Innovative Zn-I₂ Battery Design Achieves High Capacity and Durability with Enhanced Electrocatalysis
- A novel zinc-iodine (Zn-I₂) battery design using Molybdenum carbide (MoC) nanoclusters embedded in porous nitrogen-doped carbon fibers with atomic Zn-N4 sites has been developed to overcome the limitations of iodine. This design enhances electron and ion transfer efficiency, enabling reversible redox conversion while preventing polyiodide shuttle effects.
- The new battery structure, known as Zn-SA-MoC/NCFs, achieves an impressive capacity of 230.6 mAh g⁻¹ and maintains 90% of its capacity after 20,000 cycles, demonstrating both high performance and durability.
Overcoming Iodine’s Limitations in Zinc-Iodine Batteries
- Aqueous zinc-ion batteries (ZIBs) are gaining attention due to their high safety, environmental compatibility, and the widespread availability of raw materials. Iodine, abundant in seawater, has high theoretical capacity (211 mAh g⁻¹) and a favorable redox potential (0.54 V), making it an attractive candidate for use in zinc-iodine batteries. However, its low electrical conductivity and the formation of soluble polyiodides that migrate to the zinc anode have hindered efficient redox conversion and caused capacity degradation.
A Novel Approach to Enhance Performance
- To overcome these challenges, the research team developed an innovative method to encapsulate molybdate ions into zeolitic imidazolate framework-8 (ZIF-8), followed by electrospinning and calcination. This process created free-standing porous carbon fibers integrated with Zn single-atom sites and MoC clusters (Zn-SA-MoC/NCFs). The hierarchical porous carbon framework facilitated mass transfer, and the combination of molybdenum carbide and single-atom catalysts enhanced iodine species adsorption and modulated catalytic activity, improving charge redistribution.
- The assembled Zn-I₂ batteries demonstrated a large specific capacity of 230.6 mAh g⁻¹ at a current density of 0.5 C and showed excellent retention, maintaining 90% of their capacity after 20,000 cycles.
Broader Implications and Future Prospects
- This study is the first to demonstrate how the electrocatalytic activity of MoC clusters can be enhanced through the incorporation of Zn-N4 sites for iodine redox reactions. The strategy of electronic structure modulation provides valuable insights for creating advanced iodine catalysts and optimizing battery performance, marking a significant advancement in the development of high-performing Zn-I₂ batteries.
