Electrolyte additive, nonaqueous electrolyte, and use thereof

Abstract

The application provides an electrolyte additive, a nonaqueous electrolyte and application thereof, the electrolyte additive comprises an additive A and an additive B, the additive A comprises one or a combination of at least two of compounds shown in formulas I-IV, and the additive B comprises one or a combination of at least two of compounds shown in formulas V-VI. The additive A and the additive B in the application cooperate together and synergize, so that the stability of the electrolyte can be improved, and the charge-discharge cycle life, the high-temperature storage capacity retention rate and the high-temperature storage capacity recovery rate of the battery can be improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to an electrolyte additive, a non-aqueous electrolyte, and their applications. Background Technology

[0002] The development of lithium-ion batteries has been rapid, but safety issues related to them have become increasingly prominent. In lithium-ion batteries, ion transport is achieved between the positive and negative electrodes through the electrolyte. The electrolyte and the positive and negative electrodes are unstable. During battery formation, the electrolyte reacts with the electrode materials, forming a CEI / SEI film on the surface of the positive and negative electrodes, hindering further reaction between the electrolyte and the electrodes. The battery thermal runaway process occurs due to the thermal decomposition of the CEI / SEI film. The electrolyte reacts with the exposed charged negative electrode, and as the temperature rises further, the separator shrinks and melts, causing a large-scale short circuit inside the battery. This leads to the decomposition of the electrolyte and the positive electrode, ultimately resulting in an explosion and combustion.

[0003] Because the electrolyte itself contains organic solvents with high flash points and is flammable, it is prone to overheating and ignition during the rapid charging and discharging of lithium-ion batteries, leading to serious safety issues and limiting its widespread application. Adding phosphate esters or phosphites to the electrolyte can reduce its flammability and improve the safety performance of lithium-ion batteries.

[0004] CN102150315B discloses a secondary battery in which the electrolyte contains more than 20% by volume and less than 60% by volume of trialkyl phosphate derivatives, and contains more than 1.5 mol / L and less than 3.5 mol / L of lithium tetrafluorosulfonylimide as lithium salt. The electrolyte is completely non-flammable. However, the use of high concentration of lithium tetrafluorosulfonylimide as lithium salt electrolyte results in high cost and makes it difficult to apply industrially.

[0005] JP2002141110A discloses an electrolyte for non-aqueous batteries and a secondary battery using the same, in which a phosphate ester derivative is added. By introducing halogen atoms as substitutes for the phosphate ester, the electrochemical stability of the electrolyte can be improved to a certain extent, and the cycle characteristics and high-temperature characteristics of the secondary battery can be improved. However, its high-temperature storage stability needs to be further improved.

[0006] Therefore, in this field, it is desirable to provide an electrolyte that can further improve the room temperature cycling performance, as well as the high temperature performance and safety performance of batteries. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide an electrolyte additive, a non-aqueous electrolyte, and their applications. The electrolyte additive components of the present invention exhibit a synergistic effect, enabling the electrolyte to improve the battery's room-temperature cycle performance, high-temperature performance, and safety performance.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides an electrolyte additive, the electrolyte additive comprising additive A and additive B, wherein additive A comprises one or a combination of at least two compounds represented by formulas I-IV, and additive B comprises one or a combination of at least two compounds represented by formulas V-VI.

[0010]

[0011] Where R1-R 12 Each of the groups is independently selected from organic groups having 1 to 10 carbon atoms, and X1 to X6 are independently selected from fluorine, chlorine, bromine or iodine.

[0012] In this invention, the electrolyte additives, through the combined action of additives A and B, achieve a synergistic effect, thereby improving the battery's room-temperature cycle performance, high-temperature performance, and safety performance. Additives A and B participate in the electrochemical reactions on the positive and negative electrode surfaces, forming a low-resistance composite film of phosphate or phosphite, lithium halide, and organic polymers, stabilizing the electrode-electrolyte interface and reducing side reactions between the electrolyte and electrodes. Additive A contains halogens, which improves the oxidative stability of the electrolyte, forms halogen free radicals and phosphorus free radicals, scavenges oxygen free radicals, and inhibits battery gas production; it also forms an electrolyte interface film containing lithium halide and halophosphate components at the negative electrode, improving battery cycle performance. Additive B is an electron-rich alkaline compound that can bind to acidic PF5 and POF3 impurities in the electrolyte, which is beneficial for stabilizing the electrolyte. Since the bond energy of PO bonds differs from that of PX (X = F, Cl, Br, or I) bonds, it can be considered that the chemical bond energy of the mixture can be adjusted by regulating the ratio of additives A and B, thereby adjusting the ease with which additives A and B participate in electrochemical reactions.

[0013] In this invention, the combined use of additives A and B has a synergistic effect, which can improve the stability of the electrolyte and enhance the charge-discharge cycle life, high-temperature storage capacity retention rate, and high-temperature storage capacity recovery rate of the battery.

[0014] In this invention, the organic group having 1-10 carbon atoms is preferably an alkyl group with 1-10 substituted or unsubstituted carbon atoms, an alkenyl group with 2-10 substituted or unsubstituted carbon atoms, an alkynyl group with 2-10 substituted or unsubstituted carbon atoms, an aryl group with 6-10 substituted or unsubstituted carbon atoms, or a five- or six-membered heterocycle with 2-10 substituted or unsubstituted carbon atoms. When the group has substituents, the substituents are selected from halogens, cyano, alkylcyano, sulfonyl, sulfonyloxy, fluorosulfonyl, fluorosulfonyloxy, carbonyl, carbonyloxy, or silicon-containing groups.

