Strong oxidation induced quinone-rich dopamine polymerization onto porous carbons as ultrahigh-capacity organic cathode for sodium-ion batteries

Organic cathodes have emerged as promising candidate for sodium ions batteries (SIBs) because of their high theoretical capacity, molecular diversity, and sustainability. However, the inferior rate performance and poor cycle life still restrict their large-scale applications. Herein, a facile strategy for the synthesis of ultrathin quinone-rich polydopamine (PDA) coating which is tightly adhered on 3D porous carbon surface (PC-PDA-APS) is prepared through a superfast (∼1.5 h) heterogeneous nucleation process. Ammonium persulfate (APS) used as initiating agent can not only restrain the self-nucleation of dopamine, but also promote the transformation from bi-hydroxyl to bi-carbonyl with an ultra-high conversion rate up to 81%. Having benefited from the synergistic effect of inter-connective 3D carbon skeleton, ultrathin PDA coating, and ultrahigh quinone content, the PC-PDA-APS exhibits significantly high specific capacity (322 mA h g⁻¹ at 0.1 A g⁻¹), and excellent rate performance (102 mA h g⁻¹ at 10 A g⁻¹). More specially, the combination of DFT calculations and in-situ FTIR spectroscopy verifies the synergistic Na⁺ storage mechanisms of reversible enol reaction of C=O groups with Na⁺ and imine groups (R=N-R') with Na⁺. This research fundamentally provides a structural engineering method for remarkably improving the performance of sodium-organic cathode.