Failure Modes of Flexible LiCoO Cathodes Incorporating Polyvinylidene Fluoride Binders with Different Molecular Weights.

Understanding the mechanical failure modes of lithium-ion battery [Li-ion batteries (LIBs)] electrodes is exceptionally important for enabling high specific energy and flexible LIB technologies. In this work, the failure modes of lithium cobalt oxide (LCO) cathodes under repeated bending and the role of the polymer binder in improving the mechanical durability of the LCO electrodes for use in flexible LIBs are investigated. Mechanical and electrochemical evaluations of LCO electrodes (areal capacity of ≥2.

Lithium Dendrite Propagation in Ta-Doped LiLaZrO (LLZTO): Comparison of Reactively Sintered Pyrochlore-to-Garnet LLZTO by Solid-State Reaction and Conventional Sintering.

Ta-doped LiLaZrO (LLZTO) garnet is a promising Li-ion-conducting ceramic electrolyte for solid-state batteries. However, it is still challenging to use LLZTO in Li metal batteries operating at high current densities because of the tendency for Li metal to nucleate and propagate along the grain boundaries. In this study, we carry out a detailed investigation to elucidate the effect of microstructure and grain size on the electrochemical properties and short circuit behavior in LLZTO.

Self-supported polypyrrole flexible electrodes for electrochemical reduction of nitrite.

The efficiency of an electrochemical oxidation/reduction process strongly depends on the working electrode's surface area to volume ratio. By making electrodes flexible and employing different configurations such as roll-to-roll membrane, the surface area to volume ratio can be enhanced, therefore improving the overall efficiency of electrochemical processes. Conductive polymers emerge as a new framework to enable alternative electrochemical water treatment cell configurations.

Electrochemical Flux Synthesis of Type-I NaSi Clathrates: Particle Size Control Using a Solid or Molten Na-Sn Mass Transport Mediator.

Sodium-filled silicon clathrates have a host of interesting properties for thermoelectric, photovoltaic, and battery applications. However, the metastability of the clathrates has made it difficult to synthesize them with the desired morphology and crystallite size. Herein, we demonstrate an electrochemical method whereby NaSi dissolved in a Sn-based flux is converted to the NaSi type-I clathrate using galvanostatic (constant current) oxidation.

Synthesis of Type II Ge and Ge-Si Alloyed Clathrates Using Solid-State Electrochemical Oxidation of Zintl Phase Precursors.

Germanium clathrates with the type II structure are open-framework materials that show promise for various applications, but the difficulty of achieving phase-pure products via traditional synthesis routes has hindered their development. Herein, we demonstrate the synthesis of type II Ge clathrates in a two-electrode electrochemical cell using NaGeSi ( = 0, 1) Zintl phase precursors as the working electrode, Na metal as the counter/reference electrode, and Na-ion conducting β″-alumina as the solid electrolyte. The galvanostatic oxidation of NaGe resulted in voltage plateaus around 0.

High-Density Oxygen Doping of Conductive Metal Sulfides for Better Polysulfide Trapping and Li S-S Redox Kinetics in High Areal Capacity Lithium-Sulfur Batteries.

Exploring new materials and methods to achieve high utilization of sulfur with lean electrolyte is still a common concern in lithium-sulfur batteries. Here, high-density oxygen doping chemistry is introduced for making highly conducting, chemically stable sulfides with a much higher affinity to lithium polysulfides. It is found that doping large amounts of oxygen into NiCo S is feasible and can make it outperform the pristine oxides and natively oxidized sulfides.

Structural and Electrochemical Properties of Type VIII BaGaSn Clathrate (δ ≈ 1) during Lithiation.

Clathrates of the tetrel (Tt = Si, Ge, Sn) elements are host-guest structures that can undergo Li alloying reactions with high capacities. However, little is known about how the cage structure affects the phase transformations that take place during lithiation. To further this understanding, the structural changes of the type VIII clathrate BaGaSn (δ ≈ 1) during lithiation are investigated and compared to those in β-Sn with X-ray total scattering measurements and pair distribution function (PDF) analysis.

Monitoring the Structure Evolution of Titanium Oxide Photocatalysts: From the Molecular Form via the Amorphous State to the Crystalline Phase.

Amorphous Ti O with high surface area has attracted significant interest as photocatalyst with higher activity in ultraviolet (UV) light-induced water splitting applications compared to commercial nanocrystalline TiO . Under photocatalytic operation conditions, the structure of the molecular titanium alkoxide precursor rearranges upon hydrolysis and leads to higher connectivity of the structure-building units. Structurally ordered domains with sizes smaller than 7 Å form larger aggregates.

In situ total scattering experiments of nucleation and crystallisation of tantalum-based oxides: from highly dilute solutions via cluster formation to nanoparticles.

