Meaning
Thermodynamic energy dissipation per unit volume quantifies total heat production within an electrochemical cell during charge and discharge processes. Joule heating from internal ohmic resistance combines with entropic heat from reversible phase transitions in active materials. The resulting heat generation rate determines thermal management cooling requirements under dynamic power profiles.
Cell operating safety hinges on balancing thermal dissipation against internal heat output.
Ohmic Loss
Current density magnitude dominates irreversible thermal dissipation through internal resistive losses. Electron transport resistance across current collectors, active coatings, and separator membranes scales quadratically with applied electrical current. Higher heat generation rate values occur during fast charging due to increased overpotentials across electrochemical cell components.
Entropic Heat
Reversible thermal changes accompany chemical phase transformations as lithium ions intercalate into host crystal lattices. Depending on the state of charge, entropic contributions can temporarily cool or heat the cell structure. Tracking heat generation rate variations across the entire state of charge window enables precise thermal modeling for battery packs.
Thermal Runaway
Exothermic decomposition reactions initiate when internal cell temperatures exceed critical material thresholds. Uncontrolled thermal feedback accelerates reaction rates, releasing gas and heat in a self-sustaining cycle. Excessive heat generation rate conditions trigger thermal runaway if module cooling systems fail to extract excess heat rapidly.
