A method for preparing a positive electrode material

Abstract

The application provides a preparation method of a positive electrode material, comprising the following steps: grinding and sieving one-dimensional conductive agents and fast ion conductors respectively, and then dispersing the agents into an organic solvent to obtain a first suspension; grinding and sieving a base material, and then dispersing the material into an organic solvent to obtain a second suspension; uniformly mixing the first suspension and the second suspension to obtain a mixed slurry, and then performing spray drying to obtain a positive electrode material precursor; and roasting the positive electrode material precursor to obtain the positive electrode material. The application can improve the electronic conductivity and the ion conductivity of the positive electrode material, thereby improving the performance of a lithium ion battery.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to a method for preparing a cathode material. Background Technology

[0002] Lithium-ion batteries are characterized by high energy density, high operating voltage, low self-discharge rate, small size, and light weight, and are widely used in various fields such as energy storage, portable electronic devices, and electric vehicle power supply.

[0003] With the rapid development of electric vehicles and mobile electronic devices, people have increasingly higher requirements for the energy density, safety, and cycle performance of lithium-ion batteries. There is an urgent need to improve the cathode materials in lithium-ion batteries to enhance the cycle performance and electrochemical stability of existing lithium-ion batteries. Summary of the Invention

[0004] The purpose of this application is to provide a method for preparing a cathode material to further improve the electronic conductivity and ionic conductivity of the cathode material, thereby improving the performance of lithium-ion batteries. The specific technical solution is as follows:

[0005] This application provides a method for preparing a cathode material, including the following steps:

[0006] First suspension preparation steps: Grind the one-dimensional conductive agent and the fast ion conductor separately and then sieve them. Disperse the sieved one-dimensional conductive agent and the sieved fast ion conductor in an organic solvent to obtain the first suspension.

[0007] The second suspension preparation steps are as follows: the matrix material is ground and then sieved, and the sieved matrix material is dispersed in an organic solvent to obtain the second suspension;

[0008] Suspension mixing step: The first suspension and the second suspension are mixed to obtain a mixed slurry; the mixed slurry is spray-dried to obtain a cathode material precursor; and

[0009] Calcination step: The cathode material precursor is calcined to obtain the cathode material.

[0010] In one embodiment of this application, the atmosphere of the calcination step is selected from at least one of argon, helium, neon or nitrogen, the calcination temperature of the calcination step is 300°C to 800°C, and the calcination time of the calcination step is 6h to 24h.

[0011] In one embodiment of this application, the organic solvent includes at least one of methanol or ethanol.

[0012] In one embodiment of this application, the solid content of the first suspension is 35% to 65%, the solid content of the second suspension is 35% to 65%, and the solid content of the mixed slurry is 40% to 60%.

[0013] In one embodiment of this application, based on the total mass of the matrix material, the one-dimensional conductive agent, and the fast ion conductor, the mass percentage of the one-dimensional conductive agent is 0.05% to 5%, and the mass percentage of the fast ion conductor is 0.05% to 5%.

[0014] In one embodiment of this application, the mass ratio of the one-dimensional conductive agent to the fast ion conductor is 0.1:1 to 10:1.

[0015] In one embodiment of this application, the matrix material includes at least one of lithium manganese iron phosphate, lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, or lithium cobalt oxide, wherein the molar ratio of manganese to iron in the lithium manganese iron phosphate is 0.01 to 10, and the one-dimensional conductive agent includes at least one of carbon nanotubes or carbon fibers.

[0016] In one embodiment of this application, the fast ion conductor comprises a compound with the chemical formula Li. x La y Zr z M a O b Wherein, 6≤x≤8, 2≤y≤4, 1≤z≤3, 0≤a≤0.5, 11≤b≤13, and the M element is selected from at least one of the Ta element or the W element.

[0017] In one embodiment of this application, the fast ion conductor comprises Li 10 GeP2S 12 or Li7La3Zr2O 12 At least one of them.

[0018] In one embodiment of this application, the matrix material includes at least one of ZrO2, SnO2, ZnO, MgO, Al2O3, TiO2, CeO2, AlF3 or Li3AlF6.

[0019] This application provides a method for preparing a cathode material. The method involves preparing a first suspension containing a one-dimensional conductive agent and a fast-ion conductor, and a second suspension containing a matrix material. The first and second suspensions are then mixed into a slurry and spray-dried to obtain a cathode material precursor. The cathode material precursor is then calcined to obtain the cathode material. In this cathode material, the one-dimensional conductive agent can form point-to-line contact with the matrix material, thereby creating a more complete conductive network and improving the electronic conductivity of the cathode material. The one-dimensional conductive agent provides numerous attachment sites for the fast-ion conductor, resulting in a surface with more fast-ion conductors. These fast-ion conductors have a wide electrochemical window, stable properties, and high ionic conductivity, thus improving the ionic conductivity of the cathode material and consequently enhancing the cycle performance and electrochemical stability of electrochemical devices (e.g., lithium-ion batteries). Attached Figure Description

[0020] To more clearly illustrate the technical solutions of this application and the prior art, the drawings used in the embodiments and the prior art are briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other technical solutions can be obtained based on these drawings.

[0021] Figure 1 This is a SEM image of the cathode material in Example 1 of this application;

[0022] Figure 2 This is a schematic diagram showing the lithium-ion battery cycle test results of Example 1 and Comparative Example 1 of this application. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments.

[0024] It should be noted that, in the specific embodiments of this application, lithium-ion batteries are used as an example of electrochemical devices to explain this application, but the electrochemical devices of this application are not limited to lithium-ion batteries.

