Positive electrode material, and preparation method therefor and use thereof

Abstract

A positive electrode material, and a preparation method therefor and the use thereof. The positive electrode material has a core-shell structure, wherein a core layer comprises the elements of Li, Ni, M, Q and O, and a shell layer comprises the elements of X and A; the core layer comprises a transition layer having oxygen vacancies, the oxygen vacancies can be detected by XPS, the XPS peak positions thereof being at 529-533 eV, and the transition layer is close to the shell layer; the element M includes at least one of Co, Mn, and Al; the element Q includes at least one of Mo, Nb, W, Ta, and B; the element X includes at least one of Mo and B; and the element A includes at least one of C, S, and N. The shell layer on a surface of the positive electrode material can improve the electronic conductivity, and the transition layer has oxygen vacancy defects, which can effectively decelerate the trend of oxygen release; and by means of the coordination and cooperation of all the layer structures, the positive electrode material has good structural stability and a high capacity.

Description

Positive electrode material, preparation method and application thereof

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application with application number 202311809967.X filed with the State Intellectual Property Office of China on December 26, 2023, entitled “Positive Electrode Materials, Preparation Methods and Applications Thereof,” the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present invention relates to the field of battery technology, and in particular to a positive electrode material and a preparation method and application thereof. Background Art

[0004] Nickel-containing layered cathode materials have been widely used and have broad application prospects due to their high specific capacity, high energy density, low cost, and good safety. In layered cathode materials with relatively high nickel content, as the voltage increases, the crystal structure undergoes a phase transition and oxygen release begins, leading to rapid deterioration of battery safety and electrical performance. This oxygen release causes the released singlet oxygen to react with the electrolyte, generating large amounts of gas and heat, which further triggers chemical reactions in the battery system and ultimately thermal runaway, resulting in safety accidents. Oxygen release also destroys the crystal structure of the cathode material, rapidly degrading cycle performance and capacity, leading to battery failure. Furthermore, the low electronic conductivity of the cathode material results in a high overpotential during use, causing the cathode material to be subjected to higher voltages and exacerbating oxygen release reactions. This property poses significant challenges to the energy density and cycle life of the cathode material.

[0005] Therefore, a simple, low-cost method to improve the high-voltage stability of cathode materials is urgently needed.

[0006] In view of this, the present invention is proposed.

[0007] Summary of the Invention

[0008] One object of the present invention is to provide a positive electrode material that, through the coordination of various layers, can effectively reduce the overpotential of the positive electrode material, help inhibit the release of oxygen from the positive electrode material under high voltage, and improve the structural stability and capacity of the material.

[0009] Another object of the present invention is to provide a method for preparing the positive electrode material. By coordinating various steps, a transition layer containing oxygen vacancy defects is formed during the coating process, which helps to suppress the oxygen release phenomenon of the positive electrode at high voltage, thereby improving the structural stability and capacity of the battery.

[0010] Another object of the present invention is to provide a positive electrode sheet.

[0011] Another object of the present invention is to provide a battery as described above.

[0012] Another object of the present invention is to provide an electrical device as described above.

[0013] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0014] A cathode material having a core-shell structure, wherein the core layer comprises the elements Li, Ni, M, Q, and O, and the shell layer comprises the elements X and A; the core layer comprises a transition layer having oxygen vacancies, and the oxygen vacancies can be detected by XPS, and the XPS peak position is located at 529-533 eV, and the transition layer is close to the shell layer;

[0015] The element M includes at least one of Co, Mn and Al, the element Q includes at least one of Mo, Nb, W, Ta and B, the element X includes at least one of Mo and B, and the element A includes at least one of C, S and N.

[0016] In one embodiment, the chemical formula of the positive electrode material is Li q Ni a M b Q c X h A k O 2-d , where 1 <q<1.56,0.25<a<0.98,0.02<b<0.75,0<c<0.1,0<h<0.1,0<k<h,0<d<h+k。

[0017] In one embodiment, the thickness of the transition layer is 0.01 to 100 nm extending inward from the outer surface of the core layer.

[0018] In one embodiment, the diameter of the core layer is 2.5 to 10 μm, and the thickness of the shell layer is 0.1 to 500 nm.

[0019] A method for preparing a positive electrode material comprises the following steps:

[0020] subjecting a first mixture of a precursor material, a compound containing element Q, and a lithium source to a first heat treatment to obtain a first material; subjecting the first material to a second mixture of a compound containing element X and a compound containing element A to a second heat treatment;

[0021] The precursor material includes a hydroxide containing elements Ni and M, the element M includes at least one of Co, Mn and Al; the element Q includes at least one of Mo, Nb, W, Ta and B; the element X includes at least one of Mo and B; and the element A includes at least one of C, S and N.

[0022] In one embodiment, the chemical formula of the precursor material is Ni r M j (OH)2, of which 0.3 <i<0.98,0.02<j<0.7。

[0023] In one embodiment, the D50 particle size of the precursor material is 2.5 to 15 μm, and the specific surface area of ​​the precursor material is 10 to 35 m 2 / g.

[0024] In one embodiment, the molar ratio of the lithium element in the lithium source, the precursor material and the element Q in the compound containing the element Q is (1-1.56):1:x1,0 <x1<0.1。

[0025] In one embodiment, the compound containing element Q includes at least one of an oxide of element Q and a hydroxide of element Q.

[0026] In one embodiment, the compound containing element X includes at least one of element X nitride, element X sulfide, and element X oxide.

[0027] In one embodiment, the molar ratio of the lithium source, the compound containing element X and the compound containing element A is (1-1.56):x2:x3, calculated as lithium element, X element and A element, respectively. <x2<0.1,0<x3<x2。

[0028] In one embodiment, the first mixture and the second mixture are obtained by independently using at least one of a grinding device, a high mixing device and a ploughshare mixing device.

