High‐capacity potassium ion storage mechanisms in a soft carbon revealed by solid‐state NMR spectroscopy
Jing-Heng Han, Jia He, Qi-Yao Zou, Jie Zhang, Zhilin Yang, Zhiwei Zhao, Huixin Chen, Hongjun Yue, Dawei Wang, Haichen Lin, Hao-Dong Liu, Guiming Zhong, Zhangquan Peng
Abstract
Abstract Carbon materials are crucially important for the realization of potassium‐ion batteries. However, the potassium storage mechanisms in various carbon materials are incompletely understood. Herein, solid‐state 13 C nuclear magnetic resonance (NMR) spectroscopy coupled with Raman and X‐ray diffraction (XRD) techniques are employed to study the reaction mechanism in a soft carbon quantitatively. It is revealed that the insertion of potassium ions into the soft carbon firstly induces a transformation of the disordered region to short‐range ordered stacking, involving both the pristine local unorganized and organized carbon layers. Subsequently, potassium ions intercalate into the rearranged carbon structure, finally producing the nano‐sized KC 8 . Moreover, a remarkable capacity of 322 mAh·g −1 with a low mid potassiation voltage of < 0.3 V is present for the prepared soft carbon, which is on account of the underlying potassium storage sites, including the disordered stacking carbon as a main component of the soft carbon. These results suggest that regulating the disordered stacking region in the turbostratic structure of soft carbon is a critical issue for further improving the potassium storage performance.