Boron “gluing” nitrogen heteroatoms in a prepolymerized ionic liquid-based carbon scaffold for durable supercapacitive activity

Abstract

The incorporation of heterogeneous active sites into the carbon scaffold offers great potential to break the energy limitation in state-of-the-art supercapacitors, but rich heteroatomic motifs essentially thwart the scaffold firmness, leading to poor power/cycling durability under wide operational voltages/temperatures. Herein, a high-crosslinking prepolymerized ionic liquid p[ABA-co-MA][PA] network is designed to initially trap volatile heterogeneous segments during annealing, and gives the final N/B/O-doped porous carbon scaffolds (CPILs) with rich electroactive sites and pre-supposed structural superiorities. B-doped sites on the scaffold are bridged to glue/fix more electroactive N (4.21–9.05 at%) compared with the solely N-doped sample (2.87 at%), and the high binding energy of the consequent B–C bonds further consolidates the porous carbon scaffold for durable ion/electron transfer. As a result, the highly electroactive CPIL surface with 2629 m² g⁻¹ surface area and 23.13 at% electroactive N/B/O enables a large specific capacitance (359 F g⁻¹ @ 0.5 A g⁻¹) and slight capacitance fade (19% @ 20 A g⁻¹) in H₂SO₄ electrolyte, as well as maximized electrode capacitance up to 211 F g⁻¹ at 3.5 V in EMIM-BF₄ owing to the strong electrosorption ability of the electrolyte ions. Moreover, the CPIL-loaded symmetric supercapacitor in TMA-BF₄/EMIM-BF₄ electrolyte yields a high energy output of 116 W h kg⁻¹ @ 400 W kg⁻¹ under a high potential of 4 V, durable service life (98.2% retention after 10 000 cycles) and wide temperature applicability from −3.5 to 82 °C. This work highlights the comprehensive improvement of multi-heteroatom doping in supercapacitive activity and durability, which provides an appealing strategy to enrich various applications.