Carbon Nanotube Enhanced Lithium Ion Batteries

Abstract

Lithium ion battery electrode designs employing carbon nanotubes (CNTs) have recently demonstrated increased battery energy and power densities through use as a conductive additive or a current collector replacement. CNTs as conductive additives can enhance the loading (thickness and areal capacity) of composite coatings, rate capability, and thermal stability of electrodes with traditional active materials. Anodes consisting of germanium nanoparticles (Ge-NP) and single wall carbon nanotube (SWCNT) additives have recently demonstrated active material specific capacities ~3x greater than traditional graphitic anodes. Rate performance is dramatically improved with SWCNT conductive additives, which is necessary for Li + extraction rates above C/5 at increased areal capacities. In addition, free-standing CNT electrodes provide a lightweight, conductive structure to effectively support high capacity anode active materials like Si and Ge. The electrode extraction capacities of Si-CNT anodes are shown to exceed 1000 mAh/g. Since nanostructured anodes exhibit large irreversible first cycle capacity loss, Stabilized Lithium Metal Powder has been effectively used to pre-lithiate both Si-CNT and Ge NP anodes. Thus, application of these pre-lithiated anodes can allow for the intended capacity to be realized in full batteries when paired with a traditional cathode. An example of Si-CNT anodes paired with NCA cathodes has shown successful capacity matching, has achieved over 1500 cycles, and demonstrated the potential for a cell energy density of 300 Wh/kg.