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Lithium ion storage between graphenes.

Chan Y, Hill JM - Nanoscale Res Lett (2011)

Bottom Line: The number densities of lithium ions between the two graphenes are estimated from existing semi-empirical molecular orbital calculations, and the graphene sheets giving rise to the triple ion layers admit the largest storage capacity at all temperatures, followed by a marginal decrease of storage capacity for the case of double ion layers.These two configurations exceed the maximum theoretical storage capacity of graphite.Although the single ion layer provides the least charge storage, it turns out to be the most stable configuration at all temperatures.

View Article: PubMed Central - HTML - PubMed

Affiliation: Nanomechanics Group, School of Mathematical Sciences, The University of Adelaide, Adelaide, SA 5005, Australia. yue.chan@adelaide.edu.au.

ABSTRACT
In this article, we investigate the storage of lithium ions between two parallel graphene sheets using the continuous approximation and the 6-12 Lennard-Jones potential. The continuous approximation assumes that the carbon atoms can be replaced by a uniform distribution across the surface of the graphene sheets so that the total interaction potential can be approximated by performing surface integrations. The number of ion layers determines the major storage characteristics of the battery, and our results show three distinct ionic configurations, namely single, double, and triple ion forming layers between graphenes. The number densities of lithium ions between the two graphenes are estimated from existing semi-empirical molecular orbital calculations, and the graphene sheets giving rise to the triple ion layers admit the largest storage capacity at all temperatures, followed by a marginal decrease of storage capacity for the case of double ion layers. These two configurations exceed the maximum theoretical storage capacity of graphite. Further, on taking into account the charge-discharge property, the double ion layers are the most preferable choice for enhanced lithium storage. Although the single ion layer provides the least charge storage, it turns out to be the most stable configuration at all temperatures. One application of the present study is for the design of future high energy density alkali batteries using graphene sheets as anodes for which an analytical formulation might greatly facilitate rapid computational results.

No MeSH data available.


Related in: MedlinePlus

Number of lithium ions stored between graphenes under an additional external energy.
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Figure 9: Number of lithium ions stored between graphenes under an additional external energy.

Mentions: External effects arising for example from either pressure, electrical, or magnetic fields will modify the potential landscape of the proposed physical system and hence vary the number of lithium ions stored between graphenes. We may capture such effects by adding an additional homogeneous energy term V into Equation (3). We fix T = 300 K and r = 10 Å to determine the variation of the lithium storage as a function of this external energy V, and the numerical results are shown in Figure 9. We comment that in all scenarios, ion storages for three different layer configurations reduce from the corresponding results in Figure 8 at T = 300 K, and the storage capacity decreases due to the presence of a positive external energy. Again, the deeper potential well depth for the single ion layer minimizes the rate of ion leakage for the case of the single layer in comparison to that of the double and triple layers. Rather surprisingly, the storage capacity of the double layers surpasses that of the triple layers when V exceeds 0.0135 eV, which might easily arise during a charging process. This outcome strengthens the adoption of using double layers as the ideal ion storage configuration.


Lithium ion storage between graphenes.

Chan Y, Hill JM - Nanoscale Res Lett (2011)

Number of lithium ions stored between graphenes under an additional external energy.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211259&req=5

Figure 9: Number of lithium ions stored between graphenes under an additional external energy.
Mentions: External effects arising for example from either pressure, electrical, or magnetic fields will modify the potential landscape of the proposed physical system and hence vary the number of lithium ions stored between graphenes. We may capture such effects by adding an additional homogeneous energy term V into Equation (3). We fix T = 300 K and r = 10 Å to determine the variation of the lithium storage as a function of this external energy V, and the numerical results are shown in Figure 9. We comment that in all scenarios, ion storages for three different layer configurations reduce from the corresponding results in Figure 8 at T = 300 K, and the storage capacity decreases due to the presence of a positive external energy. Again, the deeper potential well depth for the single ion layer minimizes the rate of ion leakage for the case of the single layer in comparison to that of the double and triple layers. Rather surprisingly, the storage capacity of the double layers surpasses that of the triple layers when V exceeds 0.0135 eV, which might easily arise during a charging process. This outcome strengthens the adoption of using double layers as the ideal ion storage configuration.

Bottom Line: The number densities of lithium ions between the two graphenes are estimated from existing semi-empirical molecular orbital calculations, and the graphene sheets giving rise to the triple ion layers admit the largest storage capacity at all temperatures, followed by a marginal decrease of storage capacity for the case of double ion layers.These two configurations exceed the maximum theoretical storage capacity of graphite.Although the single ion layer provides the least charge storage, it turns out to be the most stable configuration at all temperatures.

View Article: PubMed Central - HTML - PubMed

Affiliation: Nanomechanics Group, School of Mathematical Sciences, The University of Adelaide, Adelaide, SA 5005, Australia. yue.chan@adelaide.edu.au.

ABSTRACT
In this article, we investigate the storage of lithium ions between two parallel graphene sheets using the continuous approximation and the 6-12 Lennard-Jones potential. The continuous approximation assumes that the carbon atoms can be replaced by a uniform distribution across the surface of the graphene sheets so that the total interaction potential can be approximated by performing surface integrations. The number of ion layers determines the major storage characteristics of the battery, and our results show three distinct ionic configurations, namely single, double, and triple ion forming layers between graphenes. The number densities of lithium ions between the two graphenes are estimated from existing semi-empirical molecular orbital calculations, and the graphene sheets giving rise to the triple ion layers admit the largest storage capacity at all temperatures, followed by a marginal decrease of storage capacity for the case of double ion layers. These two configurations exceed the maximum theoretical storage capacity of graphite. Further, on taking into account the charge-discharge property, the double ion layers are the most preferable choice for enhanced lithium storage. Although the single ion layer provides the least charge storage, it turns out to be the most stable configuration at all temperatures. One application of the present study is for the design of future high energy density alkali batteries using graphene sheets as anodes for which an analytical formulation might greatly facilitate rapid computational results.

No MeSH data available.


Related in: MedlinePlus