The behavior of 2D materials has become of great interest in the wake of development of electrochemical double-layer capacitors (EDLCs) and the discovery of monolayer graphene by Geim and Novoselov. This study aims to analyze the response variance of 2D electrode materials for EDLCs prepared through the liquid-phase exfoliation method when subjected to differing conditions. Once exfoliated, samples are tested with a series of structural characterization methods, including tunneling electron microscopy, atomic force microscopy, Raman spectroscopy, and x-ray photoelectron spectroscopy. A new ionic liquid for EDLC use, 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate is compared in performance to 6M potassium hydroxide aqueous electrolyte. Devices composed of liquid-phase exfoliated graphene / MoS2 composites are analyzed by concentration for ideal performance. Device performance under cold extreme temperatures for the ionic fluid is presented as well. A brief overview of by-layer analysis of graphene electrode materials is presented as-is. All samples were tested with cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy, with good capacitive results. The evolution of electrochemical behavior through the altered parameters is tracked as well.

Neste trabalho, foi desenvolvido um material híbrido inédito carvão ativado/nanotubos de carbono/nanopartículas de prata para as aplicações em bateria de íons de lítio e capacitor eletroquímico de dupla camada. O compósito foi preparado por crescimento dos nanotubos de carbono diretamente sobre o carvão ativado via deposição química de vapor e depois nanopartículas de prata foram incorporadas no carvão ativado/nanotubos de carbono. A morfologia do compósito foi analisada por microscopia eletrônica de varredura. Investigação das propriedades de intercalação de lítio no carvão ativado (CA), carvão ativado/nanotubos de carbono (CA/NTC), carvão ativado/prata (CA/Ag) e carvão ativado/nanotubos de carbono/prata (CA/NTC/Ag) foi conduzida por voltametria cíclica e ciclos de carga/descarga, utilizando dois diferentes eletrólitos. Verificou-se que o ânodo de CA/NTC/Ag apresenta mais elevado valor de capacidade específica reversível que a grafita em eletrólito comercial, provavelmente devido à rede tridimensional com elevada condutividade eletrônica formada por nanotubos de carbono e nanopartículas de prata nos poros e nas rugosidades do substrato. Além disso, os nanotubos de carbono podem exibir elevada capacidade de armazenamento de lítio. Outra vantagem do CA/NTC/Ag é que a rede de nanotubos de carbono acomoda a expansão de volume das partículas de prata durante a ciclagem do eletrodo, mantendo-as bem adsorvidas na superfície do CA/NTC. Os resultados confirmaram a existência do sinergismo entre os componentes do CA/NTC/Ag, que promove características eletroquímicas superiores àquelas dos constituintes isolados. / In this work, an unpublished hybrid material activated carbon/carbon nanotubes/silver nanoparticles was developed for lithium ion battery and electrochemical double layer capacitor applications. The composite was prepared by growing carbon nanotubes directly on the activated carbon via chemical vapor deposition and after silver nanoparticles were incorporated on the activated carbon/carbon nanotubes. The composites morphology was analyzed by scanning electron microscopy. Investigation of lithium intercalation properties in activated carbon (AC), activated carbon/carbon nanotubes (AC/CNT), activated carbon/silver (AC/Ag) and activated carbon/carbon nanotubes/silver (AC/CNT/Ag) was carried out by cyclic voltammetry and charge/discharge cycles by making use of two different electrolytes. It was found that the AC/CNT/Ag anode presents higher reversible specific capacity value in comparison with graphite in commercial electrolyte, probably due to the three dimensional network with high electronic conductivity formed by carbon nanotubes and silver nanoparticles in the substrates pores and roughness. Furthermore, carbon nanotubes can exhibit high lithium storage capacity. Another advantage of the AC/CNT/Ag is that the network of carbon nanotubes accommodates volume expansion of the silver particles during electrode cycling, keeping them well adsorbed on the surface of the AC/CNT. The results confirmed the existence of synergism between the components of the AC/CNT/Ag, which promotes electrochemical characteristics that are higher than those of the individual constituents.

Neste trabalho, foi desenvolvido um material híbrido inédito carvão ativado/nanotubos de carbono/nanopartículas de prata para as aplicações em bateria de íons de lítio e capacitor eletroquímico de dupla camada. O compósito foi preparado por crescimento dos nanotubos de carbono diretamente sobre o carvão ativado via deposição química de vapor e depois nanopartículas de prata foram incorporadas no carvão ativado/nanotubos de carbono. A morfologia do compósito foi analisada por microscopia eletrônica de varredura. Investigação das propriedades de intercalação de lítio no carvão ativado (CA), carvão ativado/nanotubos de carbono (CA/NTC), carvão ativado/prata (CA/Ag) e carvão ativado/nanotubos de carbono/prata (CA/NTC/Ag) foi conduzida por voltametria cíclica e ciclos de carga/descarga, utilizando dois diferentes eletrólitos. Verificou-se que o ânodo de CA/NTC/Ag apresenta mais elevado valor de capacidade específica reversível que a grafita em eletrólito comercial, provavelmente devido à rede tridimensional com elevada condutividade eletrônica formada por nanotubos de carbono e nanopartículas de prata nos poros e nas rugosidades do substrato. Além disso, os nanotubos de carbono podem exibir elevada capacidade de armazenamento de lítio. Outra vantagem do CA/NTC/Ag é que a rede de nanotubos de carbono acomoda a expansão de volume das partículas de prata durante a ciclagem do eletrodo, mantendo-as bem adsorvidas na superfície do CA/NTC. Os resultados confirmaram a existência do sinergismo entre os componentes do CA/NTC/Ag, que promove características eletroquímicas superiores àquelas dos constituintes isolados. / In this work, an unpublished hybrid material activated carbon/carbon nanotubes/silver nanoparticles was developed for lithium ion battery and electrochemical double layer capacitor applications. The composite was prepared by growing carbon nanotubes directly on the activated carbon via chemical vapor deposition and after silver nanoparticles were incorporated on the activated carbon/carbon nanotubes. The composites morphology was analyzed by scanning electron microscopy. Investigation of lithium intercalation properties in activated carbon (AC), activated carbon/carbon nanotubes (AC/CNT), activated carbon/silver (AC/Ag) and activated carbon/carbon nanotubes/silver (AC/CNT/Ag) was carried out by cyclic voltammetry and charge/discharge cycles by making use of two different electrolytes. It was found that the AC/CNT/Ag anode presents higher reversible specific capacity value in comparison with graphite in commercial electrolyte, probably due to the three dimensional network with high electronic conductivity formed by carbon nanotubes and silver nanoparticles in the substrates pores and roughness. Furthermore, carbon nanotubes can exhibit high lithium storage capacity. Another advantage of the AC/CNT/Ag is that the network of carbon nanotubes accommodates volume expansion of the silver particles during electrode cycling, keeping them well adsorbed on the surface of the AC/CNT. The results confirmed the existence of synergism between the components of the AC/CNT/Ag, which promotes electrochemical characteristics that are higher than those of the individual constituents.