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Highly Siderophile Elements (HSE) Geochemistry in Magmatic Systems
No full textThe highly Siderophile Elements (HSE) comprise Re and Au, along with the six platinum-group elements Os, Ir, Ru, Pt, Rh and Pd. Importantly, for geologists and metallurgists, the HSEs are valued for their distinctive geochemical properties as both siderophile and chalcophile elements, i.e. having a strong affinity for both metal and sulphur phases.
Micro-sized metal particles (nuggets) in quenched silicate melts have been a major obstacle in the experimental study of HSE geochemistry. The persistence of even a small fraction of nuggets can have a significant influence on the measurement of the very low HSE concentrations in quenched silicate melts (glasses). Consequently, experimentally reported partition coefficients between metals, sulfide liquids, and silicate melts can be severely compromised, leading to erroneous and misleading inferences. Furthermore, the influence of sulfur on the solubility of the HSE requires further evaluation, despite sulfur being one of the most abundant volatiles in terrestrial magmas. Published HSE partition coefficients between metals, sulfide liquids, and silicate melts can vary by orders of magnitude, and these differences can be due to failing to eliminate the nugget effect or to underestimating the influence of S on the solubility of the HSE in silicate melts.
The primary objectives of this study were to: (i) develop and evaluate strategies to minimize the nugget effect, (ii) improve analytical methods for quantifying trace HSE analyses using silicate melt-based standards (e.g., GM-01), (iii) quantitatively assess the effect of sulfur on HSE solubility in silicate melts, and (iv) identify the dissolution mechanisms of HSEs in silicate melts.
The experiments were conducted at ambient pressure using synthetic silicate melts. Both sulfur-free (S-free) and sulfur-bearing (S-bearing) conditions were studied, at controlled oxygen fugacity (fO2) and sulfur fugacity (fS2). Strategies to suppress nuggets included oxidation state management to prevent initial oversaturation and extended duration experiments to eliminate or manage nuggets through Ostwald ripening. Samples with low Pt were analysed by laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICPMS), which has an order-of-magnitude lower detection limit for Pt than conventional ICP-MS analyses.
Nugget formation was eliminated or reduced to a manageable level through a combination of redox control and extended experiments (Ostwald ripening), facilitating high-quality data acquisition. Under S-free conditions, Au and Pd solubility increased with fO2 with Au1+ and Pd1+ identified as dominant species alongside neutral valences. Sulphur significantly enhanced Au solubility in S-bearing systems confirming dissolution via a previously unrecognised AuS2 complex. Pd solubility, however, was independent of sulfur, indicating no ligand preference. Pt exhibited increased solubility with fS2, with Pt0 and Pt2+ species in silicate melt together with PtS under S-bearing conditions. Rhodium solubility is also dependent on fO2
and fS2, but the effect of S is less constrained due to limited data. The effect of S on the solubility of the HSE in silicate melts is established as Au > Pt > Rh > Pd, reflecting sulfur's variable influence.
