BiOIO₃@Zn₃(PO₄)₂·4H₂O Heterojunction with Fast Ionic Diffusion Kinetics for Long-Life "Rocking-Chair" Zinc Ion...

Increasing insertion host materials are developed as high-performance anodes of "rocking-chair" zinc ion batteries. However, most of them show unsatisfactory rate capabilities. Herein, layered BiOIO₃ is reported as an excellent insertion host and a zinc ion conductor, i.e., Zn₃(PO₄)₂·4H₂O (ZPO), is introduced to construct a BiOIO₃@ZPO heterojunction with a built-in electric field (BEF). Both ZPO and a BEF obviously enhance Zn²⁺ transfer and storage, which is proven by theoretical calculations and experimental studies. The conversion-type mechanism of BiOIO₃ is revealed through ex situ characterizations. The optimized electrode exhibits a high reversible capacity of 130 mAh g^-1 at 0.1 A g^-1, a low average discharge voltage of 0.58 V, an ultrahigh rate performance with 68 mAh g^-1 at 5 A g^-1 (52% of capacity at 0.1 A g^-1), and an ultralong cyclic life of 6000 cycles at 5 A g^-1. Significantly, the BiOIO₃@ZPO//Mn₃O₄ full cell shows a good cyclic life of 67 mAh g^-1 over 1000 cycles at 0.1 A g^-1. This work provides a new insight into the design of anodes with excellent rate capability.