Exploring Cobalt-Based Lithiated Spinel Cathodes

Abstract

Over recent years, our group has demonstrated that the incorporation of a spinel (S) component into ‘layered-layered’ (LL) composite electrode structures serves, as a stabilizing unit, to slow transition metal migration during electrochemical cycling.[1] However, unraveling the mechanism by which the S component operates in actual ‘layered-layered-spinel’ (LLS) materials is a challenging task because of the highly complex, inhomogeneous arrangements of the cations (typically Li, Mn, Ni, and Co) within multiple nano-domains. Moreover, relatively little is known about the structure and electrochemical properties of Co-based spinel materials, which were first reported in early 1990s[2,3], compared to Mn-based spinels. The lithiated spinel Li2Co2O4 is particularly attractive as a stabilizing agent in LLS composite electrodes for two reasons. First, cobalt has a lower propensity to migrate during electrochemical Co3+/4+ redox reactions and, second, lithium extraction from Li2−zCo2O4 (0 ≤ z ≤ 1), occurs at a potential (∼3.6 V) that is significantly higher than that of its lithiated manganese-oxide spinel analogue, Li2Mn2O4 (∼2.9 V). In this presentation, we will discuss the structure and electrochemical properties of substituted lithiated spinel materials that are easier to produce as a single phase, thereby eliminating the propensity for Li2Co2O4 samples to be contaminated by some layered LiCoO2.