Electrolyte, battery and electric device

Abstract

The invention relates to an electrolyte, a battery and a power utilization device, the electrolyte comprises metal ions and an additive which are connected in a complexing manner, and the additive comprises at least one of a monothiophosphoric acid additive and a dithiophosphoric acid additive and a dithiophosphoric acid additive.

Description

Technical Field

[0001] The present application relates to an electrolyte, a battery and an electrical device. Background Art

[0002] Batteries have the characteristics of high capacity and long life, so they are widely used in electronic devices, such as mobile phones, laptops, battery cars, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes and electric tools, etc. As batteries have made great progress, higher requirements are placed on battery performance. In order to improve battery performance, the electrolyte in the battery is usually optimized and improved.

[0003] However, when electrolytes are currently used in batteries, the battery reliability and cycle performance are still poor. Summary of the invention

[0004] The present application provides an electrolyte, a battery and an electrical device, and the use reliability and cycle performance of the battery described in the present application can be improved.

[0005] In a first aspect, an embodiment of the present application proposes an electrolyte, wherein the electrolyte includes metal ions and additives connected in a complex manner, and the additives include at least one of a monothiophosphate additive and a dithiophosphate additive and a dithiophosphinic acid additive.

[0006] Therefore, the electrolyte in the embodiment of the present application includes metal ions and additives connected in a complexing manner, and the additives include at least one of a monothiophosphate additive and a dithiophosphate additive and a dithiophosphinic acid additive. The additive can form a complex with metal ions such as iron ions, copper ions, zinc ions, etc., stably complex the metal ions in the complex, reduce the content of metal ions in the electrolyte, thereby reducing the number of metal ions migrating to the negative electrode plate, increasing the position of active ions embedded in the negative electrode plate, and improving the reversible capacity of the battery cell; and alleviate the risk of metal ions precipitating on the surface of the negative electrode plate to form metal dendrites, and improve the reliability of the battery cell; thereby, the self-discharge rate of the battery cell can be reduced, and the cycle performance of the battery cell can be improved.

[0007] In some embodiments, the additives include monothiophosphoric acid additives, dithiophosphoric acid additives and dithiophosphinic acid additives. When the additives include the above materials, the selectivity and complexing ability of the additives can be improved.

[0008] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the dithiophosphinic acid additive is A%, the total mass percentage of the monothiophosphoric acid additive and the dithiophosphoric acid additive is B%, 0.1≤A / B≤2.0; optionally, 0.001%≤A%≤0.500%; and / or 0.001%≤B%≤1.000%. When the amount of the additive used is adjusted to meet the above range, the content of metal ions can be further reduced in the embodiments of the present application.

[0009] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the monothiophosphate additive is B1%, the mass percentage of the dithiophosphate additive is B2%, 0.5≤B1 / B2≤2.0; optionally, 0.001%≤B1%≤0.50%; and / or 0.001%≤B2%≤0.50%. In the embodiments of the present application, when the amount of the additive is adjusted to meet the above range, the monothiophosphate additive and the dithiophosphate additive can work together to improve the complexing ability of different metal ions in the electrolyte, improve the overall complexing ability of metal ions in the electrolyte, reduce the content of free metal ions in the electrolyte, and further reduce the content of metal ions.

[0010] In some embodiments, the dithiophosphinic acid additive includes at least one of a dithiophosphinic acid alkali metal salt and a dithiophosphinic acid alkaline earth metal salt; optionally, the dithiophosphinic acid additive includes a compound represented by formula (A),

[0011] In formula (A),

[0012] R 11 and R 12 Each independently includes a substituted or unsubstituted C1 to C6 alkyl, or a substituted or unsubstituted C2 to C6 alkenyl;

[0013] M1 includes at least one of an alkali metal element and an alkaline earth metal element; optionally, M1 includes at least one of Li, Na or K;

[0014] n represents the absolute value of the valence of M1.

[0015] In some embodiments, the dithiophosphinic acid additive includes at least one of the compounds represented by formula (A-1) to the compounds represented by formula (A-7),

[0016]

[0017] In some embodiments, the monothiophosphate additive includes at least one of a monothiophosphate alkali metal salt and a monothiophosphate alkaline earth metal salt;

[0018] Optionally, the monothiophosphoric acid additive includes a compound represented by formula (B),

[0019] In formula (B),

[0020] R 21 and R 22 Each independently includes a substituted or unsubstituted C1 to C6 alkyl, or a substituted or unsubstituted C2 to C6 alkenyl;

[0021] M2 includes at least one of an alkali metal element and an alkaline earth metal element; optionally, M2 includes at least one of Li, Na or K;

[0022] m represents the absolute value of the valence of M2.

[0023] In some embodiments, the monothiophosphate additive includes at least one of the compounds represented by formula (B-1) to the compounds represented by formula (B-8),

[0024]

[0025] In some embodiments, the dithiophosphoric acid additive may include at least one of an alkali metal dithiophosphoric acid salt and an alkaline earth metal dithiophosphoric acid salt;

[0026] Optionally, the dithiophosphoric acid additive includes a compound represented by formula (C),

[0027] In formula (C),

[0028] R 31 and R 32 Each independently includes a substituted or unsubstituted C1 to C6 alkyl, or a substituted or unsubstituted C2 to C6 alkenyl;

[0029] M3 includes at least one of an alkali metal element and an alkaline earth metal element; optionally, M3 includes at least one of Li, Na or K;

[0030] r represents the absolute value of the valence of M3.

[0031] In some embodiments, the dithiophosphoric acid additive includes at least one of the compounds represented by formula (C-1) to the compounds represented by formula (C-8),

[0032]

[0033] In some embodiments, the electrolyte further includes an organic solvent, and the organic solvent includes at least one of a cyclic carbonate solvent and a linear carbonate solvent; optionally, the cyclic carbonate solvent includes one or more of ethylene carbonate EC, propylene carbonate PC, vinylene carbonate VC, vinyl ethylene carbonate VEC, dioctyl carbonate CC, ethylene carbonate EC, and propylene carbonate PC; optionally, the linear carbonate solvent includes one or more of ethyl allyl carbonate AEC, diphenyl carbonate DPC, methyl allyl carbonate MAC, methyl ethyl carbonate MEC, dimethyl carbonate DMC, diethyl carbonate DEC, methyl propyl carbonate MPC, and ethyl propyl carbonate EPC. Cyclic carbonate solvents have a higher dielectric constant and can improve the ionic conductivity of the electrolyte; linear carbonate solvents have a lower viscosity and can improve the migration rate of active ions such as lithium ions in the electrolyte.

