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Hydrogen as an energy carrier is very versatile in energy storage applications. Developments in novel, sustainable technologies towards a CO2-free society are needed and the exploration of all-solid-state batteries (ASSBs) as well as solid-state hydrogen storage applications based on metal hydrides can provide solutions for such technologies. However, there are still many technical challenges for both hydrogen storage material and ASSBs related to designing low-cost materials with low-environmental impact. The current materials considered for all-solid-state batteries should have high conductivities for Na+, Mg2+ and Ca2+, while Al3+-based compounds are often marginalised due to the lack of suitable electrode and electrolyte materials. In hydrogen storage materials, the sluggish kinetic behaviour of solid-state hydride materials is one of the key constraints that limit their practical uses. Therefore, it is necessary to overcome the kinetic issues of hydride materials before discussing and considering them on the system level. This review summarizes the achievements of the Marie Sklodowska-Curie Actions (MSCA) innovative training network (ITN) ECOSTORE, the aim of which was the investigation of different aspects of (complex) metal hydride materials. Advances in battery and hydrogen storage materials for the efficient and compact storage of renewable energy production are discussed.

In this research, new lithium ion conductor glass-ceramics with NASICON-type structure (Li1+x+yAlxCryGe2-x-y (PO4)3, x+y=0.5) were synthesized using melt-quenching method and converted to glass-ceramics through heat treatment. Influence of addition of different concentrations of aluminum and chromium in LiGe2(PO4)3 glass-ceramic was investigated for ionic conduction improvement. Substitution of Ge4+ ions in NASICON structure by Al3+ and Cr3+ ions induced more Li+ ions in A2 vacant sites to obtain charge balance and also changed the unit cell parameters. These two factors led to ionic conductivity improvement of synthesized glass-ceramics. The glass-ceramics were characterized and the amorth structures were investigated by X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy-Dispersive X-ray spectroscopy (EDX), Differential Scanning Calorimetry (DSC) and Complex Impedance Spectroscopy (CIS). The highest lithium ion conductivity of 8.82×10-3 S/cm was obtained for x=0.4 and y=0.1 (Li1.5Al0.4Cr0.1Ge1.5(PO4)3) crystallized at 850 oC for 8 h with minimum activation energy of 0.267 eV. &nbsp

Computational and experimental investigation of lithium and sodium ion conduction in metastable alkali lanthanide pyrosilicates., In this thesis the synthesis, structure, and ionic conductivity of the sodium and lithium lanthanide pyrosilicates, A3LnSi2O7 (A = Li, Na; Ln = Gd-Er, Y), are reported. The Na- silicates, Na3LnSi2O7, were made by the ceramic method. The meta-stable Li-silicates, Li3LnSi2O7, were formed by a molten salt ion exchange of Li+ for Na+ in Na3LnSi2O7. Structural models for the two compounds were refined against powder X-ray and neutron diffraction data using the Rietveld method, and Fourier difference maps were used to identify the location of the lithium ions in Li3LnSi2O7. The refined structural models show that both alkali compounds are characterised by the P63/m space group and exhibit the same LnSi2O7 framework but possess a remarkably different arrangement of alkali ions. The Na-compounds exhibit four crystallographically distinct alkali-sites whereas the Li-compounds exhibit two such sites, only one of which is equivalent to that in the Na-structure. The new lithium site inhabits an atypical square planar environment. These structural models were corroborated by pair distribution function analysis, bond length analysis, and bond-valence calculations. Potential conduction pathways within the A3LnSi2O7 structures were identified with bond-valence methods and used to propose conduction mechanisms for alkali ion trans- port. Variable temperature impedance spectroscopy measurements were used to show the Li-silicates exhibit an ionic conductivity significantly greater than that of the Na-silicates. The maximum ionic conductivity measured in the Na-compounds was 1.08(7)×10−7 S/cm at 285.5(3) ◦C in Na3HoSi2O7, while that measured in the Li-compounds was 6.7(6)×10−6 S/cm at 286.17(14) ◦C in Li3HoSi2O7. A variable temperature impedance control system was developed to enable these measurements. A microcontroller was used to automate the measurement process; a custom software library was written to allow a user to orchestrate the process with a simple program; and a least squares fitting algorithm was implemented to allow for batch data analysis. This work may be further adapted to accelerate the discovery of new solid state electrolytes for application in all solid state batteries., EPSRC funded.

