Charge Discharge Method Research Articles

Synthesis and electrochemical characterization of carbon spheres as anode material for lithium-ion battery

Carbon spheres were synthesized by the thermal decomposition of RF precursor which was synthesized by surfactant-assisted polycondensation of resorcinol with formaldehyde. The morphology of precursor was preserved during the decomposition process. EDS, TG, SEM, CV and galvanostatic charge–discharge methods are used to characterize the composition, morphology, and electrochemical performance of carbon spheres. The results revealed that these carbon spheres had a spherical morphology, smooth surface and probable size of about 400 nm. When the carbon spheres were used as anode materials for lithium-ion battery, they exhibited a high lithium storage capacity and good cycle performance. In addition, the possible progress for the preparation of carbon spheres was proposed.

Synergistic enhancement of supercapacitance upon integration of nickel (II) octa [(3,5-biscarboxylate)-phenoxy] phthalocyanine with SWCNT-phenylamine

Supercapacitive behaviour of a novel functional material, nickel (II) octa [(3,5-biscarboxylate)-phenoxy] phthalocyanine (NiOBCPPc) upon covalent integration with phenylamine functionalized single-walled carbon nanotubes (SWCNT-phenylamine ) is reported for the first time. The supercapacitive behaviour of the hybrid (NiOBCPPc-SWCNT-phenylamine) was investigated using galvanostatic charge–discharge and electrochemical impedance spectroscopy. Using a more reliable galvanostatic charge–discharge method, the NiOBCPPc-SWCNT-phenylamine hybrid exhibited superior geometrical capacitance (∼186 mF cm −2) compared to either NiOBCPPc (∼54 mF cm −2) or SWCNT-phenylamine (∼74 mF cm −2) at a current density of 138 μA cm −2. The NiOBCPPc-SWCNT-phenylamine gave excellent stability of over 1000 charge–discharge continuous cycling.

Preparation and Electrochemical Properties of Polyaniline/Carbon Nanofiber Composite Materials

Polyaniline/carbon nanofiber (PANI/CNF) composite materials were prepared by in situ polymerization. The functional group, composition, surface morphology, and specific surface area of composite materials were characterized by Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and Brunauer-Emmelt-Teller analysis. Cyclic voltammetry (CV) and galvanotactic charge-discharge methods were used to study the electrochemical properties of the PANI/CNF composite materials. Results showed that the composite materials had a rough surface with a burry PANI structure that was uniformly distributed over the CNF. The composite materials, as electrodes, showed good reversibility in redox reactions. The specific capacitance of 44.4%(w) PANI/CNF was 587.1 F.g(-1), the specific energy was 66.1 Wh.kg(-1) at a current density of 100 mA.g(-1), and the specific power was 1014.2 W.kg(-1) at a current density of 800 mA.g(-1). Moreover, the specific capacitance of PANI/CNF only decreased by 28% after 1000 charge-discharge cycles. Therefore, the PANI/CNF composite material is an excellent material for use in supercapacitors because of its high electrical conductivity and large specific capacitance.

Investigation of Co–B–S system as anode material for secondary alkaline battery

A series of novel Co–S–B systems were prepared by simple chemical reduction method as the anode material for secondary alkaline batteries. The prepared samples were investigated by inductivity coupled plasma optical emission spectrum (ICP), Brunauer–Emmetr–Teller (BET) method, scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray energy dispersive spectroscopy (EDS) and charge–discharge method. It was found that the BET surface area of Co–S–B system increases and its particle size decreases with increasing the sulfur content. Sulfur incorporation suppresses initial capacity fading of Co–B compound due to irreversible dissolution of boron, and Co–S–B electrodes show enhanced electrochemical capacity and excellent cycle performance. The discharge capacity of Co 75.4B 17S 7.6 reaches 513.6 mAh/g at a moderate current density of 100 mA/g and 470 mAh/g after 60 cycles, which is about 1.5 times that of conventional AB 5-type alloy. A proper mechanism was proposed to explain the electrochemical reaction process of Co–S–B electrode.

