Fig. 3 shows the microstructure of LTAPO powder and the LTAPO–
PTFE composite electrolyte, containing liquid electrolyte. Synthesized LTAPO powder (a) by sol–gel
process displays a uniform particle size with a spherical shape. In case of LTAPO–PTFE composite
electrolyte (b), LTAPO powders are uniformly dispersed in the composite solid electrolyte and the
liquid electrolyte fills in the gap between LTAPO and PTFE. The filled liquid electrolyte will not
only reduce the boundary resistance between the LTAPO powder and PTFE, but also enhance the contact
between the solid electrolyte and electrode. Good flexibility of the ceramic-polymer-composite
electrolyte is shown in Fig. 3(c) and as- cribes to the entangling ability of the polymer chain.
The high flexibility of the composite solid electrolyte should facilitate an application into a
high safety flexible battery.