Positive electrode active material, positive electrode sheet, electrochemical energy storage device, secondary battery, electric device, and manufacturing method

Abstract

The application discloses a positive electrode active material, which comprises A particles and B particles, wherein the A particles have a single crystal or single crystal-like structure, and the B particles are secondary particles comprising a plurality of primary particles, wherein the D v 50 of the A particles is less than the D v 50 of the B particles, the mass percentage of the A particles is greater than or equal to the mass percentage of the B particles, and the D v 50 represents the particle size corresponding to the cumulative volume distribution percentage of 50% of the material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy and the technical field of secondary batteries, further relates to a positive electrode active material, a positive electrode sheet, an electrochemical energy storage device, a secondary battery, a power utilization device and a preparation method. BACKGROUND

[0002] The statements herein are provided only to complement the background of the present application and are not necessarily prior art.

[0003] In recent years, the new energy industry has developed rapidly. However, the current new energy vehicles have the problems of low endurance and poor service life, which greatly limits the development of the new energy industry. Therefore, it is urgent to develop energy storage devices with high energy density and long service life.

[0004] High-nickel materials (such as high-nickel ternary materials, etc.) have the characteristics of high capacity and low cycle decay, and have attracted widespread attention in the industry. However, the current high-nickel materials have high watt-hour cost, which restricts their popularization and application. SUMMARY

[0005] In view of the above problems, the present application provides a positive electrode active material, a positive electrode sheet, an electrochemical energy storage device, a secondary battery, a power utilization device and a preparation method. The positive electrode active material is a high-nickel positive electrode material, which has small particles and large particles with a specific structure, and the content of small particles is higher than that of large particles. The prepared positive electrode sheet has high mass specific capacity and excellent structural stability. Further, in the cell level, the mass energy density and cycle life of the cell can be significantly improved, and the side reaction between the cell and the electrolyte can be reduced, and the gas production of the cell can be reduced.

[0006] In a first aspect, the present application provides a positive electrode active material, which comprises A particles and B particles, the molar ratio R of nickel element to lithium element in the A particles and the B particles is Ni / Li each independently ≥ 0.33; wherein the A particles have a single crystal or single crystal-like structure, and the B particles are secondary particles comprising a plurality of primary particles, wherein the D v 50 is less than the D v 50 of the B particles, and the mass percentage of the A particles is greater than or equal to the mass percentage of the B particles.

[0007] wherein D v N represents the particle size corresponding to the cumulative volume distribution percentage of N% of the material, and N is a value selected from 0-100.

[0008] For the positive electrode material, the traditional high-nickel material (such as high-nickel ternary material, etc.) is prone to material cracking during the cycle process, and the cracking degree is prone to deepen at high voltage, resulting in a decrease in cycle life, and during storage, due to the enhancement of positive electrode oxidation activity, it is easy to contact with electrolyte and cause severe chemical reaction to cause the decrease of battery life and the increase of unit capacity gas production. In the present application, the positive electrode active material includes high-nickel positive electrode materials of different particle sizes, wherein the D v 50 The small particles and the large particles are distinguished, the A particles with single crystal or single crystal-like structure are taken as the small particles, the B particles formed by the agglomeration of primary particles are taken as the large particles, and the mass content of the A particles is controlled to be higher than that of the B particles; the A particles with special crystal phase structure have a homogeneous system or a near-homogeneous system, and during the process of lithium extraction from the material, stress is not easy to occur in the material, so the material is not easy to crack under the stress, and thus it is more conducive to improve the cycle and storage performance of the battery under high voltage conditions; the B particles are formed by the agglomeration of primary particles, which is conducive to improving the power performance and the compaction density, by controlling the content between the A particles and the B particles and controlling the content of the B particles to be less than that of the A particles, the stress caused by the shrinkage and expansion of the large particle lattice can be reduced, so as to avoid the cracking of the positive electrode material under high voltage conditions, avoid the generation of new interfaces due to the cracking of the material, and further avoid the deterioration of the battery performance and the intensification of gas production caused by the side reaction between the new interfaces and the electrolyte, thereby enhancing the cycle stability under high voltage conditions and prolonging the service life of the battery. Further, the increase of the content of the small-size A particles is also conducive to improving the storage capacity retention rate of the battery and improving the storage calendar life of the material. In addition, the small-size A particles adopt a pure single crystal system, compared with a mixed system, the electrode sheet compaction and the battery power performance of the material will be significantly reduced, and the improvement of the compaction density of the electrode sheet can improve the volume specific capacity of the material, so that the battery has longer endurance in smaller volume.

[0009] In some embodiments of the present application, the particle size of the A particles satisfies 2 μm ≤ D v 50 < 5 μm, and the particle size of the B particles satisfies 5 μm < D v 50 ≤ 25 μm.

[0010] Optionally, the Span value of the A particles is greater than that of the B particles; wherein, Span = (D v 90 -D v 10) / D v 50.

[0011] Optionally, the Span value of the A particles is selected from 0.1 to 3.0; and the Span value of the B particles is selected from 0.1 to 3.0.

[0012] Optionally, the particle size of the B particles satisfies 8 μm < D v50 ≤ 20 μm.

[0013] By controlling the particle size of the A particles and the B particles in a more appropriate range, it is beneficial to better improve the high-voltage resistance of the positive electrode material, reduce the stress caused by large particles, and thus better avoid the cracking of the positive electrode material under high-voltage conditions, enhance the cycle stability under high-voltage conditions, avoid the intensification of gas production, prolong the service life of the battery cell, and further more, it is also more beneficial to improve the specific capacity and mass energy density of the positive electrode sheet. In addition, further defining the widening coefficient Span (Span = (D v 90 - D v 10) / D v 50) of the multi-particle system can represent the dispersion degree of the particle size. The larger the widening coefficient Span is, the wider the particle distribution of the material is in terms of distribution. By reasonably matching the particle size gradation and the widening coefficient combination of the large and small particles, the higher the compaction density of the material sheet is, and it is more beneficial to improve the volume specific capacity of the material, so that the battery cell has a longer endurance in a smaller volume.

[0014] In some embodiments of the present application, the B particles include B1 particles and B2 particles, wherein the particle size of the B1 particles satisfies 5 μm < D v 50 ≤ 10 μm, and the particle size of the B2 particles satisfies 10 μm < D v 50 ≤ 25 μm.

[0015] Optionally, the weight percentage of the B1 particles in the B particles is selected from 50% to 100%;

[0016] Optionally, the weight percentage of the B2 particles in the B particles is selected from 0% to 50%;

[0017] Optionally, the Span value of the A particles is selected from 0.1 to 2.0; the Span value of the B1 particles is selected from 0.1 to 2.0; and the Span value of the B2 particles is selected from 0.1 to 2.0; wherein, Span = (D v 90 - D v 10) / D v 50.

[0018] On the basis of distinguishing the small particles (A particles) from the large particles (B particles), the B particles are further distinguished into B1 particles and B2 particles, so that the D v 50 of the B1 particles is smaller than the D v50. In this way, the positive electrode active material can include particles of three size gradations, and the particle size of the larger particles can be controlled more precisely. Furthermore, by reasonably controlling the proportion of particles of different sizes and the broadening coefficient Span, while improving the compaction density, increasing the specific capacity and mass energy density of the positive electrode sheet, the power performance can also be better improved by reasonably controlling the content of intermediate-sized B1 particles. This can avoid excessive dense packing that affects the wettability of the electrolyte, and prevent the electrolyte from failing to contact the internal active material of the electrode sheet, thus avoiding concentration differences and adverse limitations on lithium-ion transport.

[0019] In some embodiments of this application, the B particles include B1' particles, B2' particles, and B3' particles, wherein the particle size of the B1' particles satisfies 8 μm < D. v 50 ≤ 12 μm, the particle size of the B2' particles satisfies 12 μm < D v 50 ≤ 15 μm, the particle size of the B3' particles satisfies 15 μm < D v 50 ≤ 20 μm;

[0020] Optionally, the weight percentage of the B1' particles in the B particles is selected from 40% to 80%;

[0021] Optionally, the weight percentage of the B2' particles in the B particles is selected from 20% to 30%;

[0022] Optionally, the weight percentage of the B3' particles in the B particles is selected from 0% to 30%;

[0023] Optionally, the span value of particle A is selected from 0.1 to 2.0, the span value of particle B1' is selected from 0.1 to 2.0, the span value of particle B2' is selected from 0.1 to 2.0, and the span value of particle B3' is selected from 0.1 to 2.0; wherein, Span = (D v 90-D v 10) / D v 50.

[0024] Based on the distinction between small particles (particle A) and large particles (particle B), particle B is further classified into D particles. vThe sequentially increasing B1', B2', and B3' particles (50 in total) make the positive electrode active material comprise four particle size gradations, allowing for more precise control over the particle size of larger particles. Furthermore, by rationally controlling the proportions of the four particles and the broadening factor Span, the power performance can be further improved by rationally controlling the content of intermediate-sized B1' and B2' particles. This avoids excessive packing that could affect the wettability of the electrolyte, prevents the electrolyte from failing to contact the internal active material of the electrode, thus avoiding concentration differences and adverse limitations on lithium-ion transport.

[0025] In some embodiments of this application, particle A and particle B each independently comprise the element combination Ni. x Co y M 1-x-y Where x ≥ 0.4, y ≥ 0, (1-xy) ≥ 0; the M element includes one or both of Mn and Al;

[0026] Optionally, 0.40 ≤ x ≤ 1.00, 0 ≤ y ≤ 0.15, (1-xy) ≥ 0;

[0027] Optionally, 0.50 ≤ x ≤ 1.00; Optionally, 0.60 ≤ x ≤ 1.00;

[0028] Optionally, y > 0; Optionally, 0 < y ≤ 0.15;

[0029] Optionally, (1-xy) > 0;

[0030] Optionally, y > 0, and (1-xy) > 0;

[0031] Optionally, particle A and particle B each independently comprise particles with the chemical formula Li. k-a Q a (Ni x Co y M 1-x-y ) 1- z N z O 2-c X cThe material contains the following properties: 0.9 ≤ k ≤ 1.1, 0 ≤ a ≤ 0.2, 0.60 ≤ x ≤ 1.00, 0 ≤ y ≤ 0.15, 0 ≤ (1-xy), 0 ≤ z ≤ 0.5, 0 ≤ c ≤ 1. The M element includes one or both of Mn and Al; the Q element includes one or more of Na, K, Rb, and Ca; the N element includes one or more of Al, Ti, Zr, Nb, Sr, Sb, Y, Ba, Co, Mn, Mg, W, Si, Mo, P, and C; and the X element includes one or more of B, F, S, and Cl.

[0032] Optionally, 0.92 ≤ k ≤ 1.08; Optionally, 0.95 ≤ k ≤ 1.05; Optionally, 0.96 ≤ k ≤ 1.04; Optionally, 0.98 ≤ k ≤ 1.02; Optionally, 0.99 ≤ k ≤ 1.01; Optionally, k=1;

[0033] Optionally, 0.50 ≤ x ≤ 1.00; Optionally, 0.60 ≤ x ≤ 1.00; Optionally, 0.70 ≤ x1 ≤ 1.00;

[0034] Optionally, where 0 ≤ a ≤ 0.2, 0.60 ≤ x < 1.00, 0 < y ≤ 0.15, 0 < (1-xy), 0 ≤ z ≤ 0.5, and 0 ≤ c ≤ 1.

[0035] In some embodiments of this application, the nickel-lithium molar ratio R in particle A and particle B is... Ni / Li Each independently ≥ 0.4;

[0036] Optionally, the nickel-lithium molar ratio R in particle A and particle B is... Ni / Li Each independently ≥ 0.5;

[0037] Optionally, the nickel-lithium molar ratio R in particle A and particle B is... Ni / Li Each independently ≥ 0.6;

[0038] Optionally, the nickel-lithium molar ratio R in particle A and particle B is... Ni / Li Each independently ≥ 0.7;

[0039] Optionally, the nickel-lithium molar ratio R in particle A and particle B is... Ni / Li Each independently ≥ 0.8;

[0040] Optionally, the nickel-lithium molar ratio R in particle A Ni / Li Selected from 0.7 to 1.0;

[0041] Optionally, the nickel-lithium molar ratio R in the B particles Ni / Li Selected from 0.8 to 1.0;

[0042] Optionally, the nickel-lithium molar ratio R in the B particles Ni / Li Selected from 0.8 to 0.96.

[0043] In traditional nickel-rich cathode materials (such as nickel-rich ternary cathode materials), the cell parameters change during cycling due to lithium insertion / extraction. This change in cell parameters generates internal stress, which accumulates with each charge-discharge cycle, leading to structural phase transitions and particle cracking, significantly disrupting the material's reversible cycling performance. In high-voltage systems, the degree of lithium insertion / extraction in nickel-rich materials (such as nickel-rich ternary materials) intensifies further. In this application, the cathode active material can be a traditional nickel-rich ternary cathode material. Furthermore, introducing nitrogen doping into the ternary cathode active material can reduce the degree of lattice change, stabilizing the lattice and improving the cycling performance of the nickel-rich ternary material. Additionally, it helps prevent the new interfaces formed by cracking from accelerating side reactions with the electrolyte, thus improving cell gas generation.

[0044] In some embodiments of this application, the true density of particle A and particle B is each independently greater than 4.0 g / cc;

[0045] Optionally, the true density of particle A and particle B are each independently selected from 4.0 g / cc to 4.8 g / cc;

[0046] Optionally, the true density of each of the A particles is independently selected from 4.6 g / cc to 4.8 g / cc;

[0047] Optionally, the true density of each of the B particles is independently selected from 4.5 g / cc to 4.8 g / cc.

[0048] In this application, true density is one of the main factors determining the compaction density of the cathode material. By reasonably controlling the true density of particles A and B, it is beneficial to improve the volumetric specific capacity and energy density of the cathode sheet, thereby improving the material cracking problem under high voltage and better improving the cell performance. For the multi-particle system with gradation in this application, the more tightly packed the particles are, the higher the theoretically achievable volumetric specific capacity of the cathode material.

[0049] In some embodiments of this application, particle A and particle B each independently include a body structure and an oxide layer covering at least a portion of the surface of the body structure;

[0050] in,

[0051] The bulk structure includes a chemical formula of Li k1-a1 Q a1 (Ni x1 Co y1 M 1-x1-y1 ) 1-z1 N z1 The material of O2 has the following properties: 0.9 ≤ k1 ≤ 1.1, 0 ≤ a1 ≤ 0.20, 0.40 ≤ x1 ≤ 1.00, 0 ≤ y1 ≤ 0.15, 0 ≤ (1-x1-y1), 0 ≤ z1 ≤ 0.5, and the Q element includes one or more of Na, K, Rb and Ca, the M element includes one or two of Mn and Al, and the N element includes one or more of Al, Ti, Zr, Nb, Sr, Sb, Y, Ba, Co, Mn, Mg, Si, P, Mo, C and W.

[0052] Optionally, 0.92 ≤ k1 ≤ 1.08; Optionally, 0.95 ≤ k1 ≤ 1.05; Optionally, 0.96 ≤ k1 ≤ 1.04; Optionally, 0.98 ≤ k1 ≤ 1.02; Optionally, 0.99 ≤ k1 ≤ 1.01; Optionally, k1 equals 1.

