Regular lithium-rich single crystal positive electrode material and preparation method therefor, positive electrode, and battery

Abstract

A regular lithium-rich single crystal positive electrode material and a preparation method therefor, a positive electrode, and a battery. According to the regular lithium-rich single crystal positive electrode material, the regularity α of the positive electrode material is greater than 0.65, and a method for measuring α comprises: calculating the projection area S of each single crystal particle in a microscopic image of a positive electrode material, and measuring and calculating the circumscribed circle area S' of the corresponding single crystal particle, wherein the total calculated number of particles is n, and α=Σ(S / S') / n. The preparation method for the regular lithium-rich single crystal positive electrode material comprises: mixing and sintering a metal hydroxide precursor and a compound containing a doped metal to obtain an intermediate product, and mixing and sintering the intermediate product and a lithium source. The BET of the metal hydroxide precursor is greater than 12 m2 / g. The positive electrode material has relatively high regularity, by means of the preparation method, the positive electrode material having relatively high regularity can be prepared, and the positive electrode material having high regularity has good electrochemical performance.

Description

Regular lithium-rich single crystal positive electrode material and preparation method thereof, positive electrode and battery

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application number 2023116413978 filed with the China Patent Office on November 30, 2023, entitled “Regular lithium-rich single crystal positive electrode material and its preparation method, positive electrode and battery”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the technical field of battery materials, and in particular to a regular lithium-rich single crystal positive electrode material and a preparation method thereof, a positive electrode and a battery. Background Art

[0004] The development of new energy and its industrial chain is a core measure for my country to achieve carbon peak and carbon neutrality. Among them, electric vehicles and energy storage solutions with lithium-ion batteries as the core are an important part of it. Lithium-ion batteries have obvious advantages over other batteries in terms of mass-energy ratio, volume-energy ratio, instantaneous power density and environmental pollution level. Among them, lithium-rich positive electrode materials have always been one of the core components of lithium-ion batteries due to their cost share in lithium-ion batteries and their impact on the performance of the overall battery. With the development of the market and the maturity of technology, consumers have put forward higher requirements for product performance, especially in terms of product safety and durability. Therefore, how to solve the stability of lithium-rich positive electrode materials and improve the capacity level of products after multiple charge and discharge has become a focus of market research.

[0005] Single-crystal lithium-rich positive electrode materials have gradually become the mainstream in the current lithium battery positive electrode material market due to their good voltage tolerance, relatively simple material preparation process, and good material processing performance. At present, the main ways to improve the long-cycle performance of such materials are still concentrated on the two aspects of element doping and surface coating of the material substrate. This improvement method improves the cycle performance of the product to a certain extent from the bulk and interface structure of the material, but ignores the influence of the material morphology on the electrochemical performance. According to the basic thermodynamic characteristics of the material, the irregular parts (convex polygonal parts) on the surface of the material will become lattice oxygen loss, especially the sites with sharp angles, which have higher local specific surface area, higher surface energy, and stronger local thermal effect, making it easier to be attacked by hydrofluoric acid generated in the battery side reaction, and the reaction is gradually accelerated due to the exothermic effect of the reaction. In addition, the lattice oxygen coordination number on the irregular edge is usually low. In the highly delithiation state, due to the imbalance of charge and the change of the valence of metal elements, the oxygen in the material is released from the material and enters the battery system, which not only causes irreversible damage to the material, but also accelerates the decomposition of the electrolyte, leading to abnormal phenomena such as bulging of the battery pack, affecting the overall life of the battery. Summary of the Invention

[0006] The purpose of this application is to provide a regular lithium-rich single crystal positive electrode material and a preparation method thereof, a positive electrode and a battery.

[0007] This application is implemented as follows:

[0008] In a first aspect, the present application provides a regular lithium-rich single crystal positive electrode material, wherein the regularity α of the positive electrode material is greater than 0.65, and the method for determining α is:

[0009] Count the projected area S of each single crystal particle in a microscopic image of the positive electrode material, and calculate the circumscribed circle area S' of the corresponding single crystal particle. The total number of statistical particles is n, α = Σ(S / S') / n

[0010] In an optional embodiment, the regular lithium-rich single crystal positive electrode material has the molecular formula Li x Ni y Co z M k O r , where 0.95≤x≤1.10, 0≤y≤1, 0≤z≤1, 0≤k≤1, y+z+k=1, 1.8≤r≤2;

[0011] M is selected from at least one of Mn and Al, and the positive electrode material further contains a doped metal, the doped metal includes a metal element A and a metal element B, the metal element A is selected from at least one of Ca, Sr, Ba, Na, Mg, and K, and the metal element B is selected from at least one of Zr, Nb, Al, W, Ce, B, P, Sb, Mo, and Ti.

[0012] Optionally, 0.55≤y≤0.98, 0<z≤0.3, 0<k≤0.3;

[0013] Optionally, the doping amount of the metal element A relative to the positive electrode material is 300 to 2000 ppm, and the doping amount of the metal element B relative to the positive electrode material is 2000 to 10000 ppm.

