Patent Description:
The present disclosure belongs to the technical field of lithium-ion batteries (LIBs), and in particular relates to a high-nickel ternary cathode material and a preparation method thereof.

With the development of new energy vehicles, the requirements for mileage continue to increase. Therefore, for lithium battery cathode materials, it is one of the research interests to develop high-nickel materials. High-nickel cathode materials have a very significant capacity advantage, with an actual capacity of about <NUM> mAh/g. In addition, high-nickel materials have a price advantage due to the use of less Co. Although there is currently no large-scale application in the field of power battery energy storage due to constraints such as stability and cycling performance, with the continuous development of new doping-coating techniques and precursor techniques, these drawbacks are gradually compensated.

There are currently two development directions for high-nickel cathode materials. High-nickel cathode materials are mainly distinguished from the morphology, including spherical secondary particles and single-crystal panicles. At present, there are relatively mature preparation methods for materials of the two morphologies. Chinese patent <CIT> introduces a preparation method of a high-nickel secondary particle material to prepare a high-nickel cathode material with a spherical secondary particle morphology. Due to the constraints of poor high-temperature cycling, rapid high-temperature DC internal resistance (DCR) growth, gas production, and other factors, secondary particle materials are more likely to be used in the field of energy storage, and less likely to be used in the field of power. Chinese patent <CIT> introduces a preparation method of a high-nickel single-crystal material to prepare a high-nickel cathode material with a single-crystal morphology. Single-crystal material have large advantages in gas production, cycling, and the like, but have low capacity, which reduces the advantage of high-nickel materials to bring high endurance power for electric vehicles. The high-nickel cathode materials of the two morphologies each have respective shortcomings, which has become the main technical bottleneck. Another Chinese patent, <CIT> introduces a cathode material for a lithium ion battery, in particular to a graded high nickel ternary cathode material and a preparation method and application thereof. The modified ternary polycrystalline and single crystal grading material is produced by mixing a high nickel polycrystalline material and a ternary single crystal material and performing surface coating treatment by re-sintering.

The above-mentioned materials of the two morphologies have been used in combination (as shown in Chinese patent <CIT>), but a combined product does not include W. The cathode materials of the two morphologies are directly mixed usually through physical blending to obtain a high-nickel cathode material with both spherical and single-crystal morphologies. Due to the different preparation processes of the materials of the two morphologies, such as different preparation conditions, sintering temperatures, doping materials, and coating materials, the materials of the two morphologies have quite different basic cell parameters, and this difference requires the use of different battery systems to adjust. Therefore, simple physical blending has significant drawbacks. Simple physical blending cannot effectively improve the capacity and cycling performance of the material; cannot overcome the disadvantages of gas production, rapid internal resistance growth, and the like; and cannot better match a battery system, but can simply increase the compacted density. Therefore, simple physical blending cannot substantially solve the problems of existing high-nickel materials, and may even backfire.

The technical problem to be solved by the present disclosure is to overcome the shortcomings and deficiencies mentioned in the background art and provide a W-containing high-nickel ternary cathode material in which spherical secondary particles and single-crystal particles coexist. Moreover, the present disclosure also provides a preparation method of the high-nickel cathode material, where through the control on precursors and sintering conditions, one-time sintering is conducted to obtain the high-nickel cathode material with both single-crystal particles and spherical secondary particles.

In order to solve the above technical problems, the present disclosure adopts the following technical solutions: A W-containing high-nickel ternary cathode material is provided, with a chemical formula of LiaNixCoyMn<NUM>-x-yWbMcO<NUM>, where the high-nickel ternary cathode material includes both spherical secondary particles and single-crystal particles; there is basically no W inside the single-crystal particles (if there is W inside the single-crystal particles, single-crystal particles are difficult to exist and are easy to grow into secondary spheres); and the spherical secondary particles are doped with W (because a precursor is doped with W and W restricts the growth of primary particles and promotes the generation of secondary spheres, the spherical secondary particles necessarily include W).

