Positive electrode active material, positive electrode sheet, secondary battery and electrical device

Abstract

The present application provides a positive electrode active material, a positive electrode plate, a secondary battery and an electrical device. The positive electrode active material includes a first lithium nickel transition metal oxide and a second lithium nickel transition metal oxide. The first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide both contain zirconium, and the molar content of the zirconium element in the first lithium nickel transition metal oxide is less than the molar content of the zirconium element in the second lithium nickel transition metal oxide. The first lithium nickel transition metal oxide is a single crystal particle or one or more structures of a quasi-single crystal particle, and the second lithium nickel transition metal oxide is a secondary particle formed by the agglomeration of multiple primary particles. The first lithium nickel transition metal oxide has a stable structure, high strength, and better cycle performance at high temperatures; lithium ions in the second lithium nickel transition metal oxide diffuse more easily and have better rate performance. The zirconium content of the first lithium nickel transition metal oxide is less than that of the second lithium nickel transition metal oxide, which better improves the cycle life of the battery cell as a whole.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a positive electrode active material, a positive electrode sheet, a secondary battery, and an electrical device. Background Art

[0002] The high price, non-renewable nature of fossil energy, and its irreversible impact on the environment make the development of green, low-carbon, and environmentally friendly new energy sources urgent. As electrochemical energy storage devices, lithium-ion batteries are favored by the energy storage and power battery industries due to their large capacity, lack of memory effect, and wide application window. However, with the development of the industry, the pursuit of battery life and lifespan has become an increasing pain point and consensus in the industry. Ternary materials have attracted widespread attention due to their low cost and high capacity. Currently, in order to achieve higher capacity for ternary materials, increasing their operating voltage is the most effective way. However, under high voltage conditions, the lifespan of ternary materials decreases significantly, especially under high temperature conditions. Therefore, improving the energy density of ternary materials while ensuring their service life has become an industry challenge. Summary of the Invention

[0003] The present application provides a positive electrode active material, a positive electrode plate, a secondary battery and an electrical device to improve the energy density and cycle life of the positive electrode active material.

[0004] The first aspect of the present application provides a positive electrode active material, which includes a first lithium nickel transition metal oxide and a second lithium nickel transition metal oxide, the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide both contain zirconium, and the molar content of the zirconium element of the first lithium nickel transition metal oxide is less than the molar content of the zirconium element of the second lithium nickel transition metal oxide, the first lithium nickel transition metal oxide is a single crystal particle or one or more structures of a quasi-single crystal particle, and the second lithium nickel transition metal oxide is a secondary particle formed by the agglomeration of multiple primary particles.

[0005] In the positive electrode active material of the present application, the first lithium nickel transition metal oxide is one or more structures of single crystal or quasi-single crystal. This structure is stable and has relatively high strength, and is not prone to cracking during cycling, especially with better cycling performance at high temperatures. The second lithium nickel transition metal oxide is secondary particles formed by the aggregation of multiple primary particles. In this material, the diffusion of lithium ions is easier. Therefore, the discharge specific capacity is larger than that of single crystal or quasi-single crystal structures with the same particle size, and the rate performance is better. Moreover, the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide contain zirconium elements, which further improve the particle strength of the oxide. The enhancement of particle strength can significantly improve the cracking resistance of the positive electrode material during cycling. In particular, by controlling the molar content of zirconium element in the first lithium nickel transition metal oxide to be less than that in the second lithium nickel transition metal oxide, the difference in strength between the two oxides is reduced, and the cycling life of the battery cell can be better improved as a whole, the charge and discharge depth can be increased, and the mass energy density can be increased.

[0006] In any implementation manner of the first aspect, the ratio of the molar content of zirconium element in the first lithium nickel transition metal oxide to the molar content of zirconium element in the second lithium nickel transition metal oxide is d, and 0.5 ≤ d < 1. Optionally, 0.7 < d < 1. Further optionally, 0.8 ≤ d ≤ 0.9. By controlling the relationship of zirconium content, the comprehensive performance of their strength and rate is improved.

[0007] In any implementation manner of the first aspect, the particle strength of the first lithium nickel transition metal oxide is greater than the particle strength of the second lithium nickel transition metal oxide.

[0008] In any implementation manner of the first aspect, the particle strength of the first lithium nickel transition metal oxide is 30 MPa - 300 MPa, and further optionally 110 MPa - 230 MPa.

[0009] In any implementation manner of the first aspect, the particle strength of the second lithium nickel transition metal oxide is 20 MPa - 250 MPa, and further optionally 90 MPa - 210 MPa.

[0010] In any implementation manner of the first aspect, the difference between the particle strength of the first lithium nickel transition metal oxide and the particle strength of the second lithium nickel transition metal oxide is between 10 MPa - 50 MPa, and further optionally between 20 MPa - 30 MPa. By controlling the above strength, the formation of interfacial cracks in the positive electrode active material during cycling is further reduced, the cycling stability is improved, and the life of the positive electrode active material is prolonged.

[0011] In any implementation manner of the first aspect, the number of single crystals contained in the quasi-single crystal of the first lithium nickel transition metal oxide in the SEM image ≤ 5 grains / μm

[0011] , , ,

[0009] , ,

[0010] , ,

[0007] , 2 ,

[0008] , In any embodiment of the first aspect, the number of primary particles contained in the secondary particles of the second lithium nickel transition metal oxide in the SEM image is 3 / μm 2 -30 pieces / μm 2 The charging and discharging of the battery cell will cause the material to shrink and expand, which may cause the material to crack due to stress. Limiting the number of material particles and reducing the volume change of the positive electrode active material during the cycle can effectively improve the cycle stability of the battery cell.

[0012] In any embodiment of the first aspect, the volume particle size distribution curve of the positive electrode active material is a bimodal curve, wherein the low peak particle size of the bimodal curve is a first peak particle size, the high peak value is a second peak particle size, the first peak particle size is 2μm-6μm, and / or the second peak particle size is 6μm-15μm. Optimizing the material particle size distribution can effectively improve the voltage window and compaction density of the material. A high voltage window and compaction density are beneficial for obtaining high volume energy density and mass density, thereby significantly improving the battery life of the secondary battery.

[0013] In any embodiment of the first aspect, the bimodal curve is subjected to peak fitting to obtain a small particle fitting peak type and a large particle fitting peak type, and the particle size concentration S1 obtained according to the small particle fitting peak type and the particle size concentration S2 obtained according to the large particle fitting peak type are each independently 0.1-5, and optionally S1 and S2 are each independently 0.1-3, wherein S1 = (Dv190-Dv110) / Dv150, S2 = (Dv290-Dv210) / Dv250, Dv1N is the particle size corresponding to the cumulative volume distribution percentage in the small particle fitting peak type reaching N%, Dv2N is the particle size corresponding to the cumulative volume distribution percentage in the large particle fitting peak type reaching N%, and N is 10, 50 or 90. The above D is measured using a laser particle size analyzer. V N. The particle size of the positive electrode active material is graded in the above manner, and the filling between particles is better, thereby further improving the compaction density of the positive electrode material.

[0014] In any embodiment of the first aspect, the volume particle size distribution of the first lithium nickel transition metal oxide satisfies a small particle fitting peak shape, and the volume particle size distribution of the second lithium nickel transition metal oxide satisfies a large particle fitting peak shape. This allows the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide to achieve a better compatibility in terms of both composition and particle size, further improving compaction density and alleviating cyclic cracking defects.

