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Slow-Moving Phase Boundary in Li4/3+ x Ti5/3 O4
Yug Joshi1, Robert Lawitzki1, Guido Schmitz1
1Chair of Materials Physics, Institute of Materials Science, University of Stuttgart, 70569, Stuttgart, Germany.
Small Methods
|December 20, 2021
Summary
Lithium titanate
Area of Science:
- Materials Science
- Electrochemistry
- Solid-state Chemistry
Background:
- Lithium titanate is a promising anode material for high-power batteries.
- Understanding lithium ion transport kinetics is crucial for optimizing its performance.
- Poor lithium diffusivity in end phases of lithium titanate challenges high-rate applications.
Purpose of the Study:
- To elucidate the kinetics of lithium transport in lithium titanate.
- To investigate the influence of Li concentration on lithium diffusivity.
- To clarify the role of phase boundary migration in lithium titanate electrode reactions.
Main Methods:
- In situ optical microscopy of sputter-deposited thin-film lithium titanate samples.
- Utilizing a thermostatically controlled electrochemical cell for temperature-dependent studies.
- Quantitative analysis of lithium transport and phase formation dynamics.
Main Results:
- Lithium diffusivity is poor in fully lithiated and delithiated phases but increases at intermediate Li concentrations within the spinel phase (Li 4/3+δ Ti 5/3 O 4 ).
- Phase boundary migration, not lithium diffusion, initially controls the formation of the Li-rich rock-salt phase.
- Rock-salt phase growth becomes diffusion-controlled only after Li diffusion into the spinel phase diminishes.
Conclusions:
- The study reveals kinetic limitations in lithium titanate electrode performance.
- Phase boundary kinetics play a critical, previously underestimated, role in initial lithiation stages.
- Findings contrast with theoretical models suggesting facile interface behavior, highlighting the importance of experimental observation.
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