Electrolyte and battery containing the same

Abstract

The present invention provides an electrolyte and a battery containing the electrolyte. The present invention forms an interface film containing LiSO3 and ROSO2Li on the surface of the positive electrode during the first charge and discharge of a fluorinated sulfonate compound, which is tough, not easy to break, and has strong high-temperature resistance. It also forms an interface film rich in LiF components on the negative electrode, which has good mechanical properties and excellent toughness. During the first charge process, a cyclic carboxylate compound forms an interface film containing components such as Li2CO3, alkyl lithium, hydroxy lithium, and carboxyl lithium on the negative electrode. These components have excellent ion conductivity and can accelerate the transmission of lithium ions, thereby enabling the battery to have better rate and low-temperature performance. By regulating the type and addition amount of fluorinated sulfonate compounds and cyclic carboxylate compound additives, the high and low temperature discharge characteristics and cycle life of 12V lithium iron phosphate batteries are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and in particular relates to an electrolyte and a battery containing the electrolyte. Background Art

[0002] With the booming global new energy industry, a green, low-carbon, circular economic system with carbon peak and carbon neutrality is gradually taking shape. Automotive start-stop power supplies primarily use lead-acid batteries, which have low energy density, short cycle life, and significant environmental pollution, contradicting the green, low-carbon development theme. 12V lithium iron phosphate batteries, with their high specific energy, long cycle life, excellent safety, low cost, and environmental friendliness, better meet the demands of energy conservation and emission reduction. Furthermore, 12V lithium iron phosphate batteries, as direct replacements for lead-acid batteries, place particularly high demands on the battery's high and low temperature output characteristics, cycle performance, and safety.

[0003] The main factors that affect the high and low temperature output characteristics of the battery are: high viscosity of the electrolyte at low temperature, slow Li+ transfer rate, poor thermal stability of the electrolyte at high temperature; poor compatibility of the electrolyte with the electrode material at low temperature, increased electrode interface impedance, and low solid-liquid phase diffusion rate of Li+. In order to improve the high and low temperature output characteristics of 12V lithium iron phosphate batteries, the current optimization is mainly carried out through the following aspects: (1) Positive electrode: by ion doping, surface coating, reducing particle size and other measures to modify the positive electrode material to improve the material stability, while reducing the activation energy of the Li+ reaction, thereby reducing the interfacial charge transfer resistance; (2) Negative electrode: by SEI film modification, material composite, reducing particle size and other measures to improve the material conductivity, reduce the solid phase diffusion of ions in the negative electrode, and weaken the negative electrode polarization; (3) Electrolyte: using co-solvent, low Melting point solvent and additive strategy adjusts the solvent structure to improve liquid phase mass transfer and charge transfer dynamics; (4) Improve the positive electrode / electrolyte interface reaction: by adding positive electrode film-forming additives to the electrolyte, a surface film is covered on the positive electrode surface, so that the positive electrode surface potential is evenly distributed, preventing the electrolyte from oxidizing and decomposing on the positive electrode surface during high-temperature cycling and storage of the battery; (5) Improve the negative electrode / electrolyte interface reaction: by adding a large amount of negative electrode film-forming additives, a dense SEI film is formed on the negative electrode to prevent the electrolyte from contacting with the negative electrode active components.

[0004] However, the current 12V lithium iron phosphate battery still has the following problems: (1) It is difficult to balance the high and low temperature performance of the lithium iron phosphate battery. Under the premise of meeting the high temperature discharge, the low temperature discharge retention rate is poor. (2) It is difficult to balance the various performances of the lithium iron phosphate battery to meet the high and low temperature discharge conditions, and the cycle life is short. Summary of the Invention

[0005] To address the challenges of existing 12V lithium iron phosphate batteries, which struggle to meet high and low temperature discharge characteristics and maintain a long cycle life, the present invention provides an electrolyte and a battery containing the electrolyte. The fluorinated sulfonate compounds of the present invention can form an interfacial film containing LiSO3 and ROSO2Li on the positive electrode surface during the initial charge and discharge process; the fluorinated sulfonate compounds form an interfacial film rich in LiF on the negative electrode surface; and the cyclic carboxylate compounds of the present invention form an interfacial film containing Li2CO3, alkyl lithium, lithium hydroxy, and lithium carboxyl on the negative electrode surface during the initial charge process.

