Prediction of size- and shape-dependent lithium storage capacity of carbon nano-spheres (quantum dots)

Abstract

Despite the large number of experimental works divulging the use of carbonaceous materials in LIB anodes, there are very few reports modeling the relationships between the characteristics of the electrode active materials and their lithium storage capacity. In this work, it is aimed to model the influence of the size and shape of carbon nano-spheres (carbon dots) on their lithium storage capacity. This study divides lithium storage of carbon nano-spheres into two segregate surface- and bulk-related mechanisms and calculates the capacity as the summation of these two components. Accordingly, a novel model employing a new factor called normalized volume, to accurately add the contribution of the surface lithium storage component to the bulk one, is introduced. The model also considers the size and morphology of the carbonaceous nano-particles simultaneously to estimate the specific capacity of the LIB anodes. The model revealed the fact that the decrease in the size of carbon nano-spheres below 20 nm dramatically results in the enhancement of the lithium storage capacity. The comparison of the estimated values with the experimental data of the literature confirmed the satisfactory consistency of the measured and predicted capacities. More importantly, this model is capable of being utilized as a fundamental tool to predict the specific lithium storage capacity of various carbon nano-structures considering their shape and dimension.