Positive electrode material and application thereof

Abstract

The invention provides a positive electrode material and application thereof. The positive electrode material includes primary particles having a composition of formula 1; li Co M < c > A < 1d > A < 2e > A < 3f > O < 2 >; 0.8 < = a < = 1.03, and 0.86 < = blt; 1, 0lt; c is less than or equal to 0.015, 0 lt; d is less than or equal to 0.055, 0 lt; e < = 0.05, 0 < = f < = 0.02, 0.1 < = d / c < = 7; m comprises at least one of Te, Sb, Bi and Se, A1 comprises at least one of Mg, Sr and Ba, A2 comprises at least one of Al, Ga and In, and A3 comprises at least one of F, Ti, Zr, Y, La, W and Si; m elements are non-uniformly distributed in the primary particles; in an X-ray diffraction pattern, the positive electrode material has characteristic peaks when 2 theta is 18 degrees to 18.5 degrees, 19.5 degrees to 20.3 degrees, 20.5 degrees to 21.1 degrees and 22.5 degrees to 23.4 degrees. The positive electrode material is stable in structure under high voltage and excellent in gram volume.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical technology, and in particular to a positive electrode material and its application. Background Art

[0002] As consumers demand longer battery life in consumer electronics, the capacity of lithium-ion batteries is also increasing. As the source of lithium-ion battery capacity, the capacity of the positive electrode material directly affects the battery's ultimate capacity. Lithium-ion batteries primarily use materials such as lithium cobalt oxide, ternary materials, lithium iron phosphate, lithium manganese oxide, and lithium titanate as positive electrode materials. Lithium cobalt oxide, with its highest energy density among these materials, is widely used in consumer lithium-ion batteries, which have high energy density requirements.

[0003] However, with the market's increasing demand for battery energy density, the charging cut-off voltage of lithium cobalt oxide materials is constantly increasing, which means that the lithium content released by the material itself is constantly increasing. As the amount of lithium released from lithium cobalt oxide materials continues to increase, the material itself is prone to structural phase changes or even collapse, resulting in poor battery cycle performance. Although doping with metal elements is beneficial to improving structural stability, the continuous increase in the content of doping elements will also lead to a continuous decline in the gram capacity of the material itself, and the resulting gram capacity benefits are also getting lower and lower.

[0004] Therefore, it is necessary to develop positive electrode materials with stable structure and excellent specific capacity at high voltage. Summary of the Invention

[0005] In view of this, the present invention provides a positive electrode material, which has a stable structure at high voltage and excellent specific capacity. When the positive electrode material of the present invention is applied to a battery, the battery can have excellent cycle performance and high rate (0.5 or 0.7C) performance at high voltage.

[0006] The present invention provides a positive electrode material, wherein the positive electrode material comprises primary particles having Formula 1;

[0007] Li a Co b M c A 1 d A 2 e A 3 f O2 formula 1

[0008] In formula 1, 0.8≤a≤1.03, 0.86≤b<1, 0 <c≤0.015,0<d≤0.055,0<e≤0.05,0≤f≤0.02,0.1≤d / c≤7;

[0009] M includes at least one of Te, Sb, Bi, and Se, and A 1 Contains at least one of Mg, Sr and Ba, A 2 Including at least one of Al, Ga and In, A 3 including at least one of F, Ti, Zr, Y, La, W, and Si;

[0010] The M element is non-uniformly distributed in the primary particles;

[0011] In the X-ray diffraction pattern, the positive electrode material has characteristic peaks at 2θ of 18°-18.5°, 19.5°-20.3°, 20.5°-21.1° and 22.5°-23.4°.

[0012] The positive electrode material as described above, wherein

[0013] The primary particles include a matrix and a coating layer located on at least a portion of the surface of the matrix, wherein the matrix includes a first portion and a second portion from the inside out;

[0014] wherein the concentration of the M element in the coating layer is greater than the concentration of the M element in the second portion, and the concentration of the M element in the second portion is greater than the concentration of the M element in the first portion;

[0015] Preferably, R1:R2=(0.7-0.99):0.1, R1 is the radius of the first portion, R2 is the ring width of the second portion; and / or the thickness of the coating layer is 0.05-0.1 μm;

[0016] And / or, the Dv50 of the primary particles is 2-17 μm.

[0017] The positive electrode material as described above, wherein the primary particles include first primary particles and second primary particles, wherein the second primary particles form secondary particles;

[0018] In the secondary particles, the second primary particles include a grain boundary region and a non-grain boundary region;

[0019] The secondary particles include first secondary particles and second secondary particles;

[0020] In the second primary particles of the first secondary particles, the grain boundary region does not contain M element; and / or,

[0021] In the second primary particle of the second secondary particle, the grain boundary region has the M element;

[0022] Preferably, in the second primary particles of the second secondary particles, the concentration of the M element in the grain boundary region is greater than the concentration of the M element in the non-grain boundary region;

[0023] and / or,

[0024] The primary particles include crack regions and non-crack regions, and the concentration of the M element in some of the crack regions is greater than the concentration of the M element in the non-crack regions.

[0025] The positive electrode material as described above, wherein the surface of the primary particles has third particles, the size of the third particles is 50-500 nm; and / or the third particles include M element.

[0026] The positive electrode material as described above, wherein the coating layer has A 1 The concentration of the element is greater than that of A in the second part 1 The concentration of the element, in the second part A 1 The concentration of the element is greater than that of A in the first part 1 the concentration of the element; and / or,

[0027] A 2 The element is uniformly distributed in the first portion, the second portion and the coating layer; and / or,

[0028] The concentration of the A3 element in the second portion gradually increases along the direction from the first portion to the coating layer.

[0029] The positive electrode material as described above, wherein the content of the M element in the positive electrode material is ≤32000ppm; and / or,

[0030] A 1 The content of the element is ≤ 63000ppm; and / or,

[0031] A 2 The content of elements is ≤58000ppm;

[0032] Preferably, when M includes Te, the content of Te in the positive electrode material is ≤19500ppm; and / or,

[0033] When M includes Se, the content of Se in the positive electrode material is ≤12000ppm; and / or,

[0034] When M includes Bi, the content of Bi element in the positive electrode material is ≤32000 ppm.

[0035] The positive electrode material as described above, wherein

[0036] The specific surface area of the positive electrode material is 0.1-1.2 m2 / g; and / or,

[0037] The Dv50 of the positive electrode material is 5 μm-20 μm; and / or,

[0038] The positive electrode material has a Dv10 less than 5 μm; and / or

[0039] The Dv90 of the positive electrode material is greater than 25 μm.

[0040] The present invention provides a positive electrode sheet, which includes the positive electrode material described above.

[0041] The present invention provides a lithium-ion battery, comprising the positive electrode sheet described above.

[0042] The lithium-ion battery as described above, further comprising an electrolyte, wherein the electrolyte comprises a nitrile compound;

[0043] Preferably, the mass percentage of the nitrile compound in the electrolyte is 2-8%;

[0044] Preferably, the nitrile compound includes at least one of succinonitrile, adiponitrile, 1,2-bis-(2-cyanoethoxy)ethane and 1,3,6-hexanetrinitrile.

[0045] The positive electrode material of the present invention has a special composition. When applied to a battery, the battery can have excellent cycle performance and rate performance at high voltage, especially can have excellent cycle performance and rate performance at a voltage of 4.55V or 4.6V. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 Schematic diagram of the cross-sectional structure of the positive electrode material in some embodiments of the present invention;

[0047] Figure 2 This is a SEM image of the intermediate positive electrode material of Example 1 of the present invention;

[0048] Figure 3 This is an EDS graph of the M element in the intermediate positive electrode material of Example 1 of the present invention;

[0049] Figure 4 A in the intermediate positive electrode material of Example 1 of the present invention 1 EDS diagram of elements;

[0050] Figure 5 A in the intermediate positive electrode material of Example 1 of the present invention 2 EDS diagram of elements;

[0051] Figure 6 This is a SEM image of the positive electrode material in Example 1 of the present invention at one magnification;

[0052] Figure 7 This is a SEM image of the positive electrode material in Comparative Example 5 of the present invention;

[0053] Figure 8 is a SEM image of the positive electrode material in Example 1 of the present invention at another magnification;

[0054] Figure 9 This is the XRD pattern of the positive electrode material in Example 1 of the present invention.

