Hybridization of PPy/C toward high capacity and stability for sodium-ion batteries

Abstract

Hybrid composites are widely regarded as the most promising choice for anode material in sodium-ion batteries. However, integrating high capacity and excellent cyclic stability into composites remains challenging. This work demonstrates a thin-liquid-layer polymerization approach to fabricate an integrated porous polypyrrole/carbon composite (PPy/C) for a high-performance sodium storage anode. By adjusting the monomer concentration reasonably and combining with heterostructure engineering, the optimized PPy/C was used as the anode for sodium-ion batteries, achieving rapid electrochemical kinetics and satisfactory reversible capacity. The reaction mechanism between PPy and Na+ in the Faraday reaction was revealed by ex-situ electrochemical impedance spectroscopy (EIS). DFT calculations illustrate that the synergistic effect between porous carbon and PPy can regulate the electron transfer mode around Na atoms, which contributes to anchoring Na in the PPy/C composite structure. Moreover, the PPy/C offers an ultrahigh capacity of 552 mA h g−1 at 0.1 A g−1 and a capacity retention rate of 86.5 % after 200 cycles. A full cell assembled with PPy/C and Na3V2(PO4)3 demonstrates a high energy density of 243.1 W h kg–1 at 125 W kg−1 power density. This work would offer valuable thought for advancing the practical application of conductive polymer/carbon composites.