Electrolyte additive, electrolyte and battery

Abstract

The invention relates to the technical field of electrolytes, in particular to an electrolyte additive, an electrolyte and a battery. The electrolytic additive has a structure as shown in a formula (1), the structure contains a nitrate group and an organic group containing carbon and oxygen, nitrogen-containing SEI is formed through decomposition of the nitrate group, transmission of lithium ions in the SEI is accelerated, lithium deposition is more uniform, and formation of lithium dendrites is reduced; the solubility of the additive in an electrolyte can be remarkably improved through the organic groups containing carbon and oxygen, and the organic groups containing carbon and oxygen can be decomposed to generate organic components, so that the toughness of an SEI film is enhanced; the electrolytic additive is introduced into the electrolyte, so that the decomposition of the electrolyte can be inhibited, and the consumption of active lithium metal can be reduced.

Description

Technical Field

[0001] The present application relates to the technical field of electrolytes, and in particular to electrolyte additives, electrolytes, and batteries. Background Art

[0002] Various electrolyte strategies (high-concentration electrolytes, locally high-concentration electrolytes, fluorinated electrolytes, weakly solvated electrolytes, dual salt electrolytes, sacrificial additives, etc.) have been reported to construct robust passivation layers to cope with the intense interfacial chemical reactions in lithium metal batteries. Among them, the use of sacrificial additives is a simple and effective method to tune the physicochemical properties of the interface.

[0003] The use of sacrificial additives, such as LiNO3, has a certain positive gain effect on improving the performance of lithium batteries. However, due to the low solubility of LiNO3 in the electrolyte, the concentration of LiNO3 is at a low level in the early stage of the battery cycle. As the cycle time increases, the side reactions at the lithium negative electrode interface increase, and LiNO3 will be rapidly consumed, thereby affecting the battery cycle life and cycle performance. It cannot solve the problem of limited additives being rapidly consumed due to repeated destruction and repair of SEI. Summary of the Invention

[0004] In view of this, the present application provides an electrolyte additive having a structure as shown in formula (1) to at least partially solve the above technical problems.

[0005] In a first aspect of the present application, an electrolyte additive is provided, having a structure as shown in formula (1):

[0006] Formula (1); Wherein: R is at least one of substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkynyl, substituted or unsubstituted C1-C10 alkoxy, substituted or unsubstituted C2-C10 alkoxycarbonyl, substituted or unsubstituted C2-C20 heterocyclic group, substituted or unsubstituted C6-C12 aryl, and C3-C6 cycloalkyl; n is an integer from 1 to 8.

[0007] According to a second aspect of the present application, an electrolyte is provided, comprising a lithium salt, a solvent, and the electrolyte additive described in the first aspect.

[0008] Optionally, based on the total mass of the electrolyte, the mass percentage of the electrolyte additive is 0.1% to 15%.

[0009] Optionally, the lithium salt is selected from one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorooxalatoborate), lithium bis(oxalatoborate), lithium tetrafluoroborate, lithium hexafluorophosphate, lithium difluorooxalatophosphate, and lithium difluorophosphate; Based on the total mass of the electrolyte, the mass percentage of the lithium salt is 5% to 35%; and / or, the solvent includes a coordinating solvent and a non-coordinating solvent; Based on the total mass of the electrolyte, the mass percentage of the solvent is 64.9% to 94.9%.

[0010] Optionally, based on the total mass of the electrolyte, the mass percentage of the electrolyte additive is 1% to 10%, the mass percentage of the lithium salt is 22% to 24%, and the mass percentage of the solvent is 66% to 77%.

[0011] The third aspect of the present application provides a battery comprising the electrolyte described in the second aspect.

[0012] The electrolyte additive provided in the present application has a structure of formula (1), which contains a nitrate group and a carbon-oxygen-containing organic group. The nitrogen-containing SEI is formed by the decomposition of the nitrate group, which accelerates the transmission of lithium ions in the SEI, makes lithium deposition more uniform, reduces the formation of lithium dendrites and reduces the consumption of active lithium ions. The solubility of the additive in the electrolyte can be significantly increased by the carbon-oxygen-containing organic group, and the carbon-oxygen-containing organic group can decompose to generate organic components, thereby enhancing the toughness of the SEI film. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. 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 these drawings without creative work.

[0014] Figure 1 Schematic diagram of the cyclic charge and discharge curves of the lithium secondary battery in Example 1 and Comparative Example 1.

[0015] Figure 2 Schematic diagram of the capacity retention rate of the lithium secondary battery in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of this application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application and are not used to limit the present application.

