Pseudocapacitive Li-ion storage boosts high-capacity and long-life performance in multi-layer CoFeO/rGO/C composite.

Due to the intrinsic low electrical conductivity and large volume expansion of the CoFeO based active materials, designing more novel structures is still one of the most important challenges for its lithium ion battery application. In this work, the CoFeO/reduced graphene oxide/carbon (CFO/rGO/C) composite with integrated multi-layer structure has been synthesized through a facial two-step hydrothermal method. Benefiting from the introduction of the graphene network and amorphous carbon coating layer, as well as the accompanying synergistic effect, this composite can exhibit fast and reversible lithium intercalation/deintercalation reactions. With the aid of a surface-induced capacitive process, the CFO/rGO/C composite delivers a superior specific capacity (945 mA h g at 0.1 A g) and excellent long-term cyclic stability (421 mA h g at 4 A g with closely 100% Coulombic efficiency after 2000 cycles). Significantly, at a high current density of 1 A g, the reversible capacity exhibits a rapid increasing after 100 cycles and finally shows an ultra-high-capacity of 1430 mA h g over 500 cycles. This method could be generalized to the preparation of other similar transition metal oxide-based materials for the development of high-performance energy storage systems.