Electrolyte with wide temperature range, high voltage and fast charge and application thereof
By using an electrolyte system with fluorinated carboxylic acid esters and nitrile compounds as co-solvents, the problems of low conductivity and cycle life degradation of lithium-ion batteries at extreme temperatures have been solved, achieving improved performance in a wide temperature range, high voltage, and fast charging.
Patent Information
- Application Number
- CN202511346626.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-19
- Publication Date
- 2026-01-27
AI Technical Summary
Existing lithium-ion batteries have low conductivity and severely reduced cycle life under extreme temperatures, and their high voltage and fast charging performance are insufficient, making them unable to operate stably over a wide temperature range.
An electrolyte system with wide temperature range, high voltage and fast charging characteristics is adopted, including fluorinated carboxylic acid esters and nitrile compounds as co-solvents, combined with film-forming additives and lithium salts to form an electrolyte system that improves conductivity and high voltage resistance.
Within a wide temperature range of -60℃ to 100℃, the battery exhibits high capacity and long cycle life, good stability at high voltage, significantly improved fast charging performance, accelerated ion migration, and reduced side reactions.
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Figure CN121416623A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrochemical technology, specifically relating to an electrolyte that combines wide temperature range, high voltage and fast charging, and its applications. Background Technology
[0002] Lithium-ion batteries are playing an increasingly important role in daily life, from portable electronics to electric vehicles. However, in low-temperature environments (such as -25 °C), commercial vehicle batteries can only maintain 30% of their room-temperature driving range, with a sharp decline in battery capacity and stability, and severe polarization. Similarly, in high-temperature environments, side reactions and gas generation can lead to reduced coulombic efficiency and capacity decay. Therefore, developing electrolytes that can operate stably over a wide temperature range is crucial.
[0003] NCM811 is widely recognized as an ideal cathode material for lithium-ion batteries due to its high cutoff voltage, high theoretical specific capacity (200 mAh / g), and high rate performance. Graphite, with its abundant reserves and high theoretical specific capacity (372 mAh / g), is widely used as an anode material in lithium-ion batteries. Therefore, NCM811 and graphite are commonly used to form the positive and negative electrodes of lithium-ion full batteries. However, limited by the liquid range and high-temperature instability of commercial electrolytes, current lithium-ion batteries generally operate only within the range of -25 °C to 45 °C. Furthermore, because NCM811 is prone to lattice distortion and structural fragmentation at high voltages, the maximum charging voltage of lithium-ion batteries is generally 4.2 V, which significantly limits the improvement of battery energy density. In addition, commercial batteries also face significant limitations in charging and discharging at higher rates (>3 C) because battery polarization increases significantly, leading to a decrease in charge and discharge capacity. Therefore, researching new electrolytes that enable lithium-ion batteries to be rapidly charged over a wide temperature range and at high voltages is of great significance.
[0004] Electrolytes are a crucial component of batteries and are key to solving the aforementioned problems. Currently, the main components of commercially available electrolytes, such as ethylene carbonate (EC) and dimethyl carbonate (DMC), each have their drawbacks. EC has a high melting point of 36.4 °C, severely limiting its application at low temperatures, and its high viscosity (1.9 mP·s) leads to slow ion migration. DMC, on the other hand, has a low dielectric constant (3.2), making lithium salt dissociation difficult and resulting in low electrolyte conductivity. Furthermore, commercially available electrolytes are unstable at high temperatures, leading to severe side reactions. To address these issues, solvents with suitable dielectric constants, wide liquid ranges, and weak solvation capabilities should be explored. Specifically, solvents with suitable dielectric constants can effectively dissociate lithium salts, ensuring high ionic conductivity of the electrolyte; wide liquid ranges lay the foundation for applications at both high and low temperatures; and solvents with suitable dielectric constants can effectively dissociate lithium salts, ensuring high ionic conductivity of the electrolyte; wide liquid ranges lay the foundation for applications at both high and low temperatures; and in the case of Li... + During the intercalation process, weakly solvated solvents facilitate the solvation of Li. +Desolventize at the interface to expose Li + The morphology is embedded in the electrode material, suppressing solvent co-intercalation. Furthermore, when the solvent competes with the anion for entry into Li... + When solvating the sheath, weak solvation solvents can promote the reaction of more anions with Li. + Coordination. Even at low salt concentrations, abundant ion pairs or aggregates can form, resulting in anion-derived interfacial films. These films can significantly reduce Li... + Energy transfer barriers enhance battery rate performance, fast charging capability, and cycle stability.
