Lifetime Rapid Evaluation Method for Lithium-Ion Battery with Li(NiMnCo)O2 Cathode

This paper conducts battery cyclic life tests under a full state-of-charge range (0-100%) and five partitioned state-of-charge ranges (0–20%, 20%–40%, 40%–60%, 60%–80% and 80%–100%). The attenuation of state-of-health indicator parameters along with cycle times under different state-of-charge ranges is compared. For the batteries cycled under 20% state-of-charge depth, loss of lithium inventory (LLI) is the leading factor resulting in capacity degradation. Expanding cycle state-of-charge depth accelerates the loss of electrode active material, but has little effects on LLI. When suffering identical cycle times, the sum of the decrements of state-of- health indicator parameter related to LLI under the five partitioned state-of-charge ranges is equal to 0–100% state-of-charge, which proves the additivity of LLI. Considering the linear correlation between capacity and state-of-health indicator parameters, a linear regression capacity model is established. Then, based on the additivity of LLI and capacity estimation model, an innovative evaluation method of battery lifetime with less testing time consumption is proposed, which conducts cycle aging tests under the partitioned state-of-charge ranges replacing full state-of-charge range to reduce testing time. Using this method, time consumption can be reduced by 75%, and the estimation error of capacity and lifetime is 3% and 10% respectively.