Positive electrode material and preparation method thereof, electrochemical device, and electronic equipment

Abstract

The application discloses a positive electrode material and a preparation method thereof, an electrochemical device and electronic equipment. The positive electrode material comprises, from inside to outside, a core, a first coating layer and a second coating layer; the core comprises lithium nickel manganese oxide doped with phosphorus elements; the first coating layer is in a film shape, and the first coating layer comprises a phosphate; and the second coating layer is in an island shape or a chain shape, and the second coating layer comprises a phosphate. The electrochemical device (especially a lithium ion battery) obtained by using the positive electrode material can slow down Mn dissolution and improve high-temperature cycle stability.

Description

TECHNICAL FIELD

[0001] The present application relates to a positive electrode material, a preparation method thereof, an electrochemical device and an electronic equipment. BACKGROUND

[0002] Lithium-ion batteries (LIBs) as the current mainstream energy storage technology, are widely used in electric vehicles (EVs), consumer electronics and grid energy storage, etc. However, the traditional positive electrode materials (such as LiCoO2, LiFePO4, NCM / NCA) have limitations in energy density, cost or safety, and it is urgent to develop higher performance positive electrode materials. The voltage platform (~4.7 V) of nickel-manganese spinel LiNi 0.5 Mn 1.5 O4 (LNMO) is much higher than that of traditional positive electrode materials (such as LiCoO2 ~3.9 V, LiFePO4 ~3.4 V), which can significantly improve the energy density of the battery (the theoretical energy density can reach ~650 Wh / kg, close to high-nickel NCM), and LNMO can be combined with high-capacity negative electrodes (such as silicon-carbon, lithium metal) to build high-energy-density full batteries. Therefore, due to the high operating voltage (~4.7 V vs. Li + / Li) of LNMO, low cost (no cobalt), excellent thermal stability and rate performance, it has become one of the important candidate materials for the next generation of high-energy-density lithium-ion batteries.

[0003] However, although LNMO has many advantages, its practical application still faces problems such as electrolyte compatibility, cycle stability and interface transmission. When combined with traditional carbonate-based electrolyte (such as EC / DMC), it is easy to oxidize at >4.3 V, which leads to unstable CEI and decreased battery cycle stability. Moreover, as a manganese-containing positive electrode material, manganese dissolution and structural phase transition are inevitable during battery charge and discharge cycles, which destroys the electrode structure and further leads to a significant decrease in the cycle stability of the battery, especially under high-temperature conditions. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the defects of severe Mn dissolution and poor high-temperature cycle performance of lithium-ion batteries obtained by the existing lithium nickel manganese oxide, and to provide a positive electrode material, a preparation method thereof, an electrochemical device and an electronic equipment. The electrochemical device (especially lithium-ion battery) obtained by using the positive electrode material can slow down the Mn dissolution and improve the high-temperature cycle stability.

[0005] The present application solves the above technical problems by the following technical solutions:

[0006] The first aspect of the present application provides a positive electrode material, which comprises, from inside to outside, an inner core, a first coating layer and a second coating layer; the inner core comprises lithium nickel manganese oxide doped with phosphorus elements; the first coating layer is in a film shape, and the first coating layer comprises a phosphate; the second coating layer is in an island shape or a chain shape, and the second coating layer comprises a phosphate.

[0007] The second aspect of the present application provides a preparation method of a positive electrode material, which comprises the following steps:

[0008] S1, performing first sintering on a first mixture to obtain a first precursor; wherein the first mixture comprises a lithium nickel manganese oxide precursor, γ-Li3PO4 and a lithium salt;

[0009] S2, performing second sintering on a second mixture to obtain a second precursor; wherein the second mixture comprises the first precursor and β-Li3PO4;

[0010] S3, performing third sintering on a third mixture to obtain the positive electrode material; wherein the third mixture comprises the second precursor and amorphous Li3PO4.

[0011] The third aspect of the present application provides a positive electrode material, which is prepared by using the preparation method of the positive electrode material.

[0012] The fourth aspect of the present application provides an electrochemical device, wherein the positive electrode sheet of the electrochemical device comprises the positive electrode material.

[0013] The fifth aspect of the present application provides an electronic device, which comprises the electrochemical device.

[0014] On the basis of common sense in the art, the above-mentioned preferred conditions can be combined arbitrarily, that is, to obtain each preferred example of the present application.

[0015] The reagents and raw materials used in the present application are commercially available.

[0016] The positive progress effect of the present application is that:

[0017] The positive electrode material provided in the present application is prepared by doping phosphorus elements in lithium nickel manganese oxide and setting a double-layer coating layer comprising a phosphate on the surface of the lithium nickel manganese oxide, wherein the stability of Mn elements is better, and the electrochemical device (especially a lithium ion battery) obtained by using the positive electrode material can slow down the Mn dissolution and improve the high-temperature cycle stability of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is an SEM image of the first precursor in Example 1.

[0019] Figure 2 It is an SEM image of the second precursor in Example 1.

[0020] Figure 3 SEM image of the positive electrode material obtained in Example 1. DETAILED DESCRIPTION

[0021] The application will be further described in the following examples without limiting the application to the examples described. The experimental methods in the following examples, for which no specific conditions are indicated, are selected in accordance with the conventional methods and conditions, or in accordance with the instructions of the commercial products.

[0022] The first aspect of the application provides a positive electrode material, which comprises, in order from the inside to the outside, an inner core, a first coating layer and a second coating layer; the inner core comprises lithium nickel manganese oxide doped with phosphorus elements; the first coating layer is in a film shape, and the first coating layer comprises a phosphate; the second coating layer is in an island shape or a chain shape, and the second coating layer comprises a phosphate.

