Nonaqueous organic high-voltage electrolyte and lithium-ion battery containing same

Abstract

The present application provides a non-aqueous organic high-voltage electrolyte and a lithium-ion battery containing the same. [Means] The nonaqueous organic high-voltage electrolyte comprises a lithium salt and a nonaqueous organic solvent, the nonaqueous organic solvent comprising a sulfolane derivative and a diluent, the sulfolane derivative having a structure represented by formula (1). The electrolyte of the present application has high-voltage resistance, allowing lithium-ion batteries using the electrolyte to have excellent high-voltage cycling performance and be compatible with all currently known high-voltage positive electrode active materials. It also has flame retardancy, ensuring stable cycle charging and discharging at high voltages while preventing the potential risk of electrolyte combustion, far superior to current EC-based high-voltage electrolytes.

Description

[Technical Field]

[0001] This application relates to the technical field of lithium ion batteries, for example, to non-aqueous organic high voltage electrolytes and lithium ion batteries containing the same. [Background technology]

[0002] Since the emergence of commercial lithium-ion batteries in the 1990s, the importance of rechargeable batteries has rapidly increased due to the ever-increasing need for high-performance energy storage devices in portable electronic devices and electric vehicles. However, conventional lithium-ion batteries are approaching their energy density limits and are unable to meet the ever-increasing energy storage demands. Therefore, there is a common demand in various fields for continuously improving the energy density of lithium-ion batteries.

[0003] Currently, the energy density of lithium-ion batteries can be improved in two ways:

[0004] 1. Select positive and negative electrode active materials with high specific capacity and high press density.

[0005] 2. To improve the operating voltage of lithium-ion batteries.

[0006] Many researchers are working to develop positive and negative electrode active materials with higher specific capacities or higher plateau voltages, while electrolytes have received little attention. Currently, researchers are developing several high-voltage positive electrode active materials. However, conventional commercial electrolytes are primarily carbonate-based electrolytes based on ethylene carbonate (EC). During high-voltage charging and discharging, these electrolytes are prone to oxidative decomposition side reactions with the surface of the positive electrode material. This not only impacts the performance of the high-voltage positive electrode active material, but also rapidly deteriorates the battery's cycle performance and causes severe battery swelling, resulting in a decline in overall battery performance and significantly limiting the application of high-voltage lithium-ion batteries. Therefore, the development of novel electrolytes compatible with high-voltage positive electrode materials is particularly important.

[0007] Currently, the primary method for improving the high-voltage swelling and cycling performance of lithium-ion batteries is the addition of high-voltage functional additives. For example, CN105449277A discloses an electrolyte containing a fluorosulfite ester-based compound, which can meet the high-voltage recycling requirements of lithium-ion batteries and extend their service life. CN107528088A discloses a positive electrode film-forming additive for high-voltage electrolytes, consisting of tri(hexafluoroisopropyl)phosphate ester and a nitrile-based additive. The resulting high-voltage electrolyte is applicable to charging voltages of 4.5 to 5.0 V. However, these high-voltage functional additives acting on the positive or negative electrode only account for a small proportion of EC-based carbonate electrolytes, thus failing to change the fundamental fact that they are still classified as EC-based electrolytes. Therefore, the actual improvement effect of additives on the high-voltage stable cycling performance of batteries remains to be confirmed.

[0008] On the other hand, the development of high-voltage electrolytes that do not rely on high-voltage functional additives and deviate from the EC system has had a profound impact on the research and development field of electrolytes and has practical application value. Summary of the Invention [Problem to be solved by the invention]

[0009] The following is a general summary of the subject matter described in detail herein, which is not intended to limit the scope of the claims.

[0010] The present application provides a non-aqueous organic high-voltage electrolyte and a lithium-ion battery containing the same. [Means for solving the problem]

[0011] In one aspect, the present application provides a nonaqueous organic high-voltage electrolyte solution, the nonaqueous organic high-voltage electrolyte solution comprising a lithium salt and a nonaqueous organic solvent, the nonaqueous organic solvent comprising a sulfolane derivative and a diluent, the sulfolane derivative having a structure represented by Formula 1: [ka] (Note that R1, R2, R3, and R4 are each independently one or a combination of at least two selected from a hydroxy group, a nitro group, a cyano group, a carboxyl group, an amino group, an alkyl group, a silyl group, a silyloxy group, hydrogen, fluorine, chlorine, bromine, and iodine, and R1, R2, R3, and R4 are not simultaneously hydrogen.) A non-aqueous organic high voltage electrolyte is provided.

