Amorphous MoS3-modified porous Co4S3-embedded N,S co-doped carbon polyhedron as new high-capacity and high-rate anode materials for sodium-ion half/full cells

In this study, amorphous MoS3-modified porous Co4S3-embedded N,S co-doped carbon polyhedron (Co4S3@NSC/MoS3) was rationally prepared via a multi-step method. One-dimensional linear-like MoS3 with a high specific capacity of 894 mAh g-1 and abundant active sites compensated for the low capacity of Co4S3, thus enhancing the sodium ion storage capacity of the entire electrode. Moreover, three-dimensional N,S co-doped carbon networks (NSC) significantly inhibited large volumetric fluctuations in Co4S3 and MoS3, thereby sustaining the structural stability and enhancing the electron transfer efficiency. As a new anode material for sodium-ion half batteries, the constructed Co4S3@NSC/MoS3 with rapid Na+ diffusion and charge transfer kinetics demonstrated better sodium storage properties than Co4S3@NSC. At a rate of 0.5 A g-1 over 100 cycles, the reversible specific capacity of Co4S3@NSC/MoS3 reached 594 mAh g-1. Even when cycled at a rate of 2 A g-1 for 600 cycles, the charge capacity was stable at 435 mAh g-1. The rate performance of Co4S3@NSC/MoS3 was also found to be remarkable; when the rate increased to 10 A g-1, the average capacity was retained at 382 mAh g-1. Apart from half cells, reduced graphene oxide (rGO)-modified Na3V2(PO4)3 composite (Na3V2(PO4)3@rGO) was used as the cathode material to match with Co4S3@NSC/MoS3. The assembled full batteries were analyzed and their electrochemical properties were discussed. They also exhibited outstanding rate capability and high-rate long-life cyclic property. Even at 1 A g-1 over 500 cycles, the discharge capacity was stably maintained at 246 mAh g-1. The outstanding sodium storage properties of Co4S3@NSC/MoS3 mainly depended on the cooperative effects of MoS3 and Co4S3@NSC, indicating the potential application of Co4S3@NSC/MoS3 in energy storage fields.