Lithium ion battery electrolyte and lithium ion battery thereof

Abstract

The application discloses a lithium ion battery electrolyte and a lithium ion battery thereof, which comprises a lithium salt, an organic solvent and an additive; the additive comprises a phosphoric acid siloxane compound A with a structure of formula I, and / or a lithium sulfate salt compound B with a structure of formula II, and / or a triisocyanate compound C with a structure of formula III, and / or a film-forming additive D; in the formula I, R1 and R2 are selected from alkyl, alkenyl and alkynyl with 1-5 carbon atoms, and R3, R4, R5, R6, R7 and R8 are selected from alkyl, alkenyl, alkynyl with 1-5 carbon atoms, or trifluoromethyl and fluorine atoms; in the formula II, X is selected from alkenyl, alkynyl with 1-5 carbon atoms, or alkyl substituted by fluorine atoms; and in the formula III, Y is selected from alkyl with 1-10 carbon atoms, or alkyl with 1-10 carbon atoms substituted by fluorine atoms.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery electrolyte technology, and more particularly to a lithium-ion battery electrolyte and a lithium-ion battery thereof. Background Technology

[0002] Lithium-ion batteries have advantages such as high energy density, no memory effect, and environmental friendliness, and are currently widely used in consumer electronics and power batteries. As the lithium-ion battery market expands, higher demands are being placed on their overall performance.

[0003] With the advancement of research into lithium-ion batteries, performance improvements have reached a bottleneck. Therefore, there is an urgent need for an electrolyte that can significantly enhance the overall performance of lithium-ion batteries. Summary of the Invention

[0004] The purpose of this invention is to provide a lithium-ion battery electrolyte and a lithium-ion battery thereof, which can significantly improve the overall performance of lithium-ion batteries.

[0005] This invention discloses a lithium-ion battery electrolyte, comprising a lithium salt, an organic solvent, and additives; the additives include a phosphosiloxane compound A of formula I, and / or a lithium sulfate compound B of formula II, and / or a triisocyanate compound C of formula III, and / or a film-forming additive D.

[0006]

[0007]

[0008] In Formula I, R1 and R2 are selected from alkane groups, alkenyl groups, and alkyne groups with 1-5 carbon atoms; R3, R4, R5, R6, R7, and R8 are selected from alkyl groups, alkenyl groups, alkyne groups, or trifluoromethyl groups and fluorine atoms with 1-5 carbon atoms; in Formula II, X is selected from alkenyl groups, alkyne groups, or alkane groups substituted with fluorine atoms with 1-5 carbon atoms; in Formula III, Y is selected from alkane groups with 1-10 carbon atoms or alkane groups with 1-10 carbon atoms substituted with fluorine atoms.

[0009] Film-forming additive D is selected from two or more of the following: fluoroethylene carbonate (FEC), vinylene carbonate (VC), 1,3-propanesulfonate lactone (PS), vinyl sulfate (DTD), methanedisulfonate methylene (MMDS), propenesulfonate lactone (PST), succinic anionyl (SN), adiponitrile (ADN), 1,3,6-hexanetrionitrile (HTCN), lithium difluorophosphate (LiPO2F2), lithium difluoro(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium tetrafluoroborate (LiBF4), lithium bis(oxaloacetate borate) (LiBOB), and lithium difluorooxaloacetate borate (LiDFOB), wherein at least one of them contains FEC; wherein, by mass percentage, the content of said FEC accounts for 0.5 to 20 wt% of the total mass of the organic solvent, and the content of said film-forming additive D of the remaining types accounts for 0.1 to 8 wt% of the total mass of the organic solvent;

[0010] By mass percentage, the phosphate siloxane compound A, the lithium sulfate compound B, and the triisocyanate compound C each account for 0.1 to 3 wt% of the total mass of the organic solvent.