[0012] The sulfolane derivative selected in this application has a high dielectric constant and excellent high voltage resistance, and after being mixed with a lithium salt and a carbonate ester-based diluent to form an electrolyte, it can be stably cycled in the high voltage range of 2.8 to 5.0 V.

[0013] In this application, by using a sulfolane derivative as a non-aqueous organic solvent component, the electrolyte has high-voltage resistance performance, and lithium-ion batteries using this electrolyte have excellent high-voltage (4.5 V or higher) cycle performance, are compatible with all currently known high-voltage positive electrode active materials, and have flame-retardant properties, ensuring stable cycle charging and discharging at high voltages and preventing the potential risk of electrolyte combustion, which are far superior to current EC-based high-voltage electrolytes.

[0014] In one embodiment, at least one of R2 and R3 is selected from a nitro group.

[0015] In one embodiment, at least one of R2 and R3 is selected from fluorine.

[0016] In one embodiment, R2 and R3 are fluorine and R1 and R 4 is hydrogen

[0017] In one embodiment, the diluent is one or a combination of at least two of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, propyl ether, butyl ether, ethyl acetate, methyl propionate, ethyl propionate, butyl propionate, ethyl butyrate, fluoroethylene carbonate, fluoroethyl methyl carbonate, fluorodimethyl carbonate, fluorodiethyl carbonate, and hydrofluoroethers.

[0018] In one embodiment, the diluent is one or a combination of at least two of dimethyl carbonate, ethyl methyl carbonate, and hydrofluoroether.

[0019] In one embodiment, the lithium salt is one or more of lithium bisfluorosulfonylimide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF), lithium perchlorate (LiClO), lithium tetrafluoroborate (LiBF), lithium bisoxalatoborate (LiBOB), lithium hexafluoroarsenate (LiAsF), lithium difluorooxalatoborate (LiDFOB), lithium difluorophosphate (LiPFO), and lithium 4,5-dicyano-2-trifluoromethylimidazolium (LiDTI).

[0020] In one embodiment, the lithium salt is one or a combination of at least two of lithium hexafluorophosphate (LiPF6), lithium bisfluorosulfonylimide (LiFSI), and lithium difluorooxalatoborate (LiDFOB).

[0021] In one embodiment, the molar concentration of the lithium salt in the nonaqueous organic high-voltage electrolyte solution is 0.05 to 25 mol / L, for example, 0.05 mol / L, 0.08 mol / L, 0.1 mol / L, 0.5 mol / L, 0.8 mol / L, 1 mol / L, 3 mol / L, 5 mol / L, 8 mol / L, 10 mol / L, 12 mol / L, 15 mol / L, 18 mol / L, 20 mol / L, 22 mol / L, or 25 mol / L, preferably 0.8 to 1.2 mol / L, and more preferably 1.2 mol / L.

[0022] In one embodiment, the mass ratio of the sulfolane derivative to the non-aqueous organic solvent is 0.2% to 75%, for example, 0.2%, 0.5%, 0.8%, 1%, 3%, 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 35%, 38%, 40%, 43%, 45%, 48%, 50%, 55%, 58%, 60%, 65%, 68%, 70%, 73%, or 75%, preferably 5% to 50%, and more preferably 30 to 50%.

[0023] In one embodiment, the mass ratio of the diluent to the non-aqueous organic solvent is 25% to 99.8%, for example, 25%, 28%, 30%, 35%, 38%, 40%, 45%, 48%, 50%, 55%, 58%, 60%, 63%, 65%, 68%, 70%, 75%, 78%, 80%, 83%, 85%, 88%, 90%, 93%, 95%, 98%, or 99.8%, and is preferably 50% to 92%.

