Positive electrode material and preparation method thereof, positive plate, battery and electric device

Abstract

In order to solve the problems that an existing battery is low in energy density and poor in cycle performance due to a positive electrode material, the invention provides a positive electrode material and a preparation method thereof, a positive plate, a battery and a power utilization device, the positive electrode material comprises an inner core and a protective layer wrapping the outer side of the inner core, the inner core is a positive electrode active material, and the protective layer is a negative electrode active material. The protective layer comprises halide solid electrolyte, the content of an element A in any area in the protective layer is K1, the total content of the element A in the protective layer is K2, K1 / K2 is 0.01-100, and the element A is any element in the protective layer.

Description

Technical Field

[0001] The present invention belongs to the technical field of cathode materials for batteries, and particularly relates to a cathode material, a preparation method thereof, a cathode sheet, a secondary battery, and an electrical device. Background Art

[0002] In the field of batteries, finding lithium-ion batteries with high energy density and high power density has become the focus of researchers. The cathode material is one of the key parts restricting the specific capacity, energy density, and power density of lithium-ion batteries. To obtain good ion channels in the cathode, a solid electrolyte needs to be mechanically mixed and added to the composite cathode. To ensure close interfacial contact and good ion transport, a solid electrolyte is often added, resulting in a significant dilution of the battery energy density. During the cycling process, the volume of the cathode material inevitably changes, and chemical and mechanical expansion generates internal stress, leading to continuous loss of contact between the solid electrolyte and the cathode particles in the composite cathode, and deterioration of the cycling stability. Summary of the Invention

[0003] Aiming at the problems of low energy density and poor cycling performance of existing batteries due to the cathode material, the present invention provides a cathode material, a preparation method thereof, a cathode sheet, a secondary battery, and an electrical device.

[0004] The technical solutions adopted by the present invention to solve the above technical problems are as follows: In the first aspect, the present invention provides a cathode material, including a core and a protective layer wrapped outside the core. The core is a cathode active material, and the protective layer includes a halide solid electrolyte. The content of element A in any region of the protective layer is K1, and the total content of element A in the protective layer is K2, where K1 / K2 is 0.8 - 1.5. Here, element A is any one of the elements in the protective layer.

[0005] Optionally, the charge-discharge curve of the cathode material in any voltage range of 4.3 - 4.8 V and at any rate does not have a dQ / dV peak.

[0006] Optionally, the structural general formula of the halide solid electrolyte is Li a (M b )X c X’ d , where M includes at least one of Ga, Y, In, Mg, Sr, Sc, Sn, Pb, Ti, Zr, Hf, Nb, Ta, W, Fe, Ru, Al, V, Cr, and lanthanide metal elements; X includes at least one of halogen elements; X’ includes at least one of halide ions, N ions, oxygen-containing anion groups, and pseudohalide anions; 0.5 ≤ a ≤ 5, 0.2 ≤ b ≤ 4, c + d = a + bε, where ε is the weighted average valence of element M.

[0007] Optionally, the oxyanion group includes O 2- , S 2- , CN - , CO3 2- , PO4 3- , P2O7 4- , SO4 2- and at least one of the following; the pseudohalide anion includes SCN - , PF6 - , NH2 - , AlF4 - , BF4 - and at least one of the following.

[0008] Optionally, the mass content of the protective layer is 0.01% to 20%.

[0009] Optionally, the mass content of the protective layer is 0.05% to 2%.

[0010] Optionally, the positive electrode active material includes lithium nickel cobalt manganese oxide LiNi x1 Co y1 Mn z1 O2 (x1 + y1 + z1 = 1), lithium nickel cobalt aluminate LiNi x2 Co y2 Al z2 O2 (x2 + y2 + z2 = 1), lithium iron manganese phosphate LiFe x3 Mn y3 PO4 (x3 + y3 = 1), lithium iron phosphate LiFePO4, lithium manganese oxide LiMn2O4, lithium cobalt oxide LiCoO2, lithium nickel oxide LiNiO2, lithium-rich manganese-based x’Li2MnO 3· (1 - x’)LiMO2 (M = Ni, Co, Mn, 0 < x’ < 1), lithium nickel manganese oxide LiNi x5 Mn 2-x5 O4 (0 < x5 < 2), lithium vanadium phosphate (Li3V2(PO4)3, LiVOPO4), or one or more thereof.

[0011] Optionally, the positive electrode active material further includes a doping element, and the doping element includes at least one of Al, B, Ba, Bi, Ca, Cr, Ce, Co, Er, Ga, Ge, Ho, K, La, Mg, Mo, Na, Nb, Pd, P, Si, Sb, Sr, Se, Ru, Rh, Ta, Te, Ti, W, V, Y, Zr, and Zn.

[0012] Optionally, the positive electrode material further includes a coating layer located between the positive electrode active material and the protective layer, and the elements in the coating layer include at least one of Al, B, Ba, Bi, Ca, Cr, Ce, Co, Er, Ga, Ge, Ho, K, La, Mg, Mo, Na, Nb, Pd, P, Si, Sb, Sr, Se, Ru, Rh, Ta, Te, Ti, W, V, Y, Zr, and Zn.

[0013] Optionally, the protective layer further includes amorphous carbon or a sulfide solid electrolyte.

[0014] In a second aspect, the present invention further provides a method for preparing a positive electrode material as described in any one of the above, including the following steps: Dissolve the raw materials of the protective layer in a solvent to obtain a protective layer precursor solution; Add the positive electrode active material to the protective layer precursor solution and disperse to obtain a mixed slurry; Heat the mixed slurry under stirring, the protective layer precursor solution forms the halide solid electrolyte and deposits on the surface of the positive electrode active material, and then heat treatment is performed to obtain the positive electrode material.

[0015] Optionally, the solvent includes at least one of water and an organic solvent; the organic solvent includes anhydrous ethanol.

[0016] Optionally, the raw materials of the protective layer are selected from at least two of a compound containing M’, a compound containing X, a compound containing X’, a compound containing NH4 + compound, and a composite compound containing X and X’, where M’ includes one or more of Li, Na, Ga, Y, In, Mg, Sr, Sc, Sn, Pb, Ti, Zr, Hf, Nb, Ta, W, Fe, Ru, Al, V, Cr, lanthanide metal elements, X includes one or more of halogen elements, X’ includes one or more of halide ions, N ions, oxygen-containing anion groups, pseudohalide anions, where the oxygen-containing anion groups include NO3 - O2 - S 2- CN - CO3 2- HCO3 - PO4 3- P2O7 4- SO4 2- one or more of, and the pseudohalide anions include SCN - PF6 - NH2 - AlF4 - or BF4 -One or more of them.

