Lithium-ion-conducting glass-ceramics of a boron-containing alkali sodalite Li₈B₆Si₆O₂₄Cl₂

Abstract

Alkali sodalites containing boron (B) as the main framework cation are scarce. A cubic lithium sodalite containing B in the sodalite framework, Li₈B₆Si₆O₂₄Cl₂, whose lattice parameter [7.8856(1) Å] is the smallest of the known alkali sodalites, has been discovered, and Li₈B₆Si₆O₂₄Cl₂-based glass-ceramics have been prepared from the Li₂O–B₂O₃–SiO₂–LiCl quaternary system. The relative density of the resulting glass-ceramics and weight fraction of Li₈B₆Si₆O₂₄Cl₂ in their crystalline part reached ∼0.98 and ≳0.9, respectively. The dc conductivity recorded at 60 °C with non-blocking Li–Au electrodes was ∼1.5 × 10⁻⁶ and ∼2.3 × 10⁻⁷ S cm⁻¹ in partially and highly crystallized samples, respectively, and the activation energy of conductivity was ∼0.5–0.6 eV. The glass-ceramics were stable in contact with Li metal and the transport number of Li⁺ ion was ∼0.95.