Non-aqueous organic high-voltage electrolyte and lithium-ion battery comprising same

Abstract

A non-aqueous organic high-voltage electrolyte and a lithium-ion battery comprising same. The non-aqueous organic high-voltage electrolyte comprises a lithium salt and a non-aqueous organic solvent. The non-aqueous organic solvent comprises a sulfolane derivative and a diluent, and the sulfolane derivative has the structure shown in formula (1). The non-aqueous organic high-voltage electrolyte exhibits high-voltage resistance, so that lithium-ion batteries using the electrolyte have excellent high-voltage cycle performance. The electrolyte is compatible with all currently known high-voltage positive electrode active materials and has flame-retardant properties, preventing potential combustion risks of the electrolyte while ensuring stable high-voltage charge-discharge cycling.

Description

A non-aqueous organic high-voltage electrolyte and a lithium-ion battery containing the same Technical Field

[0001] The present application relates to the technical field of lithium-ion batteries, for example, a non-aqueous organic high-voltage electrolyte and a lithium-ion battery comprising the same. Background Art

[0002] Since the commercialization of lithium-ion batteries in the 1990s, the demand for high-performance energy storage devices in portable electronics and electric vehicles has grown, and the importance of rechargeable batteries has skyrocketed. However, lithium-ion batteries based on traditional technologies are approaching the limits of their energy density and are increasingly unable to meet the growing demand for energy storage. Therefore, continuously improving the energy density of lithium-ion batteries is a common pursuit in various fields.

[0003] Currently, the energy density of lithium-ion batteries can be improved mainly through the following two methods:

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

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

[0006] Many researchers have been committed to developing positive and negative electrode active materials with higher specific capacity or positive electrode active materials with higher platform voltage. In comparison, electrolytes have received less attention. At present, researchers have developed a variety of high-voltage positive electrode active materials. However, traditional commercial electrolytes are mainly carbonate-based electrolytes based on ethylene carbonate (EC). When charging and discharging at high voltage, they are prone to oxidative decomposition side reactions with the surface of the positive electrode material, which not only affects the performance of the high-voltage positive electrode active material, but also causes the battery cycle performance to deteriorate rapidly and the battery to swell severely, thereby causing a decline in the overall performance of the battery, greatly limiting the application of high-voltage lithium-ion batteries. Therefore, it is particularly important to develop new electrolytes that match high-voltage positive electrode materials.

[0007] At present, the method for improving the flatulence and cycle performance of lithium-ion batteries under high voltage is mainly to add high-voltage functional additives. For example, CN105449277A discloses an electrolyte with the addition of fluorosulfite compounds, which can meet the recycling of lithium-ion batteries under high voltage conditions and extend their service life. CN 107528088A discloses a positive electrode film-forming additive for high-voltage electrolyte, which is composed of tris (hexafluoroisopropyl) phosphate and nitrile additives. The high-voltage electrolyte provided can be used for a charging voltage of 4.5 to 5.0V. However, these high-voltage functional additives acting on the positive or negative electrode side account for a small proportion in EC-based carbonate electrolytes, and have failed to change the basic fact that they still belong to EC-based electrolytes. Therefore, the actual improvement effect of the additives on the high-voltage stable cycle performance of the battery remains to be determined.

[0008] In contrast, developing a high-voltage electrolyte that does not rely on high-voltage functional additives and is independent of the EC system will have a profound impact on the field of electrolyte research and development and have practical application value.

[0009] Summary of the Invention

[0010] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0011] The present application provides a non-aqueous organic high-voltage electrolyte and a lithium-ion battery comprising the same.

[0012] In one aspect, the present application provides a non-aqueous organic high-voltage electrolyte, comprising a lithium salt and a non-aqueous organic solvent; the non-aqueous organic solvent comprises a sulfolane derivative and a diluent, wherein the sulfolane derivative has a structure as shown in Formula 1:

[0013] Wherein, R1, R2, R3 and R4 are each independently selected from one or a combination of at least two of hydroxyl, nitro, cyano, carboxyl, amino, alkyl, silyl, siloxy, hydrogen, fluorine, chlorine, bromine and iodine; and R1, R2, R3 and R4 are not hydrogen at the same time.