[0055] Description of reference numerals:

[0056] 2: coating layer;

[0057] 11: Part I;

[0058] 12: Part 2. DETAILED DESCRIPTION

[0059] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0060] A first aspect of the present invention provides a positive electrode material, the positive electrode material comprising primary particles having a composition of Formula 1;

[0061] Li a Co b M c A 1 d A 2 e A 3 f O2 formula 1

[0062] In formula 1, 0.8≤a≤1.03, 0.86≤b<1, 0 <c≤0.015,0<d≤0.055,0<e≤0.05,0≤f≤0.02,0.1≤d / c≤7;

[0063] M includes at least one of Te, Sb, Bi, and Se, and A 1 Contains at least one of Mg, Sr and Ba, A 2 Including at least one of Al, Ga and In, A 3 including at least one of F, Ti, Zr, Y, La, W, and Si;

[0064] The M element is non-uniformly distributed in the primary particles;

[0065] In the X-ray diffraction pattern, the positive electrode material has characteristic peaks at 2θ of 18°-18.5°, 19.5°-20.3°, 20.5°-21.1° and 22.5°-23.4°.

[0066] In the present invention, a, b, c, d, e and f can be tested by conventional methods in the art, for example, discharging the battery to 0% SOC, disassembling the positive electrode sheet, and soaking it in dimethyl carbonate (DMC) solvent for 12 hours; then rinsing it with DMC solvent to remove the lithium salt attached to the positive electrode sheet, calcining it in a muffle furnace at 400° C. for 3 hours, gently scraping the positive electrode active layer from the surface of the positive electrode current collector, and using the scraped powder as a test sample, or directly taking the positive electrode material and using an inductively coupled plasma-optical emission spectrometer (ICP-OES) to test the element content. The specific operation method is carried out in accordance with GB / T 30902-2014.

[0067] The positive electrode material of the present invention comprises primary particles (unagglomerated particles) having a composition of Formula 1, wherein the primary particles of Formula 1 comprise at least Li, Co, M, A 1 and A 2 In some embodiments, the primary particles of Formula 1 may further include A 3 The positive electrode material of the present invention has a characteristic peak of a superlattice structure in the XRD diagram.

[0068] The non-uniform distribution of the M element in the primary particles of the present invention can be understood as different concentrations of the M element in different regions of the primary particles, which can be manifested as the M element being concentrated in one region and dispersed in another region.

[0069] The present invention introduces elements M and A with specific molar contents into lithium cobalt oxide. 1 , thus forming a superlattice structure with a heterojunction structure, which not only improves the lithium ion insertion / extraction activity of the material, but also stabilizes the lattice structure of the material, so that the positive electrode material has good structural stability while effectively improving the lithium ion transmission efficiency and gram capacity. Further, when the element A is introduced 2 and A 3 The electron cloud can be balanced and repaired at the same time, further improving the structural stability of the material while ensuring high gram capacity and lithium ion transmission efficiency.

[0070] At the same time, the inventors discovered in the study that when the M element is unevenly distributed in the primary particles, a preferred electron or ion transmission path can be formed in the primary particles, thereby reducing the charge transfer impedance and improving the conductivity and ion diffusion rate of the positive electrode material; and the unevenly distributed M element can also form a protective layer or passivation layer to protect the primary particles, effectively reducing the possibility of side reactions between the positive electrode material and the electrolyte, and improving the stability of the positive electrode material under high voltage; at the same time, the unevenly distributed M element can optimize the local lattice structure of the primary particles and improve the stability of the positive electrode material; the unevenly distributed M element can also adjust the internal stress distribution of the positive electrode material to avoid degradation and failure of the positive electrode material due to internal stress concentration.

[0071] In summary, the cathode material of the present invention has excellent stability and capacity at high voltages, and when used in batteries, can improve the battery's rate performance and cycle performance. In some embodiments, the gram capacity of the cathode material of the present invention can be 10 mAh / g higher than that of conventional lithium cobalt oxide, and the gram capacity of the cathode material of the present invention can be greater than 210 mAh / g.

[0072] In the X-ray diffraction pattern, the positive electrode material has characteristic peaks at 2θ of 18°-18.5°, 19.5°-20.3°, 20.5°-21.1° and 22.5°-23.4°, indicating that the positive electrode material has a superlattice structure.

[0073] In some embodiments, in the X-ray diffraction pattern, the positive electrode material has a (003) peak with a 2θ of 18.8° to 19.1°, a (006) peak with a 2θ of 37.3° to 37.6°, a (012) peak with a 2θ of 38.9° to 39.2°, and a (104) peak with a 2θ of 45.1° to 45.4°, indicating that the positive electrode material is a lithium cobalt oxide structure.

[0074] Figure 1 Schematic diagram of the cross-sectional structure of the positive electrode material in some embodiments of the present invention. Figure 1 As shown, in some embodiments of the present invention, the primary particle includes a matrix and a coating layer 2 located on at least a portion of the surface of the matrix, and the matrix includes a first portion 11 and a second portion 12 from the inside out;

[0075] The concentration of the M element in the coating layer 2 is greater than the concentration of the M element in the second portion 12 , and the concentration of the M element in the second portion 12 is greater than the concentration of the M element in the first portion 11 .

[0076] It is understood that in the present invention, the coating layer 2 may be located on a portion of the substrate surface or on the entire substrate surface. The primary particles of the present invention have a core-shell structure comprising, from the inside out, a substrate and a coating layer 2. Furthermore, the primary particles comprise, from the inside out, a first portion 11, a second portion 12, and a coating layer 2, with the concentration of the M element increasing from the inside out.

[0077] In the primary particles of the present invention, the concentration of the M element increases from the inside to the outside. When the concentration of the M element is higher near the outside, the primary particles can be protected, effectively reducing the possibility of side reactions between the positive electrode material and the electrolyte, and improving the stability of the positive electrode material under high voltage; at the same time, the lattice structure near the outside of the primary particles can be fully optimized to avoid the collapse of the primary particles during the battery cycle, thereby improving the stability of the positive electrode material; the stress distribution near the outside of the primary particles can also be adjusted to improve the stability of the positive electrode material.

[0078] Furthermore, R1:R2=(0.7-0.99):0.1, R1 is the radius of the first part, and R2 is the ring width of the second part. Since the primary particles may be irregular spherical particles in the actual production process, R1 can be understood as the average radius of the first part, and R2 can be understood as the average ring width of the second part. When the ratio of R1 to R2 meets the above range, the internal crystal phase structure and stress distribution of the primary particles can be more fully adjusted while ensuring the capacity of the positive electrode material, so that the positive electrode material has both better stability and capacity.

[0079] The thickness of the coating layer is 0.05-0.1 μm, which can better protect the substrate while ensuring the capacity of the positive electrode material, so that the positive electrode material has both excellent capacity and stability.

[0080] Furthermore, when the Dv50 of the primary particles is 2-17 μm, the stability of the positive electrode material can be improved while ensuring the rate performance of the positive electrode material.

[0081] In some embodiments of the present invention, the primary particles include first primary particles and second primary particles, wherein the second primary particles form secondary particles;

[0082] In the secondary particles, the second primary particle includes a grain boundary region and a non-grain boundary region;

[0083] The secondary particles include first secondary particles and second secondary particles;

[0084] In the second primary particles of the first secondary particles, the grain boundary region contains no M element; and / or

[0085] In the second primary particle of the second secondary particle, the grain boundary region has the M element;

[0086] The primary particles of the present invention include first primary particles and second primary particles, wherein the second primary particles are aggregated to form secondary particles, and the first primary particles are not aggregated.

[0087] The second primary particles forming the secondary particles have a grain boundary region (the interface between any two adjacent second primary particles can be considered as a grain boundary region) and a non-grain boundary region.

[0088] The secondary particles include first secondary particles having M elements in their grain boundary regions and second secondary particles not having M elements in their grain boundary regions (some secondary particles have M elements in their grain boundary regions and others do not).

[0089] When the grain boundary regions of some secondary particles contain M elements, the M elements can form a protective layer or a passivation layer in the grain boundary regions to protect the secondary particles, thereby further improving the stability of the positive electrode material.

[0090] Furthermore, when the concentration of the M element in the grain boundary region of the second primary particle of the second secondary particle is greater than the concentration of the M element in the non-grain boundary region, the stress distribution of the secondary particles can be better adjusted, an optimized ion transmission channel can be provided, and the secondary particles can be protected, so that the positive electrode material has both better stability and capacity.

[0091] In some embodiments of the present invention, the primary particles include crack areas and non-crack areas. When the concentration of the M element in some crack areas is greater than the concentration of the M element in the non-crack areas, the M element can form a protective layer or a passivation layer in the crack areas to protect the primary particles, thereby reducing the risk of damage and collapse of the primary particles from the cracks during long-term use, and further improving the stability of the positive electrode material.

[0092] In some embodiments of the present invention, the surface of the primary particles has third particles, and when the third particles include the M element, the stability and capacity of the positive electrode material can be further improved.

