An electrolyte and a battery comprising the same

Abstract

The application provides an electrolyte and a battery comprising the same, wherein the electrolyte comprises an electrolyte salt, a solvent, a fluorovinyl ether compound, an ether nitrile compound and a tetra-vinyl silane; the fluorine functional group in the fluorovinyl ether compound in the electrolyte is in the ortho position of an ether bond, is easy to participate in an interface reaction to form LiF, and after the removal of HF, forms a carbon-carbon double bond; the two compounds after the removal of F interact with each other through an unsaturated bond and the tetra-vinyl silane in the electrolyte, polymerize on the surface of the negative electrode of the battery to form a tough and firm SEI composite film; meanwhile, the lone pair of electrons on the nitrogen atom in the cyano group of the ether nitrile compound in the electrolyte can adsorb the removed HF, further stabilizes the positive electrode, inhibits the dissolution of metal ions, and reduces the side reaction heat on the positive electrode side.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolytes, and in particular to an electrolyte and a battery containing the electrolyte. Background Art

[0002] Since their commercialization, lithium-ion batteries have been widely used in digital, energy storage, power, military, aerospace, and communications equipment due to their high specific energy and excellent cycle performance. With the increasing popularity of lithium-ion batteries, consumers are increasingly demanding the use environments and battery life of their electronic devices. This requires lithium-ion batteries to have both high safety performance and high energy density.

[0003] Among them, silicon-carbon battery is one of the effective means to improve battery energy density, and the electrolyte is one of the main materials of silicon-carbon lithium-ion battery, which plays the role of transmitting Li in silicon-carbon lithium-ion battery. + Therefore, the research and development of electrolytes are crucial for silicon-carbon lithium-ion batteries. However, it is not easy to develop an electrolyte that can alleviate the large cyclic expansion of the silicon negative electrode and take into account safety performance. At this stage, the use of additives in the electrolyte is an efficient weapon to solve the above problems. However, the electrolyte additives currently developed are often difficult to form a strong and tough SEI film to withstand the damage caused by the expansion of the silicon negative electrode during the cycle, and the continuous fragmentation and recombination of the SEI film aggravates the heat generation of the side reaction, which seriously affects the safety performance of the battery. Therefore, there is an urgent need to develop an electrolyte suitable for silicon-carbon system lithium-ion batteries that can improve the safety performance and cycle life of the battery. Summary of the Invention

[0004] In view of this, the present invention provides an electrolyte and a battery containing the same, wherein the electrolyte can effectively alleviate the problems of large battery cycle expansion, short battery cycle life, and difficulty in balancing battery safety performance.

[0005] In order to solve the technical problems raised in the background technology, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides an electrolyte, comprising:

[0007] Electrolyte salts, solvents, fluorovinyl ether compounds, ether nitrile compounds and tetravinylsilane;

[0008] Wherein, the structural formula of the fluorovinyl ether compound is shown in formula (1):

[0009]

[0010] In formula (1), R1 is selected from H, a Substituted C 1-3alkyl; R a at least one selected from halogen, C1-4alkyl.

[0011] Further, the ether nitrile compound includes at least one of 1,2-bis(cyanoethoxy)ethane and 1,2,3-tris(2-cyanoethoxy)propane.

[0012] Further, the fluorinated vinyl ether compound is added in an amount of 0.2wt% to 5.0wt% of the total mass of the electrolyte; and / or the ether nitrile compound is added in an amount of 0.5wt% to 5.0wt% of the total mass of the electrolyte; and / or the tetra-vinyl silane is added in an amount of 0.2wt% to 1.0wt% of the total mass of the electrolyte.

[0013] Further, the fluorinated vinyl ether compound includes at least one of structural formula 1-1 to structural formula 1-6:

[0014]

[0015] Further, the solvent includes at least one of a carbonate, a carboxylic acid ester, and a fluorinated ether; wherein the carbonate includes at least one of vinyl carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, and methyl propyl carbonate; the carboxylic acid ester includes at least one of propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, propyl propionate, ethyl propionate, methyl butyrate, and ethyl n-butyrate; and the fluorinated ether includes 1,1,2,3-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0016] Further, the electrolyte further includes an additive; the additive includes at least one of 1,3-propane sultone, ethylene sulfite, ethylene sulfate, vinylene carbonate, fluorinated vinylene carbonate, lithium bis(oxalato)borate, lithium bis(fluorooxalato)borate, lithium bis(fluorooxalato)phosphate, and vinyl vinylene carbonate.

