Quasi-two-dimensional topological Co3Sn2S2 composite toward high rate sodium ion storage

Abstract

Topological semimetal Co3Sn2S2 with a quasi-two-dimensional (quasi-2D) structure is an attractive anode candidate for sodium ion storage. However, its structure stability and sodiation/desodiation mechanism remain elusive. Herein, the sodium ion storage behavior of Co3Sn2S2 is explored, in which carbon nano onions (CNOs) are introduced to further improve its performance. Co3Sn2S2-CNOs exhibits a superior rate capacity of 130.5 mAh g−1 at 50 A g−1, as well as a much improved cycle life. The stability of the host structure of Co3Sn2S2 can be well-maintained by CNOs, which ensures efficient diffusion channel of sodium ions in its quasi-2D structure. The synergistic effect of electrons and ions, as well as increased active sites across the interface between Co3Sn2S2 and CNOs boosts the rate performance. The multistep conversion and alloying reactions mechanism is proposed. Assemble sodium ion capacitors (SICs) based on the Co3Sn2S2-CNOs anode delivers the maximum energy density of 140 Wh kg−1 and maximum power density of 39 kW kg−1, which also maintains a capacity retention of 80.41% after 5000 cycles at 1 A g−1. This exploration provides a new perspective of a topological semimetal anode for high rate sodium ion storage.