Long cyclic stability of acidic aqueous zinc-ion batteries achieved by atomic layer deposition: the effect of the induced orientation growth of the Zn anode

Aqueous Zn-ion batteries with economical ZnSO 4 solution as the electrolyte suffer from a tremendous tendency of dendrite formation under mildly acidic conditions; moreover, utilization of Zn(CF 3 SO 3 ) 2 delivers superior performance, but is expensive. Herein, we optimize the ZnSO 4 electrolyte by inducing 50 μL of 10 M sulfuric acid in 10 mL electrolyte, which can achieve long cycle life (1000 h at 0.1 mA cm −2 , 300 h at 1 mA cm −2 and 250 h at 10 mA cm −2 ) when the Zn foil is protected by three metallic oxides deposited by atomic layer deposition (ALD). The nucleation behaviour of the (002) facet has proved to play a critical role in the reversible lifespan. The Al 2 O 3 layer would restrict the stripping procedure, leading to the highest overpotential, while the TiO 2 layer and Fe 2 O 3 layer tended to strip all orientations but the (002) facet. Al 2 O 3 @Zn demonstrated a preference for a compact hillock-like (101) orientation texture in the deposition procedure, while TiO 2 @Zn and Fe 2 O 3 @Zn were favourable to obtain a smooth terrace texture. Additionally, symmetric cells with Fe 2 O 3 @Zn expressed the lowest overpotential (31.64 mV) and minimal voltage hysteresis (23.6 mV) at 1 mA cm −2 . A Zn-MnO 2 battery with Fe 2 O 3 @Zn also displayed superior capacity, which could reach 280 mA h g −1 at a current density of 1 A g −1 . The diffusion coefficient of Zn 2+ discloses that among the three ALD layers, full cells with Fe 2 O 3 @Zn are the most favourable for diffusion of Zn 2+ in acidic electrolyte. The relationships between the Zn orientation textures and ultrathin mental oxide layers deposited by atomic layer deposition were exposed in Zn-ion batteries.