[0017] Further, the additive is added in an amount of 0wt% to 20.0wt% of the total mass of the electrolyte.

[0018] In a second aspect, the present application provides a battery, which includes:

[0019] the electrolyte as described above;

[0020] a positive electrode sheet containing a positive electrode active material;

[0021] a negative electrode sheet containing a negative electrode active material;

[0022] a separator film.

[0023] Further, the negative active material comprises a carbon-based negative material and / or a silicon-based negative material; wherein the carbon-based negative material comprises at least one of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon and soft carbon; and the silicon-based negative material comprises at least one of nano-silicon, silicon-oxygen negative material (SiO x , 0 < x < 2) and silicon-carbon negative material (SiC).

[0024] The beneficial effects of the above technical solutions of the present application are as follows:

[0025] The present application provides an electrolyte and a battery comprising the same, the electrolyte comprising: an electrolyte salt, a solvent, a fluorovinyl ether compound, an ether nitrile compound and a tetravinylsilane; wherein the fluorovinyl ether compound has a structural formula as shown in formula (1):

[0026]

[0027] In formula (1), R1 is selected from H, C1-6 alkyl substituted with at least one R a ; R 1-3 is selected from at least one of halogen and C1-6 alkyl. a

[0028] In the present application, the fluorine functional group in the fluorovinyl ether compound in the electrolyte is at the ortho position of the ether bond, which is easy to participate in the interface reaction to form LiF, and after the removal of HF, a carbon-carbon double bond is formed. The two compounds after F removal interact with each other through the unsaturated bond and the tetravinylsilane in the electrolyte, and polymerize on the surface of the battery negative electrode to form a tough and firm SEI composite film, which has a significant inhibitory effect on the cycle expansion of the negative material, and can greatly reduce the occurrence of side reactions, inhibit the heat generation of side reactions, thereby prolonging the cycle life of the battery and improving the safety performance of the battery. At the same time, the lone pair of electrons on the nitrogen atom in the cyano group of the ether nitrile compound in the electrolyte can adsorb the removed HF, further stabilize the positive electrode, inhibit the dissolution of metal ions, and reduce the heat generation of side reactions on the positive electrode side. In summary, the combination of fluorovinyl ether compound, ether nitrile compound and tetravinylsilane can simultaneously reduce the occurrence of side reactions on both positive and negative electrodes, inhibit the heat generation of side reactions, greatly improve the safety performance of the battery, and form a more firm SEI film, reduce the expansion of the silicon negative electrode and prolong the cycle life. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is the structural formula of the fluorovinyl ether compound. DETAILED DESCRIPTION

[0030] ​For a further understanding of the present application, preferred embodiments thereof will be described in conjunction with examples below, it should be understood, however, that these descriptions are merely by way of further illustration of the features and advantages of the present application, but not limit the present application.

[0031] The electrolyte and the battery comprising the electrolyte in the present application are further explained below in conjunction with specific examples.

[0032] In a first aspect, the present application provides an electrolyte, which comprises:

[0033] an electrolyte salt, a solvent, a fluoro-vinyl ether compound, an ether nitrile compound and a tetravinylsilane;

[0034] wherein the fluoro-vinyl ether compound has a structure as shown in formula (1):

[0035]

[0036] In formula (1), R1 is selected from H, -CH3, -CH2CH3, -CH2CH2CH3 and -CH(CH3)CH3, which are substituted by at least one R a substituted C 1-3 alkyl group; R a is selected from at least one of halogen and C1 alkyl.

[0037] According to some embodiments of the present application, R1 is selected from H, -CH3, -CH2CH3, -CH2CH2CH3 and -CH(CH3)CH3, which are substituted by at least one R a substituted -CH3, -CH2CH3, -CH2CH2CH3 and -CH(CH3)CH3; R a is selected from at least one of -F and -CH3.

[0038] The present application provides an electrolyte, which comprises a fluoro-vinyl ether compound, an ether nitrile compound and a tetravinylsilane; wherein the fluorine functional group in the fluoro-vinyl ether compound is adjacent to the ether bond and is easy to participate in interface reaction to form LiF, which will form a carbon-carbon double bond after the removal of HF, and the two compounds after the removal of F will interact with each other through the unsaturated bond and the tetravinylsilane in the electrolyte to form a tough and firm SEI composite film on the surface of the negative electrode, which has a significant inhibitory effect on the cycle expansion of the negative electrode material, can greatly reduce the occurrence of side reactions, inhibit the heat generation of side reactions, thereby prolonging the cycle life of the battery and improving the safety performance of the battery. At the same time, the lone pair of electrons on the nitrogen atom in the cyano group of the ether nitrile compound in the electrolyte can adsorb the removed HF, further stabilize the positive electrode, inhibit the dissolution of metal ions, and reduce the heat generation of side reactions on the positive electrode side. In summary, the combination of the fluoro-vinyl ether compound, the ether nitrile compound and the tetravinylsilane can simultaneously reduce the occurrence of side reactions on both sides of the positive and negative electrodes, inhibit the heat generation of side reactions, greatly improve the safety performance of the battery, and form a more firm SEI film to reduce the expansion of the silicon negative electrode and prolong the cycle life.

