Preparation and characterization of a new nanosized silicon–nickel–graphite composite as anode material for lithium ion batteries

A new type of nanosized silicon–nickel–graphite (Si–Ni–G) composite was prepared by high energy mechanical milling (HEMM) and pyrolysis using SiO as the precursor of Si for the first time. X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM) and scanning electron microscopy (SEM) were used to determine the phases obtained and to observe the microstructure and distribution of the composite. The composite powders consisted of Si, Ni, SiO₂, NiO and a series of Si–Ni alloys. The formation of the inactive SiO₂ and Si–Ni alloy phases could accommodate the large volume changes of the active particles during cycling. In addition, cyclic voltammetry (CV) and galvanostatic discharge/charge tests were carried out to characterize the electrochemical properties of the composite. The composite electrodes exhibited an initial discharge and charge capacity of 1450.3 and 956.4 mAh g⁻¹, respectively, maintaining a reversible capacity of above 900 mAh g⁻¹ for nearly 60 cycles.     

Aligned nickel–cobalt oxide nanosheet arrays for lithium ion battery applications

Aligned nickel–cobalt nanosheet arrays are deposited on nickel foam substrates by means of chemical bath deposition technique. The nanosheet arrays are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The electrochemical performances as anode materials of lithium ion batteries are investigated by galvanostatic charge–discharge cycle and cyclic voltammetry (CV) tests. The results show that the nickel–cobalt oxide film prepared from the solution in which Ni/Co = 3/1 has the best performance. Its initial charge capacity at 0.1 A g⁻¹ is 798 mAh g⁻¹. When cycled at higher current densities of 0.5 and 1.0 A g⁻¹, the initial charge capacities are 570 and 500 mAh g⁻¹, and 84% and 86% can be retained after 50 cycles, respectively. It is believed that the interconnected nanosheet-array structure and the nickel–cobalt binary composition play important roles in their electrochemical performances.     

Development of trimetallic Ni–Cu–Zn anode for low temperature solid oxide fuel cells with composite electrolyte

Trimetallic alloys of Ni_0.6Cu_0.4−xZn_x (x = 0, 0.1, 0.2, 0.3, 0.4) have been investigated as promising anode materials for low temperature solid oxide fuel cells (SOFCs) with composite electrolyte. The alloys have been obtained by reduction of Ni_0.6Cu_0.4−xZn_xO oxides, which are synthesized by using the glycine–nitrate process. Increasing the Zn content x decreases the particle sizes of the oxides at a given sintering temperature. Fuel cells have been constructed using lithiated NiO as cathode and as-prepared alloys as anodes based on the composite electrolyte. Peak power densities are observed to increase with the increasing Zn addition concentration into the anode. The maximum power density of 624 mW cm⁻² at 600 °C, 375 mW cm⁻² at 500 °C has been achieved for the fuel cell equipped with Ni_0.6Zn_0.4 anode. A.c. impedance results show that the resistances dramatically decrease with increasing temperatures under open circuit voltage state. Both cathodic and anodic interfacial polarization resistances increase with the amplitude of applied DC voltage. Possible reaction process for H₂ oxidation reaction at anode based on composite electrolyte has been proposed for the first time. The stability of the fuel cell with Ni_0.6Cu_0.2Zn_0.2 composite anode has been investigated. The results indicate that the trimetallic Ni_0.6Cu_0.4−xZn_x anodes are considerable for low temperature SOFCs.     

Alkaline composite PEO–PVA–glass-fibre-mat polymer electrolyte for Zn–air battery

An alkaline composite PEO–PVA–glass-fibre-mat polymer electrolyte with high ionic conductivity (10⁻² S cm⁻¹) at room temperature has been prepared and applied to solid-state primary Zn–air batteries. The electrolyte shows excellent mechanical strength. The electrochemical characteristics of the batteries were experimentally investigated by means of ac impedance spectroscopy and galvanostatic discharge. The results indicate that the PEO–PVA–glass-fibre-mat composite polymer electrolyte is a promising candidate for application in alkaline primary Zn–air batteries.     

Synergistic effects in an AB5–Co material as an anode for a secondary alkaline battery

The AB₅ alloy and Co powders have been mixed at various weight ratios to form AB₅–Co composite electrodes. The discharge properties such as discharge capacity, discharge plateau, and cycling stability are investigated by charge and discharge testing using Arbin battery testing equipment. Synergistic effects in the composite electrodes contribute to significant improvements of the discharge behavior. For instance, the composite AB₅–25%Co electrode shows a high discharge capacity of 395.1 mAh/g, which is significantly higher than that of AB₅ or Co electrode, and good cycling stability. The discharge process is also characterized by electrochemical impedance spectroscopy. Moreover, the electrochemical discharge mechanism is discussed.     

