  We explore LiNiO2-based cathode materials with two-element substitutions by
an ab initio simulation based materials informatics (AIMI) approach. According
to our previous study, a higher cycle performance strongly correlates with less
structural change during charge-discharge cycles; the latter can be used for
evaluating the former. However, if we target the full substitution space, full
simulations are infeasible even for all binary combinations. To circumvent such
an exhaustive search, we rely on Bayesian optimization. Actually, by searching
only 4% of all the combinations, our AIMI approach discovered two promising
combinations, Cr-Mg and Cr-Re, whereas each atom itself never improved the
performance. We conclude that the synergy never emerges from a common strategy
restricted to combinations of "good" elements that individually improve the
performance. In addition, we propose a guideline for the binary substitutions
by elucidating the mechanism of crystal structure change.
