The electrochemical insertion properties and safety characteristics of the alternative Li-ion positive electrode material, lithium iron sulfide (Li2FeS2) are presented. The active material is synthesized by a low cost, proprietary solid-state method. In terms of specific energy, the Li2FeS2 material offers a significant advantage over conventional lithium-ion positive electrode materials. The fully de-lithiated (charged) Li2−x FeS2 phase also demonstrates outstanding thermal stability suggesting that it may represent an excellent choice for safe, large format Li-ion battery applications.