Self-Organized Core–Shell Structure for High-Power Electrode in Solid-State Lithium Batteries

Effect of Al-substitution for Co on the electrode properties of LiCoO 2 is investigated in a sulfide solid electrolyte. The substitution decreases the electrode resistance and thus improves the high-rate capability. Investigation of the post-annealing effect revealed that, although the crystal structure or morphology of the LiAl x Co 1– x O 2 are not significantly changed by the post-annealing, the electrode properties are highly dependent on the post-annealing conditions, which suggests that the improvement in high-rate capability comes from the change in surface structure of the LiAl x Co 1– x O 2 particles (i.e., self-organized core–shell structure). The Al-substituted LiCoO 2 obtained through this study delivers a discharge capacity of 115 mAh g –1 at 1 C and 84 mAh g –1 even at a high discharge rate of 5 C at 25 °C, which is one of the highest rate capabilities observed in solid-state cells.