提交时间： 2017-05-02
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
Deng, W [Deng, Wei][ 1 ]
Fang, QL [Fang, Qile][ 1 ]
Zhou, XF [Zhou, Xufeng][ 1 ]
Cao, HL [Cao, Hailiang][ 1 ]
Liu, ZP [Liu, Zhaoping][ 1 ]
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.
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
Zhang, LY [Zhang, Leyuan][ 1 ]
Chen, L [Chen, Liang][ 1 ]
Zhou, XF [Zhou, Xufeng][ 1 ]
Liu, ZP [Liu, Zhaoping][ 1 ]
摘要： Zinc hexacyanoferrate (ZnHCF) which is a dimorphic (cubic or rhombohedral) Prussian blue analogue and can be intercalated by both monovalent and divalent ions,is a promising cathode material for rechargeable aqueous metal-ion batteries.In this paper, a simple co-precipitation method is developed to tune the particle morphology of ZnHCF by adjusting the dropping speed at room temperature. Three polyhedral ZnHCF particles, with cubooctahedral, truncated octahedral or octahedral shapes, are obtained at room temperature. Structural transformation from cubic phase of as-prepared ZnHCF to rhombohedral phase is observed by further dehydration of the sample at 70 °C, whereas the dehydrated ZnHCF crystals still hold the identical polyhedral shape as that of the cubic phase particles. Then the in uence of shape and facets on electrochemical performance is studied for polyhedral ZnHCF with rhombohedral structure (RZnHCF). RZnHCF sample with cubooctahedral shape possesses the best rate capability and cyclic stability comparing with RZnHCF particles having truncated octahedral or octahedral shapes. Furthermore, the structure of cuboctahedron RZnHCF particles during electrochemical cycling has been monitored with ex situ X-ray di raction to demonstrate the reversible zinc-ion intercalation mechanism.
提交时间： 2017-05-02
Chen, L [Chen, Liang][ 1 ]
Shao, HZ [Shao, Hezhu][ 1 ]
Zhou, XF [Zhou, Xufeng][ 1 ]
Liu, GQ [Liu, Guoqiang][ 1 ]
Jiang, J [Jiang, Jun][ 1 ]
Liu, ZP [Liu, Zhaoping][ 1 ]
摘要： Rechargeable aqueous metal-ion batteries made from non-flammable and low-cost materials offer promising opportunities in large-scale utility grid applications, yet low voltage and energy output, as well as limited cycle life remain critical drawbacks in t
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
Shen, T [Shen, Tao][ 1,2 ]
Zhou, XF [Zhou, Xufeng][ 1 ]
Cao, HL [Cao, Hailiang][ 1 ]
Zheng, C [Zheng, Chao][ 1 ]
Liu, ZP [Liu, Zhaoping][ 1 ]
摘要： A TiO2(B)–CNT–graphene ternary composite material was prepared by in situ growth of TiO2(B) on a conductive network composed of both graphene and CNTs. TiO2(B) has nanorod morphology and is dispersed uniformly in the carbon matrices. Graphene in this composite acts as sheet-like mini-current collectors that loads TiO2(B), whereas CNTs further enhance the electrical conductivity of TiO2(B) by intimate contact between the two components in local regions, and also prevent the restacking between graphene layers. The composite anode material exhibits a capacity of 190 mA h g 1 even after 200 cycles at 1 C, presenting excellent rate performance.
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： Here, we report a two-step synthesis of graphene/sulfur/carbon ternary composite with a multilayer structure. In this composite, ultrathin S layers are uniformly deposited on graphene nanosheets and covered by a thin layer of amorphous carbon derived from β-cyclodextrin on the surface. Such a unique microstructure, not only improves the electrical conductivity of sulfur, but also effectively inhibits the dissolution of polysulfides during charging/discharging processes. As a result, this ternary nanocomposite exhibits excellent electrochemical performance. It can deliver a high initial discharge and charge capacity of 1410 mAh·g−1 and 1370 mAh·g−1, respectively, and a capacity retention of 63.8% can be achieved after 100 cycles at 0.1 C (1 C = 1675 mA·g−1). A relatively high specific capacity of 450 mAh·g−1 can still be retained after 200 cycles at a high rate of 2 C. The synthesis process introduced here is simple and broadly applicable to the modification of sulfur cathode for better electrochemical performance.
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
Cao, HL [Cao, Hailiang][ 1 ]
Zhou, XF [Zhou, Xufeng][ 1 ]
Deng, W [Deng, Wei][ 1 ]
Liu, ZP [Liu, Zhaoping][ 1 ]
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.
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