Single crystal ternary positive electrode material and preparation method therefor and use thereof

Abstract

The present application provides a single crystal ternary positive electrode material and a preparation method therefor and a use thereof. The single crystal ternary positive electrode material meets the following relationships: 1 μm≤P<5 μm, 1≤D2 / D1<10, and 3 μm<D50<8 μm, wherein P is the single crystal size of the single crystal ternary positive electrode material, D1 is the mass ratio of the single crystal ternary positive electrode material having a single crystal size of smaller than 2.5 μm, D2 is the mass ratio of the single crystal ternary positive electrode material having a single crystal size of greater than or equal to 2.5 μm, and D50 is the median particle size of the single crystal ternary positive electrode material. The single crystal ternary positive electrode material provided by the present application comprises two single crystal materials having different sizes, and the single crystal ternary positive electrode material has relatively high compaction density and good cycle performance by defining the particle sizes and proportions of single crystal materials having different sizes.

Description

A single crystal ternary cathode material and its preparation method and application

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on November 24, 2023, with application number 202311586595.9 and application name “A single crystal ternary positive electrode material, its preparation method and application”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of battery materials, and in particular to a single crystal ternary positive electrode material and its preparation method and application. Background Art

[0003] Single crystal ternary materials have better cycle stability than polycrystalline ternary materials, but the diffusion rate of lithium ions in single crystal ternary materials is not high, so the rate performance is low. In order to improve the rate performance of single crystal ternary materials, the commonly used method is to reduce the particle size of single crystal ternary materials (generally <2μm). However, the compaction density of small-sized single crystal ternary materials is relatively low. To solve the above problem, the existing technology mixes small-sized single crystal ternary materials and large-sized polycrystalline ternary materials to improve the compaction density of single crystal ternary materials. However, this method usually sacrifices some cycle performance, and the application scenarios of positive electrode materials are limited.

[0004] Application Contents

[0005] In view of this, the present application provides a single-crystal ternary positive electrode material, which includes two single-crystal materials of different sizes, and by limiting the ratio of single-crystal materials of different sizes, it has a higher compaction density and good cycle performance.

[0006] The present application also provides a method for preparing a single crystal ternary positive electrode material, which can prepare the above-mentioned single crystal ternary positive electrode material and has a simple process.

[0007] The present application also provides a positive electrode sheet. Since the positive electrode sheet includes the above-mentioned single crystal ternary positive electrode material, the positive electrode sheet is used in a battery to improve the electrical performance and cycle performance of the battery.

[0008] The present application also provides a battery, which includes the above-mentioned positive electrode sheet, so that the battery has excellent electrical performance and cycle stability.

[0009] In a first aspect, the present application provides a single crystal ternary cathode material that satisfies the following formulas 1 to 3: 1 μm ≤ P < 5 μm Formula 1, 1 ≤ D2 / D1 < 10 Formula 2, 3 μm < D50 < 8 μm Formula 3;

[0010] Wherein, P is the crystal size of the single-crystal ternary cathode material, D1 is the mass ratio of the single-crystal ternary cathode material with a crystal size < 2.5 μm, D2 is the mass ratio of the single-crystal ternary cathode material with a crystal size ≥ 2.5 μm, and D50 is the median particle size of the single-crystal ternary cathode material.

[0011] Preferably, the following formula 4 is also satisfied: 1 < N2 / N1 < 1.2 Formula 4

[0012] Wherein, N1 is the Ni content of the single-crystal ternary cathode material with a crystal size ≥ 2.5 μm, and N2 is the Ni content of the single-crystal ternary cathode material with a crystal size < 2.5 μm.

[0013] Preferably, the single-crystal ternary cathode material includes a core and a coating layer covering at least part of the surface of the core. The molecular formula of the core is Li

[0015] [Ni x Co y Mn z M b N c O2, where 0 < a < 0.1, 0 < b < 0.2, 0 < c < 0.2, 0.5 ≤ x < 1, 0 < y < 0.3, 0 < z < 0.3, x + y + z + b + c = 1, M is selected from one or more of Zr, Mg, Ti, Al, La, Ca, Sr, Sb, Nb, Pb, V, Ge, W, Mo, Zn, Ce, Y; N is selected from one or more of B, P, S, Si, Se, Te; the coating layer is a metal lithium compound containing one or more of Co, Ti, La, Al, Nb, W, Zr, Y, Ta elements; and / or a non-metal lithium compound containing one or more of B, P, S, Si, Se, Te elements.

[0014] Preferably, the specific surface area of the single-crystal ternary cathode material is 0.3 - 1 m 2 / g.

[0015] Preferably, the thickness of the coating layer is 5 - 100 nm. [[ID=三十二]]

[0016] Preferably, in the single-crystal ternary cathode material, the degree of lithium-nickel mixing is < 2%.

[0017] In a second aspect, the present application provides a preparation method of the above-mentioned single-crystal ternary cathode material, including the following steps:

[0018] 1) A nickel-cobalt-manganese hydroxide precursor, a lithium source, an M source, and a N source are mixed to obtain a primary mixture, the primary mixture is heated to 400-600° C. at a heating rate of 1-5° C. / min, kept warm for 4-10 hours, then heated to 900-1000° C. at a heating rate of 1-5° C. / min, kept warm for 6-12 hours, and crushed and classified to obtain first particles;

[0019] 2) a nickel-cobalt-manganese hydroxide precursor, a lithium source, an M source, and a N source are mixed to obtain a secondary mixture, the secondary mixture is heated to 400-600° C. at a heating rate of 1-5° C. / min, kept warm for 4-10 hours, then heated to 700-890° C. at a heating rate of 1-5° C. / min, kept warm for 6-12 hours, and crushed and classified to obtain second particles;

[0020] 3) mixing the first particles, the second particles and the coating agent to obtain a tertiary mixture, heating the tertiary mixture to 250-800° C. at a heating rate of 1-5° C. / min, and keeping the temperature for 5-12 hours to obtain the single crystal ternary cathode material;

[0021] The compositions of the primary mixture and the secondary mixture are the same or different.

[0022] Preferably, the particle size of the nickel-cobalt-manganese hydroxide precursor is 2 to 5 μm, and the specific surface area is 5 to 30 m 2 / g.

[0023] In a third aspect, the present application provides a positive electrode sheet comprising the above-mentioned single crystal ternary positive electrode material.

[0024] In a fourth aspect, the present application provides a battery comprising the above-mentioned positive electrode sheet.

