Solid electrolyte and preparation method therefor, and all-solid-state lithium battery comprising solid electrolyte

Abstract

The present invention provides a solid electrolyte and a preparation method therefor, and an all-solid-state lithium battery comprising the solid electrolyte. The solid electrolyte comprises a polyanionic halide LixMCl6-a-bOaFb, wherein M is selected from transition metals of subgroup IV and subgroup V, metals of group III, and combinations thereof, and preferably selected from Zr, In and Ta and combinations thereof; and 1≤x≤4, 0<a≤1, and 0<b≤1. The solid electrolyte is constructed by means of a strategy of anionic engineering, which solves the dilemma of simultaneously improving the ionic conductivity and high-voltage stability of a halide solid electrolyte. In addition, the solid electrolyte can generate a stable positive electrode-solid electrolyte interface in situ, thereby improving the cycle stability of an all-solid-state lithium battery.

Description

A solid electrolyte, its preparation method, and an all-solid-state lithium battery containing the solid electrolyte. Technical Field

[0001] This invention relates to the field of all-solid-state lithium battery technology, and more specifically, to halide solid electrolytes, methods for their preparation, and all-solid-state lithium batteries (ASSLB) comprising such solid electrolytes. Background Technology

[0002] The explosive growth of electronic devices and electric vehicles has driven the development of safe, high-energy-density batteries. Compared to traditional lithium-ion batteries, all-solid-state lithium batteries are considered one of the most promising next-generation energy storage devices because they use non-flammable inorganic solid electrolytes instead of flammable organic electrolytes, resulting in greater safety.

[0003] Solid electrolyte (SE) is one of the key materials in all-solid-state lithium batteries and plays a decisive role in battery performance. Common inorganic solid electrolytes include sulfide solid electrolytes and oxide solid electrolytes.

[0004] Sulfide solid electrolytes have high ionic conductivity and good processing performance, but they have low oxidation potential, poor high-voltage stability, and are prone to decomposition during cycling. They also undergo severe interfacial side reactions with high-voltage cathode active materials, which limits their compatibility with high-voltage cathode materials and thus limits the capacity and cycle stability of ASSLB.

[0005] Although oxide solid electrolytes have better high voltage stability, they have low ionic conductivity and poor contact with electrode materials, often requiring the introduction of a small amount of liquid electrolyte to wet the interface.

[0006] Halogen electrolytes combine the high ionic conductivity of sulfide electrolytes with the high voltage stability of oxide electrolytes, making them promising candidates for next-generation solid-state electrolytes.

[0007] However, current halide solid electrolytes are typically crystalline halides, whose ionic conductivity remains low (<1 mS / cm). -1 Furthermore, its oxidation potential still cannot meet the requirements of high-voltage cathode materials such as 9-series ternary materials (ternary lithium-ion battery cathode active materials with an elemental ratio of Ni:Co:Mn = 9:0.5:0.5, LiNi). 0.9 Co 0.05 Mn 0.05 O2, also known as NCM955) requirements (>4.35V vs. Li / Li + On the one hand, cation doping strategies (such as doping with Mg, Fe, Er ions, etc.) can modulate Li +The ratio of vacancy concentration to ion concentration broadens the ion transport pathways in the lattice and improves the ionic conductivity of halide solid electrolytes, but its improvement on high-voltage stability is limited because the root cause of high-voltage degradation lies in the instability and oxidation of anions. On the other hand, to improve high-voltage stability, it is necessary to use elements such as F, which have stronger electronegativity than Cl, but the use of F will strengthen the interaction between the anionic framework and Li in the crystalline phase. + The interaction between them severely reduces ionic conductivity.

[0008] Therefore, new control strategies must be developed to address the challenge of simultaneously achieving high voltage stability and high ionic conductivity in halide solid electrolytes. Summary of the Invention

[0009] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a halide solid electrolyte that can achieve high ionic conductivity and high voltage stability, and can even improve the contact between the solid electrolyte and the electrode material, thereby achieving a stable positive electrode-electrolyte interface (CEI) in all-solid-state lithium batteries, which can be advantageously used in all-solid-state lithium batteries.

[0010] Another object of the present invention is to provide a solid electrolyte membrane containing the solid electrolyte, which can be operated and used independently.

[0011] Another objective of this invention is to provide a method for preparing the solid electrolyte and its membrane, which is simple, reproducible, and easy to scale up for production.

[0012] Another object of the present invention is to provide an all-solid-state lithium battery comprising the solid electrolyte.

