Consequently, ionic conductivity of
the composite electrolyte is 2 × 103 times higher than the LTAPO– PTFE composite membrane. This is
because the mixed liquid electrolyte fills the gaps between the ceramic electrolyte and polymer,
resulting in decreasing boundary resistance. This improves ions mobility by creating a direct path
for Li ions to travel between the electrodes [22]. Fig. 4(b) shows the pathway of Li-ions in a
LTAPO solid electrolyte, LTAPO–PTFE composite membrane and LTAPO–PTFE–LiPF6–EC/DMC composite
electrolyte. On LTAPO solid electrolyte of compact contact, ions transfer in all directions by ion
hopping. However, the LTAPO– PTFE composite membrane shows one-dimensional ion transfer along with
contacted LTAPO powder. The LTAPO–PTFE composite solid elec- trolyte enables two ion-transference
mechanisms with ion hopping and plasticizer transport. In the composite electrolyte, the increase
of LTAPO content increases the lithium ion transference number, while the ionic conductivity is
decreased. On the other hand, the increase of soaked liquid electrolyte increases the ionic
conductivity but the lithium ion transference number is decreased. The detailed information about
the mechanism needs further confirmation.