Enhanced Interfacial Kinetics of Carbon Monolith Boosting Ultrafast Na‐Storage

Slow ion kinetics of negative electrode materials is the main factor of limiting fast charge and discharge of batteries. Sluggish Na⁺ kinetics property leads to large electrode polarization, resulting in poor rate and cyclic performances. Herein, an electrode of ultrasmall tin nanoparticles decorated in N, S codoped carbon monolith (TCM) with exceptional high‐rate capability and ultrastable cycling behavior for Na‐storage is reported. The resulted TCM electrode exhibits an extremely high retention of 96% initial charge capacity after 500 cycles at a current density of 500 mA g^?1. Significantly, when the current density is elevated to an ultrahigh rate of 5000 mA g^?1, a high reversible capacity of 228 mAh g^?1 after the 2000th cycle is still maintained. More importantly, the stable and fast Na‐storage of TCM is investigated and understood by experimental characterizations and kinetics calculations, including interfacial ion/electron transport behavior, ion diffusion, and quantitative pseudocapacitive analysis. These investigations elucidate that the TCM shows improved ion/electron conductivity and enhanced interfacial kinetics. An entirely new perspective to deep insights into the fast ion/electron transport mechanisms revealed by interfacial kinetics of sodiation/desodiation, which contributes to the profound understanding for developing fast charging/discharging and long‐term stable electrodes in sodium‐ion batteries, is provided.     

Impedance sensing of DNA binding drugs using gold substrates modified with gold nanoparticles

Interfacial interactions between immobilized DNA probes and DNA-specific sequence binding drugs were investigated using impedance spectroscopy toward the development of a novel biosensing scheme. The impedance measurements are based on the charge-transfer kinetics of the [Fe(CN)6]3-/4- redox couple. Compared to bare gold surfaces, the immobilization of DNA and then the DNA-drug interaction on electrode surfaces altered the capacitance and the interfacial electron resistance and thus diminished the charge-transfer kinetics by reducing the active area of the electrode or by preventing the redox species from approaching the electrode. Electrochemical deposition of gold nanoparticles on a gold electrode surface showed significant improvement in sensitivity. DNA-capped gold nanoparticles on electrodes act as selective sensing interfaces with tunable sensitivity due to higher amounts of DNA probes and the concentric orientation of the DNA self-assembled monolayer. The specificity of the interactions of two classical minor groove binders, mythramycin, a G-C specific-DNA binding anticancer drug, netropsin, an A-T specific-DNA binding drug and an intercalator, nogalamycin on AT-rich DNA-modified substrate and GC-rich DNA-modified substrate are compared. Using gold nanoparticle-deposited substrates, impedance spectroscopy resulted in a 20-40-fold increase in the detection limit. Arrays of deposited gold nanoparticles on gold electrodes offered a convenient tool to subtly control probe immobilization to ensure suitably adsorbed DNA orientation and accessibility of other binding molecules.     

Near-ohmic behavior for conducting polymers: extension beyond PEDOT on gold-plated platinum to other polymer-counterion/substrate combinations

Conducting polymers constitute a class of materials for which electrochemical and electron transport properties are a function not only of their chemical identity but also of their complex morphology. In this paper, we investigate and compare the frequency dependence behavior of the impedance of poly(3,4-ethylenedioxythiophene), or PEDOT, and that of poly(3,4-ethylenedioxypyrrole), or PEDOP, which are doped with a series of polyatomic anions during electrodeposition. We also contrast the behavior of PEDOT on Pt|Au, Pt, glassy carbon, and gold. Initial results for polycarbazole, PCz, electrodes are, in addition, included. Deposition parameters were adjusted to produce morphologically similar films for PEDOT, PEDOP, and PCz. In doing so, we have been successful in producing frequency-independent impedance behavior similar to that previously reported for PEDOT on Pt|Au. Although the impedance behavior of these polymers appears to be primarily determined by morphological features, the impact of counterion identity (beyond ionic charge transport) is also discussed. These studies suggest that choice of polymer/dopant combination and electrodeposition parameters can be manipulated to tune the impedance characteristics of electrodes, thereby optimizing them for capacitive or faradaic charge injection, or some combination of the two.     

