Ionic Conduction through Reaction Products at the Electrolyte-Electrode Interface in All-Solid-State Li⁺ Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• All-solid-state lithium-ion batteries offer enhanced safety and energy density.
• Maintaining high rate capability in these batteries is hindered by electrode-electrolyte interface resistance.
• Reactivity at interfaces leads to degradation and limits long-term performance.

Purpose of the Study:

• To investigate the interfacial phenomena limiting rate capability in all-solid-state lithium-ion batteries.
• To identify the critical pathways for lithium-ion diffusion at electrode-electrolyte interfaces.
• To understand the role of product phases formed at interfaces in battery performance.

Main Methods:

• Examined interfaces between eight solid electrolytes (e.g., garnet, LiPON, LGPS) and seven electrode materials (e.g., NCM cathode, Li metal anode).
• Utilized density functional theory (DFT) with statistical sampling of phase diagrams to account for errors, metastability, and temperature.
• Employed machine-learned interatomic potentials for on-the-fly evaluation of lithium-ion conductivities in interfacial product phases.

Main Results:

• Identified rapid lithium-ion diffusion pathways through metastable product phases at interfaces.
• Nearly all evaluated electrode-electrolyte interfaces showed limited lithium-ion conduction within the interphase product layers.
• The formation of specific product phases significantly impacts interfacial resistance.

Conclusions:

• Lithium-ion conduction through interfacial product phases is predicted to be the rate-limiting step for most all-solid-state battery configurations.
• Understanding and mitigating interfacial resistance is crucial for advancing high-rate solid-state battery technology.
• This research provides fundamental insights into interfacial chemistry governing solid-state battery performance.