[Wu, Zhong-Shuai; Ren, Wencai; Xu, Li; Li, Feng; Cheng, Hui-Ming] Chinese Acad Sci, Shenyang Natl Lab Mat Sci, Inst Met Res, Shenyang 110016, Peoples R China.;Ren, WC (reprint author), Chinese Acad Sci, Shenyang Natl Lab Mat Sci, Inst Met Res, 72 Wenhua Rd, Shenyang 110016, Peoples R China;wcren@imr.ac.cn cheng@imr.ac.cn

Doped Graphene Sheets As Anode Materials with Superhigh Rate and Large Capacity for Lithium Ion Batteries

Nitrogen-doped carbon nanofiber webs (CNFWs) with high surface areas are successfully prepared by carbonization-activation of polypyrrole nanofiber webs with KOH. The as-obtained CNFWs exhibit a superhigh reversible capacity of 943 mAh g(-1) at a current density of 2 A g(-1) even after 600 cycles, which is ascribed to the novel porous nanostructure and high-level nitrogen doping.

Nitrogen‐Doped Porous Carbon Nanofiber Webs as Anodes for Lithium Ion Batteries with a Superhigh Capacity and Rate Capability

The number of research reports published in recent years on electrochemical water splitting for hydrogen generation is higher than for many other fields of energy research. In fact, electrochemical water splitting, which is conventionally known as water electrolysis, has the potential to meet primary energy requirements in the near future when coal and hydrocarbons are completely consumed. Due to the sudden and exponentially increasing attention on this field, many researchers across the world, including our group, have been exerting immense efforts to improve the electrocatalytic properties of the materials that catalyze the oxygen evolution reaction (OER) at the anode and the hydrogen evolution reaction (HER) at the cathode, aided by the recent revolutionary discovery of nanomaterials. However, the pressure on the researchers to publish their findings rapidly has caused them to make many unnoticed and unintentional errors, which is mainly due to lack of clear insight on the activity parameters. In this perspective, we have discussed the use and validity of ten important parameters, namely overpotential at a defined current density, iR-corrected overpotential at a defined current density, Tafel slope, exchange current density (j0), mass activity, specific activity, faradaic efficiency (FE), turnover frequency (TOF), electrochemically active surface area (ECSA) and measurement of double layer capacitance (Cdl) for different electrocatalytic materials that are frequently employed in both OER and HER. Experimental results have also been provided in support of our discussions wherever required. Using our critical assessments of the activity parameters of water splitting electrocatalysis, researchers can ensure precision and correctness when presenting their data regarding the activity of an electrocatalyst.

Precision and correctness in the evaluation of electrocatalytic water splitting: revisiting activity parameters with a critical assessment

In this paper, we report on Li storage in hierarchically porous carbon monoliths with a relatively higher graphite-like ordered carbon structure. Macroscopic carbon monoliths with both mesopores and macropores were successfully prepared by using meso-/macroporous silica as a template and using mesophase pitch as a precursor. Owing to the high porosity (providing ionic transport channels) and high electronic conductivity (ca. 0.1 S cm–1), this porous carbon monolith with a mixed conducting 3D network shows a superior high-rate performance if used as anode material in electrochemical lithium cells. A challenge for future research as to its applicability in batteries is the lowering of the irreversible capacity.

Synthesis of hierarchically porous carbon monoliths with highly ordered microstructure and their application in rechargeable lithium batteries with high-rate capability

The development of the next generation of advanced lithium-ion batteries (LIBs) requires new & advanced materials and novel fabrication techniques in order to push the boundaries of performance and open up new and exciting markets. Structured carbon materials, with controlled pore features on the micron and nanometer scales, are explored as advanced alternatives to conventional graphite as the active material of the LIB anode. Mesoporous carbon materials, carbon nanotube-based materials, and graphene-based materials have been extensively investigated and reviewed. Morphology control (e.g., colloids, thin films, nanofibrous mats, monoliths) and hierarchical pores (particularly the presence of large pores) exhibit an increasing influence on LIB performance. This tutorial review focuses on the synthetic techniques for preparation of porous carbon spheres and carbon monoliths, including hydrothermal carbonization, emulsion templating, ice templating and new developments in making porous carbons from sustainable biomass and metal-organic framework templating. We begin with a brief introduction to LIBs, defining key parameters and terminology used to assess the performance of anode materials, and then address synthetic techniques for the fabrication of carbon spheres & monoliths and the relevant composites, followed, respectively, by a review of their performance as LIB anode materials. The review is completed with a prospective view on the possible direction of future research in this field.

Porous carbon spheres and monoliths: morphology control, pore size tuning and their applications as Li-ion battery anode materials

Graphitized carbon nanobeads with an onion texture as a lithium-ion battery negative electrode for high-rate use

TEM and electron tomography studies of carbon nanospheres for lithium secondary batteries

Specific capacitance of electrochemical capacitor using RuO2 loading arc-soot/activated carbon composite electrode

Spherical carbon nanoparticles with 200 nm diameter were heat-treated in Ar atmosphere, and their microtexture was characterized with transmission electron microscopy (TEM). According to the observation of carbon 0 0 2 lattice images, pristine sample had a homogeneous, concentric orientation of aromatic layers. Microtexture in the particle began to be separated at 1800 °C, where a sign of polyhedronization started to be seen in the outside region of the particle, while the concentric orientation was still kept in the central region. At 2500 °C and over, the heat-treated particle represented the outside and central texture clearly separated each other: The outside region had well-developed stacking structure of aromatic layers with the obvious feature of polygonization, while the center region consisted of non-graphitic microtexture. From the macroscopic viewpoint, polygonization behavior could be understood by the Cahn's formula indicating the proportional relation between the number of dislocation per area and reciprocal of curvature, while the thickness of outside/central textures was independent of the radius curvature. It is expected that the textural discontinuity can be caused as a result of orientation of aromatic layers originated from the surface of the spherical carbon nanoparticles.

TEM observation of heterogeneous polyhedronization behavior in graphitized carbon nanospheres

PROBLEM TO BE SOLVED: To provide a carbon nano balloon hollow structure having a relatively large closed space and a method for manufacturing the carbon nano balloon structure which easily and stably produces such structure. SOLUTION: The carbon nano balloon structure comprises the hollow structure obtained by evaporating the soot or carbon generated by arc discharge using a carbon electrode by irradiation with a laser or by subjecting carbon black of ≥1,000 m 2 /g in specific surface area and ≥20 nm in primary particle size to high-temperature heating in an inert gaseous atmosphere and arranged with graphite layers so as to bond and to form a curved surface as a whole. COPYRIGHT: (C)2006,JPO&NCIPI

Kazuo Yoshikawa

Papers

Graphitized carbon nanobeads with an onion texture as a lithium-ion battery negative electrode for high-rate use

TEM and electron tomography studies of carbon nanospheres for lithium secondary batteries

Specific capacitance of electrochemical capacitor using RuO2 loading arc-soot/activated carbon composite electrode

TEM observation of heterogeneous polyhedronization behavior in graphitized carbon nanospheres

Carbon nano balloon structure and method for manufacturing the same, and electron emitter