Theoretical Study on the Quantum Capacitance Origin of Graphene Cathodes in Lithium Ion Capacitors

Abstract

Quantum capacitance (QC) is a very important character of the graphene cathode in lithium ion capacitors (LIC), which is a novel kind of electrochemical energy conversion and storage device. However, the QC electronic origin of the graphene cathode, which will affect the electrochemical reaction at the electrode/electrolyte interface, is still unclear. In this article, the QC of various kinds of graphene cathode is investigated systematically by DFT calculation. It was found that the value and origin of QC strongly depend on the defects and alien atoms of graphene. Graphene with pentagon defects possesses a higher QC than pristine graphene due to the contribution from the electronic states localized at the carbon pentagon. The introduction of graphitic B can contribute to QC, while graphitic N and P does not work in the voltage range of the LIC cathode. Single vacant defect graphene and pyrrolic N-doped graphene demonstrate very high QC due to the presence of states associated with the σ orbital of unbonded carbon atoms. However, pyridinic graphene shows an even higher QC because of the states from the N atom. For the residual O in graphene, its QC mainly originated from the pz states of carbon atoms and the effect of O, especially the O in bridged oxygen functional group (–COC–), is very limited. These results provide new insight into further study of the catalytic behavior and the design of a high performance graphene cathode for LIC.

Effects of Intrinsic Pentagon Defects on Electrochemical Reactivity of Carbon Nanomaterials

“…First, the outstanding EDLCs performance can be attributed to the abundant pore structure with high specific surface area that is favorable for fast mass and charge transfer. Furthermore, the local electronic redistribution induced by intrinsic pentagon defects can promote the quantum capacitance of carbon materials, thereby improving the overall capacitance . The nitrogen dopants in PD/N‐C result in the enhanced conductivity and wettability of carbon matrix, further elevating the capacitance …”

Computational Insights into the Interaction between Li2S/Li2S2 and Heteroatom‐Doped Graphene Materials

“…It is discovered peaks of p orbital make the major contribution of electronic properties of O atoms. Compared to peaks of N p orbital in Figure (a) and (b), both peaks of O p orbitals locate below −2.0 eV, which is consistent with our previous work . This result suggests that electrons of p orbitals in O atoms of r‐GO are not as active as those in N atoms of PD−N and PL−N doped graphene, hence the ability of electronic transfer of O atoms is weaker.…”

Модельные Оценки Квантовой Емкости Аморфных И Эпитаксиальных Графеноподобных Соединений

“…Обсуждалась КЕ однолистного [3,[5][6][7]9] и двухлистного [5,7] графенов, эпитакcиального графена на карбиде кремния [8], графеновой наноленты [3,4,9] и одномерной углеродной структуры -карбина [9]. Более того, в недавно появившихся статьях [10][11][12] вопрос о КЕ графеновых структур обсуждается в связи с проблемой суперконденсаторов и хранения энергии [13][14][15]. С другой стороны, одним из следствий большого числа работ по функционализации графена для приборного применения стал поиск (в основном теоретический) графеноподобных соединений (GLC), среди которых несомненный интерес представляют двумерные (2D) аналоги классических трехмерных (3D) полупроводников A N B 8−N [16][17][18].…”