An Environmentally Benign and Cost-Effective Modified Graphene Oxide/Sodium Alginate-Based Gel Electrolyte for Practical Quasi-Solid-State Zinc-Ion Batteries

Quasi-solid-state zinc-ion batteries (ZIBs) have attracted extensive attention owing to their intrinsic safety, low cost, and environmental sustainability. Sodium alginate (SA), as a natural polysaccharide, is a promising gel electrolyte matrix for sustainable ZIBs. However, the practical application of SA-based gel electrolytes is limited by insufficient ionic conductivity, unstable electrode/electrolyte interfaces, and uncontrolled Zn deposition. To address these problems, a modified graphene oxide/sodium alginate-based gel electrolyte (TCGSA) was prepared by incorporating TiO2/CaCO3 co-modified graphene oxide (TCGO) and erythritol (ER) into the SA matrix. The synergistic interaction among TCGO, ER, and SA was conducive to the transport of Zn2+ and the homogenization of interfacial ion flux, and the ionic conductivity of TCGSA was 23.8 mS·cm-1. Specifically, the polar TiO2-containing groups in TCGO provided additional Zn2+ interaction sites, while the hydrogen-bonding network formed by ER and SA enhanced the structural stability of the gel electrolyte and inhibited interfacial side reactions. When the TiO2 content in TCGO was 3.3 wt %, the Zn||MnO2 full cell assembled by the TCGSA gel electrolyte delivered a maximum capacity of 483 mAh·g-1 at 0.1 A·g-1 and retained 60.92% of its initial capacity after 1900 cycles at 2 A·g-1. Meanwhile, the Zn||Zn symmetric cell exhibited stable cycling for over 1200 h. The cost of the TCGSA pouch cell was relatively low (only $0.026 mAh-1) according to the estimation of raw material prices, and it was a potential candidate for the large-scale production of low-cost and environmentally friendly quasi-solid-state ZIBs.