[0013] Other objectives of the present invention may be apparent from the following.

[0014] According to the present invention, O is introduced into multi-anionic halides based on zirconium, indium and / or tantalum using an anion engineering strategy. 2 - Ions significantly reduce the crystallinity of solid electrolytes, even achieving an amorphous powder form, thereby promoting lithium-ion conduction and reducing F... - The adverse effects of ions on ionic conductivity; on the other hand, the introduction of F - Ions enhance the oxidation resistance of solid electrolytes, enabling the solid electrolyte to generate a stable positive electrode-solid electrolyte interface in situ, thereby improving the cycle stability of all-solid-state lithium batteries and achieving the aforementioned objective.

[0015] Thus, a first aspect of the present invention provides a solid electrolyte, which comprises one or more metals selected from transition metals of Group IVB and VB and metals of Group IIIA, especially polyanionic halides based on zirconium, indium and / or tantalum, having the chemical formula Li x MCl 6-2a-b O a F b , where 1 ≤ x ≤ 4, 0 < a ≤ 1, 0 < b ≤ 1, where M is selected from transition metals of Group IVB and VB and metals of Group IIIA and combinations thereof, preferably selected from Zr, In and Ta and combinations thereof.

[0016] In a second aspect, a method for preparing the solid electrolyte according to the present invention is provided, comprising the following steps: under the protection of an inert gas, mixing LiCl, MCl m , MF m , Li2O in a stoichiometric ratio and performing high-energy ball milling to prepare a polyanionic halide, where M is selected from transition metals of Group IVB and VB and metals of Group IIIA and combinations thereof, preferably selected from Zr, In, Ta and combinations thereof, and m is the valence state of metal M.

[0017] In a third aspect, a all-solid-state lithium battery is provided, comprising a positive electrode, a negative electrode and the solid electrolyte of the present invention.

[0018] Other aspects and beneficial effects of the present invention will be clearly apparent from the following detailed description of the invention and the specific embodiments in conjunction with the accompanying drawings.

[0019] Solid electrolyte

[0020] In a first aspect of the present invention, the present invention provides a solid electrolyte, which comprises one or more metals selected from transition metals of Group IVB and VB and metals of Group IIIA, preferably polyanionic halides based on zirconium, indium and / or tantalum, having the chemical formula Li x MCl 6-2a-b O a F b , where 1 ≤ x ≤ 4, 0 < a ≤ 1, 0 < b ≤ 1, where M is selected from transition metals of Group IVB and VB and metals of Group IIIA and combinations thereof, preferably selected from Zr, In and Ta and combinations thereof.

[0021] In a preferred embodiment, the metal M is Zr. Thus, the polyanionic halide is Li x ZrCl 6-2a-b O a F b, where 1 ≤ x ≤ 4, 0 < a ≤ 1, 0 < b ≤ 1. Such polyanionic halides can also be simply referred to as LZCFO.

[0022] In the present invention, through an anion engineering strategy, O ions are introduced into polyanionic halides based on transition metals of Group IVB and Group VB and / or metals in Group IIIA, preferably based on zirconium, indium, and / or tantalum, which significantly reduces the crystallinity of the solid electrolyte and promotes the conduction of lithium ions. Introducing F ions enhances the oxidation resistance of the solid electrolyte, enabling the in-situ formation of a stable cathode-solid electrolyte interface, thereby improving the cycle stability of all-solid-state lithium batteries. 2- ions significantly reduce the crystallinity of the solid electrolyte and promote the conduction of lithium ions. Introducing F - ions enhances the oxidation resistance of the solid electrolyte, enabling the in-situ formation of a stable cathode-solid electrolyte interface, thereby improving the cycle stability of all-solid-state lithium batteries.

[0023] In the polyanionic halides of the present invention, 0 < a ≤ 1 and 0 < b ≤ 1. If the content of O is too high (a > 1), a heterophase with low ionic conductivity will be formed. If the content of F is too high (b > 1), it will also lead to a decrease in ionic conductivity.

[0024] In a preferred embodiment, the solid electrolyte may further comprise a binder, thereby enhancing the adhesion within the solid electrolyte material, improving the adhesion of the solid electrolyte to the cathode and anode materials, and also facilitating the further preparation of an independently operable and usable solid electrolyte membrane. Suitable binders that can be used can be one or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC), and polytetrafluoroethylene (PTFE) is particularly preferably used.

