Halogen anion doped lithium-rich phase fluorine-based solid electrolyte material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of new energy, and relates to a halogen anion doped lithium-rich phase fluorine-based solid electrolyte material as well as a preparation method and application thereof. In order to develop a fluorine-based solid electrolyte material system for a solid-state lithium battery with high ionic conductivity, low electronic conductivity and a wide electrochemical window, the invention provides a halogen anion doped lithium-rich phase fluorine-based solid electrolyte material, and the chemical composition of the halogen anion doped lithium-rich phase fluorine-based solid electrolyte material is Li < 3 > MF < 6-a > X , wherein 0 < a < = 1, and M is at least one of Al and Ga; x is at least one of Cl, Br and I. The halogen anion doped lithium-rich phase fluorine-based solid electrolyte material has an open ion channel inside, lithium enrichment is realized, and the intrinsic ion conductivity is improved by increasing the concentration of transferable lithium ions.

Description

Technical Field

[0001] The present invention belongs to the field of new energy technology, and particularly relates to a halogen anion-doped lithium-rich fluorine-based solid electrolyte material and a preparation method thereof, as well as the application of a solid-state lithium battery based on the solid electrolyte material. Background Art

[0002] Solid-state lithium metal batteries based on inorganic solid electrolytes can effectively solve the safety issues caused by the flammability of organic liquid electrolytes and the dendrite growth of lithium metal anodes, and are one of the most promising next-generation energy storage systems. At the same time, solid electrolytes can better match high-voltage or multi-electron conversion reaction-type positive electrodes, such as conversion-type fluoride positive electrodes, allowing them to provide higher energy density. Therefore, it is extremely important to develop solid-state lithium ion conductors with high lithium ion conductivity and good electrochemical stability to match lithium metal anodes and specific positive electrodes, but it is challenging.

[0003] After the early accumulation of inorganic solid electrolytes, a variety of systems have been developed. Among them, the fluoride solid electrolyte formed by the perfluorinated anion skeleton shows obvious advantages. Fluoride electrolytes are considered to have the widest electrochemical window and excellent air stability. Although LiF formed by the strong bond between lithium and fluoride ions has high stability, it also hinders the diffusion movement of Li ions. Therefore, it is hoped that fluoride solid electrolytes will achieve rapid ion diffusion without compromising their inherent high electrochemical stability. The biggest problem facing fluoride solid electrolytes is poor ionic conductivity, rare structural configuration, and lack of suitable experimental synthesis schemes. In previous work, this research team reported Li3AlF6 and Li3GaF6 in cryolite phase, which have the highest 8.8×10 -5 Although Li3AlF6 and Li3GaF6 have achieved record-breaking high lithium ion conductivity in the fluoride system, achieving higher conductivity close to that of the chloride family remains a huge challenge.

[0004] To date, most halide-based solid-state batteries (HSBs) have been paired with traditional intercalation-type oxide cathodes, resulting in limited battery energy density. Fluoride-based solid-state electrolytes, on the other hand, offer promising applications in solid-state batteries due to their excellent air and electrochemical stability. Lithium metal batteries employing conversion-type iron fluoride cathodes can theoretically offer energy densities up to 850 Wh / kg. However, the liquid electrolyte in Li / FeF3 batteries typically dissolves the conversion reaction products, causing them to dissolve or deactivate, leading to rapid capacity decay of the active material. Solid-state battery architectures can enhance the volume compression and material confinement effects of the conversion products and inhibit the extrusion (or dissolution) of active materials into the electrolyte. Recently, our team successfully realized a series of ceramic-based solid-state Li / FeF3 batteries with high cycling reversibility. However, achieving stable contact between the lithium anode and ceramic electrolyte interface still presents several thorny challenges, often requiring the careful design of complex interfacial layers. Driving solid-state Li / FeF3 batteries with fluorine-based solid electrolytes remains a significant challenge.

[0005] In summary, there is an urgent need in this field to develop a fluorine-based solid electrolyte material system for solid-state lithium batteries with high ionic conductivity, low electronic conductivity, and a wide electrochemical window. The production process of the material is simple and suitable for large-scale application. Summary of the Invention

[0006] The object of the present invention is to provide a halogen anion-doped lithium-rich fluorine-based solid electrolyte material, a preparation method thereof, and a solid-state battery based on such an electrolyte.

[0007] In the first aspect, the present invention provides a halogen anion doped lithium-rich fluorine-based solid electrolyte material, wherein the chemical composition of the halogen anion doped lithium-rich fluorine-based solid electrolyte material is Li3MF 6-a X a ; wherein 0<a≤1, M is at least one of Al and Ga; X is at least one of Cl, Br and I.

