A safe and economical electrochemically active material useful in rechargeable battery cell electrode compositions comprises a nanostructure amalgam of a transition metal fluoride and carbon. The nanoamalgam may be prepared by subjecting a precursor mixture of a transition metal fluoride, such as FeF.sub.3, and carbon to extreme, high energy impact comminution milling which results in the conversion of the mixture to a unique and distinct nanostructure material. When incorporated as active electrode material in lithium battery cell fabrications, the nanoamalgam enables the attainment of stable specific discharge capacities in the range of 250 to 500 mAh/g.