Electrolyte, battery and electronic equipment

Abstract

The invention provides an electrolyte which comprises an electrolyte salt, an organic solvent and a functional additive as shown in a formula (I), and also provides a battery comprising the electrolyte and electronic equipment comprising the battery. The compound as shown in the formula (I) is used as a functional additive of the electrolyte, so that the interface impedance can be reduced, the side reaction of the electrolyte at a positive and negative electrode interface can be inhibited, and the consumption and decomposition of the electrolyte and the damage to a positive electrode structure in a battery cycle process can be reduced, thereby improving the cycle performance and coulombic efficiency of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to an electrolyte, a battery and an electronic device. BACKGROUND

[0002] Compared with other batteries, lithium ion batteries have the advantages of high energy density, high working voltage and long cycle life, and have been widely concerned and applied in the fields of 3C digital products, electric tools and energy storage. However, with the continuous improvement of market demand, the requirement for electrochemical energy storage is increasing, which promotes people to urgently develop high-energy-density lithium ion batteries, and the application of high-voltage positive electrode materials is the most effective way to improve the energy density of lithium ion batteries.

[0003] At present, the commercial lithium ion battery electrolyte is composed of lithium hexafluorophosphate and carbonate solvent, which will undergo serious oxidative decomposition when the voltage exceeds 4.3V. Therefore, in order to improve the performance of lithium ion batteries under high voltage conditions, more new high-voltage additives need to be developed in order to form a good interface, inhibit the side reaction of electrolyte and positive and negative electrode materials, and better realize the cycle stability of high-voltage batteries and the commercialization of high-energy-density batteries. However, the stability of the interface film generated by the commonly used electrolyte additives under high voltage still cannot meet the requirements, and the additives that can form a stable interface film will increase the impedance of the battery, resulting in the inability to compromise other performance of lithium ion batteries. SUMMARY

[0004] Based on this, the present application provides an electrolyte which can form a stable interface film on the surface of the positive and negative electrodes, improve the cycle life of the battery under high voltage, and also reduce the interface impedance of the battery.

[0005] The present application provides an electrolyte, which comprises an electrolyte salt, an organic solvent and a functional additive as shown in formula (I):

[0006]

[0007] In formula (I), R1 is selected from C 1～10 alkyl, C 1～10 alkyl, C 2～10 alkyl, C 2～10 alkyl, C

[0008] R2 is selected from C 1～10 alkyl, C 1～10 alkyl, C 2～10 alkyl, C 2～10 alkyl, C 2～10 alkyl, C2～10 alkyl, -OS(O)2-C 6～12 aryl, or -OS(O)2-C 6～12 aryl; the substituent is selected from halogen or cyano.

[0009] The present application takes the compound as shown in formula (I) as a functional additive of electrolyte, and the substituent directly connected with the sulfur atom is C 1～10 alkyl, C 1～10 alkyl, C 2～10 alkenyl, C 2～10 alkenyl, C 2～10 alkynyl, C 2～10 alkynyl, -S(O)2-C 6～12 aryl, or -S(O)2-C 6～12 When the substituent is aryl, compared with the compound in which the substituent is phenyl, the interface impedance can be further reduced, the side reaction of the electrolyte at the interface of the positive and negative electrodes can be inhibited, the consumption, decomposition and damage to the positive electrode structure of the electrolyte during the battery cycle can be reduced, and thus the cycle performance and coulombic efficiency of the battery can be improved.

[0010] In some specific implementations, the functional additive has a structure of formula (2), formula (3), formula (4), formula (5) or formula (6):

[0011]

[0012] In the compound shown in formula (I), the introduction of a trifluoromethyl (-CF3) functional group can produce an interface film rich in lithium fluoride (LiF), and further improve the cycle performance and coulombic efficiency of the battery.

[0013] In some specific implementations, the electrolyte further includes a conventional additive selected from fluoroethylene carbonate (FEC), 1,3 propane sultone (PS), adiponitrile (ADN), succinonitrile (SN), ethylene glycol bis (propionitrile) ether (DENE) or 1,3,6 hexanetricarbonitrile (HTCN), etc. The functional additive shown in formula (I) and the above conventional additive can synergistically inhibit the side reaction of the electrolyte at the interface of the positive and negative electrodes, and improve the cycle performance and coulombic efficiency of the battery.

[0014] The present application provides a battery including a positive electrode, a negative electrode, a separator arranged between the positive electrode and the negative electrode, and the electrolyte of the above technical solution. The battery provided by the present application has low interface impedance, good cycle efficiency and high coulombic efficiency.

[0015] The application also provides an electronic device comprising the battery described in the technical scheme. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 Cycle life curve of the electrolyte prepared in Example 1 in Gr / LCO button cell;

[0017] Figure 2 Charge-discharge curve of the electrolyte prepared in Example 1 in Gr / LCO button cell;

[0018] Figure 3 Cycle life curve of the electrolyte prepared in Example 2 in Gr / LCO button cell.

[0019] Figure 4 Charge-discharge curve of the electrolyte prepared in Example 2 in Gr / LCO button cell.

[0020] Figure 5 Cycle life curve of the electrolyte prepared in Example 3 in Gr / LCO button cell.

