Quantifying Lithium Inventory Losses during Extended Calendar Aging Protocols
Extended calendar aging consumes cyclable lithium through solid electrolyte growth, requiring differential capacity verification before warranty assignment.
IEC 62133 Capacity Retention
Meaning
Standardized testing protocols define the ability of a rechargeable lithium cell to maintain its stored electrical charge during prolonged storage under specified temperature conditions. Compliance with IEC 62133 capacity retention requires a cell to undergo a twenty-eight day storage period before its remaining capacity is measured. This safety-oriented metric establishes the baseline stability of the electrochemical system against self-discharge.
Testing Protocol
Charging procedures dictate that the cell must be fully charged according to the manufacturer’s recommended method before being placed into storage. The ambient temperature is maintained at twenty degrees Celsius during the storage interval. This constant thermal condition prevents accelerated chemical degradation that higher temperatures would otherwise induce, ensuring a reproducible evaluation of the electrochemistry.
Performance Baseline
Residual capacity is determined by discharging the cell at a continuous rate of zero point two amperes after the storage duration has elapsed. To pass the test, the cell must return a capacity that meets or exceeds the minimum recovery threshold specified by the standard. This verification ensures that the cell remains functional and does not suffer from irreversible structural or chemical decay during periods of inactivity.
Safety Implication
Excessive self-discharge rates during this test point to internal micro-shorts or chemical instabilities that compromise long-term safety. Cells exhibiting poor retention are prone to localized thermal issues during subsequent charging.