Positive electrode material, preparation method therefor, lithium-ion battery and electric device

Abstract

A positive electrode material. The positive electrode material has the following chemical formula: LiaNixCoyMn1-x-yMbO2-cQc, wherein 0.2≤a≤1.2, x≥0.6, y＞0, b＞0, c＞0, M comprises a high-valence cation, and Q comprises an anion. By doping a high-valence cation and an anion in a nickel-rich ternary positive electrode material, the body structure of the nickel-rich ternary positive electrode material under lithium intercalation is stabilized, side reactions, lattice oxygen evolution and transition metal dissolution are reduced, and the cycling stability, the high-temperature storage performance and the rate capability are improved. In addition, the outer surface of the positive electrode material can be further coated with a selenium-containing substance coating layer (2), a selenium-containing substance in the selenium-containing substance coating layer (2) can react with residual lithium compounds on the surface of the positive electrode material, and the remaining selenium-containing substance can be combined with lattice oxygen released in a high-delithiation state to prevent an electrolyte solution from being oxidized. Moreover, a conductive substance coating layer (3) can be further prepared on the outer surface of the selenium-containing substance coating layer (2), thereby preventing direct contact between the selenium-containing substance and the electrolyte solution, and inhibiting side reactions.

Description

Positive electrode material, method for preparing positive electrode material, lithium ion battery, and electrical device

[0001] Related applications

[0002] This application claims priority to Chinese patent application No. 202311439210.6 filed on November 1, 2023, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of battery positive electrode materials, and in particular to a positive electrode material, a method for preparing the positive electrode material, a lithium-ion battery, and an electrical device. Background Art

[0004] Lithium-ion batteries (LIBs) have attracted much attention due to their long lifespan, high energy density, and low maintenance cost. Currently, LIBs have been widely used in electric vehicles, portable electronic devices, energy storage systems, and other fields.

[0005] However, the energy density, safety, and lifespan of LIBs currently do not fully meet various requirements. Cathode materials are crucial for achieving breakthroughs. Ternary cathode materials have become a hot topic in recent years due to their high reversible capacity and low cost. Researchers typically increase the energy density of LIBs by continuously increasing their nickel content.

[0006] However, as the nickel content in the ternary positive electrode material increases, a series of problems will arise. On the one hand, the increase in nickel content will lead to a decrease in the thermal stability of the material. In the high SOC delithiation state, the lattice releases oxygen, the internal cracks expand, the electrolyte easily enters the interior of the particles to cause side reactions, and transition metal dissolution occurs at the same time, resulting in deterioration of life and safety performance. On the other hand, as the nickel content increases, the material will produce surface residual lithium compounds (RLCs) and poor interface stability, bringing a series of side effects, including first effect, deterioration of cycle and storage performance, etc. Considering the various adverse effects of RLCs on the surface of the above-mentioned ternary positive electrode materials, it is necessary to remove surface RLCs and inhibit their subsequent formation. Therefore, the existing nickel-rich ternary positive electrode materials still need to be improved.

[0007] Summary of the Invention

[0008] The present application is made in view of the above-mentioned problems, and its purpose is to provide a positive electrode material, a method for preparing the positive electrode material, a lithium ion battery, and an electrical device.

[0009] The first aspect of the present application provides a positive electrode material having the following chemical formula: Li a Ni x Co y Mn 1-x-y M b O2-c Q c , wherein 0.2≤a≤1.2, x≥0.6, y>0, b>0, c>0, M includes high-valent cations, Q includes anions, the high-valent cations include cations with a valence of four or more, the anions include S 2- 、Se 2- 、Te 2- 、P 3- At least one of them. The high-valent cations doped into the nickel-rich positive electrode material can affect the crystal growth direction of the positive electrode material, resulting in grain refinement, eliminating the harmful stress caused by the lattice shrinkage of the H2-H3 phase transition through fracture toughening, and can eliminate the local component unevenness of the material. In addition, the doped high-valent cations can also play a pillar effect to stabilize the stability of the delithiation structure. The doped anions can replace the oxygen site, strengthen the metal-oxygen bond, inhibit the precipitation of lattice oxygen, and at the same time reduce the interaction force between the lithium layer and the oxygen layer to increase the distance between the lithium layer and the oxygen layer, reduce the migration barrier of lithium ions, and accelerate the transmission of lithium ions. The present application stabilizes the bulk structure of the nickel-rich positive electrode material under lithium deintercalation and the interface stability with the electrolyte by combining the bulk doping of high-valent cations and the surface gradient doping of anions, reduces side reactions, lattice oxygen precipitation and transition metal dissolution, and improves cycle stability, high-temperature storage performance and rate performance.

[0010] In some embodiments of the present application, the high-valent cations include Mo 6+ 、Sb 5+ 、Zr 4+ 、Ti 4+ 、Nb 5+ 、W 6+ 、Y 5+ 、Ta 5+ The high-valent cations mentioned above can affect the growth direction of the cathode material crystals, leading to grain refinement, and eliminate the harmful stress caused by the lattice contraction of the H2-H3 phase transition through fracture toughening. They can also eliminate the problem of local component inhomogeneity in the material and play a pillar effect to stabilize the delithiation structure.

[0011] The anions described in this application include S 2- 、Se 2- 、Te 2- 、P 3-At least one of the above types of anions can replace oxygen sites, enhance the binding force of the metal-oxygen bond, inhibit the precipitation of lattice oxygen, and at the same time reduce the interaction force between the lithium layer and the oxygen layer to increase the distance between the lithium layer and the oxygen layer, reduce the migration barrier of lithium ions, and accelerate the transmission of lithium ions. By combining the bulk doping of high-valent cations and the surface gradient doping of anions, the bulk structure of the nickel-rich positive electrode material under lithium insertion and deintercalation and the interface stability with the electrolyte are stabilized, side reactions, lattice oxygen precipitation and transition metal dissolution are reduced, and the cycle stability, high-temperature storage performance and rate performance are improved.

[0012] In some embodiments of the present application, 0.0005≤b≤0.01, and / or, 0.001≤c≤0.1. The doping amount of high-valent cations and anions in the positive electrode material within the above range is beneficial to stabilizing the bulk structure of the nickel-rich positive electrode material under lithium intercalation and deintercalation and the interfacial stability with the electrolyte, reducing side reactions, lattice oxygen precipitation, and transition metal dissolution, and improving cycle stability, high-temperature storage performance, and rate performance. It is not easy for the above-mentioned effects to be difficult to achieve due to too little doping, nor is it easy for the battery capacity to be affected due to too high a doping amount, resulting in a decrease in the electrochemical performance of the battery.

