-layer membrane. The microstructure of the prepared electrolyte membrane was observed using a scanning electron microscope. The pore size distribution ranged from 1 to 20 μm, and the thickness was 1100 μm. The mechanical properties of the material were tested using a tensile tester. The tensile rate of the sample was 100 mm / min, and the elongation at break was as high as 137%.

[0104] 2. Assembly and testing of all-solid-state lithium-ion batteries

[0105] The synthesized porous electrolyte membrane was used as the electrolyte and assembled with lithium foil and lithium iron phosphate cathode (lithium iron phosphate: polyvinylidene fluoride: acetylene black = 8:1:1) to form a 2035 coin cell. The impedance spectrum of the resulting cell was measured at 60°C, with a frequency range of 10... 3 -10 6 The Ω value is 450 Ω at 60℃. At room temperature, a charge-discharge rate of 0.1C yields an initial discharge capacity of 164 mAh g⁻¹. -1 .

[0106] Example 4

[0107] 1. Synthesis of porous sandwich-structured solid electrolytes

[0108] 1.0 g of polyethylene oxide with a molecular weight of 40 W and 1 g of lithium bis(fluorosulfonyl)imide (LiFSI) were dissolved in 20 mL of acetonitrile and magnetically stirred at room temperature for 24 h. This solution is denoted as solution A.

[0109] 1.0 g of 40 W polyethylene oxide and 1 g of lithium bis(fluorosulfonyl)imide (LiFSI) were dissolved in 20 mL of acetonitrile and magnetically stirred at room temperature for 24 h. Then, 0.7 g of Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Stir magnetically at room temperature for 24 hours, and this solution is denoted as solution B.

[0110] Solution A was uniformly coated onto a polytetrafluoroethylene (PTFE) plate using an 800 μm spatula and placed in a vacuum oven at 60 °C for 24 h. After drying, a 3 cm thick layer of solution B was coated every 3 cm on the dry film. After standing for 5 min, the coating was smoothed with an 800 μm spatula and placed in a vacuum oven at 60 °C for 24 h. After drying, a 3 cm thick layer of solution B was coated every 3 cm on the dry film. After standing for 5 min, the coating was smoothed with an 800 μm spatula and placed in a vacuum oven at 60 °C for 24 h. After drying, a 3 cm thick layer of solution A was coated every 3 cm on the dry film. After standing for 5 min, the coating was smoothed with an 800 μm spatula, resulting in a porous four-layer membrane. The microstructure of the prepared electrolyte membrane was observed using a scanning electron microscope. The pore size distribution ranged from 1 to 20 μm, and the thickness was 1100 μm. The mechanical properties of the material were tested using a tensile tester. The tensile rate of the sample was 100 mm / min, and the elongation at break was 110%.

[0111] 2. Assembly and testing of all-solid-state lithium-ion batteries

[0112] The synthesized porous electrolyte membrane was used as the electrolyte and assembled with lithium foil and lithium iron phosphate cathode (lithium iron phosphate: polyvinylidene fluoride: acetylene black = 8:1:1) to form a 2035 coin cell. The resulting cell was subjected to impedance analysis at 60°C, with a Re value of 500 Ω. The test frequency range was 10... 3 -10 6 Ω. At room temperature, a charge-discharge rate of 0.1C yielded an initial discharge capacity of 161 mAh g. -1 .

[0113] Example 5

[0114] 1. Synthesis of porous sandwich-structured solid electrolytes

[0115] 2g of polyethylene oxide with a molecular weight of 40W and 1g of lithium bis(fluorosulfonyl)imide (LiFSI) were dissolved in 20mL of acetonitrile and magnetically stirred at room temperature for 24h. This solution is denoted as solution A.

[0116] 2g of 40W polyethylene oxide and 1g of lithium bis(fluorosulfonyl)imide (LiFSI) were dissolved in 20mL of acetonitrile and magnetically stirred at room temperature for 24h. Then, 0.8g of Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Stir magnetically at room temperature for 24 hours, and this solution is denoted as solution B.

[0117] Solution A was uniformly coated onto a polytetrafluoroethylene (PTFE) plate using a 1000 μm spatula and placed in a vacuum oven at 60 °C for 24 h. After drying, a 5 cm thick layer of solution B was coated every 5 cm on the dry film. After standing for 3 min, the coating was smoothed with a 1000 μm spatula and placed in a vacuum drying oven at 60 °C for 24 h. After drying, a 5 cm thick layer of solution A was coated every 5 cm on the dry film. After standing for 3 min, the coating was smoothed with a 1000 μm spatula and placed in a vacuum drying oven at 60 °C for 24 h, resulting in a porous three-layer membrane. The microstructure of the prepared electrolyte membrane was observed using a scanning electron microscope. The pore size distribution was 1-20 μm, and the thickness was 1000 μm. The mechanical properties of the material were tested using a tensile tester at a tensile rate of 100 mm / min, and the elongation at break was as high as 100%.

