Iron Tungsten Nanorods Electrode with High Capacitance: An Extraordinary Cycling Stability for Durable Aqueous Supercapacitors

Improving cycle life and rate capability through unique morphological features is beneficial for developing the energy storage capacity of supercapacitors (SC). The evolving use of abundant earth metals in low-cost metal tungstate (MWO4) with superior specific capacitance and excellent stability in nontoxic electrolytes continues to be a challenge. This work develops nanorods (NRs) architectured iron tungsten (FeWO4) electrode material for supercapacitors using a simple and industrially scalable method. The developed FeWO4 nanorods display an excellent specific capacitance of 465 F g-1 at a current density of 2 A g-1 with an admirable 98% capacitive retention over 3000 cycles. The electrode's diffusive and capacitive impacts are investigated for a detailed understanding. Next, an FeWO4 NR-based symmetric supercapacitor was assembled in an aqueous electrolyte which displays areal capacitance of 116 mF cm-2 in a potential window of 1.2 V. Surprisingly, the assembled device shows a capacitance retention of ∼93% over 50 »000 continuous cycles with no noticeable changes in electrochemical behavior. Besides giving valuable insights toward the electrochemical properties of FeWO4, this work demonstrates the potential of a device with exceptional stability in a nontoxic aqueous electrolyte that might compete with the most stable commercial carbon-based electrochemical capacitors.