Understanding Interphases and Interfaces of Battery Materials at the Nanoscale.

Battery performance and longevity are critically dependent on interfacial characteristics, regardless of whether these interfaces are organic, inorganic, or buried. Comprehensive understanding of these regions is essential for optimizing electrochemical performance. Characterization of battery interfaces presents significant challenges due to their nanometer-scale thickness, complex composition (often a mixture of organic and inorganic decomposition products), and susceptibility to environmental factors and beam damage. In situ and operando techniques, often utilizing synchrotron or neutron sources, are preferred to minimize contamination and capture dynamic interfacial evolution. However, experimental constraints limit universal applicability; vacuum-based methods suitable for solid-state batteries are incompatible with liquid electrolyte systems, while buried interfaces pose unique analytical hurdles. A lack of standardized characterization protocols contributes to data variability and potential bias within literature. This review addresses strategies for investigating buried interfaces and examines advanced characterization techniques commonly employed in lithium-ion battery interface studies. This study specifically addresses concerns surrounding data interpretation and the inherent sensitivity of these layers, highlighting the need for careful methodological consideration and rigorous data validation to ensure accurate representation of interfacial behavior.