Secondary battery and power consumption device

Abstract

This application provides a secondary battery and a power consumption device. The secondary battery includes a negative electrode plate, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer. The negative electrode film layer has a first surface away from the negative electrode current collector and a second surface disposed opposite to the first surface. Denote the thickness of the negative electrode film layer as H, and denote the region within the thickness range from the second surface of the negative electrode film layer to 0.3H as the first region of the negative electrode film layer, and denote the region within the thickness range from the first surface of the negative electrode film layer to 0.3H as the second region of the negative electrode film layer. The first region contains a first active material, the second region contains a second active material. The first active material includes a first carbon-based material and a first silicon-based material. The first carbon-based material includes primary particles, and the first silicon-based material includes secondary particles formed by aggregation of primary particles.

Description

Technical Field

[0001] This application belongs to the field of battery technology, and specifically relates to secondary batteries and power consumption devices.

Background Art

[0002] In recent years, secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. As the application range of secondary batteries becomes increasingly wide, people pose strict challenges to the performance of secondary batteries. For example, it is required to make various performances such as energy density, rate performance, and service life compatible in secondary batteries.

Summary of the Invention

[0003] This application provides a secondary battery and a power consumption device that can make the secondary battery have good rate performance and cycle performance on the premise of having a high energy density.

[0004] The first aspect of this application provides a secondary battery, which includes a negative electrode plate. The negative electrode plate includes a negative electrode current collector and a negative electrode film layer. Here, the negative electrode film layer has a first surface away from the negative electrode current collector and a second surface disposed opposite to the first surface. The thickness of the negative electrode film layer is denoted as H, and the region within the thickness range from the second surface of the negative electrode film layer to 0.3H is denoted as the first region of the negative electrode film layer, and the region within the thickness range from the first surface of the negative electrode film layer to 0.3H is denoted as the second region of the negative electrode film layer.

[0005] The first region contains a first active material, and the second region contains a second active material.

[0006] The first active material includes a first carbon-based material and a first silicon-based material. The first carbon-based material includes primary particles, and the first silicon-based material includes secondary particles formed by aggregation of primary particles.

[0007] By including a first carbon-based material and a first silicon-based material in a first region of the negative electrode film layer, the first carbon-based material includes primary particles, and the first silicon-based material includes secondary particles formed by aggregation of the primary particles. On the premise that the secondary battery has a high energy density, good rate performance and cycle performance are achieved simultaneously.

[0008] In any of the embodiments of the present application, the surface of the first carbon-based material has a carbon coating layer. Optionally, the carbon coating layer contains hard carbon. This is advantageous for further optimizing the rate performance of the secondary battery.

[0009] In any of the embodiments of the present application, the ratio of the number of the primary particles of the first carbon-based material in the first carbon-based material is ≧70%, and optionally 75%-90%. This is advantageous for enabling the secondary battery to achieve good cycle performance, rate performance and a higher energy density simultaneously.

[0010] In any of the embodiments of the present application, the ratio of the number of the first silicon-based material of the secondary particles in the first silicon-based material is ≧55%, and optionally 60%-85%. This is advantageous for enabling the secondary battery to achieve good cycle performance, rate performance and a higher energy density simultaneously.

[0011] In any of the embodiments of the present application, the porosity of the first silicon-based material of the secondary particles is ≧4%, and optionally 5%-20%. By further adjusting the porosity of the first silicon-based material of the secondary particles, it is advantageous for further optimizing the rate performance of the secondary battery.

[0012] In any embodiment of the present application, the volume distribution particle size Dv50 of the first carbon-based material is 10-16 μm, and optionally 12-14 μm. When the volume distribution particle size Dv50 of the first carbon-based material is within the above range, it is advantageous for enhancing the transport performance of ions and electrons, thereby further enhancing the rate performance of the secondary battery. Also, the specific surface area of the first carbon-based material can be reduced, and side reactions can be decreased, thereby further improving the cycle performance of the secondary battery.

[0013] In any embodiment of the present application, the volume distribution particle size Dv90 of the first carbon-based material is 20-28 μm, and optionally 22-26 μm. When the volume distribution particle size Dv90 of the first carbon-based material is within the above range, the consistency of the first carbon-based material particles is relatively good, which is advantageous for enhancing the transport performance of ions and electrons, thereby further enhancing the rate performance of the secondary battery.

[0014] In any embodiment of the present application, the first carbon-based material satisfies that (Dv90-Dv10) / Dv50 is 0.8-1.6, and optionally 1.1-1.4. When (Dv90-Dv10) / Dv50 of the first carbon-based material is within the above range, the first carbon-based material has excellent particle deposition performance, which is advantageous for improving the compaction density of the negative electrode film layer, thereby further improving the energy density of the secondary battery. Also, it is advantageous for the negative electrode film layer to have an appropriate pore structure, thereby further improving the rate performance of the secondary battery.

[0015] In any embodiment of the present application, the specific surface area of the first carbon-based material is 1.0-1.8 m 2 / g, and optionally 1.2-1.6 m 2 / g. When the specific surface area of the first carbon-based material is within the above range, it is advantageous for reducing side reactions, thereby enabling the secondary battery to have better cycle performance.

[0016] In any embodiment of the present application, the powder compaction density of the first carbon-based material at 20000 N is 1.75 - 2.0 g / cm 3 and optionally 1.8 - 1.95 g / cm 3 When the powder compaction density of the first carbon-based material is within the above range, the compaction density of the negative electrode film layer can be increased, thereby further increasing the energy density of the secondary battery. Moreover, it is advantageous for the negative electrode film layer to have an appropriate pore structure, which can improve the ion and electron transport performance, improve the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte, and further improve the rate performance and / or cycle performance of the secondary battery.

[0017] In any embodiment of the present application, the tap density of the first carbon-based material is 1.1 - 1.3 g / cm 3 and optionally 1.15 - 1.25 g / cm 3 When the tap density of the first carbon-based material is within the above range, the compaction density of the negative electrode film layer can be increased, thereby further increasing the energy density of the secondary battery. Moreover, it is advantageous for the negative electrode film layer to have an appropriate pore structure, which can improve the ion and electron transport performance, improve the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte, and further improve the rate performance and / or cycle performance of the secondary battery.

[0018] In any embodiment of the present application, the graphitization degree of the first carbon-based material is ≥ 93%, and optionally 94% - 96%. When the graphitization degree of the first carbon-based material is within the above range, it is advantageous for improving the ion transport performance of the negative electrode film layer, thereby enabling the secondary battery to achieve both high energy density and good rate performance.

[0019] In any embodiment of the present application, the gram capacity of the first carbon-based material is ≧360 mAh / g, and optionally 361 - 365 mAh / g. When the gram capacity of the first carbon-based material is within the above range, on the one hand, the energy density of the secondary battery can be improved, and on the other hand, the carbon-based material can be provided with good ion transport performance, which is also advantageous for improving the rate performance of the secondary battery.

[0020] In any embodiment of the present application, the powder OI value of the first carbon-based material is 5 - 15, and optionally 7 - 12. Since the powder OI value of the first carbon-based material is relatively small, it can quickly receive ions from the positive electrode, thereby further improving the rate performance of the secondary battery.

[0021] In any embodiment of the present application, the first carbon-based material contains graphite, and optionally contains artificial graphite.

[0022] In any embodiment of the present application, the mass ratio of the first carbon-based material in the first active material is ≧50%, and optionally 60% - 98%. By adjusting the content of the first carbon-based material within the above range, the cycle performance of the secondary battery can be improved, and good rate performance of the secondary battery can be achieved at the same time.

[0023] In any embodiment of the present application, the volume distribution particle size Dv50 of the first silicon-based material is 8 - 15 μm, and optionally 10 - 13 μm.

[0024] In any embodiment of the present application, the volume distribution particle size Dv90 of the first silicon-based material is 15 - 25 μm, and optionally 16 - 24 μm.

[0025] When the volume distribution particle size Dv50 and / or Dv90 of the first silicon-based material is within the above range, the ion storage channels in the negative electrode film layer can be increased, which is also advantageous for the rapid diffusion of ions from the particle surface layer to the bulk phase, thereby being advantageous for the further optimization of the rate performance of the secondary battery.

[0026] In any embodiment of the present application, the first silicon-based material satisfies that (Dv90 - Dv10) / Dv50 is 0.7 - 1.5, and is selectively 0.9 - 1.3. When (Dv90 - Dv10) / Dv50 of the first silicon-based material is within the above range, the first silicon-based material has excellent particle deposition performance, is advantageous for improving the consolidation density of the negative electrode film layer, thereby enabling further improvement of the energy density of the secondary battery. Moreover, it is also advantageous for the negative electrode film layer to have an appropriate pore structure, thereby enabling further improvement of the rate performance of the secondary battery.

[0027] In any embodiment of the present application, the specific surface area of the first silicon-based material is 0.7 - 2.0 m 2 / g, and is selectively 0.8 - 1.6 m 2 / g. When the specific surface area of the first silicon-based material is within the above range, the ion intercalation channels in the negative electrode film layer can be increased, which is also advantageous for the rapid diffusion of ions from the particle surface layer to the bulk phase, thereby being advantageous for further optimization of the rate performance of the secondary battery. Also, when the specific surface area of the first silicon-based material is within the above range, it is advantageous for reducing side reactions, thereby enabling the secondary battery to have better cycle performance.

[0028] In any embodiment of the present application, the powder consolidation density of the first silicon-based material at 50000 N is 1.0 - 1.7 g / cm 3 and is selectively 1.2 - 1.6 g / cm 3 When the powder consolidation density of the first silicon-based material is within the above range, the consolidation density of the negative electrode film layer can be increased, thereby enabling further increase of the energy density of the secondary battery. Moreover, it is also advantageous for the negative electrode film layer to have an appropriate pore structure, which improves the transport performance of ions and electrons, improves the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte, and can further improve the rate performance and / or cycle performance of the secondary battery.

[0029] In any embodiment of the present application, the tap density of the first silicon-based material is 1.0 - 1.5 g / cm 3 and selectively 1.1 - 1.4 g / cm 3 When the tap density of the first silicon-based material is within the above range, the consolidation density of the negative electrode film layer can be increased, thereby further increasing the energy density of the secondary battery. Moreover, it is advantageous for the negative electrode film layer to have an appropriate pore structure, which can improve the transport performance of ions and electrons, improve the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte, and further improve the rate performance and / or cycle performance of the secondary battery.

[0030] In any embodiment of the present application, the powder resistivity of the first silicon-based material at 4 Mpa is ≤ 15 Ω·cm, and selectively 0.5 - 12 Ω·cm. By adjusting the powder resistivity of the first silicon-based material within the above range, the electron conductivity of the negative electrode film layer can be improved, and the rate performance of the secondary battery can be further improved.

[0031] In any embodiment of the present application, the mass ratio of the first silicon-based material in the first active material is ≤ 50%, and selectively 2% - 40%. By adjusting the content of the first silicon-based material within the above range, the rate performance and energy density of the secondary battery can be improved, and good cycle performance of the secondary battery can be achieved at the same time.

[0032] In any embodiment of the present application, the first silicon-based material includes one or more of silicon single crystal, silicon oxide, silicon carbon material, and silicon alloy material. Selectively, the first silicon-based material does not contain alkali metal and does not contain alkaline earth metal, and includes secondary particles formed by aggregation of at least one of primary particles of silicon oxygen material, primary particles of silicon oxygen material containing alkali metal or alkaline earth metal, primary particles of silicon carbon material, primary particles of silicon single crystal, and primary particles of silicon alloy.

[0033] In any embodiment of the present application, the second active material includes a second carbon-based material.

[0034] In any embodiment of the present application, the second carbon-based material includes secondary particles formed by aggregation of primary particles, and the proportion of the second carbon-based material in the secondary particles to the second carbon-based material is ≧60%, and selectively 70%-85%. This is advantageous for better achieving both good rate performance and cycle performance in the secondary battery.

[0035] In any embodiment of the present application, the surface of the second carbon-based material has a carbon coating layer, and selectively, the carbon coating layer includes soft carbon. The presence of the carbon coating layer can increase the ion diffusion channel, which is advantageous for further optimizing the rate performance of the secondary battery. Soft carbon has the advantage of a large interlayer spacing, which can accelerate the ion diffusion rate, which is advantageous for further optimizing the rate performance of the secondary battery. At the same time, soft carbon has few structural defects, which can reduce side reactions and achieve good cycle performance in the secondary battery.

[0036] In any embodiment of the present application, the surface of the first carbon-based material has a carbon coating layer, the surface of the second carbon-based material has a carbon coating layer, and the mass percentage content of the carbon coating layer of the second carbon-based material is greater than the mass percentage content of the carbon coating layer of the first carbon-based material. By providing carbon coating layers on both the first carbon-based material and the second carbon-based material, the rate performance of the secondary battery can be further improved. By making the mass percentage content of the carbon coating layer of the second carbon-based material greater than the mass percentage content of the carbon coating layer of the first carbon-based material, ions can be more rapidly moved to the surface layer of the second carbon-based material, thereby enabling the secondary battery to have better rate performance and cycle performance.

[0037] In any embodiment of the present application, the volume distribution particle size Dv50 of the second carbon-based material is smaller than the volume distribution particle size Dv50 of the first carbon-based material. By making the volume distribution particle size Dv50 of the second carbon-based material smaller than that of the first carbon-based material, a good consolidation density difference can be provided between the second region and the first region of the negative electrode film layer. As a result, the consistency between the porosity and the ion concentration distribution in the thickness direction of the negative electrode film layer becomes better, which is advantageous for improving the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte, advantageous for ion transport, and further enables the secondary battery to have better rate performance and cycle performance.

[0038] In any embodiment of the present application, the specific surface area of the second carbon-based material is smaller than the specific surface area of the first carbon-based material. By making the specific surface area of the second carbon-based material smaller than that of the first carbon-based material, it is advantageous for ions to move rapidly to the surface layer of the second carbon-based material, and at the same time, side reactions are reduced, which enables the secondary battery to have better rate performance and cycle performance.

[0039] In any embodiment of the present application, the powder consolidation density of the second carbon-based material at 20,000 N is smaller than the powder consolidation density of the first carbon-based material at 20,000 N. By making the powder consolidation density of the second carbon-based material at 20,000 N smaller than that of the first carbon-based material at 20,000 N, a good pore structure can be provided in the second region and the first region of the negative electrode film layer. As a result, it better matches the concentration distribution of ions in the thickness direction of the negative electrode film layer, improves the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte, is more advantageous for ion transport, and further enables the secondary battery to have better rate performance and cycle performance.

[0040] In any embodiment of the present application, the tap density of the second carbon-based material is smaller than the tap density of the first carbon-based material. By making the tap density of the second carbon-based material smaller than that of the first carbon-based material, the pore structure in the thickness direction of the negative electrode film layer can be optimized, the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte can be improved, which is more advantageous for ion transport, and furthermore, the secondary battery can have better rate performance and cycle performance.

[0041] In any embodiment of the present application, the graphitization degree of the second carbon-based material is smaller than the graphitization degree of the first carbon-based material. By adjusting the graphitization degree of the second carbon-based material to be smaller than that of the first carbon-based material, it is advantageous for the secondary battery to achieve both high energy density and good rate performance.

