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 Co^3+/4+ redox reactions and, second, lithium extraction from Li_2−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.

References

[1] M.M. Thackeray, J.R. Croy, E. Lee, A. Gutierrez, M. He, J.S. Park, B.T. Yonemoto, B.R. Long, J.D. Blauwkamp, C.S. Johnson, Y. Shin, and W.I.F. David, “The quest for manganese-rich electrodes for lithium batteries: strategic design and electrochemical behavior,” Sustainable Energy & Fuels 2, 1375-1397, (2018).

[2] R.J. Gummow, M.M. Thackeray, W.I.F. David, S. Hull, “Structure and electrochemistry of lithium cobalt oxide synthesized at 400^oC," Mater. Res. Bull. 27, 327-337, (1992).

[3] E. Lee, J. Blauwkamp, F.C. Castro, J. Wu, V.P. Dravid, P. Yan, C. Wang, S. Kim, C. Wolverton, R. Benedek, F. Dogan, J.S. Park, J.R. Croy, M.M. Thackeray, "Exploring Lithium-Cobalt-Nickel Oxide Spinel Electrodes for ≥3.5 V Li-Ion Cells," ACS Appl. Mater. Inter. 8, 27720-27729, (2016).