The role of polymers in lithium solid-state batteries with inorganic solid electrolytes Sudeshna Sen, Enrico Trevisanello, Elard Niem ¨ oller, Bing-Xuan Shi, Fabian J. Simon† and Felix H. Richter * Solid-state batteries have gained increasing attention with the discovery of new inorganic solid electrolytes, some of which rival the ionic conductivity of liquid electrolytes. With the additional benefit of being single- ion conductors, several inorganic solid electrolytes achieve the lithium ion conduction required for solid- state batteries to become the next generation of energy storage device in combination with lithium metal. However, the challenges faced when preparing thin layers and stable interfaces of solely inorganic and brittle materials limit the performance of lithium solid-state batteries that are made purely of inorganic materials. Therefore, the best-performing solid-state batteries also introduce polymers to the system to improve the interfaces, cohesion, manufacture and mechanical properties of the cell as a whole. This article highlights recent developments made with the combination of polymer and inorganic materials in the form of composite electrolytes, interlayers, protective coatings and binders. The role of polymers regarding interface chemistry, interface resistance and lithium transfer is discussed and the importance of polymers for the processing of solid-state batteries is described. Taken as a whole, the article surveys the relevance of polymers at each cell component and discerns how polymers may provide the key to access the full potential of solid-state batteries with inorganic solid electrolytes. Dr Sudeshna Sen obtained her PhD degree from Indian Insti- tute of Science in Bangalore, India. She pursued her post- doctoral studies at GSK's Carbon Neutral Laboratory, University of Nottingham and University College London, United Kingdom. She has been awarded Royal Society-SERB Newton fellowship from Univer- sity of Glasgow. Currently, she is working in the junior research group of Dr Felix H. Richter and the research group of Professor J¨ urgen Janek at the Justus-Liebig-University Gießen. Her current research involves the development of polymer protective layers for solid-state batteries and the degradation analysis of solid-state battery interfaces. Enrico Trevisanello studied Materials Science at the Univer- sity of Padua, where he received his BSc and MSc working in the eld of electrochemical synthesis of polymers. His doctoral research, supervised by Dr Felix H. Richter and Professor J¨ urgen Janek at the Justus-Liebig-University Gießen, focuses on the study of hybrid electrolytes for lithium batteries, investigating the electro-chemo- mechanical interplay between polymers, ceramic electrolyte and cathode active materials. Center for Materials Research, Institute of Physical Chemistry, Justus-Liebig-Universit¨ at Gießen, Heinrich-Buff-Ring 17, 35392 Gießen, Germany. E-mail: felix.h.richter@pc.jlug.de † Current address: Robert Bosch GmbH, T¨ ubingerstr. 123, 72762, Reutlingen, Germany. Cite this: J. Mater. Chem. A, 2021, 9, 18701 Received 2nd April 2021 Accepted 12th July 2021 DOI: 10.1039/d1ta02796d rsc.li/materials-a This journal is © The Royal Society of Chemistry 2021 J. Mater. Chem. A, 2021, 9, 18701–18732 | 18701 Journal of Materials Chemistry A HIGHLIGHT Published on 20 July 2021. Downloaded on 9/16/2021 11:36:30 AM. View Article Online View Journal | View Issue