[0025] Lithium manganese iron phosphate (LMP) is a novel cathode active material. Compared to lithium iron phosphate (LFP), although the theoretical specific capacity is the same (170 mAh / g), LMP boasts a higher voltage platform, resulting in higher energy density. It also shares the same olivine structure as LFP, offering good safety performance. However, LMP's low electronic and ionic conductivity leads to a low lithium-ion migration rate, resulting in poor electrochemical activity in cathode materials. While existing LMP cathode materials can improve electronic conductivity, the improvement in ionic conductivity is limited. Lithium-ion batteries made with existing LMP cathode materials still exhibit low cycle performance, especially after high-rate cycling, with significant capacity decay. Furthermore, if only a conductive agent is used to coat the matrix material, the dissolution of metals (such as Mn) in the cathode material is not suppressed, causing metal ions to deposit on the negative electrode. This leads to continuous regeneration of the solid electrolyte interphase (SEI) film, consuming active lithium in the lithium-ion battery and resulting in rapid capacity decay.

[0026] In view of this, this application provides a method for preparing a cathode material, comprising the following steps:

[0027] First suspension preparation steps:

[0028] The one-dimensional conductive agent and the fast ion conductor were ground and sieved separately. The sieved one-dimensional conductive agent and the sieved fast ion conductor were then dispersed in an organic solvent to obtain the first suspension.

[0029] Second suspension preparation step:

[0030] The matrix material is ground and sieved, and then dispersed in an organic solvent to obtain a second suspension.

[0031] Spray drying steps:

[0032] The first suspension and the second suspension are mixed to obtain a mixed slurry, and the mixed slurry is spray-dried to obtain a cathode material precursor.

[0033] Roasting steps:

[0034] The cathode material precursor is calcined to obtain the cathode material.

[0035] This application does not impose any particular restrictions on the mesh size of the sieve used for sieving one-dimensional conductive agents, fast ion conductors, and matrix materials, as long as the purpose of this application is achieved. For example, it is acceptable if no large particles are observed to the naked eye after sieving. The mesh size can be, for example, 300 to 600 mesh.

[0036] This application does not impose any particular limitation on the solid content of the first and second suspensions, as long as the purpose of this application is achieved. For example, the solid content of the first suspension can be 35% to 65%, and the solid content of the second suspension can be 35% to 65%, but it should not be too low, otherwise the subsequent spray drying process will be difficult. In addition, this application does not impose any particular limitation on the solid content of the mixed slurry, for example, 40% to 60%, as long as the mass percentage of the one-dimensional conductive agent in the positive electrode material and the mass percentage of the fast ion conductor in the positive electrode material are 0.05% to 5% after mixing.

[0037] This application does not impose any particular restrictions on the organic solvents used to disperse one-dimensional conductive agents, fast ion conductors, and matrix materials, as long as they meet the requirements of this application. For example, they may include at least one of ethanol or anhydrous methanol, and the ethanol may be anhydrous ethanol.

[0038] This application does not impose any particular restrictions on the calcination atmosphere. For example, it can be selected from at least one of argon, helium, neon or nitrogen. This is because when calcined in air, the composition or structure of the cathode material may change to varying degrees at high temperatures, which would damage the particle structure of the cathode material and affect the stability of the material. An inert gas environment can avoid the above situation and is beneficial to the structural stability of the cathode material.

[0039] This application does not impose any particular restrictions on the spray drying process, as long as it can achieve the purpose of this application. For example, centrifugal spray drying can be used, with a centrifugal speed of 500 rpm to 5000 rpm.

[0040] This application does not impose specific limitations on the calcination temperature, but it should not be too low or too high. This is because if the calcination temperature is too low, the conductive agent and fast ion conductor will be unevenly distributed, resulting in little improvement in the performance of the lithium-ion battery; if the calcination temperature is too high, the material is prone to overheating, leading to decreased material stability and affecting the performance and safety of the lithium-ion battery. If the calcination time is too short, the conductive agent and fast ion conductor will be unevenly distributed, resulting in little improvement in the performance of the lithium-ion battery; if the calcination time is too long, the material stability will decrease, affecting the cycle performance and capacity of the lithium-ion battery. In one embodiment of this application, the calcination temperature of the calcination step is 300°C to 800°C, and the calcination time of the calcination step is 6 hours to 24 hours.

[0041] In one embodiment of this application, based on the total mass of the positive electrode material, the mass percentage of the one-dimensional conductive agent is 0.05% to 5%, preferably 0.2% to 3%; the mass percentage of the fast ion conductor is 0.05% to 5%, preferably 0.2% to 3%, and the remainder is matrix material, which can give the positive electrode material good structural stability, electronic conductivity and ionic conductivity.

[0042] In one embodiment of this application, the mass ratio of the one-dimensional conductive agent to the fast ion conductor is 0.1:1 to 10:1, preferably 0.2:1 to 5:1, but is not limited to any particular theory. When the mass ratio between the one-dimensional conductive agent and the fast ion conductor is too large, the number of fast ion conductors is relatively small, and there are not enough fast ion conductors attached to the one-dimensional conductive agent, which is detrimental to improving the structural stability of the cathode material. When the mass ratio between the one-dimensional conductive agent and the fast ion conductor is too small, the number of one-dimensional conductive agents is relatively small, and the number of fast ion conductors not attached to the surface of the one-dimensional conductive agent increases, resulting in a decrease in the proportion of matrix material in the cathode material and affecting the energy density of the lithium-ion battery. By controlling the mass ratio of the one-dimensional conductive agent to the fast ion conductor within the above-mentioned range, the cathode material can have good structural stability, electronic conductivity, and ionic conductivity.

[0043] In one embodiment of this application, the matrix material may include a material with an olivine-type structure, such as lithium manganese iron phosphate (LiMn). 1-x Fe x Lithium iron phosphate (LiFePO4, abbreviated as LMFP), lithium iron phosphate (LiFePO4, abbreviated as LFP), or lithium manganese phosphate (LiMnPO4) are all materials with good safety and high energy density. Other materials may also be included, such as at least one of the following ternary materials: lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide (specifically including NCM811, NCM622, NCM523, or NCM333), or at least one of the following spinel-type structural materials: lithium cobalt oxide or lithium manganese oxide.

