Unveiling the Cation Exchange Reaction between the NASICON Li1.5Al0.5Ge1.5(PO4)3 Solid Electrolyte and the pyr13TFSI Ionic Liquid.

Recently, the formation of the ceramic-ionic liquid composite has attracted huge interest in the scientific community. In this work, we investigated the chemical reactions occurring between NASICON LAGP ceramic electrolyte and ionic liquid pyr13TFSI. This study allowed us to identify the cation exchange reaction pyr13-Li occurring on the LAGP surface, forming a LiTFSI salt that was detected by the nuclear magnetic resonance analysis. In addition, using 6Li foils, we succeeded in demonstrating that both LAGP and LiTFSI:pyr13TFSI participate in the diffusion of Li ions by the formation of an ionic bridge between two species.

Generation of novel n-p-n (CeO2-PPy-ZnO) heterojunction for photocatalytic degradation of micro-organic pollutants.

Recently, hetero junction materials (p-n-p and n-p-n) have been developed for uplifting the visible light activity to destroy the harmful pollutants in wastewater. This manuscript presents a vivid description of novel n-p-n junction materials namely CeO2-PPy-ZnO. This novel n-p-n junction was applied as the photocatalyst in drifting the mobility of charge carriers and hence obtaining the better photocatalytic activity when compared with p-n and pure system. Such catalyst's syntheses were successful via the copolymerization method. The structural, morphological and optical characterization techniques were applied to identify the physio-chemical properties of the prepared materials. Additionally, the superior performance of this n-p-n nanostructured material was demonstrated in the destruction of micro organic (chlorophenol) toxic wastes under visible light. The accomplished ability of the prepared catalysts (up to 92% degradation of chlorophenol after 180 min of irradiation) and their profound degradation mechanism was explained in detail.

Thermal evolution of NASICON type solid-state electrolytes with lithium at high temperature via in situ scanning electron microscopy.

We present the thermal evolution of two NASICON-type ceramics namely LATP (Li1+xAlxTi2-x(PO4)3) and LAGP (Li1+xAlxGe2-x(PO4)3) by monitoring the electrode-electrolyte interfaces (i.e., Li/LATP and Li/LAGP) at temperatures up to 330 °C via in situ scanning electron microscopy, post-mortem energy-dispersive spectroscopy, and X-ray diffraction. Upon melting of Li and contacting electrolytes, LAGP decomposes completely to form Li based alloys, while LATP is partially decomposed without alloying.

On high-temperature evolution of passivation layer in Li-10 wt % Mg alloy via in situ SEM-EBSD.

Li-10 wt % Mg alloy (Li-10 Mg) is used as an anode material for a solid-state battery with excellent electrochemical performance and no evidence of dendrite formation during cycling. Thermal treatment of Li metal during manufacturing improves the interfacial contact between a Li metal electrode and solid electrolyte to achieve an all solid-state battery with increased performance. To understand the properties of the alloy passivation layer, this paper presents the first direct observation of its evolution at elevated temperatures (up to 325°C) by in situ scanning electron microscopy. We found that the morphology of the surface passivation layer was unchanged above the alloy melting point, while the bulk of the material below the surface was melted at the expected melting point, as confirmed by in situ electron backscatter diffraction. In situ heat treatment of Li-based materials could be a key method to improve battery performance.

Synthesis and Performance of MOF-Based Non-Noble Metal Catalysts for the Oxygen Reduction Reaction in Proton-Exchange Membrane Fuel Cells: A Review.

Hydrogen is widely regarded as a prime energy carrier for bridging the gap between renewable energy supply and demand. As the energy-generating component of the hydrogen cycle, affordable and reliable fuel cells are of key importance to the growth of the hydrogen economy. However, the use of scarce and costly Pt as an electrocatalyst for the oxygen reduction reaction (ORR) remains an issue to be addressed, and in this regard, metal-organic frameworks (MOFs) are viewed as promising non-noble alternatives because of their self-assembly capability and tunable properties. Herein, recent (2018-2020) works on MOF-based electrocatalysts containing N-doped C, Mn, Fe, Co, multiple metals, and multiple sites are reviewed and summarized with a focus on ORR activity, and the principal physicochemical properties and electrochemical performance of these catalysts realized using rotating electrodes are compared.

