Fluorinated carbonate-based electrolyte engineering solvation structure for high-voltage Li||LiNiO2 cell

Abstract

Ni-rich layered oxides are considered ideal positive electrode materials for next-generation state-of-the-art Li-based batteries owing to their high energy densities. However, the structural degradation of Ni-rich positive electrodes and electrolyte decomposition presents significant challenges, particularly at high cut-off voltages. Herein, we report a novel electrolyte consisting of fluorinated solvents that enables the long lifespan of a Li||LiNiO2 cell with a cut-off voltage of up to 4.5 V. The Li||LiNiO2 cell retains 93.8% of its initial capacity after 200 cycles. The cycling stability was ascribed to the fluorinated solvents dominating the first structural shell of Li+ and deriving a robust cathode-electrolyte interphase (CEI) on the positive electrode. Compared to commercial electrolytes, the fluorinated electrolyte inhibits the structural degradation, stress corrosion cracking, and interphase side reactions of the LiNiO2 electrode. On the Li negative electrode side, ideal Li plating/stripping and the inhibition of the attack of Ni2+ are achieved. Furthermore, the 4.5 V-Li||LiNiO2 cell exhibited a capacity retention of 80.2% after 100 cycles, even under extremely fast-charging conditions.