Electrolyte and battery

Abstract

The application discloses an electrolyte and a battery, and relates to the technical field of batteries. The electrolyte comprises a lithium salt, a solvent and an additive, and a structural formula of the additive is shown in formula (I): A ‑ selected from inorganic acid radical ions. The electrolyte provided by the application is beneficial to improving the film forming performance of the SEI film and improving the film forming quality of the SEI film.

Description

[0001] This application is a divisional application. The original application number is 202410557219.5, the application date is May 7, 2024, and the invention title is: Electrolyte and Battery. Technical Field

[0002] This application relates to the field of battery technology, and more particularly to an electrolyte and a battery. Background Technology

[0003] Lithium-ion batteries possess advantages such as high safety, high energy density, high voltage, and long lifespan, and are considered the most promising rechargeable batteries. Traditional lithium-ion batteries generally use organic electrolytes, but organic electrolytes pose safety hazards due to their flammability and explosiveness. Solid-state electrolytes, on the other hand, exhibit high ionic conductivity, a wide electrochemical stability window, and excellent thermodynamic properties such as high strength and elastic modulus, and are widely used in lithium-ion batteries.

[0004] In lithium-ion batteries, although lithium metal anodes possess extremely high energy densities (lithium anode 3860 mAh / g vs. graphite anode 372 mAh / g), their inherent problems of lithium dendrite formation and anode expansion remain difficult to resolve, leading to decreased battery cycle performance, short circuits, thermal runaway, and even explosions. To obtain a stable and efficient lithium metal battery system, researchers have successively proposed strategies such as constructing artificial passivation films on the lithium electrode surface, modifying the lithium electrode interface with electrolyte additives, and modifying the structure of the lithium metal anode. For example, film-forming additives can promote the formation of a stable and effective solid electrolyte interface (SEI) film on the electrode material surface. Among these, the technical route using electrolyte additives avoids complex lithium electrode pretreatment processes and has the advantages of simplicity and low cost. Therefore, it is particularly important to stably construct and regulate the electrolyte composition and find an electrolyte system with good compatibility with the lithium metal anode.

[0005] Existing additives have limited effect on improving the film-forming properties of SEI films and further improvements are needed. Summary of the Invention

[0006] In view of this, this application provides an electrolyte and a battery.

[0007] The embodiments of this application are implemented as follows: an electrolyte includes a lithium salt, a solvent, and an additive, wherein the additive has the structural formula shown in formula (Ⅰ):

[0008]

[0009] Among them, A - Selected from inorganic acid radicals;

[0010] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 Each group is independently selected from hydrogen, deuterium, halogen, amino, cyano, hydroxyl, carboxyl, aldehyde, nitro, amide, substituted or unsubstituted C1-C groups. 20 Alkyl or heteroalkyl, substituted or unsubstituted C2-C 20 alkenyl or heteroalkenyl, substituted or unsubstituted C2-C 20 alkynyl or heteroyneyl, substituted or unsubstituted C1-C 20 alkoxy, substituted or unsubstituted C1-C 20 Acyloxy group, substituted or unsubstituted C1-C 20 alkoxycarbonyl, substituted or unsubstituted C3-C 20 heterocyclic groups, substituted or unsubstituted C6-C 20 One or more of the aryl groups.

[0011] Optionally, in some embodiments of this application,

[0012] The inorganic acid radical ions are selected from NO3. - F - I - ,Br - One or more of them; and / or

[0013] R1 is selected from substituted or unsubstituted C5-C. 15 Alkyl or heteroalkyl, substituted or unsubstituted C5-C 15 alkenyl or heteroalkenyl, substituted or unsubstituted C5-C 15 alkynyl or heteroyynyl, substituted or unsubstituted C5-C 15 alkoxy, substituted or unsubstituted C5-C 15 Acyloxy group, substituted or unsubstituted C5-C 15 One or more of the alkoxycarbonyl groups; and / or; and / or

[0014] R2 is selected from substituted or unsubstituted C6-C. 15 heterocyclic groups, substituted or unsubstituted C8-C 15 One or more of the aryl groups; and / or

[0015] R3, R4, R5, R6, R7, R8, R9, R 10 Each group is independently selected from hydrogen, deuterium, halogen, amino, cyano, hydroxyl, carboxyl, aldehyde, nitro, amide, sulfonic acid, sulfonyl, substituted or unsubstituted C5-C groups. 15 Alkyl or heteroalkyl, substituted or unsubstituted C5-C 15 alkenyl or heteroalkenyl, substituted or unsubstituted C5-C 15One or more of the alkynyl or heteroalkynyl groups.

[0016] Optionally, in some embodiments of this application,

[0017] The halogen includes one or more of fluorine, chlorine, bromine, and iodine; and / or

[0018] The alkyl group includes one or more of methyl, ethyl, isopropyl, tert-butyl, hexyl, octyl, decyl, dodecyl, and heptadecanyl; and / or

[0019] The alkenyl group includes one or more of vinyl, propenyl, butenyl, hexenyl, octenyl, decenyl, dodecenyl, 9-heptadecenyl, 1,4-pentadienyl, 1,5-hexadienyl, 1,6-heptadienyl, 1,7-octadienyl, 1,8-nonadienyl, and 1,9-decadienyl; and / or

[0020] The alkynyl group includes one or more of ethynyl, propynyl, pentynyl, hepynyl, hexynyl, octyynyl, decynyl, and dodecanynyl; and / or

[0021] The alkoxy group includes one or more of methoxy, ethoxy, propoxy, butoxy, pentoxy, heptaoxy, hexoxy, octoxy, decoxy, and dodecoxy; and / or

