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CO2 oxidation of carbon nanotubes for lithium-sulfur batteries with improved electrochemical performance
- Wang, Datao, Wang, Ke, Wu, Hengcai, Luo, Yufeng, Sun, Li, Zhao, Yuxing, Wang, Jing, Jia, Lujie, Jiang, Kaili, Li, Qunqing, Fan, Shoushan, Wang, Jiaping
- Carbon 2018 v.132 pp. 370-379
- air, batteries, carbon, carbon dioxide, carbon nanotubes, cathodes, dispersions, electrochemistry, electrolytes, electrostatic interactions, oxidation, sulfur
- The fabrication of high-performance cathodes with high sulfur content is essential for the practical realization of lithium–sulfur (Li–S) systems. The preparation of high-sulfur-content electrodes is currently hindered by poor dispersion of the conductive agents; nonuniformly distributed conductive agents cannot provide sufficient sulfur-loading sites, thereby resulting in aggregation of sulfur/Li2S and severe polarization. To deal with this issue, we prepare CO2 modified carbon nanotube (CNT)-based cathodes for Li–S batteries. CNTs are exposed to CO2 at 900 °C, resulting in uniformly distributed negative charges on the external surface of the tubes; the electrostatic repulsion facilitated the dispersion of CNTs. Compared with the previous work on CNTs prepared by air oxidation (denoted as air-CNTs), the dispersions of the CO2-treated CNTs (denoted as CO2-CNTs) are more stable, which allows higher sulfur loading and improves sulfur utilization. A free-standing CO2-CNT&S electrode with a sulfur content of 80 wt% is fabricated through a sonication-assisted method. The excellent dispersion of the CO2-CNT&S network results in little kinetic barriers, low polarization, and fast charge transport at the interface of the electrode and electrolyte. The CO2-CNT&S electrode delivers a lower capacity fading rate and superior rate performance compared with the air-CNT&S electrode.