A nickel-rich layered oxide material, its preparation method and application

Abstract

The present invention belongs to the field of battery materials, and particularly relates to a nickel-rich layered oxide material, a preparation method thereof, and an application thereof. The crystal structure of the nickel-rich layered oxide material provided by the present invention is a hexagonal phase R-3m space group, and the lattice microstrain is ≤0.25%. Through the design of a high-entropy system of multivalent and various metal cations, combined with the optimization of the precursor (hydroxide precipitate) composition and the calcination formula, the present invention utilizes the retarded diffusion effect of the high-entropy components during the calcination process to regulate the internal element distribution of the material, induce the particles to grow in the low-stress direction, and reduce the microstrain intensity in the crystal structure of the bulk material. The nickel-rich layered oxide material provided by the present invention has a low microstrain, and has good structural stability and safety at high potentials.

Description

Technical Field

[0001] The present invention belongs to the field of battery materials, and particularly relates to a nickel-rich layered oxide material, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, the rapid development of new energy vehicles has put forward higher requirements for the energy density, cycle life, and power density of lithium secondary batteries, and the cathode material is a key factor for the performance breakthrough of lithium secondary batteries. The LiNiO2 material has advantages such as high specific capacity, rich resources, and low cost, but there are obvious defects such as Li + / Ni 2+ cation mixing, non-stoichiometry, and high de-lithiated state safety problems, which hinder its practical application. Researchers have partially substituted Ni by introducing metal ions such as Co, Mn, Al, Mg, Ti, etc. 3+ to form binary or ternary layered oxides, improving the structural stability and cycle performance of the materials. Among them, the ratio of Co and Mn is flexibly adjusted to balance the material components and electrochemical performance, and a nickel-rich NCM or NCA ternary cathode material with a higher energy density is constructed. However, during the cycling process of the nickel-rich ternary cathode material, the anisotropic shrinkage and expansion of primary particles generated by the H2-H3 phase transformation will exacerbate the internal stress of the material, induce the generation and expansion of microcracks inside the material, and then lead to the separation and pulverization between primary particles, accelerate the side reaction between the electrolyte and microcracks, and ultimately cause the material to fail.

[0003] High-entropy materials are a class of single-phase materials containing 5 or more elements proposed in recent years, which are mutually solid-solved in an equimolar or near-molar ratio, and exhibit unique effects in terms of thermodynamics, kinetics, microstructure, and performance, namely high-entropy effect, sluggish diffusion effect, lattice distortion effect, etc. Therefore, combining the performance advantages of high-entropy materials, optimizing the structural characteristics of cathode materials, and developing lithium battery cathode materials with good structural stability and safety at high potentials have very important significance. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a nickel-rich layered oxide material, a preparation method thereof, and an application thereof. The nickel-rich layered oxide material provided by the present invention has good structural stability and safety at high potentials.

[0005] The present invention provides a nickel-rich layered oxide material, and the crystal structure of the nickel-rich layered oxide material is a hexagonal R-3m space group, and the lattice micro-strain ≤ 0.25%.

[0006] Preferably, the chemical general formula of the nickel-rich layered oxide material is: LiNi x A a B b Cc D d O2, where Ni is in the +3 oxidation state, A is a +2-valent metal cation, B is a +3-valent metal cation, C is a +4-valent metal cation, D is a metal cation with a valence of +5 or higher, 0.8 ≤ x < 1, a > 0, b > 0, c > 0, d ≥ 0, and x + a + b + c + d = 1;

[0007] Among all the types of metal cations included in B, C, and D, at least two metal cations have a higher content at the surface of the primary particles of the nickel-rich layered oxide material than at the particle center.

[0008] Preferably, A is Mg 2+ , Ni 2+ and Sr 2+ or one or more of them; B is Al 3+ , Co 3+ , Ga 3+ , Y 3+ , La 3+ and Yb 3+ or one or more of them; C is Mn 4+ , Zr 4+ , Ti 4+ , Sn 4+ and Ce 4+ or one or more of them; D is V 5+ , Nb 5 + , Sb 5+ , Ta 5+ , Mo 6+ and W 6+ or one or more of them.

[0009] Preferably, the nickel-rich layered oxide material satisfies at least one of the following conditions:

[0010] The D 50 particle size of the nickel-rich layered oxide material is 2 - 20 μm;

[0011] The specific surface area of the nickel-rich layered oxide material is 0.2 - 2 m 2 / g;

[0012] The morphology of the nickel-rich layered oxide material is primary particles or spherical secondary particles.

[0013] The present invention provides a method for preparing a nickel-rich layered oxide material, comprising the following steps:

[0014] a) Mix solution I, solution II, sodium hydroxide, and a complexing agent, and control the amounts of the sodium hydroxide and the complexing agent so that the pH value of the mixed system is maintained at 10 - 13 for complexation and precipitation reactions to obtain a hydroxide precipitate;

[0015] In step a), the components of solution I include a nickel source compound and water; the components of solution II include a first metal source compound and water; the first metal source compound is at least one of a C source compound and a D source compound, or a mixture of at least one of a C source compound and a D source compound and at least one of an A source compound and a B source compound; the A source compound is a water-soluble metal salt corresponding to a +2 valence metal cation, the B source compound is a water-soluble metal salt corresponding to a +3 valence metal cation, the C source compound is a water-soluble metal salt corresponding to a +4 valence metal cation, and the D source compound is a water-soluble metal salt corresponding to a +5 valence or higher metal cation;

[0016] b) Mix the hydroxide precipitate, a lithium source compound, and a second metal source compound to obtain a mixed material;

[0017] In step b), the second metal source compound is one or more of an A source compound, a B source compound, a C source compound, and a D source compound;

[0018] c) Carry out stepwise calcination of the mixed material in an oxygen-containing atmosphere to obtain a nickel-rich layered oxide material; the crystal structure of the nickel-rich layered oxide material is a hexagonal R-3m space group, and the lattice microstrain ≤ 0.25%.

[0019] Preferably, in step a), the concentration of metal ions in solution I is 1 - 5 mol / L; the total concentration of metal ions in solution II is 0.5 - 5 mol / L.

[0020] Preferably, in step a), the sodium hydroxide participates in the mixing in the form of an aqueous sodium hydroxide solution, and the concentration of the aqueous sodium hydroxide solution is 0.5 - 4 mol / L; the complexing agent is one or more of ammonia water, ethylenediaminetetraacetic acid, and ethylenediamine, and the complexing agent participates in the mixing in the form of an aqueous complexing agent solution, and the concentration of the aqueous complexing agent solution is 0.5 - 10 mol / L.

[0021] Preferably, in step a), the stirring rate of the complexation and precipitation reaction is 200 - 1000 r / min; the temperature of the complexation and precipitation reaction is 30 - 70 °C; the time of the complexation and precipitation reaction is 10 - 50 h.

[0022] Preferably, in step c), the specific process of the stepwise calcination includes:

[0023] i) Heat from the ambient temperature to the first calcination temperature and perform a heat preservation calcination once.

[0024] The first calcination temperature is 300 - 600 °C; the heating rate to the first calcination temperature is 1 - 6 °C / min; the time of the one-time heat preservation calcination is 4 - 10 h.

[0025] ii) Continue to heat to the second calcination temperature and perform a secondary heat preservation calcination.

[0026] The second calcination temperature is 700 - 1000 °C; the heating rate to the second calcination temperature is 1 - 6 °C / min; the time of the secondary heat preservation calcination is 1 - 5 h.

[0027] iii) Adjust the temperature to the third calcination temperature and perform a third heat preservation calcination.

