Sulfide-based solid composite electrolyte film

A process for manufacturing a free-standing solid composite electrolyte film, comprising the steps of

• a) mixing (i) at least one sulfide-based solid ionic conducting inorganic particle and (ii) at least one tetrafluoroethylene (TFE) (co)polymer to form a paste;
• and
• b) calendaring or extruding the paste to produce a film,
• wherein the step a) mixing comprises a1) homogenizing the (i) at least one sulfide-based solid ionic conducting inorganic particle and (ii) at least one TFE (co)polymer into powders and a2) blending the powders into a paste.

A free-standing solid composite electrolyte film comprising

• (i) at least one sulfide-based solid ionic conducting inorganic particle;
• and
• (ii) at least one TFE (co)polymer,
• wherein an amount of the (ii) at least one TFE (co)polymer is from 1.0 to 20.0 wt %, based on the total weight of the film.