Atomic layer deposition of lithium phosphates as solid-state electrolytes for all-solid-state microbatteries.

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Atomic layer deposition (ALD) is a key technique for fabricating uniform, pinhole-free thin films in 3D structures.
• ALD is crucial for developing 3D all-solid-state microbatteries, particularly for creating solid-state electrolytes.
• Optimizing ALD processes for solid-state electrolytes is essential for advancing microbattery technology.

Purpose of the Study:

• To investigate the growth of lithium phosphate solid-state electrolytes using ALD at various temperatures.
• To characterize the structural and electrical properties of ALD-deposited lithium phosphate films.
• To determine the optimal ALD conditions for high-performance solid-state electrolytes in microbatteries.

Main Methods:

• Lithium phosphate thin films were deposited using ALD with lithium tert-butoxide and trimethylphosphate precursors.
• Deposition temperatures were varied (250, 275, 300, and 325 °C) to study their effect on film properties.
• X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS) were used for characterization.

Main Results:

• Uniform lithium phosphate films with linear thickness dependence on ALD cycles were achieved at all temperatures.
• Growth rates increased with temperature, ranging from 0.57 to 0.72 Å/cycle.
• The film deposited at 300 °C exhibited the highest ionic conductivity (1.73 × 10⁻⁸ S cm⁻¹ at 323 K) with a 0.51 eV activation energy.

Conclusions:

• ALD is a viable method for producing lithium phosphate solid-state electrolytes for 3D microbatteries.
• Optimizing deposition temperature is critical for achieving desired ionic conductivity.
• The study demonstrates ALD's potential for fabricating high-performance solid-state electrolytes.