[0039] According to some embodiments of the present application, the ether nitrile compound includes at least one of 1,2-bis(cyanoethoxy)ethane and 1,2,3-tris(2-cyanoethoxy)propane.

[0040] According to some embodiments of the present application, the fluorovinyl ether compound is added in an amount of 0.2wt% to 5.0wt% of the total mass of the electrolyte. Exemplarily, the fluorovinyl ether compound can be added in an amount of 0.2wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, or in a range value and any point value within the range value formed by any two of the aforementioned values. The amount of the fluorovinyl ether compound added in the present application needs to be controlled within a suitable range, because if the amount of the fluorovinyl ether compound added is too low, it cannot form an interface protection film sufficiently, and if the amount of the fluorovinyl ether compound added is too high, it will affect the conductivity of the electrolyte itself, thereby failing to reduce the impedance. Preferably, the amount of the fluorovinyl ether compound added is 0.5wt% to 2.0wt% of the total mass of the electrolyte.

[0041] According to some embodiments of the present application, the fluorovinyl ether compound includes at least one of structural formula 1-1 to structural formula 1-6:

[0042]

[0043] According to some embodiments of the present application, the fluorovinyl ether compound can be obtained by commercial purchase or prepared by a method known in the art.

[0044] According to some embodiments of the present application, the ether nitrile compound is added in an amount of 0.5wt% to 5.0wt% of the total mass of the electrolyte. Exemplarily, the ether nitrile compound can be added in an amount of 0.2wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, or in a range value and any point value within the range value formed by any two of the aforementioned values.

[0045] According to some embodiments of the present application, the tetra-vinyl silane is added in an amount of 0.2wt% to 1.0wt% of the total mass of the electrolyte. Exemplarily, the ether nitrile compound can be added in an amount of 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, and 1.0wt%, or in a range value and any point value within the range value formed by any two of the aforementioned values.

[0046] According to some embodiments of the present application, the solvent comprises at least one of carbonates, carboxylic acid esters and fluorinated ethers; wherein the carbonates comprise at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate; the carboxylic acid esters comprise at least one of propyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isoamyl acetate, propyl propionate, ethyl propionate, methyl butyrate and ethyl n-butyrate; and the fluorinated ethers comprise 1,1,2,3-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0047] According to some embodiments of the present application, the electrolyte salt comprises at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluoro oxalate borate, lithium bis-trifluoromethylsulfonylimide, lithium difluoro bis-oxalate phosphate, lithium tetrafluoroborate, lithium bis-oxalate borate, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis(pentafluoroethylsulfonyl)imide, lithium tris(trifluoromethylsulfonyl)methide and lithium bis(trifluoromethylsulfonyl)imide.

[0048] In the electrolyte provided by the present application, the added amount of the electrolyte salt is 10.0wt% to 20.0wt% of the total mass of the electrolyte. Exemplarily, the added amount of the electrolyte salt can be 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, 20wt%, or a range value formed by any two of the above values and any point value within the range.

[0049] According to some embodiments of the present application, the electrolyte further comprises an additive; and the additive comprises at least one of 1,3-propane sultone, ethylene sulfite, ethylene sulfate, vinylene carbonate, fluorinated vinylene carbonate, lithium bis-oxalate borate, lithium difluoro oxalate borate, lithium difluoro bis-oxalate phosphate and vinylene carbonate. The additive can protect the positive and negative electrodes when forming films.

[0050] According to some embodiments of the present application, the added amount of the additive is 0wt% to 20.0wt% of the total mass of the electrolyte.

[0051] In a second aspect, the present application provides a preparation method of the electrolyte as described above, which comprises: adding an electrolyte salt, a fluorinated vinyl ether compound, an ether nitrile compound and a tetra-vinyl silane into a solvent and mixing them uniformly to obtain the electrolyte.

