Low-temperature lithium-ion battery electrolyte and preparation method thereof

Abstract

The invention discloses low-temperature lithium-ion battery electrolyte and a preparation method thereof. The low-temperature lithium-ion battery electrolyte is prepared from the following raw material in mass percent: 82 to 87% of non-water organic solvent, 11 to 14% of lithium salt and 1 to 5 % of low-temperature-resistant additive, wherein the non-water organic solvent is a mixture of propylene carbonate, dimethyl sulfite and trimethylene sulfite, and a mass fraction ratio of the propylene carbonate to the dimethyl sulfite to the trimethylene sulfite is 1 to 2 to 1; the lithium salt is lithium difluoroborate (LiODFB) and lithium bis(oxalate)borate (LiBOB), and a molar ratio of the lithium difluoroborate to the lithium bis(oxalate)borate is (25 to 40) : (75 to 60); the low-temperature-resistant additive is glycol sulfite and chain-like carboxylic ester, and a mass fraction ratio of the glycol sulfite to the chain-like carboxylic ester is 1 : (2 to 4). The obtained low-temperature lithium-ion battery electrolyte has better electrochemical stability in a work voltage range of a battery, a discharge plateau and discharge capacity of the lithium-ion battery containing the electrolyte are both effectively improved under low temperature, and a low-temperature application range of the battery is widened.

Description

technical field [0001] The invention relates to the technical field of lithium-ion batteries, in particular to a low-temperature lithium-ion battery electrolyte and a preparation method thereof. Background technique [0002] The energy problem will be a major challenge facing mankind in the 21st century, and the whole world is actively exploring and seeking high-energy electrochemical power sources. As a new generation of high-energy power supply, lithium-ion batteries are widely used in various fields such as military industry, electronic equipment, power tools, and electric vehicles. Lithium-ion batteries have been widely used in various climatic conditions around the world due to their advantages such as long life, large specific capacity, and no memory effect since they were commercialized. In the prior art, much attention has been paid to the cycle life and safety of lithium-ion batteries, and related research has mainly focused on the capacity fading and safety issues...

AI Technical Summary

Problems solved by technology

However, the operating efficiency of the existing lithium-ion battery electrolyte is low at low temperature. Specifically, the viscosity of the electrolyte increases at low temperature, and even partially solidifies, resulting in low ion conductivity; at low temperature, the diffusion coefficient of lithium ions in the active material decreases. The charge transfer resistance (Rct) increases significantly; the compatibility between the electrolyte, the negative electrode and the separator becomes poor at low temperature, which cannot meet the actual use requirements of the environment for lithium-ion batteries