Oxyfluoride active material, process for its preparation and use

Abstract

The application relates to the technical field of all-solid-state lithium batteries, and discloses an oxyfluoride active substance and a preparation method and application thereof, the preparation method steps are as follows: FeF3.3H2O and transition metal fluoride are mixed and ground, and then ball milling is carried out; the ball milling product is added into an organic solvent to carry out a solvothermal reaction, and after the reaction is completed, cooling and standing are carried out; the FeF3.3H2O is dispersed in the organic solvent, and after uniform stirring, the system after standing is dripped into, and then the solvothermal reaction is continuously carried out by heating; after the reaction is completed, the product is separated and dried to obtain the oxyfluoride active substance. The oxyfluoride active substance with a core-shell gradient structure is constructed through step-by-step high-energy ball milling and controlled heat treatment, the band gap and the crystal structure of the material are accurately controlled, and therefore a fluorine oxide-based composite positive electrode material with the advantages of structural stability, fast ion transmission kinetics, good interface compatibility, high specific capacity and good cycle stability is obtained.

Description

Technical Field

[0001] This invention relates to the field of all-solid-state lithium battery technology, and in particular to a fluorine oxide active material, its preparation method, and its application. Background Technology

[0002] The energy density of all-solid-state lithium batteries is largely limited by the performance of the cathode material. Traditional intercalation cathode materials (such as LiFePO4, LiMn2O4, LiCoO2, LiNi) x Co y Mn 1-x-y O2, etc., through Li + Energy storage is achieved by embedding / extracting lithium ions at fixed sites within the material. However, due to the influence of the material structure, the saturation embedding of lithium ions is limited, so the theoretical specific capacity is usually difficult to exceed 200 mAh g⁻¹. -1 This, in turn, limits the battery's energy density. In contrast, conversion-type cathode materials achieve lithium storage through multi-electron redox reactions. During this process, chemical bonds break or recombine, valence changes occur, and the crystal lattice transforms, resulting in higher specific capacity and energy densities as high as 1600~2500 Wh / kg. -1 .

[0003] Among numerous conversion-type cathode materials, transition metal fluorides (MF) stand out. n (M represents transition metal elements such as Ti, V, Cr, Mn, Fe, Co, Ni, Cu, etc.) Iron trifluoride (FeF3) has superior specific energy density. Among them, it stands out due to its high theoretical operating potential (2.74 V) and theoretical capacity (712 mAh g⁻¹). -1 Theoretical energy density (1922 Wh kg) -1 FeF3 has attracted much attention due to its abundant crustal reserves. However, the intrinsic properties of FeF3 pose serious challenges: the high ionicity of the Fe-F bond results in poor intrinsic electronic conductivity, low ion diffusion rate, slow conversion reaction kinetics, and severe voltage hysteresis and irreversible structural degradation during lithiation / delithiation, leading to problems such as rapid capacity decay, poor rate performance, and low energy efficiency.

[0004] To address the aforementioned problems, various modification strategies exist in existing technologies. For example, constructing a three-dimensional conductive network by combining it with conductive materials can improve the intrinsic conductivity of FeF3, while simultaneously enhancing the conductivity of Li. +Diffusion provides additional transport channels, thereby improving high-current cycling performance and rate performance. Furthermore, surface modification strategies stabilize the cathode-electrolyte interface, suppressing drastic changes in cathode volume during charge and discharge. Additionally, doping FeF3 with heteroatoms restructures the internal charge distribution, effectively enhancing its redox activity. For example, patent CN106099074A discloses a modified iron fluoride nanocomposite cathode material, its preparation method, and its application, which is doped with Cr metal ions. 3+ Adjusting the lattice parameters of the crystal can significantly improve the diffusion performance of lithium ions and enhance their conductivity. However, the above methods are still limited in practical applications by inherently insufficient intercalation reaction capacity and slow reaction kinetics. Summary of the Invention

[0005] The present invention aims to overcome the aforementioned problems in the prior art by providing a fluoride oxide active material, its preparation method, and its application. By designing a fluoride oxide active material with a core-shell gradient structure, precise control of the material's band gap and crystal structure is achieved, thereby obtaining a fluoride oxide-based composite cathode material with stable structure, fast ion transport kinetics, good interfacial compatibility, high specific capacity, and good cycle stability.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a fluoride active substance, comprising the following steps: (1) FeF3·3H2O was mixed and ground with transition metal fluorides and then ball-milled; (2) Add the ball-milled product to an organic solvent, heat and stir to carry out a solvothermal reaction, and cool and let stand after the reaction is completed; (3) Disperse FeF3·3H2O in an organic solvent, stir evenly, and then drop it into the system after standing in step (2). Then raise the temperature to continue the solvothermal reaction. After the reaction is completed, separate and dry the product to obtain the fluorine oxide active material.