[0029] In one embodiment, the first heat treatment includes calcination treatment in at least two constant temperature sections, and the temperatures of the multiple constant temperature sections increase gradually.

[0030] In one embodiment, the second heat treatment includes a sintering process in at least one constant temperature section, and the temperatures of the multiple constant temperature sections are gradually increased.

[0031] In one embodiment, the first heat treatment includes a first sintering treatment and a second sintering treatment; the temperature of the first sintering treatment is 400-600°C, and the time of the first sintering treatment is 0.5-5 hours; the temperature of the second sintering treatment is 700-900°C, and the time of the second sintering treatment is 5-15 hours.

[0032] In one embodiment, the first heat treatment includes a first sintering treatment and a second sintering treatment; the heating rates of the first sintering treatment and the second sintering treatment are independently 3 to 10° C. / min.

[0033] In one embodiment, the first heat treatment is performed in an atmosphere containing oxygen.

[0034] In one embodiment, the second heat treatment includes a third sintering treatment, a fourth sintering treatment and a fifth sintering treatment; the temperature of the third sintering treatment is 100-300°C, and the time of the third sintering treatment is 0.5-3 hours; the temperature of the fourth sintering treatment is 320-450°C, and the time of the fourth sintering treatment is 1-4 hours; the temperature of the fifth sintering treatment is 500-700°C, and the time of the fourth sintering treatment is 3-8 hours.

[0035] In one embodiment, the second heat treatment includes a third sintering treatment, a fourth sintering treatment, and a fifth sintering treatment; the heating rates of the third sintering treatment, the fourth sintering treatment, and the fifth sintering treatment are each independently 3-10° C. / min.

[0036] In one embodiment, the sintering atmosphere of the second heat treatment includes nitrogen or an atmosphere containing oxygen.

[0037] A positive electrode sheet comprises the positive electrode material, or the positive electrode material prepared by the positive electrode material preparation method.

[0038] A battery comprises the positive electrode sheet.

[0039] An electrical device comprises the battery.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) The positive electrode material of the present invention has a surface shell layer that can improve electronic conductivity, and the transition layer has oxygen vacancy defects that can effectively reduce the tendency of oxygen release; at the same time, the shell layer can effectively reduce the overpotential of the positive electrode material, which helps to further suppress the oxygen release of the positive electrode material under high voltage; through the coordinated cooperation of the various layer structures, the positive electrode material has excellent structural stability and high capacity.

[0042] (2) The preparation method of the positive electrode material of the present invention is beneficial to improving the electrochemical performance of the positive electrode material through the coordination of various raw materials and steps; by coating the first material, the electronic conductivity of the layered positive electrode material can be effectively improved, the overpotential of the positive electrode material can be reduced, and the capacity and structural stability can be improved; at the same time, the transition layer containing oxygen vacancy defects formed can help to suppress the oxygen release phenomenon of the positive electrode under high voltage, thereby improving the structural stability and capacity.

[0043] (3) The battery of the present invention has excellent reversible capacity and cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0045] FIG1 is a scanning electron microscope image of the positive electrode material in Example 1 of the present invention;

[0046] FIG2 is a scanning electron microscope image of the positive electrode material in Comparative Example 1 of the present invention;

[0047] FIG3 is an X-ray photoelectric spectrum of the positive electrode material of Example 3 of the present invention;

[0048] FIG4 is an X-ray photoelectric spectrum of the positive electrode material of Comparative Example 1 of the present invention;

[0049] FIG5 is an X-ray diffraction diagram of Example 1 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0050] The embodiments of the present invention will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present invention and should not be construed as limiting the scope of the invention. Where specific conditions are not specified in the examples, the methods were performed according to conventional conditions or the conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments are not specified, they are all commercially available conventional products.

[0051] According to one aspect of the present invention, the present invention relates to a positive electrode material, wherein the positive electrode material has a core-shell structure, wherein the core layer includes the elements Li, Ni, M, Q and O, and the shell layer includes the elements X and A; the core layer includes a transition layer having oxygen vacancies, and the oxygen vacancies can be detected by XPS, and the XPS peak position is located at 529-533 eV, and the transition layer is close to the shell layer;

[0052] Among them, element M includes at least one of Co, Mn, and Al, element Q includes at least one of Mo, Nb, W, Ta, and B, element X includes at least one of Mo and B, and element A includes at least one of C, S, and N.

[0053] For the cathode material of the present invention, the surface shell layer can improve the electronic conductivity, and the transition layer has oxygen vacancy defects, which can effectively reduce the oxygen release tendency; at the same time, the shell layer can effectively reduce the overpotential of the cathode material, which helps to further inhibit the oxygen release problem of the cathode material under high voltage.

[0054] The improvement of the electronic conductivity of the cathode material can be obtained by powder pressing and testing the resistance of the pressed powder. The oxygen vacancies in the transition layer of the cathode material can be obtained by XPS testing and analyzing the peak position of oxygen.

[0055] In one embodiment, the carbon element includes at least one of graphite and amorphous carbon.

[0056] In one embodiment, the chemical formula of the cathode material is Li q Ni a M b Q c X h A k O 2-d where 1 < q < 1.56, 0.25 < a < 0.98, 0.02 < b < 0.75, 0 < c < 0.1, 0 < h < 0.1, 0 < k < h, 0 < d < h + k. In one embodiment, the value of q includes but is not limited to 1.05, 1.1, 1.2, 1.3, 1.4, 1.45, or 1.5, etc.; the value of a includes but is not limited to 0.28, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, etc.; the value of b includes but is not limited to 0.03, 0.05, 0.06, or 0.07, etc.; c includes but is not limited to 0.01, 0.02, 0.03, 0.05, 0.06, 0.07, or 0.08, etc.; the value of h includes but is not limited to 0.01, 0.02, 0.03, 0.05, 0.06, 0.08, 0.09, 0.098, etc.; the value of k includes but is not limited to 0.008, 0.01, 0.02, 0.03, 0.05, 0.06, 0.08, 0.09, etc.; the value of d includes but is not limited to 0.01, 0.02, 0.03, 0.05, 0.06, 0.08, 0.09, 0.1, 0.11, etc.

