Tuning Interphase Chemistry to Stabilize High-Voltage LiCoO₂ Cathode Material via Spinel Coating

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Cathode electrolyte interphases (CEIs) are crucial for the stability of high-voltage cathodes in batteries.
• The formation mechanisms and properties of CEIs are not fully understood, hindering battery performance.

Purpose of the Study:

• To investigate the control of CEI composition through abundant species in the inner Helmholtz layer (IHL).
• To demonstrate material-based tuning of CEIs for improved battery cycling stability.

Main Methods:

• Analysis of the IHL composition of LiCoO2 (LCO) before and after charging.
• Application of a passivated spinel Li4Mn5O12 coating to modify the IHL.
• In situ microscopy to observe CEI behavior at elevated temperatures.

Main Results:

• The IHL of LCO changes post-charging to a solvent-rich environment, yielding fragile organic-rich CEIs.
• Spinel coating results in an anion-rich IHL, forming robust LiF-rich CEIs.
• LiF-rich CEIs maintain integrity at 500°C, unlike organic-rich CEIs which form voids/cracks.

Conclusions:

• CEI composition is controllable via IHL species, offering a pathway for material-based tuning.
• Spinel-coated LCO demonstrates significantly improved specific capacity and cycling retention.
• This research provides insights into modulating CEIs for advanced lithium-ion batteries.