Ionic liquids as electrolytes for energy storage applications – A modelling perspective

Ionic liquids as electrolytes for energy storage devices is a promising field. Here, the various approaches of how ionic liquids can be modelled are discussed along with how the modelling connects to experimental results. Recent theoretical developments are highlighted along with extended discussion of what molecular dynamics simulation options are now available and what key results can be extracted. Ab initio work is also discussed, this includes some of the spectral properties, both of ionic liquids and their electrolyte formulations

Towards standard electrolytes for sodium-ion batteries: physical properties, ion solvation and ion-pairing in alkyl carbonate solvents

The currently emerging sodium-ion battery technology is in need of an optimized standard organic solvent electrolyte based on solid and directly comparable data. With this aim we have made a systematic study of "simple"electrolyte systems consisting of two sodium salts (NaTFSI and NaPF6) dissolved in three different alkyl carbonate solvents (EC, PC, DMC) within a wide range of salt concentrations and investigated: (i) their more macroscopic physico-chemical properties such as ionic conductivity, viscosity, thermal stability, and (ii) the molecular level properties such as ion-pairing and solvation. From this all electrolytes were found to have useful thermal operational windows and electrochemical stability windows, allowing for large scale energy storage technologies focused on load levelling or (to a less extent) electric vehicles, and ionic conductivities on par with analogous lithium-ion battery electrolytes, giving promise to also be power performant. Furthermore, at the molecular level the NaPF6-based electrolytes are more dissociated than the NaTFSI-based ones because of the higher ionic association strength of TFSI compared to PF6- while two different conformers of DMC participate in the Na+ first solvation shells-a Na+ affected conformational equilibrium and induced polarity of DMC. The non-negligible presence of DMC in the Na+ first solvation shells increases as a function of salt concentration. Overall, these results should both have a general impact on the design of more performant Na-conducting electrolytes and provide useful insight on the very details of the importance of DMC conformers in any cation solvation studies

Trends in Fish Price Volatility: Icelandic Whitefish

For centuries, the Icelandic people has relied on its abundance of natural resources and fisheries in particular. In today’s volatile and homogenous economy of Iceland, fisheries is one of its main export industries, together with power-intensive manufacturing and tourism. Consequently, movements in fish prices have a significant effect on the economy as a whole, making the small nation of Iceland vulnerable to fish price volatility.  In this study, we investigate market price uncertainty of exported whitefish in Iceland. Among whitefish, cod is the most important fish species for the Icelandic fisheres, with haddock and pollack following. We model the price volatility for a set of whitefish speiees and establish empirically that price volatility is stable or in a downward trend. Contributing factors such as the food price trends and trends in world whitefish markets are discussed. In addition, we account for other contributing factors to volatility such as the financial crisis, exchange rates, quota restriction and policy implications

Towards standard electrolytes for sodium-ion batteries: physical properties, ion solvation and ion-pairing in alkyl carbonate solvents.

The currently emerging sodium-ion battery technology is in need of an optimized standard organic solvent electrolyte based on solid and directly comparable data. With this aim we have made a systematic study of "simple" electrolyte systems consisting of two sodium salts (NaTFSI and NaPF6) dissolved in three different alkyl carbonate solvents (EC, PC, DMC) within a wide range of salt concentrations and investigated: (i) their more macroscopic physico-chemical properties such as ionic conductivity, viscosity, thermal stability, and (ii) the molecular level properties such as ion-pairing and solvation. From this all electrolytes were found to have useful thermal operational windows and electrochemical stability windows, allowing for large scale energy storage technologies focused on load levelling or (to a less extent) electric vehicles, and ionic conductivities on par with analogous lithium-ion battery electrolytes, giving promise to also be power performant. Furthermore, at the molecular level the NaPF6-based electrolytes are more dissociated than the NaTFSI-based ones because of the higher ionic association strength of TFSI compared to PF6- while two different conformers of DMC participate in the Na+ first solvation shells - a Na+ affected conformational equilibrium and induced polarity of DMC. The non-negligible presence of DMC in the Na+ first solvation shells increases as a function of salt concentration. Overall, these results should both have a general impact on the design of more performant Na-conducting electrolytes and provide useful insight on the very details of the importance of DMC conformers in any cation solvation studies

