Atomistic Origins of High Rate Capability and Capacity of N-Doped Graphene for Lithium Storage

Abstract

Distinct from pure graphene, N-doped graphene (GN) has been found to possess high rate capability and capacity for lithium storage. However, there has still been a lack of direct experimental evidence and fundamental understanding of the storage mechanisms at the atomic scale, which may shed a new light on the reasons of the ultrafast lithium storage property and high capacity for GN. Here we report on the atomistic insights of the GN energy storage as revealed by in situ transmission electron microscopy (TEM). The lithiation process on edges and basal planes is directly visualized, the pyrrolic N "hole" defect and the perturbed solid-electrolyte-interface configurations are observed, and charge transfer states for three N-existing forms are also investigated. In situ high-resolution TEM experiments together with theoretical calculations provide a solid evidence that enlarged edge {0002} spacings and surface hole defects result in improved surface capacitive effects and thus high rate capability and the high capacity are owing to short-distance orderings at the edges during discharging and numerous surface defects; the phenomena cannot be understood previously by standard electron or X-ray diffraction analyses.

High lithium anodic performance of highly nitrogen-doped porous carbon prepared from a metal-organic framework

“…The structured instability would increase after undergoing many charge-discharge cycles. Hence, it is suggested that the high quaternary N content in N-C-900 results in the bad cycling performance 23 . To activate the electrode, a current density of 0.2 A g À 1 was used for the first two cycles, and then the cycling performance of the N-rich carbon materials was evaluated at 5 A g À 1 in the range of 0.01-3.0 V versus Li/Li þ .…”

“…Moreover, the N atoms incorporated into graphitic networks facilitate the formation of stronger interactions between the N-doped carbon structure and the Li ions, which are favourable for Li insertion. For example, Wang et al 23 reported that doping with 3.9 atom% nitrogen could improve the Li storage capacity by up to 600 mAh g À 1 , which is higher than pure graphene. Wang et al 22 reported that N-doped graphene nanosheets exhibit a high reversible capacity of up to 900 mA h g À 1 and a significantly enhanced cycling stability.…”

Electrochemical Intercalation Behaviors of Lithium Ions into Graphene-Like Graphite

“…z E-mail: ymatsuo@eng.u-hyogo.ac.jp the intercalation behavior of lithium ions into GLG especially at the early stages of it has not yet been studied, which would be strongly related to the formation of SEI. Moreover, the mechanism of lithium storage in graphene-based carbons is not well understood because of their poor structural regularity, except for the results reported by Wang et al 11 They have indicated that lithium ions are intercalated between carbon layers, based on the TEM observation of lithium introduced nitrogen doped graphene operated in an all-solid-state cell.In this study, the structural changes of various GLG samples during the first charging process especially at high cell voltage regions were investigated and the mechanism of the intercalation of lithium ions was discussed based on the thermodynamic considerations. We also think that the results in this study would give a new insight into the lithium storage not only in carbon materials with large interlayer spacings such as graphene-based carbons but also in soft carbons.…”

Cu/Li4Ti5O12 scaffolds as superior anodes for lithium-ion batteries

“…25 Generally, the Cu/Li4Ti5O12 scaffolds for Li-ion batteries X Wang et al high density of atomic steps is believed to be one of the important origins of the high catalytic or electrochemical activities of small nanomaterials. [10][11][12][13] Similarly, this feature of Cu/LTO may facilitate the enhancement of the electrochemical performance of LTO.…”

“…8 Accompanied by the development of nanotechnology and science, nanostructured electrode materials with exposed highly reactive crystal planes ( Figure 1a) can now demonstrate promising properties, including higher electrochemical performance. [10][11][12][13] A good example is the (111) facet of Co 3 O 4 nanocrystals; 10 the (111) facet is desirable for LIBs and shows a larger capacity than the (001) plane. Another example is Li 4 Ti 5 O 12 films with (111) planes, which showed better ion transport properties and thus greater Li storage performance than samples with other planes exposed.…”