Positive active material, positive plate and battery

Abstract

The invention relates to the field of batteries, in particular to a positive electrode active material, a positive plate comprising the positive electrode active material and a battery. The positive electrode active material provided by the invention has relatively high capacity and stability. Comprising the positive electrode active material can effectively improve the gas production problem and considers the energy density, the cycle performance and the furnace temperature safety performance.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to a positive electrode active material, a positive electrode sheet including the positive electrode active material, and a battery. Background Technology

[0002] High-nickel ternary cathode materials are widely used in high-energy-density systems due to their high specific capacity. However, batteries containing high-nickel ternary cathode materials are prone to gas generation during cycling, which can severely degrade cycle performance and even pose safety hazards.

[0003] Therefore, it is necessary to improve the gas generation problem in batteries, including those using high-nickel ternary cathode materials, during cycling. Summary of the Invention

[0004] The purpose of this invention is to overcome the aforementioned problems in the prior art and to provide a positive electrode active material, a positive electrode sheet including the positive electrode active material, and a battery. The positive electrode active material of this invention exhibits high capacity and stability. Batteries including the positive electrode active material of this invention can effectively improve gas generation issues while maintaining energy density, cycle performance, and furnace temperature safety.

[0005] In related technologies, batteries containing high-nickel ternary cathode materials are prone to gas generation during cycling. The inventors of this invention discovered that the cause of this problem lies in the poor stability of the high-nickel ternary cathode material due to its manufacturing process and inherent material characteristics, particularly its surface stability. For example, residual lithium or other active materials on the surface can exacerbate side reactions with the electrolyte, releasing gas and causing severe gas generation during battery cycling. As gas accumulates, it intensifies adverse reactions between internal battery components, ultimately leading to safety issues such as leakage, fire, and explosion. Based on these findings, the inventors believe that the high-nickel ternary cathode material can be modified by coating. Through a special design of the cathode active material coating layer, rapid lithium-ion transport can be ensured while effectively suppressing the escape of lattice oxygen, mitigating electrolyte attack, and enhancing the stability of the CEI film formed with the electrolyte; thereby improving the battery's cycle performance and furnace temperature safety.

[0006] The first aspect of this invention provides a positive electrode active material, the positive electrode active material comprising a first particle and a second particle, the first particle comprising a single crystal particle and the second particle comprising a polycrystalline particle; the first particle comprising a chemical formula of Li a1 Ni b1 Co c1 Mn d1 M 1 e1For O2, 0.8 ≤ a1 ≤ 1.3, 0.8 ≤ b1 ≤ 0.98, 0.02 ≤ c1 ≤ 0.2, 0.01 ≤ d1 ≤ 0.14, 0 ≤ e1 ≤ 0.08, M 1 The second particle includes at least one of the elements Al, Zr, B, Y, Sr, W, Ti, and Nb; the second particle includes the chemical formula Li. a2 Ni b2 Co c2 Mn d2 M 2 e2 For O2, the following conditions apply: 0.9 ≤ a² ≤ 1.3, 0.8 ≤ b² ≤ 0.98, 0.02 ≤ c² ≤ 0.3, 0.01 ≤ d² ≤ 0.12, 0 ≤ e² ≤ 0.1, M 2 The first particle includes at least one of the elements Al, Zr, B, Y, Sr, W, Ti, and Nb; the second particle includes a first coating layer located on the outer surface of the first particle; the second particle includes a second coating layer located on the outer surface of the second particle; the thickness of the first coating layer is t1 in nm, the thickness of the second coating layer is t2 in nm, and t1 / t2 ≤ 1.

[0007] Polycrystalline particles are formed by the agglomeration and growth of small primary particles, making them prone to microcracks during battery cycling. This exposes grain boundaries to the electrolyte, exacerbating side reactions. Applying a coating layer to the outer surface of polycrystalline particles increases their strength, thereby suppressing microcrack formation. While monocrystalline particles possess relatively high stability due to their uniform internal crystal structure, they are also susceptible to side reactions with the electrolyte. Therefore, applying a coating layer to the outer surface of monocrystalline particles can also enhance their stability. However, simply applying a coating layer to the outer surface of both monocrystalline and polycrystalline particles without control can affect lithium-ion transport in the battery, leading to poor rate performance. Therefore, the inventors of this invention, through extensive research, discovered that by controlling the ratio of the thickness of the coating layer on the surface of monocrystalline particles to that on the surface of polycrystalline particles, the battery can achieve a balance between energy density, cycle performance, furnace temperature safety, and rate performance. This is because polycrystalline particles have poorer surface stability than monocrystalline particles, thus requiring a thicker coating layer to increase their strength. The Li content of single-crystal particles relative to polycrystalline particles + The transmission performance is poor, therefore a thicker cladding layer will exacerbate the degradation of Li. +The thickness of the coating layer is too thick, which increases the lithium-ion transport distance, negatively impacting rate performance and increasing battery heat generation, thus affecting furnace temperature safety. However, when the ratio of the coating layer thickness on the surface of the single-crystal particles to that on the surface of the polycrystalline particles is within a specific range, the single-crystal and polycrystalline particles are well-matched, allowing the positive electrode active material to balance stability and lithium-ion transport performance. + This improves transmission performance, enabling the battery to have high energy density while having low gas production risk, as well as excellent cycle performance, furnace temperature safety performance, and rate performance.

[0008] A second aspect of the present invention provides a positive electrode sheet, the positive electrode sheet comprising the positive electrode active material described in the first aspect of the present invention.

[0009] A third aspect of the present invention provides a battery comprising the positive electrode active material described in the first aspect of the present invention and / or the positive electrode sheet described in the second aspect of the present invention.

[0010] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art:

[0011] (1) The positive electrode active material of the present invention has high capacity, stability and Li + Transmission performance;

[0012] (2) The battery of the present invention can take into account energy density, cycle performance and rate performance, and can effectively suppress gas production.

[0013] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Attached Figure Description

[0014] Figure 1 The image shown is a scanning electron microscope (SEM) image of the positive electrode sheet in an example of the present invention. Detailed Implementation

[0015] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0016] The first aspect of the present invention provides a positive electrode active material, which may include a first particle and a second particle, wherein the first particle may include a single crystal particle and the second particle may include a polycrystalline particle.

[0017] In this invention, the first particle may include a chemical formula of Li. a1 Ni b1 Co c1 Mn d1 M 1 e1 O2 substances, wherein 0.8 ≤ a1 ≤ 1.3 (e.g., 0.8, 0.9, 1, 1.1, 1.2, or 1.3), 0.8 ≤ b1 ≤ 0.98 (e.g., 0.8, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, or 0.98), and 0.02 ≤ c1 ≤ 0.2 (e.g., 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, or 0.0 8, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19 or 0.2), 0.01≤d1≤0.14 (e.g., 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13 or 0.14), 0≤e1≤0.08 (e.g., 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07 or 0.08), M 1 It may include at least one of the elements Al, Zr, B, Y, Sr, W, Ti, and Nb.

[0018] In this invention, the second particle may include a particle with the chemical formula Li a2 Ni b2 Co c2 Mn d2 M 2 e2O2 substances, wherein 0.9 ≤ a² ≤ 1.3 (e.g., 0.9, 1, 1.1, 1.2, or 1.3), 0.8 ≤ b² ≤ 0.98 (e.g., 0.8, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, or 0.98), and 0.02 ≤ c² ≤ 0.3 (e.g., 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13), 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, or 0.3), 0.01≤d2≤0.12 (e.g., 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, or 0.12), 0≤e2≤0.1 (e.g., 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1), M 2 It may include at least one of the elements Al, Zr, B, Y, Sr, W, Ti, and Nb.

[0019] In this invention, the first particle may include a first coating layer, which may be located on the outer surface of the first particle. The second particle may include a second coating layer, which may be located on the outer surface of the second particle. The thickness of the first coating layer is t1, in nm, and the thickness of the second coating layer is t2, in nm, where t1 / t2 ≤ 1, and is, for example, 1, 0.95, 0.9, 0.85, 0.8, 0.75, 0.7, 0.65, 0.6, 0.55, 0.5, 0.45, 0.4, 0.35, 0.3, 0.25, 0.2, 0.15, or 0.1.

[0020] In one instance, 0.2 ≤ t1 / t2 ≤ 0.85.

[0021] In one instance, 0.62 ≤ t1 / t2 ≤ 0.83.

[0022] In this invention, t1 can be 1-10, with the unit being nm, for example, 1nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm or 10nm.

[0023] In one example, t1 is 2-6.5 nm.

[0024] When t1 / t2 is within a specific range, if t1 is large (e.g., greater than 10nm), the coating layer on the outer surface of the first particle is too thick, which will increase the diffusion resistance of lithium ions and cause the rate performance of the battery to deteriorate; while if t1 is small (e.g., less than 1nm), the coating layer on the outer surface of the first particle is too thin and cannot play an effective protective role.

[0025] In this invention, t2 can be 2-15, with the unit being nm, for example, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm or 15nm.

[0026] In one instance, t2 is 3-8.5 nm.

[0027] When t1 / t2 is within a specific range, and t2 is within that range, the positive electrode active material can achieve a balance between stability and Li. + Transmission performance. When t2 is too large (e.g., greater than 15nm), the coating layer on the outer surface of the second particle is too thick, which increases the diffusion resistance of lithium ions and leads to a deterioration in the rate performance of the battery; while when t2 is too small (e.g., less than 2nm), the coating layer on the outer surface of the second particle is too thin and cannot play an effective protective role.

