Electrolyte and lithium ion battery

Abstract

The application discloses an electrolyte and a lithium ion battery, wherein the electrolyte comprises a lithium salt, a nonaqueous organic solvent and an additive; the lithium salt comprises lithium hexafluorophosphate; and the additive comprises a compound A shown in a structural formula I and a compound B shown in a structural formula II, wherein R1-R4 are each independently selected from hydrogen, an alkyl group, an alkenyl group and an alkynyl group; and R5-R6 are each independently selected from halogen, an alkyl group and a halogen-substituted alkyl group. The compound A and the compound B in the electrolyte of the application can produce a synergistic effect, significantly alleviate the increase of an acid value in a later stage of battery circulation, effectively inhibit decomposition of an SEI interface, and further form a sulfur and phosphorus composite interface, so that the electrolyte of the application can improve low-temperature transmission characteristics of lithium ions and high-temperature stability of the electrolyte, and thus the lithium ion battery has good high and low temperature performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of lithium ion batteries, and particularly relates to an electrolyte and a lithium ion battery. BACKGROUND

[0002] In recent years, as one of China's strategic emerging industries, new energy vehicles, high-performance lithium battery technology is the key to achieve the national new energy vehicle strategy. The performance of lithium ion battery will be affected by the oxidative decomposition of electrolyte, especially under the conditions of cyclic use and high temperature storage, the dissolution of metal ions will further lead to significant decline in battery performance. However, with the growth of demand for lithium ion batteries in the market, the requirement for its comprehensive performance is also increasing.

[0003] In order to improve the comprehensive performance of lithium ion battery, using specific additives is an effective strategy. For example, it is pointed out that using sulfate compounds as negative electrode film forming agent can improve the electrochemical properties of the battery. However, this kind of compound will react with lithium hexafluorophosphate in electrolyte under high voltage and high temperature conditions, generating harmful hydrofluoric acid (HF); in addition, lithium hexafluorophosphate in electrolyte will also gradually decompose during the charging and discharging cycle of lithium ion battery, generating free hydrofluoric acid. With the increase of hydrofluoric acid concentration in electrolyte, the acid value of electrolyte also increases, which will lead to the change of electrolyte properties and damage the stability of the formed SEI layer; once the SEI layer is damaged, it will lead to the decline of battery performance, such as capacity attenuation, impedance increase, cycle life shortening and other problems.

[0004] Therefore, there is an urgent need for an electrolyte and a lithium ion battery to solve the problems of the prior art. SUMMARY

[0005] In view of the above problems, the purpose of the present application is to provide an electrolyte and a lithium ion battery. The compound A and the compound B in the electrolyte can produce a synergistic effect, significantly alleviate the increase of acid value in the later stage of battery cycle, and effectively inhibit the decomposition of SEI interface; it can also form a sulfur and phosphorus composite interface, improve the low temperature transmission characteristics of lithium ion and the high temperature stability of electrolyte, so that the electrolyte of the present application can make the lithium ion battery have good high and low temperature performance.

[0006] To achieve the above purpose, the first aspect of the present application provides an electrolyte, which comprises a lithium salt, a non-aqueous organic solvent and an additive, the lithium salt comprises lithium hexafluorophosphate, and the additive comprises a compound A represented by structural formula I and a compound B represented by structural formula II,

[0007]

[0008] wherein R1-R4 are each independently selected from hydrogen, alkyl, alkenyl, alkynyl; R5-R6 are each independently selected from halogen, alkyl, halogen-substituted alkyl.

[0009] Compared with existing technologies, the electrolyte of this invention includes compound A as shown in structural formula 1 and compound B as shown in structural formula II. Compound B reacts with lithium hexafluorophosphate at high voltage and high temperature to produce HF, which damages the battery interface stability and leads to poor battery performance. Compound A, on the other hand, can inhibit the forward reaction of lithium hexafluorophosphate to produce acid, shifting the chemical equilibrium towards lithium hexafluorophosphate and greatly reducing the acid value of the electrolyte. Therefore, compound A can significantly alleviate the increase in acid value in the later stages of battery cycling and effectively inhibit the decomposition of the SEI interface. In addition, compounds A and B can form a composite interface layer at the electrode-electrolyte interface. This composite interface layer has superior lithium-ion transport characteristics, is not prone to pore formation at low temperatures, and can maintain lithium-ion transport channels at low temperatures, improving the low-temperature performance of lithium-ion batteries. At the same time, this composite interface contains sulfur and phosphorus interfaces, resulting in superior high-temperature stability of the electrolyte. In summary, compounds A and B of the present invention can produce a synergistic effect, significantly alleviating the increase in acid value in the later stages of battery cycling and effectively inhibiting the decomposition of the SEI interface; they can also form a sulfur- and phosphorus-containing composite interface, improving the low-temperature transport characteristics of lithium ions and the high-temperature stability of the electrolyte. Therefore, the electrolyte of the present invention enables lithium-ion batteries to have better high and low temperature performance.

