Cathode Depolarization Enables 1300‐Cycle Ah‐Level Anode‐Free Sodium Batteries

ABSTRACT Nonuniform sodium deposition limits the cyclability of anode‐free sodium batteries (AFSBs), and current research mainly focuses on anode‐targeted strategies. However, the influence of the cathode kinetics on sodium deposition behavior has been overlooked. Here, we firstly reveal the critical role of cathode polarization on sodium deposition uniformity via electric field coupling. Accordingly, cathode‐specific charging (CSC) protocols are established for AFSBs to depolarize the cathode, where the charging current is dynamically regulated based on the state of charge (SOC)‐dependent direct current inner resistance (DCIR). As expected, the CSC protocols effectively depolarize the cathodes and thus homogenize sodium deposition on the anode. Impressively, a 1.6 Ah Al/C||NFPP pouch cell reaches a record‐high cyclability of 1370 cycles at 2 C, and a 3.6 Ah pouch cell reaches a high energy density of 180 Wh kg − 1 with stable cycling for 890 cycles at 0.5 C. More importantly, the cathode depolarization strategy shows application universality for diverse anode‐free full cells based on Na 4 Fe 3 (PO 4 ) 2 (NFPP), Na 3 V 2 (PO 4 ) 3 (NVP), and NaNi 1/3 Fe 1/3 Mn 1/3 O 2 (NFM) cathodes. This work opens an avenue for fabricating durable practical AFSBs.