Investigation of the charge/discharge characteristics of aqueous zinc–ferric chloride batteries

In a Zn–FeCl₃ battery, zinc granules were used as the anode and ammonium chloride as the electrolyte in both the anode and cathode zones, with ferric chloride as the active cathode substance and carbon felt as an inert cathode. A PE-01 homogeneous membrane was used as the membrane between the anode and cathode zones, with 100 ml of solution in both the anode and cathode zones. The charge/discharge characteristic of the battery was investigated for various concentrations of ferric chloride and ammonium chloride. At present, there are still some difficulties in using this zinc–ferric chloride battery as a rechargeable battery because zinc cannot be electrodeposited very well. However, it can possibly be used as a fuel cell and the operating lifetime of the fuel cell is very long. The actual energy density of a Zn–FeCl₃ fuel cells is approximately equal to the actual energy density of a Pb–PbO₂ battery. When a mixed solution of 2 M ferric chloride and 2 M ammonium chloride was used in the cathode zone with 4–5 M ammonium chloride in the anode zone, a better discharge characteristic was obtained, with a discharge time of approximately 14–15 h at 5 Ω. The most remarkable advantages for Zn–FeCl₃ fuel cell are that both zinc and ferric chloride are very cheap and environmentally friendly, with flat discharge voltage characteristics.     

The electrochemical properties of /polyaniline composites

The La_0.7Mg_0.25Ti_0.05Ni_2.975Co_0.525 (AB₃) alloy was modified with different contents of polyaniline (PANI) through ball milling. XRD, SEM and FTIR were used to characterize the properties of the AB₃/x PANI composites (x=1, 2, 3 and 4 wt%). The effects of PANI on the electrochemical properties of AB₃ alloy electrode were studied by charge–discharge, electrochemical impedance spectroscopy (EIS), linear polarization (LP) and potentiostatic discharge experiments. The XRD, SEM and FTIR results showed that ball milling did not change the characterizations of PANI and AB₃ alloy but decreased the average particle size of AB₃ alloy. The charge–discharge results indicated that the maximum discharge capacity of AB₃ alloy electrode decreased with the addition of PANI. However, the discharge cycle stability of AB₃/PANI composite electrodes increased firstly and then decreased with the increase in PANI content. The EIS and LP curves showed the same trends with the discharge cycle stability. The hydrogen diffusion coefficients of AB₃/PANI composites were estimated from the potentiostatic discharge curves, indicated the opposite trend with the discharge cycle stability. When the PANI content was equal to 3 wt%, the AB₃/PANI composite electrode exhibited an optimal electrochemical kinetic property.     

Synthesis of polyaniline/graphite composite as a cathode of Zn-polyaniline rechargeable battery

The characteristics of polyaniline/graphite composites (PANi/G) have been studied in aqueous electrolyte. PANi/G films with different graphite particle sizes were deposited on a platinum electrode by means of cyclic voltammetry. The film was employed as a positive electrode (cathode) for a Zn-PANi/G secondary battery containing 1.0 M ZnCl₂ and 0.5 M NH₄Cl electrolyte at pH 4.0. The cells were charged and discharged under a constant current of 0.6 mA cm⁻². The assembled battery showed an open-circuit voltage (OCV) of 1.55 V. All the batteries were discharge to a cut off voltage of 0.7 V. Maximum discharge capacity of the Zn-PANi/G battery was 142.4 Ah kg⁻¹ with a columbic efficiency of 97–100% over at least 200 cycles. The mid-point voltage (MPV) and specific energy were 1.14 V and 162.3 Wh kg⁻¹, respectively. The constructed battery showed a good recycleability. The structure of these polymer films was characterized by FTIR and UV–vis spectroscopies. Electrochemical impedance spectroscopy (EIS) was used as a powerful tool for investigation of charge transfer resistance in cathode material. The scanning electron microscopy (SEM) was employed as a morphology indicator of the cathodes.     