Electropolymerization of ionic liquid substituted polyphenylene as supercapacitors materials

A new type of polyphenylene, ionic liquid (IL) 1,3-methylimidazolium hexafluorophosphate substituted, has been prepared by electrodeposition on Au electrode surface via pulse galvanostatic method in 1-butyl-3-methylimidazolium hexafluorophosphate solution. The obtained polymer film had a spherulitic morphology with smallest grains of around 500 nm. Infrared spectrometry revealed that polyphenylene was deposited to a certain extent. The capacitive behavior of the IL substituted polyphenylene was investigated by cyclic voltammetry (CV) and galvanostatic charge–discharge method in 0.2 mol L −1 H 2SO 4 aqueous solutions or pure IL [bmim]PF 6. The specific capacitance of the polymer at the charge–discharge current density of 1 mA cm −2 equaled 206 F g −1 in acidic aqueous solution or 164 F g −1 in [bmim]PF 6. Additionally, excellent charge–discharge cycle stability (over 85% value of specific capacitance remained after 600 charge–discharge cycles) and power characteristics of the polymer electrode were observed in both electrolytes.

High dispersion of γ-MnO 2 on well-aligned carbon nanotube arrays and its application in supercapacitors

The well-aligned carbon nanotube arrays (ACNTs) were used as supporting material and the γ-MnO 2/ACNT electrode with high dispersion of γ-MnO 2 has been prepared by electrochemically induced deposition method. The crystal structure and morphology of the γ-MnO 2/ACNT electrode were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The capacitive properties of γ-MnO 2/ACNT electrode were characterized by cyclic voltammetry and galvanostatic charge–discharge method. The specific capacitance of the γ-MnO 2/ACNT electrode is as high as 784 F g − 1 based on γ-MnO 2 and 234 F g − 1 based on γ-MnO 2/ACNT composites in 0.1 M Na 2SO 4 aqueous solution from 0 to 1 V when the charge–discharge current density is 1 mA cm − 2 . Additionally, the electrode shows excellent power characteristics, high electrochemical reversibility and excellent long-term charge–discharge cycle stability.

Preparation of cobalt oxide thin films and its use in supercapacitor application

Present work explored a room temperature, simple and low cost chemical route for the cobalt oxide film onto copper substrate from cobalt chloride (CoCl 2·6H 2O) precursor and characterization for its structural and electrochemical properties for supercapacitor application. The morphology and crystal structure of the film were investigated by scanning electron microscopy and X-ray diffraction techniques, respectively. The electrochemical supercapacitive properties of cobalt oxide film were evaluated using cyclic voltammetry and galvanostatic charge–discharge methods. The film showed maximum specific capacitance of (165 F/g) in 1.0 M aqueous KOH electrolyte at scan rate 10 mV/s.

Structure and electrochemical characterization of LiNi0.3Co0.3Mn0.3Fe0.1O2 cathode for lithium secondary battery

A lithium insertion material having the composition LiNi0.3Co0.3Mn0.3Fe0.1O2 was synthesized by simple sol-gel method. The structural and electrochemical properties of the sample were investigated using X-ray diffraction spectroscopy (XRD) and the galvanostatic charge-discharge method. Rietvelt analysis of the XRD patterns shows that this compound can be classified as α-NaFeO2 structure type (R3m; a=2.8689(5) A and 14.296(5) A in hexagonal setting). Rietvelt fitting shows that a relatively large amount of Fe and Ni ion occupy the Li layer (3a site) and a relatively large amount of Li occupies the transition metal layer (3b site). LiNi0.3Co0.3Mn0.3Fe0.1O2 when cycled in the voltage range 4.3–2.8 V gives an initial discharge capacity of 120 mAh/g, and stable cycling performance. LiNi0.3Co0.3Mn0.3Fe0.1O2 in the voltage range 2.8–4.5 V has a discharge capacity of 140 mAh/g, and exhibits a significant loss in capacity during cycling. Ex-situ XRD measurements were performed to study the structure changes of the samples after cycling between 2.8–4.3 V and 2.8–4.5 V for 20 cycles. The XRD and electrochemical results suggested that cation mixing in this layered structure oxide could be causing degradation of the cell capacity.

Analytical solution for the voltage distribution in one-dimensional porous electrode subjected to cyclic voltammetric (CV) conditions

An analytical solution for the voltage distribution in one-dimensional porous electrode subjected to cyclic voltammetric (CV) conditions was developed by considering the resistivity of both electrode and electrolyte. Voltage distribution inside the electrode as a function of dimensionless distance was generated at different electrode phase resistances. The analytical solution of voltage distribution for cyclic voltammetric conditions was employed in deriving the charging currents. Capacitance studies were conducted on carbons derived from catechol-formaldehyde gels prepared at pH conditions of 3, 6, and 7.5 in 30 wt.% H 2SO 4 electrolyte using CV and constant current charge/discharge studies. Charging currents derived from voltage distribution were fitted with experimental anodic part of CV curves and equivalent series resistance (ESR) was generated. Thus, generated ESR values were compared with that obtained using constant current charge–discharge curves. The model fitted resistance values matched closely with resistance values obtained from galvanostatic constant current charge–discharge method.

