A fractional-order electrochemical lithium-ion batteries model considering electrolyte polarization and aging mechanism for state of health estimation

Accurate state of health (SOH) estimation of lithium-ion batteries is critical for the safe and reliable operation of battery power system. To achieve better SOH estimation with low computational complexity, a fractional-order model considering electrolyte polarization and aging mechanism (FOMeA) is proposed. The proposed model simplifies solid phase lithium-ion distribution with fractional-order Pade approximation and electrolyte phase lithium-ion distribution with a two-state system. The solid electrolyte interphase (SEI) layer formation and lithium plating side reactions, which lead to battery aging, are modeled to establish the relationship between the cycle number and the aging parameters in the proposed simplified electrochemical model. Finally, FOMeA is compared with the pseudo-2D (P2D) aging model. The result shows that FOMeA can achieve accurate voltage prediction and SOH estimation in whole battery cycle life, and greatly save computational time.