[0021] Figure 6 Charge-discharge curve of the electrolyte prepared in Example 3 in Gr / LCO button cell.

[0022] Figure 7 Cycle life curve of the electrolyte prepared in Example 4 in Gr / LCO button cell.

[0023] Figure 8 Charge-discharge curve of the electrolyte prepared in Example 4 in Gr / LCO button cell.

[0024] Figure 9 Cycle life curve of the electrolyte prepared in Example 5 in Gr / LCO button cell.

[0025] Figure 10 Charge-discharge curve of the electrolyte prepared in Example 5 in Gr / LCO button cell.

[0026] Figure 11 Cycle life curve of the electrolyte prepared in Example 6 in Gr / LCO button cell.

[0027] Figure 12 Charge-discharge curve of the electrolyte prepared in Example 6 in Gr / LCO button cell.

[0028] Figure 13 Cycle life curve of the electrolyte prepared in Example 7 in Gr / LCO button cell.

[0029] Figure 14 Charge-discharge curve of electrolyte prepared in Example 7 in Gr / LCO coin cell;

[0030] Figure 15 Cycle life curve of electrolyte prepared in Example 8 in Gr / LCO coin cell;

[0031] Figure 16 Charge-discharge curve of electrolyte prepared in Example 8 in Gr / LCO coin cell;

[0032] Figure 17 Cycle life curve of electrolyte prepared in Example 9 in Gr / LCO coin cell;

[0033] Figure 18 Charge-discharge curve of electrolyte prepared in Example 9 in Gr / LCO coin cell;

[0034] Figure 19 Cycle life curve of electrolyte prepared in Example 10 in Gr / LCO coin cell;

[0035] Figure 20 Charge-discharge curve of electrolyte prepared in Example 10 in Gr / LCO coin cell;

[0036] Figure 21 Cycle life curve of electrolyte prepared in Example 11 in Gr / LCO coin cell;

[0037] Figure 22 Charge-discharge curve of electrolyte prepared in Example 11 in Gr / LCO coin cell;

[0038] Figure 23 Cycle life curve of electrolyte prepared in Example 12 in Gr / LCO coin cell;

[0039] Figure 24 Charge-discharge curve of electrolyte prepared in Example 12 in Gr / LCO coin cell;

[0040] Figure 25 Cycle life curve of electrolyte prepared in Example 13 in Gr / LCO coin cell;

[0041] Figure 26 Charge-discharge curve of electrolyte prepared in Example 13 in Gr / LCO coin cell;

[0042] Figure 27Cycle life plot for electrolyte prepared in Example 14 in Gr / LCO coin cell;

[0043] Figure 28 Charge-discharge plot for electrolyte prepared in Example 14 in Gr / LCO coin cell;

[0044] Figure 29 Cycle life plot for electrolyte prepared in Comparative Example 1 in Gr / LCO coin cell;

[0045] Figure 30 Charge-discharge plot for electrolyte prepared in Comparative Example 1 in Gr / LCO coin cell;

[0046] Figure 31 Cycle life plot for electrolyte prepared in Comparative Example 2 in Gr / LCO coin cell;

[0047] Figure 32 Charge-discharge plot for electrolyte prepared in Comparative Example 2 in Gr / LCO coin cell.

[0048] Figure 33 Cycle life plot for electrolyte prepared in Comparative Example 3 in Gr / LCO coin cell.

[0049] Figure 34 Charge-discharge plot for electrolyte prepared in Comparative Example 3 in Gr / LCO coin cell. DETAILED DESCRIPTION

[0050] In the present embodiments, the word "exemplary" or "for example" is used to mean serving as an example, instance, or illustration. Any embodiment or design described herein as "exemplary" or "for example" should not be construed as preferred or advantageous over other embodiments or designs. Rather, the exemplary or for example embodiments are presented so as to enable a clear and concise disclosure of the present embodiments. Expressions such as "example," "for example," "e.g.," "for instance" and the like are intended to mean that the item(s) in question is an example, instance, or illustration.

[0051] Unless otherwise defined, technical terms or scientific terms used in the present application shall have the same meaning as those commonly understood by a person of ordinary skill in the art to which the present application belongs. The terms "first", "second", and similar terms in the present application do not denote any order, quantity, or importance, but are used to distinguish different components. Similarly, the terms "one", "a", or "the" do not denote a quantity restriction, but mean that there is at least one. The terms "include", "comprise", and similar terms mean that the elements or objects before the terms encompass the elements or objects listed after the terms and their equivalents, and do not exclude other elements or objects. The terms "connect" or "connected" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms "upper", "lower", "left", "right", and the like are used only to represent relative positional relationships, and when the absolute positions of the described objects are changed, the relative positional relationships can also be changed accordingly.