[0014] In an optional embodiment, the average value of the circumscribed circle radius of particles of the regular lithium-rich single crystal positive electrode material is 0.1 to 2.5 μm;

[0015] Optionally, the average value of the circumscribed circle radius of particles of the regular lithium-rich single crystal positive electrode material is 0.8 to 1.8 μm.

[0016] In an optional embodiment, the D of the particles of regular lithium-rich single crystal positive electrode material is v10 0.5~3.0μm, D v50 1.8~6.0μm, D v90 5.0~12.0μm;

[0017] Alternatively, the D of the particles of regular lithium-rich single crystal cathode material v10 0.8~1.8μm, D v50 2.5~4.5μm, D v90 6.5~9.5μm.

[0018] In an optional embodiment, the surface of the particles of the regular lithium-rich single crystal positive electrode material has a metal oxide coating layer, and the metal oxide coating layer is formed by the oxide of at least one metal of Ti, Sr, Ba, Na, Mg, K, Co, Mn, Nb, Al, W, Ce, B, P, Sb and Mo.

[0019] In a second aspect, the present application provides a method for preparing a regular lithium-rich single crystal positive electrode material according to any one of the aforementioned embodiments, comprising:

[0020] Mixing a metal hydroxide precursor with a compound containing a metal element A and a compound containing a metal element B and sintering the mixture to obtain an intermediate product, and mixing the intermediate product with a lithium source and sintering the mixture;

[0021] Alternatively, a metal hydroxide precursor is mixed with a compound containing metal element A and sintered to obtain an intermediate product, and the intermediate product is mixed with a compound containing metal element B and a lithium source and sintered.

[0022] BET of metal hydroxide precursors>12m 2 / g,D v10 0.3~2.2μm, D v50 1.5~6.0μm, D v90 4.0~25.0μm;

[0023] The metal element A is selected from at least one of Ca, Sr, Ba, Na, Mg, and K, and the metal element B is selected from at least one of Zr, Nb, Al, W, Ce, B, P, Sb, Mo, and Ti.

[0024] In an optional embodiment, at least one of the following features (1) to (4) is also included:

[0025] (1) D of metal hydroxide precursor v10 0.5~2.0μm, D v50 2.0~5.0μm, D v90 4.5~12.0μm;

[0026] (2) mixing a metal hydroxide precursor with a lithium source and sintering the mixture to obtain a primary product;

[0027] The primary product is crushed into a material with a particle size Dv10 of 0.5 to 3.0 μm, Dv50 of 1.8 to 6.0 μm, and Dv90 of 5.0 to 12.0 μm, and then sintered at least once;

[0028] Optionally, before the second sintering, the crushed primary product is mixed with a compound containing a coating metal, and the mixture is uniformly mixed and then sintered again, wherein the coating metal is selected from at least one of Ti, Sr, Ba, Na, Mg, K, Co, Mn, Nb, Al, W, Ce, B, P, Sb and Mo;

[0029] Optionally, the coating amount of the metal element in the metal oxide coating layer relative to the positive electrode material is 2000 to 10000 ppm;

[0030] Optionally, the sintering conditions for each sintering when performing at least one more sintering are as follows: an oxygen concentration of 25% to 90% in a synthetic atmosphere furnace, a heating rate of 1 to 10° C. / min, a maximum sintering temperature of 500 to 900° C., and a total sintering time of 12 to 30 hours;

[0031] (3) sintering the metal hydroxide precursor and the lithium source under the following sintering conditions: an oxygen concentration of 25% to 99% in a synthetic atmosphere furnace, a heating rate of 1 to 10°C / min, a maximum sintering temperature of 700 to 1200°C, and a total sintering time of 16 to 35 hours;

[0032] (4) Compounds containing metal element A and compounds containing metal element B are collectively referred to as compounds containing doped metals. v50 Less than 2.0μm.

[0033] In an optional embodiment, when a metal hydroxide precursor is mixed with a compound containing a doped metal and sintered to obtain an intermediate product, the sintering conditions are an oxygen concentration of 25% to 90% in a synthetic atmosphere furnace, a heating rate of 1 to 10°C / min, a maximum sintering temperature of 500 to 1000°C, and a total sintering time of 10 to 25 hours.

[0034] In a third aspect, the present application provides a positive electrode, which is made using the positive electrode material provided in the aforementioned embodiment or the positive electrode material prepared by the preparation method of any one of the aforementioned embodiments.

[0035] In a fourth aspect, the present application provides a battery comprising a positive electrode as described in the aforementioned embodiment.

