A high energy density lithium/sulfur–oxygen hybrid battery

In this paper we introduce a lithium/sulfur–oxygen (Li/S–O₂) hybrid cell that is able to operate either in an air or in an environment without air. In the cell, the cathode is a sulfur–carbon composite electrode containing appropriate amount of sulfur. In the air, the cathode first functions as an air electrode that catalyzes the reduction of oxygen into lithium peroxide (Li₂O₂). Upon the end of oxygen reduction, sulfur starts to discharge like a normal Li/S cell. In the absence of oxygen or air, sulfur alone serves as the active cathode material. That is, sulfur is first reduced to form a soluble polysulfide (Li₂S_x, x ≥ 4) that subsequently discharges into Li₂S through a series of disproportionations and reductions. In general, the Li/S–O₂ hybrid cell presents two distinct discharge voltage plateaus, i.e., one at ～2.7 V attributing to the reduction of oxygen and the other one at ～2.3 V attributing to the reduction of sulfur. Since the final discharge products of oxygen and sulfur are insoluble in the organic electrolyte, it is shown that the overall specific capacity of Li/S–O₂ hybrid cell is determined by the carbon composite electrode, and that the specific capacity varies with the discharge current rate and electrode composition. In this work, we show that a composite electrode composed by weight of 70% M-30 activated carbon, 22% sulfur and 8% polytetrafluoroethylene (PTFE) has a specific capacity of 857 mAh g^?1 vs. M-30 activated carbon at 0.2 mA cm^?2 in comparison with 650 mAh g^?1 of the control electrode consisting of 92% M-30 and 8% PTFE. In addition, the self-discharge of the Li/S–O₂ hybrid cell is expected to be substantially lower when compared with the Li/S cell since oxygen can easily oxidize the soluble polysulfide into insoluble sulfur.     

Sonochemical synthesis of amorphous manganese oxide coated on carbon and application to high power battery

The nanocomposite material of amorphous manganese oxide and acetylene black (HSMO/AB), was synthesized by sonochemical method. The acetylene black particles were homogeneously coated with amorphous manganese oxide. In order to demonstrate that these characteristic structures were suitable for rapid discharge–charge, the composite material was tested under large current density. The result exhibited 185 mAh g⁻¹ in specific discharge capacity under 10 A g⁻¹ in current density. Assuming that an operating voltage of 2.5 V, this capacity corresponded 20 kW kg⁻¹ in power density and 90 Wh kg⁻¹ in energy density.     

Electrochemical profile of nano-particle CoAl double hydroxide/active carbon supercapacitor using KOH electrolyte solution

A nano-structured CoAl double hydroxide with an average particle size of 60–70 nm was prepared by a chemical co-precipitation. It was used as a positive electrode for the asymmetric hybrid supercapacitor in combination with an active carbon negative electrode in KOH electrolyte solution. The electrochemical capacitance performance of this kind of hybrid supercapacitor was investigated by means of cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge–discharge tests. A specific capacitance of 77 F g⁻¹ with a specific energy density of 15.5 wh kg⁻¹ was obtained for the hybrid supercapacitor within the voltage range of 0.9–1.5 V. The supercapacitor also exhibits a good cycling performance and keep 90% of initial capacity over 1000 cycles.     

Properties of containing Sn nanoparticles activated carbon fiber for a negative electrode in lithium batteries

Activated carbon fiber (ACF) containing Sn nanoparticles were prepared by impregnation and were investigated as a negative electrode material in lithium batteries. The tin particle size was controlled by selecting an ACF with an adequate surface structure. This Sn/ACF composite cycled versus Li metal showed a first discharge capacity as high as 200 mAh g⁻¹ compared to the pristine ACF which showed only 87 mAh g⁻¹. Excellent cyclability with these composites was obtained with ACF BET SSA as large as 2000 m² g⁻¹ and 30 wt.% Sn.     