[0052] In a third aspect, the present application provides a battery comprising: the electrolyte as described above; a positive electrode sheet containing a positive electrode active material; a negative electrode sheet containing a negative electrode active material; and a separator.

[0053] As a preference, the battery according to the present application is a lithium ion battery, and the positive electrode of the lithium ion battery has a charge cut-off voltage ≥ 4.4 V.

[0054] According to some embodiments of the present application, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer coated on one or both sides of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material, a conductive agent and a binder.

[0055] According to some embodiments of the present application, the positive electrode active material is selected from one or more of LiCoO2, LiNiO2, LiMn2O4, LiFePO4, Li x Ni y M 1-y O2, wherein 0.9≤x≤1.2, 0.5≤y<1, and M is selected from one or more of Co, Mn, Al, Mg, Ti, Zr, Fe, Cr, Mo, Cu, Ca.

[0056] According to some embodiments of the present application, the mass percentage of each component in the positive electrode active material layer is: 80-99.8 wt% of the positive electrode active material, 0.1-10 wt% of the conductive agent, and 0.1-10 wt% of the binder. Preferably, the mass percentage of each component in the positive electrode active material layer is: 84-99 wt% of the positive electrode active material, 0.5-8 wt% of the conductive agent, and 0.5-8 wt% of the binder. More preferably, the mass percentage of each component in the positive electrode active material layer is: 90-99 wt% of the positive electrode active material, 0.5-5 wt% of the conductive agent, and 0.5-5 wt% of the binder.

[0057] According to some embodiments of the present application, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer coated on one or both sides of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, a conductive agent, a binder and a dispersant.

[0058] According to some embodiments of the present application, the negative electrode active material comprises a carbon-based negative electrode material and / or a silicon-based negative electrode material; wherein the carbon-based negative electrode material comprises at least one of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon and soft carbon; and the silicon-based negative electrode material comprises at least one of nano-silicon, a silicon-oxygen negative electrode material (SiO x , 0

[0059] Further, the nano-silicon and / or SiO x1-55 wt% of the total mass of the silicon-carbon negative electrode material, illustratively, can be 1 wt%, 2 wt%, 5 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%.

[0060] According to some embodiments of the present application, the median particle diameter D50 of the negative active material is 8-25 μm. 50 and the specific surface area is 0.7-5.0 m 2 / g.

[0061] According to some embodiments of the present application, the negative active material has a tap density of 1.60-1.85 mg / cm 3 .

[0062] According to some embodiments of the present application, the mass percentage of each component in the negative active material layer is: 70-99.7 wt% of the negative active material, 0.1-10 wt% of the binder, 0.1-10 wt% of the dispersant, and 0.1-10 wt% of the conductive agent. Preferably, the mass percentage of each component in the negative active material layer is: 76-98.5 wt% of the negative active material, 0.5-8 wt% of the binder, 0.5-8 wt% of the dispersant, and 0.5-8 wt% of the conductive agent. More preferably, the mass percentage of each component in the negative active material layer is: 85-98.5 wt% of the negative active material, 0.5-5 wt% of the binder, 0.5-5 wt% of the dispersant, and 0.5-5 wt% of the conductive agent.

[0063] According to some embodiments of the present application, the binder is selected from at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyethyleneimine (PEI), polyaniline (PAN), polyacrylic acid (PAA), sodium alginate, styrene butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), phenol formaldehyde resin, or epoxy resin, and the like.

[0064] According to some embodiments of the present application, the dispersant is selected from at least one of polyvinyl alcohol (PVA), cetyl ammonium bromide, sodium dodecyl benzene sulfonate, silane coupling agent, ethanol, N-methyl pyrrolidone (NMP), N,N-dimethylformamide (DMF), and the like, and more preferably, is at least one of cetyl ammonium bromide, sodium dodecyl benzene sulfonate, silane coupling agent, and ethanol.

[0065] According to some embodiments of the present application, the conductive agent is selected from at least one of carbon nanotubes (CNTs), carbon fibers (VGCF), conductive graphite (KS-6, SFG-6), mesocarbon microbeads (MCMB), graphene, ketjen black, Super P, acetylene black, conductive carbon black, or hard carbon.

[0066] According to some embodiments of the present application, the separator is a separator known in the art, such as a polyethylene separator, a polypropylene separator, or the like.

