Lithium-ion battery positive electrode material, and preparation method therefor and use thereof

Abstract

A lithium-ion battery positive electrode material, and a preparation method therefor and a use thereof, relating to the technical field of new energy. The lithium-ion battery positive electrode material comprises a lithium layered metal oxide, a perovskite layer and a fast ionic conductor layer from the center to the surface, and the chemical formula of the perovskite layer comprises M'(Nix'Coy'Mnz')O3. The designed structure can effectively improve the ionic conductivity and the electronic conductivity of the lithium-ion battery positive electrode material, further reduces the impedance of the lithium-ion battery positive electrode material, provides a wrapping protection effect, and improves the overall cycle performance and rate capability of the lithium-ion battery positive electrode material. Also provided are a preparation method for the lithium-ion battery positive electrode material and a use of the lithium-ion battery positive electrode material.

Description

A lithium-ion battery positive electrode material and its preparation method and application Technical Field

[0001] The present application relates to the field of new energy technology, and in particular to a lithium-ion battery positive electrode material and a preparation method and application thereof. Background Art

[0002] With the rapid development of new energy vehicles, the demand for high-energy-density lithium-ion batteries is increasing. Cathode materials are a key factor in determining the energy density of lithium-ion batteries. Currently, the main commercially used cathode materials for lithium-ion batteries include lithium cobalt oxide, lithium iron phosphate, and ternary materials. Among them, lithium cobalt oxide is relatively expensive; lithium iron phosphate has a relatively low gram-to-gram capacity. Ternary materials, namely lithium nickel cobalt manganese (NCM) cathode materials, are widely used in power lithium batteries due to their controllable cost, high energy density, good cycle performance, and long cycle life.

[0003] To further improve the energy density of ternary materials, it is necessary to increase the nickel content, which may lead to an increase in the amount of lithium / nickel mixed discharge, thereby reducing the electrochemical performance of the ternary materials. To further improve the rate performance of ternary materials, it is necessary to increase the specific surface area of ​​ternary materials, but this will reduce the cycling performance of the materials.

[0004] In summary, it is difficult for the ternary positive electrode materials in traditional technologies to simultaneously take into account energy density, rate performance and cycle performance. Summary of the Invention

[0005] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a lithium-ion battery positive electrode material that effectively improves the ionic and electronic conductivity of the lithium-ion battery positive electrode material, thereby reducing its impedance, providing a protective wrapping effect, and overall improving the cycling performance and rate performance of the resulting lithium-ion battery positive electrode material.

[0006] The present application also provides a method for preparing the above-mentioned lithium-ion battery positive electrode material.

[0007] The present application also provides a lithium ion secondary battery comprising the above lithium ion battery positive electrode material.

[0008] According to the embodiment of the first aspect of the present application, a lithium ion battery positive electrode material is provided, wherein the chemical formula of the lithium ion battery positive electrode material is Li a Ni x Co y Mn z M w O 2±b, wherein 1.03≤a≤1.3, 0.3≤x≤1, preferably 0.3≤x≤0.8, 0≤y≤0.4, 0≤z≤0.4, 0≤w≤0.1, x+y+z+w=1, 0≤b≤0.1; M is selected from at least one of La, Al, Ca, Ti, Zr, W, Sr, B, Nb and Ba, preferably selected from at least one of La, Al, Ti, Zr, W, Sr, B, Nb.

[0009] From the center to the surface of the lithium-ion battery positive electrode material, it includes a lithium layered metal oxide, a perovskite layer and a fast ion conductor layer; the chemical formula of the perovskite layer includes M'(Ni x’ Co y’ Mn z’ )O3, preferably, the perovskite layer comprises a perovskite material, the chemical formula of which includes M'(Ni x’ Co y’ Mn z’ )O3, wherein 0.3≤x'≤1, 0≤y'≤0.4, 0≤z'≤0.4, x'+y'+z'=1, and M' is selected from at least one of La, Sr, Ca, and Ti.

[0010] According to some embodiments of the present application, the chemical formula of the perovskite layer is M'(Ni x’ Co y’ Mn z’ )O3 and the chemical formula of the lithium ion battery positive electrode material Li a Ni x Co y Mn z M w O 2±b In the above, M and M', x and x', y and y', or z and z' may be the same or different.

[0011] According to the embodiment of the first aspect of the present application, a lithium ion battery positive electrode material is further provided, wherein:

[0012] The lithium-ion battery positive electrode material has a double-layer core-shell structure, which includes a lithium layered metal oxide (core), a perovskite layer and a fast ion conductor layer from the center to the surface of the lithium-ion battery positive electrode material;

[0013] The chemical formula of the lithium layered metal oxide is Li a Ni x Co y Mn z M w O 2±b, wherein, 1.03≤a≤1.3, 0.3≤x≤1, preferably 0.3≤x≤0.8, 0≤y≤0.4, 0≤z≤0.4, 0≤w≤0.1, preferably 0.02≤w≤0.06, x+y+z+w=1, 0≤b≤0.1; M is selected from at least one of Zr, W, Ti, Al, B, Nb, Ba, and Ca, preferably at least one of Zr, W, Ti, Al, B, and Nb;

[0014] The perovskite layer includes a perovskite material, the chemical formula of which is M'(Ni x’ Co y’ Mn z’ )O3, wherein 0.3≤x'≤1, preferably 0.3≤x'≤0.8, 0≤y'≤0.4, 0≤z'≤0.4, x'+y'+z'=1, and M' is selected from at least one of La, Sr, Ca, and Ti, preferably selected from at least one of La and Sr.

[0015] According to the embodiment of the first aspect of the present application, a lithium ion battery positive electrode material is further provided, wherein:

[0016] The fast ion conductor layer comprises a LiMO type fast ion conductor material, and the M is selected from at least one of Zr, W, Ti, Al, B, Nb, Ba, and Ca, preferably selected from at least one of Zr, W, Ti, Al, B, and Nb.

[0017] The lithium-ion battery positive electrode material according to the embodiment of the present application has at least the following beneficial effects:

[0018] In the lithium-ion battery positive electrode material provided by the present application, the perovskite layer comprises an ABO3 type perovskite material, which is not limited to comprising only an ABO3 type perovskite material, but may also comprise a lithium layered metal oxide. M', Ni, Co, and Mn in the ABO3 type perovskite material can all be partially replaced by other metal ions with similar radii, while keeping its crystal structure basically unchanged. The ABO3 type perovskite material has no strict restrictions on the valence of the metal elements therein, and includes divalent, trivalent, tetravalent, and so on. The perovskite material is a semiconductor material with high electronic conductivity, which can effectively improve the electrical conductivity of the lithium-ion battery positive electrode material and reduce impedance; that is, the perovskite layer can significantly improve the electronic conductivity, and the fast ion conductor layer can significantly improve the ionic conductivity. Through the combined effect of the two, the impedance performance of the obtained lithium-ion battery positive electrode material can be significantly reduced.