[0053] Optionally, 0.50 ≤ x1 ≤ 1.00; Optionally, 0.60 ≤ x1 ≤ 1.00; Optionally, 0.9 ≤ k2 ≤ 1.1, 0.70 ≤ x1 ≤ 1.00;

[0054] Optionally, the nitrogen element includes one or more of Al, Ti, Zr, Nb, Sr, Sb, Y, Mg, and W;

[0055] Optionally, 0 ≤ a1 ≤ 0.20, 0.60 ≤ x1 < 1.00, 0 < y1 ≤ 0.15, 0 < (1-x1-y1), 0 ≤ z1 ≤ 0.5;

[0056] The oxide layer comprises Li k2-a2 Q' a2 (Ni) x2 Co y2 M' 1-x2-y2 ) 1-z2 N' z2 O 2-c2 X c2The material has the following properties: 0 ≤ a2 ≤ 0.20, 0.40 ≤ x2 ≤ 1.00, 0 ≤ y2 ≤ 0.15, 0 ≤ (1-x2-y2), 0 < z2 ≤ 0.5, 0 ≤ c2 ≤ 1, and the Q' element includes one or more of Na, K, Rb and Ca, the M' element includes one or two of Mn and Al, the N' element includes one or more of Al, Ti, Zr, Nb, Sr, Sb, Y, Ba, Co, Mn, Mg, W, Mo, Si, C and P, and the X element includes one or more of B, Cl, S and F.

[0057] Optionally, 0.92 ≤ k2 ≤ 1.08; Optionally, 0.95 ≤ k2 ≤ 1.05; Optionally, 0.96 ≤ k2 ≤ 1.04; Optionally, 0.98 ≤ k2 ≤ 1.02; Optionally, 0.99 ≤ k2 ≤ 1.01; Optionally, k2 equals 1.

[0058] Optionally, 0.50 ≤ x2 ≤ 1.00; Optionally, 0.60 ≤ x2 ≤ 1.00; Optionally, 0.70 ≤ x2 ≤ 1.00;

[0059] Alternatively, Q' a2 Ni x2 Co y2 M' 1-x-y With Q a1 Ni x1 Co y1 M 1-x1-y1 same;

[0060] Optionally, the N' element includes one or more of Al, Ti, Zr, Sr, Sb, Mo, Nb, Mg, Y, and W;

[0061] Alternatively, 0 ≤ a2 ≤ 0.20, 0.60 ≤ x2 < 1.00, 0 < y2 ≤ 0.15, 0 < (1-x2-y2), 0 < z2 ≤ 0.5, 0 ≤ c2 ≤ 1.

[0062] In this application, Q' elements (such as Na, K, Rb, Ca, etc.) can be doped into the bulk structure of the positive electrode active material to improve the lithium-ion diffusion coefficient and reduce lithium-nickel mixing. Alternatively, the surface of the positive electrode active material can be coated to form an oxide layer doped with specific N' elements. This reduces the surface reactivity of the material with the electrolyte, decreases oxygen release, improves the structural stability of the active material, increases ionic conductivity, and enhances the material's capacity. For example, by doping the oxide layer with elements such as Zr, Al, Mg, W, Mo, Co, Sr, Sb, and Nb, Mg, Ti, Al, and Mo can reduce lattice deformation during charge-discharge cycles, thereby improving the material's structural stability. Similarly, doping the oxide layer with elements such as B, F, and Cl can improve capacity and rate performance. Furthermore, by combining particle size design with structural design, the material can achieve a higher specific capacity while simultaneously reducing side reactions and phase transitions between the positive electrode material and the electrolyte, resulting in lower watt-hour costs and longer cycle life. Compared to the coated structure design, the uncoated material interface may undergo a large number of side reactions with the electrolyte, leading to the oxidation of the electrolyte and the generation of gases such as carbon dioxide and oxygen. Moreover, without a coating, the layered structure on the surface of the positive electrode active material is more likely to transform into a rock salt structure, causing the material surface to lose its chemical reactivity.

[0063] In some embodiments of this application, the thickness of the oxide layer is 0 ~ 100 nm;

[0064] Optionally, the thickness of the oxide layer is 1 nm to 100 nm;

[0065] Optionally, the thickness of the oxide layer is 1 nm to 20 nm.

[0066] In some embodiments of this application, the oxide layer has a mass percentage of 0.01% to 5% relative to the bulk structure;

[0067] Optionally, the oxide layer has a mass percentage of 0.05% to 4% relative to the bulk structure.

[0068] In some embodiments of this application, the nitrogen element in the oxide layer accounts for 0.01% to 4% of the mass of the positive electrode active material;

[0069] Optionally, the N element in the oxide layer accounts for 0.05% to 4% of the mass of the positive electrode active material.

[0070] By rationally controlling the amount of surface oxide layer, such as the thickness of the oxide layer, the mass percentage of the oxide layer, and the amount of nitrogen doping, the aforementioned doping and coating objectives can be better achieved. This allows for better regulation of the chemical reactivity and structural stability of the material, better integration of particle size design with structural design, and also imparts higher specific capacity to the material. It also reduces the degree of side reactions and phase transitions between the cathode material and the electrolyte, resulting in lower watt-hour costs and higher cycle life for the battery.

[0071] In some embodiments of this application, the average specific surface area of ​​the positive electrode active material is 0.3 cm². 2 / g~ 1.5 cm 2 / g.

[0072] By rationally controlling the overall specific surface area of ​​the positive electrode active material, it is more conducive to increasing the energy density as much as possible while increasing the compaction density of the positive electrode material.

[0073] In some embodiments of this application, the free lithium content in the positive electrode active material is less than 3000 ppm by mass.

[0074] In this application, the content of free lithium (such as lithium carbonate, lithium hydroxide, etc.) in the positive electrode active material can be reasonably controlled to avoid excessive gas generation during cycling under high voltage conditions. If the free lithium content is too high, it will undergo an acid-base neutralization reaction with hydrofluoric acid produced by electrolyte decomposition during cycling under high voltage conditions, generating a large amount of gas. This causes the cell to bulge and become enlarged, affecting the cell and potentially leading to cell safety accidents.

[0075] In some embodiments of this application, the ratio of I003 grain content to I104 grain content of the positive electrode active material, I003 / I104 ≥ 1.2, is calculated as the ratio of the characteristic peak areas of the I003 crystal plane to the I104 crystal plane in the XRD pattern.

[0076] Optionally, I003 / I104 are selected from 1.2 to 2;

[0077] Optionally, I003 / I104 are selected from 1.3 to 2;

[0078] Optionally, I003 / I104 are selected from 1.3 to 1.6.

[0079] By rationally controlling the ratio of I003 grain content to I104 grain content in the positive electrode active material (e.g., ≥1.2), the degree of lithium-nickel mixing can be better controlled, avoiding excessive nickel elements occupying lithium element lattice positions, which would lead to a decrease in reversible capacity and a decrease in the lithium ion diffusion coefficient.

[0080] In some embodiments of this application, at least a portion of the primary particles in the B particles are oriented radially.

[0081] For the secondary spherical particles of this application, the primary particles can be oriented in a certain direction along the radial direction, thereby suppressing the shrinkage and expansion that may occur under high voltage, avoiding the increase of internal stress, and thus better preventing the material from breaking under high voltage. In addition, it can also improve cycle performance. The higher the degree of radial orientation and the lower the degree of random non-orientation, the more obvious the improvement.

[0082] In a second aspect, this application provides a positive electrode sheet, which includes a positive current collector and a positive active material layer located on at least one surface of the positive current collector, the positive active material layer comprising the positive active material described in the first aspect of this application.

[0083] The positive electrode active material of the first aspect of this application can be used to prepare a positive electrode sheet with high nickel content. By designing the particle size and content of the positive electrode active material, cracking of the material under high voltage can be avoided, and the cycle and storage performance of the cell under high voltage conditions can be improved. Furthermore, the chemical reactivity and structural stability of the material can be adjusted by using doping and / or coating structure design, which can make the material have a higher specific capacity, while reducing the degree of side reactions and phase transitions between the positive electrode material and the electrolyte, so that the battery has a lower watt-hour cost and a higher cycle life.

[0084] In some embodiments of this application, the compaction density of the positive electrode sheet is 3.3 g / cm³. 3 ~ 3.7 g / cm 3 .

[0085] In this application, by controlling the compaction density of the positive electrode sheet to a suitable level, it is possible to better avoid material cracking under high voltage conditions while imparting better specific capacity and energy density to the electrode sheet. It should be understood that the compaction density of the positive electrode sheet is also limited by the true density of the A and B particles it contains. Increasing the compaction density of the electrode sheet can improve the volumetric specific capacity of the material, enabling the battery cell to have a longer operating range in a smaller volume.

[0086] Thirdly, this application provides an electrochemical energy storage device, which includes the positive electrode, the negative electrode, and the separator as described in the second aspect of this application, wherein the separator is disposed between the positive electrode and the negative electrode.

[0087] Fourthly, this application provides a secondary battery, which includes at least one of the positive electrode sheet described in the second aspect of this application and the electrochemical energy storage device described in the third aspect of this application.

[0088] Fifthly, this application provides an electrical device comprising at least one of the positive electrode sheet described in the second aspect of this application, the electrochemical energy storage device described in the third aspect of this application, and the secondary battery described in the fourth aspect of this application.

[0089] Using the positive electrode active material of the first aspect of this application to prepare a high-nickel content positive electrode sheet, and then to prepare an electrochemical energy storage device, a secondary battery, and an electrical device, the particle size and content of the positive electrode active material can be designed to avoid material cracking under high voltage, improve the cell cycle and storage performance under high voltage conditions, and further utilize doping and / or coating structure design to adjust the chemical reactivity and structural stability of the material, which can make the material have a higher specific capacity, while reducing the degree of side reactions and phase transitions between the positive electrode material and the electrolyte, so that the battery has a lower watt-hour cost and a higher cycle life.

[0090] In a sixth aspect, this application provides a method for preparing a positive electrode active material, comprising the following steps: mixing the A particles and the B particles according to a preset mass ratio to prepare the positive electrode active material; the A particles and B particles are as defined in the first aspect of this application;

[0091] The A particles are prepared using a method comprising the following steps: lithium hydroxide, nickel-cobalt M-body precursor material Ni x Co y M 1-x-y (OH)2 and optional Q additive and optional N additive are mixed and sintered once in the presence of oxygen and at temperature T1; optionally, at least one of X additive and N additive is added to the primary sintered product, mixed, and sintered again in the presence of oxygen.

[0092] The B particles are prepared using a method comprising the following steps: lithium hydroxide, nickel-cobalt M-body precursor material Ni x Co y M 1-x-y (OH)2 and optional Q additive and optional N additive are mixed and sintered once in the presence of oxygen and at temperature T2; optionally, at least one of X additive and N additive is added to the primary sintered product, mixed, and sintered a second time in the presence of oxygen.

[0093] Wherein, the Q additive, N additive, and X additive are respectively additives containing the Q element, additives containing the N element, and additives containing the X element;

[0094] Wherein, the elements x, y, M, Q, X and N are as defined in the first aspect of this application;

[0095] The temperature T1 is higher than the temperature T2;

[0096] Optionally, in the step of preparing the A particles, in the step of sintering under the presence of oxygen, the primary sintering temperature is 700 °C ~ 950 °C, optionally 750 °C ~ 900 °C, and the secondary sintering temperature is 300 °C ~ 600 °C, optionally 350 °C ~ 550 °C;

[0097] Optionally, in the step of preparing the B particles, during the sintering step in the presence of oxygen, the primary sintering temperature is 700 °C ~ 900 °C, optionally 750 °C ~ 850 °C, and the secondary sintering temperature is 300 °C ~ 600 °C, optionally 350 °C ~ 550 °C.

[0098] When the positive electrode active particles (particle A or particle B) provided in the first aspect of this application are coated with an oxide layer, a stepwise sintering method can be used. First, the precursor of the bulk structure is sintered in an oxidizing atmosphere at a relatively high temperature (e.g., 700 °C ~ 950 °C for particle A, and 700 °C ~ 900 °C for particle B) to form the bulk structure. Then, it is mixed with the coating layer additive and sintered in an oxidizing atmosphere at a relatively low temperature (e.g., 300 °C ~ 600 °C) to form the oxide layer, thereby preparing particles A or B with a coating layer. During the first sintering, at a higher sintering temperature, the particles inside the particles are more likely to connect. Therefore, at a relatively high first sintering temperature (T1), large-sized single crystal or near-single crystal particles (particle A) can be prepared by fully connecting the particles, while small-sized secondary particles (particle B) can be prepared at a relatively low first sintering temperature (T2). In this case, the fine particles in the secondary particles are not connected or only partially connected.

[0099] Details of one or more embodiments of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0100] To better describe and illustrate embodiments or examples of the applications disclosed herein, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the embodiments or examples currently described, or the best mode of conduct of these applications as currently understood. Furthermore, throughout the drawings, the same reference numerals denote the same parts. In the drawings:

[0101] Figure 1This is a schematic diagram of the structure of particle A and particle B in one embodiment of this application, wherein particle A has a single crystal or near-single crystal structure, and particle B is a secondary particle including multiple primary particles; in (a) neither particle A nor particle B has a coating layer, and in (b) both particle A and particle B have a coating layer.

[0102] Figure 2 This is a SEM image (1000x magnification) of particle A raw material in one embodiment of this application, with a scale bar of 20 μm.

[0103] Figure 3 This is a SEM image (10000x magnification) of particle A raw material in one embodiment of this application, with a scale bar of 2 μm.

[0104] Figure 4 This is a SEM image (1000x magnification) of particle B raw material in one embodiment of this application, with the scale bar at 20 μm.

[0105] Figure 5 This is a SEM image (10000x magnification) of particle B raw material in one embodiment of this application, with a scale bar of 2 μm.

[0106] Figure 6 This is a cross-sectional SEM image of particle B material in one embodiment of this application, with the scale bar in the image being 3 μm;

[0107] Figure 7 This is a schematic diagram of the structure of the positive electrode sheet in one embodiment of this application, wherein particle A has a D v 50 smaller than particle B in D v 50. The mass percentage of particle A is greater than or equal to the mass percentage of particle B.

[0108] Figure 8 This is a schematic diagram of the structure of a positive electrode sheet in one embodiment of this application, which includes particle A, particle B1, and particle B2, and particle D of particle A, particle B1, and particle B2. v The mass percentage of particle A is greater than or equal to the sum of the mass percentages of particles B1 and B2, with the mass percentages increasing sequentially from 50.

[0109] Figure 9 This is a schematic diagram of a secondary battery according to an embodiment of this application;

[0110] Figure 10 yes Figure 9 An exploded view of a secondary battery according to an embodiment of this application is shown;

[0111] Figure 11 This is a schematic diagram of an electrical device in which a secondary battery is used as a power source, according to an embodiment of this application.

[0112] Explanation of reference numerals in the attached figures:

[0113] 5. Secondary battery; 51. Housing; 52. Electrode assembly; 53. Cover plate; 6. Electrical device. Detailed Implementation

[0114] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode active material, positive electrode sheet, electrochemical energy storage device, secondary battery, power-consuming device, and preparation method of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0115] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0116] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0117] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0118] Unless otherwise specified, all steps in this 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 it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0119] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0120] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". Further, the condition "A or B" is satisfied by any of the following conditions: 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).

[0121] In this application, the terms "multiple", "various", "multiple times", etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more than or equal to two.

