Fresh Electrodes Research Articles

Silica graphite as an ink additive for stencil printed electrodes: A novel approach for electroanalytical determination of sulfanilamide

Silica-graphite composites present a high surface area, mechanical and chemical stability, and high functionality to be applied in electrochemical sensing. Indeed, those materials have been successfully employed to build composite electrodes such as carbon paste electrodes for a wide range of applications. Despite excellent performance, this kind of electrodes have been replaced by stencil printed electrodes (SPEs), emerging as a scalable alternative for manufacture offering sensors disposables, low-cost, customizable, and miniaturized. Based on this, herein a novel silica-graphite (SiG) composite is described as an ink additive aiming scalable production of SPEs with high functionality and surface area. The SPE as well as SiG were characterized by electrochemical impedance spectroscopy, scanning electron microscopy, thermogravimetric analysis, and contact angle. After an accumulation step, SiG-SPE pretreated has shown a significant improvement on oxidation of sulfanilamide compared with unmodified SPE. Electrochemical surface activation and pre-concentration conditions were investigated to enhance sensitivity and selectivity. Under optimized conditions, silica-graphite stencil printed electrode (SiG-SPE) was employed for the electrochemical determination of sulfanilamide by using square wave-adsorptive stripping voltammetry (SWAdSV). It was possible to achieve a linear dynamic range (LDR) from 2 to 20 mmol L−1 with a limit of detection (LOD) and quantification (LOQ) of 0.34 and 1.13 mmol L−1, respectively. The stability of the sensors was evaluated over five weeks, and a decrease of around 5.5 % in response was observed compared to fresh electrodes. SiG-SPE also presented high selectivity and low matrix interference for sulfanilamide determination with a recovery range of 96.2–100.1 % for urine and 98.2–106.1 % for commercial fat milk. Those results suggest that SiG is a promising ink additive for the production of low-cost and high-performance sensors, showing enhanced analytical properties, mechanical resistance, and chemical stability.

(Invited) Effects of LiPF6 Salt Concentration on the Cycling Performance of NMC532 Cell Containing Organic Carbonate Solvents

Pouch-type cells with NMC532 cathode, MCMB anode (A/C loading ratio of 1.1) and electrolytes containing various LiPF6 concentrations in EC/EMC (3:7 by volume) + 2wt% VC were prepared for investigating the effects of lithium salt concentration on the cycling performance of NMC532 cells. These cells were cycled at 0.5 C rate within 3.0 and 4.2 V until their residual capacity become lower than 70% of their initial capacities, respectively, as shown in Figure 1. After end of life, these cells were disassembled for post-mortem study. The cycled electrodes were used to assemble into coin-type cells with lithium metal for estimating their losses of lithium inventory (LLI), losses of cathode material (LAMC) and losses of anode material (LAMA) by comparing their specific capacities of first and second cycles of the coin-cells with those of the coin-cells prepared with fresh electrodes, respectively. XRD, SEM, HRTEM and XPS were also used to reveal the phase evolution, structure and morphology changes of the electrode materials after cycling. Results suggest that the fast capacity fade of the cell prepared with the electrolyte containing 1 M LiPF6 salt concentration can be attributed to the carbonate solvent oxidation via dehydrogenation on the cathode surface at voltages higher than 3.8 V as reported by Zhang et al.(1) The oxidation can not only accelerate the increase of impedances at anode side, the losses of lithium inventory and anode material by the SEI formation from the reactions between the oxidation products and lithium ions, but also cause the loss of cathode active material and resistance growth at the cathode side, though they are less significant. They can be caused by the phase evolution of spinel and rock-salt phases on the surface of cathode particles, which had been observed from the HRTEM and SAD studies of the cathode particle collected from the cycled cell prepared with 1 M LiPF6 in EC/EMC electrolyte after 600 cycles. It was also found that the amounts of spinel and rock-salt phases formed on the NMC particle surface, rates of capacity fading and resistance growth of the aged cells decreased with the increased LiPF6 salt concentration contained in the electrolytes of the cells. It can be due to the higher salt concentration can induce the less free solvent for being oxidized on the cathode particle surface at voltages higher than 3.8 V. Whereas the layered NMC phase only can be found on the surface of NMC particle collected from the cathode of the cycled cell prepared with 3 M LiPF6 electrolyte after 1100 cycles. This cell shows lower LLI, LAMC, LAMA and impedances growth after 1100 cycles than those of the cell with electrolyte of 1 M concentration after 600 cycles.Reference: Zhang, Y. Katayama, R. Tatara, L. Giordano, Y. Yu, D. Fraggedakis, J. G. Sun, F. Maglia, R. Jung, M. Z. Bazant and Yang Shao-Horn, Energy Environ. Sci., 2020, 13, 183-199.

