Secondary battery, battery module, battery pack, and electric device

Abstract

The application provides a secondary battery, a battery module, a battery pack and a power utilization device. The secondary battery comprises a negative electrode sheet and a positive electrode sheet; the negative electrode active material comprises a first negative electrode active material selected from one or more of a silicon-based material and a tin-based material; and the positive electrode active material comprises a first positive electrode active material, the molecular formula of the first positive electrode active material being M1 x Mn y M2 z O a A b , M1 represents one or both of Mg and Al, M2 represents one or both of Co and Ni, A represents one or more of N, P and S, 0 The application can make the secondary battery have high energy density and significantly improved cycle performance and storage performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and particularly relates to a secondary battery, a battery module, a battery pack and a power utilization device. BACKGROUND

[0002] In recent years, secondary batteries are widely applied in energy storage power supply systems such as hydraulic, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. With the application and promotion of secondary batteries, their energy density has attracted more and more attention. The energy density of a secondary battery is closely related to the gram capacity of the positive and negative active materials. At present, the improvement of the energy density of a secondary battery is very limited no matter what kind of positive active material is selected. Therefore, researchers consider using high-gram-capacity negative active materials to improve the overall energy density of a secondary battery. Graphite is the most commonly used negative active material, but its theoretical gram capacity is only 372 mAh / g, which has been difficult to meet the actual needs of high-energy-density secondary batteries. Among non-carbon negative active materials, silicon-based materials and tin-based materials have become one of the most promising negative active materials due to their ultra-high capacity advantage (for example, the theoretical gram capacity of silicon is 4200 mAh / g, and the theoretical gram capacity of tin is 990 mAh / g) and low cost advantage. However, silicon-based materials and tin-based materials will undergo a huge volume change during charging and discharging, resulting in poor cycle performance and storage performance of the secondary battery, which is currently difficult to be used on a large scale in commercial use. SUMMARY

[0003] The purpose of the application is to provide a secondary battery, a battery module, a battery pack and a power utilization device, aiming to make the secondary battery have high energy density and significantly improved cycle performance and storage performance.

[0004] The first aspect of the application provides a secondary battery, comprising a negative electrode sheet and a positive electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, the negative electrode film layer comprising a negative active material; the positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, the positive electrode film layer comprising a positive active material. Wherein the negative active material comprises a first negative active material, the first negative active material being selected from one or more of silicon-based materials and tin-based materials; the positive active material comprises a first positive active material, the molecular formula of the first positive active material being M1 x Mn y M2 z O a A bM1 represents one or both of Mg and Al, M2 represents one or both of Co and Ni, A represents one or more of N, P, and S, 0

[0005] When the positive electrode active material comprises a first positive electrode active material with a molecular formula of M1 x Mn y M2 z O a A b The first positive electrode active material can reserve more expandable space for the silicon-based material and the tin-based material, thereby reducing the negative effects of the volume expansion of the silicon-based material and the tin-based material, and further the secondary battery of the present application can have significantly improved cycle performance and storage performance while having high energy density.

[0006] In any embodiment of the present application, the mass percentage content of the first positive electrode active material is 2% to 70% based on the total mass of the positive electrode film layer. Alternatively, the mass percentage content of the first positive electrode active material is 2.4% to 55%. When the mass percentage content of the first positive electrode active material is within the appropriate range, the negative effects of the volume expansion of the silicon-based material and the tin-based material can be effectively reduced, and further the cycle performance and storage performance of the secondary battery can be improved.

[0007] In any embodiment of the present application, the mass ratio of the first positive electrode active material to the first negative electrode active material is (0.48 to 0.70):1. When the mass ratio of the first positive electrode active material to the first negative electrode active material is within the appropriate range, the secondary battery can have high energy density while also having significantly improved cycle performance and storage performance.

[0008] In any embodiment of the present application, the mass percentage content of the first negative electrode active material is 5% to 50% based on the total mass of the negative electrode film layer. Alternatively, the mass percentage content of the first negative electrode active material is 5% to 29%. When the mass percentage content of the first negative electrode active material is within the appropriate range, the secondary battery can have high energy density while also having significantly improved cycle performance and storage performance.

[0009] In any embodiment of the present application, 0

[0010] In any embodiment of the present application, 0

[0011] In any embodiment of the present application, 0

[0012] In any embodiment of the present application, 0

[0013] In any embodiment of the present application, the first positive electrode active material has a spinel structure and / or a layered structure, thereby facilitating the extraction and insertion of M1 ions.

[0014] In any embodiment of the present application, the first positive electrode active material comprises one or more of MgMn2O4, Mg2Mn2O4, Al2Mn2O5, MgAlMnO4, Mg2AlMnO5, Mg2Mn 1.5 Ni 0.5 O4, Mg2Mn 1.5 Ni 0.5 O 3.2 S 0.8 .

[0015] In any embodiment of the present application, the first positive electrode active material has a volume average particle size Dv50 of 8 μm to 20 μm. When the volume average particle size Dv50 of the first positive electrode active material is within the appropriate range, the negative effects of the volume expansion of the silicon-based material and the tin-based material can be effectively reduced, and the cycle performance and storage performance of the secondary battery can be further improved.

[0016] In any embodiment of the present application, the first positive electrode active material has a specific surface area of 0.2 m 2 / g to 0.9 m 2 / g. When the specific surface area of the first positive electrode active material is within the appropriate range, the negative effects of the volume expansion of the silicon-based material and the tin-based material can be effectively reduced, and the cycle performance and storage performance of the secondary battery can be further improved.

[0017] In any embodiment of the present application, the silicon-based material comprises one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material.

[0018] In any embodiment of the present application, the tin-based material comprises one or more of elemental tin, tin oxide, tin-carbon composite, and tin alloy material.

[0019] In any embodiment of the present application, the secondary battery is a lithium ion battery, a sodium ion battery, a potassium ion battery, a zinc ion battery, a calcium ion battery, or a barium ion battery.

[0020] The second aspect of the present application provides a battery module comprising the secondary battery of the first aspect of the present application.

[0021] The third aspect of the present application provides a battery pack comprising one of the secondary battery of the first aspect of the present application and the battery module of the second aspect of the present application.

[0022] The fourth aspect of the present application provides a power consumption device comprising at least one of the secondary battery of the first aspect, the battery module of the second aspect, and the battery pack of the third aspect of the present application.

[0023] The positive electrode sheet of the secondary battery of the present application comprises a first positive electrode active material with a molecular formula of M1 x Mn y M2 z O a A b The first positive electrode active material can reserve more expandable space for silicon-based materials and tin-based materials, thereby reducing the negative effects of volume expansion of the silicon-based materials and tin-based materials. Therefore, the secondary battery of the present application can have significantly improved cycle performance and storage performance while having high energy density. The battery module, the battery pack, and the power consumption device of the present application comprise the secondary battery provided by the present application, and thus at least have the same advantages as the secondary battery. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the drawings.

[0025] FIG. 1 is a schematic diagram of an embodiment of the secondary battery of the present application.

[0026] FIG. 2 is an exploded schematic diagram of the embodiment of the secondary battery shown in FIG. 1

[0027] FIG. 3 is a schematic diagram of an embodiment of the battery module of the present application.

[0028] FIG. 4 is a schematic diagram of an embodiment of the battery pack of the present application.

[0029] FIG. 5 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 4

[0030] FIG. 6 is a schematic diagram of an embodiment of the power consumption device comprising the secondary battery of the present application as a power supply.

