Composite solid electrolyte film and preparation method thereof, battery and electric equipment

Abstract

The invention provides a composite solid electrolyte film and a preparation method thereof, a battery and electric equipment, and relates to the field of lithium batteries. The composite solid electrolyte film comprises a polymer composite material and a base film with pores, the polymer composite material fills part or all of the pores and covers part or all of the surface of the base film; the base membrane comprises the following raw materials: an inorganic ceramic solid electrolyte material and a binder. The preparation method of the composite solid electrolyte film comprises the following steps: providing a base film; mixing a lithium salt, an ionic liquid, a cross-linking agent and an initiator to obtain a polymer composite material precursor solution; the polymer composite material precursor solution is arranged on part or all of the pores and part or all of the surface of the base membrane; and performing in-situ curing to obtain the composite solid electrolyte film. The composite solid electrolyte thin film provided by the invention is high in ionic conductivity, high in ionic migration coefficient, high in tensile strength and good in matching contact with a positive electrode and a negative electrode.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium batteries, in particular to a composite solid-state electrolyte film, a preparation method thereof, a battery and an electrical equipment. BACKGROUND

[0002] At present, lithium ion batteries play a vital role in various fields from portable electronic devices to grid-level energy storage, and have become an indispensable part of human life. However, traditional lithium ion batteries have gradually failed to meet future power demands due to their low energy density, flammable organic electrolyte, and explosive characteristics. Developing all-solid-state lithium batteries (ASSB) with solid-state electrolyte instead of liquid electrolyte is one of the effective strategies to overcome these bottlenecks. Solid-state electrolyte has non-flammable characteristics and can prevent lithium metal anode from pulverization and dendrite formation.

[0003] Solid-state electrolytes are mainly divided into solid polymer electrolytes, inorganic ceramic electrolytes, and composite polymer-ceramic electrolytes. Among them, polymer electrolytes have good mechanical flexibility and close contact with electrodes, and are easy to prepare into thin films, but have low ion conductivity at room temperature, insufficient electrochemical stability, and poor flammability, which seriously limits their practical application. At the same time, inorganic ceramic solid electrolytes have high ion conductivity at room temperature, strong electrochemical stability, and are not flammable, which has great application potential in high-safety lithium metal batteries. However, the interface contact between ceramic solid-state electrolyte and electrode is poor, and the ceramic solid-state electrolyte is usually thick and fragile, and has poor processing ability.

[0004] The combination of polymer and inorganic ceramic becomes the mainstream solution for solid-state batteries, and the composite solid-state electrolyte is composed of polymer, ceramic filler and lithium salt. Because of its high ion conductivity, good interface compatibility, high flexibility and easy processability, it is considered as an ideal material for manufacturing all-solid-state batteries.

[0005] Currently, composite solid-state electrolytes mainly add inorganic particles to polymer electrolytes or substrates to reduce polymer crystallinity and increase ion conductivity, such as using PEO (polyethylene oxide) or PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene copolymer) as a substrate, and LATP (lithium titanium aluminum phosphate), LLZTO (tantalum-doped lithium lanthanum zirconium oxide) or SiO2 (silicon dioxide) as inorganic particles. Although such composite solid-state electrolytes can increase the ion conductivity (>0.5 mS / cm) to a certain extent, the ion conductivity is still low (<1 mS / cm), and the ion transference number is low (t+<0.6), which limits the development of solid-state batteries. SUMMARY The purpose of the present application is to provide a composite solid-state electrolyte film, a preparation method thereof, a battery and an electrical equipment to solve the above problems.

[0006] To achieve the above object, the application adopts the following technical solutions: A composite solid electrolyte film, comprising a polymer composite and a base film with pores; The polymer composite fills part or all of the pores and covers part or all of the surface of the base film; The raw material of the base film comprises an inorganic ceramic solid electrolyte material and a binder; The polymer composite comprises, calculated based on the total mass of its raw material as 100%, 3%-10% of lithium salt, 85%-95% of ionic liquid, 1%-5% of cross-linking agent, and 0.1%-0.5% of initiator, the ionic liquid comprises imidazole ionic liquid, and the molecular weight of the cross-linking agent is 150-2000.

[0007] Preferably, the composite solid electrolyte film satisfies one or more of the following conditions: (1) The mass ratio of the base film to the lithium salt-containing polymer is (85-95):(3-14); (2) The binder comprises one or more of PTFE (polytetrafluoroethylene), PVDF (polyvinylidene fluoride), and PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene copolymer); (3) The amount of the binder is 1%-5% of the mass of the inorganic ceramic solid electrolyte material; (4) The inorganic ceramic solid electrolyte material comprises halide inorganic ceramic solid electrolyte and / or sulfide inorganic ceramic solid electrolyte; Preferably, the halide inorganic ceramic solid electrolyte comprises one or more of LiYCl, LiInCl, and LiAlClO; Preferably, the sulfide inorganic ceramic solid electrolyte comprises one or more of Li 10 GeP2S 12 , Li6PS5Cl, and 70Li2S•30P2S5; (5) The ionic conductivity of the inorganic ceramic solid electrolyte material is not less than 1 mS / cm.

[0008] Preferably, the composite solid electrolyte film satisfies one or more of the following conditions: (1) The lithium salt comprises one or more of fluorine-containing lithium salt, boron-containing lithium salt, and phosphorus-containing lithium salt, preferably one or more of LiTFSI (lithium bis-trifluoromethanesulfonimide), LiFSI (lithium bis-fluorosulfonimide), LiBF4 (lithium tetrafluoroborate), LiDFOB (lithium difluoro oxalate borate), LiDFBOP (lithium difluoro di-oxalate phosphate), LiBOB (lithium bis-oxalate borate), and LiPO2F2 (lithium difluorophosphate); (2) the imidazole ionic liquid comprises one or more of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI); (3) the cross-linking agent comprises one or more of acrylate cross-linking agents, preferably polyethylene glycol dimethacrylate (PEGDMA), ethoxylated trimethylpropane triacrylate (ETPTA), diethylene glycol diacrylate (DEGDA); (4) the initiator comprises azobisisobutyronitrile (AIBN).

[0009] Preferably, the composite solid electrolyte thin film satisfies one or more of the following conditions: (1) the porosity of the base film is not higher than 20%, preferably 5%-15%; (2) the thickness of the base film is 15 μm-90 μm, preferably 15 μm-30 μm; (3) the average thickness of the single side of the surface of the base film covered by the polymer composite material is 1-5 μm; (4) the tensile strength of the composite solid electrolyte thin film is not less than 2 MPa, preferably 2-8 MPa; (5) the ionic conductivity of the composite solid electrolyte thin film is not less than 1 mS / cm, preferably 1-5 mS / cm; (6) the ionic transference number of the composite solid electrolyte thin film is not less than 0.7, preferably 0.7-0.9.

[0010] The application also provides a preparation method of the composite solid electrolyte thin film, comprising: providing the base film; mixing the lithium salt, the ionic liquid, the cross-linking agent, and the initiator to obtain a polymer composite material precursor solution; arranging the polymer composite material precursor solution in part or all of the pores and part or all of the surface of the base film; solidifying in situ to obtain the composite solid electrolyte thin film.

[0011] Preferably, the preparation method of the base film comprises: mixing the inorganic ceramic solid electrolyte material and the binder to obtain a mixture, and then performing fibrillation on the mixture to obtain a fibrillated material, and pressing the fibrillated material to obtain the base film; Preferably, the fibrillation comprises: mixing the mixture at-20℃ to-10℃ by using an air flow mill, and then extruding the mixture by using a screw extruder to obtain the fibrillated material.