These results provide refined metal-silicate melt partition coefficients (D(Metal/SM)) for the HSEs, which have applications in geodynamic modelling of planetary differentiation and Pt-Pd-rich horizons in layered intrusions (e.g., Skaergaard, Stillwater and Bushveld complexes). The solubility models will help metallurgists optimize HSE extraction during smelting. Future work should expand data on D(Sulfide liquid/Metal)and integrate thermodynamic parameters for the sulfur content of silicate melts at sulfide saturation (SCSS) to advance predictive frameworks for HSE behavior in natural and industrial systems
Cruelty, Coverture, and Colonial Women's Writings: A Cultural and Social History of Domestic Violence in New South Wales, Queensland, and Victoria, 1880-1914
No full textWhen Australian Prime Minister Anthony Albanese declared domestic violence to be a 'national crisis' in April 2024, he was likely unaware that he echoed Victorian Chief Justice Sir John Madden, who, 110 years earlier, similarly declared domestic violence, or 'wife-desertion and wife-persecution', to be a 'national crime' and a 'social menace'. Although the nature and prevalence of domestic violence in Australia have received significant scholarly, public, political, and legal attention in the last decade, historians have been at pains to demonstrate that it is not a new issue. This thesis builds on and revises existing scholarship, using a corpus of new evidence to explore the formative period of 1880-1914 when domestic violence was arguably at its most visible. As the writings of feminist authors, wives, judges, and journalists reveal, not only was 'wife-beating' a considerable source of cultural debate and social anxiety in this period, but from 1890 onwards, judicial delineations of 'cruelty' expanded. Influenced by the lived experiences that victim-survivors graphically detailed in their divorce petitions, judges redefined 'cruelty' to include what we would now term coercive control, reproductive coercion and abuse, marital rape, and economic abuse as unacceptable masculine marital behaviours. Examining this expanded conceptualisation of marital cruelty, this thesis reconciles contemporary understandings of domestic violence with historical social and cultural understandings to offer one of the first period-specific histories of domestic violence in Australia - with a focus on New South Wales, Queensland, and Victoria - that also sheds light on the long and insidious history of our 'national crisis'.
The thesis focuses on both the rhetoric and realities of domestic violence in this period, drawing 35 literary works by five key colonial female writers (Barbara Baynton, Ada Cambridge, Leontine Cooper, Louisa Lawson, and Rosa Praed), 320 petitions for the dissolution of marriage, and articles from over 60 local and regional newspapers into conversation with each other. It argues that a significant but hitherto unexplored group of feminist writers including victim-survivors, journalists, and colonial female authors used print, press, and the petition to protest the enduring grasp of coverture and challenge cultural stereotypes of 'wife-beating' as purely physical abuse inflicted by drunk, working-class men. These women articulated the multiple physical and non-physical forms a husband's abuse could take, which they demonstrated to be perpetrated by even the most 'respectable' or 'gentlemanly' of husbands in both urban and rural spaces. In doing so, they elevated domestic violence to the status of a national failing, even when their suffragist sisters were silent on the very same subject. Indeed, this thesis disrupts existing understandings about the historical relationship between domestic violence and feminism by challenging misconceptions about the level of concern Australian suffragists devoted to the issue and spotlighting the women who did make domestic violence a key topic of contemporary calls for social and cultural reform of gender relations. In doing so, this thesis not only elucidates the endemic and multifaceted nature of domestic violence at the time of Australia's national, political, and cultural foundation, but also shows it as the pivotal period when domestic violence first became simultaneously a 'feminist' and national issue
Strengthening regional arrangements for the protection and promotion of human rights in the Pacific
No full textStates as duty bearers have an obligation under international law to protect and promote human rights. All Pacific Islands Forum (PIF) Member States embed these obligations within various normative and institutional frameworks. These regulatory systems are designed to enhance the protection of human rights. However, there are significant protection gaps at the national or State level and at the (Pacific) regional level. This dissertation responds to the question of how Pacific States can address these human rights protection gaps and strengthen State obligations to protect and promote human rights. Using a qualitative study, this research adopts a Pacific talanoa method of sharing information and ideas on issues and in this context, human rights in the Pacific. The dissertation examines the conceptualisation of human rights at the national and regional level and the role of Pacific States in safeguarding human rights. I found that while human rights understanding is evolving in the Pacific and is widely accepted across the region, human rights tensions remain. The challenges and tensions are in its enforcement and conceptualisation.
