Graphene-Karst Cave Flower-like Ni-Mn Layered Double Oxides Nanoarrays with Energy Storage Electrode

- The composite markedly improves electrochemical properties through the Ni-Mn LDO possessing good pseudocapacity and 3D GOS has better electrical conductivity.
- The interconnected 3D GOS macropores reduce the diffusion distances from the external electrolyte to the interior surfaces, improve conductivity, and enable a fast reversible Faradaic reaction.
- The structure obviously alleviates the reunion of LDO and the graphene layer of GOS, which can enhance the specific surface area. In addition, the carbon-based material can protect the electrodes to improve stability.
- The hierarchical configuration of nanowalls consisting of numerous nanosheet structures offers a short ion diffusion path with small resistance.
- All of these advantages allow the synergistic effects of LDO and 3D carbon materials.

A hierarchically flower-like structure with nanoarrays coupled with 3D macroporous sponge graphene combines the preponderances of the hierarchical nanoarchitecture and composition to enhance electrochemical performance. A graphene-karst cave flower-like Ni-Mn layered double oxides (GL) electrode material was prepared through a mild hydrothermal-carbonization process. As an electrode material, the resulting GL composite exhibited excellent performance with high specific capacitance (1,648 and 1,252 F g−1 at 0.5 and 10 A g−1, respectively) and good cycling stability (almost 96% retention after 6,000 charge-discharge cycles) for energy storage electrode. The GL composite material acting as a positive electrode for the asymmetric supercapacitor also exhibited high specific capacitance of 116.56 F g−1 at 0.5 A g−1 and excellent cycling stability with 86.7% capacitance retention after 6,000 cycles at a current density of 5 A g−1. This outstanding electrochemical performance may be attributed to the synergistic effect of the layered double oxides and 3D macroporous graphene oxide sponge.

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