Meaning
Loss of stored chemical energy in a cell over time without an external electrical load describes a spontaneous internal process. This electrochemical self discharge diminishes the available capacity and degrades the cell health over extended storage periods. The phenomenon occurs across all chemistries and remains measurable until the cell reaches a fully discharged state.
Loss Mechanism
Spontaneous reactions at the electrode-electrolyte interface consume active materials and generate parasitic currents. During storage, electrochemical self discharge occurs as lithium ions migrate across the separator to neutralize charged sites on the cathode. These parasitic actions are accelerated by elevated temperatures and high states of charge, which increase the chemical potential difference.
A secondary mechanism involves the slow oxidation of the electrolyte, which permanently reduces the lifetime capacity of the battery. Engineers calculate this loss by storing cells under controlled conditions and measuring the open circuit voltage drop.
Storage Behavior
Inventory management for battery cells relies heavily on predicting the rate of voltage decline over time. Cells exhibiting elevated levels of electrochemical self discharge are segregated and rejected before pack assembly. This screening ensures that finished packs do not suffer from cell-to-cell imbalance, which would otherwise limit the usable capacity of the entire pack.
Material Quality
Impurity levels in raw materials directly influence the rate of spontaneous energy loss.