[0005] Therefore, there is an urgent need to develop a new electrolyte system that combines weak solvation energy, high voltage resistance, and high conductivity over a wide temperature range to solve the problem of cycle life degradation in lithium-ion batteries under extreme temperatures. Summary of the Invention
[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide an electrolyte for lithium-ion batteries that has high conductivity at extreme temperatures, as well as wide temperature range, high voltage and fast charging characteristics, and its application.
[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: An electrolyte exhibiting wide temperature range, high voltage, and fast charging capability includes a co-solvent, a solute, and a film-forming additive. The co-solvent comprises fluorocarboxylic acid esters and nitrile compounds. The fluorocarboxylic acid esters have the structural formula shown in formula (I). Equation (I) In equation (Ⅰ), R1, R2 = C x H 2x+2-y F y x = 1 - 10, y = 0 - 22, y is not 0 at the same time in R1 and R2, and both R1 and R2 exist.
[0008] Nitrile compounds have the structural formula shown in formula (II): Formula (II) In equation (II), R3 = C z H 2z+2 z = 1 - 10.
[0009] As a further improvement to the above technical solution: The fluorocarboxylic acid ester compounds include at least one of structural formulas (1), (2), and (3): Structural formula (1) Structural formula (2) Structural formula (3).
[0010] The nitrile compounds include at least one of structural formulas (4), (5), and (6): Structural formula (4) Structural formula (5) Structural formula (6).
[0011] The fluorocarboxylic acid esters and nitrile compounds account for 0.1-0.9% of the volume of the electrolyte, respectively.
[0012] The volume ratio of the fluorocarboxylic acid ester compound, the nitrile compound, and the film-forming additive is 2-8:1-7:1.
[0013] The film-forming additives include one or more of the following: fluoroethylene carbonate (FEC), difluoroethylene carbonate, vinylene carbonate, vinyl sulfite, vinyl sulfate, tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, tris(2,2,2-trifluoroethyl) phosphate, tripropylene phosphite, triargyl phosphate, 1,3,6-hexanetrionitrile, ethylene glycol bis(propionitrile) ether, vinyltrimethylsilane, phenyltrivinylsilane, difluorodiphenylsilane, and perfluorooctyltrimethoxysilane. The solute is a lithium salt, including one or more of lithium bis(fluorosulfonyl)imide (LiFSI), lithium trifluoromethanesulfonate, lithium bis(fluoromethanesulfonyl)imide, lithium tri(trifluoromethanesulfonyl)methyl, lithium dioxoyl borate, lithium difluorodioxolane phosphate, lithium difluorophosphate, lithium perchlorate, lithium tetrafluorooxolane phosphate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium difluoro(1,2-dihydroxyethane-1,1,2,2-tetracarboxynitrile)borate, LiSbF6, LiTaF6, LiAlCl4, LiP(C2O4)3, LiN(SO2RF)2, and LiN(SO2F)(SO2RF); RF = -C n F 2n+1 , n=1 - 10.
[0014] The concentration of the solute is 0.1 - 2.0 mol / L.
[0015] The aforementioned electrolyte, which combines wide temperature range, high voltage, and fast charging characteristics, is used in lithium-ion batteries.
