Nanoporous CaCO₃ Coatings Enabled Uniform Zn Stripping/Plating for Long-Life Zinc Rechargeable Aqueous Batteries

Zn-based batteries are safe, low cost, and environmentally friendly, as well as delivering the highest energy density of all aqueous battery systems. However, the application of Zn-based batteries is being seriously hindered by the uneven electrostripping/electroplating of Zn on the anodes, which always leads to enlarged polarization (capacity fading) or even cell shorting (low cycling stability). How a porous nano-CaCO₃ coating can guide uniform and position-selected Zn stripping/plating on the nano-CaCO₃-layer/Zn foil interfaces is reported here. This Zn-deposition-guiding ability is mainly ascribed to the porous nature of the nano-CaCO₃-layer, since similar functionality (even though relatively inferior) is also found in Zn foils coated with porous acetylene black or nano-SiO₂ layers. Furthermore, the potential application of this strategy is demonstrated in Zn|ZnSO₄+MnSO₄|CNT/MnO₂ rechargeable aqueous batteries. Compared with the ones with bare Zn anodes, the battery with a nano-CaCO₃-coated Zn anode delivers a 42.7% higher discharge capacity (177 vs 124 mAh g⁻¹ at 1 A g⁻¹) after 1000 cycles.