A New strategy for stabilizing zinc metal Anodes: Using grain boundaries to strengthen grain boundaries

Aqueous zinc ion batteries are considered one of the promising electrochemical energy storage. However, as a polycrystalline active metal, the corrosion of Zn anode in non-neutral solutions hinders the application, especially in the weak acid system, where the grain boundaries (GB) of the Zn are more susceptible to the erosion of H⁺. In this paper, we reveal the corrosion behavior of the GB and demonstrate that GB atoms have high activity, which is the weak link of the corrosion. It is proposed to fully utilize the high reactivity of GB to construct Zn anode with the GB strengthed by TiO₂ (S-Zn). Experimental and theoretical calculations have demonstrated that TiO₂ can stabilize the outer electrons of the Zn atoms and reduce the depolarizing effect of H⁺, while TiO₂ with wide bandgap enriched in the GB can serve as an electron-blocking layer to improve the intergranular impedance, inhibit intergranular corrosion. Benefiting from above, S-Zn can be deposited stably up to 300 h at a current density of 0.1 mA cm⁻², and the symmetric cell can be cycled 6, 000 times at 10 mA cm⁻². The full cell using MnO₂ cathode can be cycled more than 800 times with a capacity retention of 92.7 %.