Regulating the Nanosheets Structures in Pitch-Derived Amorphous Carbons for Efficient Sodium-Ion Storage.

Abstract

Amorphous carbon (AC), prized for their cost-effectiveness and excellent performance, are promising as an anode material for sodium-ion batteries (SIBs). However, its amorphous structure challenges balancing high rate capability with high capacity. This study regulates the nanosheets structure of pitch-derived-AC (PDAC) through pre-polymerization-induced polycyclic aromatic hydrocarbons growth, enabling simultaneous enhancement of rate capability and maintenance of high capacity. The regulation of the nanosheets length to 12.27 nm can increase the closed pore volume to 0.062 cm³ g^-1, thereby facilitating the formation of quasi-metallic sodium clusters, which elevates the specific capacity of PDAC to 377.4 mAh g^-1 in an ester-based-electrolyte, with the plateau region contributing up to 68.0%. Furthermore, the extended nanosheets maintain a spacing of 0.396 nm, overcoming the kinetics limitations inherent in accessing plateau capacity at high current. Consequently, a specific capacity of 357.8 mAh g^-1 (incl. 248.1 mAh g^-1 plateau capacity) is achieved at 200 mA g^-1, with retention of 253.6 mAh g^-1 at 500 mA g^-1. Additionally, the PDAC demonstrates exceptional cycling stability, retaining 90.4% of its initial capacity after 1000 cycles. The critical roles of extending nanosheets, maintaining interlayer spacing, and increasing closed pore volume in enabling efficient Na⁺ storage and advancing fast-charging SIBs are systematically elucidated.