A positive electrode material, a preparation method and application thereof

Abstract

The application provides a positive electrode material, a preparation method and application thereof. The positive electrode material comprises a positive electrode material base, a first coating layer coated on the surface of the positive electrode material base, and a second coating layer coated on the surface of the first coating layer. The positive electrode material base is a low-cobalt or cobalt-free positive electrode material, the first coating layer is a low-nickel high-cobalt material, and the second coating layer is a titanium-aluminum solid solution. The positive electrode material is used as a lithium ion battery positive electrode material, and can improve the interface activity, specific capacity, coulomb efficiency or cycle performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a positive electrode material, a preparation method and application thereof. BACKGROUND

[0002] The application of new energy vehicles is imperative, and the power source lithium ion battery is the core part of new energy vehicles, and the positive electrode material in the lithium ion battery system is a decisive factor. In the existing positive electrode material system, the ternary material has the advantages of high specific energy density and good cycle performance, and is the mainstream material of new energy vehicles.

[0003] The main raw material cobalt used in ternary materials has low global reserves, which is difficult to meet the rapid development of new energy vehicles, so the overall development trend of ternary materials in the future must be low-cobalt or cobalt-free materials. However, the cobalt element in the ternary material system is beneficial to improve the conductivity of the material, improve the rate performance of the material, inhibit the increase of DCR in the cycle process, and also can improve the interface stability, reduce the residual alkali content, and inhibit the swelling in the cycle process. Therefore, the conventional low-cobalt or cobalt-free ternary material is difficult to meet the use requirements of new energy vehicles, and it is necessary to improve the rate performance of the material and inhibit the residual alkali of the material.

[0004] For lithium ion batteries, the essence of electrochemical reaction is first to carry out interface reaction, and then to carry out lithium ion deintercalation. Among them, the interface reaction is difficult, which is the bottleneck of electrochemical reaction. In order to improve the rate performance of low-cobalt or cobalt-free material, a layer of fast ion conductor can be coated on the surface of the material. For example, CN106299305A discloses a fast ion conductor coated lithium ion battery ternary positive electrode material, the coating liquid (a mixed solution of LiOH, H2O, H3BO3 and LiF) is mixed with the ternary material, and then dried, ground, heat treated, re-ground and sieved, to obtain a lithium boron fluoride lithium fast ion conductor coated ternary positive electrode material. The impedance of the battery is reduced, and the cycle stability of the material is improved, but the specific capacity of the fast ion conductor coated ternary positive electrode material is low, and the coulomb efficiency needs to be improved.

[0005] In addition, low-cobalt and cobalt-free materials are easily eroded by electrolyte during charging and discharging, which leads to the collapse of the structure, so interface coating is very important. The existing technology mainly uses single coating or composite coating. Although the composite coating can combine the advantages of multiple coating agents to some extent, it is still a single unit and cannot maximize the advantages of each unit. SUMMARY

[0006] Therefore, the purpose of the present application is to provide a positive electrode material, a preparation method and application thereof. The positive electrode material can improve the specific capacity, coulomb efficiency or cycle performance of the lithium ion battery.

[0007] In a first aspect, the present invention provides a positive electrode material, comprising a positive electrode material matrix, a first coating layer and a second coating layer, wherein the first coating layer covers the surface of the positive electrode material matrix and the second coating layer covers the surface of the first coating layer;

[0008] The cathode material matrix is ​​a low-cobalt or cobalt-free cathode material;

[0009] The first coating layer is a low-nickel, high-cobalt material;

[0010] The second coating layer is a titanium-aluminum solid solution.

[0011] Those skilled in the art will understand that cobalt-free cathode materials contain no cobalt, while low-cobalt cathode materials contain a small amount of cobalt, for example, with an atomic content of less than 5%, or even less than 3%. Low-nickel, high-cobalt materials contain a relatively low content of nickel and a relatively high content of cobalt, for example, with an atomic content of less than 30%, which can be 10% to 30%; and an atomic content of not less than 50%, or even not less than 55%.

[0012] Preferably, the chemical formula of the positive electrode material matrix is: Li z Ni x Co y Mn (1-x-y) O2, where z = 1.04 to 1.08, 0.65 ≤ x ≤ 0.75, y ≤ 0.05.

[0013] Preferably, the chemical formula of the first coating layer is: Li c Ni a Co b Mn (1-a-b) O2, where c = 1.04 to 1.08, 0.1 ≤ a ≤ 0.3, 0.5 ≤ b ≤ 0.6.