[0025] The single-crystal ternary positive electrode material provided in this application includes two single-crystal materials of different sizes. This application limits the particle size and proportion of single-crystal materials of different sizes, so that the battery has a higher electrode compaction density, excellent cycle performance and lower battery cell expansion rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0027] FIG1 is an electron microscope image of a single crystal ternary cathode material according to Example 1 of the present application;

[0028] FIG2 is an XRD diagram of the single crystal ternary cathode material of Example 1 of the present application;

[0029] FIG3 is an electron microscope image of the single crystal ternary cathode material of Example 2 of the present application;

[0030] FIG4 is an electron microscope image of the single crystal ternary cathode material of Example 3 of the present application;

[0031] FIG5 is an electron microscope image of the single crystal ternary cathode material of Example 4 of the present application;

[0032] FIG6 is an electron microscope image of the single crystal ternary cathode material of Comparative Example 1 of the present application;

[0033] FIG7 is an electron microscope image of the single crystal ternary cathode material of Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0034] To enable those skilled in the art to better understand the solutions of the present application, the present application is further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present application. The examples cited are only used to explain the present application and do not limit the scope of the present application. Based on the embodiments of the present application, all other implementation methods obtained by those of ordinary skill in the art without making creative efforts are within the scope of protection of this application.

[0035] In order to improve the compaction density of the positive electrode material containing small-sized single crystal ternary materials and ensure the cycle performance of the positive electrode material, the present application adopts the following technical solutions:

[0036] In a first aspect, the present application provides a single crystal ternary cathode material that satisfies the following formulas 1 to 3: 1 μm ≤ P < 5 μm Formula 1, 1 ≤ D2 / D1 < 10 Formula 2, 3 μm < D50 < 8 μm Formula 3;

[0037] Among them, P is the single crystal size of the single crystal ternary positive electrode material, D1 is the mass proportion of the single crystal ternary positive electrode material with a single crystal size of less than 2.5 μm, D2 is the mass proportion of the single crystal ternary positive electrode material with a single crystal size of ≥2.5 μm, and D50 is the median particle size of the single crystal ternary positive electrode material.

[0038] It can be understood that the single crystal size of the single crystal ternary positive electrode material of the present application is in the range of 1-5 μm, including single crystal ternary positive electrode materials with a single crystal size of less than 2.5 μm and single crystal ternary positive electrode materials with a single crystal size of ≥2.5 μm.

[0039] In the present application, by controlling the blending ratio, particle size and other parameters of large-sized single crystal ternary materials and small-sized single crystal ternary materials, the small-sized single crystal particles fill the gaps between the large-sized single crystal particles, and the small-sized single crystal particles provide force support points for the large-sized single crystal particles, which is beneficial to improving the compaction density of the positive electrode material system; at the same time, the mixed positive electrode material system of large-sized single crystal ternary materials and small-sized single crystal ternary materials also has excellent stability, which ensures the cycle stability of the assembled battery.

[0040] In the present application, the P value measurement method is: use SEM to obtain a surface morphology image of the single crystal ternary positive electrode material, and the magnification of the SEM image is 2000 times; take a test point in the image and measure the size of the single crystal particles in the test point; the single crystal particles of the single crystal ternary positive electrode material are preferably irregular blocks with distinct particles and smooth edges and corners; the median particle size D50 represents the particle size value corresponding to the cumulative amount of 50% (by volume) in the particle size cumulative distribution curve, which is generally obtained by testing with a laser diffraction particle size distribution instrument.

[0041] In a preferred embodiment, the following formula 4 is also satisfied: 1<N2 / N1<1.2 Formula 4,

[0042] Among them, N1 is the Ni content of the single crystal ternary positive electrode material with a single crystal size of ≥2.5 μm, and N2 is the Ni content of the single crystal ternary positive electrode material with a single crystal size of <2.5 μm.

[0043] The present application found that the single crystal ternary positive electrode material that meets the conditions of Formula 4 can further improve its electrical properties such as specific capacity.

[0044] In a preferred embodiment, the single crystal ternary cathode material comprises a core and a coating layer coated on at least a portion of the surface of the core, wherein the molecular formula of the core is Li 1+a [Ni x Co y Mn z M b N cO2, where 0 < a < 0.1, 0 < b < 0.2, 0 < c < 0.2, 0.5 ≤ x < 1, 0 < y < 0.3, 0 < z < 0.3, x + y + z + b + c = 1, M is selected from one or more of Zr, Mg, Ti, Al, La, Ca, Sr, Sb, Nb, Pb, V, Ge, W, Mo, Zn, Ce, Y; N is selected from one or more of B, P, S, Si, Se, Te; the coating layer is a metal lithium compound containing one or more of Co, Ti, La, Al, Nb, W, Zr, Y, Ta elements; and / or a non-metal lithium compound containing one or more of B, P, S, Si, Se, Te elements; preferably a lithium compound containing one or more of B, P, Co, Ti, Nb, W elements.

[0045] It should be noted that in this application, the molecular formula of the single-crystal ternary cathode material with a single-crystal size ≥ 2.5 μm may be different from the specific chemical composition of the single-crystal ternary cathode material with a single-crystal size < 2.5 μm. For example: the single-crystal ternary cathode material with a single-crystal size ≥ 2.5 μm includes a core and a coating layer covering at least part of the surface of the core, and the molecular formula of its core is Li 1+a [Ni x Co y Mn z M b N c O2, the single-crystal ternary cathode material with a single-crystal size < 2.5 μm includes a core and a coating layer covering at least part of the surface of the core, and the molecular formula of its core is Li 1+a [Ni x' Co y Mn <000​​​​​​​​​​​The present application found that the charging cut-off voltage of the battery is related to the content of Ni element in the single crystal ternary positive electrode material. When x is 0.5-0.6, the charging cut-off voltage of the battery is 4.5-4.6V; when x is 0.6-0.8, the charging cut-off voltage of the battery is 4.4-4.5V; when x is 0.8-1 (excluding 0.8), the charging cut-off voltage of the battery is 4.25-4.4V; the present application controls the size of the single crystal ternary material and the Ni content of materials of different sizes, and at the corresponding charging cut-off voltage, can achieve a capacity of more than 200mAh / g, while ensuring higher cycle performance, rate performance and lower cell expansion rate.

[0047] Among them, the content of Ni element in the single crystal ternary positive electrode material can be obtained by inductively coupled plasma spectrometer (ICP) testing. In some embodiments, the single crystal ternary positive electrode material is first divided into two parts, one part has a single crystal size of <2.5μm, and the other part has a single crystal size of ≥2.5μm. Finally, the two parts of single crystal ternary positive electrode materials are respectively tested for their Ni element content using ICP.

