A cyclic sulfite compound, electrolyte and lithium ion battery

Abstract

The present application relates to a cyclic sulfite compound additive. The present application also relates to an electrolyte and a lithium-ion battery containing the additive. When the cyclic sulfite compound additive in the present application is used in an energy storage device, the growth of the DC internal resistance can be suppressed, thereby improving the high temperature performance and low temperature performance of the energy storage device.

Description

Technical Field

[0001] The present application relates to the field of lithium-ion batteries, and in particular to a cyclic sulfite compound, an electrolyte, and a lithium-ion battery containing the electrolyte. Background Art

[0002] Due to the unsustainability and high pollution of fossil energy, the development of new green and environmentally friendly energy has become a consensus among people. Lithium-ion batteries have the characteristics of high energy density, long cycle life, wide operating temperature range and environmental friendliness. They have been widely used in mobile phones, notebooks, electric vehicles and other fields.

[0003] The direct-current internal resistance (DCIR) of a battery is an important parameter that affects battery performance. DCIR affects the battery's low-temperature discharge, rate discharge and other performances. Generally speaking, sulfur-containing additives can reduce the impedance of the negative electrode and form a protective film on the positive electrode due to the reduction of sulfur-containing additives to generate components such as ROSO2Li and Li2SO3 at the negative electrode. Therefore, sulfur-containing additives can reduce the direct-current internal resistance of the battery and improve the low-temperature and high-temperature performance of the battery. At present, diethyl sulfate (DTD) is a commonly used sulfur-containing additive. DTD has a certain effect on reducing the direct-current internal resistance of the battery and improving the high and low-temperature performance of the battery. However, due to the poor structural stability of DTD itself, it needs to be stored at low temperature to prevent deterioration, which is very inconvenient in actual use. Therefore, it is urgent to develop new sulfur-containing additives that can reduce the direct-current internal resistance and improve the high and low-temperature performance of the battery. Summary of the invention

[0004] The purpose of the present application is to provide an additive, an electrolyte and a lithium-ion battery containing the electrolyte, wherein the electrolyte can reduce the DC internal resistance of the battery and improve the high and low temperature performance of the battery.

[0005] In order to achieve the above-mentioned object, the first aspect of the present application provides a cyclic sulfite compound, wherein the cyclic sulfite compound has a structure shown in formula (I), formula (II) or formula (III):

[0006]

[0007] In formula (I) to formula (III): X is O, S, NR3 or CR4R5, R1-R 11 Each is independently H, halogen, hydroxyl, cyano, ester, sulfonyl, fluorosulfonyl, sulfonic acid, fluorosulfonic acid, saturated or unsaturated alkyl of 1 to 10 carbon atoms, saturated or unsaturated halogenated alkyl of 1 to 10 carbon atoms, alkoxy of 1 to 10 carbon atoms or fluoroalkoxy of 1 to 10 carbon atoms.

[0008] Wherein, the cyclic sulfite compound is the following compound 1-1 to compound 1-13:

[0009]

[0010] The second aspect of the present application provides a method for preparing the cyclic sulfite compound, wherein the method comprises: contacting a dihydroxy compound with SOCl under condensation reaction conditions in the presence of a reaction catalyst and a reaction solvent; the dihydroxy compound has a structure shown in formula (A), formula (B) or formula (C):

[0011]

[0012] In formula (A), formula (B) and formula (C): X is O, S, NR3 or CR4R5, R1-R 11 Each is independently H, halogen, hydroxyl, cyano, ester, sulfonyl, fluorosulfonyl, sulfonic acid, fluorosulfonic acid, saturated or unsaturated alkyl of 1 to 10 carbon atoms, saturated or unsaturated halogenated alkyl of 1 to 10 carbon atoms, alkoxy of 1 to 10 carbon atoms or fluoroalkoxy of 1 to 10 carbon atoms.

[0013] Optionally, the dihydroxy compound has any of the following structures:

[0014]

[0015] Wherein, the reaction catalyst is selected from at least one of SiO2 and Si(OC2H5)4, the reaction solvent is at least one of CH3OH, CH3CH2OH and CH3CN, and the condensation reaction conditions include: temperature of 20-200°C and time of 30-600 minutes.

