Secondary batteries and electrical devices

Abstract

A secondary battery including a negative electrode piece, the negative electrode piece including a negative electrode current collector and a negative electrode film layer having a first surface adjacent to the negative electrode current collector and a second surface opposite to the first surface, wherein the thickness of the negative electrode film layer is denoted as H, a region of the negative electrode film layer within a thickness range of 0.3H from the first surface is denoted as a first region of the negative electrode film layer, and a region of the negative electrode film layer within a thickness range of 0.3H from the second surface is denoted as a second region of the negative electrode film layer, the first region includes a first active material including a silicon-oxygen-based material, and the second region includes a second active material including a silicon-carbon composite material.

Description

[Technical Field]

[0001] The present application relates to the field of battery technology, and in particular to secondary batteries and electrical devices. [Background technology]

[0002] In recent years, as the application range of secondary batteries becomes wider and wider, secondary batteries are widely used in energy storage power supply systems such as hydroelectric power, thermal power, wind power and solar power plants, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment and aerospace.

[0003] Silicon-based materials are considered as potential negative electrode active materials, but they have the problem of volume expansion during use, which affects the cycle performance of the battery. Summary of the Invention

[0004] In view of the above problems, the present application provides a new type of negative electrode piece, a secondary battery and an electric device, which are described below.

[0005] In a first aspect, the present application provides a secondary battery including a negative electrode piece, wherein the negative electrode piece includes a negative electrode current collector and a negative electrode film layer having a first surface adjacent to the negative electrode current collector and a second surface disposed opposite to the first surface, wherein the thickness of the negative electrode film layer is denoted as H, a region of the negative electrode film layer within a thickness range of 0.3H from the first surface is denoted as a first region of the negative electrode film layer, and a region of the negative electrode film layer within a thickness range of 0.3H from the second surface is denoted as a second region of the negative electrode film layer; the first region comprises a first active material and the second region comprises a second active material; The first active material comprises a silicon-oxygen based material, and the second active material comprises a silicon-carbon composite material.

[0006] Compared to silicon carbon composites, silicon oxygen-based materials have a relatively high energy density. Compared to silicon oxygen-based materials, silicon carbon composites have relatively good structural stability, relatively good electrolyte interfacial properties, and relatively good cycle performance. When the first region of the negative electrode film layer contains a silicon oxygen-based material and the second region contains a silicon carbon composite, the advantages of the two materials can be fully utilized while complementing each other's shortcomings, thereby further improving the cycle performance and fast charging performance of the secondary battery. Without being bound by theory, the silicon oxygen-based material located in the first region is advantageous for increasing the bonding density of the electrode pieces, while the silicon carbon composite located in the second region can fully contact the electrolyte, maintaining good structural stability during long cycles and improving the battery's cycle performance.

[0007] In some embodiments, the mass ratio of the silicon-oxygen-based material in the first active material is denoted as A1, and the mass ratio of the silicon-carbon composite material in the second active material is denoted as A2. A2 / A1≦2, and optionally 0.2≦A2 / A1≦0.8. Within the above ranges, the silicon-oxygen-based material and the silicon-carbon composite material exhibit a further enhanced synergistic effect. Based on this configuration, the secondary battery exhibits further improved cycle performance and / or fast charging performance.

[0008] In some embodiments, the mass proportion of the silicon-oxygen-based material in the first active material is 30 wt% or less, optionally 10 wt% to 25 wt%, and / or the mass proportion of the silicon-carbon composite material in the second active material is 25 wt% or less, optionally 5 wt% to 20 wt%. Within these ranges, the silicon-oxygen-based material and the silicon-carbon composite material exhibit a further enhanced synergistic effect. Within these ranges, the silicon-oxygen-based material and the silicon-carbon composite material exhibit a further enhanced synergistic effect. Based on this embodiment, the secondary battery exhibits further improved cycle performance and / or fast charging performance.

[0009] In some embodiments, the volume average particle size Dv50 of the silicon carbon composite is larger than the volume average particle size Dv50 of the silicon oxygen-based material. By making the volume average particle size Dv50 of the silicon carbon composite larger than the volume average particle size Dv50 of the silicon oxygen-based material, a good difference in the compression density can be achieved between the second region and the first region of the negative electrode film layer, which improves the consistency of the porosity and ion concentration distribution in the thickness direction of the negative electrode film layer, which is beneficial to improving the electrolyte penetration and retention properties of the negative electrode film layer and ion transport, and furthermore, the secondary battery can have better cycle performance and / or fast charging performance.

[0010] In some embodiments, 3×10 of the silicon carbon composite material 4 The powder compaction density tested under a pressure of N is 3 x 10 for the silicon-oxygen based materials mentioned above. 4 The pressed density is smaller than the powder density tested under a pressure of N. By making the pressed density of the silicon carbon composite material larger than that of the silicon oxygen-based material, the second region and the first region of the negative electrode film layer can have a good pore structure, which can better match the ion concentration distribution in the thickness direction of the negative electrode film layer, improve the electrolyte infiltration and retention properties of the negative electrode film layer, and be more favorable for ion transport, and further enable the secondary battery to have better cycle performance and / or fast charging performance.

[0011] In some embodiments, the tap density of the silicon carbon composite is smaller than that of the silicon oxygen-based material. By making the tap density of the silicon carbon composite smaller than that of the silicon oxygen-based material, the pore structure in the thickness direction of the negative electrode film layer can be optimized, the electrolyte permeation and retention properties of the negative electrode film layer can be improved, and ion transport can be more favorable. Furthermore, the secondary battery can have better cycle performance and / or fast charging performance.

[0012] In some embodiments, the specific surface area of ​​the silicon carbon composite material is larger than that of the silicon oxygen-based material, which is advantageous for rapidly transferring ions to the first region of the negative electrode piece while reducing side reactions, thereby enabling the secondary battery to have better cycle performance and / or fast charging performance.

[0013] In some embodiments, the powder resistivity of the silicon carbon composite material when tested under a pressure of 16 MPa is greater than the powder resistivity of the silicon oxygen-based material when tested under a pressure of 16 MPa. By making the powder resistivity of the silicon carbon composite material greater than that of the silicon oxygen-based material, it is advantageous to improve the electronic conductivity of the negative electrode film layer, thereby further improving the fast charging performance of the secondary battery.

[0014] In some embodiments, the silicon carbon composite material includes a carbon matrix and a silicon-based material disposed in the carbon matrix, and based on this configuration, the secondary battery exhibits further improved cycle performance.

[0015] In some embodiments, the silicon carbon composite has an initial coulombic efficiency of ≧90 wt%, and optionally 91 wt% to 94 wt%. Based on this configuration, the secondary battery exhibits further improved initial coulombic efficiency.

[0016] In some embodiments, the silicon carbon composite has a volume particle size Dv50 of 3 μm to 15 μm, and optionally 5 μm to 12 μm. This particle size range is advantageous for improving the ion and electron transport performance of the material, thereby further improving the fast charging performance of the secondary battery, and also for reducing the specific surface area of ​​the material and reducing side reactions, thereby further improving the cycle performance of the secondary battery.

[0017] In some embodiments, the silicon carbon composite material has a volume distribution particle size Dv90 of ≦60 μm, preferably 20 μm to 40 μm. When the volume distribution particle size Dv90 of the material is within this range, the particle alignment is relatively good, which is advantageous for improving the ion and electron transport performance, thereby further improving the fast charging performance of the secondary battery.

[0018] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the silicon carbon composite material is 1.0 to 3.0, and preferably 1.0 to 2.0. When the (Dv90-Dv10) / Dv50 of the material is within this range, the particle packing performance is relatively good, which is advantageous for improving the compression 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 a suitable pore structure, which is advantageous for further improving the fast charging performance of the secondary battery.

[0019] In some embodiments, the silicon carbon composite has a BET specific surface area of ​​20 m 2 / g or less, and selectively 1m 2 / g~10m 2 When the specific surface area of ​​the material is within the above range, it is advantageous to reduce side reactions, so that the secondary battery can have better cycle performance.

[0020] In some embodiments, the powder resistivity of the silicon carbon composite material under a pressure of 16 MPa is ≦300 Ω·cm, and optionally ≦50 Ω·cm, which is advantageous for improving the electronic conductivity of the negative electrode film layer and thereby further improving the fast charging performance of the secondary battery.

[0021] In some embodiments, the silicon carbon composite has a tap density of 0.8 g / cm 3 ~1.0g / cm 3 and selectively 0.9 g / cm 3 ~1.0g / cm 3When the tap density is within the above range, the compression density of the negative electrode film layer can be improved, thereby further improving the energy density of the secondary battery, and the negative electrode film layer has an appropriate pore structure, which can improve the ion and electron transport performance, improve the electrolyte infiltration and retention properties of the negative electrode film layer, and further improve the fast charging performance and / or cycle performance of the secondary battery.

[0022] In some embodiments, the silicon content of the silicon carbon composite is 30 wt% or more, preferably 40 wt%-60 wt%, so that the silicon carbon composite exhibits satisfactory electrochemical performance.

[0023] In some embodiments, the carbon content of the silicon carbon composite is 40 wt% or more, preferably 45 wt% to 60 wt%, so that the silicon carbon composite exhibits satisfactory electrochemical performance.

[0024] In some embodiments, the oxygen content in the silicon carbon composite is 10 wt% or less, and preferably 1 wt% to 5 wt%, so that the silicon carbon composite exhibits satisfactory electrochemical performance.

[0025] In some embodiments, the silicon-oxygen-based material comprises an alkali metal-containing or alkaline earth metal-containing silicate, and based on this configuration, the secondary battery exhibits further improved first coulombic efficiency performance.

[0026] In some embodiments, the silicon-oxygen-based material includes an alkali metal-containing silicate, and the silicon-oxygen-based material satisfies the following: in an XRD diffraction pattern, the half-width of a diffraction peak corresponding to the alkali metal-containing silicate is 0.5° to 2.0°, and / or the crystal grain size of the silicate corresponding to the alkali metal-containing silicate is 4 nm to 17 nm. Based on this aspect, the secondary battery exhibits further improved initial coulombic efficiency.

[0027] In some embodiments, the silicon-oxygen-based material includes an alkaline earth metal-containing silicate, and the silicon-oxygen-based material satisfies the following: in an XRD diffraction pattern, the half-width of a diffraction peak corresponding to the alkaline earth metal-containing silicate is 0.3° to 0.6°, and / or the crystal grain size of the silicate corresponding to the alkaline earth metal-containing silicate is 12 nm to 20 nm. Based on this aspect, the secondary battery exhibits further improved first coulombic efficiency.

[0028] In some embodiments, the silicon-oxygen-based material has a volume particle size Dv50 of 3 μm to 20 μm, and optionally 5 μm to 15 μm. This particle size range is advantageous for improving the ion and electron transport performance of the material, thereby further improving the rapid charging performance of the secondary battery, and also for reducing the specific surface area of ​​the material and reducing side reactions, thereby further improving the cycle performance of the secondary battery.

[0029] In some embodiments, the silicon-oxygen-based material has a volume distribution particle size Dv90 of ≦60 μm, preferably 10 μm to 25 μm. When the volume distribution particle size Dv90 of the material is within this range, the particle alignment is relatively good, which is advantageous for improving the transport performance of ions and electrons, thereby further improving the rapid charging performance of the secondary battery.

[0030] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the silicon-oxygen-based material is 1.0 to 2, preferably 1.0 to 1.5. When the (Dv90-Dv10) / Dv50 of the material is within the above range, the particle packing performance is relatively good, which is advantageous for improving the compression 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 a suitable pore structure, which is advantageous for further improving the fast charging performance of the secondary battery.