[0007] This invention constructs a fluoride oxide active material with a core-shell gradient structure through stepwise high-energy ball milling and controlled heat treatment, achieving precise control over the material's band gap and crystal structure. This structure is composed of richly doped metal ions (such as Ni). 2+ Co 2 + Mn 2+The material consists of a core (such as a core-shell composite cathode) and a shell with low doping levels of metal ions. The core, through metal ion doping, introduces additional redox active sites, enhancing the material's theoretical specific capacity. Its expanded interlayer spacing provides a fast channel for lithium-ion transport. The shell exhibits fluorine-rich properties, which can stabilize surface lattice oxygen by altering the electronic environment, enhancing structural stability. It also facilitates the formation of a stable electrode / electrolyte interface in the early stages of cycling, effectively suppressing interfacial side reactions and reducing lithium-ion cross-interface transport impedance. This gradient distribution of composition and structure acts as a stress gradient buffer during charge and discharge. Due to the difference in expansion behavior between the core and shell, a continuous mechanical property gradient can be formed within the material, dispersing lattice stress throughout the gradient region, avoiding stress concentration and microcrack propagation at the interface, and significantly suppressing structural distortion during cycling. In summary, this fluorine oxide-based composite cathode with a core-shell gradient structure achieves synergistic effects of composition control, stress optimization, and enhanced transport through microstructural design. It possesses characteristics such as structural stability, fast ion transport kinetics, good interfacial compatibility, high specific capacity, and excellent cycling performance, providing a key material foundation for the practical application of high-energy-density all-solid-state lithium batteries.

[0008] Preferably, the molar ratio of FeF3·3H2O to the transition metal in the transition metal fluoride in step (1) is 95:5~50:50; the mass ratio of FeF3·3H2O added in step (1) to FeF3·3H2O added in step (3) is 50~99:1~50.

[0009] Preferably, the transition metal fluoride in step (1) is selected from at least one of ferrous fluoride, copper fluoride, cobalt fluoride, nickel fluoride, manganese fluoride, bismuth fluoride, and chromium fluoride; and the organic solvent in steps (2) and (3) is selected from at least one of n-propanol, isopropanol, n-butanol, and isobutanol.

[0010] Preferably, in step (1), the mixing and grinding time is 20-40 min; the ball-to-material ratio during ball milling is 50-100:1, and the ball milling is performed at 300-500 rpm for 1-4 h; in step (2), the heating and stirring temperature is 60-80℃, and the time is 30 min-6 h; the solvothermal reaction temperature is 170-200℃, and the time is 10-18 h; after the reaction, the temperature is lowered to below 80℃, and the standing time is 4-8 h; in step (3), the solvothermal reaction temperature is 200-220℃, and the time is 10-18 h.

[0011] Secondly, the present invention provides a fluorine oxide active material prepared using the above method.

[0012] Thirdly, the present invention provides a fluorine oxide-based composite positive electrode, the components of which include the above-mentioned fluorine oxide active material, conductive agent and solid electrolyte.

[0013] Preferably, the mass ratio of the fluoride active material to the conductive agent is 3:1 to 7:1; and the mass ratio of the total mass of the fluoride active material and the conductive agent to the mass of the solid electrolyte is 1:2 to 4:1.

[0014] Preferably, the solid electrolyte is selected from Li6PS5Cl and Li 5.5 PS 4.5 Cl 1.5 Li 10 GeP2S 12 The conductive agent is selected from at least one of Li3YCl6, Li3InCl6, LiBH4, and Li4(BH4)3I; the conductive agent is selected from at least one of Ketjen Black, acetylene black, vapor-grown carbon fiber, carbon nanotube, graphene, and Super P.

[0015] Fourthly, the present invention provides a method for preparing the above-mentioned fluoride-oxide-based composite positive electrode, comprising the following steps: mixing and grinding a fluoride-oxide active material and a conductive agent, followed by ball milling; mixing and grinding the ball-milled mixture with a solid electrolyte, followed by ball milling, to obtain the fluoride-oxide-based composite positive electrode.

[0016] Fifthly, the present invention provides an application of the above-mentioned fluoride oxide-based composite cathode in an all-solid-state lithium battery, wherein the electrolyte of the all-solid-state lithium battery is selected from Li6PS5Cl, Li 5.5 PS 4.5 Cl 1.5 Li 10 GeP2S 12 The anode is selected from at least one of Li3YCl6, Li3InCl6, LiBH4, and Li4(BH4)3I; the cathode is selected from at least one of lithium metal cathode, lithium-based alloy cathode, silicon-based cathode, carbon-based cathode, and lithium titanate cathode.

