A method for synthesizing cyclic sulfate and its application in lithium-ion batteries

Abstract

The present invention provides a synthetic method for preparing cyclic sulfate, comprising the steps of: adding hydrogen peroxide dropwise to a mixture containing cyclic sulfite, an organic solvent and a solid catalyst for oxidation reaction; the solid catalyst adopts vanadium-based V / SBA-15 molecular sieve. The product recovery rate obtained by the method is high and the purity is high; the recovered solvent and catalyst can be directly recycled, which is cost-saving for production, and the process byproducts have no high-salt wastewater, which is green and environmentally friendly, suitable for large-scale production, and has broad market prospects. The obtained compound can be used as an electrolyte additive, and synergistically acts with fluoroethylene carbonate to improve the rate performance of lithium ion batteries under high voltage, and improve the discharge capacity of lithium batteries under 5C high current.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and in particular relates to a cyclic sulfate ester for lithium ion batteries, and specifically relates to a synthesis method of the cyclic sulfate ester and application of the cyclic sulfate ester in lithium ion batteries. Background Art

[0002] Organic cyclic sulfate additives are an important class of film-forming additives that can inhibit the decline in the initial capacity of the battery, increase the initial discharge capacity, improve the high and low temperature cycle performance, reduce the battery expansion after high temperature placement, and improve the battery's charge and discharge performance and cycle times. Although traditional vinyl sulfate additives have superior performance in batteries, they have their essential defects, such as easy water absorption and hydrolysis in the air, thermal instability, color change at room temperature, storage temperature of 2 to 8 ° C, and cold chain logistics, which brings many inconveniences to industrial production preparation and transportation. It is particularly important to synthesize a sulfate additive that not only has good thermal stability but also can improve battery performance. Sulfate compounds with multi-ring connections have a larger molecular weight and better thermal stability than traditional sulfate compounds. In addition, this type of additive can also form an SEI layer on the anode surface or cathode surface, reduce battery expansion after high temperature placement, and improve discharge capacity at low temperatures.

[0003] The production processes of cyclic sulfates reported so far mainly include acylation, sulfonation addition, and oxidation. Although the acylation method uses cheap raw materials, it has low yield, strong corrosive byproducts, high equipment requirements, environmental pollution, and is not suitable for large-scale preparation (Chem. Eur. J. 1997, 3, 517-522.). The sulfonation addition method uses ethylene oxide (Fr. Dermande, 1992, 10, Jan., 2664274; CN108658928A) or pentaerythritol (CN114478570A) to react with sulfur trioxide for sulfonation addition. These lines all use highly corrosive and irritating sulfur trioxide.

[0004] Oxidation is a commonly used preparation method. There are many literature reports. The first is to use sodium hypochlorite to oxidize cyclic sulfite. Although the oxidizing property is strong, the oxygen content is low, and a large amount of sodium chloride wastewater is produced as a byproduct, which is not environmentally friendly. In addition, a large amount of sodium ions and chloride ions are introduced into the system, and the addition of additives makes it difficult to purify in the later stage. In addition, in this system, precious metals are used as catalysts, and such catalysts are difficult to recycle, which leads to high production costs (Can. J. Chem. 2013, Vol. 91; CN112694484A; CN114380844A;). The second method is to use sodium periodate as an oxidant to oxidize sulfite. Sodium periodate is expensive and also has the problem of being difficult to recycle and not suitable for industrial production (J. Chem. Soc., Perkin Trans. 2001, 1, 407-414; Can. J. Chem. 2001, Vol. 79; J. Org. Chem., 1998, 63, 5240-5244).

