以预锂化多壁碳纳米管为负极的锂离子电容器性能

采用内部短路方式对多壁碳纳米管负极进行不同程度的预嵌锂处理,预嵌锂时间为5,30,60min,以预嵌锂多壁碳纳米管极片作为负极,活性炭极片作为正极,组装成锂离子电容器。利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)对多壁碳纳米管及电极极片进行表征分析,采用恒流充放电(GCD)和交流阻抗谱(EIS)研究预嵌锂多壁碳纳米管负极和未预嵌锂处理多壁碳纳米管负极锂离子电容器的性能。电化学测试结果表明,多壁碳纳米管负极预嵌锂大幅提高了电容器充放电性能,对比未嵌锂多壁碳纳米管电容器,在相同的电流密度下(100mA/g),能量密度提高400%。预嵌锂60min,电流密度100mA/g时,其比容量达到57F/g。在电流密度为100～3200mA/g范围内,其最高能量密度与功率密度分别达到90Wh/kg,4130W/kg。1000次充放电循环后,容量保持率维持在85%以上,表现出良好的超级电容器性能。     

A hierarchical Ti2Nb10O29 composite electrode for high-power lithium-ion batteries and capacitors

Ti₂Nb₁₀O₂₉ (TNO) is a suitable electrode for high-performance lithium-ion batteries and capacitors because of its large lithium storage capacity and high Li⁺ diffusivity. Currently, the rate or power capability of TNO-based systems is limited by the poor electronic conductivity of the material. Here we report our findings in design, synthesis, and characterization of a hierarchical N-rich carbon conductive layer wrapped TNO structure (TNO@NC) using a novel polypyrrole-chemical vapor deposition (PPy-CVD) process. It was found that carbon coating with PPy–carbon partially reduces Ti and Nb cations, forms TiN, and creates oxygen vacancies in the TNO@NC structure that further increase overall electronic and ionic conductivity. Various defect models and density functional theory (DFT) calculations are used to show how oxygen vacancies influence the electronic structure and Li-ion diffusion energy of the TNO@NC composite. The optimized TNO@NC sample shows notable rate capability in half-cells with a reversible capacity of 300 mAh g⁻¹ at 1 C rate and maintains 211 mAh g⁻¹ at a rate of 100 C, which is superior to that of most M_xNb_yO_z materials. Full cell LiNi_0.5Mn_1.5O₄ (LNMO)||TNO@NC lithium-ion batteries (LIB) and active carbon (AC)||TNO@NC hybrid lithium-ion capacitors (LIC) exhibited notable volumetric and gravimetric energy and power densities.     

退火调控的3D交联TiNb2O7纳米棒电极用于高效柔性锂离子电容器（英文）

TiNb2O7的理论比容量高达280 mA h g^-1,是一类有前景的锂离子电容器负极材料.然而其较差的电子导电性严重限制了其倍率性能的提升.在本文中,我们在柔性碳布表面直接生长3D交联的TiNb2O7纳米棒多孔负极,并将其首次应用于柔性锂离子电容器;碳布的高导电性,单晶纳米棒结构较短的离子/电子传输路径以及良好的结构稳定性,有效提高了材料的倍率性能和循环稳定性.研究表明,Ti Nb2O7负极表现出优异的倍率性能(从1到40 C,容量保持率高达66.3%),出色的循环稳定性(>2000圈),以及良好的柔韧性(连续弯曲500次后容量无损失).此外,将无粘结剂的Ti Nb2O7负极和商用活性炭正极搭配成锂离子电容器,展现出了较高的质量和体积能量/功率密度(~100.6 W h kg^-1/4108.8 W kg^-1;10.7 m W h cm^-3/419.3 mW cm^-3),优于先前报道的混合超级电容器,同时该器件可以在180°弯曲状态下为LED灯供电.     

