An electrolyte and a lithium battery containing the electrolyte.

Abstract

This invention provides an electrolyte and a lithium battery containing the same. The electrolyte comprises a lithium salt, a solvent, and an inducing agent; the solvent comprises one or more siloxane compounds of Formula I; the inducing agent is selected from one or more of C1-C5 haloalkanes, C1-C5 halocycloalkanes, C2-C6 haloaliphatic ethers, and C6-C12 haloaromatic compounds. The electrolyte provided by this invention utilizes the intermolecular interaction forces between the siloxane compound and the inducing agent to achieve the dissolution of the lithium salt in the solvent. This electrolyte exhibits high compatibility with lithium metal anodes, has a wide electrochemical window, and can be well matched with high-voltage cathode materials and lithium metal anode materials, thus contributing to improved battery cycle life and coulombic efficiency.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to an electrolyte and a lithium battery containing the electrolyte. Background Technology

[0002] Lithium-ion batteries have become a hot research topic in the energy storage field due to their high energy density and cycle performance. However, the performance improvement of lithium-ion batteries based on the traditional lithium cobalt oxide, graphite anode, and commercial electrolyte framework is nearing its limit and can no longer keep up with the ever-growing demands of consumers.

[0003] Lithium metal, due to its extremely low standard potential and density, can significantly improve the energy density of lithium-ion batteries when used as an anode, making it a candidate anode material for high-energy-density lithium-ion batteries. However, lithium metal exhibits high reactivity and readily undergoes side reactions with traditional carbonate-based electrolytes, leading to a continuous thickening of the solid electrolyte interphase (SEI) film on the anode surface. This increases impedance with cycling, resulting in capacity decay. Furthermore, uneven lithium ion deposition on the anode surface can cause lithium dendrite growth, triggering short circuits and even fires and explosions. Therefore, designing a novel electrolyte system to replace traditional carbonate-based electrolytes and improve the safety of lithium metal batteries is crucial.

[0004] Lithium-ion battery electrolytes, as a crucial component of batteries, are generally composed of lithium salts, solvents, and additives, which collectively determine the electrolyte's performance. Key issues for lithium metal battery electrolytes include: 1) stability against the lithium metal anode, and 2) good oxidation resistance against the cathode. While ethylene glycol dimethyl ether-based electrolytes, widely reported to have good compatibility with the anode and coulombic efficiency (CE) exceeding 99%, exhibit poor oxidation stability (<4V) at the cathode, making them unsuitable for lithium metal batteries using high-voltage cathode materials such as lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, and lithium cobalt oxide. High-concentration electrolytes (containing high-concentration lithium salts) or locally high-concentration electrolytes (containing high-concentration lithium salts and fluoroether diluents) can improve the oxidation resistance of the cathode solvent molecules to some extent due to the reduced amount of free solvent, but require large amounts of lithium salts and the high cost of fluoroether diluents, undoubtedly increasing the electrolyte's manufacturing cost.

[0005] Therefore, designing and developing a novel electrolyte with a wide electrochemical window that balances high-voltage stability on the positive electrode side and stability on the lithium metal negative electrode side is of great significance for promoting the rapid development of high-energy-density lithium metal batteries. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an electrolyte and a lithium battery containing the electrolyte. This electrolyte exhibits good stability against both high-voltage cathodes and lithium metal anodes, possesses a wide electrochemical window, and is well-matched with both high-voltage cathode and lithium metal anode materials. It can be used in high-energy-density lithium metal batteries, contributing to improved cycle life and coulombic efficiency.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides an electrolyte comprising: a lithium salt, a solvent, and an inducing agent;

[0009] The solvent includes one or more of the siloxane compounds shown in Formula I;

[0010]

[0011] Wherein, X1 and X2 are each independently selected from one of C1-C4 (e.g., C1, C2, C3, C4) alkyl groups, and R is selected from one of *-OLO-*; or, X1 and X2 are each independently selected from one of C1-C4 (e.g., C1, C2, C3, C4) alkoxy groups, and R is selected from one of C2-C4 (e.g., C2, C3, C4) alkylene groups and *-OLO-*;

[0012] L is selected from C2-C4 (e.g., C2, C3, C4) alkylene groups, *-Y1-O-Y2-*, One of them; Y1 and Y2 are each independently selected from one of C1-C2 alkylene groups, and Y3 is selected from one of C1-C3 (e.g., C1, C2, C3) alkylene groups;

[0013] -* represents the linking site of a functional group;

[0014] The inducing agent is selected from one or more of the following: C1-C5 (e.g., C1, C2, C3, C4, C5) haloalkanes, C1-C5 (e.g., C1, C2, C3, C4, C5) halocycloalkanes, C2-C6 (e.g., C2, C3, C4, C5, C6) haloaliphatic ethers, and C6-C12 (e.g., C6, C7, C8, C9, C10, C11, C12) haloaromatic compounds.

