Positive electrode material, and electrochemical device and electronic device comprising same

Abstract

The present application relates to a positive electrode material, and an electrochemical device and an electronic device comprising the same. The present application provides a positive electrode material comprising a composite material, wherein the composite material comprises a metal fluoride, the molar ratio of fluorine element F to metal element M in the metal fluoride is y, the molar ratio of fluorine element F to metal element M in the composite material is z, wherein y < z < y + 2; and wherein the M comprises at least one of Al, Cu, Co, Ni, Mn, Fe or Ag. The positive electrode material of the present application has the advantages of wide raw material sources, simple preparation process, easy operation, low production cost, etc. The lithium battery prepared from the positive electrode material of the present application has improved specific capacity, rate performance and cycle performance of the positive electrode material, and better charge-discharge performance.

Description

Technical Field

[0001] This application relates to the field of energy storage, specifically to a cathode material and an electrochemical and electronic device containing the same, particularly an all-solid-state secondary lithium battery. Background Technology

[0002] With the widespread adoption of consumer electronics such as laptops, mobile phones, tablets, power banks, and drones, the requirements for their electrochemical devices are becoming increasingly stringent. For example, batteries are not only required to be lightweight, but also to have high capacity and long lifespan. Lithium-ion batteries, with their outstanding advantages such as high energy density, high safety, no memory effect, and long lifespan, have already gained a mainstream position in the market. Summary of the Invention

[0003] This application provides a cathode material in an attempt to solve at least one problem existing in related fields to some extent. This application also provides a cathode, an electrochemical device, and an electronic device using the cathode material.

[0004] In one embodiment, this application provides a positive electrode material comprising a composite material comprising a metal fluoride, wherein the molar ratio of fluorine element F to metal element M in the metal fluoride is y, and the molar ratio of fluorine element F to metal element M in the composite material is z, wherein y < z ≤ y + 2; and wherein M comprises at least one of Al, Cu, Co, Ni, Mn, Fe or Ag.

[0005] In another embodiment, this application provides a method for preparing a composite material, the method comprising:

[0006] (1) Mix the metal fluoride and fluorinated graphite, and dry them; and

[0007] (2) Annealing at 200℃ to 600℃ for 10 to 72 hours, crushing and sieving to obtain composite material;

[0008] The molar ratio of fluorine (F) to metal (M) in the metal fluoride is y; the molar ratio of fluorine (F) to metal (M) in the cathode material is z, where y < z ≤ y + 2; and

[0009] The M includes at least one of Al, Cu, Co, Ni, Mn, Fe, or Ag.

[0010] In another embodiment, this application provides a positive electrode comprising the positive electrode material described in embodiments of this application.

[0011] In another embodiment, this application provides an electrochemical device including a positive electrode as described in embodiments of this application.

[0012] In some embodiments, the electrochemical device is an all-solid-state rechargeable lithium battery. In some embodiments, the all-solid-state rechargeable lithium battery includes a positive electrode, a negative electrode, and a solid electrolyte. In some embodiments, the positive electrode includes the positive electrode material described in the above embodiments.

[0013] In another embodiment, this application provides an electronic device that includes the electrochemical device described in the embodiments of this application.

[0014] The cathode material of this application has advantages such as wide availability of raw materials, simple preparation process, ease of operation, and low production cost. Lithium batteries prepared from the cathode material of this application exhibit improved specific capacity, rate performance, and cycle performance, as well as better charge-discharge performance.

[0015] Additional aspects and advantages of the embodiments of this application will be described and shown in part in the following description, or illustrated by practice of the embodiments of this application. Attached Figure Description

[0016] The accompanying drawings, necessary for describing embodiments of this application or the prior art, will be briefly described below to facilitate the depiction of embodiments of this application. It is obvious that the drawings described below represent only a portion of the embodiments in this application. Those skilled in the art will be able to derive other embodiments from the structures illustrated in these drawings without requiring inventive effort.

[0017] Figure 1 This diagram illustrates the electrochemical reaction that occurs after the first charge and discharge of the composite positive electrode active material in Example 9 of this application.