The exact formation mechanism of tantalum oxides (and in general, metal/mixed metal oxides) from alkoxide precursors is still not fully understood, particularly when forming cluster-like or amorphous materials. The structural evolution of Ta-based oxides was studied in detail using X-ray total scattering experiments along with subsequent pair distribution function (PDF) analyses. Starting from a tantalum alkoxide precursor (Ta(OEt)), the formation of hydrolysed TaOH clusters in highly diluted aqueous solution was analysed.

Highly Conductive Garnet-Type Electrolytes: Access to LiLaZrTaO Prepared by Molten Salt and Solid-State Methods.

Tantalum-doped garnet (LiLaZrTaO, LLZTO) is a promising candidate to act as a solid electrolyte in all-solid-state batteries owing to both its high Li conductivity and its relatively high robustness against the Li metal. Synthesizing LLZTO using conventional solid-state reaction (SSR) requires, however, high calcination temperature (>1000 °C) and long milling steps, thereby increasing the processing time. Here, we report on a facile synthesis route to prepare LLZTO using a molten salt method (MSS) at lower reaction temperatures and shorter durations (900 °C, 5 h).

Tissue paper-derived porous carbon encapsulated transition metal nanoparticles as advanced non-precious catalysts: Carbon-shell influence on the electrocatalytic behaviour.

Porous carbon encapsulated non-precious metal nanocatalysts have recently opened the ways towards the development of high-performance water remediation and energy conversion technologies. Herein, we report a facile, scalable and green synthetic methodology to fabricate porous carbon encapsulated transition metal nanocatalysts (M@TP: M = Cu, Ni, Fe and Co) using commercial tissue paper. The morphology, crystalline structure, chemical composition and textural properties of the M@TP nanocatalysts were thoroughly characterized.

Nonaqueous Polymer Combustion Synthesis of Cubic LiLaZrO Nanopowders.

Garnet-type lithium lanthanum zirconate (LiLaZrO, LLZO) shows great promise as a solid electrolyte for future solid-state lithium batteries as it possesses a uniquely beneficial combination of high ionic conductivity, electrochemical stability against metallic lithium, and generally low reactivity in ambient conditions. Conventionally synthesized by using solid-state reactions, LLZO powders have also been prepared by using variations of sol-gel or combustion synthesis with sacrificial organic templates or polymers containing metal nitrate precursors. Herein, a novel nonaqueous polymer (NAP) method using metalorganic precursors and poly(vinylpyrrolidone) is demonstrated to easily form LLZO nanopowders.

Laser Fragmentation-Induced Defect-Rich Cobalt Oxide Nanoparticles for Electrochemical Oxygen Evolution Reaction.

Sub-5 nm cobalt oxide nanoparticles are produced in a flowing water system by pulsed laser fragmentation in liquid (PLFL). Particle fragmentation from 8 nm to 4 nm occurs and is attributed to the oxidation process in water where oxidative species are present and the local temperature is rapidly elevated under laser irradiation. Significantly higher surface area, crystal phase transformation, and formation of structural defects (Co defects and oxygen vacancies) through the PLFL process are evidenced by detailed structural characterizations by nitrogen physisorption, electron microscopy, synchrotron X-ray diffraction, and X-ray photoelectron spectroscopy.

Titanium Dioxide-Layered Double Hydroxide Composite Material for Adsorption-Photocatalysis of Water Pollutants.

Although adsorption has gained favor among numerous water treatment technologies as an effective pollutant removal method, its application is often hindered by challenges with its resource- and energy-intensive regeneration procedure once the available adsorption sites are exhausted. Herein, we present adsorption-photocatalysis composite materials combining layered double hydroxides (LDHs) and titanium dioxide (TiO) for water treatment. Incorporation of the photocatalyst into the material opens opportunities to harness light from the sun or lamps for oxidative degradation of the adsorbed contaminants on the material surface, to free adsorption sites for material reuse.

Highly Active Cobalt-Based Electrocatalysts with Facile Incorporation of Dopants for the Oxygen Evolution Reaction.

In situ formation of electroactive cobalt species for the oxygen evolution reaction is simply achieved by applying an anodic bias to a commercially available cobalt precursor and Nafion binder mixture coated on a glassy carbon electrode. This preparation does not require energy-intensive materials preparation steps or noble metals, yet a low overpotential of 322 mV at 10.2 mA cm and a high current density of more than 300 mA cm at 1.

Experimental and Computational Study of the Lithiation of BaAl Ge Based Type I Germanium Clathrates.

In this work, we investigate the electrochemical properties of BaAl Ge ( y = 0, 4, 8, 12, 16) clathrates prepared by arc-melting. These materials have cage-like structures with large cavity volumes and can also have vacancies on the Ge framework sites, features which may be used to accommodate Li. Herein, a structural, electrochemical, and theoretical investigation is performed to explore these materials as anodes in Li-ion batteries, including analysis of the effect of the Al content and framework vacancies on the observed electrochemical properties.