[0015] In this invention, the range of carbon atoms defined in the group refers to any integer within the defined range. For example, the number of carbon atoms is 1-10, and the number of carbon atoms can be 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10. The number of carbon atoms is 5-10, which means that the number of carbon atoms can be 5, 6, 7, 8, 9 or 10.

[0016] Preferably, the organic group having 1-10 carbon atoms is selected from substituted or unsubstituted alkyl groups having 1-6 carbon atoms, substituted or unsubstituted alkenyl groups having 2-6 carbon atoms, substituted or unsubstituted alkynyl groups having 2-6 carbon atoms, or phenyl groups. When the group has substituents, the substituents are selected from halogens, cyano groups, alkyl cyano groups, sulfonyl groups, sulfonyloxy groups, fluorosulfonyl groups, fluorosulfonyloxy groups, carbonyl groups, carbonyloxy groups, or silicon-containing groups.

[0017] Preferably, the silicon-containing group is an alkylsilyl group with 1-10 carbon atoms or an alkylsiloxy group with 1-10 carbon atoms.

[0018] Preferably, the organic group having 1-10 carbon atoms is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, cyclopropyl, 1-methylcyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, vinyl, 2-propenyl, 3-butenyl, 2-butenyl, 2-(methyl)-2-propenyl, cyclopentenyl, 2-propynyl, 3-butynyl, 2-fluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 3-fluoropropyl, 3,3,3-trifluoropropyl, 2,2,3,3-tetrafluoropropyl, 2,2,3,3,3-pentafluoropropyl, 2,2-difluoropropyl, 1,1 1-Trifluoroisopropyl, hexafluoroisopropyl, 4,4,4-trifluorobutyl, 3,3,4,4,4-pentafluorobutyl, 2,2,3,4,4,4-hexafluorobutyl, 2,2,3,3,4,4,4-heptafluorobutyl, 2-(cyano)ethyl, 2-(acetoxy)ethyl, acetylethyl, 3-(acetoxy)propyl, acetylpropyl, 4-(acetoxy)-2-butenyl, 4-(acetoxy)-2-butynyl, 2-(methanesulfonyloxy)ethyl, 2-(methanesulfonyloxy)ethyl, 3-(methanesulfonyloxy)propyl, 3-(methanesulfonyloxy)propyl, 4-(methanesulfonyloxy)-2-butenyl, 4- (methanesulfonyloxy)-2-butynyl, 2-(fluorosulfonyloxy)ethyl, 2-(fluorosulfonyloxy)ethyl, 3-(fluorosulfonyloxy)propyl, 3-(fluorosulfonyloxy)propyl, 4-(fluorosulfonyloxy)-2-butenyl, 4-(fluorosulfonyloxy)-2-butynyl, trimethylsilyl, (trimethylsilyl)methyl, (trimethylsilyl)ethyl, (trimethylsilyl)propyl, 2-(trimethylsilyloxy)ethyl, 3-(trimethylsilyloxy)propyl, 4-(trimethylsilyl)-2-butenyl, 4-(trimethylsilyl)-2-butynyl, phenyl, 2-fluorophenyl, 2,4-difluorophenyl, 2,6-difluorophenyl 2,5-Difluorophenyl, 2-(cyano)phenyl, 3-(cyano)phenyl, 4-(cyano)phenyl, 2-(acetyl)phenyl, 3-(acetyl)phenyl, 4-(acetyl)phenyl, 2-(acetoxy)phenyl, 3-(acetoxy)phenyl, 4-(acetoxy)phenyl, 2-(methanesulfonyloxy)phenyl, 3-(methanesulfonyloxy)phenyl, 4-(methanesulfonyloxy)phenyl, 2-(fluorosulfonyloxy)phenyl, 3-(fluorosulfonyloxy)phenyl, 4-(fluorosulfonyloxy)phenyl, 2-(trimethylsiloxy)phenyl, 3-(trimethylsiloxy)phenyl or 4-(trimethylsiloxy)phenyl.

[0019] The organic groups with 1-10 carbon atoms listed above include their cis-trans isomers, R / S chiral isomers, isomers formed by different substitution positions on the carbon chain, and conformational isomers caused by the rotation of chemical bonds.

[0020] Preferably, R1-R 12Each compound is independently selected from methyl, ethyl, n-propyl, isopropyl, cyclopropyl, vinyl, 2-propenyl, 2-propynyl, 2-fluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 3-fluoropropyl, 3,3,3-trifluoropropyl, 2,2,3,3-tetrafluoropropyl, 2,2,3,3,3-pentafluoropropyl, 2,2-difluoropropyl, 1,1,1-trifluoroisopropyl, hexafluoroisopropyl, 2-(cyano)ethyl, and 2-(acetoxy). Ethyl, acetylacetyl, 2-(methanesulfonyloxy)ethyl, 2-(methanesulfonyl)ethyl, 2-(fluorosulfonyloxy)ethyl, 2-(fluorosulfonyl)ethyl, trimethylsilyl, (trimethylsilyl)methyl, (trimethylsilyl)ethyl, 2-(trimethylsiloxy)ethyl, phenyl, 2-fluorophenyl, 2,4-difluorophenyl, 2,6-difluorophenyl, 2,5-difluorophenyl, 2-(cyano)phenyl, 3-(cyano)phenyl, or 4-(cyano)phenyl. These groups include their cis-trans isomers, R / S chiral isomers, isomers formed by different substitution positions on the carbon chain, and conformational isomers caused by rotation of chemical bonds.

