Highly Exfoliated 2D Nanosheets of MnO₂ Assembled Alternatively with Carbon Layers for High Performance of Thick Electrode (at High Loading Mass)

Owing to high theoretical capacitance and high natural abundance, manganese dioxide (MnO₂) has received great attention as a promising pseudocapacitive material. Unfortunately, the charge storage performance of MnO₂ is usually limited for commercially available mass loading electrodes because of the significant decrease of electron and ion migration kinetics in thick electrodes. Here, we report an alternatively assembled two-dimensional (2D) layered material consisting of exfoliated MnO₂ nanosheets and nitrogen-doped carbon layers for ultrahigh-mass-loading supercapacitors without sacrificing energy storage performance. A layered birnessite-type MnO₂ is efficiently exfoliated and intercalated by carbon precursor of dopamine using a fluid dynamic-induced process, resulting in interlayer-expanded MnO₂/nitrogen-doped carbon (MnO₂/C) materials after self-polymerization and carbonization. The alternatively intercalated carbon layers between MnO₂ nanosheets enable to expand interlayers of MnO₂, thus providing a fast and efficient electron and ion pathways.