Mixed-Conductive FeS ₂ Composite Cathode for High Areal Capacity Thin-Film Lithium Batteries

Pyrite (FeS2) thin-film cathode holds great potential for all-solid-state thin-film lithium batteries (ASSTFBs) due to its high theoretical volumetric capacity. However, fabricating FeS2 thin films using conventional physical vapor deposition techniques presents significant challenges including low deposition rates and limited areal capacities. Herein, a simple tape-casting process is novelly employed to fabricate FeS2-based composite thin-film cathodes with superior mixed ionic-electronic conductivity (MIEC-FeS2 cathode). Benefiting from the inhibitory effect of lithium-phosphorus-oxynitride thin-film solid electrolyte on the shuttle effect of Li-polysulfides, along with its excellent ionic conductivity and interfacial contact, the MIEC-FeS2 cathode can deliver a high areal capacity of 277.3 μAh cm–2 at 20 μA cm–2 and outstanding cycling stability of up to 3000 cycles in a solid-state system. More importantly, the MIEC-FeS2 based ASSTFBs could deliver a high areal capacity of 180.1 μAh cm–2. This work paves the way for the scalable, low-temperature fabrication of stable ASSTFBs with high areal capacities.