Electrolyte using blend salts of LiTFSI and LLZO for long-term high-safety lithium ion battery

Abstract

It is crucial to obtain a reliable electrolyte system that is used for replacing thermally unstable and the moisture sensitive LiPF6 salt in liquid electrolytes for developing excellent cycle stability lithium ion batteries with high safety. In this work, a kind of hybrid electrolytes, adding Ga–Bi co-doped Li7La3Zr2O12 (LLZO) into LiTFSI based commercial electrolyte, was successfully prepared. The results shows that adding Ga–Bi co-doped LLZO ceramic particles is benefit for enhancing conductivity of LiTFSI based commercial electrolyte, which is 3.14 mS cm−1 from 3.02 mS cm−1. Furthermore, the LiFePO4| |Li cell assembling with LiTFSI based electrolyte with Ga–Bi co-doped LLZO ceramic particles shows good cycle performance and coulomb efficiency (100% except for the initial cycle value of 88%) due to a passivation multi-element film formed for preventing severe corrosion to the Al foil. The battery delivered a high first cycle discharge capacity of 144.2 mAh g−1 (85% of theoretical LiFePO4.) and a maximum value of 152.6 mAh g−1 after the 69th cycle. After the 300 stable cycle, the capacity of 130.8 mAh g−1 (85.7% of the maximum data) remained.