Graphenic materials used as anodes in lithium-ion batteries have the lowest specific capacity at around 2000 °C. Consequently, graphite is predominantly used, and few studies have investigated the intermediate annealing temperature range of 2000 °C. Starting from a graphitizable coke, this study investigates the lithium-intercalation capacity of graphite materials at increasing carbonization temperatures (1700, 2000, 2100, and 2500 °C). The results are correlated with the structural evolution determined via X-ray diffraction (XRD). The variation in Li-intercalation performance is assigned to the evolution of graphene stacking sequences. Intercalation begins during the early stages of graphitization with the appearance of AB pairs (AB stacking sequence), indicating that the mechanism starts even before the formation of the true graphitic structure. The sample carbonized at 2100 °C exhibits the highest concentration of AB pairs of graphenes, approaching 50%. Consequently, electrical characteristics during lithiation/delithiation reveal a marked transition from stage 1/stage 2 to stage 2/stage 2L in turbostratically stacked samples, while more graphitized samples with AB pairs and then graphitic (ABA, etc.) sequences display a stage 2/stage 2L to stage 2L/stage 3 transition. Raman spectroscopy and anode color changes confirm the various stages. This research enhances our understanding of the lithium-intercalation process in graphite materials in relation to the structural composition of the average crystallite.

Room temperature sodium–sulfur (RT Na-S) battery with high theoretical energy density and low cost has spurred tremendous interest, which is recognized as an ideal candidate for large-scale energy storage applications. However, serious sodium polysulfide shutting and sluggish reaction kinetics lead to rapid capacity decay and poor Coulombic efficiency. Recently, catalytic materials capable of adsorbing and catalyzing the conversion of polysulfides are profiled as a promising method to improve electrochemical performance. In this review, the research progress is summarized that the application of catalytic materials in RT Na-S battery. For the role of catalyst on the conversion of sulfur species, specific attention is focused on the influence factors of reaction rate during different redox processes. Various catalytic materials based on lightweight and high conductive carbon materials, including heteroatom-doped carbon, metals and metal compounds, single-atom and heterostructure, promote the reaction kinetic via lowered energy barrier and accelerated charge transfer. Additionally, the adsorption capacity of the catalytic materials is the key to the catalytic effect. Particular attention to the interaction between polysulfides and sulfur host materials is necessary for the exploration of catalytic mechanism. Lastly, the challenges and outlooks toward the desired design of efficient catalytic materials for RT Na-S battery are discussed.