All-Solid-State Lithium Secondary Battery with Li[sub 2]S–C Composite Positive Electrode Prepared by Spark-Plasma-Sintering Process

Electrochemically active lithium sulfide–carbon composite positive electrodes, prepared by the spark plasma sintering process, were applied to all-solid-state lithium secondary batteries with a glass electrolyte. The electrochemical tests demonstrated that cells showed the initial charge and discharge capacities of ca. 1010 and , respectively, which showed higher discharge capacity and coulombic efficiency (ca. 91%) than the cells with nonaqueous liquid electrolytes (ca. and ca. 27%, respectively). The ex situ S K-edge X-ray absorption fine structure measurements suggested the appearance and disappearance of elemental sulfur in the positive electrodes after charging and discharging, respectively, indicating that the ideal electrochemical reaction proceeded in the present all-solid-state cells. Such ideal electrochemical reaction, due probably to the suppression of the dissolution of in the form of polysulfides into the electrolytes, would result in higher coulombic efficiency and discharge capacity as compared with those of the liquid-electrolyte cells.