For the high-nickel ternary cathode material, preferably, the spherical secondary particles may have a particle size of <NUM> to <NUM>; and the single-crystal particles may have a particle size of <NUM> to <NUM>. Preferably, the high-nickel ternary cathode material may have a median diameter of <NUM> to <NUM>. In the present disclosure, particles with small D50 are adopted to maximize the capacity; W is doped to form a W coating layer through process control in a later stage, which is favorable for the cycling; and single-crystal particles are also introduced, which is also beneficial to the improvement of cycling performance. Therefore, the present disclosure can achieve an improvement in overall performance through the comprehensive regulation of particle size and particle structure.

For the high-nickel ternary cathode material, preferably, a mass ratio of the spherical secondary particles to the single-crystal particles in the high-nickel ternary cathode material may be determined by a ratio of a W-containing precursor B to a W-free precursor A in a raw material. In the present disclosure, the ratio of the W-containing precursor B to the W-free precursor A can be controlled to finally control the ratio of the spherical secondary particles to the single-crystal particles in the high-nickel ternary cathode material. The ratio of the two precursors is the ratio of spherical secondary particles to single-crystal particles in a product obtained after the sintering. By accurately controlling the ratio of the two morphologies, a high-nickel cathode material with ideal morphology and performance can be obtained. More preferably, a mass ratio of the precursor B to the precursor A may be (<NUM>-<NUM>): <NUM>. Most preferably, a mass ratio of the precursor B to the precursor A may be (<NUM>-<NUM>): <NUM>, in which case, an obtained high-nickel cathode material has the optimal capacity and cycling performance.

For the high-nickel ternary cathode material, preferably, a surface of the high-nickel ternary cathode material may be at least partly or completely coated with a lithium tungstate layer. The lithium tungstate layer is preferably formed from W inside the spherical secondary particles during a high-temperature sintering process, where one part of the W forms a lithium tungstate coating layer on the surface of the spherical secondary particles, and one part of the W forms a lithium tungstate coating layer on the surface of nearby single-crystal particles.

For the high-nickel ternary cathode material, preferably, in the molecular formula of LiaNixCoyMn<NUM>-x-yWbMcO<NUM>, <NUM> ≤ a ≤ <NUM>, <NUM> < x < <NUM>, <NUM> < y < <NUM>, <NUM> < b+c < <NUM>, and the M may be one or more from the group consisting of Zr, Mg, Ti, Al, Si, La, Ba, Sr, Nb, Cr, Mo, Ca, Y, In, Sn, and F; and the high-nickel ternary cathode material may have a specific surface area (SSA) of <NUM> ± <NUM><NUM>/g.

For the high-nickel ternary cathode material, preferably, on the premise of ignoring element loss during a preparation process, a Ni-Co-Mn molar ratio in the spherical secondary particles may be consistent with a Ni-Co-Mn molar ratio in the single-crystal particles. In the prior art, even if there are some public mentions of spherical secondary particles and single-crystal particles, the two particles may have different Ni mass fractions or atomic proportions, which makes the two particles fail to be well matched in a battery system. However, the two different microscopic particles of the present disclosure have basically the same nickel content, such that the two particles can well coexist in a battery system.

As a general technical idea, the present disclosure also provides a preparation method of the high-nickel ternary cathode material, including the following steps:.

In existing methods, W is rarely used to control a particle size when spherical secondary particles or single-crystal particles are prepared, and a particle size of primary particles is controlled mainly by adjusting a sintering temperature. In the above preparation method, the precursor A and the precursor B are separately obtained in the precursor preparation stage. W in the W-containing precursor B has a large ionic radius, which can inhibit the fusion growth of single-crystal particles to some extent, and thus the precursor B can react with the lithium source to form spherical secondary particles with small primary particles and perfect crystal form during the high-temperature sintering process. The W-free precursor A can react with the lithium source and normally grow into single-crystal particles under high-temperature sintering. In the W-containing high-nickel ternary cathode material prepared by this process, the single-crystal particles have large primary particles, resulting in prominent cycling performance; and the spherical secondary particles have a similar particle size to the single-crystal particles, and are small-particle secondary spheres, resulting in high capacity. On the whole, the material of the present disclosure maintains the dominant position in cycling performance, capacity, and compacted density. In the preparation method of the present disclosure, during the high-temperature sintering, a sintering temperature for preparing a single crystal is adopted (a temperature for generating a single crystal with a perfect crystal form). Because W is doped, small secondary spheres can be formed from agglomeration of small primary particles. One precursor is doped with W and the other precursor is not doped with W, such that particles of the two morphologies can be generated through one-time sintering, and the particles of the two morphologies show excellent and complementary performance.