[0023] In the application, by introducing Li3PO4 with different structures into lithium nickel manganese oxide, specifically by γ-Li3PO4, P replaces part of the O sites in lithium nickel manganese oxide to achieve doping of phosphorus elements, and β-Li3PO4 and amorphous Li3PO4 are respectively used to form the first coating layer and the second coating layer, so as to slow down the Mn dissolution and improve the high-temperature cycle stability based on the synergistic effect of Li3PO4 with different structures. The synergistic effect of Li3PO4 with different structures is specifically embodied in:

[0024] (1) For doped γ-Li3PO4: γ-Li3PO4 has the characteristics of high-temperature stability, and using γ-Li3PO4 as a phosphorus acid source can ensure that PO4 3- replaces O 2- sites to form anion doping, while stabilizing the spinel structure of the main body and inhibiting the oxygen loss of the spinel material under high-voltage conditions, and the doped PO4 3- can stabilize the Mn 4+ of the system, thereby reducing the Mn 3+ content in the system to achieve the effect of reducing Mn dissolution;

[0025] (2) For the first coating layer: β-Li3PO4 has strong chemical inertness, and using β-Li3PO4 as an intermediate layer phosphorus acid source can form a film-shaped coating layer on the surface of the material particles, which can block the direct contact between the spinel positive electrode material and the electrolyte, β-Li3PO4 can resist the erosion of HF produced by the decomposition of the electrolyte, and β-Li3PO4 can protect the surface of LNMO from Mn 3+ dissolution, and the lattice channel of β-Li3PO4 (~0.4 Å) allows Li +By blocking solvent molecules (such as EC, ~0.5 Å), reducing the interface impedance, and the thermal expansion coefficient of β-Li3PO4 (~10 -6 / °C) is close to that of LNMO (~8×10 -6 / °C), the interface peeling in the cycle can be reduced;

[0026] (3) For the second coating layer: amorphous Li3PO4 can further form an island-shaped or chain-shaped discontinuous coating layer composed of small particles on the surface of the first coating layer, thereby further isolating the direct contact of the main body metal material (nickel, manganese, etc.) with the electrolyte; In the present application, amorphous Li3PO4 is particularly used as the outermost layer of the phosphoric acid source. The high compactness of this amorphous structure can effectively block the Mn 3+ disproportionation generated by the Mn 2+ from reacting with the electrolyte;

[0027] In particular, by adopting the two-layer coating structure obtained by using Li3PO4 and amorphous Li3PO4, in which the first coating layer β-Li3PO4 serves as the outermost second coating layer and the transition layer of the main body spinel structure, the interface structure bridge can be made more compact. The combination of the two structures can improve the mechanical strength of the first coating layer and the second coating layer, reduce the occurrence of interface peeling of the second coating layer in the long cycle process, and thus long-term protect the main body spinel structure from being eroded by the electrolyte.

[0028] In the present application, the "film-like" coating layer refers to a continuous and smooth coating layer on the surface of the material particles. Under SEM magnification of 10-20K times, a substantially continuous and smooth surface structure is presented.

[0029] In the present application, the "island-shaped or chain-shaped" coating layer refers to a discontinuous coating layer composed of small particles on the surface of the material particles. Under SEM magnification of 10-20K times, the surface of the material particles presents a discrete particle-like and rough surface structure.

[0030] In some embodiments, the inner core does not contain other metal ions such as Fe in addition to Ni, Li and Mn. Wherein "does not contain" means that the content of other metal ions in addition to Ni, Li and Mn is <500ppm, which is considered as not containing.

[0031] In some preferred embodiments, in the first coating layer, the cation of the phosphate is Ni, Mn and Li.

[0032] In some embodiments, the first coating layer does not contain other metal ions such as Fe in addition to Ni, Li and Mn. Wherein "does not contain" means that the content of other metal ions in addition to Ni, Li and Mn is <500ppm, which is considered as not containing.

[0033] In some preferred embodiments, the cation of the phosphate in the second coating layer is Li.

[0034] In some embodiments, the second coating layer is free of metal ions other than Ni, Li and Mn, such as Fe, etc. Wherein, "free of" means that the content of metal ions other than Ni, Li and Mn is < 500 ppm, which is considered as free of.

[0035] In the present application, the positive electrode material is generally primary particles. The average particle size of the positive electrode material can be 2.5-2.6 μm.

[0036] In some preferred embodiments, the average thickness of the first coating layer is 3-10 nm, preferably 3-8 nm, for example 5 nm.

[0037] In some preferred embodiments, the average thickness of the second coating layer is 3-10 nm, preferably 3-8 nm, for example 5 nm.

[0038] In some preferred embodiments, the ratio of the average thickness of the first coating layer and the second coating layer is 1: (0.5-2), for example 1:1.

[0039] In some preferred embodiments, the raw material of the first coating layer comprises β-Li3PO4.

[0040] Wherein, the average particle size of the β-Li3PO4 is preferably 30-40 nm, for example 35 nm.

[0041] In some preferred embodiments, the raw material of the second coating layer comprises amorphous Li3PO4.

[0042] Wherein, the average particle size of the amorphous Li3PO4 is preferably 0.1-0.2 μm, for example 0.15 μm.

[0043] In some preferred embodiments, the raw material of the phosphorus element in the core is γ-Li3PO4.

[0044] Wherein, the average particle size of the γ-Li3PO4 is preferably 30-40 nm, for example 35 nm.

[0045] In some more preferred embodiments, the mass ratio of the lithium nickel manganese oxide and the γ-Li3PO4 is 1: (0.001-0.005), for example 1:0.003.

[0046] In some more preferred embodiments, the mass ratio of the γ-Li3PO4, the β-Li3PO4 and the amorphous Li3PO4 is 1: (0.5-1): (0.5-1), for example 1:0.75:0.75.

[0047] In the present application, the positive electrode material with the above composition, structure and performance can be prepared by the preparation method of the positive electrode material provided by the second aspect of the present application.

[0048] The second aspect of the present application provides a preparation method of a positive electrode material, which comprises the following steps:

[0049] S1, performing first sintering on a first mixture to obtain a first precursor; wherein the first mixture comprises a lithium nickel-manganese phosphate precursor, γ-Li3PO4 and a lithium salt;

[0050] S2, performing second sintering on a second mixture to obtain a second precursor; wherein the second mixture comprises the first precursor and β-Li3PO4;

[0051] S3, performing third sintering on a third mixture to obtain the positive electrode material; wherein the third mixture comprises the second precursor and amorphous Li3PO4.

[0052] In some preferred embodiments, in step S1, the lithium salt is lithium carbonate.

