High‐Performance Flexible All‐Solid‐State Supercapacitors Based on Ultralarge Graphene Nanosheets and Solvent‐Exfoliated Tungsten Disulfide Nanoflakes

Flexible all-solid-state supercapacitors (FASS) attract tremendous attention as energy supplies for wearable electronic devices. Graphene nanosheets have gained lots of interest in paper-like flexible electrodes in FASS due to their unique 2D structure and high mechanical and electrical properties. However, the essential feature of electric double-layer performance for simple graphene nanosheet-based FASS restricts the improvement of their capacitive performance and practical applications. This study reports the design of FASS based on ultralarge graphene nanosheets and solvent-exfoliated tungsten disulfide (WS2) nanoflakes. The free-standing ultralarge graphene nanosheets/WS2 nanoflakes composite paper electrodes are assembled by vacuum-assisted filtration. With WS2 nanoflakes intercalated between graphene nanosheets, the ultralarge graphene nanosheets/solvent-exfoliated WS2 nanoflakes composite paper still exhibits excellent mechanical stability, flexibility, and electrical conductivity. The nacre-like structures of the papers could efficiently integrate both merits of pseudocapacitive WS2 nanoflakes and conducting graphene, resulting in extraordinary electrochemical performance in FASS. The highest areal specific capacitance of 312.4 mF cm−2 for FASS is achieved with a high capacity retention of ≈88.1% after 5000 charge–discharge cycles. Meantime, the areal power and energy densities of the ultralarge graphene nanosheets/WS2 nanoflakes paper-based FASS device have a high energy density of 23.1 Wh kg−1 at a power density of 83.2 W kg−1.