Examining Hysteresis in Composite xLi2MnO3·(1–x)LiMO2 Cathode Structures

Abstract

This paper reports the results of an initial investigation into the phenomenon of hysteresis in the charge–discharge profile of high-capacity, lithium- and manganese-rich “layered–layered” xLi2MnO3·(1–x)LiMO2 composite cathode structures (M = Mn, Ni, Co) and “layered–layered-spinel” derivatives that are of interest for Li-ion battery applications. In this study, electrochemical measurements, combined with in situ and ex situ X-ray characterization, are used to examine and compare electrochemical and structural processes that occur during charge (lithium extraction) and discharge (lithium insertion) of preconditioned cathodes. Electrochemical measurements of the open-circuit voltage versus lithium content demonstrate a ∼1 V hysteresis in site energy for approximately 12% of the total lithium content during the early cycles, which is markedly different from the hysteresis commonly observed in other intercalation materials. X-ray absorption data indicate structural differences in the cathode at the same stat...