Electrocatalytic characteristics of the metal hydride electrode for advanced Ni/MH batteries

The electrocatalytic characteristics of a metal hydride (MH) electrode for advanced Ni/MH batteries include the hydrogen adsorption/desorption capability at the electrode/electrolyte interface. The hydrogen reactions at the MH electrode/electrolyte interface are also related to factors such as the surface area of the MH alloy powder and the nature of additives and binder materials. The high-rate discharge capability of the negative electrode in a Ni/MH battery is mainly determined by the mass transfer process in the bulk MH alloy powder and the charge transfer process at the interface between the MH alloy powder and the electrolyte. In this study, an AB₅-type hydrogen-absorbing alloy, Mm (Ni, Co, Al, Mn)_5.02 (where Mm denotes Mischmetal, comprising 43.1 wt.% La, 3.5 wt.% Ce, 13.3 wt.% Pr and 38.9 wt.% Nd), was used as the negative MH electrode material. The MH electrode was charged and discharged for up to 200 cycles. The specific discharge capacity of the alloy electrode decreases from a maximum value of 290–250 mAh g⁻¹ after 200 charge/discharge cycles. A cyclic voltammetry technique is used to analyze the charge transfer reactions at the electrode/electrolyte interface and the hydrogen surface coverage capacity.     

The capacitive characteristics of supercapacitors consisting of activated carbon fabric–polyaniline composites in NaNO3

A sandwich-type supercapacitor consisting of two similar activated carbon fabric–polyaniline (ACF–PANI) composite electrodes was demonstrated to exhibit excellent performance (i.e., highly reversibility and good stability) in NaNO₃. Polyaniline with the charge density of polymerization less than or equal to 9 C cm⁻² synthesized by means of a potentiostatic method showed a high specific capacitance of 300 F g⁻¹. Influences of the polymerization charge density (i.e., the polymer loading) on the capacitive characteristics of ACF–PANI composites were compared systematically. The capacity of an ACF–PANI electrode reach ca. 3.4 F cm⁻² (a 100% increase in total capacity) when the charge density of polymerization is equal to 9 C cm⁻². The surface morphology of these ACF–PANI composites was examined by a scanning electron microscope (SEM).     

Carbon anode for dry-polymer electrolyte lithium batteries

A spherical carbon material of meso-carbon microbead (MCMB) was examined as an anode in a polyethylene oxide (PEO) based polymer electrolyte lithium battery. The electrochemical performance of the carbon electrode with the polymer electrolyte depended on the electrode thickness and the particle size of MCMB. The 30 μm-thick electrode of MCMB with the particle size of 20–30 μm showed a reversible capacity comparable with that in a liquid electrolyte, but the 100 μm-thick electrode showed a half of the 30 μm-thick electrode. The smaller particle size of 5–8 μm exhibited a high irreversible capacity at the first charge–discharge cycle. The reaction heat between MCMB and the polymer electrolyte was 0.5 J mAh^?1, which was much lower compared to those between lithium metal and the polymer electrolyte, 1.2 J mAh^?1, and MCMB and conventional liquid electrolyte, 4.3 J mAh^?1.     

Multilayered Sn–Zn–Cu alloy thin-film as negative electrodes for advanced lithium-ion batteries

Sn-based alloy compounds have been considered as possible alternatives for carbon in lithium-ion batteries and attract great attentions because of their large electrochemical capacity compared with that of carbon. In this work, a multilayered Sn–Zn/Zn/Cu alloy thin-film electrode has been prepared by electroplating method. The structure and performance of the electrode before and after heat treatment have been investigated. It is found that Cu₆Sn₅ phase and multilayered structure in electrode are formed after heat treatment. This optimized structure of the heat-treated electrode results in enhanced cycle life. The capacity of the electrode is over 320 mA h g⁻¹ after 100 cycles; though it is 83 mA h g⁻¹ after 20 cycles for as-plated electrode. The Sn–Cu and Zn–Cu alloy formed a network in the electrode is considered to strengthen the electrode and reduce the effect of volume expansion and phase transition during cycling. Experimental results also reveal that lower cut-off potential (0.05 V) for charging and higher one (1.2 V) for discharging result in long cycle life and high discharge capacity, respectively. The reason of capacity decay of the heat-treatment electrode during cycling has also been investigated. All these results show that the electroplated Sn–Zn-based alloy film on Cu foil would be a promising negative material with high capacity and low cost for Li secondary batteries.     

