New Protective Layer for Long Time Stable Sodium Metal Anodes

Abstract

Facing the challenges of degradation processes in sodium metal batteries, a lot of new anode materials were prepared and tested. Especially Hard Carbon is a promising candidate for sodium ion batteries.[1] However, the competitive battery performance as gravimetric and volumetric energy density cannot be achieved without metallic sodium as an anode.[2]Another way to stabilize a sodium metal battery is the formation of an artificial solid-electrolyte interface (SEI). In the recent years, a lot of efforts were devoted for development of organic and inorganic protective layers. Most of the processes to form an artificial SEI are not easy for application, or result in a weak long-term stability of a sodium metal battery.[3]Here, we can introduce a new artificial SEI, which can easily be formed on top of metallic sodium and is also stable upon a long-term cycling. The capacity retention in a full cell setup (Swagelok cell, layered sodium cobalt titanium oxide as a cathode material, 1 M NaClO4 in EC/PC as an electrolyte) is of nearly 85 % after 500 cycles with a 1C current density. A reference full cell with non-protected sodium only reaches 20 % after the same cycling conditions.A possible explanation for the observed improvement in the cell performance was done based on comprehensive electrochemical, chemical and structural studies. Acknowledgment This work was supported by the Bundesministerium für Bildung und Forschung is carried out as part of the HeNa project (03XP0390C). Additional information Patent pending.