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Al-doped Li7La3Zr2O12 (LLZ) was prepared by a sol-gel process using lithium nitrate, lanthanum nitrate hexahydrate, zirconium propoxide and aluminum tri sec-butoxide as starting materials. Single phase of cubic LLZ was obtained by a heat treatment at 700 o C, which is lower than that in the solid state reaction process. The LLZ powders were sintered at 900°C using LiBO2 or Li3BO3 to form composite solid electrolyte. In the composite sintered with LiBO2, La2Zr2O7 was formed as an impurity phase. On the other hand, in the composite sintered with Li3BO3, single phase of cubic LLZ was obtained. The composite of Al-doped LLZ and Li3BO3 sintered at 900°C showed the total electrical conductivity of 1.9×10-5 S cm-1 , while Al-doped LLZ pellet without additives showed 1.6×10-6 S cm-1 .

Low-melting oxide glasses are promising as electrolytes for all-solid-state lithium rechargeable batteries. Glasses in the pseudobinary system Li 3 BO 3 Li 2 SO 4 were prepared by a mechanochemical technique. Raman spectra revealed that the glasses contained no macroanions which form networks but consisted only of Li + ions and two discrete ortho-oxoanions, BO 3 3¹ and SO 4 2¹. The density and molar volume increased and elastic moduli decreased with an increase in the Li 2 SO 4 content in the glasses. The heat treatment of the Li 3 BO 3 Li 2 SO 4 glasses at around 300°C brought about the crystallization to form ion conducting glassceramics. Electrical conductivities of the glasses and glass-ceramics in this system were maximized with the mixing of Li 3 BO 3 and Li 2 SO 4 . The conductivities were higher in the glass-ceramics of the compositions with small amounts of Li 2 SO 4 , ranging from 3 © 10 ¹6 to 1 © 10 ¹5 S cm ¹1 at room temperature, compared to the corresponding glasses. This conductivity enhancement by the heat treatment is probably due to the precipitation of solid solutions with a high temperature Li 3 BO 3 phase.

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