[0028] The third calcination temperature is 700 - 900 °C and ≤ the second calcination temperature; the rate of adjusting the temperature to the third calcination temperature is 0 - 10 °C / min; the time of the third heat preservation calcination is 10 - 20 h.

[0029] Preferably, during the step-by-step calcination process, oxygen is continuously introduced into the used calcination equipment to provide an oxygen-containing atmosphere required for calcination; the oxygen intake rate in step i) is 0.5 - 5 m 3 / h, the oxygen intake rate in step ii) is 0.5 - 5 m 3 / h, and the oxygen intake rate in step iii) is 0.5 - 5 m 3 / h.

[0030] The present invention provides a lithium-ion secondary battery, and the positive electrode material of the lithium-ion secondary battery includes the nickel-rich layered oxide material described in the above technical solution or the nickel-rich layered oxide material prepared by the preparation method described in the above technical solution.

[0031] The present invention provides an electrical device, and the electrical device is equipped with the lithium-ion secondary battery described in the above technical solution.

[0032] Compared with the prior art, the present invention provides a nickel-rich layered oxide material, a preparation method thereof and an application. The crystal structure of the nickel-rich layered oxide material provided by the present invention is a hexagonal R-3m space group, and the lattice microstrain ≤ 0.25%. Through the design of a high-entropy system of multivalent and various metal cations, combined with the optimization of the precursor (hydroxide precipitate) composition and the calcination formula, the present invention utilizes the retarded diffusion effect of the high-entropy components during the calcination process to regulate the internal element distribution of the material, induce the particles to grow in the low-stress direction, and reduce the microstrain intensity in the crystal structure of the bulk material. The nickel-rich layered oxide material provided by the present invention has a low microstrain and good structural stability and safety at high potentials. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0034] Figure 1 SEM image of the nickel-rich layered oxide material of Example 1 provided by the present invention;

[0035] Figure 2 Distribution diagrams of Zr and W elements at different depths on the surface of primary particles in the nickel-rich layered oxide material of Example 1 provided by the present invention;

[0036] Figure 3 XRD and LeBail structure refinement diagram of the nickel-rich layered oxide of Example 1 provided by the present invention;

[0037] Figure 4 Williamson-Hall diagram of the oxide materials prepared in Example 1 and Comparative Examples 1-3 provided by the present invention;

[0038] Figure 5 Cycling performance comparison diagram of the oxide materials prepared in Example 1 and Comparative Examples 1-3 provided by the present invention in lithium secondary battery tests. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The following clearly and completely describes the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0040] To overcome the technical defects of existing nickel-rich layered oxide cathode materials, the present invention provides a nickel-rich layered oxide material, its preparation method and application. The core technical problem to be solved is that due to the H2-H3 phase transition at high potentials, the nickel-rich layered oxide cathode material has poor structural stability and safety. The present invention designs a high-entropy system of multivalent and various metal cations, combines the optimization of precursor components and calcination methods, and utilizes the retarded diffusion effect of high-entropy components during the calcination process to regulate the internal element distribution of the material, induce the particles to grow in the low-stress direction, reduce the microscopic strain intensity in the crystal structure of the bulk material, thereby reducing the stress accumulation of the material at high potentials and improving the structural stability and safety.

[0041] It should be noted that compared with the traditional nickel-rich layered oxide materials doped with metal ions, the key difference in the technical solution of the present invention is that in traditional single-metal ion or multi-metal ion doping, the stability of the crystal structure is usually enhanced by a relatively high metal-oxygen bond energy; while in the nickel-rich layered oxide of the present invention, a nickel-rich high-entropy solid solution is formed by introducing multivalent and various metal cations, the precursor components and calcination methods are optimized, and the special effect (retarded diffusion effect) of high-entropy components during the calcination process is used to reduce the microscopic strain in the crystal structure of the material, thereby alleviating the stress accumulation at high potentials and achieving the improvement of electrochemical performance and safety.

[0042] To achieve the above object, the present invention specifically proposes the following technical solutions:

[0043] The present invention provides a nickel-rich layered oxide material, whose crystal structure is a hexagonal R-3m space group, and the lattice micro-strain ≤ 0.25%. In the present invention, the lattice micro-strain can specifically be 0.05%, 0.08%, 0.14%, 0.16%, 0.19% or 0.22%.

[0044] In the nickel-rich layered oxide material provided by the present invention, the chemical general formula of the nickel-rich layered oxide material is preferably: LiNi x A a B b C c D d O2; where Ni is +3 valence; A is a +2 valence metal cation, preferably one or more of Mg 2+ 、Ni 2+ and Sr 2+ ; B is a +3 valence metal cation, preferably one or more of Al 3+ 、Co 3+ 、Ga 3+ 、Y 3+ 、La 3+ and Yb 3+one or more of; C is a +4 valence metal cation, preferably Mn 4+ , Zr 4+ , Ti 4+ , Sn 4+ and Ce 4+ one or more of; D is a metal cation with a valence of +5 or higher, preferably V 5+ , Nb 5+ , Sb 5+ , Ta 5+ , Mo 6+ and W 6+ one or more of; 0.8 ≤ x < 1, a > 0, b > 0, c > 0, d ≥ 0, and x + a + b + c + d = 1; among all the types of metal cations contained in B, C, and D, at least two metal cations have a content at the surface of the primary particles of the nickel-rich layered oxide material greater than that at the particle center. In the present invention, the concentration gradient of two or more metal cations in the primary particles can stabilize the surface structure of the material through a synergistic effect, inhibit the loss of oxygen at high potentials, and improve the electrochemical stability of the material.

[0045] In the nickel-rich layered oxide material provided by the present invention, the at least two metal cations with a content at the surface of the primary particles greater than that at the particle center can be metal cations of the same valence state or metal cations of different valence states, and the present invention does not make a special limitation.

[0046] In the nickel-rich layered oxide material provided by the present invention, the D of the nickel-rich layered oxide material 50 particle size is preferably 2 - 20 μm, and specifically can be 2 μm, 3 μm, 3.2 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 10.2 μm, 10.5 μm, 11 μm, 12 μm, 12.5 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm or 20 μm.

[0047] In the nickel-rich layered oxide material provided by the present invention, the specific surface area of the nickel-rich layered oxide material is preferably 0.2 - 2 m 2 / g, and specifically can be 0.2 m 2 / g, 0.25 m 2 / g, 0.3 m 2 / g, 0.33 m 2 / g, 0.35 m 2 / g, 0.4 m 2 / g, 0.42 m 2 / g, 0.45 m 2 / g, 0.46 m 2 / g, 0.5 m 2 / g, 0.55 m 2 / g, 0.6 m 2 / g, 0.7 m 2 / g, 0.76 m 2 / g, 0.8 m 2 / g, 0.9 m 2 / g, 1 m 2 / g, 1.1 m 2 / g, 1.2 m 2 / g, 1.3 m 2 / g, 1.4 m 2 / g, 1.5 m 2 / g, 1.6 m 2 / g, 1.7 m 2 / g, 1.8 m 2 / g, 1.9 m 2 / g or 2 m 2 / g.

[0048] In the nickel-rich layered oxide material provided by the present invention, the morphology of the nickel-rich layered oxide material is preferably primary particles or spherical secondary particles.