[0016] A lithium-ion battery includes an electrolyte, a positive electrode, and a negative electrode, wherein the electrolyte includes the aforementioned electrolyte that combines wide temperature range, high voltage, and fast charging capability.
[0017] The active material of the positive electrode is a lithium-ion transition metal phosphate or a transition metal oxide; the active material of the negative electrode is a carbon material.
[0018] The cathode includes at least one of ternary cathode materials, LiFePO4, LiCoPO4, LiMn2O4, LiCoO2, lithium nickel manganese oxide, and lithium-rich manganese-based materials.
[0019] The negative electrode includes at least one of artificial graphite, natural graphite, carbon black, graphene, and graphitized mesophase carbon microspheres.
[0020] The high voltage in this application refers to a charging voltage greater than 4.2 V. Currently, the highest charging voltage of commercial lithium-ion batteries is 4.2 V (ternary material batteries). The highest charging cut-off voltage in this application is 4.5 V. The "wide temperature range" in this application refers to an operating temperature between -60℃ and 100℃.
[0021] The applicant discovered that the carboxyl group in fluorocarboxylic acid esters and the cyano group in nitrile compounds endow fluorocarboxylic acid esters and nitrile compounds with high pressure resistance and wide liquid range properties. The carbonyl group and -F substituent in fluorocarboxylic acid esters achieve weak solvation. Compared to methyl acetate, the methyl group on the carbonyl side of methyl difluoroacetate is replaced by two F atoms. The F atoms attract electrons, reducing the electron cloud density around the carbonyl group, thus weakening the attraction of the carbonyl group to lithium ions. This is equivalent to weakening the attraction of the difluoroacetate solvent molecule to lithium ions, thus achieving a weak solvation effect. The high dielectric constant of nitrile compounds is attributed to their cyano groups; appropriately increasing or decreasing the length of the alkyl chain does not fundamentally affect the properties of the molecule itself.
[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides an electrolyte that combines wide temperature range, high voltage, and fast charging capabilities. It features the characteristic structures of carbonyl and -F substituents in fluorocarboxylic acid esters and cyano groups in nitrile compounds. Both fluorocarboxylic acid esters and nitrile compounds possess high voltage resistance and a wide temperature range; their synergistic effect improves battery performance, enabling operation within a temperature range of -60°C to 100°C. Fluorocarboxylic acid esters impart a significant weak solvation capability to the electrolyte, allowing solvated lithium ions to rapidly desolvate and intercalate between electrode materials at low temperatures or high rates, exhibiting good fast charging and low-temperature characteristics. Nitrile compounds possess high dielectric constants, effectively improving the ionic conductivity of the electrolyte and accelerating ion migration. Simultaneously, the electrolyte exhibits fewer side reactions and better stability at high temperatures. This fast-charging electrolyte effectively ensures that the lithium-ion battery system exhibits high capacity and long cycle life under wide temperature, high voltage, and high rate conditions. Attached Figure Description
[0023] Figure 1 The rate performance of the NCM811|| graphite full cell assembled using Example 1 is shown.
[0024] Figure 2 The low-temperature performance of the NCM811|| graphite full cell assembled using Example 1 is shown.
[0025] Figure 3 The high-temperature performance of the NCM811|| graphite full cell assembled using Example 1 is shown.
[0026] Figure 4 The cycle performance of the NCM811|| graphite full cell assembled using Example 1 is shown.
[0027] Figure 5 The high-temperature performance of the graphite-lithium half-cell assembled using Example 1 is shown.
[0028] Figure 6 The low-temperature performance of the NCM811|| graphite full cell assembled using Example 2 is shown.
[0029] Figure 7 The low-temperature performance of the NCM811|| graphite full cell assembled using Example 3 is shown.
[0030] Figure 8 The low-temperature performance of the NCM811|| graphite full cell assembled using Example 4 is shown.
[0031] Figure 9 The low-temperature performance of the NCM811||graphite full cell assembled using Comparative Example 1 is shown.
