Lithium-ion battery cathode and anode potential observer based on reduced-order electrochemical single particle model

The fast charging of Lithium-ion batteries within electric vehicles can accelerate the side reaction of lithium plating due to an anode potential that occurs as state of charge increases. It is important to monitor the anode potential during battery charging, but it is not practical to measure the inside of the battery directly for a commercial cell. This paper proposes an observer for estimating the cathode and anode potentials based on the reduced-order electrochemical model, which only needs terminal voltage to track the cathode and anode potentials and their internal charge concentration. The observer design is based on the model order reduction and linearisation of a single particle model with electrolyte (SPMe) to achieve acceptable accuracy with a low calculation cost. The linearised model and the designed observer are validated by the experimental results of a three-electrode cell. The results show that the linearised model reduces the operation time by more than 99% compared with the full-order SPMe model using the same processor. The results also verify that the root mean square error of the cathode and anode potential estimated by the observer is less than 0.02 V for a charging current range from 0.3C to 1C. This shows that the developed cathode and anode potential observer based on the reduced-order electrochemical model can be used within real-time control applications to detect the anode potential in real time to avoid battery degradation caused by lithium plating.