Collector Electrode Research Articles

Charge transport in CdZnTe coplanar grid detectors examined by laser induced transient currents

Laser-induced transient current technique was used for the visualization of charge transfer in the coplanar CdZnTe radiation detector including distinction to the collecting and noncollecting grids. Transient current waveforms measured at different intergrid biasing allowed us the identification of principal charge transit features and the final redistribution of collected charge between grids. We have demonstrated that while at the initial period of the charge passage through the detector bulk the current waveform shapes on the collection and non-collection electrodes are nearly the same, the intergrid biasing entails significant current deviation at the final part of the transients, where inverted current through the non-collecting grid induces markedly reduced/enhanced collected charge in the non-collecting/collecting electrode. An optimum ratio of cathode/intergrid biasing was found to be close to the ratio of detector/intergrid dimensions. Theoretical simulations demonstrating all charge-transfer characteristics were presented and proved the validity of the experimental data.

Numerical investigation of the characteristics of an ion drag pump

Simple, lightweight electrohydrodynamic pumps having no moving parts and producing no mechanical vibration or noise can enhance heat transfer, control fluid flows, and increase drying. This paper reports a numerical investigation of electrohydrodynamic (EHD) pumps having one centrally located emitter and two collector electrodes. Results show that optimum sizes exist in the length of and spacing between the collectors. Collector electrodes with triangular cross-sections can yield better performance than those having rectangular cross-sections. The magnitude and distribution of the charge density significantly influence pump performance.

Improving the photovoltaic conversion efficiency of ZnO based dye sensitized solar cells by indium doping

Indium doped zinc oxide nanoparticles (NPs) with various indium concentrations were prepared by cost effective and low temperature aqueous solution method. The structure and chemical composition of the material were characterized using X-ray diffraction analysis (XRD) and X-ray photoelectron spectroscopy (XPS). The results demonstrated that indium doped ZnO maintained a hexagonal wurtzite structure, and that indium atoms were successfully incorporated into the lattice of ZnO. The doping of indium has a significant influence on the optical properties of ZnO. Indium doping into ZnO nanoparticle photoanodes could simultaneously capture and transport photogenerated electrons injected into ZnO by excited dyes. This approach was useful for electrons to fluently transfer to the collection electrode due to the decreased internal resistance and electron recombination loss. The dye sensitized solar cells (DSSCs) based on 0.2 mm indium doped ZnO photoanode exhibited a high short-circuit photocurrent density of 12.58 mA/cm2 and a power conversion efficiency (PCE) of 2.7% whereas DSSCs made from pure ZnO NPs exhibited a current density of 8.02 mA/cm2 with 1.8% efficiency. Both the improved surface area and the enhanced light scattering could increase the light-harvesting efficiency of the photoelectrode and, thus, promote the overall conversion efficiency of solar cells.

Electrochemical Measurement of Coenzyme Q10 Using Disposable Interdigitatad Array Electrode