Thermal Behavior Test and Simulation of Fresh and Aged Lfp/Lto Rechargeable Cells

The thermal behavior of fresh and aged LiFePO4/Li4Ti5O12 (LFP/LTO) 26650 cells at 30% and 100% state of charge (SOC) was studied by Accelerating Rate Calorimetry (ARC). No thermal runaway was observed from the ARC tests on the LFP/LTO cells. The heat generation of each reaction during the thermal heating including LFP/electrolyte, LTO/electrolyte, and electrolyte decomposition was analyzed using Differential Scanning Calorimetry (DSC). Thermal parameters were extracted from DSC test results and used in the ARC simulation to analyze the contribution of heat generation of each component. Major contribution of the heat generation at 100% SOC is the reaction between LTO and electrolyte at around 200oC. Reactions between LFP and electrolyte occurs at a high temperature close to the electrolyte decomposition at temperature above 250oC. At 30% SOC, the heat generation amount from both electrodes are similar. Aged cell electrodes showed benign thermal behavior comparing to the fresh cell electrodes. In spite of the observation of solid electrolyte interface (SEI) decomposition on the DSC of LTO/electrolyte, no corresponding heat generation was captured in the ARC test of full cell, which indicates the difference on SEI formation in full cell and half-cell contains LTO. Overall the LFP/LTO shows minimal self-heating under ARC conditions and exhibits beneficial safety features.

Electrocatalysts for High Temperature (100-200 ºC) and Pressure (45 bar) Alkaline Electrolysis

Electrolytic hydrogen production is key in transitioning to a sustainable energy system, as it enables the production of sustainable fuels and chemicals from renewable electricity sources and a means to address their intermittent nature at the same time. Amongst the main electrolysis technologies, Alkaline Electrolysis (AE) is the most suitable for the hundreds of GW capacity that is required, as it relies only on abundant, low-cost materials, and has a proven record of reliability and scalability. However, AE suffers from poor efficiency and productivity. Increasing operating temperature and pressure offers a means to overcome this limitation [1, 2]. Nevertheless, electrodes with good long-term stability in the hot corrosive alkaline environment are required. Here, we report the performance of Co3O4 and NiMoOx coated nickel foam (NF) electrodes for the anode and cathode, respectively. The electrodes are tested from room temperature to 150 ºC at 45 bar pressure in 45 wt.% KOH. The Co3O4 coated NF (Co3O4/NF) anode performance is compared to that of commercial pristine NF and Inconel coated NF (Inconel/NF) electrodes. At room temperature the Inconel/NF electrode outperforms both the pristine NF as well as the Co3O4/NF electrodes. At 150 ºC and 45 bar pressure, the Co3O4/NF and Inconel/NF electrode perform quite similar. During the 108 h long-term stability test at 150 ºC and 45 bar, the Co3O4/NF electrode remains stable requiring an overpotential of ~185 mV at 500 mA.cm-2, whereas the overpotential of the Inconel/NF electrode increased from 178 mV to 209 mV after 84 h of operation at the same conditions. The structural and chemical evolution of these electrodes was explored by post-mortem scanning electron microscopy (SEM) in comparison to the fresh electrodes. The NiMoOx coated NF (NiMoOx/NF) cathode showed a low and stable overpotential (~130 mV) at the same conditions, similar to a precious metal coated nickel perforated plate electrode (~125 mV). References C. Chatzichristodoulou, F. Allebrod, and M. B. Mogensen, J. Electrochem. Soc., 163, F3036–F3040 (2016).F. Allebrod, C. Chatzichristodoulou, and M. B. Mogensen, J. Power Sources, 229, 22–31 (2013).

Influence of the Ambient Storage of LiNi0.8Mn0.1Co0.1O2 Powder and Electrodes on the Electrochemical Performance in Li-ion Technology

Nickel-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) is one of the most promising Li-ion battery cathode materials and has attracted the interest of the automotive industry. Nevertheless, storage conditions can affect its properties and performance. In this work, both NMC811 powder and electrodes were storage-aged for one year under room conditions. The aged powder was used to prepare electrodes, and the performance of these two aged samples was compared with reference fresh NMC811 electrodes in full Li-ion coin cells using graphite as a negative electrode. The cells were subjected to electrochemical as well as ante- and postmortem characterization. The performance of the electrodes from aged NM811 was beyond expectations: the cycling performance was high, and the power capability was the highest among the samples analyzed. Materials characterization revealed modifications in the crystal structure and the surface layer of the NMC811 during the storage and electrode processing steps. Differences between aged and fresh electrodes were explained by the formation of a resistive layer at the surface of the former. However, the ageing of NMC811 powder was significantly mitigated during the electrode processing step. These novel results are of interest to cell manufacturers for the widespread implementation of NMC811 as a state-of-the-art cathode material in Li-ion batteries.