[0031] In some embodiments, the silicon-oxygen based material has a BET specific surface area of ​​1 m 2 / g~6m 2 / g, and selectively 1m 2 / g~5m 2 When the specific surface area of ​​the material is within the above range, it is advantageous to reduce side reactions, so that the secondary battery can have better cycle performance.

[0032] In some embodiments, the silicon-oxygen based material has a tap density of 1.05 g / cm 3 ~1.25g / cm 3 and selectively 1.1 g / cm 3 ~1.2g / cm 3 When the tap density is within the above range, the compression density of the negative electrode film layer can be improved, thereby further improving the energy density of the secondary battery, and the negative electrode film layer has an appropriate pore structure, which can improve the ion and electron transport performance, improve the electrolyte infiltration and retention properties of the negative electrode film layer, and further improve the fast charging performance and / or cycle performance of the secondary battery.

[0033] In some embodiments, the silicon content of the silicon-oxygen-based material is 40 wt% or more, and preferably 45 wt%-65 wt%, so that the silicon-oxygen-based material exhibits satisfactory electrochemical performance.

[0034] In some embodiments, the content of oxygen element in the silicon-oxygen based material is 30 wt% or more, and preferably 30 wt%-50 wt%, so that the silicon-oxygen based material exhibits satisfactory electrochemical performance.

[0035] In some embodiments, the carbon content in the silicon-oxygen-based material is less than 8 wt%, and preferably 2 wt%-5 wt%, so that the silicon-oxygen-based material exhibits satisfactory electrochemical performance.

[0036] In some embodiments, the first active material and / or the second active material further comprises a carbon-based material, and optionally the carbon-based material comprises at least one of artificial graphite, natural graphite, soft carbon, and hard carbon. Based on this configuration, the secondary battery exhibits further improved cycle performance.

[0037] In some embodiments, the first active material comprises a first carbonaceous material, the second active material comprises a second carbonaceous material, the first carbonaceous material comprises primary particles, and optionally, the number proportion of the primary particles in the first carbonaceous material is ≧70%. Based on this configuration, the secondary battery further exhibits improved cycle performance.

[0038] In some embodiments, the first active material comprises a first carbonaceous material, the second active material comprises a second carbonaceous material, and the second carbonaceous material comprises secondary particles, optionally with a quantitative proportion of the secondary particles in the second carbonaceous material of ≥ 70%. The specific surface area of ​​the primary particles is typically relatively small, which can reduce side reactions and improve the cycle performance of the secondary battery. The capacity of the primary particles is also relatively high, which can improve the energy density of the secondary battery.

[0039] The terms primary particles and secondary particles both have the meanings known in the art. Primary particles refer to particles in a non-aggregated state. Secondary particles refer to particles in an aggregated state formed by the aggregation of two or more primary particles. Primary particles and secondary particles can be distinguished by using scanning electron microscope (SEM) images.

[0040] In some embodiments, the first active material comprises a first carbonaceous material, and the second active material comprises a second carbonaceous material, wherein the volume average particle size Dv50 of the first carbonaceous material is smaller than the volume average particle size Dv50 of the second carbonaceous material. This allows the second region and the first region of the negative electrode layer to have a good difference in compaction density, which improves the consistency of the porosity and ion concentration distribution in the thickness direction of the negative electrode layer, favors the improvement of the electrolyte penetration and retention properties of the negative electrode layer, favors ion transport, and further allows the secondary battery to have better cycle performance and / or fast charging performance.

[0041] In some embodiments, the first active material comprises a first carbonaceous material, the second active material comprises a second carbonaceous material, and the tap density of the first carbonaceous material is greater than the tap density of the second carbonaceous material. This can improve the compression density of the negative electrode film layer, thereby further improving the energy density of the secondary battery. It is also advantageous for the negative electrode film layer to have a suitable pore structure, which can improve the ion and electron transport performance, improve the electrolyte infiltration and retention properties of the negative electrode film layer, and further improve the fast charging performance and / or cycle performance of the secondary battery.

[0042] In some embodiments, the first active material comprises a first carbonaceous material, the second active material comprises a second carbonaceous material, and the first carbonaceous material has a greater pressed density than the second carbonaceous material. This allows the second and first regions of the negative electrode layer to have a good pore structure, which can better match the ion concentration distribution in the thickness direction of the negative electrode layer, improve the electrolyte wetting and retention properties of the negative electrode layer, and facilitate ion transport. Furthermore, the secondary battery can have better cycle performance and / or fast charging performance.

[0043] In some embodiments, the first carbon-based material has a volume particle size Dv50 of 5 μm to 20 μm, and optionally 8 μm to 15 μm. This particle size range is advantageous for improving the ion and electron transport performance of the material, thereby further improving the rapid charging performance of the secondary battery, and also for reducing the specific surface area of ​​the material and reducing side reactions, thereby further improving the cycle performance of the secondary battery.

[0044] In some embodiments, the volume distribution particle size Dv90 of the first carbon-based material is ≦50 μm, and optionally 25 μm to 40 μm. When the volume distribution particle size Dv90 of the material is within this range, the particle alignment is relatively good, which is advantageous for improving the ion and electron transport performance, and thereby further improving the rapid charging performance of the secondary battery.

[0045] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the first carbon-based material is 1.0 to 2.5, preferably 1.0 to 1.8. When the (Dv90-Dv10) / Dv50 of the material is within this range, the particle packing performance is relatively good, which is advantageous for improving the compression density of the negative electrode film layer, thereby further improving the energy density of the secondary battery, and is also advantageous for the negative electrode film layer to have an appropriate pore structure, which is advantageous for further improving the fast charging performance of the secondary battery.

[0046] In some embodiments, the first carbon-based material has a BET specific surface area of ​​0.5 m 2 / g~4m 2 / g, and selectively 1m 2 / g~3m 2 When the specific surface area of ​​the material is within the above range, it is advantageous to reduce side reactions, so that the secondary battery can have better cycle performance.

[0047] In some embodiments, the tap density of the first carbon-based material is 1.0 g / cm 3 ~1.25g / cm 3 and selectively 1.1 g / cm 3 ~1.2g / cm 3 When the tap density is within the above range, the compression density of the negative electrode film layer can be improved, thereby further improving the energy density of the secondary battery, and the negative electrode film layer has an appropriate pore structure, which can improve the ion and electron transport performance, improve the electrolyte infiltration and retention properties of the negative electrode film layer, and further improve the fast charging performance and / or cycle performance of the secondary battery.

[0048] In some embodiments, the first carbon-based material has a powder compaction density of 1.6 g / cm when tested under a pressure of 30,000 N. 3 ~1.9g / cm 3 and selectively 1.65 g / cm 3 ~1.8g / cm 3 Based on this, the secondary battery has an improved energy density.

[0049] In some embodiments, the second carbon-based material has a volume particle size Dv50 of 8 μm to 25 μm, and optionally 12 μm to 18 μm. This particle size range is advantageous for improving the ion and electron transport performance of the material, thereby further improving the rapid charging performance of the secondary battery, and also for reducing the specific surface area of ​​the material and reducing side reactions, thereby further improving the cycle performance of the secondary battery.

[0050] In some embodiments, the volume distribution particle size Dv90 of the second carbon-based material is ≦60 μm, and optionally 35 μm to 50 μm. When the volume distribution particle size Dv90 of the material is within this range, the particle alignment is relatively good, which is advantageous for improving the transport performance of ions and electrons, and thereby further improving the rapid charging performance of the secondary battery.

[0051] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the second carbon-based material is 1.0 to 2.0, preferably 1.0 to 1.5. When the (Dv90-Dv10) / Dv50 of the material is within this range, the particle packing performance is relatively good, which is advantageous for improving the compression density of the negative electrode film layer, thereby further improving the energy density of the secondary battery, and is also advantageous for the negative electrode film layer to have an appropriate pore structure, which is advantageous for further improving the fast charging performance of the secondary battery.

[0052] In some embodiments, the second carbon-based material has a BET specific surface area of ​​1 m 2 / g~5m 2 / g, and selectively 1m 2 / g~3m 2 When the specific surface area of ​​the material is within the above range, it is advantageous to reduce side reactions, so that the secondary battery can have better cycle performance.

[0053] In some embodiments, the powder resistivity of the second carbon-based material under a pressure of 16 MPa is ≦5×10 1 Ω·cm, and selectively ≦2×10- 1 When the powder resistivity is within the above range, the electronic conductivity of the negative electrode film layer can be improved, and the rapid charging performance of the secondary battery can be further improved.

[0054] In some embodiments, the tap density of the second carbon-based material is 0.9 g / cm 3 ~1.2g / cm3 and selectively 1.0 g / cm 3 ~1.1g / cm 3 When the tap density is within the above range, the compression density of the negative electrode film layer can be improved, thereby further improving the energy density of the secondary battery, and the negative electrode film layer has an appropriate pore structure, which can improve the ion and electron transport performance, improve the electrolyte infiltration and retention properties of the negative electrode film layer, and further improve the fast charging performance and / or cycle performance of the secondary battery.

[0055] The powder compact density of the second carbon-based material tested under a pressure of 30,000 N was 1.5 g / cm 3 ~1.75g / cm 3 and selectively 1.55 g / cm 3 ~1.7g / cm 3 Based on this, the secondary battery has an improved energy density.

[0056] In a second aspect, the present application provides an electrical device including any one of the secondary batteries described above.

[0057] Beneficial Effects: One or more embodiments of the present application include one or more of the following.

[0058] (1) The secondary battery has improved fast charging performance, (2) The secondary battery has improved cycle performance. [Brief explanation of the drawings]

[0059] [Figure 1] 1A to 1C are cross-sectional schematic views of negative electrode pieces according to some embodiments of the present application. [Figure 2] 1A and 1B are a schematic view and an exploded view of a secondary battery according to an embodiment of the present application; [Figure 3] 1 is a schematic diagram of a battery module according to an embodiment of the present application; [Figure 4]1 is a schematic diagram of a battery pack according to an embodiment of the present application; [Figure 5] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application. [Figure 6] 1 is a schematic diagram of an electrical device that uses a secondary battery as a power source according to an embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0060] Hereinafter, embodiments specifically disclosing the present application's anode piece and its manufacturing method, cathode piece, anode piece, secondary battery, battery module, battery pack, and device will be described in detail with appropriate reference to the drawings. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and repeated description of substantially the same structure may be omitted. This is to avoid unnecessarily lengthening the following description and to facilitate understanding by those skilled in the art. Furthermore, 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 scope of the claims.

[0061] The "ranges" disclosed herein are defined by lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, with the selected lower and upper limits defining the boundaries of that particular range. Such defined ranges may be inclusive or exclusive of both endpoints and may be arbitrarily combined; i.e., any lower limit can be combined with any upper limit to form a single range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if the minimum range values ​​listed are 1 and 2, and the maximum range values ​​are 3, 4, and 5, then the ranges 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all contemplated. Unless otherwise specified, the numerical range "a to b" herein represents an abbreviation for any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 and 5" have already been listed in this specification, and "0 to 5" is simply an abbreviation for combinations of those numbers. Also, when a parameter is described as an integer ≧2, this is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0062] Unless otherwise specified, all embodiments and optional embodiments in the present application can be combined with each other to form a new technical solution.

[0063] Unless otherwise specified, all steps in the present application may be performed sequentially or randomly, but are preferably performed sequentially. For example, when the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, when the method described above may further include step (c), it means that step (c) can be added to the method in any order. For example, 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.

[0064] Unless otherwise specified, the terms "comprise" and "comprises" used in this application may be open or closed. For example, the terms "comprise" and "comprises" may further include or include other components not listed, or may include or include only the listed components.