[0019] In the lithium-ion battery positive electrode material provided in the present application, a perovskite layer and a fast ion conductor layer are provided on the surface of the lithium layered metal oxide (core), which is equivalent to a double-layer core-shell structure. This can protect the positive electrode material from being easily corroded by the electrolyte to a certain extent, thereby improving its stability in terms of circulation and other aspects.

[0020] According to the above chemical formula, the lithium-ion battery positive electrode material provided in this application is obtained by adjusting the NCM ternary positive electrode material as the matrix, and has the advantages of low cost and high energy density of the NCM ternary positive electrode material.

[0021] According to some embodiments of the present application, the lithium-ion battery positive electrode material has a pore structure; preferably, at least part of the pore structure is a through-hole.

[0022] The presence of the pore structure gives the lithium-ion battery positive electrode material a loose structure; the through-holes can directly reach the interior of the lithium-ion battery positive electrode material particles; this structural design can improve the wettability of the electrolyte to the lithium-ion battery positive electrode material, thereby improving the rate performance of the obtained lithium-ion battery positive electrode material.

[0023] According to some embodiments of the present application, the lithium-ion battery positive electrode material has an oil absorption of 20 to 60 ml / 100 g. Within this oil absorption range, the lithium-ion battery positive electrode material has moderate porosity, a suitable contact area with the electrolyte, is easily wetted, and has high rate performance. Furthermore, side reactions caused by contact with the electrolyte are also within a controllable range, and cycling stability and other aspects are not compromised.

[0024] According to some embodiments of the present application, the oil absorption of the lithium-ion battery positive electrode material is 20-60 ml / 100 g, preferably 40-55 ml / 100 g, for example, about 45 ml / 100 g, 50 ml / 100 g, 52 ml / 100 g, or 53 ml / 100 g.

[0025] According to some embodiments of the present application, the lithium occupancy rate of the lithium-ion battery positive electrode material is ≥95%. The lithium occupancy rate reflects, to a certain extent, the degree of lithium / nickel intermixing, further reflects the microscopic order in the lithium-ion battery positive electrode material, and ultimately affects the impedance of the resulting lithium-ion battery positive electrode material. Specifically, when the lithium occupancy rate is within the above range, the impedance of the lithium-ion battery positive electrode material is low, especially low-temperature impedance.

[0026] According to some embodiments of the present application, the lithium occupancy rate of the lithium-ion battery positive electrode material is ≥ 97%. For example, it can be approximately 98%, 98.1%, 98.2%, or 98.5%. The lithium occupancy rate of the lithium-ion battery positive electrode material is, for example, 95%-99%, preferably 97%-98.5%.

[0027] According to some embodiments of the present application, the Span value of the lithium-ion battery positive electrode material is between 0.4 and 1.4; and Span = (D 90 -D 10 ) / D50 A lower Span value indicates a higher uniformity in the particle size of the lithium-ion battery positive electrode material and a greater difficulty in preparation. A higher Span value indicates a more dispersed particle size of the lithium-ion battery positive electrode material and a higher viscosity of the slurry during the subsequent homogenization process. Span values ​​within the above range do not significantly increase the difficulty of the preparation method, thereby enhancing the industrial applicability of the lithium-ion battery positive electrode material.

[0028] According to some embodiments of the present application, the D50 of the lithium-ion battery positive electrode material is 2.5 μm to 15 μm, preferably 2.5 μm to 11 μm, more preferably 3.0 μm to 6.0 μm, for example, specifically 3.0 μm to 5.0 μm, and more specifically about 3.8 μm.

[0029] According to some embodiments of the present application, the crystallite size of the lithium ion battery positive electrode material is to If the crystallite size is too small, it means that the crystal structure has not yet fully grown, the crystallinity is poor, and the crystals contain many defects, which will affect the initial performance of the material. If the crystallite size is too large, the crystals are prone to deformation, resulting in poor structural stability. When the crystallite size is within the above range, the resulting lithium-ion battery positive electrode material has a complete structure and high stability.

[0030] According to some embodiments of the present application, the impedance value of the lithium-ion battery positive electrode material at -30°C is ≤330Ω. For example, it can be approximately 250Ω, 280Ω, 300Ω, 310Ω, or 320Ω.

[0031] According to some embodiments of the present application, Li a Ni x Co y Mn z M w O 2±b Among them, 1.03≤a≤1.3, preferably 1.08≤a≤1.25. Specifically, for example, 1.1≤a≤1.2. More specifically, about 1.15.

[0032] According to some embodiments of the present application, Li a Ni x Co y Mn z M w O 2±b , 0.3≤x≤1, preferably 0.3≤x≤0.92, more preferably 0.3≤x≤0.8, and even more preferably 0.5≤x≤0.7. For example, x can be 0.3, 0.33, 0.4, 0.5, 0.6, 0.7, or 0.8.

[0033] According to some embodiments of the present application, Li a Ni x Co y Mn z M w O 2±b In the embodiment, 0≤y≤0.4, preferably 0≤y≤0.3, specifically 0.1≤y≤0.2, more specifically 0.15≤y≤0.2, and even more specifically, y is about 0.18 or 0.19.

[0034] According to some embodiments of the present application, Li a Ni x Co y Mn z M w O 2±b , 0≤z≤0.4, preferably 0≤z≤0.3. Specifically, for example, 0.2≤z≤0.3, more specifically 0.25≤z≤0.3. More specifically, z is about 0.27, 0.28, or 0.29.

[0035] According to some embodiments of the present application, Li a Ni x Co y Mn z M w O 2±b 0≤w≤0.1, preferably 0.01≤w≤0.08, more preferably 0.02≤w≤0.06. More specifically, w is about 0.01, 0.015, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, or 0.08.

[0036] According to some embodiments of the present application, Li a Ni x Co y Mn z M w O 2±b 0≤b≤0.11, preferably 0≤b≤0.1, more preferably 0.01≤b≤0.105, further preferably 0.085≤b≤0.105.

[0037] According to some embodiments of the present application, Li a Ni x Co y Mn z M w O 2±b Here, M includes a combination of Zr+W+Ti, a combination of Zr+Al+W, and a combination of Nb+B.

[0038] According to some embodiments of the present application, the lithium layered metal oxide includes a ternary cathode material or a doped ternary cathode material.

