Lithiation-Driven LiCrSe₂ Shell Growth on Metallic CrSe₂ Core Governs the Plateau-Slope Behavior.

Area of Science:

• Materials Science
• Electrochemistry
• Computational Materials Science

Background:

• High-performance lithium-ion batteries (LIBs) require advanced cathode materials with high capacity, stability, and fast charge-discharge rates.
• Layered transition-metal chalcogenides are candidates, but their electrochemical behavior needs further elucidation.

Purpose of the Study:

• To investigate the potential of layered chromium diselenide (CrSe2) as a cathode material for LIBs.
• To validate theoretical predictions of CrSe2's ion diffusion properties using experimental methods.

Main Methods:

• First-principles calculations to predict CrSe2's structural and diffusion properties.
• Muon spin rotation (µ+SR) spectroscopy to experimentally confirm Li+ diffusion.
• Electrochemical testing (cycling, rate capability) and in operando X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS).

Main Results:

• First-principles calculations predicted a stable CrSe2 framework accommodating Li+ and fast Li+ diffusion.
• µ+SR measurements confirmed rapid Li+ diffusion in pre-lithiated CrSe2.
• Electrochemical tests yielded a reversible capacity of 125.3 mAh g-1 at 0.1 C with stable cycling and good rate performance.
• In operando studies revealed reversible topotactic transitions and lithiation-driven core-shell evolution.

Conclusions:

• CrSe2 exhibits excellent electrochemical performance, approaching theoretical capacity, making it a viable cathode material for LIBs.
• Lithiation-induced conductivity changes are key to CrSe2's electrochemical behavior.
• This research offers insights into intercalation mechanisms in layered materials and guides the design of fast-charging electrodes.