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Controlling the microstructure of biomass-derived carbon is of essential importance for directing its use. Herein, a hollow spherical carbon (HSC) was prepared from corncob lignin through spray drying and subsequent heat treatment. The HSC, which is characterized by its hierarchically porous structure, delivers high rate capability when it is directly used as electrode material for supercapacitors. This strategy that uses lignin as the precursor avoids the intrinsic difficulty in tuning the microstructure of the biomass-derived carbons and is suitable for mass production for practical use., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Nitrogen and sulfur co-doped porous carbon spheres (NS-PCSs) were prepared using L-cysteine to control the structure and functionalization during the hydrothermal reaction of glucose and the subsequent activation process. As the sulfur hosts in Li-S batteries, NS-PCSs combine strong physical confinement and surface chemical interaction to improve the affinity of polysulfides to the carbon matrix.

Sheets of Li4Ti5O12 with high crystallinity are coated with nitrogen-doped carbon (NC-LTO) using a controlled process, comprising hydrothermal reaction followed by chemical vapor deposition (CVD). Acetonitrile (CH3 CN) vapor is used as carbon and nitrogen source to obtain a thin coating layer of nitrogen-doped carbon. The layer enables the NC-LTO material to maintain its sheet structure during the high-temperature CVD process and to achieve high crystallinity. Doping with nitrogen introduces defects into the carbon coating layer, and this increased degree of disorder allows fast transportation of lithium ions in the layer. An electrode of NC-LTO synthesized at 700 °C exhibits greatly improved rate and cycling performance due to a markedly decreased total cell resistance and enhanced Li-ion diffusion coefficient (D(Li)). Specific capacities of 159.2 and 145.8 mA h g(-1) are obtained using the NC-LTO sheets, at charge/discharge rates of 1 and 10 C, respectively. These values are much higher than values for LTO particles did not undergo the acetonitrile CVD treatment. A capacity retention value as high as 94.7% is achieved for the NC-LTO sheets after 400 cycles in a half-cell at 5 C discharge rate., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Carbon materials are the key hosts for the sulfur cathode to improve the conductivity and confine the lithium polysulfides (LiPSs) in lithium–sulfur batteries (LSBs), owing to their high electronic conductivity and strong confinement effect. However, physical or chemical trapping methods have limitations in preventing the dissolution and accumulation of LiPSs in the electrolyte. Catalysis has emerged as a fundamental solution to accelerate the sluggish redox kinetics, and carbon materials acting as catalyst supports or direct catalysts significantly impact the reaction efficiency. Herein, the roles of carbon in the catalysis of LSBs are systematically discussed, focusing on the influence of surface area, pore structure, and surface chemistry on sulfur conversion. Then, two modification strategies, vacancy defects and heteroatom doping, that endow carbon with catalytic activity are summarized. Finally, the remaining challenges and solutions are outlined in terms of the preparation and characterization of the functional carbon in LSBs. This perspective provides essential insights and guidance for the rational design of carbon‐based catalysts in LSBs. [ABSTRACT FROM AUTHOR]

Hard carbons have been identified as competitive anodes for Li/Na/K‐ion batteries but their Li/Na/K‐ion storage mechanisms significantly vary in different batteries. It is fundamental to understand the basic science behind the difference. Herein, it is theoretically revealed that defects on the carbon layers generally have an influential impact on the atomic interactions including the metal–metal (M–M) and metal–carbon (M–C) interactions, thereby determining whether the stored alkali‐metal atoms are in ionic or quasi‐metallic states. Upon increasing the number of metal atoms on a carbon layer composed of only hexatomic rings, K tends to be stored in an ionic state similar to Li due to the dominant M–C interaction, while on a carbon layer with defects, K tends to be stored in a quasi‐metallic state similar to Na due to the dominant M–M interaction. For experimental verification, a glassy carbon, the extreme form of hard carbon with dominant sp2 hybridization and only Stone–Wales defects, is selected as a model anode, and its Li/Na/K‐ion storage mechanisms are exactly consistent with the theoretical prediction. More profoundly, for the first time, the quasi‐metallic K cluster information is captured by ex situ electron paramagnetic resonance. [ABSTRACT FROM AUTHOR]

