Non-aqueous electrolyte and lithium ion battery containing same

Abstract

The invention relates to a non-aqueous electrolyte and a lithium ion battery containing the same. In order to solve the problem that an existing lithium ion battery is difficult to consider high temperature, low temperature, multiplying power and safety performance at the same time, the invention provides a non-aqueous electrolyte which comprises a lithium salt, an additive and an organic solvent, the additive comprises a compound with a specific structure, and the compound can form a stable protective film on a negative electrode and form a protective film on a positive electrode through oxidation. The silicon-oxygen structure can inhibit the hydrolysis of LiPF6, remove corrosive HF and reduce the damage of acidic substances to CEI and SEI, so that the high-temperature storage and cycle performance of the lithium ion battery is improved, and the low-temperature rate discharge and overcharge safety performance of the battery is improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more specifically to a non-aqueous electrolyte and a lithium-ion battery containing such an electrolyte. Background Technology

[0002] Lithium-ion batteries (LIBs) are finding increasingly widespread applications in electric vehicles, renewable energy storage, defense, and aerospace. However, existing LIBs exhibit significant performance degradation under both high and low temperature conditions, which is closely related to the properties of the positive electrode-electrolyte interface (CEI) and negative electrode-electrolyte interface (SEI). The presence of the CEI and SEI layers is crucial for the battery's stability and structural integrity; therefore, for LIBs, it is essential to regulate the electrolyte formulation to form high-performance CEI and SEI. Consequently, further research on electrolytes is necessary to develop more electrolytes that can effectively improve the high-temperature storage and cycle performance of lithium-ion batteries, while also ensuring low-temperature rate discharge performance and overcharge safety. Summary of the Invention

[0003] The purpose of this invention is to provide a non-aqueous electrolyte that can improve the high-temperature storage, cycle performance, low-temperature rate discharge, and overcharge safety performance of lithium-ion batteries.

[0004] Another object of the present invention is to provide a lithium-ion battery with excellent overall performance, which contains the above-mentioned non-aqueous electrolyte.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] This invention provides a non-aqueous electrolyte comprising an organic solvent, a lithium salt, and an additive, wherein the additive comprises one or more compounds represented by formula A and formula B, wherein formula A is as follows:

[0007] m and n are independently 1, 2, 3, 4, 5, or 6, and R1 and R2 are independently H or And at least one is R3, R4, and R5 are each an alkyl group with 1 to 6 carbon atoms;

[0008] Formula B is as follows:

[0009] f and q are independently 1, 2, 3, 4, 5, or 6; R6 is an alkyl group with 1-6 carbon atoms or an alkenyl group with 2-6 carbon atoms; R7 and R8 are independently H or H, respectively. And at least one is R3, R4, and R5 are each an alkyl group with 1 to 6 carbon atoms.

[0010] Furthermore, in formula A, R3, R4, and R5 are methane groups, respectively.

[0011] Furthermore, in equation A, m and n are independently 1, 2, or 3.

[0012] Furthermore, in formula B, R6 is methane, ethane, propane, or propenyl, and R3, R4, and R5 are methane, respectively.

[0013] Furthermore, in equation B, f and q are independently 1, 2, or 3.

[0014] Furthermore, in equation B, R7 and R8 are respectively

[0015] In embodiments of the present invention, the compound represented by formula A includes:

[0016]

[0017]

[0018] The compounds shown in Formula B include:

[0019]

[0020] Furthermore, the additive accounts for 0.05% to 5% of the total mass of the non-aqueous electrode solution.

[0021] Furthermore, the additive accounts for 0.1% to 2% of the total mass of the non-aqueous electrode solution.

[0022] Furthermore, the additive accounts for 0.3% to 1% of the total mass of the non-aqueous electrode solution.

[0023] Furthermore, the organic solvent includes one or more of the following: substituted or unsubstituted carbonates, substituted or unsubstituted carboxylic esters, substituted or unsubstituted ethers, substituted or unsubstituted sulfones, substituted or unsubstituted sulfoxides, and substituted or unsubstituted benzenes.

[0024] Furthermore, the organic solvent is a mixture of two or more of the following: fluoroethylene carbonate, difluoroethylene carbonate, fluoroethyl sulfone, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, methyl ethyl carbonate, ethylene glycol dimethyl ether, γ-butyrolactone, methyl acetate, ethyl acetate, difluoroethyl acetate, propyl acetate, butyl acetate, methyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, sulfolane, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl ethyl sulfone, dimethyl sulfoxide, fluorobenzene, and methyl trifluoroethyl carbonate.

