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 comprises a matrix material Lim[NixCoyMnz]O2, wherein 0.98<m<1.03, 0.6≤x<1, 0<y<0.1, and 0<z<0.1; the matrix material is doped with an element Ce, an element M1, and an element M2; the element M1 comprises at least one of Mo, W, and Te, and the element M2 comprises at least one of Al, Zr, Y, La, Ta, and Ga; moreover, in the X-ray diffraction pattern of the positive electrode material, the diffraction peak of a (111) crystal plane of CeO2 having a full width at half maximum of 0.09-0.2 is present at a position where 2θ is 28°-29°; the mass percentage content of the element Ce is 2,500-5,000 ppm. The single-crystal ternary positive electrode material has high structural stability and thermal stability, and can effectively improve the cycle performance and safety of a battery.

Description

Single-crystal ternary positive electrode material and preparation method and application thereof

[0001] The present application claims priority to the Chinese patent application No. 202410797823.5, filed on June 19, 2024, and entitled "Single-crystal ternary positive electrode material and preparation method and application thereof", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application belongs to the field of lithium ion batteries, and relates to a single-crystal ternary positive electrode material, in particular to a single-crystal ternary positive electrode material and a preparation method and application thereof. BACKGROUND

[0003] High-nickel ternary positive electrode materials have become one of the most important positive electrode materials for electric vehicle power batteries due to their advantages in energy density and cycle life. In practical applications, higher requirements are put forward for ternary positive electrode materials in order to obtain longer cruising range.

[0004] Currently, the cruising range is mainly prolonged by increasing the nickel content in the ternary positive electrode material or increasing the charge cut-off voltage of the positive electrode material. However, both methods will greatly damage the structural stability and thermal stability of the ternary positive electrode material, thereby greatly reducing the cycle life and safety performance of the battery. Single-crystal ternary positive electrode materials have higher structural stability and thermal stability than polycrystal ternary positive electrode materials, which can improve the cycle performance and safety performance of the battery to some extent, but still cannot meet the requirements.

[0005] Therefore, it is urgent to study a single-crystal ternary positive electrode material with higher cycle performance and safety performance. SUMMARY

[0006] In view of the above defects, the present application provides a single-crystal ternary positive electrode material, which has higher structural stability and thermal stability, and can effectively improve the cycle performance and safety performance of lithium ion batteries.

[0007] The present application provides a preparation method of a single-crystal ternary positive electrode material, which has higher structural stability and thermal stability, and can effectively improve the cycle performance and safety performance of lithium ion batteries.

[0008] The present application provides a positive electrode sheet, which comprises the single-crystal ternary positive electrode material described above or the single-crystal ternary positive electrode material prepared by the preparation method described above. Therefore, the application of the positive electrode sheet in lithium ion batteries can effectively improve the cycle performance and safety performance of the batteries.

[0009] The application provides a lithium ion battery comprising the single-crystal ternary positive electrode material, or the single-crystal ternary positive electrode material prepared by the preparation method, or the positive electrode sheet, so that the lithium ion battery has a long cycle life and high safety performance.

[0010] The application provides a single-crystal ternary positive electrode material, which comprises a base material with a chemical composition of Li m [Ni x Co y Mn z ]O2, wherein 0.98 < m < 1.03, 0.6 < x < 1, 0 < y < 0.1, and 0 < z < 0.1.

[0011] The base material is doped with Ce elements, M1 elements and M2 elements, the M1 elements comprise at least one of Mo, W and Te, and the M2 elements comprise at least one of Al, Zr, Y, La, Ta and Ga.

[0012] In an X-ray diffraction pattern of the single-crystal ternary positive electrode material, a diffraction peak of a (111) crystal plane of CeO2 exists at 28°-29°, and a half-peak width of the diffraction peak is 0.09-0.2.

[0013] A mass percentage of the Ce elements in the single-crystal ternary positive electrode material is 2500-5000 ppm.

[0014] The application provides a single-crystal ternary positive electrode material, which comprises a base material with a chemical composition of Li m [Ni x Co y Mn z ]O2, wherein 0.98 < m < 1.03, 0.6 < x < 1, 0 < y < 0.1, and 0 < z < 0.1.

[0015] The base material is doped with Ce elements, M1 elements and M2 elements, the M1 elements comprise at least one of Mo, W and Te, and the M2 elements comprise at least one of Al, Zr, Y, La, Ta and Ga.

[0016] In an X-ray diffraction pattern of the single-crystal ternary positive electrode material, a diffraction peak of a (111) crystal plane of CeO2 exists at 28°-29°, and a half-peak width of the diffraction peak is 0.09-0.2.

[0017] A mass percentage of the Ce elements in the single-crystal ternary positive electrode material is 2500-5000 ppm.

[0018] Further, the mass percentage content of the M1 element in the single-crystal ternary positive electrode material is 500-2000 ppm.

[0019] Further, the mass percentage content of the M2 element in the single-crystal ternary positive electrode material is 500-4000 ppm.

[0020] Further, the single-crystal ternary positive electrode material comprises the base material and a coating layer coated on at least part of the surface of the base material, the base material is doped with M2 in the bulk phase, the surface of the base material is doped with Ce and M1, and the coating layer is CeO2.

[0021] Further, in the X-ray diffraction pattern of the single-crystal ternary positive electrode material, there is a diffraction peak of the (003) crystal face at 2θ of 18.2°-19.0°, a diffraction peak of the (012) crystal face at 2θ of 38.2°-38.3°, and a diffraction peak of the (104) crystal face at 2θ of 44.35°-44.45°.

[0022] The surface energy E of the (104) crystal face (104) The surface energy E of the (003) crystal face (003) The surface energy E of the (012) crystal face (012) satisfy formula 1 and formula 2,

[0023] 50% E (003) <E (104) 70% E (003) Formula 1

[0024] 20% E (012) <E (104) 30% E (012) Formula 2.

[0025] Further, the single-crystal ternary positive electrode material comprises single-crystal primary particles;

[0026] The average particle size of the single-crystal primary particles is 1.5-4 μm.

[0027] Further, the median particle size of the single-crystal ternary positive electrode material is 3-8 μm.

[0028] Further, the specific surface area of the single-crystal ternary positive electrode material is 0.2-1 m 2 / g.

[0029] Further, the tap density of the single-crystal ternary positive electrode material is >2.2 g / cm 3 .

[0030] Further, the thermal decomposition temperature of the single-crystal ternary cathode material is not less than 225 DEG C in a DSC test.

[0031] Further, the lithium-nickel mixing rate of the single-crystal ternary cathode material is less than 2%.

