LiH2PO4 crystal as a solid electrolyte

Abstract

Lithium dihydrogen phosphate (LiH2PO4) powder was purchased from Aldrich Chemical Co. From the scanning electron microscope (SEM) observation, these polycrystals have dimensions in the range of 25-250 μm. The electrical conductivity was measured at a measuring frequency of 1 kHz on heating polycrystalline lithium dihydrogen phosphate (LiH2PO4) from room temperature to 493 K. Two anomalies appeared at 451 K (Tp1) and 469 K (Tp2). The electrical conductivity reached the magnitude of the superprotonic phases: 3×10-2 Ω -1cm-1 at 451 K (Tp1) and 1.2×10 Ω-1 cm-1 at 469 K (Tp2). It is uncertain whether the superprotonic phase transformations are due to polymorphic transitions in the bulk, surface transitions, or chemical reactions (thermal decomposition) at the surface. Considering several previous thermal studies (differential scanning calorimetry and thermogravimetry), our experimental results seem to be related to the last case: chemical reactions (thermal decomposition) at the surface with the progressive solid-state polymerization.