Study on the regulation mechanism of sodium biphenyl concentration on the electrochemical performance of porous carbon anodes

Amorphous carbon exhibits low initial coulombic efficiency due to its high specific surface area, abundant functional groups, and structural defects, limiting its application in sodium-ion batteries. The development of anode pre-sodiation reagents has diversified and achieved significant progress, yet research on the impact of reagent concentration on electrode electrochemical performance remains an unexplored area. This study systematically investigated the influence of pre-sodiation concentration on the electrochemical performance of porous carbon electrodes by subjecting them to chemical pre-sodiation treatment using sodium biphenyl solutions of varying concentrations. The results indicate that pre-sodiation treatment significantly enhances the electrode initial coulombic efficiency and cycling stability. When the pre-sodiation level is controlled to yield an initial coulombic efficiency below 100%, the electrode sodium storage capacity is promoted; however, when the initial coulombic efficiency exceeds 100%, the capacity is instead suppressed. In summary, rationally designing the concentration of sodium biphenyl solution to maximize the benefits of pre-sodiation is crucial for enhancing the electrochemical performance of sodium-ion batteries.