[0048] In addition, in the above embodiment, by bulk doping of M and N elements and surface modification, the single crystal ternary positive electrode material has better electrochemical properties, overcoming the defects of the current single crystal ternary positive electrode material in capacity and rate performance, and further improving the specific capacity of the single crystal ternary material.

[0049] In some specific embodiments, the content of the doping elements M and N is 1 to 10,000 ppm, preferably 500 to 3,000 ppm.

[0050] In a preferred embodiment, the above-mentioned single crystal ternary cathode material is prepared by a method comprising the following steps:

[0051] 1) A nickel-cobalt-manganese hydroxide precursor, a lithium source, an M source, and a N source are mixed to obtain a primary mixture, the primary mixture is heated to 400-600° C. at a heating rate of 1-5° C. / min, kept warm for 4-10 hours, then heated to 900-1000° C. at a heating rate of 1-5° C. / min, kept warm for 6-12 hours, and crushed and classified to obtain first particles;

[0052] 2) a nickel-cobalt-manganese hydroxide precursor, a lithium source, an M source, and a N source are mixed to obtain a secondary mixture, the secondary mixture is heated to 400-600° C. at a heating rate of 1-5° C. / min, kept warm for 4-10 hours, then heated to 700-890° C. at a heating rate of 1-5° C. / min, kept warm for 6-12 hours, and crushed and classified to obtain second particles;

[0053] 3) mixing the first particles, the second particles and the coating agent to obtain a tertiary mixture, heating the tertiary mixture to 250-800° C. at a heating rate of 1-5° C. / min, and keeping the temperature for 5-12 hours to obtain the single crystal ternary cathode material;

[0054] The compositions of the primary mixture and the secondary mixture are the same or different.

[0055] It should be noted that there is no specific order for the above steps 1) and 2) and they can be performed simultaneously or sequentially.

[0056] Exemplarily, the M source is an oxide of one or more of Zr, Mg, Ti, Al, La, Ca, Sr, Sb, Nb, Pb, V, Ge, W, Mo, Zn, Ce, and Y; the N source is an oxide of one or more of B, P, S, Si, Se, and Te; the lithium source is selected from one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium oxalate, lithium acetate, and lithium oxide; the coating agent is a raw material for the coating layer, selected from metal oxides containing one or more of the elements Co, Ti, La, Al, Nb, W, Zr, Y, and Ta; and / or non-metal oxides containing one or more of the elements B, P, S, Si, Se, and Te.

[0057] In a preferred embodiment, the specific surface area of ​​the single crystal ternary cathode material is 0.3 to 1 m 2 / g. Among them, the single crystal ternary cathode material with this specific surface area can further ensure the specific capacity and is conducive to reducing the residual alkali on the surface.

[0058] In a preferred embodiment, the coating layer has a thickness of 5 to 100 nm, preferably 10 to 50 nm. This embodiment can further improve the rate performance of the positive electrode material by controlling the thickness of the coating layer.

[0059] In a preferred embodiment, the lithium-nickel mixing degree in the single crystal ternary positive electrode material is less than 2%. 2+ Mixing will lead to the intensification of interfacial side reactions and make the changes in the electrochemical environment of the Ni element during the charging and discharging process more complicated, which is also an important reason for the capacity loss during the first charging and discharging process; and in the single crystal ternary positive electrode material of the present application, the degree of lithium nickel mixing is less than 2%, which can improve the stability of the crystal structure and is helpful to improve the cycle stability of the material.

[0060] In a second aspect, the present application provides a method for preparing the above-mentioned single crystal ternary cathode material, comprising the following steps:

[0061] 1) A nickel-cobalt-manganese hydroxide precursor, a lithium source, an M source, and a N source are mixed to obtain a primary mixture, the primary mixture is heated to 400-600° C. at a heating rate of 1-5° C. / min, kept warm for 4-10 hours, then heated to 900-1000° C. at a heating rate of 1-5° C. / min, kept warm for 6-12 hours, and crushed and classified to obtain first particles;

[0062] 2) a nickel-cobalt-manganese hydroxide precursor, a lithium source, an M source, and a N source are mixed to obtain a secondary mixture, the secondary mixture is heated to 400-600° C. at a heating rate of 1-5° C. / min, kept warm for 4-10 hours, then heated to 700-890° C. at a heating rate of 1-5° C. / min, kept warm for 6-12 hours, and crushed and classified to obtain second particles;

[0063] 3) mixing the first particles, the second particles and the coating agent to obtain a tertiary mixture, heating the tertiary mixture to 250-800° C. at a heating rate of 1-5° C. / min, and keeping the temperature for 5-12 hours to obtain the single crystal ternary cathode material;

[0064] The compositions of the primary mixture and the secondary mixture are the same or different.

[0065] In the above preparation method, by controlling the sintering process of the primary mixture, first particles with a larger size (≥2.5μm) can be obtained, and then the sintering process of the secondary mixture is controlled to obtain second particles with a smaller size (<2.5μm). Subsequently, the first particles, the second particles and the coating agent are mixed as needed, and coated and sintered to obtain any single crystal ternary positive electrode material described in the first aspect of this application.

[0066] It should be noted that there is no order between the above steps 1) and 2), and they can be performed simultaneously or sequentially; the purpose of step 3) is only to coat the first particle and the second particle with a coating agent, respectively, that is, the first particle and the second particle themselves do not undergo a new reaction, and since the thickness of the coating agent is nanometer-scale, the amount required to be added is very small, and therefore, its effect on the particle size and mass of the first particle and the second particle can be ignored. Therefore, in this application, the calculation method for the mass proportion (D1) of the single crystal ternary positive electrode material with a single crystal size of <2.5 μm can be: second particle / (first particle + The mass proportion (D2) of the single crystal ternary positive electrode material with a single crystal size ≥2.5μm can be calculated as: first particle / (first particle + second particle) · 100%; alternatively, the calculation method of D1 and D2 can also be to grade the finished single crystal ternary positive electrode materials, and then calculate the mass proportion (D1) of the single crystal ternary positive electrode material with a single crystal size <2.5μm and the mass proportion (D2) of the single crystal ternary positive electrode material with a single crystal size ≥2.5μm respectively. Regardless of the calculation method, the single crystal ternary positive electrode material provided in the present application satisfies the conditions of the above formula 2.