[0036] This application has the following beneficial effects:

[0037] The regular lithium-rich single crystal positive electrode material provided by the embodiment of the invention has a high regularity of α>0.65, and the overall convex polygonal edge accounts for a small proportion. The measurement of α is assisted by SEM (scanning electron microscope), and the image processing software is used to measure the projected area S and the circumscribed circle area S' of each single crystal positive electrode active material (Figure 1), so as to determine the morphological state of the material. According to the defined regularity formula, α=Σ(S / S') / n, it can be judged that when the regularity of the material is higher, the overall edge of the material is smoother and the edge has fewer sharp corners. Therefore, the positive electrode material provided by the present application is less susceptible to attack by hydrofluoric acid generated in the battery side reaction due to its high regularity, and the electrochemical reaction process is stable; in addition, materials with higher regularity can effectively reduce high-activity sites on the surface, inhibit local side reactions, and improve long-term performance levels such as battery cycling.

[0038] The preparation method of the positive electrode material provided in the present application comprises the following steps: before the precursor is mixed and sintered with the lithium source, the precursor is mixed and sintered with a compound containing a doped metal, and the BET value is selected to be greater than 12m 2 / g,D v10 In the range of 0.3 to 2.2 μm, D v50 In the range of 1.5 to 6.0 μm, D v90 By preparing a precursor within the range of 4.0 to 25.0 μm, a positive electrode material with a regularity α>0.65 can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 is a schematic diagram of the regularity measurement of a single particle;

[0041] FIG2 is a SEM image of the positive electrode material prepared in Example 1;

[0042] FIG3 is a SEM image of the positive electrode material prepared in Comparative Example 1;

[0043] FIG4 is a SEM image of the positive electrode material prepared in Comparative Example 2;

[0044] FIG5 is a cycle comparison curve diagram of Example 1 and various comparative examples. DETAILED DESCRIPTION

[0045] To make the purpose, technical solutions and advantages of the examples of the present application clearer, the technical solutions in the examples of the present application will be described clearly and completely below. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0046] The present application provides a regular lithium-rich single crystal positive electrode material. The regularity α of the positive electrode material is greater than 0.65. The method for determining α is as follows:

[0047] Count the projected area S of each single crystal particle in a microscopic image of the positive electrode material, and calculate the circumscribed circle area S' of the corresponding single crystal particle. The total number of statistical particles is n, α = Σ(S / S') / n

[0048] The regular lithium-rich single crystal positive electrode material provided in the embodiment of the present application has a high regularity α>0.65, and the overall convex polygonal edge accounts for a small proportion. The measurement of α is assisted by SEM (scanning electron microscope), and the image processing software is used to measure the projected area S and the circumscribed circle area S' of each single crystal positive electrode active material (Figure 1), and the total number of statistical particles is n. The morphological state of the material is thereby determined. According to the defined regularity formula, α=Σ(S / S') / n, it can be judged that when the regularity of the material is higher, the overall edge of the material is smoother and the edge has fewer sharp corners. Therefore, the positive electrode material provided in the present application is less susceptible to attack by the hydrofluoric acid generated in the battery side reaction due to its high regularity, and the electrochemical reaction process is stable; in addition, materials with higher regularity can effectively reduce high-activity sites on the surface, inhibit local side reactions, and improve long-term performance levels such as battery cycling.

[0049] In an optional embodiment, the regular lithium-rich single crystal positive electrode material has the molecular formula Li x Ni y Co z M k O r , where 0.95≤x≤1.10, 0≤y≤1, 0≤z≤1, 0≤k≤1, y+z+k=1, 1.8≤r≤2;

[0050] M is selected from at least one of Mn and Al, and the positive electrode material further contains a doping metal, the doping metal includes a metal element A and a metal element B, the metal element A is selected from at least one of Ca, Sr, Ba, Na, Mg, and K, and the metal element B is selected from at least one of Zr, Nb, Al, W, Ce, B, P, Sb, Mo, and Ti;

[0051] Optionally, 0.55≤y≤0.98, 0<z≤0.3, 0<k≤0.3;

[0052] Optionally, the doping amount of metal element A relative to the positive electrode material is 300 to 2000 ppm (for example, 300 ppm, 500 ppm, 700 ppm, 1000 ppm, 1500 ppm or 2000 ppm), and the doping amount of metal element B relative to the positive electrode material is 2000 to 10000 ppm (for example, 2000 ppm, 3000 ppm, 5000 ppm, 8000 ppm, 9000 ppm or 10000 ppm).

[0053] Optionally, the average value of the circumscribed circle radius of the particles of regular lithium-rich single crystal positive electrode material is 0.1 to 2.5 μm (for example, 0.1 μm, 0.5 μm, 1 μm, 2 μm or 2.5 μm), and can be optionally 0.8 to 1.8 μm (for example, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm or 1.8 μm).

[0054] Alternatively, the D of the particles of regular lithium-rich single crystal cathode material v10 0.5 to 2.2 μm (e.g., 0.5 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, or 2.2 μm), D v50 1.8~6.0μm (such as 1.8μm, 2.5μm, 3μm, 3.5μm, 4μm, 5μm or 6μm), D v90 5.0 to 12.0 μm (e.g., 5.0 μm, 8 μm, 10 μm, or 12 μm);

[0055] Alternatively, the D of the particles of regular lithium-rich single crystal cathode material v10 0.8 to 1.8 μm (e.g., 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, or 1.8 μm), D v50 2.5 to 4.5 μm (e.g., 2.5 μm, 3 μm, 3.5 μm, 4 μm, or 4.5 μm), D v90 6.5 to 9.5 μm (e.g., 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm or 9.5 μm).

