In operando mechanism analysis on nanocrystalline silicon anode material for reversible and ultrafast sodium storage

Presently, lithium-ion batteries (LIBs) are the most promising commercialized electrochemical energy storage systems. Unfortunately, the limited resource of Li results in increasing cost for its scalable application and a general consciousness of the need to find new type of energy storage technologies. Very recently, substantial effort has been invested to sodium-ion batteries (SIBs) due to their effectively unlimited nature of sodium resources. Furthermore, the potential of Li/Li+ is 0.3 V lower than that of Na/Na+, which makes it more effective to limit the electrolyte degradation on the outer surface of the electrode.[1] Nevertheless, one major obstacle for the commercial application of SIBs is the larger ionic radius of Na+ (0.98 Å) which is 0.29 Å larger than that of Li+, resulting in easier structural degradation for the Na+ host materials.[2,3] As anode materials for SIBs, the traditional carbon-based materials like hard carbon[4] and porous carbon,[5,6] tin (Sn),[7] and antimony (Sb)[8] show poor cycle performance due to their large volume expansion caused by Na+ insertion.