Poly(imide-co-siloxane) as a Thermo-Stable Binder for a Thin Layer Cathode of Thermal Batteries

The polymer binder, poly(imide- co -siloxane) (PIS), was synthesized and applied to form a thin cathode layer of composites for a thermal battery that has an unusually high operating temperature of 450 °C. The PIS was prepared through cross-linking of the polyimide with polysiloxane. The morphology of FeS 2 /PIS composites showed that FeS 2 particles was coated with the PIS cross-linked gel. The FeS 2 /PIS composites enabled to fabricate mechanically stable thin cathode layer that was 10–20% of the thickness of a conventional pellet-type cathode. The FeS 2 /PIS composites were stable up to 400 °C and maintained their morphology at this temperature. PIS coating layers decomposed at 450 °C, and a new residue was generated, which was observed by transmission electron microscopy, and the compositional change was analyzed. The FeS 2 /PIS composites showed enhanced thermal stability over that of FeS 2 in thermogravimetric analysis. The thermal battery with the PIS polymer binder showed a 20% discharge capacity increase when compared to a conventional pellet-type cathode.