[0013] In some embodiments of the present application, the outer surface of the positive electrode material further includes a first coating layer, wherein the first coating layer includes a selenium-containing substance. The selenium-containing substance can react with the lithium ions (RCLs) on the surface of the nickel-rich positive electrode material to form CEIs such as lithium selenoselenate (Li2Se2O3) and lithium selenate (Li2SeO4) in situ, thereby increasing the migration rate of lithium ions in the surface layer. At the same time, the remaining selenium-containing substance can bind to the lattice oxygen released in the highly delithiated state to prevent oxidation and gasification of the electrolyte.

[0014] In some embodiments of the present application, the selenium-containing material includes at least one of elemental selenium (Se), selenium oxide (SeO2), selenium sulfide (SeS2), and tellurium selenide (TeSe). These types of selenium-containing materials readily react with the miscellaneous lithium on the surface of the nickel-rich positive electrode material to form CEI (electrolyte interface) such as lithium selenoselenate and lithium selenate in situ.

[0015] In some embodiments of the present application, the content of selenium in the positive electrode material comprising the first coating layer is 0.03%-5%. It should be noted that the content here refers to the mass percentage.

[0016] In some embodiments of the present application, the amount of the selenium-containing substance added is in the range of 0.1% to 5% based on 100% of the total mass of the positive electrode material. Within this range, the selenium-containing substance is unlikely to be insufficiently added to effectively remove RLCs, resulting in insignificant improvement in positive electrode material performance. Excessive addition of the selenium-containing substance is also unlikely to result in a reduction in the proportion of active material, a decrease in battery capacity, or even the occurrence of excessive selenium-containing substance catalyzing the decomposition of the electrolyte solvent and producing gas.

[0017] In some embodiments of the present application, based on 100% of the total mass of the positive electrode material, the added amount of the selenium-containing substance is in the range of 0.5% to 2%.

[0018] In some embodiments of the present application, the particle size Dv50 of the selenium-containing material is 100 nm to 1000 nm. Selenium-containing materials with excessively large particle sizes are not conducive to reaction with RLCs, and a large amount of RLCs may remain. Nanosized selenium-containing materials, on the other hand, have a larger specific surface area, increasing the reaction contact area and forming a dense selenium-containing coating.

[0019] In some embodiments of the present application, the particle size Dv50 of the selenium-containing substance is 100 nm-500 nm.

[0020] In some embodiments of the present application, the positive electrode material further includes a second coating layer, coated on the surface of the first coating layer, and comprising a conductive polymer. Because selenium-containing substances readily catalyze the decomposition of electrolyte ester solvents to generate oxidizing gases, the conductive polymer in the second coating layer can isolate the selenium-containing substance from direct contact with the electrolyte, inhibiting side reactions. Furthermore, the conductive polymer's excellent electrical conductivity enhances the electronic conductivity of the material, reducing interfacial impedance and improving the battery's cycling performance.

[0021] In some embodiments of the present application, the conductive polymer includes at least one of polyaniline, polypyrrole, polypyridine, and polythiophene. These conductive polymers readily react to form a coating layer, which helps prevent direct contact between the selenium-containing substance and the electrolyte and inhibits side reactions. Furthermore, these conductive polymers also have excellent electrical conductivity, enhancing the electronic conductivity of the positive electrode material, reducing interfacial impedance, and improving the battery's cycling performance.

[0022] In some embodiments of the present application, the thickness of the second coating layer is 50nm-500nm, which is not likely to affect the lithium ion transmission effect of the battery due to excessive thickness, nor is it likely to be difficult to achieve the purpose of reducing side reactions by reducing the contact between selenium-containing substances and the electrolyte due to being too thin.

[0023] In some embodiments of the present application, the thickness of the second coating layer is 50 nm to 200 nm.

[0024] The second aspect of the present application provides a method having the above chemical formula Li a Ni x Co y Mn 1-x-y M b O 2-c Q c The preparation method of the positive electrode material comprises the following steps:

[0025] The preparation method of the positive electrode material comprises the following steps:

[0026] A nickel-rich ternary cathode material precursor is mixed with a high-valent cation dopant, and the mixture is sintered to obtain a high-valent cation-doped cathode material A; the cathode material A is mixed with an anion dopant, and the mixture is sintered to obtain the cathode material, which is referred to as cathode material C. The cathode material C contains high-valent cations and anions, wherein the high-valent cations include cations with a valence of four or more;

[0027] or,

[0028] The preparation method of the positive electrode material comprises the following steps:

[0029] A nickel-containing positive electrode material precursor is mixed with an anion dopant and sintered to obtain an anion-doped positive electrode material B. The positive electrode material B is mixed with a high-valent cation dopant and sintered to obtain the positive electrode material, which is recorded as positive electrode material C. The positive electrode material C contains high-valent cations and anions, and the high-valent cations include cations with a valence of four or more.

[0030] In the present application, a positive electrode material C co-doped with high-valent cations and anions is obtained by first doping a nickel-rich ternary positive electrode material with high-valent cations and then doping with anions, or first doping with anions and then doping with high-valent cations. It should be noted that in the present application, the purpose of mixing a high-valent cation dopant and sintering is to impart the high-valent cations to the final prepared positive electrode material, while the purpose of mixing an anion dopant and sintering is to impart the anions to the final prepared positive electrode material.

[0031] In some embodiments of the present application, in the step of preparing the positive electrode material A, the sintering includes primary sintering and secondary sintering, the temperature of the primary sintering is 350℃-500℃, the primary sintering time is 2-7h, the temperature of the secondary sintering is 600℃-800℃, and the secondary sintering time is 3-6h.

[0032] In some embodiments of the present application, in the step of preparing the positive electrode material B, the sintering temperature is 400°C-650°C.

[0033] A third aspect of the present application provides a method for preparing a positive electrode material, comprising the following steps:

[0034] The positive electrode material C described above in this application and a selenium-containing substance are mixed and heated to obtain a positive electrode material, which is recorded as positive electrode material D. The surface of positive electrode material D has a coating layer of the selenium-containing substance. The positive electrode material D prepared in this example is the positive electrode material having a first coating layer on the outer surface as described above.

[0035] In some embodiments of the present application, the heating temperature is 230° C.-500° C.;

[0036] And / or, the heating time is 15 min-120 min.

