Battery monomer, battery comprising battery monomer and power utilization device

Abstract

The invention provides a battery monomer, a battery comprising the same and an electric device. The battery monomer comprises a positive electrode active material, a negative electrode active material and an electrolyte, wherein the positive electrode active material comprises a nickel-cobalt-manganese ternary material. The negative electrode active material comprises a silicon material, and the mass fraction of the silicon material in the negative electrode active material is s%. The electrolyte comprises a first additive, the first additive comprises a halogen-containing annular structure, the mass fraction of the first additive in the electrolyte is P1%, and P1 meets the relation that P1 is larger than or equal to 1 and smaller than or equal to 0.8 * s-0. 12; or the electrolyte comprises a first additive, the first additive has attenuation, and the mass fraction P1% of the first additive in the electrolyte and the residual electric quantity q of the single battery meet the relation that P1 is smaller than or equal to 2.4 * q + 0.2.

Description

Battery cell, battery containing same, and electric device Technical Field

[0001] The present application relates to a battery cell, a battery containing the same, and an electric device. Background Art

[0002] In recent years, secondary batteries have been widely used in energy storage systems such as hydropower, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. With the application and promotion of secondary batteries, the requirements for their energy density and cycle performance have become increasingly stringent.

[0003] Summary of the Invention

[0004] The present application provides a battery cell, a battery comprising the same, and an electrical device. The battery cell can have both high energy density and good cycle performance.

[0005] In a first aspect, the present application provides a battery cell comprising a positive electrode active material, a negative electrode active material, and an electrolyte. The positive electrode active material comprises a nickel-cobalt-manganese ternary material. The negative electrode active material comprises a silicon material, and the mass fraction of the silicon material in the negative electrode active material is s%. The electrolyte comprises a first additive, the first additive comprises a halogen-containing cyclic structure, the mass fraction of the first additive in the electrolyte is P1%, and P1 satisfies the relationship: 1≤P1≤0.8×s-0.12; or, the electrolyte comprises the first additive, the first additive exhibits attenuation, and the mass fraction P1% of the first additive in the electrolyte and the remaining charge q of the battery cell satisfy the relationship: P1≤2.4×q+0.2.

[0006] Without intending to be limited by any theory or explanation, when the positive electrode active material of the battery cell includes a nickel-cobalt-manganese ternary material, the negative electrode active material includes a silicon material, and an appropriate amount of a first additive is included in the electrolyte, it can not only effectively increase the cut-off voltage of the battery, thereby increasing the energy density of the secondary battery, but also extend the cycle life of the battery.

[0007] Specifically, when the electrolyte contains a first additive, it can interact with the negative electrode active material, thereby forming an SEI film on the surface of the negative electrode plate in preference to the organic solvent. The inventors of this application have discovered that in high-voltage silicon systems (i.e., battery systems where the positive electrode material is a high-energy-density ternary material and the negative electrode is a silicon-based material), the first additive must meet specific conditions to effectively improve battery performance. Through analysis and other research, it was found that battery performance can only be significantly improved when the first additive content meets the requirements of the aforementioned relationship. The higher the content of the first additive, the denser the SEI film formed on the surface of the negative electrode plate, and the stronger its ability to inhibit contact between solvent molecules and the silicon material. When the content of the first additive is too low, the SEI film formed on the surface of the negative electrode plate is too thin, with poor uniformity and density, making it difficult to inhibit side reactions between the silicon material and the electrolyte, thereby shortening the battery's cycle life. However, when the content of the first additive is too high, the first additive may react with the electrolyte during cycling or storage, resulting in excessive gas production and reduced battery reliability. Based on the above relationship, when the content of the first additive in the electrolyte and the content of the silicon material in the negative electrode active material meet the ranges given in the embodiments of the present application, a stable, dense, and appropriately thick SEI film can be formed on the surface of the negative electrode plate, thereby reducing the probability of side reactions between the silicon material and the electrolyte due to volume changes during the cycle. In this way, not only can the irreversible loss of active lithium ions be reduced and the capacity of the silicon material be improved, but the cycle stability of the battery can also be improved and the cycle life of the battery can be extended. Therefore, the battery cell provided in the embodiments of the present application can have both high energy density and long cycle life.

[0008] In any embodiment of the present application, the mass fraction s% of the silicon material in the negative electrode active material satisfies: 0<s≤50, optionally, 0<s≤25. This is beneficial to further improve the energy density of the battery and extend the cycle life of the battery.

[0009] In any embodiment of the present application, the first additive comprises an ester group.

[0010] Optionally, the first additive comprises at least one of the compounds represented by Formula I.

[0011] p represents 1, 2, or 3.

[0012] R 11 represents an oxygen atom or C(Y 1 )2,Y 1Each independently includes one of a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkenyloxy group having 2 to 20 carbon atoms, an alkynyloxy group having 2 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, and a haloaryloxy group having 6 to 20 carbon atoms.

[0013] R 12 、R 13 、R 14 、R 15 each independently includes one of a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkenyloxy group having 2 to 20 carbon atoms, an alkynyloxy group having 2 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, and a haloaryloxy group having 6 to 20 carbon atoms, and R 12 、R 13 、R 14 、R 15 At least one of the group includes a halogen atom, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, and a haloaryloxy group having 6 to 20 carbon atoms.

[0014] When the electrolyte contains the first additive, it can increase the inorganic content of the negative electrode SEI film, making the SEI film denser. This dense SEI film can restrain the expansion of the silicon material during cycling. In addition, the first additive represented by Formula I has good compatibility with the silicon material and can reduce the degree of damage to the SEI film on the silicon material surface during cycling, thereby reducing the loss of active lithium. This is conducive to improving the battery's capacity and rate performance.

[0015] In any embodiment of the present application, p represents 1 or 2.

[0016] Optionally, R 11 represents an oxygen atom or C(Y 1 )2,Y 1 Each independently represents one of a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a propyl group, a fluoromethyl group, a fluoroethyl group, a fluoropropyl group, a methoxy group, an ethoxy group, and a propoxy group.

[0017] Optionally, R 12 Each independently represents a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a propyl group, a fluoromethyl group, a fluoroethyl group, a fluoropropyl group, a methoxy group, an ethoxy group, or a propoxy group.

[0018] Optionally, R 13 Each independently represents a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a propyl group, a fluoromethyl group, a fluoroethyl group, a fluoropropyl group, a methoxy group, an ethoxy group, or a propoxy group.

[0019] Optionally, R 14 Each independently represents a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a propyl group, a fluoromethyl group, a fluoroethyl group, a fluoropropyl group, a methoxy group, an ethoxy group, or a propoxy group.

[0020] Optionally, R 15 Each independently represents a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a propyl group, a fluoromethyl group, a fluoroethyl group, a fluoropropyl group, a methoxy group, an ethoxy group, or a propoxy group.

[0021] When in formula Ⅰ, p, R 12 、R 13 、R 14 、R 15 When one or more of the above conditions are met, the risk of silicon material being pulverized and deactivated by side reactions with the electrolyte can be effectively reduced, further improving the cycle performance and storage performance of the battery.

[0022] In any embodiment of the present application, the first additive includes at least one of the following compounds H1 to H6.

[0023] The above compounds H1 to H6 can decompose to produce a SEI film with a high inorganic content, thereby improving the cycle performance of the battery.

[0024] In any embodiment of the present application, the electrolyte further includes a second additive, and the second additive includes one or more boron-containing cyclic compounds.

[0025] Optionally, the second additive includes at least one of the compounds represented by Formula II-1 and Formula II-2.

[0026] R 21 、R 22 each independently includes one of a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkenyloxy group having 2 to 20 carbon atoms, an alkynyloxy group having 2 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, and a haloaryloxy group having 6 to 20 carbon atoms, and R 21 、R 22 At least one of the group includes a halogen atom, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, and a haloaryloxy group having 6 to 20 carbon atoms.