Fabrication and electrochemical performances of porous carbon nanotubes/polyaniline-modified carbon nanotube fiber

通过低电压电泳沉积的方法在碳纳米管纤维（CNF）表面沉积多孔碳纳米管（CNTs）,然后在其表面电化学沉积一层聚苯胺（PANI）,得到CNTs@PANI三维多孔网络结构修饰的核-鞘型纤维电极材料。通过扫描电镜、透射电镜和拉曼光谱表征电极材料表面形貌和微观结构,并利用电化学工作站测试电化学性能,研究结果表明,沉积的多孔CNTs结构可以为PANI提供更多的氧化还原反应活性位点,而PANI也具有固定CNTs的作用,在电流密度为1 mA/cm²时,CNTs和PANI修饰的电极面积比电容达77.28 mF/cm²。以聚二甲基硅氧烷薄膜为基底、PVA-H₃PO₄为电解质制备的对称型固态柔性超级电容器在电流密度为0.25 mA/cm²时,面积比电容为61.25 mF/cm²,恒流充放电4000次后,电容值仍维持在80%,并且串联两个电容器可以点亮电压为1.8 V的LED灯泡。     

Electrocatalysis for dioxygen reduction by a μ-oxo decavanadium complex in alkaline medium and its application to a cathode catalyst in air batteries

The redox behavior of a decavanadium complex [(V=O)₁₀(μ₂-O)₉(μ₃-O)₃(C₅H₇O₂)₆] (1) was studied using cyclic voltammetry under acidic and basic conditions. The reduction potential of V(V) was found at less positive potentials for higher pH electrolyte solutions. The oxygen reduction at complex 1 immobilized on a modified electrode was examined using cyclic voltammetry and rotating ring-disk electrode techniques in the 1 M KOH solutions. On the basis of measurements using a rotating disk electrode (RDE), the complex 1 was found to be highly active for the direct four-electron reduction of dioxygen at −0.2 V versus saturated calomel electrode (SCE). The complex 1 as a reduction catalyst of O₂ with a high selectivity was demonstrated using rotating ring-disk voltammograms in alkaline solutions. The application of complex 1 as an oxygen reduction catalyst at the cathode of zinc–air cell was also examined. The zinc–air cell with the modified electrode showed a stable discharge potential at approximately 1 V with discharge capacity of 80 mAh g⁻¹ which was about five times larger than that obtained with the commonly used manganese dioxide catalyst.     

Polyaniline@spherical ordered mesoporous carbon/sulfur nanocomposites for high-performance lithium-sulfur batteries

Lithium-sulfur batteries have attracted a lot of attention in the recent years. However, the electrochemical performance of lithium-sulfur batteries is greatly affected owing to several issues. In this paper, we designed a polyaniline@spherical ordered mesoporous carbon/sulfur nanocomposite (PANI@S-OMC/S), and S-OMC/S was wrapped by PANI via in-situ polymerization. The inherently conducting nature of PANI increased conductivity of PANI@S-OMC/S electrode to improve the free transfer of electrons, and PANI shell also provided a barrier between the lithium polysulfides and electrolyte to further prevent the occurrence of the “shuttle effect”. Moreover, mesoporous pores are wonderful hosts to contain sulfur to trap the long-chain lithium polysulfides and prevent them from dissolving in electrolyte. A high initial discharge capacity of 1626 mAh/g was achieved for the PANI@S-OMC/S electrode in first cycle at 0.1 C, and the composite maintains 1338 mAh/g after 100 cycles while the coulombic efficiency still remains ～98%.     

Polyaniline/fullerene derivative nanocomposite for highly efficient supercapacitor electrode

The effect of intercalation of fullerene derivative Phenyl-C60-butyric acid methyl ester (PCBM) into polyaniline (PANI) matrix with different ratio is reported. The PANI/PCBMx (where x = 0, 2.5, 5 and 10) nanocomposites are characterized by UV-VIS spectroscopy, Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray diffraction spectroscopy (XRD). The results confirm that the PANI/PCBM nanocomposites are synthesized successfully. The prepared nanocomposites are cast onto Nickel foam as a current collector and tested as a supercapacitor electrode in 2 M KOH electrolyte using cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD). The effect of different current collector substrates including stainless steel, nickel metal and graphite sheet on the supercapacitor performance is compared. The electrochemical measurements show an improvement by more than two times in the specific capacitance of PANI/PCBM5 electrode compared to pure PANI electrode. It is found that, the specific capacitance is 2201 F/g at a current density of 2 A/g with a good rate capability of about 73% at 10 A/g. The energy and power densities of PANI/PCBM5 electrode are 61.9 W h/Kg and 2250 W/Kg, respectively. Furthermore, the PANI/PCBM5 electrode shows an excellent cycling stability with 96% of the capacity retention after 1000 cycles.     

