Preparation of Cobalt-Based Bi-Metal-Oxides and the Application in the Field of Electrochemical Energy Storage

The development of new electrode materials are required due to the high performance Li-ion batteries (LIBs) and supercapacitors (SCs) for application in electric vehicles (EVs) and hybrid electric vehicles (HEVs). Among a wide variety of electrode materials, transition metal oxides (Co3O4, CoO, NiO, et al.) are accounted as promising ones for both LIBs and SCs owing to the high theoretical capacities. However, its practical use is hindered because of the low electronic conductivity, the large volume change during charge/recharge progress and fair rate capability. With the purpose to improve the electrochemical performance, many researchers have focused on studying cobalt-based bi-metal-oxides (MCo2O4, M=Ni, Mn, Zn, et al.) due to the chemical and thermal stability, low cost and good electrical conductivity. Therefore, it is meaningful to review the recent development of MCo2O4 in the field of electrochemical energy storage including their energy densities, cycling stability and rate capability. In this paper, the recent advances of MCo2O4 and these composites as electrode materials of LIBs and SCs are reviewed. The researches are classified by types, preparation method and characteristics of materials including NiCo2O4, ZnCo2O4, MnCo2O4, and so on. Their advantages and disadvantages are summarized and the possible electrochemical reaction mechanisms are explained. In addition, it is also discussed how to improve the electrochemical performance of MCo2O4 in the future.