[0093] Furthermore, when the size of the third particles is 50-500nm, the primary particles can have a suitable specific surface area, which can increase the contact area between the positive electrode material and the electrolyte while ensuring the stability of the positive electrode material, promote charge transfer and ion exchange, and thus further improve the capacity of the positive electrode material; at the same time, it can also optimize the interface performance between the positive electrode material and the electrolyte, further improving the rate performance of the positive electrode material.

[0094] The inventors also found in their research that by 1 Element,A 2 Elements and A 3Designing the distribution of elements can further improve the capacity and stability of the positive electrode material.

[0095] In some embodiments of the present invention, the coating layer A 1 The concentration of the element is greater than that of A in the second part 1 The concentration of the element, Part II A 1 The concentration of the element is greater than that of A in the first part 1 The concentration of the element. That is, the positive electrode material from the inside out, A 1 The concentration of the element gradually increases. In the positive electrode material, the M element and the A 1 The distribution trends of the elements are consistent.

[0096] In the present invention, the M element usually has a larger ionic radius, which helps to provide better structural support in the lattice of the positive electrode material and reduce the structural collapse caused by the volume change of the positive electrode material during the charge and discharge process. 1 Elements can enhance the mechanical strength of the positive electrode material. 1 When the distribution trend of elements is consistent, M element can be 1 The elements work synergistically to optimize the crystal structure and stress distribution of the positive electrode material, further improving the mechanical properties and stability of the positive electrode material.

[0097] In some embodiments of the present invention, A 2 The elements are evenly distributed in the first part, the second part and the coating layer. 2 The elements are evenly distributed in the positive electrode material.

[0098] When A 2 When the elements are evenly distributed in the positive electrode material, the lattice structure of the positive electrode material can be made more stable, the possibility of side reactions between the positive electrode material and the electrolyte can be reduced, and the cycle stability of the positive electrode material can be further improved.

[0099] In some embodiments of the present invention, A 3 The elements are evenly distributed in the coating layer, and the second part A 3 When the concentration of the element gradually increases from the first part to the coating layer, the A 3 The role of elements makes M and A 1 、A 2 and A 3 The synergistic effect further hinders the side reactions between the electrolyte and the positive electrode material, thereby improving the capacity and stability of the positive electrode material.

[0100] The coating layer of the present invention includes M elements, A 1 Elements and A 2 element, M element, A 1 Elements and A2 The elements will form inert metal oxides to hinder the corrosion of the electrolyte on the matrix and improve the cycle performance of the positive electrode material; the hexavalent M elements and divalent A 1 The element will dope some defects in the transition metal layer of lithium cobalt oxide, forming a local strong electron-withdrawing and electron-donating interlaced region, which can effectively improve the electron cloud density of the lithium cobalt oxide surface interface, thereby being beneficial to the stability of the transition metal layer and more beneficial to the transmission of lithium ions. The direct result is the improvement of lithium ion extraction and embedding and solid-phase transmission efficiency, which is manifested as an improvement in rate and capacity in the battery; further, the M element and A 1 The concentration of the element in the second part is higher than that in the first part, and the concentration in the grain boundary area is higher than that in the non-grain boundary area. This can improve the stability of the positive electrode material while ensuring the capacity of the positive electrode material, thereby enabling the battery to have both excellent cycle performance and rate performance.

[0101] In some embodiments of the present invention, when the content of element M in the positive electrode material is ≤32000ppm; and / or,

[0102] A 1 The content of the element is ≤ 63000ppm; and / or,

[0103] A 2 When the element content is ≤58000ppm, it can further improve the lithium ion transmission efficiency and gram capacity while ensuring the high stability of the positive electrode material.

[0104] Preferably, when M includes Te, the content of Te in the positive electrode material is ≤19500ppm; and / or, when M includes Se, the content of Se in the positive electrode material is ≤12000ppm; and / or,

[0105] When M includes Bi, the content of Bi element in the positive electrode material is ≤32000ppm.

[0106] In some embodiments of the present invention, M comprises Te, A 1 Including Mg, A 2 When Al is included, a positive electrode material having both excellent stability and capacity can be prepared.

[0107] Furthermore, in the positive electrode material, the content of Te element is 1000-15000 ppm, the content of Mg element is 1000-5000 ppm, and the content of Al element is 900-12000 ppm; and / or,

[0108] In the positive electrode material, the molar ratio of Te element to Co element is (0.001-0.015):1, the molar ratio of Mg element to Co element is (0.003-0.026):1, and the molar ratio of Al element to Co element is (0.001-0.04):1;

[0109] More preferably, in the matrix, when the content of Te element is 3000-5500 ppm, the content of Mg element is 700-1200 ppm, and the content of Al element is 200-2000 ppm, the structural stability of the positive electrode material can be improved and the side reaction between the positive electrode material and the electrolyte can be reduced.

[0110] In some embodiments of the present invention, the specific surface area of the positive electrode material is 0.1-1.2 m2 / g. The specific surface area of the positive electrode material can be measured by conventional methods in the art, for example, using a TriStar II Plus specific surface area analyzer, with a positive electrode material sample weight of 3 g, a degassing temperature of 260° C., a degassing time of 2 h, and the test performed in a liquid nitrogen environment (temperature of approximately -196° C.), a test pressure of 760 mmHg, and a test gas of high-purity nitrogen (purity ≥ 99.99%).

[0111] In some embodiments of the present invention, the Dv50 of the cathode material is 5 μm-20 μm; and / or,

[0112] The Dv10 of the positive electrode material is less than 5 μm; and / or

[0113] The Dv90 of the positive electrode material is greater than 25 μm.

[0114] The particle sizes Dv10, Dv50 and Dv90 of the positive electrode material can be measured by conventional methods in the art, such as a laser particle size analyzer.

[0115] When the specific surface area and particle size Dv10, Dv50 and Dv90 of the positive electrode material are within a specific range, the packing density of the positive electrode material is more appropriate, which is beneficial to improving the energy density of the battery; and the contact area with the electrolyte is more appropriate, which is not only beneficial to the electrolyte infiltration of the positive electrode material to improve the lithium ion transmission rate of the positive electrode material, but also can reduce the risk of side reactions between the electrolyte and the positive electrode material, which is beneficial to improving the cycle stability of the positive electrode material.

[0116] The present invention also provides a method for preparing the positive electrode material, which comprises at least the following steps:

[0117] (1) Co3O4 precursor, lithium source, M source, A 1 Source and First A 2 The sources are mixed and a first sintering process is performed to obtain an intermediate positive electrode material;

[0118] Wherein, M includes at least one of Te, Sb, Bi and Se, A 1 Contains at least one of Mg, Sr and Ba, A 2 Including at least one of Al, Ga and In; Co3O4 precursor calculated as Co, lithium source calculated as Li, M source calculated as M, A 1 A 1 Source and A 2 The first A 2 The molar ratio of the sources is (0.86-1):(1.03-1.07):(0.001-0.015):(0.001-0.055):(0-0.05);

[0119] (2) Combine the intermediate positive electrode material with the second A 2 Source and A 3 The source is mixed and a second sintering process is performed to obtain a positive electrode material;

[0120] Among them, the intermediate cathode material in terms of Co, 2 Second A 2 Source and A 3 A 3 The molar ratio of the sources is (0.86-1):(0-0.05):(0-0.02).

[0121] In the present invention, the lithium source includes at least one of lithium hydroxide, lithium nitrate, lithium carbonate, lithium oxalate, lithium acetate, lithium oxide and lithium citrate; the M source can be a compound containing the M element commonly used in the art, illustratively, the M source can be at least one of an oxide, chloride, hydroxide, carbonate, sulfate, nitrate, oxalate and acetate of the M element; A 1 The source can be a commonly used A 1 Compounds of elements, illustratively, A 1 The source can include A 1 At least one of the oxides, chlorides, hydroxides, carbonates, sulfates, nitrates, oxalates and acetates of an element; A 2 Source includes first A 2 Source and Second A 2 Source, First A 2 Source and Second A 2 The sources are each independently A 2 At least one of the oxides, chlorides, hydroxides, carbonates, sulfates, nitrates, oxalates and acetates of an element; A 3 The source can be a commonly used A 3 Compounds of elements, illustratively, A 3 The source can include A 3At least one of the oxides, chlorides, hydroxides, carbonates, sulfates, nitrates, oxalates and acetates of an element.

[0122] In the present invention, the conditions of the first sintering treatment include: the atmosphere is air atmosphere, the temperature is 900℃-1200℃ (for example, 900℃, 1000℃, 1100℃ or 1200℃), and the time is 8h-14h (for example, 8h, 9h, 10h, 11h, 12h, 13h or 14h).

