A non-aqueous electrolyte and a battery containing the same

Abstract

The present invention discloses a non-aqueous electrolyte and a battery containing the non-aqueous electrolyte. The non-aqueous electrolyte comprises a lithium salt, an organic solvent and a silane additive containing a heterocyclic ring. The additive added to the non-aqueous electrolyte of the present invention can undergo electrolytic polymerization near a positive electrode, and the generated polymer adheres to the surface of the positive electrode to form an interface film to protect the positive electrode material. At the same time, the chain silane molecule part forms a monomolecular film layer and exists on the surface of the interface film layer, which can serve as a protective layer of the interface film, effectively blocking the contact between the electrolyte solvent molecules and the interface film layer, reducing the occurrence of side reactions, thereby reducing the degradation of the electrolyte and improving the battery life.

Description

[0001] The present invention is a divisional application based on the invention with application number 201810381135.5, application date April 25, 2018, applicant being BYD Co., Ltd., and invention name being “A non-aqueous electrolyte and a battery containing the non-aqueous electrolyte”. Technical Field

[0002] The present invention relates to the field of non-aqueous electrolytes, and in particular to a non-aqueous electrolyte and a battery containing the non-aqueous electrolyte. Background Art

[0003] Lithium-ion batteries have the advantages of high energy density, high open circuit voltage, no memory effect, low self-discharge, etc., and are widely used in consumer electronics, military products, and aviation products. At present, the materials of lithium-ion batteries mainly include lithium manganese oxide, lithium cobalt oxide, ternary materials, lithium iron phosphate, etc., and their charging cut-off voltage generally does not exceed 4.2V. In recent years, with the expansion of the application of lithium-ion batteries, high-energy-density lithium-ion batteries have become the object of people's attention, and high-voltage (5V) positive electrode materials are one of the more popular research directions, which mainly improves the battery energy density by increasing the charging depth of the positive electrode material. Then, while increasing the voltage of the positive electrode material, the electrolyte matching the high-voltage positive electrode material has also become a top priority. This is mainly because when the battery is running at a high voltage, the electrolyte will easily undergo a parasitic reaction (generally an oxidative decomposition reaction) at the interface with the positive electrode material, thereby causing the battery life to decay. Increasing the oxidation decomposition potential of the electrolyte and forming a passivation film on the positive electrode surface are the main methods to solve the decomposition of the electrolyte at the interface of the positive electrode material. The former mainly relies on seeking new solvents to improve the overall stability of the electrolyte, thereby reducing the side reactions of the electrolyte and increasing the battery life; the latter mostly selects one or several sacrificial additives, which can cause oxidation decomposition reactions on the positive electrode surface before the electrolyte decomposes to form a film layer that can hinder the side reactions between the electrolyte and the positive electrode, thereby hindering the further decomposition of the electrolyte, thereby increasing the battery life.

[0004] However, there are certain problems in choosing new solvents to replace the existing solvent system, such as low conductivity or high viscosity. The use of additives is also a good compromise. At present, most additives are based on increasing the oxidative decomposition potential of the entire electrolyte system. Therefore, there is a possibility that a small amount of solvent in the electrolyte will still be oxidized and decomposed at a high potential, causing the electrolyte to be consumed in the end, resulting in a capacity drop during the battery cycle. The positive electrode film-forming additives also have such disadvantages. The film layer will be damaged by the electrolyte due to contact with the electrolyte. Summary of the invention

[0005] In order to solve the above problems, the present application provides a non-aqueous electrolyte, which comprises a lithium salt, an organic solvent and an additive, wherein the additive has a structure shown in formula (1):

[0006]

[0007] Wherein, R1 and R2 are each independently selected from one of a sulfur atom, an oxygen atom, a nitrogen atom and a carbon atom, and R1 and R2 are not carbon atoms at the same time; M1, M2, and M3 are each independently selected from one of a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkoxy group, a halogenated alkoxy group, and a phenyl group; N1, N2, and N3 are each independently selected from one of a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkoxy group, a halogenated alkoxy group, a phenyl group, an oxygen-containing heterocycle, a nitrogen-containing heterocycle, and a sulfur-containing heterocycle; wherein the halogen in the halogenated alkyl group and the halogenated alkoxy group is one of F, Cl and Br.