[0021] Preferably, additive A comprises any one or a combination of at least two of the following compounds:

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037] Preferably, the additive B comprises any one or a combination of at least two of the following compounds:

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045] Preferably, the mass ratio of additive A to additive B is 1,000,000:1 to 1,000:1, for example, 1,000,000:1, 100,000:1, 10,000:1, or 1,000:1.

[0046] In a second aspect, the present invention provides a non-aqueous electrolyte, the non-aqueous electrolyte comprising a non-aqueous solvent, an electrolyte, and an additive, the additive comprising the electrolyte additives as described in the first aspect.

[0047] In this invention, the electrolyte additive is used in non-aqueous electrolytes. Additive A and additive B work together to stabilize the battery positive electrode and simultaneously complex acidic substances such as PF5 and POF3 in the electrolyte, thereby improving the electrolyte's stability. Furthermore, it can participate in the construction of the positive and negative electrode interface film to form an organic protective film, and simultaneously react with lithium salts to form phosphate and lithium halide inorganic protective films. The resulting organic-inorganic composite film is stable and has low impedance. Moreover, the formed positive and negative electrode interface film inhibits electrolyte reactions at the electrodes, reduces gas production and expansion, and improves the battery's charge-discharge cycle life, high-temperature storage capacity retention, and high-temperature storage capacity recovery rate.

[0048] Preferably, the electrolyte additive content is 0.0001% to 10% by mass, based on 100% of the non-aqueous electrolyte. For example, 0.0001%, 0.001%, 0.01%, 0.1%, 1%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, or 10%. If the content is greater than 10%, the conductivity of the non-aqueous electrolyte decreases, leading to a deterioration in battery performance.

[0049] Preferably, based on the mass of the non-aqueous electrolyte (100%), the mass percentage content of additive A in the electrolyte additive is 0.001–10%, and the mass percentage content of additive B is 0.001–100 ppm. For example, the mass percentage content of additive A is 0.001%, 0.01%, 0.1%, 1%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, or 10%, and the mass percentage content of additive B is 0.001 ppm, 0.01 ppm, 0.1 ppm, 1 ppm, 2 ppm, 5 ppm, 10 ppm, 20 ppm, 30 ppm, 50 ppm, 80 ppm, or 100 ppm. Insufficient use of additive A or additive B will not allow it to function properly; excessive use of additive A will cause a decrease in electrolyte conductivity, leading to battery performance deterioration; excessive use of additive B will increase battery impedance and worsen battery cycle performance.

[0050] More preferably, based on the mass of the non-aqueous electrolyte (100%), the mass percentage content of additive A in the electrolyte additive is 0.5%–10%, and the mass percentage content of additive B is 0.1–100 ppm. For example, the mass percentage content of additive A is 0.5%, 1%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, or 10%, and the mass percentage content of additive B is 10 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 80 ppm, or 100 ppm.

[0051] Preferably, the non-aqueous solvent is selected from one or a combination of at least two of cyclic carbonates, chain carbonates, cyclic carboxylic esters, chain carboxylic esters, fluorocarbonates, fluoroether solvents, or sulfone solvents.

[0052] More preferably, the non-aqueous solvent includes, but is not limited to, one or a combination of at least two of ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), propylene carbonate (PC), ethyl acetate (EA), propyl acetate (PA), propyl propionate (PP), γ-valerolactone (VL), methyl acetate (MA), methyl butyrate (MB), ethyl butyrate (EB), or propyl butyrate (PB).

[0053] Preferably, the electrolyte is an alkali metal salt, and the alkali metal salt is preferably a lithium salt.

[0054] Preferably, the lithium salt is selected from any one or a combination of at least two of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiN(SO2F)2), lithium bis(trifluorosulfonyl)imide (LiN(SO2CF3)2), lithium bis(oxalateborate)borate (LiBOB), lithium difluorooxalateborate (LiDFOB), lithium difluorophosphate (LiPO2F2), or lithium difluorobis(oxalateborate).

[0055] Preferably, the concentration of the electrolyte in the non-aqueous electrolyte is 0.5 to 1.5 mol / L, for example, 0.5 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, 1.4 mol / L or 1.5 mol / L.

[0056] Preferably, the non-aqueous electrolyte further includes other additives, which include any one or a combination of at least two of carbonates, sulfonates, sulfates, cyanate compounds, borates, or silicon compounds.

[0057] In this invention, the addition of other additives can stabilize the film formation at the positive and negative electrodes or increase the oxidation resistance potential of the electrolyte, thereby improving the cycle performance and high-temperature storage performance of the battery.

[0058] Preferably, the other additives include, but are not limited to, fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), vinylene carbonate (VC), ethylene ethylene carbonate (VEC), 1,3-propanesulfonate lactone (PS), 1,4-propanesulfonate lactone (BS), 2,4-butanesulfonate lactone, 1,3-propenesulfonate lactone (PES), methyl disulfonate methylene ester (MMDS), vinyl sulfite (ES), vinyl sulfate (DTD), and 4-methyl... The first or a combination of any one or at least two of the following: vinyl ester sulfate, 4-propyl vinyl ester sulfate, succinate (SN), adiponitrile (ADN), ethylene glycol bis(propionitrile) ether (DENE), 1,3,6-hexanetrionitrile (HTCN), trimethyl borate (TMB), triethyl borate (TEB), triethylene borate, triisopropyl borate, triallyl borate (TAB), triphenyl borate, tri(trimethylsilyl)borate (TMSB), or tetravinylsilane (TVSi).

[0059] Preferably, based on the mass of the non-aqueous electrolyte (100%), the mass percentage content of the other additives is 0.001% to 10%, for example, 0.001%, 0.01%, 0.1%, 1%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, or 10%.