Fabrication of organic field effect transistor by directly grown poly(3 hexylthiophene) crystalline nanowires on carbon nanotube aligned array electrode

We fabricated organic field effect transistors (OFETs) by directly growing poly (3-hexylthiophne) (P3HT) crystalline nanowires on solution processed aligned array single walled carbon nanotubes (SWNT) interdigitated electrodes by exploiting strong π-π interaction for both efficient charge injection and transport. We also compared the device properties of OFETs using SWNT electrodes with control OFETs of P3HT nanowires deposited on gold electrodes. Electron transport measurements on 28 devices showed that, compared to the OFETs with gold electrodes, the OFETs with SWNT electrodes have better mobility and better current on-off ratio with a maximum of 0.13 cm(2)/(V s) and 3.1 × 10(5), respectively. The improved device characteristics with SWNT electrodes were also demonstrated by the improved charge injection and the absence of short channel effect, which was dominant in gold electrode OFETs. The enhancement of the device performance can be attributed to the improved interfacial contact between SWNT electrodes and the crystalline P3HT nanowires as well as the improved morphology of P3HT due to one-dimensional crystalline nanowire structure.     

Scalable synthesis of TiO<Subscript>2</Subscript> crystallites embedded in bread-derived carbon matrix with enhanced lithium storage performance

TiO₂/carbon (C/TiO₂) composites have been synthesized via an in-situ pyrolysis method using bread as carbon source and investigated as anodes for lithium-ion batteries. As a cheap and common staple food with a sponge-like structure, bread contains a certain amount of moisture, enabling the hydrolysis of tetrabutyl orthotitanate. It is characterized that TiO₂ nanocrystallites are embedded in bread-derived carbon matrix, and their synergetic effect on improving electrochemical properties is demonstrated as well. Partially surface lithium storage of ultrasmall TiO₂ particles is credited to the unique embedment structure. Meanwhile, the carbon species are of importance in enhancing reversible capacities and accelerating interfacial charge transfer. It delivers a reversible capacity of 231 mAh g^?1 at a specific current of 100 mA g^?1 after 200 cycles for the resultant C/TiO₂ composite with 38.8 wt.% carbon. This work presents a facile strategy toward scalable and eco-friendly preparation of metal oxides compositing with carbonaceous materials.     

Nanowires network for biomolecular detection using contactless impedance tomoscopy technique

Here we present the detection of ultralow concentrations of biomolecules in a device made from a polycarbonate membrane containing a network of gold nanowires and using a "contactless" impedance tomoscopy technique. The sensor comprises a thin dielectric layer with two parallel band electrodes on the one side and a microchannel containing gold nanowires onto which the adsorption of antibodies occurs. Upon applying a high-frequency ac voltage between the two electrodes, the adsorption process occurring at the surface of the gold nanowires can be followed through contactless impedance measurements. The configuration allows the real-time detection of biomolecules with a bulk concentration in the picomolar range.     

Few‐Layer Bismuthene with Anisotropic Expansion for High‐Areal‐Capacity Sodium‐Ion Batteries

Bismuth is a promising anode material for state‐of‐the‐art rechargeable batteries due to its high theoretical volumetric capacity and relatively low working potential. However, its charge storage mechanism is unclear, hindering further improvement of the cell performance. Here, using in situ transmission electron microscopy and X‐ray diffraction techniques as well as theoretical analysis, it is found that a large anisotropic volume expansion of 142% occurs along the z‐axis largely due to the alloy reaction during sodiation, significantly reducing the electrochemical performance of bismuth electrodes. To address this problem, ultrathin few‐layer bismuthene with a large aspect ratio is rationally synthesized, and can relieve the expansion strain along the z‐axis. A free‐standing bismuthene/graphene composite electrode with tunable thickness achieves a strikingly stable and high areal sodium storage capacity of 12.1 mAh cm^?2, which greatly exceeds that of most reported electrode materials. The clarification of the charge storage mechanism and the superior areal capacity achieved should facilitate the development of bismuth‐based high‐performance anodes for practical electrochemical energy‐storage applications.     

A Top‐Down Strategy toward SnSb In‐Plane Nanoconfined 3D N‐Doped Porous Graphene Composite Microspheres for High Performance Na‐Ion Battery Anode

Engineering of 3D graphene/metal composites with ultrasmall sized metal and robust metal–graphene interfacial interaction for energy storage application is still a challenge and rarely reported. In this work, a facile top‐down strategy is developed for the preparation of SnSb‐in‐plane nanoconfined 3D N‐doped porous graphene networks for sodium ion battery anodes, which are composed of several tens of interconnected empty N‐graphene boxes in‐plane firmly embedded with ultrasmall SnSb nanocrystals. The all‐around encapsulation (plane‐to‐plane contact) architecture that provides a large interface between N‐graphene and SnSb nanocrystal not only effectively enhances the electron conductivity and structural integrity of the overall electrode, but also offers excess interfacial sodium storage, thus leading to much enhanced high‐rate sodium storage capacity and stability, which has been proven by both experimental results and first‐principles simulations. Moreover, this top‐down strategy can enable new paths to the low‐cost and high‐yield synthesis of 3D graphene/metal composites for applications in energy‐related fields and beyond.     

