NaNO3 Solubilization in Ester Electrolyte by CuCl2 Additives to Enhance the Stability of Hard Carbon Anode.

Cost-effective NaNO3 additive in the electrolyte shows an outstanding stabilizing effect on hard carbon anodes by forming a Na3N-rich solid electrolyte interface (SEI) film. However, the low solubility in solvent limits the effectiveness. In this study, a Cu2+ promoting NaNO3 cluster dissociation strategy is developed based on the strong coordination effect of Cu2+ on NO3-. With the addition of 0.0078 M CuCl2 in 1,2-dimethoxyethane (DME), the solubility of NaNO3 increases from 0.0137 to 0.0224 M. The electrolyte system with NaNO3 solubilization helps in the construction of a more NaF, Na3N, and NaCl-rich SEI film. Results show that these inorganics significantly enhance the ionic conductivity, electronic insulation, and mechanical properties of the SEI film and ensure that the SEI film on the hard carbon electrode surface remains structurally intact after long cycling, extending the battery life. As a result, after 300 cycles, the capacity retention of cells increases from 85.75% to 91.52%. This study develops a strategy to achieve nitrate solubilization and enhances the effectiveness of electrolyte interface engineering in improving battery performance.