[0012] Preferably, the arrangement comprises: placing the polymer composite precursor solution on the surface of the base film, and then performing negative pressure infiltration; Preferably, the pressure of the negative pressure infiltration is -10 MPa to -20 MPa, and the time is 2 h to 6 h. Preferably, the mass ratio of the polymer composite precursor solution to the base film is 1: (4-10).

[0013] Preferably, the temperature of the in-situ curing is 70℃ to 90℃, and the time is 2-4h. The in-situ curing is performed under vacuum conditions.

[0014] The application also provides a battery comprising the composite solid electrolyte film.

[0015] The application also provides a battery comprising the composite solid electrolyte film.

[0016] Compared with the prior art, the application has the following beneficial effects: The composite solid electrolyte film provided by the application uses inorganic ceramic solid electrolyte material and a binder as raw materials of the base film, which provides a material basis for the composite solid electrolyte film to have a high ionic conductivity and a lithium ion transference coefficient; the polymer composite material fills part or all of the pores of the base film and covers part or all of the surface of the base film, which on the one hand can increase the tensile strength (> 2 MPa) of the composite solid electrolyte film through physical and chemical cross-linking, so that the final thickness of the composite solid electrolyte film can be less than 30 μm, and on the other hand, the lithium salt in the raw materials of the polymer composite material dissolves into the ionic liquid to fill the gaps in the ceramic internal voids, improve the organic / inorganic interface compatibility, make the internal lithium ion channel smoother, and reduce the internal interface impedance of the electrolyte; on the other hand, after being assembled into a battery, the polymer composite material forms an elastic CEI or SEI on the surface of the positive and negative electrodes to adapt to the volume change in the charging and discharging process, increase the cycle life of the battery, and improve the interface stability. In addition, a large amount of imidazole ionic liquid and small molecules (molecular weight 100-2000) are used (raw material ratio 85%-90%) to achieve high flowability and low viscosity, which is convenient for filling the pores of the base film.

[0017] The preparation method of the composite solid electrolyte film provided by the application has low process cost and is beneficial to industrial large-scale production.

[0018] The battery and the electrical equipment provided by the application have excellent electrical performance. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced as follows. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope of the present application.

[0020] Figure 1 An appearance diagram of a ceramic-based film converted into a composite film; Figure 2 A schematic diagram of a lithium ion transmission path inside a composite film; Figure 3 A real front view of the base film obtained in Example 1; Figure 4 An ion conductivity impedance diagram corresponding to Example 1; Figure 5 A battery charge-discharge diagram corresponding to Example 1; Figure 6 A coulomb efficiency and capacity release diagram corresponding to Example 1; Figure 7 An ion conductivity impedance diagram corresponding to Comparative Example 1; Figure 8 A battery charge-discharge diagram of Comparative Example 1; Figure 9 A lithium symmetric impedance diagram of Example 1 and Comparative Example 1; Figure 10 A comparison diagram of electrolyte film tensile strength of Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0021] In order to better illustrate the technical solutions provided by the present application, before the embodiments, the technical solutions are stated as a whole, as follows: A composite solid-state electrolyte film, comprising a polymer composite material and a base film having pores; The polymer composite material fills part or all of the pores and covers part or all of the surface of the base film; The raw material of the base film comprises an inorganic ceramic solid-state electrolyte material and a binder; the polymer composite material comprises, calculated based on the total mass of the raw material as 100%, lithium salt 3%-10%, ionic liquid 85%-95%, crosslinking agent 1%-5% and initiator 0.1%-0.5%, the ionic liquid comprises imidazole ionic liquid, and the molecular weight of the crosslinking agent is 150-2000.

[0022] The polymer composite material is selected by the formula, first, to ensure that the lithium salt has a good concentration (the lithium salt concentration referred to in the application refers to the mass content of the lithium salt in the ionic liquid) dissolved in the ionic liquid, has a lower viscosity (25-50 cp), the polymer composite material can effectively penetrate into the internal pores of the ceramic base film, ensure the smoothness of lithium ion conduction, and the crosslinking agent effectively improves the strength of the composite film. And the polymer composite material formula exceeds this proportion, such as too high lithium salt concentration, will cause the viscosity of the polymer composite material precursor solution to be too large, no matter whether it is used for conventional coating penetration, solution immersion penetration, or negative pressure penetration, it is impossible to completely fill the pores of the base film, and too low lithium salt concentration, even if the pores are filled, it is impossible to ensure effective lithium ion conduction between inorganic particles, etc., which affects the comprehensive performance of the composite solid electrolyte film. The ionic liquid is low in amount, the viscosity of the polymer composite material precursor solution is high, and the base film cannot be effectively filled; the ionic liquid is high in amount, and it is difficult to bind and disperse in the polymer composite material. The molecular weight of the crosslinking agent is too large, which will make the viscosity of the polymer composite material precursor solution too large and not conducive to filling the base film; and the molecular weight is too small, which cannot bind the ionic liquid, and affects the strength of the final composite solid electrolyte film.

[0023] The polymer composite material fills part or all of the pores and part or all of the surface of the base film, and the lithium guide material fills the pores in the ceramic film, which can construct a good ion path; due to the presence of the crosslinking agent, the tensile strength of the film can be greatly improved (>2 MPa); the ionic liquid coated ceramic powder (high ion conductive sulfide is generally unstable) can prevent direct contact with the positive and negative electrodes, which can increase the interface stability and compatibility.

[0024] The composite solid electrolyte film provided by the application is different from the mainstream composite electrolyte film in that it does not contain organic solvents, has low volatility, is easy to prepare, can be filled with lithium-containing polymer into the pores of the base film by negative pressure penetration, has high stability, and constructs a composite solid electrolyte film with ceramic electrolyte as the main body and polymer as the guest to cooperatively guide lithium ions.

[0025] The appearance of the ceramic base film converted into a composite film is shown in Figure 1 .

[0026] Optionally, the mass fraction of lithium salt in the raw material of the polymer composite material can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any value between 3% and 10%, the mass fraction of ionic liquid can be 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, or any value between 85% and 95%, the mass fraction of crosslinking agent can be 1%, 2%, 3%, 4%, 5%, or any value between 1% and 5%, and the mass fraction of initiator can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or any value between 0.1% and 0.5%. The molecular weight of the crosslinking agent can be 150, 200, 500, 1000, 1500, 2000, or any value between 150 and 2000.

[0027] In an optional embodiment, the composite solid electrolyte film satisfies one or more of the following conditions: (1) the mass ratio of the base film to the polymer composite material is (85-95):(3-14); Currently, there is no report on high ceramic composite films with a content of more than 85%, and generally, the strength of a >50wt% film is very low, <0.8MPa. To achieve such a high content of inorganic ceramic material with high ionic conductivity, it is necessary to systematically solve the problems of low film strength, difficulty in loading polymer, and low loading amount.

[0028] Optionally, in the raw material of the composite solid electrolyte film, the mass of the inorganic ceramic solid electrolyte material to the polymer composite material can be 85:14, 90:5, 95:3, or any value between (85-95):(3-14); (2) the binder includes one or more of PTFE, PVDF, and PVDF-HFP; (3) the amount of the binder is 1%-5% of the mass of the inorganic ceramic solid electrolyte material; Optionally, the amount of the binder can be 1%, 2%, 3%, 4%, 5%, or any value between 1% and 5% of the mass of the inorganic ceramic solid electrolyte material; (4) the inorganic ceramic solid electrolyte material includes a halide inorganic ceramic solid electrolyte and / or a sulfide inorganic ceramic solid electrolyte; Optionally, the halide inorganic ceramic solid electrolyte includes one or more of LiYCl, LiInCl, and LiAlClO; Optionally, the sulfide inorganic ceramic solid electrolyte includes one or more of Li 10 GeP2S 12 , Li6PS5Cl, and 70Li2S•30P2S5; (5) The inorganic ceramic solid electrolyte material has an ionic conductivity of not less than 1 mS / cm.