[0067] In the present application, when the composition of the primary mixture and the secondary mixture is the same, the main difference between the prepared second particles and the second particles is the size. When the composition of the primary mixture and the secondary mixture is different, for example, the added amount and / or type of the M source and the N source are different, the prepared second particles and the second particles are different in size as well as in the bulk doping elements. This is more conducive to the synergistic effect of different doping elements, so that the single crystal ternary positive electrode material has better electrochemical properties.

[0068] Preferably, when the coating agent contains one or more of the elements Co, Ti, La, Al, Nb, W, Zr, Y, and Ta, the three mixtures are heated to 500-800°C at a heating rate of 1-5°C / min and kept warm for 5-10 hours to obtain third particles; when the coating agent also contains one or more of the elements B, P, S, Si, Se, and Te, the third particles are heated to 250-500°C at a heating rate of 1-5°C / min, kept warm for 5-10 hours, and sieved to obtain the single crystal ternary positive electrode material.

[0069] More preferably, when the coating agent contains only one or more of the elements B, P, S, Si, Se, and Te, the third particles are directly heated to 250-500°C at a heating rate of 1-5°C / min, kept warm for 5-10 hours, and the single crystal ternary positive electrode material is obtained by sieving.

[0070] Exemplarily, the M source is one or more oxides of Zr, Mg, Ti, Al, La, Ca, Sr, Sb, Nb, Pb, V, Ge, W, Mo, Zn, Ce, Y; the N source is one or more oxides of B, P, S, Si, Se, Te; the lithium source is selected from one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium oxalate, lithium acetate, lithium oxide; the coating agent is the raw material of the coating layer, selected from metal oxides containing one or more of Co, Ti, La, Al, Nb, W, Zr, Y, Ta elements; and / or non-metal oxides containing one or more of B, P, S, Si, Se, Te elements.

[0071] When the single crystal ternary cathode material prepared in this application satisfies Equation 4, that is, it is required to synthesize the first particles and the second particles with different Ni contents in steps 1) and 2). At this time, we generally achieve this by controlling the molecular formula of the nickel-cobalt-manganese hydroxide precursor, that is, the molecular formulas of the nickel-cobalt-manganese hydroxide precursors in steps 1) and 2) are different. For example: in step 1), the molecular formula of the nickel-cobalt-manganese hydroxide precursor is Ni x Co y Mn z (OH)2, where 0.5 ≤ x < 1, 0 < y < 0.3, 0 < z < 0.3, x + y + z = 1; in step 2), the molecular formula of the nickel-cobalt-manganese hydroxide precursor is Ni x' Co y' Mn z' (OH)2, where 0.5 ≤ x ' < 1, 0 < y ' < 0.3, 0 < z ' < 0.3, x ' + y ' + z ' = 1; and 1 < x ' / x < 1.2.

[0072] In this application, the nickel-cobalt-manganese hydroxide precursor can be directly purchased or prepared by conventional methods. For example: mix soluble nickel salts and manganese salts to prepare a mixed salt solution, introduce a protective gas into the reaction kettle, add the mixed salt solution, alkali solution, and complexing agent for coprecipitation reaction. After reacting for 3 - 5 h, adjust the pH value of the mixed solution until the particle size of the product grows to the required particle size and then stop the reaction. After the reaction is completed, the obtained mixed solution is aged, filtered, washed, and dried to obtain the required nickel-cobalt-manganese hydroxide precursor; where the nickel salts and manganese salts are corresponding sulfates, nitrates, chlorides, etc.

[0073] In the present application, the mixing in step 1) or step 2) is preferably uniformly mixed in a high-speed mixer; in step 1) or step 2), the crushing and classification preferably specifically include jaw crushing, double rollers, mechanical crushing and screening operations; the purpose of these operations is to separate the synthesized agglomerated solid product into primary particles, and remove a small amount of solid particles that do not meet the size requirements of this application through screening.

[0074] In some embodiments, the jaw crushing can be performed by a jaw crusher, and the mechanical crushing can be performed by an air flow crusher.

[0075] In a more preferred embodiment, the primary mixture is heated to 450-550°C at a heating rate of 3-5°C / min, kept warm for 4-6 hours, then heated to 900-1000°C at a heating rate of 3-5°C / min, kept warm for 6-8 hours, and crushed and classified to obtain first particles; the average particle size of the first particles is 3-4 μm; the secondary mixture is heated to 450-550°C at a heating rate of 3-5°C / min, kept warm for 4-6 hours, then heated to 750-850°C at a heating rate of 3-5°C / min, kept warm for 6-8 hours, and crushed and classified to obtain second particles; the average particle size of the first particles is 1-2 μm.

[0076] In a preferred embodiment, the particle size of the nickel-cobalt-manganese hydroxide precursor is 2 to 5 μm, and the specific surface area is 5 to 30 m 2 / g.

[0077] The particle size of the nickel-cobalt-manganese hydroxide precursor is referred to as D50 of the nickel-cobalt-manganese hydroxide precursor, which represents the particle size value corresponding to 50% (by volume) of the cumulative amount in the particle size cumulative distribution curve, and can be obtained by testing using a laser diffraction particle size distribution instrument.

[0078] In some embodiments, the particle size of the nickel-cobalt-manganese hydroxide precursor is any one of 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or a range consisting of any two of the above, and the specific surface area is 5 m 2 / g、6m 2 / g、7m 2 / g、8m 2 / g、9m 2 / g、10m 2 / g、11m 2 / g、15m 2 / g、16m 2 / g、17m 2 / g、18m 2 / g、19m 2 / g, 20m 2 / g, 21m 2 / g、22m 2 / g、23m 2 / g、24m 2 / g, 25m 2 / g, 26m 2 / g、27m 2 / g、28m 2 / g、29m 2 / g、30m 2 / g, or a range consisting of any two of the above.

[0079] The present application found that when a nickel-cobalt-manganese hydroxide precursor with specific parameters is selected, it is beneficial to prepare a mixed single-crystal ternary positive electrode material of a specific size, so as to increase the proportion of single-crystal ternary positive electrode materials that meet the size requirements of Formulas 1-3 of the present application.

[0080] In a third aspect, the present application provides a positive electrode sheet comprising the above-mentioned single crystal ternary positive electrode material.

