Cathode-electrolyte material interactions during manufacturing of inorganic solid-state lithium batteries

Solid-state lithium batteries comprising a ceramic electrolyte instead of a liquid one enable safer high-energy batteries. Their manufacturing usually requires a high temperature heat treatment to interconnect electrolyte, electrodes, and if applicable, further components like current collectors. Tantalum-substituted Li₇La₃Zr₂O₁₂ as electrolyte and LiCoO₂ as active material on the cathode side were chosen because of their high ionic conductivity and energy density, respectively. However, both materials react severely with each other at temperatures around 1085 °C thus leading to detrimental secondary phases. Thin-film technologies open a pathway for manufacturing compounds of electrolyte and active material at lower processing temperatures. Two of them are addressed in this work to manufacture thin electrolyte layers of the aforementioned materials at low temperatures: physical vapor deposition and coating technologies with liquid precursors. They are especially applicable for electrolyte layers since electrolytes require a high density while at the same time their thickness can be as thin as possible, provided that the separation of the electrodes is still guaranteed.