[0017] In this application, unless otherwise indicated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of a device in actual use or operation, specifically in the drawing directions of the accompanying drawings; whereas "inner" and "outer" refer to the outline of the device. Furthermore, in the description of this application, the term "including" means "including but not limited to." Terms such as first, second, and third are used merely as designations and do not impose numerical requirements or establish a sequential order.

[0018] In this application, "and / or" describes the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural.

[0019] In this application, "at least one" means one or more, and "plurality" means two or more. "One or several," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c," or "at least one of a, b, and c," can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can each be single or plural.

[0020] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a hard limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0021] As used herein, the term "alkyl" refers to a linear or branched monovalent saturated hydrocarbon group (e.g., a C1-C10 alkyl group, wherein C1-C10 indicates that the group contains 1-10 carbon atoms). Examples of alkyl groups include C1-C6 alkyl groups, C1-C4 alkyl groups, C1-C3 alkyl groups, C1-C2 alkyl groups, and the like.

[0022] Specifically, the alkyl group of the C1~C10 alkyl group may be methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, isobutyl, sec-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, or the like.

[0023] As used herein, "alkenyl" refers to a straight or branched hydrocarbon group containing at least one carbon-carbon double bond and no carbon-carbon triple bond, such as C2~C10 alkenyl, C2~C8 alkenyl, C2~C6 alkenyl, C2~C5 alkenyl, C2~C4 alkenyl, C2~C3 alkenyl; examples of alkenyl include ethenyl, 1-propenyl, 2-propenyl, 2-methyl-1-propenyl, 1-butenyl and 2-butenyl.

[0024] As used herein, "alkynyl" refers to a linear or branched hydrocarbon group containing at least one carbon-carbon triple bond, such as C2-C10 alkynyl, C2-C8 alkynyl, C2-C6 alkynyl, C2-C5 alkynyl, C2-C4 alkynyl, and C2-C3 alkynyl. Examples of alkynyl groups include ethynyl, 1-propynyl, 1-methyl-2-propynyl, 2-propynyl, 1-butynyl, and 2-butynyl.

[0025] As used herein, "alkoxy" refers to AO-, wherein A is an alkyl group as described herein. Preferably, the alkoxy group is a C1-C6 alkoxy group, such as methoxy, ethoxy, etc.

[0026] As used herein, "alkoxycarbonyl" refers to -C(=O)-OA, where A is an alkyl group as described herein. Preferred alkoxycarbonyl groups are -C(=O)-OA, where A is a C1-C6 alkyl group, such as methoxycarbonyl (-C(=O)-OCH3), ethoxycarbonyl (-C(=O)-OCH2-CH3), and the like.

[0027] As used herein, "heterocyclyl" refers to a cyclic group having three or more ring atoms, generally consisting of C2 to C20 carbon atoms and 1-3 heteroatoms selected from O, N, and S. In some embodiments, the heterocyclyl group has 3 to 20 ring atoms. In some embodiments, the heterocyclyl group has 3 to 10 ring atoms. Examples of heterocyclyl groups include tetrahydrofuranyl, pyranyl, piperidinyl, and piperazinyl.

[0028] As used herein, "cycloalkyl" is a saturated or unsaturated carbocyclic ring having 3 or more ring carbon atoms. In some embodiments, a cycloalkyl has 3 to 6 ring carbon atoms (C3-C6 cycloalkyl). In some specific embodiments, a cycloalkyl has 5 to 6 ring carbon atoms (C5-C6 cycloalkyl). Examples of cycloalkyl groups include cyclopentyl, cyclohexyl, cyclopropyl, and cyclobutyl.

[0029] As used herein, "aryl" refers to a monocyclic, bicyclic, or tricyclic aromatic group containing 6 to 12 carbon atoms, i.e., a C6-C12 aryl group. Examples of aryl groups include phenyl, naphthyl, indenyl, azulenyl, biphenyl, and biphenylene.

[0030] Current research has found that some additives, such as LiNO3, have low solubility in the electrolyte, resulting in low additive concentrations at the initial stage of the battery cycle. As the cycle time increases, side reactions at the lithium negative electrode interface increase, and the additives are rapidly consumed, thereby affecting the battery cycle life and cycle performance. The problem of limited additives being rapidly consumed due to repeated destruction and repair of SEI cannot be solved.

