Single-crystal polyvalent positive electrode material and its manufacturing method, lithium-ion battery

Abstract

A single crystal type polyvalent positive electrode material and its manufacturing method and a lithium ion battery are disclosed. The polyvalent positive electrode material includes quasi-single crystal particles consisting of a plurality of crystal grains, and a G element is present at the grain boundary between the crystal grains, and the concentration of the G element at the g site of the grain boundary gradually decreases as the distance between the g site and the surface of the quasi-single crystal particle increases, and the G element is selected from at least one of Ni, Co, Mn, Ta, Cr, Mo, W, La, Al, Y, Ti, Zr, V, Nb, Ce, Er and B. The single crystal type polyvalent positive electrode material having the above special structure significantly reduces the erosion of the grain boundary by the electrolyte, improves the grain boundary stability of the positive electrode material, and significantly improves the cycle life, energy density, rate performance, impedance increase rate, etc. of a lithium ion battery including the positive electrode material.

Description

[Technical Field]

[0001] The present invention relates to the field of lithium ion battery technology, and more particularly to a monocrystalline polyvalent positive electrode material and a method for producing the same, and a lithium ion battery. [Background technology]

[0002] With the rapid development of the new energy industry, the market has placed higher demands on the performance of lithium-ion batteries. As the core material that most influences battery performance, cathode materials are being improved toward the goals of high energy density, long cycle life, high safety, and low cost. Polyvalent materials such as nickel cobalt manganese oxide (NCM) and nickel cobalt aluminate (NCA) have become one of the most widely used cathode materials due to their excellent energy density. To achieve higher specific capacity, the Ni content in polyvalent materials is constantly increasing, which reduces the stability of the material and leads to a corresponding deterioration in cycle life and safety performance. Therefore, the application of more stable single-crystalline nickel cobalt manganese oxide materials is becoming more widespread.

[0003] Single-crystal polyvalent materials can be divided into two states according to the crystal growth arrangement form. One is a pure single-crystal state, where each single-crystal particle is composed of one independent crystal particle, and the other is a quasi-single-crystal state, where multiple crystal grains are bonded together. There are no vacancies or interfaces inside the pure single-crystal particles, and Li +Because the oxygen absorption and release pathways are long and the capacity and rate performance of the material are poor, current commercial single-crystal materials contain varying proportions of the aforementioned pure single-crystal and quasi-single-crystal particles. However, as described in a 2022 Nano Letters article by Zhang et al. entitled "Accelerated Degradation in a Quasi-Single-Crystalline Layered Oxide Cathode for Lithium-Ion Batteries Caused by Residual Grain Boundaries," during charge / discharge cycling, these quasi-single-crystal particles experience relatively concentrated anisotropic stress at the grain boundaries where different crystal grains are interconnected due to the change in crystalline cell volume caused by the H2-H3 phase transformation. This causes interlayer slippage, dislocations, and stacking faults at the grain boundaries, accelerating the loss of active oxygen and irreversible phase transformation, resulting in a decrease in electrochemical capacity. Furthermore, the stress concentration can cause cracks along the grain boundaries, creating new, highly active surfaces that further accelerate side reactions between the material and the electrolyte, resulting in reduced cycle life and increased resistance.

[0004] Common methods for improving material stability include bulk doping and surface coating. However, conventional techniques mainly address the stabilization of the internal structure of the material crystal and the particle surface, and there is no effective solution to the problem of grain boundary degradation in quasi-single crystal particles. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention aims to provide a single-crystal polyvalent positive electrode material, a method for producing the same, and a lithium-ion battery, in order to overcome the problem of poor grain boundary stability of quasi-single-crystal positive electrode material particles present in conventional technologies, resulting in deterioration of electrochemical performance such as battery capacity and rate performance. The single-crystal polyvalent positive electrode material includes quasi-single-crystal particles consisting of a plurality of crystal grains, and a G element is present at the grain boundaries between the crystal grains. The concentration of the G element at the g site of the grain boundary gradually decreases as the distance between the g site and the surface of the quasi-single-crystal particle increases, thereby significantly mitigating erosion within the grain boundaries by the electrolyte and improving the grain boundary stability of the positive electrode material. The cycle life, energy density, rate performance, and impedance increase rate of a lithium-ion battery including the positive electrode material can all be significantly improved. [Means for solving the problem]

[0006] In order to achieve the above object, a first aspect of the present invention provides a single-crystal polyvalent positive electrode material, the polyvalent positive electrode material including quasi-single-crystal particles consisting of a plurality of crystal grains, and a G element present at grain boundaries between the crystal grains, The concentration of G elements at the g site of the grain boundary gradually decreases as the distance between the g site and the surface of the quasi-single crystal grain increases. The G element is characterized by being selected from at least one of Ni, Co, Mn, Ta, Cr, Mo, W, La, Al, Y, Ti, Zr, V, Nb, Ce, Er, and B.

[0007] A second aspect of the present invention provides a method for producing a monocrystalline polyvalent positive electrode material, the method comprising: a step of mixing a multivalent positive electrode material matrix with a grain boundary stabilizer containing a G element, and then sintering the mixture to obtain the single-crystal multivalent positive electrode material; the G element is selected from at least one of Ni, Co, Mn, Ta, Cr, Mo, W, La, Al, Y, Ti, Zr, V, Nb, Ce, Er, Mg, Sr, Ba, and B; The grain boundary stabilizer has a D50 of 0.01-10 μm, and the D10, D50, and D90 of the grain boundary stabilizer satisfy K90=(D90-D10) / D50≧1.5.

[0008] A third aspect of the present invention provides a single-crystal polyvalent positive electrode material produced by the above-described production method.

[0009] A fourth aspect of the present invention provides a lithium ion battery comprising the above-mentioned single crystal polyvalent positive electrode material.

[0010] By the above technical means, the single crystal polyvalent positive electrode material, the manufacturing method thereof, and the lithium ion battery according to the present invention have the following beneficial effects.

[0011] The monocrystalline polyvalent positive electrode material of the present invention comprises quasi-single crystalline particles consisting of multiple crystal grains, with G elements present at the grain boundaries between the crystal grains. The concentration of G elements at the g sites of the grain boundaries gradually decreases as the distance between the g sites and the surfaces of the quasi-single crystalline particles increases, allowing the G elements to fully penetrate and fill the grain boundaries of the positive electrode material. This reduces stress concentration at the grain boundaries of the positive electrode material due to changes in the crystalline cell volume during charge-discharge cycling, improving the grain boundary stability of the positive electrode material and significantly improving the cycle life of lithium-ion batteries containing the positive electrode material. At the same time, the improved grain boundary stability and reduced grain boundary cracking reduce the occurrence of new internal interfaces, resulting in a lower impedance increase rate for lithium-ion batteries containing the positive electrode material after multiple cycles and long-term storage. Specifically, compared to conventional positive electrode materials, lithium-ion batteries containing the positive electrode material of the present invention show at least a 4% improvement in cycling capacity retention and a at least a 15% reduction in impedance increase rate after 80 half-cycles at 1C at 45°C.

[0012] Furthermore, in the single-crystal polyvalent positive electrode material of the present invention, the gradient packing of the G element at the grain boundary position functions as a conductive medium, and Li +The outward diffusion of the positive electrode material is advantageous, and when the positive electrode material is used in a lithium ion battery, its capacity is fully utilized and its rate performance is better. Specifically, compared with conventional positive electrode materials, the 0.1 C discharge capacity of a lithium ion battery using the positive electrode material of the present invention can be improved by more than 1 mAh / g in the voltage range of 3.0-4.3 V at 25°C, and the discharge at 1 C rate can be improved by more than 2%.