[0008] The fluorine-based solid electrolyte material Li3MF proposed in this invention 6-a X a It is a lithium-rich aluminum-based or gallium-based fluoride. This fluoride solid electrolyte has an open ion channel inside and realizes its lithium enrichment at the same time. By increasing the concentration of mobile lithium ions, it is beneficial to improve its intrinsic ionic conductivity. This fluorine-based electrolyte does not require the use of expensive rare earth metal elements, nor does it require the use of redox-active transition metal elements. The solid electrolyte of the present invention can be used in the construction of perfluorinated solid-state batteries to suppress the battery performance degradation caused by the migration of elements (especially highly electronegative elements, such as fluorine) at the positive electrode-electrolyte solid-solid interface.

[0009] Preferably, 0<a≤0.5.

[0010] Preferably, M is Al; X is Cl or Br; preferably, when X is Cl, a=0.05-0.2; preferably, when X is Br, a=0.1-0.5.

[0011] Preferably, the chemical composition of the halogen anion doped lithium-rich fluorine-based solid electrolyte material is Li3AlF 5.87 Cl 0.13 、Li3AlF 5.85 Cl 0.15 or Li3AlF 5.58 Br 0.42 .

[0012] In a second aspect, the present invention provides a method for preparing a halogen anion-doped lithium-rich fluorine-based solid electrolyte material, wherein the halogen anion-doped lithium-rich fluorine-based solid electrolyte material is synthesized based on liquid phase deposition of a mixed ionic liquid.

[0013] The preferred ones include: (1) The ionic liquid containing the halogen anion X is mixed with the ionic liquid containing BF4 - The anionic liquid solvent is mixed at 25-150°C to obtain an anion X - and BF4 - Mixed ionic liquid solvents; (2) Add the precursor salt containing Li element and the precursor salt containing M element to the precursor salt containing anion X - and BF4 - The mixture is stirred in a mixed ionic liquid solvent at 25 to 150° C. for 6 to 12 hours to obtain a precipitate; (3) The obtained precipitate is washed and dried to obtain the halogen anion-doped lithium-rich phase fluorine-based solid electrolyte material.

[0014] To further improve the conductivity of fluoride solid electrolytes, heteroatoms with different radii and electronegativity (such as halogen atoms) are introduced into the fluoride lattice to promote ion dissociation, thereby increasing the overall conductivity. Soft chemical fluorination methods can better regulate the rigid sublattice induced by fluoride cations and the sublattice composed of mobile dopant anions and main anions. When synthesizing fluoride solid electrolytes via liquid-phase methods, the soft template strategy based on ionic liquids has some unique advantages.

[0015] Specifically, the present invention provides a method for preparing such a halogen anion-doped lithium-rich fluorine-based solid electrolyte material to expand its improvement potential in terms of doping and surface modification, and overcome the technical problems existing in the current solid-state battery architecture and its key electrolyte materials. The present invention uses for the first time a halogenation deposition synthesis based on a mixed ionic liquid to prepare such a double halogen-containing solid electrolyte. The fluorination of the mixed ionic liquid (accompanied by chlorination, bromination or iodination) is beneficial to the control of the nanomorphology of the electrolyte particles and the surface modification of the ionic liquid components. In the preparation and synthesis process of the present invention, a thin layer of solidified ionic liquid is attached to the surface of the electrolyte particles to achieve sufficient contact and bonding between the particles and the formation of conductive regions at the particle boundaries, which is beneficial to reducing the particle boundary resistance.

[0016] The material of the present invention does not generate any toxic or harmful substances during the production and preparation process, is green and environmentally friendly, and the synthesis method is easy to operate, the process flow is simple, and large-scale mass production can be easily achieved.

[0017] Preferably, in step (1): containing BF4 - Ionic liquids and halogen-containing anions X - The mass ratio of the ionic liquid is (6-18):1.

[0018] Preferably, in step (2), the ratio of the precursor salt containing the M element to the mixed ionic liquid is (1-3) g:10 mL.

[0019] Preferably, in step (3): the organic solvent used for washing is at least one of anhydrous acetone, anhydrous ethanol, and anhydrous isopropanol.

[0020] In a third aspect, the present invention provides a solid-state lithium battery, comprising: the above-mentioned halogen anion-doped lithium-rich phase fluorine-based solid electrolyte material.

[0021] In a fourth aspect, the present invention provides a lithium metal symmetric solid-state battery based on a halogen anion-doped lithium-rich fluorine-based solid electrolyte, comprising the aforementioned halogen anion-doped lithium-rich fluorine-based solid electrolyte and lithium metal sheets positioned on either side of the halogen anion-doped lithium-rich fluorine-based solid electrolyte. The lithium metal symmetric battery based on the fluorine-based solid electrolyte exhibits good interfacial stability and low interfacial impedance, achieving a small voltage polarization difference during lithium metal deposition / stripping cycles. The electrolyte sheets remain dense and smooth even after long-term cycling of the symmetric battery.

