Fullerene Materials for Lithium-ion Battery Applications

Abstract

Novel and high-performance anode materials based on modified fullerene materials, for lithium-ion rechargeable batteries were developed. The technical feasibility of lithium-ion intercalation and de-intercalation based on the degree of anion or atomic modification of the fullerene was examined. In this approach the fullerene molecule is viewed as a large anchor molecule to which various anion or atoms can be attached to form C ₆₀ A _x , where A could be hydrogen. The lithium-ion intercalation and de-intercalation could be driven by the formation of C ₆₀ A_xLi_x. This could result in anode materials with a potential capacity of >1200 mAh/g. Fullerenes (mixed C ₆₀ /C ₇₀ , pure C ₆₀ , and pure C ₇₀ ) and hydrogenated fullerenes, both as thin film and as pasted powdered electrode in solid polymer and liquid electrolyte, were investigated. The results of this investigation demonstrated that (1) capacities of a thin film fullerene electrode in a solid polymer electrolyte were found to be low, corresponding to three lithium ions per fullerene molecule, (2) thin film hydrogenated fullerene electrodes resulted in a significant increase in capacity, and lithium-ion intercalation was found to correspond exactly to the degree of hydrogenation of fullerenes, and (3) only certain hydrogenated fullerenes were, surprisingly, found to be effective as high-performance anode materials in liquid electrolyte. Capacities as high as 1100 mAh/g of hydrogenated fullerenes were achieved. This capacity was again found to correspond to the degree of fullerenes hydrogenation of this specific fullerene. In addition, it was found that hydrogenated fullerenes can be added in small quantities to commercial carbon to significantly reduce the irreversible capacity and improve their reversible capacity.