Introduction Coenzyme Q10 (CoQ10) is an important component of the mitochondrial respiratory chain which exists as both oxidized form, CoQ10, and reduced form, CoQ10H2. CoQ10 is also known as an antioxidant in plasma, binding with lipoproteins during circulation. The antioxidative activity of CoQ10 depends on total CoQ10 concentration and percentage of CoQ10H2 in total CoQ10 in plasma. Since the ratio of CoQ10H2 is lower in patients with oxidative stress related diseases, it is considered to be an important marker for oxidative stress. At present, plasma CoQ10 and CoQ10H2 are usually determined by LC-electrochemical detector or LC-MS1,2) which are time-consuming, professional use and expensive analyzers. Considering the development of point of care (POCT) or on site sensor, simple, reliable, economical handy-type disposable test strip for CoQ10is favorable. Interdigitated array electrodes (IDAE) have excellent performances, such as high current density and high sensitivity, due to their hemisphere diffusion and array configuration. In this study, we will present electrochemical measurement of CoQ10using disposable IDAE for POCT or on site sensor. Methods Various concentrations of CoQ10 or CoQ10H2solution were prepared in mixture of 2-propanol and ammonium acetate aqueous solution . Amperometric measurements were performed by single mode or dual mode using IDAE. All solutions were bubbled with Ar before use. Results We first measured the dual mode redox current of working electrode 1 (collector electrode) and working electrode 2 (generator electrode), which were applied oxidizing potential and reducing potential, respectively. When CoQ10 solution was applied to sensor strip, faradaic signal from both generator and collector electrodes were soon reached to steady-state value. The response current on both generator and collector electrodes showed positive correlation with CoQ10 concentration. When CoQ10 oxidized form was applied to the strip, oxidation current was observed, indicating that CoQ10oxidized form was reduced onto the generator electrode and diffused and re-oxidized onto the collector electrode, thus redox cycle occurred successfully. Next, we measured the single mode redox current of working electrode 1 by applying reduction potential or oxidation potential. Reduction current was observed for CoQ10 and oxidation current was observed for CoQ10H2 and both of them exhibit steady- state currents soon after the potential application. The response current detected on working electrode 1 when reduction potential was applied to CoQ10 solution, oxidized form, showed positive correlation with CoQ10 concentration. When the oxidation potential was applied to CoQ10H2 solution, positive correlation with CoQ10H2concentration was observed. These results indicate that using IDAE, total CoQ10 concentration can be determined by dual mode amperometry and CoQ10 oxidized form or CoQ10H2can be determined by single mode amperometry (1) P. H. Tang et al., Clin. Chem. 2, 47 (2001) (2) J. Lagendijk, J. B. Ubbink, and W. J. H. Vermaak, J. Lipid Res. 1, 37 (1996) Figure 1

Effect of Temperature on Platinum Dissolution from PEFC Catalysts

The durability of polymer electrolyte fuel cells (PEFCs) is a big concern for its applications like FCVs to be commercialized on a large scale. In particular, the instability of Pt-based cathode catalyst has been discussed intensively. Platinum (Pt) dissolution is recognized as one of the degradation mechanisms for carbon supported Pt catalysts (Pt/C) in PEFCs. It has been found that repeated potential cycles accelerate Pt dissolution.[1-3] Fundamental studies in aqueous media revealed preliminary behaviors of Pt dissolution during one potential cycle. The up-to-date data were mostly obtained near room temperature, and a dominant cathodic dissolution during reduction of Pt oxide was understood. As reported by Fuller et al.,[4] however, degradation of Pt/Cs at an elevated temperature near 60 to 80 °C, whereat a PEFC normally operates, was severer than that at room temperatures. Thus, it is necessary to evaluate Pt dissolution from Pt/Cs at such temperatures. In prior studies,[5-6] we compared Pt dissolution at 25 °C and 65 °C by inductively coupled plasma mass spectrometry (ICP-MS) and a channel flow double electrode (CFDE). The experiments had some difficulties, but the results showed a ca. 5-time enhancement from 25 to 65 °C. The cathodic dissolution was enhanced because larger amount of Pt oxide was formed at 65 °C. The effect of temperature on the anodic dissolutions and the place exchange process remains unclear yet. In this study, we evaluate Pt dissolution under temperatures ranging from 20 to 80 °C. We test a series of commercial Pt/C catalysts produced by TKK that have Pt loadings from 20 to 70 wt% and average Pt particle size from ca. 1.5 to 5 nm. We limited the potential region between 0.6 and 1.4 V, which is closely related to the operation region of a PEFC cathode. We use ICP-MS to evaluate to overall dissolutions and a CFDE to analyze the dissolution behavior in one potential cycle. The attached Figure showed a typical CFDE data presenting the current on a working electrode loading a 30wt% Pt/C (TEC10E30A) under potential cycling (I WE) and the current recorded on a collector electrode (I CE) at 80 °C in 0.5 M H2SO4. The I CE helps to understand the dissolution of Pt4+ and Pt2+ complex during one potential cycle. Similar analysis will be discussed at other temperatures like 20, 40, and 80 °C in the presentation. Reference Z. Wang, E. Tada, and A. Nishikata, J. Electrochem. Soc., 161, F380 (2014).A.A. Topalov, S. Cherevko, A.R. Zeradjanin, J.C. Meier, I. Katsounaros, and K.J.J. Mayrhofer, Chem. Sci., 5, 631 (2014).P. Jovanovič, A. Pavlišič, V.S. Šelih, M. Šala, N. Hodnik, M. Bele, S. Hočevar, and M. Gaberšček, ChemCatChem, 6, 449 (2014).W. Bi and T.F. Fuller, J. Electrochem. Soc., 155, B215 (2008).Z. Wang, E. Tada, and A. Nishikata, J. Electrochem. Soc., 163, F1-F3 (2016).Z. Wang, E. Tada, and A. Nishikata, ECS Trans., 69, 255 (2015). Figure 1