[0044] The molar ratio of manganese to iron in the lithium manganese iron phosphate is between 0.01 and 10. Since the energy density of lithium iron phosphate batteries is lower than that of lithium manganese phosphate batteries, while lithium manganese iron phosphate batteries are in between, but the conductivity of lithium manganese phosphate itself is lower than that of lithium iron phosphate, from the perspective of improving the energy density of the battery and making the positive electrode material have higher conductivity, the molar ratio of manganese to iron is controlled to the above ratio.

[0045] This application does not impose any particular limitation on the one-dimensional conductive agent, which may include at least one of carbon nanotubes or carbon fibers, wherein the carbon nanotubes may include at least one of single-walled carbon nanotubes or multi-walled carbon nanotubes. In an optional embodiment, the specific surface area of ​​the carbon nanotubes is 25 g / m². 2 Up to 300g / m 2 The above-mentioned specific surface area range can provide more attachment sites for fast ion conductors, thereby improving the ionic conductivity of the cathode material.

[0046] In one embodiment of this application, the aspect ratio of the one-dimensional conductive agent is 100 to 6250. By controlling the aspect ratio within this range, more attachment sites for fast ion conductors can be provided, resulting in more fast ion conductors on the surface of the one-dimensional conductive agent, thereby further improving the ionic conductivity of the material. In an optional embodiment, the length of the one-dimensional conductive agent is 300 nm to 50000 nm, preferably 1000 nm to 30000 nm, and more preferably 1000 nm to 10000 nm. In an optional embodiment, the diameter (outer diameter) of the one-dimensional conductive agent is 8 nm to 50 nm. By controlling the length and diameter of the one-dimensional conductive agent within the above ranges, the cathode material of this application can have better electronic conductivity.

[0047] This application does not impose any particular limitation on fast ion conductors, as long as they achieve the purpose of this application. For example, it can be a fast ion conductor doped with element M, wherein element M is selected from at least one of elements Ta or W. By doping with element M, the ionic conductivity of the fast ion conductor can be further improved. On the one hand, the above-mentioned fast ion conductor has high ionic conductivity. By attaching to a one-dimensional conductive agent, mixing between the matrix material particles and contacting the matrix material particles, it plays the role of conducting ions and electrons, and can simultaneously improve the electronic conductivity and ionic conductivity of the cathode material. On the other hand, Mn in lithium manganese iron phosphate (LMFP) 3+ Mn 2+ With an operating potential of around 4.0V, lithium manganese iron phosphate batteries exhibit poor thermal and electrochemical stability under higher voltage conditions, which in turn affects their electrochemical and safety performance. For example, due to the John-Teller effect of manganese, manganese leaching can lead to short circuits in lithium-ion batteries and gas buildup caused by the reaction between the positive electrode and the electrolyte. In contrast, the aforementioned fast ion conductors have a stable structure and, through bridging with one-dimensional conductive agents, exist around the matrix material particles. This improves the mechanical properties of the positive electrode material, stabilizes the crystal structure on the surface of the matrix material particles, thereby enhancing the overall structural stability of the positive electrode material, inhibiting the leaching of manganese from the positive electrode material, and thus reducing short circuits and gas buildup caused by manganese leaching in lithium-ion batteries, ultimately improving the electrochemical performance of lithium-ion batteries.

[0048] Furthermore, this application does not impose any particular limitation on the doping amount of element M, as long as the purpose of this application is achieved. For example, the fast ion conductor doped with element M mentioned above can be Li doped with element Ta. x La y Zr z M a O b, where 6 ≤ x ≤ 8, 2 ≤ y ≤ 4, 1 ≤ z ≤ 3, 0 < a ≤ 0.5, 11 ≤ b ≤ 13, the doping amount of Ta element is 0.01 mole to 0.5 mole, indicating that for every 1 mole of Li x La y Zr z M a O b contains 0.01 mole to 0.5 mole of Ta element. Specifically, it can be 0.3 mole of Ta element doped into Li7La3Zr2O 12 .

[0049] In one embodiment of the present application, the fast ion conductor may include Li7La3Zr2O 12 (LLZO) or Li 10 GeP2S 12 (LGPS) or at least one of them.

[0050] In one embodiment of the present application, the ionic conductivity of the fast ion conductor is 1×10 -4 S / cm to 2.7×10 -2 S / cm, which can improve the ionic conductivity of the cathode material and thus improve the performance of the lithium-ion battery.

[0051] In one embodiment of the present application, the surface layer of the matrix material may include at least one of ZrO2, SnO2, ZnO, MgO, Al2O3, TiO2, CeO2, AlF3 or Li3AlF6. Without being limited to any theory, due to the stability of the above oxides or fluorides themselves, the matrix material can have better structural stability. Of course, the matrix material may have oxides or fluorides in at least part of the surface layer, or the entire surface layer may be oxides or fluorides. In the present application, no special limitation is made on the content of the oxides or fluorides. For example, based on the total mass of the matrix material, the mass percentage content of the oxides or fluorides may be 0.1% to 3%.

[0052] The preparation method of this application involves spray drying a cathode material precursor in which fast-ion conductors can adhere to the surface of a one-dimensional conductive agent. This one-dimensional conductive agent with attached fast-ion conductors is mixed between matrix material particles. Subsequent high-temperature calcination further solidifies the one-dimensional conductive agent with attached fast-ion conductors, allowing it to form between and contact the matrix material particles, thus conducting ions and electrons and resulting in a cathode material with excellent ionic and electronic conductivity. Compared to other cathode materials, the cathode material prepared by this method enriches the ion and electron transport channels, constructing a mixed ion-electron conductive network, and effectively reduces interfacial resistance. Furthermore, the preparation method allows for the adjustment of parameters such as reaction temperature, one-dimensional conductive agent content, and fast-ion conductor content to obtain cathode materials with different component contents, making it suitable for various operating conditions. The preparation method of this application is easy to control, has mature technology, and the synthesized cathode material exhibits excellent ionic and electronic conductivity. The particle structure of the cathode material is stable, effectively improving the electrochemical performance of lithium-ion batteries.

