Showing papers by "Bing Ding published in 2014"

Porous nitrogen-doped hollow carbon spheres derived from polyaniline for high performance supercapacitors

Abstract: Porous nitrogen-doped hollow carbon spheres (PNHCS) had been prepared by pyrolysis of hollow polyaniline spheres (HPS), which were synthesized by the use of sulfonated polystyrene spheres (SPS) as a hard template. PNHCS have a specific surface area of 213 m2 g−1 and a pore volume of 0.24 cm3 g−1. At a current density of 0.5 A g−1, the specific capacitance of the PNHCS prepared is ca. 213 F g−1. The capacity retention after 5000 charge/discharge cycles at a current density of 1 A g−1 is more than 91%. The enhanced electrochemical performance can be attributed to the unique carbon nanostructure and nitrogen-doping of the PNHCS electrodes. The hollow macro-structure plays the role of an “ion-buffering” reservoir. The micropores of the PNHCS enlarge the specific surface area, while the mesopores offer larger channels for liquid electrolyte penetration. Nitrogen groups in the PNHCS not only improve the wettability of the carbon surface, but also enhance the capacitance by addition of a pseudocapacitive redox process.

High performance lithium–sulfur batteries: advances and challenges

Abstract: The development of high-energy batteries is highly attractive for powering advanced communication equipment and electric vehicles in future. Lithium–sulfur batteries have attracted much attention in recent years due to their low cost, high theoretical specific capacity and energy density. However, lithium–sulfur batteries have not been commercialized because of their intrinsic shortcomings, including the insulation of the active cathode materials, the high solubility of lithium polysulfides in organic liquid electrolytes, and the lithium dendrite in the anode. In this feature article, recent research progress in cathode materials, electrolytes, anode materials, and others is reviewed and commented upon. Some perspectives and directions on future development of lithium–sulfur batteries are pointed out based on knowledge from previous studies and our experience.

Prussian blue analogues: a new class of anode materials for lithium ion batteries

Abstract: Metal–organic frameworks (MOFs) have attracted extensive interest in the context of energy storage due to their high surface areas, controllable structures and excellent electrochemical properties. In particular, Prussian blue analogues (PBAs) have recently gained attention as a new class of cathode materials for rechargeable batteries. However, the anode properties of the host framework have been very limited. Herein, we demonstrate that nanoparticles of cobalt hexacyanocobaltate and manganese hexacyanocobaltate, typical Prussian blue analogues with the chemical formula M3II[CoIII(CN)6]2·nH2O (M = Co, Mn), can be operated as novel battery anodes in an organic liquid-carbonate electrolyte. The Co3[Co(CN)6]2 material exhibits a clear electrochemical activity in the voltage range of 0.01–3 V vs. Li/Li+ with a reversible capacity of 299.1 mA h g−1. Furthermore, superior rate capability (as the current density increases from 20 to 2000 mA g−1, the capacity retains about 34%) could be achieved, attributing to the small particle sizes and rapid transport of Li+ ions through large channels in the open-framework. We believe that this work provides a new insight into the electrochemical properties of PBAs and opens new perspectives to develop anode materials for rechargeable batteries.

Synthesis of NASICON-type structured NaTi2(PO4)3–graphene nanocomposite as an anode for aqueous rechargeable Na-ion batteries

Abstract: A new solvothermal strategy combined with calcination has been developed to synthesize NaTi2(PO4)3–graphene nanocomposites. X-ray diffraction, thermogravimetric analysis, field-emission scanning electron microscopy and transmission electron microscopy were performed to characterize their microstructures and morphologies. It was found that NASICON-type structured NaTi2(PO4)3 nanoparticles with highly crystallinity were homogeneously anchored on the surface of conducting graphene nanosheets, forming a two-dimensional hybrid nanoarchitecture. A possible growth mechanism was also discussed based on time-dependent experiments. When used as anode materials for Na-ion batteries, the nanocomposites exhibited excellent electrochemical performance with high-rate capability and excellent cycling stability in 1 M Na2SO4 aqueous electrolyte. The electrode delivered high specific capacities of 110, 85, 65, 40 mA h g−1 at 2, 5, 10 and 20 C, respectively, and still retained 90% of the initial capacity after 100 cycles at 2 C.

Hierarchically porous carbon encapsulating sulfur as a superior cathode material for high performance lithium-sulfur batteries.

Abstract: Lithium-sulfur (Li-S) batteries are deemed to be a promising energy storage device for next-generation high energy power system. However, insulation of S and dissolution of lithium polysulfides in the electrolyte lead to low utilization of sulfur and poor cycling performance, which seriously hamper the rapid development of Li-S batteries. Herein, we reported that encapsulating sulfur into hierarchically porous carbon (HPC) derived from the soluble starch with a template of needle-like nanosized Mg(OH)2. HPC has a relatively high specific surface area of 902.5 m(2) g(-1) and large total pore volume of 2.60 cm(3) g(-1), resulting that a weight percent of sulfur in S/HPC is up to 84 wt %. When evaluated as cathodes for Li-S batteries, the S/HPC composite has a high discharge capacity of 1249 mAh g(-1) in the first cycle and a Coulombic efficiency as high as 94% with stable cycling over prolonged 100 charge/discharge cycles at a high current density of 1675 mA g(-1). The superior electrochemical performance of S/HPC is closely related to its unique structure, exhibiting the graphitic structure with a high developed porosity framework of macropores in combination with mesopores and micropores. Such nanostructure could shorten the transport pathway for both ions and electrons during prolonged cycling.