[0022] The acyloxy group includes one or more of the following: formyloxy, acetyloxy, propionyloxy, butyryloxy, valeryloxy, heptayloxy, hexanoyloxy, octanoyloxy, decanoyloxy, dodecanoyloxy, palmitoyloxy, and stearoyloxy; and / or

[0023] The alkoxycarbonyl group includes one or more of methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, heptaoxycarbonyl, hexoxycarbonyl, decoxycarbonyl, dodecoxycarbonyl, octoxycarbonyl, palmitoxycarbonyl, and stearoxycarbonyl; and / or

[0024] The heteroatom in the heteroalkyl group, the heteroalkenyl group, the heteroynyl group, or the heterocyclic group includes one or more of O, P, N, and S; and / or

[0025] The heterocyclic group includes one or more of the following: thiazolyl, thiophenel, furanyl, pyrrolyl, pyridyl, pyrimidinyl, imidazolyl, azole, pyrazinyl, indolyl, quinolinyl, pteridinyl, and acridineyl; and / or

[0026] The aryl group includes one or more of phenyl, p-tolyl, p-nitrophenyl, o-methoxyphenyl, m-methoxyphenyl, p-methoxyphenyl, and p-nitromethoxyphenyl; and / or

[0027] The substituted groups each independently include one or more of -NH2, -F, -Cl, -Br, -I, -OH, -COOH, -NO2, -SO3H, -CHO, -SH, and -CN.

[0028] Optionally, in some embodiments of this application, the additive is selected from one of the following structural formulas:

[0029]

[0030]

[0031] Optionally, in some embodiments of this application,

[0032] The mass ratio of the lithium salt, the additive, and the solvent is (5-20):(0.1-1):(5-20); and / or

[0033] The lithium salt includes one or more of organic lithium salts and inorganic lithium salts; and / or

[0034] The solvent includes one or more of ether solvents, ester solvents, and nitrile solvents.

[0035] Optionally, in some embodiments of this application,

[0036] The organolithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalateborate, and lithium bis(oxalateborate); and / or

[0037] The inorganic lithium salt includes one or more of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium difluorophosphate; and / or

[0038] The ether solvent includes one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and ethylene glycol diethyl ether; and / or

[0039] The ester solvents include one or more of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate; and / or

[0040] The nitrile solvents include one or more of acetonitrile and succinic anhydride.

[0041] Optionally, in some embodiments of this application, the electrolyte further includes a diluent.

[0042] Optionally, in some embodiments of this application,

[0043] The diluent includes fluorobenzene diluents; the fluorobenzene diluent includes one or more of fluorobenzene, trifluorotoluene, m-fluorotoluene, chloropentafluorobenzene, 1,2,4-trifluorobenzene, 1,2,3,4-tetrafluorobenzene, and 1,4-dibromotetrafluorobenzene; and / or

[0044] The mass ratio of the solvent to the diluent is (5-20):(70-90); and / or

[0045] The volume fraction of the diluent in the total volume of the diluent and the solvent is 85% to 95%; and / or

[0046] In the electrolyte, the molar concentration of the lithium salt is 0.3 mol / L to 1.3 mol / L.

[0047] Accordingly, embodiments of this application also provide a battery, including a positive electrode, a negative electrode, a separator located between the positive electrode and the negative electrode, and the electrolyte described above.

[0048] Optionally, in some embodiments of this application,

[0049] The positive electrode material includes one or more of lithium nickel manganese oxide, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, and lithium nickel cobalt manganese oxide; and / or

[0050] The negative electrode includes one or more of the following: lithium metal negative electrode, lithium metal alloy negative electrode, graphite negative electrode, silicon-based negative electrode, silicon-graphite composite negative electrode, and copper foil lithium-free negative electrode; and / or

[0051] The diaphragm includes one or more of the following: woven membrane, nonwoven membrane, microporous membrane, composite membrane, diaphragm paper, rolled membrane, single-layer polypropylene membrane, single-layer polyethylene membrane, PP+ceramic coating, PE+ceramic coating, double-layer PP / PE, triple-layer PP / PE / PP, polyester membrane, cellulose membrane, polyimide membrane, polyamide membrane, spandex membrane, and aramid membrane.

[0052] The electrolyte provided in this application contains inorganic acid radical ions (A... - It can reduce and decompose the inorganic components that form the membrane, improving the membrane's density, reducing impedance, and facilitating lithium-ion transport; the shared carbon atoms between the triphenyl fused rings (naphthalene) contribute to the formation of the organic components of the membrane; simultaneously, N... + As a pyron ion with lone pairs of electrons, it can act as an electron donor, providing lithium-loving sites, thereby promoting uniform deposition of lithium ions, improving film formation, and effectively enhancing the film quality of SEI films.

[0053] In this application, the aforementioned additive is used as a film-forming additive. Adding it to the electrolyte improves the lithium-ion conductivity of the electrolyte and helps address the problem of a narrow electrochemical window in the electrolyte. When the electrolyte is used in a battery, the additive preferentially undergoes redox reactions with other electrolyte components, reducing electrolyte decomposition at the cathode and anode, altering the structure of the solid electrolyte interface film, effectively inhibiting lithium crystal formation, reducing electrolyte consumption, and thus improving battery safety and cycle performance. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 This is the linear sweep voltammetric curve of the electrolyte provided in Example 1 of this application;

[0056] Figure 2 This application provides the cycle curves of the batteries provided in Example 1 and Comparative Examples 1-2. Detailed Implementation

[0057] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of this application and are not intended to limit this application.

