Electrolyte and battery comprising same

Abstract

An electrolyte and a battery comprising same. The electrolyte comprises an electrolyte salt, a solvent, a fluorovinyl ether compound and a first additive, wherein the first additive comprises at least one of a sulfonic acid additive, an ether nitrile compound and tetraalkenyl silane. The electrolyte can solve the problem of poor high-temperature storage performance.

Description

Electrolyte and battery containing the same Technical Field

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

[0002] Over the past decade, lithium-ion battery technology has advanced rapidly, and its application has gradually expanded. As energy storage devices, it is used in portable electronics, large-scale energy storage, and electric vehicles. Research and development of lithium-ion batteries with higher energy density has always been a key focus of the industry and a major demand of the current lithium-ion industry.

[0003] To achieve higher battery energy density, options include using higher-density positive and negative electrode plates, or using higher-coating positive and negative electrode plates. However, higher density and higher areal density significantly increase the requirements for battery kinetics. The high impedance of the battery leads to insufficient kinetics and significantly degrades low-temperature discharge performance. Insufficient kinetics degrades battery performance, making it impossible to meet commercial requirements.

[0004] Currently, many additives are often added to electrolytes to enhance the positive and negative electrode interfaces and broaden the electrolyte's oxidation and reduction resistance. Traditionally, large amounts of low-viscosity solvents are added to achieve kinetic improvements, but this also results in poor high-temperature storage performance. Optimizing additives is expected to improve the battery's high-temperature storage performance. Therefore, to improve the battery's high-temperature storage performance, among other things, the development of an effective electrolyte additive is urgently needed.

[0005] Summary of the Invention

[0006] In view of this, the present disclosure provides an electrolyte and a battery containing the same, wherein the electrolyte can solve problems such as poor high-temperature storage performance.

[0007] To solve the technical problems raised in the background technology, the present disclosure adopts the following technical solutions:

[0008] In a first aspect, the present disclosure provides an electrolyte solution, comprising: an electrolyte salt, a solvent, a fluorovinyl ether compound, and a first additive; wherein the fluorovinyl ether compound has a structural formula as shown in formula (1):

[0009] 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;

[0010] The first additive includes at least one of a sulfonic acid additive, an ether nitrile compound, and a tetraenylsilane.

[0011] In some embodiments, the content of the fluorovinyl ether compound is 0.1 wt% to 10 wt% of the total mass of the electrolyte, preferably 0.2 wt% to 5 wt%.

[0012] In some embodiments, the fluorovinyl ether compound comprises at least one of structural formula 1-1 wt% to structural formula 1-6:

[0013] In some embodiments, the solvent comprises at least one of a carbonate, a carboxylate, and a fluoroether.

[0014] In some embodiments, the carbonate includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methylpropyl carbonate, and methylethyl carbonate.

[0015] In some embodiments, 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.

[0016] In some embodiments, the fluoroether comprises 1,1,2,3-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0017] In some embodiments, the electrolyte salt includes at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bis(trifluoromethylsulfonyl)imide, lithium difluorobis(oxalatophosphate), lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis(pentafluoroethylsulfonyl)imide, lithium tris(trifluoromethylsulfonyl)methyllithium, and lithium bis(trifluoromethylsulfonyl)imide.

[0018] In some embodiments, the sulfonic acid additive includes at least one of 1,3-propane sultone, 1-propylene-1,3-sultone, 5-methyloxathiolane 2,2-dioxide, 1,3-propylene sultone, 2,4-butane sultone, and 1,4-butane sultone.

[0019] In some embodiments, the ether nitrile compound includes at least one of 1,2-bis(cyanoethoxy)ethane and 1,2,3-tris(2-cyanoethoxy)propane.

[0020] In some embodiments, the tetraenylsilane has a structural formula as shown in formula (2):

[0021] Here, R2 to R5 are each independently an alkyl chain having 0 to 15 carbon atoms and a degree of unsaturation of 0 to 6, or a phenyl group.

[0022] In some embodiments, the tetraenylsilane comprises At least one of .

[0023] In some embodiments, the content of the electrolyte salt is 10 wt % to 20 wt % of the total mass of the electrolyte.

[0024] In some embodiments, the content of the sulfonic acid additive is 0.01 wt % to 10 wt % of the total mass of the electrolyte.

[0025] In some embodiments, the content of the ether nitrile compound is 0.5 wt% to 5.0 wt% of the total mass of the electrolyte; and / or the content of the tetraenylsilane is 0.2 wt% to 2 wt% of the total mass of the electrolyte.

[0026] In some embodiments, the electrolyte further includes: a nitrile compound.

[0027] In some embodiments, the nitrile compound includes at least one of adiponitrile, succinonitrile, and 1,3,6-hexanetrinitrile.

[0028] In some embodiments, the nitrile compound accounts for 0.01 wt% to 8 wt% of the total mass of the electrolyte.

[0029] In some embodiments, the electrolyte further comprises a second additive; the second additive comprises at least one of vinyl sulfite, vinyl sulfate, vinyl carbonate, fluoroethylene carbonate, lithium dioxalatoborate, lithium difluorooxalatoborate, lithium difluorooxalatophosphate and vinyl vinyl carbonate.

[0030] In some embodiments, the content of the second additive is 0 wt % to 20.0 wt % of the total mass of the electrolyte.

[0031] In a second aspect, the present disclosure provides a battery, which includes: 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.

[0032] In some embodiments, the negative electrode active material includes a carbon-based negative electrode material and / or a silicon-based negative electrode material.

[0033] In some embodiments, the carbon-based negative electrode material includes at least one of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon, and soft carbon;

[0034] In some embodiments, the silicon-based negative electrode material includes at least one of nano-silicon, silicon-oxygen negative electrode material, and silicon-carbon negative electrode material.

[0035] The beneficial effects of the above technical solution disclosed in the present invention are as follows:

[0036] The present disclosure provides an electrolyte solution, comprising: an electrolyte salt, a solvent, a fluorovinyl ether compound, and a first additive; wherein the structural formula of the fluorovinyl ether compound is as shown in formula (1):

[0037] 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;

[0038] The first additive includes at least one of a sulfonic acid additive, an ether nitrile compound, and a tetraenylsilane.

[0039] The electrolyte can solve the problem of poor high-temperature storage performance, and under some preferred conditions can also solve the problems of high-density batteries being prone to excessive impedance, significantly deteriorating low-temperature performance, and deteriorating furnace temperature safety.

[0040] When fluorovinyl ether compounds and sulfonic acid additives are preferably included, in addition to significantly improving battery impedance and enhancing low-temperature and high-temperature performance of the battery, the residual sulfonic acid additives in the electrolyte can also effectively inhibit gas generation during high-temperature storage, thereby reducing battery cycle and storage gas production.

[0041] The preferred combination of fluorovinyl ether compounds, ether nitrile compounds and tetraenylsilane can also reduce the occurrence of side reactions on both the positive and negative electrodes, inhibit the heat generation of side reactions, greatly improve the safety performance of the battery, and form a stronger SEI film, reduce the expansion of the silicon negative electrode and extend the cycle life. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is the structural formula of fluorovinyl ether compounds. DETAILED DESCRIPTION

[0043] In order to further understand the present disclosure, preferred embodiments of the present disclosure are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present disclosure, rather than limiting the present disclosure.