[0034] In some embodiments, the electrolyte further comprises a lithium salt, and the lithium salt includes at least one of lithium hexafluorophosphate LiPF6, lithium perchlorate LiClO4, lithium hexafluoroarsenate LiAsF6, lithium bis(trifluoromethanesulfonyl imide), and lithium trifluoromethanesulfonate.

[0035] In a second aspect, an embodiment of the present application further provides a battery, wherein the battery comprises the electrolyte as described in any embodiment of the first aspect of the present application.

[0036] In a third aspect, an embodiment of the present application further proposes an electrical device, comprising a battery as described in any embodiment of the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.

[0038] Figure 1 It is a schematic diagram of an embodiment of a battery cell of the present application.

[0039] Figure 2 yes Figure 1 An exploded schematic diagram of an embodiment of a battery cell.

[0040] Figure 3 It is a schematic diagram of an embodiment of a battery module of the present application.

[0041] Figure 4 It is a schematic diagram of an embodiment of the battery pack of the present application.

[0042] Figure 5yes Figure 4 An exploded schematic diagram of an embodiment of a battery pack is shown.

[0043] Figure 6 It is a schematic diagram of an embodiment of an electric device including the battery cell of the present application as a power source.

[0044] The drawings are not necessarily drawn to scale.

[0045] The following are the descriptions of the reference numerals:

[0046] 1. Battery pack; 2. Upper box; 3. Lower box; 4. Battery module;

[0047] 5. Battery cell; 51. Housing; 52. Electrode assembly;

[0048] 53. Cover plate;

[0049] 6. Electrical equipment. DETAILED DESCRIPTION

[0050] Below, the embodiments of the electrolyte, battery cells, batteries and electrical devices of the present application are specifically disclosed in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures 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 descriptions 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.

[0051] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a 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 a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present 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 real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it 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.

[0052] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0053] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0054] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means 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), which means 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.

[0055] The term "chain alkyl" encompasses straight and branched alkyl groups. For example, the alkyl group may be a C1 to C50 alkyl group, a C1 to C40 alkyl group, a C1 to C30 alkyl group, a C1 to C20 alkyl group, a C1 to C12 alkyl group, a C1 to C10 alkyl group, a C1 to C6 alkyl group, a C1 to C4 alkyl group. In certain embodiments, the alkyl group includes a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a cyclobutyl group, a pentyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, a heptyl group, a cycloheptyl group, an octyl group, a cyclooctyl group, a nonyl group, and a decyl group. In addition, the alkyl group may be optionally substituted. The term "haloalkyl" refers to an alkyl group in which a hydrogen atom is partially or completely replaced by a halogen atom, and the term "halogen atom" refers to a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, and the like.

[0056] The term "cycloalkyl" refers to a closed alkyl ring system. For example, the cycloalkyl can be a C3 to C50 cycloalkyl, a C3 to C40 cycloalkyl, a C3 to C30 cycloalkyl, a C3 to C20 cycloalkyl, a C3 to C12 cycloalkyl, a C3 to C8 cycloalkyl, wherein the C3 to C8 cycloalkyl refers to a cycloalkyl containing 3 to 8 carbon atoms for forming a ring. In addition, the cycloalkyl can be optionally substituted, and the carbon atoms in the cycloalkyl ring are replaced by heteroatoms, which can include nitrogen atoms, oxygen atoms, sulfur atoms, etc.

[0057] The term "aryl" refers to a closed aromatic ring or ring system. For example, aryl can be C6 to C50 aryl, C6 to C40 aryl, C6 to C30 aryl, C6 to C20 aryl, C6 to C10 aryl, wherein C6 to C30 aryl refers to containing 6 to 30 carbon atoms for forming a ring. In certain embodiments, aryl includes phenyl, naphthyl, phenanthrenyl, anthracenyl, biphenyl, triphenylene, pyrenyl, spiro bifluorenyl, pyrenyl, peryl, indenyl and azulenyl etc. In addition, aryl can be optionally substituted, and carbon atoms in the aryl ring are replaced by heteroatoms, and heteroatoms can include nitrogen atoms, oxygen atoms, sulphur atoms etc.

[0058] The term "halogen atom" means a fluorine atom, a chlorine atom, a bromine atom or the like.

[0059] The term "hydrogen" refers to 1H (protium, H), 2H (deuterium, D) or 3H (tritium, T). In various embodiments, "hydrogen" may be 1H (protium, H).

[0060] In various places of this specification, the substituent of compound is disclosed with group or scope.It is clearly expected that this description includes each individual subcombination of the member of these groups and scope.For example, it is clearly expected that the term "C1 to C8 alkyl" discloses C1, C2, C3, C4, C5, C6, C7, C8, C1 to C8, C1 to C7, C1 to C6, C1 to C5, C1 to C4, C1 to C3, C1 to C2, C2 to C8, C2 to C7, C2 to C6, C2 to C5, C2 to C4, C2 to C3, C3 to C8, C3 to C7, C3 to C6, C3 to C5, C3 to C4, C4 to C8, C4 to C7, C4 to C6, C4 to C5, C5 to C8, C5 to C7, C5 to C6, C6 to C8, C6 to C7 and C7 to C8 alkyl.

[0061] As other examples, the integers in the range of 5 to 40 are specifically intended to disclose individually 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, and 40; the integers in the range of 1 to 20 are specifically intended to disclose individually 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20. Accordingly, other groups or ranges are specifically contemplated.

[0062] When the above groups are substituted, the substituents may be independently selected from halogen atoms or heteroatoms.

[0063] The battery cell includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte. The separator is located between the positive electrode sheet and the negative electrode sheet to separate the positive electrode sheet and the negative electrode sheet. The positive electrode sheet includes a positive electrode active material. The positive electrode active material is a donor of active ions such as sodium ions and lithium ions provided by the battery cell. The negative electrode sheet is an acceptor of active ions. The electrolyte provides a migration path for active ions between the positive electrode sheet and the negative electrode sheet. During the production process of battery cells, the positive electrode active material and / or the electrolyte will inevitably introduce metal impurity ions such as iron, copper, zinc, cadmium and other ions. During the charging process of the battery cell, the metal impurity ions in the positive electrode active material can dissolve in the electrolyte, and the content of metal impurity ions in the electrolyte increases. The metal impurity ions have a lower reduction potential than the active ions. These metal impurity ions can be embedded in the negative electrode plate in preference to the active ions, reducing the position of the active ion embedding and reducing the reversible capacity of the battery cell; and the metal impurity ions may precipitate on the surface of the negative electrode plate to form metal dendrites. The growth of metal dendrites may pierce the isolation membrane of the battery cell, resulting in direct contact between the positive electrode plate and the negative electrode plate, causing a short circuit, thereby reducing the reliability of the battery cell, and the self-discharge rate of the battery cell is too fast, and the cycle performance of the battery cell is deteriorated.

