Origins of Dendrite Formation in Sodium–Oxygen Batteries and Possible Countermeasures

Abstract

Abstract One limiting phenomenon for the cycle life of metal–oxygen batteries is the growth of dendrites during metal plating (cell charging). For the relatively new sodium–oxygen cell, this subject has been scarcely investigated, until now. Therefore, dendrite formation is systematically investigated herein, with the aim of gaining a more detailed understanding of the underlying mechanisms and relevant control parameters. Electrochemical impedance spectroscopy, cycling experiments, and optical characterization techniques are applied in situ and ex situ; sodium dendrite growth is directly visualized, for the first time, by means of a tubular glass cell. The growth of instable surface morphologies is discussed from a theoretical perspective to comprehend the experimentally observed dendrite growth. Furthermore, countermeasures against issues with dendrites are discussed, with the aim of increasing the cycle life of sodium–oxygen batteries.