[0014] The sulfolane derivatives used in this application have a high dielectric constant and excellent high-voltage resistance. After being prepared into an electrolyte with lithium salts and carbonate diluents, they can stably circulate in the high voltage range of 2.8-5.0V.

[0015] In the present application, a sulfolane derivative is used as a non-aqueous organic solvent component, so that the electrolyte has high voltage resistance, and the lithium-ion battery using the electrolyte has excellent high voltage (above 4.5V) cycle performance, is compatible with all currently known high voltage positive electrode active materials, and has flame retardant properties. While ensuring high voltage stable cyclic charge and discharge, it prevents the potential combustion risk of the electrolyte, which is greatly superior to the current EC-based high voltage electrolyte.

[0016] In one embodiment, at least one of R2 and R3 is selected from nitro.

[0017] In one embodiment, at least one of R2 and R3 is selected from fluorine.

[0018] In one embodiment, R2 and R3 are fluorine and R1 and R2 are hydrogen.

[0019] In one embodiment, the diluent is one 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, or a combination of at least two thereof.

[0020] In one embodiment, the diluent is one or a combination of at least two of dimethyl carbonate, ethyl methyl carbonate and hydrofluoroether.

[0021] In one embodiment, the lithium salt is one or more of lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium bis(oxalatoborate) (LiBOB), lithium hexafluoroarsenate (LiAsF6), lithium difluorooxalatoborate (LiDFOB), lithium difluorophosphate (LiPF2O2), and lithium 4,5-dicyano-2-trifluoromethylimidazolium (LiDTI).

[0022] In one embodiment, the lithium salt is one or a combination of at least two of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium difluorooxalatoborate (LiDFOB).

[0023] In one embodiment, the molar concentration of the lithium salt in the non-aqueous organic high-voltage electrolyte is 0.05-25 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, optionally 0.8-1.2 mol / L, further optionally 1.2 mol / L.

[0024] In one embodiment, the mass proportion of the sulfolane derivative in the non-aqueous organic solvent is 0.2%-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%, optionally 5%-50%, further optionally 30-50%.

[0025] In one embodiment, the mass proportion of the diluent in the non-aqueous organic solvent is 25%-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%, optionally 50%-92%.

[0026] On the other hand, the present application provides a lithium-ion battery, which includes a positive electrode sheet, a negative electrode sheet, a separator, and the aqueous organic high-voltage electrolyte as described above.

[0027] In one embodiment, the active material of the positive electrode sheet contains one or a combination of at least two of lithium, iron, cobalt, nickel, manganese, aluminum and phosphorus;

[0028] In one embodiment, the active material of the positive electrode plate is doped or coated with one or at least two elements selected from the group consisting of aluminum, magnesium, zirconium, titanium, scandium, lanthanum, nickel, manganese, yttrium and strontium.

[0029] More optionally, the positive electrode plate is 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 material.

[0030] Furthermore, the separator is a thin layer membrane with a porous structure that can block electron transmission and promote lithium ion transmission.

[0031] 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.

[0032] Based on the common sense in this field, the above optional conditions can be freely combined without exceeding the scope of protection of this application.

[0033] In the present application, the method for preparing the lithium-ion battery comprises the following steps:

[0034] A sulfone derivative and a diluent are first prepared into a homogeneous solution according to the mass ratios specified in the claims, and then a lithium salt of a corresponding concentration is dissolved. The non-aqueous organic high-voltage electrolyte prepared herein is then encapsulated between a positive electrode sheet and a negative electrode sheet with a separator to produce a lithium-ion battery.

[0035] Compared with the related art, this application has the following beneficial effects:

[0036] (1) This application breaks away from the traditional method of adding high-voltage functional additives to EC-based electrolytes and directly proposes a new high-voltage electrolyte based on cyclopentane derivatives. (2) The high-voltage electrolyte designed in this application has excellent high-voltage (>4.5V) cycle performance and is compatible with all currently known high-voltage positive electrode active materials. (3) The high-voltage electrolyte designed in this application has flame retardant properties. While ensuring high-voltage stable cyclic charge and discharge, it prevents the potential combustion risk of the electrolyte, which is greatly superior to the current EC-based high-voltage electrolyte. (4) The high-voltage electrolyte designed in this application breaks the traditional view that sulfone compounds cannot be used as the main solvent for organic electrolytes, and will surely provide great support for the further development of high-voltage electrolytes.

