UC San Diego

Thin film LiPON and LLTO are promising solid electrolyte candidates in the development of next generation batteries. These materials can be deposited via RF magnetron sputtering, which is a technique suitable for thin film mass production. In this work, the deposition conditions for LiPON and LLTO are optimized to improve film quality. The thickness of LiPON films is shown to be tunable with the approximation of deposition rate. LiPON films as thin as 325 nm are produced to exhibit sufficient ionic conductivity and low electronic conductivity. Strong electrochemical performance means LiPON can remain a cohesive film even at very thin scales. With this, LiPON has potential to improve volumetric energy density when implemented into thin film batteries. Bulk LLTO is characterized to relate ionic conductivity to Li amount, and the composition with highest ionic conductivity influences the choice of LLTO sputtering target. LLTO film deposition rate is studied as a function of both RF power and deposition pressure, and RF power is shown to have a much stronger effect on deposition rate. Film delamination issues are addressed by decreasing LLTO film thickness, and adhesion to the Si substrate is maintained during the post annealing process. EDS analysis yields the La/Ti ratios of LLTO films, illustrating changes in LLTO composition due to deposition pressure.