[0060] Thirdly, the present invention provides an electrochemical device comprising a positive electrode, a negative electrode, a diaphragm disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte as described in the second aspect.

[0061] In this invention, the positive electrode sheet includes a positive current collector and a positive electrode film coated on the surface of the positive current collector. The positive electrode film includes a positive active material, a positive conductive agent, and a positive binder.

[0062] Preferably, the positive electrode active material is lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, aluminum nickel cobalt manganese oxide, lithium-rich manganese-based solid solution, or high-nickel ternary material LiNi. (1-x-y-z) Co x Mn y Al z Any one of O2, where: 0≤x≤1, 0≤y≤1, 0≤z≤1 and 0≤x+y+z≤1.

[0063] In this invention, the positive electrode conductive agent and the positive electrode binder are not particularly limited, and commonly used positive electrode conductive agents and positive electrode binders in the art can be selected.

[0064] Preferably, the negative electrode sheet includes a negative current collector and a negative electrode film coated on the surface of the negative current collector, wherein the negative electrode film includes a negative electrode active material, a negative electrode conductive agent and a negative electrode binder.

[0065] Preferably, the negative electrode active material is any one of artificial graphite, natural graphite, silicon-carbon negative electrode, or silicon negative electrode.

[0066] In this invention, the negative electrode conductive agent and the negative electrode binder are not particularly limited, and commonly used negative electrode conductive agents and negative electrode binders in the art can be selected.

[0067] Compared with the prior art, the present invention has the following beneficial effects:

[0068] In this invention, the electrolyte additives, through the combined action of additive A and additive B, achieve a synergistic effect, thereby improving the battery's room temperature cycle performance, high temperature performance, and safety performance. Specifically, this offers the following advantages:

[0069] (1) The combined use of additives A and B can participate in the construction of the positive and negative electrode interface film of the battery, thereby improving the charge-discharge cycle life of the battery. Additives A and B participate in the formation of organic protective film, and at the same time react with lithium salt to form inorganic protective films of phosphate and lithium halide. The resulting organic-inorganic composite film is stable and has low impedance.

[0070] (2) The combined use of additives A and B improves the high-temperature storage performance of the battery. The positive and negative electrode interface films formed by additives A and B inhibit the reaction of the electrolyte at the electrodes. At the same time, the P and F contained in additives A and B form free radicals that can scavenge oxygen free radicals that decompose the electrolyte, thereby inhibiting the high-temperature gas generation of the battery.

[0071] (3) Additive A contains halogens, which improves the oxidation stability of the electrolyte. It reacts with lithium salts to form lithium halide and lithium halide phosphate film components at the electrode interface. Additive B has an electron-rich structure, which can stabilize the positive electrode of the battery. At the same time, it complexes acidic substances such as PF5 and POF3 in the electrolyte, thereby improving the stability of the electrolyte. The combination of additives improves battery performance. Detailed Implementation

[0072] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0073] It should be noted that, unless otherwise specified, all percentages used in this invention are based on mass. In this specification, unless otherwise specified, the symbols, units, abbreviations, and terms have the following meanings. For example, when using ~ or - to indicate a numerical range, they include both endpoints, and the units are common. For example, 5–25% means 5% or more and 25% or less. ppm means parts per million.

[0074] All raw materials and reagents used in this invention were purchased from mainstream manufacturers. Those without specified manufacturers or concentrations are all analytically pure raw materials or reagents that are readily available. There are no particular restrictions as long as they achieve the intended effect. The glove box, moisture analyzer, potentiometric titrator, conductivity meter, stirrer, and other instruments and equipment used in this embodiment were all purchased from major manufacturers. There are no particular limitations as long as they achieve the intended effect. Where specific techniques or conditions are not specified in the embodiments of this invention, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions.

[0075] The raw materials and instruments used in the examples and comparative examples are as follows:

[0076] The glove box was purchased from Shanghai Microna Electromechanical Technology Co., Ltd.; the non-aqueous solvent was purchased from Shenzhen Xinzhoubang Technology Co., Ltd.; the lithium salt was purchased from Cheonbo Industrial Co., Ltd. of South Korea; the other additives were purchased from Hebei Shengtai Materials Co., Ltd. and Fujian Chuangxin Technology Development Co., Ltd.; the additive compounds were purchased from Aladdin Chemical Reagent Network or Maclean Chemical Reagent Network.

[0077] The specific structures of additives A and B used in the examples are as follows:

[0078]

[0079]

[0080]

[0081] Example 1

[0082] The electrolyte additives provided in the examples include additive A and additive B, wherein additive A is compound I-1 and additive B is compound V-1, and their amounts are shown in Table 1.

[0083] The non-aqueous electrolyte containing this electrolyte additive is prepared by the following method:

[0084] In an argon-atmosphere glove box with a water content <0.01ppm, ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) in a volume ratio of 3:5:2 were mixed thoroughly. The temperature was controlled at 15°C. Lithium hexafluorophosphate (LiPF6) was dissolved in the mixed solvent to prepare a 1.0 mol / L solution. Additives A and B, as shown in Table 1, were added to the solution, and the mixture was stirred to obtain a non-aqueous electrolyte.