Phase Transformation of Doped LiCoPO4 during Galvanostatic Cycling.

In situ X-ray diffraction was employed to investigate the crystal structure changes in Cr/Si co-doped Li(Co,Fe)PO4 cathode material during a galvanostatic charge/discharge process at a slow rate of C/30. The evolution of the X-ray patterns revealed that the phase transformation between the Cr/Si-Li(Co,Fe)PO4 and Cr/Si-(Co,Fe)PO4 is a two-step process, which involves the formation of an intermediate compound of Cr/Si-Li0.62(Co,Fe)PO4 upon the extraction of Li ions from the pristine phase. Different from the previously reported two biphasic transition steps, the phase transformation of the Cr/Si-Li(Co,Fe)PO4 followed a solid solution and a biphasic reaction pathway at different stages of the delithiation/lithiation process, respectively.

Application of Magnetic Resonance Techniques to the In Situ Characterization of Li-Ion Batteries: A Review.

In situ magnetic resonance (MR) techniques, such as nuclear MR and MR imaging, have recently gained significant attention in the battery community because of their ability to provide real-time quantitative information regarding material chemistry, ion distribution, mass transport, and microstructure formation inside an operating electrochemical cell. MR techniques are non-invasive and non-destructive, and they can be applied to both liquid and solid (crystalline, disordered, or amorphous) samples. Additionally, MR equipment is available at most universities and research and development centers, making MR techniques easily accessible for scientists worldwide. In this review, we will discuss recent research results in the field of in situ MR for the characterization of Li-ion batteries with a particular focus on experimental setups, such as pulse sequence programming and cell design, for overcoming the complications associated with the heterogeneous nature of energy storage devices. A comprehensive approach combining proper hardware and software will allow researchers to collect reliable high-quality data meeting industrial standards.

Behavior of Solid Electrolyte in Li-Polymer Battery with NMC Cathode via in-Situ Scanning Electron Microscopy.

We present the first results of in situ scanning electron microscopy (SEM) of an all-solid Li battery with a nickel-manganese-cobalt-oxide (NMC-622) cathode at 50 °C and an operating voltage of 2.7-4.3 V. Experiments were conducted under a constant current at several C rates (nC rate: cycling in 1/n h): C/12, C/6, and C/3. The microstructure evolution during cycling was monitored by continuous secondary electron imaging. We found that the chemical degradation of the solid polymer electrolyte (SPE) was the main mechanism for battery failure. This degradation was observed in the form of a gradual thinning of the SPE as a function of cycling time, resulting in gas generation from the cell. We also present various dynamic electrochemical and mechanical phenomena, as observed by SEM images, and compare the performance of this battery with that of an all-solid Li battery with a LiFePO4 cathode.

Protection of LiFePO4 against Moisture.

In this study, a carbon-coated LiFePO4 (LFP/C) powder was chemically grafted with trifluoromethylphenyl groups in order to increase its hydrophobicity and to protect it from moisture. The modification was carried out by the spontaneous reduction of in situ generated 4-trifluoromethylphenyl ions produced by the diazotization of 4-trifluoromethylaniline. X-ray photoelectron spectroscopy was used to analyze the surface organic species of the modified powder. The hydrophobic properties of the modified powder were investigated by carrying out its water contact angle measurements. The presence of the trifluoromethylphenyl groups on the carbon-coated LiFePO4 powder increased its stability in deionized water and reduced its iron dissolution in the electrolyte used for assembling the battery. The thermogravimetric and inductively coupled plasma atomic emission spectroscopy analyses revealed that 0.2-0.3 wt.% Li was deinserted during grafting and that the loading of the grafted molecules varied from 0.5 to 0.8 wt.% depending on the reaction conditions. Interestingly, the electrochemical performance of the modified LFP/C was not adversely affected by the presence of the trifluoromethylphenyl groups on the carbon surface. The chemical relithiation of the grafted samples was carried out using LiI as the reducing agent and the lithium source in order to obtain fully lithiated grafted powders.

Boosting Ultra-Fast Charge Battery Performance: Filling Porous nanoLi4Ti5O12 Particles with 3D Network of N-doped Carbons.

