High-performance LiMn2O4/graphene composite for lithium-ion batteries

Abstract

The improvement of the electrochemical characteristics of lithium-manganese spinel LiMn2O4 is one of the most important tasks for researchers in the field of lithium-ion batteries. Graphene materials can have a positive effect on the functional characteristics of LiMn2O4-based composite electrodes due to their unique properties. Therefore, the composite electrodes based on spinel LiMn2O4 with commercial samples of graphene nanoplatelets were investigated. Structural, morphological and surface characteristics of LiMn2O4 and graphene samples studied using X-ray diffraction, scanning electron microscopy and nitrogen adsorption–desorption methods. Electrochemical test of the composite electrodes was performed in CR2016 coin cells with lithium metal anode. It is shown that the nature of LiMn2O4 is the main factor that determines electrochemical behavior of composite electrodes in terms of their cycling stability and rate capability. At the same time, the influence of graphene type within one spinel is relatively small, but the presence of graphene is important to ensure the required level of conductivity of the electrode structure. Despite the lower initial specific capacity, the composites with LiMn2O4 sample synthesized by a citric acid-aided route demonstrate better cycling stability and higher maximum discharge currents up to 40 C compared to composites based on LiMn2O4 synthesized by a solid-state method. The electrochemical characteristics obtained are in good agreement with the results of electrochemical impedance spectroscopy.