Secondary battery and power consumption device

Abstract

The present application provides a secondary battery and a power consumption device, the secondary battery including a negative electrode plate, the negative electrode plate including a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material, the negative electrode active material including a carbon-based material and a silicon-based material, the carbon-based material including secondary particles formed by agglomeration of primary particles, and the silicon-based material including secondary particles formed by agglomeration of primary particles.

Description

[Technical Field]

[0001] The present application relates to the field of battery technology, and more particularly to secondary batteries and power consuming devices. [Background technology]

[0002] In recent years, secondary batteries have been widely used in energy storage power systems such as hydroelectric, thermal, wind, 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 range of applications of secondary batteries becomes increasingly wider, people are facing severe challenges in the performance of secondary batteries, and secondary batteries are required to achieve various performance characteristics such as high energy density and good rate performance. However, a problem currently faced is that increasing the energy density of secondary batteries often affects the rate performance of secondary batteries. Summary of the Invention

[0003] The present application has been developed in consideration of the above technical issues, and its purpose is to provide a secondary battery and a power consumption device that can achieve good rate performance in a secondary battery while having a high energy density.

[0004] A first aspect of the present application provides a secondary battery, comprising a negative electrode plate, wherein the negative electrode plate comprises a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and comprising a negative electrode active material, the negative electrode active material comprising a carbon-based material and a silicon-based material, the carbon-based material comprising secondary particles formed by agglomeration of primary particles, and the silicon-based material comprising secondary particles formed by agglomeration of primary particles.

[0005] In the negative electrode active material of the present application, both the carbon-based material and the silicon-based material contain secondary particles formed by aggregation of primary particles, which increase the ion absorption channels and reduce the negative electrode-electrolyte interface resistance, thereby enabling the secondary battery to have a high energy density and excellent rate performance.

[0006] In any embodiment of the present application, the volume distribution particle size Dv50 of the carbon-based material is larger than the volume distribution particle size Dv50 of the silicon-based material. By making the volume distribution particle size Dv50 of the carbon-based material larger than the volume distribution particle size Dv50 of the silicon-based material, the adverse effect of large particles of the silicon-based material on the rate performance of the secondary battery can be reduced. In addition, the combination of large particles and small particles improves the compaction density of the negative electrode plate, contributing to improving the energy density of the secondary battery.

[0007] In any embodiment of the present application, the ratio of the number of the secondary particles in the carbon-based material is greater than the ratio of the number of the secondary particles in the silicon-based material. By making the ratio of the number of the secondary particles in the carbon-based material greater than the ratio of the number of the secondary particles in the silicon-based material, it is possible to balance the cycle performance and energy density of the secondary battery.

[0008] In any embodiment of the present application, the number ratio of the secondary particles in the carbon-based material is ≧70%, and optionally 75%-90%. When the carbon-based material contains an appropriate ratio of secondary particles, it can increase the ion absorption channels in the negative electrode film layer and reduce the negative electrode-electrolyte interface resistance, which is beneficial to further optimizing the rate performance of the secondary battery and can also reduce battery polarization, thereby providing the secondary battery with good cycle performance.

[0009] In any embodiment of the present application, the number ratio of the secondary particles in the silicon-based material is ≧55%, and optionally 60%-85%. When the silicon-based material contains an appropriate ratio of secondary particles, it can increase the ion absorption channel in the negative electrode film layer and reduce the negative electrode-electrolyte interface resistance, which is beneficial to further optimizing the rate performance of the secondary battery, and can also reduce battery polarization, thereby providing the secondary battery with good cycle performance.

[0010] In any embodiment of the present application, the porosity of the silicon-based material of the secondary particles is ≧4%, and optionally 5%-20%. Further adjusting the porosity of the silicon-based material of the secondary particles can contribute to further optimizing the rate performance of the secondary battery.

[0011] In any embodiment of the present application, the volume distribution particle size Dv50 of the carbon-based material is 12-18 μm, and optionally 13-17 μm.

[0012] In any embodiment of the present application, the volume distribution particle size Dv90 of the carbon-based material is 20-26 μm, and optionally 21-25 μm.

[0013] When the volume distribution particle size Dv50 and / or Dv90 of the carbon-based material is within the above range, it is advantageous to improve the ion and electron transport performance, thereby further improving the rate performance of the secondary battery, and also to reduce the specific surface area of the carbon-based material, thereby reducing side reactions and further improving the cycle performance of the secondary battery.

[0014] In any embodiment of the present application, the carbon-based material satisfies (Dv90-Dv10) / Dv50 of 0.6-1.5, and optionally 0.9-1.3. When the (Dv90-Dv10) / Dv50 of the carbon-based material is within the above range, its particle deposition performance is better, which is advantageous for improving the compaction density of the negative electrode film layer, thereby further improving the energy density of the secondary battery, and further advantageous for the negative electrode film layer to have an appropriate pore distribution, thereby further improving the rate performance of the secondary battery.

[0015] In any embodiment of the present application, the specific surface area of the carbon-based material is 1.5-3.5 m 2 / g, and selectively 1.7-2.7m 2 When the specific surface area of the 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 carbon-based material at 20,000 N is 1.65-1.85 g / cm 3 and selectively 1.70-1.80 g / cm 3 When the powder compaction density of the carbon-based material is within the above range, the compaction density of the negative electrode film layer can be increased, which increases the energy density of the secondary battery, and is advantageous in that the negative electrode film layer has an appropriate pore distribution, which improves the transport performance of ions and electrons, and improves the electrolyte infiltration properties of the negative electrode film layer, thereby further improving the rate performance and / or cycle performance of the secondary battery.

[0017] In any embodiment of the present application, the tap density of the carbon-based material is 0.9-1.2 g / cm 3 and selectively 0.9-1.1 g / cm 3 When the tap density of the carbon-based material is within the above range, the compaction density of the negative electrode film layer can be increased, which increases the energy density of the secondary battery, and is advantageous in that the negative electrode film layer has an appropriate pore distribution, which improves the transport performance of ions and electrons, and improves the infiltration properties of the negative electrode film layer with respect to the electrolyte, thereby further improving the rate performance and / or cycle performance of the secondary battery.

[0018] In any embodiment of the present application, the graphitization degree of the carbon-based material is ≥ 92%, and optionally 93%-94%, which 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 carbon-based material is ≧354 mAh / g, and optionally 355-360 mAh / g. When the gram capacity of the carbon-based material is within the above range, on the one hand, it can improve the energy density of the secondary battery, and on the other hand, it can provide the carbon-based material 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 OI value of the carbon-based material powder is 2 to 10, and optionally 3 to 6. The carbon-based material powder has a relatively small OI value and has ion absorption openings in all directions of the particles, so that it can quickly accept ions from the positive electrode, thereby further improving the rate performance of the secondary battery.

[0021] In any embodiment of the present application, the volume distribution particle size Dv50 of the silicon-based material is 8-15 μm, and optionally 10-13 μm.

[0022] In any embodiment of the present application, the silicon-based material has a volume distribution particle size Dv90 of 15-25 μm, and optionally 16-24 μm.

[0023] When the volume distribution particle size Dv50 and / or Dv90 of the silicon-based material is within the above range, it is advantageous to improve the transport performance of ions and electrons, thereby further improving the rate performance of the secondary battery, and also to reduce the specific surface area of the silicon-based material and reduce side reactions, thereby further improving the cycle performance of the secondary battery.

[0024] In any embodiment of the present application, the silicon-based material satisfies (Dv90-Dv10) / Dv50 is 0.7-1.5, and optionally 0.9-1.3.

[0025] When the (Dv90-Dv10) / Dv50 of the silicon-based material is within the above range, its particle deposition performance is better, which 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 distribution, which can further improve the rate performance of the secondary battery.

[0026] In any embodiment of the present application, the specific surface area of the silicon-based material is 0.7-2.0 m 2 / g, and selectively 0.8-1.6m 2 / g.

[0027] When the specific surface area of the silicon-based material is within the above range, it is advantageous in reducing side reactions, thereby enabling the secondary battery to have better cycle performance, and also improving the processability of the negative electrode slurry.

[0028] In any embodiment of the present application, the powder compaction density of the silicon-based material at 50,000 N is 1.0-1.7 g / cm 3 and selectively 1.2-1.6g / cm 3 is.

[0029] When the powder compaction density of the silicon-based material is within the above range, the compaction density of the negative electrode film layer can be increased, which increases the energy density of the secondary battery. Furthermore, it is advantageous for the negative electrode film layer to have an appropriate pore distribution, which improves the transport performance of ions and electrons, and improves the infiltration properties of the negative electrode film layer with respect to the electrolyte, thereby further improving the rate performance and / or cycle performance of the secondary battery.

[0030] In any embodiment of the present application, the tap density of the silicon-based material is 1.0-1.5 g / cm 3 and selectively 1.1-1.4 g / cm 3 is.