[0008] Optionally, M1, M2, M3, N1, N2, and N3 are each independently selected from an alkyl group having 1 to 5 carbon atoms, a haloalkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, and a haloalkoxy group having 1 to 5 carbon atoms.

[0009] Optionally, M1, M2, M3, N1, N2, and N3 are each independently selected from a fluorinated alkyl group having 1 to 5 carbon atoms and a fluorinated alkoxy group having 1 to 5 carbon atoms.

[0010] Optionally, at least one of M1, M2, and M3 is selected from H atoms.

[0011] Optionally, the phenyl group is selected from one of a benzene ring, a halogenated benzene ring, nitrobenzene, and aminobenzene, wherein the halogen atom in the halogenated benzene ring is selected from one of F, Cl, and Br.

[0012] Optionally, the oxygen-containing heterocycle, nitrogen-containing heterocycle and sulfur-containing heterocycle include a five-membered heterocycle, a six-membered heterocycle and a condensed heterocycle.

[0013] Optionally, the additive is selected from one or more of dimethylbis(ethyl-thiophene)silane, triethoxy-2-thiophenesilane, triethoxy-2-furansilane, 1-(triisopropylsilyl)pyrrole, trimethylsilylethyl-thiazole and 2-(tert-butyldimethylsilyl)thiazole.

[0014] Optionally, based on the total mass of the organic solvent and the lithium salt, the content of the additive is 0.05-50 parts by weight.

[0015] Optionally, based on the total mass of the organic solvent and the lithium salt, the content of the additive is 0.05-20 parts by weight.

[0016] Optionally, the non-aqueous electrolyte further contains auxiliary additives, which include one or more of 1,3-propane sultone, 1,4-butane sultone, propenyl-1,3-sultone, vinyl sulfate, propylene sulfate, butylene sulfite, vinylene carbonate, fluoroethylene carbonate, lithium bis(oxalatoborate), and lithium bis(fluorosulfonyl)imide.

[0017] Optionally, based on the total mass of the organic solvent and the lithium salt, the content of the auxiliary additive is 0.05-20 parts by weight.

[0018] Optionally, the organic solvent is selected from one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methylpropyl carbonate, dipropyl carbonate, ethylene carbonate, propylene carbonate, vinylene carbonate, γ-butyrolactone, sultone, vinyl sulfite, propylene sulfite, methyl sulfide, diethyl sulfite, methyl formate, methyl acrylate, methyl butyrate and ethyl acetate.

[0019] Optionally, the lithium salt is selected from one or more of LiBOB, LiPF6, LiBF4, LiSbF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO4, LiAsF6, LiAlCl4, LiCl, LiI and low-fatty acid lithium carbonate, and the concentration of the lithium salt is 0.3-3 mol / L.

[0020] The second object of the present application is to provide a battery, which includes a battery case and a battery cell and a non-aqueous electrolyte sealed in the battery case, wherein the battery cell includes a positive electrode, a negative electrode and a separator, and the non-aqueous electrolyte is the non-aqueous electrolyte provided above.

[0021] Compared with the prior art, the present application has the beneficial effect that the additive added to the non-aqueous electrolyte can undergo electrolytic polymerization near the positive electrode, and the generated polymer adheres to the surface of the positive electrode to form an interface film to protect the positive electrode material. At the same time, the chain silane molecular part forms a monomolecular film layer and exists on the surface of the interface film layer, which can serve as a protective layer of the interface film, effectively blocking the contact between the electrolyte solvent molecules and the interface film layer, reducing the occurrence of side reactions, thereby reducing the degradation of the electrolyte and improving the battery life. DETAILED DESCRIPTION

[0022] The following detailed description of the present application will make the features and advantages of the present application clearer and more explicit.

