(Fe0.5Ni0.5)0.96S with Bimetallic Cation Vacancy Defect as an Efficient Catalyst for Regulating the Reaction Kinetics of Li2S

Recently, defect-engineered modified materials with abundant active sites are considered promising hosts of sulfur cathodes in lithium sulfur batteries (LSBs). Here, a multifunctional (Fe0.5Ni0.5)0.96S-reduced graphene oxide composite (NFS-rGO) has been fabricated by the combination of highly conductive rGO and bimetallic cation vacancy structure and was utilized as a sulfur host. The bimetallic cation vacancies provide plentiful active sites for the adsorption and accelerated conversion of lithium polysulfides (LiPSs). The rGO afforded a highly conductive network and inhibited the aggregation of (Fe0.5Ni0.5)0.96S nanoparticle. After sulfur loading, the NFS-rGO/S exhibited satisfactory electrochemical performances, and it presented a high capacity of 729.3 mAh g–1 at 3 C and a lower capacity attenuation rate of 0.066% per cycle during 700 cycles at 1 C. In addition, the galvanostatic intermittent titration technique and Li2S deposition results indicated that the nucleation barrier of Li2S is effectively reduced, and the polarization is also alleviated. This work provided a simple preparation technique for the fabrication of bimetallic cation vacancy materials and offered a foundation for application of such materials in LSBs.