[0122] The terms “combinations of,” “any combination of,” and “any combination of” used in this article include all suitable combinations of any two or more of the listed items.

[0123] In this document, the term "suitable" as used in "suitable combination", "suitable method", "any suitable method", etc., refers to the technical solution that enables the implementation of this application.

[0124] In this document, terms such as "preferred," "better," "more suitable," and "ideal" are merely descriptions of more effective implementation methods or embodiments, and should be understood not to limit the scope of protection of this application. If multiple "preferred" terms appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "preferred" term shall be independent.

[0125] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0126] In this application, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0127] In this application, the term "room temperature" generally refers to 4 °C to 35 °C, and preferably 20 °C ± 5 °C. In some embodiments of this application, room temperature refers to 20 °C to 30 °C.

[0128] In this application, if the unit of a data range is only followed by the right endpoint, it indicates that the units of the left and right endpoints are the same. For example, 3~5 h or 3-5 h both indicate that the units of the left endpoint "3" and the right endpoint "5" are both h (hours).

[0129] The mass or weight of the relevant components mentioned in the embodiments of this application can refer not only to the content of each component, but also to the proportional relationship of mass or weight between the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Furthermore, the mass or weight mentioned in the embodiments of this application can be a mass or weight unit known in the chemical industry, such as μg, mg, g, kg.

[0130] The new energy industry has developed rapidly in recent years. However, current new energy vehicles suffer from low range and short lifespan, which greatly limits the development of the new energy industry. Therefore, the development of energy storage devices with high energy density and long service life is urgently needed.

[0131] For cathode materials, high-nickel materials (such as high-nickel ternary materials) have attracted widespread attention in the industry due to their high capacity and low cycle decay. However, the high watt-hour cost of high-nickel materials currently restricts their widespread application. One effective means to reduce the watt-hour cost of materials is to improve their mass energy density. Currently, the common methods to improve the mass energy density of high-nickel materials (such as high-nickel ternary materials) mainly include increasing the charge and discharge voltage and increasing the nickel content in the cathode material. Due to the extremely high price of cathode raw materials, increasing the charge and discharge voltage of the material has become the most attractive way to improve the mass energy density. However, for traditional high-nickel materials (such as high-nickel ternary materials), increasing the voltage will cause the material to crack more deeply during cycling, reducing cycle life. At the same time, during storage, due to the increased oxidation activity of the cathode, it is easy to have violent chemical reactions with the electrolyte, resulting in a decrease in cell life and an increase in gas production per unit capacity. All of these factors combined lead to the instability of high-nickel materials under high voltage conditions, thus creating application obstacles to improving mass energy density by increasing the charge and discharge voltage. According to the applicant's research, no relevant reports have been found.

[0132] Based on extensive experimental research, the inventors of this application discovered that when traditional nickel-rich materials (such as nickel-rich ternary cathode materials) are subjected to charge-discharge cycles under high voltage conditions (e.g., without referring to 4.3V or higher), the cell performance exhibits a rapid decline in capacity retention with increasing cycle count, coupled with excessively high DC resistance. In cell calendar life tests, storage capacity decays and gas production deteriorates. The inventors speculate that this is likely due to the lithium-ion insertion and extraction during cycling of nickel-rich cathode materials (such as nickel-rich ternary cathode materials), causing lattice contraction and expansion. This contraction and expansion are particularly pronounced under high voltage conditions, increasing the material's susceptibility to cracking. The resulting fresh interface cathode reacts with the electrolyte, leading to deterioration in cell performance. Furthermore, under high voltage conditions, the cathode's oxidizing power is stronger, easily oxidizing organic solvents in the electrolyte to generate gases such as carbon dioxide and oxygen, resulting in increased gas production within the cell.

[0133] In the context of this application, unless otherwise specified, a high voltage condition refers to a voltage ≥ 4.3V.

[0134] Based on this, in a first aspect, this application provides a positive electrode active material, which includes particles A and B, wherein the molar ratio of nickel to lithium in particles A and particles B (which can be denoted as the nickel-lithium molar ratio R) is... Ni / Li Each of the following is independently ≥ 0.33; wherein, particle A has a single crystal or near-single crystal structure, and particle B is a secondary particle comprising multiple primary particles, wherein the D of particle A is... v 50 is smaller than the D of the B particles v 50, the mass percentage of particle A is greater than or equal to the mass percentage of particle B;

[0135] Among them, D v N represents the particle size corresponding to the cumulative volume distribution percentage of the material reaching N%, where N is a value selected from 0 to 100.

[0136] The structures of particles A and B in the aforementioned positive electrode active material can be found in [reference needed]. Figure 1 (a).

[0137] In the application, "nickel-rich" and "high-nickel" have the same meaning and can be used interchangeably, referring to a higher proportion of nickel in the cathode active material. Taking NCM811 ternary cathode material as an example, the molar ratio of nickel, cobalt, and manganese is 80:10:10. Increasing the nickel content in the cathode active material is beneficial to improving energy density and thus battery capacity.

[0138] In this application, for positive electrode active materials, positive electrode materials, and positive electrode sheets, the nickel content can be characterized by the molar ratio of nickel to lithium. This molar ratio can be called the nickel-lithium molar ratio and can be denoted as R. Ni / Li In this application, R Ni / Li Each occurrence can independently be greater than or equal to 0.33, further can independently be greater than or equal to 0.4, even further can independently be greater than or equal to 0.5, even further can independently be greater than or equal to 0.6, even further can independently be greater than or equal to 0.7, and even further can independently be greater than or equal to 0.8. In some embodiments of this application, the nickel-lithium molar ratio R... Ni / Li It can also be selected from any one of the following values ​​or a range consisting of any two of the following values: 0.33, 1 / 3, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.02, 0.05, 0.9, 0.95, 1, etc. In some embodiments of this application, the nickel-lithium molar ratio R... Ni / Li It can also be selected from any of the following numerical ranges (any numerical endpoint here may be included or excluded independently): 0.4~1, 0.5~1, 0.6~1, 0.7~1, 0.8~1, 0.8~0.96, etc.

[0139] In the context of this application, the volumetric cumulative distribution particle size D can be used. v N (where N represents any value selected from 0 to 100) is used to characterize the particle size of the material, referring to the particle size corresponding to the cumulative volume distribution percentage of the material reaching N%, and the particle size is less than or equal to D. v N's volume percentage is N%. D v N can be obtained from the volumetric cumulative distribution curve of the material particles. Unless otherwise specified, the volumetric cumulative distribution curve is accumulated from zero on the smaller particle size side. Let D... v 99. D v90. D v 50. D v For example, D in 10 v 99 refers to the particle size corresponding to a cumulative volume distribution percentage of 99% for a material; D v 90 refers to the particle size corresponding to a cumulative volumetric distribution percentage of 90% for a material; D v 50 refers to the particle size corresponding to a cumulative volumetric distribution percentage of 50% for the material; D v 10 refers to the particle size corresponding to a cumulative volumetric distribution percentage of 10% for the material. (The last part, "D," appears to be a typo and can be left as is.) v For example, 50 means that the particle size of 50% of the material volume is less than or equal to D. v 50, and particles accounting for 50% of the material volume have a particle size greater than D. v 50. With D v For example, 90 indicates that 90% of the material's volume consists of particles with a diameter less than or equal to D. v 90, and particles accounting for 10% of the material volume have a particle size greater than D. v 90. With D v For example, 10 indicates that particles accounting for 10% of the material volume have a particle size less than or equal to D. v 10, and the particle size of particles accounting for 90% of the material volume is greater than D. v 10. Those skilled in the art will understand D v 99. D v 90. D v 50. D v The meaning of 10 can be determined using instruments and methods known in the field. For example, it can be conveniently determined using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer or the LS-909 laser particle size analyzer from Malvern Instruments Ltd., UK, by referring to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method.

[0140] In this application, "quasi-single crystal" generally refers to a primary particle size greater than 1 μm, but with some agglomeration of the primary particles; "single crystal" generally refers to a primary particle size greater than 1 μm, without obvious agglomeration.

[0141] In this application, "primary particle" and "secondary particle" are terms well known in the art. "Primary particle" refers to a single crystal grain. "Secondary particle" refers to an aggregated particle composed of two or more primary particles. Primary and secondary particles can be easily distinguished by taking SEM images using a scanning electron microscope.

[0142] Traditional high-nickel materials (such as high-nickel ternary materials) are prone to cracking during cycling, and the cracking is exacerbated under high voltage, leading to a decrease in cycle life. Furthermore, during storage, the increased oxidation activity of the positive electrode makes it susceptible to violent chemical reactions with the electrolyte, resulting in a decrease in cell life and an increase in gas production per unit capacity. In this application, the positive electrode active material includes high-nickel positive electrode materials with different particle sizes, wherein, through D... v 50. A distinction is made between small and large particles. Small particles are A-particles with single-crystal or near-single-crystal structures, while large particles are B-particles formed from primary particle agglomeration. The mass content of A-particles is controlled to be higher than that of B-particles. A-particles with a special crystal phase structure have a homogeneous or near-homogeneous bulk phase. During lithium insertion / extraction, the material is less prone to internal stress, thus reducing the likelihood of cracking under stress and improving cell cycle and storage performance under high voltage conditions. B-particles, formed from primary particle agglomeration, improve power performance and compaction density. By controlling the content of A and B particles, ensuring that the content of B particles is less than that of A particles, the stress caused by the contraction and expansion of the large particle lattice is reduced. This prevents the cathode material from cracking under high voltage conditions, avoids the formation of new interfaces due to material breakage, and prevents side reactions between the new interfaces and the electrolyte that could lead to deterioration of cell performance and increased gas production. This enhances cycle stability under high voltage conditions and extends cell lifespan. Furthermore, increasing the content of small-sized A-particles also helps improve the cell's storage capacity retention rate and extends the material's storage calendar life. In addition, the small-sized A particles adopt a pure single crystal system. Compared with the mixed system, the electrode compaction and cell power performance of the material will be significantly reduced. However, the increase in electrode compaction density can improve the volumetric capacity of the material, so that the cell can have a longer range in a smaller volume.

[0143] In some embodiments, the particle size of particle A satisfies 2 μm ≤ D v 50 ≤ 5 μm, the D of particle A v 50 can also be selected from any of the following particle sizes or any two of the following ranges: 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc.

[0144] In some embodiments, the particle size of the B particles satisfies 5 μm < D. v 50 ≤ 25 μm, the D of the B particles v50 can also be selected from any of the following particle sizes or any two intervals: 5.1 μm, 5.2 μm, 5.3 μm, 5.4 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm, 19 μm, 19.5 μm, 20 μm, 20.5 μm, 21 μm, 21.5 μm, 22 μm, 22.5 μm, 23 μm, 23.5 μm, 24 μm, 24.5 μm, 25 μm, etc.

[0145] In some embodiments, the particle size of particle A satisfies 2 μm ≤ D v 50 ≤ 5 μm, the particle size of B particles satisfies 5 μm < D v 50 ≤ 25 μm.

[0146] In this application, the broadening factor Span = (D) for multi-particle material systems is also defined. v 90 - D v 10) / D v 50. The broadening factor Span can represent the degree of dispersion of particle size. The larger the broadening factor Span, the wider the particle distribution of the material.

[0147] In some implementations, the Span value of particle A is greater than the Span value of particle B.

[0148] In some embodiments, the Span value of particle A is selected from 0.1 to 3.0, and more particularly from 0.1 to 2.0. Non-limiting examples include 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, and 0.95. 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, etc.

[0149] The Span value of the B particles is selected from 0.1 to 3.0, further selected from 0.1 to 2.0, and even further selected from 1.1 to 2.0. Non-limiting examples include 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, etc. 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2, etc.

[0150] In some embodiments, the Span value of particle A is selected from 0.1 to 2.0; the Span value of particle B is selected from 0.1 to 2.0.

[0151] In some embodiments, the particle size of the B particles satisfies 8 μm < D. v 50 ≤ 20 μm.

[0152] By controlling the particle sizes of particles A and B within a suitable range, it is beneficial to improve the high-voltage withstand capability of the cathode material, reduce the stress caused by large particles, and thus better prevent the cathode material from cracking under high voltage conditions. This enhances the cycle stability under high voltage conditions, avoids excessive gas generation, extends the lifespan of the battery cell, and further improves the specific capacity and gravimetric energy density of the cathode electrode. By rationally combining the particle size distribution and broadening coefficient of different particle sizes, the compaction density of the electrode can be increased, which is more conducive to improving the volumetric specific capacity of the material, allowing the battery cell to have a longer range in a smaller volume.

[0153] In some embodiments, the B particles include B1 particles and B2 particles, and the D of the B1 particles... v 50 is smaller than the D of the B2 particles v 50.

[0154] Furthermore, in some embodiments, the particle size of the B1 particles satisfies 5 μm < D. v 50 ≤ 10 μm, the particle size of the B2 particles satisfies 10 μm < D v 50 ≤ 25 μm.

[0155] In some embodiments, the particle size of the B1 particles satisfies 5 μm < D. v 50 ≤ 10 μm, the D of the B1 particles v50 can also be selected from any of the following particle sizes or any two of the following ranges: 5.1 μm, 5.2 μm, 5.3 μm, 5.4 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, etc.

[0156] In some embodiments, the particle size of the B2 particles satisfies 10 μm < D. v 50 ≤ 25 μm, the D of the B2 particles v 50 can also be selected from any of the following particle sizes or any two of the following ranges: 10.1 μm, 10.2 μm, 10.3 μm, 10.4 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm, 19 μm, 19.5 μm, 20 μm, 20.5 μm, 21 μm, 21.5 μm, 22 μm, 22.5 μm, 23 μm, 23.5 μm, 24 μm, 24.5 μm, 25 μm, etc.

[0157] In some embodiments, the weight percentage of the B1 particles in the B particles can be selected from 50% to 100%, or can be selected from any one of the following percentages or a range of any two percentages: 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, etc.

[0158] In some embodiments, the weight percentage of the B2 particles in the B particles can be selected from 0% to 50%, or can be selected from any one percentage or a range of any two percentages: 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.

[0159] In some embodiments, the Span value of particle A can be selected from 0.1 to 2.0, and non-limiting examples include 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0, etc.

[0160] In some embodiments, the Span value of the B1 particles can be selected from 0.1 to 2.0, with non-limiting examples such as 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0, etc.

[0161] In some embodiments, the Span value of the B2 particles can be selected from 0.1 to 2.0, with non-limiting examples such as 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0, etc.

[0162] In some embodiments, the Span value of particle A is selected from 0.1 to 2.0; the Span value of particle B1 is selected from 0.1 to 2.0; the Span value of particle B2 is selected from 0.1 to 2.0; wherein, the definition of Span is consistent with the foregoing, Span = (D v 90-D v 10) / D v 50.

[0163] Based on the distinction between small particles (particle A) and large particles (particle B), particle B is further divided into particles B1 and particles B2, making particle D of particle B1... v 50 smaller than B2 particles D v 50. In this way, the positive electrode active material can include particles of three size gradations, and the particle size of the larger particles can be controlled more precisely. Furthermore, by reasonably controlling the proportion of particles of different sizes and the broadening coefficient Span, while improving the compaction density, increasing the specific capacity and mass energy density of the positive electrode sheet, the power performance can also be better improved by reasonably controlling the content of intermediate-sized B1 particles. This can avoid excessive dense packing that affects the wettability of the electrolyte, and prevent the electrolyte from failing to contact the internal active material of the electrode sheet, thus avoiding concentration differences and adverse limitations on lithium-ion transport.