[0017] Optionally, the mass ratio of the positive electrode active material to the solvent is 1:(0.1 - 100).

[0018] Optionally, the stirring speed during heating of the mixed slurry is 100 - 400 rpm; And / or, the heat treatment is carried out under vacuum, the temperature of the heat treatment is 120 - 500 °C, and the time is 0.2 - 48 h.

[0019] In a third aspect, the present invention provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode active material layer provided on at least one side of the positive electrode current collector, wherein the positive electrode active material layer comprises the positive electrode material as described in any one of the above, or the positive electrode active material layer comprises a positive electrode material prepared by the preparation method of the positive electrode material as described in any one of the above.

[0020] In a fourth aspect, the present invention provides a battery, comprising a negative electrode and the positive electrode sheet as described in any one of the above.

[0021] In a fifth aspect, the present invention provides an electrical device, comprising the battery as described in any one of the above.

[0022] In the present invention, by coating a halide solid electrolyte protective layer outside the positive electrode active material, the interfacial surface chemical properties can be optimized, and the cycle stability can be effectively improved. The halide solid electrolyte has a wide electrochemical window, enabling the positive electrode material to have high voltage stability and improving the interfacial stability under high voltage; the interaction between the halogen -1 valence anions and lithium ions in the halide is weak, having better lithium ion conduction ability, and high ionic conductivity is beneficial to enhancing the interfacial kinetic performance; at the same time, the halide solid electrolyte has good mechanical deformation ability, which is beneficial to the contact with the surface of the positive electrode material and inhibits the volume change of the positive electrode material during charge and discharge. And, by defining the ratio of the content K1 of element A in any region of the protective layer to the total content K2 of element A in the protective layer as 0.01 - 100, the protective layer is uniformly coated on the surface of the positive electrode active material. At the same time, K1 / K2 being 0.01 - 100 is beneficial to improving the lithium ion conduction ability of the positive electrode material. When the K1 / K2 value is too high, it indicates that the coating amount in the selected region deviates significantly from the set value and the coating at the selected position is too thick, resulting in + hindered Li shuttle, increased impedance, and decreased capacity and rate performance; when the K1 / K2 value is too low, it indicates that the coating amount in the selected region deviates significantly from the set value and the coating at the selected position is too thin, unable to improve the interfacial contact deterioration caused by the volume change during the cycle, resulting in decreased cycle performance; K1 / K2 being in the range of 0.01 - 100 indicates that the coating layer is uniform, which is beneficial to the comprehensive improvement of capacity, rate, and cycle performance.

[0023] When the positive electrode material is applied to a liquid battery, it can effectively improve the rate performance and cycle stability of the material; when it is applied to a solid-state battery, it can significantly reduce the amount of solid electrolyte in the composite positive electrode, avoid significant dilution of the energy density, and at the same time, effectively inhibit the deterioration of the contact between the solid electrolyte and the positive electrode particles caused by the internal stress due to the volume change of the positive electrode material, and improve the cycle stability. In summary, the positive electrode material of the present invention has extremely high ionic conductivity and structural stability, thereby improving the capacity, initial efficiency and cycle performance of the material, and can be widely used in liquid batteries, semi-solid batteries and solid-state batteries. In addition, the operation method of the present invention is simple and suitable for industrial production. Brief Description of the Drawings Figure 1 It is a schematic structural diagram of the positive electrode material provided by an embodiment of the present invention; Figure 2 It is an SEM (scanning electron microscope) image corresponding to the positive electrode material of Example 1; Figure 3 It is an SEM image corresponding to the positive electrode material of Example 2; Figure 4 It is an EDS (energy dispersive spectroscopy) test image corresponding to the positive electrode material of Example 1; Figure 5 It is an XRD (X-ray diffraction spectrum) image corresponding to the positive electrode material of Example 2; Figure 6 It is a charge-discharge curve graph corresponding to the solid-state battery of Example 1; Figure 7 It is a charge-discharge curve graph corresponding to the solid-state battery of Example 2 in the range of 2.5 - 4.6 V; Figure 8 It is a dQ / dV graph corresponding to the solid-state battery of Example 2 in the range of 2.5 - 4.6 V; Figure 9 It is a charge-discharge curve graph corresponding to the solid-state battery of Example 2 in the range of 2.5 - 4.8 V; Figure 10 It is a dQ / dV graph corresponding to the solid-state battery of Example 2 in the range of 2.5 - 4.8 V; Figure 11 It is a dQ / dV graph of Example 2 without coating with a halide solid electrolyte. Detailed Embodiments

[0024] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] An embodiment of the present invention provides a cathode material, which includes a core 1 and a protective layer 2 wrapped around the outer side of the core 1. The core 1 is a cathode active material, and the protective layer 2 includes a halide solid electrolyte. The content of element A in any region of the protective layer 2 is K1, and the total content of element A in the protective layer 2 is K2, and K1 / K2 is 0.01 to 100, where element A is any element in the protective layer 2.

[0026] K1 / K2 can be, for example, 0.01, 0.1, 0.5, 0.8, 1, 1.2, 1.5, 2, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100.

[0027] In one embodiment, the value of K1 / K2 is detected by an energy dispersive spectrometer.

[0028] In this embodiment, by coating the cathode active material with the halide solid electrolyte protective layer 2, the interfacial surface chemical properties can be optimized, and the cycle stability can be effectively improved. The halide solid electrolyte has a wide electrochemical window, enabling the cathode material to have high voltage stability and improving the interfacial stability under high voltage; the interaction between the halogen -1 valence anions and lithium ions in the halide is weak, having better lithium ion conduction ability, and high ionic conductivity is beneficial to improving the interfacial kinetic performance; at the same time, the halide solid electrolyte has good mechanical deformation ability, which is beneficial to the contact with the surface of the cathode material and inhibits the volume change of the cathode material during charge and discharge. Moreover, by defining the ratio of the content K1 of element A in any region of the protective layer 2 to the total content K2 of element A in the protective layer 2 as 0.01 to 100, the protective layer 2 is uniformly coated on the surface of the cathode active material. At the same time, K1 / K2 being 0.01 to 100 is beneficial to improving the lithium ion conduction ability of the cathode material. When the value of K1 / K2 is too high, it indicates that the coating amount in the selected region deviates from the set value by a large amount and the coating at the selected position is too thick, resulting in + hindered Li shuttle, increased impedance, and decreased capacity and rate performance; when the value of K1 / K2 is too low, it indicates that the coating amount in the selected region deviates from the set value by a large amount and the coating at the selected position is too thin, unable to improve the interfacial contact deterioration caused by volume change during the cycle, resulting in decreased cycle performance; when K1 / K2 is in an appropriate range, it indicates that the coating layer is uniform, which is beneficial to the comprehensive improvement of capacity, rate, and cycle performance.

