Manipulating micropore structure of hard carbon as high-performance anode for Sodium-Ion Batteries

Hard carbon (HC) is the most promising anode material for sodium-ion batteries (SIBs), but its low initial coulombic efficiency (ICE) and specific capacity limit its practical application. Herein, a chemical vapor deposition (CVD) strategy is used to address these challenges via filling the micropores of sucrose-based HC with pyrolysis by-products from acetonitrile, thereby reducing the specific surface area of HC microspheres. This approach mitigates the formation of solid electrolyte interphase (SEI) film leading to an enhancement in ICE. Moreover, the conversion of open micropores into closed pores creates additional storage space for sodium ions, effectively extending the specific capacity within the plateau region. Specifically, the HC prepared with a deposition duration of 1 h demonstrates the most favorable electrochemical performance. The optimal HC anode manifests an enhanced specific capacity of 307.6 mAh g(-1) with an ICE of 66.01 % and exhibits excellent cycle stability (84.9 % capacity retention after 200 cycles at 100 mAh g(-1)). This study provides a feasible approach to optimize hard carbon anode materials for SIBs.