[0017] Therefore, the present invention has the following beneficial effects: (1) A core-shell gradient structure of fluorine oxide active material is constructed by stepwise high-energy ball milling and controlled heat treatment. The core is doped to introduce additional redox active sites to improve the theoretical specific capacity. Its expanded interlayer spacing provides a fast channel for lithium-ion transport. The shell exhibits fluorine-rich characteristics, which can stabilize the surface lattice oxygen by changing the electronic environment, enhance the structural stability, and also help to form a stable electrode / electrolyte interface in the early stage of cycling, effectively suppressing interfacial side reactions and reducing the lithium-ion cross-interface transport impedance. This gradient structure can play a stress buffering role during charging and discharging, suppressing crack propagation and structural distortion by dispersing lattice stress, thereby significantly improving the structural and interfacial stability of the cathode. (2) Fluorine oxide active material with core-shell gradient structure is combined with solid electrolyte and conductive agent to form a positive electrode material with continuous ion-electron transport network. This composite positive electrode has high specific capacity, excellent ion transport kinetics, good interfacial compatibility and long cycle stability. It is suitable for high energy density and high safety all-solid-state lithium battery system and can comprehensively improve the electrochemical performance of battery. Attached Figure Description

[0018] Figure 1 Fe prepared in Example 1 0.9 Ni 0.1 SEM images of OF active substances.

[0019] Figure 2 Fe prepared in Example 1 0.9 Ni 0.1 OF||Li-In all-solid-state lithium battery cycle performance image at 30℃, 0.6~2.4V vs. Li-In, 0.1C.

[0020] Figure 3 Fe prepared in Example 1 0.9 Ni 0.1 OF||Li-In all-solid-state lithium battery charge-discharge curve image at 30℃, 0.6~2.4V vs. Li-In, 0.1C.

[0021] Figure 4 Fe prepared in Example 1 0.9 Ni 0.1 EISNyquist curves of OF||Li-In all-solid-state lithium batteries after different number of cycles.

[0022] Figure 5 Fe prepared in Example 2 0.8 Mn 0.1 Ni 0.1 SEM images of OF active substances.

[0023] Figure 6 Fe prepared in Example 2 0.8 Mn 0.1 Ni 0.1 Image showing the cycle performance of an OF||Li-In all-solid-state lithium battery at 30°C, 0.6~2.4V vs. Li-In, 0.1C.

[0024] Figure 7 Fe prepared in Example 2 0.8 Mn 0.1 Ni 0.1OF||Li-In all-solid-state lithium battery charge-discharge curve image at 30℃, 0.6~2.4V vs. Li-In, 0.1C.

[0025] Figure 8 Fe prepared in Example 3 0.9 Ni 0.1 Image showing the cycle performance of an OF||Li7Si3 all-solid-state lithium battery at 60℃, 0.5~3V, and 0.05C.

[0026] Figure 9 Fe prepared in Example 3 0.9 Ni 0.1 The charge / discharge curves of the OF||Li7Si3 all-solid-state lithium battery at 60℃, 0.5~3V, and 0.05C.

[0027] Figure 10 Fe prepared for Comparative Example 1 0.9 Ni 0.1 OF||Li-In all-solid-state lithium battery cycle performance image at 30℃, 0.6~2.4V vs. Li-In, 0.1C.

[0028] Figure 11 Fe prepared for Comparative Example 1 0.9 Ni 0.1 OF||Li-In all-solid-state lithium battery charge-discharge curve image at 30℃, 0.6~2.4V vs. Li-In, 0.1C. Detailed Implementation

[0029] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0030] In this invention, unless otherwise specified, all equipment and raw materials are available from the market or commonly used in the industry. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art.

[0031] General Implementation Examples: A method for preparing a fluoride active substance includes the following steps: (1) FeF3·3H2O was mixed and ground with transition metal fluorides and then ball-milled; (2) Add the ball-milled product to an organic solvent, heat and stir to carry out a solvothermal reaction, and cool and let stand after the reaction is completed; (3) Disperse FeF3·3H2O in an organic solvent, stir evenly, and then drop it into the system after standing in step (2). Then raise the temperature to continue the solvothermal reaction. After the reaction is completed, separate and dry the product to obtain the fluorine oxide active material.