[0015] In the electrolyte provided by this invention, the inducing agent can alter the molecular configuration of the siloxane compound shown in Formula I, causing a sharp increase in the electronegativity of the O atom. Utilizing the intermolecular interaction between the two, the lithium salt is dissolved in the solvent. The siloxane compound exhibits fewer side reactions on the positive electrode side and higher antioxidant performance due to the strong Si-O bond energy and hyperconjugated interaction. Simultaneously, due to the strong anti-reduction ability of the siloxane compound and the weak solvation ability generated by the intermolecular interaction between the siloxane compound and the inducing agent, a LiF-rich SEI film is formed on the negative electrode side, primarily produced by anion decomposition, effectively preventing further reaction between the solvent and the lithium metal negative electrode. Therefore, the electrolyte provided by this invention exhibits good stability for both high-voltage positive electrode materials and lithium metal negative electrode materials, improving the long cycle life and coulombic efficiency of lithium batteries.

[0016] In some embodiments of the present invention, the molar ratio of the siloxane compound to the inducing agent is 1:(2-6); for example, it can be 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5 or 1:6, etc.

[0017] In this invention, when the molar ratio of the siloxane compound to the inducer is maintained within the above-mentioned range, it exhibits good solubility for lithium salts. If the molar ratio is too high or too low, its solubility for lithium salts will be poor.

[0018] In some embodiments of the present invention, the siloxane compound is selected from one or more of 1,2-bis(trimethylsiloxy)ethane, 1,3-bis(trimethylsiloxy)propane, 1,2-bis(tert-butyldimethylsiloxy)ethane, bis[2-(trimethylsiloxy)ethyl] ether, 1,2-bis(dimethylethoxysilyl)ethane, trimethylsilanol trisiloxane glycolate, and 2,3-bis(trimethylsiloxy)-1,3-butadiene, preferably 1,2-bis(trimethylsiloxy)ethane and / or 1,3-bis(trimethylsiloxy)propane.

[0019] In some embodiments of the present invention, the halogen substituents in the C1-C5 haloalkanes, C1-C5 halocycloalkanes, C2-C6 haloaliphatic ethers and C6-C12 haloaromatic compounds are fluorine and / or chlorine.

[0020] Since inducing agents containing bromine and iodine substituents have a weaker inducing effect on the siloxane compound than those containing fluorine and chlorine substituents, and also have poor high-pressure resistance, the halogen substituents in this invention are preferably fluorine and / or chlorine.

[0021] In some embodiments of the present invention, the C1-C5 haloalkane is selected from one or more of chloroform, dichloromethane, 1,2-dichloroethane, 1,3-dichloropropane, 1,1,2,2-tetrachloroethane, 2,2-dichloro-1,1,1-trifluoroethane, and pentafluorobutane.

[0022] In some embodiments of the present invention, the C1-C5 halocycloalkane is heptafluorocyclopentane.

[0023] In some embodiments of the present invention, the C2-C6 halogenated aliphatic ether is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether and / or 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether.

[0024] In some embodiments of the present invention, the C6-C12 halogenated aromatic compounds are selected from one or more of fluorobenzene, chlorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene and 1,2,3,4-tetrafluorobenzene.

[0025] In some embodiments of the present invention, the inducing agent is selected from one or more of 1,2-dichloroethane, 1,3-dichloropropane, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene and 1,4-difluorobenzene.

[0026] In some embodiments of the present invention, the lithium salt is selected from one or more of inorganic anionic lithium salts and organic anionic lithium salts.

[0027] In some embodiments of the present invention, the inorganic anionic lithium salt is lithium hexafluorophosphate (LiPF6) and / or lithium tetrafluoroborate (LiBF4).

[0028] In some embodiments of the present invention, the organic anionic lithium salt is selected from one or more of lithium bisfluorosulfonylimide (LiFSI), lithium bis(trifluoromethanesulfonylimide) (LiTFSI), lithium oxalate borate (LiBOB), and lithium difluorooxalate borate (LiDFOB). Lithium bis(fluorosulfonylimide) (LiFSI) and / or lithium bis(trifluoromethanesulfonylimide) (LiTFSI) are preferred.

