Zinc−Ion−Assisted Catalytic Synthesis of Hard Carbon with Superior Plateau Capacity and ICE for Sodium−Ion Batteries

ABSTRACT Hard carbon is regarded as a highly attractive candidate for the anode in sodium−ion batteries (SIBs). Nevertheless, its practical commercial application is severely limited by unsatisfactory low−voltage plateau capacity (<0.1 V), low initial Coulombic efficiency (ICE), and slow electrochemical kinetics in the plateau region. Herein, we propose a simple and cost−effective one−step zinc−ion catalytic pyrolysis strategy to optimize cellulose hard carbon, which exhibits a combination of ultrahigh initial capacity of 480.8 mA h g ⁻¹ , a high ICE of 89.8%, and a plateau capacity of 326.5 mA h g ⁻¹ . During carbonization, the Zn ²⁺ ions act simultaneously as a graphitization catalyst and a pore−forming agent due to its vaporization, enabling in situ construction of a closed pore architecture at high temperatures. In addition, the residual Zn ²⁺ serve as anchoring sites that coordinate with nitrogen species to form a Zn─N ₄ ─C configuration, which significantly enhances the dynamic diffusion of Na ⁺ and improves electron transfer kinetics. This facile and cost−effective method exhibits broad applicability to biomass precursors, providing valuable insights for the design of high−performance carbonaceous anodes in SIBs.