[0044] The electrolyte and the battery containing the electrolyte in the present disclosure are further explained below with reference to specific embodiments.

[0045] In a first aspect, the present disclosure provides an electrolyte, comprising:

[0046] Electrolyte salt, solvent, fluorovinyl ether compound and first additive;

[0047] Wherein, the structural formula of the fluorovinyl ether compound is shown in formula (1):

[0048] 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;

[0049] The first additive includes at least one of a sulfonic acid additive, an ether nitrile compound, and a tetraenylsilane.

[0050] In some embodiments of the present disclosure, an electrolyte is provided, comprising an electrolyte salt, a solvent, and a fluorovinyl ether compound, wherein the fluorine functional group in the fluorovinyl ether compound is in the ortho position of the ether bond, easily participating in an interfacial reaction to form LiF, and forming a carbon-carbon double bond after removing HF. The two compounds after removing F further undergo a polymerization reaction through an unsaturated bond to form an organic interfacial film, thereby ultimately forming an organic-inorganic hybrid interfacial protective film. The interfacial protective film has the characteristics of being dense and having high electrical conductivity, and can provide the battery with better high-temperature storage performance.

[0051] In some embodiments, the present disclosure provides an electrolyte comprising:

[0052] Electrolyte salt, solvent, fluorovinyl ether compound and sulfonic acid additive; wherein the structural formula of the fluorovinyl ether compound is as shown in formula (1):

[0053] In formula (1), R1 is selected from H, a Substituted C 1-3 Alkyl; R a At least one selected from halogen, C1 alkyl. The sulfonic acid additive in the electrolyte can help form a film on the negative electrode in the electrolyte, that is, it can cooperate with the fluorovinyl ether compound in the electrolyte to form a more solid interface protective film on the surface of the negative electrode, and can greatly suppress the gas production on the surface of the negative electrode. The inventors found through testing that by adding the fluorovinyl ether compound shown in formula (1) and the sulfonic acid additive to the electrolyte at the same time, the battery impedance can be significantly improved, and the low-temperature performance of the battery can also be improved. Furthermore, during high-temperature storage, the residual sulfonic acid additive in the electrolyte can also better suppress the generation of gas, thereby reducing the battery cycle and storage gas production.

[0054] 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. + However, it is not easy to develop an electrolyte that can alleviate the large expansion of the silicon negative electrode during cycling and take into account safety performance. The electrolyte additives currently developed often have difficulty in forming a strong and resilient SEI film to withstand the damage caused by the expansion of the silicon negative electrode during cycling. In addition, the continuous fragmentation and recombination of the SEI film exacerbates the heat generated by the side reaction, seriously affecting the safety performance of the battery. In some embodiments, an electrolyte and a battery containing the same are provided, wherein the electrolyte includes: an electrolyte salt, a solvent, a fluorovinyl ether compound, an ether nitrile compound, and a tetraenylsilane; wherein the structural formula of the fluorovinyl ether compound is shown in formula (1):

[0055] In formula (1), R1 is selected from H, a Substituted C 1-3 Alkyl; R a At least one selected from halogen, C1 alkyl. Wherein, the fluorine functional group in the fluorovinyl ether compound is in the ortho position of the ether bond, and is easy to participate in the interfacial reaction to form LiF. After removing HF, a carbon-carbon double bond is formed. The two compounds after removing F interact with the tetravinyl silicon in the electrolyte through an unsaturated bond, and polymerize on the surface of the negative electrode of the battery to form a tough and firm SEI composite film, which has a significant inhibitory effect on the cyclic expansion of the negative electrode material, and can also greatly reduce the occurrence of side reactions, suppress the heat generated by side reactions, thereby extending the cycle life of the battery and improving the battery safety performance. 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, suppress the dissolution of metal ions, and reduce the heat generated by the side reactions on the positive electrode side. In summary, the combination of fluorovinyl ether compounds, ether nitrile compounds and tetraenylsilane can simultaneously reduce the occurrence of side reactions on both sides of the positive and negative electrodes, suppress the heat generated by side reactions, greatly improve the safety performance of the battery, and form a stronger SEI film, reduce the expansion of the silicon negative electrode and extend the cycle life.

[0056] In some embodiments, the R1 is selected from H, a -CH3 substituted by at least one R a -CH2CH3 substituted by at least one R a -CH2CH2CH3 substituted by at least one R a Substituted -CH(CH3)CH3; R a At least one selected from -F and -CH3.

[0057] In some embodiments, the content of the fluorovinyl ether compound is 0.1wt% to 10.0wt% of the total mass of the electrolyte. For example, the content of the fluorovinyl ether compound can be 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, or a range value consisting of any two of the aforementioned values ​​and any point value within the range value. The content of the fluorovinyl ether compound described in the present disclosure needs to be controlled within a suitable range, because when the content of the fluorovinyl ether compound is too low, an interfacial protective film cannot be fully formed. At the same time, when the content of the fluorovinyl ether compound is too high, the conductivity of the electrolyte itself will be affected, thereby failing to reduce the impedance.

[0058] In some embodiments, when the fluorovinyl ether compound is used in combination with a sulfonic acid additive, the content of the fluorovinyl ether compound is 0.1 wt % to 2.0 wt % of the total mass of the electrolyte.

[0059] In some embodiments, when the fluorovinyl ether compound is used in combination with an ether nitrile compound and a tetraenylsilane, the content of the fluorovinyl ether compound is 0.2 wt% to 5.0 wt% of the total weight of the electrolyte. For example, the content of the fluorovinyl ether compound can be 0.2 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, or any range consisting of any two of the aforementioned values ​​and any point within the range. Preferably, the content of the fluorovinyl ether compound is 0.5 wt% to 2.0 wt% of the total weight of the electrolyte.

[0060] In some embodiments, the fluorovinyl ether compound includes at least one of the compounds represented by structural formula 1-1 to the compounds represented by structural formula 1-6:

[0061] In some embodiments, the fluorovinyl ether compound includes the compound represented by Structural Formula 1-1 and the compound represented by Structural Formula 1-5.

[0062] In some embodiments, the fluorovinyl ether compound includes a compound represented by Structural Formula 1-3 and a compound represented by Structural Formula 1-6.

[0063] In some embodiments, the fluorovinyl ether compound includes the compound represented by Structural Formula 1-1, the compound represented by Structural Formula 1-3, and the compound represented by Structural Formula 1-6.

[0064] In some embodiments, the fluorovinyl ether compound can be purchased from commercial sources or prepared using methods known in the art.

[0065] In some embodiments, the solvent comprises at least one of a carbonate, a carboxylate, and a fluoroether.

[0066] In some embodiments, the carbonate includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and methylpropyl carbonate.

[0067] In some embodiments, 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.

[0068] In some embodiments, the fluoroether comprises 1,1,2,3-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0069] In some embodiments, the solvent includes: carbonate and / or carboxylate; the carbonate may include at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate; the carboxylate may include 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. Preferably, the solvent also includes a fluorinated carbonate (such as fluorinated ethylene carbonate) and / or a fluorinated carboxylate (such as ethyl difluoroacetate). This solvent can be suitable for use when the fluorinated vinyl ether compound is used in conjunction with a sulfonic acid additive.

