Synergistic regulation of crosslinking degree and Zn/S co-doping in phenolic resin-derived hard carbon for enhanced sodium storage performance

Hard carbon (HC) are prepared through a one-step carbonized method to obtain Zn/S co-doping. • The spacing of layers of HC is regulated through the crosslinking degrees of phenolic resins. • The prepared HC has a high performance for sodium-ion batteries. • The heteroaton co-doping and the regulation of layers spacing play a synergistic effect to improve the performance of HC. The abundance and low cost of sodium make sodium-ion batteries a promising candidate for large-scale energy storage applications. However, the development of high-performance anode materials remains a critical challenge. Herein, a series of Zn/S co-doped hard carbon materials are synthesized by high-temperature pyrolysis using phenolic resins with different crosslinking degrees as precursors, zinc chloride as zinc source, and trithiocyanuric acid as sulfur source. The synergistic effect between precursor crosslinking density and heteroatom co-doping on the microstructure and sodium storage performance of hard carbon is systematically investigated. Electrochemical tests demonstrate that the Zn/S-HC 7.5:10-HMTA delivers high reversible capacity, excellent Coulombic efficiency, and stable long-term cycling. Kinetic analysis reveals a dominant capacitive contribution and the highest Na⁺ diffusion coefficient among all samples. This work reveals that an effective approach to achieving high-performance hard carbon anodes for sodium-ion batteries is to optimize precursor crosslinking together with Zn/S co-doping. Download: Download high-res image (139KB) Download: Download full-size image