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.
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
and porous carbon,[5,6] tin (Sn), and antimony (Sb) show
poor cycle performance due to their large volume expansion
caused by Na+ insertion.