[0006] When the electrolyte system contains both fluorinated sulfonate compounds and cyclic carboxylate compounds, an interface film containing LiSO3 and ROSO2Li can be formed on the positive electrode surface. This interface film is tough, not easy to break, and has strong high-temperature resistance. An interface film containing components such as LiF, Li2CO3, alkyl lithium, hydroxy lithium, and carboxyl lithium can be formed on the negative electrode surface. This interface film has excellent ion conductivity and can accelerate the transmission of lithium ions. At the same time, the interface film has good mechanical properties and good toughness, so the battery can have better rate and low-temperature performance. The present invention provides a 12V lithium iron phosphate battery that takes into account high and low temperature discharge characteristics and long cycle life and wide temperature by regulating the type and addition amount of fluorinated sulfonate compounds and cyclic carboxylate compound additives.

[0007] The object of the present invention is achieved through the following technical solutions:

[0008] An electrolyte comprises an electrolyte salt, an organic solvent and an additive, wherein the additive comprises a fluorine-containing sulfonate compound and a cyclic carboxylate compound.

[0009] According to an embodiment of the present invention, the electrolyte is used in a lithium iron phosphate battery.

[0010] According to an embodiment of the present invention, the fluorinated sulfonate compound is selected from at least one of the compounds represented by Formula 1:

[0011] Formula 1

[0012] In Formula 1, R1 is a substituted or unsubstituted heteroaryl, a substituted or unsubstituted aryl, a substituted or unsubstituted alkyl, a substituted or unsubstituted alkenyl, a substituted or unsubstituted alkynyl, a substituted or unsubstituted cycloalkyl, or a -CO-alkyl group; if substituted, the substituent is a halogen or an alkyl group.

[0013] According to an embodiment of the present invention, R1 is a substituted or unsubstituted 5-20 membered heteroaryl, a substituted or unsubstituted C 6-20 Aryl, substituted or unsubstituted C 1-12 Alkyl, substituted or unsubstituted C2-12 Alkenyl, substituted or unsubstituted C 2-12 Alkynyl, substituted or unsubstituted C 3-20 Cycloalkyl, -COC 1-12 Alkyl; if substituted, the substituent is halogen or C 1-12 alkyl.

[0014] According to an embodiment of the present invention, R1 is a substituted or unsubstituted 5-10 membered heteroaryl, a substituted or unsubstituted C 6-10 Aryl, substituted or unsubstituted C 1-6 Alkyl, substituted or unsubstituted C 2-6 Alkenyl, substituted or unsubstituted C 2-6 Alkynyl, substituted or unsubstituted C 3-10 Cycloalkyl, -COC 1-6 Alkyl; if substituted, the substituent is halogen or C 1-6 alkyl.

[0015] According to an embodiment of the present invention, R1 is a substituted or unsubstituted 5-6 membered heteroaryl, a substituted or unsubstituted C 6-8 Aryl, substituted or unsubstituted C 1-3 Alkyl, substituted or unsubstituted C 2-3 Alkenyl, substituted or unsubstituted C 2-3 Alkynyl, substituted or unsubstituted C 3-6 Cycloalkyl, -COC 1-3 Alkyl; if substituted, the substituent is halogen or C 1-6 alkyl.

[0016] According to an embodiment of the present invention, R1 is trifluoroacetyl, trifluoroethyl, thienyl, propargyl, cyclopropyl and 3,3-difluorobutenyl.

