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Garnet solid electrolyte-based Li-ion batteries can be used in energy storage devices with high energy densities and thermal stability. However, the tendency of garnets to form lithium hydroxide and carbonate on the surface in an ambient atmosphere poses significant processing challenges. In this work, the decomposition of surface layers under various gas environments is studied by using the surface sensitive techniques, near ambient pressure x-ray photoelectron spectroscopy and grazing incidence diffraction. It is found that heating to 500 °C under oxygen atmosphere (of 1 mbar and above) leads to a clean garnet surface, whereas low oxygen partial pressures (i.e., in argon or vacuum) lead to additional graphitic carbon deposits. The clean surface of garnets reacts directly with moisture and carbon dioxide below 400 and 500 °C respectively. This suggests that additional CO2 concentration controls are needed for the handling of garnets. By heating under O2 along with avoiding H2O and CO2, symmetric cells with less than 10 Ωcm2 interface resistance are prepared without the use of any interlayers; plating currents of greater than 1 mAcm-2 without dendrite initiation are demonstrated.

Li- and Mn-rich layered oxides (Li1.2Ni0.2Mn0.6O2) are actively pursued as high energy and sustainable alternatives to the current Li-ion battery cathodes that contain Co. However, the severe decay in discharge voltage observed in these cathodes needs to be addressed before they can find commercial applications. A few mechanisms differing in origin have been proposed to explain the voltage fade, which may be caused by differences in material composition, morphology and electrochemical testing protocols. Here, these challenges are addressed by synthesising Li1.2Ni0.2Mn0.6O2 using three different hydrothermal and solid-state approaches and studying their degradation using the same cell design and cycling protocols. The voltage fade is found to be similar under the same electrochemical testing protocols, regardless of the synthesis method. X-ray absorption near edge, extended X-ray absorption fine structure spectroscopies, and energy loss spectroscopy in a scanning transmission electron microscope indicate only minor changes in the bulk Mn oxidation state but reveal a much more reduced particle surface upon extended cycling. No spinel phase is seen via the bulk structural characterisation methods of synchrotron X-ray diffraction, 7Li magic angle spinning solid state nuclear magnetic resonance and Raman spectroscopy. Thus, the voltage fade is believed to largely result from a heavily reduced particle surface. This hypothesis is further confirmed by galvanostatic intermittent titration technique analysis, which indicates that only very small shifts in equilibrium potential take place, in contrast to the overpotential which builds up after cycling. This suggests that a major source of the voltage decay is kinetic in origin, resulting from a heavily reduced particle surface with slow Li transport.

Funder: Cambridge Trust, Funder: Blavatnik Family Foundation, Funder: Studienstiftung des Deutschen Volkes, Funder: Fonds der Chemischen Industrie, All-solid-state batteries based on non-combustible solid electrolytes are promising candidates for safe energy storage systems. In addition, they offer the opportunity to utilize metallic lithium as an anode. However, it has proven to be a challenge to design an electrolyte that combines high ionic conductivity and processability with thermodynamic stability toward lithium. Herein, we report a new highly conducting solid solution that offers a route to overcome these challenges. The Li-P-S ternary was first explored via a combination of high-throughput crystal structure predictions and solid-state synthesis (via ball milling) of the most promising compositions, specifically, phases within the Li3P-Li2S tie line. We systematically characterized the structural properties and Li-ion mobility of the resulting materials by X-ray and neutron diffraction, solid-state nuclear magnetic resonance spectroscopy (relaxometry), and electrochemical impedance spectroscopy. A Li3P-Li2S metastable solid solution was identified, with the phases adopting the fluorite (Li2S) structure with P substituting for S and the extra Li+ ions occupying the octahedral voids and contributing to the ionic transport. The analysis of the experimental data is supported by extensive quantum-chemical calculations of both structural stability, diffusivity, and activation barriers for Li+ transport. The new solid electrolytes show Li-ion conductivities in the range of established materials, while their composition guarantees thermodynamic stability toward lithium metal anodes.