[0010] Furthermore, R1 to R4 in this invention are each independently selected from hydrogen, C1-C6 alkyl, C2-C6 alkenyl, and C2-C6 alkynyl; R5 to R6 are each independently selected from halogen, C1-C6 alkyl, and halogen-substituted C1-C6 alkyl. Specifically, C1-C6 alkyl refers to a straight-chain or branched saturated hydrocarbon group containing 1 to 6 carbon atoms. These alkyl groups can be straight-chain (normal) or branched (isomer), such as, but not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, etc. Halogens can be fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). Halogen-substituted C1-C6 alkyl refers to a straight-chain or branched alkane containing 1 to 6 carbon atoms in which one or more hydrogen atoms are replaced by halogen atoms (fluorine F, chlorine Cl, bromine Br, iodine I); such halogen-substituted C1-C6 alkyl can be, but is not limited to, chloromethane, fluoromethane, difluoromethane, trichloromethane, trifluoromethane, or trifluoroethane.

[0011] Furthermore, compound A of the present invention is selected from at least one of compounds A1 to A3:

[0012]

[0013] Furthermore, compound B of the present invention is selected from at least one of compounds B1 to B4:

[0014]

[0015] Further, the mass percentage of compound A in the electrolyte is 0.1% to 5.0%; and the mass percentage of compound B in the electrolyte is 0.1% to 10.0%. Specifically, the mass percentage of compound A in the electrolyte can be, but is not limited to, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, and 5%; and the mass percentage of compound B in the electrolyte can be, but is not limited to, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 9.8%, and 10%. Preferably, the mass percentage of compound A in the electrolyte is 0.1% to 2%; and the mass percentage of compound B in the electrolyte is 0.1% to 5%.

[0016] Furthermore, the lithium salt of the present invention also includes at least one of lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium methanesulfonate, lithium trifluoromethanesulfonate, lithium fluorosulfonate, lithium dioxalate borate, lithium difluorooxalate borate, lithium difluorophosphate, lithium difluorobis(oxalate) phosphate, lithium bis(fluorosulfonyl)imide, lithium diphosphate, and lower aliphatic carboxylic acids. Specifically, the lithium salt in the electrolyte is 5% to 30% by mass, such as, but not limited to, 5%, 10%, 15%, 20%, 25%, and 30%; preferably, the lithium salt in the electrolyte is 5% to 18% by mass.

[0017] Furthermore, the non-aqueous organic solvent of the present invention is at least one of carbonates, carboxylic esters, and ethers. Carbonate compounds have high dielectric constants (favorable for lithium salt dissociation) and good stability. Carboxylic ester compounds can provide relatively high dielectric constants, which helps to improve the solubility of lithium salts in electrolytes and exhibits good compatibility with certain cathode materials. Ether compounds have low viscosity and freezing point, meaning they maintain good ion transport properties even at low temperatures.

[0018] Furthermore, the carbonate compounds of the present invention include cyclic carbonates and chain carbonates. Specifically, cyclic carbonates may be, but are not limited to, ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), amyl carbonate, vinyl carbonate (VC), or derivatives thereof; chain carbonates include, but are not limited to, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and propylene carbonate.

[0019] Furthermore, the carboxylic acid ester compounds of the present invention include at least one of cyclic carboxylic acid esters and chain carboxylic acid esters. Specifically, cyclic carboxylic acid esters may include, but are not limited to, at least one of γ-butyrolactone (GBL), γ-valerolactone (GVL), and δ-valerolactone (DVL); chain carboxylic acid esters include, but are not limited to, methyl acetate (MAC), ethyl acetate (EA), propyl acetate (PA), butyl acetate (BA), propyl propionate (PP), and butyl propionate (BP).

