A High Performance Ceramic-Polymer Separator for Lithium Batteries

A three-layered (ceramic-polymer-ceramic) hybrid separator was prepared by coating ceramic electrolyte [lithium aluminum germanium phosphate (LAGP)] over both sides of polyethylene (PE) polymer membrane using electron beam physical vapor deposition (EB-PVD) technique. Ionic conductivities of membranes were evaluated after soaking PE and LAGP/PE/LAGP membranes in a 1 Molar (1M) lithium hexafluroarsenate (LiAsF6) electrolyte in ethylene carbonate (EC), dimethyl carbonate (DMC) and ethylmethyl carbonate (EMC) in volume ratio (1:1:1). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were employed to evaluate morphology and structure of the separators before and after cycling performance tests to better understand structure-property correlation. As compared to regular PE separator, LAGP/PE/LAGP hybrid separator showed: (i) higher liquid electrolyte uptake, (ii) higher ionic conductivity, (iii) lower interfacial resistance with lithium and (iv) lower cell voltage polarization during lithium cycling at high current density of 1.3 mA cm−2 at room temperature. The enhanced performance is attributed to higher liquid uptake, LAGP-assisted faster ion conduction and dendrite prevention. Optimization of density and thickness of LAGP layer on PE or other membranes through manipulation of PVD deposition parameters will enable practical applications of this novel hybrid separator in rechargeable lithium batteries with high energy, high power, longer cycle life, and higher safety level

Phosphatidylserine Targets Single-Walled Carbon Nanotubes to Professional Phagocytes In Vitro and In Vivo

Broad applications of single-walled carbon nanotubes (SWCNT) dictate the necessity to better understand their health effects. Poor recognition of non-functionalized SWCNT by phagocytes is prohibitive towards controlling their biological action. We report that SWCNT coating with a phospholipid “eat-me” signal, phosphatidylserine (PS), makes them recognizable in vitro by different phagocytic cells - murine RAW264.7 macrophages, primary monocyte-derived human macrophages, dendritic cells, and rat brain microglia. Macrophage uptake of PS-coated nanotubes was suppressed by the PS-binding protein, Annexin V, and endocytosis inhibitors, and changed the pattern of pro- and anti-inflammatory cytokine secretion. Loading of PS-coated SWCNT with pro-apoptotic cargo (cytochrome c) allowed for the targeted killing of RAW264.7 macrophages. In vivo aspiration of PS-coated SWCNT stimulated their uptake by lung alveolar macrophages in mice. Thus, PS-coating can be utilized for targeted delivery of SWCNT with specified cargoes into professional phagocytes, hence for therapeutic regulation of specific populations of immune-competent cells

Graphene Nanosheets Based Cathodes for Lithium-Oxygen Batteries

Lithium-oxygen batteries have attracted considerable attention as a promising energy storage system. Although these batteries have many advantages, they face several critical challenges. In this work, we report the use of graphene nanosheets (GNSs), nitrogen-doped graphene nanosheets (N-GNSs), exfoliated nitrogen-doped graphene nanosheets (Ex-N-GNSs), and a blend of Ex-N-GNSs with nitrogen-doped carbon (Hybrid 1) as oxygen cathodes. These cathode materials were characterized by the Brunauer-Emmett-Teller (BET) surface area analysis, cyclic voltammetry (CV) and scanning electron microscopy (SEM). In order to mitigate safety issues, all solid-state cells were designed and fabricated using lithium aluminum germanium phosphate (LAGP) as ceramic electrolyte. The cathodes prepared from GNSs, N-GNSs, Ex-N-GNSs, and Hybrid 1 exhibit remarkable enhancement in cell capacity in comparison to conventional carbon cathodes. This superior cell performance is ascribed to beneficial properties arising from GNSs and nitrogen doped carbon. GNSs have unique morphology, higher oxygen reduction activity, whereas nitrogen-doped carbon has higher surface area

Mesoporous Nitrogen-Doped Carbon-Glass Ceramic Cathodes for Solid-State Lithium–Oxygen Batteries

The composite of nitrogen-doped carbon (N–C) blend with lithium aluminum germanium phosphate (LAGP) was studied as cathode material in a solid-state lithium–oxygen cell. Composite electrodes exhibit high electrochemical activity toward oxygen reduction. Compared to the cell capacity of N–C blend cathode, N–C/LAGP composite cathode exhibits six times higher discharge cell capacity. A significant enhancement in cell capacity is attributed to higher electrocatalytic activity and fast lithium ion conduction ability of LAGP in the cathode

Long-Term Performance of Pt-Decorated Carbon Nanotube Cathodes in Phosphoric Acid Fuel Cells

We report the electrochemical properties and performance of Pt-decorated carbon nanotube (Pt-CNT) catalysts for long-term operation in phosphoric acid fuel cells (PAFCs). Electrochemical measurements of Pt-CNT catalysts including cyclic voltammetry, rotating ring disk electrode voltammetry, and electrochemical impedance spectroscopy were conducted to evaluate the catalyzed oxygen reduction reaction (ORR). Furthermore, we tested the long-term performance of the Pt-CNT catalysts in 2′′ × 2′′ PAFC cathodes operating at 190 °C in 85% H₃PO₄ for extended periods (up to 240 days). Lifetime studies show that electrodes containing the Pt-CNT catalysts were approximately 20 times more stable than conventional Pt-C catalyst materials, even with a substantially thinner catalyst layer. This finding of the enhanced Pt-CNT catalyst stability bodes well for possible personal electronics or automotive applications, where catalyst longevity is an essential requirement

A high performance ceramic-polymer separator for lithium batteries

A three-layered (ceramic-polymer-ceramic) hybrid separator was prepared by coating ceramic electrolyte [lithium aluminum germanium phosphate (LAGP)] over both sides of polyethylene (PE) polymer membrane using electron beam physical vapor deposition (EB-PVD) technique. Ionic conductivities of membranes were evaluated after soaking PE and LAGP/PE/LAGP membranes in a 1 Molar (1M) lithium hexafluroarsenate (LiAsF6) electrolyte in ethylene carbonate (EC), dimethyl carbonate (DMC) and ethylmethyl carbonate (EMC) in volume ratio (1:1:1). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were employed to evaluate morphology and structure of the separators before and after cycling performance tests to better understand structure-property correlation. As compared to regular PE separator, LAGP/PE/LAGP hybrid separator showed: (i) higher liquid electrolyte uptake, (ii) higher ionic conductivity, (iii) lower interfacial resistance with lithium and (iv) lower cell voltage polarization during lithium cycling at high current density of 1.3 mA cm−2 at room temperature. The enhanced performance is attributed to higher liquid uptake, LAGP-assisted faster ion conduction and dendrite prevention. Optimization of density and thickness of LAGP layer on PE or other membranes through manipulation of PVD deposition parameters will enable practical applications of this novel hybrid separator in rechargeable lithium batteries with high energy, high power, longer cycle life, and higher safety level