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

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 similar to 95 mAhg(-1) accompanied by substantial, initial capacity fading, the AQ/carbon fiber composite shows a remarkably high discharge capacity of similar to 307 mAhg(-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 pi-pi 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.