Paving Pathways Toward Long‐Life Graphite/LiNi0.5Mn1.5O4 Full Cells: Electrochemical and Interphasial Points of View

AbstractThe high‐voltage spinel cathode LiNi0.5Mn1.5O4 (LNMO) with no cobalt and low nickel content is promising for lithium‐ion batteries due to its high energy and power densities, good thermal stability, and low cost. However, its high operating voltage (≈4.7 V) results in a decomposition of the electrolyte, severe chemical crossover, and deterioration of electrode‐electrolyte interphases (EEIs), hindering its practical viability. It is demonstrated here that by electrochemically pre‐cycling the graphite in an electrolyte containing 30 wt.% fluoroethylene carbonate, a robust LiF‐rich artificial solid electrolyte interphase can be constructed for surface protection; on the other hand, an electrochemical pre‐lithiation of Fe‐doped LNMO serves as a lithium source for graphite at a full‐cell voltage of 2.6 V. As a result, the full cells with the as‐modified electrodes deliver a high capacity of 129 mA h g−1 with an excellent capacity retention of 93% after 200 cycles, vastly outperforming the full cells with fresh electrodes (120 mA h g−1 initial capacity with 78% retention). Finally, pathways toward long‐life graphite||LNMO full cells are pictured based on the inspirations from the electrochemical modifications and in‐depth analyses of the EEIs in this study.

From the Direct Observation of a PAA‐Based Binder Using STEM‐VEELS to the Ageing Mechanism of Silicon/Graphite Anode with High Areal Capacity Cycled in an FEC‐Rich and EC‐Free Electrolyte

AbstractThe polymer binder is a key constituent of silicon‐based electrode formulation for lithium‐ion batteries. However, its extremely difficult visualization in fresh electrodes becomes completely impossible in cycled electrodes. Here, the combination of scanning transmission electron microscopy—valence electron energy‐loss spectroscopy with the use of a specific electrolyte solvent composition (a mixture of dimethyl carbonate and fluoroethylene carbonate, without ethylene carbonate) allows the visualization, for the first time, of the binder in silicon‐based electrodes, even cycled up to 100 cycles. Such an observation is possible as the only solid degradation product of this electrolyte is LiF, as confirmed by quantitative 7Li and 19F magic angle spinning nuclear magnetic resonance. The electrodes, based on a blend of silicon and graphite, have a very high surface capacity, 6.5 mAh cm−2, which makes them meaningful for electric vehicle applications. The performance is appreciable, in particular the first cycle efficiency approaching that of commercial graphite electrodes, as well as the capacity retention in full cell, versus LiNi0.5Mn0.3Co0.2O2, 60% after 100 cycles. This work also illustrates the ultimate state of destructuration of silicon after long cycling, which invites new ways of thinking about the design of this material.

Strategy to assess the carbon electrode modifications associated with the high voltage ageing of electrochemical capacitors in organic electrolyte

This contribution presents a strategy to assess the electrode modifications leading to a fade of performance during high voltage operation of an electrical double-layer capacitor (EDLC) in organic electrolyte. To get rid of the commonly faced binder overlap in the post-mortem experiments, the activated carbon-based electrodes were here manufactured with a water washable carboxymethyl cellulose (CMC) binder, which was then eliminated by Soxhlet extraction from the aged (after ageing the EDLC by potentiostatic floating) and fresh electrodes. The washed fresh and aged electrodes were analyzed by temperature programmed desorption (TPD) and nitrogen adsorption/desorption to qualitatively and quantitatively determine the oxygenated functionalities created by ageing and to establish correlations with the pore volume modifications. By subtracting the TPD and gas adsorption data on the washed fresh electrode material from the results obtained on the washed positively and negatively aged electrode coatings, we could reveal that a relatively important amount of carboxylic, anhydride, carbonyl and quinone groups is created on the positive electrode due to its oxidation, contributing to reduce the volume corresponding to pores ranging between 1.2 and 2.6 nm. By contrast, under negative polarization, the functionalities initially observed for the fresh electrode are essentially transformed into more thermally stable ones, without any important change of the pore volume.

