Development of metal sulfide based nanocomposite for high performance sodium-ion batteries /

Abstract

Over the past few decades lithium-ion batteries (LIBs) were commercialized and had dominated the market as a small-large scale energy store device but recently, rapid increase in lithium prices was observed because of its high demand and low resource ratio. Ultimately, this makes lithium highly unfeasible for large scale applications and to meet those requirements, alternate electrochemical energy storage systems have to be looked at. Considering this, Sodium has the potential to fill the gap left by LIBs owing to the fact that sodium ion batteries (NIBs) follows the same electrochemistry mechanism as LIBs and more importantly, highly resource availability thus, making a cheaper alternative. However, because of large sodium ion radii than lithium ion and low electrochemical reduction potential than lithium, NIB electrodes face serious amount of volume expansion during cycling and also fail to deliver same volumetric and gravimetric energy density as LIBs. Among different available anode materials, metal chalcogenides have piqued interest because of its high theoretical capacity however, since it undergoes partial alloying-conversion reaction phenomena during cycling, it also experiences large volume expansion which reduces its cyclic life and capacity retention. One such materials is tin sulfide-based anode materials and many approaches have been devised so far to improve its cyclic life, capacity retention and initial coulombic efficiency of NIB anode such as by adding a matrix material like graphene, carbon black or by tuning its morphology etc. Here in this work, via solvothermal route, doped carbon nanotubes were added SnS which created a network with SnS and enhanced its electrochemical performance. XRD, SEM revealed its amorphous nature and cauliflower like morphology while TGA gave us an estimated amount of CNTs that were used to create this amorphous framework. Galvanostatic charge/discharge analysis revealed that this nanocomposite shows better initial coulombic efficiency and also delivers good cyclic life with enhanced capacity retention. CV confirmed partial alloying/conversion reaction mechanism that it follows and EIS revealed reduction to Na+ diffusion resistance was observed. This enhanced electrochemical performance in nanocomposite can be ascribed to heteroatom dopants forcing nanocomposite to develop an amorphous structure thus, providing sufficient space, which act as a buffer to volume expansion.