Bond Length as a Unified Descriptor for Stable Iodine Battery

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Engineering

Background:

• Active material dissolution and shuttling in electrolytes are key challenges for stable rechargeable batteries, especially with high-solubility cathodes like iodine.
• Quantifying the interaction strength between iodine and host electrodes/electrolytes is crucial for electrochemical stability but lacks a suitable parameter.

Purpose of the Study:

• To propose a unified descriptor for predicting iodine electrode stability.
• To demonstrate the descriptor's utility in designing stable electrodes and electrolytes for rechargeable batteries.

Main Methods:

• Investigated iodine's interaction strength as a Lewis acid, influenced by ligand nucleophilicity.
• Proposed and validated the I-I bond length, measurable via Raman spectroscopy, as a descriptor for iodine electrode stability.
• Applied the descriptor to design host electrodes and screen electrolyte solvents.

Main Results:

• The I-I bond length effectively predicts iodine electrode stability.
• Rational electrode design enhanced iodine-host binding.
• Optimized electrolytes minimized active material shuttling.
• Achieved stable cycling of lithium-iodine (Li-I2) batteries at 0.1 C for over 4000 hours.

Conclusions:

• The I-I bond length serves as a unified descriptor for iodine electrode stability.
• This descriptor accelerates the design of advanced electrodes and electrolytes.
• Overcoming active material dissolution is key to high-performance rechargeable batteries.