[0042] In any embodiment of the present application, the gram capacity of the second carbon-based material is smaller than the gram capacity of the first carbon-based material. By adjusting the gram capacity of the second carbon-based material to be smaller than that of the first carbon-based material, it is advantageous for the secondary battery to achieve both high energy density and good rate performance.

[0043] In any embodiment of the present application, the powder OI value of the second carbon-based material is smaller than the powder OI value of the first carbon-based material. By adjusting the powder OI value of the second carbon-based material to be smaller than that of the first carbon-based material, it is advantageous for the secondary battery to have better rate performance.

[0044] In any embodiment of the present application, the volume distribution particle size Dv50 of the second carbon-based material is 9 - 15 μm, and optionally 11 - 13 μm.

[0045] In any embodiment of the present application, the volume distribution particle size Dv90 of the second carbon-based material is 20 - 26 μm, and optionally 21 - 25 μm.

[0046] When the volume distribution particle sizes Dv50 and / or Dv90 of the second carbon-based material are within the above ranges, it is advantageous for enhancing the transport performance of ions and electrons, thereby further improving the rate performance of the secondary battery.

[0047] In any of the embodiments of the present application, the second carbon-based material satisfies that (Dv90 - Dv10) / Dv50 is 0.8 - 1.6, and optionally 1.0 - 1.4. When (Dv90 - Dv10) / Dv50 of the second carbon-based material is within the above range, the second carbon-based material has excellent particle deposition performance, is advantageous for improving the compaction density of the negative electrode film layer, thereby further improving the energy density of the secondary battery, and is also advantageous for the negative electrode film layer to have an appropriate pore structure, thereby further improving the rate performance of the secondary battery.

[0048] In any of the embodiments of the present application, the specific surface area of the second carbon-based material is 0.5 - 1.5 m 2 / g, and optionally 0.7 - 1.2 m 2 / g. When the specific surface area of the second carbon-based material is within the above range, it is advantageous for reducing side reactions, thereby enabling the secondary battery to have better cycle performance.

[0049] In any of the embodiments of the present application, the powder compaction density of the second carbon-based material at 20000 N is 1.6 - 1.8 g / cm 3 , and optionally 1.65 - 1.75 g / cm 3 . When the powder compaction density of the second carbon-based material is within the above range, the compaction density of the negative electrode film layer can be increased, thereby further increasing the energy density of the secondary battery. It is also advantageous for the negative electrode film layer to have an appropriate pore structure, improving the transport performance of ions and electrons, improving the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte, and further improving the rate performance and / or cycle performance of the secondary battery.

[0050] In any of the embodiments of the present application, the tap density of the second carbon-based material is 0.9 - 1.2 g / cm3 and selectively 1.0 - 1.1 g / cm 3 When the tap density of the second carbon-based material is within the above range, the consolidation density of the negative electrode film layer can be increased, thereby further increasing the energy density of the secondary battery. Furthermore, it is advantageous for the negative electrode film layer to have an appropriate pore structure, which can improve the ion and electron transport performance, improve the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte, and further improve the rate performance and / or cycle performance of the secondary battery.

[0051] In any embodiment of the present application, the graphitization degree of the second carbon-based material is ≧ 92.5%, and selectively 93% - 94%. When the graphitization degree of the second carbon-based material is within the above range, it is advantageous for improving the ion transport performance of the negative electrode film layer, thereby enabling both high energy density and good rate performance in the secondary battery.

[0052] In any embodiment of the present application, the gram capacity of the second carbon-based material is ≧ 354 mAh / g, and selectively 355 - 359 mAh / g. When the gram capacity of the second carbon-based material is within the above range, on the one hand, the energy density of the secondary battery can be improved, and on the other hand, the carbon-based material can have good ion transport performance, which is also advantageous for improving the rate performance of the secondary battery.

[0053] In any embodiment of the present application, the volume distribution particle size Dv50 of the second carbon-based material is denoted as A, with the unit of μm, and the specific surface area of the second carbon-based material is denoted as B, with the unit of m 2 / g, and A / B is 9.0 - 20, and selectively 11 - 15. By adjusting A / B within the above range, the ion storage channels in the negative electrode film layer can be increased, which is advantageous for the rapid diffusion of ions from the surface layer of the second carbon-based material particles to the bulk phase, thereby being advantageous for further optimizing the rate performance of the secondary battery. It is also advantageous for reducing side reactions, thereby enabling the secondary battery to have better cycle performance.

[0054] In any embodiment of the present application, the OI value of the powder of the second carbon-based material is 2-8, and optionally 4-6. The OI value of the powder of the second carbon-based material is relatively small, and ions from the positive electrode can be quickly received, thereby further improving the rate performance of the secondary battery.

[0055] In any embodiment of the present application, the second carbon-based material contains graphite, and optionally contains artificial graphite.

[0056] In any embodiment of the present application, the mass ratio of the second carbon-based material in the second active material is ≧85%, and optionally 90%-97%. This is advantageous for improving the rate performance of the secondary battery.

[0057] In any embodiment of the present application, the second active material contains a second silicon-based material, thereby further increasing the energy density of the secondary battery.

[0058] In any embodiment of the present application, the second silicon-based material contains one or more of primary particles and secondary particles formed by aggregation of primary particles, and optionally contains primary particles.

[0059] In any embodiment of the present application, the second silicon-based material contains primary particles, and the ratio of the number of the second silicon-based material of the primary particles in the second silicon-based material is ≧60%, and optionally 70%-95%. When the second silicon-based material is mainly primary particles, it is advantageous to reduce the probability of particle crushing and improve the compaction density of the negative electrode film layer, thereby further improving the energy density of the secondary battery.

[0060] In any embodiment of the present application, the mass ratio of the second active material in the second silicon-based material is smaller than the mass ratio of the first active material in the first silicon-based material. By making the mass ratio of the second active material in the second silicon-based material smaller than the mass ratio of the first active material in the first silicon-based material, side reactions can be reduced, which is advantageous for the secondary battery to have better cycle performance.

[0061] In any embodiment of the present application, the volume distribution particle size Dv50 of the second silicon-based material is smaller than the volume distribution particle size Dv50 of the first silicon-based material. By adjusting the volume distribution particle size Dv50 of the second silicon-based material to be smaller than that of the first silicon-based material, not only can the probability of the second silicon-based material particles being crushed be reduced, but also the electronic conductivity of the second silicon-based material can be increased, and further the ion storage channels of the negative electrode film layer can be increased, thereby enabling the secondary battery to have both high energy density and good rate performance.

[0062] In any embodiment of the present application, the specific surface area of the second silicon-based material is smaller than the specific surface area of the first silicon-based material. When the specific surface area of the second silicon-based material is smaller than that of the first silicon-based material, it is advantageous for reducing side reactions, which is advantageous for the secondary battery to have better cycle performance.

[0063] In any embodiment of the present application, the powder compaction density of the second silicon-based material at 50000 N is greater than the powder compaction density of the first silicon-based material at 50000 N. By adjusting the powder compaction density of the second silicon-based material to be greater than that of the first silicon-based material, it is advantageous to improve the energy density of the secondary battery and improve the cycle performance of the secondary battery.

[0064] In any embodiment of the present application, the tap density of the second silicon-based material is greater than the tap density of the first silicon-based material. By adjusting the tap density of the second silicon-based material to be greater than the tap density of the first silicon-based material, it is advantageous to improve the energy density of the secondary battery and to improve the cycle performance of the secondary battery.

[0065] In any embodiment of the present application, the powder resistivity of the second silicon-based material at 4 MPa is less than the powder resistivity of the first silicon-based material at 4 MPa. By adjusting the powder resistivity of the second silicon-based material to be less than the powder resistivity of the first silicon-based material, it is advantageous to improve the electron conductivity of the negative electrode film layer, and thereby it is advantageous to further improve the rate performance of the secondary battery.

[0066] In any embodiment of the present application, the volume distribution particle size Dv50 of the second silicon-based material is 4 - 12 μm, and optionally 5 - 11 μm.

[0067] In any embodiment of the present application, the volume distribution particle size Dv90 of the second silicon-based material is 8 - 18 μm, and optionally 9 - 17 μm.

[0068] When the volume distribution particle size Dv50 and / or Dv90 of the second silicon-based material is within the above range, it is advantageous to enhance the transport performance of ions and electrons, and thereby the rate performance of the secondary battery can be further enhanced.

[0069] In any embodiment of the present application, the second silicon-based material satisfies that (Dv90 - Dv10) / Dv50 is 0.7 - 1.3, and is selectively 0.8 - 1.2. When (Dv90 - Dv10) / Dv50 of the second silicon-based material is within the above range, the second silicon-based material has excellent particle deposition performance, is advantageous for improving the consolidation density of the negative electrode film layer, thereby further improving the energy density of the secondary battery, and is also advantageous for the negative electrode film layer to have an appropriate pore structure, thereby further improving the rate performance of the secondary battery.

[0070] In any embodiment of the present application, the specific surface area of the second silicon-based material is 0.6 - 1.6 m 2 / g, and is selectively 0.7 - 1.5 m 2 / g. When the specific surface area of the second silicon-based material is within the above range, it is advantageous for reducing side reactions, thereby enabling the secondary battery to have better cycle performance.

[0071] In any embodiment of the present application, the powder consolidation density of the second silicon-based material at 50000 N is 1.2 - 1.8 g / cm 3 and is selectively 1.3 - 1.7 g / cm 3 When the powder consolidation density of the second silicon-based material is within the above range, the consolidation density of the negative electrode film layer can be increased, thereby further increasing the energy density of the secondary battery. It is also advantageous for the negative electrode film layer to have an appropriate pore structure, improving the transport performance of ions and electrons, improving the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte, and further improving the rate performance and / or cycle performance of the secondary battery.

[0072] In any embodiment of the present application, the tap density of the second silicon-based material is 1.1 - 1.7 g / cm 3 and is selectively 1.2 - 1.6 g / cm 3When the tap density of the second silicon-based material is within the above range, the consolidation density of the negative electrode film layer can be increased, thereby further increasing the energy density of the secondary battery. Further, it is advantageous for the negative electrode film layer to have an appropriate pore structure, improving the transport performance of ions and electrons, improving the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte, and further improving the rate performance and / or cycle performance of the secondary battery.

[0073] In any of the embodiments of the present application, the powder resistivity of the second silicon-based material at 4 MPa is ≤5 Ω·cm, and selectively 0.3 - 4 Ω·cm. By adjusting the powder resistivity of the second silicon-based material within the above range, the electron conductivity of the negative electrode film layer can be improved, and the rate performance of the secondary battery can be further improved.

[0074] In any of the embodiments of the present application, the mass ratio of the second silicon-based material in the second active material is ≤15%, and selectively 3% - 10%. By adjusting the content of the second silicon-based material within the above range, the rate performance and energy density of the secondary battery can be improved, and the secondary battery can have better cycle performance.

[0075] In any of the embodiments of the present application, the second silicon-based material includes one or more of silicon single crystal, silicon oxide, silicon carbon material, and silicon alloy material.

[0076] In any of the embodiments of the present application, the intermediate region located between the first region and the second region includes the first active material and / or the second active material.

[0077] In any of the embodiments of the present application, the porosity of the negative electrode film layer is ≥15%, and selectively 20% - 45%. This is advantageous for the negative electrode film layer to achieve both high capacity and an appropriate pore structure, and further advantageous for the secondary battery to achieve both high energy density and good cycle performance and rate performance.

[0078] In any embodiment of the present application, the consolidation density of the negative electrode film layer is ≥ 1.5 g / cm 3 and optionally 1.6 - 1.8 g / cm 3 . This is advantageous for enabling the negative electrode film layer to achieve both high capacity and good ion and electron transport performance, and further advantageous for enabling the secondary battery to achieve both high energy density and good cycle performance and rate performance.

[0079] In any embodiment of the present application, the areal density of the negative electrode film layer is ≥ 7 mg / cm 2 and optionally 9 - 30 mg / cm 2 . This is advantageous for enabling the negative electrode film layer to achieve both high capacity and good ion and electron transport performance, and further advantageous for enabling the secondary battery to achieve both high energy density and good cycle performance and rate performance.

[0080] The second aspect of the present application provides a power consumption device including the secondary battery of the first aspect of the present application.

[0081] Since the power consumption device of the present application includes the secondary battery according to the present application, it has at least the same advantages as the secondary battery.

Brief Description of the Drawings

[0082] To more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings that need to be used in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can also obtain other drawings based on these drawings on the premise of not paying creative labor. In the drawings, the drawings are not necessarily drawn to actual scale.

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Embodiments for Carrying Out the Invention

[0083] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing the secondary battery and the power consumption device of the present application will be described in detail. However, detailed descriptions that are not necessary may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of structures that are actually the same may be omitted. This is to avoid making the following description unnecessarily redundant and to enable those skilled in the art to easily understand. Note that the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the theme described in the claims.

[0084] The "ranges" disclosed in this application are limited in the form of a lower limit and an upper limit. A given range is defined by selecting one lower limit and one upper limit, and the selected lower limit and upper limit define the boundaries of a specific range. The ranges thus defined may or may not include the limit values, and any combination is possible, that is, any lower limit may 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 conceivable. In addition, if 1 and 2 are listed as the minimum range values and 3, 4, and 5 are listed as the maximum range values, all of the ranges 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5 are conceivable. In this application, unless otherwise specified, the numerical range "a - b" represents a shortened expression of any combination of real numbers between a and b, where both a and b are real numbers. For example, the numerical range "0 - 5" represents that all real numbers between "0 - 5" have already been listed in this specification, and "0 - 5" is only a shortened expression of the combinations of these numerical values. Also, when a certain parameter is expressed as an integer ≧2, it corresponds to disclosing that this parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0085] Unless otherwise specified, all embodiments and alternative embodiments of this application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure content of this application.

[0086] Unless otherwise specified, all technical features and alternative technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure content of this application.

[0087] Unless otherwise specified, all steps of this application may be performed in order or randomly, preferably in order. For example, the fact that the method includes steps (a) and (b) means that the method may include steps (a) and (b) performed in order, or steps (b) and (a) performed in order. For example, the fact that the above-mentioned method may further include step (c) means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or steps (a), (c), and (b), or steps (c), (a), and (b), etc.

[0088] Unless otherwise specified, the terms "comprising" and "including" mentioned in this application may represent an open type or a closed type. For example, the above "comprising" and "including" may further comprise or include other components not listed, or may comprise or include only the listed components.

[0089] Unless otherwise specified, the term "or" in this application is inclusive. For example, the phrase "A or B" represents "A, B, or both A and B". More specifically, any of the conditions where A is true (or exists) and B is false (or does not exist), where A is false (or does not exist) but B is true (or exists), and where both A and B are true (or exist) satisfy "A or B".

[0090] Unless otherwise specified, the terms used in this application have the well-known meanings generally understood by those skilled in the art.

[0091] Unless otherwise specified, the numerical values of each parameter mentioned in this application can be measured using various test methods commonly used in the art. For example, they can be measured according to the test methods according to this application. Unless otherwise specified, the temperature during the test is 25°C in all cases.

