Jinhyup Han

Department of Energy Engineering

(Battery Science and Technology)

Graduate School of UNIST

2019

2.2 Experimental detail

2.2.1 Preparation of solid electrolyte

NASICON (Na3Zr2Si2PO12) was used as a solid electrolyte to separate the seawater cathode from the anode. The NASICON was fabricated by a solid-state reaction based on our previous study 38, 75, 76. Briefly, the precursor powders of Na3PO4·12H2O, SiO2, and ZrO2 (Aldrich) were uniformly mixed using a planetary ball mill (Xiamen Tmaxcn Inc.)and calcined at 400 °C and 1,100 °C in ambient air. The calcined powder was ground and uniaxially pressed into pellets at 7 MPa. The pellets were sintered at 1,230 °C for 10 h in ambient air. The diameter and thickness of final NASICON membranes were 16 mm and 1.0 mm, respectively, and the measured density was around 3.07 g cm-3(~94% of the theoretical value)

2.2.2 Assembly of coin-type anode compartment

 The seawater coin-cells were assembled by the following procedure. For the anode compartment, the solid electrolyte (NASICON membrane) was attached to the open and round upper cap (anode top part) made of polypropylene. Na metal (99.9%, Sigma Aldrich) was attached to the surface of a round stainless steel spacer and the non-aqueous electrolyte (~20 µl) was injected. Polyethyleneseparators with a thickness of 16 µm and a diameter of 19 mm (Celgard) were inserted between the Na metal and NASICON and then the upper cap and anode bottom part were sealed by using an epoxy glue (J-B Weld 8280), which was dried for 24 h in ambient air. A 1.0 M NaCF3SO3 (Sigma Aldrich) salt was dissolved in tetraethylene glycol dimethylether (Sigma Aldrich) and stirred for 4h in Ar atmosphere, which was used as a non-aqueous electrolyte. The coin-cell assembly was performed in a vacuum glove box (Xiamen Tmaxcn Inc.) under a high purity Ar atmosphere (oxygen and water < 1.0 ppm).