[0058] In this application, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in its actual use or operating state, specifically the orientation shown in the accompanying drawings; while "inner" and "outer" refer to the outline of the device. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". The terms first, second, third, etc., are used merely as illustrative purposes and do not impose numerical requirements or establish a numerical order.

[0059] In this application, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural.

[0060] In this application, "at least one" means one or more, and "more than one" means two or more. "One or more", "at least one of the following", or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0061] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has 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., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0062] In this application, "aryl or aromatic group" refers to an aromatic hydrocarbon group derived from an aromatic ring compound by removing one hydrogen atom. It can be a monocyclic aryl, a fused-ring aryl, or a polycyclic aryl, and for polycyclic rings, at least one of them is an aromatic ring system. For example, "substituted or unsubstituted aryl having 6 to 40 ring atoms" refers to an aryl containing 6 to 40 ring atoms, preferably a substituted or unsubstituted aryl having 6 to 30 ring atoms, more preferably a substituted or unsubstituted aryl having 6 to 18 ring atoms, particularly preferably a substituted or unsubstituted aryl having 6 to 14 ring atoms, and optionally further substituted on the aryl group; suitable examples include, but are not limited to: phenyl, biphenyl, terphenyl, naphthyl, anthracene, phenanthrene, fluoranyl, triphenylene, pyrene, perylene, tetraphenyl, fluorenyl, dinaphthylphenyl, acenaphthyl, and their derivatives. Understandably, multiple aryl groups can also be interrupted by short non-aromatic units (e.g., <10% non-H atoms, such as C, N, or O atoms), specifically acenaphthene, fluorene, or 9,9-diarylfluorene, triarylamines, and diaryl ether systems should also be included in the definition of aryl. The heteroatom in the heterocycle is one or more of oxygen, sulfur, nitrogen, and phosphorus atoms.

[0063] Traditional carbonate electrolytes are easily reduced, and the resulting SEI film has high impedance. Ether electrolytes are more resistant to reduction than carbonates, but they suffer from cathode oxidation. Existing film-forming additives used in carbonates have higher film-forming potentials than ethers, failing to form a suitable cathode film for protection. Current electrolytes have narrow electrochemical windows and poor performance. Adding ionic liquids to electrolytes is commonly used to improve performance, but ionic liquid electrolytes are complex to synthesize, costly, and face significant commercialization challenges. High-concentration electrolytes require higher lithium salt content, significantly increasing costs and viscosity, which is detrimental to ion conduction.

[0064] The technical solution of this application is as follows:

[0065] In a first aspect, embodiments of this application provide an electrolyte comprising a lithium salt, a solvent, and an additive, wherein the additive has the structural formula shown in formula (I):

[0066]

[0067] A - Selected from inorganic acid radicals;

[0068] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 Each group is independently selected from hydrogen, deuterium, halogen, amino, cyano, hydroxyl, carboxyl, aldehyde, nitro, amide, substituted or unsubstituted C1-C groups. 20 Alkyl or heteroalkyl, substituted or unsubstituted C2-C 20 alkenyl or heteroalkenyl, substituted or unsubstituted C2-C 20 alkynyl or heteroyneyl, substituted or unsubstituted C1-C 20 alkoxy, substituted or unsubstituted C1-C 20 Acyloxy group, substituted or unsubstituted C1-C 20 alkoxycarbonyl, substituted or unsubstituted C3-C 20 heterocyclic groups, substituted or unsubstituted C6-C 20 One or more of the aryl groups.

[0069] It should be noted that when R1 is selected from heteroalkyl, heteroalkenyl, or heteroynyl groups, it can be specifically selected from groups containing onium ions. In this case, the additive also includes anion corresponding to the onium ion in R1, and the anion can be selected from inorganic acid radical ions.

[0070] The electrolyte provided in this application contains inorganic acid radical ions (A... - It can reduce and decompose the inorganic components that form the membrane, improving membrane density, reducing impedance, and facilitating lithium-ion transport; the shared carbon atoms between the triphenyl fused rings (naphthalene) contribute to the formation of the organic components of the membrane; simultaneously, N+ As a pyron ion with lone pairs of electrons, it can act as an electron donor, providing lithium-loving sites, thereby promoting uniform deposition of lithium ions, improving film formation, and effectively enhancing the film quality of SEI films.

[0071] In this application, the aforementioned additive is used as a film-forming additive. Adding it to the electrolyte improves the lithium-ion conductivity of the electrolyte and helps address the problem of a narrow electrochemical window in the electrolyte. When the electrolyte is used in a battery, the additive preferentially undergoes redox reactions with other electrolyte components, reducing electrolyte decomposition at the cathode and anode, altering the structure of the solid electrolyte interface film, effectively inhibiting lithium crystal formation, reducing electrolyte consumption, and thus improving battery safety and cycle performance.

[0072] In some embodiments, the inorganic acid radical ion is selected from NO3. - F - I - ,Br - One or more of them.

[0073] In some embodiments, R1 is selected from substituted or unsubstituted C5-C. 15 Alkyl or heteroalkyl, substituted or unsubstituted C5-C 15 alkenyl or heteroalkenyl, substituted or unsubstituted C5-C 15 alkynyl or heteroyynyl, substituted or unsubstituted C5-C 15 alkoxy, substituted or unsubstituted C5-C 15 Acyloxy group, substituted or unsubstituted C5-C 15 One or more of the alkoxycarbonyl groups.

[0074] In some embodiments, R2 is selected from substituted or unsubstituted C6-C. 15 heterocyclic groups, substituted or unsubstituted C8-C 15 One or more of the aryl groups.

