Facile Synthesis of Metal Oxide and Conductive Polymers around Silicon Nanowire Arrays for a High-Performance Aqueous Supercapacitor

Abstract

Si-based supercapacitors have drawn much attention due to their compatibility with current Si-based microelectronics. However, complicated and expensive manufacturing technologies greatly restrict their practical applications. In this work, a supercapacitor electrode based on metal oxide and conductive polymers around silicon nanowire arrays (SiNWs) was first designed with a simple, facile, and low-cost method. The manganese dioxide (MnO2) and poly(3,4-ethylenedioxythiophene) (PEDOT) composite (PM) was coelectrodeposited on the SiNWs followed by spin-coating the high conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layer doped with silver nanowires (PsAg). Thin reduced graphene oxide (rGO) sheets were inserted between the PM and PsAg for further enhancing the capacity of the electrode. Resulting from the large gaps caused by the tetramethylammonium hydroxide (TMAH) solution treatment, a three-dimensional (3D) hierarchical double-shelled structure of current collect layers (PsAg combined with rGO) and active material (PM) decorated SiNWs was formed (Si/PM/rGO-PsAg), which not only reduced the contact resistance between the active materials and current collector but also shortened the ion and electron diffusion paths. With the smart design, the prepared Si/PM/rGO-PsAg could be measured in an aqueous solution and exhibited outstanding electrochemical properties, including high areal capacitance (100.98 mF cm–2 at 1.5 mA cm–2) and excellent cycling stability (80.85% capacitance retention after 2000 cycles). Additionally, the practical applicability of the synthesized Si/PM/rGO-PsAg was investigated by fabricating a symmetric device, which displayed 85.91% retention over 5000 cycles and a maximum energy density of 0.0034 mWh cm–2. Our design concept opens up an avenue to prepare 3D silicon nanostructures based on metal oxide and conductive polymers for low-cost and high-performance supercapacitors.