Reactivity at the Electrode–Electrolyte Interfaces in Li-Ion and Gel Electrolyte Lithium Batteries for LiNi_0.6Mn_0.2Co_0.2O₂ with Different Particle Sizes

The layered oxide LiNi0.6Mn0.2Co0.2O2 is a very attractive positive electrode material, as shown by the good reversible capacity, chemical stability, and cyclability upon long-range cycling in Li-ion batteries and, hopefully, in the near future, in all-solid-state batteries. Three samples with variable primary particle sizes of 240 nm, 810 nm, and 2.1 μm on average and very similar structures close to the ideal 2D layered structure (less than 2% Ni2+ ions in Li+ sites) were obtained by coprecipitation followed by a solid-state reaction at high temperatures. The electrochemical performances of the materials were evaluated in a conventional organic liquid electrolyte in Li-ion batteries and in a gel electrolyte in all-solid-state batteries. The positive electrode/electrolyte interface was analyzed by X-ray photoelectron spectroscopy to determine its composition and the extent of degradation of the lithium salt and the carbonate solvents after cycling, taking into account the changes in particle size of the positive electrode material and the nature of the electrolyte.