Positive electrode active material and method for manufacturing the same, positive electrode tab, battery, and electrical device

Abstract

This application discloses a positive electrode active material, a method for manufacturing the same, a positive electrode tab, a battery, and an electrical device. Herein, the positive electrode active material includes secondary particles formed by the deposition of primary particles, the secondary particles include open and closed pores, and the porosity P of the open pores of the positive electrode active material. o The total porosity P of the positive electrode active material t It accounts for 25% to 85% of the total.

Description

[Technical Field]

[0001] This invention belongs to the field of batteries, and more specifically relates to positive electrode active material and a method for producing the same, positive electrode tab, battery, and electrical device. [Background technology]

[0002] Lithium-ion batteries are widely used in various electronic products and transportation devices such as electric vehicles due to their characteristics such as light weight, low pollution, high energy density, and high cell voltage. Consumer demands for range and lifespan in electronic products and transportation devices like electric vehicles are increasing day by day. To meet consumer demands, repeated upgrades to lithium-ion batteries with high energy density and long cyclic life are being continuously pursued in both research and development and application devices.

[0003] In lithium-ion batteries, the cathode active material is the component that has the greatest impact on performance. Currently, the main direction of development is to improve energy density by increasing the Ni content in ternary cathode materials. However, the associated issues of circulating performance and safety have become serious enough to be ignored. [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] This application aims to solve, at least to some extent, one of the existing technical challenges in related technologies. Therefore, one objective of this application is to propose a positive electrode active material, a method for producing the same, a positive electrode tab, a battery, and an electrical device, thereby enabling the acquisition of a positive electrode active material that exhibits high electrochemical reaction activity, lithium-ion transition capability, energy density, and particle strength, and furthermore, combines excellent performance such as high energy density, good rate performance, and long cycle life. [Means for solving the problem]

[0005] This application is proposed primarily based on the following problems and findings.

[0006] Polycrystalline or pseudo-single-crystal ternary cathode materials typically consist of secondary particles formed by the aggregation of multiple primary particles, resulting in numerous pores on the surface or within the material. Currently, research is underway to design the structure and arrangement of cathode active material particles to adjust and control the material's intrinsic cycle performance and safety performance. For example, a total pore volume of 0.008 cm³ below 200 nm from the surface is considered desirable. 3 / g~0.012cm 3 There are ternary cathode materials that are limited to a certain value per gram, and also limited to the proportion of pore volume of 15 nm or less in the total pore volume not exceeding 50%. There are also cathode materials that are limited to having high porosity in the center of the cross-section of secondary particles, low porosity on the surface, and simultaneously, the ratio of the short axis length to the long axis length of secondary particles in the cross-section, and the ratio of the total pore area to the total particle area in the cross-section, respectively, to satisfy predetermined requirements. Furthermore, there are cathode materials that are limited to having the ratio of the cross-sectional area of ​​secondary particles to the area of ​​the pore portion satisfy predetermined requirements. In practice, appropriately controlling the pore volume or porosity is extremely important in the design of cathode active materials and electrode tabs, as it not only affects the electrochemical performance of the cathode active material but also affects the particle strength, press density, and cycle life of the material. In this application, by adjusting and controlling the interrelationship and / or structure between open and closed pores in the positive electrode active material (for example, by adjusting and controlling the aggregation effect between primary particles), it is possible to solve to some extent the balance problem between the particle strength, energy density and cycle stability of the material. Furthermore, by providing the material with high electrochemical activity and high rate performance, transient side reactions between the material surface and the electrolyte are avoided, and the objective of ensuring particle strength and press density is achieved. Ultimately, it is desirable to obtain a positive electrode active material with high energy density, high particle strength and long cycle life.

[0007] In view of the above, in the first aspect of the present application, the positive electrode active material includes secondary particles formed by the deposition of primary particles, the secondary particles include open and closed pores, and the porosity P of the open pores of the positive electrode active material o P is the total porosity of the positive electrode active material. t We propose a positive electrode active material that accounts for 25% to 85% of the total.

[0008] In aggregated cathode active materials such as ternary cathode active materials, porosity can reflect the degree of fusion and aggregation between primary particles. A small portion of the pores are exposed to the surface and become open pores; this portion relates to the surface activity of the material and the wetting area of ​​the electrolyte. The majority of the pores are closed pores, located inside the secondary particles of the material that are not wetted by the electrolyte; this portion relates to the particle strength of the material, the contact effect between primary particles, and the expansion and contraction space of the material during cycling. The lower the ratio of open pore porosity to total porosity, i.e., the higher the ratio of closed pore porosity, the worse the media transport performance and conductivity performance between primary particles inside the secondary particles, and the lower the particle strength. However, an appropriate amount of closed pore porosity can provide expansion and contraction space during charging and discharging of the material, releasing compressive stress between primary particles and accordingly improving cycling performance. In this application, the porosity P of the open pores of the cathode active material is used. o By controlling the ratio of to the total porosity to 25% to 85%, the material can be endowed with high particle strength, high rate performance, and good cycle stability to withstand expansion and contraction during the charge-discharge process.

[0009] Furthermore, the positive electrode active material according to the above embodiment of the present application may have the following additional constituent elements.

[0010] In some embodiments of the present application, the porosity P of the pores of the positive electrode active material o The percentage is between 0.5% and 3%.

[0011] In some embodiments of this application, the average pore diameter D of the openings in the positive electrode active material o The range is 10nm to 50nm.

[0012] In some embodiments of the present application, the pore volume V of the pores in the positive electrode active material o is 0.002 cm 3 / g to 0.01 cm 3 / g.

[0013] In some embodiments of the present application, the skeletal volume V of the positive electrode active material t is 0.2 cm 3 / g to 0.25 cm 3 / g.

[0014] In some embodiments of the present application, the total porosity P of the positive electrode active material t is 1% to 10%.

[0015] In some embodiments of the present application, in the secondary particles, the average pore diameter D of the closed pores C is 40 nm to 200 nm.

[0016] In some embodiments of the present application, the specific surface area of the positive electrode active material is S 0 , and the specific surface area of the positive electrode active material after being fractured at a pressure of 3.5 tons is S 3.5 , and the specific surface area change rate ΔSSA of the positive electrode active material is 0 to 50%, and ΔSSA = (S 3.5 -S​​​​​​​​​​​​​​​​​​​​​​​​​​​​

[0018] In some embodiments of the present application, the positive electrode active material is Li 1+a Ni x Co y Mn z M m It contains O2, where -0.05≦a≦0.3, 0.8≦x≦1, 0≦y≦0.2, 0≦z≦0.2, and 0≦m≦0.01, and M contains at least one of Mg, La, Al, Sr, Ba, Y, Zr, Ca, Fe, Zn, Sn, W, V, Mo, Sb, Ta, Ti, Nb, S, P, and B.

[0019] In some embodiments of the present application, M comprises at least one of Sn, W, V, La, Mo, Sb, Ta, Ti, and Nb, and the full width at half maximum of the diffraction peaks corresponding to the 10⁴ crystal plane in the XRD profile of the primary particles is 0.245 to 0.270.

[0020] In some embodiments of the present application, M comprises at least one of S, P, and B, and the full width at half maximum of the diffraction peaks corresponding to the 10⁴ crystal plane in the XRD profile of the primary particle is 0.250 to 0.275.

[0021] In some embodiments of the present application, M comprises at least one of Mg, Al, Sr, Ba, Y, Zr, Ca, Fe, and Zn, and the full width at half maximum of the diffraction peaks corresponding to the 10⁴ crystal plane in the XRD profile of the primary particles is 0.255 to 0.280.

