Abstract
Tin and its compounds hold promise for the development of high-capacity anode materials that could replace graphitic carbon used in current lithium-ion batteries. However, the introduced porosity in current electrode designs to buffer the volume changes of active materials during cycling does not afford high volumetric performance. Here, we show a strategy leveraging a sulfur sacrificial agent for controlled utility of void space in a tin oxide/graphene composite anode. In a typical synthesis using the capillary drying of graphene hydrogels, sulfur is employed with hard tin oxide nanoparticles inside the contraction hydrogels. The resultant graphene-caged tin oxide delivers an ultrahigh volumetric capacity of 2123 mAh cm–3 together with good cycling stability. Our results suggest not only a conversion-type composite anode that allows for good electrochemical characteristics, but also a general synthetic means to engineering the packing density of graphene nanosheets for high energy storage capabilities in small volumes.
Highlights
Tin and its compounds hold promise for the development of high-capacity anode materials that could replace graphitic carbon used in current lithium-ion batteries
The buffer space available is determined by controlling the amount of sulfur, and this is applicable for any other noncarbon anode materials
Thermogravimetric analysis (TGA) under an inert atmosphere shows that the sulfur was almost completely removed by a mild thermal treatment of 400 oC36(Supplementary Fig. 1c)
Summary
Tin and its compounds hold promise for the development of high-capacity anode materials that could replace graphitic carbon used in current lithium-ion batteries. Unsuitable voids for the noncarbon component always exist due to the roughly designed and controlled carbon network produced during in situ synthesis Mechanical compression is another simple and practical method to reduce the surplus void space and increase the density of hybrid materials, but such a shrinkage from exterior to interior inevitably destroys the hybrid structure and is unfavorable to retain the stable electrode structure in discharge–charge process[28]. To yield an enough void space to buffer volume changes in carbon cages in the reported works, the template technique using removable templates of Si spheres[32], nickel (Ni) foam[33], polystyrene (PS) spheres[25] and some salt templates[34,35] is mainly used These templates used are somewhat incompatible with the noncarbon particles, and usually create template shape-induced voids, making it difficult to a Shrinking
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