Simple and novel strategy to fabricate ultra-thin, lightweight, stackable solid-state supercapacitors based on MnO2-incorporated CNT-web paper

Thin, lightweight, stackable, solid-state supercapacitors are in great demand in the electronics industry because of their use in miniaturized devices. Herein, we report a simple and novel strategy to fabricate ultra-thin, lightweight, and stackable symmetric supercapacitors using MnO2-incorporated carbon nanotube (CNT)-web paper. SEM and TEM analyses revealed a uniform nanometer-scale coating of MnO2 on the individual fibers of the CNT-web paper after simple deposition at room temperature. The network structure of free-standing conductive CNT-web paper provides a short diffusion path, allowing for complete utilization of MnO2 in the charge storage process. A MnO2/CNT-web paper electrode showed an excellent areal capacitance of 135 mF cm−2 at 5 mV s−1 with a remarkable capacitance retention of 95% after 10,000 cycles. A symmetric solid-state supercapacitor containing MnO2/CNT-web paper displayed a high areal capacitance of 57 mF cm−2 with an energy density of 0.018 mWh cm−2 and a capacitance retention as high as 86% after 10,000 cycles. In addition, the voltage and capacitance were tripled by simply stacking three symmetric supercapacitors and connecting them in series and in parallel, respectively. We are optimistic that the excellent performance of the ultra-thin CNT-web paper-based supercapacitors demonstrated here will facilitate the development of compact supercapacitor banks in the near future.