[0070] In some embodiments, the electrolyte salt includes at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bis(trifluoromethylsulfonyl)imide, lithium difluorobis(oxalatophosphate), lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis(pentafluoroethylsulfonyl)imide, lithium tris(trifluoromethylsulfonyl)methyllithium, and lithium bis(trifluoromethylsulfonyl)imide.

[0071] In the electrolyte provided by the present disclosure, the content of the electrolyte salt is 10.0 wt% to 20.0 wt% of the total mass of the electrolyte. For example, the content of the electrolyte salt may be 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, or 20 wt%, or any range consisting of any two of the foregoing values, or any point within the range.

[0072] In some embodiments, the sulfonic acid additive includes at least one of 1,3-propane sultone, 1-propylene-1,3-sultone, 5-methyloxathiolane 2,2-dioxide, 1,3-propylene sultone, 2,4-butane sultone, and 1,4-butane sultone.

[0073] In some embodiments, the sulfonic acid additive accounts for 0.01 wt% to 10 wt% of the total mass of the electrolyte.

[0074] The sulfonic acid additive in the present disclosure can be selected from at least one of 1,3-propane sultone, 1-propylene-1,3-sultone, 5-methyloxathiolane 2,2-dioxide, 1,3-propylene sultone, 2,4-butane sultone, and 1,4-butane sultone, and the sulfonic acid additive accounts for 0.01 wt% to 10 wt% of the total mass of the electrolyte. Exemplarily, the content of the sulfonic acid additive can be 0.01 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%, or any range consisting of any two of the aforementioned values, or any point within the range. Sulfonic acid additives in the electrolyte can help form a film on the negative electrode, thereby significantly affecting the gas production on the negative electrode surface. During high-temperature storage, the residual sulfonic acid additives in the electrolyte can also effectively inhibit the generation of gas, thereby reducing the gas production during battery circulation and storage.

[0075] In some embodiments, the ether nitrile compound includes at least one of 1,2-bis(cyanoethoxy)ethane and 1,2,3-tris(2-cyanoethoxy)propane.

[0076] In some embodiments, the content of the ether nitrile compound is 0.5 wt % to 5.0 wt % of the total mass of the electrolyte. For example, the content of the ether nitrile compound can be 0.2 wt %, 0.5 wt %, 1 wt %, 2 wt %, 3 wt %, 4 wt %, 5 wt %, or any range consisting of any two of the aforementioned values, or any point within the range.

[0077] In some embodiments, the tetraenylsilane has a structural formula as shown in formula (2):

[0078] Here, R2 to R5 are each independently an alkyl chain having 0 to 15 carbon atoms and a degree of unsaturation of 0 to 6, or a phenyl group.

[0079] In some embodiments, the tetraenylsilane comprises

[0080] At least one of .

[0081] In some embodiments, the tetraenylsilane is tetravinylsilane.

[0082] In some embodiments, the content of the tetraenylsilane is 0.2 wt % to 2 wt % of the total mass of the electrolyte. For example, the content of the ether nitrile compound can be 0.2 wt %, 0.3 wt %, 0.4 wt %, 0.5 wt %, 0.6 wt %, 0.7 wt %, 0.8 wt %, 0.9 wt % and 1.0 wt %, 1.2 wt %, 1.3 wt %, 1.4 wt %, 1.5 wt %, 1.6 wt %, 1.7 wt %, 1.8 wt %, 1.9 wt % and 2 wt %, or any range consisting of any two of the aforementioned values ​​and any point within the range.

[0083] In some embodiments, the electrolyte further comprises a nitrile compound. The nitrile compound may include at least one of adiponitrile, succinonitrile, and 1,3,6-hexanetrinitrile. In some embodiments, the nitrile compound accounts for 0.01 wt% to 8 wt% of the total mass of the electrolyte.

[0084] In some embodiments, the electrolyte described in the present disclosure also includes a nitrile compound, and the nitrile compound can specifically be selected from at least one of adiponitrile, succinonitrile and 1,3,6-hexanetrinitrile. The content of the nitrile compound can be 0.01wt%, 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, or a range value composed of any two of the aforementioned values ​​and any point value within the range value.

[0085] The carbon-nitrogen triple bond energy in the nitrile compounds disclosed herein is very high, so nitrile compounds have good stability and strong oxidation resistance at the positive electrode. At the same time, the cyano group has a strong coordination ability and can combine with the active sites on the electrode surface to shield these active ions on the positive electrode surface and reduce the decomposition effect of the electrode on the electrolyte. At the positive electrode, it is very stable and can complex some active ions. Therefore, the nitrile compounds can enhance the resistance of the electrolyte to positive electrode oxidation, thereby achieving the cycle life of the battery under high voltage.

[0086] In one embodiment of the present disclosure, when fluorovinyl ether compounds and sulfonic acid additives are used together, a strong interfacial protective film can be formed on the surface of the negative electrode, which can greatly suppress the gas production on the surface of the negative electrode, thereby significantly improving the battery impedance and also improving the low-temperature performance of the battery. Nitrile compounds form a stable interfacial protection on the positive electrode of the battery, reduce the consumption of electrolyte during the battery cycle, and increase the cycle life of the battery under high temperature and high pressure. When fluorovinyl ether compounds, sulfonic acid additives and nitrile compounds are used together, they play a role in improving the battery performance by supplementing the shortcomings and synergizing the effects.

[0087] In some embodiments, the electrolyte further includes a second additive comprising at least one of 1,3-propane sultone, vinyl sulfite, vinyl sulfate, vinylene carbonate, fluoroethylene carbonate, lithium dioxalatoborate, lithium difluorooxalatoborate, lithium difluorooxalatophosphate, and vinyl vinyl carbonate. Each of these additives can provide protection during film formation of the positive and negative electrodes.

[0088] In some embodiments, the electrolyte further comprises a second additive; the second additive is at least one of vinyl sulfite, vinyl sulfate, vinyl carbonate, fluoroethylene carbonate, lithium dioxalatoborate, lithium difluorooxalatoborate, lithium difluorooxalatophosphate and vinyl vinyl carbonate.

[0089] In some embodiments, the content of the additive is 0wt% to 20.0wt% of the total mass of the electrolyte, and can be 0wt%, 0.01wt%, 0.1wt%, 0.5wt%, 1wt%, 2wt%, 4wt%, 6wt%, 8wt%, 10wt%, 12wt%, 14wt%, 16wt%, 18wt%, 20wt%, or a range value composed of any two of the aforementioned values ​​and any point value within the range value.

[0090] In some embodiments, the present disclosure provides a method for preparing the electrolyte as described above, the method comprising: adding an electrolyte salt, a fluorovinyl ether compound, and a first additive into a solvent and mixing them uniformly to obtain the electrolyte.

[0091] In some embodiments, the present disclosure provides a method for preparing the electrolyte as described above, the preparation method comprising: adding an electrolyte salt, a fluorovinyl ether compound, and a sulfonic acid additive into a solvent and mixing them uniformly to obtain the electrolyte.

