Multinary positive electrode material and preparation method thereof, lithium ion battery

Abstract

This invention relates to the field of lithium-ion battery technology, and discloses a multi-element cathode material, its preparation method, and a lithium-ion battery. The surface of the multi-element cathode material includes dot-like coatings and / or island-like coatings; the cumulative particle size distribution of the multi-element cathode material is such that 1% of the particles have a diameter D1 ≥ 0.7 μm; the arithmetic mean roughness Ra of the coatings, measured by a three-dimensional scanning electron microscope, satisfies: 20 nm ≤ Ra ≤ 200 nm; the coverage Q of the dot-like coatings and / or island-like coatings of the multi-element cathode material satisfies: 3% ≤ Q ≤ 30%. The surface of the multi-element cathode material contains dot-like coatings and / or island-like coatings, and these coatings have specific arithmetic mean roughness and coverage, and the multi-element cathode material has a large particle size distribution D1, thereby reducing the content of micropowder in the multi-element cathode material, resulting in lithium-ion batteries containing this cathode material exhibiting excellent capacity and cycle performance.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a multi-element cathode material and its preparation method, and a lithium-ion battery. Background Technology

[0002] In recent years, lithium-ion batteries have been widely used in portable electronic devices, electric vehicles, and energy storage systems due to their high energy density.

[0003] Although lithium-ion batteries are widely used, electric vehicles still cannot meet the needs of most consumers compared to gasoline vehicles. The main reasons are the low driving range, poor low-temperature performance, and safety issues of electric vehicles.

[0004] The cathode material is a major factor limiting the performance of lithium-ion batteries. Graphite anodes can achieve an energy density of 360 mAh / g, while ternary 622 cathode materials, for example, only have an energy density of 180 mAh / g. Furthermore, the cathode material is the most expensive and heaviest component of a lithium-ion battery. Therefore, improving the energy density of cathode materials and enhancing cycle stability can effectively reduce the weight and price of electric vehicles. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem that the capacity and cycle performance of existing lithium-ion battery cathode materials cannot meet practical needs, and to provide a multi-element cathode material, its preparation method, and a lithium-ion battery. The surface of the multi-element cathode material includes dot-like coatings and / or island-like coatings, and the coatings have specific arithmetic mean roughness and coverage. Furthermore, the multi-element cathode material has a large particle size distribution D1, thereby reducing the content of micropowder in the multi-element cathode material, so that the lithium-ion battery containing the cathode material has excellent capacity and cycle performance.

[0006] To achieve the above objectives, the first aspect of the present invention provides a multi-element cathode material, wherein the surface of the multi-element cathode material includes dot-shaped coatings and / or island-shaped coatings;

[0007] The cumulative particle distribution of the multi-element cathode material is that 1% of the particles have a diameter D1 ≥ 0.7 μm;

[0008] The arithmetic mean roughness Ra of the coating of the multi-element cathode material, as measured by a three-dimensional scanning electron microscope, satisfies: 20nm≤Ra≤200nm;

[0009] The coverage rate Q of the dot-shaped and / or island-shaped coatings of the multi-element cathode material satisfies: 3% ≤ Q ≤ 30%.

[0010] A second aspect of the present invention provides a method for preparing a multi-element cathode material, the method comprising:

[0011] (1) Mix the multi-component cathode material precursor, the first lithium source and optional dopant, and then sinter at a first high temperature to obtain the multi-component cathode material process product 1.

[0012] (2) After coarsely crushing the multi-element cathode material process product 1, it is successively washed with acid solution, washed with water and dried to obtain multi-element cathode material process product 2.

[0013] (3) The multi-element cathode material process product 2, optionally the second lithium source and the coating agent are mixed, and the mixture is subjected to a second high-temperature sintering and sieve to obtain the multi-element cathode material;

[0014] The conditions for rinsing with the acid solution include: the concentration of the acid solution is 0.01-0.05 g / mL, and the rinsing time is 1-120 s;

[0015] The sintering temperature T2 for the second high-temperature sintering is 200-1000℃;

[0016] The amount of the coating agent added is based on a stoichiometric ratio of 0 < [n(J)] / [n(Ni)+n(Co)+n(Mn)] ≤ 0.03.

[0017] A third aspect of the present invention provides a multi-element cathode material prepared by the above method.

[0018] A fourth aspect of the present invention provides a lithium-ion battery comprising the aforementioned multi-element cathode material.

[0019] Through the above technical solutions, the multi-element cathode material, its preparation method, and the lithium-ion battery provided by this invention achieve the following beneficial effects:

[0020] The multi-element cathode material provided by the present invention has dot-shaped coatings and / or island-shaped coatings on its surface, and the coatings have specific arithmetic mean roughness and coverage. Furthermore, the multi-element cathode material has a large particle size distribution D1, thereby reducing the content of micro powder in the multi-element cathode material and enabling lithium-ion batteries containing the cathode material to have excellent capacity and cycle performance.