[0029] In some embodiments of the present invention, the concentration of lithium salt in the electrolyte is 0.33-1 mol / L; for example, it can be 0.33 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.75 mol / L, 0.8 mol / L, 0.85 mol / L, 0.9 mol / L, 0.95 mol / L, or 1 mol / L, etc. Preferably, it is 0.66-1 mol / L.

[0030] In this invention, maintaining the lithium salt concentration within the aforementioned range helps ensure that the lithium battery has a high cycle life and coulombic efficiency. If the lithium salt concentration is too low, the proportion of anion decomposition decreases, leading to a decrease in the LiF content in the SEI, which easily results in a decrease in the battery's coulombic efficiency. If the lithium salt concentration is too high, it leads to a strong competitive relationship between the lithium salt and the inducer for solvent coordination, making the solvation structure unstable and easily resulting in a decrease in the battery's coulombic efficiency.

[0031] In a second aspect, the present invention provides a lithium battery comprising the electrolyte as described in the first aspect.

[0032] In some embodiments of the present invention, the positive electrode active material in the lithium battery includes one or more of lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, and lithium cobalt oxide, preferably lithium nickel cobalt manganese oxide.

[0033] In some embodiments of the present invention, the negative electrode active material in the lithium battery includes metallic lithium.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The electrolyte provided by this invention utilizes the intermolecular interactions between siloxane compounds and inducers to dissolve lithium salts in solvents. Due to the strong Si-O bond energy and hyperconjugated interactions, siloxane compounds exhibit fewer side reactions on the positive electrode side and higher oxidation resistance. Simultaneously, the strong anti-reduction ability of siloxane compounds and the weak solvation ability generated by the intermolecular forces between siloxane compounds and inducers lead to the formation of a LiF-rich SEI film on the negative electrode side, primarily produced by anion decomposition. This effectively prevents further reactions between the solvent and the lithium metal negative electrode. The electrolyte provided by this invention exhibits good stability for both high-voltage positive and lithium metal negative electrodes, possesses a wide electrochemical window, and is well-matched with both high-voltage positive and lithium metal negative electrode materials. It can be used in high-energy-density lithium metal batteries, contributing to improved cycle life and coulombic efficiency. Attached Figure Description

[0036] Figure 1The graph shows the LSV test results of the Li / Al asymmetric cell using the electrolyte provided in Example 1.

[0037] Figure 2 The graph shows the coulombic efficiency test results of the Li / Cu asymmetric battery using the electrolyte provided in Example 1.

[0038] Figure 3 The graph shows the cycle performance and coulombic efficiency test results of the NCM811 / Li battery using the electrolyte provided in Example 1.

[0039] Figure 4 The graph shows the LSV test results of the Li / Al asymmetric cell using the electrolyte provided in Example 2.

[0040] Figure 5 The graph shows the coulombic efficiency test results of the Li / Cu asymmetric battery using the electrolyte provided in Example 2.

[0041] Figure 6 The graph shows the cycle performance and coulombic efficiency test results of the NCM811 / Li battery using the electrolyte provided in Example 2;

[0042] Figure 7 The LSV test results of the Li / Al asymmetric cell using the electrolyte provided in Example 3 are shown in the figure.

[0043] Figure 8 The graph shows the coulombic efficiency test results of the Li / Cu asymmetric battery using the electrolyte provided in Example 3.

[0044] Figure 9 The graph shows the cycle performance and coulombic efficiency test results of the NCM811 / Li battery using the electrolyte provided in Example 3.

[0045] Figure 10 The graph shows the LSV test results of the Li / Al asymmetric cell using the electrolyte provided in Example 4.

[0046] Figure 11 The graph shows the coulombic efficiency test results of the Li / Cu asymmetric battery using the electrolyte provided in Example 4.

[0047] Figure 12 The graph shows the cycle performance and coulombic efficiency test results of the NCM811 / Li battery using the electrolyte provided in Example 4;

[0048] Figure 13 The LSV test results of the Li / Al asymmetric cell using the electrolyte provided in Example 5 are shown in the figure.

[0049] Figure 14The graph shows the coulombic efficiency test results of the Li / Cu asymmetric battery using the electrolyte provided in Example 5.

[0050] Figure 15 The graph shows the cycle performance and coulombic efficiency test results of the NCM811 / Li battery using the electrolyte provided in Example 5.

