The development of high-performance energy storage systems is in urgent need to match the rapid growth in renewable energy technologies. Lithium-ion batteries are currently among the most widely used state-of-the-art battery systems, but suffer from several limitations. Its low abundance does not make it ideal to be applied in large-scale energy storage. In comparison, sodium-ion batteries possess more potential since the cost of sodium is lower. However, the absence of appropriate anode materials has been a longstanding bottleneck for the development of sodium-ion batteries. Some anode materials of lithium-ion batteries show poor performance ranging from low specific capacity and slow kinetics to large volume changes when applied in sodium-ion batteries because of sodium's larger molecular size in comparison to that of lithium.

Prof. T. S. Zhao has led a research team at The Hong Kong University of Science and Technology to identify high-performance anode materials that are compatible in sodium-ion batteries. They have recently hypothesized that phosphorene-like SiS and SiSe could be the promising anode materials for sodium-ion batteries via first-principles calculations. Phosphorene is a newly synthesized two-dimensional material exhibiting a desirable puckered surface, but its application in sodium-ion batteries is hindered by instability towards O2 and H2O. Attempting to incorporate the unique structure of phosphorene while overcoming its shortcomings, Prof. T.S. Zhao et al. proposed to apply the "atomic transmutation" method designed phosphorene-like SiS and SiSe as the anode materials for sodium-ion batteries. Their calculations showed that the maximum Na/SiS and Na/SiSe ratios are 1.0, corresponding to the high theoretical specific capacities of 445.6 and 250.4 mAh g-1 respectively. In addition, during the whole sodium loading process, the volume changes of SiS and SiSe are very small, ensuring good structural stabilities in the repeated charge/discharge process. More importantly, sodium diffuses rapidly on SiS and SiSe with energy barriers of just 0.135 and 0.158 eV, values which are lower than those of conventional anode materials such as Na2Ti3O7 and Na3Sb, which can lead to high rate capabilities for Na-ion batteries.

###

This research was fully supported by the grant from the Research Grants Council of the Hong Kong Special Administrative Region, China (16213414).

See the article: Haoran Jiang, Tianshou Zhao, Yuxun Ren, Ruihan Zhang, Maochun Wu, Ab initio prediction and characterization of phosphorene-like SiS and SiSe as anode materials for sodium-ion batteries, Science Bulletin, 2017, Vol.62, No. 8: 572-578.