Lithiation Gradients and Tortuosity Factors in Thick NMC111-Argyrodite Solid-State Cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• High energy density in all-solid-state lithium batteries necessitates the use of thick cathodes.
• These thick cathodes must operate reversibly under standard conditions for practical applications.

Purpose of the Study:

• To investigate the localized lithium content distribution within thick composite cathodes for all-solid-state lithium batteries.
• To understand how varying material loadings affect lithium distribution and performance.

Main Methods:

• Utilized high-energy depth-profiling X-ray diffraction to analyze lithium distribution across 110 μm thick composite cathodes.
• Employed microstructural analysis and cathode modeling to correlate structure with electrochemical behavior.
• Studied composite cathodes composed of Li_1-Ni_1/3Mn_1/3Co_1/3O₂ (NMC111) and Li₆PS₅Cl (LPSC) solid electrolyte at C/10 cycling rate.

Main Results:

• Observed substantial lithiation gradients across the thickness of the composite cathodes during cycling.
• Demonstrated that altering the NMC111 mass loading influenced the nature and severity of these lithiation gradients.
• Identified high tortuosities, particularly in the solid electrolyte phase, as a key factor contributing to gradients, with tortuosity increasing during initial charging.

Conclusions:

• Current distributions are evident in sulfide-based composite cathodes.
• High tortuosity in the solid electrolyte phase significantly impacts lithium distribution and battery performance.
• These findings are critical considerations for the practical design and optimization of all-solid-state batteries with thick cathodes.