Three-dimensional cross-linked interface with high ionic transference number and electrical conductivity for high-performance aqueous Zn-ion batteries

Abstract

Aqueous zinc-ion batteries (AZIBs) have been the subject of considerable research due to their safety and energy density, but these processes are constrained by the growth of dendrites and interfacial side reactions. Herein, a three-dimensional cross-linked polypyrrole and microcrystalline cellulose (PPy/MCC) composites are fabricated through the force of hydrogen bonding on the surface of zinc anodes. The distinctive cross-linking conductive network could enhance the Zn²⁺ transport process and storage, ensuring uniform charge distribution and further elevating the Zn²⁺ transference number. The abundant functional groups of PPy/MCC offer numerous zincophilic nucleation sites thereby promoting uniform zinc deposition. Additionally, the hydrophobic PPy/MCC coating acts as a barrier, shielding the zinc anode from the aqueous electrolyte and effectively inhibiting side reactions like corrosion and hydrogen production. Consequently, the zinc anode coated with the PPy/MCC layer (PPy/MCC@Zn) achieves steady and reversible Zn cycling. The PPy/MCC@Zn//PPy/MCC@Zn symmetric batteries harvest a long cycling stability exceeding 3400 h at a current density of 1 mA cm⁻², 1 mAh cm⁻². The PPy/MCC@Zn//Cu battery achieves a remarkable average Coulombic efficiency (CE) of 99.48 % at 2 mA cm⁻², 2 mAh cm⁻². The practical full battery, coupled with the I₂- activated carbon (AC) cathode, also demonstrates stable performance over 4000 cycles.