Analyzing Suitability of Pulsing Techniques for Fast-Charging of Commercial Nmc811/Graphite Li-Ion Batteries

Fast-charging in lithium-ion batteries is recognized to speed up capacity deterioration and facilitate SEI layer growth, consequently reducing overall battery longevity. This study examines the impact of pulse-current constant-voltage (PCCV) charging on the performance and degradation of NMC811 lithium-ion batteries (LIBs) in comparison to the CC-CV approach. 10 unique experiments were performed, altering pulse frequencies, duty cycles, and peak current levels to assess their effects on charging duration, discharge capacity, SEI growth, and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Li}^{+}$</tex> concentration. Results indicate that the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.1 \text{Hz}, 50 {\%}$</tex> duty cycle PC-CV charging technique decreased charging duration by 9.1 % relative to the 1 C CC-CV method, while limiting capacity degradation to 4.4 Ah after 200 cycles, 6.9 % higher than CC-CV. This enhancement is attributed to the relaxation intervals during pulsing, which reduce the side reaction current density, enabling battery recovery and improving its overall efficiency. Impedance growth was significantly reduced, staying around <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$27 \mathrm{m} \Omega$</tex> compared to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$40 \mathrm{m} \Omega$</tex> for slower pulse rates. These results underscore the efficacy of improved PC-CV techniques in facilitating rapid charging while maintaining battery health, rendering them appropriate for fast-charging applications.