CN-122000473-A - Wide-temperature-range high-magnification lithium battery ester-based electrolyte and application thereof

Abstract

The invention relates to the technical field of batteries, in particular to a wide-temperature-range high-rate lithium battery ester-based electrolyte and application thereof. The electrolyte comprises soluble lithium salt and a liquid component, wherein the liquid component is a solvent, the solvent comprises at least three of propylene carbonate, fluoroethylene carbonate, isopropyl trifluoroacetate, ethyl acetate, methyl acetate and methyl trifluoroacetate, and at least two of the lithium salts are commonly used in lithium salt lithium batteries. The electrolyte developed by the invention is used in a lithium battery, can stably work at-40 ℃ to 60 ℃, has the discharge specific capacity of 62.83% of room temperature even at-30 ℃ and 4 ℃ multiplying power, and has excellent wide-temperature quick-charge performance. In addition, the electrolyte effectively inhibits lithium dendrite growth and electrode-electrolyte interface side reaction at low temperature, and promotes the formation of a solid interface film rich in inorganic matters and low in interface impedance. The invention has reasonable component design and excellent product performance, and is convenient for industrialized application.

Inventors

• ZHOU LIANGJUN
• LUO QIAO
• Liao Xuanyuan
• HUANG XIAOWEI
• YANG ZHENGZHAO
• TANG XIAOWEI
• WEI WEIFENG

Assignees

• 中南大学
• 江西赣锋锂电科技股份有限公司

Dates

Publication Date

20260508

Application Date

20260209

Claims (10)

1. 1. The wide-temperature-range high-rate lithium battery ester-based electrolyte is characterized by comprising soluble lithium salt and a liquid component, wherein the liquid component is a solvent, and the solvent comprises at least three of propylene carbonate, fluoroethylene carbonate, isopropyl trifluoroacetate, ethyl acetate, methyl acetate and methyl trifluoroacetate.
2. 2. The wide temperature range high rate lithium battery ester-based electrolyte of claim 1, wherein the soluble lithium salt comprises at least two of lithium bis (trifluoromethanesulfonyl imide), lithium bis (fluorosulfonyl imide), lithium tetrafluoroborate, lithium difluorooxalato borate, lithium dioxaato borate, lithium hexafluorophosphate, lithium difluorophosphate, lithium perchlorate, and lithium nitrate.
3. 3. The wide temperature range high rate lithium battery ester-based electrolyte of claim 2, wherein the soluble lithium salt comprises lithium bis (trifluoromethanesulfonyl) imide and lithium difluoro oxalato borate.
4. 4. The wide temperature range high rate lithium battery ester-based electrolyte according to claim 1, wherein the molar concentration of the soluble lithium salt in the electrolyte is 0.8-1.5 mol/L, and more preferably 0.9-1.2 mol/L.
5. 5. The wide temperature range high rate lithium battery ester-based electrolyte and application of the wide temperature range high rate lithium battery ester-based electrolyte as claimed in claim 1, wherein the selected solvent comprises at least one of propylene carbonate, fluoroethylene carbonate and isopropyl trifluoroacetate.
6. 6. The wide-temperature-range high-rate lithium battery ester-based electrolyte according to claim 3, wherein the selected soluble lithium salt is composed of LiTFSI and LiDFOB in a molar ratio of 3.8-4.2:1, and more preferably, the molar ratio of LiTFSI to LiDFOB is 3.9-4.1:1.
7. 7. The wide-temperature-range high-rate lithium battery ester-based electrolyte according to claim 1, wherein the solvent is at least one of propylene carbonate, fluoroethylene carbonate and isopropyl trifluoroacetate, and preferably the solvent is composed of propylene carbonate, fluoroethylene carbonate and isopropyl trifluoroacetate, and preferably the liquid component is composed of propylene carbonate, fluoroethylene carbonate and isopropyl trifluoroacetate in a volume ratio of 3-10:0.2-4:0.2-6.
8. 8. The wide temperature range high rate lithium battery ester-based electrolyte according to claim 7, wherein the volume ratio of propylene carbonate, fluoroethylene carbonate and isopropyl trifluoroacetate is 4-8:1-3.5:3, and preferably the volume ratio of propylene carbonate, fluoroethylene carbonate and isopropyl trifluoroacetate is 4.8-5.2:1.8-2.2:2.8-3.2.
9. 9. An ester-based electrolyte for a wide temperature range high rate lithium battery and application thereof according to any one of claims 1-8, wherein the application comprises the use of the electrolyte in a lithium battery.
10. 10. The wide temperature range high rate lithium battery ester-based electrolyte and application of the electrolyte according to claim 9, wherein the application is characterized in that: The lithium battery comprises the wide-temperature-range high-rate lithium battery ester-based electrolyte, a lithium metal negative electrode and a high-voltage positive electrode material; the high-voltage positive electrode material is selected from at least one of nickel cobalt manganese oxide, lithium cobalt oxide and nickel-based oxide.

