Unveiling Interstitial Anionic Electron-Driven Ultrahigh K-Ion Storage Capacity in a Novel Two-Dimensional Electride Exemplified by Sc 3 Si 2 .

Two-dimensional (2D) electrides, characterized by excess interstitial anionic electron (IAE) in a crystalline 2D material, offer promising opportunities for the development of electrode materials, in particular in rechargeable metal-ion batteries applications. Although a few such potential electride materials have been reported, they generally show low metal-ion storage capacity, and the effect of IAE on the ion storage performance remains elusive so far. Here we report a novel 2D electride, [ScSi]·1e, with fascinating IAE-driven high alkali metal-ion storage capacity. In particular, its K-ion specific capacity can reach up to 1497 mA h g, higher than any previously reported 2D materials-based anodes in K-ion batteries (PIBs). The IAE in the [ScSi]·1e crystal accounts for such high capacity behavior, which can drift away and balance the charge on the metal-cation, playing a crucial role in stabilizing the metal-ion adsorption and enhancing multilayer-ions adsorption. This proposed IAE-driven storage mechanism provides an unprecedented avenue for the future design of high storage capacity electrode materials.