Fluorine-containing sulfonyl compound, preparation method thereof and application of fluorine-containing sulfonyl compound in battery

Abstract

The invention provides a fluorine-containing sulfonyl compound, a preparation method thereof and application of the fluorine-containing sulfonyl compound in a battery. The lithium ion battery electrolyte comprises a non-aqueous organic solvent, an electrolyte salt and an additive. The additive comprises a fluorine-containing sulfonyl compound, the fluorine-containing sulfonyl compound is a compound 1, and the fluorine-containing sulfonyl compound accounts for 0.1-5.0% of the mass of the lithium ion battery electrolyte. The fluorine-containing sulfonyl compound can be used in a lithium ion battery and can capture oxygen free radicals generated in the use process of the lithium ion battery, so that the function of protecting a positive electrode and a negative electrode is achieved, and the cycle performance of the battery is improved. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to the technical field of material synthesis, and in particular to a compound used in a battery, and more particularly to a fluorine-containing sulfonyl compound and a preparation method thereof, and application of the compound in a battery. Background Art

[0002] Lithium cobalt oxide positive electrode active materials are prone to produce oxygen free radicals during high-voltage cycling, which leads to unstable electrolyte and electrode interfaces and severe gas production during the cycling process, resulting in a short battery cycle life. Therefore, overcoming the damage caused by oxygen free radicals during the battery cycling process can increase the battery cycle life.

[0003] To overcome the destructive effects of oxygen free radicals, we can start from two aspects: first, we can inhibit the generation of oxygen free radicals at the source; second, we can remove oxygen free radicals in time after they are generated. Although there are many electrolyte additives on the market that can improve the cycle performance of batteries, they usually form a stable SEI film, and there are few additives that can overcome the destructive effects of oxygen free radicals. Summary of the invention

[0004] Based on the above problems, the purpose of the present invention is to provide a new fluorinated sulfonyl compound and a preparation method thereof. The fluorinated sulfonyl compound can be used in lithium-ion batteries and can capture oxygen free radicals generated during the use of lithium-ion batteries, thereby protecting the positive and negative electrodes to improve the cycle performance of the battery.

[0005] To achieve the above objectives, the first aspect of the present invention provides a fluorine-containing sulfonyl compound, which is compound 1.

[0006]

[0007] Compound 1 in the fluorinated sulfonyl compound of the present invention is a novel fluorinated sulfonyl compound, which contains an intracyclic sulfur group, has strong reducing properties, has more empty orbitals, and can capture oxygen free radicals generated during the use of lithium-ion batteries, thereby protecting the positive and negative electrodes to improve the cycle performance of the battery.

[0008] As a technical solution of the present invention, the fluorine-containing sulfonyl compound has a gas spectrum purity of 99.0-99.5%, a water content of 50-60 ppm, and an acid value of 8-15 ppm.

[0009] The second aspect of the present invention provides a method for preparing a fluorine-containing sulfonyl compound, comprising the steps of: adding thiomorpholine, acetonitrile and triethylamine into a reaction container, stirring evenly in an ice water bath at 0 to 5°C, slowly introducing a formulated amount of sulfuryl fluoride for reaction, concentrating to remove the acetonitrile, and then distilling under reduced pressure.

[0010] The preparation method of the invention is simple, and utilizes thiomorpholine and thiomorpholine to carry out nucleophilic addition reaction under the action of triethylamine at low temperature, and the prepared fluorine-containing sulfonyl compound can improve the cycle performance of the battery.

[0011] The third aspect of the present invention provides the use of fluorine-containing sulfonyl compounds in batteries.

[0012] The fourth aspect of the present invention provides a lithium-ion battery electrolyte, comprising a non-aqueous organic solvent, an electrolyte salt and an additive, wherein the additive comprises the aforementioned fluorine-containing sulfonyl compound or a fluorine-containing sulfonyl compound prepared by the aforementioned method for preparing a fluorine-containing sulfonyl compound, and the fluorine-containing sulfonyl compound accounts for 0.1 to 5.0% of the mass of the lithium-ion battery electrolyte.

[0013] The structure of the fluorinated sulfonyl compound contains an intracyclic sulfur group, which has strong reducing properties and more empty orbitals. Compared with the extracyclic sulfur group or sulfonyl group, it can capture oxygen free radicals generated during the use of lithium-ion batteries, thereby protecting the positive and negative electrodes and improving the battery's cycle performance.

[0014] As a technical solution of the present invention, the electrolyte salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium methanesulfonate, lithium trifluoromethylsulfonate, lithium bis(oxalato)borate, lithium difluorooxalatoborate, difluorophosphoric acid and lithium difluorobis(oxalato)phosphate.