Predicting low-impedance interfaces for solid-state batteries

All-solid-state batteries are an exciting technology for increased safety and energy density compared to traditional lithium-ion cells. Recently, we developed a theory of mapping inner potentials and thermodynamic driving forces specific to the solid-state batteries, allowing prediction of the “intrinsic” interfacial lithium barriers. This potential mapping methodology, based purely on calculated bulk and surface properties, enables fast screening of a variety of advanced solid electrolyte materials as well as a selection of cutting-edge high-voltage cathode materials, predicting properties of 48 distinct battery configurations. A number of cathode/electrolyte pairs are identified which have low “intrinsic” barriers to both the charge and discharge process at all states of charge, suggesting that they will most benefit from engineering efforts to reduce extrinsic interfacial impedance. These predictions agree well with available experimental measurements, which form only a subset of the predicted interfaces. Thus, this interface potential model will accelerate the design process from emerging materials to all-solid-state battery devices.     

High rate capabilities Fe3O4-based Cu nano-architectured electrodes for lithium-ion battery applications

All battery technologies are known to suffer from kinetic problems linked to the solid-state diffusion of Li in intercalation electrodes, the conductivity of the electrolyte in some cases and the quality of interfaces. For Li-ion technology the latter effect is especially acute when conversion rather than intercalation electrodes are used. Nano-architectured electrodes are usually suggested to enhance kinetics, although their realization is cumbersome. To tackle this issue for the conversion electrode material Fe3O4, we have used a two-step electrode design consisting of the electrochemically assisted template growth of Cu nanorods onto a current collector followed by electrochemical plating of Fe3O4. Using such electrodes, we demonstrate a factor of six improvement in power density over planar electrodes while maintaining the same total discharge time. The capacity at the 8C rate was 80% of the total capacity and was sustained over 100 cycles. The origin of the large hysteresis between charge and discharge, intrinsic to conversion reactions, is discussed and approaches to reduce it are proposed. We hope that such findings will help pave the way for the use of conversion reaction electrodes in future-generation Li-ion batteries.     

Facile Synthesis of Ultrasmall CoS2 Nanoparticles within Thin N‐Doped Porous Carbon Shell for High Performance Lithium‐Ion Batteries

Cobalt sulfide (CoS₂) is considered one of the most promising alternative anode materials for high‐performance lithium‐ion batteries (LIBs) by virtue of its remarkable electrical conductivity, high theoretical capacity, and low cost. However, it suffers from a poor cycling stability and low rate capability because of its volume expansion and dissolution of the polysulfide intermediates in the organic electrolytes during the battery charge/discharge process. In this study, a novel porous carbon/CoS₂ composite is prepared by using nano metal–organic framework (MOF) templates for high‐preformance LIBs. The as‐made ultrasmall CoS₂ (15 nm) nanoparticles in N‐rich carbon exhibit promising lithium storage properties with negligible loss of capacity at high charge/discharge rate. At a current density of 100 mA g^?1, a capacity of 560 mA h g^?1 is maintained after 50 cycles. Even at a current density as high as 2500 mA g^?1, a reversible capacity of 410 mA h g^?1 is obtained. The excellent and highly stable battery performance should be attributed to the synergism of the ultrasmall CoS₂ particles and the thin N‐rich porous carbon shells derieved from nanosized MOF precusors.     

Space charge distributions of an electric double layer capacitor with carbon nanotubes electrode

Space charge distributions of an electric double layer capacitors (EDLCs) based on polarizable nanoporous electrodes, containing carbon nanotubes (CNTs) as electrode material, were investigated by a pulsed electro acoustic (PEA) method. The EDLCs samples were prepared using CNTs and carbon black (i.e. acetylene and ketjen black) as electrode materials with different types pore structures. The charge distributions of positive/negative ions were spatially uneven and charge accumulation region concentrated on central part of electrode. The polarizable electrodes with ketjen black and CNTs-5 wt.% had higher space charge density. From the results of discharge characteristics, it is clear that EDLCs based on the ketjen black/CNTs-3 wt.% have better capacitive behavior. The specific capacitance of about 14 F/g of EDLCs using the polarizable electrodes with ketjen black and CNTs-3 wt.% were obtained. It can be found that CNTs plays an essential role in the improvement of the charge density and the electrostatic capacity in EDLCs. The use of PEA method allowed us to perform the direct observations of spatio-temporal charge distributions in EDLCs based on CNTs.     