[0020] Furthermore, the ether compounds of the present invention include cyclic ethers or chain ethers. Specifically, cyclic ethers may include, but are not limited to, at least one of 1,3-dioxolane (DOL), 1,4-dioxolane (DX), crown ethers, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH3-THF), and 2-trifluoromethyltetrahydrofuran (2-CF3-THF); chain ethers may specifically include, but are not limited to, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether.

[0021] Furthermore, the electrolyte of the present invention further includes additives selected from vinylene carbonate (VC), vinylene carbonate (VEC), fluoroethylene carbonate (FEC), vinyl sulfite (ES), 1,3-propanesulfonate lactone (PS), 1,3-propenesulfonate lactone (PES), 1,4-butanesulfonate lactone (BS), vinyl sulfate (DTD), succinic anhydride (SA), maleic anhydride (MA), 2-methylmaleic anhydride (MMA), methyl carbonate-2-propynyl ester, tetraethylenesilane, and triallyl isocyanate. The additives are selected from at least one of the following: cyanurate, hexamethylene diisocyanate, o-phenanthroline, terephthalic acid diisocyanate, 2,4-toluene diisocyanate, N-phenylbis(trifluoromethanesulfonyl)imide, vinyl disulfate, phenyl methanesulfonate, vinyl disulfate, dispironyl sulfate, hydroquinone difluorosulfonate, triallyl phosphate, triargyl phosphate, 2,4-butane sulpholol, isocyanoethyl methacrylate, methylene disulfonate, tri(trimethylsilane)borate, tri(trimethylsilane) phosphate, and tri(vinyldimethylsilane) phosphate. Specifically, the additives of the present invention constitute 0.1% to 5% by mass in the electrolyte, and the additive content may be, but is not limited to, 0.1%, 0.5%, 1%, 1.6%, 1.9%, 2.6%, 3.2%, 3.8%, 4.3%, 4.8%, and 5%. Preferably, the mass percentage of the additive in the electrolyte is 0.1% to 2%.

[0022] Accordingly, a second aspect of the present invention also provides a lithium-ion battery, including a positive electrode, a negative electrode, and the electrolyte mentioned above.

[0023] Compared with the prior art, the electrolyte of the present invention has a synergistic effect between compounds A and B, which significantly alleviates the increase of acid value in the later stage of battery cycling and effectively inhibits the decomposition of the SEI interface; it can also form a sulfur- and phosphorus-containing composite interface, which improves the low-temperature transport characteristics of lithium ions and the high-temperature stability of the electrolyte. Therefore, the lithium-ion battery of the present invention has better high and low temperature performance.

[0024] Furthermore, the active material of the positive electrode of the present invention includes lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. Specifically, the lithium phosphates with an olivine structure include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. The lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (structures such as LiNi). x Co y Mn 1-x-y M z O2, where 0.6 ≤ x < 0.9, x + y < 1, 0 ≤ z < 0.08, and M is at least one of Al, Mg, Zr, and Ti. Preferably, the active material of the positive electrode of the present invention is LiNi. 0.8 Co 0.1 Mn 0.1 Zr 0.03 O2.

[0025] Furthermore, the active material of the negative electrode of the present invention includes at least one of carbon-based negative electrode, silicon-based negative electrode, tin-based negative electrode, and lithium negative electrode. The carbon-based negative electrode may include graphite, hard carbon, soft carbon, graphene, mesophase carbon microspheres, etc.; the silicon-based negative electrode may include silicon materials, silicon oxides, silicon-carbon composite materials, and silicon alloy materials, etc.; the tin-based negative electrode may include tin, tin-carbon, tin oxide, and tin metal compounds; the lithium negative electrode may include metallic lithium or lithium alloys, wherein the lithium alloy may specifically be at least one of lithium-silicon alloy, lithium-sodium alloy, lithium-potassium alloy, lithium-aluminum alloy, lithium-tin alloy, and lithium-indium alloy. Detailed Implementation

[0026] To further illustrate the purpose, technical solution, and beneficial effects of this invention, the invention will be further described below in conjunction with specific embodiments. It should be noted that, unless specific conditions are specified in the embodiments and comparative examples, conventional conditions or conditions recommended by the manufacturer can be followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0027] Example 1