For the preparation method, preferably, in step (<NUM>), the soluble tungsten salt may include one or more from the group consisting of ammonium metatungstate (AMT), phosphotungstic acid (PTA), sodium tungstate, and ammonium paratungstate (APT); and
a molar ratio of tungsten in the soluble tungsten salt to a sum of nickel, cobalt, and manganese in the precursor B may be (<NUM>-<NUM>): <NUM>.

For the preparation method, preferably, in step (<NUM>), the lithium source may be one or more from the group consisting of lithium carbonate, lithium hydroxide, lithium acetate, and lithium oxalate; and
a molar ratio of lithium in the lithium source to a sum of main metal elements in the precursor B, the precursor A, and the doping element M-containing compound may be (<NUM>-<NUM>): <NUM>.

For the preparation method, preferably, in step (<NUM>), the doping element M-containing compound may be one or more from the group consisting of a hydroxide, a phosphate, a hydrophosphate, an oxide, and an anhydride of the M element. More preferably, the doping element M-containing compound may be an oxide of the M element, and the oxide of the M element may be at least one from the group consisting of ZrO<NUM>, MgO, TiO<NUM>, Al<NUM>O<NUM>, SiO<NUM>, La<NUM>O<NUM>, BaO, SrO, NbzOs, Cr<NUM>O<NUM>, MoO<NUM>, CaO, Y<NUM>O<NUM>, In<NUM>O<NUM>, and SnO<NUM>.

For the preparation method, preferably, in step (<NUM>), the mixing may be conducted for <NUM> to <NUM> by stirring at <NUM>,<NUM> r/min to <NUM>,<NUM> r/min.

For the preparation method, preferably, in step (<NUM>), the high-temperature sintering may be conducted at <NUM> to <NUM>. A sintering temperature for spherical secondary particles is generally lower than that for single-crystal particles in the art, especially in the field of high-nickel cathode materials. In the present disclosure, the precursor B is doped with W and thus can still form spherical secondary particles at a high temperature, which is not limited by the low generation temperature of spherical secondary particles. As the metal element M is doped, the high-temperature sintering at <NUM> to <NUM> can be adopted, which can make metal ions stably occupy nickel, cobalt, and manganese sites in the lithium-nickel-manganese-cobalt oxide (LNMCO) material with the two morphologies, thereby achieving a prominent doping modification effect.

For the preparation method, preferably, in step (<NUM>), the sintering may be conducted for <NUM> to <NUM> at an oxygen flow rate of <NUM>/min to <NUM>/min. In the process of sintering the precursors and the lithium source into the cathode material in the present disclosure, the sintering time and the oxygen flow rate can be controlled to make W ions in the W-doped precursor B diffuse from inside to outside of the particles, and the uniformly diffusing W can inhibit the fusion and growth of particles. Part of the W ions diffuse to the surface of the W-free precursor A during the sintering process. Due to a large radius, the W ions cannot diffuse into the interior of the W-free precursor, and thus do not show an inhibitory effect on the growth of the W-free precursor. Therefore, a uniform and stable lithium tungstate coating layer can be formed on the surface of the W-free precursor, which helps to further improve the cycling performance of the material.

For the preparation method, preferably, in step (<NUM>), the high-temperature sintering may be conducted once. The two precursors are first mixed and then subjected to one-time sintering at a specified temperature to form the cathode material with two morphologies. The same sintering conditions and atmosphere can ensure that cell parameters of the particles of the two morphologies are consistent as much as possible (the spherical secondary particles are also obtained by high-temperature sintering, and thus have a perfect crystal form), and result in low process cost and high process stability.

Generally, compared with the prior art, the present disclosure and the preferred technical solutions mainly have the following advantages:.

To describe the technical solutions in examples of the present disclosure or in the prior art more clearly, the accompanying drawings required for describing the examples or the prior art will be briefly described below. Apparently, the accompanying drawings in the following description show some examples of the present disclosure, and a person of ordinary skill in the art may still derive other drawings from these accompanying drawings without creative efforts.