All-solid-state batteries based on non-combustible solid electrolytes are promising candidates for safe energy storage systems. In addition, they offer the opportunity to utilize metallic lithium as an anode. However, it has proven to be a challenge to design an electrolyte that combines high ionic conductivity and processability with thermodynamic stability toward lithium. Herein, we report a new highly conducting solid solution that offers a route to overcome these challenges. The Li-P-S ternary was first explored via a combination of high-throughput crystal structure predictions and solid-state synthesis (via ball milling) of the most promising compositions, specifically, phases within the Li

Fast migration of lithium (Li)-ions in oxide materials is fundamental to the operation of Li-ion batteries. The intercalation of Li-ions into oxides can further lead to emergent electronic property changes. Some of the fastest Li-ion conductors are 4d oxides, and of these, the niobium oxide polymorph T-Nb2O5 is especially interesting with its two-dimensional fast ion migration channels. However, the growth of single-crystalline T-Nb2O5 films is challenging due to its stability over only a limited synthesis temperature window, the existence of many other polymorphs, and its large orthorhombic unit cell. Here, we first demonstrate the epitaxial growth of single domain T-Nb2O5 thin films, critically with the ion channels oriented perpendicular to the film's surface. We show that the insertion of just a small amount of Li using ionic liquids results in conversion of the initially insulating film to a metallic state with a colossal change in resistivity of almost eleven orders of magnitude. In situ experiments, in conjunction with theoretical calculations, reveal a series of transitions between distinct crystal and electronic structures as the lithium content is systematically increased. These include hidden phases that have not previously been identified. Furthermore, replacing the Au electrode with a Li-oxide electrode allows for a significant reduction of the gate voltage at which metallization takes place. Our study opens a new path towards the exploration of hidden phases and the development of novel electrochemically controlled electronic devices.

Chemical communications 58, 11949 - 11952 (2022). doi:10.1039/D2CC04241J, The structure of a new ZIF-8 polymorph with quartz topology (qtz) is reported. This qtz-[Zn(mIm)$_2$] phase was obtained by mechanically amorphising crystalline ZIF-8, before heating the resultant amorphous phase to between 282 and 316 °C. The high-temperature phase structure was obtained from powder X-ray diffraction, and its thermal behaviour, CO$_2$ gas sorption properties and dye adsorption ability were investigated., Published by Soc., Cambridge

Proceedings of the National Academy of Sciences of the United States of America 119(12), e2119616119 (2022). doi:10.1073/pnas.2119616119, Coherent nonlinear spectroscopies and imaging in the X-ray domain provide direct insight into the coupled motions of electrons and nuclei with resolution on the electronic length and time scale. The experimental realization of such techniques will strongly benefit from access to intense, coherent pairs of femtosecond X-ray pulses. We have observed phase-stable X-ray pulse pairs containing more than 3*107 photons at 5.9 keV (2.1 ��) with ~1 fs duration and 2-5 fs separation. The highly directional pulse pairs are manifested by interference fringes in the superfluorescent and seeded stimulated manganese K�� emission induced by an X-ray free-electron laser. The fringes constitute the time-frequency X-ray analogue of Young���s double-slit interference allowing for frequency-domain X-ray measurements with attosecond time resolution., Published by National Acad. of Sciences, Washington, DC

Perovskite oxides have exhibited promising catalytic performance in photocatalysis, electrocatalysis, and thermocatalysis, and the performance can be potentially enhanced by tuning their flexible e...

The organic matrix of a bone mainly composed of a collagen matrix serves as a crucial component for remarkable toughness and strength in bones. The porous collagen matrix can also serve as an efficient template for various applications such as nanoparticle synthesis, catalysis or catalysis supports, electrochemical separator, filtration membrane, and tissue engineering. However, fabricating collagen matrix from bones without degrading its morphological structure still remains a challenge. Here, we present evidence of how ceramic crystals from a bone can be removed to fabricate a complete ‘transparent bone’ structure with improved porosity and elasticity. We show that demineralization or selective etching using dilute acid (citric) can remove ceramic mineral nanoparticles without degrading the collagen matrix. The transparent bone collagen matrix is investigated as the separator in electrochemical supercapacitor with aqueous electrolyte where it shows better performance compared with conventional separators.

Mobile ad hoc networks (MANETs) is a multi-hop wireless network having the capability to self-conFigure and self-organize when affected by node mobility. Routing becomes a problem in MANET because nodes continuously change their position due to movement. As a result, a packet path must be dynamically adapted according to the node movement. Most routing protocols in MANET are characterized by low packet success ratio and low throughput. This work proposes an effective routing algorithm assisted by artificial neural networks for mobility prediction in order to improve the routing performances, thereby increasing the packet success ratio and throughput.

