MnCo2O4@Co(OH)2 coupled with N-doped carbon nanotubes@reduced graphene oxide nanosheets as electrodes for solid-state asymmetric supercapacitors

Abstract

In this work, we report an effective approach to synthesize self-supported MnCo2O4@Co(OH)2 core-shell heterostructures (CSHs) as the positive electrode and N-doped carbon nanotubes (N-CNTs)@reduced graphene oxide (rGO) CSHs as the negative electrode. Benefiting from the unique CSHs by wrapping urchin-like MnCo2O4 microflowers assembled from nanorods with Co(OH)2 nanosheets, the prepared MnCo2O4@Co(OH)2 CSHs electrode demonstrates a higher electrochemical performance (1185 C g−1 at 1 A g−1, 78% capacity retention at 20 A g−1, and 96% capacity retention after 5000 cycles at 5 A g−1) than the pristine MnCo2O4 and Co(OH)2 electrodes. Likewise, the prepared N-CNTs@rGO CSHs electrode also exhibits an improved capacitive performance compared to the pristine N-CNTs electrode, such as a specific capacitance of as high as 393 F g−1 at 2 A g−1, good capability with 71% capacitance retention at 20 A g−1 as well as excellent cycle stability with 96% capacitance retention after 5000 cycles at 10 A g−1. With good matching of these two electrodes in microstructures and electrochemical properties, the fabricated MnCo2O4@Co(OH)2//N-CNTs@rGO solid-state ASCs can deliver a high energy density of 67.2 W h kg−1 at a power density of 800 W kg−1 and good cycle stability with 94% capacitance retention over 5000 cycles at 10 A g−1. This work not only provides an attractive strategy for rationally constructing high-performance CSHs electrodes materials for ASCs, but also offers an available way to develop next-generation advanced energy storage devices.