Elucidating the rate limitation of lithium-ion batteries under different charging conditions through polarization analysis

The charging performance of lithium-ion batteries is significantly affected by the polarization effect, which leads to increased resistance and prolonged charging time. This paper combines experimental testing with numerical simulation to qualitatively and quantitatively investigate the polarization effects under different charging conditions. The results indicate that the proportions of positive and negative polarization to cell polarization are comparable and basically constant with variations in the charging rate. The polarization voltages of different categories within the electrode are positively correlated with the charging rate. At high charging rates (6C), electrochemical polarization (47%–50%) accounts for the majority, followed by solid-phase (34%–39%) and liquid-phase concentration polarization (10%–17%), while solid-phase and liquid-phase ohmic polarization is relatively negligible (<2%). On the other hand, cell polarization exhibits a non-linear trend with temperature. The lower the temperature, the greater the proportion of negative polarization, while positive polarization is insensitive to temperature. During low-temperature charging (−15°C), the solid-phase concentration polarization of the negative electrode accounts for the majority of electrode polarization (65%), which can be attributed to the larger lithium-ion concentration gradient induced by the sluggish diffusion of ions in the active material. An in-depth investigation of the polarization effect will provide guidance for achieving more efficient charging under different operating conditions.