Ultraheli-pihustuspürolüüsi meetodiga sadestatud elektrolüüdikihid kesktemperatuursele tahkeoksiidsele kütuseelemendile

Väitekirja elektrooniline versioon ei sisalda publikatsioone.Jätkuvalt kasvava maailma energianõudluse tõttu on vajalik märkimisväärne üleminek efektiivsemale energiamuundamisele koos suuremahulise energia salvestamisega. Antud valdkonnas toimub hetkel paljude uute tehnoloogiate arendus. Tahkeoksiidse kütuseelemendi eeliseks on efektiivne elektri- ja soojusenergia tootmine erinevatest kütustest nagu metaan, prügila- ja sünteesgaas. Kuna mainitud seadme töötemperatuur on küllaltki kõrge (800-1000 ºC), on selle tehnoloogia täiemahuline kommertsialiseerimine viibinud lühikese eluea ja kõrge maksumuse tõttu. Üheks strateegiaks tahkeoksiidse kütuseelemendi tasuvuse tõstmiseks on selle töötemperatuuri alandamine kesktemperatuursesse vahemikku (600-800 °C). Paraku ei ole klassikalise tsirkooniumoksiidil põhineva elektrolüüdi ioonjuhtivus alandatud temperatuuridel piisav. Lisaks on probleemne kõrge keemiline reaktiivsus tsirkooniumoksiidse elektrolüüdi ja mõningate haruldaste muldmetallide kobaltiidkatoodide vahel mõõdukatel temperatuuridel. Dopeeritud tseeriumoksiidset vahekihti on kasutatud mainitud komponentide vahel keemilise barjäärkihina, kuigi on esinenud teatud katioonide difusiooni. Tseeriumoksiidil ja baariumtseraadil põhinevat elektrolüüti on välja pakutud alternatiivina tsirkooniumoksiidile. Paraku ilmneb oksiidioonjuht tseeriumoksiidil soovimatu elektronjuhtivus redutseerivas keskkonnas ja prootonjuhtkeraamilistel baariumtseraatidel ilmnevad stabiilsusprobleemid CO2 keskkonnas. Antud töös uuriti odava ultraheli-pihustuspürolüüsi meetodiga sadestatud kaitsekihtide omadusi mainitud probleemide valguses. Leiti, et terbiumkatioonid kaasdopandina väikeses kontsentratsioonis alandavad tseeriumoksiidi soovimatut elektronjuhtivust redutseerivates tingimustes. Optimaalselt kuumtöödeldud tseeriumoksiidne ja tsirkonaatne kaitsekiht toimisid tõhusalt vastavalt katioonide difusiooni alandamisel ning baariumtseraatse elektrolüüdi CO2 taluvuse tõstmisel.Continuously increasing world energy consumption requires a considerable shift in power generation towards more efficient energy conversion and large-scale energy storage methods. A variety of technologies are being developed at the moment. Solid oxide fuel cells have the advantage to generate electricity and heat with high efficiency from the fuels already available like methane, landfill gas and synthetic gas. As the operating temperatures of SOFC are quite high (800-1000 ºC), problems related to lifetime and material cost have inhibited their full-scale commercialization. One strategy to make the solid oxide cells more economical is to lower their operating temperature to the intermediate range (600-800 ºC). However, ionic conductivity of the classical zirconia-based electrolyte is not sufficient at intermediate temperatures. Additionally, some cathode materials like rare-earth cobaltites have high reactivity with the zirconia electrolyte. Ceria interlayer applied between the zirconia electrolyte and rare-earth cobaltite cathodes has been proved to be an efficient chemical barrier layer, although cation mobility has been observed. Ceria- and barium cerate-based electrolytes have been proposed as the attractive alternative electrolyte materials for zirconia. However, ceria in reducing fuel atmosphere exhibits the undesirable electronic conductivity and perovskite barium cerates have the stability issues in CO2 environment. In this work different protective layers were deposited using the low-cost ultrasonic spray pyrolysis method and their properties were analyzed in the light of the issues mentioned above. It was found that terbium as a co-dopant in low concentrations suppressed the electronic conductivity of ceria in reducing conditions. The ceria and barium zirconate protective layers with optimum thermal treatment were effective in suppressing the undesirable cation diffusion and enhancing the CO2 tolerance of barium cerate electrolyte, respectively

2020 roadmap on solid-state batteries

Li-ion batteries have revolutionized the portable electronics industry and empowered the electric vehicle (EV) revolution. Unfortunately, traditional Li-ion chemistry is approaching its physicochemical limit. The demand for higher density (longer range), high power (fast charging), and safer EVs has recently created a resurgence of interest in solid state batteries (SSB). Historically, research has focused on improving the ionic conductivity of solid electrolytes, yet ceramic solids now deliver sufficient ionic conductivity. The barriers lie within the interfaces between the electrolyte and the two electrodes, in the mechanical properties throughout the device, and in processing scalability. In 2017 the Faraday Institution, the UK's independent institute for electrochemical energy storage research, launched the SOLBAT (solid-state lithium metal anode battery) project, aimed at understanding the fundamental science underpinning the problems of SSBs, and recognising that the paucity of such understanding is the major barrier to progress. The purpose of this Roadmap is to present an overview of the fundamental challenges impeding the development of SSBs, the advances in science and technology necessary to understand the underlying science, and the multidisciplinary approach being taken by SOLBAT researchers in facing these challenges. It is our hope that this Roadmap will guide academia, industry, and funding agencies towards the further development of these batteries in the future

Operando high-temperature near-ambient pressure X-ray photoelectron spectroscopy and impedance spectroscopy study of Ni−Ce0.9Gd0.1O2−δ solid oxide fuel cell anode

In this study we present the results of operando high temperature near-ambient-pressure x-ray photoelectron spectroscopy (HT-NAP-XPS) measurements of a pulsed laser deposited thin film Ni−Ce0.9Gd0.1O2−δ model electrode. In our measurements, we have used the novel three electrode dual-chamber electrochemical cell developed in our previous work at different H2 pressures and at different electrochemical conditions at around 650 °C. The possible redox reactions on the anode surface (Ni2+↔Ni0,Ce4+↔Ce3+) were investigated by HT-NAP-XPS technique simultaneously with electrochemical impedance spectroscopy measurements. The oxygen partial pressure in counter and reference electrode compartment was controlled at 0.2 bar. Changes in electronic structure of the Ce3d and Ni2p photoelectron spectra caused by electrode potential and H2 pressure variations were observed and estimated by curve fitting procedure. The O1s and valence band photoelectron signals were used for depth probing of the chemical composition and redox changes at Ni-GDC and for studying the influence of the electrochemical polarization on the chemical state of Ni-GDC surface atoms. As a result changes in oxidation state of electrode surface atoms caused by electrode polarization and oxide ion flux through the membrane were detected with simultaneous significant variation of electrochemical impedance