[0085] Battery making:

[0086] Natural graphite, conductive carbon black (SP), styrene-butadiene rubber (SBR) binder, and carboxymethyl cellulose (CMC) thickener were thoroughly mixed in a deionized water solvent system at a mass ratio of 96.7:1.0:1.8:0.5 to obtain a negative electrode slurry. This slurry was coated onto both sides of a copper foil and dried to obtain a negative electrode sheet. The negative electrode sheet was then cut into pieces 20 mm wide and 150 mm long to serve as the negative electrode. Lithium nickel cobalt manganese oxide (LiNCM811), conductive carbon black, and polyvinylidene fluoride (PVDF) binder were thoroughly mixed in an N-methylpyrrolidone (NMP) solvent at a mass ratio of 97.7:1.0:1.3 to obtain a positive electrode slurry. This slurry was coated onto both sides of an aluminum foil serving as the positive electrode current collector and dried to obtain a positive electrode sheet. The positive electrode sheet was then cut into pieces 20 mm wide and 150 mm long to serve as the positive electrode. Tabs were installed on the negative and positive electrodes prepared accordingly, and a porous polypropylene film with a width of 25 mm and a length of 200 mm was wound to form a battery cell. The battery cell was placed in a sealed battery case in a dry argon atmosphere, and the lithium-ion battery electrolyte prepared in the embodiments and comparative examples of this invention was injected. The battery was then encapsulated, allowed to stand, formed (0.02C constant current charging for 2 hours, 0.1C constant current charging for 2 hours), shaped, and its capacity was tested to produce a battery.

[0087] The battery performance of the examples and comparative examples was tested using the following methods:

[0088] (1) Charge-discharge cycle test:

[0089] The prepared lithium-ion secondary battery was charged at 45℃ using a constant current and constant voltage of 50mA until it reached 4.2V, with a cutoff current of 0.02C. After resting for 5 minutes, it was discharged at a constant current of 10mA until the voltage reached 3.0V, and then rested for 5 minutes. The discharge capacity of the battery after the first cycle at 25℃ was recorded. The battery was then charged again at a constant current and constant voltage of 50mA until it reached 4.2V, with a cutoff current of 0.02C, and then rested for 5 minutes. This cycle was repeated until the voltage reached 3.0V, and then rested for 5 minutes. This charge-discharge cycle was repeated 500 times, and the discharge capacity after the 500th cycle was recorded.

[0090] Cycle capacity retention (%) = Discharge capacity after 500 cycles / Discharge capacity in the first cycle × 100%

[0091] (2) High-temperature storage performance test:

[0092] First, at 25℃, the secondary battery was charged to 4.2V using a constant current and constant voltage of 0.33C, with a cutoff current of 0.02C. After resting for 5 minutes, it was discharged to 3.0V using 0.33C, and the discharge capacity C0 before storage was recorded. Then, the battery was charged to a fully charged state of 4.2V using a constant current and constant voltage of 0.33C, and the volume V0 before high-temperature storage was measured using the water displacement method. The battery was then stored in a 60℃ constant temperature chamber for 28 days. After storage, the battery was removed, placed at 25℃ for 12 hours, and the volume V1 after storage was measured. The battery volume expansion rate after 28 days of constant temperature storage at 60℃ was calculated. The battery was then discharged to 3.0V using a constant current of 0.33C, rested for 5 minutes, and the discharge capacity C1 was recorded. Then, one charge-discharge cycle at 0.33C was performed, recorded as C2. The capacity retention rate and capacity recovery rate of the battery after 28 days of constant temperature storage at 60℃ were calculated using the following formulas:

[0093] Battery volume expansion rate (%) after storage at 60℃ for 28 days = (V1-V0) / V0×100%;

[0094] Capacity retention rate (%) after 28 days of storage at 60℃ = C1 / C0 × 100%;

[0095] Capacity recovery rate (%) after 28 days of storage at 60℃ = C2 / C0 × 100%;

[0096] Examples 2-36 and Comparative Examples 1-9 used the same electrolyte preparation, battery manufacturing and testing steps as Example 1, the difference being the addition of different additives, as detailed in Table 1.

[0097] Table 1

[0098]

[0099]

[0100] As can be seen from the embodiments of the present invention, the electrolyte additive of the present invention can enable the battery to maintain a capacity retention rate of more than 70% or even more than 85% after 500 cycles at 45°C, and a volume expansion rate of less than 18.5% or even less than 10% after 28 days of storage at 60°C, with a capacity retention rate of more than 77% or even more than 90%, and a capacity recovery rate of more than 82% or even more than 93%.

[0101] Comparing Examples 1-20 and Comparative Example 1, it can be seen that the addition of additives A and B can improve the cycle life, capacity retention rate, and capacity recovery rate of the battery during high-temperature storage. The volume expansion of the battery during high-temperature storage is significantly suppressed, thanks to the participation of additives A and B in the electrochemical reactions on the positive and negative electrode surfaces, forming a low-resistance composite film of phosphate or phosphite, lithium fluoride, and organic polymers. This stabilizes the electrode-electrolyte interface and reduces side reactions between the electrolyte and the electrode.

[0102] Comparing Examples 2 and 21-36, it can be seen that the appropriate dosage of additive A in the electrolyte is 0.001-10%, and the appropriate dosage of additive B is 0.001-100 ppm. When the dosage of additive A is less than 0.001% or the dosage of additive B is less than 0.001 ppm, it is insufficient to exert its effect. When the dosage of additive A exceeds 10% or the dosage of additive B exceeds 100 ppm, it causes a decrease in the conductivity and viscosity of the electrolyte, resulting in a decrease in battery cycle performance.