[0016] A third aspect of the present application provides a lithium-ion battery electrolyte, wherein the lithium-ion battery electrolyte contains an organic solvent, a lithium salt and an additive.

[0017] Optionally, the concentration of the additive in the electrolyte is 0.01-10 wt %, preferably 0.01-5 wt %.

[0018] Optionally, the cyclic sulfite compound is selected from one or more of 3,4-dihydroxythiophene sulfite, 2-methyl-3,4-dihydroxythiophene sulfite, 2,5-dimethyl-3,4-dihydroxythiophene sulfite, 2-trifluoromethyl-3,4-dihydroxythiophene sulfite, 2,5-dimethyl dicarboxylate-3,4-dihydroxythiophene sulfite, N-methyl-3,4-dihydroxypyrrole sulfite, 2-methyl-N-methyl-3,4-dihydroxypyrrole sulfite, 2,5-dimethyl-N-methyl-3,4-dihydroxypyrrole sulfite, 3,4-dihydroxyfuran sulfite, 2-methyl-3,4-dihydroxyfuran sulfite, 2,5-dimethyl-3,4-dihydroxyfuran sulfite, 2,3-dihydroxypyridine sulfite and 3,4-dihydroxypyridine sulfite.

[0019] Optionally, the electrolyte further contains a second additive, and the second additive is selected from one or more compounds represented by formula (IV), formula (V) or formula (VI):

[0020]

[0021] In formula (IV)-formula (VI): R 14 -R 18 R is independently H, halogen, hydroxyl, cyano, sulfonyl, fluorosulfonyl, sulfonic acid, fluorosulfonic acid, saturated or unsaturated alkyl of 1 to 10 carbon atoms, saturated or unsaturated halogenated alkyl of 1 to 10 carbon atoms, alkoxy of 1 to 10 carbon atoms or fluoroalkoxy of 1 to 10 carbon atoms; 12 -R 13 Each is independently a saturated or unsaturated alkyl group having 1 to 10 carbon atoms, a saturated or unsaturated halogenated alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or a fluoroalkoxy group having 1 to 10 carbon atoms.

[0022] Optionally, the concentration of the second additive in the electrolyte is 0.05-2wt%, preferably 0.3-1wt%.

[0023] Wherein, the second additive is selected from one or more of acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride, caproic anhydride, isobutyric anhydride, pivalic anhydride, succinic anhydride, maleic anhydride, citraconic anhydride, bromomaleic anhydride and trifluoromethylmaleic anhydride.

[0024] Optionally, the electrolyte further contains a third additive, which is a cyano or cyanoalkoxy substituted alkane, and the cyano or cyanoalkoxy substituted alkane is selected from one or more of acetonitrile, propionitrile, butyronitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, 1,2-bis(2-cyanoethoxy)ethane, 1,2-bis(2-cyanoethoxy)propane, 1,2-bis(3-cyanopropoxy)ethane, 1,3,6-hexanetrinitrile, 1,2,3-propanetrinitrile, 1,3,5-pentanetrinitrile, 3,3-bis(cyanomethyl)glutaronitrile, 3,3-bis(cyanomethyl)adiponitrile and 1,2,3-tris(2-cyanoethoxy)propane.

[0025] Wherein, the concentration of the third additive in the electrolyte is 0.01-10wt%, preferably 1-5wt%, and more preferably 1-3wt%.

[0026] Optionally, the organic solvent is selected from carbonates and / or carboxylates, the carbonates are selected from one or more of cyclic carbonates and linear carbonates: ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate; the carboxylates are selected from one or more of the following solvents: ethyl acetate, methyl acetate, ethyl propionate, methyl propionate, propyl propionate, butyrolactone.

[0027] Optionally, the lithium salt is selected from one or more of lithium difluoro(oxalato)borate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate and lithium perchlorate.

[0028] Wherein, the concentration of the lithium salt in the electrolyte is 0.5-2 mol / L, preferably 0.8-1.2 mol / L.

[0029] A fourth aspect of the present application provides a lithium-ion battery, comprising a positive electrode material, a negative electrode material and an electrolyte, wherein the electrolyte is the aforementioned electrolyte.

[0030] Optionally, the positive electrode material includes at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium iron phosphate and ternary materials; the negative electrode material includes at least one of soft carbon, hard carbon, carbon fiber, graphitized carbon microspheres, artificial graphite, natural graphite, silicon, silicon carbide and silicon-carbon composite materials.