[0065] 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, any of the following conditions satisfy the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or both A and B are true (or exist).

[0066] [Secondary battery] Secondary batteries, also called rechargeable batteries or storage batteries, refer to batteries that can be continuously used by activating the active materials by charging them after discharging.

[0067] Typically, a secondary battery contains positive and negative electrode pieces, a separator film, and an electrolyte. During the charge and discharge process, active ions (e.g., lithium ions) are repeatedly inserted and removed between the positive and negative electrode pieces. The separator film is placed between the positive and negative electrode pieces and primarily serves to prevent short circuits between the positive and negative electrodes while allowing the active ions to pass through. The electrolyte is placed between the positive and negative electrode pieces and primarily serves to conduct the active ions.

[0068] An example of a secondary battery is a lithium-ion battery. A lithium-ion battery primarily consists of a positive electrode, a negative electrode, a separator film, and an electrolyte. The positive and negative electrodes are separated by a separator film to prevent short circuits, and an electrolyte is infiltrated between them to ensure ionic conduction. During charging, Li+ ions are released from the positive electrode and inserted into the negative electrode through the electrolyte, penetrating the separator film and the electrolyte. This places the positive electrode in a high-potential lithium-deficient state, while the negative electrode in a low-potential lithium-rich state. During discharging, the reverse occurs: Li+ ions are released from the negative electrode and inserted into the positive electrode through the electrolyte, penetrating the separator film and the electrolyte, returning the positive electrode to a lithium-rich state. To maintain charge balance, the same number of electrons during charging and discharging are transferred via an external circuit and migrate with the Li+ ions between the positive and negative electrodes, causing oxidation and reduction reactions at the positive and negative electrodes, respectively. Lithium ions can reversibly move between the positive electrode and the negative electrode in the electrolyte, and both the positive electrode and the negative electrode are made of an insertion-type material that allows reversible insertion and desorption of lithium ions.

[0069] An example of a secondary battery is a sodium-ion battery. A sodium-ion battery mainly consists of a positive electrode, a negative electrode, a separator film, and an electrolyte. The positive and negative electrodes are separated by a separator film to prevent short circuits, and an electrolyte is infiltrated between them to ensure ionic conduction. During charging, Na+ ions are released from the positive electrode and inserted into the negative electrode through the electrolyte, penetrating the separator film and then into the negative electrode, creating a high-potential sodium-deficient state and a low-potential sodium-rich state for the negative electrode. During discharging, the reverse occurs: Na+ ions are released from the negative electrode and inserted into the positive electrode through the electrolyte, penetrating the separator film and then finally into the positive electrode, restoring the positive electrode to a sodium-rich state. To maintain charge balance, the same number of electrons are transferred via an external circuit and transported with Na+ between the positive and negative electrodes, causing oxidation and reduction reactions at the positive and negative electrodes, respectively. Sodium ions can reversibly move between the positive electrode and the negative electrode in the electrolyte, and both the positive electrode and the negative electrode are made of an insertion-type material that allows reversible insertion and desorption of sodium ions.

[0070] The present application provides a new type of secondary battery having a new type of negative electrode piece and having improved energy density and cycle performance.

[0071] 1A to 1C are schematic diagrams of an embodiment of a negative electrode piece of the secondary battery of the present application.

[0072] As shown in the figure, the present application provides a secondary battery including a negative electrode piece 10, wherein the negative electrode piece 10 includes a negative electrode current collector 101 and a negative electrode film layer 102 having a first surface 102b adjacent to the negative electrode current collector and a second surface 102a opposite to the first surface, the thickness of the negative electrode film layer 102 is denoted as H, a region within a thickness range of 0.3H from the first surface 102b of the negative electrode film layer is denoted as a first region 1021 of the negative electrode film layer, and a region within a thickness range of 0.3H from the second surface 102a of the negative electrode film layer is denoted as a second region 1022 of the negative electrode film layer, the first region 1021 comprises a first active material and the second region 1022 comprises a second active material; The first active material comprises a silicon-oxygen based material, and the second active material comprises a silicon-carbon composite material.

[0073] Compared with silicon carbon composites, silicon oxygen-based materials have a relatively high energy density. Compared with silicon carbon composites, silicon carbon composites have relatively good cycle performance and fast charging performance. When the first region of the negative electrode film layer contains a silicon oxygen-based material and the second region contains a silicon carbon composite, the advantages of the two materials can be fully utilized while complementing each other's shortcomings, thereby further improving the cycle performance and fast charging performance of the secondary battery. Without being bound by theory, the silicon oxygen-based material located in the first region is advantageous for improving the electrode sheet compression density and the battery's fast charging capability, while the silicon carbon composite located in the second region can fully contact the electrolyte, maintaining good structural stability during long cycles and improving the battery's cycle performance.

[0074] Compared with secondary batteries containing only pure silicon-oxygen-based materials, the secondary batteries of the present invention have better cycle performance. Compared with secondary batteries containing only silicon-carbon composite materials, the secondary batteries of the present invention have higher energy density. It should be emphasized that the positioning order of the silicon-oxygen-based material and the silicon-carbon composite is important. When the first region of the negative electrode film layer contains a silicon-oxygen-based material and the second region contains a silicon-carbon composite, the silicon-oxygen-based material and the silicon-carbon composite can exert a synergistic effect, exhibiting the advantages of each other and compensating for each other's shortcomings. When the positioning order of the silicon-oxygen-based material and the silicon-carbon composite is reversed, the synergistic effect cannot be exerted.

[0075] In some embodiments, the mass ratio of the silicon-oxygen-based material in the first active material is denoted as A1, and the mass ratio of the silicon-carbon composite material in the second active material is denoted as A2. A2 / A1≦2, and optionally 0.2≦A2 / A1≦0.8. Within the above ranges, the silicon-oxygen-based material and the silicon-carbon composite material exhibit a further enhanced synergistic effect. Based on this configuration, the secondary battery exhibits further improved cycle performance and / or fast charging performance.

[0076] In some embodiments, the value of A2 / A1 is 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, or a range consisting of any two of the above numbers. For example, 0.1-2.0, 0.1-1.8, 0.1-1.6, 0.1-1.4, 0.1-1.2, 0.1-1.0, 0.1-0.8, 0.1-0.6, 0.2-2.0, 0.2-1.8, 0.2-1.6, 0.2-1.4, 0.2-1.2, 0.2-1.0, 0.2-0.8, 0.2-0.6, 0.3-2.0, 0.3-1.8, 0.3-1.6, 0.3-1.4, 0.3-1.2, 0.3-1.0, 0.3-0.8, 0.3-0.6, 0.4-2.0, 0.4-1.8, 0.4-1.6, 0.4-1.4, 0.4-1.2, 0. 4 to 1.0, 0.4 to 0.8, 0.4 to 0.6, 0.5 to 2.0, 0.5 to 1.8, 0.5 to 1.6, 0.5 to 1.4, 0.5 to 1.2, 0.5 to 1.0, 0.5 to 0.8, 0.6 to 2.0, 0.6 to 1.8, 0.6 to 1.6, 0.6 to 1.4, 0.6 to 1.2, 0.6 to 1.0, 0.8 to 2.0, 0.8 to 1.8, 0.8 to 1.6, 0.8 to 1.4, 0.8 to 1.2, 1.0 to 2.0, 1.0 to 1.8, 1.0 to 1.6, 1.0 to 1.4, 1.1 to 2.0, 1.1 to 1.8, 1.1 to 1.6, 1.1 to 1.4.

[0077] In some embodiments, the mass fraction of the silicon-oxygen-based material in the first active material is 30 wt% or less, and optionally 10 wt% to 25 wt%.

[0078] In some embodiments, the mass proportion of the silicon carbon composite in the second active material is 25 wt% or less, and optionally 5 wt% to 20 wt%, within this range, the silicon oxygen-based material and the silicon carbon composite exhibit a further enhanced synergistic effect.

[0079] Within the above range, the silicon-oxygen-based material and the silicon-carbon composite material exhibit a further enhanced synergistic effect, and based on this configuration, the secondary battery exhibits further improved cycle performance and / or fast charging performance.

[0080] In some embodiments, the value of A1 is 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, or a range consisting of any two of the foregoing values. For example, it can be 1 wt% to 30 wt%, 5 wt% to 30 wt%, 10 wt% to 30 wt%, 15 wt% to 30 wt%, 20 wt% to 30 wt%, 25 wt% to 30 wt%, 1 wt% to 25 wt%, 5 wt% to 25 wt%, 10 wt% to 25 wt%, 15 wt% to 25 wt%, 20 wt% to 25 wt%, 1 wt% to 20 wt%, 5 wt% to 20 wt%, 10 wt% to 20 wt%, 15 wt% to 20 wt%, 1 wt% to 10 wt%, or 5 wt% to 10 wt%.

[0081] In some embodiments, the value of A2 is 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, or a range consisting of any two of the foregoing values. For example, it can be 1 wt% to 25 wt%, 5 wt% to 25 wt%, 10 wt% to 25 wt%, 15 wt% to 25 wt%, 20 wt% to 25 wt%, 1 wt% to 20 wt%, 5 wt% to 20 wt%, 10 wt% to 20 wt%, 15 wt% to 20 wt%, 1 wt% to 10 wt%, or 5 wt% to 10 wt%.

[0082] In some embodiments, the negative electrode pieces can be sampled using methods known in the art to analyze their structure. For example, a method for sampling the negative electrode pieces includes washing the negative electrode pieces with dimethyl carbonate (DMC) and then drying them, and then washing the negative electrode pieces with deionized water and then drying them. After ion-polishing the cross section of the negative electrode piece, the cross section is observed using a scanning electron microscope to determine the boundary between the first and second negative electrode films, and the thickness (H) of the first and second negative electrode films is measured and recorded. As shown in FIG. 1 , the powder in the second region 1022 is scraped from the side of the negative electrode piece 10 away from the current collector 101. The thickness change is monitored with a micrometer, and the scraping thickness is controlled to 0.3H so that all of the scraped powder is from the second region 1022. The negative electrode film is completely peeled off from the current collector with strong tape, and the powder in the first region 1021 is scraped off from the side of the negative electrode film that is closest to the current collector. The change in thickness is monitored with a micrometer, and the scraping thickness is controlled to 0.3H so that all the scraped powder comes from the first region 1021.

[0083] In some embodiments, the mass fraction A1 of the silicon-oxygen-based material in the first active material can be determined by a method known in the art. For example, the value of A1 can be obtained by testing the first active material at 800°C for 4 hours in air to obtain a silica material, and then calculating the molar mass of silicon in the material to back-calculate the silicon-oxygen content of the material. In some embodiments, the mass fraction of the silicon carbon composite material in the second active material is determined by a method known in the art and designated as A2. For example, the value of A2 can be obtained by testing the following method: inspecting an active material pole piece containing the second region to test the CP, selecting silicon carbon particles in a 3×3 μm region, measuring the silicon to carbon content ratio, sintering the second active material in air at 800°C for 4 hours to obtain a silica material, and calculating the molar mass of silicon in the material to back-calculate the silicon carbon content of the material; In some embodiments, the volume average particle size Dv50 of the silicon carbon composite is larger than the volume average particle size Dv50 of the silicon oxygen-based material. By making the volume average particle size Dv50 of the silicon carbon composite larger than the volume average particle size Dv50 of the silicon oxygen-based material, a good difference in the compression density can be achieved between the second region and the first region of the negative electrode film layer, which improves the consistency of the porosity and ion concentration distribution in the thickness direction of the negative electrode film layer, which is beneficial to improving the electrolyte penetration and retention properties of the negative electrode film layer and ion transport, and furthermore, the secondary battery can have better cycle performance and / or fast charging performance.