[0067] In a fourth aspect, the present application further provides a preparation method of the battery as described above, the preparation method comprising the following steps:

[0068] (1) preparing a positive electrode sheet and a negative electrode sheet, the positive electrode sheet containing a positive electrode active material, and the negative electrode sheet containing a negative electrode active material;

[0069] (2) mixing a solvent, a fluorovinyl ether compound, an ether nitrile compound, a tetra-vinyl silane, and a lithium salt to prepare an electrolyte;

[0070] (3) winding the positive electrode sheet, the separator, and the negative electrode sheet to obtain a bare cell without electrolyte injection; placing the bare cell in an outer packaging foil, and injecting the electrolyte of step (2) into the dried bare cell to prepare the lithium ion battery.

[0071] Exemplarily, the preparation method specifically comprises the following steps:

[0072] (1) positive electrode sheet preparation

[0073] The positive electrode active material LiCoO2, the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black are mixed in a weight ratio of 97.5:1.3:1.2, N-methyl pyrrolidone (NMP) is added, and stirring is performed under the action of a vacuum stirrer until the mixed system becomes a positive electrode slurry with uniform fluidity; the positive electrode slurry is uniformly coated on an aluminum foil with a thickness of 9-12 μm; the coated aluminum foil is baked in an oven, and then dried in an oven at 120°C for 8 h, and then subjected to rolling, slitting to obtain the required positive electrode sheet.

[0074] (2) silicon-carbon negative electrode sheet preparation

[0075] The silicon-carbon negative electrode material (formed by compounding SiO and graphite, and the mass percentage of SiO is 5%), single-walled carbon nanotube (SWCNT) conductive agent (mass percentage is 0.1%), conductive carbon black (SP) conductive agent (mass percentage is 0.8%), carboxymethyl cellulose sodium (CMC) dispersant (mass percentage is 1%), and butadiene-styrene rubber (SBR) binder (mass percentage is 1.1%) with a mass percentage of 97.0% are prepared into negative electrode slurry by a wet process; the negative electrode slurry is uniformly coated on a copper foil with a thickness of 9-12 μm; the coated copper foil is baked in an oven, and then dried in an oven at 85°C for 5 h, and then rolled and cut to obtain the required silicon-carbon negative electrode sheet.

[0076] (3) Preparation of electrolyte

[0077] In an argon-filled glove box with qualified water oxygen content, ethylene carbonate, propylene carbonate, propyl propionate and propyl acetate are uniformly mixed in a mass ratio of 1:2:5:2, and then 1 mol / L (12.5 wt%) of fully dried lithium hexafluorophosphate (LiPF6), fluoro vinyl ether compounds, ether nitrile compounds and tetra-vinyl silane are quickly added to obtain the electrolyte.

[0078] (4) Preparation of separator

[0079] A polyethylene separator with a thickness of 7-9 μm is selected.

[0080] (5) Preparation of lithium ion battery

[0081] The prepared positive electrode sheet, separator and negative electrode sheet are wound to obtain a bare cell without liquid injection; the bare cell is placed in an outer packaging foil, and the prepared electrolyte is injected into the dried bare cell, and then vacuum packaging, standing, formation, shaping, sorting and other processes are performed to obtain the required lithium ion battery.

[0082] The electrolyte and the battery containing the same in the present application are further described below through some specific examples.

[0083] Example 1

[0084] 1.1 Preparation of electrolyte: In an argon-filled glove box with qualified water oxygen content, ethylene carbonate, propylene carbonate, propyl propionate and propyl acetate are uniformly mixed in a mass ratio of 1:2:5:2, and then 1 mol / L (12.5 wt%) of fully dried lithium hexafluorophosphate (LiPF6), fluoro vinyl ether compounds, ether nitrile compounds and tetra-vinyl silane are quickly added to obtain the electrolyte.

[0085] 1.2 Preparation of lithium ion battery:

[0086] (1) Preparation of positive electrode sheet:

[0087] The positive electrode active material LiCoO2, the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black were mixed in a weight ratio of 97.5:1.3:1.2, N-methyl pyrrolidone (NMP) was added, and stirring was performed under the action of a vacuum stirrer until the mixed system became a positive electrode slurry with uniform fluidity; the positive electrode slurry was uniformly coated on an aluminum foil with a thickness of 10 μm; the coated aluminum foil was baked in an oven, and then dried in an oven at 120°C for 8 h, followed by rolling and slitting to obtain the desired positive electrode sheet.