[0031] Through the above technical solution, the cyclic sulfate ester compound disclosed in the present application can inhibit the growth of DC internal resistance, thereby improving the high temperature performance and low temperature performance of the energy storage device.

[0032] Other features and advantages of the present application will be described in detail in the subsequent detailed description. DETAILED DESCRIPTION

[0033] The specific implementation of the present application is described in detail below. It should be understood that the specific implementation described here is only used to illustrate and explain the present application, and is not used to limit the present application.

[0034] The present application provides a cyclic sulfite compound, wherein the cyclic sulfite compound has a structure shown in formula (I), formula (II) or formula (III):

[0035]

[0036] In formula (I) to formula (III): X is O, S, NR3 or CR4R5, R1-R 11 Each is independently H, halogen, hydroxyl, cyano, ester, sulfonyl, fluorosulfonyl, sulfonic acid, fluorosulfonic acid, saturated or unsaturated alkyl of 1 to 10 carbon atoms, saturated or unsaturated halogenated alkyl of 1 to 10 carbon atoms, alkoxy of 1 to 10 carbon atoms or fluoroalkoxy of 1 to 10 carbon atoms.

[0037] Wherein, the cyclic sulfite additive is selected from one or more of the following compounds 1-1 to 1-13:

[0038]

[0039]

[0040] The present application provides a method for preparing a cyclic sulfite compound, wherein the method comprises: contacting a dihydroxy compound with SOCl under condensation reaction conditions in the presence of a reaction catalyst and a reaction solvent; the dihydroxy compound has a structure shown in formula (A), formula (B) or formula (C):

[0041]

[0042] In formula (A), formula (B) and formula (C): X is O, S, NR3 or CR4R5, R1-R 11 Each is independently H, halogen, hydroxyl, cyano, ester, sulfonyl, fluorosulfonyl, sulfonic acid, fluorosulfonic acid, saturated or unsaturated alkyl of 1 to 10 carbon atoms, saturated or unsaturated halogenated alkyl of 1 to 10 carbon atoms, alkoxy of 1 to 10 carbon atoms or fluoroalkoxy of 1 to 10 carbon atoms.

[0043] The dihydroxy compound has any of the following structures:

[0044]

[0045] The reaction catalyst is selected from at least one of SiO2 and Si(OC2H5)4, the reaction solvent is at least one of CH3OH, CH3CH2OH and CH3CN, and the condensation reaction conditions include: temperature of 20-200°C and time of 30-600 minutes.

[0046] According to the present disclosure, the concentration of the additive in the electrolyte is 0.01-10wt%, preferably 0.01-5wt%. The performance of the battery is closely related to the amount of additive added, and the performance of the battery often shows a trend of first getting better and then getting worse as the content of the additive increases. However, the optimal additives of different additives also fluctuate slightly with the changes of other components in the electrolyte. When the content of the additive in the electrolyte is too low (such as less than 0.01wt%), the degree of participation in the film formation of the positive and negative electrodes is extremely low, there is no obvious modification effect on the positive or negative electrode interface, and there is no obvious improvement in the performance of the battery; when the content of the additive in the electrolyte is high (such as higher than 5wt%), it forms thicker CEI and SEI films at the positive and negative electrodes, making its impedance too large, which is not conducive to the transmission of lithium ions in the SEI film, increases the polarization of the battery, and deteriorates the battery performance.

[0047] Cyclic sulfite compounds are aromatic derivatives of vinyl sulfite. When applied to energy storage devices, during the first charge, the additive is the first to obtain electrons and be reduced due to its lower LUMO orbit, so that it forms a stable, uniform, and thin SEI film on the surface of the negative electrode of the energy storage device, which can inhibit the embedding of solvents in the electrolyte into the negative electrode and reductive decomposition. In addition, since the additive generates alkylated lithium sulfate (ROSO2Li) and lithium sulfite (Li2SO3) after reduction, the S element is introduced into the SEI film, which improves the ionic conductivity of the SEI film and reduces the DC internal resistance of the battery. In addition, the unsaturated bonds in the unsaturated sulfite compounds can passivate the positive electrode surface, inhibit the dissolution of positive transition metal ions, and prevent the electrolyte from being directly in contact with the positive electrode active material and being oxidized and decomposed, thereby improving the stability of the energy storage device under high temperature conditions.