[0052] The currently used electrolyte additives either cannot improve the cycle performance of the battery or, although they can improve the cycle performance of the battery, they increase the impedance of the battery. For example, the cycle number of a LiCoO2 / Li button cell with lithium hexafluorophosphate as the electrolyte is only 188 cycles when the capacity retention rate is 80% without adding an additive; when 1,3,6-hexanetricarbonitrile is added to the electrolyte, not only cannot it improve the cycle number when the capacity retention rate is 80%, but also increases the impedance of the battery; when butanedinitrile is added to the electrolyte, it has no significant effect on the impedance of the battery, but it also cannot improve the cycle number when the capacity retention rate is 80%; when 2,2-trifluoroethoxysulfonylbenzene is added to the electrolyte, although it can improve the cycle number when the capacity retention rate is 80%, it increases the impedance of the battery; when hexanedinitrile is added to the electrolyte, although it can improve the cycle number when the capacity retention rate is 80%, it increases the impedance of the battery.

[0053] Based on this, the present application provides an electrolyte, comprising an electrolyte salt, an organic solvent, and a functional additive as shown in formula (I):

[0054]

[0055] In formula (I), R1 is selected from C 1～10 alkyl, C 1～10 alkyl, C 2～10 alkyl, C 2～10 alkyl, C

[0056] R2 is selected from C 1～10 alkyl, C 1～10 alkyl, C 2～10alkenyl, C 2～10 alkenyl, C 2～10 alkynyl, C 2～10 alkynyl, -OS(O)2-C 6～12 aryl, or -OS(O)2-C 6～12 aryl; the substituent is selected from halogen or cyano.

[0057] The present application uses a compound as shown in formula (I) as a functional additive of electrolyte, and the substituent directly connected with the sulfur atom is C 1～10 alkyl, C 1～10 alkyl, C 2～10 alkenyl, C 2～10 alkenyl, C 2～10 alkynyl, C 2～10 alkynyl, -OS(O)2-C 6～12 aryl, or -OS(O)2-C 6～12 aryl, compared with the compound in which the substituent is phenyl, can further reduce the interface impedance, inhibit the side reaction of electrolyte at the interface of positive and negative electrodes, reduce the consumption, decomposition and damage to the structure of positive electrode of electrolyte in the battery cycle process, thereby improving the cycle performance and coulombic efficiency of the battery.

[0058] In some specific implementations, R1 is selected from C 1～6 alkyl, C 1～6 alkyl, C 2～6 alkenyl, C 2～6 alkenyl or pyridyl; R2 is selected from C 1～6 alkyl, C 1～6 alkyl, C 2～6 alkenyl, C 2～6 alkenyl, C 2～6 alkynyl, C 2～6 alkynyl, -OS(O)2-C 6～10 aryl, or -OS(O)2-C 6～10 aryl; the substituent is selected from halogen or cyano, wherein halogen includes Br, Cl, I or F.

[0059] In some specific implementations, R1 is selected from C 1～3 alkyl, C 1～3 alkyl, C 2～3 alkenyl, C 2～3alkenyl, C 1～3 alkyl, C 1～3 alkyl, C 2～3 alkenyl, C 2～3 alkenyl, C 2～3 alkynyl, C 2～3 alkynyl, -OS(O)2-C 6～8 aryl, or -OS(O)2-C 6～8 aryl.

[0060] In some specific embodiments, in formula (I), at least one of R1and R2is selected from fluorine-substituted alkyl. The fluorine-containing functional group is advantageous for generating a lithium fluoride (LiF)-rich interface film, further improving the cycle performance and coulombic efficiency of the battery. In some specific embodiments, at least one of R1and R2is selected from alkyl containing a trifluoromethyl group.

[0061] In some specific embodiments, the functional additive has a structure of formula (2), formula (3), formula (4), formula (5), or formula (6):

[0062]

[0063] The source of the functional additive is not particularly limited in the present application, and can be prepared by known methods in the art or purchased through commercial channels.

[0064] In some specific embodiments, the functional additive accounts for 0.1wt% to 10wt% of the electrolyte, for example, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, 2wt%, 2.2wt%, 2.5wt%, 2.8wt%, 3wt%, 3.3wt%, 3.5wt%, 3.8wt%, 4wt%, 4.2wt%, 4.5wt%, 4.8wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, or 10wt%, preferably 0.2wt% to 5wt%, more preferably 0.2wt% to 2.5wt%. When the amount of the functional additive is higher than 10wt%, the improvement effect on the battery performance is poor. When the amount of the functional additive is lower than 0.1wt%, the improvement effect is not obvious.

[0065] The electrolyte provided by the present application uses an organic solvent as a solvent, which is not particularly limited in the present application, including but not limited to carbonates and carboxylic acid esters, wherein the carbonates include but are not limited to the following solvents which are fluorine-substituted or unsubstituted: ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC); the carboxylic acid esters include but are not limited to the following solvents which are fluorine-substituted or unsubstituted: propyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isoamyl acetate, propyl propionate (PP), ethyl propionate, methyl butyrate, and ethyl n-butyrate. In the present application, the organic solvent can be one or more of the above-mentioned compounds, and when it is a combination of multiple substances, the content of each specific substance is not particularly limited in the present application. In some specific implementations, the organic solvent is EC, PC, PP, and DEC. In some specific implementations, the mass ratio of EC, PC, PP, and DEC is 15:10:40:10.