Non-graphitic carbons are promising anode candidates for sodium-ion batteries, while their variable and complicated microstructure severely limits the rational design of high-energy carbon anodes that could accelerate the commercialization of sodium-ion batteries, as is the case for graphite in lithium-ion batteries. Here, we propose sieving carbons, featuring highly tunable nanopores with tightened pore entrances, as high-energy anodes with extensible and reversible low-potential plateaus (<0.1 V). It is shown that the tightened pore entrance blocks the formation of the solid electrolyte interphase inside the nanopores and enables sodium clustering to produce the plateau. Theoretical and spectroscopic studies also show that creating a larger area of sodiophilic pore surface leads to an almost linearly increased number of sodium clusters, and controlling the pore body diameter guarantees the reversibility of sodium cluster formation, producing a sieving carbon anode with a record-high plateau capacity of 400 mAh g–1. More excitingly, this approach to preparing sieving carbons has the potential to be scalable for modifying different commercial porous carbons. [ABSTRACT FROM AUTHOR]

Carbon materials show their importance in electrochemical energy storage (EES) devices as key components of electrodes, such as active materials, conductive additives and buffering frameworks. To meet the requirements of vastly developing markets related to EES, especially for electric vehicles and large scale energy storage, the rational design of functional carbon materials with the basis of a deep understanding of the structure‐property relationships is demanded, in which dimensionality variations and hybridizations of the carbon materials play critical roles in improving electrochemical performances of EES devices. This review focuses on the dimensionality manipulation in functional carbon materials, including transition, matching and integration, to optimize the reaction space, interface and framework in electrodes, respectively. This review gives a comprehensive review on how the dimensionality manipulation improves performance of the carbon‐based electrodes in kinetics optimization, electron transfer acceleration, mechanical stabilization and thermal dissipation upon charging/discharging. The report ends with a critical perspective on the future challenges facing carbon‐based electrodes with dimensionality dependence. The progress highlighted here is expected to provide a guidance for the precise design and targeted synthesis of dimensionality varied carbon‐based electrode materials towards safe and high performance EES devices and the resulting optimized energy deployments. [ABSTRACT FROM AUTHOR]

Abstract: Carbon materials are usually used as the sulfur host in rechargeable lithium–sulfur (Li–S) batteries that are considered as promising electrochemical energy storage systems. However, the “shuttling” caused by the soluble lithium polysulfides (LiPSs) formed by the reaction of Li and sulfur causes rapid capacity fade and low sulfur utilization, greatly hindering their practical use. The carbon materials can also be tailored to prevent LiPS shuttling because of their abundant porosity and controllable surface chemical properties, which are divided into four specific functions: confining, trapping, blocking, and breaking up. Confinement means physically confining the LiPSs in pores in the carbon while trapping refers to chemical adsorption on the carbon surface to restrict their diffusion and promote their transformation to insoluble Li2S2/Li2S. Blocking means placing a barrier in the cells to inhibit LiPS diffusion to the anode, while breaking up means decreasing the size of the sulfur moiety to increase its affinity with carbons. The advantages and disadvantages of functional carbons in relation to these four functions are summarized and the specific ways to achieve them are highlighted. The design of advanced carbons with synergistic functions is discussed and some perspectives on the future development of carbons in Li–S batteries are given. [ABSTRACT FROM AUTHOR]

Environmental and energy issues are hot topics in the sustainable development of our planet. Air pollution, as a vital environmental issue, has puzzled us for decades, and a green and economical approach to control air pollutants is urgently required. New energy-storage techniques have emerged as fascinating routes to reduce potential environmental problems. Therefore, the combination of air pollutants with energy-storage devices is an appealing solution for air pollution. Herein, the principles of recovering air pollutants for use in energy-storage materials are proposed, including their direct use as active materials, their conversion into active materials, and their use as dopants to modify the electrode. Typical air pollutants are selected to demonstrate their potential use in green energy storage. Future prospects of the broad application of air pollutants in energy-related fields are also commented on. [ABSTRACT FROM AUTHOR]

