Aluminum electrodeposition and electrodissolution in mixtures of AlCl 3 and 1-ethyl-3-methylimidazolium chloride on carbon paper electrodes consisting of graphitized fibers were investigated. Porous electrodes, such as carbon paper electrodes, often offer possible advantages such as higher nominal current densities and less dendrite formation, over solid planar electrodes. Cyclic voltammetry, chronoamperometry and pulse current deposition were used to investigate Al plating and stripping on this porous structure. The Al morphology on the carbon paper was probed using SEM. Composition and temperature affect the Al electrode performance through their influence on the diffusivity of ions. Therefore, control of the diffusion process during Al plating/stripping is essential. Aluminum (Al) is the third most abundant element in the Earth's crust 1 and has three transferable electrons leading to a large theoretical specific capacity (2978 Ah/kg) when aluminum is oxidized and reduced. This makes it an excellent candidate for high energy density electrodes.2 Al plating/stripping on/from electrodes at room temperature has been investigated AlCl 3 /l-ethyl-3-methylimidazolium chloride (EMIC) electrolytes.3-9 The electrochemical reaction on the Al (negative) electrode is written as:Aluminum dendrite formation has been observed, especially at high current density; 4,5 this phenomena can result in a short circuited cell.In an effort to limit dendrite formation, three-dimensional porous carbon materials are being studied for Al plating and stripping. Based on observations of Al plating on porous carbon materials, there are several potential advantages for plating/stripping Al on porous materials over the solid planar substrates: (1) A high surface-to-volume ratio of porous materials provides the possibility of high nominal current densities. (2) By plating/stripping Al inside porous materials, formation may be controlled inside the porous structure. (3) An electrode could be designed to enhance the plating/stripping performance even further and achieve even higher current densities.
ExperimentalEMIC was synthesized by using the reported procedure.10,11 AlCl 3 (Fluka, >99%) was purified by sublimation in a heavy wall glass tube, as described previously.11 The chloroaluminate melt was prepared by slowly adding EMIC onto solid AlCl 3 crystals. The voltammetry cell and the 3 mm diameter disk Glass Carbon (GC) electrode were purchased from Bioanalytical Systems Inc. A carbon paper electrode was prepared by cutting 2050-A carbon paper (Fuel Cell Store) to a 5 mm × 10 mm size and adhering the prepared carbon paper to one end of a copper rod (McMaster-Carr) using a silver conductive epoxy (McMaster-Carr). The surface area of the carbon paper electrode was maintained at ca. 0.5 cm 2 (5 mm × 5 mm, double sides) by using epoxy to seal the remaining electrode surface. The geometric electrode area was measured and used to calculate the current density. The reference electrode was a 1 mm diameter Al wire (Alfa Aesar, 99.999%) immersed into t...