LiBH4-NaX (X=Cl, I) composites with enhanced lithium ionic conductivity

In the present study, ball-milled LiBH4-NaX (X = Cl, I) composites were investigated as fast ionic conductors, in which both halide solid solution LiBH4-xClx and eutectic composite LiBH4-NaBH4 coexist and facilitate the ionic transportation jointly within the system. Measurements by differential scanning calorimetry (DSC) observed that both transition enthalpies and transition temperatures were all reduced, implying that the high temperature phase of LiBH4 was stabilized. LiBH4-NaX (X = Cl, I) composites deliver a conductivity value of 10−2 S cm−1 when temperature is higher than 373 K. At the same time, these values are almost 100 times higher than that of pristine LiBH4 at a temperature below 373 K. A window voltage of 3 V was identified by means of the cyclic voltammetry (CV) measurements on LiBH4-NaX (X = Cl, I) composites for 4 cycles. Furthermore, the structural stability of LiBH4-NaX (X = Cl, I) composites during the ramping process from room temperature to 393 K were demonstrated by in-situ X-ray diffraction (XRD) as well as Fourier Transform infrared spectroscopy (FTIR). It can be concluded that additional NaX (X = Cl or I) plays important roles in the enhancement of ionic conductivity of LiBH4 due to stabilizing the high-temperature phase of LiBH4.