[0064] In view of the above problems, the embodiment of the present application proposes an electrolyte, which includes metal ions and additives connected in a complex manner, and the additives include at least one of a monothiophosphate additive and a dithiophosphate additive and a dithiophosphinic acid additive. The additive can form a complex with the metal ions, stably complex the metal ions in the complex, reduce the content of metal ions in the electrolyte, thereby reducing the number of metal ions migrating to the negative electrode plate, increasing the position of active ions embedded in the negative electrode plate, and improving the reversible capacity of the battery cell; and alleviate the risk of metal ions precipitating on the surface of the negative electrode plate to form metal dendrites, thereby improving the reliability of the battery cell; thereby, the self-discharge rate of the battery cell can be reduced, and the cycle performance of the battery cell can be improved.

[0065] Electrolyte

[0066] In a first aspect, an embodiment of the present application provides an electrolyte comprising metal ions and additives connected in a complex manner, wherein the additives include at least one of a monothiophosphate additive and a dithiophosphate additive and a dithiophosphinic acid additive.

[0067] The metal ions are derived from the metal impurity ions carried by the electrolyte, or the metal impurity ions dissolved into the electrolyte by the positive electrode active material. For example, the metal ions may include at least one of iron ions, copper ions, zinc ions, cadmium ions, chromium ions, manganese ions, cobalt ions, and nickel ions. This part of the metal ions usually does not include active ions such as lithium ions, sodium ions, and potassium ions. It can be understood that the valence of the metal ion is greater than or equal to divalent.

[0068] Since active ions such as lithium ions and sodium ions have a low valence, additives are not easy to react with active ions; additives in the electrolyte can react with high-valence (e.g., divalent or higher) metal ions to form complexes, thereby stabilizing the metal ions in the electrolyte system and reducing the risk of metal ions migrating to the negative electrode. Specifically, since the dithiophosphinic acid additives have strong selectivity for the above-mentioned metal ions and poor selectivity for active ions, the dithiophosphinic acid additives can be used as a selector to preferentially select the above-mentioned metal ions, and the dithiophosphinic acid additives also have a capture effect and can form a complex with the above-mentioned metal ions; since at least one of the monothiophosphoric acid additives and the dithiophosphoric acid additives has a strong capture effect on the above-mentioned metal ions, it can be used as a capture agent and can form a stable complex with the above-mentioned metal ions, and the dithiophosphinic acid additives can increase the probability of the monothiophosphoric acid additives and the dithiophosphoric acid additives capturing metal ions, thereby improving the overall capture ability of the additives; and the dithiophosphinic acid additives can improve the leaching of the monothiophosphoric acid additives and the dithiophosphoric acid additives in the electrolyte. The selector can improve the wetting performance and the dispersion uniformity of the monothiophosphate additives and the dithiophosphate additives, which is beneficial to further enhance their energy of capturing metal ions; it can be understood that the selector preferentially selects metal ions, and the selector can improve the dispersion performance and capture ability of the capture agent. Under the joint complexation of the selector and the capture agent, the selector and the capture agent can form a stable complex with the metal ions, and the metal ions are not easy to escape from the complex, thereby reducing the content of free metal ions in the electrolyte, reducing the number of metal ions migrating to the negative electrode sheet, increasing the position of active ions embedded in the negative electrode sheet, and improving the reversible capacity of the battery cell; and alleviating the risk of metal ions precipitating on the surface of the negative electrode sheet to form metal dendrites, thereby improving the reliability of the battery cell; thereby, the self-discharge rate of the battery cell can be reduced, and the cycle performance of the battery cell can be improved.

[0069] Optionally, the thiophosphorous acid additive includes a thiophosphorous acid structure and a first branched chain connected to the thiophosphorous acid structure, and the first branched chain includes at least one of a linear alkyl group and a linear alkenyl group. The core structure of the dithiophosphinic acid additive is a thiophosphorous acid structure, and the core structure is connected to a branched chain such as an alkyl group and / or an alkenyl group. Since the alkyl group and / or the alkenyl group are linear structures (linear alkyl groups and / or linear alkenyl groups), interference of the branched chain on selection and complexation can be reduced, and its selectivity and complexation can be improved.

[0070] Optionally, the monothiophosphoric acid additive includes a monothiophosphoric acid structure and a second branched chain connected to the monothiophosphoric acid structure, and the second branched chain includes at least one of a linear alkyl group and a linear alkenyl group. The core structure of the monothiophosphoric acid additive is a monothiophosphoric acid structure, and the core structure is connected to a branched chain such as an alkyl group and / or an alkenyl group. Since the alkyl group and / or the alkenyl group are linear structures (linear alkyl group and / or linear alkenyl group), the interference of the branched chain on the complexing reaction can be reduced, and the complexing reaction can be improved.

[0071] Optionally, the dithiophosphoric acid additive includes a dithiophosphoric acid structure and a third branched chain connected to the dithiophosphoric acid structure, and the third branched chain includes at least one of a linear alkyl group and a linear alkenyl group. The core structure of the dithiophosphoric acid additive is a dithiophosphoric acid structure, and the core structure is connected to a branched chain such as an alkyl group and / or an alkenyl group. Since the alkyl group and / or the alkenyl group are linear structures (linear alkyl groups and / or linear alkenyl groups), the interference of the branched chain on the complexing reaction can be reduced, and the complexing reaction can be improved.

[0072] Since the electrolyte may contain a variety of metal ions, for example, the metal ions may include at least two of iron ions, copper ions, zinc ions, cadmium ions, chromium ions, manganese ions, cobalt ions, and nickel ions. In order to improve the selectivity and complexing ability of the additive to different ions, in some embodiments, the capture agent includes a monothiophosphoric acid additive and a dithiophosphoric acid additive, that is, the additive may include a monothiophosphoric acid additive, a dithiophosphoric acid additive, and a dithiophosphinic acid additive. Since the capture agent can capture the above-mentioned metal ions, it can also alleviate the damage of the above-mentioned metal ions to the SEI film formed on the surface of the negative electrode plate, improve the protection ability of the negative electrode plate, and help to further improve the cycle performance of the battery cell.