[0032] In one specific implementation, the molar ratio of FeF3·3H2O to the transition metal in the transition metal fluoride in step (1) is 95:5~50:50; the mass ratio of FeF3·3H2O added in step (1) to FeF3·3H2O added in step (3) is 50~99:1~50.

[0033] In one specific embodiment, the transition metal fluoride mentioned in step (1) is selected from at least one of ferrous fluoride, copper fluoride, cobalt fluoride, nickel fluoride, manganese fluoride, bismuth fluoride, and chromium fluoride; the organic solvent mentioned in steps (2) and (3) is selected from at least one of n-propanol, isopropanol, n-butanol, and isobutanol.

[0034] As a specific implementation method, the mixing and grinding time in step (1) is 20~40 min; the ball-to-material ratio during ball milling is 50~100:1, and the ball milling is carried out at 300~500 rpm for 1~4 h; the heating and stirring temperature in step (2) is 60~80℃, and the time is 30 min~6 h; the solvothermal reaction temperature is 170~200℃, and the time is 10~18 h; after the reaction, the temperature is lowered to below 80℃, and the standing time is 4~8 h; the solvothermal reaction temperature in step (3) is 200~220℃, and the time is 10~18 h.

[0035] A method for preparing a fluoride-oxide-based composite positive electrode containing the above-mentioned fluoride-oxide active material includes the following steps: mixing and grinding the fluoride-oxide active material and a conductive agent, followed by ball milling; mixing and grinding the ball-milled mixture with a solid electrolyte, followed by ball milling, to obtain the fluoride-oxide-based composite positive electrode.

[0036] In one specific implementation, the mass ratio of the fluoride active material to the conductive agent is 3:1 to 7:1; the total mass ratio of the fluoride active material and the conductive agent to the solid electrolyte is 1:2 to 4:1.

[0037] In one specific embodiment, the solid electrolyte is selected from Li6PS5Cl, Li 5.5 PS 4.5 Cl 1.5 Li 10 GeP2S 12 The conductive agent is selected from at least one of Li3YCl6, Li3InCl6, LiBH4, and Li4(BH4)3I; the conductive agent is selected from at least one of Ketjen Black, acetylene black, vapor-grown carbon fiber, carbon nanotube, graphene, and Super P.

[0038] In one specific embodiment, the fluoride active material and the conductive agent are mixed and ground for 15-30 minutes, and then ball-milled at 200-600 rpm for 1-4 hours at a ball-to-material ratio of 30:1-100:1; the ball-milled mixture is then ground with a solid electrolyte at a mass ratio of 1:2-4:1 for 15-45 minutes, and then ball-milled at 200-400 rpm for 1-2 hours at a ball-to-material ratio of 30:1-100:1; all the above processes are carried out in an argon atmosphere glove box.

[0039] A solid-state lithium battery, using the aforementioned fluorine oxide-based composite cathode as the positive electrode; the electrolyte is selected from Li6PS5Cl, Li 5.5 PS 4.5 Cl 1.5 Li 10 GeP2S 12 The anode is selected from at least one of Li3YCl6, Li3InCl6, LiBH4, and Li4(BH4)3I; the cathode is selected from at least one of lithium metal cathode, lithium-based alloy cathode, silicon-based cathode, carbon-based cathode, and lithium titanate cathode.

[0040] In one specific embodiment, the negative electrode is a sheet-like negative electrode or a powdered negative electrode; The sheet-shaped negative electrode is selected from at least one of the following: directly formed lithium metal negative electrode, lithium indium alloy negative electrode, lithium aluminum alloy negative electrode, lithium magnesium alloy negative electrode, and lithium silver alloy negative electrode. The powdered anode comprises, by mass percentage, 60-100% active material, 0-20% conductive agent, and 0-20% electrolyte; the active material is selected from at least one of silicon-based anode materials, carbon-based anode materials, and lithium titanate anode materials; the solid electrolyte is selected from Li6PS5Cl and Li 5.5 PS 4.5 Cl 1.5 Li 10 GeP2S 12 At least one of Li3YCl6, Li3InCl6, LiBH4, and Li4(BH4)3I; the conductive agent is selected from at least one of KB, AB, VGCF, CNT, graphene, and SP.

[0041] As one specific embodiment, the preparation method of the powdered negative electrode is as follows: the active material, solid electrolyte and conductive agent are mixed and ground evenly, and the above process is carried out in an argon atmosphere glove box; then the mixture is added to a ball mill jar and ball milled at 200-600 rpm for 1-4 hours at a ball-to-material ratio of 30:1 to 100:1 to obtain the powdered negative electrode.