[0066] The electrolyte provided by the present application includes an electrolyte, which is not particularly limited in the present application and can be a lithium salt or a sodium salt. In some specific implementations, the electrolyte is a lithium salt, which includes but is not limited to lithium tetrafluoroborate, lithium hexafluorophosphate, lithium nitrate, lithium difluoro(oxalato)borate, bis(oxalato)borate, bis(difluorosulfonyl)imide lithium, lithium perchlorate, bis(trifluoromethylsulfonyl)imide lithium, and lithium difluorophosphate, and can be one or more of inorganic anion lithium salts and organic anion lithium salts, and when it is a combination of multiple substances, the content of each specific substance is not particularly limited in the present application. In some specific implementations, the electrolyte is preferably lithium hexafluorophosphate. In some specific implementations, in the electrolyte, the concentration of the electrolyte salt is 0.1 mol / L to 3.0 mol / L, for example, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, and the like, and is preferably 0.5 mol / L to 2.5 mol / L.

[0067] In some embodiments, the electrolyte further comprises an additive. The functional additive of formula (I) can synergize with conventional additives to inhibit side reactions of the electrolyte at the interface between the positive and negative electrodes, and improve the cycle performance and coulombic efficiency of the battery. In some embodiments, the additive comprises, but is not limited to, fluoroethylene carbonate (FEC), 1,3-propane sultone (PS), adiponitrile (ADN), succinonitrile (SN), ethylene glycol bis(propionitrile) ether (DENE), or 1,3,6-hexanetricarbonitrile (HTCN), etc., which can be one or more of them, and when they are a combination of multiple substances, the content of each specific substance is not particularly limited in the present application. In some embodiments, the additive is 0.1wt% to 10wt% of the electrolyte, preferably 0.5wt% to 5wt%. In some embodiments, the additive is PS, FEC and ADN, and the mass ratio of PS, FEC and ADN is 2:5:1.

[0068] The method for preparing the electrolyte is not particularly limited in the present application, and can be prepared according to methods familiar to those skilled in the art, for example, in an inert gas-filled glove box (O2<0.1ppm, H2O<0.1ppm), organic solvents are mixed according to the volume ratio, then the electrolyte salt is slowly added to the mixed solution to obtain the base electrolyte, and then the functional additive is added to the base electrolyte to obtain the electrolyte. When the electrolyte further comprises a conventional additive, the conventional additive is first added after the electrolyte salt is added, and then the functional electrolyte is added.

[0069] The present application also provides a battery comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and the electrolyte of the above technical solution.

[0070] The battery comprises a positive electrode, which comprises a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector. In some embodiments, the positive electrode current collector can be a metal foil, including but not limited to aluminum foil, nickel foil, stainless steel, etc., for example, the positive electrode current collector can be aluminum foil. The positive electrode current collector is provided with a positive electrode active material layer, which comprises a positive electrode material, an optional conductive agent and an optional binder. In some embodiments, the mass ratio of the positive electrode material, the conductive agent and the binder is 70-99.8:0.1-15:0.1-15, preferably 75-95:1-10:1-10, more preferably 80-90:2-8:2-8. In some embodiments, the positive electrode material comprises, but is not limited to, lithium cobaltate (LiCoO2), lithium manganate (LiMn2O4), lithium iron phosphate (LiFePO4), ternary material, LiNi x Co y Mn 1-x-y O2、 、Li(Ni 0.5 Mn 0.5 ) x Fe 1-x O2, Li3V2(PO4)3, Li2FeFe(CN)6, etc., one or more of which can be used, and when the positive electrode material is a mixture of multiple specific substances, the present application does not make too many limitations on the ratio between the specific substances. In some specific implementations, the conductive agent includes but is not limited to conductive carbon black, acetylene black, ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, metal powder, carbon fiber, etc., one or more of which can be used, and when the conductive agent is a mixture of multiple specific substances, the present application does not make too many limitations on the ratio between the specific substances. The binder includes but is not limited to polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, polyamide, lithium polyacrylate, methacrylate, sodium polymethyl cellulose, aluminum dihydrogen phosphate, etc., one or more of which can be used, and when the binder is a mixture of multiple specific substances, the present application does not make too many limitations on the ratio between the specific substances.

[0071] The present application does not have special limitations on the preparation method of the positive electrode. The positive electrode material, optional conductive agent and optional binder are mixed uniformly in a solvent, such as N-methyl pyrrolidone (NMP), and coated on the positive electrode current collector in an optional manner. After drying, the positive electrode is obtained. Further, after drying, it also includes rolling, slicing, etc., which are not specially limited by the present application.