[0018] Figure 2 The curves showing the capacity retention rate of the all-solid-state secondary lithium batteries of Comparative Examples 2, 4 and 4 of this application as a function of the number of cycles are shown. Detailed Implementation

[0019] The embodiments of this application will be described in detail below. These embodiments should not be construed as limiting the scope of this application.

[0020] Quantities, ratios, and other numerical values ​​are presented in range format in this document. It should be understood that this range format is for convenience and brevity and should be interpreted flexibly to include not only numerical values ​​explicitly specified as range limits, but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0021] In the detailed description and claims, a list of items connected by the terms "one of," "among," "a kind of," or other similar terms may mean any of the listed items. For example, if items A and B are listed, then the phrase "one of A and B" means only A or only B. In another example, if items A, B, and C are listed, then the phrase "one of A, B, and C" means only A; only B; or only C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0022] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0023] I. Cathode Materials

[0024] In some embodiments, this application provides a positive electrode material comprising a composite material comprising a metal fluoride, wherein the molar ratio of fluorine element F to metal element M in the metal fluoride is y, and the molar ratio of fluorine element F to metal element M in the composite material is z, wherein y < z ≤ y + 2; and wherein M comprises at least one of Al, Cu, Co, Ni, Mn, Fe or Ag.

[0025] In some embodiments, M includes Cu, Fe, or a combination thereof.

[0026] In some embodiments, y < z ≤ y + 1.5. In some embodiments, y < z ≤ y + 0.05, y < z ≤ y + 0.1, y < z ≤ y + 0.15, y < z ≤ y + 0.2, y < z ≤ y + 0.5, y < z ≤ y + 0.7, y < z ≤ y + 0.9, y < z ≤ y + 1, or y < z ≤ y + 1.2.

[0027] In some embodiments, the composite material further comprises fluorinated graphite, wherein the fluorinated graphite has the structural formula CF. x The CF x The molar ratio of fluorine (F) to carbon (C) is x, where 0 < x ≤ 1.

[0028] In some embodiments, 0 < x ≤ 0.9. In some embodiments, 0 < x ≤ 0.8. In some embodiments, 0 < x ≤ 0.7. In some embodiments, 0 < x ≤ 0.6. In some embodiments, 0 < x ≤ 0.5, 0 < x ≤ 0.4, 0 < x ≤ 0.3, or 0 < x ≤ 0.2.

[0029] In some embodiments, the mass ratio of the fluorinated graphite to the metal fluoride is w, where 0 < w ≤ 0.2. In some embodiments, 0 < w ≤ 0.15. In some embodiments, 0 < w ≤ 0.1. In some embodiments, 0 < w ≤ 0.05. In some embodiments, w may also be 0.02, 0.03, 0.06, 0.07, etc.

[0030] In some embodiments, the metal fluoride includes at least one selected from CoF3, NiF3, MnF2, FeF3, FeF2, AlF3, or CuF2. In some embodiments, the metal fluoride includes FeF3, CuF2, or a combination thereof.

[0031] In some embodiments, the cathode material contains lithium. In some embodiments, the cathode material does not contain lithium.

[0032] In some embodiments, the positive electrode material may be represented as a composite material MF. y .w(CF x ), where M, w, x, and y are defined as described above.

[0033] II. Preparation methods of composite materials

[0034] This application provides a method for preparing composite materials, the method comprising:

[0035] (1) Mix the metal fluoride and fluorinated graphite, and dry them; and

[0036] (2) Annealing at 200℃ to 600℃ for 10 to 72 hours, crushing and sieving to obtain composite material;

[0037] The molar ratio of fluorine (F) to metal (M) in the metal fluoride is y; the molar ratio of fluorine (F) to metal (M) in the composite material is z, where y < z ≤ y + 2; and

[0038] The M includes at least one of Al, Cu, Co, Ni, Mn, Fe, or Ag.

[0039] In some embodiments, metal fluorides and fluorinated graphite are defined as described above.

[0040] In some embodiments, mixing is carried out using a ball mill, V-type mixer, three-dimensional mixer, airflow mixer, or horizontal agitator. In some embodiments, mixing is high-energy ball milling.

[0041] In some embodiments, the ball milling is either wet ball milling or dry ball milling. In some embodiments, the ball milling is wet ball milling.

[0042] In some embodiments, a ball milling dispersant is used during the ball milling process. In some embodiments, the ball milling dispersant includes anhydrous ethanol.