[0053] The negative electrode sheet in this application is not particularly limited, as long as it achieves the purpose of this application. For example, the negative electrode sheet typically comprises a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector is not particularly limited; any negative electrode current collector known in the art can be used, such as copper foil, aluminum foil, aluminum alloy foil, and composite current collectors. The negative electrode active material layer comprises a negative electrode active material, and the negative electrode active material is not particularly limited; any negative electrode active material known in the art can be used. For example, it can include at least one of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, hard carbon, silicon, silicon-carbon, lithium titanate, etc.

[0054] The separator of this application includes, but is not limited to, at least one selected from polyethylene, polypropylene, polyethylene terephthalate, polyimide, and aramid. For example, polyethylene includes at least one component selected from high-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene. In particular, polyethylene and polypropylene have good effects in preventing short circuits and can improve the stability of lithium-ion batteries through the turn-off effect.

[0055] The surface of the separator may further include a porous layer disposed on at least one surface of the separator. The porous layer comprises inorganic particles and a binder. The inorganic particles are selected from one or more combinations of alumina (Al₂O₃), silicon dioxide (SiO₂), magnesium oxide (MgO), titanium dioxide (TiO₂), hafnium dioxide (HfO₂), tin oxide (SnO₂), cerium dioxide (CeO₂), nickel oxide (NiO), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO₂), yttrium oxide (Y₂O₃), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder is selected from one or more combinations of polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0056] The porous layer can improve the heat resistance, oxidation resistance and electrolyte wetting properties of the separator, and enhance the adhesion between the separator and the positive or negative electrode.

[0057] The battery in this application also includes an electrolyte, which may be one or more of a gel electrolyte, a solid electrolyte, and an electrolyte solution, wherein the electrolyte solution includes lithium salts and non-aqueous solvents.

[0058] In some embodiments of this application, the lithium salt is selected from one or more of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, and lithium difluoroborate. For example, LiPF6 can be selected as the lithium salt because it can provide high ionic conductivity and improve cycling characteristics.

[0059] The non-aqueous solvent may be a carbonate compound, a carboxylic acid ester compound, an ether compound, other organic solvents, or a combination thereof.

[0060] The aforementioned carbonate compounds may be chain carbonate compounds, cyclic carbonate compounds, fluorocarbonate compounds, or combinations thereof.

[0061] Examples of the aforementioned chain carbonate compounds are dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), and combinations thereof. Examples of the aforementioned cyclic carbonate compounds are ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), vinyl ethylene carbonate (VEC), and combinations thereof. Examples of the aforementioned fluorinated carbonate compounds are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, and combinations thereof.

[0062] Examples of the above-mentioned carboxylic acid ester compounds are methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanoic acid lactone, valerate lactone, mevalonic acid lactone, caprolactone, and combinations thereof.

[0063] Examples of the above-mentioned ether compounds are dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.

[0064] Examples of other organic solvents mentioned above include dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters and combinations thereof.

[0065] This application also provides a positive electrode sheet, which includes a positive electrode active material layer. The positive electrode active material layer comprises the positive electrode material described in any of the above embodiments. Because this positive electrode material has good structural stability, electronic conductivity, and ionic conductivity, the positive electrode sheet of this application also has good structural stability, electronic conductivity, and ionic conductivity. The film resistance of the positive electrode active material layer in this application is from 0.1 mΩ to 50 mΩ, and the method for testing the resistance of its positive electrode active material layer will be shown below.

[0066] This application also provides an electrode assembly, including a positive electrode, a negative electrode, and a separator, wherein the separator is located between the positive electrode and the negative electrode, and the electrode assembly includes the positive electrode described in the above embodiments of this application.

[0067] This application also provides an electrochemical device, including an electrolyte and an electrode assembly according to the above embodiments, which has good cycle performance and capacity retention performance.

[0068] This application also provides an electronic device that includes the electrochemical device described in the embodiments of this application, which has a longer service life and greater safety.

[0069] The electronic device described in this application is not particularly limited and can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, laptops, pen-based 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, and lithium-ion capacitors, etc.

[0070] The fabrication process of electrochemical devices is well known to those skilled in the art, and this application does not impose any particular limitations. For example, a lithium-ion battery can be manufactured through the following process: overlapping the positive and negative electrodes via a separator, and then, as needed, winding, folding, or performing other operations, placing them into a casing; injecting the electrolyte into the casing and sealing it; wherein the negative electrode used is the aforementioned negative electrode sheet provided in this application. Furthermore, overcurrent protection elements, conductive plates, etc., can be placed in the casing as needed to prevent pressure rise and overcharging / discharging inside the lithium-ion battery.

[0071] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0072] Example 1

[0073] <Preparation of cathode materials>

[0074] <Preparation of the first suspension>

[0075] One-dimensional conductive agent CNT and fast ion conductor LLZO were ground separately and passed through a 400-mesh sieve. The sieved CNT and sieved LLZO were dispersed in anhydrous ethanol at a mass ratio of 1:1 to obtain a first suspension with a solid content of 50%.

[0076] <Preparation of the Second Suspension>

[0077] The matrix material, lithium manganese iron phosphate (LMFP), was ground and passed through a 400-mesh sieve. The sieved LMFP was then dispersed in anhydrous ethanol to obtain a second suspension with a solid content of 50%. The molar ratio of manganese to iron in the LMFP was 6:4.

[0078] <Mixing of suspensions>

[0079] The first suspension and the second suspension were mixed evenly to obtain a mixed slurry with a solid content of 50%. The mixed slurry was spray-dried to obtain a positive electrode material precursor. The precursor contained in the slurry was 1.5% by mass of the matrix material, one-dimensional conductive agent and fast ion conductor, 1.5% by mass of CNT, 1.5% by mass of LLZO, and the remainder was the matrix material LMFP.