Controlling the microstructure of biomass-derived carbon is of essential importance for directing its use. Herein, a hollow spherical carbon (HSC) was prepared from corncob lignin through spray drying and subsequent heat treatment. The HSC, which is characterized by its hierarchically porous structure, delivers high rate capability when it is directly used as electrode material for supercapacitors. This strategy that uses lignin as the precursor avoids the intrinsic difficulty in tuning the microstructure of the biomass-derived carbons and is suitable for mass production for practical use. [ABSTRACT FROM AUTHOR]

Nitrogen-doped ordered mesoporous carbons (N-OMCs) with different morphologies are prepared as oxygen reduction reaction (ORR) catalysts through pyrolysis of iron phthalocyanine-infiltrated SBA-15 silica with different mesochannel lengths. Excellent ORR activity with a nearly four-electron transfer process is observed in both alkaline and acidic media. In particular, the difference in half-wave potential for ORR relative to commercial Pt/C catalyst is only 50 mV negative in acidic medium, whereas it is 50 mV more positive in alkaline medium. Interestingly, it is found that although the use of iron is necessary for the preparation of highly active nitrogen-doped ORR carbon catalysts, its presence is not necessary for N-OMC to be active in the ORR in either alkaline or acidic media. In addition, the ORR activity increases gradually with decreasing mesopore channel length, with maximum activity in N-OMC with short channels, demonstrating the high synergistic influence of structural morphology on ORR in heteroatom-doped carbon. [ABSTRACT FROM AUTHOR]

Poly(triazine imides) intercalated with Li+ and X− (PTI/X, X=Cl or Br), which are described widely as crystalline polymeric carbon nitrides, were synthesized in a facile manner by heating a mixture of melamine and LiX. This method has the advantages of low cost, scalable production, and high efficiency. Importantly, both PTI/Cl and PTI/Br exhibit an enhanced photocatalytic performance compared to conventional graphitic polymeric carbon nitride in the degradation of rhodamine B under visible-light irradiation because of their higher visible-light-harvesting ability and charge carrier separation efficiency. [ABSTRACT FROM AUTHOR]

Abstract: Ordered microporous carbon that was synthesized in the nanochannels of zeolite Y is characterized by an extremely large surface area, surprisingly uniform micropores and a long-range periodicity originating from the parent zeolite. However, the molecular structure of this zeolite templated carbon (ZTC) has been completely unknown. In this study, an attempt was made to construct a possible molecular model for ZTC. The proposed model is made up of buckybowl-like nanographenes assembled into a three-dimensionally regular network, which reflects all the experimental results obtained from Raman spectroscopy, electron energy-loss spectroscopy, and previously obtained analyses with several other means. Starting from this idealized model, possible forms of defects that would be included in the actual ZTC were also investigated. Moreover, the amount and the type of oxygen functional groups were analyzed and, as per the results, some functional groups were bound to the edge sites of each buckybowl unit in the molecular model. The elemental composition, pore curvature, pore size and pore volume and surface area estimated from such oxygen-containing model agree well with the corresponding experimentally obtained results. The present model can be considered as a reasonable starting point for future refinements of the structure of this quite novel carbon material. [Copyright &y& Elsevier]

"Compact energy storage" means to store as much energy as possible in as compact a space as possible and is the only way to deal with the "space anxiety" concern in electrochemical energy storage devices. The shrinkable carbon network built from the graphene units shows potential to produce small yet sufficient reaction space together with smooth charge delivery that facilitate battery reactions, and plays a vital role in optimizing the volumetric performance of the electrode and the battery. [Display omitted] Storing as much energy as possible in as compact a space as possible is an ever-increasing concern to deal with the emerging "space anxiety" in electrochemical energy storage (EES) devices like batteries, which is known as "compact energy storage". Carbons built from graphene units can be used as active electrodes or inactive key materials acting as porous micro- or even nano-reactors that facilitate battery reactions and play a vital role in optimizing the volumetric performance of the electrode and the battery. In this review, we discuss and clarify the key issues and specific strategies for compact energy storage, especially in batteries. The use of shrinkable carbon networks to produce small yet sufficient reaction space together with smooth charge delivery is highlighted as the simplest structure–function-performance relationship when used in supercapacitors and is then extended to overcome problems in compact rechargeable lithium/sodium/potassium batteries. Special concerns about cycling stability, fast charging and safety in compact batteries are discussed in detail. Strategies for compact energy storage ranging from materials to electrodes to batteries are reviewed here to provide guidance for how to produce a compact high energy battery by densifying the electrodes using customized carbon structures. [ABSTRACT FROM AUTHOR]

