Battery monomer, battery comprising battery monomer and power utilization device

Abstract

The invention provides a battery monomer, a battery comprising the battery monomer and an electric device, the battery monomer comprises a positive pole piece and an electrolyte, the positive pole piece comprises a positive active material, the positive active material comprises an inner core and a coating layer coating the inner core, the inner core comprises Lix (NiaCobMnc) dMeOfAy, x, a, b, c, d, e, f and y are respectively described in the specification, M comprises one or more of Zr, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb or Al, and the coating layer comprises one or more of Ni, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb or Al. A comprises one or more of S, N, F, Cl, Br or I; the coating layer comprises an element Y, and the element Y comprises one or more of Co, Zr, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb or Al; the electrolyte solution includes a first additive including an organic material including a Si-N bond and a Si-O bond.

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 including the same, and an electrical device. The battery cell and the battery including the same can have both high energy density and good cycle performance.

[0005] In a first aspect, an embodiment of the present application provides a battery cell comprising a positive electrode plate and an electrolyte, wherein the positive electrode plate comprises a positive electrode active material, and the positive electrode active material comprises a core and a coating layer coating the core.

[0006] The core includes Li x (Ni a Co b Mn c ) d M e O f A y , wherein, 0.2≤x≤1.3, 0.3≤a≤0.7, 0.01≤b≤0.15, 0.1≤c≤0.5, 0.95≤d≤1, 0≤e≤0.05, 1.8≤f≤2, 0≤y≤0.1, M includes one or more of Zr, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb or Al, and A includes one or more of S, N, F, Cl, Br or I.

[0007] The coating layer contains element Y, and element Y includes one or more of Co, Zr, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb or Al.

[0008] The electrolyte includes a first additive including an organic substance containing Si—N bonds and Si—O bonds.

[0009] Without intending to be bound by any theory or explanation, the battery cell of the embodiment of the present application includes the above-mentioned positive electrode active material, which includes a core comprising a doped nickel-cobalt-manganese ternary material and a coating layer covering the core, wherein the coating layer includes a specific element Y. When subjected to charge and discharge cycles at high voltage, the positive electrode active material can maintain high structural stability. Furthermore, the electrolyte of the battery cell of the embodiment of the present application also includes a first additive. The Si-N bond of the first additive easily combines with nucleophilic substances in the electrolyte to form a silicon-based derivative, thereby forming a low-impedance interface film on the surface of the positive electrode plate and the surface of the negative electrode plate. This not only reduces the impedance of the positive electrode plate, but also inhibits the decomposition of LiPF6, thereby reducing HF generation, inhibiting the dissolution of transition metals, and improving the battery's cycling performance at high voltage. At the same time, the silicon in the silicon-based derivative can react with fluorine, thereby inhibiting the formation of LiF on the surface of the positive electrode plate, improving the ionic conductivity of the positive electrode plate surface, thereby reducing the capacity fade of the battery and improving the initial DCR of the battery. In addition, the lone electron pair of the oxygen atom in the Si-O bond of the first additive can also capture protons (H + ), thereby further suppressing the generation of HF and improving the cycle performance of the battery at high voltage.

[0010] Therefore, the battery cell of the embodiment of the present application can have both high energy density and good cycle performance.

[0011] In any embodiment of the present application, the coating layer comprises one or more of the element Y, its oxide, boride, phosphate, oxalate, carbonate, sulfate, or thermal decomposition product thereof. This can improve the interfacial stability of the positive electrode active material at high voltages, reduce the DCR increase during cycling, and further improve the cycling performance of the battery.

[0012] In any embodiment of the present application, the content of element Y, u ppm, based on the total mass of the positive electrode active material, satisfies the following: 3000 ≤ u ≤ 15000. Alternatively, 5000 ≤ u ≤ 10000. This allows the coating layer to maintain good lithium ion transport performance, thereby facilitating improved gram capacity of the positive electrode active material and enhancing the energy density and cycle performance of the battery.

[0013] In any embodiment of the present application, the first additive includes one or more compounds represented by Formula 1 and Formula 2.

[0014] In Formula 1 and Formula 2, R1, R2, R3, R4, R5, R6, R7, and R8 each independently represent a hydrogen atom or one of the following substituted or unsubstituted groups.

[0015] C1-C12 alkyl or alkoxy, C2-C12 alkenyl or alkenyloxy, C2-C12 alkynyl or alkynyloxy, C3-C12 cycloalkyl or epoxyalkyl, C1-C12 cyano or cyanooxy, C1-C12 silanyl. Optionally, the substituent includes halogen.

[0016] Optionally, R1, R2, R3, R4, R5, and R6 each independently represent a substituted or unsubstituted C1-C5 alkyl or alkoxy group, a substituted or unsubstituted C2-C6 alkenyl or alkenyloxy group, and at least one of R1, R2, R3, R4, R5, and R6 is a C1-C3 alkyl or alkoxy group; R7 represents a substituted or unsubstituted C1-C3 alkyl or alkoxy group; R8 represents a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl or alkoxy group, and a substituted or unsubstituted C1-C4 silyl group.

[0017] The compounds represented by Formula 1 and Formula 2 can react with nucleophilic substances in the electrolyte to form a low-impedance interfacial film on the surfaces of the positive and negative electrodes. This not only reduces the impedance of the positive electrode, but also inhibits the decomposition of LiPF6, thereby reducing HF generation, inhibiting the dissolution of transition metals, and improving the battery's cycling performance at high voltages.