[0056] Optionally, the surface of the particles of the regular lithium-rich single crystal positive electrode material has a metal oxide coating layer, and the metal oxide coating layer is formed by an oxide of at least one metal selected from the group consisting of Ti, Sr, Ba, Na, Mg, K, Co, Mn, Nb, Al, W, Ce, B, P, Sb and Mo;

[0057] Optionally, the coating amount of the metal element in the metal oxide coating layer relative to the positive electrode material is 2000 to 10000 ppm (eg, 2000 ppm, 4000 ppm, 5000 ppm, 8000 ppm or 10000 ppm).

[0058] The present application provides a method for preparing the above-mentioned regular lithium-rich single crystal positive electrode material, comprising:

[0059] Mixing a metal hydroxide precursor with a compound containing a metal element A and a compound containing a metal element B and sintering the mixture to obtain an intermediate product, and mixing the intermediate product with a lithium source and sintering the mixture;

[0060] Alternatively, a metal hydroxide precursor is mixed with a compound containing metal element A and sintered to obtain an intermediate product, and the intermediate product is mixed with a compound containing metal element B and a lithium source and sintered.

[0061] BET of metal hydroxide precursors>12m 2 / g,D v10 0.3~2.2μm, D v50 1.5~6.0μm, D v90 4.0~25.0μm;

[0062] The metal element A is selected from at least one of Ca, Sr, Ba, Na, Mg, and K, and the metal element B is selected from at least one of Zr, Nb, Al, W, Ce, B, P, Sb, Mo, and Ti.

[0063] In order to effectively synthesize highly regular ternary cathode materials, the particle size of the selected metal hydroxide precursor needs to be limited to a certain extent, taking into account the inheritance from the precursor to the final product. The selected precursor should match the particle size of the finished product as much as possible to avoid the unstable grain boundaries generated during the crystal fusion process being disintegrated again during the crushing process, thereby generating irregular edges. Therefore, considering the characteristics of the material during sintering, the D of the selected metal hydroxide precursor is v10 In the range of 0.3 to 2.2 μm, D v50 In the range of 1.5 to 6.0 μm, D v90 At 4.0~25.0μm. The role of doping metal A is to utilize its fusion-inducing characteristics to accelerate the fusion reaction of the surface oxide during the transformation of hydroxide to oxide; doping metal B mainly plays the role of layered structure support and ion conductivity improvement; first, the doping metal is mixed with the metal hydroxide precursor and sintered, and the characteristics of the doping metal are utilized to accelerate the fusion reaction of the surface oxide during the transformation of hydroxide to oxide. At the same time, due to the reaction potential energy and oxygen overflow effect, the fusion of the internal hydroxide of the material is accelerated, avoiding the grain boundary formed by the internal and external reaction difference, and generating irregular boundaries after the subsequent powder making process. Therefore, in order to make the doping metal penetrate into the interior of the precursor, it is necessary to select a BET greater than 12m 2 / g of precursor, and such a loose precursor also provides more sufficient development space for the crystal, so that after the lithium source is mixed in, there is sufficient space for the material to expand in a certain direction under certain conditions, avoiding the formation of irregular edges caused by the mutual squeezing of materials inside the precursor, which causes the regularity of the material to be reduced.

[0064] Optionally, the metal hydroxide precursor D v10 0.5 to 2.0 μm (e.g., 0.5 μm, 0.8 μm, 1 μm, 1.5 μm, or 2 μm), D v50 2.0 to 5.0 μm (e.g., 2 μm, 3 μm, 4 μm, or 5 μm), D v90 4.5 to 12.0 μm (e.g., 4.5 μm, 6 μm, 8 μm, 10 μm, or 12 μm).

[0065] Alternatively, to achieve better fusion of the precursor and the doping metal, the D v50 Less than 2.0μm.

[0066] The preparation method is specifically as follows:

[0067] S1. First sintering

[0068] The metal hydroxide precursor is uniformly mixed with a compound containing a metal element A and then sintered to obtain an intermediate product. The doping metal here is a compound of an alkali metal and an alkaline earth metal, including but not limited to: NaOH, Na2CO3, Na2SO4, NaS2O3, Na2MoO4, SrOH, Sr2CO3, SrMoO4, BaSO4, BaCO3, MgCO3, MgSO4, Mg(OH)2, K2CO3, K2SO4, Ca(OH)2, or CaCO3.