[0031] To this end, the first aspect of the present application provides an electrolyte additive, wherein the electrolyte additive has a structure as shown in formula (1):

[0032] Formula (1); Wherein: R is at least one of substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkynyl, substituted or unsubstituted C1-C10 alkoxy, substituted or unsubstituted C2-C10 alkoxycarbonyl, substituted or unsubstituted C2-C20 heterocyclic group, and substituted or unsubstituted C6-C12 aryl; n is an integer from 1 to 8, such as 1, 2, 3, 4, 5, 6, 7 or 8.

[0033] Through the above technical solution, a compound having a structure as shown in formula (1) is used as an electrolyte additive. The structure contains a nitrate group and a carbon-oxygen organic group. The carbon-oxygen organic group can significantly increase the solubility of the electrolyte additive in the electrolyte. When the electrolyte additive is introduced into the electrolyte, the electrolyte additive can be maintained at a high concentration at the beginning of the battery cycle. As the cycle time is delayed, even if the electrolyte additive is rapidly consumed, the concentration of the electrolyte additive decreases to a certain extent, but it still maintains a high concentration content, ensuring the battery cycle life and cycle performance. At the same time, the nitrate ions participate in the formation of an interface film with high ionic conductivity. By decomposing the carbon-oxygen organic group, an organic component can be generated. The organic component can enhance the toughness of the interface film. The interface film promotes the uniform deposition and densification of lithium by regulating the migration path and deposition behavior of lithium ions. In this process, the stability of the interface film reduces the unevenness of local current density and reduces dendrite growth and the generation of isolated lithium. At the same time, the chemical inertness of the interfacial film inhibits the side reactions of the electrolyte and the decomposition of lithium salts and solvents; the high ionic conductivity of the interfacial film enables lithium to be deposited uniformly and densely, inhibiting the formation of lithium dendrites, thereby significantly reducing the mass accumulation of dead lithium.

[0034] The present application does not limit the source of the electrolyte additive having the structure of formula (1), which may be a commercially available product or prepared by a known method.

[0035] In some examples, the substituted substituent is selected from halogen or C1~C4 alkyl, such as F, Cl, Br, I, preferably F or Cl; C1~C4 alkyl, including methyl, ethyl, propyl, butyl, preferably methyl or ethyl.

[0036] In some examples, n is an integer from 1 to 6, for example, n=1, 2, 3, 4, 5, 6, 7 or 8, and n is preferably 1 or 2.

[0037] In some examples, R is at least one of a substituted or unsubstituted C1-C8 alkoxy group and a substituted or unsubstituted C2-C10 heterocyclic group. Exemplary C1-C8 alkoxy groups include C2 alkoxy (ethoxy), C3 alkoxy (e.g., n-propoxy, isopropoxy), C4 alkoxy (e.g., n-butoxy, isobutoxy, sec-butoxy, tert-butoxy), C5 alkoxy, C6 alkoxy, C7 alkoxy, C8 alkoxy, C9 alkoxy, or C10 alkoxy. Exemplary C2-C10 heterocyclic groups include tetrahydrofuranyl, pyrrolyl, thienyl, thiazolyl, pyridyl, indolyl, quinolyl, carbazolyl, and oxacyclopropyl.

[0038] In some examples, the electrolyte additive is selected from at least one of the following compounds 1 to 8: .

[0039] For example, the Cas number of compound 1 is 87-33-2; the Cas number of compound 2 is 59331-87-2; the Cas number of compound 3 is 88097-96-5; the Cas number of compound 4 is 88097-95-4; the Cas number of compound 5 is 28079-67-6; the Cas number of compound 6 is 874674-36-9; the Cas number of compound 7 is 62796-21-8; and the Cas number of compound 8 is 22703-81-7.

[0040] The present application does not limit the source of the above electrolyte additives, which may be commercially available products or prepared by known methods.

[0041] According to a second aspect of the present application, an electrolyte is provided, comprising the electrolyte additive described above. By introducing the electrolyte additive into the electrolyte, the electrolyte additive forms a nitrogen-rich solid electrolyte interface film on the surface of the lithium salt, promoting rapid lithium ion transport and uniform lithium deposition, thereby inhibiting electrolyte decomposition and reducing consumption of active lithium metal.

[0042] In some specific embodiments, based on the total mass of the electrolyte, the mass percentage of the electrolyte additive is 0.1% to 15%. Within this mass percentage range, the electrolyte additive can be dissolved in the electrolyte, and the nitrate group in the electrolyte additive can decompose to form a nitrogen-rich interface layer, and the organic group can decompose to form an interface layer rich in organic compounds, thereby reducing the consumption of active lithium metal and improving the cycle life of the battery; illustratively, the mass percentage of the electrolyte additive can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, and ranges between any two of the above values.