[0029] When it is applied to liquid batteries, it can effectively improve the rate performance and cycle stability of materials; when it is applied to solid-state batteries, it can significantly reduce the amount of solid electrolyte in the composite cathode, avoid significant dilution of energy density. At the same time, it can effectively inhibit the deterioration of contact between the solid electrolyte and the cathode particles caused by the internal stress of the volume change of the cathode material, and improve the cycle stability. In summary, the cathode material of the present invention has extremely high ionic conductivity and structural stability, thereby improving the capacity, initial efficiency and cycle performance of the material, and can be widely used in liquid batteries, semi-solid batteries and solid-state batteries. In addition, the operation method of the present invention is simple and suitable for industrial production.

[0030] In some embodiments, the structural general formula of the halide solid electrolyte is Li a (M b )X c X’ d , where M includes at least one of Ga, Y, In, Mg, Sr, Sc, Sn, Pb, Ti, Zr, Hf, Nb, Ta, W, Fe, Ru, Al, V, Cr, lanthanide metal elements, X includes at least one of halogen elements, X’ includes at least one of halide ions, N ions, oxygen-containing anion groups, pseudohalide anions, 0.5≤a≤5, 0.2≤b≤4, c + d = a + bε, where ε is the weighted average valence of M element. By selecting the above-mentioned halide solid electrolyte, the voltage stability, interfacial thermal stability and ionic conductivity of the cathode material are further improved.

[0031] In some embodiments, the oxygen-containing anion group includes O 2- , S 2- , CN - , CO3 2- , PO4 3- , P2O7 4- , SO4 2- ; the pseudohalide anion includes at least one of SCN - , PF6 - , NH2 - , AlF4 - , BF4 - . By selecting the above ion groups, the ionic conductivity of the cathode material is effectively improved.

[0032] In some embodiments, the mass content of the protective layer 2 in the cathode material is 0.01% - 20%. When the mass content of the protective layer 2 in the cathode material is within the above range, the cathode active material can be uniformly coated, so that the battery obtains the optimal capacity and rate performance. If the mass content of the protective layer 2 is too small, the coating effect cannot be achieved; if the mass content of the protective layer 2 is too large, the lithium ion charge transfer will be reduced.

[0033] Specifically, the mass content of the protective layer 2 includes, but is not limited to, 0.01%, 0.05%, 1%, 1.3%, 1.6%, 2%, 5%, 8%, 11%, 14%, 17% or 20%.

[0034] In a preferred embodiment, the mass content of the protective layer 2 in the cathode material is 0.05% - 2%. By limiting the protective layer 2 within the above range, the battery can obtain optimal capacity and rate performance.

[0035] In one embodiment, the mass content of the protective layer 2 in the cathode material is detected by an energy dispersive spectrometer.

[0036] In one embodiment, the charge-discharge curve of the cathode material has no dQ / dV peak in any voltage range from 4.3 to 4.8 V and at any rate. That is to say, within this voltage range, no obvious phase change occurs in the cathode material, the material structure remains relatively stable, and no structural distortion, lattice distortion, etc. caused by phase change will occur. As a result, the battery can provide a relatively stable output voltage within this voltage range, with a lower degree of polarization during the charge-discharge process, improving the charge-discharge efficiency of the battery, reducing energy loss, and being beneficial to improving the use performance and safety of the battery. The absence of a dQ / dV peak in the cathode material at any rate indicates that the battery can maintain good performance consistency at different charge-discharge rates. That is, the cathode material can quickly respond to the insertion and extraction reactions of lithium ions and will not show obvious performance decay or abnormality due to changes in the charge-discharge rate, indicating that the battery has good rate performance and can meet the requirements of different application scenarios for the charge-discharge speed of the battery.

[0037] In one embodiment, the charge-discharge curve of the cathode material is measured by a Blue Power battery tester.

[0038] In some embodiments, the halide solid electrolyte is uniformly coated on the surface of the cathode active material in a spheroid-like grain shape. In the cathode material, the halide solid electrolyte in a spheroid-like grain shape can provide a relatively smooth ion conduction path and shorten the diffusion distance of lithium ions, enabling lithium ions to be extracted or inserted from the cathode active material more quickly, thereby improving the charge-discharge efficiency of the battery.

[0039] In some embodiments, the cathode active material includes lithium nickel cobalt manganese oxide LiNi x1 Co y1 Mn z1 O2 (x1 + y1 + z1 = 1), lithium nickel cobalt aluminate LiNi x2 Co y2 Al z2 O2 (x2 + y2 + z2 = 1), lithium iron manganese phosphate LiFe x3 Mn y3PO4 (x3 + y3 = 1), lithium iron phosphate LiFePO4, lithium manganese oxide LiMn2O4, lithium cobalt oxide LiCoO2, lithium nickel oxide LiNiO2, lithium-rich manganese-based x’Li2MnO 3· (1 - x’)LiMO2 (M = Ni, Co, Mn, 0 < x’ < 1), lithium nickel manganese oxide LiNi x5 Mn 2-x5 O4 (0 < x5 < 2), one or more of lithium vanadium phosphate (Li3V2(PO4)3, LiVOPO4).

[0040] In this application, "multiple" means two or more than two.

[0041] Furthermore, the average particle size of the positive electrode active material is 1 - 30 μm. Specifically, the average particle size of the positive electrode active material includes but is not limited to 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm or 30 μm.

[0042] In some embodiments, the positive electrode active material further includes a doping element, and the doping element includes at least one of Al, B, Ba, Bi, Ca, Cr, Ce, Co, Er, Ga, Ge, Ho, K, La, Mg, Mo, Na, Nb, Pd, P, Si, Sb, Sr, Se, Ru, Rh, Ta, Te, Ti, W, V, Y, Zr and Zn. By doping elements in the positive electrode active material, the lattice structure of the positive electrode active material is changed, the lithium ion diffusion channels are broadened, and the diffusion coefficient of lithium ions in the positive electrode material is increased. During the charge and discharge process of the battery, lithium ions can be embedded and extracted more quickly inside the positive electrode material, thereby improving the rate performance of the battery.

