Design of free-standing porous carbon nanofibers anodes for lithium/sodium/potassium storage batteries

Abstract

Porous carbon nanofibers (PCNFs) are promising anode materials for alkali metal-ion batteries due to their 3D conductive network structure, large specific surface area and active storage sites for low-valance metal ions. However, the effects of PCNFs with different pore structures on the electrochemical performances and energy storage mechanism are still unknown. Herein, mesoporous F127-PCNF and macroporous SiO₂-etched-PCNF are prepared by electrospinning method as independent anodes for lithium-ion batteries (LIBs), sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs), respectively. The experimental results and DFT calculations indicate that intercalation is the main energy storage mechanism in LIBs. The enlarged interlayer spacing of SiO₂-etched-PCNF is more conducive to intercalation/deintercalation of Li⁺, and it can deliver a reversible capacity of 716 mAh g⁻¹ after 200 cycles at 0.1 A g⁻¹, which is clearly higher than that of F127-PCNF (568 mAh g⁻¹). In contrast, the adsorption mechanism is dominant in SIBs and PIBs. The higher specific surface area and abundant defect sites of F127-PCNF achieve efficient adsorption of Na⁺/K⁺, resulting in superior cycling and rate performance compared to SiO₂-etched-PCNF. This comparative study provides a reference for the understanding of different energy storage mechanisms and furnishes guidelines for the effective development of PCNFs-based anode materials.