The ionic conductivities, stabilities and ionic mobilities of xLiBH4-Li2NH (x = 1, 2, 4) composites as fast ion conductor

LiBH 4 possesses high ionic conductivity (σ) at a temperature over 373 K and wide window voltage over 5 V, but low σ value below 373 K. Li 2 NH owns excellent ionic conductivity at low temperature but performs in a narrow window voltage (only 0.7 V). xLiBH 4 -Li 2 NH composites (x = 1, 2, 4) were therefore synthesized to eliminate their respective drawbacks. By alternating current impedance spectra, we observed that xLiBH 4 -Li 2 NH (x = 1, 2, 4) composites offer σ of 10 −2 Scm −1 at a temperature over 373 K, and lift σ value by 100 times from that of LiBH 4 at a temperature below 373 K. According to the cyclic voltammetry (CV for 10 cycles) results, the window voltage of 3 V can be achieved for LiBH 4 -Li 2 NH (1:1). X-ray diffraction (XRD) and Fourier Transform infrared spectroscopy (FTIR) measurements on xLiBH 4 -Li 2 NH (x = 1, 2, 4) samples inform that original phases were well preserved after ball milling and temperature ramping. Their chemical stabilities were also demonstrated by differential scanning calorimetry (DSC) measurements. The enhanced lithium mobility at low temperature in LiBH 4 -Li 2 NH should be ascribed to the favorable boundaries between both phases according to the investigations by both in-situ nuclear magnetic resonance (NMR) and high-resolution transmission electron microscope (HRTEM). However, at a temperature above 373 K, the enhanced ionic mobility of LiBH 4 -Li 2 NH should be mainly contributed by HT-LiBH 4 phase.