Critical Evaluation of Pulsed Current as a Fast‐Charging Strategy for Commercial NFPP and Hard Carbon Sodium‐Ion Pouch Cells

Pulsed current (PC) charging—which implies the use of an interrupted, time‐dependent current pattern—is increasingly mentioned in the literature as a fast‐charging strategy for lithium‐ion batteries (LIBs). Although many studies have investigated PC charging for LIBs, this work represents, to the best of our knowledge, the first instance in which PC charging is applied to sodium‐ion batteries (SIBs). Using a transparent measurement and evaluation protocol, we show that PC charging provides no apparent fast‐charging benefit for commercial Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) and hard carbon 40 20 35 pouch cells with 150 mAh nominal capacity. Compared to conventional constant current charging, PC charging results in an increased overpotential because higher current amplitudes are required to compensate for charging interruptions. In addition, PC charging does not effectively shorten the duration of a subsequent constant voltage step. We further discuss that PC protocols with high pulse frequencies (>100 Hz), often reported in scientific literature, may not be reliably generated due to instrumental limitations. Moreover, we illustrate that PC charging data must be interpreted carefully to avoid misleading conclusions about alleged fast‐charging benefits. This work contributes to the optimization of fast−charging protocols for the emerging commercialization of SIBs.