[0014] Preferably, the titanium-aluminum solid solution is composed of titanium dioxide and aluminum oxide, with the chemical formula dTiO2·Al2O3, where d = 0.8 to 1.2, that is, the molar ratio of titanium dioxide to aluminum oxide is (0.8 to 1.2):1.

[0015] Secondly, the present invention provides a method for preparing the aforementioned positive electrode material, comprising the following steps:

[0016] (1) The raw material forming the first coating layer is mixed with the cathode material matrix precursor to obtain a first intermediate. The raw material of the first coating layer includes at least a nickel source and a cobalt source. The cathode material matrix precursor is a low-cobalt or cobalt-free cathode material precursor.

[0017] (2) The first intermediate is mixed with a lithium source and calcined to obtain the second intermediate;

[0018] (3) mixing the second intermediate with a titanium-aluminum solid solution and then calcining to obtain the positive electrode material.

[0019] Preferably, the chemical formula of the positive electrode material matrix precursor is Ni x Co y Mn (1-x-y) (OH)2, wherein 0.65≤x≤0.75 and y≤0.05.

[0020] Preferably, the titanium-aluminum solid solution is obtained by mixing titanium oxide and aluminum oxide, drying, and then calcining.

[0021] Preferably, the mixing of the titanium oxide and the aluminum oxide is specifically as follows: sand-milling the mixture of the titanium oxide, the aluminum oxide, and water.

[0022] Preferably, the sand-milling is until the particle size D 50 of the mixture is ≤0.1 μm.

[0023] Preferably, during the reaction process of forming the titanium-aluminum solid solution, the drying temperature is 200-300℃.

[0024] Preferably, during the reaction process of forming the titanium-aluminum solid solution, the calcining temperature is 700-750℃ and the calcining time is 6-12h.

[0025] Preferably, the mass ratio of the titanium-aluminum solid solution to the second intermediate is (0.001-0.003):1.

[0026] Preferably, the calcining temperature in step (2) is 900-950℃ and the calcining time is 10-16h.

[0027] Preferably, the calcining temperature in step (3) is 450-500℃ and the calcining time is 6-12h.

[0028] In a third aspect, the present application provides a positive electrode or a lithium ion battery, which comprises the positive electrode material or the positive electrode material prepared according to the preparation method.

[0029] Compared with the prior art, the present application has the following advantages:

[0030] (1) The present application can significantly improve the interface activity, specific capacity, or coulombic efficiency by coating a low-nickel high-cobalt material on the surface of the positive electrode material matrix, and the low-nickel high-cobalt material itself is an electrochemically active material, which does not cause capacity loss.

[0031] (2) The application can effectively combine the advantages of high lithium ion diffusion coefficient of titanium and good stability of aluminum by coating a titanium-aluminum solid solution layer on the surface of the positive electrode material substrate coated with a low-nickel high-cobalt material, thereby significantly improving the cycle performance of the material compared with single coating or simple composite coating. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 SEM image of the positive electrode material obtained in Example 1. DETAILED DESCRIPTION

[0033] The technical solutions of the application will be described in detail below with reference to the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0034] All raw materials involved in the application are not particularly limited in source, and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0035] The application provides a positive electrode material, comprising a positive electrode material substrate, a first coating layer and a second coating layer, wherein the first coating layer is coated on the surface of the positive electrode material substrate, and the second coating layer is coated on the surface of the first coating layer.

[0036] In the application, the positive electrode material substrate is a low-cobalt or cobalt-free positive electrode material. The application preferably uses a material with a chemical formula of Li Z Ni x Co y Mn (1-x-y) O2 as the positive electrode material substrate, wherein z = 1.04-1.08, 0.65≤x≤0.75, and y≤0.05. The first coating layer is a low-nickel high-cobalt material, and the application preferably uses a material with a chemical formula of Li C Ni a Co b Mn (1-a-b) O2 as the first coating layer, wherein c = 1.04-1.08, 0.1≤a≤0.3, and 0.5≤b≤0.6. The second coating layer is a titanium-aluminum solid solution, which is preferably composed of titanium dioxide and aluminum oxide, and has a chemical formula of dTiO2·Al2O3, wherein d = 0.8-1.2, i.e., the molar ratio of titanium dioxide to aluminum oxide is (0.8-1.2):1.