[0042] As one specific implementation method, the above-mentioned method for preparing an all-solid-state lithium battery includes the following steps: S1: Preparation of electrolyte tablets: Weigh 80~100mg of electrolyte powder, add it into a solid battery mold, apply a pressure of 200~400MPa using a powder tablet press and hold the pressure for 30s~1min to obtain electrolyte tablets; S2: Preparation of the positive electrode sheet: according to 2~10mg cm -2 The active material loading is determined by weighing the fluorine oxide-based composite positive electrode powder, adding it to the positive end of the solid-state battery mold, applying a pressure of 200~400MPa using a powder press and holding the pressure for 30s~1min to obtain the positive electrode sheet; S3: Preparation of negative electrode sheet: For sheet-shaped negative electrode, it is directly added to the negative end of the solid-state battery mold; for powdered negative electrode, the powdered negative electrode material is weighed and added to the negative end of the solid-state battery mold, and a pressure of 200~400MPa is applied using a powder press and held for 30s~1min to obtain the negative electrode sheet. All of the above processes were carried out in an argon atmosphere glove box; S4: Apply pressure to the outside of the solid-state battery mold using a stainless steel frame with a torque of 3~10 N·m to obtain a fully solid-state lithium battery.

[0043] Example 1:

[0044] (1) Fe 0.9 Ni 0.1 Preparation of OF active substances: The total feed was calculated based on a Fe to Ni molar ratio of 9:1. First, 80 wt% of FeF3·3H2O (based on the total iron content) was mixed with all NiF2 and ground for 20 min. Then, the mixture was transferred to a ball mill jar and ball-milled at 400 rpm for 1 h at a ball-to-material ratio of 50:1. Next, the milled product was added to n-propanol and heated and stirred at 80 °C for 1 h. The mixture was then transferred to a tetrafluoroethylene-lined high-temperature, high-pressure reactor and reacted at 180 °C for 12 h. After the reaction, the system was cooled to 80 °C and allowed to stand for 6 h. The remaining 20 wt% of FeF3·3H2O was dispersed in n-propanol and stirred for 1 h until homogeneous, then slowly added dropwise to the above-mentioned system after standing. The reaction temperature was then raised to 210 °C and the reaction continued for 12 h. The resulting suspension was centrifuged and washed three times at 4000–10000 rpm, and the precipitate was finally vacuum-dried at 80 °C for 24 h to obtain Fe. 0.9 Ni 0.1 OF active substance; its SEM image is as follows Figure 1 As shown in the image.

[0045] (2) Fe 0.9 Ni 0.1 Preparation of OF-based composite cathode: In an argon atmosphere glove box, Fe 0.9 Ni 0.1OF active material and KB conductive agent were mixed and ground at a mass ratio of 4:1 for 30 min. The mixture was then added to a ball mill jar and ball-milled at 400 rpm for 2 h at a ball-to-material ratio of 80:1. The mixed material was then ground with Li6PS5Cl solid electrolyte at a mass ratio of 1:1 for 45 min, and then added to the ball mill jar again and ball-milled at 400 rpm for 2 h at a ball-to-material ratio of 80:1. After the materials were thoroughly mixed, Fe was obtained. 0.9 Ni 0.1 OF-based composite cathode.

[0046] (3) Fe 0.9 Ni 0.1 Preparation of OF||Li-In all-solid-state lithium batteries: In an argon-atmospheric glove box, 100 mg of Li6PS5Cl electrolyte powder was weighed and added to a solid-state battery mold. A powder press was used to apply a pressure of 300 MPa and hold for 1 minute to obtain electrolyte tablets. Following the 2 mg / cm³ formula... -2 The active material loading was weighed out as Fe 0.9 Ni 0.1 OF-based composite cathode powder was added to the positive terminal of a solid-state battery mold. A powder press was used to apply a pressure of 300 MPa and hold for 1 minute to obtain the cathode sheet. A lithium-indium alloy anode sheet was added to the negative terminal of the solid-state battery mold. A stainless steel frame was then used to apply pressure to the outside of the solid-state battery mold at a torque of 5 N·m to obtain Fe. 0.9 Ni 0.1 OF||Li-In all-solid-state lithium battery.

[0047] (4) Fe 0.9 Ni 0.1 OF||Li-In all-solid-state lithium battery cycle performance test: Fe was tested at 30℃, 0.6~2.4V vs. Li-In, 0.1C. 0.9 Ni 0.1 The cycle performance and charge / discharge performance of OF||Li-In all-solid-state lithium batteries are shown in the following results. Figure 2 and Figure 3 As shown; the discharge specific capacity after 50 cycles is approximately 760 mAh g. -1 .

