Sodium Hybrid Capacitor: A Next Generation Energy Storage System

Abstract

Sodium ion batteries are emerging candidate for next generation high energy application including electrical vehicles and grid storage.[1] Rather than the similar working principle, the wide availability and low cost of sodium made them a suitable and an interesting candidate for large energy applications. The research for sodium ion batteries is majorly on improving their poor kinetics due to their large ionic radii resulting in low energy and power density.[2]The possible solution could be designing a hybrid capacitor which greatly improves the energy density and power density simultaneously because of their fast kinetics. In this work, we have developed and fabricated a new high performing 3 V sodium hybrid capacitor (NHC) using NASICON structured Na3V2(PO4)3 – (NVP) and a carbon derived from bio resource in an organic electrolyte. Two reactions occurs simultaneously, (i) intecalaction / deintercalation of sodium ions in NVP which brings high energy density, (ii) adsorption/ desorption of anion in the bio carbon giving high power density. An energy density of 118 Wh kg−1 has been achieved at a specific power of 95 W kg−1, retaining 60 Wh kg−1 of energy at high specific power of 850 W kg−1. A superior and an extremly outstanding stability of 95% is achieved after 10,000 cycles. The obtained results are one of the highest ever reported and it outperforms the present lithium hybrid capacitor by all means (energy density, power density, stability). The results will be presented and discussed in detail.