[0048] According to the present disclosure, the electrolyte further contains a second additive, and the second additive is selected from one or more compounds represented by formula (IV) or formula (V) or formula (VI):

[0049]

[0050] In formula (IV)-formula (VI): R 14 -R 18R is independently H, halogen, hydroxyl, cyano, sulfonyl, fluorosulfonyl, sulfonic acid, fluorosulfonic acid, saturated or unsaturated alkyl of 1 to 10 carbon atoms, saturated or unsaturated halogenated alkyl of 1 to 10 carbon atoms, alkoxy of 1 to 10 carbon atoms or fluoroalkoxy of 1 to 10 carbon atoms; 12 -R 13 Each is independently a saturated or unsaturated alkyl group having 1 to 10 carbon atoms, a saturated or unsaturated halogenated alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or a fluoroalkoxy group having 1 to 10 carbon atoms.

[0051] The second additive can obtain electrons at the negative electrode interface and be reduced to form a SEI film. The formed SEI film has good thermal stability, but large impedance. When the cyclic sulfite compound and the second additive are used together, the cyclic sulfite compound and the second additive form a composite SEI film at the negative electrode interface. Compared with the SEI film formed by the cyclic sulfite compound alone, it has better thermal stability; compared with the SEI film formed by the second additive alone, it has lower impedance. Therefore, the combination of the cyclic sulfite compound and the second additive can take into account both the thermal stability and impedance of the negative electrode SEI film.

[0052] Optionally, the second additive has any of the following structures:

[0053]

[0054] Specifically, the concentration of the second additive in the electrolyte is 0.05-2wt%, preferably 0.3-1wt%.

[0055] According to the present disclosure, the electrolyte further contains a third additive, which is a cyano or cyanoalkoxy substituted alkane, and the cyano or cyanoalkoxy substituted alkane is selected from one or more of acetonitrile, propionitrile, butyronitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, 1,2-bis(2-cyanoethoxy)ethane, 1,2-bis(2-cyanoethoxy)propane, 1,2-bis(3-cyanopropoxy)ethane, 1,3,6-hexanetrinitrile, 1,2,3-propanetrinitrile, 1,3,5-pentanetrinitrile, 3,3-bis(cyanomethyl)glutaronitrile, 3,3-bis(cyanomethyl)adiponitrile and 1,2,3-tris(2-cyanoethoxy)propane.

[0056] The third additive can complex the transition metal ions at the positive electrode interface, stabilize the positive electrode interface, thereby protecting the electrolyte from oxidation and improving stability. It can also complex the dissolved metal ions, reduce the deposition of metal ions at the negative electrode interface due to electron gain, and reduce the damage to the SEI film. In addition, the cyano group can also combine with HF to eliminate free HF and avoid HF corrosion of the positive electrode active material. However, the introduction of the third additive will increase the interface impedance. When the cyclic sulfite compound and the third additive are used in combination, the cyclic sulfite compound forms a low-impedance SEI film at the negative electrode, and at the same time works with the third additive to form a positive electrode CEI film. Compared with the use of the third additive alone, its interface impedance is lower; compared with the use of the cyclic sulfite compound alone, its antioxidant property is further enhanced and its thermal stability is improved. Therefore, the combination of the cyclic sulfite compound and the third additive can enhance the interface stability of the positive and negative electrodes, and take into account the impedance.

[0057] Specifically, the concentration of the cyano compound in the electrolyte is 0.01-10 wt %, preferably 1-5 wt %, and more preferably 1-3 wt %.

[0058] According to the present disclosure, the organic solvent is selected from carbonates and / or carboxylates, the carbonates are selected from one or more of cyclic carbonates and linear carbonates: ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate; the carboxylates are selected from one or more of the following solvents: ethyl acetate, methyl acetate, ethyl propionate, methyl propionate, propyl propionate, butyrolactone.

[0059] According to the present disclosure, the lithium salt is selected from one or more of lithium difluoro(oxalato)borate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium perchlorate.

[0060] Specifically, the concentration of lithium salt in the electrolyte is 0.5-2 mol / L, preferably 0.8-1.2 mol / L.