[0048] (5) Fe 0.9 Ni 0.1 Impedance test of Li-In all-solid-state lithium battery after different number of cycles: The Fe was studied using a Bio-Logic SP-300 electrochemical workstation. 0.9 Ni 0.1Electrochemical impedance spectroscopy (EIS) was performed on the OF||Li-In all-solid-state lithium battery. The frequency range was 4MHz to 0.1Hz, and the test temperature was 30℃. The resulting EIS Nyquist curves are shown below. Figure 4 As shown in the image.

[0049] Example 2:

[0050] (1) Fe 0.8 Mn 0.1 Ni 0.1 Preparation of OF active substances: The total feed was calculated based on a Fe:Mn:Ni molar ratio of 8:1:1. First, FeF3·3H2O (75 wt% of the total iron content) was mixed with all MnF2 and NiF2 and ground for 20 min. Then, the mixture was transferred to a ball mill jar and ball-milled at 400 rpm for 1 h at a ball-to-material ratio of 50:1. Next, the ball-milled product was added to isopropanol and heated and stirred at 80°C for 1 h. The mixture was then transferred to a tetrafluoroethylene-lined high-temperature, high-pressure reactor and reacted at 180°C for 12 h. After the reaction, the system was cooled to 80°C and allowed to stand for 6 h. The remaining 25 wt% FeF3·3H2O was dispersed in isopropanol and stirred for 1 h until homogeneous, then slowly added dropwise to the above-mentioned system after standing. The reaction temperature was then raised to 210°C and the reaction continued for 12 h. The resulting suspension was centrifuged and washed three times at 8000 rpm, and the precipitate was finally vacuum-dried at 80°C for 24 h to obtain Fe. 0.8 Mn 0.1 Ni 0.1 OF active substance; its SEM image is as follows Figure 5 As shown in the image.

[0051] (2) Fe 0.8 Mn 0.1 Ni 0.1 Preparation of OF-based composite cathode: In an argon atmosphere glove box, Fe 0.8 Mn 0.1 Ni 0.1 OF active material and CNT conductive agent were mixed and ground at a mass ratio of 4:1 for 30 min. The mixture was then added to a ball mill jar and ball-milled at 400 rpm for 2 h at a ball-to-material ratio of 80:1. The mixed material was then combined with Li... 5.5 PS 4.5 Cl 1.5 The solid electrolyte was ground at a 1:1 mass ratio for 45 minutes, then added to a ball mill jar and ball-milled at 400 rpm for 2 hours at a ball-to-material ratio of 80:1. Once all materials were uniformly mixed, Fe was obtained. 0.8 Mn 0.1 Ni 0.1 OF-based composite cathode.

[0052] (3) Fe 0.8 Mn 0.1 Ni 0.1 Preparation of OF||Li-In all-solid-state lithium batteries: In an argon atmosphere glove box, weigh 100 mg of Li 5.5 PS 4.5 Cl 1.5 Electrolyte powder was added to a solid-state battery mold, and a powder tablet press was used to apply a pressure of 300 MPa and hold the pressure for 1 minute to obtain electrolyte tablets; 2 mg cm -2 The active material loading was weighed out as Fe 0.8 Mn 0.1 Ni 0.1 OF-based composite cathode powder was added to the positive terminal of a solid-state battery mold. A powder press was used to apply a pressure of 300 MPa and hold for 1 minute to obtain the cathode sheet. A lithium-indium alloy anode sheet was added to the negative terminal of the solid-state battery mold. A stainless steel frame was then used to apply pressure to the outside of the solid-state battery mold at a torque of 5 N·m to obtain Fe. 0.8 Mn 0.1 Ni 0.1 OF||Li-In all-solid-state lithium battery.

[0053] (4) Fe 0.8 Mn 0.1 Ni 0.1 OF||Li-In all-solid-state lithium battery cycle performance test: Fe was tested at 30℃, 0.6~2.4V vs. Li-In, 0.1C. 0.8 Mn 0.1 Ni 0.1 The cycle performance and charge / discharge performance of OF||Li-In all-solid-state lithium batteries are shown in the following results. Figure 6 and Figure 7 As shown, the discharge specific capacity after 50 cycles is approximately 560 mAhg. -1 .

[0054] Example 3:

[0055] (1) Preparation of Li7Si3-based powdered negative electrode: In an argon-atmospheric glove box, Li7Si3 active material, LiBH4·LiI solid electrolyte and SP conductive agent were mixed and ground evenly at a mass ratio of 60:20:20; then the mixture was added to a ball mill jar and ball milled at 400 rpm for 2 hours at a ball-to-material ratio of 80:1 to obtain Li7Si3-based powdered negative electrode.