[0031] When the tap density of the silicon-based material is within the above range, the compaction density of the negative electrode film layer can be increased, which increases the energy density of the secondary battery. Furthermore, it is advantageous for the negative electrode film layer to have an appropriate pore distribution, which improves the ion and electron transport performance and the electrolyte infiltration properties of the negative electrode film layer, thereby further improving the rate performance and / or cycle performance of the secondary battery.

[0032] In any embodiment of the present application, the powder resistivity of the silicon-based material at 4 MPa is ≦15 Ω·cm, and optionally 0.5-12 Ω·cm.

[0033] By adjusting the powder resistivity of the silicon-based material to fall within the above range, the electronic conductivity of the negative electrode film layer can be improved, and the rate performance of the secondary battery can be further improved.

[0034] In any embodiment of the present application, the carbon-based material of the secondary particles includes artificial graphite.

[0035] In any embodiment of the present application, the silicon-based material includes one or more of elemental silicon, silicon oxide, silicon carbon material, and silicon alloy material.

[0036] In any embodiment of the present application, the silicon-based material includes secondary particles formed by aggregation of at least one of: (1) primary particles of a silicon-oxygen material that does not contain an alkali metal and does not contain an alkaline earth metal; (2) primary particles of a silicon-oxygen material that contains an alkali metal or an alkaline earth metal; (3) primary particles of a silicon-carbon material; (4) primary particles of elemental silicon; and (5) primary particles of a silicon alloy.

[0037] In any embodiment of the present application, the surface of the carbon-based material or the silicon-based material has a carbon coating layer, which is advantageous for improving the rate performance of the secondary battery.

[0038] In any embodiment of the present application, the surface of the carbon-based material and the surface of the silicon-based material both have a carbon coating layer.

[0039] In any embodiment of the present application, the surface of the carbon-based material has a carbon coating layer, and the carbon coating layer includes hard carbon, which has the advantage of a large interlayer spacing and can increase the ion diffusion rate, which is advantageous for further improving the rate performance of the secondary battery.

[0040] In any embodiment of the present application, the carbon-based material further comprises primary particles, which can reduce side reactions and improve the cycle performance of the secondary battery.

[0041] In any embodiment of the present application, the ratio of the number of the secondary particles in the carbon-based material is greater than the ratio of the number of the primary particles in the carbon-based material, which allows the negative electrode film layer to have many ion occlusion channels, which is advantageous for reducing the negative electrode-electrolyte interface resistance and providing the secondary battery with better rate performance, and also allows the secondary battery to have good cycle performance.

[0042] In any embodiment of the present application, the carbon-based material further includes primary particles, and the primary particles of the carbon-based material include at least one of artificial graphite and natural graphite.

[0043] In any embodiment of the present application, the silicon-based material further comprises primary particles, which can reduce side reactions and improve the cycle performance of the secondary battery.

[0044] In any embodiment of the present application, the ratio of the number of the secondary particles in the silicon-based material is greater than the ratio of the number of the primary particles in the silicon-based material, which allows the negative electrode film layer to have many ion occlusion channels, which is advantageous for reducing the negative electrode-electrolyte interface resistance and providing the secondary battery with better rate performance, and also allows the secondary battery to have good cycle performance.

[0045] In any embodiment of the present application, the mass proportion of the silicon-based material in the negative electrode active material is ≦50%, and optionally 2%-40%. By adjusting the content of the silicon-based material within this range, the rate performance and energy density of the secondary battery can be improved, and the secondary battery can have good cycle performance.

[0046] In any embodiment of the present application, the volume distribution particle size Dv50 of the negative electrode active material is 10-17.5 μm, and optionally 12-17 μm.

[0047] In any embodiment of the present application, the volume distribution particle size Dv90 of the negative electrode active material is 18-25.5 μm, and optionally 19-24.5 μm.

[0048] When the volume distribution particle size Dv50 and / or Dv90 of the negative electrode active material is within the above range, it is advantageous to improve the transport performance of ions and electrons, thereby further improving the rate performance of the secondary battery, reducing side reactions, and improving the cycle performance of the secondary battery.

[0049] In any embodiment of the present application, the negative electrode active material satisfies the (Dv90-Dv10) / Dv50 ratio of 0.65-1.5, and optionally 0.9-1.3. When the particle size distribution (Dv90-Dv10) / Dv50 of the negative electrode active material is within this range, its particle deposition performance is better, which 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 forming an optimal pore structure between the particles of the negative electrode film layer, thereby further improving the rate performance of the secondary battery.

[0050] In any embodiment of the present application, the porosity of the negative electrode membrane layer is ≧15%, and optionally 18%-50%, which is advantageous for the negative electrode membrane layer to have both high capacity and a suitable pore structure, and is also advantageous for the secondary battery to have both high energy density and good cycle performance and rate performance.

[0051] In any embodiment of the present application, the negative electrode film layer has a compaction density of ≦1.75 g / cm 3 and selectively 1.30-1.60 g / cm 3 This is advantageous for the negative electrode film layer to have both high capacity and good ion and electron transport performance, and is also advantageous for the secondary battery to have both high energy density and good cycle performance and rate performance.

[0052] In any embodiment of the present application, the areal density of the negative electrode film layer is ≦10.4 mg / cm 2and selectively 5-9 mg / cm 2 This is advantageous for making the negative electrode film layer achieve both high capacity and good ion and electron transport performance, and further advantageous for making the secondary battery achieve both high energy density and good cycle performance and rate performance.

[0053] In any embodiment of the present application, the secondary battery includes a positive electrode plate, the positive electrode plate includes a positive electrode active material, and the positive electrode active material has a general formula of Li a Ni b Co c M d M’ e O f A g and includes one or more of a layered lithium transition metal oxide and its modified compound thereof, where 0.8 ≦ a ≦ 1.2, 0.6 ≦ b < 1, 0 < c < 1, 0 < d < 1, 0 ≦ e ≦ 0.1, 1 ≦ f ≦ 2, 0 ≦ g ≦ 1, M includes Mn and / or Al, M’ includes one or more of Zr, Mn, Al, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, A includes one or more of N, F, S, and Cl, and optionally, 0.65 ≦ b < 1.

[0054] The second aspect of the present application provides a power consumption device including the secondary battery of the first aspect of the present application.

[0055] 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 Drawings

[0056] 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. It is self-evident that 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 without creative efforts. [Figure 1] It is a schematic diagram of an embodiment of the secondary battery of the present application. [Figure 2]1 is an exploded schematic view of an embodiment of a secondary battery of the present application. [Figure 3] 1 is a schematic diagram of one embodiment of a battery module of the present application. [Figure 4] 1 is a schematic diagram of one embodiment of a battery pack of the present application. [Figure 5] FIG. 5 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 4. [Figure 6] 1 is a schematic diagram of an embodiment of the present application including a secondary battery-powered power consuming device;

[0057] In the drawings, the drawings are not necessarily drawn to scale. DETAILED DESCRIPTION OF THE INVENTION

[0058] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing the secondary battery and power consumption device of the present application will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters or repeated description of actually identical structures may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. 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 subject matter described in the claims.

[0059] The "ranges" disclosed in this application are defined in the form of lower and upper limits. A given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the particular range. Such defined ranges may be inclusive or exclusive, and may be arbitrarily combined; i.e., any lower limit may be combined with any upper limit to form a single range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if 1 and 2 are listed as minimum range values and 3, 4, and 5 are listed as maximum range values, the ranges 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 are all contemplated. In this application, unless otherwise specified, the numerical range "ab" represents a shorthand notation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" represents that the specification has already listed all real numbers between "0-5," and "0-5" is merely a shorthand representation of combinations of these numbers. Also, expressing a parameter as an integer ≧2 is equivalent to disclosing that this parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0060] Unless otherwise stated, all embodiments and optional embodiments of the present 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 the present application.

[0061] Unless otherwise stated, all technical features and optional technical features of the present 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 the present application.

[0062] Unless otherwise specified, all steps in this application may be performed in order or randomly, preferably in order. For example, a description of a method including 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, a description of a method that may further include step (c) means that step (c) may be added to the method in any order, e.g., the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0063] Unless otherwise specified, the terms "comprise" and "comprises" used in this application may be open ended or closed ended. For example, the terms "comprise" and "comprises" may indicate that other components not listed may be further included or included, or that only the listed components may be included or included.

[0064] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, "A or B" is satisfied when A is true (or exists) and B is false (or does not exist), when A is false (or does not exist) but B is true (or exists), or when both A and B are true (or exist).

[0065] Unless otherwise explained, terms used in this application have the known meanings commonly understood by those skilled in the art.

[0066] Unless otherwise specified, the values of the parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, according to the test method of this application. Unless otherwise specified, the test temperature was 25°C.

[0067] As used in this application, the terms "plurality" and "various" mean two or more.

[0068] As a key component of secondary batteries, the impact of its performance on the performance of secondary batteries is extremely important. Currently, graphite is the most common negative electrode active material, and the energy density and rate performance of secondary batteries using graphite are both close to theoretical values. Silicon-based materials have the advantage of high theoretical energy density, and when combined with graphite, they can significantly improve the energy density of secondary batteries. However, the relatively high electronic resistivity of silicon-based materials leads to rapid decay of the reversible capacity of secondary batteries, and this decay phenomenon becomes more severe at high rates, resulting in insufficient improvement in the rate performance of secondary batteries. Therefore, how to combine graphite and silicon-based materials to achieve better rate performance has not yet been found, and a simple and feasible solution has not yet been found.