[0037] The present application can significantly improve the interface activity, specific capacity or coulombic efficiency by coating low-nickel high-cobalt material on the surface of the positive electrode material substrate, without causing energy loss. In addition, further coating titanium-aluminum solid solution on the surface of the low-nickel high-cobalt material effectively combines the advantages of high lithium ion diffusion coefficient of titanium and good stability of aluminum compared with simple composite coating and single coating, which can significantly improve the cycle performance of the material.

[0038] The present application also provides a preparation method of the positive electrode material, comprising the following steps:

[0039] (1) mixing raw materials for forming a first coating layer with a positive electrode material substrate precursor to obtain a first intermediate, wherein the raw materials for forming the first coating layer at least include a nickel source and a cobalt source, and the positive electrode material substrate precursor is a low-cobalt or cobalt-free positive electrode material precursor;

[0040] (2) mixing the first intermediate with a lithium source and performing calcination to obtain a second intermediate;

[0041] (3) mixing the second intermediate with a titanium-aluminum solid solution and performing calcination to obtain the positive electrode material.

[0042] In the present application, the raw materials for forming the first coating layer are preferably mixed with the positive electrode material substrate precursor to obtain the first intermediate.

[0043] The raw materials for forming the first coating layer preferably include a nickel source, a cobalt source and a manganese source. The positive electrode material substrate precursor is preferably Ni x Co y Mn (1-x-y) (OH)2, wherein 0.65≤x≤0.75, y≤0.05. The Ni x Co y Mn (1-x-y) (OH)2 can be purchased on the market or prepared according to conventional preparation methods well known to those skilled in the art. It is more preferred in the present application that the raw materials for forming the first coating layer, i.e. the nickel source, the cobalt source and the manganese source, are mixed with water and then sand-milled to obtain slurry I, and then slurry I is mixed with the positive electrode material substrate precursor and dried to obtain the first intermediate. In the present application, the nickel source preferably includes nickel hydroxide and / or nickel oxide. The cobalt source preferably includes cobalt hydroxide and / or cobalt oxide. The manganese source preferably includes any one or more of manganese carbonate, dimanganese trioxide or manganese dioxide. The molar ratio of the nickel source, the cobalt source and the manganese source is preferably (0.1-0.3):(0.5-0.6):(0.1-0.4), and more preferably (0.1-0.2):(0.5-0.6):(0.2-0.4). In the present application, the particle size D 50≤0.1 μm. The present application does not have a particular limitation on the order of adding the slurry I and the positive electrode material matrix precursor, and preferably the positive electrode material matrix precursor is added to the slurry I to obtain slurry II. In the present application, the ratio of the amount of substance of the positive electrode material matrix precursor to the sum of the amounts of substance of the nickel source, the cobalt source and the manganese source in the first coating layer is preferably (98.5-99.5): 1, and more preferably (98.5-99): 1. After obtaining the slurry II according to the present application, drying is performed to obtain material III, i.e. the first intermediate. The present application does not have a particular limitation on the drying method, and conventional drying operations well known to those skilled in the art can be used. The temperature of the spray drying is preferably 550-650°C, and more preferably 600-650°C.

[0044] After obtaining material III, i.e. the first intermediate, the present application preferably mixes material III with a lithium source to obtain material IV and performs calcination to obtain material V, i.e. the second intermediate. In the present application, the amount of substance of the lithium source is preferably (1.04-1.08) x (the amount of substance of nickel in the slurry I + the amount of substance of manganese + the amount of substance of manganese) + (1.04-1.08) x the amount of substance of the positive electrode material matrix precursor. The lithium source preferably includes lithium hydroxide. The present application preferably performs calcination of material V in an oxygen atmosphere, and the temperature of the calcination is preferably 900-950°C, and more preferably 920-950°C, and the time of the calcination is preferably 10-16 h, and more preferably 12-16 h.

[0045] According to the present application, material V is preferably subjected to a crushing treatment to obtain material VI, and the particle size D 50 is preferably 3.4-4.2 μm.

