A great deal of attention has been paid on developing plant-derived hard carbon(HC)materials as anodes for sodium-ion batteries(SIBs).So far,the regulation of HC has been handicapped by the well-known ambiguity of Na+storage mechanism,which fails to differentiate the Na+adsorption and Na+insertion,and their relationship with the size of d-interlayer spacing and structural porosity.Herein,bagasse-derived HC materials have been synthesized through a combination of pyrolysis treatment and micro-wave activation.The combined protocol has enabled to synergistically control the d-interlayer spacing and porosity.Specifically,the microwave activation has created slit pores into HC and these pores allow for an enhanced Na+adsorption with an increased sloping capacity,establishing a strong correlation between the porosity and sloping capacity.Meanwhile,the pyrolysis treatment promotes the graphitiza-tion and it contributes to an intensified Na+insertion with an increased plateau capacity,proving that the plateau capacity is largely contributed by the Na+insertion between interlayers.Therefore,the structural regulation of bagasse-derived HC has provided a proof on positively explaining the Na+storage with HC materials.The structural changes in the pore size distribution,specific surface area,d-interlayer spacing,and the electrochemical properties have been comprehensively characterized,all supporting our under-standing of Na+storage mechanism.As a result,the HC sample with an optimized d-interlayer spacing and porosity has delivered an improved reversible capacity of 323.6 mAh g-1 at 50 mA g-1.This work provides an understanding of Na+storage mechanism and insights on enhancing the sloping/plateau capacity by rationally regulating the graphitization and porosity of HC materials for advanced SIBs.