[0028] In this invention, the thickness t1 of the first coating layer and the thickness t2 of the second coating layer can be obtained by conventional methods in the art, such as by using a transmission electron microscope (TEM) to randomly select at least 20 first particles (second particles) in the field of view, randomly select at least 10 sites on each first particle (second particle), measure the coating layer thickness corresponding to each site, and take the average value.

[0029] In this invention, the first coating layer may include at least one of the elements Al, Zr, B, Y, Sr, W, Ti, and Nb. The second coating layer may include at least one of the elements Al, Zr, B, Y, Sr, Ti, and Nb.

[0030] In one instance, the first coating layer includes at least one of the elements Al, W, Zr, and B.

[0031] In one instance, the first covering layer includes element B.

[0032] In one instance, the first covering layer comprises elements A1 and B.

[0033] In one instance, the first covering layer includes elements W and B.

[0034] In one instance, the first covering layer includes elements Zr and B.

[0035] In one instance, the second covering layer includes element B.

[0036] In one instance, the second coating layer comprises elements A1 and B.

[0037] In one instance, the second covering layer does not contain element W.

[0038] In one instance, the first coating layer includes element W, and the second coating layer does not contain element W.

[0039] The inventors of this invention have discovered that when the first and second coating layers include specific elements, the specific capacity of the positive electrode active material can be further improved, and the gas generation problem during battery cycling can be effectively suppressed. For example, introducing element W into the first coating layer can refine the particle size of the first particles and stabilize the surface structure of the first particles; however, introducing element W into the second coating layer will lead to a decrease in the overall uniformity of the second coating layer, thereby exacerbating gas generation during battery cycling.

[0040] In this invention, a1, a2, b1, b2, c1, c2, d1, d2, e1, and e2 can be obtained by methods conventional in the art, such as inductively coupled plasma optical emission spectrometer (ICP-OES) or energy dispersive spectrometer (EDS).

[0041] In one instance, the first particle is a single-crystal particle.

[0042] In one example, the second particle is a polycrystalline particle. The second particle is composed of a plurality of primary particles. The term "a plurality of" means that the number of the primary particles constituting the second particle is greater than or equal to 2.

[0043] In this invention, the average particle size D1 of the first particle can be 0.5μm-4.5μm, for example, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm or 4.5μm.

[0044] In this invention, the average particle size D2 of the primary particles of the second particle can be 100nm-900nm, for example, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm ​​or 900nm.

[0045] In one example, the average particle size D2 of the primary particles of the second particle is 100nm-500nm.

[0046] In this invention, the average particle size D3 of the second particle can be 6μm-18μm, for example, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm or 18μm.

[0047] In one example, the average particle size D3 of the second particle is 7 μm-15 μm.

[0048] In this invention, the average particle size D1 of the first particle, the average particle size D2 of the primary particles of the second particle, and the average particle size D3 of the second particle can be obtained by conventional methods in the art, such as by scanning electron microscopy (SEM). Specifically: take a positive electrode sheet, test the particle size of the first particle within the field of view at 7.3 mm * 10 kX, and take the average value to obtain the average particle size D1 of the first particle; test the particle size of the primary particles of the second particle within the field of view, and take the average value to obtain the average particle size D2 of the primary particles of the second particle; test the particle size of the second particle within the field of view, and take the average value to obtain the average particle size D3 of the second particle.

[0049] In this invention, 0.05≤D1 / D3≤0.5, for example, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4 or 0.5.

[0050] In one instance, 0.15 ≤ D1 / D3 ≤ 0.3.

[0051] The inventors of this invention have discovered that when the ratio of the average particle size D1 of the first particle to the average particle size D3 of the second particle is within a specific range, the active area of ​​the positive electrode active material in contact with the electrolyte is smaller, the compaction density is higher, the main material and auxiliary material are more tightly bonded, and the peeling force is improved, thereby improving the structural stability of the positive electrode sheet and further improving the cycle performance and furnace temperature safety performance of the battery.

[0052] In this invention, the median particle size Dv of the first particle 1 50 can be 0.5μm-5μm, for example, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm or 5μm.

[0053] In this invention, the median particle size Dv of the second particle 2 50 can be 6μm-18μm, for example, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm or 18μm.

[0054] In this invention, the median particle size Dv of the first particle 1 50 and the median particle size Dv of the second particle 2 50 can be obtained by methods conventional in the art, such as laser particle size analyzers.

[0055] In this invention, 0.04 ≤ Dv 1 50 / Dv 2 50≤0.6, for example, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5 or 0.6.

[0056] In this invention, the first particle can be a layered material. The second particle can be a layered material.

[0057] In this invention, based on the total weight of the positive electrode active material, the content C1 of the first particle is 70% ≤ C1 < 100%, for example, 70%, 80%, 90% or 99.9%.

[0058] In one example, the content of the first particle C1 is 73%-93% based on the total weight of the positive electrode active material.

[0059] Single-crystal grains exhibit excellent structural stability due to their uniform internal crystal structure, consistent grain orientation, and the absence of grain boundaries; however, the relatively large spacing between single-crystal grains can increase the viscosity of Li. + The reduced transport distance decreases lithium-ion transport efficiency, leading to a decline in the material's capacity and rate performance. Polycrystalline particles, composed of numerous primary particles, have grain boundaries that negatively impact the material's structural stability. Furthermore, excessive grain boundaries in polycrystalline particles increase the risk of side reactions between the primary particles and the electrolyte, further increasing the likelihood of structural collapse during cycling. However, the smaller particle size of the primary particles in polycrystalline particles significantly shortens the lithium-ion transport distance. + The transmission distance is therefore advantageous for Li + The transfer of energy between the positive electrode and the electrolyte is improved, resulting in better capacity utilization and rate performance. While blending polycrystalline and monocrystalline particles can improve cycle performance and rate performance to some extent, the improvement effect is not significant. Further controlling the weight content of the first particle in the positive electrode active material can reduce the risk of side reactions (such as gas generation) between the positive electrode active material and the electrolyte, thereby improving the battery's cycle performance.

[0060] In this invention, the first coating layer can be distributed in an island-like pattern on the surface of the first particle. The island-like distribution refers to the first coating layer being divided into several discontinuous blocks distributed on the surface of the first particle.

[0061] The inventors of this invention discovered that the island-shaped first coating layer not only provides sufficient stability to the surface of the first particle, but also improves the Li... + It improves the transmission capacity; it also helps the additives in the electrolyte to form a stable protective film on the surface of the first particle, thereby mitigating the risk of side reactions between the electrolyte and the first particle.

[0062] In this invention, the first coating layer can be prepared by a dry coating process. Using a dry coating process, a stable island-shaped coating layer can be obtained on the outer surface of the first particle.

[0063] In this invention, the coverage of the first coating layer on the surface of the first particle can be 5%-95%, for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95%.

[0064] The inventors of this invention have discovered that when the coverage of the first coating layer on the surface of the first particle is within a specific range, it can not only improve the Li + The improved transmission capacity also helps the additives in the electrolyte to form a stable protective film on the surface of the first particle, thereby mitigating the risk of side reactions between the electrolyte and the first particle.

[0065] In this invention, the coverage of the first coating layer on the surface of the first particle can be tested using conventional methods in the art, such as TEM or scanning electron microscopy (SEM). At least 20 first particles are randomly selected in the field of view, and the coverage of a single particle is obtained by comparing the area of ​​the coating on each observed particle with the surface area of ​​that particle. The coverage of the first coating layer on each first particle is measured sequentially, and the average value is taken.

[0066] In this invention, t1 / d1 can be 20-300, for example, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250 or 300.

[0067] In one instance, t1 / d1 is 86-200.

[0068] The inventors of this invention have discovered that the content of element Mn in the first particle not only affects the thickness of the first coating layer on its surface, but also the content of element Mn is related to the adhesion of the first coating layer on the first particle. When the ratio of the thickness of the first coating layer to the content of element Mn in the first particle is within a specific range, a first coating layer with suitable thickness and good stability can be obtained, thereby improving the structural stability and ion transport performance of the first particle.

[0069] In this invention, high-nickel ternary cathode material refers to cathode active material that includes elements Ni, Co and Mn, and the number of Ni atoms in the chemical formula of cathode active material is greater than or equal to 0.8, that is, b1≥0.8, b2≥0.8.

[0070] In one instance, d1 is 0.01-0.07.

[0071] In this invention, the first particle may include element Y. The weight content of element Y in the first particle is C. Y1 The specific surface area of ​​the first particle is BET1, in m². 2 / g, C Y1 And BET1 satisfies 0≤C Y1 / BET1≤0.005, for example, 0, 0.0001, 0.0002, 0.0003, 0.0004, 0.0005, 0.0006, 0.0007, 0.0008, 0.0009, 0.001, 0.002, 0.003, 0.004 or 0.005.

[0072] In one instance, 0.0003 ≤ C Y1 / BET1≤0.0025.

[0073] When the first particle contains element Y, the first coating layer changes during battery charging and discharging, allowing it to remove HF and reduce side reactions between the positive electrode active material and the electrolyte. Therefore, doping with element Y can stabilize the surface structure of the first particle; within a certain doping range, the content of element Y is positively correlated with the surface stability of the first particle. The specific surface area of ​​the first particle also reflects its surface stability to some extent. A larger specific surface area means a larger contact area between the particle and the electrolyte, resulting in poorer surface stability; conversely, a smaller specific surface area means a smaller contact area, resulting in better surface stability. Therefore, by controlling the relationship between the weight content of element Y in the first particle and its specific surface area, the surface stability of the first particle can be further improved, thereby enhancing the cycle stability of the battery.

