Key Takeaways & Executive Findings
- •• Developed an entropy-enhanced AgCuZnSnS4 loaded graphite felt (ACZTS/GF) electrode via in-situ solvothermal synthesis, achieving high energy efficiency of 88.5% at 20 mA·cm−2 and a maximum power density of 119.8 mW·cm−2 in polysulfide/iodide flow batteries. • Introduced a targeted orbital hybridization-optimized electron density strategy that enhances catalytic activity by modulating electronic density of states and promoting synergistic effects among multinary components. • Demonstrated that multicomponent sulfides with high configurational entropy significantly improve interfacial charge transfer kinetics and bulk conductivity, overcoming sluggish iodide redox kinetics. • Achieved excellent long-term cycling stability with only 5% degradation, highlighting the practical viability of the engineered electrode for large-scale energy storage applications.
Abstract
Despite their attractive features of high energy density, low cost, and safety, polysulfide/iodide flow batteries (SIFBs) are hampered by the sluggish kinetics of the iodide redox couple, which restricts overall performance. Multicomponent sulfides are demonstrated as promising catalysts for accelerating redox reactions. Concurrently, the enhanced configurational entropy arising from multinary compositions drives synergistic effects among constituent elements, establishing a viable pathway to optimize catalytic performance. Building on these foundations, this work introduces a targeted orbital hybridization-optimized electron density strategy to enhance the catalytic activity. Implementing this concept, we developed an in-situ solvothermal synthesis process for an entropy-enhanced AgCuZnSnS4 loaded graphite felt (ACZTS/GF) electrode. The engineered electrode demonstrates exceptional electrocatalytic performance with improved bulk conductivity and interfacial charge transfer kinetics within a SIFB. The cell achieves a high energy efficiency of 88.5% at 20 mA·cm−2 with 10% state-of-charge. Furthermore, the battery delivers a maximum power density of 119.8 mW·cm−2 and exhibits excellent long-term cycling stability. These significant results stem from orbital hybridization-driven electronic state optimization and entropy effect-induced synergistic catalysis.
1. Introduction
Rising global energy demand and accelerating renewable integration underscore the urgent need for efficient, cost-effective large-scale energy storage. Among aqueous redox flow batteries (RFBs)—noted for intrinsic safety and scalability—polysulfide/iodide redox flow batteries (SIFBs) emerge as a leading candidate, distinguished by their synergistic combination of high energy density, environmental benignity, and low material costs. However, the I−/I3− redox chemistry suffers from intrinsically sluggish kinetics [1–2], characterized by elevated polarization resistance and poor reaction reversibility, which can limit the overall performance. Consequently, the development of efficient and stable catalytic electrodes capable of accelerating the sluggish redox transformations of these couples is paramount for unlocking the full potential of SIFBs.
Multicomponent sulfides are promising catalysts, enabled by the sulfur anion’s large ionic radius and high polarizability, which lead to distinct metal–sulfur bonding characteristics. For instance, quaternary sulfides such as stannite-type Cu2ZnSnS4 [3] and wurtzite-derived Cu2ZnGeS4 [4] nanocrystals demonstrate significantly superior electrocatalytic activity for the I−/I3− compared to their unary or binary sulfides. As evidenced by recent studies, highly active catalysts like NiCo2S4 [5] and CuFeS2 [6] significantly boost SIFB performance by enhancing I−/I3− kinetics. The synergistic interplay between multivalent metal centers and sulfur ligands in these materials facilitates efficient charge transfer and reduces polarization losses in SIFB.
Critically, the configurational entropy inherent in multinary systems drives synergistic effects that optimize catalytic performance [7–8]. Increased cationic diversity facilitates cooperative interactions between metal sites, dynamically tailoring charge distribution [9]. For example, (FeCoNiCuZn)N demonstrates improved catalytic kinetics and durability, directly attributed to its configurational entropy-optimized electronic structure [10]. This entropy-mediated synergy enhances active-site electronic states and accelerates interfacial charge transfer kinetics. Concurrently, compositional flexibility enables precise engineering of band structures and defect landscapes. Through strategic modulation of cation identity and stoichiometry, multicomponent sulfides achieve tailored electronic configurations that fulfill specific catalytic requirements.
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Wenjing Li, Renhua Qian, Boxu Dong, Zhou Xu, Changyu Yan, Menghan Yang, Yuxuan Liu, Xinrui Yan, Jiantao Zai, Xuefeng Qian (2025). Orbital hybridization-engineered electronic structure in multicomponent sulfides boosts the performance of polysulfide/iodide flow batteries. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-025-3268-6
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Frequently Asked Questions
What is the main challenge in polysulfide/iodide flow batteries (SIFBs) addressed in this study?
The main challenge is the sluggish kinetics of the iodide redox couple (I−/I3−), which restricts the overall performance of SIFBs. The study introduces an orbital hybridization-engineered multicomponent sulfide electrode to accelerate these redox reactions.
How does the AgCuZnSnS4 loaded graphite felt (ACZTS/GF) electrode improve battery performance?
The ACZTS/GF electrode enhances catalytic activity through orbital hybridization-optimized electron density and entropy-induced synergistic effects. It improves bulk conductivity and interfacial charge transfer kinetics, leading to a high energy efficiency of 88.5% at 20 mA·cm−2 and a maximum power density of 119.8 mW·cm−2.
What is the significance of configurational entropy in multicomponent sulfides for catalysis?
Configurational entropy in multicomponent sulfides drives synergistic effects among constituent elements, optimizing catalytic performance. It enhances active-site electronic states and accelerates interfacial charge transfer kinetics, as demonstrated by improved kinetics and durability in catalysts like (FeCoNiCuZn)N.
What synthesis method was used to prepare the ACZTS/GF electrode?
The ACZTS/GF electrode was prepared via an in-situ surfactant-free solvothermal synthesis process, which allowed for the controlled growth of AgCuZnSnS4 on graphite felt, resulting in enhanced catalytic properties.
What are the key performance metrics achieved by the SIFB with the ACZTS/GF electrode?
The SIFB achieved an energy efficiency of 88.5% at 20 mA·cm−2 with 10% state-of-charge, a maximum power density of 119.8 mW·cm−2, and excellent long-term cycling stability with only 5% degradation, representing an 11.3% improvement over pristine carbon electrodes.
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