[0013] The method for producing a single crystal polyvalent positive electrode material according to the present invention is simple, easy to control, and suitable for industrial production. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing a quasi-single crystal particle of a single crystal type polyvalent positive electrode material according to the present invention. FIG. [Figure 2] FIG. 1 is a schematic diagram showing that the grain boundary stabilizer cobalt hydroxide used in Example 1 contains micron and submicron ions. [Figure 3] 1 is a cross-sectional schematic diagram of a single-crystal polyvalent positive electrode material produced in Example 1, and the numbers in the figure indicate examples of measurement sites for element concentrations within grain boundaries. [Figure 4] 1 is a graph showing the cycle performance comparison of the positive electrode materials prepared in Preparation Example 1, Example 1, and Comparative Example 1 at a 1C rate, where the test temperature is 45° C. and the voltage range is 3.0-4.3V. DETAILED DESCRIPTION OF THE INVENTION

[0015] The endpoints of ranges and any value disclosed herein should be understood to be not limited to such exact ranges or values, but to include values ​​close to those ranges or values. In the case of ranges of numerical values, values ​​between the endpoints of each range, between the endpoints of each range and any single point value, and between any single point value can be combined with each other to create one or more new numerical ranges, and these numerical ranges are considered to be specifically disclosed in the specification.

[0016] A first aspect of the present invention provides a single-crystal polyvalent positive electrode material, the polyvalent positive electrode material including quasi-single-crystal particles consisting of a plurality of crystal grains, and a G element present at grain boundaries between the crystal grains; The concentration of G elements at the g site of the grain boundary gradually decreases as the distance between the g site and the surface of the quasi-single crystal grain increases. The G element is characterized by being selected from at least one of Ni, Co, Mn, Ta, Cr, Mo, W, La, Al, Y, Ti, Zr, V, Nb, Ce, Er, and B.

[0017] In the present invention, the grain boundary refers to the contact interface and / or gap between multiple crystal grains that constitute a quasi-single crystal particle. In the present invention, a single-crystal polyvalent positive electrode material is obtained by co-development of a large number of crystal nuclei, so that most of the crystal grains fuse together during the crystal growth process. When the crystal grows to a certain size, that is, when the single-crystal polyvalent positive electrode material described in the present invention is formed, some crystal grains that are not completely fused exist, and the orientation of these crystal grains is different, and the interface between them is the grain boundary described in the present invention.

[0018] In the present invention, the single-crystal polyvalent positive electrode material comprises quasi-single crystalline particles consisting of a plurality of crystal grains, and a G element is present at the grain boundaries between the crystal grains. The concentration of the G element at the g site of the grain boundary gradually decreases as the distance between the g site and the surface of the quasi-single crystalline particle increases. The G element is sufficiently permeated and filled into the grain boundaries of the positive electrode material, which reduces the stress concentration generated at the grain boundaries of the positive electrode material due to the change in crystalline cell volume during charge and discharge cycling, improves the grain boundary stability of the positive electrode material, and significantly improves the cycle life of lithium-ion batteries containing this positive electrode material. At the same time, the improved grain boundary stability and fewer grain boundary cracks reduce the occurrence of new internal interfaces, resulting in a lower impedance increase rate of lithium-ion batteries containing this positive electrode material after multiple cycles and long-term storage conditions.

[0019] Furthermore, the G element is selected from at least one of Mn, Co, W, La, Al, Ti, Zr, and Nb.

[0020] According to the present invention, in an SEM image of a cross-sectional sample of the quasi-single crystal particle, the concentration of the G element at the g site at the grain boundary satisfies the following relationship: 1.2C1≧C g ≧0.8C2 formula I

number

[0021] In the present invention, L is the total length of the grain boundary passing through the g site, which means the sum of the approximate lengths of the two shortest grain boundary sections that start from the g site and extend along two opposite directions parallel to the crystal plane to the surface of the quasi-single crystal grain. g means the approximate length of the shortest grain boundary path that starts at the g site and extends along a direction parallel to the grain boundary to the surface of the quasi-single crystal grain.

[0022] In the present invention, L and L g The reason why approximate values ​​were used in all of the above is that the grain boundary flow is not a straight line and cannot be measured, so a simulation was performed by drawing multiple straight lines along the grain boundary flow, and the actual length of the grain boundary was approximately replaced by the length of the straight lines.

[0023] In the present invention, C1, C2 and C gwas measured by scanning electron microscope spectroscopy. A cross-sectional sample of the single-crystal polyvalent positive electrode material was prepared by ion milling, and a scanning electron microscope spectroscopy analyzer was used to select quasi-single-crystal single-crystal particles in the cross-sectional sample, and energy spectrum analysis points were tested at different sites on the particle boundaries to obtain the atomic percentage of the elements at those sites. At least five sets of data were tested for each position, and the average value was calculated.

[0024] In the present invention, in order to embody the concentration change trend of the G element, multiple different sites along the grain boundary are randomly selected for testing and evaluation, and the selected sites should be relatively dispersed to avoid excessive concentration.

[0025] Due to limitations in the stability of the detection method, there may be individual abnormal data that exceed the calculation results of Formula II, and these should be eliminated during evaluation. 75% or more of the data should be considered to meet the technical effects and required scope of the present invention if they meet the rule that the concentration of the G element at the g site of the grain boundary described in the present invention gradually decreases as the distance between the g site and the surface of the quasi-single crystal particle increases.

[0026] Furthermore, 1.1C1 ≥ C g ≧0.9C2.

[0027] According to the present invention, spectroscopic analysis using a scanning electron microscope reveals that the total length L of the grain boundary satisfies 0.01 μm≦L≦8 μm.

[0028] According to the present invention, C1-C2≧0.1%.

[0029] Furthermore, C1-C2≧0.2%.

[0030] According to the present invention, when C1>5%, the value range of k is 0.9 to 1.1, and when C1≦5%, the value range of k is 0.8 to 1.2.

[0031] As shown in FIG. 1, FIG. 1 is a schematic diagram of a quasi-single crystalline particle of a single-crystal polyvalent positive electrode material according to the present invention. As can be seen from FIG. 1, the positive electrode material according to the present invention comprises a quasi-single crystalline particle consisting of a plurality of crystal grains as shown in the figure, and the contact surface between each crystal grain is the grain boundary according to the present invention. Taking the g site in the figure as an example, the total length L of the grain boundary through the g site and along the grain boundary to the surface of the quasi-single crystalline particle includes two parts, the L1 and L2 directions and the L3 and L4 directions, and the value of the total length L can be obtained by L1 + L2 + L3 + L4. The g site is the shortest path length L along the grain boundary direction to the surface of the quasi-single crystalline particle. g can be obtained by L3 + L4, where the concentration C1 of the G element on the surface of the quasi-single crystal particle is obtained by testing at different positions on the surface and taking the average value, and the concentration C2 of the G element in the bulk phase of the quasi-single crystal particle is obtained by testing at central positions inside different crystal grains and taking the average value.

[0032] According to the present invention, the major axis D1 of the quasi-single crystal particle satisfies 0.1 μm≦D1≦20 μm, and the minor axis D2 thereof satisfies 0.1 μm≦D2≦20 μm.

