Secondary battery and electric device

Abstract

The application provides a secondary battery, which comprises a positive electrode sheet, the positive electrode sheet has a positive electrode active material thereon, the positive electrode active material comprises agglomerate type positive electrode material and single crystal type positive electrode material; the volume average particle size Dv50 of the agglomerate type positive electrode material is 8-15 mu m, and the primary particle size of the agglomerate type positive electrode material is 0.1-0.6 mu m; the volume average particle size Dv50 of the single crystal type positive electrode material is 2.5-4 mu m, and the primary particle size of the single crystal type positive electrode material is 0.8-2 mu m; the mass ratio of the agglomerate type positive electrode material and the single crystal type positive electrode material is greater than or equal to 1; and the application also relates to a corresponding electric device. The secondary battery has high energy density and good cycle life.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of secondary batteries, in particular to a secondary battery and a power utilization device. BACKGROUND

[0002] In recent years, with the application range of secondary batteries becoming more and more extensive, secondary batteries are widely used in energy storage power supply systems such as hydraulic, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles and electric vehicles.

[0003] Since the secondary battery has achieved great development, higher requirements are put forward for the battery performance. The secondary battery with high energy density and long cycle life has high requirements for the positive electrode sheet. For example, the positive electrode sheet of the secondary battery with high energy density and long cycle life should have a high compaction density, and should also have a long service life.

[0004] Therefore, one of the focuses of the person skilled in the art is to seek a secondary battery with high energy density and good cycle life. SUMMARY

[0005] The present application is carried out in view of the above-mentioned problems, and one of the purposes is to provide a secondary battery with high energy density and good cycle life.

[0006] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a secondary battery, comprising a positive electrode sheet, wherein the positive electrode sheet has a positive electrode active material thereon, and the positive electrode active material comprises an agglomerate type positive electrode material and a single crystal type positive electrode material.

[0007] The volume average particle size Dv50 of the agglomerate type positive electrode material is 8 μm to 15 μm, and the primary particle size of the agglomerate type positive electrode material is 0.1 μm to 0.6 μm.

[0008] The volume average particle size Dv50 of the single crystal type positive electrode material is 2.5 μm to 4 μm, and the primary particle size of the single crystal type positive electrode material is 0.8 μm to 2 μm.

[0009] The mass ratio of the agglomerate type positive electrode material to the single crystal type positive electrode material is greater than or equal to 1.

[0010] The application can ensure high pressure density of the positive plate, and can make the positive plate have good cycle life and capacity, so that the secondary battery using the positive plate has high energy density and long cycle life.

[0011] In any embodiment, the mass ratio of the agglomerate type positive material and the quasi-single crystal type positive material is 1-9:1.

[0012] In any embodiment, the mass ratio of the agglomerate type positive material and the quasi-single crystal type positive material is 2.3-3:1. In this way, the energy density and cycle life of the secondary battery can be further improved.

[0013] In any embodiment, the volume average particle size Dv50 of the quasi-single crystal type positive material is 3-3.5 μm, and / or the primary particle size of the quasi-single crystal type positive material is 1.2-1.5 μm. In this way, the energy density of the secondary battery can be further improved.

[0014] In any embodiment, the primary particle size of the agglomerate type positive material is 0.2-0.4 μm. In this way, the energy density of the secondary battery can be further improved.

[0015] In any embodiment, the agglomerate type positive material has a chemical formula of Li x1 Ni y1 Co z1 M 1-y1-z1 O2, wherein 0.9≤x1≤1, 0.9≤y1≤0.98, 0.05≤z1≤0.1, and M includes one or more of Mn, Al, B, Zr, Sr, Y, Sb, W, Ti, Mg and Nb. In this way, the capacity of the positive plate can be further improved, and the energy density of the secondary battery can be further improved.

[0016] In any embodiment, 0.9≤y1≤0.96. In this way, the nickel content of the agglomerate type positive material is appropriately reduced while ensuring that the positive plate has high capacity.

[0017] In any embodiment, the quasi-single crystal type positive material has a chemical formula of Li x2 Ni y2 Co z2 M′ 1-y2-z2O2, wherein 0.9≤x2≤1, 0.9≤y2≤0.98, 0.05≤z2≤0.1, and M' comprises one or more of Mn, Al, B, Zr, Sr, Y, Sb, W, Ti, Mg, and Nb. In this way, the capacity of the positive electrode tab can be further improved, and the energy density of the secondary battery can be improved.

[0018] In any embodiment, 0.92≤y2≤0.98. In this way, the capacity of the positive electrode tab can be further improved, and the energy density of the secondary battery can be improved.

[0019] In any embodiment, y2>y1. In this way, the capacity of the positive electrode tab can be better improved, and the energy density of the secondary battery can be improved, without the overall nickel content of the positive electrode active material being relatively very high.

[0020] In any embodiment, the particle size distribution span (Dv90-Dv10) / Dv50 of the agglomerate-type positive electrode material is ≤1.5. In this way, the positive electrode tab can be provided with sufficient filling space and capacity play, the capacity of the positive electrode tab can be improved, and the energy density of the secondary battery can be improved.

[0021] In any embodiment, the particle size distribution span (Dv90-Dv10) / Dv50 of the agglomerate-type positive electrode material is 0.7-1.4. In this way, the positive electrode tab can be better provided with sufficient filling space, the capacity of the positive electrode tab can be better improved, and the energy density of the secondary battery can be improved.

[0022] In any embodiment, the BET specific surface area of the agglomerate-type positive electrode material is 0.2m 2 / g-0.8m 2 / g. In this way, the excessive active surface of the agglomerate-type positive electrode material can be prevented from contacting the electrolyte, and the excessive corrosion of the agglomerate-type positive electrode material by the electrolyte can be avoided, so that the life of the positive electrode tab can be improved, and the cycle life of the secondary battery can be improved.

[0023] In any embodiment, the BET specific surface area of the agglomerate-type positive electrode material is 0.3m 2 / g-0.6m 2 / g. In this way, the life of the positive electrode tab can be better improved, and the cycle life of the secondary battery can be improved.

[0024] In any embodiment, the particle size distribution span (Dv90-Dv10) / Dv50 of the single-crystal-like positive electrode material is ≥1.2. In this way, the pressure resistance of the positive electrode tab can be improved, and the life of the positive electrode tab can be improved, and the cycle life of the secondary battery can be improved.

[0025] In any embodiment, the particle size distribution span (Dv90-Dv10) / Dv50 of the single-crystal-like positive electrode material is 1.3-1.5. In this way, the compression resistance of the positive electrode sheet can be improved, the life of the positive electrode sheet can be improved, and the cycle life of the secondary battery can be improved.

[0026] In any embodiment, the BET specific surface area of the single-crystal-like positive electrode material is 0.8 m 2 / g-1.3 m 2 / g. In this way, a morphology with high dispersity can be achieved, which is conducive to improving the space utilization of the positive electrode sheet.

[0027] In any embodiment, the BET specific surface area of the single-crystal-like positive electrode material is 0.85 m 2 / g-1.15 m 2 / g. In this way, the space utilization of the positive electrode sheet can be further improved.

[0028] In any embodiment, the particle size distribution span (Dv90-Dv10) / Dv50 of the positive electrode active material is 1.5-2.1. In this way, the positive electrode sheet can obtain a higher compaction density and processing performance at a higher membrane loading.

[0029] In any embodiment, the BET specific surface area of the positive electrode active material is 0.5 m 2 / g-0.7 m 2 / g. In this way, the positive electrode sheet can also obtain a higher compaction density and processing performance at a higher membrane loading, and the energy density of the secondary battery can be improved.

[0030] In any embodiment, the mass percentage of the positive electrode active material in the positive electrode film layer in the positive electrode sheet is 95%-99.5%. In this way, the gram capacity of the positive electrode active material in the secondary battery can be ensured, the capacity of the positive electrode sheet can be improved, and the energy density of the secondary battery can be improved.