[0046] According to the present application, after achieving the first coating layer, i.e. the low-nickel high-cobalt material, to coat the positive electrode material matrix, the preparation of the material of the second coating layer is started. In the present application, the second coating layer is a titanium aluminum solid solution, and preferably titanium dioxide, aluminum oxide and water are mixed, subjected to sand milling, dried, and then calcined to obtain material VII, i.e. the titanium aluminum solid solution. In the present application, the molar ratio of the titanium dioxide and the aluminum oxide is preferably (0.8-1.2): 1, more preferably (0.9-1.2): 1, and most preferably (1.0-1.2): 1. In the present application, the particle size D 50≤0.1 μm, and then is subjected to a drying treatment. The drying method is not particularly limited in the present application, and a conventional drying operation well known to those skilled in the art can be employed. The temperature of the spray drying is preferably 200-300°C, and more preferably 230-300°C. The calcination of the material VII is preferably performed in an air or oxygen atmosphere, and the temperature of the calcination is preferably 700-750°C, and more preferably 720-750°C, and the time of the calcination is preferably 6-12 h, and more preferably 8-12 h. In comparison with the prior art using a single coating or simple composite coating, the titanium-aluminum solid solution can effectively combine the advantages of high lithium ion diffusion coefficient of titanium and good stability of aluminum, and significantly improve the cycle performance of the material.

[0047] According to the present application, the material VIII is preferably subjected to a crushing treatment to obtain a material IX, wherein the particle size D 50 Preferably, ≤0.5 μm.

[0048] According to the present application, the material VI and the material IX are preferably mixed and then are subjected to a calcination to obtain a material X, i.e. a positive electrode material. In the present application, the mass ratio of the material IX to the material VI is preferably (0.001-0.003):1, and more preferably (0.002-0.003):1. The calcination is preferably performed in an air or oxygen atmosphere, and the temperature of the calcination is preferably 450-500°C, and more preferably 480-500°C, and the time of the calcination is preferably 6-12 h, and more preferably 8-12 h.

[0049] After obtaining the positive electrode material, the present application preferably subjects the positive electrode material to a crushing, a magnetic field removing and a packaging treatment in sequence to obtain a final applicable product.

[0050] The present application also provides a positive electrode or a lithium ion battery, wherein the lithium ion battery comprises a positive electrode, a negative electrode and an electrolyte, and the positive electrode comprises the positive electrode material as described above.

[0051] The present application uses the above positive electrode material, and the positive electrode is obtained by mixing the positive electrode material with a conductive material and a binder. The method for preparing the positive electrode is not particularly limited in the present application, and a conventional preparation method well known to those skilled in the art can be employed. The selection of the conductive material and the binder is not particularly limited in the present application, and in the present application, the conductive material is preferably acetylene black, and the binder is preferably polyvinylidene fluoride (PVDF), and the mass ratio of the positive electrode material, the conductive material acetylene black and the binder PVDF is preferably 80:10:10. The present application preferably adds an appropriate amount of N-methyl pyrrolidone (NMP) into the mixture of the positive electrode material, the acetylene black and the binder, and then is subjected to a stirring to obtain a uniform mixture, and then is coated on a 0.17 mm thick aluminum foil, and is subjected to a vacuum drying at 80°C for 10 h, and then is cut into pieces and is subjected to a compacting, and then is subjected to a vacuum drying at 120°C for 10 h, and then is punched into a round piece with a diameter of 1.3 cm to obtain a positive electrode piece.

[0052] The present application does not have special restrictions on the negative electrode and electrolyte, and can use a lithium sheet as the negative electrode, a polyethylene (PE) film as the separator, and LB315 lithium ion battery electrolyte as the electrolyte. In the LB315 lithium ion battery electrolyte, the mass ratio of dimethyl carbonate, diethyl carbonate and ethylene carbonate is 1:1:1. The present application assembles the positive electrode, negative electrode and separator into a button lithium ion battery in an argon-filled glove box.

[0053] In order to further illustrate the present application, the following examples are described in detail below. The raw materials used in the following examples of the present application are not particularly limited in terms of their source, and can be purchased on the market or prepared according to conventional methods well known to those skilled in the art.

[0054] Example 1

[0055] The present embodiment provides a lithium ion battery positive electrode material, and the preparation method is as follows:

[0056] (1) In terms of element molar ratio, nickel hydroxide, cobalt hydroxide and manganese carbonate are weighed according to the ratio of Ni:Co:Mn=0.1:0.5:0.4, mixed with deionized water and then put into a sand mill for sand milling to obtain slurry I, and the particle size D 50 ≤0.1 μm;

[0057] (2) The positive electrode material matrix precursor Ni 0.65 Co 0.05 Mn 0.3 (OH)2 is added to the slurry I and mixed uniformly to obtain slurry II, wherein the amount of substance of Ni 0.65 Co 0.05 Mn 0.3 (OH)2 / (amount of substance of nickel in slurry I+amount of substance of cobalt+amount of substance of manganese)=98.5:1;