[0092] In this application, the terms "a plurality of" and "various" mean two or more.

[0093] As an important component of a secondary battery, the performance of the negative electrode plate has a very important impact on the performance of the secondary battery. Currently, graphite is the most common negative electrode active material, but the energy density and rate performance of secondary batteries using this material are both approaching theoretical values and can no longer meet the increasingly stringent usage requirements. Silicon-based materials have the advantage of high theoretical energy density and can significantly improve the energy density of secondary batteries. However, the silicon-based material itself has a high electron resistivity, which results in a relatively rapid decay of the reversible capacity of the secondary battery, and such a decay phenomenon is more serious at high rates.

[0094] In view of this, the inventor has skillfully improved the composition of the negative electrode film layer, which enables the secondary battery to have both good rate performance and cycle performance on the premise of having a high energy density.

[0095] Specifically, the first aspect of the embodiment of this application provides a secondary battery.

[0096] This application is not particularly limited to the type of secondary battery. For example, the secondary battery may be a lithium-ion battery or the like. Generally, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte, etc. During the charge and discharge process of the secondary battery, ions reciprocate between the positive electrode plate and the negative electrode plate for insertion and deinsertion, and the electrolyte plays a role in conducting ions. This application is not particularly limited to the type of electrolyte and can be selected according to actual needs. For example, the electrolyte may be selected from at least one of a solid electrolyte and a liquid electrolyte (i.e., an electrolytic solution). Some secondary batteries using an electrolytic solution and some secondary batteries using a solid electrolyte may further include a separator. The separator is installed between the positive electrode plate and the negative electrode plate and mainly serves to isolate.

[0097] [Negative electrode plate] Figures 1 to 3 are schematic diagrams of the embodiments of the negative electrode plate of this application.

[0098] As shown in FIGS. 1 to 3, the negative electrode plate 10 includes a negative electrode current collector 101 and a negative electrode film layer 102 formed on at least one surface of the negative electrode current collector 101. The negative electrode film layer 102 has a first surface 102a away from the negative electrode current collector 101 and a second surface 102b disposed opposite to the first surface 102a. The thickness of the negative electrode film layer 102 is denoted as H, and the region within the thickness range from the second surface 102b of the negative electrode film layer to 0.3H is denoted as the first region 1021 of the negative electrode film layer, and the region within the thickness range from the first surface 102a of the negative electrode film layer to 0.3H is denoted as the second region 1022 of the negative electrode film layer.

[0099] The first region 1021 contains a first active material, and the second region 1022 contains a second active material.

[0100] The first active material includes a first carbon-based material and a first silicon-based material. The first carbon-based material includes primary particles, and the first silicon-based material includes secondary particles formed by aggregation of primary particles.

[0101] The thickness H of the negative electrode film layer is the thickness of the negative electrode film layer located on one side of the negative electrode current collector.

[0102] By including the first carbon-based material and the first silicon-based material in the first region of the negative electrode film layer, the first carbon-based material includes primary particles, and the first silicon-based material includes secondary particles formed by aggregation of primary particles. On the premise that the secondary battery has a high energy density, good rate performance and cycle performance are achieved simultaneously.

[0103] Compared with a pure carbon-based material as the negative electrode active material, the first active material of the present application simultaneously includes a first carbon-based material and a first silicon-based material. Therefore, the gram capacity of the first active material of the present application is higher, and a higher energy density can be achieved under the same surface density condition.

[0104] The first carbon-based material contains primary particles. The specific surface area of the primary particles is generally relatively small, which can reduce side reactions, improve the cycle performance of the secondary battery, and also improve the energy density of the secondary battery because the capacity of the primary particles is relatively high.

[0105] The first silicon-based material contains secondary particles, which can also increase the ion intercalation channels of the first silicon-based material, being advantageous for further optimization of the rate performance of the secondary battery. Also, the pressure resistance of the silicon-based material of the secondary particles is relatively poor. By improving the structure of the negative electrode film layer, the destruction of the silicon-based material structure of the secondary particles due to the roll press pressure can be reduced, and the high-capacity superiority of the first silicon-based material can be fully exerted.

[0106] Since the first active material contains the first silicon-based material, the first silicon-based material has the superiority of high capacity. Thus, compared with the conventional graphite negative electrode, a higher energy density can be obtained under the same surface density condition. Under the high surface density condition, the ionic liquid-phase diffusion resistance is relatively high. By optimizing the particle structure of the first silicon-based material to include secondary particles in the first silicon-based material, the pore structure of the first region of the negative electrode film layer can be improved. As a result, during the charge and discharge process, the electrolyte can flow back quickly. Thereby, on the premise that the secondary battery has a high energy density, the rate performance and cycle performance of the secondary battery can be further optimized.

[0107] Since the resistivity of the first silicon-based material itself is relatively high, therefore, it is also advantageous to improve the electron conductivity of the negative electrode film layer by including primary particles in the first carbon-based material and including secondary particles in the first silicon-based material, reducing battery polarization, and being further advantageous for further optimization of the rate performance and cycle performance of the secondary battery.

[0108] Both the primary particles and the secondary particles have meanings known in the art. The primary particles are non-aggregated particles. The secondary particles are aggregated particles formed by the aggregation of two or more primary particles. The primary particles and the secondary particles can be distinguished using a scanning electron microscope (SEM) image.

[0109] In some embodiments, the surface of the first carbon-based material may have a carbon coating layer. The presence of the carbon coating layer can further increase the ion diffusion channels, accelerate the ion diffusion rate, and improve the electrical contact between the first carbon-based material and the first silicon-based material, thereby being advantageous for further optimization of the rate performance of the secondary battery.

[0110] In some embodiments, 80% or more of the surface of the first carbon-based material is coated with a carbon coating layer. Optionally, 90%-100% of the surface of the first carbon-based material is coated with a carbon coating layer.

[0111] In some embodiments, the surface of the first carbon-based material may have a carbon coating layer, and the carbon coating layer contains hard carbon. Hard carbon has the advantage of a large interlayer spacing and can increase the ion diffusion rate, thereby being advantageous for further optimization of the rate performance of the secondary battery.

[0112] The carbon coating layer on the surface of the first carbon-based material may be formed by carbonizing an organic carbon source. The organic carbon source may use a carbon-containing material suitable for coating known in the art, and may include, for example, one or more of coal pitch, petroleum pitch, phenolic resin, coconut shell, etc.

[0113] In some embodiments, the proportion of the first carbon-based material of the primary particles in the first carbon-based material may be ≧70%, for example, ≧72.5%, ≧75%, ≧77.5%, ≧80%. When an appropriate proportion of primary particles is included in the first carbon-based material, the first carbon-based material can have relatively high structural stability, reduce side reactions, improve the cycle performance and / or rate performance of the secondary battery, and also increase the compaction density of the negative electrode film layer, thereby improving the energy density of the secondary battery.

[0114] In further research, the inventor found that the proportion of the first carbon-based material of the primary particles in the first carbon-based material should not be too large. At this time, the compaction density of the first region of the negative electrode film layer is relatively large, which is likely to cause a decrease in the porosity of the entire negative electrode film layer, and conversely increase the internal resistance of the secondary battery, affecting the further improvement effect on the rate performance and / or cycle performance of the secondary battery. Optionally, in some embodiments, the proportion of the first carbon-based material of the primary particles in the first carbon-based material may be 70%-95%, 70%-90%, 70%-85%, 70%-80%, 75%-95%, 75%-90%, 75%-85%, 75%-80%. This is advantageous for the secondary battery to achieve both good cycle performance and rate performance and a higher energy density.

[0115] In some embodiments, the first carbon-based material may further include secondary particles, and the proportion of the first carbon-based material of the secondary particles in the first carbon-based material may be ≦30%.

[0116] In some embodiments, the proportion of the first silicon-based material of the secondary particles in the first silicon-based material may be ≧55%, for example, ≧57.5%, ≧60%, ≧62.5%, ≧65%, etc. When an appropriate proportion of secondary particles is included in the first silicon-based material, the ion storage channels in the negative electrode film layer can be increased, which is also beneficial for the rapid diffusion of ions from the particle surface layer to the bulk phase, thereby being advantageous for the further optimization of the rate performance of the secondary battery.

[0117] In further research, the inventor found that the proportion of the first silicon-based material in the secondary particles in the first silicon-based material is not too large. In this case, there are many side reactions in the secondary battery, which also affects the further improvement effect on the cycle performance of the secondary battery. Optionally, in some embodiments, the proportion of the first silicon-based material of the secondary particles in the first silicon-based material may be 55%-90%, 60%-90%, 65%-90%, 55%-85%, 60%-85%, 65%-85%, 55%-80%, 60%-80%, 65%-80%. This is advantageous for the secondary battery to achieve both good cycle performance, rate performance and higher energy density.

[0118] In some embodiments, the first silicon-based material may further include primary particles (here referring to non-aggregated particles), and the proportion of the first silicon-based material of the primary particles in the first silicon-based material may be ≤45%. The specific types of the first silicon-based material of the primary particles and the first silicon-based material of the secondary particles may be the same or different.

[0119] In some embodiments, the porosity of the first silicon-based material of the secondary particles may be ≥4%, and optionally 5%-20%. The inventor noticed in further research that further adjusting the porosity of the first silicon-based material of the secondary particles is advantageous for the further optimization of the rate performance of the secondary battery. When the porosity of the first silicon-based material of the secondary particles is within the above range, it is advantageous to improve the pore structure of the negative electrode film layer, improve the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte, thereby accelerating the transport rate of the ionic liquid phase, and also increasing the ion storage channels of the first silicon-based material, which is advantageous for quickly diffusing ions from the particle surface layer to the bulk phase, and thus is advantageous for the further optimization of the rate performance of the secondary battery.

[0120] In some embodiments, the volume distribution particle size Dv50 of the first carbon-based material may be 10-16 μm, and optionally 12-14 μm.

[0121] When the volume distribution particle size Dv50 of the first carbon-based material is within the above range, it is advantageous for enhancing the transport performance of ions and electrons, thereby further improving the rate performance of the secondary battery. In addition, the specific surface area of the first carbon-based material can be reduced, and side reactions can be decreased, thereby further improving the cycle performance of the secondary battery.

[0122] As a result of further research, the inventors found that when the first carbon-based material satisfies the above design and further satisfies one or more of the following conditions, the performance of the secondary battery can be further improved. For example, at least one of the energy density, cycle performance, and rate performance of the secondary battery can be further improved.

[0123] In some embodiments, the volume distribution particle size Dv90 of the first carbon-based material may be 20-28 μm, and optionally 22-26 μm. When the volume distribution particle size Dv90 of the first carbon-based material is within the above range, the consistency of the first carbon-based material particles is relatively good, which is advantageous for enhancing the transport performance of ions and electrons, thereby further improving the rate performance of the secondary battery.

[0124] In some embodiments, the first carbon-based material satisfies that (Dv90-Dv10) / Dv50 may be 0.8-1.6, and optionally 1.1-1.4. When (Dv90-Dv10) / Dv50 of the first carbon-based material is within the above range, the first carbon-based material has excellent particle deposition performance, which is advantageous for improving the compaction density of the negative electrode film layer, thereby further improving the energy density of the secondary battery. In addition, it is advantageous for the negative electrode film layer to have an appropriate pore structure, thereby further improving the rate performance of the secondary battery.

[0125] In some embodiments, the specific surface area of the first carbon-based material may be 1.0-1.8 m 2 / g, and optionally 1.2-1.6 m 2 / g. When the specific surface area of the first carbon-based material is within the above range, it is advantageous for reducing side reactions, thereby enabling the secondary battery to have good cycle performance.

[0126] In some embodiments, the powder compaction density of the first carbon-based material at 20000 N may be 1.75-2.0 g / cm 3 and optionally 1.8-1.95 g / cm 3 . When the powder compaction density of the first carbon-based material is within the above range, the compaction density of the negative electrode film layer can be increased, thereby further increasing the energy density of the secondary battery. Moreover, it is advantageous for the negative electrode film layer to have an appropriate pore structure, improving the transport performance of ions and electrons, improving the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte, and further improving the rate performance and / or cycle performance of the secondary battery.

[0127] In some embodiments, the tap density of the first carbon-based material may be 1.1-1.3 g / cm 3 and optionally 1.15-1.25 g / cm 3 . When the tap density of the first carbon-based material is within the above range, the compaction density of the negative electrode film layer can be increased, thereby further increasing the energy density of the secondary battery. Moreover, it is advantageous for the negative electrode film layer to have an appropriate pore structure, improving the transport performance of ions and electrons, improving the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte, and further improving the rate performance and / or cycle performance of the secondary battery.

[0128] In some embodiments, the graphitization degree of the first carbon-based material may be ≧93%, and optionally 94%-96%. When the graphitization degree of the first carbon-based material is within the above range, it is advantageous for improving the ion transport performance of the negative electrode film layer, thereby enabling the secondary battery to have both high energy density and good rate performance.

[0129] In some embodiments, the gram capacity of the first carbon-based material may be ≥ 360 mAh / g, and optionally 361 - 365 mAh / g. When the gram capacity of the first carbon-based material is within the above range, on the one hand, the energy density of the secondary battery can be improved, and on the other hand, the carbon-based material can be provided with good ion transport performance, thereby also being advantageous for improving the rate performance of the secondary battery.

[0130] In some embodiments, the powder OI value of the first carbon-based material may be 5 - 15, and optionally 7 - 12. Since the powder OI value of the first carbon-based material is relatively small, ions from the positive electrode can be quickly received, thereby further improving the rate performance of the secondary battery.

[0131] In some embodiments, the first carbon-based material may include graphite, and optionally includes artificial graphite.

[0132] In some embodiments, the first carbon-based material may include artificial graphite of primary particles. Optionally, the proportion of the number of artificial graphite of primary particles in the first carbon-based material may be ≥ 70%, ≥ 72.5%, ≥ 75%, ≥ 77.5%, ≥ 80%. As an example, the proportion of the number of artificial graphite of primary particles in the first carbon-based material may be 70% - 95%, 70% - 90%, 70% - 85%, 70% - 80%, 75% - 95%, 75% - 90%, 75% - 85%, 75% - 80%.

[0133] In some embodiments, the first carbon-based material may include artificial graphite of primary particles, and has a carbon coating layer on the surface of the artificial graphite of primary particles. Optionally, the carbon coating layer includes hard carbon.

[0134] In some embodiments, the mass ratio of the first carbon-based material in the first active material may be ≧50%, and optionally 60%-98%, 70%-98%, 80%-98%, 85%-98%, 60%-97%, 70%-97%, 80%-97%, 85%-97%. By adjusting the content of the first carbon-based material within the above range, the cycle performance of the secondary battery can be improved, and good rate performance can be achieved simultaneously in the secondary battery.

[0135] As a result of further research, the inventor found that when the first silicon-based material satisfies the above design and further satisfies one or more of the following conditions, the performance of the secondary battery can be further improved. For example, at least one of the energy density, cycle performance, and rate performance of the secondary battery can be further improved.

[0136] In some embodiments, the volume distribution particle size Dv50 of the first silicon-based material may be 8-15 μm, and optionally 10-13 μm.

