Polyacrylonitrile (PAN) was combined with elemental sulfur (S) using a facile procedure that produces a highly conductive and high capacity active material, PAN-S. PAN-S is shown in this work to be capable of extremely high energy density and good cycle stability in all-solid-state lithium batteries utilizing a sulfide based solid electrolyte. All-solid-state batteries employing PAN-S as active material maintained over 605 mAh g(-1) for 50 cycles, and composite active materials containing less sulfur resulted in lower overall specific capacity but excellent cycle stability with less than 1% loss over 50 cycles. A high energy density of over 700 Wh kg(-1) was achieved for all-solid-state lithium battery electrodes incorporating 57% active material into the cathode composite. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.052207jes] All rights reserved.