[0022] In some embodiments of the present application, the secondary particles include a substrate and a coating layer, wherein the substrate is Li 1+a Ni x Co y Mn z M m The substrate contains O2, and the coating layer is provided on at least a portion of the surface of the substrate.

[0023] In some embodiments of the present application, the coating layer contains element J, which includes at least one of Al, Zr, Ti, F, B, Cl, Br, I, S, W, Co, Sn, and Mo.

[0024] In some embodiments of the present application, the coating layer contains element J, and the ratio of the total number of moles of Ni, Co, Mn, and M in the substrate to the number of moles of element J in the coating layer is 1:(0~0.05).

[0025] A second aspect of the present application provides a method for producing the positive electrode active material described above, (1) A step of obtaining precursor particles by coprecipitation reaction of aqueous solutions of a nickel source, a cobalt source and a manganese source under alkaline conditions, and (2) We propose a method for obtaining a positive electrode active material by mixing the precursor particles with a lithium source and an M source and performing a sintering process.

[0026] According to the method for producing a positive electrode active material in the second aspect of the present application, by combining the nickel-cobalt-manganese composition, control of the precursor porosity, and the amount of M element doping, the temperature and time of the sintering process, as well as the dimensions and arrangement of the primary grains, can be adjusted and controlled, thereby further adjusting and controlling the aggregation effect between primary particles in the secondary particles. This contributes to obtaining a positive electrode active material in which the ratio of porosity of open pores to total porosity is 25% to 85%, and the material can be endowed with high particle strength, high rate performance, and good cycle stability to withstand expansion and contraction during the charge-discharge process.

[0027] In some embodiments of the present invention, step (1) is performed under alkaline conditions where the pH value is 10 to 11.5.

[0028] In some embodiments of the present application, step (2) includes holding the sintering process at 650°C to 900°C for 4 to 15 hours.

[0029] In some embodiments of the present application, step (2) further includes mixing the sintered product with a coating material containing the J source and holding the mixture at 300°C to 700°C for 5 to 10 hours.

[0030] In a third aspect of this application, a positive electrode tab is proposed that includes the positive electrode active material described above, or a positive electrode active material manufactured by the method described above. The features and advantages described above for the positive electrode active material and the manufacturing method described above are also applicable to this positive electrode tab, and therefore their explanation is omitted here. In short, this positive electrode tab has good cycle stability and a long cycle life.

[0031] A fourth aspect of this application proposes a battery including the positive electrode tab described above.

[0032] In the fifth aspect of this application, an electrical device including the battery described above is proposed. [Brief explanation of the drawing]

[0033] [Figure 1] Figure 1 is a cross-sectional view of a precursor prepared according to Example 1 of this application. [Figure 2] Figure 2 shows the distribution of closed pores and pore diameters in a cross-section of a positive electrode active material fabricated according to Example 1 of this application. [Modes for carrying out the invention]

[0034] The following describes embodiments of the present application in detail. The embodiments described below are illustrative and intended to be interpretable in the present application, and should not be understood as limiting the present application.

[0035] In a first aspect of the present invention, a positive electrode active material is proposed that includes secondary particles formed by the deposition of primary particles, the secondary particles including open and closed pores (see Figure 1), and the porosity P of the positive electrode active material. o P is the total porosity of the positive electrode active material. t It accounts for 25% to 85% of the total.

[0036] For example, the porosity P of the positive electrode active material. o P is the total porosity of the positive electrode active material. tIt may account for 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or 85%, etc. Here, the porosity P of the open pores. o The positive electrode active material has a pore volume V of open pores that can be filled with nitrogen gas. o This is the ratio of the positive electrode active material to the total volume of the positive electrode active material, and is obtained by performing thermal tests and analyses such as adsorption and desorption of N2 on the positive electrode active material. For example, it can be obtained by testing with a surface meter of the Tristar 3020 model manufactured by Micromeritics. Refer to Figure 2 for the total porosity P. t This is the total pore area S of the cross-section of the positive electrode active material in an electron microscope. t and the total cross-sectional area S of the material m It may also be the ratio of to raised to the power of 3 / 2. That is, S t / S m It may also be raised to the power of 3 / 2. Here, the total porosity P t This is obtained by the average value of the total porosity of multiple secondary particles in the test sample. Specifically, the procedure involves obtaining cross-sections of multiple secondary particles by ion cutting of the positive electrode active material sample using an ion grind gauge (e.g., Hitachi IM4000 II ion grind gauge), then performing image sampling of the material cross-sections using a scanning electron microscope, and finally obtaining the image contrast analysis using the LIBMAS intelligent image analysis system. The number of secondary particles to be sampled in the test sample should be ≥6. For example, it may be ≥8, ≥10, ≥15, ≥20, ≥30, ≥40, or ≥50. Those skilled in the art can flexibly select according to their actual requirements. Furthermore, when capturing images of the sample with a scanning electron microscope, the sample to be photographed should be as close as possible to the center of the secondary particle's sphere or a cross-section close to the center of the secondary particle's sphere to improve the accuracy of the total porosity test, and the diameter of the cross-section should be the particle size D of the material. 50 ~D 80 It is best to select a sample that is between these two. Here, D 50 This is the particle size that corresponds when the volume distribution of the positive electrode active material accumulates up to 50% (i.e., the particle size is D 50 The portion smaller than this accounts for 50%), D 80This is the particle size that corresponds when the volume distribution of the positive electrode active material accumulates to 80% (i.e., the particle size is D). 80 (The portion smaller than this accounts for 80%).

[0037] Here, when primary particles are deposited as secondary particles, they form open pores that communicate with the outside environment and closed pores that do not come into contact with the gas or electrolyte in the outside environment. In aggregated cathode active materials such as ternary cathode active materials, porosity can reflect the degree of fusion and aggregation between primary particles. A small portion of the pores are exposed to the surface and become open pores; this portion relates to the surface activity of the material and the wetting area of ​​the electrolyte. The majority of the pores are closed pores, located inside the secondary particles of the material that are not wetted by the electrolyte; this portion relates to the particle strength of the material, the contact effect between primary particles, and the expansion and contraction space of the material during cycling. The lower the ratio of open porosity to total porosity, i.e., the higher the ratio of closed porosity, the worse the medium transport performance and conductivity performance between primary particles inside the secondary particles, and the lower the particle strength. However, an appropriate amount of closed porosity can provide expansion and contraction space during charging and discharging of the material, releasing compressive stress between primary particles and accordingly improving cycling performance. In this application, the porosity P of the pores of the positive electrode active material is specified. o By controlling the ratio of to the total porosity to 25% to 85%, the material can be endowed with high particle strength, high rate performance, and good cycle stability to withstand expansion and contraction during the charge-discharge process.

[0038] The positive electrode active material in the above embodiment of this application will be described in detail below with reference to Figures 1 and 2.

[0039] In some specific embodiments of the present application, the method for obtaining a positive electrode active material having a desired porosity structure is not particularly limited and can be flexibly selected by those skilled in the art according to their practical needs. For example, by adjusting and controlling one or more of the particle size, morphology, and arrangement of primary particles, the aggregation effect when primary particles are deposited as secondary particles can be adjusted and controlled, and further by adjusting and controlling the porosity structure of the positive electrode active material, a positive electrode active material having a desired porosity structure can be obtained. Based on this, the porosity structure of the positive electrode active material can be further adjusted and controlled by selecting one or more of the following: whether or not to provide a coating layer, the selection of the coating layer material, and the thickness of the coating layer.