Li7La3Zr2O12 (LLZO) and related compounds are considered as promising candidates for future all-solid-state Li-ion battery applications. Still, the processing of those materials into thin membranes with the right stoichiometry and crystal structure is difficult and laborious. The sensitivity of the Li-ion conductive garnets against moisture and the associated Li+/H+ cation exchange makes their processing even more difficult. Formulation of suitable polymer/ceramic hybrid solid state electrolytes could be a prosperous way to reach the future large scale production of solid state Li-ion batteries. In fact, solvent mediated and/or slurry based wet-processing of the LLZO, e.g., tape-casting, could result in irreversible Li-ion loss of the pristine material due to Li+/H+ cation exchange. The concomitant structural changes and loss in functionality in terms of Li-ion conductivity are the results of the above process. Therefore, in the present work a systematic study on the chemical stability and structural retention of Al-substituted LLZO in different solvents is reported. It was found that Li+/H+ exchange in LLZO occurs upon solvent immersion, and its magnitude is dependent on the availability of −OH functional groups of the solvent molecules. As a result, a larger degree of Li+/H+ exchange causes higher increase of the lattice parameter of the LLZO, determined by synchrotron diffraction analyses. The expansion of the cubic unit cell was ascertained, when Li+ was replaced by H+ in the host lattice, by ab initio computational studies. The application of the most common solvent as dispersion medium, i.e., high purity water, causes the most significant Li+/H+ exchange and, therefore, structural change, while acetonitrile was proven to be the best suitable solvent for wet postprocessing of LLZO. Finally, computational calculations suggested that the Li+/H+ exchange could result in diminished ionic, i.e., mixed Li+-H+, conductivity due to the insertion of protons with lower mobility than that of Li-ions.

Bu çalışmada lityum karbonat (Li2CO3), lantan oksit (La2O3) ve zirkonyum oksit (ZrO2) maddelerine mekaniksel karışım ve ardından ısıl işlem uygulanarak Li7La3Zr2O12 Li-iyon iletkeni sentezlenmiştir. Sentez sırasında uygulanan farklı öğütme sürelerinin kristal yapıdaki faz oluşumlarına, morfolojik özelliklere ve parçacık boyutlarına etkisi X-ışını kırınımı deseni (XRD) ve taramalı elektron mikroskobu (SEM) ile incelenmiştir. Elde edilen yapıya ait XRD görüntüsünün MAUD yazılımı ile yapılan ayrıntılı kristal yapı analizi, ilk öğütme süresinin Li7La3Zr2O12 kristalinin yüksek iyonik iletken faz sentezinde etkili olduğunu gösterirken son öğütme süresinin ise kristalite boyutunda etkili olduğunu göstermiştir., In this study Li7La3Zr2O12 Li-ion conductor was synthesized by applying a mechanical activation followed by heat treatment to a mixture of lithium carbonate (Li2CO3), lanthanium oxide (La2O3) and zirconium oxide (ZrO2). The effect of different milling times during synthesis on the formation of crystal structure phases, morphological properties and particle size were investigated by X-ray diffraction (XRD) pattern and scanning electron microscope (SEM). Detailed crystal structure analysis done by MAUD software demonstrated while first milling time is effective on synthesis of the high ionic conductive phase of the Li7La3Zr2O12 cyrstal last milling time is effective on the cyrstallite size.

Model systems for electrochemical impedance spectroscopy (EIS) studies of solid-state electrolytes based on ceramic lithium ion conductor Li7La3Zr2O12 (LLZO) and polymer electrolyte P(EO)20-LiClO4 are investigated for the first time. The aim of the present study is to identify and quantify the lithium ion transition resistance of the ceramic/polymer interface. Symmetrical model systems consisting of LLZO pellets with sheets of P(EO)20-LiClO4 are manufactured and investigated in detail. In such symmetric model systems we observed an additional ion-transfer process, which we attributed to the interface processes (i.e. distributed Li+ transition across the interface). Based on the EIS measurement data obtained above the polymer electrolyte's melting temperature, at 70°C the interface resistance of the lithium ion transition is estimated to be ∼9 kO cm² and the capacitance of the process is in the order of 0.1 mF/cm². According to our investigations, it is possible to predict interface resistivity of lithium ion transport for different polymer/ceramic composite electrolytes for solid state lithium battery applications.

The structural change of the (100-x) (0.6Li 2 S.0.4SiS 2 ).xLi 3 PO 4 oxysulfide glasses during crystallization was analyzed by means of solid-state nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS). The unique tetrahedral units of SiO n S 4-n (n=1, 2, 3) and PO n S 4-n (n=1, 2, 3) present in the glass samples vanished and the SiS 4 , SiO 4 , PS 4 and PO 4 units increased with proceeding of the crystallization process. Nonbridging sulfur and oxygen atoms decreased while bridging oxygens and S 2- increased with proceeding of the crystallization process. Large structural difference between the glass and the corresponding crystallized sample explained the high stability against crystallization found in the oxysulfide glass with the composition of x=5.