[0069] Optionally, the sintering conditions are an oxygen concentration in a synthetic atmosphere furnace of 25% to 90% (for example, 25%, 3%, 40%, 50%, 60%, 70%, 80% or 90%), a heating rate of 1 to 10°C / min (for example, 1°C / min, 3°C / min, 5°C / min, 8°C / min or 10°C / min), a maximum sintering temperature of 500 to 900°C (for example, 500°C, 600°C, 700°C, 800°C or 900°C), and a total sintering time of 10 to 25h (for example, 10h, 12h, 15h, 18h, 20h, 23h or 25h).

[0070] S2, second sintering

[0071] The intermediate product obtained in step S1 is mixed with a lithium source and sintered; or the intermediate product obtained in step S1 is mixed with a lithium source and a compound containing metal element B and sintered.

[0072] Optionally, the sintering conditions of this step are: synthetic atmosphere furnace oxygen concentration of 25% to 99% (for example, 25%, 3%, 40%, 50%, 60%, 70%, 80% or 99%), heating rate of 1 to 10°C / min (for example, 1°C / min, 3°C / min, 5°C / min, 8°C / min or 10°C / min), maximum sintering temperature of 800 to 1000°C (for example, 800°C, 850°C, 900°C, 950°C or 1000°C), and total sintering time of 16 to 35h (for example, 16h, 20h, 25h, 30h or 35h).

[0073] S3, Crushing

[0074] After sintering in step S2, a primary material is obtained, and the primary material is crushed by air flow.

[0075] It should be noted that the current mainstream air flow crushing process does not cause changes in particle regularity. Therefore, in this application, the particle regularity of the final product has almost no obvious correlation with the crushing process. The current mainstream crushing process is specifically, for example, using air flow crushing equipment with a crushing pressure of 0.1 to 0.8 MPa (for example, 0.1 MPa, 0.2 MPa, 0.5 MPa or 0.8 MPa). Equipment feeding frequency, nozzle, induced draft frequency and other parameters are set according to the equipment scale and equipment air duct structure.

[0076] S4, re-sintering

[0077] The crushed primary material is mixed evenly with a compound containing a coating metal and then sintered.

[0078] Optionally, the sintering conditions for this step are as follows: the oxygen concentration in the synthetic atmosphere furnace is 25% - 90% (such as 25%, 3%, 40%, 50%, 60%, 70%, 80% or 90%), the heating rate is 1 - 10 °C / min (such as 1 °C / min, 3 °C / min, 5 °C / min, 8 °C / min or 10 °C / min), the maximum sintering temperature is 300 - 800 °C (such as 300 °C, 400 °C, 500 °C, 600 °C, 700 °C or 800 °C), and the total sintering time is 12 - 30 h (such as 12 h, 15 h, 20 h, 25 h or 30 h). A cathode material coated with a metal oxide can be obtained. The sintering temperatures in steps S1, S2 and S4 are different. Generally, in the temperature settings of each step, S4 < S1 < S2. This is because in the S2 process, since the material needs to fully combine with a large amount of lithium source, the highest growth temperature is required. In the S1 process, the alkali and alkaline earth metals need to fully fuse inside and outside the material, so a relatively high temperature is also required. As the re-sintering in S4 is a coating process, it needs to stay on the surface of the primary material based on the full reaction of the additive with the primary material, so the temperature is relatively low, but the temperature range is relatively wide.

[0079] Optionally, the doping metal and the coating metal can each independently be selected from at least one of Ti, Sr, Ba, Na, Mg, K, Co, Mn, Nb, Al, W, Ce, B, P, Sb and Mo; the compounds containing the doping metal and the compounds containing the coating metal mentioned in this application can be oxides, hydroxides, carbonates, sulfates, molybdates, etc. of the above metal elements. Specifically, for example: NaOH, Na2CO3, Na2SO4, NaS2O3, Na2MoO4, SrOH, Sr2CO3, SrMoO4, BaSO4, BaCO3, MgCO3, MgSO4, Mg(OH)2, K2CO3, K2SO4, Ca(OH)2 or CaCO3.

[0080] A cathode provided by an embodiment of this application is made of the cathode material provided by an embodiment of this application or the cathode material prepared by the preparation method provided by an embodiment of this application.

[0081] A battery provided by an embodiment of this application includes the cathode provided by an embodiment of this application.

[0082] The features and properties of this application will be further described in detail below in conjunction with embodiments.

[0083] Example 1

[0084] (1) Take Ni 0.6 Co 0.1 Mn 0.3(OH)2 and SrO are mixed by a high-speed mixer, wherein the proportion of SrO is 500-2000ppm. 0.6 Co 0.1 Mn 0.3 (OH)2D v10 2.8μm, D v50 3.5μm, D v90 5.0μm, BET=20m 2 / g. D of SrO v50 =1.8μm; the mixed material is placed into a sagger and placed into an atmosphere furnace for sintering. The sintering atmosphere is a mixed atmosphere of oxygen and air, wherein the oxygen accounts for 40% by volume. The sintering furnace is heated from room temperature to 760°C for 6 hours and a holding time of 10 hours to obtain an intermediate product.