[0017] According to an embodiment of the present invention, the fluorinated sulfonate compound is selected from at least one of Compound A to Compound F:

[0018]

[0019] Compound A Compound B

[0020]

[0021] Compound C Compound D

[0022]

[0023] Compound E Compound F.

[0024] According to an embodiment of the present invention, the fluorine-containing sulfonate compound can be purchased through commercial channels or prepared by methods known in the art.

[0025] According to an embodiment of the present invention, the mass of the fluorinated sulfonate compound accounts for 0.3~1.5wt% of the total mass of the electrolyte, such as 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt% or any point value in the range consisting of any two of the above point values.

[0026] According to an embodiment of the present invention, the cyclic carboxylate compound is selected from at least one of the compounds represented by Formula 2 or Formula 3:

[0027] Formula 2 Formula 3

[0028] In Formula 2 and Formula 3, Y is absent, substituted or unsubstituted methylene; if substituted, the substituent is halogen or alkyl; X is -B(R)2- or -P(R)4-; R is halogen, substituted or unsubstituted alkyl; if substituted, the substituent is halogen or alkyl; X' is -B- or -P(R)2-; R is halogen, substituted or unsubstituted alkyl; if substituted, the substituent is halogen or alkyl.

[0029] According to an embodiment of the present invention, in Formula 2, Y is absent, substituted or unsubstituted methylene; if substituted, the substituent is halogen, C 1-6 Alkyl; X is -B(R)2-, -P(R)4-; R is halogen, substituted or unsubstituted C 1-6 Alkyl; if substituted, the substituent is halogen, C 1-6 Alkyl; X' is -B-, -P(R)2-; R is halogen, substituted or unsubstituted C 1-6 Alkyl; if substituted, the substituent is halogen, C 1-6 alkyl.

[0030] According to an embodiment of the present invention, in Formula 2, Y is absent, substituted or unsubstituted methylene; if substituted, the substituent is halogen, C 1-3 Alkyl; X is -B(R)2-, -P(R)4-; R is halogen, substituted or unsubstituted C 1-3 Alkyl; if substituted, the substituent is halogen, C 1-3 Alkyl; X' is -B-, -P(R)2-; R is halogen, substituted or unsubstituted C 1-3 Alkyl; if substituted, the substituent is halogen, C1-3 alkyl.

[0031] According to an embodiment of the present invention, in Formula 2, Y is absent, substituted or unsubstituted methylene; if substituted, the substituent is F, CH3; X is -B(R)2-, -P(R)4-; R is F, substituted or unsubstituted CH3; if substituted, the substituent is F, CH3; X' is -B-, -P(R)2-; R is F, substituted or unsubstituted CH3; if substituted, the substituent is F, CH3.

[0032] According to an embodiment of the present invention, the cyclic carboxylate compound can be purchased from commercial sources or prepared by methods known in the art.

[0033] According to an embodiment of the present invention, the mass of the cyclic carboxylate compound accounts for 0.3~1wt.% of the total mass of the electrolyte, for example, 0.3wt.%, 0.4wt.%, 0.5wt.%, 0.6wt.%, 0.7wt.%, 0.8wt.%, 0.9wt.%, 1wt.% or any point value in the range composed of any two of the above point values.

[0034] According to an embodiment of the present invention, the cyclic carboxylate compound is selected from at least one of Compounds 1 to 4 shown below:

[0035]

[0036] Compound 1 Compound 2

[0037]

[0038] Compound 3 Compound 4.

[0039] According to an embodiment of the present invention, the electrolyte salt is selected from at least one of electrolyte lithium salt, electrolyte sodium salt, electrolyte magnesium salt, and the like.

[0040] According to an embodiment of the present invention, the electrolyte lithium salt is selected from lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide. The electrolyte lithium salt is selected from lithium hexafluorophosphate with good electrochemical stability and lithium bis(fluorosulfonyl)imide with strong thermal stability as the solute, thereby improving the ionic conductivity of the electrolyte.

