Synthesis and characterization of the iron/copper composite as an electrode material for the rechargeable alkaline battery

Iron/copper composite particles were synthesized by a chemical reduction method and then used as the anode material for a rechargeable alkaline battery. The particle size and structure of the samples were characterized by SEM and XRD. Their electrochemical performance was also studied. The results showed that the iron/copper composite prepared by this method is nanosized. Copper improves the electron transfer between particles, and the nanosized iron/copper composite not only has a high electrochemical capacity of up to 800 mAh g⁻¹(Fe to Fe(III)), but also has an excellent rate-capacity performance at a current density of 3200 mA g⁻¹. Compared with the iron nanoparticle without copper, the iron/copper composite sample maintains a smaller particle size during electrochemical cycling, and therefore improves the cycling stability of the iron electrode.     

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.     

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.     

All-solid-state rechargeable lithium batteries with Li2S as a positive electrode material

The Li₂S–Cu composite electrode materials were prepared by mechanical milling and applied to all-solid-state lithium cells using the Li₂S–P₂S₅ glass–ceramic electrolyte. The addition of Cu and the mechanical activation improved the electrochemical performance of Li₂S in all-solid-state cells. The In/Li₂S–Cu cells were charged and then discharged at room temperature, suggesting that Li₂S was utilized as a lithium source. The cells exhibited high discharge capacity of about 490 mAh g⁻¹ at the 1st cycle. The SEM and EDX analyses suggested that the amorphous Li_xCuS domain was partially formed by milling, and the domain played an important role in the improvement of capacity. The electrochemical reaction mechanism of the Li₂S–Cu composites was discussed on the basis of the mechanism of the S–Cu composite electrode.     

Structure and electrochemical properties of ball-milled Co-carbon nanotube composites as negative electrode material of alkaline rechargeable batteries

A series of cobalt-carbon nanotube (CNT) composites is synthesized by direct ball-milling of Co and CNT powders with different Co/CNT weight ratios. The microstructure, morphology and chemical state of the ball-milled Co-CNT composites are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). It is found that metallic Co nanoparticles of 50-100 nm in size are highly dispersed on the inactive CNT matrix after ball-milling. The electrochemical performance of Co-CNT composites as negative electrode material of alkaline rechargeable batteries is investigated by galvanostatic charge-discharge, linear polarization and cyclic voltammetry (CV) techniques. The results show that the Co-CNT composite (weight ratio 5/1, BM 10 h) displays the optimized electrochemical performance, including discharge capacity and cycle stability. The reversible faradaic reaction between Co and Co(OH)₂ is dominant for ball-milled Co-CNT composites.     

Novel hedgehog-like 5 V LiCoPO4 positive electrode material for rechargeable lithium battery

Hedgehog-like LiCoPO₄ with hierarchical microstructures is first synthesized via a simple solvothermal process in water-benzyl alcohol mixed solvent at 200 °C. Morphology and crystalline structure of the samples are characterized by scanning electron microscope, transmission electron microscopy and X-ray diffraction. The hedgehog-like LiCoPO₄ microstructures in the size of about 5-8 μm are composed of large numbers of nanorods in diameter of ca. 40 nm and length of ca. 1 μm, which are coated with a carbon layer of ca. 8 nm in thickness by in situ carbonization of glucose during the solvothermal reaction. As a 5 V positive electrode material for rechargeable lithium battery, the hedgehog-like LiCoPO₄ delivers an initial discharge capacity of 136 mAh g⁻¹ at 0.1 C rate and retains its 91% after 50 cycles, showing much better electrochemical performances than sub-micrometer LiCoPO₄ synthesized by conventional high-temperature solid-state reaction.     