[0023] The purpose of the present application is to provide an electrolyte, comprising an organic solvent, a lithium salt and an additive, wherein the additive has a structure shown in formula (1):

[0024]

[0025] Among them, R1 and R2 can be the same or different, and are independently selected from one or two of sulfur atoms, oxygen atoms, nitrogen atoms and carbon atoms. R1 and R2 cannot be carbon atoms at the same time. If they are carbon atoms at the same time, the five-membered ring in this proposal becomes a cycloalkane, and there is no electropolymerization performance. For example, when R1 is C, R2 is one of S, O, and N, or when R2 is C, R1 is one of S, O, and N. When R1 and R2 are not C atoms at the same time, the heterocyclic main body of the additive can be a five-membered ring of thiophene, furan, pyrrole, imidazole, and thiazole.

[0026] M1, M2, and M3 may all be the same, may all be different, or two of them may be the same and the other one may be different, and each is independently selected from a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkoxy group, a halogenated alkoxy group, and a phenyl group.

[0027] When at least one of M1, M2, and M3 is an alkyl group, it can be a chain alkyl group or a cycloalkyl group. The chain alkyl group can be a straight chain or a branched chain. The alkyl group can be an alkyl group with 1 to 10 carbon atoms, and further an alkyl group with 1 to 5 carbon atoms can be selected. The inventors of the present application have found through many experiments that when there are too many carbon atoms in the alkyl group, the chain length is too long, which will cause the molecular weight to be too large and difficult to dissolve. As examples of alkyl groups, specifically: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, and cyclohexyl. When the aforementioned M1, M2, and M3 are alkyl groups substituted by halogen atoms, haloalkyl groups, haloalkyl groups with 1 to 10 carbon atoms, and haloalkyl groups with 1 to 5 carbon atoms are formed in turn, wherein the halogen atoms are F, Cl, and Br; in some embodiments of the present application, the halogen atoms are F and Cl. The inventors of the present application have discovered through many experiments that when F and Cl are used for substitution, the prepared additive has a small atomic weight, forms a stable molecule, and is relatively easy to synthesize. In the formed halogenated group, the halogen atoms replace some or all hydrogen atoms.

[0028] When at least one of M1, M2, and M3 is an alkoxy group, the alkoxy group may be a chain alkyl group or a cycloalkoxy group. The chain alkoxy group may be a straight chain or a branched chain. The alkyl group may be an alkoxy group having 1 to 10 carbon atoms, and further an alkoxy group having 1 to 5 carbon atoms may be selected. The inventors of the present application have found through many experiments that when the number of carbon atoms in the alkyl group is too large and the chain length is too long, the molecular weight will be too large and difficult to dissolve. Examples of alkoxy groups include: methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy, isopentyloxy, neopentyloxy, cyclopentyloxy, and cyclohexyloxy. When the aforementioned M1, M2, and M3 are alkoxy groups substituted by halogen atoms, haloalkoxy groups, haloalkoxy groups with 1 to 10 carbon atoms, and haloalkoxy groups with 1 to 5 carbon atoms are formed respectively, wherein the halogen atoms are F, Cl, and Br; in some embodiments of the present application, the halogen atoms are F and Cl. The inventors of the present application have found through many experiments that when replaced with F and Cl, the prepared additive has a small atomic weight, a stable molecule, and is relatively easy to synthesize. In the formed halogenated group, the halogen atoms replace some or all of the hydrogen atoms.

[0029] Examples of halogenated groups include: trifluoromethyl, 2-fluoroethyl, 3-fluoro-n-propyl, 2-fluoroisopropyl, 4-fluoro-n-butyl, 3-fluoro-sec-butyl, 5-fluoro-n-pentyl, 4-fluoroisopentyl, trifluoromethoxy, 2-fluoroethoxy, 3-fluoro-n-propoxy, 2-fluoroisopropoxy, 4-fluoro-n-butoxy, 3-fluoro-sec-butoxy, 5-fluoro-n-pentyloxy and 4-fluoroisopentyloxy. In the above specific examples, F may be substituted by Cl and / or Br.

[0030] When at least one of M1, M2, and M3 is a phenyl group, the phenyl group may be a benzene ring, a halogenated benzene ring, nitrobenzene, or aminobenzene, and the structural formula includes Wherein, X is H, F, Cl, Br, -NO2, -NH2.