[0051] Figure 16 The graph shows the coulombic efficiency test results of the Li / Cu asymmetric battery using the electrolyte provided in Example 13.

[0052] Figure 17 The figure shows the LSV test results of the Li / Al asymmetric cell using the electrolyte provided in Comparative Example 3.

[0053] Figure 18 The figure shows the coulombic efficiency test results of the Li / Cu asymmetric cell using the electrolyte provided in Comparative Example 4. Detailed Implementation

[0054] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that the specific embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0055] In this embodiment of the invention, the performance of the electrolyte is tested according to the following method:

[0056] (1) Electrochemical window

[0057] The electrochemical window of the electrolyte was tested using a Li / Al asymmetric battery. A polyethylene (PE) membrane was used as the electrolyte load, with an electrolyte injection volume of 75 μL. The battery case was a 2032 model, and the sealing pressure was 1000 kg. Linear sweep voltammetry (LSV) was used for testing, with a scan rate of 5 mV / s and a scan voltage range of 3–5.5 V.

[0058] (2) Coulomb efficiency

[0059] The coulombic efficiency of the electrolyte was tested using a Li / Cu asymmetric battery. A polyethylene (PE) membrane was used as the electrolyte load, with an electrolyte injection volume of 75 μL. The battery casing was a 2032 type, and the sealing pressure was 1000 kg. The test current density was 0.5 mA / cm². 2 The initial deposition rate was 5 mAh / cm³. 2 Subsequently, at 1mAh / cm 2 The process is repeated 10 times, and finally all the lithium deposited on the Cu side is plated back onto the lithium metal anode side.

[0060] (3) Cyclic performance

[0061] The cycle performance of the electrolyte was tested using a Li / NCM811 battery. A polyethylene (PE) membrane was used as the electrolyte load, with an electrolyte injection volume of 75 μL. The battery casing was a 2032 model, and the sealing pressure was 1000 kg. For the preparation of the positive electrode, NCM811 powder, PVDF binder, and carbon black were mixed uniformly in N-methylpyrrolidone at a mass ratio of 96:2:2. The mixture was then evenly coated onto Al foil using a coating machine and subsequently dried in an 80°C oven for 12 hours to remove the solvent, yielding the experimental positive electrode. The test voltage range was 2.7–4.4 V, and the test rate was 0.2C charge / discharge.

[0062] Example 1

[0063] This embodiment provides an electrolyte, the preparation method of which is as follows:

[0064] 1 mL (0.0038 mol) of solvent 1,3-bis(trimethylsiloxy)propane was thoroughly mixed with 2 mL (0.021 mol) of inducer fluorobenzene, and then 0.561 g of LiFSI with a lithium salt concentration of 1 mol / L was added. The mixture was stirred until completely clear to obtain the electrolyte.

[0065] Figure 1 The graph shows the linear sweep voltammetry (LSV) test results for the Li / Al asymmetric cell using the electrolyte provided in Example 1. From... Figure 1 It can be seen that within the scanning range of 3–5.5V, the current passing through is on the order of 10. -6 A indicates that the electrolyte provided in Example 1 has good high-voltage resistance and can be matched with high-voltage cathode materials.

[0066] Figure 2 The graph shows the coulombic efficiency test results of the Li / Cu asymmetric battery using the electrolyte provided in Example 1. From... Figure 2 It can be seen that its lithium metal coulombic efficiency reaches 99.6%.

[0067] Figure 3 The graph shows the cycle performance and coulombic efficiency test results of the NCM811 / Li battery using the electrolyte provided in Example 1. From... Figure 3 It can be seen that the capacity retention rate is 100% after 200 cycles, and the average coulombic efficiency is above 99.9%.

[0068] Example 2

[0069] This embodiment provides an electrolyte that differs from that in Example 1 in that the inducing agent fluorobenzene is replaced with an equal volume (0.025 mol) of 1,2-dichloroethane.

[0070] Figure 4The graph shows the linear sweep voltammetry (LSV) test results for the Li / Al asymmetric cell using the electrolyte provided in Example 2. Figure 4 It can be seen that within the scanning range of 3–5.5V, the current passing through is on the order of 10. -6 A indicates that the electrolyte provided in Example 2 has good high-voltage resistance and can be matched with high-voltage cathode materials.

[0071] Figure 5 The graph shows the coulombic efficiency test results of the Li / Cu asymmetric battery using the electrolyte provided in Example 2. From... Figure 5 It can be seen that its lithium metal coulombic efficiency reaches 99.4%.

