Meaning
Heterogeneous chemical processes occurring at the boundary between solid electrode materials and liquid or solid electrolytes govern charge transfer kinetics. An interfacial reaction includes charge transfer, ion desolvation and chemical passivation occurring within the sub-nanometer interface zone. This phenomenon governs internal resistance and power capability, operating whenever potential differences exist between solid phase host materials and phase-adjacent electrolyte media.
Passivation Layer
Chemical decomposition of electrolyte components under strong oxidizing or reducing potentials generates a solid interphase layer on electrode surfaces. An interfacial reaction between lithium ions and organic solvents forms passivating species including lithium carbonate, lithium fluoride and lithium alkyl carbonates. Controlled interphase growth protects electrolyte molecules from ongoing electron transfer while allowing lithium ion diffusion across the solid boundary layer.
Continuous mechanical expansion during charge cycling causes interface fracturing, which triggers secondary passivation reactions that consume active electrolyte components.
Kinetic Impedance
Interfacial resistance increases when dense passivation layers accumulate non-conductive reaction products. High interfacial impedance reduces power output during high rate discharge, creating significant voltage drops under cold ambient temperatures.
Interface Stability
Stable electrode boundaries prevent thermal runaway and continuous capacity decay in high voltage systems. Electrolyte additives stabilize the solid interphase, suppressing parasitic side reactions during high temperature operation.