Textural and electrochemical characterization of porous carbon nanofibers as electrodes for supercapacitors

Porous carbon nanofibers (CNFs) enriched with the graphitic structure were synthesized by thermal decomposition from a mixture containing polyethylene glycol and nickel chloride (catalyst). The textural and electrochemical properties of porous CNFs were systematically compared with those of commercially available multi-walled carbon nanotubes (MWCNTs). The high ratio of mesopores and large amount of open edges of porous CNFs with a higher specific surface area, very different from that of MWCNTs, are favorable for the penetration of electrolytes meanwhile the graphene layers of porous CNFs serve as a good electronic conductive medium of electrons. The electrochemical properties of porous CNFs and MWCNTs were characterized for the application of supercapacitors using cyclic voltammetry, galvanostatic charge–discharge method, and electrochemical impedance spectroscopic analyses. The porous CNFs show better capacitive performances ( C S = 98.4 F g −1 at 25 mV s −1 and an onset frequency of behaving as a capacitor at 1.31 kHz) than that of MWCNTs ( C S = 17.8 F g −1 and an onset frequency at 1.01 kHz). This work demonstrates the promising capacitive properties of porous CNFs for the application of electrochemical supercapacitors.

Electrochemical Lithium Intercalation/Deintercalation of Single-Crystalline V2O5 Nanowires

This paper reports on the electrochemical lithium intercalation/deintercalation of single-crystalline nanowires that were synthesized by a two-step approach including a hydrothermal process and a post-calcinating treatment. Techniques of X-ray diffraction, field-effect scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy were used to characterize the structure, morphology, and composition of the as-prepared nanowires. It was found that nanowires were of high purity with the diameter of and the length up to . The electrochemical lithium intercalation/deintercalation of the nanowires was investigated by cyclic voltammograms and galvanostatic charge-discharge methods. The results showed that the single-crystalline nanowires exhibited high initial discharge capacity of , indicating their potential application as the cathode materials of rechargeable lithium-ion batteries.

Preparation and capacitive properties of cobalt–nickel oxides/carbon nanotube composites

In this paper, nickel–cobalt oxides/carbon nanotube (CNT) composites were prepared by adding and thermally decomposing nickel and cobalt nitrates directly onto the surface of carbon nanotube/graphite electrode to form nickel and cobalt oxides. Carbon nanotubes used in this paper were grown directly on graphite substrate by chemical vapor deposition technique. The capacitive behavior of nickel–cobalt oxides/CNT electrode was investigated by cyclic voltammetry and galvanostatic charge–discharge method in 1 M KOH aqueous solutions. The results show that nickel–cobalt oxides/CNT composite electrode has excellent charge–discharge cycle stability (0.2% and 3.6% losses of the specific capacitance are found at the 1000th and 2000th charge–discharge cycles, respectively) and good charge–discharge properties at high currrent density. Additionally, the effect of Ni/Co molar ratio on specific capacitance of the composite electrode was investigated and the highest specific capacitance (569 F g −1 at 10 mA cm −2) is obtained at Ni/Co molar ratio = 1:1.

Preparation and characterization of manganese oxide/CNT composites as supercapacitive materials

Manganese oxide was synthesized and dispersed on carbon nanotube (CNT) matrix by thermally decomposing manganese nitrates. CNTs used in this paper were grown directly on graphite disk by chemical vapor deposition technique. The capacitive behavior of manganese oxide/CNT composites was investigated by cyclic voltammetry and galvanostatic charge–discharge method in 1 M Na 2SO 4 aqueous solutions. When the loading mass of MnO 2 is 36.9 μg cm − 2 , the specific capacitance of manganese oxide/CNT composite (based on MnO 2) at the charge–discharge current density of 1 mA cm − 2 equals 568 F g − 1 . Additionally, excellent charge–discharge cycle stability (ca. 88% value of specific capacitance remained after 2500 charge–discharge cycles) and power characteristics of the manganese oxide/CNT composite electrode can be observed. The effect of loading mass of MnO 2 on specific capacitance of the electrode has also been investigated.