الاستخلاص بالطور الصلب لادوية اضطراب حركة الجهاز الهضمي في المستحضرات الصيدلانية باستخدام البوليمر بالطبعة الجزيئية بتقنيات تحليلية مختلفة

Liquid electrodes of domperidone maleate (DOMP) imprinted polymer were synthesis based on precipitation polymerization mechanism. The molecularly imprinted (MIP) and non-imprinted (NIP) polymers were synthesized using DOMP as a template. By methyl methacrylate (MMA) as monomer, N,Nmethylenebisacrylamide (NMAA) and ethylene glycol dimethacrylate (EGDMA) as cross-linkers and benzoyl peroxide (BP) as an initiator. The molecularly imprinted membranes were synthesis using acetophenone (APH), di-butyl sabacate (DBS), Di octylphthalate (DOPH) and triolyl phosphate (TP)as plasticizers in PVC matrix. The slopes and limit of detection of liquid electrodes obtained from the calibration curves ranged from (-18.88– -29.01) mV/decade and (4.0 × 10-5 – 6.0 × 10-5) M, respectively and the response time was about 60 seconds. The Liquid electrodes were filled with (10-2 M) standard solution of the drug and observed stable response for a pH ranged from 2.0 to 11.0 and with good selectivity for over several species. The fresh electrodes of synthesis were effectively used in the pharmaceutical sample to determine DOMP without any time consuming pretreatment measures.

Synthesis New Liquid Electrodes for Determination Lansoprzole Based on a Molecularly Imprinted Polymer

Liquid electrodes of Lansoprazole (LP) imprinted polymer was synthesis based on precipitation polymerization mechanism. The molecularly imprinted (MIP) and non-imprinted (NIP) polymers were synthesized using LP as a template. By methyl methacrylate (MMA) as a monomer, Pentaerythritol tetraacrylate (PTA) and ethylene glycol dimethacrylate (EGDMA) as cross-linkers and benzoyl peroxide (BP) as an initiator. The molecularly imprinted membranes were synthesized using Dimethyl adipate (DMA), Dibutyl phthalate (DBPH), Dioctyl phthalate(DOPH), and Nitrobenzene (NB) as plasticizers in PVC matrix. The slopes and limit of detection of liquid electrodes obtained from the calibration curves ranged from (-17.85– -20.89) mV/decade and 1.8 x 10-5–6.0 x 10-6 M, respectively, and the response time was about 60 seconds. The Liquid electrodes were filled with 10-2 M standard solution of the drug and observed stable response for a pH ranged from 2.0 to 11.0 and with good selectivity for over several species. The fresh electrodes of synthesis were effectively used in the pharmaceutical sample to determine LP without any time-consuming pretreatment measures.

Synthesis New Liquid Electrodes For Determination Pyrazinamide Based On A Molecularly Imprinted Polymer

Liquid electrodes of Pyrazinamide (PZD) imprinted polymer were synthesis based on precipitation polymerization mechanism. The molecularly imprinted (MIP) and non-imprinted (NIP) polymers were synthesized using PZD as a template. By 1-Vinylimidazole (VIZ) and methyl methacrylate (MMA) as monomers, trimethylolpropane trimethacrylate(TPT) cross-linkers and benzoyl peroxide (BPO) as an initiator. The molecularly imprinted membranes were synthesis using Dibutyl Sebacate (DBS), Dibutyl phthalate (DBPH), Dioctyl phthalate(DOPH), and Nitrobenzene (NO) as plasticizers in PVC matrix. The slopes and limit of detection of liquid electrodes obtained from the calibration curves ranged from (-27.86– 29.96) mV/decade and 1.8 x 10-5 – 6.0 x 10-6 M, respectively, and the response time was about 60 seconds. The Liquid electrodes were filled with 10-1 M standard solution of the drug and observed stable response for a pH ranged from 2.0 to 11.0 and with good selectivity for over several species. The fresh electrodes of synthesis were effectively used in the pharmaceutical sample to determine PZD without any time-consuming pretreatment measures. How to cite this article: Mudhi, M.A., Al-Bayati, Y.K. and Al-Samarrai, K.F. (2019). Synthesis New Liquid Electrodes For Determination Pyrazinamide Based On A Molecularly Imprinted Polymer. International Journal of Drug Delivery Technology, 9(4): 645-650. Source of support: Nil. Conflict of interest: None.

