General synthesis of MFe2O4/carbon (M = Zn, Mn, Co, Ni) spindles from mixed metal organic frameworks as high performance anodes for lithium ion batteries

Abstract

A general method has been developed for the synthesis of the spindle-like MFe₂O₄/C (M = Zn, Co, Ni, Mn). The synthetic procedure involves the preparation of mixed metal organic frameworks (i.e. Fe₂M-MOFs) and their subsequent calcination. The obtained MFe₂O₄/C spindles show an intriguing structure, which consists of carbon coated secondary MFe₂O₄ nanoparticles with an interconnected carbon network. This makes them highly promising as the active materials for various applications with enhanced performance. For example, when used as the anode for lithium ion batteries (LIBs), the MFe₂O₄/C spindles exhibit higher reversible capacities and higher cycling stability in comparison to the MFe₂O₄ materials reported previously. Most interestingly, these MFe₂O₄/C spindles exhibit good morphology preservation during cycling. This shows that the volumetric expansion of MFe₂O₄ upon lithiation leads to the leaching of some active materials to the surface of the MFe₂O₄/C spindles along the percolation channels. This alleviates the volumetric expansion energy and prevents the structural destruction of MFe₂O₄/C spindles. The leached active materials do not detach from the MFe₂O₄/C spindles and participate in the lithiation/delithiation reactions throughout the whole cycling process, giving the MFe₂O₄/C spindles with high specific capacity and good durability. The approach reported here is highly versatile and might be applicable to the synthesis of other MFe₂O₄/C spindles for various applications.