scholarly journals Ionic liquid based EDLCs: influence of carbon porosity on electrochemical performance

2014 ◽  
Vol 172 ◽  
pp. 163-177 ◽  
Author(s):  
Asa Noofeli ◽  
Peter J. Hall ◽  
Anthony J. R. Rennie
Keyword(s):  
Electrochemical Performance ◽  
Pore Size ◽  
Electrochemical Impedance ◽  
Constant Current ◽  
Peak Performance ◽  
Promising Alternative ◽  
Electrochemical Stabilities ◽  
Electrochemical Double Layer ◽  
Improved Performance ◽  
Operating Potential

Electrochemical double layer capacitors (EDLCs) are a category of supercapacitors; devices that store charge at the interface between electrodes and an electrolyte. Currently available commercial devices have a limited operating potential that restricts their energy and power densities. Ionic liquids (ILs) are a promising alternative electrolyte as they generally exhibit greater electrochemical stabilities and lower volatility. This work investigates the electrochemical performance of EDLCs using ILs that combine the bis(trifluoromethanesulfonyl)imide anion with sulfonium and ammonium based cations. Different activated carbon materials were employed to also investigate the influence of varying pore size on electrochemical performance. Electrochemical impedance spectroscopy (EIS) and constant current cycling at different rates were used to assess resistance and specific capacitance. In general, greater specific capacitances and lower resistances were found with the sulfonium based ILs studied, and this was attributed to their smaller cation volume. Comparing electrochemical stabilities indicated that significantly higher operating potentials are possible with the ammonium based ILs. The marginally smaller sulfonium cation performed better with the carbon exhibiting the largest pore width, whereas peak performance of the larger sulfonium cation was associated with a narrower pore size. Considerable differences between the performance of the ammonium based ILs were observed and attributed to differences not only in cation size but also due to the inclusion of a methoxyethyl group. The improved performance of the ether bond containing IL was ascribed to electron donation from the oxygen atom influencing the charge density of the cation and facilitating cation–cation interactions.

scholarly journals Femtosecond Laser-Induced Surface Modification of the Electrolyte in Solid Oxide Electrolysis Cells

Energies ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 6562
Author(s):  
Tobias Marquardt ◽  
Jan Hollmann ◽  
Thomas Gimpel ◽  
Wolfgang Schade ◽  
Stephan Kabelac
Keyword(s):  
Femtosecond Laser ◽  
Electrochemical Performance ◽  
Laser Treatment ◽  
Mechanical Stability ◽  
Electrochemical Impedance ◽  
Specific Resistance ◽  
Solid Oxide ◽  
Constant Current ◽  
Reference Cell ◽  
Area Specific Resistance

Electrolyte-supported solid oxide cells are often used for steam electrolysis. Advantages are high mechanical stability and a low degradation rate. The aim of this proof of concept study was to use a femtosecond laser to process the electrolyte of an electrolyte-supported solid oxide cell and evaluate the effect of this laser treatment on the electrochemical performance. The femtosecond laser treatment induces a macroscopic and a superimposed microscopic structure. It can be proven that the electrolyte remains gas tight and the electrochemical performance increases independently of the laser parameters. The initial area-specific resistance degradation during a constant current measurement of 200 h was reduced from 7.9% for a non-treated reference cell to 3.2% for one of the laser-treated cells. Based on electrochemical impedance measurements, it was found that the high frequency resistance of the laser-treated cells was reduced by up to 20% with respect to the reference cell. The impedance spectra were evaluated by calculating the distribution of relaxation times, and in advance, a novel approach was used to approximate the gas concentration resistance, which was related to the test setup and not to the cell. It was found that the low frequency polarization resistance was increased for the laser-treated cells. In total, the area-specific resistance of the laser-treated cells was reduced by up to 14%.

scholarly journals The Synthesis and Electrochemical Performance of Si Composite with Hollow Carbon Microtubes by the Carbonization of Milkweed from Nature as Anode Template for Lithium Ion Batteries

