Low‐Resistive LiCoO 2 /Li 1.3 Al 0.3 Ti 2 (PO 4 ) 3 Interface Formation by Low‐Temperature Annealing Using Aerosol Deposition

Interfacial resistance at electrode‐high Li + conductive solid electrolytes must be reduced well to develop high‐power all‐solid‐state batteries using oxide‐based solid electrolytes (Ox‐SSBs). Herein, crystalline electrode films of LiCoO 2 (LCO) are formed on a high Li + conductive crystalline‐glass solid electrolyte sheet, Li 1.3 Al 0.3 Ti 2 (PO 4 ) 3 (LATP) ( σ 25 °C  = 1 × 10 −4  S cm −1 ), at room temperature by aerosol deposition (AD), and the effects of the annealing temperature on the interfacial resistivities ( R int ) at the LCO/LATP are investigated. The R int visibly increases by annealing over 500 °C with the growth of Co 3 O 4 as a reactant. In contrast, R int is reduced to ≈100 Ω cm 2 by low‐temperature annealing at 250–350 °C due to superior contact through the structural rearrangement of an artificial metastable interface formed by the AD. These results are applied to bulk‐type Ox‐SSB, Li/Li 7 La 3 Zr 2 O 12 (LLZ)/LCO–LATP, and our best Ox‐SSB delivers a discharge capacity of 100 mA cm −2 at 100 °C.