Large-scale lithium-ion batteries (LLB) are crucial energy sources for hybrid electrical vehicles. Predicting their electrochemical states is critical in maintaining the safety and performance of LLB. Electrochemical behaviors of LLB have spatiotemporal dynamics. Their physical model is coupled partial differential equations which are not suitable for online states estimation. In this article, we present a space-time separation method to intelligently modeling the internal states distribution, including potential of electrodes and depth of discharge. The proposed models are validated by simulation.