[0039] According to an embodiment of the second aspect of the present application, a method for preparing the positive electrode material of a lithium ion battery is provided, the preparation method comprising the following steps:

[0040] S1. Using co-precipitation method, Ni x Co y Mn z M'-doped Ni is deposited on the (OH)2 surface x Co y Mn z (OH)2, to obtain the precursor;

[0041] S2 in an oxygen atmosphere, pre-calcining the precursor, the pre-calcining temperature is 300 ℃ ~ 700 ℃, to obtain a pre-calcined product;

[0042] S3. The calcined product obtained in step S2, a lithium source and a doping source containing M are mixed, and the resulting mixture is calcined in an oxygen atmosphere and cooled to obtain a lithium-ion battery cathode material;

[0043] The calcination temperature is 700° C. to 1000° C.; the cooling process goes through a cooling platform, and the temperature of the cooling platform is 300° C. to 600° C.

[0044] The mechanism of the preparation method is as follows:

[0045] Step S1 is the precursor synthesis step, including the nucleation and core growth stage, and the shell growth stage. The co-precipitation method is used to add the doping element M' used to make perovskite at the end of the shell growth stage. x Co y Mn z M'-doped Ni is deposited on the surface of (OH)2 x Co y Mn z (OH)2, to obtain the precursor;

[0046] In step S2, the Ni surface doped with M' x Co y Mn z (OH)2, after pre-burning in step S2, M' and the nearby Ni x Co y Mn z (OH)2 reacts to form M'(Ni x’ Co y’ Mn z’)O3 perovskite layer; the perovskite layer structure is stable and will not decompose at the calcination temperature of step S3; and the metal element valence state is high, the calcination of step S3 is preferably carried out in an oxygen environment, so in step S3, M'(Ni x’ Co y’ Mn z’ )O3 will remain intact and will not react with the lithium source.

[0047] In step S2, the precursor is pre-fired in an oxygen atmosphere at a temperature of 300° C. to 700° C. to make the transition metal hydroxide precursor Ni x Co y Mn z (OH)2 generates the corresponding transition metal oxide.

[0048] Regarding the pre-firing temperature in step S2, if the pre-firing temperature is too low, Ni doping with M' cannot be promoted. x Co y Mn z (OH)2 generates the corresponding perovskite. If the pre-calcination temperature is too high, it will cause excessive oxidation reaction of the precursor. The pre-calcined product obtained within the above pre-calcination temperature range has a complete crystal structure and excellent electrochemical performance.

[0049] In step S3, the pre-calcined product obtained in step S2, the lithium source and the M-containing doping source are mixed, calcined in an oxygen atmosphere, and cooled to obtain a lithium-ion battery positive electrode material; the calcination temperature is 700°C to 1000°C; the cooling process experiences a cooling platform, and the temperature of the cooling platform is 300°C to 600°C.

[0050] Most of the lithium source reacts with the transition metal oxide to generate the lithium layered metal oxide; at the same time, most of the M element mixed in step S3 will pass through the perovskite layer and enter the lithium layered metal oxide lattice, existing as a dopant. The remaining lithium source reacts with the remaining doping source containing M to generate a LiMO type fast ion conductor layer containing a LiMO type fast ion conductor material. For example, when the M element mixed in step S3 includes aluminum, the fast ion conductor includes LiAlO2. For example, when M includes tungsten, the fast ion conductor may include Li2WO4 or Li4WO5. For example, when M includes multiple elements, it is a composite of lithium oxides of multiple elements.

[0051] In step S3, if the calcination temperature is too low, the reaction is incomplete, resulting in a high level of residual free lithium on the surface, which affects the processing and electrical properties of the resulting lithium-ion battery cathode material. If the calcination temperature is too high, the degree of crystallization is too high, the grain diameter is too large, which is not conducive to the insertion and deinsertion of lithium ions and affects the material impedance. Within the above calcination temperature range, a lithium-ion battery cathode material with excellent processing and electrochemical properties can be obtained.

[0052] Because some of the fast ion conductor material generated in step S3 decomposes at high temperatures, a cooling platform is added after high-temperature calcination, allowing the decomposed fast ion conductor material to be regenerated at the low-temperature cooling platform stage. Simultaneously, some of the doping element M from the high-temperature calcination stage dopes the lithium-ion battery positive electrode material. This single calcination achieves both elemental doping and fast ion conductor coating. Compared to conventional calcination methods that directly cool to room temperature after holding at a high temperature, the production process provided by this application is simpler and easier to operate, and can adjust the microstructure of the resulting lithium-ion battery positive electrode material.

[0053] In step S3, if the temperature of the cooling platform is too high, the regeneration of the fast ion conductor cannot be promoted, and if the temperature is too low, the cooling platform does not function. Within the temperature range of the cooling platform, a good coating can be formed and the low-temperature impedance of the obtained lithium-ion battery positive electrode material can be significantly reduced.

[0054] According to some embodiments of the present application, the method for preparing the positive electrode material for a lithium-ion battery is the method for preparing the positive electrode material for a lithium-ion battery comprising the above-mentioned lithium layered metal oxide, a perovskite layer and a fast ion conductor layer.

[0055] The preparation method according to the embodiment of the present application has at least the following beneficial effects:

[0056] In the preparation method provided in the present application, the elemental composition of each stage in the precursor synthesis step is precisely controlled. At the same time, the pre-firing, calcination and cooling platforms are carefully set, and specific temperature parameters are determined. In addition, the layered structure and coating structure of the material are precisely controlled. In combination with the lithium / metal ratio in the chemical formula of the lithium-ion battery positive electrode material, the amount of lithium source added in step S3 is regulated to ensure the completion of the lithiation reaction, increase the lithium occupancy rate in the obtained lithium-ion battery positive electrode material, and ensure the formation of the perovskite layer and the surface fast ion conductor layer. Ultimately, the low-temperature impedance of the obtained lithium-ion battery positive electrode material is significantly reduced, and the cycle performance such as capacity retention rate is improved, thereby achieving unexpected technical effects.

[0057] According to some embodiments of the present application, in step S1, when the Ni x Co y Mn zWhen the particle size of (OH)2 is 90% to 99% of the precursor particle size, the M'-doped Ni x Co y Mn z During the continuous production process, the particle size of the semi-finished product is constantly changing. Therefore, it is possible to start doping the M element within the expected particle size range of 90% to 99%, without significantly affecting the performance of the resulting lithium-ion battery positive electrode material.

[0058] According to some embodiments of the present application, the precursor synthesis step S1 specifically includes the following sub-steps:

[0059] S1a. The metal salt solution and the alkaline solution are flowed into the bottom liquid to react for nucleation and core growth;

[0060] S1b the metal salt solution, alkaline solution and ammonia solution and flow to the mixture obtained in step S1a, continue the reaction, shell growth;

[0061] In the late stage of the shell growth stage, when the particle size of the precursor particles is 90% to 99%, a metal salt solution containing the element M' (M' soluble salt solution) is added to dope the surface of the precursor particles with the element M';

[0062] S1c. The mixture obtained in step S1b is subjected to solid-liquid separation, aging, washing and drying to obtain a precursor.