[0103] Comparing Examples 1, 9, 13, and 17 with Comparative Examples 2-9, it is evident that the combined use of additives A and B has a synergistic effect, resulting in better battery cycle performance and high-temperature storage characteristics. Additives A and B participate in the electrochemical reactions on the positive and negative electrode surfaces, forming a low-resistance composite film of phosphates or phosphites, lithium halides, and organic polymers. This stabilizes the electrode-electrolyte interface and reduces side reactions between the electrolyte and electrodes. Additive A contains halogens, which improves the oxidative stability of the electrolyte, forms halogen and phosphorus free radicals, scavenges oxygen free radicals, and inhibits battery gas production. It also forms an electrolyte interface film containing lithium halides and halogenated phosphates at the negative electrode, improving battery cycle performance. Additive B is an electron-rich alkaline compound that can bind to acidic PF5 and POF3 impurities in the electrolyte, thus stabilizing the electrolyte. The bond energy of PO bonds differs from that of PX (X = F, Cl, Br or I) bonds. It can be assumed that the chemical bond energy of the mixture can be adjusted by regulating the ratio of additive A and additive B, thereby adjusting the ease with which additive A and additive B participate in electrochemical reactions.

[0104] Examples 37-47 and Comparative Examples 10-11 used the same electrolyte preparation, battery manufacturing and testing steps as Example 1, the difference being the types and contents of additives and other auxiliaries as shown in Table 2.

[0105] Table 2

[0106]

[0107] Comparative Examples 1-25, 37-47, and 10-11, the addition of other additives with specific structures does not impair the beneficial effects of the present invention; on the contrary, it further improves battery performance. Fluoroethylene carbonate (FEC) has the advantage of low film-forming impedance, and lithium difluorobis(oxalato)borate (LiDFOB) can stabilize the positive and negative electrodes of the battery. The additives of the present invention can suppress the high-temperature gas generation phenomenon caused by the use of FEC or LiDFOB. The synergistic effect of the additives of the present invention and FEC or LiDFOB further improves the high-temperature storage and cycle performance of the battery.

[0108] The applicant declares that this invention illustrates the electrolyte additive, non-aqueous electrolyte, and their applications through the above embodiments, but this invention is not limited to the above embodiments, that is, it does not mean that this invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials in the product of this invention, addition of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of this invention.

Claims

1. A non-aqueous electrolyte, characterized in that, The non-aqueous electrolyte includes a non-aqueous solvent, an electrolyte, and electrolyte additives; The electrolyte additive includes additive A and additive B, wherein additive A comprises one or a combination of at least two compounds shown in formulas I-IV, and additive B comprises one or a combination of at least two compounds shown in formulas V-VI. ； R1-R5 and R7-R9 are each independently selected from organic groups having 1-10 carbon atoms; R6 is selected from alkyl groups having 1-6 carbon atoms (substituted or unsubstituted), alkenyl groups having 2-6 carbon atoms (substituted or unsubstituted), alkynyl groups having 2-6 carbon atoms (substituted or unsubstituted), or phenyl groups (substituted or unsubstituted). When the group has a substituent, the substituent is selected from halogen, sulfonyl, sulfonyloxy, fluorosulfonyl, fluorosulfonyloxy, carbonyl, carbonyloxy, or a silicon-containing group. R 10 -R 12 They are the same, and both are organic groups with 2-10 carbon atoms; X1 to X6 are each independently selected from fluorine, chlorine, bromine, or iodine; The mass ratio of additive A to additive B is 1,000,000:1 to 1,000:1; Based on the mass of the non-aqueous electrolyte as 100%, the mass percentage content of the electrolyte additive is 0.0001~10%, the mass percentage content of additive A in the electrolyte additive is 0.001~10%, and the mass percentage content of additive B is 0.001~100ppm.

2. The non-aqueous electrolyte according to claim 1, characterized in that, The organic group having 1-10 carbon atoms is a substituted or unsubstituted alkyl group having 1-10 carbon atoms, a substituted or unsubstituted alkenyl group having 2-10 carbon atoms, a substituted or unsubstituted alkynyl group having 2-10 carbon atoms, a substituted or unsubstituted aryl group having 6-10 carbon atoms, or a substituted or unsubstituted five- or six-membered heterocycle having 2-10 carbon atoms. When the group has a substituent, the substituent is selected from halogen, cyano, alkylcyano, sulfonyl, sulfonyloxy, fluorosulfonyl, fluorosulfonyloxy, carbonyl, carbonyloxy, or a silicon-containing group. The organic group having 2-10 carbon atoms is a substituted or unsubstituted alkyl group having 2-10 carbon atoms, a substituted or unsubstituted alkenyl group having 2-10 carbon atoms, a substituted or unsubstituted alkynyl group having 2-10 carbon atoms, a substituted or unsubstituted aryl group having 6-10 carbon atoms, or a substituted or unsubstituted five- or six-membered heterocycle having 2-10 carbon atoms. When the group has a substituent, the substituent is selected from halogen, cyano, alkylcyano, sulfonyl, sulfonyloxy, fluorosulfonyl, fluorosulfonyloxy, carbonyl, carbonyloxy, or a silicon-containing group.

3. The non-aqueous electrolyte according to claim 2, characterized in that, The organic group having 1-10 carbon atoms is selected from substituted or unsubstituted alkyl groups having 1-6 carbon atoms, substituted or unsubstituted alkenyl groups having 2-6 carbon atoms, substituted or unsubstituted alkynyl groups having 2-6 carbon atoms, or phenyl groups. When the group has a substituent, the substituent is selected from halogen, cyano, alkylcyano, sulfonyl, sulfonyloxy, fluorosulfonyl, fluorosulfonyloxy, carbonyl, carbonyloxy, or silicon-containing groups. The organic group having 2-10 carbon atoms is selected from substituted or unsubstituted alkyl groups having 2-6 carbon atoms, substituted or unsubstituted alkenyl groups having 2-6 carbon atoms, substituted or unsubstituted alkynyl groups having 2-6 carbon atoms, or phenyl groups. When the group has substituents, the substituents are selected from halogens, cyano groups, alkyl cyano groups, sulfonyl groups, sulfonyloxy groups, fluorosulfonyl groups, fluorosulfonyloxy groups, carbonyl groups, carbonyloxy groups, or silicon-containing groups.