A new nickel–ceria composite for direct-methane solid oxide fuel cells

Various Ni–La_xCe_1−xO_y composites were synthesized and their catalytic activity, catalytic stability and carbon deposition properties for steam reforming of methane were investigated. Among the catalysts, Ni–La_0.1Ce_0.9O_y showed the highest catalytic performance and also the best coking resistance. The Ni–La_xCe_1−xO_y catalysts with a higher Ni content were further sintered at 1400 °C and investigated as anodes of solid oxide fuel cells for operating on methane fuel. The Ni–La_0.1Ce_0.9O_y anode presented the best catalytic activity and coking resistance in the various Ni–La_xCe_1−xO_y catalysts with different ceria contents. In addition, the Ni–La_0.1Ce_0.9O_y also showed improved coking resistance over a Ni–SDC cermet anode due to its improved surface acidity. A fuel cell with a Ni–La_0.1Ce_0.9O_y anode and a catalyst yielded a peak power density of 850 mW cm⁻² at 650 °C while operating on a CH₄–H₂O gas mixture, which was only slightly lower than that obtained while operating on hydrogen fuel. No obvious carbon deposition or nickel aggregation was observed on the Ni–La_0.1Ce_0.9O_y anode after the operation on methane. Such remarkable performances suggest that nickel and La-doped CeO₂ composites are attractive anodes for direct hydrocarbon SOFCs and might also be used as catalysts for the steam reforming of hydrocarbons.     

Synthesis and characterisation of high-performance 3Li4Ti5O12·NiO composite anode material for lithium-ion batteries

A 3Li₄Ti₅O₁₂·NiO composite anode material was prepared by a spray-drying method. The physical and electrochemical properties of samples were characterised by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical test. X-ray diffraction results revealed that incorporation of NiO did not alter the structure of Li₄Ti₅O₁₂. Scanning electron microscopy images of both Li₄Ti₅O₁₂ and 3Li₄Ti₅O₁₂·NiO exhibited spherical particles with the sizes of 0.5–3?μm. Electrochemical tests showed that the 3Li₄Ti₅O₁₂·NiO composite material exhibited much better rate and cycling performances than those of Li₄Ti₅O₁₂ per se. It delivered the specific capacities of 372.8, 252.6 and 204.8?mAh?g^??1 at 0.1, 1 and 2°C rates, respectively. After 300 cycles, the discharge specific capacity remained as high as 202.1?mAh?g^??1 at 2°C rate.     

Fabrication and characteristics of a composite cathode of sulfonated polyaniline and Ramsdellite–MnO2 for a new rechargeable lithium polymer battery

The ionic conductivity of a polyacrylonitrile (PAN)-based solid polymer electrolyte is 1.4×10⁻³ S cm⁻¹, which is sufficient for the electrolyte to be used in a rechargeable lithium polymer battery. The anodic stability of the solid polymer electrolyte is over 4.6 V (vs. Li/Li⁺). A reduced, highly sulfonated form of polyaniline (SPAn) and Ramsdellite–MnO₂ (R-MnO₂) are synthesized and used as a cathodic material for a rechargeable lithium polymer battery. Three kinds of cathodes are prepared from SPAn, R-MnO₂, and a mixture of SPAn and R-MnO₂. The electrochemical properties and diffusion coefficient of lithium ions in each cathode, and the interface between the solid polymer electrolyte and each cathode are investigated by cyclic voltammetry and impedance spectroscopy. The redox processes of the SPAn cathode are two-step reactions. The cathodic and anodic peak currents increase as the cycle number increases. In the redox processes of the R-MnO₂ cathode, the cathodic peak current on the second cycle is 62% of that on the first cycle. The Li/R-MnO₂ battery has a very high initial discharge capacity, but very poor cycleability. For the composite cathode, the cathodic peak current on the second cycle is 72% of that on the first cycle, i.e., higher than that for the R-MnO₂ cathode. The diffusion coefficient of the composite cathode during the discharge process is close to the sum of each variation in the SPAn and R-MnO₂ cathodes. The instability of the R-MnO₂ cathode at x=0.3 and x=0.2 during the charge process is not observed with the composite cathode. The discharge–charge performance of three types of battery are investigated. The initial discharge capacity of the Li/composite cathode battery is 97.0 m Ah g⁻¹. This battery has higher discharge capacity than the Li/SPAn battery (66.8 m Ah g⁻¹), and better cycleability than the Li/R-MnO₂ battery.     

