Water-Deactivating and Corrosion-Eliminating Acidic Electrolyte Additive for Highly Reversible Zn Anode

Abstract Aqueous zinc metal batteries (ZMBs) have emerged as a promising alternative to lithium-ion batteries, owing to their high theoretical capacity, low redox potential, and intrinsic safety. However, the Zn anode suffers from three interrelated critical issues (Zn dendrite growth, the hydrogen evolution reaction (HER), and corrosion reaction), which collectively impede the practical application of ZMBs. Herein, we focus on addressing HER and corrosion reaction via electrolyte modification to boost the overall performance of ZMBs. Pyrrolidone carboxylic acid (PCA), a natural moisturizing factor (NMF), was introduced as an additive into the ZnSO4 electrolyte, with two synergistic functions: (1) forming stronger hydrogen bonds with H2O molecules that reduce water activity to suppress HER; and (2) dissociating and creating an acidic environment that eliminates the corrosion products Zn4SO4(OH)6·xH2O and its analogs (collectively referred to as ZSH) to mitigate corrosion reaction. Benefiting from these effects, the Zn||Zn symmetric cell maintained stable cycling for 5000 h at 1 mA cm–2 and 1 mAh cm–2 (only 220 h without PCA), the Zn||Cu asymmetric cell exhibited a high coulombic efficiency of 99.66% at 1 mA cm–2 (only 98.30% without PCA), and the Zn||V2O5 full cell still delivered a high discharge capacity of 116.3 mAh g–1 at 1200th cycle at 5 A g–1 (only 69.7 mAh g–1 without PCA). This work provides a facile and eco-friendly strategy for constructing highly reversible Zn anodes and high-performance ZMBs.