To address these tensions, my dissertation argues that institutionalising human rights will significantly contribute to its understanding and practical implementation. The thesis advances scholarly understanding of the roles of both national and regional human rights institutions in addressing protection gaps by (1) conceptualising human rights in a local and regional context, (2) vernacularising human rights, and (3) supporting the implementation of human rights commitment and obligations. I demonstrate this by drawing on two case studies showing how Fiji and Samoa's national human rights institutions (NHRI) are advancing human rights protection and understanding in their nations. Samoa's NHRI annual human rights reports (the first and only such mechanism in the Pacific) serve as a monitoring mechanism for the State in gauging its human rights obligations on various thematic issues and implementation. This unique form of monitoring and accountability by the NHRI enhances the credibility of promoting human rights understanding in the community, especially in linking the important cultural concept of fa'aSamoa to human rights. Moreover, the thesis finds that Fiji's NHRI amicus curae role significantly contributes to creating accountability of the State's legal obligation to protect human rights by enforcing the obligations in Fiji's normative legal instruments and those derived under human rights treaties. Furthermore, both Samoa and Fiji NHRI advance human rights education, awareness, and build human rights capacity through training across all levels of society.
The dissertation also examines human rights protection at the regional level. It argues that significant human rights protection gaps exist because of the lack of institutional mechanisms. Using a comparative lens by drawing from the human rights' architectural experiences of the African, inter-American and European regions, the thesis argues for the establishment of a Pacific human rights architecture to address the region's protection gaps, especially in the context of climate change. This dissertation builds on the initial work on the conceptualisation of a (Pacific) regional human rights mechanism by the Law Associations for Asia and the Pacific (LAWASIA) in 1985. However, the dissertation makes an original contribution on how human rights institutions, both at the national and regional level, can contribute to vernacularising human rights by synergising human rights principles with Pacific values. The dissertation argues for the establishment of human rights institutions at the national and regional level to address the human rights protection gaps in the Pacific
Enduring burden of intensive care
No full textBackground:
Existing literature on PICS and PICS-F focuses predominantly on intubated ICU survivors, limiting understanding of non-intubated survivors' outcomes. Gaps remain in local epidemiology of long-term psychological/QOL outcomes, dyadic interactions, and ward rehabilitation barriers for survivors and families.
Objectives:
1. To determine long-term psychological and QOL outcomes of ICU survivors
2. To determine long-term psychological and QOL outcomes of family members of ICU survivors
3. To investigate dyadic influences between survivor-family pairs
4. To assess ward-based rehabilitation practices and to identify barriers to delivering effective post-ICU rehabilitation care
Methods:
A prospective, multicentre observational cohort study was conducted across four Australian ICUs. Adult survivors and their paired family members were recruited and longitudinally followed up post-ICU discharge. Participants were screened for persistent psychological (post-traumatic stress disorder [PTSD], depression, anxiety) symptoms and QOL impairments. Clinically significant psychological symptoms were defined according to established cut-off scores for validated screening instruments. Dyadic analyses were performed to examine associations between psychological symptoms and QOL impairments within the survivor-family pairs. Additionally, a locally developed, single-centre survey of multidisciplinary healthcare professionals caring for ICU survivors was used to address the final study objective.
Results:
Patients: Of the 133 ICU survivors, 47 % had at least one clinically significant psychological symptom at follow-up. There was no difference in the clinically significant scores for psychological symptoms at 3-months (p=0.38) or 12-months (p=0.57) between the intubated and non-intubated survivors. Usual activities and mobility were the most commonly affected QOL domains, with > 30 % at 3 months and > 20 % at 12-months of overall survivors reporting >/= moderate problems in these domains.
Families: In family members of intubated vs non-intubated survivors, clinically significant psychological symptoms (PTSD/depression/anxiety) were reported by 48% vs 33% at 3-months (p = 0.15); and 39% vs 25% at 12-months (p = 0.23). With regards to QOL, > 30% of the family members, reported problems in pain/discomfort or anxiety/depression domains at 12-months. Dyads: Family members were more likely to have persistent psychological symptoms of PTSD (p = 0.01) or depression (p = 0.001); or QoL domain problems with pain/discomfort (p = 0.03) or anxiety/depression (p = 0.04), when the paired survivor also reported the same symptoms.
