Tailoring Mn3O4 nanoparticle morphology via polyethylene glycol mediation for aqueous rechargeable zinc-ion batteries

Abstract

Aqueous rechargeable zinc-ion batteries (ARZIBs) are highly promising next-generation energy storage systems, yet their deployment is often hindered by sluggish cathode diffusion kinetics. Herein, morphology-tuned Mn₃O₄ nanoparticles were successfully synthesized via a facile, eco-friendly route employing polyethylene glycol (PEG 3350) as a structure-directing soft template. FESEM and TEM confirmed the formation of uniform spherical morphology. The engineered nanostructure exhibited an optical band gap of 3.87 eV and enhanced surface hydrophilicity, which significantly optimized electrolyte–electrode interfacial contact. When evaluated as an ARZIBs cathode, the cell demonstrated highly reversible Zn²⁺/H⁺ co-intercalation chemistry with a dominant diffusion-controlled pseudo-capacitive charge storage mechanism. Driven by initial phase transformation and electrochemical self-activation, the cathode delivered a remarkable peak specific discharge capacity of 274.82 mAh g⁻¹ at a current density of 0.1 A g⁻¹ and maintained a capacity retention of 76.12% after 500 cycles. EIS confirmed low initial charge-transfer resistance, validating the superior kinetics of the morphology-tailored cathode. This study highlights green morphology engineering as an effective paradigm to construct high-performance manganese-based cathodes for advanced ARZIBs applications.