Differential impedance spectroscopy for monitoring protein immobilization and antibody-antigen reactions

This work describes the theoretical and experimental approaches for monitoring the interfacial biomolecular reaction between immobilized antibody and the antigen binding partner using novel differential impedance spectroscopy. The prerequisite of any biosensor is the immobilization of macromolecules onto the surface of a transducer. It is clear that the function of most macromolecules changes from what is observed in solution once immobilization has occurred. In the worst case, molecules entirely lose their binding activity almost immediately after immobilization. Certain conditions (e.g., denaturation, interfacial effects based on ionic strength, surface charge, dielectric constants, etc.) at interfaces are responsible for alterations of binding activity; it is not clear whether a combination of such processes is understood. However, these processes in combination must be reliably modeled in order to predict the outcome for most macromolecules. This work presents the theoretical and practical means for elucidating the surface reactivity of biomolecular reagents using ion displacement model with antibody-antigen (Ab-Ag) reaction as the test case. The Ab-Ag reaction was directly monitored using a dual-channeled, impedance analyzer capable of 1 measurement/s using covalent immobilization chemistry and polymer-modified electrodes in the absence of a redox probe. The evidence of Ab-Ag binding was revealed through the evolution of differential admittance. The surface loading obtained using the covalent immobilization chemistry was 9.0 x 10(16)/cm2, whereas with polymer-modified electrodes, the surface loading was 9.0 x 10(15)/cm2, representing a 10 times increase in surface reactivity. The proposed approach may be applicable to monitoring other surface interfacial reactions such as DNA-DNA interactions, DNA-protein interactions, and DNA-small molecule interactions.     

Enhanced Interfacial Magnetization is Responsible for the Negative Capacity Fading of Cobalt Ditelluride Anodes for Lithium Storage

In lithium-ion batteries (LIBs), the stabilized capacities of transition metal compound anodes usually exhibit higher values than their theoretical values due to the interfacial charge storage, the formation of reversible electrolyte-derived surface layer, or interfacial magnetization. But the effectively utilizing the mechanisms to achieve novel anodes is rarely explored. Herein, a novel nanosized cobalt ditelluride (CoTe₂) anodes with ultra-high capacity and long term stability is reported. Electrochemical tests show that the lithium storage capacity of the best sample reaches 1194.7 mA h g⁻¹ after 150 cycles at 0.12 A g⁻¹, which increases by 57.8% compared to that after 20 cycles. In addition, the sample offers capacities of 546.6 and 492.1 mA h g⁻¹ at 0.6 and 1.8 A g⁻¹, respectively. During cycles, CoTe₂ particles (average size 20 nm) are gradually pulverized into the smaller nanoparticles (<3 nm), making the magnetization more fully due to the larger contact area of Co/Li₂Te interface, yielding an increased capacity. The negative capacity fading is observed, and verified by ex situ structural characterizations and in situ electrochemical measurements. The proposed strategy can be further extended to obtain other high-performance ferromagnetic metal based electrodes for energy storage applications.     

Structure and electrochemical performance of ZnO/CNT composite as anode material for lithium-ion batteries

Metal oxides are well-known potential alternatives to graphite as anode materials of lithium-ion batteries, and they can deliver much higher reversible capacities than graphite even at high current densities. In this study, hexagonal disk-shaped ZnO are synthesized by a facile solution reaction of ZnCl₂ and its composite is prepared in the presence of carbon nanotubes (CNTs). The as prepared ZnO/CNT composite has been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, fourier transform-infrared spectroscopy and Rutherford backscattering spectroscopy. Electrochemical characterization by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic discharge/charge tests demonstrate that the conversion reactions in ZnO and ZnO/CNT electrodes enable reversible capacity of 478 and 602 mAh g^?1, respectively for up to 50 cycles. Our investigation highlights the importance of anchoring of small ZnO particles on CNTs for maximum utilization of electrochemically active ZnO and CNTs for energy storage application in lithium-ion batteries.     

