Wang Tianshuai; Qu Jiale; Legut Dominik; Qin Jian; Li Xifei; Zhang Qianfan. Unique Double-Interstitialcy Mechanism and Interfacial Storage Mechanism in the Graphene/Metal Oxide as the Anode for Sodium-Ion Batteries. Nano Letters. 2019, vol. 19, issue 5, s. 3122-3130. ISSN 1530-6984, eISSN 1530-6992, DOI: https://doi.org/10.1021/acs.nanolett.9b00544.
This work, published in NANO LETTERS reveals the utilization of the graphene/metal oxides (G/MO) composite materials as
the anode of sodium ion batteries (SIBs) due to the high theoretical capacity. However, most metal oxides operate, based on the conversion and alloying mechanism, in such a way that they change to Na2O after the first cycle. The influence of G/Na2O (G/N) on the subsequent sodiation process has never been clearly elucidated. In this work, we report a systematic investigation on the G/N interface from both aspects of theoretical simulation and experiment characterization. By applying quantum-mechanical calculations, we find that the sluggish kinetics in the G/MO materials is mainly caused by the high diffusion barrier (0.51 eV) inside the Na2O bulk, while the G/N interface shows a much faster transport kinetics (barrier of 0.25 eV) via unique double-interstitialcy mechanism. G/N interface possesses an interfacial storage of Na atom through the charge separation mechanism. The experimental evidence confirms that high interfacial ratio of the G/N structure greatly improves the rate performance and endows G/MO materials the interfacial storage. Next, the effects of (N, O, S) doping in graphene systems at the G/N interface were explored. This work provides a fundamental comprehension on the G/MO interface structure during the sodiation process, which is helpful to design energy storage materials with high performance rate and large capacity.