[0049] In one embodiment provided by the present invention, the chemical formula of the nickel-rich layered oxide material is any one of the following chemical formulas:

[0050] LiNi 0.874 Sr 0.0045 Co 0.058 Al 0.015 Mn 0.0388 Zr 0.0078 W 0.0019 O2;

[0051] LiNi 0.814 Mg 0.003 Co 0.108 Al 0.01 Mn 0.058 Ti 0.0048 Ta 0.0022 O2;

[0052] LiNi 3+ 0.905 Ni 2+ 0.004 Co 0.059 Y 0.005 Mn 0.019 Zr 0.0058 Nb 0.0022 O2;

[0053] LiNi 0.867 Mg 0.005 Co 0.108 Al 0.01Zr 0.004 Ti 0.004 W 0.002 O₂;

[0054] LiNi 0.818 Sr 0.006 Co 0.060 Yb 0.005 Mn 0.109 Ta 0.002 O₂;

[0055] LiNi 3+ 0.9 Ni 2+ 0.004 Co 0.039 Al 0.01 Mn 0.039 Zr 0.006 W 0.002 O₂;

[0056] LiNi 0.943 Mg 0.01 Al 0.01 Mn 0.02 Zr 0.007 Ti 0.008 Sb 0.002 O₂。

[0057] The present invention also provides a method for preparing the nickel-rich layered oxide material described in the above technical solution, comprising the following steps:

[0058] a) Mix solution I, solution II, sodium hydroxide and a complexing agent, and control the amounts of the sodium hydroxide and the complexing agent so that the pH value of the mixed system is maintained at 10-13 for complexation and precipitation reactions to obtain a hydroxide precipitate;

[0059] b) Mix the hydroxide precipitate, a lithium source compound and a second metal source compound to obtain a mixture;

[0060] c) Carry out stepwise calcination of the mixture in an oxygen-containing atmosphere to obtain the nickel-rich layered oxide material.

[0061] In the preparation method provided by the present invention, in step a), the components of solution I include a nickel source compound and water; the nickel source compound is a soluble salt of nickel, preferably one or more of sulfates, chlorides and nitrates; the concentration of metal ions in solution I is preferably 1-5 mol / L, and specifically can be 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L or 5 mol / L.

[0062] In the preparation method provided by the present invention, in step a), the components of the solution II include a first metal source compound and water; the first metal source compound is at least one of a C source compound and a D source compound, or a mixture of at least one of a C source compound and a D source compound and at least one of an A source compound and a B source compound. In the present invention, the A source compound, B source compound, C source compound, and D source compound are respectively water-soluble metal salts corresponding to the divalent metal cation A, trivalent metal cation B, tetravalent metal cation C, and pentavalent or higher metal cation D introduced above. The metal element in the water-soluble metal salt is the same as the corresponding metal cation, and the valence states can be the same or different, without special limitation. In the present invention, the total concentration of metal ions in the solution II is preferably 0.5 to 5 mol / L, specifically 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, or 5 mol / L.

[0063] In the preparation method provided by the present invention, in step a), the sodium hydroxide preferably participates in the mixing in the form of an aqueous sodium hydroxide solution, and the concentration of the aqueous sodium hydroxide solution is preferably 0.5 to 4 mol / L, specifically 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, or 4 mol / L.

[0064] In the preparation method provided by the present invention, in step a), the complexing agent is preferably one or more of ammonia water, ethylenediaminetetraacetic acid, and ethylenediamine; the complexing agent preferably participates in the mixing in the form of an aqueous complexing agent solution, and the concentration of the aqueous complexing agent solution is preferably 0.5 to 10 mol / L, specifically 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, 6 mol / L, 6.5 mol / L, 7 mol / L, 7.5 mol / L, 8 mol / L, 8.5 mol / L, 9 mol / L, 9.5 mol / L, or 10 mol / L.

[0065] In the preparation method provided by the present invention, in step a), the mixing is preferably carried out in a reaction kettle with water added as the bottom liquid; the pH value of the mixing system can specifically be maintained at 10, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, 11, 11.1, 11.2, 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, 11.9, 12, 12.1, 12.2, 12.3, 12.4, 12.5, 12.7, 12.8, 12.9 or 13; the stirring rate of the complexation and precipitation reaction is preferably 200 - 1000 r / min, specifically 200 r / min, 250 r / min, 300 r / min, 350 r / min, 400 r / min, 450 r / min, 500 r / min, 550 r / min, 600 r / min, 650 r / min, 700 r / min, 750 r / min, 800 r / min, 850 r / min, 900 r / min, 950 r / min or 1000 r / min; the temperature of the complexation and precipitation reaction is preferably 30 - 70 °C, specifically 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, 55 °C, 56 °C, 60 °C, 65 °C or 70 °C; the time of the complexation and precipitation reaction is preferably 10 - 50 h, specifically 10 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 42 h, 45 h or 50 h.

[0066] In the preparation method provided by the present invention, in step a), it is preferred to wash and dry the obtained hydroxide precipitate; the drying temperature is preferably 100 - 300 °C, specifically 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, 150 °C, 160 °C, 170 °C, 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, 250 °C, 260 °C, 270 °C, 280 °C, 290 °C or 300 °C.

[0067] In the preparation method provided by the present invention, in step b), the lithium source compound is preferably one or more of LiOH, Li₂CO₃, Li₂SO₄, LiCl and LiNO₃; the second metal source compound is one or more of the A source compound, B source compound, C source compound and D source compound.

[0068] In the preparation method provided by the present invention, in step c), the oxygen-containing atmosphere includes but is not limited to air and pure oxygen, and is preferably pure oxygen.

[0069] In the preparation method provided by the present invention, in step c), the specific process of the stepwise roasting includes:

[0070] i) Heat from the ambient temperature to the first roasting temperature and perform a heat preservation roasting once.

[0071] ii) Continue to heat to the second roasting temperature and perform a heat preservation roasting twice.

[0072] iii) Adjust the temperature to the third roasting temperature and perform a heat preservation roasting three times.

[0073] In the above roasting process provided by the present invention, in step i), the first roasting temperature is preferably 300 - 600 °C, specifically it can be 300 °C, 310 °C, 320 °C, 330 °C, 340 °C, 350 °C, 360 °C, 370 °C, 380 °C, 390 °C, 400 °C, 410 °C, 420 °C, 430 °C, 440 °C, 450 °C, 460 °C, 470 °C, 480 °C, 490 °C, 500 °C, 510 °C, 520 °C, 530 °C, 540 °C, 550 °C, 560 °C, 570 °C, 580 °C, 590 °C or 600 °C; the heating rate to the first roasting temperature is preferably 1 - 6 °C / min, specifically it can be 1 °C / min, 1.5 °C / min, 2 °C / min, 2.5 °C / min, 3 °C / min, 3.5 °C / min, 4 °C / min, 4.5 °C / min, 5 °C / min, 5.5 °C / min or 6 °C / min; the time of the first heat preservation roasting is preferably 4 - 10 h, specifically it can be 4 h, 4.5 h, 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h or 10 h.

[0074] In the above roasting process provided by the present invention, in step ii), the second roasting temperature is preferably 700 - 1000 °C, specifically it can be 700 °C, 710 °C, 720 °C, 730 °C, 740 °C, 750 °C, 760 °C, 770 °C, 780 °C, 790 °C, 800 °C, 810 °C, 820 °C, 830 °C, 840 °C, 850 °C, 860 °C, 870 °C, 880 °C, 890 °C, 900 °C, 910 °C, 920 °C, 930 °C, 940 °C, 950 °C, 960 °C, 970 °C, 980 °C, 990 °C or 1000 °C; the heating rate to the second roasting temperature is preferably 1 - 6 °C / min, specifically it can be 1 °C / min, 1.5 °C / min, 2 °C / min, 2.5 °C / min, 3 °C / min, 3.5 °C / min, 4 °C / min, 4.5 °C / min, 5 °C / min, 5.5 °C / min or 6 °C / min; the time of the second heat preservation roasting is preferably 1 - 5 h, specifically it can be 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h or 5 h.