基于碳膜的柔性神经微电极阵列加工

为了实现长期安全有效的神经电刺激,避免电极腐蚀情况,提出了一种基于热解光刻胶形成碳膜作为导电材料的柔性视网膜神经微电极阵列．首先,通过高温热解图形化的光刻胶形成导电碳膜,然后利用光敏性聚酰亚胺（Durimide 7510）作为基底材料,通过光刻结合转膜、键合和牺牲层腐蚀技术,实现了具有柔性特征的碳膜神经微电极阵列．实验结果显示这种碳膜电极的电荷存储能力达到6．625mC／cm2．是金电极的12．4倍,显示了良好的电化学稳定性和电荷注入能力,有利于其长期植入和安全有效地工作,可应用于新一代人工视网膜系统的构建．     

High-Precision Displacement Sensing of Monolithic Piezoelectric Disk Resonators Using a Single-Electron Transistor

A single-electron transistor (SET) can be used as an extremely sensitive charge detector. Mechanical displacements can be converted into charge, and hence, SETs can become sensitive detectors of mechanical oscillations. For studying small-energy oscillations, an important approach to realize the mechanical resonators is to use piezoelectric materials. Besides coupling to traditional electric circuitry, the strain-generated piezoelectric charge allows for measuring ultrasmall oscillations via SET detection. Here, we explore the usage of SETs to detect the shear-mode oscillations of a 6-mm-diameter quartz disk resonator with a resonance frequency around 9 MHz. We measure the mechanical oscillations using either a conventional DC SET, or use the SET as a homodyne or heterodyne mixer, or finally, as a radio-frequency single-electron transistor (RF-SET). The RF-SET readout is shown to be the most sensitive method, allowing us to measure mechanical displacement amplitudes below \(10^{-13}\) m. We conclude that a detection based on a SET offers a potential to reach the sensitivity at the quantum limit of the mechanical vibrations.     

Sustainable Solid‐State Supercapacitors Made of 3D‐Poly(3,4‐ethylenedioxythiophene) and κ‐Carrageenan Biohydrogel

3D‐Poly(3,4‐ethylenedioxythiophene) (PEDOT) electrodes are prepared using the multi‐step template‐assisted approach. Specifically, poly(lactic acid) nano‐ and microfibers collected on a previously polymerized PEDOT film are used as templates for PEDOT nano‐ and microtubes, respectively. Morphological analysis of the samples indicates that 3D‐PEDOT electrodes obtained using a low density of templates, in which nano‐ and microtubes are clearly identified, exhibit higher porosity, and specific surface than conventional 2D‐PEDOT electrodes. However, a pronounced leveling effect is observed when the density of templates is high. Thus, electrodes with microtubes still present a 3D‐morphology but much less marked than those prepared using a low density of PLA microfibers, whereas the morphology of those with nanotubes is practically identical to that of films. Electrochemical studies prove that solid supercapacitors prepared using 3D‐PEDOT electrodes and κ‐carrageenan biohydrogel as electrolytic medium, exhibit higher ability to exchange charge reversibly and to storage charge than the analogues prepared with 2D‐electrodes. Furthermore, solid devices prepared using 3D‐electrodes and κ‐carrageenan biohydrogel exhibit very similar specific capacitances that those obtained using the same electrodes and a liquid electrolyte (i.e., acetonitrile solution with 0.1 M LiClO₄). These results prove that the success of 3D‐PEDOT electrodes is independent of the electrolytic medium.

     

CNTs添加对MmMn0.4Co0.7Al0.3Ni3.4贮氢合金负极性能的影响

对商用MmMn_0.4Co_0.7Al_0.3Ni_3.4贮氢合金中添加多壁碳纳米管(CNTs)、Ni的电化学性能进行了研究.结果表明,CNTs的加入可以提高电极的放电容量和初始活化性能,合金中添加CNTs、CNTs+Ni的电极完全活化只需11个循环,其最大放电容量分别为255、271mAh/g.而添加Ni的电极则需24个循环才达到最大容量(245mAh/g);合金中添加CNTs、CNTs+Ni的电极具有更高的放电平台和更好的高倍率放电性能(HRD),在1000mAh/g放电电流下,添加CNTs、CNTs+Ni、Ni以及未添加电极的HRD值依次为80.5%、83.9%、66.9%和62.4%,线性极化和电化学阻抗测试表明,CNTs的加入可有效减少欧姆电阻、提高电极表面的电荷迁移速率,更有利于在大电流下进行放电.     

碳基电化学双层电容器及复合电源系统的研制

碳基电化学超电容器作为一种新一代储能系统具有广泛的应用.多种测试及研究手段表明本文制备的炭材料具有适合电化学超电容器用途的特殊结构和型貌.直流充放电、循环伏安以及交流阻抗等实验显示了使用该材料组装的电容器具有良好的电化学性能,活性物质的比容量为168.5F/g,在大功率充放电条件下的活性物质的能量密度>5.0Wh/kg,同时具有10⁵以上的循环寿命,脉冲放电实验证明超电容器能有效改善镍氢电池的大电流脉冲放电性能.