[0123] In the present invention, the conditions for the second sintering treatment include: the atmosphere is air atmosphere, the temperature is 800℃-1050℃ (for example, 800℃, 900℃, 1000℃ or 1050℃), and the time is 8h-14h (for example, 8h, 9h, 10h, 11h, 12h, 13h or 14h).

[0124] The preparation method of the positive electrode material of the present invention introduces elements M and A with specific molar contents into lithium cobalt oxide through high temperature solid phase doping technology. 1 , thus forming a superlattice structure with a heterogeneous structure, which not only improves the lithium ion insertion / extraction activity of the material, but also stabilizes the lattice structure of the material, so that the positive electrode material has good structural stability while effectively improving the lithium ion transmission efficiency and gram capacity. Furthermore, the element A is introduced at the same time 2 、A 3 It can further improve the structural stability of the positive electrode material while ensuring higher gram capacity and lithium ion transmission efficiency.

[0125] In some embodiments, in order to improve the dispersion of the raw materials and improve the stability and capacity of the positive electrode material, A 1 The source and the M source are first mixed to form a mixture, and then mixed with the Co3O4 precursor, the lithium source and the first A 2 Source mixing.

[0126] In some embodiments, when the M element in the M source is Te, the M source may be telluric acid, A 1 A in the source 1 When the element is Mg, A 1 The source can be magnesium oxide and / or basic magnesium carbonate. Telluric acid can be mixed with magnesium oxide and / or basic magnesium carbonate, and then mixed with Co3O4 precursor, lithium source and first A 2Since magnesium oxide and / or basic magnesium carbonate are solid dispersants, telluric acid can be evenly distributed. During the mixing process, telluric acid will bond with magnesium oxide and / or basic magnesium carbonate, so that during the subsequent sintering process, the distribution trends of Te element and Mg element in the positive electrode material are consistent, which is manifested as the concentration of Te element in the coating layer is greater than the concentration of Te element in the second part, the concentration of Te element in the second part is greater than the concentration of Te element in the first part, the concentration of Mg element in the coating layer is greater than the concentration of Mg element in the second part, and the concentration of M element in the second part is greater than the concentration of Mg element in the first part.

[0127] In some embodiments, since part of the M element cannot enter the interior of the primary particles during the first sintering process, third particles including the M element are formed on the surface of the primary particles.

[0128] In some embodiments, after the M source is mixed with the Co3O4 precursor, the M source will be adsorbed on the surface of the Co3O4 precursor. During the sintering process, some M elements cannot enter the interior of the primary particles, but are accumulated in the grain boundary region of the primary particles, thereby causing the positive electrode material to show that the concentration of M elements in the grain boundary region is greater than the concentration of M elements in the non-grain boundary region.

[0129] A second aspect of the present invention provides a positive electrode sheet comprising the positive electrode material of the first aspect.

[0130] In the present invention, the positive electrode sheet includes a positive electrode current collector and a positive electrode active layer located on at least one surface of the positive electrode current collector. The positive electrode active layer includes a positive electrode material. The positive electrode active layer may further include additives commonly used in the art, such as at least one of a positive electrode conductive agent and a positive electrode binder. The stoichiometric ratio of the positive electrode material, positive electrode conductive agent, and positive electrode binder may be set as commonly used in the art.

[0131] A third aspect of the present invention provides a lithium-ion battery comprising the positive electrode sheet of the second aspect.

[0132] It can be understood that the battery also includes a diaphragm, a negative electrode sheet, an outer packaging and an electrolyte. In the present invention, the positive electrode sheet, the diaphragm and the negative electrode sheet can be assembled into an electrode assembly, and then the electrode assembly can be placed in the outer packaging, and the electrolyte can be injected into the outer packaging. After sealing and formation, a lithium-ion battery is formed.

[0133] In some embodiments of the present invention, when the electrolyte includes a nitrile compound, it has a high compatibility with the positive electrode material of the present invention. This is because the nitrile compound has a special structure and is compatible with the elements M and A in the positive electrode material. 1 It has a strong protective effect, thereby being able to protect the superlattice structure of the positive electrode material, which is beneficial to further improve the performance of the positive electrode material under high voltage.

[0134] In the present invention, the mass content of the nitrile compound in the electrolyte can be measured by conventional methods in the art, such as gas chromatography (GC).

[0135] In the present invention, the nitrile compound includes, for example, at least one of succinonitrile (SN), adiponitrile (ADN), 1,2-bis-(2-cyanoethoxy)ethane (DENE) and 1,3,6-hexanetricarbonitrile (HTCN).

[0136] Preferably, the mass percentage of the nitrile compound in the electrolyte is 2-8%.

[0137] The present invention will be further described below with reference to specific embodiments:

[0138] Example 1a

[0139] The positive electrode material of this embodiment is prepared by a method comprising the following steps:

[0140] 1) Co3O4 precursor calculated as Co, lithium carbonate powder calculated as Li (particle size of about 5 μm), TeO3 calculated as Te, SrO calculated as Sr and Ga2O3 calculated as Ga are placed in a high-speed mixing equipment according to a molar ratio of 0.981:1.04:0.008:0.005:0.001, and the mixture is mixed at a speed of 300 rpm for 3 minutes, at a speed of 500 rpm for 5 minutes, and at a speed of 1000 rpm for 10 minutes, and then the mixture is taken out (after confirming that there are no white lithium carbonate spots in the mixture, it is considered that the mixture is uniform); the mixture is placed in a ceramic crucible and a muffle furnace (well type with the equipment model VBF-1200X) is used for the first sintering treatment to obtain an intermediate positive electrode material, wherein the heating rate is 5°C / min, and the temperature is raised to 1085°C for constant temperature sintering for 10 hours. After sintering, the sample is taken out after naturally cooling to room temperature;

[0141] 2) The obtained intermediate positive electrode material calculated as Co, ZrO2 calculated as Zr, La2O3 calculated as La, Y2O3 calculated as Y, LiF calculated as F and Al2O3 calculated as Al are placed in a high-speed mixing device and mixed evenly according to a molar ratio of 0.981:0.001:0.001:0.001:0.001:0.001; the mixed material is placed in a ceramic crucible and subjected to a second sintering treatment in a muffle furnace to obtain a positive electrode material, wherein the heating rate is 5°C / min, and the temperature is raised to 950°C and constant temperature sintering is performed for 12 hours;

[0142] Among them, the chemical formula of the positive electrode material is LiCo 0.981 Te 0.008 Sr 0.005 Ga 0.001 Al 0.001 Zr 0.001 La0.001 F 0.00 1Y 0.001 O2;

[0143] In the positive electrode material, the molar ratio of M element to Co element is 0.0082:1, A 1 The molar ratio of the element to the Co element is 0.0051:1, 2 The molar ratio of the element to the Co element is 0.002:1;

[0144] The content of M element is 10348ppm, A 1 The content of elements is 4441ppm, A 2 The content of the element is 980ppm; the positive electrode material includes a substrate and a coating layer coated on the surface of the substrate. In the substrate, the content of the M element is 3500ppm, and the A 1 The content of the element is 1000ppm, A 2 The content of the element is 250ppm;

[0145] The specific surface area is 0.172m 2 / g, particle size Dv10 is 4.41μm, Dv50 is 15.69μm, and Dv90 is 27.33μm.