[0040] In some specific embodiments of this application, the porosity P of the pores of the positive electrode active material is o The total porosity P of the positive electrode active material t This may account for 30% to 60% of the material. This helps to give the material high particle strength, high rate performance, and good cycle stability to withstand expansion and contraction during the charge and discharge process.

[0041] In some specific embodiments of this application, the porosity P of the pores of the positive electrode active material is o The porosity of the pores in the positive electrode active material may be 0.5% to 3%, for example, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, or 3%. The porosity of the pores in the positive electrode active material is related to the surface activity of the material and the area of ​​electrolyte penetration. The larger the porosity of the pores, the more surface interface reaction channels there are for lithium ion insertion and deinsertion, resulting in higher reaction activity and better charge / discharge capacity, initial effect, and rate performance of the material. Appropriately reducing the porosity of the pores in the positive electrode active material contributes to reducing side reactions between the surface of the positive electrode active material and the electrolyte. In this application, the porosity of the pores P of the positive electrode active material oThe fact that the specified range is met is advantageous in providing the positive electrode active material with high electrochemical reaction activity and high rate performance. In addition, it contributes to reducing the risk of excessive side reactions between the material surface and the electrolyte due to excessive porosity of the openings, and further reduces the risk of a decrease in material storage, gas generation, and cycle performance. Furthermore, it is advantageous in providing the positive electrode active material with both high capacity and a long service life. Moreover, the porosity P of the openings of the positive electrode active material o This can be between 1.0% and 2.5%.

[0042] In some specific embodiments of this application, the average pore diameter D of the pores in the positive electrode active material o The pore size may be between 10 nm and 50 nm, for example, 0 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, or 50 nm. The average pore size of the cathode active material is obtained by surface measurement using the BJH (Barrett Joyner Halenda) model. For example, it can be obtained by measurement using a Tristar 3020 surface meter manufactured by Micromeritics. The BJH model and pore size test are explained in detail below. The pore shape is assumed to be cylindrical, and the Kelvin relation is satisfied based on the relative pressure between the pore size where capillary condensation occurs and N2. The distribution of material pore sizes is expressed by measuring the amount of N2 adsorbed at different partial pressures and corresponding pore sizes, and the average pore size is obtained by multiplying each pore size by a ratio coefficient. The pore size distribution obtained from adsorption isotherms often originates from the diameter inside the pore, while the pore size distribution obtained from desorption isotherms often originates from the diameter at the pore entrance. In this application, the pore diameter of the pore inlet may be obtained using a desorption isotherm. In this application, the fact that the pore diameter of the openings in the positive electrode active material is within a predetermined range is advantageous for relatively uniform distribution of the pores on the surface of the material to the surface of the secondary particles, and is also advantageous for uniform diffusion and reaction rates of lithium ions. Furthermore, the average pore diameter D of the openings in the positive electrode active material o The wavelength can be 15nm to 45nm.

[0043] In some specific embodiments of this application, the pore volume V of the positive electrode active material oThis is 0.002 cm 3 / g~0.01cm 3 It may also be expressed as / g, for example, 0.003cm 3 / g, 0.004cm 3 / g, 0.005cm 3 / g, 0.006cm 3 / g, 0.007cm 3 / g, 0.008cm 3 / g, 0.009cm 3 / g or 0.01cm 3 It may also be expressed as / g. The pore volume of the positive electrode active material may be tested and analyzed using a surface meter based on N2 adsorption / desorption isotherms. For example, it can be obtained by measuring with a surface meter of the Tristar 3020 model manufactured by Micromeritics. Specifically, the test based on N2 adsorption / desorption isotherms may include using a general measuring device (such as Tristar 3020) to gradually add N2 to a sample of the material to be measured, from a vacuum state, from which physical adsorbed components have been removed, and calculating the pressure change due to N2 adsorption by the constant volume method, and obtaining the amount of N2 adsorbed based on the gas equation. This will give an N2 adsorption isotherm from 0 atmospheres to 0.995 atmospheres at liquid nitrogen temperature. After reaching 0.995 atmospheres, the N2 pressure is gradually reduced to 0 atmospheres, and an N2 desorption isotherm from 0.995 atmospheres to 0 atmospheres is obtained, and the N2 adsorption / desorption isotherms are obtained together. The analysis based on the N2 adsorption / desorption isotherms is as follows. The pore volume of the openings is determined from the amount of N2 adsorbed when the relative pressure (p / p0) of the N2 adsorption isotherm is 0.995. The pores of the positive electrode active material are largely distributed on the surface of the secondary particles. In this application, by ensuring that the pore volume of the openings of the positive electrode active material satisfies a predetermined range, it is possible to provide more lithium ion reaction passages on the one hand, and on the other hand, it is advantageous in reducing the risk of the electrolyte eroding into the interior of the material more than necessary. By having the electrolyte form an appropriate CEI layer only on the surface layer and surface pores of the material, the positive electrode active material can be endowed with high initial charge / discharge efficiency, good storage performance and cycle performance. Furthermore, the pore volume V of the openings of the positive electrode active material o This is 0.002 cm 3 / g~0.008cm 3It may also be / g.

[0044] In some specific embodiments of the present application, the skeletal volume V of the positive electrode active material o is 0.2 cm 3 / g to 0.25 cm 3 / g may also be, for example, 0.2 cm 3 / g, 0.21 cm 3 / g, 0.22 cm 3 [[ID=1Q]] / g, 0.23 cm 3 / g, 0.24 cm 3 / g, or 0.25 cm 3 / g etc. may also be. The skeletal volume of the positive electrode active material can be measured in combination with an apparatus such as a true density meter by the gas replacement method. For example, it is obtained from a test using the Accupy II1345 true density meter manufactured by Micromeritics. Here, the gas replacement method specifically includes using an inert gas N2 as a replacement medium, sealing the sample in a sample chamber filled with N2, opening the expansion chamber to diffuse the gas, and after stabilization, calculating the volume of the sample from the pressure change before and after gas diffusion. Note that since N2 can be quickly filled into pores with a diameter on the order of angstroms, the measured volume is only the skeletal volume of the material. In the present application, the fact that the skeletal volume of the positive electrode active material satisfies a predetermined range is advantageous for the compatibility of the particle size and the specific density of the material, and the positive electrode active material can be provided with a high charge-discharge specific capacity. Furthermore, the skeletal volume V of the positive electrode active material t is 0.2 cm 3 / g to 0.25 cm 3 / g may also be.

[0045] In some specific embodiments of the present application, the total porosity P of the positive electrode active material o may be 1% to 10%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10% etc. may also be. The total porosity P of the positive electrode active material tincludes the porosity of open pores and the porosity of closed pores, and moreover, by making the porosity of closed pores usually larger than the porosity of open pores, the total porosity of the positive electrode active material can satisfy a predetermined range. Thereby, it is possible to provide space for the expansion and contraction in the charge and discharge process of the positive electrode active material, which is also advantageous for improving the cycle stability of the positive electrode active material and enhancing the cycle performance of the material. Furthermore, the total porosity P of the positive electrode active material t may be 1.5% to 8.5%.