[0080] <Roasting>

[0081] The cathode material precursor was calcined in an argon atmosphere at a temperature of 600℃ for 15 hours.

[0082] Among them, CNTs are single-walled, with an aspect ratio of 1000, a length of 20000 nm, a diameter of 20 nm, and a specific surface area of ​​42 g / m². 2 The ionic conductivity of LLZO is 5 × 10⁻⁶. -4 S / cm.

[0083] <Preparation of the positive electrode>

[0084] The prepared positive electrode material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 95:3:2. N-methylpyrrolidone (NMP) was then added as a solvent to prepare a slurry with a solid content of 75%, which was stirred evenly. The slurry was uniformly coated onto one surface of a 12 μm thick aluminum foil, dried at 90°C, and cold-pressed to obtain a positive electrode sheet with a 100 μm thick active material layer. The above steps were repeated on the other surface of the same positive electrode sheet to obtain a positive electrode sheet with active material layers coated on both sides. The positive electrode sheet was cut into 74 mm × 867 mm dimensions and tabs were welded on for later use.

[0085] <Preparation of Negative Electrode Sheets>

[0086] Artificial graphite (negative electrode active material), acetylene black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) were mixed in a weight ratio of 95:2:2:1. Deionized water was then added as a solvent to prepare a slurry with a solid content of 70%, which was stirred evenly. The slurry was then uniformly coated onto one surface of a 10 μm thick copper foil, dried at 110°C, and cold-pressed to obtain a single-sided negative electrode sheet with a 150 μm thick negative electrode active material layer. The coating process was repeated on the other surface of this negative electrode sheet to obtain a double-sided negative electrode sheet. The negative electrode sheet was cut into 74 mm × 867 mm pieces and tabs were welded on for later use.

[0087] <Preparation of Electrolyte>

[0088] In a dry argon atmosphere, organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 30:50:20. Then, lithium hexafluorophosphate (LiPF6) is added to the organic solvent to dissolve and mix evenly to obtain an electrolyte, wherein the molar concentration of LiPF6 in the electrolyte is 1.15 mol / L.

[0089] <Preparation of Lithium-ion Batteries>

[0090] Using a 15μm thick porous polyethylene (PE) film as the separator, the prepared positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrodes are then wound to obtain the electrode assembly. The electrode assembly is placed in a housing, injected with the prepared electrolyte, and encapsulated. After formation, degassing, and edge trimming processes, a lithium-ion battery is obtained.

[0091] Example 2

[0092] Except for the fact that the mass percentages of the one-dimensional conductive agent and the fast ion conductor are 0.05% respectively, the rest is the same as in Example 1.

[0093] Example 3

[0094] Except for the fact that the mass percentages of the one-dimensional conductive agent and the fast ion conductor are 0.1% respectively, everything else is the same as in Example 1.

[0095] Example 4

[0096] Except for the fact that the mass percentages of the one-dimensional conductive agent and the fast ion conductor are 0.2% respectively, everything else is the same as in Example 1.

[0097] Example 5

[0098] Except for the fact that the mass percentages of the one-dimensional conductive agent and the fast ion conductor are 0.5% respectively, everything else is the same as in Example 1.

[0099] Example 6

[0100] Except for the fact that the mass percentages of the one-dimensional conductive agent and the fast ion conductor are 3%, the rest is the same as in Example 1.

[0101] Example 7

[0102] Except for the fact that the mass percentages of the one-dimensional conductive agent and the fast ion conductor are 5%, the rest is the same as in Example 1.

[0103] Example 8

[0104] Except that the mass percentage of the one-dimensional conductive agent is 0.15% and the mass percentage of the fast ion conductor is 1.5%, i.e. the mass ratio of the one-dimensional conductive agent to the fast ion conductor is 0.1:1, everything else is the same as in Example 1.

[0105] Example 9

[0106] Except that the mass percentage of the one-dimensional conductive agent is 0.3% and the mass percentage of the fast ion conductor is 1.5%, i.e., the mass ratio of the one-dimensional conductive agent to the fast ion conductor is 0.2:1, everything else is the same as in Example 1.

[0107] Example 10

[0108] Except that the mass percentage of the one-dimensional conductive agent is 2.25% and the mass percentage of the fast ion conductor is 1.5%, i.e., the mass ratio of the one-dimensional conductive agent to the fast ion conductor is 1.5:1, everything else is the same as in Example 1.

[0109] Example 11

[0110] Except that the mass percentage of the one-dimensional conductive agent is 3% and the mass percentage of the fast ion conductor is 1.5%, i.e., the mass ratio of the one-dimensional conductive agent to the fast ion conductor is 2:1, everything else is the same as in Example 1.

[0111] Example 12

[0112] Except that the mass percentage of the one-dimensional conductive agent is 1.5% and the mass percentage of the fast ion conductor is 0.3%, i.e., the mass ratio of the one-dimensional conductive agent to the fast ion conductor is 5:1, everything else is the same as in Example 1.

[0113] Example 13

[0114] Except that the mass percentage of the one-dimensional conductive agent is 1.5% and the mass percentage of the fast ion conductor is 0.75%, i.e., the mass ratio of the one-dimensional conductive agent to the fast ion conductor is 2:1, everything else is the same as in Example 1.

[0115] Example 14

[0116] Except that the mass percentage of the one-dimensional conductive agent is 1.5% and the mass percentage of the fast ion conductor is 2.25%, i.e., the mass ratio of the one-dimensional conductive agent to the fast ion conductor is 0.67:1, everything else is the same as in Example 1.

[0117] Example 15

[0118] Except that the mass percentage of the one-dimensional conductive agent is 1.5% and the mass percentage of the fast ion conductor is 4.5%, i.e. the mass ratio of the one-dimensional conductive agent to the fast ion conductor is 0.33:1, everything else is the same as in Example 1.

