Electrochemically exfoliated graphene-graphite architecture with MnO2 for redox pseudocapacitive process

An electrochemical exfoliation-deposition strategy is provided to fabricate the MnO2-based electrode. After the efficient exfoliation in MnSO4 electrolyte, the stacked graphite expands into open structure, with vertical graphene sheets strongly bonded on the surface. This unique architecture not only provides sufficient surface areas for the anchoring of oxygen vacancy-enriched MnO2, but also ensures transportation pathways for the charge transfer and electrolyte ions diffusion. Thus, the resultant electrode exhibits an areal specific capacitance of 447.5 mF cm−2 at 0.5 mA cm−2 and promising cycling stability. It outperforms the analogues exfoliated in another Mn-based electrolyte because of the anion effect. In situ Raman spectra are taken to reveal the structural evolutions of the resultant electrode coupled with Na+ ions insertion-extraction behaviors in the redox pseudocapacitive process.