Boosting Sodium Storage in Pitch-Derived Hard Carbon via MgO Catalytic Preoxidation.

Abstract

Pitch-based hard carbon (HC) materials at low cost and high carbon yield represent a promising anode for sodium-ion batteries. However, their limited capacity poses a significant challenge to their practical use. Here, we report a universal strategy to boost sodium storage of pitch-based HC materials via catalytic oxidation with magnesium oxide to produce a high-oxygen pitch. The oxygenic groups suppress pitch softening and molecular rearrangement during carbonization, resulting in a highly disordered structure and substantially closed pores in the obtained HC materials. As a result, the optimized HC materials achieve a specific capacity of 321.7 mAh g^-1 with a significant 80.5% increase over typical pitch-based carbon materials, along with a high initial Coulombic efficiency up to 88.5 and 88.3% capacity retention after 600 cycles. This study provides new insights into the rational design of high-capacity pitch-based HC and holds potential for application in other carbon-based materials.