Graphene-supported binary active Mn0.25Co0.75O solid solution derived from a CoMn-layered double hydroxide precursor for highly improved lithium storage

Abstract

Dispersion of multiple chemically active components strongly affects the electrochemical performances of electrode nanomaterials for lithium-ion batteries. We herein describe highly improved lithium storage of a graphene-supported binary active solid solution (Mn_0.25Co_0.75O) derived from CoMn-layered double hydroxide/graphene oxide precursor (CoMn-LDH/GO). Ex situ X-ray diffraction characterization clarifies the topotactic transformation from the CoMn-LDH/GO precursor to the resulting Mn_0.25Co_0.75O solid solution with increasing temperatures. The electrochemical test shows that the Mn_0.25Co_0.75O solid-solution electrode is able to exhibit highly improved electrochemical performances, which are superior to those of the electrodes of individual CoO/G, MnO/G, and the mixture (mMnO + CoO/G). The reversible capacity of the Mn_0.25Co_0.75O electrode reaches 980 mA h g⁻¹ after 100 cycles at 100 mA g⁻¹, and especially up to 1087 mA h g⁻¹ after 1300 cycles at a high current density of 2 A g⁻¹. TEM observations and Nyquist plots provide information on the morphological preservation of the solid-solution nanoplatelets consisting of small nanoparticles observed after the super-long cycling, and the low charge transfer resistance to underlie the improvements, respectively. Our LDH precursor-based protocol may be extended to prepare other multiple-component well-dispersed metal oxides or even sulfides, and thus provide a new strategy for construction of high-performance electrodes for energy storage.