Unveiling the Roles of Trace Fe and F Co-doped into High-Ni Li-Rich Layered Oxides in Performance Improvement

Area of Science:

• Materials Science
• Electrochemistry
• Inorganic Chemistry

Background:

• High-nickel lithium-rich layered oxides (HNLOs) mitigate voltage decay in lithium-rich manganese-based layered oxides (LRMLOs).
• However, HNLOs often exhibit reduced capacity and cycling stability.
• Existing strategies require improvement for practical applications.

Purpose of the Study:

• To develop an effective, scalable co-doping strategy for HNLOs.
• To enhance the electrochemical performance of HNLOs by introducing trace Fe and F ions.
• To investigate the synergistic effects of Fe and F co-doping.

Main Methods:

• A facile expanded graphite template-sacrificed approach for co-doping.
• Synthesis of Fe and F co-doped HNLOs.
• Electrochemical characterization (cycling stability, rate capability).
• Density Functional Theory (DFT) calculations.

Main Results:

• Co-doping with trace Fe and F synergistically improved rate capability and cycling stability.
• Fe doping increased capacity and enhanced electronic/ionic conductivity.
• F doping suppressed lattice oxygen escape, improving stability.
• Co-doped cathode retained 90% capacity after 200 cycles at 1 C, compared to 64% for pristine.

Conclusions:

• Trace Fe and F co-doping is a highly effective strategy for improving HNLO performance.
• The synergistic effect of Fe and F offers superior benefits over individual doping.
• This approach provides a new avenue for developing high-performance lithium-rich layered oxide cathodes.