[0063] According to some embodiments of the present application, in step S1a, the base liquid is a dilute alkaline solution, and the pH of the base liquid is 11-14; for example, it can be specifically about 12.

[0064] According to some embodiments of the present application, in step S1a, the metal salt solution includes nickel salt, cobalt salt and manganese salt. The ratio of the nickel salt, manganese salt and cobalt salt is as follows: a Ni x Co y Mn z M w O 2±b The range of the subscript parameters in is determined.

[0065] According to some embodiments of the present application, in step S1a, the total concentration of the metal salt solution is 1.5 mol / L to 2.5 mol / L. For example, it can be about 2 mol / L. Unless otherwise specified, the concentration of the metal salt solution refers to the concentration of the transition metal ion.

[0066] According to some embodiments of the present application, in step S1a, the concentration of the alkaline solution is 2 mol / L to 12 mol / L, preferably 3 mol / L to 6 mol / L, for example, about 4 mol / L or 5 mol / L.

[0067] According to some embodiments of the present application, in step S1a, the solute of the alkaline solution includes at least one of sodium hydroxide, potassium hydroxide, and lithium hydroxide, for example, sodium hydroxide.

[0068] According to some embodiments of the present application, in step S1b, the concentration of the ammonia water is 3 mol / L to 20 mol / L, preferably 4 mol / L to 10 mol / L, more preferably 4 mol / L to 6 mol / L, for example, about 5 mol / L or 6 mol / L.

[0069] According to some embodiments of the present application, during the continued reaction in step S1b, the ammonium concentration in the system is 5 g / L to 20 g / L, preferably 10 g / L to 18 g / L, for example, about 10 g / L, 15 g / L, or 18 g / L.

[0070] According to some embodiments of the present application, in step S1a, the particle size grown during the nucleation and core growth phase is 0.5 μm to 8.0 μm, preferably 0.5 μm to 3.0 μm. For example, it can be 0.8 μm to 1.2 μm. More specifically, it can be about 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, or 1.2 μm.

[0071] According to some embodiments of the present application, in step S1a and step S1b, the pH of the reaction and the continued reaction are independently selected from 9.5 to 13; for example, specifically, it can be about 9.5, 10, 10.5, 11, 11.5, 12, 12.5, or 13.

[0072] According to some embodiments of the present application, in step S1a and step S1b, the reaction temperature and the continued reaction temperature are independently selected from 30°C to 60°C, for example, about 45°C.

[0073] According to some embodiments of the present application, in step S1a and step S1b, the stirring speeds of the reaction and the continued reaction are independently selected from 300 rpm to 1000 rpm, for example, specifically about 600 rpm.

[0074] According to some embodiments of the present application, in step S1a and step S1b, the reaction and the continued reaction are carried out in a protective atmosphere. The protective atmosphere includes at least one of nitrogen and argon. For example, it can be nitrogen.

[0075] According to some embodiments of the present application, in step S1, the Ni doped with M' x Co y Mn z The deposition of (OH)2 includes:

[0076] The metal salt solution, the M' soluble salt solution, the alkaline solution and the ammonia solution are simultaneously added to the aqueous dispersion containing the precursor core, wherein the parameter control is the same as that of step S1b.

[0077] According to some embodiments of the present application, the metal salt solution and the M'-soluble salt solution are mixed to obtain a mixed metal salt solution.

[0078] According to some embodiments of the present application, the M' soluble salt includes at least one of a sulfate, a nitrate, and an acetate of M'.

[0079] According to some embodiments of the present application, in step S1, the particle size of the precursor is 2.5μm to 15μm, preferably 2.5μm to 11μm, and more preferably 3.0μm to 6.0μm. For example, it can be about 3.0μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, 4.0μm, 4.1μm, 4.2μm, 4.3μm, 4.4μm, 4.5μm, 5.0μm or 6.0μm.

[0080] According to some embodiments of the present application, in step S2, the pre-calcination temperature is 300°C to 700°C, preferably 350°C to 650°C, for example, 400°C to 600°C, and more specifically, about 500°C.

[0081] According to some embodiments of the present application, in step S2, the pre-burning time is 2 hours to 8 hours, for example, 3 hours to 7 hours, and more specifically, about 5 hours.

[0082] According to some embodiments of the present application, the molar ratio of M' in step S1 to M in step S3 is 1:0.5-10, preferably 1:1-5.

[0083] According to some embodiments of the present application, the molar percentage of the doping element M' added in step S1 to the elements (Ni+Co+Mn+M') in the precursor is 0.01mol% to 3.0mol%, preferably 0.01mol% to 2.0mol%, more preferably 0.05mol% to 1.5mol%, and further preferably 0.5mol% to 1.5mol%. For example, it can be 0.1mol%, 0.3mol%, 0.5mol%, 0.6mol%, 0.7mol%, 0.8mol%, 0.9mol%, 1.0mol%, 1.1mol%, 1.2mol%, 1.3mol%, 1.4mol%, 1.5mol%, 1.6mol%, 1.8mol%, or 2.0mol%.

[0084] In fact, in step S1 and step S3, the molar percentage of M' / M refers to the molar ratio of M' / M relative to the obtained lithium-ion battery positive electrode material Ni+Co+Mn+M' / M. However, since the difference in the total amount of metal elements (excluding Li) between the precursor and the positive electrode material (as the denominator) is very small and can be basically ignored, they can be regarded as the same. For the convenience of calculation, the total amount of metal elements in the precursor can also be used as the denominator for calculation in step S1.

[0085] According to some embodiments of the present application, the molar amount of the doping element M added in step S3 is 0.1% to 10% of the total molar amount of the elements (Ni+Co+Mn+M') in the calcined product, preferably 0.1% to 8%, more preferably 1% to 8%, and even more preferably 2% to 6%. For example, the molar amount can be 0.1%, 0.2%, 0.5%, 0.8%, 1.0%, 1.5%, 1.8%, 2.0%, 2.1%, 2.5%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, or 8.0%.

[0086] M' in step S1 and M in step S3 may be the same or different, and are independently selected from at least one of Zr, W, Ti, Al, B, Nb, Ba and Ca.

[0087] According to some embodiments of the present application, M' in step S1 is selected from at least one of La, Sr, Ca, and Ti, and preferably selected from at least one of La and Sr.

[0088] According to some embodiments of the present application, M in step S3 is selected from at least one of Zr, W, Ti, Al, B, Nb, Ba, and Ca, and is preferably selected from at least one of Zr, W, Ti, Al, B, and Nb. For example, it can be a mixture of Zr and W, a mixture of W and Ti, a mixture of Zr and B, a mixture of Al and B, a mixture of Nb and B, a mixture of Zr and Ti, a mixture of Zr, W and Nb, a mixture of Zr, Al and W, or a mixture of Zr, W and Ti. For example, when a mixture of multiple elements is used, there is no special requirement for the mixing ratio as long as the total amount is met, and for example, it can be equal proportions or unequal proportions.

