3D N-Ti3C2Tx/Co/N-CNT Composites as a Sodiophilic Framework for Dendrite-Free Sodium Metal Anodes

Abstract

Benefiting from the high theoretical capacity, abundant resource and low working potential, Na metal has been considered as a promising anode for sodium-based batteries. However, the growth of Na dendrites and severe volume variation upon cycling greatly hinder the development of Na metal anodes. Herein, N-doped Ti3C2Tx/ N-doped carbon nanotubes-based composites, where N-doped carbon nanotubes are distributed on N-doped Ti3C2Tx MXene, are fabricated by Lewis acidic salts etching and subsequent annealing treatment. As a proof of concept, owing to superior sodiophilicity derived from -O termination and ample N species, outstanding Na+ diffusion kinetics and electronic conducticity as well as large sepecific area, N-doped Ti3C2Tx/Co/N-doped carbon nanotubes (TCC) can induce the Na uniform nucleation and deposition, mitigate volume expansion and accelerate the plating/stripping kinetics when used as three-dimensional frameworks for Na metal anode, thus achieving dendrite-free growth and considerably enhanced electrochemical performance. Specifically, TCC electrode exhibits a low nucleation overpotential of 6 mV at 1 mA cm-2 and a high average coulombic efficiency of 99.9% at 2 mA cm-2 in asymmetric cells, and stably cycles for 1300 h at 1 mA cm-2 and 1 mAh cm-2 in symmetric cells. Moreover, superb cycling performance can be attained by the full cells with a capacity retention of 85.5% after 1200 cycles at 4 C.