[0073] Since the above-mentioned metal ions are mainly impurity ions carried in the raw materials, their content is relatively low. The embodiment of the present application adjusts the amount of additives used to minimize the content of metal ions. In some embodiments, based on the total mass of the electrolyte, the mass percentage of the dithiophosphinic acid additive is A%, the total mass percentage of the monothiophosphoric acid additive and the dithiophosphoric acid additive is B%, and 0.1≤A / B≤2.0. It should be noted that, in the case where the capture agent only includes monothiophosphoric acid additives, the mass percentage of the dithiophosphoric acid additive is 0, that is, the total mass percentage of the monothiophosphoric acid additive and the dithiophosphoric acid additive is the mass percentage of the monothiophosphoric acid additive; in the case where the capture agent only includes dithiophosphoric acid additives, the mass percentage of the monothiophosphoric acid additive is 0, that is, the total mass percentage of the monothiophosphoric acid additive and the dithiophosphoric acid additive is the mass percentage of the dithiophosphoric acid additive.

[0074] When the mass percentage ratio of the selector and the capture agent is within the above range, the selector and the capture agent work together to complex the metal ions in the system, reduce the content of free metal ions in the electrolyte, and improve the reliability of the battery cell; further reduce the self-discharge rate of the battery cell and improve the cycle performance of the battery cell.

[0075] Illustratively, the mass percentage ratio A / B of the selection agent to the capture agent can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0 or a range consisting of any two of the above values.

[0076] In some embodiments, 0.001%≤A%≤0.500%. When the mass percentage of the dithiophosphinic acid additive is within the above range, the selectivity for metal ions can be further improved.

[0077] Illustratively, the mass percentage A% of the dithiophosphinic acid additive can be 0.001%, 0.002%, 0.005%, 0.008%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.15%, 0.18%, 0.20%, 0.22%, 0.25%, 0.26%, 0.28%, 0.30%, 0.32%, 0.35%, 0.38%, 0.40%, 0.42%, 0.45%, 0.48%, 0.50% or a range consisting of any two of the above values.

[0078] In some embodiments, 0.001%≤B%≤1.000%. When the total mass percentage of the monothiophosphoric acid additive and the dithiophosphoric acid additive is within the above range, the complexing ability with metal ions can be further improved, which is beneficial to further reduce the content of free electrolyte in the electrolyte.

[0079] For example, the total mass percentage B% of the monothiophosphoric acid additive and the dithiophosphoric acid additive can be 0.001%, 0.002%, 0.005%, 0.008%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.15%, 0.18%, 0.20%, 0.22%, 0.25%, 0.26%, 0.28%, 0.30%. , 0.32%, 0.35%, 0.38%, 0.40%, 0.42%, 0.45%, 0.48%, 0.50%, 0.52%, 0.55%, 0.58%, 0.60%, 0.62%, 0.65%, 0.68%, 0.70%, 0.72%, 0.75%, 0.78%, 0.80%, 0.82%, 0.85%, 0.88%, 0.90%, 0.92%, 0.95%, 0.98%, 1.00% or a range consisting of any two of the above values.

[0080] In some embodiments, the selective agent may include a monothiophosphate additive and a dithiophosphate additive. Based on the total mass of the electrolyte, the ratio of the mass percentage content B1% of the monothiophosphate additive to the mass percentage content B2% of the dithiophosphate additive may be 0.5≤B1 / B2≤2.0. The monothiophosphate additive and the dithiophosphate additive may work together to improve the complexing ability of different metal ions in the electrolyte, improve the overall complexing ability of metal ions in the electrolyte, and reduce the content of free metal ions in the electrolyte.

[0081] Illustratively, the mass percentage ratio B1 / B2 of the monothiophosphate additive and the dithiophosphate additive can be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0 or a range consisting of any two of the above values.

[0082] For example, 0.001%≤B1%≤0.50%. For example, the mass percentage content B1 of the monothiophosphoric acid additive can be 0.001%, 0.002%, 0.005%, 0.008%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.15%, 0.18%, 0.20%, 0.22%, 0.25%, 0.26%, 0.28%, 0.30%, 0.32%, 0.35%, 0.38%, 0.40%, 0.42%, 0.45%, 0.48%, 0.50% or a range consisting of any two of the above values.

[0083] For example, 0.001%≤B2%≤0.50%. For example, the mass percentage content B2 of the dithiophosphoric acid additive can be 0.001%, 0.002%, 0.005%, 0.008%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.15%, 0.18%, 0.20%, 0.22%, 0.25%, 0.26%, 0.28%, 0.30%, 0.32%, 0.35%, 0.38%, 0.40%, 0.42%, 0.45%, 0.48%, 0.50% or a range consisting of any two of the above values.

[0084] The introduction of additives can reduce the content of free metal ions in the electrolyte, and by further selecting the structure of the additives, the additives can be given more functions.

[0085] In some embodiments, the dithiophosphinic acid additive may include at least one of a dithiophosphinic acid alkali metal salt and a dithiophosphinic acid alkaline earth metal salt. For example, the dithiophosphinic acid alkali metal salt may include at least one of a dithiophosphinic acid lithium salt, a dithiophosphinic acid sodium salt, and a dithiophosphinic acid potassium salt; the dithiophosphinic acid alkaline earth metal salt may include at least one of a dithiophosphinic acid calcium salt and a dithiophosphinic acid magnesium salt. Optionally, the dithiophosphinic acid additive may include a dithiophosphinic acid alkali metal salt. When the battery cell is an alkali metal ion battery, by adding corresponding alkali metal ions to the additive, alkali metal ions can be supplemented in the battery cell system. For example, when the battery cell is a lithium ion battery, the additive includes a dithiophosphinic acid lithium salt, and the lithium ions in the dithiophosphinic acid lithium salt can migrate to the negative electrode plate, increasing the number of lithium ions in the system, thereby facilitating the improvement of the capacity of the battery cell, etc.

[0086] In some embodiments, the dithiophosphinic acid additive includes a compound represented by formula (A),

[0087] In formula (A),

[0088] R 11 and R 12 Each independently includes a substituted or unsubstituted C1 to C6 alkyl group, or a substituted or unsubstituted C2 to C6 alkenyl group; M1 includes at least one of an alkali metal element and an alkaline earth metal element; optionally, M1 includes at least one of Li, Na or K; n represents the absolute value of the valence of M1. The above compound can effectively select metal ions, and has high compatibility with the organic solvent in the electrolyte, can be uniformly dispersed in the electrolyte, and the viscosity of the electrolyte is not too high.