[0037] A fourth aspect of the present application further provides a method for preparing a positive electrode material, comprising the following steps:

[0038] A conductive polymer is dissolved in an organic solvent to obtain a conductive polymer solution. The conductive polymer solution, an initiator, and the positive electrode material D described above are mixed and reacted, filtered, washed, and dried to obtain a positive electrode material, which is referred to as positive electrode material E. The surface of positive electrode material E has a conductive material coating layer. The positive electrode material E prepared in this example is the positive electrode material having the first coating layer and the second coating layer respectively provided on the outer surface as described above.

[0039] It should be noted that the above preparation method can be understood as preparing a conductive material coating layer on the outer surface of the selenium-containing material coating layer of the positive electrode material D, thereby forming the positive electrode material E, which contains both the selenium-containing material coating layer and the conductive material coating layer.

[0040] In some embodiments of the present application, based on 100% of the total mass of the positive electrode material D, the added amount of the conductive polymer is 0.5%-10%. It is not easy to affect the lithium ion transmission effect of the battery due to excessive addition, nor is it easy to achieve the purpose of reducing side reactions by reducing the contact between selenium-containing substances and the electrolyte due to too little addition.

[0041] In a fifth aspect, the present application further provides a lithium-ion battery, which includes the positive electrode material described above in the present application, and the battery includes any one of a battery cell, a battery module, and a battery pack.

[0042] A fifth aspect of the present application further provides an electrical device, which includes the lithium-ion battery described above in the present application.

[0043] Beneficial effects that this application can achieve:

[0044] The present application provides a positive electrode material that is co-doped with high-valent cations and anions. The high-valent cations doped into the nickel-rich positive electrode material affect the direction of crystal growth, resulting in grain refinement, eliminating the harmful stress caused by the lattice shrinkage of the H2-H3 phase transition through fracture toughening, and can eliminate the local component unevenness of the material. The doped high-valent cations can also play a pillar effect to stabilize the stability of the delithiation structure. The doped anions can replace oxygen sites, strengthen the metal-oxygen bond, inhibit the precipitation of lattice oxygen, and at the same time reduce the interaction force between the lithium layer and the oxygen layer to increase the distance between the lithium layer and the oxygen layer, reduce the migration barrier of lithium ions, and accelerate the transmission of lithium ions. By combining the bulk doping of high-valent cations and the surface gradient doping of anions, the bulk structure of the nickel-rich positive electrode material under lithium insertion and removal and the interfacial stability with the electrolyte are stabilized, side reactions, lattice oxygen precipitation and transition metal dissolution are reduced, and the cycle stability, high-temperature storage performance and rate performance are improved.

[0045] In addition, a first coating layer containing selenium can be prepared on the outer surface of the positive electrode material. The selenium-containing substance can undergo an oxidation-reduction reaction with the lithium-rich RCLs on the surface of the nickel-rich positive electrode material to remove part of the RCLs and form CEI (electrolyte interface) such as lithium selenoselenate (Li2Se2O3) and lithium selenate (Li2SeO4) in situ, which is beneficial to improving the migration rate of lithium ions in the surface layer. At the same time, the remaining selenium-containing substance can combine with the lattice oxygen released in the highly delithiation state to prevent the electrolyte from being oxidized and producing gas. The remaining RCLs can further react and be converted into active lithium for secondary utilization during the formation process after the battery cell is made.

[0046] Furthermore, a second coating layer of conductive material can be prepared on the surface of the selenium-containing material coating layer of the positive electrode material. The conductive material coating layer can prevent direct contact between the selenium-containing material and the electrolyte, inhibit the occurrence of side reactions, and at the same time, the excellent conductivity of the conductive polymer can enhance the electronic conductivity of the positive electrode material, reduce the interface impedance, and improve the cycle performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] FIG1 is a schematic diagram of the structure of the positive electrode material according to one embodiment of the present application.

[0048] Explanation of reference numerals: 1 active material; 2 selenium-containing material coating layer; 3 conductive material coating layer.

[0049] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0050] The following detailed description of the insulating heat-radiating coating and its preparation method, the insulating heat-radiating coating and its preparation method, the battery casing, the battery, and the electrical device of the present application is disclosed with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially the same structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0051] " range " disclosed in the application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be combined arbitrarily, and promptly any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0052] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0053] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0054] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0055] Increasing the nickel content in cathode materials creates a series of problems. For one thing, increased nickel content can lead to a decrease in the thermal stability of the material. In the high SOC (delithiation) state, oxygen is released from the lattice, internal cracks expand, and electrolyte easily enters the particles, causing side reactions and transition metal dissolution, leading to a deterioration in lifespan and safety performance.

[0056] In view of this, the present application proposes a positive electrode material having the following chemical formula: Li a Ni x Co y Mn 1-x-y M b O 2-c Q c , wherein 0.2≤a≤1.2, x≥0.6, y>0, b>0, c>0, M includes high-valent cations, Q includes anions, and the high-valent cations include cations with a valence of four or more; the anions include S 2- 、Se 2- 、Te 2- 、P 3- At least one of .

[0057] In some embodiments, the high valence cations include Mo 6+ 、Sb 5+ 、Zr 4+ 、Ti 4+ 、Nb 5+ 、W 6+ 、Y 5+ 、Ta 5+ At least one of the above types of high-valent cations can affect the growth direction of the positive electrode material crystal, resulting in grain refinement, and eliminate the harmful stress caused by the H2-H3 phase transition lattice contraction through fracture toughening, and can eliminate the problem of uneven local component of the material, while playing a pillar effect to stabilize the stability of the delithiation structure.

[0058] The anions in the positive electrode materials mentioned above include S 2- 、Se 2- 、Te2- 、P 3- At least one of the above types of anions can replace oxygen sites, enhance the binding force of the metal-oxygen bond, inhibit the precipitation of lattice oxygen, and at the same time reduce the interaction force between the lithium layer and the oxygen layer to increase the distance between the lithium layer and the oxygen layer, reduce the migration barrier of lithium ions, and accelerate the transmission of lithium ions. By combining the bulk doping of high-valent cations and the surface gradient doping of anions, the bulk structure of the nickel-rich positive electrode material under lithium insertion and deintercalation and the interface stability with the electrolyte are stabilized, side reactions, lattice oxygen precipitation and transition metal dissolution are reduced, and the cycle stability, high-temperature storage performance and rate performance are improved.