[0081] It can be understood that the positive electrode sheet includes a current collector and a positive electrode slurry coated on the current collector; illustratively, the positive electrode slurry includes: the above-mentioned single crystal ternary positive electrode material, a conductive agent, a binder and a solvent; the binder may include any one of polyvinylidene fluoride, polyvinyl pyrrolidone, sodium hydroxymethyl cellulose and styrene-butadiene rubber, or a combination of at least two; the solvent may include any one of deionized water, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide and anhydrous ethanol, or a combination of at least two; the conductive agent may include any one of conductive graphite, carbon nanotube conductive carbon black, acetylene black, Ketjen black, vapor-grown carbon fiber and expanded graphite, or a combination of at least two.

[0082] In a fourth aspect, the present application provides a battery comprising the above-mentioned positive electrode sheet.

[0083] The present application is further described below with reference to specific embodiments:

[0084] Example 1

[0085] A single crystal ternary cathode material is provided, and its preparation method is as follows:

[0086] (1) Preparation of large-size single crystal ternary semi-finished product A: Li / (Ni+Co+Mn)=1.05 in molar ratio, Zr addition amount is 1500ppm, Mo addition amount is 1000ppm, lithium hydroxide, Ni 0.83 Co 0.06 Mn 0.11 (OH)2, ZrO2, MoO3 (D50 = 3.5 μm, specific surface area of ​​about 15m 2 / g), mixed evenly in a high-speed mixer, the mixed material was put into a sagger and sintered in a high-temperature atmosphere box furnace. In an oxygen atmosphere, the temperature was raised to 500℃ at 3℃ / min, kept warm for 4h, and then raised to 950℃ and kept warm for 6h. The sintered material was then crushed by jaw crusher, roller crusher, crushing and screening to obtain large-sized single crystal ternary semi-finished Li 1.03 Ni 0.83 Co 0.0574 Mn 0.11 Mo 0.001 Zr 0.0016 O2, the single crystal size of the semi-finished product is ≥2.5μm, with an average value of 3.0μm.

[0087] (2) Preparation of small-sized single crystal ternary semi-finished product a: Li / (Ni+Co+Mn)=1.04 in molar ratio, 1000ppm Al addition, 1000ppm Mo addition, lithium hydroxide, Ni 0.85 Co 0.05 Mn 0.10 (OH)2(D50=3.5μm, specific surface area is about 15m 2 / g), Al2O3, MoO3, mix them evenly in a high-speed mixer, put the mixed materials into a sagger and sinter them in a high-temperature atmosphere box furnace. In an oxygen atmosphere, heat it to 500℃ at 3℃ / min, keep it warm for 4h, then heat it to 850℃, keep it warm for 6h, and then crush the sintered materials through a jaw crusher, a roller, an air flow machine and sieve to obtain a small-sized single crystal ternary semi-finished product Li 1.03 Ni 0.85 Co 0.0454 Mn 0.10 Mo 0.001 Al 0.0036 O2, the single crystal size of the semi-finished product is less than 2.5μm, with an average value of 1.2μm.

[0088] (3) Preparation of finished single crystal ternary cathode material: Mix two single crystal ternary semi-finished product particles A and a at a weight ratio of 9:1, then weigh nano additives Al2O3 and TiO2 at 1500ppm of Al element and 1000ppm of Ti element respectively, and mix them evenly with the two semi-finished single crystal ternary materials A and a. The mixed materials are placed in a sagger and sintered in a high-temperature atmosphere box furnace. In an oxygen atmosphere, the temperature is raised to 650℃ at 3℃ / min and kept warm for 6h. After cooling, the material was powdered and sieved to obtain single-crystal ternary positive electrode materials with two mixed sizes. The parameters of the single-crystal ternary positive electrode material, the ratio of the mass proportion of the single-crystal ternary positive electrode material with a single crystal size ≥2.5μm to the mass proportion of the single-crystal ternary positive electrode material with a single crystal size <2.5μm, the median particle size of the single-crystal ternary positive electrode material are shown in Table 1. The XRD test results are shown in Figure 2. XRD refinement analysis shows that the degree of lithium-nickel mixing is 1.90%.

[0089] Example 2

[0090] Provided is a single crystal ternary positive electrode material, the preparation method of which is different from that of Example 1 in that: in step (3), two single crystal ternary semi-finished product particles A and a are mixed in a weight ratio of 8:2, and XRD refinement analysis shows that the degree of lithium-nickel mixing is 1.85%. Parameters such as the single crystal size of the single crystal ternary positive electrode material, the ratio of the mass proportion of the single crystal ternary positive electrode material with a single crystal size ≥2.5 μm to the mass proportion of the single crystal ternary positive electrode material with a single crystal size <2.5 μm, and the median particle size of the single crystal ternary positive electrode material are shown in Table 1.

[0091] Example 3

[0092] Provided is a single crystal ternary positive electrode material, the preparation method of which differs from that of Example 1 in that: in step (3), two single crystal ternary semi-finished product particles A and a are mixed in a weight ratio of 7:3, and XRD refinement analysis shows that the degree of lithium-nickel mixing is 1.86%. Parameters such as the single crystal size of the single crystal ternary positive electrode material, the ratio of the mass proportion of the single crystal ternary positive electrode material with a single crystal size ≥2.5 μm to the mass proportion of the single crystal ternary positive electrode material with a single crystal size <2.5 μm, and the median particle size of the single crystal ternary positive electrode material are shown in Table 1.

[0093] Example 4

[0094] Provided is a single crystal ternary positive electrode material, the preparation method of which is different from that of Example 1 in that: in step (3), two single crystal ternary semi-finished product particles A and a are mixed in a weight ratio of 6:4, and XRD refinement analysis shows that the degree of lithium-nickel mixing is 1.80%. Parameters such as the single crystal size of the single crystal ternary positive electrode material, the ratio of the mass proportion of the single crystal ternary positive electrode material with a single crystal size ≥2.5 μm to the mass proportion of the single crystal ternary positive electrode material with a single crystal size <2.5 μm, and the median particle size of the single crystal ternary positive electrode material are shown in Table 1.

[0095] Example 5

[0096] Provided is a single crystal ternary positive electrode material, the preparation method of which differs from that of Example 1 in that: in step (3), two single crystal ternary semi-finished product particles A and a are mixed in a weight ratio of 5:5, and XRD refinement analysis shows that the degree of lithium-nickel mixing is 1.75%. Parameters such as the single crystal size of the single crystal ternary positive electrode material, the ratio of the mass proportion of the single crystal ternary positive electrode material with a single crystal size ≥2.5 μm to the mass proportion of the single crystal ternary positive electrode material with a single crystal size <2.5 μm, and the median particle size of the single crystal ternary positive electrode material are shown in Table 1.