Nano-NiOOH prepared by splitting method as super high-speed charge/discharge cathode material for rechargeable alkaline batteries

The present paper introduces a new method to prepare nano-NiOOH by oxidizing and cracking spherical Ni(OH)₂ of nano-structure in NaClO–NaOH solution. The prepared samples were characterized by X-ray powder diffraction (XRD), field emission scan electronic microscope (FESEM) and transmission electron microscopy (TEM). Results indicate that the synthesized sample is nano-NiOOH rod of 60–150 nm in width. The charge/discharge tests show that the nano-NiOOH cathode shows good cycling reversibility at high current density of 10,000 mA g⁻¹, provides a high capacity of 276 mAh g⁻¹ and reduces the charge time to as short as 1.83 min. Furthermore, the nano-NiOOH still keeps a reversible capacity of 93.7% after 120 cycles at a super high charge/discharge current of 10,000 mA g⁻¹, showing a good charge/discharge property.     

The effect of dispersion of nano-carbon on electrochemical behavior of Fe/nano-carbon composite electrode

In order to estimate the effect of the dispersion of nano-carbon species into a composite electrode, ultrasonic pretreatments under various conditions have been carried out for two kinds of nano-carbons, vapor grown carbon fiber (VGCF) and acetylene black, before preparing a composite electrode with iron powder. The cyclic voltammetry behavior of the resulting Fe/nano-carbon composite electrodes is significantly influenced by the kind of nano-carbon and the pretreatment conditions in spite of as a low content of nano-carbon as 20 wt.%. The largest redox current at initial cycle is obtained for Fe/VGCF composite electrode with the 30 min pretreatment of VGCF in ethanol. The dispersion of nano-carbon verifies the apparent density of the composite, and then affects the feature of three-phase interface among the ion-conducting electrolyte, the redox reaction surface, and the electron conductor.     

Ag/C nanoparticles as an cathode catalyst for a zinc-air battery with a flowing alkaline electrolyte

The cyclic voltammetry indicated that the oxygen reduction reaction (ORR) proceeded by the four-electron pathway mechanism on larger Ag particles (174 nm), and that the ORR proceeded by the four-electron pathway and the two-electron pathway mechanisms on finer Ag particles (4.1 nm), simultaneously. The kinetics towards ORR was measured at a rotating disk electrode (RDE) with Ag/C electrode. The number of exchanged electrons for the ORR was found to be close to four on larger Ag particles (174 nm) and close to three on finer Ag particles (4.1 nm). The zinc-air battery with Ag/C catalysts (25.9 nm) was fabricated and examined.     

Designing current collector/composite electrode interfacial structure of organic radical battery

Charge/discharge processes of organic radical batteries based on the radical polymer's redox reaction should be largely influenced by the structure and the composition of the composite electrodes. AC impedance measurement of the composite electrodes reveals a strong correlation between the overall electron transfer resistance of the composite electrode and the material of the current collector, and suggests that the electric conduction to the current collector through the contact resistance should be crucial. We also find that the adhesion and the contact area between the composite electrode and the current collector strongly influence the contact resistance rather than the work functions and the volume resistivities of the composite electrode and the current collector. It is also confirmed that the charge/discharge performance of the composite electrode is related to the overall electron transfer resistance of the composite electrode. These results indicate that the charge/discharge performance of the radical battery is dominated by the interfacial electron transfer processes at the current collector/carbon fiber interface. In fact, the composite electrode which has a high adhesion to the current collector shows a small overall electron transfer resistance and an excellent charge/discharge performance. The rate performance would be much improved by suitably designing the interfacial structure including adhesion and contact area.     

Synthesis and evaluation of polythiocyanogen (SCN)x as a rechargeable lithium-ion battery electrode material

Polythiocyanogen, (SCN)_x, is a promising lithium-ion battery electrode material due to its high theoretical capacity (462 mAh g⁻¹), safe operation, inexpensive raw materials, and a simple and less energy-intensive manufacturing process. The (SCN)_x was prepared from the solution of trithiocyanate (SCN)₃⁻ in methylene dichloride (MDC), which was prepared by electrochemical oxidation of ammonium thiocyanate (NH₄SCN) in a two-phase electrolysis medium of 1.0 M NH₄SCN in 0.50 M H₂SO₄ + MDC. The (SCN)₃⁻ underwent auto catalytic polymerization to (SCN)_x during MDC removal. Battery electrodes with (SCN)_x as the active material were prepared, and tested in Swagelok cells using lithium foil as the counter and reference electrode. The cells delivered capacities in the range of 200-275 mAh g⁻¹ at the discharge-charge rate of 0.2 C. The cells were tested up to 20 cycles and showed repeatable performance with a coulombic efficiency of 97% at the 20th cycle. The results presented here indicate that (SCN)_x is a promising lithium-ion battery electrode-material candidate for further studies.     