[0164] In some embodiments, the B particles include B1' particles, B2' particles, and B3' particles, and the B1' particles, the B2' particles, and the B3' particles D v The numbers increase sequentially from 50.

[0165] Furthermore, in some embodiments, the particle size of the B1' particles satisfies 8 μm < D. v 50 ≤ 12 μm, the particle size of the B2' particles satisfies 12 μm < D v 50 ≤ 15 μm, the particle size of the B3' particles satisfies 15 μm < D v 50 ≤ 20 μm.

[0166] In some embodiments, the particle size of the B1' particles satisfies 8 μm < D. v 50 ≤ 12 μm, the D of the B1 particles v 50 can also be selected from any of the following particle sizes or any two of the following ranges: 8.1 μm, 8.2 μm, 8.3 μm, 8.4 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, etc.

[0167] In some embodiments, the particle size of the B2' particles satisfies 12 μm < D. v 50 ≤ 15 μm, the D of the B2 particles v 50 can also be selected from any of the following particle sizes or any two of the following ranges: 12.1 μm, 12.2 μm, 12.3 μm, 12.4 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, etc.

[0168] In some embodiments, the particle size of the B3' particles satisfies 15 μm < D. v 50 ≤ 20 μm, the D of the B2 particles v 50 can also be selected from any of the following particle sizes or any two of the following ranges: 15.1 μm, 15.2 μm, 15.3 μm, 15.4 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm, 19 μm, 19.5 μm, 20 μm, etc.

[0169] In some embodiments, the weight percentage of the B1' particles in the B particles is selected from 40% to 80%, and may also be selected from any one of the following percentages or a range of any two percentages: 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc.

[0170] In some embodiments, the weight percentage of the B2' particles in the B particles is selected from 20% to 30%, and may also be selected from any one of the following percentages or a range of any two percentages: 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 8%, 9%, 30%, etc.

[0171] In some embodiments, the weight percentage of the B3' particles in the B particles is selected from 0% to 30%, and may also be selected from any one percentage or any two percentage ranges: 2%, 4%, 5%, 6%, 8%, 10%, 12%, 15%, 16%, 18%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 8%, 9%, 30%, etc.

[0172] In some embodiments, the Span value of particle A can be selected from 0.1 to 2.0, and non-limiting examples include 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0, etc.

[0173] In some embodiments, the Span value of the B1' particles can be selected from 0.1 to 2.0, with non-limiting examples such as 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0, etc.

[0174] In some embodiments, the Span value of the B2' particles can be selected from 0.1 to 2.0, with non-limiting examples such as 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0, etc.

[0175] In some embodiments, the span value of the B3' particles can be selected from 0.1 to 2.0, and more specifically from 0.1 to 1.4. Non-limiting examples include 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0, etc.

[0176] In some embodiments, the span value of particle A is selected from 0.1 to 1.5, the span value of particle B1' is selected from 0.1 to 1.5, the span value of particle B2' is selected from 0.1 to 1.4, and the span value of particle B3' is selected from 0.1 to 1.4; wherein, the definition of span is consistent with the foregoing, Span = (D v 90 - D v 10) / D v 50.

[0177] Based on the distinction between small particles (particle A) and large particles (particle B), particle B is further classified into D particles. v The sequentially increasing B1', B2', and B3' particles (50 in each category) result in a positive electrode active material comprising four particle size gradations, allowing for more precise control over the particle size of larger particles. Furthermore, by rationally controlling the proportions of these four particles and the broadening factor (Span), the compaction density, specific capacity, and gravimetric energy density of the positive electrode sheet can be improved. Simultaneously, by rationally controlling the content of intermediate-sized B1' and B2' particles, power performance can be further improved. This avoids excessive packing that could affect electrolyte wettability, prevents the electrolyte from failing to contact the internal active material of the electrode sheet, thus avoiding concentration gradients and adverse limitations on lithium-ion transport.

[0178] In some embodiments, particle A and particle B each independently comprise the element combination Ni. x Co y M 1-x-y The formula is defined as follows: x ≥ 0.4, y ≥ 0, (1-xy) ≥ 0; element M includes one or both of Mn and Al. In some embodiments, 0.40 ≤ x ≤ 1.00, 0 ≤ y ≤ 0.15, (1-xy) ≥ 0. The aforementioned x can be independently selected from any suitable value described above. In some embodiments, 0.50 ≤ x ≤ 1.00. In some embodiments, 0.60 ≤ x ≤ 1.00. In some embodiments, y > 0; further, 0 < y ≤ 0.15 can be satisfied, in which case the presence of cobalt can increase battery cycle and rate performance, and can also suppress cation mixing (including lithium-nickel mixing) to improve material stability. In some embodiments, (1-xy) > 0, in which case one or both of manganese and aluminum can be present; wherein, the introduction of manganese can have other effects that improve battery safety; the introduction of aluminum can suppress cation mixing and improve cycle performance. In some embodiments, the positive electrode active material does not contain cobalt, which helps to reduce costs.

[0179] In some implementations, y > 0 and (1-xy) > 0. In this case, ternary materials of nickel, cobalt, and M can be present, wherein examples of M include at least one of manganese and aluminum, and more specifically, manganese or aluminum. This is advantageous for achieving excellent overall performance in terms of energy density, battery capacity, rate performance, cycle performance, and battery stability.

[0180] In some embodiments, particle A and particle B each independently comprise particles with the chemical formula Li. k-a Q a (Ni x Co y M 1-x-y ) 1-z N z O 2-c X cThe material has the following properties: 0.9 ≤ k ≤ 1.1, 0 ≤ a ≤ 0.2, 0.60 ≤ x ≤ 1.00, 0 ≤ y ≤ 0.15, 0 ≤ (1-xy), 0 ≤ z ≤ 0.5, 0 ≤ c ≤ 1. The M element may include one or both of Mn and Al, the Q element may include one or more of Na, K, Rb and Ca, the N element may include one or more of Al, Ti, Zr, Nb, Sr, Sb, Y, Ba, Co, Mn, Mg, W, Si, Mo, P and C, and the X element may include one or more of B, F, S and Cl. In some embodiments, 0.92 ≤ k ≤ 1.08; alternatively, 0.95 ≤ k ≤ 1.05; alternatively, 0.96 ≤ k ≤ 1.04; alternatively, 0.98 ≤ k ≤ 1.02; alternatively, 0.99 ≤ k ≤ 1.01; alternatively, k=1. In some embodiments, 0.50 ≤ x ≤ 1.00; alternatively, 0.60 ≤ x ≤ 1.00; alternatively, 0.70 ≤ x1 ≤ 1.00. In other embodiments, 0 ≤ a ≤ 0.2, 0.60 ≤ x < 1.00, 0 < y ≤ 0.15 (containing cobalt), 0 < (1-xy) (may contain at least one of manganese and aluminum), 0 ≤ z ≤ 0.5, 0 ≤ c ≤ 1.

[0181] In some embodiments, the chemical formula of particle A (or particle B) is Li(Ni) 0.8 Co 0.1 Mn 0.1 ) 0.95 Zr 0.03 Al 0.02 O2, at this time, the nickel-lithium molar ratio R Ni / Li It is 0.76.

[0182] In some embodiments, the molar ratio R of nickel to lithium in particle A and particle B is... Ni / Li Each independently is ≥0.33. In some embodiments, the nickel-lithium molar ratio R in particle A is... Ni / Li Independently ≥0.3, and can also independently ≥0.4, and can also independently ≥0.5, and can also independently ≥0.6, and can also independently ≥0.7, and can also independently ≥0.8. In some embodiments, the nickel-lithium molar ratio R in the B particles Ni / Li Independently ≥0.3, and can also independently ≥0.4, and can also independently ≥0.5, and can also independently ≥0.6, and can also independently ≥0.7, and can also independently ≥0.8. In some embodiments, the nickel-lithium molar ratio R in particle A and particle B is... Ni / LiThe values ​​can also be independently selected from any one of the following values ​​or any range of two values: 0.33, 1 / 3, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.02, 0.05, 0.9, 0.95, 1, etc. In some embodiments of this application, the nickel-lithium molar ratio R in particle A and particle B is... Ni / Li The values ​​can also be independently selected from any of the following numerical ranges (each numerical endpoint may be included or excluded independently): 0.4~1, 0.5~1, 0.6~1, 0.7~1, 0.8~1, 0.8~0.96, etc. In some embodiments, the nickel-lithium molar ratio R in particle A is... Ni / Li Selected from 0.7 to 1.0. In some embodiments, the nickel-lithium molar ratio R in the B particles is... Ni / Li Selected from 0.8 to 1.0. In some embodiments, the nickel-lithium molar ratio R in the B particles is... Ni / Li Selected from 0.8 to 0.96.

[0183] In traditional nickel-rich cathode materials (such as nickel-rich ternary cathode materials), the cell parameters change during cycling due to lithium insertion / extraction. This change in cell parameters generates internal stress, which accumulates with each charge-discharge cycle, leading to structural phase transitions and particle cracking, significantly disrupting the material's reversible cycling performance. In high-voltage systems, the degree of lithium insertion / extraction in nickel-rich materials (such as nickel-rich ternary materials) is further amplified. In this application, the cathode active material can be a traditional nickel-rich ternary cathode material. Furthermore, introducing nitrogen doping into the ternary cathode active material can reduce the degree of lattice change, stabilizing the lattice and improving the cycling performance of the nickel-rich ternary material. Additionally, it helps prevent the new interfaces formed by cracking from accelerating side reactions with the electrolyte, thus improving cell gas generation.

[0184] In some embodiments, particles A and B may employ cathode active materials known in the art for use in batteries. Cathode active materials suitable for particles A and B in this application may include at least one of the following: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as cathode active materials for batteries may also be used. These cathode active materials may be used alone or in combination of two or more. Non-limiting examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi).1 / 3 Co 1 / 3Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0185] In some embodiments, the positive electrode active material is any suitable ternary positive electrode material. Non-limiting examples include NCM (nickel-cobalt-manganese ternary material), NCA (nickel-cobalt-aluminum ternary material), etc. Among them, non-limiting examples of NCM materials include NCM... 523 NCM 622 NCM 811 The molar ratio of nickel, cobalt, and aluminum in NCA materials is typically controlled based on the theoretical value of 80:15:5.

[0186] In some embodiments of this application, the true density of particle A and particle B can each be independently greater than 4.0 g / cc.

[0187] In some embodiments, the true density of particle A and particle B are each independently selected from 4.0 g / cc to 4.8 g / cc.

[0188] In some embodiments, the true density of each of the A particles is independently selected from 4.6 g / cc to 4.8 g / cc.

[0189] In some embodiments, the true density of each B particle is independently selected from 4.5 g / cc to 4.8 g / cc.

[0190] In some embodiments, the true density of particle A is 4.6 g / cc to 4.8 g / cc, and the true density of particle B is selected from 4.6 g / cc to 4.8 g / cc.

[0191] The term "true density" as used in this application has a meaning known in the art, referring to the ratio of the mass of a positive electrode active material or positive electrode active particle to its true volume, where true volume is the actual volume of the solid material, excluding the volume corresponding to the pores within the particle. It can be expressed in g / cc, for example, the mass in g and the corresponding cm³ / cc. 3 The true density value can be obtained by comparing the ratio of the true volume to the unit of volume.

[0192] In this application, true density is one of the main factors determining the compaction density of the cathode material. By reasonably controlling the true density of particles A and B, it is beneficial to improve the volumetric specific capacity and energy density of the cathode sheet, thereby improving the material cracking problem under high voltage and better improving the cell performance. For the multi-particle system with gradation in this application, the more tightly packed the particles are, the higher the theoretically achievable volumetric specific capacity of the cathode material.

[0193] In some embodiments, particle A and particle B each independently include a bulk structure and an oxide layer covering at least a portion of the surface of the bulk structure;

[0194] in,

[0195] In some embodiments, the bulk structure includes the chemical formula Li k1-a1 Q a1 (Ni x1 Co y1 M 1-x1-y1 ) 1-z1 N z1The material of O2, wherein 0.9 ≤ k1 ≤ 1.1 (optionally, 0.92 ≤ k1 ≤ 1.08; optionally, 0.95 ≤ k1 ≤ 1.05; optionally, 0.96 ≤ k1 ≤ 1.04; optionally, 0.98 ≤ k1 ≤ 1.02; optionally, 0.99 ≤ k1 ≤ 1.01; optionally, k1 equals 1), 0 ≤ a1 ≤ 0.20, 0.40 ≤ x1 ≤ 1.00 (optionally, 0.50 ≤ x1 ≤ 1.00; optionally, 0.60 ≤ x1 ≤ 1.00; optionally, 0.70 ≤ x1 ≤ 1.00), 0 ≤ y1 ≤ 0.15, 0 ≤ (1-x1-y1), 0 ≤ z1 ≤ 0.5, and the Q element includes one or more of Na, K, Rb and Ca, the M element includes one or two of Mn and Al, and the N element includes one or more of Al, Ti, Zr, Nb, Sr, Sb, Y, Ba, Co, Mn, Mg, Si, P, Mo, C and W;

[0196] In some of these embodiments, 0 ≤ a1 ≤ 0.20, 0.60 ≤ x1 < 1.00, 0 < y1 ≤ 0.15, 0 < (1-x1-y1), and 0 ≤ z1 ≤ 0.5;

[0197] In some other embodiments, the N element includes one or more of Al, Ti, Zr, Nb, Sr, Sb, Y, Mg, and W;

[0198] In some embodiments, the oxide layer comprises a chemical formula of Li k2-a2 Q' a2 (Ni) x2 Co y2 M' 1-x2-y2 ) 1-z2 N' z2 O 2-c2 X c2The material, wherein .9 ≤ k2 ≤ 1.1 (optionally, 0.92 ≤ k2 ≤ 1.08; optionally, 0.95 ≤ k2 ≤ 1.05; optionally, 0.96 ≤ k2 ≤ 1.04; optionally, 0.98 ≤ k2 ≤ 1.02; optionally, 0.99 ≤ k2 ≤ 1.01; optionally, k2 equals 1), 0 ≤ a2 ≤ 0.20, 0.40 ≤ x2 ≤ 1.00 (optionally, 0.50 ≤ x2 ≤ 1.00; optionally, 0.60 ≤ x2 ≤ 1.00; optionally, 0.70 ≤ x2 ≤ 1.00), 0 ≤ y2 ≤ 0.15, 0 ≤ (1-x2-y2), 0 < z2 ≤ 0.5, 0 ≤ c2 ≤ 1, and the Q' element includes one or more of Na, K, Rb and Ca, the M' element includes one or two of Mn and Al, the N' element includes one or more of Al, Ti, Zr, Nb, Sr, Sb, Y, Ba, Co, Mn, Mg, W, Mo, Si, C and P, and the X element includes one or more of B, Cl, S and F;

[0199] In some of these embodiments, 0 ≤ a2 ≤ 0.20, 0.60 ≤ x2 < 1.00, 0 < y2 ≤ 0.15, 0 < (1-x2-y2), 0 < z2 ≤ 0.5, and 0 ≤ c2 ≤ 1.

[0200] In some embodiments, both particle A and particle B have an oxide layer (coating layer), see reference. Figure 1 (b).

