Sn restriction and Li2S reversible properties of novel sandwiched SnS@graphene hollow-sphere architecture for lithium storage

Abstract

Low reversion of Li2S and the Sn aggregation causing irreversible capacity loss are the primary cause of poor cycle performances in tin sulfide-based composites. These problems can be mitigated by confining SnS nanoparticles in sandwiched hollow-spherical graphene skeleton (Sandwich-SnS/GS), in which a large number of tiny SnS nanoparticles are inserted in between the interlayers of the sphere-like graphene shell with homogeneous distribution, while the spherical graphene interconnects each other forming a three-dimensional interconnected conductive network. This novel spherical graphene skeleton can immobilize the SnS and the lithiated products (Sn and Li2S) and suppress the local accumulation of metallic Sn at the largest extent, thus prompting the close contact of Sn/Li2S and their in-situ reverse transformation into SnS. In addition, the closed graphene sphere could inhibit the shuttle of lithium polysulfides derived from Li2S during charging, promote reversible transformation between Li2S and S8, providing an additional capacity contribution and ensuring the sustained capacity of the whole electrode without distinct decay. Thus, a high and stable reversible specific capacity of 756.7 mA h g−1 is retained in the Sandwich-SnS/GS composite after 200 cycles at 100 mA g−1, significantly higher than those of traditional hollow sphere and sandwich-like lamellar composite structures.