[0057] In one embodiment, the region of the transition layer is such that the outer surface of the core layer extends inward by 0.01 to 100 nm, including but not limited to 0.1 nm, 0.5 nm, 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 50 nm, 60 nm, 80 nm, 100 nm, etc. In one embodiment, the thickness of the transition layer is 1 to 100 nm. The present invention is more conducive to suppressing the oxygen evolution phenomenon of the positive electrode under high voltage and improving the structural stability and capacity performance through the transition layer region with an appropriate thickness.

[0058] In one embodiment, the diameter of the core layer is 2.5 to 10 μm, such as 2.5 μm, 5 μm, 6 μm, 8 μm, 10 μm, etc.; the thickness of the shell layer is 0.1 to 500 nm, such as 0.1 nm, 10 nm, 40 nm, 50 nm, 100 nm, 200 nm, 300 nm, 500 nm, etc.

[0059] According to another aspect of the present invention, the present invention also relates to a method for preparing a positive electrode material, comprising the following steps:

[0060] Performing a first heat treatment on a first mixture of a precursor material, a compound containing element Q, and a lithium source to obtain a first material; performing a second heat treatment on the first material and a second mixture of a compound containing element X and a compound containing element A;

[0061] The precursor material includes a hydroxide containing elements Ni and M, and element M includes at least one of Co, Mn, and Al; element Q includes at least one of Mo, Nb, W, Ta, and B; element X includes at least one of Mo and B; element A includes at least one of C, S, and N.

[0062] The method for preparing the positive electrode material of the present invention is conducive to improving the electrochemical performance of the positive electrode material through the cooperation of various raw materials and steps; through the coating of the first material, the electronic conductivity of the layered positive electrode material can be effectively improved, the overpotential of the positive electrode material can be reduced, which helps to improve the capacity performance and structural stability; at the same time, the formed transition layer containing oxygen vacancy defects helps to suppress the oxygen evolution phenomenon of the positive electrode under high voltage and improve the structural stability and capacity performance.

[0063] In one embodiment, the chemical formula of the precursor material is Ni r M j (OH)2, where 0.3 < i < 0.98 and 0.02 < j < 0.7. In one embodiment, the value of i includes but is not limited to 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, etc.; the value of j includes but is not limited to 0.02, 0.05, 0.08, 0.1, 0.2, 0.3, 0.4, 0.5, or 0.6, etc.

[0064] In one embodiment, the D50 particle size of the precursor material is 2.5 to 15 μm, including but not limited to 2.5 μm, 3 μm, 5 μm, 6 μm, 7 μm, 8 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm, etc. The specific surface area of the precursor material is 10 to 35 m 2 / g, including but not limited to 10 m 2 / g, 12 m 2 / g, 15 m 2 / g, 18 m 2 / g, 20 m 2 / g, 25 m 2 / g, 30 m 2 / g, 35 m 2 / g, etc. The precursor material of the present invention has appropriate particle size and specific surface area, which is more conducive to improving the structural stability and capacity of the finally obtained cathode material.

[0065] In one embodiment, the molar ratio of lithium element in the lithium source, element Q in the precursor material and element Q in the compound containing element Q is (1 to 1.56):1:x1, where 0 < x1 < 0.1, such as 1.1:1:0.01, 1.3:1:0.05, 1.5:1:0.08, etc. In one embodiment, the compound containing element Q includes at least one of an oxide of element Q and a hydroxide of element Q. In one embodiment, the compound containing element X includes at least one of a nitride of element X, a sulfide of element X and an oxide of element X. For example, boron nitride, molybdenum sulfide, etc.

[0066] In one embodiment, the molar ratio of the lithium source, the compound containing element X and the compound containing element A in terms of lithium element, X element and A element respectively is (1 to 1.56):x2:x3, where 0 < x2 < 0.1 and 0 < x3 < x2.

[0067] In one embodiment, the obtaining of the first mixture and the obtaining of the second mixture are each independently carried out by using at least one of a grinding device, a high-speed mixing device and a plow blade mixing device. The high-speed mixing device is a high-speed mixer, also called a plastic high-speed mixer, which has the functions of high-speed mixing and heating and can uniformly mix the materials. The plow blade mixing device is a plow blade mixer. The plow blades inside it rotate with the main shaft to make the materials move in a radial circular turbulent motion along the cylinder wall. At the same time, the radial materials flow along the line through the flying knife group and are scattered by the high-speed rotating flying knives, constantly changing and compounding, so that the materials can reach uniform mixing in a relatively short time. Through the cooperation of one or more of the above devices, the first mixture and the second mixture obtained in the present invention can be made more uniform and have appropriate particle size.

[0068] In one embodiment, the first heat treatment includes calcination treatment in at least two constant temperature sections, wherein the temperature of the multiple constant temperature sections increases gradually. The sintering treatment with multiple increasing constant temperature sections ensures more complete crystal growth of the first material.