[0032] The application provides a preparation method of the single-crystal ternary cathode material, comprising the following steps:

[0033] (1) mixing a ternary cathode material precursor Li m Ni x Co y Mn z (OH)2, a Li source, a Ce source, a M1 source and a M2 source, and performing first sintering, second sintering, third sintering and fourth sintering under an oxygen atmosphere;

[0034] The temperature T1 of the first sintering is 400-600 DEG C, and the holding time t1 is 4-6 h;

[0035] The temperature T2 of the second sintering is 900-1000 DEG C, and the holding time t2 is t1-1≤t2

[0036] The temperature T3 of the third sintering is T2-100

[0037] The temperature T4 of the fourth sintering is T3-70

[0038] Preferably, the temperature T3 of the third sintering is T2-100

[0039] The temperature T4 of the fourth sintering is T3-70

[0040] (2) after the fourth sintering is completed, natural cooling is performed to obtain the single-crystal ternary cathode material.

[0041] The application provides a positive electrode sheet, which comprises the single-crystal ternary cathode material according to any one of the above or prepared by the preparation method.

[0042] The application provides a lithium ion battery, which comprises the single-crystal ternary cathode material according to any one of the above or prepared by the preparation method, or the positive electrode sheet.

[0043] The single-crystal ternary cathode material of the present application comprises a base material with a chemical composition of Li m [Ni x Co y Mn z ]O2, wherein the base material is doped with Ce elements, M1 elements and M2 elements, and the mass percentage of the Ce elements in the single-crystal ternary cathode material is controlled to be 2500-5000 ppm, and the X-ray diffraction pattern of the single-crystal ternary cathode material has a diffraction peak of the (111) crystal plane of CeO2 at 2θ of 28°-29°, and the half-peak width of the diffraction peak is 0.09-0.2, preferably 0.09-0.1, so that the single-crystal ternary cathode material has high structural stability and thermal stability, thereby effectively improving the cycle performance and safety performance of the lithium ion battery. BRIEF DESCRIPTION OF DRAWINGS

[0044] FIG. 1 is an XRD pattern of the single-crystal ternary cathode material prepared in Example 1 and Comparative Example 1 of the present application;

[0045] FIG. 2 is an SEM image of the single-crystal ternary cathode material prepared in Example 1 of the present application;

[0046] FIG. 3 is an SEM image of the single-crystal ternary cathode material prepared in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0047] To make the objectives, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described below in a clear and complete manner in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort fall within the scope of protection of the present application.

[0048] The first aspect of the present application provides a single-crystal ternary cathode material, which comprises a base material with a chemical composition of Li m [Ni x Co y Mn z ]O2, wherein 0.98

[0049] The base material is doped with Ce elements, M1 elements and M2 elements, the M1 elements include at least one of Mo, W and Te, and the M2 elements include at least one of Al, Zr, Y, La, Ta and Ga;

[0050] The X-ray diffraction pattern of the single-crystal ternary cathode material has a diffraction peak of the (111) crystal plane of CeO2 at 28°-29°, and the half-peak width of the diffraction peak is 0.09-0.2;

[0051] The mass percentage of the Ce element in the single-crystal ternary cathode material is 2500-5000 ppm.

[0052] The Ce element, the M1 element and the M2 element in the application can exist in the form of oxides or be doped in the matrix material in the form of elements.

[0053] The single-crystal ternary cathode material in the application is prepared by doping specific elements in a matrix material with a chemical composition of Li m [Ni x Co y Mn z ]O2, controlling the mass percentage of the Ce element, and making the X-ray diffraction pattern of the single-crystal ternary cathode material have a diffraction peak with a specific half-peak width at a specific position, so that the single-crystal ternary cathode material has high thermal stability and structural stability, thereby effectively improving the cycle performance and safety performance of the lithium ion battery. Based on this phenomenon, the inventors analyzed the single-crystal ternary cathode material and believed that the reason can be that when the matrix material is doped with the Ce element with a specific mass percentage and the M1 element and the M2 element, and the XRD pattern of the single-crystal ternary cathode material has a CeO2(111) crystal plane diffraction peak with a half-peak width of 0.09-0.1 at 28°-29°, the Ce element, the M1 element and the M2 element synergize with each other, promote the growth of primary particles of the cathode material, and form a CeO2 coating layer on the surface of the primary particles, which helps to separate the primary particles, inhibits the agglomeration of the primary particles, and improves the dispersibility of the primary particles; at the same time, the internal stress of the primary particles can be adjusted, the internal stress distribution is more uniform, the morphology uniformity of the primary particles is improved, thereby improving the non-uniform lithium ion deintercalation caused by the uneven morphology of the single-crystal material; in addition, it is also helpful to uniformly distribute the M2 element in the matrix material and form a more stable M2-O chemical bond with the oxygen element in the matrix material, effectively enhancing the lattice and interface stability; thereby comprehensively improving the structural stability and thermal stability of the single-crystal ternary cathode material, thereby making the battery have high safety performance and cycle performance.

[0054] In addition, the single-crystal ternary cathode material can also reduce the side reaction between the electrolyte and the cathode material, further improving the cycle performance and safety performance of the battery.

[0055] The application also provides a single-crystal ternary cathode material, which has a chemical composition of Li m [Ni x Coy Mn z ]O2, wherein 0.98 < m < 1.05, 0.6 < x < 1, 0 < y < 0.1, and 0 < z < 0.3;

[0056] The base material is doped with Ce elements, M1 elements and M2 elements, the M1 elements include at least one of Mo, W and Te, and the M2 elements include at least one of Al, Zr, Y, La, Ta and Ga;

[0057] In the X-ray diffraction pattern of the single-crystal ternary positive electrode material, a diffraction peak of a (111) crystal plane of CeO2 exists at 2θ of 28°-29°, and a half-peak width of the diffraction peak is 0.09-0.2;

[0058] The mass percentage content of the Ce elements in the single-crystal ternary positive electrode material is 2500-5000 ppm.

[0059] In a specific embodiment, the mass percentage content of the M1 elements in the single-crystal ternary positive electrode material is 500-2000 ppm. Within this range, the Ce elements, the M1 elements and the M2 elements can better cooperate with each other, not only can the morphology uniformity of the primary particles be further improved, so that the battery has higher cycle performance, but also the problems of too small particle size and poor morphology uniformity of the single-crystal primary particles caused by too much M1 elements can be avoided, so that the capacity of the battery is improved.

[0060] In a specific embodiment, the mass percentage content of the M2 elements in the single-crystal ternary positive electrode material is 500-4000 ppm. Within this range, the Ce elements, the M1 elements and the M2 elements can better cooperate with each other, and have stronger binding energy with oxygen, so that the bulk structure stability of the positive electrode material is improved, the cycle performance is improved, and the capacity is not affected by too much content.