[0031] In the drawings, the drawings are not necessarily drawn according to the actual scale. DETAILED DESCRIPTION

[0032] ​​Hereinafter, specific embodiments of a secondary battery, a battery module, a battery pack, and an electric device of the present application will be described in detail with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters known to those skilled in the art, repeated description of substantially identical configurations, is omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0033] The ranges disclosed herein are defined by their lower and upper limits. Ranges can be defined by any upper and lower limits, whether or not they are explicitly disclosed. Ranges can be combined, i.e., any lower limit of a range or a value can be combined with any upper limit of another range or value. For example, if a range of 60-120 and a range of 80-110 are disclosed, it is understood that a range of 60-110 and a range of 80-120 are also disclosed. Furthermore, if a minimum range value of 1 and 2 are disclosed, and if a maximum range value of 3, 4, and 5 are disclosed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise indicated, a numerical range "a-b" means a range of any integer between a and b, wherein a and b are both integers. For example, the numerical range "0-5" means that all integers between 0 and 5 are contemplated herein, and "0-5" is merely a shorthand for listing all of those integers. Also, when a parameter is stated to be an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0034] If not specifically stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0035] If not specifically stated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0036] If not specified otherwise, all steps of the present application can be performed in sequence or randomly, preferably in sequence. For example, the method comprising steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method can further comprise step (c) means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0037] If not specified otherwise, the terms "comprising" and "including" as used in the present application are open-ended and also include the case where the listed component is the only component. For example, the terms "comprising" and "including" can mean that the method or composition can include other components not listed.

[0038] If not specified otherwise, the term "or" as used in the present application 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).

[0039] If not specified otherwise, the term "silicon-based material" as used in the present application refers to a type of negative active material comprising silicon element and having high gravimetric capacity, which can include but is not limited to one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, silicon alloy material.

[0040] If not specified otherwise, the term "tin-based material" as used in the present application refers to a type of negative active material comprising tin element and having high gravimetric capacity, which can include but is not limited to one or more of elemental tin, tin oxide, tin-carbon composite, tin alloy material.

[0041] If not specified otherwise, the term "active ion" as used in the present application refers to an ion that can be reversibly intercalated and deintercalated between the positive and negative electrodes of a secondary battery, including but not limited to lithium ion, sodium ion, potassium ion, zinc ion, calcium ion, or barium ion, etc.

[0042] Secondary batteries, also known as rechargeable batteries or accumulators, are batteries that can be activated by charging after discharging and continue to be used. Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. During the charging and discharging process of the battery, active ions are embedded and de-embedded between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent short circuiting of the positive and negative electrodes, and at the same time to allow the active ions to pass through. The electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet. Currently, secondary batteries are widely used in energy storage power systems such as hydroelectric, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. In order to better adapt to the sustainable development strategy of the environment and energy, secondary batteries need to meet high energy density and excellent cycle performance and storage performance at the same time.

[0043] The theoretical gram capacity of silicon is 4200 mAh / g, and the theoretical gram capacity of tin is 990 mAh / g, which is much higher than the theoretical gram capacity of graphite of 372 mAh / g. Therefore, both of them are negative active materials with potential application value for high energy density secondary batteries. However, silicon and tin will undergo a huge volume change during the charging and discharging process, which will generate a large stress inside the negative active material particles, and the negative active material is prone to pulverization and detachment from the negative electrode film layer, and the capacity of the secondary battery is prone to rapid decay and deterioration of the cycle performance. When silicon and tin undergo a huge volume change during the charging and discharging process, they are also prone to extruding the electrode sheet (such as the positive electrode sheet, the negative electrode sheet), thereby increasing the risk of electrode sheet fracture. In addition, when silicon and tin undergo a huge volume change during the charging and discharging process, the porosity of the electrode sheet is prone to decrease due to extrusion, thereby increasing the internal resistance of the secondary battery, and the active ions (such as lithium ions, etc.) are prone to be reduced and precipitated on the surface of the negative electrode sheet, thereby seriously affecting the safety performance of the secondary battery.

[0044] Although preparing silicon (or tin) into an oxide or forming a composite of silicon (or tin) and other materials (such as carbon materials) can inhibit the volume change during the charging and discharging process to some extent, the technical effect is limited, and the improvement of the cycle performance of the secondary battery is not obvious.

[0045] The inventors of the present application have conducted in-depth research and proposed a technical solution that can effectively reduce the negative effects of volume expansion of silicon-based materials and tin-based materials, and make the secondary battery have significantly improved cycle performance and storage performance, and is suitable for large-scale commercial use.

[0046] In a first aspect, the present application provides a secondary battery, which comprises a negative electrode tab and a positive electrode tab. The negative electrode tab comprises a negative current collector and a negative film layer arranged on at least one surface of the negative current collector, the negative film layer comprising a negative active material; the positive electrode tab comprises a positive current collector and a positive film layer arranged on at least one surface of the positive current collector, the positive film layer comprising a positive active material. The negative active material comprises a first negative active material selected from one or more of a silicon-based material and a tin-based material; the positive active material comprises a first positive active material having a molecular formula of M1 x Mn y M2 z O a A b , M1 represents one or both of Mg and Al, M2 represents one or both of Co and Ni, A represents one or more of N, P, and S, 0 < x ≤ 3, 0 < y ≤ 6, 0 ≤ z ≤ 6, 0 < y + z ≤ 8, 0 < a ≤ 12, 0 ≤ b ≤ 12, and 0 < a + b ≤ 15.

[0047] The secondary battery of the present application is not particularly limited, and may be, for example, a lithium ion battery, a sodium ion battery, a potassium ion battery, a zinc ion battery, a calcium ion battery, or a barium ion battery.

[0048] In the secondary battery of the present application, the negative active material comprises one or more of a silicon-based material and a tin-based material, and thus the secondary battery of the present application can have the advantage of high energy density.

[0049] In the secondary battery of the present application, the positive active material comprises a first positive active material having a molecular formula of M1 x Mn y M2 z O a A b , M1 represents one or both of Mg and Al, and the ionic radius of M1 is smaller than that of an active ion (e.g., a lithium ion, a sodium ion, a potassium ion, a zinc ion, a calcium ion, or a barium ion). During charging of the secondary battery, M1 ions can react with the silicon-based material and the tin-based material to form alloying products in preference to active ions. Since the ionic radius of M1 is smaller than that of the active ion, the alloying products formed by M1 ions can have smaller volume expansion, so that the negative active material is less likely to be pulverized, thereby inhibiting rapid capacity decay of the secondary battery and significantly improving the cycle performance, storage performance, and safety performance of the secondary battery. The alloying products formed by M1 ions have smaller volume expansion, which can provide more space for expansion of the active ion during the reaction of the active ion with the silicon-based material and the tin-based material to form alloying products.

[0050] Therefore, when the positive active material comprises a first positive active material having a molecular formula of M1 x Mn y M2 z O a A b When the first positive active material has a molecular formula of M1

[0051] The M1 ions can also preferentially react with the silicon-based material and the tin-based material to form porous materials (e.g., MgO, Mg2SiO4, Mg2SiO3, etc.) such as M1-O, M1-N, M1-Si-O, M1-Si-N, M1-Sn-O, etc. that have no electrochemical activity. These porous materials can hardly participate in the reaction in the subsequent cycle process, but can play a role in buffering volume expansion, inhibiting the pulverization of the negative active material, stabilizing the solid electrolyte interface film (SEI film) on the surface of the negative active material, and reducing the continuous irreversible consumption of active ions, thereby improving the cycle performance and storage performance of the secondary battery.

[0052] The secondary battery of the present application has a simple preparation process, high energy density, and excellent cycle performance and storage performance, and is suitable for large-scale commercial use.

[0053] In some embodiments, 0 < y < 5, 0 < y < 4, 0 < y < 3, or 0 < y < 2.

[0054] In some embodiments, z = 0.

[0055] In some embodiments, 0 < z < 6. Alternatively, 0 < z < 5, 0 < z < 4, 0 < z < 3, 0 < z < 2, or 0 < z < 1.

[0056] In some embodiments, 0 < y < 6, z = 0.

[0057] In some embodiments, 0 < y < 3, z = 0.

[0058] In some embodiments, 0 < y < 3, 0 < z < 1, and 0 < y + z < 4.

[0059] In some embodiments, 0 < y < 6, 0 < z < 1, and 0 < y + z < 7.

[0060] In some embodiments, 0 < a < 12, b = 0.

[0061] In some embodiments, b = 0.