[0069] In one embodiment, the first heat treatment includes a first sintering treatment and a second sintering treatment; the temperature of the first sintering treatment is 400-600°C, for example, 400°C, 450°C, 480°C, 500°C, 550°C, 600°C, etc.; the time of the first sintering treatment is 0.5-5h, for example, 0.5h, 1h, 1.5h, 2h, 3h, 4h or 5h, etc.; the temperature of the second sintering treatment is 700-900°C, for example, 700°C, 720°C, 750°C, 800°C, 820°C, 850°C, 880°C or 900°C, etc.; the time of the second sintering treatment is 5-15h, for example, 5h, 6h, 7h, 8h, 10h, 12h or 15h, etc. The heating rates of the first sintering treatment and the second sintering treatment are independently 3 to 10°C / min, for example, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 10°C / min, etc. The first heat treatment is performed in an atmosphere containing oxygen, such as an oxygen atmosphere or an air atmosphere. By adopting appropriate first treatment conditions, the present invention ensures the dispersibility of the first material and the integrity of the crystal structure, laying a good foundation for subsequently obtaining a positive electrode material with even better electrochemical performance.

[0070] In one embodiment, the second heat treatment includes at least one constant temperature section sintering process, wherein the temperature of the multiple constant temperature sections is gradually increased. The electrochemical performance of the final cathode material is ensured by the sintering process of the multiple gradually increasing constant temperature sections.

[0071] In one embodiment, the second heat treatment includes a third sintering treatment, a fourth sintering treatment, and a fifth sintering treatment; the temperature of the third sintering treatment is 100-300°C, including but not limited to 100°C, 120°C, 150°C, 180°C, 200°C, 220°C, 250°C, or 300°C; the time of the third sintering treatment is 0.5-3 hours, including but not limited to 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, etc. The temperature of the fourth sintering treatment is 320°C-450°C, including but not limited to 320°C, 350°C, 370°C, 380°C, 400°C, 410°C, 420°C, 430°C, 450°C, etc.; the time of the fourth sintering treatment is 1-4 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, etc. The temperature of the fifth sintering treatment is 500-700°C, including but not limited to 500°C, 520°C, 550°C, 600°C, 650°C, 680°C, 700°C, etc. The time of the fourth sintering treatment is 3-8h, for example, the time of the fourth sintering treatment is 3h, 4h, 5h, 6h, 7h or 8h, etc. The heating rates of the third sintering treatment, the fourth sintering treatment and the fifth sintering treatment are each independently 3-10°C / min, for example, 3°C / min, 4°C / min, 5°C / min, 8°C / min, 10°C / min, etc. The sintering atmosphere of the second heat treatment includes nitrogen or an oxygen-containing atmosphere, and the oxygen-containing atmosphere includes an oxygen atmosphere or an air atmosphere. The present invention adopts a second heat treatment under appropriate conditions to ensure better coating and form bulk oxygen vacancy defects, which can effectively inhibit the oxygen release reaction of the positive electrode material under high pressure and improve the reversible capacity and cycle stability of the positive electrode material.

[0072] According to another aspect of the present invention, the present invention relates to a positive electrode sheet, comprising the positive electrode material, or the positive electrode material prepared by the method for preparing the positive electrode material.

[0073] In one embodiment, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer disposed on at least one side of the positive electrode current collector; the positive electrode material layer includes the above-mentioned positive electrode material, a conductive agent, and a binder; the mass ratio of the positive electrode material, the conductive agent, and the binder is (92-96): (2-4): (2-4). The conductive agent includes conductive carbon black, etc., and the binder includes polyvinylidene fluoride (PVDF).

[0074] According to another aspect of the present invention, the present invention also relates to a battery, comprising the positive electrode sheet.

[0075] The battery of the present invention has excellent reversible capacity and cycle stability.

[0076] In one embodiment, the battery includes the above-mentioned positive electrode sheet, negative electrode sheet, separator and electrolyte.

[0077] According to another aspect of the present invention, the present invention also relates to an electric device comprising the battery, such as an electric vehicle, a household appliance, and the like.

[0078] The following is further explained with reference to specific embodiments and comparative examples.

[0079] Example 1

[0080] A method for preparing a positive electrode material comprises the following steps:

[0081] (1) 1000g of Ni 0.35 Co 0.65 OH)2 was mixed with 4g tungsten oxide and 640g lithium hydroxide monohydrate by a plowshare mixer to obtain a first mixture at a speed of 1000r / min and a mixing time of 40min. 0.35 Co 0.65 The D50 particle size of (OH)2 is 10 μm, and the specific surface area of ​​the precursor material is 30 m 2 / g.

[0082] (2) The first mixture is placed in an oxygen atmosphere furnace and subjected to the first sintering and the second sintering in sequence. The temperature of the first sintering is 500°C, the time of the first sintering is 4 hours, and the heating rate is 3°C / min. The temperature of the second sintering is 900°C, the time of the second sintering is 15 hours, and the heating rate is 3°C / min. After the sintering is completed and the mixture is cooled to room temperature, it is crushed and sieved to obtain the first material.

[0083] (3) 1000 g of the first material was mixed evenly with 1 g of boron nitride, 1 g of molybdenum sulfide and 2 g of glucose using a plowshare mixer at a speed of 1000 r / min for 30 min to obtain a second mixture.

[0084] (4) The second mixture was placed in a heating furnace in a nitrogen atmosphere for a third sintering process at a temperature of 200°C, a time of 1 hour, and a heating rate of 3°C / min. The temperature was then raised to 350°C for a fourth sintering process at a time of 3 hours and a heating rate of 3°C / min. Finally, the temperature was raised to 700°C for a fifth sintering process at a time of 8 hours and a heating rate of 3°C / min. The sintered material was crushed and sieved to obtain a layered positive electrode material with surface coating and controlled bulk oxygen vacancy concentration.

[0085] Example 2

[0086] A method for preparing a positive electrode material comprises the following steps:

[0087] (1) 1000g of Ni 0.35 Co0.65 (OH)2 was mixed with 4g tungsten oxide and 640g lithium hydroxide monohydrate by a plowshare mixer to obtain a first mixture at a speed of 1000r / min and a mixing time of 40min. 0.35 Co 0.65 The D50 particle size of (OH)2 is 10 μm, and the specific surface area of ​​the precursor material is 30 m 2 / g.