[0015] In any embodiment of the first aspect, the chemical formulas of the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide are each independently Li a Ni x Co y M z Rb O c , 0.9≤a≤1.2, 0.3≤x≤1, 0≤y≤0.4, 0<z≤0.2, 0<b≤0.2, 1.8≤c≤2.2, x+y+z+b=1, M is one or two of Mn and Al, R includes one or more of Na, Sb, C, K, Ca, Zr, Sr, Al, B, Ba, Nb, W, Mo, Co, P and C, and R must contain Zr. Optionally, the molar amount of Zr in R per mole of the first lithium nickel transition metal oxide or the second lithium nickel transition metal oxide is less than or equal to 0.15, and further optionally, the molar amount of Zr in R per mole of the first lithium nickel transition metal oxide or the second lithium nickel transition metal oxide is less than or equal to 0.11.

[0016] In any embodiment of the first aspect, the Ni content in the first lithium nickel transition metal oxide is 0.5≤x≤0.98, and the Ni content in the second lithium nickel transition metal oxide is 0.6≤x≤0.98.

[0017] High-nickel or medium-low-nickel lithium-nickel transition metal oxides can be further doped with M and / or R elements to further improve the power performance of the oxide or enhance the structural stability of the oxide.

[0018] In any embodiment of the first aspect, the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide each independently include a core and a coating layer covering the core, and the chemical formula of the core is each independently Li a Ni x Co y M z R b O c , 0.9≤a≤1.2, 0.3≤x≤1, 0≤y≤0.4, 0≤z≤0.2, 0<b≤0.2, 1.8≤c≤2.2, x+y+z+b=1, M is one or two of Mn and Al, R includes one or more of Na, Sb, C, K, Ca, Zr, Sr, Al, B, Ba, Nb, W, Mo, Co, P and C, and R must contain Zr. Optionally, the molar amount of Zr in R per mole of the first lithium nickel transition metal oxide or the second lithium nickel transition metal oxide is less than or equal to 0.15. The Ni element content in the first lithium nickel transition metal oxide is 0.5≤x≤0.98, and the Ni element content in the second lithium nickel transition metal oxide is 0.6≤x≤0.98. The positive electrode active material and the electrolyte are mechanically separated by the coating layer, which reduces the occurrence of interfacial side reactions and reduces the material cracking of the positive electrode active material during the cyclic charge and discharge process, thereby improving the cycle performance.

[0019] In any embodiment of the first aspect, the coating layer comprises a single oxide coating layer or two oxide coating layers. And / or the inner layer of the two oxide coating layers is an island-shaped oxide coating layer, and the outer layer is a layered oxide coating layer. Interfacial performance is a key indicator for improving the performance of positive electrode materials. By adopting different coating structures, capacity can be increased while reducing side effects with the electrolyte, achieving a win-win situation.

[0020] In any embodiment of the first aspect, the coating layer has a thickness of 0.1 nm to 200 nm, optionally 0.1 nm to 100 nm, and further optionally 0.1 nm to 50 nm, so as to avoid obvious obstruction of ion diffusion caused by excessive coating thickness.

[0021] In any embodiment of the first aspect, the oxide coating layer comprises one or more elements selected from the group consisting of Zr, Al, P, B, Ti, W, Co, Nb, Mo, and Mg. The oxide coating layer comprising these elements improves the interfacial stability of the positive electrode active material / electrolyte, thereby enhancing cyclability and safety.

[0022] In any embodiment of the first aspect, the weight ratio of the first lithium nickel transition metal oxide in the positive electrode active material is 10%-95%, and optionally 50%-90%. By adjusting the weight ratio of the first lithium nickel transition metal oxide, the overall structural stability and energy density of the positive electrode active material can be adjusted.

[0023] A second aspect of the present application provides a positive electrode sheet comprising a current collector and a positive electrode film layer, wherein the positive electrode film layer comprises a positive electrode active material, wherein the positive electrode active material is any of the above-mentioned positive electrode active materials. The positive electrode active material of the present application has good structural and interfacial stability, thereby reducing the positive electrode-electrolyte interface effect, reducing cracking of the positive electrode active material, and reducing side reactions between the positive electrode and the electrolyte, reducing the formation of interfacial microcracks, thereby improving the energy density and lifespan of the positive electrode sheet.

[0024] The third aspect of the present application provides a secondary battery comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the positive electrode sheet is the positive electrode sheet described above. The secondary battery of the present application has the advantages of high energy density and high cycle performance.

[0025] A fourth aspect of the present application provides an electrical device comprising a secondary battery selected from the aforementioned secondary batteries. The electrical device of the present application operates more stably and safely at high temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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 of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0027] Figure 1 This is a scanning electron microscope image of the first lithium nickel transition metal oxide particles in Example 1.

[0028] Figure 2 This is a scanning electron microscope image of the second lithium nickel transition metal oxide particles in Example 1.

[0029] Figure 3 Schematic diagram of a secondary battery according to one embodiment of the present application.

[0030] Figure 4 yes Figure 3 FIG. 1 is an exploded view of a secondary battery according to an embodiment of the present application.

[0031] Figure 5 Schematic diagram of a battery module according to one embodiment of the present application.

[0032] Figure 6 Schematic diagram of a battery pack according to one embodiment of the present application.

[0033] Figure 7 yes Figure 6 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0034] Figure 8 FIG. 1 is a schematic diagram of an electrical device using a secondary battery according to an embodiment of the present application as a power source.

[0035] In the drawings, the drawings are not drawn to scale.

[0036] Description of reference numerals:

[0037] 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 secondary battery; 51 housing; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0038] The following detailed description of the embodiments of the present application is provided in conjunction with the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present application, but are not intended to limit the scope of the present application, that is, the present application is not limited to the described embodiments.

[0039] Below, the embodiments of the positive electrode active material, positive electrode sheet, secondary battery and electric device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0040] The "ranges" disclosed herein are defined in terms of lower and upper limits, where a given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive of the end values ​​and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise indicated, the numerical range "a to b" is a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0041] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0042] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0043] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0044] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0045] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0046] [Secondary battery]

[0047] Secondary batteries, also known as rechargeable batteries or storage batteries, are batteries that can be recharged to activate the active materials after discharge and continue to be used.

[0048] Typically, a secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. During the battery's charge and discharge process, active ions (such as lithium ions) are embedded and released back and forth between the positive and negative electrode sheets. The separator is set between the positive and negative electrode sheets, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through. The electrolyte between the positive and negative electrode sheets mainly plays the role of conducting active ions.

[0049] [Positive electrode active material]

[0050] One embodiment of the present application provides a positive electrode active material, which includes a first lithium nickel transition metal oxide and a second lithium nickel transition metal oxide, wherein the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide both contain zirconium, and the molar content of the zirconium element of the first lithium nickel transition metal oxide is less than the molar content of the zirconium element of the second lithium nickel transition metal oxide, the first lithium nickel transition metal oxide is a single crystal particle or one or more structures of a quasi-single crystal particle, and the second lithium nickel transition metal oxide is a secondary particle formed by agglomeration of multiple primary particles.

[0051] Ternary cathode materials can crack during cycling, especially under high cutoff voltage conditions. Extensive cracking can significantly increase the internal resistance and gas production of the battery cell, accelerating capacity decay during cycling. Increased gas production also increases the cell's expansion force, potentially leading to safety issues. Therefore, reducing cathode material cracking during cycling is the fundamental solution to this problem.

