High-adhesion zinc anode protective film with metal-ion-doped conductive polymer-coated carbon nanotubes for zinc ion batteries

Owing to their high safety, aqueous Zn-ion batteries are suitable for use in energy storage systems. Their stability and lifespan can be increased by enhancing the degradation properties of the anode, such as corrosion, hydrogen generation, and dendrite formation. Importantly, the functionality and durability of the Zn anode's protective layer, provided to prevent damage to the anode from mildly acidic electrolytes, should be enhanced. Here, we propose a high-adhesion protective film Zn-doped-polypyrrole-coated CNT film for the anode. The polypyrrole (PPy) coating is well integrated with the CNT and facilitates strong adhession between the protective film and the Zn anode surface. Furthermore, Zn doping of PPy increases the polymer's electrical conductivity and adsorption energy as well as the number of nucleation sites, leading to uniform Zn deposition. This was observed through experimental studies and density functional theory calculations. A high-adhesion Zn anode with an optimized protective film exhibited a high specific capacity of 199 mAh g⁻¹ at 0.3 C and an excellent rate capability of 94 mAh g⁻¹ at 2.0 C. Thus, Zn-doped-PPy-coated CNT film is a promising protective material for Zn anodes.