[0028] This embodiment provides a method for preparing a lithium-ion battery, the steps of which include:

[0029] (1) Ternary material LiNi 0.8 Co 0.1 Mn 0.1 Zr 0.03 O2, conductive agent SuperP, binder PVDF, and carbon nanotubes (CNTs) were mixed uniformly in a mass ratio of 96.5:1.5:1:1 to prepare a lithium-ion battery positive electrode slurry of a certain viscosity. This slurry was then coated onto aluminum foil used as a current collector, with a coating weight of 324 g / m². 2 After drying at 85℃, the material is cold-pressed; then it is trimmed, cut into sheets, and slit. After slitting, it is dried at 85℃ for 4 hours under vacuum conditions, and then the tabs are welded to produce a positive electrode sheet that meets the requirements.

[0030] (2) Artificial graphite and silicon are mixed at a mass ratio of 90:10, and then mixed with conductive agent SuperP, thickener CMC and binder SBR (styrene-butadiene rubber emulsion) at a mass ratio of 95:1.5:1.0:2.5 to make a slurry. After mixing evenly, the slurry is coated on both sides of copper foil, dried and rolled to obtain a negative electrode sheet, thus making a negative electrode sheet that meets the requirements.

[0031] (3) In a nitrogen-filled glove box (O2 < 1 ppm, H2O < 1 ppm), ethylene carbonate (EC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl acetate (MAC), and butyl acetate (BA) are mixed evenly in a mass ratio of 4:2:3:3:2 to obtain a mixed solvent as a non-aqueous organic solvent. Additives and auxiliaries are then added to obtain a mixed solution. The mixed solution is sealed and packaged and frozen in a freezer (-4℃) for 2 hours. After being removed, lithium hexafluorophosphate (LiPF6) is slowly added to the mixed solution in a nitrogen-filled glove box (O2 < 1 ppm, H2O < 1 ppm). After mixing evenly, the electrolyte is prepared.

[0032] (4) The above-mentioned positive electrode, negative electrode and separator are stacked to form a lithium-ion battery with a thickness of 4.7 mm, a width of 55 mm and a length of 60 mm. The battery is vacuum baked at 75°C for 10 h and then injected with the above-mentioned electrolyte. After standing for 24 h, it is charged to 4.4 V with a constant current of 0.1 C (180 mA), and then charged to 0.05 C (90 mA) with a constant voltage of 4.4 V until the current drops to 0.05 C (90 mA). Then it is discharged to 3.0 V with 0.2 C (180 mA). The charge and discharge are repeated twice. Finally, the battery is charged to 3.8 V with 0.2 C (180 mA) to obtain a lithium-ion battery.

[0033] The electrolyte formulations of Examples 1-16 and Comparative Examples 1-6 are shown in Table 1. The preparation processes of the electrolytes, positive electrode sheets, negative electrode sheets, and lithium-ion batteries of Examples 2-16 and Comparative Examples 1-6 are the same as those of Example 1.

[0034] Table 1. Composition of the electrolytes in the examples and comparative examples.

[0035]

[0036] The lithium-ion batteries prepared in Examples 1-16 and Comparative Examples 1-6 were subjected to high-temperature storage performance test, high-temperature cycle performance test, room-temperature cycle performance test, and low-temperature performance test under the following conditions, and the results are shown in Table 2.

[0037] High temperature storage performance test :

[0038] Under normal temperature (25℃) conditions, the lithium-ion battery was subjected to one 0.5C / 0.5C charge and discharge cycle (battery discharge capacity recorded as C0), with an upper limit voltage of 4.4V. Then, the battery was charged to 4.4V under constant current and constant voltage conditions at 0.5C, and the battery thickness was measured (thickness recorded as D0). The battery was placed in a 60℃ oven for 30 days, removed, and the battery thickness was measured (thickness recorded as D1). The battery was placed in a 25℃ environment and discharged at 0.5C (discharge capacity recorded as C1). The lithium-ion battery was then subjected to one more 0.5C / 0.5C charge and discharge cycle under normal temperature (25℃) conditions (battery discharge capacity recorded as C2), with an upper limit voltage of 4.4V. The capacity retention rate, capacity recovery rate, and thickness expansion rate were calculated.