[0084] In some embodiments, the Dv10, Dv50, and Dv90 of the negative electrode active material have meanings known in the art and can be measured using methods known in the art, such as those described in standard GB / T19077-2016, using a laser particle size analyzer (e.g., Malvern Master Size 3000).

[0085] The physical definitions of Dv10, Dv50, and Dv90 are the particle sizes corresponding to the cumulative volume distribution percentages of the negative electrode active material reaching 10%, 50%, and 90%, respectively.

[0086] In some embodiments, 3×10 of the silicon carbon composite material 4 The powder compaction density tested under a pressure of N is 3 x 10 for the silicon-oxygen based materials mentioned above. 4 The pressed density is smaller than the powder density tested under a pressure of N. By making the pressed density of the silicon carbon composite material larger than that of the silicon oxygen-based material, the second region and the first region of the negative electrode film layer can have a good pore structure, which can better match the ion concentration distribution in the thickness direction of the negative electrode film layer, improve the electrolyte infiltration and retention properties of the negative electrode film layer, and be more favorable for ion transport, and further enable the secondary battery to have better cycle performance and / or fast charging performance.

[0087] In some embodiments, the powder compaction density of a material has a meaning known in the art and can be measured using equipment and methods known in the art. For example, see GB / T24533-2009 and can be measured using an electronic pressure tester (e.g., a UTM7305 type electronic pressure tester). In an exemplary test method, 1 g of sample powder is weighed out and measured to determine whether the powder compaction density has a base area of ​​1.327 cm. 2 The powder was placed in a mold, and the required pressure was applied. After holding the pressure for 30 seconds, the pressure was released and maintained for 10 seconds. The pressure was recorded and calculated to obtain the powder compaction density under the required pressure of the material.

[0088] In some embodiments, the tap density of the silicon carbon composite is smaller than that of the silicon oxygen-based material. By making the tap density of the silicon carbon composite smaller than that of the silicon oxygen-based material, the pore structure in the thickness direction of the negative electrode film layer can be optimized, the electrolyte permeation and retention properties of the negative electrode film layer can be improved, and ion transport can be more favorable. Furthermore, the secondary battery can have better cycle performance and / or fast charging performance.

[0089] In some embodiments, the tap density of a material 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 can be a 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 frequency of 5000 times, and a measuring cylinder of 25 mL.

[0090] In some embodiments, the specific surface area of ​​the silicon carbon composite material is larger than that of the silicon oxygen-based material, which is advantageous for rapidly transferring ions to the first region of the negative electrode piece while reducing side reactions, thereby enabling the secondary battery to have better cycle performance and / or fast charging performance.

[0091] In some embodiments, the specific surface area of ​​a material has a meaning known in the art and can be measured using methods known in the art, such as GB / T19587-2017, which is based on the nitrogen adsorption specific surface area analysis test method and can be calculated using the Brunauer Emmett Teller (BET) method, where the nitrogen adsorption specific surface area analysis test can be performed using a Tri-Star 3020 specific surface area pore size analyzer manufactured by Micromeritics, Inc., USA.

[0092] In some embodiments, the powder resistivity of the silicon carbon composite material when tested under a pressure of 16 MPa is greater than the powder resistivity of the silicon oxygen-based material when tested under a pressure of 16 MPa. By making the powder resistivity of the silicon carbon composite material greater than that of the silicon oxygen-based material, it is advantageous to improve the electronic conductivity of the negative electrode film layer, thereby further improving the fast charging performance of the secondary battery.

[0093] In some embodiments, the powder resistivity of a material is defined as being within the meaning known in the art and can be tested using equipment and methods known in the art. For example, a test is performed using a resistivity tester (e.g., a Suzhou Jingge Electronics Co., Ltd. ST2722 powder resistivity tester). During the test, 1 g of powder sample is taken, placed between the electrodes of the resistivity tester, and a constant pressure (e.g., 4 MPa) is applied using an electronic pressure machine and maintained for 15 to 25 seconds to obtain a sheet-like sample. The powder resistivity δ of the material is calculated according to the formula δ = (S × R) / h, where h is the height of the sheet-like sample in cm, R is the resistance in Ω, and S is the area of ​​the sheet-like sample in cm. 2 is.

[0094] In some embodiments, the silicon carbon composite material includes a carbon matrix and a silicon-based material disposed in the carbon matrix, and based on this configuration, the secondary battery exhibits further improved cycle performance.

[0095] In some embodiments, the silicon carbon composite has an initial coulombic efficiency of ≧90 wt%, and optionally 91 wt% to 94 wt%. Based on this configuration, the secondary battery exhibits further improved initial coulombic efficiency.

[0096] In some embodiments, the silicon carbon composite has a volume particle size Dv50 of 3 μm to 15 μm, and optionally 5 μm to 12 μm. This particle size range is advantageous for improving the ion and electron transport performance of the material, thereby further improving the fast charging performance of the secondary battery, and also for reducing the specific surface area of ​​the material and reducing side reactions, thereby further improving the cycle performance of the secondary battery.

[0097] In some embodiments, the silicon carbon composite material has a volume distribution particle size Dv90 of ≦60 μm, preferably 20 μm to 40 μm. When the volume distribution particle size Dv90 of the material is within this range, the particle alignment is relatively good, which is advantageous for improving the ion and electron transport performance, thereby further improving the fast charging performance of the secondary battery.

[0098] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the silicon carbon composite material is 1.0 to 3.0, and preferably 1.0 to 2.0. When the (Dv90-Dv10) / Dv50 of the material is within this range, the particle packing performance is relatively good, which is advantageous for improving the compression 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 a suitable pore structure, which is advantageous for further improving the fast charging performance of the secondary battery.

[0099] In some embodiments, the silicon carbon composite has a BET specific surface area of ​​20 m 2 / g or less, and selectively 1m 2 / g~10m 2 When the specific surface area of ​​the material is within the above range, it is advantageous to reduce side reactions, so that the secondary battery can have better cycle performance.

[0100] In some embodiments, the powder resistivity of the silicon carbon composite material under a pressure of 16 MPa is ≦300 Ω·cm, and optionally ≦50 Ω·cm, which is advantageous for improving the electronic conductivity of the negative electrode film layer and thereby further improving the fast charging performance of the secondary battery.

[0101] In some embodiments, the silicon carbon composite has a tap density of 0.8 g / cm 3 ~1.0g / cm 3 and selectively 0.9 g / cm 3 ~1.0g / cm 3When the tap density is within the above range, the compression density of the negative electrode film layer can be improved, thereby further improving the energy density of the secondary battery, and the negative electrode film layer has an appropriate pore structure, which can improve the ion and electron transport performance, improve the electrolyte infiltration and retention properties of the negative electrode film layer, and further improve the fast charging performance and / or cycle performance of the secondary battery.

[0102] In some embodiments, the silicon content of the silicon carbon composite is 30 wt% or more, preferably 40 wt% to 60 wt%, so that the silicon carbon composite has satisfactory electrochemical performance.

[0103] In some embodiments, the carbon content of the silicon carbon composite is 40 wt% or more, preferably 45 wt% to 60 wt%, so that the silicon carbon composite has satisfactory electrochemical performance.

[0104] In some embodiments, the oxygen content in the silicon carbon composite is 10 wt% or less, preferably 1 wt%-5 wt%, so that the silicon carbon composite has satisfactory electrochemical performance.

[0105] In some embodiments, the silicon-oxygen-based material comprises an alkali metal-containing or alkaline earth metal-containing silicate, and based on this configuration, the secondary battery exhibits further improved first coulombic efficiency performance.

[0106] In some embodiments, the silicon-oxygen-based material includes an alkali metal-containing silicate, and the silicon-oxygen-based material satisfies the following: in an XRD diffraction pattern, the half-width of a diffraction peak corresponding to the alkali metal-containing silicate is 0.5° to 2.0°, and / or the crystal grain size of the silicate corresponding to the alkali metal-containing silicate is 4 nm to 17 nm. Based on this aspect, the secondary battery exhibits further improved initial coulombic efficiency.

[0107] In some embodiments, the alkali metal-containing silicate comprises M2Si2O5, M2SiO3, or a combination thereof, where M comprises one or more alkali metal elements, such as, for example, one or more of Li, Na, and K.

[0108] In some embodiments, the silicon-oxygen-based material includes an alkaline earth metal-containing silicate, and the silicon-oxygen-based material satisfies the following: in an XRD diffraction pattern, the half-width of a diffraction peak corresponding to the alkaline earth metal-containing silicate is 0.3° to 0.6°, and / or the crystal grain size of the silicate corresponding to the alkaline earth metal-containing silicate is 12 nm to 20 nm. Based on this aspect, the secondary battery exhibits further improved first coulombic efficiency.

[0109] In some embodiments, the alkaline earth metal-containing silicate comprises QSiO3 or a combination thereof, where Q comprises one or more alkaline earth metal elements, such as, for example, one or more of Mg, Ca, Be, and Sr.

[0110] In some embodiments, the silicon-oxygen-based material has a volume particle size Dv50 of 3 μm to 20 μm, and optionally 5 μm to 15 μm. This particle size range is advantageous for improving the ion and electron transport performance of the material, thereby further improving the rapid charging performance of the secondary battery, and also for reducing the specific surface area of ​​the material and reducing side reactions, thereby further improving the cycle performance of the secondary battery.

[0111] In some embodiments, the silicon-oxygen-based material has a volume distribution particle size Dv90 of ≦60 μm, preferably 10 μm to 25 μm. When the volume distribution particle size Dv90 of the material is within this range, the particle alignment is relatively good, which is advantageous for improving the transport performance of ions and electrons, thereby further improving the rapid charging performance of the secondary battery.

[0112] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the silicon-oxygen-based material is 1.0 to 2, preferably 1.0 to 1.5. When the (Dv90-Dv10) / Dv50 of the material is within the above range, the particle packing performance is relatively good, which is advantageous for improving the compression 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 a suitable pore structure, which is advantageous for further improving the fast charging performance of the secondary battery.

[0113] In some embodiments, the silicon-oxygen based material has a BET specific surface area of ​​1 m 2 / g~6m 2 / g, and selectively 1m 2 / g~5m 2 When the specific surface area of ​​the material is within the above range, it is advantageous to reduce side reactions, so that the secondary battery can have better cycle performance.

[0114] In some embodiments, the silicon-oxygen based material has a tap density of 1.05 g / cm 3 ~1.25g / cm 3 and selectively 1.1 g / cm 3 ~1.2g / cm 3When the tap density is within the above range, the compression density of the negative electrode film layer can be improved, thereby further improving the energy density of the secondary battery, and the negative electrode film layer has an appropriate pore structure, which can improve the ion and electron transport performance, improve the electrolyte infiltration and retention properties of the negative electrode film layer, and further improve the fast charging performance and / or cycle performance of the secondary battery.

[0115] In some embodiments, the silicon content of the silicon-oxygen-based material is 40 wt% or more, and preferably 45 wt% to 65 wt%, so that the silicon-oxygen-based material has improved electrochemical performance.

[0116] In some embodiments, the content of oxygen element in the silicon-oxygen based material is 30 wt% or more, and preferably 30 wt% to 50 wt%, so that the silicon-oxygen based material has improved electrochemical performance.

[0117] In some embodiments, the carbon content in the silicon-oxygen-based material is 8 wt% or less, and preferably 2 wt%-5 wt%, so that the silicon-oxygen-based material has improved electrochemical performance.

[0118] In some embodiments, the first active material and / or the second active material further comprises a carbon-based material, and optionally the carbon-based material comprises at least one of artificial graphite, natural graphite, soft carbon, and hard carbon. Based on this configuration, the secondary battery exhibits further improved cycle performance.