[0092] In some embodiments, the present disclosure provides a method for preparing the electrolyte as described above, the preparation method comprising: adding an electrolyte salt, a fluorovinyl ether compound, an ether nitrile compound and a tetraenylsilane (such as tetravinylsilane) into a solvent and mixing them evenly to obtain the electrolyte.

[0093] In a second aspect, the present disclosure provides a battery, which includes: 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.

[0094] Preferably, the battery in the present disclosure is a lithium-ion battery, and the positive electrode charging cut-off voltage of the lithium-ion battery is ≥4.4V.

[0095] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on one side or both sides of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material, a conductive agent, and a binder.

[0096] In some embodiments, the positive electrode active material is selected from one or more of transition metal lithium oxide, lithium iron phosphate, and lithium manganate; the chemical formula of the transition metal lithium oxide is Li 1+x Ni y Co z M (1-y-z) O2, wherein -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; wherein M is one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo and Zr.

[0097] In some embodiments, the positive electrode active material is selected from LiCoO2, LiNiO2, LiMn2O4, LiFePO4, Li x Ni y M 1- y One or more of 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, and Ca.

[0098] In some embodiments, the mass percentage of each component in the positive electrode active material layer is: 80-99.8 wt % of positive electrode active material, 0.1-10 wt % of conductive agent, and 0.1-10 wt % of binder.

[0099] In some embodiments, the mass percentage of each component in the positive electrode active material layer is: 90-99.6 wt % of positive electrode active material, 0.2-5 wt % of conductive agent, and 0.2-5 wt % of binder.

[0100] In some embodiments, the mass percentage of each component in the positive electrode active material layer is: 84-99 wt % of positive electrode active material, 0.5-8 wt % of conductive agent, and 0.5-8 wt % of binder.

[0101] In some embodiments, the mass percentage contents of the components in the positive electrode active material layer are as follows: 90 - 99 wt% of positive electrode active material, 0.5 - 5 wt% of conductive agent, and 0.5 - 5 wt% of binder.

[0102] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder.

[0103] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material, a conductive agent, a binder, and a dispersant.

[0104] In some embodiments, the mass percentage contents of the components in the negative electrode active material layer are as follows: 80 - 99.8 wt% of negative electrode active material, 0.1 - 10 wt% of conductive agent, and 0.1 - 10 wt% of binder. Preferably, the mass percentage contents of the components in the negative electrode active material layer are as follows: 90 - 99.6 wt% of negative electrode active material, 0.2 - 5 wt% of conductive agent, and 0.2 - 5 wt% of binder.

[0105] In some embodiments, the negative electrode active material includes a carbon-based negative electrode material, and the carbon-based negative electrode material includes at least one of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon, and soft carbon.

[0106] In some embodiments, the negative electrode active material may further include a silicon-based negative electrode material, and the silicon-based negative electrode material is selected from at least one of nano-silicon, silicon-oxide negative electrode material (SiO x , 0 < x < 2), or silicon-carbon negative electrode material. The mass ratio of the carbon-based negative electrode material to the silicon-based negative electrode material in the negative electrode active material is (10:0) to (1:19).

[0107] In some embodiments, in the negative electrode active material, the content of the carbon-based negative electrode material is 5 wt% - 100 wt%, and the content of the silicon-based negative electrode material is 0 wt% - 95 wt%.

[0108] In some embodiments, 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 includes at least one of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon, and soft carbon; the silicon-based negative electrode material includes at least one of nano-silicon, silicon-oxide negative electrode material (SiO x , 0 < x < 2), and silicon-carbon negative electrode material (such as SiC).

[0109] In some embodiments, the carbon-based negative electrode material accounts for 45-99wt% of the total mass of the silicon-carbon negative electrode material. For example, it can be 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, 90wt%, 95wt%, or 59wt%.

[0110] In some embodiments, the nano-silicon and / or SiO x It accounts for 1-55wt% of the total mass of the silicon-carbon negative electrode material. For example, it can be 1wt%, 2wt%, 5wt%, 8wt%, 10wt%, 12wt%, 15wt%, 18wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, or 55wt%.

[0111] In some embodiments, the median particle size D of the negative electrode active material is 50 The particle size is 8-25 μm, and the specific surface area is 0.7-5.0 m 2 / g.

[0112] In some embodiments, the negative electrode material has a compaction density of 1.60-1.85 mg / cm 3 .

[0113] In some embodiments, the weight percentages of the components in the negative electrode active material layer are: 70-99.7 wt% negative electrode active material, 0.1-10 wt% binder, 0.1-10 wt% dispersant, and 0.1-10 wt% conductive agent. Preferably, the weight percentages of the components in the negative electrode active material layer are: 76-98.5 wt% negative electrode active material, 0.5-8 wt% binder, 0.5-8 wt% dispersant, and 0.5-8 wt% conductive agent. More preferably, the weight percentages of the components in the negative electrode active material layer are: 85-98.5 wt% negative electrode active material, 0.5-5 wt% binder, 0.5-5 wt% dispersant, and 0.5-5 wt% conductive agent.

[0114] In some embodiments, 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.

[0115] In some embodiments, the conductive agent is selected from at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber.

[0116] In some embodiments, the binder is selected from at least one of sodium carboxymethyl cellulose, styrene-butadiene latex, polytetrafluoroethylene, and polyethylene oxide.

[0117] In some embodiments, the binder is selected from at least one of high molecular polymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyethyleneimine (PEI), polyaniline (PAN), polyacrylic acid (PAA), sodium alginate, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), phenolic resin or epoxy resin.

[0118] In some embodiments, the dispersant is selected from at least one of polypropylene (PVA), hexadecyl ammonium bromide, sodium dodecylbenzene sulfonate, a silane coupling agent, ethanol, N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), etc., more preferably at least one of hexadecyl ammonium bromide, sodium dodecylbenzene sulfonate, a silane coupling agent, and ethanol.

[0119] In some embodiments, the diaphragm is a diaphragm known in the art, such as a polyethylene diaphragm, a polypropylene diaphragm, and the like.

[0120] The present disclosure also provides a method for preparing the battery as described above, the method comprising the following steps:

[0121] (1) preparing a positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet contains a positive electrode active material and the negative electrode sheet contains a negative electrode active material;

[0122] (2) mixing a solvent, a fluorovinyl ether compound, a first additive, and a lithium salt to prepare an electrolyte;

[0123] (3) Winding the positive electrode sheet, the separator, and the negative electrode sheet to obtain a bare cell without liquid 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.

[0124] Exemplarily, the preparation method specifically comprises the following steps:

[0125] (1) Preparation of positive electrode sheet

[0126] 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, and N-methylpyrrolidone (NMP) is added and stirred under the action of a vacuum mixer until the mixed system becomes a positive electrode slurry with uniform fluidity; the positive electrode slurry is evenly coated on an aluminum foil with a thickness of 9 to 12 μm; the coated aluminum foil is baked in an oven, and then dried in an oven at 120°C for 8 hours, and then rolled and cut to obtain the required positive electrode sheet.