[0072] Figure 6 The graph shows the cycle performance and coulombic efficiency test results of the NCM811 / Li battery using the electrolyte provided in Example 2. From... Figure 6 It can be seen that the capacity retention rate is 100% after 150 cycles, and the average coulombic efficiency is above 99.8%.

[0073] Example 3

[0074] This embodiment provides an electrolyte that differs from that in Example 1 in that the inducing agent fluorobenzene is replaced with an equal volume (0.020 mol) of 1,2-difluorobenzene.

[0075] Figure 7 The graph shows the linear sweep voltammetry (LSV) test results for the Li / Al asymmetric cell using the electrolyte provided in Example 3. From... Figure 7 It can be seen that within the scanning range of 3–5.5V, the current passing through is on the order of 10. -6 A indicates that the electrolyte provided in Example 3 has good high-voltage resistance and can be matched with high-voltage cathode materials.

[0076] Figure 8 The graph shows the coulombic efficiency test results of the Li / Cu asymmetric battery using the electrolyte provided in Example 3. From... Figure 8 It can be seen that its lithium metal coulombic efficiency reaches 99.2%.

[0077] Figure 9 The graph shows the cycle performance and coulombic efficiency test results of the NCM811 / Li battery using the electrolyte provided in Example 3. From... Figure 9 It can be seen that the capacity retention rate is 97% after 180 cycles, and the average coulomb efficiency is above 99.8%.

[0078] Example 4

[0079] This embodiment provides an electrolyte that differs from that in Example 1 in that the solvent 1,3-bis(trimethylsiloxy)propane is replaced with an equal volume (0.004 mol) of 1,2-bis(trimethylsiloxy)ethane, and the lithium salt concentration is 0.66 mol / L.

[0080] Figure 10 The graph shows the linear sweep voltammetry (LSV) test results for the Li / Al asymmetric cell using the electrolyte provided in Example 4. Figure 10 It can be seen that within the scanning range of 3–5.5V, the current passing through is on the order of 10. -6 A indicates that the electrolyte provided in Example 4 has good high-voltage resistance and can be matched with high-voltage cathode materials.

[0081] Figure 11 The graph shows the coulombic efficiency test results of the Li / Cu asymmetric battery using the electrolyte provided in Example 4. From... Figure 11 It can be seen that its lithium metal coulombic efficiency reaches 99.2%.

[0082] Figure 12 The graph shows the cycle performance and coulombic efficiency test results of the NCM811 / Li battery using the electrolyte provided in Example 4. Figure 12 It can be seen that the capacity retention rate is 98% after 200 cycles, and the average coulomb efficiency is above 99.9%.

[0083] Example 5

[0084] This embodiment provides an electrolyte that differs from that in Example 4 in that the inducing agent fluorobenzene is replaced with an equal volume (0.0132 mol) of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0085] Figure 13 The graph shows the linear sweep voltammetry (LSV) test results for the Li / Al asymmetric cell using the electrolyte provided in Example 5. From... Figure 13 It can be seen that within the scanning range of 3–5.5V, the current passing through is on the order of 10. -6 A indicates that the electrolyte provided in Example 5 has good high-voltage resistance and can be matched with high-voltage cathode materials.

[0086] Figure 14 The graph shows the coulombic efficiency test results of the Li / Cu asymmetric battery using the electrolyte provided in Example 5. From... Figure 14 It can be seen that its lithium metal coulombic efficiency reaches 99.5%.

[0087] Figure 15 The graph shows the cycle performance and coulombic efficiency test results of the NCM811 / Li battery using the electrolyte provided in Example 5. From... Figure 15 It can be seen that the capacity retention rate is 99% after 200 cycles, and the average coulombic efficiency is above 99.9%.

[0088] Example 6

[0089] This embodiment provides an electrolyte, the preparation method of which is as follows:

[0090] 1 mL (0.003 mol) of solvent 1,2-bis(tert-butyldimethylsiloxy)ethane was thoroughly mixed with 0.4 mL (0.006 mol) of inducing agent dichloromethane, and then LiTFSI with a lithium salt concentration of 1 mol / L was added. The mixture was stirred until completely clear to obtain the electrolyte.

[0091] The linear sweep voltammetry (LSV) test results of the Li / Al asymmetric cell using the electrolyte provided in Example 6 show that, within the sweep range of 3–5.5 V, the current passing through the cell is on the order of 10. -6 A indicates that the electrolyte provided in Example 6 has good high-voltage resistance and can be matched with high-voltage cathode materials.