[0069] With this in mind, the inventors have gone through a great deal of research and have proposed the present application.

[0070] Specifically, an embodiment of the present application provides a secondary battery.

[0071] The present application does not particularly limit the type of secondary battery, and for example, the secondary battery may be a lithium-ion battery. Generally, a secondary battery includes a positive electrode plate, a negative electrode plate, and an electrolyte. During the charge / discharge process of a secondary battery, ions move back and forth between the positive electrode plate and the negative electrode plate to absorb and release ions, and the electrolyte functions to conduct ions between the positive electrode plate and the negative electrode plate. The present application does not particularly limit the type of electrolyte, and it 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). Secondary batteries using an electrolytic solution and some secondary batteries using a solid electrolyte may further include a separator. The separator is disposed between the positive electrode plate and the negative electrode plate and mainly functions as an insulator.

[0072] [Negative electrode plate] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material, the negative electrode active material including a carbon-based material and a silicon-based material, the carbon-based material including secondary particles formed by aggregation of primary particles, and the silicon-based material including secondary particles formed by aggregation of primary particles.

[0073] Compared with the case where a pure carbon-based material is used as the negative electrode active material, the present application uses a mixture of a carbon-based material and a silicon-based material as the negative electrode active material, and therefore the gram capacity of the negative electrode active material of the present application is higher, and a relatively high energy density can be achieved with only a relatively low areal density.

[0074] In the course of research, the inventors noticed that at a relatively low areal density, the impact of the negative electrode-electrolyte interface resistance on the rate performance of the secondary battery increases, and the impact of ion diffusion resistance on the rate performance of the secondary battery decreases. Furthermore, in further research, the inventors discovered that optimizing the particle structures of the carbon-based material and the silicon-based material is advantageous for further optimizing the rate performance of the secondary battery.

[0075] In the negative electrode active material of the present application, both the carbon-based material and the silicon-based material contain secondary particles formed by aggregation of primary particles, which increase the ion absorption channels and reduce the negative electrode-electrolyte interface resistance, thereby enabling the secondary battery to have a high energy density and excellent rate performance.

[0076] In some embodiments, the volume distribution particle size Dv50 of the carbon-based material may be larger than the volume distribution particle size Dv50 of the silicon-based material. The electronic conductivity and ionic conductivity of the silicon-based material itself are both weaker than those of the carbon-based material. By making the volume distribution particle size Dv50 of the carbon-based material larger than the volume distribution particle size Dv50 of the silicon-based material, the adverse effect of large particles of the silicon-based material on the rate performance of the secondary battery can be reduced. In addition, the combination of large and small particles improves the compaction density of the negative electrode plate, contributing to improving the energy density of the secondary battery.

[0077] In some embodiments, the proportion of the secondary particles in the carbon-based material may be greater than the proportion of the secondary particles in the silicon-based material. If the pressure resistance of the silicon-based material of the secondary particles is relatively low and the proportion of the secondary particles is too high, the particles of the silicon-based material are likely to burst at high compaction density, which can significantly reduce the cycle performance of the secondary battery. If the compaction density is reduced by reducing the particle fracture of the silicon-based material, the energy density of the secondary battery will also be sacrificed. By increasing the proportion of the secondary particles in the carbon-based material compared to the proportion of the secondary particles in the silicon-based material, the cycle performance and energy density of the secondary battery can be balanced.

[0078] In some embodiments, the number ratio of the secondary particles in the carbon-based material may be ≧70%, and optionally 70%-95%, 70%-92%, 70%-90%, 70%-88%, 75%-95%, 75%-92%, 75%-90%, or 75%-88%. When the carbon-based material contains an appropriate ratio of secondary particles, it can increase the ion absorption channels in the negative electrode film layer and reduce the negative electrode-electrolyte interfacial resistance, which is beneficial to further optimizing the rate performance of the secondary battery and can also reduce battery polarization, thereby providing the secondary battery with good cycle performance.

[0079] In some embodiments, the number ratio of the secondary particles in the silicon-based material may be ≧55%, and optionally 55%-90%, 55%-85%, 55%-80%, 55%-75%, 55%-70%, 60%-90%, 60%-85%, 60%-80%, 60%-75%, or 60%-70%. When the silicon-based material contains an appropriate ratio of secondary particles, it can increase the ion absorption channels in the negative electrode film layer and reduce the negative electrode-electrolyte interfacial resistance, which is beneficial to further optimizing the rate performance of the secondary battery and can also reduce battery polarization, thereby providing the secondary battery with good cycle performance.

[0080] In some embodiments, the number fraction of the secondary particles in the carbon-based material is 75%-90% and the number fraction of the secondary particles in the silicon-based material is 60%-85%.

[0081] The terms primary particles and secondary particles have the meanings known in the art. Primary particles are particles in a non-agglomerated state. Secondary particles are particles in an agglomerated state formed by the agglomeration of two or more primary particles. Primary particles and secondary particles can be distinguished using scanning electron microscope (SEM) images.

[0082] For example, the method for testing the proportion of secondary particles in carbon-based materials can be as follows: negative active material (obtained from a negative electrode plate) is placed on a conductive adhesive and bonded to produce a 6 cm x 1.1 cm test sample. The particle morphology is then examined using a scanning electron microscope. For this test, reference can be made to JY / T010-1996. To ensure the accuracy of the test results, multiple (e.g., 10) different areas of the test sample are randomly selected for scanning, and the ratio of the number of secondary particles in each test area to the total number of carbon-based particles is calculated at a certain magnification (e.g., 500x or 1000x). The average of the results from the multiple test areas can be used as the test result. To ensure the accuracy of the test results, multiple test samples (e.g., 5 or 10) can be prepared and the above test repeated, with the average value of each test sample taken as the final test result. The proportion of secondary particles in silicon-based materials can also be tested in a similar manner.

[0083] The proportion of the number of secondary particles in the carbon-based material can be adjusted by methods known in the art. For example, when the carbon-based material is graphite, the proportion of the number of secondary particles may be adjusted by adjusting production parameters (e.g., the type of coke raw material, the shaping process, the granulation process, the type and amount of granulating agent, etc.), or by adjusting the mixing ratio of graphite primary particles and graphite secondary particles (the types of graphite primary particles and graphite secondary particles may be the same or different).

[0084] The proportion of the number of secondary particles in the silicon-based material can be adjusted in a similar manner. For example, the proportion of the number of secondary particles may be adjusted by adjusting production parameters (e.g., the type of raw material, the granulation process, the type and amount of granulating agent, etc.), or the proportion of the number of secondary particles may be adjusted by adjusting the mixing ratio of the silicon-based material of primary particles to the silicon-based material of secondary particles.

[0085] In some embodiments, the porosity of the silicon-based material of the secondary particles may be ≧4%, and optionally 5%-20%. Further adjusting the porosity of the silicon-based material of the secondary particles can contribute to further optimizing the rate performance of the secondary battery.

[0086] As a result of further research, the present inventors have found that when a carbon-based material satisfies the above design and also satisfies one or more of the following conditions, the performance of the secondary battery can be further improved, and for example, at least one of the energy density, cycle performance, and rate performance of the secondary battery can be improved.

[0087] In some embodiments, the carbon-based material of the secondary particles comprises artificial graphite.

[0088] In some embodiments, the carbon-based material further comprises primary particles (which here refer to non-agglomerated particles), which can reduce side reactions and improve the cycle performance of the secondary battery.

[0089] In some embodiments, the ratio of the number of the secondary particles in the carbon-based material is greater than the ratio of the number of the primary particles in the carbon-based material, which allows the negative electrode film layer to have more ion occlusion channels, which is advantageous for reducing the negative electrode-electrolyte interface resistance and providing the secondary battery with better rate performance, and also allows the secondary battery to have good cycle performance.

[0090] In some embodiments, the carbon-based material further comprises primary particles, and the primary particles of the carbon-based material comprise at least one of artificial graphite and natural graphite, and optionally artificial graphite.

[0091] In some embodiments, the surface of the carbon-based material may have a carbon coating layer, which is advantageous for improving the rate performance of the secondary battery.

[0092] In some embodiments, the carbon-based material comprises artificial graphite having a carbon coating layer on its surface.

[0093] In some embodiments, 80% or more of the surface of the carbon-based material has a carbon coating layer, and optionally 90%-100% of the surface of the carbon-based material has a carbon coating layer.

[0094] In some embodiments, the carbon in the carbon coating layer on the surface of the carbon-based material contains amorphous carbon, which is advantageous for improving the rate performance of the secondary battery.

[0095] The carbon coating layer may be formed by carbonizing an organic carbon source, which may be any carbon-containing material known in the art that is suitable for coating, such as coal pitch, petroleum pitch, phenolic resin, coconut shell, or the like.

