In modern Li-based batteries, alloying anode materials have the potential to drastically improve the volumetric and specific energy storage capacity. For the past decade silicon has been viewed as a ...“Holy Grail” among these materials; however, severe stability issues limit its potential. Herein, we present amorphous substoichiometric silicon nitride (SiN x ) as a convertible anode material, which allows overcoming the stability challenges associated with common alloying materials. Such material can be synthesized in a form of nanoparticles with seamlessly tunable chemical composition and particle size and, therefore, be used for the preparation of anodes for Li-based batteries directly through conventional slurry processing. Such SiN x materials were found to be capable of delivering high capacity that is controlled by the initial chemical composition of the nanoparticles. They exhibit an exceptional cycling stability, largely maintaining structural integrity of the nanoparticles and the complete electrodes, thus delivering stable electrochemical performance over the course of 1000 charge/discharge cycles. Such stability is achieved through the in situ conversion reaction, which was herein unambiguously confirmed by pair distribution function analysis of cycled SiN x nanoparticles revealing that active silicon domains and a stabilizing Li2SiN2 phase are formed in situ during the initial lithiation.
In order to acquire reproducible electrodes relevant for Li ion batteries new MgH2 electrodes are successfully obtained from homogenous slurries in N-Methyl-2-Pyrrolidone “NMP” solvent. The ...electrodes are aimed to elucidate the contribution of the cell components to the electrochemical cycling, in terms of morphology and composition. Various electrode preparations were tested and compared regarding their interaction with Li in a half-cell. The obtained electrochemical cycling curves are discussed according to the ball-milling-induced structural morphology changes and presence of carbon additives, along with the effect of the kinetic rate on the conversion reaction mechanism.
•Reproducible MgH2 anodes (26 μm thick) optimized and electrochemically tested.•Morphology-cycling relationship demonstrated for MgH2 electrodes upon milling time.•Mg/LiH byproducts become inactive and dependent on cycling rate and particle size.•Failure mechanism may be associated to solid–liquid interface degradation aspects.
Silicon is often regarded as a likely candidate to replace graphite as the main active anode material in next-generation lithium ion batteries; however, a number of problems impacting its cycle ...stability have limited its commercial relevance. One approach to solving these issues involves the use of convertible silicon sub-oxides. In this work we have investigated amorphous silicon sub-nitride as an alternative convertible silicon compound by comparing the electrochemical performance of a-SiN
thin films with compositions ranging from pure Si to SiN
. We have found that increasing the nitrogen content gradually reduces the reversible capacity of the material, but also drastically increases its cycling stability, e.g. 40 nm a-SiN
thin films exhibited a stable capacity of more than 1,500 mAh/g for 2,000 cycles. Consequently, by controlling the nitrogen content, this material has the exceptional ability to be tuned to satisfy a large range of different requirements for capacity and stability.
Nano-crystalline Mg2Si (Mg67Si33) and its Si-rich eutectic (Mg47Si53) composition were synthesized by hydrogen desorption-recombination process, casting and rapid solidification techniques. The ...synthesis of Mg2Si meets experimental challenges due to a significant difference in the melting temperatures of Mg (650 °C) and Si (1414 °C) and due to easy vaporization of magnesium metal. As cast alloys were obtained by induction melting the precursors, Mg and Si, followed by the casting and water quenching. These alloys were rapidly solidified using a chill block melt spinning which produces ribbons with fine dendritic morphology and a grain size close to 100 nm. Hydrogen desorption-recombination process of MgH2-Si mixture resulted in a release of ∼4.67 wt % H and formation of Mg2Si. The microstructure of the alloys has been studied using Scanning Electron Microscopy and the relationship between microstructure and electrochemical properties as anodes of the lithium ion batteries was characterised. The electrochemical tests indicate that Si rich eutectic electrode shows a higher charge-discharge capacity than the Mg2Si intermetallic. Rapidly solidified Mg2Si and Mg2Si + Si alloys showed the highest initial discharge capacities of 989 mAh/g and 1283 mAh/g, respectively, superior to the alloys prepared by hydrogen desorption-recombination process and casting. The presence of electrolyte additives FEC (5%) and VC (1%) resulted in the formation of the stable SEI layer and enhanced the cycling capacity of the electrodes. Electrochemical Impedance Spectroscopy (EIS) was used to characterize the anode electrodes on cycling. A mathematical model for accounting the impedance response was utilised. The EIS response showed an increased overall resistance for the Mg2Si eutectic Si-containing alloy electrodes when compared to the electrodes based on a stoichiometric Mg2Si. Long-term cycling resulted in increased charge transfer resistance, which slowed down the electrochemical processes at the surface of the electrodes.
Electrochemical performance of Mg-Si alloys used as anodes of the lithium ion battery significantly improves when the eutectic alloy Mg2Si+Si is subjected to the Rapid Solidification leading to its nanostructuring and in presence of additives to the electrolyte allowing to form a stable SEI layer. Display omitted
•Nanostructured Mg2Si and Mg2Si+Si eutectic alloys as anodes of Li ion battery.•Effect of microstructure on the electrochemical capacity.•Rapid Solidification resulted is a reduced grain size of 100 nm.•VC and FEC electrolyte additives to LiPF6 improved anode performance.•Electrochemical Impedance Spectroscopy was used to analyse cycling stability.
