Molecular and atomic manipulation of metal-organic framework-derived LiCoMnO4: An oxygen-deficient strategy for advanced lithium storage

Abstract

As a novel class of high-voltage cathode materials, spinel lithium transition metal oxides have been faced with demerits including pronounced structural instability caused by Jahn-Teller distortion (especially at the lower voltage region) and severe capacity degradation despite their intriguing electrochemical properties. To extend their functionalities as broad-voltage cathodes, the sacrificial template method has been regarded as a promising way to realize structural and compositional control for desirable electrochemical behaviors. Herein, we report a synthetic protocol to directionally prepare LiCoMnO4 (LCMO) using carboxyl-based metal-organic frameworks (MOFs) as self-sacrificing templates. Impressively, LCMO derived from CoMn-BDC (H2BDC = 1,4-benzenedicarboxylate) displays superior electrochemical performances with a specific capacity of 151.6 mAh g−1 at 1 C (150 mA g−1) after 120 cycles and excellent rate capacity of 91.9 mAh g−1 at 10 C due to the morphology control, microstructural modulation, and atomic manipulation of the MOF precursor. Bestowed by the optimized atomic and electronic structure, abundant oxygen vacancies, and the nanostructure retained from MOF precursors, LCMO materials display extraordinary electrochemical properties, which have been extensively verified by both experimental and theoretical studies. This work not only provides guidelines for the directional design of spinel materials at molecular and atomic levels but also sheds light on the practical use of LIBs with broad range voltage.