[0039] Capacity retention rate = (C1 / C0) * 100%

[0040] Capacity recovery rate = (C2 / C0) * 100%

[0041] Thickness expansion rate = (D1 / D0) * 100%

[0042] Normal temperature cycle performance test :

[0043] Under normal temperature (25℃) conditions, a lithium-ion battery is subjected to one 1.0C / 1.0C charge and discharge cycle (battery discharge capacity is C0), with an upper limit voltage of 4.4V. Then, under normal temperature conditions, it is subjected to 500 cycles of 1.0C / 1.0C charge and discharge (battery discharge capacity is C1), and the capacity retention rate is calculated.

[0044] Capacity retention rate = (C1 / C0) * 100%

[0045] High temperature cycle test :

[0046] Under high temperature (45℃) conditions, a lithium-ion battery is subjected to one 1.0C / 1.0C charge and discharge cycle (battery discharge capacity is C0), with an upper limit voltage of 4.4V. Then, under normal temperature conditions, it is subjected to 400 cycles of 1.0C / 1.0C charge and discharge (battery discharge capacity is C1), and the capacity retention rate is calculated.

[0047] Capacity retention rate = (C1 / C0) * 100%

[0048] Low temperature performance test :

[0049] Under normal temperature (25℃) conditions, a lithium-ion battery is subjected to a 0.5C / 0.5C charge-discharge cycle (battery cutoff voltage 3.0V, discharge capacity C0), with an upper limit voltage of 4.4V (cutoff current 0.05C). Then, the battery is fully charged to 4.4V at 0.5C (cutoff current 0.05C) at room temperature (25℃), and then transferred to -20℃ for 4 hours. It is then discharged at 0.5C to 3.0V, with a discharge capacity of C1. The capacity retention rate is calculated.

[0050] Capacity retention rate = (C1 / C0) * 100%

[0051] The acid values ​​of the electrolytes of the lithium-ion batteries prepared in Examples 1-6 and Comparative Examples 1, 5, and 6 before and after high-temperature cycling were tested under the following conditions, and the results are shown in Table 3.

[0052] Electrolyte acid value test:

[0053] The determination of free acid in electrolytes for lithium-ion batteries was carried out in accordance with section 4.5.1 of SJ / T 11723-2018. After calibrating the potentiometric titrator, 10.00 g of electrolyte sample was accurately weighed and added to 50 mL of anhydrous ethanol. Titration was performed with a 0.01 mol / L weak organic base, and the titration volume was recorded. The instrument automatically calculated the free acid content (calculated as HF) in the electrolyte.

[0054] Table 2. Performance test results of lithium-ion batteries

[0055]

[0056] Table 3. Acid value test results of electrolyte before and after high-temperature cycling.

[0057]

[0058] As shown in Table 3, compared with Comparative Example 1 and Comparative Examples 1 and 6, the electrolytes of Examples 1 to 6 have relatively lower acid values ​​after high-temperature cycling. This indicates that compound B reacts with lithium hexafluorophosphate at high voltage and high temperature to produce HF. Compound A can inhibit the forward reaction of lithium hexafluorophosphate to produce acid, and the chemical equilibrium shifts towards lithium hexafluorophosphate, resulting in a significant reduction in the acid value of the electrolyte. Therefore, compound A can significantly alleviate the increase in acid value in the later stages of battery cycling and effectively suppress the decomposition of the SEI interface.

[0059] As shown in Tables 2 and 3, compared with Comparative Examples 1 and 5-6, the lithium-ion batteries of Examples 1-6 exhibit better high and low temperature performance. This is because the electrolyte of the present invention includes compound A shown in structural formula 1 and compound B shown in structural formula II. Compound B reacts with lithium hexafluorophosphate at high voltage and high temperature to produce HF, which damages the battery interface stability and leads to a deterioration in battery performance. Compound A, on the other hand, can hinder the forward reaction of lithium hexafluorophosphate to produce acid, shifting the chemical equilibrium towards lithium hexafluorophosphate and greatly reducing the acid value of the electrolyte. Therefore, compound A can significantly alleviate the increase in acid value in the later stages of battery cycling and effectively suppress the decomposition of the SEI interface. In addition, compounds A and B can form a composite interface layer at the electrode-electrolyte interface. This composite interface layer has superior lithium-ion transport characteristics, is not prone to pore formation at low temperatures, and can maintain lithium-ion transport channels at low temperatures, improving the low-temperature performance of the lithium-ion battery. At the same time, this composite interface contains sulfur and phosphorus interfaces, resulting in better high-temperature stability of the electrolyte. In summary, compounds A and B of the present invention can produce a synergistic effect, significantly alleviating the increase in acid value in the later stages of battery cycling and effectively inhibiting the decomposition of the SEI interface; they can also form a sulfur- and phosphorus-containing composite interface, improving the low-temperature transport characteristics of lithium ions and the high-temperature stability of the electrolyte. Therefore, the electrolyte of the present invention enables lithium-ion batteries to have better high and low temperature performance.

