Composition-Tailored 2D Mn1-xRuxO2 Nanosheets and Their Reassembled Nanocomposites: Improvement of Electrode Performance upon Ru Substitution

Composition-tailored Mn1-xRuxO2 2D nanosheets and their reassembled nanocomposites with mesoporous stacking structure are synthesized by a soft-chemical exfoliation reaction and the subsequent reassembling of the exfoliated nanosheets with Li+ cations, respectively. The tailoring of the chemical compositions of the exfoliated Mn1-xRuxO2 2D nanosheets and their lithiated nanocomposites can be achieved by adopting the Ru-substituted layered manganese oxides as host materials for exfoliation reaction. Upon the exfoliation-reassembling process, the substituted ruthenium ions remain stabilized in the layered Mn1-xRuxO2 lattice with mixed Ru3+/Ru4+ oxidation state. The reassembled Li-Mn1-xRuxO2 nanocomposites show promising pseudocapacitance performance with large specific capacitances of approximately 330Fg(-1) for the second cycle and approximately 360Fg(-1) for the 500th cycle and excellent cyclability, which are superior to those of the unsubstituted Li-MnO2 homologue and many other MnO2-based materials. Electrochemical impedance spectroscopy analysis provides strong evidence for the enhancement of the electrical conductivity of 2D nanostructured manganese oxide upon Ru substitution, which is mainly responsible for the excellent electrode performance of Li-Mn1-xRuxO2 nanocomposites. The results underscore the powerful role of the composition-controllable metal oxide 2D nanosheets as building blocks for exploring efficient electrode materials.