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

Abstract

AbstractLithium‐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─O bonds with strong bonding interaction and covalence, low bond energy Li─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.