A lithium–sulfur full cell with ultralong cycle life: influence of cathode structure and polysulfide additive

Lithium–sulfur batteries are highly attractive energy storage systems, but suffer from structural anode and cathode degradation, capacity fade and fast cell failure (dry out). To address these issues, a carbide-derived carbon (DUT-107) featuring a high surface area (2088 m² g⁻¹), high total pore volume (3.17 cm³ g⁻¹) and hierarchical micro-, meso- and macropore structure is applied as a rigid scaffold for sulfur infiltration. The DUT-107/S cathodes combine excellent mechanical stability and high initial capacities (1098–1208 mA h gs ⁻¹) with high sulfur content (69.7 wt% per total electrode) and loading (2.3–2.9 mgs cm⁻²). Derived from the effect of the electrolyte-to-sulfur ratio on capacity retention and cyclability, conducting salt is substituted by polysulfide additive for reduced polysulfide leakage and capacity stabilization. Moreover, in a full cell model system using a prelithiated hard carbon anode, the performance of DUT-107/S cathodes is demonstrated over 4100 cycles (final capacity of 422 mA h gs ⁻¹), with a very low capacity decay of 0.0118% per cycle. Application of PS additive further boosts the performance (final capacity of 554 mA h gs ⁻¹), although a slightly higher decay of 0.0125% per cycle is observed

Cross-realm assessment of climate change impacts on species' abundance trends

Climate change, land-use change, pollution and exploitation are among the main drivers of species' population trends; however, their relative importance is much debated. We used a unique collection of over 1,000 local population time series in 22 communities across terrestrial, freshwater and marine realms within central Europe to compare the impacts of long-term temperature change and other environmental drivers from 1980 onwards. To disentangle different drivers, we related species' population trends to species- and driver-specific attributes, such as temperature and habitat preference or pollution tolerance. We found a consistent impact of temperature change on the local abundances of terrestrial species. Populations of warm-dwelling species increased more than those of cold-dwelling species. In contrast, impacts of temperature change on aquatic species' abundances were variable. Effects of temperature preference were more consistent in terrestrial communities than effects of habitat preference, suggesting that the impacts of temperature change have become widespread for recent changes in abundance within many terrestrial communities of central Europe.Additionally, we appreciate the open access marine data provided by the International Council for the Exploration of the Sea. We thank the following scientists for taxonomic or technical advice: C. Brendel, T. Caprano, R. Claus, K. Desender, A. Flakus, P. R. Flakus, S. Fritz, E.-M. Gerstner, J.-P. Maelfait, E.-L. Neuschulz, S. Pauls, C. Printzen, I. Schmitt and H. Turin, and I. Bartomeus for comments on a previous version of the manuscript. R.A. was supported by the EUproject LIMNOTIP funded under the seventh European Commission Framework Programme (FP7) ERA-Net Scheme (Biodiversa, 01LC1207A) and the long-term ecological research program at the Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB). R.W.B. was supported by the Scottish Government Rural and Environment Science and Analytical Services Division (RESAS) through Theme 3 of their Strategic Research Programme. S.D. acknowledges support of the German Research Foundation DFG (grant DO 1880/1-1). S.S. acknowledges the support from the FP7 project EU BON (grant no. 308454). S.K., I.Kü. and O.S. acknowledge funding thorough the Helmholtz Association’s Programme Oriented Funding, Topic ‘Land use, biodiversity, and ecosystem services: Sustaining human livelihoods’. O.S. also acknowledges the support from FP7 via the Integrated Project STEP (grant no. 244090). D.E.B. was funded by a Landes–Offensive zur Entwicklung Wissenschaftlich–ökonomischer Exzellenz (LOEWE) excellence initiative of the Hessian Ministry for Science and the Arts and the German Research Foundation (DFG: Grant no. BO 1221/23-1).Peer Reviewe

An experimental method to determine the measurement error of reference electrodes within lithium‐ion batteries

Reference electrodes (REs) play a crucial role in the accurate assessment and control of battery potentials, but their confidence is overestimated. Researchers have tracked the source of the error to the RE design that blocks the lithium-ion path between anode and cathode. These errors or potential deviations are mostly modeled or less-frequently estimated after observing Li plating post-mortem. This is the first study to showcase an experimental method that allows a more precise error quantification in-operando of a RE. The key idea is to relate the error-affected reference potential to an unaffected quantity, such as the cell dilatation. Although our experimental setups are special, this approach can also be applied to different setups and REs. Using the presented method, we provoked Li plating in NMC811/graphite pouch cells and determined the potential deviation of our perforated RE to be 12 mV under fast charging conditions. In contrast to previous studies, we found the error to be positive, offering a new explanation of the error mechanism of REs