[0088] (2) Preparation of silicon-carbon negative electrode sheet:

[0089] A negative electrode slurry was prepared by a wet process using 97.0% by mass of a silicon-carbon negative electrode material (composed of SiO and graphite, with a SiO mass fraction of 5%), 0.1% by mass of a single-walled carbon nanotube (SWCNT) conductive agent, 0.8% by mass of a conductive carbon black (SP) conductive agent, 1% by mass of carboxymethyl cellulose sodium (CMC) dispersant, and 1.1% by mass of butadiene-styrene rubber (SBR) binder; the negative electrode slurry was uniformly coated on a copper foil with a thickness of 10 μm; the coated copper foil was baked in an oven, and then dried in an oven at 85°C for 5 h, followed by rolling and slitting to obtain the desired silicon-carbon negative electrode sheet.

[0090] (3) Preparation of electrolyte: as shown in 1.1 above.

[0091] (4) Preparation of lithium ion battery

[0092] A bare cell without liquid injection was obtained by winding the prepared positive electrode sheet, the separator, and the negative electrode sheet; the bare cell was placed in an outer packaging foil, the prepared electrolyte was injected into the dried bare cell, and the lithium ion battery was obtained after the processes of vacuum packaging, standing, formation, shaping, and sorting.

[0093] Example 2

[0094] 1.1 Preparation of electrolyte: the method of preparing the electrolyte was the same as in Example 1, except that the types and amounts of the fluorovinyl ether compound, the ether nitrile compound, and the tetra-vinyl silane were different, and the specific amounts and selections are shown in Table 1.

[0095] 1.2 Preparation of lithium ion battery: the same as in Example 1.

[0096] Example 3

[0097] 1.1 Preparation of electrolyte: The method of preparing electrolyte is the same as example 1, except that the type and amount of addition of fluoro vinyl ether compound, the type and amount of addition of ether nitrile compound, the amount of addition of tetra vinyl silane are different, the specific amount and selection are shown in table 1.

[0098] 1.2 Preparation of lithium ion battery: The same as example 1.

[0099] Example 4

[0100] 1.1 Preparation of electrolyte: The method of preparing electrolyte is the same as example 1, except that the type and amount of addition of fluoro vinyl ether compound, the type and amount of addition of ether nitrile compound, the amount of addition of tetra vinyl silane are different, the specific amount and selection are shown in table 1.

[0101] 1.2 Preparation of lithium ion battery: The same as example 1.

[0102] Example 5

[0103] 1.1 Preparation of electrolyte: The method of preparing electrolyte is the same as example 1, except that the type and amount of addition of fluoro vinyl ether compound, the type and amount of addition of ether nitrile compound, the amount of addition of tetra vinyl silane are different, the specific amount and selection are shown in table 1.

[0104] 1.2 Preparation of lithium ion battery: The same as example 1.

[0105] Example 6

[0106] 1.1 Preparation of electrolyte: The method of preparing electrolyte is the same as example 1, except that the type and amount of addition of fluoro vinyl ether compound, the type and amount of addition of ether nitrile compound, the amount of addition of tetra vinyl silane are different, the specific amount and selection are shown in table 1.

[0107] 1.2 Preparation of lithium ion battery: The same as example 1.

[0108] Example 7

[0109] 1.1 Preparation of electrolyte: The method of preparing electrolyte is the same as example 1, except that the type and amount of addition of fluoro vinyl ether compound, the type and amount of addition of ether nitrile compound, the amount of addition of tetra vinyl silane are different, the specific amount and selection are shown in table 1.

[0110] 1.2 Preparation of lithium ion battery: The same as example 1.

[0111] Example 8

[0112] 1.1 Preparation of electrolyte: the method of preparing electrolyte is the same as example 1, the difference is that the type and the amount of addition of fluoro vinyl ether compound is different, the type and the amount of addition of ether nitrile compound is different, the amount of addition of tetra-vinyl silane is different, the specific amount and selection is shown in table 1.

[0113] 1.2 Preparation of lithium ion battery: the same as example 1.

[0114] Example 9

[0115] 1.1 Preparation of electrolyte: the method of preparing electrolyte is the same as example 1, the difference is that the type and the amount of addition of fluoro vinyl ether compound is different (and two kinds of structure of fluoro vinyl ether compound is added), the type and the amount of addition of ether nitrile compound is different, the amount of addition of tetra-vinyl silane is different, the specific amount and selection is shown in table 1.

[0116] 1.2 Preparation of lithium ion battery: the same as example 1.

[0117] Example 10

[0118] 1.1 Preparation of electrolyte: the method of preparing electrolyte is the same as example 1, the difference is that the type and the amount of addition of fluoro vinyl ether compound is different (and two kinds of structure of fluoro vinyl ether compound is added), the type and the amount of addition of ether nitrile compound is different, the amount of addition of tetra-vinyl silane is different, the specific amount and selection is shown in table 1.