[0024] In another aspect, the present application provides a positive electrode piece, a negative electrode piece, a separator, and the above-mentioned No A lithium ion battery is provided that includes an aqueous organic high voltage electrolyte.

[0025] In one embodiment, the active material of the positive electrode strips includes one or a combination of at least two of the elements lithium, iron, cobalt, nickel, manganese, aluminum, and phosphorus.

[0026] In one embodiment, the active material of the positive electrode strip is doped or coated with one or at least two elements, such as aluminum, magnesium, zirconium, titanium, scandium, lanthanum, nickel, manganese, yttrium, and strontium.

[0027] More preferably, the positive electrode pieces are doped or coated with one or at least two of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, nickel-cobalt-manganese ternary electrode material, nickel-cobalt-aluminum ternary electrode material, and lithium-rich manganese-based materials.

[0028] Furthermore, the separator is a thin film having a porous structure that can block electron transport and promote lithium ion transport.

[0029] Furthermore, the negative electrode active material is one or a combination of at least two of carbon-based materials, silicon-based materials, boron-based materials, metallic lithium, metallic bismuth, nitrides, magnesium-based alloys, transition metal oxides, and phosphides.

[0030] As long as it is in line with common knowledge in the art, the above-mentioned optional conditions can be freely combined without exceeding the scope of protection of the present application.

[0031] In this application, the method for manufacturing the lithium ion battery includes the following steps:

[0032] First, the sulfone derivative and diluent are mixed in a uniform solution in the mass ratio described in the claims, and then the corresponding concentration of lithium salt is dissolved in the solution.Then, the nonaqueous organic high-voltage electrolyte prepared in the present application is sealed between the positive and negative electrode pieces with separators to obtain a lithium-ion battery. [Effects of the Invention]

[0033] Compared with the prior art, the present application has the following beneficial effects:

[0034] (1) This application departs from the conventional method of adding a high-voltage functional additive to an EC-based electrolyte and directly proposes a high-voltage electrolyte based on a novel sulfolane derivative. (2) The high-voltage electrolyte designed in this application has excellent high-voltage (over 4.5 V) cycling performance and is compatible with all currently known high-voltage positive electrode active materials. (3) The high-voltage electrolyte of this application has flame retardancy, ensuring stable cycling at high voltages while preventing potential electrolyte combustion risks, far superior to current EC-based high-voltage electrolytes. (4) The high-voltage electrolyte designed in this application overcomes the previously known view that sulfone-based compounds cannot be used as the main solvent in organic electrolytes, and will undoubtedly make a significant contribution to the further development of high-voltage electrolytes.

[0035] Other aspects may be appreciated after reading and understanding the detailed description. DETAILED DESCRIPTION OF THE INVENTION

[0036] The technical solution of the present application will be further described below through specific embodiments, which are merely for the understanding of those skilled in the art and should not be regarded as specifically limiting the present application.

[0037] Example 1 Preparation of Electrolyte 1 and Fabrication of Experimental Battery 1 (1)Preparation of electrolyte 1: In a glove box filled with argon gas (water content less than 0.1 ppm, oxygen content less than 0.1 ppm), 3-nitrosulfolane (Formula 2) and dimethyl carbonate were dissolved in a mass ratio of 2:3 and mixed uniformly. 1 mol / L of lithium hexafluorophosphate was then gradually dissolved in the mixture. After stirring uniformly, a high-voltage electrolyte was obtained. [ka]

[0038] (2) Preparation of the positive electrode material: NCM111, carbon black, and PVDF (binder) were mixed in a weight ratio of 93:5:2, and N-methylpyrrolidone was added and mixed uniformly to form a paste. The paste was applied to a 12-micrometer-thick aluminum foil, dried, and then roll-pressed to obtain the positive electrode material.

[0039] (3) Preparation of negative electrode material: Artificial graphite, acetylene black, and SBR (binder) were mixed in a weight ratio of 85:10:5, and deionized water was added to the mixture. The paste was then applied to an 8-micrometer-thick copper foil, dried, and roll-pressed to obtain the negative electrode material.

