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

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.