[0022] In a fifth aspect, the present invention provides a solid-state lithium metal full battery based on a halogen anion-doped lithium-rich phase fluorine-based solid electrolyte, comprising: a positive electrode, a negative electrode, and the above-mentioned halogen anion-doped lithium-rich phase fluorine-based solid electrolyte located between the positive electrode and the negative electrode; Preferably, the negative electrode is a metal lithium sheet; Preferably, the positive electrode is at least one of FeF3, FeF2, iron oxyfluoride, CuF2, CuOHF, carbon-sulfur composite, FeS2, LiMn2O4, LiFePO4, LiCoO2, nickel-rich ternary system and lithium-rich manganese-based solid solution.

[0023] Preferably, the positive electrode is FeF3. When the solid electrolyte is used in a Li||FeF3 solid-state lithium metal battery, the reversibility and cycling stability of the Li||FeF3 conversion reaction battery are greatly enhanced thanks to the compensation of fluorine origin at the fluorine-rich interface between the electrolyte and the positive electrode and the electrochemical stability of the lithium negative electrode. The reversible capacity of the battery is as high as 430 mAh / g and can be stably cycled for more than 60 times.

[0024] The present invention has the following positive and beneficial effects: (1) The halogen anion-doped lithium-rich fluorine-based solid electrolyte proposed in the present invention exhibits advantages such as a wide electrochemical window, good air stability, and strong ability to inhibit lithium dendrites compared to other solid electrolyte systems (such as sulfides and chlorides); (2) The fluorine-based solid electrolyte doped with lithium-rich halogen anions has an open framework structure. The present invention realizes the application of the open crystal framework structure prototype in the fluoride solid electrolyte and simultaneously realizes its lithium enrichment, which is beneficial to improve its intrinsic ionic conductivity by increasing the concentration of mobile lithium ions. This type of fluorine-based solid electrolyte does not require the use of expensive rare earth metal elements or redox-active transition metal elements; (3) This invention uses for the first time a halogenation deposition synthesis based on mixed ionic liquids to prepare this type of solid electrolyte. This low-energy synthesis strategy has obvious advantages. First, ionic liquids, as medium- and low-temperature halogenating agents and template directing agents, can realize a lithium-rich phase in which the electrolyte has open ion channels. Second, the residual ionic liquid solidified on the surface of the particles can achieve a rich charge modification effect at the particle boundaries, thereby bonding these electrolyte particles together and significantly improving the ionic conductivity of the system. Thanks to the enhanced lithium ion transport in the internal structure and particle boundaries, the lithium ion conductivity of the halogen anion-doped lithium-rich phase fluorine-based solid electrolyte reaches 2×10 at 30°C. -4 S / cm (e.g. 6.5×10 -5 S / cm~2×10 -4 S / cm), which is the highest level of fluorine-based solid electrolytes at present; the activation energy of ion migration (eV) is reduced to 0.42~0.55eV; (4) This type of solid electrolyte in the present invention can be used in the construction of perfluorinated solid-state batteries to inhibit element migration (especially the highly electronegative fluorine element) at the solid-solid interface of the fluoride cathode and the fluoride electrolyte, thereby maintaining stable battery capacity performance; (5) The materials described in the present invention do not produce toxic or hazardous substances during the production process, are environmentally friendly, and the synthesis method is easy to operate, the process flow is simple, and large-scale mass production is easily achieved. The present invention can provide new ideas for the development of halide solid electrolytes with high ionic conductivity, air stability, and a wide voltage window, and their corresponding high-energy-density solid-state batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Li3AlF is synthesized based on mixed ionic liquid method. 5.87 Cl 0.13 XRD pattern of Figure 2 Li3AlF is synthesized based on mixed ionic liquid method. 5.87 Cl 0.13 SEM images of Figure 3 Li3AlF is synthesized based on mixed ionic liquid method. 5.87 Cl 0.13 AC impedance diagram during the cooling stage; Figure 4 Li3AlF is synthesized based on mixed ionic liquid method. 5.87 Cl 0.13 Arrhenius diagram during the cooling phase; Figure 5 Li3AlF is synthesized based on mixed ionic liquid method. 5.87 Cl 0.13 The lithium metal symmetric battery as a solid electrolyte at a current density of 0.05 mA / cm 2 Potential curve of lithium metal deposition / stripping cycle; Figure 6 Li3AlF is synthesized based on mixed ionic liquid method. 5.87 Cl 0.13 Cycling performance of a Li||FeF3 solid-state battery as a solid electrolyte at a current density of 75 μA / mg and a voltage range of 1.2-4.2 V. Inset: Charge and discharge curves at different electrochemical cycling stages. Figure 7 Li3AlF is synthesized based on mixed ionic liquid method. 5.58 Br 0.42 XRD pattern of Figure 8 Li3AlF is synthesized based on mixed ionic liquid method. 5.58 Br 0.42 AC impedance diagram at 30℃; Figure 9 Li3AlF is synthesized based on mixed ionic liquid method. 5.58 Br 0.42Arrhenius plot during the cooling stage. Detailed implementation manners

[0026] The present invention will be further illustrated by the following implementation manners. It should be understood that the following implementation manners are only used to illustrate the present invention and do not limit the present invention.