[0053] In some preferred embodiments, in step S1, the lithium nickel-manganese phosphate precursor comprises nickel hydroxide and / or manganese hydroxide.

[0054] In some preferred embodiments, in step S1, in the first mixture, the mass ratio of the lithium nickel-manganese phosphate precursor and the lithium salt is 1: (0.1-0.3).

[0055] In some preferred embodiments, in step S1, the average particle size of the first precursor is 2.5-2.6 μm.

[0056] In some preferred embodiments, in step S1, the temperature of the first sintering is 850-950℃, for example 900℃.

[0057] In some preferred embodiments, in step S1, the time of the first sintering is 8-12h, for example 10h.

[0058] In some preferred embodiments, the average particle size of the γ-Li3PO4 is 30-40 nm, for example 35 nm.

[0059] In some preferred embodiments, the mass ratio of the lithium nickel manganese oxide and the γ-Li3PO4 is 1:(0.001-0.005), for example 1:0.003.

[0060] In some preferred embodiments, the mass ratio of the γ-Li3PO4, β-Li3PO4 and amorphous Li3PO4 is 1:(0.73-0.76):(0.73-0.76).

[0061] In some preferred embodiments, in step S2, the average particle size of the second precursor is 2.5-2.6 μm.

[0062] In some preferred embodiments, in step S2, the average particle size of the β-Li3PO4 is 30-40 nm, for example 35 nm.

[0063] In some preferred embodiments, in step S3, the average particle size of the amorphous Li3PO4 is 0.1-0.2 μm, for example 0.15 μm.

[0064] In some preferred embodiments, in step S2, the temperature of the second sintering is 350-450℃, for example 400℃.

[0065] In some preferred embodiments, in step S2, the time of the second sintering is 5-8 h, for example 6 h.

[0066] In some preferred embodiments, in step S2, in the second mixture, the mass ratio of the first precursor and β-Li3PO4 is 1:(0.0023-0.0026).

[0067] In some preferred embodiments, in step S3, the temperature of the third sintering is 300-400℃, for example 350℃.

[0068] In some preferred embodiments, in step S3, the time of the third sintering is 5-8 h, for example 6 h.

[0069] In some preferred embodiments, in step S3, in the third mixture, the mass ratio of the second precursor and amorphous Li3PO4 is 1:(0.0023-0.0026).

[0070] A third aspect of the present application provides a positive electrode material prepared by the method for preparing a positive electrode material as described above.

[0071] In the present application, the composition, structure and performance of the positive electrode material are the same as those of the positive electrode material of the first aspect.

[0072] The fourth aspect of the present application provides an electrochemical device, wherein a positive electrode sheet of the electrochemical device comprises the positive electrode material as described above.

[0073] In the present application, the electrochemical device is preferably a battery.

[0074] In the present application, the electrochemical device is preferably a lithium ion battery. The lithium ion battery can be a liquid battery, a solid battery or a semi-solid battery. For example, the liquid lithium ion battery comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; the solid lithium ion battery comprises a positive electrode, a negative electrode and a solid electrolyte. The type of battery does not limit the scope of protection of the present application.

[0075] The technical content of the present application is described below with the liquid battery as a specific embodiment.

[0076] In an alternative embodiment, the electrochemical device is a lithium ion battery; the lithium ion battery comprises a negative electrode sheet, a positive electrode sheet, an electrolyte and a separator, wherein the positive electrode sheet comprises the positive electrode material as described above.

[0077] Positive electrode sheet

[0078] In the present application, the positive electrode sheet can comprise a positive electrode current collector and a positive electrode material layer, wherein the positive electrode material layer is disposed on at least one surface of the positive electrode current collector; and the positive electrode material layer comprises the positive electrode material as described above.

[0079] In some embodiments, the positive electrode material layer further comprises a conductive agent. The conductive agent is an agent for ensuring that the electrode has good charge and discharge performance. It can be optionally selected from graphite materials such as natural graphite and artificial graphite, carbon black materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal cracking carbon black, conductive fibers such as carbon fibers and metal fibers, metal powders such as fluorinated carbon powder, aluminum powder, nickel powder and other metal powders, conductive whiskers such as zinc oxide and potassium titanate, and conductive metal oxides such as titanium dioxide, and polyphenylene derivatives, for example, carbon black.

[0080] In some embodiments, the positive electrode material layer further comprises a binder. The binder can be a component that helps to bind the positive electrode material and the conductive agent and helps to bind the positive electrode material and the positive electrode current collector. It can be generally selected from polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber and various copolymers, for example, PVDF.

[0081] In some embodiments, the positive electrode material layer comprises the positive electrode material, polyvinylidene fluoride and conductive carbon black.

[0082] In some embodiments, the mass ratio of the positive electrode material, polyvinylidene fluoride and conductive carbon black is 90:5:5.

[0083] In the present application, the positive electrode current collector can be a conventional positive electrode current collector in the art. For the positive electrode current collector, a material that does not cause chemical change and has high conductivity can be used without limitation. For example, stainless steel, aluminum, nickel, titanium or calcined carbon, or an aluminum or stainless steel material surface-treated with carbon, nickel, titanium, silver or the like can be generally used. In order to enhance adhesion, micro-embossing can be formed on the surface of the positive electrode current collector. The positive electrode current collector can be used in various forms such as a film, a sheet, a foil, a mesh or a porous body, etc.

[0084] In some alternative embodiments, the positive electrode current collector is an aluminum foil.

[0085] In some alternative embodiments, the thickness of the positive electrode current collector can be 8-16 μm, for example, 15 μm.

[0086] In the present application, the positive electrode sheet can be prepared by a conventional method in the art.

[0087] In some alternative embodiments, the method for preparing the positive electrode sheet comprises the following steps:

[0088] After mixing the positive electrode material, the binder and the conductive agent in a certain mass ratio, a solvent is added and mixed uniformly to obtain a positive electrode slurry; then the positive electrode slurry is uniformly coated on at least one surface of the positive electrode current collector; and then the positive electrode sheet is prepared through processes such as drying, rolling, slitting, etc.

[0089] In some embodiments, the coating area density of the positive electrode slurry is 8.6-8.7 mg / cm 2 .

