A new approach to investigate Li2MnO3 and Li(Ni0.5Mn0.3Co0.2)O2 mixed phase cathode materials

Abstract

In this work, cathodes consisting of a Mn–rich electrochemically inactive Li₂MnO₃ phase and a Li(Ni_0.5Mn_0.3Co_0.2)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.