[0032] Figure 10 The low-temperature performance of the NCM811||graphite full cell assembled using Comparative Example 2 is shown.
[0033] Figure 11 The low-temperature performance of the NCM811||graphite full cell assembled using Comparative Example 3 is shown.
[0034] Figure 12 The low-temperature performance of the NCM811||graphite full cell assembled using Comparative Example 4 is shown. Detailed Implementation
[0035] The present invention will be further described in detail below. Unless otherwise specified, the instruments or materials used in the present invention are commercially available.
[0036] Example 1: This embodiment features a wide temperature range, high voltage, and fast-charging electrolyte, comprising a co-solvent, a lithium salt (solute), and a film-forming additive. The co-solvent is a mixture of methyl difluoroacetate (structural formula 1) and isobutyronitrile (structural formula 4), and the film-forming additive is fluoroethylene carbonate (FEC). The volume ratio of methyl difluoroacetate, isobutyronitrile, and fluoroethylene carbonate is 4:5:1, and the lithium salt is LiFSI with a molar concentration of 1 mol / L.
[0037] Structural formula (1) Structural formula (4) The application of this embodiment of a wide-temperature-range, high-voltage, and fast-charging electrolyte in lithium-ion batteries includes the following steps: Under anhydrous and oxygen-free conditions, an electrolyte was prepared using methyl difluoroacetate (structural formula 1), isobutyronitrile (structural formula 4), and FEC in a volume ratio of 4:5:1. LiFSI was dissolved in the electrolyte at a molar concentration of 1 mol / L. A coin cell was assembled using NCM811 as the positive electrode material and artificial graphite as the negative electrode material.
[0038] Tests showed that at room temperature (25 °C), the capacity was 206 mAh / g at 0.2 C, and 121 mAh / g at 10 C. Figure 1 At a low temperature of -60 °C, the capacity at 0.1 C is 101 mAh / g ( Figure 2 At a high temperature of 45 °C, the capacity at 0.1 C is 203 mAh / g. Figure 3 Meanwhile, at room temperature (25 °C), after 500 cycles, the capacity retention was 63.1%. Figure 4 ).
[0039] This embodiment utilizes a wide-temperature-range, high-voltage, and fast-charging electrolyte in lithium-ion batteries, comprising the following steps: assembling a coin cell using artificial graphite as the positive electrode material, lithium metal as the negative electrode material, and the electrolyte of this embodiment. Testing showed that at a high temperature of 100 °C, the capacity at 0.1 C was 334 mAh / g. Figure 5 See Table 1.
[0040] Example 2: (Different volume ratio compared to Example 1) This embodiment features a wide temperature range, high voltage, and fast-charging electrolyte, comprising a co-solvent, a lithium salt (solute), and a film-forming additive. The co-solvent is a mixture of methyl difluoroacetate (structural formula 1) and isobutyronitrile (structural formula 4), and the film-forming additive is fluoroethylene carbonate (FEC). The volume ratio of methyl difluoroacetate, isobutyronitrile, and fluoroethylene carbonate is 8:1:1, and the lithium salt is LiFSI with a molar concentration of 1 mol / L.
[0041] Structural formula (1) Structural formula (4) The application of this embodiment of a wide-temperature-range, high-voltage, and fast-charging electrolyte in lithium-ion batteries includes the following steps: Under anhydrous and oxygen-free conditions, an electrolyte was prepared using methyl difluoroacetate (structural formula 1), isobutyronitrile (structural formula 4), and FEC in a volume ratio of 8:1:1. LiFSI was dissolved in the electrolyte at a molar concentration of 1 mol / L. A coin cell was assembled using NCM811 as the positive electrode material and artificial graphite as the negative electrode material.