[0118] 2. Assembly and testing of all-solid-state lithium-ion batteries

[0119] The synthesized porous electrolyte membrane was used as the electrolyte and assembled with lithium foil and lithium iron phosphate cathode (lithium iron phosphate: polyvinylidene fluoride: acetylene black = 8:1:1) to form a 2035 coin cell. The impedance spectrum of the resulting cell was measured at 60°C, with a frequency range of 10... 3 -10 6 Ω. The Re at 60℃ is 600Ω. At room temperature, with a charge-discharge rate of 0.1C, the initial discharge capacity is 155mAh g. -1 .

[0120] Example 6

[0121] 1. Synthesis of porous sandwich-structured solid electrolytes

[0122] 2g of polyethylene oxide with a molecular weight of 30W and 1g of lithium bis(fluorosulfonyl)imide (LiTFSI) were dissolved in 20mL of acetonitrile and magnetically stirred at room temperature for 24h. This solution is denoted as solution A.

[0123] 2g of 60W polyethylene oxide and 1g of lithium bis(fluorosulfonyl)imide (LiTFSI) were dissolved in 20mL of acetonitrile and magnetically stirred at room temperature for 24h. Then, 0.8g of Li 6.4 La3Zr 1.4 Ta0.6 O 12 Stir magnetically at room temperature for 24 hours, and this solution is denoted as solution B.

[0124] Solution A was uniformly coated onto a polytetrafluoroethylene (PTFE) plate using a 1000 μm spatula and placed in a vacuum oven at 60 °C for 24 h. After drying, a 3 cm thick layer of solution B was coated every 3 cm on the dry film. After standing for 5 min, the coating was smoothed with a 1000 μm spatula and placed in a vacuum drying oven at 60 °C for 24 h. This process was repeated to obtain a porous three-layer membrane. The microstructure of the prepared electrolyte membrane was observed using a scanning electron microscope, revealing a non-penetrating pore structure. The pore size distribution of the prepared electrolyte membrane was 1-20 μm, and the thickness was 1000 μm. The mechanical properties of the material were tested using a tensile tester. The tensile rate of the sample was 100 mm / min, and the elongation at break was as high as 110%.

[0125] 2. Assembly and testing of all-solid-state lithium-ion batteries

[0126] The synthesized porous electrolyte membrane was used as the electrolyte and assembled with lithium foil and lithium iron phosphate cathode (lithium iron phosphate: polyvinylidene fluoride: acetylene black = 8:1:1) to form a 2035 coin cell. The impedance spectrum of the resulting cell was measured at 60°C, with a frequency range of 10... 3 -10 6 Ω. The Re at 60℃ is 408Ω. At room temperature, with a charge-discharge rate of 0.1C, the initial discharge capacity is 162mAh g. -1 .

[0127] Example 7

[0128] 1. Synthesis of porous sandwich-structured solid electrolytes

[0129] 2g of polyethylene oxide with a molecular weight of 40W and 1g of lithium bis(fluorosulfonyl)imide (LiFSI) were dissolved in 20mL of acetonitrile and magnetically stirred at room temperature for 24h. This solution is denoted as solution A.

[0130] 2 g of 40 W polyethylene oxide and 1 g of lithium bis(fluorosulfonyl)imide (LiFSI) were dissolved in 20 mL of N,N-dimethylacetamide and magnetically stirred at room temperature for 24 h. Then 0.8 g of Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Stir magnetically at room temperature for 24 hours, and this solution is denoted as solution B.

[0131] Solution A was uniformly coated onto a polytetrafluoroethylene (PTFE) plate using a 1000 μm spatula and placed in a vacuum oven at 60 °C for 24 h. After drying, a 1 cm thick layer of solution B was coated onto the dry film every 1 cm. After standing for 5 min, the coating was smoothed with a 1000 μm spatula and placed in a vacuum drying oven at 60 °C for 24 h. This process was repeated to obtain a porous three-layer membrane. The microstructure of the prepared electrolyte membrane was observed using a scanning electron microscope (SEM), revealing no pore size distribution. The thickness was 1000 μm. The mechanical properties of the material were tested using a tensile tester at a tensile rate of 100 mm / min, yielding an elongation at break of 100%.

