Evolution of Fe-Antisite Defects in Standard Hydrothermal LiFePO4 Synthesis and Their Accelerated Removal with Ca2+

Abstract

Based on neutron powder diffraction (NPD), high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), Electron Energy Loss Spectroscopy (EELS), X-Ray Photoelectron Spectroscopy (XPS) we show that Fe-antisites defects are surface defects (see Figure 1) and slowly eliminated by Fe-Li cation exchange during standard hydrothermal synthesis1. Recently2 we demonstrated that the calcium ions help eliminate the Fe antisite defects by controlling the nucleation and evolution of the LiFePO4 particles during their hydrothermal synthesis. The final Ca:LFP particles present Fe-antsite defects confined in a thin surface layer compared to standard LFP. Fig. 1. Figure 1: Schematic representation of Fe-antisite defects elimination during standard hydrothermal synthesis of LFP Reference 1. Paolella, A. et al. Cation exchange mediated elimination of the Fe-antisites in the hydrothermal synthesis of LiFePO 4. Nano Energy 16, 256–267 (2015). 2. Paolella, A. et al. Accelerated Removal of Fe-Antisite Defects while Nanosizing Hydrothermal LiFePO 4 with Ca 2+. Nano Lett. 2–7 (2016). doi:10.1021/acs.nanolett.6b00334 Figure 1