[0005] In addition to the above synthesis methods, Zhangjiagang Guotai Huarong Chemical New Materials Co., Ltd. uses titanium silicon molecular sieve as a catalyst and hydrogen peroxide as an oxidant, which is green and environmentally friendly (CN 111285884 A), but the reaction time is long and the yield is low. The reaction system uses a two-step reaction and is carried out in two different solvents. The subsequent solvent separation and reuse is difficult and the solvent treatment amount is large. Changshu Changji Chemical Co., Ltd. uses direct oxidation with hydrogen peroxide. The solid catalyst used contains active components, active additives and oxide carriers. Although the production process does not produce waste salt and the catalyst is recyclable, its product yield is low and the economic benefit is not high (CN111909129A). Summary of the invention

[0006] One of the purposes of the present invention is to provide a synthetic method for preparing cyclic sulfate esters, which can solve the above-mentioned problems existing in the existing synthetic methods, and to use the compound as an additive in lithium ion batteries.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing cyclic sulfate by oxidizing cyclic sulfite with hydrogen peroxide comprises the following steps:

[0009] Adding hydrogen peroxide dropwise into a mixture containing cyclic sulfite, an organic solvent and a solid catalyst to carry out an oxidation reaction;

[0010] The solid catalyst adopts vanadium-based V / SBA-15 molecular sieve;

[0011] The organic solvent is a single organic solvent and is compatible with the cyclic sulfite and the target cyclic sulfate.

[0012] According to an embodiment of the present invention, the reaction process of the cyclic sulfite to obtain the cyclic sulfate is as follows:

[0013]

[0014] Wherein, R1 and R2 are the same or different and are independently selected from hydrogen, halogen, C 1-12 Alkyl, C 2-12 Alkenyl, C 2-12 Alkynyl, C 1-12 Alkoxy, halogen substituted C 1-12 Alkyl or halogen substituted C 1-12 Alkoxy;

[0015] a, b are the same or different and are independently selected from 1, 2 or 3;

[0016] m, n, x, y, p and q are the same or different and are independently selected from 0, 1, 2 or 3.

[0017] According to an embodiment of the present invention, the halogen atom is fluorine, chlorine, bromine or iodine, preferably fluorine, chlorine or bromine.

[0018] According to an embodiment of the present invention, the reaction is stirred at -5 to 120°C for 0.5 to 24 hours, such as 0.5 to 7 hours.

[0019] According to the embodiment of the present invention, after the reaction is completed, the solid catalyst can be filtered out, the filtrate is allowed to stand for stratification, MgSO4 is added to the organic layer for drying, the filtrate is filtered again and frozen and crystallized, and the finished cyclic sulfate is directly obtained after the crystals are dried. The solvent (organic layer) and catalyst recovered in the above method can be directly recycled, that is, used as the solvent for the above reaction again, and there is no limit on the number of times.

[0020] According to an embodiment of the present invention, the vanadium-based V / SBA-15 molecular sieve can be prepared by referring to the method described in Journal of Liaoning Petrochemical University, 2013, 33(1): 1168-1171.

[0021] In a preferred embodiment of the present invention, the reaction solvent is one of dichloromethane, dichloroethane, tetrahydrofuran, acetonitrile, toluene, benzene, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0022] In a preferred embodiment of the present invention, the conditions of the oxidation reaction are: reaction temperature is 0-35° C., and reaction time is 0.5-7 hours.

[0023] In a preferred embodiment of the present invention, the molar ratio of the cyclic sulfite to the hydrogen peroxide in hydrogen peroxide is 1:1-20, for example 1:1-5.

[0024] In a preferred embodiment of the present invention, the mass concentration of the hydrogen peroxide is 25-35%, for example, 30-31%.

[0025] In a preferred embodiment of the present invention, hydrogen peroxide is added to the reaction system in a dropwise manner.

[0026] In a preferred embodiment of the present invention, the amount of the solid catalyst is 0.2-80% of the mass of the cyclic sulfite, such as 1-50%, such as 4-10%.

[0027] In a preferred embodiment of the present invention, the cyclic sulfite is selected from, but not limited to, one of the following:

[0028]

[0029]

[0030] Wherein, R1, R2, R3, R4 are the same or different and are independently selected from hydrogen, halogen, C 1-6 Alkyl, C 2-6 Alkenyl, C 2-6 Alkynyl, C 1-6 Alkoxy, halogen substituted C 1-6 Alkyl or halogen substituted C 1-6 Alkoxy.