Supercapacitors based on conducting polymers/nanotubes composites

Three types of electrically conducting polymers (ECPs), i.e. polyaniline (PANI), polypyrrole (PPy) and poly-(3,4-ethylenedioxythiophene) (PEDOT) have been tested as supercapacitor electrode materials in the form of composites with multiwalled carbon nanotubes (CNTs). The energy storage in such a type of composite combines an electrostatic attraction as well as quick faradaic processes called pseudo-capacitance. It has been shown that carbon nanotubes play the role of a perfect backbone for a homogenous distribution of ECP in the composite. It is well known that pure conducting polymers are mechanically weak, hence, the carbon nanotubes preserve the ECP active material from mechanical changes (shrinkage and breaking) during long cycling. Apart of excellent conducting and mechanical properties, the presence of nanotubes improves also the charge transfer that enables a high charge/discharge rate. For an optimal use of ECPs in electrochemical capacitors, a special electrode composition with ca. 20 wt.% of CNTs and a careful selection of the potential range is necessary. The capacitance values ranging from 100 to 330 F g⁻¹ could be reached for different asymmetric configurations with a capacitor voltage from 0.6 to 1.8 V. It is also noteworthy that such a type of ECP/CNTs composite does not need any binding substance that is an important practical advantage.     

SnO2-carbon composites for lithium-ion battery anodes

A SnO₂-carbon composite prepared by heat treating a mixture of colloidal SnO₂ and sucrose demonstrated a reversible lithium storage capacity of 680 mA h/g on the 1st cycle. The discharge curve of the composite did not exhibit the 1.0 V plateau characteristic of SnO₂. The high reversible capacity of the composite suggests that lithium is stored in both tin and carbon. The composite demonstrated reduced capacity fade over SnO₂ as well as SnO:graphite and Sn:graphite composites.     

Electrochemical properties of Zn/orange dye aqueous solution/carbon cell

An investigation is made of the electrochemical properties of a Zn/orange dye aqueous solution/carbon cell. In this cell, a solution of 3 wt.% orange dye (C₁₇H₁₇N₅O₂) in distilled water is used as the electrolyte and zinc and carbon rods serve as electrodes. The cell is fabricated in a cylindrical glass vessel and has a length and a diameter of 4 and 2 cm, respectively. The discharge voltage–current, charge voltage/current–time and discharge voltage/current–time studies are made. It is found that the cell is rechargeable. The open-circuit voltage and short-circuit current of the fully charged cell is 1.5 V and 0.45 mA, respectively. The efficiency of current discharge/charge is 67%. The discharge voltage/current–time characteristics exhibit stable and constant behaviour.     

Discharge process of Li/PVdF/S cells at room temperature

The Li/PVdF/S cell showed the first discharge capacity of 1268 mAh g⁻¹, which was about 78% utilization of theoretical value. There were two plateau regions at the first discharge curve. From the XRD, DSC results of the sulfur electrode, elemental sulfur disappeared at the upper plateau region and Li₂S was formed at the low plateau region. We suggested the discharge process of Li/polymer electrolyte/S cell. The elemental sulfur changed into Li₂S_n (n > 4) and subsequently changed into Li₂S at a lower plateau potential region.     

