Progressive Self-Leveling Deposition Improves the Cyclability of Anode-less Sodium Metal Batteries Revealed by In Situ EPR Imaging

Anode-less sodium–metal batteries (SMBs) with high theoretical capacity and low cost are promising candidates for next-generation rechargeable batteries. However, the poor cyclability resulting from uneven Na deposition with unstable solid electrolyte interphase (SEI) and accumulative dead sodium has severely impeded their practical use. This work proposed a simple strategy, that is, coating current collector with Ketjenblack, which could maintain good cycling stability in anode-less SMBs. Moreover, in situ EPR (electron paramagnetic resonance) imaging reveals that the Ketjenblack coating can not only facilitate the homogeneous Na deposition but also eliminate nonuniformity of Na deposits exhibiting progressive self-leveling behavior during repeated sodium plating/stripping.