[0031] The present invention also provides an electrolyte containing the cyclic sulfate ester obtained by the above method and application thereof in a lithium ion battery.

[0032] The cyclic sulfate prepared by the present invention can be used as an electrolyte additive. The lithium ion battery also includes a positive electrode material, a negative electrode material and an electrolyte; when used as an electrolyte additive, it can also synergize with fluoroethylene carbonate to improve the ionic conductivity of the lithium ion electrolyte and improve the rate performance of the lithium ion battery.

[0033] The present invention provides an electrolyte, the electrolyte comprising a lithium salt, an anhydrous organic solvent and an electrolyte additive, wherein the electrolyte additive is the cyclic sulfate ester compound and fluoroethylene carbonate (FEC) as described above,

[0034]

[0035] Preferably, the cyclic sulfate compound is specifically as follows:

[0036]

[0037]

[0038] Wherein, R1, R2, R3, R4 are independently selected from hydrogen, halogen, C 1-6 Alkyl, C 1-6 Alkoxy, halogen substituted C 1-6 Alkyl or halogen substituted C 1-6 Alkoxy.

[0039] According to the present invention, the cut-off operating voltage of the lithium-ion battery is 4.5V.

[0040] According to the present invention, the lithium ion battery can achieve a discharge capacity of 165.4 mAh / g at a 5C rate.

[0041] According to the present invention, the cyclic sulfate accounts for 0.05-10 wt % of the total mass of the electrolyte, and the fluoroethylene carbonate accounts for 1-12 wt % of the total mass of the electrolyte.

[0042] According to the present invention, the organic solvent accounts for 8 to 85 wt% of the total mass of the electrolyte; the total concentration of the lithium salt in the electrolyte is 0.6 to 1.3 mol·L -1 .

[0043] According to the present invention, the organic solvent is a linear carbonate or a cyclic carbonate, for example, a mixture of any one or more of ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and ethyl methyl carbonate (DMC), preferably two or three of the above organic solvents.

[0044] According to the present invention, the lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), lithium tetrafluoroborate (LiBF4), lithium bis(oxalatoborate) (LiBOB), lithium difluorooxalatoborate (LiODFB), and lithium perchlorate (LiClO4).

[0045] According to the present invention, there is no particular limitation on the specific types of the positive electrode active material and the negative electrode active material.

[0046] According to the present invention, the positive electrode active material of the lithium-ion battery includes one or more of lithium cobalt oxide, nickel-manganese binary material, nickel-cobalt-manganese-lithium ternary material, lithium iron phosphate and lithium manganese oxide.

[0047] According to the present invention, the negative electrode material is metallic lithium, graphite-like carbon material, coke, mesophase carbon microbeads or silicon-based material.

[0048] According to the present invention, the positive electrode material is LiNi 0.6 Co 0.2Mn 0.2 O2, the negative electrode material is a metal lithium sheet, the electrolyte includes a lithium salt, an organic solvent and an additive, the lithium salt is selected from LiPF6, and the concentration of LiPF6 is 1.0 mol·L -1 The organic solvent is selected from EC:EMC:DMC=1:1:1 (mass ratio), which is defined as the basic electrolyte; the additives are cyclic sulfate and fluoroethylene carbonate (FEC), wherein the cyclic sulfate accounts for 0.5% of the total mass of the electrolyte and the FEC accounts for 3% of the total mass of the electrolyte.

[0049] The present invention has the following advantages and effects:

[0050] The synthesis method of the cyclic sulfate ester provided by the present invention uses the highly efficient and inexpensive V / SBA-15 molecular sieve as a catalyst, and the cyclic sulfate ester is obtained by directly oxidizing the cyclic sulfite with hydrogen peroxide. On the one hand, no high-salt wastewater is generated, and the production process is green and environmentally friendly; on the other hand, a single solvent is used, the reaction is mild, the steps are simple, and the reaction yield is high; thirdly, the catalyst is recyclable, and the production cost is reduced, which has outstanding advantages.