[0027] R 23 、R 24 Each independently represents a carbonyl group C=O or C(Y 2 )2,Y 2 Each independently includes one of a hydrogen atom, a halogen atom, an alkyl group having 1 to 3 carbon atoms, and a halogenated alkyl group having 1 to 3 carbon atoms, and R 23 、R 24 It does not represent a carbonyl group C═O at the same time.

[0028] R 25 、R 26 each independently includes one of a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkenyloxy group having 2 to 20 carbon atoms, an alkynyloxy group having 2 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, and a haloaryloxy group having 6 to 20 carbon atoms, and R 25 、R 26At least one of the group includes a halogen atom, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, and a haloaryloxy group having 6 to 20 carbon atoms.

[0029] R 27 、R 28 Each independently includes one of a hydrogen atom, a halogen atom, an alkyl group having 1 to 3 carbon atoms, and a halogenated alkyl group having 1 to 3 carbon atoms.

[0030] The second additive can form a denser, more stable, and more lithium-ion-conducting interfacial film on the surface of the positive electrode active material before the organic solvent. This interfacial film helps reduce the charge transfer resistance on the positive electrode side, thereby slowing the increase in internal resistance of the battery during cycling, and further extending the battery's cycle life.

[0031] In any embodiment of the present application, R 21 represents one of a hydrogen atom, a methyl group, an ethyl group, and a fluoromethyl group.

[0032] Optionally, R 22 represents one of a hydrogen atom, a methyl group, an ethyl group, and a fluoromethyl group.

[0033] Optionally, R 23 represents one of a hydrogen atom, a methyl group, an ethyl group, and a carbonyl group.

[0034] Optionally, R 24 represents one of a hydrogen atom, a methyl group, an ethyl group, and a carbonyl group.

[0035] In any embodiment of the present application, R 25 represents one of a hydrogen atom, a methyl group, an ethyl group, and a fluoromethyl group.

[0036] Optionally, R 26 represents one of a hydrogen atom, a methyl group, an ethyl group, and a fluoromethyl group.

[0037] Optionally, R 27 represents one of a hydrogen atom, a methyl group, and an ethyl group.

[0038] Optionally, R 28 represents one of a hydrogen atom, a methyl group, and an ethyl group.

[0039] When Formula II-1 and / or Formula II-1 meet one or more of the above conditions, a denser, more stable and more lithium-ion-conducting SEI film can be formed on the surface of the positive electrode active material, thereby helping to further extend the cycle life of the battery and improve the cycle stability of the battery.

[0040] In any embodiment of the present application, the second additive includes at least one of the following compounds J1 to J4.

[0041] The above compounds J1 to J4 can form a film on the positive electrode, reducing the risk of oxidative decomposition of the electrolyte under high voltage, thereby improving the structural stability of the positive electrode active material and further improving the cycle stability of the battery.

[0042] In any embodiment of the present application, the mass content of the second additive in the electrolyte is P2%, where P2 satisfies the relationship: 0.11 + 0.01 × t ≤ P2 ≤ 1.2, where t% is the mass percentage of the nickel-cobalt-manganese ternary material in the positive electrode film layer of the battery cell. This helps to improve the structural stability of the positive electrode active material, thereby improving the cycling stability of the battery.

[0043] In any embodiment of the present application, 50≤t<100. When the content of the nickel-cobalt-manganese ternary material in the positive electrode film layer is within the above-mentioned suitable range, it is beneficial for the positive electrode active material to have both high capacity and high cycle stability, thereby further improving the energy density of the battery and extending the cycle life of the battery.

[0044] In any embodiment of the present application, the ratio of the mass content of the second additive in the electrolyte to the mass content of the first additive in the electrolyte is 1:40 to 1:1, optionally, 1:5 to 1:2.

[0045] When the contents of the second additive and the first additive in the electrolyte satisfy the given relationship, the second additive and the first additive can work synergistically, thereby not only reducing the initial internal resistance of the battery and the growth of internal resistance during cycling, but also reducing gas production during storage, thereby contributing to a long cycle life and high reliability of the battery.

[0046] In any embodiment of the present application, the charge cut-off voltage of the battery cell is greater than or equal to 4.2 V, and optionally, the charge cut-off voltage is greater than or equal to 4.3 V. This is beneficial to improving the capacity and cycle stability of the battery, thereby improving the energy density of the battery and extending the cycle life of the battery.

[0047] In any embodiment of the present application, the molar content of Ni in the transition metal elements in the nickel-cobalt-manganese ternary material is less than or equal to 0.7, which is beneficial to further improve the cycle stability of the positive electrode active material, thereby extending the cycle life of the battery.

[0048] In any embodiment of the present application, the positive electrode active material includes a first nickel-cobalt-manganese ternary material in which the molar content of Ni element in the transition metal element is greater than 0.5.

[0049] Optionally, the positive electrode active material further comprises a second nickel-cobalt-manganese ternary material in which the molar content of Ni element in the transition metal element is less than 0.5.

[0050] Optionally, the positive electrode active material further includes a lithium-rich manganese-based positive electrode material.

[0051] Optionally, the positive electrode active material further includes a lithium-containing phosphate positive electrode material. When the positive electrode active material includes one or more of the above positive electrode materials, the positive electrode active material can have both high theoretical specific capacity and good cycle stability, thereby further improving the energy density of the battery and extending the cycle life of the battery.

[0052] In any embodiment of the present application, the silicon material includes at least one of nano-silicon, silicon oxide compounds, and silicon carbon compounds.

[0053] In any embodiment of the present application, the negative electrode active material further comprises a carbon material, and the carbon material comprises at least one of artificial graphite, natural graphite, and hard carbon. When the negative electrode active material further comprises a carbon material, it is not only advantageous to flexibly adjust parameters such as the compaction density and porosity of the negative electrode film layer by combining silicon-based negative electrode active material particles with the carbon material, but also advantageously improve the electron transport performance of the negative electrode, thereby facilitating the improvement of the safety and electrochemical performance of the secondary battery.

[0054] In any embodiment of the present application, the volume distribution particle size Dv50 of the silicon material is 3 μm to 20 μm, and optionally, the volume distribution particle size Dv50 of the silicon material is 3 μm to 15 μm. This allows the battery cell of the embodiment of the present application to have a high energy density.

[0055] In any embodiment of the present application, the electrolyte further comprises a cyclic carbonate, which is beneficial to further reduce the capacity loss of the battery and improve the cycle stability of the battery.

[0056] In any embodiment of the present application, at 25° C., the conductivity of the electrolyte is 7 ms / cm to 11 ms / cm, and optionally 8 ms / cm to 9 ms / cm, thereby improving the cycle performance and charging capacity of the battery.

[0057] In any embodiment of the present application, at 25° C., the viscosity of the electrolyte is 2.5 mPa.s / cP to 5 mPa.s / cP, and optionally, 3 mPa.s / cP to 4 mPa.s / cP, which is beneficial for improving the cycle performance of the battery and the low-temperature charging capability of the battery.

[0058] A second aspect of the present application provides a battery, comprising the battery cell of the first aspect of the present application.

[0059] A third aspect of the present application provides an electrical device comprising the battery cell of the first aspect or the battery of the second aspect of the present application.

[0060] The electric device of the present application includes the battery cell or battery provided by the present application, and thus has at least the same advantages as the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] To more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on the drawings without inventive effort.

[0062] FIG1 is a schematic diagram of an embodiment of a battery cell provided in the present application.

[0063] FIG2 is an exploded schematic diagram of an embodiment of a battery cell provided in the present application.

[0064] FIG3 is a schematic diagram of an embodiment of a battery module provided in the present application.

[0065] FIG4 is a schematic diagram of an embodiment of a battery pack provided in the present application.

[0066] FIG. 5 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 4 .

[0067] FIG6 is a schematic diagram of an embodiment of an electric device including the battery cell provided in the present application as a power source.

[0068] In the accompanying drawings, which are not necessarily drawn to scale, the reference numerals are as follows: 1. battery pack; 2. upper housing; 3. lower housing; 4. battery module; 5. battery cell; 51. housing; 52. electrode assembly; 53. cover plate. DETAILED DESCRIPTION

[0069] Below, the embodiments of the battery cell, the battery containing the same, and the electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0070] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0071] Unless otherwise specified, 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.

