Parameter Obtaining And Ageing Analysis For Lithium-ion Batteries Based On Improved Single Particle Model

Lithium-ion batteries have been widely used due to its advantages. The existed battery management system still has a lot of problems in the aspects of improving safety, reliability and economy. The electrochemical model of lithium-ion batteries is based on the internal physical and chemistry processes, which can adapt to a larger range of operating conditions, with higher simulation precision, and the model parameters have explicit physical meanings. Meanwhile, its evolution rule can reflect the state of health. In this paper, the improved single particle model is furthure improved, the parameters acquisition method of the model is studied, the ageing experiment is carried out, and the model parameters and the evolution laws inside the batteries are systematically analyzed.Firstly, basing on the single particle model, the electrolyte phase diffusion simplified calculation method and the solid phase diffusion three-parameter approximation solution is recommended, and the ohm polarization process is enriched. Otherwise, the thermal behavior description of the batteries is added into the model which improves the simulation precision of the model, and realizes the simulation of the temperature prediction.Secondly, a parameter acquisition method based on excitation response analysis is proposed. On the basis of further study in the internal physical-chemical processes and characteristics of the model, the method is to design different charge and discharge conditions to disintegrate overpotentials in the principle of time-saving and accuracy, and then combine together as a set of dynamic condition. Measure the key segments of voltage characteristics or the voltage jump points, and parameters can be got by decomposing the overpotentials. Take several put aside cooling curves in temperature curve to calculate the temperature-dependent parameter. It can be proved that the parameters acquired from the method can simulate the terminal voltage and the temperature external features accurately.Finally, base on the improved single particle model and combine with parameter acquisition method to conduct the aging research. Select environmental temperature and work current as the two influencing factors of ageing process, using fuzzy clustering method to select batteries with better consistency to do ageing experiments. Obtain the parameters and capacity of different ageing stage by the designed experiments, then establish the aging model by least square method, and analyze each parameter’s ageing mechanisms. After that, get the incidence of the environment temperature, charge and discharge rate and the interaction of the two factors to other parameters by using variance analyzing method combining with F test. Finally decompose the terminal voltage under different aging model to get the changes of overpotentials in the aging process, then the degration conditions of overpotentials and the influence on the terminal voltage are get. Combine with mechanism to analysis reasons for such changes.This paper lays the foundation for the lithium-ion battery electrochemistry model in the application of the battery management system, and points out the direction for further research work..