[0061] The present application provides a lithium-ion battery, comprising a positive electrode material, a negative electrode material and an electrolyte, wherein the electrolyte is the aforementioned electrolyte.

[0062] According to the present disclosure, the positive electrode material includes at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium iron phosphate, and ternary materials; the negative electrode material includes at least one of soft carbon, hard carbon, carbon fiber, graphitized carbon microspheres, artificial graphite, natural graphite, silicon, silicon carbide, and silicon-carbon composite materials.

[0063] In one embodiment of the present application, the electrolyte is composed of: ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethylene carbonate (EC), catechol cyclic sulfite, and lithium hexafluorophosphate. EC:EMC+DEC in the electrolyte = 20%-40%:60%-80% (mass ratio total 100%). Within the above ratio range, the EC content is ensured to account for 20%-40% of the solvent in order to ensure that lithium hexafluorophosphate has a good dissociation ability and the electrolyte has a good conductivity; linear carbonate is mainly used to adjust the viscosity of the electrolyte, and its proportion is usually 60%-80%; the concentration of lithium hexafluorophosphate is 9-20wt%. Under normal circumstances, the lithium salt concentration is controlled at around 1mol / L, and the electrolyte conductivity is at a higher value. However, it can also be adjusted according to specific costs and usage requirements. 9-20wt% is a relatively wide range, which basically covers the lithium salt concentration in common formulas.

[0064] The present application is further described below by comparative examples and embodiments, but the present application is not limited thereto.

[0065] The preparation methods of compounds 1-1 to 1-13 and the product confirmation results are as follows:

[0066] The preparation process of compound 1-1 is as follows:

[0067]

[0068] Weigh 11.60g (0.1mol) 3,4-dihydroxythiophene, 20.24g (0.2mol) triethylamine and 6.24g (0.03mol) Si (OC2H5) 4 into a 250mL round-bottom flask, add 50.0mL acetonitrile, and stir at room temperature for 6h. Then slowly add SOCl2 dropwise while stirring, add a total of 59.00g (0.5mol) SOCl2, add dropwise for about 15min, and continue stirring for 3h. After the reaction is completed, filter, wash the filter cake with n-hexane several times, collect the filtrate and remove the solvent to obtain a crude product, and further obtain compound 1-1 by column chromatography with a yield of 80.6%. 1 H NMR (300MHz, CDCl3, δ, ppm): 7.76 (s, 2H).

[0069] The preparation process of compounds 1-2, 1-3, 1-4, 1-5, 1-6, 1-7, 1-8, 1-9, 1-10, 1-11, 1-12 and 1-13 is similar to that of compound 1-1. For the sake of simplicity, they are not described one by one here. The obtained products are as follows:

[0070] Compound 1-2:

[0071] 1H NMR (300MHz, CDCl3, δ, ppm): 7.65 (s, 1H), 2.30 (s, 3H).

[0072] Compound 1-3:

[0073] 1 H NMR (300MHz, CDCl3, δ, ppm): 2.36 (s, 6H).

[0074] Compound 1-4:

[0075] 1 H NMR (300MHz, CDCl3, δ, ppm): 7.29 (s, 1H).

[0076] Compounds 1-5:

[0077] 1 H NMR (300MHz, CDCl3, δ, ppm): 3.84 (s, 6H).

[0078] Compounds 1-6:

[0079] 1 H NMR (300MHz, CDCl3, δ, ppm): 7.06 (s, 2H), 4.15 (s, 3H).

[0080] Compound 1-7:

[0081] 1 H NMR (300MHz, CDCl3, δ, ppm): 6.80 (s, 1H), 3.59 (s, 3H), 2.12 (s, 3H).

[0082] Compound 1-8:

[0083] 1 H NMR (300MHz, CDCl3, δ, ppm): 3.33 (s, 3H), 2.12 (s, 6H).

[0084] Compound 1-9:

[0085] 1 H NMR (300MHz, CDCl3, δ, ppm): 7.70 (s, 2H).

[0086] Compound 1-10:

[0087] 1 H NMR (300MHz, CDCl3, δ, ppm): 7.65 (s, 1H), 2.30 (s, 3H).

[0088] Compound 1-11:

[0089] 1 H NMR (300MHz, CDCl3, δ, ppm): 2.30 (s, 6H).

