Deactivating Defects in Graphenes with Al₂O₃ Nanoclusters to Produce Long‐Life and High‐Rate Sodium‐Ion Batteries

Abstract Carbon materials are the most promising anodes for sodium‐ion batteries (SIBs), but low initial Coulombic efficiency (ICE) and poor cyclic stability hinder their practical use. It is shown herein, that an effective but simple remedy for these problems can be achieved by deactivating defects in the carbon with Al₂O₃ nanocluster coverage. A 3D porous graphene monolith (PGM) is used as the model material and Al₂O₃ nanoclusters around 1 nm are grown on the defects of graphene. It is shown that these Al₂O₃ nanoclusters suppress the decomposition of conductive sodium salt in the electrolyte, resulting in the formation of a thin and homogenous solid electrolyte interphase (SEI). In addition, Al₂O₃ nanoclusters appear to reduce the detrimental etching of the SEI by hydrogen fluoride (HF) and improve its stability. Therefore, after the introduction of Al₂O₃ nanoclusters, the ICE, cyclic stability, and rate capability of the PGM are greatly improved. A higher ICE (70.2%) and capacity retention (82.9% after 500 cycles at 0.5 A g⁻¹) than those of normally reported for large surface area carbons are achieved. This work indicates a new way to deactivate defects and modify the SEI of carbon materials, and hopefully accelerate the commercialization of carbon materials as anode materials for SIBs.