Interface-induced fast Li⁺ transport in mixed ionic-electronic conductors.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Interfacial instability between lithium metal and solid-state electrolytes is a major challenge in all-solid-state lithium metal batteries (ASSLBs).
• This instability leads to parasitic reactions, uneven lithium-ion flux, and the growth of lithium dendrites, compromising battery performance and safety.
• Existing solutions often struggle to balance interfacial stability with efficient ionic transport.

Purpose of the Study:

• To develop a novel composite interlayer that enhances interfacial stability and ionic transport in ASSLBs.
• To investigate the mechanism behind improved ionic conductivity in the composite interlayer.
• To demonstrate the effectiveness of the interlayer in suppressing dendrite growth and improving critical current density.

Main Methods:

• Fabrication of a composite interlayer using anti-perovskite Li₂OHCl_0.75Br_0.25 (AP) and carbon nanotubes (CNTs).
• Characterization of the interlayer's structural and electrochemical properties.
• Testing of lithium symmetric cells incorporating the AP-CNT interlayer under various conditions, including electrochemical impedance spectroscopy and galvanostatic cycling.
• Analysis of interfacial electron transfer and the generation of a built-in electric field.

Main Results:

• The AP-CNT composite interlayer demonstrated significantly enhanced Li⁺ conductivity compared to bare electrolytes.
• Interfacial electron transfer between AP and CNTs was identified as the mechanism generating a built-in electric field, facilitating Li⁺ migration.
• Lithium symmetric cells with the interlayer achieved a high critical current density of 2.4 mA cm^-2 at 55 °C.
• The interlayer effectively suppressed lithium dendrite growth, ensuring stable cycling.

Conclusions:

• The developed AP-CNT composite interlayer provides a robust solution for interfacial instability in ASSLBs.
• The design integrates chemical robustness with efficient coupled ion-electron transport, enabling dendrite-free lithium metal plating.
• This strategy offers a generalizable approach for advancing the safety and performance of all-solid-state lithium metal batteries.