Stable and high-capacity SiO negative electrode held in reversibly deformable sponge-like matrix of carbon nanotubes

A lightweight, high-capacity negative electrode was developed by suspending carbon-coated silicon monoxide (SiO/C) particles in a sponge-like matrix of carbon nanotubes (CNTs) without using metal foils or polymeric binders. High initial delithiation capacities per electrode (SiO/C + CNT) of >1200 mA h gelectrode−1 and >1100 mA h cmelectrode−3 were achieved with an optimum SiO/C content of 85 mass%. The lithiation/delithiation cycle with capacity control at a 45% SiO utilization ratio achieved a high delithiation capacity of 584 mA h gelectrode−1 for 236 cycles. In addition, the flexible and electrically conductive CNT sponge matrix enabled reversible expansion/shrinkage of the entire electrode during lithiation/delithiation, as evidenced by scanning electron microscopy.