[0072] The battery comprises a negative electrode, which comprises a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector. In some specific implementations, the negative electrode current collector can be a metal foil, including but not limited to an aluminum foil, a nickel foil, a stainless steel, etc. For example, the negative electrode current collector can be an aluminum foil. The negative electrode current collector is provided with a negative electrode active material layer, which comprises a negative electrode material, an optional conductive agent, an optional binder, and an optional thickening agent. In some specific implementations, the mass ratio of the negative electrode material, the conductive agent, the binder, and the thickening agent is 70-99.8:0.1-15:0.1-15, preferably 75-95:1-10:1-10, and more preferably 80-95:2-8:1-5. In some specific implementations, the negative electrode material includes but is not limited to a mesocarbon microbead, artificial graphite, natural graphite, hard carbon, soft carbon, lithium titanate, silicon-based composite material, tin-based composite material, and can be one or more of them. When the negative electrode material is a mixture of multiple specific substances, the present application does not make too many limitations on the ratio between the specific substances. In some specific implementations, the conductive agent includes but is not limited to conductive carbon black, acetylene black, ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, metal powder, carbon fiber, etc., and can be one or more of them. When the conductive agent is a mixture of multiple specific substances, the present application does not make too many limitations on the ratio between the specific substances. The binder includes but is not limited to styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC-Na), polyacrylic acid (PAA), polytetrafluoroethylene (PTFE), polyimide (PI), etc., and can be one or more of them. When the binder is a mixture of multiple specific substances, the present application does not make too many limitations on the ratio between the specific substances. The thickening agent includes but is not limited to sodium hydroxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC-Na), polyacrylic acid (PAA), polytetrafluoroethylene (PTFE), polyimide (PI), etc., and can be one or more of them. When the thickening agent is a mixture of multiple specific substances, the present application does not make too many limitations on the ratio between the specific substances.

[0073] The present application does not make special limitations on the preparation method of the negative electrode. The negative electrode material, the optional conductive agent, the optional binder, and the optional thickening agent are uniformly mixed in a solvent, such as deionized water, coated on the negative electrode current collector in an optional manner, and dried to obtain the negative electrode. Further, after drying, it also includes rolling, slicing, etc., and the present application does not make special limitations thereon.

[0074] In some specific implementations, the separator includes but is not limited to a glass fiber microporous membrane, a polyester microporous membrane, a polyethylene microporous membrane, a polypropylene microporous membrane, a polytetrafluoroethylene microporous membrane, a ceramic-coated separator, etc.

[0075] In some specific implementations, the electrode liquid, as described above, is added with the compound additive of formula (I), which can reduce the interface impedance, inhibit the side reaction of the electrolyte at the positive and negative electrode interface, significantly improve the stability of the electrolyte and the electrode interface, reduce the consumption, decomposition and damage to the positive electrode structure of the electrolyte during the battery cycle, thereby improving the cycle performance and coulombic efficiency of the battery.

[0076] The present application stacks the positive electrode sheet, the separator and the negative electrode sheet in sequence to obtain a battery cell assembly, seals it in an aluminum plastic bag, and injects electrolyte, and after packaging, standing, formation and other processes, a lithium ion battery is obtained.

[0077] The present application also provides an electronic device comprising the battery of the above technical solution. The electronic device provided by the present application includes but is not limited to notebook computers, mobile phones, tablet computers, smart watches, digital cameras, MP3 and other products that require battery to provide endurance capability. The electronic device comprises the battery with excellent cycle performance, and can have a longer service life.

[0078] The electrolyte, battery and electronic device provided by the present application are further described below in combination with examples.

[0079] The experimental methods used in the following examples are conventional methods unless otherwise specified; the reagents, materials, etc. used in the following examples can be obtained from commercial channels unless otherwise specified.

[0080] In the following examples, the preparation method of the lithium ion battery comprises:

[0081] (1) Preparation of positive electrode sheet:

[0082] Lithium cobalt oxide (LiCoO2, LCO), binder polyvinylidene fluoride (PVDF) and conductive carbon black were added to an appropriate amount of N-methyl pyrrolidone (NMP) in a mass ratio of 90:5:5, uniformly mixed to obtain a slurry, then uniformly coated on an aluminum foil current collector, dried at 110°C, and then cut to obtain the required positive electrode sheet.

[0083] (2) Preparation of negative electrode sheet:

[0084] Artificial graphite (graphite, Gr), binder polyacrylonitrile (LA133) and conductive carbon black were added to deionized water in a mass ratio of 93:5:2, uniformly mixed to obtain a slurry, then uniformly coated on a copper foil current collector, dried at 90°C, and then cut to obtain the required negative electrode sheet.

[0085] (3) Preparation of electrolyte:

[0086] In the glove box (O2<0.1ppm, H2O<0.1ppm), the organic solvent was mixed according to the volume ratio, then the lithium salt was slowly added to the mixed solution to obtain the base electrolyte, and different contents of additives were added to the base electrolyte to obtain the electrolyte of the corresponding examples and comparative examples.

[0087] (4) Battery assembly:

[0088] In the glove box (O2<0.1ppm, H2O<0.1ppm), the positive shell-positive sheet-separator-negative sheet-stainless steel sheet-spring sheet-negative shell were assembled in order to form a button cell, and an appropriate amount of electrolyte was added, and finally packaged to obtain the corresponding test battery.

[0089] (5) Battery test:

[0090] The Gr||LCO (3V~4.55V) button cell assembled by the examples and comparative examples was activated for 2 cycles at room temperature (25℃) at 0.1C rate, and then the direct current resistance (DCR) of the button cell at 50% state of charge (SOC) was tested, and then the long cycle test was carried out at 0.5C rate, and the cycle number corresponding to the cycle capacity retention rate decayed to 80% was recorded.