[0074] In this invention, C Y1 It can be 100ppm-1800ppm, for example, 100ppm, 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1100ppm, 1200ppm, 1300ppm, 1400ppm, 1500ppm, 1600ppm, 1700ppm or 1800ppm.

[0075] In one instance, C Y1 The value is 500ppm-1500ppm.

[0076] In this invention, the weight content of element Y in the first particle can be obtained by methods conventional in the art, such as inductively coupled plasma (ICP) or EDS.

[0077] In this invention, BET1 can be 0.7 ≤ BET1 ≤ 1.6, and the unit is m. 2 / g, for example, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1m 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.4m 2 / g, 1.5m 2 / g or 1.6m 2 / g.

[0078] In one example, 0.7 ≤ BET1 ≤ 1.4, and the unit is m. 2 / g.

[0079] In this invention, the specific surface area of ​​the second particle is BET2, where 0.4 ≤ BET2 ≤ 1.1, and the unit is m². 2 / g, for example, 0.4m 2 / g, 0.5m 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1m 2 / g or 1.1m 2 / g.

[0080] In one instance, 0.4 ≤ BET2 ≤ 0.85, and the unit is m. 2 / g.

[0081] When BET1 and / or BET2 are within a certain range, it is beneficial for the electrolyte to wet the positive electrode active material, which can improve the capacity utilization of the positive electrode active material and improve the cycle performance of the battery.

[0082] In this invention, the specific surface area BET1 of the first particle and the specific surface area BET2 of the second particle can be obtained by conventional methods in the art, such as nitrogen adsorption method.

[0083] In this invention, the first coating layer may include element B, and the weight content of element B in the first coating layer is C, based on the total weight of the first particles. B1 C B1 It can be 200ppm-2000ppm, for example, 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1100ppm, 1200ppm, 1300ppm, 1400ppm, 1500ppm, 1600ppm, 1700ppm, 1800ppm, 1900ppm or 2000ppm.

[0084] In one instance, C B1 The concentration ranges from 300ppm to 1500ppm.

[0085] In this invention, the weight content of element B in the first particle can be obtained by methods conventional in the art, such as ICP or EDS.

[0086] A second aspect of the present invention provides a positive electrode sheet, which may include the positive electrode active material described in the first aspect of the present invention.

[0087] like Figure 1 The image shown is a scanning electron microscope (SEM) image of the positive electrode sheet in an example of the present invention. As can be seen from the image, the positive electrode sheet includes a positive electrode active material, which includes a first particle and a second particle.

[0088] In this invention, the residual alkali content of the positive electrode active material is C, C B1 And C satisfy 1≤C / C B1 ≤25, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 or 25.

[0089] In one instance, 2 ≤ C / C B1 ≤16.

[0090] Element B in the first coating layer can form a fast-ion conductor with residual lithium on the surface of the first particle, thereby reducing the residual alkali on the surface of the positive electrode active material. When C / C B1 When the concentration is high (e.g., greater than 25), the residual alkali content is too high, and the fast-ion conductor material generated by element B is insufficient to reduce the residual alkali content, which will affect the structural stability of the positive electrode. In addition, the fast-ion conductor material can also enhance the Li... + The transmission rate is increased, reducing the risk of electrolyte gelation; and it can also reduce the probability of the positive electrode active material layer expanding and falling off during battery charging and discharging.

[0091] In this invention, C can be 2000ppm-9000ppm, for example, 2000ppm, 3000ppm, 4000ppm, 5000ppm, 6000ppm, 7000ppm, 8000ppm or 9000ppm.

[0092] In this invention, the residual alkali content of the positive electrode active material can be obtained by methods conventional in the art, such as acid-base titration.

[0093] In this invention, the porosity of the positive electrode is m. Y1 And m satisfy 0≤C Y1 / m≤0.01, for example, 0, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009 or 0.01.

[0094] In one instance, 0.002 ≤ C Y1 / m≤0.005.

[0095] Doping with element Y can stabilize the surface structure of the first particle; therefore, within a certain doping range, the content of element Y is positively correlated with the surface stability of the first particle. The porosity of the cathode plate can reflect the contact area between the cathode plate and the electrolyte to some extent. The greater the porosity of the cathode plate, the larger its contact area with the electrolyte, and the greater the risk of side reactions. Therefore, by controlling the relationship between the weight content of element Y in the first particle and the porosity of the cathode plate, the cycle stability of the battery can be further improved.

[0096] In this invention, m can be 20%-40%, for example, 20%, 30% or 40%.

[0097] In one instance, m is 24%–31%.

[0098] In this invention, the positive electrode sheet may include a positive current collector and a positive active material layer on at least one side surface of the positive current collector. The positive active material layer may include the positive active material. The positive active material layer may also include a positive conductive agent and a positive binder. The positive conductive agent may include conductive agents conventionally used in the art, such as at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, and carbon nanotubes (including at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes). The positive binder may include binders conventionally used in the art, such as at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, polytetrafluoroethylene, and polyethylene oxide.

[0099] In one example, the positive conductive agent comprises single-walled carbon nanotubes.

[0100] Single-walled carbon nanotubes have good electrical conductivity due to their unique three-dimensional structure. Furthermore, the contact between single-walled carbon nanotubes and the positive electrode active material has changed from the traditional point-to-point to line-to-point, which greatly increases the contact area and improves the conductivity of the positive electrode. This is beneficial for increasing the capacity of the positive electrode active material, thereby further improving the energy density and rate performance of the battery.

[0101] In this invention, based on the total weight of the positive electrode active material layer, the content of the positive electrode active material can be 80-99.8% by weight (e.g., 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 99, or 99.8% by weight), the content of the positive electrode conductive agent can be 0.1-10% by weight (e.g., 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5, or 0.1% by weight), and the content of the positive electrode binder can be 0.1-10% by weight (e.g., 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5, or 0.1% by weight).

[0102] A third aspect of the present invention provides a battery, which may include the positive electrode active material described in the first aspect of the present invention and / or the positive electrode sheet described in the second aspect of the present invention.

[0103] In this invention, the battery may further include a negative electrode sheet. The negative electrode sheet may include a negative current collector and a negative active material layer on at least one side surface of the negative current collector. The negative active material layer may include a negative active material, which may include a silicon-based material. The weight content of the silicon-based material in the negative active material layer may be 0.01%-50%, for example, 0.01%, 0.05%, 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%.

[0104] In one example, the silicon-based material has a weight content of 4%-25% in the negative electrode active material layer.

[0105] Silicon-based materials have high specific capacity and good compatibility with the positive electrode active material described in this invention. The positive electrode active material of this invention has a low discharge temperature rise and high positive electrode stability, which can greatly reduce the damage of metal dissolution to the SEI film on the negative electrode side and has a good inhibitory effect on the volume expansion of silicon-based materials, resulting in higher cycle performance and energy density of the battery.

[0106] In this invention, the negative electrode active material layer may include the silicon-based material. The silicon-based material may include at least one of elemental silicon, silicon-oxygen, silicon-carbon, and silicon alloys. Silicon-oxygen refers to a material comprising elemental silicon and elemental oxygen. Silicon-carbon refers to a material comprising elemental silicon and elemental carbon.

[0107] In one example, the silicon-based material comprises silicon-carbon. The silicon-carbon comprises elemental silicon distributed within a carbon framework.

[0108] In one example, the battery is a lithium-ion battery.

[0109] In this invention, the positive electrode sheet may further include a positive electrode tab, and the negative electrode sheet may further include a negative electrode tab. The positive electrode tab is electrically connected to the positive current collector, and the negative electrode tab is electrically connected to the negative current collector. In the battery, the total number of the positive electrode tab and the negative electrode tab is greater than or equal to 2, for example, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0110] In one instance, the total number of the positive electrode tabs and the negative electrode tabs is greater than 2.

[0111] The inventors of this invention have discovered that when the total number of positive and negative electrode tabs is greater than two, the energy density, rate performance, and furnace temperature safety performance of the battery can be further improved. This is because a larger current-carrying area of ​​the tabs facilitates heat dissipation and increases electron transport rate, effectively reducing the internal resistance of the positive / negative electrode sheets and decreasing heat generation in the battery. This, in turn, alleviates the stress on the high-nickel positive electrode active material at high temperatures. + / Ni 2+ The degree of mixing. Furthermore, the volume expansion of silicon-containing anodes is relatively sensitive to temperature. When the anode sheet includes element Si, a total number of positive and negative electrode tabs greater than 2 can significantly reduce heat generation and increase heat dissipation, thereby improving the overall high-temperature resistance of the battery.

[0112] In this invention, the negative electrode active material layer may further include a negative electrode conductive agent and a negative electrode binder. The negative electrode conductive agent may include conductive agents conventionally used in the art, such as at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, and carbon nanotubes (including at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes). The negative electrode binder may include binders conventionally used in the art, such as at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, polytetrafluoroethylene, and polyethylene oxide.

[0113] In this invention, based on the total weight of the negative electrode active material layer, the content of the negative electrode active material can be 80-99.8% by weight (e.g., 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 99, or 99.8% by weight), the content of the negative electrode conductive agent can be 0.1-10% by weight (e.g., 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5, or 0.1% by weight), and the content of the negative electrode binder can be 0.1-10% by weight (e.g., 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5, or 0.1% by weight).

[0114] In this invention, the battery may further include a separator. The separator may include a base film and a ceramic layer located on at least one surface of the base film.