[0060] A comparison of Examples 8 and Examples 10-13 shows that adding additives to the additives of this invention can further improve the high-temperature storage performance, high-temperature cycle performance, low-temperature performance, and lithium-ion cycle performance of lithium-ion batteries, resulting in better expansion rate.

[0061] A comparison of Examples 14-16 and Examples 10-11 shows that when a VC / FEC mixed additive is used in the electrolyte, the high-temperature and low-temperature performance of the lithium-ion battery is significantly improved, and the expansion rate is further improved.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. An electrolyte comprising a lithium salt, a non-aqueous organic solvent, and an additive, wherein the lithium salt comprises lithium hexafluorophosphate, characterized in that, The additives include compound A, represented by structural formula 1, and compound B, represented by structural formula II. R1 to R4 are each independently selected from hydrogen or alkyl; R5 to R6 are the same and are selected from halogen, alkyl or halogen-substituted alkyl. The mass percentage of compound A in the electrolyte is 0.1-5.0%; the mass percentage of compound B in the electrolyte is 0.1-10.0%.

2. The electrolyte as described in claim 1, characterized in that, R1 to R4 are each independently selected from hydrogen or C1 to C6 alkyl; R5 to R6 are the same, selected from halogen, C1 to C6 alkyl, or halogen-substituted C1 to C6 alkyl.

3. The electrolyte as described in claim 1, characterized in that, The compound A is selected from at least one of compounds A1 to A3: 。 4. The electrolyte as described in claim 1, characterized in that, The compound B is selected from at least one of compounds B1 to B4: 。 5. The electrolyte as described in claim 1, characterized in that, The lithium salt further includes at least one of lithium perchlorate, lithium tetrafluoroborate, lithium difluorosulfonylimide, lithium bis(trifluoromethylsulfonylimide), lithium methanesulfonate, lithium trifluoromethylsulfonate, lithium fluorosulfonate, lithium dioxalate borate, lithium difluorooxalate borate, lithium difluorophosphate, lithium difluorobis(oxalate) phosphate, lithium difluorosulfonylimide, lithium diphosphide, and lithium lower aliphatic carboxylic acids.

6. The electrolyte as described in claim 1, characterized in that, The non-aqueous organic solvent is at least one of carbonates, carboxylic acid esters, and ether compounds.

7. The electrolyte as described in claim 1, characterized in that, It also includes additives selected from vinylene carbonate, vinylene ethylene carbonate, fluoroethylene carbonate, vinyl sulfite, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, 1,4-butanesulfonate lactone, vinyl sulfate, succinic anhydride, maleic anhydride, 2-methylmaleic anhydride, methyl carbonate-2-propynyl ester, tetraethylenesilane, triallyl isocyanurate, hexamethylene diisocyanate, o-phenanthroline, terephthalic diisocyanate, 2, At least one of the following: 4-toluene diisocyanate, N-phenylbis(trifluoromethanesulfonyl)imide, vinyl disulfate, phenyl methanesulfonate, vinyl disulfate, propylene dispironate, hydroquinone difluorosulfonate, triallyl phosphate, triargyl phosphate, 2,4-butane sulpholol, isocyanate ethyl methacrylate, methylene disulfonate, tri(trimethylsilane)borate, tri(trimethylsilane) phosphate, and tri(vinyldimethylsilane) phosphate.

8. A lithium-ion battery, comprising a positive electrode and a negative electrode, characterized in that, It also includes the electrolyte as described in any one of claims 1 to 7.

9. The lithium-ion battery as described in claim 8, characterized in that, The active materials of the positive electrode include lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds.

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