Structural and stoichiometric alterations in cathode materials with high intercalation voltages have been a bottleneck for next generation lithium ion batteries. Moreover, structure damage with the slightest of temperature elevation is predominant in known cathode systems. Monoclinic Li3V2(PO4)3 (LVP) with high intercalation voltage (>4.0 V) is a potential high-power cathode for lithium ion batteries owing to extraordinary stability of the phosphate anion framework. However, severe vanadium dissolution and lattice re-arrangement remains the biggest nuisance. Modification of electron conduction pathways by doping LVP lattice with Cr3+ is studied here and the efficacy of Cr3+ to stabilize the structure is understood. Vacant d-orbital sites in Cr3+ promote de-localization of electrons suppressing disproportionation and hence vanadium dissolution resulting in improved electrochemical performance for robust cycling conditions. Significant enhancement in specific capacity retention (from 26% to 84%) and improved cycle life of 400 high power cycles was observed on doping suggesting excellent performance of the cathode at high temperature (60 °C) environments.

Thermal fragility of the solid electrolyte interphase (SEI) is a major source of performance decay in graphite anodes, and efforts to overcome the issues offered by extreme environments to Li-ion batteries have had limited success. Here, we demonstrate that the SEI can be extensively reinforced by carrying the formation cycles at elevated temperatures. Under these conditions, decomposition of the ionic liquid present in the electrolyte favored the formation of a thicker and more protective layer. Cells in which the solid electrolyte interphase was cast at 90 °C were significantly less prone to self-discharge when exposed to high temperature, with no obvious damages to the formed SEI. This additional resilience was accomplished at the expense of rate capability, as charge transfer became growingly inefficient in these systems. At slower rates, however, cells that underwent SEI formation at 90 °C presented superior performances, as a result of improved Li+ transport through the SEI, and optimal wetting of graphite by the electrolyte. This work analyzes different graphite hosts and ionic liquids, showing that this effect is more pervasive than anticipated, and offering the unique perspective that, for certain systems, temperature can actually be an asset for passivation.

In the present study, influence of In3+ doping on the structural and luminescence properties of ZnGa2O4 nanoparticles has been investigated in detail. In3+ doped ZnGa2O4 nanoparticles with size less than 10 nm have been prepared at a relatively low temperature of 120 °C. From X-ray diffraction (XRD) and photoluminescence (PL) studies, different Ga3+ structural units, with varying number of In3+ as next nearest neighbors (NNN) around Ga3+ in GaO6 octahedra, have been identified and their relative extent is evaluated by assuming a binomial distribution of Ga3+ and In3+ cations in the lattice. The GaO6 octahedra are found to be unaffected by In3+ doping as confirmed by the identical values of oxygen positional parameter “x” derived from Rietveld refinement of the XRD patterns. Alternating current powder electroluminescence (ACPEL) has been demonstrated for the first time from the nanoparticles of undoped and In3+ doped ZnGa2O4. Due to the formation of GaO6 structural units with varying number of In3+ as next near neighbors around Ga3+, tuning of emission wavelength is observed from the nanoparticles upon UV excitation. However, under an applied electric field during electroluminescence (EL) measurements, only regular GaO6 structural units undergo excitation and Ga-O-In linkages mainly act as scattering centers leading to less favorable electrical excitation of corresponding GaO6 structural units. The findings have potential relevance in the area of wide band gap semiconductor technology employing doped ZnGa2O4 nanoparticles.

In the evaluation of compatibility of different components of cell for high-energy and extreme-conditions applications, the highly focused are positive and negative electrodes and their interaction with electrolyte. However, for high-temperature application, the other components are also of significant influence and contribute toward the total health of battery. In present study, we have investigated the behavior of aluminum, the most common current collector for positive electrode materials for its electrochemical and temperature stability. For electrochemical stability, different electrolytes, organic and room temperature ionic liquids with varying Li salts (LiTFSI, LiFSI), are investigated. The combination of electrochemical and spectroscopic investigations reflects the varying mechanism of passivation at room and high temperature, as different compositions of decomposed complexes are found at the surface of metals.