Structural Optimization of Locally Continuous Fiber-Reinforcements for Short Fiber-Reinforced Plastics

The integration of continuous fiber-reinforced structures into short or long fiber-reinforced plastics allows a significant increase in stiffness and strength. In order to make the best possible use of the high stiffness and strength of continuous fiber-reinforcements, they must be placed in the direction of load in the most stressed areas. A frequently used tool for identifying the most heavily loaded areas is topology optimization. Commercial topology optimization programs usually do not take into account the material properties associated with continuous fiber-reinforced hybrid structures. The anisotropy of the reinforcing material and the stiffness of the base material surrounding the reinforcement are not considered during topology optimization, but only in subsequent steps. Therefore in this publication, existing optimization methods for hybrid and anisotropic materials are combined to a new approach, which takes into account both the anisotropy of the continuous fiber-reinforcement and the stiffness of the base material. The results of the example calculations not only show an increased stiffness at the same material input but also a simplification of the resulting reinforcement structures, which allows more economical manufacturing

Application of perforated reference electrodes in small cell formats for rate tests and electrochemical impedance spectroscopy

The use of reference electrodes (REs) in lithium-ion batteries allows enhanced electrochemical analysis of individual electrodes via potential monitoring or electrochemical impedance spectroscopy (EIS). The previous publication presents a concept for a laser-perforated RE (PRE). Herein, this PRE is applied in ≈60 mAh graphite/NMC811 pouch cells. Despite more than 17% of the electrode surface being covered by the PRE, only negligible capacity differences are observed for charge rates up to 2C compared to cells without PRE. At higher rates up to 5C, the blocking effect is present but stable. Reproducible and plausible anode voltage curves are obtained and the beginning of Li plating is detected. Cell EIS spectra are in good agreement with comparison cells without RE. The impedance spectra of the individual electrodes recorded by the PRE are confirmative and, with one exception, artifact-free. The results demonstrate that our PRE can be reliably applied for investigating lab-scale electrode coatings in small pouch cell formats

Technologies for high-energy and long cycle life lithium-sulfur pouch-cell batteries

The current lithium-ion battery technol. is limited to about 250 Wh kg♂1. In contrast the lithium-sulfur battery is expected to achieve more than 400 Wh kg♂1 on cell level. To date the biggest drawback of lithium- sulfur is its limited cycle stability of less than 200 cycles. Further, high energy densities can only be achieved if no excess of lithium and electrolyte is used and the areal loading of sulfur is high. Here we demonstrate how the cycle stability can be extended to 1000 cycles using alternative silicon-carbon and all-carbon anodes instead of metallic lithium. We also present a dry-processing technol. for the sulfur cathode prepn. Besides no drying step and no toxic solvents, our process enables also twice the areal capacity (4-5 mAli cm2) of slurry based technologies. In addn. we give results on the cycle stability and energy d. of our lithium-sulfur pouch- cells (2.5+ Ah)

Formation of SiC nanoparticles in an atmospheric microwave plasma

We describe the formation of SiC nanopowder using an atmospheric argon microwave plasma with tetramethylsilane (TMS) as precursor. The impact of several process conditions on the particle size of the product is experimentally investigated. Particles with sizes ranging from 7 nm to about 20 nm according to BET and XRD measurements are produced. The dependency of the particle size on the process parameters is evaluated statistically and explained with growth-rate equations derived from the theory of Ostwald ripening. The results show that the particle size is mainly influenced by the concentration of the precursor material in the plasma

Cystatin F is a biomarker of prion pathogenesis in mice

Misfolding of the cellular prion protein (PrPC) into the scrapie prion protein (PrPSc) results in progressive, fatal, transmissible neurodegenerative conditions termed prion diseases. Experimental and epidemiological evidence point toward a protracted, clinically silent phase in prion diseases, yet there is no diagnostic test capable of identifying asymptomatic individuals incubating prions. In an effort to identify early biomarkers of prion diseases, we have compared global transcriptional profiles in brains from pre-symptomatic prion-infected mice and controls. We identified Cst7, which encodes cystatin F, as the most strongly upregulated transcript in this model. Early and robust upregulation of Cst7 mRNA levels and of its cognate protein was validated in additional mouse models of prion disease. Surprisingly, we found no significant increase in cystatin F levels in both cerebrospinal fluid or brain parenchyma of patients with Creutzfeldt-Jakob disease compared to Alzheimer's disease or non-demented controls. Our results validate cystatin F as a useful biomarker of early pathogenesis in experimental models of prion disease, and point to unexpected species-specific differences in the transcriptional responses to prion infections