A novel 3D bacterial cellulose network as cathodic scaffold and hydrogel electrolyte for zinc-ion batteries

Aqueous zinc-ion batteries (ZIB) have been subject to intensive research, motivated by the high theoretical specific capacity and relatively low cost of metallic zinc. Nevertheless, cathode dissolution and structural instability result in slow Zn-ion migration dynamics and severe electrode degradation, impeding the development of ZIB. Herein, to our best knowledge, this is the first time a novel 3D bacterial cellulose (BC) network is successfully used as cathodic scaffold to provide sufficient ion pathways and stabilize the host material. Meanwhile, BC hydrogel electrolyte with high ionic conductivity and flexibility enables the use of ZIB in wearable applications. Carbon nanofibers (CNFs)@Mn₃O₄ are obtained through carbonization of BC network and pre-absorption of Mn salt. The CNFs@Mn₃O₄/BC electrolyte/Zn full cell possesses a low inner resistance and thus delivers a high capacity of 415.2 mAh g⁻¹ at 0.1 A g⁻¹. Further, the full cell shows excellent coulombic efficiency above 99% and capacity retention of 88.2% after 1000 cycles at high current density of 2 A g⁻¹. The charge storage mechanism and stability of assembled batteries, unveiled via ex-situ characterization, confirm the reversible diffusion of Zn²⁺. A flexible ZIB fabricated via facile lamination shows an outstanding energy density of 179 mAh g⁻¹ at 1 A g⁻¹, illustrating potential in wearable applications.