[0051] In addition, the cyclic sulfate prepared by the present invention can be used as an additive for lithium battery electrolytes, and can be used in combination with fluoroethylene carbonate (FEC) additives to improve the ionic conductivity of lithium ion electrolytes and enhance the rate performance of lithium ion batteries.

[0052] Definitions and explanations of terms

[0053] The term "C 1-12 "Alkyl" is understood to mean a straight-chain or branched saturated monovalent hydrocarbon group having 1 to 12 carbon atoms. Preferably "C 1-6 Alkyl". 1-6 Alkyl represents a straight chain and branched alkyl group having 1, 2, 3, 4, 5, or 6 carbon atoms. The alkyl group is, for example, methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, isopentyl, 2-methylbutyl, 1-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, neopentyl, 1,1-dimethylpropyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 2-ethylbutyl, 1-ethylbutyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 2,3-dimethylbutyl, 1,3-dimethylbutyl or 1,2-dimethylbutyl or the like or isomers thereof.

[0054] The term "C 2-12 "Alkenyl" is understood to mean a linear or branched monovalent hydrocarbon radical containing one or more double bonds and having 2 to 12 carbon atoms, preferably "C 2-6 "C 2-6"Alkenyl" is understood to mean preferably a linear or branched monovalent hydrocarbon radical which contains one or more double bonds and has 2, 3, 4, 5, 6 carbon atoms, in particular 2 or 3 carbon atoms ("C 2-3 "alkenyl"), it being understood that, in the case where the alkenyl contains more than one double bond, the double bonds may be separated from one another or conjugated. The alkenyl is, for example, vinyl, allyl, (E)-2-methylvinyl, (Z)-2-methylvinyl, (E)-but-2-enyl, (Z)-but-2-enyl, (E)-but-1-enyl, (Z)-but-1-enyl, pent-4-enyl, (E)-pent-3-enyl, (Z)-pent-3-enyl, -enyl, (E)-pent-2-enyl, (Z)-pent-2-enyl, (E)-pent-1-enyl, (Z)-pent-1-enyl, hex-5-enyl, (E)-hex-4-enyl, (Z)-hex-4-enyl, (E)-hex-3-enyl, (Z)-hex-3-enyl, (E)-hex-2-enyl, (Z)-hex-2-enyl, (E)-hex-1-enyl, (Z)-hex-1-enyl, isopropenyl, 2-hexenyl, (E)-pent-2-enyl, (Z)-pent-2-enyl, (E)-pent-1-enyl, (Z)-pent ...1-enyl, (Z)-pent-1-enyl, isopropenyl, 2-hexenyl, (E)-pent-2- -methylprop-2-enyl, 1-methylprop-2-enyl, 2-methylprop-1-enyl, (E)-1-methylprop-1-enyl, (Z)-1-methylprop-1-enyl, 3-methylbut-3-enyl, 2-methylbut-3-enyl, 1-methylbut-3-enyl, 3-methylbut-2-enyl, (E)-2-methylbut-2-enyl, (Z)-2-methylbut-2-enyl, (E)-1-methylbut-2-enyl 1-ethylprop-1-enyl, 1-propylvinyl, and 1-isopropylvinyl.