[0011] Optionally, the structural formula of the phosphosiloxane compound A is one of the following:

[0012]

[0013] Optionally, the lithium sulfate compound B has one of the following structural formulas:

[0014]

[0015] Optionally, the structural formula of the triisocyanate compound C is one of the following:

[0016]

[0017] Optionally, the concentration of the lithium salt in the electrolyte is 0.5M to 2M.

[0018] Optionally, the lithium salt is selected from one or more of hexafluorophosphate, hexafluoroarsenate, perchlorate, lithium trifluorosulfonyl, lithium difluoro(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium tri(trifluoromethylsulfonyl)methyl.

[0019] Optionally, the concentration of the lithium salt in the electrolyte is 1.1M.

[0020] Optionally, the organic solvent is selected from two or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl formate, ethyl formate, ethyl propionate, propyl propionate, methyl butyrate, tetrahydrofuran, and fluorinated organic solvents, wherein at least one of them is a fluorinated organic solvent; the structural formula of the fluorinated organic solvent is as follows:

[0021]

[0022] Z1 and Z2 are selected from alkane groups and olefin groups with 1 to 5 carbon atoms replaced by 1 to 6 fluorine atoms.

[0023] Optionally, the fluorinated organic solvent has one of the following structural formulas:

[0024]

[0025] The present invention also discloses a lithium-ion battery, comprising the lithium-ion battery electrolyte as described above.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] (1) The siloxane phosphate compound A of Formula I in this invention has a siloxane structure that can effectively remove trace amounts of water and acidic HF products from electrolyte decomposition, preventing HF from corroding the electrode material and causing structural damage. The Si-O bond can withstand higher temperatures and has better thermal stability, effectively improving the battery's thermal shock resistance and high-temperature cycling performance. The siloxane structure and phosphate group can regulate the LiF composition in the SEI film, resulting in a porous and permeable SEI film that effectively reduces the battery's internal resistance.

[0028] (2) In this invention, the unsaturated olefin structure and fluorine element in lithium sulfate salt compound B with formula II are conducive to the participation of additives in the formation of electrode interface film. The lithium sulfate structure of the additive can form a high-conductivity SEI film component on the electrode surface, which works synergistically with additive A to effectively reduce the internal resistance of the battery and improve the low-temperature rate performance of the battery.

[0029] (3) In this invention, the isocyanate group in the triisocyanate-based compound C can form a good protective film at the positive electrode, complexing transition metal ions at the positive electrode and inhibiting the dissolution of metal ions and the decomposition of the electrolyte at the positive electrode. The substitution of hydrogen atoms on the alkyl group of the isocyanate group by fluorine atoms leads to a decrease in activation energy and a reduction in the HOMO-LUMO energy level, thereby increasing the reduction potential and oxidation potential of the additive. A high reduction potential can form an effective SEI film, further inhibiting excessive decomposition of the electrolyte and significantly improving the cycle performance of the battery. The HOMO-LUMO energy levels, collectively referred to as frontier orbitals, respectively refer to the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO).

[0030] (4) In this invention, the FEC in the film-forming additive D can continuously modify the SEI film damaged during cycling, avoiding direct contact between the electrode interface and the electrolyte and causing side reactions, thus effectively improving the battery cycle performance. FEC is easily decomposed at high temperatures to generate HF, while phosphate siloxane compound A can effectively remove HF. Therefore, phosphate siloxane compound A and film-forming additive D have a synergistic effect.

[0031] (5) The F atoms in the fluorinated organic solvents of this invention have strong electronegativity and weak polarity, which makes the fluorinated solvents have high oxidation resistance. The inventors found through a large number of experiments that if too many fluorine atoms are substituted or the chain hydrocarbon is too long, it will easily lead to an increase in the viscosity of the solvent, which is not conducive to improving the low-temperature rate performance of the battery.

[0032] (6) In this invention, the above four additives and fluorinated solvents can interact with each other when used together in the electrolyte. Compared with using only one or two of them, the performance of the electrolyte can be effectively improved.

