Self–Encapsulated Sb/C Nanocomposite with High Capacity and Stability As an Anode Material for Na-Ion Batteries

Li–ion batteries (LIBs) have been studied extensively in the past decades and become one of the most successful energy storage devices, which have rapidly penetrated into our lives. However, due to the limited supply and uneven global distribution of Li resources, the cost of LIBs may increase severely in the near future. Therefore, it is vital to develop more economical alternative energy storage system. In this regard, Na–ion batteries (SIBs) are attractive as promising alternative to LIBs due to the natural abundance of Na resources. Nevertheless, critical obstacles still exist for the commercialization of SIBs due to the lack of appropriate anode materials. Recently, Na-alloy type materials such as Sn and Sb have attracted attention due to their high theoretical specific capacity and low sodiation potential. In particular, Sb-based materials are very attractive as anode materials due to the low and suitable potentials for alloying/dealloying and high theoretical Na–storage capacity (660 mAh g -1 ) corresponding to formation of Na 3 Sb phase. However, these Na-alloy type materials can suffer from large volume change and resultant pulverization by the repeated alloying/dealloying processes. Although issues related to poor capacity retention of Na-alloy type materials caused by the large volume change during alloying/dealloying have been addressed using new binders and electrolyte additives, the practical application of Na-alloy type materials in SIBs is still challenge. In this study, a self–encapsulated Sb/C nanocomposite as an anode material for SIBs was successfully synthesized using the citric method followed by calcination process in an inert N 2 atmosphere. In addition, effect of the content of carbon as a buffer layer on the electrochemical performance of the Sb/C nanocomposite electrode was investigated. The obtained results revealed that the Sb-C nanocomposite with an optimized Sb content of 50.87% exhibited the best electrochemical performance. The electrode showed almost 77.6% capacity retention of 585 mAh g -1 after 300 cycles of charge-discharge at the rate of C/10. Impressively, even at the high rate of 10 C, the specific capacity of 281 mAh g -1 ­ was maintained. Furthermore, a full cell composed of Sb/C composite anode and NaCoO 2 cathode exhibited satisfactory specific capacity and cyclability, which confirms the potential of Sn/C anode for high performance SIBs.