Sodium (Na) ion battery (NIB) has recently attracted increasing interest worldwide as a promising next-generation energy storage technology, because of the natural abundance, wide availability and low cost of Na resources. Operating at ambient temperature, NIBs provide a safer and sustainable energy storage solution [1,2]. These batteries could potentially approach the performance of Li-ion batteries if optimal electrode and electrolyte materials are identified.  

In this project, we focus on the design of the negative electrode materials  for Na ion batteries [2]. Nanoporous carbons are one of the materials that have been used as negative electrode materials, providing the necessary low cost, low voltage and good capacity. However, the intercalation mechanism of Na ions into the complicated 3D porous structure is still unknown; these carbons need to be designed  and optimized for best performance in NIBs.

By means of atomistic molecular dynamics simulations [3], the diffusion of sodium (Na) ions is investigated for different carbon electrode geometries, such as slit nanopore and rough nanopore, and nanopore sizes.  Slit and rough nanopores predict a different Na ion dynamics. Also, for sub-nanometer pore sizes the electrostatic surface charge decreases the Na ions diffusivity inside the nanopore. Our goal is to understand the fundamentals of adsorption and diffusion of Na ions in nanoporous carbons and develop an improved carbon model for the design of these materials. 

Acknowledgement

The authors are grateful for funding support from EPSRC.

 References 

[1] H. Kang, Y. Liu, K. Cao, Y. Zhao, L. Jiao, Y. Wang, H. Yuan, J. Mater. Chem. A 3,  17899 (2015).

[2] V. L. Chevrier and G. Ceder, Journal of The Electrochemical Society, 158, A1011-A1014 (2011).

[3] G. Kamath, R. W. Cutler, S. A. Deshmukh, M. S. Fard, R. Parrish, J. Huether, D. P. Butt, H. Xiong, S. K. R. S. Sankaranarayanan, J. Phys. Chem. C, 118, 13406, (2014).