[0043] In some specific embodiments, the electrolyte further includes a lithium salt, which provides mobile lithium ions and transfers charge between the positive and negative electrodes, thereby realizing the charge and discharge cycle of the battery; the lithium salt is selected from common lithium salts in electrolytes, such as one or more selected from lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium bis(fluorooxalatoborate) (LiDFOB), lithium bis(oxalatoborate) (LiBOB), lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), lithium difluorooxalatophosphate (LiDFOP), and lithium difluorophosphate (LiDFP).

[0044] In some examples, based on the total mass of the electrolyte, the mass percentage of the lithium salt is 5% to 35%. Within this mass percentage range, the lithium salt can provide more mobile lithium ions to achieve higher ionic conductivity. Exemplarily, the mass percentage of the lithium salt can be 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%, and ranges between any two of the above values.

[0045] In some specific embodiments, the electrolyte further includes a solvent that can dissolve lithium salts and promote their dissociation into free ions, thereby ensuring that the electrolyte has sufficient ionic conductivity. The solvent includes a coordinating solvent and a non-coordinating solvent; wherein the coordinating solvent is selected from one or more of ethylene glycol dimethyl ether (DME), ethylene glycol diethyl ether (DEE), 1,3-dimethoxypropane (DMP), dimethoxymethane (DMM), tetrahydrofuran (THF), tetrahydropyran (THP), 1,3-dioxolane (DOL), dimethyl carbonate (DMC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC); The non-coordinating solvent is selected from one or more of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), 2,2,2-trifluoroethyl ether (BTFE), 1,1,1,2,2,3,4,5,5,5-decafluoropentane (HFC), heptafluoroane (SFE), and tris(trifluoroethoxy)methane (TFEO).

[0046] In some examples, based on the total mass of the electrolyte, the mass percentage of the solvent is 64.9% to 94.9%. Within this mass percentage range, the solvent can better dissolve lithium salts and electrolyte additives. The mass percentage of the solvent can be 64.9%, 65%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 77%, 78%, 82%, 83%, 88%, 91%, 92%, 93%, 74.5%, 85.2%, 86.1%, 94.9%, and the range between any two of the above values.

[0047] The present application does not specifically limit the preparation method of the electrolyte. Exemplarily, the preparation method of the electrolyte includes the following steps: S1. Under the protection of inert gas, add lithium salt to the configuration container, and then add the coordination solvent to the configuration container and mix well; S2, adding a non-coordinating solvent to the preparation container and mixing evenly; S3. Add additives to the preparation container and mix evenly to obtain an electrolyte.

[0048] According to a third aspect of the present application, a battery is provided, comprising the above-mentioned electrolyte. The battery comprises a lithium-ion battery.

[0049] The electrolyte additive, electrolyte, and battery provided in this application are described in detail below through specific examples.

[0050] 1. Implementation Example 1 1.1. An electrolyte comprising: Electrolyte additive, using compound 1, its mass percentage is 5%;

[0051] Lithium salt, using lithium bis(fluorosulfonyl)imide (LiFSI), with a mass percentage of 24%; The coordination solvent is ethylene glycol dimethyl ether (DME), with a mass percentage of 21%; The non-coordinating solvent used was 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE), with a mass percentage of 50%.

[0052] 1.2. The preparation method of the above electrolyte comprises the following steps: S1. Under the protection of inert gas, add lithium salt to the configuration container, and then add the coordination solvent to the configuration container and mix well; S2, adding a non-coordinating solvent to the preparation container and mixing evenly; S3. Add electrolyte additives to the configuration container and mix evenly to obtain an electrolyte.

[0053] Example 2 Compared with Example 1, the difference is that compound 2 is used as the electrolyte additive.

[0054]

[0055] Example 3 Compared with Example 1, the difference is that compound 3 is used as the electrolyte additive.

[0056]

[0057] Example 4 Compared with Example 1, the difference is that compound 4 is used as the electrolyte additive.

[0058]

[0059] Example 5 Compared with Example 1, the difference is that compound 5 is used as the electrolyte additive.

[0060]

[0061] Example 6 Compared with Example 1, the difference is that compound 6 is used as the electrolyte additive.

[0062]

[0063] Example 7 Compared with Example 1, the difference is that compound 7 is used as the electrolyte additive.

[0064]

[0065] Example 8 Compared with Example 1, the difference is that compound 8 is used as the electrolyte additive.

