Electrolyte-Regulated Epitaxial-Like Gradient Interface for Stable 4.8 V LiCoO₂

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Increasing energy density in lithium-ion batteries requires pushing cathode materials like lithium cobalt oxide (LiCoO2) to higher operating voltages.
• Interfacial instability of LiCoO2 at ultrahigh voltages (>4.6 V) leads to structural degradation and limits performance.

Purpose of the Study:

• To engineer a stable cathode-electrolyte interphase for ultra-high-voltage LiCoO2 operation.
• To enhance the energy density and cycling stability of LiCoO2-based batteries.

Main Methods:

• Developing a fluorine-rich lithium salt to form an epitaxial-like gradient protective layer.
• Utilizing LiCoO2 at an ultrahigh cutoff voltage of 4.8 V.
• Characterizing the protective layer and battery performance through electrochemical testing and structural analysis.

Main Results:

• LiCoO2 demonstrated excellent cycling stability at 4.8 V, achieving 251 mAh g-1 (91.7% of theoretical capacity) over 220 cycles.
• A 6.82 Ah pouch cell delivered a specific energy of 557 Wh kg-1 with 85.2% capacity retention after 60 cycles.
• The study elucidated the salt anion decomposition mechanism and the atomic structure of the gradient interface.

Conclusions:

• An epitaxial-like gradient interface effectively stabilizes ultra-high-voltage LiCoO2 cathodes.
• The proposed strategy offers a pathway for designing advanced electrolyte components and interfacial layers for next-generation high-energy-density batteries.