[0040] (4) Fabrication of lithium-ion battery 1: Positive electrode pieces, polyolefin separator, and negative electrode pieces were stacked in order in a dry environment controlled at a dew point of -50°C or less, ensuring that the separator completely separates the positive and negative electrode pieces and that the negative electrode completely covers the positive electrode. A cell was fabricated using the stacked pieces, and sealed in a fixed-size aluminum laminate film with an adhesive tab to form a soft-pack battery into which the electrolyte was poured. The electrolyte prepared in step (1) was then poured into the soft-pack battery, followed by sealing, chemical conversion, aging, secondary sealing, and capacity grading, to obtain an experimental battery 1 for measurement.

[0041] Example 2 Preparation of electrolyte 2 and fabrication of experimental battery 2 The only difference from Example 1 is that in the preparation process of electrolyte solution 2, 3-cyano-4-nitrosulfolane (Formula 3) and ethyl methyl carbonate were dissolved in a mass ratio of 3:7, mixed uniformly, and then 1 mol / L of lithium bisfluorosulfonylimide was added. [ka]

[0042] Example 3 Preparation of Electrolyte 3 and Fabrication of Experimental Battery 3 The only difference from Example 1 is that in preparing electrolyte solution 3, 3,4-dinitrosulfolane (Formula 4) and dimethyl carbonate were dissolved in a mass ratio of 1:4, mixed uniformly, and then 0.8 mol / L of lithium hexafluorophosphate was dissolved. [ka]

[0043] At the same time, metallic lithium was used as the negative electrode.

[0044] Example 4 Preparation of Electrolyte 4 and Fabrication of Experimental Battery 4 The only difference from Example 1 is that in the preparation process of electrolyte solution 4, 3-fluoro-4-fluorosulfolane (Formula 5) and ethyl methyl carbonate were dissolved in a mass ratio of 3:7, mixed uniformly, and then 1 mol / L of lithium bisfluorosulfonylimide was added. [ka]

[0045] At the same time, metallic lithium was used as the negative electrode.

[0046] Example 5 The only difference from Example 1 is that in the process of preparing electrolyte solution 5, 3-fluorosulfolane (Formula 6) and ethyl methyl carbonate were dissolved in a mass ratio of 5:5, mixed uniformly, and then 1 mol / L of lithium hexafluorophosphate was added. [ka]

[0047] At the same time, metallic lithium was used as the negative electrode.

[0048] Example 6 The difference from Example 1 is the electrolyte 6 In the preparation process of (1), 2-fluorosulfolane (formula 7) and ethyl methyl carbonate are dissolved in a mass ratio of 3:7, mixed uniformly, and then 1 mol / L of lithium hexafluorophosphate is added. [ka]

[0049] Comparative Example 1 The only difference from Example 1 is that the electrolyte is a commercialized EC-based electrolyte, the mass ratio of ethylene carbonate to dimethyl carbonate is 3:7, and the molar concentration of lithium hexafluorophosphate is 1 mol / L.

[0050] Comparative Example 2 The only difference from Example 1 is that unsubstituted commercially available sulfolane replaces the 3-nitrosulfolane in Example 1 during the preparation of the electrolyte solution.

[0051] Comparative Example 3 The only difference from Example 1 is that the 3-nitrosulfolane used in Example 1 is replaced with 3-methacrylate sulfolane.

[0052] Comparative Example 4 The only difference from Example 1 is that the 3-nitrosulfolane used in Example 1 is replaced with 3-ethoxysulfolane.

[0053] The performance of the electrolyte solutions and batteries prepared in Examples 1 to 6 and Comparative Examples 1 to 4 of the present application was examined. Charge-discharge cycle measurements were carried out on the experimental batteries at 25°C.

[0054] After capacity grading, the experimental batteries of Examples 1 to 6 and Comparative Examples 1 to 4 were placed in a thermostatic case at 25°C and connected to a charge / discharge measurement device. First, they were charged to 4.8 V at a constant current and voltage of 0.5 C, with a cutoff current of 0.05 C. After 5 minutes, they were discharged to 2.8 V at a constant current of 0.5 C. This charge / discharge measurement cycle was performed, and the discharge capacity at each cycle was recorded. The cell capacity retention rates at 200 cycles, 400 cycles, and 800 cycles were calculated. Here, the cycle capacity retention rate (%) at N cycles of the lithium-ion cell = discharge capacity at N cycles / initial discharge capacity * 100%, and the experimental results are shown in Table 1. [Table 1]

[0055] The ambient temperature cycling performance shown in Table 1 indicates that the sulfolane derivative electrolyte described herein exhibits superior cycling stability and capacity retention to both lithium metal and graphite anodes compared to conventional EC-based electrolytes and unsubstituted sulfolane electrolytes.