[0061] In a specific embodiment, the single-crystal ternary positive electrode material includes a base material and a coating layer coated on at least part of the surface of the base material, the base material is doped with M2 in the bulk phase, the surface of the base material is doped with Ce and M1, and the coating layer is CeO2. At this time, the primary particles in the single-crystal ternary positive electrode material have higher morphology uniformity and dispersity, which helps to further improve the cycle performance and safety of the battery; at the same time, a higher tap density can also be achieved, so that the compaction density of the positive electrode sheet and the energy density of the battery are improved.

[0062] In a specific embodiment, in the X-ray diffraction pattern of the single-crystal ternary positive electrode material, a diffraction peak of a (003) crystal plane exists at 2θ of 18.2°-19.0°, a diffraction peak of a (012) crystal plane exists at 2θ of 38.2°-38.3°, and a diffraction peak of a (104) crystal plane exists at 2θ of 44.35°-44.45°.

[0063] the surface energy E of the (104) crystal face (104) the surface energy E of the (003) crystal face (003) the surface energy E of the (012) crystal face (012) satisfy formula 1 and formula 2,

[0064] 50% E (003) <E (104) 70% E (003) Formula 1

[0065] 20% E (012) <E (104) 30% E (012) Formula 2. Specifically, the surface energy can be further controlled by controlling the type or doping amount of the Ce element and the M1 element in the preparation process, so that the surface energy of the (104) crystal face satisfies formula 1 and formula 2 at the same time. Since the (104) crystal face has a fast lithium ion diffusion channel, when E (104) When formula 1 and formula 2 are satisfied at the same time, the single-crystal ternary positive electrode material has high rate performance.

[0066] The surface energy of the (104) crystal face, the surface energy of the (003) crystal face and the surface energy of the (012) crystal face in the present application are calculated by DFT (density functional theory).

[0067] In one specific embodiment, the single-crystal ternary positive electrode material comprises single-crystal primary particles; the average particle size of the single-crystal primary particles is 1.5-4 μm. When the average particle size of the single-crystal primary particles is in this range, the primary particle size is large, the specific surface area is small, the contact area with the electrolyte can be reduced, thereby reducing the side reaction with the electrolyte, and the cycle performance and safety of the battery can be further improved; at the same time, the large size can improve the dispersibility of the positive electrode material, thereby effectively improving the tap density, making the uniformity of the positive electrode slurry better, the compaction density of the positive electrode sheet larger, and the energy density of the battery higher.

[0068] The average particle size in the present application refers to that the single-crystal ternary positive electrode material is subjected to SEM testing, the diameters of not less than 100 primary particles in any 3000 times area are measured, and the average value is taken as the average particle size of the single-crystal primary particles.

[0069] In one specific embodiment, the median particle size of the single-crystal ternary positive electrode material is 3-8 μm.

[0070] In one specific embodiment, the specific surface area of the single-crystal ternary positive electrode material is 0.2-1 m 2 / g.

[0071] In an embodiment, the tap density of the single-crystal ternary cathode material is greater than 2.2 g / cm 3 .

[0072] When the median particle size of the single-crystal ternary cathode material is in the above range, it is helpful to achieve a smaller specific surface area and a larger tap density, so that the specific surface area is between 0.2 and 1 m 2 / g, and the tap density is greater than 2.2 g / cm 3 , thereby further improving the uniformity of the cathode slurry, thereby improving the compaction density of the cathode sheet, and enabling the battery to have higher cycle performance and volumetric energy density.

[0073] The median particle size in the present application is measured by a laser particle size analyzer.

[0074] The specific surface area and tap density in the present application are measured by conventional methods in the art.

[0075] In an embodiment, the thermal decomposition temperature of the single-crystal ternary cathode material in the DSC test is not less than 225°C. Specifically, the thermal stability of the single-crystal ternary cathode material can be improved by controlling the process parameters in the preparation process, such as the doping amounts of Ce element, M1 element and M2 element, sintering temperature, holding time, so that the thermal decomposition temperature of the single-crystal ternary cathode material at the charge cut-off voltage is not less than 225°C. At this time, the lithium ion battery comprising the cathode material has higher safety performance.

[0076] The DSC test in the present application includes: at 25°C, under normal pressure (0.1 MPa), the single-crystal ternary cathode material, conductive carbon black and binder polyvinylidene fluoride (PVDF) in the present application are mixed uniformly in N-methyl pyrrolidone solvent at a mass percentage ratio of 95:3:2 to obtain a cathode slurry, the cathode slurry is coated on the surface of an aluminum foil, and after drying and cold pressing, a cathode sheet comprising a 100 μm cathode active layer is obtained, the compaction density of the cathode sheet is 4.5 g / cm 3 ; the cathode sheet, lithium sheet, separator and electrolyte are assembled into a CR2032 button cell in a button cell box, wherein the electrolyte comprises ethylene carbonate (EC), methyl ethyl carbonate (EMC) and LiPF6, the volume ratio of ethylene carbonate (EC) and methyl ethyl carbonate (EMC) is 3:7, and the mass percentage of LiPF6 in the electrolyte is 12.5wt%.

[0077] After the prepared CR2032 button cell is charged at a rate of 0.2C to a cut-off voltage of 4.3V, the positive plate is disassembled, and the positive plate is subjected to DSC test. The DSC test conditions are as follows: the disassembled positive plate is cleaned with DMC and dried, a certain amount of electrolyte (1 / 3 of the mass of the sample) is added, and a TA-DSC thermal analyzer is used to test the thermal decomposition curve to obtain the thermal decomposition temperature of the single-crystal ternary positive electrode material. In the test, the equilibrium temperature is set to 50°C, the heating rate is set to 10°C / min, the temperature range is 50-350°C, the sample mass is 2-3mg, the purge gas is N2, and the flow value is 10mL / min.

[0078] In a specific embodiment, the lithium-nickel mixing rate of the single-crystal ternary positive electrode material is <2%. Specifically, by controlling the process parameters in the preparation process, such as the doping amounts of the Ce element, the M1 element and the M2 element, the sintering temperature and the holding time, the structural stability of the single-crystal ternary positive electrode material can be improved, so that the lithium-nickel mixing rate of the single-crystal ternary positive electrode material is <2%. At this time, the rapid embedding and migration of lithium ions can be realized, so that the lithium ions of the positive electrode active material can migrate smoothly in the charging and discharging process, effectively improving the first coulomb efficiency, capacity and cycle performance of the lithium ion battery comprising the positive electrode material.

[0079] The second aspect of the present application provides a preparation method of the single-crystal ternary positive electrode material of the first aspect, comprising the following steps:

[0080] (1) mixing a ternary positive electrode material precursor Li m Ni x Co y Mn z (OH)2, a Li source, a Ce source, an M1 source and an M2 source, and performing first sintering, second sintering, third sintering and fourth sintering in an oxygen atmosphere;

[0081] The temperature T1 of the first sintering is 400-600°C, and the holding time t1 is 4-6h;

[0082] The temperature T2 of the second sintering is 900-1000°C, and the holding time t2 is t1-1≤t2

[0083] The temperature T3 of the third sintering is T2-100

[0084] The temperature T4 of the fourth sintering is T3-70

[0085] Preferably, the temperature T3 of the third sintering is T2-100

[0086] The temperature T4 of the fourth sintering is T3-70 < T4≤ T3-30, and the holding time t4 is t2 < t4 < t1+1;

[0087] (2) After the fourth sintering is completed, natural cooling is performed to obtain the single-crystal ternary positive electrode material.