[0119] In some embodiments, the first active material comprises a first carbonaceous material, the second active material comprises a second carbonaceous material, and the first carbonaceous material comprises primary particles, optionally with a proportion of the primary particles in the first carbonaceous material of ≥ 70%. The primary particles typically have a relatively small specific surface area, which can reduce side reactions and improve the cycle performance of the secondary battery. The primary particles also have a relatively high capacity, which can improve the energy density of the secondary battery.

[0120] In some embodiments, the first active material comprises a first carbonaceous material, the second active material comprises a second carbonaceous material, and the second carbonaceous material comprises secondary particles, optionally with a quantity ratio of the secondary particles in the second carbonaceous material of ≧70%. Based on this configuration, the secondary battery further exhibits improved cycle performance.

[0121] The terms primary particles and secondary particles both have the meanings known in the art. Primary particles refer to particles in a non-aggregated state. Secondary particles refer to particles in an aggregated state formed by the aggregation of two or more primary particles. Primary particles and secondary particles can be distinguished by using scanning electron microscope (SEM) images.

[0122] For example, the test method for determining the proportion of the first carbon-based material in the primary particles of a first carbon-based material can be performed by placing the obtained first active material on a conductive adhesive, bonding it, and then preparing a 6 cm x 1.1 cm sample to be measured. The particle shape can be examined using a scanning electron microscope. For this test, see JY / T010-1996. To ensure the accuracy of the test results, multiple (e.g., 10) different areas of the sample to be measured can be randomly selected and scanned. At a certain magnification (e.g., 500x or 1000x), the ratio of the number of the first carbon-based material in the primary particles to the total amount of the first carbon-based material in each test area can be calculated, and 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 (e.g., 5 or 10) test samples can be prepared and the test can be repeated. The average of the results from each test sample can be used as the final test result. Similarly, the proportion of the first silicon-based material in the secondary particles of a first silicon-based material can also be tested.

[0123] For example, the test method for determining the proportion of the second carbon-based material in the secondary particles of a second carbon-based material can be performed by placing the obtained second active material on a conductive adhesive, bonding it, and then preparing a 6 cm x 1.1 cm sample to be measured. The particle shape can be examined using a scanning electron microscope. For this test, see JY / T010-1996. To ensure the accuracy of the test results, multiple (e.g., 10) different areas of the sample to be measured can be randomly selected and scanned. At a certain magnification (e.g., 500x or 1000x), the ratio of the quantity of the second carbon-based material in the secondary particles to the total amount of the second carbon-based material in each test area can be calculated, and 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 (e.g., 5 or 10) test samples can be prepared and the test can be repeated. The average of the results from each test sample can be used as the final test result. Similarly, the proportion of the second silicon-based material in the primary particles of a second silicon-based material can also be tested.

[0124] The quantitative ratio of primary particles (here, this refers to non-aggregated particles) to secondary particles in the carbon-based material (e.g., the first carbon-based material or the second carbon-based material) can be adjusted by methods known in the art. For example, when the carbon-based material is graphite, the quantitative ratio of primary particles to secondary particles can be adjusted by adjusting production parameters (e.g., the type of coke raw material, the molding process, the granulation process, the type and amount of granulating agent, etc.), and the quantitative ratio of primary particles to secondary particles can also be adjusted by adjusting the mixing ratio of graphite primary particles to graphite secondary particles.

[0125] In some embodiments, the first active material comprises a first carbonaceous material, and the second active material comprises a second carbonaceous material, wherein the volume average particle size Dv50 of the first carbonaceous material is smaller than the volume average particle size Dv50 of the second carbonaceous material. This allows the second region and the first region of the negative electrode layer to have a good difference in compaction density, which improves the consistency of the porosity and ion concentration distribution in the thickness direction of the negative electrode layer, favors the improvement of the electrolyte penetration and retention properties of the negative electrode layer, favors ion transport, and further allows the secondary battery to have better cycle performance and / or fast charging performance.

[0126] In some embodiments, the first active material comprises a first carbonaceous material, the second active material comprises a second carbonaceous material, and the tap density of the first carbonaceous material is greater than that of the second carbonaceous material. When the tap density is within this range, the negative electrode layer can be made more compact, thereby further improving the energy density of the secondary battery. In addition, the negative electrode layer can have a suitable pore structure, which can improve the ion and electron transport performance, improve the electrolyte penetration and retention properties of the negative electrode layer, and further improve the fast charging performance and / or cycle performance of the secondary battery.

[0127] In some embodiments, the first active material comprises a first carbonaceous material, the second active material comprises a second carbonaceous material, and the first carbonaceous material has a greater pressed density than the second carbonaceous material. This allows the second and first regions of the negative electrode layer to have a good pore structure, which can better match the ion concentration distribution in the thickness direction of the negative electrode layer, improve the electrolyte wetting and retention properties of the negative electrode layer, and facilitate ion transport. Furthermore, the secondary battery can have better cycle performance and / or fast charging performance.

[0128] In some embodiments, the first carbon-based material has a volume particle size Dv50 of 5 μm to 20 μm, and optionally 8 μm to 15 μm. This particle size range is advantageous for improving the ion and electron transport performance of the material, thereby further improving the rapid charging performance of the secondary battery, and also for reducing the specific surface area of ​​the material and reducing side reactions, thereby further improving the cycle performance of the secondary battery.

[0129] In some embodiments, the volume distribution particle size Dv90 of the first carbon-based material is ≦50 μm, and optionally 25 μm to 40 μm. When the volume distribution particle size Dv90 of the material is within this range, the particle alignment is relatively good, which is advantageous for improving the ion and electron transport performance, and thereby further improving the rapid charging performance of the secondary battery.

[0130] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the first carbon-based material is 1.0 to 2.5, preferably 1.0 to 1.8. When the (Dv90-Dv10) / Dv50 of the material is within this range, the particle packing performance is relatively good, which is advantageous for improving the compression density of the negative electrode film layer, thereby further improving the energy density of the secondary battery, and is also advantageous for the negative electrode film layer to have an appropriate pore structure, which is advantageous for further improving the fast charging performance of the secondary battery.

[0131] In some embodiments, the first carbon-based material has a BET specific surface area of ​​0.5 m 2 / g~4m 2 / g, and selectively 1m 2 / g~3m 2 When the specific surface area of ​​the material is within the above range, it is advantageous to reduce side reactions, so that the secondary battery can have better cycle performance.

[0132] In some embodiments, the tap density of the first carbon-based material is 1.0 g / cm 3 ~1.25g / cm 3 and selectively 1.1 g / cm 3 ~1.2g / cm 3 When the tap density is within the above range, the compression density of the negative electrode film layer can be improved, thereby further improving the energy density of the secondary battery, and the negative electrode film layer has an appropriate pore structure, which can improve the ion and electron transport performance, improve the electrolyte infiltration and retention properties of the negative electrode film layer, and further improve the fast charging performance and / or cycle performance of the secondary battery.

[0133] In some embodiments, the first carbon-based material has a powder compaction density of 1.6 g / cm when tested under a pressure of 30,000 N. 3 ~1.9g / cm 3 and selectively 1.65 g / cm 3 ~1.8g / cm 3 Based on this, the secondary battery has an improved energy density.

[0134] In some embodiments, the second carbon-based material has a volume particle size Dv50 of 8 μm to 25 μm, and optionally 12 μm to 18 μm. This particle size range is advantageous for improving the ion and electron transport performance of the material, thereby further improving the rapid charging performance of the secondary battery, and also for reducing the specific surface area of ​​the material and reducing side reactions, thereby further improving the cycle performance of the secondary battery.

[0135] In some embodiments, the volume distribution particle size Dv90 of the second carbon-based material is ≦60 μm, and optionally 35 μm to 50 μm. When the volume distribution particle size Dv90 of the material is within this range, the particle alignment is relatively good, which is advantageous for improving the transport performance of ions and electrons, and thereby further improving the rapid charging performance of the secondary battery.

[0136] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the second carbon-based material is 1.0 to 2.0, preferably 1.0 to 1.5. When the (Dv90-Dv10) / Dv50 of the material is within this range, the particle packing performance is relatively good, which is advantageous for improving the compression density of the negative electrode film layer, thereby further improving the energy density of the secondary battery, and is also advantageous for the negative electrode film layer to have an appropriate pore structure, which is advantageous for further improving the fast charging performance of the secondary battery.

[0137] In some embodiments, the second carbon-based material has a BET specific surface area of ​​1 m 2 / g~5m 2 / g, and selectively 1m 2 / g~3m 2 When the specific surface area of ​​the material is within the above range, it is advantageous to reduce side reactions, so that the secondary battery can have better cycle performance.

[0138] In some embodiments, the tap density of the second carbon-based material is 0.9 g / cm 3 ~1.2g / cm 3 and selectively 1.0 g / cm 3 ~1.1g / cm 3When the tap density is within the above range, the compression density of the negative electrode film layer can be improved, thereby further improving the energy density of the secondary battery, and the negative electrode film layer has an appropriate pore structure, which can improve the ion and electron transport performance, improve the electrolyte infiltration and retention properties of the negative electrode film layer, and further improve the fast charging performance and / or cycle performance of the secondary battery.

[0139] In some embodiments, the second carbon-based material has a powder compaction density of 1.5 g / cm when tested under a pressure of 30,000 N. 3 ~1.75g / cm 3 and selectively 1.55 g / cm 3 ~1.7g / cm 3 Based on this, the secondary battery has an improved energy density.

[0140] As shown in FIGS. 1A to 1C, the negative electrode film layer 102 further includes a central region 1023 located between the first region 1021 of the negative electrode film layer and the second region 1022 of the negative electrode film layer, and having a thickness of 0.4H (H denotes the thickness of the negative electrode film layer 102).

[0141] In some embodiments, a central region 1023 located between the first region 1021 and the second region 1022 comprises the silicon carbon composite material and / or the silicon oxygen based material. For example, as shown in FIG. 1B, the central region 1023 can have the same structure as the first region 1021, whereby the distribution region of the first active material in the thickness direction of the negative electrode film layer 102 is within a thickness range of 0.7H from the second surface 102b of the negative electrode film layer; or as shown in FIG. 1C, the central region 1023 can have the same structure as the second region 1022, whereby the distribution region of the second active material in the thickness direction of the negative electrode film layer 102 is within a thickness range of 0.7H from the first surface 102a of the negative electrode film layer; or as shown in FIG. 1A, the central region 1023 simultaneously includes the first active material and the second active material, whereby the central region 1023 simultaneously includes a layer structure having the first active material and a layer structure having the second active material, and the two-layer structure can further include a layer interface.

[0142] In some embodiments, the second region 1022 of the negative electrode film layer can further include other negative electrode active materials known in the art other than the second carbon-based material and the second silicon-based material, such as one or more of a tin-based material, lithium titanate, and the like.

[0143] In some embodiments, the central region 1023 of the negative electrode film layer may further include one or more of a tin-based material, lithium titanate, or the like.

[0144] In some embodiments, the first region, the second region, and the central region of the negative electrode film layer optionally further comprise a negative electrode conductive agent and / or a negative electrode adhesive.

[0145] The present application is not particularly limited by the type of the negative electrode conductive agent. For example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0146] The present application is not particularly limited by the type of the negative electrode adhesive. For example, the negative electrode adhesive may include one or more of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0147] In some embodiments, the first region, the second region, and the central region of the negative electrode film layer optionally further include other additives, such as thickeners such as sodium carboxymethylcellulose (CMC) and PTC thermistor materials.