[0029] In an optional embodiment, the composite solid electrolyte film satisfies one or more of the following conditions: (1) The lithium salt comprises one or more of a fluorine-containing lithium salt, a boron-containing lithium salt, and a phosphorus-containing lithium salt, preferably one or more of LiTFSI, LiFSI, LiBF4, LiDFOB, LiDFBOP, LiBOB, and LiPO2F2; The use of lithium salts containing F, B, or P can form a tough CEI or SEI with the positive and negative electrodes, adapting to the volume change of the solid-state battery during charging and discharging.

[0030] It is particularly important to note that the present application preferably uses a dual lithium salt system, such as any one of LiTFSI and LiFSI in combination with any one of LiDFOB and LiDFBOP to form a dual lithium salt system (measured by total moles, 0.8 LiFSI + 0.2 LiDFOB or 0.6 LiFSI + 0.4 LiDFBOP, etc.). The main advantage is that LiFSI has higher ionic conductivity, but is unstable to lithium metal and corrodes the positive electrode aluminum foil, while LiDFOB and LiDFBOP have lower ionic conductivity but have the function of passivating lithium metal and aluminum foil. The dual salt system can combine the advantages of both, such as: ① LiDFOB and LiDFBOP, which contain oxalate salts, can easily form a dense oxalate alkyl organic salt component or inorganic lithium phosphate salt with Li metal, forming a dense and stable SEI layer to prevent continuous reaction of lithium metal with LiTFSI and LiFSI (LiTFSI and LiFSI react with lithium metal to produce dendrites) ② LiDFOB and LiDFBOP can passivate Al foil to prevent continuous corrosion of aluminum foil by LiTFSI and LiFSI. In summary, the combination of active lithium salts with high ionic conductivity and stable SEI formed with lithium maximizes the performance of the dual salt system.

[0031] (2) The imidazolium ionic liquid comprises one or more of 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI); The particularity of introducing only imidazolium ionic liquid is that imidazolium ionic liquid has low symmetry, weak intermolecular forces, and uniform distribution of cationic charge, which can promote the dissolution of Li +The solvation structure of the solvent and the prevention of free anion formation help to improve ion conductivity, promote the derivation of anion interface layer, and enhance the stability of electrolyte. The imidazole ionic liquid containing one or more of F, B, and P elements is preferred because the introduction of BF4, F, or P elements forms an interface layer such as LiF / LiF / LiPO3 during the contact of electrolyte with lithium metal, prevents the contact of lithium dendrites with sulfide and halide solid electrolyte particles, and causes the deterioration of the main substrate performance of ceramic.

[0032] (3) The crosslinking agent includes an acrylate crosslinking agent, and preferably one or more of polyethylene glycol dimethacrylate PEGDMA (molecular weight 1079.27), ethoxylated trimethylpropane triacrylate ETPTA (molecular weight 428), and diethylene glycol diacrylate DEGDA (molecular weight 214.2152). In addition, the imidazole ionic liquid contains N-H bonds, and the polymer composite material contains ether oxygen bonds after the crosslinking agent reacts, both of which can form hydrogen bonds, further facilitating the binding and uniform dispersion of the high content of ionic liquid used in the polymer composite material.

[0033] During the conversion of the crosslinking agent monomer into a long-chain polymer molecule, the lithium salt dissociates in the ionic liquid and can then be anchored in the polymer network, assisting in the dissociation and complexation of lithium ions during charging and discharging, promoting the ion conductivity of the composite solid electrolyte film. When the polymer composite material is filled in the pores as a filler, it provides a fast transmission path and a stable permeation network for lithium ion migration.

[0034] This filler also has good compatibility with the ceramic particle interface. From the overall structural framework, the ceramic body serves as the main transmission lithium ion as the substrate architecture, and the polymer composite material serves as the auxiliary support for lithium ion transmission, constructing a composite solid electrolyte film with ceramic electrolyte as the main body and polymer composite material as the guest to cooperatively guide lithium ions.

[0035] The schematic diagram of the lithium ion transmission path inside the composite film is shown in Figure 2 .

[0036] (4) The initiator includes azobisisobutyronitrile AIBN.

[0037] The selection of the initiator is only required to be able to initiate the polymerization reaction of the crosslinking agent; in the case of selecting one or more of polyethylene glycol dimethacrylate PEGDMA, ethoxylated trimethylpropane triacrylate ETPTA, and diethylene glycol diacrylate DEGDA as the crosslinking agent, AIBN is preferably used as the initiator to better achieve the polymerization reaction of the crosslinking agent.

[0038] In an alternative embodiment, the composite solid electrolyte film satisfies one or more of the following conditions: (1) the porosity of the base film is not higher than 20%, preferably 5%-15%; Optionally, the porosity of the base film can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20% or any value not higher than 20%; The porosity is relatively low, and therefore higher requirements are placed on the composition and amount of the polymer composite precursor solution and the loading method. It should be understood that the polymer composite of the present application not only achieves porosity filling of a base film with a large filling difficulty and low porosity, but also has good filling effect for a base film with a large porosity (for example, 20%-90%, specifically 21%, 30%, 50%, 70%, 90%, etc.) and low filling difficulty.

[0039] (2) the thickness of the base film is 15 μm-90 μm, preferably 15 μm-30 μm; The presence of the polymer composite enables a thinner film thickness under the conditions of a high content of inorganic ceramic solid electrolyte material and high strength, and the final composite solid electrolyte film thickness can be lower than 30 μm.

[0040] Optionally, the thickness of the base film can be 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm or any value between 15 μm and 90 μm; (3) the average thickness of the single side of the base film covered with the polymer composite is 1-5 μm; The polymer composite forms a structure similar to a protective layer on the surface of the base film, which can improve the stability of the composite solid electrolyte film.

[0041] Optionally, the average thickness of the single side of the base film covered with the polymer composite can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or any value between 1 μm and 5 μm; (4) the tensile strength of the composite solid electrolyte film is not less than 2 MPa, preferably 2-8 MPa; (5) the ionic conductivity of the composite solid electrolyte film is not less than 1 mS / cm, preferably 1-5 mS / cm; (6) the ion transference number of the composite solid electrolyte film is not less than 0.7, preferably 0.7-0.9.

[0042] The application also provides a preparation method of the composite solid electrolyte film, comprising: providing a base film; mixing the lithium salt, the ionic liquid, the cross-linking agent and the initiator to obtain a polymer composite precursor solution; arranging the polymer composite precursor solution in part or all of the pores and part or all of the surface of the base film; in-situ curing to obtain the composite solid electrolyte film.

[0043] In an optional embodiment, the preparation method of the base film comprises: mixing the inorganic ceramic solid electrolyte material and the binder to obtain a mixture, then fibrillating the mixture to obtain a fibrillated material, and pressing the fibrillated material to obtain the base film; Preferably, the fibrillation comprises: mixing the mixture at-20℃ to-10℃ by air flow mill, and then extruding the mixture by a screw extruder to obtain the fibrillated material.

[0044] The mixing can be performed by, for example, air flow mill mixing. The fibrillation can be performed by, for example, processing the mixed material by a screw extruder.