[0088] Specifically, in step (1), the ternary positive electrode material precursor with a chemical composition of Li m Ni x Co y Mn z (OH)2 is uniformly mixed with a Li source, a Ce source, an M1 source and an M2 source, and then first sintering is performed in an oxygen atmosphere. The temperature T1 of the first sintering is 400-600°C, and the holding time t1 is 4-6 h. After the first sintering is completed, the temperature is raised to the second sintering temperature. The temperature T2 of the second sintering is 900-1000°C, and the holding time t2 is t1-1≤ t2 < t1. After the second sintering is completed, the temperature is lowered to the third sintering temperature. The temperature T3 of the third sintering is T2-100 < T3≤ T2-30, and the holding time t3 is t2 < t3≤ t1+2. After the third sintering is completed, the temperature is lowered to the fourth sintering temperature. The temperature T4 of the fourth sintering is T3-70 < T4≤ T3-30, and the holding time t4 is t2 < t4≤ t1+2.

[0089] The Li source in the present application refers to a raw material providing lithium element, the Ce source refers to a raw material providing Ce element, the M1 source refers to a raw material providing M1 element, and the M2 source refers to a raw material providing M2 element. As long as the target element (Li, Ce, M1, M2) is contained, it belongs to the definition of the present application. For example, the Li source includes at least one of lithium hydroxide, lithium carbonate and lithium nitrate; the Ce source includes at least one of cerium oxide and cerium nitrate; the M1 source includes at least one of molybdenum oxide, tellurium dioxide, tungsten dioxide, molybdenum disulfide, yellow tungsten and purple tungsten; and the M2 source includes at least one of aluminum oxide, zirconium dioxide, yttrium sesquioxide, lanthanum sesquioxide, tantalum pentoxide and gallium oxide.

[0090] The source of the ternary positive electrode material precursor, the Li source, the Ce source, the M1 source and the M2 source is not specifically limited in the present application, and can be obtained by commercial or conventional preparation means.

[0091] The amount of the Ce source added is not specifically limited in the present application, as long as the mass percentage content of Ce element in the finally prepared single-crystal ternary positive electrode material is 2500-5000 ppm, and a diffraction peak of the (111) crystal plane of CeO2 exists at 2θ of 28°-29° in the X-ray diffraction pattern of the single-crystal ternary positive electrode material, and the half-peak width of the diffraction peak is 0.09-0.2.

[0092] The application does not make specific limitation on the amount of the lithium source, only needs to make the chemical composition of the matrix material included in the finally prepared single-crystal ternary cathode material be Li m [Ni x Co y Mn z ]O2.

[0093] The application does not make specific limitation on the amount of the M1 source and the M2 source, further, the mass percentage content of the M1 element in the single-crystal ternary cathode material can be further controlled to be 500-2000 ppm, and / or the mass percentage content of the M2 element in the single-crystal ternary cathode material can be further controlled to be 500-4000 ppm, by controlling the amount of the M1 source and / or the M2 source.

[0094] The application does not make specific limitation on the heating rate and the cooling rate in the sintering process.

[0095] The application does not make specific limitation on the mixing method, only needs to uniformly mix the ternary cathode material precursor, the lithium source, the cerium source, the M1 source and the M2 source, for example, can be mixed by a high-speed mixer.

[0096] In step (2), after the fourth sintering is finished, natural cooling to room temperature is performed, and the obtained product is crushed and sieved to obtain the single-crystal ternary cathode material.

[0097] The application adds the lithium source, the cerium source, the M1 source and the M2 source into the ternary cathode material precursor Li m Ni x Co y Mn zThe (OH)2, Li source, Ce source, M1 source and M2 source are mixed and sintered at specific different temperature platforms for a certain time. Specifically, two-stage temperature rising sintering and two-stage temperature falling sintering are respectively performed. In the process of temperature rising sintering, the Ce element and the M1 element are gradually doped into the surface of the matrix material, the M2 element is gradually doped into the bulk phase of the matrix material, and as the temperature decreases, the Ce element gradually accumulates on the surface of the matrix material, and finally a CeO2 coating layer in rock salt phase is formed on the surface. Thus, the Ce source, the M1 source and the M2 source in the finally prepared single-crystal ternary positive electrode material synergize with each other to promote the growth of primary particles, and the CeO2 coating layer can promote the atomic diffusion of crystal faces in the sintering process of the single-crystal material, separate the primary particles, and improve the dispersity of the primary particles. At the same time, the segmented sintering at specific different temperature platforms also helps to relieve the residual stress in the crystal during the sintering process, which further improves the morphology uniformity and dispersity of the single-crystal primary particles. In addition, the distribution order of the M2 element in the crystal can also be improved, so that the M2 element is uniformly distributed in the bulk phase of the crystal, and the stability of the crystal lattice and the interface is improved, thereby further improving the structural stability of the positive electrode material. Thus, the structural stability and thermal stability of the positive electrode active material are comprehensively improved, and the cycle performance and safety performance of the battery are improved.

[0098] The third aspect of the present application provides a positive electrode sheet comprising the single-crystal ternary positive electrode material of the first aspect or the single-crystal ternary positive electrode material prepared by the preparation method of the second aspect. Since the single-crystal ternary positive electrode material has high thermal stability and structural stability, the cycle performance and safety performance of the lithium ion battery comprising the positive electrode sheet can be effectively improved.

[0099] In a specific embodiment, the compaction density of the positive electrode sheet is not less than 3.5 g / cm3. 3 Within this range, the compaction density of the positive electrode sheet is high, which can effectively improve the energy density of the lithium ion battery.

[0100] The fourth aspect of the present application provides a lithium ion battery comprising the single-crystal ternary positive electrode material of the first aspect or the single-crystal ternary positive electrode material prepared by the preparation method of the second aspect or the positive electrode sheet of the third aspect, which has a long cycle life and high safety performance.

[0101] Hereinafter, the single-crystal ternary positive electrode material of the present application will be described in detail through specific embodiments.

