Experimental Visualization and the Mechanism of Current-Collector Geometry Effects on Ion Distribution and Device...

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Electrode performance in electrochemical devices is critically dependent on cation distribution.
• Current collector geometry is known to induce uneven current, charge distribution, and partial aging, but experimental evidence and solutions are lacking.

Purpose of the Study:

• To experimentally investigate the 3D ion distribution in transition-metal-oxide cathodes.
• To elucidate the intrinsic mechanisms behind the 'bottom effect' caused by current collector size.
• To develop and verify solutions for mitigating bottom aging and improving electrode longevity.

Main Methods:

• Experimental visualization of 3D ion distribution, trapped cation accumulation, and bottom aging.
• Proposal and verification of an "end reflection model" for current collector design.
• Design modifications including extra-wide bottoms and bottom blanks on current collectors.

Main Results:

• The ubiquitous 'bottom effect' was experimentally visualized, showing cation accumulation and aging at the bottom of transition-metal-oxide cathodes.
• The proposed "end reflection model" accurately describes the observed phenomena.
• Current collector designs based on the model successfully eliminated the bottom effect.

Conclusions:

• Current collector geometry significantly influences ion distribution and electrode aging in electrochemical devices.
• The developed "end reflection model" provides a new framework for understanding and optimizing current collector design.
• Optimized current collector designs doubled the cyclic life of electrodes, offering a significant advancement in battery technology.