[0033] According to the present invention, the major axis D3 of the crystal grains satisfies 0.1 μm≦D3≦12 μm, and the minor axis D4 thereof satisfies 0.1 μm≦D4≦12 μm.

[0034] According to the present invention, the grain boundary has a width of 1 to 50 nm, and the difference between the maximum grain boundary width and the minimum grain boundary width is 20 nm or less.

[0035] In the present invention, the grain boundary width is the distance between the surfaces of adjacent grains on both sides of the grain boundary along the surface direction of the material. The grain boundary width was measured using a scanning electron microscope. When the difference between the maximum and minimum grain boundary widths exceeds 20 nm, the concentration of the G element at the wide grain boundary site increases relatively, and the concentration of the G element at that site does not fit the formula shown in Equation II.

[0036] In the present invention, the addition of the grain boundary stabilizer does not change the difference between the total length L of the grain boundaries, the major diameter D1 of the quasi-single crystal particles, the minor diameter D2 of the quasi-single crystal particles, the major diameter D3 of the crystal grains, the minor diameter D4 of the crystal grains, the width (H) of the grain boundaries, and the maximum value (H max ) and the minimum value (H min ) of the width of the grain boundaries. The difference between the total length L of the grain boundaries, the major diameter D1 of the quasi-single crystal particles, the minor diameter D2 of the quasi-single crystal particles, the major diameter D3 of the crystal grains, the minor diameter D4 of the crystal grains, the width (H) of the grain boundaries, and the maximum value (H max ) and the minimum value (H max ) of the width of the grain boundaries of the single crystal type polyvalent cathode material is the same as that of the polyvalent cathode matrix material before the mixed sintering of the grain boundary stabilizer.

[0037] In the present invention, the total length L of the grain boundaries, the major diameter D1 of the quasi-single crystal particles, the minor diameter D2 of the quasi-single crystal particles, the major diameter D3 of the crystal grains, the minor diameter D4 of the crystal grains, the width (H) of the grain boundaries, the maximum value (H max ) and the minimum value (H max ) of the width of the grain boundaries in the polyvalent cathode material are measured by SEM. Specifically, in the SEM diagram of the polyvalent cathode material, 300 quasi-single crystal particles of the polyvalent cathode material are randomly selected as samples, and the average value is obtained.

[0038] According to the present invention, the single crystal type polyvalent cathode material includes a matrix and a coating layer coated on the matrix, the matrix has a structure as shown in Formula III, Li 1+a (Ni x Co y Me z M w )O2 Formula III Here, -0.1 ≤ a ≤ 0.1, 0 < x < 1, 0 < y ≤ 0.4, 0 < z ≤ 0.6, 0 ≤ w ≤ 0.2, Me is selected from Mn and / or Al, and M is selected from at least one element of Ta, Cr, Mo, W, La, Al, Y, Ti, Zr, V, Nb, Ce, Er, Mg, Sr, and Ba, the coating layer is selected from a lithium oxygen compound of element G and / or an oxide of element G, G is at least one element selected from the group consisting of Ni, Co, Mn, Ta, Cr, Mo, W, La, Al, Y, Ti, Zr, V, Nb, Ce, Er, and B; The molar ratio of the coating layer in terms of n(G) to the matrix in terms of [n(Ni)+n(Co)+n(Me)+n(M)] is 0.001 to 0.05.

[0039] Furthermore, -0.06≦a≦0.06, 0.4 <x<1、0<y≦0.3、0<z≦0.5、0<w≦0.1とする。

[0040] Furthermore, Me is selected from Mn and / or Al.

[0041] Furthermore, M is at least one element selected from the group consisting of W, La, Al, Y, Ti, Zr, Nb, Ce, Mg, and Sr.

[0042] Furthermore, G is at least one element selected from the group consisting of Mn, Co, W, La, Al, Ti, Zr, and Nb.

[0043] Furthermore, the molar ratio of the coating layer in terms of n(G) to the matrix in terms of [n(Ni)+n(Co)+n(Me)+n(M)] is 0.005-0.04.

[0044] A second aspect of the present invention provides a method for producing a monocrystalline polyvalent positive electrode material, the method comprising: a step of mixing a multivalent positive electrode material matrix with a grain boundary stabilizer containing a G element, and then sintering the mixture to obtain the single-crystal multivalent positive electrode material; the G element is selected from at least one of Ni, Co, Mn, Ta, Cr, Mo, W, La, Al, Y, Ti, Zr, V, Nb, Ce, Er, Mg, Sr, Ba, and B; The grain boundary stabilizer has a D50 of 0.01-10 μm, and the D10, D50, and D90 of the grain boundary stabilizer satisfy K90=(D90-D10) / D50≧1.5.

[0045] In the present invention, a polyvalent positive electrode matrix and a grain boundary stabilizer containing a G element having a specific particle size and particle size distribution are mixed and sintered to obtain a single-crystal polyvalent positive electrode material according to the first aspect of the present invention. Specifically, the positive electrode material includes quasi-single crystalline particles composed of a plurality of crystal grains, with the G element present at the grain boundaries between the crystal grains, and the concentration of the G element at the g sites of the grain boundaries gradually decreases as the distance between the g sites and the surfaces of the quasi-single crystalline particles increases, allowing the G element to fully penetrate and fill the grain boundaries of the positive electrode material, reducing stress concentration at the grain boundaries of the positive electrode material due to changes in the crystalline cell volume during charge and discharge cycling, improving the grain boundary stability of the positive electrode material, and significantly improving the cycle life of lithium-ion batteries containing the positive electrode material. At the same time, the improved grain boundary stability and fewer grain boundary cracks reduce the occurrence of new internal interfaces, resulting in a lower impedance increase rate for lithium-ion batteries containing the positive electrode material after multiple cycles and long-term storage.

[0046] In particular, the method for producing a single crystal polyvalent positive electrode material according to the present invention is simple, easy to control, and suitable for industrial production.

[0047] Furthermore, the G element is selected from at least one of Mn, Co, W, La, Al, Ti, Zr, and Nb.

[0048] Furthermore, the grain boundary stabilizer is selected from at least one of oxides, oxyhydroxides, hydroxides, fluorides, sulfates, nitrates, carbonates, and oxalates containing the G element.

[0049] Furthermore, the grain boundary stabilizer has a D50 of 0.1 to 8 μm, and the D10, D50, and D90 of the grain boundary stabilizer satisfy K90=(D90−D10) / D50≧2.

[0050] According to the present invention, the specific surface area of ​​the grain boundary stabilizer is 10 m 2 / g or more.

[0051] In the present invention, the use of an interfacial stabilizer with a large specific surface area is advantageous for uniform dispersion with the material during mixing with the material, and the high specific surface area of ​​the interfacial stabilizer can achieve higher reaction activity. This is advantageous for diffusion into the grain boundaries during sintering, and the interfacial stabilizer can achieve a better grain boundary gradient filling effect.

[0052] Furthermore, the specific surface area of ​​the grain boundary stabilizer is 20-100 m 2 / g.

[0053] According to the present invention, the grain boundary stabilizer is added in an amount such that the stoichiometric ratio is 0.001≦n(G)n[n(Ni)+n(Co)+n(Me)+n(M)]≦0.05.