[0089] Exemplarily, the dithiophosphinic acid additive includes at least one of the compounds represented by formula (A-1) to the compounds represented by formula (A-7),

[0090]

[0091]

[0092] In some embodiments, the monothiophosphate additive may include at least one of a monothiophosphate alkali metal salt and a monothiophosphate alkaline earth metal salt. For example, the monothiophosphate alkali metal salt may include at least one of a monothiophosphate lithium salt, a monothiophosphate sodium salt, and a monothiophosphate potassium salt; the monothiophosphate alkaline earth metal salt may include at least one of a monothiophosphate calcium salt and a monothiophosphate magnesium salt. Optionally, the monothiophosphate additive may include a monothiophosphate alkali metal salt. When the battery cell is an alkali metal ion battery, by adding corresponding alkali metal ions to the additive, alkali metal ions can be supplemented in the battery cell system. For example, when the battery cell is a lithium ion battery, the additive includes a monothiophosphate lithium salt. The lithium ions in the monothiophosphate lithium salt can migrate to the negative electrode plate, increase the number of lithium ions in the system, and thus help to improve the capacity of the battery cell.

[0093] In some embodiments, the monothiophosphate additive includes a compound represented by formula (B),

[0094] In formula (B),

[0095] R 21 and R 22Each independently includes a substituted or unsubstituted C1 to C6 alkyl group, or a substituted or unsubstituted C2 to C6 alkenyl group; M2 includes at least one of an alkali metal element and an alkaline earth metal element; optionally, M2 includes at least one of Li, Na or K; and m represents the absolute value of the valence of M2. The above compound can effectively complex metal ions, and has high compatibility with organic solvents in the electrolyte, can be uniformly dispersed in the electrolyte, and the viscosity of the electrolyte is not too high.

[0096] Illustratively, the monothiophosphoric acid additive includes at least one of the compounds represented by formula (B-1) to the compounds represented by formula (B-8),

[0097]

[0098]

[0099] In some embodiments, the dithiophosphate additive may include at least one of an alkali metal dithiophosphate salt and an alkaline earth metal dithiophosphate salt. Exemplarily, the alkali metal dithiophosphate salt may include at least one of a lithium dithiophosphate salt, a sodium dithiophosphate salt, and a potassium dithiophosphate salt; the alkaline earth metal dithiophosphate salt may include at least one of a calcium dithiophosphate salt and a magnesium dithiophosphate salt. Optionally, the dithiophosphate additive may include an alkali metal dithiophosphate salt. When the battery cell is an alkali metal ion battery, by adding corresponding alkali metal ions to the additive, alkali metal ions can be supplemented in the battery cell system. For example, when the battery cell is a lithium ion battery, the additive includes a lithium dithiophosphate salt. The lithium ions in the lithium dithiophosphate salt can migrate to the negative electrode plate, increasing the number of lithium ions in the system, thereby facilitating the improvement of the capacity of the battery cell, etc.

[0100] Exemplarily, the additives may include dithiophosphinate lithium salts, monothiophosphate lithium salts and disulfide lithium salts; the lithium ions in the additives can migrate to the negative electrode plate, increase the number of lithium ions in the system, and improve the capacity of the battery cell.

[0101] In some embodiments, the dithiophosphoric acid additive includes a compound represented by formula (C),

[0102] In formula (C),

[0103] R 31 and R 32Each independently includes a substituted or unsubstituted C1 to C6 alkyl group, or a substituted or unsubstituted C2 to C6 alkenyl group; M3 includes at least one of an alkali metal element and an alkaline earth metal element; optionally, M3 includes at least one of Li, Na or K; r represents the absolute value of the valence of M3. The above compound can effectively complex metal ions, and has high compatibility with organic solvents in the electrolyte, can be uniformly dispersed in the electrolyte, and the viscosity of the electrolyte is not too high.

[0104] Exemplarily, the dithiophosphoric acid additive includes at least one of the compounds represented by formula (C-1) to the compounds represented by formula (C-8),

[0105]

[0106] In some embodiments, the electrolyte further includes an organic solvent, and the organic solvent includes at least one of a cyclic carbonate solvent and a linear carbonate solvent. The cyclic carbonate solvent has a high dielectric constant and can improve the ionic conductivity of the electrolyte; the linear carbonate solvent has a low viscosity and can improve the migration rate of active ions such as lithium ions in the electrolyte. The cyclic carbonate solvent and the linear carbonate solvent are used in combination, so that the electrolyte has a high dielectric constant and low viscosity, which can improve the ionic conductivity of the electrolyte; and the electrochemical stability of the electrolyte is high, and the electrochemical window is significantly improved.

[0107] In some embodiments, based on the total mass of the electrolyte, the mass content of the organic solvent is 30% to 90%. Exemplarily, the mass content of the organic solvent can be 30%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, 52%, 53%, 55%, 56%, 57%, 58%, 59%, 60%, 62%, 65%, 66%, 68%, 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90% or a range consisting of any two of the above values.

[0108] Illustratively, the cyclic carbonate solvent includes one or more of ethylene carbonate EC, propylene carbonate PC, vinylene carbonate VC, vinyl vinyl carbonate VEC, dioctyl carbonate CC, ethylene carbonate EC, and propylene carbonate PC.

[0109] Exemplarily, the linear carbonate solvent includes one or more of ethyl allyl carbonate AEC, diphenyl carbonate DPC, methyl allyl carbonate MAC, methyl ethyl carbonate MEC, dimethyl carbonate DMC, diethyl carbonate DEC, methyl propyl carbonate MPC and ethyl propyl carbonate EPC.

[0110] In some embodiments, the electrolyte includes a lithium salt, and the lithium salt includes at least one of lithium hexafluorophosphate LiPF6, lithium perchlorate LiClO4, lithium hexafluoroarsenate LiAsF6, lithium bis(trifluoromethanesulfonyl imide), and lithium trifluoromethanesulfonate.

[0111] In some embodiments, the mass content of the lithium salt is 8% to 15% based on the total mass of the electrolyte.

[0112] Illustratively, the mass content of the lithium salt may be 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or a range consisting of any two of the above values.

[0113] In some embodiments, the organic solvent may include but is not limited to at least one of a nitrile solvent, an ether solvent, and a sulfone solvent. For example, the nitrile solvent may include acetonitrile, etc., the ether solvent may include at least one of tetrahydrofuran and 2-methyltetrahydrofuran; the sulfone solvent may include at least one of cyclopentane sulfone (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE).

[0114] In some embodiments, the electrolyte may further include additives. For example, the additives may include film-forming additives such as positive electrode film-forming additives, etc., and may also 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.