[0043] In some embodiments, the positive electrode material further includes a coating layer, the coating layer is located between the positive electrode active material and the protective layer 2, and the elements in the coating layer include at least one of Al, B, Ba, Bi, Ca, Cr, Ce, Co, Er, Ga, Ge, Ho, K, La, Mg, Mo, Na, Nb, Pd, P, Si, Sb, Sr, Se, Ru, Rh, Ta, Te, Ti, W, V, Y, Zr and Zn. By elementally coating the positive electrode active material, the positive electrode active material is prevented from being oxidized, and at the same time, the conductivity of the positive electrode active material is improved.

[0044] In some embodiments, the protective layer 2 further includes amorphous carbon, and amorphous carbon is beneficial to improving electronic conductivity and reducing battery impedance.

[0045] In some embodiments, the protective layer 2 further includes a sulfide solid electrolyte, thereby improving the ionic conductivity.

[0046] An embodiment of the present invention further provides a method for preparing the cathode material described in any one of the above, comprising the following steps: Dissolve the raw materials of the protective layer 2 in a solvent to obtain a precursor solution of the protective layer 2; Add the cathode active material to the precursor solution of the protective layer 2 and disperse to obtain a mixed slurry; Heat the mixed slurry under stirring, and the precursor solution of the protective layer 2 forms the halide solid electrolyte and deposits on the surface of the cathode active material, and then heat treatment is carried out to obtain the cathode material.

[0047] During the process of heating the mixed slurry under stirring, the precursor solution of the protective layer 2 gradually forms a saturated solution and precipitates uniformly on the surface of the cathode active material. As the solvent is removed, the halide continuously crystallizes and accumulates on the surface of the cathode active material, and uniformly coats the surface of the cathode active material.

[0048] By adopting this preparation method, uniform coating of the protective layer 2 can be realized, which is beneficial to comprehensively improving the capacity, rate performance and cycle performance. Moreover, compared with the preparation method directly using the halide solid electrolyte as the raw material, this preparation method can reduce the cost.

[0049] The raw materials of the protective layer 2 are selected from at least two of the compounds containing M', the compounds containing X, the compounds containing X', the compounds containing NH4 + and the composite compounds containing X and X', wherein M' includes one or more of Li, Na, Ga, Y, In, Mg, Sr, Sc, Sn, Pb, Ti, Zr, Hf, Nb, Ta, W, Fe, Ru, Al, V, Cr, lanthanide metal elements, X includes one or more of halogen elements, and X' includes one or more of halide ions, N ions, oxygen-containing anion groups, pseudohalide anions, wherein the oxygen-containing anion groups include NO3 - , O2 - , S 2- , CN - , CO3 2- , HCO3 - , PO4 3- , P2O7 4- , SO4 2- and one or more of them, and the pseudohalide anions include SCN - , PF6 - , NH2 - , AlF4 - , or BF4 - and one or more of them.

[0050] The methods for drying the mixed slurry by heating include but are not limited to sun drying, boiling dry, baking dry, spray drying, vacuum drying or freeze drying.

[0051] In some embodiments, the solvent includes at least one of water and an organic solvent; the organic solvent includes absolute ethanol. By using an organic solvent, water, or a mixture thereof as the solvent, it is convenient for the halide solid electrolyte to crystallize and accumulate on the surface of the positive electrode active material.

[0052] In some embodiments, the mass ratio of the positive electrode active material to the solvent is 1:(0.1 - 100). By defining the mass ratio of the positive electrode active material to the solvent, it is convenient for the positive electrode active material to be dispersed in the solvent, thereby forming a uniform protective layer 2 on the surface of the positive electrode active material.

[0053] In a preferred embodiment, the mass ratio of the positive electrode active material to the solvent is 1:(1 - 2).

[0054] In some embodiments, the stirring speed during heating of the mixed slurry is 100 - 400 rpm. By controlling the stirring speed, the formation of the protective layer 2 is prevented from being damaged during the stirring process.

[0055] In some embodiments, the heat treatment is carried out under vacuum, the temperature of the heat treatment is 120 - 500 °C, and the time is 0.2 - 48 h. By carrying out the heat treatment under vacuum, the purity of the halide in the protective layer 2 is ensured.

[0056] The present invention also provides a positive electrode sheet, including a current collector and a positive electrode active material layer coated on at least one side of the current collector, the positive electrode active material layer including a conductive agent, an additive, and the above positive electrode material, or a positive electrode material prepared by the preparation method of the above positive electrode material.

[0057] In some embodiments, the conductive agent includes one or more of graphite, hard carbon, soft carbon, carbon nanotubes, graphene, porous carbon, Super P, Acetylene Black, Furnace Black.

[0058] In some embodiments, the additive includes one or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), silicone rubber, styrene-butadiene rubber (SBR), hydrogenated nitrile rubber (HNBR), boronated polyethylene glycol, cellulose, cellulose ester, cellulose ether, nitrocellulose, carboxyalkyl cellulose, cellulose salt, sodium carboxymethyl cellulose and cellulose salt derivatives, polyacrylic acid (PAA), polyamide (PAI), polyvinyl alcohol (PVA), polyethyleneimine (PEI), polyimide (PI).

[0059] In some embodiments, the mass percentage content of each component in the positive electrode active material layer is as follows: 80% - 99% of the positive electrode material, 0.5% - 10% of the conductive agent, and 0.5% - 10% of the auxiliary agent.

[0060] In some embodiments, the positive electrode active material layer further contains 0.1% - 30% of a solid electrolyte, and the ratio of the remaining components remains unchanged. The solid electrolyte includes, but is not limited to, one or more of NASICON (sodium fast ion conductor) type solid electrolytes, LISICON (lithium fast ion conductor) type solid electrolytes, garnet type solid electrolytes, perovskite type solid electrolytes, inverse perovskite type solid electrolytes, sulfide solid electrolytes, halide solid electrolytes, and polymer electrolytes. The polymer electrolyte includes a polymer and a lithium salt; the polymer includes, but is not limited to, PEO (polyethylene oxide), PVDF (polyvinylidene fluoride), PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene), PMMA (polymethyl methacrylate), PAN (polyacrylonitrile); the lithium salt includes, but is not limited to, LiPF6, LiTFSI, LiFSI, LiDFOB.

[0061] In some embodiments, the positive electrode current collector is selected from metal materials that can conduct electrons. Preferably, the positive electrode current collector includes one or more of aluminum, copper, nickel, tin, copper, and stainless steel. In a more preferred embodiment, the positive electrode current collector is selected from aluminum foil.

[0062] There are two methods for preparing the positive electrode sheet.

[0063] Method 1: Wet preparation S1: Mix the positive electrode active material, the conductive agent, and the auxiliary agent in a preset ratio to form a positive electrode slurry. S2: Coating the obtained positive electrode slurry on the positive electrode current collector at a certain loading. S3: Dry the positive electrode current collector coated with the positive electrode slurry, and then roll it to obtain the positive electrode sheet.