[0119] Example 16

[0120] Except for the matrix material being lithium iron phosphate (LFP), everything else is the same as in Example 1.

[0121] Example 17

[0122] Except for the roasting temperature of 300°C, it is the same as in Example 1.

[0123] Example 18

[0124] Except for the roasting temperature of 500°C, it is the same as in Example 1.

[0125] Example 19

[0126] Except for the roasting temperature of 800°C, it is the same as in Example 1.

[0127] Example 20

[0128] Except for the roasting time of 8 hours, it is the same as in Example 1.

[0129] Example 21

[0130] Except for the roasting time of 20 hours, it is the same as in Example 1.

[0131] Example 22

[0132] Except for the fact that the one-dimensional conductive agent is carbon fiber, everything else is the same as in Example 1.

[0133] Example 23

[0134] Except for the fast ion conductor being LGPS, everything else is the same as in Example 1.

[0135] Example 24

[0136] Besides the fast ion conductor being Ta-doped Li7La3Zr2O12 Except for (Ta-LLZO), the rest is the same as in Example 1, wherein the doping amount of Ta element is 0.3 moles.

[0137] Example 25

[0138] Except that the length of the one-dimensional conductive agent is 800 nm, the diameter of the one-dimensional conductive agent is 8 nm, and the aspect ratio of the one-dimensional conductive agent is 100, everything else is the same as in Example 1.

[0139] Example 26

[0140] Except that the length of the one-dimensional conductive agent is 3500 nm, the diameter of the one-dimensional conductive agent is 10 nm, and the aspect ratio of the one-dimensional conductive agent is 350, everything else is the same as in Example 1.

[0141] Example 27

[0142] Except that the length of the one-dimensional conductive agent is 8000 nm, the diameter of the one-dimensional conductive agent is 10 nm, and the aspect ratio of the one-dimensional conductive agent is 800, everything else is the same as in Example 1.

[0143] Example 28

[0144] Except that the length of the one-dimensional conductive agent is 30,000 nm, the diameter of the one-dimensional conductive agent is 15 nm, and the aspect ratio of the one-dimensional conductive agent is 2000, everything else is the same as in Example 1.

[0145] Example 29

[0146] Except that the length of the one-dimensional conductive agent is 50,000 nm, the diameter of the one-dimensional conductive agent is 8 nm, and the aspect ratio of the one-dimensional conductive agent is 6250, everything else is the same as in Example 1.

[0147] Example 30

[0148] In addition to the one-dimensional conductive agent having a specific surface area of ​​25 g / m² 2 Except for the above, the rest is the same as in Example 1.

[0149] Example 31

[0150] In addition to the one-dimensional conductive agent having a specific surface area of ​​32 g / m² 2 Except for the above, the rest is the same as in Example 1.

[0151] Example 32

[0152] In addition to the one-dimensional conductive agent having a specific surface area of ​​82 g / m² 2 Except for the above, the rest is the same as in Example 1.

[0153] Example 33

[0154] In addition to the one-dimensional conductive agent having a specific surface area of ​​176 g / m² 2 Except for the above, the rest is the same as in Example 1.

[0155] Example 34

[0156] In addition to the one-dimensional conductive agent having a specific surface area of ​​300 g / m² 2 Except for the above, the rest is the same as in Example 1.

[0157] Comparative Example 1

[0158] Except for the preparation process of the cathode material, which is different from that in Example 1, everything else is the same as in Example 1.

[0159] The preparation process of the cathode material is as follows:

[0160] LMFP was directly calcined in an argon atmosphere at a temperature of 600℃ for 15 hours.

[0161] Comparative Example 2

[0162] Except for the preparation process of the cathode material, which is different from that in Example 1, everything else is the same as in Example 1.

[0163] The preparation process of the cathode material is as follows:

[0164] Based on Comparative Example 1, replace LMFP with LFP.

[0165] Comparative Example 3

[0166] Except for the preparation process of the cathode material, which is different from that in Example 1, everything else is the same as in Example 1.

[0167] The preparation process of the cathode material is as follows:

[0168] CNTs were ground and passed through a 400-mesh sieve. The sieved CNTs were then dispersed in anhydrous ethanol to obtain a first suspension with a solid content of 50%.

[0169] LMFP was ground and passed through a 400-mesh sieve. The sieved LMFP was then dispersed in anhydrous ethanol to obtain a second suspension with a solid content of 50%.

[0170] The first suspension and the second suspension were mixed evenly to obtain a mixed slurry with a solid content of 50%. The mixed slurry was spray-dried to obtain a cathode material precursor. The CNT content was 1.5% based on the total mass of CNT and LMFP, and the remainder was LMFP.

[0171] The cathode material precursor was calcined in an argon atmosphere at a temperature of 600℃ for 15 hours.

[0172] Among them, CNTs are single-walled, with an aspect ratio of 1000, a length of 20000 nm, a diameter of 20 nm, and a specific surface area of ​​42 g / m². 2 The ionic conductivity of LLZO is 5 × 10⁻⁶. -4 S / cm.

[0173] Comparative Example 4

[0174] Except for the preparation process of the cathode material, which is different from that in Example 1, everything else is the same as in Example 1.

[0175] The preparation process of the cathode material is as follows:

[0176] LLZO was ground and passed through a 400-mesh sieve. The sieved LLZO was then dispersed in anhydrous ethanol to obtain a first suspension with a solid content of 50%.

[0177] LMFP was ground and passed through a 400-mesh sieve. The sieved LMFP was then dispersed in anhydrous ethanol to obtain a second suspension with a solid content of 50%.

[0178] The first suspension and the second suspension were mixed evenly to obtain a mixed slurry with a solid content of 50%. The mixed slurry was spray-dried to obtain a cathode material precursor, wherein, based on the total mass of LLZO and LMFP, the mass percentage of LLZO was 1.5%, and the remainder was LMFP.

