High-Capacity Layered Magnesium Vanadate with Concentrated Gel Electrolyte toward High-Performance and Wide-Temperature Zinc-Ion Battery

Abstract

Aqueous zinc-ion batteries (ZIBs) have emerged as the most promising alternative energy storage system, but the development of a suitable cathode and the issues of Zn anodes have remained challenging. Herein, an effective strategy of high-capacity layered Mg_0.1V₂O₅·H₂O (MgVO) nanobelts together with a concentrated 3 M Zn(CF₃SO₃)₂ polyacrylamide gel electrolyte was proposed to achieve a durable and practical ZIB system. By adopting the designed concentrated gel electrolyte which not only inherits the high-voltage window and wide operating temperature of the concentrated electrolyte but also addresses the Zn dendrite formation problem, the prepared cathode exhibits an ultrahigh capacity of 470 mAh g^-1 and a high rate capability of 345 mAh g^-1 at 5.0 A g^-1, and the assembled quasi-solid-state ZIBs achieve 95% capacity retention over 3000 cycles as well as a wide operating temperature from -30 to 80 °C, demonstrating a promising prospect for large-scale energy storage. <i>In situ</i> X-ray diffraction, X-ray photoelectron spectroscopy, and thermogravimetric analysis (TGA) investigations also demonstrate a complex reaction mechanism for this cathode involving the (de)insertion of Zn²⁺, H⁺, and water molecules during cycling. The water molecules will reinsert into the interlayer and act as "pillars" to stabilize the host structure when Zn²⁺ is fully extracted.