Electrochemical characteristics of iron carbide as an active material in alkaline batteries

Electrochemical properties of iron carbide (Fe₃C) for use as an alkaline battery anode were investigated during charge–discharge cycles. Results of electrochemical measurements and Mössbauer spectroscopy suggested that Fe₃C is oxidized irreversibly to Fe₃O₄ during discharge processes and that the produced Fe₃O₄ is subsequently changed to Fe(OH)₂ and Fe during the charging process, raising the discharge/charge capacity in further galvanostatic cycles. In addition, the electrode particles were observed to be less than 100 nm in diameter and to be highly dispersed on the surface of carbon black. These phenomena seems to be caused by dissolution and deposition of Fe(OH)₂ and Fe via intermediate iron species, leading to exposure of a fresh Fe₃C surface to the electrolyte after the second discharge.     

Preparation and enhanced capacitance of core–shell polypyrrole/polyaniline composite electrode for supercapacitors

Polypyrrole (PPy) nanotubes were synthesized by using the complex of methyl orange (MO)/FeCl₃ as a template. Then the core–shell polypyrrole/polyaniline (PPy/PANI) composite was prepared by in situ chemical oxidation polymerization of aniline on the surface of PPy nanotubes. The morphology and molecular structure were characterized by transmission electron microscopy (TEM), infrared spectroscopy (IR) and X-ray diffraction (XRD). TEM images confirmed that the composite was core–shell nanotubes. The electrochemical properties of the PPy/PANI composite electrode were investigated by cyclic voltammetry (CV), galvanostatic charge–discharge and electrochemical impedance spectroscopy (EIS). The electrochemical experiments showed that the specific capacitance of the PPy/PANI composite was 416 F g⁻¹ in 1 M H₂SO₄ electrolyte and 291 F g⁻¹ in 1 M KCl electrolyte. Furthermore, the composite electrode exhibited a good rate capability and maintained 91% of initial capacity at a current density of 15 mA cm⁻² in 1 M H₂SO₄ electrolyte.     

New composite electrodes made of polypyrrole and graphite: Construction, optimization and characterization

In this work, new composite electrodes were developed, optimized and characterized for possible, future use in batteries and/or super-capacitors. These composite electrodes were prepared from chemically synthesized polypyrrole (Ppy), graphite carbon and Teflon and their physico-chemical performances were tested using different techniques. Their conductivity and porosity were investigated under various conditions. Their macroporous structure was also studied by the BET method. Two distinct electrochemical reactions were found to take place at these electrodes, including a redox reaction with insertion and expulsion of anions, and a capacitive reaction at the electrode/electrolyte interface. The specific capacity, experimentally obtained with an electrode containing 40 wt% of Ppy (99.6 mAh g⁻¹), was larger than the theoretical one, due to double-layer effects at the Ppy/electrolyte interface. The double-layer capacitance at the electrode/electrolyte interface of the composite electrodes, investigated by electrochemical impedance spectroscopy, was found to represent at most 0.1% of the total electrode capacitance.     

Charge–discharge and high temperature reaction of LiCoO2 in ionic liquid electrolytes based on cyano-substituted quaternary ammonium cation

The charge–discharge performance of LiCoO₂ positive electrode was observed in a mixed electrolyte system consisting of two ionic liquids: cyano-substituted quaternary ammonium bis(trifluoromethane)sulfoneimide (TFSI) and a same-anion salt of 1-ethyl-3-methyl imidazolium (EMI). The positive electrode exhibited a discharge capacity rather close to the theoretical one when N,N,N,N-cyanoethyl trimethyl ammonium salt was applied. Differential scanning calorimetry (DSC) studies revealed that these electrolytes exhibited exotherm only around 260 °C, 50 °C higher than conventional carbonate-based electrolytes. This is the first attempt to reveal the thermal stability of ionic liquid electrolyte under a practical situation.     

