Synthesis and electrochemical investigation of garnet-polymer composite electrolytes for solid state batteries

Solid state lithium batteries are considered an alternative to currently available lithium ion batteries. The development of a suitable electrolyte is essential for commercialisation of bulk-type solid state batteries. This thesis is concerned with the synthesis of a solid state electrolyte as a composite of ceramic Li7La3Zr2O12 (LLZO) and a polymer electrolyte based on poly(ethylene oxide) (PEO). First, the synthesis of Al substituted LLZO by means of co-precipitation is described. The obtained powder is characterised with regard to its structural, chemical and electrochemical properties. In the second part, free-standing and flexible composite membranes (containing up to 40 vol% LLZO in polymer electrolyte (PEO20LiClO4) matrix) are manufactured by tape casting. In the third part, the LLZO/PEO20LiClO4 interface is identified as obstructive to continuous Li ion conduction. A model system is developed and investigated by means of impedance spectroscopy

Interface effects in solid electrolytes for Li-ion batteries

Diese Arbeit konzentriert sich auf die Untersuchung von heterogenen Oxysulfiden (100-x) Li3PS4-xLi3PO4 (10 ≤ x ≤ 40) und mehrschichtigen Dünnschicht-LiON-Al2O3-Festkörperelektrolyten (SEs) für Lithium-Ionen-Batterien (LIBs). Insbesondere wurden heterostrukturierte Oxysulfide vom Bulk-Typ und mehrschichtige Dünnschicht LiON-Al2O3 SEs durch zweistufiges mechanisches Mahlen bzw. Atomlagenabscheidung (ALD) synthetisiert. Ihre physikochemischen und elektrochemischen Eigenschaften wurden mit verschiedenen Techniken untersucht und die Arbeit an SEs ist in zwei Abschnitte unterteilt, wie nachstehend beschrieben: (I) Heterogene Oxysulfide (100-x)Li3PS4-xLi3PO4 (10 ≤ x ≤ 40) SEs. Eine Reihe von (100-x)Li3PS4-xLi3PO4 mit glaskeramischen Eigenschaften wurde erfolgreich durch Beimischung von Li3PO4 in Li3PS4 hergestellt. Dabei wurden die Oxysulfideinheiten [PS3O]3-, [PS2O2]3- und [PSO3]3- in den Gemischen durch 31P MAS NMR (Magic-Angle-Spinning Kernspinresonanz) nachgewiesen. In der Impedanzspektroskopie zeigen Oxysulfide (100-x)Li3PS4-xLi3PO4 mit x = 20 und 15 eine höhere Wechselstrom-Ionenleitfähigkeit (1,6 x 10-4 S/cm) als reines Li3PS4 (1,6 x 10-4 S/cm) bei Zimmertemperatur (RT). Dieses Phänomen wird auf die gegensätzlichen Einflüsse des Raumladungseffekts gegenüber dem Blockierungseffekt zurückgeführt. Nach der Stabilisierung durch Li-Plating und -Stripping steigen die Gleichstrom-Ionenleitfähigkeiten von Li/80Li3PS4-20Li3PO4/Li und Li/85Li3PS4-15Li3PO4/Li bei RT auf 2,4 × 10-3 S/cm bzw. 9,5 × 10-4 S/cm. Die Einführung von Li3PO4 in Li3PS4 führt zu einer verbesserten Grenzflächenstabilität zwischen Li und den Oxysulfiden, was mittels zeitaufgelöster Impedanzspektroskopie und Li-Plating und -Stripping festgestellt wurde. Für Li3PS4 wurden dagegen durch Cyclovoltammetrie an symmetrischen Zellen Li/Li3PS4/Li starke Nebenreaktionen beobachtet. Darüber hinaus wurde eine LiCoO2-Kathode in einer Machbarkeitsstudie zusammen mit den heterogenen Oxysulfid-SEs für x = 20 und x = 15 untersucht, die im Vergleich zu reinem Li3PS4 eine verbesserte Kapazität und Zyklen-Stabilität aufweisen. Die ausgezeichnete Stabilität der SEs/Li-Grenzfläche dieser beiden Oxysulfide wurde in der Vollzelle ebenfalls durch ihren stabilen Widerstand nach über 60 Lade-Entlade-Zyklen bewiesen. Trotz ihrer Verbesserungen leidet die positive LiCoO2-Elektrode in den ersten Zyklen aufgrund des enormen Widerstands der Grenzfläche zwischen SE und LiCoO2 immer noch unter Kapazitätsverlust. (II) Mehrschichtige Dünnschicht-LiON-Al2O3 SEs. Eine Reihe von flachen und defektfreien mehrschichtigen Dünnschicht-LiON-Al2O3 wurde erfolgreich hergestellt. Die amorphe Struktur von bei 200 °C abgeschiedenem LiON-Al2O3 wurde durch Röntgenbeugung unter streifendem Anfall (GIXRD) und Magic-Angle-Spinning Kernspinresonanzspektroskopie (MAS-NMR) nachgewiesen. Die schichtweise Struktur und Zusammensetzung von dünnschichtigem LiON-Al2O3 wurde unter Verwendung von Querschnitt-HRTEM und XPS Tiefenprofilen bestätigt, wobei die LiON-Lagen hauptsächlich aus LiOH, Li2CO3, Li-N und Li2O bestehen und durch Al2O3-Lagen getrennt sind. LiON-Al2O3-Dünnschichten zeigen aufgrund der Einführung von Stickstoff und Al2O3 eine verbesserte Ionenleitfähigkeit im Vergleich zur reinen 600LiON-Dünnschicht, da Al2O3 Hetero-Grenzflächen eingebracht werden, wobei die Ionenleitung entlang dieser Grenzflächen beschleunigt ist. Bemerkenswerterweise ist die Gesamtkonzentration an Li+-Ionen in diesen Heterostrukturen im Vergleich zum reinen LiON-Dünnschicht geringer, aber die Gesamtionenleitfähigkeit wird trotz zunehmender Aktivierungsenergie erhöht. Raumladungseffekte an der Hetero-Grenzfläche werden als der Mechanismus für diese Verbesserung angesehen, wobei lokale strukturelle Unordnung, induziert durch die isolierenden Al2O3-Zwischenschichten die Ursache der erhöhten Aktivierungsenergien sein können. Die Kombination von einer 3,2 nm dicken LiON-Zwischenschicht und einer 1 nm dicken Al2O3-Zwischenschicht zeigt die höchste Ionenleitfähigkeit (6,2 x 10-4 S/cm at 160 °C) und die niedrigste Aktivierungsenergie (0,57±0.02 eV) unter allen eingesetzen mehrschichtigen Heterostrukturen. Diese Arbeit bietet einen neuen Ansatz für das Design heterostrukturierter mehrschichtiger Dünnschicht-Festkörperelektrolyte mit hochionenleitenden Grenzflächen über ALD für ionische Bauteile

