Regulating the Zn/Electrolyte Interface by Natural Proline Additive for Durable Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) have garnered significant attention as promising alternatives to traditional lithium-ion batteries in sustainable energy storage systems. However, their further development is hindered by critical challenges, such as severe dendrite growth and side reactions. Meanwhile, the performance improvement of AZIBs using common single-function electrolyte additives is limited. In this study, a natural proline with dual functionality is introduced to regulate the electrochemical properties of the interface, guide uniform deposition of Zn, regulate the solvation structure of Zn²⁺, and induce exposure of the Zn (002) surface. After testing, the modified Zn symmetric cell exhibits exceptional durability of more than 1700 h at 4.0 mA h cm^–2/1.0 mA cm^–2 and over 200 h at 50 mA cm^–2/10 mA h cm^–2. Furthermore, the Zn//MnO₂ full cell, which has a proline-containing electrolyte, demonstrates high specific capacity (294.3 mA h g^–1 at 0.3 A g^–1) and outstanding cycle stability with a high-capacity retention of 60% after 2000 cycles, much better than that of ZIBs with the pristine ZnSO₄ electrolyte. Zn//MnO₂ pouch cell (3.8 × 1.3 cm) also exhibits excellent cycling stability with a retention of 53.6% after 1000 cycles at a current density of 3 A g^–1. This research provides a multipurpose electrolyte additive that serves as an effective reference for advancing the capability of AZIBs.