[0096] In some embodiments, the surface of the carbon-based material has a carbon coating layer, and the carbon coating layer includes hard carbon, which has an advantage of having a large interlayer spacing and can increase the ion diffusion rate, which is advantageous for further improving the rate performance of the secondary battery.

[0097] In some embodiments, the carbon-based material may have a volume distribution particle size Dv50 of 12-18 μm, and optionally 13-17 μm.

[0098] In some embodiments, the carbon-based material may have a volume distribution particle size Dv90 of 20-26 μm, and optionally 21-25 μm.

[0099] When the volume distribution particle size Dv50 and / or Dv90 of the carbon-based material is within the above range, it is advantageous to improve the ion and electron transport performance, thereby further improving the rate performance of the secondary battery, and also to reduce the specific surface area of the carbon-based material, thereby reducing side reactions and further improving the cycle performance of the secondary battery.

[0100] In some embodiments, the carbon-based material may satisfy (Dv90-Dv10) / Dv50 of 0.6-1.5, and optionally 0.9-1.3.

[0101] When the (Dv90-Dv10) / Dv50 of the carbon-based material is within the above range, its particle deposition performance is better, which 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 distribution, which can further improve the rate performance of the secondary battery.

[0102] In some embodiments, the specific surface area of the carbon-based material is 1.5-3.5 m 2 / g, and optionally 1.7-2.7m 2 / g.

[0103] When the specific surface area of the 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.

[0104] In some embodiments, the carbon-based material has a powder compaction density of 1.65-1.85 g / cm at 20,000 N. 3 and optionally 1.70-1.80 g / cm 3 is.

[0105] When the powder compaction density of the carbon-based material is within the above range, the compaction density of the negative electrode film layer can be increased, which increases the energy density of the secondary battery. This is advantageous for the negative electrode film layer to have an appropriate pore distribution, which improves the ion and electron transport performance and the electrolyte infiltration properties of the negative electrode film layer, thereby further improving the rate performance and / or cycle performance of the secondary battery.

[0106] In some embodiments, the tap density of the carbon-based material is 0.9-1.2 g / cm 3 and optionally 0.9-1.1 g / cm 3 is.

[0107] When the tap density of the carbon-based material is within the above range, the compaction density of the negative electrode film layer can be increased, which increases the energy density of the secondary battery. This is also advantageous for the negative electrode film layer to have an appropriate pore distribution, which improves the ion and electron transport performance and the electrolyte infiltration properties of the negative electrode film layer, thereby further improving the rate performance and / or cycle performance of the secondary battery.

[0108] In some embodiments, the degree of graphitization of the carbon-based material may be ≧92%, and optionally 93%-94%.

[0109] When the graphitization degree of the 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.

[0110] In some embodiments, the gram capacity of the carbon-based material may be ≧354 mAh / g, optionally 355-360 mAh / g.

[0111] When the gram capacity of the 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 in improving the rate performance of the secondary battery.

[0112] In some embodiments, the powder OI value of the carbon-based material may be 2-10, and optionally 3-6.

[0113] The carbonaceous material powder has a relatively small OI value and has ion absorption openings in all directions of the particles, allowing it to quickly accept ions from the positive electrode, thereby further improving the rate performance of the secondary battery.

[0114] As a result of further research, the inventor of the present invention has found that when the 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 improved.

[0115] In some embodiments, the silicon-based material may include one or more of elemental silicon, silicon oxide (SiO x , 0 < x ≤ 2), silicon-carbon material, and silicon alloy material. This 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.

[0116] In some embodiments, the silicon-based material may include secondary particles formed by aggregation of at least one of (1) primary particles of a silicon-oxygen material that does not contain an alkali metal and does not contain an alkaline earth metal, (2) primary particles of a silicon-oxygen material that contains an alkali metal or an alkaline earth metal, (3) primary particles of a silicon-carbon material, (4) primary particles of elemental silicon, and (5) primary particles of a silicon alloy.

[0117] Optionally, the alkali metal includes Li. Optionally, the alkaline earth metal includes Mg.

[0118] For example, the silicon-based material includes secondary particles formed by agglomeration of primary particles of a silicon-oxygen material that is neither alkali metal nor alkaline earth metal, secondary particles formed by agglomeration of primary particles of a silicon-oxygen material that is neither alkali metal nor alkaline earth metal and primary particles of a silicon-oxygen material that contains an alkali metal or an alkaline earth metal, secondary particles formed by agglomeration of primary particles of a silicon-oxygen material that contains an alkali metal or an alkaline earth metal, secondary particles formed by agglomeration of primary particles of a silicon-carbon material, secondary particles formed by agglomeration of primary particles of a silicon-carbon material and primary particles of a silicon-oxygen material that is neither alkali metal nor alkaline earth metal, and secondary particles formed by agglomeration of primary particles of a silicon-carbon material and primary particles of a silicon-oxygen material that contains an alkali metal or an alkaline earth metal.

[0119] In some embodiments, the silicon-based material may further include primary particles (which refer to non-aggregated particles). This can reduce side reactions and improve the cycle performance of the secondary battery. The specific types of the silicon-based material of the primary particles and the silicon-based material of the secondary particles may be the same or different.

[0120] In some embodiments, the ratio of the number of the secondary particles in the silicon-based material may be greater than the ratio of the number of the primary particles in the silicon-based material, which allows the negative electrode film layer to have more ion absorption channels, which is advantageous for reducing the negative electrode-electrolyte interface resistance and providing the secondary battery with better rate performance, and also allows the secondary battery to have good cycle performance.

[0121] In some embodiments, the surface of the silicon-based material may have a carbon coating layer, which improves the electronic conductivity of the silicon-based material and the rate performance of the secondary battery. The carbon coating layer can be formed by chemical vapor deposition, pyrolysis, hydrothermal deposition, or the like.

[0122] In some embodiments, 80% or more of the surface of the silicon-based material has a carbon coating layer, and optionally, 90%-100% of the surface of the silicon-based material has a carbon coating layer.

[0123] In some embodiments, the surface of the carbon-based material and the surface of the silicon-based material both have a carbon coating layer.

[0124] In some embodiments, the volume distribution particle size Dv50 of the silicon-based material may be 8-15 μm, and optionally 10-13 μm.

[0125] In some embodiments, the volume distribution particle size Dv90 of the silicon-based material may be 15-25 μm, and optionally 16-24 μm.

[0126] When the volume distribution particle size Dv50 and / or Dv90 of the silicon-based material is within the above range, it is advantageous to improve the transport performance of ions and electrons, thereby further improving the rate performance of the secondary battery, and also to reduce the specific surface area of the silicon-based material and reduce side reactions, thereby further improving the cycle performance of the secondary battery.

[0127] In some embodiments, the silicon-based material satisfies that (Dv90-Dv10) / Dv50 may be 0.7-1.5, and optionally 0.9-1.3.

[0128] When the (Dv90-Dv10) / Dv50 of the silicon-based material is within the above range, its particle deposition performance is better, which 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 distribution, which can further improve the rate performance of the secondary battery.

[0129] In some embodiments, the specific surface area of the silicon-based material is 0.7-2.0 m 2 / g, and optionally 0.8-1.6m2 / g.

[0130] When the specific surface area of the silicon-based material is within the above range, it is advantageous in reducing side reactions, thereby enabling the secondary battery to have better cycle performance, and also improving the processability of the negative electrode slurry.

[0131] In some embodiments, the silicon-based material has a powder compaction density of 1.0-1.7 g / cm at 50,000 N. 3 and optionally 1.2-1.6 g / cm 3 is.

[0132] When the powder compaction density of the silicon-based material is within the above range, the compaction density of the negative electrode film layer can be increased, which increases the energy density of the secondary battery. Furthermore, it is advantageous for the negative electrode film layer to have an appropriate pore distribution, which improves the transport performance of ions and electrons, and improves the infiltration properties of the negative electrode film layer with respect to the electrolyte, thereby further improving the rate performance and / or cycle performance of the secondary battery.

[0133] In some embodiments, the tap density of the silicon-based material is 1.0-1.5 g / cm 3 and optionally 1.1-1.4 g / cm 3 is.

[0134] When the tap density of the silicon-based material is within the above range, the compaction density of the negative electrode film layer can be increased, which increases the energy density of the secondary battery. Furthermore, it is advantageous for the negative electrode film layer to have an appropriate pore distribution, which improves the ion and electron transport performance and the electrolyte infiltration properties of the negative electrode film layer, thereby further improving the rate performance and / or cycle performance of the secondary battery.

[0135] In some embodiments, the powder resistivity of the silicon-based material at 4 MPa may be ≦15 Ω cm, and optionally 0.5-12 Ω cm. By adjusting the powder resistivity of the silicon-based material within the above range, the electronic conductivity of the negative electrode film layer can be improved, and the rate performance of the secondary battery can be further improved.

[0136] In some embodiments, the mass proportion of the silicon-based material in the negative electrode active material may be ≦50%, and optionally 2%-40%, 2%-30%, 2%-20%, 3%-40%, 3%-30%, or 3%-20%. By adjusting the content of the 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 good cycle performance.

