Tailoring zincophilicity via amorphous Se-rich selenides coating for stable Zn anode

Abstract

Aqueous Zn-ion batteries (AZIBs) are being extensively studied for promising energy storage applications owing to their advantages of excellent safety, and high theoretical capacity. Nevertheless, the Zn anode in electrolytes obstinately suffers from irreversibility issues, e.g., the low coulombic efficiency and dendrite growth during cycling. Thus, it remains a severe challenge to obtain high cycling stability of Zn anodes. Tuning zincophilicity has been a high-interest topic as a class of Zn anode optimization. Herein, tailoring zincophilicity via amorphous Se-rich selenides coating for a stable Zn anode is reported. The Zn foils were surface-modified by coating with intrinsic zincophobic selenide (i.e., WSe2 and MoSe2, resulting in WSe2-Zn and MoSe2-Zn, respectively). Interestingly, a Se-rich layer with a particular amorphous structure was manufactured on the Zn anode. The enrichment of Se was electrochemically induced to form ZnSe, which improves zincophilicity of the Zn anode and provides nucleation sites for Zn ions. Accordingly, homogeneous deposition and exfoliation of Zn ions were promoted, and the growth of Zn dendrites during cycles was inhibited. Along with suppressed side-product generation, the outputs of AZIBs with modified electrodes were vastly improved. The symmetric batteries with selenides exhibit a low polarization and prolonged life over 1700 h. Besides, it is shown that the specific capacity and stability of the full batteries using sodium vanadate as cathodes are remarkably enhanced by selenide modification. Further, when assembled with Mn-based cathodes, good capacity retention (77.5% for WSe2-Zn, 74.7% for MoSe2-Zn, and 49.5% for pristine Zn) at 2 A/g was achieved over 3500 cycles. A facile route to tune intrinsic zincophobicity into zincophilicity is demonstrated, which brings about massive opportunities for developing high-performance electrode materials for AZIBs.