Rate capability of LiNi0.8Co0.15Al0.05O2 in solid-state cells was investigated with 70Li2S-30P2S5 glass-ceramics as a sulfide solid electrolyte. It showed higher rate capability than LiCoO2; discharge capacity observed at a current density of 10mAcm−2 was ca. 70mAhg−1. Surface coating with Li4Ti5O12 onto the LiNi0.8Co0.15Al0.05O2 particles further improved the high-rate performance to give ca. 110mAhg−1. The rate capability promises to realize all-solid-state lithium secondary batteries with very high performance.