Accurate battery models are essential for the assessment of battery states and performance. Traditional equivalent circuit model (ECM), e.g. second-order RC model, cannot imitate non-linear characters of Lithium-ion battery especially in low state of charge (SOC) area. Considering the advantages of battery electrochemical and ECM, the paper proposes an electrochemistry-based equivalent circuit model (E-ECM). With only two parameters more than second-order RC model, E-ECM can simulate battery voltage response better. Next, different from the previous model parameters optimization method, a decoupling parameters extraction (DPE) method is studied to derive the more appropriate model parameters for the proposed E-ECM first. The DPE method is believed to relate to battery electrochemical characters. Experiment results show that the obtained E-ECM is of a good performance no matter in the dynamic working conditions, or constant current working condition, especially in low SOC area. Moreover, the proposed E-ECM is able to describe battery rate capability with high accuracy.