[0075] In the above-mentioned roasting process provided by the present invention, in step iii), the third roasting temperature is preferably 700-900 °C, specifically, it can be 700 °C, 710 °C, 720 °C, 730 °C, 740 °C, 750 °C, 760 °C, 770 °C, 780 °C, 790 °C, 800 °C, 810 °C, 820 °C, 830 °C, 840 °C, 850 °C, 860 °C, 870 °C, 880 °C, 890 °C or 900 °C, and the third roasting temperature ≤ the second roasting temperature; the rate of temperature adjustment to the third roasting temperature is preferably 0-10 °C / min, specifically, it can be 0 (i.e., no temperature adjustment), 0.5 °C / min, 1 °C / min, 1.5 °C / min, 2 °C / min, 2.5 °C / min, 3 °C / min, 3.5 °C / min, 4 °C / min, 4.5 °C / min, 5 °C / min, 5.5 °C / min, 6 °C / min, 6.5 °C / min, 7 °C / min, 7.5 °C / min, 8 °C / min, 8.5 °C / min, 9 °C / min, 9.5 °C / min or 10 °C / min; the time of the three-time heat preservation roasting is preferably 10-20 h, specifically, it can be 10 h, 10.5 h, 11 h, 11.5 h, 12 h, 12.5 h, 13 h, 13.5 h, 14 h, 14.5 h, 15 h, 15.5 h, 16 h, 16.5 h, 17 h, 17.5 h, 18 h, 18.5 h, 19 h, 19.5 h or 20 h.

[0076] In the above-mentioned roasting process provided by the present invention, during the stepwise roasting process, it is preferably to continuously introduce oxygen into the roasting equipment used to provide an oxygen-containing atmosphere required for roasting. Among them, the oxygen inlet rate in step i) is preferably 0.5-5 m 3 / h, specifically, it can be 0.5 m 3 / h, 1 m 3 / h, 1.5 m 3 / h, 2 m 3 / h, 2.5 m 3 / h, 3 m 3 / h, 3.5 m 3 / h, 4 m 3 / h, 4.5 m 3 / h or 5 m 3 / h; the oxygen inlet rate in step ii) is preferably 0.5-5 m 3 / h, specifically, it can be 0.5 m 3 / h, 1 m 3 / h, 1.5 m 3 / h, 2 m 3 / h, 2.5 m 3 / h, 3 m 3 / h, 3.5 m 3 / h, 4 m3 / h, 4.5 m 3 / h or 5 m 3 / h; The oxygen inlet rate in step iii) is preferably 0.5 - 5 m 3 / h, specifically it can be 0.5 m 3 / h, 1 m 3 / h, 1.5 m 3 / h, 2 m 3 / h, 2.5 m 3 / h, 3 m 3 / h, 3.5 m 3 / h, 4 m 3 / h, 4.5 m 3 / h or 5 m 3 / h.

[0077] In the preparation method provided by the present invention, after the roasting is completed, it is preferably to cool the obtained product and then carry out crushing and sieving.

[0078] The present invention also provides a lithium-ion secondary battery, including a positive electrode, a negative electrode, an electrolyte, and a separator between the positive electrode and the negative electrode; wherein, the material of the positive electrode includes the nickel-rich layered oxide material described in the above technical solution or the nickel-rich layered oxide material prepared by the preparation method described in the above technical solution.

[0079] The present invention also provides an electrical device, and the electrical device is equipped with the lithium-ion secondary battery described in the above technical solution.

[0080] For the sake of clarity, the following will be described in detail through the following examples and comparative examples.

[0081] Example 1

[0082] Weigh 4594.6 g of NiSO4 and dissolve it in deionized water to prepare a 2 mol / L salt solution I. Weigh 326.1 g of CoSO4, 24.6 g of NaAlO2, 173.1 g of MnSO4, 55.4 g of Zr(SO4)2 and 10.2 g of ammonium tungstate, dissolve them in deionized water to prepare a high-entropy element solution II with a metal ion concentration of 1 mol / L, prepare a 1.5 mol / L NaOH solution III and a 2.0 mol / L ammonia complexing agent solution IV; add deionized water as the bottom liquid in the reaction kettle, and simultaneously pump solutions I, II, III, and IV into the reaction kettle for complexation and precipitation reactions. Control the flow rates of the NaOH solution and the ammonia complexing agent solution so that the pH of the mixed reaction solution in the reaction kettle always remains within the range of 11.2 ± 0.05. Set the stirring speed of the mixed solution in the reaction kettle to 800 r / min, the reaction temperature to 50 ± 1 °C, and continue the reaction for 40 h. Then, discharge the obtained precipitate, wash it with deionized water and dry it. The drying temperature is 150 °C to obtain a hydroxide precursor X.

[0083] Fully mix the above hydroxide precursor X, 873.6 g of LiOH and 10.9 g of Sr(OH)2 using a high-speed mixer to obtain a mixture Y.

[0084] Place the above mixture Y in an oxygen atmosphere furnace for step-by-step roasting. Continuously introduce oxygen into the furnace throughout the roasting process. The specific process is as follows: First, heat up to 550 °C and roast for 4 h (heating rate is 3 °C / min, oxygen inlet rate is 3 m 3 / h), then heat up to 800 °C and roast for 1 h (heating rate is 3 °C / min, oxygen inlet rate is 4 m 3 / h), and then cool down to 780 °C and roast for 14 h (cooling rate is 4 °C / min, oxygen inlet rate is 3 m 3 / h).

[0085] After the roasting is completed, cool it down with the furnace, and then crush and screen the product to obtain a nickel-rich layered oxide material with the chemical formula LiNi 0.874 Sr 0.0045 Co 0.058 Al 0.015 Mn 0.0388 Zr 0.0078 W 0.0019 O2.

[0086] The nickel-rich layered oxide material prepared in this example was observed by scanning electron microscopy (SEM). The results are as Figure 1 shown, Figure 1 which is the SEM image of the nickel-rich layered oxide material of Example 1 provided by the present invention. Through Figure 1It can be seen that the material has a smooth surface and is composed of spherical secondary particles formed by the aggregation of primary particles (D 50 with a particle size of about 400 nm), and the particle size of the secondary particles is about 12.8 μm.

[0087] The nickel-rich layered oxide material prepared in this example was subjected to D 50 particle size and specific surface area detection, and the results were: the median particle size D 50 was 12.5 μm, and the specific surface area was 0.45 m 2 / g.

[0088] A time-of-flight secondary ion mass spectrometry instrument (ToF-SIMS) was used to detect the metal ion content at different depths of the nickel-rich layered oxide material prepared in this example, and the sputtering rate was set to 0.15 nm / s. The experimental results are as Figure 2 shown, Figure 2 which is the distribution diagram of Zr and W elements at different depths on the surface of primary particles in the nickel-rich layered oxide material of Example 1 provided by the present invention. Through Figure 2 it can be seen that the contents of Zr and W elements within 50 nm of the surface depth of the primary particles are much higher than those at the particle center.

[0089] The nickel-rich layered oxide material prepared in this example was subjected to X-ray diffraction (XRD) testing. The Cu-Kα target was used for the XRD test, the emission wavelength λ = 0.1548 nm, the scanning voltage was 40 kV, the current was 40 mA, the step scanning method was used, the step width was 0.01°, the step time was 3 seconds, and the scanning range was 10° to 80°. The experimental results are as Figure 3 shown, Figure 3 which is the XRD and LeBail structure refinement diagram of the nickel-rich layered oxide of Example 1 provided by the present invention. Through Figure 3 it can be seen that the diffraction peaks of the material correspond to a hexagonal layered structure, space group R-3m.