[0046] In some specific embodiments of the present application, in the secondary particles, the average pore diameter D of the closed pores CThe wavelength may be 40 nm to 200 nm, for example, 40 nm, 50 nm, 60 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, or 200 nm. Referring to Figure 2, the average pore diameter of closed pores in secondary particles may be obtained by performing contrast analysis on an electron microscope image of the cross-section of the secondary particle using the LIBMAS intelligent image analysis system to obtain the cross-sectional area of ​​each pore, and then assuming that the pore shape in the electron microscope image of the cross-section is circular, and obtaining the average pore diameter of the cross-section. Here, the average pore diameter of closed pores of a single secondary particle may be set to satisfy a predetermined range, or the average pore diameter of closed pores of all secondary particles in the positive electrode active material may be set to satisfy a predetermined range. In that case, when testing a sample of the positive electrode active material, referring to the method for testing the total porosity of the positive electrode active material described above, multiple secondary particles may be sampled and selected from the test sample, the average pore diameter of the closed pores corresponding to each of the multiple secondary particles may be obtained, and then the average value may be calculated. By ensuring that the average pore size of the closed pores in the secondary particles meets a predetermined range, it is possible for voids within the material to exist in the form of small pores, while also allowing for a relatively uniform distribution within the particles, contributing to improved structural stability and particle strength of the positive electrode active material. In addition, the fine pores between primary particles can provide a large expansion and contraction space for charge-discharge cycles, contributing to improved cycle performance of the positive electrode active material. Furthermore, it is advantageous for providing the positive electrode active material with good rate performance by avoiding unnecessary losses of good conductivity and media transport performance between materials. Moreover, in the secondary particles, the average pore size D of the closed pores C The range may be 60nm to 180nm.

[0047] In some specific embodiments of this application, the specific surface area of ​​the positive electrode active material is S 0 The specific surface area of ​​the positive electrode active material after fracturing under a pressure of 3.5 tons is S. 3.5 Therefore, the rate of change of specific surface area ΔSSA of the positive electrode active material is 0-50%, and ΔSSA = (S 3.5 -S 0 ) / S 0This is multiplied by 100%. For example, ΔSSA may be 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%. The specific surface area of ​​the positive electrode active material may be measured by a surface meter based on the static adsorption principle of N2. For example, it can be obtained by testing with a Tristar 3020 surface meter manufactured by Micromeritics. The specific procedure is as follows: In the measuring apparatus, under vacuum conditions, N2 is gradually added to a sample of the material to be measured from which physical adsorbed components have been removed beforehand. The pressure change due to N2 adsorption is calculated using the constant volume method, and the amount of N2 adsorbed is obtained based on the gas equation. This allows obtaining the amount of N2 adsorbed from 0 atmospheres to 0.3 atmospheres at liquid nitrogen temperature, and this is then converted to the specific surface area per unit weight. A positive electrode active material whose rate of change in specific surface area before and after fracturing under a pressure of 3.5 tons satisfies a given range has good pressure resistance characteristics. In the subsequent manufacturing process of electrode tabs, this contributes to avoiding the risk of the electrode tabs fracturing during the pressing process, leading to improved battery stability and reduced safety risks. On the other hand, it allows the positive electrode active material to have a pressable density that is highly susceptible to stress, potentially further improving the energy density of the positive electrode tabs and the battery.

[0048] In some specific embodiments of this application, when the volume distribution of the positive electrode active material accumulates to 10%, the corresponding particle size is D 10 0 Therefore, when the volume distribution of the positive electrode active material after fracturing under a pressure of 3.5 tons accumulates to 10%, the corresponding particle size is D 10 3.5 The particle size change rate ΔD of the positive electrode active material is 10 The range is 0-20%, and ΔD 10 =(D 10 0 -D 10 3.5 ) / D 10 0 It is ×100%. For example, ΔD 10The concentration may be 0%, 2%, 5%, 8%, 10%, 12%, 15%, 18%, or 20%, etc. The particle size of the positive electrode active material is obtained by testing with a laser particle size analyzer. For example, it can be obtained by testing with a Hydro2000mu laser particle size analyzer manufactured by Marvern. A positive electrode active material whose particle size change rate before and after fracturing at a pressure of 3.5 tons satisfies a given range has good pressure resistance and generates less fracturing fine powder at high pressure, which is advantageous for further improving the stability of the positive electrode active material in the manufacturing process of electrode tabs and leads to a reduction in safety risks.

[0049] In some specific embodiments of this application, the positive electrode active material is Li 1+a Ni x Co y Mn z M m It contains O2, where -0.05≦a≦0.3, 0.8≦x≦1, 0≦y≦0.2, 0≦z≦0.2, and 0≦m≦0.01, and M may contain at least one of Mg, La, Al, Sr, Ba, Y, Zr, Ca, Fe, Zn, Sn, W, V, Mo, Sb, Ta, Ti, Nb, S, P, and B. For example, the value of a may be -0.05, -0.02, 0, 0.05, 0.1, 0.1, 0.2, 0.25, or 0.3, the value of x may be 0.8, 0.85, 0.9, 0.95, or 1, the value of y may be 0, 0.05, 0.1, 0.15, or 0.2, the value of z may be 0, 0.05, 0.1, 0.15, or 0.2, and the value of m may be 0, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, or 0.01. Selectively, m > 0, and further selectively, 0.002 ≤ m ≤ 0.01. Positive electrode active materials within a given range have high energy density and operating voltage, and relatively good cycle characteristics, which can further improve the battery's cycle life.

[0050] In some specific embodiments of this application, when m>0, the positive electrode active material may contain at least one of Sn, W, V, La, Mo, Sb, Ta, Ti, and Nb, and the full width at half maximum of the diffraction peaks corresponding to the 10⁴ crystal planes in the XRD profile of the primary particles may be 0.245 to 0.270. For example, it may be 0.245, 0.250, 0.255, 0.260, 0.265, or 0.270. The full width at half maximum of the diffraction peaks corresponding to the 10⁴ crystal planes in the XRD profile of the primary particles is obtained by characterizing it with an X-ray diffractometer. For example, it can be obtained by testing with a Smart Lab9 KW manufactured by Nippon Rigakusha. By using a predetermined type of high-valence element as a doping element, the particle size of the primary particles of the positive electrode active material can be refined, or the arrangement effect of the primary particles can be affected, thereby influencing the aggregation state when the primary particles are formed as secondary particles, and also affecting the pore structure of the entire positive electrode active material. By ensuring that the full width at half maximum (FWHM) of the 10⁴ crystal planes of the primary particles of a positive electrode active material having a predetermined type of high-valence doped element satisfies a predetermined range, it is possible to obtain primary particles with relatively large average dimensions even if the FWHM of the 10⁴ crystal planes of the primary particles is small. Furthermore, this is advantageous for obtaining a good porous structure when the primary particles are deposited and formed into secondary particles.

[0051] In some specific embodiments of this application, when m>0, M may include at least one of S, P, and B, and the full width at half maximum of the diffraction peaks corresponding to the 10⁴ crystal planes in the XRD profile of the primary particles may be 0.250 to 0.275. For example, it may be 0.250, 0.255, 0.260, 0.265, 0.270, or 0.275. By using a predetermined type of element as a doping element, a pore-forming effect can also be obtained. Many of these doping elements can be doped and concentrated between primary particles, and after washing with water, pores can be left between the primary particles. In this case, the full width at half maximum of the 10⁴ crystal planes of the primary particles satisfies the particle dimensions corresponding to a predetermined range, which is also advantageous for obtaining a good porous structure when deposited and formed as secondary particles.