Assembly strategies that reinforce the roles of carbon architectures as active materials, electrochemical reaction frameworks, and current collectors in high-energy and high-power lithium-ion batteries are summarized.To enhance structural stability and volumetric performance, the rational design of carbon architectures for high-capacity noncarbons in terms of the interface, network skeleton, void space, and densification, is discussed in detail.Designing carbon cages that protect the electroactive noncarbon is highlighted as a promising strategy that solves the challenges associated with future high-capacity noncarbon anode construction. Lithium-ion batteries (LIBs), which are high-energy-density and low-safety-risk secondary batteries, are underpinned to the rise in electrochemical energy storage devices that satisfy the urgent demands of the global energy storage market. With the aim of achieving high energy density and fast-charging performance, the exploitation of simple and low-cost approaches for the production of high capacity, high density, high mass loading, and kinetically ion-accessible electrodes that maximize charge storage and transport in LIBs, is a critical need. Toward the construction of high-performance electrodes, carbons are promisingly used in the enhanced roles of active materials, electrochemical reaction frameworks for high-capacity noncarbons, and lightweight current collectors. Here, we review recent advances in the carbon engineering of electrodes for excellent electrochemical performance and structural stability, which is enabled by assembled carbon architectures that guarantee sufficient charge delivery and volume fluctuation buffering inside the electrode during cycling. Some specific feasible assembly methods, synergism between structural design components of carbon assemblies, and electrochemical performance enhancement are highlighted. The precise design of carbon cages by the assembly of graphene units is potentially useful for the controlled preparation of high-capacity carbon-caged noncarbon anodes with volumetric capacities over 2100 mAh cm−3. Finally, insights are given on the prospects and challenges for designing carbon architectures for practical LIBs that simultaneously provide high energy densities (both gravimetric and volumetric) and high rate performance. [ABSTRACT FROM AUTHOR]

Although considerable effort has been devoted to purifying nitrogen oxides (NO x), it is still challenging to effectively reduce NO x at room temperature and ambient pressure without catalysts. In this study, as a proof-of-concept, we have for the first time demonstrated the room-temperature reduction of nitrogen dioxide (NO 2) using a rechargeable lithium-nitrogen dioxide (Li-NO 2) battery. The battery shows a capacity of 884 mAh g−1 at 50 mA g−1 (an actual energy density of 666 Wh kg−1) and a promising electrochemical Faraday efficiency (FE) of 67%. The unique properties of Li-NO 2 rechargeable batteries not only provide a way to reduce and recycle NO 2 but also highlight the potential of oxidative air pollutants as energy sources for next-generation electrochemical energy storage (EES) systems. [ABSTRACT FROM AUTHOR]

A kind of porous carbon material with tunable pore structure and morphology was successfully built up from a knitting based bottom-up method. This porous carbon material feature abundant porosity and remarkably high-efficiency restrain for the pore collapse after the pyrolysis process, namely, a specific surface area retention (SSRA) high up to 45% in the absence of pore forming agent. Based on this unique porous carbon material, further compositing with MWCNT can enhance its performance for Li-S batteries, specifically, 1 C for 631 mA h/g and 2 C for 574 mA h/g after 300 cycles, with capacity decay as low as only 0.104% and 0.07%, respectively, which may further open the opportunity for a new family of porous carbon materials with well-controlled structures and properties for high performance applications in energy conversion and storage fields. [ABSTRACT FROM AUTHOR]