[0115] In the embodiments of the present application, the type or content of each substance in the electrolyte has a well-known meaning in the art, and can be detected by using commonly used equipment and methods in the art, for example, taking the electrolyte as a sample, or taking the electrolyte in a fresh battery cell as a sample, and detecting it by an inductively coupled plasma spectrometer ICP. Among them, the fresh battery cell refers to a battery cell that has been cycled for less than 10 times.

[0116] Battery Cell

[0117] In the second aspect, the embodiment of the present application proposes a battery cell, wherein the battery cell includes an electrolyte. The electrolyte includes the electrolyte of any embodiment of the first aspect of the present application. During the charge and discharge process of the battery cell, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet, and the electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet. By adopting the above electrolyte, the reliability, self-discharge performance and cycle performance of the battery cell can be improved.

[0118] [Positive electrode]

[0119] In some embodiments, the battery cell further includes a positive electrode tab.

[0120] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0121] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is disposed on any one or both of the two facing surfaces of the positive electrode current collector.

[0122] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0123] In some embodiments, the positive electrode active material may be a positive electrode active material for a battery cell known in the art. As an example, the positive electrode active material may include at least one of the following materials, a layered positive electrode active material (e.g., ternary, lithium nickelate / sodium, lithium cobaltate / sodium, lithium manganate / sodium, lithium-rich / sodium layered and rock salt phase layered materials), an olivine-type phosphate active material, a spinel structured positive electrode active material (e.g., spinel lithium manganate, spinel nickel lithium manganate, lithium-rich spinel lithium manganate, and lithium nickel lithium manganate, etc.).

[0124] For example, the general formula of the layered positive electrode active material is Li x A y Ni a Co b Mn c M (1-a-b-c) Y z , wherein 0≤x≤2.1, 0≤y≤2.1, and 0.9≤x+y≤2.1; 0≤a≤1, 0≤b≤1, 0≤c≤1, and 0.1≤a+b+c≤1; 1.8≤z≤3.5; A includes one or more of Na, K, and Mg; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; and Y includes one or more of O and F. Specifically, the layered positive electrode active material may include lithium cobalt oxide LCO, lithium nickel oxide LNO, lithium manganese oxide LMO, and the like.

[0125] Optionally, the layered positive electrode active material is a ternary material, for example, 0<a≤1, 0<b≤1, 0<c≤1, illustratively, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811) and LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523) or more.

[0126] For example, the general formula of the olivine phosphate active material is Li x A y Me a M b P 1-c X c Y z , wherein 0≤x≤1.3, 0≤y≤1.3, and 0.9≤x+y≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, and N; and Y includes one or more of O and F. Specifically, the olivine-type phosphate active material includes one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0127] For example, the general formula of the positive electrode active material of the spinel structure is Li x A y Mn a M 2-a Y z , wherein 0≤x≤2, 0≤y≤1, and 0.9≤x+y≤2; 0.5≤a≤2; 3≤z≤5; A includes one or more of Na, K, and Mg; M includes one or more of Ni, Co, B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; and Y includes one or more of O and F. Specifically, the positive active materials of the spinel structure include LiMn2O4, LiNi0.5 Mn 1.5 O4、LiCr 0.3 Mn 1.7 O4、Li 1.1 Al 0.1 Mn 1.9 O4, Li2Mn2O4 and Li 1.5 One or more of Mn2O4.

[0128] The battery cell will be accompanied by the deintercalation and consumption of active ions such as Li during the charge and discharge process, and the molar content of Li in the battery cell is different when it is discharged to different states. In the list of positive electrode active materials in the embodiments of the present application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode active material is used in the battery system, and the molar content of Li may change after charge and discharge cycles.

[0129] In some embodiments, the positive electrode active material layer may further include a binder. As an example, the 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 acrylate resin.

[0130] In some embodiments, the positive electrode active material layer may further include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0131] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0132] [Negative electrode]

[0133] In some embodiments, the battery cell further includes a negative electrode tab.

[0134] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material. For example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0135] The negative electrode active material may be a negative electrode active material for a battery cell known in the art. As an 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. The silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material. The tin-based material may include at least one of elemental tin, tin oxide, and tin alloy material.

[0136] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent. The embodiment of the present application has no particular restrictions on 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. In some embodiments, based on the total weight of the negative electrode film layer, the mass percentage of the negative electrode conductive agent is ≤5wt%.

[0137] In some embodiments, the negative electrode film layer may also optionally include a negative electrode binder. The embodiment of the present application has no particular restrictions on the type of the negative electrode binder. As an example, 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). In some embodiments, based on the total weight of the negative electrode film layer, the mass percentage of the negative electrode binder is ≤5wt%.

[0138] In some embodiments, the negative electrode film layer may further include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc. In some embodiments, based on the total weight of the negative electrode film layer, the mass percentage of the other additives is ≤2wt%.

[0139] 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, a 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, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and 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).

[0140] The negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional auxiliary agents in a solvent and stirring them uniformly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0141] 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 described in the embodiments of the present application further includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode collector and the negative electrode film layer and disposed on the surface of the negative electrode collector. In some other embodiments, the negative electrode plate described in the embodiments of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0142] [Isolation film]

[0143] In some embodiments, the battery cell further includes a separator.

[0144] The present application has no particular limitation on the type of isolation membrane, and any known porous isolation membrane with good chemical stability and mechanical stability can be selected.

[0145] 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, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0146] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet may be formed into an electrode assembly by a winding process and / or a lamination process.

[0147] In some embodiments, the battery cell may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0148] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).

[0149] The present application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape. Figure 1 The battery cell 5 is a square structure as an example.

[0150] In some embodiments, Figure 2 As shown, the outer package 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 film can form 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 infiltrated 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.

[0151] The preparation method of the battery cell of the present application is well known. In some embodiments, the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, the separator and the negative electrode sheet can be formed into an electrode assembly through a winding process and / or a lamination process, and the electrode assembly is placed in an outer package, and the electrolyte is injected after drying, and the battery cell is obtained through vacuum packaging, standing, forming, shaping and other processes.

[0152] In some embodiments of the present application, the battery cells according to the present application may be assembled into a battery module. The battery module may contain multiple battery cells, and the specific number may be adjusted according to the application and capacity of the battery module.

[0153] Figure 3 FIG. 4 is a schematic diagram of a battery module 4 as an example. Figure 3 As shown, in the battery module 4, the plurality of 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. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0154] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0155] In some embodiments, the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0156] Figure 4 and Figure 5 is a schematic diagram of a battery pack 1 as an example. Figure 4 and Figure 5 As shown, the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3, wherein the upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0157] The battery according to the embodiment of the present application may include one battery cell or a plurality of battery cells. When the battery includes a plurality of battery cells, the battery may include a battery module or a battery pack.