[0059] In this application, the cathode material Li a Ni x Co y Mn 1-x-y M b O 2-c Q c Where 0.2≤a≤1.2, for example, a can be any value in the range of 0.2 to 1.2, such as 0.2, 0.25, 0.28, 0.3, 0.32, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.18, or 1.2. It should be noted that the above molar content range of lithium element in the positive electrode material includes the molar content of lithium element in batteries using the positive electrode material under different charge and discharge states.

[0060] In some embodiments, 0.0005≤b≤0.01, and / or, 0.001≤c≤0.1. For example, b can be any value in the range of 0.0005 to 0.01, such as 0.0005, 0.0006, 0.0007, 0.0008, 0.0009, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, etc.; c can be any value in the range of 0.001 to 0.1, such as 0.001, 0.003, 0.005, 0.006, 0.008, 0.009, 0.01, 0.015, 0.02, 0.03, 0.04, 0.05, 0.055, 0.06, 0.07, 0.08, 0.085, 0.09, 0.095, 0.01, etc. The doping amount of high-valent cations and anions in the positive electrode material is within the above range, which is conducive to stabilizing the bulk structure of the nickel-rich positive electrode material under lithium deintercalation and the interface stability with the electrolyte, reducing side reactions, lattice oxygen precipitation and transition metal dissolution, and improving cycle stability, high-temperature storage performance and rate performance. It is not easy for the above effects to be difficult to play due to too little doping, nor is it easy for the battery capacity to be affected due to too high a doping amount, resulting in a decrease in the electrochemical performance of the battery.

[0061] On the other hand, as the nickel content increases, RLCs (residual lithium compounds on the surface) will be produced in the electrode, the interface stability will be poor, and a series of side effects will be brought about, including first effect, deterioration of cycle and storage performance, etc. Considering the various adverse effects of RLCs on the surface of the above-mentioned ternary positive electrode materials, it is necessary to remove surface RLCs and inhibit their subsequent formation.

[0062] In view of this, the present application further designs a first coating layer on the outer surface of the positive electrode material doped with anions and high-valent cations, wherein the first coating layer includes a selenium-containing substance.

[0063] Selenium-containing substances can undergo redox reactions with the mixed lithium RCLs on the surface of nickel-rich positive electrode materials to remove some RCLs and form CEI (electrolyte interface) such as lithium selenoselenate (Li2Se2O3) and lithium selenate (Li2SeO4) in situ, which is beneficial to improving the migration rate of lithium ions in the surface layer. At the same time, the remaining selenium-containing substances can combine with the lattice oxygen released in the highly delithiation state to prevent the electrolyte from being oxidized and producing gas. The remaining RCLs can further react and be converted into active lithium for secondary utilization during the formation process after the battery cell is made.

[0064] In some embodiments, the selenium-containing material includes at least one of elemental selenium (Se), selenium oxide (SeO2), selenium sulfide (SeS2), and tellurium selenide (TeSe). These selenium-containing materials readily undergo redox reactions with the heterolithium RCLs on the surface of the nickel-rich cathode material to form CEIs such as lithium selenoselenate and lithium selenate in situ, removing some of the RCLs and preventing excessive RCL content from affecting the interfacial stability of the lithium-ion battery, leading to a series of side effects such as first efficiency, deteriorated cycling performance, and poor storage performance.

[0065] In this embodiment, the content of selenium in the positive electrode material including the first coating layer is in the range of 0.03% to 5%, for example, it can be 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.2%, 0.3%, 0.5%, 0.8%, 0.9%, 1%, 1.05%, 1.1%, 1.2%, 1.3%, 1.5%, %, 1.8%, 1.9%, 1.91%, 1.95%, 2%, 2.2%, 2.3%, 2.5%, 2.6%, 2.7%, 2.76%, 2.8%, 2.9%, 3.%, 3.5%, 3.56%, 3.6%, 3.7%, 3.9%, 4%, 4.2%, 4.5%, 4.8%, 4.9%, 5%, etc., any value in the range of 0.03%-5%.

[0066] In some embodiments, based on 100% of the total mass of the positive electrode material, the addition amount of the selenium-containing substance is in the range of 0.1%-5%, and further, it can be 0.5%-2%. For example, it can be 0.1%, 0.3%, 0.4%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.6%, 2.9%, 3%, 3.3%, 3.5%, 3.8%, 3.9%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, 4.9%, 5%, etc. Any value in the range of 0.1%-5%. It can be understood that the total mass of the positive electrode material described in this embodiment refers to the positive electrode material having the above chemical formula Li a Ni x Co y Mn 1-x-y M b O 2-c Q c The total mass of the positive electrode material, that is, the positive electrode material for which the first coating layer has not yet been prepared.

[0067] The present application does not limit the particle size Dv50 of the selenium-containing material. In some embodiments, the particle size Dv50 of the selenium-containing material is 100 nm-1000 nm, or 100 nm-500 nm. For example, the particle size Dv50 can be any value in the range of 100 nm-1000 nm, such as 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, or the like.

[0068] However, selenium-containing substances easily catalyze the decomposition of electrolyte ester solvents to generate oxidizing gases. In view of this, in some embodiments, the above-mentioned positive electrode material containing a first coating layer also includes a second coating layer, which is coated on the surface of the first coating layer and includes a conductive polymer.

[0069] The conductive polymer of the second coating layer can prevent the direct contact between the selenium-containing substance and the electrolyte, inhibit the occurrence of side reactions, and at the same time the excellent conductivity of the conductive polymer enhances the electronic conductivity of the positive electrode material, reduces the interface impedance, and improves the cycle performance of the battery.

[0070] In some embodiments, the conductive polymer includes at least one of polyaniline, polypyrrole, polypyridine, and polythiophene. These conductive polymers readily react to form a coating layer, which helps prevent direct contact between the selenium-containing substance and the electrolyte and inhibits side reactions. Furthermore, these conductive polymers have excellent electrical conductivity, which can enhance the electronic conductivity of the positive electrode material, reduce interfacial impedance, and improve the battery's cycling performance.

[0071] The application does not limit the thickness of the second coating layer. In certain embodiments, the thickness of the second coating layer is 50nm-500nm, or can be 50nm-200nm. For example, the thickness of the second coating layer is any thickness value in the 50nm-500nm scope such as 50nm, 80nm, 100nm, 120nm, 150nm, 80nm, 100nm, 120nm, 150nm, 180nm, 200nm, 250nm, 300nm, 350nm, 400nm, 420nm, 450nm, 480nm, 490nm, 500nm. The second coating layer in the above thickness range condition is not easy to affect the lithium ion transmission effect of battery because of the excessive thickness of thickness, is also not easy to reach the purpose of reducing side reaction by reducing the contact of selenium-containing material with electrolyte because of being too thin.