[0146] Example 2a

[0147] The positive electrode material of this embodiment is prepared by a method comprising the following steps:

[0148] 1) Co3O4 precursor calculated as Co, lithium carbonate powder calculated as Li (particle size of about 5 μm), SbO2 calculated as Sb, MgO calculated as Mg and In2O3 calculated as In are placed in a high-speed mixing equipment according to a molar ratio of 0.956:1.04:0.012:0.02:0.0085, and the mixture is mixed at a speed of 300 rpm for 3 minutes, at a speed of 500 rpm for 5 minutes, and at a speed of 1000 rpm for 10 minutes, and then the mixture is taken out (after confirming that there are no white lithium carbonate spots in the mixture, it is considered that the mixture is uniform); the mixture is placed in a ceramic crucible and a muffle furnace is used for a first sintering treatment to obtain an intermediate positive electrode material, wherein the heating rate is 5°C / min, and when the temperature is raised to 1085°C, constant temperature sintering is performed for 10 hours, and the sample is taken out after naturally cooling to room temperature after sintering;

[0149] 2) the obtained intermediate positive electrode material calculated as Co, ZrO2 calculated as Zr, La2O3 calculated as La, Y2O3 calculated as Y, LiF calculated as F and Al2O3 calculated as Al are placed in a high-speed mixing device and mixed evenly in a molar ratio of 0.956:0.0005:0.0005:0.0005:0.0005:0.0015; the mixed material is placed in a high-speed mixing device and mixed evenly; the mixed material is placed in a ceramic crucible and subjected to a second sintering treatment in a muffle furnace to obtain a positive electrode material, wherein the heating rate is 5°C / min, and the temperature is raised to 950°C and constant temperature sintering is performed for 12 hours;

[0150] Among them, the chemical formula is LiCo 0.956 Sb 0.012 Mg 0.02 In 0.0085 Al 0.0015 Zr 0.0005 La 0.0005 F 0.0005 Y 0.0005 O2;

[0151] In the positive electrode material, the molar ratio of M element to Co element is 0.0126:1, A 1 The molar ratio of the element to the Co element is 0.0209:1, 2 The molar ratio of the element to the Co element is 0.0105:1;

[0152] The content of M element is 14841ppm, A 1 The content of the element is 4937ppm, A 2 The content of the element is 1440ppm; the positive electrode material includes a substrate and a coating layer coated on the surface of the substrate. In the substrate, the content of the M element is 5019ppm, and the A 1 The content of the element is 1111ppm, A 2 The element content is 367ppm; the specific surface area is 0.47m 2 / g, particle size Dv10 is 3.8μm, Dv50 is 14.3μm, and Dv90 is 39μm.

[0153] Example 3a

[0154] The positive electrode material of this embodiment is prepared by a method comprising the following steps:

[0155] 1) Co3O4 precursor calculated as Co, lithium carbonate powder calculated as Li (particle size of about 5 μm), BiO2 calculated as Bi, BaO calculated as Ba and Al2O3 calculated as Al are placed in a high-speed mixing equipment according to a molar ratio of 0.951:1.04:0.003:0.01:0.028, and the mixture is mixed at a speed of 300 rpm for 3 minutes, at a speed of 500 rpm for 5 minutes, and at a speed of 1000 rpm for 10 minutes, and then the mixture is taken out (after confirming that there are no white lithium carbonate spots in the mixture, it is considered that the mixture is uniform); the mixture is placed in a ceramic crucible and a muffle furnace is used for a first sintering treatment to obtain an intermediate positive electrode material, wherein the heating rate is 5°C / min, and when the temperature is raised to 1085°C, constant temperature sintering is performed for 10 hours, and the sample is taken out after naturally cooling to room temperature after sintering;

[0156] 2) The obtained intermediate positive electrode material calculated as Co, ZrO2 calculated as Zr, La2O3 calculated as La, Y2O3 calculated as Y, LiF calculated as F and Al2O3 calculated as Al are placed in a high-speed mixing device and mixed evenly according to a molar ratio of 0.951:0.0015:0.0015:0.0015:0.0015:0.0015:0.002; the mixed material is placed in a ceramic crucible and subjected to a second sintering treatment in a muffle furnace to obtain a positive electrode material, wherein the heating rate is 5°C / min, and the temperature is raised to 950°C and constant temperature sintering is performed for 12 hours;

[0157] Among them, the chemical formula is LiCo 0.951 Bi 0.003 Ba 0.01 Al 0.03 Zr 0.0015 La 0.0015 F 0.0015 Y 0.0015 O2; In the positive electrode material, the molar ratio of M element to Co element is 0.0032:1, A 1 The molar ratio of the element to the Co element is 0.0105:1, 2 The molar ratio of the element to the Co element is 0.0315:1;

[0158] The content of M element is 6347ppm, A 1 The content of elements is 13904ppm, A 2 The content of the element is 546ppm; the positive electrode material includes a substrate and a coating layer coated on the surface of the substrate. In the substrate, the content of M element is 2146ppm, A 1 The content of the element is 3130ppm, A 2 The content of the element is 2020ppm;

[0159] The specific surface area is 0.39m 2 / g, particle size Dv10 is 4.4μm, Dv50 is 16μm, and Dv90 is 42μm.

[0160] Example 4a

[0161] The preparation method of the positive electrode material of this embodiment is basically the same as that of embodiment 1a, except that the addition amount of each element is different. The chemical formula of the prepared positive electrode material is LiCo 0.988 Te 0.001 Sr 0.005 Ga 0.001 Al 0.001 Zr 0.001 La 0.00 1F 0.001 Y 0.001 O2;

[0162] In the positive electrode material, the molar ratio of M element to Co element is 0.0010:1, A 1 The molar ratio of the element to the Co element is 0.0051:1, 2 The molar ratio of the element to the Co element is 0.002:1;

[0163] The content of M element is 1300ppm, A 1 The content of the element is 4464ppm, A 2 The content of the element is 985ppm; the positive electrode material includes a substrate and a coating layer coated on the surface of the substrate. In the substrate, the content of the M element is 440ppm, and the A 1 The content of the element is 1005ppm, A 2 The content of the element is 251ppm;

[0164] The specific surface area of the positive electrode material is 0.33m 2 / g, particle size Dv10 is 4.9μm, Dv50 is 16μm, and Dv90 is 45μm.

[0165] Example 5a

[0166] The preparation method of the positive electrode material of this embodiment is basically the same as that of embodiment 1a, except that the addition amount of each element is different. The chemical formula of the prepared positive electrode material is LiCo 0.974 Te 0.015 Sr 0.005 Ga 0.001 Al 0.001 Zr 0.001 La 0.00 1F 0.001 Y 0.001 O2;

[0167] In the positive electrode material, the molar ratio of M element to Co element is 0.0154:1, A 1 The molar ratio of the element to the Co element is 0.0051:1, 2 The molar ratio of the element to the Co element is 0.002:1;

[0168] The content of M element is 19314ppm, A 1 The content of elements is 4421ppm, A 2 The content of the element is 976ppm; the positive electrode material includes a substrate and a coating layer coated on the surface of the substrate. In the substrate, the content of M element is 6532ppm, and A 1 The content of the element is 995ppm, A 2 The content of the element is 248ppm;

[0169] The specific surface area of the positive electrode material is 1.23m 2 / g, particle size Dv10 is 2.6μm, Dv50 is 9μm, and Dv90 is 26μm.

[0170] Example 6a

[0171] The preparation method of the positive electrode material of this embodiment is basically the same as that of embodiment 1a, except that the addition amount of each element is different. The chemical formula of the prepared positive electrode material is LiCo 0.985 Te 0.008 Sr 0.001 Ga 0.001 Al 0.001 Zr 0.001 La 0.00 1F 0.001 Y 0.001 O2;

[0172] In the positive electrode material, the molar ratio of M element to Co element is 0.0081:1, A 1 The molar ratio of the element to the Co element is 0.001:1, 2 The molar ratio of the element to the Co element is 0.002:1;

[0173] The content of M element is 10363ppm, A 1 The content of the element is 890ppm, A 2 The content of the element is 982ppm; the positive electrode material includes a substrate and a coating layer coated on the surface of the substrate. In the substrate, the content of M element is 3505ppm, and A 1 The content of the element is 200ppm, A 2 The content of the element is 232ppm;

[0174] The specific surface area of the positive electrode material is 0.46m2 / g, particle size Dv10 is 3.9μm, Dv50 is 14.5μm, and Dv90 is 40μm;

[0175] Example 7a

[0176] The preparation method of the positive electrode material of this embodiment is basically the same as that of embodiment 1a, except that the addition amount of each element is different. The chemical formula of the prepared positive electrode material is LiCo 0.931 Te 0.008 Sr 0.055 Ga 0.001 Al 0.001 Zr 0.001 La 0.00 1F 0.001 Y 0.001 O2;

[0177] In the positive electrode material, the molar ratio of M element to Co element is 0.0086:1, A 1 The molar ratio of the element to the Co element is 0.0591:1, 2 The molar ratio of the element to the Co element is 0.0021:1;

[0178] The content of M element is 10203ppm, A 1 The content of elements is 48166ppm, A 2 The content of the element is 966ppm; the positive electrode material includes a substrate and a coating layer coated on the surface of the substrate. In the substrate, the content of M element is 3450ppm, A 1 The content of the element is 10845ppm, A 2 The content of the element is 246ppm;

[0179] The specific surface area of the positive electrode material is 0.42m 2 / g, particle size Dv10 is 3.9μm, Dv50 is 15μm, and Dv90 is 45μm.

