Composite positive electrodes composed of a LiNbO3-coated LiCoO2 active material and a Li10GeP2S12 solid electrolyte were fabricated using a mill pot rotator, applying varying rotation rates, mixing durations and mill ball sizes. Mild grinding with a low rotation rate prevented significant aggregation of Li10GeP2S12 particles during the mixing process, leading to a well-dispersed composite with a large contact area between the LiCoO2 and Li10GeP2S12. An all-solid-state battery using the optimized composite cathode with the Li10GeP2S12 electrolyte and an In-Li anode delivered a first discharge capacity of 124 mAh g(-1), which is equal to the theoretical value for LiCoO2. (C) 2015 Elsevier B.V. All rights reserved.