[0075] In some embodiments, R3, R4, R5, R6, R7, R8, R9, R 10 Each group is independently selected from hydrogen, deuterium, halogen, amino, cyano, hydroxyl, carboxyl, aldehyde, nitro, amide, sulfonic acid, sulfonyl, substituted or unsubstituted C5-C groups. 15 Alkyl or heteroalkyl, substituted or unsubstituted C5-C 15 alkenyl or heteroalkenyl, substituted or unsubstituted C5-C 15 It contains one or more of the alkynyl or heteroalkynyl groups. It can be understood that halogen, amino, cyano, hydroxyl, carboxyl, aldehyde, nitro, amide, sulfonic acid, and sulfonyl groups are lithium-philic groups, which can promote the dynamic formation of the film and further improve the film-forming performance.

[0076] Preferably, for the same additive, R3, R4, R5, R6, R7, R8, R9, R 10 One or two groups are selected from the above-mentioned lithiophilic groups. There should not be too many lithiophilic groups to avoid affecting the formation quality of the SEI film.

[0077] In some embodiments, the halogen includes one or more of fluorine, chlorine, bromine, and iodine.

[0078] The alkyl group includes one or more of methyl, ethyl, isopropyl, tert-butyl, hexyl, octyl, decyl, dodecyl, and heptadecanyl.

[0079] The alkenyl group includes one or more of vinyl, propenyl, butenyl, hexenyl, octenyl, decenyl, dodecenyl, 9-heptadecenyl, 1,4-pentadienyl, 1,5-hexadienyl, 1,6-heptadienyl, 1,7-octadienyl, 1,8-nonadienyl, and 1,9-decadienyl.

[0080] The alkyne group includes one or more of ethynyl, propynyl, pentynyl, heptynyl, hexynyl, octyynyl, decynyl, and dodeynyl.

[0081] The alkoxy group includes one or more of methoxy, ethoxy, propoxy, butoxy, pentoxy, heptoxy, hexoxy, octoxy, decoxy, and dodecoxy.

[0082] The acyloxy group includes one or more of the following: formyloxy, acetyloxy, propionyloxy, butyryloxy, valeryloxy, heptayloxy, hexanoyloxy, octanoyloxy, decanoyloxy, dodecanoyloxy, palmitoyloxy, and stearyloxy.

[0083] The alkoxycarbonyl group includes one or more of the following: methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, heptoxycarbonyl, hexoxycarbonyl, decoxycarbonyl, dodecoxycarbonyl, octoxycarbonyl, palmoxycarbonyl, and stearoxycarbonyl.

[0084] The heteroatoms in the heteroalkyl, heteroalkenyl, heteroynyl, and heterocyclic groups include one or more of O, P, N, and S.

[0085] The heterocyclic group includes one or more of the following: thiazolyl, thiophene, furanyl, pyrrolyl, pyridyl, pyrimidinyl, imidazolyl, azole, pyrazinyl, indolyl, quinolinyl, pteridinyl, and acridineyl.

[0086] The aryl group includes one or more of phenyl, p-tolyl, p-nitrophenyl, o-methoxyphenyl, m-methoxyphenyl, p-methoxyphenyl, and p-nitromethoxyphenyl.

[0087] The substituted groups each independently include one or more of -NH2, -F, -Cl, -Br, -I, -OH, -COOH, -NO2, -SO3H, -CHO, -SH, and -CN.

[0088] It is understood that the substituted group refers to substituents in the following categories: substituted alkyl or heteroalkyl, substituted alkenyl or heteroalkenyl, substituted alkynyl or heteroalkynyl, substituted alkoxy, substituted acyloxy, substituted alkoxycarbonyl, substituted heterocyclic, and substituted aryl.

[0089] In some embodiments, the additive is selected from one of the following structural formulas:

[0090]

[0091]

[0092] in, It is ethidium bromide (CAS::1239-45-8); It is ethidium bromide-N,N'-bisacrylamide (CAS: 480438-67-3); It is propidium iodide (CAS: 25535-16-4).

[0093] It can be prepared by reacting ethidium bromide with lithium nitrate and potassium nitrate.

[0094] It can be prepared by reacting ethidium bromide-N,N'-bisacrylamide with lithium nitrate and potassium nitrate.

[0095] It can be prepared by reacting propidium iodide with lithium fluoride and potassium fluoride.

[0096] In some embodiments, the lithium salt includes one or more of organic lithium salts and inorganic lithium salts.

[0097] Furthermore, the organic lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium difluorooxalateborate (LiDFOB), and lithium bis(oxalateborate)borate (LiBOB).

[0098] The inorganic lithium salt includes one or more of lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), and lithium difluorophosphate (LiP2F2).

[0099] In some embodiments, the solvent includes one or more of ether solvents, ester solvents, and nitrile solvents.

[0100] Furthermore, the ether solvent includes one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and ethylene glycol diethyl ether.

[0101] The ester solvents include one or more of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

[0102] The nitrile solvents include one or more of acetonitrile and succinic anhydride.

[0103] In some embodiments, the mass ratio of the lithium salt, the additive, and the solvent is (5–20):(0.1–1):(5–20), for example, 7:0.5:10, 8:0.5:10, 10:0.5:10, 12:0.5:10, 15:0.5:10, 18:0.5:10, 10:0.3:10, 10:0.6:10, 10:0.8:10, 10:0.5:8, 10:0.5:12, 10:0.5:15, 10:0.5:18, etc. Within the range of the mass ratio, the lithium salt and the additive can be uniformly dispersed in the solvent.

[0104] In some embodiments, the electrolyte further includes a diluent. The diluent can adjust the viscosity of the electrolyte and improve its wettability.

[0105] In some embodiments, the diluent includes fluorobenzene-based diluents.