Oxygen Transport in Electrodes with Degraded d-PtCo/C Cathode Catalyst

We have investigated the mechanism of increase in oxygen transport resistance (Rm) due to aging of electrodes with low-loaded de-alloyed PtCo cathode catalysts supported on high surface area carbon (d-PtCo/C). Commercially available membrane electrode assemblies with 0.05, 0.1 and 0.15 mg/cm2 Pt loadings in d-PtCo/C cathode catalysts were assembled into cells and subjected to accelerated stress tests (ASTs) that consisted of 0.6-0.95 V square wave potentials with 3-s hold at upper and lower potential limits. Catalyst degradation was characterized by measuring mass activity for the oxygen reduction reaction, electrochemically active surface area (ECSA) and polarization performance in H2/air at beginning of test (BOT) and after 15k and 30k (EOT) potential cycles in H2/N2. Concurrently, limiting current densities (iL) were measured for different pressures (1.3, 1.8, 2.3, 2.8 and 3.2 atm) and oxygen concentrations (0.01, 0.02 and 0.04 O2 mole fraction in dry air) at 80oC and 90% relative humidity (RH). We observed that the O2 transport resistance inferred from the measured limiting current densities depends not only on pressure (P), catalyst loading and aging, but also on the current density itself. The observed increase in Rm with iL is almost linear and independent of pressure, suggesting the following new representation for Rm: Rm = {Rg P/Pr + Rd P/Pr} + RKn + {Rf + Ri i/ir}, Rf = RO2/SPt In this representation, the various terms denote the resistance for O2 transport across the boundary layer in the gas channel (Rg), across the gas diffusion layer (Rd), across the microporous layer and secondary pores in cathode electrode (RKn), and across the ionomer film on Pt particles supported on carbon (Rf). Note that Rf is inversely proportional to roughness (SPt, cmPt 2/cm2), and Ri is the portion of Rm that depends linearly on the normalized current density (ir = 1 A/cm2). As in earlier formulations, Rg and Rd are pressure dependent (Pr = 1 atm) as they are related to molecular diffusivity of O2 in gas channel (GC) and in gas diffusion layer (DM), whereas RKn and Rf are pressure-independent as they are related to Knudsen diffusion in <50-nm pores and O2 permeability across the ionomer film. Using the new representation for the three cells with different loadings, we determined Ri from the current density dependence of Rm at BOT as 0.306 ± 0.1 s/cm; Ri was found to be nearly independent of pressure. We estimated Rg + Rd from the pressure dependence of Rm at BOT as 0.409 ± 0.032 s/cm. Knowing Rg, Rd, and Ri, we calculated RKn + Rf from Rm, and plotted it as a function of 1/ SPt to determine RKn from the intercept and Rf from the slope. Using all the available data at BOT and after 15k and 30k potential cycles, the estimated values are 0.07 s/cm for RKn and 9.15 s/cm for RO2. This value of RO2 compares favorably with the reported literature data for fresh electrodes. To explain the current density dependence of Rm, we conducted O2 transport simulations on an electrode microstructure determined from nano-computed X-ray tomography at an APS (Advanced Photo Source) beamline. The microstructure was digitized at a resolution of 2.5 nm to reconstruct the connectivity and heterogeneous size and spatial distributions of secondary pores, primary pores, carbon, catalyst particles, and ionomer phases. Assuming that the secondary pores are dry at 90% RH, the primary pores were progressively filled with liquid water to match the measured increase in electrode resistance at higher limiting current densities. The water-filling algorithm follows the concept of capillary condensation whereby the smallest primary pores are allowed to preferentially saturate first. In these simulations, changing the primary pore saturation from 0 (dry) to 1 (flooded) results in the limiting current density increasing from 0 to 1 A/cm2 and the electrode resistance from 0.2 to 0.65 s/cm. Figure 1 summarizes the effects of Pt loading and catalyst aging on O2 transport resistance at one set of reference conditions: 1.5 atm operating pressure, 4% O2 mole fraction, 80oC and 90% RH. At BOT, reducing Pt loading to 0.05 from 0.15 mg/cm2 causes a 31% increase in Rm and a 23% drop in iL. After 30k cycles, Rm increases by 12% for the 0.15 mg/cm2 loading and by 43% for the 0.05 mg/cm2 loading, and is 66% higher in the lower loaded cell even though iL is 40% smaller. More telling is the increase in the electrode resistance (Rf + Ri i/ir) after 30 k cycles: 35% for 0.15 mg/cm2 loading and 115% for 0.05 mg/cm2 loading. Figure 1

Degradation mechanisms of high capacity 18650 cells containing Si-graphite anode and nickel-rich NMC cathode