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 5124
Author(s):  
Eun Hyuk Chung ◽  
Jong Pil Kim ◽  
Hyun Gyu Kim ◽  
Jae-Min Chung ◽  
Sei-Jin Lee ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Electrical Conductivity ◽  
Electrochemical Performance ◽  
Pore Size ◽  
Lithium Ion Batteries ◽  
Polyvinylidene Fluoride ◽  
Lithium Ion ◽  
Size Analysis ◽  
Pore Size Analysis ◽  
Hollow Carbon

It has been reported that improving electrical conductivity and maintaining stable structure during discharge/charge process are challenge for Si to be used as an anode for lithium ion batteries (LIB). To address this problem, milkweed (MW) was carbonized to prepare hollow carbon microtubes (HCMT) derived from biomass as an anode template for LIB. In order to improve electrical conductivity, various materials such as chitosan (CTS), agarose, and polyvinylidene fluoride (PVDF) are used as carbon source (C1, C2, and C3) by carbonization. Carbon coated HCMT@Si composits, HCMT@Si@C1, HCMT@Si@C1@C2, and HCMT@Si@C1@C3, have been successfully synthesized. Changes in structure and crystallinity of HCMT@Si composites were characterized by using X-ray diffraction (XRD). Specific surface area for samples was calculated by using BET (Brunauer–Emmett–Teller). Also, pore size and particle size were obtained by particle and pore size analysis system. The surface morphology was evaluated using high resolution scanning electron microscopy (HR-SEM), Field Emission transmission electron microscopy (TEM). The thermal properties of HCMT@Si composites were analyzed by thermogravimetric analysis (TGA). Our research was performed to study the synthesis and electrochemical performance of Si composite with HCMT by the carbonization of natural micro hollow milkweed to form an inner space. After carbonization at 900 °C for 2 h in N2 flow, inner diameter of HCMT obtained was about 10 μm. The electrochemical tests indicate that HCMT@Si@C1@C3 exhibits discharge capacity of 932.18 mAh/g at 0.5 A/g after 100 cycles.

An Experimental Research on Electrochemical Impedance Spectra of New High-Specific Energy EDLC

2011 ◽  
Vol 675-677 ◽  
pp. 65-68 ◽  
Author(s):  
Zi Lei Liang ◽  
Chong Kuan Cheng ◽  
Ji Bo Liu ◽  
Guo Min Mi
Keyword(s):  
Specific Energy ◽  
Electrochemical Impedance ◽  
Discharge Process ◽  
Electrochemical Impedance Spectra ◽  
Charge Voltage ◽  
Electrochemical Double Layer Capacitors ◽  
Complex Capacitance ◽  
Electrochemical Double Layer ◽  
High Specific Energy ◽  
Double Layer Capacitors

The real times Electrochemical Impedance Spectroscopy (EIS) analysis which corresponds to the charge and discharge process was reported in order to evaluate the relationships between impedance and potential for new high specific energy electrochemical double-layer capacitors (EDLC). Also the Niquist plots were presented and the impedance of the EDLC was discussed in terms of complex capacitance. It was found that the high frequency impedance changed with its potential in charging or discharging process, the medium frequency impedance Rct belonged to the resistance of ions diffusion into micro pore or the inner of electrode material decreased with increasing charge voltage and had a certain capacitance of about 1F.