[0085] (2) The intermediate product is mixed with LiOH, Li2CO3, ZrO2, TiO2, Al2O3 and WO3 by a high-flow mixer, and the mixed material is placed in a sagger and sent into an atmosphere furnace for sintering. The sintering atmosphere is a mixed atmosphere of oxygen and air, wherein the volume ratio of oxygen is 80%. The sintering furnace is heated from room temperature to 943°C, the heating time is 10 hours, and the holding time is 12 hours. After being taken out of the furnace, the material is dispersed by air flow crushing. The crushing equipment is Saishan Y0200T. The crushing operating parameters are crushing pressure 0.25Mpa, feeding frequency 80Hz, and the primary material is generated. The primary material composition is Li 1.02 Ni 0.6 Co 0.1 Mn 0.3 O2, and with Sr, Zr, Ti, Al, W as doping elements, and the doping amounts of Sr, Zr, Ti, Al, and W are 500ppm, 2500ppm, 700ppm, 500ppm, and 1500ppm, respectively.

[0086] (3) The primary material is mixed with Al2O3, TiO2 and WO3 by a high-speed mixer. The mixed material is then placed in a sagger and placed in an atmosphere furnace for sintering. The sintering atmosphere is a mixed atmosphere of oxygen and air, wherein the volume ratio of oxygen is 50%. The sintering furnace is heated from room temperature to 400-500°C, the heating time is 4 hours, and the holding time is 8 hours, and finally a finished regular lithium-rich single crystal positive electrode material Li with a coating layer is obtained. 1.02 Ni 0.6 Co 0.1 Mn 0.3 O2, which has Zr, Ti, Al, W, and Sr as doping elements, with doping amounts of 500ppm, 2500ppm, 700ppm, 500ppm, and 1500ppm, respectively.

[0087] It also contains Al, Ti, and W as coating elements, with coating amounts of 700ppm, 1200ppm, and 600ppm, respectively.

[0088] Example 2

[0089] This embodiment is basically the same as the first embodiment, except that:

[0090] (1) Ni 0.68 Co 0.07 Mn 0.25 (OH)2 and Ba(OH)2 were mixed by a high-speed mixer. The BET of the metal hydroxide used was 17m 2 / g,D v10 2μm, D v50 5μm, D v90 12μm. D of Ba(OH)2 v50 =1.5μm.

[0091] (2) sintering the intermediate product, LiOH, and Li2CO3 together with ZrO2, Al2O3, and WO3 to obtain a primary material with Zr, Al, W, and Ba doping amounts of 2500 ppm, 1000 ppm, 1300 ppm, and 700 ppm, respectively;

[0092] (3) Mixing the primary material with Al2O3 and TiO2 and sintering them, the finished regular lithium-rich single crystal cathode material with a coating layer is finally obtained. 1.04 Ni 0.68 Co 0.07 Mn 0.25 O2, and with Zr, Al, W, Ba as doping elements, the doping amounts are 2500ppm, 1000ppm, 1300ppm and 700ppm respectively, and with Al, Ti as coating elements, the coating amounts are 1000ppm and 1200ppm respectively.

[0093] Example 3

[0094] This embodiment is basically the same as the first embodiment, except that:

[0095] The BET value of the metal hydroxide used is 20 m 2 / g,D v10 0.5μm, D v50 2μm, D v90 It is 4.5μm.

[0096] Example 4

[0097] This embodiment is basically the same as embodiment 1, except that the BET value of the metal hydroxide used is 18m 2 / g,D v10 2.2μm, D v50 6.0μm, D v90 25μm.

[0098] Example 5

[0099] This embodiment is basically the same as embodiment 1, except that the BET value of the metal hydroxide used is 16m 2 / g,D v10 0.3μm, D v50 1.5μm, D v90 is 4.0μm.

[0100] Example 6

[0101] This embodiment is basically the same as embodiment 1, except that the BET value of the metal hydroxide used is 16m 2 / g,D v10 0.5μm, D v50 2.0μm, D v90 It is 4.5μm.

[0102] Example 7

[0103] This embodiment is basically the same as embodiment 1, except that: compared with embodiment 1, there is no step (3).

[0104] Example 8

[0105] This embodiment is basically the same as embodiment 1, except that the precursor Ni 0.65 Co 0.07 Mn 0.28 (OH)2, BET is 25m 2 / g,D v10 0.8μm, D v50 3.7μm, D v90 The first sintering temperature is 500℃, the second sintering temperature is 700℃, and the third sintering temperature is 500℃.

[0106] Example 9

[0107] This embodiment is basically the same as embodiment 2, except that the precursor Ni 0.58 Co 0.14 Mn 0.28 The BET of (OH)2 is 26m 2 / g,D v10 0.6μm, D v50 3.0μm, D v90The first sintering temperature is 860℃, the second sintering temperature is 980℃, and the third sintering temperature is 800℃.

[0108] Comparative Example 1

[0109] This embodiment is basically the same as embodiment 1, except that step (1) is omitted, i.e., SrO is not doped.