[0115] In one example, the membrane further includes a polymer layer. The polymer layer may be located on at least one outer surface of the membrane.

[0116] In one example, the ceramic layer is positioned at least directly opposite the positive electrode.

[0117] As a crucial barrier between the positive and negative electrodes of a lithium-ion battery, the separator provides a good ion pathway for lithium ion transport while blocking electron conduction. The positive electrode side has a higher oxidizing potential, and the ceramic layer of the separator typically includes inorganic particles, giving it high oxidation resistance. Therefore, placing the positive electrode sheet and the ceramic layer directly opposite each other can further improve the battery's cycle performance.

[0118] In this invention, the battery may further include a casing. The casing may include at least one of a flexible casing and a rigid casing. The flexible casing may include at least one of an aluminum-plastic film and a polymer film. The rigid casing may include at least one of a steel casing, an aluminum casing, and an alloy casing.

[0119] Understandably, rigid casings provide excellent protection for batteries, have a high degree of integration, and offer high safety; while flexible casings allow for flexible design of battery size and shape, and their lighter weight allows for a significant increase in battery energy density.

[0120] In this invention, the battery may further include an electrolyte. The electrolyte may include electrolytes conventionally used in the art.

[0121] It should be noted that the numerical designations such as "first" and "second" in this invention are only used to distinguish different substances or methods of use, and do not represent a difference in order.

[0122] The present invention will be described in detail below through embodiments. The embodiments described herein are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0123] In the following examples, unless otherwise specified, all materials used are commercially available analytical grade.

[0124] The following embodiments illustrate the battery of the present invention.

[0125] Example 1

[0126] The battery is prepared according to the following method:

[0127] (1) Preparation of the first particle

[0128] LiOH·H₂O, Ni(OH)₂, Co(OH)₂, Mn(OH)₂, and NaOH were mixed evenly in a molar ratio of 1.5:0.93:0.02:0.05:0.5 (the total weight of Li, Ni, Co, and Mn was 0.67a). Then, Al(OH)₃, Y₂O₃, and ZrO₂ were added, with Al(OH)₃ accounting for 0.43%a, Y₂O₃ for 0.27%a, and ZrO₂ for 0.23%a. After mixing evenly, the mixture was added... The crucible was placed in a box-type muffle furnace (oxygen atmosphere, gas flow rate 20 ml / min), and heated to 450℃ at a heating rate of 5℃ / min, held at that temperature for 12 h, and then naturally cooled to room temperature. After crushing, 0.54% a H3BO3 and 0.32% a Al2O3 were added, and the mixture was heated to 350℃ and held for 5 h. After crushing and sieving, the first particles were obtained, wherein the thickness t1 of the first coating layer was 4.3 nm, the first coating layer consisted of Al and B, D1 was 2.6 μm, and Dv was... 1 50 is 2.5 μm, the first coating layer is distributed in an island-like pattern on the surface of the first particle, with a coverage of 5%-95%, d1 is 0.05, b1>0.8, C Y1 It is 1000ppm, and BET1 is 1m. 2 / g, C Y1 / BET1 is 0.001, C B1 The value is 900 ppm, the first particle is a single crystal particle, and the t1 / d1 is 86.

[0129] (2) Preparation of positive electrode sheet

[0130] The positive electrode active material (first particle and second particle) is mixed at a weight ratio of 80:20, wherein the second particle is commercially available and is a polycrystalline particle, the thickness t2 of the second coating layer is 5.2 nm, the second coating layer includes elements Al and B, D2 is 300 nm, D3 is 10 μm, and Dv is... 2 50 is 10.2 μm, and BET2 is 0.6 μm. 2 / g, based on the total molar number of elements Ni, Co, and Mn in the second particle (with Ni molar number of 0.9), polyvinylidene fluoride, single-walled carbon nanotubes, and multi-walled carbon nanotubes were mixed uniformly in a weight ratio of 97.4:1.2:0.4:1, and N-methylpyrrolidone (NMP) was added to obtain a positive electrode slurry (solid content of 65%). The positive electrode slurry was uniformly coated onto aluminum foil (thickness of 10μm) using a coating machine, baked at 120℃ for 12h, and then rolled to obtain a positive electrode sheet, wherein t1 / t2 is 0.83, D1 / D3 is 0.26, the porosity m of the positive electrode sheet is 28%, and C Y1 / m is 0.00357;

[0131] (3) Preparation of negative electrode sheet

[0132] A negative electrode active material (artificial graphite and silicon carbide), single-walled carbon nanotubes, multi-walled carbon nanotubes, polyvinylidene fluoride, and sodium carboxymethyl cellulose were mixed evenly in a weight ratio of 96.1:0.25:0.15:2.9:0.6 to obtain a material. Ethylene carbonate (EC) accounting for 1% of the total weight of the material was added, and deionized water was added to obtain a negative electrode slurry (solid content of 45%). The negative electrode slurry was uniformly coated on high-strength carbon-coated copper foil (thickness of 4μm), dried, and then rolled to obtain a negative electrode sheet, wherein the weight content of silicon carbide in the negative electrode active material layer was 20%.

[0133] (4) Preparation of electrolyte

[0134] In a glove box filled with inert gas (argon) (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate, propylene carbonate, diethyl carbonate, and propyl propionate are mixed evenly in a weight ratio of 15:10:10:65. Then, 1.25 mol / L of fully dried lithium hexafluorophosphate is quickly added and stirred evenly. Finally, 0.42% of vinylene carbonate based on the total weight of the electrolyte is added. After passing the tests for moisture and free acid, the desired electrolyte is obtained.

[0135] (5) Battery fabrication

[0136] The positive electrode sheet prepared in step (2), the negative electrode sheet prepared in step (3), and the separator (including a 5μm thick polyethylene substrate, a 2μm thick ceramic layer on one side of the substrate, and a 1μm thick polyvinylidene fluoride layer on the other side of the substrate) are wound by a winding machine to obtain a battery core in which the positive and negative electrode sheets are separated by the separator. The battery core is placed in the shell and then processed through welding, encapsulation, liquid injection, formation, gas bag cutting, sorting and other processes to obtain the battery. Its structure is multi-tab winding (the sum of the number of positive electrode tabs and the number of negative electrode tabs is 44). The ceramic layer of the separator faces the positive electrode sheet, and the shell is an aluminum-plastic film.

[0137] Example 2

[0138] The procedure is carried out in accordance with Example 1, except that steps (1) and (2) are as follows:

[0139] (1) Preparation of the first particle

[0140] LiOH·H₂O, Ni(OH)₂, Co(OH)₂, Mn(OH)₂, and NaOH were mixed evenly in a molar ratio of 1.5:0.93:0.06:0.01:0.5 (the total weight of Li, Ni, Co, and Mn was 0.67a). Then, Al(OH)₃, Y₂O₃, and ZrO₂ were added, with Al(OH)₃ accounting for 0.43%a, Y₂O₃ for 0.13%a, and ZrO₂ for 0.23%a. After mixing evenly, [the mixture was then added]. The material was placed in a crucible and then placed in a box-type muffle furnace (oxygen atmosphere, gas flow rate 20 ml / min). The temperature was increased to 450℃ at a heating rate of 5℃ / min and held for 12 hours. After natural cooling to room temperature, the material was crushed, and then 0.18% a H3BO3 and 0.32% a Al2O3 were added. The mixture was heated to 350℃ and held for 5 hours. After crushing and sieving, the first particles were obtained. The thickness t1 of the first coating layer was 2 nm, and the first coating layer consisted of Al and B. D1 was 1.2 μm, and Dv... 1 50 is 1.5 μm, the first coating layer is distributed in an island-like pattern on the surface of the first particle, with a coverage of 5%-95%, d1 is 0.01, b1>0.8, C Y1 It is 500ppm, and BET1 is 1.4m. 2 / g, C Y1 / BET1 is 0.00036, C B1 The value is 300 ppm, the first particle is a single crystal particle, and t1 / d1 is 200.

[0141] (2) Preparation of positive electrode sheet

[0142] The positive electrode active material (first particle and second particle) was mixed at a weight ratio of 73:27, wherein the second particle was commercially available and was a polycrystalline particle, the thickness t2 of the second coating layer was 3.1 nm, the second coating layer included elements Al and B, D2 was 100 nm, D3 was 7 μm, and Dv was... 2 50 is 7.1 μm, and BET2 is 0.85 μm. 2 / g, based on the total molar number of elements Ni, Co, and Mn in the second particle (with Ni molar number of 0.9), polyvinylidene fluoride, single-walled carbon nanotubes, and multi-walled carbon nanotubes were mixed uniformly in a weight ratio of 97.4:1.2:0.4:1, and N-methylpyrrolidone (NMP) was added to obtain a positive electrode slurry (solid content of 65%). The positive electrode slurry was uniformly coated onto aluminum foil (thickness of 10μm) using a coating machine, baked at 120℃ for 12h, and then rolled to obtain a positive electrode sheet, wherein t1 / t2 is 0.65, D1 / D3 is 0.17, the porosity m of the positive electrode sheet is 24%, and C Y1 / m is 0.0021.