[0062] In some embodiments, 0 < b < 12, optionally, 0 < b < 10, 0 < b < 8, 0 < b < 6, or 0 < b < 4, 0 < b < 2, or 0 < b < 1.

[0063] In some embodiments, 0 < a < 12, b = 0.

[0064] In some embodiments, 0 < a < 5, b = 0.

[0065] In some embodiments, 0 < a < 5, 0 < b < 1, and 0 < a + b < 6.

[0066] In some embodiments, 0 < a < 12, 0 < b < 2, and 0 < a + b < 14.

[0067] In some embodiments, 0 < x < 3, 0 < y < 3, z = 0, 0 < a < 5, b = 0.

[0068] In some embodiments, 0 < x < 3, 0 < y < 3, 0 < z < 1, 0 < a < 5, b = 0.

[0069] In some embodiments, 0 < x < 3, 0 < y < 3, z = 0, 0 < a < 5, 0 < b < 1.

[0070] In some embodiments, 0 < x < 3, 0 < y < 3, 0 < z < 1, 0 < a < 5, 0 < b < 1.

[0071] In some embodiments, M1represents Mg.

[0072] In some embodiments, M1represents Al.

[0073] In some embodiments, M1represents a combination of Mg and Al.

[0074] In some embodiments, as examples, the first positive electrode active material comprises one or more of MgMn2O4, Mg2Mn2O4, Al2Mn2O5, MgAlMnO4, Mg2AlMnO5, Mg2Mn 1.5 Ni 0.5 O4, Mg2Mn 1.5 Ni 0.5 O 3.2 S 0.8 In some embodiments, as examples, the first positive electrode active material comprises one or more of MgMn2O4, Mg2Mn2O4, Al2Mn2O5, MgAlMnO4, Mg2AlMnO5, Mg2Mn

[0075] In some embodiments, the first positive electrode active material has a spinel structure and / or a layered structure. M1 x Mn y M2 z O a A b When having a spinel structure or a layered structure, it is beneficial for the extraction and insertion of M1 ions.

[0076] In some embodiments, the first positive electrode active material has a volume average particle size Dv50 of 8 μm to 20 μm. For example, the first positive electrode active material has a volume average particle size Dv50 of 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm or any range formed by any of the above values. Alternatively, the first positive electrode active material has a volume average particle size Dv50 of 8 μm to 18 μm, 8 μm to 16 μm, 8 μm to 14 μm, 8 μm to 12 μm, 8 μm to 10 μm, 10 μm to 20 μm, 10 μm to 18 μm, 10 μm to 16 μm, 10 μm to 14 μm, 10 μm to 12 μm, 12 μm to 20 μm, 12 μm to 18 μm, 12 μm to 16 μm, 12 μm to 14 μm, 14 μm to 20 μm, 14 μm to 18 μm, 14 μm to 16 μm, 16 μm to 20 μm, 16 μm to 18 μm, or 18 μm to 20 μm. When the volume average particle size Dv50 of the first positive electrode active material is large, the first positive electrode active material can have a high tap density, but the crystal structure of the first positive electrode active material can be deformed, leading to a decrease in the specific capacity, thereby possibly reducing the cycle performance and storage performance of the secondary battery. When the volume average particle size Dv50 of the first positive electrode active material is small, the boundaries between the first positive electrode active material particles increase, and the electron transport is difficult, thereby possibly increasing the polarization of the secondary battery and reducing the cycle performance and storage performance of the secondary battery. When the volume average particle size Dv50 of the first positive electrode active material is within an appropriate range, the negative effects of the volume expansion of the silicon-based material and the tin-based material can be effectively reduced, and the cycle performance and storage performance of the secondary battery can be further improved.

[0077] In the present application, the volume average particle size Dv50 of the first positive electrode active material has the meaning known in the art, which represents the particle size corresponding to the cumulative volume distribution percentage of 50%, and can be measured by using the instruments and methods known in the art. For example, GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method can be referred to, and a laser particle size analyzer, such as Mastersizer 2000E laser particle size analyzer of Malvern Instruments Ltd., UK, can be conveniently used for the measurement.

[0078] In some embodiments, the specific surface area of the first positive electrode active material is 0.2 m 2 / g~0.9m 2 / g. For example, the specific surface area of the first positive electrode active material is 0.2m 2 / g, 0.3m 2 / g, 0.4m 2 / g, 0.5m 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g or any range derived from any two of the above. Alternatively, the specific surface area of the first positive electrode active material is 0.2m 2 / g~0.8m 2 / g, 0.2m 2 / g~0.7m 2 / g, 0.2m 2 / g~0.6m 2 / g, 0.2m 2 / g~0.5m 2 / g, 0.2m 2 / g~0.4m 2 / g, 0.2m 2 / g~0.3m 2 / g, 0.3m 2 / g~0.9m 2 / g, 0.3m 2 / g~0.8m 2 / g, 0.3m 2 / g~0.7m 2 / g, 0.3m 2 / g~0.6m 2 / g, 0.3m 2 / g~0.5m 2 / g, 0.3m 2 / g~0.4m 2 / g, 0.4m 2 / g~0.9m 2 / g, 0.4m 2 / g~0.8m 2 / g, 0.4m 2 / g~0.7m 2 / g, 0.4m 2 / g~0.6m 2 / g, 0.4m 2 / g~0.5m 2 / g, 0.5m 2 / g~0.9m 2 / g, 0.5m 2 / g~0.8m 2 / g, 0.5m2 / g~0.7m 2 / g, 0.5m 2 / g~0.6m 2 / g, 0.6m 2 / g~0.9m 2 / g, 0.6m 2 / g~0.8m 2 / g, 0.6m 2 / g~0.7m 2 / g, 0.7m 2 / g~0.9m 2 / g, 0.7m 2 / g~0.8m 2 / g, or 0.8m 2 / g~0.9m 2 / g. When the specific surface area of the first positive electrode active material is large, more M1 ions are lost during the cycle of the secondary battery, thereby reducing the content of active M1 ions, which is not conducive to reducing the negative effects of volume expansion of the silicon-based material and the tin-based material. When the specific surface area of the first positive electrode active material is low, the wettability of the first positive electrode active material with the electrolyte is poor, which is not conducive to the extraction and embedding of M1 ions, thereby the cycle performance and storage performance of the secondary battery are poor. When the specific surface area of the first positive electrode active material is within an appropriate range, the negative effects of volume expansion of the silicon-based material and the tin-based material can be effectively reduced, and the cycle performance and storage performance of the secondary battery can be further improved.

[0079] In the present application, the specific surface area of the first positive electrode active material has the meaning known in the art and can be determined by instruments and methods known in the art. For example, GB / T 19587-2017 can be referred to, and the nitrogen adsorption specific surface area analysis test can be tested by the Tri-Star 3020 type specific surface area pore size analyzer of the American Micromeritics company, and the BET (Brunauer Emmett Teller) method is used for calculation.

[0080] The first positive electrode active material M1 x Mn y M2 z O a A bThe first positive electrode active material can be prepared according to methods known in the art. An exemplary preparation method includes the steps of: mixing a Mn source and an ammonium salt in a certain proportion, filtering and drying to obtain a precursor; adding the precursor into a reducing solvent to reduce to obtain a sol; aging the sol with an optional M2 element precursor at a certain temperature for a certain time to obtain a gel; performing ion exchange of the gel with an M1 element precursor aqueous solution, then transferring to a reactor and continuing hydrothermal reaction with an optional A element precursor at a certain temperature for a certain time to obtain a precipitate; filtering, washing and drying the precipitate to obtain a first positive electrode active material with a molecular formula of M1 x Mn y M2 z O a A b .