Synthesis and Electrochemical Properties of Spherical LiFePO4/C Composite via Spray Drying

2015 ◽  
Vol 1120-1121 ◽  
pp. 554-558 ◽  
Author(s):  
Juan Mei Wang ◽  
Bing Ren ◽  
Ying Lin Yan ◽  
Qing Zhang ◽  
Yan Wang
Keyword(s):  
Diffusion Coefficient ◽  
Electrochemical Properties ◽  
Spray Drying ◽  
Electrochemical Impedance ◽  
Retention Rate ◽  
Lithium Ion ◽  
Constant Current ◽  
Ion Diffusion ◽  
Electrochemical Tests ◽  
Li Ion

In this work, spherical LiFePO4/C composite had been synthesized by co-precipitation and spray drying method. The structure, morphology and electrochemical properties of the samples were characterized by X-ray diffraction (XRD), scanning electron micrograph (SEM), transmission electron microscope (TEM), constant current charge-discharge tests and electrochemical impedance spectroscopy (EIS) tests. The spherical LiFePO4/C particles consisted of a number of smaller grains. The results showed that the morphology of LiFePO4/C particles seriously affected the Li-ion diffusion coefficient and electrochemical properties of lithium ion batteries. Electrochemical tests revealed the spherical LiFePO4/C composite had excellent Li-ion diffusion coefficient which was calculated to be 1.065×10-11 cm2/s and discharge capacity of 149 (0.1 C), 139 (0.2 C), 133 (0.5 C), 129 (1 C) and 124 mAhg-1(2 C). After 50 cycles, the capacity retention rate was still 93.5%.

scholarly journals Dependence of Capacitive Properties of an EDLC on Exfoliation Time of Graphite Electrodes

2021 ◽  
Author(s):  
Dinithi S. K. Rajaguru ◽  
Kamal Vidanapathirana ◽  
Kumudu S. Perera
Keyword(s):  
Electrochemical Impedance ◽  
Low Cost ◽  
Gel Polymer Electrolyte ◽  
Storage Device ◽  
Graphite Electrodes ◽  
Discharge Capacitance ◽  
Capacitive Properties ◽  
Device Applications ◽  
Specific Discharge ◽  
Electrochemical Double Layer

Abstract The scientific focus has been directed through the production and application of ‘wonder material- graphene’ after its discovery in 2004. But the mass production cost has become a huge disadvantage towards commercializing graphene based manufactures. As alternative low cost material, exfoliated graphite (EG) has emerged to be a novel nanostructured carbon material with a potential for electrochemical energy storage device applications owed to its unique characteristics similar to graphene. In this study a series of EG samples were prepared by a surfactant mediated liquid phase exfoliation method by changing the exfoliation time. Electrochemical double layer capacitors (EDLCs) were fabricated using different EG samples as an electrode material and a gel polymer electrolyte (GPE). They were characterized by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and galvanostatic charge discharge (GCD) techniques. EDLC having EG electrodes of 10 h exfoliation time showed the highest results with single electrode specific capacitance (Csc) of 4.12 F g− 1, single electrode specific discharge capacitance (Csd) of 1.10 F g− 1 and relaxation time of 0.22 s from CV, GCD and EIS respectively.

Porous carbon spheres and monoliths: morphology control, pore size tuning and their applications as Li-ion battery anode materials

2014 ◽  
Vol 43 (13) ◽  
pp. 4341-4356 ◽  
Author(s):  
Aled D. Roberts ◽  
Xu Li ◽  
Haifei Zhang
Keyword(s):  
Pore Size ◽  
Porous Carbon ◽  
Anode Materials ◽  
Morphology Control ◽  
Li Ion Battery ◽  
Carbon Spheres ◽  
Li Ion ◽  
Improved Performance ◽  
Porous Carbon Spheres ◽  
Battery Anode

Various synthetic techniques are employed to fabricate porous carbon spheres and monoliths for improved performance as Li-ion battery anode materials.

scholarly journals Enhanced Structural Integrity and Electrochemical Performance of AlPO4-Coated MoO2 Anode Material for Lithium-Ion Batteries

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
José I. López-Pérez ◽  
Edwin O. Ortiz-Quiles ◽  
Khaled Habiba ◽  
Mariel Jiménez-Rodríguez ◽  
Brad R. Weiner ◽  
...  
Keyword(s):  
Surface Modification ◽  
Electrochemical Performance ◽  
Anode Material ◽  
Structural Integrity ◽  
Electrochemical Impedance ◽  
Lattice Structure ◽  
Rate Capability ◽  
Lithium Ion ◽  
Microscopy Imaging ◽  
Voltage Range