[0180] Example 8a

[0181] The preparation method of the positive electrode material of this embodiment is basically the same as that of embodiment 2a, except that the addition amount of each element is different. The chemical formula of the prepared positive electrode material is LiCo 0.971 Sb 0.012 Mg 0.005 In 0.0085 Al 0.0015 Zr 0.0005 La 0.0005 F 0.0005 Y 0.0005 O2;

[0182] In the positive electrode material, the molar ratio of M element to Co element is 0.0124:1, A 1 The molar ratio of the element to the Co element is 0.0051:1, 2 The molar ratio of the element to the Co element is 0.0102:1;

[0183] The content of M element is 14770ppm, A 1 The content of the element is 1228ppm, A 2 The content of the element is 1433ppm; the positive electrode material includes a substrate and a coating layer coated on the surface of the substrate. In the substrate, the content of the M element is 4995ppm, and the A 1 The content of the element is 276ppm, A 2 The content of the element is 365ppm;

[0184] The specific surface area of the positive electrode material is 0.46m 2 / g, particle size Dv10 is 4.1μm, Dv50 is 14.8μm, and Dv90 is 38μm.

[0185] Example 9a

[0186] The preparation method of the positive electrode material of this embodiment is basically the same as that of embodiment 3a, except that the addition amount of each element is different. The chemical formula of the prepared positive electrode material is LiCo 0.941 Bi 0.003 Ba 0.02 Al 0.03 Zr 0.0015 La 0.0015 F 0.001 5Y 0.0015 O2;

[0187] In the positive electrode material, the molar ratio of M element to Co element is 0.0032:1, A 1 The molar ratio of the element to the Co element is 0.0213:1, 2 The molar ratio of the element to the Co element is 0.0319:1;

[0188] The content of M element is 6329ppm, A 1 The content of the element is 27727ppm, A 2 The content of the element is 7899ppm; the positive electrode material includes a substrate and a coating layer coated on the surface of the substrate. In the substrate, the content of M element is 2140ppm, A 1 The content of the element is 6243ppm, A 2 The content of the element is 2014ppm;

[0189] The specific surface area of the positive electrode material is 0.46m2 / g, particle size Dv10 is 4μm, Dv50 is 14.7μm, and Dv90 is 36.5μm.

[0190] Example 10a

[0191] The preparation method of the positive electrode material of this embodiment is basically the same as that of embodiment 1a, except that the addition amount of each element is different. The chemical formula of the prepared positive electrode material is LiCo 0.982 Te 0.008 Sr 0.005 Al 0.001 Zr 0.001 La 0.001 F 0.00 1Y 0.001 O2;

[0192] In the positive electrode material, the molar ratio of M element to Co element is 0.0082:1, A 1 The molar ratio of the element to the Co element is 0.0051:1, 2 The molar ratio of the element to the Co element is 0.002:1;

[0193] The content of M element is 10352ppm, A 1 The content of the element is 6963ppm, A 2 The content of the element is 998ppm; the positive electrode material includes a substrate and a coating layer coated on the surface of the substrate. In the substrate, the content of M element is 3501ppm, A 1 The content of the element is 1568ppm, A 2 The content of the element is 255ppm;

[0194] The specific surface area of the positive electrode material is 0.6m 2 / g, particle size Dv10 is 3.6μm, Dv50 is 12.2μm, and Dv90 is 31.5μm.

[0195] Comparative Example 1a

[0196] The positive electrode material of this comparative example was prepared by a method comprising the following steps:

[0197] A Co3O4 precursor calculated as Co, lithium carbonate powder calculated as Li (particle size of about 5 μm), and TeO3 calculated as Te are placed in a high-speed mixing device at a molar ratio of 0.992:1.04:0.008, and mixed at a speed of 300 rpm for 3 minutes, a speed of 500 rpm for 5 minutes, and a speed of 1000 rpm for 10 minutes, and then the mixture is taken out (after confirming that there are no white lithium carbonate spots in the mixture, it is considered that the mixture is uniform); the mixture is placed in a ceramic crucible and sintered at a high temperature in a muffle furnace, wherein the heating rate is 5°C / min, and the temperature is raised to 1085°C for constant temperature sintering for 10 hours. After sintering, the sample is taken out after naturally cooling to room temperature;

[0198] Among them, the chemical formula is LiCo 0.992 Te 0.008 O2.

[0199] Comparative Example 2a

[0200] The positive electrode material of this comparative example was prepared by a method comprising the following steps:

[0201] A Co3O4 precursor calculated as Co, lithium carbonate powder calculated as Li (particle size of about 5 μm) and MgO calculated as Mg were placed in a high-speed mixing equipment in a molar ratio of 0.98:1.04:0.02, and mixed at a speed of 300 rpm for 3 minutes, a speed of 500 rpm for 5 minutes, and a speed of 1000 rpm for 10 minutes, and then the mixture was taken out (after confirming that there were no white lithium carbonate spots in the mixture, it was considered that the mixture was uniform); the mixture was placed in a ceramic crucible and sintered at a high temperature in a muffle furnace, wherein the heating rate was 5°C / min, and the temperature was raised to 1085°C for constant temperature sintering for 10 hours. After sintering, the sample was taken out after naturally cooling to room temperature;

[0202] Among them, the chemical formula is LiCo 0.98 Mg 0.02 O2.

[0203] Comparative Example 3a

[0204] The positive electrode material of this comparative example was prepared by a method comprising the following steps:

[0205] A Co3O4 precursor calculated as Co, lithium carbonate powder calculated as Li (particle size of about 5 μm) and Al2O3 calculated as Al were placed in a high-speed mixing device in a molar ratio of 0.97:1.04:0.03, mixed at a speed of 300 rpm for 3 minutes, mixed at a speed of 500 rpm for 5 minutes, and mixed at a speed of 1000 rpm for 10 minutes, and then the mixture was taken out (after confirming that there were no white lithium carbonate spots in the mixture, it was considered that the mixture was uniform); the mixture was placed in a ceramic crucible and sintered at a high temperature in a muffle furnace, wherein the heating rate was 5°C / min, and constant temperature sintering was carried out when the temperature was raised to 1100°C for 10 hours. After sintering, the sample was taken out after the temperature naturally dropped to room temperature;

[0206] Among them, the chemical formula is LiCo 0.97 Al 0.03 O2.

[0207] Comparative Example 4a

[0208] The positive electrode material of this comparative example was prepared by a method comprising the following steps:

[0209] Compared with the embodiment, the positive electrode material of this comparative example does not include A 1 element;

[0210] 1) Co3O4 precursor calculated as Co, lithium carbonate powder calculated as Li (particle size of about 5 μm), TeO3 calculated as Te and Ga2O3 calculated as Ga are placed in a high-speed mixing equipment according to a molar ratio of 0.986:1.04:0.008:0.001, and the mixture is mixed at a speed of 300 rpm for 3 minutes, at a speed of 500 rpm for 5 minutes, and at a speed of 1000 rpm for 10 minutes, and then the mixture is taken out (after confirming that there are no white lithium carbonate spots in the mixture, it is considered that the mixture is uniform); the mixture is placed in a ceramic crucible and a muffle furnace is used for a first sintering treatment to obtain an intermediate positive electrode material, wherein the heating rate is 5°C / min, and when the temperature is raised to 1085°C, constant temperature sintering is performed for 10 hours, and the sample is taken out after naturally cooling to room temperature after sintering;

[0211] 2) The obtained intermediate positive electrode material calculated as Co, ZrO2 calculated as Zr, La2O3 calculated as La, Y2O3 calculated as Y, LiF calculated as F and Al2O3 calculated as Al are placed in a high-speed mixing device and mixed evenly according to a molar ratio of 0.986:0.001:0.001:0.001:0.001:0.001; the mixed material is placed in a ceramic crucible and subjected to a second sintering treatment in a muffle furnace to obtain a positive electrode material, wherein the heating rate is 5°C / min, and the temperature is raised to 950°C and constant temperature sintering is performed for 12 hours;

[0212] Among them, the chemical formula is LiCo 0.986 Te0.008 Ga 0.001 Al 0.001 Zr 0.001 La 0.001 F 0.001 Y 0.001 O2.

