Tuning Electrochemical Properties of Tungsten Oxides Nanoplates via Sn Doping and Mixed-Phase Formation for Superior Quasi-Solid-State Asymmetric Supercapacitor

Abstract

The development of high-performance electrode materials remains a critical challenge in advancing next-generation pseudocapacitors due to its low electrical conductivity, slow ion diffusion, and structural instability during long-term cycling. The hydrated tungsten oxide (WO3·H2O) has emerged as a promising candidate owing to its layered structure and abundant interlayer water. However, its electrochemical performance is still constrained by limited active sites and inefficient charge-transfer kinetics. To overcome these limitation, Sn doping and controlled phase engineering of WO3·H2O have been implemented to enhance the intrinsic electrochemical properties. Sn-doped WO3·H2O was synthesized at various doping concentrations via a simple wet chemical method, followed by annealing to achieve mixed phases of Sn-doped WO3·H2O and WO3. Furthermore, the electrochemical measurements exhibited a significant enhancement in specific capacitance, with doping concentration i.e. W0, SnW5, and SnW25 delivering specific capacitance of 115 F g-1, 146 F g-1, and 182 F g-1 at 1 A g-1, respectively. Similarly, among annealed samples (SnW200, SnW400 and SnW600), SnW200 exhibited the highest capacitance of 323 F g-1, demonstrating the synergestic effect of defect modulation and mixed-phase interaction. Eventually, the fabricated quasi-solid-state asymmetric supercapacitor (QSSAS) device achieved 36 F g-1, an energy density of 11 W h kg-1, and a power density of 5795 W kg-1, while retaining 72% capacitance over 10,000 cycles. This work highlights Sn-doped tungsten oxides as a promising and scalable route for developing durable, high-energy-density pseudocapacitors.