AlPO4 nanoparticles were synthesized via chemical deposition method and used for the surface modification of MoO2 to improve its structural stability and electrochemical performance. Structure and surface morphology of pristine and AlPO4-coated MoO2 anode material were characterized by electron microscopy imaging (SEM and TEM) and X-ray diffraction (XRD). AlPO4 nanoparticles were observed, covering the surface of MoO2. Surface analyses show that the synthesized AlPO4 is amorphous, and the surface modification with AlPO4 does not result in a distortion of the lattice structure of MoO2. The electrochemical properties of pristine and AlPO4-coated MoO2 were characterized in the voltage range of 0.01–2.5 V versus Li/Li+. Cyclic voltammetry studies indicate that the improvement in electrochemical performance of the AlPO4-coated anode material was attributed to the stabilization of the lattice structure during lithiation. Galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS) studies reveal that the AlPO4 nanoparticle coating improves the rate capability and cycle stability and contributes toward decreasing surface layer and charge-transfer resistances. These results suggest that surface modification with AlPO4 nanoparticles suppresses the elimination of oxygen vacancies in the lattice structure during cycling, leading to a better rate performance and cycle life.

A High Rate, High Capacity and Long Life (LiFePO4+AC)/Li4Ti5O12 Hybrid Battery-Supercapacitor

2014 ◽  
Vol 936 ◽  
pp. 496-502
Author(s):  
Xue Bu Hu ◽  
Zi Ji Lin ◽  
Yong Long Zhang
Keyword(s):  
Leakage Current ◽  
Electrochemical Impedance ◽  
Discharge Rate ◽  
Performance Testing ◽  
High Energy ◽  
High Energy Density ◽  
Constant Current ◽  
Electrochemical Performances ◽  
Capacity Loss ◽  
Charge Discharge

A hybrid battery-supercapacitor (LiFePO4+AC)/Li4Ti5O12 using a Li4Ti5O12 anode and a LiFePO4/activated carbon (AC) composite cathode was built. The electrochemical performances of the hybrid battery-supercapacitor (LiFePO4+AC)/Li4Ti5O12 were characterized by constant current charge-discharge, rate charge-discharge, electrochemical impedance spectra, internal resistance, leakage current, self-discharge and cycle performance testing. The results show that (LiFePO4+AC)/Li4Ti5O12 hybrid battery-supercapacitors have rapid charge-discharge performance, high energy density, long cycle life, low resistance, low leakage current and self-discharge rate, which meet the requirements of practical power supply and can be applied in auxiliary power supplies for hybrid electric vehicles. At 4C rate, the capacity loss of (LiFePO4+AC)/Li4Ti5O12 hybrid battery-supercapacitors in constant current mode is no more than 7.71% after 2000 cycles, and the capacity loss in constant current-constant voltage mode is no more than 4.51% after 1500 cycles.

scholarly journals Exploring the electrochemical performance of graphite and graphene paste electrodes composed of varying lateral flake sizes

2018 ◽  
Vol 20 (30) ◽  
pp. 20010-20022 ◽  
Author(s):  
Anthony J. Slate ◽  
Dale A. C. Brownson ◽  
Ahmed S. Abo Dena ◽  
Graham C. Smith ◽  
Kathryn A. Whitehead ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electrochemical Performance ◽  
Direct Relationship ◽  
Graphite Electrodes ◽  
Improved Performance ◽  
Electron Transfer Properties ◽  
Transfer Properties

A direct relationship is shown with respect to the lateral flake size comprising graphene and graphite electrodes and their corresponding electron transfer properties, with smaller flake sizes (increased edge plane contributions) resulting in improved performance.

Sign in / Sign up

Export Citation Format

Share Document