[0052] By doping the ternary material with zirconium, the structural stability of the material can be improved, mitigating cyclic cracking. Furthermore, the combination of single crystals and polycrystalline materials can achieve a higher compaction density while also mitigating the severe polycrystalline cracking at high voltages, thereby extending the battery cell lifespan.

[0053] In the positive electrode active material of the present application, the first lithium nickel transition metal oxide is a single crystal particle or one or more structures in a quasi-single crystal particle, which is stable, strong, and not easy to crack during the cycle, especially the cycle performance at high temperature is better; the second lithium nickel transition metal oxide is a secondary particle formed by the agglomeration of multiple primary particles. Lithium ions in the material are more easily diffused, so the discharge specific capacity is larger than that of a single crystal or a quasi-single crystal structure of equal particle size, and the rate performance is better. Moreover, by doping zirconium elements in the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide, the particle strength of the oxide is further improved, especially by doping more zirconium elements in the second lithium nickel transition metal oxide, thereby more effectively improving the particle strength of the second lithium nickel transition metal oxide, effectively reducing the cracking of the secondary particles, and reducing the difference in strength between the two oxides, thereby synergizing with the first lithium nickel transition metal oxide to better improve the cycle life of the battery cell; at the same time, the use of zirconium elements can increase the charge and discharge depth of the positive electrode active material and improve the mass energy density.

[0054] Glossary:

[0055] Single crystal particle: refers to a complete particle, not an agglomerate of primary particles. Generally, in this application, the size of a single crystal particle is micrometer-level.

[0056] Quasi-single crystal particles: refers to particles formed by the agglomeration of 2 to 10 single crystal particles. The number of single crystal particles is small and the size ranges from a few hundred nanometers to 2 to 5 μm.

[0057] Secondary particles: Agglomerates formed by the agglomeration of multiple primary particles. The term "multiple" generally refers to more than 10 particles.

[0058] In some embodiments, the ratio of the zirconium content of the first lithium nickel transition metal oxide to that of the second lithium nickel transition metal oxide is d, and 0.5 ≤ d < 1, optionally 0.7 < d < 1, and further optionally 0.8 ≤ d ≤ 0.9. By controlling the doping amount of zirconium, the comprehensive performance of the strength and rate of the two is improved. The above d can be any point value within the range formed by any two of 0.51, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9 or 0.98.

[0059] In the lithium nickel transition metal oxide, doping with zirconium elements can effectively improve the particle strength of the material. However, an increase in the doping amount of zirconium elements will significantly reduce the capacity of the cathode material. Therefore, by optimizing the amount of zirconium used, the relationship between the capacity and particle strength of the cathode material is balanced.

[0060] The doping amount of zirconium elements in the above mixture can be determined by inductively coupled plasma emission spectrometry. By separately measuring the proportion of zirconium elements in the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide, the proportion of zirconium elements in the two lithium nickel transition metal oxides is determined.

[0061] In some embodiments, the particle strength of the first lithium nickel transition metal oxide is greater than that of the second lithium nickel transition metal oxide. Optionally, the particle strength of the first lithium nickel transition metal oxide is 30 MPa - 300 MPa. For example, it can be any point value within the range formed by any two of 30 MPa, 50 MPa, 80 MPa, 100 MPa, 110 MPa, 120 MPa, 150 MPa, 200 MPa, 230 MPa, 250 MPa or 300 MPa, and further optionally 110 MPa - 230 MPa. The particle strength of the second lithium nickel transition metal oxide is 20 MPa - 250 MPa. For example, it is any point value within the range formed by any two of 20 MPa, 50 MPa, 70 MPa, 90 MPa, 120 MPa, 150 MPa, 180 MPa, 200 MPa, 210 MPa or 250 MPa, and further optionally 90 MPa - 210 MPa. By further controlling the particle strength of the two oxides, the particle strength of each is improved, thereby further reducing the formation of interfacial cracks in the cathode active material during the cycling process, improving the cycling stability, and prolonging the life of the cathode active material.

[0062] In some embodiments, the difference between the particle strength of the first lithium nickel transition metal oxide and the particle strength of the second lithium nickel transition metal oxide is between 10 MPa and 50 MPa, and further optionally between 20 MPa and 30 MPa. The strength matching of the two particles is improved, and excessive extrusion stress between the two particles due to the too large strength difference is avoided, thereby effectively controlling the cracking of the two particles caused by extrusion.

[0063] The particle strength can be measured using a dynamic ultramicrohardness tester (Shimadzu DUH-211S). The particle strength of the material is tested under a 115° triangular cone probe and a pressure of 0-20 mN, and the force and pressure at which the material breaks are recorded.

[0064] In some embodiments, the number of single crystals contained in the quasi-single crystal of the first lithium nickel transition metal oxide in the SEM image is ≤5 / μm. 2 , such as 1, 2, 3, 4 or 5. In some embodiments, the number of primary particles contained in the secondary particles of the second lithium nickel transition metal oxide in the SEM image is 3 / μm 2 -30 pieces / μm 2 , such as 3, 5, 8, 10, 12, 15, 20, 25 or 30. Single crystal particles are usually prone to agglomeration due to the high sintering temperature and small particle size, forming quasi-single crystals. When there are too many quasi-single crystals, anisotropic shrinkage and expansion occur during the cycle, causing them to crack due to stress, reducing the cycle stability of the single crystal; in addition, the number of primary particles in the polycrystalline secondary particles is too large, making the material more active and the risk of cracking during the cycle is higher. By limiting the number of material particles by the above parameters and reducing the volume change of the positive active material during the cycle, the cycle stability of the battery cell can be effectively improved.

[0065] The number of single crystals and the number of primary particles contained in the secondary particles in the above SEM images were obtained by measuring the SEM images at a magnification of 30,000 times. Of course, due to instrument differences, it is feasible to obtain the above test results at lower or higher magnifications.

[0066] In some embodiments, the volume particle size distribution curve of the positive electrode active material is a bimodal curve, the low peak particle size of the bimodal curve is the first peak particle size, the high peak value is the second peak particle size, the first peak particle size is 2 μm-6 μm, and / or the second peak particle size is 6 μm-15 μm.

[0067] The positive electrode active material contains two types of particles with different particle size distributions. This allows the smaller particles to fill the gaps between the larger particles. This particle size optimization effectively improves the material's voltage window and compaction density. A high voltage window and compaction density contribute to high volumetric energy density and mass density, significantly improving the battery's endurance.

[0068] In some embodiments, the bimodal curve is subjected to peak fitting to obtain a small particle fitting peak type and a large particle fitting peak type. The particle size concentration S1 obtained according to the small particle fitting peak type and the particle size concentration S2 obtained according to the large particle fitting peak type are each independently 0.1-5, and optionally S1 and S2 are each independently 0.1-3, wherein S1 = (Dv190-Dv110) / Dv150, S2 = (Dv290-Dv210) / Dv250, Dv1N is the particle size corresponding to the cumulative volume distribution percentage in the small particle fitting peak type reaching N%, Dv2N is the particle size corresponding to the cumulative volume distribution percentage in the large particle fitting peak type reaching N%, and N is 10, 50 or 90. The above D is measured using a laser particle size analyzer. V N. The particle size of the positive electrode active material is graded in the above manner, and the filling between particles is better, thereby further improving the compaction density of the positive electrode material.