[0025] In this embodiment of the invention, the organic solvent includes alkyl carbonate and olefin carbonate, and the mass ratio of the alkyl carbonate to the olefin carbonate is 1:(2-3).

[0026] According to some specific embodiments of the present invention, the organic solvent includes ethylene carbonate, diethyl carbonate, propylene carbonate, and methyl ethyl carbonate, wherein the mass ratio of ethylene carbonate, diethyl carbonate, propylene carbonate, and methyl ethyl carbonate is (1-3):(2-5):1:(4-8).

[0027] Furthermore, the organic solvent accounts for 60% to 90% of the total weight of the electrolyte.

[0028] Furthermore, the organic solvent accounts for 70% to 85% of the total weight of the electrolyte.

[0029] Furthermore, the organic solvent accounts for 80% to 85% of the total weight of the electrolyte.

[0030] Further, the lithium salt includes one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium dioxalate borate, lithium difluoroborate oxalate, lithium difluorooxalate phosphate, lithium tetrafluorooxalate phosphate, lithium fluorosulfonate, and lithium 4,5-dicyano-2-trifluoromethylimidazolium.

[0031] Furthermore, the lithium salt includes at least lithium hexafluorophosphate.

[0032] According to some specific embodiments of the present invention, the lithium salt includes lithium hexafluorophosphate, lithium difluorophosphate and lithium difluorosulfonylimide, wherein the mass ratio of lithium hexafluorophosphate, lithium difluorophosphate and lithium difluorosulfonylimide is (25-30):1:(2-8).

[0033] Furthermore, the lithium salt accounts for 8% to 30% of the total weight of the electrolyte.

[0034] Furthermore, the lithium salt accounts for 10% to 20% of the total weight of the electrolyte.

[0035] Furthermore, the lithium salt accounts for 15% to 18% of the total weight of the electrolyte.

[0036] Furthermore, the non-aqueous electrolyte also includes other additives selected from one or more of the following: cyclic carbonates containing double bonds, cyclic carbonates containing halogens, sulcolides, sulfonates, sulfates, sulfites, benzene compounds, fluorobenzene compounds, nitrile compounds, boron compounds, phosphorus compounds, amine compounds, silicon-containing compounds, and heterocyclic compounds.

[0037] Specifically, the other additives include vinylene carbonate, ethylene ethylene carbonate, fluoroethylene carbonate, vinyl sulfate, propylene sulfate, methanedisulfonate, vinyl sulfite, 1,3-propanesulfonate lactone, biphenyl, cyclohexylbenzene, tert-butylbenzene, tert-amylbenzene, m-fluorotoluene, 3,4-difluorotoluene, p-fluorotoluene, p-xylene, 1,2-dimethoxy-4-nitrobenzene, N-phenylmaleimide, pentafluoroanisole, 2,5-di-tert-butyl, 1,4-dimethoxybenzene, adiponitrile, hexanetrionitrile, butanediol, etc. One or more of the following: nitrile, 1,2,3-tris(2-cyanethoxy)propane, N,N-dicyclohexylcarbodiimide, N,N-diethylaminetrimethylsilane, hexamethyldisilazane, tris(trimethylsilane) phosphate, tris(trimethylsilane) borate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, triphenyl phosphate, heptanonitrile, 2-ethoxy-2,4,4,6,6-pentafluorotripolyphosphazene, 2-fluoropyridine, tris(2,2,2-trifluoroethyl) phosphite, and 1,3-dioxane.

[0038] Furthermore, the other additives include at least vinyl sulfate, which accounts for 0.5% to 2% of the total mass of the electrolyte, and the other additives also include vinylene carbonate and / or 1,3-propanesulfonate lactone.

[0039] Furthermore, the other additives account for 0.3% to 10% of the total weight of the electrolyte.

[0040] More preferably, the other additives account for 0.3% to 5% of the total weight of the electrolyte.

[0041] More preferably, the other additives account for 0.3% to 2% of the total weight of the electrolyte.

[0042] A second aspect of the present invention also provides a lithium-ion battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte is the aforementioned non-aqueous electrolyte.