[0158] Electrical devices

[0159] The third aspect of the embodiment of the present application provides an electric device, which includes at least one of the battery cells, battery modules or battery packs of the present application. The battery cells, battery modules or battery packs can be used as the power source of the electric device, and can also be used as the energy storage unit of the electric device. The electric 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 and a satellite, an energy storage system, etc.

[0160] The electrical device may select a battery cell, a battery module or a battery pack according to its usage requirements.

[0161] Figure 6 Schematic diagram of an exemplary electric device 6. The electric device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electric device 6 for high power and high energy density, a battery pack or a battery module may be used.

[0162] As another example, the electric device may be a mobile phone, a tablet computer, a notebook computer, etc. The electric device is usually required to be light and thin, and a battery cell may be used as a power source.

[0163] Example

[0164] The following embodiments describe the contents disclosed in the present application in more detail, and these embodiments are only used for illustrative explanations, because it is obvious to those skilled in the art that various modifications and changes are made within the scope of the present application disclosure. Unless otherwise stated, all parts, percentages and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized according to conventional methods, and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0165] Preparation of Lithium Ion Batteries in Examples and Comparative Examples

[0166] 1. Preparation of positive electrode sheet

[0167] Aluminum foil with a thickness of 12 μm was used as the positive electrode current collector.

[0168] The positive electrode active material LiNi 0.5 Co 0.2 Mn 0.3 O2, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in a proper amount of solvent NMP at a weight ratio of 97.5:1.4:1.1 to form a uniform positive electrode slurry; the positive electrode slurry is evenly coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained.

[0169] 2. Preparation of negative electrode sheet

[0170] A copper foil with a thickness of 8 μm was used as the negative electrode current collector.

[0171] The negative electrode active material artificial graphite, the binder styrene-butadiene rubber (SBR), the thickener sodium carboxymethyl cellulose (CMC-Na), and the conductive agent carbon black (Super P) are fully stirred and mixed in an appropriate amount of solvent deionized water at a weight ratio of 96.2:1.8:1.2:0.8 to form a uniform negative electrode slurry; the negative electrode slurry is evenly coated on the surface of the negative electrode current collector copper foil, and after drying and cold pressing, a negative electrode sheet is obtained.

[0172] 3. Isolation film

[0173] A porous polyethylene (PE) film was used as the isolation membrane.

[0174] 4. Preparation of electrolyte

[0175] In an environment where the water content is less than 10 ppm, an organic solvent, an additive and a lithium salt are uniformly mixed to obtain an electrolyte.

[0176] 5. Preparation of battery cells

[0177] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then they are wound to obtain an electrode assembly; the electrode assembly is placed in an outer packaging shell, and after drying, the electrolyte is injected, and after vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0178] Example 1

[0179] The lithium ion battery is prepared by the above steps, and the preparation of the electrolyte includes:

[0180] In an environment with a water content of less than 10ppm, organic solvents ethylene carbonate EC and diethyl carbonate DMC are mixed in a volume ratio of 1:1 to obtain a mixed solvent, and additives and lithium salts are added to the mixed solvent and mixed evenly. The additives include lithium diisobutyl didithiophosphinate (0.001%), a compound diisobutyl monothiophosphate (0.001%), and a compound diisobutyl dithiophosphate (0.005%), and the lithium salt includes 13.5% lithium hexafluorophosphate LiPF6.

[0181] Comparative Example 1

[0182] A lithium ion battery is prepared by a method similar to that of Example 1, except that the preparation of the electrolyte includes:

[0183] In an environment with a water content of less than 10 ppm, organic solvents ethylene carbonate EC and diethyl carbonate DMC are mixed in a volume ratio of 1:1 to obtain a mixed solvent, and lithium salt is added into the mixed solvent and mixed evenly, wherein the lithium salt includes 13.5% lithium hexafluorophosphate LiPF6.

[0184] Comparative Example 2

[0185] A lithium ion battery was prepared by a method similar to that of Example 1. The difference from Example 1 is that the preparation of the electrolyte includes:

[0186] In an environment with a water content of less than 10ppm, organic solvents ethylene carbonate EC and diethyl carbonate DMC are mixed in a volume ratio of 1:1 to obtain a mixed solvent, and additives and lithium salts are added to the mixed solvent and mixed evenly, including the compound diisobutyl didithiophosphinate lithium (0.001%) shown in formula (A-3), and the lithium salt includes 13.5% lithium hexafluorophosphate LiPF6.

[0187] Comparative Example 3

[0188] A lithium ion battery is prepared by a method similar to that of Example 1, except that the preparation of the electrolyte includes:

[0189] In an environment with a water content of less than 10ppm, organic solvents ethylene carbonate EC and diethyl carbonate DMC are mixed in a volume ratio of 1:1 to obtain a mixed solvent, and additives and lithium salts are added to the mixed solvent and mixed evenly, including the compound diisobutyl dithiophosphate lithium (0.005%) shown in formula (C-4), and the lithium salt includes 13.5% lithium hexafluorophosphate LiPF6.

[0190] Example 2-1 to Example 2-6

[0191] A lithium ion battery was prepared by a method similar to that of Example 1, except that the type of additive in the electrolyte was adjusted.

[0192] Example 3-1 to Example 3-5

[0193] A lithium ion battery was prepared by a method similar to that of Example 1, except that the content of the additive in the electrolyte was adjusted.

[0194] The relevant parameters of the embodiments and comparative examples are shown in Table 1.

[0195] Test Section

[0196] 1. Cycle performance test of lithium-ion batteries

[0197] At 25°C, the lithium-ion battery is charged to 4.25V at 2C constant current, then charged to 0.05C at 4.25V constant voltage, and then discharged to 2.8V at 1C constant current. This is a charge and discharge cycle. Taking the capacity of the first discharge as 100%, calculate the capacity retention rate of the battery after 500 cycles. The capacity retention rate of the battery after 500 cycles (%) = discharge capacity of the 500th cycle / capacity of the first discharge × 100%.

[0198] 2. K value test

[0199] The K value can be used to describe the physical quantity of the self-discharge rate of a battery cell. It can be calculated by dividing the open circuit voltage difference between two tests by the time interval △t between the two voltage tests. The formula is: K = (OCV2-OCV1) / △t. That is, K can represent the voltage drop per unit time. Generally speaking, the larger the K value, the faster the open circuit voltage drops or the larger the amplitude is, and there may be a micro-short circuit in the battery cell.

