3D sodiophilic mixed-ion-electron-conducting framework of hierarchical nanowire arrays for ultra-stable sodium-metal batteries

Abstract

Sodium metal batteries (SMBs) have attracted increasing attentions as next-generation energy storage systems, regarding its high energy density and raw materials abundance. However, its practical application is impeded by the inferior reversibility of Na anode, stemmed from the non-uniform Na plating/stripping process and formation of “dead Na”. Herein, a three-dimensional (3D) mixed-ion-electron-conducting scaffold (MIECS) is in-situ established by self-assembled hierarchical Cu2S nanowire arrays, which renders enhanced sodiophilicity, high surface area, and robust architecture to the current collector, thereby promoting interfacial kinetics, homogenizing Na deposition, and ensuring “top-down” dissolution. As a result, Cu2S NWs@Cu MIECS enabled Na metal anode with exceptional Coulombic efficiency as high as 99.94 % over 1600 cycles at 4 mA cm−2, as well as steady plating/stripping profile for at least 2000 h at depth of discharge of 75 %. Impressively, full-cell SMB achieves ultra-stable cycling of 2000 cycles, exhibiting capacity retention as high as 96.3 % at high cathode loading of 14.7 mg cm−2, or that of 87.8 % at 5 C, with limited Na excess (N/P = 3). The 3D sodiophilic Cu2S NWs@Cu MIECS provides a promising route to highly reversible Na metal anode for developing high-energy-density SMBs.