[0031] In any embodiment, the areal density of the positive electrode active material in the positive electrode sheet is 21.5 mg / cm 2 -32.5 mg / cm 2 . In this way, by using thick positive electrode coating and combining with high compaction density, the capacity of the positive electrode sheet can be further improved, and the energy density of the secondary battery can be improved.

[0032] The second aspect of the present application provides a power utilization device, which comprises the secondary battery of the first aspect of the present application.

[0033] The positive electrode of the secondary battery of this application is graded by using a near-monocrystalline positive electrode material with a Dv50 of 2.5μm to 4μm and a primary particle size of 0.8μm to 2μm, and an agglomerated positive electrode material with a Dv50 of 8μm to 15μm and a primary particle size of 0.1μm to 0.6μm, at a mass ratio greater than or equal to 1. While ensuring the high voltage density of the positive electrode, the positive electrode can obtain better life and capacity, thereby enabling the secondary battery to have high energy density and long cycle life. Attached Figure Description

[0034] To better describe and illustrate embodiments and / or examples of this application, 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 currently described embodiments and / or examples, or the best mode of these applications as currently understood.

[0035] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application;

[0036] Figure 2 yes Figure 1 An exploded view of a secondary battery according to an embodiment of this application is shown.

[0037] Figure 3 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0038] Explanation of reference numerals in the attached figures:

[0039] 5. Secondary battery; 51. Housing; 52. Electrode assembly; 53. Cover plate; 6. Electrical device. Detailed Implementation

[0040] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode sheet, its preparation method, secondary battery, and power-consuming device 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.

[0041] 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 understood that ranges of 60–110 and 80–120 are also expected. 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 "a–b" 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.

[0042] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0043] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0044] 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.

[0045] 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.

[0046] 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". More specifically, 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).

[0047] The weights mentioned in this application specification may be in units of weight known in the chemical industry, such as μg, mg, g, and kg.

[0048] Currently, with the increasingly widespread application of rechargeable batteries, higher requirements are being placed on their performance. Energy density and cycle life are two crucial performance indicators for rechargeable batteries. The energy density and cycle life of traditional rechargeable batteries need improvement. Therefore, providing a rechargeable battery with high energy density and good cycle life has become an important research direction in this field. To address this, this application provides a rechargeable battery that, primarily through the selection and proportioning of the positive electrode active material in the positive electrode sheet, achieves high compaction density and long service life, while also possessing high capacity, thereby enabling the rechargeable battery to have high energy density and a long cycle life.

[0049] One aspect of this application provides a secondary battery, including a positive electrode sheet with a positive active material on it. The positive active material includes an aggregated positive electrode material and a near-monocrystalline positive electrode material. The aggregated positive electrode material has a volume average particle size Dv50 of 8 μm to 15 μm and a primary particle size of 0.1 μm to 0.6 μm. The near-monocrystalline positive electrode material has a volume average particle size Dv50 of 2.5 μm to 4 μm and a primary particle size of 0.8 μm to 2 μm. The mass ratio of the aggregated positive electrode material to the near-monocrystalline positive electrode material is greater than or equal to 1.

[0050] To achieve high energy densities of 360Wh / kg to 500Wh / kg in rechargeable batteries, the design requires high-nickel active materials for the positive electrode and a high coating density. Correspondingly, the negative electrode uses graphite combined with high-silicon content materials as its active material. However, the thick coating design of the positive electrode leads to two problems for rechargeable batteries: Firstly, with a high coating density (CW), the compaction density of the positive electrode sheet is limited, typically <3.3 g / cm³. 3 On the one hand, a smaller compaction of the positive electrode sheet will reduce the energy density of the battery; on the other hand, when the positive electrode active material is a polycrystalline material, the specific surface area is large, the side reactions increase, and the cycle performance of high energy density lithium-ion batteries decreases.

[0051] The secondary battery described above in this application has a positive electrode active material in its positive electrode sheet, which includes an aggregated positive electrode material and a near-monocrystalline positive electrode material. Specifically, the volume average particle size Dv50 of the aggregated positive electrode material is controlled to be between 8 μm and 15 μm, and the primary particle size of the aggregated positive electrode material is between 0.1 μm and 0.6 μm. The volume average particle size Dv50 of the near-monocrystalline positive electrode material is controlled to be between 2.5 μm and 4 μm, and the primary particle size of the near-monocrystalline positive electrode material is between 0.8 μm and 2 μm. Furthermore, the mass ratio of the aggregated positive electrode material to the near-monocrystalline positive electrode material is controlled to be greater than or equal to 1.

[0052] Thus, by using aggregated cathode materials with specific volume average particle size Dv50 and specific primary particle size, and quasi-monocrystalline cathode materials with specific volume average particle size Dv50 and specific primary particle size, and mixing them in a specific mass ratio; the aggregated cathode material has a larger particle size, which acts as a skeleton and can increase the electrode capacity; the quasi-monocrystalline cathode material has a smaller particle size, which can fill the gaps between the aggregated cathode material particles, increase the compaction density of the cathode sheet, and the quasi-monocrystalline cathode material has a longer lifespan, which can extend the service life of the electrode sheet.

[0053] Combining the above two different types and particle sizes of positive electrode active materials can significantly improve the porosity and volume utilization between particles, thereby enhancing the compressive strength of the positive electrode sheet. Agglomerated positive electrode materials with a Dv50 of 8μm to 15μm can serve as the framework for the positive electrode sheet. Excessively large particle sizes can easily lead to edge cracks and limit specific capacity, while excessively small particle sizes lack a skeletal function. Quasi-single-crystal positive electrode materials with a Dv50 of 2.5μm to 4μm serve as secondary fillers for agglomerated positive electrode materials, improving space utilization. Due to their high dispersibility and compressive strength, they can fully fill the pores between the agglomerated positive electrode material particles.

[0054] Since the specific capacity of high-nickel single-crystal cathode materials is lower than that of agglomerated cathode materials, and agglomerated cathode materials are not pressure resistant, controlling the mass ratio of the two to be greater than or equal to 1 can maximize the compatibility of specific capacity and compaction density. Furthermore, such dense packing is less likely to cause particle displacement / slippage under high pressure, thereby avoiding large elongation of the electrode sheet and increasing its brittleness.

[0055] In addition, the Dv50 of the quasi-single-crystal cathode material is 2.5μm to 4μm, and its primary particle size is 0.8μm to 2μm, which ensures cathode capacity and lifespan while achieving high cathode pressure density. When the Dv50 of the near-monocrystalline cathode material is too large, the compaction density of the electrode will decrease. When the primary particle size of the near-monocrystalline cathode material is less than 0.8 μm, the number of primary particles required to form the near-monocrystalline cathode material is too large, and its morphology will be closer to that of an agglomerate. The active surface area of ​​the near-monocrystalline cathode material is exposed too much, making it susceptible to corrosion by the electrolyte, which leads to a decrease in the lifespan of the cathode and a decrease in compressive strength. When the primary particle size of the near-monocrystalline cathode material is greater than 2 μm, the number of primary particles required to form the near-monocrystalline cathode material is too small. It may only take 2 to 3 primary particles to form the near-monocrystalline cathode material. The active surface area of ​​the near-monocrystalline cathode material is exposed too little, the lithium-ion transport path is limited, the kinetic performance deteriorates, and the capacity and lifespan of the cathode are affected.

[0056] This application employs a near-monocrystalline cathode material with a Dv50 of 2.5μm to 4μm and a primary particle size of 0.8μm to 2μm, and aggregated cathode material with a Dv50 of 8μm to 15μm and a primary particle size of 0.1μm to 0.6μm, graded at a mass ratio of 1 to 9:1. This approach ensures high voltage density of the cathode while achieving good lifespan and capacity, thereby improving the energy density and cycle life of the secondary battery. The specific capacity of the cathode material in the secondary battery of this application can reach 215mAh / g to 230mAh / g at 0.33C.

