Enhanced Electrochemical Capacity of Spherical Co-Free Li$_{1.2}$Mn$_{0.6}$Ni$_{0.2}$O$_{2}$ Particles after a Water and Acid Treatment and its Influence on the Initial Gas Evolution Behavior

Li-rich layered oxides (LRLO) with specific energies beyond 900 Wh kg$^{−1}$ are one promising class of high-energy cathode materials. Their high Mn-content allows reducing both costs and the environmental footprint. In this work, Co-free Li$_{1.2}$Mn$_{0.6}$Ni$_{0.2}$O$_{2}$ was investigated. A simple water and acid treatment step followed by a thermal treatment was applied to the LRLO to reduce surface impurities and to establish an artificial cathode electrolyte interface. Samples treated at 300 °C show an improved cycling behavior with specific first cycle capacities of up to 272 mAh g$^{−1}$, whereas powders treated at 900 °C were electrochemically deactivated due to major structural changes of the active compounds. Surface sensitive analytical methods were used to characterize the structural and chemical changes compared to the bulk material. Online DEMS measurements were conducted to get a deeper understanding of the effect of the treatment strategy on O$_2$ and CO$_2$ evolution during electrochemical cycling.