[0018] In any embodiment of the present application, the first additive includes one or more of N,O-bistrimethylsilylhydroxylamine, N-methyl-N,O-bis(trimethylsilyl)hydroxylamine, N,N,O-tris(trimethylsilyl)hydroxylamine, N,O-bistrimethylsilylacetamide, N,O-bis(trimethylsilyl)trifluoroacetamide, N,O-bis(diethylsilyl)trifluoroacetamide, N,O-bis(ethyldimethylsilyl)trifluoroacetamide, N,O-bis(propyldimethylsilyl)trifluoroacetamide, N,O-bis(tert-butyldimethylsilyl)trifluoroacetamide or N,O-bis(propylenedimethylsilyl)trifluoroacetamide.

[0019] Optionally, the first additive includes one or more of N,O-bis(trimethylsilyl)hydroxylamine, N,O-bis(trimethylsilyl)acetamide, or N,O-bis(trimethylsilyl)trifluoroacetamide.

[0020] When the first additive is selected from the above-mentioned substances, the initial DCR of the battery can be further reduced and the cycle performance of the battery can be improved.

[0021] In any embodiment of the present application, the mass percentage v% of the first additive, based on the total mass of the electrolyte, satisfies: 0.1≤v≤3. Alternatively, 0.3≤v≤1. This helps optimize the initial DCR and suppress DCR growth during battery cycling.

[0022] In any embodiment of the present application, the battery cell satisfies: 0.1≤(u / v)×10 -4 ≤15. Optionally, 0.5≤ (u / v)×10 -4 ≤3. Wherein, u ppm represents the content of element Y based on the total mass of the positive electrode active material; v% represents the mass percentage of the first additive based on the total mass of the electrolyte.

[0023] When the content of element Y and the mass percentage of the first additive in the electrolyte satisfy the given relationship, not only can the positive electrode active material have high structural stability, but the positive electrode plate can also have low impedance and good ion conductivity. As a result, the battery cell can maintain a low initial DCR and good cycle performance at high voltage.

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

[0025] Optionally, the second additive includes one or more of p-methylphenyl isocyanate, p-toluenesulfonyl isocyanate, trimethylsilyl isocyanate, hexamethylene diisocyanate or isophorone diisocyanate.

[0026] Isocyanate compounds can react with water and HF in the electrolyte, which can not only significantly reduce the acidity of the electrolyte, reduce the water in the electrolyte, and reduce the damage of HF and water to the surface of the electrode, but also improve PF6 - The thermal stability of the plasma enables the battery to maintain a high discharge capacity after being stored at high temperatures for a period of time. Therefore, the battery cells of the embodiments of the present application can have low storage gas production, good high-temperature cycle performance and good high-temperature storage performance. In addition, the isocyanate compound can also participate in the formation of the interface film on the surface of the electrode. Due to the special properties of the long carbon chain, the interface film formed with the participation of the isocyanate compound has a certain elasticity, which can better protect the negative electrode interface, thereby helping to improve the long-term cycle performance of the battery at high voltage and giving the battery a long cycle life.

[0027] In any embodiment of the present application, the mass percentage of the second additive, w%, based on the total mass of the electrolyte, satisfies the following conditions: 0.1 ≤ w ≤ 2. Alternatively, 0.1 ≤ w ≤ 1. When the mass percentage of the second additive in the electrolyte satisfies the given range, capacity decay of the battery during long-term storage at high temperatures can be suppressed.

[0028] In any embodiment of this application, the battery cell satisfies the following relationship: 0.2 ≤ v / w ≤ 30. Alternatively, 0.3 ≤ v / w ≤ 10. Where v% represents the mass percentage of the first additive based on the total mass of the electrolyte; w% represents the mass percentage of the second additive based on the total mass of the electrolyte. When the mass percentages of the first and second additives in the electrolyte satisfy the given relationship, the battery's high-temperature storage performance and high-temperature cycling performance can be further improved.

[0029] In any embodiment of the present application, the volume distribution particle size Dv50 of the positive electrode active material is 2 μm to 7 μm.

[0030] In any embodiment of the present application, the volume distribution particle size Dv10 of the positive electrode active material is 1 μm to 3 μm.

[0031] In any embodiment of the present application, the volume distribution particle size Dv90 of the positive electrode active material is 5 μm to 15 μm.

[0032] When the volume distribution particle size of the positive electrode active material meets the given range, it helps the positive electrode active material to have both high capacity and suitable lithium ion transmission path, thereby improving the energy density of the battery and extending the cycle life of the battery.

[0033] In any embodiment of the present application, the specific surface area of ​​the positive electrode active material is 0.45 m 2 / g~0.99m 2 / g.

[0034] In any embodiment of the present application, the 4T powder compaction density of the positive electrode active material is 2.5 g / cm 3 ~4.5g / cm 3 .

[0035] When the specific surface area and / or powder compaction density of the positive electrode active material meets the given range, it is beneficial to improve the specific capacity of the positive electrode active material and the electrolyte infiltration performance of the positive electrode sheet, thereby helping to improve the energy density and rate performance of the battery.

[0036] In a second aspect, an embodiment of the present application provides a battery comprising the battery cell of the first aspect of the present application. Thus, the battery of the embodiment of the present application can have both high energy density and good cycle performance.

[0037] In a third aspect, an embodiment 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.

[0038] 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

[0039] 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.

[0040] FIG1 is a schematic diagram of an embodiment of a battery cell provided in the present application.

[0041] FIG2 is an exploded schematic diagram of an embodiment of a battery cell provided in the present application.

[0042] FIG3 is a schematic diagram of an embodiment of a battery module provided in the present application.

[0043] FIG4 is a schematic diagram of an embodiment of a battery pack provided in the present application.

[0044] FIG. 5 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 4 .

[0045] 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.

[0046] 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

[0047] 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.

[0048] " 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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).

[0054] 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.

[0055] In this application, the terms "plurality", "multiple" and the like refer to two or more.