[0033] (7) The electrolyte provided by the present invention has excellent film-forming performance on the electrode surface through the synergistic effect of phosphate siloxane compound A, lithium sulfate salt compound B, triisocyanate group compound C, film-forming additive D and fluorinated solvent. The additive can effectively remove acidic by-products of the electrolyte, and the electrolyte has stronger oxidation resistance and thermal stability, which effectively improves the high-temperature cycle performance, thermal shock resistance and low-temperature discharge capability of lithium-ion batteries. Detailed Implementation

[0034] It should be understood that the terminology, specific structural and functional details used herein are merely for describing particular embodiments and are representative. However, the invention can be implemented in many alternative forms and should not be construed as being limited to the embodiments set forth herein.

[0035] The following optional embodiments illustrate the invention in detail.

[0036] As an embodiment of the present invention, a lithium-ion battery electrolyte is disclosed, comprising a lithium salt, an organic solvent, and additives; the additives include a phosphosiloxane compound A of formula I, and / or a lithium sulfate compound B of formula II, and / or a triisocyanate compound C of formula III, and / or a film-forming additive D.

[0037]

[0038] In Formula I, R1 and R2 are selected from alkane groups, alkenyl groups, and alkyne groups with 1-5 carbon atoms; R3, R4, R5, R6, R7, and R8 are selected from alkyl groups, alkenyl groups, alkyne groups, or trifluoromethyl groups and fluorine atoms with 1-5 carbon atoms. In Formula II, X is selected from alkenyl groups, alkyne groups, or alkane groups substituted with fluorine atoms with 1-5 carbon atoms. In Formula III, Y is selected from alkane groups with 1-10 carbon atoms or alkane groups with 1-10 carbon atoms substituted with fluorine atoms.

[0039] The film-forming additive D is selected from two or more of the following: fluoroethylene carbonate (FEC), vinylene carbonate (VC), 1,3-propanesulfonate lactone (PS), vinyl sulfate (DTD), methanedisulfonate methylene (MMDS), propenesulfonate lactone (PST), succinic anionyl (SN), adiponitrile (ADN), 1,3,6-hexanetrionitrile (HTCN), lithium difluorophosphate (LiPO2F2), lithium difluoro(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium tetrafluoroborate (LiBF4), lithium bis(oxaloacetate borate) (LiBOB), and lithium difluorooxaloacetate borate (LiDFOB), wherein at least one of them contains FEC; wherein, by mass percentage, the content of said FEC accounts for 0.5 to 20 wt% of the total mass of the organic solvent, and the content of said remaining film-forming additive D accounts for 0.1 to 8 wt% of the total mass of the organic solvent.

[0040] By mass percentage, the phosphate siloxane compound A, the lithium sulfate compound B, and the triisocyanate compound C each account for 0.1 to 3 wt% of the total mass of the organic solvent.

[0041] Specifically, the structural formula of the phosphosiloxane compound A is one of the following:

[0042]

[0043] Specifically, the lithium sulfate compound B has one of the following structural formulas:

[0044]

[0045] Specifically, the structural formula of the triisocyanate compound C is one of the following:

[0046]

[0047] Specifically, the lithium salt is selected from one or more of hexafluorophosphate, hexafluoroarsenate, perchlorate, lithium trifluorosulfonyl, lithium difluoro(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium tri(trifluoromethylsulfonyl)methyl.

[0048] Specifically, the concentration of the lithium salt in the electrolyte is 0.5M to 2M. Specifically, the concentration of the lithium salt can be 0.5M, 0.6M, 0.7M, 0.8M, 0.9M, 1M, 1.1M, 1.2M, 1.3M, 1.4M, 1.5M, 1.6M, 1.7M, 1.8M, 1.9M, or 2M.

