Metal Chloride-Induced Hydrogen Transfer Enables Efficient Conversion of Aromatic Hydrocarbons for Sodium Storage

The cost-effective synthesis of high-performance hard carbons (HCs) is a key step of sodium-ion batteries toward practical applications. Considering the rich resource of low-value aromatic hydrocarbons (e.g., pitch), there is tremendous interesting in its conversion into value-added HCs. Unfortunately, it still lacks an efficient way for the synthesis, in addition to the time-consuming oxygen contamination of the carbon framework. Herein, a universal strategy is reported that enables the efficient synthesis of HCs from pitch by modulating hydrogen transfer using metal chlorides. CuCl₂ is selected as the model modulator and the effect of different metal chlorides (FeCl₃, AlCl₃, ZnCl₂, and MgCl₂) are further explored. Based on material characterizations and density functional theory calculation employing 1-methylnaphthalene as the model molecule, it shows that the hydrogen capture and chlorination reactions mediated by CuCl₂ and FeCl₃ are thermodynamically favored, which promote the crosslinking of pitch to form HCs. After optimization, the derived HC exhibits superior performance of reversible capacity of 304.8 mAh g⁻¹ and a high initial Columbic efficiency of 88.4%. These discoveries provide new insights into the synthesis of HCs from aromatic hydrocarbons, facilitating their utilization in electrochemical energy storage.