New Insights into the Structural Stability of Carbonyl Sodium-Storage Anodes Based on Janus Dione

Abstract Developing advanced sodium-storage electrodes is of great importance for the advancement of sodium-ion batteries; herein, s-indacene-1,3,5,7(2H,6H)-tetraone (ICTO) is employed for the first time as an anode material for sodium-ion batteries (SIBs). By converting anhydride groups into conjugated carbonyl groups, the structural stability during sodium storage is largely enhanced. The ICTO half-cell delivers a high specific capacity of 379 mAh g–1 at 0.05 A g–1, with an adsorption-dominated sloping region contributing 350 mAh g–1. When assembled into a full cell with a sodium iron pyrophosphate phosphate (NFPP) cathode, the ICTO||NFPP system achieves an ultrahigh energy density of 190.04 Wh kg–1 and an exceptional initial Coulombic efficiency (ICE) of 99.99%. This work provides a new strategy for enhancing sodium storage performance in conjugated carbonyl organic small molecules.