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

FeS₂ shows significantpotential as cathodematerial for all-solid-state lithiumbatteries (ASSLBs) due to its high theoretical specific capacity, lowcost, and environmental friendliness. However, the poor ion/electronconductivity and large volume variation effect of FeS₂ inhibitits practical applications. Here, the influence of particle size of FeS₂ onthe corresponding sulfide-based solid-state batteries iscarefully investigated by tuning FeS₂ size. Moreover, lowoperating temperature is chosen to mitigate the large volume changes duringcycling in the battery. S-FeS₂ with smallerparticle sizes delivers superior electrochemicalperformances than that of the larger L-FeS₂ inLi_5.5PS_4.5Cl_1.5-based ASSLBs under differentoperating temperatures. S-FeS₂ shows stabledischarge 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 of146.9 mAh/g and maintains 63% of the capacity after 100 cycles. This workcontributes to constructing ASSLBs enables excellent electrochemicalperformances under extreme operating temperatures.