[0090] Negative electrode sheet

[0091] In some embodiments, the negative electrode sheet is a lithium foil.

[0092] In other embodiments, the negative electrode sheet can comprise a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, and the negative electrode material layer comprises a negative electrode material.

[0093] In the present application, the negative electrode material in the negative electrode material layer can be a conventional negative electrode material used in the art, such as a graphite-based negative electrode material, a silicon-oxygen-based negative electrode material or a silicon-carbon-based negative electrode material.

[0094] In some embodiments, the negative electrode material comprises one or more of lithium titanate, artificial graphite, natural graphite, soft carbon, hard carbon, mesocarbon microbeads, silicon monoxide and silicon-carbon material.

[0095] In some embodiments, the negative electrode material layer further comprises a conductive agent.

[0096] The conductive agent is not particularly limited as long as it has conductivity without causing chemical changes in the battery. For example, graphite such as natural graphite or artificial graphite; carbon-based materials such as conductive carbon black (Super P, abbreviated as SP), carbon nanotubes (CNT), acetylene black, ketjen black, slot black, furnace black, lamp black, thermal carbon black, or carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, or silver; conductive whisker such as zinc oxide whisker or potassium titanate whisker; conductive metal oxide such as titanium dioxide; or conductive polymer such as polyphenylene derivative can be specifically used.

[0097] In some specific embodiments, the conductive agent in the negative electrode material layer is carbon black Super P.

[0098] In some embodiments, the negative electrode material layer further comprises a binder.

[0099] The type of the binder is not particularly limited and can be optionally selected from polyvinylidene fluoride, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid (PAA), ethylene-propylene-diene terpolymer and sulfonated products thereof, styrene butadiene rubber (SBR), fluororubber, and various copolymers, for example, SBR.

[0100] In some embodiments, the negative electrode material layer further comprises a thickening agent.

[0101] The addition of the thickening agent can increase the system viscosity of the components in the negative electrode slurry, and can be a thickening agent commonly used in the art for preparing negative electrode sheets, for example, sodium carboxymethyl cellulose (CMC).

[0102] In the present application, the negative electrode current collector can be a conventional negative electrode current collector in the art. The negative electrode current collector serves as a substrate to support the negative electrode material layer, and is usually a metal foil with a thickness of 3-500 μm. The material is not particularly limited as long as it has high electrical conductivity and does not cause chemical reactions in the system of the secondary battery. For example, it can be a foil formed after surface treatment of nickel, titanium, aluminum, nickel, silver, stainless steel, carbon, etc. The negative electrode current collector usually has a smooth surface, but fine lines or the like can also be formed on its surface to improve the adhesion between the negative electrode material layer and the current collector. In addition to the foil, the negative electrode current collector can also be used in any one or a combination of multiple forms such as film, mesh, porous, foam, or non-woven fabric. Generally, the negative electrode current collector is a copper foil.

[0103] In some embodiments, the method for preparing the negative electrode sheet comprises the following steps: coating the negative electrode slurry obtained by sufficiently stirring and mixing the components of the negative electrode material layer in a solvent on at least one surface of the negative electrode current collector, drying, cold-pressing, and slitting to obtain the negative electrode sheet.

[0104] Electrolyte

[0105] In some embodiments, the electrolyte can be an electrolyte commonly used in the art for batteries, and generally comprises a non-aqueous solvent and a lithium salt.

[0106] In the present application, the non-aqueous solvent can be a non-aqueous solvent commonly used in the art.

[0107] In some embodiments, the non-aqueous solvent preferably comprises an ester solvent and / or dimethyl sulfoxide (DMSO), and more preferably comprises a carbonate solvent. The carbonate solvent can optionally be one or more of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate, propylene carbonate, and butylene carbonate (BC). The non-aqueous solvent can also comprise ethyl acetate.

[0108] In the present application, the lithium salt can be a lithium salt commonly used in the art, and is preferably one or more of LiPF6, LiBF4, LiClO4, LiCF3SO3, and LiN(CF3SO2)2, for example LiPF6.

[0109] In the present application, the electrolyte can comprise an additive, which can be an additive commonly used in the art, for example fluoroethylene carbonate (FEC).

[0110] In some embodiments, the electrolyte comprises LiPF6, ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0111] The volume ratio of the ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate is, for example, 1:2:1.

[0112] The concentration of the lithium salt is, for example, 1 mol / L.

[0113] In some embodiments, the electrolyte can be prepared by a method commonly used in the art, and is optionally prepared by the following method: mixing the non-aqueous solvent and the additive in a ratio in an argon glove box with a water content of <10 ppm, and then adding a sufficiently dried lithium salt and mixing uniformly to obtain the electrolyte.

[0114] Separator

[0115] In some alternative embodiments, the separator can be a polypropylene film or a polyethylene film.

[0116] In a specific embodiment, the separator is a polypropylene film; the thickness of the separator is 11 μm.

[0117] In the present application, the preparation method of the lithium ion battery can be a conventional preparation method in the art, which can be sequentially winding the positive electrode sheet, the separator and the negative electrode sheet to obtain an electric core, then performing packaging shell packaging and injecting the electrolyte; or can be sequentially stacking the positive electrode sheet, the separator and the negative electrode sheet to obtain an electric core, then performing packaging shell packaging and injecting the electrolyte; and then performing processes such as standing, hot and cold pressing, formation, clamp, and capacity distribution to obtain a lithium ion battery.

[0118] The fifth aspect of the present application provides an electronic device comprising the electrochemical device as described above.

[0119] Exemplarily, the electronic device of the present application can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a notebook computer, a video recorder, a portable printer / copier, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system and a backup power supply, etc.

[0120] On the basis of common knowledge in the art, the above-mentioned preferred conditions can be combined arbitrarily, thereby obtaining preferred examples of the present application.

