Three-dimensional carbon felt host for stable sodium metal anode

Metallic Na possesses high specific capacity and lowest electrochemical potential of all possible candidates, and therefore being regarded as one of the most promising anode materials for Na batteries. Nevertheless, unstable solid electrolyte interface, infinite volume change and uncontrollable dendritic Na growth upon repeated Na plating/stripping processes lead to low Coulombic efficiency, poor cyclability and safety concerns of Na metal anode. Herein, a three-dimensional carbon felt host was employed to suppress Na dendrite growth, thus achieving highly reversible Na plating/stripping process. The interstitial space inside the carbon felt framework accommodates Na deposition, and the plentiful active sites guide homogenous Na nucleation and growth without dendrite formation. As a result, the carbon felt exhibits stable cycling lifetime for 1100 h and 350 h at 1 mA cm(-2) and 2 mA cm(-2) respectively, which are 5.6 and 3.9 times longer than that of Al foil. Moreover, the carbon felt possesses high average Coulombic efficiency of similar to 99.3% for 500 cycles at 0.5 mA cm(-2). When paired with Na2/3Ni1/3Mn2/3O2 cathode, the full cell delivers a high capacity retention of 95.1% over 150 cycles. (C) 2019 Elsevier Ltd. All rights reserved.