Anodic Rate Performance in Lithium-Ion Batteries of Graphite Materials Based on Carbonaceous Wastes

Abstract

The rate performance as anode in lithium-ion batteries of two graphite materials denoted A/CVP/2700 and B/CIQ5/2600 that were prepared by high temperature heat-treatment of carbonaceous wastes from coal combustion fly ashes is herein investigated using galvanostatic cycling at increasing electric current densities (C/20–2C charge-discharge interval rate) and subsequent electrochemical impedance spectroscopy (EIS). These materials show a remarkable stable capacity along cycling with capacity retention values >90% as well as an excellent efficiency of cycling (discharge/charge capacity ratio close to 100%) in the whole interval of rates studied and a significant resistance to aging. Provided they have a graphite-like structure as evaluated by XRD and Raman spectroscopy, the excellent rate capability appears to be also related to the small size and irregular shape of the particles which, respectively, improve the diffusion of the lithium ions in the electrode bulk and reduce the lithium migration resistances as confirmed by the EIS results. Furthermore, the capacities delivered by A/CVP/2700 and B/CIQ5/2600 materials at any rate were larger than those of the reference graphite with much larger development of the crystalline structure, which is commercialized for anodes of LIBs.