Barriers to rehabilitation: Most respondents (66%, 126/190) were unfamiliar with the term post-intensive care syndrome (PICS). There were multifaceted barriers to patient mobilisation, with inadequate multidisciplinary staffing, lack of medical order for mobilisation, and inadequate physical space near the bed as common institutional barriers and patient frailty and cardiovascular instability as the commonly perceived patient-related barriers.
Conclusions:
Nearly one-in-two (47 %) of the intubated and non-intubated ICU survivors reported clinically significant psychological symptoms at 3 and 12-month follow-ups. The presence of psychological symptoms and HRQOL impairments was similar between the survivor groups. Almost one-third of the family members of ICU survivors also reported persistent psychological symptoms and QoL problems at 12-months. There was a noticeable dyad effect with family members more likely to have persistent symptoms of PTSD, depression, and problems in QoL domains when the paired ICU survivors experienced similar symptoms. Future long-term follow-up should include non-intubated ICU survivors and recovery intervention trials should be aimed at ICU family-survivor dyads. Additionally, there are multiple potentially modifiable barriers to the ongoing rehabilitation of ICU survivors
Towards understanding and targeting the Plasmodium falciparum CoA biosynthesis pathway
No full textPantothenate, a precursor of the fundamental enzyme cofactor coenzyme A (CoA), is an essential nutrient for the intraerythrocytic stage of the human malaria parasite Plasmodium falciparum. P. falciparum has been shown to be capable of de novo synthesis of CoA from pantothenate via a five-step universal pathway. Pantothenate kinase (PanK) catalyses the first step of the CoA biosynthesis, which has been suggested to determine the rate of CoA biosynthesis in many organisms. In contrast, the phosphopantothenoylcysteine synthetase (PPCS)-mediated step has been proposed as the flux control step of the parasite CoA biosynthesis. P. falciparum expresses two PanKs, PfPanK1 and PfPanK2, which assemble into a unique heteromeric complex with a potential regulatory protein, Pf14-3-3I. Similarly, the parasite expresses two putative PfPPCSs, PfPPCS1 and PfPPCS2, neither of which have been characterised.
Site-directed mutagenesis of key residues in PfPanK1 and PfPanK2 predicted to be involved in active site stabilisation was performed. Bioinformatic and mutagenesis studies revealed that the heteromeric PfPanK complex only possesses one functional active site. A parasite line that allows inducible knockdown of PfPanK2 was generated and PfPanK2 was found to be essential for normal intraerythrocytic proliferation of P. falciparum. Mass spectrometry analyses of phospho-peptide enriched, immunoprecipitated PfPanK samples revealed phosphorylation sites in PfPanK1 and PfPanK2 that were additional to the previously reported sites. Mutagenesis of four predicted Pf14-3-3I binding sites in PfPanK1 significantly reduced the amount of Pf14-3-3I bound to the PfPanK complex, with S334 being the most likely binding site. Heterologous expression of the PfPanK complex was attempted using the insect cell protein expression system. Although some of the expressed components aggregated, enough remained soluble, naturally formed the complex in situ and, crucially, when purified, the complex was functional. Further, results from both the heterologous expression and P. falciparum mutagenesis studies suggest that Pf14-3-3I may be non-essential for PfPanK activity.
To investigate the two putative PfPPCSs, transgenic parasites overexpressing a green fluorescent protein tagged PfPPCS1 or PfPPCS2 were generated. Results from western blots, fluorescence-coupled size exclusion chromatography and mass spectrometry revealed that the two PfPPCSs associate into a single, functional PPCS heteromer that, unlike any other eukaryotic PPCS reported to date, is unable to use ATP for activity. Bioinformatic analyses uncovered a prokaryote-like helical component of PfPPCS as important for the nucleotide specificity and potentially holding the key for its stringency for CTP. Moreover, it was found that the complex is the target of multiple antiplasmodial pantothenate analogues and may interact with other pantothenate analogues that target different steps in CoA biosynthesis/utilisation.
