Revealing sodium ion storage mechanism in hard carbon

Elucidating the Effect of Planar Graphitic Layers and Cylindrical Pores on the Storage and Diffusion of Li, Na, and K in Carbon Materials

“…This separation will, range up to 8 Å, with a short discussion of separations up to 15 Å included. [ 29,30 ] To assess the effect of curvature and pore size on metal storage, five different CNT models (representing cylindrical pores) with diameters ranging from 1 to 5 nm were constructed using the Atomsk code [ 56 ] (177, 300, 420, 600, and 800 atoms for the 1, 2, 3, 4, and 5 nm diameter CNTs, respectively). The curvature of these CNT models represents curved pores in hard carbons with a radius of curvature of 0.5, 1, 1.5, 2, and 2.5 nm, respectively.…”

“…[ 23,25,28,29 ] The dependence of local structure on the Na diffusion coefficients was also recently probed by Alvin et al, [ 30 ] showing that the Na diffusion coefficients and behavior in the different voltage regions has contributions from Na adsorption on surfaces and defects, on micropores, and from intercalation between graphitic sheets. [ 30 ] These different storage mechanisms in the different carbon motifs that form the complex hard carbon structure will be discussed in the next section.…”

“…These pores have a wide range of pore diameters (which could also be referred to as interlayer distances for the planar graphitic layer micropores), ranging up to around 5 nm. [ 29,30,36,37 ] Experimental studies have shown that the interlayer distance of the planar graphitic layers in hard carbons has a direct influence on the ability to insert and extract Na, with interlayer distances of up to 8 Å reported. [ 29,30 ] It has also been shown that, apart from the planar graphitic layers, curved and rumpled domains are present in hard carbon systems.…”

“…[ 29,30,36,37 ] Experimental studies have shown that the interlayer distance of the planar graphitic layers in hard carbons has a direct influence on the ability to insert and extract Na, with interlayer distances of up to 8 Å reported. [ 29,30 ] It has also been shown that, apart from the planar graphitic layers, curved and rumpled domains are present in hard carbon systems. [ 9,38–44 ] To fully understand the effect of carbon structure on metal storage mechanisms, it is important to have an atomic scale study to bring insight into how the different isolated local carbon structures influence metal adsorption, binding, and migration, to further develop and commercialize these battery technologies.…”

High‐Performance Sodium‐Ion Battery Anode via Rapid Microwave Carbonization of Natural Cellulose Nanofibers with Graphene Initiator

“…To analyze the Na + insertion mechanism during the sodiation of MrGO‐CNF, we carried out the ex situ X‐ray diffraction and ex situ Raman spectroscopy (Figure S9, Supporting Information) . The Bragg peak of pristine MrGO‐CNF centered at 2θ = 22.86° is corresponding to the parallel stacking of graphene sheets.…”