[0106] Furthermore, the fluorobenzene diluent includes one or more of fluorobenzene, trifluorotoluene, m-fluorotoluene, chloropentafluorobenzene, 1,2,4-trifluorobenzene, 1,2,3,4-tetrafluorobenzene, and 1,4-dibromotetrafluorobenzene.

[0107] In some embodiments, the mass ratio of the solvent to the diluent is (5-20):(70-90), for example, 8:80, 10:80, 12:80, 15:80, 18:80, 10:72, 10:75, 10:78, 10:82, 10:85, 10:88, 10:89, etc. Alternatively, the volume fraction of the diluent in the total volume of the diluent and the solvent is 85%-95%, for example, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, etc. Thus, a higher proportion of diluent is beneficial for reducing the viscosity of the electrolyte, improving the processability and wettability of the electrolyte, and further increasing the lithium-ion conductivity of the electrolyte.

[0108] In some embodiments, when the electrolyte does not contain a diluent, the molar concentration of the lithium salt in the electrolyte is 8 mol / L to 10 mol / L, for example, it can be 8.2 mol / L, 8.5 mol / L, 8.8 mol / L, 9 mol / L, 9.2 mol / L, 9.5 mol / L, 9.8 mol / L, etc. When a diluent is added to the electrolyte, the molar concentration of the lithium salt in the electrolyte is 0.3 mol / L to 1.3 mol / L, for example, it can be 0.35 mol / L, 0.42 mol / L, 0.45 mol / L, 0.48 mol / L, 0.5 mol / L, 0.52 mol / L, 0.55 mol / L, 0.58 mol / L, 0.6 mol / L, 0.62 mol / L, 0.65 mol / L, 0.68 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, etc. Adding a diluent reduces costs, lowers viscosity, and facilitates ion conduction.

[0109] It is understood that the electrolyte can be obtained by adding lithium salts and additives to a solvent, or by further adding a diluent and then stirring.

[0110] The electrolyte may also contain conventional additives, such as conductive additives, wetting promoters, high / low temperature resistant additives, overcharge protection additives, and flame retardant additives, depending on the requirements.

[0111] Secondly, embodiments of this application also provide a battery, including a positive electrode, a negative electrode, a separator located between the positive electrode and the negative electrode, and the electrolyte described above.

[0112] During battery charging, an external power source drives electrons to flow from the negative electrode to the positive electrode, while ions move towards the positive electrode in the electrolyte. During battery discharging, redox reactions occur in the positive and negative electrode materials, causing electrons to flow from the positive electrode to the negative electrode, and ions to move from the positive electrode to the negative electrode. This process enables the battery to convert chemical energy into electrical energy.

[0113] A separator is a permeable membrane located between the positive and negative electrodes. Its main function is to keep the positive and negative electrodes separated to prevent short circuits in the battery. At the same time, the separator also needs to allow charge carriers to pass through to ensure the closure of the chemical battery circuit. The separator is usually a polymer membrane with micropores, which needs to have certain chemical and electrochemical stability to the electrolyte and electrode materials, and also needs sufficient mechanical strength to withstand the stress during battery assembly.

[0114] Electrolyte is the liquid medium responsible for ion transport in a battery. Its working principle involves oxidation-reduction reactions between the positive and negative electrode materials. The performance of the electrolyte directly affects the battery's charge-discharge efficiency and cycle life. During battery cycling, the electrolyte undergoes a series of reactions with the surface of the negative electrode, forming a solid electrolyte interphase (SEI) film. The formation and properties of the SEI film have a significant impact on battery performance and lifespan. On one hand, the SEI film prevents direct contact between the electrode surface and the electrolyte, avoiding reactions between the solute and solvent in the electrolyte and the electrodes, thereby improving the stability of electrochemical energy storage devices. On the other hand, the SEI film also plays a role in ion transport, promoting ion transport balance between the positive and negative electrodes by selectively conducting cations and blocking the diffusion of solvent and negative ions.

[0115] The electrolyte provided in this application can undergo a redox reaction with the negative electrode to form an SEI film on the surface of the negative electrode. The inorganic acid ions and lithium salts in the additives, after reacting with the negative electrode, can generate LiN. x O y Additives such as Li3N can react to form organic components, and onium ions and some lithium-loving groups can promote the uniform deposition of lithium ions and the dynamic formation of SEI film, so as to form a uniform and dense SEI film, improve the film-forming properties of SEI film, and thus improve the safety and cycle performance of battery.

[0116] In some embodiments, the positive electrode material includes one or more of lithium nickel manganese oxide, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, and lithium nickel cobalt manganese oxide.

[0117] In some embodiments, the negative electrode includes one or more of the following: lithium metal negative electrode, lithium metal alloy negative electrode, graphite negative electrode, silicon-based negative electrode, silicon-graphite composite negative electrode, and copper foil lithium-free negative electrode.

[0118] In some embodiments, the diaphragm includes one or more of the following: woven membrane, nonwoven membrane (non-woven fabric), microporous membrane, composite membrane, diaphragm paper, rolled membrane, single-layer polypropylene membrane (PP), single-layer polyethylene membrane (PE), PP+ceramic coating, PE+ceramic coating, double-layer PP / PE, triple-layer PP / PE / PP, polyester membrane (PET), cellulose membrane, polyimide membrane (PI), polyamide membrane (PA), spandex membrane, and aramid membrane.

[0119] The present application will be specifically described below through specific embodiments. The following embodiments are only some embodiments of the present application and are not intended to limit the present application.