[0045] The prior art (for example, patent document CN112421114A) discloses mixing and dispersing a solid electrolyte and a fiberized binder, and performing shear mixing, the fiberized binder is changed from a fluffy state to a spider web state, thereby winding and bonding the particles of the solid electrolyte, and performing hot rolling, thereby partially solving the problem of poor flexibility of the inorganic ceramic electrolyte. However, there are still problems of pores between the particles of the solid electrolyte, which causes poor ion conductivity, and the ionic conductivity is only (2.1×10 -4 S / cm), which cannot meet the requirement of high ionic conductivity in the practical application of solid-state batteries.

[0046] The application, by means of fibrillation, causes the binder to adhere to the surface of the inorganic ceramic solid electrolyte material, to form a fibrillated material “with the inorganic ceramic solid electrolyte material as the core, and the binder as a long-chain organic carbon material growing on the surface of the core”, and then by dry forming, the proportion of the inorganic ceramic solid electrolyte material in the base film can reach and exceed 85wt%, and finally the ionic conductivity of the composite solid electrolyte film is ensured to be >1mS / cm and the ion transference coefficient is ≥0.8.

[0047] The simple dry preparation of the film has a maximum tensile strength of 0.8MPa, exhibits low tensile strength, and exhibits unstable Li contact characteristics, and cannot meet the requirements of high tensile strength and chemical stability in practical applications.

[0048] In an optional embodiment, the arranging comprises: The polymer composite precursor solution is placed on the surface of the base film, and then negative pressure infiltration is performed. In an optional embodiment, the pressure of the negative pressure infiltration is -10 MPa to -20 MPa, and the time is 2 h to 6 h. Optionally, the pressure of the negative pressure infiltration can be -10 MPa, -15 MPa, -20 MPa, or any value between -10 MPa and -20 MPa, and the time can be 2 h, 3 h, 4 h, 5 h, 6 h, or any value between 2 h and 6 h. In an optional embodiment, the mass ratio of the polymer composite precursor solution to the base film is 1: (4-10).

[0049] Since the base film is prepared by the dry method in the present application, the porosity is low (≤20%), and the pores are small. The traditional immersion method cannot fill the polymer composite into the pores, but only on the surface of the substrate, resulting in poor comprehensive performance of the composite film. There is still a great technical difficulty. The negative pressure infiltration method adopted in the present application can achieve full interstitial filling of the polymer composite into the internal pores of the base film.

[0050] The polymer composite precursor solution is cast onto the base film, and during the subsequent processing process, there may be some loss. In order to ensure the proportion of the polymer composite in the final obtained composite solid electrolyte thin film, an excess amount is generally used to determine the amount of polymer precursor solution.

[0051] Optionally, the mass ratio of the polymer composite precursor solution to the base film can be 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, or any value between 1: (4-10).

[0052] In an optional embodiment, the in-situ curing temperature is 70℃-90℃, and the time is 2-4h. The in-situ curing is performed under vacuum conditions.

[0053] Optionally, the in-situ curing temperature can be 70℃, 80℃, 90℃, or any value between 70℃ and 90℃, and the time can be 2h, 3h, 4h, or any value between 2h and 4h. The present application also provides a battery comprising a composite solid electrolyte thin film.

[0054] Non-limiting examples, the battery can be a solid-state battery or a semi-solid-state battery, and the structure can be, for example, NCM / composite solid electrolyte thin film / Li foil.

[0055] The present application also provides an electrical equipment comprising a battery.

[0056] The power consuming device referred to in the present application refers to a device that directly or indirectly uses the above-mentioned battery for power supply. Non-limiting examples, the power consuming device can be an electric vehicle, an electric bicycle, a mobile power supply, an energy storage system, etc.

[0057] The embodiments of the present application will be described in detail below with specific examples, but those skilled in the art will understand that the following examples are only for illustration of the present application and should not be regarded as limiting the scope of the present application. If the specific conditions are not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0058] Example 1 The present example provides a composite solid electrolyte film, which comprises a polymer composite material and a base film. The thickness of the base film is 20 μm, the porosity is 15% tested by a true density instrument, the polymer composite material is filled in the pores of the base film and covers the surfaces on both sides of the base film, and the average thickness of the single side covered with the polymer composite electrolyte on both sides of the base film is 1 μm.

[0059] The polymer composite material is composed of 6% lithium salt (specifically LiFSI and LiDFBOP with a mass ratio of 4:1), 92% ionic liquid (specifically 1-ethyl-3-methylimidazole tetrafluoroboric acid), 1.7% crosslinking agent (specifically ETPTA) and 0.3% initiator (specifically AIBN), calculated based on the total mass of raw materials as 100%. The raw materials of the base film are composed of inorganic ceramic solid electrolyte material Li6PS5Cl and adhesive PTFE, and the amount of the adhesive is 3% of the mass of the inorganic ceramic solid electrolyte material. The mass ratio of the inorganic ceramic solid electrolyte material to the polymer composite material is 10:1.46 (about 85:12.4).

[0060] The preparation method of the above-mentioned composite solid electrolyte film is as follows: 10 g of Li6PS5Cl electrolyte and 0.3 g of PTFE were mixed under low temperature (-10℃) by airflow milling, then extruded by a double screw with a linear speed of 1 m / s, and the extruded powder was put into a hot roller press to be rolled into a base film with a thickness of 20 μm at a hot roller pressing temperature of 80℃ (the actual photo is shown in Figure 3 The polymer composite material precursor solution was prepared: 4.8 g of LiFSI and 1.2 g of LiDFBOP were added to 92 g of 1-ethyl-3-methylimidazole tetrafluoroboric acid ionic liquid, then 1.7 g of ETPTA (molecular weight 428) was added as the total mass of the polymer to mix at 400 rpm for 6 h, and then 0.3 g of AIBN was added as an initiator to mix at 200 rpm for 2 h to obtain the polymer composite material precursor solution. ​

[0061] Take 2g of the above polymer composite precursor liquid on both sides of the above base film, put into vacuum negative pressure (-15MPa) infiltration treatment for 10h, after fully infiltrated, take out and put into 80℃ curing for 2h, get high ceramic content composite solid electrolyte film, compared with the base film, the weight gain is 1.46g (data details see table 1, same below).

[0062] Example 2 The example provides a kind of composite solid electrolyte film, including polymer composite material and base film.The thickness of base film is 20 μm, and porosity is 15% using true density instrument test, polymer composite material fills in the porosity of base film and covers on the surface of both sides of base film, and the average thickness of single side of polymer composite electrolyte covered on both sides of base film is 1 μm.

[0063] The polymer composite material is composed of 3% lithium salt (specifically LiFSI and LiDFBOP with a mass ratio of 4:1), 95% ionic liquid (specifically 1-ethyl-3-methylimidazole tetrafluoroboric acid), 1.8% crosslinking agent (specifically ETPTA) and 0.2% initiator (specifically AIBN), calculated based on the total mass of raw materials as 100%. The raw materials of the base film are composed of inorganic ceramic solid electrolyte material Li6PS5Cl and adhesive PTFE, and the amount of adhesive is 3% of the mass of inorganic ceramic solid electrolyte material. The mass ratio of inorganic ceramic solid electrolyte material to polymer composite material is 10:1.51 (90:13.59).

[0064] The preparation method of the above-mentioned composite solid electrolyte film is as follows: Mix 10g Li6PS5Cl electrolyte and 0.3g PTFE at low temperature (-10℃) in an air flow mill, then extrude with a double screw rod linear velocity of 1m / s, and put the extruded powder into a hot roller press to roll into a base film of 20μm for standby; Prepare polymer composite precursor liquid: add 2.4g LiFSI and 0.6g LiDFBOP into 95g 1-ethyl-3-methylimidazole tetrafluoroboric acid ionic liquid, then add 1.8g ETPTA and mix at 400rpm for 6h, then add 0.2g AIBN as initiator and mix at 200rpm for 2h to obtain polymer composite precursor liquid.