[0021] In the method for preparing multi-element cathode materials provided by the present invention, acid solution washing is used to achieve the dissociation of the multi-element cathode material process product 1 obtained by the first high-temperature sintering. This can achieve a better dissociation effect and does not produce micropowder, thus avoiding the generation of a large amount of micropowder caused by traditional strong dissociation methods. This also avoids the reduction in the cycle performance and storage performance of lithium-ion batteries caused by poor slurry dispersion, uneven coating, and consumption of electrolyte due to the presence of excessive micropowder. Attached Figure Description

[0022] Figure 1Here is a SEM image of the multi-element cathode material process product 2 prepared in Example 1;

[0023] Figure 2 This is a SEM image of the multi-element cathode material prepared in Example 1; the boxes indicate areas selected at 1 μm. 2 Calculate the coverage area.

[0024] Figure 3 SEM image of the multi-element cathode material process product 2 prepared in Comparative Example 1;

[0025] Figure 4 SEM image of the multi-element cathode material prepared in Comparative Example 1;

[0026] Figure 5 The graph shows the cycling performance of the cathode materials prepared in Example 1 and Comparative Example 1 at a 1C rate, where the test temperature was 45°C and the voltage range was 3-4.3V. Detailed Implementation

[0027] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0028] The first aspect of the present invention provides a multi-element cathode material, characterized in that the surface of the multi-element cathode material includes dot-shaped coatings and / or island-shaped coatings;

[0029] The cumulative particle distribution of the multi-element cathode material is that 1% of the particles have a diameter D1 ≥ 0.7 μm;

[0030] The arithmetic mean roughness Ra of the coating of the multi-element cathode material, as measured by a three-dimensional scanning electron microscope, satisfies: 20nm≤Ra≤200nm;

[0031] The coverage rate Q of the dot-shaped and / or island-shaped coatings of the multi-element cathode material satisfies: 3% ≤ Q ≤ 30%.

[0032] In the existing technology, the multi-component cathode material is mostly a hard block with severe adhesion between particles. After strong dissociation, it is easy to form micro powder, which remains on the surface of the multi-component cathode or is mixed in the multi-component cathode material. During the battery manufacturing process, this will lead to poor slurry dispersion and uneven coating. In addition, the micro powder will consume more electrolyte, thus affecting the cycle and storage performance of lithium-ion batteries.

[0033] In this invention, the multi-element cathode material has a large particle size distribution D1, indicating that there are fewer small particles in the multi-element cathode material and a lower content of micro powder, which makes the lithium-ion battery containing this cathode material have excellent capacity and cycle performance.

[0034] Furthermore, surface coating of cathode materials can significantly improve the structural stability of the materials. In the prior art, in order to improve the cycle and storage performance of lithium-ion batteries, most studies have focused on the influence of the type of coating element on the material. However, the inventors of this invention have found that the amount and state of the coating on the surface of the multi-element cathode material also have a very important influence on the multi-element cathode material. Specifically, when the dot-shaped coating and / or island-shaped coating contained on the surface of the multi-element cathode material have the arithmetic mean roughness and coverage defined in this invention, the lithium-ion battery made from the multi-element cathode material has better electrical performance.

[0035] Furthermore, in this invention, the multi-element cathode material has a low micron powder content, which avoids excessive adsorption of micron powder by the coating agent, leading to a reduction in effective coating and consequently a decrease in the capacity of the lithium-ion battery containing the multi-element cathode material. At the same time, the low micron powder content of the multi-element cathode material in this invention enables the lithium-ion battery made from it to still exhibit excellent cycle performance and capacity while reducing the amount of coating agent used.

[0036] In this invention, the surface arithmetic mean roughness of the coating of the multi-element cathode material was measured using a three-dimensional scanning electron microscope (3D-SEM) according to the method of JIS B 0601 (2001). The coverage of the coating was calculated to be 1 μm on the surface of a single particle under electron microscopy. 2 The total area of ​​dot-like and / or island-like coatings within the region divided by 1 μm 2 The area of ​​the region. For example... Figure 2 The area marked by the Chinese box is the average value of the area from 300 different particles.

[0037] In a preferred embodiment of the present invention, the cumulative particle distribution of the multi-element cathode material is such that 1% of the particles have a particle size that satisfies 1μm≤D1≤2μm;

[0038] The arithmetic mean roughness Ra of the coating of the multi-element cathode material, as measured by a three-dimensional scanning electron microscope, satisfies 30nm≤Ra≤100nm;

[0039] The coverage rate Q of the dot-shaped and / or island-shaped coatings of the multi-element cathode material satisfies: 5% ≤ Q ≤ 15%.

[0040] According to the present invention, the cumulative particle distribution of the multi-element cathode material is 50% of the particle size D.50 The size is 2-8 μm, preferably 2.5-7 μm.

[0041] In this invention, the particle size D1 of the multi-element cathode material has a cumulative particle distribution of 1%, and the particle size D1 has a cumulative particle distribution of 50%. 50 The particle size was measured using a laser particle size analyzer.

[0042] According to the present invention, the average primary particle size P of the multi-element cathode material is measured by SEM. 50 The size is 0.8-6μm, preferably 1-4μm.

[0043] According to the present invention, the specific surface area S of the multi-element cathode material satisfies: 0.2 m² / s². 2 / g≤S≤1.2m 2 / g, and / or, 1 / P 50 -0.1≤S≤1 / P 50 +0.2.

[0044] In this invention, P 50 S is in μm, and S is in m 2 The units are / g, and the above relationships are only numerical.