[0097] Example 6

[0098] A single crystal ternary cathode material (its structural parameters are shown in Table 1) is provided. The preparation method thereof is different from that of Example 2 in that: in step (2), the precursor is Ni 0.88 Co 0.05 Mn 0.07 (OH)2, XRD analysis shows that its lithium nickel mixing degree is 1.95%. The parameters such as the single crystal size of the single crystal ternary positive electrode material, the ratio of the mass proportion of the single crystal ternary positive electrode material with a single crystal size ≥2.5μm to the mass proportion of the single crystal ternary positive electrode material with a single crystal size <2.5μm, and the median particle size of the single crystal ternary positive electrode material are shown in Table 1.

[0099] Example 7

[0100] A single crystal ternary cathode material is provided, and its preparation method is as follows:

[0101] (1) Prepare a large-sized single crystal ternary semi-finished product A as described in Example 1.

[0102] (2) Prepare a small-sized single crystal ternary semi-finished product a as described in Example 1.

[0103] (3) Preparation of finished single crystal ternary cathode material: The two single crystal ternary semi-finished particles A and a were mixed in a weight ratio of 8:2, and then the nano-additives Al2O3 and CeO2 were weighed at 1500ppm of Al element and 1000ppm of Ce element respectively, and mixed evenly with the two semi-finished single crystal ternary materials A and a. The mixed material was placed in a sagger and sintered in a high-temperature atmosphere box furnace. In an oxygen atmosphere, the temperature was raised to 650℃ at 3℃ / min and kept warm for 6h. After cooling, the material was powdered and sieved to obtain two sizes of mixed single crystal ternary cathode materials. XRD refinement analysis showed that the lithium nickel mixing degree was 1.82%. The parameters of the single crystal ternary cathode material, the ratio of the mass proportion of the single crystal ternary cathode material with a single crystal size ≥2.5μm to the mass proportion of the single crystal ternary cathode material with a single crystal size <2.5μm, and the median particle size of the single crystal ternary cathode material are shown in Table 1.

[0104] Example 8

[0105] A single crystal ternary cathode material is provided, and its preparation method is as follows:

[0106] (1) Prepare a large-sized single crystal ternary semi-finished product A as described in Example 1.

[0107] (2) Prepare a small-sized single crystal ternary semi-finished product a as described in Example 1.

[0108] (3) Preparation of finished single crystal ternary cathode material: Mix two single crystal ternary semi-finished particles A and a at a weight ratio of 8:2, and then weigh nano-additives Al2O3, Nb2O5 and WO3 according to 1500ppm of Al element, 1000ppm of Nb element and 800ppm of W element, and mix them evenly with the two semi-finished single crystal ternary materials A and a. The mixed materials are placed in a sagger and sintered in a high temperature atmosphere box furnace under an oxygen atmosphere at 3℃ / mi nThe temperature was raised to 600℃ and kept warm for 6h. After cooling, the material was powdered and sieved to obtain single-crystal ternary positive electrode materials with two mixed sizes. XRD refinement analysis showed that the degree of lithium-nickel mixing was 1.73%. The parameters of the single-crystal ternary positive electrode material, the ratio of the mass proportion of the single-crystal ternary positive electrode material with a single crystal size ≥2.5μm to the mass proportion of the single-crystal ternary positive electrode material with a single crystal size <2.5μm, and the median particle size of the single-crystal ternary positive electrode material are shown in Table 1.

[0109] Example 9

[0110] A single crystal ternary cathode material is provided, and its preparation method is as follows:

[0111] (1) Prepare a large-sized single crystal ternary semi-finished product A as described in Example 1.

[0112] (2) Prepare a small-sized single crystal ternary semi-finished product a as described in Example 1.

[0113] (3) Preparation of finished single crystal ternary cathode material: The two single crystal ternary semi-finished particles A and a are mixed in a weight ratio of 8:2, and the nano additive H3BO3 is weighed according to 1000ppm of element B, and mixed evenly with the two semi-finished single crystal ternary materials A and a. The mixed material is placed in a sagger and sintered in a high-temperature atmosphere box furnace. In an oxygen atmosphere, the temperature is raised to 300℃ at a rate of 3℃ / min and kept warm for 10h. After cooling, the material is powdered and sieved to obtain two sizes of mixed single crystal ternary cathode materials. XRD refinement analysis shows that the degree of lithium nickel mixing is 1.74%. The parameters of the single crystal size of the single crystal ternary cathode material, the ratio of the mass proportion of the single crystal ternary cathode material with a single crystal size ≥2.5μm to the mass proportion of the single crystal ternary cathode material with a single crystal size <2.5μm, and the median particle size of the single crystal ternary cathode material are shown in Table 1.

[0114] Comparative Example 1

[0115] A single crystal ternary cathode material is provided, and its preparation method is as follows:

[0116] (1) Lithium hydroxide, Ni, Co, Mn, and Zr were weighed in a molar ratio of Li / (Ni+Co+Mn) = 1.05, and the amount of Zr and Mo added was 1500 ppm and 1000 ppm, respectively. 0.85 Co 0.05 Mn0.1 (OH)2(D50=3.5μm, specific surface area is about 15m 2 / g), ZrO2, and MoO3 are mixed evenly in a high-speed mixer, and the mixed material is put into a sagger and sintered in a high-temperature atmosphere box furnace. In an oxygen atmosphere, the temperature is raised to 500°C at a rate of 3°C / min, kept warm for 4 hours, and then raised to 950°C and kept warm for 6 hours. The sintered material is then subjected to jaw crushing, rolling, crushing and sieving to obtain a large-size single crystal ternary semi-finished product, the single crystal size of the semi-finished product being ≥2.5μm, with an average value of 3.0μm.

[0117] (2) Then, nano-additives Al2O3 and TiO2 were weighed at 1500ppm of Al element and 1000ppm of Ti element, respectively, and mixed evenly with the semi-finished single crystal ternary material. The mixed material was placed in a sagger and sintered in a high-temperature atmosphere box furnace. In an oxygen atmosphere, the temperature was raised to 650℃ at 3℃ / min and kept warm for 6h. After cooling, the material was powdered and sieved to obtain a large-sized single crystal ternary positive electrode material (its structural parameters are shown in Table 1). XRD refinement analysis showed that its lithium-nickel mixing degree was 1.93%.

