Influência da densidade de corrente e da composição do eletrólito no desempenho eletroquímico de monocamada de grafeno em bateria de íons de lítio.

Abstract

To satisfy industrial applications and the growing consumption of fossil fuels, researches have been performed on the development of materials and technologies for energy storage in a renewable and sustainable way. Graphene is a material that has interested recent studies due to its excellent physical-chemical, mechanical, thermal, electrical and optical properties. In a lithium-ion battery, graphene overcomes the capacity limitations of graphite, commonly used as anode material. In this work, monolayer graphene using as anode was studied in a lithium-ion battery to verify the influence of current density and electrolyte composition on the electrochemical performance of electrode material. Current density was applied in three different levels: 3, 5 and 10 μA/cm2. The electrolyte tested was LiPF6 1M in ethylene carbonate/diethyl carbonate (50/50v) (EC-DEC), ethyl methyl carbonate (EMC) or propylene carbonate (PC). AFM and Raman microscopy analysis exhibited a uniform monolayer graphene over substrate surface. The EIS spectra of discharged cell were analyzed to investigate the kinetics of electrode process in different electrolytes. Results showed a process controlled by charge transfer but with great contribution of lithium-ion diffusion in case of EC-DEC solvent. Irreversible capacity in the 1st cycle ranged from 11.39 to 77.47%, as function of applied current density, and the highest discharge capacity was 21,575 mAh/g, for 3 μA/cm2. With application of this current density value, the average coulombic efficiency was 67.12% and the discharge capacity was reduced by 87.90% over 20 cycles. Results confirmed the great potential of graphene for application in energy storage systems.