[0137] In some embodiments, the negative electrode active material includes a carbon-based material and a silicon-based material, the carbon-based material includes secondary particles formed by agglomeration of primary particles, the silicon-based material includes secondary particles formed by agglomeration of primary particles, the surface of the carbon-based material has a carbon coating layer, the volume distribution particle diameter Dv50 of the carbon-based material is larger than the volume distribution particle diameter Dv50 of the silicon-based material, the number ratio of the secondary particles in the carbon-based material is larger than the number ratio of the secondary particles in the silicon-based material, the number ratio of the secondary particles in the carbon-based material is ≧70%, optionally 75%-90%, and the number ratio of the secondary particles in the silicon-based material is ≧55%, optionally 60%-85%. This improves the rate performance of the secondary battery and also provides better cycle performance of the secondary battery.

[0138] In some embodiments, the negative electrode active material has a volume distribution particle size Dv50 of 10-17.5 μm, and optionally 12-17 μm.

[0139] In some embodiments, the negative electrode active material has a volume distribution particle size Dv90 of 18-25.5 μm, and optionally 19-24.5 μm.

[0140] By adjusting the parameters of the carbonaceous material and / or silicon-based material, such as the volume distribution particle size, particle size distribution, and mass content, the volume distribution particle size Dv50 and / or Dv90 of the negative electrode active material can be adjusted to fall within the above ranges. When the volume distribution particle size Dv50 and / or Dv90 of the negative electrode active material falls within the above ranges, it is advantageous to improve the ion and electron transport performance, thereby further improving the rate performance of the secondary battery, reducing side reactions, and improving the cycle performance of the secondary battery.

[0141] In some embodiments, the negative electrode active material may satisfy the requirement that (Dv90-Dv10) / Dv50 be 0.65-1.5, and optionally 0.9-1.3. The particle size distribution (Dv90-Dv10) / Dv50 of the negative electrode active material can be within the above range by adjusting parameters such as the volume distribution particle size, particle size distribution, and mass content of the carbon-based material and / or silicon-based material. When the particle size distribution (Dv90-Dv10) / Dv50 of the negative electrode active material is within the above range, the particle deposition performance is better, which is beneficial for improving the compaction density of the negative electrode film layer, thereby further improving the energy density of the secondary battery, and is also beneficial for forming an optimal pore structure between the particles of the negative electrode film layer, thereby further improving the rate performance of the secondary battery.

[0142] In some embodiments, the negative electrode film layer may further include other negative electrode active materials known in the art other than the carbon-based material and silicon-based material. For example, the negative electrode film layer may further include one or more of lithium titanate and tin-based materials.

[0143] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent. The present application does not particularly limit the type of the negative electrode conductive agent, and the negative electrode conductive agent may include, for example, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0144] In some embodiments, the negative electrode film layer may further optionally include a negative electrode adhesive. The present application is not particularly limited to the type of the negative electrode adhesive, and for example, the negative electrode adhesive may include one or more of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-soluble acrylic acid-based resin (e.g., polyacrylic acid (PAA), polymethacrylic acid (PMAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0145] In some embodiments, the negative electrode membrane layer may further optionally include other additives, such as thickeners, e.g., sodium carboxymethylcellulose (CMC), PTC thermistor materials, etc.

[0146] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. An example of a metal foil sheet is copper foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal layer may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymer base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0147] The negative electrode film layer is typically formed by coating a negative electrode slurry on a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is typically formed by dispersing a negative electrode active material, an optional conductive agent, an optional adhesive, and other optional additives in a solvent and uniformly stirring the resulting mixture. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0148] The negative electrode active materials (for example, silicon-based materials, carbon-based materials) mentioned above may be commercially available or may be prepared by the following method of the present application.

[0149] In some embodiments, the silicon-based material containing secondary particles may be prepared by preparing a solution containing primary particles, an adhesive, and a solvent, and then spray-drying the solution to obtain a silicon-based material containing secondary particles. The adhesive is not particularly limited, but specific examples include one or more of pitch, starch, phenolic resin, polyvinyl alcohol, epoxy resin, polyvinyl perchloride resin, butyl rubber, etc. The solvent is not particularly limited as long as it sufficiently disperses the primary particles, and specific examples include one or more of water, alcohol, N-methylpyrrolidone (NMP), dimethyl sulfoxide, acetonitrile, acetone, tetrahydrofuran, diethyl ether, toluene, 1,2-dichlorobenzene, etc. The spray-drying temperature may be 100°C to 250°C.

[0150] Alternatively, the secondary particles of the silicon-based material may be produced by mixing the primary particles with an adhesive, granulating the mixture, and then heat-treating the mixture to obtain the silicon-based material containing the secondary particles. The adhesive is not particularly limited, but specific examples include one or more of pitch, starch, phenolic resin, polyvinyl alcohol, epoxy resin, polyvinyl chloride resin, butyl rubber, etc.

[0151] By adjusting the aggregation state, the porosity of the secondary particles of the silicon-based material can be adjusted to an appropriate range. Specifically, the secondary particles are immersed in a high-temperature molten liquid of a filler, pressurized to control the degree of filler loading, and then subjected to high-temperature carbonization, thereby achieving adjustment of the porosity. Specific examples of fillers include one or more of pitch, starch, phenolic resin, polyvinyl alcohol, epoxy resin, polyvinyl chloride resin, butyl rubber, polymethyl methacrylate, etc.

[0152] When producing secondary particles of a silicon-based material, the types of primary particles used may be the same or different.

[0153] In some embodiments, the secondary particles of the carbon-based material may be produced by crushing and shaping a coke raw material, then mixing and granulating the coke raw material with an adhesive, and then graphitizing the coke raw material to obtain a carbon-based material containing secondary particles. 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.

[0154] The above manufacturing process does not include a step of forming a carbon coating layer on the surface of the material. For example, the carbon coating layer on the surface of the carbon-based material may be formed by carbonizing an organic carbon source. The organic carbon source may be a carbon-containing material known in the art that is suitable for coating, such as 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 may be formed by chemical vapor deposition, pyrolysis, hydrothermal method, etc.

[0155] The negative electrode plate does not exclude additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode plate described herein further includes a conductive undercoating (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 herein further includes a protective layer covering the surface of the negative electrode film layer.

[0156] In some embodiments, the porosity of the negative electrode film layer may be ≧15%, and optionally 18%-50%, which is advantageous for the negative electrode film layer to have both high capacity and a suitable pore structure, and further advantageous for the secondary battery to have both high energy density and good cycle performance and rate performance.

[0157] In some embodiments, the negative electrode film layer has a compacted density of ≦1.75 g / cm 3 and optionally 1.30-1.60 g / cm 3 This is advantageous for the negative electrode film layer to have both high capacity and good ion and electron transport performance, and is also advantageous for the secondary battery to have both high energy density and good cycle performance and rate performance.

[0158] In some embodiments, the areal density of the negative electrode film layer is ≦10.4 mg / cm 2 and optionally 5-9 mg / cm 2 This is advantageous for the negative electrode film layer to have both high capacity and good ion and electron transport performance, and is also advantageous for the secondary battery to have both high energy density and good cycle performance and rate performance.

[0159] The negative electrode current collector has two surfaces facing each other in the thickness direction thereof, and the negative electrode film layer is disposed on one or both of the two facing surfaces of the negative electrode current collector. It should be noted that the negative electrode film layer parameters (e.g., compaction density, areal density, porosity, etc.) given in this application refer to the parameters 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 satisfy the present application, it is considered to fall within the protection scope of the present application.

[0160] Whether or not a carbon coating layer is present on the surface of a material (for example, a carbon-based material, a silicon-based material, etc.) can be determined using a transmission electron microscope.

[0161] The volume distribution particle sizes Dv10, Dv50, and Dv90 of a material (e.g., carbon-based material, silicon-based material, negative electrode active material, etc.) have the meanings known in the art and represent the particle sizes corresponding to the cumulative volume distribution percentages of the material reaching 10%, 50%, and 90%, respectively. They can be measured using equipment and methods known in the art. For example, they may be measured using a laser particle size analyzer in accordance with GB / T 19077-2016. The testing equipment may be a Mastersizer 3000 laser particle size analyzer manufactured by Malvern Instruments, UK.

[0162] The specific surface area of a material (e.g., a carbon-based material, a silicon-based material, etc.) has a meaning known in the art and can be measured using equipment and methods known in the art. For example, it can be tested using the nitrogen gas adsorption specific surface area analysis test method in accordance with GB / T 19587-2017 and calculated using the Brunauer Emmett Teller (BET) method. The test equipment can be a Tri-Star 3020 specific surface area pore size analyzer manufactured by Micromeritics, USA.

[0163] The powder compaction density of a material (e.g., a carbon-based material, a silicon-based material, etc.) has a meaning known in the art and can be measured using equipment and methods known in the art. For example, it can be measured with an electronic pressure tester (e.g., a UTM7305 type electronic pressure tester) with reference to GB / T 24533-2009. An exemplary test method is to weigh 1 g of sample powder and measure the powder compaction density to determine whether the powder has a base area of 1.327 cm. 2 The mold is added, pressurized to the required pressure, held for 30 seconds, then released and held for 10 seconds, and then recorded and calculated to obtain the powder compaction density of the material at the required pressure.