[0213] Comparative Example 5a

[0214] The positive electrode material of this comparative example was prepared by a method comprising the following steps:

[0215] Compared with the embodiment, the positive electrode material of this comparative example does not include the M element;

[0216] 1) Co3O4 precursor calculated as Co, lithium carbonate powder calculated as Li (particle size of about 5 μm), SrO calculated as Sr, and Ga2O3 calculated as Ga are placed in a high-speed mixing equipment in a molar ratio of 0.989:1.04:0.005:0.001, mixed at a speed of 300 rpm for 3 minutes, mixed at a speed of 500 rpm for 5 minutes, and mixed at a speed of 1000 rpm for 10 minutes, and then the mixture is taken out (after confirming that there are no white lithium carbonate spots in the mixture, it is considered that the mixture is uniform); the mixture is placed in a ceramic crucible and a muffle furnace is used for a first sintering treatment to obtain an intermediate positive electrode material, wherein the heating rate is 5°C / min, and when the temperature is raised to 1085°C, constant temperature sintering is performed for 10 hours, and the sample is taken out after naturally cooling to room temperature after sintering;

[0217] 2) The obtained intermediate positive electrode material calculated as Co, ZrO2 calculated as Zr, La2O3 calculated as La, Y2O3 calculated as Y, LiF calculated as F and Al2O3 calculated as Al are placed in a high-speed mixing device and mixed evenly in a molar ratio of 0.989:0.001:0.001:0.001:0.001:0.001; the mixed material is placed in a ceramic crucible and subjected to a second sintering treatment in a muffle furnace to obtain a positive electrode material, wherein the heating rate is 5°C / min, and the temperature is raised to 950°C and constant temperature sintering is performed for 12 hours;

[0218] Among them, the chemical formula is LiCo 0.989 Sr 0.005 Ga 0.001 Al 0.001 Zr 0.001 La 0.001 F 0.001 Y 0.001 O2.

[0219] Performance Testing

[0220] The following performance tests were performed on the positive electrode materials and batteries in the examples and comparative examples, and the results are shown in Table 1.

[0221] 1) SEM test

[0222] Figure 2 This is a SEM image of the intermediate positive electrode material of Example 1 of the present invention; Figure 3 This is an EDS graph of the M element in the intermediate positive electrode material of Example 1 of the present invention; Figure 4 This is an EDS graph of the Al element in the intermediate positive electrode material of Example 1 of the present invention; Figure 5 This is an EDS graph of the A2 element in the intermediate positive electrode material of Example 1 of the present invention; Figure 6 This is a SEM image of the positive electrode material in Example 1 of the present invention at one magnification;

[0223] Figure 7 This is a SEM image of the positive electrode material in Comparative Example 5 of the present invention; Figure 8 This is a SEM image of the positive electrode material in Example 1 of the present invention at another magnification.

[0224] from Figure 2-5 It can be seen that in the intermediate positive electrode material in the embodiment of the present invention, the concentration of the M element in the second part is higher than the concentration of the M element in the first part (R1:R2 is 9:1), the concentration of the M element in the grain boundary area is higher than the concentration of the M element in the non-grain boundary area, and the concentration of the M element in the crack area is higher than the concentration of the M element in the non-crack area; and the distribution areas of the A1 element and the M element in the positive electrode material are consistent; the A2 element is evenly distributed in the positive electrode material.

[0225] from Figure 8 It can be seen that the surface of the positive electrode material in the embodiment of the present invention has third particles, and the size of the third particles is between 50-500 nm.

[0226] from Figure 6 and Figure 7 It can be seen that the surface morphology of the positive electrode material in the embodiment of the present invention is inconsistent with the surface morphology of the positive electrode material in the comparative example.

[0227] 2) XRD test

[0228] The positive electrode material prepared in the preparation example was subjected to XRD testing. The specific testing method was as follows: the positive electrode material powder was evenly spread in the XRD sample trough, and an X-ray diffractometer (Bruker D8 Advance, Germany) was used, equipped with a Cu target (wavelength of 0.1542 nm); the test mode was θ-2θ scanning mode, with a step of 0.01°, a scanning range of 20° to 80°, a speed of 5° / min, and a voltage of 40 kV. Figure 9 This is the XRD pattern of the positive electrode material in Example 1 of the present invention. Figure 9As shown, it has characteristic peaks at 2θ of 18°-18.5°, 19.5°-20.3°, 20.5°-21.1° and 22.5°-23.4°; and a 003 peak at 18.6°-19.1°, a 006 peak at 37.1°-37.6°, a 012 peak at 38.7°-39.5° and a 104 peak at 45.0°-45.5°. The XRD diffraction patterns of the positive electrode materials prepared in the other embodiments all meet the following requirements: characteristic peaks at 2θ of 18°-18.5°, 19.5°-20.3°, 20.5°-21.1°, and 22.5°-23.4°; a 003 peak at 18.6°-19.1°, a 006 peak at 37.1°-37.6°, a 012 peak at 38.7°-39.5°, and a 104 peak at 45°-45.5°.

[0229] 2) Cycle test

[0230] The positive electrode materials prepared in the examples and comparative examples were prepared into button batteries for testing. The button batteries were prepared by a method comprising the following steps:

[0231] The positive electrode material, acetylene black, and polyvinylidene fluoride were mixed in 10 ml of N-methylpyrrolidone in a mass ratio of 8:1:1, stirred thoroughly to form a slurry, coated on the surface of aluminum foil, and cut into appropriate sizes after drying. A button cell was assembled in an argon-protected glove box using a lithium sheet as the negative electrode and a lithium hexafluorophosphate solution as the electrolyte using a 2032-type button cell shell.

[0232] At 45°C, the battery was charged to 4.30V at a current density of 1.2C, then charged at a constant voltage of 4.30V with a cutoff current of 0.8C, then allowed to stand for 1 minute, and then continued to charge to 4.60V at a current density of 0.8C, then charged at a constant voltage of 4.6V with a cutoff current of 0.05C, then allowed to stand for 10 minutes, and then discharged to 3.0V at a current density of 0.5C, then allowed to stand for 10 minutes. The discharge capacity of the battery at this time was recorded as the initial capacity; the above charge and discharge process was repeated until the 500th cycle of constant voltage charging process was completed and allowed to stand for 10 minutes, and then discharged to 3.0V at a current density of 0.5C, allowed to stand for 10 minutes, and the discharge capacity of the battery at this time was recorded as the capacity after the cycle. The cycle capacity retention rate = capacity after the cycle × 100% / initial capacity, and the cycle capacity retention rate is recorded in Table 1.

[0233] 3) Rate test

[0234] At 25°C, the battery was charged at a constant current density of 1.2C to 4.30V, then charged at a constant voltage of 4.30V with a cutoff current of 0.8C, then allowed to stand for 1 min, and continued to be charged at a constant current density of 0.8C to 4.60V, then charged at a constant voltage of 4.6V with a cutoff current of 0.05C, then allowed to stand for 10 min, and then discharged at a current density of 0.1C to 3.0V, followed by standing for 10 min. The above charge and discharge process was repeated three times, and the discharge capacity of the above three batteries was recorded as the discharge capacity at 0.1C;

[0235] Similarly, after the same charging process, when the battery reaches 4.6V, it is discharged to 3.0V at current densities of 0.2C, 0.5C, and 1C, respectively. Three discharges are performed at each different rate to obtain the average value as the discharge capacity at that rate.

[0236] Then the rate retention rate = specific rate discharge capacity / 0.1C rate discharge capacity × 100%; for example, the 0.2C capacity is 210mAh / g, and the 0.1C capacity is 215mAh / g, then the 0.2C / 0.1C rate is 210 / 215=97.6%,

[0237] Table 1

[0238]

[0239] Table 1 shows that the positive electrode material of the comparative example has a relatively low capacity, exhibiting only approximately 190 mAh / g of gram capacity at 3V-4.6V and 0.1C charge / discharge conditions. In contrast, the positive electrode material prepared in the example exhibits an average gram capacity of ≥215 mAh / g under the same conditions. Furthermore, the positive electrode material of the present invention exhibits higher cycling stability and lithium ion transfer efficiency than the comparative example.

[0240] Example 1b

[0241] The battery of the present invention is prepared by a method comprising the following steps:

[0242] 1) Preparation of positive electrode

[0243] The positive electrode material of Example 1a, polyvinylidene fluoride, and acetylene black were mixed in a mass ratio of 97:1.5:1.5, N-methylpyrrolidone was added, and the mixture was stirred in a vacuum mixer until the mixture formed a positive electrode slurry with uniform fluidity. The positive electrode slurry was evenly coated on an aluminum foil with a thickness of 9 μm. The coated aluminum foil was baked in an oven with five different temperature gradients and then dried in an oven at 120° C. for 8 h. The desired positive electrode sheet was obtained by roller pressing and slitting.

[0244] 2) Preparation of negative electrode sheet

[0245] A negative electrode slurry was prepared by a wet process using artificial graphite, single-walled carbon nanotubes, conductive carbon black, sodium carboxymethyl cellulose, and styrene-butadiene rubber in a mass ratio of 96.9:0.1:0.9:0.8:1.3. The slurry was then coated on the surface of the negative electrode current collector copper foil. The negative electrode sheet was obtained by drying (temperature 85°C, time 5h), rolling, and die-cutting.