[0072] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0073] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may 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.

[0074] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0075] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: 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).

[0076] Unless otherwise specified, in this application, the terms "first", "second", etc. are used to distinguish different objects rather than to describe a specific order or a primary-secondary relationship.

[0077] In this application, the terms "plurality", "multiple" and the like refer to two or more.

[0078] Unless otherwise specified, the terms used in this application have the common meanings that are commonly understood by those skilled in the art.

[0079] Unless otherwise stated, the numerical values ​​of the various parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in the examples of this application. Unless otherwise stated, the test temperature of each parameter is 25°C.

[0080] It should be noted that, in this document, the volume distribution particle size Dv50 refers to the particle size corresponding to the cumulative volume distribution percentage of the material reaching 50%. In this application, the volume distribution particle size Dv50 of the material can be measured using laser diffraction particle size analysis. For example, with reference to standard GB / T 19077-2016, a laser particle size analyzer (e.g., Malvern Master Size 3000) can be used for measurement.

[0081] In this article, term " coating " refers to the material layer coated on the kernel, and described material layer can coat the kernel completely or partially, and using " coating " is just for the convenience of description, and is not intended to limit the present invention. In addition, each layer of coating can be completely coated, also can be partially coated.

[0082] As used herein, the term "source" refers to a compound that is the source of an element. Examples of the "source" include, but are not limited to, carbonates, sulfates, nitrates, elements, halides, oxides, and hydroxides.

[0083] As used herein, the terms "plurality" and "multiple" refer to two or more.

[0084] As used herein, the term "alkyl" refers to a saturated hydrocarbon group, including both straight-chain and branched structures. Examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl (e.g., n-propyl, isopropyl), butyl (e.g., n-butyl, isobutyl, sec-butyl, tert-butyl), and pentyl (e.g., n-pentyl, isopentyl, neopentyl). In various embodiments, a C1-C6 alkyl group, i.e., an alkyl group, may contain 1 to 6 carbon atoms.

[0085] As used herein, the term "haloalkyl" refers to a group resulting from the replacement of at least one hydrogen atom in an alkyl group with a halogen atom. The number of halogen atoms in a haloalkyl group may be one or more; when multiple halogen atoms are present, these halogen atoms may be the same or different.

[0086] As used herein, the term "alkoxy" refers to an alkyl group containing an oxygen atom (-O-). Examples of alkoxy groups include, but are not limited to, methoxy, ethoxy, and propoxy. In various embodiments, a C1-C6 alkoxy group, i.e., an alkoxy group, may contain 1 to 6 carbon atoms.

[0087] As used herein, the term "haloalkoxy" refers to a group in which at least one hydrogen atom in an alkoxy group is replaced by a halogen atom. The number of halogen atoms in a haloalkoxy group may be one or more; when multiple halogen atoms are present in a haloalkoxy group, the multiple halogen atoms may be the same or different.

[0088] Herein, the halogen atom refers to a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. Alternatively, the halogen atom is a fluorine atom.

[0089] Throughout this specification, substituents of compounds are disclosed in groups or ranges. It is expressly intended that such descriptions include every individual subcombination of the members of these groups and ranges. For example, it is expressly intended that the term "C1-C6 alkyl" individually discloses C1, C2, C3, C4, C5, C6, C1-C6, C1-C5, C1-C4, C1-C3, C1-C2, C2-C6, C2-C5, C2-C4, C2-C3, C3-C6, C3-C5, C3-C4, C4-C6, C4-C5, and C5-C6 alkyl.

[0090] The charge and discharge process of a battery is accompanied by the deintercalation and consumption of active lithium ions. The molar content of lithium in the positive electrode active material varies when the battery is discharged to different states. The molar content of Li in the list of positive electrode active materials in this application refers to the initial state of the material, that is, the state before the material is added. The molar content of Li will change after the positive electrode material is used in the battery system and undergoes charge and discharge cycles. During the preparation process of the positive electrode material, the oxygen content in the positive electrode material varies due to different process controls such as oxygen content. The molar content of O in the list of positive electrode materials in this application is only a theoretical state value; the actual molar content of O will fluctuate.

[0091] battery cells

[0092] Typically, a battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charge and discharge process of the battery cell, active ions (such as lithium ions) are embedded and released back and forth between the positive and negative electrodes. The separator is set between the positive and negative electrodes to prevent the positive and negative electrodes from short-circuiting while allowing active ions to pass through. The electrolyte plays the role of conducting active ions between the positive and negative electrode sheets.

[0093] The battery cells provided in the embodiments of the present application include a positive electrode active material and a negative electrode active material. The positive electrode active material includes a nickel-cobalt-manganese ternary material, and the negative electrode active material includes a silicon material, wherein the mass fraction of the silicon material in the negative electrode active material is s%. In the battery cells of the embodiments of the present application, the electrolyte includes a first additive, which is a halogen-containing cyclic structure. The mass fraction of the first additive in the electrolyte is P1%, and P1 satisfies the relationship: 1≤P1≤0.8×s-0.12. The first additive in the electrolyte exhibits attenuation, and the mass fraction P1% of the first additive in the electrolyte and the remaining charge q of the battery cell satisfy the relationship: P1≤2.4×q+0.2.

[0094] The nickel-cobalt-manganese ternary material may include one or more of lithium nickel-cobalt-manganese oxide and its modified compounds. The modified compounds of lithium nickel-cobalt-manganese oxide may include materials well known in the art, such as lithium nickel-cobalt-manganese oxide that has been doped or surface-modified.

[0095] The halogen-containing cyclic structure may include a halogen-containing cyclic ester compound, and the halogen may include one or more of F, Cl, Br, and I. The halogen-containing cyclic structure may be obtained by replacing hydrogen atoms on the cyclic structure with halogen atoms, or by replacing hydrogen atoms on the cyclic structure with atomic groups containing halogens.

[0096] The above-mentioned remaining capacity can be characterized by the battery state of health (SOH), which can indicate the percentage of the discharge capacity of the battery cell after full discharge to the initial capacity. The initial capacity has a meaning well known in the art and can be measured using equipment and methods known in the art. Typically, after the battery cell is manufactured, the initial capacity of the battery cell is measured and marked on the battery cell product. Therefore, the initial capacity of the battery cell can be determined by the marking of the battery cell.

[0097] Increasing the battery's charge cutoff voltage is considered an effective method for increasing battery energy density. Currently, the cathode materials for commercial high-capacity lithium-ion batteries primarily consist of nickel-cobalt-manganese ternary materials. Silicon, due to its extremely high theoretical specific capacity, far exceeding that of carbon materials, has become a highly promising anode active material. However, the volume expansion of silicon-based materials during charging can destabilize the solid electrolyte interface (SEI) film on the anode surface, negatively impacting the silicon material's capacity and the battery's cycle life.

[0098] Without intending to be limited by any theory or explanation, when the positive electrode active material of the battery cell includes a nickel-cobalt-manganese ternary material, the negative electrode active material includes a silicon material, and an appropriate amount of a first additive is included in the electrolyte, it can not only effectively increase the cut-off voltage of the battery, thereby increasing the energy density of the secondary battery, but also extend the cycle life of the battery.

[0099] Specifically, when the electrolyte contains a first additive, it can interact with the negative electrode active material, thereby forming an SEI film on the surface of the negative electrode plate in preference to the organic solvent. The inventors of this application have discovered that in high-voltage silicon systems (i.e., battery systems where the positive electrode material is a high-energy-density ternary material and the negative electrode is a silicon-based material), the first additive must meet specific conditions to effectively improve battery performance. Through analysis and other research, it was found that battery performance can only be significantly improved when the first additive content meets the requirements of the aforementioned relationship. The higher the content of the first additive, the denser the SEI film formed on the surface of the negative electrode plate, and the stronger its ability to inhibit contact between solvent molecules and the silicon material. When the content of the first additive is too low, the SEI film formed on the surface of the negative electrode plate is too thin, with poor uniformity and density, making it difficult to inhibit side reactions between the silicon material and the electrolyte, thereby shortening the battery's cycle life. However, when the content of the first additive is too high, the first additive may react with the electrolyte during cycling or storage, resulting in excessive gas production and reduced battery reliability. Based on the above relationship, when the content of the first additive in the electrolyte and the content of the silicon material in the negative electrode active material meet the ranges given in the embodiments of the present application, a stable, dense and appropriately thick SEI film can be formed on the surface of the negative electrode plate, thereby reducing the probability of side reactions between the silicon material and the electrolyte due to volume changes during the cycle.