[0127] (2) Preparation of silicon-carbon negative electrode sheets

[0128] A negative electrode slurry is prepared by a wet process using a silicon-carbon negative electrode material (composite of SiO and graphite, with SiO accounting for 5% by mass) with a mass proportion of 97.0%, a single-walled carbon nanotube (SWCNT) conductive agent with a mass proportion of 0.1%, a conductive carbon black (SP) conductive agent with a mass proportion of 0.8%, a sodium carboxymethyl cellulose (CMC) dispersant with a mass proportion of 1% and a styrene-butadiene rubber (SBR) binder with a mass proportion of 1.1%. The negative electrode slurry is evenly coated on a copper foil with a thickness of 9 to 12 μm. The coated copper foil is baked in an oven and then dried in an oven at 85°C for 5 hours. The required silicon-carbon negative electrode sheet is then obtained by roller pressing and slitting.

[0129] (3) Preparation of electrolyte

[0130] In a glove box filled with argon and with a qualified water and oxygen content, ethylene carbonate, propylene carbonate, propyl propionate and ethyl propionate were evenly mixed in a mass ratio of 1:2:5:2, and then 1 mol / L (12.5 wt%) of fully dried lithium hexafluorophosphate (LiPF6), fluorovinyl ether compounds, ether nitrile compounds and tetravinylsilane were quickly added thereto to obtain an electrolyte.

[0131] (4) Preparation of diaphragm

[0132] A polyethylene diaphragm with a thickness of 7 to 9 μm is selected.

[0133] (5) Preparation of lithium-ion batteries

[0134] The positive electrode sheet, separator and negative electrode sheet prepared above 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. After vacuum packaging, standing, forming, shaping, sorting and other processes, the required lithium-ion battery is obtained.

[0135] The electrolyte and the battery containing the same in the present disclosure are further described below through some specific examples.

[0136] The Chinese and English names of the organic solvents used in the following examples are shown in Table 1:

[0137] Table 1

[0138] 1. Example A Group and Comparative Example A Group

[0139] Examples A1a to A1f

[0140] (1) Preparation of electrolyte

[0141] In a glove box filled with argon and with a qualified water and oxygen content, ethylene carbonate, propylene carbonate, propyl propionate and ethyl propionate were evenly mixed in a mass ratio of 1:2:5:2, and then 1 mol / L (12.5 wt%) of fully dried lithium hexafluorophosphate (LiPF6), 8 wt% of fluoroethylene carbonate and other additives (including fluorovinyl ether compounds, sulfonic acid additives, nitrile compounds, ether nitrile compounds and tetravinylsilane, the specific amounts and selections are shown in Table 2) were quickly added thereto to obtain an electrolyte.

[0142] The types of fluorovinyl ether compounds in Examples A1a to A1f are different.

[0143] (2) Preparation of positive electrode sheet:

[0144] The positive electrode active materials lithium cobalt oxide (LiCoO2), polyvinylidene fluoride (PVDF), SP (super P) and carbon nanotubes (CNT) are mixed in a mass ratio of 96:2:1.5:0.5, N-methylpyrrolidone (NMP) is added, and the mixture is stirred under the action of a vacuum mixer until the mixed system becomes a positive electrode active slurry with uniform fluidity; the positive electrode active slurry is evenly coated on both surfaces of an aluminum foil; the coated aluminum foil is dried, and then rolled and cut to obtain the desired positive electrode sheet.

[0145] (3) Preparation of negative electrode sheet:

[0146] The negative electrode active materials artificial graphite, sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber, conductive carbon black (SP) and single-walled carbon nanotubes (SWCNTs) were mixed in a mass ratio of 94.5:2.5:1.5:1:0.5, deionized water was added, and a negative electrode active slurry was obtained under the action of a vacuum mixer; the negative electrode active slurry was evenly coated on both surfaces of the copper foil; the coated copper foil was dried at room temperature, then transferred to an 80°C oven for drying for 10 hours, and then cold pressed and slit to obtain the negative electrode sheet.

[0147] (4) Preparation of lithium-ion batteries

[0148] Take an 8μm thick polyethylene separator, and wind the prepared positive electrode sheet, separator, and negative electrode sheet to obtain a bare battery cell without liquid injection; place the bare battery cell in the outer packaging foil, and inject the prepared electrolyte into the dried bare battery cell. After vacuum packaging, standing, formation, shaping, sorting and other processes, the required lithium-ion battery is obtained.

[0149] Examples A2a to A2c

[0150] The electrolyte and lithium-ion battery were prepared according to the method described in Example A1a, except that the composition and content of the fluorovinyl ether compound were different, as shown in Table 2.

[0151] Examples A3a-A3b

[0152] The electrolyte and lithium-ion battery were prepared according to the method described in Example A1a, except that the content of the fluorovinyl ether compound was different, as shown in Table 2.

[0153] Examples A4a to A4e

[0154] The electrolyte and lithium-ion battery were prepared according to the method described in Example A1a, except that the type and content of the sulfonic acid additive were different, as shown in Table 2.

[0155] Examples A5a to A5e

[0156] The electrolyte and lithium-ion battery were prepared according to the method described in Example A1a, except that the type and content of the nitrile compound were different, as shown in Table 2.

[0157] Examples A6a to A6d

[0158] The electrolyte and lithium-ion battery were prepared according to the method described in Example A1a, except that the type and content of the ether nitrile compound were different, as shown in Table 2.

[0159] Examples A7a to A7c

[0160] The electrolyte and lithium-ion battery were prepared according to the method described in Example A1a, except that the content of tetravinylsilane was different, as shown in Table 2.

[0161] Examples A8a to A8d

[0162] The electrolyte and lithium-ion battery were prepared according to the method described in Example A1a, except that the sulfonic acid additive, the ether nitrile compound, the tetravinylsilane content, and at least two of the nitrile compounds were not added, as shown in Table 2.

[0163] Comparative Example A1

[0164] The electrolyte and lithium-ion battery were prepared according to the method described in Example A1a, except that no fluorovinyl ether compound was added, as shown in Table 2.

[0165] Comparative Example A2

[0166] The electrolyte and lithium-ion battery were prepared according to the method described in Example A1a, except that the sulfonic acid additive, ether nitrile compound and tetravinylsilane were not added, as shown in Table 2.

[0167] Table 2

[0168] Note: In Table 2, * indicates the same as Example A1a, and the content is in wt%; “ / ” indicates no addition, that is, the addition amount is 0.

[0169] Group A test:

[0170] The high temperature storage performance test was performed on the batteries obtained from the comparative example group A and the example group A. The specific operation was as follows:

[0171] 60℃ storage performance test

[0172] The prepared lithium-ion battery was charged at a rate of 1C to the cut-off voltage and a cut-off current of 0.025C at 25°C, and then allowed to stand for 5 minutes. The thickness of the lithium-ion battery was measured (this was the thickness before storage). The fully charged cell / battery was placed in an open circuit at (60±2)°C for 35 days. After 35 days of storage, it was placed in an open circuit at room temperature for 2 hours. The thickness after storage was measured and the thickness expansion rate of the lithium-ion battery was calculated as follows:

[0173] Thickness expansion ratio = [(thickness after storage - thickness before storage) / thickness before storage] x 100%.

[0174] The results are shown in Table 3.

