Mn3O4 embedded 3D multi-heteroatom codoped carbon sheets/carbon foams composites for high-performance flexible supercapacitors

In this work, a kind of novel Mn3O4 embedded 3D N/P-codoped carbon sheets/carbon foams (Mn3O4–NPCN/CF) composites is directly prepared by high-temperature pyrolysis. The Mn3O4–NPCN/CF with highly opened porous structure has outstanding advantages, such as providing abundant channels for ion fast transport, increasing electrolyte permeation rate, ensuring effective contact between electrode and electrolyte, and enhancing electron conduction. The nitrogen (N) and phosphorus (P) heteroatoms enhance the surface wettability of the Mn3O4–NPCN/CF electrode and widen the voltage window. Mn3O4 embedded in the N/P-codoped carbon sheet stably provides pseudocapacitance. Consequently, the Mn3O4–NPCN/CF electrode displays a high specific capacitance of 519 F g−1 and cycle stability (96% after 5000 cycles) in 6 M KOH electrolyte. Moreover, the Mn3O4–NPCN/CF-based all-solid-state symmetric supercapacitors still show prominent capacitance value of 207 F g−1 and 141 F g−1 in polyvinylalcohol/KOH and polyvinylalcohol/Na2SO4 gel electrolyte, respectively. Significantly, the all solid-state symmetric supercapacitors retain above 90% capacitance after 500 mechanical bending and wide-temperature range cycles (−20 to 80 °C). This work provides a facile, low-cost and environmental friendliness process to prepare high-performance electrode materials in energy storage field.