[0066]

[0067] Example 9 Compared with Example 1, the difference is that the electrolyte includes: Electrolyte additive, using compound 1, its mass percentage is 5%; Lithium salt: lithium bis(fluorosulfonyl)imide (LiFSI) with a mass percentage of 22%; and lithium bis(fluorosulfonyl)imide (LiTFSI), which has a mass percentage of 2%; The coordination solvent is ethylene glycol diethyl ether (DEE), with a mass percentage of 21%; The non-coordinating solvent used was 2,2,2-trifluoroethyl ether (BTFE), with a mass percentage of 50%.

[0068] Example 10 Compared with Example 1, the difference is that the electrolyte includes: Electrolyte additive, using compound 1, its mass percentage is 5%; Lithium salt: lithium bis(fluorooxalato)borate (LiFSI) with a mass percentage of 22%; and lithium tetrafluoroborate (LiBF4), 2% by mass; The coordination solvent is ethylene glycol diethyl ether (DEE), with a mass percentage of 21%; The non-coordinating solvent used is 1,1,1,2,2,3,4,5,5,5-decafluoropentane (HFC), and its mass percentage is 50%.

[0069] Example 11 Compared with Example 1, the difference is that the electrolyte includes: Electrolyte additive, using compound 1, its mass percentage is 5%; Lithium salt: lithium difluorooxalatoborate (LiDFOB) with a mass percentage of 17%; Lithium bis(oxalatoborate) (LiBOB), with a mass percentage of 1%; and lithium difluorophosphate (LiDFP), 2% by mass; The coordination solvent is ethylene glycol diethyl ether (DME), with a mass percentage of 25%; The non-coordinating solvent used was tris(trifluoroethoxy)methane (TFEO), with a mass percentage of 50%.

[0070] Example 12 Compared with Example 1, the difference is that the electrolyte includes: Electrolyte additive, using compound 1, its mass percentage is 5%; Lithium salt: lithium difluorooxalatoborate (LiDFOB) with a mass percentage of 10%; Lithium bis(oxalatoborate) (LiBF4), with a mass percentage of 8%; and lithium difluorophosphate (LiDFP), 2% by mass; The coordination solvent is ethylene glycol diethyl ether (EMC), with a mass percentage of 25%; Fluoroethylene carbonate (FEC), with a mass percentage of 28%; and dimethyl carbonate (DMC), with a mass percentage of 22%.

[0071] Example 13 Compared with Example 1, the difference is that the electrolyte includes: Electrolyte additive, using compound 1, its mass percentage is 5%; Lithium salt: lithium bifluorooxalatoborate (LiPF6) with a mass percentage of 15%; and lithium difluorophosphate (LiDFP), with a mass percentage of 1%; The coordination solvent is dimethyl carbonate (DMC), with a mass percentage of 44%; and fluoroethylene carbonate (FEC), with a mass percentage of 35%.

[0072] Example 14 Compared with Example 1, the difference is that the electrolyte includes: Electrolyte additive, using compound 1, its mass percentage is 5%; Lithium salt: lithium bis(fluorooxalato)borate (LiFSI) with a mass percentage of 20%; and lithium difluorophosphate (LiDFP), with a mass percentage of 1%; The coordination solvent is 1,3-dimethoxypropane (DMP), with a mass percentage of 24%; The non-coordinating solvent used was sevoflurane (SFE), with a mass percentage of 50%.

[0073] Example 15 Compared with Example 1, the difference is that the electrolyte includes: Electrolyte additive, using compound 1, its mass percentage is 5%; Lithium salt: lithium bis(fluorooxalato)borate (LiFSI) with a mass percentage of 20%; The coordination solvent is ethylene glycol diethyl ether (DME), with a mass percentage of 12%; and 1,3-dioxolane (DOL), with a mass percentage of 13%; The non-coordinating solvent used is 1,1,1,2,2,3,4,5,5,5-decafluoropentane (HFC), and its mass percentage is 50%.

[0074] Example 16 Compared with Example 1, the difference is that the electrolyte includes: Electrolyte additive, using compound 1, its mass percentage is 5%; Lithium salt: lithium bis(fluorooxalato)borate (LiFSI) with a mass percentage of 20%; The coordination solvent is tetrahydropyran (THP), with a mass percentage of 25%; and tetrahydrofuran (TMP), 5% by mass; The non-coordinating solvent used was 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE), with a mass percentage of 45%.

[0075] Example 17 Compared with Example 1, the difference is that the electrolyte includes: Electrolyte additive, using compound 1, its mass percentage is 0.1%; Lithium salt: lithium bis(fluorosulfonyl)imide (LiFSI) with a mass percentage of 5%; The coordination solvent is ethylene glycol diethyl ether (DME), with a mass percentage of 24.9%; The non-coordinating solvent used was 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE), with a mass percentage of 70%.