[0175] Table 3

[0176] 2. Example B Group and Comparative Example B Group

[0177] Example B1

[0178] Preparation of electrolyte

[0179] 1.1 The electrolyte includes the following components:

[0180] Organic solvent: ethylene carbonate (EC) 7wt%, propylene carbonate (PC) 14wt%, diethyl carbonate (DEC) 28wt%, propyl propionate (PP) 21.5wt%, fluoroethylene carbonate 12wt%; a total of 82.5wt%;

[0181] Electrolyte salt: lithium hexafluorophosphate (LiPF6), 13 wt%;

[0182] Fluorovinyl ether compound: structural formula 1-1; 0.5wt%;

[0183] Sulfonic acid additive: 1,3-propane sultone; 2wt%;

[0184] Nitrile compound: 1,3,6-hexanetrinitrile; 2 wt%.

[0185] 1.2 Preparation method: In a glove box filled with argon (H2O <0.1ppm, O2 <0.1ppm), first add and mix the organic solvent according to the ratio. After mixing evenly, quickly add 1 mol / L of fully dried lithium hexafluorophosphate (LiPF6), mix well and shake well. After shaking well, add fluoroethylene carbonate, fluorovinyl ether compounds, sulfonic acid additives and nitrile compounds, stir evenly to obtain the desired electrolyte.

[0186] Examples B2 to B4

[0187] The preparation was carried out according to the same operation as Example B1. The difference from Example B1 was the different contents of the fluorovinyl ether compound and propyl propionate (PP) in the electrolyte, as shown in Table 4 for details.

[0188] Example B5

[0189] The preparation was carried out in the same manner as in Example B1, except that the electrolyte contained the following components:

[0190] Organic solvent: ethylene carbonate (EC) 7wt%, propylene carbonate (PC) 14wt%, diethyl carbonate (DEC) 22wt%, propyl propionate (PP) 20wt%, fluoroethylene carbonate 12wt%; total 75wt%;

[0191] Electrolyte salt: lithium hexafluorophosphate (LiPF6), 13 wt%;

[0192] Fluorinated vinyl ether compound: structural formula 1-1; 8 wt%;

[0193] Sulfonic acid additive: 1,3-propane sultone; 2wt%;

[0194] Nitrile compound: 1,3,6-hexanetrinitrile; 2 wt%.

[0195] Example B6

[0196] The preparation was carried out according to the same operation as in Example B1, except that the content of the fluorovinyl ether compound was 10 wt %; the content of diethyl carbonate (DEC) was 22 wt %; and the content of propyl propionate (PP) was 18 wt %.

[0197] Examples B7 to B11

[0198] The preparation was carried out according to the same operation as Example B1. The difference from Example B5 was that the structural formulas of the fluorovinyl ether compounds were Structural Formula 1-2, Structural Formula 1-3, Structural Formula 1-4, Structural Formula 1-5 and Structural Formula 1-6, respectively.

[0199] Example B12

[0200] The preparation was carried out in the same manner as in Example B1, except that the electrolyte contained the following components:

[0201] Organic solvent: ethylene carbonate (EC) 7wt%, propylene carbonate (PC) 14wt%, diethyl carbonate (DEC) 22wt%, propyl propionate (PP) 20wt%, fluoroethylene carbonate 12wt%; total 75wt%;

[0202] Electrolyte salt: lithium hexafluorophosphate (LiPF6), 13 wt%;

[0203] Fluorinated vinyl ether compound: structural formula 1-2; 8 wt%;

[0204] Sulfonic acid additive: 1-propylene-1,3-sultone; 2wt%;

[0205] Nitrile compound: 1,3,6-hexanetrinitrile; 2 wt%.

[0206] Example B13

[0207] The preparation was carried out in the same manner as in Example B1, except that the electrolyte contained the following components:

[0208] Organic solvent and electrolyte salt: the same as in Example B12;

[0209] Fluorinated vinyl ether compound: structural formula 1-3; 8 wt%;

[0210] Sulfonic acid additive: 1-propylene-1,3-sultone; 2wt%;

[0211] Nitrile compound: adiponitrile; 2 wt%.

[0212] Example B14

[0213] The preparation was carried out in the same manner as in Example B1, except that the electrolyte contained the following components:

[0214] Organic solvent and electrolyte salt: the same as in Example B12;

[0215] Fluorovinyl ether compound: structural formula 1-4; 8 wt%;

[0216] Sulfonic acid additive: 2,4-butane sultone; 2wt%;

[0217] Nitrile compound: adiponitrile; 2 wt%.

[0218] Example B15

[0219] The preparation was carried out in the same manner as in Example B1, except that the electrolyte contained the following components:

[0220] Organic solvent and electrolyte salt: the same as in Example B12;

[0221] Fluorovinyl ether compound: structural formula 1-5; 8 wt%;

[0222] Sulfonic acid additive: 1,4-butane sultone; 2wt%;

[0223] Nitrile compound: adiponitrile; 2 wt%.

[0224] Example B16

[0225] The preparation was carried out in the same manner as in Example B1, except that the electrolyte contained the following components:

[0226] Organic solvent and electrolyte salt: the same as in Example B12;

[0227] Fluorinated vinyl ether compound: structural formula 1-6; 8 wt%;

[0228] Sulfonic acid additive: 1,3-propylene sultone; 2wt%;

[0229] Nitrile compound: succinonitrile; 2 wt%.

[0230] Example B17

[0231] The preparation was carried out according to the same operation as in Example B1, except that no nitrile compound was added to the electrolyte, and the content of propyl propionate (PP) was 22 wt %.

[0232] Comparative Example B1

[0233] The preparation was carried out according to the same operation as in Example B1, except that no fluorovinyl ether compound was added to the electrolyte, and the content of propyl propionate (PP) was 22 wt %.

[0234] Comparative Example B2

[0235] The preparation was carried out in the same manner as in Example B1. The difference from Example B7 was that the electrolyte

[0236] No sulfonic acid additive was added, and the content of propyl propionate (PP) was 22 wt %.

[0237] The types and contents of the fluorovinyl ether compounds in Examples B1 to 17 and Comparative Examples B1 to 2 are shown in Table 4.

[0238] Table 4

[0239] Preparation example of group B

[0240] Preparation of lithium-ion batteries

[0241] 1) Preparation of positive electrode sheet

[0242] The positive electrode active materials lithium cobalt oxide (LiCoO2), polyvinylidene fluoride (PVDF), SP (super P) and carbon nanotubes (CNT) are mixed in a mass ratio of 96:2:1.5:0.5, N-methylpyrrolidone (NMP) is added, and the mixture is stirred under the action of a vacuum mixer until the mixed system becomes a positive electrode active slurry with uniform fluidity; the positive electrode active slurry is evenly coated on both surfaces of an aluminum foil; the coated aluminum foil is dried, and then rolled and cut to obtain the desired positive electrode sheet.

[0243] 2) Negative electrode preparation

[0244] The negative electrode active materials artificial graphite, sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber, conductive carbon black (SP) and single-walled carbon nanotubes (SWCNTs) were mixed in a mass ratio of 94.5:2.5:1.5:1:0.5, deionized water was added, and a negative electrode active slurry was obtained under the action of a vacuum mixer; the negative electrode active slurry was evenly coated on both surfaces of the copper foil; the coated copper foil was dried at room temperature, then transferred to an 80°C oven for drying for 10 hours, and then cold pressed and slit to obtain the negative electrode sheet.

