Quantitative assessment of basal-, edge- and defect-surfaces of carbonaceous materials and their influence on electric double-layer capacitance

Activated carbon is widely used as electrode materials in supercapacitors, and its capacitive performance is significantly influenced by the specific surface area. However, different types of wall surfaces, such as basal-, edge- and defect-surfaces, exist in carbonaceous materials due to the complex structure and atomic distribution of carbon atoms, rendering different influences on capacitive charge storage behavior. Therefore, it is of utmost significance to quantitatively determine their contribution to the capacitive performance. Herein, the commercial graphite powder is ball milled to introduce different types of edges and defects, resulting in different proportions of basal-, edge- and defect-surfaces. Moreover, a modified non-local density functional theory calculations method is adopted to quantitatively evaluate the basal-, edge- and defect-surface area. Then, a relationship is established between the electrode capacitance and wall surface area by the linear regression method. The results reveal that the basal-, edge- and defect-surfaces contributed an areal capacitance of 0.04 μF cm−2, 1.65 μF cm−2 and 7.95 μF cm−2, respectively. Hence, the capacitance is mainly provided by the defects of wall surfaces.