Facile synthesis and electrochemical properties of Fe3O4 nanoparticles for Li ion battery anode

Nanostructured Fe₃O₄ nanoparticles were prepared by a simple sonication assisted co-precipitation method. Transmission electron microscopy, X-ray diffraction and BET surface area analysis confirmed the formation of ∼20 nm crystallites that constitute ∼200 nm nanoclusters. Galvanostatic charge-discharge cycling of the Fe₃O₄ nanoaprticles in half cell configuration with Li at 100 mA g⁻¹ current density exhibited specific reversible capacity of 1000 mAh g⁻¹. The cells showed stability at high current charge-discharge rates of 4000 mA g⁻¹ and very good capacity retention up to 200 cycles. After multiple high current cycling regimes, the cell always recovered to full reversible capacity of ∼1000 mAh g⁻¹ at 0.1 C rate.     

Fe content effects on electrochemical properties of Fe-substituted Li2MnO3 positive electrode material

Fe-substituted Li₂MnO₃ including a monoclinic layered rock-salt structure (C2/m), (Li_1+x(Fe_yMn_1−y)_1−xO₂, 0 < x < 1/3, 0.1 ≤ y ≤ 0.5) was prepared by coprecipitation-hydrothermal-calcination method. The sample was assigned as two-phase composite structure consisting of the cubic rock-salt () and monoclinic ones at high Fe content above 30% (y ≥ 0.3), while the sample was assigned as a monoclinic phase (C2/m) at low Fe content less than 20%. In the monoclinic Li₂MnO₃-type structure, the Fe ion tends to substitute a Li (2b) site, which corresponds to a center position of Mn⁴⁺ hexagonal network in Mn-Li layer. The electrochemical properties including discharge characteristics under high current density (<3600 mA g⁻¹ at 30 °C) and low temperature (<−20 °C at 40 mA g⁻¹) were severely affected by chemical composition (Fe content and Li/(Fe + Mn) ratio), crystal structure (monoclinic phase content) and powder property (specific surface area). Under the optimized Fe content (0.2 < y < 0.4), the Li/sample cells showed high initial discharge capacity (240-300 mAh g⁻¹) and energy density (700-950 mWh g⁻¹) between 1.5 and 4.8 V under moderate current density, 40 mA g⁻¹ at 30 °C. Results suggest that Fe-substituted Li₂MnO₃ would be a non-excludable 3 V positive electrode material.     

β-CoOOH coated spherical β-NiOOH as the positive electrode material for alkaline Zn-NiOOH battery

β-CoOOH coated spherical β-NiOOH powders were synthesized as the positive electrode material for a new type of alkaline Zn-NiOOH battery. The scanning electron microscope (SEM), X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), storage stability and electrochemical properties of the samples were investigated. The results showed that the β-CoOOH coated spherical β-NiOOH exhibited superior electrochemical performance and storage stability than uncoated spherical β-NiOOH. AA size alkaline Zn-NiOOH batteries were assembled by directly using β-CoOOH coated spherical β-NiOOH as the positive electrode material. The discharge–charge experiments revealed that the alkaline Zn-NiOOH battery displayed longer discharge time and higher discharge voltage than the conventional alkaline Zn-MnO₂ battery under heavy load. Moreover, the Zn-NiOOH battery can be used not only conveniently as primary battery but also repeatedly as rechargeable battery.     

Highly dispersed sulfur in ordered mesoporous carbon sphere as a composite cathode for rechargeable polymer Li/S battery

A mesoporous carbon sphere with the uniform channels (OMC) is employed as the conductive matrix in the sulfur cathode for the lithium sulfur battery based on all-solid-state PEO₁₈Li(CF₃SO₂)₂N-10 wt%SiO₂ electrolyte. Cyclic voltammograms (CV) and electrochemical impedance spectrum (EIS) suggest that the electrochemical stability of the S-OMCs is obviously superior to the pristine sulfur cathode. The S-OMCs composite shows excellent cycling performance with a reversible discharge capacity of about 800 mAh g⁻¹ after 25 cycles. This would be attributed to an appropriate conductive structure in which the active sulfur is highly dispersed in and contacted with the OMCs matrix.     