电活性双酚A的合成及其锂离子电池防过充性能研究

对双酚A进行结构修饰,经甲醚化、氰基取代,设计合成了2,2-双-(4-(β-氰基乙氧基)苯基)丙烷（DBDCN）、2-(4-(β-氰基乙氧基)苯基)-2'-(4-甲氧基苯基)丙烷（DBMCN）和2,2-双-(4-甲氧基苯基)丙烷（DBMB）,将三种化合物作为锂离子电池的防过充添加剂开展研究。在锂离子电池电解液1 mol/L LiPF₆/[碳酸乙烯酯（EC）+ 碳酸二乙酯（DEC） + 碳酸甲乙酯（EMC） （1∶1∶1,体积比）]中分别添加0.1 mol/L的DBDCN、DBMB和DBMCN,采用循环伏安、过充测试、电化学阻抗、恒流充放电和扫描电子显微镜等手段研究DBDCN、DBMB和DBMCN的防过充性能,并探讨添加剂与正极材料LiFePO₄的相容性。这些化合物的氧化还原电位均为4.1 V,显著提高了电池的过充保护。100%过充测试和5 V截止电压测试结果表明,DBMB的防过充性能明显优于DBDCN和DBMCN。以0.5 C倍率电流循环100圈,基础电解液和分别添加0.1 M DBDCN、DBMB、DBMCN的电池放电比容量分别为134.5 mA∙h/g、135.3 mA∙h/g、132.8 mA∙h/g和127.0 mA∙h/g,容量保持率分别为87.7%、87.0%、89.5%和84.3%。结果表明,DBMB对电池防过充作用最明显。     

In situ neutron radiography of lithium-ion batteries: the gas evolution on graphite electrodes during the charging

In situ neutron radiography (NR) was used to study the gas evolution on graphite electrodes in lithium-ion cells containing different PVDF-based gel-type electrolytes. The amount of gas bubbles and channels was calculated by image analysis. Gas production was extremely high in the case of the electrolyte containing ethylene carbonate (EC) and propylene carbonate (PC) (2:3, w/w), 1 M LiClO₄. About 60% of the electrode surface consisted of the gas phase which resulted in an inhomogeneous local current distribution. In contrast, the electrolyte containing EC and γ-butyrolactone (GBL) (1:1, w/w), 1 M LiBF₄ only showed a small increase of the gas volume between the electrodes of about 3%. In situ NR also revealed the displacement of the electrolyte due to gas evolution and volume changes of the electrodes.     

Effect of compounding process on the structure and electrochemical properties of ordered mesoporous carbon/polyaniline composites as electrodes for supercapacitors

Polyaniline (PANI) loaded ordered mesoporous carbon (OMC) composites were prepared via different processes, involving the in situ polymerization of aniline in the presence of OMC or its precursor and the direct physical mixing method. On the basis of analyzing the morphologies and structures of these three OMC/PANI composites, the influence of compounding processes on the electrochemical properties as electrodes for supercapacitors was first investigated. It was observed that regardless of compounding process, two distinct electrochemical behaviors took place on all of the composite electrodes, including a redox reaction with insertion and deinsertion of electrolyte ions, and electrostatic attraction at the electrode/electrolyte interface. Additionally, these OMC/PANI composites showed higher specific capacitances compared with pure OMC and PANI. Most significantly, the in situ synthesized OMC/PANI composite using OMC as a starting material exhibited the highest specific capacitance of 747 F g⁻¹ at a current density of 0.1 A g⁻¹ and excellent rate capability, which was attributed to the high degree of dispersion of PANI and the contact of PANI with electrolyte as well as the double fixing effects of surface and mesopore of OMC on PANI.     

The use of polyaniline films on flexible tape for supercapacitor applications

A sticky surface of a tape was adhered to a graphite surface and then the tape was peeled off. The insulator tape was coated with thin graphite and became conductive in order to use flexible tape as a current collector. Aniline was electrodeposited onto a flexible tape substrate having graphite layer by electrochemical polymerization method from an aqueous (H₂SO₄ solution containing aniline monomers) and non-aqueous media (a deep eutectic solvent containing aniline). The prepared polymeric electrodes were characterized by Fourier transform infrared spectroscopy, Raman, thermogravimetric analysis and scanning electron microscopy techniques. The electrochemical properties of coated and uncoated electrodes were also examined by cyclic voltammetry and galvanostatic charge discharge techniques. The polyaniline (PANI) coated tape can be used as a flexible electrode in supercapacitor applications because PANI coated electrodes are highly electroactive in Na₂SO₄ electrolyte. After 3000 cycles, the capacitance retention of PANI film electrodeposited from Ethaline bath was 90%, while the areal capacitance of PANI film obtained from acidic medium reaches 50% after 500 cycles. As PANI electrode is stable in an ionic liquid for long cycling, Ethaline ionic liquid can be used as electrolyte for PANI based supercapacitor electrode. PANI coated graphite on tape, which is prepared in an easy and inexpensive way is a promising flexible material for high performance supercapacitors.     