Isoxazole or thiazole substitution of the labile amide bond in pantothenamides (PanAms) led to identification of several novel PanAm-mimics with sub-micromolar potency against intraerythrocytic stage P. falciparum and were non-cytotoxic to mammalian cells. Kinetic studies identified the selected compounds as substrates of the human PanK3 enzyme, but with much lower affinity compared to that of pantothenate. Computational modelling showed that minor modifications can significantly influence the optimal side chain-configurations and the biological activity.
This study has advanced our knowledge of the heteromeric PfPanK complex, marked the identification of the first heteromeric PPCS complex and contributed to a better understanding of the parasite CoA biosynthesis. This study offers new opportunities for designing inhibitors that exploit the unique features of the PfPPCS complex, and hopefully, may expedite the identification of new drugs targeting P. falciparum pantothenate utilisation
Platformed care in the age of fintech: the moral promise of consumer credit
No full textRecent years have seen a growth in lenders using digital data and platforms to reach consumers and inform lending decisions. Scholarship on these fintech (financial technology) lenders has shown how they accumulate profit and data from financialised subjects. I extend this scholarship by attending to a less studied aspect of fintech: the moral promises that industry actors make about the ability of fintech to improve people's lives. Across three interconnected sites, I examine how fintech reshapes the moral meanings of consumer credit through digital data, platforms and these promises.
In this thesis, I draw on the anthropology and sociology of morality, economic anthropology and sociology, science and technology studies (STS), and critical data studies. I show how fintech lenders re-moralise consumer credit as morally acceptable for both themselves and borrowers by examining the affordances of digital platforms and associated websites and documents across three sites. I argue this re-moralisation occurs through a process that reconfigures fintechs as caring providers and borrowers as careful and caring consumers. This process, which I term platformed care, primarily relies on fintech actors constructing and maintaining the datafied consumer - the continual re-contextualisation of consumer data for multiple audiences. Through the datafied consumer, fintech lenders assume the burden of care through the digital platform. Although care is often considered benevolent, scholars in STS and other disciplines have shown that care is fraught with tension and is profoundly political. I argue that platformed care positions the fintech platform and its users as partners, albeit unequal and dependent, in achieving a future financed by fintech credit.
In the first site, I examine buy now, pay later (BNPL) fintechs. These fintechs, which offer a contentious form of credit-as-payment, use platform affordances to promise responsible consumption through their intermediary position in the purchase-payment chain. In the second, I examine online lenders that promise financial health for young adults. By combining platform affordances with a metaphorical reference to physical health, these fintechs re-moralise access to credit as essential to the good life, thus managing the moral stigma associated with credit and generating demand. In the final site, I examine a key infrastructure: the Australian Government's Consumer Data Right (CDR), which is positioned as the morally preferable way for companies such as fintech lenders to access consumer data. Through the CDR, the government and data intermediaries work to morally attach consumers and fintechs to financial data by promising a better financial future through data. Together, these three sites elucidate how the fintech assemblage re-moralises consumer credit.
As fintech platforms and their data-driven algorithmic design increasingly dominate our financialised lives, we need to examine how these platforms and data are used to promise sociodigital futures that are enacted in the present. By examining the moral and political implications that extend down the fintech stack, this thesis contributes to conceptual and empirical work on digital data, platforms and financialisation
A Supersonic Bidirectional Vortex Enhanced Radio-Frequency Inductively Coupled Plasma Torch for Electrothermal Propulsion Applications.
No full textRadio-frequency (RF) inductively coupled plasma (ICP) torches have numerous applications in material processing, analytical chemistry, and testing of thermal protection materials. When combined with a supersonic nozzle they also offer applications for electrothermal space propulsion. However, due to historical thermal efficiency limitations, they have not been able to provide the required performance for propulsion. This thesis investigates a supersonic RF ICP torch for propulsion applications that utilises a novel gas injection configuration to overcome such limitations and enhance performance. There are three key objectives: to investigate the influence of gas injection, study the influence of nozzle geometry and obtain stable operation at high pressures.