[0100] The mass fraction of the first additive in the electrolyte described above is P1%, and P1 satisfies the relationship: 1≤P1≤0.8×s-0.12, which refers to the mass fraction of the first additive in the original state, that is, the amount of the first additive added before the battery is formed. Because the battery needs to undergo a formation process, the first additive will be consumed. During subsequent use, the first additive will further attenuate. The first additive in the electrolyte described above attenuates. The mass fraction P1% of the first additive in the electrolyte and the remaining charge q of the battery cell satisfy the relationship: P1≤2.4×q+0.2, which refers to the content of the first additive in the battery after formation and under normal use.

[0101] This not only reduces the irreversible loss of active lithium ions and improves the capacity of silicon materials, but also improves the cycle stability of the battery and extends the cycle life of the battery.

[0102] Therefore, the battery cells provided by the embodiments of the present application can have both high energy density and long cycle life.

[0103] In some embodiments, the mass fraction s% of the silicon material in the negative electrode active material may satisfy the following: 0<s≤50. For example, the mass fraction of the silicon material in the negative electrode active material may be 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or a range consisting of any two of the above values.

[0104] Optionally, in some embodiments, the mass fraction s% of the silicon material in the negative electrode active material may satisfy: 0<s≤25. For example, the mass fraction of the silicon material in the negative electrode active material may be 1%, 5%, 8%, 10%, 15%, 18%, 20%, 25%, or a range consisting of any two of the above values.

[0105] Without intending to be bound by any theory or explanation, adjusting the silicon content in the negative electrode active material to meet the given range can, on the one hand, enable the negative electrode active material to have a high theoretical capacity, thereby allowing the battery to have a high energy density; on the other hand, it can ensure that the content of the first additive in the electrolyte is appropriate, thereby reducing the risk of excessive gas generation during battery cycling or storage. This is conducive to further improving the battery's energy density and extending the battery's cycle life.

[0106] In some embodiments, the first additive may include an ester group.

[0107] Optionally, in some embodiments, the first additive may include at least one of the compounds represented by Formula I.

[0108] In formula I, p may represent 1, 2 or 3.

[0109] R 11 Can represent oxygen atom or C(Y 1 )2,Y 1 Each independently includes one of a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkenyloxy group having 2 to 20 carbon atoms, an alkynyloxy group having 2 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, and a haloaryloxy group having 6 to 20 carbon atoms.

[0110] R 12 、R 13 、R 14 、R 15Each of the following may independently include a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkenyloxy group having 2 to 20 carbon atoms, an alkynyloxy group having 2 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, and a haloaryloxy group having 6 to 20 carbon atoms, and R 12 、R 13 、R 14 、R 15 At least one of the group includes a halogen atom, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, and a haloaryloxy group having 6 to 20 carbon atoms.

[0111] When the electrolyte contains the first additive represented by Formula I, it can increase the inorganic content in the negative electrode SEI film, making the SEI film denser. This dense SEI film can restrain the expansion of the silicon material during cycling. Furthermore, the first additive represented by Formula I has good compatibility with the silicon material and can reduce the degree of damage to the SEI film on the silicon material surface during cycling, thereby reducing the loss of active lithium. This is beneficial for improving the battery's capacity and rate performance.

[0112] In some embodiments, in the above formula I, p may represent 1 or 2.

[0113] In some embodiments, R 11 Can represent oxygen atom or C(Y 1 )2,Y 1 Each independently represents a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a propyl group, a fluoromethyl group, a fluoroethyl group, a fluoropropyl group, a methoxy group, an ethoxy group, and a propoxy group.

[0114] In some embodiments, R 12 It can represent one of a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a fluoromethyl group, and a methoxy group.

[0115] In some embodiments, R 13 It can represent one of a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a fluoromethyl group, and a methoxy group.

[0116] In some embodiments, R 14 It can represent one of a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a fluoromethyl group, and a methoxy group.

[0117] In some embodiments, R 15 It can represent one of a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a fluoromethyl group, and a methoxy group.

[0118] In some embodiments, R 12 、R 13 、R 14 、R 15 Each independently represents a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a fluoromethyl group, a methoxy group, and R 12 、R 13 、R 14 、R 15 At least one of the fluorine atoms and the fluoromethyl groups includes one of the fluorine atoms and the fluoromethyl groups.

[0119] Without intending to be bound by any theory or explanation, in Formula I, p, R 12 、R 13 、R 14 、R 15 When one or more of the above conditions are met, a denser, more stable SEI film with stronger lithium ion conductivity can be formed on the surface of the negative electrode active material. Even after long-term charge and discharge, the SEI film can still effectively inhibit the contact between the negative electrode active material and the electrolyte, thereby effectively reducing the risk of pulverization and deactivation of the silicon material due to side reactions with the electrolyte, and further improving the cycle performance and storage performance of the battery.

[0120] In some embodiments, the first additive may include at least one of the following compounds H1 to H6.

[0121] Without intending to be bound by any theory or explanation, the above compounds H1 to H6 can decompose to produce a SEI film with a high inorganic content, thereby improving the cycle performance of the battery.

[0122] In some embodiments, the electrolyte may further include a second additive, and the second additive may include one or more boron-containing cyclic compounds.

[0123] In some embodiments, the second additive may include at least one of the compounds represented by Formula II-1 and Formula II-2.

[0124] In formula II-1, R 21 、R 22Each of the following may independently include a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkenyloxy group having 2 to 20 carbon atoms, an alkynyloxy group having 2 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, and a haloaryloxy group having 6 to 20 carbon atoms, and R 21 、R 22 At least one of the group includes a halogen atom, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, and a haloaryloxy group having 6 to 20 carbon atoms.

[0125] R 23 、R 24 Each independently represents a carbonyl group C=O or C(Y 2 )2,Y 2 Each of the following may independently include a hydrogen atom, a halogen atom, an alkyl group having 1 to 3 carbon atoms, or a halogenated alkyl group having 1 to 3 carbon atoms, and R 23 、R 24 It does not represent a carbonyl group C═O at the same time.

[0126] In Formula II-2, R 25 、R 26 Each of the following may independently include a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkenyloxy group having 2 to 20 carbon atoms, an alkynyloxy group having 2 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, and a haloaryloxy group having 6 to 20 carbon atoms, and R 25 、R 26At least one of the group includes a halogen atom, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, and a haloaryloxy group having 6 to 20 carbon atoms.

[0127] R 27 、R 28 Each of them may independently include one of a hydrogen atom, a halogen atom, an alkyl group having 1 to 3 carbon atoms, and a halogenated alkyl group having 1 to 3 carbon atoms.

[0128] Without intending to be bound by any theory or explanation, the second additive may form a denser, more stable, and more lithium-ion-conducting interfacial film on the surface of the positive electrode active material in preference to the organic solvent. This interfacial film helps reduce the charge transfer resistance on the positive electrode side, thereby mitigating the increase in internal resistance of the battery during cycling, thereby further extending the battery's cycle life.

[0129] In some embodiments, in Formula II-1, R 21 It can represent any one of a hydrogen atom, a methyl group, an ethyl group, and a fluoromethyl group.

[0130] Optionally, R 22 It can represent any one of a hydrogen atom, a methyl group, an ethyl group, and a fluoromethyl group.

[0131] Optionally, R 23 It can represent any one of a hydrogen atom, a methyl group, an ethyl group, and a carbonyl group.