Emerging opportunities for nanotechnology to enhance water security.

No other resource is as necessary for life as water, and providing it universally in a safe, reliable and affordable manner is one of the greatest challenges of the twenty-first century. Here, we consider new opportunities and approaches for the application of nanotechnology to enhance the efficiency and affordability of water treatment and wastewater reuse. Potential development and implementation barriers are discussed along with research needs to overcome them and enhance water security.

Coffee-Waste Templating of Metal Ion-Substituted Cobalt Oxides for the Oxygen Evolution Reaction.

A facile and scalable method using coffee waste grounds as a hard template has been developed to fabricate nanostructured Co O for the oxygen evolution reaction (OER). Co O incorporating metals with different valences (M/Co=1:4; M=Cu, Ni, Fe, Cr, and W) were also prepared with similar sheet-like structures comprising nanosized crystallites. After detailed characterization by X-ray diffraction, electron microscopy, and nitrogen sorption, the oxides were employed as OER electrocatalysts.

Anodes for Lithium-Ion Batteries Based on Type I Silicon Clathrate BaAlSi - Role of Processing on Surface Properties and Electrochemical Behavior.

Type I silicon clathrates based on BaAlSi (8 < y < 12) have been studied as potential anodes for lithium-ion batteries and display electrochemical properties that are distinct from those found in conventional silicon anodes. Processing steps such as ball-milling (typically used to reduce the particle size) and acid/base treatment (used to remove nonclathrate impurities) may modify the clathrate surface structure or introduce defects, which could affect the observed electrochemical properties. In this work, we perform a systematic investigation of BaAlSi clathrates with y ≈ 16, i.

Composite Polymer Electrolytes with LiLaZrO Garnet-Type Nanowires as Ceramic Fillers: Mechanism of Conductivity Enhancement and Role of Doping and Morphology.

Composite polymer solid electrolytes (CPEs) containing ceramic fillers embedded inside a polymer-salt matrix show great improvements in Li ionic conductivity compared to the polymer electrolyte alone. Lithium lanthanum zirconate (LiLaZrO, LLZO) with a garnet-type crystal structure is a promising solid Li conductor. We show that by incorporating only 5 wt % of the ceramic filler comprising undoped, cubic-phase LLZO nanowires prepared by electrospinning, the room temperature ionic conductivity of a polyacrylonitrile-LiClO-based composite is increased 3 orders of magnitude to 1.

Exfoliation of LiNiMnCoO into Nanosheets Using Electrochemical Oxidation and Reassembly with Dialysis or Flocculation.

Two-dimensional (2D) materials such as nanosheets are increasingly attracting attention for applications in energy storage and conversion. Many conventional battery compounds have layered structures, which can facilitate the exfoliation of these materials into nanosheet morphologies. In this work, LiNiMnCoO (NMC) particles were exfoliated into nanosheets using an electrochemical oxidation method enabled by the intercalation of tetraethylammonium cations into the interlayer space.

AlO and SiO Atomic Layer Deposition Layers on ZnO Photoanodes and Degradation Mechanisms.

Strategies for protecting unstable semiconductors include the utilization of surface layers composed of thin films deposited using atomic layer deposition (ALD). The protective layer is expected to (1) be stable against reaction with photogenerated holes, (2) prevent direct contact of the unstable semiconductor with the electrolyte, and (3) prevent the migration of ions through the semiconductor/electrolyte interface, while still allowing photogenerated carriers to transport to the interface and participate in the desired redox reactions. Zinc oxide (ZnO) is an attractive photocatalyst material due to its high absorption coefficient and high carrier mobilities.

Spent Tea Leaf Templating of Cobalt-Based Mixed Oxide Nanocrystals for Water Oxidation.

The facile synthesis of nanostructured cobalt oxides using spent tea leaves as a hard template is reported. Following an impregnation-calcination and template removal pathway, sheetlike structures containing nanosized crystallites of CoO are obtained. CoO incorporated with Cu, Ni, Fe, and Mn (M/Co = 1/8 atomic ratio) are also prepared, and the materials are thoroughly characterized using X-ray diffraction, electron microscopy, and N sorption.

Dual-Templated Cobalt Oxide for Photochemical Water Oxidation.

Mesoporous Co3 O4 was prepared using a dual templating approach whereby mesopores inside SiO2 nanospheres, as well as the void spaces between the nanospheres, were used as templates. The effect of calcination temperature on the crystallinity, morphology, and textural parameters of the Co3 O4 replica was investigated. The catalytic activity of Co3 O4 for photochemical water oxidation in a [Ru(bpy)3 ](2+) [S2 O8 ](2-) system was evaluated.