Quantitative Analysis Method for Full Lifecycle Aging Pathways of Lithium-Ion Battery Systems Based on Equilibrium Potential Reconstruction

High-specific-energy lithium-ion batteries face accelerated degradation and safety risks. To ensure stable and safe operation of such batteries in electric vehicles throughout their service life, this study proposes a quantitative aging mechanism analysis method based on electrode equilibrium potential reconstruction under rest conditions. First, by integrating the single-particle electrochemical model with equilibrium potential reconstruction, a quantitative mapping framework between State of Charge (SOC) and electrode lithiation concentration is established. Subsequently, to address the strong nonlinearity between equilibrium potential and lithiation concentration, the State Transition Algorithm (STA) is introduced to solve the high-dimensional coupled parameter identification problem, enhancing aging parameter estimation accuracy. Finally, the effectiveness of the proposed method was validated using a commercial NCM622/graphite power cell as the research object, and the battery’s aging pathways were analyzed using differential voltage analysis (DVA) and incremental capacity analysis (ICA) methods. Experimental results indicate that the OCV curve fitting achieved a maximum Root Mean Square Error of 0.00932, while quantitatively revealing the degradation patterns of electrode lithiation degrees during aging under both fully charged (SOC = 100%) and fully discharged (SOC = 0%) states.