A kind of high-voltage lithium-ion battery ternary cathode material electrolyte and preparation method thereof

Abstract

The invention discloses a high-voltage lithium-ion battery ternary cathode material electrolyte and a preparation method thereof. The high-voltage lithium-ion battery ternary cathode material electrolyte comprises 15-20% of a lithium salt mixture and 71.2% of a high-voltage-resistant organic solvent. 79.7%, the flame retardant content is 3-5% and the auxiliary additive content is 2.3%-3.8%; the lithium salt mixture includes lithium hexafluorophosphate and lithium phosphate salt; the high-pressure-resistant organic solvent is cyclic carbonate, chain carbonate and nitrile compounds, the flame retardant is dimethyl methylphosphonate, and the auxiliary additives are tris(pentafluorophenyl)phosphine and lithium fluorozirconate; Fluorophenyl) phosphine, lithium fluorozirconate and flame retardant dimethyl methylphosphonate, the performance of the electrolyte containing this function is relatively stable, and the high-voltage cycle performance of the prepared lithium-ion battery at 3-5V is improved, making The thermal stability between the positive electrode and the electrolyte is improved.

Description

technical field [0001] The invention belongs to the technical field of lithium-ion batteries, and in particular relates to a high-voltage lithium-ion battery ternary cathode material electrolyte and a preparation method thereof. Background technique [0002] Lithium-ion batteries have the advantages of high energy density, power density, high working voltage, good cycle performance and low self-discharge rate. They are known as "green power sources". Lithium-ion batteries are widely used in portable electronics Tools such as laptops, mobile phones, electronic watches, etc.; vehicles such as electric bicycles, electric vehicles, etc.; aerospace such as satellites, aerospace vehicles, etc.; defense systems such as weapons and equipment, individual power supplies, etc. At this stage, environmental problems are becoming more and more serious, and lithium-ion batteries are used to improve the environmental status. Therefore, it is of great practical significance and broad develop...

AI Technical Summary

Problems solved by technology

[0003] At present, the working voltage of ternary cathode materials widely researched and applied is 4.6V. In order to meet the urgent needs of the market, the energy density of lithium-ion batteries must be increased as much as possible. However, the existing ones use carbonate as solvent and lithium hexafluorophosphate as lithium salt. The electrolyte system cannot meet the requirements of the high-voltage working conditions of the ternary battery. When the voltage is higher than 4.3V, it will be oxidized and decomposed in large quantities, causing the interface impedance between the electrode and the electrolyte to increase continuously, and inhibiting the performance of the battery.

[0004] With the continuous improvement of the working potential of the positive electrode of lithium batteries, the task of developing high-voltage electrolytes has become urgent and important. At present, the performance of the electrolyte is mainly improved by adding functional additives with strong oxidizing ability or adding high-pressure solvents. Under voltage conditions, the additive loses electrons before the organic solvent, undergoes an oxidation reaction, and forms a passivation film on the surface of the positive electrode to stabilize the battery system; however, in the battery, the material used for the diaphragm is generally polyolefin, because polyolefin The price of the material is cheap and the electrochemical performance is relatively stable, but its heat resistance is poor. When the battery encounters a collision, the battery will experience high temperature. The continuous high temperature will cause the diaphragm to shrink and cause thermal deformation. , if the diaphragm shrinks and deforms, the positive and negative electrodes of the battery will be in direct contact with each other, resulting in a short circuit. If the situation is serious, there will be a risk of fire or even explosion

[0005] Therefore, while adding a high-pressure solvent to improve the performance of the electrolyte, it is also necessary to add a flame retardant to prevent the internal structure of the battery from being damaged due to continuous high temperature and affecting its working life.

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