A booming of researches has been developed on sodium ion batteries (SIBs) with low cost, ubiquitous distribution resources, and similar physical and chemical properties with lithium in many aspects. Compared with carbonous materials, metallic sodium anodes have attracted great attention because of their high capacity and low redox potential. However, they still encounter various challenges in stripping/plating efficiency and cycling performance due to the dendrite formation and large volume fluctuation. To address these issues, we engineer a 3D mixed conducting scaffold for metallic sodium anodes in which the interconnected ion conductive pathway is incorporated by adding active additives, which firmly bonding with sodium at high temperature, and the 3D Ni foam offers the electron transport pathway with inherent high electron conductivity (Figure 1a). SEM and EDS results show the uniform distribution of both sodium and carbon in Ni foam framework, which effectively accelerate electron/ion kinetic during cycling in Figure 1b,c. Such a 3D mixed conducting scaffold can stabilize ions stripping/plating behavior. As shown in Figure 1d, the Ni-HC@Ni exhibit the longest cycling life of up to 550 hours (225 cycles) and the smallest average overpotential of less than 60 mV at a current density of 0.5 mA cm<sup>-2</sup> with 0.5 mAh cm<sup>-2</sup> capacity loading. We believe that the design principle provides an alternative strategy to achieve stable and safe metallic anodes and sheds light on the development of high-energy-density batteries.

Design of a 3D mixed conducting scaffold toward stable metallic sodium anodes

ACS Fall 2021

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