Tuning Nanopore Structure of Hard Carbon Anodes by Zinc Gluconate for High Capacity Sodium Ion Batteries

Abstract Hard carbon serves as a highly promising anode material for sodium‐ion batteries due to its stable structure and cost‐effectiveness. Although the hard template method is commonly employed to enhance the sodium storage capacity, the reported process steps are complicated. In this study, we introduced a facile approach by utilizing ZnO as a self‐sacrificed template to engineer pore structures with one step for template removal without using harmful chemicals. Our investigations reveal that pretreatment of the material before carbonization can reduce the specific surface area and defect degree of the final hard carbon. When utilized as an anode material, the as‐prepared hard carbon demonstrated a reversible capacity of 334 mAh g −1 at 0.05 A g −1 with an initial Coulombic efficiency of 84 %. Even at a high current density of 2 A g −1 , the capacity stabilized at 183 mAh g −1 after 1000 continuous cycles. Electrochemical storage behavior and ex‐situ Raman spectroscopy unveiled insights into the potential sodium storage mechanism. These findings present a new approach to enhancing the reversible properties of hard carbon anode materials for high‐performance sodium‐ion batteries.