VIEIRA SEGUNDO, J. E. D.; http://lattes.cnpq.br/1388540284365683; VIEIRA SEGUNDO, José Etimógenes Duarte.
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.