Description

Wide-temperature-range high-magnification lithium battery ester-based electrolyte and application thereof Technical Field The invention relates to the technical field of batteries, in particular to a wide-temperature-range high-rate lithium battery ester-based electrolyte and application thereof. Background With the increasing severity of global energy crisis and environmental pollution, lithium batteries have become an important component of new energy fields. Because of the theoretical limit of the energy density of lithium ion batteries of about 350 Wh kg -1, the demand for higher energy density energy storage systems for electric vehicles and portable devices is increasing. Metallic lithium anodes are considered to be ideal high energy density materials for replacing existing graphite anodes due to their low density (0.535 g cm -3) and high theoretical capacity (3830 mAh g -1). However, the Solid Electrolyte Interface (SEI) formed in commercial carbonate electrolytes has poor electrochemical and mechanical stability, and the unstable SEI structure continuously exposes new active lithium surfaces during cycling, causing uncontrolled growth of lithium dendrites, which may penetrate the separator to cause battery shorting and thermal runaway. This problem may be more serious when the battery is operated at high and low temperatures and at high rates. This critical safety issue severely restricts the practical application of lithium metal batteries under wide temperature range and high rate conditions. In terms of solvents, propylene carbonate is a widely used solvent in lithium metal batteries due to its wide liquid phase temperature range (-49-240 ℃), strong solvation ability and high oxidation stability, but its higher viscosity results in lower conductivity at low temperatures, thus limiting the application at low temperatures and high magnifications. In addition, since propylene carbonate solvent has a strong binding force with lithium ions, lithium ions have a high desolvation energy barrier, resulting in severe dendrite growth, and solvation sheaths composed of solvent molecules and lithium salts are easily decomposed at interfaces, and form unstable interfacial films, resulting in deterioration of performance. The key is to lower the lithium ion desolvation energy barrier and adjust the solvation sheath to form an inorganic rich SEI with better stability, and in terms of lithium salts, commercial LiPF 6 has lower conductivity at low temperature and exhibits thermal instability, is prone to HF generation, results in SEI film destruction and transition metal dissolution, and is unsuitable for use as a lithium salt for wide temperature range electrolytes. Based on the above problems, it is critical to weaken the binding force between lithium ions and a solvent to accelerate the desolventizing process of lithium ions, thereby inhibiting the growth of lithium dendrites and forming an inorganic-rich SEI layer having good stability. Modulation of solvation sheath structure by competitive coordination is a simple and effective way to improve ion transport kinetics and regulate the composition, structure, and morphology of the SEI layer. The fluorinated solvent generally has lower melting point and viscosity, is favorable for maintaining higher ionic conductivity at low temperature, has lower LUMO energy level, can be decomposed preferentially at the interface of the negative electrode, has moderate molecular polarity, can regulate the lithium ion solvation sheath structure, promotes the formation of an anion derived interface, and improves the ion transmission dynamics. Therefore, the fluoro-substituted solvent with moderate coordination ability with lithium ions and strong oxidation resistance is selected, and the fluoro-substituted solvent is an excellent method for adjusting a solvating sheath layer and stabilizing an interfacial film. It should be noted that the information disclosed in the above background section is only for understanding the background of the application and thus may include information that does not form the prior art that is already known to those of ordinary skill in the art. Disclosure of Invention The invention aims to provide a preparation method and application of a wide-temperature-range high-rate ester-based electrolyte, wherein the oxidation potential of the electrolyte is greater than 5.5V, a battery prepared by using the electrolyte can be stably and reversibly charged and discharged within a wide temperature range of-40-60 ℃, meanwhile, the capacity retention rate of the prepared battery after being cycled for 120 circles under the conditions of low temperature of-30 ℃ and 1C is as high as 94.2%, the capacity retention rate after being cycled for 200 circles under the conditions of 25 ℃ and 4.5V is 82.79%, the battery still shows excellent cycling stability at the high temperature of 60 ℃, and the problems in the prior art are solved. The problems in the prior art are th