Going beyond lithium hybrid capacitors: proposing a new high-performing sodium hybrid capacitor system for next-generation hybrid vehicles made with bio-inspired activated carbon

Abstract

A novel sodium hybrid capacitor (NHC) is constructed with an intercalation-type sodium material [carbon coated-Na3V2(PO4)(3), C-NVP] and high surface area-activated carbon derived from an eco-friendly resource cinnamon sticks (CDCs) in an organic electrolyte. This novel NHC possesses a combination of high energy and high power density, along with remarkable electrochemical stability. In addition, the C-NVP/CDC system outperforms present, well-established lithium hybrid capacitor systems in all areas, and can thus be added to the list of candidates for future electric vehicles. A careful optimization of mass balance between electrode materials enables the C-NVP/CDC cell to exhibit extraordinary capacitance performance. This novel NHC produces an energy density of 118 Wh kg(-1) at a specific power of 95 W kg(-1) and retains an energy density of 60 Wh kg(-1) with high specific power of 850 W kg(-1). Furthermore, a discharge capacitance of 53 F g(-1) is obtained from the C-NVP/CDC cell at a 1 mA cm(-2) current density, along with 95% capacitance retention, even after 10 000 cycles. The sluggish kinetics of the Na ion battery system is successfully overcome by developing a stable, high-performing NHC system.