[0076] Example 18 Compared with Example 1, the difference is that the electrolyte includes: Electrolyte additive, using compound 1, its mass percentage is 15%; Lithium salt: lithium bis(fluorosulfonyl)imide (LiFSI) with a mass percentage of 35%; The coordination solvent is ethylene glycol diethyl ether (DME), with a mass percentage of 30%; The non-coordinating solvent used was 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE), with a mass percentage of 20%.

[0077] Example 19 Compared with Example 1, the difference is that the mass percentage of compound 1 in the electrolyte additive is 1%, the mass percentage of lithium bis(fluorosulfonyl)imide (LiFSI) is 24%, the mass percentage of ethylene glycol dimethyl ether (DME) is 25%, and the mass percentage of 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) is 50%.

[0078] Example 20 Compared with Example 1, the difference is that the mass percentage of compound 1 in the electrolyte additive is 10%, the mass percentage of lithium bis(fluorosulfonyl)imide (LiFSI) is 24%, the mass percentage of ethylene glycol dimethyl ether (DME) is 21%, and the mass percentage of 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) is 45%.

[0079] During the preparation process, it was found that in Examples 1 to 20, the electrolyte additives were all completely dissolved in the electrolyte.

[0080] 2. Comparative Example Comparative Example 1 Compared with Example 1, the difference is that compound 1 is not added to the electrolyte.

[0081] Comparative Example 2 Compared with Example 9, the difference is that compound 1 is not added to the electrolyte.

[0082] Comparative Example 3 Compared with Example 10, the difference is that compound 1 is not added to the electrolyte.

[0083] Comparative Example 4 Compared with Example 13, the difference is that the electrolyte includes: LiNO3, its mass percentage is 15%; Lithium salt: lithium bis(fluorosulfonyl)imide (LiFSI) with a mass percentage of 35%; The coordination solvent is ethylene glycol diethyl ether (DME), with a mass percentage of 30%; The non-coordinating solvent used was 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE), with a mass percentage of 20%.

[0084] During the preparation process, it was found that LiNO3 could not be completely dissolved in the electrolyte.

[0085] Comparative Example 5 Compared with Example 14, the difference is that the electrolyte includes: LiNO3, its mass percentage is 1%; Lithium salt, using lithium bis(fluorosulfonyl)imide (LiFSI), with a mass percentage of 24%; The coordination solvent is ethylene glycol dimethyl ether (DME), with a mass percentage of 25%; The non-coordinating solvent used was 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE), with a mass percentage of 50%.

[0086] During the preparation process, it was found that LiNO3 could not be completely dissolved in the electrolyte.

[0087] 3. Experimental Examples 1. The electrolytes in Examples 1 to 20 and Comparative Examples 1 to 5 were assembled into Li||NCM811 soft-pack batteries in an argon atmosphere.

[0088] 2. Test methods (1) 25°C cycle performance test: The batteries prepared in the examples and comparative examples were charged at 25°C at a constant current and constant voltage of 0.2C to 4.2V, and then discharged at a constant current of 0.5C to 3.0V. This was considered one cycle, and the number of cycles until the battery reached 80% SOH was recorded.

[0089] (2) Dead lithium quality In lithium metal batteries, hydrogen-gas chromatography titration (H2-GCT) can be used to quantify dead lithium ("dead lithium" encapsulated by SEI). Its core principle is to use the reaction of dead lithium with water to generate hydrogen (H2), accurately measure the volume of H2 through gas chromatography (GC), and then convert it into the mass of dead lithium. The specific steps are as follows: S1. Cut the cycled lithium metal anode into 14 mm diameter discs to expose fresh, active lithium (lithium metal not encapsulated by the SEI). Immerse the discs in a biphenyl / THF solution (6 wt% biphenyl) and allow to stand at room temperature for 36-48 hours to dissolve the active lithium. The remaining dead lithium (lithium encapsulated by the SEI) remains intact due to the chemical stability of the SEI in biphenyl / THF. Separate the discs containing the dead lithium, rinse with THF to remove any residual biphenyl / THF solution, dry, and transfer to an airtight glass bottle.

[0090] S2. Use an airtight syringe to inject deionized water into the glass bottle, seal it, and shake it well to allow the dead lithium wrapped in the SEI to come into contact with the water (the SEI partially dissolves in the water, releasing the lithium inside to participate in the reaction). The dead lithium reacts chemically with water: , the volume of H2 generated is proportional to the mass of dead lithium.