[0065] Take 2g of the above polymer composite precursor liquid on both sides of the above base film, put into vacuum negative pressure (-15MPa) infiltration treatment for 10h, after fully infiltrated, take out and put into 80℃ curing for 2h, get high ceramic content composite solid electrolyte film, compared with the base film, the weight gain is 1.46g (data details see table 1, same below).

[0066] Example 3 The embodiment provides a composite solid electrolyte film, which comprises a polymer composite material and a base film. The thickness of the base film is 20 mu m, the porosity is 15% tested by a true density instrument, the polymer composite material is filled in the pores of the base film and covers the surfaces on both sides of the base film, and the average thickness of the single side of the base film covered with the polymer composite electrolyte is 1 mu m.

[0067] The polymer composite material is composed of 10% of a lithium salt (specifically, LiFSI and LiDFBOP with a mass ratio of 4:1), 85% of an ionic liquid (specifically, 1-ethyl-3-methylimidazole tetrafluoroboric acid), 4.6% of a crosslinking agent (specifically, ETPTA) and 0.4% of an initiator (specifically, AIBN), with the total mass of raw materials being 100%. The raw materials of the base film are composed of inorganic ceramic solid electrolyte material Li6PS5Cl and a binder PTFE, and the amount of the binder is 3% of the mass of the inorganic ceramic solid electrolyte material. The mass ratio of the inorganic ceramic solid electrolyte material to the polymer composite material is 10:1.48 (90:13.32).

[0068] The preparation method of the composite solid electrolyte film is as follows: 10g of Li6PS5Cl electrolyte and 0.3g of PTFE are fully mixed in airflow milling at low temperature (-10 DEG C), and then extruded by using a double screw rod with a linear velocity of 1m / s, and the extruded powder is placed in a hot roller press to be rolled into a base film with a thickness of 20 mu m for standby; The polymer composite material precursor solution is configured as follows: 8g of LiFSI and 2g of LiDFBOP are added into 85g of 1-ethyl-3-methylimidazole tetrafluoroboric acid ionic liquid, then 4.6g of ETPTA is added and mixed at 400rpm for 6h, and then 0.4g of AIBN is added as an initiator and mixed at 200rpm for 2h to obtain the polymer composite material precursor solution.

[0069] 2g of the polymer composite material precursor solution is coated on both sides of the inorganic film prepared by the dry method, and then placed in a vacuum negative pressure (-15MPa) infiltration treatment for 10h, so that the polymer composite material is fully infiltrated, and then taken out and placed in a solidification treatment at 80 DEG C for 2h to obtain a composite solid electrolyte film with high ceramic content, and the weight of the composite solid electrolyte film is increased by 1.48g compared with the base film.

[0070] Embodiment 4 Different from embodiment 1, Li6PS5Cl is replaced by LiYCl. The porosity of the obtained base film is 14%.

[0071] Embodiment 5 Different from embodiment 1, Li6PS5Cl is replaced by Li 10 GeP2S 12 The porosity of the obtained base film is 15%.

[0072] Example 6 The difference from Example 1 is that the lithium salt (4.8 g LiFSI and 1.2 g LiDFBOP) is replaced by 6 g LiBOB.

[0073] Example 7 The difference from Example 1 is that the lithium salt (4.8 g LiFSI and 1.2 g LiDFBOP) is replaced by 6 g LiTFSI.

[0074] Example 8 The difference from Example 1 is that the lithium salt (4.8 g LiFSI and 1.2 g LiDFBOP) is replaced by 6 g LiPO2F2.

[0075] Example 9 The difference from Example 1 is that the ionic liquid is replaced by 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.

[0076] Example 10 The difference from Example 1 is that the thickness of the base film is 15 μm. The rolling method is used for pressing, and the rolling temperature is 40 °C, so that the porosity of the base film is 20%.

[0077] Example 11 The difference from Example 1 is that the thickness of the base film is 90 μm. The pressing is performed by putting into a hot isostatic press, the pressure is set to 400 Mpa, and the temperature is 80 °C. After pressing for 2 h, the porosity of the base film is 5%.

[0078] Example 12 The difference from Example 1 is that only single-sided setting is made, and the thickness is 5 μm.

[0079] Example 13 The difference from Example 1 is that the negative pressure penetration pressure is -10 MPa.

[0080] Example 14 The difference from Example 1 is that the negative pressure penetration pressure is -20 MPa.

[0081] Example 15 The difference from Example 1 is that the crosslinking agent is polyethylene glycol, and the molecular weight is 200.

[0082] Example 16 The difference from Example 1 is that the crosslinking agent is polyethylene glycol, and the molecular weight is 1500.

[0083] Example 17 The difference from Example 1 is that the crosslinking agent is polyethylene glycol, and the molecular weight is 500.

[0084] Comparative Example 1 The base film of this comparative example is used as a control, and the raw materials of the base film are composed of inorganic ceramic solid electrolyte material Li6PS5Cl and binder PTFE, and the amount of the binder is 3% of the mass of the inorganic ceramic solid electrolyte material.

[0085] The preparation method is as follows: 10 g of Li6PS5Cl electrolyte and 0.3 g of PTFE are fully mixed in a jet mill at low temperature (-10°C), and then extruded at a double screw rod linear speed of 1 m / s. The extruded powder is placed in a hot roller press, and a base film of 20 μm is rolled at a hot roller pressing temperature of 80°C. The inorganic ceramic base film is obtained for testing, and the porosity is 15%.

[0086] Comparative Example 2 This comparative example provides a composite solid electrolyte film, which includes a polymer composite material and a base film. The thickness of the base film is 20 μm, and the porosity is 15% tested by a true density instrument. The polymer composite material is filled in the pores of the base film and covers the surfaces on both sides of the base film. The average thickness of the single side of the base film covered with the polymer composite electrolyte is 1 μm.

[0087] The polymer composite material is composed of 2% of lithium salt (specifically, LiFSI and LiDFBOP with a mass ratio of 4:1), 96% of ionic liquid (specifically, 1-ethyl-3-methylimidazole tetrafluoroboric acid), 1.7% of crosslinking agent (specifically, ETPTA), and 0.3% of initiator (specifically, AIBN), calculated based on the total mass of the raw materials as 100%. The raw materials of the base film are composed of inorganic ceramic solid electrolyte material Li6PS5Cl and binder PTFE, and the amount of the binder is 3% of the mass of the inorganic ceramic solid electrolyte material.

[0088] The preparation method of the above-mentioned composite solid electrolyte film is as follows: 10 g of Li6PS5Cl electrolyte and 0.3 g of PTFE are fully mixed in a jet mill at low temperature (-10°C), and then extruded at a double screw rod linear speed of 1 m / s. The extruded powder is placed in a hot roller press, and a base film of 20 μm is rolled at a hot roller pressing temperature of 80°C. The inorganic ceramic base film is obtained for testing, and the porosity is 15%. Prepare the polymer composite material precursor solution: add 1.6 g of LiFSI and 0.4 g of LiDFBOP to 96 g of 1-ethyl-3-methylimidazole tetrafluoroboric acid ionic liquid, then add 1.7 g of ETPTA and mix at 400 rpm for 6 h, and then add 0.3 g of AIBN as an initiator and mix at 200 rpm for 2 h to obtain the polymer composite material precursor solution.

