Animal disease and narratives of nature: Farmers' reactions to the neoliberal governance of bovine Tuberculosis

This paper examines the relationship between neoliberal styles of animal disease governance and farmers' understandings of disease and nature. In the UK, new styles of animal disease governance has promised to shift the costs and responsibilities of disease management to farmers, creating opportunities for farmers to take responsibility for disease control themselves and opening up new markets for disease control interventions. Focussing on the management of bovine Tuberculosis (bTB) and drawing on interviews with 65 cattle farmers, the paper examines how farmer responses to these new styles of animal disease governance are shaped by their own knowledges and understandings of nature and disease. In particular, the paper examines how two key narratives of nature – the idea of ‘natural balance’ and ‘clean and dirty badgers’ – lead farmers to think about the control of bTB in wildlife (such as the choice between badger culling and/or vaccination) in very specific ways. However, whilst discourses of cost and responsibility appear to open up choice opportunities for farmers, that choice is constrained when viewed from the perspective of farmer subjectivities and narratives of nature. Discourses of neoliberalism as control rather than choice are therefore revealed, drawing attention to the complexities and plural strategies of neoliberal governance

Lithium-sulfur batteries: an investigation into the electrolyte and the polysulfide species within

The lithium-sulfur (Li-S) battery is one of the most promising candidates in next generation energy storage, offering high theoretical specific capacities through the use of inexpensive and environmentally benign positive electrode materials. However, full commercialisation has been prevented by several technical challenges, most notably polysulfide shuttling. Despite significant scientific interest in recent years, the mechanism of the discharge and charge processes is still poorly understood. Whilst it is known that a variety of different processes occur between electrochemically active species during cycling, the identity of the polysulfides species remains unknown. Additionally, the polysulfide concentrations at different stages of discharge and charge, as well as their thermodynamic and kinetic properties are still poorly understood.In this project, the significance of cell design on the cycling performance of a Li-S battery is highlighted. The reproducibility of a selected cell design and the effect of lithium nitrate as an electrolyte additive is investigated. To obtain a thorough understanding of the electrolyte system used throughout this report (LiTFSI in DOL), various electrolytes containing different concentrations of the electrolyte salt are prepared and analysed. Using a Walden plot, it is revealed that at high salt concentrations, this electrolyte system begins to exhibit properties similar to that of an ionic liquid. Additionally, employing high salt concentrations improves the cycling performance of the Li-S battery. Two methods have been developed to quantitatively determine the total ‘sulfur’ content of an electrolyte containing polysulfides, as well as its average oxidation state. These techniques have enabled production of the first experimental ternary phase diagram for the Li-S battery. Finally, the galvanostatic intermittent titration technique (GITT) method is quantitatively analysed using a model redox system to assess its ability to determine the diffusion coefficient of the redox system. This study offers a unique assessment of the ability to use GITT to study the mass transport of polysulfide intermediates within a Li-S battery

A simple, experiment-based model of the initial self-discharge of lithium-sulphur batteries

One of the main challenges in the development of lithium-sulphur batteries is the so called “shuttle mechanism”, which involves the diffusion of sulphur and polysulphides from the sulphur electrode to the lithium electrode, where they get reduced via chemical reactions with lithium. The shuttle mechanism decreases the capacity delivered by the battery, hampers its rechargeability, and promotes battery self-discharge. We have developed a simple model of the shuttle mechanism that reproduces quantitatively the rate of the initial self discharge of lithium-sulphur batteries. The rate of sulphur and polysulphide diffusion has been quantified by studying cells with varying number of separators between the electrodes. We have found that it is essential that the model incorporates the presence of carbon additive in the sulphur electrode, which slows down the decrease of the open circuit potential with time. The model also reproduces well the rate of self-discharge of lithium-sulphur cells containing sulphur dissolved in the electrolyte. In conclusion, the present model provides a basic understanding of the mechanism of self-discharge of lithium-sulphur cells, and allows quantifying the two main causes of sulphur loss at the sulphur electrode: sulphur diffusion across a concentration gradient and sulphur reaction with polysulphides formed at the lithium electrode

Impedance characterization of the transport properties of electrolytes contained within porous electrodes and separators useful for Li-S batteries

Impedance spectroscopy is used to characterize the key transport properties (effective conductivity, MacMullin number, porosity and tortuosity) of electrolyte solutions confined in porous separators and carbon-sulfur composite electrodes useful for application in Li-S batteries. Three relevant electrolyte concentrations, ranging between 1 and 5 molal, are studied. Impedance measurements are performed in symmetrical cells with two identical electrodes, which overcome complications associated with the contributions of the counter-reference electrode. The electrolyte-filled carbon-sulfur composite electrodes can be represented by an “open” Warburg element, modelling the finite-diffusion of ions through the pores coupled to the double-layer charging of the electrode-electrolyte interface. The carbon-sulfur composite electrodes are at a high enough potential (ca. 3 V vs. Li+/Li) so that charge-transfer reactions of sulfur reduction to polysulfide species are absent during the impedance measurements, and hence capacitive-like behavior is observed at low frequencies. The analysis of the results shows that the rate of transport of ions through porous structures is markedly dependent on the electrode's structure and composition as well as the electrolyte concentration. Synergistic effects, able to enhance the effective conductivity of the electrolyte inside porous composite electrodes, are observed for particular electrode/electrolyte combinations, which are correlated to enhanced performance in Li-S cells

