Balanced approach to safety of high capacity silicon–germanium–carbon nanotube free-standing lithium ion battery anodes

Abstract

The electrochemical performance and safety of high capacity free-standing anodes for lithium ion batteries have been enhanced by the addition of silicon to Ge-nanoparticle-single wall carbon nanotube (Ge-NP:SWCNT) hybrid electrodes. Materials characterization of electrodes indicated amorphous silicon was deposited through a low-pressure chemical vapor deposition (LPCVD) process resulting in a reduction in surface area from over 900m2/g to 113m2/g after 70%w/w addition of Si. Electrochemical performance of the electrodes showed extraction capacities over 1200mAh/g for Si–Ge-NP:SWCNT free-standing anodes with coulombic efficiencies of >85% on the first cycle; this demonstrates a >40% improvement over previous free-standing Ge-NP:SWCNT electrode capacities. The thermal safety of the Si–Ge-NP:SWCNT electrodes, as measured by differential scanning calorimetry (DSC), was also improved over pure SWCNT and Ge-NP:SWCNT electrodes, evidenced by a reduced exothermic energy release. These high capacity free-standing anodes show for the first time the use of nanostructured-tailoring to balance improvements in electrochemical performance and safety.