[0043] Furthermore, the positive electrode active material is LiNi. x Co y M z O2 (where M includes Mn and Al, and x and y are values ​​between 0 and 1, and x+y+z=1), lithium iron phosphate (LiFePO4), lithium manganese oxide (LiMn2O4), lithium manganese iron phosphate (LiMn a Fe 1-a PO4, where a is a value between 0 and 1, is one or more of these.

[0044] Furthermore, the negative electrode active material is graphite (including natural graphite and artificial graphite), mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, and spinel-structured lithiated TiO2-Li4Ti5O. 12 One or more of Li-Al alloys.

[0045] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0046] This invention improves the high-temperature storage and cycle performance, low-temperature rate discharge, and overcharge safety performance of lithium-ion batteries by adding compounds with specific structures to non-aqueous electrolytes. By using other conventional additives in combination, better electrochemical performance can be achieved with lower additive dosages, thereby reducing electrolyte costs. Detailed Implementation

[0047] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific applications, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0048] Examples 1-8 and Comparative Examples 1-2

[0049] Prepare the non-aqueous electrolytes of Examples 1-8 and Comparative Examples 1-2 in a glove box according to the formulations in Table 1.

[0050] Table 1

[0051]

[0052] Examples 9-16 and Comparative Examples 3-4

[0053] Prepare the non-aqueous electrolytes of Examples 9-16 and Comparative Examples 3-4 in a glove box according to the formulations in Table 2.

[0054] Table 2

[0055]

[0056] Examples 17-24 and Comparative Examples 5-6

[0057] Prepare the non-aqueous electrolytes of Examples 17-24 and Comparative Examples 5-6 in a glove box according to the formulations in Table 3.

[0058] Table 3

[0059]

[0060] Examples 25-51

[0061] Prepare Examples 25–51 in a glove box according to the formulas in Table 4.

[0062] Table 4

[0063]

[0064]

[0065] In Tables 1 to 4, “%” represents mass percentage, i.e., “wt%”.

[0066] In Tables 1 to 4, EC: ethylene carbonate; DEC: diethyl carbonate; EMC: methyl ethyl carbonate; VC: vinylene carbonate; PC: propylene carbonate; LiFSI: lithium difluorosulfonyl imide; LiDFP: lithium difluorophosphate; PS: 1,3-propanesulfonate lactone; LiPF6: lithium hexafluorophosphate; DTD: ethylene sulfate.

[0067] AD-1: AD-2: AD-3: AD-4: AD-5: AD-6: AD-7: AD-8:

[0068] Performance testing:

[0069] The electrolytes obtained in Examples 1-51 and Comparative Examples 1-6 were injected into the same batch of 1.2 Ah LiNi. 0.8 Co 0.1 Mn 0.1 In the O2|| artificial graphite polymer pouch battery, the following tests were performed respectively:

[0070] 1) After the battery is fully charged at 4.25V and left at 70℃ for 28 days, the thickness and internal resistance are tested to obtain the thickness swelling rate H% (thickness after storage - thickness before storage) / thickness before storage * 100%).

[0071] 2) After the battery is charged to 4.25V at 1C constant current and constant voltage at 45℃, it is discharged to 2.75V at 1C constant current and cycled for 1000 cycles to obtain the capacity retention rate Q1% (1000-cycle discharge capacity / average discharge capacity 10 weeks ago * 100%).

[0072] 3) After the battery is charged to 4.25V at 0℃ using 1C constant current and constant voltage, it is then discharged to 2.75V using 1C constant current. After 500 cycles, the capacity retention rate Q2% is obtained (500-cycle discharge capacity / average discharge capacity 10 weeks ago * 100%).

[0073] 4) Charge the battery at a constant current of 1C to 6.3V, and then charge it at a constant voltage of 6.3V. End the experiment when the current is less than 0.2C, and record the highest temperature T during the test.

[0074] The experimental results are shown in Table 5.

[0075] Table 5

[0076]

[0077]

[0078]

[0079] Table 5 shows that in LiNi 0.8 Co 0.1 Mn 0.1 In O2||In artificial graphite polymer pouch batteries, the addition of compounds with specific structures improves the high-temperature storage, cycle performance, low-temperature rate discharge, and overcharge safety of lithium-ion batteries. The inventors believe that these compounds can form stable protective films on both the positive and negative electrodes. Furthermore, their silicon-oxygen structure inhibits LiPF6 hydrolysis and removes corrosive HF, reducing the damage of acidic substances to the CEI and SEI, thereby improving the high-temperature storage and cycle performance of lithium-ion batteries, as well as their low-temperature rate discharge and overcharge safety.