In order to facilitate the understanding of the present disclosure, the present disclosure is described in detail below in conjunction with the accompanying drawings of the specification and the preferred examples, but the protection scope of the present disclosure is not limited to the following specific examples.

Unless otherwise defined, all technical terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are merely for the purpose of describing specific examples, and are not intended to limit the protection scope of the present disclosure.

Unless otherwise specified, various raw materials, reagents, instruments, equipment, and the like used in the present disclosure can be purchased from the market or can be prepared by existing methods.

A W-containing high-nickel ternary cathode material of the present disclosure was provided, with a chemical formula of Li<NUM>Ni<NUM>Co<NUM>Mn<NUM>W<NUM>Al<NUM>O<NUM>. The high-nickel ternary cathode material included both spherical secondary particles and single-crystal particles, where there was basically no W inside the single-crystal particles and the spherical secondary particles were doped with W; and the high-nickel ternary cathode material had a median diameter of <NUM> and an SSA of <NUM><NUM>/g.

A preparation method of the W-containing high-nickel ternary cathode material in this example was as follows:.

The product prepared in Example <NUM> was subjected to field emission-scanning electron microscopy (FE-SEM), and a resulting image in <FIG> showed that, in the high-nickel cathode material prepared in this example, there were both spherical secondary particles and single-crystal particles, and the spherical secondary particles had uniform sphericity and were uniformly distributed. A mass ratio of the spherical secondary particles to the single-crystal particles in the high-nickel ternary cathode material was adjusted by adjusting a ratio of the W-containing precursor B to the W-free precursor A in the raw material, and was about <NUM>:<NUM>. A powder of the cathode material had a compacted density of <NUM>/cm<NUM>, a median particle size of <NUM> (as shown in <FIG>), an SSA of <NUM><NUM>/g, and a pH of <NUM>. The spherical secondary particles had a particle size range of <NUM> to <NUM> (as shown in <FIG>), and the single-crystal particles had a particle size range of <NUM> to <NUM> (as shown in <FIG>). Through the EDS analysis shown in <FIG> in combination with the subsequent test of comparative examples, it can be seen that W was mainly distributed in the spherical secondary particles (which was not only internally doped, but also coated on the surface of the spherical secondary particles); and for the single-crystal particles, only the surface was covered with a W-containing coating layer, and there was almost no W inside, indicating that the W was only distributed on the surface. According to Gibbs free energy, lithium tungstate was easily formed, and thus a lithium tungstate layer was preferentially formed on a surface with W and Li. Al was uniformly distributed on the surface of single-crystal and spherical secondary particles, resulting in uniform doping. The Rietveld refinement was conducted on XRD data, and a resulting pattern was shown in <FIG>, with a c value of <NUM> and an a value of <NUM>. The c value and the c/a value were both significantly increased, indicating that W effectively increased the c value. On the premise of ignoring element loss during the preparation process, a Ni-Co-Mn molar ratio in the spherical secondary particles was consistent with a Ni-Co-Mn molar ratio in the single-crystal particles, and the particles of the two morphologies had the same crystal structure and lattice parameters.

The high-nickel ternary cathode material with two morphologies prepared in this example was made into a coin-type cell with a lithium sheet as a negative electrode for evaluation test:.

A W-containing high-nickel ternary cathode material of the present disclosure was provided, with a chemical formula of Li<NUM>Ni<NUM>Co<NUM>Mn<NUM>W<NUM>Zr<NUM>O<NUM>. The high-nickel ternary cathode material included both spherical secondary particles and single-crystal particles, where there was basically no W inside the single-crystal particles and the spherical secondary particles were doped with W; and the high-nickel ternary cathode material had a median diameter of <NUM> and an SSA of <NUM><NUM>/g.

