As vehicle electrification rapidly progresses, the battery type, charging parameters, infrastructure and timing composition of such vehicles are key considerations in accelerating the transition to electrification. According to foreign media reports, researchers from the WMG College of the University of Warwick used commercial batteries to explore the impact of high-current operation on the aging of battery batteries, and to clarify the limitations and effects of high-speed cycles on lithium iron phosphate cylindrical batteries.
They passed two tests to determine the maximum current value before the cell failed; then applied the current according to this value until the cell failed; and then tested again to determine that the cycle parameters could exceed the manufacturer's recommendation.
During the test, when the electric flux was increased to 100C cycle conditions, the charge and discharge capabilities exceeded the manufacturer's requirements by up to 1.38 and 4.4 times, respectively. This added current is suitable for 500 charge and discharge cycles. However, during the first 60 cycles, the applied current causes a rapid drop in capacity while the resistance rises. In addition, in the remaining steps of cooling the battery core, the charge and discharge process of natural convection is performed, so that the application of current will cause the temperature of the battery core to rise. Batteries operate within an optimal temperature range, and any deviation outside of that range will cause the components and chemicals inside the battery to start to break down.Also read:https://www.aimeno.com/lithium-battery-pack/199.html
They also found that during testing and aging, the jellyrolls (roll-shaped electrodes and separator) deformed, forming lithium plating. The deformation spreads axially from the center of the cell to the outside of the cell, which indicates that the center of the cell is the hottest place.
We want to make sure the battery is run in the safest way possible and maintains an appropriate lifespan. The test results show that there is a window for operating the battery above the manufacturer's specified current limit, while maintaining the manufacturer's specified voltage limit.
We also found that thermal fatigue was the cause of the deformation of the jelly rolls. With each charge-discharge cycle, batteries experience thermal stress that causes their components to deform. As the number of cycles increases, the deformation gradually increases, while the jelly roll is mechanically restrained by the hard outer layer and the center pin.Also read:https://www.aminobattery.com/lithium-battery/206.html
If convective cooling can be performed in the center of the cell, where the cell is hottest, deformation can be mitigated and controlled, allowing the cell to maintain capacity for a longer period of time and meet resistance standards.