[0045] In this invention, the multi-element cathode material has a large particle size distribution D1 and a small specific surface area S, and the specific surface area increases with the average size P of the primary particles. 50 The specific surface area S decreases as the number of particles increases, and the average primary particle size P decreases as the number of particles increases. 50 Size showed a clear correlation, establishing the relationship between macroscopic indicators and microscopic particle size. Specifically, when the specific surface area S of the multi-element cathode material simultaneously satisfies 0.2 m²... 2 / g≤S≤1.2m 2 / g and 1 / P 50 -0.1≤S≤1 / P 50 +0.2 indicates that appropriate dissociation and coating-reheating conditions were used during the preparation of the cathode material. This demonstrates that the multi-element cathode material provided by this invention neither excessively dissociates to produce micropowder nor suffers from excessive adhesion due to insufficient dissociation. If the particle size distribution D1 is too small (i.e., the micropowder content is high), the specific surface area S of the multi-element cathode material will be too large. Insufficient dissociation leading to excessive adhesion results in a smaller specific surface area S of the multi-element cathode material. Therefore, the specific surface area S and the average size P of the primary particles are related. 50 Unable to establish good arithmetic relationships.

[0046] In this invention, the surface coating condition also affects the specific surface area of ​​the material. Excessive surface coating residue results in a larger specific surface area, while insufficient surface coating residue results in a smaller specific surface area. Only when the surface coating residue is within a suitable range can the above relationship be established, and the electrochemical performance of the multi-element cathode material is better.

[0047] Furthermore, the specific surface area S of the multi-element cathode material satisfies: 0.3 m² / s. 2 / g≤S≤1m 2 / g, and / or, 1 / P 50 -0.05≤S≤1 / P 50 +0.05.

[0048] In a preferred embodiment of the present invention, the specific surface area S of the multi-element cathode material satisfies: 0.2 m² / s². 2 / g≤S≤1.2m 2 / g, and 1 / P 50 -0.1≤S≤1 / P 50 +0.2;

[0049] Preferably, 0.3m 2 / g≤S≤1m 2 / g, and 1 / P 50 -0.05≤S≤1 / P 50 +0.05.

[0050] According to the present invention, the multi-element cathode material is a spherical and / or ellipsoidal particle.

[0051] According to the present invention, the matrix of the multi-element cathode material has the composition shown in Formula I, and the coating includes lithium oxide compound containing element J and / or oxide containing element J;

[0052] Li a Ni x Mn y Co z M b O2 type I;

[0053] Where, 0.9≤a≤1.1, 0.5≤x<1, 0 <y<0.5,0<z<0.5,0≤b≤0.02;

[0054] The content of the matrix and the coating is such that 0 < [n(J)] / [n(Ni)+n(Co)+n(Mn)] ≤ 0.03 in the cathode material;

[0055] M and J are each independently selected from at least one of Ba, Ra, Zr, Fe, Ca, Zn, B, W, Nb, Cd, Pb, Si, Mo, Cu, V, Ta, Cr, La, Al, Ce, Er, Ho, Y, Mg, Sr, and Ti.

[0056] In this invention, the lithium oxide compound containing element J and / or the oxide containing element J may also include at least one element selected from Ni, Co, Mn, and M from the matrix.

[0057] Furthermore, 1≤a≤1.06, 0.6≤x<1, 0≤y≤0.4, 0≤z≤0.4, 0.001≤b≤0.01;

[0058] The content of the matrix and the coating is such that 0.001 ≤ [n(J)] / [n(Ni)+n(Co)+n(Mn)] ≤ 0.01 in the cathode material;

[0059] M and J are each independently selected from at least one of Ba, Zr, B, W, Nb, La, Al, Y, Mg, Sr and Ti.

[0060] A second aspect of the present invention provides a method for preparing a multi-element cathode material, the method comprising:

[0061] (1) Mix the multi-component cathode material precursor, the first lithium source and optional dopant, and then sinter at a first high temperature to obtain the multi-component cathode material process product 1.

[0062] (2) After coarsely crushing the multi-element cathode material process product 1, it is successively washed with acid solution, washed with water and dried to obtain multi-element cathode material process product 2.

[0063] (3) The multi-element cathode material process product 2, optionally the second lithium source and the coating agent are mixed, and the mixture is subjected to a second high-temperature sintering and sieve to obtain the multi-element cathode material;

[0064] The conditions for rinsing with the acid solution include: the concentration of the acid solution is 0.01-0.05 g / mL, and the rinsing time is 1-120 s;

[0065] The sintering temperature T2 for the second high-temperature sintering is 200-1000℃;

[0066] The amount of the coating agent added is based on a stoichiometric ratio of 0 < [n(J)] / [n(Ni)+n(Co)+n(Mn)] ≤ 0.03.

[0067] In the existing technology, due to the high sintering temperature during the preparation of multi-element cathode materials, hard blocks are easily formed after sintering, and the particles are severely adhered to each other. Strong dissociation methods are required for dissociation, and strong dissociation methods are prone to forming micro powder.

[0068] In this invention, the method for preparing multi-element cathode materials uses acid solution rinsing to achieve the dissociation of the multi-element cathode material process product 1 obtained from the first high-temperature sintering. This achieves a good dissociation effect and does not produce micropowder, avoiding the generation of a large amount of micropowder caused by traditional strong dissociation methods. This also avoids the reduction in the cycle performance and storage performance of lithium-ion batteries caused by poor slurry dispersion, uneven coating, and consumption of electrolyte due to excessive micropowder.

