Understanding capacity fade in silicon based electrodes for lithium-ion batteries using three electrode cells and upper cut-off voltage studies

Commercial Li-ion batteries are typically cycled between 3.0 and 4.2 V. These voltages limits are chosen based on the characteristics of the cathode (e.g. lithium cobalt oxide) and anode (e.g. graphite). When alternative anode/cathode chemistries are studied the same cut-off voltages are often, mistakenly, used. Silicon (Si) based anodes are widely studied as a high capacity alternative to graphite for Lithium-ion batteries. When silicon-based anodes are paired with high capacity cathodes (e.g. Lithium Nickel Cobalt Aluminium Oxide; NCA) the cell typically suffers from rapid capacity fade. The purpose of this communication is to understand how the choice of upper cut-off voltage affects cell performance in Si/ NCA cells. A careful study of three-electrode cell data will show that capacity fade in Si/NCA cells is due to an ever-evolving silicon voltage profile that pushes the upper voltage at the cathode to >4.4 V (vs. Li/Liþ). This behaviour initially improves cycle efficiency, due to liberation of new lithium, but ultimately reduces cycling efficiency, resulting in rapid capacity fade

Whole-genome sequencing reveals host factors underlying critical COVID-19

Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2,3,4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes—including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)—in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease

Thermal Conductivity Measurements of Weathered Limestone

Thermal properties of geological materials are required for analysis and design of energy geostructures. In Florida the weathered limestone bedrock, which has highly variable engineering properties, can be found near the ground surface and its thermal properties will need to be incorporated into the design of such systems. Thermal conductivity values for split tension sized specimens were determined using a specially designed thermal apparatus. The apparatus is capable of determining four thermal conductivity values for each specimen, which provided a measure of variability of the measurements. Thermal conductivities ranged between 2.65 and 3.75 W/m-K with specimen measurement standard deviations and coefficient of variations as high as 0.415 W/m-K and 11.1%, respectively. The variability of the results can be attributed to both dissolution, which would decrease thermal conductivity, and dolotomitization, which would increase thermal conductivity. Thermal conductivity values are in the lower range of values reported in the literature

Thermal Conductivity Measurements of Weathered Limestone

Thermal properties of geological materials are required for analysis and design of energy geostructures. In Florida the weathered limestone bedrock, which has highly variable engineering properties, can be found near the ground surface and its thermal properties will need to be incorporated into the design of such systems. Thermal conductivity values for split tension sized specimens were determined using a specially designed thermal apparatus. The apparatus is capable of determining four thermal conductivity values for each specimen, which provided a measure of variability of the measurements. Thermal conductivities ranged between 2.65 and 3.75 W/m-K with specimen measurement standard deviations and coefficient of variations as high as 0.415 W/m-K and 11.1%, respectively. The variability of the results can be attributed to both dissolution, which would decrease thermal conductivity, and dolotomitization, which would increase thermal conductivity. Thermal conductivity values are in the lower range of values reported in the literature

Binder-free Sn–Si heterostructure films for high capacity Li-ion batteries

Open access articleThis study fabricated and demonstrated a functional, stable electrode structure for a high capacity Li-ion battery (LIB) anode. Effective performance is assessed in terms of reversible lithiation for a significant number of charge–discharge cycles to 80% of initial capacity. The materials selected for this study are silicon and tin and are co-deposited using an advanced manufacturing technique (plasma-enhanced chemical vapour deposition), shown to be a scalable process that can facilitate film growth on 3D substrates. Uniform and hybrid crystalline–amorphous Si nanowire (SiNW) growth is achieved via a vapour–liquid–solid mechanism using a Sn metal catalyst. SiNWs of less than 300 nm diameter are known to be less susceptible to fracture and when grown this way have direct electrical conductivity to the current collector, with sufficient room for expansion. Electrochemical characterisation shows stable cycling at capacities of 1400 mA h g 1 (>4 the capacity limit of graphite). This hybrid system demonstrates promising electrochemical performance, can be grown at large scale and has also been successfully grown on flexible carbon paper current collectors. These findings will have impact on the development of flexible batteries and wearable energy storage

Fossil frogs from the central highlands of Papua New Guinea

Characteristic features of the pelves of 15 species of extant New Guinean highland frogs (Hylidae and Microhylidae) are described and figured. Ilia among species in these families were found to be relatively invariate with similar sized species often indistinguishable; thus fossil species diversity is therefore likely to be underestimated in such deposits. Nine-two disarticulated ilia from the highland Nombe rockshelter deposit represent a minimum of six species: two Hylidae and four Microhylidae; most of these ilia were deposited in the late Pleistocene before significant human activity at the site. Problems of drawing conclusions about the Pleistocene frog fauna of the area, especially what the main predator was, from such a small sample and limited understanding of the site taphonomy are discussed. © AAP