[0043] In some embodiments, during the ball milling step, the volume ratio of the milling material to the grinding balls is 1:3 to 1:20. In some embodiments, the volume ratio of the milling material to the grinding balls is 1:10.

[0044] In some embodiments, the rotational speed during the ball milling step is from 300 r / min to 1200 r / min. In some embodiments, the rotational speed during the ball milling step is 800 r / min.

[0045] In some embodiments, the ball milling time is 4 hours to 24 hours. In some embodiments, the ball milling time is a range of 4 hours, 6 hours, 10 hours, 15 hours, 20 hours, 24 hours, or any combination of these values.

[0046] In some embodiments, the drying temperature is from 60°C to 120°C. In some embodiments, the drying temperature is a range of 60°C, 70°C, 80°C, 100°C, 120°C, or any combination of these values.

[0047] In some embodiments, the annealing temperature is from 200°C to 600°C. In some embodiments, the annealing temperature is a range of 200°C, 250°C, 300°C, 350°C, 400°C, 500°C, 600°C, or any combination of these values.

[0048] In some embodiments, the annealing time is from 10 hours to 72 hours. In some embodiments, the annealing time is a range of 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 50 hours, 60 hours, 65 hours, 72 hours, or any combination of these values.

[0049] In some embodiments, the annealing process is performed in an atmosphere sintering furnace. In some embodiments, the atmosphere sintering furnace can be an atmosphere tube furnace, an atmosphere box furnace, or other sintering furnaces with similar atmosphere protection functions.

[0050] In some embodiments, the atmosphere used in the atmosphere sintering furnace is an inert gas. In some embodiments, the inert gas is high-purity argon or high-purity nitrogen.

[0051] In recent years, with the advent of electric vehicles and the 5G era, the demand for high-energy-density and high-safety lithium batteries has become increasingly urgent. Lithium metal, with its high specific capacity (3860 mAh / g) and low electrochemical potential (-3.040 V relative to the standard hydrogen electrode), is considered the most ideal high-energy-density anode material. Therefore, solid-state lithium batteries using lithium metal as the anode have become a current research hotspot. Traditional lithium-ion batteries mostly use organic liquid electrolytes or gel electrolytes; the flammable and explosive organic liquids pose significant safety hazards to the battery system.

[0052] Solid-state lithium batteries operate on the same principle as traditional lithium-ion batteries, with the structural change being the replacement of the traditional liquid organic electrolyte and separator with a solid electrolyte, making the battery safer. Furthermore, the structure of solid-state lithium batteries is simpler, mainly consisting of a positive electrode, a solid electrolyte, and a negative electrode. Currently, the positive electrodes used in solid-state lithium batteries are mostly traditional lithium-containing materials, such as LiCoO2 and LiFePO4. The specific capacity of these lithium-containing positive electrode materials is far lower than that of the negative electrode, which cannot meet the requirements of high-energy-density all-solid-state lithium batteries. Therefore, solid-state lithium batteries using lithium metal as the negative electrode must be paired with positive electrode materials with higher energy density. Metal fluoride (such as FeF3, FeF2, and CuF2) positive electrode materials can provide energy densities as high as 1000Wh / Kg to 1600Wh / Kg, far exceeding the 600Wh / Kg to 800Wh / Kg of the LiCoO2 system, thus possessing great application potential. In addition, lithium-free cathode materials such as metal fluorides often use inexpensive iron, thus having advantages such as abundant resources, low cost, and environmental friendliness.

[0053] Currently, lithium-free cathode materials such as metal fluorides have the following significant drawbacks: First, the conductivity of metal fluorides is generally low; it has been reported that the conductivity of FeF3 is only 10. -17 With a voltage of S / cm, it is almost an insulator; during charging and discharging, the discharge voltage is lower than the charging voltage, resulting in the so-called voltage hysteresis phenomenon, and the material has poor rate capability and cycle stability. Second, transition metal ions are easily dissolved from the positive electrode material during charging and discharging, enter the electrolyte, and undergo side reactions, accelerating capacity decay during cycling.

