A new approach to investigate Li2MnO3 and Li(Ni0.5Mn0.3Co0.2)O2 mixed phase cathode materials
In this work, cathodes consisting of a Mn–rich electrochemically inactive Li2MnO3 phase and a Li(Ni0.5Mn0.3Co0.2)O2 (NMC) phase are processed by pulsed laser deposition (PLD). Different from the traditional bulk/powder synthesis approach, pure materials of the two phases are either uniformly integrated by co-deposition of the two phases or deposited sequentially as a layered structure, to emulate Li-rich mixed phase cathode materials. A high deposition temperature, 750 °C, was used to grow the films on c-cut sapphire and stainless steel substrates. The films either in a random form or in a more controlled multilayer-type, both show excellent film quality. The multilayer composite films show superior capacity, cycling and rate capabilities, with a capacity of 293 mA h g−1 at 0.05 C. This method gives much better control of the Mn content of the cathode, phase purity and combination schemes, i.e., mixing at the atomic level or embedding Li2MnO3 domains of different sizes in the NMC matrix or both. Moreover, this approach can be applied to screen lithium-rich Mn phase and other novel material combinations in a more controlled and expedient manner.