Limiting cobalt fraction in lithium rich cathode materials for stable and fast activation

Abstract

Li-rich layered oxides (LRLOs) have been considered as promising cathode materials for high-energy Li-ion batteries. However, considerable fractionsof costly Co and Ni are normally needed in LRLOs to access the high capacity. In this work, a series of Ni/Co-poor LRLOs is designed to study the effect of Ni:Co ratio on their electrochemical behavior. Due to the lowest-lying Co t2g band, the introduction of minor Co significantly promotes the activation of Li-rich phase. While high Co content exacerbates the interfacial reactions to form a thick and unstable cathode-electrolyte film. Consequently, the low-Co LRLO (ca. 4 % of transition metal) attains stable and fast activation, maintaining 233.3 mA h g−1 after 300 cycles at 1C. Moreover, the low-Co LRLO//graphite full cell retains 86.4 % of its capacity after 200 cycles. This work will shed light on the compositional design of LRLOs towards higher electrochemical performance and lower materials cost.