[0245] 3) The positive electrode sheet, negative electrode sheet, and separator prepared above were stacked in the order of positive electrode sheet, separator, and negative electrode sheet, and then wound to obtain a battery cell. The battery cell was placed in an outer packaging aluminum foil, and the electrolyte prepared in Example Group B and Comparative Example Group B was respectively injected into the outer packaging. After vacuum packaging, standing, formation, shaping, and sorting, different lithium-ion batteries were obtained. The battery of this group of examples had a charge and discharge range of 3.0-4.5V.

[0246] Group B test:

[0247] The lithium-ion batteries obtained from Example B and Comparative Example B were subjected to impedance EIS tests and low-temperature discharge tests, respectively. The test results are shown in Table 5.

[0248] 1) 0℃ impedance EIS test

[0249] The battery was left at 25°C for 1 hour, then charged and discharged at a rate of 1C, with a charge cutoff voltage of 4.5V and a cutoff current of 0.05C. After the charge cycle was complete, it was discharged with a discharge cutoff voltage of 3V, and the discharge capacity was recorded. After the first cycle of charge and discharge, the battery was recharged to 50% capacity and then left at 0°C for 12 hours. An EIS test was then performed on the battery, and the battery impedance value R was recorded. The results are shown in Table 5.

[0250] 2) Low temperature discharge performance test

[0251] Discharge the battery at 0.2C to the lower voltage limit at 25°C, with a cutoff current of 0.05C, and let it rest for 4 hours. Charge at 0.7C to the upper voltage limit, with a cutoff current of 0.05C, and let it rest for 4 hours. After standing in a constant temperature chamber at -20°C for 4 hours, discharge at 0.2C to the lower voltage limit and record the discharge capacity C1.

[0252] Then, the battery was placed at 25°C for 4 hours, charged at 0.7C to the upper voltage limit, and the cut-off current was 0.05C. After that, the battery was placed at 25°C for 4 hours in a constant temperature box and discharged at 0.2C to the lower voltage limit, and the discharge capacity C2 was recorded.

[0253] -20°C low-temperature discharge capacity retention rate = [-20°C discharge capacity C1 / 25°C discharge capacity C2] × 100%. The results are shown in Table 5.

[0254] Table 5

[0255] It can be seen from the test results that including fluorovinyl ether compounds and sulfonic acid additives in the electrolyte can significantly improve the battery impedance and also improve the low-temperature performance of the battery.

[0256] 3. Example C Group and Comparative Example C Group

[0257] Example C1

[0258] Preparation of lithium-ion batteries:

[0259] (1) Preparation of electrolyte: In a glove box filled with argon and with a qualified water and oxygen content, ethylene carbonate, propylene carbonate, propyl propionate and ethyl propionate were 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), 12 wt% of fluoroethylene carbonate and other additives (including fluorovinyl ether compounds, ether nitrile compounds and tetravinylsilane, the specific amounts and selections are shown in Table 6) were quickly added thereto to obtain an electrolyte.

[0260] (2) Preparation of positive electrode sheet:

[0261] 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, and N-methylpyrrolidone (NMP) is added and stirred under the action of a vacuum mixer until the mixed system becomes a positive electrode slurry with uniform fluidity; the positive electrode slurry is evenly coated on an aluminum foil with a thickness of 10 μm; the coated aluminum foil is baked in an oven, and then dried in an oven at 120°C for 8 hours, and then rolled and cut to obtain the required positive electrode sheet.

[0262] (3) Preparation of silicon-carbon negative electrode sheet:

[0263] A negative electrode slurry was prepared by a wet process using 97.0% by mass of a silicon-carbon negative electrode material (composite of SiO and graphite, with a SiO mass proportion 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 a sodium carboxymethyl cellulose (CMC) dispersant, and 1.1% by mass of a styrene-butadiene rubber (SBR) binder; the negative electrode slurry was evenly coated on a copper foil with a thickness of 10 μm; the coated copper foil was baked in an oven, dried in an oven at 85°C for 5 hours, and then rolled and slit to obtain the required silicon-carbon negative electrode sheet.

[0264] (4) Preparation of lithium-ion batteries

[0265] Take an 8μm thick polyethylene separator, and wind the prepared positive electrode sheet, separator, and negative electrode sheet to obtain a bare battery cell without liquid injection; place the bare battery cell in the outer packaging foil, and inject the prepared electrolyte into the dried bare battery cell. After vacuum packaging, standing, formation, shaping, sorting and other processes, the required lithium-ion battery is obtained.

[0266] Examples C2 to C11

[0267] The electrolyte and lithium-ion battery were prepared in the same manner as in Example C1, except that the type and content of the fluorovinyl ether compound, the content of the ether nitrile compound, and the content of tetravinylsilane were different. The specific amounts and selections are shown in Table 6.

[0268] Example C12

[0269] An electrolyte and a lithium-ion battery were prepared in the same manner as in Example C1, except that an additive, 1,3-propane sultone, was further added in Example C12. The type and content of the additive are shown in Table 6.

[0270] Example C13

[0271] An electrolyte and a lithium-ion battery were prepared in the same manner as in Example C1, except that an additive, lithium bis(oxalatoborate), was further added in Example C12. The type and content of the additive are shown in Table 6.

[0272] Comparative Example C1

[0273] The electrolyte and lithium-ion battery were prepared in the same manner as in Example C1, except that no ether nitrile compound and tetravinylsilane were added. The specific amounts and selections are shown in Table 6.

[0274] Comparative Example C2

[0275] The electrolyte and lithium-ion battery were prepared in the same manner as in Example C1, except that no fluorovinyl ether compound and tetravinylsilane were added. The specific amounts and selections are shown in Table 6.

[0276] Comparative Example C3

[0277] The electrolyte and lithium-ion battery were prepared in the same manner as in Example C1, except that no fluorovinyl ether compound and ether nitrile compound were added. The specific amounts and selections are shown in Table 6.

[0278] Comparative Example C4

[0279] The electrolyte and lithium-ion battery were prepared in the same manner as in Example C1, except that tetravinylsilane was not added. The specific amount and selection are shown in Table 6.

[0280] Comparative Example C5

[0281] The electrolyte and lithium-ion battery were prepared in the same manner as in Example C1, except that no ether nitrile compound was added. The specific amounts and selections are shown in Table 6.

[0282] Comparative Example C6

[0283] The electrolyte and lithium-ion battery were prepared in the same manner as in Example C1, except that no fluorovinyl ether compound was added. The specific amount and selection are shown in Table 6.

[0284] The types and contents of the components in the above Examples C1 to C13 and Comparative Examples C1 to C6 are shown in Table 6.

