Synthesis and characterization of lithium-ion-conductive glassceramics of lithium chloroboracite Li4+xB7O12+x/2Cl (x = 0-1)

Abstract

Nearly single-phase and almost fully-crystallized glass-ceramics of lithium chloroboracite Li4+xB7O12+x/2Cl (x = 01) were prepared by crystallization of precursor glasses derived from the Li2O-B2O3-LiCl ternary system. The crystal structure of Li4B7O12Cl (x = 0) was refined by the Rietveld method in the space group F43c (no. 219). The precursor glass partially crystallized into Li2B4O7 at ∼500°C and was subsequently converted to Li4B7O12Cl at ∼600°C. The decomposition of Li4B7O12Cl started at ∼700°C. The conductivity of Li4B7O12Cl was much higher than that of Li5B7O12.5Cl (x = 1). The glass-ceramic sample with the highest weight fraction of Li4B7O12Cl (∼0.98 of crystalline part with a degree of crystallinity of ∼0.96) exhibited a conductivity of ∼4.6 × 10-4Scm-1 at 200°C and an activation energy of conductivity of ∼0.52 eV.