Sandwich-like Nitrogen-Doped Porous Carbon Nanosheet/MnO₂ Nanosheet Composites for Asymmetric Supercapacitors

The hybrid of MnO2 and advanced carbon materials is an effective route to develop high-performance supercapacitors. Herein, a distinctive nanohybrid architecture of sandwich-like nitrogen-doped porous carbon nanosheets/MnO2 nanosheets (N-PCNs/MnO2) is controllably prepared via a simple explosion-assisted activation strategy and a subsequent hydrothermal reaction in KMnO4 solution and applied in high energy density asymmetric supercapacitors. A series of characterization results show that the crisscross and continuous MnO2 nanosheets are well deposited on the porous carbon substrate as core materials. Under the optimized feeding concentration of the KMnO4 solution, the resultant typical sample N-PCNs/MnO2-30 nanohybrid exhibits a large specific surface area of up to 116.1 m2 g–1 and good electrochemical performance such as a high specific capacitance of 295 F g–1 at 0.5 A g–1 coupled with remarkable cycling stability (93.1% capacitance retention after 5000 cycles). Meanwhile, the assembled asymmetric supercapacitor device possesses a wide operating voltage (2.0 V) in the Na2SO4 aqueous electrolyte and shows a high energy density of 41.66 W h kg–1 at a power density of 522.6 W kg–1 with 93% capacitance retention after 5000 charge–discharge cycles. The observed findings suggest that the sandwich-like N-PCNs/MnO2-30 nanohybrid has promising potential for practical application in state-of-the-art energy storage devices.