Sol-gel derived lithium iron phosphate films for efficient lithium-ion intercalation

Sol-gel derived nanostructured LiFePO4 films with controlled crystallinity and a small fraction of carbon uniformly dispersed have been fabricated and studied as cathodes for efficient lithium-ion intercalation. With appropriate control of micro-, nano- and crystal structures and surface chemistry, both high specific energy and specific power are readily achieved. For example, at a current density of 200mA/g, LiFePO4 films demonstrated an initial lithium-ion intercalation capacity of 312 mAh/g, and 218mAh/g after 20 cycles, far exceeding the theoretical storage capacity of conventional LiFePO4 electrode. The relationship between the processing condition, controlled impurities and defects, micro-, nano-, and crystal structures and the lithium-ion intercalation properties are discussed and possible mechanisms for high lithium-ion intercalation have been proposed.