[0049] Specifically, the organic solvent is selected from two or more of the following: ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl formate, ethyl formate, ethyl propionate, propyl propionate, methyl butyrate, tetrahydrofuran, and fluorinated organic solvents, wherein at least one of them is a fluorinated organic solvent; the structural formula of the fluorinated organic solvent is as follows:

[0050]

[0051] Z1 and Z2 are selected from alkane groups and olefin groups with 1 to 5 carbon atoms replaced by 1 to 6 fluorine atoms.

[0052] Specifically, the fluorinated organic solvent has one of the following structural formulas:

[0053]

[0054] Compared with the prior art, the present invention has at least the following beneficial effects:

[0055] (1) The siloxane phosphate compound A of Formula I in this invention has a siloxane structure that can effectively remove trace amounts of water and acidic HF products from electrolyte decomposition, preventing HF from corroding the electrode material and causing structural damage. The Si-O bond can withstand higher temperatures and has better thermal stability, effectively improving the battery's thermal shock resistance and high-temperature cycling performance. The siloxane structure and phosphate group can regulate the LiF composition in the SEI film, resulting in a porous and permeable SEI film that effectively reduces the battery's internal resistance.

[0056] (2) In this invention, the unsaturated olefin structure and fluorine element in lithium sulfate salt compound B with formula II are conducive to the participation of additives in the formation of electrode interface film. The lithium sulfate structure of the additive can form a high-conductivity SEI film component on the electrode surface, which works synergistically with additive A to effectively reduce the internal resistance of the battery and improve the low-temperature rate performance of the battery.

[0057] (3) In this invention, the isocyanate group in the triisocyanate-based compound C can form a good protective film at the positive electrode, complexing transition metal ions at the positive electrode and inhibiting the dissolution of metal ions and the decomposition of the electrolyte at the positive electrode. The substitution of hydrogen atoms on the alkyl group of the isocyanate group by fluorine atoms leads to a decrease in activation energy and a reduction in the HOMO-LUMO energy level, thereby increasing the reduction potential and oxidation potential of the additive. A high reduction potential can form an effective SEI film, further inhibiting excessive decomposition of the electrolyte and significantly improving the cycle performance of the battery.

[0058] HOMO-LUMO energy levels, collectively known as frontier orbitals, refer to the highest occupied molecular orbital and the lowest unoccupied molecular orbital, respectively.

[0059] (4) In this invention, the FEC in the film-forming additive D can continuously modify the SEI film damaged during cycling, avoiding direct contact between the electrode interface and the electrolyte and causing side reactions, thus effectively improving the battery cycle performance. FEC is easily decomposed at high temperatures to generate HF, while phosphate siloxane compound A can effectively remove HF. Therefore, phosphate siloxane compound A and film-forming additive D have a synergistic effect.

[0060] (5) The F atoms in the fluorinated organic solvents of this invention have strong electronegativity and weak polarity, which makes the fluorinated solvents have high oxidation resistance. The inventors found through a large number of experiments that if too many fluorine atoms are substituted or the chain hydrocarbon is too long, it will easily lead to an increase in the viscosity of the solvent, which is not conducive to improving the low-temperature rate performance of the battery.

[0061] (6) In this invention, the above four additives and fluorinated solvents can interact with each other when used together in the electrolyte. Compared with using only one or two of them, the performance of the electrolyte can be effectively improved.

[0062] (7) The electrolyte provided by the present invention has excellent film-forming performance on the electrode surface through the synergistic effect of phosphate siloxane compound A, lithium sulfate salt compound B, triisocyanate group compound C, film-forming additive D and fluorinated solvent. The additive can effectively remove acidic by-products of the electrolyte, and the electrolyte has stronger oxidation resistance and thermal stability, which effectively improves the high-temperature cycle performance, thermal shock resistance and low-temperature discharge capability of lithium-ion batteries.

