Hybrid material passivation approach to stabilize the silicon nanowires in aqueous electrolyte for high-energy efficient supercapacitor

The rapid oxidation of silicon nanowires (SiNWs) in an aqueous electrolyte imposes boundaries on their real-world applications. To alleviate this drawback, we propose a novel yet simple hybrid material passivation strategy to increase the energy storage capacity and aqueous electrolyte stability of SiNWs for high-energy efficient supercapacitor (SC) applications. Initially, a porous-activated carbon coating was applied to one-dimensional (1-D) metal-assisted chemically-etched (MACE) SiNWs. Later, the redox-active binary nickel cobaltite (NiCo2O4) fine nanoflakes were directly deposited over the carbonized SiNWs via a hydrothermal route. The resultant 1D core-shell architectured hierarchical SiNWs/carbon(C)/NiCo2O4(NCO) (SiNWs/C/NCO) electrode exhibit a peak capacitance of 2166 F/g, with excellent cycling stability over 10,000 charge-discharge cycles in a KOH electrolyte demonstrates its potential practical applications. To prove this claim, the symmetric hybrid SCs was designed. Notably, the symmetric hybrid SCs delivered an excellent energy density of 1.31 mWh/cm(3) at a current density of 1 mA/cm(2) with an outstanding energy efficiency (similar to 70-80% over all current densities), which signified a lower energy waste during the discharge process. These results showed that the hybrid material passivation strategy is useful for boosting the energy storage capacity and aqueous electrolyte stability of SiNWs to develop low-cost, high-energy SCs for real-life applications.