OPTIMIZING ZNSO₄-LI₂SO₄ ELECTROLYTES FOR STABLE AQUEOUS ZINC-ION BATTERIES

Aqueous zinc-ion batteries (AZIBs) are considered as one of the most attractive candidates for safe, low-cost, and environmentally benign energy storage systems. However, the widespread implementation of these systems is still limited due to major problems with the zinc metal anode, including uncontrolled dendrite formation, hydrogen evolution, and the low reversibility of zinc plating and stripping. These issues lead to rapid capacity fading and shortened cycle life, highlighting the urgent need for electrolyte optimization as a simple and effective strategy to overcome anode instability. The purpose of this work was systematically investigated the electrochemical behavior of zinc anodes in a series of electrolytes with different ZnSO₄-Li₂SO₄ compositions, namely 2M ZnSO₄, 1.5M ZnSO₄ + 0.5M Li2SO₄, 0.5M ZnSO₄ + 1.5M Li₂SO₄, 1M ZnSO₄ + 1M Li₂SO₄, and 2M Li₂SO₄. The electrochemical performance was evaluated using cyclic voltammetry (CV) and galvanostatic charge-discharge tests, and then post-cycle morphological characterization was performed using scanning electron microscopy (SEM). The results show that adding Li₂SO₄ to the ZnSO₄ electrolyte significantly changes the structure of the Zn₂+ solution, thereby increasing the reversibility of zinc plating/stripping and suppressing dendrite formation. In particular, mixed electrolytes exhibit sharper voltage profiles and reduced polarization compared to single-salt systems. Among the tested formulations, the equimolar mixture of 1M ZnSO₄ + 1M Li₂SO₄ achieved the most balanced performance, delivering stable cycling and a uniform zinc dendrite morphology. This study highlights electrolyte engineering as a practical and scalable approach to stabilize zinc anodes, providing new insights into the design of high-performance aqueous zinc batteries for future large-scale energy storage applications.

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