Predicting the composition and formation of solid products in lithium-sulfur batteries by using an experimental phase diagram

Lithium–sulfur batteries discharge via the transformation of solid sulfur to solid lithium sulfide via the formation of several polysulfide species that have only been observed in solution. Reported here is the first experimental phase diagram of a S8–Li2S-electrolyte system, which is shown to be a practical tool to determine the solution composition and formation of solid (S8 and Li2S) phases in lithium–sulfur batteries. The phase diagram is constructed by the combination of measurements of the total sulfur concentration [S]T and average oxidation state (Sm?) of polysulfide solutions prepared by reaction of S8 and Li2S. The phase diagram is used to predict the equilibrium discharge/charge profile of lithium–sulfur batteries as a function of the amount of electrolyte and the onset of precipitation and dissolution of solid products. High energy batteries should operate with a minimum amount of electrolyte, where both solid S8 and Li2S will be present during most of the charge and discharge of the cell, in which case we predict the observation of only one voltage plateau, instead of the two voltage plateaus commonly reporte

Dataset for PhD thesis "Cell designs and methods for characterisation of lithium protective membranes, solid electrolytes and beyond"

Dataset for PhD thesis &quot;Cell designs and methods for characterisation of lithium protective membranes, solid electrolytes and beyond&quot; by Nina Meddings. Awarded 2020</span

Ion speciation and transport properties of LiTFSI in 1,3-dioxolane solutions: A case study for Li–S battery applications

The Lithium–Sulfur battery is considered to be one of the main candidates for the “post-lithium-ion” battery generation, because of its high theoretical specific capacity and inherently low cost. The role of the electrolyte is particularly important in this system and remarkable battery performances have been reported by tuning the amount of salt in the electrolyte. To further understand the reasons for such improvements we chose the lithium bis(trifluoromethanesulfonyl)imide in 1,3-dioxolane electrolyte as a model salt-solvent system for a systematic study of conductivity and viscosity over a wide range of concentration from 10-5 up to 5 molal. The experimental results, discussed and interpreted with reference to the theory of electrolyte conductance, lead to the conclusion that triple ions formation is responsible for the highest molal conductivity values before reaching the maximum at 1.25 molal. At higher concentrations, the molal conductivity drops quickly due to a rapid increase in viscosity and the salt–solvent system can be treated as a diluted form of molten salt

Dataset for Impedance Characterisation of the Transport Properties of Electrolytes Contained Within Porous Electrodes and Separators Useful For Li-S Batteries

Dataset supports: Raccichinia, Rinaldo (2018). Impedance Characterization of the Transport Properties of Electrolytes Contained within Porous Electrodes and Separators Useful for Li-S Batteries. Journal of the Electrochemical Society.Impedance spectroscopy is used to characterise the key transport properties (effective conductivity, MacMullin number, porosity and tortuosity) of electrolyte solutions confined in porous separators and carbon-sulfur composite electrodes useful for application in Li-S batteries. Three relevant electrolyte concentrations, ranging between 1 molal and 5 molal, are studied. Impedance measurements are carried out using symmetrical cell configurations, which significantly improve the accuracy of the results and avoids complications associated with the contributions of the counter-reference electrode in two-electrode cell measurements. The impedance response of the electrolyte-filled carbon-sulfur composite electrodes can be represented by an &ldquo;open&rdquo; Warburg element, modelling the finite-diffusion of ions through the pores coupled to the double-layer charging of the electrode-electrolyte interface. The as-prepared carbon-sulfur composite electrodes are at a high enough potential (ca. 3 V vs. Li+/Li) so that charge-transfer reactions of sulfur reduction to polysulfide species are absent during the impedance measurements, and hence capacitive-like behaviour (i.e., blocking behaviour) is observed at low frequencies. The analysis of the results shows that the rate of transport of ions through porous structures is markedly dependent on the electrode&rsquo;s structure and composition as well as the electrolyte concentration. Synergistic effects, able to enhance the effective conductivity of the electrolyte inside porous composite electrodes, are observed for particular electrode/electrolyte combinations, which are correlated to enhanced performance in Li-S cells.</span

Ion Speciation and Transport Properties of LiTFSI in 1,3-Dioxolane Solutions: A Case Study for Li–S Battery Applications

Lithium–sulfur battery is considered to be one of the main candidates for “post-lithium-ion” battery generation because of its high theoretical specific capacity and inherently low cost. The role of electrolyte is particularly important in this system, and remarkable battery performances have been reported by tuning the amount of salt in the electrolyte. To further understand the reasons for such improvements, we chose the lithium bis­(trifluoromethanesulfonyl)­imide in 1,3-dioxolane electrolyte as a model salt–solvent system for a systematic study of conductivity and viscosity over a wide range of concentration from 10^–5 up to 5 <i>m</i>. The experimental results, discussed and interpreted with reference to the theory of electrolyte conductance, lead to the conclusion that triple ion formation is responsible for the highest molal conductivity values before reaching the maximum at 1.25 <i>m</i>. At higher concentrations, the molal conductivity drops quickly because of a rapid increase in viscosity and the salt–solvent system can be treated as a diluted form of molten salt