Dandelion-like\nMn/Ni Co-doped CoO/C Hollow Microspheres\nwith Oxygen Vacancies for Advanced Lithium Storage

Abstract

Hollow\nstructures have attracted great attention based on the advantage\nto accommodate volume expansion. However, template removal usually\nresults in structure destruction. Herein, dandelion-like Mn/Ni co-doped\nCoO/C hollow microspheres (CMNC-10h) are synthesized <i>via</i> an Ostwald ripening process without templates. The high-angle annular\ndark field mapping images at the atomic level indicate the successful\ndoping of Mn and Ni into CoO. <i>Via</i> an annular bright\nfield image, oxygen vacancies induced by doping can be clearly observed.\nThe residual two electrons in the oxygen vacancy site are highly delocalized,\nas confirmed by density functional theory calculations, effectively\nimproving electrical conductivity. According to electron holography\nanalysis, the dielectric polarization field in superficial regions\nof primary nanoparticles can facilitate insertion of Li⁺ ions into nanoparticles and thus enhance electrochemical kinetics.\nCombining those advantages, CMNC-10h demonstrates a high capacity\nof 1126 mAh g^–1 at 1 A g^–1 after\n1000 cycles as anode material for a lithium-ion battery. Additionally,\nbased on the strong adsorption toward polysulfide, the porous structure\nto accommodate sulfer/polysulfide, and the effects of oxygen vacancies\nto immobilize and catalyze polysulfide, CMNC-10h-S as cathode material\nfor a lithium–sulfur battery also displays a high capacity\nof 642 mAh g^–1 after 500 cycles at 1 C.