Exploration of aqueous zinc–hydrogen peroxide batteries

In zinc–hydrogen peroxide batteries, an active metal ? zinc piece is used as the anode and ammonium chloride is used as the electrolyte in the anode zone. A soluble oxidant, hydrogen peroxide, is used as the active cathode substance, and sulfuric acid as an electrolyte in the cathode zone. Carbon felt, the sum of two apparent areas of which is 24 cm², is used as an inert cathode with a PE‐01 homogeneous membrane between the anode and cathode zones and 50 mL of solution in both the anode and cathode zones. The discharge characteristics of the batteries at 5 Ω were investigated for various concentrations of hydrogen peroxide, sulfuric acid and ammonium chloride solutions. When a 5‐M ammonium chloride solution was used in the anode zone with a 3.2‐M sulfuric acid and 3.52‐M hydrogen peroxide mixed solution in the cathode zone, an average discharge current of 190 mA, an average output voltage of approximately 0.95 V and an actual gravimetric energy density of 42.73 W h kg^?1 were obtained, and the discharge time of the batteries was more than 30 h. Copyright © 2011 John Wiley & Sons, Ltd.     

Lithium metal rechargeable cells using Li2MnO3 as the positive electrode

Rechargeable lithium cells have been fabricated using Li₂MnO₃ as the positive electrode, lithium metal as the negative electrode and 1 M LiAsF₆ in DMC/EC (1:1 v/v) as the electrolyte. Charge/discharge behaviour was evaluated and the cells showed improved performance after the first five cycles. The cells could be cycled at least 15 times without loss in capacity. Similar electrochemical trends were observed with LiPF₆ in a EC/DEC mixture.     

Electrochemical characteristics and cycle performance of LiMn2O4/a-Si microbattery

A LiMn₂O₄ thin film and an amorphous Si (a-Si) thin film were prepared by radio-frequency (rf) magnetron sputtering. Each thin film was electrochemically evaluated by cyclic voltammetry (CV) and galvanostatic cycling. The rate of capacity fade on cycling was monitored as a function of the voltage window and current density. This was compared with the cycle performance of cathode and anode using two kinds of electrolyte, 1 M LiPF₆ in EC/DMC and PC, for 100 cycles. It was found that the discharge capacity of optimized LiMn₂O₄/a-Si full-cell reached 24 μAh/(cm²-μm) in the first cycle, and a reversible capacity of about 16 μAh/(cm² μm) was still maintained after 100 cycles. In a voltage window of 3.0–4.2 V, LiMn₂O₄/a-Si full-cell exhibits relatively stable cycle performance compared to a voltage window of 2.75–4.2 V.     

Anthraquinone modified carbon fabric supercapacitors with improved energy and power densities

Supercapacitors with improved energy and power densities have been constructed with anthraquinone modified carbon fabric (Spectracarb 2225) as the negative electrode and unmodified carbon fabric as the positive electrode. A Nafion separator and 1 M sulfuric acid electrolyte were employed. The performances of the supercapacitors were characterized by cyclic voltammetry and constant current discharging. Use of the anthraquinone modified electrode as the negative electrode (anode during discharge) in the supercapacitor provides 40% higher average capacitance, 56–86% higher energy density, and improved power duration.     

Sm0.5Sr0.5CoO3 + Sm0.2Ce0.8O1.9 composite cathode for cermet supported thin Sm0.2Ce0.8O1.9 electrolyte SOFC operating below 600 °C

The cathode is a key component in low temperature solid oxide fuel cells. In this study, composite cathode, 75 wt.% Sm_0.5Sr_0.5CoO₃ (SSC) + 25 wt.% Sm_0.2Ce_0.8O_1.9 (SDC), was applied on the cermet supported thin SDC electrolyte cell which was fabricated by tape casting, screen-printing, and co-firing. Single cells with the composite cathodes sintered at different temperatures were tested from 400 to 650 °C. The best cell performance, 0.75 W cm⁻² peak power operating at 600 °C, was obtained from the 1050 °C sintered cathode. The measured thin SDC electrolyte resistance R_s was 0.128 Ω cm² and total electrode polarization R_p(a + c) was only 0.102 Ω cm² at 600 °C.