[0069] Furthermore, acid rinsing corrodes the surface of the ternary cathode material 1, increasing the surface roughness of the resulting ternary cathode material 2. Simultaneously, the absence of adhering particles on the surface of ternary cathode material 2 allows for a tighter bond between the coating and the surface of the resulting ternary cathode material after a second high-temperature sintering process with the coating agent. Moreover, the coating is less likely to detach from the cathode material surface during lithium-ion battery cycling, achieving a better coating effect. Specifically, controlling the acid rinsing conditions to meet the aforementioned range ensures that the particles of the resulting ternary cathode material separate from each other without generating micropowder. Specifically, if the acid solution concentration is too low or the rinsing time is too short, separation cannot be achieved; if the acid solution concentration is too high or the rinsing time is too long, the surface structure of the ternary cathode material will be damaged, ultimately leading to a decrease in the performance of the lithium-ion battery containing this ternary cathode material.

[0070] Furthermore, in this invention, by rinsing the multi-component cathode material process product 1 with an acid solution, the multi-component cathode material has a low micron powder content. This ensures that the lithium-ion battery containing the multi-component cathode material provided by this invention still has excellent cycle performance and high capacity even when the amount of coating agent added is reduced.

[0071] In this invention, the multi-element cathode material process product 2 is a spherical and / or ellipsoidal particle with good independence.

[0072] Furthermore, rinsing with an acid solution washes away residual lithium carbonate and lithium hydroxide on the surface of the ternary cathode material, leading to a decrease in residual lithium on the surface of the prepared ternary cathode material and a tendency for the surface layer to be lithium-deficient. Therefore, a second lithium source is added during the second high-temperature sintering process to ensure that the lithium-ion battery containing the prepared ternary cathode material has a high capacity. Moreover, the second lithium source also acts as a solubilizer; adding it during the second high-temperature sintering process can lower the sintering temperature and reduce energy consumption.

[0073] According to the present invention, the multi-element cathode material precursor is a nickel-cobalt-manganese ternary cathode material precursor.

[0074] In this invention, the multi-element cathode material precursor can be commercially available or self-made.

[0075] According to the present invention, the first lithium source and the second lithium source are each independently selected from one of lithium carbonate, lithium hydroxide, lithium oxide and lithium acetate.

[0076] According to the present invention, the dopant and the coating agent are each independently selected from carbonates, hydroxides, oxides and acetates capable of providing at least one element selected from Ba, Ra, Zr, Fe, Ca, Zn, B, W, Nb, Cd, Pb, Si, Mo, Cu, V, Ta, Cr, La, Al, Ce, Er, Ho, Y, Mg, Sr and Ti.

[0077] According to the present invention, the acid solution is selected from at least one of sulfuric acid, carbonic acid, acetic acid and oxalic acid.

[0078] According to the present invention, the total amount of the first lithium source and the second lithium source added is added according to the stoichiometric ratio of 0.9≤[n(Li1)+n(Li2)] / [n(Ni)+n(Co)+n(Mn)]≤1.1.

[0079] Furthermore, the total amount of the first lithium source and the second lithium source added is added according to the stoichiometric ratio 1≤[n(Li1)+n(Li2)] / [n(Ni)+n(Co)+n(Mn)]≤1.06.

[0080] In this invention, there is no particular limitation on the amount of the first lithium source and the second lithium source added, as long as the total amount of the first lithium source and the second lithium source added meets the above range.

[0081] In one specific embodiment of the present invention, the first lithium source is added in a chemical ratio of 0.9 ≤ [n(Li1)] / [n(Ni)+n(Co)+n(Mn)] ≤ 1.05, and the second lithium source is added in a chemical ratio of 0 ≤ [n(Li2)] / [n(Ni)+n(Co)+n(Mn)] ≤ 0.05.

[0082] In a preferred embodiment of the present invention, the first lithium source is added in a chemical ratio of 0.99≤[n(Li1)] / [n(Ni)+n(Co)+n(Mn)]≤1.05, and the second lithium source is added in a chemical ratio of 0.01≤[n(Li2)] / [n(Ni)+n(Co)+n(Mn)]≤0.01.

[0083] According to the present invention, the amount of the dopant added is in accordance with the stoichiometric ratio 0≤[n(M)] / [n(Ni)+n(Co)+n(Mn)]≤0.02, preferably 0≤[n(M)] / [n(Ni)+n(Co)+n(Mn)]≤0.01.

[0084] According to the present invention, the amount of the coating agent added is based on a stoichiometric ratio of 0 < [n(J)] / [n(Ni)+n(Co)+n(Mn)] ≤ 0.03.

[0085] In this invention, by controlling the amount of coating agent added to meet the above-mentioned range, it can be ensured that the prepared multi-element cathode material has an appropriate amount of coating material, thereby ensuring that the prepared multi-element cathode material has a stable structure and that there is not too much coating material remaining on the surface. Specifically, when the amount of coating agent added is too high, too much coating material remains on the surface of the material, which affects lithium-ion transport and results in poor capacity and rate performance of lithium-ion batteries containing multi-element cathode materials; while when the amount of coating agent added is too low, it cannot play a coating role, and during cycling, the electrolyte is prone to destroy the surface structure of the multi-element cathode material, resulting in a reduction in the performance of lithium-ion batteries containing the multi-element cathode material.