[0054] To address the above problems, this invention provides a lithium battery cathode material. The cathode material is initially a composite material of metal fluoride and fluorinated graphite. Compared to metal fluoride cathode materials, the composite material of metal fluoride and fluorinated graphite of this application has the following advantages as a cathode material: (1) the addition of fluorinated graphite can significantly improve the specific capacity of the cathode material; (2) as... Figure 1As shown, during the first discharge, the fluorinated graphite on the surface of the positive electrode material reacts chemically with the lithium ions released from the negative electrode, generating nano-carbon in situ, thereby increasing the conductivity of the positive electrode, which is beneficial for stabilizing the discharge voltage and improving the discharge efficiency; and (3) as Figure 1 As shown, after the first discharge reaction is completed, in addition to generating nano-carbon in situ, fluorinated graphite will also generate LiF. These products can also be used as lithium sources to compensate for the lithium loss of the cathode material during multiple cycles, thereby improving the long-term cycle stability.

[0055] In addition, the present invention has achieved the following beneficial effects:

[0056] 1) The metal fluoride and fluorinated graphite composite cathode material of the present invention has higher specific capacity and improved rate performance and cycle performance.

[0057] 2) The lithium battery cathode material provided by this invention has a wide range of raw material sources, a simple preparation process, is easy to operate, and has a low production cost.

[0058] 3) The all-solid-state secondary lithium battery prepared with the cathode material of the present invention has good charge and discharge performance and has great application prospects in the fields of 3C electronic products and electric vehicle batteries.

[0059] III. Electrochemical Device

[0060] Embodiments of this application provide an electrochemical device, which includes any device in which an electrochemical reaction occurs.

[0061] In some embodiments, the electrochemical device of this application includes a negative electrode having a negative electrode active material capable of adsorbing and releasing metal ions; a positive electrode according to an embodiment of this application; an electrolyte; and a separating membrane disposed between the positive electrode and the negative electrode.

[0062] In some embodiments, the electrochemical device of this application includes, but is not limited to, a secondary battery.

[0063] In some embodiments, the electrochemical device is a lithium secondary battery.

[0064] In some embodiments, the lithium secondary battery includes, but is not limited to: lithium metal secondary battery, lithium-ion secondary battery, lithium polymer secondary battery or lithium-ion polymer secondary battery, and all-solid-state secondary lithium battery.

[0065] 1. Negative electrode

[0066] The materials, composition, and manufacturing methods of the negative electrode used in the electrochemical device of this application may include any techniques disclosed in the prior art. In some embodiments, the negative electrode is the negative electrode described in U.S. Patent Application US9812739B, which is incorporated herein by reference in its entirety.

[0067] In some embodiments, the negative electrode includes a current collector and a negative electrode active material layer located on the current collector. In some embodiments, the negative electrode active material layer includes a negative electrode active material. In some embodiments, the negative electrode active material includes, but is not limited to: lithium metal, structured lithium metal, natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, silicon-oxygen materials, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, and spinel-structured lithiated TiO2-Li4Ti5O. 12 Li-Al alloys or any combination thereof.

[0068] In some embodiments, the negative electrode active material layer includes an adhesive. In some embodiments, the adhesive includes, but is not limited to: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon.

[0069] In some embodiments, the negative electrode active material layer includes a conductive material. In some embodiments, the conductive material includes, but is not limited to: natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, metal powder, metal fiber, copper, nickel, aluminum, silver, or polyphenylene derivatives.

[0070] In some embodiments, the current collector includes, but is not limited to: copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or a polymer substrate coated with a conductive metal.

[0071] In some embodiments, the negative electrode can be obtained by mixing an active material, a conductive material, and a binder in a solvent to prepare an active material composition, and then coating the active material composition onto a current collector.

[0072] In some embodiments, the solvent may include, but is not limited to, deionized water and N-methylpyrrolidone.

[0073] In some embodiments, the negative electrode in an all-solid-state secondary lithium battery is a metallic lithium foil.

[0074] 2. Positive electrode

[0075] This application provides a positive electrode. In some embodiments, the positive electrode in an all-solid-state secondary lithium battery includes the positive electrode material and conductive agent according to any embodiment of this application.

[0076] In some embodiments, the positive electrode includes a current collector and a positive electrode active material layer located on the current collector. The positive electrode active material layer includes a positive electrode material according to embodiments of this application.