[0072] The second aspect of the present application provides a method having the above chemical formula Li a Ni x Co y Mn 1-x-y M b O 2-c Qc A method for preparing a positive electrode material, the method comprising the following steps:

[0073] A nickel-rich ternary cathode material precursor is mixed with a high-valent cation dopant and sintered to obtain a high-valent cation-doped cathode material A; the cathode material A is mixed with an anion dopant and sintered to obtain the above-mentioned cathode material, which is recorded as cathode material C. The cathode material C contains high-valent cations and anions, wherein the high-valent cations include cations with a valence of four or more;

[0074] or,

[0075] The preparation method of the positive electrode material comprises the following steps:

[0076] A nickel-containing positive electrode material precursor is mixed with an anion dopant and sintered to obtain an anion-doped positive electrode material B. The positive electrode material B is mixed with a high-valent cation dopant and sintered to obtain the above-mentioned positive electrode material, which is recorded as positive electrode material C. The positive electrode material C contains high-valent cations and anions, wherein the high-valent cations include cations with a valence of four or more.

[0077] It should be noted that the positive electrode material C prepared by this preparation method has the above chemical formula of this application: Li a Ni x Co y Mn 1-x-y M b O 2-c Q c , wherein 0.2≤a≤1.2, x≥0.6, y>0, b>0, c>0, M includes high-valent cations, Q includes anions, the high-valent cations include cations with a valence of four or more, and the anions include S 2- 、Se 2- 、Te 2- 、P 3- At least one of .

[0078] It can be understood that the purpose of mixing high-valent cation dopants and sintering in this application is to make the final prepared positive electrode material carry the above-mentioned high-valent cations, and mixing anion dopants and sintering is to make the final prepared positive electrode material also carry the above-mentioned anions. This application does not limit the doping order of high-valent cations and anions. The positive electrode material A can be prepared by doping high-valent cation dopants in the nickel-rich ternary positive electrode material precursor, and then anions are doped in the positive electrode material A to obtain a positive electrode material C co-doped with high-valent cations and anions. In addition, an anion dopant can be added to the nickel-rich ternary positive electrode material precursor to obtain an anion-doped positive electrode material B, and then a high-valent cation dopant can be added to the positive electrode material B to obtain a high-valent cation and anion co-doped positive electrode material C. The positive electrode material C prepared by the above two preparation methods can be understood as the same type of positive electrode material, that is, a positive electrode material co-doped with high-valent cations and anions.

[0079] In some embodiments, a nickel-rich ternary cathode material precursor is first doped with high-valent cations to prepare cathode material A. In the process of preparing cathode material A, the sintering process includes a primary sintering and a secondary sintering. The primary sintering temperature is 350°C-500°C, the primary sintering time is 2-7 hours, and the secondary sintering temperature is 600°C-800°C, and the secondary sintering time is 3 hours-6 hours.

[0080] In some embodiments, anions are first doped into a nickel-rich ternary cathode material precursor, ie, cathode material B is prepared. During the preparation of cathode material B, the sintering temperature is 400°C to 650°C.

[0081] In some embodiments, the nickel-rich ternary positive electrode material precursor and the high-valent cationic dopant are mixed and placed in a ball mill for ball milling to obtain a mixed powder a. Sintering the mixed powder a is beneficial to improving the sintering efficiency and making the nickel-rich ternary positive electrode material precursor and the high-valent cationic dopant more evenly mixed.

[0082] In some embodiments, the nickel-rich ternary positive electrode material precursor and the cathode dopant are mixed and placed in a ball mill for ball milling to obtain a mixed powder b. Sintering the mixed powder b is beneficial to improving the sintering effect, so that the nickel-rich ternary positive electrode material precursor and the anion dopant are mixed more evenly.

[0083] Similarly, after the positive electrode material A doped with high-valent cations is mixed with an anion dopant, or after the positive electrode material B doped with anions is mixed with a high-valent cation dopant, the sintering speed can be increased by ball milling to make the raw materials mixed more evenly.

[0084] Based on the preparation method of the positive electrode material C co-doped with high-valent cations and anions proposed in the second aspect of the present application, the third aspect of the present application further proposes a preparation method of the positive electrode material, comprising the following steps:

[0085] The positive electrode material C described above in the present application and the selenium-containing substance are mixed and heated to obtain a positive electrode material, which is recorded as positive electrode material D. The surface of the positive electrode material D has a selenium-containing substance coating layer.

[0086] It should be noted that the above preparation method can be understood as preparing a selenium-containing substance coating layer on the outer surface of the positive electrode material C, thereby forming the positive electrode material D.

[0087] In the present application, a selenium-containing coating layer is prepared on the surface of a positive electrode material C co-doped with high-valent cations and anions. The selenium-containing substance can undergo an oxidation-reduction reaction with the lithium-rich RCLs on the surface of the nickel-rich positive electrode material to remove part of the RCLs and form CEI (electrolyte interface) such as lithium selenoselenate (Li2Se2O3) and lithium selenate (Li2SeO4) in situ, which is beneficial to improving the migration rate of lithium ions in the surface layer. At the same time, the remaining selenium-containing substance can combine with the lattice oxygen released in the high-delithiation state to prevent the electrolyte from being oxidized and producing gas. The remaining RCLs can further react and be converted into active lithium for secondary utilization during the formation process after the battery cell is made.

[0088] Under heating conditions, the selenium-containing substance forms a molten state and diffuses evenly on the surface of the positive electrode material C to form a dense coating layer. In some embodiments, the heating temperature is 230°C-500°C. For example, the heating temperature can be any temperature value in the range of 230°C-500°C, such as 230°C, 240°C, 250°C, 280°C, 300°C, 350°C, 400°C, 420°C, 450°C, 480°C, 500°C, etc. The above temperature conditions can cause selenium-containing substances such as elemental selenium (Se), selenium oxide (SeO2), selenium sulfide (SeS2), and tellurium selenide (TeSe) to form a molten state, which is conducive to wrapping the co-doped positive electrode material and forming a uniform selenium-containing substance coating layer on its surface.

[0089] In some embodiments, the heating time is 15 min to 120 min. For example, the heating time can be any time value within the range of 15 min to 120 min, such as 15 min, 20 min, 50 min, 60 min, 80 min, 90 min, 100 min, 110 min, or 120 min. Under the above heating time conditions, the selenium-containing substance can be molten and wrap the co-doped positive electrode material, forming a uniform coating of the selenium-containing substance on its surface. At the same time, it is not easy to damage other substances in the co-doped positive electrode material due to excessive heating time.

