Li-ion batteries have seen remarkable success in electric vehicles over the past decade. The anode and electrolyte materials face interfacial challenges stemming from the thermodynamic instability of nearly all electrolytes at anode potentials, but can be kinetically stabilized by formation of the solid electrolyte interphase (SEI) derived from electrolyte and active material. The SEI performs crucial protective, transport, and mechanical functions and intimately controls cycle life. Despite its crucial role, the SEI has remained notoriously difficult to characterize, and connections between chemistry, properties, function, and performance are still being uncovered.
New insights have been enabled by improved computational and experimental tools, and advances in materials design of both liquid and solid electrolytes have yielded vast new platforms for study. With this Discussion, we aim to highlight such advances and emergent understanding while deepening and integrating connections with the foundations of SEI science and engineering, providing perspective on the state of the field and research needs in coming years.
This volume brings together internationally leading researchers in this exciting field to expand the understanding of the SEI on reactive lithium metal anodes and beyond.
In this volume the topics covered include:

• Lithium anodes with liquid electrolytes
• Lithium anodes with solid electrolytes
• Beyond lithium chemistries
• Characterisation techniques