[0064] Method 2: Dry preparation S1: Mix the positive electrode active material, the conductive agent, and the auxiliary agent in a preset ratio, and apply a shearing force to the mixed powder to make the auxiliary agent fibrillate to obtain a blank. S2: Extrude or roll the blank into a self-supporting film. S3: Load the self-supporting film onto the positive electrode current collector that rolls between two rollers, and roll it to form the positive electrode sheet.

[0065] The present invention also provides a battery, including the positive electrode sheet as described above.

[0066] The battery of the present application further includes a negative electrode sheet, a separator, and an electrolyte in addition to the above positive electrode sheet. In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material, a conductive agent, a binder, and a thickener.

[0067] In one embodiment, the negative electrode active material includes, but is not limited to, metallic lithium Li or a metallic lithium alloy Li-M, artificial graphite, natural graphite, modified graphite, fast-charging graphite, soft carbon, hard carbon, vapor-phase silicon carbon, milled silicon carbon, SiO x , pre-lithiated silicon monoxide, pre-magnesiated silicon monoxide, or one or more of them; wherein, the metallic lithium alloy Li-M can be an alloy formed by metallic lithium and one or more of substances such as gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus, etc., and the mass content of metallic lithium is 1% to 99%.

[0068] In some embodiments, the negative electrode conductive agent includes one or several of Super-P (conductive carbon black), VGCF (vapor-grown carbon fiber), and CNT (carbon nanotube).

[0069] In some embodiments, the negative electrode binder includes one or more of PVDF (polyvinylidene fluoride), SBR (styrene-butadiene rubber), NBR (nitrile butadiene rubber), BR (polybutene rubber), CMC (sodium carboxymethyl cellulose), and PAA (polyacrylic acid).

[0070] In some embodiments, the thickener includes one or more of sodium alginate, sodium carboxymethyl cellulose, and carboxymethyl chitosan.

[0071] In some embodiments, the mass percentage content of each component in the negative electrode active material layer is: 80-100wt% of the negative electrode active material, 0-10wt% of the conductive agent, and 0-10wt% of the binder.

[0072] The negative electrode current collector is selected from metallic materials that can conduct electrons. Preferably, the negative electrode current collector includes one or more of aluminum, nickel, tin, copper, and stainless steel. In a more preferred embodiment, the negative electrode current collector is selected from copper foil.

[0073] The negative electrode sheet can be prepared by conventional methods in the art. For example, the negative electrode active material layer is usually formed by making a negative electrode slurry of the negative electrode active material, the negative electrode conductive agent, the negative electrode binder, and any other components, coating it on the negative electrode current collector, and then drying and cold-pressing. The solvent can be an aqueous solvent, but is not limited thereto.

[0074] The separator includes a base film, which is one or several of a PE separator, a PP separator, a non-woven fabric separator, and a PI separator.

[0075] In some embodiments, at least one side of the base film contains a coating; the coating includes: an oxide solid electrolyte, a basic oxide, and a polymer adhesive; the oxide solid electrolyte and the basic oxide are dispersed in the polymer adhesive; the basic oxide includes at least one of alumina and boehmite. The oxide solid electrolyte includes at least one of NASICON-type solid electrolytes, garnet-type solid electrolytes, and perovskite-type solid electrolytes.

[0076] Electrolyte: Liquid electrolytes include, but are not limited to: conventional electrolytes, including organic solvents, lithium salts, and additives, and the solvents include, but are not limited to, one or more of PC (propylene carbonate), EC (ethylene carbonate), DMC (dimethyl carbonate), EMC (ethyl methyl carbonate), DEC (diethyl carbonate), and DME (dimethyl ethylene glycol); gel electrolytes, including a polymer matrix, a plasticizing solvent, and a lithium salt; in-situ polymerization electrolytes, including polymer monomers, lithium salts, solvents, and initiators; eutectic electrolytes, including small molecule polar matrices and lithium salts; and ionic liquid electrolytes, including ionic liquids and lithium salts. Lithium salts include, but are not limited to, one or more of lithium hexafluorophosphate LiPF6, lithium hexafluoroarsenate LiAsF6, lithium tetrafluoroborate LiBF4, lithium hexafluoroantimonate LiSbF6, lithium bis(trifluoromethanesulfonyl)imide LiTFSI or LiN(SO2CF2)2, lithium trifluoromethanesulfonate LiCF3SO3, lithium bis(fluorosulfonyl)imide LiFSI or LiN(SO2CF3)2, lithium perchlorate LiClO4, lithium iodide LiI, and lithium magnesium bis(fluorosulfonyl)imide Li2Mg(N(SO2CF3)2)2.

[0077] Solid electrolytes include, but are not limited to, one or more of NASICON-type solid electrolytes, LISICON-type solid electrolytes, garnet-type solid electrolytes, perovskite-type solid electrolytes, inverse perovskite-type solid electrolytes, sulfide solid electrolytes, halide solid electrolytes, and polymer electrolytes. Polymer electrolytes include polymers and lithium salts; the polymers include, but are not limited to, PEO, PVDF, PVDF-HFP, PMMA, and PAN; the lithium salts include, but are not limited to, one or more of LiPF6, LiTFSI, LiFSI, and LiDFOB.

[0078] Electrolytes include liquid electrolytes, semi-solid electrolytes, and all-solid electrolytes. The semi-solid electrolytes are obtained by blending liquid electrolytes and solid electrolytes in any proportion. Liquid electrolytes are applied to one or more of soft-pack batteries, cylindrical batteries, or prismatic batteries; semi-solid electrolytes are applied to one or more of soft-pack batteries, cylindrical batteries, or prismatic batteries; all-solid electrolytes are applied to one or more of soft-pack batteries, cylindrical batteries, or prismatic batteries.

[0079] The present invention will be further described below by way of examples.

[0080] Example 1 This example is used to illustrate the cathode material and its preparation method disclosed by the present invention. The preparation of the cathode material includes the following operating steps: Mix the ternary precursor Ni 0.90 Co 0.05 Mn 0.05 (OH)2 with lithium hydroxide monohydrate and the dopant zirconia (ZrO2, Zr doping amount 1000 ppm), sinter at 735 °C for 10 h in an oxygen atmosphere to obtain a first-sintered product and crush it to obtain the ternary cathode material to be coated. Its morphology is polycrystalline, and D50 is 12 μm; Take 0.37 g of LiCl and 0.64 g of InCl3, the raw materials of the protective layer 2, dissolve them in 100 mL of solvent (deionized water), take 100 g of the ternary cathode active material to be coated and stir and mix at a rotation speed of 400 rpm to obtain a mixed slurry; The obtained mixed slurry is dried in vacuum at 100 °C, and stirred at 400 rpm during the drying process. Then, it is heat-treated at 200 °C for 2 h under vacuum conditions to obtain a modified ternary cathode material coated with 1.0% Li3InCl6.