[0091] Example 1

[0092] LiPF6 was slowly dissolved in solvents EC, PC, PP and DEC to make the mass ratio of LiPF6, EC, PC, PP and DEC 15:15:10:40:10, and then an appropriate amount of additives PS, FEC, ADN, etc. was slowly added to make PS, FEC and ADN account for 2%, 5% and 1% of the total mass of the electrolyte, respectively, to prepare the reference electrolyte;

[0093] The functional additive represented by formula (2) was added to the reference electrolyte, and the functional additive accounted for 0.2% of the total mass of the electrolyte, and was mixed uniformly until completely dissolved to obtain the electrolyte.

[0094]

[0095] The electrolyte was prepared into a battery according to the above scheme, and its performance was tested, and the results are shown in Figure 1 , Figure 2 and Table 1, Figure 1 is the cycle life curve of the electrolyte prepared in Example 1 in Gr / LCO button cell, Figure 2 is the charge-discharge curve of the electrolyte prepared in Example 1 in Gr / LCO button cell, Table 1 is the amount of additives and the cycle performance of the battery of the examples and comparative examples, and Table 2 is the direct current resistance test results of the batteries of the examples and comparative examples.

[0096] Table 1: Amount of additives and battery cycle performance of examples and comparative examples

[0097]

[0098]

[0099] Table 2: Battery DC impedance test results of examples and comparative examples

[0100] Example 25 °C cell direct current impedance (Ω) 1 9.2 2 8.7 3 8.1 4 7.5 5 9.0 6 8.3 7 7.6 8 7.1 9 9.5 10 8.9 11 8.3 12 8.0 13 7.4 14 7.3 Comparative Example 1 10.8 Comparative Example 2 9.2 Comparative Example 3 9.6

[0101] By Figure 1 And Figure 2 It can be seen that the capacity retention of the above-mentioned electrolyte is attenuated to 80% after 469 cycles at a charge cut-off voltage of 4.55V, and the average coulombic efficiency is close to 100%.

[0102] Example 2

[0103] The difference from Example 1 is that the amount of functional additive is 0.5%, and the results are shown in Figure 3 , Figure 4 , Table 1 and Table 2, Figure 3 is the cycle life curve of the electrolyte prepared in Example 2 in Gr / LCO button cell, Figure 4 is the charge-discharge curve of the electrolyte prepared in Example 2 in Gr / LCO button cell, which is shown in Figure 3 And Figure 4 It can be seen that the capacity retention of the above-mentioned electrolyte is attenuated to 80% after 402 cycles at a charge cut-off voltage of 4.55V.

[0104] Example 3

[0105] The difference from Example 1 is that the amount of functional additive is 1%, and the results are shown in Figure 5 , Figure 6 , Table 1 and Table 2, Figure 5 is the cycle life curve of the electrolyte prepared in Example 3 in Gr / LCO button cell, Figure 6 is the charge-discharge curve of the electrolyte prepared in Example 3 in Gr / LCO button cell, which is shown in Figure 5 And Figure 6 It can be seen that the capacity retention of the above-mentioned electrolyte is attenuated to 80% after 378 cycles at a charge cut-off voltage of 4.55V.

[0106] Example 4

[0107] The difference from Example 1 is that the amount of functional additive is 1.5%, and the results are shown in Figure 7 , Figure 8Tables 1 and 2 Figure 7 This is a cycle life curve of the electrolyte prepared in Example 4 in a Gr / LCO coin cell. Figure 8 This is a charge-discharge curve of the electrolyte prepared in Example 4 in a Gr / LCO coin cell, from... Figure 7 and Figure 8 It can be seen that after the electrolyte is cycled for 254 cycles at a charging cutoff voltage of 4.55V, the capacity retention rate decreases to 80%.

[0108] Example 5

[0109] The difference from Example 1 is that the functional additive is as shown in Formula (3), with the Chinese name: 2,2,2-trifluoroethyltrifluoromethane sulfonate. See the results below. Figure 9 , Figure 10 Tables 1 and 2 Figure 9 This is a cycle life curve of the electrolyte prepared in Example 5 in a Gr / LCO coin cell. Figure 10 This is a charge-discharge curve of the electrolyte prepared in Example 5 in a Gr / LCO coin cell, from... Figure 9 and Figure 10 It can be seen that after the electrolyte is cycled for 274 cycles at a charging cutoff voltage of 4.55V, the capacity retention rate decreases to 80%.

[0110]

[0111] Example 6

[0112] The difference from Example 5 is that the amount of functional additive used is 0.5%, and the results are shown in [link to example]. Figure 11 , Figure 12 Tables 1 and 2 Figure 11 This is a cycle life curve of the electrolyte prepared in Example 6 in a Gr / LCO coin cell. Figure 12 This is a charge-discharge curve of the electrolyte prepared in Example 6 in a Gr / LCO coin cell, from... Figure 11 and Figure 12 It can be seen that after the electrolyte is cycled for 378 cycles at a charging cutoff voltage of 4.55V, the capacity retention rate decreases to 80%.