[0056] Unless otherwise specified, the terms used in this application have the common meanings that are commonly understood by those skilled in the art.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] As used herein, the terms "plurality" and "multiple" refer to two or more.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] As used herein, the term "substituted" refers to a compound or chemical moiety in which at least one hydrogen atom is replaced by a substituent. The substituent may include, but is not limited to, hydroxyl, sulfhydryl, amino, cyano, nitro, aldehyde, halogen, alkenyl, alkynyl, aryl, heteroaryl, C1-C6 alkyl, and C1-C6 alkoxy.

[0068] battery cells

[0069] 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.

[0070] The battery cell provided in the embodiment of the present application has a positive electrode sheet comprising a positive electrode active material, wherein the positive electrode active material comprises a core and a coating layer covering the core. x (Ni a Co b Mn c ) d Me O f A y , wherein 0.2≤x≤1.3, 0.3≤a≤0.7, 0.01≤b≤0.15, 0.1≤c≤0.5, 0.95≤d≤1, 0≤e≤0.05, 1.8≤f≤2, 0≤y≤0.1, M comprises one or more of Zr, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb, or Al, and A comprises one or more of S, N, F, Cl, Br, or I. The coating layer comprises element Y, wherein element Y comprises one or more of Co, Zr, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb, or Al. The electrolyte of the battery cell comprises a first additive, wherein the first additive comprises an organic substance comprising Si-N bonds and Si-O bonds.

[0071] Increasing the charge cutoff voltage of a battery is considered an effective way to increase the energy density of a battery. The positive electrode materials of currently commercialized high-capacity lithium-ion batteries mainly include nickel-cobalt-manganese ternary materials. However, charge and discharge cycles at high voltages may aggravate the cation mixing phenomenon of the nickel-cobalt-manganese ternary material, causing the nickel-cobalt-manganese ternary material to undergo irreversible phase changes and aggravate changes in the crystal structure during the charge and discharge process, thereby increasing the capacity decay of the battery and shortening the cycle life. Coating the nickel-cobalt-manganese ternary material can reduce the contact area between the electrolyte and the nickel-cobalt-manganese ternary material, improve the interfacial stability of the nickel-cobalt-manganese ternary material, thereby reducing metal dissolution and inhibiting interfacial side reactions during storage. However, the coating layer will cause the intrinsic internal resistance of the nickel-cobalt-manganese ternary material to increase. In addition, the coating layer usually has poor lithium ion conductivity, which will affect the insertion and extraction of lithium ions in the nickel-cobalt-manganese ternary material to a certain extent, thereby reducing the capacity of the nickel-cobalt-manganese ternary material and worsening the initial direct current resistance (DCR) of the battery.

[0072] Without intending to be bound by any theory or explanation, the battery cell of the embodiment of the present application includes the above-mentioned positive electrode active material, which includes a core comprising a doped nickel-cobalt-manganese ternary material and a coating layer covering the core, wherein the coating layer includes a specific element Y. When subjected to charge and discharge cycles at high voltage, the positive electrode active material can maintain high structural stability. Furthermore, the electrolyte of the battery cell of the embodiment of the present application also includes a first additive. The Si-N bond of the first additive easily combines with nucleophilic substances in the electrolyte to form a silicon-based derivative, thereby forming a low-impedance interface film on the surface of the positive electrode plate and the surface of the negative electrode plate. This not only reduces the impedance of the positive electrode plate, but also inhibits the decomposition of LiPF6, thereby reducing HF generation, inhibiting the dissolution of transition metals, and improving the battery's cycling performance at high voltage. At the same time, the silicon in the silicon-based derivative can react with fluorine, thereby inhibiting the formation of LiF on the surface of the positive electrode plate, improving the ionic conductivity of the positive electrode plate surface, thereby reducing the capacity fade of the battery and improving the initial DCR of the battery. In addition, the lone electron pair of the oxygen atom in the Si-O bond of the first additive can also capture protons (H + ), thereby further suppressing the generation of HF and improving the cycle performance of the battery at high voltage.

[0073] Therefore, the battery cell of the embodiment of the present application can have both high energy density and good cycle performance.

[0074] During the charge and discharge process, active lithium ions are deintercalated and consumed, resulting in different molar contents of lithium in the positive electrode active material when the battery is discharged to different states. Those skilled in the art will understand that in a battery or electrical device, some elements in the core may be consumed due to processes such as formation and cycling. For example, as lithium ions are consumed during the formation and cycling of the battery, the measured lithium content x in the core may be less than 1. At the same time, if the positive and negative electrode sheets are supplemented with lithium, the measured lithium content x in the core may be greater than 1 after the battery undergoes processes such as formation and cycling. Furthermore, as oxygen may be lost in the core during cycling, the measured oxygen content f in the core may be less than 2. The above definition of the content of each element in the core includes the molar content of each element under different charge and discharge states of the battery (usually when the battery voltage is between 2V and 5V).

[0075] In an embodiment of the present application, the chemical composition of the core can be measured by inductively coupled plasma emission spectrometry (ICP). For example, the substance to be tested is heated to 500°C and calcined for 2 hours, and then cooled to room temperature. Aqua regia is added to dissolve the calcined product, and then the elemental analysis can be performed by inductively coupled plasma emission spectrometry (ICP, Ametek, model: SPECTROARCOSICP-OES) with reference to the standards YS / T1006.2-2014, GB / T23367.2-2009 or YS / T1028.5-2015. This test can obtain the ratio of each element, and the chemical formula Li can be determined by the ratio of each element. x (Ni a Co b Mn c ) d M e O f A y x, a, b, c, d, e, f, and y in .

[0076] In the embodiments of the present application, the composition and content of the Y element in the coating layer can be measured by inductively coupled plasma optical emission spectrometry (ICP). For example, the composition and content of the Y element in the coating layer can be determined by elemental analysis using inductively coupled plasma optical emission spectrometry (ICP, Ametek, model: SPECTROARCOS ICP-OES) with reference to standards YS / T1006.2-2014, GB / T23367.2-2009, or YS / T1028.5-2015.