[0025] The solid electrolyte according to the present invention may further comprise other inorganic solid electrolytes. The other inorganic solid electrolytes may be selected, for example, from sulfide solid electrolytes (such as Li7P3S 11 , Li 10 GeP2S 12 , Li 6-a PS 5-a X 1+a (X = Cl, Br, I; 0 ≤ a ≤ 0.5)), oxide solid electrolytes (such as Li7La3Zr2O 12 , Li 0.5 La 0.5 TiO3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3), and other halide electrolytes (such as Li a MX6, where M = Y, Zr, In, Yb, etc.; X = F, Cl, Br, and I; 1 ≤ a ≤ 3)) and combinations thereof.

[0026] The solid electrolyte of this invention can achieve an ionic conductivity of 0.1-10 mS / cm at room temperature. -1 .

[0027] Here, room temperature refers to 25℃.

[0028] Preparation methods of solid electrolytes

[0029] The present invention also provides a method for preparing the above-mentioned solid electrolyte, comprising the following steps:

[0030] Under inert gas protection, LiCl and MCl m MF m Li₂O is mixed in stoichiometric ratio and ball-milled at high energy, wherein M is selected from transition metals of Group IV and Group V and metals of Group III and combinations thereof, preferably selected from Zr, In and Ta and combinations thereof, and m is the valence state of M.

[0031] In this method, preferably, the LiCl and MCl... m MF m The molar ratio of Li₂O is (1-4):(0.5-1):(0.1-0.5):(0.1-1).

[0032] The inert gases that can be used include nitrogen, argon, etc.

[0033] In the high-energy ball milling process, a speed of 400-650 rpm can be used, and the ball milling time can be 6-40 hours.

[0034] High-energy ball milling refers to a method that uses the rotation or vibration of a ball mill to intensely impact, grind, and stir raw materials with hard balls, pulverizing powder into nano-sized particles. High-energy ball milling is also known as mechanical alloying.

[0035] High-energy ball milling processes can be performed using high-energy ball milling equipment commonly used in the field. For example, a zirconium dioxide ball mill jar can be used.

[0036] When the solid electrolyte contains a binder, a self-supporting solid electrolyte membrane that can be operated and used independently can be prepared. This solid electrolyte membrane can be prepared by a method comprising the following steps: ball milling and mixing a polyanionic halide and a binder, and then rolling them into a film.

[0037] The mass ratio of the polyanionic halide to the binder can be 1:(0.001-5).

[0038] Ball milling of polyanionic halides and binders is a conventional ball milling process. Common ball milling equipment used in this field can be employed for the process. Speeds of 50-150 rpm can be used. The milling time can range from 0.5 to 2 hours.

[0039] A mixture of materials that has been ball-milled can be calendered into a film using roller mills or calenders commonly used in the art. For example, two-roll, three-roll, or more-roll roller mills or calenders can be used.

[0040] Using the solid electrolyte according to the present invention, films with a thickness of 3-100 micrometers, preferably ultrathin films of 3-10 micrometers, can be prepared.

[0041] Applications of solid-state electrolytes and all-solid-state lithium batteries

[0042] The solid electrolyte comprising the multi-anion halide according to the present invention achieves high ionic conductivity and high voltage stability, and is therefore advantageous for use in all-solid-state lithium batteries.

[0043] Therefore, the present invention also provides an all-solid-state lithium battery comprising the above-described solid electrolyte.

[0044] In this document, the term "solid-state battery" is a synonym for all commonly used names of galvanic elements and batteries that employ at least one solid electrolyte as a compound that conducts ions between the positive and negative electrodes, such as metal solid-state batteries, metal solid-state rechargeable batteries, all-solid-state batteries (ASSB), cells, solid-state cells, polymer cells, and rechargeable batteries. Rechargeable batteries (secondary batteries) are particularly included. The terms "battery," "cell," and "electrochemical battery" are used as synonyms.

[0045] The all-solid-state lithium battery according to the present invention may include a positive electrode (also called a cathode), a negative electrode (also called an anode) and a solid electrolyte as an electrolyte, wherein the solid electrolyte comprises the solid electrolyte according to the present invention.

[0046] In a preferred embodiment, the solid electrolyte according to the invention is used as an electrolyte layer in the form of a membrane.

[0047] In the all-solid-state lithium battery according to the present invention, both the positive and negative electrodes have at least one active material capable of receiving (inserting) or releasing (deintercalating) lithium ions and simultaneously surrendering or absorbing electrons. For use in an electrochemical battery or cell, such an active material can be applied to a carrier, preferably a metal carrier, preferably aluminum for the positive electrode or copper for the negative electrode. This carrier is also referred to as a "current collector" or current-collecting film.