Fabrication of porous carbon spheres for high-performance electrochemical capacitors

Abstract: Porous carbon spheres (PCS) with meso/microporous structure are designed and fabricated through a facile hydrothermal method by employing glucose as a carbon precursor and sodium molybdate (Na2MoO4) as a porogen, structure-direct agent and catalyst. With the assistance of Na2MoO4, the porous structure of the carbon sphere is significantly enhanced. In addition, the meso/microporous structure can be modulated by adjusting the proportion of the reactants. In optimal conditions, the PCS exhibit a high specific surface area (SSA, 757.3 m2 g−1) and pore volume (0.24 cm3 g−1). When evaluated as an electrode for electrochemical capacitors, the PCS exhibits a high specific capacitance of 260 F g−1 with remarkable high-rate performance and long-term cycling stability. The excellent electrochemical performances are exclusively attributed to the micro/mesoporous structure, which maximize the ion accumulation on the electrode surface and facilitate fast ion transportation. The well-defined porous nanostructure plus easy strategy make current study provide new opportunities for hydrothermal carbonization of biomass as electrode materials for energy storage.

Enhanced Performance of Aqueous Sodium‐Ion Batteries Using Electrodes Based on the NaTi2(PO4)3/MWNTs–Na0.44MnO2 System

Abstract: Sodium-ion batteries with good electrochemical performance are of great significance for grid-scale energy storage applications. Herein, an aqueous rechargeable Na-ion battery has been fabricated with multiwalled carbon nanotube (MWNT)-containing NaTi2(PO4)3/MWNTs nanocomposites as the anode and Na0.44MnO2 nanorods as the cathode in a 1 M aqueous Na2SO4 electrolyte and the device was carefully studied. Owing to the open framework structures (containing large interstitial sites) that both NaTi2(PO4)3 and Na0.44MnO2 possess, the fast Na-ions will facilitate free transport. Benefiting from their unique structural features, the aqueous battery system exhibited an average charge and discharge voltage of approximately 1.1 V, a high energy density of 58.7 Wh kg−1 in terms of total electroactive materials, and could deliver a reversible capacity of approximately 50 mAh g−1 after 300 cycles at 2 C rate; the corresponding coulombic efficiency was nearly constant at approximately 95 %. These results, together with the safety and cost perspectives of aqueous electrolytes indicated that the aqueous Na-ion battery may be a good candidate for safe, inexpensive, high-power energy storage systems.

Synthesis of hydrogenated TiO2-reduced-graphene oxide nanocomposites and their application in high rate lithium ion batteries

Abstract: A hydrogenated TiO2–reduced-graphene oxide (H-TiO2–RGO) nanocomposite is synthesised via a facile one-pot hydrogenation treatment process. The morphologies and structures are characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The nitrogen adsorption–desorption isotherms revealed that the H-TiO2–RGO exhibited large specific surface area of 114.4 m2 g−1. Compared with the TiO2–RGO nanocomposite, the H-TiO2–RGO nanocomposite exhibits a much higher rate capability and better capacity retention. At a current rate of 5 C, the reversible capacity of the H-TiO2–RGO electrode is up to 166.3 mA h g−1 and with only 2.4% capacity loss after 100 cycles. The excellent electrochemical performance is strongly related to the high electronic conductivity derived from hydrogenated TiO2 frameworks and the good contact between the zero-dimensional (0D) H-TiO2 nanoparticles with two-dimensional (2D) reduced-graphene oxide nanosheets, which efficiently shortened the Li+ diffusion path lengths, enhanced the electrolyte–active material contact area and facilitated rapid e− transfer.

Design of a Nitrogen-Doped, Carbon-Coated Li4Ti5O12 Nanocomposite with a Core–Shell Structure and Its Application for High-Rate Lithium-Ion Batteries

Abstract: A facile solution-based synthesis and characterization of a nitrogen-doped, carbon-coated Li4Ti5O12 (NC-LTO) nanocomposite is reported The mesoporous TiO2 nanoparticles (NPTiO2) are first prepared by using nanocrystalline cellulose (NCC) as a template and subsequently transform in situ into an NC-LTO nanocomposite with a core–shell structure by using the ionic liquid 1-ethyl-3-methylimdazolium tricyanomethanide as the carbon source Various state-of-the-art techniques, including field-emission SEM, TEM, scanning transmission electron microscopy, XRD, X-ray photoelectron spectroscopy, and thermogravimetric analysis, were performed to characterize the morphologies, structures, and compositions Such NC-LTO nanocomposites have a well-defined LTO core and thin uniform carbon shell with a thickness of 1–2 nm Electrochemical tests reveal that the NC-LTO nanocomposite delivers a reversible capacity of 1715 mAh g−1 at 02 C, and shows remarkable rate capability by maintaining 63 % of the capacity at 60 C (vs 02 C), as well as excellent cycling stability with a capacity retention of 95 % after 300 cycles at a rate of 10 C The excellent electrochemical performance is attributed exclusively to the well-defined core–shell nanostructure and high electric conductivity The nanosized LTO core can significantly shorten the transport lengths of lithium ions and the admirable electric conductivity of the nitrogen-doped carbon shell can act as an “expressway” for electrons and lithium ions to transport them between the anode material core and the electrolytes