High-Performance On-Chip Supercapacitors Based on Mesoporous Silicon Coated with Ultrathin Atomic Layer-Deposited In2O3 Films.

On-chip supercapacitors have attracted considerable attention because of their high power density, long cycling life, and compatibility with integrated circuits. One critical drawback that restricts their practical application is the low energy density. In this work, low-resistivity mesoporous silicon with a high aspect ratio is prepared by Pt film-assisted chemical etching and utilized as the scaffold of the supercapacitors. Subsequently, low-resistivity (<0.0015 Ω·cm) and ultrathin In2O3 films are coated on the mesoporous silicon scaffold by atomic layer deposition at 200 °C, serving as the active electrode material. The electrochemical measurements reveal that the coating of the In2O3 film remarkably improves the performance of the supercapacitors compared with those without the In2O3 coating. The supercapacitors with a 4.5 nm In2O3 film coating exhibit a capacitance density of 1.36 mF/cm2 at a scan rate of 10 mV/s as well as a better stability against the scan rate. In addition, it is found that the pristine mesoporous silicon walls are collapsed after 400 times of sweeping while those with the In2O3 film coating are still intact even after 2000 times of sweeping. Meanwhile, a high energy density is also achieved without sacrificing the power performance.