Computational Modelling Study on Electrochemical Activity of Nanoporous and Bulk Beta MnO2

Abstract

Nanostructured manganese dioxides (MnO2) are among the promising materials for high-capacity lithium-ion batteries [1], lithium air batteries [2] and supercapacitors [3], that can be used in electric vehicles and other consumer electronics. They further have several advantages owing to their high specific energy capacity, low fabrication cost, abundance of the materials in the earth, and environmentally friendly nature [4]. Various experimental methods have been employed for the synthesis of MnO2 with various nano-architectures such as the spheres, sheets, porous, wires, rods [5,6] etc. Simulated amorphisation recrystallisation method has been successfully used to nucleate and crystallise bulk and nanoporous β-MnO2 [7]. In the current study molecular dynamics simulation reveals that the reason nanoporous β-MnO2 is electrochemically active, in contrast to the parent bulk material, is because strain imposed upon nanoporous β-MnO2 during lithium intercalation does not influence the structure or dimensions of the 1D tunnels in which the lithium ions intercalate and reside. Conversely, the parent bulk material suffers structural collapse of the 1D tunnels under strain. [1] B.X. Li, G.X. Rong, Y. Xie, L.F. Huang and C.Q. Feng, Inorg. Chem. 2006, 45, 6404. [2] A. Débart, A.J. Paterson, J. Bao and P.G. Bruce, Angew. Chem., Int. Ed. 2008, 47, 4521. [3] W. Wei, X. Cui, W. Chen and D.G. Ivey, Chem. Soc. Rev. 2011, 40, 1697. [4] S. Devaraj and N. Munichandraiah, J. Phys. Chem. C 2008, 112, 4406. [5] J.H. Cheng, G.A. Shao, H.J. Yu and J.J. Xu, J. Alloys Compd. 2010, 505, 163. [6] X. Wang and Y. Li, Chem. Eur. J. 2003, 9, 300. [7] P.E.Ngoepe, R.R. Maphanga and D.C. Sayle, (2013), “Towards the Nanoscale”, Chapter 9 in Computational Approaches to Energy Materials, pp 261-290, edited by C.R.A. Catlow, A. Sokol and A. Welsch, John Wiley and Sons Ltd.