[0132] Optionally, R 24 It can represent any one of a hydrogen atom, a methyl group, an ethyl group, and a carbonyl group.

[0133] In some embodiments, in Formula II-2, R 25 It can represent any one of a hydrogen atom, a methyl group, an ethyl group, and a fluoromethyl group.

[0134] Optionally, R 26 It can represent any one of a hydrogen atom, a methyl group, an ethyl group, and a fluoromethyl group.

[0135] Optionally, R 27 It can represent any one of a hydrogen atom, a methyl group, and an ethyl group.

[0136] Optionally, R 28 It can represent any one of a hydrogen atom, a methyl group, and an ethyl group.

[0137] Without intending to be bound by any theory or explanation, when Formula II-1 and / or Formula II-1 satisfy one or more of the above conditions, a denser, more stable SEI film with stronger lithium ion conductivity can be formed on the surface of the positive electrode active material, thereby effectively reducing the oxidation reaction of the electrolyte on the positive electrode surface and further slowing the increase in the internal resistance of the battery during cycling. This is conducive to further extending the cycle life of the battery and improving the cycling stability of the battery.

[0138] In some embodiments, the second additive may include at least one of the following compounds J1-J4.

[0139] Without intending to be bound by any theory or explanation, the above-mentioned compounds J1 to J4 can form a film on the positive electrode, reducing the risk of oxidative decomposition of the electrolyte under high voltage, thereby improving the structural stability of the positive electrode active material and further improving the cycle stability of the battery.

[0140] In some embodiments, the second additive comprises P2% by weight in the electrolyte, where P2 satisfies the relationship: 0.11 + 0.01 × t ≤ P2 ≤ 1.2, where t% is the weight percentage of the nickel-cobalt-manganese ternary material in the positive electrode mixture film layer of the battery cell. This helps improve the structural stability of the positive electrode active material, thereby enhancing the cycling stability of the battery.

[0141] In some embodiments, 50≤t<100.

[0142] Without intending to be limited by any theory or explanation, when the content of nickel-cobalt-manganese ternary material in the positive electrode film layer is within the above-mentioned appropriate range, it is beneficial for the positive electrode active material to have both high capacity and high cycle stability, thereby further improving the energy density of the battery and extending the cycle life of the battery.

[0143] In some embodiments, the ratio of the mass content of the second additive in the electrolyte to the mass content of the first additive in the electrolyte can be 1:40 to 1:1, for example, 1:40 to 1:1, 1:30 to 1:1, 1:20 to 1:1, 1:10 to 1:1, 1:5 to 1:1, 1:4 to 1:1, 1:3 to 1:1, 1:2 to 1:1, 1:1.5 to 1:1, 1:1.2 to 1:1.

[0144] Optionally, in some embodiments, the ratio of the mass content of the second additive in the electrolyte to the mass content of the first additive in the electrolyte can be 1:5 to 1:2, 1:4.5 to 1:2, 1:4 to 1:2, 1:3.5 to 1:2, 1:3 to 1:2, 1:2.5 to 1:2, 1:5 to 1:3, 1:4.5 to 1:3, 1:4 to 1:3, 1:4.5 to 1:3, 1:5 to 1:4.

[0145] Without intending to be bound by any theory or explanation, when the contents of the second additive and the first additive in the electrolyte satisfy the given relationship, the second additive and the first additive can work synergistically. This not only helps reduce the initial internal resistance of the battery and the growth of internal resistance during cycling, but also helps reduce gas generation during storage, thereby contributing to a long cycle life and high reliability of the battery.

[0146] In some embodiments, the charge cut-off voltage of the battery cell may be greater than or equal to 4.2V, for example, 4.2V, 4.25V, 4.3V, 4.35V, 4.4V, 4.45V, 4.5V, or a range consisting of any two of the above values.

[0147] Optionally, in some embodiments, the charge cut-off voltage of the battery cell may be greater than or equal to 4.3V, for example, 4.3V, 4.35V, 4.4V, 4.45V, 4.5V, or a range consisting of any two of the above values.

[0148] Without intending to be bound by any theory or explanation, the electrolyte of the battery cell provided in the embodiment of the present application includes a first additive, which is conducive to the formation of a dense and stable SEI film on the surface of the negative electrode. Optionally, the electrolyte of the battery cell provided in the embodiment of the present application may further include a second additive, which is conducive to the formation of a dense and stable interface film on the surface of the positive electrode. This is conducive to improving the stability of the electrode active material structure and the stability of the interface film on the electrode surface, thereby allowing the battery cell to be charged and discharged at a higher charge cut-off voltage. This is conducive to improving the capacity utilization and cycle stability of the battery, thereby helping to improve the energy density of the battery and extend the cycle life of the battery.

[0149] In some embodiments, the molar content of Ni in the transition metal element in the nickel-cobalt-manganese ternary material may be less than or equal to 0.7. For example, the molar content of Ni in the transition metal element may be 0.7, 0.65, 0.6, 0.55, 0.5, 0.45, 0.4, 0.35, 0.3, 0.25, 0.2, 0.15, 0.1, or a range consisting of any two of the above values. The molar content of Ni in the transition metal element is less than or equal to 0.7, which can be expressed as follows: in the nickel-cobalt-manganese ternary material, based on the total molar amount of the transition metal element, the molar content of Ni in the transition metal element is less than or equal to 0.7. As an example, when the nickel-cobalt-manganese ternary material is an undoped nickel-cobalt-manganese ternary material, the molar content of Ni in the transition metal element is less than or equal to 0.7, which can be expressed as: the value of the molar amount of nickel element / (molar amount of nickel element + molar amount of cobalt element + molar amount of manganese element) is less than or equal to 0.7. For example, the nickel-cobalt-manganese ternary material in which the molar content of Ni in the transition metal element is less than or equal to 0.7 may include LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622) and so on.

[0150] The molar content of Ni in the transition metal elements in the nickel-cobalt-manganese ternary material satisfies the given range, which is beneficial to further improve the cycle stability of the positive electrode active material, thereby helping to extend the cycle life of the battery.

[0151] In some embodiments, the positive electrode active material may include a first nickel-cobalt-manganese ternary material having a molar content of Ni element in the transition metal element of 0.5 or more. As an example, the first nickel-cobalt-manganese ternary material may include Li x Ni a Co b Mn c M y O2 and Li x Ni a Co b Mn c M y At least one of the composite materials obtained by doping modification and / or surface modification of O2, wherein 1.05≥x>0.9, 1>a≥0.5, 0.1≥b>0, 0.5≥c≥0, 0.05≥y≥0, and M includes one or more of Ti, Al, Zr, Mg, Zn, Ba, Mo, and B.

[0152] Optionally, in some embodiments, the positive electrode active material may further include a second nickel-cobalt-manganese ternary material in which the molar content of Ni in the transition metal element is less than 0.5. As an example, the second nickel-cobalt-manganese ternary material may include Li x1 Nia1 Co b1 Mn c1 M 1 y1 O2 and Li x1 Ni a1 Co b1 Mn c1 M 1 y1 At least one of the composite materials obtained by doping modification and / or surface modification of O2, wherein 1.05≥x1>0.9, 0.5>a1≥0.2, 0.1≥b1>0, 0.8≥c1≥0.35, 0.05≥y1≥0, M 1 Including one or more of Ti, Al, Zr, Mg, Zn, Ba, Mo, and B.

[0153] Optionally, in some embodiments, the positive electrode active material may further include a lithium-rich manganese-based positive electrode material. As an example, the lithium-rich manganese-based positive electrode material may include Li x2 Ni a2 Co b2 Mn c2 M 2 y2 O2 and Li x2 Ni a2 Co b2 Mn c2 M 2 y2 At least one of the composite materials obtained by doping modification and / or surface modification of O2, wherein 1.25≥x2>1.05, 0.7≥a2≥0, 0.2≥b2≥0, 0.7≥c2>0.4, 0.1≥y2≥0, M 2 Including one or more of Ti, Al, Nb, Zr, Mg, Zn, W, Na, Cr, Cd, K, Cu, Fe, Ba, Mo, B, F, Cl, Si, optionally, 0.5≥a2>0, 0.15≥b2≥0.

