Influence of Anode Reactivity and Chemical Crossover on the Formation of Cathode‐Electrolyte Interphase in High‐Nickel Layered Oxide Cathodes

As the push for lithium‐ion batteries (LIBs) with high‐energy density grows, systems pairing high‐nickel cathodes with high‐capacity anodes have become attractive; however, these electrodes individually suffer from high surface reactivities, leading to interfacial instabilities. When paired together, further issues arise, with cathode‐to‐anode crossover being a well‐known phenomenon. In contrast, anode‐to‐cathode crossover remains underexplored, especially in systems that undergo large volume changes. Here, a comparison of the influence of anode reactivity on cathode surface degradation is presented by pairing LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) cathode with graphite, prelithiated silicon suboxide (SiO x ), and lithium‐metal anodes. Voltage curves and differential capacity analysis show that all cells experience polarization growth throughout cycling. A combination of electrochemical techniques, such as operando galvanostatic electrochemical impedance spectroscopy (GEIS), and surface analyses, such as scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS), reveal that cycling against more reactive anodes promotes the formation of a thicker, organic‐rich cathode electrolyte interphase (CEI), which suffers from impedance growth and large irreversible capacity loss. Post‐mortem characterization with XPS and SEM confirms compositional and morphological changes at the cathode surface and the cycled separator. The findings provide insights into the role of anode‐driven degradation of high‐Ni cathodes, promoting further understanding of two‐way crossover in LIBs.