The product prepared in this example was subjected to FE-SEM, and a resulting image showed that, in the high-nickel cathode material prepared in this example, there were both spherical secondary particles and single-crystal particles, and the spherical secondary particles had uniform sphericity and were uniformly distributed. A mass ratio of the spherical secondary particles to the single-crystal particles in the high-nickel ternary cathode material was adjusted by adjusting a ratio of the W-containing precursor B to the W-free precursor A in the raw material, and was about <NUM>:<NUM>. A powder of the cathode material had a compacted density of <NUM>/cm<NUM>, a median particle size of <NUM>, an SSA of <NUM><NUM>/g, and a pH of <NUM>. The spherical secondary particles had a particle size range of <NUM> to <NUM>, and the single-crystal particles had a particle size range of <NUM> to <NUM>. Through the EDS analysis in combination with the subsequent test of comparative examples, it can be seen that W was mainly distributed in the spherical secondary particles (which was not only internally doped, but also coated on the surface of the spherical secondary particles); and for the single-crystal particles, only the surface was covered with a W-containing coating layer, and there was almost no W inside, indicating that the W was only distributed on the surface. According to Gibbs free energy, lithium tungstate was easily formed, and thus a lithium tungstate layer was preferentially formed on a surface with W and Li. Zr was uniformly distributed on the surface of single-crystal and spherical secondary particles, resulting in uniform doping. The Rietveld refinement was conducted on XRD data, and a resulting pattern was shown in <FIG>, with a c value of <NUM> and an a value of <NUM>. The c value and the c/a value were both significantly increased, indicating that W effectively increased the c value. On the premise of ignoring element loss during the preparation process, a Ni-Co-Mn molar ratio in the spherical secondary particles was consistent with a Ni-Co-Mn molar ratio in the single-crystal particles, and the particles of the two morphologies had the same crystal structure and lattice parameters.

A W-containing high-nickel ternary cathode material of the present disclosure was provided, with a chemical formula of Li<NUM>Ni<NUM>Co<NUM>Mn<NUM>W<NUM>La<NUM>O<NUM>. The high-nickel ternary cathode material included both spherical secondary particles and single-crystal particles, where there was basically no W inside the single-crystal particles and the spherical secondary particles were doped with W; and the high-nickel ternary cathode material had a median diameter of <NUM> and an SSA of <NUM><NUM>/g.

According to FE-SEM, in the high-nickel ternary cathode material prepared, there were both spherical secondary particles and single-crystal particles, and the spherical secondary particles had uniform sphericity and were uniformly distributed. A mass ratio of the spherical secondary particles to the single-crystal particles in the high-nickel ternary cathode material was about <NUM>:<NUM>. A powder of the cathode material had a compacted density of <NUM>/cm<NUM>, a median particle size of <NUM>, an SSA of <NUM><NUM>/g, and a pH of <NUM>. The spherical secondary particles had a particle size range of <NUM> to <NUM>, and the single-crystal particles had a particle size range of <NUM> to <NUM>. Through the EDS analysis in combination with the subsequent test of comparative examples, it can be seen that W was mainly distributed in the spherical secondary particles (which was not only internally doped, but also coated on the surface of the spherical secondary particles); and for the single-crystal particles, only the surface was covered with a W-containing coating layer, and there was almost no W inside, indicating that the W was only distributed on the surface. According to Gibbs free energy, lithium tungstate was easily formed, and thus a lithium tungstate layer was preferentially formed on a surface with W and Li. La was uniformly distributed on the surface of single-crystal and spherical secondary particles, resulting in uniform doping. The Rietveld refinement was conducted on XRD data, and it can be known that a c value was <NUM> and an a value was <NUM>. The c value and the c/a value were both significantly increased, indicating that W effectively increased the c value. On the premise of ignoring element loss during the preparation process, a Ni-Co-Mn molar ratio in the spherical secondary particles was consistent with a Ni-Co-Mn molar ratio in the single-crystal particles, and the particles of the two morphologies had the same crystal structure and lattice parameters.

The high-nickel ternary cathode material with two morphologies was made into a coin-type cell with a lithium sheet as a negative electrode for evaluation test:.

A W-containing high-nickel ternary cathode material of the present disclosure was provided, with a chemical formula of Li<NUM>Ni<NUM>Co<NUM>Mn<NUM>W<NUM>Ti<NUM>O<NUM>. The high-nickel ternary cathode material included both spherical secondary particles and single-crystal particles, where there was basically no W inside the single-crystal particles and the spherical secondary particles were doped with W; and the high-nickel ternary cathode material had a median diameter of <NUM> and an SSA of <NUM><NUM>/g.