[0086] According to the present invention, the amount of the coating agent added is based on a stoichiometric ratio of 0.001≤[n(J)] / [n(Ni)+n(Co)+n(Mn)]≤0.01.

[0087] According to the present invention, the conditions for the first high-temperature sintering include: a sintering temperature T1 of 700-1200°C, a sintering time of 10-30 h, and a sintering atmosphere of oxygen and / or air.

[0088] Furthermore, the conditions for the first high-temperature sintering include: a sintering temperature T1 of 700-1050℃, a sintering time of 15-25h, and a sintering atmosphere of oxygen and / or air.

[0089] According to the present invention, the conditions for rinsing with the acid solution include: the concentration of the acid solution is 0.02-0.04 g / mL, and the rinsing time is 5-60 s.

[0090] In this invention, the coarse crushing can be carried out using conventional methods well known to those skilled in the art, with the aim of breaking down large blocks into smaller blocks with weak dissociation strength and less micro powder production, such as dissociation by rollers with wide gaps.

[0091] In this invention, the purpose of rinsing the product after acid solution rinsing with water is to remove residual acid solution.

[0092] According to the present invention, the sintering temperature of the second high-temperature sintering is 300-900℃.

[0093] According to the present invention, the sintering time of the second high-temperature sintering is 5-20h, preferably 6-15h.

[0094] According to the present invention, the second high-temperature sintering is carried out in air and / or oxygen.

[0095] According to the present invention, the sintering temperature T2 of the second high-temperature sintering is 200-1000℃, and the sintering temperature T2 is related to the melting point T of the coating agent. m The following relationship must be satisfied:

[0096] 100×lnT m -200≤T2≤100×lnT m +100.

[0097] In this invention, the inventors discovered that by adjusting the sintering temperature of the second high-temperature sintering according to the different types of coating agents, the coating effect of the coating agent on the cathode material can be better achieved. Specifically, when the melting point of the coating agent and the sintering temperature of the second high-temperature sintering satisfy the above-mentioned relationship, a better coating effect can be obtained.

[0098] Furthermore, the sintering temperature T2 of the second high-temperature sintering is 300-900℃, and the sintering temperature T2 is related to the melting point T of the coating agent. m Satisfy the following relationship: 100×lnT m -100≤T2≤100×lnT m +50.

[0099] A third aspect of the present invention provides a multi-element cathode material prepared by the above-described preparation method.

[0100] A fourth aspect of the present invention provides a lithium-ion battery comprising the aforementioned multi-element cathode material.

[0101] The present invention will be described in detail below through embodiments. In the following embodiments, unless otherwise specified, all raw materials are commercially available products.

[0102] Unless otherwise specified, the room temperature referred to in this invention is 25±2℃.

[0103] In the following examples and comparative examples, the relevant parameters were obtained through testing using the following methods:

[0104] (1) Particle size test: laser particle size analyzer.

[0105] (2) Morphology and surface roughness test: ERA-9200 scanning electron microscope from ELIONIX Corporation of Japan.

[0106] (3) Specific surface area test: Micromeritics Tristar 3020 specific surface area meter.

[0107] (4) Electrochemical performance testing:

[0108] In the following examples and comparative examples, the electrochemical performance of the multi-element cathode material was tested using a 2025 coin cell.

[0109] The specific manufacturing process of the 2025 coin cell is as follows:

[0110] Electrode preparation: A homogeneous slurry is formed by thoroughly mixing a multi-element positive electrode material, acetylene black, and polyvinylidene fluoride (PVDF) at a mass ratio of 95:3:2 with an appropriate amount of N-methylpyrrolidone (NMP). The slurry is coated onto aluminum foil and dried at 120°C for 12 hours. Then, it is pressed into a positive electrode sheet with a diameter of 12 mm and a thickness of 120 μm using a pressure of 100 MPa. The loading of the multi-element positive electrode material is 15 mg / cm³. 2 .

[0111] Battery Assembly: In an argon-filled glove box with both water and oxygen content less than 5 ppm, the positive electrode, separator, negative electrode, and electrolyte were assembled into a 2025 coin cell and then left to stand for 6 hours. The negative electrode used a 17 mm diameter, 1 mm thick lithium metal sheet; the separator used a 25 μm thick polyethylene porous membrane (Celgard 2325); and the electrolyte was a mixture of equal parts ethylene carbonate (EC) and diethyl carbonate (DEC) containing 1 mol / L LiPF6.

[0112] Electrochemical performance testing:

[0113] In the following examples and comparative examples, the electrochemical performance of the 2025 coin cell was tested using the Shenzhen Xinwei Battery Testing System, with a charge / discharge current density of 200 mA / g at 0.1C.

[0114] The charge / discharge voltage range was controlled between 3.0 and 4.3V. At room temperature, the coin cells were charged and discharged at 0.1C to evaluate the initial charge / discharge specific capacity and initial charge / discharge efficiency of the multi-element cathode material.

[0115] Cyclic performance test: The charge and discharge voltage range was controlled at 3.0-4.3V. At a constant temperature of 45℃, the coin cell was charged and discharged twice at 0.1C and then charged and discharged 80 times at 1C to evaluate the high-temperature capacity retention of the multi-element cathode material.

