Few-Layered MoSe₂ Nanosheets Confined in N,P-Doped Carbon Polyhedra for Sodium/Potassium-Ion Storage

Few-layered MoSe2 nanosheets are significant for energy storage due to more active edges and improved conductivity. Herein, the cavity confinement effect of structure-defected UiO-66-NH2 is applied to host H3PMo12O40 units, which can be transformed into few-layered MoSe2 nanosheets confined into N,P-doped carbon polyhedrons (MoSe2/N,P-C) for fast Na+/K+-ion storage. Also, this unique architecture can provide sufficient active sites, alleviate the mechanical strain, and offer spacious channels for Na+/K+-ion transfer. Particularly, MoSe2/N,P-C(5:1) possesses superior sodium storage capability (316 mA h g–1 at 2.0 A g–1 within 300 cycles), promoted by the accelerated reaction kinetics and capacitive effect. In addition, an ultralong cycling stability with an expected capacity of 177 mA h g–1 (1.0 A g–1 after 1000 cycles) and a high rate capability (139.9 mA h g–1 at 10.0 A g–1) can be achieved for the K+-ion storage. Ex situ Raman spectra and X-ray diffraction analysis imply a combined mechanism of a reversible intercalation–conversion process for active MoSe2 and partial reversibility of the N,P-C skeleton. In addition, the assembled MoSe2/N,P-C//Na3V2(PO4)3/C full cell also exhibits a capacity of 322.5 mA h g–1 at 0.5 A g–1, implying the potential application in practice.