[0027] The present invention provides a halogen anion-doped lithium-rich phase fluorine-based solid electrolyte for solid-state lithium batteries. This type of electrolyte has an open framework structure, and its internal lithium-rich and open lithium ion channels are conducive to ion transport. The results show that the room temperature conductivity of the fluorine-based solid electrolyte doped with a small amount of halogen anions reaches 10 -4 S / cm magnitude, which is the highest conductivity in the fluoride solid electrolyte family so far.

[0028] The chemical formula of the halogen anion-doped lithium-rich phase fluorine-based solid electrolyte material of the present invention is Li3MF 6-a Xa, where 0 < a ≤ 1, preferably 0 < a ≤ 0.5, M is at least one of Al or Ga, and X is at least one of Cl, Br or I. The electrolyte material is composed of a lithium-rich phase aluminum-based or gallium-based fluoride. As an example, in the electrolyte material, the lithium-rich phase aluminum-based fluoride can be Li3AlF 5.87 Cl 0.13 ,Li3AlF 5.85 Cl 0.15 and Li3AlF 5.58 Br 0.42 or one of them.

[0029] The present invention also provides a scheme for preparing such solid electrolytes based on mixed ionic liquids. Mainly: using a fluorine-containing ionic liquid and a small amount of ionic liquids containing other halogen ions as synthesis solvents, and obtaining a halogen anion-doped fluoride solid electrolyte through fluorination accompanied by other halogenations (chlorination, bromination or iodination) at a certain temperature. In the solid electrolyte framework, the F - coordination sites are replaced by a small amount of larger-sized halogen anions, which causes the Li-F polyhedron to distort, significantly improving the migration efficiency of Li + in the mixed lattice.

[0030] The present invention provides a scheme for synthesizing halogen anion-doped lithium-rich phase fluorine-based solid electrolytes by halogenation deposition based on mixed ionic liquids. The scheme makes full use of the functions of ionic liquids as soft template agents or structure-directing agents, and uses the physical / chemical adsorption of the charged groups of ionic liquids on the surface defects of the product to achieve the control of the nano-morphology of solid electrolytes and the surface modification of ionic liquid components, realizing the full contact and adhesion between electrolyte particles and the formation of a conductive region at the particle boundary, and significantly reducing the particle boundary resistance. As an example, for example, it includes the following steps.

[0031] First, the halogen anion X - The ionic liquid contains BF4 - The anionic ionic liquid solvent is mixed at 25 to 150°C.

[0032] The mixed ionic liquid may contain BF4 - Anion, halogen X - A low-temperature molten salt composed of anion and cationic groups, wherein the cation is an organic cation selected from at least one of 1,3-dialkyl-substituted imidazolium ions, N-alkyl-substituted pyridinium ions, alkyl quaternary ammonium ions, and alkyl quaternary phosphine ions.

[0033] Secondly, Li3MF 6-a X a The precursor salts of the metal elements in the mixture are added with anion BF4 according to the chemical dosage ratio. - and X - The mixture is stirred in an ionic liquid solvent at 25 to 150° C. for 6 to 12 hours to obtain a precipitate.

[0034] Salts of the element Li include, but are not limited to, carbonates (Li2CO3), nitrates (LiNO3), and sulfates (Li2SO4). Salts of the element M include, but are not limited to, nitrates of M and / or hydrates thereof (e.g., Al(NO3)3·9H2O, Ga(NO3)3·bH2O (b=3-9)), chlorides of M and / or hydrates thereof (e.g., AlCl3·cH2O (c=3-6), GaCl3·dH2O (d=3-6)). For example, the molar ratio of Li2CO3:Al(NO3)3·9H2O or Li2CO3:Ga(NO3)3·eH2O (e=3-9) required to synthesize Li3AlF6 or Li3GaF6 is 1.5:1. 1-3 g of a precursor mixture based on Al(NO3)3·9H2O or Ga(NO3)3·fH2O (f=3~9) was added to 10 mL of ionic liquid, and precipitates were obtained at different reaction temperatures and different ionic liquid environments.

