Boosting sodium storage in flexible textile anodes via silk fibroin-derived N-doped carbon surface modulation

Abstract

Carbonized cotton textiles show great promise for flexible energy storage but suffer from limited reversible capacity and rate performance. To address this, we fabricated a hierarchical carbonized silk fibroin/carbon cloth (CSC) composite by electrospinning silk fibroin onto a cotton textile substrate, followed by pyrolysis. This process creates an N-doped carbon layer derived from silk fibroin on the carbon textile surface, significantly enhancing electrical conductivity. Moreover, the electrospun nanofibers on the original carbon microfibers generate additional active sites for sodium storage. The optimized CSC-700 electrode delivers a stable capacity of 97.5 mAh g⁻¹ after 200 cycles at 100 mA g⁻¹ and exhibits outstanding rate capabilities with reversible capacities of 130.6, 102.4, 85.6, 70.3, 60.4, and 52.5 mAh g⁻¹ at current densities ranging from 0.1 to 2.0 A g⁻¹. This superior performance is attributed to favorable charge transfer kinetics and a dominant capacitive contribution reaching 81% at 2.0 mV s⁻¹.