Harbin Institute of Technology, School of Chemical Engineering and Technology, Xidazhi Street, 150001 Harbin, China.
Nanoscale. 2015 May 21;7(19):8819-28. doi: 10.1039/c5nr01831e.
Electron transfer and lithium ion diffusion rates are the key factors limiting the lithium ion storage in anisotropic LiFePO4 electrodes. In this work, we employed a facile solvothermal method to synthesize a "platelet-on-sheet" LiFePO4/graphene composite (LFP@GNs), which is LiFePO4 nanoplatelets in situ grown on graphene sheets with highly oriented (010) facets of LiFePO4 crystals. Such a two-phase contact mode with graphene sheets cross-linked to form a three-dimensional porous network is favourable for both fast lithium ion and electron transports. As a result, the designed LFP@GNs displayed a high rate capability (∼56 mA h g(-1) at 60 C) and long life cycling stability (∼87% capacity retention over 1000 cycles at 10 C). For comparison purposes, samples ex situ modified with graphene (LFP/GNs) as well as pure LiFePO4 platelets (LFP) were also prepared and investigated. More importantly, the obtained LFP@GNs can be used as a basic unit for constructing more complex structures to further improve electrochemical performance, such as coating the exposed LFP surface with a thin layer of carbon to build a C@LFP@GN composite to further enhance its cycling stability (∼98% capacity retention over 1000 cycles at 10 C).
电子转移和锂离子扩散速率是限制各向异性 LiFePO4 电极中锂离子存储的关键因素。在这项工作中，我们采用了一种简便的溶剂热方法来合成“ platelet-on-sheet ” LiFePO4/石墨烯复合材料（LFP@GNs），其中 LiFePO4 纳米板原位生长在具有高度取向（010）面的石墨烯片上。这种两相接触模式，其中石墨烯片交联形成三维多孔网络，有利于锂离子和电子的快速传输。结果，设计的 LFP@GNs 表现出高倍率性能（在 60 C 时约为 56 mA h g(-1)）和长循环寿命稳定性（在 10 C 时约为 1000 次循环后 87%的容量保持率）。为了比较起见，还制备并研究了用石墨烯（LFP/GNs）原位改性的样品以及纯 LiFePO4 纳米片（LFP）。更重要的是，所得到的 LFP@GNs 可以用作构建更复杂结构的基本单元，以进一步提高电化学性能，例如在暴露的 LFP 表面涂覆一层薄薄的碳以构建 C@LFP@GN 复合材料，以进一步提高其循环稳定性（在 10 C 时约为 1000 次循环后 98%的容量保持率）。
