Pyrite FeS2 is considered a promising conversion cathode material due to its high energy density, low cost, and environmental benignity. However, its huge volume variation induced particle pulverization and slow kinetic properties during cycling are the main obstacles to further commercial applications. In this work, a dual-functional polydimethylsiloxane/carbon nanotubes(PDMS/CNTs) coating layer is introduced to overcome these drawbacks. The ultra-elastic PDMS layer can hold the drastic volume change and protect FeS2 from pulverization. Meanwhile, the carbon nanotubes dispersed in PDMS can function as highways to facilitate electron transport kinetics. As a result, FeS2@PDMS-CNTs display a better discharge specific capacity of 559 mAh·g−1, while bare FeS2 only shows an inferior discharge specific capacity of 235 mAh·g−1 after 100 cycles. This work provides a straightforward coating strategy for the formation of a conductively elastic core-shell composite to improve electrochemical performances for the conversion-type reaction materials.