[0057] It should be noted that quasi-single-crystal cathode materials are irregular structures formed by the accumulation of several primary particles; while agglomerated cathode materials are regular small spheres formed by a larger number of smaller spherical primary particles. It can be understood that the volume average particle size Dv50 of quasi-single-crystal cathode materials can be, but is not limited to, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, 3.0μm, 3.1μm, 3.2μm, 3.3μm, 3.4μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, and 4μm. The primary particle size of quasi-single-crystal cathode materials can be, but is not limited to, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, and 2 μm. The volume average particle size (Dv50) of agglomerated cathode materials can be, but is not limited to, 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, and 15 μm. The primary particle size of agglomerated cathode materials can be, but is not limited to, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, and 0.6 μm. The mass ratio of agglomerated cathode materials and quasi-single-crystal cathode materials can be, but is not limited to, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, and 9:1.

[0058] In some embodiments, the mass ratio of agglomerated cathode material to quasi-monocrystalline cathode material is 1 to 9:1. This can further improve the energy density and cycle life of the secondary battery.

[0059] In some embodiments, the mass ratio of agglomerated cathode material to near-monocrystalline cathode material is 2.3 to 3:1. Using such a particle mass ratio can further improve the energy density and cycle life of the secondary battery.

[0060] In some embodiments, the volume average particle size Dv50 of the near-monocrystalline cathode material is 3 μm to 3.5 μm, and the primary particle size of the near-monocrystalline cathode material is 1.2 μm to 1.5 μm. This is more conducive to improving the energy density of secondary batteries using this cathode electrode.

[0061] In some embodiments, the primary particle size of the agglomerated cathode material is 0.2 μm to 0.4 μm. This is more conducive to improving the energy density and cycle life of the secondary battery.

[0062] In some embodiments, the agglomerate-type cathode material has the chemical formula Li. x1 Niy1 Co z1 M 1-y1-z1 O2, where 0.9≤x1≤1, 0.9≤y1≤0.98, 0.05≤z1≤0.1, and M includes one or more of Mn, Al, B, Zr, Sr, Y, Sb, W, Ti, Mg, and Nb. Thus, using high-nickel active materials in agglomerated cathode materials can increase the capacity of the cathode sheet, thereby improving the energy density of the secondary battery.

[0063] It is understood that in the chemical formula of agglomerate-type cathode materials, x1 can be, but is not limited to, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1; y1 can be, but is not limited to, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98; and z1 can be, but is not limited to, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1.

[0064] In some embodiments, the chemical formula of the agglomerate-type cathode material contains 0.9 ≤ y1 ≤ 0.96. Because the primary particle size of the agglomerate-type cathode material is relatively small and there are more grain boundaries within the agglomerates, it is more conducive to lithium-ion transport, thus achieving high capacity even with a relatively low nickel content.

[0065] In some embodiments, the chemical formula of the quasi-single-crystal cathode material is Li. x2 Ni y2 Co z2 M′ 1-y2-z2 O2, where 0.9≤x²≤1, 0.9≤y²≤0.98, 0.05≤z²≤0.1, and M′ includes one or more of Mn, Al, B, Zr, Sr, Y, Sb, W, Ti, Mg, and Nb. Thus, even using high-nickel active materials in quasi-single-crystal cathode materials can further improve the capacity of the cathode sheet and increase the energy density of the secondary battery.

[0066] It is understood that in the chemical formula of the quasi-single-crystal cathode material, x2 can be, but is not limited to, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1; in the chemical formula of the quasi-single-crystal cathode material, y2 can be, but is not limited to, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98; and in the chemical formula of the quasi-single-crystal cathode material, z2 can be, but is not limited to, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1.

[0067] In some implementations, 0.92 ≤ y2 ≤ 0.98. Because the primary particle size of the quasi-monocrystalline cathode material is relatively larger, and the secondary sphere size of the quasi-monocrystalline cathode material is smaller than that of the secondary sphere size of the agglomerated cathode material, and there is no interface for rapid lithium-ion transport inside the quasi-monocrystalline cathode material, setting the nickel content y2 of the quasi-monocrystalline cathode material to 0.92–0.98 can further improve the capacity of the cathode sheet and increase the energy density of the secondary battery.

[0068] In some implementations, y2 > y1. That is, the nickel content of the quasi-monocrystalline cathode material is greater than that of the agglomerated cathode material. This setting allows for a better increase in the capacity of the cathode sheet, thereby improving the energy density of the secondary battery, even when the overall nickel content of the cathode active material is not very high.

[0069] It should be noted that the elements M in the chemical formula of quasi-single-crystal cathode materials and M′ in the chemical formula of aggregated cathode materials are different, and their roles in the cathode material synthesis process are also different. For example, when M and M′ are high-valence elements such as Sb and Nb, they can refine the grains, making the primary particle size of the cathode material smaller, further improving the capacity and power performance of the cathode material. When M and M′ are Sr, they can act as a flux, allowing cathode materials of the corresponding particle size to be obtained without too high a temperature during the sintering process, reducing the formation of rock salt phase, and thus improving the capacity and cycle life of the cathode sheet. The element types of M and M′ in the chemical formula of the cathode material can be determined according to actual needs.

[0070] In some embodiments, the particle size distribution span (Dv90-Dv10) / Dv50 of the agglomerated cathode material is ≤1.5. Controlling the particle size distribution span (Dv90-Dv10) / Dv50 of the agglomerated cathode material to ≤1.5 can provide sufficient filling space and specific capacity for the cathode sheet.

[0071] It is understandable that the particle size distribution range (Dv90-Dv10) / Dv50 of the agglomerate type cathode material can be, but is not limited to, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, and 1.5.

[0072] In some embodiments, the particle size distribution range (Dv90-Dv10) / Dv50 of the agglomerated cathode material is 0.7 to 1.4. This allows for better provision of sufficient filling space for the cathode sheet, thereby improving the specific capacity of the cathode sheet and increasing the energy density of the secondary battery.

[0073] In some embodiments, the BET specific surface area of ​​the agglomerated cathode material is 0.2 m².2 / g~0.8m 2 / g. The BET specific surface area of ​​the agglomerated cathode material was controlled at 0.2m². 2 / g~0.8m 2 The ratio between / g can prevent excessive contact between the active surface of the agglomerated cathode material and the electrolyte, thus avoiding excessive corrosion of the agglomerated cathode material by the electrolyte, thereby improving the life of the cathode sheet and the cycle life of the secondary battery.

[0074] It is understandable that the BET specific surface area of ​​agglomerated cathode materials can be, but is not limited to, 0.2 m². 2 / g, 0.3m 2 / g, 0.4m 2 / g, 0.5m 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g.

[0075] In some embodiments, the BET specific surface area of ​​the agglomerated cathode material is 0.3 m². 2 / g~0.6m 2 / g. This can better improve the lifespan of the positive electrode and the cycle life of the secondary battery.

[0076] In some embodiments, the particle size distribution span (Dv90-Dv10) / Dv50 of the near-monocrystalline cathode material is ≥1.2. Controlling the particle size distribution span (Dv90-Dv10) / Dv50 of the near-monocrystalline cathode material to ≥1.2 can improve the compressive strength of the cathode sheet, thereby increasing the lifespan of the cathode sheet and the cycle life of the secondary battery. It can be understood that the particle size distribution span (Dv90-Dv10) / Dv50 of the near-monocrystalline cathode material can be, but is not limited to, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.0.

[0077] In some embodiments, the particle size distribution span (Dv90-Dv10) / Dv50 of the quasi-monocrystalline cathode material is 1.3 to 1.5. This can better improve the compressive strength of the cathode sheet, better improve the life of the cathode sheet, and improve the cycle life of the secondary battery.