[0055] The term "C 2-12The term "alkynyl" is understood as meaning a linear or branched monovalent hydrocarbon radical which contains one or more triple bonds and has 2 to 12 carbon atoms, preferably a "C2-C6-alkynyl radical". The term "C2-C6-alkynyl" is understood as preferably meaning a linear or branched monovalent hydrocarbon radical which contains one or more triple bonds and has 2, 3, 4, 5, 6 carbon atoms, in particular 2 or 3 carbon atoms ("C2-C3-alkynyl"). Such alkynyl radicals are, for example, ethynyl, prop-1-ynyl, prop-2-ynyl, but-1-ynyl, but-2-ynyl, but-3-ynyl, pent-1-ynyl, pent-2-ynyl, pent-3-ynyl, pent-4-ynyl, hex-1-ynyl, hex-2-ynyl, hex-3-ynyl, hex-4-ynyl, hex-5-ynyl, 1-methylprop-2-ynyl, 2-methylbut-3-ynyl, 1-methylbut-3-ynyl, 2-methyl -ynyl, 1-methylbut-2-ynyl, 3-methylbut-1-ynyl, 1-ethylprop-2-ynyl, 3-methylpent-4-ynyl, 2-methylpent-4-ynyl, 1-methylpent-4-ynyl, 2-methylpent-3-ynyl, 1-methylpent-3-ynyl, 4-methylpent-2-ynyl, 1-methylpent-2-ynyl, 4-methylpent-1-ynyl, 3-methylpent-1-ynyl, 2-methylpent-4-ynyl, 1-methylpent-4-ynyl, 2-methylpent-3-ynyl, 1-methylpent-3-ynyl, 4-methylpent-2-ynyl, 1-methylpent-2-ynyl, 4-methylpent-1-ynyl, 3-methylpent-1-ynyl, 2 In some embodiments, the alkynyl group is ethynyl, prop-1-ynyl or prop-2-ynyl.

[0056] The term "C 1-12 "Alkoxy" is understood to mean -OC 1-12 Alkyl, where C 1-12 Alkyl has the above definition.

[0057] The term "halogen" means fluorine, chlorine, bromine and / or iodine. Correspondingly, the term "halogen-substituted" refers to fluorine, chlorine, bromine and / or iodine. Within the scope of this article, when an atom, residue, group or moiety is halogenated, the atom at the halogenated position may be monosubstituted, disubstituted or polysubstituted up to full substitution by halogen atoms. For example, "halogen-substituted C 1-12 Alkoxy", "halogen-substituted C 1-12 Alkyl". Among them, C 1-12 Alkyl and C 1-12 Alkoxy has the same meaning as defined above. DETAILED DESCRIPTION

[0058] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0059] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0060] Example 1: Preparation of Vanadium-based V / SBA-15 Molecular Sieve

[0061] Add a certain amount of ammonium metavanadate and deionized water to a beaker, add a certain amount of citric acid after dissolving, adjust the solution acid value to pH=3 with hydrochloric acid, and form a transparent solution A. Weigh 11g P123 and dissolve it in 250g deionized water, stir it in a 40℃ water bath for 5h, then add 24g tetraethyl orthosilicate TEOS and A solution, adjust the solution to pH 3 with hydrochloric acid again, stir it for 20h, put the mixed solution into a water heating tank, crystallize it at 100℃ for 24h, filter and wash it, dry it in an oven at 80℃, and sinter it at 650℃ in a muffle furnace for 5h to obtain a vanadium-based V / SBA-15 molecular sieve catalyst.

[0062] Example 2: Preparation of compound (1)

[0063]

[0064] Add 150g of pentaerythritol sulfite, 350g of acetonitrile and 6.5g of V / SBA-15 molecular sieve to the reaction bottle in sequence, and start stirring at the same time. After fully dissolving, drip 210g of hydrogen peroxide with a mass concentration of 30% into the reaction system, drip it within 2 hours, and continue stirring in a normal temperature water bath for 3 hours after dripping. After the reaction is completed, filter and collect the molecular sieve catalyst, let the filtrate stand to take the organic layer, dry the organic layer over magnesium sulfate, and put the filtered filtrate into a freezer for freezing and crystallization overnight, filter out the crystals, and evaporate the residual solvent and water at 80 degrees Celsius in vacuum to obtain 166.7g of pentaerythritol sulfate with the structural formula of formula (1), with a purity of 99.8% and a yield of 97.5%.