[0088] (2) The first mixture is placed in an oxygen atmosphere furnace and subjected to the first sintering and the second sintering in sequence. The temperature of the first sintering is 500°C, the time of the first sintering is 4 hours, and the heating rate is 3°C / min. The temperature of the second sintering is 900°C, the time of the second sintering is 15 hours, and the heating rate is 3°C / min. After the sintering is completed and the mixture is cooled to room temperature, it is crushed and sieved to obtain the first material.

[0089] (3) 1000 g of the first material was mixed evenly with 1 g of boron nitride, 2 g of molybdenum sulfide and 6 g of glucose using a plowshare mixer at a speed of 1000 r / min for 30 min to obtain a second mixture.

[0090] (4) The second mixture was placed in a heating furnace in a nitrogen atmosphere for a third sintering process at a temperature of 200°C, a time of 1 hour, and a heating rate of 3°C / min. The temperature was then raised to 350°C for a fourth sintering process at a time of 3 hours and a heating rate of 3°C / min. Finally, the temperature was raised to 400°C for a fifth sintering process at a time of 8 hours and a heating rate of 3°C / min. The sintered material was crushed and sieved to obtain a layered positive electrode material with surface coating and controlled bulk oxygen vacancy concentration.

[0091] Example 3

[0092] A method for preparing a positive electrode material comprises the following steps:

[0093] (1) 1000g of Ni 0.35 Co 0.65 (OH)2 was mixed with 4g tungsten oxide and 640g lithium hydroxide monohydrate by a plowshare mixer to obtain a first mixture at a speed of 1000r / min and a mixing time of 40min. 0.35 Co 0.65 The D50 particle size of (OH)2 is 10 μm, and the specific surface area of ​​the precursor material is 30 m 2 / g.

[0094] (2) The first mixture is placed in an oxygen atmosphere furnace and subjected to the first sintering and the second sintering in sequence. The temperature of the first sintering is 500°C, the time of the first sintering is 4 hours, and the heating rate is 3°C / min. The temperature of the second sintering is 900°C, the time of the second sintering is 15 hours, and the heating rate is 3°C / min. After the sintering is completed and the mixture is cooled to room temperature, it is crushed and sieved to obtain the first material.

[0095] (3) 1000 g of the first material was mixed evenly with 1 g of molybdenum sulfide and 2 g of glucose using a plowshare mixer at a speed of 1000 r / min for 30 min to obtain a second mixture.

[0096] (4) The second mixture was placed in a heating furnace in a nitrogen atmosphere for a third sintering process at a temperature of 200°C, a time of 1 hour, and a heating rate of 3°C / min. The temperature was then raised to 350°C for a fourth sintering process at a time of 3 hours and a heating rate of 3°C / min. Finally, the temperature was raised to 400°C for a fifth sintering process at a time of 8 hours and a heating rate of 3°C / min. The sintered material was crushed and sieved to obtain a layered positive electrode material with surface coating and controlled bulk oxygen vacancy concentration.

[0097] Example 4

[0098] A method for preparing a positive electrode material comprises the following steps:

[0099] (1) 1000g of Ni 0.35 Co 0.65 (OH)2 was mixed with 4g tungsten oxide and 640g lithium hydroxide monohydrate by a plowshare mixer to obtain a first mixture at a speed of 1000r / min and a mixing time of 40min. 0.35 Co 0.65 The D50 particle size of (OH)2 is 10 μm, and the specific surface area of ​​the precursor material is 30 m 2 / g.

[0100] (2) The first mixture is placed in an oxygen atmosphere furnace and subjected to the first sintering and the second sintering in sequence. The temperature of the first sintering is 500°C, the time of the first sintering is 4 hours, and the heating rate is 3°C / min. The temperature of the second sintering is 900°C, the time of the second sintering is 15 hours, and the heating rate is 3°C / min. After the sintering is completed and the mixture is cooled to room temperature, it is crushed and sieved to obtain the first material.

[0101] (3) 1000 g of the first material, 1 g of boron nitride, and 2 g of glucose were uniformly mixed using a plowshare mixer at a speed of 1000 r / min for 30 min to obtain a second mixture.

[0102] (4) The second mixture was placed in a heating furnace in a nitrogen atmosphere for a third sintering process at a temperature of 200°C, a time of 1 hour, and a heating rate of 3°C / min. The temperature was then raised to 350°C for a fourth sintering process at a time of 3 hours and a heating rate of 3°C / min. Finally, the temperature was raised to 400°C for a fifth sintering process at a time of 8 hours and a heating rate of 3°C / min. The sintered material was crushed and sieved to obtain a layered positive electrode material with surface coating and controlled bulk oxygen vacancy concentration.

[0103] Example 5

[0104] A method for preparing a positive electrode material comprises the following steps:

[0105] (1) 1000g of Ni 0.35 Co 0.65 (OH)2 was mixed with 3g niobium oxide, 1g tantalum oxide and 640g lithium hydroxide monohydrate by a plow mixer to obtain a first mixture at a speed of 1000r / min and a mixing time of 40min. 0.35 Co 0.65 The D50 particle size of (OH)2 is 10 μm, and the specific surface area of ​​the precursor material is 30 m 2 / g.

[0106] (2) The first mixture is placed in an oxygen atmosphere furnace and subjected to the first sintering and the second sintering in sequence. The temperature of the first sintering is 500°C, the time of the first sintering is 4 hours, and the heating rate is 3°C / min. The temperature of the second sintering is 900°C, the time of the second sintering is 15 hours, and the heating rate is 3°C / min. After the sintering is completed and the mixture is cooled to room temperature, it is crushed and sieved to obtain the first material.

[0107] (3) 1000 g of the first material was mixed evenly with 1 g of boron nitride, 1 g of molybdenum sulfide and 2 g of glucose using a plowshare mixer at a speed of 1000 r / min for 30 min to obtain a second mixture.