[0164] The tap density of a material (e.g., carbon-based material, silicon-based material, etc.) has a meaning known in the art and can be measured using equipment and methods known in the art. For example, it can be measured using a powder tap density tester in accordance with GB / T 5162-2006. The test equipment used is the Dandong Baite BT-301, and the test parameters are a vibration frequency of 250±15 times / min, an amplitude of 3±0.2 mm, a vibration count of 5000 times, and a 25 mL measuring cylinder.

[0165] The graphitization degree of a carbon-based material has a meaning known in the art and can be tested using equipment and methods known in the art. For example, it can be tested using an X-ray diffractometer (e.g., Bruker D8 Discover). The test is carried out by measuring the average layer spacing d of the C(002) crystal plane in the material crystal structure with reference to JIS K 0131-1996 and JB / T 4220-2011. 002 and obtain the formula g = (0.344 - d 002 The degree of graphitization can be calculated from the formula: d ) / (0.344-0.3354)×100%. 002 is the average layer spacing of the C(002) crystal planes in the material's crystal structure, expressed in nanometers (nm).

[0166] The powder OI value of a carbon-based material has a meaning known in the art and can be tested using equipment and methods known in the art. For example, the test can be performed using an X-ray diffraction device (e.g., Bruker D8 Discover). JIS K 0131-1996 and JB / T 4220-2011 can be referenced for the test. The X-ray diffraction pattern of a powder sample is obtained, and the OI value = I 004 / I 110 Calculate the powder OI value of the sample based on I 004 is the integrated area of the diffraction peak of the crystalline carbon 004 crystal plane in the powder sample, and I 110is 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 radiation is used as the radiation source, the radiation wavelength is λ=1.5418 Å, the scanning 2θ angle range is 20°-80°, and the scanning speed is 4° / min.

[0167] The powder resistivity of silicon-based materials is a known value in the art and can be tested using equipment and methods known in the art. For example, a resistivity tester (e.g., the ST2722 powder resistivity tester from Suzhou Grid Electronics Co., Ltd.) can be used to test. A 1g powder sample is taken and placed between the electrodes of the resistivity tester. A constant test pressure (e.g., 4 MPa) is applied using an electronic press and maintained for 15-25 seconds to obtain a sheet sample. The powder resistivity δ of the material is calculated using the formula δ = (S × R) / h, where h is the height of the sheet sample in cm, R is the resistance in Ω, and S is the area of the sheet sample in cm. 2 is.

[0168] The gram capacity of a carbon-based material is a known value in the art and can be measured using known equipment and methods in the art. An exemplary test method is as follows: a sample powder, a conductive agent carbon black (Super P), and an adhesive polyvinylidene fluoride (PVDF) are uniformly mixed with a solvent N-methylpyrrolidone (NMP) in a mass ratio of 91.6:1.8:6.6 to prepare a slurry. The slurry is applied to the surface of a negative electrode current collector copper foil and dried in an oven for use. Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent. LiPF6 is then dissolved in the organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L. Next, a CR2430 button cell battery was assembled in an argon-protected glove box using a lithium metal sheet as the counter electrode and polyethylene (PE) film as the separator with the above electrolyte. The resulting button cell was allowed to stand for 12 hours, then discharged at a constant current of 0.05 C to 0.005 V at 25°C, allowed to stand for 10 minutes, discharged again at a constant current of 50 μA to 0.005 V, allowed to stand for 10 minutes, discharged again at a constant current of 10 μA to 0.005 V, and then charged at a constant current of 0.1 C to 2 V. The charge capacity was recorded. The ratio of the charge capacity to the sample mass is the gram capacity.

[0169] The porosity of the secondary particle silicon-based material can be measured using a method known in the art. For example, the true density ρ of the secondary particle silicon-based material can be measured using a true density tester (e.g., AccuPyc II 1340 type). r Specifically, a sample of a certain mass (denoted as m) is weighed, placed in a true density tester, the test system is sealed, and helium gas is introduced according to the procedure, and the gas pressure in the sample chamber and the expansion chamber is detected. Then, the true volume Vr of the secondary particle silicon-based material is calculated according to Boll's law (PV=nRT), and the true density ρ of the secondary particle silicon-based material is obtained. r =m / V rThe apparent density of the secondary particle silicon-based material is determined by placing a sample of a certain mass (denoted as m) in a cylindrical mold with an inner diameter of 10 mm, applying a pressure of 200 MPa to obtain the apparent volume V0 of the secondary particle silicon-based material, and the apparent density of the secondary particle silicon-based material is ρ0=m / V0. If the porosity of the secondary particle silicon-based material is P, then P=(1-ρ0 / ρ r )×100%.

[0170] The areal density of the negative electrode film layer has a meaning known in the art and can be tested using methods known in the art. For example, a negative electrode plate after one side has been coated and cold-pressed (if the negative electrode plate is coated on both sides, the negative electrode film layer on one side can be wiped off first) can be taken and punched into a small disk with an area of S1, which can then be weighed and recorded as M1. Next, the negative electrode film layer of the weighed negative electrode plate is wiped off, and the weight of the negative electrode current collector is weighed and recorded as M0. The areal density of the negative electrode plate = (M1 - M0) / S1.

[0171] The compaction density of the negative electrode film layer has a meaning known in the art and can be determined by testing using methods known in the art. Compaction density of the negative electrode film layer = areal density of the negative electrode film layer / thickness of the negative electrode film layer. The thickness of the negative electrode film layer has a meaning known in the art and can be determined by testing using methods known in the art, for example, using a micrometer (e.g., Mitutoyo 293-100 type, accuracy 0.1 μm).

[0172] The porosity of the negative electrode film layer has a meaning known in the art and can be measured using methods known in the art. An exemplary test method is as follows: a negative electrode plate coated on one side and cold-pressed (if the negative electrode plate is coated on both sides, the negative electrode film layer on one side can be wiped off first) is taken and punched into a small circular sample of a certain area, and the apparent volume V1 of the negative electrode plate is calculated. Referring to GB / T 24586-2009, an inert gas (e.g., helium gas or nitrogen gas) is used as the medium, and a gas displacement method is used to measure the true volume V2 of the negative electrode plate using a true density tester. The porosity of the negative electrode film layer = (V1 - V2) / V1 × 100%. Several (e.g., 30) negative electrode plate samples with good appearance and no edge powdering are tested, and the results can be averaged to improve the accuracy of the test results. The test equipment may be a Micromeritics AccuPyc II 1340 true density tester.

[0173] It should be noted that the above-mentioned various parameter tests on the negative electrode active material or the negative electrode film layer can be performed by sampling and testing from a secondary battery manufactured according to the following steps.

[0174] The secondary battery is discharged (for safety reasons, the secondary battery is generally fully discharged), the negative electrode plate is removed from the secondary battery, and the negative electrode plate is immersed in dimethyl carbonate for a certain period of time (e.g., 2-10 hours). The negative electrode plate is then removed and dried at a certain temperature for a certain period of time (e.g., 60°C for 4 hours or more). After drying, the negative electrode plate is removed. At this point, various parameters related to the negative electrode film layer, such as the surface density, compaction density, and porosity of the negative electrode film layer, can be sampled and tested from the dried negative electrode plate.

[0175] The dried negative electrode plate is baked at a certain temperature for a certain time (for example, 400°C for 2 hours or more), and the negative electrode active material is sampled from any region of the baked negative electrode plate (the powder may be scraped off using a blade for sampling), and the collected negative electrode active material is sieved (for example, sieved through a 200-mesh sieve) to finally obtain a sample that can be used to test each of the above-mentioned negative electrode active material parameters.

[0176] [Positive electrode plate] In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector. For example, the positive electrode current collector has two surfaces facing each other in a thickness direction thereof, and the positive electrode film layer is disposed on one or both of the two facing surfaces of the positive electrode current collector.

[0177] The positive electrode current collector may be a metal foil sheet or a composite current collector. An example of the metal foil sheet is aluminum foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal layer may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymer base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0178] The positive electrode film layer typically includes a positive electrode active material, an optional adhesive, and an optional conductive agent. The positive electrode film layer is typically obtained by coating a positive electrode slurry on the positive electrode current collector, drying, and cold pressing. The positive electrode slurry is typically formed by dispersing the positive electrode active material, the optional conductive agent, the optional adhesive, and any other components in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP). For example, the adhesive 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 a fluorine-containing acrylate resin. For 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.

[0179] The positive electrode active material may be a positive electrode active material used in secondary batteries known in the art.

[0180] When the secondary battery of the present application is a lithium ion battery, the positive electrode active material may include, but is not limited to, one or more of lithium transition metal oxides, lithium-containing phosphates, and their 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 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 modified compounds.