[0154] Optionally, in some embodiments, the positive electrode active material may further include a lithium-containing phosphate positive electrode material. As an example, the lithium-containing phosphate positive electrode material may include Li x3 Fe d Mn c3 M 3 y3 PO4 or Li x3 Fe d Mn c3 M 3 y3At least one of the composite materials obtained by doping modification and / or surface modification of PO4, wherein 1≥x3>0.9, 1≥c3≥0, 0.1≥y3≥0, 1≥d≥0, M 3 It includes transition metal elements other than Fe and Mn and one or more non-transition metal elements.

[0155] The first nickel-cobalt-manganese ternary material, the second nickel-cobalt-manganese ternary material, the lithium-rich manganese-based positive electrode material and the lithium-containing phosphate positive electrode material can be arranged on one side or both sides of the current collector by physical mixing or layering.

[0156] As an example, the positive electrode active material may include LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622). Optionally, the positive electrode active material may further include LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811),Li 1.2 Co 0.13 Ni 0.13 Mn 0.54 O2(LRM114), Li 1.15 Co 0.09 Ni 0.18 Mn 0.55 O2、Li 1.11 Ni 0.3 Mn 0.6 O2、Li 1.15 Co 0.03 Ni 0.18 Mn 0.55 O2、LiFePO4、LiMnPO4、LiMn 1-x4 Fe x4 One or more of PO4, where 1>x4>0.

[0157] Without intending to be limited by any theory or explanation, when the positive electrode active material comprises one or more of the above-mentioned positive electrode materials, the positive electrode active material can have both high theoretical specific capacity and good cycle stability, thereby helping to further improve the energy density of the battery and extend the cycle life of the battery.

[0158] In some embodiments, the silicon material may include at least one of nano-silicon, silicon oxide compounds, and silicon carbon compounds.

[0159] In some embodiments, the negative electrode active material may further include a carbon material, which may include at least one of artificial graphite, natural graphite, and hard carbon. When the negative electrode active material also includes a carbon material, it is not only advantageous to flexibly adjust parameters such as the compaction density and porosity of the negative electrode film layer by combining silicon-based negative electrode active material particles with the carbon material, but also advantageously improve the electron transport performance of the negative electrode, thereby improving the safety and electrochemical performance of the secondary battery.

[0160] In some embodiments, the volume distribution particle size Dv50 of the silicon material can be 3 μm to 20 μm, for example, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, or a range consisting of any two of the above values.

[0161] Optionally, in some embodiments, the volume distribution particle size Dv50 of the silicon material can be 3 μm to 15 μm, for example, 3 μm, 4 μm, 5 μm, 8 μm, 10 μm, 12 μm, 14 μm, 15 μm, or a range consisting of any two of the above values.

[0162] Without intending to be limited by any theory or explanation, when the silicon material has a larger volume distribution particle size, it generally has a higher gram capacity, but correspondingly, the volume expansion effect of the silicon material will also be exacerbated. In the battery cell provided in the embodiment of the present application, the presence of the first additive helps to form a stable and dense SEI film on the surface of the negative electrode active material. Thus, when the silicon material undergoes volume expansion, the SEI film can effectively inhibit the silicon material from contacting the electrolyte, thereby reducing the risk of pulverization and inactivation of the silicon material due to side reactions. Therefore, it is possible to use the above-mentioned silicon material with a larger particle size in the battery cell of the embodiment of the present application, thereby allowing the battery cell of the embodiment of the present application to have a high energy density.

[0163] The volume distribution particle size Dv50 of the silicon material has a meaning well known in the art, and may represent the particle size corresponding to the cumulative particle size distribution percentage of the silicon material in the volume-based particle size distribution reaching 50%. The volume distribution particle size Dv50 can be measured using equipment and methods known in the art. For example, it can be measured using a laser particle size analyzer (e.g., Malvern Master Size 3000) in accordance with GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method.

[0164] In some embodiments, the electrolyte may further include a cyclic carbonate. When the electrolyte further includes a cyclic carbonate, it helps the first additive to smoothly form a stable and dense SEI film on the surface of the negative electrode active material, thereby further reducing the capacity loss of the battery and improving the cycle stability of the battery.

[0165] In some embodiments, at 25° C., the conductivity of the electrolyte can be 7 ms / cm to 11 ms / cm, for example, 7 ms / cm, 8 ms / cm, 9 ms / cm, 10 ms / cm, 11 ms / cm, or a range consisting of any two of the above values.

[0166] Optionally, in some embodiments, at 25° C., the conductivity of the electrolyte may be 8 ms / cm to 9 ms / cm, for example, 8 ms / cm, 8.2 ms / cm, 8.4 ms / cm, 8.6 ms / cm, 8.8 ms / cm, 9 ms / cm, or a range consisting of any two of the above values.

[0167] Without intending to be bound by any theory or explanation, when the conductivity of the electrolyte satisfies the given range, it is beneficial to enhance the cycle performance of the battery and improve the charging capacity of the battery.

[0168] The conductivity of the electrolyte has a well-known meaning in the art and can be measured by equipment and methods known in the art, for example, by using a conductivity meter according to HG / T 4066-4067-2008.

[0169] In some embodiments, at 25°C, the viscosity of the electrolyte can be 2.5mPa.s / cP to 5mPa.s / cP, for example, 2.5mPa.s / cP, 3mPa.s / cP, 3.5mPa.s / cP, 4mPa.s / cP, 4.5mPa.s / cP, 5mPa.s / cP or a range consisting of any two of the above values.

[0170] Optionally, in some embodiments, at 25°C, the viscosity of the electrolyte can also be 3mPa.s / cP~4mPa.s / cP, 3.2mPa.s / cP~4mPa.s / cP, 3.5mPa.s / cP~4mPa.s / cP, 3.8mPa.s / cP~4mPa.s / cP, 3mPa.s / cP~3.8mPa.s / cP, 3.2mPa.s / cP~3.8mPa.s / cP, 3.5mPa.s / cP~3.8mPa.s / cP, 3mPa.s / cP~3.5mPa.s / cP, 3.2mPa.s / cP~3.5mPa.s / cP, 3mPa.s / cP~3.2mPa.s / cP.

[0171] Without intending to be bound by any theory or explanation, when the viscosity of the electrolyte falls within the given range, it is beneficial to enhance the cycle performance of the battery and improve the low-temperature charging capability of the battery.

[0172] The viscosity of the electrolyte has a well-known meaning in the art and can be measured by equipment and methods known in the art. For example, it can be measured using a viscometer, such as a DV-2TLV viscometer, with reference to SJ / T 11723-2018.

[0173] In some embodiments, in the battery cells of the embodiments of the present application, the positive electrode sheet of the electrode assembly may include a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and comprising a positive electrode active material. For example, the positive electrode current collector may have two opposing surfaces in its thickness direction, and the positive electrode film layer may be disposed on either or both of the two opposing surfaces of the positive electrode current collector.

[0174] In some embodiments, the positive electrode film layer may further include a positive electrode conductive agent. The present application does not particularly limit the type of the positive electrode conductive agent. For example, the positive electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0175] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. This application does not particularly limit the type of positive electrode binder. As an example, the positive electrode binder 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 fluorine-containing acrylic resin.

[0176] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include at least one 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 may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0177] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0178] In some embodiments, in the battery cells of the embodiments of the present application, the negative electrode sheet of the electrode assembly may include a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and comprising a negative electrode active material. For example, the negative electrode current collector may have two opposing surfaces in the thickness direction of the negative electrode current collector, and the negative electrode film layer may be disposed on either or both of the two opposing surfaces of the negative electrode current collector.

[0179] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. The present application does not particularly limit the type of the negative electrode conductive agent. As an example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0180] In some embodiments, the negative electrode film layer may further optionally include a negative electrode binder. The present application does not particularly limit the type of the negative electrode binder. As examples, the negative electrode binder may include at least one 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).

