Confining PMo12 in flexible nanocages for enhanced electrochemical energy storage

The confinement can effectively overcome aggregation and detachment of polyoxometalates (POMs) from supports, thereby enhancing their energy storage properties. However, static confinement still inevitably leads to insufficient exposure of active sites, affecting the full stimulation of their activities. Herein, by tailoring the functional groups of the crosslinker, we engineered nanocages with a transition from rigid to flexible structures, enabling dynamic confinement of phosphomolybdic acid (PMo 12 ) in a hybrid hydrogel. Theoretical calculations reveal that compared to rigid nanocages, flexible nanocages with abundant structural configurations enable dynamic confinement of PMo 12 without detachment. Moreover, structural flexibility of nanocages stimulates more active sites of PMo 12 , accelerating proton-coupled electron transfer during the charge/discharge process. Thus, the flexible nanocage-based symmetrical supercapacitor delivers a high power density of 35.0 mW cm −2 at energy density of 0.052 mWh cm −2 . This work provides a flexible nanocage confinement strategy for anchoring POMs in energy-related applications