Ion sieving function of MoS₂ and Alg-Zn hybrid coating endows high stability of Zn anode for aqueous Zn-ion batteries

Abstract

Aqueous Zn-ion batteries (AZIBs) have emerged as promising energy storage systems due to their high safety, low cost, and environmental friendliness. However, the practical application of zinc metal anodes is hindered by challenges such as Zn dendrite growth and side reactions, which degrade the cycle performance and energy efficiency of AZIBs. To address these issues, a facile and functional coating composed of zinc alginate gel (Alg-Zn) and 2H-molybdenum disulfide (2H-MoS₂) was used to modify the Zn anode (MAZ@Zn). Combined experimental and theoretical investigations reveal that, in addition to the Zn²⁺ guiding effect of ion conductive Alg-Zn, the 2H-MoS₂ functions as an ion sieve. This facilitates the fast Zn²⁺ migration and even distribution because of the lower ion migration energy along the MoS₂ surface, ensuring fast Zn²⁺ diffusion in the MAZ@Zn coating and uniform Zn deposition. Moreover, the barrier effect of MoS₂ against H₂O helps suppress side reactions such as hydrogen evolution, thereby further enhancing the interfacial stability of the Zn anode. As a result, the MAZ@Zn symmetric cells exhibit excellent cyclic stability, achieving a lifespan of 880 h at 1 mA cm^-2 and 1 mAh cm^-2, with low voltage polarization and low charge transfer energy. In contrast, the bare Zn anode only sustains 150 h of cycling under identical conditions. In Zn//sodium vanadate full batteries, the MAZ@Zn anode demonstrates outstanding performance, retaining 88.4% of its capacity after 1,000 cycles at 4 A g^-1. This work offers a simple and effective strategy for developing high-performance Zn anodes for long-life AZIBs.

Keywords

Aqueous Zn-ion batteries / uniform Zn deposition / zinc alginate / molybdenum disulfide / cycle stability