[0089] Take 2 g of the above polymer composite precursor liquid on both sides of the dry prepared inorganic thin film, put into vacuum negative pressure (-15 MPa) infiltration treatment 10 h, after fully immersed, take out and put into 80 ℃ curing 2 h, get composite solid electrolyte thin film, compared with the base film, weight gain 1.30 g.

[0090] Comparative example 3 Compared with example 2, the difference is that the polymer composite is composed of 2.4% LiFSI, 0.6% LiDFBOP, 96% 1-ethyl-3-methylimidazole tetrafluoroboric acid ionic liquid, 0.8% crosslinking agent ETPTA and 0.2% initiator AIBN, accounting for 100% of the total mass of raw materials.

[0091] The difference between the preparation method and example 2 is that when the polymer composite precursor liquid is configured, 2.4 g of LiFSI and 0.6 g of LiDFBOP are added to 96 g of 1-ethyl-3-methylimidazole tetrafluoroboric acid ionic liquid, then 0.8 g of ETPTA is added and mixed at 400 rpm for 6 h, and then 0.2 g of AIBN is added as initiator and mixed at 200 rpm for 2 h to obtain the polymer composite precursor liquid.

[0092] Comparative example 4 Compared with example 1, the difference is that the polymer composite is composed of 11.2% LiFSI, 2.8% LiDFBOP, 84% 1-ethyl-3-methylimidazole tetrafluoroboric acid ionic liquid, 1.7% crosslinking agent ETPTA and 0.3% initiator AIBN, accounting for 100% of the total mass of raw materials.

[0093] Compared with example 1, the difference is that when the polymer composite precursor liquid is configured, 11.2 g of LiFSI and 2.8 g of LiDFBOP are added to 84 g of 1-ethyl-3-methylimidazole tetrafluoroboric acid ionic liquid.

[0094] Comparative example 5 Compared with example 1, the difference is that the polymer composite is composed of 4.8% LiFSI, 1.2% LiDFBOP, 84% 1-ethyl-3-methylimidazole tetrafluoroboric acid ionic liquid, 9.7% crosslinking agent ETPTA and 0.3% initiator AIBN, accounting for 100% of the total mass of raw materials.

[0095] The preparation method is different from that of Example 1 in that 4.8 g of LiFSI and 1.2 g of LiDFBOP are added to 84 g of 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid, then 9.7 g of ETPTA is added for mixing at 400 rpm for 6 h, and then 0.3 g of AIBN is added as an initiator for mixing at 200 rpm for 2 h to obtain a polymer composite precursor solution.

[0096] Comparative Example 6 The present comparative example provides a composite solid electrolyte film including a polymer composite and a base film. The thickness of the base film is 20 μm, the porosity is 15% tested by a true density instrument, the polymer composite is filled in the pores of the base film and covers the surfaces on both sides of the base film, and the average thickness of the single side of the base film covered with the polymer composite electrolyte is 1 μm.

[0097] The polymer composite is composed of 6% of lithium salt (specifically, LiFSI and LiDFBOP in a mass ratio of 4:1), 5% of ionic liquid (specifically, 1-ethyl-3-methylimidazolium tetrafluoroborate), 88.7% of crosslinking agent (specifically, ETPTA), and 0.3% of initiator (specifically, AIBN), with the total mass of raw materials being 100%. The raw materials of the base film are composed of inorganic ceramic solid electrolyte material Li6PS5Cl and adhesive PTFE, and the amount of the adhesive is 3% of the mass of the inorganic ceramic solid electrolyte material.

[0098] The preparation method of the above composite solid electrolyte film is as follows: 10 g of Li6PS5Cl electrolyte and 0.3 g of PTFE are fully mixed by airflow milling at low temperature (-10°C), and then extruded by a double screw with a linear speed of 1 m / s. The extruded powder is placed in a hot roller press to be rolled into a base film with a thickness of 20 μm at a hot roller pressing temperature of 80°C for standby use; The polymer composite precursor solution is configured by adding 4.8 g of LiFSI and 1.2 g of LiDFBOP to 5 g of 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid, then adding 88.7 g of ETPTA (molecular weight 428) as the total mass of the polymer for mixing at 400 rpm for 6 h, and then adding 0.3 g of AIBN as an initiator for mixing at 200 rpm for 2 h to obtain the polymer composite precursor solution.

[0099] 2 g of the above polymer composite precursor solution is coated on both sides of the inorganic film prepared by dry method, and then placed in a vacuum negative pressure (-15 MPa) infiltration treatment for 10 h. After being fully infiltrated, it is taken out and placed in a solidification at 80°C for 2 h to obtain a composite solid electrolyte film with high ceramic content, with a weight gain of 1.2 g compared with the base film.

[0100] Comparative Example 7 The comparative example provides a composite solid electrolyte film, which comprises a polymer composite material and a base film. The thickness of the base film is 20 μm, the porosity is 15% tested by a true density instrument, the polymer composite material is filled in the pores of the base film and covers the surfaces on both sides of the base film, and the average thickness of the single side of the base film covered with the polymer composite electrolyte is 1 μm.

[0101] The polymer composite material is composed of 6% lithium salt (specifically LiFSI and LiDFBOP with a mass ratio of 4:1), 92% ionic liquid (specifically decyl triethyl ammonium bis(trifluoromethanesulfonyl) imide salt ionic liquid), 1.7% crosslinking agent (specifically ETPTA), and 0.3% initiator (specifically AIBN), with the total mass of raw materials being 100%.

[0102] The preparation method of the above-mentioned composite solid electrolyte film is as follows: 10 g of Li6PS5Cl electrolyte and 0.3 g of PTFE are fully mixed in an airflow mill at low temperature (-10°C), and then extruded with a double screw rod linear velocity of 1 m / s. The extruded powder is placed in a hot roller press to be rolled into a base film with a thickness of 20 μm at a hot roller pressing temperature of 80°C for standby; A polymer composite material precursor solution is prepared: 4.8 g of LiFSI and 1.2 g of LiDFBOP are added to 92 g of decyl triethyl ammonium bis(trifluoromethanesulfonyl) imide salt ionic liquid, then 1.7 g of ETPTA is added and mixed at 400 rpm for 6 h, and then 0.3 g of AIBN is added as an initiator and mixed at 200 rpm for 2 h to obtain the polymer composite material precursor solution.

[0103] 2 g of the above-mentioned polymer composite material precursor solution is coated on both sides of the inorganic film prepared by dry method, and then placed in a vacuum negative pressure (-15 MPa) infiltration treatment for 10 h. After being fully infiltrated, it is taken out and placed in a solidification at 80°C for 2 h to obtain a composite electrolyte film. Compared with the base film, the weight gain is 1.0 g. Comparative example 8 In order to prove the influence of the type of crosslinking agent on the composite solid electrolyte film, the following scheme is tried for preparation: Different from example 1, the polymer composite material is composed of 6% lithium salt (specifically LiFSI and LiDFBOP with a mass ratio of 4:1), 92% ionic liquid (specifically 1-ethyl-3-methyl imidazole tetrafluoroboric acid), 1.7% crosslinking agent (specifically MMA, methyl methacrylate, molecular weight 100.116), and 0.3% initiator (specifically AIBN), with the total mass of raw materials being 100%.

[0104] The preparation method differs from that of Example 1 in that 1.7 g of MMA is added as a crosslinking agent when the polymer composite precursor solution is configured.

[0105] It should be noted that the scheme of Comparative Example 8 cannot obtain an effective composite solid electrolyte film after curing because the material is brittle, and the electrochemical performance and tensile performance cannot be tested.