[0090] Example 2

[0091] Weigh 3869.6 g of NiCl₂ and dissolve it in deionized water to prepare salt solution I with a concentration of 2.5 mol / L. Weigh 607.2 g of CoSO₄, 258.7 g of MnSO₄, and 18.2 g of TiCl₄ and dissolve them in deionized water to prepare high-entropy element solution II with a metal ion concentration of 0.5 mol / L. Prepare NaOH solution III with a concentration of 2.0 mol / L and ammonia complexing agent solution IV with a concentration of 2.5 mol / L. Add deionized water as the bottom liquid to the reaction kettle, and simultaneously pump solutions I, II, III, and IV into the reaction kettle for complexation and precipitation reactions. Control the flow rates of the NaOH solution and the ammonia complexing agent solution so that the pH of the mixed reaction solution in the reaction kettle always remains within the range of 12.0 ± 0.05. Set the stirring speed of the mixed solution in the reaction kettle to 800 r / min, the reaction temperature to 55 ± 1 °C, and continue the reaction for 36 h. Then, discharge the obtained precipitate, wash it with deionized water, and dry it at a drying temperature of 150 °C to obtain hydroxide precursor X.

[0092] Fully mix the above hydroxide precursor X, 769.6 g of Li₂CO₃, 5 g of MgCO₃, 15.6 g of Al(OH)₃, and 9.7 g of Ta₂O₅ using a high-speed mixer to obtain mixture Y.

[0093] Place the above mixture Y in an oxygen atmosphere furnace for step-by-step roasting. Continuously introduce oxygen into the furnace throughout the roasting process. The specific process is as follows: First, heat up to 500 °C and roast for 6 h (heating rate: 4 °C / min, oxygen inlet rate: 2 m 3 / h), then heat up to 820 °C and roast for 2 h (heating rate: 4 °C / min, oxygen inlet rate: 5 m 3 / h), and then cool down to 810 °C and roast for 10 h (cooling rate: 5 °C / min, oxygen inlet rate: 3 m 3 / h).

[0094] After the roasting is completed, cool it down with the furnace, and then crush and screen the product to obtain a nickel-rich layered oxide with the chemical formula LiNi 0.814 Mg 0.003 Co 0.108 Al 0.01 Mn 0.058 Ti 0.0048 Ta 0.0022 O₂.

[0095] Characterize the nickel-rich layered oxide material prepared in this example. The results are as follows: The morphology is spherical secondary particles, the median particle size D 50 is 10.2 μm, the specific surface area is 0.55 m 2 / g, and the contents of Ti and Ta elements within 50 nm of the surface of the primary particles of the material are much higher than those at the particle center.

[0096] Example 3

[0097] Weigh 4778.6 g of NiSO4 and dissolve it in deionized water to prepare a 4.0 mol / L salt solution I. Weigh 280.8 g of CoCl2, 84.8 g of MnSO4 and 41.2 g of Zr(SO4)2 and dissolve them in deionized water to prepare a high-entropy element solution II with a metal ion concentration of 2.5 mol / L. Prepare a 3.0 mol / L NaOH solution III and a 5.0 mol / L EDTA complexing agent solution IV. Add deionized water as the bottom liquid to the reaction kettle, and pump solutions I, II, III, and IV into the reaction kettle simultaneously for complexation and precipitation reactions. Control the flow rates of the NaOH solution and the EDTA complexing agent solution to keep the pH of the mixed reaction solution in the reaction kettle always within the range of 12.3 ± 0.05. Set the stirring speed of the mixed solution in the reaction kettle to 1000 r / min, and the reaction temperature to 58 ± 1 °C. After reacting for 30 h, discharge the obtained precipitate, wash it with deionized water and dry it. The drying temperature is 180 °C to obtain a hydroxide precursor X.

[0098] Fully mix the above hydroxide precursor X, 873.6 g of LiOH, 11.3 g of Y2O3 and 5.8 g of Nb2O5 using a high-speed mixer to obtain a mixture Y.

[0099] Place the above mixture Y in an oxygen atmosphere furnace for step-by-step roasting. Continuously introduce oxygen into the furnace throughout the roasting process. The specific process is as follows: First, heat up to 500 °C and roast for 6 h (heating rate is 4 °C / min, oxygen inlet rate is 2 m 3 / h), then heat up to 850 °C and roast for 3 h (heating rate is 4 °C / min, oxygen inlet rate is 2 m 3 / h), and then cool down to 800 °C and roast for 11 h (cooling rate is 5 °C / min, oxygen inlet rate is 2 m 3 / h).

[0100] After the roasting is completed, cool it with the furnace, and then crush and sieve the product to obtain a nickel-rich layered oxide with the chemical formula LiNi 3+ 0.905 Ni 2+ 0.004 Co 0.059 Y 0.005 Mn 0.019 Zr 0.0058 Nb 0.0022 O2.

[0101] Characterize the nickel-rich layered oxide material prepared in this example. The results are as follows: The morphology is monodisperse primary particles, and the median particle size D 50is 3.0 μm, and the specific surface area is 0.76 m 2 / g. The contents of Y, Zr, and Nb elements within 50 nm from the surface of the primary particles of the material are much higher than those at the particle center.

[0102] Example 4

[0103] Weigh 4557.8 g of NiSO4 and dissolve it in deionized water to prepare salt solution I with a concentration of 1.5 mol / L. Weigh 513.9 g of CoCl2, 28.4 g of Zr(SO4)2, and 15.2 g of TiCl4 and dissolve them in deionized water to prepare high-entropy element solution II with a metal ion concentration of 3.0 mol / L. Prepare NaOH solution III with a concentration of 2.0 mol / L and ammonia complexing agent solution IV with a concentration of 6.0 mol / L. Add deionized water as the bottom liquid into the reaction kettle, and simultaneously pump solutions I, II, III, and IV into the reaction kettle for complexation and precipitation reactions. Control the flow rates of the NaOH solution and the ammonia complexing agent solution so that the pH of the mixed reaction solution in the reaction kettle is always maintained within the range of 11.5 ± 0.05. Set the stirring speed of the mixed solution in the reaction kettle to 600 r / min, the reaction temperature to 55 ± 1 °C, and keep reacting for 50 h. Then, discharge the obtained precipitate, wash it with deionized water, and dry it. The drying temperature is 120 °C to obtain hydroxide precursor X.

[0104] Fully mix the above hydroxide precursor X, 873.6 g of LiOH, 8.4 g of MgCO3, 10.2 g of Al2O3, and 9.3 g of WO3 using a high-speed mixer to obtain mixture Y.

[0105] Place the above mixture Y in an oxygen atmosphere furnace for step-by-step roasting. Continuously introduce oxygen into the furnace throughout the roasting process. The specific process is as follows: First, heat up to 550 °C and roast for 5 h (heating rate is 4 °C / min, oxygen inlet rate is 5 m 3 / h), then heat up to 760 °C and roast for 2 h (heating rate is 4 °C / min, oxygen inlet rate is 3 m 3 / h), and then maintain at 760 °C and continue roasting for 10 h (oxygen inlet rate is 3 m 3 / h).

[0106] After the roasting is completed, cool it with the furnace, and then crush and screen the product to obtain nickel-rich layered oxide with the chemical formula LiNi 0.867 Mg 0.005 Co 0.108 Al 0.01 Zr 0.004 Ti 0.004 W 0.002 O2.

[0107] The nickel-rich layered oxide material prepared in this example was characterized, and the results were as follows: the morphology was spherical secondary particles, and the median diameter D 50 was 15.0 μm, the specific surface area was 0.33 m 2 / g, and the contents of Zr, Ti, and W elements within 50 nm of the surface depth of the primary particles of the material were much higher than those at the particle center.

