Novel ion-conductive inorganic/organic composites were prepared from lithium chloroboracite (Li 4 B 7 O 12 Cl) and polyethylene glycol (PEG). Li 4 B 7 O 12 Cl was stable under ambient conditions and was easily prepared by a sol–gel reaction. The maximum ionic conductivity of the composites was observed when the composite was prepared in the ratio of Li 4 B 7 O 12 Cl/PEG=60/40 (weight/weight), and it was 1.6×10 −6 S/cm at 30 °C and 2.0×10 −5 S/cm at 80 °C, respectively. Addition of LiN(SO 2 CF 3 ) 2 to the polymer matrix of the composites increased the ionic conductivity. The Li 4 B 7 O 12 Cl/PEG composites were mechanically tougher than Li 4 B 7 O 12 Cl itself.