Long-circulation stable lithium ion battery electrolyte and lithium ion battery

Abstract

The application discloses a long-circulation stable lithium ion battery electrolyte, which comprises a main lithium salt, an organic solvent and an additive. Specifically, the additive comprises a first additive which is an alkynyl borate compound and a second additive which is selected from a fluorophosphonate or lithium fluorophosphonate compound. The specific structure and definition of the first additive and the second additive can be known from the description. The additive composition of the application can significantly reduce the battery internal resistance and the internal resistance growth of the battery during the cycle process, inhibit the high-temperature gas production of the battery, and improve the long-period cycle performance of the battery.

Description

Technical Field

[0001] This invention relates to lithium-ion battery electrolytes, and particularly to lithium-ion battery electrolytes and lithium-ion batteries that exhibit long-cycle stability under high voltage. Background Technology

[0002] The solid electrolyte interface (SEI) is crucial for the performance of lithium-ion batteries. During the first charge, film-forming additives are reduced and decomposed on the negative electrode to form an SEI layer. Ideally, the SEI film should be electronically insulating but ionicly conductive, preventing further electrolyte decomposition while still allowing lithium ions to reversibly insert / extract from the graphite negative electrode. Therefore, the SEI film dominates battery safety, power performance, and battery life. Vinylene carbonate (VC), 1,3-propanesulfonate lactone (PS), and fluoroethylene carbonate (FEC) are among the most commonly used film-forming additives, capable of forming an SEI film on the graphite negative electrode surface, thereby inhibiting the continued decomposition of the electrolyte on the electrode surface.

[0003] However, although existing film-forming additives have good performance under normal conditions, they are prone to repeated dissolution and reforming under high temperature (>60℃) and high voltage (>4.3V), which causes the electrolyte to undergo continuous decomposition reaction, resulting in a series of problems such as gas production and capacity reduction in the battery under high temperature conditions.

[0004] To address the issue of poor high-temperature performance, a common approach is to use high-resistivity film-forming additives, such as ethylene ethylene carbonate (VEC), 1,3-propenyl sulfonate (PST), and methane disulfonate (MMDS). However, the resulting interfacial films often exhibit high interfacial resistance, leading to poor battery rate performance and low-temperature performance. Furthermore, when the coating density and compaction density of the battery electrodes are high, lithium plating is prone to occur, resulting in a reduction or even a significant drop in battery capacity.

[0005] Therefore, there is an urgent need to develop an additive that combines film-forming and low-impedance properties to construct an electrolyte system that is stable over long cycles, can withstand both high and low temperatures, and has low internal resistance. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a long-cycle stable lithium-ion battery electrolyte that reduces internal resistance growth, battery gas generation, and capacity decay during high-voltage cycling.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A long-cycle stable lithium-ion battery electrolyte, comprising a main lithium salt, an organic solvent, and additives, specifically, the additives comprising:

[0009] The first additive is an alkynyl borate ester compound as shown in formula (I):

[0010]

[0011] In the formula, R1, R2, and R3 are independently selected from C1-C6 alkyl, C1-C6 fluoroalkyl, C2-C6 alkenyl, C2-C6 fluoroalkenyl, C2-C6 alkynyl, C2-C6 fluoroalkynyl, and cyano-substituted C2-C6 alkyl; and at least two of R1, R2, and R3 contain an alkynyl group;

[0012] The second additive is selected from at least one of the following formulas (II-1), (II-2), (II-3), (II-4), (II-5), (II-6), (II-7), (II-8): fluorophosphates or lithium fluorophosphate compounds;

[0013]

[0014] The first additive accounts for 0.1 to 5.0 wt% of the total mass of the electrolyte, preferably 0.2 to 4.0 wt%, more preferably 0.2 to 3.0 wt%.

[0015] The second additive accounts for 0.1 to 5.0 wt% of the total mass of the electrolyte, preferably 0.2 to 4.0 wt%, more preferably 0.2 to 3.0 wt%.

