HC-Based Anode Materials: Synthesis, Study and Evaluation of the Charge Storage Mechanism

Abstract

Hard carbon is a class of carbon materials widely used in sodium-ion batteries which are characterized by sp2 hybridized carbon atoms forming highly irregular structure consisting of randomly oriented graphene layers[1]. These materials have a number of advantages including high capacity, good cycling stability, low cost and can potentially be easily up-scaled. However, hard carbon is still largely underinvestigated and its comprehensive study is of great importance. In particular, a mechanism of sodium ion intercalation should be thoroughly analyzed. Moreover, a controllable and reproducible technology for their synthesis is highly demanded. The most commonly used precursor for hard carbons are saccharides, phenolic resins, pitch, starch and cellulose. The latter draw great attention due to its abundance and a bunch of carbon materials with various properties can be obtained from cellulose by changing synthesis conditions[2]. In this study, samples of hard carbon were synthesized from cellulose using two different approaches. In the first approach, the samples were obtained by hydrothermal carbonization of cellulose dispersed in water at 185 °C and further hydrochars pyrolysis at 1300 °C under argon atmosphere. In the second approach, dehydration of cellulose powder was performed at 295 °C in air with further pyrolysis at 1300 °C under argon atmosphere. The morphology and microstructure of the obtained samples were characterized by X-ray scattering diffraction and scanning electron microscopy. Electrochemical methods were used to analyze the obtained materials and it was found that the samples demonstrated capacity more than 250 mAh/g. Charge storage behavior was estimated by linear voltammetry in anodic area at different sweep rates[3]. This work was supported by the Russian Science Foundation (Grant No. 17-73-30006).