[0200] 3. ICP test of metal ion content

[0201] ICP instrument model: ICAP 7200ICP-OES, manufactured by ThermoFisher Technology (formerly Thermo Fisher Scientific);

[0202] Test conditions: The sample must be an electrolyte liquid. If it contains solid particles, it needs to be digested with acid or filtered to remove the solid particles. The range of the measured elements must be within the range of the standard curve. If it exceeds the range, the sample needs to be diluted.

[0203] Main operating procedures: 1. Test standard curve; 2. Dilute the sample to be tested; 3. Test the diluted sample; 4. Calculate and process the data to obtain the concentration of the element to be tested.

[0204] Test Results

[0205] The test results are shown in Table 1

[0206] Table 1

[0207]

[0208]

[0209] In Table 1, the K value represents the K value obtained by testing at a time interval of 14 days.

[0210] It can be seen from Table 1 that, compared with Comparative Example 1, Comparative Examples 2 and 3 respectively add additives, selectors or capture agents to the electrolyte, which can react with metal impurity ions, but the effect is weak and cannot effectively reduce the content of metal ions.

[0211] The additives in the embodiments of the present application include at least one of a monothiophosphoric acid additive and a dithiophosphoric acid additive and a dithiophosphinic acid additive. The additives can form a complex with metal ions, stably complex the metal ions in the complex, reduce the content of metal ions in the electrolyte, thereby reducing the number of metal ions migrating to the negative electrode plate, increasing the position where active ions are embedded in the negative electrode plate, and improving the reversible capacity of the battery cell; and reducing the risk of metal ions precipitating on the surface of the negative electrode plate to form metal dendrites, improving the reliability of the battery cell; thereby, the self-discharge rate of the battery cell can be reduced, and the cycle performance of the battery cell can be improved.

[0212] By adjusting the content of at least one of the monothiophosphoric acid additive and the dithiophosphoric acid additive and the dithiophosphinic acid additive, the interaction with the metal impurity ions can be further enhanced.

[0213] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the present application, and that changes, substitutions and modifications may be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. An electrolyte comprising metal ions and additives connected in a complex manner, wherein the additives include at least one of a monothiophosphoric acid additive and a dithiophosphoric acid additive and a dithiophosphinic acid additive.

2. The electrolyte according to claim 1, wherein The additives include monothiophosphoric acid additives, dithiophosphoric acid additives and dithiophosphinic acid additives.

3. The electrolyte according to claim 1 or 2, wherein Based on the total mass of the electrolyte, the mass percentage of the dithiophosphinic acid additive is A%, the mass percentage of the monothiophosphoric acid additive and the dithiophosphoric acid additive is B%, and 0.1≤A / B≤2.0; Optionally, 0.001%≤A%≤0.500%; and / or 0.001%≤B%≤1.000%.

4. The electrolyte according to any one of claims 1 to 3, wherein Based on the total mass of the electrolyte, the mass percentage of the monothiophosphoric acid additive is B1%, the mass percentage of the dithiophosphoric acid additive is B2%, and 0.5≤B1 / B2≤2.0; Optionally, 0.001%≤B1%≤0.50%; and / or 0.001%≤B2%≤0.50%.

5. The electrolyte according to any one of claims 1 to 4, wherein The dithiophosphinic acid additive includes at least one of a dithiophosphinic acid alkali metal salt and a dithiophosphinic acid alkaline earth metal salt; Optionally, the dithiophosphinic acid additive includes a compound represented by formula (A), In formula (A), R 11 and R 12 Each independently includes a substituted or unsubstituted C1 to C6 alkyl, or a substituted or unsubstituted C2 to C6 alkenyl; M1 includes at least one of an alkali metal element and an alkaline earth metal element; optionally, M1 includes at least one of Li, Na or K; n represents the absolute value of the valence of M1.

6. The electrolyte according to claim 5, wherein The dithiophosphinic acid additive includes at least one of the compounds represented by formula (A-1) to the compounds represented by formula (A-7), 7. The electrolyte according to any one of claims 1 to 6, wherein The monothiophosphate additive includes at least one of a monothiophosphate alkali metal salt and a monothiophosphate alkaline earth metal salt; Optionally, the monothiophosphoric acid additive includes a compound represented by formula (B), In formula (B), R 21 and R 22 Each independently includes a substituted or unsubstituted C1 to C6 alkyl, or a substituted or unsubstituted C2 to C6 alkenyl; M2 includes at least one of an alkali metal element and an alkaline earth metal element; optionally, M2 includes at least one of Li, Na or K; m represents the absolute value of the valence of M2.

8. The electrolyte according to claim 7, wherein The monothiophosphoric acid additive includes at least one of the compounds represented by formula (B-1) to the compounds represented by formula (B-8), 9. The electrolyte according to any one of claims 1 to 8, wherein The dithiophosphoric acid additive may include at least one of a dithiophosphoric acid alkali metal salt and a dithiophosphoric acid alkaline earth metal salt; Optionally, the dithiophosphoric acid additive includes a compound represented by formula (C), In formula (C), R 31 and R 32 Each independently includes a substituted or unsubstituted C1 to C6 alkyl, or a substituted or unsubstituted C2 to C6 alkenyl; M3 includes at least one of an alkali metal element and an alkaline earth metal element; optionally, M3 includes at least one of Li, Na or K; r represents the absolute value of the valence of M3.

10. The electrolyte according to claim 9, wherein The dithiophosphoric acid additive includes at least one of the compounds represented by formula (C-1) to the compounds represented by formula (C-8), 11. The electrolyte according to any one of claims 1 to 10, wherein The electrolyte further comprises an organic solvent, wherein the organic solvent comprises at least one of a cyclic carbonate solvent and a linear carbonate solvent; Optionally, the cyclic carbonate solvent includes one or more of ethylene carbonate EC, propylene carbonate PC, vinylene carbonate VC, vinyl ethylene carbonate VEC, dioctyl carbonate CC, ethylene carbonate EC and propylene carbonate PC; Optionally, the linear carbonate solvent includes one or more of ethyl allyl carbonate AEC, diphenyl carbonate DPC, methyl allyl carbonate MAC, methyl ethyl carbonate MEC, dimethyl carbonate DMC, diethyl carbonate DEC, methyl propyl carbonate MPC and ethyl propyl carbonate EPC.

12. The electrolyte according to any one of claims 1 to 11, wherein The electrolyte also contains lithium salt, and the lithium salt includes at least one of lithium hexafluorophosphate LiPF6, lithium perchlorate LiClO4, lithium hexafluoroarsenate LiAsF6, lithium bis(trifluoromethanesulfonyl imide), and lithium trifluoromethanesulfonate.

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

14. An electrical device comprising the battery as claimed in claim 13.

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