[0058] (3) The above slurry II is spray dried at 550°C to obtain material III;

[0059] (4) The above material III and lithium hydroxide are mixed uniformly in a high-speed mixer to obtain material IV, wherein the amount of substance of lithium hydroxide=1.04×(amount of substance of nickel in slurry I+amount of substance of cobalt+amount of substance of manganese)+1.04×amount of substance of Ni 0.65 Co 0.05 Mn 0.3 (OH)2;

[0060] (5) The above material IV is placed in a roller kiln and calcined at 900°C for 16h in an oxygen atmosphere to obtain material V;

[0061] (6) The above material V is subjected to air flow crushing to obtain material stream VI, and the particle size D50 = 3.4 μm;

[0062] (7) Weigh titanium dioxide and alumina, mix with deionized water, and then add to a sand mill for sand milling. The particle size D 50 ≤ 0.1 μm after sand milling is 3.4 μm. Then spray drying (temperature 200°C) is performed to obtain material VII, wherein the amount of substance of titanium dioxide / amount of substance of alumina = 0.8;

[0063] (8) The above material VII is placed in a roller kiln, calcined at 700°C for 16h in an oxygen atmosphere to obtain material VIII, i.e. a titanium-aluminum solid solution. The material VIII is crushed to obtain material IX, wherein the particle size D50≤ 0.5 μm;

[0064] (9) The material stream VI obtained in step (6) is mixed with the material IX in a high-speed mixer to obtain material X, wherein the mass of material IX / mass of material VI = 0.001;

[0065] (10) The above material X is placed in a roller kiln, calcined at 450°C for 12h in an oxygen atmosphere, crushed, demagnetized, and packaged to obtain the final lithium ion battery cathode material.

[0066] The morphology of the cathode material obtained in Example 1 is characterized by a scanning electron microscope, and the results are shown in FIG. 1. It can be seen that the surface of the cathode material is coated with a double layer. Figure 1

[0067] Example 2

[0068] This example provides a lithium ion battery cathode material, and the preparation method is as follows:

[0069] (1) Weigh nickel hydroxide, cobalt hydroxide, and manganese carbonate in an elemental molar ratio of Ni:Co:Mn = 0.3:0.6:0.1, mix with deionized water, and then add to a sand mill for sand milling to obtain slurry I, wherein the particle size D 50 ≤ 0.1 μm of the slurry I is 3.4 μm;

[0070] (2) Add the cathode material matrix precursor Ni 0.65 Co 0.05 Mn 0.3 (OH)2 to the slurry I and mix uniformly to obtain slurry II, wherein the amount of substance of Ni 0.65 Co 0.05 Mn 0.3 (OH)2 / (amount of substance of nickel + amount of substance of cobalt + amount of substance of manganese in the slurry I) = 99.5:1;

[0071] (3) Spray drying is performed on the above slurry II at 560°C to obtain material III; ​

[0072] (4) Put the above material III and lithium hydroxide into a high-speed mixer and mix them evenly to obtain material IV, wherein the amount of substance of lithium hydroxide = 1.08 x (the amount of substance of nickel in slurry I + the amount of substance of cobalt + the amount of substance of manganese) + 1.08 x Ni 0.65 Co 0.05 Mn 0.3 (OH)2;

[0073] (5) Put the above material IV into a roller kiln, calcine it at 950℃ for 10h in an oxygen atmosphere, and obtain material V;

[0074] (6) Perform air flow crushing on the above material V to obtain material stream VI, and the particle size D 50 of material stream VI = 4.2 μm;

[0075] (7) Weigh titanium dioxide and aluminum oxide, mix them with deionized water, and then put them into a sand mill for sand grinding, and then perform spray drying (at a temperature of 300℃) after the particle size D 50 ≤ 0.1 μm, to obtain material VII, wherein the amount of substance of titanium dioxide / the amount of substance of aluminum oxide = 1.2;

[0076] (8) Put the above material VII into a roller kiln, calcine it at 750℃ for 6h in an air atmosphere, and obtain material VIII, i.e., a titanium-aluminum solid solution, crush it to obtain material IX, and the particle size D50 of the crushed material ≤ 0.5 μm;

[0077] (9) Mix material stream VI obtained in step (6) and material IX in a high-speed mixer to obtain material X, wherein the mass of material IX / the mass of material VI = 0.003;

[0078] (10) Put the above material X into a roller kiln, calcine it at 500℃ for 12h in an oxygen atmosphere, crush it, remove the magnetism, and package to finally obtain a lithium ion battery positive electrode material.

