Passivation of silicon nanowires with Ni particles and a PEDOT/MnOX composite for high-performance aqueous supercapacitors

Considering its integration with other electronics, three-dimensional (3D) silicon with a large surface area is an attractive electrode substrate for supercapacitors (SCs). However, the poor silicon surface stability as well as the corresponding complicated and expensive protective fabrication process impede the practical applications of silicon-based SCs. In this work, a novel electrode was developed with a simple and facile solution method, where electrodeposited Ni particles served as the current collector layer (CC-layer) and the composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and manganese dioxide (MnOx) prepared via the one-step co-electrodeposition method worked as active materials. The compact layer generated from Ni particles and PM was tightly wrapped around SiNWs, protecting the silicon surface from oxidation/corrosion. The deposition time of the Ni particles and PM was investigated. To further improve the electrochemical performance of the electrode, Pt nanoparticles (NPs) were introduced into the PM layer. The NP introduction not only enhanced the conductivity of the electrode but also made the surface become more hydrophilic, favoring the ion/charge transport. Benefiting from the large surface areas of SiNWs, the high conductivity of the CC-layer generated from the Ni particles, the high-capacity of PM and the hydrophilic surface resulting from Pt decoration, the synthesized NSi@PM–Pt electrode demonstrates a high areal specific capacitance of 207.43 mF cm−2 at 1 mA cm−2. The symmetric device delivers a maximum energy density of 0.006 mW cm−2 with a good stability retention up to 94.6% over 5000 cycles. The results afford a promising solution strategy to prepare high-performance silicon-based SCs with a simple, facile and cost-effective method.