[0015] As a technical solution of the present invention, the non-aqueous organic solvent includes one or more of chain carbonate compounds, cyclic carbonate compounds, carboxylate compounds and ether compounds.

[0016] As a technical solution of the present invention, the non-aqueous organic solvent includes one or more of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, ethyl acetate, propyl acetate, ethyl propionate, propyl propionate, butyl acetate, ethyl butyrate, propyl propionate and ethylene glycol dimethyl ether.

[0017] As a technical solution of the present invention, the additive further includes one or more of vinylene carbonate, fluoroethylene carbonate, 1,3-propane sultone and vinyl sulfate.

[0018] A fifth aspect of the present invention provides a lithium-ion battery, comprising a positive electrode active material, a negative electrode active material and the aforementioned lithium-ion battery electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the fluorine spectrum of the fluorine-containing sulfonyl compound of Example 1.

[0020] Figure 2This is the hydrogen spectrum of the fluorine-containing sulfonyl compound of Example 1. DETAILED DESCRIPTION

[0021] The fluorine-containing sulfonyl compound of the present invention can be used in material synthesis and batteries. In particular, the fluorine-containing sulfonyl compound is used in secondary batteries such as lithium-ion batteries. The fluorine-containing sulfonyl compound can be used as an electrolyte additive to improve the cycle performance of the secondary battery.

[0022] Secondary batteries include positive electrode active materials, negative electrode active materials and electrolytes. If used in lithium-ion batteries, the positive electrode active materials may be layered transition metal lithium oxides or olivine-type lithium compounds. Layered transition metal lithium oxides may be, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides (chemical formula LiNi x Co y Mn (1-x-y) M z O2, wherein 0.6≤x<0.9, x+y<1, 0≤z<0.08, M is at least one of Al, Mg, Zr and Ti) and coatings and dopants of the above materials. Olivine-type lithium compounds are lithium-containing phosphates with an olivine structure, which may be, but are not limited to, lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate and coatings and dopants of the above materials. These positive electrode active materials may be used alone or in combination of two or more. Preferably, the positive electrode active material of the present invention is lithium cobalt oxide, and the fluorine-containing sulfonyl compound can solve the problem of damage to the electrode by oxygen free radicals generated by lithium cobalt oxide.

[0023] The negative electrode active material includes at least one of a carbon-based material, a silicon-based material and a tin-based material. Among them, the carbon-based material may be, but is not limited to, at least one of artificial graphite, natural graphite, hard carbon, soft carbon, graphene and mesophase carbon microspheres. The silicon-based material may be, but is not limited to, at least one of a silicon element, a silicon-oxygen composite material, a silicon-carbon composite material and a silicon alloy material. The tin-based material may include a tin element, a tin-carbon composite material, a tin-oxygen composite material, and a tin alloy compound.

[0024] Lithium-ion battery electrolytes include electrolyte salts, non-aqueous organic solvents, and additives.

[0025] The electrolyte salt may be, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethylsulfonate (LiCF3SO3), lithium bis(oxalatoborate) (C4BLiO8), lithium difluorooxalatoborate (C2BF2LiO4), lithium difluorophosphate (LiPO2F2) and lithium difluorobis(oxalatophosphate) (LiDFBP).

[0026] The non-aqueous organic solvent includes one or more of linear carbonate compounds, cyclic carbonate compounds, carboxylate compounds and ether compounds. Further, the non-aqueous organic solvent is selected from one or more of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethylene carbonate (PC), propylene carbonate (PC), ethyl acetate, propyl acetate, ethyl propionate, propyl propionate, butyl acetate, ethyl butyrate, propyl propionate and ethylene glycol dimethyl ether.

[0027] The additive includes a fluorinated sulfonyl compound, and further, the additive is compound 1. The fluorinated sulfonyl compound accounts for 0.1 to 5.0% of the mass of the electrolyte. As an example, the proportion of the fluorinated sulfonyl compound can be, but is not limited to, 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, and 5.0%. Further, the additive also includes one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), 1,3-propane sultone (PS), and diethylene sulfate (DTD).

[0028]

[0029] The preparation method of fluorine-containing sulfonyl compounds comprises the steps of: adding thiomorpholine, acetonitrile and triethylamine into a reaction container, stirring evenly in an ice water bath at 0-5°C, slowly introducing a formula amount of sulfuryl fluoride for reaction, concentrating to remove acetonitrile, and then distilling under reduced pressure. The reaction formula is as follows.

