Insights on Electrochemical Behaviors of Sodium Peroxide as a Sacrificial Cathode Additive for Boosting Energy Density of Na-Ion Battery

The development of Na-ion full cells (NIFCs) suffers from the issue that the solid electrolyte interphase formation on the carbon anode consumes the limited sodium from cathode and thus incurs the decreased energy density and poor cyclic stability. To address these issues, we herein report that Na₂O₂ could be used as a sacrificial Na source through spraying its slurry on the surface of cathode, and investigate its stability as well as electrochemical behavior toward NIFCs. The results show that Na₂O₂ has good chemical and storage stability under a dry atmosphere and has no negative effect on the electrochemical performance of the cathode. Compared with the pristine cathode, the Na₂O₂-decorated cathode exhibits higher discharge capacity, superior capacity retention, and rate capability in a full cell with a carbon anode. Our cathode Na compensation strategy provides an effective avenue to make up for the irreversible Na⁺ loss cause by the formation of solid electrolyte interphase on the anode, thereby promoting the electrochemical performance and energy density of NIFCs toward the large-scale application.