Hierarchical novel NiCo2O4/BiVO4 hybrid heterostructure as an advanced anode material for rechargeable lithium ion battery

Hybrid metal oxide heterostructures have been considered as ideal and potential anode materials for lithium ion batteries (LIBs) due to their better electrochemical performances, such as reversible capacity, structural stability and electronic conductivity. Herein, we have demonstrated synthesis of NiCo₂O₄/BiVO₄ heterostructures by simple hydrothermal strategy to construct hybrid xNiCo₂O₄/(1–x)BiVO₄ heterostructures with four selected compositions, that is, x = 10%, 20%, 30% and 40%. XRD shows the phases of NiCo₂O₄ and BiVO₄ and FE-SEM data revealed strong interface coupling between NiCo₂O₄ nanowires and BiVO₄ dendrites. Upon testing for electrochemical properties, the optimized composition of 30%NiCo₂O₄-70% BiVO₄ showed higher reversible capacity of 408.6 mAh/g at a constant current rate of 0.5 A/g after 1000 cycles with columbic efficiency around 99% suggesting potential electrode material for high-performance LIBs. The higher capacity is mainly attributed to the large surface area which can provide more channels and locations for fast Li ion intercalation/de-intercalation into electrode materials. Additionally, improved Li ion storage capacity with superior rate capability of BN-30 electrode could be attributed to its lower charge-transfer resistance. The dendritic and nanowire heterostructure novel system with good stable capacity for LIBs is hitherto unattempted.     

Effect of chemical oxidation for nano-size γ-Fe2O3 as lithium battery cathode

Surface treatment of nano-crystalline γ-Fe₂O₃ was examined to improve its electrochemical performances for lithium battery. Removal of residual phases on the surface by chemical oxidation with NO₂BF₄ was confirmed by TG measurement and FT-IR spectroscopy, and the process improved charge–discharge characteristics; higher capacity and better reversibility were obtained. The charge–discharge mechanism was studied by X-ray diffraction measurement and Mössbauer spectroscopy. The reversible charge–discharge reaction of the nano-size γ-Fe₂O₃ was proceeded by a phase transition between the spinel and the disordered rock-salt type, which was previously claimed to be an irreversible process for the bulk materials. The nano-size effect of the phase transitions and the charge–discharge mechanism will be discussed.     

Nickel oxyhydroxide/manganese dioxide composite as a candidate electrode material for alkaline secondary cells

Nickel hydroxide and manganese dioxide are used in alkaline cells as positive electrode materials. Positive electrodes comprising a nickel oxyhydroxide/manganese dioxide composite, with modification by Bi₂O₃, deliver a combined reversible discharge capacity of 2.25e per metal atom (650 mAh g⁻¹ metal content), which is higher than that realized from electrodes of either component taken singly. The composite discharges with two potential plateaux, the first appearing at 325 mV corresponds to the discharge of the nickel component, whereas the second at −600 mV is due to the manganese component. Composites of NiO(OH)/MnO₂ can be used as a new electrode material with higher discharge capacity than conventional electrodes.     

Converting cobalt oxide subunits in cobalt metal-organic framework into agglomerated Co3O4 nanoparticles as an electrode material for lithium ion battery

Co₃O₄ nanoparticles are prepared via converting cobalt oxide subunits in a cobalt metal-organic framework (Co₃(NDC)₃(DMF)₄, NDC = 2,6-naphthalene- dicarboxylate; DMF = N,N′-dimethylformamide) by pyrolysis in air. The as-prepared Co₃O₄ shows an agglomerated secondary structure with an average diameter of around 250 nm comprised of small primary Co₃O₄ particles with a size of about 25 nm. This agglomerated structure favors the enhanced capacity, improved rate capability and prolonged cycle life as an electrode material for lithium ion batteries.