Study on Dissolution Behavior of Pt-M Binary Alloys Under Potential Cycling By Channel Flow Multi Electrodes

Introduction Pt-M alloys catalysts have attracted attention over the years and expected to be used in proton exchange membrane fuel cells (PEMFCs) cathode catalysts due to their high oxygen reduction activity than pure Pt and reduction of Pt usage in PEMFCs [1]. However, Pt-M catalysts is easily degraded by both Pt and M dissolution from Pt-M alloys during on-off cycle and load cycle, which leads the performance loss of PEMFCs [2]. Thus, to understand the nature of dissolution mechanism of both Pt and M from Pt–M alloy catalysts is very significant to advance durability of PEMFCs under its operating conditions. In this study, we investigated that the dissolution mechanism of Pt-50 at% Fe alloy (Pt50-Fe50) and Pt50-Cu50 under potential cycling with a channel flow multi electrodes (CFME), and elucidate the effect of additive element to the dissolution behavior of Pt50-M50. Experimental Pt50-Fe50 and Pt50-Cu50 were subjected to potential cycling tests at 298 K using Ar-purged 0.5 M H2SO4 solution with a CFME. A double junction KCl-saturated Ag / Ag-Cl electrode was used as reference electrode, and Au coil was used as the counter electrode. Flow rate of the electrolyte was 10 cm s-1 in order to establish laminar flow condition. Potential cycling tests were employed between 0.05 V and 1.4 V vs. SHE at 20 mV s-1. Before potential cycling, Pt50-M50 was set at 0.45 V vs. SHE in order to remove Pt oxide layer formed on Pt–M alloy surface in ambient air and to measure baseline currents of collector electrodes (CEs). Reactions and potentials for detecting the dissolved Fe2+, Fe3+, and Cu2+ on Au-CEs are as follows, Fe2+ → Fe3+ + e- (E c = 1.0 V vs. SHE) (1) Fe3+ + e-→ Fe2+ (E c = 0 V vs. SHE) (2) Cu2+ + 2e-→ Cu (E c = 0 V vs. SHE) (3) Dissolved Fe2+, Fe3+, and Cu2+ from Pt50-M50 are monitored by the current change of CEs. Results and discussion Figure 1 shows M detection current with a CFME during potential cycling, and red and blue line show the results of Pt50-Fe50 and Pt50-Cu50, respectively. As shown in inset, Fe dissolution from Pt50-Fe50 starts from around 0.3 V in anodic scan. Then Fe dissolution is clearly enhanced between 0.6 and 1.4 V in both anodic and cathodic scan, and finally terminate at 0.3 V in cathodic scan. Wang et al reported that Pt dissolution occur above approximately 0.6 V [3], accordingly major Fe dissolution is enhanced by Pt dissolution. On the contrary, minor Fe dissolution between 0.3 and 0.6 V in both anodic and cathodic scan is contributed by Pt surface diffusion, because Pt atoms are easily diffuse on Pt-M alloy surface in this potential range due to no adsorbed species on its surface [4]. Cu dissolution from Pt50-Cu50 only appears above 0.6 V, whereas Fe dissolution from Pt50-Fe50 starts from 0.3 V. Moreover, the amount of Cu dissolved from Pt50-Cu50 is smaller than that from Pt50-Fe50, which indicate that Cu is more durable elements than Fe. This is explained by the difference of standard electrode potentials between Cu and Fe. Pt-enriched layer formed on Pt50-Cu50 is denser and flatter than that on Pt50-Fe50, because the amount of dissolved Cu is small due to more noble standard electrode potential than Fe. Flat Pt-enriched layer inhibits Pt surface diffusion between 0.3 and 0.6 V, and Pt dissolution above 0.6 V. Reference [1] V. R. Stamenkovic, B. S. Mun, M. Arenz, K. J. J. Mayrhofer, C. A.Lucas, G. Wang, P. N. Ross, and N. M. Markovic: Nat. Mater. 6 (2007) 241–247. [2] H. A. Gasteiger, S. S. Kocha, B. Sompalli, and F. T. Wagner: Appl. Catal. B: Environ. 56 (2005) 9–35. [3] Z. Wang, E. Tada, and A. Nishikata: J. Electrochem. Soc. 161 (4) (2014) F380–F385 [4] Q. Xu, E. Kreidler, and T. He: Electrochim. Acta 55 (2010) 7551–7557. Figure 1

