CO₂-Derived Oxygen-Rich Carbon with Enhanced Redox Reactions as a Cathode Material for Aqueous Zn-Ion Batteries

Aqueous Zn-ion batteries based on carbon cathode materials show high potential in the application of energy storage due to their low cost, high safety and long cycling lifespan, but the low reversible capacity and energy density hinder their practical. Herein, CO₂-derived oxygen-rich carbons by molten salt electrolysis are proposed as attractive cathode materials with enhanced redox reactions. By optimizing the electrolysis current density at 50 mA cm⁻², electrolytic carbon featuring honeycomb-like morphology, high specific surface area and O content, as well as abundant defect is realized. Owing to the enhanced electrochemical reactions originating from the oxygen-rich functional group in the electrolytic carbon, improved electrochemical Zn storage performance is achieved, showing a high capacity of 257 mAh g⁻¹ at 0.05 A g⁻¹, which is one of the highest values reported, and it preserves good cycling stability after 10000 cycles at 1 A g⁻¹. It is revealed that C=O group in electrolytic carbon shows high reactivity and can reversibly storage and release Zn²⁺ ions, which is accompanied by the formation and dissolution of Zn_xOTf_y(OH)_2x-y⋅nH₂O layer. This work offers effective strategy to improve the electrochemical performance of carbons by manipulating the surface reaction of carbon for aqueous Zn-ion batteries.