[0090] Compound 1-12:

[0091] 1 H NMR (300MHz, CDCl3, δ, ppm): 7.29 (m, 1H), 6.97 (m, 1H), 6.26 (m, 1H).

[0092] Compound 1-13:

[0093] 1 H NMR (300MHz, CDCl3, δ, ppm): 8.12 (s, 1H), 7.77 (d, 1H), 6.73 (d, 1H).

[0094] Comparative Example 1

[0095] Preparation of electrolyte: The electrolyte contains 13.5wt% lithium hexafluorophosphate (LiPF6) as lithium salt, 4wt% fluoroethylene carbonate (FEC) and 2wt% adiponitrile (ADN) as additives, and a mixture of ethylene carbonate (EC), diethyl carbonate (DEC) and propyl propionate (PP) as non-aqueous organic solvent, which are mixed in a mass percentage of EC:DEC:PP=30:30:40.

[0096] Preparation of positive electrode sheet: The positive electrode active material LiCoO2, the conductive agent CNT, the binder polyvinylidene fluoride (PVDF) are mixed with N-methylpyrrolidone (NMP) in a mass ratio of 97.6:0.8:1.6 to form a positive electrode slurry, which is coated on the current collector aluminum foil and dried at 85°C and then cold pressed. Then, it is trimmed, cut into pieces, and divided into strips, and then dried under vacuum conditions at 85°C for 4 hours. The pole ears are welded to make positive electrode sheets.

[0097] Preparation of negative electrode sheet: The negative electrode active material graphite, conductive agent Super-P, thickener CMC, and binder SBR are mixed with deionized water in a mass ratio of 96.6:1.0:1.2:1.2 to form a negative electrode slurry, which is coated on the current collector copper foil and dried at 85°C and then cold pressed. Then, it is trimmed, cut into pieces, and divided into strips, and then dried at 110°C under vacuum conditions for 4 hours. The pole ears are welded to make negative electrode sheets.

[0098] Preparation of lithium-ion batteries: using a PE porous polymer film as a separator; stacking the prepared positive electrode sheet, separator, and negative electrode sheet in order, placing the separator between the positive and negative electrode sheets, and winding to obtain a bare battery cell; placing the bare battery cell in an outer package, injecting the above-prepared electrolyte (the moisture content of the configured electrolyte is less than 20 ppm, and the acidity is less than 30 ppm) into the dried bare battery cell, encapsulating, standing, forming (charging at a constant current of 0.02C to 3.4V, and then charging at a constant current of 0.1C to 3.9V), shaping, and capacity testing to complete the preparation of a soft-pack lithium-ion battery (the thickness of the soft-pack lithium-ion battery is 4.3 mm, the width is 6.3 mm, and the length is 8.3 mm).

[0099] Examples 1 to 23

[0100] Examples 1 to 23 are used to compare and illustrate the electrolyte, battery and preparation method thereof disclosed in the present application, and include the operating steps of Comparative Example 1, except that electrolyte additives as shown in Examples 1 to 23 in Table I are added.

[0101] Table I Comparative Example 1 and Examples 1 to 23 electrolyte additive composition and addition amount

[0102]

[0103] Performance Testing

[0104] The performance of the lithium-ion batteries prepared in Comparative Example 1 and Examples 1 to 23 was tested.

[0105] 23 degrees DCIR: Charge the formed lithium-ion battery to 4.43V at room temperature with 0.7C constant current and constant voltage, cut off at 0.02C, and then discharge at 0.05C constant current for 8h. Discharge the lithium-ion battery at 23 degrees with 0.1C (I1) constant current for 10s, and record the test voltage as V1; discharge with 1C (I2) current for 200ms, and record the test voltage as V2. DC internal resistance = (V1-V2) / (I2-I1)).

[0106] 0 degree DCIR: Charge the formed lithium-ion battery to 4.43V at room temperature with 0.7C constant current and constant voltage, cut off at 0.02C, and then discharge at 0.05C constant current for 8 hours. After the lithium-ion battery is left at 0 degrees for 4 hours, it is discharged with 0.1C (I1) constant current for 10 seconds, and the test voltage is recorded as V1; when it is discharged with 1C (I2) current for 200ms, the test voltage is recorded as V2. DC internal resistance = (V1-V2) / (I2-I1)).

