Hierarchical Spatial Confinement Unlocking the Storage Limit of MoS₂ for Flexible High-Energy Supercapacitors

Molybdenum sulfide (MoS₂) is a promising electrode material for supercapacitors; however, its limited Mo/S edge sites and intrinsic inert basal plane give rise to sluggish active electronic states, thus constraining its electrochemical performance. Here we propose a hierarchical confinement strategy to develop ethylene molecule (EG)-intercalated Co-doped sulfur-deficient MoS₂ (Co-EG/S_V-MoS₂) for efficient and durable K-ion storage. Theoretical analyses suggest that the intercalation-confined EG and lattice-confined Co can enhance the interfacial K-ion storage capacity while reducing the K-ion diffusion barrier. Experimentally, the intercalated EG molecules with mildly reducing properties induced the creation of sulfur vacancies, expanded the interlayer spacing, regulated the 2H-1T phase transition, and strengthened the structural grafting between layers, thereby facilitating ion diffusion and ensuring structural durability. Moreover, the Co dopants occupying the initial Mo sites initiated charge transfer, thus activating the basal plane. Consequently, the optimized Co-EG/S_V-MoS₂ electrode exhibited a substantially improved electrochemical performance. Flexible supercapacitors assembled with Co-EG/S_V-MoS₂ delivered a notable areal energy density of 0.51 mW h cm^-2 at 0.84 mW cm^-2 with good flexibility. Furthermore, supercapacitor devices were integrated with a strain sensor to create a self-powered system capable of real-time detection of human joint motion.