[0137] In some embodiments, the volume distribution particle size Dv90 of the first silicon-based material may be 15-25 μm, and optionally 16-24 μm.

[0138] When the volume distribution particle size Dv50 and / or Dv90 of the first silicon-based material is within the above range, the ion storage channels in the negative electrode film layer can be increased, which is also beneficial for the rapid diffusion of ions from the particle surface layer to the bulk phase, thereby being advantageous for the further optimization of the rate performance of the secondary battery.

[0139] In some embodiments, the first silicon-based material may satisfy that (Dv90 - Dv10) / Dv50 is 0.7 - 1.5, and is selectively 0.9 - 1.3. When (Dv90 - Dv10) / Dv50 of the first silicon-based material is within the above range, the first silicon-based material has excellent particle deposition performance, is advantageous for improving the consolidation density of the negative electrode film layer, thereby further improving the energy density of the secondary battery, and is also advantageous for the negative electrode film layer to have an appropriate pore structure, thereby further improving the rate performance of the secondary battery.

[0140] In some embodiments, the specific surface area of the first silicon-based material may be 0.7 - 2.0 m 2 / g, and is selectively 0.8 - 1.6 m 2 / g. When the specific surface area of the first silicon-based material is within the above range, the ion storage channels in the negative electrode film layer can be increased, which is also advantageous for the rapid diffusion of ions from the particle surface layer to the bulk phase, thereby being advantageous for further optimizing the rate performance of the secondary battery. Also, when the specific surface area of the first silicon-based material is within the above range, it is advantageous for reducing side reactions, thereby enabling the secondary battery to have better cycle performance.

[0141] In some embodiments, the powder consolidation density of the first silicon-based material at 50000 N may be 1.0 - 1.7 g / cm 3 and is selectively 1.2 - 1.6 g / cm 3 . When the powder consolidation density of the first silicon-based material is within the above range, the consolidation density of the negative electrode film layer can be increased, thereby further increasing the energy density of the secondary battery, and is also advantageous for the negative electrode film layer to have an appropriate pore structure, improving the transport performance of ions and electrons, improving the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte, and further improving the rate performance and / or cycle performance of the secondary battery.

[0142] In some embodiments, the tap density of the first silicon-based material is 1.0 - 1.5 g / cm 3It may also be selectively 1.1-1.4 g / cm 3 It is. When the tap density of the first silicon-based material is within the above range, the consolidation density of the negative electrode film layer can be increased, thereby further increasing the energy density of the secondary battery. Furthermore, it is advantageous for the negative electrode film layer to have an appropriate pore structure, improving the transport performance of ions and electrons, improving the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte, and further improving the rate performance and / or cycle performance of the secondary battery.

[0143] In some embodiments, the powder resistivity of the first silicon-based material at 4 MPa may be ≦15 Ω·cm, and is selectively 0.5-12 Ω·cm. By adjusting the powder resistivity of the first silicon-based material within the above range, the electron conductivity of the negative electrode film layer can be improved, and the rate performance of the secondary battery can be further improved.

[0144] In some embodiments, the mass ratio of the first silicon-based material in the first active material may be ≦50%, and is selectively 2%-40%, 2%-30%, 2%-20%, 2%-15%, 3%-40%, 3%-30%, 3%-20%, 3%-15%. By adjusting the content of the first silicon-based material within the above range, the rate performance and energy density of the secondary battery can be improved, and good cycle performance can be achieved for the secondary battery.

[0145] In some embodiments, the first silicon-based material may include one or more of silicon single crystal, silicon oxide (SiO x , 0 < x ≦ 2), silicon carbon material, and silicon alloy material. The present application does not specifically limit the structure of the silicon carbon material. For example, nanosilicon can be dispersed in the carbon material by high-energy ball milling, nanosilicon can be dispersed in porous carbon, the carbon material can be dispersed in porous silicon, the carbon material can be coated on the surface of nanosilicon, and nanosilicon and nanocarbon can be co-deposited, etc.

[0146] In some embodiments, the first silicon-based material may include secondary particles formed by aggregation of at least one of primary particles of a silicon oxygen material containing no alkali metal and no alkaline earth metal, primary particles of a silicon oxygen material containing an alkali metal or an alkaline earth metal, primary particles of a silicon carbon material, primary particles of elemental silicon, and primary particles of a silicon alloy.

[0147] Optionally, the alkali metal includes Li. Optionally, the alkaline earth metal includes Mg.

[0148] For example, the first silicon-based material includes secondary particles formed by aggregation of primary particles of a silicon oxygen material containing no alkali metal and no alkaline earth metal, secondary particles formed by aggregation of primary particles of a silicon oxygen material containing no alkali metal and no alkaline earth metal and primary particles of a silicon oxygen material containing an alkali metal or an alkaline earth metal, secondary particles formed by aggregation of primary particles of a silicon oxygen material containing an alkali metal or an alkaline earth metal, secondary particles formed by aggregation of primary particles of a silicon carbon material, secondary particles formed by aggregation of primary particles of a silicon carbon material and primary particles of a silicon oxygen material containing no alkali metal and no alkaline earth metal, and secondary particles formed by aggregation of primary particles of a silicon carbon material and primary particles of a silicon oxygen material containing an alkali metal or an alkaline earth metal.

[0149] In some embodiments, the surface of the first silicon-based material may have a carbon coating layer. For example, a carbon coating layer may be provided on the surface of elemental silicon, silicon oxide, etc. to increase the electron conductivity of the first silicon-based material and reduce the powder resistivity. The powder resistivity of the first silicon-based material can be adjusted by adjusting parameters such as the thickness and graphitization degree of the carbon coating layer.

[0150] Of course, the surface of the first silicon-based material may not have a carbon coating layer. For example, the powder resistivity of the first silicon-based material may be adjusted by adjusting parameters such as the structure of the silicon carbon material and the carbon element content.

[0151] The carbon coating layer on the surface of the first silicon-based material can be formed by chemical vapor deposition, pyrolysis, hydrothermal method, etc.

[0152] The second region 1022 contains a second active material different from the first active material.

[0153] In some embodiments, the second active material may include a second carbon-based material.

[0154] In some embodiments, the second carbon-based material may include secondary particles formed by aggregation of primary particles. By including secondary particles in the second carbon-based material, the ion transport rate can be increased, thereby further improving the rate performance of the secondary battery.

[0155] In some embodiments, the proportion of the second carbon-based material of the secondary particles in the second carbon-based material may be ≧60%, for example, ≧62.5%, ≧65%, ≧67.5%, ≧70%. When the second carbon-based material contains an appropriate proportion of secondary particles, the ion storage channels in the negative electrode film layer can be increased, which is advantageous for further optimizing the rate performance of the secondary battery.

[0156] The inventor further found in the research that the proportion of the second carbon-based material of the secondary particles in the second carbon-based material should not be too large. In this case, there are many side reactions in the secondary battery, which also affects the further improvement effect on the cycle performance of the secondary battery. Optionally, in some embodiments, the proportion of the second carbon-based material of the secondary particles in the second carbon-based material may be 60%-90%, 60%-85%, 60%-80%, 60%-75%, 65%-90%, 65%-85%, 65%-80%, 65%-75%, 70%-90%, 70%-85%, 70%-80%, 70%-75%. This is advantageous for better achieving both good rate performance and cycle performance in the secondary battery.

[0157] In some embodiments, the second carbon-based material may further include primary particles (herein referring to non-aggregated particles), and the proportion of the second carbon-based material of the primary particles in the second carbon-based material may be ≤ 40%.

[0158] In some embodiments, the surface of the second carbon-based material may have a carbon coating layer. The presence of the carbon coating layer can increase the ion diffusion channel, which is advantageous for further optimizing the rate performance of the secondary battery.

[0159] In some embodiments, more than 80% of the surface of the second carbon-based material is coated with a carbon coating layer. Optionally, 90%-100% of the surface of the second carbon-based material is coated with a carbon coating layer.

[0160] In some embodiments, the surface of the second carbon-based material may have a carbon coating layer, and the carbon coating layer contains soft carbon. Soft carbon has the advantage of a large interlayer spacing, which can increase the ion diffusion rate, thereby being advantageous for further optimizing the rate performance of the secondary battery. At the same time, soft carbon has few structural defects, which can reduce side reactions and enable good cycle performance of the secondary battery.

[0161] The carbon coating layer on the surface of the second carbon-based material may be formed by carbonizing an organic carbon source. The organic carbon source may use a carbon-containing material suitable for coating known in the art, and may include, for example, one or more of coal pitch, petroleum pitch, phenolic resin, coconut shell, etc.

[0162] In some embodiments, the surface of the first carbon-based material has a carbon coating layer, the surface of the second carbon-based material has a carbon coating layer, and the mass percentage content of the carbon coating layer of the second carbon-based material is greater than that of the carbon coating layer of the first carbon-based material. By providing carbon coating layers on both the first carbon-based material and the second carbon-based material, the rate performance of the secondary battery can be further improved. By making the mass percentage content of the carbon coating layer of the second carbon-based material greater than that of the carbon coating layer of the first carbon-based material, ions can be more rapidly moved to the surface layer of the second carbon-based material, thereby enabling the secondary battery to have better rate performance and cycle performance.

[0163] In some embodiments, the volume distribution particle size Dv50 of the second carbon-based material may be smaller than the volume distribution particle size Dv50 of the first carbon-based material. By making the volume distribution particle size Dv50 of the second carbon-based material smaller than that of the first carbon-based material, a good compaction density difference can be provided between the second region and the first region of the negative electrode film layer, thereby improving the consistency between the porosity and the ion concentration distribution in the thickness direction of the negative electrode film layer, being advantageous for improving the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte, being advantageous for ion transport, and further enabling the secondary battery to have better rate performance and cycle performance.

[0164] In some embodiments, the specific surface area of the second carbon-based material may be smaller than the specific surface area of the first carbon-based material. By making the specific surface area of the second carbon-based material smaller than that of the first carbon-based material, it is advantageous for ions to rapidly move to the surface layer of the second carbon-based material, while reducing side reactions, thereby enabling the secondary battery to have better rate performance and cycle performance.

[0165] In some embodiments, the powder compaction density of the second carbon-based material at 20,000 N may be smaller than the powder compaction density of the first carbon-based material at 20,000 N. By making the powder compaction density of the second carbon-based material smaller than the powder compaction density of the first carbon-based material at 20,000 N, a good pore structure can be provided in the second region and the first region of the negative electrode film layer, so that it can better match the concentration distribution of ions in the thickness direction of the negative electrode film layer, improve the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte, be more advantageous for ion transport, and further endow the secondary battery with better rate performance and cycle performance.

[0166] In some embodiments, the tap density of the second carbon-based material may be smaller than the tap density of the first carbon-based material. By making the tap density of the second carbon-based material smaller than the tap density of the first carbon-based material, the pore structure in the thickness direction of the negative electrode film layer can be optimized, the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte can be improved, it is more advantageous for ion transport, and further the secondary battery can be endowed with better rate performance and cycle performance.

[0167] In some embodiments, the graphitization degree of the second carbon-based material may be smaller than the graphitization degree of the first carbon-based material. The graphitization degree of the second carbon-based material is relatively small, whereby its interlayer spacing is relatively large, which is advantageous for the rapid desorption of ions. The graphitization degree of the first carbon-based material is relatively high, and furthermore its gram capacity is relatively high. Therefore, by adjusting the graphitization degree of the second carbon-based material to be smaller than the graphitization degree of the first carbon-based material, it is advantageous for the secondary battery to achieve both high energy density and good rate performance.

[0168] In some embodiments, the gram capacity of the second carbon-based material may be smaller than the gram capacity of the first carbon-based material. By adjusting the gram capacity of the second carbon-based material to be smaller than the gram capacity of the first carbon-based material, it is advantageous for the secondary battery to achieve both high energy density and good rate performance.

[0169] In some embodiments, the OI value of the powder of the second carbon-based material may be smaller than the OI value of the powder of the first carbon-based material. Since the OI value of the powder of the second carbon-based material is relatively small and it has ion storage openings in all directions of the particles, ions from the positive electrode can be quickly received. By adjusting the OI value of the powder of the second carbon-based material to be smaller than the OI value of the powder of the first carbon-based material, it is advantageous for the secondary battery to have better rate performance.

[0170] As a result of further research, the inventors found that when the second carbon-based material satisfies the above design and further satisfies one or more of the following conditions, the performance of the secondary battery can be further improved. For example, at least one of the energy density, cycle performance, and rate performance of the secondary battery can be further improved.

[0171] In some embodiments, the volume distribution particle size Dv50 of the second carbon-based material may be 9-15 μm, and optionally 11-13 μm.

[0172] In some embodiments, the volume distribution particle size Dv90 of the second carbon-based material may be 20-26 μm, and optionally 21-25 μm.

[0173] When the volume distribution particle sizes Dv50 and / or Dv90 of the second carbon-based material are within the above ranges, it is advantageous to enhance the transport performance of ions and electrons, thereby further enhancing the rate performance of the secondary battery.

[0174] In some embodiments, the second carbon-based material may satisfy that (Dv90 - Dv10) / Dv50 is 0.8 - 1.6, and is selectively 1.0 - 1.4. When (Dv90 - Dv10) / Dv50 of the second carbon-based material is within the above range, the second carbon-based material has excellent particle deposition performance, is advantageous for improving the compaction density of the negative electrode film layer, thereby further improving the energy density of the secondary battery, and is also advantageous for the negative electrode film layer to have an appropriate pore structure, thereby further improving the rate performance of the secondary battery.

[0175] In some embodiments, the specific surface area of the second carbon-based material may be 0.5 - 1.5 m 2 / g, and is selectively 0.7 - 1.2 m 2 / g. When the specific surface area of the second carbon-based material is within the above range, it is advantageous for reducing side reactions, thereby enabling the secondary battery to have better cycle performance.

[0176] In some embodiments, the powder compaction density of the second carbon-based material at 20000 N may be 1.6 - 1.8 g / cm 3 and is selectively 1.65 - 1.75 g / cm 3 . When the powder compaction density of the second carbon-based material is within the above range, the compaction density of the negative electrode film layer can be increased, thereby further increasing the energy density of the secondary battery, and is also advantageous for the negative electrode film layer to have an appropriate pore structure, improving the transport performance of ions and electrons, improving the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte, and further improving the rate performance and / or cycle performance of the secondary battery.

[0177] In some embodiments, the tap density of the second carbon-based material may be 0.9 - 1.2 g / cm 3 and is selectively 1.0 - 1.1 g / cm 3When the tap density of the second carbon-based material is within the above range, the consolidation density of the negative electrode film layer can be increased, thereby further increasing the energy density of the secondary battery. Moreover, it is advantageous for the negative electrode film layer to have an appropriate pore structure, which can improve the ion and electron transport performance, improve the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte, and further improve the rate performance and / or cycle performance of the secondary battery.

[0178] In some embodiments, the graphitization degree of the second carbon-based material may be ≧ 92.5%, and optionally 93% - 94%. When the graphitization degree of the second carbon-based material is within the above range, it is advantageous for improving the ion transport performance of the negative electrode film layer, thereby enabling the secondary battery to achieve both high energy density and good rate performance.