[0069] In some embodiments, the volume particle size distribution of the first lithium nickel transition metal oxide satisfies a small particle fitting peak shape, while the volume particle size distribution of the second lithium nickel transition metal oxide satisfies a large particle fitting peak shape. This allows the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide to achieve a better matching relationship in terms of both composition and particle size, further improving compaction density and reducing cyclic cracking defects.

[0070] The first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide of the present application can be high nickel or low nickel lithium nickel transition metal oxides commonly used in the field for positive electrode materials. In some embodiments, the chemical formulas of the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide are each independently Li a Ni x Co y M z R b O c, 0.9≤a≤1.2, 0.3≤x≤1, 0≤y≤0.4, 0≤z≤0.2, 0<b≤0.2, 1.8≤c≤2.2, x+y+z+b=1, M is one or two of Mn and Al, R includes one or more of Na, Sb, C, K, Ca, Zr, Sr, Al, B, Ba, Nb, W, Mo, Co, P and C, and R must contain Zr. Optionally, the molar amount of Zr in R per mole of the first lithium nickel transition metal oxide or the second lithium nickel transition metal oxide is less than or equal to 0.15; further optionally, the molar amount of Zr in R per mole of the first lithium nickel transition metal oxide or the second lithium nickel transition metal oxide is less than or equal to 0.11. Optionally, the Ni content in the first lithium nickel transition metal oxide is 0.5≤x≤0.98, and the Ni content in the second lithium nickel transition metal oxide is 0.6≤x≤0.98. High-nickel or medium-low-nickel lithium-nickel transition metal oxides can be further doped with M and R elements to further improve the power performance or enhance the structural stability of the oxide. The presence of Zr in the first and second lithium-nickel transition metal oxides can significantly enhance the structural stability of the materials.

[0071] In some embodiments, the chemical formulas of the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide are each independently Li a Ni x Co y M z R b O c , 0.9≤a≤1.0, 0.5≤x≤0.8, 0.1≤y≤0.2, 0.05≤z≤0.2, 0.001<b≤0.2, 1.8≤c≤2.2, x+y+z+b=1.

[0072] To further reduce the interface side reaction, in some embodiments, the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide each independently include a core and a coating layer covering the core, and the chemical formula of the core is each independently Li a Ni x Co y M z R b O c, 0.9≤a≤1.2, 0.3≤x≤1, 0≤y≤0.4, 0≤z≤0.2, 0<b≤0.2, 1.8≤c≤2.2, x+y+z+b=1, M is one or two of Mn and Al, R includes one or more of Na, Sb, C, K, Ca, Zr, Sr, Al, B, Ba, Nb, W, Mo, Co, P and C, and R must contain Zr; Optionally, the molar amount of Zr in R per mole of the first lithium nickel transition metal oxide or the second lithium nickel transition metal oxide is less than or equal to 0.15. Optionally, the Ni element content in the first lithium nickel transition metal oxide is 0.5≤x≤0.98, and the Ni element content in the second lithium nickel transition metal oxide is 0.6≤x≤0.98. The coating layer mechanically separates the positive electrode active material and the electrolyte, reduces the occurrence of interfacial side reactions, reduces the material cracking of the positive electrode active material during the cyclic charge and discharge process, and improves the cycle performance.

[0073] In some embodiments, the coating layer includes one oxide coating layer or two oxide coating layers; further optionally, the inner layer of the two oxide coating layers is an island oxide coating layer, and the outer layer is a layered oxide coating layer.

[0074] Terminology Notes:

[0075] Island oxide coating: a coating formed by oxide in the form of discrete islands;

[0076] Layered oxide coating: A coating layer formed by oxide in a continuous layered form. The layered structure may be a layered structure with uniform thickness or a layered structure with non-uniform thickness. As long as it is a continuous oxide film layer, it is a layered oxide coating.

[0077] Island oxide coatings can avoid the problem of reduced material conductivity caused by thick layer coatings. Adding a layered oxide coating outside the island oxide coating is more effective in improving the material's cycling performance. By adopting different coating structures, it is possible to increase capacity while reducing side effects with the electrolyte, achieving a win-win situation.

[0078] In some embodiments, the coating layer thickness is controlled to be 0.1 nm-200 nm, optionally 0.1-100 nm, and further optionally 0.1-50 nm, to avoid significant hindrance to ion diffusion and consequently decreased ionic conductivity caused by excessive coating thickness. The coating layer thickness is measured using a transmission electron microscope.

[0079] In some embodiments, the oxide coating layer includes one or more elements selected from the group consisting of Zr, Al, P, B, Ti, W, Co, Nb, Mo, and Mg. The oxide coating layer comprising these elements improves the interfacial stability of the cathode active material / electrolyte, thereby enhancing cyclability and safety.

[0080] In some embodiments, the overall structural stability and energy density of the positive electrode active material are adjusted by adjusting the weight proportion of the first lithium nickel transition metal oxide. The weight proportion of the first lithium nickel transition metal oxide in the positive electrode active material is 10% to 90%. To improve the material's compaction density and cycling performance, the weight proportion of the first lithium nickel transition metal oxide in the positive electrode active material can be selected to be 50% to 90%.

[0081] When reversely determining the composition of the positive electrode active material, the following method can be used as a reference:

[0082] If the Ni / Co / Mn components of the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide are different, the total ratio of Ni, Co, and Mn in the positive electrode active material in the positive electrode sheet can be first tested by ICP, and then the Ni, Co, and Mn ratios of the two morphological particles can be tested separately in combination with EDX. Based on the above ICP and EDX test results, assuming that the mass proportion of the first material is x and the other is (1-x), the mass proportions of the two materials can be obtained by substituting them into the equation for calculation.

[0083] If the Ni / Co / Mn components of the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide are the same, the positive electrode active material is sieved through sieves of different mesh sizes to obtain active materials of different particle sizes, and the ratio and content of the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide are determined based on the ICP measured data.

[0084] The positive electrode active material of the present invention can be prepared by referring to conventional methods after the composition ingredients of the present invention. In some embodiments, the following steps can be used to prepare the positive electrode active material: lithium hydroxide or lithium carbonate, nickel cobalt M precursor material Ni x Co y M 1-x-y (OH)2 and N additive are mixed and sintered in the presence of oxygen. The sintering conditions are controlled to obtain a first lithium nickel transition metal oxide and a second lithium nickel transition metal oxide respectively. The first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide are mixed according to a preset mass ratio to prepare a positive electrode active material.

[0085] When the first lithium nickel transition metal oxide and / or the second lithium nickel transition metal oxide of the positive electrode active material have a coating layer, island-like and layer-like coating of the lithium nickel transition metal oxide can be achieved by controlling the coating element and coating temperature. For example, aluminum typically forms island-like coatings on the surface at 300-400°C, while boron more easily forms layer-like coatings on the surface. Specific coating methods can be referenced to existing technologies and will not be detailed in this application.

[0086] [Positive electrode]

[0087] The positive electrode sheet generally includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

[0088] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0089] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0090] In some embodiments, the positive electrode active material is any one of the positive electrode active materials provided herein. The positive electrode active material of the present invention has good structural and interfacial stability, thereby reducing the positive electrode-electrolyte interface effect. This reduces cracking of the positive electrode active material and reduces side reactions between the positive electrode and the electrolyte, reducing the formation of interfacial microcracks, thereby improving the energy density and life of the positive electrode sheet.