[0063] This invention also discloses a lithium-ion battery, comprising the lithium-ion battery electrolyte as described above. Specifically, the lithium-ion battery further includes a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrode. Preferably, the positive electrode includes a positive current collector and a positive electrode film, the negative electrode includes a negative current collector and a negative electrode film, the positive electrode film includes a positive active material, a conductive agent, and a binder, and the negative electrode film includes a negative active material, a conductive agent, and a binder; the positive active material is LiNi. 1-x-y-z Co x Mn y Al z O2 where: 0≤x≤1, 0≤y≤1, 0≤z≤1 and 0≤x+y+z≤1; the negative electrode active material is selected from graphite and / or silicon, such as natural graphite, artificial graphite, mesophase micro carbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon or silicon-carbon composite material composed of silicon or SiOw and graphite (where: 1<w<2), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel structure lithiated TiO2-Li4Ti5O 12 Li-Al alloy.

[0064] Preferably, non-limiting examples of adhesives include polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0065] Preferably, non-limiting examples of conductive agents include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.

[0066] The present invention will be further illustrated by the following examples.

[0067] Example 1

[0068] This embodiment illustrates the lithium-ion battery and its preparation method disclosed in this invention, and includes the following steps:

[0069] Electrolyte preparation: EC, DEC, and PC were mixed in a mass ratio of 1:1:1 as an organic solvent. Additives in the mass percentages shown in Example 1 of Table 1 were added to the organic solvent, and after thorough mixing, LiPF6 was added to obtain an electrolyte with a LiPF6 concentration of 1.1 mol / L.

[0070] Fabrication of the positive electrode sheet: The positive electrode active material (LiCoO2), conductive agent CNT (Carbon Nanotube), and binder PVDF (polyvinylidene fluoride) are thoroughly mixed in N-methylpyrrolidone solvent at a mass ratio of 97:1.5:1.5 to form a uniform positive electrode slurry. This slurry is coated onto the positive electrode current collector Al foil, dried, and cold-pressed to obtain the positive electrode sheet.

[0071] Fabrication of the negative electrode sheet: The negative electrode active material (silicon-oxygen-carbon composite material), conductive agent (acetylene black), binder (styrene-butadiene rubber), and thickener (sodium carboxymethyl cellulose) are thoroughly mixed in an appropriate amount of deionized water solvent at a mass ratio of 95:2:2:1 to form a uniform negative electrode slurry. This slurry is then coated onto the negative electrode current collector (Cu foil), dried, and cold-pressed to obtain the negative electrode sheet.

[0072] Lithium-ion battery fabrication: using PE porous polymer film as the separator.

[0073] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The stacked electrodes and separator are then wound together to form a core. The core is placed in a pre-formed aluminum-plastic film bag, and the electrolyte prepared above is injected into the baked and dried core. After vacuum sealing, settling, and formation processes, the lithium-ion battery is successfully manufactured.

[0074] Examples 2-6

[0075] Examples 2-6 include most of the operational steps as in Example 1, except that in the electrolyte preparation operation, additives are added to the organic solvent in the mass percentage amounts shown in Table 1 for Examples 2-6.

[0076] Comparative Examples 1-7

[0077] Comparative Examples 1 to 7 are used to compare and illustrate the lithium-ion battery electrolyte, lithium-ion battery and preparation method disclosed in this invention, including most of the operation steps as in Example 1, except that in the electrolyte preparation operation: additives with the mass percentage content shown in Comparative Examples 1 to 7 in Table 1 are added to the organic solvent.

[0078] Table 1

[0079]

[0080]

[0081] The lithium-ion batteries prepared in Examples 1-6 and Comparative Examples 1-7 were subjected to the following performance tests:

[0082] (1) High-temperature cycle performance test: At 45℃, the battery after capacity division is charged to 4.45V at 1C constant current and constant voltage, with a cutoff current of 0.05C, and then discharged to 3.0V at 0.5C constant current. This cycle is repeated. After 500 charge-discharge cycles, the capacity retention rate at the 500th cycle is calculated using the following formula:

[0083] 500-week cycle capacity retention (%) = (500-week cycle discharge capacity / initial cycle discharge capacity) × 100%.

