A Novel Two-Step Synthesis for Li2CoPO4F as High-Voltage Cathode Material
We herein present a novel 2-step synthesis route towards Li2CoPO4F. In the first step we synthesize a LiCoPO4/LiF powder via solvothermal synthesis. We investigated the influence of different solvents, such as ethylene glycol, diethylene glycol, tetraethylene glycol and glycerol, on particle size and phase purity. The obtained powder is converted into Li2CoPO4F in a second step in a tube furnace under steady Ar-flow at 660 °C for 1 h and subsequent quenching to room temperature. Characterization of the resulting product was performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen sorption, simultaneous thermal analysis (STA), inductively coupled plasma optical emission spectroscopy (ICP-OES) and electrochemical methods.
Our new procedure allows us to directly convert the LiCoPO4/LiF nano-powder obtained from solvothermal synthesis without any additional steps such as ball milling or pelletizing. Furthermore, the rapid conversion time at 660 °C of only 1 h, is highly advantageous compared to the recent literature (2, 4, 6, 8).
We obtained submicron Li2CoPO4F particles after the two step synthesis as can be seen in Figure 1. The different solvents applied in the solvothermal synthesis have a strong influence on phase purity and particle size of Li2CoPO4F.
Figure 1: SEM image of as synthesized Li2CoPO4F
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