[0054] In the present invention, if the amount of grain boundary stabilizer used is too low, i.e., n(G) / [n(Ni)+n(Co)+n(Me)+n(M)] is less than 0.001, the added ratio of G element is too low and the gradient effect cannot be realized. If the amount of grain boundary stabilizer used is too high, i.e., n(G) / [n(Ni)+n(Co)+n(Me)+n(M)] is greater than 0.05, the G element will be excessively deposited on the particle surface, thereby suppressing the electrochemical activity of the multivalent positive electrode material, and the excess G element will generate more active Li. + Therefore, the capacity of a battery containing the polyvalent positive electrode material decreases due to the consumption of the G element. By controlling the amount of the grain boundary stabilizer used so that it satisfies the above range, an optimal gradient change in the grain boundary concentration of the G element can be achieved, thereby realizing the technical effect of the present invention.

[0055] Furthermore, the grain boundary stabilizer is added in an amount such that the stoichiometric ratio is 0.005≦n(G) / [n(Ni)+n(Co)+n(Me)+n(M)]≦0.04.

[0056] In the present invention, when two or more types of grain boundary stabilizers and a multivalent positive electrode material matrix are mixed to produce a single-crystal multivalent positive electrode material, the amount of each of the various grain boundary stabilizers used is not particularly limited, and the total amount of grain boundary stabilizers added may be within the above range.

[0057] According to the present invention, the mixing conditions include mixing in a device including a stirring paddle, and a linear velocity at the end of the blade of the stirring paddle being 20 m / s or more.

[0058] In the present invention, mixing under the above conditions provides high mixing strength and ensures sufficient and uniform mixing of the grain boundary stabilizer and the polyvalent positive electrode material, while also providing a certain polishing effect to the grain boundary stabilizer, causing the fine powder therein to aggregate at the grain boundaries on the surfaces of the quasi-single crystal particles, making it easier to penetrate and fill the grain boundaries during sintering.

[0059] In the present invention, the equipment containing the stirring paddle is not limited as long as it contains a stirring paddle, and can be, for example, a stirring paddle rotary mixer such as a plowshare mixer, a high-speed mixer, or a mechanical blender.

[0060] In the present invention, the linear velocity v at the end of the blade is expressed as blade diameter x π x rotation speed.

[0061] Further, the mixing conditions include that the mixing is carried out in a device including a stirring paddle, and the linear velocity at the end of the blade of the stirring paddle is 30 to 50 m / s.

[0062] According to the present invention, the sintering conditions include a sintering temperature of 400° C. or higher and a sintering time of 4 hours or longer.

[0063] In the present invention, sintering under the above conditions can achieve effective diffusion and reaction of the grain boundary stabilizer, ensure sufficient depth into the grain boundaries, and create the effect of gradient packing. If the temperature is too low or the time is too short, the grain boundary stabilizer will not react sufficiently, and the technical effect of the present invention will not be achieved. If the temperature is too high or the time is too long, the crystal structure of the polyvalent material will change, resulting in a loss of performance of the positive electrode material.

[0064] Furthermore, the sintering conditions include a sintering temperature of 600 to 900° C. and a sintering time of 6 to 10 hours.

[0065] In the present invention, the type of the polyvalent cathode material is not particularly limited. Conventional polyvalent cathode materials in this field are preferably lithium nickel cobalt manganese oxide cathode materials and / or lithium nickel cobalt aluminum oxide cathode materials.

[0066] In a specific embodiment of the present invention, the polyvalent cathode material matrix has a configuration as shown in Formula IV, Li 1+a (Ni x Co y Me z M w )O2 Formula IV Here, -0.1 ≦ a ≦ 0.1, 0 < x < 1, 0 < y ≦ 0.4, 0 < z ≦ 0.6, 0 ≦ w ≦ 0.2. Me is selected from Mn and / or Al, and M is at least one of Ta, Cr, Mo, W, La, Al, Y, Ti, Zr, V, Nb, Ce, Er, Mg, Sr, and Ba.

[0067] Furthermore, -0.06 ≦ a ≦ 0.06, 0.4 < x < 1, 0 < y ≦ 0.3, 0 < z ≦ 0.5, 0 < w ≦ 0.1.

[0068] Furthermore, Me is selected from Mn and / or Al.

[0069] Furthermore, M is selected from at least one of W, La, Al, Y, Ti, Zr, Nb, Ce, Mg, and Sr.

[0070] In the present invention, the origin of the polyvalent cathode material matrix is not particularly limited, and it can be purchased in the market or made by oneself. The manufacturing method of the polyvalent cathode material is not particularly limited, and it can be manufactured by a conventional manufacturing method in this field.

[0071] In a specific embodiment of the present invention, the polyvalent cathode material matrix is manufactured by a step of obtaining the polyvalent cathode material by mixing a cathode material precursor, a lithium source, and a dopant and then performing heat treatment.

[0072] In the present invention, the cathode material precursor has a structure as shown in Formula V: Ni x Co y Me z (OH)2 Formula V Here, 0 < x < 1, 0 < y ≤ 0.4, 0 < z ≤ 0.6, and Me is selected from Mn and / or Al.

[0073] In the present invention, the lithium source may be a conventional lithium source in this field, such as Li2CO3 and / or LiOH, etc.

[0074] In the present invention, the dopant is a compound containing M, and M is selected from at least one element of Ta, Cr, Mo, W, La, Al, Y, Ti, Zr, V, Nb, Ce, Er, Mg, Sr, and Ba.

[0075] In the present invention, depending on the usage amounts of the lithium source and the cathode material precursor, 0.9 ≤ n(Li) / [n(Ni) + n(Co) + n(Me) + n(M)] ≤ 1.1, and preferably, 0.94 ≤ n(Li) / [n(Ni) + n(Co) + n(Me) + n(M)] ≤ 1.06.

[0076] In the present invention, depending on the usage amounts of the dopant and the cathode material precursor, 0 ≤ n(M) / [n(Ni) + n(Co) + n(Me) + n(M)] ≤ 0.2, and preferably, 0 ≤ n(M) / [n(Ni) + n(Co) + n(Me) + n(M)] ≤ 0.1.

[0077] In the present invention, the dopant is mixed with Ni, Co, and Me in the cathode material precursor, so that n(Ni) + n(Co) + n(Me) + n(M) = 1 in the obtained cathode material. However, when the usage amount of the dopant is low, its content cannot be accurately detected by conventional detection means. At this time, the influence of the ratio of the doping element M to Ni, Co, and Me is small, and n(Ni) + n(Co) + n(Me) + n(M) in the expression formula is slightly larger than 1.

[0078] In the present invention, the heat treatment conditions include a heat treatment temperature of 850 to 950° C. and a heat treatment time of 8 to 10 hours.

[0079] A third aspect of the present invention provides a single-crystal polyvalent positive electrode material produced by the above-described production method.

[0080] A fourth aspect of the present invention provides a lithium ion battery comprising the above-mentioned single crystal polyvalent positive electrode material.