[0092] The lithium metal coulombic efficiency of the Li / Cu asymmetric battery using the electrolyte provided in Example 6 reached 98.5%.

[0093] The NCM811 / Li battery using the electrolyte provided in Example 6 retained 97% of its capacity after 200 cycles, and had an average coulombic efficiency of over 99.5%.

[0094] Example 7

[0095] This embodiment provides an electrolyte, the preparation method of which is as follows:

[0096] 1 mL (0.0035 mol) of the solvent bis[2-(trimethylsiloxy)ethyl] ether was thoroughly mixed with 1.05 mL (0.0105 mol) of the inducing agent 2,2-dichloro-1,1,1-trifluoroethane. Then, LiBOB with a lithium salt concentration of 1 mol / L was added and stirred until completely clear to obtain the electrolyte.

[0097] The linear sweep voltammetry (LSV) test results of the Li / Al asymmetric cell using the electrolyte provided in Example 7 show that, within the sweep range of 3–5.5 V, the current passing through the cell is on the order of 10. -6 A indicates that the electrolyte provided in Example 7 has good high-voltage resistance and can be matched with high-voltage cathode materials.

[0098] The lithium metal coulombic efficiency of the Li / Cu asymmetric battery using the electrolyte provided in Example 7 reached 98.8%.

[0099] The NCM811 / Li battery using the electrolyte provided in Example 7 retained 97.5% of its capacity after 200 cycles, and its average coulombic efficiency was above 99.5%.

[0100] Example 8

[0101] This embodiment provides an electrolyte, the preparation method of which is as follows:

[0102] 1 mL (0.0036 mol) of solvent 1,2-bis(dimethylethoxysilyl)ethane was thoroughly mixed with 2.1 mL (0.0144 mol) of inducer pentafluorobutane, and then LiDFOB with a lithium salt concentration of 1 mol / L was added. The mixture was stirred until completely clear to obtain the electrolyte.

[0103] The linear sweep voltammetry (LSV) test results of the Li / Al asymmetric cell using the electrolyte provided in Example 8 show that, within the sweep range of 3–5.5 V, the current passing through the cell is on the order of 10. -6 A indicates that the electrolyte provided in Example 8 has good high-voltage resistance and can be matched with high-voltage cathode materials.

[0104] The lithium metal coulombic efficiency of the Li / Cu asymmetric battery using the electrolyte provided in Example 8 reaches 99%.

[0105] The NCM811 / Li battery using the electrolyte provided in Example 8 retained 98% of its capacity after 200 cycles, and had an average coulombic efficiency of over 99.6%.

[0106] Example 9

[0107] This embodiment provides an electrolyte, the preparation method of which is as follows:

[0108] 1 mL (0.004 mol) of the solvent trimethylsilanol trisiloxyethanolate was thoroughly mixed with 2.54 mL (0.02 mol) of the inducing agent heptafluorocyclopentane, and then LiPF6 with a lithium salt concentration of 1 mol / L was added. The mixture was stirred until completely clear to obtain the electrolyte.

[0109] The linear sweep voltammetry (LSV) test results of the Li / Al asymmetric cell using the electrolyte provided in Example 9 show that, within the sweep range of 3–5.5 V, the current passing through the cell is on the order of 10. -6 A indicates that the electrolyte provided in Example 9 has good high-voltage resistance and can be matched with high-voltage cathode materials.

[0110] The lithium metal coulombic efficiency of the Li / Cu asymmetric battery using the electrolyte provided in Example 9 reaches 98%.

[0111] The NCM811 / Li battery using the electrolyte provided in Example 9 retained 95% of its capacity after 200 cycles and had an average coulombic efficiency of over 99%.

[0112] Example 10

[0113] This embodiment provides an electrolyte, the preparation method of which is as follows:

[0114] 1 mL (0.0038 mol) of solvent 2,3-bis(trimethylsiloxy)-1,3-butadiene and 2.35 mL (0.228 mol) of inducer 1,2,3-trifluorobenzene were thoroughly mixed, and then LiBF4 with a lithium salt concentration of 1 mol / L was added. The mixture was stirred until completely clear to obtain the electrolyte.

