A Comprehensive Strategy Enables High-Loading BiOBr@BiOIO3 Cathodes for Quasi Ah-Level Aqueous Zn-Ion Batteries.

Abstract

Aqueous Zn-ion batteries (AZIBs) recently have attracted broad attention. To achieve high energy density of AZIBs, constructing high-loading cathodes is the prerequisite. However, the cycling stability of high-loading cathodes still faces great challenges. Herein, a comprehensive strategy is proposed to improve the structural stability of the cathode material and mechanical stability of the high-loading cathode. The BiOBr@BiOIO₃ heterostructure are successfully constructed via sharing the interfacial oxygen atoms, in which the interfacial effect can effectively enhance the reaction dynamics and structural stability. Meanwhile, a biomimetic binder is skillfully designed via in situ dual cross-linking between guar gum and cation ions to achieve the application of water-based and sustainable polymer binder in AZIBs. Density functional theory calculations demonstrate the guar gum possesses strong affinity toward BiOBr@BiOIO₃ to firmly adhere the active materials. Quantitative nanomechanic technology visually demonstrates the robust mechanical properties of the as-obtained BiOBr@BiOIO₃ cathode. As a result, when the active material loading increases to as high as 100.71 mg cm^-2, an ultrahigh areal capacity of 20.02 mAh cm^-2 can be achieved. Specially, a quasi-Ah-level (0.244 Ah) pouch-type cell with a loading of 1.17 g can be constructed, showing the practical application potential.