High-Performance LiNiO2 Cathodes with Practical Loading Cycled with Li metal Anodes in Fluoroethylene Carbonate-Based Electrolyte Solution

Abstract

LiNiO2 is one of the most promising cathode materials for high energy density Li ion batteries because of its high theoretical capacity (275 mAh g–1) and reasonable cost. However, cathodes comprising pure LiNiO2 suffer from intrinsic instability problems, which lead to their capacity fading during cycling. We report herein on highly stable Li (metal)–LiNiO2 prototype cells with practical areal loading of the electrodes due to the quality of the cathode material and the use of a suitable electrolyte solution in which both the Li metal anodes and the LiNiO2 cathodes are stabilized. The electrolyte solution contains 1 M LiPF6 in 1:4 (by volume) mixture of fluoroethylene carbonate (FEC) and dimethyl carbonate (DMC)). The cells with practical cathode loading (4 mAh cm–2), low amount of the electrolyte solution (33 μL cm–2), and Li metal anodes were cycled at 0.8–1 mA cm–2 for more than 700 cycles with excellent capacity retention. We attribute these results to the combination of optimal structure and morphology of the synthesized LiNiO2 and the formation of highly passivating surface films, which behave as a stable solid electrolyte interphase on the surfaces of the Li anodes and the LiNiO2 cathodes. Reactions of FEC at low and high potentials induce favorable surface chemistry on both negative and positive electrodes in Li batteries.