Additive-Free Anode with High Stability: Nb<sub>2</sub>CT<sub><i>x</i></sub> MXene Prepared by HCl-LiF Hydrothermal Etching for Lithium-Ion Batteries
Xiaoxue Zhu, Kai Yang, Zhen Zhang, Siyuan He, Zihao Shen, Wei Jiang, Yiling Huang, Yan Xu, Qiutong Jiang, Limei Pan, Qian Li, Jian Yang
Abstract
MXenes, represented by Ti 3 C 2 T x, have been widely studied in the electrochemical energy storage fields, including lithium-ion batteries, for their unique two-dimensional structure, tunable surface chemistry, and excellent electrical conductivity. Recently, Nb 2 CT x, as a new type of MXene, has attracted more and more attention due to its high theoretical specific capacity of 542 mAh g –1 . However, the preparation of few-layer Nb 2 CT x nanosheets with high-quality remains a challenge, which limits their research and application. In this work, high-quality few-layer Nb 2 CT x nanosheets with a large lateral size and a high conductivity of up to 500 S cm –1 were prepared by a simple HCl-LiF hydrothermal etching method, which is 2 orders of magnitude higher than that of previously reported Nb 2 CT x . Furthermore, from its aqueous ink, the viscosity-tunable organic few-layer Nb 2 CT x ink was prepared by HCl-induced flocculation and N -methyl-2-pyrrolidone treatment. When using the organic few-layer Nb 2 CT x ink as an additive-free anode of lithium-ion batteries, it showed excellent cycling performance with a reversible specific capacity of 524.0 mAh g –1 after 500 cycles at 0.5 A g –1 and 444.0 mAh g –1 after 5000 cycles at 1 A g –1 . For rate performance, a specific capacity of 159.8 mAh g –1 was obtained at a high current density of 5 A g –1, and an excellent capacity retention rate of about 95.65% was achieved when the current density returned to 0.5 A g –1 . This work presents a simple and scalable process for the preparation of high-quality Nb 2 CT x and its aqueous/organic ink, which demonstrates important application potential as electrodes for electrochemical energy storage devices.