[0079] Example 3

[0080] This example provides a lithium ion battery positive electrode material, and the preparation method is as follows:

[0081] (1) Weigh nickel hydroxide, cobalt hydroxide and manganese carbonate in an element molar ratio of Ni:Co:Mn = 0.3:0.5:0.2, mix them with deionized water, and then put them into a sand mill for sand grinding to obtain slurry I, and the particle size D 50 of slurry I ≤ 0.1 μm;

[0082] (2) Crush the positive electrode material matrix precursor Ni 0.75 Co 0.05 Mn 0.2(OH)2 is added into the slurry I and mixed uniformly to obtain slurry II, wherein Ni 0.75 Co 0.05 Mn 0.2 (OH)2 / (Ni + Co + Mn) = 99:1;

[0083] (3) The slurry II is spray dried at 600℃ to obtain material III;

[0084] (4) The material III and lithium hydroxide are mixed uniformly in a high-speed mixer to obtain material IV, wherein the amount of substance of lithium hydroxide = 1.06×(Ni + Co + Mn) + 1.06×Ni 0.75 Co 0.05 Mn 0.2 (OH)2;

[0085] (5) The material IV is placed in a roller kiln and calcined at 900℃ for 16h in an oxygen atmosphere to obtain material V;

[0086] (6) The material V is subjected to air flow crushing to obtain material flow VI, and the particle size D 50 = 4μm;

[0087] (7) Titanium dioxide and aluminum oxide are weighed, mixed with deionized water, and then added into a sand mill for sand milling, and the particle size D 50 ≤ 0.1μm, and then spray dried (at a temperature of 300℃) to obtain material VII, wherein the amount of substance of titanium dioxide / aluminum oxide = 1.0;

[0088] (8) The material VII is placed in a roller kiln and calcined at 750℃ for 6h in an oxygen atmosphere to obtain material VIII, i.e., a titanium-aluminum solid solution, which is crushed to obtain material IX, and the particle size D50≤ 0.5μm;

[0089] (9) The material flow VI obtained in step (6) and the material IX are mixed uniformly in a high-speed mixer to obtain material X, wherein the mass of material IX / mass of material VI = 0.002;

[0090] (10) The material X is placed in a roller kiln and calcined at 450℃ for 8h in an oxygen atmosphere, and then crushed, demagnetized, and packaged to obtain a lithium ion battery positive electrode material.

[0091] Example 4

[0092] This example provides a lithium ion battery positive electrode material, and the preparation method is as follows:

[0093] (1) Take nickel hydroxide, cobalt hydroxide and manganese carbonate in the proportion of Ni:Co:Mn=0.2:0.6:0.2 in terms of element molar ratio, mix with deionized water and then add into a sand mill for sand grinding to obtain slurry I, the particle size D50 of the slurry I is ≤0.1 μm; 50 ≤0.1 μm;

[0094] (2) Add positive electrode material matrix precursor Ni 0.75 Co 0.05 Mn 0.2 (OH)2 into the slurry I and mix uniformly to obtain slurry II, wherein the amount of substance of Ni 0.75 Co 0.05 Mn 0.2 (OH)2 / (amount of substance of nickel in the slurry I+amount of substance of cobalt+amount of substance of manganese)=99:1;

[0095] (3) Spray dry the above slurry II at 600 ℃ to obtain material III;

[0096] (4) Mix the above material III and lithium hydroxide uniformly in a high-speed mixer to obtain material IV, wherein the amount of substance of lithium hydroxide=1.06×(amount of substance of nickel in the slurry I+amount of substance of cobalt+amount of substance of manganese)+1.06×amount of substance of Ni 0.75 Co 0.05 Mn 0.2 (OH)2;

[0097] (5) Place the above material IV in a roller kiln, calcine at 900 ℃ for 16 h in an oxygen atmosphere to obtain material V;

[0098] (6) Airflow crush the above material V to obtain material flow VI, the particle size D 50 =4 μm;

[0099] (7) Take titanium dioxide and aluminum oxide, mix with deionized water and then add into a sand mill for sand grinding, the particle size D 50 ≤0.1 μm, and then spray dry (temperature is 200 ℃) to obtain material VII, the amount of substance of titanium dioxide / amount of substance of aluminum oxide=1.0;

[0100] (8) Place the above material VII in a roller kiln, calcine at 750 ℃ for 6 h in an oxygen atmosphere to obtain material VIII, i.e. titanium-aluminum solid solution, crush the same to obtain material IX, the particle size D50 of which is ≤0.5 μm;

[0101] (9) Mix the material flow VI obtained in step (6) and material IX uniformly in a high-speed mixer to obtain material X, wherein the mass of material IX / the mass of material VI=0.002;

[0102] (10) The material XI is placed in a roller kiln, calcined at 450°C for 8h in an oxygen atmosphere, crushed, demagnetized, packaged, and finally a lithium ion battery cathode material is obtained.

