An improved electrochemical equivalent circuit model and precise state-of-charge estimation comparative study for lithium-rich manganese-based battery

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State-of-charge (SOC) serves as a crucial metric for lithium-ion batteries. A precise battery model is an essential factor influencing the accuracy of SOC estimation. Notably, lithium-rich manganese-based (LRMB) layered oxide batteries exhibit distinct voltage characteristics that differentiate them from other battery types. Experimental findings reveal that traditional equivalent circuit models (ECMs) are not well-suited for capturing the behavior of LRMB batteries. To address the aforementioned problem and its attendant phenomenon of large SOC estimation error, in this paper, we proposed an improved electrochemical equivalent circuit model (IEECM) for LRMB batteries that concurrently enhances accuracy and mitigates error. The proposed model comprehensively accounts for the long-term diffusion process of lithium ions within the solid phase, thereby offering a more precise representation of the battery's behavior. The results indicate that under different operating conditions, the RMSE of voltage error remains below 31.3 mV. Notably, under UDDS conditions, the MAE and RMSE are merely 15.1 mV and 20.6 mV, respectively. To further validate its effectiveness, we utilize three common SOC estimation algorithms under various operation conditions. Experimental results show that the RMSEs of SOC estimation based on the proposed model under different algorithms are lower than 2.21 %, which is better than ECMs. Consistently, our findings indicate that this model is particularly well-suited for LRMB batteries, leading to a notable enhancement in SOC estimation accuracy.