[0102] Example 1

[0103] Lithium hydroxide, ternary positive electrode material precursor Ni 0.83 Co 0.06 Mn 0.11The Li2Ni0.5Mn0.5O2, CeO2, MoO3 and Al2O3 are mixed uniformly in a high-speed mixer, the mixture is loaded into a crucible, and sintering is performed in a high-temperature atmosphere box furnace with an oxygen atmosphere; the temperature is raised to 500 DEG C at a rate of 3 DEG C / min to perform first sintering, after 4 h of heat preservation, the temperature is raised to 930 DEG C at a rate of 3 DEG C / min to perform second sintering, after 3 h of heat preservation, the temperature is lowered to 860 DEG C to perform third sintering, after 6 h of heat preservation, the temperature is lowered to 800 DEG C to perform fourth sintering, after 6 h of heat preservation, the temperature is lowered to room temperature naturally, and a sintered product is obtained; after roller, crushing and sieving of the sintered product, the single-crystal ternary positive electrode material of the example is obtained, and the chemical composition of the matrix material in the single-crystal ternary positive electrode material is Li 1.05 [Ni 0.83 Co 0.06 Mn 0.11 ]O2, the doping amount of Ce element is 3000 ppm, the doping amount of Mo element is 1000 ppm, and the doping amount of Al element is 1000 ppm.

[0104] Example 2

[0105] The preparation method of the single-crystal ternary positive electrode material in the example is basically the same as that in example 1, except that the chemical composition of the ternary positive electrode material precursor is Ni 0.6 Co 0.1 Mn 0.3 (OH)2; the temperature of second sintering is 970 DEG C; and the chemical composition of the matrix material in the single-crystal ternary positive electrode material prepared in the example is Li 1.05 [Ni 0.6 Co 0.1 Mn 0.3 ]O2, the doping amount of Ce element is 3000 ppm, the doping amount of Mo element is 1000 ppm, and the doping amount of Al element is 1000 ppm.

[0106] Example 3

[0107] The preparation method of the single-crystal ternary positive electrode material in the example is basically the same as that in example 1, except that the chemical composition of the ternary positive electrode material precursor is Ni 0.9 Co 0.05 Mn 0.05 (OH)2; the temperature of second sintering is 910 DEG C; and the chemical composition of the matrix material in the single-crystal ternary positive electrode material prepared in the example is Li 1.05 [Ni 0.9 Co 0.05 Mn 0.05 ]O2, the doping amount of Ce element is 3000 ppm, the doping amount of Mo element is 1000 ppm, and the doping amount of Al element is 1000 ppm.

[0108] Example 4

[0109] The preparation method of the single-crystal ternary cathode material in this example is basically the same as that in Example 1, except that the adding amounts of CeO2, MoO3 and Al2O3 in the mixture are changed; the chemical composition of the base material in the single-crystal ternary cathode material prepared in this example is Li 1.05 [Ni 0.6 Co 0.1 Mn 0.3 ]O2, the doping amount of Ce element is 4000 ppm, the doping amount of Mo element is 800 ppm, and the doping amount of Al element is 800 ppm.

[0110] Example 5

[0111] The preparation method of the single-crystal ternary cathode material in this example is basically the same as that in Example 1, except that the adding amounts of CeO2 and MoO3 in the mixture are changed; the chemical composition of the base material in the single-crystal ternary cathode material prepared in this example is Li 1.05 [Ni 0.6 Co 0.1 Mn 0.3 ]O2, the doping amount of Ce element is 5000 ppm, the doping amount of Mo element is 1200 ppm, and the doping amount of Al element is 1000 ppm.

[0112] Example 6

[0113] The preparation method of the single-crystal ternary cathode material in this example is basically the same as that in Example 1, except that WO2 is used to replace MoO3, ZrO2 is used to replace Al2O3, and the adding amount of ZrO2 is changed; the chemical composition of the base material in the single-crystal ternary cathode material prepared in this example is Li 1.05 [Ni 0.6 Co 0.1 Mn 0.3 ]O2, the doping amount of Ce element is 3000 ppm, the doping amount of W element is 1000 ppm, and the doping amount of Zr element is 2000 ppm.

[0114] Example 7

[0115] The preparation method of the single-crystal ternary cathode material in this example is basically the same as that in Example 1, except that TeO2 is used to replace MoO3, Y2O3 is used to replace Al2O3, and the adding amount of Y2O3 is changed; the chemical composition of the base material in the single-crystal ternary cathode material prepared in this example is Li 1.05 [Ni 0.6 Co 0.1 Mn 0.3Li2 / 3Mn2 / 3Ni1 / 6Co1 / 6O2, the doping amount of Ce element is 3000ppm, the doping amount of Te element is 1000ppm, and the doping amount of Y element is 1200ppm.

[0116] Example 8

[0117] The preparation method of the single-crystal ternary cathode material in the example is basically the same as that in Example 1, except that La2O3 is used to replace Al2O3, and the addition amount of La2O3 is changed. The chemical composition of the base material in the single-crystal ternary cathode material prepared in the example is Li 1.05 [Ni 0.6 Co 0.1 Mn 0.3 ]O2, the doping amount of Ce element is 3000ppm, the doping amount of Mo element is 1000ppm, and the doping amount of La element is 800ppm.

[0118] Example 9

[0119] The preparation method of the single-crystal ternary cathode material in the example is basically the same as that in Example 1, except that WO2 is used to replace MoO3, and Ta2O5 is used to replace Al2O3. The chemical composition of the base material in the single-crystal ternary cathode material prepared in the example is Li 1.05 [Ni 0.6 Co 0.1 Mn 0.3 ]O2, the doping amount of Ce element is 3000ppm, the doping amount of W element is 1000ppm, and the doping amount of Ta element is 1000ppm.

[0120] Example 10

[0121] The preparation method of the single-crystal ternary cathode material in the example is basically the same as that in Example 1, except that TeO2 is used to replace MoO3, and Ga2O3 is used to replace Al2O3. The chemical composition of the base material in the single-crystal ternary cathode material prepared in the example is Li 1.05 [Ni 0.6 Co 0.1 Mn 0.3 ]O2, the doping amount of Ce element is 3000ppm, the doping amount of Te element is 1000ppm, and the doping amount of Ga element is 800ppm.

[0122] Example 11

[0123] The preparation method of the single-crystal ternary cathode material in the example is basically the same as that in Example 1, except that the addition amount of MoO2 is changed. The chemical composition of the base material in the single-crystal ternary cathode material prepared in the example is Li 1.05 [Ni 0.6Co 0.1 Mn 0.3 ]O2, the doping amount of Ce element is 3000 ppm, the doping amount of Mo element is 2500 ppm, and the doping amount of Al element is 1000 ppm.

[0124] Example 12

[0125] The preparation method of the single-crystal ternary positive electrode material in the example is basically the same as that in Example 1, except that the addition amount of Al2O3 is changed. The chemical composition of the base material of the single-crystal ternary positive electrode material prepared in the example is Li 1.05 [Ni 0.6 Co 0.1 Mn 0.3 ]O2, the doping amount of Ce element is 3000 ppm, the doping amount of Mo element is 2500 ppm, and the doping amount of Al element is 1000 ppm.