Lithium titanium oxide (Li4Ti5O12)-based cells are a promising technology for ultra-fast charge-discharge and long life-cycle batteries. However, the surface reactivity of Li4Ti5O12 and lack of electronic conductivity still remains problematic. One of the approaches toward mitigating these problems is the use of carbon-coated particles. In this study, we report the development of an economical, eco-friendly, and scalable method of making a homogenous 3D network coating of N-doped carbons. Our method makes it possible, for the first time, to fill the pores of secondary particles with carbons; we reveal that it is possible to cover each primary nanoparticle. This unique approach permits the creation of lithium-ion batteries with outstanding performances during ultra-fast charging (4C and 10C), and demonstrates an excellent ability to inhibit the degradation of cells over time at 1C and 45 °C. Furthermore, using this method, we can eliminate the addition of conductive carbons during electrode preparation, and significantly increase the energy density (by weight) of the anode.

Hydrogen Storage for Mobility: A Review.

Numerous reviews on hydrogen storage have previously been published. However, most of these reviews deal either exclusively with storage materials or the global hydrogen economy. This paper presents a review of hydrogen storage systems that are relevant for mobility applications. The ideal storage medium should allow high volumetric and gravimetric energy densities, quick uptake and release of fuel, operation at room temperatures and atmospheric pressure, safe use, and balanced cost-effectiveness. All current hydrogen storage technologies have significant drawbacks, including complex thermal management systems, boil-off, poor efficiency, expensive catalysts, stability issues, slow response rates, high operating pressures, low energy densities, and risks of violent and uncontrolled spontaneous reactions. While not perfect, the current leading industry standard of compressed hydrogen offers a functional solution and demonstrates a storage option for mobility compared to other technologies.

Computational study of H2 binding to MH3 (M = Ti, V, or Cr).

A series of amorphous materials based on hitherto elusive early transition metal hydrides MH3 (M = Ti, V, and Cr) and capable of binding H2via the Kubas interaction has shown great promise for hydrogen storage applications, approaching US DoE system targets in some cases [Phys. Chem. Chem. Phys., 2015, 17, 9480; Chem. Mat., 2013, 25, 4765; J. Phys. Chem. C, 2016, 120, 11407]. We here apply quantum chemical computational techniques to study models of the H2 binding sites in these materials. Starting with monomeric MH3 (M = Ti, V, and Cr) we progress to M2H6 and then pentametallic systems, analyzing the H2 binding geometries, energies, vibrational frequencies and electronic structure, finding clear evidence of significant Kubas binding. Dihydrogen binding energies range from 22 to 53 kJ mol-1. In agreement with experiment, we conclude that while TiH3 binds H2 exclusively through the Kubas interaction, VH3 and CrH3 additionally physisorb dihydrogen, making these more attractive for practical applications.

High Capacity and High Efficiency Maple Tree-Biomass-Derived Hard Carbon as an Anode Material for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) are in the spotlight because of their potential use in large-scale energy storage devices due to the abundance and low cost of sodium-based materials. There are many SIB cathode materials under investigation but only a few candidate materials such as carbon, oxides and alloys were proposed as anodes. Among these anode materials, hard carbon shows promising performances with low operating potential and relatively high specific capacity. Unfortunately, its low initial coulombic efficiency and high cost limit its commercial applications. In this study, low-cost maple tree-biomass-derived hard carbon is tested as the anode for sodium-ion batteries. The capacity of hard carbon prepared at 1400 °C (HC-1400) reaches 337 mAh/g at 0.1 C. The initial coulombic efficiency is up to 88.03% in Sodium trifluoromethanesulfonimide (NaTFSI)/Ethylene carbonate (EC): Diethyl carbonate (DEC) electrolyte. The capacity was maintained at 92.3% after 100 cycles at 0.5 C rates. The in situ X-ray diffraction (XRD) analysis showed that no peak shift occurred during charge/discharge, supporting a finding of no sodium ion intercalates in the nano-graphite layer. Its low cost, high capacity and high coulombic efficiency indicate that hard carbon is a promising anode material for sodium-ion batteries.

A photochemical diode artificial photosynthesis system for unassisted high efficiency overall pure water splitting.