[0091] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0092] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0093] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0094] [Negative electrode]

[0095] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0096] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0097] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0098] In some embodiments, the negative electrode active material may adopt negative electrode active materials for batteries that are well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. Silicon-based materials include at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials include at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0099] In some embodiments, the negative electrode film layer may further include a binder. For example, the binder includes at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0100] In some embodiments, the negative electrode film layer may further include a conductive agent. For example, the conductive agent includes at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0101] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0102] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0103] [Electrolytes]

[0104] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0105] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0106] In some embodiments, the electrolyte salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0107] In some embodiments, the solvent includes at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0108] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0109] [Isolation film]

[0110] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0111] In some embodiments, the material of the separator includes at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0112] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0113] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0114] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0115] The present application has no particular limitation on the shape of the secondary battery, which can be cylindrical, square or any other shape. For example, Figure 3 The secondary battery 5 is a square structure as an example.

[0116] In some embodiments, reference Figure 4 , the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0117] In some embodiments, secondary batteries can be assembled into a battery module. The number of secondary batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0118] Figure 5 4 is an example of a battery module. Figure 5In the battery module 4, the plurality of secondary batteries 5 may be arranged in sequence along the length of the battery module 4. Of course, they may also be arranged in any other manner. The plurality of secondary batteries 5 may further be fixed by fasteners.

[0119] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of secondary batteries 5 are accommodated in the accommodation space.

[0120] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0121] Figure 6 and Figure 7 The battery pack 1 is used as an example. Figure 6 and Figure 7 The battery pack 1 may include a battery box and multiple battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner in the battery box.

[0122] In addition, the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0123] As the electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0124] Figure 8 This is an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0125] [Example]

[0126] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0127] Example 1

[0128] Preparation of positive electrode active materials

[0129] The ternary precursor (Ni 0.5 Co 0.1 Mn 0.4 )OH2(particle size D v 50 is about 3.1μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.99:1.04:0.01, and then sintered at 920℃ in an oxygen atmosphere to obtain the first lithium nickel transition metal oxide particles. The specific powder parameters are shown in Table 1. Its SEM image is shown in Figure 1 shown.

[0130] The ternary precursor (Ni 0.5 Co 0.1 Mn 0.4 )OH2(particle size D v 50 is about 9.5μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.98:1.04:0.02, and then sintered at 830℃ in an oxygen atmosphere to obtain the second lithium nickel transition metal oxide particles. The specific powder parameters are shown in Table 1. Its SEM image is shown in Figure 2 shown.

[0131] The first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles prepared in sequence were mixed at a mass ratio of 2:8 to prepare a positive electrode active material.

[0132] Preparation of positive electrode

[0133] The positive electrode active material, polyvinylidene fluoride and conductive carbon black were mixed in a mass ratio of 90:5:5, and then N-methylpyrrolidone (NMP) was added and stirred at 1000r / min for 1h until the mixture was uniformly mixed to obtain a positive electrode slurry. The positive electrode slurry was evenly coated on the single side surface of a 13-micron thick aluminum foil current collector. After coating, it was dried in a drying oven at 100°C, cold pressed, and cut to obtain positive electrode sheets.

[0134] Preparation of electrolyte

[0135] A mixed solvent was prepared by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:2. Then, in an argon atmosphere glove box, thoroughly dried lithium hexafluorophosphate was dissolved in the mixed solvent and mixed thoroughly to obtain an electrolyte solution. The lithium salt concentration in the electrolyte was 1 mol / L.

[0136] Preparation of negative electrode sheet

[0137] The negative electrode active materials graphite, sodium carboxymethyl cellulose, styrene-butadiene rubber and acetylene black were mixed in a mass ratio of 96:1:1:2, deionized water was added, and the mixture was stirred evenly in a blender. The slurry was then coated on both sides of an 8-micron-thick copper foil, dried in an oven at 100°C, cold pressed, and cut to obtain negative electrode sheets.

[0138] Preparation of battery cells

[0139] The positive electrode sheet, isolation film, and negative electrode sheet are stacked from top to bottom, ensuring that the positive and negative electrode sheets cannot touch each other. Then they are wound into bare cells using a winding needle, placed in a square aluminum shell, and the electrolyte is injected. The cells are prepared by steps such as standing, formation, and capacity measurement.

[0140] Example 2

[0141] Preparation of positive electrode active materials

[0142] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.2 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain first lithium nickel transition metal oxide particles. Specific powder parameters are shown in Table 1.

[0143] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.6 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.99:1.04:0.01, and then sintered at 820°C in an oxygen atmosphere to obtain second lithium nickel transition metal oxide particles. Specific powder parameters are shown in Table 1.

[0144] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 3:7 to prepare a positive electrode active material.

[0145] The preparation process of the secondary battery is the same as that of Example 1, and the positive electrode active material is the positive electrode active material of Example 2.

[0146] Example 3

[0147] Preparation of positive electrode active materials

[0148] The ternary precursor (Ni 0.8 Co 0.1 Al 0.1 )OH2(particle size D v 50 is about 3.3 μm), LiOH·H2O, ZrO2 and Nb2O5 are mixed in a mixer at a molar ratio of 0.99:1.04:0.008:0.001, and then sintered at 860°C in an oxygen atmosphere to obtain the first lithium nickel transition metal oxide particles. Specific powder parameters are shown in Table 1.

[0149] The ternary precursor (Ni 0.8 Co 0.1 Al 0.1 )OH2(particle size D v 50 is about 9.4 μm), LiOH·H2O, ZrO2 and Nb2O5 are mixed in a mixer at a molar ratio of 0.99:1.04:0.009:0.0005, and then sintered at 820°C in an oxygen atmosphere to obtain second lithium nickel transition metal oxide particles. Specific powder parameters are shown in Table 1.

[0150] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 6:4 to prepare a positive electrode active material.

[0151] Example 4

[0152] Preparation of positive electrode active materials

[0153] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.3μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere. The first lithium nickel transition metal oxide particles obtained above and alumina are mixed in a mixer at a molar ratio of 1:0.005, and then sintered at 400°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide having an Al2O3 island coating layer with a thickness of 2nm on its surface. Specific powder parameters are shown in Table 1.

[0154] The ternary precursor (Ni 0.8 Co 0.1 Mn0.1 )OH2(particle size D v 50 is about 9.2μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.991:1.04:0.009, and then sintered at 820°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0155] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 6:4 to prepare a positive electrode active material.

[0156] The rest is the same as in Example 1.

[0157] Example 5

[0158] Preparation of positive electrode active materials

[0159] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.2μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere. The first lithium nickel transition metal oxide particles obtained above and boric acid are mixed in a mixer at a molar ratio of 1:0.01, and then sintered at 400°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide having a B2O3 layered coating layer with a thickness of 5nm. Specific powder parameters are shown in Table 1.

[0160] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.3μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.991:1.04:0.009, and then sintered at 820°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0161] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 6:4 to prepare a positive electrode active material.

[0162] Example 6

[0163] Preparation of positive electrode active materials

[0164] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1)OH2(particle size D v 50 is about 3.7μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere. The first lithium nickel transition metal oxide particles obtained above, boric acid and aluminum oxide are mixed in a mixer at a molar ratio of 1:0.02:0.005, and then sintered at 400°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide having a coating layer with a thickness of 20nm on its surface, an Al2O3 island coating layer inside, and a B2O3 island coating layer outside. Specific powder parameters are shown in Table 1.

[0165] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.9 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.991:1.04:0.009, and then sintered at 820°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0166] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 6:4 to prepare a positive electrode active material.