Although silicon/carbon (Si/C) nanohybrid materials are promising to improve the energy density of lithium ion batteries, their nano-sized features severely hinder their practical application, as the current battery assembly process favors micron-sized electrode materials. In this work, to combine the merits of nano- and micron-sized materials together, micron-sized carbon coated graphene wrapped Si/carbon black (Si/CB@G@C) spherical hybrids are synthesized via a water-in-oil (W/O) emulsion system. In the obtained hierarchical structure, Si and CB nanoparticles (NPs) are embedded in the micron-sized graphene sphere, well encapsulated by the flexible graphene sheets, and these hybrids are further coated by an amorphous carbon layer. Thus, the graphene sphere can accommodate the volume expansion of Si NPs during lithiation, protect them from direct exposure to the electrolyte and enhance the electrical conductivity. Furthermore, the CB particles between Si NPs and graphene, together with the carbon coating layer can provide highly conductive network for the transport of electrons, also preventing Si NPs from directly contact with the electrolyte. As a result, the as-prepared Si/CB@G@C hybrids exhibit a significantly improved cycling stability compared with pure Si and Si@G hybrids, along with an excellent rate performance (728 mAh g −1 at 2 A g −1 ). [ABSTRACT FROM AUTHOR]

This work demonstrates how a very low fraction of graphene greatly enhances the usage efficiency of carbon-based conductive additive in LiCoO 2 -based lithium ion batteries (LIB) and develops a strategy using binary conductive additive to have a high performance battery, especially with excellent rate performance. With a much lower fraction of carbon additive for a commercial LIB, only 0.2 wt% graphene nanosheet (GN) together with 1 wt% Super-P (SP) constructing an effective conductive network, the prepared battery exhibits outstanding cycling stability (146 mAhg −1 at 1C with retention of 96.4% after 50 cycles) and rate capability (116.5 mAhg −1 even at 5C). In this battery, a composite conducting network is formed with a long-range electron pathway formed by a trace amount of GN and the short-range electron pathway by aggregation of SP particles. More interestingly, in micro-sized LiCoO 2 system, the GN additive does not present hindrance effect for lithium ion transport even in high rate discharge, which is entirely different from the nano-sized LiFePO 4 system. This study further demonstrates commercial potential of GN additive for high performance LIB and more importantly gives a well-designed recipe for its real application. [ABSTRACT FROM AUTHOR]

Carbon-based materials are important in energy storage and conversion materials, because of their different possible morphologies and superior performance. We discuss relationships between the structure and properties of carbon-based materials as the cathode of the lithium-air battery, discuss the importance of structure design and performance control, specify the research priorities for carbon-based materials for lithium-air batteries, and explore the potential applications of carbon-based materials in lithium-air batteries. [New Carbon Materials 2014, 29(4): 265–271] [ABSTRACT FROM AUTHOR]

Because of high electrical conductivity, graphene has been widely investigated as conductive additive in lithium-ion batteries. Whereas, it is found that graphene has quite different influences on the rate performance in diverse evaluation systems, such as commercial soft-packed cells and coin half-cells. It has been proved that the coin cells show better high-rate performance with the increase of graphene content, while it is of the opposite trend in commercial cells. In normal cases, the electrode thickness of coin cells is much smaller than that of commercial cells. Herein, it is found that the electrode thickness has a considerable effect on the high-rate performance of LiFePO 4 electrode in which graphene is used as the conductive additive. Thicker electrode results in a longer Li-ion diffusion path, and thus the steric effect that graphene could hinder the Li-ion diffusion is amplified, inducing much higher polarization and poorer performance at high rate. Comparatively, this phenomenon is not obvious in thinner electrode. Thus, when more graphene is introduced in thick electrode, the power performance is greatly weakened as is observed in the commercial cells. This finding is of great importance for designing a high-performance commercial lithium-ion battery with graphene additives. [ABSTRACT FROM AUTHOR]

Silicon (Si) has been regarded as one of the most attractive anode materials for the next generation lithium-ion batteries because of its large theoretical capacity, high safety, low cost and environmental benignity. However, the architecture of Si-based anode material still needs to be well designed to overcome the structure degradation and instability of the solid-electrolyte interphase caused by a large volume change during cycling. Here we report the electrochemical performances of a novel binder-free Si/carbon composite film consisting of alternatively stacked Si-porous carbon layers and graphene layers, which is synthesized by electrostatic spray deposition followed by heat treatment. For this composite film, Si nanoparticles are embedded in the porous carbon layer composed of nitrogen-doped carbon framework, carbon black and carbon nanotubes. And the combined Si-porous carbon layer is further sandwiched by flexible and conductive graphene sheets. The multilayered Si-porous carbon/graphene electrode shows a maximum reversible capacity of 1020 mAh g −1 with 75% capacity retention after 100 cycles and a good rate capability on the basis of the total electrode weight. The excellent electrochemical performances are attributed to the fact that the layer-by-layer porous carbon matrix can accommodate the volume change of Si particles and maintain the structural and electrical integrities. [ABSTRACT FROM AUTHOR]