[0108] Example 5

[0109] Weigh 3874.3 g of NiCl₂ and dissolve it in deionized water to prepare a salt solution I with a concentration of 2.0 mol / L. Weigh 331.7 g of CoSO₄ and 427.5 g of MnCl₂ and dissolve them in deionized water to prepare a high-entropy element solution II with a metal ion concentration of 4.0 mol / L. Prepare a NaOH solution III with a concentration of 1.5 mol / L and an ethylenediamine complexing agent solution IV with a concentration of 6.0 mol / L; add deionized water as the bottom liquid to the reaction kettle, and simultaneously pump solutions I, II, III, and IV into the reaction kettle for complexation and precipitation reactions. Control the flow rates of the NaOH solution and the ethylenediamine complexing agent solution so that the pH of the mixed reaction solution in the reaction kettle always remains within the range of 12.5 ± 0.05. Set the stirring speed of the mixed solution in the reaction kettle to 1000 r / min, the reaction temperature to 50 ± 1 °C, and continue the reaction for 20 h. Then, discharge the obtained precipitate, wash it with deionized water and dry it. The drying temperature is 180 °C to obtain the hydroxide precursor X.

[0110] Fully mix the above hydroxide precursor X, 769.6 g of Li₂CO₃, 17.7 g of SrCO₃, 19.7 g of Yb₂O₃, and 8.8 g of Ta₂O₅ using a high-speed mixer to obtain a mixture Y.

[0111] Place the above mixture Y in an oxygen atmosphere furnace for step-by-step roasting. Continuously introduce oxygen into the furnace throughout the roasting process. The specific process is as follows: First, heat up to 600 °C and roast for 4 h (heating rate: 4 °C / min, oxygen inlet rate: 5 m 3 / h), then heat up to 890 °C and roast for 3 h (heating rate: 4 °C / min, oxygen inlet rate: 2 m 3 / h), and then cool down to 800 °C and roast for 11 h (cooling rate: 6 °C / min, oxygen inlet rate: 4 m 3 / h).

[0112] After the roasting is completed, cool it with the furnace, and then crush and screen the product to obtain a nickel-rich layered oxide with the chemical formula LiNi 0.818 Sr 0.006 Co 0.060 Yb 0.005 Mn 0.109 Ta0.002 O2.

[0113] The nickel-rich layered oxide material prepared in this example was characterized, and the results were as follows: the morphology was monodisperse primary particles, the median particle size D 50 was 3.2 μm, the specific surface area was 0.70 m 2 / g, and the contents of Yb and Ta elements within 50 nm of the surface depth of the material primary particles were much higher than those at the particle center.

[0114] Example 6

[0115] Weigh 4278.4 g of NiCl2 and dissolve it in deionized water to prepare a 3.0 mol / L salt solution I. Weigh 219.3 g of CoSO4, 154.4 g of MnCl2, and 10.8 g of ammonium tungstate and dissolve them in deionized water to prepare a high-entropy element solution II with a metal ion concentration of 1.0 mol / L. Prepare a 4.0 mol / L NaOH solution III and an 8.0 mol / L ammonia complexing agent solution IV; add deionized water as the bottom liquid to the reaction kettle, and simultaneously pump solutions I, II, III, and IV into the reaction kettle for complexation and precipitation reactions. Control the flow rates of the NaOH solution and the ammonia complexing agent solution so that the pH of the mixed reaction solution in the reaction kettle always remains within the range of 11.0 ± 0.05. Set the stirring speed of the mixed solution in the reaction kettle to 1000 r / min, the reaction temperature to 55 ± 1 °C, and continue the reaction for 60 h. Then, discharge the obtained precipitate, wash it with deionized water, and dry it. The drying temperature is 140 °C to obtain the hydroxide precursor X.

[0116] Fully mix the above hydroxide precursor X, 873.6 g of LiOH, 5.9 g of NiO, 15.6 g of Al(OH)3, and 14.6 g of ZrO2 using a high-speed mixer to obtain a mixture Y.

[0117] Place the above mixture Y in an oxygen atmosphere furnace for step-by-step roasting. Continuously introduce oxygen into the furnace throughout the roasting process. The specific process is as follows: First, heat up to 580 °C and roast for 5 h (heating rate is 3 °C / min, oxygen inlet rate is 4 m 3 / h), then heat up to 780 °C and roast for 2 h (heating rate is 3 °C / min, oxygen inlet rate is 6 m 3 / h), and then cool down to 750 °C and roast for 12 h (cooling rate is 3 °C / min, oxygen inlet rate is 3 m 3 / h).

[0118] After the roasting is completed, cool it down with the furnace, and then crush and screen the product to obtain a nickel-rich layered oxide with the chemical formula LiNi 0.9 Ni 2+ 0.004Co 0.039 Al 0.01 Mn 0.039 Zr 0.006 W 0.002 O2.

[0119] The nickel-rich layered oxide material prepared in this example was characterized, and the results showed that the morphology was spherical secondary particles with a medium particle size D 50 The surface area is 12.0 μm and the specific surface area is 0.46 m 2 / g, the content of Zr and W elements within 50nm depth on the surface of the primary particles of the material is much higher than that in the center of the particles.

[0120] Example 7

[0121] 4957.4 g of NiSO4 was weighed and dissolved in deionized water to prepare a 4.0 mol / L salt solution I, 89.2 g of MnSO4, 49.7 g of Zr(SO4)2 and 30.3 g of TiCl4 were weighed and dissolved in deionized water to prepare a high entropy element solution II with a metal ion concentration of 1.0 mol / L, a NaOH solution III with a concentration of 2.0 mol / L and an EDTA complexing agent solution IV with a concentration of 6.0 mol / L were prepared; deionized water was added into the reactor as The bottom liquid is prepared by pumping solutions I, II, III and IV into the reactor at the same time for complexation and precipitation reaction. The flow rates of the NaOH solution and the EDTA complexing agent solution are controlled to keep the pH of the mixed reaction liquid in the reactor within the range of 12.3±0.05. The stirring speed of the mixed solution in the reactor is set to 900r / min, and the reaction temperature is 56±1°C. After the reaction is continued for 48h, the obtained precipitate is discharged, washed with deionized water and dried at a drying temperature of 160°C to obtain a hydroxide precursor X.

[0122] The above-mentioned hydroxide precursor X, 873.6 g of LiOH, 16.8 g of MgCO3, 15.6 g of Al(OH)3 and 6.5 g of Sb2O5 were fully mixed using a high-speed mixer to obtain a mixture Y.

[0123] The mixture Y was placed in an oxygen atmosphere furnace for step-by-step calcination. Oxygen was continuously introduced into the furnace during the whole calcination process. The specific process was as follows: first, the temperature was raised to 520°C and calcined for 5 h (the heating rate was 5°C / min, the oxygen inlet rate was 3 m / min), and then the mixture was calcined at 520°C for 5 h. 3 / h), and then heated to 770℃ and calcined for 5h (heating rate was 3℃ / min, oxygen inlet rate was 5m 3 / h), then cooled to 740℃ and calcined for 10h (cooling rate 5℃ / min, oxygen inlet rate 3m 3 / h).

[0124] After the roasting is completed, it is cooled in the furnace, and then the product is crushed and sieved to obtain a nickel-rich layered oxide with the chemical formula LiNi 0.943 Mg 0.01 Al 0.01 Mn 0.02 Zr 0.007 Ti 0.008 Sb 0.002 O2.

