Realizing four-electron conversion chemistry for all-solid-state Li||I₂ batteries at room temperature

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Liquid organic electrolytes in rechargeable lithium-iodine (Li||I2) batteries face challenges like polyiodide shuttling and safety concerns.
• Current all-solid-state Li||I2 batteries exhibit limited capacity and require elevated temperatures due to a two-electron chemistry (I-/I2).
• These limitations hinder the performance of solid-state Li||I2 batteries compared to state-of-the-art lithium-ion batteries.

Purpose of the Study:

• To develop a high-capacity, stable, and fast four-electron solid-conversion chemistry (I-/I2/I+) for all-solid-state Li||I2 batteries at room temperature.
• To overcome the performance limitations of existing two-electron solid-state Li||I2 battery systems.
• To enable solid-state Li||I2 batteries to rival the performance of conventional lithium-ion batteries.

Main Methods:

• Strategic use of a highly conductive, chlorine-rich solid electrolyte, Li4.2InCl7.2, as a catholyte.
• Activation of the I2/I+ redox couple through robust iodine-chlorine (I-Cl) interhalogen interaction.
• Facilitation of an interface-mediated heterogeneous oxidation mechanism for enhanced electrochemical performance.

Main Results:

• Demonstration of a fast, stable, and high-capacity four-electron solid-conversion I-/I2/I+ chemistry in all-solid-state Li||I2 batteries at room temperature.
• Achieved a high specific capacity of 449 mAh g-1 (based on I2 mass) at 44 mA g-1.
• Exhibited impressive cycling stability with 91% capacity retention over 600 cycles at 440 mA g-1 and 25°C.

Conclusions:

• The developed solid-state Li||I2 battery system effectively utilizes a four-electron redox chemistry, significantly enhancing energy storage capacity.
• The Li4.2InCl7.2 catholyte not only facilitates Li-ion conduction but also participates reversibly in the redox reactions, contributing to capacity.
• This advancement paves the way for high-performance, safe, and stable all-solid-state lithium-iodine batteries operating efficiently at room temperature.