High-rate laminar Zn plating in aqueous zinc batteries: from S-PANI grafted bacterial cellulose to a stable metal anode

Abstract

A self-assembled BC scaffold, derived from natural sources, regulates Zn²⁺ electrodeposition in rechargeable aqueous zinc-ion batteries (RAZIBs). Like plant cellulose, BC consists of glucose units linked by β-1,4-glycosidic bonds, forming a porous fibrous biopolymer, (C₆H₁₀O₅)_n. The hydroxyl-rich surface of BC provides abundant coordination sites for Zn²⁺, facilitating chemisorption and improving interfacial ion transport. A biodegradable interlayer was crafted by grafting S-PANI onto BC to mitigate anode degradation. The presence of –SO₃H groups on the aromatic rings of S-PANI significantly reduces the surface contact angle with water, transforming the polymer from a hydrophobic to a hydrophilic state. Furthermore, due to the low pK_a of the ring-substituted sulfonic acid groups, these moieties undergo complete deprotonation even in neutral aqueous media, yielding fixed anionic –SO₃⁻ sites along the polymer chain. These immobilized sulfonate anions act as intramolecular dopants, protonating the imine nitrogen atoms of the polyaniline (PANI) backbone, thereby inducing self-doping that stabilizes the conducting emeraldine salt form. It also promotes flat Zn²⁺ nucleation and suppresses parasitic hydrogen evolution reaction (HER) by regulating proton activity. Symmetric Zn‖Zn cells incorporating this interlayer exhibited stable cycling beyond 2000 h at a constant current density and specific capacity of 1 mA cm⁻² and 1 mA h cm⁻², respectively. Zn‖Prussian blue analog (PBA) full cells rendered approximately 99.00% coulombic efficiency (CE) and 97.98% capacity retention after 5000 cycles at 1 A g⁻¹. This eco-friendly, scalable approach leverages bio-derived nanomaterials to enhance the durability and electrochemical performance of Zn-based batteries.