Samarium ion-induced interfacial regulation to construct high-performance anodes for aqueous zinc metal batteries

Abstract

Zinc metal batteries (ZMBs) are attracting wide attention due to their high safety, low cost and environment-friendly nature. Nevertheless, the loose deposits and dendrites on Zn anodes significantly hinder the cycling life of ZMBs. Herein, we propose the incorporation of samarium chloride (SmCl₃) as an additive into an aqueous electrolyte to construct ZMBs. The SmCl₃ additive diminishes the thickness of the electric double layer (EDL) on the Zn anodes to minimize the repulsive forces between Zn deposits and thus promote the dense deposition of metallic Zn. Furthermore, the Sm³⁺ ions are not only preferentially adsorbed at the active sites (i.e. the protrusions of Zn anodes) to effectively suppress the formation of Zn dendrites but also optimize the Zn²⁺ ion diffusion rate and inhibit the existence of highly active water molecules on the surface of the Zn anodes to reduce the side reactions. Hence, Zn‖Zn symmetric batteries containing the SmCl₃ additive stably operate for 2100 h at 2 mA cm⁻² and even show stable discharge/charge curves for 100 h under a high current of 50 mA cm⁻². HNaV₆O₁₆·4H₂O (HNVO)-based ZMBs with the SmCl₃ additive achieve a high initial discharge capacity (257 mA h g⁻¹) and remarkable cycling life (1000 cycles) at 1 A g⁻¹ and also show a good capacity retention of 96.39% after 36 h of resting. When combined with polyaniline (PANI) cathodes, the corresponding SmCl₃-based battery also displays good cycling performance (1000 cycles at 5 A g⁻¹). This work highlights the multi-functions of rare earth metal-based additives in aqueous ZMBs.