Chemical bonding of perovskite LaFeO3 with Li1.2Mn0.6Ni0.2O2 to moderate anion redox for achieving high cycling stability

Abstract

Oxygen anion redox reaction provides a high theoretical capacity for Li-rich manganese-based cathodes. However, irreversible surface oxygen release often results in further oxygen loss and exacerbates the decomposition of the electrolyte, which could reduce the capacity contribution from the anionic redox and produce more acidic substances to corrode the surface of the material. In this paper, the surface oxygen release is suppressed by moderating oxygen anion redox activity via constructing chemical bonds between M (M = Fe and La) in LaFeO3 and surface oxygen anions of Li1.2Mn0.6Ni0.2O2. The constructed interface layer stabilizes the surface lattice oxygen and retards the electrolyte from being attacked by the nucleophilic oxygen generated in the process of oxygen release, as evidenced by Differential Electrochemical Mass Spectrometry (DEMS) and X-ray Photoelectron Spectroscopy (XPS) detections. Moreover, in the charge and discharge process, the formed FeF3, located at the cathode electrolyte interfacial layer, is conducive to the stability of the cathode surface. The modified Li1.2Mn0.6Ni0.2O2 electrode with 3 wt% LaFeO3 exhibits a high specific capacity of 189.5 mA h g−1 at 1C (200 mA g−1) after 150 cycles with capacity retentions of 96.6%, and 112.6 mA h g−1 (84.7%) at 5C after 200 cycles higher than the pristine sample. This study provides a rational design chemical bonding method to suppress the oxygen release from the cathode surface and enhance cyclic stability.