[0126] Comparative Example 1

[0127] The preparation method of the single-crystal ternary positive electrode material in the example is basically the same as that in Example 1, except that the addition amount of Al2O3 is changed. The chemical composition of the base material of the single-crystal ternary positive electrode material prepared in the example is Li 1.05 [Ni 0.6 Co 0.1 Mn 0.3 ]O2, the doping amount of Ce element is 3000 ppm, the doping amount of Mo element is 2500 ppm, and the doping amount of Al element is 1000 ppm.

[0128] Comparative Example 2

[0129] The preparation method of the single-crystal ternary positive electrode material in the example is basically the same as that in Example 1, except that the addition amount of Al2O3 is changed. The chemical composition of the base material of the single-crystal ternary positive electrode material prepared in the example is Li 1.05 [Ni 0.6 Co 0.1 Mn 0.3 ]O2, the doping amount of Ce element is 3000 ppm, the doping amount of Mo element is 2500 ppm, and the doping amount of Al element is 1000 ppm.

[0130] Comparative Example 3

[0131] The preparation method of the single-crystal ternary cathode material in the present comparative example is basically the same as that in Example 1, except that the mixture is sintered in a high-temperature atmosphere box furnace, and the sintering atmosphere is oxygen; the temperature is raised to 500 DEG C at a rate of 3 DEG C / min, and after 4 h of heat preservation, the temperature is raised to 930 DEG C, and after 15 h of heat preservation, the temperature is naturally lowered to room temperature to obtain the single-crystal ternary cathode material of the present comparative example.

[0132] The chemical composition of the matrix material in the single-crystal ternary cathode material prepared in the present comparative example is Li 1.05 [Ni 0.83 Co 0.06 Mn 0.11 ]O2, the doping amount of Ce element is 3000 ppm, the doping amount of Mo element is 1000 ppm, and the doping amount of Al element is 1000 ppm.

[0133] Comparative Example 4

[0134] The preparation method of the single-crystal ternary cathode material in the present comparative example is basically the same as that in Example 1, except that the mixture does not include CeO2.

[0135] The chemical composition of the matrix material in the single-crystal ternary cathode material prepared in the present comparative example is Li 1.05 [Ni 0.83 Co 0.06 Mn 0.11 ]O2, the doping amount of Mo element is 1000 ppm, and the doping amount of Al element is 1000 ppm.

[0136] Comparative Example 5

[0137] The preparation method of the single-crystal ternary cathode material in the present comparative example is basically the same as that in Example 1, except that the mixture does not include MoO3.

[0138] The chemical composition of the matrix material in the single-crystal ternary cathode material prepared in the present comparative example is Li 1.05 [Ni 0.83 Co 0.06 Mn 0.11 ]O2, the doping amount of Ce element is 3000 ppm, and the doping amount of Al element is 1000 ppm.

[0139] Comparative Example 6

[0140] The preparation method of the single-crystal ternary cathode material in the present comparative example is basically the same as that in Example 1, except that the mixture does not include Al2O3.

[0141] The chemical composition of the matrix material in the single-crystal ternary cathode material prepared in the present comparative example is Li 1.05 [Ni 0.83Co 0.06 Mn 0.11 ]O2, the doping amount of Ce element is 3000ppm, and the doping amount of Mo element is 1000ppm.

[0142] Comparative Example 7

[0143] The preparation method of the single-crystal ternary positive electrode material in the comparative example is basically the same as that in Example 1, except that the temperature of the first sintering is adjusted to 450℃, and the holding time is adjusted to 3h; the temperature of the second sintering is adjusted to 890℃, and the holding time is adjusted to 2h, and the others remain unchanged.

[0144] The chemical composition of the matrix material in the single-crystal ternary positive electrode material prepared in the comparative example is Li 1.05 [Ni 0.83 Co 0.06 Mn 0.11 ]O2, the doping amount of Ce element is 3000ppm, and the doping amount of Mo element is 1000ppm.

[0145] Comparative Example 8

[0146] The preparation method of the single-crystal ternary positive electrode material in the comparative example is basically the same as that in Example 1, except that the temperature of the third sintering is adjusted to 750℃, and the holding time is adjusted to 2.5h.

[0147] The chemical composition of the matrix material in the single-crystal ternary positive electrode material prepared in the comparative example is Li 1.05 [Ni 0.83 Co 0.06 Mn 0.11 ]O2, the doping amount of Ce element is 3000ppm, and the doping amount of Mo element is 1000ppm.

[0148] Comparative Example 9

[0149] The preparation method of the single-crystal ternary positive electrode material in the comparative example is basically the same as that in Example 1, except that the temperature of the fourth sintering is adjusted to 700℃, and the holding time is adjusted to 2.5h.

[0150] The chemical composition of the matrix material in the single-crystal ternary positive electrode material prepared in the comparative example is Li 1.05 [Ni 0.83 Co 0.06 Mn 0.11 ]O2, the doping amount of Ce element is 3000ppm, and the doping amount of Mo element is 1000ppm.

[0151] Test Example

[0152] 1. Physicochemical property characterization of the single-crystal ternary cathode material prepared in the above examples and comparative examples:

[0153] (1) X-ray diffraction

[0154] The XRD (X-ray diffraction) test was performed on the single-crystal ternary cathode material powder prepared in the above examples and comparative examples, and the corresponding XRD diffraction pattern was obtained. The CeO2(111) crystal face diffraction peak at 2θ of 28°-29° and the half-peak width of the diffraction peak, and the lithium-nickel mixing rate of the single-crystal ternary cathode material were obtained.

[0155] The test results are shown in Table 1, Table 3 and FIG. 1.

[0156] FIG. 1 is the XRD spectrum of the single-crystal ternary cathode material in Example 1 and Comparative Example 1. As shown in FIG. 1, the single-crystal ternary cathode material in Example 1 has a CeO2(111) crystal face diffraction peak at 2θ of 28.53°, and the half-peak width of the diffraction peak is 0.15; while the single-crystal ternary cathode material in Comparative Example 1 obviously does not have the diffraction peak.

[0157] (2) ICP-AES test

[0158] The mass percentage of each element in the single-crystal ternary cathode material prepared in the above examples and comparative examples was determined, and the results are shown in Table 1.

[0159] (3) Surface energy

[0160] The single-crystal ternary cathode material prepared in the above examples and comparative examples was modeled and calculated by DFT (density functional theory), and the surface energy of the (003) crystal face, (012) crystal face and (104) crystal face of the single-crystal ternary cathode material in each example and comparative example was obtained.

[0161] The test results are shown in Table 2.

[0162] (4) SEM test

[0163] The single-crystal ternary cathode material prepared in the above examples and comparative examples was subjected to SEM test, and the SEM test image under 3000 times was obtained. The diameters of not less than 100 primary particles in the SEM image were measured and averaged to obtain the average particle size of the primary particles. The measurement results are shown in Table 3 and FIG. 2 and FIG. 3.

