Von-Alpen Type Nasicon for Seawater Battery Application

Abstract

For utilization of renewable energy, energy storage systems (ESS) are becoming more important. Seawater battery have attracted attention for large scale ESS system due to high capacity, good cyclability and environment friendly. The seawater battery consists of seawater, cathode current collector, solid electrolyte, organic electrolyte and anode. Among the components, solid electrolyte does critical role for selective transfer of sodium ion. The requirements for the solid electrolyte are high sodium ion conductivity at room temperature, high chemical stability against seawater, wide electrochemical window (0~5V), thermostability (4oC~25oC) and strong mechanical strength. The possible candidates were sodium beta alumina and Hong type NASICON (Na3Zr2Si2PO12). In the previous research, Hong type NASICON has superior seawater stability than sodium beta alumina. So the conventional seawater battery utilizes Hong-type NASICON as solid electrolyte due to applicable properties. Among the NASICON solid electrolytes composition, Na3.1Zr1.55Si2.3P0.7O11 composition was proposed by V. von Alpen et al in 1981. As far as we know, there has no research about Na3.1Zr1.55Si2.3P0.7O11 composition on electrochemical device. In this study, Na3.1Zr1.55Si2.3P0.7O11 composition was used as solid electrolyte for seawater battery application. We investigated on the required properties and compared with Hong-type NASICON. The resulting Na3.1Zr1.55Si2.3P0.7O11 exhibited higher sodium ion conductivity due to bigger grain size and strong mechanical strength. When it applied into the seawater battery, it showed smaller overpotential and higher power with over 1 thousand hours cycling. Thus, Na3.1Zr1.55Si2.3P0.7O11 composition solid electrolyte satisfied the above requirements and exhibited superior properties than previously researched solid electrolytes for seawater battery. References Y. Kim, H. Kim, S. Park, I. Seo, and Y. Kim, Electrochimica Acta , 191, 1–7 (2016)V. Von Alpen, M.F. Bell and H.H. Hofer, Solid State Ionics, 3-4,215-218 (1981).S.M. Hwang, J. Park, Y.Kim, W.Go, J.Han, Y.Kim and Y.Kim, Advanced Materials , 1804936 (2018)