[0167] Example 7

[0168] Preparation of positive electrode active materials

[0169] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.8μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0170] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v50 is about 9.7μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.991:1.04:0.009, and then sintered at 820°C in an oxygen atmosphere to obtain second lithium nickel transition metal oxide particles. The second lithium nickel transition metal oxide particles obtained above and alumina are mixed in a mixer at a molar ratio of 1:0.005, and then sintered at 400°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide having an Al2O3 island coating layer with a thickness of 2nm on its surface. Specific powder parameters are shown in Table 1.

[0171] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 6:4 to prepare a positive electrode active material.

[0172] Example 8

[0173] Preparation of positive electrode active materials

[0174] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2 (particle size Dv50 is about 3.3 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0175] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2 (particle size Dv50 is about 9.6μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.991:1.04:0.009, and then sintered at 820°C in an oxygen atmosphere to obtain second lithium nickel transition metal oxide particles. The above-obtained second lithium nickel transition metal oxide particles and boric acid are mixed in a mixer at a molar ratio of 1:0.01, and then sintered at 400°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide having a B2O3 layered coating layer with a thickness of 5nm. For specific powder parameters, see Table 1.

[0176] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 6:4 to prepare a positive electrode active material.

[0177] Example 9

[0178] Preparation of positive electrode active materials

[0179] The ternary precursor (Ni 0.8 Co 0.1 Mn0.1 )OH2 (particle size Dv50 is about 3.4μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0180] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2 (particle size Dv50 is about 9.4μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.991:1.04:0.009, and then sintered at 820°C in an oxygen atmosphere to obtain second lithium nickel transition metal oxide particles. The second lithium nickel transition metal oxide particles obtained above, boric acid and aluminum oxide are mixed in a mixer at a molar ratio of 1:0.02:0.005, and then sintered at 400°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide, the surface of which has a coating layer with a thickness of 20nm, an internal Al2O3 island coating layer, and an external B2O3 island coating layer. Specific powder parameters are shown in Table 1.

[0181] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 6:4 to prepare a positive electrode active material.

[0182] Example 10

[0183] Preparation of positive electrode active materials

[0184] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.6μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0185] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.6μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.99:1.04:0.01, and then sintered at 820℃ in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0186] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 1:9 to prepare a positive electrode active material.

[0187] Example 11

[0188] Preparation of positive electrode active materials

[0189] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.7 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0190] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.9 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.99:1.04:0.01, and then sintered at 820°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0191] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 9:1 to prepare a positive electrode active material.

[0192] Example 12

[0193] Preparation of positive electrode active materials

[0194] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.5μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0195] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v50 is about 9.2μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.99:1.04:0.01, and then sintered at 820℃ in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0196] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 5:5 to prepare a positive electrode active material.

[0197] Example 13

[0198] The first lithium nickel transition metal oxide particles prepared in Example 12 were mixed with the second lithium nickel transition metal oxide particles prepared in Example 12 at a mass ratio of 0.5:9.5 to prepare a positive electrode active material.

[0199] The rest is the same as in Example 1.

[0200] Example 14

[0201] The first lithium nickel transition metal oxide particles prepared in Example 12 were mixed with the second lithium nickel transition metal oxide particles prepared in Example 12 at a mass ratio of 9.5:0.5 to prepare a positive electrode active material.

[0202] The rest is the same as in Example 1.

[0203] Example 15

[0204] Preparation of positive electrode active materials

[0205] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.7 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.999:1.04:0.001, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0206] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.4 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.998:1.04:0.002, and then sintered at 820°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0207] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 5:5 to prepare a positive electrode active material.

[0208] Example 16

[0209] Preparation of positive electrode active materials

[0210] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.4 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.9:1.04:0.1, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0211] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.7 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.895:1.04:0.105, and then sintered at 820°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0212] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 5:5 to prepare a positive electrode active material.

[0213] Example 17

[0214] Preparation of positive electrode active materials

[0215] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.2μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.85:1.04:0.15, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0216] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v50 is about 9.5μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.8:1.04:0.2, and then sintered at 820°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0217] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 5:5 to prepare a positive electrode active material.

[0218] Example 18

[0219] Preparation of positive electrode active materials

[0220] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 1.5 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.994:1.04:0.006, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0221] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.1 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.99:1.04:0.01, and then sintered at 820°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0222] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 5:5 to prepare a positive electrode active material.

[0223] Example 19

[0224] Preparation of positive electrode active materials

[0225] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.9 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0226] The ternary precursor (Ni0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.4 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.99:1.04:0.01, and then sintered at 820°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0227] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 6:4 to prepare a positive electrode active material.

[0228] Example 20

[0229] Preparation of positive electrode active materials

[0230] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.1 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0231] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.3μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.99:1.04:0.01, and then sintered at 820℃ in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0232] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 5:5 to prepare a positive electrode active material.

[0233] Example 21

[0234] Preparation of positive electrode active materials

[0235] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v50 is about 3.3 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.994:1.04:0.006, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0236] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.7 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.99:1.04:0.01, and then sintered at 820°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0237] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 4:6 to prepare a positive electrode active material.

[0238] Example 22

[0239] Preparation of positive electrode active materials

[0240] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.2μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0241] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.4 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.95:1.04:0.05, and then sintered at 820°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0242] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 3:7 to prepare a positive electrode active material.

[0243] Example 23

[0244] Preparation of positive electrode active materials

[0245] The ternary precursor (Ni0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.4 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0246] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.3μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.98:1.04:0.02, and then sintered at 820℃ in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0247] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 5:5 to prepare a positive electrode active material.

[0248] Example 24

[0249] Preparation of positive electrode active materials

[0250] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.5μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0251] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.8μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.9918:1.04:0.0082, and then sintered at 820°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0252] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 5:5 to prepare a positive electrode active material.

[0253] Example 25

[0254] Preparation of positive electrode active materials

[0255] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.7 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0256] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.9 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.99:1.04:0.01, and then sintered at 820°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0257] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 7:3 to prepare a positive electrode active material.

[0258] Example 26

[0259] Preparation of positive electrode active materials

[0260] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 6.4 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0261] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.5μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.99:1.04:0.01, and then sintered at 820°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0262] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 7:3 to prepare a positive electrode active material.

[0263] Example 27

[0264] Preparation of positive electrode active materials

[0265] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.6μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0266] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.6μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.99:1.04:0.01, and then sintered at 820℃ in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0267] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 7:3 to prepare a positive electrode active material.

[0268] Example 28

[0269] Preparation of positive electrode active materials

[0270] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.8μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0271] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v50 is about 9.4 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.99:1.04:0.01, and then sintered at 820°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0272] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 7:3 to prepare a positive electrode active material.

[0273] Example 29

[0274] Preparation of positive electrode active materials

[0275] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.2μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0276] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.8μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.99:1.04:0.01, and then sintered at 820℃ in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0277] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 7:3 to prepare a positive electrode active material.

[0278] Example 30

[0279] Preparation of positive electrode active materials

[0280] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.4 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0281] The ternary precursor (Ni0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 15.2μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.99:1.04:0.01, and then sintered at 820℃ in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0282] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 7:3 to prepare a positive electrode active material.

[0283] Example 31

[0284] Preparation of positive electrode active materials

[0285] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.3 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0286] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.5μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.99:1.04:0.01, and then sintered at 820°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0287] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 7:3 to prepare a positive electrode active material.

