The microstructure of HC is characterized by a disordered carbonaceous matrix of randomly oriented graphitic layers. Structural features such as large graphene interlayer spacing, curved graphitic domains, and high nanoporosity result in high reversible capacity and stable cycling performance. The typical potential-capacity curve of HC exhibits two distinct electrochemical signatures: a sloping region at high potentials (~0.1-2.5 V vs Na/Na + ) and a plateau region at low potentials (~0-0.1 V vs Na/Na + ), as shown in Figure . During the first sodiation, the multiple slopes in the high potential region may correspond to distinct sodium storage processes with binding energy changes (as indicated by larger voltage drops during sodium insertion) that vary proportionally to the slope. The capacity and steepness of the gradients in the high voltage region also vary with pyrolysis temperature, indicating a dependence on the HC microstructure.