[0035] Finally, the precipitate is washed with an organic solvent and dried to obtain a halogen anion-doped lithium-rich fluorine-based solid electrolyte material. For example, the precipitate is centrifugally washed 3-5 times with anhydrous acetone, then dried in a vacuum environment at 60°C. The powder can be used for physical property characterization or pressed into solid electrolyte sheets (1-1.5 cm thick, 10 mm diameter) for conductivity testing or solid-state battery testing.

[0036] The specific test method for conductivity is as follows: a double-electrode Swagelok cell is used to test the halogen anion-doped lithium-rich fluorine-based solid electrolyte material. First, 120-150 mg of sample powder is taken and pressed into an electrolyte sheet with a thickness of about 1-1.5 mm and a diameter of 1 cm at a pressure of 16-20 MPa. Then, gold is plated on both sides of the electrolyte sheet to construct a double-sided blocking electrode structure. A Solartron impedance analyzer (1260-1296) is used to measure the conductivity of the electrolyte sheet at 1×10 7 The AC impedance spectrum of the electrolyte sheet was obtained in the -0.1 Hz frequency range. For the temperature-varying impedance test, the Swagelok cell was first placed in an oven and the oven was raised to a certain temperature. The ambient temperature was then lowered in steps of 10°C. At each temperature point, the cell was held for 1-2 hours to ensure that the temperature of the entire solid electrolyte sheet reached equilibrium.

[0037] The present invention also provides a solid-state battery comprising the halogen anion-doped fluorine-based solid electrolyte material, realizing for the first time a solid-state battery based on a fluoride electrolyte that utilizes a Li / FeF3 conversion reaction. The solid-state battery comprising the halogen anion-doped lithium-rich fluorine-based solid electrolyte provided by the present invention can be a solid-state lithium metal battery.

[0038] The solid-state lithium metal symmetric battery system based on a halogen anion-doped lithium-rich fluorine-based solid electrolyte provided by the present invention is a battery with lithium metal sheets on both sides, wherein the current density of the lithium deposition and stripping cycle test of the lithium metal symmetric battery system can be 0.03-0.6 mA / cm 2 The deposition or stripping time in each cycle can be 0.5 to 1 hour.

[0039] The solid-state lithium metal battery provided by the present invention comprises a lithium metal sheet as the negative electrode and a positive electrode selected from at least one of FeF3, FeF2, CuF2, CuOHF, a carbon-sulfur composite, FeS2, LiMn2O4, LiFePO4, LiCoO2, a nickel-rich ternary system, and a lithium-rich manganese-based solid solution. A halogen anion-doped lithium-rich fluorine-based solid electrolyte is placed between the positive and negative electrodes.

[0040] The following examples are further given to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all fall within the scope of protection of the present invention. The specific process parameters and the like in the following examples are only examples within a suitable range, that is, those skilled in the art can make selections within a suitable range through the description herein, and are not limited to the specific numerical values ​​exemplified below.

[0041] Example 1 1) Chlorine-doped lithium-rich fluorine-based solid electrolyte Li3AlF prepared based on mixed ionic liquid 5.87 Cl 0.13 Preparation: First, 2g of 1-butyltrimethylimidazolium chloride BmimCl (solid at room temperature) was added to 15ml of 1-butyl-3-methylimidazolium tetrafluoroborate BmimBF4. The above ionic liquid mixture was stirred at 90 ° C for 6 hours, and then 886.68mg of Li2CO3 was added as a lithium source, and 3001mg of Al(NO3)3·9H2O were added. Stirring was continued for more than 12 hours until a white precipitate appeared. The obtained precipitate was washed with acetone by centrifugation at least 5 times, and then dried in a vacuum oven at 60 ° C for 12 hours to obtain a white powder product. The obtained Li3AlF 5.87 Cl 0.13 The X-ray diffraction (XRD) pattern of the solid electrolyte is as follows: Figure 1 As shown in the figure, it can be seen that a small amount of chlorine doping does not cause significant changes in its crystal structure. In this structure, Cl atoms probabilistically replace fluorine atoms and are distributed in the positions originally occupied by fluorine atoms. 5.87 Cl 0.13 It still has a cryolite-like structure, and the anion lattice framework of this structure is filled with high concentrations of lithium ions, which greatly increases the number of lithium ions that can be transferred. 5.87 Cl 0.13 SEM images of solid electrolyte nanoparticles are shown in the attached Figure 1 As shown, the sample presents a morphology of nano-grains interwoven with each other. It can be seen that after chlorine doping, a large number of primary nanoparticles with a size of 70-110nm aggregated together to form secondary particles of about 300nm, fully demonstrating the nano-sizing effect of solid electrolyte particles brought about by the liquid phase synthesis strategy.