[0143] Example 3

[0144] The procedure is carried out in accordance with Example 1, except that steps (1) and (2) are as follows:

[0145] (1) Preparation of the first particle

[0146] LiOH·H₂O, Ni(OH)₂, Co(OH)₂, Mn(OH)₂, and NaOH were mixed evenly in a molar ratio of 1.5:0.925:0.005:0.07:0.5 (the total weight of Li, Ni, Co, and Mn was 0.67a). Then, Al(OH)₃, Y₂O₃, and ZrO₂ were added, with Al(OH)₃ accounting for 0.43%a, Y₂O₃ for 0.4%a, and ZrO₂ for 0.23%a. After mixing evenly, [the mixture was then added]. The material was placed in a crucible and then placed in a box-type muffle furnace (oxygen atmosphere, gas flow rate 20 ml / min). The temperature was increased to 450℃ at a heating rate of 5℃ / min and held for 12 hours. After natural cooling to room temperature, the material was crushed and then 0.9% a H3BO3 and 0.32% a Al2O3 were added. The mixture was heated to 350℃ and held for 5 hours. After crushing and sieving, the first particles were obtained. The thickness t1 of the first coating layer was 6.5 nm, and the first coating layer consisted of Al and B. D1 was 4.3 μm, and Dv... 1 50 is 4.5 μm, the first coating layer is distributed in an island-like pattern on the surface of the first particle, with a coverage of 5%-95%, d1 is 0.07, b1>0.8, C Y1 It is 1500ppm, and BET1 is 0.7m. 2 / g, C Y1 / BET1 is 0.0021, C B1 The concentration was 1500 ppm, the first particle was a single crystal particle, and the t1 / d1 ratio was 92.86.

[0147] (2) Preparation of positive electrode sheet

[0148] The positive electrode active material (first particle and second particle) was mixed at a weight ratio of 93:7, wherein the second particle was commercially available and was a polycrystalline particle, the thickness t2 of the second coating layer was 8.3 nm, the second coating layer included elements Al and B, D2 was 500 nm, D3 was 15 μm, and Dv was... 2 50 is 14.8 μm, and BET2 is 0.4 μm. 2 / g, based on the total molar number of elements Ni, Co and Mn in the second particle (with Ni molar number of 0.9), polyvinylidene fluoride, single-walled carbon nanotubes and multi-walled carbon nanotubes were mixed uniformly in a weight ratio of 97.4:1.2:0.4:1, and N-methylpyrrolidone (NMP) was added to obtain a positive electrode slurry (solid content of 65%). The positive electrode slurry was uniformly coated onto aluminum foil (thickness of 10μm) using a coating machine, baked at 120℃ for 12h, and then rolled to obtain a positive electrode sheet, wherein t1 / t2 is 0.78, D1 / D3 is 0.29, the porosity m of the positive electrode sheet is 31%, and C Y1 / m is 0.0048.

[0149] Example 4

[0150] This embodiment is used to verify the impact of the change in "t1 / t2".

[0151] The procedure was carried out in accordance with Example 2, except that t1 / t2 was changed by changing the second particle, as follows: the second particle from Example 3 was used, wherein t1 / t2 was 0.24.

[0152] Example 5 group

[0153] This embodiment is used to verify the impact of changes to "t1 and / or t2".

[0154] This set of embodiments is based on Embodiment 1 or Embodiment 2, except that the first particle and / or the second particle are changed, as follows:

[0155] Example 5a was carried out in accordance with Example 1, except that the first particle was changed. LiOH·H2O, Ni(OH)2, Co(OH)2, Mn(OH)2, and NaOH were mixed evenly in a molar ratio of 1.5:0.93:0.02:0.05:0.5 (the total weight of Li, Ni, Co, and Mn was 0.67a). Then Al(OH)3, Y2O3, and ZrO2 were added, wherein the weight of Al(OH)3 was 0.43%a, the weight of Y2O3 was 0.27%a, and the weight of ZrO2 was... The amount of 0.23% a was mixed and added to a crucible. The crucible was placed in a box-type muffle furnace (oxygen atmosphere, gas flow rate 20 ml / min), and heated to 450℃ at a heating rate of 5℃ / min and held for 12 h. After natural cooling to room temperature, it was crushed and then 0.12% a of H3BO3 and 0.32% a of Al2O3 were added. The mixture was heated to 350℃ and held for 5 h. After crushing and sieving, the first particles were obtained. The thickness t1 of the first coating layer was 1.2 nm, and the first coating layer included Al and B. D1 was 2.5 μm and Dv was 0. 1 50 is 2.5 μm, the first coating layer is distributed in an island-like pattern on the surface of the first particle, with a coverage of 5%-95%, d1 is 0.05, b1>0.8, C Y1 It is 1000ppm, and BET1 is 1m. 2 / g, C Y1 / BET1 is 0.001, C B1 The value is 200 ppm, the first particle is a single crystal particle, t1 / d1 is 24, and t1 / t2 is 0.23;

[0156] Example 5b is performed in accordance with Example 1, except that the second particle is changed to a polycrystalline particle, the thickness t2 of the second coating layer is 10.3 nm, the second coating layer includes elements Al and B, D2 is 300 nm, D3 is 10 μm, and Dv... 2 50 is 10μm, BET2 is 0.6m 2 / g, based on the total number of moles of elements Ni, Co and Mn in the second particle, the number of moles of element Ni is 0.9, where t1 / t2 is 0.42;

[0157] Example 5c is performed in accordance with Example 1, except that the first particle and the second particle are changed, as follows:

[0158] LiOH·H₂O, Ni(OH)₂, Co(OH)₂, Mn(OH)₂, and NaOH were mixed evenly in a molar ratio of 1.5:0.93:0.02:0.05:0.5 (the total weight of Li, Ni, Co, and Mn was 0.67a). Then, Al(OH)₃, Y₂O₃, and ZrO₂ were added, with Al(OH)₃ accounting for 0.43%a, Y₂O₃ for 0.27%a, and ZrO₂ for 0.23%a. After mixing evenly, [the mixture was then added]. The material was placed in a crucible and then placed in a box-type muffle furnace (oxygen atmosphere, gas flow rate 20 ml / min). The temperature was increased to 450℃ at a heating rate of 5℃ / min and held for 12 hours. After natural cooling to room temperature, the material was crushed, and then 1.2% a H3BO3 and 0.32% a Al2O3 were added. The mixture was heated to 350℃ and held for 5 hours. After crushing and sieving, the first particles were obtained. The thickness t1 of the first coating layer was 10 nm, and the first coating layer consisted of Al and B, with D1 being 2.5 μm and Dv... 1 50 is 2.7 μm, the first coating layer is distributed in an island-like pattern on the surface of the first particle, with a coverage of 5%-95%, d1 is 0.05, b1>0.8, C Y1 It is 1000ppm, and BET1 is 1m. 2 / g, C Y1 / BET1 is 0.001, C B1 The concentration is 2000 ppm, the first particle is a single crystal particle, and t1 / d1 is 200.

[0159] The second particle was commercially available. It is a polycrystalline particle with a second coating layer thickness t2 of 12.1 nm. The second coating layer includes elements Al and B. D2 is 300 nm, D3 is 10 μm, and Dv... 2 50 is 9.9 μm, and BET2 is 0.6 μm. 2 / g, based on the total number of moles of elements Ni, Co and Mn in the second particle, the number of moles of element Ni is 0.9; t1 / t2 is 0.83.

[0160] Example 6 group

[0161] This set of examples is used to verify the impact of changes in the "elements in the first coating layer".

[0162] This set of embodiments is based on Embodiment 1, except that the first particle is changed, as follows:

[0163] In Example 6a, LiOH·H₂O, Ni(OH)₂, Co(OH)₂, Mn(OH)₂, and NaOH were mixed uniformly in a molar ratio of 1.5:0.93:0.02:0.05:0.5 (the total weight of Li, Ni, Co, and Mn was 0.67a). Then, Al(OH)₃, Y₂O₃, and ZrO₂ were added, wherein the weight of Al(OH)₃ was 0.43%a, the weight of Y₂O₃ was 0.27%a, and the weight of ZrO₂ was 0.23%a. After homogenization, the solution is added to a crucible, which is then placed in a box-type muffle furnace (oxygen atmosphere, gas flow rate 20 ml / min). The temperature is increased to 450℃ at a heating rate of 5℃ / min and held for 12 hours. After natural cooling to room temperature, the mixture is crushed and then 0.54% a H3BO3 and 0.13% a WO3 are added. The mixture is heated to 350℃ and held for 5 hours. After crushing and sieving, the first particles are obtained. The thickness t1 of the first coating layer is 4.2 nm, and the first coating layer includes W and B. The diameter D1 is 2.6 μm, and the diameter Dv is... 1 50 is 2.7 μm, the first coating layer is distributed in an island-like pattern on the surface of the first particle, with a coverage of 5%-95%, d1 is 0.05, b1>0.8, C Y1 It is 1000ppm, and BET1 is 1m. 2 / g, C Y1 / BET1 is 0.001, C B1 The concentration was 900 ppm, and the first particle was a single crystal particle.

[0164] In Example 6b, LiOH·H₂O, Ni(OH)₂, Co(OH)₂, Mn(OH)₂, and NaOH were mixed evenly in a molar ratio of 1.5:0.93:0.02:0.05:0.5 (the total weight of Li, Ni, Co, and Mn was 0.67a). Then, Al(OH)₃, Y₂O₃, and ZrO₂ were added, wherein the weight of Al(OH)₃ was 0.43%a, the weight of Y₂O₃ was 0.27%a, and the weight of ZrO₂ was 0.23%a, and the mixture was stirred evenly. The solution was then added to a crucible, which was placed in a box-type muffle furnace (oxygen atmosphere, gas flow rate 20 ml / min). The temperature was increased to 450℃ at a heating rate of 5℃ / min and held for 12 hours. After natural cooling to room temperature, the solution was crushed, and then 0.54% a H3BO3 and 0.11% a ZrO2 were added. The mixture was heated to 350℃ and held for 5 hours. After crushing and sieving, the first particles were obtained. The thickness t1 of the first coating layer was 4.2 nm, and the first coating layer consisted of Zr and B. D1 was 2.6 μm, and Dv... 1 50 is 2.5 μm, the first coating layer is distributed in an island-like pattern on the surface of the first particle, with a coverage of 5%-95%, d1 is 0.05, b1>0.8, C Y1 It is 1000ppm, and BET1 is 1m. 2 / g, C Y1 / BET1 is 0.001, C B1 The concentration is 900 ppm, and the first particle is a single crystal particle.

