Surface Charge Engineering for Covalently Assembling Three-Dimensional MXene Network for All-Climate Sodium Ion Batteries
Xin Wang, Jie Wang, Jinwen Qin, Xi Xie, Rui Yang, Minhua Cao
Abstract
MXenes, as excellent candidate anode materials for sodium ion batteries (SIBs), suffer from sluggish ion-diffusion kinetics resulting from the anchoring effect of the negatively charged functional groups on their surface on sodium ions. Herein, we introduce positively charged conductive polyaniline (PANI) to induce self-assembly of Ti3C2Tx MXenes into a three-dimensional PANI/Ti3C2Tx network. In this PANI/Ti3C2Tx network, PANI not only intercalates into Ti3C2Tx nanosheets to enlarge the interlayer spacing, but also promotes negative-to-positive transition of the surface charges of the Ti3C2Tx nanosheets, significantly improving ion-diffusion kinetics. Electrochemical test results further confirm the superb ion-diffusion kinetics of the PANI/Ti3C2Tx network. Meanwhile, a covalent interaction (Ti–N) between PANI and Ti3C2Tx, proved by X-ray photoelectron spectra (XPS) and X-ray absorption near-edge structure (XANES) tests, plays a key role in stabilizing this network structure. Therefore, PANI/Ti3C2Tx exhibits excellent sodium storage performances with a high specific capacity, superior rate performance and ultralong lifespan at high current density. More importantly, when operated at rigorous temperatures from +50 to −30 °C, PANI/Ti3C2Tx also exhibits good electrochemical performances. The present work presents a simple strategy for designing 3D porous MXene-based materials to realize high rate performance and all-climate energy storage device.