The Li+ ion conductor Li7La3Zr2O12 was synthesized by solid state reaction as a ceramic with tetragonal and cubic crystal structure. The synthesis parameters were varied for these polycrystalline samples, e.g. the starting materials for Li and Zr, the crucible materials and the thermal treatments. Product formation is sensitive to the ZrO2 starting powder as well as the crucible material due to reactions between the powder mixture and the crucible wall. In this study, only the use of an alumina crucible or the addition of alumina resulted in the successful preparation of cubic Li7La3Zr2O12. For single-crystal preparation, flux growth experiments were carried out at 1000 and 1200 °C either in alumina crucibles lined with a gold foil or in magnesia crucibles and using Li2CO3 (Li2O) as flux. The small crystals were separated from the solidified flux by washing larger lumps in water. Irrespective of the additions of alumina, only tetragonal micro-crystals of Li7La3Zr2O12 were obtained. These micro-crystals were studied by micro-Raman scattering spectroscopy. Polarized Raman spectra were recorded either in nearly backscattering or 90° geometry. The majority of Raman modes expected for the tetragonal phase (space group I41/acd, Z = 8) were satisfactorily displayed. So far, it has not been possible to make unambiguous symmetry assignments of the observed peaks because of the unknown orientation of the micro-crystals.

Werkstoffe auf Basis von ß-Eukryptit LiAlSiO4 sind aufgrund ihrer speziellen physikalischen Eigenschaften von großer technischer Bedeutung. Der ß-Eukryptit besitzt einen negativen thermischen Ausdehnungskoeffizient, hohe chemische und thermische Stabilität und gute Lithiumionenleitfähigkeit. Dies macht den Einsatz des ß-Eukryptits als Feststoffelektrolyt in Hochtemperaturbatterien möglich. Im Rahmen dieser Arbeit wurde feinkristalline ß-Eukryptit-Keramik mittels Optimierung der bereits in der Literatur beschriebenen nasschemischen Wege zur ß-LiAlSiO4-Darstellung und Anwendung neuer Synthesevarianten hergestellt. Der Gegenstand dieser Arbeit war die Untersuchung des Einflusses spezifischer Syntheseparameter auf anwendungsorientierte Produktcharakteristika, deren gezielte Optimierung dazu dienen sollte die elektrischen Eigenschaften von keramischem ß-LiAlSiO4 zu verbessern. Zu den untersuchten Charakteristika gehören die Phasenreinheit, die Realbau- und Mikro/Strukturparameter (u. a. Gitterverzerrung, Kristallit- und Partikelgröße, Ordnungsgrad der Struktur des ß-Eukryptits), die für eine Hochleistungskeramik mit Ionenleitfähigkeit wichtig sind. Die Messmethoden umfassen thermische Analyse, Röntgen- und Neutronenbeugung, Rasterelektronenmikroskopie und Pyknometrie. Zur quantitativen Elementanalyse wurden atomemissions- und absorptionsspektroskopische Methoden verwendet. Anhand der Impedanzspektroskopie wurden Untersuchungen der ionischen Leitfähigkeit durchgeführt. Die Ergebnisse der Probencharakterisierung zeigten, dass sich unter der Variierung der Syntheseparameter und/oder -bedingungen (vor allem eingesetzte Edukte und Art der thermischen Behandlung) ein spezifisches Muster der Nebenphasen, gefördertes Kristallitwachstum und daher unterschiedliche Charakteristika der Endprodukte ergeben. Anhand der rasterelektronenmikroskopischen Untersuchungen wurde festgestellt, dass die angewendeten Herstellungsvarianten eine erhebliche Auswirkung auf Gestalt und Teilchengröße des Xerogels haben. Die nach der Alkoholat-Sol-Gel-Synthese erhaltenen ß-LiAlSiO4-Keramikprodukte zeigen eine bessere Lithiumionenleitfähigkeit. Die im Rahmen dieser Arbeit durchgeführten Versuche zur Dotierung mit den Übergangsmetallen M = Cr, Mn und Fe (Li1-xAl1-x-yMySi1+xO4) ergaben, dass die Substitution von Al gegen M in einem geringeren Maße und lediglich unter einer intensiven Temperaturbehandlung stattfindet. In den Fe-dotierten Präparaten wurde keine dotierungsbedingte Veränderung der Li+-Leitfähigkeit festgestellt. Materials based on ß-eucryptite, LiAlSiO4 are of great technical importance due to their particular physical properties. ß-eucryptite owns a negative thermal expansion coefficient, high chemical and thermal stability and good lithium-ion conductivity. These properties allow the use of ß-eucryptite as a solid electrolyte in high-temperature batteries. In the course of this work fine-crystalline ß-eucryptite ceramic was produced by optimising the wet-chemical methods for the synthesis of ß-LiAlSiO4 which have already been described in relevant literature, and the application of new methods of synthesis. The object of this work was to study the influence of specific synthesis parameters on application-orientated material characteristics, with a view to their optimisation in order to improve the electrical properties of ceramic ß-LiAlSiO4. The properties studied included phase purity, the microstructure and structure parameters (inter alia strain, crystallite and particle size, degree of the ordering of the ß-eucryptite structure), which are relevant for a high-performance ceramic featuring ionic conductivity. The measuring methods applied include thermal analysis, X-ray and neutron diffraction, scanning electron microscopy and density measurement. For the quantitative element analysis atomic emission and absorption spectroscopic methods were used. Ionic conductivity was determined by impedance spectroscopy. Sample characterisation showed that changes in synthesis parameters and/or conditions (especially precursors and type of thermal treatment) result in a specific pattern of secondary phases, of crystallite growth and consequently in different characteristics of the final products. The scanning electron microscope study proved that the variations of the methods have a considerable effect on the microstructure of the xerogel and the size of its particles. The ß-LiAlSiO4 ceramic products obtained by the alkoxide sol-gel synthesis resulted in better lithium ion conductivity. Doping with transition metals M = Cr, Mn and Fe (Li1-xAl1-x-yMySi1+xO4) showed that substitution of Al by M takes place only in a low proportion and only under a strong temperature treatment. No alteration of the Li+ conductivity in the Fe-doped samples was observed.

