分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Graphene-based electrodes with high gravimetric and high volumetric capacity simultaneously are crucial to the realization of high energy storage density, but still proved to be challenging to prepare. Herein, we report a three-dimensional porous graphene/Co aerogel with hierarchical porous structure and compressible features as a high-performance binder-free lithium-ion battery anode. In this composite aerogel, graphene nanosheets interconnect to form continuous macropores, and cobalt nanoparticles stemming from decomposition of cobalt salt not only react with carbon atoms of graphene to form nanopores on the graphene nanosheets, but also increase the conductivity of the aerogel. With efficient ion and electron transport pathways as well as high packing density, the compressed porous graphene/ Co electrode exhibits significantly improved electrochemical performance including high gravimetric and volumetric capacity, excellent rate capability, and superior cycling stability. After compression, such a porous graphene/Co nanocomposite can deliver a gravimetric capacity of 900 mA h g 1 and a volumetric capacity of 358 mA h cm 3 at a current density of 0.05 A g 1. Furthermore, after 300 discharge/charge cycles at 1 A g 1, the specific capacity still remains at 163 mA h cm 3, corresponding to 90.5% retention of its initial capacity.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Pore size is a critical parameter that affects the basic physicochemical properties and applications of porous graphene foam, but the preparation of graphene foam with controllable pore size is still a big challenge, especially by a self-assembly method. In this work, graphene oxide (GO) sheets with different lateral sizes by controlling the delamination conditions of graphite oxide were used as building blocks to form graphene foams with adjustable pore size, by a convenient one-step hydrothermal self-assembly method. The pore sizes of graphene foams can be effectively controlled by simply altering the sheet sizes of GO, and the smallest average pore size is $500 nm, which is much smaller than the micrometer-scale pores in the reported graphene foam materials. Static contact angles, nitrogen adsorption–desorption isotherms and adsorption of methylene blue are measured to demonstrate the strong dependence of some important physicochemical properties of graphene foams on their pore sizes. This simple method offers a novel way to rationally synthesize graphene foam with appropriate pore size for various practical applications.