[0078] In some implementations, the BET specific surface area of ​​the quasi-monocrystalline cathode material is 0.8 m². 2 / g~1.3m 2 / g. The BET specific surface area of ​​the quasi-monocrystalline cathode material was controlled at 0.8m². 2 / g~1.3m 2Within the range of / g, a highly dispersed morphology can be achieved, which is beneficial for improving the space utilization of the positive electrode sheet. It can be understood that the BET specific surface area of ​​the quasi-single-crystal positive electrode material can be, but is not limited to, 0.8m². 2 / g, 0.9m 2 / g, 1.0m 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g.

[0079] In some implementations, the BET specific surface area of ​​the quasi-monocrystalline cathode material is 0.85 m². 2 / g~1.15m 2 / g. In this way, the space utilization rate of the positive electrode can be further improved.

[0080] In some embodiments, the particle size distribution span (Dv90-Dv10) / Dv50 of the positive electrode active material is 1.5 to 2.1. This allows the positive electrode sheet to achieve higher compaction density and processing performance with a higher film loading, thereby improving the energy density of the secondary battery. It is understood that the particle size distribution span (Dv90-Dv10) / Dv50 of the mixed positive electrode active material can be, but is not limited to, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, or 2.1.

[0081] It should be noted that the volume average particle sizes Dv10, Dv50, and Dv90 of the cathode material are well-known concepts in the art. Specifically, Dv10 refers to the particle size that reaches 10% of the total volume from the smallest particle size in the particle size distribution of the powder, typically expressed in μm. Dv50 refers to the particle size that reaches 50% of the total volume from the smallest particle size in the particle size distribution of the powder, and Dv90 refers to the particle size that reaches 90% of the total volume from the smallest particle size in the particle size distribution of the powder, based on volume.

[0082] In some embodiments, the BET specific surface area of ​​the positive electrode active material is 0.5 m². 2 / g~0.7m 2 / g. In this way, the positive electrode sheet can achieve higher compaction density and processing performance under higher film loading, thereby improving the energy density of the secondary battery. It is understood that the BET specific surface area of ​​the mixed positive electrode active material can be, but is not limited to, 0.5m². 2 / g, 0.55m 2 / g, 0.6m 2 / g, 0.65m 2 / g, 0.7m 2 / g. By adopting the above-mentioned particle size distribution range and BET specific surface area of ​​the mixed positive electrode active material, the elongation of the positive electrode sheet after cold pressing can be ≤0.8%.

[0083] In some embodiments, the positive electrode active material accounts for 95% to 99.5% of the mass percentage of the positive electrode film in the positive electrode sheet. Controlling the mass percentage of the positive electrode active material in the positive electrode film layer within this range ensures the specific capacity of the positive electrode active material in the secondary battery, thereby improving the energy density of the secondary battery. It is understood that the mass percentage of the positive electrode active material in the positive electrode film layer can be, but is not limited to, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, and 99.5%.

[0084] In some embodiments, the areal density of the positive electrode active material coating in the positive electrode sheet is 21.5 mg / cm². 2 ~32.5mg / cm 2 The positive electrode sheet of this application can achieve a high compaction density while maintaining a high surface density of the positive electrode active material coating, with a compaction density reaching 3.7 g / cm³. 3 Furthermore, the elongation of the cold-pressed electrode is relatively small, making it less prone to breakage during later use. Therefore, it is understandable that the surface density of the positive electrode active material coating in the positive electrode can be, but is not limited to, 21.5 mg / cm³. 2 22mg / cm 2 22.5 mg / cm 2 23mg / cm 2 23.5 mg / cm 2 24mg / cm 2 24.5 mg / cm 2 25mg / cm 2 25.5 mg / cm 2 26mg / cm 2 26.5 mg / cm 2 27mg / cm 2 27.5 mg / cm 2 28mg / cm 2 28.5 mg / cm 2 29mg / cm 2 29.5 mg / cm 2 30mg / cm 2 30.5 mg / cm 2 31mg / cm 2 31.5 mg / cm 2 32mg / cm 232.5 mg / cm 2 .

[0085] In some embodiments, the positive electrode includes a positive current collector, which may be a metal foil or a composite current collector. The metal foil may be aluminum foil, and the composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate.

[0086] In some embodiments, the method for preparing the positive electrode sheet in a secondary battery includes the following steps:

[0087] A slurry is formed by mixing a positive electrode active material with a conductive agent, a binder, and a solvent; and

[0088] The slurry is coated onto the positive current collector, dried, and then pressed to obtain the positive electrode sheet.

[0089] In some embodiments, the mass ratio of the positive electrode active material, conductive agent, and binder in the slurry is (90-96):(2-5):(2-5), and the solid content of the slurry is 70%-99.5%. Thus, by varying the particle size distribution of the agglomerated and near-monocrystalline positive electrode materials, the positive electrode active material, conductive agent, and binder are mixed in a specific mass ratio, and the slurry is adjusted to a specific solid content using a solvent. By combining the particle size distribution of the positive electrode active material with a specific positive electrode slurry formulation, the performance of the positive electrode active material can be fully utilized, and the compaction density of the positive electrode sheet can be better improved.

[0090] In some embodiments, aggregated cathode materials and near-monocrystalline cathode materials are added to a mixing tank in a mass ratio, and conductive agents and binders are added for premixing. Solvents are added and the mixture is rapidly stirred under vacuum to form a cathode slurry. The cathode slurry is uniformly and double-sidedly coated onto the cathode current collector aluminum foil. The coated electrode sheet is dried at 100°C to 130°C, removed, and cold-pressed to obtain the cathode electrode sheet.

[0091] In some embodiments, a lithium source, a high-nickel ternary precursor, and additives are mixed uniformly in a mixer according to a certain ratio and sintered at 550°C to 800°C in an oxygen atmosphere for 5 to 20 hours to obtain an agglomerated cathode material; a lithium source, a high-nickel ternary precursor, and additives are mixed uniformly in a mixer according to a certain ratio and sintered at 600°C to 900°C in an oxygen atmosphere for 5 to 20 hours to obtain a near-monocrystalline cathode material.

[0092] In some embodiments, the conductive agent includes one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0093] In some embodiments, the binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0094] In some embodiments, the secondary battery further includes a negative electrode sheet containing a negative electrode active material, wherein the mass percentage of silicon-based material in the negative electrode active material is 20% to 100%. Thus, by combining the positive electrode sheet of the first aspect of this application with a negative electrode sheet with a high silicon content to form a secondary battery, a higher energy density can be achieved. It is understood that the mass percentage of silicon-based material in the negative electrode active material can be, but is not limited to, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%.

[0095] A second aspect of this application provides an electrical device including the secondary battery of the first aspect of this application.

[0096] The secondary battery and power-consuming device of this application will be described below with appropriate reference to the accompanying drawings.

[0097] Unless otherwise specified, the battery components, material types or contents mentioned apply to both lithium-ion and sodium-ion secondary batteries.

[0098] In one embodiment of this application, a secondary battery is provided.

[0099] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0100]

Positive Electrode

[0101] 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.

[0102] As an 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.

[0103] 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 material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material on the polymer material substrate. The metal material includes, but is not limited to, aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The polymer material substrate may be (e.g., polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0104] In some embodiments, the positive electrode active material may comprise a positive electrode active material known in the art for use in batteries.

[0105] As an example, the positive electrode active material of a lithium-ion secondary battery may include at least one of the following materials: 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 positive electrode active materials of batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. 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 / 3 Mn 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 0.05At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure 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.

[0106] As an example, the positive electrode active material of a sodium-ion secondary battery may include at least one of the following materials: sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. However, this application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries may also be used.

[0107] As an optional technical solution in this application, the transition metal in the sodium transition metal oxide can be at least one selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. For example, the sodium transition metal oxide is Na. x MO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0 < x ≤ 1.

[0108] As an optional technical solution in this application, the polyanionic compound can be a compound containing sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n- A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; n represents (YO4). n- The price state.

[0109] Polyanionic compounds can also contain sodium ions, transition metal ions, or tetrahedral (YO4) ions. n- A class of compounds containing anionic units and halide anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; the halogen can be at least one of F, Cl and Br.

