Molecular Descriptor-Directed Microstructural Regulation of Asphalt-Derived Hard Carbons for Advanced Sodium-Ion...

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Engineering

Background:

• Asphalt is a cost-effective precursor for hard carbon anodes in sodium-ion batteries.
• The complex molecular structure of asphalt hinders controlled carbonization and predictable performance.

Purpose of the Study:

• To develop quantitative molecular descriptors for correlating asphalt precursor topology with hard carbon microstructure.
• To enable rational design of high-performance hard carbon anodes for sodium-ion batteries.

Main Methods:

• Development of two molecular descriptors: aromatic substitution index (f_a^s) and short-chain substitution index (R).
• Systematic solvent fractionation and multi-scale characterization of asphalt-derived carbons.
• Correlation analysis between precursor molecular features and resulting hard carbon microstructure.

Main Results:

• High R values (short-chain alkyl groups) suppress graphitization via oxidative crosslinking.
• High f_a^s values (aromatic substitution) promote uniform pore formation and structural disorder.
• Optimized hard carbon exhibits excellent sodium storage: 326 mAh g^-1, 93% retention over 500 cycles, and 204 mAh g^-1 at 5 A g^-1.

Conclusions:

• Molecular descriptors provide fundamental insights into hard carbon microstructure formation.
• This descriptor-based approach offers a practical strategy for selecting asphalt precursors.
• Enables the rational design of advanced hard carbon anodes for enhanced sodium-ion battery performance.