[0081] The present invention will now be described in detail with reference to examples. The composition of the single-crystal polyvalent positive electrode material was determined by inductively coupled plasma spectroscopy. The concentration of the G element in the single-crystal polyvalent positive electrode material is measured by a scanning electron microscope spectroscopic analysis method. The grain boundary length, grain boundary width, major axis, and minor axis of the quasi-single crystal particles in the single crystal type polyvalent positive electrode material are measured by scanning electron microscopy. The major and minor axes of the crystal grains in the single-crystal polyvalent positive electrode material are measured using a scanning electron microscope. The D10, D50, and D90 of the grain boundary stabilizer are measured by the laser diffraction method GB / T 19077-2016. The specific surface area of ​​grain boundary stabilizer is measured by BET method testing GB-T19587-2017, The cycle life, energy density and rate performance of lithium-ion batteries are tested using 2025-type buckle batteries. The manufacturing process of the 2025 type buckle battery is as follows: Preparation of electrode sheet: A polyvalent positive electrode material, acetylene black, and polyvinylidene fluoride (PVDF) were thoroughly mixed with an appropriate amount of N-methylpyrrolidone (NMP) in a mass ratio of 95:3:2 to form a uniform slurry. The slurry was then coated on aluminum foil, dried at 120°C for 12 hours, and press-molded at a pressure of 100 MPa to prepare a positive electrode sheet with a diameter of 12 mm and a thickness of 120 μm. The amount of the polyvalent positive electrode material supported was 15 to 16 mg / cm. 2 is.

[0082] Battery assembly: The positive electrode sheet, separator, negative electrode sheet, and electrolyte were assembled into a 2025-type buckle battery in a gas glove box filled with argon gas with a water and oxygen content of less than 5 ppm, and then left to stand for 6 hours. The negative electrode sheet was a metallic lithium sheet with a diameter of 17 mm and a thickness of 1 mm, the separator was a 25 μm thick polyethylene porous film (Celgard 2325), and the electrolyte was a mixture of equal parts of 1 mol / L LiPF6, ethylene carbonate (EC), and diethyl carbonate (DEC).

[0083] Electrochemical performance testing, In the following examples and comparative examples, [ka] The electrochemical performance test was carried out on the 2025 type buckle battery using the Newwell battery test system, and the 0.1C charge / discharge current density was 200mA / g. The charge / discharge voltage range is controlled to 3.0-4.3V, and the buckled battery is charged / discharged at 0.1C at room temperature to evaluate the initial discharge specific capacity of the multivalent positive electrode material. Cycling performance test: The charge / discharge voltage range was controlled to 3.0-4.3V, and the buckle-type battery was cycled at 0.1C twice at a constant temperature of 45°C, and then cycled at 1C 80 times to evaluate the high-temperature capacity retention of the multivalent positive electrode material.

[0084] Rate performance test: The charge / discharge voltage range was controlled to 3.0-4.3V, and the buckled battery was charged / discharged twice at 0.1C at room temperature, and then charged / discharged once each at 0.2C, 0.33C, 0.5C, and 1C. The rate performance of the multivalent positive electrode material was evaluated by the ratio of the first discharge specific capacity at 0.1C to the discharge specific capacity at 1C. The first discharge specific capacity at 0.1C was the discharge specific capacity of the first cycle of the buckled battery, and the discharge specific capacity at 1C was the discharge specific capacity of the sixth cycle of the buckled battery.

[0085] Impedance increase rate test: The charge / discharge voltage range is controlled to 3.0~4.3V, and the buckled battery is charged to a constant volume of 0.1C at room temperature and tested for HPPC-DCR at 50% SOC. The initial resistance is R1. The buckled battery is then charged / discharged twice at 0.1C at a constant temperature of 45℃, and then charged / discharged 80 times at 1C. After cycling, the buckled battery is charged to a constant volume of 0.1C at room temperature and tested for HPPC-DCR at 50% SOC. The post-cycling resistance is R2. The impedance increase rate of the material is calculated using the formula (R2-R1) / R1×100%.

[0086] Manufacturing example This is to illustrate a method for producing a multivalent positive electrode material.

[0087] Manufacturing Example 1 Ni 0.6 Co 0.2 Mn 0.2 The (OH) precursor, the lithium source LiCO, LiOH, and the dopant Al-containing compound were mixed in a molar ratio of n(Li) / [n(Ni)+n(Co)+n(Mn)+n(Al)]=1.05 and n(Al) / [n(Ni)+n(Co)+n(Mn)+n(Al)]=0.1, and then heat-treated at 900°C for 10 hours to obtain a multivalent positive electrode material P1, whose composition is Li 1.05 Ni 0.54 Co 0.18 Mn 0.18 Al 0.1 It is O2.

[0088] Manufacturing Example 2 Ni 0.8 Co 0.1 Mn 0.1 The (OH)2 precursor, the lithium source LiOH, and the dopant Zr-containing compound are mixed in the molar ratios of n(Li) / [n(Ni)+n(Co)+n(Mn)+n(Zr)]=1.05 and (n(Zr) / [n(Ni)+n(Co)+n(Mn)+n(Zr)]=0.002, and then heat-treated at 850°C for 10 hours to obtain the multivalent positive electrode material P2, whose composition is Li 1.05 Ni 0.8 Co 0.1 Mn 0.1 Zr 0.002 It is O2.

[0089] Manufacturing Example 3 Ni 0.96 Co 0.02 Al 0.02 The (OH)2 precursor, the lithium source LiOH, and the dopant Ti-containing compound were mixed in the ratio of n(Li) / [n(Ni)+n(Co)+n(Al)+n(Ti)]=1.03 and n(Ti) / [n(Ni)+n(Co)+n(Al)+n(Ti)]=0.001, and then heat-treated at 800°C for 10 hours to obtain the multivalent positive electrode material P3, whose composition is Li 1.03 Ni 0.96 Co 0.02 Al 0.02 Ti 0.001 It is O2.

[0090] Manufacturing Example 4 Ni 0.6 Co 0.2 Mn 0.2 The (OH) precursor, lithium source Li2CO3 and LiOH were mixed in a molar ratio of n(Li) / [n(Ni)+n(Co)+n(Mn)]=1.05, and then heat-treated at 900 °C for 10 h to obtain the multivalent positive electrode material P4, whose composition is Li 1.05 Ni 0.6 Co 0.2 Mn 0.2 It is O2.

[0091] The total length L of the grain boundary in the multivalent positive electrode material in the manufacturing example, the width (H) of the grain boundary, and the maximum width (H max ) and minimum value (H min The difference between the diameters of the grains, the major diameter D1 and minor diameter D2 of the quasi-single crystal particles, and the major diameter D3 and minor diameter D4 of the crystal grains were tested, and the results are shown in Table 1.

[0092] [Table 1]

[0093] Example 1

[0094] (1) Mixing polyvalent positive electrode material P1 with cobalt hydroxide powder to obtain a mixture. The mixing equipment is a high-speed blender, and the linear velocity at the end of the mixing blade is 35 m / s. The polyvalent positive electrode material and cobalt hydroxide are added in a stoichiometric ratio of n(Co) / [n(Ni)+n(Co)+n(Mn)+n(Al)]=0.025. The cobalt hydroxide powder contains nanometer-order and submicron-order particles, with D50=0.5 μm, K90=2.3, and a specific surface area of ​​20 m 2 / g. (2) The mixture is sintered at 750°C for 6 hours in an oxygen atmosphere to obtain the single crystal polyvalent positive electrode material A1, which includes a matrix and a coating layer coated on the matrix, and the matrix is ​​composed of Li 1.05 Ni 0.54 Co 0.18 Mn 0.18 Al 0.1 O2, the coating layer is mainly lithium cobalt oxide with a small amount of cobalt oxide, and the molar ratio of the coating layer in terms of n(Co) to the matrix in terms of [n(Ni) + n(Co) + n(Mn) + n(Al)] is 0.025.