[0077] In some embodiments, the positive electrode active material layer further includes a binder and / or a conductive agent. The binder improves the bonding between the positive electrode active material particles and also improves the bonding between the positive electrode active material and the current collector.

[0078] In some embodiments, the adhesive comprises at least one of the following compounds: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon, etc.

[0079] In some embodiments, the conductive agent includes at least one of the following compounds: conductive carbon black, carbon fiber, acetylene black, Ketjen black, graphene, and carbon nanotubes.

[0080] In some embodiments, the current collector may include, but is not limited to, aluminum.

[0081] The positive electrode can be prepared by methods known in the art. For example, the positive electrode can be obtained by mixing an active material, a conductive material, and a binder in a solvent to prepare an active material composition, and then coating the active material composition onto a current collector. In some embodiments, the solvent may include, but is not limited to, N-methylpyrrolidone.

[0082] 3. Electrolyte

[0083] The electrolyte that can be used in the embodiments of this application can be an electrolyte known in the prior art.

[0084] In some embodiments, the electrolyte comprises an organic solvent, a lithium salt, and additives. The organic solvent of the electrolyte according to this application may be any organic solvent known in the art that can be used as an electrolyte solvent. There are no limitations on the electrolyte used in the electrolyte according to this application; it may be any electrolyte known in the art. The additives of the electrolyte according to this application may be any additives known in the art that can be used as electrolyte additives.

[0085] In some embodiments, the organic solvent includes, but is not limited to: ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate, or ethyl propionate.

[0086] In some embodiments, the lithium salt includes at least one of an organic lithium salt or an inorganic lithium salt.

[0087] In some embodiments, the lithium salt includes, but is not limited to: lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis(trifluoromethanesulfonyl)imide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)amide Li(N(SO2F)2) (LiFSI), lithium bis(oxalateborate)borate LiB(C2O4)2 (LiBOB), or lithium difluorooxalateborate LiBF2(C2O4) (LiDFOB).

[0088] In some embodiments, the concentration of lithium salt in the electrolyte is: 0.5 mol / L to 3 mol / L, 0.5 mol / L to 2 mol / L, or 0.8 mol / L to 1.5 mol / L.

[0089] In some embodiments, the solid electrolyte for use in all-solid-state secondary lithium batteries includes at least one of the following compounds: Li3YCl6, Li3YBr6, Li3OCl, LiPON, Li 0.5 La 0.5 TiO3, Li 1+x Al x Ti 2-x (PO4)3, Li7La3Zr2O 12 Li 10 GeP2S 12 (LGPS), Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 Li 3.25 Ge 0.25 P 0.75 S4, Li 11 AlP2S 12 and Li7P3S 11 .

[0090] 4. Separating membrane

[0091] In some embodiments, a separator is provided between the positive and negative electrodes to prevent short circuits. The material and shape of the separator used in this application are not particularly limited and can be any technology disclosed in the prior art. In some embodiments, the separator comprises a polymer or inorganic material formed from a material stable to the electrolyte of this application.

[0092] For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a nonwoven fabric, membrane, or composite membrane with a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be selected.

[0093] A surface treatment layer is disposed on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic substances.

[0094] The inorganic layer comprises inorganic particles and a binder. The inorganic particles are selected from one or more of the following: alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder is selected from one or more of the following: polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0095] The polymer layer contains a polymer, the polymer material of which is selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, or poly(vinylidene fluoride-hexafluoropropylene).

[0096] IV. Electronic Devices

[0097] The electronic device of this application can be any device that uses the electrochemical device according to the embodiments of this application.

[0098] In some embodiments, the electronic device includes, but is not limited to: laptop computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries or lithium-ion capacitors, etc.

[0099] The following uses a lithium battery as an example and specific embodiments to illustrate the preparation of a lithium battery. Those skilled in the art will understand that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application.

[0100] Example

[0101] The following describes the performance evaluation based on the embodiments and comparative examples of the all-solid-state secondary lithium battery of this application.