[0048] The active material used for the positive electrode, or the active positive electrode material, can be any material known from relevant prior art. These include, for example, LiNi. 0.9 Co 0.05 Mn 0.05O2 (NCM955), Lithium cobalt oxide LiCoO2 (LCO), Lithium nickel oxide (LNO), NMC111 (LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2), NMC622(LiNi 0.6 Mn 0.2 Co 0.2 O2), lithium nickel cobalt aluminum oxide NCA (LiNi 0.8 Co 0.15 Al 0.05 Lithium nickel manganese cobalt oxide (NMC), lithium-rich and manganese-rich lithium nickel manganese cobalt oxide or lithium nickel manganese oxide (LMR), high-energy NCM (HE-NCM), lithium manganese iron phosphate (LMFP), lithium nickel manganese oxide spinel (LNMO), lithium iron phosphate (LFP) or Li-Mn spinel (LiMn2O4, LMO) and their derivatives and combinations thereof. To improve conductivity, the active material may contain additional substances, preferably carbon-containing compounds, or carbon, preferably carbon black, especially conductive carbon black or graphite.

[0049] The solid electrolyte of the present invention is particularly advantageous for use with high-nickel 9-series ternary cathode material NCM955.

[0050] The active material used for the negative electrode, or the active negative electrode material, can be any material known from the relevant prior art. The active negative electrode material can be, for example, selected from lithium, lithium alloys, indium, indium alloys, lithium-metal oxides such as lithium titanium oxide, metal oxides (e.g., Fe2O3, ZnO, ZnFe2O4), carbon-containing materials such as graphite (synthetic graphite, natural graphite), graphene, mesophase carbon, doped carbon, hard carbon, soft carbon, fullerenes, mixtures of silicon and carbon, silicon, silicon suboxide, silicon alloys, tin, tin alloys, aluminum alloys, cobalt alloys, niobium pentoxide, titanium dioxide, titanates such as lithium titanate (Li4Ti5O4). 12 Tin dioxide, materials and mixtures thereof that can be alloyed with lithium.

[0051] For all-solid-state lithium batteries, lithium, lithium alloys, indium alloys, silicon alloys, tin alloys, aluminum alloys, cobalt alloys and their mixtures are preferred as negative electrode active materials, especially Li or Li-In can be used as negative electrode active materials.

[0052] Active materials used for the positive or negative electrode can be bonded together by one or more binders. The one or more binders may be selected from polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyethylene oxide (PEO), polytetrafluoroethylene, polyacrylate, styrene-butadiene rubber, carboxymethyl cellulose (CMC), and mixtures and copolymers thereof.

[0053] An additional inorganic solid electrolyte layer can be inserted between the halide solid electrolyte and the negative electrode according to the invention to prevent side reactions between them. The inorganic solid electrolyte can be, for example, selected from sulfide solid electrolytes, such as Li7P3S. 11 Li 10 GeP2S 12 Li 6-a PS 5-a X 1+a (X = Cl, Br, I; 0 ≤ a ≤ 0.5), especially Li6PS5Cl.

[0054] In one embodiment, the solid electrolyte of the present invention can be mixed with the cathode material to form a composite cathode, which is more conducive to the preparation of high-performance all-solid-state lithium batteries.

[0055] In the composite cathode, the mass ratio of the solid electrolyte (preferably an amorphous powder material) to the cathode material can be (2-4):(8-6). The solid electrolyte and the cathode material can be mixed by ball milling, for example, at a speed of 50-150 rpm and a time of 0.5-2 hours, thereby preparing the composite cathode. Beneficial effects

[0056] This invention offers the following advantages and effects compared to existing technologies: By increasing the amorphous nature of the solid electrolyte material and introducing highly electronegative anions, it solves the problem of halide solid electrolytes' difficulty in simultaneously improving ionic conductivity and high voltage stability. Furthermore, it provides a simple method for preparing solid electrolyte membrane materials, offering advantages such as simple process, good repeatability, and ease of scale-up production. Simultaneously, the all-solid-state lithium battery provided by this method exhibits high discharge specific capacity and cycle stability, good structural stability, and excellent safety. Attached Figure Description

[0057] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings.

