Sodium Acetate as Residual-Free Presodiation Additive for Enhancing the Energy Density of Sodium-Ion Batteries

Sodium-ion batteries (SIBs) suffer from undesirable initial Coulombic efficiency caused by irreversible sodium loss at the anode. Here, we utilized sodium acetate (NaAc) as a sacrificial material to provide extra sodium. A noteworthy aspect of the NaAc additive generates gas, thus forming the pores within the electrode that enhance ion movement. The elimination of gas ensures that the cycling stability remains uncompromised, resulting in a substantial improvement in the rate performance of the presodiated electrode. Electrochemical simulations reveal a more uniform local current density to enhance the capacity utilization of a thick presodiated electrode. The "dead mass" of the NaAc additive can be eliminated following the release of sodium ion and gas. As a result, the Na3V2(PO4)3–10%NaAc || hard carbon pouch cell shows an increase in energy density, a 38% improvement over that without the additive. Our findings provide a new perspective on the cathode additives for sodium compensation to achieve high-energy-density SIBs.