Solvation Modulation Enhances Anion-Derived Solid Electrolyte Interphase for Deep Cycling of Aqueous Zinc Metal Batteries

Stable Zn anodes with a high utilization efficiency pose a challenge due to notorious dendrite growth and severe side reactions. Therefore, electrolyte additives are developed to address these issues. However, the additives are always consumed by the electrochemical reactions over cycling, affecting the cycling stability. Here, hexamethylphosphoric triamide (HMPA) is reported as an electrolyte additive for achieving stable cycling of Zn anodes. HMPA reshapes the solvation structures and promotes anion decomposition, leading to the in situ formation of inorganic-rich solid-electrolyte-interphase. More interestingly, this anion decomposition does not involve HMPA, preserving its long-term impact on the electrolyte. Thus, the symmetric cells with HMPA in the electrolyte survive & AP;500 h at 10 mA cm(-2) for 10 mAh cm(-2) or & AP;200 h at 40 mA cm(-2) for 10 mAh cm(-2) with a Zn utilization rate of 85.6 %. The full cells of Zn||V2O5 exhibit a record-high cumulative capacity even under a lean electrolyte condition (E/C ratio=12 & mu;L mAh(-1)), a limited Zn supply (N/P ratio=1.8) and a high areal capacity (6.6 mAh cm(-2)).

Automated summary

An electrolyte additive, hexamethylphosphoric triamide (HMPA), is reported for achieving stable cycling of Zn anodes. HMPA reshapes the solvation structures and promotes anion decomposition, leading to the in situ formation of inorganic-rich solid-electrolyte-interphase. Symmetric cells with HMPA in the electrolyte can survive over 500 hours at 10 mA cm(-2) or over 200 hours at 40 mA cm(-2) with a Zn utilization rate of 85.6%. Full cells of Zn||V2O5 exhibit a record-high cumulative capacity even under a lean electrolyte condition, limited Zn supply, and high areal capacity.