[0041] Preferably, the mass ratio of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide is 1:(0.2-2.0), for example, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2.0;

[0042] According to an embodiment of the present invention, the mass of the electrolyte salt accounts for 13-20 wt % of the total mass of the electrolyte, and more preferably 14-18 wt %, for example 13 wt %, 14 wt %, 15 wt %, 16 wt %, 17 wt %, 18 wt %, 19 wt % or 20 wt %.

[0043] According to an embodiment of the present invention, the organic solvent is selected from a mixed solvent of at least one selected from cyclic carbonates and at least one selected from linear carbonates or linear carboxylates; for example, a mixed solvent of at least one selected from cyclic carbonates and at least one selected from linear carbonates, or a mixed solvent of at least one selected from cyclic carbonates and at least one selected from linear carboxylates; or a mixed solvent of at least one selected from cyclic carbonates, at least one selected from linear carbonates and at least one selected from linear carboxylates;

[0044] Preferably, the cyclic carbonate is at least one of propylene carbonate and ethylene carbonate;

[0045] Preferably, the linear carbonate is at least one of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate;

[0046] Preferably, the linear carboxylate is at least one of methyl acetate, ethyl acetate, propyl acetate, propyl propionate, ethyl propionate, ethyl butyrate, and propyl butyrate.

[0047] According to an embodiment of the present invention, the selection of the organic solvent can reduce the melting point and viscosity of the carbonate electrolyte, and improve the low-temperature performance of the carbonate electrolyte.

[0048] The present invention also provides a battery, comprising the above-mentioned electrolyte.

[0049] According to an embodiment of the present invention, the battery is a lithium-ion battery.

[0050] According to an embodiment of the present invention, the battery further includes a positive electrode sheet containing a positive electrode active material, a negative electrode sheet containing a negative electrode active material, and a separator.

[0051] According to an embodiment of the present invention, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on one or both sides of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, a conductive agent, and a binder.

[0052] According to an embodiment of the present invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both sides of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder.

[0053] According to an embodiment of the present invention, the mass percentages of the components in the positive electrode active material layer are: 80-99.8 wt % of the positive electrode active material, 0.1-10 wt % of the conductive agent, and 0.1-10 wt % of the binder.

[0054] Preferably, the mass percentage of each component in the positive electrode active material layer is: 90-99.6 wt % of positive electrode active material, 0.2-5 wt % of conductive agent, and 0.2-5 wt % of binder.

[0055] According to an embodiment of the present invention, the mass percentages of the components in the negative electrode active material layer are: 80-99.8 wt % of the negative electrode active material, 0.1-10 wt % of the conductive agent, and 0.1-10 wt % of the binder.

[0056] Preferably, the mass percentage of each component in the negative electrode active material layer is: 90-99.6 wt % of the negative electrode active material, 0.2-5 wt % of the conductive agent, and 0.2-5 wt % of the binder.

[0057] According to an embodiment of the present invention, the conductive agent is selected from at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, and metal powder.

[0058] According to an embodiment of the present invention, the binder is selected from at least one of sodium carboxymethyl cellulose, styrene-butadiene latex, polytetrafluoroethylene, and polyethylene oxide.

[0059] According to an embodiment of the present invention, the positive electrode active material is selected from lithium iron phosphate.

[0060] According to an embodiment of the present invention, the negative electrode active material is selected from at least one of artificial graphite, natural graphite, hard carbon, soft carbon, mesophase carbon microbeads, silicon-based negative electrode materials and lithium-containing metal composite oxide materials.

[0061] According to an embodiment of the present invention, the charging cut-off voltage of the battery is 3.65V or above.

