Porously Assembled 2D Nanosheets of Alkali Metal Manganese Oxides with Highly Reversible Pseudocapacitance Behaviors

Abstract

Porously assembled 2D nanosheets of alkali metal manganese oxides were synthesized via the flocculation of exfoliated MnO2 nanosheets with alkali metal cations. According to X-ray diffraction and electron microscopic analyses, the MnO2 nanosheets were porously restacked with alkali metal cations, resulting in the mesoporous assembly of lamellar crystallites with surface expansion (∼50−70 m2 g− 1). Mn K-edge X-ray absorption spectroscopy clearly demonstrated that manganese ions in the reassembled materials were stabilized in octahedral symmetry with the mixed oxidation state of Mn3+/Mn4+. The present reassembled manganates showed large capacitances of ∼140−160 F g−1 and excellent cyclability of ∼93−99% up to the 1000th cycle. The electrochemical cycling did not induce notable frustration in the crystal structure of manganate nanosheets, underscoring the high structural stability of the reassembled manganates. This study provided strong evidence for the effectiveness of the exfoliation−reassembling method in enhancing the capacitance performance of layered metal oxides.

Cobalt oxide (Co3O4)/graphene nanosheets (GNS) composite prepared by novel route for supercapacitor application

“…Energy storage has been revolutionized after the introduction of electrochemical capacitors or supercapacitors. Owing to their high power density, long cycle life, short charging time, good safety, and so forth [1][2][3][4][5]. They possess higher energy density compared to conventional capacitors and high power density than batteries.…”

Mixed Colloidal Suspensions of Reduced Graphene Oxide and Layered Metal Oxide Nanosheets: Useful Precursors for the Porous Nanocomposites and Hybrid Films of Graphene/Metal Oxide

“…[7][8][9][10] The reassembling of anionic transition-metal oxide nanosheets with cationic guest species yields highly porous pillared metal oxides with a tailored pore structure and strongly coupled electronic structure. [10][11][12][13] If we take into account the remarkably expanded surface area and redox capability of component transition-metal ions, the reassembled nanohybrids of transition-metal oxide nanosheets are supposed to show promising electrode performance for supercapacitors and lithium-ion batteries. [13] Since the component transition-metal oxides possess relatively poor electrical conductivity, the electrode performance of these nanosheet-assembled materials can be further improved by the hybridization with conductive carbon species.…”

“…[10][11][12][13] If we take into account the remarkably expanded surface area and redox capability of component transition-metal ions, the reassembled nanohybrids of transition-metal oxide nanosheets are supposed to show promising electrode performance for supercapacitors and lithium-ion batteries. [13] Since the component transition-metal oxides possess relatively poor electrical conductivity, the electrode performance of these nanosheet-assembled materials can be further improved by the hybridization with conductive carbon species. Given the common 2D morphology of graphene and transition-metal oxide nanosheets, the combination of these two materials is expected to yield strongly coupled nanohybrid materials with optimized functionalities.…”

Effect of Percolation on the Capacitance of Supercapacitor Electrodes Prepared from Composites of Manganese Dioxide Nanoplatelets and Carbon Nanotubes

“…25 Moreover, a growing selection of layered oxides and hydroxides are showing great promise in this area. 3,[26][27][28][29][30][31][32][33][34][35] To best employ the high intrinsic pseudocapacitance of any material requires the maximum number of redox active sites be in contact with the electrolyte and therefore available for charge storage. This makes the layered oxides described above extremely attractive so long as they can be exfoliated into thin flakes.…”