[0110] Polyanionic compounds can also be sodium-containing tetrahedral (YO4) compounds. n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. Y can be at least one of P, S, and Si, and n represents (YO4). n-The valence state; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; m represents (ZO) y ) m+ The valence state; the halogen can be at least one of F, Cl and Br.

[0111] Polyanionic compounds include, for example, NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2 (P2O7), NaM'PO4F (M' is one or more of V, Fe, Mn and Ni), and Na3(VO4) y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0112] Prussian blue compounds can be compounds containing sodium ions, transition metal ions, and cyanide ions (CN). - A class of compounds. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Prussian blue compounds include, for example, Na. a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 < a ≤ 2, 0 < b < 1, 0 < c < 1.

[0113] The positive electrode active material accounts for 80-100% by weight in the positive electrode film, based on the total weight of the positive electrode film.

[0114] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a terpolymer of PVDF-tetrafluoroethylene-propylene, a terpolymer of PVDF-hexafluoropropylene-tetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorinated acrylate resin. The binder constitutes 0–20% by weight of the positive electrode film layer, based on the total weight of the positive electrode film layer.

[0115] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The conductive agent accounts for 0-20% by weight of the positive electrode film, based on the total weight of the positive electrode film.

[0116] 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, wherein the solid content of the positive electrode slurry is 40% by mass (wt%) to 80 wt%, and the viscosity at room temperature is adjusted to 5000 mPa·s to 25000 mPa·s. The positive electrode slurry is coated on the surface of the positive current collector, dried, and then cold-pressed by a cold rolling mill to form the positive electrode sheet.

[0117] The thickness T of the positive electrode film can be measured using a micrometer, such as a Mitutoyo 293-100 micrometer with an accuracy of 0.1 μm. It should be noted that the thickness of the positive electrode film mentioned in this application refers to the thickness of the positive electrode film in the positive electrode sheet used for battery assembly after cold pressing and compaction.

[0118] [Negative electrode plate]

[0119] 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.

[0120] As an 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.

[0121] 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 material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material on the polymer material substrate. The metal material includes, but is not limited to, copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc., and the polymer material substrate includes, but is not limited to, polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0122] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries.

[0123] As an example, the negative electrode active material of a lithium-ion secondary battery may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of 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.

[0124] As an example, the negative electrode active material of a sodium-ion secondary battery is typically a hard carbon material, a two-dimensional metal carbide, or a nitride. Preferably, the negative electrode active material of a sodium-ion secondary battery is a hard carbon material.

[0125] The negative electrode active material accounts for 70-100% by weight in the negative electrode film, based on the total weight of the negative electrode film.

[0126] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). The binder accounts for 0–30% by weight of the negative electrode film layer, based on the total weight of the negative electrode film layer.

[0127] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The conductive agent accounts for 0 to 20% by weight of the negative electrode film, based on the total weight of the negative electrode film.

[0128] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)). The other additives constitute 0–15% by weight of the negative electrode film, based on the total weight of the negative electrode film.

[0129] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry, wherein the solid content of the negative electrode slurry is 30wt% to 70wt%, and the viscosity at room temperature is adjusted to 2000 mPa·s to 10000 mPa·s; the obtained negative electrode slurry is coated onto a negative electrode current collector, and after a drying process, cold-pressed, for example, by rollers, to obtain the negative electrode sheet. The areal density of the negative electrode powder coating is 75 mg / m². 2 ~220mg / m 2 The compacted density of the negative electrode sheet is 1.2 g / m³. 3 )~2.0g / m 3 .

[0130] The mass M of the negative electrode active material per unit area of ​​the negative electrode membrane can be obtained by weighing using a standard balance.

[0131] The thickness T of the negative electrode film can be measured using a micrometer, such as a Mitutoyo 293-100 micrometer with an accuracy of 0.1 μm. It should be noted that the thickness of the negative electrode film mentioned in this application refers to the thickness of the negative electrode film in the negative electrode sheet used for battery assembly after cold pressing and compaction.

[0132] Electrolytes

[0133] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0134] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0135] In some embodiments, the electrolyte salt of the lithium-ion secondary battery may be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0136] The electrolyte salt for sodium-ion secondary batteries can be selected from one or more of the following: sodium hexafluorophosphate, sodium difluorosulfonamide, sodium ditrifluoromethanesulfonamide, sodium trifluoromethanesulfonate, sodium tetrafluoroborate, sodium difluorophosphate, sodium perchlorate, and sodium chloride.

[0137] The concentration of the electrolyte salt is typically 0.5 mol / L to 5 mol / L.

[0138] In some embodiments, the solvent may be selected from one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0139] 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.

[0140]

Isolation Film

[0141] 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.

[0142] In some embodiments, the material of the separator can be selected from at least one of 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.

[0143] In some embodiments, the thickness of the isolation membrane is 6 μm to 40 μm, and optionally 12 μm to 20 μm.

[0144] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0145] 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.

[0146] 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.

[0147] 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 1 This is an example of a square-structured secondary battery 5.

[0148] In some implementations, refer to Figure 2 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 specific practical needs.

[0149] In some embodiments, the secondary battery 5 can be assembled into a battery module, and the number of secondary batteries 5 contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0150] In the battery module, multiple secondary batteries 5 can be arranged sequentially along the length of the battery module. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be secured with fasteners.

[0151] Optionally, the battery module may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0152] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0153] The battery pack may include a battery box and multiple battery modules disposed within the battery box. The battery box includes an upper body and a lower body, with the upper body covering the lower body to form a closed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery box.

[0154] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack 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 (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0155] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0156] Figure 3 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0157] 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.

[0158] The following are some examples.

[0159] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0160] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0161] I. Implementation Examples

[0162] Example 1:

[0163] 1) Positive electrode plate

[0164] The positive electrode active material is a mixture of aggregated positive electrode material with a Dv50 of 12 μm (primary particle size of 0.4 μm) and quasi-single crystal positive electrode material with a Dv50 of 3 μm (primary particle size of 1.2 μm) in a mass ratio of 7:3.

[0165] Among them, the chemical formula of the aggregate-type cathode material is Li x1 Ni y1 Co z1 M 1-y1-z1 O2; the chemical formula of the single-crystal-like cathode material is Li. x2 Ni y2 Co z2 M′ 1-y2-z2 O2. x1 is 1, y1 is 0.93, z1 is 0.05, x2 is 1, y2 is 0.91, z2 is 0.07; the particle size distribution span (Dv90-Dv10) / Dv50 of the agglomerated cathode material is 1.25, and the particle size distribution span (Dv90-Dv10) / Dv50 of the near-single-crystal cathode material is 1.35; the BET specific surface area of ​​the agglomerated cathode material is 0.56 m². 2 / g, the BET specific surface area of ​​the near-monocrystalline cathode material is 1.05m². 2 / g; the particle size distribution span (Dv90-Dv10) / Dv50 of the mixed positive electrode active material is 1.78, and the BET specific surface area is 0.66m². 2 / g.

[0166] The above-mentioned positive electrode active material was placed in a 5L stirred tank, and then the conductive agent acetylene black (SP) and the binder polyvinylidene fluoride (PVDF) were added and premixed for 30 minutes. Then, the solvent N-methylpyrrolidone (NMP) was added and the mixture was rapidly stirred under vacuum to form a positive electrode slurry. The mass ratio of positive electrode active material:acetylene black:polyvinylidene fluoride was 96:2:2, and the solid content of the slurry was 70%.

[0167] The positive electrode slurry was uniformly and double-sided coated onto a 12 μm thick aluminum foil for the positive electrode current collector. After drying in an oven at 100℃–130℃ for half an hour, the coated electrode was removed and cold-pressed using rollers to obtain the positive electrode sheet. The active material loading of the positive electrode film layer on the electrode sheet was 21.5 mg / cm³. 2 .

