A Biomimetic Bidirectional Interphase Enabled by a Single Molecule for Ultra‐Stable Zn‐I2 Batteries

Why It Matters

By solving dendrite growth, HER, and polyiodide shuttle with one additive, SCS dramatically improves the lifespan and energy density of Zn‑I2 batteries, positioning them as a viable, low‑cost option for grid‑scale storage.

Key Takeaways

• Sodium camphorsulfonate serves as a bidirectional electrolyte additive
• SCS guides (002)‑oriented Zn deposition and suppresses hydrogen evolution
• SCS strongly binds polyiodides, blocking shuttle at the I2 cathode
• Full cell retains 154 mAh g⁻¹ after 26,000 cycles at 5 A g⁻¹
• Pouch cell delivers 175 mAh g⁻¹ after 500 cycles with high‑loading cathode

Pulse Analysis

Zinc‑iodine batteries have attracted attention for large‑scale energy storage because they combine aqueous safety with high theoretical capacity. Yet practical deployment has been hampered by three intertwined problems: dendritic Zn growth that pierces separators, hydrogen evolution that wastes charge, and the polyiodide shuttle that erodes cathode performance. Conventional solutions typically involve separate additives or complex electrode engineering, adding cost and manufacturing steps. The introduction of a single, inexpensive molecule that can simultaneously address all three challenges marks a notable shift in battery chemistry design.

Sodium camphorsulfonate (SCS) draws inspiration from biomimetic surface‑active agents. In the electrolyte, SCS participates in Zn²⁺ solvation, reducing the activity of free water and thereby suppressing the hydrogen evolution reaction. Its sulfonate head preferentially adsorbs on Zn, aligning crystal growth along the (002) facet, which is less prone to dendrite formation. On the cathode side, the camphor backbone exhibits strong affinity for iodine species, anchoring polyiodides and preventing their migration. This creates a protective interphase on both electrodes without the need for additional coatings or separators.

The performance gains are striking: a symmetric Zn cell operated for 1,449 hours at 5 mA cm⁻², while a full Zn‑I2 cell maintained 154 mAh g⁻¹ after 26,000 cycles at a high current of 5 A g⁻¹. Moreover, a pouch prototype with a thin 20 µm Zn foil and a high‑loading 10.5 mg cm⁻² cathode delivered 175 mAh g⁻¹ after 500 cycles, demonstrating scalability. These results suggest that SCS could lower the cost barrier for aqueous batteries, offering a durable, high‑energy solution for renewable integration and peak‑shaving applications. Future work will likely explore commercial electrolyte formulations and long‑term safety testing, but the single‑additive strategy provides a clear pathway toward market‑ready Zn‑I2 systems.