Advantages and disadvantages of discussed solid electrolyte synthesis routes.

Method	Advantage	Disadvantage
Classical high-temperature solid-state syntheses	Well-explored; much background knowledge	Bulk material production is time and energy consuming and not suitable for practical use
		Not suitable for non-equilibrium phase formation
Mechanochemical syntheses	Scalable material production; synthesis of non-equilibrium phases, reduced post synthesis processing time and temperature	Difficult to control the particle morphology. Optimization of processing parameters is needed
Solution syntheses	Scalable, cost-effective approach; synthesis of non-equilibrium phases, reduced post-synthesis processing time and temperature. Possibility controlled particle morphology	Underlying reaction chemistry sometimes poorly understood, as well as interactions between reagents and solvent
		Solvent choice can be critical but is nontrivial. Solvent residue or carbonized solvent can remain in product
Sol–gel syntheses	Scalable; non-equilibrium phases attainable	Expensive alkoxide routes. Not universally applicable since it is difficult to choose the right alkoxide reagents having similar reactivity for a given stoichiometry
Microwave syntheses	Energy-efficient and cost-effective synthesis process	Not well-optimized; influence on phase formation is not well understood yet
Post-synthetic treatments	Controlled material density, particle size and morphology, crystallinity and associated conductivity	Materials decomposition if the conditions are not carefully monitored