[0168] 2) Negative electrode plate

[0169] The negative electrode active materials—graphite and silicon carbide, carbon black (SP), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC)—were dissolved in deionized water at a weight ratio of 95:2:2:1. After stirring, a uniformly dispersed negative electrode slurry was obtained. This slurry was then evenly coated onto the surface of the negative electrode current collector copper foil. Following drying, cold pressing, and cutting, the negative electrode sheet was obtained. The silicon carbide component comprised 30% of the negative electrode active materials.

[0170] 3) Separating membrane

[0171] Polyethylene (PE) porous polymer film is used as the separator.

[0172] 4) Electrolyte

[0173] In an argon-atmospheric glove box, 8% lithium hexafluorophosphate (LiPF6), 2% vinylene carbonate (VC), 0.5% hexamethylene diisocyanate (HDI), 25% ethylene carbonate (EC), 10% dimethyl carbonate (DMC), 20% ethyl methyl carbonate (EMC), and the remainder is supplemented to 100% with diethyl carbonate (DEC) to obtain the corresponding electrolyte.

[0174] 5) Battery assembly

[0175] The positive electrode, separator, and negative electrode are sequentially stacked, wound, and assembled into a bare cell. The bare cell is then placed in a battery casing, and electrolyte is injected to form a secondary battery.

[0176] Example 2:

[0177] This embodiment is basically the same as Embodiment 1, except that the Dv50 of the agglomerated cathode material in the cathode active material is different. In this embodiment, the Dv50 of the agglomerated cathode material is 8.2 μm.

[0178] Example 3:

[0179] This embodiment is basically the same as Embodiment 1, except that the particle size of the primary particles of the agglomerated cathode material in the cathode active material is different. In this embodiment, the particle size of the primary particles of the agglomerated cathode material is 0.2 μm.

[0180] Example 4:

[0181] This embodiment is basically the same as Embodiment 1, except that the particle size distribution span (Dv90-Dv10) / Dv50 (i.e., SPAN) of the agglomerated positive electrode material is different. In this embodiment, the particle size distribution span SPAN of the agglomerated positive electrode material is 1.39.

[0182] Example 5:

[0183] This embodiment is basically the same as Embodiment 1, except that the molecular formula of the agglomerate-type cathode material in the cathode active material is different. In this embodiment, the molecular formula of the agglomerate-type cathode material has y1 of 0.98 and z1 of 0.01.

[0184] Example 6:

[0185] This embodiment is basically the same as Embodiment 1, except that the BET specific surface area of ​​the agglomerated cathode material in the positive electrode active material is different. In this embodiment, the BET specific surface area of ​​the agglomerated cathode material is 0.78 m². 2 / g.

[0186] Example 7:

[0187] This embodiment is basically the same as Embodiment 1, except that the Dv50 of the quasi-monocrystalline cathode material in the cathode active material is different. In this embodiment, the Dv50 of the quasi-monocrystalline cathode material is 3.8 μm.

[0188] Example 8:

[0189] This embodiment is basically the same as Embodiment 1, except that the particle size of the primary particles of the quasi-monocrystalline cathode material in the cathode active material is different. In this embodiment, the particle size of the primary particles of the quasi-monocrystalline cathode material is 0.9 μm.

[0190] Example 9:

[0191] This embodiment is basically the same as Embodiment 1, except that the particle size distribution span (Dv90-Dv10) / Dv50 (i.e., SPAN) of the quasi-monocrystalline cathode material in the cathode active material is different. In this embodiment, the particle size distribution span SPAN of the quasi-monocrystalline cathode material is 1.47.

[0192] Example 10:

[0193] This embodiment is basically the same as Embodiment 1, except that the molecular formula of the quasi-single-crystal cathode material is different. In this embodiment, the molecular formula of the quasi-single-crystal cathode material has y2 of 0.97 and z2 of 0.02.

[0194] Example 11:

[0195] This embodiment is basically the same as Embodiment 1, except that the BET specific surface area of ​​the quasi-monocrystalline cathode material in the positive electrode active material is different. In this embodiment, the BET specific surface area of ​​the quasi-monocrystalline cathode material is 0.85 m². 2 / g.

[0196] Example 12:

[0197] This embodiment is basically the same as Embodiment 1, except that the mass ratio of agglomerated cathode material to quasi-monocrystalline cathode material in the cathode active material is different. In this embodiment, the mass ratio of agglomerated cathode material to quasi-monocrystalline cathode material is 8:2.

[0198] Example 13:

[0199] This embodiment is basically the same as Embodiment 1, except that the particle size distribution span (Dv90-Dv10) / Dv50 (i.e., SPAN) of the mixed positive electrode active material is different. In this embodiment, the particle size distribution span SPAN of the positive electrode active material is 2.03.

[0200] Example 14:

[0201] This embodiment is basically the same as Embodiment 1, except that the BET specific surface area of ​​the mixed positive electrode active material is different. In this embodiment, the BET specific surface area of ​​the positive electrode active material is 0.52 m². 2 / g.

[0202] Example 15:

[0203] This embodiment is basically the same as Embodiment 1, except that the content of silicon-based material in the negative electrode active material of the negative electrode sheet is different. In this embodiment, the mass content of silicon-based material in the negative electrode active material is 90%.

[0204] Example 16:

[0205] In this embodiment, the Dv50 of the agglomerated cathode material is 14.9 μm, the primary particle size of the agglomerated cathode material is 0.3 μm, the particle size distribution span (SPAN) of the agglomerated cathode material is 0.72, the molecular formula of the agglomerated cathode material has y1 of 0.94 and z1 of 0.05, and the BET specific surface area of ​​the agglomerated cathode material is 0.3 m². 2 / g; The Dv50 of the quasi-monocrystalline cathode material is 3.5μm, the primary particle size of the quasi-monocrystalline cathode material is 1.5μm, the particle size distribution span (SPAN) of the quasi-monocrystalline cathode material is 1.44, the y2 of the molecular formula of the quasi-monocrystalline cathode material is 0.92, the z2 is 0.06, and the BET specific surface area of ​​the quasi-monocrystalline cathode material is 0.9m². 2 / g; the mass ratio of agglomerated cathode material to near-monocrystalline cathode material is 65:35, the particle size distribution span (SPAN) of the cathode active material is 1.55, and the BET specific surface area of ​​the cathode active material is 0.53m². 2 / g, the mass content of silicon-based material in the negative electrode active material is 50%, and the rest is the same as in Example 1.

[0206] Example 17:

[0207] In this embodiment, the Dv50 of the agglomerated cathode material is 9.5 μm, the primary particle size of the agglomerated cathode material is 0.13 μm, the particle size distribution span (SPAN) of the agglomerated cathode material is 1.33, the molecular formula of the agglomerated cathode material has y1 of 0.94 and z1 of 0.05, and the BET specific surface area of ​​the agglomerated cathode material is 0.2 m². 2 / g; The Dv50 of the quasi-monocrystalline cathode material is 3.5μm, the primary particle size of the quasi-monocrystalline cathode material is 1.5μm, the particle size distribution span (SPAN) of the quasi-monocrystalline cathode material is 1.44, the y2 of the molecular formula of the quasi-monocrystalline cathode material is 0.92, the z2 is 0.06, and the BET specific surface area of ​​the quasi-monocrystalline cathode material is 0.83m². 2 / g; the mass ratio of agglomerated cathode material to near-monocrystalline cathode material is 75:25, the particle size distribution span (SPAN) of the cathode active material is 1.9, and the BET specific surface area of ​​the cathode active material is 0.53 m². 2 / g, the mass content of silicon-based material in the negative electrode active material is 50%, and the rest is the same as in Example 1.

