Multifunctional SnO2/3D Graphene Composites for Lithium-Ion and Sodium-Ion Batteries

Abstract

Although both Li-ion batteries (LIBs) and Na-ion batteries (NIBs) were investigated in the similar era (1980’s), LIBs are a current technology of choice for portable electronics and electric vehicle applications due to NIBs’ lower gravimetric/volumetric energy density. Recently, NIBs have gained another momentum for grid-scale energy storage systems (ESS) where the weight and volume limitations are relatively low. The most important requirements of EES would be the cost, reliability and long service life, while the high-energy density would be still viewed as an advantage. While looking slightly similar, Li and Na metals (and their cations) have distinct physical and chemical properties. It would be interesting to develop the multifunctional materials which can be used as effective electrode materials for both batteries. SnO2 is an attractive material due to high theoretical capacity (for both LIBs and NIBs), low cost, abundance and ease of synthesis. But there are many drawbacks that need to be overcome for SnO2 to be applied to actual batteries. Various technical issues include the large volume expansion during discharge/charge process in batteries, the formation of unstable solid electrolyte interface (SEI), and the aggregation of Sn particles during battery operation, all of which can lead to the rapid capacity fading of batteries. In this work, ultra-fine SnO2 nanoparticles dispersed within unique 3D-graphene structure (SnO2/3D GS) were synthesized by easy and simple hydrothermal process. These 3D-graphene structure could accommodate large volume change, prevent aggregation of Sn, and provide much facile electron transfer during battery operation. The SnO2/3D GS material exhibited outstanding electrochemical performances as anodes for both LIBs and NIBs. The structure-property-performance relation was investigated by various methods including SEM, TEM, EIS, CV, and XRD. The focus was on comparative studies of the internal resistance and diffusivity of Li-ions and Na-ions in SnO2/3D GS composites. Furthermore, the direct conversion from SnO2 to amorphous Sn during discharge/charge of 1st cycle in LIBs and NIBs was monitored by in-situ XRD. Figure 1