[0042] Tests showed that at room temperature (25 °C) and 0.2 C, the capacity was 201 mAh / g; at low temperature (-60 °C) and 0.1 C, the capacity was 73 mAh / g. Figure 6 At a high temperature of 45 °C, the capacity at 0.1 C is 176 mAh / g. See Table 1.
[0043] The application of a wide-temperature-range, high-voltage, and fast-charging electrolyte in lithium-ion batteries in this embodiment includes the following steps: assembling a coin cell using artificial graphite as the positive electrode material, lithium metal as the negative electrode material, and the electrolyte of this embodiment.
[0044] The tested capacity was 315 mAh / g at 0.1°C (100 °C). See Table 1.
[0045] Example 3: (Different volume ratio compared to Example 1) The electrolyte of this embodiment features a wide temperature range, high voltage, and fast charging capability. It includes a co-solvent, a lithium salt, and a film-forming additive. The co-solvent is a mixture of methyl difluoroacetate (structural formula 1) and isobutyronitrile (structural formula 4). The film-forming additive is fluoroethylene carbonate (FEC). The volume ratio of methyl difluoroacetate, isobutyronitrile, and fluoroethylene carbonate is 6:3:1. The lithium salt is LiFSI with a molar concentration of 1 mol / L.
[0046] Structural formula (1) Structural formula (4) The application of this embodiment of a wide-temperature-range, high-voltage, and fast-charging electrolyte in lithium-ion batteries includes the following steps: Under anhydrous and oxygen-free conditions, an electrolyte was prepared using methyl difluoroacetate (structural formula 1), isobutyronitrile (structural formula 4), and FEC in a volume ratio of 6:3:1, and LiFSI was dissolved in it at a molar concentration of 1 mol / L. A coin cell was assembled using NCM811 as the positive electrode material and artificial graphite as the negative electrode material.
[0047] Tests showed that at room temperature (25 °C) and 0.2 C, the capacity was 203 mAh / g; at low temperature (-60 °C) and 0.1 C, the capacity was 82 mAh / g. Figure 7 At a high temperature of 45 °C, the capacity at 0.1 C is 186 mAh / g. See Table 1.
[0048] The application of a wide-temperature-range, high-voltage, and fast-charging electrolyte in lithium-ion batteries in this embodiment includes the following steps: assembling a coin cell using artificial graphite as the positive electrode material, lithium metal as the negative electrode material, and the electrolyte of this embodiment.
[0049] The tested capacity was 320 mAh / g at 0.1°C (100 °C). See Table 1.
[0050] Example 4: (Different volume ratio compared to Example 1) This embodiment features a wide temperature range, high voltage, and fast-charging electrolyte, comprising a co-solvent, a lithium salt, and a film-forming additive. The co-solvent is a mixture of methyl difluoroacetate (structural formula 1) and isobutyronitrile (structural formula 4), and the film-forming additive is fluoroethylene carbonate (FEC). The volume ratio of methyl difluoroacetate, isobutyronitrile, and fluoroethylene carbonate is 2:7:1, and the lithium salt is LiFSI with a molar concentration of 1 mol / L.
[0051] Structural formula (1) Structural formula (4) The application of this embodiment of a wide-temperature-range, high-voltage, and fast-charging electrolyte in lithium-ion batteries includes the following steps: Under anhydrous and oxygen-free conditions, an electrolyte was prepared using methyl difluoroacetate (structural formula 1), isobutyronitrile (structural formula 4), and FEC in a volume ratio of 2:7:1, and LiFSI was dissolved in it at a molar concentration of 1 mol / L. A coin cell was assembled using NCM811 as the positive electrode material and artificial graphite as the negative electrode material.
[0052] Tests showed that at room temperature (25 °C) and 0.2 C, the capacity was 204 mAh / g; at low temperature (-60 °C) and 0.1 C, the capacity was 87 mAh / g. Figure 8 At a high temperature of 45 °C, the capacity at 0.1 C is 193 mAh / g. See Table 1.
