Excellent electrochemical properties, Li ion dynamics and room temperature work function of Li₂MnO₃cathode thin films

Area of Science:

• Materials Science
• Electrochemistry
• Solid-state Chemistry

Background:

• Lithium manganese oxide (Li₂MnO₃) is a promising material for cathode applications in lithium-ion batteries.
• Thin-film fabrication techniques are crucial for developing advanced energy storage devices.

Purpose of the Study:

• To investigate the electrochemical properties of Li₂MnO₃ thin films fabricated using RF sputtering.
• To determine the Li-ion diffusion coefficient and work function of the Li₂MnO₃ thin films.
• To assess the suitability of Li₂MnO₃ thin films as cathode layers in all-solid thin-film batteries.

Main Methods:

• Radio Frequency (RF) sputtering technique for thin film fabrication.
• X-ray diffraction (XRD) for structural analysis.
• X-ray photoelectron spectroscopy (XPS) for elemental and oxidation state analysis.
• Scanning Kelvin probe microscopy (SKPM) for work function measurement.
• Electrochemical studies, including cyclic voltammetry and galvanostatic cycling, to evaluate performance.

Main Results:

• XRD confirmed the formation of Li₂MnO₃ in a layered structure.
• XPS verified the presence of Li and Mn ions in their appropriate oxidation states.
• Work function was measured to be 5.51 eV.
• Electrochemical studies revealed oxidation/reduction peaks at 2.98 V/2.81 V, with a discharge capacity of 10 µAh cm⁻² (1st cycle) and 9 µAh cm⁻² (100th cycle).
• Li-ion diffusion coefficients were found to be 1.6 × 10⁻¹⁴ cm²s⁻¹ and 2.56 × 10⁻¹⁴ cm²s⁻¹ before and after cycling, respectively.

Conclusions:

• Li₂MnO₃ thin films fabricated by RF sputtering possess excellent electrochemical properties.
• The films demonstrate good structural and electrochemical stability.
• Li₂MnO₃ thin films are a promising cathode material for all-solid thin-film battery applications.