[0081] As an example, the Mn source includes but is not limited to potassium permanganate; the ammonium salt includes but is not limited to one or more of tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium bromide; the A element precursor includes but is not limited to one or more of ammonium nitrate, ammonium nitrite, ammonium carbonate, ammonium bicarbonate, ammonium phosphate, phosphoric acid, ammonium sulfate, ammonium bisulfate, ammonium bisulfite, ammonium sulfite, ammonium hydrosulfide, hydrogen sulfide, sodium sulfide, ammonium sulfide and elemental sulfur; the M1 element precursor includes but is not limited to one or more of hydrochloride, nitrate and sulfate of the M1 element, such as one or more of magnesium chloride, magnesium nitrate, magnesium sulfate, aluminum chloride and aluminum nitrate; the M2 element precursor includes but is not limited to one or more of hydrochloride, nitrate, sulfate and acetate of the M2 element, such as one or more of cobalt acetate and nickel acetate.

[0082] As an example, the reducing solvent for reducing the precursor can be a mixed solvent composed of water and sec-butanol. Alternatively, the volume ratio of water to sec-butanol is 1:1 to 1:5.

[0083] As an example, the sol aging temperature is 60°C to 80°C, and the aging time is 24h to 48h.

[0084] As an example, the ion exchange time of the gel with the M1 element precursor aqueous solution is 1h to 8h.

[0085] As an example, the hydrothermal reaction temperature is 100°C to 250°C, and is optionally 150°C to 200°C; the hydrothermal reaction time is 4h to 40h.

[0086] In some embodiments, the first positive active material has a mass percentage of 2% to 70% based on the total mass of the positive electrode film layer. For example, the first positive active material has a mass percentage of 2%, 2.4%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or any range between any of these values. Alternatively, the first positive active material has a mass percentage of 2% to 65%, 2% to 60%, 2% to 55%, 2% to 50%, 2% to 45%, 2% to 40%, 2% to 35%, 2% to 30%, 2% to 25%, 2% to 20%, 2% to 15%, 2% to 10%, 2.4% to 70%, 2.4% to 65%, 2.4% to 60%, 2.4% to 55%, 2.4% to 50%, 2.4% to 45%, 2.4% to 40%, 2.4% to 35%, 2.4% to 30%, 2.4% to 25%, 2.4% to 20%, 2.4% to 15%, 2.4% to 10%, 3% to 70%, 3% to 65%, 3% to 60%, 3% to 55%, 3% to 50%, 3% to 45%, 3% to 40%, 3% to 35%, 3% to 30%, 3% to 25%, 3% to 20%, 3% to 15%, or 3% to 10%. When the mass percentage of the first positive active material is low, the negative effects of volume expansion of silicon-based materials and tin-based materials cannot be effectively reduced, and the improvement of the cycle performance and storage performance of the secondary battery is not obvious. When the mass percentage of the first positive active material is high, an SEI film with insulating properties is easily formed on the surface of the negative active material, which hinders the extraction and insertion of active ions, and at the same time, more side reactions occur between the first positive active material and the electrolyte, so the cycle performance and storage performance of the secondary battery cannot be effectively improved. When the mass percentage of the first positive active material is within an appropriate range, the negative effects of volume expansion of silicon-based materials and tin-based materials can be effectively reduced, and the cycle performance and storage performance of the secondary battery can be further improved.

[0087] In some embodiments, the mass ratio of the first positive electrode active material to the first negative electrode active material is (0.48-0.70): 1. For example, the mass ratio of the first positive electrode active material to the first negative electrode active material is 0.48: 1, 0.50: 1, 0.52: 1, 0.54: 1, 0.56: 1, 0.58: 1, 0.60: 1, 0.62: 1, 0.64: 1, 0.66: 1, 0.68: 1, 0.70: 1, or any range formed by any of the above values. Alternatively, the mass ratio of the first positive electrode active material to the first negative electrode active material is (0.48-0.68): 1, (0.48-0.66): 1, (0.48-0.64): 1, (0.48-0.62): 1, (0.48-0.60): 1, (0.48-0.58): 1, (0.48-0.56): 1, (0.48-0.54): 1, (0.48-0.52): 1, (0.50-0.70): 1, (0.50-0.68): 1, (0.50-0.66): 1, (0.50-0.64): 1, (0.50-0.62): 1, (0.50-0.60): 1, (0.50-0.58): 1, (0.50-0.56): 1, (0.50-0.54): 1, (0.52-0.70): 1, (0.52-0.68): 1, (0.52-0.66): 1, (0.52-0.64): 1, (0.52-0.62): 1, (0.52-0.60): 1, (0.52-0.58): 1, (0.52-0.56): 1, (0.54-0.70): 1, (0.54-0.68): 1, (0.54-0.66): 1, (0.54-0.64): 1, (0.54-0.62): 1, (0.54-0.60): 1, or (0.54-0.58): 1. When the mass ratio of the first positive electrode active material to the first negative electrode active material is within the appropriate range, the first positive electrode active material and the first negative electrode active material have better synergy, thereby ensuring that the secondary battery has high energy density while also having significantly improved cycle performance and storage performance.

[0088] In some embodiments, the first negative electrode active material is a silicon-based material, and the mass ratio of the first positive electrode active material to the silicon-based material is (0.48-0.70): 1.

[0089] In some embodiments, the first negative electrode active material is a tin-based material, and the mass ratio of the first positive electrode active material to the silicon-based material is (0.48-0.70): 1.

[0090] In some embodiments, the first negative active material is a combination of a silicon-based material and a tin-based material, and the ratio of the mass of the first negative active material to the sum of the masses of the silicon-based material and the tin-based material is (0.48-0.70): 1.

[0091] In some embodiments, the first negative active material has a mass percentage content of 5-50% based on the total mass of the negative electrode film layer. For example, the first negative active material has a mass percentage content of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 35%, 40%, 45%, 50%, or any range derived from any of these values. Alternatively, the first negative active material has a mass percentage content of 5-45%, 5-40%, 5-35%, 5-30%, 5-29%, 5-28%, 5-27%, 5-26%, 5-25%, 5-24%, 5-23%, 5-22%, 5-21%, 5-20%, 5-19%, 5-18%, 5-17%, 5-16%, 5-15%, 5-14%, 5-13%, 5-12%, 5-11%, or 5-10%. When the mass percentage content of the first negative active material is within an appropriate range, the secondary battery can have high energy density while also having significantly improved cycle performance and storage performance.

[0092] In some embodiments, the positive active material further includes a second positive active material. The second positive active material is selected from materials capable of deintercalating and intercalating active ions (e.g., lithium ions, sodium ions, potassium ions, zinc ions, calcium ions, or barium ions, etc.). The present application does not particularly limit the type of second positive active material, and a positive active material for a secondary battery known in the art can be used, for example, a positive active material that can be used in a lithium-ion battery, a sodium-ion battery, a potassium-ion battery, a zinc-ion battery, a calcium-ion battery, or a barium-ion battery. As an example, the second positive active material includes, but is not limited to, one or more of lithium transition metal oxides, lithium-containing phosphates, sodium transition metal oxides, potassium transition metal oxides, polyanion materials, Prussian blue materials, and modified compounds thereof. These second positive active materials can be used alone or in combination with two or more.

[0093] Examples of lithium transition metal oxides can include, but are not limited to, one or several of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium-rich manganese-based materials, and modified compounds thereof. Examples of lithium-containing phosphates can include, but are not limited to, one or several of lithium iron phosphate, a composite of lithium iron phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon, and modified compounds of each thereof.

[0094] For example, when the secondary battery of the present application is a lithium ion battery, the second positive electrode active material can include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.85 Co 0.15 Al 0.05 O2, mLi2MnO3·(1–m)LiMnO2(0<m<1), LiFePO4, and LiMnPO4. When the secondary battery of the present application is a sodium ion battery, the second positive electrode active material can include, but is not limited to, NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, NaNi 1 / 2 Ti 1 / 2 O2, NaNi 1 / 2 Mn 1 / 2 O2, Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2, NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, NaFePO4, NaMnPO4, NaCoPO4, B a1 M b1 (PO4) c1 O x1 Y 3-x1 (wherein B is selected from H + , Li + , Na + , K + , and NH4 +M is one or more of the following, M is a transition metal cation, preferably one or more of V, Ti, Mn, Fe, Co, Ni, Cu and Zn, Y is a halide anion, preferably one or more of F, Cl and Br, and 0 < a1 ≤ 4, 0 < b1 ≤ 2, 1 ≤ c1 ≤ 3, 0 ≤ x1 ≤ 2.