[0089] According to some embodiments of the present application, in step S3, the doping source containing M includes an oxide of M. For example, when M includes Zr, W, and Ti, the doping source containing M includes ZrO2, WO3, and TiO2.

[0090] According to some embodiments of the present application, in step S3, the amount of lithium source added is Li a Ni x Co y Mn z M w O 2±b For example, the metal (Ni+Co+Mn) / lithium ratio is 1:1.03-1.3, preferably 1:1.08-1.25, and more preferably about 1:1.15. The lithium source includes at least one of lithium hydroxide and lithium carbonate.

[0091] According to some embodiments of the present application, in step S3, the calcination atmosphere is dry air or dry oxygen.

[0092] According to some embodiments of the present application, in step S3, the calcination temperature is 700°C to 1000°C, preferably 800°C to 900°C, for example, specifically about 840°C or about 850°C. There is no particular limitation as long as excellent lithiation reaction effect and doping effect can be achieved.

[0093] According to some embodiments of the present application, in step S3, the calcination time is 4 to 24 hours, for example, 8 to 12 hours, and more specifically, about 10 hours, and there is no particular limitation as long as excellent lithiation reaction and doping effects can be achieved.

[0094] According to some embodiments of the present application, in step S3, the temperature of the cooling platform is 300°C to 600°C, preferably 400°C to 590°C, more preferably 450°C to 580°C. For example, it can be about 450°C, 500°C, 550°C or 580°C.

[0095] According to some embodiments of the present application, in step S3, the cooling time of the cooling platform is 1 to 7 hours, for example, 4 to 6 hours, and more specifically, about 5 hours.

[0096] According to an embodiment of the third aspect of the present application, a lithium-ion secondary battery is provided, wherein raw materials for preparing the lithium-ion secondary battery include the lithium-ion battery positive electrode material.

[0097] Since the lithium-ion secondary battery adopts all the technical solutions of the lithium-ion battery positive electrode material of the above embodiment, it has at least all the beneficial effects brought by the technical solutions of the above embodiment, that is, the lithium-ion secondary battery has excellent rate performance and cycle performance.

[0098] According to some embodiments of the present application, the lithium-ion secondary battery can be used to prepare an HEV vehicle. The obtained HEV vehicle can be used in low-temperature areas.

[0099] Unless otherwise specified, the chemical formula provided in this application is a chemical formula calculated based on the feed ratio. In fact, considering factors such as lithium source burnout, the atomic ratio in the actual lithium-ion battery positive electrode material obtained may not be exactly the same as the ratio in the chemical formula, but it still falls within the scope of protection of this application.

[0100] Unless otherwise specified, the term “about” in this application means that the error is allowed to be within the range of ±2%, for example, about 100 is actually 100±2%×100.

[0101] Unless otherwise specified, “between” in this application includes the number itself, for example, “between 2 and 3” includes the endpoint values ​​2 and 3.

[0102] Other features and advantages of the present application will be set forth in the following description, and in part will be apparent from the description, or may be learned by practicing the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0103] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0104] FIG1 is a cross-sectional SEM image of the lithium-ion battery positive electrode material obtained in Example 1 of the present application.

[0105] FIG2 is an XRD pattern of the lithium-ion battery positive electrode material obtained in Example 1 of the present application. DETAILED DESCRIPTION

[0106] The following will clearly and completely describe the concept and technical effects of this application in conjunction with the embodiments to fully understand the purpose, features and effects of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments of this application, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of this application.

[0107] Throughout the description of this application, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of this application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0108] Example 1

[0109] This example prepares a lithium-ion battery positive electrode material. The specific steps are as follows:

[0110] S1. Synthesis of precursors:

[0111] S1a. Pure water is used as the bottom liquid in the reactor, and the pH of the bottom liquid in the reactor is adjusted to 12.0 with sodium hydroxide solution. Then, the metal salt solution and sodium hydroxide solution are introduced into the reactor through a metering pump for reaction. During the reaction, the reaction temperature is 45°C, the stirring speed is maintained at 600 r / min, the pH of the reactor is controlled at about 11, and nitrogen is continuously introduced into the reactor. No ammonia water is introduced during the nucleation and inner core growth stages, so that the material particle size grows to 1.0 μm.

[0112] S1b. Maintain the reaction conditions of step S1a, while maintaining the metal salt solution and sodium hydroxide solution to continue to flow in parallel, and at the same time flow into the ammonia solution, adjust the ammonium concentration of the system to 15g / L, continue the reaction, and grow the shell until the D50 particle size grows to 3.8μm, that is, in the late stage of the shell growth stage, when the D50 particle size is within the range of 90% to 99% of the expected precursor particle size of this step, the above-mentioned metal salt solution is replaced with a mixed metal salt solution of a metal salt solution and lanthanum sulfate (CAS No.: 10099-60-2), and other conditions remain unchanged, and grow Ni doped with lanthanum (La) on the surface. 0.5 Co 0.2 Mn 0.3 (OH)2, and the molar amount of the lanthanum element accounts for 0.5 mol% of the molar amount of the precursor elements (Ni+Co+Mn+M') obtained in this step.

[0113] S1c. The mixture obtained in step S1b is subjected to solid-liquid separation, aging, washing, and drying to obtain a precursor having a D50 particle size of approximately 4.0 μm.

[0114] In the metal salt solution of step S1, the molar ratio of nickel, cobalt and manganese is 5:2:3, and the total concentration of nickel, cobalt and manganese is 2 mol / L; the concentration of the sodium hydroxide solution is 4 mol / L; and the concentration of the ammonia water is 5 mol / L.

[0115] S2. The precursor synthesized in step S1 was pre-fired at 500 ° C for 5 hours and then naturally cooled in an air pre-fired atmosphere;

[0116] S3. The calcined product obtained in step S2, the oxide of the doping element M, and lithium carbonate as a lithium salt are uniformly mixed, wherein the lithium salt is added according to a lithium metal ratio (molar ratio of Li to Ni+Co+Mn) of 1.15, and the doping element M includes Zr, W, and Ti, and these three elements are mixed according to a molar ratio of 1:1:1. The total molar amount of these three elements as the doping element M accounts for 2 mol% of the total molar amount of the obtained positive electrode material elements (Ni+Co+Mn+M). The oxide of Zr is ZrO2, the oxide of W is WO3, and the oxide of Ti is TiO2; the above mixture is sintered at 840°C for 10 hours, then cooled to 450°C and sintered for 5 hours. After cooling, it is sieved to obtain a lithium-ion battery positive electrode material with a D50 particle size of 3.8μm.