The conversion of solar energy into chemical fuels can potentially address many of the energy and environment related challenges we face today. In this study, we have demonstrated a photochemical diode artificial photosynthesis system that can enable efficient, unassisted overall pure water splitting without using any sacrificial reagent. By precisely controlling charge carrier flow at the nanoscale, the wafer-level photochemical diode arrays exhibited solar-to-hydrogen efficiency ~3.3% in neutral (pH ~ 7.0) overall water splitting reaction. In part of the visible spectrum (400-485 nm), the energy conversion efficiency and apparent quantum yield reaches ~8.75% and ~20%, respectively, which are the highest values ever reported for one-step visible-light driven photocatalytic overall pure water splitting. The effective manipulation and control of charge carrier flow in nanostructured photocatalysts provides critical insight in achieving high efficiency artificial photosynthesis, including the efficient and selective reduction of CO2 to hydrocarbon fuels.

New Avenue for Limiting Degradation in NanoLi4Ti5O12 for Ultrafast-Charge Lithium-Ion Batteries: Hybrid Polymer-Inorganic Particles.

Lithium titanium oxide (Li4Ti5O12)-based cells are a very promising battery technology for ultrafast-charge-discharge and long-cycle-life batteries. However, the surface reactivity of lithium titanium oxide in the presence of organic electrolytes continues to be a problem that may cause expansion of pouch cells. In this study, we report on the development of a simple and economical grafting method for forming hybrid polymer-Li4Ti15O12 nanoparticles, which can be successfully applied in lithium-ion batteries. This method utilizes a low-cost and scalable hydrophobic polymer that is applicable in industrial processes. The hybrid materials demonstrated exceptional capability for preventing the degradation of cells in accelerated aging and operating over 150 cycles at 1C and 45 °C.

Atomic-Scale Origin of Long-Term Stability and High Performance of p-GaN Nanowire Arrays for Photocatalytic Overall Pure Water Splitting.

The atomic-scale origin of the unusually high performance and long-term stability of wurtzite p-GaN oriented nanowire arrays is revealed. Nitrogen termination of both the polar (0001¯) top face and the nonpolar (101¯0) side faces of the nanowires is essential for long-term stability and high efficiency. Such a distinct atomic configuration ensures not only stability against (photo) oxidation in air and in water/electrolyte but, as importantly, also provides the necessary overall reverse crystal polarization needed for efficient hole extraction in p-GaN.

High-Pressure Raman and Calorimetry Studies of Vanadium(III) Alkyl Hydrides for Kubas-Type Hydrogen Storage.

Reversible hydrogen storage under ambient conditions has been identified as a major bottleneck in enabling a future hydrogen economy. Herein, we report an amorphous vanadium(III) alkyl hydride gel that binds hydrogen through the Kubas interaction. The material possesses a gravimetric adsorption capacity of 5.42 wt % H2 at 120 bar and 298 K reversibly at saturation with no loss of capacity after ten cycles. This corresponds to a volumetric capacity of 75.4 kgH2 m(-3) . Raman experiments at 100 bar confirm that Kubas binding is involved in the adsorption mechanism. The material possesses an enthalpy of H2 adsorption of +0.52 kJ mol(-1) H2 , as measured directly by calorimetry, and this is practical for use in a vehicles without a complex heat management system.

Thermodynamically neutral Kubas-type hydrogen storage using amorphous Cr(III) alkyl hydride gels.

In this paper we present amorphous chromium(III) hydride gels that show promise as reversible room temperature hydrogen storage materials with potential for exploitation in mobile applications. The material uses hydride ligands as a light weight structural feature to link chromium(III) metal centres together which act as binding sites for further dihydrogen molecules via the Kubas interaction, the mode of hydrogen binding confirmed by high pressure Raman spectroscopy. The best material possesses a reversible gravimetric storage of 5.08 wt% at 160 bar and 25 °C while the volumetric density of 78 kgH2 m(-3) compares favourably to the DOE ultimate system goal of 70 kg m(-3). The enthalpy of hydrogen adsorption is +0.37 kJ mol(-1) H2 as measured directly at 40 °C using an isothermal calorimeter coupled directly to a Sieverts gas sorption apparatus. These data support a mechanism confirmed by computations in which the deformation enthalpy required to open up binding sites is almost exactly equal and opposite to the enthalpy of hydrogen binding to the Kubas sites, and suggests that this material can be used in on-board applications without a heat management system.