[0107] 60 degree storage performance: Charge the formed lithium-ion battery to 4.43V at room temperature with 0.7C constant current and constant voltage, cut off at 0.02C, and then discharge at 0.2C constant current to 3.0V. Repeat this cycle twice, and record the second discharge capacity as the initial capacity at room temperature. Charge the lithium-ion battery to 4.43V at room temperature with 0.7C constant current and constant voltage, cut off at 0.02C, and record the thickness at full charge (tested using a fixed-force PPG). Store the fully charged lithium-ion battery in a 60°C constant temperature box for 28 days, and take it out every 7 days to test the immediate thickness. Record the thickness expansion rate after 7 days, 14 days, 21 days, and 28 days of storage ((storage 28d thickness - initial full charge thickness) / initial full charge thickness × 100%).

[0108] The test results are shown in Table II:

[0109] Table II

[0110]

[0111]

[0112] It can be seen from Table II that the addition of the cyclic sulfite compound of the present application can reduce DCIR and improve high temperature storage performance, and when the content of the cyclic sulfite compound is preferably 0.3-1wt%, DCIR can be further reduced and high temperature storage performance can be improved. Moreover, when the electrolyte preferably further contains the second additive and / or the third additive, better battery performance can be achieved.

[0113] The preferred embodiments of the present application are described in detail above; however, the present application is not limited to the specific details in the above embodiments. Within the technical concept of the present application, a variety of simple modifications can be made to the technical solution of the present application, and these simple modifications all fall within the protection scope of the present application.

[0114] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this application will not further describe various possible combinations.

[0115] In addition, the various implementation modes of the present application may be arbitrarily combined, and as long as they do not violate the concept of the present application, they should also be regarded as the contents disclosed in the present application.

Claims

1. A cyclic sulfite compound, characterized in that The cyclic sulfite compound has a structure shown in formula (I), formula (II) or formula (III): Formula (I): , formula (II): , formula (III): ; In formula (I) to formula (III): X is O, S, NR3 or CR4R5, R1-R 11 Each is independently H, halogen, hydroxyl, cyano, saturated alkyl having 1 to 10 carbon atoms, saturated halogenated alkyl having 1 to 10 carbon atoms, alkoxy having 1 to 10 carbon atoms, or fluoroalkoxy having 1 to 10 carbon atoms.

2. A cyclic sulfite compound, characterized in that The cyclic sulfite compound is the following compound 1-1 to compound 1-13:

3. A method for preparing the cyclic sulfite compound according to claim 1 or 2, wherein: The method comprises: in the presence of a reaction catalyst and a reaction solvent, contacting a dihydroxy compound with SOCl2 under condensation reaction conditions; the dihydroxy compound has a structure shown by formula (A), formula (B) or formula (C): Formula (A): , formula (B): , formula (C): ; In formula (A), formula (B) and formula (C): X is O, S, NR3 or CR4R5, R1-R 11 Each is independently H, halogen, hydroxyl, cyano, saturated alkyl having 1 to 10 carbon atoms, saturated halogenated alkyl having 1 to 10 carbon atoms, alkoxy having 1 to 10 carbon atoms, or fluoroalkoxy having 1 to 10 carbon atoms.

4. The method according to claim 3, wherein: The dihydroxy compound has any of the following structures: 。 5. The method according to claim 3 or 4, wherein: The reaction catalyst is selected from at least one of SiO2 and Si(OC2H5)4; The reaction solvent is at least one of CH3OH, CH3CH2OH and CH3CN; The condensation reaction conditions include: temperature of 20-200° C. and time of 30-600 minutes.

6. A lithium ion battery electrolyte, comprising an organic solvent, a lithium salt and an additive, characterized in that: The additive is the cyclic sulfite compound according to claim 1 or 2.

7. The lithium ion battery electrolyte according to claim 6, wherein The concentration of the cyclic sulfite compound in the electrolyte is 0.01-10 wt %.

8. The lithium ion battery electrolyte according to claim 7, wherein The concentration of the cyclic sulfite compound in the electrolyte is 0.01-5 wt %.

9. The lithium ion battery electrolyte according to claim 8, wherein The concentration of the cyclic sulfite compound in the electrolyte is 0.3-1 wt %.