[0285] Table 6

[0286] Group C Test:

[0287] The electrochemical performance tests of the batteries obtained from the comparative example C group and the example C group were carried out, and the relevant descriptions are as follows:

[0288] (1) 25°C cycle experiment: The batteries prepared from the above Example C group and Comparative Example C group were placed in a (25±2)°C environment and left to stand for 2-3 hours. When the battery body reached (25±2)°C, the battery was charged at a 1C constant current with a cutoff current of 0.05C. After the battery was fully charged, it was left for 5 minutes and then discharged at a 0.7C constant current to a cutoff voltage of 3.0V. The highest discharge capacity of the first three cycles was recorded as the initial capacity Q, and the initial thickness T of the battery cell was recorded. When the cycle reached 1000 times, the last discharge capacity Q1 and battery thickness T1 of the battery were recorded. The recorded results are shown in Table 7.

[0289] The calculation formulas used are as follows: capacity retention rate (%) = Q1 / Q×100%; thickness change rate (%) = (T1-T) / T×100%.

[0290] (2) 140°C thermal shock test: The batteries prepared in Example C and Comparative Example C were heated in a convection or circulating hot air oven at a starting temperature of 25±3°C, a temperature gradient of 5±2°C / min, and the temperature was raised to 140±2°C. The temperature was maintained for 30 min before the test was terminated. The battery status results were recorded as shown in Table 7.

[0291] (3) Overcharge test: The batteries prepared in Example C and Comparative Example C were charged to 5 V at a constant current rate of 3 C, and the battery status was recorded. The results are shown in Table 7.

[0292] (4) Needle Puncture Test: The batteries obtained in Example C and Comparative Example C were punctured with a high-temperature resistant steel needle with a diameter of 5 to 8 mm (the cone angle of the needle tip was 45°C to 60°C, and the needle surface was smooth and free of rust, oxide layer, and oil stains) at a speed of (25±5) mm / s, perpendicular to the battery plate. The puncture position was preferably close to the geometric center of the punctured surface (the needle remained in the battery). The test was terminated after 1 hour or when the maximum surface temperature of the battery dropped to 10°C or below the peak temperature. The battery status results were recorded as shown in Table 7.

[0293] Table 7

[0294] The test results show that the batteries prepared with the electrolytes in Examples C1-C13 all passed the 140°C thermal shock test, overcharge test, and needle penetration test. Furthermore, the batteries prepared with the electrolytes in Examples C1-C13 maintained a capacity retention rate of over 80% after 1000 cycles at 25°C and 1C, demonstrating significant performance improvement compared to the test data in Comparative Example C. This demonstrates that the electrolytes suitable for silicon-carbon lithium-ion batteries provided by the present disclosure, through the synergistic effect of the additives, can provide silicon-carbon lithium-ion batteries with a long cycle life while also ensuring high safety performance.

[0295] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meanings understood by persons having ordinary skills in the field to which this disclosure belongs. The words "first", "second" and similar terms used in this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. The words "connected" or "connected" and similar terms are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship also changes accordingly.

[0296] The above is a preferred embodiment of the present disclosure. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles described in the present disclosure. These improvements and modifications should also be regarded as the scope of protection of the present disclosure.

Claims

1. An electrolyte, characterized in that: The electrolyte comprises: Electrolyte salt, solvent, fluorovinyl ether compound and first additive; Wherein, the structural formula of the fluorovinyl ether compound is as shown in 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; The first additive includes at least one of a sulfonic acid additive, an ether nitrile compound and a tetraenylsilane.

2. The electrolyte according to claim 1, characterized in that The content of the fluorovinyl ether compound is 0.1 wt% to 10 wt% of the total mass of the electrolyte.

3. The electrolyte according to claim 1 or 2, characterized in that The fluorovinyl ether compound includes at least one of the compounds shown in structural formula 1-1 to the compounds shown in structural formula 1-6:

4. The electrolyte according to any one of claims 1 to 3, characterized in that The solvent comprises at least one of a carbonate, a carboxylate and a fluoroether; Preferably, the carbonate comprises at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methylpropyl carbonate and ethylmethyl carbonate; Preferably, the carboxylic acid ester comprises at least one of propyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isopentyl acetate, propyl propionate, ethyl propionate, methyl butyrate and ethyl butyrate; Preferably, the fluoroether includes 1,1,2,3-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

5. The electrolyte according to any one of claims 1 to 4, characterized in that The electrolyte salt includes at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bis(trifluoromethylsulfonyl)imide, lithium difluorobis(oxalatophosphate), lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis(pentafluoroethylsulfonyl)imide, tris(trifluoromethylsulfonyl)methyllithium and lithium bis(trifluoromethylsulfonyl)imide.

6. The electrolyte according to any one of claims 1 to 5, characterized in that The sulfonic acid additive includes at least one of 1,3-propane sultone, 1-propylene-1,3-sultone, 5-methyloxathiolane 2,2-dioxide, 1,3-propylene sultone, 2,4-butane sultone and 1,4-butane sultone.

7. The electrolyte according to any one of claims 1 to 6, characterized in that The ether nitrile compound includes at least one of 1,2-bis(cyanoethoxy)ethane and 1,2,3-tris(2-cyanoethoxy)propane; and / or The structural formula of the tetraenylsilane is shown in formula (2): wherein R2 to R5 are each independently an alkyl chain having 0 to 15 carbon atoms and a degree of unsaturation of 0 to 6 or a phenyl group; Preferably, the tetraenylsilane comprises At least one of .

8. The electrolyte according to any one of claims 1 to 7, characterized in that The content of the electrolyte salt is 10 wt % to 20 wt % of the total mass of the electrolyte.

9. The electrolyte according to any one of claims 1 to 8, characterized in that The content of the sulfonic acid additive is 0.01wt% to 10wt% of the total mass of the electrolyte; and / or The content of the ether nitrile compound is 0.5wt% to 5wt% of the total mass of the electrolyte; and / or The content of the tetraenylsilane is 0.2 wt% to 2 wt% of the total mass of the electrolyte.

10. The electrolyte according to any one of claims 1 to 9, characterized in that The electrolyte also includes a nitrile compound; Preferably, the nitrile compound includes at least one of adiponitrile, succinonitrile and 1,3,6-hexanetrinitrile.

11. The electrolyte according to claim 10, characterized in that The nitrile compound accounts for 0.01 wt% to 8 wt% of the total mass of the electrolyte.

12. The electrolyte according to any one of claims 1 to 11, characterized in that The electrolyte further comprises a second additive; the second additive comprises at least one of vinyl sulfite, vinyl sulfate, vinyl carbonate, fluoroethylene carbonate, lithium dioxalatoborate, lithium difluorooxalatoborate, lithium difluorooxalatophosphate and vinyl vinyl carbonate.

13. The electrolyte according to claim 12, characterized in that The content of the second additive is 0wt% to 20wt% of the total mass of the electrolyte.

14. A battery, characterized in that: The battery comprises: The electrolyte according to any one of claims 1 to 13; A positive electrode sheet containing a positive electrode active material; A negative electrode sheet containing a negative electrode active material; Isolation film.

15. The battery according to claim 14, characterized in that The negative electrode active material includes a carbon-based negative electrode material and / or a silicon-based negative electrode material; Preferably, the carbon-based negative electrode material includes at least one of artificial graphite, natural graphite, mesophase carbon microbeads, hard carbon and soft carbon; Preferably, 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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