[0201] In this application, the chemical formulas of particles A and B can be determined by inductively coupled plasma atomic emission spectrometry.

[0202] In this application, Q' elements (such as Na, K, Rb, Ca, etc.) can be doped into the bulk structure of the positive electrode active material to improve the lithium-ion diffusion coefficient and reduce lithium-nickel mixing. Alternatively, a coating can be applied to the surface of the positive electrode active material to form an oxide layer doped with specific N' elements. This reduces the surface reactivity of the material with the electrolyte, decreases oxygen release, improves the structural stability of the active material, increases ionic conductivity, and enhances the material capacity. Furthermore, by combining particle size design with structural design, the material can achieve a higher specific capacity while simultaneously reducing the degree of side reactions and phase transitions between the positive electrode material and the electrolyte, resulting in lower watt-hour costs and longer cycle life. Compared to the coating structure design, the uncoated material interface is more likely to undergo numerous side reactions with the electrolyte, leading to electrolyte oxidation and the generation of gases such as carbon dioxide and oxygen. Moreover, without a coating, the layered structure on the surface of the positive electrode active material is more prone to transforming into a rock salt structure, causing the material surface to lose its chemical reactivity.

[0203] By controlling the amount of oxide layer to a suitable level, the structural stability of the material can be improved, the exacerbation of surface side reactions can be better suppressed, and the cycle life of the material can be extended. When the oxide layer content is too low, the aforementioned effects are not significant. When the oxide layer content is too high, it may lead to a decrease in the material's capacity.

[0204] In some implementations, Q' b2 Ni x2 Co y2 M' 1-x-y With Q b1 Ni x1 Co y1 M 1-x1-y1 Similarly, the same process can be used to prepare particles A and B by sieving.

[0205] In some embodiments, the N' element includes one or more of Al, Ti, Zr, Sr, Sb, Mo, Nb, Mg, Y, and W.

[0206] In some implementations, the N' element includes one or more of Al, Ti, Zr, Sr, Sb, W, C, P, and Mo.

[0207] In some embodiments, the N' element includes at least one selected from Al, Zr, Nb, Sr, Sb, Co, Mg, W, and Mo. By doping the oxide layer with elements such as Zr, Al, Mg, W, Mo, Co, Sr, Sb, and Nb, wherein elements such as Mg, Ti, Al, and Mo can reduce the amount of lattice deformation during charge-discharge cycles, thereby improving the structural stability of the material.

[0208] In some embodiments, element X includes at least one of B, Cl, S, and F. Doping the oxide layer with elements such as B, Cl, S, and F improves capacity and rate performance.

[0209] In some embodiments of this application, the thickness of the oxide layer can be 0 ~ 100 nm, more specifically 1 nm ~ 100 nm, or even 1 nm ~ 20 nm. The thickness of the oxide layer can also be selected from any one or any two of the following ranges: 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 12 nm, 15 nm, 16 nm, 18 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, etc.

[0210] In some embodiments of this application, the mass percentage of the oxide layer relative to the body structure can be 0.01% to 5%, more specifically 0.01% to 4%, and even more specifically 0.05% to 4%. The mass percentage of the oxide layer relative to the body structure can also be selected from any one of the following percentages or a range consisting of any two percentages: 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.08%, 0.9%, 1%, 1.2%, 1.5%, 1.6%, 1.8%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0211] In some embodiments of this application, the mass percentage of nitrogen (N) in the oxide layer in the positive electrode active material can be 0.01%-4%, more specifically 0.05%-4%, and even more specifically 0.1%-4%. The mass percentage of N in the oxide layer in the positive electrode active material can also be selected from any one percentage or a range of any two of the following: 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.08%, 0.9%, 1%, 1.2%, 1.5%, 1.6%, 1.8%, 2%, 2.5%, 3%, 3.5%, 4%, etc.

[0212] In this application, the coating thickness in particles A and B can be measured by transmission electron microscopy.

[0213] In this application, the mass content of the coating layer in particles A and B can be determined by inductively coupled plasma atomic emission spectrometry.

[0214] In this application, the mass percentage of N element in particles A and B in the positive electrode active material described in this application can be determined by inductively coupled plasma atomic emission spectrometry.

[0215] By rationally controlling the amount of surface oxide layer, such as the thickness of the oxide layer, the mass percentage of the oxide layer, and the amount of nitrogen doping, the aforementioned doping and coating objectives can be better achieved (doping allows the dopant source to uniformly enter the bulk phase of the material, reducing shrinkage and expansion and improving structural stability; coating reduces the nickel content, passivates the interface, and reduces reactivity with the electrolyte), the chemical reactivity and structural stability of the material can be better adjusted, the particle size design of the material can be better combined with the structural design, and at the same time, the material is endowed with higher specific capacity, and the degree of side reactions and phase transitions between the cathode material and the electrolyte is reduced, so that the battery has lower watt-hour cost and higher cycle life.

[0216] In some embodiments of this application, the free lithium content in the positive electrode active material is less than 3000 ppm by mass.

[0217] In some embodiments, the content of lithium carbonate in the positive electrode active material described in this application is less than 3500 ppm, by mass.

[0218] In some embodiments, the content of lithium hydroxide in the positive electrode active material described in this application is less than 3000 ppm, by mass. Further, the content of lithium carbonate is less than 3500 ppm, by mass.

[0219] In this application, the mass percentage of free lithium in particles A and B in the positive electrode active material described in this application can be determined by a free lithium potentiometric titration method.

[0220] In this application, the content of free lithium (such as lithium carbonate, lithium hydroxide, etc.) in the positive electrode active material can be reasonably controlled to avoid excessive gas generation during cycling under high voltage conditions. If the free lithium content is too high, it will undergo an acid-base neutralization reaction with hydrofluoric acid produced by electrolyte decomposition during cycling under high voltage conditions, generating a large amount of gas. This causes the cell to bulge and become enlarged, affecting the cell and potentially leading to cell safety accidents.

[0221] In some embodiments of this application, the ratio of I003 grain content to I104 grain content of the positive electrode active material, I003 / I104 ≥ 1.2, is calculated as the ratio of the characteristic peak areas of the I003 crystal plane to the I104 crystal plane in the XRD pattern.

[0222] Optionally, I003 / I104 are selected from 1.2 to 2;

[0223] Optionally, I003 / I104 are selected from 1.3 to 2;

[0224] Optionally, I003 / I104 are selected from 1.3 to 1.6.

[0225] In the application, the grain size of the positive electrode active material can be tested using X-ray diffraction (XRD). Furthermore, the following test parameters are used: sample preparation using a flat plate method, and a test angle of 15°~70°.

[0226] By rationally controlling the ratio of I003 to I104 grains in the positive electrode active material (I003 / I104, e.g., ≥1.2), the degree of lithium-nickel mixing can be better controlled, preventing excessive nickel from occupying lithium lattice positions, which would lead to a decrease in reversible capacity and lithium-ion diffusion coefficient. If lithium ions and divalent nickel undergo cation mixing, the divalent nickel enters the lithium ions, reducing the lithium-ion diffusion coefficient, increasing impedance, leading to a decrease in capacity, and impairing cycle performance and storage performance. Generally speaking, the lower the degree of mixing and the more regular the arrangement, the better the cell performance.

[0227] In some embodiments of this application, at least a portion of the primary particles in the B particles are oriented radially.

[0228] For the secondary spherical particles of this application, by controlling parameters such as the pH value of the reaction system, the concentration of reactants, the reaction time, and the reaction temperature, the primary particles can be oriented in a certain radial direction (e.g., Figure 6 The cross-sectional morphology of B particles as shown in the SEM test results indicates that this process suppresses potential shrinkage and expansion under high voltage, avoids increased internal stress, and thus better prevents material breakage under high voltage. Furthermore, it improves cycle performance. The higher the degree of radial orientation and the lower the degree of random, unoriented arrangement, the more significant the improvement.

[0229] The positive electrode active material provided in the first aspect of this application is a high-nickel positive electrode material with small and large particles of a specific structure, and the content of small particles is higher than that of large particles. The positive electrode sheet prepared has a high specific capacity and excellent structural stability. Furthermore, at the cell level, it can significantly improve the mass energy density and cycle life of the cell, and also reduce the side reactions with the electrolyte and reduce the gas production of the cell.

[0230] In a second aspect, this application provides a positive electrode sheet, which includes a positive current collector and a positive active material layer located on at least one surface of the positive current collector, the positive active material layer comprising the positive active material described in the first aspect of this application.

[0231] The positive electrode active material of the first aspect of this application can be used to prepare a positive electrode sheet with high nickel content. By designing the particle size and content of the positive electrode active material, cracking of the material under high voltage can be avoided, and the cycle and storage performance of the cell under high voltage conditions can be improved. Furthermore, the chemical reactivity and structural stability of the material can be adjusted by using doping and / or coating structure design, which can make the material have a higher specific capacity, while reducing the degree of side reactions and phase transitions between the positive electrode material and the electrolyte, so that the battery has a lower watt-hour cost and a higher cycle life.

[0232] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. (See also...) Figure 7 and Figure 8 . Figure 7 The positive electrode active material includes particles A and particles B. Figure 8 The positive electrode active material includes particles A, particles B1, and particles B2.

[0233] As a non-limiting example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0234] In some embodiments, the positive 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 substrate and a metal layer formed on at least one surface of the polymer substrate. 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 substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0235] In some embodiments, the positive electrode film layer may optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0236] In some embodiments, the positive electrode film may optionally include a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0237] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0238] In some embodiments of this application, the compaction density of the positive electrode sheet is 3.3 g / cm³. 3 ~ 3.7 g / cm 3 Some non-limiting examples include 3.3 g / cm³. 3 3.4 g / cm 3 3.5 g / cm 3 3.6 g / cm 3 3.7 g / cm 3 wait.

[0239] As used in this application, “compacted density” has a meaning known in the art and refers to the ratio of the mass of the positive electrode active material to its volume.

[0240] In this application, by controlling the compaction density of the positive electrode sheet to a suitable level, it is possible to better avoid material cracking under high voltage conditions while imparting better specific capacity and energy density to the electrode sheet. It should be understood that the compaction density of the positive electrode sheet is also limited by the true density of the A and B particles it contains. Increasing the compaction density of the electrode sheet can improve the volumetric specific capacity of the material, enabling the battery cell to have a longer operating range in a smaller volume.

[0241] Thirdly, this application provides an electrochemical energy storage device, which includes the positive electrode, the negative electrode, and the separator as described in the second aspect of this application, wherein the separator is disposed between the positive electrode and the negative electrode.

[0242] Fourthly, this application provides a secondary battery, which includes at least one of the positive electrode sheet described in the second aspect of this application and the electrochemical energy storage device described in the third aspect of this application.

[0243] Fifthly, this application provides an electrical device comprising at least one of the positive electrode sheet described in the second aspect of this application, the electrochemical energy storage device described in the third aspect of this application, and the secondary battery described in the fourth aspect of this application.

[0244] Using the positive electrode active material of the first aspect of this application to prepare a high-nickel content positive electrode sheet, and then to prepare an electrochemical energy storage device, a secondary battery, and an electrical device, the particle size and content of the positive electrode active material can be designed to avoid material cracking under high voltage, improve the cell cycle and storage performance under high voltage conditions, and further utilize doping and / or coating structure design to adjust the chemical reactivity and structural stability of the material, which can make the material have a higher specific capacity, while reducing the degree of side reactions and phase transitions between the positive electrode material and the electrolyte, so that the battery has a lower watt-hour cost and a higher cycle life.

[0245] In this application, the secondary battery includes a positive electrode (provided in the second aspect of this application), a negative electrode, an electrolyte, and a separator. During the charging and discharging process, lithium ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator is disposed between the positive and negative electrodes, primarily to prevent short circuits between the positive and negative electrodes, while simultaneously allowing lithium ions to pass through.

[0246] Positive electrode tab

[0247] The positive electrode sheet in the third and fourth aspects of this application may be the positive electrode sheet provided in the second aspect of this application.

[0248] Negative electrode tab

[0249] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0250] As a non-limiting example, the negative electrode current collector has two surfaces opposite each other in its own 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.

[0251] 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 substrate and a metal layer formed on at least one surface of the polymer substrate. 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 substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0252] In some embodiments, the negative electrode active material may be any negative electrode active material known in the art for use in batteries. As a non-limiting example, the negative electrode active material may include materials such as artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0253] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from 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).

[0254] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0255] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0256] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0257] Electrolyte

[0258] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose any particular restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or entirely solid.

[0259] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0260] In some embodiments, the electrolyte salt may be selected from lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0261] In some embodiments, the solvent may be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate, ethyl propyl 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, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0262] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0263] Separator membrane

[0264] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0265] In some embodiments, the material of the separator can be selected from glass fiber, nonwoven 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.

[0266] Electrode assembly, electrochemical energy storage device, secondary battery, electric device

[0267] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0268] In some embodiments, the electrochemical energy storage device may include an outer packaging. This outer packaging may be used to encapsulate the aforementioned electrode assembly and electrolyte.

[0269] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0270] 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. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0271] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 9 This is an example of a square-structured secondary battery 5.

[0272] In some implementations, refer to Figure 10 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to actual needs.

[0273] In addition, this application also provides an electrical device, which includes the secondary battery provided in this application. The secondary battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Among them, mobile devices may be, for example, mobile phones, laptops, etc.; electric vehicles may be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to.

[0274] As the electrical device, a secondary battery can be selected according to its usage requirements.

[0275] Figure 11 Here is an example of an electrical device 6. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this electrical device, a battery pack or battery module can be used.

[0276] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0277] According to a sixth aspect of this application, a method for preparing a positive electrode active material includes the following steps: mixing the A particles and the B particles according to a preset mass ratio to prepare the positive electrode active material; the A particles and B particles are as defined in the first aspect of this application;

[0278] The A particles can be prepared by a method including the following steps: lithium hydroxide, nickel-cobalt M-body precursor material Ni x Co y M 1-x-y (OH)2 and optional Q additive and optional N additive are mixed and sintered once in the presence of oxygen and at temperature T1; optionally, at least one of X additive and N additive is added to the primary sintered product, mixed, and sintered again in the presence of oxygen.

[0279] The B particles can be prepared by a method including the following steps: lithium hydroxide, nickel-cobalt M-body precursor material Ni x Co y M 1-x-y (OH)2 and optional Q additive and optional N additive are mixed and sintered once in the presence of oxygen and at temperature T2; optionally, at least one of X additive and N additive is added to the primary sintered product, mixed, and sintered a second time in the presence of oxygen.

[0280] Wherein, the Q additive, N additive, and X additive are respectively additives containing the Q element, additives containing the N element, and additives containing the X element;

[0281] Furthermore, the temperature T1 is higher than the temperature T2;

[0282] The elements x, y, M, Q, and N are as defined in the first aspect of this application.

[0283] In some embodiments, during the step of preparing the A particles, in the sintering step under oxygen conditions, the primary sintering temperature (T1) is 700 °C ~ 950 °C, optionally 750 °C ~ 900 °C, and the secondary sintering temperature is 300 °C ~ 600 °C, optionally 350 °C ~ 550 °C. The primary sintering temperature T1 of the A particles can also be any one of the following temperatures or any range consisting of two of them: 700 °C, 750 °C, 800 °C, 850 °C, 900 °C, 950 °C, etc. The secondary sintering temperature can also be any one of the following temperatures or any range consisting of two of them: 350 °C, 400 °C, 450 °C, 500 °C, 550 °C, etc.

