The Application Of CNTs Current Collectors In Na/Li Metal Anodes From Theoretical Chemistry Insight

The rapid development of industrialization and technological,accelerates the demand for energy,novel energy storage devices have become the topics of technological development.At present,the research and development of high-performance Na / Li ion batteries are currently the research hotspots in the field of new energy.Na / Li metal anodes have received extensive attention from the scientific community due to their high theoretical specific capacity and low chemical potential.However,battery safety problems caused by dendrite growth have been the main challenges in practical applications of metal Na/Li anodes.To design high-performance and safe Na metal anodes for rechargeable Na-metal batteries,the dendrite-growth mechanisms during Na electroplating process await to be fully understood.Here,we provided a density functional theory(DFT)insight into essential mechanisms associated with Na dendrite formation on different current collectors,such as Cu,Al,and single wall carbon nanotube(SWCNT).Furthermore,the effect of oxygencontaininggroups of SWCNT on Na / Li dendrite formation was investigated in detail.The main results obtained are as follows:(1)We investigated the adsorption behavior of Na atoms on SWCNT,Cu(111)surface,and Al(111)surface and further compared the stability of Na dimers.The “Sodiophilic” property and electronic configuration of Cu,Al,and SWCNTs were evaluated.Meanwhile,the electron transfer and the stability of Na dimers were estimated.For the adsorption of single Na atom,SWCNT,Cu and Al performed well with the adsorption energies of-2.15,-2.93 and-2.24 e V,respectively.However,the Na dimer was not energetically favorable on SWCNTs.Based on Hirshfeld atomic charges and electron density distribution,the stable electron configuration of SWCNT was found to play a critical role in dispersing Na adatoms.In addition,the vacancy defects in SWCNT induced better “Sodiophilic” property and inhibit dendrite growth.Our results unraveled the possible mechanisms underlying dendritic electrodeposition of Na on SWCNT,Cu and Al current collectors,indicating SWCNTs can be a promising current collector to develop dendrite-free Na metal anodes for safe Na-metal batteries.(2)On the basis of the previous study,the effects of different surface oxygen species of the carbon nanotube current collector on the formation of Na / Li dendrites were investigated.We investigated the adsorption behavior of Na / Li atoms on SWCNT and the modified SWCNTs with ketocarbonyl group(-C=O),phenolic hydroxyl group(C-OH),carboxyl group(-COOH),superoxy group(CO=O)and epoxy(-O-),and the stability of Na dimers were further compared.The results show that all oxygen-containing functional groups promote the adsorption of single Na/Li atoms.Based on Hirshfeld charge analysis and deformation density,we found that the amount of electrons obtained by the O atom determines the adsorption strength of the Na / Li atom.From the energy perspective,the formation of dimers are not stable on the intrinsic SWCNT and OH-SWCNT surfaces,,thereby inhibiting the growth of dendrites.This work provides a theoretical insight for guiding the preparation of specific carbon nanotube current collector materials with no Na / Li dendrite growth.