As discussed in Chapter 10, the ionic conductivities achieved with solid polymer electrolytes, so far, have remained below 10−3 S/cm. As a result, they cannot yet be applied in common and large-scale lithium-ion batteries. Gel polymer electrolytes are a compromise between organic electrolytes and solid polymer electrolytes since they have characteristics of both polymers (good processing performance) and organic electrolytes (high ionic conductivity).