[0103] Comparative Example 1

[0104] This comparative example provides a lithium ion battery cathode material which does not include a first coating layer compared with Example 1, and the preparation method is as follows:

[0105] (1) Take the positive electrode material substrate precursor Ni 0.65 Co 0.05 Mn 0.3 (OH)2, spray drying at 550°C to obtain material I;

[0106] (2) Mix the above material I and lithium hydroxide uniformly in a high-speed mixer to obtain material II, wherein the amount of substance of lithium hydroxide = 1.04 x Ni 0.65 Co 0.05 Mn 0.3 (OH)2amount of substance;

[0107] (3) The above material II is placed in a roller kiln, calcined at 900°C for 16h in an oxygen atmosphere to obtain material III;

[0108] (4) The above material III is subjected to air flow crushing to obtain material stream IV, and the particle size D 50 = 3.4 μm;

[0109] (5) Titanium dioxide and aluminum oxide are weighed, mixed with deionized water, and then added to a sand mill for sand milling, and the particle size D 50 ≤ 0.1 μm is then spray dried (temperature 200°C) to obtain material V, and the amount of substance of titanium dioxide / amount of substance of aluminum oxide = 0.8;

[0110] (6) The above material V is placed in a roller kiln, calcined at 700°C for 16h in an oxygen atmosphere to obtain a titanium-aluminum solid solution, which is crushed, and the particle size D50 of the crushed product ≤ 0.5 μm;

[0111] (7) The material stream IV obtained in step (6) is mixed with the crushed titanium-aluminum solid solution in a high-speed mixer to obtain material VI, wherein the mass of titanium-aluminum solid solution / mass of material VI = 0.001;

[0112] (8) The above material VI is placed in a roller kiln, calcined at 450°C for 12h in an oxygen atmosphere, crushed, demagnetized, packaged, and finally a lithium ion battery cathode material is obtained.

[0113] Comparative Example 2

[0114] The comparative example provides a lithium ion battery positive electrode material, which does not form a titanium-aluminum alloy compared with Example 1, and the specific steps are as follows:

[0115] (1) Take nickel hydroxide, cobalt hydroxide and manganese carbonate in a proportion of Ni:Co:Mn=0.1:0.5:0.4 in terms of element molar ratio, mix with deionized water, and then put into a sand mill for sand milling to obtain slurry I, the particle size D 50 ≤0.1 μm of slurry I is obtained.

[0116] (2) Add the positive electrode material matrix precursor Ni 0.65 Co 0.05 Mn 0.3 (OH)2 to the slurry I and mix uniformly to obtain slurry II, wherein the amount of substance of Ni 0.65 Co 0.05 Mn 0.3 (OH)2 / (amount of substance of nickel in slurry I+amount of substance of cobalt+amount of substance of manganese)=98.5:1.

[0117] (3) Spray dry the above slurry II at 550°C to obtain material III;

[0118] (4) Mix the above material III and lithium hydroxide uniformly in a high-speed mixer to obtain material IV, wherein the amount of substance of lithium hydroxide=1.04×(amount of substance of nickel in slurry I+amount of substance of cobalt+amount of substance of manganese)+1.04×amount of substance of Ni 0.65 Co 0.05 Mn 0.3 (OH)2.

[0119] (5) Place the above material IV in a roller kiln, calcine at 900°C for 16h in an oxygen atmosphere to obtain material V;

[0120] (6) Airflow crush the above material V to obtain material stream VI, the particle size D 50 =3.4 μm of material stream VI.

[0121] (7) Mix the material stream VI obtained in step (6), titanium dioxide and aluminum oxide uniformly in a high-speed mixer to obtain material VII, wherein the amount of substance of titanium dioxide / amount of substance of aluminum oxide=0.8, and the total mass of titanium dioxide and aluminum oxide / mass of material VI=0.001.

