Soft/rigid SnS&TiS2 compounds with carbon nanotubes as heterostructure anode materials for high-performance sodium-ion batteries

SnS is a promising anode material for sodium-ion batteries (SIBs) due to its high theoretical specific capacity, but the poor intrinsic conductivity, bulk expansion and shuttle effects brought by polysulfides seriously limit its practical use. Here, soft/rigid SnS&TiS 2 compounds with carbon nanotubes (ST@CNTs) is designed to overcome the shortcomings. The rigid TiS 2 , as the strong backbone of SnS&TiS 2 , relieves the expansion stress caused by SnS after sodiation, together with CNTs improve the materials conductivity. TiS 2 generates many sulfur defects under the synergistic effect of SnS, which can regulate the sodium-ion embedding sites to stabilize the compound structure and decrease the sodium-ion diffusion energy barrier. Moreover, rigid TiS 2 can adsorb polysulfides induced by SnS, thus suppresses the shuttle effect and improves the cycling and rate performances. Fortunately, the above conclusions are confirmed by the DFT calculations. The ST@CNTs provide a specific capacity of 550 mAh/g at 1.0 A/g after 300 cycles, and a high-rate capability of 443 mAh/g at 2.0 A/g. This soft/rigid misfit strategy combines the advantages of high modulus of rigid layers and high sodium-ion storage capacity of soft layers, which gives an idea for the development of new anode candidates for SIBs.