Enabling Sodium‐Ion Batteries Over 180 Wh/kg via Organic‐Salt‐Driven Sodium Replenishment

Compensating for the substantial sodium ion deficit inherent in P2‐type layered sodium metal oxide cathodes represents a promising strategy for advancing high‐performance sodium‐ion batteries. However, current approaches still fail to reconcile the trade‐off between pre‐sodiation dosage and energy density. Herein, we introduce a soluble sodium compensator, sodium tetraphenylborate (NaBPh 4 ), rationally discovered through a combined unsupervised and supervised machine‐learning screening of boron‑centered anions, which can release sufficient sodium ions to replenish the entire sodium deficit of P2‐type oxides. In P2‐Na 0.67 Ni 0.08 Ti 0.12 Mn 0.8 O 2 || hard carbon full cells, this compensator endows the full cell with an ultra‐long cycle life exceeding 3700 cycles, while a 5 Ah pouch cell achieves a remarkable energy density of 184 Wh kg −1 at 0.1C. This work establishes a versatile strategy for addressing high sodium‐deficiency systems, thereby expanding the research scope and practical application potential of sodium‐ion full cells.