石墨球化率的数值化处理

对GB／T9441-1988标准附录A的袁1中各种形状石墨面积率的图像进行了数值化处理,并对结果进行了分类比对。结果表明：面积率难以完全描述目标的形状特性,而采用圆度对石墨球化率进行表征更具科学性和合理性,也符合当今金相分析技术向数值化发展的趋势。     

Materials for electrochemical capacitors

Electrochemical capacitors, also called supercapacitors, store energy using either ion adsorption (electrochemical double layer capacitors) or fast surface redox reactions (pseudo-capacitors). They can complement or replace batteries in electrical energy storage and harvesting applications, when high power delivery or uptake is needed. A notable improvement in performance has been achieved through recent advances in understanding charge storage mechanisms and the development of advanced nanostructured materials. The discovery that ion desolvation occurs in pores smaller than the solvated ions has led to higher capacitance for electrochemical double layer capacitors using carbon electrodes with subnanometre pores, and opened the door to designing high-energy density devices using a variety of electrolytes. Combination of pseudo-capacitive nanomaterials, including oxides, nitrides and polymers, with the latest generation of nanostructured lithium electrodes has brought the energy density of electrochemical capacitors closer to that of batteries. The use of carbon nanotubes has further advanced micro-electrochemical capacitors, enabling flexible and adaptable devices to be made. Mathematical modelling and simulation will be the key to success in designing tomorrow's high-energy and high-power devices.     

A simple approach for large-area fabrication of Ag nanorings

A simple and low-cost method based on a two-step heat treatment of AgNO(3)/SiO(2) film has been developed for fabricating metal Ag nanoring arrays. The as-prepared nanorings have an inner diameter of 70-250?nm and an average wall thickness (namely wire diameter) of approximately 30 nm with a number density of approximately 10(9)?cm(-2) on the surface of the SiO(2) matrix. X-ray diffraction (XRD) results reveal that these nanorings exhibit a face-centered cubic crystal structure. Furthermore, a new growth mechanism, namely a molten metal bubble as a self-template, is tentatively proposed for Ag nanorings.     

Seismic performance evaluation for super-long span cable-stayed bridges

Based on the capacity/demand analysis of bridge components, and life cycle and performance based seismic design principles, a practical procedure is developed for the seismic performance evaluation of super-long span cable-stayed bridges. According to the procedure, the seismic performance evaluation of the Su-Tong Bridge,which is a cable-stayed bridge with a main span of 1088m, is completed, and the practicality of the procedure is validated. The earthquake resistance level for super-long span cable-stayed bridges is discussed, including the earthquake level, its corresponding structural performance and check indices. And a set of formula for capacity/demand ratio calculation of bridge components is proposed.     

Sustainable materials for electrochemical capacitors

Highly tunable properties of materials used for the construction of electrochemical capacitors make them a perfect choice for a broad scope of applications with high power demand. The ability to design the system according to the expected power/energy profile allows them being considered as powerful alternatives to conventional capacitors and batteries. Carbon materials with the developed specific surface area are the most common electrode components of electrochemical capacitors because of their cost, versatile form, availability, easiness of processing, and eco-friendly character. Biomass is frequently used for carbon production, however, among many natural organic materials, only some of them should be regarded as a useful precursor. Ongoing research brings many novel concepts of using bio-derived materials in high-performance electrochemical capacitors. This review article summarizes the progress on the applications of abundant biomaterials and materials derived from biomass in the field. Various ‘green’ resources have been used as precursors for activated carbons, as binders, or as gel (gelating) agents for solid-state electrolytes. The authors attempt to critically evaluate a commercial potential of these materials upon ongoing trends in research & development of electrochemical capacitors. Pros and cons of utilizing the selected biomass materials are provided and perspectives for their advanced processing are discussed.     

NiO nanorings and their unexpected catalytic property for CO oxidation

Nickel oxide (NiO) nanorings were synthesized by controllable thermal decomposition of precursor Ni(OH)(2) nanoplates obtained via the reaction between Ni(NO(3))·6H(2)O and NaOH under hydrothermal conditions. The process of their formation was investigated and an unexpected catalytic property of this novel-shaped material is reported for CO oxidation.     

Polymer electrolytes for lithium-ion batteries

The motivation for lithium battery development and a discussion of ion conducting polymers as separators begin this review, which includes a short history of polymer electrolyte research, a summary of the major parameters that determine lithium ion transport in polymer matrices, and consequences for solid polymer electrolyte development. Two major strategies for the application of ion conducting polymers as separators in lithium batteries are identified: One is the development of highly conductive materials via the crosslinking of mobile chains to form networks, which are then swollen by lithium salt solutions ("gel electrolytes"). The other is the construction of solid polymer electrolytes (SPEs) with supramolecular architectures, which intrinsically give rise to much enhanced mechanical strength. These materials as yet exhibit relatively common conductivity levels but may be applied as very thin films. Molecular composites based on poly(p-phenylene)- (PPP)-reinforced SPEs are a striking example of this direction. Neither strategy has as yet led to a "breakthrough" with respect to technical application, at least not for electrically powered vehicles. Before being used as separators, the gel electrolytes must be strengthened, while the molecularly reinforced solid polymer electrolytes must demonstrate improved conductivity.     