[0119] 1.2 Preparation of lithium ion battery: the same as example 1.

[0120] Example 11

[0121] 1.1 Preparation of electrolyte: the method of preparing electrolyte is the same as example 1, the difference is that the type and the amount of addition of fluoro vinyl ether compound is different (and three kinds of structure of fluoro vinyl ether compound is added), the amount of addition of ether nitrile compound is different, the amount of addition of tetra-vinyl silane is different, the specific amount and selection is shown in table 1.

[0122] 1.2 Preparation of lithium ion battery: the same as example 1.

[0123] Example 12

[0124] 1.1 Preparation of electrolyte: the method of preparing electrolyte is the same as example 1, the difference is that the additive 1,3-propane sulfolane is added in example 12, the type and the amount of addition of the additive is shown in table 1.

[0125] 1.2 Preparation of lithium ion battery: the same as example 1.

[0126] Example 13

[0127] 1.1 Preparation of electrolyte: The method of preparing electrolyte is the same as example 1, except that the additive lithium bis(oxalato)borate is added in example 12, the type and amount of the additive is shown in table 1.

[0128] 1.2 Preparation of lithium ion battery: The same as example 1.

[0129] Comparative example 1

[0130] 1.1 Preparation of electrolyte: The method of preparing electrolyte is the same as example 1, except that the ether nitrile compound and tetra-vinyl silane are not added, the amount and selection is shown in table 1.

[0131] 1.2 Preparation of lithium ion battery: The same as example 1.

[0132] Comparative example 2

[0133] 1.1 Preparation of electrolyte: The method of preparing electrolyte is the same as example 1, except that the fluoro-vinyl ether compound and tetra-vinyl silane are not added, the amount and selection is shown in table 1.

[0134] 1.2 Preparation of lithium ion battery: The same as example 1.

[0135] Comparative example 3

[0136] 1.1 Preparation of electrolyte: The method of preparing electrolyte is the same as example 1, except that the fluoro-vinyl ether compound and ether nitrile compound are not added, the amount and selection is shown in table 1.

[0137] 1.2 Preparation of lithium ion battery: The same as example 1.

[0138] Comparative example 4

[0139] 1.1 Preparation of electrolyte: The method of preparing electrolyte is the same as example 1, except that the tetra-vinyl silane is not added, the amount and selection is shown in table 1.

[0140] 1.2 Preparation of lithium ion battery: The same as example 1.

[0141] Comparative example 5

[0142] 1.1 Preparation of electrolyte: The method of preparing electrolyte is the same as example 1, except that the ether nitrile compound is not added, the amount and selection is shown in table 1.

[0143] 1.2 Preparation of lithium ion battery: The same as example 1.

[0144] Comparative example 6

[0145] 1.1 Preparation of electrolyte: the method of preparing electrolyte is the same as example 1, the difference is that no fluorovinyl ether compound is added, the specific amount and selection are shown in table 1.

[0146] 1.2 Preparation of lithium ion battery: the same as example 1.

[0147] The types and amounts of each component in examples 1-13 and comparative examples 1-6 above are shown in table 1. It should be explained that DENE in table 1 is the English abbreviation of 1,2-bis(cyanoethoxy)ethane; 1,2,3-tris(2-cyanoethoxy)propane is simply referred to as glycerol trinitrate.

[0148] Table 1

[0149]

[0150]

[0151]

[0152] Test:

[0153] The batteries obtained in the above comparative examples and examples were tested for electrochemical performance, and the relevant descriptions are as follows:

[0154] (1) 25℃ cycle test: the batteries prepared in the above examples and comparative examples were placed in an environment of (25±2)℃, and stood for 2-3 hours. When the battery body reached (25±2)℃, the battery was charged at a constant current of 1C with a cutoff current of 0.05C. After the battery was fully charged, it was rested for 5 min, and then discharged at a constant current of 0.7C to a cutoff voltage of 3.0V. The highest discharge capacity of the first three cycles was recorded as the initial capacity Q. When the cycle reached 1000 times, the last discharge capacity Q1 and the battery thickness T1 were recorded, and the results are shown in table 2.

[0155] The calculation formula used is as follows:

[0156] Capacity retention rate (%) = Q1 / Q x 100%; thickness change rate (%) = (T1-T) / T x 100%

[0157] (2) 140℃ thermal shock test: the batteries prepared in the above examples and comparative examples were heated by convection or circulating hot air oven with an initial temperature of 25±3℃, a temperature change rate of 5±2℃ / min, and a temperature rise to 140±2℃. The test was ended after keeping for 30 min, and the battery state was recorded. The results are shown in table 2.

