All solid-state rechargeable lithium battery with a solid electrolyte is recognized as one of alternative technologies for rechargeable power source, because of likely higher energy density and improved safety. High performance solid electrolyte is the bottleneck of developing solid state lithium ion batteries. In our research, amorphous lithium lanthanum titanate (LLTO) powders were prepared by a sol-gel method with an all alkoxide based route. Results showed that unlike its crystalline counterpart which turns into an electronic conductor in direct contact with lithium metal, amorphous LLTO remains to be an electronic insulator and hence is compatible with lithium metal although it also undergoes lithium insertion and the consequent reduction of Ti⁴⁺ to Ti³⁺. This striking difference between crystalline and amorphous LLTO could be ascribed to the atomic configuration difference, ordered versus disordered. The electronic states of a disordered system could be localized. Our results on electrochemical measurements indicated that amorphous LLTO is stable up to 12V, which can potentially be used with high voltage cathode materials.