[0095] In this application, the modified compounds of each of the above-mentioned second positive electrode active materials can be doped, surface coated, or doped and surface coated at the same time.

[0096] In some embodiments, the mass percentage of the second positive electrode active material is 20% to 95% based on the total mass of the positive electrode film. Optionally, the mass percentage of the second positive electrode active material is 25% to 95%, 30% to 95%, 35% to 95%, 40% to 95%, 45% to 95%, 50% to 95%, 55% to 95%, 60% to 95%, 65% to 95%, 70% to 95%, 75% to 95%, 80% to 95%, 85% to 95%, or 90% to 95%. When the mass percentage of the second positive electrode active material is within an appropriate range, the negative impact of volume expansion of silicon-based and tin-based materials can be effectively reduced, while further improving the cycle performance and storage performance of the secondary battery.

[0097] In some embodiments, the molar ratio of the first positive electrode active material to the second positive electrode active material is 1:m, where 1≤m≤65. Optionally, 1≤m≤60, 1≤m≤55, 1≤m≤50, 1≤m≤45, 1≤m≤40, 1≤m≤35, 1≤m≤30, 1≤m≤25, 1≤m≤20, 1≤m≤15, 2≤m≤65, 2≤m≤60, 2≤m≤55, 2≤m≤50, 2≤m≤45, 2≤m≤40, 2≤m≤35, 2≤m≤30, 2≤m≤25, 2≤m≤20, 2≤m≤15, 3≤m≤65, 3≤m≤60, 3≤m≤55, 3≤m≤50, 3≤m≤45, 3≤m≤40, 3≤m≤35, 3≤m≤30, 3≤m≤25, 3≤m≤20, or 3≤m≤15. When the molar ratio of the first positive electrode active material to the second positive electrode active material is within an appropriate range, the cycle performance and storage performance of the secondary battery can be further improved.

[0098] In some embodiments, the positive electrode film layer can optionally further include a positive electrode conductive agent. The present application does not have a particular limitation on the type of the positive electrode conductive agent. As an example, the positive electrode conductive agent includes one or more of super P, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the positive electrode conductive agent is ≤ 5% based on the total mass of the positive electrode film layer. Optionally, the mass percentage of the positive electrode conductive agent is 0.5% to 5%, 0.5% to 4%, 0.5% to 3%, 0.5% to 2%, or 0.5% to 1%.

[0099] In some embodiments, the positive electrode film layer can optionally further include a positive electrode binder. The present application does not have a particular limitation on the type of the positive electrode binder. As an example, the positive electrode binder can include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. In some embodiments, the mass percentage of the positive electrode binder is ≤ 5% based on the total mass of the positive electrode film layer. Optionally, the mass percentage of the positive electrode binder is 0.5% to 5%, 0.5% to 4%, 0.5% to 3%, 0.5% to 2%, or 0.5% to 1%.

[0100] The positive electrode film layer is typically formed by coating a positive electrode slurry on a positive electrode current collector, drying, and cold-pressing. The positive electrode slurry is typically formed by dispersing and uniformly stirring a positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent. The solvent can be N-methyl pyrrolidone (NMP), but is not limited thereto.

[0101] In some embodiments, the positive electrode film layer simultaneously includes the first positive electrode active material, the second positive electrode active material, the positive electrode conductive agent, and the positive electrode binder.

[0102] The positive electrode current collector has two surfaces opposite in the thickness direction thereof, and the positive electrode film layer is disposed on either one or both of the two opposite surfaces of the positive electrode current collector. In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. As an example of the metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material can be selected from one or more of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy. As an example, the polymer material base layer can be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0103] In some embodiments, the silicon-based material comprises one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, silicon alloy material. Alternatively, the silicon-based material comprises one or more of silicon oxide, silicon-carbon composite, silicon-nitrogen composite, silicon alloy material. Further, the silicon-based material comprises one or more of silicon oxide, silicon-nitrogen composite.

[0104] Compared with elemental silicon, silicon oxide and silicon-nitrogen composite have smaller volume expansion, and due to the presence of oxygen and nitrogen atoms, silicon oxide and silicon-nitrogen composite can also react with M1ions to form M1-O, M1-N, M1-Si-O, M1-Si-N, etc. porous materials (e.g., MgO, Mg2SiO4, Mg2SiO3, etc.) that are electrochemically inactive and coated on the surface of the negative active material to form a core-shell structure of the negative active material. This part of the porous material hardly participates in the reaction in the subsequent cycle process, but can play a role in buffering volume expansion, inhibiting the pulverization of the negative active material, stabilizing the SEI film on the surface of the negative active material, and reducing the continuous irreversible consumption of active ions, thereby improving the cycle performance and storage performance of the secondary battery. In addition, the core-shell structure of the negative active material also gives more expandable space for the combination of M1ions and active ions with silicon oxide and silicon-nitrogen composite to form alloying products. Therefore, the secondary battery can have significantly improved cycle performance and storage performance.

[0105] In some embodiments, the tin-based material comprises one or more of elemental tin, tin oxide, tin-carbon composite, tin alloy material. Alternatively, the tin-based material comprises one or more of tin oxide, tin-carbon composite, tin alloy material. Further, the tin-based material comprises one or more of tin oxide.

[0106] Compared with elemental tin, tin oxide has smaller volume expansion, and due to the presence of oxygen atoms, tin oxide can also react with M1ions to form M1-O, M1-Sn-O, etc. porous materials that are electrochemically inactive and coated on the surface of the negative active material to form a core-shell structure of the negative active material. This part of the porous material hardly participates in the reaction in the subsequent cycle process, but can play a role in buffering volume expansion, inhibiting the pulverization of the negative active material, stabilizing the SEI film on the surface of the negative active material, and reducing the continuous irreversible consumption of active ions, thereby improving the cycle performance and storage performance of the secondary battery. In addition, the core-shell structure of the negative active material also gives more expandable space for the combination of M1ions and active ions with tin oxide to form alloying products. Therefore, the secondary battery can have significantly improved cycle performance and storage performance.

[0107] In the present application, the negative active material does not exclude other negative active materials other than silicon-based materials and tin-based materials. In some embodiments, the negative active material further comprises a second negative active material. The second negative active material is selected from materials capable of deintercalating and intercalating active ions (e.g., lithium ions, sodium ions, potassium ions, zinc ions, calcium ions, or barium ions, etc.). The present application does not particularly limit the type of the second negative active material, and a negative active material for a secondary battery known in the art can be used. For example, a negative active material that can be used for a lithium-ion battery, a sodium-ion battery, a potassium-ion battery, a zinc-ion battery, a calcium-ion battery, or a barium-ion battery is used. As an example, the second negative active material includes, but is not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, and lithium titanate. These second negative active materials can be used alone or in combination with two or more.

[0108] In some embodiments, the mass percentage content of the second negative active material is 40% to 90% based on the total mass of the negative film layer. For example, the mass percentage content of the second negative active material is 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or any range formed by any of these values. Alternatively, the mass percentage content of the second negative active material is 45% to 90%, 50% to 90%, 55% to 90%, 60% to 90%, 62.5% to 90%, 65% to 90%, 67.5% to 90%, 70% to 90%, 72.5% to 90%, 75% to 90%, 77.5% to 90%, 80% to 90%, 82.5% to 90%, or 85% to 90%. When the mass percentage content of the second negative active material is within an appropriate range, the secondary battery can have high energy density while also having significantly improved cycle performance and storage performance.

[0109] In some embodiments, the negative film layer can further optionally include a negative conductive agent. The present application does not particularly limit the type of the negative conductive agent, and as an example, the negative conductive agent can include one or more of super P, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage content of the negative conductive agent is ≤ 5% based on the total mass of the negative film layer. Alternatively, the mass percentage content of the negative conductive agent is 0.5% to 5%, 0.5% to 4%, 0.5% to 3%, 0.5% to 2%, or 0.5% to 1%.

