Poster Session May,2015

Battery Section

Much interest has been flowing towards the trending high energy density batteries for wide applications including the most vital grid storage, electric vehicles and portable electronics. Alloy-type anodes (Si, Ge, Sn, Al, Sb, etc.) have much higher Li storage capacity than the intercalation-type graphite anode that is currently commercially used in Li-ion batteries. The theoretical capacities of alloy anodes are 2- 10 times higher than that of graphite and 4-20 times higher than that of the lithium titanate anode. Also, these alloy based anode materials have a moderate onset potential ranging between 0.3-0.4 V above Li/Li+, gaining safety advantages over low potential graphite anode and avoiding energy penalty over LTO anode.

In the last few years, research to determine the most suitable anode and cathode materials for Na-ion batteries has gained an increased attention. It was a great surprise to discover that pure commercially available elements such as Sb, Sn, or P1-3 can react electrochemically with Na, leading to sustainable reversible capacities as high as 500 mAh/g over more than 100 cycles when carboxymethyl cellulose (CMC) binder is used. These results were unexpected, especially if we compare them to the Li-ion systems. The most commonly used Li-ion binder, polyvinylidene difluoride (PVDF), was reported to not work in the sodium system but no further investigation was done to understand the chemical reasons. Recently, Dahbi et al.4 reported on Na-CMC binder for hard carbon electrodes in Na-ion batteries. They demonstrated better electrochemical results with CMC binder than with PVDF. They also reported that fluoroethylene carbonate (FEC) was essential as an electrolyte additive to improve the cyclability of the PVDF-based electrode.

Thermal Energy Section

At present, electricity storage with advanced adiabatic compressed air energy storage (AA-CAES) is considered to the only large-scale alternative to pumped hydro storage. Thermocline storage has gained increasing interest as a solution for thermal energy storage with potentially high efficiency and low costs. The present research aims at enhancing the concept using an experimental-numerical approach to study combined sensible/latent heat storage, which is based on placing a limited amount of steel-encapsulated AlSi12 on top of a packed bed of rocks. The primary motivation for combining sensible and latent heat storage is to reduce the decrease in outflow temperature during discharging of sensible heat storage, which is favorable for downstream applications such as chemical reactions or thermodynamic power cycles. Air is used as heat transfer fluid and the storage may be operated at ambient pressure or at high pressure for the use in AA-CAES.

Single-tank, or thermocline, thermal energy storage (TES) systems, with a packed bed of low cost filler material, represent a valuable alternative to the commonly exploited two-tank solution in nowadays conventional concentrating solar power (CSP) plants. However, an intrinsic drawback of this solution is the decrease of the heat transfer fluid (HTF) outlet temperature, towards the end of the discharge phase, leading to a detrimental effect on the power block efficiency. To avoid the HTF temperature decrease during discharging, a latent heat TES, based on phase change material (PCM), might be exploited instead. However, the high cost of the PCM, along with the relatively low efficiency for large temperature ranges1, are strong limiting factors on the integration of a latent TES into a CSP plant. For this reason, the idea of adding a small amount of encapsulated PCM on top of the packed bed was proposed with the aim of mitigating the HTF temperature decrease during discharging limiting, at the same time, the increment of the overall TES system cost.

Hydrogen Section

Recently, our laboratory has developed the concept of a dual-circuit redox flow battery in order to improve the energy density of conventional redox flow batteries (RFBs)1. The battery is adapted with an external circuit that enables chemical discharge of the electrolytes on demand. This chemical discharge is a fast alternative to electrochemical discharge and enables the production of useful products simultaneously to the regeneration of the discharged electrolyte. On the negative side of the all-vanadium RFB the V(II) electrolyte is discharged to V(III) when passed over a Mo2C catalytic bed: this reaction generates hydrogen from the protons present in the solution.

Synthetic Fuel Section

Carbon dioxide is a major contributor to global warming and, beyond the mandatory reduction of our emissions, the possibility of recycling this greenhouse gas is becoming increasingly attractive. The electrochemical reduction of CO2 is an interesting pathway, since a broad range of useful products can be formed such as methanol and formic acid (fuels for PEFC), methane and ethylene (reactants for synthesis or combustion process), CO and H2 (syngas), etc. [1]. Nevertheless, on top of the high overpotential required to drive this reaction, the electrochemical reduction of CO2 suffers from a poor yield/selectivity of valuable products [2, 3].Copper-based electrocatalysts seem to be the most efficient to overcome these kinetic and barriers [3], but it has been shown that the size of the Cu (nano)particles envisaged for practical applications can influence the reaction selectivity [4]. In order to clarify this particle size effect, one needs to determine the electrochemically active surface area (ECSA) of the catalysts of interest that, for Cu, can be derived in-situ by lead underpotential deposition (Pb-UPD) [5]. Additionally, the selectivity of the CO2-reduction reaction on these well-characterized materials needs to be determined with an appropriate technique