[0058] Figure 1 shows Li in Embodiment 1 of the present invention. 2.5 ZrCl5O 0.5 F 0.5 Scanning electron microscope image of solid electrolyte powder material;

[0059] Figure 2 shows Li in Embodiment 1 of the present invention. 2.5 ZrCl5O 0.5 F 0.5 X-ray diffraction pattern of solid electrolyte powder material;

[0060] Figure 3 shows Li in Embodiment 1 of the present invention. 2.5 ZrCl5O 0.5 F0.5 Temperature impedance diagram of solid electrolyte powder materials;

[0061] Figure 4 shows Li in Embodiment 1 of the present invention. 2.5 ZrCl5O 0.5 F 0.5 Linear scan voltammetry of solid electrolyte powder materials;

[0062] Figure 5 shows Li in Embodiment 1 of the present invention. 2.5 ZrCl5O 0.5 F 0.5 Solid electrolyte powder material is matched with 9-series ternary material as a composite cathode, using Li 2.5 ZrCl5O 0.5 F 0.5 Electrochemical performance diagram of solid electrolyte membrane as electrolyte layer;

[0063] Figure 6 shows Li in Embodiment 2 of the present invention. 2.5 ZrCl 4.5 O 0.5 Scanning electron microscope image of solid electrolyte powder material F;

[0064] Figure 7 shows Li in Embodiment 2 of the present invention. 2.5 ZrCl 4.5 O 0.5 F. Room temperature impedance diagram of solid electrolyte powder material;

[0065] Figure 8 shows the Li3ZrCl in Example 3 of the present invention. 4.5 OF 0.5 Scanning electron microscope image of solid electrolyte powder material;

[0066] Figure 9 shows the Li3ZrCl in Example 3 of the present invention. 4.5 OF 0.5 Room temperature impedance diagram of solid electrolyte powder materials;

[0067] Figure 10 shows the deconvolution Cl 2p XPS spectra of LZC, LZCO, LZCF and LZCFO after linear sweep voltammetry testing;

[0068] Figure 11 shows the crystallinity analysis of LZC, LZCO, LZCF and LZCFO. Detailed Implementation

[0069] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further illustrated below with reference to embodiments. It should be understood that the embodiments described in this specification are merely illustrative and not intended to limit the scope of the invention.

[0070] 1. The following materials are used in the examples and comparative examples.

[0071] LiCl, ZrCl4, ZrF4, Li2O: purchased commercially from Aladdin.

[0072] PTFE: Purchased commercially from Daikin Fluorochemicals (China) Co., Ltd., grade F208H.

[0073] 2. Instruments, equipment, parameters, and performance measurement methods used

[0074] (1) Particle size: determined by scanning electron microscopy (SEM) using JEOL Ltd., Tokyo, Japan; magnification 7000x.

[0075] The particle size of the electrolyte powder particles in the solid electrolyte membrane was determined by scanning electron microscopy (SEM). For spherical particles, the diameter was measured; for non-spherical or irregularly shaped particles, the equivalent particle size was measured. The equivalent particle size refers to the diameter of a spherical object when a certain physical property (such as volume, surface area, or circumcircle, in this case, the area of ​​the cross-sectional image shown in the SEM image) of an irregularly shaped object is the same as that of a spherical object. The average of these dimensions from 50 sample points observed in SEM images was used as the average particle size.

[0076] (2) X-ray diffraction pattern: measured at room temperature using equipment D8 ADVANCE, Bruker.

[0077] (3) Charge-discharge test, first-cycle discharge specific capacity: Assembled Li-In / Li6PS5Cl / halide SE / halide SE-NCM955 (3:7 weight ratio) and tested at room temperature at 2.5-4.35V vs. Li / Li + The evaluation was conducted between these samples. The halide SE corresponds to or can be replaced by the solid electrolyte prepared in the following examples and comparative examples.

[0078] (4) Ionic conductivity: measured using Solartron EnergyLab XM equipment.

[0079] (5) Activation energy: determined by Solartron EnergyLab XM.

[0080] (6) Temperature impedance diagram: measured by Solartron EnergyLab XM.

[0081] (7) Electrochemical oxidation potential: Measured by Solartron EnergyLab XM, followed by CV (cyclic voltammetry) test after LSV (linear sweep voltammetry) test.

[0082] In CV testing, an assembled Li / Li6PS5Cl / halide SE / halide SE-multi-walled carbon nanotube (9:1 weight ratio) cell was used for evaluation. The halide SE corresponds to or can be replaced with the solid electrolyte prepared in the following examples and comparative examples.

