Electrochemical Performance Of Electrodes Research Articles

A facile preparation of NiO/Ni composites as high-performance pseudocapacitor materials

We report a facile way to prepare NiO/Ni composites with a positive on their specific capacitances as supercapacitor electrodes. Various NiO/Ni composites were obtained by controlling the reduction time of NiO by H2. The morphology of the products was characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The electrochemical performance of electrodes was investigated by cyclic voltammetry (CV) and the galvanostatic charge/discharge test. The results of electrochemical tests show that the as-prepared NiO and NiO/Ni all reveal stable cycling performance and remarkable rate performance. The resulting NiO/Ni40, obtained by calcining NiO in H2 for 40 min, could achieve a high specific capacitance of 760 F g−1 at 20 A g−1, significantly higher than the 480 F g−1 found for NiO. Additionally, the specific capacitance of NiO/Ni40 remained as high as 816 F g−1 after a 1000-cycle test at 4 A g−1, revealing superb electrochemical characteristics. This study provides a viewpoint that the introduction of an appropriate amount of Ni particles could enhance the specific capacitance of NiO as a supercapacitor electrode.

Study on Preparation of Modified Ti-Based Lead Dioxide Electrode and Degraded Methylene Blue

A modified electrode was prepared by the electrodeposition of a lead oxide layer on a titanium substrate. Characterize the electrochemical performance of electrode by adopting CHI860D electrochemistry workstation while evaluating the electro-catalytic performance of electrode with Methylene Blue (MB for short) solution as target degradation product. The results show that the interlayer proportion of SnCl4:SbCl3 is 6:1 when the thermal decomposition temperature is 550°C, the electrode material prepared in plating solution with a concentration of 0.15mol/L has excellent electrocatalytic performance against MB, and the degradation rate could reach above 98%.

Performance of anode-supported solid oxide fuel cell in planar-cell channel-type setup

Abstract In a planar-cell channel-type setup, the electrochemical performance of a solid oxide fuel cell strongly depends on the operating conditions. In this study, a large-area (10×10 cm 2 ) anode-supported solid oxide fuel cell was fabricated and tested in a single cell stack. It was found that the gas conversion overpotential can be significant depending on the fuel utilization, and this additional overpotential is not related to the electrode's electrochemical performance. Thus, the gas conversion overpotential must be taken into account for accurate analysis of the electrochemical performance of an SOFC stack, particularly under high fuel utilization conditions.

Hierarchical nanostructure CuO with peach kernel-like morphology as anode material for lithium-ion batteries

Copper oxide particles with different morphology (flower-like, peach kernel-like, and dandelion-like) are prepared with hydrothermal method by adjusting chitosan ((C6H11NO4)n) concentration in aqueous mixed solutions of ammonia and Cu(NO3)2. Various morphologies of porous cupric oxide (CuO) particles are formed by agglomerated nanosheet primary particles and lead to different electrochemical performance of electrodes. The peach kernel-shaped CuO exhibits high reversible capacity and rate capability. The reversible capacity is 722.7 mAh g−1 at 0.1 C in the first cycle and 339 mAh g−1 after 50 cycles at 0.2, 0.5, 1.0, and 2.0 C ratio. The higher reversible capacities and good cycling performance are attributed to the larger specific surface area, leading to better contact between CuO and electrolyte.

Preparation and Electrochemical Characteristics of Three-dimensional Manganese Oxide Micro-supercapacitor Electrode

In order to increase the electrode surface area and enhance the charge storage capacity, we study the micro electro mechanical system technology to fabricate three-dimensional high aspect ratio micro-electrode structure based on glass. The anodic constant potential method is employed to deposit manganese oxide as electroactive substances on the micro-electrode surface. Cyclic voltammetry and constant current charge-discharge method are both used to prepare electrode electrochemical performance testing, with a two-dimensional electrode without structure for comparison. Experimental results show that three-dimensional electrode structure can effectively enhance the charge storage capacity. At 1.0 mA/cm2 charge-discharge density, the three-dimensional electrode shows a capacitance of 17.88 mF/cm2, seven times higher than the two-dimensional electrode.