[0053] The application of a wide-temperature-range, high-voltage, and fast-charging electrolyte in lithium-ion batteries in this embodiment includes the following steps: assembling a coin cell using artificial graphite as the positive electrode material, lithium metal as the negative electrode material, and the electrolyte of this embodiment.
[0054] The tested capacity was 324 mAh / g at 0.1 C (100 °C). See Table 1.
[0055] Comparative Example 1: (Only fluorocarboxylic acid esters are present, nitriles are missing) The electrolyte in this comparative example includes a solvent, a lithium salt, and a film-forming additive. The solvent is methyl difluoroacetate (structural formula 1), the film-forming additive is fluoroethylene carbonate (FEC), the volume ratio of methyl difluoroacetate to fluoroethylene carbonate is 9:1, and the lithium salt is LiFSI with a molar concentration of 1 mol / L.
[0056] Structural formula (1) The application of the electrolyte in this comparative example in lithium-ion batteries includes the following steps: Under anhydrous and oxygen-free conditions, an electrolyte was prepared using methyl difluoroacetate (structural formula 1) and FEC at a volume ratio of 9:1. LiFSI was dissolved in the electrolyte at a molar concentration of 1 mol / L, and coin cells were assembled using NCM811 as the positive electrode material and artificial graphite as the negative electrode material.
[0057] Tests showed that at room temperature (25 °C) and 0.2 C, the capacity was 188 mAh / g; at low temperature (-60 °C) and 0.1 C, the capacity was 58 mAh / g. Figure 9 At a high temperature of 45 °C, the capacity at 0.1 C is 160 mAh / g. See Table 1.
[0058] The application of the electrolyte of this comparative example in lithium-ion batteries includes the following steps: assembling a coin cell using artificial graphite as the positive electrode material, lithium metal as the negative electrode material, and the electrolyte of this comparative example.
[0059] The test showed that the capacity was 203 mAh / g at a high temperature of 100 °C and a lower temperature of 0.1 C. See Table 1.
[0060] Comparative Example 2: (Only nitrile compounds are present; fluorocarboxylic acid esters are missing) The electrolyte in this comparative example includes a solvent, a lithium salt, and a film-forming additive. The solvent is isobutyronitrile (structural formula 4), the film-forming additive is fluoroethylene carbonate (FEC), the volume ratio of isobutyronitrile to fluoroethylene carbonate is 9:1, and the lithium salt is LiFSI with a molar concentration of 1 mol / L.
[0061] Structural formula (4) The application of the electrolyte in this comparative example in lithium-ion batteries includes the following steps: Under anhydrous and oxygen-free conditions, an electrolyte was prepared using isobutyronitrile (structural formula 4) and FEC at a volume ratio of 9:1. LiFSI was dissolved in the electrolyte at a molar concentration of 1 mol / L. A coin cell was assembled using NCM811 as the positive electrode material and artificial graphite as the negative electrode material.
[0062] Tests showed that at room temperature (25 °C) and 0.2 C, the capacity was 189 mAh / g; at low temperature (-60 °C) and 0.1 C, the capacity was 59 mAh / g. Figure 10 At a high temperature of 45 °C, the capacity at 0.1 C is 163 mAh / g. See Table 1.
[0063] The application of the electrolyte of this comparative example in lithium-ion batteries includes the following steps: assembling a coin cell using artificial graphite as the positive electrode material, lithium metal as the negative electrode material, and the electrolyte of this comparative example.
[0064] The test showed that the capacity was 226 mAh / g at a high temperature of 100 °C and a minimum temperature of 0.1 C. See Table 1.
[0065] Comparative Example 3: (Fluorocarboxylic acid esters are present; nitriles are replaced with methyl ethyl carbonate) The electrolyte in this comparative example includes a co-solvent, a lithium salt, and a film-forming additive. The co-solvent is a mixture of methyl difluoroacetate (structural formula 1) and ethyl methyl carbonate (structural formula 7). The film-forming additive is fluoroethylene carbonate (FEC). The volume ratio of methyl difluoroacetate, ethyl methyl carbonate, and fluoroethylene carbonate is 4:5:1. The lithium salt is LiFSI with a molar concentration of 1 mol / L.