[0081] Example 2 This example is used to illustrate the cathode material and its preparation method disclosed by the present invention, including most of the operating steps in Example 1. The difference is that the solvent is absolute ethanol.

[0082] Example 3 This example is used to illustrate the cathode material and its preparation method disclosed by the present invention, including most of the operating steps in Example 1. The difference is that the solvent is a mixed solvent of absolute ethanol and water mixed in a volume ratio of 1:1.

[0083] Example 4 This example is used to illustrate the cathode material and its preparation method disclosed by the present invention. The preparation of the cathode material includes the following operating steps: Take 0.80 g of LiCl and 1.22 g of YCl3, dissolve them in 100 mL of deionized water, and add NH4Cl as a complexing agent. Take 100 g of NCM811 with 3000 ppm Al doping and 500 ppm W coating (its morphology is single crystal, D50 is 3.2 μm), stir and mix at a rotation speed of 200 rpm to obtain a mixed slurry; The obtained mixed slurry is dried in vacuum at 80 °C, and then heat-treated at 500 °C for 4 h under vacuum conditions to obtain a modified ternary cathode material coated with 2.0% Li3YCl6.

[0084] Example 5 This example is used to illustrate the cathode material and its preparation method disclosed in the present invention, including most of the operation steps in Example 1. The difference is that the mass of the cathode active material to be coated is 50 g, and the mass content of the protective layer 2 is 2%.

[0085] Example 6 This example is used to comparatively illustrate the cathode material and its preparation method disclosed in the present invention, including most of the operation steps in Example 1. The difference is that the mass of the cathode active material to be coated is 4 g, and the mass content of the protective layer 2 is 20%.

[0086] Example 7 This example is used to comparatively illustrate the cathode material and its preparation method disclosed in the present invention, including most of the operation steps in Example 1. The difference is that the mass of the cathode active material to be coated is 3 g, and the mass content of the protective layer 2 is 25%.

[0087] Example 8 This example is used to comparatively illustrate the cathode material and its preparation method disclosed in the present invention, including most of the operation steps in Example 1. The difference is that the mass of the cathode active material to be coated is 900 g, and the mass content of the protective layer 2 is 0.1%. Example 9 This example is used to comparatively illustrate the cathode material and its preparation method disclosed in the present invention, including most of the operation steps in Example 1. The difference is that the stirring speed during drying of the mixed slurry is 100 rpm.

[0088] Example 10 This example is used to comparatively illustrate the cathode material and its preparation method disclosed in the present invention, including most of the operation steps in Example 1. The difference is that the stirring speed during drying of the mixed slurry is 200 rpm.

[0089] Comparative Example 1 Comparative Example 1 is used to comparatively illustrate the cathode material and its preparation method disclosed in the present invention, including most of the operation steps in Example 1. The difference is that the mixed slurry is not stirred during vacuum drying at 100 °C. Comparative Example 2 Comparative Example 2 is used to comparatively illustrate the cathode material and its preparation method disclosed in the present invention, including most of the operation steps in Example 1. The difference is that the halide solid electrolyte is dissolved in a solvent to prepare a solution of the protective layer 2, and the cathode active material is added for dispersion to obtain a mixed slurry. Comparative Example 3 Comparative Example 3 is used to compare and illustrate the positive electrode material and preparation method thereof disclosed in the present invention, and includes most of the operation steps in Example 1, except that: The raw materials of protective layer 2, 0.37 g LiCl and 0.64 g InCl3, were mixed and manually ground for 20 min, and then intermittently ball milled for 48 h using a ball mill at 500 r / min to obtain a halide solid electrolyte; The obtained halide solid electrolyte powder is added to the ternary positive electrode material to be coated at a mass ratio of 1:100, and placed in a high-speed mixing device and mixed at 800r / min for 30min to be evenly mixed, and then heat treated at 200°C under vacuum conditions for 2h to obtain a modified ternary positive electrode material coated with 1.0% Li3InCl6.

[0090] Test Case Preparation of positive electrode sheet: positive electrode material, conductive carbon black and binder polytetrafluoroethylene are uniformly mixed in a mass ratio of 94:3:3, and shear force is applied to the mixed powder to fibrillate polytetrafluoroethylene. The positive electrode mixture is rolled into a film using a high-temperature roller press; after repeated rolling and thinning, a dry positive electrode film is obtained; the dry positive electrode film is hot-pressed with a carbon-coated aluminum foil current collector and composited onto the current collector to obtain a dry-prepared positive electrode sheet, which is then subjected to die-cutting and other processes to obtain a positive electrode sheet that meets the requirements. When preparing a semi-solid positive electrode sheet, 10% LLZTO (lithium lanthanum zirconium tantalum oxide) solid electrolyte is added at the same time. When preparing a solid positive electrode sheet, 20% LATP (lithium aluminum titanium phosphate) solid electrolyte is added at the same time.

[0091] Preparation of negative electrode sheet: artificial graphite, conductive agent Super P (conductive carbon black), sodium carboxymethyl cellulose and binder SBR are evenly mixed in a mass ratio of 95.5:1.5:1.2:1.8. Deionized water is used as the solvent. After stirring evenly to obtain a slurry, it is coated on the copper foil current collector. The negative electrode current collector is 6μm copper foil; and cut into negative electrode sheets for use.

[0092] Or use negative electrode active material silicon carbon negative electrode, conductive agent Super P (conductive carbon black), adhesive PAA, mixed at a mass ratio of 93: 3: 4, fully stirred and mixed in deionized water solvent to form a uniform negative electrode slurry. Or use negative electrode active material silicon oxygen negative electrode, conductive agent SP, adhesive PAA, mixed at a mass ratio of 93: 3: 4, fully stirred and mixed in deionized water solvent to form a uniform negative electrode slurry. Or use pure Li metal as negative electrode. Copper foil is used as current collector, and after die-cutting and other processes, a negative electrode sheet that meets the requirements is obtained.

