Regulating Mechano-Electrochemical Process for Uniform Lithium-Ion Extraction in Ni-Rich Single-Crystal Cathodes.

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Mechanical and electrochemical processes are key to lithium-ion battery cathode performance.
• Lattice defects, both electrochemically and mechanically induced, are typically seen as detrimental to cycling stability.

Purpose of the Study:

• To investigate the impact of mechanically introduced defects during electrode fabrication on cathode performance.
• To challenge the assumption that mechanically introduced defects are always harmful.
• To understand the multiscale mechano-electrochemical coupling in battery electrodes.

Main Methods:

• Transmission electron microscopy (TEM) to analyze structural defects.
• Electrochemical cycling to assess performance and stability.
• Molecular dynamics (MD) simulations to model ion transport and stress concentration.

Main Results:

• Mechanically introduced defects are self-passivated during cycling and negligibly impact degradation.
• Electrode densification enhances cycling stability and rate capability by reducing porosity and improving electronic connectivity.
• Capacity degradation is primarily caused by lattice distortions during the H2-H3 phase transition, which are mitigated by densification.

Conclusions:

• Contrary to assumptions, mechanical compression and subsequent densification can improve cathode performance.
• Densified electrodes exhibit enhanced durability due to alleviated strain, gliding, and crack propagation.
• Optimizing electrode manufacturing through densification offers a pathway to durable, high-energy lithium-ion batteries.