Perovskite Fluoride Anode Stabilized via Ligand-Field Engineering for High-Performance Lithium-Ion Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Perovskite fluorides (AMF3) show potential as high-capacity anode materials for lithium-ion batteries (LIBs).
• Their application is limited by structural degradation and interfacial instability due to dynamic transition-metal (TM) electronic states during cycling.
• Existing extrinsic modification methods are insufficient to overcome these intrinsic limitations.

Purpose of the Study:

• To introduce a universal ligand-field engineering strategy for intrinsic regulation of TM electronic environments in perovskite fluorides.
• To utilize KFeF3 as a model system to demonstrate this strategy.
• To improve the cycling stability and performance of LIB anodes.

Main Methods:

• Isovalent Mn3+ doping of KFeF3 to tune the Fe-centered ligand field.
• Synthesis of KFe0.5Mn0.5F3@C composite material.
• Electrochemical cycling performance testing of the composite anode.
• Theoretical calculations to investigate electronic structure and interfacial properties.

Main Results:

• Mn doping suppressed Jahn-Teller distortions and spin-state fluctuations in KFeF3.
• The KFe0.5Mn0.5F3@C composite exhibited excellent cycling stability with negligible capacity decay after 500 cycles at 0.5 A g-1.
• Unprecedented capacity retention of 94.65% was achieved after 1700 cycles at 1 A g-1.
• Theoretical calculations confirmed Mn doping stabilizes a low-spin Fe state, mitigating distortions and promoting a stable LiF-rich solid-electrolyte interphase (SEI).

Conclusions:

• Ligand-field engineering provides an effective electronic-state-driven solution to coupled mechanical-chemical degradation in conversion-type electrodes.
• This strategy establishes ligand-field regulation as a fundamental principle for designing advanced anode materials for LIBs.
• The developed KFe0.5Mn0.5F3@C composite demonstrates significant potential for high-performance lithium-ion batteries.