[0148] In some embodiments, the porosity of the negative electrode film layer is ≧15%, preferably 20% to 45%, which is advantageous for achieving both high capacity and a suitable pore structure of the negative electrode film layer, and is also advantageous for achieving both high energy density, good cycle performance, and fast charging performance of the secondary battery.

[0149] In some embodiments, 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 testing method involves taking a negative electrode piece that has been coated on one side and cold-pressed (if the negative electrode piece is coated on both sides, the negative electrode film layer on one side can be wiped off first), punching it into a small circular sheet sample of a certain area, calculating the apparent volume V1 of the negative electrode piece, and then measuring the true volume V2 of the negative electrode piece using a true density tester in accordance with GB / T 24586-2009, using an inert gas (e.g., helium or nitrogen) as the medium and employing a gas displacement method. Porosity of the negative electrode film layer = (V1 - V2) / V1 × 100%. Multiple negative electrode piece samples (e.g., 30 pieces) with good appearance and no edge powdering are tested, and the results are averaged to improve the accuracy of the test results. A Micromeritics AccuPyc II 1340 true density tester can be used as the test equipment.

[0150] In some embodiments, the negative electrode film layer has a compression density of ≥ 1.5 g / cm 3 and selectively 1.6 to 1.8 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, good cycle performance, and fast charging performance.

[0151] In some embodiments, the bonding density of the negative electrode film layer has a meaning known in the art and can be tested by a method known in the art: bonding 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 tested by a method known in the art, for example, using a micrometer (e.g., Mitutoyo 293-100 type, with an accuracy of 0.1 μm).

[0152] In some embodiments, the areal density of the negative electrode film layer is ≥ 7 mg / cm 2 and selectively 9 to 30 mg / cm 2This 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, good cycle performance, and fast charging performance.

[0153] In some embodiments, the areal density of the negative electrode film layer has a meaning known in the art and can be tested by a method known in the art. For example, a negative electrode piece coated on one side and cold-pressed (if the negative electrode piece 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 sheet with an area of ​​S1, and its weight is recorded as M1. Then, the negative electrode film layer of the weighed negative electrode piece is wiped off, and the weight of the negative electrode current collector is recorded as M0. The areal density of the negative electrode piece = (M1 - M0) / S1.

[0154] The silicon carbon composite material and silicon oxygen-based material used in the present application are both commercially available or can be produced by the following method.

[0155] In some embodiments, a method for producing a silicon-oxygen based material includes: providing a raw material containing silicon and oxygen elements; adopting a vapor phase deposition method, heating the raw material to 1100-1500°C to form vapor, and then cooling the vapor to 700-900°C to form a deposit; and grinding the sediment to obtain a grinding material.

[0156] In some embodiments, the method for producing a silicon-oxygen-based material may further include an alkali metal doping step. Optionally, in the alkali metal doping reaction step, the coated product and an alkali metal source (e.g., a lithium source, a sodium source, a potassium source, etc.) are mixed in a mass ratio of 100:6-11 (e.g., 100:6-7, 100:7-8, 100:8-9, 100:9-10, or 100:10-11). Optionally, the temperature ramp rate for the alkali metal doping reaction is 0.5-1.5°C / min, 1-2°C / min, 1.5-2.5°C / min, 2-3°C / min, 2.5-3.5°C / min, 3-4°C / min, 3.5-4.5°C / min, or 4-5°C / min. Alternatively, the heating temperature for the alkali metal-doped reaction is 450-500°C / min, 500-550°C / min, 550-600°C / min, 600-650°C / min, 650-700°C / min, 700-750°C / min, or 750-800°C / min. Alternatively, the incubation time for the alkali metal-doped reaction is 3-4 hours, 4-5 hours, 5-6 hours, 6-7 hours, 7-8 hours, 8-9 hours, or 9-16 hours.

[0157] In some embodiments, the method for producing a silicon-oxygen based material may further include doping with an alkaline earth metal. Optionally, the alkaline earth metal doping step is configured so that the raw material further contains alkaline earth metal elements (e.g., Mg, Ca, etc.), and the content of the alkaline earth metal elements in the raw material is optionally 7-10 wt% (e.g., 7-8 wt%, 8-10 wt%, 9-10 wt%). Then, using the vapor deposition method, the raw material is heated to 1100-1500°C (e.g., 1100-1400°C, 1100-1300°C, 1100-1200°C, 1200-1500°C, 1300-1500°C, 1400-1500°C) to form vapor, and then the vapor is cooled to 700-900°C (e.g., 750-850°C) to form a deposit. Based on this configuration, the resulting silicon-based negative electrode active material exhibits improved first coulombic efficiency and / or cycle life.

[0158] In some embodiments, the source material includes elemental silicon, which can provide the source material with elemental Si.

[0159] In some embodiments, the source material includes silicon oxide, which can provide the O element to the source material.

[0160] In some embodiments, the raw material contains elemental silicon and silica, and the mass ratio of elemental silicon to silica is 0.8 to 1.2:1, for example, 1:1.

[0161] In some embodiments, the vapor deposition is carried out in an atmosphere having an absolute pressure of 40 Pa or less.

[0162] In some embodiments, the operation of crushing the sediment includes subjecting the sediment to coarse crushing, fine crushing, and classification according to the volume average particle size (Dv50) and specific surface area parameters of the predetermined product to obtain a product that meets the predetermined parameters. In some embodiments, the sediment can be crushed and classified using any method and equipment known in the art, such as a grinder or an airflow crusher-classifier.

[0163] In some embodiments, the method for producing a silicon-oxygen based material further comprises subjecting the silicon-oxygen based material to a coating process, such as a carbon coating process.

[0164] In some embodiments, a method for producing a silicon carbon composite material includes: providing a carbonaceous precursor (e.g., a biomass precursor or a resin precursor), such as coconut-based or starch-based biomass porous carbon; The method includes a step of carbonizing the carbonaceous precursor in a nitrogen atmosphere at a temperature of 600 to 1000°C for 2 to 10 hours to obtain porous carbon, and a step of heating the porous carbon in an atmosphere containing a silicon source gas to deposit elemental silicon on the porous carbon to obtain a silicon carbon composite material.

[0165] In some embodiments, before depositing elemental silicon on the porous carbon, the biomass is carbonized, and then the product is subjected to a pore-forming treatment to obtain porous carbon. Optionally, the volume average particle diameter Dv50 of the porous carbon is 5 to 17 μm, for example, 5 to 13 μm. Optionally, the BET specific surface area of ​​the porous carbon is 100 to 2000 m. 2 / g, for example, 1000 to 1500m 2 / g.

[0166] In some embodiments, the silicon source gas comprises a silane gas, such as monosilane, which upon heating decomposes into elemental silicon and hydrogen gas, which deposits on the porous carbon to form a silicon carbon composite.

[0167] In some embodiments, the porous carbon is heated to 400° C. to 600° C., for example, 450° C. to 550° C., in an atmosphere containing a silicon source gas.

[0168] In some embodiments, the method for producing a silicon carbon composite further comprises the step of subjecting the silicon carbon composite to a coating process, for example, a carbon coating process.

[0169] In some embodiments, the carbon coating process includes placing a target to be coated (e.g., a silicon-oxygen based material or a silicon-carbon composite material) in a deposition chamber containing a carbon source gas and heating to carbonize and deposit the carbon source gas to form a coating layer containing the carbon material.

[0170] In some embodiments, the carbon source gas comprises 5-15% of the total gas volume in the deposition chamber, and the deposition chamber may further contain a non-oxidizing gas, such as nitrogen gas or an inert gas.

[0171] In some embodiments, the carbon source gas comprises one or more of acetylene, methane, ethylene, propane, ethane, propylene, propyne, and toluene.

[0172] In some embodiments, the heating temperature in the carbon coating treatment is 600 to 1000°C.

[0173] In some embodiments, the heating time in the carbon coating treatment is 1 to 6 hours.

[0174] In some embodiments, the negative electrode current collector may be a metal foil strip or a composite current collector. For example, the metal foil strip may be a copper foil. The composite current collector may include a polymeric base layer and a metal layer formed on at least one surface of the polymeric substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy) on a polymeric substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0175] In some embodiments, the negative electrode film may further include an adhesive. For example, the adhesive may include at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0176] In some embodiments, the negative electrode film may further include a conductive agent, such as at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0177] In some embodiments, the negative electrode film can further optionally include other additives, such as a thickener (e.g., sodium carboxymethylcellulose (CMC-Na)).

[0178] In some embodiments, the negative electrode pieces can be manufactured by the following method: The components for manufacturing the negative electrode pieces, such as the negative electrode active material, the conductive agent, the adhesive, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry, which is then applied to a negative electrode current collector, and the negative electrode pieces can be obtained after processes such as drying and cold pressing.

[0179] The negative electrode piece does not exclude additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode piece described herein further includes a conductive primer layer (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 piece described herein further includes a protective layer covering the surface of the negative electrode film layer.

[0180] The negative electrode current collector has two surfaces facing each other in the thickness direction, and the negative electrode film layer is disposed on either 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., packing density, areal density, porosity, etc.) provided in the present application refer to the parameters of the negative electrode film layer on one side of the negative electrode current collector. When negative electrode film layers are disposed on both sides of the negative electrode current collector, the parameters of any one of the negative electrode film layers satisfying the present application are considered to be within the scope of protection of the present application.

[0181] In some embodiments, testing of various parameters of the first active material, the second active material, or the negative electrode film layer can be performed by taking samples from a secondary battery manufactured according to the following steps.

[0182] The secondary battery is discharged (for safety reasons, the secondary battery is usually fully discharged). After removing the secondary battery, the negative electrode piece is removed and immersed in dimethyl carbonate for a certain period of time (e.g., 2 to 10 hours). The negative electrode piece 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 piece is removed. At this time, a sample is taken from the dried negative electrode piece, and various parameters related to the negative electrode film layer described above, such as the areal density, bonding density, and porosity of the negative electrode film layer, can be tested.

[0183] The dried negative electrode pieces are baked at a certain temperature for a certain time (for example, 400°C, 2 hours or more). A sample of the second active material is first taken from a selected region of the baked negative electrode pieces (optionally, the powder can be scraped off with a doctor blade to take a sample). The sample is taken from the second region of the negative electrode film layer. Then, a sample of the first active material is taken in a similar manner from the first region of the negative electrode film layer. The collected first and second active materials are each sieved (for example, sieved through a 200-mesh sieve), and finally, samples of the first and second active materials are obtained that can be used to test the above-mentioned material parameters of the present application.

[0184] [Positive electrode piece] In some embodiments, the positive electrode piece typically includes a positive electrode current collector and a positive electrode film disposed on at least one surface of the positive electrode current collector, the positive electrode film including a positive electrode active material.

[0185] As an example, the positive electrode current collector has two surfaces that face each other in the thickness direction of the positive electrode current collector, and the positive electrode film is disposed on any one or both of the two facing surfaces of the positive electrode current collector.

[0186] In some embodiments, the positive electrode current collector may be a metal foil piece or a composite current collector. For example, the metal foil piece may be aluminum foil. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0187] In some embodiments, the positive electrode film may further include an adhesive. For example, the adhesive may include at least one 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.

[0188] In some embodiments, the positive electrode film may further include an optional conductive agent, such as at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0189] In some embodiments, the positive electrode pieces can be manufactured by a method in which the above-mentioned components for manufacturing the positive electrode pieces, such as the positive electrode active material, the conductive agent, the adhesive, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, and the positive electrode slurry is applied onto a positive electrode current collector, followed by processes such as drying and cold pressing to obtain the positive electrode pieces.

[0190] [Cathode active material] In some embodiments, the positive electrode active material can be any positive electrode active material used in secondary batteries known in the art.