[0080] Furthermore, by combining compounds with specific structures with other additives (such as DTD, PS, and VC), better electrochemical performance can be obtained even with lower concentrations of the compounds with specific structures. As shown in Table 5, the improvement in battery electrochemical performance by compounds with specific structures does not increase indefinitely with increasing dosage. The overall battery performance at 0.5 wt% of the compound with specific structures is comparable to or even better than that at 2 wt% of the compound with specific structures. Considering the cost of the electrolyte, it is preferable to add the compound with specific structures at approximately 0.5 wt% along with appropriate amounts of conventional additives such as PS or VC.

[0081] The present invention has been described in detail above, with the aim of enabling those skilled in the art to understand and implement the invention. However, this description should not be construed as limiting the scope of protection of the invention. All equivalent changes or modifications made in accordance with the spirit and essence of the invention should be included within the scope of protection of the invention.

Claims

1. A non-aqueous electrolyte comprising an organic solvent, a lithium salt, and an additive, characterized in that, The additive includes one or more compounds represented by Formula A and Formula B, wherein Formula A is as follows: m and n are independently 1, 2, 3, 4, 5, or 6, and R1 and R2 are independently H or And at least one is R3, R4, and R5 are each an alkyl group with 1 to 6 carbon atoms; Formula B is as follows: f and q are independently 1, 2, 3, 4, 5, or 6; R6 is an alkyl group with 1-6 carbon atoms or an alkenyl group with 2-6 carbon atoms; R7 and R8 are independently H or H, respectively. And at least one is R3, R4, and R5 are each an alkyl group with 1 to 6 carbon atoms.

2. The non-aqueous electrolyte according to claim 1, characterized in that, In formula A, R3, R4, and R5 are methane groups, respectively; And / or, in formula A, m and n are independently 1, 2, or 3; And / or, in formula B, R6 is methane, ethane, propane or propenyl, and R3, R4 and R5 are methane, respectively; And / or, in equation B, f and q are independently 1, 2, or 3; And / or, in equation B, R7 and R8 are respectively 3. The non-aqueous electrolyte according to claim 1, characterized in that, The compounds shown in Formula A include: The compounds shown in Formula B include:

4. The non-aqueous electrolyte according to claim 1, characterized in that, The additive accounts for 0.05% to 5% of the total mass of the non-aqueous electrode solution.

5. The non-aqueous electrolyte according to claim 1, characterized in that, The organic solvent includes one or more of the following: substituted or unsubstituted carbonates, substituted or unsubstituted carboxylic esters, substituted or unsubstituted ethers, substituted or unsubstituted sulfones, substituted or unsubstituted sulfoxides, and substituted or unsubstituted benzenes. And / or, the organic solvent accounts for 60% to 90% of the total weight of the electrolyte.

6. The non-aqueous electrolyte according to claim 5, characterized in that, The organic solvent includes alkyl carbonate and olefin carbonate, and the mass ratio of the alkyl carbonate to the olefin carbonate is 1:(2-3).

7. The non-aqueous electrolyte according to claim 1, characterized in that, The lithium salt includes one or more of lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium dioxalate borate, lithium difluoroborate oxalate, lithium difluorooxalate phosphate, lithium tetrafluorooxalate phosphate, lithium fluorosulfonate, and lithium 4,5-dicyano-2-trifluoromethylimidazolium. And / or, the lithium salt accounts for 8% to 30% of the total weight of the electrolyte.

8. The non-aqueous electrolyte according to claim 1, characterized in that, The non-aqueous electrolyte also includes other additives selected from one or more of the following: cyclic carbonates containing double bonds, cyclic carbonates containing halogens, sulopentalides, sulfonates, sulfates, sulfites, benzene compounds, fluorobenzene compounds, nitrile compounds, boron compounds, phosphorus compounds, amine compounds, silicon-containing compounds, and heterocyclic compounds. The other additives account for 0.3% to 10% of the total weight of the electrolyte.

9. The non-aqueous electrolyte according to claim 8, characterized in that, The other additives include at least vinyl sulfate.

10. A lithium-ion battery comprising a positive electrode, a negative electrode, and an electrolyte, characterized in that, The electrolyte is the non-aqueous electrolyte according to any one of claims 1 to 9.

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