[0121] Example 1

[0122] The preparation method of the positive electrode material in the present embodiment comprises the following steps:

[0123] S1, first sintering: uniformly mixing the nickel-manganese hydroxide precursor and lithium carbonate (the mass ratio of the nickel-manganese hydroxide precursor and lithium carbonate is 1:0.2) and γ-Li3PO4 (the average particle size is 35 nm, and the content is 2000 ppm) in a high-speed mixer, then putting into a box furnace for first sintering, the sintering temperature is 900℃, the sintering time is 10 h, after taking out of the furnace, crushing and sieving to obtain a powder material (the average particle size is 2.5-2.6 μm), which is the first precursor;

[0124] S2, second sintering: uniformly mixing the first precursor and β-Li3PO4 (the average particle size is 35 nm, and the content is 1000 ppm) with a high-speed mixer, then putting into a box furnace for second sintering, the sintering temperature is 400℃, the sintering time is 6 h, after sieving, a second precursor (the average particle size is 2.5-2.6 μm) is obtained;

[0125] S3, third sintering: the second precursor and amorphous Li3PO4 (average particle size is 0.15 μm, content is 1000 ppm) are mixed uniformly by a high-speed mixer and then are put into a box furnace for third sintering, the sintering temperature is 350 ℃, and the sintering time is 6 h, thereby obtaining the positive electrode material;

[0126] wherein the nickel-manganese hydroxide precursor and the lithium carbonate form lithium nickel-manganese phosphate (LiNi 0.5 Mn 1.5 O4, i.e., LNMO), the lithium nickel-manganese phosphate and the γ-Li3PO4 form the core (i.e., the phosphorus-doped lithium nickel-manganese phosphate), the β-Li3PO4 participates in forming the first coating layer, and the amorphous Li3PO4 participates in forming the second coating layer.

[0127] Example 2

[0128] The difference between this embodiment and Example 1 is that, in step S2, the content of the β-Li3PO4 is 2000 ppm, and the other conditions are the same as those in Example 1.

[0129] Example 3

[0130] The difference between this embodiment and Example 1 is that, in step S3, the content of the amorphous Li3PO4 is 2000 ppm, and the other conditions are the same as those in Example 1.

[0131] Example 4

[0132] The difference between this embodiment and Example 1 is that, in step S1, the content of the γ-Li3PO4 is 100 ppm, and the other conditions are the same as those in Example 1.

[0133] Example 5

[0134] The difference between this embodiment and Example 1 is that, in step S1, the content of the γ-Li3PO4 is 4000 ppm, and the other conditions are the same as those in Example 1.

[0135] Example 6

[0136] The difference between Example 6 and Example 1 is that, in step S1, the temperature of the first sintering is 850 ℃, and the other conditions are the same as those in Example 1.

[0137] Example 7

[0138] The difference between Example 7 and Example 1 is that, in step S1, the temperature of the first sintering is 950 ℃, and the other conditions are the same as those in Example 1.

[0139] Example 8

[0140] The difference between Example 8 and Example 1 is that, in step S2, the temperature of the second sintering is 350 ℃, and the other conditions are the same as those in Example 1.

[0141] Example 9

[0142] Example 9 and Example 1 differ only in that in step S2, the second sintering temperature is 450°C, and the rest of the conditions are the same as in Example 1.

[0143] Example 10

[0144] Example 10 and Example 1 differ only in that in step S3, the third sintering temperature is 300°C, and the rest of the conditions are the same as in Example 1.

[0145] Example 11

[0146] Example 11 and Example 1 differ only in that in step S3, the third sintering temperature is 400°C, and the rest of the conditions are the same as in Example 1.

[0147] Comparative Example 1

[0148] This comparative example and Example 1 differ only in that in step S1, γ-Li3PO4 is not added; steps S2 and S3 are not performed, and the rest of the conditions are the same as in Example 1. The obtained positive electrode material corresponds to the lithium nickel manganese oxide in Example 1.

[0149] Comparative Example 2

[0150] This comparative example and Example 1 differ only in that steps S2 and S3 are not performed, and the rest of the conditions are the same as in Example 1. The obtained positive electrode material corresponds to the inner core (i.e., the lithium nickel manganese oxide doped with phosphorus elements) in Example 1.

[0151] Comparative Example 3

[0152] This comparative example and Example 1 differ only in that step S3 is not performed, and the rest of the conditions are the same as in Example 1. The obtained positive electrode material does not have a second coating layer compared with the positive electrode material in Example 1.

[0153] Comparative Example 4

[0154] This comparative example and Example 1 differ in that step S2 is not performed; in step S3, the first precursor obtained in step S1 and amorphous Li3PO4 are used for third sintering (sintering temperature 350°C, sintering time 6 h), and the rest of the conditions are the same as in Example 1. The obtained positive electrode material does not have a first coating layer compared with the positive electrode material in Example 1.

[0155] Comparative Example 5

[0156] This comparative example and Example 1 differ only in that in step S1, γ-Li3PO4 is not added; step S3 is not performed, and the rest of the conditions are the same as in Example 1. The obtained positive electrode material does not have a second coating layer and does not have phosphorus elements doped in the inner core compared with the positive electrode material in Example 1.

[0157] Comparative Example 6

[0158] The difference between the present comparative example and Example 1 is that: in step S1, no γ-Li3PO4 is added; step S2 is not performed; in step S3, the first precursor obtained in step S1 and amorphous Li3PO4 are used to perform the third sintering (sintering temperature 350°C, sintering time 6 h), and the rest of the conditions are the same as in Example 1. The obtained positive electrode material has no first coating layer and no phosphorus element doped in the core compared with the positive electrode material in Example 1.

[0159] Comparative Example 7

[0160] The difference between the present comparative example and Example 1 is that: in step S2, the first precursor and amorphous Li3PO4 (average particle size 0.15 μm, content 1000 ppm) are used to perform the third sintering (sintering temperature 350°C, sintering time 6 h), and the obtained material is sieved to have an average particle size of 2.5-2.6 μm; in step S3, the material obtained in step S2 and β-Li3PO4 are used to perform the second sintering (sintering temperature 400°C, sintering time 6 h), and the rest of the conditions are the same as in Example 1.

[0161] Comparative Example 8

[0162] The difference between the present comparative example and Example 1 is that: in step S2, the first precursor and amorphous Li3PO4 (average particle size 0.15 μm, content 1000 ppm) are used to perform the third sintering (sintering temperature 350°C, sintering time 6 h) to obtain a second precursor (average particle size 2.5-2.6 μm); and the rest of the conditions are the same as in Example 1.