[0284] In some embodiments, during the step of preparing the B particles, in the sintering step under oxygen conditions, the primary sintering temperature is 700 °C to 900 °C, optionally 750 °C to 850 °C, and the secondary sintering temperature is 300 °C to 600 °C, optionally 350 °C to 550 °C. The primary sintering temperature can also be any one of the following temperatures or any combination of two: 700 °C, 750 °C, 800 °C, 850 °C, 900 °C, etc. The secondary sintering temperature can also be any one of the following temperatures or any combination of two: 350 °C, 400 °C, 450 °C, 500 °C, 550 °C, etc.

[0285] When the positive electrode active particles (particle A or particle B) provided in the first aspect of this application have no surface coating layer, they can be prepared by a one-time sintering method using the corresponding precursor in an oxidizing atmosphere.

[0286] When the positive electrode active particles (particle A or particle B) provided in the first aspect of this application are coated with an oxide layer, a stepwise sintering method can be used. First, the precursor of the bulk structure is sintered in an oxidizing atmosphere at a relatively high temperature (e.g., 700 °C ~ 950 °C for particle A, and 700 °C ~ 900 °C for particle B) to form the bulk structure. Then, it is mixed with the coating layer precursor and sintered in an oxidizing atmosphere at a relatively low temperature (e.g., 300 °C ~ 600 °C) to form the oxide layer, thereby preparing particles A or B with a coating layer. During the first sintering, at a higher sintering temperature, the particles inside the particle are more likely to bond together. Therefore, at a relatively high first sintering temperature (T1), the particles can be fully bonded to prepare large-sized single crystal or near-single crystal particles (particle A), and at a relatively low first sintering temperature (T2), small-sized secondary particles (particle B) can be prepared. In this case, the fine particles in the secondary particles are not bonded or only partially bonded.

[0287] In a seventh aspect, this application provides a method for preparing a positive electrode slurry, comprising the following steps: mixing A particles, B particles and optional additives to prepare the positive electrode slurry; wherein the A particles and the B particles are as defined in the first aspect of this application;

[0288] In some embodiments of this application, the preparation method satisfies one or more of the following characteristics:

[0289] (1) The pH of the positive electrode slurry is 11~12;

[0290] (2) The step of mixing particles A, particles B, and optional additives is carried out at room temperature (e.g., 25 °C); and

[0291] (3) The step of mixing particles A, particles B and optional additives is carried out under stirring conditions, with a stirring speed of 500~2000 r / min and a stirring time of 0.5 h~5 h.

[0292] By synergistically controlling the preparation parameters of the cathode slurry, such as pH, mixing temperature, stirring speed, and stirring time, the viscosity of the cathode slurry can be better controlled, and the processing performance can be improved.

[0293] The following describes some embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where detailed technical or conditional specifications are not specified in the embodiments, they are performed according to the description above, or according to the technical or conditional specifications described in the literature in the art, or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially, or can be synthesized from commercially available products using conventional methods.

[0294] In the following embodiments, room temperature refers to 20 °C ~ 30 °C, and more specifically, it can be 25 °C.

[0295] In the following examples, unless otherwise specified, the positive electrode slurry is coated onto the positive electrode current collector using a single-sided coating method, and the negative electrode slurry is coated onto the negative electrode current collector using a double-sided coating method. Furthermore, unless otherwise specified, the positive electrode sheets in each example use substantially the same single-sided coating amount, and the negative electrode sheets in each example use substantially the same single-sided coating amount. The coating amount of the slurry can be controlled by the coating mass per unit area. It should be understood that the single-sided and double-sided coating methods in the examples are for illustrative purposes only. When preparing the electrodes in this application, the preparation of the positive and negative electrode sheets can each independently employ either a single-sided or double-sided coating method.

[0296] In the following examples, "substantially the same" regarding the preparation methods means that, except for specifically specified parameter changes, the remaining parameters remain unchanged. However, it is understood that adaptive adjustments based on the specified parameter changes are acceptable. For example, when the composition and content of the target product change, the composition and amount of the raw materials are allowed to be adaptively adjusted.

[0297] Example 1.

[0298] 1.1. Preparation of positive electrode active material (bulk structure contains doped elements, no coating layer)

[0299] The particle size of the precursor determines the particle size of the cathode material. The size and distribution of particles A and B can be controlled by adjusting the size and distribution of the precursor. For those skilled in the art, the methods for adjusting the size and distribution of the precursor are known.

[0300] The ternary precursor (Ni) 0.8 Co 0.1 Mn 0.1 OH2 (particle size D) v Particles A are obtained by mixing LiOH·H2O, ZrO2 and Al2O3 in a molar ratio of 0.95:1.04:0.03:0.01 in a mixer and then sintering them at 860℃ in an oxygen atmosphere.

[0301] The ternary precursor (Ni) 0.8 Co 0.1 Mn 0.1 OH2 (particle size D) v Particles B were prepared by mixing particles A (approximately 10 μm in size), LiOH·H2O, ZrO2, and Al2O3 in a molar ratio of 0.95:1.04:0.03:0.01 in a mixer and then sintering them at 830℃ in an oxygen atmosphere to obtain particles B. Particles A and B, prepared sequentially, were then mixed in a certain mass ratio (see Tables 1 and 2) to prepare the positive electrode active material, which was then ready for use.

[0302] 1.2. Preparation of the positive electrode sheet

[0303] 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 for 2 hours. Then, the mixture was stirred in a homogenizer at 1000 r / min until it was uniformly mixed. The mixture was then uniformly coated on one side of a 13-micron thick aluminum foil current collector. After coating, the mixture was dried in a drying oven at 100 °C, cold-pressed, and slit to obtain the positive electrode sheet.

[0304] 1.3. Preparation of Electrolyte

[0305] A mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) was prepared by mixing them at a volume ratio of 1:2 to obtain a mixed solvent. Then, thoroughly dried lithium hexafluorophosphate was dissolved in the mixed solvent and mixed thoroughly in an argon-atmospheric glove box to obtain an electrolyte. The lithium salt concentration in the electrolyte was 1 mol / L.

[0306] 1.4. Preparation of the negative electrode sheet

[0307] 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 mixer. The slurry was then coated on both sides of an 8-micron thick copper foil, dried in a 100°C oven, cold-pressed, and slit to obtain the negative electrode sheet.

[0308] 1.5. Cell fabrication

[0309] The positive electrode, separator, and negative electrode are stacked in sequence from top to bottom, ensuring that the positive and negative electrode plates do not come into contact with each other. Then, they are wound into a bare cell using a winding needle, placed into a square aluminum shell, injected with electrolyte, and subjected to steps such as settling, formation, and capacity testing to produce the battery cell.

[0310] Example 2.

[0311] Example 2 uses the same method as Example 1, except that the preparation steps of the positive electrode active material are different and the additives for the positive electrode active material are different.

[0312] 2.1. Preparation of positive electrode active materials

[0313] The ternary precursor (Ni) 0.8 Co 0.1 Mn 0.1 OH2 (particle size D) v Particles A are obtained by mixing LiOH·H2O, ZrO2, Al2O3 and B2O3 in a molar ratio of 0.95:1.04:0.03:0.01:0.01 in a mixer and then sintering them at 860℃ in an oxygen atmosphere.

[0314] The ternary precursor (Ni) 0.8 Co 0.1 Mn 0.1 OH2 (particle size D) v 50 (approximately 10 μm), LiOH·H2O, ZrO2, Al2O3 and B2O3 were mixed in a mixer in a molar ratio of 0.95:1.04:0.03:0.01:0.01, and then sintered at 820℃ in an oxygen atmosphere to obtain B particles.

[0315] The prepared A particles and B particles are mixed at a certain mass ratio (see Tables 1 and 2) to prepare the positive electrode active material, which is ready for use.

[0316] Example 3.

[0317] Example 3 uses the same method as Example 1, except that the preparation steps of the positive electrode active material are different and the additives for the positive electrode active material are different.

[0318] 3.1. Preparation of positive electrode active materials

[0319] The ternary precursor (Ni) 0.8 Co 0.1 Mn 0.1OH2 (particle size Dv50 is about 4 μm), LiOH·H2O, ZrO2, Sb2O5 and Al2O3 are mixed in a mixer in a molar ratio of 0.94:1.04:0.02:0.01:0.01, and then sintered at 860℃ in an oxygen atmosphere to obtain particles A.

[0320] The ternary precursor (Ni) 0.8 Co 0.1 Mn 0.1 OH2 (particle size D) v Particles B are obtained by mixing LiOH·H2O, ZrO2, Sb2O5 and Al2O3 in a molar ratio of 0.94:1.04:0.02:0.01:0.01 in a mixer and then sintering them at 820℃ in an oxygen atmosphere.

[0321] The prepared A particles and B particles are mixed at a certain mass ratio (see Tables 1 and 2) to prepare the positive electrode active material, which is ready for use.

[0322] Examples 1a to 1d. Ternary cathode materials were used.

[0323] Examples 1a, 1b, 1c and 1d all used the same method as in Example 1, the difference being the composition of the positive electrode active material. Particles A and B both used self-made NCM ternary positive electrode material.

[0324] Examples 1a, 1b, 1c and 1d use different nickel contents (refer to Table 1) and different nickel contents of ternary precursors, while the other preparation parameters are the same.

[0325] Example 1a.

[0326] The ternary precursor (Ni) 0.8 Co 0.1 Mn 0.1 OH2 (particle size D) v 50 (approximately 4 μm) and LiOH·H2O were mixed in a mixer at a molar ratio of 1:1.04, and then sintered at 860℃ in an oxygen atmosphere to obtain particles A.

[0327] The ternary precursor (Ni) 0.8 Co 0.1 Mn 0.1 OH2 (particle size D) v 50 (approximately 10 μm) and LiOH·H2O were mixed in a mixer at a molar ratio of 1:1.04, and then sintered at 820℃ in an oxygen atmosphere to obtain B particles.

[0328] The prepared A particles and B particles were mixed at a certain mass ratio (refer to Tables 1 and 2) to prepare the positive electrode active material (Example 4-1), which was then ready for use. The D values ​​of each of the A particles and B particles in Examples 1b, 1c, and 1d are... v 10. D v 50. D v The values ​​of 90 and Span are similar to those in Example 1a.

[0329] Comparative Example 1. The same method as in Example 1 was used, except that equal mass of A particles were used instead of B particles to prepare the positive electrode sheet.

[0330] Comparative Example 2. The same method as in Example 1 was used, except that equal mass of B particles were used instead of A particles to prepare the positive electrode sheet.

[0331] Comparative Example 3. The method was basically the same as in Example 1, except that the mass content of particle A was less than that of particle B. Furthermore, the mass content of particle A in the positive electrode active material was 20%.

[0332] Comparative Example 4a. The same method as in Example 1a was used, except that equal mass of A particles (NCM811) was used instead of B particles to prepare the positive electrode sheet.

[0333] Comparative Example 4b. The same method as in Example 1a was used, except that an equal mass of B particles (NCM811) was used instead of A particles to prepare the positive electrode sheet.

[0334] Table 1.

[0335]

[0336] Table 2.

[0337]

[0338] Examples 4-6. The method is essentially the same as in Example 1, except that the positive electrode active particles include B1 particles and B2 particles, and the D of particles A, B1, and B2 is adjusted. v 50. Span and its content.

[0339] Comparative Example 5. The method was basically the same as that in Example 4, except that the content of B1 particles was adjusted.

[0340] Comparative Example 6. The method was essentially the same as in Example 6, except that the D of particles B1 and B2 was adjusted. v 50.

[0341] Comparative Examples 7-8. The method used was essentially the same as in Example 6, except that the D of the B1 and B2 particles was adjusted.v 50. Combinations of Span.

[0342] The relevant parameters for Examples 4-6 and Comparative Examples 5-8 can be found in Table 3.

[0343] Table 3.

[0344]

[0345] Example 7.

[0346] Preparation of the positive electrode sheet: Particles A, B1', B2', and B3' are mixed uniformly in a mass ratio of 5:2:2:1 to prepare the positive electrode active material. Then, the active material is mixed with polyvinylidene fluoride (PVDF) and conductive carbon black in a mass ratio of 90:5:5. The mixture is then coated, cold-pressed, and die-cut to prepare the positive electrode sheet. The chemical composition of particles A, B1', B2', and B3' is all Li(Ni). 0.8 Co 0.1 Mn 0.1 ) 0.95 Zr 0.03 Al 0.02 O2.

[0347] The remaining preparation parameters and methods are the same as in Example 1.

[0348] The positive electrode, separator, and negative electrode are stacked in order from top to bottom, ensuring that the positive and negative electrodes do not come into contact with each other. Then, they are wound into a bare cell using a winding needle, placed in a square aluminum shell, injected with electrolyte, and then allowed to stand, form, and be rated to produce the cell.

[0349] Furthermore, in Examples 7a to 7m, based on the aforementioned preparation method, the mass ratio of particles A, B1', B2', and B3' was adjusted from 5:2:2:1 to different dosage ratios shown in Table 5, while the remaining preparation steps were the same as when the mass ratio was 5:2:2:1.

[0350] Example 8.

[0351] Preparation of the positive electrode sheet: Particles A, B1', B2', and B3' are mixed uniformly in a mass ratio of 6:4:0.5:0.5 to prepare the positive electrode active material. Then, the active material is mixed with polyvinylidene fluoride (PVDF) and conductive carbon black in a mass ratio of 90:5:5. The mixture is then coated, cold-pressed, and die-cut to prepare the positive electrode sheet. The chemical composition of particles A, B1', B2', and B3' is Li(Ni) 0.8 Co 0.1 Mn 0.1 ) 0.95 Zr 0.03 Al 0.02 O2.

[0352] The remaining preparation parameters and methods are the same as in Example 1.

[0353] The positive electrode, separator, and negative electrode are stacked in order from top to bottom, ensuring that the positive and negative electrodes do not come into contact with each other. Then, they are wound into a bare cell using a winding needle, placed in a square aluminum shell, injected with electrolyte, and then allowed to stand, form, and be rated to produce the cell.

[0354] In addition, the inventors used particles A, B1', B2' and B3' from Example 8 and adopted the same method as in Example 8, only adjusting the content of each particle (as shown in Table 9 for Examples 8a to 8m) to obtain different positive electrode sheets, and then prepared secondary batteries.

[0355] Example 9.

[0356] Preparation of the positive electrode sheet: Positive electrode active material is prepared by mixing particles A, B1', B2', and B3' in a mass ratio of 7:1:1:1. Then, the active material is mixed with polyvinylidene fluoride (PVDF) and conductive carbon black in a mass ratio of 90:5:5. The mixture is then coated, cold-pressed, and die-cut to prepare the positive electrode sheet. The chemical composition of particles A, B1', B2', and B3' is Li(Ni) 0.8 Co 0.1 Mn 0.1 ) 0.95 Zr 0.03 Al 0.02 O 2。

[0357] The remaining preparation parameters and methods are the same as in Example 1.

[0358] The positive electrode, separator, and negative electrode are stacked in order from top to bottom, ensuring that the positive and negative electrodes do not come into contact with each other. Then, they are wound into a bare cell using a winding needle, placed in a square aluminum shell, injected with electrolyte, and then allowed to stand, form, and be rated to produce the cell.