The feed gas injection systems of RF ICP torches play an important role in stabilisation, gas heating and thermal management. Therefore, two gas injection systems are explored. The first is the conventional forward vortex where gas is injected into four tangential inlets at the RF ICP torch top end resulting in a vortex swirl towards the nozzle. The second is the bidirectional vortex, which is formed by injecting gas into four tangential inlets located at the downstream end of the source tube near the nozzle, resulting in two counter-propagating vortices. To enable safe operation conditions, the RF ICP source tubes are water-cooled, resulting in the cooler outer vortex propagating away from the nozzle, while the hotter inner vortex propagates downstream towards the nozzle. The second configuration is the bidirectional vortex, created by injecting gas through four tangential inlets located at the downstream end of the source tube, near the nozzle. This setup generates two counter-propagating vortices. To maintain safe operating conditions, the RF ICP source tubes are water-cooled, which causes the cooler outer vortex to move away from the nozzle, while the hotter inner vortex travels downstream toward it.
The vortex flow field structure of the bidirectional vortex is expected to play a significant role in gas heating through a reduction of conductive heat losses to the walls. Additionally, nozzle geometry significantly affects the gas exit velocity and is expected to influence both the bidirectional vortex flow field structure and the overall torch performance. In this thesis. The influence of bidirectional and forward vortex gas injection methods are investigated alongside a parametric analysis of nozzle throat diameters ranging from 1.5 mm to 4.0 mm. Their impact on the performance of a supersonic RF ICP torch is investigated across RF power levels from 200 to 1000 W and argon mass flow rates between 0 to 400 mgs. A torch instability prevents the RF ICP torch from operating at higher pressures. As a result, a preliminary characterisation of the instability is conducted, and its possible origins and causes are discussed.
The results demonstrate that the bidirectional vortex gas injection provides a significant improvement over the forward vortex, including increased gas heating, greater thermal efficiency, and superior thruster performance. Nozzle geometry is found to have an important influence on electron density, excitation temperature and thermal efficiency. An initial characterisation of the torch instability reveals a low-frequency oscillation which could be the result of neutral depletion, however further work is required to better understand the instability. The supersonic vortex-enhanced RF ICP torch displays considerable potential for optimisation across a wide range of operating conditions, offering a variety of prospective industry applications
Contextual dependencies for digital knowledge sharing to support farmers and nitrogen use efficiency in South Asia
No full textGrowing more grain with less nitrogen fertiliser mitigates climate change, improves food security, supports rural livelihoods, and reduces fertiliser subsidy costs in South Asia. Meanwhile, increased access to mobile networks offers novel opportunities for farmers to circulate knowledge of improved farming practices. But how might these two opportunities be beneficially combined? A dataset of more than 31,000 rice fields across South Asia was harmonised and analysed. This analysis found that disincentivising nitrogen fertiliser overuse was the most impactful mechanism for improving rice nitrogen use efficiency in South Asia, followed by addressing yield constraints unrelated to crop nutrition. A mixed methods randomised controlled trial was then implemented in Bihar, a state in eastern India with a particularly large opportunity to increase cereal nitrogen use efficiency. This trial explored the contextual dependencies for YouTube and WhatsApp to support the scalable use of cereal agronomy videos in Bihar and other contexts. It was found that the capacity for these digital extension tools to increase cereal NUE depended on the social inclusivity, goals, and reach of extension actors and networks that shared farming videos. From a theoretical perspective, these findings highlight the need for socio-technical theories, like affordance theory, to accurately conceptualise the use and impacts of digital tools in agricultural extension. From a practical perspective, the findings altogether highlight three contextual dependencies for digital tools to help farmers grow more grain with less nitrogen fertiliser at scale in South Asia: (1) economic incentives for cereal farmers to curb nitrogen overuse, (2) socially inclusive extension networks, and (3) equitable access to smartphones and mobile networks. The research methods only examined how human extension actors shared and discussed digital extension tools. This approach neglected algorithmic extension actors, like YouTube and chatbots powered by large language models. Further research should examine the goals and behaviours of these increasingly influential intermediaries in agricultural innovation systems
