An Anthraquinone/Carbon Fiber Composite as Cathode Material for Rechargeable Sodium‐Ion Batteries

Abstract The transition from rare to natural abundant materials in rechargeable batteries is becoming a grand challenge in developing a resource sustainable power supply. Since decades, scientists attempt to circumvent the lithium's resource problem by innovating alternative active metal ions. A cost‐effective alternative to lithium is to use sodium (Na) as the carrier ion in rechargeable batteries. We present an electrode composite material comprising anthraquinone (AQ) and nanostructured carbon fibers, as a cathode material for Na‐ion batteries. These electrodes are characterized by a large surface area, ordered porous network, large pore volume and good electrical conductivity. The material is further compared to the water soluble, mono‐substituted anthraquinone derivative, sulfonated 9,10‐anthraquinone (SAQ). While the SAQ/carbon fiber composite demonstrates a moderate initial discharge capacity of ∼95 mAh g⁻¹ accompanied by substantial, initial capacity fading, the AQ/carbon fiber composite shows a remarkably high discharge capacity of ∼307 mAh g⁻¹ and exhibit reasonable cycling stability over 115 charge/discharge cycles in a Na containing electrolyte. This may be best explained by the well‐structured intermolecular π‐π stacking of the thermally evaporated AQ layers and with the subjacent carbon fibers. Since AQ and SAQ are widely‐used industrial pigments, they may offer a cost‐effective, abundant and environmentally benign cathode material for secondary Na‐ion and Na‐flow batteries.