[0016] As a preferred option

[0017] R1, R2, and R3 are independently selected from C1-C3 alkyl, C1-C3 fluoroalkyl, C2-C3 alkenyl, C2-C3 fluoroalkenyl, C2-C3 alkynyl, C2-C3 fluoroalkynyl, and cyano-substituted C2-C3 alkyl; and at least two of R1, R2, and R3 contain an alkynyl group;

[0018] More preferably,

[0019] R1, R2, and R3 are independently selected from methyl, ethyl, trifluoromethyl, trifluoroethyl, pentafluoroethyl, vinyl, propynyl, ethynyl, propynyl, cyano-substituted methyl, and cyano-substituted ethyl; and at least two of R1, R2, and R3 contain an ynyl group;

[0020] Most preferably, the first additive is selected from at least one of the structures shown in the following formula:

[0021]

[0022] Based on the long-cycle stable lithium-ion battery electrolyte described above.

[0023] The first additive of this invention is an unsaturated alkynyl compound with boron as the central atom. It contains at least two unsaturated alkynyl groups and can form a stable cross-linked network polymer on the positive and negative electrode surfaces through a cross-linking reaction. This effectively suppresses battery gas generation and capacity decay at high temperatures, improving high-temperature cycling and high-temperature storage performance—an effect that cannot be achieved with a single unsaturated alkynyl compound. Its boron-centered group can form a boron-containing interface film on the battery positive electrode, exhibiting good high voltage stability. However, a single first additive can easily lead to excessively high battery impedance and poor performance in room-temperature cycling and low-temperature discharge.

[0024] The combined use of the second and first additives in this invention enables the formation of an organic-inorganic composite interfacial film at the negative electrode. The organic outer layer is a cross-linked network polymer, exhibiting excellent ion conductivity and electrolyte isolation properties; while the presence of the second additive forms an inorganic inner layer composed of various salts, including at least one of LiF, Li3PO4, and lithium fluorophosphate. This inorganic inner layer containing multiple salts can both block electron exchange and suppress solvent side reactions, and improve interfacial lithium-ion conductivity.

[0025] That is, in the lithium-ion battery system using the electrolyte described in this invention, an SEI composite interface film can be formed at the negative electrode, and a boron-containing interface film can be formed at the positive electrode; the SEI composite interface film includes:

[0026] An inorganic inner layer, comprising at least one of LiF, Li3PO4, and lithium fluorophosphate; and an organic outer layer, wherein the organic outer layer is a cross-linked network polymer.

[0027] The lithium-ion battery electrolyte of this invention can significantly reduce the battery's internal resistance and the increase in internal resistance during cycling, effectively solving the problem that conventional low-resistance additives are not effective in reducing resistance in mature formulations.

[0028] The main lithium salt of this invention can be any common lithium salt found in electrolytes. Preferably, the main lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluorooxalate phosphate, lithium tri(oxalate) phosphate, and lithium difluorobis(oxalate) phosphate, with a molar concentration of 0.1–4.0 mol / L, and is different from the second additive. More preferably, the main lithium salt is selected from lithium hexafluorophosphate and / or lithium bis(fluorosulfonyl)imide, with a molar concentration of 0.8–1.5 mol / L.

[0029] The organic solvent used in this invention can be any commonly used organic solvent in electrolytes. Preferably, the organic solvent is selected from at least one of C3-C6 carbonate compounds, C3-C8 carboxylic acid ester compounds, sulfone compounds, and ether compounds. Further, the C3-C6 carbonate or fluorocarbonate compounds are selected from at least one of ethylene carbonate, propylene carbonate, butenyl carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate; the C3-C8 carboxylic acid ester compounds are selected from at least one of γ-butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, and propyl propionate; the sulfone compounds are selected from at least one of sulfolane, dimethyl sulfoxide, dimethyl sulfone, and diethyl sulfone; and the ether compounds are selected from triethylene glycol dimethyl ether and / or tetraethylene glycol dimethyl ether.

[0030] To further improve the basic performance of the lithium-ion battery electrolyte, the additive also includes a basic additive selected from at least one of vinylene carbonate, 1,3-propanesulfonyl lactone, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, propylene sulfate, pentafluoroethoxycyclotriphosphazene, succinic anhydride, citrate anhydride, or succinic anhydride, and the amount added accounts for 0.1% to 5.0% of the total mass of the electrolyte.

