Control of the Phase Fractions in Layered Rock Salt and Spinel-Type Li-(Mn,Co,Ni)-O Epitaxial Thin Films: a Model Blended Cathode System for Lithium Batteries

Control over the fractions of layered rock salt and spinel-type phases in Li-(Mn,Co,Ni)-O electrodes was demonstrated using a pulsed laser deposition method. Li-(Mn,Co,Ni)-O epitaxial thin films were deposited on a SrTiO3 (110) substrate and laser energy density (or fluence) was varied to obtain phase fraction control. X-ray diffraction measurements confirmed that the thin films had layered rock salt and spinel-type phases with (1-18) and (110) orientations, respectively. Systematic changes of the phase fraction with fluence variation were clearly confirmed. Relatively low fluence (<900 mJ cm−2) favors the formation of a layered phase while the spinel phase is obtained with higher fluence values (>1000 mJ cm−2). The lithium content in the film determines the fraction of each phase, and higher fluence values lead to lower lithium contents in the spinel phase. These two-phase films show lithium (de)intercalation activities with blended electrode characteristics in their cyclic voltammograms. These films could serve as model electrodes allowing analysis of the reactions of blended Li(Mn,Co,Ni)O2 systems under battery operation conditions.