Modulation of lattice oxygen boosts the electrochemical activity and stability of Co-free Li-rich cathodes

Abstract

Co-free Li-rich layered oxide cathodes have drawn much attention owing to their low cost and high energy density. Nevertheless, anion oxidation of oxygen leads to oxygen peroxidation during the first charging process, which leads to co-migration of transition metal ions and oxygen vacancies, causing structural instability. In this work, we propose a pre-activation strategy driven by chemical impregnation to modulate the chemical state of surface lattice oxygen, thus regulating the structural and electrochemical properties of the cathodes. In-situ X-ray diffraction confirms that materials based on activated oxygen configuration have higher structural stability. More importantly, this novel efficient strategy endows the cathodes having a lower surface charge transfer barrier and higher Li+ transfer kinetics characteristic and ameliorates its inherent issues. The optimized cathode exhibits excellent electrochemical performance: after 300 cycles, high capacity (from 238 mAh g−1 to 193 mAh g−1 at 1 C) and low voltage attenuation (168 mV) are obtained. Overall, this modulated surface lattice oxygen strategy improves the electrochemical activity and structural stability, providing an innovative idea to obtain high-capacity Co-free Li-rich cathodes for next-generation Li-ion batteries.