[0031] The present invention also provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and a long-cycle stable lithium-ion battery electrolyte as described above.

[0032] The active material of the positive electrode is selected from nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium cobalt oxide materials, or lithium iron phosphate materials.

[0033] The active material of the negative electrode is selected from graphite, silicon carbide, silicon suboxide, silicon, tin, lithium metal or composite materials thereof.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] This invention uses a combination of alkynyl borate esters and fluorophosphate / lithium fluorophosphate compounds, which not only reduces the initial impedance of the battery and improves its performance in room temperature cycling and low temperature discharge, but also reduces the increase in internal resistance during battery cycling, suppresses battery gas generation and capacity decay during cycling, and improves the battery's long-cycle performance and cycle life. Attached Figure Description

[0036] Figure 1 The LSV reduction curve is shown in the basic electrolyte of this embodiment of the invention after adding 1.0% compound I-1.

[0037] Figure 2The LSV oxidation curve is shown in the basic electrolyte of this embodiment of the invention after adding 1.0% of compound I-1. Detailed Implementation

[0038] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternatives, improvements, and equivalents that may be included within the scope of the claims.

[0039] I. Preparation of Electrolyte

[0040] Preparation of the basic electrolyte: In an argon-filled glove box (moisture < 5 ppm, oxygen < 10 ppm), ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were uniformly mixed at a mass ratio of EC:EMC:DEC = 3:5:2. Lithium hexafluorophosphate (LiPF6) was slowly added to the mixed solution until the molar concentration of LiPF6 reached 1.2 mol / L, thus obtaining the basic electrolyte.

[0041] Example 1: 0.5% of compound I-1 and 0.5% of compound II-1 were added to the base electrolyte to obtain the electrolyte of this example.

[0042] Example 2: 0.5% of compound I-1 and 1.0% of compound II-1 were added to the base electrolyte to obtain the electrolyte of this example.

[0043] Example 3: 1.0% of compound I-1 and 0.5% of compound II-8 were added to the base electrolyte to obtain the electrolyte of this example.

[0044] Example 4: 3.0% of compound I-1 and 1.0% of compound II-2 were added to the base electrolyte to obtain the electrolyte of this example.

[0045] Example 5: 1.0% of compound I-2 and 0.5% of compound II-1 were added to the base electrolyte to obtain the electrolyte of this example.

[0046] Example 6: 1.0% of compound I-2 and 0.5% of compound II-2 were added to the base electrolyte to obtain the electrolyte of this example.

[0047] Example 7: 0.5% of compound I-3 and 3.0% of compound II-2 were added to the base electrolyte to obtain the electrolyte of this example.

[0048] Example 8: 0.2% of compound I-3 and 0.2% of compound II-3 were added to the base electrolyte to obtain the electrolyte of this example.

[0049] Example 9: 0.5% of compound I-4 and 0.5% of compound II-3 were added to the base electrolyte to obtain the electrolyte of this example.

[0050] Example 10: 1.0% of compound I-4 and 0.5% of compound II-4 were added to the base electrolyte to obtain the electrolyte of this example.

[0051] Example 11: The electrolyte of this example was obtained by adding 1.0% of compound I-5 and 0.5% of compound II-4 to the base electrolyte.

[0052] Example 12: The electrolyte of this example was obtained by adding 1.0% of compound I-5 and 0.5% of compound II-7 to the base electrolyte.

[0053] Example 13: The electrolyte of this example was obtained by adding 1.0% of compound I-6 and 0.2% of compound II-7 to the base electrolyte.

[0054] Example 14: 0.5% of compound I-6 and 2.0% of compound II-7 were added to the base electrolyte to obtain the electrolyte of this example.

[0055] Example 15: 1.0% of compound I-7 and 3.0% of compound II-7 were added to the base electrolyte to obtain the electrolyte of this example.

[0056] Example 16: The electrolyte of this example was obtained by adding 2.0% of compound I-7 and 0.5% of compound II-6 to the base electrolyte.

