Dandan Li,Ying-Jie Zhu,Long Cheng,Sida Xie,Han-Ping Yu,Wei Zhang,Zhenming Xu,Ming-Guo Ma,Heng Li
Achieving both high iodine loading cathode and high Zn anode depth of discharge (DOD) is pivotal to unlocking the full potential of energy-dense Zn-I 2 batteries. However, this combination exacerbates the detrimental shuttle effect of polyiodide intermediates, significantly impairing the battery's reversibility and stability. Herein, this study reports an advanced high-loading iodine cathode (denoted as MX-AB@I) enabled by a multifunctional Ti 3 C 2 T x MXene modulator, which presents high stability and energy density in Zn-I 2 batteries. Through comprehensive experimental and theoretical analyses, the intrinsic regulating mechanisms are elucidated by which the MXene modulator effectively suppresses polyiodide shuttling, enhances iodine conversion kinetics, and dramatically improves Zn anode reversibility. With the aid of the MXene modulator, the MX-AB@I composite cathode achieves a high iodine mass loading of 23 mg cm −2 and realizes a practically high areal capacity of 4.0 mAh cm −2 . When paired with a thin Zn anode (10 µm), this configuration realizes a high Zn DOD of 78.7% and a high energy density of 171.3 Wh kg −1 , surpassing the majority of Zn-I 2 battery systems reported in the literature. This study presents an effective approach to designing high-loading iodine cathodes for Zn-I 2 batteries by leveraging MXene modulators to regulate critical electrochemical reaction processes.
Aqueous zinc(Zn)-metal cells with cost-effective components and high safety have long been a promising large-scale energy storage system, but Zn anodes are intrinsically unstable with common aqueous electrolytes, causing substantial underutilization of the theoretical capacity. In this work, we report a strictly neutral aqueous Zn electrolyte at a low cost by leveraging the dynamic hydrolysis equilibrium of a dual-salt Zn(Ac) 2 /NaAc(Ac: CH 3 COO − ) formulation. With the pH regulation, the corrosion and hydrogen evolution encountered in Zn anodes can be suppressed significantly. This hybrid aqueous electrolyte not only enables dendrite-free Zn plating/stripping at a nearly 95% Coulombic efficiency[an increase of 24% compared to that of the single-salt 1 mol/L Zn(Ac) 2 electrolyte], but also supports the reversible operation of Zn cells paired with either Na 3 V 2 (PO 4 ) 3 or iodine cathodes—the former delivers a high output voltage of 1.55 V with an energy level of 99.5 W·h/kg(based on the mass of the cathode), and the latter possesses a high specific capacity of 110.9 mA·h/g while yielding long-term cyclability(thousands of cycles). These findings open up a new avenue of modifying practical electrolytes having targeted properties to stabilize multivalent metal anodes.
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