Novel doped barium cerate–carbonate composite electrolyte material for low temperature solid oxide fuel cells

A composite of a perovskite oxide proton conductor (BaCe_0.7Zr_0.1Y_0.2O_3−δ, BCZ10Y20) and alkali carbonates (2Li₂CO₃:1Na₂CO₃, LNC) is investigated with respect to its morphology, conductivity and fuel cell performance. The morphology shows that the presence of carbonate phase improves the densification of oxide matrix. The conductivity is measured by AC impedance in air, nitrogen, wet nitrogen, hydrogen, and wet hydrogen, respectively. A sharp increase of the conductivity at certain temperature is seen, which relates to the superionic phase transition at the interface phases between oxide and carbonates. Single cell with the composite electrolyte is fabricated by dry-pressing technique, using nickel oxide as anode and lithiated nickel oxide as cathode, respectively. The cell shows a maximum power density of 957 mW cm⁻² at 600 °C with hydrogen as the fuel and oxygen as the oxidant. The remarkable proton conductivity and excellent cell performance make this kind of composite material a good candidate electrolyte for low temperature solid oxide fuel cells (SOFCs).     

Zn4Sb3(C7) powders as a potential anode material for lithium-ion batteries

The electrochemical properties of β-Zn₄Sb₃ and Zn₄Sb₃C₇ as new lithium-ion anode materials were investigated. The reversible capacities of the pure Zn₄Sb₃ alloy electrode and 100 h milled Zn₄Sb₃ in the first cycle reached 503 and 566 mA h/g, respectively, but the cycle stability of Zn₄Sb₃ whether milled or not were obviously bad. It was demonstrated that cycle stability of Zn₄Sb₃ could be largely improved by milling after mixing with graphite. It was shown that Zn₄Sb₃C₇ composite has a lithium-ion extraction capacity of 581 mA h/g at the first cycle and 402 mA h/g at 10th cycle.     

The synthesis and characterizations of Li4Ti5O12–CNTs anode material

An anode material with Li₄Ti₅O₁₂ nanocrystals entangled by carbon nanotubes is prepared by polymerization of titanium tetra-isopropoxide with ethylene glycol in the presentence of carbon nanotubes. The resulted polymer is hydrolyzed in LiOH/H₂O solution, and then thermally decomposed to obtain the topic anode material. The characterizations show that the synthesis method yields a type of material that has both of high electronic conductivity and high lithium ion diffusion rate. The material has stable deep discharge capability (down to 0.01 V), high specific capacity (237 mAhg⁻¹ at 0.30 Ag^-1), and long cycling life time (254 mAhg⁻¹ at 0.10 Ag^-1, more than 500 discharge/charge cycles). High specific capacities of 258 and 158 mAhg⁻¹ are obtained at current densities of 0.10 and 3.00 Ag^-1, respectively. The deep discharge capability of the material offers an average voltage below 1.0 V (vs metal Li), which is lower than that of pristine Li₄Ti₅O₁₂ (1.55 V).     

Graphite–carbon nanotube composite electrodes for all vanadium redox flow battery

The voltammetric behaviors of graphite (GP) and its composites with carbon nanotube (CNT) were studied in 5 M H₂SO₄ + 1 M VOSO₄ solution with cyclic voltammetry (CV), and the surface morphology of the composites was observed with scanning electron microscope (SEM). The results obtained from voltammetry show that the redox couples of V(IV)/V(V) and V(II)/V(III), as positive and negative electrodes of all vanadium flow liquid battery, respectively, have good reversibility but low current on the GP electrode, and the current can be improved by CNT. It is found from the observation of SEM that the CNT is dispersed evenly on the surface of sheet GP when they are mixed together. The best composition for the positive and the negative of all vanadium flow liquid battery determined by comparing voltammetric behavior of the composite electrodes with different content of CNT is 5:95 (w_CNT/w_GP) for both positive and negative electrodes. The activity of the composite electrode can be affected by the heat treatment of CNT. CNT treated at 200 °C gives better activity to the composite electrode.     

Electrochemical properties of Co3O4, Ni–Co3O4 mixture and Ni–Co3O4 composite as anode materials for Li ion secondary batteries

By varying the synthetic temperature and time, Co₃O₄ with highly optimized electrochemical properties was obtained from the solid state reaction of CoCO₃. As a result, Co₃O₄ showed a high capacity around 700 mAh/g and stable capacity retention during cycling (93.4% of initial capacity was retained after 100 cycles). However, its initial irreversible capacity reached about 30% of capacity. Several phenomenological examinations in our previous results told us that the main causes of low initial coulombic efficiency, that is, large initial irreversible capacity, were solid electrolyte interphase (SEI) film formation on surface and incomplete decomposition of Li₂O during the first discharge process. SEI film formation cannot be restrained without the development of a special electrolyte, and there has been little research on the proper electrolyte composition, whereas in our research, Ni had the catalytic activity to facilitate Li₂O decomposition. Thus, in order to improve the low initial coulombic efficiency of Co₃O₄ (69%), Ni was added to Co₃O₄ using two methods like physical mixing and mechanical milling. When adding the same amount of Ni, the mechanical milling showed the improvement in initial coulombic efficiency, 79%, but physical mixing had no effect. Finally, when the charge–discharge mechanism of Co₃O₄ was considered and the morphologies of Ni–Co₃O₄ mixture obtained by physical mixing and Ni–Co₃O₄ composite prepared by mechanical milling were compared, it was revealed that the initial coulombic efficiency of Ni–Co₃O₄ composite depends on the contact area between the Ni and the Co₃O₄.     