Electrochemical characterization on MnFe2O4/carbon black composite aqueous supercapacitors

MnFe₂O₄–carbon black (CB) composite powders synthesized by a co-precipitation method have been characterized and optimized for their electrochemical properties for supercapacitor applications. The composite shows pseudocapacitance in electrolyte solutions of alkali and alkaline chlorides, sulfates and sulfites. For the chlorides and sulfates electrolytes, the pseudocapacitance has been identified, by in situ X-ray absorption near-edge spectroscopy study, to involve charge-transfer at both the Mn and Fe sites of the ferrite. In 1 M NaCl_(aq), the composite electrode exhibits an operating potential window of 1.0 V with a maximum leakage current of 0.3 mA F⁻¹, and it exhibits far superior cycling stability to amorphous MnO₂ electrode. Both the specific capacitance and self-discharge behavior of the composite electrode depend strongly on the composite composition. The optimum capacitance occurs at ferrite:CB weight ratio of 7:3, which gives reduced self-discharge rate as compared with CB. The composite electrode also demonstrates capability of high-power delivery.     

Synthesis and characterization of high tap-density layered Li[Ni1/3Co1/3Mn1/3]O2 cathode material via hydroxide co-precipitation

Li[Ni_1/3Co_1/3Mn_1/3]O₂ was prepared by mixing uniform co-precipitated spherical metal hydroxide (Ni_1/3Co_1/3Mn_1/3)(OH)₂ with 7% excess LiOH followed by heat-treatment. The tap-density of the powder obtained was 2.38 g cm⁻³, and it was characterized using X-ray diffraction (XRD), particle size distribution measurement, scanning electron microscope-energy dispersive spectrometry (SEM-EDS) and galvanostatic charge–discharge tests. The XRD studies showed that the material had a well-ordered layered structure with small amount of cation mixing. It can be seen from the EDS results that the transition metals (Ni, Co and Mn) in Li[Ni_1/3Co_1/3Mn_1/3]O₂ are uniformly distributed. Initial charge and discharge capacity of 185.08 and 166.99 mAh g⁻¹ was obtained between 3 and 4.3 V at a current density of 16 mA g⁻¹, and the capacity of 154.14 mAh g⁻¹ was retained at the end of 30 charge–discharge cycles with the capacity retention of 93%.     

Analysis for electrolytic oxidation and reduction of PbSO4/Pb electrode by electrochemical QCM technique

In situ observations of the mass change were carried out using the electrochemical quartz crystal microbalance (EQCM) technique for the active materials in a lead–acid battery during charge–discharge. Lead sulfate was formed on the surfaces of the pure Pb and Pb–Ca–Sn alloys immersed in 4.50 kmol m⁻³ H₂SO₄ solution at 298 K. The rates of PbSO₄ formation on the Pb–0.08 mass% Ca–Sn alloys, which are the choice materials for grids in the valve-regulated lead–acid battery (VRLA), were inhibited by the presence of Sn. This fact observed by the EQCM technique was in good agreement with the results determined by the prolonged corrosion test of 604.8 ks at 348 K. This state, in which the PbSO₄ exists in the surface and the underlying Pb is not thoroughly reacted, corresponds to the state of active materials after discharge. During electrolytic oxidation, i.e. the charging of the positive electrode, the reaction of PbSO₄→PbO₂ could take place to decrease the electrode mass when the current density exceeded a critical value. On the other hand, the reaction of PbSO₄→Pb could readily proceed at just one-fourth the current density of the electrolytic oxidation during the electrolytic reduction of the PbSO₄/Pb electrode, i.e. the charging of the negative electrode.     

Synthesis and electrochemical properties of Mo-doped Li[Ni1/3Mn1/3Co1/3]O2 cathode materials for Li-ion battery

The layered Li[Ni_(1−x)/3Mn_(1−x)/3Co_(1−x)/3Mo_x]O₂ cathode materials (x = 0, 0.005, 0.01, and 0.02) were prepared by a solid-state pyrolysis method (700, 800, 850, and 900 °C). Its structure and electrochemical properties were characterized by XRD, SEM, XPS, cyclic voltammetry, and charge/discharge tests. It can be learned that the doped sample of x = 0.01 calcined at 800 °C shows the highest first discharge capacity of 221.6 mAh g⁻¹ at a current density of 20 mA g⁻¹ in the voltage range of 2.3–4.6 V, and the Mo-doped samples exhibit higher discharge capacity and better cycle-ability than the undoped one at room temperature.     

