Boosting the electrochemical performance of Li-garnet based all-solid-state batteries with Li4Ti5O12 electrode: Routes to cheap and large scale ceramic processing

All-solid-state batteries based on fast Li+ conducting solid electrolytes such as Li7La3Zr2O12 (LLZO) give perspective on safe, non-inflammable, and temperature tolerant energy storage. Despite the promise, ceramic processing of whole battery assemblies reaching close to theoretical capacities and finding optimal strategies to process large-scale and low cost battery cells remains a challenge. Here, we tackle these issues and report on a solid-state battery cell composed of Li4Ti5O12 / c-Li6.25Al0.25La3Zr2O12 / metallic Li delivering capacities around 70-75 Ah/kg with reversible cycling at a rate of 8 A/kg (for 2.5-1.0 V, 95 A degrees C). A key aspect towards the increase in capacity and Li+ transfer at the solid electrolyte-electrode interface is found to be the intimate embedding of grains and their connectivity, which can be implemented by the isostatic pressing of cells during their preparation. We suggest that simple adaption of ceramic processing, such as the applied pressure during processing, strongly alters the electrochemical performance by assuring good grain contacts at the electrolyte-electrode interface. Among the garnet-type all-solid-state ceramic battery assemblies in the field, considerably improved capacities and cycling properties are demonstrated for Li4Ti5O12 / c-Li6.25Al0.25La3Zr2O12 / metallic Li pressed cells, giving new perspectives on cheap ceramic processing and up-scalable garnet-based all-solid-state batteries.