According to FE-SEM, in the high-nickel ternary cathode material prepared, there were both spherical secondary particles and single-crystal particles, and the spherical secondary particles had uniform sphericity and were uniformly distributed. A mass ratio of the spherical secondary particles to the single-crystal particles in the high-nickel ternary cathode material was about <NUM>:<NUM>. A powder of the cathode material had a compacted density of <NUM>/cm<NUM>, a median particle size of <NUM>, an SSA of <NUM><NUM>/g, and a pH of <NUM>. The spherical secondary particles had a particle size range of <NUM> to <NUM>, and the single-crystal particles had a particle size range of <NUM> to <NUM>. Through the EDS analysis in combination with the subsequent test of comparative examples, it can be seen that W was mainly distributed in the spherical secondary particles (which was not only internally doped, but also coated on the surface of the spherical secondary particles); and for the single-crystal particles, only the surface was covered with a W-containing coating layer, and there was almost no W inside, indicating that the W was only distributed on the surface. According to Gibbs free energy, lithium tungstate was easily formed, and thus a lithium tungstate layer was preferentially formed on a surface with W and Li. Ti was uniformly distributed on the surface of single-crystal and spherical secondary particles, resulting in uniform doping. The Rietveld refinement was conducted on XRD data, and it can be known that a c value was <NUM> and an a value was <NUM>. The c value and the c/a value were both increased, indicating that W effectively increased the c value. On the premise of ignoring element loss during the preparation process, a Ni-Co-Mn molar ratio in the spherical secondary particles was consistent with a Ni-Co-Mn molar ratio in the single-crystal particles, and the particles of the two morphologies had the same crystal structure and lattice parameters.

A high-nickel spherical-secondary-particle ternary cathode material was prepared using only a tungsten-doped precursor in Comparative Example <NUM>, which was formed by doping LNMCO with W and Al and had a molecular formula of Li<NUM>Ni<NUM>Co<NUM>Mn<NUM>W<NUM>Al<NUM>O<NUM>. A preparation method of the ternary cathode material included the following steps:.

The composition of Comparative Example <NUM> was basically the same as that of Example <NUM>, but only the W-doped precursor B was used for the preparation through sintering. It can be seen from FE-SEM images in <FIG> and <FIG> that the high-nickel ternary cathode material prepared in Comparative Example <NUM> only included uniform spherical secondary particles, which was different from the co-existence of single-crystal particles and spherical secondary particles in Example <NUM>. A powder of the cathode material in this comparative example had a compacted density of <NUM>/cm<NUM> (which was lower than that of Example <NUM> due to the lack of a combination of two morphologies), a median particle size of <NUM>, an SSA of <NUM><NUM>/g, and a pH of <NUM>. According to EDS analysis, W was uniformly distributed in the spherical secondary particles. The Rietveld refinement was conducted on XRD data, and it can be known that a c value was <NUM> and an a value was <NUM>. The c value and the c/a value were both increased, indicating that W effectively increased the c value.

The high-nickel ternary cathode materials obtained in Example <NUM> and Comparative Example <NUM> were subjected to pH titration, and titration curves were shown in <FIG>. It can be seen that the spherical-secondary-particle high-nickel ternary cathode material of Comparative Example <NUM> that was prepared by sintering only a W-doped precursor consumed a larger volume of hydrochloric acid than example <NUM> during the titration, indicating that a residual Li content in the material of Comparative Example <NUM> was higher than a residual Li content in the material of.

The spherical-secondary-particle high-nickel ternary cathode material was made into a coin-type cell with a lithium sheet as a negative electrode for evaluation test:.

A W-free cathode material was prepared in Comparative Example <NUM>, with a molecular formula of Li<NUM>Ni<NUM>Co<NUM>Mn<NUM>Al<NUM>O<NUM>. A preparation method of the cathode material included the following steps:.