[0125] The nickel-rich layered oxide material prepared in this example was characterized, and the results were as follows: the morphology was spherical secondary particles, and the median particle size D 50 was 10.5 μm, the specific surface area was 0.42 m 2 / g, and the contents of Zr, Ti, and Sb elements within 50 nm of the surface depth of the primary particles of the material were much higher than the contents at the particle center.

[0126] Comparative Example 1

[0127] Nickel sulfate, cobalt sulfate, and manganese sulfate were weighed according to the molar ratio of Ni / Co / Mn = 90:6:4, and dissolved in deionized water to prepare a mixed salt solution I with a concentration of 2 mol / L, a NaOH solution II with a concentration of 1.5 mol / L, and an ammonia complexing agent solution III with a concentration of 2.0 mol / L; deionized water was added as the bottom liquid in the reaction kettle, and solutions I, II, and III were simultaneously pumped into the reaction kettle for complexation and precipitation reactions. The flow rates of the NaOH solution and the ammonia complexing agent solution were controlled so that the pH of the mixed reaction solution in the reaction kettle was always maintained within the range of 11.2 ± 0.05. The stirring speed of the mixed solution in the reaction kettle was set to 800 r / min, the reaction temperature was 50 ± 1 °C, and after continuous reaction for 40 h, the obtained precipitate was discharged, washed with deionized water, and dried. The drying temperature was 150 °C to obtain a nickel-cobalt-manganese hydroxide precursor X.

[0128] The above nickel-cobalt-manganese hydroxide precursor X and 873.6 g of LiOH were thoroughly mixed using a high-speed mixer to obtain a mixture Y.

[0129] The above mixture Y was placed in an oxygen atmosphere furnace for stepwise roasting. Oxygen was continuously introduced into the furnace throughout the roasting process. The specific process was as follows: first, it was heated to 550 °C and roasted for 6 h (heating rate was 3 °C / min, oxygen inlet rate was 3 m 3 / h), then heated to 800 °C and roasted for 1 h (heating rate was 3 °C / min, oxygen inlet rate was 4 m 3 / h), and then cooled to 780 °C and kept warm for 14 h (cooling rate was 4 °C / min, oxygen inlet rate was 3 m 3 / h).

[0130] After the roasting is completed, it is cooled in the furnace, and then the product is pulverized and sieved to obtain a nickel-rich layered oxide material with the chemical formula LiNi 0.90 Co 0.06 Mn 0.04 O2.

[0131] The nickel-rich layered oxide material prepared in this comparative example was characterized, and the results were as follows: the morphology was spherical secondary particles, and the median diameter D 50 was 13.2 μm, and the specific surface area was 0.39 m 2 / g.

[0132] Comparative Example 2

[0133] Referring to the preparation method of Comparative Example 1, the difference is that: in the process of preparing the mixture Y, the manganese-nickel-cobalt hydroxide precursor X, 873.6 g of LiOH, 10.9 g of Sr(OH)2, 23.4 g of Al(OH)3, 19.0 g of ZrO2, and 10.2 g of ammonium tungstate were fully mixed by a high-speed mixer to obtain the mixture Y; finally, a multi-component doped nickel-rich layered oxide material was prepared, and the chemical formula was approximately LiNi 0.874 Sr 0.0045 Co 0.058 Al 0.015 Mn 0.0388 Zr 0.0078 W 0.0019 O2.

[0134] The multi-component doped nickel-rich layered oxide material prepared in this comparative example was characterized, and the results were as follows: the morphology was spherical secondary particles, and the median diameter D 50 was 13.0 μm, and the specific surface area was 0.42 m 2 / g. The Zr and W elements were segregated in an island shape on the surface of the spherical secondary particles, and no Zr and W elements were detected in the primary particles.

[0135] Comparative Example 3

[0136] Referring to the preparation method of Example 1, the difference is that: the mixture Y was placed in an oxygen atmosphere furnace for calcination, heated to 780 °C and kept warm for 18 h, the heating rate was 3 °C / min, and the gas inlet rate was 4 m 3 / h; finally, a nickel-rich layered oxide material was prepared, and the chemical formula was approximately LiNi 0.874 Sr 0.0045 Co 0.058 Al 0.015 Mn 0.0388 Zr 0.0078 W 0.0019 O2.

[0137] The nickel-rich layered oxide material prepared in this comparative example was characterized, and the results were as follows: The morphology was spherical secondary particles, and the median particle size D 50 was 12.5 μm, and the specific surface area was 0.42 m 2 / g. The elements Zr and W were mainly segregated in an island-like manner on the surface of the spherical secondary particles, and only a small amount of Zr and W elements were detected in the primary particles.

[0138] Performance evaluation

[0139] The lattice microstrain and electrochemical performance of the oxide materials prepared in Examples 1 to 7 and Comparative Examples 1 to 3 were evaluated as follows:

[0140] (1) Lattice microstrain:

[0141] The Williamson-Hall diagrams obtained after LeBail structure refinement of the oxide materials prepared in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are shown as Figure 4 shown. Figure 4 Figure 1 is the Williamson-Hall diagram of the oxide materials prepared in Example 1 provided by the present invention and Comparative Examples 1 to 3. Since both crystal size refinement and lattice microstrain (ε) can broaden the diffraction peaks of the powder XRD pattern, however, the effects of grain size and microstrain can be separated by the Williamson-Hall equation, which can be briefly described as: D·cosθ = a + b·sinθ. Among them, a and b are constant terms, D is the full width at half maximum (FWHM) of the diffraction peak of the powder XRD pattern, and θ is 1 / 2 of the diffraction angle. According to the Scherrer formula, it can be known that the broadening of the diffraction peak caused by the grain size is proportional to 1 / cosθ, and the broadening Γ = 4·ε·tanθ caused by the structural microstrain, that is, proportional to tanθ. As can be seen from the above, the slope of the Williamson-Hall diagram is proportional to the lattice microstrain in the sample, and the intercept is related to the grain size. Therefore, it can be seen that the slope of the Williamson-Hall diagram of the oxide material obtained in Example 1 is lower than that of Comparative Example 1, Comparative Example 2, and Comparative Example 3, that is, the oxide material in Example 1 has a lower lattice microstrain.

[0142] At the same time, the value of the lattice microstrain ε was calculated through the lattice spacing deviation, where ε = Δd / d. The specific calculation results of the lattice microstrain of the oxide materials prepared in Examples 1 to 7 and Comparative Examples 1 to 3 are shown in Table 1:

[0143] Table 1

[0144] Lattice Microstrain (%) Example 1 0.14 Example 2 0.05 Example 3 0.08 Example 4 0.14 Example 5 0.19 Example 6 0.16 Example 7 0.22 Comparative Example 1 0.32 Comparative Example 2 0.30 Comparative Example 3 0.30

[0145] As can be seen from Table 1, compared with Comparative Examples 1-3, the nickel-rich layered oxide materials obtained in Examples 1-7 have lower lattice micro-strain, and the lattice micro-strain is lower than 0.25% for all, indicating that the structural stability of the materials has been significantly improved.