Calligraphic solar cells: acknowledging paper and pencil

Abstract

High Cycling Stability of Electrochromic Devices Using a Metallic Counter Electrode

This work focuses on the stability of hybrid electrochromic displays that use only one electrochromic film, an industrial solid polymer electrolyte and a metallic counter electrode. The lifetime of these devices exceeds 200,000 cycles in tests with three different voltage ranges. Traces of metal deposits were found during cycling, which indicates that the metallic counter electrode combines the functions of current collector and counter electrode.

Influence of ITO layer application on electrical parameters of silicon solar cells with screen printed front electrode

Purpose The purpose of this paper was investigation and comparison of electrical and optical properties of crystalline silicon solar cells with ITO or TiO2 coating. The ITO, similar to TiO2, is very well transparent in the visible part of optical radiation; however, its low resistivity (lower that 10-3 Ohm/cm) makes it possible to use simultaneously as a transparent electrode for collection of photo-generated electrical charge carriers. This might also invoke increasing the distance between screen-printed metal fingers at the front of the solar cell that would increase of the cell’s active area. Performed optical investigation showed that applied ITO thin film fulfill standard requirements according to antireflection properties when it was deposited on the surface of silicon solar cell. Design/methodology/approach Two sets of samples were prepared for comparison. In the first one, the ITO thin film was deposited directly on the crystalline silicon substrate with highly doped emitter region. In the second case, the TCO film was deposited on the same type of silicon substrate but with additional ultrathin SiO2 passivation. The fingers lines of 80 μm width were then screen-printed on the ITO layer with two different spaces between fingers for each set. The influence of application of the ITO electrode and the type of metal electrodes patterns on the electrical performance of the prepared solar cells was investigated through optical and electrical measurements. Findings The electrical parameters such as short-circuit current (Jsc), open circuit voltage (Voc), fill factor (FF) and conversion efficiency were determined on a basis of I-V characteristics. Short-circuit current density (Jsc) was equal to 32 mA/cm2 for a solar cell with a typical antireflection layer and 31.5 mA/cm2 for the cell with ITO layer, respectively. Additionally, electroluminescence of prepared cells was measured and analysed. Originality/value The influence of the properties of ITO electrode on the electrical performance of crystalline silicon solar cells was investigated through complex optical, electrical and electroluminescence measurements.