[0066] Structural formula (1) Structural formula (7) The application of the electrolyte in this comparative example in lithium-ion batteries includes the following steps: Under anhydrous and oxygen-free conditions, an electrolyte was prepared using methyl difluoroacetate (Structure 1), ethyl methyl carbonate (Structure 7), and FEC in a volume ratio of 4:5:1, and LiFSI was dissolved in it at a molar concentration of 1 mol / L. A coin cell was assembled using NCM811 as the positive electrode material and artificial graphite as the negative electrode material.
[0067] Tests showed that at room temperature (25 °C) and 0.2 C, the capacity was 168 mAh / g; at low temperature (-60 °C) and 0.1 C, the capacity was 21 mAh / g. Figure 11 At a high temperature of 45 °C, the capacity at 0.1 C is 132 mAh / g. See Table 1.
[0068] The application of the electrolyte of this comparative example in lithium-ion batteries includes the following steps: assembling a coin cell using artificial graphite as the positive electrode material, lithium metal as the negative electrode material, and the electrolyte of this comparative example.
[0069] The test showed that the capacity was 167 mAh / g at a high temperature of 100 °C and a minimum temperature of 0.1 C. See Table 1.
[0070] Comparative Example 4: (Fluorocarboxylic acid esters were replaced with methyl ethyl carbonate; only nitrile compounds were included) The electrolyte in this comparative example includes a co-solvent, a lithium salt, and a film-forming additive. The co-solvent is a mixture of ethyl methyl carbonate (structural formula 7) and isobutyronitrile (structural formula 4). The film-forming additive is fluoroethylene carbonate (FEC). The volume ratio of ethyl methyl carbonate, isobutyronitrile, and fluoroethylene carbonate is 4:5:1. The lithium salt is LiFSI with a molar concentration of 1 mol / L.
[0071] Structural formula (7) Structural formula (4) The application of the electrolyte in this comparative example in lithium-ion batteries includes the following steps: Under anhydrous and oxygen-free conditions, an electrolyte was prepared using ethyl methyl carbonate (structural formula 7), isobutyronitrile (structural formula 4), and FEC in a volume ratio of 4:5:1, and LiFSI was dissolved in it at a molar concentration of 1 mol / L. A coin cell was assembled using NCM811 as the positive electrode material and artificial graphite as the negative electrode material.
[0072] Tests showed that at room temperature (25 °C) and 0.2 C, the capacity was 167 mAh / g; at low temperature (-60 °C) and 0.1 C, the capacity was 25 mAh / g. Figure 12 At a high temperature of 45 °C, the capacity at 0.1 C is 136 mAh / g. See Table 1.
[0073] The application of the electrolyte of this comparative example in lithium-ion batteries includes the following steps: assembling a coin cell using artificial graphite as the positive electrode material, lithium metal as the negative electrode material, and the electrolyte of this comparative example.
[0074] The test showed that the capacity was 175 mAh / g at a high temperature of 100 °C and a lower temperature of 0.1 C. See Table 1.
[0075]
[0076] As shown in Table 1, the full-cell capacities of Examples 1 to 4 at room temperature (25 °C) were 206, 201, 203, and 204 (mAh / g), respectively; at low temperature (-60 °C) were 101, 73, 82, and 87 (mAh / g), respectively; at high temperature (45 °C) were 203, 176, 186, and 193 (mAh / g), respectively; and at high temperature (100 °C) were significantly higher than those of Comparative Examples 1 to 4. Methyl difluoroacetate and isobutyronitrile have a significant synergistic effect, thus proving the synergistic advantage of fluorocarboxylic acid esters and nitrile compounds.