[0065] Example 3: Preparation of compound (2)

[0066]

[0067] The preparation method is basically the same as that of Example 2, except that pentaerythritol sulfite is replaced by ethylene dithionite, to obtain 166.6 g of compound (2) with a purity of 99.6% and a yield of 96.5%.

[0068] Example 4: Preparation of compound (3)

[0069]

[0070] The preparation method is basically the same as in Example 2, except that pentaerythritol sulfite is replaced by Cyclic sulfite was obtained to obtain 165.5 g of compound (3) with a purity of 99.7% and a yield of 95.1%.

[0071] Example 5: Repeated synthesis of compound (2) vinyl dithionate using recovered V / SBA-15 molecular sieve catalyst

[0072] The catalyst recovered in Example 3 was used to repeat the preparation experiment of compound (2) vinyl dithionate according to the feed amount and process of Example 2, and the solid catalyst was continuously recovered and recycled. It was reused 6 times in total. The results of the 6 experiments are shown in the following table:

[0073]

[0074] It can be seen from the above table that the vanadium-based V / SBA-15 molecular sieve catalyst used can be directly put into the next reaction system without any treatment and can be recycled and reused. The catalyst has stable reaction activity, high product conversion rate and high purity. At the same time, it can reduce the use of precious metal catalysts, reduce raw material costs, and save costs in production.

[0075] Example 6: Preparation of a lithium ion battery containing compound (1)

[0076] Preparation of electrolyte: In a glove box filled with argon (water content <1ppm, oxygen content <1ppm), the organic solvent EC:EMC:DMC = 1:1:1 (mass ratio) and lithium salt LiPF6 were prepared to a concentration of 1.0 mol·L -1 The electrolyte of Example 6 was obtained by adding the compound (1) obtained in Example 2 and fluoroethylene carbonate (FEC), wherein the amount of compound (1) added was 0.2% of the total mass of the electrolyte, and the amount of fluoroethylene carbonate added was 3% of the total mass of the electrolyte. After stirring evenly, the electrolyte of Example 6 was obtained.

[0077] Preparation of the battery: The positive electrode active material nickel-cobalt-manganese high-nickel ternary material LiNi 0.6 Co 0.2 Mn 0.2O2, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in a N-methylpyrrolidone (NMP) system at a mass ratio of 8:1:1. The mixed slurry is coated on aluminum foil with an automatic coating machine, and the coated electrode is placed in an 80°C vacuum oven for drying for 10 hours. After drying and rolling, the positive electrode is obtained. The next day, the large electrode is rolled and cut into 16mm small discs at room temperature. The cut small discs are then vacuumed at 80 degrees Celsius for 12 hours. The dried electrode is assembled into a 2025 button battery with a diaphragm, electrolyte, lithium sheet, and positive and negative electrode shells in a glove box filled with argon (water <1ppm, oxygen <1ppm).

[0078] Rate test method: 0.1C constant current charge to 4.5V, 0.1C constant current discharge to 3.0V, cycle 10 weeks, 0.2C constant current charge to 4.5V, 0.2C constant current discharge to 3.0V, cycle 10 weeks, 0.5C constant current charge to 4.5V, 0.5C constant current discharge to 3.0V, cycle 10 weeks, 1C constant current charge to 4.5V, 1C constant current discharge to 3.0V, cycle 10 weeks, 2C constant current charge to 4.5V, 2C constant current discharge to 3.0V, cycle 10 weeks, 5C constant current charge to 4.5V, 5C constant current discharge to 3.0V, cycle 10 weeks, 0.1C constant current charge to 4.5V, 0.1C constant current discharge to 3.0V. The test results are shown in Table 1.

[0079] Example 7: Preparation of a lithium ion battery containing compound (2)

[0080] Preparation of electrolyte: In a glove box filled with argon (water content <1ppm, oxygen content <1ppm), the organic solvent EC:EMC:DMC = 1:1:1 (mass ratio) and lithium salt LiPF6 were prepared to a concentration of 1.0 mol·L -1 The electrolyte of Example 7 is obtained by adding the compound (2) obtained in Example 3 and fluoroethylene carbonate, wherein the amount of compound (2) added is 0.5% of the total mass of the electrolyte, and the amount of fluoroethylene carbonate added is 3% of the total mass of the electrolyte. After stirring evenly, the electrolyte of Example 7 is obtained.

