Flexible All-Solid-State Supercapacitors of High Areal Capacitance Enabled by Porous Graphite Foams with Diverging Microtubes

The practical applications of wearable electronics rely on the successful development of flexible and integrable energy devices with small footprints. This work reports a completely new type of graphite foam made of strategically created superstructures with covalently attached diverging microtubes, and their applications as electrode supports for binder-free and additive-free flexible supercapacitors. Because of the enhanced volumetric surface areas compared to conventional graphite foams, a high loading of pseudocapacitive materials (Mn3O4, 3.91mg cm(-2), 78 wt%) is achieved. The supercapacitors provide areal capacitances as high as 820 mF cm(-2) at 1mV s(-1), while still maintaining high rate capability and 88% retention of capacitance after 3000 continuous charging and discharging cycles. When assembled as all-solid-state flexible symmetric supercapacitors, they offer one of the highest full-cell capacitances (191 mF cm(-2)) among similar manganese oxide/graphene foams, and retain 80% capacitance after 1000 mechanical cycles. The potential of such flexible supercapacitors is also manifested by directly powering electric nanomotors that can trace along letters U and T, which is the first demonstration of flexible supercapacitors for wireless/portable nanomanipulation systems. This work could inspire a new paradigm in designing and creating 3D porous micro/nanosuperstructures for an array of self-powered electronic and nanomechanical applications.