Impact of Anode to Cathode Crossover in Lithium‐metal Batteries With High‐Nickel Cathodes

ABSTRACT The advancement of high‐energy‐density lithium‐metal batteries (LMBs) is hindered by the chemical instability of both lithium‐metal anode and high‐nickel layered oxide cathodes. While cathode‐to‐anode crossover is well‐documented, the reverse process of anode‐to‐cathode crossover remains underexplored. Here, we systematically investigate such crossovers and the degradation pathway in pouch cells with a localized high‐concentration electrolyte, comparing NMC622, NMC811, and NMC90 cathodes paired with lithium‐metal and graphite anodes. Despite delivering higher initial capacities, LMBs exhibit faster capacity fade under long‐term cycling at 45 °C. To isolate cathode‐side degradation, galvanostatic electrochemical impedance spectroscopy (GEIS) measurements of cycled cathodes paired with delithiated lithium iron phosphate (LFP) counter electrodes reveal significantly higher charge‐transfer resistance in cathodes cycled with lithium‐metal. Surface characterization via X‐ray photoelectron spectroscopy (XPS) and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) reveals greater electrolyte decomposition on cathodes cycled with lithium metal, leading to thicker, more organic‐rich cathode–electrolyte interphases (CEIs), consistent with the elevated charge‐transfer resistance observed in GEIS measurements. Notably, NMC90 shows the most pronounced CEI thickening, linking higher cathode surface reactivity to greater susceptibility to anode‐to‐cathode crossover. This work presents compelling evidence of crosstalk degradation originating from lithium‐metal anodes and underscores the importance of cross‐interface stability for the design of durable LMBs.