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 (NaBPh4), 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-Na0.67Ni0.08Ti0.12Mn0.8O2 || 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.