[0031] Optionally, at least one of M1, M2, and M3 is H. The inventors of the present application found that when at least one of M1, M2, and M3 is H, the electrolyte additive has the best film-forming effect.

[0032] N1, N2, and N3 may be the same or different, or two of them may be the same and the other one may be different, and each may be independently selected from one or more of a hydrogen atom, an alkyl group, a haloalkyl group, an alkoxy group, and a haloalkoxy group. When N1, N2, and N3 are independently selected from one or more of an alkyl group, a haloalkyl group, an alkoxy group, and a haloalkoxy group, the description of M1, M2, and M3 being independently selected from one or more of an alkyl group, a haloalkyl group, an alkoxy group, a haloalkoxy group, and a phenyl group may be referred to, and no further description is given here.

[0033] When N1, N2, and N3 are selected from oxygen-containing heterocycles, nitrogen-containing heterocycles, and heterocycles, there may be one heteroatom or two or more heteroatoms, and the heteroatom may be one atom or two different atoms, and the heterocycle may be a three-membered heterocycle, a four-membered heterocycle, a five-membered heterocycle, a six-membered heterocycle, or a seven-membered heterocycle. Optionally, the heterocyclic compound includes a five-membered heterocyclic compound, such as thiophene, furan, pyrrole, imidazole, thiazole, and derivatives thereof, a six-membered heterocyclic compound, such as pyridine, pyrazine, pyrimidine, pyridazine, and derivatives thereof, and a fused heterocyclic compound, such as indole, quinoline, pteridine, acridine, and derivatives thereof. The present application does not limit the substitution position of the heterocyclic compound. For example, when N1, N2, and N3 are six-membered heterocycles, they may be para-substituted, ortho-substituted, and meta-substituted. The invention of the present application has been obtained through multiple experiments, and when the heterocyclic compound is a five-membered heterocyclic compound, a six-membered heterocyclic compound, a fused heterocyclic compound, and derivatives thereof, the electrolyte additive has the best film-forming effect.

[0034] Optionally, the additive is selected from one or more of dimethylbis(ethyl-thiophene)silane, triethoxy-2-thiophenesilane, triethoxy-2-furansilane, 1-(triisopropylsilyl)pyrrole, trimethylsilylethyl-thiazole and 2-(tert-butyldimethylsilyl)thiazole.

[0035] In the present application, the additive triethoxy-2-thiophene silane mentioned can be commercially available (CAS No.: 17984-89-3) or synthesized by itself. Other compounds can be synthesized by referring to the method of triethoxy-2-thiophene silane.

[0036] The additive having the structure of formula (1) is added to the electrolyte. The additive can undergo electrolytic polymerization at the positive electrode and the negative electrode. The generated polymer adheres to the surface of the positive electrode to form an interface film to protect the positive electrode. At the same time, the silane molecular chain in the additive exists on the surface of the interface film layer, forming an ultra-thin protective film with a monomolecular layer size, which can be used as a protective layer of the interface film, effectively blocking the contact between the electrolyte solvent molecules and the interface film layer, thereby reducing the degradation of the electrolyte and improving the battery life. This protection mechanism is secondary protection. The additive forms a film to protect the positive electrode surface. The silane chains on the additive molecules spontaneously form a monomolecular film layer on the positive electrode surface, thereby protecting the interface film and reducing the loss of the interface film.

[0037] According to the non-aqueous electrolyte proposed by the present invention, the non-aqueous electrolyte may be added with one of the above additives alone, or with multiple additives added at the same time. The content of the additive may be 0.05-50 parts by weight relative to 100 parts by weight of the non-aqueous solvent, and optionally, the content of the additive may be 0.05-20 parts by weight. Adding the additive of the present application in the electrolyte in this weight portion can achieve a good film-forming effect without causing a significant impact on the performance of the battery.

[0038] According to the non-aqueous electrolyte of the present invention, optionally, the non-aqueous electrolyte further contains an auxiliary additive, and the auxiliary additive includes at least one of 1,3-propane sultone, 1,4-butane sultone, propenyl-1,3-sultone, vinyl sulfate, propenyl sulfate, butylene sulfite, vinylene carbonate, fluoroethylene carbonate, lithium bis(oxalatoborate), and lithium bis(fluorosulfonyl)imide. The auxiliary additive is used together with the additive described in the present application of the present invention in the electrolyte to improve the stability of the battery.