Abstract: We report a novel monolithic porous carbon constructed by the hydrothermal self-assembly of graphene oxide sheets with poly (vinyl alcohol) as the linker in the formation process of a three-dimensional (3D) structure. All the pores in this carbon have circular cross-sections and range from micropores to mesopores to macropores and are formed by the gradual removal of trapped water. This 3D graphene network together with unique spheroidal and hierarchical pore structure with macropore openings at the surface allows fast ion and electron transport into the innermost micropores. The carbon not only exhibits excellent capability for removal of dye pollutants and oils but also shows a good performance as an electrode material in lithium ion batteries. Moreover, it is also proved to be an ideal buffer for expanded active materials in electrochemical energy storage. [Copyright &y& Elsevier]

Abstract: The lithium ion batteries using Li4Ti5O12 as the anode material are easily being inflated during charge and discharge, which, however, does not occur in the batteries using graphite as the anode material. The high reduction reactivity of electrolyte on the Li4Ti5O12 material may be the main reason. In this work, the reduction reactivities of electrolyte on the uncoated and carbon-coated Li4Ti5O12 electrodes are compared for the first time. The results show that the reduction decomposition of electrolyte does occur on the uncoated Li4Ti5O12 electrode at around 0.7V, while it only takes place at the first cycle on the carbon-coated Li4Ti5O12 electrode. The carbon coating layers cover the catalytic active sites of Li4Ti5O12 particles and separate the Li4Ti5O12 particles from the electrolyte. A successive solid electrolyte interface (SEI) film is formed on the carbon layer during the formation process, which can prevent the further reduction decomposition of electrolyte at around 0.7V. The impurity phases of rutile and anatase TiO2 do not influence the reduction reactivity of electrolyte. This work is not only important to understand the reduction decomposition mechanism of electrolyte on the Li4Ti5O12 electrode, but also provides an effective solution to suppress the reduction decomposition of electrolyte in the batteries. [Copyright &y& Elsevier]

Multi-walled carbon nanotubes (MWNTs) with different mean outer diameters in the range of 13–53 nm, synthesized by the catalytic decomposition of hydrocarbons using a floating catalyst method, were purified and pretreated with the same procedure for volumetric hydrogen adsorption/desorption measurements. It was found that the hydrogen storage capacity of the purified and pretreated MWNTs was proportional to their diameter, and that hydrogen in all types of MWNTs measured could not be completely desorbed at room temperature and ambient pressure. A possible mechanism for the above behavior was proposed based on the results of cryogenic nitrogen adsorption analysis and high-resolution transmission electron microscopy observations. It was considered that small “carbon islands” might be the main hydrogen adsorption site in MWNTs. The effects of metal catalyst as well as an etched cavity on the surface of MWNTs on the hydrogen adsorption/desorption of MWNTs were also discussed. [Copyright &y& Elsevier]

The graphene-based macroform (GM) is a new category of macroscopic carbon materials assembled from graphene nanosheets. It possesses superior physical and chemical properties inherited from individual graphene nanosheets, and moreover, has a tunable micro-texture and controlled macro-morphology, which is useful in various areas. In this paper, different macroscopic forms and preparation methods of GM are reviewed, where the self-assembly method is highlighted. The physical and chemical properties of GM are briefly introduced, and the potential applications including energy storage and conversion, catalysis, bio-medicine and other aspects are discussed in detail. Finally, the opportunities and challenges of research and applications of GM are commented on, and it is concluded that the assembly of graphenes into fibers, films and blocks is an effective strategy towards their practical applications. [New Carbon Materials 2013, 28(3): 161–171] [ABSTRACT FROM AUTHOR]