Regulation of both Bulk and Surface Structure by W/S Co-Doping for Li-Rich Layered Cathodes with Remarkable Voltage and Capacity Stability

Lithium-rich layered oxides (LLOs) have gained significant attention due to their high capacity of over 250 mAh g-1, which originates from the charge compensation of oxygen anions activated under high voltage. However, the charge compensation of oxygen anions is prone to over-oxidation, leading to serious irreversible oxygen release, surface-interface reactions, and structural evolution. These detriments make LLOs undergo fast voltage decay and capacity fading, which have hindered their practical applications for many years. Herein, this work develops a multifunctional co-doping strategy and constructs W & horbar;O bonds with strong bonding interaction and covalence, low bond energy Li & horbar;S bonds with non-binding electrons near the Fermi level, and continuous and homogeneous surface spinel-like layer induced by W/S co-doping. Their synergistic effect significantly mitigates the irreversible oxygen release and surface-interface reactions and improves structural stability of Li-rich layered cathodes. Thus, the designed and prepared Co-free Li-rich layered cathode (Li1.232Mn0.574Ni0.191W0.003O1.995S0.005) delivers superior voltage and capacity stability. Its capacity retention after 400 cycles is as large as 86%, and its voltage decay rate from the 10th to the 400th cycle is only 0.626 mV cycle-1. The surface and bulk structure of a Co-free LLO cathode is regulated by W/S co-doping, which constructs continuous and homogeneous surface spinel-like layer, strong bonding interaction, and covalence W & horbar;O bonds, and low bond energy Li & horbar;S bonds with non-binding electrons. It significantly improves structural stability and mitigates oxygen release and surface-interface reactions, showing superior voltage stability. image