[0030]

[0031] The reaction time can be 3 to 10 hours, the temperature during concentration can be 40 to 60° C., and the distillation can be performed at 100 to 140° C. The gas spectrum purity of the obtained fluorinated sulfonyl compound is 99.0 to 99.5%, the water content is 50 to 60 ppm, and the acid value is 8 to 15 ppm.

[0032] In order to better illustrate the purpose, technical scheme and beneficial effects of the present invention, the present invention will be further described below in conjunction with specific embodiments. It should be noted that the following implementation method is a further explanation of the present invention and should not be used as a limitation of the present invention.

[0033] Part I: Preparation of fluorinated sulfonyl compounds

[0034] Example 1

[0035] This embodiment is for preparing compound 1, and its preparation method comprises the steps of: adding 103.2g of thiomorpholine, 258g of acetonitrile and 101.2g of triethylamine in sequence into a three-necked flask filled with nitrogen atmosphere, stirring evenly in an ice-water bath at 0-5°C, and then slowly passing 102.1g of sulfuryl fluoride, reacting for 4h after passing the sulfuryl fluoride to obtain a light yellow solution, concentrating at 45°C to remove the reaction solvent acetonitrile, and then vacuum distilling at 120°C to obtain 156.2g of colorless and transparent product, with a gas spectrum purity of 99.1%, a water content of 53ppm, an acid value of 12ppm, and a yield of 84.3%.

[0036] The product was subjected to mass spectrometry detection, and the results were as follows Figure 1 and Figure 2 As shown, the NMR (60MHz) data are F19: 47.4, H19: 4.2, 3.2, respectively. The explanation shows one fluorine and two hydrogens, which are consistent with the target structure, indicating that compound 1 has been synthesized.

[0037] Part II: Application of fluorinated sulfonyl compounds in batteries

[0038] 1.1 Preparation of non-aqueous electrolyte

[0039] In a glove box filled with nitrogen (O2 <1ppm, H2O <10ppm, nitrogen purity >99.9999%), 85g of the mixed solvent obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a mass ratio of 3:7 was used as an organic solvent, and 1g of compound 1 prepared in Example 1 was added to obtain a mixed solution. The mixed solution was sealed and packaged and placed in a quick freezer (-4°C) for 2h and then taken out. In a glove box filled with nitrogen (O2 <1ppm, H2O <1ppm), 14g of lithium hexafluorophosphate (LiPF6) was slowly added to the mixed solution, and non-aqueous electrolyte 1# was obtained after mixing evenly.

[0040] The formulas of non-aqueous electrolytes 2# to 21# are shown in Table 1, and their preparation processes are the same as the preparation of non-aqueous electrolytes in Section 1.1.

[0041] Table 1 Formula of non-aqueous electrolyte 2#~21#

[0042]

[0043]

[0044] 1.2 Preparation of positive electrode

[0045] LiCoO2, PVDF and conductive carbon black were mixed in a weight ratio of 96:2:2, and an equal weight of N-methylpyrrolidone (NMP) was added. After stirring evenly, the mixture was smeared on aluminum foil and dried at 120°C to obtain a positive electrode sheet with a moisture content of <100ppm.

[0046] 1.3 Preparation of negative electrode

[0047] Graphite, styrene-butadiene rubber and carbon black were mixed in a weight ratio of 96:3:1, and an equal weight of deionized water was added for slurrying. The slurry was evenly applied to the copper foil, and the temperature was raised to 90°C for drying to obtain a negative electrode sheet with a moisture content of <300ppm.

[0048] 1.4 Preparation of lithium-ion batteries

[0049] The positive electrode sheet, negative electrode sheet and separator prepared according to the above process are laminated to form a lithium-ion battery with a thickness of 4.7mm, a width of 55mm, a length of 60mm and a total capacity of 2Ah. They are vacuum-baked at 75°C for 10h and non-aqueous electrolytes 1# to 21# are injected respectively. After standing for 24h, they are charged to 3.65V with a constant current of 0.1C (200mA), and then charged with a constant voltage of 3.65V until the current drops to 0.05C (100mA); then discharged to 2.5V with 0.2C (400mA), and the charge and discharge are repeated twice. Finally, the battery is charged to 3.65V with 0.1C (200mA), and lithium-ion batteries 1# to 21# are manufactured.

[0050] The performance of lithium-ion batteries 1# to 21# was tested. The test results are shown in Table 1. The test conditions are as follows.

