Conformal Reconstruction and Dual-Vacancy Engineering Breaks Kinetics Limitations for Energetic Aqueous Dual-Cation Storage

Abstract

Efficient aqueous energy storage with non-metallic ions is highly desired but challenged by achieving kinetically favorable surface/interface storage chemistry. Herein, by refining the surface proton environment, layered double hydroxides (LDHs) with hydrogen-aluminum dual vacancies and 3D diffusion channels are demonstrated upon conformal surface reconstruction. An energetic NH4+/H+ dual-ion co-intercalation chemistry is enabled, leading to a remarkable gravimetric specific capacity of up to 604 mAh g-1 and long-cycle stability. Combining in-situ Raman spectroscopy and in-situ electrochemical quartz crystal microbalance (EQCM) techniques, we reveal and visualize the conformal reconstruction process and the reversible dual-cation storage mechanism. Density functional theory (DFT) calculation shows that the dual-vacancy coupling helps the dissolution of inert Al from LDH for enriching active sites. At the same time, the residual Al shows the pining effect on the [MnO6] octahedron to restrain the Jahn-Teller distortion. The manganese sites adjacent to Al vacancies promote the adsorption of NH4+/H+ and the H vacancies facilitate the adsorption of NH4+, responsible for an optimal dual-cation storage chemistry. This work demonstrates how the dual vacancies emerge to modulate the carrier migration and thereby the capacity, providing a viable solution of surface/interface optimization for efficient aqueous energy storage.