[0115] Linear sweep voltammetry (LSV) tests of the Li / Al asymmetric cell using the electrolyte provided in Example 10 show that, within the sweep range of 3–5.5 V, the current passing through the cell is on the order of 10. -6 A indicates that the electrolyte provided in Example 6 has good high-voltage resistance and can be matched with high-voltage cathode materials.

[0116] The lithium metal coulombic efficiency of the Li / Cu asymmetric battery using the electrolyte provided in Example 10 reached 98.6%.

[0117] The NCM811 / Li battery using the electrolyte provided in Example 10 retained 97% of its capacity after 200 cycles and had an average coulombic efficiency of over 99.6%.

[0118] Example 11

[0119] This embodiment provides an electrolyte, the preparation method of which is as follows:

[0120] 1 mL (0.0038 mol) of solvent 1,3-bis(trimethylsiloxy)propane was thoroughly mixed with 0.5 mL (0.0052 mol) of inducing agent fluorobenzene, and then 0.187 g of LiFSI was added and stirred. It was found that the lithium salt could not be completely dissolved, and the mass of undissolved lithium salt was 0.15 g.

[0121] Example 12

[0122] This embodiment provides an electrolyte, the preparation method of which is as follows:

[0123] 1 mL (0.0038 mol) of solvent 1,3-bis(trimethylsiloxy)propane was thoroughly mixed with 2.5 mL (0.0266 mol) of inducer fluorobenzene, and then 0.187 g of LiFSI was added and stirred. It was found that the lithium salt could not be completely dissolved, and the mass of undissolved lithium salt was 0.1 g.

[0124] Example 13

[0125] This embodiment provides an electrolyte, the preparation method of which is as follows:

[0126] 1 mL (0.0038 mol) of solvent 1,3-bis(trimethylsiloxy)propane and 2 mL (0.021 mol) of inducer fluorobenzene were thoroughly mixed, followed by the addition of 0.187 g of LiFSI with a lithium salt concentration of 0.33 mol / L. The mixture was stirred until completely clear to obtain the electrolyte.

[0127] Figure 16 The graph shows the coulombic efficiency test results of the Li / Cu asymmetric battery using the electrolyte provided in Example 13. From... Figure 13 It can be seen that its lithium metal coulombic efficiency is 98%, indicating that when the lithium salt concentration is low, the compatibility of the electrolyte with the lithium metal anode decreases.

[0128] Comparative Example 1

[0129] In this comparative example, 0.187 g of LiFSI was added to 1 mL of 1,3-bis(trimethylsiloxy)propane and stirred. The results showed that the lithium salt could not dissolve. This indicates that without an inducing agent, this type of siloxane solvent cannot dissociate the lithium salt; therefore, single-phase siloxane solvents are unsuitable for use as electrolytes in lithium metal batteries.

[0130] Comparative Example 2

[0131] In this comparative example, 0.187 g of LiFSI was added to 1 mL of the inducing agent fluorobenzene, and the mixture was stirred. The results showed that the lithium salt could not dissolve. This indicates that the inducing agent itself cannot serve as a solvent for the electrolyte.

[0132] Comparative Example 3

[0133] This comparative example provides an electrolyte, the preparation method of which is as follows:

[0134] 0.187 g of LiFSI was added to 1 mL of ethylene glycol dimethyl ether, with a lithium salt concentration of 1 mol / L. The mixture was stirred until completely clear to obtain the electrolyte.

[0135] Figure 17 The graph shows the linear sweep voltammetry (LSV) test results for the Li / Al asymmetric cell using the electrolyte provided in Comparative Example 3. From... Figure 17 It can be seen that within the scanning range of 0–4.5V, the current passing through is on the order of 10. -6 A indicates that the electrolyte provided in Comparative Example 3 does not have high voltage resistance and is therefore incompatible with high voltage cathode materials.

[0136] Comparative Example 4

[0137] This comparative example provides an electrolyte, the preparation method of which is as follows:

[0138] Mix 1 mL of ethylene carbonate and 1 mL of dimethyl carbonate thoroughly, add 0.3038 g of lithium hexafluorophosphate (1 mol / L lithium salt), and stir until completely clear to obtain the electrolyte.

[0139] Figure 18 The graph shows the coulombic efficiency test results of the Li / Cu asymmetric cell using the electrolyte provided in Comparative Example 4. Figure 18 It can be seen that its lithium metal coulombic efficiency is 84%, indicating that the carbonate-based electrolyte has poor compatibility with lithium metal and is not suitable for use as an electrolyte in lithium metal batteries.