[0039] According to the non-aqueous electrolyte proposed in the present invention, the content of the auxiliary additive can be 0.05-50 parts by weight relative to 100 parts by weight of the non-aqueous solvent; in some embodiments of the present application, the content of the auxiliary additive is 0.5-20 parts by weight relative to 100 parts by weight of the non-aqueous solvent. The auxiliary additive can promote the additive described in the present application to form a stable SEI film on the surface of the negative electrode, protect the negative electrode, and further improve the cycle performance of the battery, but adding too much of the auxiliary additive will cause excessive consumption of active lithium.

[0040] According to the non-aqueous electrolyte provided by the present invention, the organic solvent can use the non-aqueous solvent conventionally used by those skilled in the art, for example, it can include one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, dipropyl carbonate, ethylene carbonate, propylene carbonate, vinylene carbonate, γ-butyrolactone, sultone, vinyl sulfite, propylene sulfite, methyl sulfide, diethyl sulfite, methyl formate, methyl acrylate, methyl butyrate and ethyl acetate.

[0041] According to the non-aqueous electrolyte of the present invention, there is no special requirement for the selection of the lithium salt, which can be a lithium salt commonly used in non-aqueous electrolytes, for example, it can include one or more of LiBOB, LiPF6, LiBF4, LiSbF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO4, LiAsF6, LiAlCl4, LiCl, LiI and low-fatty acid lithium carbonate. The concentration of the lithium salt is known to those skilled in the art, generally 0.3-3 mol / L; in some embodiments of the present application, the concentration of the lithium salt is 0.8-1.2 mol / L.

[0042] The preparation method of the non-aqueous electrolyte for a battery provided by the present invention is a method conventionally used by those skilled in the art, that is, the components (including lithium salt, non-aqueous solvent and additive) are uniformly mixed, and the present invention has no special restrictions on the mixing method and order. For example, the organic solvent is uniformly mixed, then the lithium salt is added and mixed, and then the electrolyte additive is added and mixed, and the auxiliary additive can be added together with the electrolyte additive.

[0043] The present invention also provides a battery, which comprises a battery shell, a battery core and a non-aqueous electrolyte sealed in the battery shell.

[0044] The non-aqueous electrolyte is the non-aqueous electrolyte as described above, and the battery cell comprises a positive electrode, a negative electrode and a separator. Since the present invention only involves the improvement of the non-aqueous electrolyte of the prior art battery, there is no special limitation on other components and structures of the battery.

[0045] For example, the positive electrode can be any positive electrode known to those skilled in the art, usually including a positive electrode collector and a positive electrode material coated and / or filled on the positive electrode collector. The positive electrode collector can be any positive electrode collector known to those skilled in the art, such as aluminum foil, copper foil, and nickel-plated steel strip. The present invention uses aluminum foil as the positive electrode collector. The positive electrode material can be any positive electrode material known to those skilled in the art, usually including a mixture of a positive electrode active material, a conductive material, and a binder. The positive electrode active material can be selected from conventional positive electrode active materials for batteries, such as LixNi (1-y) CoO2 (where 0.9≤x≤1.1, 0≤y≤1.0), Li m Mn (2-n) B n O2 (where B is a transition metal, 0.9≤m≤1.1, 0≤n≤1.0), Li (1+a) M b Mn (2－b)O4 (wherein, -0.1≤a≤0.2, 0≤b≤1.0, M is one or more of lithium, boron, magnesium, aluminum, titanium, chromium, iron, cobalt, nickel, copper, zinc, gallium, yttrium, fluorine, iodine, and sulfur).

[0046] The positive electrode material of the present invention has no particular restrictions on the binder, and all binders known in the art that can be used for batteries can be used. It can be selected from fluorine-containing resins and / or polyolefin compounds, such as one or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF) and styrene-butadiene rubber. Based on the weight of the positive electrode active material, the content of the binder is 0.01-8% by weight; in some embodiments of the present application, based on the weight of the positive electrode active material, the content of the binder is 1-5% by weight.