[0095] Example 2

[0096] (1) Mixing polyvalent positive electrode material P1 and tungsten oxide powder to obtain a mixture. The mixing equipment is a high-speed blender, and the linear velocity at the end of the mixing blade is 35 m / s. The polyvalent positive electrode material P1 and tungsten oxide are added in a stoichiometric ratio of n(W) / [n(Ni)+n(Co)+n(Mn)+n(Al)]=0.025. The tungsten oxide powder contains nanometer-order and submicron-order particles, with D50=4 μm, K90=3.4, and a specific surface area of ​​14 m. 2 / g. (2) The mixture is sintered at 750°C for 6 hours in an oxygen atmosphere to obtain the single crystal polyvalent positive electrode material A2, which includes a matrix and a coating layer coated on the matrix, and the matrix is ​​composed of Li 1.05 Ni 0.54 Co 0.18 Mn 0.18 Al0.1 O2, the coating layer is mainly lithium tungsten oxide and also contains a small amount of tungsten oxide, and the molar ratio of the coating layer in terms of n(W) to the matrix in terms of [n(Ni) + n(Co) + n(Mn) + n(Al)] is 0.025.

[0097] Example 3 (1) Mixing the polyvalent positive electrode material P1 with titanium boride powder to obtain a mixture. The mixing equipment is a high-speed blender, and the linear velocity at the end of the mixing blade is 35 m / s. The positive electrode material and titanium boride are added in a stoichiometric ratio of n(Ti) / [n(Ni)+n(Co)+n(Mn)+n(Al)]=0.025. The titanium boride powder contains nanometer-order and submicron-order particles, with D50=1 μm, K90=5.6, and a specific surface area of ​​45 m 2 / g. (2) The mixture is sintered at 750°C for 6 hours in an oxygen atmosphere to obtain the single crystal polyvalent positive electrode material A3, which includes a matrix and a coating layer coated on the matrix, and the matrix is ​​composed of Li 1.05 Ni 0.54 Co 0.18 Mn 0.18 Al 0.1 O2, the coating layer is mainly lithium titanium oxide and also contains a small amount of titanium oxide, and the molar ratio of the coating layer in terms of n(Ti) to the matrix in terms of [n(Ni) + n(Co) + n(Mn) + n(Al)] is 0.025.

[0098] Example 4 (1) Mixing the polyvalent positive electrode material P1 with alumina powder to obtain a mixture. The mixing equipment is a high-speed blender, and the linear velocity at the end of the mixing blade is 35 m / s. The positive electrode material and alumina are added in a stoichiometric ratio of n(Al) / [n(Ni)+n(Co)+n(Mn)+n(Al)]=0.025. The alumina powder contains nanometer-order and submicron-order particles, with D50=3.8 μm, K90=2, and a specific surface area of ​​78 m. 2 / g. (2) The mixture is sintered at 750°C for 6 hours in an oxygen atmosphere to obtain the single crystal polyvalent positive electrode material A4, which includes a matrix and a coating layer coated on the matrix, and the matrix is ​​composed of Li 1.05 Ni 0.54 Co 0.18 Mn 0.18 Al 0.1 O2, the coating layer is mainly lithium aluminum oxide, and also contains a small amount of aluminum oxide, and the molar ratio of the coating layer in terms of n(Al) to the matrix in terms of [n(Ni) + n(Co) + n(Mn) + n(Al)] is 0.025.

[0099] Example 5 (1) Mixing the polyvalent positive electrode material P1 with alumina and zirconia powder to obtain a mixture. The mixing equipment is a high-speed blender, and the linear velocity at the end of the mixing blade is 35 m / s. The alumina is added in a stoichiometric ratio of n(Al) / [n(Ni)+n(Co)+n(Mn)+n(Al)]=0.025. The zirconia is added in a stoichiometric ratio of n(Zr) / [n(Ni)+n(Co)+n(Mn)+n(Al)]=0.025. The alumina powder contains nanometer-order and submicron-order particles, with D50=3.8 μm, K90=2, and a specific surface area of ​​78 m. 2 / g, the zirconia powder contains nanometer-order and submicron-order particles, its D50=6 μm, K90=2.8, and specific surface area is 34 m 2 / g. (2) The mixture is sintered at 600°C for 8 hours in an oxygen atmosphere to obtain a single crystal polyvalent positive electrode material A5, which includes a matrix and a coating layer covering the matrix, and the matrix is ​​composed of Li 1.05 Ni 0.54 Co 0.18 Mn 0.18 Al 0.1O2, and the coating layer mainly contains lithium aluminum oxide and lithium zirconium oxide, with small amounts of aluminum oxide and zirconium oxide. The molar ratio of the coating layer in terms of [n(Al) + n(Zr)] to the matrix in terms of [n(Ni) + n(Co) + n(Mn) + n(Al)] is 0.05. Within the coating layer, the molar ratio of the alumina in terms of n(Al) to the lithium aluminum oxide in terms of [n(Ni) + n(Co) + n(Mn) + n(Al)] to the matrix in terms of [n(Ni) + n(Co) + n(Mn) + n(Al)] is 0.025, and the molar ratio of the zirconia in terms of n(Zr) to the lithium zirconium oxide in terms of [n(Ni) + n(Co) + n(Mn) + n(Al)] to the matrix in terms of [n(Ni) + n(Co) + n(Mn) + n(Al)] is 0.025.

[0100] Example 6 A single crystal multivalent positive electrode material was prepared by the method of Example 1, except that P2 was used instead of P1. A single crystal multivalent positive electrode material A6 was obtained, which included a matrix and a coating layer coated on the matrix. The matrix was composed of Li 1.05 Ni 0.8 Co 0.1 Mn 0.1 Zr 0.002 O2, the coating layer is mainly lithium cobalt oxide and also contains a small amount of cobalt oxide, and the molar ratio of the coating layer in terms of n(Co) to the matrix in terms of [n(Ni) + n(Co) + n(Mn) + n(Zr)] is 0.025.

[0101] Example 7 A single-crystal multivalent positive electrode material was prepared by the method of Example 1, except that P3 was used instead of P1. A single-crystal multivalent positive electrode material A7 was obtained, which included a matrix and a coating layer coated on the matrix. The matrix was composed of Li 1.03 Ni 0.96 Co 0.02 Al 0.02 Ti 0.001O2, the coating layer is mainly lithium cobalt oxide with a small amount of cobalt oxide also present, and the molar ratio of the coating layer in terms of n(Co) to the matrix in terms of [n(Ni) + n(Co) + n(Al) + n(Ti)] is 0.025.

[0102] Example 8 A single crystal polyvalent positive electrode material was prepared by the method of Example 1, except that P4 was used instead of P1. A single crystal polyvalent positive electrode material A8 was obtained, which included a matrix and a coating layer coated on the matrix. The matrix was composed of Li 1.05 Ni 0.6 Co 0.2 Mn 0.2 O2, the coating layer is mainly lithium cobalt oxide and also contains a small amount of cobalt oxide, and the molar ratio of the coating layer in terms of n(Co) to the matrix in terms of [n(Ni) + n(Co) + n(Mn)] is 0.025.

[0103] Example 9 A single-crystal polyvalent positive electrode material was prepared by the method of Example 1, except that the polyvalent positive electrode material and cobalt hydroxide were added in a stoichiometric ratio of n(Co) / [n(Ni)+n(Co)+n(Mn)+n(Al)]=0.001. A single-crystal polyvalent positive electrode material A9 was obtained, which included a matrix and a coating layer coated on the matrix. The matrix was composed of Li 1.05 Ni 0.6 Co 0.2 Mn 0.2 O2, the coating layer is mainly lithium cobalt oxide and also contains a small amount of cobalt oxide, and the molar ratio of the coating layer in terms of n(Co) to the matrix in terms of [n(Ni) + n(Co) + n(Mn)] is 0.001.