[0056] (2) Fe 0.9 Ni0.1 Fabrication of OF||Li7Si3 all-solid-state lithium batteries: In an argon-atmospheric glove box, 100 mg of LiBH4·LiI electrolyte powder was weighed and added to a solid-state battery mold. A powder press was used to apply a pressure of 300 MPa and hold for 1 minute to obtain electrolyte tablets. Following the 3 mg / cm³ formula... -2 The active material loading was determined by weighing the Fe obtained in Example 1. 0.9 Ni 0.1 OF-based composite cathode powder was added to the positive terminal of a solid-state battery mold. A powder press was used to apply a pressure of 300 MPa and hold for 1 minute to obtain the cathode sheet. Controlling N / P = 1.3, a certain amount of Li7Si3-based powdered anode material was weighed and added to the negative terminal of the solid-state battery mold. A powder press was used to apply a pressure of 300 MPa and hold for 1 minute to obtain the anode sheet. Finally, a stainless steel frame was used to apply pressure to the outside of the solid-state battery mold at a torque of 6 N·m to obtain Fe. 0.9 Ni 0.1 OF||Li7Si3 all-solid-state lithium battery.

[0057] (3) Fe 0.9 Ni 0.1 Electrochemical performance testing of OF||Li7Si3 all-solid-state lithium batteries: Fe was tested at 60℃, 0.5~3V, and 0.05C. 0.9 Ni 0.1 The cycle performance and charge / discharge performance of the OF||Li7Si3 all-solid-state lithium battery are shown in the following results. Figure 8 and Figure 9 As shown, the discharge specific capacity after 30 cycles is approximately 630 mAh g. -1 .

[0058] Comparative Example 1 (without core-shell structure): (1) Fe 0.9 Ni 0.1 Preparation of OF active substances: The total feed was calculated based on a Fe to Ni molar ratio of 9:1. FeF3·3H2O and NiF2 were mixed and ground for 20 min. The mixture was then transferred to a ball mill jar and ball-milled at 400 rpm for 1 h at a ball-to-material ratio of 50:1. The milled product was then added to n-propanol and heated and stirred at 80 °C for 1 h. The mixture was then transferred to a tetrafluoroethylene-lined high-temperature, high-pressure reactor and reacted at 180 °C for 12 h. After the reaction, the resulting suspension was centrifuged and washed three times at 4000–10000 rpm. Finally, the precipitate was vacuum-dried at 80 °C for 24 h to obtain Fe. 0.9 Ni 0.1 OF active substances.

[0059] (2) Fe 0.9 Ni 0.1 Preparation of OF-based composite cathode: In an argon atmosphere glove box, the obtained Fe 0.9 Ni 0.1 OF active material and KB conductive agent were mixed and ground at a mass ratio of 4:1 for 30 min. The mixture was then added to a ball mill jar and ball-milled at 400 rpm for 2 h at a ball-to-material ratio of 80:1. The mixed material was then ground with Li6PS5Cl solid electrolyte at a mass ratio of 1:1 for 45 min, and then added to the ball mill jar again and ball-milled at 400 rpm for 2 h at a ball-to-material ratio of 80:1. After the materials were thoroughly mixed, Fe was obtained. 0.9 Ni 0.1 OF-based composite cathode.

[0060] (3) Fe 0.9 Ni 0.1 Preparation of OF||Li-In all-solid-state lithium batteries: In an argon-atmospheric glove box, 100 mg of Li6PS5Cl electrolyte powder was weighed and added to a solid-state battery mold. A powder press was used to apply a pressure of 300 MPa and hold for 1 minute to obtain electrolyte tablets. Following the 2 mg / cm³ formula... -2 The active material loading was weighed out as Fe 0.9 Ni 0.1 OF-based composite cathode powder was added to the positive terminal of a solid-state battery mold. A powder press was used to apply a pressure of 300 MPa and hold for 1 minute to obtain the cathode sheet. A lithium-indium alloy anode sheet was added to the negative terminal of the solid-state battery mold. A stainless steel frame was then used to apply pressure to the outside of the solid-state battery mold at a torque of 5 N·m to obtain Fe. 0.9 Ni 0.1 OF||Li-In all-solid-state lithium battery.

[0061] (4) Fe 0.9 Ni 0.1 OF||Li-In all-solid-state lithium battery cycle performance test: Fe was tested at 30℃, 0.6~2.4V vs. Li-In, 0.1C. 0.9 Ni 0.1 The cycle performance and charge / discharge performance of OF||Li-In all-solid-state lithium batteries are shown in the following results. Figure 10 and Figure 11 As shown; the discharge specific capacity after 50 cycles is approximately 554 mAh g. -1 .

