Bio-inspired Mn3O4@N, P-doped carbon cathode for 2.6 V flexible aqueous asymmetric supercapacitors

Optimizing the performance of electrode materials is crucial for improving the energy density of aqueous supercapacitors. Herein, a novel strategy inspired by biomimetic mineralization is developed to acquire a hierarchical flower-like Mn 3 O 4 @N, P-doped carbon (NPC) composite, which consists of multi-intercalated Mn 3 O 4 nanosheets and NPC cores. The Mn 3 O 4 nanosheets offer abundant active regions, and their C-O-Mn bonds with NPC ensure the fast electron transfer kinetics. It is noteworthy that the intercalation pseudocapacitance mechanism of Mn 3+ /Mn 4+ transformation in Mn 3 O 4 @NPC not only extends the potential window to 0–1.3 V (vs Ag/AgCl) but also significantly increased pseudocapacitance. Benefits from the advantages of structure and energy storage mechanism, the Mn 3 O 4 @NPC electrode delivers a high specific capacitance of 370.8 F g −1 and superior rate performance. A 2.6 V flexible aqueous asymmetric supercapacitor (FAAS) is fabricated by integrating Mn 3 O 4 @NPC cathode with an electrochemically reduced porous   carbon anode and a PVA-Na 2 SO 4 hydrogel electrolyte. Notably, the FAAS delivers a high energy density of 76.96 Wh kg −1 as well as excellent rate capability. The device exhibited an excellent stability during 10,000 cycles and additional 240 h floating test. The strategy will pave the way for the development of electrode materials for FAASs.