Metal hydrides for lithium-ion batteries

Classical electrodes for Li-ion technology operate via an insertion/de-insertion process. Recently, conversion electrodes have shown the capability of greater capacity, but have so far suffered from a marked hysteresis in voltage between charge and discharge, leading to poor energy efficiency and voltages. Here, we present the electrochemical reactivity of MgH(2) with Li that constitutes the first use of a metal-hydride electrode for Li-ion batteries. The MgH(2) electrode shows a large, reversible capacity of 1,480 mAh g(-1) at an average voltage of 0.5 V versus Li(+)/Li(o) which is suitable for the negative electrode. In addition, it shows the lowest polarization for conversion electrodes. The electrochemical reaction results in formation of a composite containing Mg embedded in a LiH matrix, which on charging converts back to MgH(2). Furthermore, the reaction is not specific to MgH(2), as other metal or intermetallic hydrides show similar reactivity towards Li. Equally promising, the reaction produces nanosized Mg and MgH(2), which show enhanced hydrogen sorption/desorption kinetics. We hope that such findings can pave the way for designing nanoscale active metal elements with applications in hydrogen storage and lithium-ion batteries.     

Nanomaterials for lithium-ion rechargeable batteries

In lithium-ion batteries, nanocrystalline intermetallic alloys, nanosized composite materials, carbon nanotubes, and nanosized transition-metal oxides are all promising new anode materials, while nanosized LiCoO2, LiFePO4, LiMn2O4, and LiMn2O4 show higher capacity and better cycle life as cathode materials than their usual larger-particle equivalents. The addition of nanosized metal-oxide powders to polymer electrolyte improves the performance of the polymer electrolyte for all solid-state lithium rechargeable batteries. To meet the challenge of global warming, a new generation of lithium rechargeable batteries with excellent safety, reliability, and cycling life is needed, i.e., not only for applications in consumer electronics, but especially for clean energy storage and for use in hybrid electric vehicles and aerospace. Nanomaterials and nanotechnologies can lead to a new generation of lithium secondary batteries. The aim of this paper is to review the recent developments on nanomaterials and nanotechniques used for anode, cathode, and electrolyte materials, the impact of nanomaterials on the performance of lithium batteries, and the modes of action of the nanomaterials in lithium rechargeable batteries.     

Magnetic Graphitic Nanocapsules for Programmed DNA Fishing and Detection

Graphene nanomaterials are typically used in biosensing applications, and they have been demonstrated as good fluorescence quenchers. While many conventional amplification platforms are available, developing new nanomaterials and establishing simple, enzyme‐free and low‐cost strategies for high sensitivity biosensing is still challenging. Therefore, in this work, a core–shell magnetic graphitic nanocapsule (MGN) material is synthesized and its capabilities for the detection of biomolecules are investigated. MGN combines the unique properties of graphene and magnetic particles into one simple and sensitive biosensing platform, which quenches around 98% of the dye fluorescence within minutes. Based on a programmed multipurpose DNA capturing and releasing strategy, the MGN sensing platform demonstrates an outstanding capacity to fish, enrich, and detect DNA. Target DNA molecules as low as 50 pM could be detected, which is 3‐fold lower than the limit of detection commonly achieved by carbon nanotube and graphene‐based fluorescent biosensors. Moreover, the MGN platform exhibits good sensing specificity against DNA mismatch tests. Overall, therefore, these magnetic graphitic nanocapsules demonstrate a promising tool for molecular disease diagnosis and biomedicine. This simple fishing and enrichment strategy may also be extended to other biological and environmental applications and systems.     

Transient modeling of ferroelectric capacitors for nonvolatilememories

Present ferroelectric (FE) capacitor models mostly rely on continuous hysteresis loop characteristics of FE materials. Our experimental results show that this approach overestimates the remanent and saturation polarizations available for nonvolatile semiconductor memories by more than 50%. A behavioral transient model based on pulse measurement results is proposed and implemented as an HSPICE macro-model. The model mainly consists of two nonlinear capacitors, corresponding to the two different polarization states of an FE capacitor