[0120] Example 1

[0121] This embodiment provides an electrolyte, including a lithium salt, a solvent, and an additive. The additive has the following structural formula:

[0122]

[0123] The preparation method of the additive includes: taking 784 mg ethidium bromide, 138 mg lithium nitrate, and 202 mg potassium nitrate, dissolving them in 50 mL of a mixed solution of anhydrous ethanol and deionized water (anhydrous ethanol and deionized water are mixed in a 1:1 volume ratio), stirring at room temperature for 72 h, reacting in a microwave reactor for 0.5 h, filtering, washing three times each with N,N'-dimethylformamide, tetrahydrofuran, and methanol, and then drying in a vacuum oven at 60 °C for 24 h to obtain the additive;

[0124] The preparation method of the electrolyte includes: adding 10g of lithium salt LiFSI (0.053mol / L) and 0.147g of additive to 6.7g of solvent diethylene glycol dimethyl ether (0.05mol / L), stirring thoroughly for 3-5 hours until a homogeneous, transparent and viscous solution system is formed, then adding 72g of diluent fluorobenzene (0.75mol / L), stirring thoroughly until a homogeneous and transparent solution is formed, thus obtaining the electrolyte. The concentration of lithium salt in the electrolyte is 0.65mol / L.

[0125] Example 2

[0126] This embodiment is basically the same as Embodiment 1, except that the additive is replaced with: The preparation method includes: taking 502 mg of ethidium bromide-N,N'-bisacrylamide (CAS: 480438-67-3), 275 mg of lithium nitrate, and 404 mg of potassium nitrate, dissolving them in 50 mL of a mixed solution of anhydrous ethanol and deionized water (anhydrous ethanol and deionized water are mixed in a 1:1 volume ratio), stirring at room temperature for 72 h, reacting in a microwave reactor for 0.5 h, filtering, washing three times each with N,N'-dimethylformamide, tetrahydrofuran, and methanol, and then drying in a vacuum oven at 60 °C for 24 h to obtain the additive.

[0127] Example 3

[0128] This embodiment is basically the same as Embodiment 1, except that the additive is replaced with: The preparation method includes: taking 669 mg of propidium iodide, 104 mg of lithium fluoride, and 232 mg of potassium fluoride, dissolving them in a mixed solution of 50 mL of anhydrous ethanol and deionized water (anhydrous ethanol and deionized water are mixed in a 1:1 volume ratio), purging with nitrogen and stirring in an ice bath, reacting for 72 h, filtering, washing three times each with N,N'-dimethylformamide, tetrahydrofuran, and methanol, and then drying in a vacuum oven at 60 °C for 24 h to obtain the additive.

[0129] Example 4

[0130] This embodiment is basically the same as Embodiment 1, except that the additive is replaced with ethidium bromide in this embodiment.

[0131] Example 5

[0132] This embodiment is basically the same as Embodiment 1, except that in this embodiment, the lithium salt LiFSI is replaced with LiPF6 (0.066 mol).

[0133] Example 6

[0134] This embodiment is basically the same as Embodiment 1, except that the solvent diethylene glycol dimethyl ether is replaced with diethyl carbonate in this embodiment.

[0135] Example 7

[0136] This embodiment is basically the same as Embodiment 1, except that the diluent fluorobenzene is replaced with 1,4-dibromotetrafluorobenzene in this embodiment.

[0137] Example 8

[0138] This embodiment is basically the same as Embodiment 1, except that the mass of the additive in this embodiment is 5g.

[0139] Example 9

[0140] This embodiment is basically the same as Embodiment 1, except that the mass of the additive in this embodiment is 0.1g.

[0141] Example 10

[0142] This embodiment is basically the same as Embodiment 1, except that the mass of lithium salt in this embodiment is 20g and the concentration of lithium salt in the electrolyte is 1.3mol / L.

[0143] Example 11

[0144] This embodiment is basically the same as Embodiment 1, except that the mass of lithium salt in this embodiment is 5g and the concentration of lithium salt in the electrolyte is 0.33mol / L.

[0145] Example 12

[0146] This embodiment is basically the same as Embodiment 1, except that the mass of the diluent in this embodiment is 90g.

[0147] Example 13

[0148] This embodiment is basically the same as Embodiment 1, except that the mass of the diluent in this embodiment is 70g.

[0149] Example 14

[0150] This embodiment is basically the same as Embodiment 1, except that no diluent is added in this embodiment, and the concentration of lithium salt in the electrolyte is 9.3 mol / L.

[0151] Comparative Example 1

[0152] This comparative example is basically the same as Example 1, except that the electrolyte in this comparative example does not contain any additives.

[0153] Comparative Example 2

[0154] This comparative example is basically the same as Example 12, except that the electrolyte in this comparative example does not contain any additives.

[0155] Comparative Example 3

[0156] This comparative example is basically the same as Example 1, except that the electrolyte in this comparative example does not contain any additives, and the diluent fluorobenzene is replaced with 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether.

[0157] The high voltage resistance of the electrolyte in Example 1 was tested using the linear sweep voltammetry (LSV method), and the LSV curve of the electrolyte was obtained as follows: Figure 1 As shown.

[0158] The LSV curve testing method is as follows: Under an argon atmosphere, a button cell is formed by combining the electrolyte with a stainless steel sheet and a lithium sheet (where the stainless steel sheet is used as the working electrode, and the lithium sheet is used as the reference electrode and counter electrode). The electrochemical window is tested on an electrochemical workstation (CHI760D), with a test range of OCV (initial open circuit voltage) - 6V and a scan rate of 0.5mV / s. The scan data is plotted to obtain the LSV curve of the electrolyte.

[0159] Depend on Figure 1 It can be seen that the voltage range of the electrolyte in Example 1 is about 6V, and the induced current increases slightly, far exceeding the voltage range required by the battery, thus overcoming the problem of the narrow electrochemical window of existing electrolytes.