[0037] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0038] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0039] Example 1

[0040] Preparation of electrolyte 1 and experimental cell 1

[0041] Preparation of electrolyte 1: In an argon-filled glove box (moisture <0.1 ppm, oxygen <0.1 ppm), 3-nitrosulfolane (Formula 2) and dimethyl carbonate were dissolved and mixed in a mass ratio of 2:3. Then, 1 mol / L lithium hexafluorophosphate was slowly dissolved and stirred to obtain a high-voltage electrolyte.

[0042] (2) Preparation of positive electrode material: NCM111, carbon black, and PVDF (binder) were mixed in a weight ratio of 93:5:2, and N-methylpyrrolidone was added to form a slurry. The slurry was coated on a 12-μm-thick aluminum foil, dried, and rolled to obtain the positive electrode material.

[0043] (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 thereto. The slurry was then coated on an 8-μm copper foil, dried and rolled to obtain the negative electrode material.

[0044] (4) Preparation of lithium-ion battery 1: The positive electrode sheet, polyolefin separator, and negative electrode sheet are stacked in order in a dry environment with a dew point controlled below -50°C, ensuring that the separator completely separates the positive and negative electrode sheets and the negative electrode completely covers the positive electrode. The battery cells are made by stacking the sheets and encapsulated in an aluminum-plastic film of a fixed size using glue-coated tabs to form a soft-pack battery to be filled with liquid. The electrolyte prepared in step (1) is then injected into the soft-pack battery, which is then sealed, formed, aged, and sealed twice for capacity separation to obtain an experimental battery 1 for testing.

[0045] Example 2

[0046] Preparation of electrolyte 2 and experimental cell 2

[0047] The only difference from Example 1 is that during the preparation of electrolyte 2, 3-cyano-4-nitrocyclopentane sulfone (Formula 3) and ethyl methyl carbonate were dissolved and mixed uniformly in a mass ratio of 3:7, and then 1 mol / L lithium bis(fluorosulfonyl)imide was added.

[0048] Example 3

[0049] Preparation of electrolyte 3 and experimental cell 3

[0050] The only difference from Example 1 is that when preparing electrolyte 3, 3,4-dinitrosulfolane (Formula 4) and dimethyl carbonate are dissolved and mixed evenly in a mass ratio of 1:4, and then 0.8 mol / L lithium hexafluorophosphate is dissolved.

[0051] At the same time, metallic lithium is used as the negative electrode.

[0052] Example 4

[0053] Preparation of electrolyte 4 and experimental cell 4

[0054] The only difference from Example 1 is that during the preparation of electrolyte 4, 3-fluoro-4-fluorocyclopentane sulfone (Formula 5) and ethyl methyl carbonate are dissolved and mixed uniformly in a mass ratio of 3:7, and then 1 mol / L lithium bis(fluorosulfonyl)imide is added.

[0055] At the same time, metallic lithium is used as the negative electrode.

[0056] Example 5

[0057] The only difference from Example 1 is that during the preparation of electrolyte 5, 3-fluorosulfolane (Formula 6) and ethyl methyl carbonate are dissolved and mixed uniformly in a mass ratio of 5:5, and then 1 mol / L lithium hexafluorophosphate is added.

[0058] At the same time, metallic lithium is used as the negative electrode.

[0059] Example 6

[0060] The only difference from Example 1 is that during the preparation of electrolyte 5, 2-fluorosulfolane (Formula 7) and ethyl methyl carbonate are dissolved and mixed uniformly in a mass ratio of 3:7, and then 1 mol / L lithium hexafluorophosphate is added.

[0061] Comparative Example 1

[0062] The only difference from Example 1 is that the electrolyte is directly a commercial 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.

[0063] Comparative Example 2

[0064] The only difference from Example 1 is that during the preparation of the electrolyte, unsubstituted commercially available sulfolane is used instead of the 3-nitrosulfolane in Example 1.

[0065] Comparative Example 3

[0066] The only difference from Example 1 is that the 3-nitrosulfolane used in Example 1 is replaced by 3-methacrylatesulfolane.

[0067] Comparative Example 4

[0068] The only difference from Example 1 is that the 3-nitrosulfolane used in Example 1 is replaced by 3-ethoxysulfolane.

