Accelerated Degradation Wiener Model for Lithiumion Battery Considering Individual Difference

Accelerated degradation is a pivotal section for lithium cells for a long cycle life. Wiener process as an important part of stochastic process, plays a key role for the accelerated degradation analysis. In general, the basic Wiener process is modeled with the constant drift rate and diffusion parameter. That indicates the lithium-ion batteries have the same degradation process for the same stress and the complexity of the algorithm is reduced. However, due to the differences in production processes and materials, the individual variations exist. The general Wiener process ignores the individual variations. That leads to reduction of algorithm accuracy. To improve the algorithm accuracy, this paper proposes a Wiener model for the accelerated degradation analysis, considering individual variation. The accelerated model with individual variation is modeled. First, degradation model parameters for each sample are estimated separately. Then, the varieties in the estimation results of each sample parameters are analyzed. That provides the theoretical reference for the parameters of Wiener process. In addition, the coefficient of variation is used as a measure of drift rate and diffusion parameters. Meanwhile, combining with the Wiener process and accelerated model, parameters are optimized by the `maximum likelihood estimation (MLE). Finally, the proposed model is demonstrated for the effectiveness by a practical example.