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

摘要

Atomic layer deposition (ALD) has been shown as a powerful technique to build three-dimensional (3D) all-solid-state microbattery, because of its unique advantages in fabricating uniform and pinhole-free thin films in 3D structures. The development of solid-state electrolyte by ALD is a crucial step to achieve the fabrication of 3D all-solid-state microbattery by ALD. In this work, lithium phosphate solid-state electrolytes were grown by ALD at four different temperatures (250, 275, 300, and 325 degrees C) using two precursors (lithium tert-butoxide and trimethylphosphate). A linear dependence of film thickness on ALD cycle number was observed and uniform growth was achieved at all four temperatures. The growth rate was 0.57, 0.66, 0.69, and 0.72 angstrom/cycle at deposition temperatures of 250, 275, 300, and 325 degrees C, respectively. Furthermore, x-ray photoelectron spectroscopy confirmed the compositions and chemical structures of lithium phosphates deposited by ALD. Moreover, the lithium phosphate thin films deposited at 300 degrees C presented the highest ionic conductivity of 1.73 x 10(-8) S cm(-1) at 323 K with similar to 0.51 eV activation energy based on the electrochemical impedance spectroscopy. The ionic conductivity was calculated to be 3.3 x 10(-8) S cm(-1) at 26 degrees C (299 K).