[0093] Dissolve the lithium salt LiPF6 in the organic solvent EC-DMC (ethylene carbonate - dimethyl carbonate) (1:1 volume ratio) at a concentration of 1 M to obtain a liquid electrolyte. Mix the organic polymer PVDF, the lithium salt LiTFSI, and the additive LLZTO in a mass ratio of 6:4:1 in the organic solvent DMF (dimethylformamide), and coat and dry it to obtain a solid electrolyte membrane.

[0094] The separator is a 7+3μm mixed-coated separator (substrate + PVDF&ceramic mixed coating).

[0095] Preparation of the battery: Preparation of the liquid battery: Stack the positive electrode sheet, the separator, and the negative electrode sheet in sequence, with the separator in the middle of the positive and negative electrodes to play an isolation role. Then, wind one end of the positive electrode sheet, the separator, and the negative electrode sheet around the electrolyte separator to form a core. Then, place the wound core in an aluminum-plastic film bag that has been formed by punching the shell. Inject the electrolyte prepared above into the baked and dried battery cell, and after processes such as vacuum packaging, standing, and formation, a battery with a capacity of 1 Ah is obtained.

[0096] Preparation of the semi-solid battery: Stack the positive electrode sheet, the solid electrolyte membrane, and the negative electrode sheet in sequence, with the solid electrolyte membrane in the middle of the positive and negative electrodes to play an isolation and lithium-ion conduction role. Then, stack the positive electrode sheet, the separator, and the negative electrode sheet in sequence, place them in an aluminum-plastic film bag, inject the prepared liquid electrolyte into the baked and dried battery cell, and after processes such as vacuum packaging, standing, and formation, a battery with a capacity of 1 Ah is obtained.

[0097] Preparation of the solid battery: Stack the positive electrode sheet, the solid electrolyte membrane, and the negative electrode sheet in sequence, with the solid electrolyte membrane in the middle of the positive and negative electrodes to play an isolation and lithium-ion conduction role. Then, stack the positive electrode sheet, the separator, and the negative electrode sheet in sequence, place them in an aluminum-plastic film bag, and the baked and dried battery cell, after processes such as vacuum packaging, standing, and formation, a battery with a capacity of 1 Ah is obtained.

[0098] Taking the examples and comparative examples with pure Li metal as the negative electrode as an example, the following performance tests are carried out on the liquid batteries, semi-solid batteries, and solid batteries prepared from the above examples and comparative examples: 1. First discharge specific capacity test At room temperature, use a constant current and constant voltage charge and discharge instrument to perform charge and discharge cycles at a set current density.

[0099] Test steps: (1). Charge to the set cut-off voltage of 4.3V at the set current density (0.1C).

[0100] (2). Discharge at the same current density (0.1C) until the set discharge cut-off voltage of 2.5V is reached.

[0101] (3) Record the specific capacity of the first discharge in mAh / g. The test results are shown in Table 1. 2. First cycle coulomb efficiency test At room temperature, a constant current and constant voltage charge and discharge instrument is also used to measure the amount of electricity passing through the battery during the first charge and discharge process.

[0102] Test steps: (1) Charge to the set voltage and record the total charged power (Q_charge).

[0103] (2) Discharge to the set cut-off voltage and record the total discharged power (Q_discharge).

[0104] (3) Calculate the first cycle coulomb efficiency: Coulomb efficiency = (Q_discharge / Q_charge) × 100%. The test results are shown in Table 2. 3.100-week capacity retention test The positive electrode active material was subjected to 100 charge and discharge cycles at room temperature under the same current density and voltage window.

[0105] (1) Perform 100 charge and discharge cycles on the battery, and periodically record the discharge capacity of each cycle; (2) Calculate the capacity retention rate after 100 cycles: capacity retention rate = (100th cycle discharge capacity / first discharge capacity) × 100%. The test results are shown in Table 3.

[0106] Table 1 Table 2 Table 3 It can be seen from the above table that the K1 / K2 value of the material of the present invention is controlled within a certain range, with high capacity, high initial efficiency, and good cycle performance, and can be applied to liquid batteries, semi-solid batteries, and all-solid-state batteries.

[0107] Figure 2 , Figure 3 These are the SEM images corresponding to the positive electrode materials of Example 1 and Example 2, respectively. It can be seen that when water is selected as the solvent, the coating layer is relatively loose, and when anhydrous ethanol is selected, the coating layer is denser and has better cycle performance. Figure 4It is the EDS test diagram corresponding to the cathode material of Example 1. It can be seen that the distribution profiles of In and Cl elements on the material surface are the same as those of Ni elements in the bulk phase, indicating that the surface coating is very uniform. The EDS peak values of In element and Cl element are 24.2101 and 2.6219 keV respectively. Figure 5 It is the XRD diagram corresponding to the cathode material of Example 2. Each peak of the material coincides with that of the ternary cathode material, and it has a good α-NaFeO2 layered structure, indicating that the crystal structure of the material has not been changed during the coating process. Among them Figure 5 The abscissa is the 2θ diffraction angle (degree), and the ordinate is the diffraction intensity.

[0108] Figures 7 to 10 It is the charge-discharge curve diagram and dQ / dV diagram of the solid-state battery of Example 2 corresponding to 2.5~4.6 V and 2.5~4.8 V; Figure 11 It is the dQ / dV diagram without coating with halide solid electrolyte. Among them, Q is the gram capacity and V is the voltage. It can be seen that the material of the present invention can be used at high voltages, and there are no dQ / dV peaks in the charge-discharge curves in any voltage range from 4.3~4.8 V. In the dQ / dV diagram without coating with halide solid electrolyte, there is a dQ / dV peak near 4.55 V. The phase change at 4.55 V is an irreversible phase change, corresponding to the phase transition from H3 phase to H3 b phase. This difference indicates that the halide coating can inhibit the irreversible phase change of the material, thereby significantly improving the cycling performance of the material.

[0109] In Comparative Example 1, stirring was not maintained, and in Comparative Example 3, dry coating was used, both of which resulted in uneven coating. The K1 / K2 value was not in the range of 0.01~100, and the performance was poor. From the test results of Example 1, 9, 10 and Comparative Example 1, it can be seen that in the comparative example, due to the lack of stirring, there are areas with too thick coating, and the K1 / K2 value of the test points is too high. The rotation speed of Example 1 is higher than that of Example 9 and Example 10, and the coating is more uniform. The K1 / K2 value of the test points in Comparative Example 3 is 0, indicating that there are uncoated areas, which is an inherent problem of dry coating. When the K1 / K2 value is too high, it means that the coating amount in the selected area deviates from the set value by a large amount and the coating at the selected position is too thick, resulting in + hindered Li shuttle, increased impedance, and decreased capacity and rate performance; when the K1 / K2 value is too low, it means that the coating amount in the selected area deviates from the set value by a large amount and the coating at the selected position is too thin or even not coated, and it is impossible to improve the deterioration of the interface contact caused by the volume change during cycling, resulting in a decrease in cycling performance; when K1 / K2 is in an appropriate range, it indicates that the coating layer is uniform, which is beneficial to the comprehensive improvement of capacity, rate and cycling performance. The performance of Comparative Example 2 is close to that of Example 1, but directly using halide solid electrolyte as the raw material significantly increases the cost.