Pulsed current electrodeposition parameters to control the Sn particle size to enhance electrochemical performance as anode material in lithium ion batteries

Abstract The Sn nanoparticles were synthesized through pulsed current electrodeposition in an acidic electrochemical bath containing polyvinylpyrrolidone (PVP) in order to control the electrodeposition rate of Sn reduction on copper collector electrode. The anode prepared at electrochemical bath containing PVP concentration of about 10 g·L−1 showed highest discharge capacity and cycleability as two main criteria in lithium ion batteries. Also, the pulsed current characteristics such as frequency and current density were investigated and 10 Hz and 20 mA·cm− 2, respectively, are obtained as the optimum parameters. The synthesis of Sn nanoparticles in such media was successfully developed. The sizes and morphologies of NPs were characterized by X-ray diffraction and scanning electron microscopy. Our findings indicated that the nanosized spherical particles with a diameter ranging from 80 to 100 nm could be formed at optimum concentration. The discharge capacity of synthesized Sn nanoparticles was obtained about 1350 mAh g− 1, indicating a 32% increase compared to the synthesized Sn particles with constant current electrodeposition method. Additionally, the discharge capacity of around 550 mAh g–1 is obtained in the 50th cycle, which shows an appropriate cycleability compared to the Sn film electrode prepared by a constant current electrodeposition. The discharge capacities obtained indicated a considerable improvement compared to similar works. The particles size of coated Sn on collector electrode is resulted from interplay between the rate of nucleation and growing rate of particles. PVP affects the kinetic of electrodeposition through surface capping and complexing of Sn2 + species.

A Novel Single-Excitation Capacitive Angular Position Sensor Design.

This paper presents a high-precision capacitive angular position sensor (CAPS). The CAPS is designed to be excited by a single voltage to eliminate the matching errors of multi-excitations, and it is mainly composed of excitation electrodes, coupling electrodes, petal-form sensitive electrodes and a set of collection electrodes. A sinusoidal voltage is applied on the excitation electrodes, then the voltage couples to the coupling electrodes and sensitive electrodes without contact. The sensitive electrodes together with the set of collection electrodes encode the angular position to amplitude-modulated signals, and in order to increase the scale factor, the sensitive electrodes are patterned in the shape of petal-form sinusoidal circles. By utilizing a resolver demodulation method, the amplitude-modulated signals are digitally decoded to get the angular position. A prototype of the CAPS is fabricated and tested. The measurement results show that the accuracy of the sensor is 0.0036°, the resolution is 0.0009° and the nonlinearity over the full range is 0.008° (after compensation), indicating that the CAPS has great potential to be applied in high-precision applications with a low cost.

A numerical study on the influence of interface recombination on performance of carbon nanotube/GaAs solar cells

Carbon nanotubes (CNT) have unique electronic properties and remarkable optical properties. Despite of on layer thickness of CNTs, it has able to absorb photons from visible to far infrared and terahertz. These unique properties lets to create heterojunction devices by semiconductor/CNTs or metal/CNTs junctions e.g. photodiodes, sensor and heterojunction solar cell. The CNTs can play the role of a heterojunction component for charge separation as a high conductive network for charge transport and as a transparent electrode for light illumination and charge collection. The main objective of the present article is to establish a relation between interface recombination and the characteristics parameters of the heterojunction solar cell based on armchair single walled carbon nanotube as absorber and GaAs as window. It is shown that by increasing the interface recombination open circuit voltage decreases dramatically. Depletion current, J–V characteristic and ideality factor variation in terms of interface recombination has been calculated. Interface recombination at the SWCNT/GaAs interface of the cell leads to a considerable drop of the cell voltage and to a lesser extent to the associated reduction in the cell short circuit current.

Plasmonic nanostructures for electronic designs of photovoltaic devices: plasmonic hot-carrier photovoltaic architectures and plasmonic electrode structures

The tunable and amazing properties of plasmonic nanostructures have received significant attentions in the fields of solar energy conversion. Plasmonic nanostructures provide pathways to directly convert solar energy into electric energy by hot-carrier generation. They can also serve as economical electrodes for high-efficient carrier collection. Both have promising potential for manufacturing new generation solar cells. Here, we review recent advances in plasmonic nanostructures for electronic designs of photovoltaic devices and specially focus on plasmonic hot-carrier photovoltaic architectures and plasmonic electrode structures. Technical challenges toward low-cost and high-performance plasmonics-based solar cells are also discussed.