The use of silicon (Si) in the form of nanoparticles is one of the most promising routes for boosting the capacity of modern Li‐ion batteries. Many parameters influence the performance of Si making ...the comparison of materials complicated. The present work demonstrates a direct comparison of Si nanoparticles with amorphous and crystalline structures prepared through the same chemistry with the same particle size and morphology. The amorphous Si nanoparticles with an average diameter of 100 nm were synthesized through silane pyrolysis, and their crystalline analogues were obtained through subsequent annealing not altering size or morphology of the nanoparticles. Such direct comparison allows evaluation of the specific impact of crystallinity on the material's performance. From electrochemical analysis of these materials, the electrodes prepared from amorphous nanoparticles were found to exhibit improved cycle life compared to electrodes prepared from crystalline nanoparticles when the delithiation capacity of the anode was limited to 1000 mAh/gSi.
Compare and contrast: Silicon has recently become a “holy grail” for boosting the capacity of modern Li‐ion batteries. Many parameters influence the performance of Si making the comparison of materials complicated. The present work demonstrates a direct comparison of Si nanoparticles with amorphous and crystalline structures with the same particle size and morphology. As a result, the electrodes prepared from the amorphous material demonstrated better cycle life compared to the crystalline material when the delithiation capacity was limited.
The wide distribution and dominance of invasive inbreeding species in many forest ecosystems seems paradoxical in face of their limited genetic variation. Successful establishment of invasive species ...in new areas is nevertheless facilitated by clonal reproduction: parthenogenesis, regular self‐fertilization, and regular inbreeding. The success of clonal lineages in variable environments has been explained by two models, the frozen niche variation (FNV) model and the general‐purpose genotype (GPG) model. We tested these models on a widely distributed forest pest that has been recently established in Costa Rica—the sibling‐mating ambrosia beetle Xylosandrus morigerus. Two deeply diverged mitochondrial haplotypes coexist at multiple sites in Costa Rica. We find that these two haplotypes do not differ in their associations with ecological factors. Overall the two haplotypes showed complete overlap in their resource utilization; both genotypes have broad niches, supporting the GPG model. Thus, probable or not, our findings suggest that X. morigerus is a true ecological generalist. Clonal aspects of reproduction coupled with broad niches are doubtless important factors in the successful colonization of new habitats in distant regions.
The wide distribution and dominance of invasive inbreeding species in many forest ecosystems seems paradoxical in face of their limited genetic variation. Successful establishment of invasive species in new areas is nevertheless facilitated by clonal reproduction: parthenogenesis, regular self‐fertilization, and regular inbreeding. The success of clonal lineages in variable environments has been explained by two models, the frozen niche variation (FNV) model and the general‐purpose genotype (GPG) model. We tested these models on a widely distributed forest pest that has been recently established in Costa Rica—the sibling‐mating ambrosia beetle Xylosandrus morigerus.
Oxidation of bovine serum albumin (BSA) was investigated using different oxidants: The water-soluble azo-initiator 2,2′azo-bis-(2-amidinopropane) hydrochloride (AAPH), a combination of FeCl3 and ...ascorbate or the Fenton oxidant consisting of FeCl2, H2O2 and EDTA. In addition, the effects of exogenous compounds such as tert-butyl hydroperoxide (tBuOOH) or solvents such as tetrahydrofuran (THF), often used in model systems, was evaluated. The extent of protein damage was studied by measuring protein carbonyl groups and protein hydroperoxides. The interaction between Fenton oxidant and EDTA, THF or tBuOOH was further characterized using spin trapping electron spin resonance (ESR) spectroscopy. The results showed that the extent of protein oxidation depended on the oxidant used. The Fenton oxidant was the most reactive of the initiators tested. However, in the absence of EDTA, the Fenton system produced protein carbonyl groups on BSA equivalent to that obtained with the other oxidants, however, significantly more protein hydroperoxide was produced. Surprisingly, it was also found that addition of tBuOOH or THF to BSA reduced protein damage when the oxidation was initiated with the Fenton oxidant. ESR investigation showed that EDTA played a key role in the generation of free radicals. It was also revealed that in an EDTA containing system both tBuOOH and THF were able to react with radicals without inducing protein damage in effect protecting BSA from oxidative damage.
We report the first two genome-wide screens for linkage disequilibrium between putative multiple sclerosis (MS) susceptibility genes and genetic markers performed in the genetically homogenous ...Scandinavian population, using 6000 microsatellite markers and DNA pools of approximately 200 MS cases and 200 controls in each screen. Usable data were achieved from the same 3331 markers in both screens. Nine markers from eight genomic regions (1p33, 3q13, 6p21, 6q14, 7p22, 9p21, 9q21 and Xq22) were identified as potentially associated with MS in both screens.
In this study, the results from three Nordic linkage disequilibrium screens in multiple sclerosis (MS) were investigated, in a new sample set of 314 Nordic MS trios from Denmark, Norway, Sweden and ...Iceland. Among 30 non-HLA and two HLA microsatellite markers individually genotyped, eight markers displayed distorted transmission with uncorrected P-value <0.05, ranked in this order: D6S2443 (6p21.32, HLA class II) (P corrected =0.01), D2S2201 (2p24), D19S552 (19q13), D3S3584 (3q21), D17S975 (17q11), D1S2627 (1p22), D6S273 (6p21.33, HLA class III) and D12S1051 (12q23). These non-HLA regions need further investigation as possible MS candidate gene regions in our population. Multiple Sclerosis 2007; 13: 584-589. http://msj.sagepub.com
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