[0118] Comparative Example 2

[0119] A single crystal ternary cathode material is provided, and its preparation method is as follows:

[0120] (1) Lithium hydroxide, Ni, Co, Mn, and Mg are weighed in a molar ratio of Li / (Ni+Co+Mn) = 1.04, with an Al addition amount of 1000 ppm and a Mo addition amount of 1000 ppm. 0.88 Co 0.05 Mn 0.07 (OH)2(D50=3.5μm, specific surface area is about 15m 2 / g), Al2O3, and MoO3 are mixed evenly in a high-speed mixer, and the mixed material is put into a sagger and sintered in a high-temperature atmosphere box furnace. In an oxygen atmosphere, the temperature is raised to 500°C at a rate of 3°C / min, kept warm for 4 hours, and then raised to 850°C and kept warm for 6 hours. The sintered material is then subjected to jaw crushing, rolling, crushing and sieving to obtain a large-size single crystal ternary semi-finished product. The single crystal size of the semi-finished product is less than 2.5μm, and the average value is 1.2μm.

[0121] (2) Nano-additives Al2O3 and TiO2 were weighed at 1500ppm of Al and 1000ppm of Ti, respectively, and mixed evenly with the semi-finished single crystal ternary material. The mixed material was placed in a sagger and sintered in a high-temperature atmosphere box furnace. In an oxygen atmosphere, the temperature was raised to 650℃ at 3℃ / min and kept warm for 6h. The cooled material was powdered and sieved to obtain a small-sized single crystal ternary positive electrode material (its structural parameters are shown in Table 1). XRD refinement analysis showed that its lithium-nickel mixing degree was 1.89%.

[0122] Comparative Example 3

[0123] A single crystal ternary cathode material (its structural parameters are shown in Table 1) is provided. The preparation method is the same as that of Example 1, except that in step (3), two single crystal ternary semi-finished product particles A and a are mixed in a weight ratio of 4:6.

[0124] Comparative Example 4

[0125] The preparation method is the same as that of Example 1, except that the precursor in step (1) is Ni 0.85 Co 0.05 Mn 0.10 (OH)2(D50=3.5μm, specific surface area is about 15m 2 / g), the precursor of step (2) is Ni 0.83 Co 0.06 Mn 0.11 (OH)2(D50=3.5μm, specific surface area is about 15m 2 / g).

[0126] Comparative Example 5

[0127] A single crystal ternary cathode material (its structural parameters are shown in Table 1) is provided. The preparation method is the same as that of Example 1, except that: in step (1), the temperature is raised to 500°C at 3°C / min, kept at this temperature for 4 hours, and then raised to 1000°C and kept at this temperature for 6 hours.

[0128] Test method:

[0129] Buckle Capacity: At 25°C and atmospheric pressure (0.1 MPa), the single crystal ternary cathode material of each embodiment and comparative example, conductive carbon black, and binder polyvinylidene fluoride (PVDF) were thoroughly mixed in an N-methylpyrrolidone solvent at a mass ratio of 95:3:2 to obtain a positive electrode slurry. The slurry was coated onto aluminum foil, dried, and cold-pressed to obtain a positive electrode sheet containing a 100μm thick positive electrode active layer. The positive electrode sheet, lithium sheet, separator, and electrolyte were assembled in a buckle box to form a button cell. The battery was charged at a constant current rate of 0.2C to the cutoff voltage, then charged at a constant voltage at the cutoff voltage until the current was less than 0.05C. The charge capacity at this point was recorded as the first-cycle charge capacity. The battery was then allowed to rest for 5 minutes and then discharged at a constant current rate of 0.2C to a voltage of 2.5V. The discharge capacity at this point was recorded as the battery's first-cycle discharge capacity, also known as the initial capacity.

[0130] Rate performance: prepare button batteries according to the method in the button capacity test, charge at a constant current rate of 0.1C to the cut-off voltage, then charge at a constant voltage under the cut-off voltage condition until the current is less than 0.05C, then let it stand for 5 minutes, and then discharge at a constant current rate of 0.1C to a voltage of 2.5V. The capacity at this time is recorded as the discharge capacity at 0.1C rate; let it stand for 10 minutes, charge at a constant current rate of 1C to the cut-off voltage, then charge at a constant voltage under the cut-off voltage condition until the current is less than 0.05C, then let it stand for 5 minutes, and then discharge at a constant current rate of 1C to a voltage of 2.5V. The capacity at this time is recorded as the discharge capacity at 1C rate. The ratio of the discharge capacity at 1C rate to the discharge capacity at 0.1C rate is the 1C rate performance.

[0131] Full electric cycle: According to the method in the withholding capacity test, the positive electrode material is coated into the positive electrode sheet, the negative electrode is made of graphite, and the separator polyethylene and the electrolyte (the electrolyte is LiPF6 and the solvent is EC / DMC) are used to form a full battery. Under the charge and discharge conditions of 1C rate, the battery is cycled, and the capacity of each cycle is compared with the first cycle to confirm the capacity retention rate; at 45°C, the capacity retention rate is calculated after 300 cycles.

[0132] Single crystal size measurement: Use SEM to obtain the surface morphology of the positive electrode material (see Figures 1, 2-7), and the magnification of the SEM image of the positive electrode material is 2000 times; take test points in the SEM image, and test the sizes of 300 single crystal particles with a size greater than or equal to 2.5μm, and calculate the average value to obtain the size of the large-sized single crystal particles; then test the sizes of 300 single crystal particles with a size less than 2.5μm, and calculate the average value to obtain the size of the small-sized single crystal particles.

[0133] BET measurement: Take ~5g of single crystal ternary positive electrode material samples of each embodiment and comparative example, respectively, and put them into long tubes with bulbs. First, vacuum treat them under the conditions of 2h / 200℃, and then pass N2 for gas adsorption. The adsorption amount of the adsorbate molecules (N2) of the measured sample is determined according to the pressure or weight change before and after adsorption, thereby obtaining the specific surface area BET.

[0134] Cell expansion: Assemble a full battery according to the method in the full electric cycle test, fully charge the battery to the set voltage of 4.3V, use a PPG battery thickness gauge to test the battery thickness, and then place the battery in a 70℃ constant temperature box for 28 days. After that, take out the battery and use a PPG battery thickness gauge to test the battery thickness at this time. The battery thickness expansion rate is calculated using the following formula: Battery thickness expansion rate = (battery thickness after constant temperature - battery thickness before constant temperature) / battery before constant temperature.

[0135] Pole sheet compaction: Pole sheet surface density / (pole sheet thickness after rolling - current collector thickness).

