Identification of Lithium-Ion Battery Degradation Mechanisms During Pulsed Current Charging Through Non-invasive and Post-Mortem Analysis

Considering various parameters of frequency, duty cycle, offset, and pulse waveform, many pulse current charging strategies have been designed for lithium-ion batteries. However, the battery degradation mechanism of lithium-ion batteries with varied parameters is still unclear. To fill this gap, improved non-invasive and post-mortem diagnosis techniques are utilized with pulsed current charging. To explore the effect of different factors on battery aging, differential voltage analysis is investigated as a non-invasive battery diagnostic method. To express the degradation inside the battery intuitively, X-ray powder diffraction, Raman, and scanning electron microscope are performed for the fresh and aged electrodes as a comprehensive tool. The effect of duty cycles on battery degradation is analyzed from multiple perspectives by differential voltage analysis, internal resistance, electrochemical impedance spectroscopy, X-ray powder diffraction, Raman, and scanning electron microscope. Experimental results show that a pulse current with a frequency of 0.05 Hz and a duty cycle of 50% can achieve a 108% increase in capacity compared to traditional constant current charging. With the help of invasive testing, the main reason for an extended lifetime of batteries under pulsed conditions is found: the effective suppression of the growth of interfacial impedance. The proposed method provides a broad reference value for the future application of pulse charging strategy to extend battery lifetime as well as whole-life-cycle safety guarantee.