[0062] Beneficial effects of the present invention:

[0063] The present invention provides an electrolyte and a battery containing the electrolyte. The present invention forms an interface film containing LiSO3 and ROSO2Li on the surface of the positive electrode during the first charge and discharge of a fluorinated sulfonate compound, which is tough, not easy to break, and has strong high-temperature resistance. It also forms an interface film rich in LiF components on the negative electrode, which has good mechanical properties and excellent toughness. During the first charge process, a cyclic carboxylate compound forms an interface film containing components such as Li2CO3, alkyl lithium, hydroxy lithium, and carboxyl lithium on the negative electrode. These components have excellent ion conductivity and can accelerate the transmission of lithium ions, thereby enabling the battery to have better rate and low-temperature performance. By regulating the type and addition amount of fluorinated sulfonate compounds and cyclic carboxylate compound additives, the high and low temperature discharge characteristics and cycle life of 12V lithium iron phosphate batteries are improved. DETAILED DESCRIPTION

[0064] The present invention will be described in further detail below with reference to specific examples. It should be understood that the following examples are merely illustrative and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are encompassed within the scope of protection that the present invention is intended to protect.

[0065] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the reagents, materials, etc. used in the following examples are all commercially available unless otherwise specified.

[0066] Lithium-ion battery preparation

[0067] (1) Preparation of positive electrode sheet

[0068] The positive electrode active material lithium iron phosphate LiFePO4 (abbreviated as LFP), the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black are mixed in a weight ratio of 95.5:2:2.5, and N-methylpyrrolidone (NMP) is added. The mixture is stirred under the action of a vacuum mixer until the mixed system becomes a positive electrode slurry with uniform fluidity; the positive electrode slurry is evenly coated on an aluminum foil with a thickness of 12μm; the coated aluminum foil is baked in an oven with 5 different temperature gradients, and then dried in an oven at 120°C for 8h, and then the positive electrode sheet is obtained after roller pressing and die cutting.

[0069] (2) Preparation of negative electrode sheet

[0070] The negative electrode active material artificial graphite, thickener sodium carboxymethyl cellulose (CMC-Na), binder styrene-butadiene rubber, conductive agent acetylene black, and conductive agent single-walled carbon nanotube (SWCNT) were mixed in a weight ratio of 96:1:1.8:1:0.2, and deionized water was added to obtain a negative electrode slurry under the action of a vacuum mixer; the negative electrode slurry was evenly coated on a copper foil with a thickness of 8 μm; and the negative electrode sheet was obtained after drying (temperature: 85°C, time: 5 h), rolling, and die-cutting.

[0071] (3) Preparation of electrolyte

[0072] In an argon-filled glove box (moisture <10 ppm, oxygen <1 ppm), the organic solvent (specific amount and selection are shown in Table 1) was mixed evenly, and the lithium salt (specific amount and selection are shown in Table 1) and additives (specific amount and selection are shown in Table 1) were quickly added to the mixed solution and stirred evenly to obtain an electrolyte.

[0073] (4) Preparation of diaphragm

[0074] A coated polyethylene diaphragm with a thickness of 8 μm was selected.

[0075] (5) Preparation of lithium-ion batteries

[0076] The positive electrode sheet, separator and negative electrode sheet prepared above are wound to obtain a bare cell without liquid injection; the bare cell is placed in an outer packaging foil, and the prepared electrolyte is injected into the dried bare cell. After vacuum packaging, standing, formation, secondary sealing, sorting and other processes, the required lithium-ion battery is obtained.

[0077] The lithium ion batteries of Comparative Examples 1-5 and Examples 1-13 were all prepared according to the above preparation method. The specific lithium salt, organic solvent and additive combinations and contents are shown in Table 1.

[0078] The electrochemical performance test results of the lithium ion batteries of Comparative Examples 1-5 and Examples 1-13 are shown in Table 2.

[0079] Table 1 Composition of the electrolytes of the lithium ion batteries of Comparative Examples 1-5 and Examples 1-13

[0080]

[0081] Table 2 Performance test results of lithium-ion batteries of Comparative Examples 1-5 and Examples 1-13

[0082]

[0083] (1) Cycle performance test of lithium-ion batteries:

[0084] At 45°C, the lithium-ion battery is charged at a constant current of 3C (nominal capacity) to a voltage of 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C. After standing for 10 minutes, it is discharged at a constant current of 3C to a cut-off voltage of 2.2V. The above is one charge and discharge cycle.