[0179] In some embodiments, the gram capacity of the second carbon-based material may be ≧ 354 mAh / g, and optionally 355 - 359 mAh / g. When the gram capacity of the second carbon-based material is within the above range, on the one hand, the energy density of the secondary battery can be improved, and on the other hand, the carbon-based material can be provided with good ion transport performance, which is also advantageous for improving the rate performance of the secondary battery.

[0180] In some embodiments, the volume distribution particle size Dv50 of the second carbon-based material is denoted as A, with the unit being μm, and the specific surface area of the second carbon-based material is denoted as B, with the unit being m 2 / g, and A / B may be 9.0 - 20, and optionally 11 - 15. By adjusting A / B within the above range, the ion storage channels in the negative electrode film layer can be increased, which is advantageous for the rapid diffusion of ions from the surface layer of the second carbon-based material particles to the bulk phase, thereby being advantageous for further optimizing the rate performance of the secondary battery. Moreover, it is also advantageous for reducing side reactions, thereby enabling the secondary battery to have better cycle performance.

[0181] In some embodiments, the OI value of the powder of the second carbon-based material may be 2-8, and optionally 4-6. The OI value of the powder of the second carbon-based material is relatively small, and ions from the positive electrode can be quickly received, thereby further improving the rate performance of the secondary battery.

[0182] In some embodiments, the second carbon-based material may include graphite, and optionally includes artificial graphite.

[0183] In some embodiments, the second carbon-based material may include artificial graphite of secondary particles. Optionally, the proportion of the number of the artificial graphite of the secondary particles in the second carbon-based material may be ≧60%, for example, ≧62.5%, ≧65%, ≧67.5%, ≧70%. As an example, the proportion of the number of the artificial graphite of the secondary particles in the second carbon-based material may be 60%-90%, 60%-85%, 60%-80%, 60%-75%, 65%-90%, 65%-85%, 65%-80%, 65%-75%, 70%-90%, 70%-85%, 70%-80%, 70%-75%.

[0184] In some embodiments, the second carbon-based material may include artificial graphite of secondary particles, and the surface of the artificial graphite has a carbon coating layer. Optionally, the carbon coating layer includes soft carbon.

[0185] In some embodiments, the mass ratio of the second carbon-based material in the second active material may be ≧85%, and optionally 85%-100%, 88%-100%, 90%-100%, 92%-100%, 85%-97%, 88%-97%, 90%-97%, 92%-97%. This is advantageous for improving the rate performance of the secondary battery.

[0186] In some embodiments, the mass ratio of the second carbon-based material in the second active material may be 100%.

[0187] In some embodiments, the second active material may further include a second silicon-based material in addition to the second carbon-based material, thereby further increasing the energy density of the secondary battery.

[0188] In some embodiments, the second silicon-based material may include one or more of primary particles and secondary particles formed by aggregation of the primary particles, and selectively includes primary particles.

[0189] In some embodiments, the second silicon-based material may include primary particles, and the proportion of the second silicon-based material of the primary particles in the second silicon-based material may be ≧60%, and selectively 70%-95%. When the second silicon-based material is mainly primary particles, it is advantageous to reduce the probability of particle crushing and improve the compaction density of the negative electrode film layer, thereby further improving the energy density of the secondary battery.

[0190] In some embodiments, the second silicon-based material may further include secondary particles, and the proportion of the second silicon-based material of the secondary particles in the second silicon-based material may be ≦40%. The specific types of the second silicon-based material of the primary particles and the second silicon-based material of the secondary particles may be the same or different.

[0191] In some embodiments, the mass ratio of the second silicon-based material in the second active material may be smaller than the mass ratio of the first silicon-based material in the first active material. The second silicon-based material is in direct contact with the electrolyte, and by making the mass ratio of the second silicon-based material in the second active material smaller than the mass ratio of the first silicon-based material in the first active material, side reactions can be reduced, which is advantageous for the secondary battery to have better cycle performance.

[0192] In some embodiments, the volume - distribution particle size Dv50 of the second silicon - based material may be smaller than the volume - distribution particle size Dv50 of the first silicon - based material. In the manufacturing process of the negative electrode plate, the second silicon - based material is more affected by the pressing roll and the particles are more easily crushed. By adjusting the volume - distribution particle size Dv50 of the second silicon - based material to be smaller than that of the first silicon - based material, not only can the probability of the second silicon - based material particles being crushed be reduced, but also the electronic conductivity of the second silicon - based material can be increased, and further the ion - storage channels of the negative electrode film layer can be increased, thereby enabling the secondary battery to have both high energy density and good rate performance.

[0193] In some embodiments, the specific surface area of the second silicon - based material may be smaller than the specific surface area of the first silicon - based material. When the specific surface area of the second silicon - based material is smaller than that of the first silicon - based material, it is advantageous for reducing side reactions, and thereby it is advantageous for the secondary battery to have better cycle performance.

[0194] In some embodiments, the powder compaction density of the second silicon - based material at 50000 N may be greater than the powder compaction density of the first silicon - based material at 50000 N. By adjusting the powder compaction density of the second silicon - based material to be greater than that of the first silicon - based material, it is advantageous for improving the energy density of the secondary battery and improving the cycle performance of the secondary battery.

[0195] In some embodiments, the tap density of the second silicon - based material may be greater than the tap density of the first silicon - based material. By adjusting the tap density of the second silicon - based material to be greater than that of the first silicon - based material, it is advantageous for improving the energy density of the secondary battery and improving the cycle performance of the secondary battery.

[0196] In some embodiments, the powder resistivity of the second silicon-based material at 4 MPa may be smaller than the powder resistivity of the first silicon-based material at 4 MPa. By adjusting the powder resistivity of the second silicon-based material to be smaller than that of the first silicon-based material, it is advantageous for improving the electron conductivity of the negative electrode film layer, and thereby advantageous for further improving the rate performance of the secondary battery.

[0197] As a result of further research, the inventor found that when the second silicon-based material satisfies the above design and further satisfies one or more of the following conditions, the performance of the secondary battery can be further improved. For example, at least one of the energy density, cycle performance, and rate performance of the secondary battery can be further improved.

[0198] In some embodiments, the volume distribution particle size Dv50 of the second silicon-based material may be 4 - 12 μm, and optionally 5 - 11 μm.

[0199] In some embodiments, the volume distribution particle size Dv90 of the second silicon-based material may be 8 - 18 μm, and optionally 9 - 17 μm.

[0200] When the volume distribution particle size Dv50 and / or Dv90 of the second silicon-based material is within the above range, it is advantageous for enhancing the transport performance of ions and electrons, and thereby the rate performance of the secondary battery can be further enhanced.

[0201] In some embodiments, the second silicon-based material may satisfy that (Dv90 - Dv10) / Dv50 is 0.7 - 1.3, and is selectively 0.8 - 1.2. When (Dv90 - Dv10) / Dv50 of the second silicon-based material is within the above range, the second silicon-based material has excellent particle deposition performance, which is advantageous for improving the compaction density of the negative electrode film layer, thereby further improving the energy density of the secondary battery. Also, it is advantageous for the negative electrode film layer to have an appropriate pore structure, thereby further improving the rate performance of the secondary battery.

[0202] In some embodiments, the specific surface area of the second silicon-based material may be 0.6 - 1.6 m 2 / g, and is selectively 0.7 - 1.5 m 2 / g. When the specific surface area of the second silicon-based material is within the above range, it is advantageous for reducing side reactions, thereby enabling the secondary battery to have better cycle performance.

[0203] In some embodiments, the powder compaction density of the second silicon-based material at 50000 N may be 1.2 - 1.8 g / cm 3 and is selectively 1.3 - 1.7 g / cm 3 . When the powder compaction density of the second silicon-based material is within the above range, the compaction density of the negative electrode film layer can be increased, thereby further increasing the energy density of the secondary battery. Also, it is advantageous for the negative electrode film layer to have an appropriate pore structure, improving the transport performance of ions and electrons, improving the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte, and further improving the rate performance and / or cycle performance of the secondary battery.

[0204] In some embodiments, the tap density of the second silicon-based material may be 1.1 - 1.7 g / cm 3 and is selectively 1.2 - 1.6 g / cm 3When the tap density of the second silicon-based material is within the above range, the consolidation density of the negative electrode film layer can be increased, thereby further increasing the energy density of the secondary battery. Furthermore, it is advantageous for the negative electrode film layer to have an appropriate pore structure, which can improve the transport performance of ions and electrons, improve the infiltration and retention characteristics of the negative electrode film layer with respect to the electrolyte, and further improve the rate performance and / or cycle performance of the secondary battery.

[0205] In some embodiments, the powder resistivity of the second silicon-based material at 4 MPa may be ≤ 5 Ω·cm, and optionally 0.3 - 4 Ω·cm. By adjusting the powder resistivity of the second silicon-based material within the above range, the electron conductivity of the negative electrode film layer can be improved, and the rate performance of the secondary battery can be further improved.

[0206] In some embodiments, the mass ratio of the second silicon-based material in the second active material may be ≤ 15%, and optionally 3% - 10%. By adjusting the content of the second silicon-based material within the above range, the rate performance and energy density of the secondary battery can be improved, and the secondary battery can have better cycle performance.

[0207] In some embodiments, the second silicon-based material may include one or more of silicon alone, silicon oxide (SiO x , 0 < x ≤ 2), silicon carbon material, and silicon alloy material. The present application does not specifically limit the structure of the silicon carbon material. For example, nanosilicon can be dispersed in the carbon material by high-energy ball milling, nanosilicon can be dispersed in porous carbon, the carbon material can be dispersed in porous silicon, the carbon material can be coated on the surface of nanosilicon, and nanosilicon and nanocarbon can be co-deposited, etc.

[0208] In some embodiments, the surface of the second silicon-based material may have a carbon coating layer. For example, a carbon coating layer may be provided on the surface of single silicon, silicon oxide, etc., to improve the electron conductivity of the second silicon-based material and reduce the powder resistivity. The powder resistivity of the second silicon-based material can be adjusted by adjusting parameters such as the thickness and graphitization degree of the carbon coating layer.

[0209] Of course, the surface of the second silicon-based material may not have a carbon coating layer. For example, the powder resistivity of the second silicon-based material may be adjusted by adjusting parameters such as the structure of the silicon-carbon material and the content of carbon elements.

[0210] The carbon coating layer on the surface of the second silicon-based material can be formed by chemical vapor deposition, thermal decomposition, hydrothermal method, etc.

[0211] In some embodiments, the first active material includes a first carbon-based material and a first silicon-based material. The first carbon-based material includes primary particles, and the surface of the first carbon-based material has a carbon coating layer. The ratio of the number of the primary particles of the first carbon-based material in the first carbon-based material is ≧70%, optionally 75%-90%. The first silicon-based material includes secondary particles formed by aggregation of primary particles. The ratio of the number of the secondary particles of the first silicon-based material in the first silicon-based material is ≧55%, optionally 60%-85%. The second active material includes a second carbon-based material. The second carbon-based material includes secondary particles formed by aggregation of primary particles. The ratio of the number of the secondary particles of the second carbon-based material in the second carbon-based material is ≧60%, optionally 70%-85%. The surface of the second carbon-based material has a carbon coating layer.

[0212] In some embodiments, the first active material includes a first carbon-based material and a first silicon-based material. The first carbon-based material includes primary particles, and the surface of the first carbon-based material has a carbon coating layer. The proportion of the first carbon-based material of the primary particles in the first carbon-based material is ≧70%, optionally 75%-90%. The first silicon-based material includes secondary particles formed by aggregation of primary particles. The proportion of the first silicon-based material of the secondary particles in the first silicon-based material is ≧55%, optionally 60%-85%. The second active material includes a second carbon-based material and a second silicon-based material. The second carbon-based material includes secondary particles formed by aggregation of primary particles. The proportion of the second carbon-based material of the secondary particles in the second carbon-based material is ≧60%, optionally 70%-85%. The surface of the second carbon-based material has a carbon coating layer. The second silicon-based material includes primary particles. The proportion of the second silicon-based material of the primary particles in the second silicon-based material is ≧60%, optionally 70%-95%.

[0213] As shown in FIGS. 1 to 3, the negative electrode film layer 102 further includes an intermediate region 1023 located between the first region 1021 of the negative electrode film layer and the second region 1022 of the negative electrode film layer and having a thickness of 0.4H (H represents the thickness of the negative electrode film layer 102).

[0214] In some embodiments, the intermediate region 1023 contains the first active material and / or the second active material. For example, as shown in FIG. 2, the intermediate region 1023 may have the same composition as the first region 1021. Thus, the distribution region of the first active material in the thickness direction of the negative electrode film layer 102 is within the thickness range from the second surface 102b of the negative electrode film layer to 0.7H. Or, as shown in FIG. 3, the intermediate region 1023 may have the same composition as the second region 1022. Thus, the distribution region of the second active material in the thickness direction of the negative electrode film layer 102 is within the thickness range from the first surface 102a of the negative electrode film layer to 0.7H. Or, as shown in FIG. 1, the intermediate region 1023 contains both the first active material and the second active material simultaneously. At this time, the intermediate region 1023 simultaneously includes a layer structure having the first active material and a layer structure having the second active material, and the two-layer structure may further have a layer interface.

[0215] In some embodiments, the first region 1021 of the negative electrode film layer may further contain other negative electrode active materials known in the art other than the first carbon-based material and the first silicon-based material. For example, it may further contain one or more of a tin-based material, lithium titanate, etc.

[0216] In some embodiments, the second region 1022 of the negative electrode film layer may further contain other negative electrode active materials known in the art other than the second carbon-based material and the second silicon-based material. For example, it may further contain one or more of a tin-based material, lithium titanate, etc.

[0217] In some embodiments, the intermediate region 1023 of the negative electrode film layer may further contain one or more of a tin-based material, lithium titanate, etc.

[0218] In some embodiments, the first region, the second region, and the intermediate region of the negative electrode film layer selectively further contain a negative electrode conductive agent and / or a negative electrode binder.

[0219] This application is not particularly limited with respect to the type of the negative electrode conductive agent. For example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0220] This application is not particularly limited with respect to the type of the negative electrode adhesive. For example, the negative electrode adhesive may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0221] In some embodiments, the first region, the second region, and the intermediate region of the negative electrode film layer selectively further include other auxiliaries. For example, the other auxiliaries may include a thickener such as sodium carboxymethyl cellulose (CMC), a PTC thermistor material, and the like.

[0222] In some embodiments, the porosity of the negative electrode film layer may be ≧15%, and selectively 20%-45%. This is advantageous for the negative electrode film layer to achieve both high capacity and an appropriate pore structure, and further advantageous for the secondary battery to achieve both high energy density and good cycle performance and rate performance.

[0223] In some embodiments, the consolidation density of the negative electrode film layer may be ≧1.5 g / cm 3 and selectively 1.6 - 1.8 g / cm 3 This is advantageous for the negative electrode film layer to achieve both high capacity and good ion and electron transport performance, and further advantageous for the secondary battery to achieve both high energy density and good cycle performance and rate performance.

[0224] In some embodiments, the areal density of the negative electrode film layer may be ≥ 7 mg / cm² 2 and may selectively be 9 - 30 mg / cm² 2 This is advantageous for enabling the negative electrode film layer to achieve both high capacity and good ion and electron transport performance, and further advantageous for enabling the secondary battery to achieve both high energy density and good cycle performance and rate performance.