[0181] 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 the layered lithium transition metal oxides and their modified compounds having the general formula Li a Ni b Co c M d M’ e O f A g where 0.8 ≦ a ≦ 1.2, 0.6 ≦ b < 1, 0 < c < 1, 0 < d < 1, 0 ≦ e ≦ 0.1, 1 ≦ f ≦ 2, 0 ≦ g ≦ 1, M includes Mn and / or Al, M’ includes one or more of Zr, Mn, Al, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A includes one or more of N, F, S, and Cl. Optionally, 0.65 ≦ b < 1.

[0182] In some embodiments, for example, the positive electrode active material used in the lithium ion battery is LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(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 include one or more of O2, LiFePO4, and LiMnPO4.

[0183] The modifying compounds for the positive electrode active materials are used to modify the positive electrode active materials by doping and / or surface coating.

[0184] [Electrolyte] In some embodiments, the electrolyte employs an electrolytic solution, the electrolytic solution including an electrolyte salt and a solvent.

[0185] The type of the electrolyte salt is not specifically limited and can be selected according to actual needs.

[0186] When the secondary battery of the present application is a lithium-ion battery, for example, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), 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 (LiPOF), lithium difluorobis(oxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0187] 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).

[0188] In some embodiments, the electrolyte solution may further optionally include additives. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive that can improve some performance of the secondary battery, such as an additive that improves the overcharge performance of the secondary battery, an additive that improves the high-temperature performance of the secondary battery, or an additive that improves the low-temperature power performance of the secondary battery.

[0189] [Separator] The present application does not particularly limit the type of the separator, and any known porous structure separator having good chemical stability and mechanical stability may be selected.

[0190] In some embodiments, the separator may be made of one or more of glass fiber, nonwoven 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.

[0191] In some embodiments, the positive electrode plate, the separator, and the negative electrode plate may be fabricated into an electrode assembly by a winding process or a stacking process.

[0192] In some embodiments, the secondary battery may include an exterior body, which may be used to package the electrode assembly and the electrolyte.

[0193] In some embodiments, the outer casing may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The outer casing may be a pouch, such as a bag-like pouch. The pouch may be made of plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0194] The present application does not particularly limit the shape of the secondary battery, and the secondary battery may be cylindrical, rectangular, or any other shape. Figure 1 shows an example of a secondary battery 5 having a rectangular structure.

[0195] In some embodiments, as shown in FIG. 2 , the exterior body may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and side plates connected to the bottom plate, which together form a surrounding accommodating cavity. The case 51 has an opening communicating with the accommodating cavity, and the cover plate 53 is used to cover the opening and seal the accommodating cavity. The positive electrode plate, the negative electrode plate, and the separator may be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged in the accommodating cavity. An electrolyte is impregnated 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 as needed.

[0196] The method for manufacturing the secondary battery of the present application is well known. In some embodiments, a secondary battery can be formed by assembling a positive electrode plate, a separator, a negative electrode plate, and an electrolyte. For example, the positive electrode plate, the separator, and the negative electrode plate can be wound or stacked to form an electrode assembly, which can then be placed in an outer casing, dried, and then injected with an electrolyte. The secondary battery can then be obtained through processes such as vacuum packaging, standing, chemical formation, and shaping.

[0197] 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 can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0198] Fig. 3 is a schematic diagram of an example battery module 4. As shown in Fig. 3, in the battery module 4, a plurality of secondary batteries 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 may be fixed by fasteners.

[0199] Optionally, the battery module 4 may further include a housing having an accommodating space, and the plurality of secondary batteries 5 are accommodated in this accommodating space.

[0200] In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0201] 4 and 5 are schematic diagrams of an example battery pack 1. As shown in FIGS. 4 and 5, 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 covers the lower housing 3 and is used to form a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0202]

[0010] An embodiment of the present application further provides a power consuming device, the power consuming device including 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 for the power consuming device or as an energy storage unit for the power consuming device. The power consuming device may be, but is not limited to, a mobile device (e.g., a mobile phone, a tablet PC, a laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

[0203] The power consumption device may select a secondary battery, a battery module, or a battery pack according to its usage needs.

[0204] 6 is a schematic diagram of an example power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, that may employ a battery pack or battery module to meet the high power and high energy density demands of the power consuming device.

[0205] Other examples of power consuming devices include mobile phones, tablet computers, notebook computers, etc. These power consuming devices generally require a thin design and can employ secondary batteries as their power source.

[0206] Example The following examples will more specifically describe the contents disclosed in this application, and these examples are for illustrative purposes only, as various modifications and variations within the scope of the contents disclosed in this application will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are by weight, 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.

[0207] The carbon-based materials of Comparative Examples 1 and 3 are both primary particles, and may be commercially available products, or may be produced by crushing petroleum coke, shaping the crushed particles, and then graphitizing the crushed particles at a temperature ranging from 2800°C to 3200°C, followed by sieving to obtain the carbon-based material.

[0208] In the following examples and comparative example 2, the carbonaceous material may be a commercially available product, or may be produced by crushing petroleum coke, shaping it, mixing it with adhesive pitch, granulating it, and then graphitizing it at a temperature between 2800°C and 3200°C, and then sieving it to obtain the carbonaceous material. The ratio of the number of primary particles to secondary particles can be adjusted by adjusting the production process parameters (e.g., the shaping process, the granulation process, the type and amount of pitch, etc.).

[0209] In the following examples and comparative examples, the carbon coating layer on the surface of the carbon-based material may be formed by mixing the graphitized material with petroleum pitch and then subjecting it to a carbonization treatment.

[0210] The silicon-based materials of Comparative Examples 1 and 2 are both primary particles, and may be commercially available.

[0211] In the following Examples and Comparative Example 3, the secondary particles of silicon-based material may be commercially available, or may be produced by mixing primary particles of silicon-based material with adhesive pitch and then heat-treating. The ratio of the number of secondary particles is adjusted by adjusting production parameters (e.g., granulation process, type and amount of pitch added, etc.). The ratio of the number of primary particles to secondary particles can also be adjusted by adjusting the mixing ratio of the primary particles of silicon-based material (which may be commercially available) and the secondary particles of silicon-based material (which may be commercially available).

[0212] 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.

[0213] The secondary batteries of Examples 1-22 and Comparative Examples 1-3 were all manufactured according to the following method.

[0214] The negative electrode active material (a mixture of carbonaceous and siliconaceous materials; see Table 1 for details), conductive agent carbon black (Super P), carbon nanotubes (CNTs), adhesive styrene butadiene rubber, and thickener sodium carboxymethyl cellulose were mixed with an appropriate amount of solvent deionized water in a weight ratio of 96.2:0.7:0.1:1.8:1.2, and stirred thoroughly to form a negative electrode slurry. The negative electrode slurry was applied to both surfaces of a negative electrode current collector copper foil, dried, and cold-pressed to obtain a negative electrode plate. The porosity on one side of the negative electrode film layer was 25%, and the compaction density was 1.65 g / cm. 3 and the surface density is 9 mg / cm 2 The sum of the ratio of the number of secondary particles and the ratio of the number of primary particles in the 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 silicon-based material is 100%. Therefore, the ratio of the number of secondary particles or the ratio of the number of primary particles can be calculated from the ratio of the number of primary particles or the ratio of the number of secondary particles in Table 1.

[0215] LiNi 0.8 Co0.1 Mn 0.1 O2 (NCM811), conductive agent Super P, and adhesive polyvinylidene fluoride were mixed in a weight ratio of 96.5:1.5:2, and an appropriate amount of NMP solvent was added and stirred uniformly to obtain a positive electrode slurry. The positive electrode slurry was then applied to both surfaces of a positive electrode current collector aluminum foil, dried, and cold-pressed to obtain a positive electrode plate.

[0216] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and LiPF6 was dissolved in the organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L.

[0217] The PP / PE composite film is used as a separator, which is arranged in order with the positive and negative electrode plates prepared above. The separator is positioned in the center between the positive and negative electrode plates to perform isolation, and then wound up to obtain an electrode assembly. The electrode assembly is placed in an outer casing, dried, and then an electrolyte is injected. After vacuum packaging, standing, chemical formation, aging, and other processes, a secondary battery is obtained.

[0218] Performance Test (1) Secondary battery rate performance test At 25°C, the secondary battery fabricated above was discharged at a constant current of 1C to 2.8V. It was then charged at a constant current of 1C to 4.3V, followed by constant voltage charging until the current reached 0.05C, at which point the secondary battery was fully charged. After allowing the fully charged secondary battery to stand for 5 minutes, it was discharged at a constant current of 0.33C and 3C to 2.8V, and the discharge capacities of the secondary battery at 0.33C and 3C rates were recorded, respectively. The rate performance of the secondary battery was characterized by the ratio of the discharge capacity at 3C to the discharge capacity at 0.33C.

[0219] (2) DC impedance test of secondary batteries At 25°C, the secondary battery prepared above is charged at a constant current of 1C up to 4.3V, then charged at a constant voltage until the current reaches 0.05C, and then discharged at a constant current of 0.5C for 30 minutes to adjust the secondary battery to 50% SOC. The voltage of the secondary battery at this time is denoted as U1. The secondary battery is then discharged at 3C for 30 seconds, and the voltage of the secondary battery after discharge is denoted as U2, the discharge current is denoted as I1, and the DC impedance (DCR) of the secondary battery = (U1-U2) / I1.

