Revealing the size effect of FeS2 on solid-state battery performances at different operating temperatures

FeS2 shows significant potential as cathode material for all-solid-state lithium batteries (ASSLBs) due to its high theoretical specific capacity, low cost, and environmental friendliness. However, the poor ion/electron conductivity and large volume variation effect of FeS2 inhibit its practical applications. Here, the influence of particle size of FeS2 on the corresponding sulfide-based solid-state batteries is carefully investigated by tuning FeS2 size. Moreover, low operating temperature is chosen to mitigate the large volume changes during cycling in the battery. S-FeS2 with smaller particle sizes delivers superior electrochemical performances than that of the larger L-FeS2 in Li5.5PS4.5Cl1.5-based ASSLBs under different operating temperatures. S-FeS2 shows stable discharge capacities during 50 cycles with a current density of 0.1 mA/cm2 under -20 °C. When the current density rises to 1.0 mA/cm2, it delivers an initial discharge capacity of 146.9 mAh/g and maintains 63% of the capacity after 100 cycles. This work contributes to constructing ASSLBs enables excellent electrochemical performances under extreme operating temperatures.