Auditing Factory Process Control Indices to Validate Cell Test Certificates
Auditing factory process control indices validates cell test certificates by proving batch uniformity and preventing latent field defects.
Lithium Plating Mechanism
Meaning
Electrochemical side reactions occur when lithium ions fail to intercalate into the host structure of the anode and instead deposit as metallic film on the surface. The lithium plating mechanism typically triggers when the charging rate exceeds the diffusion capability of the graphite or silicon material. This reaction competes with the desired storage process and reduces the efficiency of the cell.
It generally ceases once the charging current is removed or the temperature rises to a level that restores normal diffusion rates.
Kinetic Constraint
Diffusion kinetics determine the threshold at which this deposition begins to compete with normal intercalation. A lithium plating mechanism becomes more likely at low temperatures because the movement of ions through the electrolyte and into the electrode slows down. Once the local potential at the anode surface drops below the reference potential of lithium, the metal starts to accumulate.
Safety Consequence
Internal degradation follows the growth of these metallic layers which can evolve into needle like dendrites. This physical change poses a risk of piercing the separator and creating an internal short circuit. Metal growth persists.
Thermal Influence
Battery life shortens because the plated metal often becomes electrically isolated or reacts with the electrolyte to form irreversible products.