Molecular reconfiguration of pitch-derived hard carbon anodes with balanced thermodynamic stability and rapid sodium storage kinetics for high-performance sodium-ion batteries

Abstract

Pre-oxidation, a key modification method to enhance the sodium storage properties of pitch-based amorphous carbon through molecular reconfiguration, results in suboptimal sodium storage kinetics within the extended plateau region. Therefore, it is of great significance to clarify the effects of pre-oxidation and carbonization on the pitch-derived carbon microstructure and electrochemical behavior. In this work, the pitch precursors with different pre-oxidation degrees were carbonized to unveil the crucial effects of molecular reconfiguration and carbonization temperature on the microstructural evolution by various characterization methods. In situ Raman and electrochemical analyses reveal that defects govern Na⁺ diffusion kinetics, while interlayer spacing/pore structures dictate storage thermodynamics. Consequently, PHC-A-1100 synthesized via 300 ℃ pre-oxidation followed by 1100 ℃ carbonization achieves synergistic regulation of Na⁺-storage kinetics and thermodynamics through controlled molecular reconfiguration-carbonization coupling, enabling Ah-level capacity in 18650 cylindrical cells with 80.04 % capacity retention after 200 cycles at 1 C. Moreover, this study provides a comprehensive insight into optimizing sodium storage behavior for constructing high-performance carbon anodes of sodium-ion batteries.