[0117] The chemical formula of lithium layered metal oxide calculated according to the feed ratio is Li 1.15 (Ni 0.5 Co 0.2 Mn 0.3 ) 0.98 M 0.02 O 2.085 The molar ratio of Zr:W:Ti in M ​​is 1:1:1. The positive electrode material of lithium-ion battery has a double shell structure, the first shell contains La(Ni 0.5 Co 0.2 Mn 0.3 )O3 perovskite layer, and the second shell (outermost layer) is a fast ion conductor layer containing lithium zirconate, lithium tungstate, and lithium titanate.

[0118] Example 2

[0119] A lithium-ion battery positive electrode material was prepared based on Example 1. The specific steps differed from those in Example 1 in that:

[0120] (1) In step S1b, the molar amount of lanthanum (La) element in the molar amount of the precursor elements (Ni+Co+Mn+M') obtained in this step is adjusted from 0.5 mol% to 1.5 mol%;

[0121] (2) In step S3, the molar ratio of the doping element M is adjusted from 2 mol % to 6 mol %.

[0122] (3) In step S3, the D50 particle size of the obtained lithium-ion battery positive electrode material is 4.0 μm, and the chemical formula of the lithium layered metal oxide calculated based on the feed ratio is Li 1.15 (Ni 0.5 Co 0.2 Mn 0.3 ) 0.94 M 0.06 O 2.105 .

[0123] Example 3

[0124] A lithium-ion battery positive electrode material was prepared based on Example 1. The specific steps differed from those in Example 1 in that:

[0125] In step S2, the pre-firing temperature is 650° C. and the pre-firing time is 3 hours.

[0126] Example 4

[0127] A lithium-ion battery positive electrode material was prepared based on Example 1. The specific steps differed from those in Example 1 in that:

[0128] In step S2, the pre-firing temperature is 350° C. and the pre-firing time is 7 hours.

[0129] Example 5

[0130] A lithium-ion battery positive electrode material was prepared based on Example 1. The specific steps differed from those in Example 1 in that:

[0131] In step S3, the temperature of the cooling platform is 580°C.

[0132] Example 6

[0133] A lithium-ion battery positive electrode material was prepared based on Example 1. The specific steps differed from those in Example 1 in that:

[0134] The lanthanum sulfate added in step S1b was replaced with strontium sulfate (CAS No.: 7759-02-6), and other conditions remained unchanged. Ni doped with strontium (Sr) was grown on the surface. 0.5 Co 0.2 Mn 0.3 (OH)2, and the molar amount of the strontium element accounts for 0.5 mol% of the molar amount of the precursor elements (Ni+Co+Mn+M') obtained in this step.

[0135] Example 7

[0136] A lithium-ion battery positive electrode material was prepared based on Example 1. The specific steps differed from those in Example 1 in that:

[0137] (1) In step S1, the molar ratio of nickel, cobalt and manganese in the metal salt solution is 7:1:2.

[0138] (2) In step S3, the mixture is sintered at 800°C for 10 hours, then cooled to 450°C and sintered for 5 hours.

[0139] (3) In step S3, the D50 particle size of the obtained lithium-ion battery positive electrode material is 4.1 μm, and the chemical formula of the lithium layered metal oxide calculated based on the feed ratio is Li 1.15 (Ni 0.7 Co 0.1 Mn 0.2 ) 0.98 M 0.02 O 2.085 .

[0140] Example 8

[0141] A lithium-ion battery positive electrode material was prepared based on Example 1. The specific steps differed from those in Example 1 in that:

[0142] (1) In step S1, the molar ratio of nickel, cobalt and manganese in the metal salt solution is 1:1:1.

[0143] (2) In step S3, the mixture is sintered at 900°C for 10 hours, then cooled to 450°C and sintered for 5 hours.

[0144] (3) In step S3, the doping element M is Zr+Al+W, and these three elements are mixed in a molar ratio of 1:1:1.

[0145] (4) In step S3, the D50 particle size of the obtained lithium-ion battery positive electrode material is 3.8 μm, and the chemical formula of the lithium layered metal oxide calculated based on the feed ratio is Li 1.15 (Ni 1 / 3 Co 1 / 3 Mn 1 / 3 ) 0.98 M 0.02 O 2.085 The molar ratio of Zr:Al:W in M ​​is 1:1:1. The positive electrode material of lithium-ion battery has a double shell structure, the first shell contains La(Ni 1 / 3 Co 1 / 3 Mn 1 / 3 )O3 perovskite layer, and the second shell (outermost layer) is a fast ion conductor layer containing lithium zirconate, lithium aluminate, and lithium tungstate.

[0146] Example 9

[0147] A lithium-ion battery positive electrode material was prepared based on Example 1. The specific steps differed from those in Example 1 in that:

[0148] (1) In step S1, the molar ratio of nickel, cobalt and manganese in the metal salt solution is 8:1:1.

[0149] (2) In step S3, the mixture is sintered at 800°C for 9 hours, then cooled to 350°C and sintered for 5 hours.

[0150] In step S3 , the doping element M is Nb+B, and these two elements are mixed in a molar ratio of 1:1.

[0151] (3) In step S3, the D50 particle size of the obtained lithium-ion battery positive electrode material is 4.1 μm, and the chemical formula of the lithium layered metal oxide calculated based on the feed ratio is Li 1.15 (Ni 0.8 Co 0.1 Mn 0.1 ) 0.98 M 0.02 O 2.085 The molar ratio of Nb:B in M ​​is 1:1. The positive electrode material of lithium-ion battery has a double shell structure, the first shell contains La(Ni 0.8 Co 0.1 Mn 0.1 )O3 perovskite layer, and the second shell (outermost layer) is a fast ion conductor layer containing lithium niobate and lithium borate.

[0152] Comparative Example 1

[0153] A lithium ion battery positive electrode material was prepared based on Example 1. The specific steps were different from those in Example 1 in that: Ni x Co y Mn z The lanthanum sulfate used in the (OH)2 precursor was uniformly doped. That is, an amount of lanthanum sulfate equivalent to that in Example 1 was added to the metal salt solution in step S1, replacing the metal salt solutions in steps S1a and S1b as a new salt solution. As a result, no perovskite layer was formed in the resulting lithium-ion battery positive electrode material.

[0154] Comparative Example 2

[0155] A lithium-ion battery positive electrode material was prepared based on Example 1, which differs from Example 1 in that:

[0156] (1) does not include step S2;

[0157] (2) In step S3, the precursor obtained in S1, the oxide of M, and the lithium salt are mixed and pre-sintered at 500° C. for 5 h, followed by calcination and cooling in step S3 of Example 1.