Effect of the air pressure on electro-Fenton process

Electro-Fenton process is considered a very promising tool for the treatment of waste waters contaminated by organic pollutants refractant or toxic for microorganisms used in biological processes [1-6]. In these processes H2O2 is continuously supplied to an acidic aqueous solution contained in an electrolytic cell from the two-electron reduction of oxygen gas, directly injected as pure gas or bubbled air. Due to the poor solubility of O2 in aqueous solutions, two dimensional cheap graphite or carbon felt electrodes give quite slow generation of H2O2, thus resulting in a slow abatement of organics. In this context, we report here a series of studies [7-9] on the effect of air pressure on the electro-generation of H2O2 and the abatement of organic pollutants in water by electro-Fenton process. The effect of air pressure, current density, mixing and nature of the organic pollutant was evaluated. [1] E. Brillas, I. Sirés, M.A. Oturan, Chem. Rev., 109 (2009) 6570-6631. [2] C.A. Martínez-Huitle, M.A. Rodrigo, I. Sirés, O. Scialdone, Chem. Rev. 115 (2015) 13362–13407. [3] M. Panizza, G. Cerisola, Chem. Rev. 109 (2009) 6541–6569. [4] I. Sirés, E. Brillas, M.A. Oturan, M.A. Rodrigo, M. Panizza, Environ. Sci. Pollut. Res. 21 (2014) 8336–8367. [5] C.A. Martínez-Huitle, S. Ferro, Chem. Soc. Rev. 35 (2006) 1324–1340. [6] B.P.P. Chaplin, Environ. Sci. Process. Impacts. 16 (2014) 1182–1203. [7] O. Scialdone, A. Galia, C. Gattuso, S. Sabatino, B. Schiavo, Electrochim. Acta, 182 (2015) 775-780. [8] J.F. Pérez, A. Galia, M.A. Rodrigo, J. Llanos, S. Sabatino, C. Sáez, B. Schiavo, O. Scialdone, Electrochim. Acta, 248 (2017) 169-177. [9] A.H. Ltaïef, S. Sabatino, F. Proietto, A. Galia, O. Scialdone, O. 2018, Chemosphere, 202, 111-118