[0122] (8) Place the above material VII in a roller kiln, calcine at 450°C for 12h in an oxygen atmosphere, crush, remove magnetism, and package to finally obtain a lithium ion battery positive electrode material.

[0123] Performance test

[0124] The first cycle discharge specific capacity, the first DCR, the 50 cycle DCR increase and the cycle performance of the lithium ion secondary battery anode material prepared by using the anode material obtained in Examples 1-4 and Comparative Examples 1-2 to prepare button cells were tested.

[0125] The first test condition of the button cell was LR 2032, 0.1C, 2.8-4.45V, vs. Li + / Li, the cycle test condition was 45℃, 3.0-4.5V, 1.0C / 1.5C, and the charge-discharge equipment used was a blue electricity charge-discharge instrument.

[0126] The test results are shown in Table 1 below:

[0127] Table 1

[0128]

[0129] From the data in the above table, it can be seen that the anode material obtained in Examples 1-4 has a high specific capacity and capacity retention rate, a low first DCR, and a small DCR increase, and has strong application performance. The anode material obtained in Comparative Example 1 has no first coating layer, and the first discharge capacity, DCR and cycle performance and other indicators are all significantly deteriorated. The second coating layer in Comparative Example 2 is a simple titanium-aluminum composite coating, but since a titanium-aluminum solid solution is not formed, the advantages of the two cannot be effectively combined, resulting in poor adhesion between the titanium oxide and the inner layer material, and thus the first DCR and cycle performance are significantly deteriorated.

[0130] The above description of disclosed embodiments enables one of ordinary skill in the art to make or use the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A positive electrode material, comprising a positive electrode material base, a first coating layer and a second coating layer, the first coating layer coating the surface of the positive electrode material base, and the second coating layer coating the surface of the first coating layer. The positive electrode material base is a low-cobalt or cobalt-free positive electrode material. The first coating layer is a low-nickel high-cobalt material. The second coating layer is a titanium-aluminum solid solution. The titanium-aluminum solid solution is composed of titanium dioxide and aluminum oxide. The titanium-aluminum solid solution is obtained by mixing, drying and then calcining titanium dioxide and aluminum oxide.

2. The positive electrode material of claim 1, wherein, The chemical formula of the positive electrode material base is: Li z Ni x Co y Mn (1-x-y) O2, wherein z = 1.04-1.08, 0.65≤x≤0.75, y≤0.05 The chemical formula of the first coating layer is: Li c Ni a Co b Mn (1-a-b) O2, wherein, c=1.04-1.08, 0.1≤a≤0.3, 0.5≤b≤0.

6.

3. The cathode material of claim 1, wherein, The calcination temperature is 700-750℃.

4. The method of producing a cathode material according to any one of claims 1 to 3, characterized in that, The molar ratio of titanium dioxide to aluminum oxide is (0.8-1.2) :

1. The method comprises the following steps: (1) mixing a first coating layer raw material and a positive electrode material base precursor to obtain a first intermediate, the first coating layer raw material comprising at least a nickel source and a cobalt source, and the positive electrode material base precursor being a low-cobalt or cobalt-free positive electrode material precursor; (2) mixing the first intermediate with a lithium source and calcining to obtain a second intermediate; 5. The preparation method according to claim 4, characterized in that, (3) mixing the second intermediate with a titanium-aluminum solid solution and calcining to obtain the positive electrode material.

6. The preparation method according to claim 5, characterized in that, The titanium-aluminum solid solution is obtained by mixing, drying and then calcining titanium dioxide and aluminum oxide. Sand grinding to the particle size D of the material 50 ≤ 0.1 μm.

7. The preparation method according to claim 5, characterized in that, The mixing of titanium dioxide and aluminum oxide is specifically as follows: sand-milling the mixture of titanium dioxide, aluminum oxide and water; During the reaction process of forming the titanium-aluminum solid solution, the drying temperature is 200-300℃.

8. The preparation method according to claim 4, characterized in that, The calcination temperature is 700-750℃, and the calcination time is 6-12h.

9. The preparation method according to claim 4, characterized in that, The mass ratio of the titanium-aluminum solid solution to the second intermediate is (0.001-0.003) :

1. The calcination temperature in step (2) is 900-950℃, and the calcination time is 10-16h.

10. A positive electrode or lithium ion battery, characterized by, The calcination temperature in step (3) is 450-500℃, and the calcination time is 6-12h. The positive electrode material is prepared by the method of any one of claims 1-3 or the method of any one of claims 4-9.

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