In pursuit of all solid state batteries (ASSB): advances at the cathode–electrolyte interface for garnet-based ASSB

Garnet-based solid-state lithium-ion batteries offer great potential for safe and dense electrochemical energy storage. However, interfacial reactions and stability issues at the interfaces between the Li₇La₃Zr₂O₁₂ (LLZO) electrolyte and electrode materials pose challenges to the overall performance and longevity of the batteries. Discussions of the characteristics of solid electrolytes (SEs) and the solid–electrolyte interface (SEI) at the anode side have been well documented so far. This review focuses on developments at the much more complex cathode–electrolyte interface (CEI) with garnet LLZO. The first half of the review introduces the material aspects of garnet LLZO and its challenges in integrating into solid state batteries, also giving insights into its engineering aspects. The second half is dedicated to defining the CEI, and its physico-chemical properties with an emphasis on the recent attempts addressing the CEI. A table of comparison of all the all solid state batteries (ASSBs) developed using garnet LLZO as the electrolyte is also given. The table highlights the advantages and shortcomings of various engineering strategies that utilise the solid–solid contact at the CEI. As there are numerous works that identify themselves as ASSB on paper, but not in principle, this review attempts to recognise the true innovators of all solid-state batteries.