[0146] (2) Electrochemical performance:

[0147] The electrochemical performance of the oxide materials prepared in Examples 1-7 and Comparative Examples 1-3 was tested as the cathode material of a lithium secondary battery in a coin-type lithium secondary battery. The specific manufacturing methods of the lithium secondary battery and its positive electrode sheet are as follows: the prepared cathode material powder is mixed with acetylene black and polyvinylidene fluoride in a mass ratio of 90:5:5, and an appropriate amount of N-methylpyrrolidone is added as a dispersant and ground into a slurry; then the slurry is uniformly coated on aluminum foil and vacuum dried at 120 °C for 10 h, and the dried electrode sheet is roll-pressed with a roll press, and the aluminum foil is cut with a slicing machine into circular electrode sheets with a diameter of 1.3 cm, and the loading amount of the active material is controlled at 12 ± 0.2 mg / cm 2 or so; a half-cell is assembled in a glove box under an argon atmosphere with a moisture pressure ≤ 0.1 ppm and an oxygen pressure ≤ 0.1 ppm; a metal lithium is used as the counter electrode, and a 1M LiPF6 (EC / DMC, volume ratio 1:1:1) solution is used as the electrolyte to assemble a CR2032 type coin cell, and charge and discharge are carried out at room temperature using a constant current charge and discharge mode, with a voltage range of 2.5-4.3 V and a current density of 60 mA / g (0.3 C rate) for 100 charge and discharge cycles.

[0148] To analyze the thermal stability of the prepared materials, after charging the assembled battery to 4.3 V, the positive electrode sheet was taken out and disassembled in a glove box filled with argon, rinsed several times with DMC solution, vacuum dried, and the active material was recovered from the electrode sheet and placed in the sample crucible of a differential scanning calorimeter, and then DSC thermal analysis was carried out under a N2 atmosphere with a temperature rise rate controlled at 5 °C / min to compare the heat release amount and the position of the heat release peak of the materials.

[0149] The cyclic performance test results of the oxide materials prepared in Example 1 and Comparative Examples 1-3 in the lithium secondary battery test are as Figure 5 shown, Figure 5 is the cyclic performance comparison chart of the oxide materials prepared in Example 1 provided by the present invention and Comparative Examples 1-3 in the lithium secondary battery test; the first-week charge specific capacity, first-week discharge specific capacity, first-week Coulomb efficiency, capacity retention rate after 100 weeks, and DSC test data of the oxide materials prepared in Examples 1-7 and Comparative Examples 1-3 in the lithium secondary battery test are shown in Table 2:

[0150] Table 2

[0151]

[0152] As can be seen from Table 2, compared with Comparative Examples 1 to 3, the nickel-rich layered oxide materials obtained in Examples 1 to 7 have better cycling performance, higher exothermic peak temperature and lower heat release in the lithium secondary battery tests, indicating that the safety of the materials has been significantly improved.

[0153] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a nickel-rich layered oxide material, characterized in that, It includes the following steps: a) Mix solution I, solution II, sodium hydroxide and a complexing agent, and control the dosages of the sodium hydroxide and the complexing agent so that the pH value of the mixed system is maintained at 10 - 13 for complexation and precipitation reactions to obtain a hydroxide precipitate; In step a), the components of solution I include a nickel source compound and water; the components of solution II include a first metal source compound and water; the first metal source compound is at least one of a C source compound and a D source compound, or a mixture of at least one of a C source compound and a D source compound and at least one of an A source compound and a B source compound; the A source compound is a water-soluble metal salt corresponding to a +2 valence metal cation, the B source compound is a water-soluble metal salt corresponding to a +3 valence metal cation, the C source compound is a water-soluble metal salt corresponding to a +4 valence metal cation, and the D source compound is a water-soluble metal salt corresponding to a +5 valence or higher valence metal cation; b) Mix the hydroxide precipitate, a lithium source compound and a second metal source compound to obtain a mixture; In step b), the second metal source compound is one or more of an A source compound, a B source compound, a C source compound and a D source compound; c) Subject the mixture to stepwise calcination in an oxygen-containing atmosphere to obtain a nickel-rich layered oxide material; The crystal structure of the nickel-rich layered oxide material is a hexagonal R-3m space group, and the lattice microstrain ≤ 0.22%; The chemical general formula of the nickel-rich layered oxide material is: LiNi x A a B b C c D d O2, where Ni is +3 valence, A is a +2 valence metal cation, B is Al 3+ 、Co 3+ 、Ga 3+ 、Y 3+ 、La 3+ and Yb 3+ or one or more of them, C is a +4 valence metal cation, D is a +5 valence or higher metal cation, 0.8 ≤ x < 1, a > 0, b > 0, c > 0, d ≥ 0, and x + a + b + c + d = 1; Among all types of metal cations contained in B, C and D, at least two metal cations have a content at the surface of the primary particles of the nickel-rich layered oxide material greater than that at the particle center.

2. The preparation method according to claim 1, wherein A is one or more of Mg 2+ , Ni 2+ , and Sr 2+ ; C is one or more of Mn 4+ , Zr 4+ , Ti 4+ , Sn 4+ , and Ce 4+ ; D is one or more of V 5+ , Nb 5+ , Sb 5+ , Ta 5+ , Mo 6+ , and W 6 + ; 3. The preparation method according to any one of claims 1 to 2, characterized in that, The nickel-rich layered oxide material satisfies at least one of the following conditions: The D of the nickel-rich layered oxide material 50 has a particle size of 2 to 20 μm; The specific surface area of the nickel-rich layered oxide material is 0.2 to 2 m 2 / g; The morphology of the nickel-rich layered oxide material is primary particles or spherical secondary particles.

4. The preparation method according to claim 1, characterized in that, In step a), the concentration of metal ions in solution I is 1 - 5 mol / L; the total concentration of metal ions in solution II is 0.5 - 5 mol / L.

5. The preparation method according to claim 1, characterized in that, In step a), the sodium hydroxide participates in the mixing in the form of an aqueous sodium hydroxide solution, and the concentration of the aqueous sodium hydroxide solution is 0.5 - 4 mol / L; the complexing agent is one or more of ammonia water, ethylenediaminetetraacetic acid and ethylenediamine, and the complexing agent participates in the mixing in the form of an aqueous complexing agent solution, and the concentration of the aqueous complexing agent solution is 0.5 - 10 mol / L.

6. The preparation method according to claim 1, wherein, In step a), the stirring rate of the complexation and precipitation reaction is 200 - 1000 r / min; the temperature of the complexation and precipitation reaction is 30 - 70 °C; the time of the complexation and precipitation reaction is 10 - 50 h.

7. The preparation method according to claim 1, characterized in that, In step c), the specific process of the stepwise calcination includes: i) Heat from the ambient temperature to a first calcination temperature and perform a first heat preservation calcination; The first calcination temperature is 300 - 600 °C; the heating rate to the first calcination temperature is 1 - 6 °C / min; the time of the first heat preservation calcination is 4 - 10 h; ii) Continue to heat to a second calcination temperature and perform a second heat preservation calcination; The second calcination temperature is 700 to 1000 °C; the heating rate to the second calcination temperature is 1 to 6 °C / min; the time for the secondary heat preservation calcination is 1 to 5 h; iii) Adjust the temperature to the third calcination temperature and perform the third heat preservation calcination; The third calcination temperature is 700 to 900 °C and ≤ the second calcination temperature; the rate of adjusting the temperature to the third calcination temperature is 0 to 10 °C / min; the time for the third heat preservation calcination is 10 to 20 h.

8. The preparation method according to claim 7, characterized in that, During the stepwise roasting process, oxygen is continuously introduced into the roasting equipment used to provide an oxygen-containing atmosphere required for roasting; the oxygen inlet rate in step i) is 0.5 - 5 m 3 / h, the oxygen inlet rate in step ii) is 0.5 - 5 m 3 / h, and the oxygen inlet rate in step iii) is 0.5 - 5 m 3 / h.

9. A lithium ion secondary battery, characterized in that, The positive electrode material of the lithium ion secondary battery includes the nickel-rich layered oxide material prepared by the preparation method according to any one of claims 1 to 8.

10. An electrical device, characterized in that, The electrical device is equipped with the lithium ion secondary battery according to claim 9.

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