Olsson Emilia, Cottom Jonathon, Alptekin Hande, Au Heather, Crespo-Ribadeneyra Maria, Titirici Maria-Magdalena, Cai Qiong
Department of Chemical and Process Engineering, University of Surrey, Guildford, GU2 7XH, UK.
Department of Chemical Engineering, Imperial College London, London, SW7 2AZ, UK.
Small. 2022 Oct;18(43):e2200177. doi: 10.1002/smll.202200177. Epub 2022 Aug 26.
Hard carbon (HC) anodes together with ethylene carbonate (EC)-based electrolytes have shown significant promise for high-performing sodium-ion batteries. However, questions remain in relation to the initial contact between the carbon surface and the EC molecules. The surface of the HC anode is complex and can contain both flat pristine carbon surfaces, curvature, nanoscale roughness, and heteroatom defects. Combining density functional theory and experiments, the effect of different carbon surface motifs and defects on EC adsorption are probed, concluding that EC itself does not block any sodium storage sites. Nevertheless, the EC breakdown products do show strong adsorption on the same carbon surface motifs, indicating that the carbon surface defect sites can become occupied by the EC breakdown products, leading to competition between the sodium and EC fragments. Furthermore, it is shown that the EC fragments can react with a carbon vacancy or oxygen defect to give rise to CO formation and further oxygen functionalization of the carbon surface. Experimental characterization of two HC materials with different microstructure and defect concentrations further confirms that a significant concentration of oxygen-containing defects and disorder leads to a thicker solid electrolyte interphase, highlighting the significant effect of atomic-scale carbon structure on EC interaction.
硬碳（HC）阳极与基于碳酸亚乙酯（EC）的电解质一起，已显示出在高性能钠离子电池方面具有巨大潜力。然而，碳表面与EC分子之间的初始接触仍存在问题。HC阳极的表面很复杂，可能包含平坦的原始碳表面、曲率、纳米级粗糙度和杂原子缺陷。结合密度泛函理论和实验，探究了不同碳表面结构和缺陷对EC吸附的影响，得出EC本身不会阻塞任何钠存储位点的结论。然而，EC分解产物确实在相同的碳表面结构上表现出强烈吸附，这表明碳表面缺陷位点可能会被EC分解产物占据，导致钠与EC片段之间产生竞争。此外，研究表明EC片段可以与碳空位或氧缺陷反应，生成CO并进一步使碳表面发生氧官能化。对两种具有不同微观结构和缺陷浓度的HC材料进行的实验表征进一步证实，大量含氧量缺陷和无序会导致更厚的固体电解质界面，突出了原子尺度碳结构对EC相互作用的重大影响。
