3D-Printed Sodiophilic V2CTx/rGO-CNT MXene Microgrid Aerogel for Stable Na Metal Anode with High Areal Capacity.

Abstract

Featuring a high theoretical capacity, low cost, and abundant resources, sodium metal has emerged as an ideal anode material for sodium ion batteries. However, the real feasibility of sodium metal anodes is still hampered by the uncontrolled sodium dendrite problems. Herein, an artificial three-dimensional (3D) hierarchical porous sodiophilic V2CTx/rGO-CNT microgrid aerogel is fabricated by a direct-ink writing 3D printing technology and further adopted as the matrix of Na metal to deliver a Na@V2CTx/rGO-CNT sodium metal anode. Upon cycling, the V2CTx/rGO-CNT electrode can yield a superior cycling life of more than 3000 h (2 mA cm-2, 10 mAh cm-2) with an average Coulombic efficiency of 99.54%. More attractively, it can even sustain a stable operation over 900 h at 5 mA cm-2 with an ultrahigh areal capacity of 50 mAh cm-2. In situ and ex situ characterizations and density functional theory simulation analyses prove that V2CTx with abundant sodiophilic functional groups can effectively guide the sodium metal nucleation and uniform deposition, thus enabling a dendrite-free morphology. Moreover, a full cell pairing a Na@V2CTx/rGO-CNT anode with a Na3V2(PO4)3@C-rGO cathode can deliver a high reversible capacity of 86.27 mAh g-1 after 400 cycles at 100 mA g-1. This work not only clarifies the superior Na deposition chemistry on the sodiophilic V2CTx/rGO-CNT microgrid aerogel electrode but also offers an approach for fabricating advanced Na metal anodes via a 3D printing method.