Emerging processing guidelines for solid electrolytes in the era of oxide-based solid-state batteries†

Abstract

The current most mature, competitive, and dominant battery technology for electric vehicles (EVs) is the Li-ion battery (LIB). As future EVs will rely on battery technology, further innovation is essential for the success of mobility electrification towards improving the driving range and reducing the charging time and price competitiveness. The commonly cited next generation technologies are hybrid and solid-state batteries (SSBs) enabling high energy densities using lithium. Through a critical approach, we dismantle the oxide-based solid-state battery electrolytes, their chemistries and ceramic manufacture. We evaluate the relevance of solid-state electrolytes and their integration into battery types compared to Li-ion batteries considering a holistic life cycle thinking of sustainable battery production. We evaluate the relevant oxide-based materials and requirements, the material supply chain, and diverse recycling concepts. We raise critical questions about the development of oxide-based SSBs mainly for large-scale production and EV applications, which demand attention to fill current scientific and technological gaps. Next, we critically discuss three major ceramic synthesis routes toward oxide-based solid electrolytes: solid-state processing, wet-chemical solution processing, and vapor deposition. In-depth processing guidelines, hindrances, and opportunities are highlighted. Through a high-level approach, the advantages and disadvantages of each processing method are introduced, while accounting for four major processing metrics applicable for obtaining high Li-ion conducting solid-state Li oxide electrolytes: chemistry of the precursors, dopants and stoichiometry, synthesis temperature, and atmosphere and pressure. We broaden the processing discussion from a single electrolyte component to electrode/electrolyte tandems examining interfaces during cell fabrication, possible cell architectures, design-specific processing methods, challenges, and mitigating solutions for both bulk-type batteries and thin film batteries. Finally, future perspectives and key guidelines for the realization of all SSBs are analyzed and discussed.