[0056] The present application has described the nonaqueous organic high-voltage electrolyte and the lithium ion battery containing the same through the above examples, but the present application is not limited to the above examples, i.e., the present application does not mean that the present application must be carried out depending on the above examples. Those skilled in the art should understand that any improvements to the present application, equivalent substitution of each raw material of the product, addition of auxiliary components, selection of specific forms, etc. are all within the scope of protection and disclosure of the present application.

Claims

1. A non-aqueous organic high voltage electrolyte, The nonaqueous organic high-voltage electrolyte solution contains a lithium salt and a nonaqueous organic solvent. The non-aqueous organic solvent contains a sulfolane derivative and a diluent, and the sulfolane derivative has a structure represented by formula (1): 【Chemistry 1】 (However, R １ , R ２ , R ３ and R ４ are each independently one or a combination of at least two selected from a hydroxy group, a nitro group, a cyano group, a carboxyl group, an amino group, an alkyl group, a silyl group, a silyloxy group, hydrogen, fluorine, chlorine, bromine, and iodine, and R １ , R ２ , R ３ and R ４ But at the same time, it is not hydrogen.) Non-aqueous organic high voltage electrolyte.

2. R ２ and R ３ At least one of the groups is selected from a nitro group; The nonaqueous organic high-voltage electrolyte of claim 1.

3. R ２ and R ３ At least one of these is selected from fluorine; The nonaqueous organic high-voltage electrolyte according to claim 1 or 2.

4. R ２ and R ３ is fluorine, and R １ and R ２ is hydrogen, The nonaqueous organic high-voltage electrolyte according to claim 3.

5. The diluent is one or a combination of at least two of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, propyl ether, butyl ether, ethyl acetate, methyl propionate, ethyl propionate, butyl propionate, ethyl butyrate, fluoroethylene carbonate, fluoroethyl methyl carbonate, fluorodimethyl carbonate, fluorodiethyl carbonate, and hydrofluoroether. The nonaqueous organic high-voltage electrolyte according to any one of claims 1 to 4.

6. The diluent is one or a combination of at least two of dimethyl carbonate, ethyl methyl carbonate, and hydrofluoroether. The nonaqueous organic high-voltage electrolyte according to any one of claims 1 to 5.

7. The lithium salt is one or a combination of at least two of lithium bisfluorosulfonylimide, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bisoxalatoborate, lithium hexafluoroarsenate, lithium difluorooxalatoborate, lithium difluorophosphate, and lithium 4,5-dicyano-2-trifluoromethylimidazolium; The nonaqueous organic high-voltage electrolyte according to any one of claims 1 to 6.

8. The lithium salt is one or a combination of at least two of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, and lithium difluorooxalatoborate. The nonaqueous organic high-voltage electrolyte according to any one of claims 1 to 7.

9. The molar concentration of the lithium salt in the nonaqueous organic high-voltage electrolyte is 0.05 to 25 mol / L, and more preferably 1.2 mol / L. The nonaqueous organic high-voltage electrolyte according to any one of claims 1 to 8.

10. The mass ratio of the sulfolane derivative to the nonaqueous organic solvent is 0.2% to 75%, preferably 5% to 50%, and more preferably 30% to 50%. The nonaqueous organic high-voltage electrolyte according to any one of claims 1 to 9.

11. The mass ratio of the diluent to the nonaqueous organic solvent is 25% to 99.8%, preferably 50% to 92%. The nonaqueous organic high-voltage electrolyte according to any one of claims 1 to 10.

12. A battery comprising a positive electrode piece, a negative electrode piece, a separator, and the nonaqueous organic high-voltage electrolyte solution according to any one of claims 1 to 11. Lithium-ion battery.

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