[0081] The preparation of the battery and the rate test method are basically the same as those in Example 6. The test results are shown in Table 1.

[0082] Example 8: Preparation of a lithium ion battery containing compound (3)

[0083] Preparation of electrolyte: In a glove box filled with argon (water content <1ppm, oxygen content <1ppm), the organic solvent EC:EMC:DMC = 1:1:1 (mass ratio) and lithium salt LiPF6 were prepared to a concentration of 1.0 mol·L -1The electrolyte of Example 8 was obtained by adding compound (3) obtained in Example 4 and fluoroethylene carbonate, wherein the amount of compound (3) added was 2% of the total mass of the electrolyte, and the amount of fluoroethylene carbonate added was 3% of the total mass of the electrolyte. After stirring evenly, the electrolyte of Example 8 was obtained.

[0084] The preparation of the battery and the rate test method are basically the same as those in Example 6. The test results are shown in Table 1.

[0085] Example 9

[0086] Preparation of electrolyte: In a glove box filled with argon (water content <1ppm, oxygen content <1ppm), the organic solvent EC:EMC:DMC = 1:1:1 (mass ratio) and lithium salt LiPF6 were prepared to a concentration of 1.0 mol·L -1 The electrolyte of Example 9 was obtained by adding compound (1) in an amount of 0.2% of the total mass of the electrolyte and stirring.

[0087] The preparation of the battery and the rate test method are basically the same as those in Example 6. The test results are shown in Table 1.

[0088] Example 10

[0089] Preparation of electrolyte: In a glove box filled with argon (water content <1ppm, oxygen content <1ppm), the organic solvent EC:EMC:DMC = 1:1:1 (mass ratio) and lithium salt LiPF6 were prepared to a concentration of 1.0 mol·L -1 The electrolyte of Example 10 is then added with compound (2), wherein the amount of compound (2) added accounts for 0.5% of the total mass of the electrolyte. After stirring evenly, the electrolyte of Example 10 is obtained.

[0090] The preparation of the battery and the rate test method are basically the same as those in Example 6. The test results are shown in Table 1.

[0091] Embodiment 11

[0092] Preparation of electrolyte: In a glove box filled with argon (water content <1ppm, oxygen content <1ppm), the organic solvent EC:EMC:DMC = 1:1:1 (mass ratio) and lithium salt LiPF6 were prepared to a concentration of 1.0 mol·L -1 The electrolyte of Example 11 is then added with compound (3), wherein the amount of compound (3) added accounts for 2% of the total mass of the electrolyte. After stirring evenly, the electrolyte of Example 11 is obtained.

[0093] The preparation of the battery and the rate test method are basically the same as those in Example 6. The test results are shown in Table 1.

[0094] Comparative Example 1

[0095] Preparation of electrolyte: In a glove box filled with argon (water content <1ppm, oxygen content <1ppm), the organic solvent EC:EMC:DMC = 1:1:1 (mass ratio) and lithium salt LiPF6 were prepared to a concentration of 1.0 mol·L -1 The electrolyte of Comparative Example 1 was obtained by adding fluoroethylene carbonate (FEC) in an amount of 3% of the total mass of the electrolyte and stirring evenly.

[0096] The preparation of the battery and the rate test method are basically the same as those in Example 6. The test results are shown in Table 1.

[0097] Comparative Example 2

[0098] Preparation of electrolyte: In a glove box filled with argon (water content <1ppm, oxygen content <1ppm), the organic solvent EC:EMC:DMC = 1:1:1 (mass ratio) and lithium salt LiPF6 were prepared to a concentration of 1.0 mol·L -1 The electrolyte of Comparative Example 2 was obtained after stirring evenly.