[0057] Example 17: 1.0% of compound I-8 and 0.5% of compound II-8 were added to the base electrolyte to obtain the electrolyte of this example.

[0058] Example 18: The electrolyte of this example was obtained by adding 0.2% of compound I-8 and 2.0% of compound II-5 to the base electrolyte.

[0059] Example 19: 1.0% of compound I-9 and 0.5% of compound II-5 were added to the base electrolyte to obtain the electrolyte of this example.

[0060] Example 20: 0.5% of compound I-9 and 0.5% of compound II-8 were added to the base electrolyte to obtain the electrolyte of this example.

[0061] Example 21: The electrolyte of this example was obtained by adding 3.0% of compound I-9 and 0.2% of compound II-8 to the base electrolyte.

[0062] Example 22: 4.5% of compound I-1 and 0.5% of compound II-1 were added to the base electrolyte to obtain the electrolyte of this example.

[0063] Example 23: 1.0% of compound I-2 and 4.8% of compound II-1 were added to the base electrolyte to obtain the electrolyte of this example.

[0064] Comparative Example 1: 0.5% of compound I-1 and 0.5% of DTD were added to the base electrolyte to obtain the electrolyte of this comparative example.

[0065] Comparative Example 2: 0.5% of compound I-1 and 0.5% of LiFSI were added to the base electrolyte to obtain the electrolyte of this comparative example.

[0066] Comparative Example 3: 1.0% of compound I-2 and 0.5% of LiBF4 were added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0067] Comparative Example 4: 1.0% of compound I-2 and 0.5% of FEC were added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0068] Comparative Example 5: 0.5% of compound II-8 and 1.0% of PST were added to the base electrolyte to obtain the electrolyte of this comparative example.

[0069] Comparative Example 6: 0.5% of compound II-1 and 1.0% of VEC were added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0070] Comparative Example 7: 0.5% of compound I-1 was added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0071] Comparative Example 8: 1.0% of compound I-5 was added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0072] Comparative Example 9: 0.5% of compound II-1 was added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0073] Comparative Example 10: 0.5% of compound II-5 was added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0074] Comparative Example 11: Basic Electrolyte.

[0075] The mass percentages of the first additive, the second additive, and other additives in the above embodiments and comparative examples are shown in Table 1 below:

[0076] Table 1. Additive dosage for each example / comparative example

[0077]

[0078]

[0079] II. Electrochemical Performance Testing

[0080] Figure 1 , Figure 2 The reduction and oxidation curves of LSV after adding 1.0% compound I-1 to the base electrolyte are presented. Figure 1 As shown, a significant reduction peak appears at around 1.3 V, and the reduction peak of the electrolyte solvent disappears, suggesting that compound I-1 has a modifying effect on the negative electrode interface; Figure 2 As shown, a preferential oxidation peak appears at around 4.3V, suggesting that it has a positive electrode film-forming effect.

[0081] The present invention conducts electrochemical performance tests on the combined effect of the first additive and the second additive, and the specific operation is as follows:

[0082] The electrolytes from the above embodiments and comparative examples were used to fabricate 1260mAh capacity soft-pack lithium-ion batteries. Each lithium-ion battery includes a positive electrode, a negative electrode, a separator, an electrolyte, and battery auxiliary materials. The positive electrode active material is a nickel-cobalt-manganese ternary material, a nickel-cobalt-aluminum ternary material, a lithium cobalt oxide material, or a lithium iron phosphate material. The negative electrode active material is graphite, silicon, or lithium metal. The positive electrode active material is a ternary positive electrode LiNi. 0.6 Co 0.2 Mn 0.2 O2, the negative electrode active material is high-capacity graphite. The preparation process is as follows: the positive electrode sheet, separator and negative electrode sheet are wound together into a core, sealed with aluminum-plastic film and then baked to ensure that the electrode moisture meets the requirements. After baking, the cell is injected with electrolyte, and after standing, formation, capacity testing and aging processes, the finished soft-pack cell is obtained.