The chemical formula of the product of Comparative Example <NUM> was the same as the chemical formula of the product of Example <NUM> except that there was no W. It can be seen from the FE-SEM image shown in <FIG> that the high-nickel ternary cathode material prepared in Comparative Example <NUM> only included uniform single-crystal particles, which was different from the co-existence of single-crystal particles and spherical secondary particles in Example <NUM>, indicating the key role of W in the formation of spherical secondary particles. A powder of the cathode material in this comparative example had a compacted density of <NUM>/cm<NUM> (pure single-crystal particles led to a high compacted density, and thus would help improve the compacted density of spherical secondary particles when used in combination with the spherical secondary particles), a median particle size of <NUM>, an SSA of <NUM><NUM>/g, and a pH of <NUM>. According to EDS analysis, Al was uniformly distributed in the single-crystal particles. Rietveld refinement was conducted on XRD data, and it can be known that a c value was <NUM> and an a value was <NUM>. The c value and the c/a value were both reduced compared with that in Example <NUM>, indicating that the c value could not be effectively increased without W.

The single-crystal-particle high-nickel ternary cathode material was made into a coin-type cell with a lithium sheet as a negative electrode for evaluation test:.

A high-nickel ternary cathode material was prepared in Comparative Example <NUM>, which was formed by doping LNMCO with Mo and Al and had a molecular formula approximately of Li<NUM>Ni<NUM>Co<NUM>Mn<NUM>Mo<NUM>Al<NUM>O<NUM>. A preparation method of the ternary cathode material included the following steps:.

In Comparative Example <NUM>, Mo of the same subgroup and a similar ionic radius was used to replace W in Example <NUM>. It can be seen from the FE-SEM image shown in <FIG> that the high-nickel ternary cathode material prepared in Comparative Example <NUM> only included uniform single-crystal particles, which was different from the co-existence of single-crystal particles and spherical secondary particles in Example <NUM>. It can be seen that W played a key role in the formation of spherical secondary particles, and another element could not lead to the formation of the cathode material with the two morphologies. A powder of the cathode material in this comparative example had a compacted density of <NUM>/cm<NUM>, a median particle size of <NUM>, an SSA of <NUM><NUM>/g, and a pH of <NUM>. According to EDS analysis, Al was uniformly distributed in the single-crystal particles. Rietveld refinement was conducted on XRD data, and it can be known that a c value was <NUM> and an a value was <NUM>. The c value and the c/a value were both reduced compared with that in Example <NUM>, indicating that the c value could not be effectively increased without W. It showed that, after the W in the precursor B was replaced, the cathode material with the two morphologies could not be formed, but a pure single-crystal morphology was formed.

A high-nickel ternary cathode material was prepared in this comparative example, which was formed by doping LNMCO with W and Al and had a molecular formula approximately of Li<NUM>Ni<NUM>Co<NUM>Mn<NUM>W<NUM>Al<NUM>O<NUM>. A preparation method of the ternary cathode material included the following steps:.

An area was selected from the surface of the single-crystal particles in the mixed material of this comparative example to conduct EDS spectrum mapping, and as shown in <FIG>, no W was found on the single-crystal particles. An area was selected from the surface of the single-crystal particles in Example <NUM> to conduct EDS spectrum mapping, and as shown in <FIG>, there was a peak of W, indicating that, due to the blending and sintering in the precursor stage, W diffused from the interior of the spherical secondary particles and formed a uniform tungsten-containing coating layer on the single-crystal particles. The tungsten-containing coating layer facilitated the improvement of the cycling performance of the material, which could be proved from the following electrochemical performance analysis.

Claim 1:
A W-containing high-nickel ternary cathode material, with a chemical formula of LiaNixCoyMn<NUM>-x-yWbMcO<NUM>, wherein the high-nickel ternary cathode material comprises both spherical secondary particles and single-crystal particles; there is basically no W inside the single-crystal particles; the spherical secondary particles are doped with W; and in the molecular formula of LiaNixCoyMn<NUM>-x-yWbMcO<NUM>, <NUM> ≤ a ≤ <NUM>, <NUM> < x < <NUM>, <NUM> < y < <NUM>, and <NUM> < b+c < <NUM>, and the M is one or more from the group consisting of Zr, Mg, Ti, Al, Si, La, Ba, Sr, Nb, Cr, Mo, Ca, Y, In, Sn, and F; and the high-nickel ternary cathode material has a specific surface area of <NUM> ± <NUM><NUM>/g.