Toward Reversible and Moisture-Tolerant Aprotic Lithium-Air Batteries

The development of moisture-tolerant, LiOH-based non-aqueous Li-O2 batteries is a promising route to bypass the inherent limitations caused by the instability of their typical discharge products, LiO2 and Li2O2. The use of the I−/I3− redox couple to mediate the LiOH-based oxygen reduction and oxidation reactions has proven challenging due to the multiple reaction paths induced by the oxidation of I− on cell charging. In this work, we introduce an ionic liquid to a glyme-based electrolyte containing LiI and water and demonstrate a reversible LiOH-based Li-O2 battery cycling that operates via a 4 e−/O2 process with a low charging overpotential (below 3.5 V versus Li/Li+). The addition of the ionic liquid increases the oxidizing power of I3−, shifting the charging mechanism from IO−/IO3− formation to O2 evolution

Stabilisation of the superoxide anion in bis(fluorosulfonyl)imide (FSI) ionic liquid by small chain length phosphonium cations: Voltammetric, DFT modelling and spectroscopic perspectives

Ionic liquids (ILs) containing the bis(fluorosulfonyl)imide anion, FSI, have been investigated as electrolytes for metal-air batteries. Full chemical reversibility is found for the reduction of oxygen to superoxide at 60 degrees C under short time scale conditions of cyclic voltammetry at a glassy carbon electrode when the IL contains the small chain length triisobutyl(methyl)phosphonium rather than a pyrrolidinium cation. DFT calculations suggest that this is a consequence of the higher ion pair association energy and shorter intermolecular distance associated with the interaction of the superoxide anion with the phosphonium cation. Stabilization on longer timescales was also established by spectroscopic techniques when the phosphonium based ILs were exposed to KO2. Studies on superoxide stability in related ionic liquids containing the triisobutyl(methyl)phosphonium cation with the fluorosulfonyl(trifluoromethanesulfonyl)imide, FTFSI, or bis(trifluoromethanesulfonyl)imide, TFSI, anions are also reported.

A model for cash management: An aquaculture case study

Master's thesis in Industrial economicsThe problem of maximizing interest earned on cash surplus gained from a firm's operation can involve considerable complexity, especially when there are seasonal factors and uncertainty involved. The network flow model with gains and losses for use in cash management was first presented in 1979 by Golden and Libertore. Their model is deterministic, but in this thesis, stochastic techniques are implemented to the model, as well as introducing different asset classes. Value at risk (VaR) is commonly used in the financial industry to quantify risk in asset portfolios. Cash-flow-at-Risk (CFaR) has been considered the VaR alternative for non-financial firms, by quantifying the potential loss in earnings from operations. In this thesis, the CFaR is implemented to the network flow model to determine the minimum level of cash in the operation of an aquaculture company. For this strategy to be successfully implemented it is necessary to include a rolling planning horizon to achieve the optimum investment strategy. There is considerable number of risk factors involved in the operation of an aquaculture company. The price of salmon has historically been very volatile and difficult to predict. The operations of an aquaculture company involves cycles and periods of low and high margin. In such cases, effective cash management is important. By retaining earning from periods of high earning to meet the potential lower margin periods is a step toward ensuring that the company has enough cash resources to meet its future obligations

Ab initio modelling of alkali-ion battery electrolyte properties

Lithium-ion batteries are omnipresent in modern electronics. They can be found in laptops, mobile phones and electric vehicles. However, there is room for both improvement, as the thermal instability of the dominant lithium salt used in batteries today, LiPF6, causes safety concerns, and more fundamental changes, as there is a limited amount of lithium available – resulting in sodium-ion batteries being a nascent field of study.This thesis looks in detail at some underlying fundamental features affecting properties ofelectrolytes of both lithium-ion and sodium-ion batteries. These properties include the oxidative stability of the anions of the lithium and sodium salts (important for voltage and safety); the cation-anion interaction strength (important for conductivity); the solvation of the lithium and sodium cations in the common carbonate solvents (important for conductivity and the (de-)solvation at the anodes/cathodes); and the thermal stability of the anions and the possible decomposition reactions (important for safety).The properties are mainly studied for a number of both novel and well established anions. Some of the novel anions involve completely new concepts for anion design for alkali-ion battery electrolytes. The systems are studied with a number of ab initio methods, most based on density functional theory (DFT).These include high level calculations of benchmark quality. The applicability of DFT and the selection of DFT functionals is also studied. Novel calculation strategies were employed to understand thermal decomposition