[0090] In some embodiments, heating in a tube furnace is beneficial for heating the selenium-containing substance and the positive electrode material C more evenly, promoting the melting of the selenium-containing substance, and forming a uniform first coating layer on the surface of the positive electrode material C: a selenium-containing substance coating layer.

[0091] In some embodiments, the heating step is performed under a protective atmosphere such as an argon atmosphere, which helps to accelerate the melting of the selenium-containing substance and prevent air and the selenium-containing substance from reacting to generate other impurities that affect the performance of the selenium-containing substance coating layer.

[0092] Based on the preparation method of the positive electrode material D having a selenium-containing coating layer proposed in the third aspect of the present application, the fourth aspect of the present application provides another preparation method of the positive electrode material, comprising the following steps:

[0093] A conductive polymer is dissolved in an organic solvent to obtain a conductive polymer solution. The conductive polymer solution, an initiator and the above-mentioned positive electrode material D of the present application are mixed and reacted, filtered, washed and dried to obtain a positive electrode material, which is recorded as positive electrode material E. The surface of the positive electrode material E has a conductive material coating layer.

[0094] It should be noted that the above preparation method can be understood as preparing a conductive material coating layer on the outer surface of the selenium-containing material coating layer of the positive electrode material D, thereby forming the positive electrode material E, which contains both the selenium-containing material coating layer and the conductive material coating layer.

[0095] Since selenium-containing substances easily catalyze the decomposition of electrolyte ester solvents to generate oxidizing gases, coating the outermost layer of the positive electrode material with a conductive polymer can prevent direct contact between the selenium-containing substances and the electrolyte, inhibiting the occurrence of side reactions. At the same time, the excellent conductivity of the conductive polymer can enhance the electronic conductivity of the positive electrode material, reduce the interfacial impedance, and improve the cycle performance of the battery.

[0096] In some embodiments, the amount of the conductive polymer added is 0.5%-10% based on 100% of the total mass of the positive electrode material D. For example, the amount added can be any value within the range of 0.5%-10%, such as 0.5%, 1%, 2%, 3%, 5%, 6%, 7%, 8%, 9%, 9.5%, or 10%. Within the above addition amount range, the positive electrode material of the selenium-containing coating layer is advantageously completely wrapped to form a dense conductive polymer coating layer, isolating the selenium-containing material from direct contact with the electrolyte, inhibiting side reactions, and providing conductive properties to enhance the electronic conductivity of the positive electrode material, reduce interfacial impedance, and improve the cycle performance of the battery.

[0097] In some embodiments, the organic solvent includes NMP (N-methylpyrrolidone). The above organic solvent can quickly and evenly dissolve the conductive polymer.

[0098] In some embodiments, the initiator includes hydrogen peroxide, ammonium persulfate, potassium persulfate, or azobisisobutyronitrile.

[0099] In some embodiments, the reaction of the conductive polymer and the positive electrode material D is performed under a protective atmosphere, such as a nitrogen atmosphere.

[0100] In some embodiments, referring to FIG1 , the positive electrode material comprises an active material 1, a selenium-containing coating layer 2 surrounding the active material 1, and a conductive coating layer 3 as the outermost layer. The active material 1 is a nickel-rich ternary positive electrode material doped with high-valent cations and anions, i.e., the positive electrode material C mentioned above in this application. The nickel-rich ternary positive electrode material has the following chemical formula: Li a Ni x Co y Mn 1-x-y M b O 2-c Q c , wherein, 0.2≤a≤1.2, x≥0.6, y>0, b>0, c>0, M includes high-valent cations, Q includes anions, and the high-valent cations include cations with a valence of four or more.

[0101] The positive electrode material of this embodiment uses high-valent cations to affect the direction of crystal growth, resulting in grain refinement, and eliminates the harmful stress caused by the lattice shrinkage of the H2-H3 phase transition through fracture toughening, and can eliminate the local component unevenness of the positive electrode material. In addition, the doped high-valent cations can also play a pillar effect to stabilize the stability of the delithiation structure. The doped anions can replace the oxygen site, strengthen the metal-oxygen bond, inhibit the precipitation of lattice oxygen, and at the same time reduce the interaction force between the lithium layer and the oxygen layer to increase the distance between the lithium layer and the oxygen layer, reduce the migration barrier of lithium ions, and accelerate the transmission of lithium ions. The present application stabilizes the bulk structure of the nickel-rich positive electrode material under lithium insertion and removal and the interface stability with the electrolyte by combining the bulk doping of high-valent cations and the surface gradient doping of anions, reduces side reactions, lattice oxygen precipitation and transition metal dissolution, and improves cycle stability, high-temperature storage performance and rate performance.

[0102] In addition, the selenium-containing substance in the selenium-containing coating layer 2 of the positive electrode material of this embodiment can react with the lithium-rich RCLs on the surface of the nickel-rich positive electrode material to form CEI such as lithium selenoselenate (Li2Se2O3) and lithium selenate (Li2SeO4) in situ, thereby improving the migration rate of lithium ions in the surface layer. At the same time, the remaining selenium-containing substance can combine with the lattice oxygen released in the highly delithiated state to prevent the electrolyte from being oxidized and producing gas. Furthermore, the conductive substance coating layer 3 of the outermost layer of the positive electrode material can prevent the selenium-containing substance from directly contacting the electrolyte, inhibiting the occurrence of side reactions. At the same time, the excellent conductivity of the conductive polymer can enhance the electronic conductivity of the positive electrode material, reduce the interfacial impedance, and improve the cycle performance of the battery.

[0103] In a fifth aspect, the present application provides a lithium-ion battery, which includes the positive electrode material as described above in the present application, that is, a positive electrode material C co-doped with high-valent cations and anions, a positive electrode material D comprising a selenium-containing substance coating layer, and a positive electrode material E further comprising a conductive polymer coating layer.

[0104] In some embodiments, the lithium-ion battery includes any one of a battery cell, a battery module, and a battery pack.

[0105] In a sixth aspect, the present application provides an electrical device, which includes the lithium-ion battery described above in the present application. The electrical device of the present application has at least all the beneficial effects of the above-mentioned lithium-ion battery, which will not be repeated here.

[0106] The technical solution of the present application is further described in detail below in conjunction with specific embodiments. It should be understood that the following specific embodiments are only used to explain the present application and are not used to limit the present application.