[0110] Comparative Example 2

[0111] This embodiment is basically the same as embodiment 1, except that the BET of the precursor used is 8m 2 / g,D v10 3μm, D v50 3.5μm, D v90 It is 5.6μm.

[0112] Experimental Example 1

[0113] (1) Each embodiment and comparative example was laid flat on a conductive adhesive and photographed under a scanning electron microscope flex1000. An electron microscope image was taken at 4000x magnification. The electron microscope images of embodiment 1 and comparative examples 1-2 are shown in Figures 2-4.

[0114] Comparing Figure 2 with Figures 3 and 4 shows that the cathode material prepared in Example 1 is significantly more regular than the respective comparative examples. This demonstrates that: 1. sintering the precursor with the metal-doped oxide prior to sintering can improve the regularity of the cathode material; 2. Using a precursor with a higher BET value to prepare the cathode material can also improve the regularity of the cathode material.

[0115] (2) The electron microscope images were analyzed using MiPar software to obtain the area of ​​all intact particles and manually remove any particles misidentified by the equipment. The longest axis length of each particle was also obtained, from which the circumscribed circle area was calculated. To save space, only the particle data from Example 1 and Comparative Example 1 are presented, as shown in Tables 1 and 2, respectively. The regularity data calculated for each Example and Comparative Example are summarized in Table 3.

[0116] Table 1 Statistical data of the positive electrode material prepared in Example 1

[0117] Table 2 Statistical data of the positive electrode material prepared in Comparative Example 1

[0118] Table 3 Regularity of the positive electrode materials obtained in each embodiment and comparative example

[0119] Experimental Example 2

[0120] The electrochemical properties of the positive electrode materials prepared in the examples and comparative examples were tested. The details are as follows:

[0121] After the samples of Example 1 and Comparative Examples 1-3 were prepared into pole pieces by slurry mixing, coating, and roller pressing, they were combined with lithium sheets, diaphragm electrolyte, and necessary auxiliary materials to form button batteries. The button batteries were tested for capacity retention after 50 cycles at a voltage of 4.45 V, a high temperature of 45°C, and a rate of 1C. The results are shown in Figure 5 and Table 4.

[0122] Table 4 Cycle comparison between Example 1 and Comparative Example 1

[0123] In summary, the regular lithium-rich single crystal cathode material provided in the embodiments of this application has a high regularity (α>0.65) and a relatively low proportion of convex polygonal edges. Due to its high regularity, the cathode material provided in this application is less susceptible to attack by hydrofluoric acid generated in battery side reactions, and has good stability during the electrochemical reaction process. Furthermore, the highly regular material can effectively reduce highly active sites on the surface, inhibiting local side reactions and improving long-term battery performance, such as cycling.

[0124] The preparation method of the positive electrode material provided in the present application comprises the following steps: before the precursor is mixed and sintered with the lithium source, the precursor is mixed and sintered with a compound containing a doped metal, and the BET value is selected to be greater than 12m 2 / g,D v10 In the range of 0.3 to 3.2 μm, D v50 In the range of 1.5 to 6.5 μm, D v90 By preparing a precursor within the range of 4.0 to 27.0 μm, a positive electrode material with a regularity α greater than 0.65 can be obtained.

[0125] The above are merely optional embodiments of the present application and are not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included within the scope of protection of the present application. Industrial Applicability

[0126] The regularity α of the regular lithium-rich single crystal positive electrode material provided by this solution is greater than 0.65. The method for determining α is: counting the projected area S of each single crystal particle in a microscopic image of the positive electrode material, and measuring the circumscribed circle area S' of the corresponding single crystal particle. The total number of particles counted is n, and α = Σ(S / S') / n. The preparation method of the positive electrode material includes: mixing and sintering a metal hydroxide precursor with a compound containing a doped metal to obtain an intermediate product, and mixing and sintering the intermediate product with a lithium source. The BET of the metal hydroxide precursor is greater than 12m 2 The positive electrode material disclosed in the present application has a high degree of regularity, and the preparation method can produce a positive electrode material with a high degree of regularity. The positive electrode material with a high degree of regularity has good electrochemical performance.

Claims

1. A regular lithium-rich single crystal positive electrode material, characterized in that: The regularity α of the positive electrode material is greater than 0.65, and the determination method of α is: The projected area S of each single crystal particle in a microscopic image of the positive electrode material is counted, and the circumscribed circle area S' of the corresponding single crystal particle is calculated. The total number of particles counted is n, and α=Σ(S / S') / n.

2. The regular lithium-rich single crystal positive electrode material according to claim 1, characterized in that: The molecular formula of the regular lithium-rich single crystal positive electrode material is Li x Ni y Co z M k O r , where 0.95≤x≤1.10, 0≤y≤1, 0≤z≤1, 0≤k≤1, y+z+k=1, 1.8≤r≤2; M is selected from at least one of Mn and Al, the positive electrode material further contains a doped metal, the doped metal includes a metal element A and a metal element B, the metal element A is selected from at least one of Ca, Sr, Ba, Na, Mg, and K, and the metal element B is selected from at least one of Zr, Nb, Al, W, Ce, B, P, Sb, Mo, and Ti; Optionally, 0.55≤y≤0.98, 0<z≤0.3, 0<k≤0.3; Optionally, the doping amount of the metal element A relative to the positive electrode material is 300 to 2000 ppm, and the doping amount of the metal element B relative to the positive electrode material is 2000 to 10000 ppm.