[0077] In the embodiments of the present application, the electrolyte generally further comprises an electrolyte salt and a solvent. The composition of the electrolyte can be determined by equipment and methods known in the art. As an example, the organic components in the electrolyte can be quantitatively analyzed by gas chromatography with reference to the standard GB / T9722-2006. As an example, the inorganic components and lithium salt concentration in the electrolyte can be quantitatively analyzed by ion chromatography with reference to the standard JY / T020-1996.

[0078] In some embodiments, the coating layer may include one or more of a simple substance, oxide, boride, phosphate, oxalate, carbonate, sulfate, or thermal decomposition product of element Y.

[0079] Herein, the term "thermal decomposition product" refers to a substance obtained by decomposing oxides, borides, phosphates, oxalates, carbonates, and sulfates of element Y under high temperature heating (eg, 200°C-1000°C, optionally 250°C-700°C).

[0080] Without intending to be bound by any theory or explanation, when the coating layer has the above composition, the coating layer can be made denser and more uniform, thereby improving the interfacial stability of the positive electrode active material at high voltage, reducing the increase in DCR during cycling, and further improving the cycling performance of the battery.

[0081] In some embodiments, based on the total mass of the positive electrode active material, the content of element Y u ppm may satisfy: 3000 ≤ u ≤ 15000. For example, based on the total mass of the positive electrode active material, the content of element Y may be 3000 ppm, 5000 ppm, 8000 ppm, 10000 ppm, 12000 ppm, 15000 ppm, or a range consisting of any two of the above values.

[0082] Optionally, in some embodiments, based on the total mass of the positive electrode active material, the content of element Y u ppm can also satisfy 5000≤u≤10000. For example, based on the total mass of the positive electrode active material, the content of element Y can be 5000ppm, 6000ppm, 7000ppm, 8000ppm, 9000ppm, 10000ppm, or a range consisting of any two of the above values.

[0083] Without intending to be limited by any theory or explanation, when the content of element Y in the coating layer is within the above-mentioned suitable range, the coating layer can maintain good lithium ion transmission performance, thereby helping to improve the specific capacity of the positive electrode active material and enhance the energy density and cycle performance of the battery.

[0084] In some embodiments, the first additive may include one or more compounds represented by Formula 1 or Formula 2.

[0085] In Formula 1 and Formula 2, R1, R2, R3, R4, R5, R6, R7, and R8 each independently represent a hydrogen atom or one of the following substituted or unsubstituted groups: a C1-C12 alkyl group or alkoxy group, a C2-C12 alkenyl group or alkenyloxy group, a C2-C12 alkynyl group or alkynyloxy group, a C3-C12 cycloalkyl group or epoxyalkyl group, a C1-C12 cyano group or cyanooxy group, or a C1-C12 silanyl group. Optionally, the substituent includes a halogen.

[0086] Alternatively, in some embodiments, R1, R2, R3, R4, R5, and R6 each independently represent a substituted or unsubstituted C1-C5 alkyl group or alkoxy group, or a substituted or unsubstituted C2-C6 alkenyl group or alkenyloxy group, and at least one of R1, R2, R3, R4, R5, and R6 is a C1-C3 alkyl group or alkoxy group. R7 represents a substituted or unsubstituted C1-C3 alkyl group or alkoxy group. R8 represents a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group or alkoxy group, or a substituted or unsubstituted C1-C4 silyl group.

[0087] Without intending to be bound by any theory or explanation, the compounds represented by Formula 1 and Formula 2 can react with nucleophiles in the electrolyte to form a low-impedance interfacial film on the surfaces of the positive and negative electrodes. This not only reduces the impedance of the positive electrode, but also inhibits the decomposition of LiPF6, thereby reducing HF generation, inhibiting the dissolution of transition metals, and improving the battery's cycling performance at high voltages.

[0088] In some embodiments, the first additive may include one or more of N,O-bistrimethylsilylhydroxylamine, N-methyl-N,O-bis(trimethylsilyl)hydroxylamine, N,N,O-tris(trimethylsilyl)hydroxylamine, N,O-bistrimethylsilylacetamide, N,O-bis(trimethylsilyl)trifluoroacetamide, N,O-bis(diethylsilyl)trifluoroacetamide, N,O-bis(ethyldimethylsilyl)trifluoroacetamide, N,O-bis(propyldimethylsilyl)trifluoroacetamide, N,O-bis(tert-butyldimethylsilyl)trifluoroacetamide, or N,O-bis(propylenedimethylsilyl)trifluoroacetamide.

[0089] Optionally, in some embodiments, the first additive may further include one or more of N,O-bis(trimethylsilyl)hydroxylamine, N,O-bis(trimethylsilyl)acetamide, or N,O-bis(trimethylsilyl)trifluoroacetamide.

[0090] Without intending to be bound by any theory or explanation, when the first additive is selected from the aforementioned substances, it not only helps to further reduce the impedance of the interface film on the surface of the positive electrode sheet, but also helps to improve the ionic conductivity of the positive electrode sheet. This can further reduce the initial DCR of the battery and improve the battery's cycling performance.

[0091] In some embodiments, based on the total mass of the electrolyte, the mass percentage v% of the first additive may satisfy: 0.1≤v≤3. For example, based on the total mass of the electrolyte, the mass percentage of the first additive may be 0.1%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, or a range consisting of any two of the above values.

[0092] Optionally, in some embodiments, based on the total mass of the electrolyte, the mass percentage v% of the first additive can also satisfy: 0.3≤v≤1. For example, based on the total mass of the electrolyte, the mass percentage of the first additive can be 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range consisting of any two of the above values.