[0246] 3) Preparation of electrolyte

[0247] In an argon-filled glove box (moisture <10ppm, oxygen <1ppm), ethylene carbonate (EC), propylene carbonate (PC), and propyl propionate (PP) were mixed in a mass ratio of 1.5:1:2. 13% of LiPF6 and 5% of adiponitrile based on the total mass of the non-aqueous electrolyte were slowly added to the mixed solution, and the mixture was stirred to obtain an electrolyte.

[0248] 4) Preparation of batteries

[0249] The positive electrode sheet, separator (polyethylene film with a thickness of 5μm) and negative electrode sheet are wound to obtain a bare battery cell without liquid injection; the bare battery cell is placed in an outer packaging foil, and the electrolyte is injected into the dried bare battery cell. After vacuum packaging, standing, formation, shaping, sorting and other processes, a battery is obtained.

[0250] Examples 2b-10b and Comparative Examples 1b-5b

[0251] The preparation methods of the batteries of Example 2b=10b and Comparative Examples 1b-5b are substantially the same as that of Example 1b, except that the positive electrode materials in Example 1b are replaced by the positive electrode materials in Examples 2a-10a and Comparative Examples 1a-5a, respectively.

[0252] Example 11b

[0253] The preparation method of the battery of this embodiment is basically the same as that of embodiment 1b, except that the nitrile additive in embodiment 1b is replaced by succinonitrile of the same mass.

[0254] Example 12b

[0255] The preparation method of the battery of this embodiment is basically the same as that of Example 1b, except that the nitrile additive in Example 1b is replaced by 1,3,6-hexanetrinitrile of the same mass.

[0256] Example 13b

[0257] The preparation method of the battery of this embodiment is basically the same as that of Example 1b, except that the mass content of adiponitrile in the electrolyte is 2%.

[0258] Example 14b

[0259] The preparation method of the battery of this embodiment is basically the same as that of Example 1b, except that the mass content of adiponitrile in the electrolyte is 8%.

[0260] Performance Testing

[0261] The following performance tests were performed on the batteries in the examples and comparative examples, and the results are shown in Table 2.

[0262] 1) Cycle test

[0263] At 45°C, the battery was charged to 4.30V at a current density of 1.2C, then charged at a constant voltage of 4.30V with a cutoff current of 0.8C, then allowed to stand for 1 minute, and then continued to charge to 4.53V at a current density of 0.8C, then charged at a constant voltage of 4.53V with a cutoff current of 0.05C, then allowed to stand for 10 minutes, and then discharged to 3.0V at a current density of 0.5C, then allowed to stand for 10 minutes. The discharge capacity of the battery at this time was recorded as the initial capacity; the above charge and discharge process was repeated until the 400th cycle of constant voltage charging process was completed and allowed to stand for 10 minutes, and then discharged to 3.0V at a current density of 0.5C, allowed to stand for 10 minutes, and the discharge capacity of the battery at this time was recorded as the capacity after the cycle. The cycle capacity retention rate = capacity after the cycle × 100% / initial capacity. The results are recorded in Table 2.

[0264] 2) Rate test

[0265] At 25°C, the battery was charged at a constant current density of 1.2C to 4.30V, then charged at a constant voltage of 4.30V with a cutoff current of 0.8C, then allowed to stand for 1 minute, and then continued to charge at a constant current density of 0.8C to 4.53V, then charged at a constant voltage of 4.53V with a cutoff current of 0.05C, then allowed to stand for 10 minutes, and then discharged at a current density of 0.2C to 3.0V, followed by standing for 10 minutes. The above charge and discharge process was repeated three times, and the discharge capacity of the above three batteries was recorded as the discharge capacity at 0.2C;

[0266] Similarly, after the same charging process, the battery reaches 4.53V and is discharged to 3.0V at current densities of 0.3C, 0.5C, and 0.7C, respectively. Three discharges are performed at each different rate to obtain the average value as the discharge capacity at that rate.

[0267] Then, the rate retention ratio = specific rate discharge capacity / 0.2C rate discharge capacity × 100%. The rate retention ratio results are recorded in Table 2.

[0268] Table 2

[0269]

[0270]

[0271] It can be seen from Table 2 that the battery prepared with the positive electrode material of the present invention has higher cycle stability and rate performance than that of the comparative example.

[0272] In Examples 12b-14b, the capacity retention rate of the battery at high rate increases. This is because as the battery rate increases, the temperature of the battery will increase, and the temperature increase will improve the rate performance of the battery to a certain extent, which is manifested as an increase in the capacity retention rate of the battery at high rate.

[0273] 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 positive electrode material, characterized in that The positive electrode material includes primary particles having Formula 1; Li a Co b M c A 1 d A 2 e A 3 f O2 type 1 In formula 1, 0.8≤a≤1.03, 0.86≤b<1, 0 <c≤0.015,0<d≤0.055,0<e≤0.05,0≤f≤0.02,0.1≤d / c≤7; M includes at least one of Te, Sb, Bi, and Se, and A 1 Contains at least one of Mg, Sr and Ba, A 2 Including at least one of Al, Ga and In, A 3 including at least one of F, Ti, Zr, Y, La, W, and Si; The M element is non-uniformly distributed in the primary particles; In the X-ray diffraction pattern, the positive electrode material has characteristic peaks at 2θ of 18°-18.5°, 19.5°-20.3°, 20.5°-21.1° and 22.5°-23.4°.

2. The positive electrode material according to claim 1, characterized in that The primary particles include a matrix and a coating layer located on at least a portion of the surface of the matrix, wherein the matrix includes a first portion and a second portion from the inside out; wherein the concentration of the M element in the coating layer is greater than the concentration of the M element in the second portion, and the concentration of the M element in the second portion is greater than the concentration of the M element in the first portion; Preferably, R1:R2=(0.7-0.99):0.1, R1 is the radius of the first part, and R2 is the ring width of the second part.

3. The positive electrode material according to claim 2, characterized in that The primary particles include first primary particles and second primary particles, wherein the second primary particles form secondary particles; In the secondary particles, the second primary particles include a grain boundary region and a non-grain boundary region; The secondary particles include first secondary particles and second secondary particles; In the second primary particles of the first secondary particles, the grain boundary region does not contain M element; and / or, In the second primary particle of the second secondary particle, the grain boundary region has the M element; Preferably, in the second primary particles of the second secondary particles, the concentration of the M element in the grain boundary region is greater than the concentration of the M element in the non-grain boundary region; and / or, The primary particles include crack regions and non-crack regions, and the concentration of the M element in some of the crack regions is greater than the concentration of the M element in the non-crack regions.

4. The positive electrode material according to any one of claims 2 to 3, characterized in that The primary particles have third particles on their surfaces, and the third particles include M elements; and / or the third particles have a size of 50-500 nm.

5. The positive electrode material according to any one of claims 2 to 4, characterized in that A in the coating layer 1 The concentration of the element is greater than that of A in the second part 1 The concentration of the element, in the second part A 1 The concentration of the element is greater than that in the first part A 1 the concentration of the element; and / or, The second part A 3 The concentration of the element gradually increases along the direction from the first portion to the coating layer.

6. The positive electrode material according to any one of claims 1 to 5, characterized in that In the positive electrode material, the content of element M is ≤32000ppm; and / or, A 1 The content of the element is ≤ 63000ppm; and / or, A 2 The content of elements is ≤58000ppm.

7. The positive electrode material according to any one of claims 1 to 6, characterized in that When M includes Te, the content of Te in the positive electrode material is ≤19500ppm; and / or, When M includes Se, the content of Se in the positive electrode material is ≤12000ppm; and / or, When M includes Bi, the content of Bi element in the positive electrode material is ≤32000 ppm.

8. The positive electrode material according to any one of claims 1 to 7, characterized in that The specific surface area of the positive electrode material is 0.1-1.2 m2 / g; and / or, The Dv50 of the positive electrode material is 5 μm-20 μm; and / or, The positive electrode material has a Dv10 less than 5 μm; and / or The Dv90 of the positive electrode material is greater than 25 μm.

9. A lithium-ion battery, characterized in that: The invention comprises a positive electrode sheet, wherein the positive electrode sheet comprises the positive electrode material according to any one of claims 1 to 7.

10. The lithium-ion battery according to claim 9, characterized in that Also included is an electrolyte, the electrolyte including a nitrile compound; Preferably, the mass percentage of the nitrile compound in the electrolyte is 2-8%; Preferably, the nitrile compound includes at least one of succinonitrile, adiponitrile, 1,2-bis-(2-cyanoethoxy)ethane and 1,3,6-hexanetrinitrile.

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