Pseudocapacitive Kinetics in Synergistically Coupled MoS₂-Mo₂N Nanowires with Enhanced Interfaces toward All-Solid-State Flexible Supercapacitors.

Abstract

Pseudocapacitive kinetics in rationally engineered nanostructures can deliver higher energy and power densities simultaneously. The present report reveals a high-performance all-solid-state flexible symmetric supercapacitor (FSSC) based on MoS₂-Mo₂N nanowires deposited directly on stainless steel mesh (MoS₂-Mo₂N/SSM) employing DC reactive magnetron co-sputtering technology. The abundance of synergistically coupled interfaces and junctions between MoS₂ nanosheets and Mo₂N nanostructures across the nanocomposite results in greater porosity, increased ionic conductivity, and superior electrical conductivity. Consequently, the FSSC device utilizing poly(vinyl alcohol)-sodium sulfate (PVA-Na₂SO₄) hydrogel electrolyte renders an outstanding cell capacitance of 252.09 F·g^-1 (44.12 mF·cm^-2) at 0.25 mA·cm^-2 and high rate performance within a wide 1.3 V window. Dunn's and <i>b</i>-value analysis reveals significant energy storage by surface-controlled capacitive and pseudocapacitive mechanisms. Remarkably, the symmetric device boosts tremendous energy density ∼10.36 μWh·cm^-2 (59.17 Wh·kg^-1), superb power density ∼6.5 mW·cm^-2 (37.14 kW·kg^-1), ultrastable long cyclability (∼93.7% after 10,000 galvanostatic charge-discharge cycles), and impressive mechanical flexibility at 60°, 90°, and 120° bending angles.