[0288] Example 32

[0289] Preparation of positive electrode active materials

[0290] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v50 is about 3.3 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0291] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.7 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.99:1.04:0.01, and then sintered at 820°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0292] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 7:3 to prepare a positive electrode active material.

[0293] Example 33

[0294] Preparation of positive electrode active materials

[0295] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.2μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0296] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.9 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.99:1.04:0.01, and then sintered at 820°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0297] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 7:3 to prepare a positive electrode active material.

[0298] Comparative Example 1

[0299] Preparation of positive electrode active materials

[0300] The ternary precursor (Ni0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.7 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0301] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.1 μm) and LiOH·H2O are mixed in a mixer at a molar ratio of 1:1.04, and then sintered at 820°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0302] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 7:3 to prepare a positive electrode active material.

[0303] Comparative Example 2

[0304] Preparation of positive electrode active materials

[0305] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.7 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 860°C in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0306] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.4 μm), LiOH·H2O and ZrO2 are mixed in a mixer at a molar ratio of 0.992:1.04:0.008, and then sintered at 820°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0307] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 7:3 to prepare a positive electrode active material.

[0308] Comparative Example 3

[0309] Preparation of positive electrode active materials

[0310] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 3.7 μm) and LiOH·H2O are mixed in a mixer at a molar ratio of 1:1.04, and then sintered at 860° C. in an oxygen atmosphere to obtain a first lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0311] The ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH2(particle size D v 50 is about 9.3 μm) and LiOH·H2O are mixed in a mixer at a molar ratio of 1:1.04, and then sintered at 820°C in an oxygen atmosphere to obtain a second lithium nickel transition metal oxide. Specific powder parameters are shown in Table 1.

[0312] The prepared first lithium nickel transition metal oxide particles and the second lithium nickel transition metal oxide particles were mixed in a mass ratio of 7:3 to prepare a positive electrode active material.

[0313] 1. Testing of positive electrode active materials in positive electrode sheets

[0314] 1.1. Composition Test of the First Lithium Nickel Transition Metal Oxide Particles and the Second Lithium Nickel Transition Metal Oxide Particles:

[0315] Inductively coupled plasma optical emission spectroscopy was used.

[0316] 1.2. Particle size test:

[0317] Particle size test:

[0318] Particle size types: Dv10, Dv50 and Dv90 tests.

[0319] Equipment model: Malvern 2000 Laser Particle Sizer, Reference Standard Procedure: GB / T19077-2016 / ISO 13320:2009. Detailed test procedure: Take an appropriate amount of the sample to be tested (ensure the sample concentration is 8% to 12% obscuration), add 20 mL of anhydrous ethanol, and sonicate for 5 minutes (53 kHz / 120 W) to ensure complete dispersion of the sample. Then, measure the sample according to GB / T19077-2016 / ISO 13320:2009. To prevent agglomeration during the drying process from affecting the particle size measurement, the sample was washed and moistened for dispersion testing.

[0320] The first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide were tested using the above process to obtain their respective volume particle size distribution curves; the positive electrode film layer of the positive electrode sheet was scraped and tested using the above process, and the obtained volume particle size distribution curve was a bimodal curve. The bimodal curve was subjected to peak fitting using origin to obtain a small particle fitting peak type and a large particle fitting peak type. After comparison, the small particle fitting peak type basically coincided with the volume particle size distribution curve of the first lithium nickel transition metal oxide, and the large particle fitting peak type basically coincided with the volume particle size distribution curve of the second lithium nickel transition metal oxide, indicating that the peak fitting processing results are reliable. The D recorded or used in Table 1 V 10. D V 50. D V 90 is obtained from the volume particle size distribution curves of the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide.

[0321] 1.3. Particle strength:

[0322] A dynamic ultramicrohardness tester was used to characterize the particle strength. A 50-micron probe was used to test the particle strength of the material under a pressure of 0-20 mN, and the force and pressure at which the material broke were recorded.

[0323] 1.4. Test of the number of single crystals of the first lithium nickel transition metal oxide:

[0324] The first lithium nickel transition metal oxide powder was tested using an electron microscope. At a magnification of 30,000 times, ten different areas were selected to record the number of particles per square micron, and the average value of the ten areas was taken as the number of single crystals per square micron.

[0325] 1.5. Secondary Lithium Nickel Transition Metal Oxide Primary Particle Test:

[0326] The number of the second lithium nickel transition metal oxide was tested using an electron microscope. At a magnification of 30,000 times, ten different areas were selected to record the number of particles per square micron, and the average value of the ten areas was taken as the number of primary particles per square micron.

[0327] 1.6. Thickness of oxide layer (according to TEM):

[0328] The material was analyzed by TEM, and the thickness of the material coating layer was measured at ten points and the average value was taken.

[0329] The test results are recorded in Table 1.

[0330]

[0331]

[0332]

[0333] 2. Compaction density of positive electrode

[0334] The positive electrode slurry is coated on both sides of 13μm aluminum foil, with a single-side coating thickness of 110μm. After drying, the compaction density and elongation data are collected using a cold press. The compaction density corresponding to the elongation of 0.8% is used as the test value of the compaction density of the positive electrode active material.

[0335] Elongation: (length of the electrode after cold pressing - length of the electrode before cold pressing) / length of the electrode before cold pressing × 100%

[0336] 3. Battery performance test

[0337] 3.1. Gram capacity (mAh / g)

[0338] Gram capacity refers to the ratio of the electrical capacity that can be released by the active material inside the battery to the mass of the active material.

[0339] 3.2 Cycle performance: capacity retention

[0340] At 25°C, one cycle is composed of constant current and then constant voltage charge and discharge at a current rate of 1C. The first time is recorded as C0 and the nth time is Cn. The capacity retention rate of each cycle is Cn / C0.

[0341] 3.3 Gas production test (40 days of storage at 70°C)

[0342] At 25°C, first charge the lithium-ion battery at a constant current of 1 / 3C to 4.3V, then charge it at a constant voltage of 0.025C to 4.3V. Measure the volume of the lithium-ion battery in deionized water using the water displacement method (V0). Then, store the battery at 70°C and measure the volume change every six days (Vn). The volume expansion rate (%) of the lithium-ion battery after storage at 70°C = (Vn - V0) / V0 × 100%.

[0343] 3.4 Storage performance (capacity retention at 60°C for 50 days)

[0344] At 25°C, the cell was charged at a constant current of 1C to 4.3V, then charged at a constant voltage with a current of 0.05C to 4.3V, then discharged at a constant current of 1C to 2.8V, and discharged at a constant voltage with a current of 0.05C. The measured capacity was recorded as C0.

[0345] Charge the cell to 4.3V at 1C current, constant voltage charging at 0.05C. Place the fully charged cell in a constant temperature oven at 60℃. Every 30 days, remove the cell and discharge it at 25℃ at 1C constant current to 2.8V. Then, discharge it at a constant voltage current of 0.05C. The measured capacity is Cn, and the capacity retention rate = Cn / C0.

[0346] Repeat the second step to obtain a graph showing battery capacity retention changing over time.

[0347] 3.5. Cycle number (25℃ cycle until the capacity retention rate reaches 80%)

[0348] At 25°C, charge the lithium-ion battery at a constant current of 1C to a voltage of 4.3V, then charge it at a constant voltage of 4.3V with a current of 0.05C, and then discharge it at a constant current of 1C until the final voltage is 2.8V and the capacity is C1. Repeat the above steps in sequence, and the capacity measured at the nth time is Cn. The capacity retention rate (%) = (nth discharge capacity / first cycle discharge capacity) × 100%. The cycle is continued until the cell capacity retention rate decays to 80%.