[0052] In some specific embodiments of this application, when m>0, M may include at least one of Mg, Al, Sr, Ba, Y, Zr, Ca, Fe, and Zn, and the full width at half maximum (FWHM) of the diffraction peaks corresponding to the 10⁴ crystal planes in the XRD profile of the primary particles may be 0.255 to 0.280. For example, it may be 0.255, 0.260, 0.265, 0.270, 0.275, or 0.280. When a predetermined type of element is used as a doping element, by controlling the FWHM of the diffraction peaks corresponding to the 10⁴ crystal planes within a predetermined range, the FWHM of the 10⁴ crystal planes of the primary particles becomes a large value, making it possible to obtain primary particles with a relatively small average size. Furthermore, the risk of primary particles excessively fusing together and growing excessively large and dense before losing the porosity effect can be reduced, thereby contributing to the acquisition of a good porosity structure.

[0053] In some specific embodiments of the present application, the positive electrode active material may include a substrate and a coating layer, wherein the substrate is Li 1+a Ni x Co y Mn z M m The substrate may contain O2, and a coating layer may be provided on at least a portion of its surface. The presence of the coating layer allows for some degree of adjustment and control of the pore structure of the positive electrode active material, thereby reducing the porosity of the openings and achieving objectives such as decreasing side reactions between the positive electrode active material particles and the electrolyte. Furthermore, the presence of the coating layer contributes to some extent to improving the cycle stability of the positive electrode active material.

[0054] In some specific embodiments of the present application, the coating layer may contain element J, which includes at least one of Al, Zr, Ti, F, B, Cl, Br, I, S, W, Co, Sn, and Mo. By doping the coating layer with a predetermined type of element, the positive electrode active material can be protected, side reactions between the surface of the positive electrode active material and the electrolyte can be reduced, a high-quality CEI film can be formed, gas generation can be suppressed, and the storage life and electrochemical cycle performance of the positive electrode active material can be improved.

[0055] In some specific embodiments of this application, the coating layer may contain element J, and the ratio of the total number of moles of Ni, Co, Mn, and M in the substrate to the number of moles of element J in the coating layer may be 1:(0~0.05), for example, 1 / 0.01, 1 / 0.02, 1 / 0.03, 1 / 0.04, or 1 / 0.05. Meeting the predetermined range is advantageous for improving the cycle performance of the positive electrode active material, and in addition, it is possible to achieve a porosity structure of the positive electrode active material while reducing the risk of affecting the specific capacity, electrochemical activity, and rate performance of the positive electrode active material due to the high content of the coating layer. This makes it even more advantageous to give the positive electrode active material advantages such as high electrochemical activity, high energy density, high particle strength, and long cycle life.

[0056] In some specific embodiments of the present application, the method for obtaining a positive electrode active material having a desired porosity structure is not particularly limited and can be flexibly selected by those skilled in the art according to their practical needs. For example, by adjusting and controlling one or more of the precursor porosity, particle size, morphology, and arrangement of primary particles, the aggregation effect when primary particles are deposited as secondary particles can be adjusted and controlled, and further by adjusting and controlling the porosity structure of the positive electrode active material, a positive electrode active material having a desired porosity structure can be obtained. Based on this, the porosity structure of the positive electrode active material can be further adjusted and controlled by selecting one or more of the following: whether or not to provide a coating layer, the selection of the coating layer material, and the thickness of the coating layer. In addition, the porosity of the precursor of primary particles can also be adjusted and controlled by methods such as co-precipitation of the precursor.

[0057] A second aspect of the present application provides a method for producing the positive electrode active material described above, (1) A step of obtaining precursor particles by coprecipitation reaction of aqueous solutions of a nickel source, a cobalt source and a manganese source under alkaline conditions, and (2) We propose a method for obtaining a positive electrode active material by mixing precursor particles with a lithium source and an M source and performing a sintering process. In this method, by combining the nickel-cobalt-manganese composition, control of the precursor porosity, and the amount of M element doping, the temperature and time of the sintering process, as well as the size and arrangement of the primary grains, can be adjusted and controlled, and the aggregation effect between primary particles in the secondary particles can be adjusted and controlled. This contributes to obtaining a positive electrode active material in which the ratio of open porosity to total porosity is 25% to 85%, and the material can be endowed with high particle strength, high rate performance, and good cycle stability that can withstand expansion and contraction during the charge-discharge process. The characteristics and effects described above for the positive electrode active material can also be applied to the method for producing the said positive electrode active material, so their explanation is omitted here.

[0058] In some specific embodiments of the present invention, step (1) may involve carrying out the coprecipitation reaction under alkaline conditions where the pH value is 10 to 11.5. For example, in the process of the coprecipitation reaction, a nickel source, a cobalt source, and a manganese source may be dissolved in water to control the pH value of the mixture to 10 to 11.5, and the median diameter D of the particles may be controlled. 50 The crystals may be nucleated and grown until they reach a size of 9 μm to 20 μm. Here, controlling the pH of the mixture contributes to controlling the coprecipitation reaction rate, and it is also possible to create a certain amount of pores in the precursor, thereby retaining a certain porosity effect in the cathode active material during the subsequent sintering and fusion process. Selectively, aqueous ammonia may be added as a complexing agent in the coprecipitation reaction.

[0059] In some specific embodiments of the present invention, step (2) may include holding the sintering process at 650°C to 900°C for 4 to 15 hours. For example, the sintering temperature may be 650°C, 700°C, 750°C, 800°C, 850°C, or 900°C, and the holding time may be 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, or 15 hours. In the actual operation, the sintering temperature and time can be flexibly controlled according to the actual conditions such as the type of doping element M and the composition of nickel-cobalt-manganese to obtain the desired primary particle size or the full width at half maximum of the 10⁴ crystal plane, and is also advantageous for obtaining the appropriate porosity effect of the positive electrode active material.

[0060] In some specific embodiments of the present invention, step (2) may include operations such as cooling, crushing, and sieving after the completion of the sintering process.

[0061] In some specific embodiments of the present invention, step (2) may further include mixing the sintered product (i.e., sintered material) with a coating material containing the J source and holding the mixture at 300°C to 700°C for 5 to 10 hours. This allows for the formation of a coating layer containing the J element on the surface of the sintered material, thereby obtaining a positive electrode active material having a substrate and coating layer structure. The beneficial effects of forming the coating layer and the characteristics and effects of the types of J elements have already been explained in detail in the above section, so please refrain from further explanation here.

[0062] In a third aspect of this application, a positive electrode tab is proposed that includes the positive electrode active material described above, or a positive electrode active material manufactured by the method described above. The features and advantages described above for the positive electrode active material and the manufacturing method described above are also applicable to this positive electrode tab, and therefore their explanation is omitted here. In short, this positive electrode tab has good cycle stability and a long cycle life.

[0063] Typically, a positive electrode tab may include a positive electrode current collector and a positive electrode active material layer provided on at least one side of the positive electrode current collector. The positive electrode active material layer may include the positive electrode active material described above or a positive electrode active material obtained by the manufacturing method described above. Here, the positive electrode current collector may include, but is not limited to, a metal foil (e.g., aluminum foil) or a composite current collector, and the positive electrode active material layer may further include an adhesive and a conductive agent. Here, the specific types and origins of the adhesive and conductive agent are not particularly limited, and those skilled in the art can flexibly select them according to their practical needs. For example, the adhesive may include, but is not limited to, polyvinylidene fluoride. The conductive agent may include, but is not limited to, one or more of conductive carbon black, carbon nanotubes, graphene, etc.