Cresyl diphenyl phosphate effect on the thermal stabilities and electrochemical performances of electrodes in lithium ion battery

To improve the safety of lithium ion battery, cresyl diphenyl phosphate (CDP) is used as a flame-retardant additive in a LiPF 6 based electrolyte. The electrochemical performances of LiCoO 2/CDP-electrolyte/Li and Li/CDP-electrolyte/C half cells are evaluated. The thermal behaviors of Li 0.5CoO 2 and Li 0.5CoO 2–CDP-electrolyte, and Li x C 6 and Li x C 6–CDP-electrolyte are examined using a C80 micro-calorimeter. For the LiCoO 2/CDP-electrolyte/Li cells, the onset temperature of single Li 0.5CoO 2 is put off and the heat generation is decreased greatly except the one corresponding to 5% CDP-containing electrolyte. When Li 0.5CoO 2 coexists with CDP-electrolyte, the thermal stability is enhanced. CDP improves the thermal stability of lithiated graphite anode effectively and the addition of 5% CDP inhibits the decomposition of solid electrolyte interphase (SEI) films significantly. The electrochemical tests on LiCoO 2/CDP-electrolyte/Li and Li/CDP-electrolyte/C cells show that when less than 15% CDP is added to the electrolyte, the electrochemical performances are not worsen too much. Therefore, the addition of 5–15% CDP to the electrolyte almost does not worsen the electrochemical performance of LiCoO 2 cathode and graphite anode, and improves theirs thermal stability significantly; thus, it is a possible choice for electrolyte additive.

Three-dimensional random resistor-network model for solid oxide fuel cell composite electrodes

Abstract A three-dimensional reconstruction of solid oxide fuel cell (SOFC) composite electrodes was developed to evaluate the performance and further investigate the effect of microstructure on the performance of SOFC electrodes. Porosity of the electrode is controlled by adding pore former particles (spheres) to the electrode and ignoring them in analysis step. To enhance connectivity between particles and increase the length of triple-phase boundary (TPB), sintering process is mimicked by enlarging particles to certain degree after settling them inside the packing. Geometrical characteristics such as length of TBP and active contact area as well as porosity can easily be calculated using the current model. Electrochemical process is simulated using resistor-network model and complete Butler–Volmer equation is used to deal with charge transfer process on TBP. The model shows that TPBs are not uniformly distributed across the electrode and location of TPBs as well as amount of electrochemical reaction is not uniform. Effects of electrode thickness, particle size ratio, electron and ion conductor conductivities and rate of electrochemical reaction on overall electrochemical performance of electrode are investigated.

Lithium polyacrylate as a binder for tin–cobalt–carbon negative electrodes in lithium-ion batteries

A lithium polyacrylate (Li-PAA) binder has been developed by 3M Company that is useful with electrodes comprising alloy anode materials. This binder was used to prepare electrodes made with Sn 30Co 30C 40 material prepared by mechanical attrition. The electrochemical performance of electrodes using Li-PAA binder was characterized and compared to those using sodium carboxymethyl cellulose (CMC) and polyvinylidene fluoride (PVDF) binders. The Sn 30Co 30C 40 electrodes using Li-PAA and CMC binders show much smaller irreversible capacity than the ones using PVDF binder. Poor capacity retention is observed when PVDF binder is used. By contrast, the electrodes using Li-PAA binder show excellent capacity retention for Sn 30Co 30C 40 materials and a specific capacity of 450 mAh/g is achieved for at least 100 cycles. The results suggest that Li-PAA is a promising binder for electrodes made from large-volume change alloy materials.

Self-assembled synthesis of hierarchical nanostructured CuO with various morphologies and their application as anodes for lithium ion batteries

We report a simple self-assembled synthesis of hierarchical CuO particles with various morphologies such as leaf, shuttle, flower, dandelion, and caddice clew. The morphologies can be easily tailored by adjusting the pH value. The synthesis is based on dehydration and re-crystallization of precursor Cu(OH) 2 nanowires. [Cu(NH 3) 4] 2+ and OH − in the solutions are considered as the key factors to influence the assembling manner of CuO. The obtained hierarchical CuO particles serve as a good model system for the study as anodes for lithium ion batteries. Various morphologies of CuO particles result in different electrochemical performances of electrodes. Compared to others, dandelion-like and caddice clew-like CuO exhibit reversible discharge capacities of 385 mAh g −1 and 400 mAh g −1 at 0.1 C, 340 mAh g −1 and 374 mAh g −1 at 0.5 C after 50 cycles, respectively. The higher discharge capacities and better cycling performances are attributed to their larger surface area and porosity, leading to better contact between CuO and electrolyte and shorter diffusion length of lithium ions.

