2, University of Alberta, Edmonton, Alberta, Canada
We employed a polypyrrole hydrogel precursor to create a carbon framework that possesses both huge heteroatom content (13 wt% nitrogen and 11 wt% oxygen) and high surface area (945 m2g-1) that is equally divided between micropores and mesopores. A sodium ion capacitor (NIC, HIC) electrode fabricated from this N and O Functionalized Carbon (NOFC) has tremendous reversible capacity and rate capability, e.g. 437 mAh g-1 at 100 mA g-1, and 185 mAh g-1 at 1600 mA g-1. This is among the most favorable reported, and is due to copious nanoporosity that enables fast ion sorption at the many N and O moieties and graphene defects. The NOFC imbues a NIC device with energy-power characteristics that are not only state-of-the-art for Na hybrids, but also rival Li systems: Ragone chart placement is 111 Wh kg-1 and 38 Wh kg-1 at 67 W kg-1 and 14,550 W kg-1, respectively, with 90% capacity retention at over 5,000 charge/discharge cycles.