[0042] 2) Conductivity test of fluorine-based solid electrolyte sheet: The solid electrolyte powder prepared in Example 1 was pressed into 120 mg of sample powder and pressed into an electrolyte sheet with a thickness of about 0.12 cm and a diameter of about 1 cm at a pressure of 16 MPa. Subsequently, gold was plated on both sides of the electrolyte sheet to construct a double-sided blocking electrode structure. A Solartron impedance analyzer (1260-1296) was used to analyze the electrolyte sheet at 1×10 7 The AC impedance spectrum of the electrolyte sheet was obtained in the frequency range of -0.1Hz. For the variable temperature impedance test (70℃ to 30℃), the Swagelok battery was first placed in an oven, and the oven was raised to a certain temperature, and then the oven temperature was lowered in steps of 10℃ / time. At each temperature point, the battery was kept for 2 hours to ensure that the temperature of the entire solid electrolyte sheet reached equilibrium. Figure 3As shown in the figure, the ionic conductivity of the electrolyte at 30 ° C is 2×10 -4 S / cm, the highest level of fluorine-based solid electrolytes, and the activation energy of ion migration between 70°C and 30°C is 0.42 eV (e.g. Figure 4 shown).

[0043] 3) Based on chlorine-doped fluorine-based solid electrolyte Li3AlF 5.87 Cl 0.13 The assembly and testing of the lithium metal symmetric battery was carried out in an argon glove box with a water and oxygen value of less than 0.1ppm. Specifically, a metal lithium sheet with a diameter of 8mm was attached to both sides of a fluorine-based solid electrolyte sheet with a diameter of 10mm to assemble a Swagelok battery. The assembled solid-state Swagelok symmetric battery was placed in a 60℃ forced air oven and then charged and discharged on a LAND electrochemical workstation. The specific test procedure was to conduct a charge and discharge test at 0.05-0.2mA / cm 2 At a current density of , first charge at constant current for 1 hour (or 0.5 hour), then discharge at constant current for 1 hour (or 0.5 hour), detect the voltage polarization difference of metallic lithium during the deposition / stripping process, and start the cycle in this step. Figure 4 Based on chlorine-doped fluorine-based solid electrolyte Li3AlF 5.87 Cl 0.13 Solid-state lithium metal symmetric battery at 0.05 mA / cm 2 The current density is 0.05 mAh / cm 2 The cycling curve of the lithium metal deposition / stripping process at the surface capacity of 100 nm is shown in Figure 1. As can be seen from the figure, at this current density, the stable deposition / stripping process can last for at least 500 hours, and the unilateral overpotential does not exceed 170 mV.

[0044] 4) Based on chlorine-doped fluorine-based solid electrolyte Li3AlF 5.87 Cl 0.13 Preparation and testing of lithium metal full batteries: 1. Preparation of solid-state cathode: To prepare the positive electrode for solid-state lithium metal batteries, LiTFSI-PEO is introduced as an ionic conductor. In this work, the positive electrode for button cells can include fluoride cathodes, LiFePO4, or nickel-rich ternary systems. The specific protocol is as follows: First, the active material (e.g., FeF3, the preferred cathode in this example, is described. The FeF3 sample was synthesized based on our previously developed ionic liquid thermal fluorination method), conductive carbon (Super P), polyethylene oxide (PEO), and LiTFSI are mixed in a mass ratio of 60:12:20:8. The mixture is then ground into a uniform powder in a mortar and pestle, poured into N,N-dimethylformamide (DMF), and stirred overnight. The resulting slurry is then evenly coated on a carbon-coated aluminum foil surface and dried overnight at 60°C in a vacuum environment to obtain an electrode sheet. The FeF3 loading is 1 mg / cm 2 The electrode sheets were cut into 7 mm × 7 mm squares and dried in a vacuum oven at 60 °C for more than 6 h, and then transferred to an argon glove box for storage before use. 2. Assembly and testing of solid-state lithium / iron fluoride batteries: The Swagelok cell was assembled in an argon glove box with water and oxygen concentrations below 0.1 ppm. Specifically, an 8mm-diameter lithium metal sheet and a positive electrode sheet loaded with active material were attached to either side of a 10mm-diameter solid electrolyte to form a lithium metal battery. The battery was then placed in a 60°C oven and its electrochemical cycling performance was tested at various current densities using a LAND electrochemical workstation. Figure 6 Li3AlF synthesized based on mixed ionic liquid method 5.87 Cl 0.13 A solid-state Li||FeF3 battery with a solid electrolyte shows cycling performance at a current density of 75 μA / mg and a voltage range of 1.2–4.2 V. The inset shows the charge-discharge curves at different electrochemical cycling stages. The battery's initial discharge capacity reached a high of 360 mAh / g. After two cycles, the conversion reaction capacity was further electrochemically activated, increasing to approximately 430 mAh / g. This reversible capacity was maintained until the 35th cycle, after which the capacity decreased slightly. After 60 cycles, the reversible capacity remained high, exceeding 200 mAh / g.