[0085] The lithium-ion battery was subjected to 1000 charge and discharge cycles at 45°C according to the above conditions.

[0086] The capacity retention rate of the lithium-ion battery after N cycles (%) = (discharge capacity of the Nth cycle / first discharge capacity) × 100%, where N is the number of cycles of the lithium-ion battery. The test results are shown in Table 2.

[0087] (2) -30℃ 50% SOC cold start performance test

[0088] At 25°C, the lithium-ion battery was discharged at a constant current of 1C to a cut-off voltage of 2.2V. After standing for 10 minutes, it was charged at a constant current and constant voltage of 1C to 3.65V with a cut-off current of 0.05C; discharged at a constant current of 1C to a cut-off voltage of 2.2V, and the discharge capacity C0 was recorded. After standing for 10 minutes, it was charged at a constant current and constant voltage of 1C to 3.65V with a cut-off current of 0.05C; discharged at a constant current of 1C to a cut-off capacity of 50% C0; the battery cell was moved to a -30°C high and low temperature box, stood for 240 minutes, and then discharged at a constant current of 10C for 2 seconds and the voltage was recorded. The test results are shown in Table 2.

[0089] (3) Temperature characteristics (1C discharge):

[0090] The batteries obtained in the above embodiments and comparative examples were placed in a (25±2)°C environment and allowed to stand for 2-3 hours. When the battery body reached (25±2)°C, the battery was cycled at 1C / 1C for one cycle for capacity test, which was Q. After standing for 10 minutes, the battery was discharged at a constant current of 1C to 2.2V. After standing for 10 minutes, the battery was charged at a constant current and constant voltage of 1C to 3.65V with a cut-off current of 0.05 C. After standing for a specified time at corresponding different temperatures, the battery was discharged at 1C to 2.2V. The discharge capacity Q1 at different temperatures was recorded (standing for 4 hours at -30°C / -10°C / 0°C / 10°C, and standing for 2 hours at 25°C / 45°C). The recorded results are shown in Table 2.

[0091] The calculation formula used is as follows: Capacity retention rate (%) = Q1 / Q×100%.

[0092] Comparing Examples 1 to 13 with Comparative Examples 1 to 3, it can be seen that when only one of the fluorinated sulfonate compound and the cyclic carboxylate compound additive is added, or neither of them is added, the temperature characteristics, high-temperature cycle and low-temperature start-up performance are significantly deteriorated; comparing Example 1 with Examples 2 to 5, it can be seen that when too little or too much fluorinated sulfonate compound is added, the interface film formed is incomplete or too thick, resulting in direct contact between the electrolyte and the electrode to cause redox reactions or lithium ion insertion and extraction resistance is large, thereby deteriorating battery performance; comparing Example 1 with Comparative Example 4, it can be seen that adding lithium hexafluorophosphate with good electrochemical stability and lithium bis(fluorosulfonyl)imide with strong thermal stability and high conductivity as solutes significantly improves low-temperature discharge and cold start performance; comparing Example 1 with Comparative Example 5, it can be seen that although carboxylate can significantly reduce viscosity and improve conductivity, its thermal stability is poorer than that of carbonate, and it significantly deteriorates high-temperature cycle performance. In summary, the combination of fluorinated sulfonate compounds and cyclic carboxylate compound additives can significantly broaden the high and low temperature discharge characteristics and cycle life of 12V lithium iron phosphate batteries.

