Wang Fei, Mao Jian
College of Materials Science and Engineering, Sichuan University, Chengdu 610065, China.
ACS Appl Mater Interfaces. 2021 Mar 24;13(11):13191-13199. doi: 10.1021/acsami.0c22636. Epub 2021 Mar 12.
Graphene is widely used to enhance the electrochemical performance of anodes. However, graphene tends to be vertical with the lithium-ion (Li) diffusion direction, and a few heterointerfaces are formed between graphene and active materials by point-to-point contact. Herein, a graphene quantum dots (GDs) tiling hollow porous SiO (HSiO@GDs) anode is predicted by density functional theory (DFT) and is achieved by experiments. Due to the ultrasmall size, the tiling of GDs would provide Li a rapid diffusion channel and abundant heterointerfaces (face-to-face contact) between the GDs and the hollow porous SiO (HSiO). Moreover, owing to the higher electrostatic potential of SiO, the large-scale local electrical field from GDs to HSiO is established at the heterointerfaces, which provide extra Li storage sites and further facilitate the Li transfer. To our knowledge, the HSiO@GDs shows the highest specific capacities at various current densities (such as ∼1100 mA h/g at 5 A/g and ∼2250 mA h/g at 0.2 A/g) among reported silicon oxides anodes and presents excellent cycling stability (∼1000 mA h/g after 2000 cycles at 3 A/g). Moreover, the design idea is available to design other widely studied graphene-containing anodes such as the Si, SnO, TiO, and MoS.
石墨烯被广泛用于增强阳极的电化学性能。然而，石墨烯往往与锂离子（Li）的扩散方向垂直，并且通过点对点接触在石墨烯与活性材料之间形成少量异质界面。在此，通过密度泛函理论（DFT）预测了一种石墨烯量子点（GDs）平铺的中空多孔SiO（HSiO@GDs）阳极，并通过实验实现。由于尺寸超小，GDs的平铺将为Li提供快速扩散通道以及GDs与中空多孔SiO（HSiO）之间丰富的异质界面（面对面接触）。此外，由于SiO的静电势较高，在异质界面处建立了从GDs到HSiO的大规模局部电场，这提供了额外的Li存储位点并进一步促进了Li的转移。据我们所知，在报道的氧化硅阳极中，HSiO@GDs在各种电流密度下（例如在5 A/g时约为1100 mA h/g，在0.2 A/g时约为2250 mA h/g）显示出最高的比容量，并呈现出优异的循环稳定性（在3 A/g下循环2000次后约为1000 mA h/g）。此外，该设计理念可用于设计其他广泛研究的含石墨烯阳极，如Si、SnO、TiO和MoS。