[0051] (1) High temperature cycle test

[0052] Under high temperature (45°C) conditions, the lithium-ion battery was charged and discharged at 1.0C / 1.0C (the average value of the battery discharge capacity in the first three times was C0), the charging cut-off current was 0.05C, the discharge cut-off voltage was 3.0V, and 1.0C / 1.0C charging and discharging was performed at 45°C for 500 cycles (the battery discharge capacity was C1).

[0053] Capacity retention rate = (C1 / C0)*100%

[0054] (2) Low temperature cycle test

[0055] Under low temperature (15°C) conditions, the lithium-ion battery was charged and discharged at 1.0C / 1.0C (the average value of the battery discharge capacity in the first three times was C0), the charging cut-off current was 0.05C, the discharge cut-off voltage was 3.0V, and 1.0C / 1.0C charging and discharging was performed at 15°C for 500 cycles (the battery discharge capacity was C1).

[0056] Capacity retention rate = (C1 / C0)*100%

[0057] Table 2 Cyclic performance test results of each example

[0058]

[0059] From the results in Table 2, it can be seen that the cycle performance of lithium-ion batteries 1#~14# is better than that of lithium-ion batteries 15#~19#. This is because compound 1 is used as an additive in lithium-ion batteries 1#~14#, which contains an intracyclic sulfur group, has a strong reducing property, and has more empty orbitals, which can capture oxygen free radicals generated during the use of lithium-ion batteries, thereby protecting the positive and negative electrodes and improving the cycle performance of the battery.

[0060] By comparing lithium-ion batteries 7# to 14#, it can be seen that the cycle performance of the battery obtained by compounding VC, FEC, PS and DTD on the basis of compound 1 is better.

[0061] By comparing the results of lithium-ion batteries 2#~3# and lithium-ion batteries 20#~21#, it can be seen that although the structure of compound 2 is somewhat similar to compound 1, compound 2 is an intra-ring oxygen atom, its reducing property is not strong, and there is no empty orbital. It cannot capture the oxygen free radicals generated during the use of lithium-ion batteries, and the improvement of the cycle performance is limited.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A fluorine-containing sulfonyl compound, characterized in that: is compound 1, 2. The fluorine-containing sulfonyl compound according to claim 1, characterized in that: The fluorine-containing sulfonyl compound has a gas spectrum purity of 99.0-99.5%, a water content of 50-60 ppm, and an acid value of 8-15 ppm.

3. The method for preparing a fluorine-containing sulfonyl compound according to claim 1 or 2, characterized in that: The method comprises the following steps: adding thiomorpholine, acetonitrile and triethylamine into a reaction container, stirring evenly in an ice water bath at 0-5°C, slowly introducing a formula amount of sulfuryl fluoride for reaction, concentrating to remove the acetonitrile, and then distilling under reduced pressure.

4. Use of the fluorinated sulfonyl compound prepared by the fluorinated sulfonyl compound according to claim 1 or 2 or the method for preparing the fluorinated sulfonyl compound according to claim 3 in a battery.

5. A lithium ion battery electrolyte comprising a non-aqueous organic solvent, an electrolyte salt and an additive, characterized in that: The additive comprises the fluorine-containing sulfonyl compound according to claim 1 or 2 or the fluorine-containing sulfonyl compound prepared by the preparation method of the fluorine-containing sulfonyl compound according to claim 3, and the fluorine-containing sulfonyl compound accounts for 0.1 to 5.0% of the mass of the lithium-ion battery electrolyte.

6. The lithium ion battery electrolyte according to claim 5, characterized in that: The electrolyte salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethylsulfonyl imide, lithium methane sulfonate, lithium trifluoromethyl sulfonate, lithium bisoxalatoborate, lithium difluorooxalatoborate, difluorophosphoric acid, and lithium difluorobisoxalatophosphate.

7. The lithium ion battery electrolyte according to claim 5, characterized in that: The non-aqueous organic solvent includes one or more of chain carbonate compounds, cyclic carbonate compounds, carboxylate compounds and ether compounds.

8. The lithium ion battery electrolyte according to claim 7, characterized in that: The non-aqueous organic solvent includes one or more of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, ethyl acetate, propyl acetate, ethyl propionate, propyl propionate, butyl acetate, ethyl butyrate, propyl propionate and ethylene glycol dimethyl ether.

9. The lithium-ion battery electrolyte according to claim 5, characterized in that: The additive further includes one or more of vinylene carbonate, fluoroethylene carbonate, 1,3-propane sultone and vinyl sulfate.

10. A lithium ion battery, characterized in that: The invention comprises a positive electrode active material, a negative electrode active material and the lithium ion battery electrolyte according to any one of claims 5 to 9.

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