Study on Preparation and Properties of Novel Ti/Cu Laminated Composite Electrode Materials

This paper starts with the structure design of the electrode base material, Ti/Cu electrode material instead of single metal Ti as the base material which was prepared by hot diffusion welding, the change of composite material structure is influences on electrochemical properties of Ti/Cu that was analyzed by SEM, electrochemical workstation and so on. The results show that the design changes of matrix structure of traditional Ti electrode is good for enhance the electrochemical performance of electrode, due to the design of layered composite structure was used, the inner Cu of composite material is current collector electrode and conductive channel carrier , it reduces the resistivity of the electrode material (its resistivity is only 1/15 of pure titanium electrode material) and improves the electrical conductivity of the electrode, in order to realize the uniformity of the current in the electrode, the electrochemical performance of the electrode was improved for the novel Ti/Cu laminated composite electrode materials.

Effect of doping ferrocene in the working fluid of electrohydrodynamic (EHD) micropumps

The effect of doping ferrocene in the working fluid of electrohydrodynamic micropumps was investigated under the application of DC electric fields. The micropump consisted of 100 planar electrode pairs that were embedded along the bottom wall of a 100-micron-high, 5-mm-wide and 26-mm-long microchannel. The width of the emitter and collector electrodes was 20 and 40 µm, respectively, with inter-electrode spacing of 30 µm. A redox dopant, ferrocene, was diffused homogeneously into the working fluid HFE-7100 at 0.05, 0.1 and 0.2 % concentration by weight. The static pressure head generation and flow rate at different back pressure conditions were measured under different applied DC voltages. The current and pressure generated with the doped working fluid were significantly higher than with pure HFE-7100 under an applied DC field. A maximum static pressure of 6.7 kPa and flow rate of 0.47 mL/min at no back pressure were achieved at 700 V.

Modification of Ultrathin NPB Interlayer on the Electronic Structures of the CH3NH3PbI3/NPB/MoO3 Interface

Modification of the ultrathin N,N′-Di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) insertion layer on the electronic structures of the CH3NH3PbI3 (MAPbI3)/MoO3 interfaces is investigated using ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS). It is found that when an ultrathin NPB insertion layer of 16 Å is inserted between MAPbI3 and MoO3, the chemical reaction between the latter two can be effectively suppressed, and a favorable energy-level alignment is achieved. The valence band maximum (VBM) or highest occupied molecular orbital (HOMO) at the MAPbI3/NPB/MoO3 interface facilitates the hole transportation from the MAPbI3 layer through the NPB layer toward the NPB/MoO3 interface. As a result, the holes can be efficiently extracted to the hole collection electrode due to the small energy offset between the conduction band minimum (CBM) of MoO3 and the HOMO of NPB. Therefore, the modification by the ultrathin NPB interlayer on the electronic structures of the MAPbI3/MoO3 interface can greatly improve the hole extraction and thus enhance the power efficiency of the corresponding solar cells.

Performance of a pilot-scale wet electrostatic precipitator for the control of sulfuric acid mist.

The use of a wet electrostatic precipitator (WESP) is often regarded as a viable option to reduce sulfuric acid mist emitted from the wet flue gas desulfurization (WFGD) tower in coal-fired power plants. In this study, a pilot-scale wet electrostatic precipitator equipped with a wall-cooled collection electrode is investigated for the control of sulfuric acid mist from a simulated WFGD system. The results show that due to partial charging effect, the removal efficiency of sulfuric acid aerosol decreases when the aerosol size decreases to several tens of nanometers. Moreover, due to the plasma-induced effect, a large number of ultrafine sulfuric acid aerosols below 50nm formed at a voltage higher than 24kV inside the WESP. The percentages of submicron-sized aerosols significantly increase together with the voltage. To minimize the adverse plasma-induced effect, a WESP should be operated at a high gas velocity with an optimum high voltage. Even at a high flue gas velocity of 2.3ms(-1), the mass concentration and the total number concentration of uncaptured sulfuric acid aerosols at the WESP outlet are as low as ca. 0.6mgm(-3) and ca. 10(4) 1cm(-3) at 28kV, respectively. The corresponding removal efficiencies were respectively higher than 99.4 and 99.9% and are very similar to that at 1.1 and 1.6ms(-1). Moreover, the condensation-induced aerosol growth enhances the removal of sulfuric acid mist inside a WESP and enables a low emission concentration of ca. 0.65mgm(-3) with a corresponding removal efficiency superior to 99.4% even at a low voltage of 21kV, and of ca. 0.35mgm(-3) with a corresponding removal efficiency superior to 99.6% at a higher voltage level of 26kV.