[0225] In some embodiments, the negative electrode current collector may employ a metal foil sheet or a composite current collector. As an example of the metal foil sheet, a copper foil can be employed. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0226] The negative electrode plate does not exclude other additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode plate described in this application further includes a conductive undercoat (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In some embodiments, the negative electrode plate described in this application further includes a protective layer covering the surface of the negative electrode film layer.

[0227] The negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode film layer is disposed on one or both of the two opposing surfaces of the negative electrode current collector. It should be noted that each parameter (e.g., compaction density, areal density, porosity, etc.) of the negative electrode film layer provided in this application refers to the parameter of the negative electrode film layer on one side of the negative electrode current collector. When the negative electrode film layer is disposed on both sides of the negative electrode current collector, if the parameters of the negative electrode film layer on either side meet the requirements of this application, it is considered to be within the protection scope of this application.

[0228] Whether a carbon coating layer exists on the surface of a material (such as a first carbon-based material, a second carbon-based material, a first silicon-based material, a second silicon-based material, etc.) can be determined by a transmission electron microscope.

[0229] The volume distribution particle sizes Dv10, Dv50, and Dv90 of a material (such as a first carbon-based material, a second carbon-based material, a first silicon-based material, a second silicon-based material, etc.) have meanings known in the art. They respectively represent the particle sizes corresponding when the cumulative volume distribution percentage of the material reaches 10%, 50%, and 90%, and can be measured by devices and methods known in this field. For example, it may be measured using a laser particle size analyzer with reference to GB / T 19077-2016. The test device may be a Mastersizer 3000 type laser particle size analyzer manufactured by Malvern Instruments, UK.

[0230] The specific surface area of a material (such as a first carbon-based material, a second carbon-based material, a first silicon-based material, a second silicon-based material, etc.) has a meaning known in the art and can be measured by devices and methods known in this field. For example, with reference to GB / T 19587-2017, it can be tested using a nitrogen gas adsorption specific surface area analysis test method and calculated by the BET (Brunauer Emmett Teller) method. The test device may be a Tri-Star 3020 type specific surface area and pore size analyzer manufactured by Micromeritics, USA.

[0231] The powder compaction density of a material (such as a first carbon-based material, a second carbon-based material, a first silicon-based material, a second silicon-based material, etc.) has a meaning known in the art and can be measured by devices and methods known in this field. For example, with reference to GB / T 24533-2009, it can be measured by an electronic pressure tester (such as a UTM7305 type electronic pressure tester may also be used). An exemplary test method is to weigh 1 g of sample powder, and the bottom area is 1.327 cm 2In addition to the mold, pressurize it to the required pressure, hold the pressure for 30 s, then release the pressure, hold for 10 s, and then record and calculate the powder compaction density at the required pressure of the material.

[0232] The tap density of the material (such as the first carbon-based material, the second carbon-based material, the first silicon-based material, the second silicon-based material, etc.) is a known meaning in the art and can be measured by equipment and methods known in this field. For example, referring to GB / T 5162-2006, it can be measured using a powder tap density tester. The test equipment can use Dandong Baite BT-301, and the test parameters are that the vibration frequency is 250 ± 15 times / min, the amplitude is 3 ± 0.2 mm, the number of vibrations is 5000 times, and the graduated cylinder is 25 mL.

[0233] The graphitization degree of the material (such as the first carbon-based material, the second carbon-based material, etc.) is a known meaning in the art and can be tested using equipment and methods known in this field. For example, it can be tested using an X-ray diffractometer (such as Bruker D8 Discover), and the test refers to JIS K 0131-1996 and JB / T 4220-2011 to obtain the average interlayer spacing d of the C(002) crystal plane in the material crystal structure 002 and the graphitization degree can be calculated from the formula g = (0.344 - d 002 ) / (0.344 - 0.3354) × 100%. In the above formula, d 002 is the average interlayer spacing of the C(002) crystal plane in the material crystal structure expressed in nanometers (nm).

[0234] The powder OI value of the material (such as the first carbon-based material, the second carbon-based material, etc.) is a known meaning in the art and can be tested using equipment and methods known in this field. For example, it can be tested using an X-ray diffractometer (such as Bruker D8 Discover), the test can refer to JIS K 0131-1996 and JB / T 4220-2011, obtain the X-ray diffraction pattern of the powder sample, and OI value = I 004 / I 110Calculate the powder OI value of the sample based on this. I 004 is the integrated area of the diffraction peak of the 004 crystal plane of crystalline carbon in the powder sample, and I 110 is the integrated area of the diffraction peak of the 110 crystal plane of crystalline carbon in the powder sample. In the X-ray diffraction analysis test of this application, a copper target can be used as the anode target, CuKα rays are used as the radiation source, the radiation wavelength λ = 1.5418 Å, the scanning 2θ angle range is 20° - 80°, and the scanning speed is 4° / min.

[0235] The powder resistivity of a material (such as a first silicon-based material, a second silicon-based material, etc.) has a known meaning in the art and can be tested using equipment and methods known in this field. For example, a resistivity tester (such as the ST2722 powder resistivity tester of Suzhou Grid Electronics Co., Ltd.) can be used for the test. During the test, 1 g of the powder sample is taken, the powder sample is placed between the electrodes of the resistivity tester, and the test pressure (such as 4 Mpa) is set to a constant pressure with an electronic press and maintained for 15 - 25 s to obtain a sheet-like sample. The powder resistivity δ of the material is calculated based on the formula δ=(S×R) / h, and the unit is Ω·cm. h is the height of the sheet-like sample, the unit is cm, R is the resistance, the unit is Ω, and S is the area of the sheet-like sample, the unit is cm 2 is.

[0236] The gram capacity of the material (such as the first carbon-based material, the second carbon-based material, etc.) is a well-known meaning in the art and can be tested using methods known in this field. Exemplary test methods are as follows: Sample powder, conductive agent carbon black (Super P), and adhesive polyvinylidene fluoride (PVDF) are uniformly mixed with solvent N-methylpyrrolidone (NMP) at a mass ratio of 91.6:1.8:6.6 to produce a slurry. The produced slurry is applied to the surface of the negative electrode current collector copper foil, dried in an oven, and then prepared for use. Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed at a volume ratio of 1:1:1 to obtain an organic solvent. Next, LiPF6 is dissolved in the above organic solvent to produce an electrolyte solution with a concentration of 1 mol / L. Then, a metal lithium sheet is used as the counter electrode, a polyethylene (PE) film is used as the separator, and the above electrolyte solution and an argon gas-protected glove box are used to assemble a CR2430 type button battery. After the obtained button battery is left standing for 12 h, at 25 °C, it is discharged at a constant current of 0.05C to 0.005V, left standing for 10 min, discharged at a constant current of 50 μA to 0.005V again, left standing for 10 min, discharged at a constant current of 10 μA to 0.005V again, and then charged at a constant current of 0.1C to 2V, and the charging capacity is recorded. The ratio of the charging capacity to the sample mass is the gram capacity of the corresponding material (such as the first carbon-based material, the second carbon-based material, etc.).

[0237] The areal density of the negative electrode film layer is a well-known meaning in the art and can be tested using methods known in this field. For example, take the negative electrode plate after being coated on one side and cold pressed (if it is a negative electrode plate coated on both sides, the negative electrode film layer on one of the sides may be wiped off first), punch it into a small disc with an area of S1, weigh its weight, and it may be recorded as M1. Next, wipe off the negative electrode film layer of the negative electrode plate after the above weighing, weigh the weight of the negative electrode current collector, and record it as M0. The areal density of the negative electrode plate = (M1 - M0) / S1.

[0238] The consolidation density of the negative electrode film layer is a meaning known in the art and can be tested and determined using methods known in this field. The consolidation density of the negative electrode film layer = the areal density of the negative electrode film layer / the thickness of the negative electrode film layer. The thickness of the negative electrode film layer is a meaning known in the art and can be tested using methods known in this field. For example, it can be tested using a micrometer (e.g., Mitutoyo 293-100 type, accuracy 0.1 μm).

[0239] The porosity of the negative electrode film layer is a meaning known in the art and can be measured using methods known in this field. An exemplary test method is as follows: Take a negative electrode plate coated on one side and cold-pressed (if it is a negative electrode plate coated on both sides, first wipe off the negative electrode film layer on one of its sides), punch it into small disc samples of a certain area, calculate the apparent volume V1 of the negative electrode plate. Referring to GB / T 24586-2009, using an inert gas (e.g., helium gas or nitrogen gas) as the medium, using the gas replacement method, and using a true density tester to measure the true volume V2 of the negative electrode plate. The porosity of the negative electrode film layer = (V1 - V2) / V1 × 100%. Take a plurality of (e.g., 30) negative electrode plate samples with good appearance and no powder falling off at the edges for testing, and the results may take the average value, thereby improving the accuracy of the test results. The test equipment may use a Micromeritics AccuPyc II 1340 type true density tester.

[0240] The porosity of the first silicon-based material of the secondary particles can be measured using methods known in the art. For example, test with a true density tester (e.g., AccuPyc II 1340 type) to obtain the true density ρ r of the first silicon-based material of the secondary particles. Specifically, weigh a sample of a certain mass (denoted as m), place it in the true density tester, seal the test system, introduce helium gas according to the procedure, detect the gas pressure in the sample chamber and the expansion chamber, and then calculate the true volume Vr of the first silicon-based material of the secondary particles according to Boyle's law (PV = nRT). Then the true density ρ r = m / Vr It includes steps such as. The apparent density of the first silicon-based material of the secondary particles is obtained by putting a sample of a certain mass (denoted as m) into a cylindrical mold with an inner diameter of 10 mm, applying a pressure of 200 MPa to obtain the apparent volume V0 of the first silicon-based material of the secondary particles, and the apparent density ρ0 of the first silicon-based material of the secondary particles is ρ0 = m / V0. If the porosity of the first silicon-based material of the secondary particles is P, then P=(1 - ρ0 / ρ r )×100%.

[0241] It should be noted that various parameter tests for the above first active material, second active material, or negative electrode film layer can be sampled and tested from a secondary battery manufactured according to the following steps.

[0242] Perform a discharge process on the secondary battery (generally, the secondary battery is fully discharged for safety), after removing the secondary battery, take out the negative electrode plate, immerse the negative electrode plate in dimethyl carbonate for a certain time (for example, 2h - 10h), then take out the negative electrode plate and dry it at a certain temperature and time (for example, 60°C, 4h or more), and take out the negative electrode plate after drying. At this time, various parameters related to the negative electrode film layer, such as the areal density, compaction density, porosity, etc. of the negative electrode film layer can be sampled and tested on the dried negative electrode plate.

[0243] Bake the dried negative electrode plate at a certain temperature and time (for example, 400°C, 2h or more), select any area on the baked negative electrode plate, first sample the second active material (it may be sampled by scraping the powder with a blade), the sampling position is the second area of the negative electrode film layer, then sample the first active material in the same way, the sampling position is the first area of the negative electrode film layer, sieve and process the collected first active material and second active material respectively (for example, sieve with a 200-mesh sieve), and finally obtain the first active material and second active material samples that can be used to test the above material parameters of the present application.

[0244] As an example, the method for testing the ratio of the number of the first carbon-based material of the primary particles in the first carbon-based material may be as follows: Lay and adhere the obtained first active material on a conductive adhesive to produce a sample to be tested with a size of 6 cm × 1.1 cm, test the particle morphology using a scanning electron microscope, and the test can refer to JY / T010-1996. To ensure the accuracy of the test results, randomly select a plurality (for example, 10) of different regions from the sample to be tested for a scanning test, and calculate the ratio of the number of the first carbon-based material of the primary particles in each test region to the total number of the first carbon-based material at a certain magnification (for example, 500 times or 1000 times). The average value of the calculation results of the plurality of test regions can be used as the test result. To ensure the accuracy of the test results, further produce a plurality of test samples (for example, 5 or 10) and repeat the above test, and take the average value of each test sample as the final test result. Similarly, the ratio of the number of the first silicon-based material of the secondary particles in the first silicon-based material may be tested.

[0245] As an example, the method for testing the ratio of the number of the second carbon-based material of the secondary particles in the second carbon-based material may be as follows: Lay and adhere the obtained second active material on a conductive adhesive to produce a sample to be tested with a size of 6 cm × 1.1 cm, test the particle morphology using a scanning electron microscope, and the test can refer to JY / T010-1996. To ensure the accuracy of the test results, randomly select a plurality (for example, 10) of different regions from the sample to be tested for a scanning test, and calculate the ratio of the number of the second carbon-based material of the secondary particles in each test region to the total number of the second carbon-based material at a certain magnification (for example, 500 times or 1000 times). The average value of the calculation results of the plurality of test regions can be used as the test result. To ensure the accuracy of the test results, further produce a plurality of test samples (for example, 5 or 10) and repeat the above test, and take the average value of each test sample as the final test result. Similarly, the ratio of the number of the second silicon-based material of the primary particles in the second silicon-based material may be tested.

[0246] The ratio of the number of primary particles (here referring to non-aggregated particles) to secondary particles in the above carbon-based material (for example, the first carbon-based material or the second carbon-based material) may be adjusted by methods known in the art. For example, when the carbon-based material is graphite, the manufacturing parameters (such as the type of coke raw material, shaping process, granulation process, type and addition amount of granulating agent, etc.) may be adjusted to adjust the ratio of the number of primary particles to secondary particles, or the ratio of the number of primary particles to secondary particles may be adjusted by adjusting the mixing ratio of graphite primary particles and graphite secondary particles.

[0247] The ratio of the number of primary particles (here referring to non-aggregated particles) to secondary particles in the silicon-based material (for example, the first silicon-based material or the second silicon-based material) may be adjusted in a similar manner. For example, the manufacturing parameters (such as the type of raw material, granulation process, type and addition amount of granulating agent, etc.) may be adjusted to adjust the ratio of the number of primary particles to secondary particles, or the ratio of the number of primary particles to secondary particles may be adjusted by adjusting the mixing ratio of the silicon-based material of primary particles and the silicon-based material of secondary particles.

[0248] [Method for manufacturing a negative electrode plate] This application further provides a method for manufacturing the negative electrode plate of this application. The method includes the steps of providing a first slurry containing a first active material and a second slurry containing a second active material, applying the first slurry to a negative electrode current collector, applying the second slurry to the first slurry, and obtaining a negative electrode plate through drying and cold pressing.

[0249] In some embodiments, the first active material, as well as optional conductive agent, optional adhesive, and other optional auxiliaries, may be dispersed in a solvent (such as deionized water) to form the first slurry.

[0250] In some embodiments, the second active material, as well as optional conductive agent, optional adhesive, and other optional auxiliaries, may be dispersed in a solvent (such as deionized water) to form the second slurry.

[0251] In some embodiments, the first active material includes a first carbon-based material and a first silicon-based material.

[0252] In some embodiments, the second active material includes a second carbon-based material or a mixture of a second carbon-based material and a second silicon-based material.