[0106] The reason for the above results is that the molecular weight of ETPTA is different from that of MMA, and the mechanical strength and flexibility of ETPTA are better than those of MMA. ETPTA is a multifunctional acrylate compound containing three carbon-carbon double bonds, which can form a three-dimensional crosslinked structure with inorganic solid electrolyte, greatly enhancing the mechanical properties of the composite film. MMA has only one carbon-carbon double bond, and its nature is brittle, with poor mechanical properties and insufficient lithium ion conduction ability. In addition, it also lacks direct chemical linkage with inorganic electrolyte, causing the electrical and mechanical properties of the composite film to deteriorate. In order to more clearly illustrate the examples and comparative examples, the schemes are listed in Table 1 below, as follows: Table 1 Scheme List

[0107] The films obtained from the examples and comparative examples were tested for performance, as follows: ① Ion conductivity test The button cell test method was used: 1. Punch the film sample into a 18 mm circle; 2. Place the punched film circle, CR2032 type button cell components (upper and lower covers, gaskets, and springs) in a 80℃ vacuum oven for not less than 8h; 3. Assemble the button cell (standard stainless steel gasket / solid electrolyte film / standard stainless steel gasket / spring) in a dew point not less than -40℃ dry room or other glove box with lower water and oxygen content. The packaging pressure of the button cell is 5MPa. The thickness L of the film sample is measured after the test is completed, the battery is disassembled, and the total thickness L1 of the inorganic polymer composite electrolyte film and the two stainless steel gaskets is measured according to the thickness test method of GB / T 6672. Then L=L1-L2 is the thickness of the film, and the area of the standard stainless steel gasket used is recorded as S; 4. Turn on the electrochemical workstation. Connect the button cell lead terminals to the clamps of the electrochemical workstation; 5. Select impedance mode, set the frequency range to 1 MHz~1 Hz, voltage to 0.01 V, and collect impedance spectrum; 6. Based on the impedance spectrum, read the impedance value; 7. Based on the impedance value, calculate the ion conductivity according to the ion conductivity formula.

[0108] ②Tensile strength test Based on the national standard GB / T 1040.3-2006, gradually increase the tensile load in the length direction of the composite film standard sample to cause deformation until failure. The maximum tensile stress required when the sample fails is the tensile strength.

[0109] ③Battery cycle performance test Assemble the battery structure as NCM / composite electrolyte film / Li foil; then perform charge-discharge cycle test.

[0110] The test results are shown in Table 2 below: Table 2 Test results

[0111] Figure 4 The ion conductivity impedance spectrum corresponding to Example 1; Figure 5 The battery charge-discharge graph corresponding to Example 1; Figure 6 The coulombic efficiency and capacity release graph corresponding to Example 1; Figure 7 The ion conductivity impedance spectrum corresponding to Comparative Example 1; Figure 8 The battery charge-discharge graph of Comparative Example 1; Figure 9 The lithium symmetric impedance schematic diagram of Example 1 and Comparative Example 1; Figure 10 The composite electrolyte film tensile strength comparison graph of Example 1 and Comparative Example 1.

[0112] From the various drawings and Table 2, it can be seen that the composite solid-state electrolyte films provided by the various embodiments all have high ionic conductivity and ion transference number, and have strong tensile strength relative to the base film, and the comprehensive performance of the composite solid-state electrolyte film provided by Example 1 is optimal. Comparison of Example 1 with Example 6, Example 7 and Example 8 shows that the selection of a double salt as the lithium salt has an advantage over the selection of a single salt. Comparison of Example 1 with Example 7 shows that, although the ionic conductivity and tensile strength are not greatly different between a plurality of lithium salts and a single lithium salt, the single lithium salt LITFSI can corrode the positive electrode aluminum foil and is extremely unstable in contact with the lithium metal negative electrode, resulting in a substantial decrease in cycle life, while a small amount of oxalate can passivate the aluminum foil and react with lithium metal to form SEI, greatly improving the cycle stability of the solid-state battery. Comparison of Example 1 with Example 6 and Example 8 shows that the selection of a lithium salt with higher ionic conductivity can fully exert the ionic conductivity advantage of the lithium salt with high ionic conductivity in the case of a good ion channel, and the ionic conductivity and ion transference number are both significantly improved. Example 1, Example 10 and Example 11 show that, in the case of a base film with a porosity of not higher than 20%, high ionic conductivity, high tensile strength and battery cycle performance can all be achieved.

[0113] Comparison of Example 1 with Example 13 and Example 14 shows that, by adjusting the negative pressure, the polymer composite material can effectively fill the pores in the base film, thereby achieving high ionic conductivity and ion transference number.

[0114] Example 1, Example 15, Example 16, Example 17 and Comparative Example 8 show that, when the molecular weight of the crosslinking agent is controlled to be in the range of 150-2000, the polymer composite material precursor solution can have a suitable viscosity and flowability, and the polymer network formed after crosslinking and polymerization of the crosslinking agent can have a good dispersion and binding effect on the ionic liquid, thereby enabling the polymer composite material to effectively penetrate into the internal pores of the ceramic base film, ensuring smooth lithium ion conduction, effectively improving the ionic conductivity, ion transference number and tensile strength, and the battery prepared therefrom also has good cycle performance and a high capacity retention rate. Relative to the polyethylene glycol crosslinking agent in Example 17, the use of an acrylate crosslinking agent in Example 1, although the molecular weight of the crosslinking agent is similar, the ether oxygen bond formed after crosslinking and polymerization of the acrylate crosslinking agent can form a hydrogen bond with the N-H bond in the imidazole ionic liquid, which can further facilitate the binding and dispersion of the ionic liquid, thereby further improving the ionic conductivity, ion transference number and cycle performance.

[0115] Example 1 has a composite film with an ionic conductivity that is nearly 20 times that of the base film, a composite film capacity retention rate that is much higher than that of a dry film, and a tensile strength that is much higher than that of a dry film, and the composite film has obvious advantages; the main reasons are as follows: ① in terms of ionic conductivity: the internal pores of the composite film are completely filled with the ion-conducting phase, and the ion-conducting path is increased (for example,Figure 2 As shown), the unfilled dry film has a large number of voids, resulting in poor ion conductivity. ② Capacity retention: Since the internal ion pathways of the composite film are largely interconnected and there is a thin interface layer on the surface, a strong SEI can be formed when in contact with the negative electrode of the solid-state battery, protecting the high-ion-conducting inorganic ceramics from being reduced and deteriorating their performance. However, the simple dry film production causes the inorganic ceramics to be in direct contact with the highly reducing lithium metal, which is reduced and deteriorated. ③ Tensile strength: There are chemical and physical cross-linking bonds inside the composite film, and the internal pores are completely filled, so its tensile strength increases exponentially. The simple dry film production relies solely on the PTFE wire drawing and winding method to bind the particles together, so its strength is inevitably low, which can easily cause internal short circuits in the solid-state battery and make it impossible to assemble the solid-state battery.

[0116] Comparing Example 1 with Comparative Example 2, the polymer composite material of Comparative Example 2 has a lower lithium salt content and a higher ionic liquid content. Although the polymer composite material has good fluidity and viscosity, fills the pores of the base membrane well, and effectively improves the tensile properties, the ionic liquid content is relatively high and the lithium salt content is relatively low, resulting in an overall low proportion of lithium salt in the polymer composite material, a relatively low effective lithium ion content, and therefore a poor effective lithium ion migration ability and a low ionic conductivity. Moreover, the relatively low effective lithium ion content makes it impossible to form stable CEI and SEI, and when assembled into an all-solid-state battery, it is easy to cause lithium dendrite piercing during the charge and discharge process, resulting in poor cycle performance and poor capacity retention.