[0116] Rate performance testing: The charge / discharge voltage range was controlled at 3.0-4.3V. At room temperature, the coin cell was cycled twice at 0.1C, and then once each at 0.2C, 0.33C, 0.5C, and 1C. The rate performance of the multi-element cathode material was evaluated by the ratio of the initial discharge specific capacity at 0.1C to the discharge specific capacity at 1C. The initial discharge specific capacity at 0.1C is the discharge specific capacity of the coin cell in the first cycle, and the discharge specific capacity at 1C is the discharge specific capacity of the coin cell in the sixth cycle.

[0117] Example 1

[0118] This embodiment illustrates the cathode material prepared using the method of the present invention.

[0119] (1) Ni cobalt manganese hydroxide precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2, lithium hydroxide, and aluminum oxide were uniformly mixed in a ratio of n(Li):n(Al):[n(Ni)+n(Co)+n(Mn)]=1.04:0.001:1, and sintered at 890℃ for 20h in an oxygen atmosphere. After natural cooling to room temperature, the 1st product of the multi-element cathode material was obtained.

[0120] (2) After coarse crushing, the multi-component cathode material process product 1 is washed with 0.03 g / mL sulfuric acid for 30 s, and then rinsed with deionized water to remove residual sulfuric acid. After drying, multi-component cathode material process product 2 is obtained: Li 1.04 Ni 0.8 Co 0.1 Mn 0.1 Al 0.001 O2.

[0121] (3) The multi-component cathode material process product 2, lithium hydroxide, magnesium oxide and tungsten oxide are uniformly mixed in the ratio of n(Li):n(Mg):n(W):[n(Ni)+n(Co)+n(Mn)]=0.01:0.005:0.002:1, sintered at 700℃ for 12h in an oxygen atmosphere, naturally cooled to room temperature, and sieved to obtain the multi-component cathode material.

[0122] Examples 2-7

[0123] The method of Example 1 was followed, except that the formulation and process parameters were different, as shown in Table 1. All other aspects were the same as in Example 1, and a multi-element cathode material was prepared.

[0124] Table 1

[0125]

[0126]

[0127] Table 1 (continued)

[0128]

[0129] Comparative Example 1

[0130] (1) Ni cobalt manganese hydroxide precursor Ni 0.8 Co 0.1 Mn 0.1(OH)2, lithium hydroxide, and aluminum oxide were uniformly mixed in a ratio of n(Li):n(Al):[n(Ni)+n(Co)+n(Mn)]=1.04:0.001:1, and sintered at 890℃ for 20h in an oxygen atmosphere. After natural cooling to room temperature, the 1st product of the multi-element cathode material was obtained.

[0131] (2) After coarse crushing, the multi-component cathode material process product 1 is dissociated to the target particle size of 6.2 μm using a pair of rollers with narrow gaps to obtain multi-component cathode material process product 2: Li 1.04 Ni 0.8 Co 0.1 Mn 0.1 Al 0.001 O2.

[0132] (3) The multi-component cathode material process product 2, lithium hydroxide, magnesium oxide and tungsten oxide are uniformly mixed in the ratio of n(Li):n(Mg):n(W):[n(Ni)+n(Co)+n(Mn)]=0.01:0.005:0.002:1, sintered at 700℃ for 12h in an oxygen atmosphere, naturally cooled to room temperature, and sieved to obtain the multi-component cathode material.

[0133] Comparative Example 2

[0134] The method is the same as in Example 1, except that in step (3), the multi-element cathode material process 2 and lithium hydroxide are uniformly mixed in a ratio of n(Li):[n(Ni)+n(Co)+n(Mn)]=0.01:1; the rest is the same as in Example 1, to obtain the multi-element cathode material: Li 1.05 Ni 0.8 Co 0.1 Mn 0.1 Al 0.001 O2. Test data for characteristic parameters are shown in Table 2.

[0135] Comparative Example 3

[0136] The method of Example 1 is the same, except that in step (3), the ternary material process product 2, lithium hydroxide, magnesium oxide, and tungsten oxide are uniformly mixed in a ratio of n(Li):n(Mg):n(W):[n(Ni)+n(Co)+n(Mn)] = 0.01:0.03:0.03:1 and sintered at 400°C for 12 hours in an oxygen atmosphere; the rest is the same as in Example 1, and a multi-element cathode material is obtained. The characteristic parameter test data are shown in Table 2.

[0137] Comparative Example 4

[0138] The method of Example 1 was followed, except that in step (3), sintering was carried out at 1100°C in an oxygen atmosphere; the rest was the same as in Example 1, and a multi-element cathode material was obtained. The characteristic parameter test data are shown in Table 2.

[0139] Comparative Example 5

[0140] The method of Example 1 was followed, except that in step (2), the material was rinsed with 0.1 g / mL sulfuric acid for 180 s; the rest was the same as in Example 1, and a multi-element cathode material was obtained. The characteristic parameter test data are shown in Table 2.

[0141] Test case

[0142] (1) Morphological test

[0143] This invention tested the scanning electron microscope images of the cathode materials prepared in the above embodiments and comparative examples, and statistically determined the average primary particle size P of the multi-element cathode materials. 50 Arithmetic mean roughness Ra, coverage Q, such as Figure 1-4 As shown in Table 2, from Figure 1 As can be seen from Example 1, the surface of the multi-element cathode material process product 2 has no adhesion, and the particles have good independence. Figure 2 The surface of the multi-element cathode material has dot-like and island-like coatings. The multi-element cathode material process product 2 obtained in Comparative Example 1 has more micro powder and fragments on its surface, and the edges and corners are worn. In addition to the coatings, the surface of the multi-element cathode material also has a lot of micro powder.

