Concentration Gradient Induced Delithiation Failure of MoO₃ for Li-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Electric vehicles require advanced lithium-ion batteries with higher energy and power densities.
• Conversion-type metal oxides, like molybdenum trioxide (MoO3), show potential as high-capacity battery anodes.
• Low initial Coulombic efficiency (ICE) and poor capacity retention limit the application of these materials.

Purpose of the Study:

• To investigate the initial Coulombic efficiency (ICE) of conversion-type MoO3 anodes.
• To understand the failure mechanism during the delithiation process in MoO3 particles.
• To identify strategies for improving the electrochemical reversibility of conversion-type anode materials.

Main Methods:

• Computational modeling was used to predict lithium-ion (Li+) concentration gradients within MoO3 particles.
• A comparative study analyzed the performance of MoO3 particles of various sizes.
• Electrochemical testing was performed to evaluate capacity retention and delithiation behavior.

Main Results:

• Computational modeling revealed that a high concentration gradient of Li+ forms during delithiation.
• A low-conductivity layer forms in the highly delithiated outer region of MoO3 particles, impeding further delithiation.
• Electrode failure during delithiation is directly linked to this concentration gradient and the resulting resistive shell formation.
• Particle size significantly influences the delithiation failure mechanism.

Conclusions:

• The study elucidates a key failure mechanism in MoO3 anodes, attributed to a resistive shell formation.
• Understanding this mechanism is crucial for designing next-generation conversion-type anode materials.
• This research provides guidance for developing anodes with enhanced electrochemical reversibility for improved battery performance.