[0064] A fourth aspect of the present invention proposes a battery including the positive electrode tab described above. The features and effects described above for the positive electrode tab are similarly applicable to this battery and are therefore omitted from further explanation. Optionally, the battery may be a rechargeable battery.

[0065] Typically, in addition to the positive electrode tab, a battery may consist of a negative electrode tab, an electrolyte, a separator, and the like. Here, the specific structure or composition of the negative electrode tab, electrolyte, and separator are not particularly limited and can be flexibly selected by those skilled in the art according to practical needs. For example, the negative electrode tab may include a negative electrode current collector and a negative electrode active material layer provided on at least one side of the negative electrode current collector, while the negative electrode active material layer may include a negative electrode active material, an adhesive, a conductive agent, and the like. Here, the negative electrode current collector may include, but is not limited to, metal foil (e.g., copper foil) or a composite current collector. The specific types and origins of the active material, adhesive, and conductive agent in the negative electrode tab are also not particularly limited and can be flexibly selected by those skilled in the art according to practical needs. For example, the negative electrode active material may include, but is not limited to, one or more of hard carbon, soft carbon, silicon-based materials, silicon carbon materials, and the like. The adhesive may include, but is not limited to, styrene-butadiene rubber, and the like. The conductive agent may include, but is not limited to, one or more of the following: conductive carbon black, carbon nanotubes, graphene, etc. Furthermore, general components such as thickeners may be selectively added to the negative electrode active material layer. In addition, the separator may include, but is not limited to, a polyethylene (PE) film, a polypropylene (PP) film, a PP / PE / PP composite film, a composite ceramic separator, or an adhesive-coated separator. Furthermore, for example, the electrolyte may contain an organic solvent and an electrolyte salt. Taking a lithium battery as an example, the organic solvent may include one or more ester-based solvents such as dimethyl carbonate (DMC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC). The electrolyte salt may include one or more common lithium salts such as lithium hexafluorophosphate (LiPF6), lithium bisfluorosulfonylimide (Li FSI), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (Li As F6), lithium bis(oxalato)borate (Li BOB), and lithium difluorophosphate (LiO2F2), but is not limited to these. Additives may be selectively added to the electrolyte.The above-mentioned additives may include, but are not limited to, common additives such as vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0066] A fifth aspect of this application proposes an electrical device including the battery described above. The features and effects described for the battery described above are also applicable to this electrical device and are therefore omitted from further explanation. The specific type of electrical device is not particularly limited and can be flexibly selected by those skilled in the art according to practical needs. For example, it may include, but is not limited to, electronic devices, household electrical devices, vehicles, etc.

[0067] The present application will be described below with reference to specific examples. These examples are illustrative only and are not intended to limit the present application in any way. Unless otherwise specified, the examples are carried out in accordance with the techniques or conditions described in the literature in the art or in accordance with the product manual. Unless otherwise specified, the reagents or equipment used are general-purpose products available on the market.

[0068] In the following embodiments, unless otherwise specifically described, all raw materials are commercially available products.

[0069] In the following examples and comparative examples, the relevant parameters are obtained by testing using the following methods.

[0070] (1) Topography test: Obtained by testing with a Hitachi S-4800 scanning electron microscope manufactured by Hitachi, Ltd.

[0071] (2) Total porosity P tTesting: The cross-section of the positive electrode active material is obtained using a Hitachi IM4000 II ion grind gauge, image sampling of the material cross-section is performed using an S-4800 scanning electron microscope, and contrast analysis of the image is performed using the LIBMAS intelligent image analysis system. Here, the measured value for each sample is the average value of the porosity measured using six particle spheres. Here, when the image of the sample is taken with a scanning electron microscope, the diameter of the cross-section is the particle size D of the material. 50 ~D 80 Select a sample from the options provided.

[0072] (3) Average pore diameter D of closed holes C Testing for: Using the LIBMAS intelligent image analysis system, the cross-sectional area of ​​each pore is obtained by performing contrast analysis on the cross-sectional electron microscope image. Assuming the pore shape in the cross-sectional electron microscope image is circular, the average pore diameter of the cross-section is obtained. Here, the measurements for each sample are taken using six particle spheres, and the average value is taken.

[0073] (3) Test for specific surface area of ​​the material: This is obtained by testing with a Tristar3020 surface meter manufactured by Micromeritics, based on the static adsorption principle of N2. Here, static adsorption by N2 is specifically described as follows: In the measuring device, under vacuum conditions, N2 is gradually added to a sample of the material to be measured from which the physically adsorbed components have been removed beforehand. The pressure change due to N2 adsorption is calculated using the constant-volume method, and the amount of N2 adsorbed is obtained based on the gas equation. This allows for obtaining the amount of N2 adsorbed from 0 atmospheres to 0.3 atmospheres at liquid nitrogen temperature, and this is then converted into specific surface area per unit weight.

[0074] (4) Hole volume V o Testing for: Results obtained by testing and analysis based on N2 adsorption / desorption isotherms using a Tristar 3020 surface meter manufactured by Micromeritics.

[0075] Here, the test based on N2 adsorption / desorption isotherms is specifically as follows: Using a general measuring device (such as Tristar3020), N2 is gradually added to the material under test, from a vacuum state, from which the physically adsorbed components have been removed beforehand. The pressure change due to N2 adsorption is calculated using the constant-volume method, and the amount of N2 adsorbed is obtained based on the gas equation. This yields an N2 adsorption isotherm from 0 atmospheres to 0.995 atmospheres at liquid nitrogen temperature. After reaching 0.995 atmospheres, the N2 pressure is gradually reduced to 0 atmospheres, and an N2 desorption isotherm is obtained from 0.995 atmospheres to 0 atmospheres, thus obtaining all N2 adsorption / desorption isotherms together. Here, the analysis based on the N2 adsorption / desorption isotherms is as follows: The pore volume of the opening is determined from the amount of N2 adsorbed when the relative pressure (p / p0) of the N2 adsorption isotherm is 0.995.

[0076] (5) Average pore diameter D o Testing for: Obtained by testing with a Tristar3020 surface meter manufactured by Micromeritics, using the BJH (Barrett Joyner Halenda) model.

[0077] Here, the BJH model and pore size testing are specifically described below. Assuming the pore shape is cylindrical, the Kelvin relation is satisfied based on the relative pressure between the pore size where capillary condensation occurs and N2. By measuring the amount of N2 adsorbed at different partial pressures and corresponding pore sizes, the distribution of material pore sizes is represented, and the average pore size is obtained by multiplying each pore size by a ratio coefficient. In this application, the use of desorption isotherms is intended to obtain the pore size at the pore entrance.

[0078] (6) Volume V of the framework of the positive electrode active material t Testing for: Obtained by gas displacement method using a Micromeritics Accupy II 1345 true density meter. The gas displacement method is as follows: Inert gas N2 is used as the displacement medium. The sample is sealed in a sample chamber filled with N2, the expansion chamber is opened to allow the gas to diffuse, and after stabilization, the volume of the sample may be calculated from the pressure change before and after gas diffusion.

[0079] (7) XRD and finish of materials: obtained by testing with Smart Lab9 KW manufactured by Nippon Rigakusha.

[0080] (8) Testing of the particle size distribution of the material: Obtained by testing with a Hydro2000mu laser particle size analyzer manufactured by Marvern.

[0081] (9) Particle strength test: Obtained by testing the particles using a micro-compression testing machine MCT-210 manufactured by Shimadzu Corporation.

[0082] (10) Tests for electrochemical performance: In the following examples and comparative examples, the electrochemical performance of the multicomponent cathode material is tested using a 2025 coin cell.

