Auditing Battery Laboratory Accreditation Chains and Parameter Drift Boundaries
Auditing battery laboratory accreditations requires matching exact test standards against ISO 17025 scopes while enforcing drift limits on cell data.
SEI Growth Rate
Meaning
Kinetic dynamics govern the time-dependent accumulation of decomposition products on active electrode surfaces during storage and operational cycling. The SEI growth rate measures the speed at which electrolyte reduction continuously thickens the passivating surface film on graphite or metal anodes. Growth follows parabolic diffusion-limited kinetics during idle storage and accelerates under active current flow.
Parasitic film growth consumes cyclable lithium ions while raising internal cell resistance over operational lifespans. The metric ceases to follow classical diffusion models if thermal mechanical stress cracks the passivating layer.
Kinetic Mechanism
Electron tunneling through the inner inorganic layer drives continuous solvent reduction at the interface. Solvent molecules diffuse through the porous outer layer to accept electrons from the active electrode substrate. Film growth rate scales with the square root of calendar storage time under stable thermal conditions.
Influencing Factor
Elevated temperatures accelerate chemical reaction rates and increase organic salt solubility in liquid electrolyte formulations. High state-of-charge operation increases chemical potential differences across the interface, boosting parasitic reduction currents.
Cell Failure Consequence
Sustained film thickening causes capacity fade and elevates internal impedance, reducing rate capability and fast-charging performance. Non-uniform growth creates localized current density spikes that increase lithium plating risks during low-temperature charging operations.