Morphology Evolution in Sodium Metal Electrodes

Abstract

Uncontrolled dendrite growth leading to electrical short-circuits, poor recharging capability, and other safety concerns, currently delegate the feasibility of commercial utilization of sodium metal batteries. Dendrites are needle-like growths that appear on the surface of the negative electrode during the electrochemical cycling of a battery. As the fundamental knowledge in intrinsic plating/striping process of sodium metal can guide us for designing a better and safe system, here, we have thoroughly investigated the deposition and dissolution process with the aid of electrochemical analytical methods and imaging techniques using Na|Na or Na|Cu cells as exemplar systems. Engineering a separator with respectable mechanical strength to accommodate electrode volume changes and good electrolyte wettability to retain sufficient absorbed electrolyte in the interface is necessary for stabilizing the metal deposition and improving the overall battery response. Herein, different types of separators were used to understand how the separators guide the homogeneous/inhomogeneous deposition of sodium during the cycling process. The detailed knowledge in the nucleation and growth of sodium metal can provide insights into engineering a sodium cell with controlled Na growth and higher cycling stability.