[0191] For example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as the positive electrode active material of a battery may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include lithium cobalt oxide (e.g., LiCoO), lithium nickel oxide (e.g., LiNiO), lithium manganese oxide (e.g., LiMnO, LiMnO), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (e.g., LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 (may be abbreviated as "LiNi") 0.5 Co 0.2 Mn 0.3 O2(NCM 523 (may be abbreviated as "LiNi") 0.5 Co 0.25 Mn 0.25 O2(NCM 211 (may be abbreviated as "LiNi") 0.6 Co 0.2 Mn 0.2 O2(NCM 622 (may be abbreviated as "LiNi") 0.8 Co 0.1 Mn 0.1 O2(NCM 811 ), lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05O2) and modified compounds thereof, etc. Examples of the lithium-containing phosphate having an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (which may be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.

[0192] [Electrolyte] The electrolyte serves to conduct ions between the positive and negative electrodes. The present application does not specifically limit the type of electrolyte, and it can be selected according to needs. For example, the electrolyte can be liquid, gel, or completely solid.

[0193] In some embodiments, the electrolyte is in a liquid state and includes an electrolyte salt and a solvent.

[0194] In some embodiments, the electrolyte salt includes sodium perchlorate, sodium hexafluorophosphate, sodium tetrafluoroborate, and sodium hexafluoroarsenate.

[0195] In some embodiments, the solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0196] In some embodiments, the electrolyte solution optionally further comprises 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 certain performance of the battery, such as an additive that improves the overcharge performance of the battery or an additive that improves the high-temperature or low-temperature performance of the battery.

[0197] [Separator film] In some embodiments, the secondary battery further includes a separator film. The present application does not specifically limit the type of separator film, and any known separator film with a porous structure having good chemical and mechanical stability can be selected.

[0198] In some embodiments, the separator film may be made of at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film may be a single-layer thin film or a multilayer composite thin film, without any particular limitation. When the separator film is a multilayer composite thin film, the materials of the layers may be the same or different, without any particular limitation.

[0199] In some embodiments, the positive electrode strips, negative electrode strips, and separator film can be fabricated into an electrode assembly by a winding or lamination process.

[0200] In some embodiments, the secondary battery may include an outer package that can be used to encapsulate the electrode assembly and electrolyte.

[0201] In some embodiments, the exterior packaging of the secondary battery can be a hard casing, such as a hard plastic casing, an aluminum casing, a steel casing, etc. The exterior packaging of the secondary battery can also be a pouch, such as a bag-type pouch. The pouch can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0202] The present application does not particularly limit the shape of the secondary battery, which may be cylindrical, prismatic, or any other shape. For example, Figure 2 shows a secondary battery 5 having a prismatic structure as an example.

[0203] In some embodiments, referring to FIG. 2 , the exterior packaging of the secondary battery 5 may include a casing 51 and a cover plate 53. The casing 51 may include a base plate and a side plate connected to the base plate, which together form a surrounding receiving cavity. The casing 51 has an opening communicating with the receiving cavity, and the cover plate 53 may cover the opening to seal the receiving cavity. The positive electrode piece, the negative electrode piece, and the separator film may be wound or stacked to form an electrode assembly 52. ​​The electrode assembly 52 is sealed in the receiving cavity. An electrolyte is impregnated into the electrode assembly 52. ​​The secondary battery 5 may include one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0204] In some embodiments, the secondary batteries can be assembled into a battery module, and the number of secondary batteries included in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0205] Fig. 3 shows an example of a battery module 4. Referring to Fig. 3, in the battery module 4, the plurality of secondary batteries 5 may be arranged in order along the length 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 fastening members.

[0206] Optionally, the battery module 4 may further include an exterior casing having an accommodating space, and the plurality of secondary batteries 5 are accommodated in the accommodating space.

[0207] In some embodiments, the battery modules can also be assembled into a battery pack, and the number of battery modules included in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0208] 4 and 5 show an example of a battery pack 1. Referring to 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 case 2 and a lower case 3, and the upper case 2 is attached to the lower case 3 as a lid, and can form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0209] The present application also provides an electric device including at least one of the secondary battery, battery module, or battery pack provided herein. The secondary battery, battery module, or battery pack may be used as a power source for the electric device or as an energy storage unit for the electric device. The electric device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc.

[0210] The electric device can be selected as a secondary battery, a battery module or a battery pack according to the needs of the use.

[0211] 6 shows an example of an electric device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the electric device's need for high power and high energy density from secondary batteries, a battery pack or a battery module can be employed.

[0212] The following examples are provided for illustrative purposes only and are not intended to limit the scope of the present application. Unless specific techniques or conditions are described in the examples, they may be performed in accordance with techniques or conditions described in literature in the field or in accordance with the product instructions. The reagents or equipment used may be ordinary commercially available products without specifying the manufacturer.

[0213] Example E1 Manufacture of negative electrode pieces First slurry: First negative electrode active material (25%:75% silicon-oxygen-based material to first carbon-based material by mass), conductive carbon nanotubes, thickener sodium carboxymethylcellulose (CMC), adhesive styrene butadiene rubber (SBR) were mixed in a mass ratio of 96.7%:0.5%:1.0%:1.8%, then deionized water was added and the mixture was stirred under a vacuum mixer until the system was homogeneous. The first slurry was obtained. The silicon content of the silicon-oxygen-based material was 48 wt%, carbon content was 4 wt%, oxygen content was 40 wt%, magnesium content was 8%, and tap density was 1.18 g / cm. 3the powder resistivity under a pressure of 16 MPa is 0.3 Ω cm, the volume distribution particle diameter Dv50 is 6.5 μm, the volume distribution particle diameter Dv90 is 18 μm, and the particle size distribution (Dv90-Dv10) / Dv50 is 1.2; the silicon-oxygen-based material contains a magnesium-containing silicate, and the silicon-oxygen-based material has an XRD diffraction pattern in which the half width of a diffraction peak corresponding to silicate is 0.4°; the magnesium-containing silicate has a crystal grain size of 17 nm; the first carbon-based material is artificial graphite, and the proportion of the artificial graphite in the primary particles of the first carbon-based material is 80%, the volume particle diameter Dv50 is 18 μm, and the particle size distribution (Dv90-Dv10) / Dv50 is 1.2; 2 / g and

[0214] Second slurry: The second negative electrode active material (silicon carbon composite and second carbon-based material in a mass ratio of 18%:82%), conductive carbon nanotube, thickener sodium carboxymethylcellulose (CMC), and adhesive styrene butadiene rubber (SBR) were mixed in a mass ratio of 98%:0.5%:1.0%:1.5%. Deionized water was added as a solvent and the mixture was stirred under a vacuum mixer until the system was homogeneous. The A2 values ​​are shown in Table 1. The silicon carbon composite had a silicon content of 46 wt%, a carbon content of 49 wt%, an oxygen content of 5 wt%, and a tap density of 0.94 g / cm. 3 The powder resistivity under a pressure of 16 MPa was 1.46 Ω cm, the first Coulomb efficiency was 92%, the volume distribution particle diameter Dv50 was 8.5 μm, the volume distribution particle diameter Dv90 was 27 μm, the particle size distribution (Dv90-Dv10) / Dv50 was 1.4, the second carbon-based material was artificial graphite, the quantity ratio of artificial graphite in the secondary particles of the second carbon-based material was 70%, the volume particle diameter Dv50 was 16 μm, the particle size distribution (Dv90-Dv10) / Dv50 was 1.2, and the BET specific surface area was 1.5 m 2 / g.

[0215] Negative electrode pieces: Copper foil was used as a current collector. The first and second slurries were simultaneously applied to the copper foil, the first slurry was applied to the copper foil to form a first region, and the second slurry was applied to the first region to form a second region. The negative electrode pieces were then obtained through processes such as drying, cold pressing, edge trimming, slitting, and cutting.

[0216] Manufacture of cathode pieces Positive electrode active material Lithium nickel cobalt manganese oxide (LiNi 0.8 Co 0.1 Mn 0.1 O2), conductive agent Super P, and adhesive polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 97%:1.5%:1.5%, and the solvent N-methylpyrrolidone (NMP) was added. The mixture was stirred under a vacuum mixer until the system was homogeneous, yielding a positive electrode slurry. The positive electrode slurry was evenly applied to an aluminum foil positive electrode current collector, followed by drying, cold pressing, edge trimming, slitting, and cutting to obtain ready-to-use positive electrode pieces.

[0217] Electrolyte production The organic solvent was a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), with a volume ratio of 20%:20%:60% EC, EMC, and DEC. In an argon gas glove box with a water content of <10 ppm, thoroughly dried lithium salt (LiPF6) was dissolved in the organic solvent, and then 10 wt% of the additive fluoroethylene carbonate (FEC) was added and mixed uniformly to obtain an electrolyte solution. The concentration of the lithium salt in the electrolyte solution was 1 mol / L.

[0218] Separator Film A polypropylene separator film was used.

[0219] Full battery assembly The positive electrode pieces, separator film, and negative electrode pieces were stacked in this order, with the separator film between the positive and negative electrode pieces to act as insulators, and then wound around the electrode assembly, tabs were welded, the electrode assembly was placed in an outer package, the electrolyte was injected, and the package was sealed. After that, the process of standing, hot and cold pressing, chemical conversion, molding, etc. was carried out to obtain a lithium-ion battery. The battery dimensions were 135mm x 72mm x 60mm.

[0220] Examples E2-E12 were prepared similarly to Example E1, with distinctions noted in Table 1 below.

[0221] Comparative Example D1 Comparative Example D1 was prepared similarly to Example E1, with the difference being that the application locations of the first and second slurries were reversed (i.e., the second slurry was applied to the copper foil to form the first region, and the first slurry was applied to the first region to form the second region).

[0222] II. Test Method 2.1 Quick charging performance At 25°C, the batteries of the above examples and comparative examples were charged and discharged for the first time at a current of 1 C (i.e., the current value that completely discharges the theoretical capacity within 1 hour). Specifically, the batteries were charged at a constant current of 1 C to a charge cut-off voltage V1, then charged at a constant voltage of ≦0.05 C, allowed to stand for 5 minutes, and then discharged at a constant current of 0.33 C to a discharge cut-off voltage V2. The actual capacity was denoted as C0. Then, the batteries are charged at a constant current of 2.8C, 3C, 3.2C, 3.5C, 3.8C, 4.1C, 4.4C, 4.7C, 5C, 5.3C, 5.6C, and 5.9C in order to the full battery charge cut-off voltage V1 or 0V negative electrode cut-off voltage (first come, first served). After each charge is completed, the batteries must be discharged at 1C to the full battery discharge cut-off voltage V2. The SOC (State of Charge) is measured at different charge rates of 10%, 20%, 30%, ..., and 80%. The negative electrode potential corresponding to the charge was recorded when the battery was charged to a charge state (SOC). Charge rate-negative electrode potential curves were plotted at different SOC states. After linear fitting, the corresponding charge rates at the negative electrode potential of 0 V at different SOC states were obtained. These charge rates are the charge windows at the respective SOC states, which are denoted as C10%SOC, C20%SOC, C30%SOC, C40%SOC, C50%SOC, C60%SOC, C70%SOC, and C80%SOC, respectively. The charge time T for the battery to charge from 10% SOC to 80% SOC was calculated according to the formula (60 / C20%SOC + 60 / C30%SOC + 60 / C40%SOC + 60 / C50%SOC + 60 / C60%SOC + 60 / C70%SOC + 60 / C80%SOC) × 10%, in minutes. The shorter the time, the better the rapid charging performance of the battery.

