Although sodium-ion supercapacitors are promising candidates for next-generation electrochemical systems, their performance

is often hindered by the relatively large ionic radius of Na⁺, which limits facile ion insertion and thus suppresses 

capacity enhancement. The high surface area and large hexagonal tunnels make colloidal monoclinic WO2.72 nanocrystals 

attractive as electrode materials, but their use in Na⁺-based supercapacitors remains unexplored. In this study, we introduce 

colloidally synthesized monoclinic WO2.72 nanocrystals capable of effectively accommodating Na⁺ ions within their hexagonal

sites for Na+-based supercapacitors. By removing insulating organic ligands, the nanocrystals are uniformly deposited

onto hydrophilic carbon cloth (CC) through a controllable, additive-free dip-coating process. Furthermore, applying 

a conformal 1 nm Al2O3 overlayer via atomic layer deposition (ALD) enhances mechanical robustness and prevents 

nanocrystal delamination, enabling highly reversible charge-storage behavior. A symmetric supercapacitor fabricated with 

ALD-treated WO2.72/CC and a PVA/Na2SO4 gel electrolyte demonstrates stable performance without degradation under 

bending, achieving an areal energy density of 10.08 µWh/cm2 at 0.3724 mW/cm2 . These results highlight the potential of colloidal nanocrystal-based electrodes for high-performance sodium-ion supercapacitors suitable for practical, wearable 

electronic applications.