[0163] Comparative Example 9

[0164] The difference between the present comparative example and Example 1 is that: in step S3, the second precursor and β-Li3PO4 (average particle size 35 nm, content 1000 ppm) are used to perform the third sintering (sintering temperature 350°C, sintering time 6 h); and the rest of the conditions are the same as in Example 1.

[0165] Comparative Example 10

[0166] The difference between the present example and Example 1 is only that: in step S1, no γ-Li3PO4 is added, and the rest of the conditions are the same as in Example 1. The obtained positive electrode material has no phosphorus element doped in the core.

[0167] Effect Example 1

[0168] The SEM test was performed on the γ-Li3PO4, β-Li3PO4, amorphous Li3PO4, the first precursor and the second precursor in Examples 1-11 and Comparative Examples 1-10, and the obtained positive electrode material, and the TEM and TEM-EDS tests were performed on the obtained positive electrode material, and the specific test methods were as follows:

[0169] 1. SEM test

[0170] The SEM test was performed by using a scanning electron microscope equipment with the manufacturer of Japan Electronics and the model of JSM-7610FPlus.

[0171] (1) The surface morphology of the first precursor, the second precursor and the positive electrode material was characterized:

[0172] The surface morphology of the obtained first precursor, the second precursor and the obtained positive electrode material was characterized, and the SEM images were obtained, with the voltage of 5 kV and the magnification of 10K. The SEM images of the first precursor, the second precursor and the obtained positive electrode material in Example 1 are shown in Figure 1 , Figure 2 and Figure 3 respectively. As shown in Figure 2 , a continuous smooth film-shaped layer (the first coating layer) was formed on the surface of the particles after the second sintering. Taking the particles in the lower right corner of Figure 2 as an example, the surface has light and dark layers, and the dark layer is the first coating layer. Figure 3 The SEM image of the positive electrode material particles obtained after the third sintering is shown in Figure 2 . Compared with the smooth film-shaped coating layer shown in Figure 3 , it can be clearly seen that the outer surface of the particles in is more rough, and there are discrete granular protrusions, which are island-shaped coating layers (i.e. the third coating layer).

[0173] (2) The average particle size of the γ-Li3PO4, β-Li3PO4, amorphous Li3PO4, the first precursor, the second precursor and the positive electrode material was characterized:

[0174] The SEM test was performed on the γ-Li3PO4, β-Li3PO4, amorphous Li3PO4, the first precursor, the second precursor and the positive electrode material in Examples and Comparative Examples, and the SEM images were obtained, with the voltage of 5 kV and the magnification of 5K. In each SEM image, at least 200 particles were randomly selected, and the particle size value (the maximum value of the straight line distance between any two points on the particle edge) was measured by using Nanomeasurer. For each sample, 3 SEM images were obtained by the SEM test, and the particle size value of at least 600 particles was measured, and the average value was obtained to obtain the average particle size. The average particle size test results of the positive electrode material are shown in Table 1.

[0175] 2. TEM test

[0176] The TEM test was performed by using a Transmission Electron Microscope (TEM, made by Hitachi, model HT7800).

[0177] TEM test was performed on the positive electrode material obtained in the above examples and comparative examples by using a focused ion beam (FIB) to obtain a particle slice cross section. The average thickness of the first coating layer and the second coating layer was obtained according to the TEM image, specifically:

[0178] At a magnification of 200,000 times, 10 points were randomly selected in the TEM image (20 nm x 20 nm) of the same positive electrode material, and the thickness of the first coating layer and the second coating layer was measured by using Digital Micrograph. The average thickness of the first coating layer and the second coating layer was obtained by removing the maximum value and the minimum value.

[0179] Then, 10 positive electrode material particles were randomly selected, and the thickness of the first coating layer and the second coating layer of each positive electrode material was calculated. The average thickness of the first coating layer and the second coating layer of the 10 positive electrode materials was calculated as the average thickness of the first coating layer and the second coating layer of the positive electrode material.

[0180] As can be seen from the TEM image, the positive electrode material prepared by the preparation method of the positive electrode material in Example 1 comprises, from the inside to the outside, a core, a first coating layer and a second coating layer; wherein the average thickness of the first coating layer is 5 nm, and the average thickness of the second coating layer is 5 nm.

[0181] The positive electrode material prepared by the preparation method of the positive electrode material in Example 3 comprises, from the inside to the outside, a core, a first coating layer and a second coating layer; wherein the average thickness of the first coating layer is 10 nm, and the average thickness of the second coating layer is 5 nm.

[0182] The positive electrode material prepared by the preparation method of the positive electrode material in Example 4 comprises, from the inside to the outside, a core, a first coating layer and a second coating layer; wherein the average thickness of the first coating layer is 5 nm, and the average thickness of the second coating layer is 10 nm.

[0183] The above test results are shown in Table 1.

[0184] 3. TEM-EDS test

[0185] TEM-EDS test was performed by a Transmission Electron Microscope (TEM, Hitachi, HT7800) with an EDS accessory (Hitachi, EMAX Evolution).

[0186] TEM-EDS tests were performed on the positive electrode materials of Examples 1-11 and Comparative Examples 1-10, respectively. According to the characterization results, the inner core of the positive electrode material obtained in Examples 1-11 was distributed with P, O, Ni, Mn and Li, the first coating layer was distributed with P, O, Ni, Mn and Li, and the second coating layer was distributed with P, O and Li, indicating that the first coating layer of the positive electrode material obtained in the examples contained phosphate, and the second coating layer contained phosphate. Based on this, those skilled in the art should understand that the P inside the first coating layer will also bond with the surface Ni, Mn, Li and O elements; and by means of XPS, it can be further characterized that the P element in the inner core replaces part of the O element in the LNMO structure, thereby forming doped phosphorus lithium nickel manganese oxide.

