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Severe, particle-level strains induced during both production and cycling have been putatively linked to lifetime limiting damage in lithium-ion cells. Because of the presently unknown contributions of manufacturing and intercalation induced stresses in Li cells, this correlation is critical in determining optimal materials and manufacturing methods for these cells. Both global and localized loads must be estimated, in order to select materials able to resist fracture. Here, we select the LiMn 2 O 4 system for study. We present results of a set of simulation techniques, ranging from one-dimensional finite difference simulations of spherical particles, to fully three-dimensional ͑3D͒ simulations of ellipsoidal particles, to systematically study the intercalation-induced stresses developed in particles of various shapes and sizes, with the latter 3D calculations performed using a commercial finite element code. Simulations of spherical particles show that larger particle sizes and larger discharge current densities give larger intercalation-induced stresses. Simulations of ellipsoidal particles show that large aspect ratios are preferred to reduce the intercalation-induced stresses. In total, these results suggest that it is desirable to synthesize electrode particles with smaller sizes and larger aspect ratios to reduce intercalation-induced stress during cycling of lithium-ion batteries.

Intercalation-induced stress and heat generation inside Li-ion battery cathode ͑LiMn 2 O 4 ͒ particles under potentiodynamic control are simulated in this paper. We combined analyses of transport and kinetics in determining resulting stresses, which arise from concentration gradients in cathode particles, and heat generation. Two peaks in boundary reaction flux, and resulting stresses, were determined from the modeling of electrochemical kinetics and diffusion, using intrinsic material properties ͑resulting in two plateaus in the open-circuit potential͒ and the applied potential. Resistive heating was identified as the most important heat generation source. To probe the impact of the particle shape ͑equivalent radius and aspect ratio of an ellipsoidal particle͒ and the potential sweep rate on stress and heat generation, a surrogate-based analysis was also conducted. The systematic study showed that both intercalation-induced stress and time-averaged resistive heat generation rate increase with particle radius and potential sweep rate. Intercalation-induced stress increases first, then decreases as the aspect ratio of an ellipsoidal particle increases, whereas time-averaged resistive heat generation rate decreases as aspect ratio increases. This surrogate-based analysis suggests that ellipsoidal particles with larger aspect ratios are preferred over spherical particles, in improving battery performance when stress and heat generation are the only factors considered.

No abstract

Infections caused by multidrug-resistant (MDR) bacteria pose a threat to human health worldwide, making new effective antibacterial agents urgently desired. To date, it is still a great challenge to develop new antibiotics for MDR bacteria with clear antibacterial mechanisms. Herein, a novel alternative antibacterial copper clusters (CuCs) molecule is precisely synthesized utilizing an artificially designed theanine peptide. The prepared CuCs exhibit excellent broad-spectrum antibacterial activity in vitro, including gram-positive bacteria (methicillin-resistant Staphylococcus aureus [MRSA], Staphylococcus aureus, and Staphylococcus epidermidis) and gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). The robust antibacterial effect is due to its ability to not only destroy the bacterial wall structure, but also regulate the ratio of GSH/GSSG by inhibiting the activity of glutathione reductase, thus causing the outbreak of reactive oxygen species and ultimately leading to bacterial death. In addition, in vivo studies demonstrate that CuCs can significantly rescue skin wound infections and sepsis in mice caused by MRSA, and has the same therapeutic efficacy as mupirocin ointment and first-line clinically anchored anti-MRSA drug vancomycin. Moreover, CuCs exhibit extremely low cytotoxicity to normal mammalian cells compared to silver and platinum clusters. With further development and optimization, CuCs has great potential as a new class of antibacterial agents to fight antibiotic-resistant pathogens.