A Novel State of Charge Estimation Method Based on Electrochemical Impedance Spectroscopy for Solid-State Batteries of Next-Generation Space Power Sources under Different States of Health

With the increasing demand for battery energy density and safety, solid-state batteries are expected to become one of the ideal energy storage devices. Aiming at compensating for the research lack of modeling and state estimation of solid-state batteries, this paper proposes a state of charge (SOC) estimation method based on the electrochemical impedance spectra (EIS) of sample solid-state batteries that consider both accuracy and speed. The SOC estimation model is established using Gaussian process regression by extracting the low- and medium-frequency semicircular parameters that vary markedly with SOC. Considering the online application of the method, the fixed-frequency test impedance is selected as the characteristic parameter to achieve the SOC estimation that takes both accuracy and speed into account, and the method is still applicable under different state of health (SOH). Considering the existence of 3 impedance spectral semicircles in this solid-state battery, the RQ (parallel connection of resistors and constant phase element) process is added to establish a fractional-order model and the fractional-order extended Kalman filter (FOEKF) algorithm is developed. What is more, the FOEKF algorithm and SOC-OCV curve are constructed as a control group to analyze the accuracy, advantages, and disadvantages of the proposed SOC estimation method. The results show that the unique EIS performance of this solid-state battery is more conducive to achieving the estimation of the battery SOC. The application of the EIS online implementation method is expected to rely on the fixed-frequency test to achieve online accurate estimation of the SOC of solid-state batteries.