[0104] Example 10 A single crystal polyvalent positive electrode material was produced by the method of Example 1, except that the linear velocity at the end of the stirring blade was 10 m / s. A single crystal polyvalent positive electrode material A10 was obtained, which included a matrix and a coating layer coated on the matrix. The matrix was composed of Li 1.05 Ni0.54 Co 0.18 Mn 0.18 Al 0.1 O2, the coating layer is mainly lithium cobalt oxide with a small amount of cobalt oxide also present, and the molar ratio of the coating layer in terms of n(Co) to the matrix in terms of [n(Ni) + n(Co) + n(Mn) + n(Al)] is 0.025.

[0105] Example 11 A single crystal type multivalent positive electrode material was produced by the method of Example 1, except that the sintering temperature was 400°C. A single crystal type multivalent positive electrode material A11 was obtained, which included a matrix and a coating layer coated on the matrix. The matrix was composed of Li 1.05 Ni 0.54 Co 0.18 Mn 0.18 Al 0.1 O2, the coating layer is mainly lithium cobalt oxide with a small amount of cobalt oxide also present, and the molar ratio of the coating layer in terms of n(Co) to the matrix in terms of [n(Ni) + n(Co) + n(Mn) + n(Al)] is 0.025.

[0106] Example 12 A single crystal polyvalent positive electrode material was prepared by the method of Example 1, except that the sintering time was 2 hours. A single crystal polyvalent positive electrode material A12 was obtained, which included a matrix and a coating layer coated on the matrix. The matrix was composed of Li 1.05 Ni 0.54 Co 0.18 Mn 0.18 Al 0.1 O2, the coating layer is mainly lithium cobalt oxide with a small amount of cobalt oxide also present, and the molar ratio of the coating layer in terms of n(Co) to the matrix in terms of [n(Ni) + n(Co) + n(Mn) + n(Al)] is 0.025.

[0107] Comparative Example 1 A single-crystal polyvalent positive electrode material was prepared using the method of Example 1, except that the cobalt hydroxide powder contained only submicron-order particles, with a D50 of 14 μm and a K90 of 1, and a specific surface area of ​​6 m 2 A single-crystal polyvalent positive electrode material D1 is obtained, which includes a matrix and a coating layer coated on the matrix, and the matrix is ​​composed of Li 1.05 Ni 0.54 Co 0.18 Mn 0.18 Al 0.1 O2, the coating layer is mainly lithium cobalt oxide with a small amount of cobalt oxide also present, and the molar ratio of the coating layer in terms of n(Co) to the matrix in terms of [n(Ni) + n(Co) + n(Mn) + n(Al)] is 0.025.

[0108] Comparative Example 2 Ni 0.6 Co 0.2 Mn 0.2 The (OH)2 precursor, lithium sources Li2CO3 and LiOH, and the dopant Al-containing compound were mixed in the molar ratios of n(Li) / [n(Ni)+n(Co)+n(Mn)+n(Al)]=1.05 and n(Al) / [n(Ni)+n(Co)+n(Mn)+n(Al)]=0.1, and then cobalt hydroxide powder was added in the molar ratio of n(Co) / [n(Ni)+n(Co)+n(Mn)+n(Al)]=0.025. The cobalt hydroxide powder contained both nanometer-order and submicron-order particles, with D50=0.5 μm, K90=2.3, and a specific surface area of ​​20 m 2 / g, and heat treatment at 900 °C for 10 h yielded a multivalent positive electrode material D2, the composition of which is Li 1.05 Ni 0.53 Co 0.2 Mn 0.18 Al 0.09 It is O2.

[0109] [Table 2-1]

[0110] [Table 2-2]

[0111] Coexistence of G elements C1 and C2 at different sites in the multivalent positive electrode materials of the Production Examples, Examples, and Comparative Examples g , C2 (mol%) were tested, and the results are shown in Table 3.

[0112] In Table 3, when calculating whether the data proportion satisfies the formula II, the standard used is related to the content of the G element. Specifically, when C1>5%, the value range of k is 0.9-1.1, and when C1≦5%, the value range of k is 0.8-1.2.

[0113] [Table 3-1] [Table 3-2]

[0114] [Table 3-3]

[0115] [Table 3-4]

[0116] [Table 3-5]

[0117] [Table 3-6]

[0118] [Table 3-7]

[0119] [Table 3-8]

[0120] [Table 3-9]

[0121] Table 4 shows the coefficient k values ​​calculated by Equation II at each site in the examples and comparative examples.

[0122] In Table 4, when calculating whether the data satisfy the data proportion of Formula II, the standard used is related to the content of the G element. Specifically, when C1>5%, the value range of k is 0.9 to 1.1, and when C1≦5%, the value range of k is 0.8 to 1.2.

[0123] [Table 4-1]

[0124] [Table 4-2]

[0125] [Table 4-3]

[0126] [Table 4-4]

[0127] [Table 4-5]

[0128] [Table 4-6]

[0129] [Table 4-7]

[0130] [Table 4-8]

[0131] [Table 4-9]

[0132] Figure 2 is a schematic diagram of the grain boundary stabilizer cobalt hydroxide containing micron and submicron ions. As can be seen from Figure 2, the grain boundary stabilizer has a wide particle size distribution, with large differences in particle size. Figure 3 is a cross-sectional schematic diagram of the single-crystal polyvalent positive electrode material produced in Example 1. The numbers in the figure indicate examples of measurement sites for the concentration of elements within the grain boundaries.

[0133] The positive electrode materials of the Preparation Examples, Examples and Comparative Examples were assembled into lithium ion batteries, and the electrochemical performance of the lithium ion batteries was tested. The results are shown in the table below.

[0134] [Table 5]

[0135] As can be seen from Tables 3, 4, and 5, comparing Preparation Example 1 with Comparative Examples 1 and 2, the cathode materials prepared in Examples 1 to 12 of the present invention all contain an interfacial stabilizer element, and the concentration of the G element at the g site of the grain boundary gradually decreases as the distance between the g site and the surface of the quasi-single crystalline particle increases. When the cathode materials are used in lithium ion batteries, the initial discharge capacity, rate performance, and cycling performance of the lithium ion batteries can be significantly improved, and the impedance increase rate can be reduced.

[0136] Furthermore, compared to Examples 9 to 12, the concentration gradient of the grain boundary stabilizer at the grain boundaries in the positive electrode materials prepared in Examples 1 to 8 was more pronounced. In Examples 9 to 12, the gradient distribution was less uniform, the concentration at the surface of the material was higher, and the difference in concentration near the interior of the particle was smaller. Some data was outside the calculation range of Equation II. When the positive electrode materials prepared in Examples 1 to 8 were used in a lithium ion battery, the lithium ion battery could simultaneously have high first discharge specific capacity, rate performance, and cycling performance, and the impedance increase rate was lower, resulting in optimal overall battery performance.

[0137] Furthermore, Examples 2 to 4 show positive electrode materials prepared with different types of grain boundary stabilizers, all of which have good grain boundary concentration gradient filling effects. When the positive electrode materials are used in lithium ion batteries, they can improve the initial discharge capacity, rate performance, cycling performance, and impedance increase rate of the lithium ion batteries.

