Investigation of Li1.17Ni0.20Mn0.53Co0.10O2 as an Interesting Li‐ and Mn‐Rich Layered Oxide Cathode Material through Electrochemistry, Microscopy, and In Situ Electrochemical Dilatometry

Abstract Despite their high capacity, Li‐ and Mn‐rich layered oxide cathode materials suffer from capacity fading during prolonged cycling when cycled to potentials higher than 4.5 V vs. Li+/Li. In the work reported herein, we have synthesized the Li‐ and Mn‐rich Li1.17Ni0.20Mn0.53Co0.10O2 cathode material by using a sol‐gel method. The composition and structure are analyzed by ICP, XRD, SEM, and TEM. During testing in half‐cells between 2.5 and 4.6 V vs. Li+/Li at 20 mA g−1, the initial capacity of about 165 mAh g−1 increases during cycling, reaching about 200 mAh g−1 after 30 cycles. The capacity then slowly fades, reaching 188 mAh g−1 after 120 cycles. Also, a high average discharge potential of 3.8 V is obtained, which decreases to 3.6 V after 120 cycles. This study leads to new insights about the effect of Ni concentration on the stability of the Li‐ and Mn‐ rich cathode materials. The in situ electrochemical dilatometry (ECD) study demonstrates an irreversible process during the 1st cycle, which can be related to the activation of Li2MnO3. During subsequent cycles, the electrodes’ thickness does not change, which reflects a morphological stabilization, in contrast to the continuous electrochemical instability of these materials upon cycling.