[0140] As can be seen from the experimental results of the above embodiments, the electrolyte provided in Embodiments 1-10 of the present invention can dissolve lithium salts, has high compatibility with lithium metal anodes (CE>99% for Li / Cu asymmetric batteries), has a wide electrochemical window of more than 5V, can be well matched with high voltage cathode materials and lithium metal anode materials, and lithium batteries using it have a long cycle life.

[0141] Compared to Example 1, Example 11 had a lower proportion of inducer, and Example 12 had a higher proportion of inducer, both of which were detrimental to the interaction between the siloxane compound and the inducer, resulting in a decrease in their solubility for lithium salt. Compared to Example 1, Example 13 had a lower concentration of added lithium salt, resulting in a decrease in coulombic efficiency.

[0142] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An electrolyte, characterized by, The electrolyte comprises: lithium salt, solvent, and inducer; The solvent is one or more of the siloxane compounds shown in Formula I; Formula I; wherein X1, X2are each independently selected from one of C1-C4alkyl, R is selected from one of C2-C4alkylene and one of C2-C4alkylene and L is selected from C2-C4 alkylene groups. , and One of them; Y1 and Y2 are each independently selected from one of C1-C2 alkylene groups, and Y3 is selected from one of C1-C3 alkylene groups; The linking site of the representative group; The inducing agent is selected from one or more of C1-C5 haloalkanes, C1-C5 halocycloalkanes, C2-C6 haloaliphatic ethers, and C6-C12 haloaromatic compounds; The molar ratio of the siloxane compound to the inducer is 1:(2-6), and the concentration of lithium salt in the electrolyte is 0.33-1 mol / L.

2. The electrolyte according to claim 1, characterized in that, The siloxane compound is selected from one or more of 1,2-bis(trimethylsiloxy)ethane, 1,3-bis(trimethylsiloxy)propane, 1,2-bis(tert-butyldimethylsiloxy)ethane, bis[2-(trimethylsiloxy)ethyl] ether, 1,2-bis(dimethylethoxysilyl)ethane, trimethylsilanol trisiloxane glycolate, and 2,3-bis(trimethylsiloxy)-1,3-butadiene.

3. The electrolyte according to claim 2, characterized in that, The siloxane compound is 1,2-bis(trimethylsiloxy)ethane and / or 1,3-bis(trimethylsiloxy)propane.

4. The electrolyte according to any one of claims 1-3, characterized in that, The halogen substituents in the C1-C5 haloalkanes, C1-C5 halocycloalkanes, C2-C6 haloaliphatic ethers, and C6-C12 haloaromatic compounds are fluorine and / or chlorine.

5. The electrolyte according to claim 4, characterized in that, The C1-C5 haloalkanes are selected from one or more of chloroform, dichloromethane, 1,2-dichloroethane, 1,3-dichloropropane, 1,1,2,2-tetrachloroethane, 2,2-dichloro-1,1,1-trifluoroethane, and pentafluorobutane; The C1-C5 halocycloalkanes are heptafluorocyclopentanes; The C2-C6 halogenated aliphatic ethers are 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether and / or 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether. The C6-C12 halogenated aromatic compounds are selected from one or more of fluorobenzene, chlorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, and 1,2,3,4-tetrafluorobenzene.

6. The electrolyte according to claim 5, characterized in that, The inducing agent is selected from one or more of 1,2-dichloroethane, 1,3-dichloropropane, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene and 1,4-difluorobenzene.

7. The electrolyte according to any one of claims 1-3, characterized in that, The lithium salt is selected from one or more of inorganic anionic lithium salts and organic anionic lithium salts; The inorganic anionic lithium salt is lithium hexafluorophosphate and / or lithium tetrafluoroborate; The organic anionic lithium salt is selected from one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethyl)sulfonyl)imide, lithium oxalate borate, and lithium difluorooxalate borate.

8. The electrolyte according to claim 1, characterized in that, The concentration of lithium salt in the electrolyte is 0.66-1 mol / L.

9. A lithium battery, characterized in that, Includes the electrolyte as described in any one of claims 1-8.

10. The lithium battery according to claim 9, characterized in that, The positive electrode active material in the lithium battery includes one or more of lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, and lithium cobalt oxide.

11. The lithium battery according to claim 10, characterized in that, The positive electrode active material in the lithium battery is lithium nickel cobalt manganese oxide.

12. The lithium battery according to claim 9 or 10, characterized in that, The negative electrode active material in the lithium battery includes metallic lithium.

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