[0083] The performance of the prepared lithium-ion power battery (soft-pack cell) was tested, mainly including:

[0084] (1) Battery capacity test: After capacity division, the battery is charged at a constant current of 0.33C to 4.35V, and then charged at a constant voltage until the current of 0.05C is cut off; let it rest for 30 minutes; discharge it at a constant current of 1C to 2.8V to obtain the discharge capacity of the single cell.

[0085] (2) -20℃ battery discharge DCIR test: The battery was adjusted to 50% SOC state with a current of 0.33C and left to stand for 5 hours in a -20℃ environment to depolarize the battery. The open circuit voltage OCV1 was recorded after the stand was completed. The battery was discharged with a current of 3C for 10s and left to stand for 10min. The voltage OCV2 at the moment of termination of the high current discharge was tested. According to the formula DCIR=(OCV1-OCV2) / 3C, the low temperature discharge DCIR of the single cell was obtained.

[0086] (3) -20℃ battery discharge capacity test: The fully charged battery was left in a -20℃ environment for 5 hours and discharged to 2.8V with a current of 0.5C to obtain the low temperature discharge capacity of the single cell.

[0087] (4) 60℃ high temperature storage test: Charge the battery to 100% SOC and place it in an oven at 60±2℃ for 1 month. Test the volume change before and after storage to obtain the volume change rate of a single cell before and after storage at 60℃.

[0088] (5) 45℃ high temperature cycling test: The battery is cycled in an oven at 45±2℃ with a charge / discharge current of 1C / 1C. The charge capacity and discharge capacity are calculated every week. The DCIR change and volume change of the battery during the cycling process are monitored every 100 weeks. The capacity retention rate, DCIR growth rate and volume change rate of the single cell after 500 cycles at 45℃ are obtained.

[0089] Table 2 presents the test results of the basic performance (ACR internal resistance and initial capacity) and low-temperature performance of the pouch cells prepared with different electrolyte formulations in the embodiments and comparative examples of the present invention; Table 3 presents the test results of the high-temperature storage performance (volume change rate before and after storage, internal resistance growth rate before and after storage) and high-temperature cycling performance (volume change rate, DCIR internal resistance growth rate, capacity retention rate) of the pouch cells prepared with different electrolyte formulations in the embodiments and comparative examples of the present invention at 60℃ and 45℃. Two identical pouch cells were prepared for parallel testing for each electrolyte formulation, and the specific results are shown in Tables 2 and 3 below.

[0090] Table 2. Test results of basic performance and low temperature performance

[0091]

[0092]

[0093]

[0094] Table 3. Test results of high-temperature storage at 60℃ and high-temperature cycling at 45℃

[0095]

[0096]

[0097] According to the test results in Tables 2 and 3 above:

[0098] 1. Comparing Examples 1, 5, and 11, it is evident that the combination of the first and second additives added to the base electrolyte can significantly improve the high-temperature storage and cycle stability of the battery, and suppress the volume expansion of the battery at high temperatures. Simultaneously, it has minimal impact on the battery's initial impedance and low-temperature performance.

[0099] 2. Comparing Example 1 with Comparative Examples 7 and 9, and Comparing Example 12 with Comparative Examples 8 and 10, it can be seen that the composition with the addition of the first additive and the second additive has a lower initial internal resistance, improved low-temperature discharge capacity, and further improved high-temperature performance compared to using the first additive alone. Furthermore, the composition with the addition of the first additive and the second additive exhibits significant advantages in high-temperature performance compared to using the second additive alone, specifically manifested in improved high-temperature cycle retention, suppressed gas generation during high-temperature storage, and reduced increase in internal resistance during high-temperature storage.

[0100] 3. Comparing Example 1 with Comparative Examples 1 and 2, and Comparing Example 6 with Comparative Examples 3 and 4, it can be seen that the combination of adding the first additive and the second additive to the electrolyte not only significantly improves the high-temperature performance, but also shows excellent performance in terms of impedance, rate capability and low-temperature performance, compared with the combination of the first additive and low-resistance additives such as DTD, LiFSI, LiBF4, and FEC. (1) The ACR internal resistance at room temperature decreased by 2.3 mΩ, effectively reducing the initial internal resistance of the battery; (2) The DCIR growth rate at 45℃ high-temperature cycling decreased by about 10%, solving the problem of severe internal resistance growth during cycling; (3) The DCIR decreased by 30 mΩ at -20℃, and the discharge capacity at -20℃ increased by about 20 mAh, significantly improving the low-temperature performance.