[0165] Example 7 group

[0166] This set of examples is used to verify the impact of changes in the "weight content of the first particle in the positive electrode active material".

[0167] This set of embodiments is based on Embodiment 1, except that the weight ratio of the first particle to the second particle in the positive electrode active material is changed, as follows:

[0168] Example 7a: The first particle and the second particle are mixed at a weight ratio of 70:30, wherein the porosity m of the positive electrode sheet is 20%, and C Y1 / m is 0.005;

[0169] Example 7b: The first particle and the second particle are mixed at a weight ratio of 99:1, wherein the porosity m of the positive electrode sheet is 36%, and C... Y1 / m is 0.0028.

[0170] Example 8

[0171] This embodiment is used to verify the impact of changes in the "distribution state of the first coating layer on the surface of the first particle".

[0172] The procedure was carried out according to Example 1, except that the first particle was changed, specifically as follows: LiOH·H2O, Ni(OH)2, Co(OH)2, Mn(OH)2, and NaOH were mixed evenly in a molar ratio of 1.5:0.93:0.02:0.05:0.5 (the total weight of Li, Ni, Co, and Mn was 0.67a). Then, Al(OH)3, Y2O3, and ZrO2 were added, wherein the weight of Al(OH)3 was 0.43%a, the weight of Y2O3 was 0.27%a, and the weight of ZrO2 was 0.23%. a. After mixing, add the mixture to a crucible and place the crucible in a box-type muffle furnace (oxygen atmosphere, gas flow rate 20 ml / min). Heat to 450℃ at a heating rate of 5℃ / min and hold for 12 hours. Then allow to cool naturally to room temperature. After crushing, add ethanol as a solvent, followed by 0.54% a of H3BO3 and 0.32% a of Al2O3. Heat to 350℃ and hold for 5 hours. After crushing and sieving, obtain the first particles. The thickness t1 of the first coating layer is 4.2 nm, and the first coating layer includes Al and B. D1 is 2.6 μm, and Dv... 1 50 is 2.6 μm, the first coating layer continuously coats the surface of the first particle, d1 is 0.05, b1>0.8, C Y1It is 1000ppm, and BET1 is 1m. 2 / g, C Y1 / BET1 is 0.001, C B1 The value is 900 ppm, the first particle is a single crystal particle, and t1 / d1 is 84.

[0173] Example 9 group

[0174] This set of examples is used to verify "C" Y1 The impact of the change.

[0175] This set of embodiments is based on Embodiment 1, except that C is changed. Y1 The details are as follows:

[0176] In Example 9a, LiOH·H₂O, Ni(OH)₂, Co(OH)₂, Mn(OH)₂, and NaOH were mixed evenly in a molar ratio of 1.5:0.93:0.02:0.05:0.5 (the total weight of Li, Ni, Co, and Mn was 0.67a). Then, Al(OH)₃ and ZrO₂ were added, with Al(OH)₃ accounting for 0.43%a and ZrO₂ accounting for 0.23%a. After mixing evenly, the mixture was added to a crucible. The crucible was placed in a box-type muffle furnace (oxygen atmosphere, gas flow rate 20 ml / min), heated to 450℃ at a heating rate of 5℃ / min, and held at that temperature for 12 h. After natural cooling to room temperature, it was crushed, and then 0.54% a H3BO3 and 0.32% a Al2O3 were added. The mixture was heated to 350℃ and held for 5 h. After crushing and sieving, the first particles were obtained. The thickness t1 of the first coating layer was 4.3 nm, and the first coating layer consisted of Al and B. D1 was 2.5 μm, and Dv... 1 50 is 2.5 μm, the first coating layer is distributed in an island-like pattern on the surface of the first particle, with a coverage of 5%-95%, d1 is 0.05, b1>0.8, C Y1 =0, BET1 is 1m 2 / g, C Y1 / BET1 is 0, C B1 The concentration is 900 ppm, the first particle is a single crystal, and C Y1 / m is 0;

[0177] In Example 9b, LiOH·H₂O, Ni(OH)₂, Co(OH)₂, Mn(OH)₂, and NaOH were mixed evenly in a molar ratio of 1.5:0.93:0.02:0.05:0.5 (the total weight of Li, Ni, Co, and Mn was 0.67a). Then, Al(OH)₃, Y₂O₃, and ZrO₂ were added, wherein the weight of Al(OH)₃ was 0.43%a, the weight of Y₂O₃ was 0.027%a, and the weight of ZrO₂ was 0.23%a, and the mixture was stirred evenly. The solution was then added to a crucible, which was placed in a box-type muffle furnace (oxygen atmosphere, gas flow rate 20 ml / min). The temperature was increased to 450℃ at a heating rate of 5℃ / min and held for 12 hours. After natural cooling to room temperature, the mixture was crushed, and then 0.54% a H3BO3 and 0.32% a Al2O3 were added. The mixture was heated to 350℃ and held for 5 hours. After crushing and sieving, the first particles were obtained. The thickness t1 of the first coating layer was 4.4 nm, and the first coating layer consisted of Al and B. D1 was 2.6 μm, and Dv... 1 50 is 2.5 μm, the first coating layer is distributed in an island-like pattern on the surface of the first particle, with a coverage of 5%-95%, d1 is 0.05, b1>0.8, C Y1 It is 100ppm, and BET1 is 1m. 2 / g, C Y1 / BET1 is 0.0001, C B1 The concentration is 900 ppm, the first particle is a single crystal, and C Y1 / m is 0.00036;

[0178] In Example 9c, LiOH·H₂O, Ni(OH)₂, Co(OH)₂, Mn(OH)₂, and NaOH were mixed evenly in a molar ratio of 1.5:0.93:0.02:0.05:0.5 (the total weight of Li, Ni, Co, and Mn was 0.67a). Then, Al(OH)₃, Y₂O₃, and ZrO₂ were added, wherein the weight of Al(OH)₃ was 0.43%a, the weight of Y₂O₃ was 0.48%a, and the weight of ZrO₂ was 0.23%a, and the mixture was stirred evenly. The solution was then added to a crucible, which was placed in a box-type muffle furnace (oxygen atmosphere, gas flow rate 20 ml / min). The temperature was increased to 450℃ at a rate of 5℃ / min and held for 12 hours. After natural cooling to room temperature, the mixture was crushed, and then 0.54% a H3BO3 and 0.32% a Al2O3 were added. The mixture was heated to 350℃ and held for 5 hours. After crushing and sieving, the first particles were obtained. The thickness t1 of the first coating layer was 4.3 nm, and the first coating layer consisted of Al and B. D1 was 2.6 μm, and Dv... 1 50 is 2.7 μm, the first coating layer is distributed in an island-like pattern on the surface of the first particle, with a coverage of 5%-95%, d1 is 0.05, b1>0.8, CY1 It is 1800ppm, and BET1 is 1m. 2 / g, C Y1 / BET1 is 0.0018, C B1 The concentration is 900 ppm, the first particle is a single crystal, and C Y1 / m is 0.0064.

[0179] Example 10

[0180] This embodiment is used to verify the impact of changes to the "elements in the second coating layer".

[0181] The procedure was carried out in accordance with Example 1, except that the second particle was changed to a polycrystalline particle, the thickness t2 of the second coating layer was 5.2 nm, the second coating layer included element W (the weight content of element W in the second particle was 800 ppm), D2 was 300 nm, D3 was 10 μm, and Dv was... 2 50 is 10.2 μm, and BET2 is 0.6 μm. 2 / g, based on the total number of moles of elements Ni, Co and Mn in the second particle, with the number of moles of element Ni being 0.9.

[0182] Example 11

[0183] This embodiment is used to verify the impact of the change in "t1 / d1".

[0184] The procedure was carried out according to Example 3, except that the first particle was changed, specifically as follows: LiOH·H2O, Ni(OH)2, Co(OH)2, Mn(OH)2, and NaOH were mixed evenly in a molar ratio of 1.5:0.925:0.005:0.07:0.5 (the total weight of Li, Ni, Co, and Mn was 0.67a). Then Al(OH)3, Y2O3, and ZrO2 were added, wherein the weight of Al(OH)3 was 0.43%a, the weight of Y2O3 was 0.4%a, and the weight of ZrO2 was... The amount of 0.23% a was mixed and added to a crucible. The crucible was placed in a box-type muffle furnace (oxygen atmosphere, gas flow rate 20 ml / min), and heated to 450℃ at a heating rate of 5℃ / min and held for 12 h. After natural cooling to room temperature, it was crushed and then 0.18% a of H3BO3 and 0.32% a of Al2O3 were added. The mixture was heated to 350℃ and held for 5 h. After crushing and sieving, the first particles were obtained. The thickness t1 of the first coating layer was 2.2 nm, and the first coating layer included Al and B. The D1 was 4.4 μm and the Dv was... 1 50 is 4.5 μm, the first coating layer is distributed in an island-like pattern on the surface of the first particle, with a coverage of 5%-95%, d1 is 0.07, b1>0.8, C Y1It is 1500ppm, and BET1 is 0.7m. 2 / g, C Y1 / BET1 is 0.0021, C B1 The value is 300 ppm, the first particle is a single crystal particle, and t1 / d1 is 31.43.

