Robust Sodium Storage Enabled by Heterogeneous Engineering and Electrolyte Modification

Abstract

The modulation of heterointerfaces in 2D materials is critically important for improving the electrochemical performance of sodium-ion batteries (SIBs). In this context, the MoS₂/Ti₃C₂T_x MXene heterostructure is taken as a typical example to reveal the fundamental principle of high sodium storage performance by regulating the terminal groups of Ti₃C₂T_x. It is demonstrated that MoS₂/Ti₃C₂(OH)_x (M/-(OH)_x) heterostructure with a high work function difference generates an enhanced built-in electric field, which facilitates charge transfer. Moreover, ether-based electrolytes, when compared to ester-based electrolytes, provide lower solvation-free energies and exhibit high compatibility with M/-(OH)_x, resulting in superior rate capability. Notably, COMSOL simulations of sodium ion (Na⁺) concentration and Na⁺ flux distributions reveal that the M/-(OH)_x electrode has low concentration polarization and rapid diffusion kinetics in ether-based electrolytes. Consequently, the combination of M/-(OH)_x heterostructure with the ether-based electrolyte provides 224.06 mAh g⁻¹ after 1000 cycles at 5.0 A g⁻¹. Furthermore, the Na₃V₂(PO₄)₃/C//M/-(OH)_x full cell demonstrates robust electrochemical performance, delivering 116.49 mAh g⁻¹ after 140 cycles at 1.0 A g⁻¹. These findings emphasize the impact of modulating terminal functional groups to optimize the electrochemical functionality of heterostructures and highlight the crucial role of electrode/electrolyte synergistic coupling in advancing the practical applications of SIBs.