[0144] (2) Physical property testing

[0145] This invention tested the D1 and D2 of the multi-element cathode materials prepared in the above embodiments and comparative examples. 50 P 50 The specific test results for S, Ra, and Q are shown in Table 2.

[0146] Table 2

[0147]

[0148]

[0149] Table 2 (continued)

[0150]

[0151] As shown in Table 2, compared with Example 1, Example 2 had a lower sulfuric acid concentration and shorter rinsing time, resulting in a smaller S, indicating insufficient dissociation and particle adhesion; Example 3 had a higher sulfuric acid concentration and longer rinsing time, resulting in a larger S and D. 50 and P 50 The smaller value indicates that part of the surface of the positive electrode material has been corroded by sulfuric acid.

[0152] Compared with Example 1, Example 4 has a larger coating amount, more residual coating agent on the surface, and larger S, Ra, and Q; Example 5 has a higher second high-temperature sintering temperature, more coating agent is incorporated into the outer layer of the positive electrode material, less residual coating agent on the surface, and smaller S, Ra, and Q.

[0153] Examples 6 and 7 illustrate that different compositions and coating agents are also applicable.

[0154] Compared to Example 1, Comparative Example 1 used a roller to dissociate particles to the target size, resulting in more micro-powder, smaller D1, larger S, and a rougher surface with a larger Ra. Figure 3 , Figure 4 The conclusions are consistent.

[0155] Comparative Example 2 was not coated, and the particles were slightly sticky after the second high-temperature sintering, resulting in a small S. Comparative Example 3 had an excessive coating amount and a low second high-temperature sintering temperature, resulting in more residual coating agent on the surface, a large S, and a large surface roughness Ra and surface coverage Q. Comparative Example 4 had a high second high-temperature sintering temperature, and the coating agent was incorporated into the outer layer of the positive electrode material, and the particles were sticky, resulting in a very small S.

[0156] Comparative Example 5 had a higher acid solution concentration and a longer washing time, resulting in severe surface corrosion. 50 and P 50 Smaller, S is larger.

[0157] Table 3

[0158]

[0159] As can be seen from Table 3, compared with Example 1, Example 2 has a smaller S, the particles are stuck together, the material capacity is slightly lower, and the rate of return and cycle performance are slightly worse; Example 3 has a larger S, the surface is partially corroded, and the material cycle performance is poor.

[0160] Compared to Example 1, Example 4 has a larger coating amount and more residual coating agent on the surface, which hinders lithium-ion conduction, reduces material capacity, results in poor rate capability, and slightly worse cycle life. Example 5 has a higher second high-temperature sintering temperature and less residual coating agent on the surface, resulting in poorer cycle life. Example 8 does not contain a second lithium source, has a lithium-deficient surface, and has a lower capacity.

[0161] Compared with Example 1, Comparative Example 1 has more micronized powder, which consumes more electrolyte. Insufficient electrolyte results in reduced material capacity, and the micronized powder can cause instability in the battery electrodes, leading to poorer cycle life.

[0162] Comparative Example 2 was not coated, and the surface structure was prone to change during the charging and discharging process, resulting in poor cycle performance. Comparative Example 3 had more residue on the surface, which hindered lithium-ion transport and resulted in poor material rate performance. Comparative Example 4 had a high second high temperature sintering temperature, less coating agent residue, and particle adhesion, resulting in poor material cycle stability.

[0163] Comparative Example 5 showed that the acid solution had too high a solubility and a long rinsing time, resulting in severe material corrosion and poor cycle stability.

[0164] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A multi-element positive electrode material, characterized by, The multi-element cathode material includes a matrix and a coating on the surface of the matrix, wherein the coating is a dot-shaped coating and / or an island-shaped coating. The cumulative particle distribution of the multi-element cathode material is that 1% of the particles have a diameter D1 ≥ 0.7 μm; The arithmetic mean roughness Ra of the cathode material particles, measured by a three-dimensional scanning electron microscope, satisfies the following condition: 20nm≤Ra≤200nm; The coverage rate Q of the dot-shaped and / or island-shaped coatings of the multi-element cathode material satisfies: 3% ≤ Q ≤ 30%; The cumulative particle distribution of the multi-element cathode material is 50% particle size D. 50 2-8μm; The primary particle average size P of the multi-element positive electrode material is 0.8-6 μm. 50 is 0.8-6 μm; The specific surface area S of the multi-element positive electrode material satisfies: 0.2≤S≤1.2 m 2 / g; 1 / P 50 -0.1≤S≤1 / P 50 +0.2; The matrix has the composition shown in Formula I, and the coating comprises a lithium oxide compound containing element J and / or an oxide containing element J. Li a Ni x Mn y Co z M b O2formula I; Where, 0.9≤ a ≤1.1, 0.5≤ x <1, 0< y <0.5, 0< z <0.5, 0≤ b ≤0.02; The content of the matrix and coating is such that 0 < [n(J)] / [n(Ni)+n(Co)+n(Mn)] ≤ 0.03 in the cathode material; M and J are each independently selected from at least one of Ba, Zr, Fe, Ca, Zn, B, W, Nb, Cd, Pb, Si, Mo, Cu, V, Ta, Cr, La, Al, Ce, Er, Ho, Y, Mg, Sr, and Ti.