[0084] (2) Low-temperature discharge performance test: Under 25℃ environmental conditions, the capacity-graded battery was discharged at 0.2C to 3.0V and left to stand for 5 minutes; then charged at 0.2C to 4.45V. When the cell voltage reached 4.45V, it was switched to constant voltage charging at 4.45V until the charging current was less than or equal to the given cutoff current of 0.05C, and left to stand for 5 minutes; the fully charged cell was transferred to a high-low temperature chamber, set to -20℃, and left to stand for 120 minutes after the chamber temperature was reached; then discharged at 0.2C to the cutoff voltage of 3.0V and left to stand for 5 minutes; then the high-low temperature chamber temperature was adjusted to 25℃±3℃, and left to stand for 60 minutes after the chamber temperature was reached; charged at 0.2C to 4.45V. When the cell voltage reached 4.45V, it was switched to constant voltage charging at 4.45V until the charging current was less than or equal to the given cutoff current of 0.05C; left to stand for 5 minutes; the capacity retention rate at -20℃ low-temperature discharge of 3.0V was calculated. The calculation formula is as follows:

[0085] -20℃ discharge to 3.0V capacity retention rate (%) = (-20℃ discharge capacity to 3.0V / 25℃ discharge capacity to 3.0V) × 100%.

[0086] (3) Thermal shock performance: Under 25℃ ambient conditions, discharge to 3.0V with a given current of 0.2C; rest for 5 minutes; charge to 4.45V with a charging current of 0.2C. When the cell voltage reaches 4.45V, switch to 4.45V constant voltage charging until the charging current is less than or equal to the given cutoff current of 0.05C; after resting for 1 hour, put the cell into an oven. The oven temperature rises to 130±2℃ at a rate of 5±2℃ / min and is maintained for 60 minutes before stopping. The judgment criterion is that the cell does not catch fire or explode.

[0087] The test results are shown in Table 2 below:

[0088] Table 2

[0089]

[0090] (1) Thermal Shock: According to the comparative examples and embodiments, the thermal shock pass rate can be improved by adding phosphosiloxane compound A, lithium sulfate compound B, triisocyanate compound C, and film-forming additive D separately. This is because the siloxane group in phosphosiloxane compound A can remove HF decomposed at high temperatures in the electrolyte, preventing HF from causing more electrode side reactions and leading to thermal runaway of the battery cell under thermal shock; the lithium sulfate structure in lithium sulfate compound B can form a stable passivation film on the electrode surface, which is beneficial to improving the thermal shock pass rate; the isocyanate functional group in triisocyanate compound C can complex metal ions in the positive electrode, effectively improving the structural stability of the battery cell material. When all four additives are used simultaneously, the thermal shock pass rate is significantly improved.

[0091] (2) High-temperature cycling: According to the comparative examples and the actual examples, the high-temperature cycling performance of the battery can be improved by adding phosphate siloxane compound A, lithium sulfate compound B, triisocyanate compound C, film-forming additive D, or fluorinated solvent alone. The performance improvement is most significant when all four additives are used simultaneously with the fluorinated solvent. The results of Comparative Example 7 show that when the additive content exceeds 3% and the fluorinated solvent content exceeds 8%, the cycle performance of the battery decreases. This is because excessive additives increase the electrode interface impedance and deteriorate the battery performance.

[0092] (3) Low-temperature discharge: According to the comparative examples and embodiments, the addition of siloxane phosphate compound A and lithium sulfate compound B, respectively, can improve the low-temperature discharge capability of the battery. Siloxane phosphate compound A and phosphate can regulate the LiF composition in the SEI film, resulting in a porous and permeable SEI film that effectively reduces the battery's internal resistance. The lithium sulfate structure of lithium sulfate compound B can form an SEI film with higher conductivity. The combined use of additives can jointly improve the low-temperature discharge capability of the battery. The results of Comparative Example 7 show that when the additive content exceeds 3% and the fluorinated solvent exceeds 8%, excessive additives increase the electrode interface impedance, and the fluorinated solvent also increases the electrolyte viscosity, affecting the lithium-ion battery's transport and thus its low-temperature discharge performance.