[0107] Example 1 to Example 20

[0108] 1. Modification of positive electrode active materials

[0109] S1: According to Table 1, the nickel-rich ternary positive electrode material NCM and the high-valent cation dopant are mixed and added to a ball mill for ball milling to obtain a mixed powder a. The mixed powder a is placed in an alumina crucible and sintered once at 350°C-500°C for 2-7 hours, and then sintered twice at 600°C-800°C for 3 hours-6 hours to obtain the positive electrode material A; wherein the doping amount of the high-valent cation is 0.1% of the total molar mass of the nickel-rich ternary positive electrode material NCM.

[0110] S2: According to Table 1, the positive electrode material A and the cathode dopant are mixed and added to a ball mill to obtain a mixed powder b. The mixed powder b is sintered at 400°C-650°C to obtain a positive electrode material C co-doped with high-valent cations and anions; wherein the anion doping amount is 0.5% of the total molar mass of the nickel-rich ternary positive electrode material NCM.

[0111] S3: According to Table 1, the positive electrode material C and the selenium-containing substance with a particle size Dv50 of 100nm-1000nm are mixed and added to a ball mill for ball milling to obtain a mixed powder c. The mixed powder c is placed in an alumina crucible, placed in a tubular furnace and heated to 230℃-500℃ under an argon atmosphere for 15min-120min. The selenium-containing substance becomes a molten state and diffuses evenly on the surface of the positive electrode material C to form a dense coating layer, thereby obtaining a positive electrode material D having a first coating layer of selenium-containing substance on the surface; wherein, the first coating layer content (wt%) in Table 1 refers to the amount of selenium-containing substance added based on 100% of the total mass of the positive electrode material C.

[0112] S4: Dissolve the conductive polymer in N-methylpyrrolidone to obtain a conductive polymer solution, mix the positive electrode material D with the conductive polymer solution and the initiator hydrogen peroxide, filter, and wash to obtain a positive electrode material E having a second coating layer of conductive material with a thickness of 50nm-500nm, wherein the second coating layer content (wt%) in Table 1 refers to the amount of conductive polymer added based on 100% of the total mass of the positive electrode material D.

[0113] The above-mentioned positive electrode material E is a modified positive electrode material co-doped with high-valent cations and anions, and having a selenium-containing substance coating layer and a conductive substance coating layer. Referring to Figure 1, the modified positive electrode material contains an active substance 1, a selenium-containing substance coating layer 2, and a conductive substance coating layer 3, wherein the active substance 1 is a nickel-rich ternary positive electrode material doped with high-valent cations and anions.

[0114] 2. Preparation of lithium-ion batteries

[0115] 1) Positive electrode

[0116] The modified positive electrode active material nickel-cobalt-manganese ternary positive electrode material NCM, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are dissolved in the solvent N-methylpyrrolidone (NMP) in a weight ratio of 96.5:1.5:2, and the mixture is fully stirred and mixed to obtain a positive electrode slurry; the positive electrode slurry is then evenly coated on the positive electrode collector with a primer, and then dried, cold pressed, and cut to obtain a positive electrode sheet.

[0117] 2) Negative electrode

[0118] Active material graphite, silicon, conductive agent acetylene black, high molecular polymer, and thickener sodium carboxymethyl cellulose (CMC) are dissolved in deionized water in a weight ratio of 90:5:2:2:1 and uniformly mixed with the deionized water to prepare a negative electrode slurry. The slurry is coated on copper foil, dried, and then cold-pressed and cut to obtain anode sheets.

[0119] 3) Diaphragm

[0120] The diaphragm is a PE diaphragm with PVDF and alumina coating on the surface to improve adhesion and heat resistance.

[0121] 4) Electrolyte

[0122] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then LiPF6:LiFSI (2:8) was uniformly dissolved in the above solution to obtain an electrolyte. The concentration of lithium salt in the electrolyte was 1 mol / L.

[0123] 5) Assemble the battery

[0124] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative sheets to provide insulation. The cells are then wound to form bare cells, with tabs welded to the cells. The cells are then placed in aluminum shells and baked at 80°C to remove moisture. Electrolyte is then injected and sealed to create an uncharged battery. The uncharged battery then undergoes a series of processes, including resting, hot and cold pressing, formation, shaping, and capacity testing, to produce a lithium-ion battery product.

[0125] Example 21

[0126] Example 21: Referring to step S1 and step S2 of Example 1, a modified nickel-rich ternary positive electrode material C doped with high-valent cations and anions was prepared. Then, referring to the steps of preparing a lithium-ion battery in Example 1, a lithium-ion battery was prepared.

[0127] Example 22

[0128] Example 22: Referring to steps S1 to S3 of Example 1, a modified nickel-rich ternary cathode material D doped with high-valent cations and anions and having a first coating layer of a selenium-containing substance was prepared. Then, referring to the steps for preparing a lithium-ion battery in Example 1, a lithium-ion battery was prepared.

[0129] Comparative Example 1

[0130] In Comparative Example 1, the positive electrode material in the lithium-ion battery is the unmodified nickel-rich ternary positive electrode material NCM in Example 1, and other aspects refer to Example 1.

[0131] Comparative Example 2

[0132] The positive electrode material in the lithium-ion battery of Comparative Example 2 refers to that of Example 1, except that, in Comparative Example 2, only the first coating layer containing selenium is prepared according to step S3 of Example 1, high-valent cations and anions are not doped, and the second coating layer containing conductive material is not prepared.

[0133] Performance testing:

[0134] The 0.33C capacity retention rate (100 cycles), the capacity retention rate (%) after 100 days of storage at 60°C 100% SOC, and the number of days (days) when the gas production at 60°C 100% SOC reaches 0.4 MPa of the lithium-ion batteries obtained in the examples and comparative examples were measured.

[0135] Table 1 Parameter results of Examples 1 to 22 and Comparative Examples 1 to 2

[0136] As can be seen from Table 1, the present application stabilizes the bulk structure of nickel-rich positive electrode materials under lithium intercalation and deintercalation and the interfacial stability with the electrolyte by combining bulk doping of high-valent cations and surface gradient doping of anions, thereby reducing side reactions, lattice oxygen precipitation and transition metal dissolution, thereby improving the cycle stability, high-temperature storage performance and rate performance of lithium-ion batteries. In addition, by preparing a selenium-containing coating layer and a conductive coating layer on the outer surface of the positive electrode material and removing some RLCs, it is possible to prevent the interface stability of the lithium-ion battery from being affected by excessive RCLs content, resulting in a series of side effects such as first effect, deterioration of cycle and storage performance; and the conductive coating layer can prevent the direct contact of selenium-containing substances with the electrolyte, inhibit the occurrence of side reactions, and at the same time, the excellent conductivity of the conductive polymer can enhance the electronic conductivity of the positive electrode material, reduce the interface impedance, and improve the cycle performance of the battery. Therefore, the 0.33C capacity retention rate (100 cycles) of the lithium-ion batteries prepared in Examples 1 to 22 is above 96.5%, the capacity retention rate after 100 days of storage at 60°C 100% SOC is above 91.5%, and the number of days for gas production to reach 0.4 MPa at 60°C 100% SOC is above 220 days.

