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

Abstract

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_0.8Mn_0.1Co_0.1O₂ (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.