[0158] Comparative Example 3

[0159] A lithium-ion battery positive electrode material was prepared based on Example 1, which differs from Example 1 in that:

[0160] In step S3, no cooling platform is provided, and the furnace is cooled naturally.

[0161] Comparative Example 4

[0162] A lithium-ion battery positive electrode material was prepared based on Example 1, which differs from Example 1 in that:

[0163] (1) La is not added in step S1b.

[0164] (2) The chemical formula of the lithium layered metal oxide calculated based on the feed ratio is Li 1.15 (Ni 0.5 Co 0.2 Mn 0.3 ) 0.98 M 0.02 O 2.085 The doping elements M are Zr, W, and Ti, and these three elements are mixed in a molar ratio of 1:1:1.

[0165] Comparative Example 5

[0166] A lithium-ion battery positive electrode material was prepared based on Example 1, which differs from Example 1 in that:

[0167] In step S2, the pre-firing temperature is 720°C.

[0168] Comparative Example 6

[0169] A lithium-ion battery positive electrode material was prepared based on Example 1, which differs from Example 1 in that:

[0170] (1) La is not added in step S1b.

[0171] (2) In step S3, the doping elements M are La, Zr, W and Ti, and these four elements are mixed in a molar ratio of 1.5:2:2:2; the above molar amount of M is adjusted from 2 mol% to 2.5 mol%; wherein the La oxide used is La2O3.

[0172] Test Case

[0173] This example tested the cross-sectional morphology of the lithium-ion battery cathode materials obtained in the examples. The testing method involved sectioning and performing SEM analysis. The test results showed that the cross-sectional morphology of the lithium-ion battery cathode materials obtained in the examples of this application was similar, with all possessing a through-hole structure, which helps improve the electrolyte wettability and rate performance of the lithium-ion battery cathode materials. The cross-sectional morphology of the lithium-ion battery cathode material obtained in Example 1 is shown in Figure 1.

[0174] In this example, the XRD patterns of the lithium-ion battery positive electrode materials obtained in Examples 1 to 9 and Comparative Examples 1 to 6 were tested, and the lithium ion occupancy rate and crystallite size were obtained by refinement calculation. The refinement software was Fullprof. The XRD pattern detection equipment was a Japanese Rigaku XRD tester, model Smartlab 3kw. The crystallite size was read by the function of the XRD tester, where the crystallite size is the average value of the crystallite size of the characteristic peak of 0° to 70°. The test results show that the crystallite size of the lithium-ion battery positive electrode material obtained in the embodiment is The XRD test and refinement results of Example 1 are shown in FIG2 ; the calculated values ​​and experimental values ​​in FIG2 are highly consistent.

[0175] This example also tests the oil absorption of the lithium-ion battery positive electrode materials obtained in Examples 1 to 9 and Comparative Examples 1 to 6. The specific testing equipment is a HITEC DABS oil absorption tester. Paraffin oil is dripped at a uniform rate during the stirring process of the lithium-ion battery positive electrode material, and the oil absorption is calculated based on the torque value.

[0176] This example also tests the particle size of the lithium-ion battery positive electrode materials obtained in Examples 1 to 9 and Comparative Examples 1 to 6, and calculates the Span value. The particle size test is obtained by using a Malvern laser particle size analyzer. Unless otherwise specified, the particle size in this application is the volume cumulative particle size, for example, D 50 , actually D V50 The Span value was calculated as (D90 - D10) / D50. The results showed that the Span value of the lithium-ion battery cathode material obtained in the examples ranged from 0.4 to 1.4, and furthermore, primarily ranged from 0.6 to 0.8. This indicates that the particle size uniformity of the obtained lithium-ion battery cathode material was high.

[0177] This example also tested the low-temperature impedance and electrochemical performance of the lithium-ion battery positive electrode materials obtained in Examples 1 to 9 and Comparative Examples 1 to 6. The testing steps included:

[0178] Preparation of button cells:

[0179] Lithium-ion battery positive electrode material: Conductive agent SuperP, binder polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP) were mixed and stirred in a mass ratio of 90:5:5 to make a positive electrode slurry (solid content of about 40%). The slurry was coated on the current collector aluminum foil, dried at 105°C, and then rolled at room temperature to a surface density of 2.8g / cm 3 to 3.3g / cm 3 , then punch and cut into The positive electrode sheet is made of a disc. The button battery is assembled in the glove box. According to the "negative electrode shell-nickel foam-lithium sheet" -8 drops of electrolyte-diaphragm ( The battery was assembled in the following order: 16 μm thick)-8 drops of electrolyte-positive electrode sheet-positive electrode shell, wherein the electrolyte consisted of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) (EC:EMC:DMC volume ratio = 1:1:1), containing 1.0M LiPF6; the size of the battery shell (positive and negative shells) was 24 mm. The assembled button cell was placed in the mold groove of a hydraulic sealing machine (purchased from Shenzhen Kejing Zhida Technology Co., Ltd.), locked, and pressurized with a pressure of >450 kg / cm 2 , then unlock it and take out the sealed button battery.

[0180] Impedance (DCR) test:

[0181] At 25°C, the charge and discharge cycle characteristics of the button battery were tested using a blue electric test cabinet. The battery was charged and discharged at a charge and discharge rate of 0.1C in the voltage range of 2.8V to 4.25V. Specifically, the battery was charged to 4.25V at a constant current of 0.1C, then charged to a cutoff current of 0.02C at a voltage of 4.25V, left for 5 minutes, discharged to 2.8V at 0.1C, and left for 5 minutes. The battery was then charged to 4.25V at a constant current of 0.1C, then charged to a cutoff current of 0.02C at a voltage of 4.25V, left for 5 minutes, discharged at 0.1C for 5 hours, and then left to stand for 2 hours. The low-temperature impedance was then tested at -30°C using a blue electric test cabinet. The battery was left to stand at -30°C for 1 hour, then discharged at 2C for 10 seconds, and left to stand. The difference between the voltage before 2C discharge and the voltage at 10 seconds of discharge was divided by the discharge current to obtain the DCR value at -30°C. Generally, in ternary materials, as the proportion of manganese content decreases or the proportion of cobalt content increases, the impedance value will decrease.

[0182] Capacity retention test:

[0183] At 25°C, use a blue electric test cabinet to test the charge and discharge cycle characteristics of the button battery, setting 1C = 163mAh / g. Charge and discharge at a charge and discharge rate of 1C in the voltage range of 2.8V to 4.25V. Specifically, charge at a constant current of 1C to 4.25V, then charge at a constant voltage at 4.25V to a cutoff current of 0.02C, let it rest for 5 minutes, discharge at 1C to 2.8V, let it rest for 5 minutes, and record the charge and discharge capacity after the first cycle. Cycle in this manner, charge / discharge 50 times, and record the charge and discharge capacity after the 50th cycle.

