Polymers
The 1, 500mAh pouch cells for mobile phones were first charged at a current of 1, 500mA to 4. 20V/cell and then allowed to saturate to 0. 05C as part of the full charge saturation. The batteries were then discharged at 1, 500mA to 3. 0V/cell, and the cycle was repeated. The expected capacity loss of Li-ion batteries was uniform over the delivered 250 cycles and the batteries performed as expected. In 2020, small wearable batteries deliver about 300 cycles whereas modern smartphones have a cycle life requirement is 800 cycles and more. Figure 6 illustrates dynamic stress tests reflecting capacity loss when cycling Li-ion at various charge and discharge bandwidths. The largest capacity loss occurs when discharging a fully charged Li-ion to 25 percent SoC; the loss would be higher if fully discharged. Cycling between 85 and 25 percent provides a longer service life than charging to 100 percent and discharging to 50 percent. DoD constitutes a full charge followed by a discharge to the indi...