LIBs), delivers very limited reversible capacity in SIBs due to its inability to form stable low-stage graphite intercalation compounds (GICs). [4,5] Thus, most research has turned to nongraphitic carbons including nanocarbons and hard carbons, [6][7][8][9][10] whose capacities are significantly higher than graphite. It has been found that the structure could be well controlled to realize the high efficiency and reversibility. Our group has reported that the commercial carbon molecular sieves with abundant ultrasmall (0.3-0.5 nm) pores can achieve high efficiency and reversible capacity. [11] Intensive researches have also revealed that the nongraphitic carbons with low specific surface areas (SSA) exhibit a high electrochemical stability. [12][13][14][15][16] However, these carbons show limited rate capability and relatively low capacity. Thus, it is desired to improve the SSA to enhance the rate performance and capacity. Unfortunately, nongraphitic carbons with large SSA and a large number of defects typically exhibit an extremely low initial Coulombic efficiency (ICE) and unsatisfactory cyclic stability because of uncontrollable electrolyte decomposition and ineffective formation of a solid electrolyte interphase (SEI). In a previous report, we used reduced graphene oxide (rGO) as a model anode and found that an ether-based electrolyte can greatly suppress the 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 Al 2 O 3 nanocluster coverage. A 3D porous graphene monolith (PGM) is used as the model material and Al 2 O 3 nanoclusters around 1 nm are grown on the defects of graphene. It is shown that these Al 2 O 3 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, Al 2 O 3 nanoclusters appear to reduce the detrimental etching of the SEI by hydrogen fluoride (HF) and improve its stability. Therefore, after the introduction of Al 2 O 3 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.