Sodium ion conducting NaI-Na_{3PO_{4 solid electrolyte with PLLTMEDA as an additive for solid state batteries

In this work poly(L-leucine)1,3-diamino propane (PLLTMEDA) has been chosen as an additive to the binary compound sodium iodide (NaI) and sodium phosphate (Na3PO4). A small amount of PLLTMEDA was added to the optimum composition of the binary compound (0.5 NaI-0.5 Na3PO4). Results from EIS have proven this new compound is superionic with maximum conductivity of 1.12 × 10−3 S cm−1. Fourier transform infrared spectroscopy (FTIR) analysis revealed the band of C=O at 1650 cm−1 experienced a shift, indicating that some interaction had occurred. The ionic transference number was found to be ≈1 for the optimum composition with maximum conductivity which suggests that the sample is ionic in nature. The optimum composition of the sample was used as solid electrolyte in solid state sodium battery. The sodium battery was tested by the discharged characteristic at a current of ≈1.0 µA. The solid state sodium batteries exhibited a discharge capacity of 173 mAh/g.