Investigation of non-woven carbon paper as a current collector for sulfur positive electrode—Understanding of the mechanism and potential applications for Li/S batteries

Porous 3-D current collectors have been shown to be the primary choice in replacing classical 2D aluminum foil in applicable developments, especially those using carbon-based current collectors. In this study, we investigated the impact of using a non-woven carbon (NWC) based current collector for sulfur electrodes, in terms of performance and practical use in a commercial battery, keeping in mind the simplicity of electrode preparation method. The benefits of using NWC as a 3D current collector include high sulfur utilization for even highly loaded electrodes, lower polarization, and the provision of an efficient electrolyte reservoir. High discharge capacities up to ∼1200mAhg−1 can be obtained at moderate C-rates, with relatively good capacity retention (<1% loss per cycle) and practical loadings as high as 8mAhcm−2.

Innovative Non-Destructive Non-Contact Methods & Devices for Testing during Production, Optimizing Technologies, and Insuring Safety & Reliability Next Generation of Li Batteries

The safety and reliability of Li batteries are determined mainly by its basic design and chemistry. However, without adequate quality control during manufacture, defects in even the best designs can lead to inconsistent performance and early failure. Deployment of automated quality assurance technology at every stage of the manufacturing and assembly process will increase the reliability and safety of batteries while lowering overall manufacturing costs by reducing wastage and preventing defective components form being incorporated into the finished productFor the successfully coordination of stages of R&D, manufacturing and applications of the Li batteries we developed the innovative non-destructive (NDT) non-contact electromagnetic, ultrasonic, holographic interferometry, gas discharge visualization, and combined methods and equipment developed. Developed non-destructive testing methods & devices enable to optimize the technology, and quality of initial materials, components, and cells, including in-line control during battery production. These methods allow insure the safety and reliability of the batteries and reduce the cost of production Achievements include optimization of materials and technologies, increasing efficiency, improving reliability and safety, and reducing costs of production. These methods enable to evaluate properties and hidden defects of initial materials, including nano-structured powder of electrode materials, polymer and solid inorganic electrolytes; properties of electrodes during coating, including the interface between current collectors and electrode mass, multi-layered electrode structures, and renewable energy devices after assembly. Results allow also predict the properties of the Li batteries during applications. Examples of applications of NDT include: -Non-destructive non-contact testing of dry multi-layer structure. -Non-destructive non-contact systems for determination of bulk conductivity of powdered materials. -Electromagnetic non-destructive capacitance method for testing electromagnetic properties and chemical composition battery materials during synthesis, for example CFx -Non-contact testing for determination of the interface resistance between current collector and active electrode mass. -High voltage gas discharge visualization / High Voltage Electric Field Method for Quality Assurance of Hermetically Sealed Devices -Non-contact electromagnetic measurement of thickness and electro-physical parameters electrodes during coating. - Non-destructive non-contact testing of the conductivity of thin film. -Non-destructive non-contact detection of hidden faults in collector welding of batteries and ultracapacitors -Holographic interferometry for non-destructive testing of battery components during production. Major advantages of the non-destructive non-contact testing methods include: -Reliability due to non-contact mode of operation. -Efficient, fast, simple, and inexpensive to implement. -Easy to automate. Results are obtained in real-time. -Do not require any special protection for operators and equipment. Safe and less expensive than X-ray methods. -Precise determination of specific parameters and defects. -Provide 100% nondestructive control of the technological operations and the quality of the end product. -Provide quality control of material and products for which contact methods, in principle, cannot provide reliable information due to extraneous processes at the sensor/test article interface surface. -Provide quality control of new materials, including nanomaterials and thin-layered materials, which can be sensitive to mechanical contact Developed NDT methods and equipment are based on the interaction of different vector, and scalar fields with the test article: - Wave acoustic fields of different polarization. - Potential electrical and magnetic fields. - Vector eddy magnetic fields. - Gradient heat fields (infra-red spectrum). - Electron emission fields. - Glow fields of high voltage pulse discharges During presentation will be presented examples of using the innovative non-destructive testing methods during Li batteries development and production, description of the NDT methods and equipment. Some examples of the NDT equipment are presented on the photos. Figure 1

