Zero-strain electrode materials that exhibit extremely small volume changes during intercalation reactions provide unique opportunities for highly stable lithium batteries. In particular, intecalation-induced strain in electrodes is a major factor in the degradation of advanced lithium batteries. For example, recent studies of high-performance Ni-rich layered cathodes unequivocally show a clear correlation between particle fracture, due to anisotropic volume expansion of polycrystalline grains, and continuously increasing cathode impedance.[1] Such chemo-mechanical behavior of electrode materials is even more critical to all-solid-state batteries in which the solid-solid interface between the electrode and solid electrolyte is prone to cracking and disintegration, even with small volume mismatches during electrochemical cycling. The best known zero-strain electrode material is the Ti-based spinel, Li₄Ti₅O₁₂, that has been developed as a stable anode. Recently, LiRh₂O₄ spinel has been reported as a zero-strain cathode that operates at 3.2 V vs. Li/Li⁺,[2] however, its practical use is limited by the high cost of the precious metal, rhodium. A more feasible zero-strain cathode candidate is the ‘low-temperature’ (LT) form of LiCoO₂, which adopts a cubic, lithiated spinel structure, Li₂[Co₂]O₄.[3,4] On lithium extraction, LT-LiCoO₂ provides an attractive 3.6 V vs Li. However, despite the high operating voltage and minimal volume change, this zero-strain material has received little attention since its discovery because of its poor cycling stability. In this presentation we report that cation substitution greatly improves the electrochemical perperties of LT-LiCo_1-xM_xO₂ electrodes (M = cations). The different effects of various cation substituents on electrode performance will be compared and the zero-strain intercalation mechanism in LT-LiCo_1-xM_xO₂ will be discussed.

References

[1] D. Miller, C. Proff, D.P. Abraham, and J. Bareno, Adv. Energy Mater., 3, 1098 (2013).

[2] Y. Gu, K. Taniguchi, R. Tajima, S.-i. Nishimura, D. Hashizume, A. Yamada, and H. Takagi, J. Mater. Chem. A 1, 6550 (2013).

[3] R.J. Gummow, M.M. Thackeray, W.I.F. David, and S. Hull, Mater. Res. Bull., 27, 327 (1992).

[4] 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, and M.M. Thackeray, ACS Appl. Mater. Inter., 8, 27720 (2016).