[0108] (4) The second mixture was placed in a heating furnace in a nitrogen atmosphere for a third sintering process at a temperature of 200°C, a time of 1 hour, and a heating rate of 3°C / min. The temperature was then raised to 350°C for a fourth sintering process at a time of 3 hours and a heating rate of 3°C / min. Finally, the temperature was raised to 400°C for a fifth sintering process at a time of 8 hours and a heating rate of 3°C / min. The sintered material was crushed and sieved to obtain a layered positive electrode material with surface coating and controlled bulk oxygen vacancy concentration.

[0109] Example 6

[0110] A method for preparing a positive electrode material comprises the following steps:

[0111] (1) 1000g of Ni 0.35 Mn 0.65 (OH)2 and 640g of lithium hydroxide monohydrate were mixed uniformly by a plowshare mixer to obtain a first mixture at a speed of 900r / min and a mixing time of 60min. 0.35 Co 0.65 The D50 particle size of (OH)2 is 8 μm, and the specific surface area of ​​the precursor material is 32 m 2 / g.

[0112] (2) The first mixture is placed in an oxygen atmosphere furnace and subjected to a first sintering and a second sintering in sequence. The temperature of the first sintering is 400°C, the time of the first sintering is 5 hours, and the heating rate is 5°C / min. The temperature of the second sintering is 700°C, the time of the second sintering is 15 hours, and the heating rate is 5°C / min. After sintering is completed and cooled to room temperature, the mixture is crushed and sieved to obtain the first material.

[0113] (3) 1000 g of the first material was mixed evenly with 1 g of boron nitride, 1 g of molybdenum sulfide and 2 g of glucose using a plowshare mixer at a speed of 900 r / min for 50 min to obtain a second mixture.

[0114] (4) The second mixture was placed in a heating furnace in a nitrogen atmosphere for a third sintering process at a temperature of 100°C, a time of 3 hours, and a heating rate of 5°C / min. The mixture was then heated to 400°C for a fourth sintering process at a time of 0.5 hours and a heating rate of 5°C / min. Finally, the mixture was heated to 600°C for a fifth sintering process at a time of 5 hours and a heating rate of 5°C / min. The sintered material was crushed and sieved to obtain a layered positive electrode material with surface coating and controlled bulk oxygen vacancy concentration.

[0115] Example 7

[0116] A method for preparing a positive electrode material comprises the following steps:

[0117] (1) 1000g of Ni 0.35 Mn 0.65 (OH)2 and 640g of lithium hydroxide monohydrate were mixed uniformly by a plowshare mixer to obtain a first mixture at a rotation speed of 1100r / min and a mixing time of 30min. 0.35 Mn 0.65 The D50 particle size of (OH)2 is 12 μm, and the specific surface area of ​​the precursor material is 28 m 2 / g.

[0118] (2) The first mixture is placed in an oxygen atmosphere furnace and subjected to a first sintering and a second sintering in sequence. The temperature of the first sintering is 600°C, the time of the first sintering is 0.5h, and the heating rate is 5°C / min; the temperature of the second sintering is 900°C, the time of the second sintering is 5h, and the heating rate is 5°C / min. After sintering is completed and cooled to room temperature, the mixture is crushed and sieved to obtain the first material.

[0119] (3) 1000 g of the first material was mixed evenly with 1 g of boron nitride, 1 g of molybdenum sulfide and 2 g of glucose using a plowshare mixer at a speed of 900 r / min for 50 min to obtain a second mixture.

[0120] (4) The second mixture was placed in a heating furnace in a nitrogen atmosphere for a third sintering process at a temperature of 300°C, a time of 3 hours, and a heating rate of 5°C / min. The temperature was then raised to 480°C for a fourth sintering process at a time of 0.5 hours and a heating rate of 5°C / min. Finally, the temperature was raised to 700°C for a fifth sintering process at a time of 3 hours and a heating rate of 5°C / min. The sintered material was crushed and sieved to obtain a layered positive electrode material with surface coating and controlled bulk oxygen vacancy concentration.

[0121] Comparative Example 1

[0122] The method for preparing a positive electrode material comprises the following steps:

[0123] (1) 1000g of Ni 0.35 Mn 0.65 (OH)2 and 640g of lithium hydroxide monohydrate were mixed uniformly by a plowshare mixer to obtain a first mixture at a rotation speed of 1100r / min and a mixing time of 30min. 0.35 Mn 0.65 The D50 particle size of (OH)2 is 12 μm, and the specific surface area of ​​the precursor material is 28 m 2 / g.

[0124] (2) The first mixture is placed in an oxygen atmosphere furnace and subjected to a first sintering and a second sintering in sequence. The temperature of the first sintering is 600°C, the time of the first sintering is 0.5h, and the heating rate is 5°C / min; the temperature of the second sintering is 900°C, the time of the second sintering is 5h, and the heating rate is 5°C / min. After sintering is completed and cooled to room temperature, the mixture is crushed and sieved to obtain the first material.

[0125] Comparative Example 2

[0126] The method for preparing a positive electrode material comprises the following steps:

[0127] (1) 1000g of Ni 0.35 Co0.65 (OH)2 was mixed with 4g tungsten oxide and 640g lithium hydroxide monohydrate by a plowshare mixer to obtain a first mixture at a speed of 1000r / min and a mixing time of 40min. 0.35 Co 0.65 The D50 particle size of (OH)2 is 10 μm, and the specific surface area of ​​the precursor material is 30 m 2 / g.

[0128] (2) The first mixture is placed in an oxygen atmosphere furnace and subjected to the first sintering and the second sintering in sequence. The temperature of the first sintering is 500°C, the time of the first sintering is 4 hours, and the heating rate is 3°C / min. The temperature of the second sintering is 900°C, the time of the second sintering is 15 hours, and the heating rate is 3°C / min. After the sintering is completed and the mixture is cooled to room temperature, it is crushed and sieved to obtain the first material.