10. The lithium ion battery electrolyte according to claim 6, wherein: The additive is selected from one or more of 3,4-dihydroxythiophene sulfite, 2-methyl-3,4-dihydroxythiophene sulfite, 2,5-dimethyl-3,4-dihydroxythiophene sulfite, 2-trifluoromethyl-3,4-dihydroxythiophene sulfite, 2,5-dimethyl dicarboxylate-3,4-dihydroxythiophene sulfite, N-methyl-3,4-dihydroxypyrrole sulfite, 2-methyl-N-methyl-3,4-dihydroxypyrrole sulfite, 2,5-dimethyl-N-methyl-3,4-dihydroxypyrrole sulfite, 3,4-dihydroxyfuran sulfite, 2-methyl-3,4-dihydroxyfuran sulfite, 2,5-dimethyl-3,4-dihydroxyfuran sulfite, 2,3-dihydroxypyridine sulfite and 3,4-dihydroxypyridine sulfite.

11. The lithium ion battery electrolyte according to claim 6, wherein: The electrolyte further contains a second additive, which is selected from one or more compounds represented by formula (IV), formula (V) or formula (VI): Formula (IV): , formula (V): , formula (VI): ; In formula (IV) to formula (VI): R 14 -R 18 R is independently H, halogen, hydroxyl, cyano, sulfonyl, fluorosulfonyl, sulfonic acid, fluorosulfonic acid, saturated or unsaturated alkyl of 1 to 10 carbon atoms, saturated or unsaturated halogenated alkyl of 1 to 10 carbon atoms, alkoxy of 1 to 10 carbon atoms or fluoroalkoxy of 1 to 10 carbon atoms; 12 -R 13 Each is independently a saturated or unsaturated alkyl group having 1 to 10 carbon atoms, a saturated or unsaturated halogenated alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or a fluoroalkoxy group having 1 to 10 carbon atoms.

12. The lithium ion battery electrolyte according to claim 11, wherein The concentration of the second additive in the electrolyte is 0.05-2wt%.

13. The lithium ion battery electrolyte according to claim 12, wherein: The concentration of the second additive in the electrolyte is 0.3-1 wt %.

14. The lithium ion battery electrolyte according to claim 11, wherein The second additive has any of the following structures: 。 15. The lithium ion battery electrolyte according to claim 6, wherein: The electrolyte further contains a third additive, which is a cyano or cyanoalkoxy substituted alkane, and the cyano or cyanoalkoxy substituted alkane is selected from one or more of acetonitrile, propionitrile, butyronitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, 1,2-bis(2-cyanoethoxy)ethane, 1,2-bis(2-cyanoethoxy)propane, 1,2-bis(3-cyanopropoxy)ethane, 1,3,6-hexanetrinitrile, 1,2,3-propanetrinitrile, 1,3,5-pentanetrinitrile, 3,3-bis(cyanomethyl)glutaronitrile, 3,3-bis(cyanomethyl)adiponitrile and 1,2,3-tris(2-cyanoethoxy)propane.

16. The lithium ion battery electrolyte according to claim 15, wherein: The concentration of the third additive in the electrolyte is 0.01-10 wt %.

17. The lithium ion battery electrolyte according to claim 16, wherein: The concentration of the third additive in the electrolyte is 1-5 wt %.

18. The lithium ion battery electrolyte according to claim 17, wherein: The concentration of the third additive in the electrolyte is 1-3 wt %.

19. The lithium ion battery electrolyte according to claim 6, wherein: The organic solvent is selected from carbonates and / or carboxylates, the carbonates are selected from one or more of the following: ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate; the carboxylates are selected from one or more of the following solvents: ethyl acetate, methyl acetate, ethyl propionate, methyl propionate, propyl propionate, butyrolactone.

20. The lithium ion battery electrolyte according to claim 6, wherein: The lithium salt is selected from one or more of lithium difluoro(oxalato)borate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate and lithium perchlorate.

21. The lithium ion battery electrolyte according to claim 20, wherein: The concentration of the lithium salt in the electrolyte is 0.5-2 mol / L.

22. The lithium ion battery electrolyte according to claim 21, wherein: The concentration of the lithium salt in the electrolyte is 0.8-1.2 mol / L.

23. A lithium ion battery, characterized in that: The electrolyte in the lithium-ion battery is the electrolyte described in any one of claims 6 to 22.

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