Pressurized CO2 Electrochemical Conversion to Formic Acid: From Theoretical Model to Experimental Results

To curb the severely rising levels of carbon dioxide in the atmosphere, new approaches to capture and utilize this greenhouse gas are currently being investigated. In the last few years, many researches have focused on the electrochemical conversion of CO2 to added-value products in aqueous electrolyte solutions. In this backdrop, the pressurized electroreduction of CO2 can be assumed an up-and-coming alternative process for the production of valuable organic chemicals [1-3]. In this work, the process was studied in an undivided cell with tin cathode in order to produce formic acid and develop a theoretical model, predicting the effect of several operative parameters. The model is based on the cathodic conversion of pressurized CO2 to HCOOH and it also accounts for its anodic oxidation. In particular, the electrochemical reduction of CO2 to formic acid was performed in pressurized filter press cell with a continuous recirculation of electrolytic solution (0.9 L) at a tin cathode (9 cm2) for a long time (charge passed 67’000 C). It was shown that it is possible to scale-up the process by maintaining good results in terms of faradaic efficiency and generating significantly high concentrations of HCOOH (about 0.4 M) [4]. It was also demonstrated that, for pressurized systems, the process is under the mixed kinetic control of mass transfer of CO2 and the reduction of adsorbed CO2 (described by the Langmuir equation), following our proposed reaction mechanism [5]. Moreover, the theoretical model is in good agreement with the experimental results collected and well describes the effect of several operating parameters, including current density, pressure, and the type of reactor used. 1. Ma, S., & Kenis, P. J. (2013). Electrochemical conversion of CO2 to useful chemicals: current status, remaining challenges, and future opportunities. Current Opinion in Chemical Engineering, 2(2), 191-199. 2. Endrődi, B., Bencsik, G., Darvas, F., Jones, R., Rajeshwar, K., & Janáky, C. (2017). Continuous-flow electroreduction of carbon dioxide. Progress in Energy and Combustion Science, 62, 133-154. 3. Dufek, E. J., Lister, T. E., Stone, S. G., & McIlwain, M. E. (2012). Operation of a pressurized system for continuous reduction of CO2. Journal of The Electrochemical Society, 159(9), F514-F517. 4. Proietto, F., Schiavo, B., Galia, A., & Scialdone, O. (2018). Electrochemical conversion of CO2 to HCOOH at tin cathode in a pressurized undivided filter-press cell. Electrochimica Acta, 277, 30-40. 5. Proietto, F., Galia, A., & Scialdone, O. (2019) Electrochemical conversion of CO2 to HCOOH at tin cathode: development of a theoretical model and comparison with experimental results. ChemElectroChem, 6, 162-172

Growth and characterization of an all solid-state high voltage Li-ion thin film battery.

238 p.All solid-state Li-ion batteries present key technological advantages that position them as a promising alternative to State-of-the-Art liquid electrolyte-based batteries, namely a wider electrochemical stability window, low toxicity, and hindered Li dentrite formation. These directly impact on the energy density, environmentally friendliness and safety, respectively. Importantly, all solid-state configurations also allow downscaling the whole battery to micrometric thin film components, paving the way towards the fabrication of compact microbatteries for low power energy supply. In this thesis, an all solid-state high voltage Li-ion thin film battery comprised of LiNi0.5Mn1.5O4 cathode, a LiPON solid electrolyte, and a metallic lithium anode has been developed, supported on high-value stainless steel current collector substrates. Growing parameters, individual film properties and issues related to the internal solid-solid interfaces are deeply analyzed

