Iron Dissolution Pathways in Lithiated Cathode Formulations under Thermal Storage
Thermal storage above 45°C drives hydrofluoric acid attack on lithiated iron cathodes, causing iron dissolution and anode SEI degradation.
Cathode Iron Leaching
Meaning
Chemical degradation through transition metal dissolution occurs when iron impurities from positive electrode materials enter the liquid electrolyte. This phenomenon, which represents cathode iron leaching, occurs primarily under high voltage and elevated temperature conditions during battery operation. Solubilized iron ions travel across the separator and deposit on the anode, where they destroy the solid electrolyte interphase layer.
Preventing this transition metal loss is critical for maintaining long-term battery performance.
Electrochemical Impact
Acidic compounds generated by the decomposition of lithium salts accelerate the extraction of metallic and oxidized iron from the cathode grid or active material. Higher operating voltages destabilize the electrode surface, which increases the rate of chemical attack. This process reduces the mechanical stability of the active material host structure.
Anode Degradation
Migrated iron ions accept electrons at the negative electrode and deposit as metallic microstructures. These deposits catalyze the continuous decomposition of electrolyte molecules, which consumes active lithium. Over time, the localized impedance of the negative electrode increases.
Mitigation Strategy
Material selection and protective surface coatings represent the primary defenses against this metal transfer. Coating the cathode particles with oxide or phosphate compounds minimizes direct contact between the active material and the acidic electrolyte species. Purifying the raw precursors and processing equipment remains the most effective way to eliminate the source of iron.