Probing the Li₄ Ti₅ O₁₂ Interface Upon Lithium Uptake by Operando Small Angle Neutron Scattering

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• The formation of a solid-electrolyte interphase (SEI) on lithium titanate (LTO) is a contentious subject in battery research.
• Previous studies often inferred SEI presence post-cycling, lacking in-situ evidence.

Purpose of the Study:

• To synthesize mesoporous LTO with controlled pore sizes.
• To investigate the SEI formation mechanism on LTO using operando techniques.
• To correlate SEI formation with electrochemical performance.

Main Methods:

• Synthesis of cubic mesostructured LTO using triblock copolymer templating.
• Control of crystallite domain size (3-4 nm) and pore diameter (4-8 nm).
• Operando small-angle neutron scattering (SANS) and X-ray photoelectron spectroscopy (XPS).

Main Results:

• Mesoporous LTO with spherical morphology and excellent electrochemical performance (high rate capability, capacity retention) was achieved.
• Operando SANS and XPS confirmed SEI formation at 2.2 V.
• The SEI initially forms as a LiF-rich layer, followed by a carbonaceous layer, preferentially in smaller pores.

Conclusions:

• The SEI on LTO is not solely a post-cycling artifact but forms dynamically during operation.
• The pore structure influences the initial SEI nucleation and growth.
• Understanding this mechanism is crucial for optimizing LTO-based battery performance.