NOVEL SOLID-STATE ELECTROLYTES WITH IMPROVED ELECTRONIC PROPERTIES AS HYBRID IONICALLY CONDUCTING BATTERY MATERIALS

As global energy consumption moves away from fossil fuel sources to alternative energy, the concern for energy storage is paramount. Through lithium ion batteries (LIBs), secondary battery storage has been secured for both large applications of electric vehicles, solar storage, and smaller items like personal cell phones and laptops. However, LIBs use flammable liquid electrolytes and due to engineering defects or dendritic short-circuits have the potential to swell, catch on fire, or even explode because of the volatile organic solvents within the battery. In the pursuit of new commercial lithium ion battery technologies that are safe, nonflammable, and highly conductive, solid-state electrolytes (SSE) are promising candidates for these critical innovations. To achieve SSEs with electrochemically and functionally desirable properties such as ease of manufacturing, good adherence to electrodes, and high ionic conductivities, continued efforts are devoted to improving electrolyte materials. The two main electrolyte types of interest are polymer electrolytes and ceramic electrolytes. Although polymer electrolytes have desirable physical flexibility to form good contact with electrode surfaces, they continually suffer from low ionic conductivities comparatively. Meanwhile ceramic electrolytes have high ionic conductivities (especially high cationic conductivities) but suffer from both poor electrode contact and brittleness. Single-ion conductive materials (like most ceramic conductors) are necessary to increase lifetime performance of batteries. An avenue to access these necessary attributes in LIB-SSEs is explored through novel boron-containing polymers and polymer-ceramic hybrids with the focus to synthesize a material with a high lithium transference number. By exploiting the Lewis basic nature of borane centers to form negatively charged polymer backbones, novel solid-state electrolytes were synthesized with the goal of creating only cation-conductive polymer networks by incorporating the anionic component within the polymer matrix. The synthesis, chemical and electrochemical characterization of these types of polymers and polymer-ceramic hybrids are analyzed by various techniques including x-ray diffraction, thermal gravimetric analysis, nuclear magnetic spectroscopy, gel permeation chromatography, electrochemical impedance spectroscopy and lithium transference number characterization.Chemistr

MC 2019 Berlin Microscopy Conference - Abstracts

Das Dokument enthält die Kurzfassungen der Beiträge aller Teilnehmer an der Mikroskopiekonferenz "MC 2019", die vom 01. bis 05.09.2019, in Berlin stattfand

Investigating Electrochemical Performance and Interfacial Stability of Solid-State Lithium Metal Batteries: A Study of Hybrid Polymer-Ceramic Electrolyte Systems