[0093] Without intending to be bound by any theory or explanation, adjusting the mass percentage of the first additive in the electrolyte within the above-mentioned appropriate range can adjust the impedance of the interfacial film formed on the surface of the positive electrode sheet and the negative electrode sheet, thereby facilitating the optimization of the initial DCR and the suppression of the DCR growth during the battery cycle.

[0094] The mass percentage v% of the first additive based on the total mass 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 gas chromatography (GC).

[0095] In some embodiments, the battery cell may satisfy: 0.1≤(u / v)×10 -4 ≤15, for example, (u / v)×10 -4 It can be 0.1, 0.5, 1, 3, 5, 8, 10, 12, 15, or a range consisting of any two of the above values.

[0096] Optionally, in some embodiments, the battery cell may also satisfy 0.5≤(u / v)×10 -4 ≤3, 0.5≤(u / v)×10 -4 ≤2.8,0.5≤(u / v)×10 -4 ≤2.5, 0.5≤(u / v)×10 -4 ≤2, 0.5≤(u / v)×10 -4 ≤1.8,0.5≤(u / v)×10 -4 ≤1.5, 1≤(u / v)×10 -4 ≤3, 1≤(u / v)×10 -4 ≤2.8, 1≤(u / v)×10 -4 ≤2.5, 1≤(u / v)×10 -4 ≤2, 1≤(u / v)×10 -4 ≤1.8, 1≤(u / v)×10 -4 ≤1.5, etc.

[0097] (u / v)×10 -4 In the formula (a), u ppm represents the content of element Y based on the total mass of the positive electrode active material; v% represents the mass percentage of the first additive based on the total mass of the electrolyte.

[0098] Without intending to be bound by any theory or explanation, when the content of element Y is high, the coating layer can have a greater thickness, thereby making the structure of the positive electrode active material more stable, but its impedance will also increase. When the content of element Y and the mass percentage of the first additive in the electrolyte meet the given relationship, the interface film formed by the first additive on the surface of the positive electrode plate can better complement the coating layer, thereby not only providing the positive electrode active material with high structural stability, but also allowing the positive electrode plate to have low impedance and good ion conductivity. As a result, the battery cell can maintain a low initial DCR and good cycling performance at high voltage.

[0099] In some embodiments, the electrolyte may further include a second additive, wherein the second additive includes one or more isocyanate compounds.

[0100] The embodiments of the present application do not limit the type of isocyanate compound, and the isocyanate compound may include one or more isocyanate compounds known in the art. Alternatively, in some embodiments, the second additive may include one or more of p-methylphenyl isocyanate, p-toluenesulfonyl isocyanate, trimethylsilyl isocyanate, hexamethylene diisocyanate, or isophorone diisocyanate.

[0101] Without intending to be bound by any theory or explanation, isocyanate compounds can react with water and HF in the electrolyte to form new substances by breaking the carbon-nitrogen double bond, thereby significantly reducing the acidity of the electrolyte, reducing the water content in the electrolyte, and reducing the damage of HF and water to the electrode surface, and also improving the PF6 - The thermal stability of the plasma enables the battery to maintain a high discharge capacity after being stored at high temperatures for a period of time. Therefore, the battery cells of the embodiments of the present application can have low storage gas production, good high-temperature cycle performance and good high-temperature storage performance. In addition, the isocyanate compound can also participate in the formation of the interface film on the surface of the electrode. Due to the special properties of the long carbon chain, the interface film formed with the participation of the isocyanate compound has a certain elasticity, which can better protect the negative electrode interface, thereby helping to improve the long-term cycle performance of the battery at high voltage and giving the battery a long cycle life.

[0102] In some embodiments, based on the total mass of the electrolyte, the mass percentage w% of the second additive can satisfy: 0.1≤w≤2. For example, based on the total mass of the electrolyte, the mass percentage of the second additive can be 0.1%, 0.5%, 0.8%, 1.2%, 1.5%, 1.8%, 2%, or a range consisting of any two of the above values.

[0103] Optionally, in some embodiments, based on the total mass of the electrolyte, the mass percentage w% of the second additive can also satisfy: 0.1≤w≤1. For example, based on the total mass of the electrolyte, the mass percentage of the second additive can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range consisting of any two of the above values.

[0104] When the mass percentage of the second additive in the electrolyte satisfies the given range, the capacity attenuation of the battery during long-term storage at high temperature can be suppressed.

[0105] Based on the total mass of the electrolyte, the mass percentage content (w%) of the second additive can be determined by referring to the test method for the mass percentage content (v%) of the first additive.

[0106] In some embodiments, the battery cells may satisfy: 0.2≤v / w≤30. For example, v / w may be 0.2, 0.5, 1, 3, 5, 8, 10, 15, 18, 20, 25, 28, 30, or a range consisting of any two of the above values.

[0107] Optionally, in some embodiments, the battery cells may also satisfy: 0.3≤v / w≤10, 0.3≤v / w≤8, 0.3≤v / w≤5, 0.3≤v / w≤2, 0.3≤v / w≤1, 0.5≤v / w≤10, 0.5≤v / w≤8, 0.5≤v / w≤5, 0.5≤v / w≤2, 0.5≤v / w≤1, 1≤v / w≤10, 2≤v / w≤8, 3≤v / w≤5, and so on.

[0108] In v / w, v% represents the mass percentage of the first additive based on the total mass of the electrolyte; w% represents the mass percentage of the second additive based on the total mass of the electrolyte.

[0109] Without intending to be bound by any theory or explanation, when the mass percentages of the first additive and the second additive in the electrolyte satisfy the given relationship, the high-temperature storage performance and high-temperature cycle performance of the battery can be further improved.

[0110] In some embodiments, the volume distribution particle size Dv50 of the positive electrode active material can be 2 μm to 7 μm, for example, 2 μm, 3 μm, 4 μm, 4 μm, 5 μm, 6 μm, 7 μm, or a range consisting of any two of the above values.