[0138] Furthermore, Example 5 shows a positive electrode material prepared with two different types of grain boundary stabilizers. Both stabilizers have a concentration gradient filling effect, but because the total amount of grain boundary stabilizer added is higher, when used in a lithium-ion battery, the battery capacity is slightly reduced, but the cycling performance is relatively better.

[0139] Furthermore, as can be seen from Examples 6 and 7, similar effects can be achieved with different NCM configurations. In Example 7, due to the low overall concentration, the range calculated by Equation II is narrow, which limits the test stability. The percentage of sites that meet the calculated range is 89%. However, these related circumstances do not affect the assessment of the gradient concentration effect, and when used in lithium-ion batteries, this effect improves various battery performances.

[0140] Furthermore, as can be seen from Example 8, whether the positive electrode material is doped or not does not affect the improving effect of the grain boundary stabilizer on concentration gradient filling of the grain boundaries.

[0141] In the positive electrode material prepared in Comparative Example 1, the grain boundary stabilizer contains only micron-order particles, resulting in a narrow particle size distribution and low overall reactivity, and the main element of the grain boundary stabilizer is abundant on the outer surface of the quasi-single crystalline particles and cannot diffuse smoothly into the grain boundaries, resulting in the lack of concentration gradient filling effect within the grain boundaries. When used in a lithium ion battery, the overall performance is similar to that of Preparation Example 1 and does not reach the performance level of Example 1. Figure 4 compares the cycling performance at a 1C rate of the positive electrode materials prepared in Preparation Example 1, Example 1, and Comparative Example 1, and as can be seen from Figure 4, the difference in performance is significant.

[0142] The positive electrode material prepared in Comparative Example 2 was sintered after adding a grain boundary stabilizer at the stage of mixing the precursor and lithium salt. As can be seen from the results, there was no difference in concentration between the surface and bulk phases, and there was no concentration gradient distribution effect at the grain boundaries. Therefore, when used in a lithium ion battery, the performance performance did not show any significant improvement compared to Preparation Example 1.

[0143] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited thereto. Within the technical conception of the present invention, various simple modifications can be made to the technical solutions of the present invention, including combining each technical feature in any other suitable manner, and these simple modifications and combinations are also considered to be the contents disclosed in the present invention, and all belong to the protection scope of the present invention.

Claims

1. A single-crystal polyvalent positive electrode material, the polyvalent positive electrode material including quasi-single-crystal particles consisting of a plurality of crystal grains, and a G element present at grain boundaries between the crystal grains, The concentration of G elements at the g-site of the grain boundary gradually decreases as the distance between the g-site and the surface of the quasi-single crystal grain increases. the G element is selected from at least one of Ni, Co, Mn, Ta, Cr, Mo, W, La, Al, Y, Ti, Zr, V, Nb, Ce, Er, and B; the single-crystal polyvalent positive electrode material includes a matrix and a coating layer coated on the matrix, The matrix has the configuration shown in Formula III: Li １＋ａ (Ni ｘ Co ｙ Me ｚ M ｗ )O ２ Formula III -0.1≦a≦0.1, 0<x<1, 0<y≦0.4, 0<z≦0.6, 0≦w≦0.2, Me is selected from Mn and / or Al, and M is at least one element selected from Ta, Cr, Mo, W, La, Al, Y, Ti, Zr, V, Nb, Ce, Er, Mg, Sr, and Ba; the coating layer is selected from a lithium oxygen compound of a G element and / or an oxide of a G element, A single-crystal polyvalent positive electrode material, characterized in that the molar ratio of the coating layer in terms of n(G) to the matrix in terms of [n(Ni) + n(Co) + n(Me) + n(M)] is 0.001 to 0.

05.

2. In the SEM image of the cross-sectional sample of the quasi-single crystal grain, the concentration of the G element at the g site of the grain boundary satisfies the following relationship: 1.2C １ ≧C ｇ ≧0.8C ２ Formula I [Equation 1] C １ is the concentration (mol%) of the G element on the surface of the quasi-single crystal particle, and C ２ is the concentration (mol%) of the G element in the quasi-single crystal particle bulk phase, and C ｇ is the concentration (mol%) of the G element at the g site of the grain boundary, L is the total length (μm) of the grain boundary passing through the g site, and L ｇ is the shortest path length (μm) from the g site along the grain boundary to the surface of the quasi-single crystal particle, k is a coefficient, and the value range of k is 0.8 to 1.

2. The single crystal polyvalent positive electrode material according to claim 1.

3. 1.1C １ ≧C ｇ ≧0.9C ２ The monocrystalline polyvalent positive electrode material according to claim 2 ,

4. 3. The monocrystalline polyvalent positive electrode material according to claim 2, wherein the total length L of the grain boundary obtained by spectroscopic analysis using a scanning electron microscope satisfies 0.01 μm≦L≦8 μm.

5. C １ -C ２ 5. The monocrystalline polyvalent positive electrode material according to claim 4, wherein the SiO 2 content is ≧0.2%.

6. C １ >5%, the value range of k is 0.9 to 1.1, and C １ 5%, the value range of k is 0.8 to 1.

2. The monocrystalline polyvalent positive electrode material according to claim 4.

7. The major diameter D of the quasi-single crystal particle １ is 0.1 μm≦D １ ≦20 μm, and the minor diameter D ２ is 0.1 μm≦D ２ The single crystal polyvalent positive electrode material according to claim 1 or 2, wherein the particle size satisfies the following: ≦20 μm.

8. The single crystal polyvalent positive electrode material according to claim 7, wherein the grain boundary width is 1 to 50 nm, and the difference between the maximum value of the grain boundary width and the minimum value of the grain boundary width is 20 nm or less.

9. 1. A method for producing a monocrystalline polyvalent positive electrode material, the method comprising: a step of mixing a multivalent positive electrode material matrix with a grain boundary stabilizer containing a G element, and then sintering the resulting material to obtain the single-crystal multivalent positive electrode material; the G element is selected from at least one of Ni, Co, Mn, Ta, Cr, Mo, W, La, Al, Y, Ti, Zr, V, Nb, Ce, Er, and B; The grain boundary stabilizer has a D50 of 0.01 to 10 μm, and the D10, D50, and D90 of the grain boundary stabilizer satisfy K90=(D90−D10) / D50≧1.5; The multivalent positive electrode material matrix has a structure as shown in Formula IV: Li １＋ａ (Ni ｘ Co ｙ Me ｚ M ｗ )O ２ Formula IV wherein -0.1≦a≦0.1, 0<x<1, 0<y≦0.4, 0<z≦0.6, 0≦w≦0.2, Me is selected from Mn and / or Al, and M is at least one of Ta, Cr, Mo, W, La, Al, Y, Ti, Zr, V, Nb, Ce, Er, Mg, Sr, and Ba.

10. 10. The manufacturing method according to claim 9, wherein the grain boundary stabilizer is added in an amount such that the stoichiometric ratio is 0.001≦n(G) / [n(Ni)+n(Co)+n(Me)+n(M)]≦0.

05.

11. The mixing conditions are that the mixture is mixed in a facility including a stirring paddle, and the linear velocity of the end of the blade of the stirring paddle is 20 m / s or more, and the sintering conditions are that the sintering temperature is 400°C or more, and the sintering temperature is 100°C or more. The method according to claim 10, wherein the sintering time is 4 hours or more.

12. A lithium ion battery comprising the single crystal polyvalent positive electrode material according to claim 1 or 2.

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