[0083] The manufacturing process for the Type 2025 coin cell battery is as follows:

[0084] The electrode tabs are manufactured as follows: A multi-component cathode active material, acetylene black, and polyvinylidene fluoride (PVDF) are thoroughly mixed with an appropriate amount of N-methylpyrrolidone (NMP) in a mass ratio of 95:3:2 to form a uniform slurry. The slurry is then applied to aluminum foil and dried at 120°C for 12 hours. Finally, it is press-molded under a pressure of 100 MPa to produce cathode tabs with a diameter of 12 mm and a thickness of 120 μm. Here, the loading amount of the above multi-component cathode material is (15.5 ± 0.5) mg / cm³. 2 That is the case.

[0085] The battery is assembled as follows: The positive electrode tab, separator, negative electrode tab, and electrolyte are assembled into a 2025 coin cell in an Ar gas glove box with water and oxygen content of less than 5 ppm, and left to stand for 6 hours. Here, a metallic sodium sheet with a diameter of 17 mm and a thickness of 1 mm is used for the negative electrode tab, a Celgard 2325 porous membrane with a thickness of 25 μm is used for the separator, and an equal mixture of 1 mol / L NiPF6, ethylene carbonate (EC), and diethyl carbonate (DEC) is used for the electrolyte.

[0086] Testing of 2025 type coin cell batteries: In the following examples and comparative examples, electrochemical tests are performed on Type 2025 coin-type batteries using the Shenzhen Neware battery testing system. The charge / discharge current density at 0.1C is assumed to be 200 mA / g.

[0087] The charge and discharge voltage range is controlled to 3.0V to 4.3V, and charge and discharge tests are performed at 0.1C on coin-type batteries at room temperature to evaluate the electrochemical performance of the multi-component cathode material.

[0088] Cycle performance testing: The charge / discharge voltage range is controlled to 3.0~4.3V, and at a constant temperature of 45°C, the coin-type battery is charged and discharged for 2 cycles at 0.1C, followed by 80 charge / discharge cycles at 1C to evaluate the high-temperature capacity retention rate of the multi-component cathode material.

[0089] Rate Performance Test: The charge / discharge voltage range is controlled to 3.0V to 4.3V. At room temperature, a coin-type battery is charged and discharged for two cycles at 0.1C, followed by one charge / discharge cycle each at 0.2C, 0.33C, 0.5C, and 1C. The rate performance of the multi-component cathode material is evaluated by the ratio of the initial discharge ratio capacity at 0.1C to the discharge ratio capacity at 1C. Here, the initial discharge ratio capacity at 0.1C is the discharge ratio capacity of the coin-type battery after the first cycle, and the discharge ratio capacity at 1C is the discharge ratio capacity of the coin-type battery after the sixth cycle.

[0090] Example 1 (1) Nickel sulfate, cobalt sulfate, and manganese sulfate are dissolved in pure water in a molar ratio of nickel, cobalt, and manganese of 83.3:10:6 to obtain a mixed salt solution with a concentration of 2 mol / L. An 8 mol / L sodium hydroxide solution is prepared as a precipitating agent solution, and a 6 mol / L aqueous ammonia solution is prepared as a complexing agent solution. The mixed salt solution, sodium hydroxide solution, and aqueous ammonia are each added to the reaction vessel through the feed pipe, N2 is added to provide protection, the stirring speed is maintained at 600 rpm, the feed rate of the mixed salt solution is controlled to 400 mL / h, and the flow rates of the sodium hydroxide solution and aqueous ammonia are adjusted to stabilize the pH of the reaction system to 10.9 ± 0.05 and to control the temperature of the reaction system to 60°C. After the average particle size Dv50 in the reaction system has grown to 14 μm, it is aged for 1 hour, separated, washed, and dried to obtain the cathode active material precursor.

[0091] (2) The above-mentioned precursors, lithium hydroxide, aluminum oxide, and niobium pentoxide are uniformly mixed so that the sum of nickel, cobalt, and manganese elements in the precursors and the molar ratio of lithium, aluminum, and niobium elements are 0.993:1.03:0.004:0.003. The mixture is then heated in an oxygen furnace and then sintered at a constant temperature, with the oxygen concentration in the oxygen furnace exceeding 95% by volume, the heating rate being 5°C / min, the sintering temperature being 810°C, and the sintering time being 10 hours. After natural cooling to room temperature, the mixture is crushed, sieved to remove iron, and the sintered material for the positive electrode active material is obtained.

[0092] (3) The sintered material for the positive electrode active material and boric acid are placed in a high-speed mixer and mixed uniformly so that the molar ratio of the sum of Ni, Co, Mn, Al, and Nb in the sintered material for the positive electrode active material to the element boron is 1:0.001. The mixture is then sintered in an oxygen furnace at a constant temperature of 350°C, with an oxygen concentration exceeding 90% by volume, for a sintering time of 8 hours. After cooling and sieving to remove iron, the positive electrode active material Li 1.03 Ni 0.833 Co 0.100 Mn 0.060 Al 0.004 Nb 0.003Obtain O2@B. In the chemical formula of the positive electrode active material, the part before the @ is the base component, and the part after the @ is the main element in the coating layer.

[0093] Examples 2-10 and Comparative Examples 1-4 For details on the differences between Examples 2-14 and Comparative Examples 1-6 and Example 1, please refer to Tables 1 and 2.

[0094] In Example 2, zirconium dioxide and tungsten oxide were used as the dopant M source, and boric acid was used as the coating agent.

[0095] In Example 3, magnesium oxide and tin dioxide were used as the M source, and tungsten trioxide was used as the coating agent.

[0096] In Example 4, strontium oxide and antimony trioxide were used as the M source, and tungsten trioxide was used as the coating agent.

[0097] In Example 5, aluminum oxide and lithium sulfate were used as the M source, and boric acid was used as the coating agent.

[0098] In Example 6, aluminum oxide and strontium hydroxide were used as the M source, and boric acid was used as the coating agent.

[0099] In Example 7, aluminum oxide and niobium pentoxide are used as the M source.

[0100] In Example 8, aluminum oxide and boric acid were used as the M source, and cobalt hydroxide was used as the coating agent.

[0101] In Example 9, titanium dioxide and niobium pentoxide were used as the M source, and tungsten trioxide was used as the coating agent.

[0102] In Example 10, aluminum oxide and lithium sulfate were used as the M source, and boric acid was used as the coating agent.

[0103] In Comparative Example 1, aluminum oxide and niobium pentoxide were used as the M source, and boric acid was used as the coating agent.

[0104] In Comparative Example 2, aluminum oxide and niobium pentoxide were used as the M source, and boric acid was used as the coating agent.

[0105] In Comparative Example 3, aluminum oxide and niobium pentoxide were used as the M source, and boric acid was used as the coating agent.

[0106] In Comparative Example 4, aluminum oxide and niobium pentoxide were used as the M source, and boric acid was used as the coating agent.

[0107] For detailed results of the tests for Examples 1-10 and Comparative Examples 1-4, please refer to Table 2.