[0117] Compared with Example 2 and Comparative Example 3, the polymer composite material of Comparative Example 3 has a higher ionic liquid content and a lower cross-linking agent content. Therefore, the higher ionic liquid content leads to a relatively lower content of lithium salt, which in turn leads to a relatively low content of effective lithium ions, ultimately resulting in lower ionic conductivity and migration coefficient of the composite solid electrolyte film, and poor lithium ion migration efficiency. At the same time, due to the low content of the cross-linking agent, the ionic liquid and lithium salt cannot be locked, resulting in lower strength of the composite electrolyte membrane, and a low charge and discharge capacity retention rate after assembly into an all-solid-state battery.

[0118] Comparing Example 1 with Comparative Example 4, the lithium salt content in the polymer composite material of Comparative Example 4 is too high, and the ionic liquid content is correspondingly reduced. The lithium salt cannot be effectively dissociated by the ionic liquid. At the same time, the viscosity of the polymer composite precursor is too high and cannot fully penetrate into the pores of the base membrane, and the effect described in the present invention cannot be achieved. Its ionic conductivity and composite film strength are significantly reduced. When assembled into an all-solid-state battery, the battery capacity retention rate is significantly reduced after charging and discharging.

[0119] Compared with Example 1 and Comparative Example 5, the ion liquid content is too low, and the crosslinking agent content is too high. Since the crosslinking agent cannot effectively build an ion transmission network, it will reduce the lithium ion transmission efficiency to some extent, hinder the lithium ion transmission, affect the ion conductivity of the composite electrolyte film, and further reduce the charge-discharge life of the all-solid-state battery. The amount of crosslinking agent is larger than that of Example 1, so the tensile strength of the composite solid electrolyte film is higher than that of Example 1.

[0120] Compared with Example 1 and Comparative Example 6, Comparative Example 6 uses a conventional polymer composite formulation for filling pores. The ion liquid content is extremely low, and the crosslinking agent content is extremely high. It can better fill when filling a base film with larger pores, ensure a certain strength of the composite film, and improve the ion conductivity to some extent. However, when filling a base film with a small porosity (e.g., 15%), the low ion liquid content will cause the lithium salt to be unable to be effectively dissociated by the ion liquid, and the excessive proportion of crosslinking agent will greatly reduce the lithium ion transmission efficiency, resulting in low ion conductivity and low migration coefficient. When assembling an all-solid-state battery, the capacity retention rate during charge and discharge is low.

[0121] Compared with Example 1 and Comparative Example 7, Comparative Example 7 selects a quaternary ammonium salt ion liquid, and the viscosity reaches 200 cp or more. The high-viscosity ion liquid cannot effectively dissolve the lithium salt, and even if a large negative pressure is increased, the precursor liquid cannot be infiltrated into the base film containing only 15% porosity, greatly hindering lithium ion transmission, causing low ion conductivity, and failing to achieve the corresponding effect.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some or all of the technical features. These modifications or substitutions do not cause the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A composite solid electrolyte film, characterized in that: including a polymer composite material and a base film having pores; The polymer composite material fills part or all of the pores and covers part or all of the surface of the base film; The raw materials of the base film include inorganic ceramic solid electrolyte material and binder; The polymer composite material, calculated based on the total mass of its raw materials as 100%, includes: 3%-10% lithium salt, 85%-95% ionic liquid, 1%-5% crosslinking agent and 0.1%-0.5% initiator, the ionic liquid includes an imidazole ionic liquid, and the molecular weight of the crosslinking agent is 150-2000.

2. The composite solid electrolyte film according to claim 1, characterized in that One or more of the following conditions are met: (1) The mass ratio of the inorganic ceramic solid electrolyte material to the polymer composite material is (85-95): (3-14); (2) The binder includes one or more of PTFE, PVDF, and PVDF-HFP; (3) The amount of the binder is 1%-5% of the mass of the inorganic ceramic solid electrolyte material; (4) The inorganic ceramic solid electrolyte material includes a halide inorganic ceramic solid electrolyte and / or a sulfide inorganic ceramic solid electrolyte; Preferably, the halide inorganic ceramic solid electrolyte includes one or more of LiYCl, LiInCl, and LiAlClO; Preferably, the sulfide inorganic ceramic solid electrolyte includes Li 10 GeP2S 12 , Li6PS5Cl, 70Li2S•30P2S5; (5) The ionic conductivity of the inorganic ceramic solid electrolyte material is not less than 1 mS / cm.

3. The composite solid electrolyte film according to claim 1, characterized in that One or more of the following conditions are met: (1) The lithium salt includes one or more of fluorine-containing lithium salts, boron-containing lithium salts, and phosphorus-containing lithium salts, preferably one or more of LiTFSI, LiFSI, LiBF4, LiDFOB, LiDFBOP, LiBOB, and LiPO2F2; (2) The imidazole ionic liquid includes one or more of 1-ethyl-3-methylimidazolium tetrafluoroboric acid and 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide; (3) The cross-linking agent includes an acrylate cross-linking agent, preferably one or more of polyethylene glycol dimethacrylate, ethoxylated trimethylolpropane triacrylate, and diethylene glycol diacrylate; (4) The initiator includes azobisisobutyronitrile.

4. The composite solid electrolyte film according to any one of claims 1 to 3, characterized in that: One or more of the following conditions are met: (1) The porosity of the base film is not higher than 20%, preferably 5%-15%; (2) The thickness of the base film is 15 μm-90 μm, preferably 15 μm-30 μm; (3) The surface of the base film is covered with the polymer composite material with an average thickness of 1-5 μm on one side; (4) The tensile strength of the composite solid electrolyte film is not less than 2 MPa, preferably 2-8 MPa; (5) The ionic conductivity of the composite solid electrolyte film is not less than 1 mS / cm, preferably 1-5 mS / cm; (6) The ion migration coefficient of the composite solid electrolyte film is not less than 0.7, preferably 0.7-0.

9.

5. A method for preparing a composite solid electrolyte film according to any one of claims 1 to 4, characterized in that: include: providing the base film; Mixing the lithium salt, the ionic liquid, the crosslinking agent and the initiator to obtain a polymer composite material precursor solution; Disposing the polymer composite material precursor liquid in part or all of the pores and part or all of the surface of the base film; The composite solid electrolyte film is obtained by in-situ curing.

6. The method for preparing a composite solid electrolyte film according to claim 5, characterized in that: The preparation method of the basement membrane comprises: mixing the inorganic ceramic solid electrolyte material and the binder to obtain a mixture, then fibrillating the mixture to obtain a fibrillated material, and pressing the fibrillated material to obtain the base film; Preferably, the fibrillation comprises: mixing the mixture at -20°C to -10°C using a jet mill, and then extruding the mixture using a screw extruder to obtain the fibrillated material.

7. The method for preparing a composite solid electrolyte film according to claim 5, characterized in that: The settings include: placing the polymer composite material precursor liquid on the surface of the basement membrane and then performing negative pressure infiltration; Preferably, the pressure of the negative pressure infiltration is -10 MPa to -20 MPa, and the time is 2h-6h; Preferably, the mass ratio of the polymer composite material precursor solution to the base film is 1:(4-10).

8. The method for preparing a composite solid electrolyte film according to any one of claims 5 to 7, characterized in that: The in-situ curing temperature is 70°C-90°C and the time is 2-4 hours; The in-situ curing is performed under vacuum conditions.

9. A battery, characterized in that: The composite solid electrolyte film comprises the composite solid electrolyte film according to any one of claims 1 to 4.

10. An electrical device, characterized in that: A battery comprising the battery of claim 9.

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