Electrode Design and Interface Engineering for Boosting Electrochemical Performance of Aqueous Zinc-based Batteries

Abstract

Aqueous zinc-based batteries (AZBs) have emerged as promising next-generation energy storage systems due to the abundance of zinc, which expectedly should lower the battery cost. Additionally, Zn-based batteries will be environmentally sustainable and will be safer compared to the alkali metal counterparts based on lithium, sodium and potassium. Leveraging zinc as the anode provides a high theoretical specific capacity (820 mAh g⁻¹) and stable operation in aqueous electrolytes, mitigating risks associated with flammable organic solvents. Although various cathode materials, such as manganese oxides, vanadium-based compounds, and Prussian blue analogs, show potential for enhancing energy density and cycling stability, challenges like zinc dendrite formation, side reactions, and cathode instability remain untackled.1 This thesis explores a broad spectrum of aqueous zinc-based energy storage systems. The first part of the thesis, comprising of two chapters, focuses on zinc-air batteries. These offer high energy density, but the performance is restrained due to sluggish oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) kinetics.2 To address this, a bifunctional electrocatalyst was developed to efficiently catalyze both reactions, significantly enhancing battery performance.3 Furthermore, the ORR process was extended to an innovative application viz. the electrochemical generation of hydrogen peroxide (H₂O₂) for the on-site degradation of organic pollutants such as Rhodamine B.4 The second part of the thesis, comprising of three chapters, focusses on zinc-ion batteries. Here, the critical issues such as dendrite growth, byproduct formation, and cathode dissolution were dealt in detail.5 Electrolyte modifications with strategic additives altered the zinc-water solvation sheath [Zn(H₂O)₆], enabling reversible zinc stripping and plating without side reactions. 6 Usage of an alloying anode promoted 2D zinc nucleation, ensuring dendrite-free plating and improved sand time.7 On the cathode side, intrinsic (such as potassium doping of vanadium oxide) and extrinsic (graphene oxide wrapping) modifications resulted in enhanced conductivity and mitigated dissolution of vanadium-based cathodes like V₂O₅, improving stability and capacity. We envisage that the work accomplished as part of this thesis will aid in the advancement of the underlying Zn-redox processes across various Zn-based batteries. This will propel aqueous zinc-based batteries as possible alternative sustainable energy storage systems.