Processing liquid-feed flame spray pyrolysis synthesized Mg0.5Ce0.2Zr1.8(PO4)3 nanopowders to free standing thin films and pellets as potential electrolytes in all-solid-state Mg batteries

Abstract

Despite the intense concentration on lithium-based batteries, safety, ease of construction and cost continue to drive the search for alternatives that do not suffer from such restrictions. We present here preliminary work on the development of thin film Mg2+ conducting electrolytes as the key starting point for the development of all-solid-state Mg batteries. Initial studies explored compositions in the Mg0.5CexZr2-x(PO4)3 (x = 0.1, 0.2 and 0.3) system first as pellets and with somewhat optimized compositions (with x = 0.2) as thin films. Introduction of Ce allows sintering to full density at temperatures where Ce free films do not densify completely. The work reported here relies on the synthesis of nanopowders (NPs) using liquid-feed flame spray pyrolysis that offers the potential to reduce processing conditions, to control final average grain sizes (AGSs) and provide single-phase materials with good to excellent mechanical properties. The pellets and then thin (≤50 μm) films produced here show conductivities of up to 3 × 10−3 mS cm-1 at ≈ 300 °C, which if extrapolated (using an Ea of ≈30) to 400 °C would be close to 10−2 mS cm−1 in keeping with the best reported values in the literature. The thin films reported here offer nearly full densities beyond what is currently achievable by any other method. The ionic area specific resistance (IASR) values for these thin films were found to be 1400 Ω cm2 at 300 °C and are estimated to drop to 110 Ω cm2 at 400 °C, significantly lower than values for pellets reported elsewhere.