[0253] The first slurry and the second slurry may be applied simultaneously at once or separately in two steps. In some embodiments, the first slurry and the second slurry are applied simultaneously at once. Applying simultaneously at once can reduce the resistance of the negative electrode film layer, thereby further improving the rate performance and cycle performance of the secondary battery.

[0254] The coating weights of the first slurry and the second slurry may be adjusted according to the actual situation.

[0255] The first active material, the second active material, etc. mentioned above may be commercially available or may be obtained by manufacturing according to the following method of the present application.

[0256] In some embodiments, the silicon-based material of the secondary particles may be manufactured by a method of manufacturing a solution containing primary particles, an adhesive, and a solvent and spray-drying the solution to obtain a silicon-based material containing secondary particles. The binder is not particularly limited, and specific examples may include one or more of pitch, starch, phenolic resin, polyvinyl alcohol, epoxy resin, vinyl chloride resin, butyl rubber, etc. As the solvent, as long as the primary particles are sufficiently dispersed, there is no particular limitation, and specific examples may include one or more of water, alcohol, N-methylpyrrolidone (NMP), dimethyl sulfoxide, acetonitrile, acetone, tetrahydrofuran, diethyl ether, toluene, 1,2-dichlorobenzene, etc. The temperature of the spray drying may be 100°C to 250°C.

[0257] Alternatively, the silicon-based material of the secondary particles may be manufactured by a method in which primary particles are mixed with an adhesive and granulated, and then heat-treated to obtain a silicon-based material containing secondary particles. The binder is not particularly limited, and specific examples may include one or more of pitch, starch, phenolic resin, polyvinyl alcohol, epoxy resin, vinyl chloride resin, butyl rubber, and the like.

[0258] By adjusting the agglomeration state, the porosity of the silicon-based material of the secondary particles can be made within an appropriate range. Specifically, the secondary particles are immersed in a high-temperature melt of a filler, pressurized to control the filling degree of the filler, and then high-temperature carbonization is performed to realize the adjustment of the porosity. Specific examples of the filler may include one or more of pitch, starch, phenolic resin, polyvinyl alcohol, epoxy resin, vinyl chloride resin, butyl rubber, polymethyl methacrylate, and the like.

[0259] When manufacturing the silicon-based material of the secondary particles, the types of primary particles used may be the same or different.

[0260] In some embodiments, the carbon-based material of the primary particles may be manufactured by a method in which a coke raw material is crushed, shaped, and then graphitized to obtain a carbon-based material of the primary particles after completion. Specific examples of the coke raw material may include one or more of petroleum coke, needle coke, pitch coke, and metallurgical coke. The graphitization temperature may be 2800°C to 3200°C.

[0261] In some embodiments, the carbon-based material of the secondary particles may be manufactured by a method in which a coke raw material is crushed, shaped, further mixed with an adhesive and granulated, and then graphitized to obtain a carbon-based material containing secondary particles after completion. Specific examples of the coke raw material may include one or more of petroleum coke, needle coke, pitch coke, and metallurgical coke. The graphitization temperature may be 2800°C to 3200°C. Specific examples of the adhesive may include pitch.

[0262] The above manufacturing process does not include the step of forming a carbon coating layer on the material surface. As an example, the carbon coating layer on the surface of the carbon-based material may be formed by carbonizing an organic carbon source, and the organic carbon source may use a carbon-containing material suitable for coating known in this field. For example, it may include one or more of coal pitch, petroleum pitch, phenolic resin, coconut shell, etc. The carbon coating layer on the surface of the silicon-based material can be formed by chemical vapor deposition, pyrolysis, hydrothermal method, etc.

[0263] [Positive electrode plate] In some embodiments, the positive electrode plate includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. For example, the positive current collector has two opposite surfaces in its thickness direction, and the positive electrode film layer is disposed on either one or both of the two opposite surfaces of the positive current collector.

[0264] The positive current collector may employ a metal foil sheet or a composite current collector. As an example of the metal foil sheet, an aluminum foil can be employed. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE).

[0265] The positive electrode film layer generally includes a positive electrode active material, a selective binder, and a selective conductive agent. The positive electrode film layer is generally obtained by applying a positive electrode slurry onto the positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is generally formed by dispersing a positive electrode active material, a selective conductive agent, a selective binder, and any other components in a solvent and uniformly stirring them. The solvent may be N-methylpyrrolidone (NMP), but is not limited thereto. As an example, the binder used in the positive electrode film layer may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. As an example, the conductive agent used in the positive electrode film layer may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0266] The positive electrode active material may employ a positive electrode active material used in known secondary batteries in the art.

[0267] When the secondary battery of the present application is a lithium-ion battery, the positive electrode active material used in the lithium-ion battery may include, but is not limited to, one or more of lithium-containing metal oxides, lithium-containing phosphates, and their respective modified compounds. Examples of the lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds. Examples of the lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and their respective modified compounds.

[0268] In some embodiments, in order to further improve the energy density of the secondary battery, the positive electrode active material used in the lithium-ion battery may include one or more of lithium transition metal oxides and their modified compounds having the general formula Li a Ni b Co c M d O e A f where 0.8 ≦ a ≦ 1.2, 0.5 ≦ b < 1, 0 < c < 1, 0 < d < 1, 1 ≦ e ≦ 2, 0 ≦ f ≦ 1, M is one or more selected from Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A is one or more selected from N, F, S, and Cl.

[0269] In some embodiments, for example, the positive electrode active material used in the lithium-ion battery may be LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.85 Co 0.15 Al 0.05 It may contain one or more of O2, LiFePO4, and LiMnPO4.

[0270] The modified compound of each of the above cathode active materials performs doping modification and / or surface coating modification on the cathode active material.

[0271] [Electrolyte] In some embodiments, the electrolyte employs an electrolytic solution, and the electrolytic solution contains an electrolyte salt and a solvent.

[0272] The type of the electrolyte salt is not specifically limited and can be selected according to actual needs.

[0273] When the secondary battery of the present application is a lithium-ion battery, for example, the electrolyte salt may contain 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 difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0274] The type of the solvent is not specifically limited and can be selected according to actual needs. In some embodiments, by way of example, the solvent may include one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), 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), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0275] In some embodiments, the electrolyte further selectively includes additives. For example, the additives may include negative electrode film - forming additives, positive electrode film - forming additives, and additives that can improve some performances of the secondary battery, such as additives that improve the over - charge performance of the secondary battery, additives that improve the high - temperature performance of the secondary battery, additives that improve the low - temperature power performance of the secondary battery, etc.

[0276] [Separator] This application is not particularly limited with respect to the type of the separator, and any known porous - structure separator having good chemical stability and mechanical stability may be selected.

[0277] In some embodiments, the material of the separator may include one or more of glass fiber, non - woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single - layer film or a multi - layer composite film. When the separator is a multi - layer composite film, the materials of each layer may be the same or different.

[0278] In some embodiments, the positive electrode plate, the separator, and the negative electrode plate may be manufactured into an electrode assembly by a winding process or a lamination process.

[0279] In some embodiments, the secondary battery may include an outer package. This outer package may be used to package the above electrode assembly and electrolyte.

[0280] In some embodiments, the outer package may be a rigid case, such as a rigid plastic case, an aluminum case, a steel case, etc. The outer package may also be a pouch, such as a bag-shaped pouch. The material of the pouch may be plastic, for example, one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0281] This application does not particularly limit the shape of the secondary battery, and it may be cylindrical, rectangular, or any other arbitrary shape. FIG. 4 shows a rectangular-structured secondary battery 5 as an example.

[0282] In some embodiments, as shown in FIG. 5, the outer package may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and side plates connected on the bottom plate, and the bottom plate and the side plates enclose to form an accommodation cavity. The case 51 has an opening communicating with the accommodation cavity, and the cover plate 53 is used to cover the opening to seal the accommodation cavity. The positive electrode plate, the negative electrode plate, and the separator may form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is packaged in the accommodation cavity. The electrolyte is infiltrated into the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and can be adjusted according to demand.

[0283] The method for manufacturing the secondary battery of the present application is a known one. In some embodiments, a secondary battery can be formed by assembling a positive electrode plate, a separator, a negative electrode plate, and an electrolytic solution. As an example, a positive electrode plate, a separator, and a negative electrode plate can be subjected to a winding process or a lamination process to form an electrode assembly, the electrode assembly can be placed in an outer package, and after drying, the electrolytic solution can be injected, and through processes such as vacuum packaging, standing, formation, and shaping, a secondary battery can be obtained.

[0284] In some embodiments of the present application, the secondary battery according to the present application can be assembled into a battery module, and the number of secondary batteries included in the battery module may be plural, and the specific number can be adjusted according to the application and capacity of the battery module.

[0285] FIG. 6 is a schematic diagram of a battery module 4 as an example. As shown in FIG. 6, in the battery module 4, a plurality of secondary batteries 5 may be arranged in sequence along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Further, these plurality of secondary batteries 5 may be fixed by fastening tools.

[0286] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of secondary batteries 5 are accommodated in this accommodation space.

[0287] In some embodiments, the above battery module may be further assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0288] FIGS. 7 and 8 are schematic diagrams of a battery pack 1 as an example. As shown in FIGS. 7 and 8, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 is used to cover the lower housing 3 and form a sealed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0289] Embodiments of the present application further provide a power consumption device, which includes at least one of the secondary battery, battery module, or battery pack of the present application. The secondary battery, battery module, or battery pack may be used as a power source of the power consumption device, or may be used as an energy storage unit of the power consumption device. The power consumption device may be a mobile device (such as a mobile phone, tablet computer, notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, hybrid electric vehicle, plug-in hybrid electric vehicle, electric bicycle, electric scooter, electric golf cart, electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc., but is not limited thereto.

[0290] The power consumption device may select a secondary battery, battery module, or battery pack according to its usage requirements.

[0291] FIG. 9 is a schematic diagram of a power consumption device as an example. This power consumption device is a pure electric vehicle, hybrid electric vehicle, or plug-in hybrid electric vehicle, etc. In order to meet the requirements for high output and high energy density of this power consumption device, a battery pack or battery module may be adopted.

[0292] As another example of the power consumption device, it may be a mobile phone, tablet computer, notebook computer, etc. This power consumption device generally requires thinning, and a secondary battery can be adopted as a power source.

[0293] Example The following examples describe the content disclosed in this application in more detail. These examples are for illustrative purposes only and it is obvious to those skilled in the art that various modifications and changes can be made within the scope of the content disclosed in this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples can be obtained commercially or synthesized according to conventional methods and can be used directly without further treatment, and all instruments used in the examples can be obtained commercially.

[0294] The first carbon-based material of Example 4 is primary particles, which may be commercially available, or may be produced by a method in which petroleum coke is crushed, shaped, then graphitized in the range of 2800 °C to 3200 °C, cooled to room temperature, and then sieved to obtain a product.

[0295] In other examples and comparative examples, the first carbon-based material and the second carbon-based material may be commercially available, or may be produced by a method in which petroleum coke is crushed, shaped, further mixed with an adhesive pitch and granulated, then graphitized in the range of 2800 °C to 3200 °C, cooled to room temperature, and then sieved to obtain a product. By adjusting the manufacturing process parameters (such as the shaping process, granulation process, type and addition amount of pitch, etc.), the ratio of the number of primary particles to secondary particles in the first carbon-based material (second carbon-based material) may be adjusted, or the ratio of the number of primary particles to secondary particles may be adjusted by adjusting the mixing ratio of the primary particle first carbon-based material (second carbon-based material) and the secondary particle first carbon-based material (second carbon-based material).

[0296] In the following examples and comparative examples, the carbon coating layer on the surface of the first carbon-based material and the second carbon-based material may be formed by carbonization after mixing the graphitized material with petroleum pitch.

[0297] The first silicon-based material of Comparative Example 1 is primary particles and may be commercially available.

[0298] In the following examples, the first silicon-based material (second silicon-based material) of secondary particles may be commercially available, or may be produced by a method of mixing a silicon-based material of primary particles with an adhesive pitch and then performing a heat treatment. By adjusting the production parameters (for example, granulation process, type and addition amount of pitch, etc.), the ratio of the number of primary particles to secondary particles can be adjusted, and also by adjusting the mixing ratio of the silicon-based material of primary particles (which may be commercially available) and the silicon-based material of secondary particles (which may be commercially available), the ratio of the number of primary particles to secondary particles may be adjusted.

[0299] The silicon-based material of secondary particles can be immersed in a high-temperature melt of the filler pitch, pressurized to control the filling degree of the filler, and then high-temperature carbonization is performed to realize the adjustment of the porosity.

[0300] In the following examples and comparative examples, the carbon coating layer on the surface of the lithium pre-doped silicon oxide may be formed by chemical vapor deposition.

[0301] The secondary batteries of Examples 1-17 and Comparative Example 1 are all manufactured according to the following method.

[0302] An appropriate amount of deionized water as a solvent is used to sufficiently stir and mix the first active material (for details, refer to Table 1), conductive agent Super P, carbon nanotubes (CNTs), adhesive styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose according to a weight ratio of 96.2:0.7:0.1:1.8:1.2 to form a first slurry. The sum of the ratio of the number of secondary particles to the ratio of the number of primary particles in the first carbon-based material is 100%, and the sum of the ratio of the number of secondary particles to the ratio of the number of primary particles in the first silicon-based material is 100%. Thus, the ratio of the number of secondary particles or primary particles can be calculated based on the ratio of the number of primary particles or secondary particles in Table 1.

[0303] A second active material (for details, refer to Table 2), a conductive agent Super P, carbon nanotubes (CNTs), an adhesive styrene butadiene rubber, and a thickening agent sodium carboxymethyl cellulose are sufficiently stirred and mixed with an appropriate amount of a solvent deionized water according to a weight ratio of 96.2:0.7:0.1:1.8:1.2 to form a second slurry. The sum of the ratio of the number of secondary particles and the ratio of the number of primary particles in the second carbon-based material is 100%, and the sum of the ratio of the number of secondary particles and the ratio of the number of primary particles in the second silicon-based material is 100%. Thus, the ratio of the number of secondary particles or the ratio of the number of primary particles can be calculated based on the ratio of the number of primary particles or the ratio of the number of secondary particles in Table 2.

[0304] The first slurry and the second slurry are simultaneously extruded by a dual-cavity coating device. The first slurry is applied to two surfaces of a negative current collector copper foil, and the second slurry is applied to the first slurry. After drying and cold pressing, a negative electrode plate is obtained. The coating weights of the first slurry and the second slurry are the same. The areal density on one side of the negative electrode film layer is 12.5 mg / cm 2 and the consolidated density on one side of the negative electrode film layer is 1.80 g / cm 3 .

[0305] LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811) and a conductive agent Super P and an adhesive polyvinylidene fluoride are mixed according to a weight ratio of 96.5:1.5:2, an appropriate amount of a solvent NMP is added, and they are uniformly stirred to obtain a positive electrode slurry. The positive electrode slurry is applied onto two surfaces of a positive current collector aluminum foil, and after drying and cold pressing, a positive electrode plate is obtained.