[0164] Fig. 2 and Fig. 3 are SEM images of the single-crystal ternary positive electrode materials prepared in Example 1 and Comparative Example 1, respectively, from which it can be seen that the single-crystal ternary positive electrode material prepared in Example 1 is a single-crystal particle with uniform morphology and high dispersibility; while the primary particles included in the single-crystal ternary positive electrode material prepared in Comparative Example 1 have obvious agglomeration phenomenon, poor dispersibility, and also poor uniformity of morphology.

[0165] (4) Median particle size

[0166] The single-crystal ternary positive electrode materials prepared in the above examples and comparative examples were first subjected to ultrasonic dispersion in a solvent, and then particle size testing was performed using a Malvern 3000 laser particle size instrument, and the testing results are shown in Table 3.

[0167] (5) Specific surface area

[0168] 5 g of each of the single-crystal ternary positive electrode material samples prepared in the examples and comparative examples were taken and loaded into a long tube with a ball bubble, first subjected to vacuum treatment at 2 h / 200°C, and then subjected to gas adsorption by passing N2, and the adsorption amount of the measured sample to the adsorbate molecules (N2) was determined according to the pressure or weight change before and after adsorption, thereby obtaining the specific surface area, and the testing results are shown in Table 3.

[0169] (6) Tap density

[0170] Each of the single-crystal ternary positive electrode materials prepared in the examples and comparative examples was loaded into a graduated cylinder, the graduated cylinder was fixed on a mechanical vibration device, the vibration motor drove the mechanical vibration device to vibrate vertically up and down, the graduated cylinder loaded with the single-crystal ternary positive electrode material vibrated in rhythm with the mechanical vibration device, and with the increase of the vibration frequency, the powder or particles in the graduated cylinder were gradually vibrated and compacted, after the vibration frequency reached the set frequency, the mechanical vibration device stopped vibrating, the volume of the graduated cylinder was read, and according to the definition of density: mass divided by volume, the density after vibration was obtained, i.e. the tap density, and the testing results are shown in Table 3.

[0171] (7) Thermal decomposition temperature

[0172] At 25°C and under normal pressure (0.1 MPa), the single-crystal ternary positive electrode material, conductive carbon black, and binder polyvinylidene fluoride (PVDF) in the present application were mixed uniformly in N-methylpyrrolidone solvent at a mass percentage ratio of 95:3:2 to obtain a positive electrode slurry, the positive electrode slurry was coated on the surface of an aluminum foil, and after drying and cold pressing, a positive electrode sheet containing a 100 μm positive electrode active layer was obtained, and the tap density of the positive electrode sheet was 4.5 g / cm 3; the positive plate, lithium sheet, diaphragm and electrolyte are assembled into a CR2032 button cell in a button cell box, wherein the electrolyte comprises ethylene carbonate (EC), methyl ethyl carbonate (EMC) and LiPF6, the volume ratio of ethylene carbonate (EC) to methyl ethyl carbonate (EMC) is 3:7, and the mass percentage of LiPF6 in the electrolyte is 12.5%.

[0173] After the prepared CR2032 button cell is charged at a rate of 0.2C to a cutoff voltage of 4.3V, the positive plate is disassembled, and the positive plate is subjected to DSC test. The DSC test conditions are as follows: the disassembled positive plate is cleaned with DMC and dried, a certain amount of electrolyte (1 / 3 of the mass of the sample) is added, a TA-DSC thermal analyzer is used to test the thermal decomposition curve, and the thermal decomposition temperature of the single-crystal ternary positive material is obtained. In the test, the equilibrium temperature is set to 50°C, the heating rate is set to 10°C / min, the cutoff temperature is 50-350°C, the sample mass is 2-3mg, the purge gas is N2, and the flow value is 10mL / min.

[0174] The test results are shown in Table 3.

[0175] Table 1

[0176] Table 2

[0177] Table 3

[0178] From Tables 1-3, it can be seen that:

[0179] The single-crystal ternary positive material prepared in Examples 1-12 has a (111) crystal face diffraction peak with a half-peak width of 0.09-0.2 at 28°-29°, and the mass percentage of Ce element therein is between 2500-5000ppm; at the same time, the surface energy of the (104) crystal face of the single-crystal ternary positive material is smaller than that of the (003) crystal face and the (012) crystal face, which can make the battery have higher rate performance; in addition, the lithium-nickel mixing rate and thermal decomposition temperature of the single-crystal ternary positive material prepared in the examples are both high. Therefore, the single-crystal ternary positive material in the application can effectively improve the safety performance and electrochemical performance of the battery.

[0180] 2. The single-crystal ternary positive material prepared in the above examples and comparative examples is made into a button cell, including the following steps:

[0181] The capacity, rate performance, cycle performance and safety of the button cell prepared above are tested:

[0182] (1) Capacity

[0183] Charge at 0.2C rate to the cut-off voltage 4.3V, then constant voltage charge to the current less than 0.05C at the cut-off voltage, record the charge capacity at this time as the first circle charge specific capacity, then stand for 5min, discharge at 0.2C rate to the voltage 2.5V, record the discharge capacity at this time as the first circle discharge specific capacity, which is the initial capacity.

[0184] (2) Rate performance

[0185] Charge at 0.1C rate to the cut-off voltage 4.3V, then constant voltage charge to the current less than 0.05C at the cut-off voltage, then stand for 5min, discharge at 0.2C rate to the voltage 2.5V, the capacity at this time is recorded as the discharge capacity at 0.2C rate C0; stand for 10min, charge at 1C rate to the cut-off voltage 4.5V, then constant voltage charge to the current less than 0.05C at the cut-off voltage, then stand for 5min, discharge at 2C rate to the voltage 2.5V, the capacity at this time is recorded as the discharge capacity at 2C rate C1, then the 2C rate performance is the ratio of C1 and C2.

[0186] (3) Cycle performance

[0187] The single crystal ternary positive electrode material prepared in the above examples and comparative examples is prepared into a positive electrode sheet according to the preparation method in the above coin cell, the negative electrode is graphite, the separator is polyethylene, the electrolyte includes ethylene carbonate (EC), methyl ethyl carbonate (EMC) and LiPF6, the volume ratio of ethylene carbonate (EC) and methyl ethyl carbonate (EMC) is 3:7, the mass percentage of LiPF6 in the electrolyte is 12.5%, and a laminated battery is assembled.

[0188] The laminated battery prepared above is charged and discharged at 1C rate in the voltage range of 2.5-4.3V at 45℃ to obtain the first discharge capacity; after 300 cycles of cyclic charging and discharging with the charging and discharging mechanism, the discharge capacity after cycling is obtained, and then the cycle capacity retention rate is the ratio of the discharge capacity after cycling to the first discharge capacity.

