Meaning
Passivation layers formed at the solid-liquid junction inside electrochemical cells stabilize high-voltage electrode surfaces against continuous liquid oxidation. The cathode electrolyte interface forms through the decomposition of solvent molecules and salt anions under oxidizing potentials during initial formation cycles. This interfacial boundary dictates charge transfer kinetics, transition metal dissolution rates, and long-term capacity retention across high-energy lithium batteries.
Interfacial Dynamics
Chemical reactions between active material particles and liquid electrolytes generate passivating films containing inorganic carbonates and organic fluorophosphates. In high-nickel energy storage systems, the cathode electrolyte interface undergoes continuous structural rearrangement during deep cycling as lattice expansion strains the protective surface layer. Parasitic side reactions consume active lithium ions while generating resistive degradation products.
Phase transformations impair ion migration.
Composition Control
Surface coatings and electrolyte additives alter oxidation pathways to synthesize thinner, mechanically resilient passivating films. Introducing atomic layer deposition alumina onto nickel-rich cathodes stabilizes the cathode electrolyte interface by suppressing transition metal dissolution into organic solvents. Fluorinated ethylene carbonate additions generate protective lithium fluoride domain networks that withstand high voltage exposure.
Stable surface films reduce capacity fade.
Impedance Growth
Cell degradation accelerates as thick passivating layers increase charge transfer resistance at high operating potentials. Continuous breakdown of the cathode electrolyte interface consumes mobile active ions, elevating internal cell impedance and limiting high-rate discharge capability.