[0047] The positive electrode material provided by the present invention may also selectively contain a conductive agent commonly contained in the positive electrode material of the prior art. Since the conductive agent is used to increase the conductivity of the electrode and reduce the internal resistance of the battery, the present invention may contain a conductive agent. The content and type of the conductive agent are well known to those skilled in the art. For example, based on the positive electrode material, the content of the conductive agent is generally 0-15% by weight; in some embodiments of the present application, based on the positive electrode material, the content of the conductive agent is 0-10% by weight. The conductive agent may be selected from one or more of conductive carbon black, acetylene black, nickel powder, copper powder and conductive graphite.

[0048] The composition of the negative electrode is well known to those skilled in the art. Generally speaking, the negative electrode includes a negative electrode collector and a negative electrode material coated and / or filled on the negative electrode collector. The negative electrode collector is well known to those skilled in the art, for example, it can be selected from one or more of aluminum foil, copper foil, nickel-plated steel strip, and punched steel strip. The negative electrode active material is well known to those skilled in the art, and it includes a negative electrode active material and a binder. The negative electrode active material can be selected from one or more of conventional negative electrode active materials for batteries, such as natural graphite, artificial graphite, petroleum coke, organic cracked carbon, mesophase carbon microbeads, carbon fiber, tin alloy, and silicon alloy. The binder can be selected from one or more of conventional battery binders, such as polyvinyl alcohol, polytetrafluoroethylene, hydroxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR). Generally speaking, the content of the binder is 0.5-8% by weight of the negative electrode active material; in some embodiments of the present application, the content of the binder is 2-5% by weight of the negative electrode active material.

[0049] The solvent used to prepare the positive electrode slurry and the negative electrode slurry of the present invention can be selected from conventional solvents, such as N-methylpyrrolidone (NMP), dimethylformamide (DMF), diethylformamide (DEF), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF) and one or more of water and alcohols. The amount of solvent used is such that the slurry can be coated on the collector. Generally speaking, the amount of solvent used is such that the concentration of the positive electrode active material or the negative electrode active material in the slurry is 40-90% by weight; in some embodiments of the present application, the amount of solvent used is such that the concentration of the positive electrode active material or the negative electrode active material in the slurry is 50-85% by weight.

[0050] The diaphragm has electrical insulation and liquid retention properties, is disposed between the positive electrode and the negative electrode, and is sealed in the battery case together with the positive electrode, the negative electrode and the electrolyte. The diaphragm can be various diaphragms commonly used in the art, such as a composite membrane formed by welding or bonding modified polyethylene felt, modified polypropylene felt, ultrafine glass fiber felt, vinylon felt or nylon felt of various production grades produced by various well-known manufacturers by personnel in the art and a wettable polyolefin microporous membrane.

[0051] The preparation method of the battery provided by the present invention comprises preparing a positive electrode, a negative electrode and a separator into an electrode group, and sealing the obtained electrode group and an electrolyte in a battery shell to prepare a battery, wherein the electrolyte is the electrolyte provided by the present invention. The injection amount of the electrolyte is generally 1.5-4.9g / Ah, and the concentration of the electrolyte is generally 0.5-2.9 mol / L.

[0052] As in the prior art, the preparation method of the positive electrode includes coating a slurry containing a positive electrode active material, a binder and a selectively contained conductive agent on a positive electrode collector, and then drying, rolling and slicing to obtain a positive electrode. The drying is usually carried out at 50-160°C; in some embodiments of the present application, the drying is carried out at 80-150°C.

[0053] The preparation method of the negative electrode is the same as that of the positive electrode, except that the slurry containing the positive electrode active material, the binder and the conductive agent is replaced by the slurry containing the negative electrode active material and the binder.

