Revealing the Impact of Particle Size Distribution on Ageing of Lithium‐Ion Batteries with Frequency Response Analysis

In-depth analyses, including discharge behaviour, electrochemical impedance analysis, and for the first time, nonlinear frequency response analysis, are conducted on the ageing of negative electrodes with varying particle size distribution. The electrode-resolved analysis is used to distinguish the kinetic and transport losses at the respective electrodes. For fine to medium-sized particles at the negative electrode, ageing impacts are found more on the positive electrode: the impedance and nonlinear responses increase, suggesting that the charge transfer process at the positive electrode is worsened. Meanwhile, for coarse and broad negative particles, the impedance and nonlinear responses at negative electrodes decrease due to improved kinetics from micro-cracking. The second harmonic reveals a change in the nature of the charge transfer during ageing: the charge transfer process at the positive electrode becomes asymmetric for fine and medium-sized negative particles. Vice versa, the charge transfer process at the negative electrode becomes symmetric for coarse and broad negative particles.