Solid electrolytes and sulfide-based cathodes for next-generation solid-state-batteries: Synthesis, transport properties and nanostructure engineering

Hatz, Anna-Katharina (2021): Solid electrolytes and sulfide-based cathodes for next-generation solid-state-batteries: Synthesis, transport properties and nanostructure engineering. Dissertation, LMU München: Fakultät für Chemie und Pharmazie

Abstract

Thriving for a green future, ambitious goals are set for the next generation of rechargeable batteries: They should deliver a high capacity and power and enable fast charging. Solid–state–batteries are considered one of the most promising technologies to achieve that jump in battery performance while guaranteeing high safety. The development of inorganic solid electrolytes is seen as key to progress, and the substitution of lithium by sodium or potassium and the development of Cobalt– and Nickel–free cathodes offer a reduction in cost and increased sustainability. This work contributes to the latter by rationalizing the poor battery performance of the ordered, rock–salt–type cathode materials Li3NbS4 and Li3TaS4 based on their inherently poor electronic and ionic conduction properties. It investigates several solid electrolytes showing fast lithium, sodium and potassium ion conductivity. For the first time, the ionic conductivity and diffusivity of Li2SiP2 and LiSi2P3 are reported and for a series of supertetrahedral sodium phosphidosilicates (from Na23Si19P33 (T3T3) to HT–NaSi2P3(T5T5)) an increase in ionic conductivity with increasing supertetrahedra size is found. The latter insight is then applied to discover KSi2P3, the first fast, non–oxide–based potassium ion conductor. Moreover, light is shed on the trend in ionic conductivity in the Na5AlS4–Na4SiS4 solid solution series. Here, the interplay of charge carrier concentration and low site symmetry of sodium ions leads to orders of magnitude increased conductivity. To tackle the question of how to process solid electrolytes on an industrial scale, the processability of the fast solid electrolyte Li7SiPS8 in aprotic solvents with a low donor number is demonstrated and the decomposition mechanism of thiophosphates in alcohols is revealed. Last but not least, this thesis presents fast water–assisted lithium ion conduction in restacked lithium tin sulfide nanosheets demonstrating that restacking and the presence of humidity in the environment can enhance lithium ion conductivity. All of these projects contribute to a solid future of lithium ion batteries and beyond by developing and disclosing the properties of new and already known solid electrolytes and cathode materials.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Keywords: solid electrolyte, solid-state-battery, lithium ion, sodium ion, potassium ion, solution processing
• Themengebiete: 500 Naturwissenschaften und Mathematik ; 500 Naturwissenschaften und Mathematik > 540 Chemie
• Fakultäten: Fakultät für Chemie und Pharmazie
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 18. Oktober 2021
• 1. Bericht­erstatter:in: Lotsch, Bettina