[0093] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. An electrolyte for lithium iron phosphate battery, characterized in that, The electrolyte comprises an electrolyte salt, an organic solvent and an additive, wherein the additive comprises a fluorinated sulfonate compound and a cyclic carboxylate compound; The fluorinated sulfonate compound is selected from at least one of the compounds shown in Formula 1: Formula 1 In Formula 1, R1 is a substituted or unsubstituted heteroaryl, a substituted or unsubstituted alkyl, a substituted or unsubstituted alkenyl, a substituted or unsubstituted alkynyl, a substituted or unsubstituted cycloalkyl, or a -CO-alkyl; if substituted, the substituent is a halogen or an alkyl; The cyclic carboxylate compound is selected from at least one of the compounds represented by Formula 2 or Formula 3: Formula 2 Formula 3 In Formula 2 and Formula 3, Y is absent, substituted or unsubstituted methylene; if substituted, the substituent is halogen or alkyl; X is -P(R)4-; R is halogen, substituted or unsubstituted alkyl; if substituted, the substituent is halogen or alkyl; X' is -P(R)2-; R is halogen, substituted or unsubstituted alkyl; if substituted, the substituent is halogen or alkyl.

2. The electrolyte according to claim 1, characterized in that R1 is a substituted or unsubstituted 5-20 membered heteroaryl, a substituted or unsubstituted C 1-12 Alkyl, substituted or unsubstituted C 2-12 Alkenyl, substituted or unsubstituted C 2-12 Alkynyl, substituted or unsubstituted C 3-20 Cycloalkyl, -COC 1-12 Alkyl; if substituted, the substituent is halogen or C 1-12 alkyl.

3. The electrolyte according to claim 2, characterized in that R1 is a substituted or unsubstituted 5-10 membered heteroaryl, a substituted or unsubstituted C 1-6 Alkyl, substituted or unsubstituted C 2-6 Alkenyl, substituted or unsubstituted C 2-6 Alkynyl, substituted or unsubstituted C 3-10 Cycloalkyl, -COC 1-6 Alkyl; if substituted, the substituent is halogen or C 1-6 alkyl.

4. The electrolyte according to claim 3, characterized in that R1 is a substituted or unsubstituted 5-6 membered heteroaryl, a substituted or unsubstituted C 1-3 Alkyl, substituted or unsubstituted C 2-3 Alkenyl, substituted or unsubstituted C 2-3 Alkynyl, substituted or unsubstituted C 3-6 Cycloalkyl, -COC 1-3 Alkyl; if substituted, the substituent is halogen or C 1-6 alkyl.

5. The electrolyte according to claim 4, characterized in that R1 is trifluoroacetyl, trifluoroethyl, thienyl, propargyl, cyclopropyl and 3,3-difluorobutenyl.

6. The electrolyte according to claim 1, wherein The fluorinated sulfonate compound is selected from at least one of Compound A to Compound F: Compound A Compound B Compound C Compound D Compound E Compound F.

7. The electrolyte according to any one of claims 1 to 6, characterized in that The mass of the fluorinated sulfonate compound accounts for 0.3-1.5 wt % of the total mass of the electrolyte.

8. The electrolyte according to any one of claims 1 to 6, characterized in that In formula 2, Y is absent, substituted or unsubstituted methylene; if substituted, the substituent is halogen, C 1-6 Alkyl; X is -P(R)4-; R is halogen, substituted or unsubstituted C 1-6 Alkyl; if substituted, the substituent is halogen, C 1-6 Alkyl; X' is -P(R)2-; R is halogen, substituted or unsubstituted C 1-6 Alkyl; if substituted, the substituent is halogen, C 1-6 alkyl.

9. The electrolyte according to any one of claims 1 to 6, characterized in that The mass of the cyclic carboxylate compound accounts for 0.3-1 wt.% of the total mass of the electrolyte.

10. The electrolyte according to any one of claims 1 to 6, characterized in that The additive consists of a fluorine-containing sulfonate compound and a cyclic carboxylate compound.

11. A battery, characterized in that: The battery comprises the electrolyte according to any one of claims 1 to 10.

12. The battery according to claim 11, characterized in that The battery further comprises a positive electrode sheet containing a positive electrode active material, wherein the positive electrode active material is selected from lithium iron phosphate; And / or, the charging cut-off voltage of the battery is 3.65V or above.

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