[0181] In some embodiments, the negative electrode film layer may further include other additives, such as thickeners, sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like.

[0182] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include at least one of copper, a copper alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0183] The negative electrode film layer is typically formed by coating the negative electrode slurry onto the negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing the negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0184] The negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode plate also includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In some embodiments, the negative electrode plate of the present application also includes a protective layer covering the surface of the negative electrode film layer.

[0185] The embodiments of the present application do not particularly limit the type of separator used in the electrode assembly of the battery cell. Any known porous structure separator with good chemical stability and mechanical stability can be selected.

[0186] In some embodiments, the material of the isolation membrane may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The isolation membrane may be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer may be the same or different.

[0187] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet may be formed into an electrode assembly through a winding process or a lamination process.

[0188] In the battery cells of the embodiments of the present application, the electrolyte includes an electrolyte salt and a solvent. The types of the electrolyte salt and the solvent are not specifically limited and can be selected according to actual needs.

[0189] As an example, the electrolyte salt may include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0190] As an example, the solvent may include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0191] In some embodiments, the electrolyte may optionally include other additives. For example, the additives may include additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, additives that improve battery low-temperature power performance, etc.

[0192] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be made into an electrode assembly through a winding process and / or a lamination process.

[0193] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0194] In some embodiments, the outer packaging of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0195] The present application has no particular limitation on the shape of the battery cell, which can be cylindrical, square or any other shape. FIG1 shows a battery cell 5 with a square structure as an example.

[0196] In some embodiments, as shown in FIG2 , the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process and / or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be adjusted according to demand.

[0197] The preparation method of battery cells is well known. In some embodiments, a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, separator, and negative electrode sheet can be wound and / or laminated to form an electrode assembly. The electrode assembly is then placed in an outer package, dried, and then injected with electrolyte. The battery cell is then vacuum packaged, allowed to stand, formed, and shaped.

[0198] Battery

[0199] The battery mentioned in the embodiments of the present application may include one or more battery cells to provide a single physical module with higher voltage and capacity. When there are multiple battery cells, the multiple battery cells are connected in series, in parallel or in hybrid through a busbar.

[0200] In some embodiments, the battery may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. FIG3 is a schematic diagram of a battery module 4 as an example. As shown in FIG3 , in the battery module 4, the multiple battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. The multiple battery cells 5 may further be fixed by fasteners. Optionally, the battery module 4 may further include a housing having a storage space, and the multiple battery cells 5 are accommodated in the storage space.

[0201] In some embodiments, the battery may be a battery pack, which includes a case and battery cells. The battery cells or battery modules are housed in the case. The number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0202] Figures 4 and 5 are schematic diagrams of an exemplary battery pack 1. As shown in Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 covers the lower case 3 and forms an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0203] Electrical devices

[0204] The embodiments of the present application also provide an electrical device, which includes a battery cell or battery provided in the embodiments of the present application. The battery cell or battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

[0205] The electrical device can select a battery cell or a battery according to its usage requirements.

[0206] Figure 6 is a schematic diagram of an exemplary electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of this device, a battery pack or battery module may be used.

[0207] As another example, an electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0208] Example

[0209] The following examples describe the present disclosure in more detail. These examples are intended to be illustrative only, as various modifications and variations 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 by mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing. The instruments used in the examples are commercially available.

[0210] Example 1

[0211] Preparation of positive electrode

[0212] The positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiFePO4, conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) are mixed evenly in an appropriate amount of solvent N-methylpyrrolidone (NMP) in a mass ratio of 35:61.2:2.7:1.1 to obtain a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector aluminum foil, and the positive electrode sheet is obtained through drying, cold pressing, slitting, cutting and other processes.

[0213] Preparation of negative electrode sheet

[0214] The negative electrode active material silicon oxide, artificial graphite, conductive agent carbon black (Super P), binder styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC) are mixed uniformly in an appropriate amount of solvent deionized water according to a mass ratio of 1.4:95:0.7:1.8:1.1 to obtain a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector copper foil, and the negative electrode sheet is obtained through drying, cold pressing, slitting and cutting processes.

[0215] Preparation of isolation membrane

[0216] Polypropylene film is used as the isolation film.

[0217] Preparation of electrolyte

[0218] The first additive H1, ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are mixed in a mass ratio of 1:54:30:15 to obtain an organic solvent, and fully dried LiPF6 is dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0219] Preparation of secondary batteries

[0220] The positive electrode sheet, separator, and negative electrode sheet are stacked and wound in sequence to obtain an electrode assembly; the electrode assembly is placed in an outer package, dried, and then injected with electrolyte. After vacuum packaging, standing, formation, shaping and other processes, a secondary battery is obtained.

[0221] The secondary batteries of Examples 2-23 and Comparative Examples 1-3 are similar to Example 1, except that the electrolyte preparation parameters, NCM811 content, or silicon oxide content are adjusted, as shown in Table 1. The first additives H1-H6 and the second additives J1-J4 are respectively represented by the following formulas.

[0222] Test section

[0223] (1) Normal temperature cycle performance test

[0224] At 25°C, charge the secondary battery at a constant current of 0.33C to 4.3V. Then, charge it at a constant voltage of 4.3V to a current of 0.05C. After 5 minutes, discharge it at 0.33C to 3.0V. The resulting capacity is recorded as the initial capacity, C0. Repeat these steps for the same battery, recording the discharge capacity, Cn, after each cycle. When Cn / C0 × 100% ≤ 80%, record the corresponding number of cycles.

[0225] (2) Battery DC internal resistance (DCR) test

[0226] At 25°C, charge the secondary battery at a constant current of 0.33C to 4.3V. Then charge it at a constant voltage of 4.3V to a current of 0.05C. Rest it for 5 minutes. Record the voltage V1 at the last second of rest. Discharge it at 4C for 30 seconds. Record the voltage V2 at the last second of discharge. Calculate the initial DCR (DCR) by (V2 - V1) / the current corresponding to the 4C rate. Repeat this step for every 100 cycles of the same battery, and calculate the DCR at the 100th cycle. Cycle DCR Growth (%) = (DCR at the 100th cycle - Initial DCR) / Initial DCR × 100%.

[0227] The test results are shown in Table 2.

[0228] Table 1

[0229] Table 2

[0230] The remaining capacity of the battery cells of Example 1 and Example 4 and the mass fraction of the first additive in the electrolyte were monitored. When the remaining capacity of the battery cells was 70%, the mass fraction of the first additive in the electrolyte (P1% in the use state) was as shown in Table 3.

[0231] Table 3

[0232] The test results in Tables 1 to 3 indicate that the electrolyte of the battery cell includes the first additive described in the examples of this application, and the content of the first additive meets the range given in the examples of this application, which can effectively improve the cycle performance of the battery. When the electrolyte also includes the second additive described in the examples of this application, it can further suppress the increase of the battery's internal resistance, thereby further improving the battery's cycle performance.

[0233] In contrast, the electrolyte of Comparative Example 1 does not contain the first additive, and the cycle performance of its battery is far inferior to that of Examples 1 to 23. In the electrolytes of Comparative Examples 2 and 3, the amount of the first additive added does not meet the range given in the examples of this application, and the cycle performance of its batteries is also unsatisfactory.

[0234] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and within the scope of the technical solution of the present application, embodiments having substantially the same structure as the technical idea and exerting the same effects are all included in the technical scope of the present application. In addition, within the scope of the subject matter of the present application, various modifications that can be conceived by those skilled in the art to the embodiments, and other methods constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, characterized in that: The battery cell comprises a positive electrode active material, a negative electrode active material and an electrolyte, wherein the positive electrode active material comprises a nickel-cobalt-manganese ternary material; The negative electrode active material includes silicon material, and the mass fraction of the silicon material in the negative electrode active material is s%; The electrolyte includes a first additive, the first additive includes a halogen-containing cyclic structure, the mass fraction of the first additive in the electrolyte is P1%, and P1 satisfies the relationship: 1≤P1≤0.8×s-0.12; Or, the electrolyte includes the first additive, the first additive is attenuated, and the mass fraction P1% of the first additive in the electrolyte and the remaining power q of the battery cell satisfy the relationship: P1≤2.4×q+0.

