Meaning
Transition metal leaching represents a principal degradation pathway wherein positive electrode active materials lose structural transition metal ions to the liquid electrolyte during high voltage operation. Elevated cell potential accelerates cathode dissolution by destabilizing surface oxygen coordination and releasing manganese, nickel, or cobalt species into solution. Solubilized ions cross the porous separator under potential gradients and deposit onto the negative electrode, damaging the solid electrolyte interphase and promoting parasitic side reactions that drain active lithium inventory.
Dissolution Rate
Acidic species generated through electrolyte oxidation attack the metal oxide surface to free transition metal cations from their crystal coordinates. Higher operating temperatures increase reaction rates exponentially, converting stable layered structures into inactive rock salt phases near particle boundaries. Hydrogen fluoride traces produced by salt hydrolysis accelerate the leaching process, stripping transition metals directly from exposed crystal facets.
Metal Migration
Solvated cations traverse the electrolyte medium to reach the negative electrode interface. Once at the anode surface, reduced transition metal species catalyze continuous decomposition of organic solvents, creating a thicker resistive layer that elevates cell impedance and reduces rate capability.
Structural Degradation
Crystal lattice collapse reduces the capacity of the positive host material to intercalate lithium ions reversibly. Capacity retention drops precipitously as structural vacancies from cathode dissolution disrupt ionic diffusion pathways within primary particles.
