Research Progress on Electrospun Materials for Sodium-Ion Batteries

The scarce lithium resources would ultimately fail to satisfy the ever-growing industrial demand, especially for the large-scale stationary energy storage. Sodium-ion batteries (SIBs) are considered as promising next-generation power sources because sodium is widely available and exhibits similar chemistry to that of lithium-ion batteries (LIBs). Although sodium share similar physical and chemical properties to lithium, the lager ionic radius, heavier molar mass and less negative redox potential of Na+/Na of the sodium jointly lead to some issues beset the SIBs, such as sluggish sodiation kinetics, larger volume expansion and lower energy density, which need to be tackled to promote the practical applications of the SIBs. Therefore, developing appropriate electrode materials is crucial to achieve SIBs with long lifespan and high energy density. One-dimensional nanostructures can provide orientated electronic (ionic) transport and strong tolerance to volume change, thus enhancing the electrochemical performance of electrode materials. Electrospinning technique is a low cost and versatile method to fabricate continuous one-dimensional functional materials with various morphology and targeted components that has been widely applied in SIBs. The volume change could be buffered efficiently by facilely modifying the morphology of electrospun materials or in-situ compositing with carbon materials. Benefiting from the ultra-high aspect ratio, electrospun one-dimensional electrodes can reduce the ionic transport distance, while provide continuous transport way for electron along the longitudinal direction, which is helpful to improve the sluggish sodiation kinetics. It is also worth noting that free-standing or flexible fibers could be easily obtained via the electrospinning technique, which can be used as binder-free electrode to enhance the energy density of the batteries. The research progress on electrospun materials for sodium-ion batteries is summarized in this review, including cathode materials and anode materials. Their electrochemical performance in sodium storage is discussed in detail. The advantages and challenges of these materials were pointed out, and the future development of electrospun materials for sodium ion batteries was also prospected.