2.

2. The battery cell according to claim 1, characterized in that: The mass fraction s% of the silicon material in the negative electrode active material satisfies: 0<s≤50, optionally, 0<s≤25.

3. The battery cell according to claim 1 or 2, characterized in that: The first additive comprises an ester group. Optionally, the first additive comprises at least one of the compounds represented by Formula I: p means 1, 2 or 3; R 11 represents an oxygen atom or C(Y 1 )2,Y 1 each independently includes a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkenyloxy group having 2 to 20 carbon atoms, an alkynyloxy group having 2 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, and a haloaryloxy group having 6 to 20 carbon atoms, R 12 , R 13 , R 14 , R 15 each independently includes a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkenyloxy group having 2 to 20 carbon atoms, an alkynyloxy group having 2 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, or a haloaryloxy group having 6 to 20 carbon atoms, and R 12 , R 13 , R 14 , R 15 At least one of the following includes a halogen atom, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, and a haloaryloxy group having 6 to 20 carbon atoms.

4. The battery cell according to claim 3, wherein: The compound represented by formula I satisfies at least one of the following conditions (1) to (6): (1) p represents 1 or 2; (2)R 11 represents an oxygen atom or C(Y 1 )2,Y 1 Each independently represents one of a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a propyl group, a fluoromethyl group, a fluoroethyl group, a fluoropropyl group, a methoxy group, an ethoxy group, and a propoxy group; (3)R 12 independently represent one of a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a propyl group, a fluoromethyl group, a fluoroethyl group, a fluoropropyl group, a methoxy group, an ethoxy group, and a propoxy group; (4)R 13 independently represent one of a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a propyl group, a fluoromethyl group, a fluoroethyl group, a fluoropropyl group, a methoxy group, an ethoxy group, and a propoxy group; (5)R 14 independently represent one of a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a propyl group, a fluoromethyl group, a fluoroethyl group, a fluoropropyl group, a methoxy group, an ethoxy group, and a propoxy group; (6)R 15 Each of the groups independently represents a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a propyl group, a fluoromethyl group, a fluoroethyl group, a fluoropropyl group, a methoxy group, an ethoxy group, and a propoxy group.

5. The battery cell according to any one of claims 1 to 4, wherein: The first additive includes at least one of the following compounds:

6. The battery cell according to any one of claims 1 to 5, characterized in that: The electrolyte further includes a second additive, wherein the second additive includes one or more boron-containing cyclic compounds; Optionally, the second additive includes at least one of the compounds represented by Formula II-1 and Formula II-2: R 21 , R 22 each independently includes a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkenyloxy group having 2 to 20 carbon atoms, an alkynyloxy group having 2 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, or a haloaryloxy group having 6 to 20 carbon atoms, and R 21 , R 22 At least one of the following includes a halogen atom, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, or a haloaryloxy group having 6 to 20 carbon atoms; R 23 , R 24 Each independently represents a carbonyl group C=O or C(Y 2 )2,Y 2 Each independently includes a hydrogen atom, a halogen atom, an alkyl group having 1 to 3 carbon atoms, or a halogenated alkyl group having 1 to 3 carbon atoms, and R 23 , R 24 Not simultaneously represent carbonyl C=O; R 25 , R 26 each independently includes a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkenyloxy group having 2 to 20 carbon atoms, an alkynyloxy group having 2 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, or a haloaryloxy group having 6 to 20 carbon atoms, and R 25 , R 26 At least one of the following includes a halogen atom, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, or a haloaryloxy group having 6 to 20 carbon atoms; R 27 , R 28 Each independently includes one of a hydrogen atom, a halogen atom, an alkyl group having 1 to 3 carbon atoms, and a halogenated alkyl group having 1 to 3 carbon atoms.

7. The battery cell according to claim 6, characterized in that: The compound represented by formula II-1 satisfies at least one of the following conditions (1) to (4): (1)R 21 represents one of a hydrogen atom, a methyl group, an ethyl group, and a fluoromethyl group; (2)R 22 represents one of a hydrogen atom, a methyl group, an ethyl group, and a fluoromethyl group; (3)R 23 represents one of a hydrogen atom, a methyl group, an ethyl group, and a carbonyl group; (4)R 24 represents one of a hydrogen atom, a methyl group, an ethyl group, and a carbonyl group; and / or The compound represented by formula II-2 satisfies at least one of the following conditions (5) to (8): (5)R 25 represents one of a hydrogen atom, a methyl group, an ethyl group, and a fluoromethyl group; (6)R 26 represents one of a hydrogen atom, a methyl group, an ethyl group, and a fluoromethyl group; (7)R 27 represents one of a hydrogen atom, a methyl group, and an ethyl group; (8)R 28 It represents one of a hydrogen atom, a methyl group, and an ethyl group.

8. The secondary battery according to any one of claims 1 to 7, wherein: The second additive includes at least one of the following compounds:

9. The battery cell according to any one of claims 6 to 8, characterized in that: The mass content of the second additive in the electrolyte is P2%, and P2 satisfies the relationship: 0.11+0.01×t≤P2≤1.2, wherein t% is the mass percentage of the nickel-cobalt-manganese ternary material in the positive electrode film layer of the battery cell.

10. The battery cell according to claim 9, characterized in that: 50≤t<100。 11. The battery cell according to claim 9 or 10, characterized in that: The ratio of the mass content of the second additive in the electrolyte to the mass content of the first additive in the electrolyte is 1:40 to 1:1, optionally, 1:5 to 1:

2.

12. The battery cell according to any one of claims 1 to 11, characterized in that: The charging cut-off voltage of the battery cell is greater than or equal to 4.2V. Optionally, the charging cut-off voltage is greater than or equal to 4.3V.

13. The battery cell according to any one of claims 1 to 12, characterized in that: The molar content of Ni element in the transition metal elements in the nickel-cobalt-manganese ternary material is less than or equal to 0.

7.

14. The battery cell according to any one of claims 1 to 13, characterized in that: The positive electrode active material includes a first nickel-cobalt-manganese ternary material in which the molar content of Ni element in the transition metal element is greater than 0.5; Optionally, the positive electrode active material further comprises a second nickel-cobalt-manganese ternary material in which the molar content of the Ni element in the transition metal element is less than 0.5; Optionally, the positive electrode active material further comprises a lithium-rich manganese-based positive electrode material; Optionally, the positive electrode active material further includes a lithium-containing phosphate positive electrode material.

15. The battery cell according to any one of claims 1 to 14, characterized in that: The silicon material includes at least one of nano-silicon, silicon-oxygen compounds, and silicon-carbon compounds; and / or The negative electrode active material further includes a carbon material, and the carbon material includes at least one of artificial graphite, natural graphite, and hard carbon.

16. The battery cell according to any one of claims 1 to 15, characterized in that: The volume distribution particle size Dv50 of the silicon material is 3 μm to 20 μm. Optionally, the volume distribution particle size Dv50 of the silicon material is 3 μm to 15 μm.

17. The battery cell according to any one of claims 1 to 16, characterized in that: The electrolyte also includes a cyclic carbonate.

18. The battery cell according to any one of claims 1 to 17, characterized in that: At 25° C., the conductivity of the electrolyte is 7 ms / cm to 11 ms / cm, and optionally, 8 ms / cm to 9 ms / cm.

19. The battery cell according to any one of claims 1 to 18, characterized in that: At 25° C., the viscosity of the electrolyte is 2.5 mPa.s / cP to 5 mPa.s / cP, and optionally, 3 mPa.s / cP to 4 mPa.s / cP.

20. A battery, characterized in that: The battery comprises the battery cell according to any one of claims 1-19.

21. An electrical device, characterized in that: The electrical device comprises the battery cell according to any one of claims 1 to 19 or the battery according to claim 20.

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