[0101] 4. Comparing Example 3, Example 17 and Comparative Example 5, and comparing Example 5 and Comparative Example 6, it can be seen that the combination of adding the first additive and the second additive has better high-temperature performance than the combination of the second additive and conventional high-temperature additives such as PST and VEC. Specifically, it has better high-temperature storage gas generation suppression effect and higher high-temperature cycle capacity retention rate.

[0102] In summary, the combined use of the first and second additives of this invention has good compatibility with the positive and negative electrode interfaces. It can not only significantly suppress gas generation and internal resistance growth during high-temperature storage and improve high-temperature cycle capacity retention, but also reduce the initial internal resistance of the battery and reduce the internal resistance growth during battery cycling, thereby further improving the high and low temperature and rate performance of the battery.

Claims

1. A long-cycle stable lithium-ion battery electrolyte, comprising a main lithium salt, an organic solvent, and additives, characterized in that: The additives include: The first additive is an alkynyl borate ester compound as shown in formula (I): R1, R2, and R3 are independently selected from C1-C6 alkyl, C1-C6 fluoroalkyl, C2-C6 alkenyl, C2-C6 fluoroalkenyl, C2-C6 alkynyl, C2-C6 fluoroalkynyl, and cyano-substituted C2-C6 alkyl; and at least two of R1, R2, and R3 contain an alkynyl group. The second additive is a fluorophosphate or a lithium fluorophosphate compound, selected from at least one of the structures shown in formulas (II-1), (II-2), (II-3), (II-4), (II-5), (II-6), (II-7), and (II-8); The first additive accounts for 0.1 to 5.0 wt% of the total mass of the electrolyte; The second additive accounts for 0.1 to 5.0 wt% of the total mass of the electrolyte.

2. The lithium-ion battery electrolyte according to claim 1, characterized in that: R1, R2, and R3 are independently selected from C1-C3 alkyl, C1-C3 fluoroalkyl, C2-C3 alkenyl, C2-C3 fluoroalkenyl, C2-C3 alkynyl, C2-C3 fluoroalkynyl, and cyano-substituted C2-C3 alkyl; and at least two of R1, R2, and R3 contain an alkynyl group.

3. The lithium-ion battery electrolyte according to claim 2, characterized in that: R1, R2, and R3 are independently selected from methyl, ethyl, trifluoromethyl, trifluoroethyl, pentafluoroethyl, vinyl, propynyl, ethynyl, propynyl, cyano-substituted methyl, and cyano-substituted ethyl; and at least two of R1, R2, and R3 contain an ethynyl group.

4. The lithium-ion battery electrolyte according to claim 3, characterized in that: The first additive is selected from at least one of the structures shown in the following formula:

5. The lithium-ion battery electrolyte according to claim 1, characterized in that: The first additive accounts for 0.2 to 3.0 wt% of the total mass of the electrolyte; The second additive accounts for 0.2 to 3.0 wt% of the total mass of the electrolyte.

6. The lithium-ion battery electrolyte according to claim 1, characterized in that: The main lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluorooxalate phosphate, lithium tri(oxalate) phosphate, and lithium difluorobis(oxalate) phosphate, and its molar concentration is 0.1 to 4.0 mol / L; The organic solvent is selected from at least one of C3-C6 carbonate compounds, C3-C8 carboxylic acid ester compounds, sulfone compounds, and ether compounds.

7. The lithium-ion battery electrolyte according to claim 1, characterized in that: The additives also include a base additive selected from at least one of vinylene carbonate, 1,3-propanesulfonyl lactone, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, propylene sulfate, pentafluoroethoxycyclotriphosphazene, succinic anhydride, citrate anhydride, or succinic anhydride.

8. A lithium-ion battery, comprising a positive electrode, a negative electrode, and a separator, characterized in that: The lithium-ion battery further includes the long-cycle stable lithium-ion battery electrolyte as described in any one of claims 1-7.

Images