[0132] 2. Assembly and testing of all-solid-state lithium-ion batteries

[0133] The synthesized porous electrolyte membrane was used as the electrolyte and assembled with lithium foil and lithium iron phosphate cathode (lithium iron phosphate: polyvinylidene fluoride: acetylene black = 8:1:1) to form a 2035 coin cell. The impedance spectrum of the resulting cell was measured at 60°C, with a frequency range of 10... 3 -10 6 Ω. The Re at 60℃ is 605Ω. At room temperature, with a charge-discharge rate of 0.1C, the initial discharge capacity is 156mAh g. -1 .

[0134] Comparative Example 2

[0135] 1. Synthesis of porous sandwich-structured solid electrolytes

[0136] 2g of polyethylene oxide with a molecular weight of 40W and 1g of lithium bis(fluorosulfonyl)imide (LiFSI) were dissolved in 20mL of acetonitrile and magnetically stirred at room temperature for 24h. This solution is denoted as solution A.

[0137] 2 g of 40 W polyethylene oxide and 1 g of lithium bis(fluorosulfonyl)imide (LiFSI) were dissolved in 20 mL of N,N-dimethylacetamide and magnetically stirred at room temperature for 24 h. Then 0.8 g of Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Stir magnetically at room temperature for 24 hours, and this solution is denoted as solution B.

[0138] Solution A was uniformly coated onto a polytetrafluoroethylene (PTFE) plate using a 1000 μm doctor blade and placed in a vacuum oven at 60 °C for 24 h. A layer of solution B was then coated onto the dry film, left to stand for 5 min, and then smoothed with a 1000 μm doctor blade. The plate was then placed in a vacuum drying oven and heated at 60 °C for 24 h. After drying, another layer of solution A was coated onto the dry film, smoothed with a 1000 μm doctor blade, and placed in a vacuum drying oven at 60 °C for 24 h, resulting in a three-layer membrane. The microstructure of the prepared electrolyte membrane was observed using a scanning electron microscope, revealing no porous structure. The mechanical properties of the material were tested using a tensile tester at a tensile rate of 100 mm / min, yielding an elongation at break of 82%.

[0139] 2. Assembly and testing of all-solid-state lithium-ion batteries

[0140] The synthesized porous electrolyte membrane was used as the electrolyte and assembled with lithium foil and lithium iron phosphate cathode (lithium iron phosphate: polyvinylidene fluoride: acetylene black = 8:1:1) to form a 2035 coin cell. The impedance spectrum of the resulting cell was measured at 60°C, with a frequency range of 10... 3 -10 6 Ω. The Re at 60℃ is 620Ω. At room temperature, with a charge-discharge rate of 0.1C, the initial discharge capacity is 157mAh g. -1 .

[0141] The embodiments described above are merely illustrative of the detailed process of the present invention, but the present invention is not limited to the above-described process; that is, the present invention can be implemented without relying on the steps described in the above embodiments. In summary, any improvements made to the present invention by those skilled in the art, including substitutions for the raw materials and additives described in the present invention, and selections of specific implementation methods, are all within the scope of protection and disclosure of the present invention.

Claims

1. A solid electrolyte, characterized in that, The electrolyte comprises alternating A and B layers, with different materials for A and B. Each of the A and B layers contains a polymer and an alkali metal salt, and one of the A and B layers contains an inorganic filler. The solid electrolyte has multiple pores, each pore existing independently and having an irregular shape. The pores do not penetrate the layer structure of the electrolyte, and filamentous morphology runs through the pores.

2. The electrolyte according to claim 1, wherein, The solid-state electrolyte, after being assembled into a battery with a lithium iron phosphate electrode sheet, has a first discharge capacity of 160 mAh g -1 above; and / or The impedance Re of the solid electrolyte assembled with lithium iron phosphate electrode sheets at 60°C is below 500 Ω; and / or The tensile elongation at break of the solid electrolyte is greater than 100%; and / or The thickness of the solid electrolyte is 900-2000 µm.

3. The electrolyte according to claim 1 or 2, wherein, The impedance Re of the battery assembled with the solid electrolyte and lithium iron phosphate electrode sheet at 60 °C is 300-500 Ω; and / or The tensile elongation at break of the solid electrolyte is 100-150%.

4. The electrolyte according to claim 1 or 2, wherein, The aperture of the hole is 1-20 µm; and / or The electrolyte comprises N layers consisting of alternating A and B layers, where N is 2-10 layers.