[0102] I. Testing Methods

[0103] 1. Powder X-ray diffraction (XRD) test:

[0104] The positive electrode active material powders prepared in the comparative and examples were subjected to XRD tests. The testing standard referenced was JIS K0131-1996 General Rules for X-ray Diffraction Analysis. Test conditions: CuK α radiation The operating current is 250mA, it adopts continuous scanning, the operating voltage is 40kV, the scanning range is 2θ10-70°, the step size is 0.1°, and the scanning speed is 0.2 seconds / step.

[0105] The principle of XRD testing is that when a beam of monochromatic X-rays is incident on a crystal, since the crystal is composed of unit cells with atoms arranged in a regular pattern, the distance between these regularly arranged atoms is on the same order of magnitude as the wavelength of the incident X-rays. Therefore, the X-rays scattered by different atoms interfere with each other, producing strong X-ray diffraction in certain special directions. By comparing the lattice plane spacing and diffraction intensity measured in the material with the diffraction data of a standard phase, the phase present in the material can be determined.

[0106] 2. Scanning electron microscopy (SEM) test:

[0107] The positive electrode active material powders prepared in the comparative and examples were subjected to SEM testing. The SEM testing standard referred to JY / T010-1996, General Rules for Analytical Scanning Electron Microscopy. The testing principle of scanning electron microscopy: Scanning electron microscopes are based on the interaction between electrons and matter. A highly focused high-energy electron beam scans the sample, exciting various physical information. By receiving, magnifying, and displaying this information, the surface morphology of the test sample can be observed.

[0108] 3. Charge and discharge test:

[0109] The specific capacity of the all-solid-state secondary lithium batteries prepared in the comparative examples and embodiments was tested using a Blue Electric Tester (model CT2001A), and the test environment temperature was room temperature (25°C). The test method was to discharge at a set rate with constant current until the discharge cutoff voltage, and then charge at a certain rate with constant current until the charging cutoff voltage. Unless otherwise specified, the charge / discharge test rate in this invention was 0.1C, referencing the theoretical specific capacity of FeF3 (712 mAh / g) and CuF2 (893 mAh / g).

[0110] II. Preparation of All-Solid-State Secondary Lithium-ion Batteries

[0111] The positive electrode active material and conductive agent Ketjen black prepared in the examples and comparative examples were mixed evenly. The obtained powder was then mixed with the solid electrolyte Li7P3S. 11 Together, they are placed in a stainless steel cold-pressing mold and cold-pressed under a pressure of 300 MPa to obtain a double-layer sheet of positive electrode and solid electrolyte, wherein the positive electrode active material and the solid electrolyte Li7P3S are... 11 The mass ratio of lithium metal to conductive agent Ketjen black is 60:30:10. A lithium metal foil is placed on the other side of the solid electrolyte in the above double-layer film, and both are placed in a cold-pressing mold. A pressure of 200 MPa is further applied to ensure sufficient contact between the lithium metal and the solid electrolyte film, thus obtaining an all-solid-state secondary lithium battery.

[0112] III. Preparation of Positive Electrode Active Materials

[0113] Comparative Example 1

[0114] Weigh 10g of FeF3 and place it in a 50ml agate ball mill jar. Then add 40 φ5mm agate balls and 5 φ10mm agate balls, and ball mill at 500r / min for 12 hours. After ball milling, the material adheres to the wall of the ball mill jar, indicating insufficient grinding.

[0115] Comparative Example 2

[0116] Weigh 10g of FeF3 and place it in a 50ml agate ball mill jar. Then add 40 φ5mm agate balls and 5 φ10mm agate balls, along with 20ml of anhydrous ethanol. Mill the mixture at 800r / min for 12h. Remove the resulting material and transfer it to a vacuum oven to dry at 80℃. Pass the dried material through a 400-mesh sieve to obtain the positive electrode active material FeF3.

[0117] Comparative Example 3

[0118] Weigh 10g of CuF2 and place it in a 50ml agate ball mill jar. Then add 40 φ5mm agate balls and 5 φ10mm agate balls, along with 20ml of anhydrous ethanol. Ball mill at 500r / min for 12h. After ball milling, the material is uniformly dispersed in the ethanol without sticking to the walls or settling to the bottom. Remove the obtained material and transfer it to a vacuum oven to dry at 80℃. After drying, pass the material through a 400-mesh sieve to obtain the positive electrode active material CuF2.