[0160] The ionic conductivity of the electrolytes in Examples 1-14 and Comparative Examples 1-3 was tested respectively, and the results are shown in Table 1.

[0161] Ionic conductivity was measured by AC impedance spectroscopy using two lithium metal electrodes as test electrodes. The AC impedance diagram at each temperature point was obtained, and the resistance was calculated by computer and converted into ionic conductivity. The test temperature was 32℃±2℃.

[0162] Table 1

[0163]

[0164]

[0165] / : Lithium salts precipitate out, causing the solution to become cloudy.

[0166] As shown in Table 1:

[0167] As can be seen from Examples 1-7 and Comparative Example 1, the electrolyte provided in this application contains additives. Compared with Comparative Example 1, which does not contain film-forming additives, the ionic conductivity of the electrolyte is improved, which promotes the transport of lithium ions.

[0168] As can be seen from Examples 1, 8-13 and Comparative Example 1, the lithium salt, solvent, diluent and additives in the electrolyte, within the range of component proportions provided in this application, all effectively improve the ionic conductivity of the electrolyte.

[0169] As can be seen from Examples 1 and 14 and Comparative Examples 2 and 3, Comparative Examples 2 and 3 do not contain additives, nor do they contain diluents or contain conventional diluents. The ionic conductivity of the electrolyte is lower than that of the examples, and lithium salt precipitation and turbidity even occur, which is very detrimental to the performance of the electrolyte. This is because the diluent 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether is incompatible in this system, and the electrolyte is destroyed and cannot be used. The additives and diluents provided in this application can effectively improve the state of the electrolyte, improve the stability of the electrolyte, and improve the ionic conductivity of the electrolyte.

[0170] Application Example 1

[0171] This application example provides a battery, the preparation method of which is as follows:

[0172] Under the inert atmosphere of a glove box, the negative electrode shell, spring sheet, gasket, lithium sheet, electrolyte of Example 1, separator, positive electrode sheet, and positive electrode shell are assembled in sequence to form a full-electric button cell. The assembly is completed by pressing at 800 kPa for 5 seconds to obtain the battery.

[0173] Application Examples 2-14

[0174] Application Examples 2 to 14 are basically the same as Application Example 1, except that the electrolyte in Application Examples 2 to 14 is replaced with the electrolyte in Application Examples 2 to 14.

[0175] Application Comparative Examples 1-3

[0176] Application Comparative Examples 1 to 3 are basically the same as Application Example 1, except that the electrolyte in Application Comparative Examples 1 to 3 is replaced with the electrolyte in Comparative Examples 1 to 3 respectively.

[0177] The cycle performance of batteries from Examples 1-14 and Comparative Examples 1-3 was tested respectively, and the cycle curves of Examples 1 and Comparative Examples 1-2 were obtained as follows: Figure 2As shown, the data results of other embodiments and comparative examples are shown in Table 2.

[0178] The test method for cycle performance is as follows: the battery is charged at 25°C with constant current and constant voltage at 0.33C to 4.2V, and then discharged at constant current at 0.5C to 3.0V. This constitutes one cycle. The remaining capacity is the capacity retention rate. The capacity retention rate of each battery after 60 cycles is compared.

[0179] Table 2

[0180]

[0181]

[0182] / : Turbid electrolyte cannot be used to assemble a battery.

[0183] Depend on Figure 2 As shown in Table 2:

[0184] As can be seen from Application Examples 1-5 and Application Comparative Example 1, Application Examples 1-5 still retain more than 89% of their capacity after 60 cycles, while Application Comparative Example 1 is relatively stable before 40 cycles, but the capacity retention rate drops rapidly after 40 cycles, and only 80% remains after 60 cycles. This shows that the additive provided in this application, when applied to the electrolyte and the electrolyte, when applied to the battery, can effectively improve the film-forming performance of the SEI film, thereby improving the cycle performance of the battery.

[0185] As can be seen from Application Examples 1, 6-11 and Application Comparative Example 1, Application Examples 6-11 all have a capacity retention rate of over 90% after 60 cycles, which is high, indicating that the battery has good cycle performance and a long service life.

[0186] As can be seen from Application Examples 1 and 12 and Application Comparative Examples 2 and 3, the capacity of the battery in Application Comparative Example 2 decreased rapidly during cycling, and the capacity retention rate was only 80% after only 20 cycles. The battery in Application Comparative Example 3 could not be assembled due to the turbidity of the electrolyte, and its performance was worse than that of the application examples. In the battery provided by this application, the additive can promote the uniform deposition of the SEI film, improve the density of the SEI film, and thus improve the cycle performance of the battery.

[0187] The technical solutions provided by the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An electrolyte, characterized in that, It includes lithium salt, solvent and additive, the additive having the structural formula shown in formula (I): wherein A - selected from inorganic acid anions; R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 Each group is independently selected from hydrogen, deuterium, halogen, amino, cyano, hydroxyl, carboxyl, aldehyde, nitro, amide, substituted or unsubstituted C1-C groups. 20 Alkyl or heteroalkyl, substituted or unsubstituted C2-C 20 alkenyl or heteroalkenyl, substituted or unsubstituted C2-C 20 alkynyl or heteroyneyl, substituted or unsubstituted C1-C 20 alkoxy, substituted or unsubstituted C1-C 20 Acyloxy group, substituted or unsubstituted C1-C 20 alkoxycarbonyl, substituted or unsubstituted C3-C 20 heterocyclic groups, substituted or unsubstituted C6-C 20 One or more of the aryl groups; The mass ratio of the lithium salt, the additive, and the solvent is (5~20):(0.1~1):(5~20). The inorganic acid radical ions are selected from NO3. - F - I - ,Br - One or more of them.