[0083] (8) XPS spectrum: The deconvolution Cl 2p XPS spectrum was measured after LSV (linear sweep voltammetry) test by Solartron EnergyLab XM using Axis Supra+, Kratos Analytical, at a voltage of 250kV.

[0084] (9) Interface characterization: The surface of the cycled NCM955 (discharge state) was observed by high-resolution TEM (JEOL Ltd., Tokyo, Japan, voltage 120kV).

[0085] (10) Crystallinity analysis: The crystallinity of the sample was estimated by high-resolution XRD (using the D8 ADVANCE, Bruker instrument, at room temperature) and the corresponding Rietveld refinement, and a bar chart was plotted based on the obtained values.

[0086] Example 1

[0087] A total of 2 g of LiCl, ZrCl4, ZrF4, and Li2O were mixed uniformly in an argon-protected glove box at a molar ratio of 1.5:0.875:0.125:0.5. The mixture was then placed in a 50 ml zirconium dioxide ball milling jar (model YXQM-1L, Changsha Miqi Instruments & Equipment Co., China) and 40 g of zirconium dioxide grinding beads were added. The jar was sealed and milled at 450 rpm for 20 hours. The jar was then opened in the glove box, and the resulting mixture containing Li2O was collected. 2.5 ZrCl5O 0.5 F 0.5 (LZCFO) multi-anionic halide powder material.

[0088] The polyanionic halide powder material and binder PTFE were ball-milled at 150 rpm (YXQM-1L, Changsha Miqi Instruments & Equipment Co., China) at a mass ratio of 1:0.01 for 1 hour. After rolling (the rolling equipment was purchased from Kejing Company, and the conditions were room temperature), a solid electrolyte membrane material (thickness of 100 micrometers) was prepared.

[0089] The obtained product was analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD), and the results are shown in Figures 1 and 2. Its electrochemical impedance spectroscopy at different temperatures is shown in Figure 3. The linear scanning voltammogram is shown in Figure 4. A 9-series ternary material NCM955 was used as the composite cathode, and Li was employed. 2.5 ZrCl5O 0.5 F 0.5 The electrochemical performance of the solid electrolyte membrane as the electrolyte layer is shown in Figure 5.

[0090] The all-solid-state lithium battery underwent charge-discharge testing at room temperature, with a voltage range of 2.5-4.35V vs. Li / Li. + The current density (rate) is 0.1C (1C = 180mA g). -1 ).

[0091] X-ray photoelectron spectroscopy (XPS) measurements confirmed the chemical composition of the polyanionic halides, see Figure 10.

[0092] The analytical results show that the obtained electrolyte membrane contains amorphous Li 2.5 ZrCl5O 0.5 F 0.5 LZCFO is a polyanionic halide, consisting of irregular particles with a diameter of approximately 1 μm (measured by SEM). The amorphous characteristics of LZCFO can be seen in Figures 2 and 11.

[0093] The electrolyte membrane achieves a room temperature ion conductivity of 0.95 mS / cm. -1 The ionic conductivity measured at 30℃ was 1.17 mS / cm. -1 It has an activation energy of 0.29 eV and an extremely high limiting electrochemical oxidation potential of 4.87 V vs. Li / Li. + This allows for the matching of 9-series ternary materials.

[0094] The all-solid-state lithium battery has a first-cycle discharge specific capacity of 207.1 mAh g at a current density of 0.1C. -1 The first-cycle discharge specific capacity at current densities of 0.2C, 0.5C, 1.0C, and 2.0C is 184.3 mAh g. -1 155.8mAh g -1 130.9mAh g -1 108.7mAh g -1 The capacity retention rate was 70.4% after 2000 cycles at a current density of 2.0C.

[0095] Interface characterization further confirmed the formation of a flat and stable F-rich cathode-electrolyte interface (CEI), which inhibits the oxidation and degradation of the solid electrolyte (SE) and the side reactions between the cathode and SE, and improves the structural stability of the cathode and the cycle stability of the battery, especially during high-voltage cycling.

[0096] Example 2

[0097] The preparation steps are the same as in Example 1, except that the molar ratio of LiCl, ZrCl4, ZrF4, and Li2O is changed to 1.5:0.75:0.25:0.5. The resulting polyanionic halide is Li 2.5 ZrCl 4.5 O 0.5 F. The obtained product was subjected to the same characterization analysis as in Example 1, and similar results were obtained, as shown in Figures 6 and 7.

[0098] The room temperature ionic conductivity of this polyanionic halide is 0.46 mS·cm. -1 .