[0349] The test results are recorded in Table 2.

[0350] Table 2

[0351]

[0352] According to the comparison between Example 3 and Examples 4 to 9, it can be seen that when the surface of the first lithium nickel transition metal oxide or the second lithium nickel transition metal oxide constituting the positive electrode material has a coating layer, it has a significant effect on the capacity and cycle life of the material. For example, coating with boron elements significantly improves the material capacity, but the cycle performance will deteriorate accordingly, while coating with aluminum elements can significantly improve the material cycle performance, but the capacity will decrease slightly. According to the comparison between Examples 10-14 and 25, it can be seen that when the content of the first lithium nickel transition metal oxide as a single crystal in the positive electrode material gradually increases, the cycle performance of the material will be significantly improved. According to the comparison between Examples 12, 15-17, it can be seen that when the Zr content in the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide increases, it is beneficial to improve the particle strength and thus improve the cycle performance, but the specific capacity of the battery is reduced. According to the comparison between Examples 23 and 24, it can be seen that, on the basis of no significant increase in the Zr content, reducing the ratio d of the Zr content in the two materials will limit the material capacity and cycle performance, and it is difficult for the capacity and cycle of the mixed system to reach the optimal solution. According to the comparison of Examples 12, 19 to 21, it can be seen that the number of single crystal and polycrystalline particles per unit area is large, the material capacity will be improved, but the material cycle performance will deteriorate more significantly. According to the comparison of Examples 25 to 33, it can be seen that the particle size distribution concentration S value mainly affects the compaction density of the material. Within a certain range, the larger the S value, the higher the compaction will be. However, if it is too large, it will affect the material cycle performance and compaction. The capacity of the material and the cycle will decrease with D. v 50 increases and decreases, but for storage performance, D v A value higher than 50 will have an improvement effect.

[0353] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and components may be substituted with equivalents without departing from the scope of the present application. In particular, the various technical features described in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A positive electrode active material comprising a first lithium nickel transition metal oxide and a second lithium nickel transition metal oxide, wherein: Both the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide contain zirconium, and the molar content of the zirconium element in the first lithium nickel transition metal oxide is less than the molar content of the zirconium element in the second lithium nickel transition metal oxide. The first lithium nickel transition metal oxide is a single crystal particle or one or more structures of a quasi-single crystal particle, and the second lithium nickel transition metal oxide is a secondary particle formed by the agglomeration of multiple primary particles. The ratio of the molar content of the zirconium element in the first lithium nickel transition metal oxide to the molar content of the zirconium element in the second lithium nickel transition metal oxide is d, and 0.5≤d<1.

2. The positive electrode active material according to claim 1, wherein The particle strength of the first lithium nickel transition metal oxide is greater than the particle strength of the second lithium nickel transition metal oxide; The first lithium nickel transition metal oxide particle strength is 30 MPa-300 MPa, and / or The particle strength of the second lithium nickel transition metal oxide is 20 MPa-250 MPa; and / or The difference between the particle strength of the first lithium nickel transition metal oxide and the particle strength of the second lithium nickel transition metal oxide is between 10 MPa and 50 MPa.

3. The positive electrode active material according to any one of claims 1 to 2, wherein The number of single crystals contained in the quasi-single crystal of the first lithium nickel transition metal oxide is ≤5 / μm2, and / or the number of primary particles contained in the secondary particles of the second lithium nickel transition metal oxide is 3 / μm2-30 / μm2.

4. The positive electrode active material according to claim 1, wherein The volume particle size distribution curve of the positive electrode active material is a bimodal curve, the low peak particle size of the bimodal curve is a first peak particle size, the high peak value is a second peak particle size, the first peak particle size is 2 μm-6 μm, and / or The second peak particle size is 6 μm-15 μm, and / or The particle size concentration S1 of the small particle fitting peak type and the particle size concentration S2 of the large particle fitting peak type are each independently 0.1-5, wherein S1 = (Dv190 -Dv110) / Dv150, S2 = (Dv290 -Dv210) / Dv250, Dv1N is the particle size corresponding to when the cumulative volume distribution percentage in the small particle fitting peak type reaches N%, Dv2N is the particle size corresponding to when the cumulative volume distribution percentage in the large particle fitting peak type reaches N%, and N is 10, 50 or 90; The volume particle size distribution of the first lithium nickel transition metal oxide satisfies a small particle fitting peak type; the volume particle size distribution of the second lithium nickel transition metal oxide satisfies a large particle fitting peak type.

5. The positive electrode active material according to claim 1, wherein The chemical formulas of the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide are each independently LiaNixCoyMzRbOc, 0.9≤a≤1.2, 0.3≤x≤1, 0≤y≤0.4, 0≤z≤0.2, 0<b≤0.2, 1.8≤c≤2.2, x+y+z+b=1, M is one or both of Mn and Al, and R includes one or more of Na, Sb, C, K, Ca, Zr, Sr, Al, B, Ba, Nb, W, Mo, Co, P and C, and R must contain Zr; The molar amount of Zr in R of the first lithium nickel transition metal oxide or the second lithium nickel transition metal oxide is less than or equal to 0.15 per mole; and / or The Ni content in the first lithium nickel transition metal oxide is 0.5≤x≤0.98, and the Ni content in the second lithium nickel transition metal oxide is 0.6≤x≤0.

98.

6. The positive electrode active material according to claim 1, wherein The first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide each independently include a core and a coating layer covering the core, and the chemical formula of the core is each independently LiaNixCoyMzRbOc, 0.9≤a≤1.2, 0.3≤x≤1, 0≤y≤0.4, 0≤z≤0.2, 0<b≤0.2, 1.8≤c≤2.2, x+y+z+b=1, M is one or both of Mn and Al, and R includes one or more of Na, Sb, C, K, Ca, Zr, Sr, Al, B, Ba, Nb, W, Mo, Co, P and C, and R must contain Zr; The molar amount of Zr in R of the first lithium nickel transition metal oxide or the second lithium nickel transition metal oxide is less than or equal to 0.15; and / or The Ni content of the first lithium nickel transition metal oxide is 0.5≤x≤0.98, and the Ni content of the second lithium nickel transition metal oxide is 0.6≤x≤0.98; and / or The coating layer comprises one oxide coating layer or two oxide coating layers; and / or The inner layer of the two oxide coating layers is an island oxide coating layer, and the outer layer is a layered oxide coating layer; and / or The thickness of the coating layer is 0.1 nm-200 nm.

7. The positive electrode active material according to claim 6, wherein The oxide coating layer elements include one or more of the group consisting of Zr, Al, P, B, Ti, W, Co, Nb, Mo and Mg.

8. The positive electrode active material according to claim 1, wherein The weight content of the first lithium nickel transition metal oxide in the positive electrode active material is 10%-95%.

9. A positive electrode sheet comprising a current collector and a positive electrode film layer, wherein the positive electrode film layer comprises a positive electrode active material, wherein: The positive electrode active material is the positive electrode active material according to any one of claims 1 to 8.

10. A secondary battery comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein: The positive electrode sheet is the positive electrode sheet according to claim 9.

11. An electrical device comprising a secondary battery, wherein: The secondary battery is selected from the secondary battery according to claim 10.

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