Janus Solid-Liquid Interface Enabling Ultrahigh Charging and Discharging Rate for Advanced Lithium-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Lithium iron phosphate (LiFePO4) is a promising cathode material for high-capacity batteries.
• The atomic-level understanding of the LiFePO4/electrolyte solid-liquid interface remains limited.
• Interfacial chemistry is crucial for optimizing battery performance, especially at high charge rates.

Purpose of the Study:

• To investigate the atomic-level interfacial chemistry of LiFePO4 in aqueous electrolytes.
• To understand the mechanism behind the enhanced performance of LiFePO4 in aqueous systems.
• To compare the interfacial behavior in aqueous versus organic electrolytes.

Main Methods:

• Electrochemical testing of LiFePO4 nanosized particles in aqueous and organic electrolytes.
• Ab initio calculations to model the LiFePO4-H2O and LiFePO4-ethylene carbonate systems.
• Analysis of the solid-liquid interface structure and dynamics.

Main Results:

• LiFePO4 cathodes in aqueous electrolytes achieved high charging rates (600 C) with 72 mAh g(-1) energy storage.
• Performance in organic electrolytes was significantly lower (20 mAh g(-1) at 200 C).
• A transient Janus hydrated interface was identified in the LiFePO4-H2O system, facilitating Li desolvation and ion transport.

Conclusions:

• The Janus hydrated interface in aqueous electrolytes enables fast Li-ion transport across the solid-liquid interface.
• This interface formation is key to the superior high-rate performance of LiFePO4 in water-based electrolytes.
• Findings provide atomic-level insights into battery interfacial phenomena, guiding future cathode material design.