Department of Physics, Central Michigan University, Mt Pleasant, Michigan 48859, USA.
Nano Lett. 2010 Aug 11;10(8):2838-42. doi: 10.1021/nl100865a.
We study the adsorption and diffusion of Li atoms on the surface of planar graphenes by means of density functional theory. When the dimensionality of graphene is reduced to a quasi-one-dimension, armchair and zigzag edges appear. We show that the presence of these edges affects not only the reactivity of the carbon material toward the adsorption of Li adatoms but also their diffusion properties. These properties strongly depend on the specific morphology of the edges. Our results indicate that Li adatoms will diffuse toward the edges while Li diffusion channels appear along the ribbon axis. For most of the diffusion paths studied here, energy barriers are lower than those in graphene. This effect is significantly more pronounced toward the edges, where energy barriers can be up to 0.15 eV smaller than those in in graphene, producing an increase of up to 2 orders of magnitude in the diffusion coefficient at room temperature. Our results indicate that electrodes fabricated with these materials should increase the power of Li-ion batteries.
我们通过密度泛函理论研究了 Li 原子在平面石墨烯表面的吸附和扩散。当石墨烯的维度降低到准一维时，会出现扶手椅型和锯齿型边缘。我们表明，这些边缘的存在不仅影响了碳材料对 Li 吸附原子的反应性，也影响了它们的扩散性质。这些性质强烈依赖于边缘的具体形态。我们的结果表明，Li 吸附原子将向边缘扩散，而 Li 扩散通道则沿着带状轴出现。对于这里研究的大多数扩散路径，能垒低于石墨烯中的能垒。这种效应在边缘处更为明显，边缘处的能垒比石墨烯中的能垒低 0.15 eV，从而使室温下的扩散系数增加了两个数量级。我们的结果表明，用这些材料制造的电极应能提高锂离子电池的功率。
