Low-impedance long-cycle-life lithium ion battery electrolyte and preparation method thereof

Abstract

The invention discloses a low-impedance long-cycle-life lithium ion battery electrolyte and a preparation method thereof. A boroxin compound (namely an additive X) is added into the electrolyte, so that the impedance of a battery can be reduced, and the power performance of the battery can be improved; boron atoms in the compound can also be used as negative ion acceptors, hydrofluoric acid is captured, and the hydrofluoric acid generated by a lithium salt and other additives is adsorbed, so that the hydrofluoric acid is prevented from attacking a positive electrode CEI film, the cycling performance of the battery is improved, the capacity retention rate is improved, and meanwhile, the dissociation degree of the lithium salt and the migration number of lithium ions are improved; and moreover, the electrolyte is simple and easy to prepare.

Description

technical field [0001] The invention relates to the technical field of lithium ion batteries, in particular to an electrolyte solution for lithium ion batteries and a secondary battery containing the electrolyte solution. Background technique [0002] Electrolyte is one of the key raw materials of lithium-ion batteries. It plays the role of conducting and transporting energy between the positive and negative electrodes of the battery. It is the guarantee for lithium-ion batteries to obtain the advantages of high voltage and high specific energy. It is about 5%~10% of the battery production cost, but it is indispensable. [0003] Since the potential of the negative electrode of the lithium-ion battery is close to that of lithium, it is relatively active and unstable in the aqueous solution system. It is necessary to use non-aqueous and aprotic organic solvents as the carrier of lithium ions. At present, most lithium-ion batteries use carbonates, ethers, Carboxylates and / or s...

AI Technical Summary

Problems solved by technology

[0003] Since the potential of the negative electrode of the lithium-ion battery is close to that of lithium, it is relatively active and unstable in the aqueous solution system. It is necessary to use non-aqueous and aprotic organic solvents as the carrier of lithium ions. At present, most lithium-ion batteries use carbonates, ethers, Carboxylates and / or sulfur-containing organic solvents are used as carriers, while carbonates and / or ether organic solvents have low boiling points and are easy to volatilize, resulting in defects such as flammability and explosion of batteries. For example, patent CN 101867065 A discloses A flame-retardant electrolyte solution containing carbonates and / or ether organic solvents provides a flame-retardant or even completely non-combustible flame-retardant electrolyte solution, but it is found that after adding the flame-retardant additive described , although its flame retardant performance has been improved, it has an impact on the battery capacity of the lithium battery, because the flame retardant additive contains a large amount of fluorine, which leads to an increase in the impedance of the battery, resulting in poor rate performance

[0004] At the same time, lithium salts and FEC additives in the electrolyte are prone to generate HF during charging and discharging, and HF is easy to damage the positive electrode CEI film, resulting in poor cycle performance of the battery.