Application of advanced anode and cathode materials in commercial lithium-ion batteries is attracting attention due to their high capacity. Silicon (Si)/graphite anodes and nickel (Ni)-rich lithium nickel manganese cobalt oxide with layered structures have been paired in commercial 18650 high energy density cells (∼270 Wh/kg). It is crucial to investigate the cell performance and the aging behavior of this commercial cell. In this study, we present commercial cell degradation mechanisms by comparing fresh and aged electrodes, including changes of crystal structure, morphology, elemental composition, and electrochemical properties. The quantitative analysis was done based on dV/dQ incremental capacity analysis of 18650 cells. To determine the amount of cyclable lithium ions (Li+) and active material loss, the lithiation and delithiation capacity were compared for fresh and aged electrodes in half coin cells. Results showed that even with 5% (by mass) of Si added in the anode, cracks occurred across the anode leading to contact loss and thickening of the solid electrolyte interphase (SEI) layer. Additionally, the average fluorine (F) ratio of the aged anodes was higher compared to that of the fresh anodes. More severely, the F content on the Si aggregations on aged anodes increased to as high as 5 times that of the fresh anode, indicating SEI growth, especially on Si particles. Solid 7Li nuclear magnetic resonance results showed no detectable Li metal deposition on the aged anode. On the cathode side, cracks on the primary particle interfaces contributed to cathode material loss, contact loss, and impedance rise. Therefore, Li+ loss into the thickened SEI layer, particle cracking, and impedance rise are the main reasons behind cell degradation.

Flow-Electrode Capacitive Deionization (FCDI) Using Suspensions of 2D Materials As Electrodes

The increasing shortage of potable water in many part of the world is leading the development of various approaches to water purification, with desalination of sea water the prime target. The most common approach to desalination is reverse osmosis (RO), being used in 65% of currently installed plants[1], but its high costs due to the use of membranes, leading to high-energy requirements, is pushing the desalination industry to find other solutions. An alternative to the high-energy requirements of RO is a method called capacitive deionization (CDI). In this process, two porous electrodes are arranged parallel to one to the other, letting brackish water flow between them. When a voltage is applied, the ions from the feed water migrate to the surface of the electrodes and are adsorbed capacitively, reducing the overall concentration of salts in the water stream. When the voltage is removed, or reversed, the ions desorb from the surface of the electrodes, resulting in a by-product of this process, brine. One of the greatest advantages of this system is that the applied energy can be recovered during the discharge step, just like an electrochemical capacitor, that is used to store energy by means of a pair of electrodes[2]. There are a number of recent reports in the literature describing an innovative CDI technique that focuses on improving the operation of these desalination systems. A suspended electrode material flowing in a path carved on the current collector plays the same role as the porous carbon electrodes fixed on the current collector in a typical CDI process, and this has been termed “flow-electrode capacitive deionization (FCDI)”[3].The flow operates continuously by providing fresh flow electrodes with increased ion capacitance, showing a continuous desalination behaviour and high desalting efficiency that originates from this. In this study, we have tested FCDI systems using graphene and other 2D materials in suspension, as well as optimizing the FCDI system parameters, to try to improve the desalination performance of the system. The goal is to treat feed water with high salinity, close to that of seawater (35 g/L approximately). Studies of FCDI to date have used activated carbon and carbon black suspensions [4,5,6,7,8,9,10]. Graphene and 2D materials are expected to improve the overall desalination capacity of FCDI systems because of their high theoretical surface area and superior electrical conductivity. In the case of traditional CDI setups, graphene was able to increase the salt adsorption capacity 2.3 times[11], compared to previous studies made on activated carbon and carbon black electrodes.

(Invited) Commercialization of Novel Electrochemical Sensors for Volatile Organics

A variety of different methods were evaluated for the analysis of phenolic molecules in plant materials. The direct electrochemical oxidation of the phenols using square wave voltammetry showed good linearity and adequate sensitivity, provided that freshly polished electrodes were used for each measurement. The oxidation of the phenol created a reactive product that quickly fouled the surface of the electrode and limited the method to the use of fresh electrode surfaces. The results obtained with this method are well correlated with GC analysis of the same samples. If fresh electrodes are not easily obtained, then an indirect electrochemical approach seems a realistic alternative. Although some fouling was observed, the indirect method had sufficient sensitivity and linearity to be useful for these measurements. The use of both fresh electrode surfaces, as well as indirect electrochemical detection, produced improved correlations with the spiked concentrations. This is likely due to the improved fidelity of the measurement, since a fresh surface is used each time and a minimum amount of fouling is produced by the measurement.

