Expanded mesocarbon microbead cathode for sodium‐based dual‐ion battery with superior specific capacity and long‐term cycling stability
Yujia Wang, Xuewen Yu, Peng Zhang, Zheng-Jie Wang, Lei Yan, Liang He, Ze-Kai Wang, Zhi-Qiang Shi
Abstract
Abstract Dual‐ion batteries (DIBs) have attracted tremendous attention owing to their high operating voltage and are considered promising candidates for low‐cost clean energy storage devices. However, the decomposition of electrolytes and collapse of the cathode structure may lead to low Coulombic efficiency (CE) and low cycling stability of DIBs. Wide‐layered electrode materials can accommodate the intercalation/deintercalation of large anions, which is believed to overcome these issues. Herein, expanded mesocarbon microbeads (200HRO‐MCMB) possessing an enlarged interlayer spacing (0.405 nm) were prepared via modified Hummers and subcritical hydrothermal reduction methods. After the indispensable electrochemical activation, 200HRO‐MCMB (hydrothermal reduction at 200 °C) exhibited a high specific capacity (120 mAh·g −1 at 50 mA·g −1 ) when used as a cathode for a sodium‐based DIB, and the CE significantly improved within the 2.0–4.5 V voltage range. Additionally, the cycling stability exceeded over 600 cycles. Remarkably, this cathode possessed enlarged interlayers that decreased the barrier of PF 6 − transport, and the battery storage mechanism corresponded to a transitioning state between double‐layer capacitance and Faradaic intercalation. Undoubtedly, this work will expand the scope of the practical application of low‐cost sodium‐based DIBs.