Meaning
Thermal non-uniformity across the physical volume of a battery cell or pack affects the local rate of electrochemical reactions and aging. Within a lithium-ion pack, temperature gradients occur when the heat generated during charge or discharge is not removed evenly by the cooling system. This temperature variation leads to non-uniform current flow and accelerated degradation of the warmer cells.
Thermal Variance
Cells that operate at higher temperatures degrade faster, causing them to lose capacity and increase resistance more rapidly than the cooler cells. This uneven aging can quickly unbalance the battery pack, reducing its total usable energy and shortening its service life. Sourcing engineers monitor these gradients to ensure that the battery pack’s thermal management system is working effectively.
System Performance
Large temperature differences within a single cell can also cause mechanical stress as the active materials expand and contract unevenly. This mechanical stress can lead to micro-cracking of the electrodes, which increases the internal resistance of the cell. Proper control of thermal gradients is essential for maintaining the safety and reliability of high-power battery packs.
Cooling Optimization
Engineers minimize temperature differences by using liquid cooling plates or phase change materials that distribute heat evenly. They also design the flow channels to ensure that the cooling fluid is distributed uniformly. These design choices are critical for high-power operation.
