Coupling Antisite Defect and Lattice Tensile Stimulates Facile Isotropic Li-Ion Diffusion

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Lithium iron phosphate (LiFePO4) is a widely used commercial cathode material.
• Anisotropic 1D lithium-ion diffusion along the [010] direction limits LiFePO4's fast charging performance.

Purpose of the Study:

• To investigate the effect of Li-Fe antisite defects and tensile strain on LiFePO4's lithium-ion diffusion kinetics.
• To develop a new 2D diffusion pathway for enhanced fast charging performance.

Main Methods:

• Ultrafast nonequilibrium high-temperature shock technology to introduce defects and strain.
• Electrochemical experiments to evaluate battery performance.
• First-principles calculations to understand diffusion mechanisms.

Main Results:

• Controllable introduction of Li-Fe antisite defects and tensile strain in LiFePO4.
• Creation of a new 2D lithium-ion diffusion pathway across the ab plane.
• Reduced energy barrier for lithium-ion diffusion via the new 2D path.
• Achieved isotropic 2D interchannel Li+ hopping.
• Demonstrated excellent fast charging performance and cycling stability (84.4% capacity retention after 2000 cycles at 10 C).

Conclusions:

• Multiscale coupling of defects and strain promotes isotropic 2D Li+ hopping.
• This approach significantly enhances LiFePO4's rate capability and stability.
• The findings provide a new mechanism for designing high-rate battery electrodes.