[0187] Effect Example 2

[0188] The positive electrode materials prepared in Examples 1-11 and Comparative Examples 1-10 were used to prepare positive electrode sheets, and the obtained button cells (lithium ion batteries) were assembled, specifically:

[0189] The preparation method of the positive electrode sheet includes the following steps:

[0190] The prepared positive electrode material, conductive agent carbon black Super P, and binder PVDF were mixed in a mass ratio of 90:5:5. Carbon black Super P and PVDF were first added to an appropriate amount of N-methyl pyrrolidone (NMP) solvent to form a conductive glue, and then the positive electrode material was added to the conductive glue in proportion. After mixing uniformly with a homogenizer, it was coated on one surface of an aluminum foil (thickness of 240 μm), dried, rolled (roll pressure of 19T), and cut into positive electrode sheets with a diameter of 16 mm. Among them, the mass loading of the positive electrode active material was 8.6-8.7 mg·cm −2 ;

[0191] A lithium foil with a diameter of 19 mm and a thickness of 0.6 mm was used as the negative electrode sheet.

[0192] The electrolyte was obtained by dissolving LiPF6 in a mixed solvent (EC / DC / EMC = 1 / 1 / 1, volume ratio), and the concentration of LiPF6 was 1 mol / L.

[0193] Separator: Celgard 2400 polypropylene (PP) membrane was used as the separator, with a thickness of 11 μm. 35 μL of electrolyte was added to both sides of the separator.

[0194] The CR2430 type button cell was assembled using the above positive electrode sheet, negative electrode sheet, separator and electrolyte.

[0195] The CR2430 type button cell assembled above was subjected to electrochemical performance test, as follows:

[0196] The electrochemical performance test was performed using a battery tester (CT-2001A, Wuhan Land), with a charge-discharge voltage range of 3.5 V (discharge cut-off voltage) - 4.95 V (charge cut-off voltage). The following tests were performed:

[0197] (1) 45℃ 100 cycle capacity retention rate

[0198] At 45℃, the newly prepared button cell was first activated at 0.1 C for two cycles, and then cycled at 1 C for 100 cycles, to obtain the first cycle discharge gram capacity (after activation, the first cycle of 100 cycles) and the 100th cycle discharge gram capacity. Wherein 1 C = 140 mAh / g.

[0199] The 100 cycle capacity retention rate at 45℃ was calculated according to the first cycle discharge gram capacity and the 100th cycle discharge gram capacity, and the specific calculation formula was:

[0200] 100 cycle capacity retention rate (45℃) = 100th cycle discharge gram capacity / first cycle discharge gram capacity (after activation) x 100%.

[0201] (2) Manganese dissolution amount after 100 cycles at 45℃

[0202] The negative electrode sheet was obtained by disassembling the button cell cycled at 45℃ for 100 cycles, and 10 mg of powder was scraped from the surface of the negative electrode. After digestion, ICP was used to obtain the manganese dissolution amount. Among them, the deviation caused by the measurement itself is between 15-25 ppm, and the manganese dissolution amount of the battery obtained in Examples 3-11 after 100 cycles at 45℃ is within the acceptable range. Taking Examples 5 and 6 as examples, the manganese dissolution amount of the battery obtained from the positive electrode material after 100 cycles at 45℃ was 88 ppm and 66 ppm, respectively, and the overall manganese dissolution was relatively similar.

[0203] (3) Mn 3+ content

[0204] At 25℃, the newly prepared button cell was charged to the cut-off voltage of 4.95 V at a constant current and constant voltage of 0.1 C, and then discharged to a voltage of 3.5 V at a rate of 0.1 C, to obtain the charge-discharge curve, Mn3+ The content is the proportion of the platform capacity in the voltage interval 4.1-4.2V in the total discharge gram capacity in the charge-discharge curve.

[0205] (4) The first circle discharge gram capacity

[0206] At 25℃, the newly prepared button cell is charged to the cut-off voltage 4.95V by 0.1C rate, and then discharged to the voltage 3.5V by 0.1C rate, to obtain the discharge gram capacity at 0.1C.

[0207] (5) The first circle coulombic efficiency

[0208] At 25℃, the newly prepared button cell is charged to the cut-off voltage 4.95V by 0.1C rate, and then discharged to the voltage 3.5V by 0.1C rate, to obtain the discharge gram capacity at 0.1C.

[0209] The above test results are shown in Table 2.

[0210]

[0211]

[0212] Note: " / " in Table 1 indicates that the parameter is not involved in the specific experiment.

[0213]

[0214] In the positive electrode material of the application, by adopting Li3PO4 with different configurations, specifically by doping γ-Li3PO4, and by sequentially adopting β-Li3PO4 and amorphous Li3PO4 to form the first coating layer and the second coating layer from the inside to the outside of the core, respectively, the synergistic effect of Li3PO4 with different configurations is used to slow down the Mn dissolution and improve the high-temperature cycle stability. According to Table 2, the lithium ion battery obtained by using the positive electrode material in Examples 1-11 has a manganese dissolution amount of less than 150 ppm after 100 cycles at 45℃, and even less than 90 ppm; the cycle capacity retention rate at 45℃ for 100 cycles can reach more than 94%. In addition, the lithium ion battery obtained by using the positive electrode material has a Mn 3+ content of only 11% or less, a first circle discharge gram capacity of more than 134 mAh / g, and a first circle coulombic efficiency of more than 91%, and even 95%.

[0215] Compared with Example 1, the positive electrode material in Comparative Example 1 is not provided with the first coating layer and the second coating layer based on β-Li3PO4 and amorphous Li3PO4 respectively, and the core does not use γ-Li3PO4, and the lithium ion battery based on the positive electrode material has a significantly higher manganese dissolution amount after 100 cycles at 45°C, and a significantly reduced capacity retention rate after 100 cycles at 45°C, which cannot effectively slow down the Mn dissolution and has poor high-temperature cycle stability. In addition, the lithium ion battery has a significantly higher Mn content, and the first discharge specific capacity and the first coulombic efficiency are also poor. 3+

[0216] Compared with Example 1, the positive electrode material in Comparative Example 2 is not provided with the first coating layer and the second coating layer, and the lithium ion battery based on the positive electrode material has a significantly higher manganese dissolution amount after 100 cycles at 45°C, and a significantly reduced capacity retention rate after 100 cycles at 45°C.

