Electrochemical activation, voltage decay and hysteresis of Li-rich layered cathode probed by various cobalt content

The high capacity of Li-rich layered cathode materials have attracted great attention for the greater energy density lithium ion (Li-ion) batteries, but the understanding of knowledge associated with electrochemical behaviours are still needed to improve their performances further. In this study, different amount of Co content is designed in Li-rich layered compounds (0.5Li(2)MnO(3)center dot 0.5LiMn(0.5-x)Ni(0.5-x)Co(2x)O(2), 0 <= x <= 0.2), and the stepwise electrochemical activation process is applied to explore the features. We discover that the substitution of Co3+ ions can accelerate the electrochemical activation of Li2MnO3 component, and the Co-doped compound delivers much higher capacities even they suffer an apparent voltage decay comparing to the Co-free one. Besides, a fast metal ions migration exists (e. g., from the metastable tetrahedral site to the lower energy cubic site) in initial dozens of cycles (e. g., 30 cycles at 0.1C); thereafter, they likely return to the original octahedral site, as demonstrated in the voltage decay and hysteresis analysis. (c) 2018 Elsevier Ltd. All rights reserved.