[0111] In some embodiments, the volume distribution particle size Dv10 of the positive electrode active material may be 1 μm to 3 μm, for example, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, or a range consisting of any two of the above values.

[0112] In some embodiments, the volume distribution particle size Dv90 of the positive electrode active material may be 5 μm to 15 μm, for example, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, or a range consisting of any two of the above values.

[0113] Without intending to be limited by any theory or explanation, when the volume distribution particle size of the positive electrode active material meets the given range, it helps the positive electrode active material to have both high capacity and suitable lithium ion transmission path, thereby improving the energy density of the battery and extending the cycle life of the battery.

[0114] The volume distribution particle size of the positive electrode active material has a meaning well known in the art and can be measured by equipment and methods known in the art. Among them, the volume distribution particle size Dv50 refers to the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%; the volume distribution particle size Dv10 refers to the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 10%; and the volume distribution particle size Dv90 refers to the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 90%. The volume distribution particle sizes Dv50, Dv10, and Dv90 of the positive electrode active material can all be measured using laser diffraction particle size analysis. For example, with reference to standard GB / T 19077-2016, a laser particle size analyzer (such as Malvern Master Size 3000) is used for measurement.

[0115] In some embodiments, the specific surface area of ​​the positive electrode active material may be 0.45 m 2 / g~0.99m 2 / g, for example, 0.45m 2 / g,0.50m 2 / g,0.55m 2 / g,0.60m 2 / g,0.65m 2 / g,0.70m 2 / g,0.75m 2 / g,0.80m 2 / g,0.85m 2 / g,0.90m 2 / g,0.95m 2 / g,0.99m 2 / g, or a range consisting of any two of the above values.

[0116] In some embodiments, the 4T powder compaction density of the positive electrode active material can be 2.5 g / cm 3 ~4.5g / cm 3 , for example, it can be 2.5g / cm 3 , 2.8g / cm 3 , 3.0g / cm 3 , 3.2g / cm 3 , 3.5g / cm 3 , 3.8g / cm 3 , 4.0g / cm 3 , 4.2g / cm 3 , 4.5g / cm 3 , or a range consisting of any two of the above values.

[0117] Without intending to be limited by any theory or explanation, when the specific surface area of ​​the positive electrode active material and / or the 4T powder compaction density meet the given range, it is beneficial to improve the specific capacity of the positive electrode active material and the electrolyte infiltration performance of the positive electrode sheet, thereby helping to improve the energy density and rate performance of the battery.

[0118] The specific surface area of ​​a positive electrode active material has a well-known meaning in the art and can be measured using equipment and methods known in the art. As an example, the specific surface area of ​​a material can be calculated using the BET (Brunauer Emmett Teller) method using a Micromeritics Tri-Star 3020 surface area pore size analyzer (see GB / T 19587-2017) and nitrogen adsorption specific surface area analysis.

[0119] The 4T powder compaction density of the positive electrode active material has a meaning well known in the art and can be measured by equipment and methods known in the art. As an example, the compaction density of the positive electrode active material under a pressure of 4T (i.e., under a pressure of 4 tons) can be determined with reference to GB / T 24533-2009. Specifically, a certain amount of positive electrode active material powder can be placed in a special compaction mold, and then the mold can be placed on a compaction density instrument. A pressure of 4T is applied, and the thickness of the powder under a pressure of 4T (the thickness after pressure relief) is read on the device, and the powder compaction density ρ of the positive electrode active material is calculated by ρ=m / v. In some embodiments, in the battery cell of the embodiment 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 provided on at least one surface of the positive electrode current collector and including a positive electrode active material. For example, the positive electrode current collector has two surfaces opposite to each other in the thickness direction thereof, and the positive electrode film layer is provided on any one or both of the two opposite surfaces of the positive electrode current collector.

[0120] 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.

[0121] 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.

[0122] 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).

[0123] 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).

[0124] 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.

[0125] The negative electrode active material may be any negative electrode active material known in the art for use in secondary batteries. For example, the negative electrode active material may include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials may include at least one of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include at least one of elemental tin, tin oxide, and tin alloys.

[0126] 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.

[0127] 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).

[0128] 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.

[0129] 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).

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] In the battery cells of the embodiments of the present application, the electrolyte further 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.

[0136] 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).

[0137] 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).

[0138] 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.

[0139] 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.

[0140] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0141] 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).

[0142] 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 of a square structure as an example.

[0143] 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.

[0144] 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.

[0145] Battery

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] Electrical devices

[0151] 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.

[0152] The electrical device can select a battery cell or a battery according to its usage requirements.

[0153] 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.

[0154] 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.

[0155] Example

[0156] 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.

[0157] Example 1

[0158] Preparation of positive electrode

[0159] The positive electrode active material is coated with Li(Ni 0.55 Co 0.06 Mn 0.39 ) 0.996 Al 0.001 W 0.002 Zr 0.001 O2, conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) are mixed uniformly in a suitable amount of solvent N-methylpyrrolidone (NMP) at a mass ratio of 98:1:1 to form a positive electrode slurry. The positive electrode slurry is then coated onto the positive electrode current collector aluminum foil. The positive electrode sheet is obtained through drying, cold pressing, slitting, and cutting. The coating layer of the positive electrode active material contains element Y, which includes Nb, Sb, and Ti, and Nb, Sb, and Ti. The total content of element Y is 10,000 ppm.

[0160] Preparation of negative electrode sheet

[0161] The negative electrode active material artificial graphite, the conductive agent carbon black (Super P), the binder styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC) are mixed uniformly in a proper amount of solvent deionized water at a mass ratio of 97:1:1:1 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 the processes of drying, cold pressing, slitting and cutting.