[0137] In Comparative Example 1, no positive electrode material was modified, and the capacity retention and stability of the lithium-ion battery were poor.

[0138] The positive electrode material in Comparative Example 2 was only prepared with a selenium-containing coating layer, without doping high-valent cations and anions, and without preparing a conductive coating layer. The capacity retention rate and stability of the lithium-ion battery also declined.

[0139] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and within the scope of the technical solution of the present application, embodiments having substantially the same structure as the technical concept and exerting the same effects are all included in the technical scope of the present application. In addition, within the scope of the subject matter of the present application, various modifications that can be conceived by those skilled in the art to the embodiments, and other methods constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A positive electrode material, wherein: The positive electrode material has the following chemical formula: Li a Ni x Co y Mn 1-x-y M b O 2-c Q c , wherein 0.2≤a≤1.2, x≥0.6, y>0, b>0, c>0, M includes high-valent cations, Q includes anions, the high-valent cations include cations with a valence of four or more, the anions include S 2- 、Se 2- 、Te 2- , P 3- At least one of .

2. The positive electrode material according to claim 1, wherein The high-valent cations include Mo 6+ , Sb 5+ 、Zr 4+ 、Ti 4+ , Nb 5+ , W 6+ , Y 5+ 、 5+ At least one of .

3. The positive electrode material according to claim 1 or 2, wherein 0.0005≤b≤0.01, and / or, 0.001≤c≤0.

1.

4. The positive electrode material according to any one of claims 1 to 3, wherein The outer surface of the positive electrode material further includes a first coating layer, and the first coating layer includes a selenium-containing substance.

5. The positive electrode material according to claim 4, wherein The selenium-containing substance includes at least one of elemental selenium (Se), selenium oxide (SeO2), selenium sulfide (SeS2), and tellurium selenide (TeSe).

6. The positive electrode material according to claim 4 or 5, wherein The content of selenium in the positive electrode material comprising the first coating layer is 0.03%-5%.

7. The positive electrode material according to any one of claims 4 to 6, wherein: Based on 100% of the total mass of the positive electrode material, the added amount of the selenium-containing substance ranges from 0.1% to 5%.

8. The positive electrode material according to claim 7, wherein Based on 100% of the total mass of the positive electrode material, the added amount of the selenium-containing substance ranges from 0.5% to 2%.

9. The positive electrode material according to any one of claims 4 to 8, wherein: The particle size Dv50 of the selenium-containing substance is 100nm-1000nm.

10. The positive electrode material according to any one of claims 4 to 9, wherein: The particle size Dv50 of the selenium-containing substance is 100nm-500nm.

11. The positive electrode material according to any one of claims 4 to 10, wherein: The positive electrode material further includes a second coating layer, which is coated on the surface of the first coating layer, and the second coating layer includes a conductive polymer.

12. The positive electrode material according to claim 11, wherein The conductive polymer includes at least one of polyaniline, polypyrrole, polypyridine and polythiophene.

13. The positive electrode material according to claim 11 or 12, wherein The thickness of the second coating layer is 50nm-500nm.

14. The positive electrode material according to claim 13, wherein The thickness of the second coating layer is 50nm-200nm.

15. A method for preparing the positive electrode material according to any one of claims 1 to 3, wherein: The method for preparing the positive electrode material comprises the following steps: Mixing a nickel-rich ternary positive electrode material precursor with a high-valent cation dopant, and sintering to obtain a high-valent cation-doped positive electrode material A, mixing the positive electrode material A with an anion dopant, and sintering to obtain the positive electrode material, which is recorded as positive electrode material C, wherein the positive electrode material C contains high-valent cations and anions, and the high-valent cations include cations with a valence of four or more; or, The method for preparing the positive electrode material comprises the following steps: A nickel-containing positive electrode material precursor is mixed with an anion dopant, and sintered to obtain an anion-doped positive electrode material B. The positive electrode material B is mixed with a high-valent cation dopant, and sintered to obtain the positive electrode material, which is recorded as positive electrode material C. The positive electrode material C contains high-valent cations and anions, and the high-valent cations include cations with a valence of four or more.

16. The method for preparing the positive electrode material according to claim 15, wherein: In the step of preparing the positive electrode material A, the sintering includes primary sintering and secondary sintering, the primary sintering temperature is 350-500°C, the primary sintering time is 2-7h, the secondary sintering temperature is 600-800°C, and the secondary sintering time is 3-6h.

17. The method for preparing the positive electrode material according to claim 15 or 16, wherein: In the step of preparing the positive electrode material B, the sintering temperature is 400°C-650°C.

18. A method for preparing a positive electrode material, wherein: The following steps are involved: The positive electrode material C prepared by any preparation method of claims 15 to 17 and the selenium-containing substance are mixed and heated to obtain the positive electrode material, which is recorded as positive electrode material D. The surface of the positive electrode material D has a coating layer of the selenium-containing substance.

19. The method for preparing the positive electrode material according to claim 18, wherein: The heating temperature is 230°C-500°C; And / or, the heating time is 15min-120min.

20. A method for preparing a positive electrode material, wherein: The following steps are involved: The conductive polymer is dissolved in an organic solvent to obtain a conductive polymer solution, and the conductive polymer solution, an initiator and the positive electrode material D prepared by the preparation method of claim 18 or 19 are mixed for reaction; The positive electrode material is obtained by filtering, washing and drying. The positive electrode material is recorded as positive electrode material E. The surface of the positive electrode material E has a conductive material coating layer.

21. The method for preparing the positive electrode material according to claim 20, wherein: Based on 100% of the total mass of the positive electrode material D, the added amount of the conductive polymer is 0.5%-10%.

22. A lithium ion battery, wherein: The lithium-ion battery comprises the positive electrode material according to any one of claims 1 to 14.

23. An electrical device, wherein: The electrical device comprises the lithium-ion battery of claim 22.

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