Flux Synthesis of A-site Disordered Perovskite La0.5M0.5TiO3 (M=Li, Na, K) Nanorods Tailored for Solid Composite Electrolytes

Abstract

Inorganic fillers play an important role in improving the ionic conductivity of solid composite electrolytes (SCEs) for Li-ion batteries. Among inorganic fillers, perovskite-type lithium lanthanum titanate (LLTO) stands out for its high bulk Li+ conductivity on the order of 10−3 S cm−1 at room temperature. According to a literature survey, the optimal LLTO filler should possess the following characteristics: i) a single-crystal structure to minimize grain boundaries; ii) a small particle size to increase the filler/polymer interface area; iii) a 1D morphology for efficient interface channels; and iv) cubic symmetry to facilitate rapid bulk Li+ diffusion within the filler. However, the synthesis of single crystal, 1D LLTO nanomaterials with cubic symmetry is challenging. Herein, a flux strategy is developed to synthesize La0.5M0.5TiO3 (LMTO, M═Li, Na, and K) single-crystal nanorods with an A-site-disordered, cubic perovskite phase. The flux media promotes the oriented growth of nanorods, prevents nanorods from sintering, and provides multiple alkali metal ion doping at M sites to stabilize the cubic phase. SCEs compositing the Li+-conducting LMTO nanorods as fillers and poly[vinylene carbonate-co-lithium sulfonyl(trifluoromethane sulfonyl)imide methacrylate] matrix exhibit more than twice the conductivity of the neat polymer electrolyte (30.6 vs 14.0 µS cm−1 at 303 K).