The Preparation of Moldable Zinc-Ion Batteries Using Graphene Oxide Doughs

The increasing demand for electric vehicles has ignited a pursuit to enhance their energy density while simultaneously reducing manufacturing costs. Compared with Li-ion batteries, aqueous Zn-ion batteries show tremendous potential due to their attractive characteristics of having a high theoretical capacity (820 mAh g⁻¹) and a low potential (-0.76 V vs SHE). Furthermore, coupled with its safety and environmental friendliness advantages, this renders it with significant potential for large-scale applications. In this work, we use graphene oxide (GO)/carbon nanotube (CNT)/cellulose nanofibrils (CNF) composite dough as the 3D scaffold for the electrode. The composite dough is a binder-free and self-sustaining structure with moldable features. The characteristics of arbitrary shapes, highly processable and tunable microstructures endow it with significant potential for diversified applications. The composite dough combines the advantages of three different carbon materials. GO possesses a large surface area and, after annealing, maintains structural integrity to prevent collapse. CNT prevents the aggregation of GO after reduction and enhances the ionic conductivity of the composite. CNF improves the mechanical strength of the composite and its abundant hydroxyl groups enable the dough to maintain the viscoelastic state at high water content up to 90 wt%. The composite dough is then transformed into an electrode scaffold characterized by high porosity, excellent conductivity, and a large surface area. The anode features Zn powders (ZPs) integrated into the composite dough-based electrodes, which enhances control over the N/P ratio. However, zinc anodes normally suffer from issues including hydrogen evolution and corrosion. Coating TiO₂ nanoparticles onto the surface of the dough not only protects the ZPs from side reactions but also suppress dendrite growth. In addition, TiO₂ can also enhance the electrode’s hydrophilicity, zincphilicity, and facilitate Zn ion diffusion. On the cathode side, α-MnO₂ is used as the active material and is incorporated into the composite dough. Our results indicate that the MnO₂@composite dough-based electrode has higher gravimetric capacity and cycle stability compared to the MnO₂@carbon paper. The improved contact between MnO₂ and composite scaffold leads to enhanced charge transfer. The ZPs/TiO₂@composite||MnO₂@composite dough-based cell exhibits more stable cycle performance and higher discharge capacity than those of ZPs@carbon paper||MnO₂@carbon paper cell. This work offers an alternative approach for fabricating 3D and moldable electrodes, broadening the horizons for 3D electrodes in high-performance energy storage devices.