Flexible High Energy Density Silicon Composite Anode for Structural Batteries

The challenges of using high capacity metallic lithium foil as an anode for high energy density lithium battery are still remaining despite many years of research efforts, due to the intrinsic problems associated with the electrodeposition of reactive light metals such as lithium. In addition, the required excess lithium (3-5 times) to satisfy the battery long cycle life,  and the safety concern associated with the large format cells containing metallic lithium anode have force the battery community to search for other alternatives. Some of the alternative anodes may exceed the energy density of metallic lithium when the excess lithium is considered. We will present a new class of composite anode material for structural and conformal lithium batteries. Our new composite anode is based on an optimized free-standing silicon coated carbon nanofiber in the form of flexible thin-paper with capacity exceeding 1500Ah/kg for the electrode including the carbon fiber and the silicon, and with high capacity retention during extensive charge-discharge cycles. The electrode/electrolyte interface and the silicon/carbon interface have been engineered to minimize the initial irreversibility during lithiation and delithiation, to less than 10%.  In addition, the in-plan conductivity of the free standing composite anode has been optimized for high power battery application. We will report the performances of the silicon-carbon nanofiber composite anode in half cells and in full cells against high energy density lithium-rich layered oxide, and olivine based cathodes.