[0069] The performance of the electrolytes and batteries prepared in Examples 1-6 and Comparative Examples 1-4 of the present application was tested. The experimental batteries were subjected to charge and discharge cycle tests at 25°C:

[0070] The experimental batteries of Examples 1-6 and Comparative Examples 1-4 after capacity separation were placed in a constant temperature box at 25°C and connected to a charge and discharge tester. They were first charged to 4.8V at a constant current and constant voltage of 0.5C, and the cut-off current was set to 0.05C. After standing for 5 minutes, they were discharged to 2.8V at a constant current of 0.5C. The cyclic charge and discharge test was performed in this way, and the discharge capacity of each time was recorded. The capacity retention rate of the battery cell at the 200th, 400th and 800th cycles was calculated, respectively. The capacity retention rate of the lithium-ion battery cell in the Nth cycle (%) = the discharge capacity in the Nth cycle / the discharge capacity in the first cycle * 100%. The test results are shown in Table 1.

[0071] Table 1 Relevant cycle performance parameters of each group of batteries

[0072] According to the room temperature cycling performance shown in Table 1, the sulfolane-derived electrolyte described in the present application has better cycling stability and capacity retention than traditional EC-based electrolytes and unsubstituted sulfolane electrolytes, whether for lithium metal or graphite negative electrodes.

[0073] The applicant declares that this application uses the above-mentioned embodiments to illustrate the non-aqueous organic high-voltage electrolyte and lithium-ion battery containing the same, but this application is not limited to the above-mentioned embodiments, that is, it does not mean that this application must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvements to this application, equivalent replacement of various raw materials of the product of this application, addition of auxiliary components, selection of specific methods, etc., all fall within the scope of protection and disclosure of this application.

Claims

1. A non-aqueous organic high voltage electrolyte, wherein: The non-aqueous organic high-voltage electrolyte includes a lithium salt and a non-aqueous organic solvent; the non-aqueous organic solvent includes a sulfolane derivative and a diluent, and the sulfolane derivative has a structure as shown in formula (1): Wherein, R1, R2, R3 and R4 are each independently selected from one or a combination of at least two of hydroxyl, nitro, cyano, carboxyl, amino, alkyl, silyl, siloxy, hydrogen, fluorine, chlorine, bromine and iodine; and R1, R2, R3 and R4 are not hydrogen at the same time.

2. The non-aqueous organic high-voltage electrolyte according to claim 1, wherein At least one of R2 and R3 is selected from nitro.

3. The non-aqueous organic high-voltage electrolyte according to claim 1 or 2, wherein At least one of R2 and R3 is selected from fluorine.

4. The non-aqueous organic high-voltage electrolyte according to claim 3, wherein R2 and R3 are fluorine, and R1 and R2 are hydrogen.

5. The non-aqueous organic high-voltage electrolyte according to any one of claims 1 to 4, wherein: The diluent is one 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, or a combination of at least two thereof.

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

7. The non-aqueous organic high-voltage electrolyte according to any one of claims 1 to 6, wherein The lithium salt is one of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium hexafluoroarsenate, lithium difluorooxalatoborate, lithium difluorophosphate or lithium 4,5-dicyano-2-trifluoromethylimidazole, or a combination of at least two thereof.

8. The non-aqueous organic high-voltage electrolyte according to any one of claims 1 to 7, wherein The lithium salt is one or a combination of at least two of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide and lithium difluorooxalatoborate.

9. The non-aqueous organic high-voltage electrolyte according to any one of claims 1 to 8, wherein The molar concentration of the lithium salt in the non-aqueous organic high-voltage electrolyte is 0.05-25 mol / L, and can further be 1.2 mol / L.

10. The non-aqueous organic high-voltage electrolyte according to any one of claims 1 to 9, wherein The mass proportion of the sulfolane derivative in the non-aqueous organic solvent is 0.2%-75%, optionally 5%-50%, and further optionally 30-50%.

11. The non-aqueous organic high-voltage electrolyte according to any one of claims 1 to 10, wherein: The mass proportion of the diluent in the non-aqueous organic solvent is 25%-99.8%, and optionally 50%-92%.

12. A lithium ion battery, wherein: The lithium-ion battery comprises a positive electrode sheet, a negative electrode sheet, a separator, and the aqueous organic high-voltage electrolyte according to any one of claims 1 to 11.

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