2. The multinary cathode material of claim 1, wherein, The cumulative particle distribution of the multi-element cathode material is 1% with a particle size that satisfies 1μm≤D1≤2μm; The arithmetic mean roughness Ra of the cathode material particles, measured by a three-dimensional scanning electron microscope, satisfies 30nm≤Ra≤100nm. The coverage rate Q of the dot-shaped and / or island-shaped coatings of the multi-element cathode material satisfies: 5% ≤ Q ≤ 15%.

3. The multinary cathode material of claim 1 or 2, wherein, The multi-element cathode material is spherical and / or ellipsoidal particles.

4. The multinary cathode material of claim 1 or 2, wherein, The cumulative distribution of the particle size D50 of the multi-element positive electrode material is 50% of the particle size 50 is 2.5-7 μm.

5. The multinary cathode material of claim 1 or 2, wherein, The primary particle average size P of the multi-element positive electrode material is 1-4 μm. 50 is 1-4 μm.

6. A method for preparing the multi-element positive electrode material according to any one of claims 1 to 5, characterized by, The method includes: (1) Mix the multi-element cathode material precursor with the first lithium source and sinter at a first high temperature to obtain the multi-element cathode material process product 1; or, mix the multi-element cathode material precursor, the first lithium source and the dopant and sinter at a first high temperature to obtain the multi-element cathode material process product 1. (2) After coarse crushing the multi-element cathode material process product 1, it is successively washed with acid solution, washed with water, and dried to obtain multi-element cathode material process product 2; (3) The multi-element cathode material process product 2 and the coating agent are mixed, and the mixture is sintered at a second high temperature and then sieved to obtain the multi-element cathode material; or, the multi-element cathode material process product 2, the second lithium source and the coating agent are mixed, and the mixture is sintered at a second high temperature and then sieved to obtain the multi-element cathode material. The conditions for rinsing with the acid solution include: the concentration of the acid solution is 0.01-0.05 g / mL, and the rinsing time is 1-120 s; The sintering temperature T2 for the second high-temperature sintering is 200-1000℃; The amount of the coating agent added is based on a stoichiometric ratio of 0 < [n(J)] / [n(Ni)+n(Co)+n(Mn)] ≤ 0.

03.

7. The method of claim 6, wherein, The precursor for the multi-element cathode material is a nickel-cobalt-manganese ternary cathode material precursor.

8. The method of claim 6, wherein, The first lithium source and the second lithium source are each independently selected from one of lithium carbonate, lithium hydroxide, lithium oxide and lithium acetate.

9. The method of claim 6, wherein, The dopant and the coating agent are each independently selected from one of the carbonates, hydroxides, oxides and acetates of Ba, Zr, Fe, Ca, Zn, B, W, Nb, Cd, Pb, Si, Mo, Cu, V, Ta, Cr, La, Al, Ce, Er, Ho, Y, Mg, Sr and Ti.

10. The method according to claim 6, wherein, The acid solution is selected from at least one of sulfuric acid, acetic acid, and oxalic acid.

11. The method of any of claims 6-10, wherein, The total amount of the first lithium source and the second lithium source added is added according to the stoichiometric ratio of 0.9≤[n(Li1)+n(Li2)] / [n(Ni)+n(Co)+n(Mn)]≤1.

1.

12. The method of any one of claims 6-10, wherein, The dopant is added in an amount that conforms to the stoichiometric ratio of 0.0001≤[n(M)] / [n(Ni)+n(Co)+n(Mn)]≤0.

02.

13. The method of any one of claims 6-10, wherein, The coating agent is added in an amount according to a stoichiometric ratio of 0.001 ≤ [n(J)] / [n(Ni)+n(Co)+n(Mn)] ≤ 0.

01.

14. The method of any one of claims 6-10, wherein, The conditions for the first high-temperature sintering include: a sintering temperature T1 of 700-1200℃, a sintering time of 10-30h, and a sintering atmosphere of oxygen and / or air.

15. The method of any one of claims 6-10, wherein, The conditions for rinsing with the acid solution include: the concentration of the acid solution is 0.02-0.04 g / mL, and the rinsing time is 5-60 s.

16. The method of any one of claims 6-10, wherein, The sintering temperature T2 for the second high-temperature sintering is 300-900℃.

17. The method of any one of claims 6-10, wherein, The sintering time for the second high-temperature sintering is 5-20 hours.

18. The method of any one of claims 6-10, wherein, The second high-temperature sintering is carried out in air and / or oxygen.

19. The method of any one of claims 6-10, wherein, The second high-temperature sintering sintering temperature T2 is 200-1000℃, and the sintering temperature T2 is related to the melting point T of the coating agent. m The following relationship must be satisfied: 100 x lnT m - 200 ≤ T2≤ 100 x lnT m + 100.

20. The method of claim 19, wherein, The sintering temperature T2 of the second high-temperature sintering is 300-900℃, and the sintering temperature T2 and the melting point T m satisfies the following relationship: 100 x lnT m -100 ≤ T2 ≤ 100 x lnT m +50.

21. A lithium-ion battery, characterized in that, The lithium-ion battery includes the multi-element cathode material as described in any one of claims 1-5.

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