Adsorption and ultrafast diffusion of lithium in bilayer graphene:Ab initioand kinetic Monte Carlo simulation study

Abstract

In this work, we adopt first-principle calculations based on density functional theory and Kinetic Monte Carlo simulations to investigate the adsorption and diffusion of lithium in bilayer graphene (BLG) as anodes in lithium-ion batteries. Based on energy barriers directly obtained from firstprinciple calculations for single-Li and two-Li intercalated BLG, a new equation was deduced for predicting energy barriers considering Lis interactions for multi-Li intercalated BLG. Our calculated results indicate that Li energetically prefers to intercalate within rather than adsorb outside the bilayer graphene. Additionally, lithium exists in cationic state in the bilayer graphene.More excitingly, ultrafast Li diffusion coefficient (~10 −5 cm 2 s −1 ) within AB-stacked BLG near room temperature was obtained, which reproduces the ultrafast Li diffusion coefficient measured in recent experiment. However, ultrafast Li diffusion was not found within AA-stacked BLG near room temperature. The analyses of potential distribution indicate that the stacking structure of BLG greatly affects its height of potential well within BLG, which directly leads to the large difference in Li diffusion. Furthermore, it is found that both the interaction among Li ions and the stacking structure cause Li diffusion within AB-stacked BLG to exhibit directional preference. Finally, the temperature dependence of Li diffusion is described by the Arrhenius law. These findings suggest that the stacking structure of BLG has an important influence on Li diffusion within BLG, and changing the stacking structure of BLG is one possible way to greatly improve Li diffusion rate within BLG. At last, it is suggested that AB-stacked BLG can be an excellent candidate for anode material in Lithium-ion batteries. Ⅰ. INTRODUCTIONThe performance of Lithium-ion batteries (LIBs) relies predominantly on the material properties of the electrodes. Advanced electrodes not only require high storage capacity but also require ultrafast charge/discharge rates, which are characterized by Lithium-ion diffusion coefficient. Carbon-based materials are at present the most commonly used negative electrode in LIBs. There are many studies on the structure of carbon atoms layer [1][2][3], and lithium adsorption in carbon-based materials [4][5][6][7][8].Experimental results have demonstrated that graphene nanosheets have a good cyclic performance, and possess capacity up to 460 mA h g -1 after 100 cycles [9]. Due to its high lithium storage capacity, high conductivity, and good mechanical flexibility, graphene has been regarded as a suitable candidate for electrode in LIBs [10,11]. However, the reported experimental Li diffusion coefficients span a very wide range, for example, from 10 −16 cm 2 s −1 to 10 −6 cm 2 s −1 for a variety of compositegraphite electrode architectures [12][13][14][15][16][17][18][19][20]. What affects Li diffusion? How to accelerate Li diffusion?These issues are not currently addressed. Therefore, in order to optimize the performance of negative electrode for LI...

Nickel‐Catalyzed Synthesis of 3D Edge‐Curled Graphene for High‐Performance Lithium‐Ion Batteries

“…The superior Li + diffusion capacity of 3D ECG is derived from the ultrathin structure prepared by Ni catalysis, which shortens the diffusion path of Li + . Furthermore, the larger graphene layer spacing of the 3D ECG reduces the insertion resistance of Li + and also improves the Li + diffusion performance of 3D ECG …”

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“…(c) Schematic diagram and (d) energy profile for the diffusion of two lithium ions (Li 1 is assumed to be fixed while Li 2 is mobile in the system) intercalated within a stacked bilayer graphene. [99] Reproduced with permission from Ref. [99].…”

“…The energy profile for the possible diffusion pathways labelled in Figure c was illustrated in Figure d, in which it is shown that the energy barriers for certain pathways are lower than those of others (e. g., the energy barrier of H 4 →H 3 is much lower than that of H 3 →H 4 , 0.10 versus 0.40 eV). In other words, the diffusion of lithium ions shows directional preference under the influence of ion‐ion interaction …”

“…Zhong et al performed a theoretical study based on first-principles calculations and Monte Carlo simulations to investigate the diffusion behaviour of lithium ions when considering ion-ion interaction in graphene-based anode. [99,100] In a two-lithium ion model, it is assumed that Li 1 is suited fixed while the migration of Li 2 is under investigation, as shown in Figure 10c. The energy Figure 10.…”

Electrochemical Intercalation in Atomically Thin van der Waals Materials for Structural Phase Transition and Device Applications

“…By further constructing a narrow‐device geometry and measuring the local Hall voltage, the Li density/concentration at different positions of uncovered bilayer graphene is extracted in Figure 4e, and the ultrafast diffusion coefficient of Li ions along the intralayer direction in the vdWs gap of bilayer graphene is up to D δ = 7 × 10 –5 cm 2 s –1 , making it more attractive for the ultrafast energy storage and switching devices in the future. According to the first‐principle calculations based on density functional theory (DFT) and Kinetic Monte Carlo simulations, the Li ion diffusion is strongly dependent on the staking order of bilayer graphene: [ 58,59 ] ultrafast diffusion of Li ions occurs in AB‐stacked, but not in AA‐stacked bilayer graphene, which is attributed to the changes of potential wells within bilayer graphene induced by different stacking structure. Therefore, in order to improve the Li diffusion within BLG, modifying the stacking structure of BLG will be quite effective.…”