[0099] The preparation of the battery and the rate test method are basically the same as those in Example 6. The test results are shown in Table 1.

[0100] Table 1 Rate battery test results

[0101]

[0102] As can be seen from Table 1, adding the two additives, cyclic sulfate and fluoroethylene carbonate, to the electrolyte simultaneously can play a synergistic role in improving the rate performance of lithium-ion batteries under high voltage and increasing the discharge capacity of lithium batteries under a high current of 5C. However, the electrolyte of the comparative example has little effect on enhancing the rate performance of the battery.

[0103] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing cyclic sulfate by oxidizing cyclic sulfite with hydrogen peroxide, characterized in that: The steps include: Adding hydrogen peroxide dropwise into a mixture containing cyclic sulfite, an organic solvent and a solid catalyst to carry out an oxidation reaction; The solid catalyst is a vanadium-based V / SBA-15 molecular sieve; The organic solvent is a single organic solvent and is miscible with the cyclic sulfite and the target cyclic sulfate; The reaction process of the cyclic sulfite to obtain the cyclic sulfate is as follows: ； ； ； ； ； Wherein, R1 and R2 are the same or different and are independently selected from hydrogen, halogen, C 1-12 Alkyl, C 2-12 Alkenyl, C 2-12 Alkynyl, C 1-12 Alkoxy, halogen substituted C 1-12 Alkyl or halogen substituted C 1-12 Alkoxy; a, b are the same or different and are independently selected from 1, 2 or 3; m, n, x, y, p and q are the same or different and are independently selected from 0, 1, 2 or 3.

2. A method for preparing cyclic sulfate by oxidizing cyclic sulfite with hydrogen peroxide, characterized in that: The steps include: Adding hydrogen peroxide dropwise into a mixture containing cyclic sulfite, an organic solvent and a solid catalyst to carry out an oxidation reaction; The solid catalyst is a vanadium-based V / SBA-15 molecular sieve; The organic solvent is a single organic solvent and is miscible with the cyclic sulfite and the target cyclic sulfate; The cyclic sulfite is selected from one of the following: ； ； ； ； ； Wherein, R1, R2, R3, R4 are the same or different and are independently selected from hydrogen, halogen, C 1-6 Alkyl, C 2-6 Alkenyl, C 2-6 Alkynyl, C 1-6 Alkoxy, halogen substituted C 1-6 Alkyl or halogen substituted C 1-6 Alkoxy.

3. The method according to claim 1 or 2, characterized in that: The conditions for the oxidation reaction are: the reaction temperature is 0~35 o C, the reaction time is 0.5~7 hours.

4. The method according to claim 1 or 2, characterized in that: The organic solvent is one of dichloromethane, dichloroethane, tetrahydrofuran, acetonitrile, toluene, benzene, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

5. The method according to claim 1 or 2, characterized in that: The molar ratio of the cyclic sulfite to the hydrogen peroxide in the hydrogen peroxide is 1:1-20.

6. The method according to claim 1 or 2, characterized in that: After the reaction is completed, the solid catalyst is filtered out, the filtrate is allowed to stand for stratification, the organic layer is dried, and the filtrate is filtered again and frozen and crystallized. The crystals are dried to directly obtain the finished cyclic sulfate.

7. The method according to claim 1 or 2, characterized in that: The amount of the solid catalyst used is 0.2-80% of the mass of the cyclic sulfite.

8. The method according to claim 1 or 2, characterized in that: The amount of the solid catalyst used is 1-50% of the mass of the cyclic sulfite.

9. The method according to claim 1 or 2, characterized in that: The amount of the solid catalyst used is 4-10% of the mass of the cyclic sulfite.

10. An electrolyte, characterized in that: The electrolyte comprises a lithium salt, an anhydrous organic solvent and an electrolyte additive, wherein the electrolyte additive is a cyclic sulfate compound prepared by the method according to any one of claims 1 to 9 and fluoroethylene carbonate (FEC) shown in the following structure: 。

Images