Draining Over Blocking: Nano-Composite Janus Separators for Mitigating Internal Shorting of Lithium Batteries.

Catastrophic battery failure due to internal short is extremely difficult to detect and mitigate. In order to enable the next-generation lithium-metal batteries, a "fail safe" mechanism for internal short is highly desirable. Here, a novel separator design and approach is introduced to mitigate the effects of an internal short circuit by limiting the self-discharge current to prevent cell temperature rise. A nano-composite Janus separator-with a fully electronically insulating side contacting the anode and a partially electronically conductive (PEC) coating with tunable conductivity contacting the cathode-is implemented to intercept dendrites, control internal short circuit resistance, and slowly drain cell capacity. Galvanostatic cycling experiments demonstrate Li-metal batteries with the Janus separator perform normally before shorting, which then results in a gradual increase of internal self-discharge over >25 cycles due to PEC-mitigated shorting. This is contrasted by a sudden voltage drop and complete failure seen with a single layer separator. Potentiostatic charging abuse tests of Li-metal pouch cells result in dendrites completely penetrating the single-layer separator causing high short circuit current and large cell temperature increase; conversely, negligible current and temperature rise occurs with the Janus separator where post mortem electron microscopy shows the PEC layer successfully intercepts dendrites.

Facile Synthesis of Ge/N-Doped Carbon Spheres with Varying Nitrogen Content for Lithium Ion Battery Anodes.

The simple fabrication of composites of germanium nanoparticles dispersed on nitrogen-doped carbon nanospheres (Ge/NC) of varying nitrogen content and their performance in lithium ion battery anodes are reported. A heavily nitrogen-doped carbon gel was formed by condensing m-phenylenediamine with formaldehyde (PF-gel); a less heavily N-doped gel was formed by condensing resorcinol and m-phenylenediamine with formaldehyde (RPF-gel); and an undoped gel was formed by condensing resorcinol with formaldehyde (RF-gel). Pyrolises of the gels with GeCl4 at 750 °C produced nanocrystalline Ge composites with 7.5 atom % N-doped carbon, termed Ge/NC (PF), with 3.9% N-doped carbon, termed Ge/NC (RPF) and undoped carbon, termed Ge/C (RF). The heavily N-doped Ge/NC (PF) anode retained a reversible capacity of 684 mAhg-1 at a specific current of 0.2 Ag-1 after 200 cycles, versus 337 mAhg-1 retained by anode made with Ge/NC (RPF) and 278 mAhg-1 retained by anode made with undoped Ge/C (RF). At a specific current 2.0 Ag-1, the capacity of the Ge/NC (PF) anode was 472 mAhg-1, versus the 210 mAhg-1 of the Ge/NC (RPF) anode and 83 mAhg-1 of the Ge/C (RF) anode. The enhanced performance of the Ge/NC (PF) anode is attributed to the better electrical conductivity of Ge/NC (PF) and to the higher density of Li+ binding defects in its N-doped carbon.

Two TIR-like domain containing proteins in a newly emerging zoonotic Staphylococcus aureus strain sequence type 398 are potential virulence factors by impacting on the host innate immune response.

Staphylococcus aureus, sequence type (ST) 398, is an emerging pathogen and the leading cause of livestock-associated methicillin-resistant S. aureus infections in Europe and North America. This strain is characterized by high promiscuity in terms of host-species and also lacks several traditional S. aureus virulence factors. This does not, however, explain the apparent ease with which it crosses species-barriers. Recently, TIR-domain containing proteins (Tcps) which inhibit the innate immune response were identified in some Gram-negative bacteria. Here we report the presence of two proteins, S. aureus TIR-like Protein 1 (SaTlp1) and S. aureus TIR-like Protein 2 (SaTlp2), expressed by ST398 which contain domain of unknown function 1863 (DUF1863), similar to the Toll/IL-1 receptor (TIR) domain. In contrast to the Tcps in Gram-negative bacteria, our data suggest that SaTlp1 and SaTlp2 increase activation of the transcription factor NF-κB as well as downstream pro-inflammatory cytokines and immune effectors. To assess the role of both proteins as potential virulence factors knock-out mutants were created. These showed a slightly enhanced survival rate in a murine infectious model compared to the wild-type strain at one dose. Our data suggest that both proteins may act as factors contributing to the enhanced ability of ST398 to cross species-barriers.

Replacement of two aminoacids in the bovine Toll-like receptor 5 TIR domain with their human counterparts partially restores functional response to flagellin.

Flagellin potently induces inflammatory responses in mammalian cells by activating Toll-like receptor (TLR) 5. Recently, we were able to show that stimulation of bovine TLR5 resulted in neither NFκB signalling nor CXCL8 production. Like other TLRs, TLR5 recruits signalling molecules to its intracellular TIR domain, leading to inflammatory responses. Analysis of available TLR5 sequences revealed substitutions in all artiodactyl sequences at amo acid (AA) position 798 and 799. Interestingly, a putative binding site for PI3K was identified at tyrosine 798 in the human TLR5 TIR domain, analogous to the PI3K recruitment domain in the IL-1 receptor. Mutation of the artiodactyl residues at position 798, 799 or both with their corresponding human counterparts partially restored the response of bovine (bo)TLR5 to flagellin as well as phosphorylation of PI3K. Together, our results suggest a potential lack of phosphorylation of F798 and H799 in boTLR5 partially explains the lack in observed response.

To con protection: TIR-domain containing proteins (Tcp) and innate immune evasion.

The innate immune system provides the host's first line of defence against invading pathogens. Key to the stimulation of the innate immune response is pattern-recognition receptors (PRRs), such as Toll-like receptors (TLRs), which recognize microbial-associated molecular patterns (MAMPs). Binding of MAMPs to TLRs triggers a signalling cascade resulting in the production of pro-inflammatory mediators. Central to this TLR signalling pathway are heterotypic protein-protein interactions mediated through Toll/interleukin-1 receptor (TIR) domains found in both the cytoplasmic regions of TLRs and several key adaptor proteins. Interestingly, TIR-domain containing proteins (Tcps) do not seem to be unique to the mammalian TLR system, but occurs in abundance in many biological forms. Recent evidence suggests that pathogenic bacteria have developed a range of ingenuous strategies to evade the host immune mechanisms involving Tcps. There is increasing evidence to suggest that these pathogen-encoded Tcps interfere directly with the TLR signalling pathway and thus inhibit the activation of NF-κB, with different modes of action and roles in virulence. Here, we review the current state of knowledge on the possible roles and mechanisms of action of bacterial encoded Tcp.