[0099] Example 3

[0100] The preparation steps are the same as in Example 1, except that the molar ratio of LiCl, ZrCl4, ZrF4, and Li2O is changed to 1:0.875:0.125:1. The resulting polyanionic halide is Li3ZrCl 4.5 OF 0.5 The obtained product was subjected to the same characterization analysis as in Example 1, and similar results were obtained, as shown in Figures 8 and 9.

[0101] The room temperature ionic conductivity of this polyanionic halide is 0.60 mS / cm. -1 .

[0102] Comparative Example 1

[0103] The preparation steps were the same as in Example 1, except that only LiCl and ZrCl4 were used, instead of ZrF4 and Li2O. The resulting product contained Li2ZrCl6, abbreviated as LZC. This all-solid-state lithium battery underwent charge-discharge testing at room temperature, with a limiting electrochemical oxidation potential of 4.23 V vs. Li / Li. + As shown in Figure 4.

[0104] The ionic conductivity of this LZC at 30℃ is 0.35 mS / cm. -1 .

[0105] The first-cycle discharge specific capacity of the all-solid-state lithium battery at a current density of 0.1C (1C = 180mA g) -1 The following is 161.0 mAh g -1The first-cycle discharge specific capacity at current densities of 0.2C, 0.5C, 1.0C, and 2.0C is 141.6 mAh g. -1 118.0mAh g -1 95.7mAh g -1 60.3mAh g -1 After 2000 cycles at a current density of 2.0C, the capacity retention rate is 57.0%.

[0106] Comparative Example 2

[0107] The preparation steps are the same as in Example 1, except that only LiCl, ZrCl4, and Li2O are used instead of ZrF4, and the resulting product contains Li 2.5 ZrCl 5.5 O 0.5 It is abbreviated as LZCO.

[0108] The all-solid-state lithium battery was tested for charge and discharge at room temperature, and the limiting electrochemical oxidation potential was 4.16V vs. Li / Li. + As shown in Figure 4.

[0109] The ionic conductivity of this LZCO at 30℃ is 1.39 mS / cm. -1 The activation energy is 0.31 eV.

[0110] Comparative Example 3

[0111] The preparation steps are the same as in Example 1, except that only LiCl, ZrCl4, and ZrF4 are used, instead of Li2O, and the resulting product contains Li2ZrCl4. 5.5 F 0.5 It is abbreviated as LZCF.

[0112] The all-solid-state lithium battery was tested for charge and discharge at room temperature, and the limiting electrochemical oxidation potential was 4.69V vs. Li / Li. + As shown in Figure 4.

[0113] The ionic conductivity of this LZCF at 30℃ is 0.12 mS / cm. -1 The activation energy is 0.35 eV.

[0114] The results above show that the solid electrolyte material containing LZCFO according to the present invention can achieve high ionic conductivity and high voltage stability, and has a higher limiting electrochemical oxidation potential (4.87V vs. Li / Li) compared with LZC, LZCO, and LZCF. + This allows for the matching of 9-series ternary materials, which can then be advantageously used in all-solid-state lithium batteries.

[0115] The limiting electrochemical oxidation potentials of LZC and LZCO are less than 4.35 V vs. Li / Li + This indicates that they are not suitable for use in all-solid-state lithium batteries that use nickel-rich NCM as the positive electrode. They will undergo severe SE decomposition during battery cycling, thus increasing the impedance of the all-solid-state lithium battery and resulting in lower voltage stability.

[0116] As can be seen from the XPS spectrum in Figure 10, the peaks at 198.9 and 200.5 eV correspond to Cl in SE. - The peaks at 200.2 and 201.8 eV correspond to ClO. x - This peak is due to oxidation and decomposition caused by side reactions. It can be seen that LZCFO corresponds to ClO. x - The amount of the peak was the lowest (6.5%), while the proportion of this peak in LZCF was 8.3%. The content of this peak was significantly higher in LZC and LZCO, at 32.8% and 22.5%, respectively. This confirms that LZCFO according to the present invention does indeed undergo less oxidation and decomposition, and thus exhibits higher stability.

[0117] Figure 11 shows that the crystallinity of this LZCFO is significantly lower than that of the LZC, LZCO, and LZCF prepared in the comparative examples. This highly amorphous property weakens the F - The detrimental effect on ionic conductivity results in LZCFO having both high stability and high ionic conductivity.

[0118] LZCF has a significantly lower ionic conductivity, which is a disadvantage for its use in all-solid-state lithium batteries.