Preparation and Characterization of Li[sub 1.05][Ni[sub 0.35]Co[sub 025]Mn[sub 0.4]]O[sub 2] as a Cathode Material for Rechargeable Lithium Cells

A lithium insertion material Li 1 . 0 5 [Ni 0 . 3 5 Co 0 . 2 5 Mn 0 . 4 ]O 2 was synthesized by a sol-gel method. The structural and electrochemical properties of the sample were investigated using X-ray diffraction spectroscopy (XRD) and the galvanostatic charge-discharge method. Rietveld analysis of the XRD patterns shows this compound as having the α-NaFeO 2 structure (R3m; a = 2.8670(4) A, and 14.279(3) A in hexagonal setting). Li 1 . 0 5 [Ni 0 . 3 5 Co 0 . 2 5 Mn 0 . 4 ]O 2 has a discharge capacity of 164 mAh/g in the voltage range 2.8-4.5 V vs Li/Li + , a stable capacity on cycling, and good rate capability in the current range 0.1-4.0 C. When the voltage range is increased to 2.8-4.8 V, it yields a capacity of 187 mAh/g, but exhibits a significant loss of capacity during cycling. The results indicate that this novel cathode material should be useful for lithium-ion cells because it has a lower cost than LiCoO 2 -containing cells, and high performance.

The electrochemical behavior of Ni(OH) 2 in KOH solution containing aluminum hydroxide

In this paper Co-doped Al-substituted α-Ni(OH) 2 was prepared by a homogeneous precipitation method and its electrochemical behavior, in two kinds of electrolyte (7 M KOH solution and 7 M KOH saturated with Al(OH) 3), was investigated by galvanostatic charge-discharge method, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical properties of the commercial β-Ni(OH) 2 in both electrolyte was also studied in order to compare with that of α-Ni(OH) 2. The results show that Co-doped Al-substituted α-Ni(OH) 2 has the largest capacity in 7 M KOH solution (300 mAh g −1). The addition of Al to KOH solution is harmful to the reversible capacity and cycle life of both α-Ni(OH) 2 and β-Ni(OH) 2. X-ray diffraction (XRD) patterns show that, for Co-doped Al-substituted α-Ni(OH) 2, its turbostratic structure maintains after cycles in both alkaline electrolyte, despite the interlayer distance becoming smaller. For β-Ni(OH) 2, however, γ-NiOOH species appeared after cycling in both electrolyte and its content is higher after cycling in 7 M KOH saturated with Al(OH) 3. And adding Al into KOH solution caused the decrease of solution conductivity and increased the apparent diffusion coefficient which is evidenced by electrochemical impedance spectroscopy.

Structural investigation and electrochemical behaviour of Li[Ni Li(1/3−2/3)Mn(2/3−/3)]O2 compounds by a simple combustion method

Abstract Li[NixLi(1/3−2x/3)Mn(2/3−x/3)]O2 (x=0.17, 0.25, 0.33, 0.5) compounds have been prepared by a simple combustion method. Compared with the mixed hydroxide or sol–gel method, the combustion method is very simple, and will therefore reduce the manufacturing cost of the cathode material. The structural and electrochemical properties of the samples were investigated using X-ray diffraction spectroscopy (XRD) and the galvanostatic charge–discharge method. Rietvelt analysis of the XRD patterns shows that these compounds can be classified as α-NaFeO2 structure type.Compounds with high Ni content (x=0.25–0.5 in Li[NixLi(1/3−2x/3)Mn(2/3−x/3)]O2) appear to be composed of two phases, namely Ni-rich and Ni-deficient phases with the same α-NaFeO2 structure. By contrast, the Li[Ni0.17Li0.22Mn0.61]O2 compound with a low Ni content has good phase integrity with only a single phase. The initial charge–discharge and irreversible capacity become larger as x in Li[NixLi(1/3−2x/3)Mn(2/3−x/3)]O2 decreases. The Li[Ni0.50Mn0.50]O2 compound has a relatively low initial discharge capacity of 200 mAh g−1 and exhibits a large loss in capacity during cycling. On the other hand, Li[Ni0.17Li0.22Mn0.61]O2 and Li[Ni0.25Li0.17Mn0.58]O2 compounds give high initial discharge capacities of over 245 mAh g−1 and a stable cycle performance in the voltage range 4.8–2.0 V. The XRD and electrochemical results suggest that the simple combustion method is more appropriate for synthesizing Li[NixLi(1/3−2x/3)Mn(2/3−x/3)]O2 compounds with low Ni content.