[0129] (3) 1000 g of the first material and 2 g of glucose were mixed uniformly using a plowshare mixer at a speed of 1000 r / min for 30 min to obtain a second mixture.

[0130] (4) The second mixture was placed in a heating furnace under a nitrogen atmosphere for a third sintering process at a temperature of 200°C, a time of 1 hour, and a heating rate of 3°C / min. The temperature was then raised to 350°C for a fourth sintering process at a time of 3 hours and a heating rate of 3°C / min. Finally, the temperature was raised to 700°C for a fifth sintering process at a time of 8 hours and a heating rate of 3°C / min. The sintered material was crushed and sieved to obtain the positive electrode material.

[0131] Comparative Example 3

[0132] The method for preparing a positive electrode material comprises the following steps:

[0133] (1) 1000g of Ni 0.35 Co 0.65 (OH)2 was mixed with 4g tungsten oxide and 640g lithium hydroxide monohydrate by a plowshare mixer to obtain a first mixture at a speed of 1000r / min and a mixing time of 40min. 0.35 Co 0.65 The D50 particle size of (OH)2 is 10 μm, and the specific surface area of ​​the precursor material is 30 m 2 / g.

[0134] (2) The first mixture is placed in an oxygen atmosphere furnace and subjected to the first sintering and the second sintering in sequence. The temperature of the first sintering is 500°C, the time of the first sintering is 4 hours, and the heating rate is 3°C / min. The temperature of the second sintering is 900°C, the time of the second sintering is 15 hours, and the heating rate is 3°C / min. After the sintering is completed and the mixture is cooled to room temperature, it is crushed and sieved to obtain the first material.

[0135] (3) 1000 g of the first material, 1 g of boron nitride, and 1 g of molybdenum sulfide were mixed uniformly using a plow mixer at a speed of 1000 r / min for 30 min to obtain a second mixture.

[0136] (4) The second mixture was placed in a heating furnace under a nitrogen atmosphere for a third sintering process at a temperature of 200°C, a time of 1 hour, and a heating rate of 3°C / min. The temperature was then raised to 350°C for a fourth sintering process at a time of 3 hours and a heating rate of 3°C / min. Finally, the temperature was raised to 700°C for a fifth sintering process at a time of 8 hours and a heating rate of 3°C / min. The sintered material was crushed and sieved to obtain the positive electrode material.

[0137] Experimental example

[0138] 1. Graph Analysis

[0139] The morphology of the positive electrode materials prepared in Example 1 and Comparative Example 1 was characterized by scanning electron microscopy. The scanning electron microscope image of the positive electrode material in Example 1 is shown in Figure 1, and the scanning electron microscope image of the positive electrode material in Comparative Example 1 is shown in Figure 2. It can be seen that the surface of the positive electrode material in Example 1 of the present invention is relatively uniform, and no modified layer precipitation is found.

[0140] The X-ray photoelectric spectrum (XPS spectrum) of the positive electrode material of Example 3 of the present invention is shown in Figure 3, and the X-ray photoelectric spectrum of the positive electrode material of Comparative Example 1 of the present invention is shown in Figure 4; it can be seen that in the untreated positive electrode material of Comparative Example 1, the surface oxygen vacancy content is only 31.1%, while after treatment, the oxygen vacancy content in Example 3 reaches 47.5%, indicating that after treatment, the surface oxygen vacancy content is significantly increased.

[0141] FIG5 shows the X-ray diffraction (XRD) patterns of Example 1 and Comparative Example 1. The XRD patterns of the two cathode materials are consistent, indicating that the cathode material of the present invention has a lower surface modification layer content and no XRD-detectable segregation or agglomeration in the modified layer. This demonstrates the uniformity of the surface modification.

[0142] 2. Electronic conductivity test of positive electrode materials

[0143] The positive electrode material to be tested is placed in a mold, a pressure of 200 MPa is applied, and after holding the pressure for 3 minutes, the resistance is measured using an instrument to characterize the electronic conductivity of the material. After oxygen vacancy treatment, the resistance decreases, indicating an increase in electronic conductivity. After adding a carbon source such as glucose, the resistance further decreases, indicating a further increase in conductivity. In terms of heat treatment temperature, excessively high treatment temperature causes a significant increase in resistance, indicating a significant decrease in electronic conductivity.

[0144] The test results are shown in Table 1.

[0145] Table 1 Test results of electronic conductivity of positive electrode materials

[0146] 3. Battery performance test

[0147] The positive electrode materials obtained in the examples and comparative examples were used to prepare button batteries. The button battery preparation method includes: preparing the positive electrode material: conductive agent: PVDF in a mass ratio of 95:3:2, mixing with a solvent to obtain a positive electrode slurry, applying the positive electrode slurry to the surface of the positive electrode current collector, and drying to obtain a positive electrode sheet; and assembling an LR2032 button battery using lithium metal as the negative electrode sheet, commercial celgard as the separator, and EC, DC, and DMC (volume ratio of 1:1:1) as the electrolyte.

[0148] The assembled button battery was charged and discharged at a constant current of 0.3C in a voltage range of 2.5V to 4.25V for 50 cycles at a constant temperature of 45°C. The test results are shown in Table 2.

[0149] Table 2 Battery performance test results

[0150] As shown in Table 2, after surface coating modification, the positive electrode material's first-cycle charge capacity decreases due to the formation of oxygen vacancies. At the same time, the use of a high-conductivity coating layer, combined with the oxygen vacancies' inhibitory effect on lattice oxygen release, increases the reversible capacity, discharge capacity, and first-cycle coulombic efficiency. Furthermore, the protective effect of the oxygen vacancy transition layer also improves cycling performance. The batteries obtained with the positive electrode materials of Comparative Examples 1-3 exhibited poor reversible capacity and cycling stability.

