278 research outputs found
On the role of saturation in modeling ionic transport in the electrolyte of (Lithium ion) batteries
No full textRecent computational simulations of ionic conductivity across the electrolyte of commercial batteries by Salvadori et al. (2015) have shown that the concentration of ions exceeds half the saturation limit near the electrodes. This observation, which is in agreement with other approaches by Danilov and Notten (2008), implies that the widespread assumption of infinite dilution far from saturation is questionable. The present contribution is therefore devoted to investigate the role of saturation in modeling ionic transport in the electrolyte of Li-ion batteries. An important result is found, that saturation has no effect on the diffusivity, whereby the condition of electroneutrality is well approximated in the solution. However saturation affects the electric potential up to 40% near the electrodes for all charge rates
Hypochlorite reduction at GaAs : a multifaceted reaction
No full textIt is shown that the reduction of hypochlorite at p-GaAs is not a simple valence band process, as expected for a strong oxidizing agent. In the dark, reduction indeed occurs via hole injection into the valence band but the reduction rate is low. Under illumination at a low light intensity hypochlorite acts as a current doubling agent, indicating that reduction occurs in two discrete steps. It is argued that in the first step, electron transfer occurs via surface states. This is followed by a hole injection step. At high light intensity, the reduction rate is controlled by mass transport of OCl-1 ions in solution. In this case, the valence band reaction is markedly increased due to a large displacement of the semiconductor band edges as a result of negative charging of the surface states. An unexpected feature of this system is that hypochlorite etches GaAs "chemically" in the dark
Title: Electrochemical Storage of Energy in Single-wall Carbon Nanotubes Author(s): J. de Jonge; R.A.H. Niessen; P.H.L. Notten
No full textAbstract: In order to study the possibilities of reversible electrochemical storage of energy in single wall carbon nanotubes (SWNTs), it is necessary to purify the as-produced (a.p.) SWNTs. In this study an attempt was made to develop a purification procedure for a.p. arc discharge SWNT material. Subsequently, many electrochemical experiments were performed to study the electrochemical storage of hydrogen and lithium in an aqueous electrolyte and an organic electrolyte respectively. For these experiments the as-produced SWNTs, partially purified SWNTs and commercially purified SWNTs were used. In addition to these materials, also a.p. laser ablation SWNTs were used in the organic electrolyte. The purification of a.p. SWNTs was found to be a very complicated procedure. The main difficulty was to develop an effective manner to remove the impurities without causing any damage to the vulnerable nanotubes. Particularly the removal of disordered carbon and graphite from the asproduced material in a non-destructive manner was found to be extremel
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