(Invited) Commercialization of Novel Electrochemical Sensors for Volatile Organics

A combination of thermal vaporization and solid phase extraction were used with a variety of different electrochemical methods for the analysis of phenolic molecules in plant materials. The direct electrochemical oxidation of the phenols using square wave voltammetry showed good linearity and adequate sensitivity, provided that freshly polished electrodes were used for each measurement. The oxidation of the phenol created a reactive product that quickly fouled the surface of the electrode and limited the method to the use of fresh electrode surfaces. The results obtained with this method are well correlated with GC analysis of the same samples. If fresh electrodes are not easily obtained, then an indirect electrochemical approach seems a realistic alternative. Although some fouling was observed, the indirect method had sufficient sensitivity and linearity to be useful for these measurements. The use of both fresh electrode surfaces, as well as indirect electrochemical detection, produced improved correlations with the spiked concentrations. This is likely due to the improved fidelity of the measurement, since a fresh surface is used each time and a minimum amount of fouling is produced by the measurement. The combination of these approaches will be used to produce a sampling tool and sensor array for the characterization of a variety of commercial agricultural products.

Morphology Impact By Graphite Variations on Silicon-Alloy Negative Electrodes for Lithium-Ion-Batteries

Today, lithium-ion batteries represent the most widely used secondary battery. They play an important role in the further development of electric mobility or mobile applications (smartphones, laptops). They are characterized by their high energy and/or power density. In order to meet the needs of the future, higher energy and power densities, longer cycle life and higher safety standards are required. Due to their wide range of applications, the expectations of their lifetime and performance are increasing. The energy density is a critical factor for future energy storage systems in mobile applications. In order to achieve higher energy densities, an anode material must combine high specific capacities with high columbic efficiencies. Due to its low average voltage, low voltage hysteresis, good rate capability, low irreversible capacity, low volume expansion during lithiation causing excellent cycle life, graphite has been the material of choice as anode material [1]. However, the low theoretical specific capacity limits the application potential of graphite anodes. With its high theoretical specific capacity, silicon is the most promising anode material. However, the use of pure silicon is severely restricted by its mechanical behavior during charge/discharge cycling. Crystallization effects and massive volume changes during cycling seriously limit the cycle life of battery cells with Silicon as main component [2]. Therefore, Silicon/graphite blends seem to be the preferred route towards high energy anode formulations with relevant life times. In this context it is essential to understand the interplay between the various components of the blend electrodes for optimized performances, which is addressed in the current publication. Different industrially available graphites (KS6, KS6L. MCMB, LFP2, ECC Graphit) and a Silicon alloy material were used for anode preparation in order to investigate their structural morphologies and electrochemical performance of the resulting electrodes. The electrodes were tested in coin cell assemblies and charged and discharged at various rates. The morphologies of fresh and aged electrodes were investigated by means of optical and electron microscopy. Furthermore the volume changes of cells were monitored in order to relate it with the morphological appearance, porosity and graphite type.

Degradation Identification of Individual Components in the LiyNi1/3Co1/3Mn1/3O2-LiyMn2O4 Blended Cathode for Large Format Lithium Ion Battery

The degradation behaviors of individual components in the LiyNi1/3Co1/3Mn1/3O2(NCM)–LiyMn2O4(LMO) blended cathode are investigated in this paper. A prognostic/mechanistic model is applied to quantitatively analyze the capacity fading mechanism of the lithium ion battery with blended cathode. NCM and LMO are considered to be connected in parallel with a same potential during cycling. Current is distributed between NCM and LMO based on the dQ/dV curves, and the capacities of NCM and LMO can thus be quantitatively identified, respectively. The identified model parameters show that both NCM and LMO suffer loss of active material (LAM), but NCM degrades faster than LMO. Loss of lithium inventory also contributes to the capacity degradation, whereas anode shows little LAM until 330 cycles. The identified capacity degradation mechanism is validated by the coin cells test data, as the capacity degradation of the coin cells assembled with the aged electrodes compared with those made of fresh electrodes are consistent with the identified results.

Application of symmetric solid oxide fuel cell in fuel containing sulfur: I. Effect of electrodes

Symmetric solid oxide fuel cells (SFCs) with double perovskite materials serving as symmetric electrodes are applied for the first time in fuel containing sulfur, aiming to explore solution to sulfur poison. Temperature-programmed techniques, including H2-TPR, O2-TPD, were used to evaluate catalytic activities of electrodes in different atmosphere, while stabilities of electrode materials in sulfur containing fuel gas were characterized in terms of phase structures, conductivity, and microstructures by SEM, four-probe method and XRD as a function of temperature and operating time. It is evidenced that Sr2CoMoO6 (denoted as SCMO) possesses better hydrogen reducibility, oxygen desorption and stability in sulfur containing fuel gas. In configuration of Sr2XMoO6 (X = Co, Ni)|Ce0.85Sm0.15O2−δ (SDC)|Sr2XMoO6, the maximum power density Pmax reaches 95 mW cm−2 for SCMO and 68 mW cm−2 for SNMO with H2-0.1% H2S at 750 °C. Lower polarization resistance of SCMO (about 2.7 Ω cm2 at 750 °C) is achieved. It is interestingly noted that SFC performance composed of ex-situ regenerated symmetric electrodes SCMO falls only by 21%, as compared to that of fresh electrodes. The combinations of thermal analysis (TG-DTA) and surface analysis (XPS) convince that an ex-situ regeneration of symmetric electrode can be realized.