[0306] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed at a volume ratio of 1:1:1 to obtain an organic solvent, and LiPF6 is dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0307] Using the PP / PE composite film as a separator, arranging it in sequence with the above-mentioned manufactured positive electrode plate and negative electrode plate, positioning the separator in the center between the positive electrode plate and the negative electrode plate to perform the isolation function, then winding it to obtain an electrode assembly, placing the electrode assembly in an outer package, injecting an electrolyte after drying, and passing through processes such as vacuum packaging, standing, forming, and aging to obtain a secondary battery.

[0308]

Table 1

[0309]

Table 2

[0310] Performance test (1) Rate performance test of the secondary battery At 25 °C, the secondary battery manufactured above was discharged at a constant current to 2.8 V at a rate of 1C. Next, it was charged at a constant current to 4.3 V at a rate of 1C, and then charged at a constant voltage until the current reached 0.05C. At this time, the secondary battery was in a fully charged state. After the fully charged secondary battery was allowed to stand for 5 minutes, it was discharged at a constant current to 2.8 V at rates of 0.33C and 3C respectively, and the discharge capacities of the secondary battery at rates of 0.33C and 3C were recorded respectively. The rate performance of the secondary battery was characterized by the ratio of the discharge capacity of the secondary battery at a rate of 3C to the discharge capacity of the secondary battery at a rate of 0.33C.

[0311] (2) DC impedance test of the secondary battery At 25°C, the secondary battery manufactured above was charged at a constant current of 1C to 4.3V, then charged at a constant voltage until the current reached 0.05C. The secondary battery was discharged at a constant current of 0.5C for 30 minutes, and the secondary battery was adjusted to 50% SOC. The voltage of the secondary battery at this time is denoted as U1. Next, the secondary battery was discharged at 3C for 30 seconds, and the voltage of the secondary battery after discharge is denoted as U2, and the discharge current is denoted as I1. The direct current impedance (DCR) of the secondary battery = (U1 - U2) / I1.

[0312] (3) Cycle performance test of the secondary battery At 45°C, the secondary battery manufactured above was charged at a constant current of 1C to 4.3V, and then charged at a constant voltage until the current reached 0.05C. After standing for 5 minutes, the secondary battery was discharged at a constant current of 1C to 2.8V, and the discharge capacity at this time was recorded, which is the discharge capacity of the first cycle. The secondary battery was subjected to a cycle charge and discharge test according to the above method, and the discharge capacity after each cycle was recorded. The capacity retention rate (%) after 300 cycles of the secondary battery at 45°C = discharge capacity after 300 cycles / discharge capacity of the first cycle × 100%.

[0313]

Table 3

[0314] As can be seen from the comprehensive test results in Table 3, by optimizing the particle structures of the first carbon-based material and the first silicon-based material, including primary particles in the first carbon-based material and secondary particles in the first silicon-based material, on the premise that the secondary battery has a high energy density, the rate performance and cycle performance of the secondary battery can be further optimized.

[0315] As can be further seen from the comprehensive test results in Table 3, by further optimizing the second active material, the rate performance and / or cycle performance of the secondary battery can be further optimized.

[0316] It should be noted that this application is not limited to the above embodiments. The above embodiments are merely illustrative, and any embodiments that have substantially the same configuration as the technical idea within the scope of the technical solution of this application and exhibit the same effects are all included within the technical scope of this application. In addition, within the scope not departing from the gist of this application, various modifications that can be conceived by those skilled in the art to the embodiments, and other forms constituted by combining some components in the embodiments are also included within the scope of this application.

Explanation of Reference Numerals

[0317] 1 Battery pack, 2 Upper housing, 3 Lower housing, 4 Battery module, 5 Secondary battery, 51 Case, 52 Electrode assembly, 53 Cover plate, 10 Negative electrode plate, 101 Negative electrode current collector, 102 Negative electrode film layer, 102a First surface, 102b Second surface, 1021 First region, 1022 Second region, 1023 Intermediate region.

Claims

1. A secondary battery, comprising a negative electrode plate, wherein the negative electrode plate includes a negative electrode current collector and a negative electrode film layer. Here, the negative electrode film layer has a first surface away from the negative electrode current collector and a second surface disposed opposite to the first surface. The thickness of the negative electrode film layer is denoted as H, and a region within a thickness range from the second surface of the negative electrode film layer to 0.3H is denoted as the first region of the negative electrode film layer, and a region within a thickness range from the first surface of the negative electrode film layer to 0.3H is denoted as the second region of the negative electrode film layer. The first region contains a first active material, the second region contains a second active material, the first active material includes a first carbon-based material and a first silicon-based material, the first carbon-based material includes primary particles, and the first silicon-based material includes secondary particles formed by aggregation of primary particles. A secondary battery.

2. The surface of the first carbon-based material has a carbon coating layer. Optionally, the carbon coating layer contains hard carbon. The secondary battery according to claim 1.

3. The proportion of the first carbon-based material of the primary particles in the first carbon-based material is ≧ 70%, optionally 75% - 90%, and / or The proportion of the first silicon-based material of the secondary particles in the first silicon-based material is ≧ 55%, optionally 60% - 85%. The secondary battery according to claim 1 or 2.

4. The porosity of the first silicon-based material of the secondary particles is ≧ 4%, optionally 5% - 20%. The secondary battery according to any one of claims 1 to 3.

5. The volume distribution particle size Dv50 of the first carbon-based material is 10 - 16 μm, optionally 12 - 14 μm. The secondary battery according to any one of claims 1 to 4.

6. The first carbon-based material is as follows (1) - (10), (1) The volume distribution particle size Dv90 of the first carbon-based material is 20 - 28 μm, optionally 22 - 26 μm; (2) The first carbon-based material satisfies that (Dv90 - Dv10) / Dv50 is 0.8 - 1.6, optionally 1.1 - 1.4; (3) The specific surface area of the first carbon-based material is 1.0 - 1.8 m ２ / g, and preferably 1.2 - 1.6 m ２ / g, and (4) The powder consolidation density of the first carbon-based material at 20,000 N is 1.75 - 2.0 g / cm ３ and selectively 1.8 - 1.95 g / cm ３ and that (5) The tap density of the first carbon-based material is 1.1 - 1.3 g / cm ３ and selectively 1.15 - 1.25 g / cm ３ and (6) The graphitization degree of the first carbon-based material is ≧ 93%, optionally 94% - 96%; (7) The gram capacity of the first carbon-based material is ≧ 360 mAh / g, optionally 361 - 365 mAh / g; (8) The OI value of the powder of the first carbon-based material is 5 - 15, and selectively 7 - 12, (9) The first carbon-based material includes graphite, and selectively includes artificial graphite, (10) The mass ratio of the first carbon-based material in the first active material satisfies at least one of the following: ≧50%, and selectively 60% - 98%, The secondary battery according to any one of claims 1 to 5.

7. The first silicon-based material is as follows (1) - (9), (1) The volume distribution particle size Dv50 of the first silicon-based material is 8 - 15 μm, and selectively 10 - 13 μm, (2) The volume distribution particle size Dv90 of the first silicon-based material is 15 - 25 μm, and selectively 16 - 24 μm, (3) The first silicon-based material satisfies (Dv90 - Dv10) / Dv50 being 0.7 - 1.5, and selectively 0.9 - 1.3, (4) The specific surface area of the first silicon-based material is 0.7 - 2.0 m ２ / g, and selectively 0.8 - 1.6 m ２ / g, and The powder consolidation density of the first silicon-based material at 50,000 N is 1.0 - 1.7 g / cm ３ and selectively 1.2 - 1.6 g / cm ３ and (6) The tap density of the first silicon-based material is 1.0 - 1.5 g / cm ３ and selectively 1.1 - 1.4 g / cm ３ and (7) The powder resistivity of the first silicon-based material at 4 MPa is ≦15 Ω·cm, and selectively 0.5 - 12 Ω·cm, (8) The mass ratio of the first silicon-based material in the first active material is ≦50%, and selectively 2% - 40%, (9) The first silicon-based material includes one or more of silicon single crystal, silicon oxide, silicon carbon material, and silicon alloy material. Selectively, the first silicon-based material does not contain alkali metal and does not contain alkaline earth metal, and satisfies at least one of the following: the secondary particles are formed by aggregation of primary particles of silicon oxygen material, primary particles of silicon oxygen material containing alkali metal or alkaline earth metal, primary particles of silicon carbon material, primary particles of silicon single crystal, and primary particles of silicon alloy, The secondary battery according to any one of claims 1 to 6.

8. The second active material includes a second carbon-based material. The second carbon-based material includes secondary particles formed by aggregation of primary particles. Selectively, the ratio of the number of the second carbon-based material of the secondary particles in the second carbon-based material is ≧60%, and further selectively 70% - 85%. The secondary battery according to any one of claims 1 to 7.

9. The second active material includes a second carbon-based material, and the surface of the second carbon-based material has a carbon coating layer. Optionally, the carbon coating layer includes soft carbon. The secondary battery according to any one of claims 1 to 8.

10. The surface of the first carbon-based material has a carbon coating layer. The second active material includes a second carbon-based material. The surface of the second carbon-based material has a carbon coating layer. And the mass percentage content of the carbon coating layer of the second carbon-based material is greater than the mass percentage content of the carbon coating layer of the first carbon-based material. The secondary battery according to any one of claims 1 to 9.

11. The second active material includes a second carbon-based material. The first carbon-based material and the second carbon-based material are as follows (1)-(7), (1) The volume distribution particle size Dv50 of the second carbon-based material is smaller than the volume distribution particle size Dv50 of the first carbon-based material; (2) The specific surface area of the second carbon-based material is smaller than the specific surface area of the first carbon-based material; (3) The powder compaction density of the second carbon-based material at 20000 N is smaller than the powder compaction density of the first carbon-based material at 20000 N; (4) The tap density of the second carbon-based material is smaller than the tap density of the first carbon-based material; (5) The graphitization degree of the second carbon-based material is smaller than the graphitization degree of the first carbon-based material; (6) The gram capacity of the second carbon-based material is smaller than the gram capacity of the first carbon-based material; (7) The powder OI value of the second carbon-based material satisfies at least one of being smaller than the powder OI value of the first carbon-based material. The secondary battery according to any one of claims 1 to 10.

12. The second active material includes a second carbon-based material. Optionally, the second carbon-based material is as follows (1)-(12), (1) The volume distribution particle size Dv50 of the second carbon-based material is 9-15 μm, and optionally 11-13 μm; (2) The volume distribution particle size Dv90 of the second carbon-based material is 20-26 μm, and optionally 21-25 μm; (3) The second carbon-based material satisfies that (Dv90 - Dv10) / Dv50 is 0.8-1.6, and optionally 1.0-1.4; (4) The specific surface area of the second carbon-based material is 0.5 - 1.5 m ２ / g, and selectively 0.7 - 1.2 m ２ / g, and (5) The powder consolidation density of the second carbon-based material at 20,000 N is 1.6 - 1.8 g / cm ３ and selectively 1.65 - 1.75 g / cm ３ and (6) The tap density of the second carbon-based material is 0.9 - 1.2 g / cm ３ and is selectively 1.0 - 1.1 g / cm ３ and (7) The graphitization degree of the second carbon-based material is ≧92.5%, and optionally 93%-94%. (8) The gram capacity of the second carbon-based material is ≥ 354 mAh / g, and optionally 355 - 359 mAh / g, (9) Let the volume distribution particle size Dv50 of the second carbon-based material be denoted as A, with the unit being μm, and let the specific surface area of the second carbon-based material be denoted as B, with the unit being m ２ / g. A / B is 9.0 - 20, and selectively 11 - 15, and (10) The powder OI value of the second carbon-based material is 2 - 8, and optionally 4 - 6, (11) The second carbon-based material contains graphite, and optionally contains artificial graphite, (12) The mass ratio of the second carbon-based material in the second active material is ≥ 85%, and optionally 90% - 97%, satisfying at least one of the above. The secondary battery according to any one of claims 1 to 11.

13. The second active material contains a second silicon-based material, and the second silicon-based material contains one or more of primary particles and secondary particles formed by aggregation of primary particles, and optionally contains primary particles. The secondary battery according to any one of claims 1 to 12.

14. The second active material contains a second silicon-based material, and the second silicon-based material contains primary particles. The ratio of the number of the second silicon-based material of the primary particles in the second silicon-based material is ≥ 60%, and optionally 70% - 95%. The secondary battery according to any one of claims 1 to 13.

15. The second active material contains a second silicon-based material, and the first silicon-based material and the second silicon-based material satisfy the following (1) - (6): (1) The mass ratio of the second silicon-based material in the second active material is smaller than the mass ratio of the first silicon-based material in the first active material. (2) The volume distribution particle size Dv50 of the second silicon-based material is smaller than the volume distribution particle size Dv50 of the first silicon-based material. (3) The specific surface area of the second silicon-based material is smaller than the specific surface area of the first silicon-based material. (4) The powder compaction density of the second silicon-based material at 50000 N is larger than the powder compaction density of the first silicon-based material at 50000 N. (5) The tap density of the second silicon-based material is larger than the tap density of the first silicon-based material. (6) The powder resistivity of the second silicon-based material at 4 MPa is smaller than the powder resistivity of the first silicon-based material at 4 MPa, satisfying at least one of the above. The secondary battery according to any one of claims 1 to 14.

16. The second active material includes a second silicon-based material, and the second silicon-based material is as follows (1)-(9), (1) The volume distribution particle size Dv50 of the second silicon-based material is 4-12 μm, and optionally 5-11 μm, (2) The volume distribution particle size Dv90 of the second silicon-based material is 8-18 μm, and optionally 9-17 μm, (3) The second silicon-based material satisfies that (Dv90 - Dv10) / Dv50 is 0.7-1.3, and optionally 0.8-1.2, (4) The specific surface area of the second silicon-based material is 0.6 - 1.6 m ２ / g, and selectively 0.7 - 1.5 m ２ / g, and (5) The powder consolidation density of the second silicon-based material at 50,000 N is 1.2 - 1.8 g / cm ３ and selectively 1.3 - 1.7 g / cm ３ and (6) The tap density of the second silicon-based material is 1.1 - 1.7 g / cm ３ and selectively 1.2 - 1.6 g / cm ３ and (7) The powder resistivity of the second silicon-based material at 4 MPa is ≦5 Ω·cm, and optionally 0.3-4 Ω·cm, (8) The mass ratio of the second silicon-based material in the second active material is ≦15%, and optionally 3%-10%, (9) The second silicon-based material satisfies at least one of the following: including one or more of silicon single crystal, silicon oxide, silicon carbon material, and silicon alloy material, The secondary battery according to any one of claims 1 to 15.

17. The secondary battery according to any one of claims 1 to 16, wherein an intermediate region located between the first region and the second region includes the first active material and / or the second active material.

18. The negative electrode film layer is as follows (1)-(3), (1) The porosity of the negative electrode film layer is ≧15%, and optionally 20%-45%, (2) The consolidation density of the negative electrode film layer is ≧ 1.5 g / cm ３ and is selectively 1.6 - 1.8 g / cm ３ and (3) The areal density of the negative electrode film layer is ≥ 7 mg / cm ２ and selectively satisfies at least one of being 9 - 30 mg / cm ２ ​ The secondary battery according to any one of claims 1 to 17.

19. A power consumption device including the secondary battery according to any one of claims 1 to 18.

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