[0119] A comparison of the first-cycle discharge specific capacity at different current densities and the capacity retention rate after 2000 cycles at a current density of 2.0C shows that the all-solid-state lithium battery using LZCFO according to the present invention exhibits better rate performance compared to the all-solid-state lithium battery using LZC, which is due to its high ion conductivity and high voltage stability.

[0120] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, every point or individual value between the endpoints of the range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value or with other lower or upper limits to form a range not explicitly stated.

[0121] In the description of this application, it should be noted that, unless otherwise stated, "above" and "below" include the stated number, and "multiple" in "one or more" means two or more.

[0122] The foregoing description of this application is not intended to depict all embodiments or implementations of every disclosure herein. Throughout the application, guidance is provided through a series of examples, which can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

Claims

1. A solid electrolyte comprising a polyanionic halide having the chemical formula Li x MCl 6-2a-b O a F b where 1 ≤ x ≤ 4, 0 < a ≤ 1, 0 < b ≤ 1, and M is selected from transition metals of Group IVB and Group VB and metals in Group IIIA and combinations thereof, preferably selected from Zr, In, and Ta and combinations thereof.

2. The solid electrolyte according to claim 1, characterized in that, The polyanionic halide is an amorphous powder.

3. The solid electrolyte according to claim 1 or 2, characterized in that, The solid electrolyte includes a binder, preferably selected from polytetrafluoroethylene, polyvinylidene fluoride, styrene-butadiene rubber, and carboxymethyl cellulose and combinations thereof.

4. The solid electrolyte according to claim 3, characterized in that, The mass ratio of the polyanionic halide to the binder is 1:(0.001-5).

5. The solid electrolyte according to any one of claims 2-4, characterized in that, The solid electrolyte is in the form of a self-supporting membrane.

6. The solid electrolyte according to any one of claims 1-5, characterized in that, The solid electrolyte further includes one or more other inorganic electrolytes selected from sulfide solid electrolytes, oxide solid electrolytes, and other halide electrolytes and combinations thereof.

7. A method for preparing a solid electrolyte according to any one of claims 1-6, comprising the following steps: Under inert gas protection, LiCl and MCl m MF m Li₂O was prepared by mixing Li₂O in stoichiometric proportions and then ball-milling it with high energy to obtain the chemical formula Li. x MCl 6-2a-b O a F b The polyanionic halide, wherein M is selected from transition metals of Group IV and Group V and metals of Group III and combinations thereof, preferably Zr, In, Ta and combinations thereof, and m is the valence state of metal M, 1≤x≤4, 0 <a≤1,0<b≤1。 8. The method according to claim 7, characterized in that, The LiCl, MCl m MF m The molar ratio of Li2O is (1-4):(0.5-1):(0.1-0.5):(0.1-1).

9. The method according to claim 7 or 8, characterized in that, In the high-energy ball milling process, the ball milling time is 6-40 hours at a speed of 400-650 rpm.

10. The method according to any one of claims 7-9, characterized in that, The electrolyte contains a binder and the method further includes the following steps: - Provide an adhesive selected from polytetrafluoroethylene, polyvinylidene fluoride, styrene-butadiene rubber, and carboxymethyl cellulose and combinations thereof; - The polyanionic halide and binder are ball-milled and mixed together and then rolled to obtain a solid electrolyte membrane.

11. The method according to claim 10, characterized in that, In the ball milling mixing of the polyanionic halide and the binder, the ball milling is carried out at a speed of 50-150 rpm for 0.5-2 hours.

12. An all-solid-state lithium battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte comprises a solid electrolyte according to any one of claims 1-6.

13. The all-solid-state lithium battery according to claim 12, characterized in that, The solid electrolyte is mixed with the cathode material to form a composite cathode.

14. The all-solid-state lithium battery according to claim 13, characterized in that, In the composite cathode, the mass ratio of the solid electrolyte to the cathode material is (2-4):(8-6), and it is preferably prepared by ball milling at a speed of 50-150 rpm for 0.5-2 hours.

15. The all-solid-state lithium battery according to any one of claims 12-14, characterized in that... An additional inorganic solid electrolyte layer is inserted between the solid electrolyte and the negative electrode. This inorganic solid electrolyte is preferably selected from sulfide solid electrolytes, such as Li7P3S. 11 Li 10 GeP2S 12 Li 6-a PS 5-a X 1+a (X = Cl, Br, I; 0 ≤ a ≤ 0.5), especially Li6PS5Cl.

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