[0179] The cathode material precursor was calcined in an argon atmosphere at a temperature of 600℃ for 15 hours.

[0180] Among them, the ionic conductivity of LLZO is 5 × 10⁻⁶. -4 S / cm.

[0181] Comparative Example 5

[0182] Except for the preparation process of the cathode material, which is different from that in Example 1, everything else is the same as in Example 1.

[0183] The preparation process of the cathode material is as follows:

[0184] The fast ion conductor LLZO was ground and passed through a 400-mesh sieve. The sieved LLZO was then dispersed in anhydrous ethanol to obtain a first suspension with a solid content of 50%.

[0185] The matrix material LMFP was ground and passed through a 400-mesh sieve. The sieved LMFP was then dispersed in anhydrous ethanol to obtain a second suspension with a solid content of 50%.

[0186] The first and second suspensions were mixed evenly to obtain a mixed slurry with a solid content of 50%. The mixed slurry was spray-dried and then calcined in an argon atmosphere at a temperature of 600°C for 15 hours to obtain a matrix material with fast ion conductors on its surface.

[0187] The one-dimensional conductive agent CNT was ground and passed through a 400-mesh sieve. The sieved CNT was then dispersed in anhydrous ethanol to obtain a third suspension with a solid content of 50%.

[0188] A matrix material with fast ion conductors on its surface was dispersed in anhydrous ethanol to obtain a fourth suspension with a solid content of 50%.

[0189] The third and fourth suspensions were mixed thoroughly to obtain a mixed slurry with a solid content of 50%. The mixed slurry was spray-dried and then calcined under the same calcination conditions. Based on the total mass of CNTs and LMFP, the mass percentage of CNTs was 1.5%, the mass percentage of LLZO was 1.5%, and the remainder was LMFP. The CNTs were single-walled, with an aspect ratio of 1000, a length of 20000 nm, a diameter of 20 nm, and a specific surface area of ​​42 g / m². 2 The ionic conductivity of LLZO is 5 × 10⁻⁶. -4 S / cm.

[0190] Performance Testing

[0191] The cathode materials, cathode sheets, and lithium-ion batteries prepared in each embodiment and comparative example were tested using the following methods:

[0192] SEM and EDS tests on cathode materials:

[0193] The cathode material was fabricated into electrode samples and tested using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The instruments utilize the focused electron beam to excite the sample surface, generating secondary electrons, backscattered electrons, and characteristic X-rays, which are used to collect and analyze the microstructure and composition of the sample surface. The SEM test results of the cathode material in Example 1 are shown below. Figure 1 As shown in Table 2, the EDS test results are as follows. SEM and EDS test conditions: working distance 5mm to 30mm, objective aperture 100μm to 200μm, accelerating voltage 2kV to 20kV. EDS test conditions: ..., the test instrument was OXFORD EDS (X-max-20mm²).

[0194] Resistance test of the positive electrode active material layer:

[0195] Before testing, clean the ends of the upper and lower terminals of the resistance meter with anhydrous ethanol-soaked lint-free paper. Use a 20.27mΩ or 0.5mΩ standard resistor to inspect the resistance meter (model BER1200). After inspection, zero the resistance meter. During testing, the pressure should be ≥0.35T. Cut the positive electrode into 60mm×80mm pieces for resistance testing. The testing method is as follows: place the cut electrode (approximately 60×80mm) on the instrument base, cover it with the top cover, and make the electrode cover as much as possible to cover the test hole. Then place the sample stage containing the electrode into the test chamber. Move the sample stage to lock the frontmost test hole to the lower terminal, close the protective door, press the pneumatic button on the front of the instrument, and press down the lower terminal to test the overall resistance and resistivity in the thickness direction of the electrode. After testing one point, move the sample stage to change the test hole position. The test interval is 50s. Six points are collected for each sample, and then the average value is calculated. The resistance test of the positive electrode active material layer can effectively evaluate the electronic conductivity of the positive electrode and analyze the contact resistance of the material interface layer.

[0196] 0.1C discharge specific capacity test:

[0197] The lithium-ion batteries in each embodiment and comparative example were subjected to charge-discharge tests using a LAND series battery testing system to test their charge-discharge performance. At room temperature, they were charged at a constant current rate of 0.1C until the voltage reached 4.2V. They were then further charged at a constant voltage of 4.2V until the current dropped below 0.05C, bringing them to a fully charged state at 4.2V. Subsequently, they were discharged at a constant current rate of 0.1C until the voltage reached 2.5V. The resulting capacity is the 0.1C discharge specific capacity. The results are listed in Tables 1, 2, and 3.

[0198] Cyclic performance test:

[0199] The lithium-ion batteries of each embodiment and comparative example were repeatedly charged and discharged through the following steps, and the discharge capacity retention rate of the lithium-ion batteries was calculated.

[0200] In an environment of 25℃, the first charge and discharge cycle was performed. Constant current and constant voltage charging was carried out at a charging current of 0.1C until the upper limit voltage was 4.2V. Then, constant current discharge was carried out at a discharge current of 1C until the final voltage was 2.5V. The discharge capacity of the first cycle was recorded. The above steps were repeated for 100 charge and discharge cycles, and the discharge capacity of the 100th cycle was recorded.

[0201] Cycle capacity retention = (Discharge capacity of the 100th cycle / Discharge capacity of the first cycle) × 100%.

[0202] The preparation parameters and test results of each embodiment and comparative example are shown in Tables 1, 2 and 3 below:

[0203]

[0204]

[0205]

[0206] As can be seen from Examples 1-15, 17-34 and Comparative Example 1, when the matrix material is LMFP, the cycle capacity retention rate of lithium-ion batteries with the cathode material of this application is improved.