The engineering of junction formation and the electrode kinetics with respect to gas sensing has been investigated in electrochemical cells based on LiSiPO and Garnet electrolyte for the possibility of CO2 detection. Li2CO3 and Au paste were always used as sensing electrode and showed good agreement with Nernst equation. Compared all the sensors which were investigated in this work, LiMn2O4 reference electrode and LiSiPO electrolyte shows the best performance.

Hydrogen as an energy carrier is very versatile in energy storage applications. Developments in novel, sustainable technologies towards a CO2-free society are needed and the exploration of all-solid-state batteries (ASSBs) as well as solid-state hydrogen storage applications based on metal hydrides can provide solutions for such technologies. However, there are still many technical challenges for both hydrogen storage material and ASSBs related to designing low-cost materials with low-environmental impact. The current materials considered for all-solid-state batteries should have high conductivities for Na+, Mg2+ and Ca2+, while Al3+-based compounds are often marginalised due to the lack of suitable electrode and electrolyte materials. In hydrogen storage materials, the sluggish kinetic behaviour of solid-state hydride materials is one of the key constraints that limit their practical uses. Therefore, it is necessary to overcome the kinetic issues of hydride materials before discussing and considering them on the system level. This review summarizes the achievements of the Marie Skłodowska-Curie Actions (MSCA) innovative training network (ITN) ECOSTORE, the aim of which was the investigation of different aspects of (complex) metal hydride materials. Advances in battery and hydrogen storage materials for the efficient and compact storage of renewable energy production are discussed.

Phases with 0 < x ≤ 1.5 were synthesized within the system Li 1+xFexTi2-x(PO4)3, of interest for applications as high Li+ mobility material. By powder X-ray diffractometry, three modifications were found to be stable for x ≤ 0. 6 (Nasicon-type R3c), 0.6 < x < 1.1 (orthorhombic Pbca), and x ≥ 1.1 (orthorhombic Pbnd). The compound Li1.5Fe0.5Ti 1.5(PO4)3 was employed for a detailed structural investigation by high resolution powder neutron diffraction (HRPD time-of-flight diffractometer, ISIS spallation source, UK) at 298 and 673 K. Using Rietveld and Fourier difference techniques, lithium atoms were located and the two structures refined to wRp = 0.053 and 0.035, respectively. Lithium was found to be highly disordered, and distributed in similar amounts between the M1 and M2 cavities of the Nasicon framework, unlike what is usually observed in lithium Nasicon phases. A particularly large ion mobility should thus be expected. The configuration of Li sites within the M1 hollow is strongly affected on heating, so as to displace lithium towards the periphery of the cavity. The effects on the mobility pathways of Li+ ions are analyzed and discussed.