[0077] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, should fall within the protection scope of the present invention.
Claims
1. An electrolyte possessing wide temperature range, high voltage, and fast charging characteristics, comprising a co-solvent, a solute, and a film-forming additive, characterized in that, The co-solvent includes fluorinated carboxylic acid esters and nitrile compounds; the fluorinated carboxylic acid esters have the structural formula shown in formula (I): Equation (I) In equation (Ⅰ), R1, R2 = C x H 2x+2-y F y x = 1 - 10, y = 0 - 22, y is not 0 at the same time in R1 and R2, and both R1 and R2 exist; Nitrile compounds have the structural formula shown in formula (II): Formula (II) In equation (II), R3 = C z H 2z+2 z = 1 - 10.
2. The electrolyte with wide temperature range, high voltage, and fast charging characteristics according to claim 1, characterized in that: The fluorocarboxylic acid ester compounds include at least one of structural formulas (1), (2), and (3): Structural formula (1) Structural formula (2) Structural formula (3) The nitrile compounds include at least one of structural formulas (4), (5), and (6): Structural formula (4) Structural formula (5) Structural formula (6).
3. The electrolyte with wide temperature range, high voltage, and fast charging properties according to claim 1, characterized in that, The fluorocarboxylic acid esters and nitrile compounds account for 0.1-0.9% of the volume of the electrolyte, respectively.
4. The electrolyte with wide temperature range, high voltage, and fast charging characteristics according to claim 1, characterized in that, The volume ratio of the fluorocarboxylic acid ester compound, the nitrile compound, and the film-forming additive is 2-8:1-7:
1.
5. The electrolyte possessing wide temperature range, high voltage, and fast charging characteristics according to any one of claims 1 to 4, characterized in that, The film-forming additives include one or more of the following: fluoroethylene carbonate (FEC), difluoroethylene carbonate, vinylene carbonate, vinyl sulfite, vinyl sulfate, tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, tris(2,2,2-trifluoroethyl) phosphate, tripropylene phosphite, triargyl phosphate, 1,3,6-hexanetrionitrile, ethylene glycol bis(propionitrile) ether, vinyltrimethylsilane, phenyltrivinylsilane, difluorodiphenylsilane, and perfluorooctyltrimethoxysilane.
6. The electrolyte possessing wide temperature range, high voltage, and fast charging characteristics according to any one of claims 1 to 4, characterized in that, The solute is a lithium salt, including one or more of lithium bis(fluorosulfonyl)imide (LiFSI), lithium trifluoromethanesulfonate, lithium bis(fluoromethanesulfonyl)imide, lithium tri(trifluoromethanesulfonyl)methyl, lithium dioxoyl borate, lithium difluorodioxolane phosphate, lithium difluorophosphate, lithium perchlorate, lithium tetrafluorooxolane phosphate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium difluoro(1,2-dihydroxyethane-1,1,2,2-tetracarboxynitrile)borate, LiSbF6, LiTaF6, LiAlCl4, LiP(C2O4)3, LiN(SO2RF)2, and LiN(SO2F) (SO2RF); RF = -C n F 2n+1 , n=1 - 10.
7. The electrolyte possessing a wide temperature range, high voltage, and fast charging capability according to any one of claims 1 to 4, characterized in that, The concentration of the solute is 0.1 - 2.0 mol / L.
8. The application of an electrolyte with wide temperature range, high voltage and fast charging capability according to any one of claims 1 to 7 in lithium-ion batteries.
9. A lithium-ion battery, comprising an electrolyte, a positive electrode, and a negative electrode, characterized in that, The electrolyte includes the electrolyte that combines wide temperature range, high voltage and fast charging according to any one of claims 1 to 7.
10. The lithium-ion battery according to claim 9, characterized in that: The active material of the positive electrode is a lithium-ion transition metal phosphate or a transition metal oxide; the active material of the negative electrode is a carbon material.