High energy Na-Ion capacitor employing graphitic carbon fibers from waste rubber with diglyme-based electrolyte

Abstract

Co–intercalation process using glyme-based solvents has brought new prospects for the reversible Na-intercalation into the graphitic materials. We report a high-energy Na-ion capacitor (SIC) with graphitic carbon nanofibers (GCNF) as a battery-type component obtained from the depolymerization of waste rubber. The kinetic study reveals that ~ 51% contribution is originated from the diffusion-controlled Faradaic mechanism for GCNF compared to the ~ 61% for commercial graphite powder. The synthesis procedure and less crystalline nature of the GCNF lead to the lowered intercalation potential, and extended Na-ion storage capacity in the lower potential region (vs. Na+/Na) which is significant compared to the graphite powder. Further, the half-cell delivered a discharge capacity of ~ 118 mAh g−1 irrespective of the applied current rate, which signifies the importance of this concept. In a SIC configuration with activated carbon, the SIC renders an energy density of 55.58 Wh kg−1 at 25 °C. In addition, exceptional low-temperature performance (<10 °C) is noted with a maximum energy density of 54.69 Wh kg−1 and > 97% capacity retention after 5000 cycles. This low-temperature performance, high energy density, and exceptional cyclability certainly offer a unique hybrid charge storage system that eventually explores the possibility of using graphitic carbon fibers towards balanced energy and power capabilities. On a lighter note, this study also provides the opportunity to handle the waste materials effectively for sustained charge storage applications.