Carbon Nanostructures (CNS): Highly Conductive Matrix for Lithium Ion Battery Electrodes

Traditional conductive carbon and polymer binder plays an important role for fabrication of lithium ion battery electrodes. Conductive carbon provides conductive pathways between the electrode particles specially for low electrical conductivity electrode materials and current collector,at the same time, the binder helps to provide mechanical integrity for electrode material. In this work, carbon nanostructres are presented as a highly conductive matrix material for fabrication of electrode without using any polymer binder. CNS consists of highly crosslinked and covalently bonded carbon nanotubes and forms a free standing films after reassembling from a CNS dispersed solution. CNS have high surface area, high electrical conductivity, low cost   and environmently benign synthesis process. CNS/LiFePO₄ cathode is fabricated using a facile process using water/ethanol mixture. No organic solvent is used for electrode fabrication. Scanning electron micrograms of the CNS/LiFePO₄ electrode shows that LiFeO₄ electrode particles are entraped by the entangled carbon nanostructures and provide high electrical conductivity pathways. LiFePO₄/CNS electrode shows high electrical conductivity of 9.1 S/cm compared to the 0.4 S/cm for conventional LiFePO₄/Carbon electrode. Cyclic voltammetry results show that CNS/LiFePO₄ has low polarization potential compared to C/LiFePO₄. This is attributed due to highly conductive pathways offered by the CNS. Charge-discharge performance of the CNS/LiFePO₄ in half cell demonstrated improved capacity retention at high discharge rates.