Mixed-Conductive FeS₂ 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.