[0110] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A positive electrode material, characterized in that: It comprises an inner core and a protective layer wrapped around the outer side of the inner core, wherein the inner core is a positive electrode active material, the protective layer comprises a halide solid electrolyte, the content of element A in any region of the protective layer is K1, the total content of element A in the protective layer is K2, K1 / K2 is 0.01~100, and element A is any element in the protective layer.

2. The positive electrode material according to claim 1, characterized in that The charge and discharge curve of the positive electrode material at any voltage range of 4.3 to 4.8 V and any rate does not have a dQ / dV peak.

3. The positive electrode material according to claim 1, characterized in that The general structural formula of the halide solid electrolyte is Li a (M b )X c X' d , wherein M includes at least one of Ga, Y, In, Mg, Sr, Sc, Sn, Pb, Ti, Zr, Hf, Nb, Ta, W, Fe, Ru, Al, V, Cr, and lanthanide metal elements, X includes at least one of halogen elements, X' includes at least one of halide ions, N ions, oxygen-containing anion groups, and pseudohalide anions, 0.5≤a≤5, 0.2≤b≤4, c+d=a+bε, wherein ε is the weighted average valence of the M element; the oxygen-containing anion group includes O 2- , S 2- , CN - 、CO3 2- PO4 3- 、P2O7 4- 、SO4 2- At least one of the pseudohalide anions includes SCN - PF6 - NH2 - 、AlF4 - 、BF4 - At least one of .

4. The positive electrode material according to claim 1, characterized in that In the positive electrode material, the mass content of the protective layer is 0.01%~20%.

5. The positive electrode material according to claim 4, characterized in that In the positive electrode material, the mass content of the protective layer is 0.05%~2%.

6. The positive electrode material according to claim 1, characterized in that The positive electrode active material includes lithium nickel cobalt manganese oxide LiNi x1 Co y1 Mn z1 O2 (x1 + y1 + z1 = 1), lithium nickel cobalt aluminate LiNi x2 Co y2 Al z2 O2 (x2 + y2 + z2 = 1), lithium iron manganese phosphate LiFe x3 Mn y3 PO4 (x3 + y3 = 1), lithium iron phosphate LiFePO4, lithium manganese oxide LiMn2O4, lithium cobalt oxide LiCoO2, lithium nickel oxide LiNiO2, lithium-rich manganese-based x’Li2MnO 3· (1 - x’)LiMO2 (M = Ni, Co, Mn, 0 < x’ < 1), lithium nickel manganese oxide LiNi x5 Mn 2-x5 O4 (0 < x5 < 2), lithium vanadium phosphate (Li3V2(PO4)3, LiVOPO4), or one or more thereof.

7. The positive electrode material according to claim 1, characterized in that The positive electrode active material further includes a doping element, and the doping element includes at least one of Al, B, Ba, Bi, Ca, Cr, Ce, Co, Er, Ga, Ge, Ho, K, La, Mg, Mo, Na, Nb, Pd, P, Si, Sb, Sr, Se, Ru, Rh, Ta, Te, Ti, W, V, Y, Zr and Zn; And / or, the positive electrode material also includes a coating layer, the coating layer is located between the positive electrode active material and the protective layer, and the elements in the coating layer include at least one of Al, B, Ba, Bi, Ca, Cr, Ce, Co, Er, Ga, Ge, Ho, K, La, Mg, Mo, Na, Nb, Pd, P, Si, Sb, Sr, Se, Ru, Rh, Ta, Te, Ti, W, V, Y, Zr and Zn.

8. The positive electrode material according to claim 1, characterized in that The protective layer also includes amorphous carbon or sulfide solid electrolyte.

9. The method for preparing a positive electrode material according to any one of claims 1 to 7, characterized in that: The following steps are involved: Dissolving the raw material of the protective layer in a solvent to obtain a protective layer precursor solution; Adding the positive electrode active material to the protective layer precursor solution and dispersing to obtain a mixed slurry; The mixed slurry is heated under stirring, the protective layer precursor solution forms the halide solid electrolyte and is deposited on the surface of the positive electrode active material, and then heat-treated to obtain the positive electrode material.

10. The method for preparing the positive electrode material according to claim 9, characterized in that: The raw material of the protective layer is selected from a compound containing M', a compound containing X, a compound containing X', a compound containing NH4 + At least two of the compounds of X and X', wherein M' comprises one or more of Li, Na, Ga, Y, In, Mg, Sr, Sc, Sn, Pb, Ti, Zr, Hf, Nb, Ta, W, Fe, Ru, Al, V, Cr, lanthanide metal elements, X comprises one or more of halogen elements, X' comprises one or more of halide ions, N ions, oxygen-containing anion groups, pseudohalide anions, wherein the oxygen-containing anion groups comprise NO3 - 、O2 - , S 2- , CN - 、CO3 2- 、HCO3 - PO4 3- 、P2O7 4- 、SO4 2- One or more of the pseudohalide anions include SCN - PF6 - NH2 - 、AlF4 - , or BF4 - One or more of .

11. The method for preparing the positive electrode material according to claim 9, characterized in that: The solvent includes at least one of water and an organic solvent; the organic solvent includes anhydrous ethanol.

12. The method for preparing the positive electrode material according to claim 9, characterized in that: The mass ratio of the positive electrode active material to the solvent is 1:(0.1-100).

13. The method for preparing the positive electrode material according to claim 9, characterized in that: The stirring speed of the mixed slurry during heating is 100-400 rpm; And / or, the heat treatment is performed under vacuum, the heat treatment temperature is 120-500° C., and the time is 0.2-48 h.

14. A positive electrode sheet, characterized in that: It includes a positive electrode current collector and a positive electrode active material layer arranged on at least one side of the positive electrode current collector, wherein the positive electrode active material layer includes the positive electrode material according to any one of claims 1 to 8, or the positive electrode active material layer includes the positive electrode material prepared by the preparation method of the positive electrode material according to any one of claims 9 to 13.

15. A battery, characterized in that: It comprises a negative electrode and the positive electrode sheet as claimed in claim 14.

16. An electrical device, characterized in that: Comprising the battery of claim 15.

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