Capacitive and textural characteristics of hydrous manganese oxide prepared by anodic deposition

The amorphous hydrous manganese oxide (denoted as a-MnO x · nH 2O) was anodically deposited from the MnSO 4 solutions of various pH values. The capacitive characteristics and stability of this oxide without and with annealing in air for 2 h up to 400 °C were systematically investigated in aqueous electrolytes through means of cyclic voltammetry (CV) and the constant-current charge–discharge method. The redox properties of a-MnO x · nH 2O were strongly affected by the electrolytes employed and this oxide exhibited ideally capacitive behavior in 0.1 M Na 2SO 4 and 0.3 M KCl. The stability of this amorphous hydrous oxide was enhanced by the annealing treatment while its capacitance was gradually decreased with increasing the annealing temperature. The amorphous structure and surface morphologies of a-MnO x · nH 2O with annealing at different temperatures were, respectively, examined in terms of the X-ray diffraction (XRD) patterns and scanning electron microscopic (SEM) photographs. The oxidation states of these a-MnO x · nH 2O deposits were studied by X-ray photoelectron spectroscopy (XPS).

All solid electric double layer capacitors based on Nafion ionomer

The aim of the present work is to demonstrate that an efficient all solid electric double layer capacitor (EDLC) may be realised with electrolyte membrane and carbon based electrodes prepared by using a Nafion ionomer solution. Polymer membrane was prepared by a casting method. Electrodes were prepared with two overlapped layers formed of a carbon–Nafion layer and a carbon paper substrate. Three different electrolyte separators in capacitor configuration have been tested and compared: (1) a commercial Nafion 115 membrane (N115), (2) a membrane prepared by casting the Nafion 1100 solution (NRG50) and (3) a porous glass fibre matrix impregnated with a 1 M H 2SO 4 solution (FVH2SO4). The membrane and electrodes assemblies (MEA) had thickness of 0.6–0.8 mm and geometric area of 4 cm 2. The EDLCs characteristics have been studied by conductivity, cyclic voltammetry and DC charge–discharge methods. Proton conductivities of 5.7×10 −2 and 3.1×10 −2 S cm −1 have been measured at room temperature for the N115 and the NRG50, respectively. Specific capacity of 13.2 F g −1 has been obtained by capacitor utilising the cast Nafion membrane. This value is 70% of specific capacity obtained from the capacitor using sulphuric acid and about 140% of that using Nafion 115.

Polypyrrole and poly(3-methyl thiophene)-based solid state redox supercapacitors using ion conducting polymer electrolyte

Polypyrrole (pPy) and poly(3-methyl thiophene) (pMeT)-based Type I and Type II solid state redox supercapacitors have been constructed using polymeric electrolytes, polyvinyl alcohol (PVA)–H 3PO 4 blend and polyethylene oxide (PEO)–NaClO 4 complex plasticised with polyethylene glycol (PEG) and gel electrolyte, polymethyl methacrylate (PMMA)–ethylene carbonate (EC)–propylene carbonate (PC)–NaClO 4. The performance characteristics of the capacitor cells have been evaluated using galvanostatic charge–discharge method. The polypyrrole-based symmetrical Type I capacitor cells show almost symmetrical charge–discharge characteristics with the discharge capacitance of 8.0–15.0 mF cm −2. The same order of specific capacitance has been observed for pMeT-based Type I capacitors but their working voltage range is limited between 0.5 and 1.0 V. The asymmetrical Type II capacitor cells show the polarity-dependent behaviour in which the working voltage limit and capacitance values depend upon the polarity of the applied charging current.

MnO2-polypyrrole conducting polymer composite electrodes for electrochemical redox supercapacitors

Redox supercapacitors using electrochemically synthesised MnO2-polypyrrole composite electrodes have been fabricated with different electrolytes, namely polymer electrolyte film (polyvinyl alcohol, PVA-H3PO4 aqueous blend), aprotic liquid electrolyte (LiClO4-propylene carbonate, PC) and polymeric gel electrolyte [poly methyl methacrylate, (PMMA)-Ethylene carbonate (EC)-Propylene carbonate (PC)-NaClO4]. The capacitors have been characterised using galvanostatic charge-discharge methods. The cell with aqueous PVA-H3PO4 shows non-capacitive behaviour owing to some reversible chemical reaction of MnO2 with water while the MnO2-polypyrrole composite is found to be a suitable electrode material for redox supercapacitors with aprotic (non-aqueous) electrolytes. The solid state supercapacitor based on MnO2-polypyrrole composite electrodes with gel electrolyte gives stable values of capacitance of 10.0–18.0 mF cm−2 for different discharge current densities.