[0110] In some embodiments, the negative electrode film layer can optionally further include a negative electrode binder. The present application does not have a particular limitation on the kind of the negative electrode binder, and as an example, the negative electrode binder can include one or more of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethylacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS). In some embodiments, the mass percentage content of the negative electrode binder is ≤ 5% based on the total mass of the negative electrode film layer. Optionally, the mass percentage content of the negative electrode binder is 0.5% to 5%, 0.5% to 4%, 0.5% to 3%, 0.5% to 2%, or 0.5% to 1%.

[0111] In some embodiments, the negative electrode film layer can optionally further include other auxiliary agents. As an example, the other auxiliary agents can include a thickening agent, e.g., sodium carboxymethyl cellulose (CMC-Na), PTC thermistor material, etc. In some embodiments, the mass percentage content of the other auxiliary agents is ≤ 2% based on the total mass of the negative electrode film layer. Optionally, the mass percentage content of the other auxiliary agents is 0.1% to 2%, 0.1% to 1.5%, 0.1% to 1%, or 0.1% to 0.5%.

[0112] The negative electrode film layer is generally formed by coating a negative electrode slurry on a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is generally formed by dispersing and uniformly stirring a negative electrode active material, an optional conductive agent, an optional binder, and an optional other auxiliary agent in a solvent. The solvent can be N-methyl pyrrolidone (NMP) or deionized water, but is not limited thereto.

[0113] In some embodiments, the negative electrode film layer includes a first negative electrode active material, a negative electrode conductive agent, a negative electrode binder, and a thickening agent.

[0114] In some embodiments, the negative electrode film layer includes a first negative electrode active material, a second negative electrode active material, a negative electrode conductive agent, a negative electrode binder, and a thickening agent.

[0115] The negative current collector has two surfaces opposite in the thickness direction of itself, and the negative film layer is disposed on either one or both of the two opposite surfaces of the negative current collector. In some embodiments, the negative current collector can adopt a metal foil or a composite current collector. As an example of the metal foil, a copper foil can be adopted. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material can be selected from one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), and the like.

[0116] In the present application, the negative electrode tab does not exclude other additional functional layers in addition to the negative film layer. For example, in some embodiments, the negative electrode tab of the present application further includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative current collector and the negative film layer and disposed on the surface of the negative current collector. In some other embodiments, the negative electrode tab of the present application further includes a protective layer covering the surface of the negative film layer.

[0117] The secondary battery of the present application further includes an electrolyte which functions to conduct active ions between the positive electrode tab and the negative electrode tab. The type of the electrolyte is not specifically limited in the present application and can be selected as needed. For example, the electrolyte can be selected from at least one of a solid-state electrolyte and a liquid electrolyte (i.e., electrolyte solution).

[0118] In some embodiments, the electrolyte adopts an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0119] The type of the electrolyte salt is not specifically limited and can be selected as needed. In some embodiments, the electrolyte salt includes, but is not limited to, one or more of a lithium salt and a sodium salt. Optionally, the lithium salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate borate (LiDFOB), lithium difluorophosphate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluoro dioxalate phosphate (LiDFOP), and lithium tetrafluoro oxalate phosphate (LiTFOP). Optionally, the sodium salt includes one or more of NaPF6, NaClO4, NaBCl4, NaSO3CF3, and Na(CH3)C6H4SO3.

[0120] The kind of the solvent is not particularly limited and can be selected according to actual needs. In some embodiments, the solvent can include, by way of example, one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0121] In some embodiments, the electrolyte can also optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature performance of the battery, an additive capable of improving low-temperature power performance of the battery, and the like.

[0122] In some secondary batteries using an electrolyte and some secondary batteries using a solid-state electrolyte, a separator is also included. The separator is disposed between the positive electrode sheet and the negative electrode sheet and functions to separate. The kind of the separator is not particularly limited and any known porous structure separator having good chemical stability and mechanical stability can be used. In some embodiments, the material of the separator can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of the layers can be the same or different.

[0123] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be made into an electrode assembly by a winding process or a stacking process.

[0124] In some embodiments, the secondary battery can include an outer package. The outer package can be used to package the electrode assembly and the electrolyte described above.

[0125] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, and the like. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), and the like.

[0126] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. FIG. 1 This is an example of a square-structured secondary battery 5.

[0127] In some embodiments, such as FIG. 2 As shown, the outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 is used to cover the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be adjusted according to requirements.

[0128] The method for preparing the secondary battery in this application is well known. In some embodiments, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a secondary battery is obtained.

[0129] Battery module and battery pack

[0130] In some embodiments of this application, the secondary battery according to this application can be assembled into a battery module. The number of secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0131] FIG. 3 This is a schematic diagram of battery module 4 as an example. FIG. 3 As shown, in battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0132] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0133] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0134] FIG. 4 and FIG. 5 This is a schematic diagram of battery pack 1 as an example. FIG. 4 and FIG. 5As shown, the battery pack 1 can include a battery case and a plurality of battery modules 4 disposed in the battery case. The battery case includes an upper case 2 and a lower case 3, the upper case 2 being configured to cover the lower case 3 and form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery case in any manner.

[0135] Electric device

[0136] The present application also provides an electric device including at least one of the secondary battery, the battery module, or the battery pack of the present application. The secondary battery, the battery module, or the battery pack can be used as a power source of the electric device, or can be used as an energy storage unit of the electric device. The electric device can be, but is not limited to, a mobile device (e.g., a cell phone, a laptop computer, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0137] The electric device can select a secondary battery, a battery module, or a battery pack according to its use requirements.

[0138] FIG. 6 is a schematic view of an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of high power and high energy density of the electric device, a battery pack or a battery module can be used.

[0139] An electric device as another example can be a cell phone, a tablet computer, a laptop computer, etc. The electric device usually requires thin and light, and a secondary battery can be used as a power source.

[0140] Embodiments

[0141] The following examples more specifically describe the present disclosure, which are only for illustrative purposes, because various modifications and changes within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further purification, and the instruments used in the examples are commercially available.

[0142] Example 1

[0143] Preparation of first positive electrode active material

[0144] Potassium permanganate, tetraethylammonium bromide were mixed according to equal molar ratio, and the precursor was obtained by filtration and drying at room temperature; the precursor was added into the reducing solvent which was mixed by water and sec-butyl alcohol according to equal volume ratio for reduction, to obtain a sol; the sol was aged at 80℃ for 48h to obtain a gel; the gel was ion exchanged with magnesium chloride aqueous solution according to equal molar ratio, and then transferred to a reaction kettle after strong stirring for 8h, and hydrothermal reaction was carried out at 180℃ for 6h to obtain a precipitate; the precipitate was filtered, washed and dried to obtain Mg2Mn2O4, wherein the volume average particle size Dv50 of Mg2Mn2O4 is 14μm, and the specific surface area is 0.4m 2 / g.

[0145] Preparation of positive electrode sheet

[0146] The first positive electrode active material Mg2Mn2O4, the second positive electrode active material LiFePO4, the conductive agent carbon black (Super P) and the binder polyvinylidene fluoride (PVDF) were mixed according to a mass ratio of 70.8:25.2:2:2 in an appropriate amount of solvent NMP, and the mixture was fully stirred to form a uniform positive electrode slurry, and the viscosity of the positive electrode slurry was controlled at 100Pa.s-20000mPa.s; the positive electrode slurry was uniformly coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained.

[0147] Preparation of negative electrode sheet

[0148] The first negative electrode active material silicon oxide, the second negative electrode active material graphite, the conductive agent carbon black (Super P), the binder styrene-butadiene rubber (SBR) and the thickening agent sodium carboxymethyl cellulose (CMC-Na) were mixed according to a mass ratio of 14.5:82.0:1.0:1.5:1.0 in an appropriate amount of solvent deionized water, and the mixture was fully stirred to form a uniform negative electrode slurry; the negative electrode slurry was uniformly coated on the surface of the negative electrode current collector copper foil, and after drying and cold pressing, a negative electrode sheet was obtained. The mass ratio of the first positive electrode active material Mg2Mn2O4 to the first negative electrode active material silicon oxide is 0.55:1.