Advancing Electrochemical Performance of Li-S Batteries: Strategies for Polysulfide Immobilization and Catalytic Enhancement
No full textLithium-sulfur batteries are regarded as a promising next-generation energy storage system, featuring a theoretical energy density that is five to ten times higher than that of conventional Li-ion battery (LIB) cathode material. Furthermore, natural abundance, low cost, and environmental benignity make sulfur an appealing candidate for sustainable energy solutions. Despite the potential of Lithium-sulfur batteries, their commercialization is hindered by several challenges. One major issue is the shuttle effect of soluble long-chain lithium polysulfides (LiPSs), which migrate uncontrollably through the electrolyte, leading to rapid capacity fade, poor sulfur utilization, and severe corrosion of the lithium anode. Furthermore, the sluggish redox kinetics of LiPSs exacerbate these issues, reducing the overall electrochemical efficiency. Additionally, sulfur's intrinsically poor electrical conductivity and the significant volume expansion during charging-discharging create mechanical instability in the cathode. These combined factors significantly impair the long-term cycling stability, Coulombic efficiency, and overall performance, limiting their feasibility for practical application.
This thesis explores strategies for immobilizing lithium polysulfides and enhancing electrocatalytic activity in Lithium-sulfur batteries to improve overall performance. The first project investigated the energy losses induced by modified membranes in Lithium-sulfur batteries. By utilizing a commercial PP separator, energy density decreases by 20% when overpotentials exceed 250 mV in a Lithium-sulfur battery. Symmetric cell with lithium metal as electrode measurements demonstrates that certain types of membranes (GO, MoS2, and rGO) display overpotentials surpassing 250 mV at a 1C rate. This issue becomes more pronounced when these membranes are tested within H-cells with Li2S6 as catholyte. Fabrication and testing of the porous membrane with an induced level of mesoporosity and modeling confirm that the overpotentials stem from physical obstruction of lithium-ion transport, revealing the need to compromise between soluble polysulfide blocking and energy loss.
The second study was designed to redefine the approach to enhance Lithium-sulfur battery performance by emphasizing the significant role lithium-ion plays in sulfur redox reactions (SRR). Traditional membrane design strategies focus on managing the migration of lithium polysulfides (LiPSs) and catalyzing the sulfur redox reactions (SRR). However, the critical influence of lithium-ion transport on SRR kinetics is often neglected. A novel holey graphene membrane, embedded with Co9S8 (Co9S8/HG) was designed to facilitate rapid lithium-ion diffusion and efficient polysulfide conversion. This approach tackles the notorious shuttle effect of LiPSs and significantly improves SRR kinetics, overcoming the limitations of conventional membrane designs that impede lithium-ion movement. The cell incorporated with Co9S8/HG/PP achieved a notable discharge capacity of 671 mAh/g over 900 cycles at 0.2C and exhibited robust rate performance, maintaining 784 mAh/g capacity when switching from 2C to 0.2C.
In the third project, we incorporated holey Co3S4 nanosheets into the sulfur composite cathodes to enhance the conversion kinetics of LiPSs by facilitating rapid lithium-ion diffusion. Through overpotential measurements, Tafel plots, and lithium-ion diffusion coefficient analysis, we compared the electrocatalytic efficiency of the synthesized materials which exhibit varying particle sizes and porous structures due to their formation at various temperatures.
These studies have uncovered several previously unexplored challenges, which will inspire research in the sustainable energy storage field