Correlation between microstructure, optical texture and lithium storage performance in pitch-based materials

Abstract

Pitch-based materials with different microstructures were prepared at low-temperature carbonization utilizing different green cokes with four optical textures (mosaic structure, medium-grained domain, medium-grained domain/domain structure, and domain/flow domain structure) as raw materials. The optical texture index (OTI) is introduced to illustrate the optical texture. The relationships between OTI, microstructure and electrochemical performance were established. The results indicate that orderly graphite sheets generated from flow domain structure (higher OTI) contributed to the higher reversible specific capacity (503 mAh g−1 after the 200th cycle at 0.1 A g−1). While the structural defects formed disordered mosaic structures (lower OTI) can enhance the random transportation and diffusion of lithium ions in carbon layers, thereby resulting in optimal rate performance (146 mAh g−1 at 2 A g−1 current density).