2. The electrolyte as described in claim 1, characterized in that, R1 is selected from substituted or unsubstituted C5-C. 15 Alkyl or heteroalkyl, substituted or unsubstituted C5-C 15 alkenyl or heteroalkenyl, substituted or unsubstituted C5-C 15 alkynyl or heteroyynyl, substituted or unsubstituted C5-C 15 alkoxy, substituted or unsubstituted C5-C 15 Acyloxy group, substituted or unsubstituted C5-C 15 One or more of the alkoxycarbonyl groups; and / or; R2 is selected from substituted or unsubstituted C6-C. 15 heterocyclic groups, substituted or unsubstituted C8-C 15 One or more of the aryl groups; and / or R3, R4, R5, R6, R7, R8, R9, R 10 Each group is independently selected from hydrogen, deuterium, halogen, amino, cyano, hydroxyl, carboxyl, aldehyde, nitro, amide, sulfonic acid, sulfonyl, substituted or unsubstituted C5-C groups. 15 Alkyl or heteroalkyl, substituted or unsubstituted C5-C 15 alkenyl or heteroalkenyl, substituted or unsubstituted C5-C 15 One or more of the alkynyl or heteroalkynyl groups.

3. The electrolyte as described in claim 1 or 2, characterized in that, The halogen includes one or more of fluorine, chlorine, bromine, and iodine; and / or The alkyl group includes one or more of methyl, ethyl, isopropyl, tert-butyl, hexyl, octyl, decyl, dodecyl, and heptadecanyl; and / or The alkenyl group includes one or more of vinyl, propenyl, butenyl, hexenyl, octenyl, decenyl, dodecenyl, 9-heptadecenyl, 1,4-pentadienyl, 1,5-hexadienyl, 1,6-heptadienyl, 1,7-octadienyl, 1,8-nonadienyl, and 1,9-decadienyl; and / or The alkynyl group includes one or more of ethynyl, propynyl, pentynyl, hepynyl, hexynyl, octyynyl, decynyl, and dodecanynyl; and / or The alkoxy group includes one or more of methoxy, ethoxy, propoxy, butoxy, pentoxy, heptaoxy, hexoxy, octoxy, decoxy, and dodecoxy; and / or The acyloxy group includes one or more of the following: formyloxy, acetyloxy, propionyloxy, butyryloxy, valeryloxy, heptayloxy, hexanoyloxy, octanoyloxy, decanoyloxy, dodecanoyloxy, palmitoyloxy, and stearoyloxy; and / or The alkoxycarbonyl group includes one or more of methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, heptaoxycarbonyl, hexoxycarbonyl, decoxycarbonyl, dodecoxycarbonyl, octoxycarbonyl, palmitoxycarbonyl, and stearoxycarbonyl; and / or The heteroatom in the heteroalkyl group, the heteroalkenyl group, the heteroynyl group, or the heterocyclic group includes one or more of O, P, N, and S; and / or The heterocyclic group includes one or more of the following: thiazolyl, thiophenel, furanyl, pyrrolyl, pyridyl, pyrimidinyl, imidazolyl, azole, pyrazinyl, indolyl, quinolinyl, pteridinyl, and acridineyl; and / or The aryl group includes one or more of phenyl, p-tolyl, p-nitrophenyl, o-methoxyphenyl, m-methoxyphenyl, p-methoxyphenyl, and p-nitromethoxyphenyl; and / or The substituted groups each independently include one or more of -NH2, -F, -Cl, -Br, -I, -OH, -COOH, -NO2, -SO3H, -CHO, -SH, and -CN.

4. The electrolyte as described in claim 1, characterized in that, The additive is selected from one of the following structural formulas: 、 、 、 、 、 。 5. The electrolyte as described in claim 1, characterized in that, The lithium salt includes one or more of organic lithium salts and inorganic lithium salts; and / or The solvent includes one or more of ether solvents, ester solvents, and nitrile solvents; and / or R2 is selected from phenyl; R4 and R9 are each independently selected from amino or amide groups.

6. The electrolyte as described in claim 5, characterized in that, The organolithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalateborate, and lithium bis(oxalateborate); and / or The inorganic lithium salt includes one or more of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium difluorophosphate; and / or The ether solvent includes one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and ethylene glycol diethyl ether; and / or The ester solvents include one or more of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate; and / or The nitrile solvents include one or more of acetonitrile and succinic anhydride.

7. The electrolyte as described in claim 1, characterized in that, The electrolyte also includes a diluent.

8. The electrolyte as described in claim 7, characterized in that, The diluent includes fluorobenzene diluents; the fluorobenzene diluent includes one or more of fluorobenzene, trifluorotoluene, m-fluorotoluene, chloropentafluorobenzene, 1,2,4-trifluorobenzene, 1,2,3,4-tetrafluorobenzene, and 1,4-dibromotetrafluorobenzene; and / or The volume fraction of the diluent in the sum of the volumes of the diluent and the solvent is 85% to 95%.

9. A battery, characterized in that, It includes a positive electrode, a negative electrode, a membrane located between the positive electrode and the negative electrode, and an electrolyte as described in any one of claims 1 to 8.

10. The battery as claimed in claim 9, characterized in that, The positive electrode material includes one or more of lithium nickel manganese oxide, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, and lithium nickel cobalt manganese oxide; and / or The negative electrode includes one or more of the following: lithium metal negative electrode, lithium metal alloy negative electrode, graphite negative electrode, silicon-based negative electrode, silicon-graphite composite negative electrode, and copper foil lithium-free negative electrode.

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