Sodium Peroxide Dihydrate or Sodium Superoxide: The Importance of the Cell Configuration for Sodium-Oxygen Batteries

In sodium-oxygen (Na-O-2) batteries, multiple discharge products have been observed by different research groups. Given the fact that different materials, gas supplies, and cell configurations are used by different groups, it is a great challenge to draw a clear conclusion on the formation of the different products. Here, two different cell setups are used to investigate the cell chemistries of Na-O-2 batteries. With the same materials and gas supplies, a peroxide-based product is observed in a glass chamber cell and a superoxide-based product is observed in a stainless-steel cell. Ex situ high-energy X-ray diffraction (HEXRD) and Raman spectroscopy are performed to investigate the structure and composition of the product. In addition, in situ XRD is used to investigate the structure evolution of the peroxide-based product. The findings highlight the importance of the cell design and emphasize the critical environment of the formation of the discharge products of Na-O-2 batteries.