[0185] Example 12 group

[0186] This set of examples is used to verify the impact of changes in the "weight content of silicon-based materials in the negative electrode active material layer".

[0187] This set of embodiments is based on Embodiment 1, except that the weight content of silicon-based material in the negative electrode active material layer is changed, as follows:

[0188] In Example 12a, the weight content of silicon-carbon in the negative electrode active material layer is 1%;

[0189] In Example 12b, the weight content of silicon-carbon in the negative electrode active material layer is 4%;

[0190] Example 12c: The weight content of silicon-carbon in the negative electrode active material layer is 25%;

[0191] In Example 12d, the weight content of silicon-carbon in the negative electrode active material layer was 40%.

[0192] Example 13 group

[0193] This set of examples is used to verify the impact of changes in the "residual alkali content C of the positive electrode active material".

[0194] This set of embodiments is based on Embodiment 1, except that the first particle and the second particle are changed, as follows:

[0195] Example 13a

[0196] (1) Preparation of the first particle

[0197] LiOH·H₂O, Ni(OH)₂, Co(OH)₂, Mn(OH)₂, and NaOH were mixed evenly in a molar ratio of 1.5:0.86:0.09:0.05:0.5 (the total weight of Li, Ni, Co, and Mn was 0.67a). Then, Al(OH)₃, Y₂O₃, and ZrO₂ were added, with Al(OH)₃ accounting for 0.43%a, Y₂O₃ for 0.27%a, and ZrO₂ for 0.23%a. After mixing evenly, the mixture was added... The crucible was placed in a box-type muffle furnace (oxygen atmosphere, gas flow rate 20 ml / min), heated to 450℃ at a heating rate of 5℃ / min, and held at that temperature for 12 h. After natural cooling to room temperature, it was crushed, and then 0.54% a H3BO3 and 0.32% a Al2O3 were added. The mixture was heated to 350℃ and held for 5 h. After crushing and sieving, the first particles were obtained, wherein the thickness t1 of the first coating layer was 4.3 nm, the first coating layer consisted of Al and B, D1 was 2.5 μm, and Dv... 1 50 is 2.5 μm, the first coating layer is distributed in an island-like pattern on the surface of the first particle, with a coverage of 5%-95%, d1 is 0.05, b1>0.8, C Y1 It is 1000ppm, and BET1 is 1m. 2 / g, C Y1 / BET1 is 0.001, C B1 The value is 900 ppm, the first particle is a single crystal particle, and the t1 / d1 is 86.

[0198] (2) Preparation of positive electrode sheet

[0199] The positive electrode active material (first particle and second particle) is mixed at a weight ratio of 80:20, wherein the second particle is commercially available and is a polycrystalline particle, the thickness t2 of the second coating layer is 5.3 nm, the second coating layer includes elements Al and B, D2 is 300 nm, D3 is 10 μm, and Dv is... 2 50 is 10.1 μm, and BET2 is 0.6 μm. 2 / g, based on the total molar number of elements Ni, Co and Mn in the second particle (with the molar number of element Ni being 0.83), polyvinylidene fluoride, single-walled carbon nanotubes and multi-walled carbon nanotubes were mixed evenly in a weight ratio of 97.4:1.2:0.4:1, and N-methylpyrrolidone (NMP) was added to obtain a positive electrode slurry (solid content of 65%); the positive electrode slurry was evenly coated onto aluminum foil (thickness of 10μm) using a coating machine, baked at 120℃ for 12h, and then rolled to obtain a positive electrode sheet;

[0200] Example 13b

[0201] (1) Preparation of the first particle

[0202] LiOH·H₂O, Ni(OH)₂, Co(OH)₂, Mn(OH)₂, and NaOH were mixed evenly in a molar ratio of 1.5:0.96:0.03:0.01:0.5 (the total weight of Li, Ni, Co, and Mn was 0.67a). Then, Al(OH)₃, Y₂O₃, and ZrO₂ were added, with Al(OH)₃ accounting for 0.43%a, Y₂O₃ for 0.13%a, and ZrO₂ for 0.23%a. After mixing evenly, the mixture was added... The crucible was placed in a box-type muffle furnace (oxygen atmosphere, gas flow rate 20 ml / min), heated to 450℃ at a heating rate of 5℃ / min, and held at that temperature for 12 h. After natural cooling to room temperature, it was crushed, and then 0.18% a H3BO3 and 0.32% a Al2O3 were added. The mixture was heated to 350℃ and held for 5 h. After crushing and sieving, the first particles were obtained, wherein the thickness t1 of the first coating layer was 2.1 nm, the first coating layer consisted of Al and B, D1 was 2.1 μm, and Dv... 1 50 is 2.3 μm, the first coating layer is distributed in an island-like pattern on the surface of the first particle, with a coverage of 5%-95%, d1 is 0.01, b1>0.8, C Y1 It is 500ppm, and BET1 is 1.4m. 2 / g, C Y1 / BET1 is 0.00036, C B1 The value is 300 ppm, the first particle is a single crystal particle, and t1 / d1 is 210.

[0203] (2) Preparation of positive electrode sheet

[0204] The positive electrode active material (first particle and second particle) is mixed at a weight ratio of 73:27, wherein the second particle is commercially available, is a polycrystalline particle, the thickness t2 of the second coating layer is 3 nm, the second coating layer includes elements Al and B, D2 is 100 nm, D3 is 7 μm, and Dv... 2 50 is 6.9μm, and BET2 is 0.85m. 2 / g, based on the total molar number of elements Ni, Co and Mn in the second particle (with the molar number of element Ni being 0.9), polyvinylidene fluoride, single-walled carbon nanotubes and multi-walled carbon nanotubes were mixed evenly in a weight ratio of 97.4:1.2:0.4:1, and N-methylpyrrolidone (NMP) was added to obtain a positive electrode slurry (solid content of 65%); the positive electrode slurry was evenly coated onto aluminum foil (thickness of 10μm) using a coating machine, baked at 120℃ for 12h, and then rolled to obtain a positive electrode sheet.

[0205] Example 14

[0206] This embodiment is used to verify the impact of changing the "total number of positive and negative electrode tabs".

[0207] This set of embodiments is based on Embodiment 1, except that the sum of the number of positive electrode tabs and the number of negative electrode tabs is 2.

[0208] Example 15

[0209] This embodiment is used to verify the impact of changes to the "shell".

[0210] The same procedure was followed as in Example 1, except that the housing was replaced with an aluminum housing.

[0211] In the above embodiments, the chemical formula of the first particle satisfies Li a1 Ni b1 Co c1 Mn d1 M 1 e1 O2, where 0.8≤a1≤1.3, 0.8≤b1≤0.98, 0.02≤c1≤0.2, 0.01≤d1≤0.14, 0≤e1≤0.08, M 1 It includes at least one of the elements Al, Zr, B, Y, Sr, W, Ti, and Nb. The chemical formula of the second particle satisfies Li a2 Ni b2 Co c2 Mn d2 M 2 e2 O2, where 0.9≤a²≤1.3, 0.8≤b²≤0.98, 0.02≤c²≤0.3, 0.01≤d²≤0.12, 0≤e²≤0.1, M 2 It includes at least one of the elements Al, Zr, B, Y, Sr, W, Ti, and Nb.

[0212] Comparative Example 1

[0213] The procedure was carried out in accordance with Example 1, except that the first particle from Example 1 was used as the positive electrode active material.

[0214] Comparative Example 2

[0215] The procedure was carried out in accordance with Example 1, except that the second particle from Example 1 was used as the positive electrode active material.

[0216] Comparative Example 3

[0217] The procedure was carried out in accordance with Example 3, except that the second particle was replaced with the same weight of the second particle from Example 2, and t1 / t2 was 2.1.

[0218] Test case

[0219] (1) Residual alkali content test

[0220] The batteries prepared in the examples were charged to 100% SOC at 4.3V and 0.5C. They were then disassembled in a drying room (H2O < 0.1ppm, O2 < 0.1ppm), and the positive electrode sheet was removed. The positive electrode sheet was then immersed in dimethyl carbonate (DMC) solution to remove the positive electrode active material layer. The positive electrode active material layer was rinsed with acetone, air-dried, and then sintered in a muffle furnace (temperature 200℃, time 4 hours). The sintered product was transferred to a beaker containing deionized water, a magnetic stir bar was added, and the mixture was stirred for 20 minutes. The mixture was then filtered, and the filtrate was collected and titrated with a standard acid solution. The residual alkali content was calculated, and the results are recorded in Table 1.

[0221] (2) Cyclic life test

[0222] The batteries prepared in the examples and comparative examples were placed in a constant temperature environment of 45°C and subjected to charge-discharge tests at a rate of 1.8C / 4.0C. The cutoff voltage range was 2.5V-4.3V, and 300 charge-discharge cycles were performed. The cycle discharge capacity was recorded and divided by the discharge capacity of the first cycle to obtain the 300-cycle capacity retention rate. The thickness data was also recorded every 100 cycles. The thickness data after the 300th cycle was divided by the initial thickness of the battery to obtain the 300-cycle thickness expansion rate. The results of the 300-cycle capacity retention rate and the 300-cycle thickness expansion rate are recorded in Table 1.

