Nanostructure Quantification of Hard Carbon Electrodes through Advanced HRTEM Image Analysis

The currently remaining uncertainties on nanostructure has severely hindered the optimal design of hard carbon electrodes. HRTEM characterizations allow us to carry out structural measurements at the atomic level, however, extracting physically meaningful and statistically robust data from HRTEM images is not an easy process. In this work, intelligent fringe analysis and Gabor filtering algorithm were combined to reduce subjective bias and improve statistical reliability. Fringe orientation was described by nematic symmetry of second-order statistics. As a representative, detailed structural analysis of sucrose-derived hard carbon prepared at different heat treatment temperatures (HTTs) was performed. Advanced HRTEM image analysis reveals that the nanostructural evolution of hard carbon is manifested in several aspects, involving the growth and flattening of fringes, enhancement of ordering alignment, increase of stacking, and development of symmetry. More importantly, these structural parameters were quantitatively analyzed in detail. The structural parameters obtained by HRTEM are consistent with similar parameters obtained by other techniques such as XRD. This work provides an unprecedented quantitative insight into the nanostructural trends of hard carbon, with potential to aid researchers in elucidating the structure-property relationships of carbon electrodes