[0119] Comparative Example 4

[0120] Weigh 10g of FeF3 and 0.5g of conductive carbon powder, place them in a 50ml agate ball mill jar, then add 40 φ5mm agate balls and 5 φ10mm agate balls, and add 20ml of anhydrous ethanol. Ball mill at 500r / min for 12h. After ball milling, remove the material and transfer it to a vacuum oven to dry at 80℃. Pass the dried material through a 400-mesh sieve to obtain carbon-coated FeF3, which is used as the positive electrode active material.

[0121] Example 1

[0122] Weigh 10g of FeF3 and place it in a 50ml agate ball mill jar. Then add 40 φ5mm agate balls and 5 φ10mm agate balls, along with 20ml of anhydrous ethanol. Mill the mixture at 500r / min for 12 hours. After milling, the material is uniformly dispersed in the ethanol without sticking to the walls or settling to the bottom.

[0123] Example 2-13

[0124] Metal fluoride MF y and fluorinated graphite CF x The material was placed in a 50ml agate ball mill jar, along with 40 φ5mm agate balls and 5 φ10mm agate balls, and 20ml of anhydrous ethanol. The mixture was ball-milled at 500 rpm for 12 hours. After milling, the material was removed and dried in a vacuum oven at 80℃. After passing through a 300 or 400 mesh sieve, a homogeneous mixture of fluorinated graphite and metal fluoride was obtained. The resulting mixture was then transferred to a tube furnace and annealed at 3℃ / min at a rate of 3℃ under a high-purity argon gas flow of 0.3L / min for 24 hours. After annealing, the material was cooled to room temperature in the furnace, then crushed and sieved to obtain the composite material MF of metal fluoride and fluorinated graphite. y .w(CF x ), as the positive electrode active material of this application; wherein y is the molar ratio of fluorine element F to metal element M in the metal fluoride; z is the molar ratio of fluorine element F to metal element M in the composite material; x is the CF x The molar ratio of fluorine (F) to carbon (C) is given; and w is the mass ratio of the fluorinated graphite to the metal fluoride. In Example 7, no annealing treatment was performed after drying. Table 1 shows the types and amounts of raw materials used in Examples 2-13, as well as the process parameters.

[0125] Table 1

[0126]

[0127] The "-" indicates that this step was not performed.

[0128] Table 2 shows the relevant performance test results of some embodiments and comparative examples.

[0129] Table 2

[0130]

[0131] Table 3 shows the test results of some embodiments and comparative examples at different charge / discharge rates.

[0132] Table 3

[0133]

[0134] The symbol “\” indicates that the battery has no charge / discharge capacity after 20 charge / discharge cycles.

[0135] The test results of Comparative Example 1 and Example 1 show that when no dispersant is added during ball milling, the material exhibits severe adhesion to the mill wall, resulting in insufficient grinding. However, when anhydrous ethanol is added as a dispersant for wet milling, large particles develop cracks under the grinding and impact of the milling media during the ball milling process. The ethanol dispersant then enters the formed cracks, preventing them from closing and effectively allowing the cracks to propagate rapidly, thus greatly improving the ball milling efficiency.

[0136] The test results from Comparative Examples 2 and 4, as well as Examples 2-6, show that the addition of CF to FeF3... x Fluorinated graphite composite treatment can significantly improve the charge-discharge specific capacity of FeF3, and the improvement effect on charge-discharge specific capacity follows the relationship: fluorinated graphite composite treatment > conductive carbon coating treatment > untreated. These results indicate that the incorporation of F element is one of the important factors in improving the performance of FeF3 materials.

[0137] The test results of Comparative Example 2 and Examples 7-10 show that the annealing temperature has a significant impact on the specific capacity of the composite positive electrode active material of fluorinated graphite and ferric fluoride. Without annealing, the initial discharge and charge capacities of the material are 377.5 mAh / g and 232.9 mAh / g, respectively. As the annealing temperature increases from 150℃ to 350℃, the initial discharge and charge capacities of the material both increase significantly, reaching 554.8 mAh / g and 458.7 mAh / g, respectively. This is because, with increasing temperature, the specific capacity of CF... x It is more likely to undergo diffusion reactions with the FeF3 lattice.