[0359] The relevant parameters for Examples 7-9 can be found in Tables 4 and 5.

[0360] Table 4.

[0361]

[0362] Table 5.

[0363]

[0364] The chemical composition of the positive electrode active particle bulk structure in Examples 10-13 and Examples 11b, 12b, and 13b is Li(Ni) 0.8 Co 0.1Mn 0.1 ) 0.95 Zr 0.03 Al 0.02 O2.

[0365] Examples 10-12. The method is basically the same as that in Example 1, except that the active particles have a coating layer and the thickness, mass ratio and nitrogen content are changed. See Tables 6 and 7 for details.

[0366] The preparation methods for particles A and B are as follows:

[0367] Particle A is prepared by a method including the following steps: lithium hydroxide, nickel-cobalt M-body precursor material Ni x Co y M 1-x-y (OH)2(D v A mixture of ZrO2 and Al2O3 (approximately 4 μm) was sintered once in the presence of oxygen at a temperature of 850 °C; N was added to the product of the first sintering. ’’ The additives of the elements (refer to Table 6) are subjected to secondary sintering in the presence of oxygen at a sintering temperature of 350℃.

[0368] The B particles are prepared using a method comprising the following steps: lithium hydroxide, nickel-cobalt M-body precursor material Ni x Co y M 1-x-y (OH)2(D v A mixture of ZrO2 and Al2O3 (approximately 4 μm in diameter) was sintered once in the presence of oxygen at a temperature of 820 °C. Optionally, N2O3 was added to the primary sintering product. ’’ The additives of the elements (see Table 6) are subjected to secondary sintering in the presence of oxygen at a sintering temperature of 350℃.

[0369] Where M is manganese, x is 0.8, y is 0.1, and (1-xy) is 0.1. The nitrogen element in the bulk structure of particles A and B both includes Zr and Al, and the N' element in the coating layer of particles A and B includes Zr, Al, and N'' elements (see Table 6). ’’ The elements are the same. When element N'' is the same as element N, it leads to a change in the content.

[0370] Here, N'' element refers to other doping elements contained in the bulk structure. Regarding N'' element additives, when N'' element is Al, Mg, or B, the corresponding additives used during secondary sintering are Al2O3, MgO, and B2O3, respectively.

[0371] Comparative Example 9. The method is basically the same as that in Example 11, except that the coating layer thickness is different.

[0372] Example 12b. The method is basically the same as that in Example 12, except that the sintering temperature is different.

[0373] Example 13. The method is basically the same as that in Example 10, except that the sintering temperature is different.

[0374]

[0375] The “doped elements” in Table 6 include all doped elements in the bulk structure and oxide layer, including the N element in the bulk structure and the N' element in the oxide layer.

[0376] Examples 14-16 use essentially the same method as Example 5, the difference being that the material composition of the positive electrode active material is different.

[0377] In Examples 14-16, the combination of particle A + particle B1 + particle B2, the particle size parameter (D) v 10. D v 50. D v (The control of 90 and Span is similar to that in Example 5). The types of doping elements in particles A, B1, and B2 are all the same.

[0378] The bulk structure of LiNi in Example 14 0.8 Co 0.1 Mn 0.1 O2, whose bulk phase is doped with Zr and Sr elements, and whose coating layer contains Al and Mg elements.

[0379] Bulk structure of LiNi in Example 15 0.8 Co 0.1 Mn 0.1 O2, whose bulk phase is doped with Zr, Sr and Ti elements, and whose coating layer contains Mg elements.

[0380] The bulk structure of LiNi in Example 16 0.8 Co 0.1 Mn 0.1 O2, whose bulk phase is doped with Zr, Sr and W elements, and whose coating layer contains B element.

[0381] Table 7.

[0382]

[0383] Example 17.

[0384] The same active material components as in Example 1 were used, and the preparation method was basically the same. The difference was that the primary particles of the precursor were randomly arranged, which made the primary particles of B particles basically randomly distributed.

[0385] Test case

[0386] 1. Composition testing of particles A and B

[0387] Inductively coupled plasma atomic emission spectrometry was used.

[0388] 2. Particle size testing

[0389] (1) Particle size test

[0390] Particle size type: D v 10. D v 50 and D v 90 tests.

[0391] Equipment Model: Malvern 2000 (MasterSizer 2000) laser particle size analyzer; Reference Standard Procedure: GB / T19077-2016 / ISO 13320:2009; Detailed Test Procedure: Take an appropriate amount of the sample to be tested (the sample concentration should be 8%~12% opacity), add 20 mL of anhydrous ethanol, and sonicate for 5 min (53 kHz / 120 W) to ensure complete dispersion. Then, measure the sample according to GB / T19077-2016 / ISO 13320:2009. To avoid agglomeration during the drying process affecting the particle size test, use a washed and moistened sample for dispersion testing.

[0392] (2) Specific surface area test of positive electrode active material

[0393] The nitrogen adsorption specific surface area was tested using the nitrogen adsorption specific surface area analysis method and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis test can be performed using the TriStar II specific surface area and porosity analyzer from Micromeritics, USA. The test procedure can refer to GB / T 19587-2004.

[0394] Test samples: the positive electrode active materials prepared in each example.

[0395] The detailed steps are as follows: Dry the sample to be tested in a vacuum drying oven at 200℃ for 2 hours; then use argon as the adsorption gas, and plot the adsorption-desorption curve with relative pressure P / P0 of 0 to 0.99 by a specific surface area and porosity analyzer. P is the equilibrium adsorption pressure and P0 is the saturated vapor pressure. Calculate the specific surface area of ​​the positive electrode active material by the BET method.

[0396] (3) True density

[0397] The true density tester was used, and the test procedure was in accordance with GB / T 24586-2009.

[0398] Sample to be tested: Active cathode material

[0399] Steps: Pretreatment: Place a clean and dry sample cup on the balance, zero the balance, add the powder sample into the sample cup, filling it to approximately 1 / 2 of the sample cup's volume, and record the sample mass.

[0400] The sample cup containing the sample is placed in a true density analyzer. The testing system is sealed, and helium gas is introduced according to the procedure. By detecting the gas pressure in the sample chamber and the expansion chamber, and then calculating the true volume according to Bohr's law (PV=nRT), the true density is calculated.

[0401] Sample cup volume: 3.5cm 3 Analytical gas: Helium.

[0402] (4) Thickness of oxide layer (based on TEM)

[0403] TEM was used to analyze the material, and the thickness of the coating layer was measured at multiple points and the average value was taken.

[0404] (5) Oxide layer content

[0405] It was calculated based on the feed ratio of the first and second sintering processes.

[0406] (6) I003 / I104 test

[0407] The positive electrode active material was analyzed using X-ray diffraction, according to JIS K 0131-1996.

[0408] (7) Test for free lithium (including lithium carbonate and lithium hydroxide) content

[0409] The positive electrode active material was analyzed using a free lithium potentiometric titrator, in accordance with GB / T 9725-2007.

[0410] 2. Electrode

[0411] (1) Compacted density

[0412] By coating the positive electrode slurry onto one side of a 13 μm thick aluminum foil with a coating thickness of 110 μm on one side, and then drying it, the compaction density and elongation data were collected using a cold press. The compaction density corresponding to an elongation of 0.8% was taken as the test value of the electrode compaction density of the positive electrode active material.

[0413] Elongation: (Length of the electrode after cold pressing - Length of the electrode before cold pressing) / Length of the electrode before cold pressing × 100%

[0414] 3. Battery Cells

[0415] (1) Specific capacity (mAh / g)

[0416] Specific capacity refers to the ratio of the electrical capacity that the active material inside a battery can release to the mass of the active material.

[0417] (2) Cyclic performance: capacity retention

[0418] Under 25℃ conditions, one cycle is defined as a constant current charge and discharge cycle with a 1C rate, first constant current and then constant voltage. The first cycle is denoted as C0, and the nth cycle as Cn. The capacity retention rate for each cycle is Cn / C0.

[0419] (3) Gas production test (gas production during 40 days of storage at 70°C)

[0420] At 25℃, the lithium-ion battery was first charged to 4.3V with a constant current of 1 / 3C, then charged to 4.3V with a constant voltage of 0.025C. The volume of the lithium-ion battery was measured in deionized water using the water displacement method, denoted as V0. The battery was then stored at 70℃, and the volume change was recorded every six days, denoted as Vn for the nth measurement. The volume expansion rate (%) of the lithium-ion battery after storage at 70℃ is calculated as (Vn - V0) / V0 × 100%.

[0421] (4) Storage performance (capacity retention rate after 50 days at 60 °C)

[0422] At 25℃, the battery cell was charged to 4.3V with a constant current of 1C, then charged to 4.3V with a constant voltage of 0.05C, and then discharged to 2.8V with a constant current of 1C, followed by a constant voltage discharge with a current of 0.05C. The measured capacity was recorded as C0.

[0423] The battery cell was charged to 4.3V at a 1C current, followed by constant voltage charging at a current of 0.05C. The fully charged cell was then stored in a 60℃ constant temperature oven. Every 30 days, the cell was removed and discharged at 25℃ with a constant current of 1C to 2.8V, followed by constant voltage discharge with a current of 0.05C. The capacity was measured as Cn, and the capacity retention rate was calculated as Cn / C0.

[0424] Repeat step two to obtain a graph showing the change in battery capacity retention over time.

[0425] (5) Number of cycles (number of cycles at 25 °C until 80% capacity retention)

[0426] At 25°C, the lithium-ion battery is charged at a constant current of 1C to a voltage of 4.3V, then charged at a constant voltage of 4.3V with a current of 0.05C, followed by a constant current discharge of 1C until the final voltage reaches 2.8V and the capacity is C1. This process is repeated until the capacity is measured for the nth cycle, which is Cn. The capacity retention rate (%) is calculated as (nth discharge capacity / first cycle discharge capacity) × 100%. This cycle is continued until the cell capacity retention rate decreases to 80%.

[0427] Table 8.

[0428]

[0429] Figures 2 to 6 The results are the test results of the positive electrode active particles in Example 1.

[0430] The comparative analysis results of the examples and comparative examples can be found below.

[0431] In Example 1, the primary particles in particle B are radially oriented, and the number of cycles required to reach 80% capacity retention at 25 °C is 2600, with a calendar life of 40 days and a gas production of 6 ml / ah at 70 °C. The inventors speculate that this is because stress concentration is less likely to occur inside the material when the primary particles are radially oriented during charge-discharge cycling.

[0432] In Example 17, the primary particle distribution of B particles was basically random. The number of cycles required to reach 80% capacity retention at 25 °C was 1200, and the calendar life was 40 days. The gas production at 70 °C was 36 ml / ah.

[0433] Comparative Example 1 included only particle A and excluded particle B, while Comparative Example 2 included only particle B and excluded particle A. The results showed that, compared to Example 1, the cycle performance and storage performance of Comparative Examples 1 and 2 were significantly reduced, while the gas production during 40 days of storage at 70°C was significantly increased. Comparative Examples 4a and 4b showed similar results compared to Example 1a.

[0434] In Comparative Example 3, the content of B particles was greater than that of A particles. Compared with Example 1, the cycle performance and storage performance of Comparative Example 3 were significantly reduced, while the gas production during 40 days of storage at 70°C was significantly increased.

[0435] In Comparative Example 5, the content of B1 particles was relatively high. Compared with Example 4, the cycle performance and storage performance of Comparative Example 5 were significantly reduced, while the gas production during 40 days of storage at 70°C was significantly increased.

[0436] In Comparative Example 6, the content of B1 particles was relatively high. Compared with Example 6, the cycle performance and storage performance of Comparative Example 6 were significantly reduced, while the gas production during 40 days of storage at 70°C was significantly increased.

[0437] In Comparative Example 7, the content of B2 particles was higher, while that of B1 particles was lower than that of Example 6. v A value of 50 is too high, which leads to a decrease in circulation and storage performance, and an increase in high-temperature gas production.

[0438] In Comparative Example 8, the content of B1 and B2 particles was greater than that of A particles. Compared with Example 6, Comparative Example 8 resulted in decreased cycle performance and storage performance, but increased high-temperature gas production.

[0439] In Comparative Example 9, the coating layer is thicker. Compared with Example 11, Comparative Example 9 has decreased cycle performance and storage performance, but increased high-temperature gas production.

[0440] Examples 12b and 13 have adjusted the sintering process. Compared with Example 12, Example 12b has decreased cycle performance and storage performance, but increased high-temperature gas production. Compared with Example 10, Example 13 has decreased cycle performance and storage performance, but increased high-temperature gas production.

[0441] Table 9.

[0442]

[0443] In Table 9, Examples 8a to 8m show that adjusting the relative contents of particles A, B1', B2', and B3' all achieve better circulation performance but with lower gas production during storage.

[0444] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0445] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. The above-described embodiments only illustrate several embodiments of this application, and their descriptions are relatively detailed, but they should not be construed as limiting the scope of the patent. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, are also included in the scope of this application without departing from the spirit of this application. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A positive electrode active material comprising particles A and B, wherein the molar ratio R of nickel to lithium in particles A and particles B is... Ni / Li Each is independently greater than or equal to 0.33; in, The A particle has a single crystal or near-single crystal structure, and the B particle is a secondary particle comprising multiple primary particles, wherein the D of the A particle... v 50 is smaller than the D of the B particles v 50, the mass percentage of particle A is greater than the mass percentage of particle B; the particle size of particle B satisfies 5μm. <D v 50≤15μm; the B particles include B1 particles and B2 particles, and the D of the B1 particles... v 50 is smaller than the D of the B2 particles v 50, the particle size of the B1 particles satisfies 5μm < D v 50 <10μm; Among them, D v N represents the particle size corresponding to the cumulative volume distribution percentage of the material reaching N%, where N is a value selected from 0 to 100.

2. The positive electrode active material according to claim 1, wherein, The particle size of particle A satisfies 2 μm ≤ D v 50 ≤5μm.

3. The positive electrode active material according to claim 2, wherein, The particle size of particle A satisfies 3μm ≤ D v 50 ≤4μm.

4. The positive electrode active material according to claim 2 or 3, wherein, The Span value of particle A is greater than the Span value of particle B. Where Span = (D v 90 - D v 10) / D v 50; where Span = (D v 90 - D v 10) / D v 50.

5. The positive electrode active material according to claim 4, wherein, The Span value of particle A is selected from 0.1 to 3.0; the Span value of particle B is selected from 0.1 to 3.

0.

6. The positive electrode active material according to any one of claims 1 to 5, wherein, The particle size of particle B satisfies 6μm≤D v 50≤13μm.

7. The positive electrode active material according to claim 6, wherein, The particle size of B particles meets the requirement of 8μm. <D v 50≤12.5μm.

8. The positive electrode active material according to any one of claims 1 to 7, wherein, The particle size of the B1 particles meets the requirement of 5 μm. <D v 50≤9.5μm, the particle size of the B2 particles satisfies 10μm< D v 50 ≤15μm.

9. The positive electrode active material according to any one of claims 1 to 8, wherein, The weight percentage of B1 particles in the total B particles is selected from 50% to 100%.

10. The positive electrode active material according to claim 9, wherein, The weight percentage of B2 particles in the total B particles is selected from 0% to 50%.

11. The positive electrode active material according to any one of claims 1 to 10, wherein, The span value of particle A is selected from 0.1 to 2.0; the span value of particle B1 is selected from 0.1 to 2.0; the span value of particle B2 is selected from 0.1 to 2.