Solid-state batteries (SSBs) are emerging as a promising energy storage technology, surpassing traditional liquid electrolyte (LE) counterparts in performance and safety. A critical component in SSBs is the solid-state electrolyte (SSE), which plays a pivotal role in safety, efficiency and stability. SSEs, including sulfides, halides, oxides, and polymers, present distinct advantages and challenges compared to LEs. Among these, oxide-based SSEs are particularly attractive for their balance in ionic conductivity and chemical stability. This study addresses key challenges related to interfacial stability and electrochemical performance in SSBs by focusing on hybrid polymer-ceramic electrolyte systems. A major challenge to such a SSB system is the stability of the interface between the solid electrolyte and the lithium metal anode, which impacts battery capacity and lifecycle. The interfacial instability issue is deeply rooted in insufficient contacts, formation of detrimental phases and decomposition of electrolytes, causing reduced ionic conductivity, increased interfacial resistance and battery performance decay. To address these interfacial issues, we investigate hybrid polymer-ceramic electrolyte systems designed to enhance interfacial stability and improve cell performance. Specifically, we explore a multi-functional structure integrating a flexible solid polymer electrolyte (SPE) with a ceramic perovskite electrolyte, Li₆/₁₆Sr₇/₁₆Ta₃/₄Hf₁/₄O₃ (LSTH). The polymethylmethacrylate (PMMA)-polyethylene glycol diacrylate (PEGDA) SPE, with a room-temperature ionic conductivity of 2.20 × 10⁻³ S cm⁻¹, effectively minimizes interfacial resistance, protects LSTH from lithium reduction, reduces concentration polarization, and suppresses lithium dendrite formation. This configuration enables successful cyclability of Li/Li half-cells for 500 cycles and a specific discharge capacity of 129.8 mAh g⁻¹ at 0.1 C for a full cell with LiFePO₄ cathode and lithium anode. Furthermore, we investigate the copolymerization of polyethylene glycol methacrylate (PPEGMA) and polymethacrylic acid (PDEPMMA) using Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization technique to develop a hybrid polymer-ceramic composite electrolyte system. The polymer chains are then further functionalized with phosphonic acid groups to enable interactions with gadolinium-doped cerium oxide (GDC) phase. In this design, GDC serves dual function: a separator by holding the gel polymer within its scaffold microstructure and facilitating Li-ion movement in gel polymer phase through interactions between RAFT chains and anions. The ethylene glycol segments in gel polymer chains enhance Li-ion conduction and hydrophobic phosphonic acid groups improve adhesion with GDC. The hybrid electrolyte system demonstrates significant improvements in Li-ion conductivity and interfacial stability with the lithium anode, allowing Li/Li half-cell operation for over 2000 hours at 0.1 mA cm⁻² and critical current densities up to 0.8 mA cm⁻². The interfacial resistance in this system is reduced by more than 50% compared to systems with non-functionalized RAFT polymer, highlighting the effectiveness of the interaction between the RAFT polymer and GDC on performance improvement

Microscopy Conference 2021 (MC 2021) - Proceedings

Das Dokument enthält die Kurzfassungen der Beiträge aller Teilnehmer an der Mikroskopiekonferenz "MC 2021"

Garnet ceramic electrolytes for next-generation lithium batteries

All-solid-state lithium batteries are of great interest scientifically as a next-generation of electrochemical energy storage devices, owing to their superior safety features and their potential to enable new chemistries to improve performance. The properties of the solid state electrolyte are integral to the overall cell capability – to date the most promising group of materials are the garnet-structured oxides, based on Li7La3Zr2O12 (LLZO), with high room temperature ionic conductivity and a wide electrochemical stability window. There are several aspects in the development of this relatively new material which are yet to be fully understood – these are the focus of this thesis. In this work, processing cubic doped LLZO as a bulk ceramic was investigated and served as a basis for understanding its stability and electrochemical performance; it was optimised to obtain highly dense microstructures under atmosphere-controlled conditions to prevent reaction with moisture. Chemical inhomogeneities in the pellets, especially at the grain boundaries, as investigated by secondary ion mass spectrometry (SIMS) and low energy ion scattering, were shown to be important in determining the transport properties of the electrolyte - in particular the propensity for dendrite formation during cell cycling. It was shown that aluminium-rich grain boundaries in aluminium-doped LLZO favour the formation of inter-granular lithium dendrites (with a 60 % lower critical current density for cell failure) over gallium-doped LLZO. The use of germanium (Ge4+) as a dopant was studied, and shown to stabilise the cubic LLZO phase through substitution of 0.10 moles of Ge at the lithium sub-lattice (at the tetrahedral 24d sites), giving conductivities of the order 10-4 S cm-1 and redox stability over a 4.5 V range with lithium electrodes. Chemical and electrochemical characterisation of the moisture reactivity of gallium-doped LLZO was also carried out, showing a chemically-altered proton-rich region extending to 1.35 micrometres following 30 minutes immersion in H2O at 100 °C and highly reactive grain boundaries. These chemical changes led to a threefold increase in the resistance of both the electrolyte and the interface with lithium electrodes. Chemical and tracer diffusivity of protons were estimated from the diffusion profiles of H+ and D+ obtained by SIMS depth-profiling. A new methodology for measuring macroscopic lithium tracer diffusion in LLZO was introduced, using SIMS depth-profiling and isotopic labelling, in which a number of experimental parameters were varied to optimise the technique. The preliminary results for lithium diffusivity in doped LLZO obtained from this method were compared with values from other methods (impedance and nuclear magnetic resonance) and used to comment on the mechanism for lithium diffusion in the materials.Open Acces