[0207] As can be seen from Example 16 and Comparative Example 2, when the matrix material is LFP, the cycle capacity retention rate of lithium-ion batteries with the cathode material of this application is improved.

[0208] As can be seen from Examples 1, 12-15, 22-34 and Comparative Example 3, when the content of the one-dimensional conductive agent is the same and the calcination conditions are the same, the cycle capacity retention rate of the lithium-ion battery with the cathode material of this application is improved, and the 0.1C discharge specific capacity does not change much.

[0209] As can be seen from Examples 1, 8-11, 22-34 and Comparative Example 4, when the fast ion conductor content and calcination conditions are the same, the cycle capacity retention rate of lithium-ion batteries with the cathode material of this application is improved, while the 0.1C discharge specific capacity remains basically unchanged.

[0210] As can be seen from Examples 2-7, the cycle performance of lithium-ion batteries is improved as the content of one-dimensional conductive agent and fast ion conductor increases. However, when the content of one-dimensional conductive agent and fast ion conductor increases to a certain extent, the cycle performance decreases again.

[0211] As can be seen from Examples 17-19, within the calcination temperature range of 300℃ to 800℃, the cycle performance of lithium-ion batteries improves with increasing calcination temperature; however, as the temperature continues to rise, the cycle performance of lithium-ion batteries decreases. Without being limited to any particular theory, the inventors believe that calcination temperature may affect the bonding between particles, thereby affecting the cycle performance of lithium-ion batteries.

[0212] As can be seen from Examples 20, 21 and Comparative Example 1, calcination time also has a certain impact on the performance of cathode materials, but overall, the cycle capacity retention rate of lithium-ion batteries with cathode materials of this application is still improved.

[0213] As can be seen from Examples 22-23 and Comparative Example 1, the use of other one-dimensional conductive agents such as carbon fiber or other fast ion conductors can also improve the electrochemical performance of lithium-ion batteries. This is because one-dimensional conductive agents are long-range conductive agents, which can provide sufficient attachment sites for fast ion conductors. Fast ion conductors can effectively improve the ionic conductivity of materials and act as a protective layer to inhibit metal dissolution.

[0214] As can be seen from Examples 1 and 25-29, the cycle performance of lithium-ion batteries is improved as the aspect ratio of the one-dimensional conductive agent increases. However, when the aspect ratio of the one-dimensional conductive agent increases to a certain extent, the cycle performance decreases again.

[0215] As can be seen from Examples 1 and 30-34, the cycle performance of lithium-ion batteries is improved as the specific surface area of ​​the one-dimensional conductive agent increases. However, when the specific surface area of ​​the one-dimensional conductive agent increases to a certain extent, the cycle performance decreases again.

[0216] As can be seen from Example 1 and Comparative Example 5, the 0.1C discharge specific capacity and cycle capacity retention rate of Comparative Example 5 both decreased. This may be because the LLZO in Comparative Example 5 is directly on the surface of the substrate material, which leads to an increase in interface resistance, thereby affecting the capacity and cycle performance of the lithium-ion battery.

[0217] from Figure 1 As can be seen, in the cathode material of this application, the elongated one-dimensional conductive agent is relatively uniformly distributed in the matrix material, and small particles of fast ion conductors are attached near the one-dimensional conductive agent, thereby giving the cathode material excellent electronic conductivity and ionic conductivity.

[0218] As shown in Table 4, the cathode material of Example 1 of this application contains C, O, P, Mn, Fe, La and Zr elements.

[0219] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing a positive electrode material, comprising the following steps: The first suspension preparation steps are as follows: The one-dimensional conductive agent and the fast ion conductor are ground and sieved separately. The sieved one-dimensional conductive agent and the sieved fast ion conductor are then dispersed in an organic solvent to obtain the first suspension; wherein, the fast ion conductor includes Li. 10 GeP2S 12 or Li7La3Zr2O 12 At least one of them; The second suspension preparation steps are as follows: the matrix material is ground and then sieved, and the sieved matrix material is dispersed in an organic solvent to obtain the second suspension; Suspension mixing step: The first suspension and the second suspension are mixed to obtain a mixed slurry; the mixed slurry is spray-dried to obtain a cathode material precursor; and Calcination step: The cathode material precursor is calcined to obtain the cathode material; Based on the total mass of the matrix material, the one-dimensional conductive agent, and the fast ion conductor, the mass percentage of the one-dimensional conductive agent is 1.5% to 5%, the mass percentage of the fast ion conductor is 1.5% to 5%, and the mass ratio of the one-dimensional conductive agent to the fast ion conductor is 0.67:1 to 2:

1.

2. The preparation method according to claim 1, wherein, The atmosphere of the roasting step is selected from at least one of argon, helium, neon or nitrogen, the roasting temperature of the roasting step is 300°C to 800°C, and the roasting time of the roasting step is 6h to 24h.

3. The preparation method according to claim 1, wherein, The organic solvent includes at least one of methanol or ethanol.

4. The preparation method according to claim 1, wherein, The first suspension has a solid content of 35% to 65%, the second suspension has a solid content of 35% to 65%, and the mixed slurry has a solid content of 40% to 60%.

5. The preparation method according to claim 1, wherein, The matrix material includes at least one of lithium manganese iron phosphate, lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, or lithium cobalt oxide, wherein the molar ratio of manganese to iron in the lithium manganese iron phosphate is 0.01 to 10, and the one-dimensional conductive agent includes at least one of carbon nanotubes or carbon fibers.

6. The preparation method according to claim 1, wherein, The fast ion conductor includes the compound Li. x La y Zr z M a O b Wherein, 6≤x≤8, 2≤y≤4, 1≤z≤3, 0≤a≤0.5, 11≤b≤13, and the M element is selected from at least one of the Ta element or the W element.

7. The preparation method according to claim 5, wherein, The matrix material includes at least one of ZrO2, SnO2, ZnO, MgO, Al2O3, TiO2, CeO2, AlF3 or Li3AlF6.

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