| Abstract | 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 m² g⁻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 mA h g⁻¹ at 100 mA g⁻¹, and 185 mA h 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 W h kg⁻¹ and 38 W h kg⁻¹ at 67 W kg⁻¹ and 14,550 W kg⁻¹, respectively, with 90% capacity retention at over 5000 charge/discharge cycles. |
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