[0208] Example 18:

[0209] In this embodiment, the Dv50 of the agglomerated cathode material is 9.5 μm, the primary particle size of the agglomerated cathode material is 0.3 μm, the particle size distribution span (SPAN) of the agglomerated cathode material is 1.33, the molecular formula of the agglomerated cathode material has y1 of 0.94 and z1 of 0.05, and the BET specific surface area of ​​the agglomerated cathode material is 0.45 m². 2 / g; The Dv50 of the quasi-monocrystalline cathode material is 3.5μm, the primary particle size of the quasi-monocrystalline cathode material is 1.5μm, the particle size distribution span (SPAN) of the quasi-monocrystalline cathode material is 1.44, the y2 of the molecular formula of the quasi-monocrystalline cathode material is 0.92, the z2 is 0.06, and the BET specific surface area of ​​the quasi-monocrystalline cathode material is 1.14m². 2 / g; the mass ratio of agglomerated cathode material to near-monocrystalline cathode material is 7:3, the particle size distribution span (SPAN) of the cathode active material is 1.9, and the BET specific surface area of ​​the cathode active material is 0.68m². 2 / g, the mass content of silicon-based material in the negative electrode active material is 50%, and the rest is the same as in Example 1.

[0210] Example 19:

[0211] In this embodiment, the Dv50 of the agglomerated cathode material is 9.5 μm, the primary particle size of the agglomerated cathode material is 0.56 μm, the particle size distribution span (SPAN) of the agglomerated cathode material is 1.33, the molecular formula of the agglomerated cathode material has y1 of 0.94 and z1 of 0.05, and the BET specific surface area of ​​the agglomerated cathode material is 0.45 m². 2 / g; the Dv50 of the quasi-monocrystalline cathode material is 3.5μm, the primary particle size of the quasi-monocrystalline cathode material is 1.9μm, the particle size distribution span (SPAN) of the quasi-monocrystalline cathode material is 1.44, the y2 of the molecular formula of the quasi-monocrystalline cathode material is 0.92, the z2 is 0.06, and the BET specific surface area of ​​the quasi-monocrystalline cathode material is 0.9m². 2 / g; The mass ratio of agglomerated cathode material to near-monocrystalline cathode material is 8:2; the particle size distribution span (SPAN) of the cathode active material is 1.9; and the BET specific surface area of ​​the cathode active material is 0.53 m². 2 / g, the mass content of silicon-based material in the negative electrode active material is 50%, and the rest is the same as in Example 1.

[0212] Example 20:

[0213] In this embodiment, the Dv50 of the agglomerated cathode material is 9.5 μm, the primary particle size of the agglomerated cathode material is 0.3 μm, the particle size distribution span (SPAN) of the agglomerated cathode material is 1.33, the molecular formula of the agglomerated cathode material has y1 of 0.94 and z1 of 0.05, and the BET specific surface area of ​​the agglomerated cathode material is 0.45 m². 2 / g, the Dv50 of the near-monocrystalline cathode material is 2.6μm, the primary particle size of the near-monocrystalline cathode material is 1.5μm, and the particle size distribution span (SPAN) of the near-monocrystalline cathode material is 1.44; the molecular formula of the near-monocrystalline cathode material has y2 of 0.92, z2 of 0.06, and a BET specific surface area of ​​1.26m². 2 / g, the mass ratio of agglomerated cathode material to near-monocrystalline cathode material is 7:3, the particle size distribution span (SPAN) of the cathode active material is 2.07, and the BET specific surface area of ​​the cathode active material is 0.53m². 2 / g, the mass content of silicon-based material in the negative electrode active material is 50%, and the rest is the same as in Example 1.

[0214] Comparative Example 1:

[0215] In this comparative example, the Dv50 of the agglomerated cathode material is 9 μm, the primary particle size is 0.2 μm, the particle size distribution span (SPAN) is 1.2, the molecular formula has y1 = 0.94, z1 = 0.05, and the BET specific surface area is 0.45 m². 2 / g; the Dv50 of the quasi-monocrystalline cathode material is 3.3μm, the primary particle size of the quasi-monocrystalline cathode material is 0.7μm, the particle size distribution span (SPAN) of the quasi-monocrystalline cathode material is 1.4; the molecular formula of the quasi-monocrystalline cathode material has y2 of 0.93, z2 of 0.06, and a BET specific surface area of ​​0.95m². 2 / g; The mass ratio of agglomerated cathode material to near-monocrystalline cathode material is 8:2; the particle size distribution span (SPAN) of the cathode active material is 1.94; and the BET specific surface area of ​​the cathode active material is 0.61 m². 2 / g, the mass content of silicon-based material in the negative electrode active material is 40%, and the rest is the same as in Example 1.

[0216] Comparative Example 2:

[0217] This comparative example is basically the same as Comparative Example 1, except that: only aggregated positive electrode materials are used for the positive electrode active material, and no single crystal-like positive electrode materials are used; the total amount of positive electrode active material remains unchanged; and the compaction density of the positive electrode sheet is different.

[0218] Comparative Example 3:

[0219] This comparative example is basically the same as Comparative Example 1, except that: the positive electrode active material is only a near-single crystal type positive electrode material, not an agglomerate type positive electrode material, and the primary particle size of the near-single crystal type positive electrode material is 1.2 μm, while the total amount of positive electrode active material remains unchanged; the compaction density of the positive electrode sheet is different.

[0220] II. Testing Methods

[0221] 1) Dv10, Dv50, Dv90 testing

[0222] The volume average particle sizes Dv10, Dv50, and Dv90 can be determined using methods known in the art. For example, the particle size distribution can be determined using a Malvern 3000 instrument, in accordance with GB / T 19077-2016 / ISO 13320:2009, laser diffraction method.

[0223] 2) BET specific surface area test

[0224] The BET specific surface area of ​​particles can be tested using methods known in the art. For example, GB / T 19587-2017, "Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method," can be consulted, and the determination can be performed using the TriStarII 3020 instrument.

[0225] 3) Primary particle size test

[0226] In a 3000x magnified image using a scanning electron microscope, the length of the longest direction of each particle is measured individually (for regular spheres, the diameter is measured; for irregular particles, the longest direction is measured in the opposite direction). Approximately 300 measurements are taken, and the average value is calculated to obtain the particle size.

[0227] 4) Compacted density calculation

[0228] The compaction density of the positive electrode sheet can be calculated using the formula PD=M / (d×A), where M is the mass of a small circular sheet with a diameter of 40mm, which can be obtained by taking the average value of 10 weighings; d is the thickness of the positive electrode sheet after cold pressing, which can be obtained by cutting it into small circular sheets of 40mm and measuring the thickness of each sheet and taking the average value; and A is the area of ​​the small circular sheet of 40mm.

[0229] 5) Length elongation test

[0230] The elongation of the positive electrode sheet in the length direction after cold pressing can be calculated by the formula ΔEL%=(L2-L1) / L1×100%, where L1 is the marked length before cold pressing, which is generally fixed at 100mm; L2 is the distance of the marked length L1 after cold pressing.

[0231] 6) Energy density test

[0232] Battery cell capacity testing: The battery cells were left to stand at 25°C for 2 hours to ensure the temperature remained at 25°C. At 25°C, the battery cells were charged at 0.1C to the charging cutoff voltage, and then continued to be charged at this cutoff voltage under constant voltage until the current reached 0.05C, at which point charging was stopped (where C represents the rated capacity of the battery cell). The battery cells were then left to stand at 25°C for 1 hour. At 25°C, the battery cells were discharged at 0.1C to the discharge cutoff voltage. The total discharge capacity C0 and the total discharge energy E0 of the battery cells were recorded.

[0233] Battery cell weight measurement: Place the battery cell on an electronic balance until the weight stabilizes, and read the battery cell weight value M0.

[0234] Energy density calculation: The discharge energy of a single battery cell, E0, is divided by the weight of the single battery cell, M0, which is the energy density of the single battery cell.