[0054] Examples 1-6

[0055] (1) Preparation of non-aqueous electrolyte:

[0056] An electrolyte was prepared in a glove box, the oxygen content in the glove box was controlled to be <2ppm, the glove box was filled with nitrogen and the purity of the nitrogen in the glove box was controlled to be 99.999%, ethylene carbonate, diethyl carbonate and ethyl methyl carbonate were uniformly mixed in a mass ratio of 30:30:40 to obtain a non-aqueous solvent, and fully dried lithium hexafluorophosphate was added to the non-aqueous solvent to prepare a basic electrolyte with a LiPF6 concentration of 1 mol / L.

[0057] As shown in Table 1, the additives and auxiliary additive VC described in the present application are added to the basic electrolyte, wherein the amount of VC added is 1.5% of the mass of the non-aqueous electrolyte, and the contents of the additives in Table 1 are all based on the total mass of the non-aqueous electrolyte to obtain the battery non-aqueous electrolyte of the corresponding embodiment, which are recorded as C1-C6.

[0058] (2) Preparation of batteries:

[0059] The positive electrode active material (LiNi 0.5 Mn 1.5 O4), acetylene black and polyvinylidene fluoride are mixed in a ratio of 90:5:5 and then pressed onto aluminum foil to obtain a positive electrode sheet; a metal lithium sheet is used as a negative electrode sheet; a PE / PP composite diaphragm is used as an ion exchange membrane, and the non-aqueous electrolyte C1-C6 of the corresponding embodiment is used, and button batteries S1-S6 are made by conventional methods in the art.

[0060] Comparative Example 1

[0061] A basic electrolyte, a non-aqueous electrolyte and a button cell were prepared according to the method of Example 1. In Comparative Example 1, the additives described in the present application were not added, and only the auxiliary additive VC was added. The obtained non-aqueous electrolyte was recorded as DC1, and the obtained button cell was recorded as DS1.

[0062] Table 1

[0063]

[0064]

[0065]

[0066] Performance Test:

[0067] (1) Non-aqueous electrolyte oxidation decomposition potential test

[0068] The three-electrode test method was applied, with platinum sheets as working electrodes and lithium sheets as reference electrodes and counter electrodes to characterize the electropolymerization potential of the additive and the oxidative decomposition potential of the electrolyte.

[0069] The test results are shown in Table 2.

[0070] Table 2

[0071]

[0072] (2) Battery charge and discharge performance test

[0073] Each experimental button cell S1-S6 and DS1 was discharged at a constant current of 0.1 mA to 0.005 V at room temperature, and then charged at a constant current of 0.1 mA to 1.5 V, and the discharge capacity and charge capacity of the battery were recorded, and the charge-discharge efficiency (%) was calculated as charge capacity / discharge capacity × 100%. The test results are shown in Table 3.

[0074] Table 3

[0075]

[0076]

[0077] (3) Battery cycle test

[0078] The battery was charged to 4.95V at 1C rate (about 0.5mA) at constant current and constant voltage at room temperature, with a charge cut-off current of 0.05mA, and then discharged to 3.0V at a constant current of 0.5mA, and the initial charge capacity and discharge capacity were recorded, and the discharge efficiency (%) was calculated; after repeating the charge and discharge cycle for 100 times, the discharge capacity of the 100th cycle was recorded, and the capacity retention rate after the cycle (%) was calculated = discharge capacity of 100 cycles / initial discharge capacity × 100%; the cut-off voltage was 4.95V). The test results are shown in Table 4.

[0079] Table 4

[0080]

[0081] By comparing the results of the oxidation decomposition potential test of electrolytes C1-C6 and electrolyte DC1, it can be seen that when the electrolyte contains the additives described in this application, the oxidation decomposition potential of the electrolyte is significantly improved; by comparing the results of the performance test of batteries S1-S6 and battery DS1, it can be seen that when the electrolyte contains the additives described in this application, the charge and discharge performance of the battery is significantly improved, the battery has a higher capacity retention rate, and the battery has excellent cycle performance.