[0093] The above description, in conjunction with specific optional embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A lithium-ion battery electrolyte, characterized in that, It includes lithium salts, organic solvents, and additives; the additives include phosphosiloxane compounds of formula I, lithium sulfate compounds of formula II, triisocyanate compounds of formula III, and film-forming additives D; In Formula I, R1 and R2 are selected from alkane groups, alkenyl groups, and alkyne groups with 1-5 carbon atoms; R3, R4, R5, R6, R7, and R8 are selected from alkyl groups, alkenyl groups, alkyne groups, or trifluoromethyl groups and fluorine atoms with 1-5 carbon atoms; in Formula II, X is selected from alkenyl groups, alkyne groups, or alkane groups substituted with fluorine atoms with 1-5 carbon atoms; in Formula III, Y is selected from alkane groups with 1-10 carbon atoms or alkane groups with 1-10 carbon atoms substituted with fluorine atoms. Film-forming additive D is selected from two or more of the following: fluoroethylene carbonate (FEC), vinylene carbonate (VC), 1,3-propanesulfonate lactone (PS), vinyl sulfate (DTD), methanedisulfonate methylene (MMDS), propenesulfonate lactone (PST), succinic anionyl (SN), adiponitrile (ADN), 1,3,6-hexanetrionitrile (HTCN), lithium difluorophosphate (LiPO2F2), lithium difluoro(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium tetrafluoroborate (LiBF4), lithium bis(oxaloacetate borate) (LiBOB), and lithium difluorooxaloacetate borate (LiDFOB), wherein at least one of them contains FEC; wherein, by mass percentage, the content of said FEC accounts for 0.5 to 20 wt% of the total mass of the organic solvent, and the content of said film-forming additive D of the remaining types accounts for 0.1 to 8 wt% of the total mass of the organic solvent; By mass percentage, the phosphate siloxane compound A, the lithium sulfate compound B, and the triisocyanate compound C each account for 0.1 to 3 wt% of the total mass of the organic solvent; The organic solvent is selected from two or more of the following: ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl formate, ethyl formate, ethyl propionate, propyl propionate, methyl butyrate, tetrahydrofuran, and fluorinated organic solvents, wherein at least one of them is a fluorinated organic solvent; the structural formula of the fluorinated organic solvent is as follows: Z1 and Z2 are selected from alkane groups and olefin groups with 1 to 5 carbon atoms replaced by 1 to 6 fluorine atoms.

2. The lithium-ion battery electrolyte as described in claim 1, characterized in that, The structural formula of the phosphosiloxane compound A is one of the following: 。 3. The lithium-ion battery electrolyte as described in claim 1, characterized in that, The lithium sulfate compound B has one of the following structural formulas: 。 4. The lithium-ion battery electrolyte as described in claim 1, characterized in that, The structural formula of the triisocyanate group compound C is one of the following: 。 5. The lithium-ion battery electrolyte as described in claim 1, characterized in that, The concentration of the lithium salt in the electrolyte is 0.5M to 2M.

6. The lithium-ion battery electrolyte as described in claim 1, characterized in that, The lithium salt is selected from one or more of hexafluorophosphate, hexafluoroarsenate, perchlorate, lithium trifluorosulfonyl, lithium difluoro(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium tri(trifluoromethylsulfonyl)methyl.

7. The lithium-ion battery electrolyte as described in claim 6, characterized in that, The concentration of the lithium salt in the electrolyte is 1.1M.

8. The lithium-ion battery electrolyte as described in claim 1, characterized in that, The fluorinated organic solvent has one of the following structural formulas: 。 9. A lithium-ion battery, characterized in that, Includes the lithium-ion battery electrolyte as described in any one of claims 1 to 8.

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