[0162] Preparation of isolation membrane

[0163] Polypropylene film is used as the isolation film.

[0164] Preparation of electrolyte

[0165] Ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are mixed in a mass ratio of 20:10:70 to obtain an organic solvent, and fully dried LiPF6 is dissolved in the above organic solvent to a concentration of LiPF6 of 1 mol / L. Then, it is mixed with the first additive N,O-bistrimethylsilyl acetamide, fluoroethylene carbonate (FEC), and 1,3-propane sultone (PS) to obtain an electrolyte. In the electrolyte, the mass percentage v% of the first additive is 0.1%, and the mass percentages of FEC and PS are 1.5% and 1%, respectively.

[0166] Preparation of secondary batteries

[0167] 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.

[0168] The secondary batteries of Examples 2-13 and Comparative Examples 1-4 are similar to Example 1, except that the parameters for preparing the positive electrode active material or the electrolyte are adjusted. See Table 1 for details.

[0169] The secondary batteries of Examples 14-17, 20-21 are similar to Example 3, except that a second additive is added to the electrolyte. The secondary batteries of Example 18 and 20 are similar to Example 1, except that a second additive is added to the electrolyte. The secondary batteries of Example 19 and 20 are similar to Example 5, except that a second additive is added to the electrolyte. See Table 2 for details.

[0170] Test section

[0171] (1) Initial DCR test

[0172] At 25°C, the secondary battery was charged at a constant current of 0.33C to 4.5V, then charged at a constant voltage of 4.5V to a current of 0.05C, left for 5 minutes, and then discharged at 0.5C for 1 hour. After leaving for 1 hour, it was discharged at a current of 4C for 30 seconds. The initial voltage V1 at the beginning of discharge and the voltage V2 after 30 seconds of discharge were recorded. The initial DCR = (V1-V2) / 4C corresponding current.

[0173] (2) Cyclic DCR growth rate test

[0174] At 25°C, the secondary battery was charged at a constant current of 0.33C to 4.5V, then charged at a constant voltage of 4.5V to a current of 0.05C, left for 5 minutes, and then discharged at 0.5C for 1 hour. After leaving for 1 hour, it was discharged at a current of 4C for 30 seconds. The initial voltage V1 at the beginning of discharge and the voltage V2 after 30 seconds of discharge were recorded. The initial DCR = (V1-V2) / 4C corresponding current.

[0175] Then, the secondary battery is charged at a constant current of 0.5C to 4.5V, then charged at a constant voltage of 4.5V to a cut-off current of 0.05C, left for 5 minutes, and then discharged at a constant current of 1C to 2.8V, left for 5 minutes. This is one charge and discharge cycle. Repeat this cycle step for the same secondary battery.

[0176] After 1000 cycles, the secondary battery was charged at a constant current of 0.33C to 4.5V, then charged at a constant voltage of 4.5V to a current of 0.05C, left for 5 minutes, and then discharged at 0.5C for 1 hour. After a 1-hour rest, it was discharged at a current of 4C for 30 seconds. The initial voltage V3 at the start of discharge and the voltage V4 after 30 seconds of discharge were recorded. The DCR at the 1000th cycle was calculated as (V3-V4) / the current corresponding to 4C. Cycle DCR growth (%) = (DCR at the 1000th cycle - initial DCR) / initial DCR × 100%.

[0177] (3) High temperature storage performance test

[0178] At 25°C, the battery was charged at a constant current of 0.33C to a termination voltage of 4.5V, then charged at a constant voltage of 4.5V to a cutoff current of 0.05C, left for 5 minutes, and then discharged at a constant current of 0.33C to a termination voltage of 2.8V to obtain the initial discharge capacity.

[0179] The secondary battery was charged at a constant current of 0.33C to a termination voltage of 4.5V, and then charged at a constant voltage of 4.5V to a cutoff current of 0.05C, and then stored in an environment of 60°C for 3 months. Afterwards, the secondary battery was taken out and cooled to 25°C. At 25°C, it was discharged at a constant current of 0.33C to 2.8V, and then charged at a constant current of 0.33C to a termination voltage of 4.5V, and then charged at a constant voltage of 4.5V to a cutoff current of 0.05C, placed for 5 minutes, and discharged at a constant current of 0.33C to a termination voltage of 2.8V to obtain the discharge capacity after high-temperature storage. High-temperature storage capacity retention rate (%) = (discharge capacity after high-temperature storage / initial discharge capacity) × 100%.

[0180] The test results are detailed in Tables 1 and 2.

[0181] Based on the test results in Tables 1 and 2, it can be seen that in the secondary battery, the positive electrode active material has the structure and elemental composition defined in the embodiments of the present application, and the electrolyte contains the first additive, which can effectively reduce the initial DCR of the battery and suppress the growth of the battery's cyclic DCR under high voltage environments. This is conducive to improving the battery's cycling performance under high voltage. When the electrolyte also contains the second additive, it can further suppress the growth of the battery's cyclic DCR under high voltage environments and improve the battery's high-temperature storage performance.

[0182] In contrast, in the secondary battery of Comparative Example 1, the positive electrode active material does not contain a coating layer, and the electrolyte does not contain the first additive. Its initial DCR and cycle DCR growth rates are much higher than those of Examples 1-21, and its high-temperature storage performance is much lower than that of Examples 1-21. In the secondary batteries of Comparative Examples 2 and 3, the positive electrode active material does not contain a coating layer. Although their electrolytes contain the first additive, the cycle DCR growth rate and high-temperature storage performance of the batteries are still unsatisfactory. In the secondary battery of Comparative Example 4, the electrolyte does not contain the first additive. Although its positive electrode active material is the same as that of Examples 1-21, the cycle DCR growth rate and high-temperature storage performance of the battery are also unsatisfactory.

