Lithium secondary battery electrolyte with low internal resistance and lithium secondary battery

Abstract

The invention provides a lithium secondary battery electrolyte. The preparation method comprises the following steps: adding polyfluorophosphate with a specific structure and a non-aqueous solvent into LiPF6 electrolyte lithium salt, and performing reasonable mixing to obtain the electrolyte. The lithium secondary battery using the electrolyte can have good thermal stability and chemical stabilityin the high-rate charging and discharging process, and meanwhile, has low internal resistance, good low-temperature performance and long cycle life.

Description

technical field [0001] The invention relates to the field of lithium secondary battery electrolyte, in particular to an electrolyte containing a specific fluorophosphate additive. Background technique [0002] Electrolyte is the medium that realizes the migration of lithium ions between positive and negative electrodes in lithium secondary batteries, and has an important impact on lithium battery capacity, operating temperature, cycle efficiency and safety. Generally, it is prepared from raw materials such as high-purity organic solvents, electrolyte lithium salts, and main additives under certain conditions. In order to improve the various performances of lithium batteries, the improvement of the electrolyte is a current research hotspot. [0003] As a lithium salt in the electrolyte, the basic requirements that must be met are: high purity, low molecular weight, low toxicity, complete dissolution and dissociation in non-aqueous solvents, good thermal stability, strong che...

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Problems solved by technology

[0008] It can be seen that, in containing LiPF 6 In the electrolyte solution of lithium salt, due to containing LiPF 6 The electrolyte solution is prone to inevitable thermal decomposition at high temperature, resulting in the formation of HF. At the same time, various volatile and potentially toxic organic phosphate compounds will directly affect the overall performance of the battery, and the existing methods for improving the performance of lithium-ion batteries Due to the need for a large number of non-fluorinated phosphate additives, such as cyclophosphazene, halogenated benzene, boron phosphorus oxalate lithium salt, fluoroborate, etc., and the introduction of the above additives will lead to the formation of complex SEI film composition and morphology, Causes instability in the battery cycle and poses a safety hazard

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