Organic Fillers Regulating the Solvation Structure of Zinc Ions in Aqueous Electrolytes for High-Stability Zn²⁺/Li⁺ Hybrid Batteries

The aqueous hybrid ion batteries, due to electrode advantages combined with different battery systems, are promising energy storage systems. The severe side reaction caused by a highly active aqueous electrolyte is the key challenge that restricts its practical application. Exploring the microstructure of the electrolyte is of great significance to improving the electrochemical performance. Herein, the regulation mechanism of acylamide groups in an aqueous electrolyte is deeply investigated. Due to the strong coordination ability and hydrophilicity of the acylamide group, the solvation structure of cations can be regulated, and the activity of water molecules can be weakened by hydrogen bonds. Therefore, the Zn²⁺ plating/stripping process on the anode side can be orderly regulated, and the stability of the crystal structure of the cathode also could be significantly improved. Consequently, after adding 5% polyacrylamide into the electrolyte, the zinc anode can withstand long-term plating/stripping over 120 h at 1 mA cm^–2 and 0.25 mA h cm^–2. Also, the LiFePO₄ cathode could achieve a capacity resistance of 82% after 350 cycles at 0.5 A g^–1, far higher than the 24% of pure liquid electrolytes. This work provides a helpful guidance for designing the next generation of hybrid ion electrolytes.