Sodium Cyclopentadienide as a New Type of Electrolyte for Sodium Batteries

Abstract

Owing to the low cost and high abundance of sodium, sodium‐based batteries, especially those employing metallic sodium anodes, are considered for post‐lithium energy storage. In order to develop high‐performance and long‐lasting sodium‐metal batteries, however, the reversible Na‐metal stripping and plating challenge must be addressed. Most organic electrolytes suffer from non‐uniform and continuous formation of the solid electrolyte interphase as well as unfavorable dendritic growth. The use of sodium cyclopentadienide dissolved in tetrahydrofuran as the electrolyte reveals an improved reversibility of sodium dissolution and electrodeposition combined with an electrochemical stability window of around 2.2 V vs. Na/Na+ and an ionic conductivity of 1.36 mS cm−1 at 25 °C. Furthermore, the plated electrodes showed a remarkable morphology of the Na deposits, that is, no dendrite formation, whereby the above‐mentioned electrolyte could overcome the aforementioned cycling issues, thus suggesting suitability for further studies.

Interface chemistry for sodium metal anodes/batteries: a review

“…Current density and charging capacity are the key parameters affecting dendrite morphology by influencing the formation of SEI [41,42] . Wenzel et al showed that dendrites exhibit shrub-like growth with a current density of 120 µA cm -2 , while, when increased to 240 µA cm -2 , the dendrites demonstrate apparent dendritic growth [77] . It is well known that high current densities accelerate dendrite growth, but they also cause a shift from needle-like to moss-like sodium dendrites.…”