Composition-Tailored 2D Mn_(1-x)Ru_xO_2 Nanosheets and Their Reassembled Nanocomposites: Improvement of Electrode Performance upon Ru Substitution

摘要

Composition-tailored Mn_(1-x)Ru_xO_2 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 Mn_(1-x)Ru_xO_2 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 Mn_(1-x)Ru_xO_2 lattice with mixed Ru~(3+)/Ru~(4+) oxidation state. The reassembled Li- Mn_(1-x)Ru_xO_2 nanocomposites show promising pseudocapacitance performance with large specific capacitances of approximately 330 Fg~(-1) for the second cycle and approximately 360 Fg~(-1) for the 500th cycle and excellent cyclability, which are superior to those of the unsubstituted Li-MnO_2 homologue and many other MnO_2-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-Mn_(1-x)Ru_xO_2 nanocomposites. The results underscore the powerful role of the composition-controllable metal oxide 2D nanosheets as building blocks for exploring efficient electrode materials.