[0158] (3) overcharge test: the batteries prepared in the above examples and comparative examples were charged at a constant current of 3C to 5V, and the battery state was recorded. The results are shown in table 2.

[0159] (4) Needle puncture test; the battery obtained in the above examples and comparative examples is punctured by a high-temperature-resistant steel needle with a diameter of 5-8 mm (the conical angle of the needle tip is 45°-60°, the surface of the needle is smooth without rust, oxidation layer and oil stain) at a speed of (25±5) mm / s from the direction perpendicular to the battery plate, and the puncture position is preferably close to the geometric center of the punctured surface (the steel needle stays in the battery). When 1h or the maximum temperature of the battery surface decreases to 10℃ below the peak temperature, the test is stopped, and the battery state is recorded. The results are shown in Table 2.

[0160] Table 2

[0161]

[0162]

[0163] It can be seen from the test results that the batteries prepared from the electrolyte in examples 1-13 can pass the 140℃ thermal shock test, overcharge test and needle puncture test. At the same time, under the condition of 25℃ 1C cycle for 1000 times, the capacity retention rate of the battery prepared from the electrolyte in examples 1-13 can basically be maintained at more than 80%, which has obvious performance improvement compared with the test data in the comparative examples. It is proved that the electrolyte suitable for silicon-carbon system lithium ion battery provided by the present application can make the silicon-carbon system lithium ion battery have long cycle life through the synergistic effect between the additives, and also has high safety performance.

[0164] The above is the preferred embodiment of the present application, it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, can also make a number of improvements and refinements, these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. An electrolyte, characterized in that: The electrolyte comprises: Electrolyte salts, solvents, fluorovinyl ether compounds, ether nitrile compounds and tetravinylsilane; The structural formula of the fluorovinyl ether compound is shown in formula (1): Formula (1); In formula (1), R1 is selected from H, a Substituted C 1-3 Alkyl; R a At least one selected from halogen and C1 alkyl.

2. The electrolyte according to claim 1, wherein The ether nitrile compound includes at least one of 1,2-bis(cyanoethoxy)ethane and 1,2,3-tris(2-cyanoethoxy)propane.

3. The electrolyte according to claim 1, characterized in that The amount of the fluorovinyl ether compound added is 0.2 wt % to 5.0 wt % of the total mass of the electrolyte.

4. The electrolyte according to claim 1, wherein The fluorovinyl ether compound includes at least one of structural formulas 1-1 to 1-6: 。 5. The electrolyte according to claim 1, characterized in that The amount of the ether nitrile compound added is 0.5wt% to 5.0wt% of the total mass of the electrolyte; and / or The amount of tetravinylsilane added is 0.2wt%~1.0wt% of the total mass of the electrolyte.

6. The electrolyte according to claim 1, characterized in that The solvent includes: at least one of a carbonate, a carboxylate, and a fluoroether; Wherein, the carbonate comprises at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and methyl propyl carbonate; The carboxylic acid ester comprises at least one of propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, propyl propionate, ethyl propionate, methyl butyrate and ethyl n-butyrate; The fluoroether includes 1,1,2,3-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

7. The electrolyte according to claim 1, characterized in that The electrolyte further comprises: additive; The additive includes at least one of 1,3-propane sultone, vinyl sulfite, vinyl sulfate, vinylene carbonate, fluoroethylene carbonate, lithium dioxalatoborate, lithium difluorooxalatoborate, lithium difluorooxalatophosphate, and vinyl ethylene carbonate.

8. The electrolyte according to claim 7, characterized in that The amount of the additive added is 0 wt % to 20.0 wt % of the total mass of the electrolyte.

9. A battery, characterized in that: The battery includes: The electrolyte according to any one of claims 1 to 8; A positive electrode sheet containing a positive electrode active material; A negative electrode sheet containing a negative electrode active material; Isolation film.

10. The battery according to claim 9, characterized in that The negative electrode active material includes a carbon-based negative electrode material and / or a silicon-based negative electrode material; Wherein, the carbon-based negative electrode material comprises at least one of artificial graphite, natural graphite, mesophase carbon microbeads, hard carbon and soft carbon; The silicon-based negative electrode material includes at least one of nano-silicon, silicon-oxygen negative electrode material and silicon-carbon negative electrode material.

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