MnO2-Based Bifunctional Oxygen Catalyst for Rechargeable Metal/Air Batteries: The Effect of K + Intercalation

Extensive research has been undertaken to make intermittent clean and renewable energy sources more reliable. Bifunctional oxygen cathodes which can catalyze both ORR (oxygen reduction reaction) and OER (oxygen evolution reaction) are the backbone of rechargeable metal-air batteries as well as regenerative fuel cells [1-3]. Although noble metal family elements and alloys such as Pt , Pt-Au and Pt-Co are known as the best catalysts for ORR in alkaline media, their poor electrocatalytic activity toward OER as well as high price, comparing to non-PGM (non-precious group metal) compounds, limit their usage as a cost effective and active catalyst in bifunctional oxygen cathodes [2, 4]. Manganese oxides have been vastly employed as a robust cost-effective multifunctional and environmental friendly electrode material in battery industry, from primary to rechargeable metal-air batteries, as well as alkaline fuel cells and capacitors [3]. The electrolytic manganese dioxide (γ-MnO2) is known as the most electrochemically active crystallographic form of MnO2 for ORR in alkaline media with tafel slope of 40 mV dec-1 and a low overpotential of -375 mV [1, 5]. However, poor OER electrocatalytic activity of MnOx-based oxides in alkaline media diminish the hope of finding an exclusive bi-functional catalyst for both ORR and OER [1].Our research is aimed at the development of highly active MnO2-based catalysts for both ORR and OER with long cycle life by adding non-precious metal compounds as co-catalysts and intercalating potassium ions into the catalyst layer. The mechanisms for OER and ORR of the mixed catalysts and the role of K+are investigated by a combination of surface characterization methods and electrochemical techniques.In the present work, LaCoO3 were synthesized via co-precipitation methods. MnO2-based Gas diffusion electrodes (GDE) were then prepared using the method described elsewhere [1]. In order to intercalate the potassium ions into the catalyst layer, a simple yet effective method has been used. The GDEs were kept in in 6M KOH solution at open cicuit potential while rotating the sample at 400 RPM for 6 days at 313 K.Cyclic voltammetry tests were performed in O2 saturated 6 M KOH at 293 K to investigate the electrocatalytic activity of the MnO2-LaCoO3 catalyst for both OER and ORR. The longer-term durability of the electrodes was also investigated by performing 100 repeated OER-ORR voltammetric cycles. Electron energy loss spectroscopy (EELS) has been also used to further analyze the catalyst layer and study the Mn valance changes during both OER and ORR. X-ray photoelectron spectroscopy (XPS) was also used to confirm the existence of intercalated K+ions in the catalyst layer.Interestingly, huge enhancement is observed in the OER/ORR performance of the activated catalyst comparing to the fresh electrodes without any K+ activation. Fig 1-a and 1-b show the OER and ORR voltammograms, respectively, of the fresh and activated MnO2-LaCoO3 GDEs as well as fresh MnO2 electrodes. The OER overpotential for MnO2-LaCoO3 decreases to 193 from 367 mV after intercalating potassium ions in the catalyst layer (Fig. 1-a). In the ORR region, activated MnO2-LaCoO3 electrodes still provides the lowest ORR overpotential of -321 mV (Fig. 1-b), which is far better than the ORR behavior reported in the literature for Core-Corena Bifunctional Catalyst (CCBC), needle-like MnOx thin film, CoMn2O4 and even nanostructured Mn oxide thin film [1].Moreover, the activated catalyst performs almost without any degradation in OER region while suffering up to 61% decrease in the ORR current density at -250 mV (vs MOE) after 100 cycles of severe durability tests. Our results indicate that even 12 hrs of activation in 6 M KOH could enhance the electrocatalytic activity of the degraded catalyst after severe cycling to some point, mentioned before as “healing effect” [1]. The EELS analysis reveals that the Mn valance decreases during severe cycling from about 4 to 2.7 for the cycle No. 1 and 100, respectively. This confirms that the loss in the ORR electrocatalytic activity of the activated sample after 100 cycles is associated with the transformation of MnO2 to Mn3O4during severe cycling.