[0151] In summary, the positive electrode material in the present invention can improve the electronic conductivity of the positive electrode material by coating with a high electronic conductivity material. At the same time, during the coating process, the coating layer reacts with the positive electrode material matrix at high temperature to form bulk oxygen vacancy defects, which effectively inhibits the oxygen release reaction of the positive electrode material under high pressure, thereby improving the reversible capacity and cycle stability of the positive electrode material.

[0152] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cathode material, characterized in that, The positive electrode material has a core-shell structure. The core layer includes elements Li, Ni, M, Q, and O, and the shell layer includes elements X and A. The core layer includes a transition layer with oxygen vacancies, and the oxygen vacancies can be detected by XPS, and its XPS peak position is located at 529 - 533 eV. The transition layer is close to the shell layer. Among them, element M includes at least one of Co, Mn, and Al, element Q includes at least one of Mo, Nb, W, Ta, and B, element X includes at least one of Mo and B, and element A includes at least one of C, S, and N.

2. The cathode material according to claim 1, wherein It includes at least one of the following features (1) to (3): (1) The chemical formula of the positive electrode material is Li q Ni a M b Q c X h A k O 2-d , where 1 < q < 1.56, 0.25 < a < 0.98, 0.02 < b < 0.75, 0 < c < 0.1, 0 < h < 0.1, 0 < k < h, 0 < d < h + k; (2) The thickness of the transition layer is: extending from the outer surface of the core layer inward by 0.01 - 100 nm; (3) The diameter of the core layer is 2.5 - 10 μm, and the thickness of the shell layer is 0.1 - 500 nm.

3. A method for preparing a cathode material, characterized in that, It includes the following steps: Performing a first heat treatment on a first mixture of a precursor material, a compound containing element Q, and a lithium source to obtain a first material; performing a second heat treatment on the first material and a second mixture of a compound containing element X and a compound containing element A. The precursor material includes hydroxides containing elements Ni and M, and element M includes at least one of Co, Mn, and Al; element Q includes at least one of Mo, Nb, W, Ta, and B; element X includes at least one of Mo and B; element A includes at least one of C, S, and N.

4. The preparation method of the cathode material according to claim 3, characterized in that, It includes at least one of the following features (1) to (6): (1) The chemical formula of the precursor material is Ni r M j (OH)2, where 0.3 < i < 0.98 and 0.02 < j < 0.7; (2) The D50 particle size of the precursor material is 2.5 to 15 μm, and the specific surface area of the precursor material is 10 to 35 m 2 / g; (3) The molar ratio of lithium element in the lithium source, element Q in the precursor material and the compound containing element Q is (1 - 1.56):1:x1, where 0 < x1 < 0.1; (4) The compound containing element Q includes at least one of an oxide of element Q and a hydroxide of element Q; (5) The compound containing element X includes at least one of a nitride of element X, a sulfide of element X, and an oxide of element X; (6) The molar ratio of the lithium source, the compound containing element X, and the compound containing element A in terms of lithium element, X element, and A element respectively is (1 - 1.56):x2:x3, where 0 < x2 < 0.1 and 0 < x3 < x2.

5. The preparation method of the positive electrode material according to claim 3, wherein, It includes at least one of the following features (1) to (3): (1) The acquisition of the first mixture and the acquisition of the second mixture are each independently carried out using at least one of a grinding device, a high - mixing device, and a plow - blade mixing device; (2) The first heat treatment includes a calcination treatment with at least two constant - temperature segments, and the temperatures of the multiple constant - temperature segments increase in a gradient; (3) The second heat treatment includes a sintering treatment with at least one constant - temperature segment, and the temperatures of the multiple constant - temperature segments increase.

6. The method for preparing the cathode material according to claim 3, characterized in that, It includes at least one of the following features (1) to (3): (1) The first heat treatment includes a first sintering treatment and a second sintering treatment; the temperature of the first sintering treatment is 400 - 600 °C, and the time of the first sintering treatment is 0.5 - 5 h; the temperature of the second sintering treatment is 700 - 900 °C, and the time of the second sintering treatment is 5 - 15 h; (2) The first heat treatment includes a first sintering treatment and a second sintering treatment; the heating rates of the first sintering treatment and the second sintering treatment are each independently 3 to 10 °C / min; (3) The first heat treatment is carried out in an atmosphere containing oxygen.

7. The preparation method of the positive electrode material according to claim 3, characterized in that, Comprising at least one of the following features (1) to (3): (1) The second heat treatment includes a third sintering treatment, a fourth sintering treatment and a fifth sintering treatment; the temperature of the third sintering treatment is 100 to 300 °C, and the time of the third sintering treatment is 0.5 to 3 h; the temperature of the fourth sintering treatment is 320 °C to 450 °C, and the time of the fourth sintering treatment is 1 to 4 h; the temperature of the fifth sintering treatment is 500 to 700 °C, and the time of the fourth sintering treatment is 3 to 8 h; (2) The second heat treatment includes a third sintering treatment, a fourth sintering treatment and a fifth sintering treatment; the heating rates of the third sintering treatment, the fourth sintering treatment and the fifth sintering treatment are each independently 3 to 10 °C / min; (3) The sintering atmosphere of the second heat treatment includes nitrogen or an atmosphere containing oxygen.

8. A positive electrode sheet, characterized in that, Comprising the positive electrode material according to any one of claims 1 to 2, or the positive electrode material prepared by the preparation method of the positive electrode material according to any one of claims 3 to 7.

9. A battery, characterized in that, Comprising the positive electrode sheet according to claim 8.

10. An electrical device, characterized in that, Comprising the battery according to claim 9.

Images