[0062] As can be seen from the above results, the fluorine oxide-based composite cathodes with core-shell gradient structures prepared by the stepwise high-energy ball milling and controlled heat treatment method of the present invention in Examples 1-3 can significantly improve the cycle stability of all-solid-state batteries compared with the cathodes without core-shell gradient structures in Comparative Document 1. They also have high specific capacity and excellent ion transport dynamics, and are suitable for all-solid-state lithium battery systems with high energy density and high safety.

[0063] It should be noted that the specific implementation methods described above provide a detailed explanation of the technical solution and application results of the present invention. The above embodiments are only the most preferred embodiments and are not intended to limit the present invention. Modifications or equivalent substitutions made by those skilled in the art within the core theoretical scope of the present invention should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a fluoride oxide active substance, characterized in that, Includes the following steps: (1) FeF3·3H2O was mixed and ground with transition metal fluorides and then ball-milled; (2) Add the ball-milled product to an organic solvent, heat and stir to carry out a solvothermal reaction, and cool and let stand after the reaction is completed; (3) Disperse FeF3·3H2O in an organic solvent, stir evenly, and then drop it into the system after standing in step (2). Then raise the temperature to continue the solvothermal reaction. After the reaction is completed, separate and dry the product to obtain the fluorine oxide active material.

2. The method for preparing the fluoride active substance according to claim 1, characterized in that, In step (1), the molar ratio of FeF3·3H2O to the transition metal in the transition metal fluoride is 95:5~50:50; The mass ratio of FeF3·3H2O added in step (1) to FeF3·3H2O added in step (3) is 50~99:1~50.

3. The method for preparing the fluoride active substance according to claim 1 or 2, characterized in that, The transition metal fluoride mentioned in step (1) is selected from at least one of ferrous fluoride, copper fluoride, cobalt fluoride, nickel fluoride, manganese fluoride, bismuth fluoride, and chromium fluoride; The organic solvents mentioned in steps (2) and (3) are selected from at least one of n-propanol, isopropanol, n-butanol, and isobutanol.

4. The method for preparing the fluoride active substance according to claim 1 or 2, characterized in that, The mixing and grinding time in step (1) is 20~40 min; the ball-to-material ratio during ball milling is 50~100:1, and the ball milling is carried out at 300~500 rpm for 1~4 h; In step (2), the heating and stirring temperature is 60~80℃ and the time is 30min~6h; the solvothermal reaction temperature is 170~200℃ and the time is 10~18h; after the reaction, the temperature is lowered to below 80℃ and the standing time is 4~8h. In step (3), the temperature of the solvothermal reaction is 200~220℃ and the time is 10~18h.

5. A fluorine oxide active substance, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 4.

6. A fluorine oxide-based composite positive electrode, characterized in that, The components include the fluorine oxide active material, conductive agent, and solid electrolyte as described in claim 5.

7. The fluorine oxide-based composite positive electrode according to claim 6, characterized in that, The mass ratio of fluoride active material to conductive agent is 3:1 to 7:1; the total mass ratio of fluoride active material and conductive agent to solid electrolyte is 1:2 to 4:

1.

8. The fluoride-based composite positive electrode according to claim 6 or 7, characterized in that, The solid electrolyte is selected from Li6PS5Cl, Li 5.5 PS 4.5 Cl 1.5 Li 10 GeP2S 12 At least one of Li3YCl6, Li3InCl6, LiBH4, and Li4(BH4)3I; The conductive agent is selected from at least one of Ketjen Black, acetylene black, vapor-grown carbon fiber, carbon nanotubes, graphene, and Super P.

9. A method for preparing a fluorine oxide-based composite positive electrode as described in any one of claims 6 to 8, characterized in that, The process includes the following steps: mixing and grinding a fluoride active material and a conductive agent, followed by ball milling; mixing and grinding the ball-milled mixture with a solid electrolyte, followed by ball milling, to obtain the fluoride-based composite positive electrode.

10. The application of a fluorine oxide-based composite cathode as described in any one of claims 6 to 8 in an all-solid-state lithium battery, characterized in that, The electrolyte for the all-solid-state lithium battery is selected from Li6PS5Cl and Li 5.5 PS 4.5 Cl 1.5 Li 10 GeP2S 12 The anode is selected from at least one of Li3YCl6, Li3InCl6, LiBH4, and Li4(BH4)3I; the cathode is selected from at least one of lithium metal cathode, lithium-based alloy cathode, silicon-based cathode, carbon-based cathode, and lithium titanate cathode.

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