[0189] (4) Safety

[0190] The safety of the battery is characterized by the battery expansion rate, specifically, the full battery assembled above is charged to the set voltage 4.3V, the thickness L0 of the battery is tested by PPG battery thickness tester, then the battery is taken out after being placed in a 70℃ constant temperature box for 28 days, the thickness L1 of the battery at this time is tested by PPG battery thickness tester, and then the battery expansion rate is calculated by formula 1,

[0191] Battery swelling rate (%) = (L1-L0) / L0x100% Formula 1

[0192] The calculation results are shown in Table 4.

[0193] Table 4

[0194] From Table 4, it can be seen that:

[0195] The comprehensive electrochemical performance and safety of the lithium ion batteries prepared in Examples 1-12 are better than those of Comparative Examples 1-9, wherein the 1C 300 cycle retention rate of Example 2 is the highest, being 95.1%, the cell swelling rate is the lowest, being 12.3%, correspondingly, the 0.2C discharge capacity is the highest, being 201.3 mAh / g, and the 2C / 0.2C rate performance is 89.5%. It can be seen that the single-crystal ternary positive electrode material in the present application has high structural stability and thermal stability, can effectively improve the cycle performance and safety performance of the lithium ion battery, and can also have capacity and rate performance.

[0196] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A single-crystalline ternary cathode material, wherein, The single-crystal ternary positive electrode material includes a base material with a chemical composition of Li m [Ni x Co y Mn z ]O2, wherein 0.98 < m < 1.03, 0.6 ≤ x < 1, 0 < y < 0.1, and 0 < z < 0.

1. The base material is doped with Ce element, M1 element and M2 element, the M1 element includes at least one of Mo, W and Te, and the M2 element includes at least one of Al, Zr, Y, La, Ta and Ga; The X-ray diffraction pattern of the single-crystal ternary positive electrode material has a diffraction peak of a (111) crystal plane of CeO2 at 2θ of 28°-29°, and the half-peak width of the diffraction peak is 0.09-0.2; The mass percentage content of the Ce element in the single-crystal ternary positive electrode material is 2500-5000 ppm.

2. A single-crystalline ternary cathode material, wherein, The single-crystal ternary positive electrode material includes a base material with a chemical composition of Li m [Ni x Co y Mn z ]O2, wherein 0.98 < m < 1.05, 0.6 < x < 1, 0 < y < 0.1, and 0 < z < 0.

3. The base material is doped with Ce element, M1 element and M2 element, the M1 element includes at least one of Mo, W and Te, and the M2 element includes at least one of Al, Zr, Y, La, Ta and Ga; The X-ray diffraction pattern of the single-crystal ternary positive electrode material has a diffraction peak of a (111) crystal plane of CeO2 at 2θ of 28°-29°, and the half-peak width of the diffraction peak is 0.09-0.2; The mass percentage content of the Ce element in the single-crystal ternary positive electrode material is 2500-5000 ppm.

3. The single-crystalline ternary cathode material of claim 1 or 2, wherein, The mass percentage content of the M1 element in the single-crystal ternary positive electrode material is 500-2000 ppm.

4. The single-crystalline ternary cathode material of any one of claims 1-3, wherein, The mass percentage content of the M2 element in the single-crystal ternary positive electrode material is 500-4000 ppm.

5. The single-crystalline ternary cathode material of any one of claims 1-4, wherein, The single-crystal ternary positive electrode material includes the base material and a coating layer coated on at least part of the surface of the base material, the bulk phase of the base material is doped with M2, the surface of the base material is doped with Ce and M1, and the coating layer is CeO2.

6. The single-crystalline ternary cathode material of any one of claims 1-5, wherein, The X-ray diffraction pattern of the single-crystal ternary positive electrode material has a diffraction peak of a (003) crystal plane at 2θ of 18.2°-19.0°, a diffraction peak of a (012) crystal plane at 2θ of 38.2°-38.3°, and a diffraction peak of a (104) crystal plane at 2θ of 44.35°-44.45°; the surface energy E of the (104) crystal plane (104) the surface energy E of the (003) crystal plane (003) the surface energy E of the (012) crystal plane (012) satisfies formula 1 and formula 2, 50% E (003) < E (104) < 70% E (003) Formula 1 20% E (012) < E (104) < 30% E (012) Formula 2.

7. The single-crystalline ternary cathode material of any one of claims 1-6, wherein, The single-crystal ternary positive electrode material includes single-crystal primary particles; The average particle size of the single-crystal primary particles is 1.5-4 μm.

8. The single-crystalline ternary cathode material of claim 7, wherein, The median particle size of the single-crystal ternary positive electrode material is 3-8 μm.

9. The single-crystalline ternary cathode material of claim 7 or 8, wherein, The specific surface area of the single-crystal ternary positive electrode material is 0.2-1 m 2 / g.

10. The single-crystalline ternary cathode material of any one of claims 7-9, wherein, The tap density of the single-crystal ternary cathode material is > 2.2 g / cm 3 .

11. The single-crystalline ternary cathode material of any one of claims 1-10, wherein, In the DSC test of the single-crystal ternary positive electrode material, the thermal decomposition temperature of the single-crystal ternary positive electrode material is not lower than 225°C.

12. The single-crystalline ternary cathode material of any one of claims 1-11, wherein, The lithium-nickel mixing rate of the single-crystal ternary positive electrode material is less than 2%.

13. A method of producing the single-crystal ternary cathode material of any one of claims 1-12, wherein, The method comprises the following steps: (1) mixing a ternary positive electrode material precursor Li m Ni x Co y Mn z (OH)2, a Li source, a Ce source, an M1 source, and an M2 source, and performing first sintering, second sintering, third sintering, and fourth sintering under an oxygen atmosphere; The temperature T1 of the first sintering is 400-600°C, and the holding time t1 is 4-6 h; The temperature T2 of the second sintering is 900-1000°C, and the holding time t2 is t1-1≤t2 The temperature T3 of the third sintering is T2-100 The temperature T4 of the fourth sintering is T3-70 Preferably, the temperature T3 of the third sintering is T2-100 The temperature T4 of the fourth sintering is T3-70 < T4 ≤ T3-30, and the holding time t4 is t2 < t4 < t1+1; (2) After the fourth sintering is completed, natural cooling is performed to obtain the single-crystal ternary positive electrode material.

14. A positive electrode sheet, wherein The positive electrode sheet comprises the single-crystal ternary positive electrode material according to any one of claims 1-12, or the single-crystal ternary positive electrode material prepared by the preparation method of claim 13.

15. A lithium-ion battery, wherein, The lithium ion battery comprises the single-crystal ternary positive electrode material according to any one of claims 1-12, or the single-crystal ternary positive electrode material prepared by the preparation method of claim 13, or the positive electrode sheet of claim 14.

Images