Solution-processable hierarchical SiNW/PEDOT/MnOx electrodes for high-performance supercapacitors

Abstract

Si-Based supercapacitors (SCs) have drawn considerable attention due to their inherent integration with the current Si-based microelectronics. However, the complicated and expensive manufacturing processes severely limit their practical applications. Composites of metal oxides and conductive polymers are regarded as promising active materials in SCs due to their high specific capacitance, good conductivity, and easy fabrication. Nevertheless, to the best of our knowledge, there are very few reports on their applications in Si-based SCs. Herein, a composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and manganese oxide (MnO_x) modified silicon nanowire arrays (SiNWs) was elaborately designed and well prepared using a facile, simple, and low-cost method, where PEDOT was electropolymerized on SiNWs followed by dipping in KMnO₄ solution. Platinum (Pt) particles were introduced between PEDOT and MnO_x, which not only enhanced the mass-loading of MnO_x but also improved the conductivity of the composite. After spin-coating poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) layer doped with silver nanowires (PsAg) on the composite, a hierarchical core–shell electrode comprising active materials and current collector was formed. Benefiting from the large surface area of porous SiNWs/PEDOT, high mass-loading of MnO_x, and shorter electron/ion transfer paths, an excellent areal capacitance of 352.08 mF cm⁻² at 2 mA cm⁻² was achieved by the synthesized SiNW/PEDOT@Pt/MnO_x electrode, which is superior to almost all the previously reported areal capacitance values of Si-based electrodes. Additionally, a symmetric device was prepared to investigate its practical applicability, which displayed a maximum energy density of 0.049 mW h cm⁻² and considerable retention of 85.25% over 2000 cycles. These preliminary results demonstrate that the hierarchical composites of metal oxides and conductive polymers decorated three-dimensional (3D) silicon are promising electrode materials for future low-cost and high-performance SCs.