Enhancing the Initial Coulombic Efficiency of Sodium‐Ion Batteries via Highly Active Na₂S as Presodiation Additive

Abstract

Recently, sodium‐ion batteries (SIBs) have received considerable attention for large‐scale energy storage applications. However, the low initial Coulombic efficiency of traditional SIBs severely impedes their further development. Here, a highly active Na2S‐based composite is employed as a self‐sacrificial additive for sodium compensation in SIBs. The in situ synthesized Na2S is wrapped in a carbon matrix with nanoscale particle size and good electrical conductivity, which helps it to achieve a significantly enhanced electrochemical activity as compare to commercial Na2S. As a highly efficient presodiation additive, the proposed Na2S/C composite can reach an initial charge capacity of 407 mAh g−1. When 10 wt.% Na2S/C additive is dispersed in the Na3V2(PO4)3 cathode, and combined with a hard carbon anode, the full cell achieves 24.3% higher first discharge capacity, which corresponds to a 18.3% increase in the energy density from 117.2 to 138.6 Wh kg−1. Meanwhile, it is found that the Na2S additive does not generate additional gas during the initial charging process, and under an appropriate content, its reaction product has no adverse impact on the cycling stability and rate performance of SIBs. Overall, this work establishes Na2S as a highly effective additive for the construction of advanced high‐energy‐density SIBs.

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

“…This leads to only marginal enhancements in the full-cell performance. NaN 3 , Na 2 O, Na 3 P, and Na 2 S are unstable in air and require the preparation of electrodes in a glovebox, a cumbersome process that limits their large-scale application. Organic sodium salts, many of which are electrochemically unstable at high voltages, undergo irreversible decomposition to release sodium ions. , Furthermore, organic sodium salts are readily accessible, cost-effective, and environmentally friendly and offer promise for sodium replenishment in this context.…”