4. The non-aqueous electrolyte according to claim 3, characterized in that, The silicon-containing group is an alkylsilyl group with 1-10 carbon atoms or an alkylsiloxy group with 1-10 carbon atoms.

5. The non-aqueous electrolyte according to claim 3, characterized in that, The organic group having 1-10 carbon atoms is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, cyclopropyl, 1-methylcyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, vinyl, 2-propenyl, 3-butenyl, 2-butenyl, 2-(methyl)-2-propenyl, cyclopentenyl, 2-propynyl, 3-butynyl, 2-fluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 3-fluoropropyl, 3,3,3-trifluoropropyl, 2,2,3,3-tetrafluoropropyl, 2,2,3,3,3-pentafluoropropyl, 2,2-difluoropropyl, 1,1,1- Trifluoroisopropyl, hexafluoroisopropyl, 4,4,4-trifluorobutyl, 3,3,4,4,4-pentafluorobutyl, 2,2,3,4,4,4-hexafluorobutyl, 2,2,3,3,4,4,4-heptafluorobutyl, 2-(cyano)ethyl, 2-(acetoxy)ethyl, acetylethyl, 3-(acetoxy)propyl, acetylpropyl, 4-(acetoxy)-2-butenyl, 4-(acetoxy)-2-butynyl, 2-(methanesulfonyloxy)ethyl, 2-(methanesulfonyloxy)ethyl, 3-(methanesulfonyloxy)propyl, 3-(methanesulfonyloxy)propyl, 4-(methanesulfonyloxy)-2-butenyl, 4-(methanesulfonyloxy)-2-butenyl, 2-Butynyl (fluorosulfonyloxy)-2-butynyl, 2-(fluorosulfonyloxy)ethyl, 2-(fluorosulfonyloxy)ethyl, 3-(fluorosulfonyloxy)propyl, 3-(fluorosulfonyloxy)propyl, 4-(fluorosulfonyloxy)-2-butenyl, 4-(fluorosulfonyloxy)-2-butynyl, trimethylsilyl, (trimethylsilyl)methyl, (trimethylsilyl)ethyl, (trimethylsilyl)propyl, 2-(trimethylsiloxy)ethyl, 3-(trimethylsiloxy)propyl, 4-(trimethylsilyl)-2-butenyl, 4-(trimethylsilyl)-2-butynyl, phenyl, 2-fluorophenyl, 2,4-difluorophenyl, 2,6-difluorophenyl 2,5-Difluorophenyl, 2-(cyano)phenyl, 3-(cyano)phenyl, 4-(cyano)phenyl, 2-(acetyl)phenyl, 3-(acetyl)phenyl, 4-(acetyl)phenyl, 2-(acetoxy)phenyl, 3-(acetoxy)phenyl, 4-(acetoxy)phenyl, 2-(methanesulfonyloxy)phenyl, 3-(methanesulfonyloxy)phenyl, 4-(methanesulfonyloxy)phenyl, 2-(fluorosulfonyloxy)phenyl, 3-(fluorosulfonyloxy)phenyl, 4-(fluorosulfonyloxy)phenyl, 2-(trimethylsiloxy)phenyl, 3-(trimethylsiloxy)phenyl or 4-(trimethylsiloxy)phenyl.

6. The non-aqueous electrolyte according to claim 1, characterized in that, R1-R5 and R7-R9 are each independently selected from methyl, ethyl, n-propyl, isopropyl, cyclopropyl, vinyl, 2-propenyl, 2-propynyl, 2-fluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 3-fluoropropyl, 3,3,3-trifluoropropyl, 2,2,3,3-tetrafluoropropyl, 2,2,3,3,3-pentafluoropropyl, 2,2-difluoropropyl, 1,1,1-trifluoroisopropyl, hexafluoroisopropyl, 2-(cyano)ethyl, 2-(acetyl)ethyl, and 2-(acetyl)ethyl. (Oxy)ethyl, acetylacetyl, 2-(methanesulfonyloxy)ethyl, 2-(methanesulfonyl)ethyl, 2-(fluorosulfonyloxy)ethyl, 2-(fluorosulfonyl)ethyl, trimethylsilyl, (trimethylsilyl)methyl, (trimethylsilyl)ethyl, 2-(trimethylsiloxy)ethyl, phenyl, 2-fluorophenyl, 2,4-difluorophenyl, 2,6-difluorophenyl, 2,5-difluorophenyl, 2-(cyano)phenyl, 3-(cyano)phenyl or 4-(cyano)phenyl; R6 is selected from methyl, ethyl, n-propyl, isopropyl, cyclopropyl, vinyl, 2-propenyl, 2-propynyl, 2-fluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 3-fluoropropyl, 3,3,3-trifluoropropyl, 2,2,3,3-tetrafluoropropyl, 2,2,3,3,3-pentafluoropropyl, 2,2-difluoropropyl, 1,1,1-trifluoroisopropyl, hexafluoroisopropyl, 2-(acetoxy)ethyl, acetylethyl, 2-(methanesulfonyloxy)ethyl, 2-(methanesulfonyl)ethyl, 2-(fluorosulfonyloxy)ethyl, trimethylsilyl, (trimethylsilyl)methyl, (trimethylsilyl)ethyl, 2-(trimethylsilyloxy)ethyl, phenyl, 2-fluorophenyl, 2,4-difluorophenyl, 2,6-difluorophenyl, or 2,5-difluorophenyl; R 10 -R 12 The same, and all selected from ethyl, n-propyl, isopropyl, cyclopropyl, vinyl, 2-propenyl, 2-propynyl, 2-fluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 3-fluoropropyl, 3,3,3-trifluoropropyl, 2,2,3,3-tetrafluoropropyl, 2,2,3,3,3-pentafluoropropyl, 2,2-difluoropropyl, 1,1,1-trifluoroisopropyl, hexafluoroisopropyl, 2-(cyano)ethyl, 2-(acetoxy)ethyl 2-(methanesulfonyloxy)ethyl, 2-(methanesulfonyl)ethyl, 2-(fluorosulfonyloxy)ethyl, 2-(fluorosulfonyl)ethyl, trimethylsilyl, (trimethylsilyl)methyl, (trimethylsilyl)ethyl, 2-(trimethylsiloxy)ethyl, phenyl, 2-fluorophenyl, 2,4-difluorophenyl, 2,6-difluorophenyl, 2,5-difluorophenyl, 2-(cyano)phenyl, 3-(cyano)phenyl or 4-(cyano)phenyl.