[0136] The test results of the above tests are summarized in Table 1:

[0137] Table 1 Note: N1 is the Ni content of single crystal ternary cathode materials with a single crystal size ≥ 2.5 μm, and N2 is the Ni content of single crystal ternary cathode materials with a single crystal size < 2.5 μm.

[0138] It can be seen from Table 1 that, compared with the comparative example, the single crystal ternary positive electrode materials of Examples 1-9 control the blending ratio, particle size and other parameters of large-size single crystal ternary materials and small-size single crystal ternary materials, and the assembled batteries can have higher charge capacity, rate performance, cycle performance and lower battery cell expansion rate. In detail, in comparative example 1, since the single crystal size of the single crystal ternary positive electrode materials is greater than or equal to 2.5 μm, the gap between the single crystal particles is large, which affects the diffusion of lithium ions in the solid phase, resulting in poor rate performance and cycle performance of the assembled batteries, and a high battery cell expansion rate; in comparative example 2, since the single crystal size of the single crystal ternary positive electrode materials is less than 2.5 μm, its specific surface area is large, and the reaction activity is strong, which leads to increased side reactions, thereby resulting in poor battery cycle performance and battery cell The expansion rate is relatively high; the single crystal ternary positive electrode material of Comparative Example 3 has a smaller mass proportion than the single crystal ternary positive electrode material with a single crystal size ≥2.5μm and the single crystal ternary positive electrode material with a single crystal size <2.5μm, resulting in a slight decrease in the overall stability of the assembled battery, and the battery cell expansion rate is higher than that of the embodiment. The single crystal ternary positive electrode material with a single crystal size ≥2.5μm in Comparative Example 4 has a higher Ni content. Although the battery has a high charge capacity, its stability is reduced. The median particle size of the single crystal ternary positive electrode material of Comparative Example 5 is too large, the adsorption of the particles is relatively poor, and the diffusion path length of lithium ions in the solid phase increases, resulting in a slower migration rate of lithium ions during the charge and discharge process, thereby resulting in poor rate performance and cycle performance of the assembled battery and a high battery cell expansion rate.

[0139] By comparing Figure 1 and Figures 3-7, it can be seen that the single crystal ternary positive electrode materials of Examples 1-4 include a certain proportion of large-sized particles and small-sized particles, and the overall size is between 1-5 μm, while the single crystal ternary positive electrode materials of Comparative Examples 1-2 are respectively composed of large-sized single crystal particles or small-sized single crystal particles.

[0140] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A single crystal ternary cathode material, characterized in that: The following formulas 1 to 3 are satisfied: 1μm≤P<5μm Formula 1, 1≤D2 / D1<10 Formula 2, 3μm<D50<8μm Formula 3; Among them, P is the single crystal size of the single crystal ternary positive electrode material, D1 is the mass proportion of the single crystal ternary positive electrode material with a single crystal size of less than 2.5 μm, D2 is the mass proportion of the single crystal ternary positive electrode material with a single crystal size of ≥2.5 μm, and D50 is the median particle size of the single crystal ternary positive electrode material.

2. The single crystal ternary cathode material according to claim 1, characterized in that: The following formula 4 is also satisfied: 1<N2 / N1<1.2 Formula 4, Among them, N1 is the Ni content of the single crystal ternary positive electrode material with a single crystal size ≥2.5μm, and N2 is the Ni content of the single crystal ternary positive electrode material with a single crystal size <2.5μm.

3. The single crystal ternary cathode material according to claim 1 or 2, characterized in that: The single-crystal ternary cathode material includes a core and a coating layer covering at least a part of the surface of the core. The molecular formula of the core is Li 1+a [Ni x Co y Mn z M b N c O2, where 0 < a < 0.1, 0 < b < 0.2, 0 < c < 0.2, 0.5 ≤ x < 1, 0 < y < 0.3, 0 < z < 0.3, x + y + z + b + c = 1, M is selected from one or more of Zr, Mg, Ti, Al, La, Ca, Sr, Sb, Nb, Pb, V, Ge, W, Mo, Zn, Ce, Y; N is selected from one or more of B, P, S, Si, Se, Te; the coating layer is a metal lithium compound containing one or more of Co, Ti, La, Al, Nb, W, Zr, Y, Ta elements; and / or a non-metal lithium compound containing one or more of B, P, S, Si, Se, Te elements.

4. The single crystal ternary cathode material according to any one of claims 1 to 3, characterized in that: The specific surface area of ​​the single crystal ternary positive electrode material is 0.3 to 1 m 2 / g.

5. The single crystal ternary cathode material according to claim 3, characterized in that: The coating layer has a thickness of 5 to 100 nm.

6. The single crystal ternary cathode material according to any one of claims 1 to 5, characterized in that: In the single crystal ternary positive electrode material, the degree of lithium-nickel mixing is less than 2%.

7. A method for preparing a single crystal ternary cathode material according to any one of claims 1 to 6, characterized in that: The following steps are involved: 1) A nickel-cobalt-manganese hydroxide precursor, a lithium source, an M source and an N source are mixed to obtain a primary mixture, the primary mixture is heated to 400-600° C. at a heating rate of 1-5° C. / min, kept warm for 4-10 hours, then heated to 900-1000° C. at a heating rate of 1-5° C. / min, kept warm for 6-12 hours, and crushed and classified to obtain first particles; 2) A nickel-cobalt-manganese hydroxide precursor, a lithium source, an M source and a N source are mixed to obtain a secondary mixture, the secondary mixture is heated to 400-600° C. at a heating rate of 1-5° C. / min, kept warm for 4-10 hours, then heated to 700-890° C. at a heating rate of 1-5° C. / min, kept warm for 6-12 hours, and crushed and classified to obtain second particles; 3) The first particles, the second particles and the coating agent are mixed to obtain a tertiary mixture, and the tertiary mixture is heated to 250-800° C. at a heating rate of 1-5° C. / min, and kept warm for 5-12 hours to obtain the single crystal ternary positive electrode material; Wherein, the compositions of the primary mixture and the secondary mixture are the same or different.

8. The preparation method according to claim 7, characterized in that: The particle size of the nickel-cobalt-manganese hydroxide precursor is 2 to 5 μm, and the specific surface area is 5 to 30 m 2 / g.

9. A positive electrode sheet, characterized in that: It comprises the single crystal ternary positive electrode material as described in any one of claims 1 to 6.

10. A battery, characterized in that: Including the positive electrode sheet as claimed in claim 9.

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