Small Molecule Carboxylic Acids As Efficient Binders for Silicon-Based Anodes

Silicon is one of the most promising anode materials because of its high theoretical capacity of 3579 mAh/g at room temperature which is ten times higher than graphite, a common anode currently used in commercial lithium ion batteries.1 However, Si has poor cycle life because of the massive volume change during cycling followed by the pulverization of active particles and the loss of electrical contact within electrode components. 1 Binder, usually long-chain polymers, are important electrode components that help to hold particles together and to current collector. Poly(vinylidene fluoride) (PVdF) has been widely used as binder in lithium ion batteries due to its good electrochemical and thermal stability and good adhesion to electrode material and current collector.2 The performance of Si with PVdF, however, has been reported to be poor.2 Recently, the cycle life of Si was greatly improved by using binders which contains a large quantity of –OH and –COOH such as sodium carboxymethylcellulose (CMC),2 poly(acrylic acid) (PAA).3 The formation of covalent bond and/or strong interaction of hydrogen bonds between silicon particles and binders are believed the reason for the improvement.4,5 However, there is no report on using small molecule carboxylic acids as binders in lithium ion batteries. In this study, Si electrode has been prepared with silicon nanoparticles (≤50nm), conductive carbon and carboxylic acids with ratio of 50:25:25. The Si electrode with PVDF binder was also prepared for comparison. The Si anodes were then evaluated in half cells with lithium metal as current collector and reference electrodes in 1.2M LiPF6/Ethylene carbonate (EC) : Dimethyl carbonate (DEC) without and with 10 wt.% additive. In the absence of additive, Si electrode with carboxylic acids show very high first cycle specific capacity and efficiency, ~3500 mAg/g and 79%, respectively. After 30 cycles, the electrode still maintains a capacity > 1500 mAh/g. On contrary, Si electrode with PVDF binder shows a low first discharge capacity and efficiency: 1700 mAh/g and ~60%, respectively. Furthermore, the capacity fades rapidly after first cycle. The dramatic improvement cycling performance of silicon NP electrodes with carboxylic acids over PVdF are believed due to the interaction of carboxylic acids with silicon particles. We will further discuss effects of carboxylic acids for enhancing cyclability of silicion nanoparticle anode in the meeting. Acknowledgement The authors gratefully acknowledge funding from Department of Energy Office of Basic Energy Sciences EPSCoR Implementation award (DE-SC0007074) Reference 1. M. N. Obrovac and L. Christensen, Electrochem. Solid-State Lett., 7, A93 (2004). 2. H. Buqa, M. Holzapfel, F. Krumeich, C. Veit, and P. Novák, J. Power Sources, 161, 617–622 (2006). 3. A. Magasinski, B. Zdyrko, I. Kovalenko, B. Hertzberg, R. Burtovyy, C. F. Huebner, T. F. Fuller, I. Luzinov, and G. Yushin, ACS Appl. Mater. Interfaces, 2, 3004–3010 (2010). 4. N. S. Hochgatterer, M. R. Schweiger, S. Koller, P. R. Raimann, T. Wöhrle, C. Wurm, and M. Winter, Electrochem. Solid-State Lett., 11, A76–A76 (2008). 5. J.-S. S. Bridel, T. Azaı, M. Morcrette, J.-M. M. Tarascon, D. Larcher, and T. Azaïs, Chem. Mater., 22, 1229–1241 (2010).