[0138] The test results of Comparative Example 3 and Examples 11-13 show that the electrochemical performance of copper fluoride materials can also be improved by composite treatment of copper fluoride and fluorinated graphite. In addition, the charge / discharge capacity of the composite cathode material is also related to the fluorine-to-carbon molar ratio x in the fluorinated graphite material. A higher fluorine-to-carbon molar ratio is more beneficial to improving the discharge specific capacity of the material.

[0139] The test results of Comparative Example 3 and Example 13 show that the addition of CF to copper fluoride... x Subsequently, the rate performance and cycle performance of the all-solid-state secondary lithium battery prepared with the positive electrode active material of this application were significantly improved. Under the same conditions, compared with the 0.05C rate charge-discharge, Example 13 showed a significantly smaller decrease in discharge and charge capacity at the higher 0.5C rate, indicating that fluorinated graphite doping significantly improved the charge-discharge rate performance of the material. After 20 stable charge-discharge cycles, the solid-state lithium battery prepared with the positive electrode material of this invention maintained a capacity retention rate of over 85% at different rates, while the capacity in the comparative example showed a significant decrease, especially at the higher 0.2C and 0.5C rates, where almost no charge-discharge capacity remained after 20 cycles. This is because after the metal fluoride material and the fluorinated graphite material were combined in the examples, the fluorinated graphite on the surface of the positive electrode material could react with lithium during the first discharge, generating nano-carbon in situ, thereby increasing the conductivity of the positive electrode and improving the kinetics of the conversion reaction. In the first discharge process, fluorinated graphite not only generates nano-carbon in situ, but also generates lithium fluoride, which can be used as a lithium source to compensate for the lithium loss of the cathode material during multiple cycles, thereby improving the long-term cycle stability of the material.

[0140] Figure 2 The curves showing the capacity retention rate as a function of cycle number for the all-solid-state secondary lithium batteries of Comparative Examples 2, 4, and 4 of this application are illustrated. Figure 2 It can be seen that the addition of CF to FeF3 x It can significantly improve the capacity retention rate of all-solid-state rechargeable lithium batteries.

[0141] Throughout this specification, references to "some embodiments," "partial embodiments," "one embodiment," "another example," "example," "specific example," or "partial example" mean that at least one embodiment or example in this application includes a specific feature, structure, material, or characteristic described in that embodiment or example. Therefore, descriptions appearing throughout this specification, such as "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in an example," "in a specific example," or "example," do not necessarily refer to the same embodiments or examples in this application. Furthermore, specific features, structures, materials, or characteristics described herein can be combined in any suitable manner in one or more embodiments or examples.

[0142] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A positive electrode material for an all-solid-state secondary lithium battery, the positive electrode material comprising a composite material, the composite material comprising a metal fluoride and a fluorinated graphite, wherein a molar ratio of fluorine element F to metal element M in the metal fluoride is y, a molar ratio of fluorine element F and metal element M in the composite material is z, and y < z ≤ y + 2. wherein the M comprises at least one of Al, Cu, Co, Ni, Mn, Fe, or Ag; The structural formula of the fluorinated graphite is CF x , and a molar ratio of fluorine element F and carbon element C in the CF x is x, 0.8≤x≤1. a mass ratio of the fluorinated graphite to the metal fluoride is w, and 0 < w ≤ 0.

2. 2.The positive electrode material for an all-solid-state secondary lithium battery according to claim 1, wherein the metal fluoride comprises at least one of CoF 3, NiF 3, MnF 2, MnF 3, FeF 3, FeF 2, AlF 3, or CuF 2.

3. A method of preparing the positive electrode material for the all-solid-state secondary lithium battery according to claim 1, characterized by a preparation method of the composite material comprises: (1) mixing and drying the metal fluoride and the fluorinated graphite; and (2) annealing at 200 ℃ to 600 ℃ for 10 h to 72 h, crushing, and sieving to obtain the composite material. 4.A positive electrode sheet for an all-solid-state secondary lithium battery, comprising the positive electrode material for an all-solid-state secondary lithium battery according to any one of claims 1-2 or the composite material prepared according to the method of claim 3. 5.An all-solid-state secondary lithium battery, comprising the positive electrode sheet according to claim 4. 6.An electronic device, comprising the all-solid-state secondary lithium battery according to claim 5.

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