[0091] S3. Perform the entire process in an argon (Ar) atmosphere glove box. Collect the generated H2 with a gas-tight syringe and transfer it to a vacuum-evacuated aluminum foil bag. Ensure a constant volume of Ar as an internal standard gas for subsequent calibration.

[0092] S4. A gas chromatograph was used to detect the H2 concentration using the difference in thermal conductivity between H2 and the carrier gas (Ar). The H2 concentration was measured using a thermal conductivity detector (TCD). The ratio of the H2 peak area to the Ar peak area was recorded and substituted into the calibration curve to calculate the amount of H2. This was then converted to the mass of dead lithium (1 mol H2 corresponds to 2 mol Li). The calculation formula was: dead lithium mass = (nH2 × 2 × 6.941) / 1. The measurement was repeated three times and the average value was calculated. The results are summarized in Table 1.

[0093] Table 1

[0094] From Examples 1 to 20, Comparative Examples 1 to 5, and Table 1, it can be seen that: (1) Comparison between Comparative Example 1 and Example 1 In Comparative Example 1, no electrolyte additive, i.e., Compound 1, was added to the electrolyte. In Example 1, Compound 1 was added as an electrolyte additive at a mass percentage of 5% based on the total mass of the electrolyte. As shown in Table 1, the cycle performance (@80% SOH) of Example 1 reached 380 cls, far exceeding the cycle performance (@80% SOH) of 201 cls of Comparative Example 1. The dead lithium mass (@50 cls) of Example 1 was only 1.58 mg cm -3 , which is much smaller than 2.99 mg cm in Comparative Example 1. -3, the cycle performance of Example 1 is significantly improved and the dead lithium mass is reduced; it can be seen that in Example 1, by using Compound 1 as an electrolyte additive, the nitrate group in Compound 1 can be decomposed to form a nitrogen-rich interface layer, and the organic group can be decomposed to form an organic compound-rich interface layer, which effectively reduces the consumption of active lithium metal and significantly improves the battery cycle life.

[0095] Combine Figure 1 and Figure 2 It can be seen that the capacity retention rate of the soft-pack battery prepared by using the electrolyte of Example 1 is above 80% after 380 cycles, while the capacity retention rate of the soft-pack battery prepared by using the electrolyte of Comparative Example 1 is 80% after 201 cycles. Under the condition of the same capacity retention rate, the number of cycles of the soft-pack battery of Comparative Example 1 is significantly reduced, which shows that in Example 1, the number of cycles of the battery can be improved by adding Compound 1.

[0096] Similarly, compared with Example 9, Comparative Example 2 did not add the electrolyte additive, and the cycle performance of Comparative Example 2 was significantly reduced and the mass of dead lithium was significantly increased; compared with Example 10, Comparative Example 3 did not add the electrolyte additive, and the cycle performance of Comparative Example 3 was significantly reduced and the mass of dead lithium was significantly increased; (2) Examples 1 to 20 As shown in Table 1, in Examples 1 to 20, compounds 1 to 8 are used as electrolyte additives, the mass content of the electrolyte additives is 0.1% to 15%, and the batteries prepared by combining lithium salts, coordination solvents and non-coordinating solvents have a cycle performance (@80% SOH) ≥ 238 cls and a dead lithium mass ≤ 2.57 mg cm -3 , which is better than the cycle performance (@80% SOH) of comparative example 3, 222 cls, and dead lithium mass 2.70 mg cm -3 It can be seen that the batteries prepared in Examples 1 to 20 have good cycle performance and significantly reduce the mass of dead lithium.

[0097] (3) Comparison between Comparative Example 4 and Example 13 In Comparative Example 4, LiNO3 is used as an electrolyte additive with a mass percentage of 15%. In Example 13, Compound 1 is used as an electrolyte additive with a mass percentage of 15%. The mass percentage content of the electrolyte additives in Example 13 and Comparative Example 4 is the same, but the cycle performance (@80% SOH) of Comparative Example 4 is only 176 cls, which is much smaller than 264 cls of Example 13. The dead lithium mass (@50 cls) of Comparative Example 4 is as high as 3.41 mg cm -3 Much larger than 2.55 mg cm in Example 13 -3It can be seen that when LiNO3 is used as the electrolyte additive, the cycle performance of the battery is significantly worse and the quality of dead lithium is significantly higher.