[0235] 7) Cycle count test

[0236] (1) Place the full battery in a constant temperature chamber at 45°C and let it stand for 30 minutes. Then discharge it at a constant current of 0.33C to 2.8V. (2) Let it stand for 5 minutes. Then charge it at a constant current of 0.33C to 4.25V and then charge it at a constant voltage of 0.05C to 4.25V. Let it stand for 5 minutes. (3) Discharge it at a constant current of 0.33C to 2.8V. At this time, read the capacity value and record it as the initial capacity C0. Repeat steps (2) to (3) to obtain the capacity data C1 of the second cycle. C1 / C0 can be used to obtain the cycle retention rate. The number of test cycles until the cycle retention rate reaches 80% is the number of cycles.

[0237] The parameters and performance test results of the positive electrode and secondary battery in the above embodiments and comparative examples are shown in Tables 1, 2 and 3 below. In the following tables, A represents agglomerated positive electrode material and B represents quasi-monocrystalline positive electrode material.

[0238] It should be noted that, since the particle size test results for the same material may fluctuate over time, the small fluctuations in particle size (e.g., ±0.1 μm) in the embodiments of this application are within the normal error range. Similarly, the small fluctuations in the BET specific surface area (e.g., ±0.01 μm) of the same cathode material are also within the normal error range. 2 / g) is also within the normal error range.

[0239] Table 1

[0240]

[0241]

[0242] Table 2

[0243]

[0244]

[0245] Table 3

[0246]

[0247] From the data in the tables above, we can see that:

[0248] The secondary batteries of Examples 1 to 20 of this application exhibit high energy density and good cycle performance, demonstrating excellent overall performance. In Comparative Example 1, the primary particle size of the near-monocrystalline cathode material is outside the scope of this application; in Comparative Example 2, only agglomerated cathode materials are used, and near-monocrystalline cathode materials are not used; in Comparative Example 3, only near-monocrystalline cathode materials are used, and agglomerated cathode materials are not used. The overall performance of the secondary batteries of Examples 1 to 20 of this application is significantly better than that of Comparative Examples 1, 2, and 3.

[0249] The main difference between the secondary battery of Example 7 and Example 1 lies in the Dv50 of the quasi-monocrystalline cathode material. In Example 7, the Dv50 of the quasi-monocrystalline cathode material is 3.8, while in Example 1, the Dv50 is 3. The cycle performance of their secondary batteries is comparable, but Example 1 has a higher energy density.

[0250] The main difference between the secondary battery of Example 8 and Example 1 lies in the primary particle size of the quasi-monocrystalline cathode material. In Example 8, the primary particle size of the quasi-monocrystalline cathode material is 0.9 mm, while in Example 1, the primary particle size is 1.2 mm. The energy density and cycle performance of the secondary battery of Example 1 are significantly improved compared to Example 8.

[0251] The main difference between the secondary battery of Example 12 and Example 1 lies in the mixing ratio of the agglomerated cathode material and the quasi-monocrystalline cathode material. In Example 12, the mixing ratio of the agglomerated cathode material to the quasi-monocrystalline cathode material is 8:2, while in Example 1, the mixing ratio is 7:3. The energy density and cycle performance of the secondary battery of Example 1 are significantly improved compared to Example 12.

[0252] 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. 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, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A secondary battery, comprising a positive electrode sheet having a positive electrode active material thereon, the positive electrode active material comprising an aggregated positive electrode material and a near-monocrystalline positive electrode material; The volume average particle size Dv50 of the agglomerate-type cathode material is 8 μm to 15 μm, and the primary particle size of the agglomerate-type cathode material is 0.1 μm to 0.6 μm. The volume average particle size Dv50 of the quasi-monocrystalline cathode material is 2.5 μm to 4 μm, and the primary particle size of the quasi-monocrystalline cathode material is 0.8 μm to 2 μm. The mass ratio of the aggregated cathode material to the quasi-monocrystalline cathode material is greater than or equal to 1.

2. The secondary battery according to claim 1, characterized in that, The mass ratio of the aggregated cathode material to the quasi-single-crystal cathode material is 1 to 9:

1.

3. The secondary battery according to claim 2, characterized in that, The mass ratio of the aggregated cathode material to the quasi-single-crystal cathode material is 2.3 to 3:

1.

4. The secondary battery according to claim 1, characterized in that, The volume average particle size Dv50 of the quasi-monocrystalline cathode material is 3 μm to 3.5 μm, and / or the primary particle size of the quasi-monocrystalline cathode material is 1.2 μm to 1.5 μm.

5. The secondary battery according to claim 1, characterized in that, The primary particle size of the agglomerated cathode material is 0.2 μm to 0.4 μm.

6. The secondary battery according to claim 1, characterized in that, The chemical formula of the aggregate-type cathode material is Li x1 Ni y1 Co z1 M 1-y1-z1 O2, where 0.9≤x1≤1, 0.9≤y1≤0.98, 0.05≤z1≤0.1, and M includes one or more of Mn, Al, B, Zr, Sr, Y, Sb, W, Ti, Mg and Nb.

7. The secondary battery according to claim 6, characterized in that, 0.9≤y1≤0.96。 8. The secondary battery according to claim 1, characterized in that, The chemical formula of the quasi-monocrystalline cathode material is Li. x2 Ni y2 Co z2 M′ 1-y2-z2 O2, where 0.9≤x2≤1, 0.9≤y2≤0.98, 0.05≤z2≤0.1, and M′ includes one or more of Mn, Al, B, Zr, Sr, Y, Sb, W, Ti, Mg and Nb.

9. The secondary battery according to claim 8, characterized in that, 0.92≤y2≤0.98。 10. The secondary battery according to claim 8, characterized in that, y2>y1.

11. The secondary battery according to claim 1, characterized in that, The particle size distribution span (Dv90-Dv10) / Dv50 of the agglomerate-type cathode material is ≤1.

5.

12. The secondary battery according to claim 11, characterized in that, The particle size distribution range (Dv90-Dv10) / Dv50 of the agglomerate-type cathode material is 0.7~1.

4.

13. The secondary battery according to claim 1, characterized in that, The BET specific surface area of ​​the aggregated cathode material is 0.2 m². 2 / g~0.8 m 2 / g.

14. The secondary battery according to claim 13, characterized in that, The BET specific surface area of ​​the aggregated cathode material is 0.3 m². 2 / g~0.6 m 2 / g.

15. The secondary battery according to claim 1, characterized in that, The particle size distribution span (Dv90-Dv10) / Dv50 of the quasi-monocrystalline cathode material is ≥1.

2.

16. The secondary battery according to claim 14, characterized in that, The particle size distribution range (Dv90-Dv10) / Dv50 of the quasi-monocrystalline cathode material is 1.3~1.

5.

17. The secondary battery according to claim 1, characterized in that, The BET specific surface area of ​​the quasi-monocrystalline cathode material is 0.8 m². 2 / g~1.3 m 2 / g.

18. The secondary battery according to claim 17, characterized in that, The BET specific surface area of ​​the quasi-monocrystalline cathode material is 0.85 m². 2 / g~1.15 m 2 / g.

19. The secondary battery according to claim 1, characterized in that, The particle size distribution range (Dv90-Dv10) / Dv50 of the positive electrode active material is 1.5~2.

1.

20. The secondary battery according to claim 1, characterized in that, The BET specific surface area of ​​the positive electrode active material is 0.5 m². 2 / g~0.7 m 2 / g.

21. The secondary battery according to claim 1, characterized in that, The positive electrode active material in the positive electrode sheet accounts for 95% to 99.5% of the mass percentage of the positive electrode film layer.

22. The secondary battery according to claim 1, characterized in that, The areal density of the positive electrode active material in the positive electrode sheet is 21.5 mg / cm². 2 ~32.5 mg / cm 2 .

23. The secondary battery according to any one of claims 1 to 22, characterized in that, It also includes a negative electrode sheet, on which a negative electrode active material is provided, wherein the mass percentage of silicon-based material in the negative electrode active material is 20% to 100%.

24. An electrical device comprising a secondary battery as described in any one of claims 1 to 23.

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