[0108] [Table 1]

[0109] [Table 2]

[0110] Results and conclusions: As can be seen from Examples 1-10 and Comparative Examples 1-4, as well as Tables 1-2 and Figures 1-2 (Figure 1 shows the pore structure of the precursor produced by Example 1, and Figure 2 shows the distribution of closed pores in the cross-section of the positive electrode active material produced by Example 1), by using the manufacturing method in the above examples of this application, it is possible to obtain a positive electrode active material in which the porosity of open pores is 25% to 85% of the total porosity. Moreover, when the positive electrode active material is used in a battery, the positive electrode active material in which the porosity of open pores is 25% to 85% of the total porosity shows a relatively good improvement in the battery's rate performance and cycle performance, and the battery's energy density, initial performance, rate performance and cycle performance are all good, resulting in good overall performance. As can be seen from the tests, the elemental composition of the positive electrode active materials produced in Examples 1-10 is Li1+a Ni x Co y Mn z M m The material satisfies the general formula O2, where -0.05≦a≦0.3, 0.8≦x≦1, 0≦y≦0.2, 0≦z≦0.2, and 0≦m≦0.01. Furthermore, as can be seen by combining Example 1 and Example 7, the formation of a coating layer on the positive electrode active material contributes to further improvement in the electrochemical performance of the battery. Compared to Example 1, the porosity of open pores in the positive electrode active materials produced in Comparative Examples 1 and 3 is relatively low as a percentage of the total porosity, while the porosity of open pores in the positive electrode active materials produced in Comparative Examples 2 and 4 is high as a percentage of the total porosity. The reason for this is thought to be that in Comparative Example 1, the sintering temperature was high, and the fusion of particles during the sintering process reduced the volume of open and closed pores, which then affected the ratio of open pore porosity to total porosity. In Comparative Example 2, the sintering time was relatively long, and the fusion of particles during the sintering process clearly reduced the volume of closed pores and the volume of total pores. In Comparative Example 3, the amount of coating agent used was relatively large, resulting in a decrease in the porosity of the open pores of the material. In Comparative Example 4, the pH value was controlled to a relatively large extent during the coprecipitation reaction process, resulting in low porosity of both the closed pores and the total porosity of the precursor.

[0111] In this specification, reference terms such as “one embodiment,” “several embodiments,” “example,” “specific example,” or “several examples” mean that the specific constituent elements, structures, materials, or features described in combination with such embodiment or example are included in at least one embodiment or example of this application. In this specification, exemplary expressions for the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific constituent elements, structures, materials, or features described may be combined in an appropriate manner in any one or more embodiments or examples. Furthermore, a person skilled in the art may combine and link different embodiments or examples and features of different embodiments or examples described herein, as long as they do not conflict with each other.

[0112] Although embodiments of the present application have already been shown and described above, it should be understood that these embodiments are merely illustrative and should not be understood as restricting the present application. Those skilled in the art can modify, amend, switch, and transform the above embodiments within the scope of the present application.

Claims

1. It is a positive electrode active material, It contains secondary particles formed by the accumulation of primary particles, The secondary particles include open and closed pores, The porosity P of the pores in the positive electrode active material ｏ P is the total porosity of the positive electrode active material. ｔ The positive electrode active material accounts for 25% to 85% of the total.

2. The porosity P of the pores in the positive electrode active material ｏ The percentage is between 0.5% and 3%. The average pore diameter D of the openings in the positive electrode active material. ｏ The wavelength is between 10 nm and 50 nm. The pore volume V of the opening in the positive electrode active material. ｏ 0.002 cm ３ / g ~ 0.01cm ３ The fact that it is / g, and, The skeletal volume V of the positive electrode active material ｔ is 0.2 cm ３ / g to 0.25 cm ３ / g, The positive electrode active material according to claim 1, satisfying at least one of the following conditions.

3. The total porosity P of the positive electrode active material ｔ is 1% to 10%, and / or In the secondary particles, the average pore size D of the closed pores Ｃ The positive electrode active material according to claim 1 or 2, wherein the wavelength is 40 nm to 200 nm.

4. The specific surface area of ​​the positive electrode active material is S ０ And, The specific surface area of ​​the positive electrode active material after fracturing under a pressure of 3.5 tons is S. ３．５ And, The specific surface area change rate ΔSSA of the positive electrode active material is 0 to 50%. ΔSSA = (S ３．５ -S ０ ) / S ０ ×100%, and / or When the volume distribution of the positive electrode active material accumulates to 10%, the corresponding particle size is D １０ ０ And, When the volume distribution of the positive electrode active material after fracturing under a pressure of 3.5 tons accumulates to 10%, the corresponding particle size is D １０ ３．５ And, The particle size change rate ΔD of the positive electrode active material １０ The percentage is 0-20%, ΔD １０ = (D １０ ０ -D １０ ３．５ ) / D １０ ０ A positive electrode active material according to any one of claims 1 to 3, wherein the ratio is ×100%.

5. The positive electrode active material is Li １＋ａ Ni ｘ Co ｙ Mn ｚ M ｍ O ２ Includes, However, -0.05 ≤ a ≤ 0.3, 0.8 ≤ x ≤ 1, 0 ≤ y ≤ 0.2, 0 ≤ z ≤ 0.2, and 0 ≤ m ≤ 0.

01. M includes at least one of Mg, La, Al, Sr, Ba, Y, Zr, Ca, Fe, Zn, Sn, W, V, Mo, Sb, Ta, Ti, Nb, S, P, and B. The positive electrode active material according to any one of claims 1 to 4.

6. M includes at least one of Sn, W, V, La, Mo, Sb, Ta, Ti, and Nb. The full width at half maximum of the diffraction peaks corresponding to the 10⁴ crystal plane in the XRD profile of the primary particle is 0.245 to 0.270, or M includes at least one of S, P, and B. The full width at half maximum of the diffraction peaks corresponding to the 10⁴ crystal plane in the XRD profile of the primary particle is 0.250 to 0.275, or M contains at least one of Mg, Al, Sr, Ba, Y, Zr, Ca, Fe, and Zn. The full width at half maximum of the diffraction peaks corresponding to the 10⁴ crystal plane in the XRD profile of the primary particle is 0.255 to 0.

280. The positive electrode active material according to claim 5.

7. The aforementioned secondary particles include a substrate and a coating layer. The substrate is the Li １＋ａ Ni ｘ Co ｙ Mn ｚ M ｍ O ２ Includes, The positive electrode active material according to claim 5 or 6, wherein the coating layer is provided on at least a portion of the surface of the substrate.

8. The coating layer contains element J, which includes at least one of Al, Zr, Ti, F, B, Cl, Br, I, S, W, Co, Sn, Mo, and / or The positive electrode active material according to claim 7, wherein the ratio of the total number of moles of Ni, Co, Mn, and M in the substrate to the number of moles of element J in the coating layer is 1:(0 to 0.05).

9. A method for producing a positive electrode active material according to any one of claims 1 to 8, (1) A step of obtaining precursor particles by coprecipitation reaction of aqueous solutions of a nickel source, a cobalt source and a manganese source under alkaline conditions. (2) A method for obtaining a positive electrode active material by mixing the precursor particles with a lithium source and an M source and performing a sintering process.

10. In step (1), the coprecipitation reaction is carried out under alkaline conditions where the pH value is 10 to 11.

5. Step (2) includes the sintering process being maintained at 650°C to 900°C for 4 to 15 hours, and Step (2) further includes mixing the sintered product with a coating material containing the J source and holding it at 300°C to 700°C for 5 to 10 hours, satisfying at least one of the following conditions. The method according to claim 9.

11. A positive electrode tab comprising a positive electrode active material according to any one of claims 1 to 8, or a positive electrode active material manufactured by the method described in any one of claims 9 to 10.

12. A battery comprising the positive electrode tab described in claim 11.

13. An electrical device comprising the battery described in claim 12.

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