N/O codoped carbons with enriched micropore for high-energy supercapacitor in a wide temperature range

Carbon-based aqueous supercapacitors with an enlarged potential window have received considerable attention because of their safety, rapid charge/discharge rate, long-term lifespan, high power density. However, exploring micropore-enriched carbon electrode with high ion-accessible area, high-level heteroatoms dopants for meeting aqueous supercapacitors with high energy delivery and excellent operating environment tolerance pertains to be a great challenge. This study reports a facile copolymerization method to synthesize N/O codoped carbons with enriched micropore for achieving the enhanced charge accumulation and wide temperature durability in "water-in-salt" (lithium bis(trifluoromethane sulfonyl)imide, LiTFSI) electrolyte. When the electrode fabricated to a symmetric supercapacitor, a satisfied energy delivery (29.8 Wh kg−1, 560 W kg−1) and enhanced specific capacitance (166 F g−1, 0.5 A g−1) at room temperature are exploited, as well as the superb cyclability of 10,000 successive cycles with 90% capacitance retention. Furthermore, the fabricated DTQ2-based supercapacitor can operate well in a wide temperature range (−5–55 °C), yielding a highest energy density (32.5 Wh kg−1) at 55 °C and a slight loss of 21% at −5 °C. The enhancement of good electrochemical behavior can be ascribed to the enriched micropore, high-level heteroatoms dopants (N: 3.04 at.%, O: 15.78 at.%) and high ion-accessible area (2391.6 m2 g−1). The micropore-enriched carbon-based supercapacitors with high energy output at wide working temperature range provide another efficient avenue for energy conversion and storage systems.