Cu5Si–Si/C composites for lithium-ion battery anodes

Cu₅Si–Si/C composites with precursor atomic ratio of Si:Cu = 1, 2 and 4.5 have been produced by high-energy ball-milling of a mixture of copper–silicon alloy and graphite powder for anode materials of lithium-ion battery. X-ray diffraction and scanning electron microscope measurements show that Cu₅Si alloy is formed after the intensive ball milling and alloy particles along with low-crystallite Si are interspersed in graphite uniformly. Cu₅Si–Si/C composite electrodes deliver a larger reversible capacity than commercialized graphite and better cyclability than silicon. The increase of copper amount in the composites decreases reversible capacity but improves cycling performance. Cu₅Si–Si/C composite with Si:Cu = 1 demonstrates an initial reversible capacity of 612 mAh g⁻¹ at 0.2 mA cm⁻² in the voltage range from 0.02 to 1.5 V. The capacity retention is respectively 74.5 and 70.0% at the 40th cycle at the current density of 0.2 and 1 mA cm⁻².     

High power BaFe(VI)O4/MnO2 composite cathode alkaline super-iron batteries

This short communication demonstrates that not only pure Fe(VI) cathodes, but also MnO₂/Fe(VI) composite cathodes can substantially enhance the high power discharge of alkaline batteries. The 2.8 Ω and 0.7 W high power discharge of alkaline cells are investigated for 3:1 and 1:1 composite MnO₂/BaFeO₄ cathode cells, provide discharge energies intermediate to that found in the (non-composite) BaFeO₄ cathode cell. At a constant 2.8 Ω load, the 1:1 composite MnO₂/BaFeO₄ cell delivers up to 40% higher energy capacity than the MnO₂ pure cathode alkaline cell, and up to three-fold the capacity of the constant 0.7 W power MnO₂ discharge.     

Tantalum oxide–ruthenium oxide hybrid(R) capacitors

A hybrid capacitor consisting of porous tantalum oxide anode electrode and ruthenium oxide cathode electrode was examined and characterized. The capacitor has a capacitance of 35 mF and an internal resistance of 45 mΩ. It was found that the capacitance was insensitive to current density up to 110 mA/cm², and temperature ranging from −70 to 50 °C. During dc charge and discharge cycles, the potential of the cathode electrode was within the electrochemical stability window. However, a sudden voltage-jump as high as 7.5 V could occur at the cathode electrode during a short circuit discharge. A simple model was established to describe the transient behavior of cathode and anode electrodes. It was found that the voltage-jump was proportional to the ratio of the internal resistance of the cathode electrode to the total resistance of the capacitor. The resistance distribution inside the capacitor was also determined to be 47, 28, and 25% from the cathode, anode, and electrolyte, respectively.     

Cresol–formaldehyde based carbon aerogel as electrode material for electrochemical capacitor

Carbon aerogels have been prepared through a polycondensation of cresol (Cm) with formaldehyde (F) and an ambient pressure drying followed by carbonization at 900 °C. Modification of the porous structures of the carbon aerogel can be achieved by CO₂ activation at various temperatures (800, 850, 900 °C) for 1–3 h. This process could be considered as an alternative economic route to the classic RF gels synthesis. The obtained carbon aerogels have been attempted as electrode materials in electric double-layer capacitors. The relevant electrochemical behaviors were characterized by constant current charge–discharge experiments, cyclic voltammetry and electrochemical impedance spectroscopy in an electrolyte of 30% KOH aqueous solution. The results indicate that a mass specific capacitance of up to 78 F g⁻¹ for the non-activated aerogel can be obtained at current density 1 mA cm⁻². CO₂ activation can effectively improve the specific capacitance of the carbon aerogel. After CO₂ activation performed at 900 °C for 2 h, the specific capacitance increases to 146 F g⁻¹ at the same current. Only a slight decrease in capacitance, from 146 to 131 F g⁻¹, was observed when the current density increases from 1 to 20 mA cm⁻², indicating a stable electrochemical property of carbon aerogel electrodes in 30% KOH aqueous electrolyte with various currents.