Effect of microstructure and contact interfaces of cobalt MOFs-derived carbon matrix composite electrode materials on lithium storage performance

Abstract

Transition metal oxide materials have attracted the attention of researchers due to their advantages, but their development is hindered by structural instability, a small specific surface area and low electrical conductivity [1,2]. Porous carbon materials are often used in combination with transition metal oxide materials since they can produce a synergistic effect [3]. However, the interfacial properties of electrode materials have an important influence on the energy storage characteristics. In this paper, two types of composites were prepared by using three-dimensional graphene foam (3DGF) and three-dimensional porous carbon (3DPC) as the carbon matrix and Co-MOFs as the precursor. The effect of microstructure and contact interfaces on electrochemical properties was analyzed. Besides, non-equilibrium energy band models were established according to the metal semiconductor contact theory and molecular orbital theory, and the carbon-semiconductor and electrode-electrolyte contact interfaces were studied from the energy storage perspective based on the non-equilibrium carrier concentration distribution during battery cycling. Compared with the precursor conversion type (Pcver) 3DGF/Co3O4, the precursor continuation type (Pctin) 3DPC/Co/CoO had better interface compatibility since the energy band at the semiconductor side of the electrode-electrolyte interface bent more slightly. What’s more, the porous channel structure of the Pctin type 3DPC/Co/CoO electrode material endowed it with better cycle stability and more diversified lithium insertion modes. In summary, the Pctin type composite could improve the cycle stability of the electrode and the lithium intercalation model. This study provided insights into the structure design and interface analysis of electrode materials under the non-equilibrium state.