Meaning
Low-temperature operations compared against room-temperature baselines reveal distinct changes in the discharge profile of lithium batteries. The sub-zero discharge dynamics involve the physical and electrochemical changes that occur within a battery when it operates in cold conditions. These changes alter both the voltage profile and the usable capacity of the cell.
Viscosity Growth
Electrolyte solutions become increasingly viscous as temperatures drop towards freezing points. This physical change affects the sub-zero discharge dynamics by slowing the movement of lithium ions through the separator. Low mobility increases internal resistance and reduces energy output.
The ions face a higher energy barrier to leave the solvation shell and enter the solid electrode. This transport limitation becomes the primary bottleneck for cell performance.
Voltage Sag
Decreased chemical activity and increased internal resistance cause the output voltage of the cell to drop quickly when a load is applied. Under the influence of the sub-zero discharge dynamics, the voltage sag may trigger low-battery alarms even when most of the capacity remains.
Recovery Phase
Heat generated during discharge can slowly raise the internal temperature of the cell. In the context of the sub-zero discharge dynamics, this internal warming reduces electrolyte viscosity, leading to a temporary recovery of the operating voltage. This self-heating effect is observed during continuous discharge.
