Carbon Nanotubes for Rechargeable Na/Cl<sub>2</sub> Batteries
Peng Liang, Guanzhou Zhu, Weize Wang, Cheng-Liang Huang, Shu‐Chi Wu, Jingwen Zhou, Xichen Zhou, Yan Wu, Shixin Wang, Mingyue Wang, Lei Zhang, Chan Cheong Ming, Jiachen Li, Feifei Wang, Mengdie Sun, Yuan‐Yao Li, Bing‐Joe Hwang, Hongjie Dai
Abstract
Rechargeable Na/Cl 2 batteries were developed for the first time using multiwalled carbon nanotube (MWCNT) positive electrodes in SOCl 2 -based electrolytes. At room temperature, these batteries delivered high cycling specific capacities up to 3500 mA h g –1 (normalized to CNT mass) with ∼3.9 V discharge voltage at up to 2 C rates over >140 cycles. In situ Raman spectroscopy experiments combined with real-time optical microscopy imaging revealed reversible formation and reduction of SCl 2 and S 2 Cl 2 species during battery operation, responsible for the additional plateaus to the main Cl – /Cl 2 redox reactions. Cryo-TEM revealed NaCl nanocrystals inside the hollow inner space of CNTs through battery cycling, suggesting Cl – /Cl 2 redox reactions reaching hollow CNTs likely through defects and open ends on MWCNTs. High-resolution electron energy loss spectroscopy (EELS) mapping revealed Cl uniformly distributed along CNTs in the charged state, suggesting CNTs as a novel carbon material to host Cl – /Cl 2 redox and store chlorine for reversible conversion between NaCl and Cl 2 and battery rechargeability.