Claims

1. A non-aqueous electrolyte comprising a lithium salt, an organic solvent and an additive, It is characterized in that The additive has a structure shown in formula (1): Wherein, R1 and R2 are each independently selected from one of a sulfur atom, an oxygen atom, a nitrogen atom and a carbon atom, and R1 and R2 are not carbon atoms at the same time; M1, M2, and M3 are each independently selected from one of a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkoxy group, a halogenated alkoxy group, and a phenyl group; N1, N2, and N3 are each independently selected from one of a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkoxy group, a halogenated alkoxy group, a phenyl group, an oxygen-containing heterocycle, a nitrogen-containing heterocycle, and a sulfur-containing heterocycle; wherein the halogen in the halogenated alkyl group and the halogenated alkoxy group is one of F, Cl and Br.

2. The nonaqueous electrolyte according to claim 1, It is characterized in that M1, M2, M3, N1, N2, and N3 are each independently selected from an alkyl group having 1 to 5 carbon atoms, a haloalkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, and a haloalkoxy group having 1 to 5 carbon atoms.

3. The non-aqueous electrolyte according to claim 2, It is characterized in that M1, M2, M3, N1, N2, and N3 are each independently selected from a fluorinated alkyl group having 1 to 5 carbon atoms and a fluorinated alkoxy group having 1 to 5 carbon atoms.

4. The nonaqueous electrolyte according to claim 1, It is characterized in that At least one of M1, M2 and M3 is selected from H atoms.

5. The non-aqueous electrolyte according to claim 1, It is characterized in that The phenyl group is selected from one of a benzene ring, a halogenated benzene ring, nitrobenzene and aminobenzene, wherein the halogen atom in the halogenated benzene ring is selected from one of F, Cl and Br.

6. The non-aqueous electrolyte according to claim 1, It is characterized in that The oxygen-containing heterocycle, nitrogen-containing heterocycle and sulfur-containing heterocycle are one of a five-membered heterocycle, a six-membered heterocycle and a condensed heterocycle.

7. The nonaqueous electrolyte according to claim 1, It is characterized in that The additive is selected from one or more of dimethylbis(ethyl-thiophene)silane, triethoxy-2-thiophenesilane, triethoxy-2-furansilane, trimethylsilylethyl-thiazole and 2-(tert-butyldimethylsilyl)thiazole.

8. The non-aqueous electrolyte according to claim 1, It is characterized in that Based on the total mass of the organic solvent and the lithium salt, the content of the additive is 0.05-50 parts by weight.

9. The non-aqueous electrolyte according to claim 8, It is characterized in that Based on the organic solvent and the lithium salt, the content of the additive is 0.05-20 parts by weight.

10. The nonaqueous electrolyte according to claim 1, It is characterized in that The non-aqueous electrolyte further contains auxiliary additives, which include one or more of 1,3-propane sultone, 1,4-butane sultone, propenyl-1,3-sultone, vinyl sulfate, propylene sulfate, butylene sulfite, vinylene carbonate, fluoroethylene carbonate, lithium bis(oxalatoborate), and lithium bis(fluorosulfonyl)imide.

11. The nonaqueous electrolyte according to claim 10, It is characterized in that Based on the total weight of the organic solvent and the lithium salt, the content of the auxiliary additive is 0.05-20 parts by weight.

12. The nonaqueous electrolyte according to claim 1, It is characterized in that The organic solvent is selected from one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, dipropyl carbonate, ethylene carbonate, propylene carbonate, vinylene carbonate, γ-butyrolactone, sultone, vinyl sulfite, propylene sulfite, methyl sulfide, diethyl sulfite, methyl formate, methyl acrylate, methyl butyrate and ethyl acetate.

13. The nonaqueous electrolyte according to claim 1, It is characterized in that The lithium salt is selected from LiBOB, LiPF 6 , LiBF 4 、LiSbF 6 、LiClO 4 、LiCF 3 SO 3 、Li(CF 3 SO 2 ) 2 N、LiC 4 F 9 SO 3 、LiAlO 4 、LiAsF 6 、LiAlCl 4 One or more of LiCl, LiI and low fatty acid lithium carbonate, the concentration of the lithium salt is 0.3-3 mol / L.

14. A battery comprising a battery housing, a battery core sealed in the battery housing, and a non-aqueous electrolyte, wherein the battery core comprises a positive electrode, a negative electrode, and a separator, It is characterized in that The non-aqueous electrolyte is the non-aqueous electrolyte according to any one of claims 1 to 13.

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