7. The non-aqueous electrolyte according to claim 1, characterized in that, Additive A comprises any one or a combination of at least two of the following compounds: ； ； ； ； ； ； ； ； ； ； ； ； ； ； 。 8. The non-aqueous electrolyte according to claim 1, characterized in that, Additive B comprises any one or a combination of at least two of the following compounds: ； ； ； ； ； 。 9. The non-aqueous electrolyte according to claim 1, characterized in that, Based on the mass of the non-aqueous electrolyte as 100%, the mass percentage content of additive A in the electrolyte additive is 0.5~10%, and the content of additive B is 0.1-100ppm.

10. The non-aqueous electrolyte according to claim 1, characterized in that, The non-aqueous solvent is selected from one or a combination of at least two of the following: cyclic carbonates, chain carbonates, cyclic carboxylic esters, chain carboxylic esters, fluorocarbonates, fluoroether solvents, or sulfone solvents.

11. The non-aqueous electrolyte according to claim 10, characterized in that, The non-aqueous solvent includes one or a combination of at least two of the following: ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, ethyl acetate, propyl acetate, propyl propionate, γ-valerolactone, methyl acetate, methyl butyrate, ethyl butyrate, or propyl butyrate.

12. The non-aqueous electrolyte according to claim 1, characterized in that, The electrolyte is an alkali metal salt.

13. The non-aqueous electrolyte according to claim 12, characterized in that, The alkali metal salt is a lithium salt.

14. The non-aqueous electrolyte according to claim 13, characterized in that, The lithium salt is selected from any one or a combination of at least two of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluorosulfonyl)imide, lithium bis(oxalato)borate, lithium difluorooxalatoborate, lithium difluorophosphate, or lithium difluorobis(oxalato)phosphate.

15. The non-aqueous electrolyte according to claim 1, characterized in that, The concentration of the electrolyte in the non-aqueous electrolyte is 0.5~1.5 mol / L.

16. The non-aqueous electrolyte according to claim 1, characterized in that, The non-aqueous electrolyte also includes other additives, which include any one or a combination of at least two of carbonates, sulfonates, sulfates, cyanate compounds, borates, or silicon compounds.

17. The non-aqueous electrolyte according to claim 16, characterized in that, The other additives include any one or a combination of at least two of the following: fluoroethylene carbonate, difluoroethylene carbonate, vinylene carbonate, ethylene ethylene carbonate, 1,3-propanesulfonate lactone, 1,4-propanesulfonate lactone, 2,4-butanesulfonate lactone, 1,3-propenesulfonate lactone, methyl disulfonate, vinyl sulfite, vinyl sulfate, 4-methyl vinyl sulfate, 4-propyl vinyl sulfate, succinic acid, adiponitrile, ethylene glycol bis(propionitrile) ether, 1,3,6-hexanetrionitrile, trimethyl borate, triethyl borate, triethylene borate, triisopropyl borate, triallyl borate, triphenyl borate, tri(trimethylsilyl)borate, or tetravinylsilane.

18. The non-aqueous electrolyte according to claim 16, characterized in that, Based on the mass of the non-aqueous electrolyte as 100%, the mass percentage content of the other additives is 0.001~10%.

19. An electrochemical device, characterized in that, The electrochemical device includes a positive electrode, a negative electrode, a membrane disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte as described in any one of claims 1-18.

20. The electrochemical device according to claim 19, characterized in that, The positive electrode includes a positive current collector and a positive electrode film coated on the surface of the positive current collector. The positive electrode film includes a positive active material, a positive conductive agent, and a positive binder.

21. The electrochemical device according to claim 20, characterized in that, The positive electrode active material is lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, aluminum nickel cobalt manganese oxide, lithium-rich manganese-based solid solution, or ternary material. Any one of the following, where: 0 < x < 1, 0 < y < 1, 0 < z < 1 and 0 < x + y + z < 1.

22. The electrochemical device according to claim 19, characterized in that, The negative electrode sheet includes a negative current collector and a negative electrode film coated on the surface of the negative current collector. The negative electrode film includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder.

23. The electrochemical device according to claim 22, characterized in that, The negative electrode active material is any one of artificial graphite, natural graphite, silicon-carbon negative electrode, or silicon negative electrode.

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