Formation of Efficient Electron Transfer Pathways by Adsorbing Gold Nanoparticles to Self-Assembled Monolayer Modified Electrodes

The influence of the length of a self-assembled monolayer (SAM) linker on the electrochemical performance of electrode-linker-gold nanoparticle molecular constructs is investigated. Electrodes were first modified with amino-1-alkanethiols of four different lengths (C=2, 6, 8, and 11). The SAM showed progressively greater blocking ability to ruthenium hexamine as the length of the alkyl chain increased to the point where no significant Faradaic peak was observed for the amino-1-undecanethiol SAM. Upon the attachment of gold nanoparticles, distinct Faradaic electrochemistry of the ruthenium hexamine was observed for all four length SAMs with the electrochemistry being similar to that observed on a bare electrode. The charge transfer resistance to this Faradaic process was observed to be insensitive to the length of the intervening SAM, indicating it is electron transfer between the redox species and the nanoparticles, rather than tunneling across the SAM, which is the rate-limiting step. Some comments on the mechanism of charge transfer are provided. When forming multilayers of the linker-nanoparticle constructs, fabricated in a stepwise manner, whenever the distal species was the SAM the Faradaic process was blocked and whenever it was the nanoparticle a distinct Faradaic process was observed. With up to five layers of linker-nanoparticles, there was little increase in charge transfer resistance and again the charge transfer resistance was insensitive to the length of the linker.

A comparative study of electrodes comprising nanometric and submicron particles of LiNi 0.50Mn 0.50O 2, LiNi 0.33Mn 0.33Co 0.33O 2, and LiNi 0.40Mn 0.40Co 0.20O 2 layered compounds

In this paper we compare the behavior of LiNi 0.5Mn 0.5O 2, LiNi 0.33Mn 0.33Co 0.33O 2 (NMC) and LiNi 0.4Mn 0.4Co 0.2O 2 as cathode materials for advanced rechargeable Li-ion batteries. These materials were prepared by a self-combustion reaction (SCR) from the metal nitrates and sucrose, followed by calcination at elevated temperatures. The temperature and duration of calcination enabled the adjustment of the average particle size and size distribution. It was established that the annealing temperature (700–900 °C) of the as-prepared oxides influences strongly the crystallite and particle size, the morphology of the material, and the electrochemical performance of electrodes in Li-cells. Capacities up to 190, 180 and 170 mAh g −1 could be obtained with Li[NiMn]O 2, LiNi 0.4Mn 0.4Co 0.2O 2 and LiNi 0.33Mn 0.33Co 0.33O 2, respectively. In terms of rate capability, the order of these electrodes is NMC < LiNi 0.4Mn 0.4Co 0.2O 2 ≪ Li[NiMn]O 2. Many hundreds of cycles at full DOD could be obtained with Li[NiMn]O 2 and NMC electrodes in Li-cells, at room temperature. All of these materials develop a unique surface chemistry that leads to their passivation and stabilization in standard electrolyte solutions (alkyl carbonates/LiPF 6). The surface chemistry was studied by FTIR, XPS and Raman spectroscopy and is discussed herein.

Preparation and characterization on the carbon nanotube chemically modified electrode grown in situ

Carbon nanotube chemically modified electrode (CNT-CME) was prepared by growing carbon nanotube (CNT) in situ on the pretreated graphite electrode (GE) via the catalytic chemical vapor deposition. The pretreated GE was prepared by ultrasonic immersion method using Ni(NO 3) 2 as the catalyst. The CNT growing on the CNT-CME was characterized by transmission electron microscope and scanning electron microscope. The obtained electrode electrochemical performance was characterized by cyclic voltammetry with the Na 2SO 4 solution and [Fe(CN) 6] 3−/[Fe(CN) 6] 4− solution. The results showed that the obtained electrode has good current responsive sensitivity and good testing result accuracy, indicating that the obtained electrode may have great application in electrochemical testing field.