[0223] 2.2 Cycle performance At 25°C, the secondary batteries obtained in the above Examples and Comparative Examples were charged at a constant current of 0.5C until the end-of-charge voltage reached 4.2V, then charged at a constant voltage of 4.2V until the current reached 0.05C, allowed to stand for 5 minutes, and then discharged at a constant current of 0.5C until the end-of-discharge voltage reached 2.8V, and allowed to stand for 5 minutes, which constituted one charge-discharge cycle. According to this method, the batteries were subjected to a charge-discharge cycle test until the battery capacity retention rate attenuated to 80%, and the number of cycles at that time was recorded, and this was defined as the cycle life of the battery at 25°C.

[0224] [Table 1]

[0225] Summarizing the test results in Table 2, it can be seen that by optimizing the structure of the negative electrode piece and making the first active material in the first region comprise a silicon-oxygen-based material and the second active material in the second region comprise a silicon-carbon composite material, the secondary battery can have improved cycle life and fast charging performance.

[0226] The test results in Table 2 summarize the results. Further optimization of the negative electrode piece structure, for example, by adjusting the mass fraction A1 of the silicon-oxygen-based material in the first active material and the mass fraction A2 of the silicon-carbon composite material in the second active material to specific ranges, such as A1 being 25 wt% or less and A2 being 20 wt% or less, can further optimize the fast charging performance and / or cycling performance of the secondary battery. To further optimize the battery's energy density, A1 may be 10 wt% to 25 wt%, and A2 may be 5 wt% to 20 wt%. For example, Example 1 exhibits better cycling performance and rate performance than the other examples, but the relatively low content of added silicon-based material limits the improvement in the battery's energy density.

[0227] It should be understood 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 exhibits the same functions and effects within the scope of the technical solution of the present application is included within the technical scope of the present application. Furthermore, various modifications that can be conceived by a person skilled in the art to the embodiments and other forms formed by combining part 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 gist of the present application. [Explanation of symbols]

[0228] 1 battery pack, 2 upper case, 3 lower case, 4 battery module, 5 secondary battery, 51 casing, 52 electrode assembly, 53 top cover assembly, 101 negative electrode current collector, 102 negative electrode film layer, 102a first surface, 102b second surface, 1021 first region, 1022 second region, 1023 central region.

Claims

1. A secondary battery including a negative electrode piece, the negative electrode piece including a negative electrode current collector and a negative electrode film layer having a first surface adjacent to the negative electrode current collector and a second surface disposed opposite to the first surface, wherein the thickness of the negative electrode film layer is denoted as H, a region of the negative electrode film layer within a thickness range of 0.3H from the first surface is denoted as a first region of the negative electrode film layer, and a region of the negative electrode film layer within a thickness range of 0.3H from the second surface is denoted as a second region of the negative electrode film layer; the first region comprises a first active material and the second region comprises a second active material; the first active material comprises a silicon-oxygen based material and the second active material comprises a silicon-carbon composite material; Secondary battery.

2. When the mass ratio of the silicon-oxygen-based material in the first active material is denoted as A1 and the mass ratio of the silicon-carbon composite material in the second active material is denoted as A2, A2 / A1≦2, and optionally 0.2≦A2 / A1≦0.8; The secondary battery according to claim 1 .

3. the mass fraction of the silicon-oxygen-based material in the first active material is 30 wt % or less, and optionally 10 wt % to 25 wt %, and / or the mass fraction of the silicon-carbon composite material in the second active material is 25 wt % or less, and optionally 5 wt % to 20 wt %; The secondary battery according to claim 1 or 2.

4. The secondary battery satisfies at least one of the following (1) to (5): (1) the volume average particle diameter Dv50 of the silicon carbon composite material is larger than the volume average particle diameter Dv50 of the silicon oxygen-based material; (2) 3 × 10 of the silicon carbon composite material 4 The powder compaction density tested under a pressure of N was 3×10 4 The powder compaction density tested under a pressure of N is less than that of the powder compaction density tested under a pressure of N. (3) the tap density of the silicon carbon composite material is smaller than the tap density of the silicon oxygen-based material; (4) the specific surface area of ​​the silicon carbon composite material is larger than the specific surface area of ​​the silicon oxygen-based material; (5) The powder resistivity of the silicon carbon composite material tested under a pressure of 16 MPa is greater than the powder resistivity of the silicon oxygen-based material tested under a pressure of 16 MPa. The secondary battery according to any one of claims 1 to 3.

5. The silicon carbon composite material includes a carbon matrix and a silicon-based material disposed in the carbon matrix. The secondary battery according to any one of claims 1 to 6.

6. The silicon carbon composite material satisfies at least one of the following (1) to (7): (1) the initial coulombic efficiency of the silicon carbon composite is ≧90 wt %, and optionally 91 wt % to 94 wt %; (2) the volume particle size Dv50 of the silicon carbon composite material is 3 μm to 15 μm, and optionally 5 μm to 12 μm; (3) the volume particle size Dv90 of the silicon carbon composite material is ≦60 μm, optionally 20 μm to 40 μm; (4) the particle size distribution (Dv90-Dv10) / Dv50 of the silicon carbon composite material is 1.0 to 3.0, and optionally 1.0 to 2.0; (5) The BET specific surface area of ​​the silicon carbon composite material is 20 m 2 / g or less, and optionally 1m 2 / g to 10m 2 / g, (6) The powder resistivity of the silicon carbon composite material under a pressure of 16 MPa is ≦300 Ω cm, and optionally ≦50 Ω cm; (7) The tap density of the silicon carbon composite material is 0.8 g / cm 3 ~1.0 g / cm 3 and optionally 0.9 g / cm 3 ~1.0 g / cm 3 and (8) The silicon content of the silicon carbon composite material is 30 wt% or more, and optionally 40 wt% to 60 wt%; (9) The content of carbon element in the silicon carbon composite material is 40 wt% or more, and optionally 45 wt% to 60 wt%; (10) The content of oxygen element in the silicon carbon composite material is 10 wt% or less, and optionally 1 wt% to 5 wt%; The secondary battery according to any one of claims 1 to 8.

7. The silicon-oxygen-based material comprises an alkali metal-containing or alkaline earth metal-containing silicate. The secondary battery according to any one of claims 1 to 9.

8. The silicon-oxygen-based material contains an alkali metal-containing silicate, and in an XRD diffraction pattern, the silicon-oxygen-based material satisfies the following: a half-width of a diffraction peak corresponding to the alkali metal-containing silicate is 0.5° to 2.0°; and / or a crystal grain size of the silicate corresponding to the alkali metal-containing silicate is 4 nm to 17 nm. The secondary battery according to any one of claims 1 to 10.

9. The silicon and oxygen-based material contains an alkaline earth metal-containing silicate, and in an XRD diffraction pattern, the silicon and oxygen-based material satisfies the following: a half-width of a diffraction peak corresponding to the alkaline earth metal-containing silicate is 0.3° to 0.6°; and / or a crystal grain size of the silicate corresponding to the alkaline earth metal-containing silicate is 12 nm to 20 nm. The secondary battery according to any one of claims 1 to 10.

10. The silicon-oxygen-based material satisfies at least one of the following (1) to (7): (1) the volume particle diameter Dv50 of the silicon-oxygen-based material is 3 μm to 20 μm, and optionally 5 μm to 15 μm; (2) the volume particle diameter Dv90 of the silicon-oxygen-based material is ≦60 μm, optionally 10 μm to 25 μm; (3) the particle size distribution (Dv90-Dv10) / Dv50 of the silicon-oxygen-based material is 1.0 to 2, and optionally 1.0 to 1.5; (4) The BET specific surface area of ​​the silicon-oxygen-based material is 1 m 2 / g to 6m 2 / g, and optionally 1m 2 / g to 5m 2 / g, (5) The tap density of the silicon-oxygen-based material is 1.05 g / cm 3 ~1.25g / cm 3 and optionally 1.1 g / cm 3 ~1.2 g / cm 3 and (6) The silicon element content in the silicon-oxygen-based material is 40 wt% or more, and optionally 45 wt% to 65 wt%; (7) The content of oxygen element in the silicon-oxygen-based material is 30 wt% or more, and optionally 30 wt% to 50 wt%; (8) The content of carbon element in the silicon-oxygen-based material is 8 wt% or less, and optionally 2 wt% to 5 wt%; The secondary battery according to any one of claims 1 to 12.

11. The first active material and / or the second active material further include a carbon-based material, and optionally, the carbon-based material includes at least one of artificial graphite, natural graphite, soft carbon, and hard carbon. The secondary battery according to any one of claims 1 to 13.

12. When the first active material includes a first carbon-based material and the second active material includes a second carbon-based material, the secondary battery satisfies any one of the following conditions: (1) The first carbon-based material includes primary particles, and optionally, the quantity ratio of the primary particles in the first carbon-based material is ≧70%; (2) The second carbon-based material includes secondary particles, and optionally, the quantity ratio of the secondary particles in the second carbon-based material is ≧70%; (3) The volume average particle diameter Dv50 of the first carbon-based material is smaller than the volume average particle diameter Dv50 of the second carbon-based material; (4) The tap density of the first carbon-based material is greater than the tap density of the second carbon-based material; (5) The first carbon-based material has a higher compression density than the second carbon-based material. The secondary battery according to any one of claims 1 to 14.

13. The first carbon-based material satisfies at least one of the following conditions (1) to (7): (1) the volume particle diameter Dv50 of the first carbon-based material is 5 μm to 20 μm, and optionally 8 μm to 15 μm; (2) the volume particle diameter Dv90 of the first carbonaceous material is ≦50 μm, and optionally 25 μm to 40 μm; (3) the particle size distribution (Dv90-Dv10) / Dv50 of the first carbonaceous material is 1.0 to 2.5, and optionally 1.0 to 1.8; (4) The BET specific surface area of ​​the first carbon-based material is 0.5 m 2 / g to 4m 2 / g, and optionally 1m 2 / g to 3m 2 / g, (5) The tap density of the first carbon-based material is 1.0 g / cm 3 ~1.25g / cm 3 and optionally 1.1 g / cm 3 ~1.2 g / cm 3 and (6) The powder compact density of the first carbon-based material tested under a pressure of 30,000 N is 1.6 g / cm 3 ~1.9 g / cm 3 and optionally 1.65 g / cm 3 ~1.8g / cm 3 That is, The secondary battery according to any one of claims 1 to 15.

14. The second carbon-based material satisfies at least one of the following conditions (1) to (7): (1) the volume particle diameter Dv50 of the second carbon-based material is 8 μm to 25 μm, and optionally 12 μm to 18 μm; (2) the volume particle diameter Dv90 of the second carbon-based material is ≦60 μm, and optionally 35 μm to 50 μm; (3) the particle size distribution (Dv90-Dv10) / Dv50 of the second carbon-based material is 1.0 to 2.0, and optionally 1.0 to 1.5; (4) The BET specific surface area of ​​the second carbon-based material is 1 m 2 / g to 5m 2 / g, and optionally 1m 2 / g to 3m 2 / g, (5) The tap density of the second carbon-based material is 0.9 g / cm 3 ~1.2 g / cm 3 and optionally 1.0 g / cm 3 ~1.1 g / cm 3 and (6) The powder compact density of the second carbon-based material tested under a pressure of 30,000 N is 1.5 g / cm 3 ~1.75g / cm 3 and optionally 1.55 g / cm 3 ~1.7g / cm 3 That is, The secondary battery according to any one of claims 1 to 16.

15. a central region located between the first region and the second region, comprising the silicon carbon composite material and / or the silicon oxygen-based material; The secondary battery according to any one of claims 1 to 17.

16. The secondary battery according to claim 18, Electrical equipment.

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