5. The electrolyte according to claim 1 or 2, wherein, The electrolyte comprises N layers consisting of alternating A and B layers, where N is 3-5 layers.

6. The electrolyte according to claim 1 or 2, wherein, Layer A and layer B each contain a polymer and an alkali metal salt, and layer B contains an inorganic filler; the electrolyte has an AB layer arrangement structure, a BA layer arrangement structure, an ABA layer arrangement structure, a BAB layer arrangement structure, an ABAB layer arrangement structure, a BABA layer arrangement structure, an ABABA layer arrangement structure, a BABAB layer arrangement structure, an ABABAB layer arrangement structure, or a BABABA layer arrangement structure.

7. The electrolyte according to claim 1 or 2, wherein, The polymer is selected from one or more of polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, and poly(vinylidene fluoride-hexafluoropropylene); and / or Alkali metal salts are selected from one or more of sodium, potassium, and lithium salts; and / or Inorganic fillers are alumina, silica and Li 6.4 La3Zr 1.4 Ta 0.6 O 12 one or more of.

8. The electrolyte according to claim 7, wherein, The polymer is selected from one or more polyethylene oxides with a molecular weight of 40 W, 60 W, 80 W, and 100 W; and / or Alkali metal salts are selected from lithium salts.

9. The electrolyte according to claim 7, wherein, The lithium salt is selected from one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoroformyl)imide, and lithium perchlorate.

10. A method for preparing the solid electrolyte according to any one of claims 1-9, wherein, The method includes: a) Forming a slurry M from the polymer and alkali metal salt; b) Forming a slurry N from polymers, alkali metal salts, and inorganic fillers; c) Coat slurry M or slurry N into a film and heat until the solvent evaporates; apply another layer of different slurry to the surface of the film at fixed points, hold the slurry at the fixed points, scrape the slurry flat, and heat until the solvent evaporates; repeat the fixed-point coating, holding, and scraping of another layer of slurry as needed, and heat until the solvent evaporates; so that the electrolyte includes an interleaved multilayer structure; the fixed-point coating method is to apply a layer of slurry with a thickness of 2-4 cm every 2-4 cm on the dry film.

11. The preparation method according to claim 10, wherein, In slurry M and slurry N, The polymer is selected from one or more of polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, and poly(vinylidene fluoride-hexafluoropropylene); and / or Alkali metal salts are each selected from one or more of sodium, potassium, and lithium salts; and / or The solvents are each selected from one or more of acetonitrile and N,N-dimethylacetamide; and / or The inorganic filler is selected from alumina, silicon dioxide and Li. 6.4 La3Zr 1.4 Ta 0.6 O 12 One or more of them.

12. The preparation method according to claim 11, wherein, The polymer is selected from one or more polyethylene oxides with a molecular weight of 40 W, 60 W, 80 W, and 100 W; and / or Alkali metal salts are selected from lithium salts.

13. The preparation method according to claim 11, wherein, The lithium salt is selected from one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoroformyl)imide, and lithium perchlorate.

14. The preparation method according to claim 10 or 11, wherein, In slurry M, the polymer content is 0.05-0.1 g / mL; the alkali metal salt content is 0.03-0.05 g / mL. In slurry N, the polymer content is 0.05-0.1 g / mL; the inorganic filler content is 0.01-0.04 g / mL; and the alkali metal salt content is 0.03-0.05 g / mL.

15. The method according to any one of claim 10 or 11, wherein, The thickness of the scraper used for leveling is 800-1200 µm; The time for maintaining the position at the fixed point is 5-10 minutes; The heating method for heating until the solvent evaporates is vacuum drying, with a heating temperature of 40-60 ℃ and a heating time of 24-48 h.

16. The use of the solid electrolyte according to any one of claims 1-9 or the solid electrolyte prepared by the method according to any one of claims 10-15 in a battery.

17. A lithium-ion battery, characterized in that, The battery is assembled from a solid electrolyte, a positive electrode, and a lithium electrode. The solid electrolyte is the solid electrolyte described in any one of claims 1-9 or the solid electrolyte prepared by the method described in any one of claims 10-15.

18. The lithium-ion battery according to claim 17, wherein, The positive electrode contains lithium iron phosphate, polyvinylidene fluoride, and acetylene black in a mass ratio of 1-50:0.1-10:1, and the current collector is aluminum foil; and / or The initial discharge capacity of lithium-ion batteries is 160 mAh g. -1 The above; and / or The impedance Re of a lithium-ion battery at 60°C is below 500Ω.

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