[0217] Compared with Example 1, the positive electrode material not provided with the second coating layer (Comparative Example 3) or the first coating layer (Comparative Example 4) has a significantly higher manganese dissolution amount after 100 cycles at 45°C, and a significantly poorer capacity retention rate after 100 cycles at 45°C. Based on Comparative Example 3, Comparative Example 5 further does not use γ-Li3PO4, and has a higher manganese dissolution amount after 100 cycles at 45°C. Based on Comparative Example 4, Comparative Example 6 further does not use γ-Li3PO4, and has a higher manganese dissolution amount after 100 cycles at 45°C.

[0218] Although the obtained positive electrode materials are all provided with double-layer coating layers, compared with Example 1, the double-layer coating layers obtained by only using amorphous Li3PO4 or β-Li3PO4 (Comparative Examples 8-9) or sequentially using amorphous Li3PO4 and β-Li3PO4 (Comparative Example 7) have more serious Mn dissolution and poorer high-temperature cycle stability.

[0219] Compared with Example 1, the core in Comparative Example 10 does not use γ-Li3PO4, and the obtained lithium ion battery has a significantly higher manganese dissolution amount after 100 cycles at 45°C, and a lower capacity retention rate after 100 cycles at 45°C.

[0220] ​In some optional embodiments (Embodiment 1, Embodiment 6-7, Embodiment 9 and Embodiment 11), the lithium ion battery obtained by using the positive electrode material therein can achieve significantly lower manganese elution (the amount of manganese elution after 100 cycles at 45°C can be no higher than 70 ppm), and meanwhile has excellent high-temperature cycle stability (the capacity retention rate after 100 cycles at 45°C can reach more than 94%). In order to achieve the above excellent effects, the following conditions are further optimized: the temperature of the first sintering is 850-950°C, the temperature of the second sintering is 400-450°C, and the temperature of the third sintering is 350-400°C.

[0221] Although the specific embodiments of the present application are described above, those skilled in the art should understand that this is only an illustration, and the protection scope of the present application is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present application, and these changes and modifications all fall within the protection scope of the present application.

Claims

1. A positive electrode material, characterized in that, It comprises, in order from inside to outside, a core, a first coating layer and a second coating layer; the core comprises lithium nickel manganese oxide doped with phosphorus elements; the first coating layer is in a film shape, and the first coating layer comprises a phosphate; the second coating layer is in an island shape or a chain shape, and the second coating layer comprises a phosphate; In the core, the raw material of the phosphorus elements is γ-Li3PO4; The raw material of the first coating layer is β-Li3PO4; The raw material of the second coating layer is amorphous Li3PO4.

2. The positive electrode material of claim 1, wherein, The positive electrode material satisfies one or more of the following conditions a-d: a. In the first coating layer, the cation of the phosphate is Ni, Mn and Li; b. In the second coating layer, the cation of the phosphate is Li; c. The ratio of the average thickness of the first coating layer to the second coating layer is 1: (0.5-2); d. The average particle size of the positive electrode material is 2.5-2.6 μm.

3. The positive electrode material of claim 1, wherein, The positive electrode material satisfies one or more of the following conditions a-e: a. The average particle size of the γ-Li3PO4 is 30-40 nm; b. The average particle size of β-Li3PO4 in the raw material of the first coating layer is 30-40 nm; c. The average particle size of amorphous Li3PO4 in the raw material of the second coating layer is 0.1-0.2 μm; d. The mass ratio of the lithium nickel manganese oxide to the γ-Li3PO4 is 1: (0.001-0.005); e. The mass ratio of the γ-Li3PO4, the β-Li3PO4 and the amorphous Li3PO4 is 1: (0.5-1): (0.5-1).

4. A method for producing a positive electrode material, characterized by, It comprises the following steps: S1. A first mixture is subjected to first sintering to obtain a first precursor; wherein the first mixture comprises a lithium nickel manganese oxide precursor, γ-Li3PO4 and a lithium salt; the temperature of the first sintering is 850-950 ℃; S2. A second mixture is subjected to second sintering to obtain a second precursor; wherein the second mixture comprises the first precursor and β-Li3PO4; the temperature of the second sintering is 350-450 ℃; S3. A third mixture is subjected to third sintering to obtain the positive electrode material; wherein the third mixture comprises the second precursor and amorphous Li3PO4; the temperature of the third sintering is 300-400 ℃.

5. The method for preparing the cathode material as described in claim 4, characterized in that, It satisfies one or more of the following conditions a-l: a. In step S1, the lithium salt is lithium carbonate; b. In step S1, the lithium nickel manganese oxide precursor comprises nickel hydroxide and / or manganese hydroxide; c. In step S1, in the first mixture, the mass ratio of the lithium nickel manganese oxide precursor to the lithium salt is 1: (0.1-0.3); d. In step S1, the average particle size of the γ-Li3PO4 is 30-40 nm; e. In step S1, the mass ratio of the lithium nickel manganese oxide to the γ-Li3PO4 is 1: (0.001-0.005); f. In step S1, the average particle size of the first precursor is 2.5-2.6 μm; g. In step S2, the average particle size of the β-Li3PO4 is 30-40 nm; h. in the second mixture, the mass ratio of the first precursor to β-Li3PO4 is 1:(0.0023-0.0026); i. in the second precursor, the average particle size is 2.5-2.6 μm; j. in the amorphous Li3PO4, the average particle size is 0.1-0.2 μm; k. in the third mixture, the mass ratio of the second precursor to amorphous Li3PO4 is 1:(0.0023-0.0026); l. the mass ratio of the γ-Li3PO4, β-Li3PO4 and amorphous Li3PO4 is 1:(0.73-0.76):(0.73-0.76).

6. The method for preparing the cathode material as described in claim 4, characterized in that, which satisfies one or more of the following conditions a-c: a. in the first sintering, the time is 8-12 h; b. in the second sintering, the time is 5-8 h; c. in the third sintering, the time is 5-8 h.

7. A positive electrode material, characterized in that, which is prepared by the preparation method of the positive electrode material according to any one of claims 4-6.

8. An electrochemical device, characterized by, The positive electrode sheet of the electrochemical device comprises the positive electrode material according to any one of claims 1-3 and 7.

9. An electronic device, comprising: The electrochemical device comprises the positive electrode material according to claim 8.

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