[0045] Example 2 1) Bromine-doped lithium-rich fluorine-based solid electrolyte Li3AlF prepared based on mixed ionic liquid 5.58 Br 0.42 Preparation: First, 2g of 1-butyltrimethylimidazolium bromide BmimBr (solid at room temperature) was added to 15ml of 1-butyl-3-methylimidazolium tetrafluoroborate BmimBF4, and the above ionic liquid mixture was stirred at 90°C for 6 hours to obtain a mixed ionic liquid. Secondly, 886.68mg of Li2CO3 was weighed and added to the mixed ionic liquid, and stirred at 90°C for 6 hours to obtain a uniform turbid solution. Subsequently, 3001mg of Al(NO3)3·9H2O was slowly added to the solution while stirring, and the stirring was continued for 12 hours to obtain a turbid solution from which a precipitate could be precipitated. The obtained precipitate was centrifuged and washed with acetone at least 5 times, and then dried in a vacuum oven at 60°C for 12 hours to obtain a white powder product. The obtained Li3AlF 5.58 Br 0.42 XRD of solid electrolytes Figure 7 It can be seen that, similar to chlorine doping, increasing the bromine doping amount will not cause significant changes in the crystal structure. 5.58 Br 0.42 Still has a cryolite-like structure.

[0046] 2) Based on bromine-doped fluorine-based solid electrolyte material Li3AlF 5.58 Br 0.42 Conductivity test: The solid electrolyte powder prepared in Example 2 was pressed into 120 mg of sample powder and pressed into an electrolyte sheet with a thickness of about 0.12 cm and a diameter of about 1 cm at a pressure of 16 MPa. Subsequently, gold was plated on both sides of the electrolyte sheet to construct a double-sided blocking electrode structure. A Solartron impedance analyzer (1260-1296) was used to analyze the electrolyte sheet at 1×10 7 The AC impedance spectrum of the electrolyte sheet was obtained in the -0.1 Hz frequency range. The ionic conductivity of the electrolyte at 30 ° C was 1.26×10 -4 S / cm, such as Figure 8 As shown. For the variable temperature impedance test (70℃ to 30℃), the Swagelok battery was first placed in an oven, and the oven was raised to a certain temperature, and then the oven temperature was lowered in steps of 10℃. At each temperature point, the battery was kept for 2 hours to ensure that the temperature of the entire solid electrolyte sheet reached equilibrium. Figure 9 As shown in Figure 5, the activation energy of ion migration between 70°C and 30°C is 0.50 eV, which is slightly higher than that in the case of chlorine doping.

[0047] Example 3 The preparation process of the chlorine-doped lithium-rich fluorine-based solid electrolyte prepared based on the mixed ionic liquid in Example 3 is the same as that in Example 1, with the only difference being that a=0.05.

[0048] Example 4 The preparation process of the chlorine-doped lithium-rich fluorine-based solid electrolyte prepared based on the mixed ionic liquid in Example 4 is similar to that in Example 1, with the only difference being that a=0.15.

[0049] Example 5 The preparation process of the chlorine-doped lithium-rich fluorine-based solid electrolyte prepared based on the mixed ionic liquid in this Example 5 is similar to that in Example 1, with the only difference being that a=0.20.

[0050] Example 6 The preparation process of the bromine-doped lithium-rich fluorine-based solid electrolyte prepared based on the mixed ionic liquid in Example 6 is similar to that in Example 2, with the only difference being that a=0.2.

[0051] Example 7 The preparation process of the bromine-doped lithium-rich fluorine-based solid electrolyte prepared based on the mixed ionic liquid in Example 7 is similar to that in Example 2, with the only difference being that a=0.3.

[0052] Example 8 The preparation process of the bromine-doped lithium-rich fluorine-based solid electrolyte prepared based on the mixed ionic liquid in Example 8 is similar to that in Example 2, with the only difference being that a=0.5.

[0053] Comparative Example 1 The preparation process of the chlorine-doped lithium-rich fluorine-based solid electrolyte prepared based on the mixed ionic liquid in this comparative example 1 is similar to that in Example 1, with the only difference being that a=0.

[0054] Comparative Example 2 The preparation process of the bromine-doped lithium-rich fluorine-based solid electrolyte prepared based on the mixed ionic liquid in Comparative Example 2 is similar to that in Example 2, with the only difference being that a=0.