[0098] LiNO3 has a low solubility in the electrolyte. In Comparative Example 4, LiNO3 is not completely dissolved. The inventors speculate that as the cycle time increases, the side reactions at the lithium negative electrode interface increase, and LiNO3 will be rapidly consumed, thereby affecting the battery cycle life and cycle performance. However, the present application uses Compound 1 as an electrolyte additive. Compound 1 has good solubility in the electrolyte. In the early stage of the battery cycle, the electrolyte additive can be maintained at a high concentration. As the cycle time is delayed, even if the electrolyte additive is rapidly consumed, the concentration of the electrolyte additive decreases to a certain extent, but it is still maintained at a high concentration content, ensuring the battery cycle life and cycle performance. Therefore, compared with Comparative Example 4, the battery in Example 13 has better cycle performance and significantly less dead lithium mass.

[0099] (4) Comparison between Comparative Example 5 and Example 14 In Comparative Example 5, LiNO3 is used as an electrolyte additive with a mass percentage of 1%. In Example 14, Compound 1 is used as an electrolyte additive with a mass percentage of 1%. The mass percentage content of the electrolyte additives in Example 14 and Comparative Example 5 is the same, and the cycle performance (@80% SOH) of Comparative Example 5 is 231 cls, which is less than 355 cls of Example 14. The dead lithium mass (@50 cls) of Comparative Example 5 is 2.65 mg cm -3 Greater than 1.71 mg cm in Example 14 -3 It can be seen that when LiNO3 is used as the electrolyte additive, the cycle performance of the battery is significantly worse and the quality of dead lithium is significantly higher.

[0100] In Comparative Example 5, the LiNO3 was not fully dissolved. The inventors speculate that as the cycle time increases, side reactions at the lithium negative electrode interface increase, and the LiNO3 is rapidly consumed, thus affecting the battery's cycle life and performance. However, the present application uses Compound 1 as an electrolyte additive, which has good solubility in the electrolyte. Therefore, compared with Comparative Example 5, the battery in Example 14 has better cycle performance and significantly less dead lithium mass.

[0101] The above is a detailed introduction to the electrolyte additives, electrolytes, and batteries provided in the embodiments of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core ideas. At the same time, for those skilled in the art, based on the ideas of the present application, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present application.

Claims

1. An electrolyte additive, characterized in that It has the structure shown in formula (1): Formula (1); Wherein: R is at least one of substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkynyl, substituted or unsubstituted C1-C10 alkoxy, substituted or unsubstituted C2-C10 alkoxycarbonyl, substituted or unsubstituted C2-C20 heterocyclic group, substituted or unsubstituted C6-C12 aryl, and C3-C6 cycloalkyl; n is an integer from 1 to 8.

2. The electrolyte additive according to claim 1, characterized in that The substituted substituent is selected from halogen or C1~C4 alkyl; And / or, n is an integer from 1 to 6.

3. The electrolyte additive according to claim 1 or 2, characterized in that The R is at least one of a substituted or unsubstituted C1-C8 alkoxy group, a substituted or unsubstituted C2-C10 heterocyclic group, and a C5-C6 cycloalkyl group.

4. The electrolyte additive according to claim 1, characterized in that The heterocyclic group includes a cycloalkoxy group.

5. The electrolyte additive according to claim 1 or 2, characterized in that The electrolyte additive is selected from at least one of the following compounds 1 to 8: 。 6. An electrolyte, characterized in that The electrolyte comprises a lithium salt, a solvent and the electrolyte additive according to any one of claims 1 to 5.

7. The electrolyte according to claim 6, characterized in that Based on the total mass of the electrolyte, the mass percentage of the electrolyte additive is 0.1% to 15%.

8. The electrolyte according to claim 7, characterized in that The lithium salt is selected from one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorooxalatoborate), lithium bis(oxalatoborate), lithium tetrafluoroborate, lithium hexafluorophosphate, lithium difluorooxalatophosphate, and lithium difluorophosphate; Based on the total mass of the electrolyte, the mass percentage of the lithium salt is 5% to 35%; and / or, the solvent includes a coordinating solvent and a non-coordinating solvent; Based on the total mass of the electrolyte, the mass percentage of the solvent is 64.9% to 94.9%.

9. The electrolyte according to claim 8, characterized in that Based on the total mass of the electrolyte, the mass percentage of the electrolyte additive is 1% to 10%, the mass percentage of the lithium salt is 22% to 24%, and the mass percentage of the solvent is 66% to 77%.

10. A battery, characterized in that: The electrolyte additive according to any one of claims 1 to 5, or the electrolyte according to any one of claims 6 to 9.

Images