In situ formed FeS2@CoS cathode for long cycling life lithium-ion battery* *Project supported by the Fundamental Research Funds for the Central Universities, China (Grant No. ZYGX2019Z008) and the National Natural Science Foundation of China (Grant No. 52072061).

Abstract

Pyrite FeS2 exhibits an ultrahigh energy density (1671 W⋅h⋅kg−1, for the reaction of FeS2 + 4Li = Fe + 2Li2S) in secondary lithium-ion batteries, but its poor cycling stability, huge volume expansion, the shuttle effect of polysulfides, and slow kinetic properties limit its practical application. In this work, we synthesize a composite structure material CoS on FeS2 surface (FeS x @CoS, 1 < x ≤ 2) by using a cobalt-containing MOF to improve its cycle stability. It is found that CoS inhibits the side reactions and adsorbs polysulfides. As a result, the modified FeS2 shows a higher discharge capacity of 577 mA⋅h⋅g−1 (919 W⋅h⋅kg−1) after 60 cycles than 484 mA⋅h⋅g−1 (778 W⋅h⋅kg−1) of bare pyrite FeS2. This efficient strategy provides a valuable step toward the realization of high cycling stability FeS2 cathode materials for secondary lithium-ion batteries and enriches the basic understanding of the influence of FeS2 interfacial stability on its electrochemical performances.