Plasma-enhanced atomic layer deposition of titanium phosphate as an electrode for lithium-ion batteries

Publication Type:

Journal Article

Source:

Journal of Materials Chemistry A, Volume 5, Issue 1, p.330-338 (2017)

Abstract:

Titanium phosphate thin films were deposited by a new plasma-enhanced atomic layer deposition process. The process consisted of sequential exposures to trimethyl phosphate (TMP, Me3PO4) plasma, O2 plasma and titanium isopropoxide (TTIP, Ti(OCH(CH3)2)4) vapor, and it was characterized by in-situ spectroscopic ellipsometry and ex-situ X-ray reflectometry. The growth linearity, growth per cycle (GPC), and density of the resulting thin films was investigated as a function of the pulse times and the substrate temperature. The conformality of the process was characterized by deposition on micropillars. At a substrate temperature of 300 °C and using saturated pulse times, linear growth with a GPC of 0.66 nm/cycle and without nucleation delay was achieved. As-deposited films were amorphous, while crystalline TiP2O7 was formed upon annealing in air or helium atmospheres. In lithium-ion test cells, the as-deposited films showed insertion and extraction of Li+ around a potential of 2.7V vs. Li/Li+. Charge/discharge measurements revealed a volumetric capacity of 330 mAh/cm3, together with a good rate capability and minimal capacity fading.

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