[0113] Example 7

[0114] The difference from Example 5 is that the amount of functional additive used is 1.0%, and the results are shown in [link to example]. Figure 13 , Figure 14 Tables 1 and 2 Figure 13 This is a cycle life curve of the electrolyte prepared in Example 7 in a Gr / LCO coin cell. Figure 14The charge-discharge curve of the electrolyte prepared in Example 8 in Gr / LCO button cell is shown in Figure 8, and the cycle life curve is shown in Figure 9. Figure 13 and Figure 14 It can be seen that the capacity retention of the above electrolyte decays to 80% after 265 cycles at the charge cut-off voltage of 4.55V.

[0115] Example 8

[0116] The difference from Example 5 is that the amount of functional additive is 1.5%, and the results are shown in Figure 15 , Figure 16 , Table 1 and Table 2, Figure 15 The cycle life curve of the electrolyte prepared in Example 8 in Gr / LCO button cell is shown in Figure 8, Figure 16 The charge-discharge curve of the electrolyte prepared in Example 8 in Gr / LCO button cell is shown in Figure 9, and the cycle life curve is shown in Figure 10. Figure 15 and Figure 16 It can be seen that the capacity retention of the above electrolyte decays to 80% after 265 cycles at the charge cut-off voltage of 4.55V.

[0117] Example 9

[0118] The difference from Example 1 is that the functional additive is shown as formula (4), and the Chinese name is 2,2,2-trifluoroethyl methyl sulfonate, and the results are shown in Figure 17 , Figure 18 , Table 1 and Table 2, Figure 17 The cycle life curve of the electrolyte prepared in Example 9 in Gr / LCO button cell is shown in Figure 8, Figure 18 The charge-discharge curve of the electrolyte prepared in Example 9 in Gr / LCO button cell is shown in Figure 9, and the cycle life curve is shown in Figure 10. Figure 17 and Figure 18 It can be seen that the capacity retention of the above electrolyte decays to 80% after 239 cycles at the charge cut-off voltage of 4.55V.

[0119]

[0120] Example 10

[0121] The difference from Example 9 is that the amount of functional additive is 0.5%, and the results are shown in Figure 19 , Figure 20 , Table 1 and Table 2, Figure 19 The cycle life curve of the electrolyte prepared in Example 10 in Gr / LCO button cell is shown in Figure 8, Figure 20 The charge-discharge curve of the electrolyte prepared in Example 10 in Gr / LCO button cell is shown in Figure 9, and the cycle life curve is shown in Figure 10. Figure 19 and Figure 20It can be seen that the capacity retention of the above electrolyte is attenuated to 80% after 261 cycles at a charge cut-off voltage of 4.55V.

[0122] Example 11

[0123] The difference from Example 9 is that the amount of functional additive is 1%, and the results are shown in Figure 21 , Figure 22 , Table 1 and Table 2, Figure 21 is the cycle life curve of the electrolyte prepared in Example 11 in Gr / LCO button cell, Figure 22 is the charge-discharge curve of the electrolyte prepared in Example 11 in Gr / LCO button cell, which is shown in Figure 21 and Figure 22 It can be seen that the capacity retention of the above electrolyte is attenuated to 80% after 323 cycles at a charge cut-off voltage of 4.55V.

[0124] Example 12

[0125] The difference from Example 9 is that the amount of functional additive is 1.5%, and the results are shown in Figure 23 , Figure 24 , Table 1 and Table 2, Figure 23 is the cycle life curve of the electrolyte prepared in Example 12 in Gr / LCO button cell, Figure 24 is the charge-discharge curve of the electrolyte prepared in Example 12 in Gr / LCO button cell, which is shown in Figure 23 and Figure 24 It can be seen that the capacity retention of the above electrolyte is attenuated to 80% after 428 cycles at a charge cut-off voltage of 4.55V.

[0126] Example 13

[0127] The difference from Example 3 is that the functional additive is as shown in formula (5), and the Chinese name is 3-butyryl trifluorosulfonate, and the results are shown in Figure 25 , Figure 26 , Table 1 and Table 2, Figure 25 is the cycle life curve of the electrolyte prepared in Example 13 in Gr / LCO button cell, Figure 26 is the charge-discharge curve of the electrolyte prepared in Example 13 in Gr / LCO button cell, which is shown in Figure 25 and Figure 26 It can be seen that the capacity retention of the above electrolyte is attenuated to 80% after 293 cycles at a charge cut-off voltage of 4.55V.

[0128]

[0129] Example 14

[0130] The difference from Example 3 is that the functional additive is as shown in formula (6), wherein the Chinese name is ethylenesulfonated neopentyl, and the results are shown in Figure 27 , Figure 28 Table 1 and Table 2, Figure 27 is a cycle life curve of the electrolyte prepared in Example 14 in a Gr / LCO button cell, Figure 28 is a charge-discharge curve of the electrolyte prepared in Example 14 in a Gr / LCO button cell, which is Figure 27 and Figure 28 It can be seen that the capacity retention of the above electrolyte decays to 80% after 346 cycles at a charge cut-off voltage of 4.55V.