[0149] Preparation of electrolyte

[0150] Vinyl carbonate (EC), propylene carbonate (PC) and diethyl carbonate (DEC) were mixed according to a mass ratio of 30:30:40 to obtain an organic solvent, and then LiPF6 which was fully dried was dissolved in the organic solvent to prepare an electrolyte with a concentration of 1mol / L.

[0151] Preparation of separator

[0152] A porous polypropylene film with a thickness of 12μm was used as the separator film.

[0153] Preparation of secondary battery

[0154] The positive electrode sheet, the separator, and the negative electrode sheet were stacked in order and wound to obtain an electrode assembly having a thickness of 8 mm, a width of 60 mm, and a length of 130 mm. The electrode assembly was placed in an outer package, vacuum baked at 75°C for 10 h, and then injected with an electrolyte. After vacuum packaging, standing, and formation, a secondary battery was obtained.

[0155] Examples 2 to 40 and Comparative Examples 1 to 3

[0156] The preparation method of the secondary battery was similar to that of Example 1, except that the types of the first positive electrode active material and the second positive electrode active material, the mass percentage contents of the first positive electrode active material and the second positive electrode active material, and the mass ratio of the first positive electrode active material to the first negative electrode active material were adjusted. The specific parameters are shown in Tables 1 and 2. The mass ratio of the first positive electrode active material to the first negative electrode active material in each example was obtained by adjusting the type and mass of the first negative electrode active material, the type and mass of the second negative electrode active material, and the total mass of the negative electrode sheet in each example, while the ratio of the total capacity of the negative electrode sheet to the total capacity of the positive electrode sheet (i.e., the N / P ratio) was controlled to be 1.07 to 1.20. The total capacity of the negative electrode sheet = the total mass of the first negative electrode active material in the negative electrode sheet × the reversible gram capacity of the first negative electrode active material + the total mass of the second negative electrode active material in the negative electrode sheet × the reversible gram capacity of the second negative electrode active material, and the total capacity of the positive electrode sheet = the total mass of the first positive electrode active material in the positive electrode sheet × the reversible gram capacity of the first positive electrode active material + the total mass of the second positive electrode active material in the positive electrode sheet × the reversible gram capacity of the second positive electrode active material.

[0157] The preparation method of the first positive electrode active material used in Examples 19 to 26 was similar to that of Example 1, except that the hydrothermal reaction temperature was 180°C and the hydrothermal reaction time was 4 h in the preparation method of Example 19, the hydrothermal reaction temperature was 180°C and the hydrothermal reaction time was 12 h in the preparation method of Example 20, the hydrothermal reaction temperature was 180°C and the hydrothermal reaction time was 3 h in the preparation method of Example 21, the hydrothermal reaction temperature was 180°C and the hydrothermal reaction time was 14 h in the preparation method of Example 22, the hydrothermal reaction temperature was 200°C and the hydrothermal reaction time was 6 h in the preparation method of Example 23, the hydrothermal reaction temperature was 150°C and the hydrothermal reaction time was 6 h in the preparation method of Example 24, the hydrothermal reaction temperature was 210°C and the hydrothermal reaction time was 6 h in the preparation method of Example 25, and the hydrothermal reaction temperature was 120°C and the hydrothermal reaction time was 6 h in the preparation method of Example 26.

[0158] The preparation method of the first positive electrode active material used in Examples 27-29 includes the steps of: mixing potassium permanganate and tetraethylammonium bromide in an equal amount ratio, filtering and drying at room temperature to obtain a precursor; adding the precursor into a reducing solvent mixed by water and sec-butyl alcohol in an equal volume ratio to reduce and obtain a sol; aging the sol at 80°C for 48h to obtain a gel; ion exchanging the gel with an aqueous aluminum chloride solution in an equal amount ratio, stirring strongly for 8h and then transferring to a reaction kettle to hydrothermally react at 180°C for 6h to obtain a precipitate; filtering, washing and drying the precipitate to obtain Al2Mn2O5.

[0159] The preparation method of the first positive electrode active material used in Example 39 includes the steps of: mixing potassium permanganate and tetraethylammonium bromide in an equal amount ratio, filtering and drying at room temperature to obtain a precursor; adding the precursor into a reducing solvent mixed by water and sec-butyl alcohol in an equal volume ratio to reduce and obtain a sol; uniformly mixing the sol with an aqueous nickel acetate solution in a stoichiometric ratio (the molar ratio of Mn and Ni is 1.5:0.5), aging the mixture at 80°C for 48h to obtain a gel; ion exchanging the gel with an aqueous magnesium chloride solution in an equal amount ratio, stirring strongly for 8h and then transferring to a reaction kettle to hydrothermally react at 180°C for 6h to obtain a precipitate; filtering, washing and drying the precipitate to obtain Mg2Mn 1.5 Ni 0.5 O 4。

[0160] The preparation method of the first positive electrode active material used in Example 40 includes the steps of: mixing potassium permanganate and tetraethylammonium bromide in an equal amount ratio, filtering and drying at room temperature to obtain a precursor; adding the precursor into a reducing solvent mixed by water and sec-butyl alcohol in an equal volume ratio to reduce and obtain a sol; uniformly mixing the sol with an aqueous nickel acetate solution in a stoichiometric ratio, aging the mixture at 80°C for 48h to obtain a gel; ion exchanging the gel with an aqueous magnesium chloride solution in an equal amount ratio, stirring strongly for 8h and then transferring to a reaction kettle to hydrothermally react at 180°C for 6h to obtain a precipitate; filtering the precipitate and hydrothermally reacting with sodium sulfide at 100°C for 6h in a stoichiometric ratio (the molar ratio of Mn and S is 1.5:0.8), and then filtering, washing and drying to obtain Mg2Mn 1.5 Ni 0.5 O 3.2 S 0.8。

[0161] Table 1

[0162]

[0163]

[0164] Table 2

[0165]

[0166]

[0167] Test section

[0168] (1) Cyclic performance test at 25℃

[0169] At 25℃, the secondary battery is charged at a constant current of 1C to the charging cutoff voltage, and then charged at a constant voltage until the current reaches 0.05C. At this point, the secondary battery is fully charged, and the charging capacity at this point is recorded as the first charge capacity. After the secondary battery is left to stand for 5 minutes, it is discharged at a constant current of 1C to the discharge cutoff voltage. This completes one charge-discharge cycle, and the discharge capacity at this point is recorded as the first discharge capacity. The secondary battery is subjected to cyclic charge-discharge tests using the above method, and the discharge capacity after each cycle is recorded until the discharge capacity of the secondary battery decreases to 80% of the first discharge capacity. The number of cycles at this point characterizes the cycle performance of the secondary battery. The higher the number of cycles, the better the cycle performance.

[0170] The charging cutoff voltage of Examples 1-29, 39-40 and Comparative Example 1 is 3.65V and the discharging cutoff voltage is 2.8V.

[0171] The charging cutoff voltage of Examples 30-38 and Comparative Examples 2-3 is 4.35V and the discharging cutoff voltage is 2.8V.

[0172] (2) Cyclic performance test at 45℃

[0173] At 45℃, the secondary battery is charged at a constant current of 1C to the charging cutoff voltage, and then charged at a constant voltage until the current reaches 0.05C. At this point, the secondary battery is fully charged, and the charging capacity at this point is recorded as the first charge capacity. After the secondary battery is left to stand for 5 minutes, it is discharged at a constant current of 1C to the discharge cutoff voltage. This completes one charge-discharge cycle, and the discharge capacity at this point is recorded as the first discharge capacity. The secondary battery is subjected to cyclic charge-discharge tests using the above method, and the discharge capacity after each cycle is recorded until the discharge capacity of the secondary battery decreases to 80% of the first discharge capacity. The number of cycles at this point characterizes the cycle performance of the secondary battery. The higher the number of cycles, the better the cycle performance.