3. The regular lithium-rich single crystal positive electrode material according to claim 1 or 2, characterized in that: The average value of the circumscribed circle radius of the particles of the regular lithium-rich single crystal positive electrode material is 0.1 to 2.5 μm; Optionally, the average value of the circumscribed circle radius of particles of the regular lithium-rich single crystal positive electrode material is 0.8 to 1.8 μm.

4. The regular lithium-rich single crystal positive electrode material according to any one of claims 1 to 3, characterized in that: The D of the regular lithium-rich single crystal cathode material particles v10 0.5~3.0μm, D v50 1.8~6.0μm, D v90 5.0~12.0μm; Optionally, the D of the particles of the regular lithium-rich single crystal positive electrode material is v10 0.8~1.8μm, D v50 2.5~4.5μm, D v90 6.5~9.5μm.

5. The regular lithium-rich single crystal positive electrode material according to any one of claims 1 to 4, characterized in that: The particle surface of the regular lithium-rich single crystal positive electrode material has a metal oxide coating layer, and the metal oxide coating layer is formed by an oxide of at least one metal selected from Ti, Sr, Ba, Na, Mg, K, Co, Mn, Nb, Al, W, Ce, B, P, Sb and Mo; Optionally, the coating amount of the metal element in the metal oxide coating layer relative to the positive electrode material is 2000 to 10000 ppm.

6. A method for preparing a regular lithium-rich single crystal positive electrode material as claimed in any one of claims 1 to 5, characterized in that: include: Mixing a metal hydroxide precursor with a compound containing a metal element A and a compound containing a metal element B and sintering them to obtain an intermediate product, and mixing the intermediate product with a lithium source and sintering them; Alternatively, a metal hydroxide precursor is mixed with a compound containing metal element A and sintered to obtain an intermediate product, and the intermediate product is mixed with a compound containing metal element B and a lithium source and sintered; The BET of the metal hydroxide precursor is greater than 12m 2 / g,D v10 0.3~2.2μm, D v50 1.5~6.0μm, D v90 4.0~25.0μm; The metal element A is selected from at least one of Ca, Sr, Ba, Na, Mg, and K, and the metal element B is selected from at least one of Zr, Nb, Al, W, Ce, B, P, Sb, Mo, and Ti.

7. The preparation method according to claim 6, characterized in that: It also includes at least one of the following features (1) to (4): (1) D of the metal hydroxide precursor v10 0.5~2.0μm, D v50 2.0~5.0μm, D v90 4.5~12.0μm; (2) mixing a metal hydroxide precursor with a lithium source and sintering them to obtain a primary product; The primary product is crushed into a material with a particle size Dv10 of 0.5 to 3.0 μm, Dv50 of 1.8 to 6.0 μm, and Dv90 of 5.0 to 12.0 μm, and then sintered at least once; Optionally, before the second sintering, the crushed primary product is mixed with a compound containing a coating metal, and the mixture is uniformly mixed and then sintered again, wherein the coating metal is selected from at least one of Ti, Sr, Ba, Na, Mg, K, Co, Mn, Nb, Al, W, Ce, B, P, Sb and Mo; Optionally, the sintering conditions for each sintering when performing at least one more sintering are: oxygen concentration in the synthetic atmosphere furnace is 25% to 90%, heating rate is 1 to 10° C. / min, maximum sintering temperature is 500 to 900° C., and total sintering time is 12 to 30 hours; (3) The sintering conditions for mixing the metal hydroxide precursor and the lithium source are as follows: the oxygen concentration in the synthetic atmosphere furnace is 25% to 99%, the heating rate is 1 to 10° C. / min, the maximum sintering temperature is 700 to 1200° C., and the total sintering time is 16 to 35 hours; (4) The compound containing metal element A and the compound containing metal element B are collectively referred to as a compound containing a doped metal. v50 Less than 2.0μm.

8. The preparation method according to claim 6 or 7, characterized in that: When a metal hydroxide precursor is mixed with a compound containing a doped metal and sintered to obtain an intermediate product, the sintering conditions are: an oxygen concentration of 25% to 90% in a synthetic atmosphere furnace, a heating rate of 1 to 10°C / min, a maximum sintering temperature of 500 to 1000°C, and a total sintering time of 10 to 25 hours.

9. A positive electrode, characterized in that: The method is prepared by using the positive electrode material provided by claims 1 to 5 or the positive electrode material prepared by the preparation method according to any one of claims 6 to 8.

10. A battery, characterized in that: Comprising the positive electrode as claimed in claim 9.

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