[0184] Cycle capacity retention (%) = (50th cycle discharge capacity / 1st cycle discharge capacity) × 100%.

[0185] The results of the above tests are shown in Table 1.

[0186] Table 1 Properties of the positive electrode materials for lithium ion batteries obtained in Examples 1 to 9 and Comparative Examples 1 to 6

[0187] Based on the above results, the lithium-ion battery cathode material prepared by the preparation method provided in this application has low low-temperature impedance, high lithium occupancy rate, good oil absorption, and high capacity retention rate. It is expected that lithium secondary batteries containing this lithium-ion battery cathode material will have excellent rate performance and cycle performance in low-temperature environments, and are expected to be applied to HEV vehicles, and the resulting HEV vehicles are expected to be widely used in low-temperature areas.

[0188] In Comparative Example 1, M', which is used to form a perovskite intermediate layer, is uniformly doped into the precursor, but a perovskite layer cannot be formed. In Comparative Example 2, lithium is first added and then pre-fired. Due to the presence of lithium salt, a perovskite layer cannot be formed. In Comparative Example 3, no cooling platform is provided, and a complete fast ion conductor layer cannot be formed. In Comparative Example 4, La is not added in step S1b, and a perovskite intermediate layer cannot be formed. In Comparative Example 5, the pre-fired temperature exceeds the range required by this application, and the crystallization state of the obtained pre-fired product deteriorates. In Comparative Example 6, a single-layer coating is formed, which includes a fast ion conductor, and part of M forms a doping agent for the lithium layered metal oxide. In each of the above comparative examples, either a double-coating structure is not formed, or the crystallization performance of the obtained lithium-ion battery positive electrode material is deteriorated, which significantly reduces the occupancy rate of lithium ions and improves the impedance value under low temperature conditions.

[0189] In summary, in the lithium-ion battery positive electrode material provided by the present application, a synergistic effect occurs between the various layer structures and the various components. In the preparation method provided by the present application, a synergistic effect occurs between the step sequence and the process parameters, which together improve the comprehensive performance of the obtained lithium-ion battery positive electrode material.

[0190] The embodiments of the present application have been described in detail above with reference to the accompanying drawings. However, the present application is not limited to the above embodiments. Various modifications may be made within the scope of knowledge possessed by a person of ordinary skill in the art without departing from the protection of the present application. In addition, the embodiments of the present application and the features of the embodiments may be combined with each other unless there is a conflict.

Claims

1. A positive electrode material for a lithium ion battery, characterized in that: The chemical formula of the lithium ion battery positive electrode material is Li a Ni x Co y Mn z M w O 2±b , wherein 1.03≤a≤1.3, 0.3≤x≤1, 0≤y≤0.4, 0≤z≤0.4, 0≤w≤0.1, x+y+z+w=1, 0≤b≤0.1; M is selected from at least one of La, Al, Ca, Ti, Zr, W, Sr, B, Nb and Ba; The lithium ion battery positive electrode material has a double-layer core-shell structure, and from the center to the surface of the lithium ion battery positive electrode material, it includes a lithium layered metal oxide, a perovskite layer and a fast ion conductor layer; the perovskite layer includes a perovskite material, and its chemical formula includes M'(Ni x’ Co y’ Mn z’ )O3, wherein 0.3≤x'≤1, 0≤y'≤0.4, 0≤z'≤0.4, x'+y'+z'=1, and M' is selected from at least one of La, Sr, Ca, and Ti.

2. The lithium-ion battery positive electrode material according to claim 1, characterized in that The chemical formula of the lithium layered metal oxide is Li a Ni x Co y Mn z M w O 2±b , wherein 1.03≤a≤1.3, 0.3≤x≤1, preferably 0.3≤x≤0.8, 0≤y≤0.4, 0≤z≤0.4, 0≤w≤0.1, preferably 0.02≤w≤0.06, x+y+z+w=1, 0≤b≤0.1; M is selected from at least one of Zr, W, Ti, Al, B, Nb, Ba, and Ca, preferably selected from at least one of Zr, W, Ti, Al, B, and Nb; Preferably, 0.3≤x'≤0.8, and M' is selected from at least one of La and Sr; Preferably, the fast ion conductor layer comprises a LiMO type fast ion conductor material, wherein M is selected from at least one of Zr, W, Ti, Al, B, Nb, Ba, and Ca, and preferably selected from at least one of Zr, W, Ti, Al, B, and Nb.

3. The lithium ion battery positive electrode material according to claim 1 or 2, characterized in that: The lithium-ion battery positive electrode material has a pore structure; and at least part of the pore structure is a through hole.

4. The lithium ion battery positive electrode material according to claim 1 or 2, characterized in that: The oil absorption of the lithium ion battery positive electrode material is 20 to 60 ml / 100 g; Preferably, the lithium occupancy rate in the lithium-ion battery positive electrode material is ≥95%, preferably ≥97%; Preferably, the impedance value of the lithium-ion battery positive electrode material at -30°C is ≤330Ω.

5. A method for preparing a positive electrode material for a lithium ion battery, characterized in that: The preparation method comprises the following steps: S1. Using co-precipitation method, Ni x Co y Mn z Surface deposition of M'-doped Ni on (OH)2 x Co y Mn z (OH)2, to obtain the precursor; S2. Pre-calcining the precursor in an oxygen atmosphere at a temperature of 300°C to 700°C to obtain a pre-calcined product; S3. The calcined product obtained in step S2, the lithium source and the doping source containing M are mixed, calcined in an oxygen atmosphere, and cooled to obtain a positive electrode material for a lithium ion battery; The calcination temperature is 700°C to 1000°C; The cooling process goes through a cooling platform, and the temperature of the cooling platform is 300°C to 600°C.

6. The preparation method according to claim 5, characterized in that: In step S1, when the Ni x Co y Mn z When the particle size of (OH)2 is 90% to 99% of the particle size of the precursor, the M'-doped Ni x Co y Mn z (OH)2.

7. The preparation method according to claim 5, characterized in that: The molar percentage of the doping element M' added in step S1 to the elements (Ni+Co+Mn+M') in the precursor is 0.05 mol% to 1.5 mol%, preferably 0.5 mol% to 1.5 mol%.

8. The preparation method according to any one of claims 5 to 7, characterized in that: In step S2, the pre-burning time is 2 hours to 8 hours.

9. The preparation method according to any one of claims 5 to 7, characterized in that: In step S3, the calcination time is 4 hours to 24 hours; and / or the cooling time of the cooling platform is 1 hour to 7 hours.

10. A lithium ion secondary battery, characterized in that: The raw material for preparing the lithium-ion secondary battery includes the lithium-ion battery positive electrode material as claimed in any one of claims 1 to 4.

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