0. Where Span = (D v 90 - D v 10) / D v 50.

12. The positive electrode active material according to any one of claims 1 to 11, wherein, The particle size of the B1 particles satisfies 5.5 μm ≤ D v 50≤9μm.

13. The positive electrode active material according to claim 12, wherein, The particle size of the B1 particles satisfies 6μm≤D v 50≤8.5μm.

14. The positive electrode active material according to claim 12, wherein, The particle size of the B1 particles satisfies 7μm≤D v 50≤8.5μm.

15. The positive electrode active material according to any one of claims 1 to 14, wherein, The particle size of the B2 particles satisfies 10.5 μm ≤ D v 50≤14μm.

16. The positive electrode active material according to claim 15, wherein, The particle size of the B2 particles satisfies 11μm≤D v 50≤13.5μm.

17. The positive electrode active material according to claim 15, wherein, The particle size of the B2 particles satisfies 11μm≤D v 50≤12.5μm.

18. The positive electrode active material according to any one of claims 1 to 17, wherein, Particle A and particle B each independently contain the following element combination Ni x Co y M 1-x-y , where x ≥ 0.4, y ≥ 0, (1-xy) ≥ 0; the M element includes one or both of Mn and Al.

19. The positive electrode active material according to claim 18, wherein, 0.40 ≤ x ≤ 1.00, 0 ≤ y ≤0.15, (1-xy) ≥ 0.

20. The positive electrode active material according to claim 18 or 19, wherein, 0.50 ≤ x ≤ 1.00。 21. The positive electrode active material according to claim 18 or 19, wherein, 0.60 ≤ x ≤ 1.00。 22. The positive electrode active material according to any one of claims 18 to 21, wherein, y > 0。 23. The positive electrode active material according to claim 22, wherein, 0 < y ≤ 0.15。 24. The positive electrode active material according to any one of claims 18 to 21, wherein, (1-xy) > 0.

25. The positive electrode active material according to claim 22 or 23, wherein, y > 0, and (1-xy) > 0.

26. The positive electrode active material according to any one of claims 18-19 and 22-25, wherein, Particle A and particle B each independently comprise a compound with the chemical formula Li. k-a Q a (Ni x Co y M 1-x-y ) 1-z N z O 2-c X c The material has the following properties: 0.9 ≤ k ≤ 1.1, 0 ≤ a ≤ 0.2, 0.40 ≤ x ≤ 1.00, 0 ≤ y ≤ 0.15, 0 ≤ (1-xy), 0 ≤ z ≤ 0.5, 0 ≤ c ≤ 1. The M element includes one or both of Mn and Al, the Q element includes one or more of Na, K, Rb and Ca, the N element includes one or more of Al, Ti, Zr, Nb, Sr, Sb, Y, Ba, Co, Mn, Mg, W, Si, Mo, P and C, and the X element includes one or more of B, F, S and Cl.

27. The positive electrode active material according to claim 26, wherein, 0.92 ≤ k ≤ 1.08。 28. The positive electrode active material according to claim 26, wherein, 0.95 ≤ k ≤ 1.05。 29. The positive electrode active material according to claim 26, wherein, 0.96 ≤ k ≤ 1.04。 30. The positive electrode active material according to claim 26, wherein, 0.98 ≤ k ≤ 1.02。 31. The positive electrode active material according to claim 26, wherein, 0.99 ≤ k ≤ 1.01。 32. The positive electrode active material according to claim 26, wherein, k=1。 33. The positive electrode active material according to any one of claims 26 to 31, wherein, 0.50 ≤ x ≤ 1.00。 34. The positive electrode active material according to claim 33, wherein, 0.60 ≤ x ≤ 1.00。 35. The positive electrode active material according to claim 34, wherein, 0.60 ≤ x < 1.00。 36. The positive electrode active material according to any one of claims 26 to 32, wherein, 0 ≤ a ≤ 0.2, 0.60 ≤ x < 1.00, 0 < y ≤ 0.15, 0 < (1-xy), 0 ≤ z ≤ 0.5, 0 ≤ c ≤ 1.

37. The positive electrode active material according to any one of claims 1 to 36, wherein, The nickel-lithium molar ratio R in particle A and particle B Ni / Li Each independently is ≥ 0.

4.

38. The positive electrode active material according to claim 37, wherein, The nickel-lithium molar ratio R in particle A and particle B Ni / Li Each independently is ≥ 0.

5.

39. The positive electrode active material according to claim 37, wherein, The nickel-lithium molar ratio R in particle A and particle B Ni / Li Each independently is ≥ 0.

6.

40. The positive electrode active material according to claim 37, wherein, The nickel-lithium molar ratio R in particle A and particle B Ni / Li Each independently has a value ≥ 0.

7.

41. The positive electrode active material according to claim 37, wherein, The nickel-lithium molar ratio R in particle A and particle B Ni / Li Each independently has a value ≥ 0.

8.

42. The positive electrode active material according to claim 37, wherein, The nickel-lithium molar ratio R in particle A Ni / Li Selected from 0.7 to 1.

0.

43. The positive electrode active material according to claim 37, wherein, The nickel-lithium molar ratio R in particle B Ni / Li Selected from 0.8 to 1.

0.

44. The positive electrode active material according to claim 37, wherein, The nickel-lithium molar ratio R in particle B Ni / Li Selected from 0.8 to 0.

96.

45. The positive electrode active material according to any one of claims 1 to 44, wherein, The true density of particle A and particle B is independently greater than 4.0 g / cc.

46. ​​The positive electrode active material according to claim 45, wherein, The true density of particle A and particle B are each independently selected from 4.0 g / cc to 4.8 g / cc.

47. The positive electrode active material according to claim 45, wherein, The true density of each of the A particles is independently selected from 4.6 g / cc to 4.8 g / cc.

48. The positive electrode active material according to claim 45, wherein, The true density of each of the B particles is independently selected from 4.5 g / cc to 4.8 g / cc.

49. The positive electrode active material according to any one of claims 1 to 48, wherein, Each of the A particles and the B particles independently includes a body structure and an oxide layer covering at least a portion of the surface of the body structure; in, The bulk structure includes a chemical formula of Li k1-a1 Q a1 (Ni x1 Co y1 M 1-x1-y1 ) 1-z1 N z1 The material of O2 has the following properties: 0.9 ≤ k1 ≤ 1.1, 0 ≤ a1 ≤ 0.20, 0.40 ≤ x1 ≤ 1.00, 0 ≤ y1 ≤ 0.15, 0 ≤ (1-x1-y1), 0 ≤ z1 ≤ 0.5, and the element Q includes one or more of Na, K, Rb and Ca, the element M includes one or two of Mn and Al, and the element N includes one or more of Al, Ti, Zr, Nb, Sr, Sb, Y, Ba, Co, Mn, Mg, Si, P, Mo, C and W. The oxide layer comprises Li k2-a2 Q' a2 (Ni) x2 Co y2 M' 1-x2-y2 ) 1-z2 N' z2 O 2-c2 X c2 The material has the following properties: 0.9 ≤ k2 ≤ 1.1, 0 ≤ a2 ≤ 0.20, 0.40 ≤ x2 ≤ 1.00, 0 ≤ y2 ≤ 0.15, 0 ≤ (1-x2-y2), 0 < z2 ≤ 0.5, 0 ≤ c2 ≤ 1, and the element Q' includes one or more of Na, K, Rb and Ca, the element M' includes one or two of Mn and Al, the element N' includes one or more of Al, Ti, Zr, Nb, Sr, Sb, Y, Ba, Co, Mn, Mg, W, Mo, Si, C and P, and the element X includes one or more of B, Cl, S and F.

50. The positive electrode active material according to claim 49, wherein, 0.92 ≤ k1 ≤ 1.08, and / or 0.92 ≤ k2 ≤ 1.

08.

51. The positive electrode active material according to claim 49 or 50, wherein, 0.95 ≤ k1 ≤ 1.05, and / or 0.95 ≤ k2 ≤ 1.

05.

52. The positive electrode active material according to any one of claims 49 to 51, wherein, 0.96 ≤ k1 ≤ 1.04, and / or 0.96 ≤ k2 ≤ 1.

04.

53. The positive electrode active material according to any one of claims 49 to 52, wherein, 0.98 ≤ k1 ≤ 1.02, and / or 0.98 ≤ k2 ≤ 1.

02.

54. The positive electrode active material according to any one of claims 49 to 53, wherein, 0.99 ≤ k1 ≤ 1.01, and / or 0.99 ≤ k2 ≤ 1.

01.

55. The positive electrode active material according to any one of claims 49 to 54, wherein, k1 equals 1, and / or k2 equals 1.

56. The positive electrode active material according to any one of claims 49 to 55, wherein, 0.50 ≤ x1 ≤ 1.00, and / or 0.50 ≤ x2 ≤ 1.

00.

57. The positive electrode active material according to any one of claims 49 to 56, wherein, 0.60 ≤ x1 ≤ 1.00, and / or 0.60 ≤ x2 ≤ 1.

00.

58. The positive electrode active material according to any one of claims 49 to 57, wherein, 0 ≤ a1 ≤ 0.20, 0.60 ≤ x1 < 1.00, 0 < y1 ≤ 0.15, 0 < (1-x1-y1), 0 ≤ z1 ≤ 0.5; and / or, 0 ≤ a2 ≤ 0.20, 0.60 ≤ x2 < 1.00, 0 < y2 ≤ 0.15, 0 < (1-x2-y2), 0 < z2 ≤0.5, 0 ≤ c2 ≤ 1.

59. The positive electrode active material according to any one of claims 49 to 58, wherein, 0.70 ≤ x1 ≤ 1.00, and / or 0.70 ≤ x2 ≤ 1.

00.

60. The positive electrode active material according to any one of claims 49 to 59, wherein, Q' a2 Ni x2 Co y2 M' 1-x-y With Q a1 Ni x1 Co y1 M 1-x1-y1 same.

61. The positive electrode active material according to any one of claims 49 to 60, wherein, The nitrogen element includes one or more of Al, Ti, Zr, Nb, Sr, Sb, Y, Mg, and W; and / or, The N element includes one or more of Al, Ti, Zr, Sr, Sb, Mo, Nb, Mg, Y, and W.

62. The positive electrode active material according to any one of claims 49 to 61, wherein, The thickness of the oxide layer is 0~100 nm.

63. The positive electrode active material according to claim 62, wherein, The thickness of the oxide layer is 1 nm to 100 nm.

64. The positive electrode active material according to claim 62, wherein, The thickness of the oxide layer is 1 nm to 20 nm.

65. The positive electrode active material according to any one of claims 49 to 64, wherein, The oxide layer has a mass percentage of 0.01% to 5% relative to the bulk structure.

66. The positive electrode active material according to claim 65, wherein, The oxide layer has a mass percentage of 0.05% to 4% relative to the bulk structure.

67. The positive electrode active material according to any one of claims 49 to 66, wherein, The nitrogen element in the oxide layer accounts for 0.01% to 4% of the mass of the positive electrode active material.

68. The positive electrode active material according to claim 67, wherein, The nitrogen element in the oxide layer accounts for 0.05% to 4% of the mass of the positive electrode active material.

69. The positive electrode active material according to any one of claims 1 to 68, wherein, The average specific surface area of ​​the positive electrode active material is 0.3 cm². 2 / g ~ 1.5 cm 2 / g.

70. The positive electrode active material according to any one of claims 1 to 69, wherein, The free lithium content in the positive electrode active material is less than 3000 ppm by mass.

71. The positive electrode active material according to any one of claims 1 to 70, wherein, The ratio of I003 grain content to I104 grain content in the positive electrode active material is I003 / I104≥1.2, calculated as the ratio of the characteristic peak areas of the I003 crystal plane to the I104 crystal plane in the XRD pattern.

72. The positive electrode active material according to claim 71, wherein, I003 / I104 are selected from 1.2~2.

73. The positive electrode active material according to claim 71, wherein, I003 / I104 are selected from 1.3~2.

74. The positive electrode active material according to claim 71, wherein, I003 / I104 are selected from 1.3 to 1.

6.

75. The positive electrode active material according to any one of claims 1 to 74, wherein, In the B particles, at least a portion of the primary particles are oriented radially.

76. A positive electrode sheet comprising a positive current collector and a positive active material layer located on at least one surface of the positive current collector, the positive active material layer comprising the positive active material according to any one of claims 1 to 75.

77. The positive electrode sheet according to claim 76, wherein, The compaction density of the positive electrode sheet is 3.3 g / cm³. 3 ~3.7 g / cm 3 .

78. An electrochemical energy storage device comprising the positive electrode, negative electrode, and separator as described in claim 76 or 77, wherein, The separator is disposed between the positive electrode and the negative electrode.

79. A secondary battery comprising at least one of the positive electrode sheet of claim 76 or 77 and the electrochemical energy storage device of claim 78.

80. An electrical device comprising at least one of the positive electrode sheet of claim 76 or 77, the electrochemical energy storage device of claim 78, and the secondary battery of claim 79.

81. A method for preparing a positive electrode active material, comprising the following steps: mixing the A particles and the B particles according to a preset mass ratio to prepare the positive electrode active material; wherein the A particles and the B particles are as defined in any one of claims 1 to 75; in, The A-particles are prepared using a method comprising the following steps: lithium hydroxide, nickel-cobalt M-body precursor material Ni x Co y M 1-x-y (OH)2, along with optional Q and optional N additives, are mixed and sintered once in the presence of oxygen at a temperature T1. The B particles are prepared using a method comprising the following steps: lithium hydroxide, nickel-cobalt M-body precursor material Ni x Co y M 1-x-y (OH)2, along with optional Q and optional N additives, are mixed and sintered once in the presence of oxygen at a temperature T2. Wherein, the Q additive and the N additive are additives containing the Q element and additives containing the N element, respectively; Wherein, the x, y, M, Q and N elements are defined as in any one of claims 26 to 36; The temperature T1 is higher than the temperature T2.

82. The method for preparing the positive electrode active material according to claim 81, wherein, The method for preparing the A particles includes: after a first sintering in the presence of oxygen and at a temperature T1, adding at least one of additive X and additive N to the first sintering product, mixing, and then performing a second sintering in the presence of oxygen. The method for preparing the B particles includes: after a first sintering in the presence of oxygen and at a temperature T2, adding at least one of additive X and additive N to the first sintering product, mixing, and then performing a second sintering in the presence of oxygen. Wherein, the X additive is an additive containing element X, and element X includes one or more of B, F, S and Cl.

83. The method for preparing the positive electrode active material according to claim 82, wherein, In the step of preparing the A particles, in the sintering step under the presence of oxygen, the primary sintering temperature is 700 °C ~ 950 °C, and the secondary sintering temperature is 300 °C ~ 600 °C; In the step of preparing the B particles, the sintering step in the presence of oxygen has a primary sintering temperature of 700 °C ~ 900 °C and a secondary sintering temperature of 300 °C ~ 600 °C.

84. The method for preparing the positive electrode active material according to claim 82, wherein, In the step of preparing the A particles, in the sintering step under the presence of oxygen, the primary sintering temperature is 750°C ~ 900°C, and the secondary sintering temperature is 350°C ~ 550°C; In the step of preparing the B particles, the sintering step in the presence of oxygen has a primary sintering temperature of 750°C to 850°C and a secondary sintering temperature of 350°C to 550°C.

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