[0131]

[0132] Comparative Example 1

[0133] The difference from Example 1 is that no functional additive is added, and the results are shown in Figure 29 , Figure 30 Table 1 and Table 2, Figure 29 is a cycle life curve of the electrolyte prepared in Comparative Example 1 in a Gr / LCO button cell, Figure 30 is a charge-discharge curve of the electrolyte prepared in Comparative Example 1 in a Gr / LCO button cell, which is Figure 29 and Figure 30 It can be seen that the capacity retention of the above electrolyte decays to 80% after 198 cycles at a charge cut-off voltage of 4.55V.

[0134] Comparative Example 2

[0135] The difference from Example 3 is that the functional additive is as shown in formula (7), wherein the Chinese name is 3-butynyl p-toluenesulfonate, which can be obtained by commercial means, and the results are shown in Figure 31 , Figure 32 Table 1 and Table 2, Figure 31 is a cycle life curve of the electrolyte prepared in Comparative Example 2 in a Gr / LCO button cell, Figure 32 is a charge-discharge curve of the electrolyte prepared in Comparative Example 2 in a Gr / LCO button cell, which is Figure 31 and Figure 32 It can be seen that the capacity retention of the above electrolyte decays to 80% after 250 cycles at a charge cut-off voltage of 4.55V.

[0136]

[0137] Comparative Example 3

[0138] The difference from Example 3 is that the functional additive is shown as formula (8) (the Chinese name of the additive: 2,2,2-trifluoroethyl p-toluenesulfonate, which can be obtained through commercial channels), and the results are shown in Figure 33 , Figure 34 , Table 1 and Table 2, Figure 33 is a cycle life curve diagram of the electrolyte prepared in Comparative Example 3 in Gr / LCO button cells, Figure 34 is a charge-discharge curve diagram of the electrolyte prepared in Comparative Example 3 in Gr / LCO button cells, and Figure 33 and Figure 34 It can be seen that the capacity retention of the above-mentioned electrolyte decays to 80% after 240 cycles at a charge cut-off voltage of 4.55V.

[0139]

[0140] From the comparison of the examples and comparative examples, it can be seen that the electrolyte provided by the present application achieves better cycle performance and coulomb efficiency, which is mainly because the electrolyte provided by the present application can form an interface film with protection on the surface of the positive electrode. The interface can reduce the oxidation ability of the electrolyte on the surface of the positive electrode, can significantly improve the stability of the electrolyte and its interface, can reduce the consumption, decomposition and damage to the structure of the positive electrode of the electrolyte during the cycle process, and can effectively improve the cycle performance and coulomb efficiency of the lithium ion battery. At the same time, the interface film is rich in sulfur element, which is beneficial to reduce the interface impedance.

[0141] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any change or replacement within the technical scope disclosed in the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An electrolyte comprising an electrolyte salt, an organic solvent, and a functional additive as shown in formula (I): In equation (I), R1 is selected from C 1～10 Alkyl group, C substituted with at least one substituent 1～10 Alkyl, C 2～10 Alkenyl group, C group substituted with at least one substituent 2～10 alkenyl or pyridyl; R2 is selected from C 1～10 Alkyl group, C substituted with at least one substituent 1～10 Alkyl, C 2～10 Alkenyl group, C group substituted with at least one substituent 2～10 alkenyl, C 2～10 Alkyne group, C group substituted with at least one substituent 2～10 alkynyl group, -OS(O)2-C 6～12 aryl, or -OS(O)2-C substituted with at least one substituent 6～12 Aryl; The substituents are selected from halogens or cyano groups.

2. The electrolyte according to claim 1, characterized in that, In formula (I), at least one of R1 and R2 is selected from fluorine-substituted alkyl groups.

3. The electrolyte according to claim 2, characterized in that, In formula (I), at least one of R1 and R2 is selected from alkyl groups containing trifluoromethyl.

4. The electrolyte according to any one of claims 1 to 3, characterized in that, The functional additive has a structure of formula (2), formula (3), formula (4), formula (5) or formula (6):

5. The electrolyte according to claim 4, characterized in that, The functional additives account for 0.1 wt% to 10 wt% of the electrolyte.

6. The electrolyte according to claim 5, characterized in that, The electrolyte salt is a lithium salt; The concentration of the electrolyte salt is 0.1 mol / L to 3.0 mol / L.

7. The electrolyte according to claim 5, characterized in that, The organic solvent is selected from one or more of carbonates and carboxylic esters.

8. The electrolyte according to claim 5, characterized in that, It also includes additives.

9. The electrolyte according to claim 8, characterized in that, The additive is selected from at least one of fluoroethylene carbonate (FEC), 1,3-propanesulfonate lactone (PS), adiponitrile (ADN), succinate (SN), ethylene glycol bis(propionitrile) ether (DENE), or 1,3,6-hexanetrionitrile (HTCN). The additive comprises 0.1 wt% to 10 wt% of the electrolyte.

10. A battery comprising a positive electrode, a negative electrode, a separator disposed between the positive and negative electrodes, and an electrolyte according to any one of claims 1 to 9.

11. The battery according to claim 10, characterized in that, The positive electrode active material is selected from at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, and ternary materials; The negative electrode active material is selected from at least one of mesophase carbon microspheres, artificial graphite, and natural graphite.

12. An electronic device comprising the battery of claim 10 or 11.

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