[0183] For several compounds given but not listed in the examples, since their chemical properties and reaction properties when participating in electrochemical reactions are similar to those of the compounds listed in the examples, they are all suitable for the technical solution of the present invention and are therefore not listed here one by one.

[0184] 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, comprising a positive electrode plate and an electrolyte, wherein: The positive electrode sheet includes a positive electrode active material, and the positive electrode active material includes a core and a coating layer coating the core. The core includes Li x (Ni a Co b Mn c ) d M e O f A y , wherein 0.2≤x≤1.3, 0.3≤a≤0.7, 0.01≤b≤0.15, 0.1≤c≤0.5, 0.95≤d≤1, 0≤e≤0.05, 1.8≤f≤2, 0≤y≤0.1, the M comprises one or more of Zr, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb or Al, and the A comprises one or more of S, N, F, Cl, Br or I; The coating layer contains element Y, and the element Y includes one or more of Co, Zr, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb or Al; The electrolyte includes a first additive including an organic substance including a Si—N bond and a Si—O bond.

2. The battery cell according to claim 1, wherein: The coating layer contains one or more of the element Y, its oxide, boride, phosphate, oxalate, carbonate, sulfate or thermal decomposition products thereof.

3. The battery cell according to claim 1 or 2, wherein: Based on the total mass of the positive electrode active material, the content u ppm of the element Y satisfies: 3000≤u≤15000; Optionally, 5000≤u≤10000.

4. The battery cell according to any one of claims 1 to 3, wherein: The first additive includes one or more compounds represented by Formula 1 and Formula 2, Wherein, R1, R2, R3, R4, R5, R6, R7, and R8 each independently represent a hydrogen atom or one of the following substituted or unsubstituted groups: C1-C12 alkyl or alkoxy, C2-C12 alkenyl or alkenyloxy, C2-C12 alkynyl or alkynyloxy, C3-C12 cycloalkyl or epoxyalkyl, C1-C12 cyano or cyanooxy, C1-C12 silane, optionally, the substituent includes halogen; Optionally, R1, R2, R3, R4, R5, and R6 each independently represent a substituted or unsubstituted C1-C5 alkyl or alkoxy group, a substituted or unsubstituted C2-C6 alkenyl or alkenyloxy group, and at least one of R1, R2, R3, R4, R5, and R6 is a C1-C3 alkyl or alkoxy group; R7 represents a substituted or unsubstituted C1-C3 alkyl or alkoxy group; R8 represents a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl or alkoxy group, and a substituted or unsubstituted C1-C4 silyl group.

5. The positive electrode active material according to any one of claims 1 to 4, wherein The first additive includes one or more of N,O-bistrimethylsilylhydroxylamine, N-methyl-N,O-bis(trimethylsilyl)hydroxylamine, N,N,O-tris(trimethylsilyl)hydroxylamine, N,O-bistrimethylsilylacetamide, N,O-bis(trimethylsilyl)trifluoroacetamide, N,O-bis(diethylsilyl)trifluoroacetamide, N,O-bis(ethyldimethylsilyl)trifluoroacetamide, N,O-bis(propyldimethylsilyl)trifluoroacetamide, N,O-bis(tert-butyldimethylsilyl)trifluoroacetamide or N,O-bis(propylenedimethylsilyl)trifluoroacetamide; Optionally, the first additive includes one or more of N,O-bistrimethylsilylhydroxylamine, N,O-bistrimethylsilylacetamide or N,O-bis(trimethylsilyl)trifluoroacetamide.

6. The battery cell according to any one of claims 1 to 5, wherein: Based on the total mass of the electrolyte, the mass percentage v% of the first additive satisfies: 0.1≤v≤3; Optionally, 0.3≤v≤1.

7. The battery cell according to any one of claims 1 to 6, wherein: The battery cell meets the following requirements: 0.1≤(u / v)×10 -4 ≤15, optionally, 0.5≤(u / v)×10 -4 ≤3, Wherein, u ppm represents the content of the element Y based on the total mass of the positive electrode active material; v% represents the mass percentage of the first additive based on the total mass of the electrolyte.

8. The battery cell according to any one of claims 1 to 7, wherein: The electrolyte further includes a second additive, wherein the second additive includes one or more isocyanate compounds; Optionally, the second additive includes one or more of p-methylphenyl isocyanate, p-toluenesulfonyl isocyanate, trimethylsilyl isocyanate, hexamethylene diisocyanate or isophorone diisocyanate.

9. The battery cell according to claim 8, wherein: Based on the total mass of the electrolyte, the mass percentage content w% of the second additive satisfies: 0.1≤w≤2; Optionally, 0.1≤w≤1.

10. The battery cell according to claim 8 or 9, wherein: The battery cell satisfies: 0.2≤v / w≤30, optionally, 0.3≤v / w≤10, Wherein, v% represents the mass percentage of the first additive based on the total mass of the electrolyte; w% represents the mass percentage of the second additive based on the total mass of the electrolyte.

11. The battery cell according to any one of claims 1 to 10, wherein: The volume distribution particle size Dv50 of the positive electrode active material is 2 μm to 7 μm; and / or, The volume distribution particle size Dv10 of the positive electrode active material is 1 μm to 3 μm; and / or, The volume distribution particle size Dv90 of the positive electrode active material is 5 μm to 15 μm.

12. The battery cell according to any one of claims 1 to 11, wherein: The specific surface area of ​​the positive electrode active material is 0.45 m 2 / g~0.99m 2 / g; and / or, The 4T powder compaction density of the positive electrode active material is 2.5 g / cm 3 ~4.5g / cm 3 .

13. A battery comprising the battery cell according to any one of claims 1 to 12.

14. An electrical device comprising the battery cell according to any one of claims 1 to 12 or the battery according to claim 13.

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