[0055] Table 1: X a Ionic conductivity (S / cm) Ion migration activation energy (eV) Example 3 Cl 0.05 <![CDATA[7.78×10 -5 S / cm]]> 0.46 Example 1 Cl 0.13 <![CDATA[2×10 -4 S / cm]]> 0.42eV Example 4 Cl 0.15 <![CDATA[1.32×10 -4 S / cm]]> 0.45eV Example 5 Cl 0.20 <![CDATA[1.2×10 -4 S / cm]]> 0.48eV Example 6 Br 0.2 <![CDATA[6.5×10 -5 S / cm]]> 0.55eV Example 7 Br 0.3 <![CDATA[8.5×10 -5 S / cm]]> 0.53eV Example 2 Br 0.42 <![CDATA[1.26×10 -4 S / cm]]> 0.50eV Example 8 Br 0.5 <![CDATA[1.26×10 -4 S / cm]]> 0.52eV Comparative Example 1 Cl 0 <![CDATA[2.04×10 -5 S / cm]]> 0.59eV Comparative Example 2 Br 0 <![CDATA[2.04×10 -5 S / cm]]> 0.59eV .

[0056] Finally, it is necessary to explain here that the above embodiments are only used to further illustrate the technical solution of the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all fall within the scope of protection of the present invention.

Claims

1. A halogen anion-doped lithium-rich fluorine-based solid electrolyte material, characterized in that: The chemical composition of the halogen anion doped lithium-rich fluorine-based solid electrolyte material is Li3MF 6-a X a ; wherein 0<a≤1, M is at least one of Al and Ga; X is at least one of Cl, Br and I.

2. The halogen anion-doped lithium-rich fluorine-based solid electrolyte material according to claim 1, characterized in that: 0＜a≤0.5。 3. The halogen anion-doped lithium-rich fluorine-based solid electrolyte material according to claim 1 or 2, characterized in that: M is Al; X is Cl or Br; Preferably, when X is Cl, a=0.05-0.2; Preferably, when X is Br, a=0.1-0.

5.

4. The halogen anion-doped lithium-rich fluorine-based solid electrolyte material according to any one of claims 1 to 3, characterized in that: The chemical composition of the halogen anion doped lithium-rich fluorine-based solid electrolyte material is Li3AlF 5.87 Cl 0.13 、Li3AlF 5.85 Cl 0.15 or Li3AlF 5.58 Br 0.42 .

5. A method for preparing a halogen anion-doped lithium-rich fluorine-based solid electrolyte material according to any one of claims 1 to 4, characterized in that: The halogen anion-doped lithium-rich fluorine-based solid electrolyte material is synthesized based on liquid phase deposition of a mixed ionic liquid.

6. The preparation method according to claim 5, characterized in that include: (1) The ionic liquid containing the halogen anion X is mixed with the ionic liquid containing BF4 - The anionic liquid solvent is mixed at 25-150°C to obtain an anion X - and BF4 - Mixed ionic liquid solvents; (2) Add the precursor salt containing Li element and the precursor salt containing M element to the precursor salt containing anion X - and BF4 - The mixture is stirred in a mixed ionic liquid solvent at 25 to 150° C. for 6 to 12 hours to obtain a precipitate; (3) The obtained precipitate is washed and dried to obtain the halogen anion-doped lithium-rich phase fluorine-based solid electrolyte material.

7. The preparation method according to claim 6, characterized in that In step (1): containing BF4 - Ionic liquids and halogen-containing anions X - The mass ratio of the ionic liquid is (6-18):

1.

8. The preparation method according to claim 6, characterized in that In step (2): the ratio of the precursor salt containing the M element to the mixed ionic liquid is (1-3) g:10 mL.

9. The preparation method according to any one of claims 6 to 8, characterized in that In step (3): the organic solvent used for washing is at least one of anhydrous acetone, anhydrous ethanol, and anhydrous isopropanol.

10. A solid-state lithium battery, characterized in that: include: The halogen anion-doped lithium-rich fluorine-based solid electrolyte material according to any one of claims 1 to 4.

11. A lithium metal symmetric solid-state battery based on a halogen anion-doped lithium-rich phase fluorine-based solid electrolyte, characterized in that: include: The halogen anion-doped lithium-rich fluorine-based solid electrolyte according to any one of claims 1 to 4, and metallic lithium sheets located on both sides of the halogen anion-doped lithium-rich fluorine-based solid electrolyte.

12. A solid-state lithium metal full battery based on a halogen anion-doped lithium-rich fluorine-based solid electrolyte, characterized in that: include: A positive electrode, a negative electrode, and a halogen anion-doped lithium-rich fluorine-based solid electrolyte according to any one of claims 1 to 4 located between the positive electrode and the negative electrode; Preferably, the negative electrode is a metal lithium sheet; Preferably, the positive electrode is at least one of FeF3, FeF2, iron oxyfluoride, CuF2, CuOHF, carbon-sulfur composite, FeS2, LiMn2O4, LiFePO4, LiCoO2, nickel-rich ternary system and lithium-rich manganese-based solid solution.

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