Effect of surface free energy of acetylene black powder on air electrode performance

The effects of acetylene black powder surface free energy on air electrode electrochemical performance and lifetime were studied. The acetylene black was immersed in 30% H 2O 2 at room temperature and the changes of functional groups and surface free energy were investigated by X-ray Photoelectron Spectros-copy (XPS) and powder contact angle (CA). The air electrode performance was characterized by the potential polarization curves and the lifetime was measured by constant-current discharge. It shows that, its surface free energy is the lowest when the acetylene black is immersed in H 2O 2 for 240 h. The polarization potential of the air electrode prepared by the pretreated acetylene black is 0.25 V(vs. Hg/HgO), 0.21 V lower than the air electrode with untreated acetylene black when the working current density is 100 mA.cm −1. And its lifetime is over 800 h at 80 mA.cm −1. The pretreatment of acetylene black for proper time by H 2O 2 is favorable for the stability of the tri-phase reaction interface of air electrode and improvement of its performance.

The influence of the synthesis conditions of graphite/tin nanoparticle materials on their electrode electrochemical performance in Li-ion battery anodes

Electrochemical lithium insertion was carried out in tin–graphite composites obtained by two different preparation processes. In the first graphite was mixed with the products obtained by reduction of SnCl 4 with Na tert-Butanoate ( t-BuONa)-activated NaH (two-step synthesis). The second used materials synthesized by reducing SnCl 4 with a graphite and ( t-BuONa)-activated NaH suspension in THF (one-pot synthesis). Both composites were characterized by X-ray diffraction and transmission electron microscopy . It appeared that the tin particle size was controlled by the reduction time of SnCl 4. The stability of the electrochemical capacity of composites prepared by the two-step synthesis is dependent on the tin particle size: a stable capacity upon cycling was shown with subnanometer particles while a capacity fade was observed with larger nanoparticles. In materials prepared by the one pot synthesis, tin was present either as nanopartcles supported on graphite or as free aggregates. An initial reversible capacity of 630 mA hg −1 decayed to a constant value of 415 mA hg −1 after 12 charge/discharge cycles. It was hypothesized that the fraction of tin bound to graphite contributed to the stable reversible capacity while free tin aggregates were responsible for its decay.

Evaluation of Electrode Performance Using a Microstructure-Based Simulation Model

The electrochemical performance of electrodes, such as those used in solid oxide fuel cells, depends to a large extent on the microstructure of the electrode material. A modeling approach, based on the lattice Boltzmann simulation method, has been developed to describe the detailed three-dimensional transport and reaction phenomena occurring in a representative sample of porous electrode material. The model geometry is obtained by obtaining statistical information from a two-dimensional micrograph and reconstructing an equivalent three-dimensional structure. The usefulness of this modeling approach is demonstrated by simulating a simplified two-dimensional electrode.

Influence of the electrolyte content of oxygen carbon gas-diffusion electrodes on their electro-chemical performance in acid solutions

Five different methods of Teflon deposition onto the carbon surface were used to study the influence of different electrolyte contents in the carbon gas-diffusion electrodes on their electrochemical performance in acid solution. It was shown that the electrolyte content can be controlled also by the addition of carbon black and by promotion of active carbon with platinum. Electrodes prepared in accordance with these five methods of Teflon deposition differ in electrolyte content over a wide range and therefore the rate of mass transport is considerably influenced especially when the electrodes are working with air. The catalytic activity of pure active carbon is relatively low but the current—voltage characteristics of the electrodes could be positively influenced in the range controlled by the rate of mass transport and ionic conductivity, using a suitable method of Teflon deposition and by the addition of carbon black. The electrochemical performance of electrodes with active carbon promoted with platinum can be improved by the presence of optimum electrolyte content in the electrode using a suitable method of Teflon deposition and the addition of carbon black.