A facile approach to nanoarchitectured threedimensional graphene-based Li-Mn-O composite as high-power cathodes for Li-ion batteries

We report a facile method to prepare a nanoarchitectured lithium manganate/graphene (LMO/G) hybrid as a positive electrode for Li-ion batteries. The Mn ₂O ₃/graphene hybrid is synthesized by exfoliation of graphene sheets and deposition of Mn ₂O ₃ in a onestep electrochemical process, which is followed by lithiation in a molten salt reaction. There are several advantages of using the LMO/G as cathodes in Li-ion batteries: (1) the LMO/G electrode shows high specific capacities at high gravimetric current densities with excellent cycling stability, e.g., 84 mAh·g ^-1 during the 500th cycle at a discharge current density of 5625 mA·g ^-1 (~38.01 C capacity rating) in the voltage window of 3-4.5 V; (2) the LMO/G hybrid can buffer the Jahn-Teller effect, which depicts excellent Li storage properties at high current densities within a wider voltage window of 2-4.5 V, e.g., 93 mAh·g ^-1 during the 300th cycle at a discharge current density of 5625 mA·g ^-1 (~38.01 C). The wider operation voltage window can lead to increased theoretical capacity, e.g., 148 mAh·g-1 between 3 and 4.5 V and 296 mAh·g ^-1 between 2 and 4.5 V; (3) more importantly, it is found that the attachment of LMO onto graphene can help to reduce the dissolution of Mn ²⁺ into the electrolyte, as indicated by the inductively coupled plasma (ICP) measurements, and which is mainly attributed to the large specific surface area of the graphene sheets.