Sodium Metal Anode with Na/Na3Bi Penetration for Dendrite-Free and High-Rate Sodium-Ion Battery

Article Link on Science (www.sciencedirect.com)

1. Introduction

Here, we introduced “sodiophilic” Na3Bi penetration into Na anodes to build abundant phase-boundary ion-transport channels. Ion diffusion along the phase boundaries is supposed to enable several orders of magnitude faster than lattice diffusion. Thus, Na ions quickly extract/insert along the boundaries between Na and Na3Bi phase during stripping and plating processes, thus maintaining the even ion-flux distribution as shown in Fig. 1(a). Moreover, the sodiophilic bismuthide enables uniform and dense Na deposition during cycling, thus aiding high volumetric capacity. The Na3Bi-penetrated Na hybrid anode delivers a high current density of 5?mA?cm?2 along with a capacity of 5?mA?h?cm?2 for over 300?h and ultralong cycle life (over 2800?h) at 2?mA?cm?2 under 2?mA?h?cm?2. The Na3V2(PO4)3 (NVP)/(Na/Na3Bi) full cell exhibits superior electrochemical performance than those with the bare Na foil anodes.

Article link: https://www.sciencedirect.com/science/article/pii/S2095809922000145#f0005

3. Conclusions

In this work, bulk Na–metal anodes with sodiophilic Na3Bi penetration, which holds even nucleation and uniform and dense Na deposition, could deliver a high rate, a long cycle life, and a high volumetric capacity. As a result, abundant Na/Na3Bi phase boundaries, which proved to enable Na+ diffusion several orders of magnitude faster than lattice diffusion, ensure sufficient and rapid Na+ migration taking place upon plating and stripping. During initial deposition, the exposed “sodiophilic” Na3Bi framework induces uniform local ion distribution, thereby delivering homogenous inner-space Na+ plating and suppressing volume fluctuations. In subsequent stripping and plating processes, Na+ rapidly exits and enters along the boundaries of Na and Na3Bi phase, maintaining the stability of the anode/electrolyte interface. Furthermore, the obtained anode delivers superior cycling and rate performances coupled with the NVP cathodes.

Acknowledgments

This work was supported by the National Natural Science Foundation of China (21938005 and 21776197) and Key Laboratory of Coal Science and Technology, Education Ministry and Shanxi Province, Taiyuan University of Technology.