[0223] (3) Furnace temperature test

[0224] The batteries prepared in the examples and comparative examples were placed in an environment of 25°C and charged at a constant current rate of 0.5C to 4.3V, and then charged at a constant voltage rate to the cutoff current of 0.025C. After standing for 2 hours, the fully charged batteries were placed in a hot box and heated from room temperature to 130°C at a heating rate of 5°C / min. The temperature was then increased at a rate of 1°C / min, and the temperature was maintained for 30 minutes every 1°C. If the batteries did not explode or catch fire, the temperature was increased. If an explosion or fire occurred, the highest temperature of the battery before the explosion or fire was recorded.

[0225] (4) Ratio Test

[0226] The batteries prepared in the examples and comparative examples were placed at 25°C:

[0227] 1) Let it sit for 5 minutes;

[0228] 2) Discharge at 0.5C to 2.5V;

[0229] 3) Let it sit for 1 hour;

[0230] 4) 0.5C charging: When the battery terminal voltage reaches the charging limit voltage of 4.3V, switch to constant voltage charging until the charging current is ≤ the cutoff current, then stop charging.

[0231] 5) Let it sit for 30 minutes;

[0232] 6) Discharge to 2.5V at the specified rate and record the data such as capacity, internal resistance, and voltage during the process. The specific rates are as follows: 1C and 4C. Repeat steps 3)-6) until the test rate ends. In step 6), discharge according to the specified rate and sequence, and record the capacity retention rate in Table 1.

[0233] (5) Gram volume test

[0234] The positive electrode active material, conductive carbon black SP, and polyvinylidene fluoride used in the examples and comparative examples were mixed in a weight ratio of 94:3:3 and dispersed with NMP to form a slurry. This slurry was coated onto the surface of an aluminum foil sheet and dried at 80°C for 12 hours to obtain a positive electrode sheet. The dried positive electrode sheet was rolled and cut into round pieces and stored in a glove box for later use. Using the above positive electrode sheet as the positive electrode, lithium metal as the negative electrode, Celgard 2400 (microporous polypropylene membrane) as the separator, and 1 mol / L LiPF6 mixed with ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate in a weight ratio of 1:1:1 as the electrolyte, a 2032 type coin cell was assembled. The specific capacity of the obtained coin cell was tested, and the initial discharge specific capacity of the positive electrode active material was calculated by comparing the discharge capacity with the weight of the positive electrode active material, as detailed below:

[0235] 1. Let stand for 10 minutes;

[0236] 2. Constant current and constant voltage charging: Fully charge at 0.1C, cut-off current is 0.025C, cut-off voltage is 4.3V; 3. Let stand for 10 minutes;

[0237] 4. Constant current discharge: Discharge from 0.1C to 3.0V;

[0238] 5. Repeat steps 1-4 twice and record the results in Table 1.

[0239] Table 1

[0240]

[0241]

[0242] Note: " / " in Table 1 indicates no data.

[0243] As can be seen from Table 1, the battery prepared by the positive electrode active material of the present invention can effectively improve the gas generation problem compared with the comparative example, and can take into account both cycle performance and furnace temperature safety performance under the premise of similar specific capacity.

[0244] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A positive electrode active material, characterized in that, The positive electrode active material includes a first particle and a second particle, wherein the first particle includes a single crystal particle and the second particle includes a polycrystalline particle. The first particle comprises Li a1 Ni b1 Co c1 Mn d1 M 1 e1 For O2, 0.8 ≤ a1 ≤ 1.3, 0.8 ≤ b1 ≤ 0.98, 0.02 ≤ c1 ≤ 0.2, 0.01 ≤ d1 ≤ 0.14, 0 ≤ e1 ≤ 0.08, M 1 Includes at least one of the elements Al, Zr, B, Y, Sr, W, Ti, and Nb; The second particle comprises Li a2 Ni b2 Co c2 Mn d2 M 2 e2 For O2, 0.9 ≤ a² ≤ 1.3, 0.8 ≤ b² ≤ 0.98, 0.02 ≤ c² ≤ 0.3, 0.01 ≤ d² ≤ 0.12, 0 ≤ e² ≤ 0.1, M 2 Includes at least one of the elements Al, Zr, B, Y, Sr, W, Ti, and Nb; The first particle includes a first coating layer, which is located on the outer surface of the first particle. The second particle includes a second coating layer located on its outer surface; the thickness of the first coating layer is t1 (nm), and the thickness of the second coating layer is t2 (nm). It satisfies: t1 / t2≤1.

2. The positive electrode active material according to claim 1, wherein, 0.2≤t1 / t2≤0.85; preferably, 0.62≤t1 / t2≤0.83; And / or, t1 is 1-10, in nm; preferably 2-6.5, in nm; And / or, t2 is 2-15, in nm; preferably 3-8.5, in nm.

3. The positive electrode active material according to claim 1 or 2, wherein, The first coating layer includes at least one of the elements Al, Zr, B, Y, Sr, W, Ti, and Nb; preferably, the first coating layer includes at least one of the elements Al, W, Zr, and B. And / or, the second coating layer includes at least one of the elements Al, Zr, B, Y, Sr, Ti and Nb; preferably, the second coating layer does not contain the element W.

4. The positive electrode active material according to claim 1 or 2, wherein, The average particle size D1 of the first particle is 0.5μm-4.5μm, the average particle size D2 of the primary particles of the second particle is 100nm-900nm, and the average particle size D3 of the second particle is 6μm-18μm. Preferably, 0.05 ≤ D1 / D3 ≤ 0.5; More preferably, 0.15≤D1 / D3≤0.

3.

5. The positive electrode active material according to claim 1 or 2, wherein, The first particle is a layered structure material; preferably, the first particle is a single crystal particle. And / or, the second particle is a layered structure material; preferably, the second particle is a polycrystalline particle; And / or, based on the total weight of the positive electrode active material, the content C1 of the first particle is 70% ≤ C1 < 100%.

6. The positive electrode active material according to claim 1 or 2, wherein, The first coating layer is distributed in an island-like pattern on the surface of the first particle; And / or, the first coating layer has a coverage of 5%-95% on the surface of the first particle.

7. The positive electrode active material according to claim 1 or 2, wherein, t1 / d1 is 20-300; Preferably, t1 / d1 is 86-200.

8. The positive electrode active material according to claim 1 or 2, wherein, The first particle includes element Y, and the weight content of element Y in the first particle is C. Y1 The specific surface area of ​​the first particle is BET1, in m². 2 / g, C Y1 And BET1 satisfies 0≤C Y1 / BET1≤0.005; preferably, 0.0003≤C Y1 / BET1≤0.0025; And / or, C Y1 The concentration is 100ppm-1800ppm; preferably 500ppm-1500ppm. And / or, BET1 is 0.7 ≤ BET1 ≤ 1.6, in m. 2 / g.

9. A positive electrode plate, characterized in that, The positive electrode sheet comprises the positive electrode active material according to any one of claims 1-8.

10. The positive electrode according to claim 9, wherein, The first particle includes element B, and the weight content of element B in the first particle is C. B1 The residual alkali content of the positive electrode active material is C, C B1 And C satisfy 1≤C / C B1 ≤25; preferably, 2≤C / C B1 ≤16; And / or, C B1 The concentration is 200ppm-2000ppm; preferably 300ppm-1500ppm. And / or, C is 2000ppm-9000ppm.

11. The positive electrode according to claim 9 or 10, wherein, The first particle includes element Y, and the weight content of element Y in the first particle is C. Y1 The porosity of the positive electrode is m, C Y1 And m satisfy 0≤C Y1 / m≤0.01; preferably, 0.002≤C Y1 / m≤0.005; And / or, m is 20%-40%; preferably 24%-31%; And / or, the positive electrode sheet further includes a positive electrode conductive agent; preferably, the positive electrode conductive agent includes single-walled carbon nanotubes.

12. A battery, characterized in that, The battery comprises the positive electrode active material according to any one of claims 1-8 and / or the positive electrode sheet according to any one of claims 9-11.

13. The battery according to claim 12, wherein, The battery further includes a negative electrode sheet, which includes a negative electrode current collector and a negative electrode active material layer on at least one side surface of the negative electrode current collector, wherein the negative electrode active material layer includes a silicon-based material. Preferably, the silicon-based material has a weight content of 0.01%-50% in the negative electrode active material layer; Preferably, the silicon-based material includes at least one of elemental silicon, silicon oxide, silicon carbon, and silicon alloys.

14. The battery according to claim 13, wherein, The positive electrode plate includes a positive electrode tab, and the negative electrode plate includes a negative electrode tab; the positive electrode tab is electrically connected to the positive current collector of the positive electrode plate, and the negative electrode tab is electrically connected to the negative current collector; the total number of the positive electrode tab and the negative electrode tab is greater than or equal to 2. Preferably, the total number of the positive electrode tabs and the negative electrode tabs is greater than 2.

15. The battery according to any one of claims 12-14, wherein, The battery further includes a separator, which comprises a base film and a ceramic layer located on at least one surface of the base film; And / or, the membrane further includes a polymer layer located on at least one outer surface of the membrane; Preferably, the ceramic layer is disposed at least directly opposite the positive electrode sheet.

16. The battery according to any one of claims 12-14, wherein, The battery also includes a housing, which includes at least one of a flexible housing and a rigid housing; Preferably, the flexible shell comprises at least one of an aluminum-plastic film and a polymer film; Preferably, the rigid housing includes at least one of a steel housing, an aluminum housing, and an alloy housing.

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