[0220] (3) Cycle performance test of secondary batteries The secondary battery thus fabricated was charged at a constant current of 1 C to 4.3 V at 45°C, then charged at a constant voltage of 0.05 C until the current reached 0.05 C. After allowing to stand for 5 minutes, the secondary battery was discharged at a constant current of 1 C to 2.8 V, and the discharge capacity at this time was recorded, i.e., the first-cycle discharge capacity. The secondary battery was subjected to a cycle charge-discharge test according to the above method, and the discharge capacity after each cycle was recorded. The capacity retention (%) after 300 cycles of the secondary battery at 45°C was calculated as follows: discharge capacity after 300 cycles / discharge capacity at first cycle × 100%.

[0221] As can be seen from the test results in Table 1, when both the carbon-based material and the silicon-based material contain secondary particles formed by aggregation of primary particles, the secondary battery can achieve both low DC impedance and good rate performance and high-temperature cycle performance.

[0222] As can be further seen from a summary of the test results in Table 1, further adjusting the ratio of the number of secondary particles in the carbon-based material and / or silicon-based material to within an appropriate range contributes to achieving a better balance between the rate performance and high-temperature cycle performance of the secondary battery.

[0223] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any embodiment that has substantially the same configuration as the technical idea and achieves the same effects within the scope of the technical solution of the present application is included within the technical scope of the present application. In addition, various modifications that a person skilled in the art can make to the embodiments and other methods that are constructed by combining some of the components of the embodiments are also included within the scope of the present application, as long as they do not deviate from the spirit of the present application.

[0224] [Table 1] JPEG2025525853000003.jpg252159JPEG2025525853000004.jpg252160JPEG2025525853000005.jpg25268 [Explanation of symbols]

[0225] 1: battery pack, 2: upper housing, 3: lower housing, 4: battery module, 5: secondary battery, 51: case, 52: electrode assembly, 53: cover plate.

Claims

1. A secondary battery comprising: a negative electrode plate; the negative electrode plate comprising: a negative electrode current collector; and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and comprising a negative electrode active material; the negative electrode active material comprising a carbon-based material and a silicon-based material; the carbon-based material comprising secondary particles formed by agglomeration of primary particles; and the silicon-based material comprising secondary particles formed by agglomeration of primary particles.

2. The secondary battery according to claim 1 , wherein the volume distribution particle size Dv50 of the carbon-based material is larger than the volume distribution particle size Dv50 of the silicon-based material.

3. The secondary battery according to claim 1 , wherein the ratio of the number of the secondary particles in the carbon-based material is greater than the ratio of the number of the secondary particles in the silicon-based material.

4. the number fraction of the secondary particles in the carbon-based material is ≧70%, optionally 75%-90%; and / or The secondary battery according to any one of claims 1 to 3, wherein the number ratio of the secondary particles in the silicon-based material is ≧55%, and optionally 60%-85%.

5. 5. The secondary battery according to claim 1, wherein the porosity of the silicon-based material of the secondary particles is ≧4%, and optionally 5%-20%.

6. 6. The secondary battery according to claim 1, wherein the carbon-based material has a volume distribution particle size Dv50 of 12-18 μm, and optionally 13-17 μm.

7. The carbon-based material may be any of the following (1) to (8): (1) the volume distribution particle size Dv90 of the carbon-based material is 20-26 μm, and optionally 21-25 μm; (2) The carbon-based material satisfies the condition (Dv90-Dv10) / Dv50 is 0.6-1.5, and optionally 0.9-1.3; (3) The specific surface area of the carbon-based material is 1.5-3.5 m ２ / g, and optionally 1.7-2.7m ２ / g, and (4) The powder compaction density of the carbon-based material at 20,000 N is 1.65-1.85 g / cm ３ and optionally 1.70-1.80 g / cm ３ And, (5) The tap density of the carbon-based material is 0.9-1.2 g / cm ３ and optionally 0.9-1.1 g / cm ３ And, (6) the degree of graphitization of the carbon-based material is ≧92%, optionally 93%-94%; (7) the gram capacity of the carbon-based material is ≧354 mAh / g, optionally 355-360 mAh / g; (8) The powder OI value of the carbon-based material satisfies at least one of the following: 2-10, and optionally 3-6; The secondary battery according to claim 1 .

8. The silicon-based material includes the following (1) to (7): (1) the volume distribution particle size Dv50 of the silicon-based material is 8-15 μm, and optionally 10-13 μm; (2) the volume distribution particle size Dv90 of the silicon-based material is 15-25 μm, optionally 16-24 μm; (3) The silicon-based material satisfies (Dv90-Dv10) / Dv50 of 0.7-1.5, and optionally 0.9-1.3; (4) The specific surface area of the silicon-based material is 0.7-2.0 m ２ / g, and optionally 0.8-1.6 m ２ / g, and (5) The powder compaction density of the silicon-based material at 50,000 N is 1.0-1.7 g / cm ３ and optionally 1.2-1.6 g / cm ３ And, (6) The tap density of the silicon-based material is 1.0-1.5 g / cm ３ and optionally 1.1-1.4 g / cm ３ And, (7) The powder resistivity of the silicon-based material at 4 MPa satisfies at least one of the following: ≦15 Ω cm, and optionally 0.5-12 Ω cm. The secondary battery according to claim 1 .

9. The secondary battery according to claim 1 , wherein the carbon-based material of the secondary particles includes artificial graphite.

10. The secondary battery according to claim 1 , wherein the silicon-based material includes one or more of elemental silicon, silicon oxide, silicon carbon material, and silicon alloy material.

11. The silicon-based material is (1) primary particles of an alkali metal-free and alkaline earth metal-free silicon-oxygen material; (2) primary particles of a silicon-oxygen material containing an alkali metal or alkaline earth metal; (3) primary particles of a silicon carbon material; (4) primary particles of simple silicon; (5) The secondary particles are formed by agglomeration of at least one of the primary particles of the silicon alloy and the primary particles of the silicon alloy. The secondary battery according to claim 1 .

12. 12. The secondary battery according to claim 1, wherein a carbon coating layer is provided on a surface of the carbon-based material or the silicon-based material, and optionally, both the surface of the carbon-based material and the surface of the silicon-based material have a carbon coating layer.

13. The secondary battery according to claim 1 , wherein a surface of the carbon-based material has a carbon coating layer, and the carbon coating layer contains hard carbon.

14. 14. The secondary battery according to claim 1, wherein the carbon-based material further includes primary particles, and optionally, a ratio of the number of the secondary particles in the carbon-based material is greater than a ratio of the number of the primary particles in the carbon-based material.

15. The secondary battery according to claim 1 , wherein the carbon-based material further includes primary particles, and the primary particles of the carbon-based material include at least one of artificial graphite and natural graphite.

16. 16. The secondary battery according to claim 1, wherein the silicon-based material includes primary particles, and optionally, a number ratio of the secondary particles in the silicon-based material is greater than a number ratio of the primary particles in the silicon-based material.

17. 17. The secondary battery according to claim 1, wherein the mass ratio of the silicon-based material in the negative electrode active material is ≦50%, and optionally 2% to 40%.

18. The negative electrode active material comprises the following (1) to (3): (1) the negative electrode active material has a volume distribution particle size Dv50 of 10-17.5 μm, and optionally 12-17 μm; (2) the negative electrode active material has a volume distribution particle size Dv90 of 18-25.5 μm, and optionally 19-24.5 μm; (3) The negative electrode active material satisfies at least one of the following: (Dv90-Dv10) / Dv50 is 0.65-1.5, and optionally 0.9-1.3; The secondary battery according to any one of claims 1 to 17.

19. The negative electrode film layer comprises the following (1) to (3): (1) the porosity of the negative electrode film layer is ≧15%, and optionally 18%-50%; (2) The compaction density of the negative electrode film layer is ≦1.75 g / cm ３ and optionally 1.30-1.60 g / cm ３ And, (3) The surface density of the negative electrode film layer is ≦10.4 mg / cm ２ Yes, optionally 5-9 mg / cm ２ and The secondary battery according to any one of claims 1 to 18.

20. The secondary battery includes a positive electrode plate, the positive electrode plate includes a positive electrode active material, and the positive electrode active material has a general formula of Li ａ Ni ｂ Co ｃ M ｄ M' ｅ O ｆ A ｇ and m is a number from 0.8≦a≦1.2, 0.6≦b<1, 0<c<1, 0<d<1, 0≦e≦0.1, 1≦f≦2, and 0≦g≦1; M comprises Mn and / or Al; M′ comprises one or more of Zr, Mn, Al, Zn, Cu, Cr, Mg, Fe, V, Ti, and B; and A comprises one or more of N, F, S, and Cl, and optionally 0.65≦b<1.

21. 21. A power consuming device comprising a secondary battery according to any one of claims 1 to 20.

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