Meaning
Chemical degradation phenomena occur in primary lithium batteries when a protective film of lithium chloride forms on the lithium anode, restricting self-discharge but also increasing the internal resistance of the cell. In primary lithium battery passivation, this layer acts as an insulator that must be broken down by drawing a moderate load current before the cell can deliver its full rated power. If this layer is too thick, the initial voltage drop under load can cause the device to reset.
Chemical Mechanism
The formation of this passivation layer is a natural process that occurs during long storage periods or when the cell is kept at high temperatures. While it preserves the capacity of the cell by preventing self-discharge, it reduces the ability of the battery to handle sudden high-current demands. Once a current is drawn, the layer begins to dissolve, and the cell voltage recovers to its normal operating level.
System Mitigation
Design engineers use parallel capacitors or pre-discharge routines to manage the effects of this layer. Host microcontrollers can run a startup routine that draws a small, controlled current to slowly dissolve the passivation layer before activating the high-current cellular transceiver. This slow ramp prevents the voltage from dropping below the system’s reset threshold.
Field Testing
Telemetry devices must be tested under cold conditions to evaluate their vulnerability to this phenomenon. Cold temperatures increase the internal resistance of the battery, making the initial voltage drop more severe. This testing ensures that devices installed in unheated locations will boot reliably after long periods of inactivity.