[0174] The charging cutoff voltage of Examples 1-29, 39-40 and Comparative Example 1 is 3.65V and the discharging cutoff voltage is 2.8V.

[0175] The charging cutoff voltage of Examples 30-38 and Comparative Examples 2-3 is 4.35V and the discharging cutoff voltage is 2.8V.

[0176] (3) 60℃ storage performance test

[0177] At 25℃, the secondary battery was charged at 1C constant current to the charge cut-off voltage, and then continued to be charged at constant voltage until the current was 0.05C; after the secondary battery was left for 5 min, it was discharged at 1C constant current to the discharge cut-off voltage, and the discharge capacity at this time was recorded, which was the initial discharge capacity of the secondary battery. The secondary battery was charged at 1C constant current to the charge cut-off voltage, and then continued to be charged at constant voltage until the current was 0.05C, at which time the secondary battery was in a full charge state. The full charge state secondary battery was stored at 60℃, and the discharge capacity of the secondary battery was tested every 5 days until the discharge capacity of the secondary battery was attenuated to 80% of the initial discharge capacity, and the storage time at this time was used to represent the storage performance of the secondary battery. The higher the storage time of the secondary battery, the better the storage performance.

[0178] The charge cut-off voltage of Examples 1-29, 39-40 and Comparative Example 1 was 3.65V, and the discharge cut-off voltage was 2.8V.

[0179] The charge cut-off voltage of Examples 30-38 and Comparative Examples 2-3 was 4.35V, and the discharge cut-off voltage was 2.8V.

[0180] Table 3 shows the performance test results of Examples 1-40 and Comparative Examples 1-3.

[0181] Table 3

[0182] Serial number 25℃ cycle number 45℃ cycle number 60℃ storage days

[0183] Example 1 1700 cycles 900 cycles 255 days Example 2 1800 cycles 920 cycles 260 days Example 3 1900 cycles 950 cycles 265 days Example 4 2000 cycles 1000 cycles 270 days Example 5 2500 cycles 1500 cycles 350 days Example 6 2650 cycles 1600 cycles 370 days Example 7 3000 cycles 1700 cycles 400 days Example 8 2800 cycles 1650 cycles 345 days Example 9 2700 cycles 1600 cycles 355 days Example 10 2500 cycles 1500 cycles 355 days Example 11 2400 cycles 1600 cycles 360 days Example 12 2000 cycles 1400 cycles 300 days Example 13 1850 cycles 1400 cycles 280 days Example 14 1750 cycles 1200 cycles 270 days Example 15 1500 cycles 850 cycles 250 days Example 16 2900 cycles 1670 cycles 360 days Example 17 2800 cycles 1650 cycles 380 days Example 18 2100 cycles 1000 cycles 255 days Example 19 2500 cycles 1500 cycles 355 days Example 20 2650 cycles 1450 cycles 365 days Example 21 2200 cycles 1100 cycles 280 days Example 22 2100 cycles 1300 cycles 300 days Example 23 2550 cycles 1450 cycles 330 days Example 24 2600 cycles 1500 cycles 360 days Example 25 1900 cycles 1000 cycles 290 days Example 26 2250 cycles 1100 cycles 285 days Example 27 2200 cycles 1300 cycles 320 days Example 28 2600 cycles 1650 cycles 340 days Example 29 2100 cycles 1100 cycles 290 days Example 30 1200 cycles 1000 cycles 210 days Example 31 1300 cycles 1200 cycles 200 days Example 32 1700 cycles 1300 cycles 240 days Example 33 2000 cycles 1400 cycles 270 days Example 34 1250 cycles 1150 cycles 190 days Example 35 1000 cycles 800 cycles 132 days Example 36 1200 cycles 900 cycles 145 days Example 37 1500 cycles 1000 cycles 160 days Example 38 1600 cycles 1200 cycles 170 days Example 39 2500 cycles 1400 cycles 390 days Example 40 2800 cycles 1500 cycles 380 days

[0184] Comparative Example 1 1600 cycles 800 cycles 250 days Comparative Example 2 1100 cycles 800 cycles 190 days Comparative Example 3 800 cycles 500 cycles 120 days

[0185] As can be seen from the test results in Table 3, when the positive active material comprises a first positive active material of the formula M1 x Mn y M2 z O a A b , the negative effects of volume expansion of silicon-based materials and tin-based materials can be reduced, so that the secondary battery can have significantly improved cycle performance and storage performance.

[0186] In addition, when the secondary battery also satisfies one or both of the mass percentage content of the first positive active material being 2% to 70%, and the mass ratio of the first positive active material to the first negative active material being (0.48-0.70):1, the secondary battery can have further improved cycle performance and storage performance while having high energy density.

[0187] Note that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration, function, and effect as the technical idea of the present application are included in the technical scope of the present application. Furthermore, other modes constructed by applying various modifications to the embodiments, or by combining part of the configurations of the embodiments, which can be conceived by those skilled in the art, without departing from the spirit of the present application, are also included in the scope of the present application.

Claims

1. A secondary battery, comprising a negative electrode tab and a positive electrode tab, the negative electrode tab comprising a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, the negative electrode film layer comprising a negative electrode active material; the positive electrode tab comprising a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, the positive electrode film layer comprising a positive electrode active material, wherein the negative electrode active material comprises a first negative electrode active material selected from one or more of a silicon-based material and a tin-based material; the mass percentage content of the first positive electrode active material is 2%-70% based on the total mass of the positive electrode film layer; and the secondary battery is a lithium ion battery, a sodium ion battery, a potassium ion battery, a zinc ion battery, a calcium ion battery, or a barium ion battery. The mass percentage content of the first positive electrode active material is 2.4%-55% based on the total mass of the positive electrode film layer. The mass ratio of the first positive electrode active material to the first negative electrode active material is (0.48-0.70) :

1. The positive electrode active material includes a first positive electrode active material, the molecular formula of the first positive electrode active material is M1 x Mn y M2 z O a A b , M1 represents one or both of Mg, Al, M2 represents one or both of Co, Ni, A represents one or more of N, P, S, 0 The mass percentage content of the first negative electrode active material is 5%-50% based on the total mass of the negative electrode film layer.

2. The secondary battery according to claim 1, wherein The mass percentage content of the first negative electrode active material is 5%-29% based on the total mass of the negative electrode film layer.

3. The secondary battery according to claim 1 or 2, wherein The first positive electrode active material satisfies at least one of conditions (1) to (4):

4. The secondary battery according to claim 1, wherein The first positive electrode active material has a spinel structure and / or a layered structure.

5. The secondary battery according to claim 4, wherein The volume average particle size Dv50 of the first positive electrode active material is 8 μm-20 μm.

6. The secondary battery according to claim 1, wherein 11.The secondary battery according to claim 1, wherein the silicon-based material comprises one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material, and / or the tin-based material comprises one or more of elemental tin, tin oxide, tin-carbon composite, and tin alloy material. （1）0＜y≤3， （2）0＜z≤1， （3）0＜a≤5， （4）0＜b≤1。 7. The secondary battery according to claim 1, wherein 12.A battery module comprising the secondary battery according to any one of claims 1-11.

8. The secondary battery according to claim 1, wherein The first positive electrode active material includes one or more of MgMn2O4, Mg2Mn2O4, Al2Mn2O5, MgAlMnO4, Mg2AlMnO5, Mg2Mn 1.5 Ni 0.5 O4, Mg2Mn 1.5 Ni 0.5 O 3.2 S 0.8 .

9. The secondary battery according to claim 1, wherein 13.A battery pack comprising one of the secondary battery according to any one of claims 1-11 and the battery module according to claim 12.

10. The secondary battery according to claim 1, wherein The specific surface area of the first positive electrode active material is 0.2 m 2 / g ~ 0.9 m 2 / g. 14.An electric device comprising at least one of the secondary battery according to any one of claims 1-11, the battery module according to claim 12, and the battery pack according to claim 13. ​ ​ ​ ​ ​

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