Activated Zn²⁺ and NH₄⁺ Storage in MoS₂ via Homologous Substitution with Highly Electronegative Elements.

Abstract

Aqueous energy storage devices hold great promise in the renewable energy field, owing to their low cost and environmental friendliness. MoS₂ is a potential electrode material due to its open layered structure, but its performance is constrained by inherently inert basal planes and scarcity of active sites. Herein, Mo_0.99W_0.01O_0.17S_{1.83-<i>x</i>} with localized 1T phases, lattice defects, and sulfur vacancies is prepared by a highly electronegative W/O co-substitution strategy. Theoretical calculations and experiments systematically reveal the multilevel advantages of the W/O co-substitution strategy, including optimization of the electronic structure, inducing defects and vacancies, which synergistically build charge and ion channels and lower energy barriers to accelerate the reaction kinetics. Therefore, Mo_0.99W_0.01O_0.17S_{1.83-<i>x</i>} exhibits excellent Zn²⁺ (284.7 mAh g^-1 at 0.10 A g^-1 and 80.4% capacity retention after 3200 cycles) and NH₄⁺ (153.4 mAh g^-1 at 0.50 A g^-1 and 82.6% capacity retention after 12,000 cycles) storage performance. Furthermore, ex situ characterizations suggest that the energy storage mechanism is reversible insertion/extraction of Zn²⁺ in layers and reversible adsorption/desorption of NH₄⁺, as well as dynamic reconfiguration of hydrogen bonds, accompanied by 2H/1T phase transitions. This work provides an effective approach for the universal design of aqueous energy storage systems.