A new anode material for solid oxide electrolyser: The neodymium nickelate Nd2NiO4+δ

Neodymium nickelate, with composition Nd₂NiO_4+δ is integrated as oxygen electrode in a solid oxide electrolyte supported cell made of a TZ3Y electrolyte and a Ni-CGO hydrogen electrode. This cell is tested in both fuel cell (SOFC) and electrolysis (SOEC) mode and the reversible operation is proven, ASR values being slightly lower in electrolysis mode. Performances in SOEC mode are compared with a commercial cell based on the same electrolyte and cathode, but with lanthanum strontium manganite (LSM) as anode. For a voltage of 1.3 V, current densities of 0.40, 0.64 and 0.87 A cm⁻² are measured at 750, 800 and 850 °C, respectively; they are much higher than the ones measured in the same conditions for the LSM-containing cell. Indeed, for a voltage of 1.3 V, current densities are respectively 1.7, 3 and 4.2 times higher for the Nd₂NiO_4+δ cell than for the LSM one at 850, 800 and 750 °C, respectively. Consequently, Nd₂NiO_4+δ can be considered as a good candidate for operating below 800 °C as oxygen electrode for high temperature steam electrolysis.     

Fabrication of hollow metal oxide–nickel composite spheres and their catalytic activity for hydrolytic dehydrogenation of ammonia borane

In this paper, we report an effective approach to the fabrication of hollow titania–nickel composite spheres, hollow zirconia–nickel composite spheres, and hollow silica–nickel composite spheres. In this approach, metal oxide–nickel composite shells were coated on polystyrene particles by the sol–gel method and the polystyrene templates were dissolved subsequently, or even synchronously, in the same medium to form hollow spheres. Neither additional dissolution nor a calcination process was needed to remove the polystyrene templates. The as-prepared hollow metal oxide–nickel composite spheres were characterized by transmission electron microscopy. The catalytic activities of hollow titania–nickel composite spheres, hollow zirconia–nickel composite spheres, and hollow silica–nickel composite spheres for hydrolytic dehydrogenation of aqueous NaBH₄/NH₃BH₃ solution were compared. The evolutions of 64, 58, and 18 mL hydrogen were finished in about 49, 69, and 162 min in the presence of the hollow titania–nickel composite spheres, hollow zirconia–nickel composite spheres, and hollow silica–nickel composite spheres from aqueous NaBH₄/NH₃BH₃ solution, respectively. The molar ratios of the hydrolytically generated hydrogen to the initial NH₃BH₃ both in the presence of hollow titania–nickel composite spheres, hollow zirconia–nickel composite spheres, and hollow silica–nickel composite spheres are 2.8, 2.4, and 0.1 (the theoretical value of 3.0), respectively, indicating that the hollow titania–nickel composite spheres and hollow zirconia–nickel composite spheres show much higher hydrogen evolution rates and the amount of hydrogen evolution via hydrolytic dehydrogenation of ammonia borane than the hollow silica–nickel composite spheres. From the results of ATR-IR spectra, a certain amount of residual PS templates exists in hollow silica–nickel composite spheres, and the amount of the residual PS templates were able to be reduced by increasing the amount of aqueous ammonia solution used for the preparation. The catalytic activity of hollow silica–nickel composite spheres increases when the amount of residual PS templates decreases.     

Exploring MnCr2O4–Gd0.1Ce0.9O2-δ as a composite electrode material for solid oxide fuel cell

Symmetrical solid oxide fuel cell (SOFC) adopting the same material at both electrodes is potentially capable of promoting thermomechanical compatibility between near components and lowering stack costs. In this paper, MnCr₂O₄–Gd_0.1Ce_0.9O_2-δ (MCO-GDC) composite electrodes prepared by co-infiltration method for symmetrical electrolyte supported and anode supported solid oxide fuel cells are evaluated at a temperature range of 650–800 °C in wet (3% H₂O) hydrogen and air atmospheres. Without any alkaline earth elements and cobalt, the co-infiltrated MCO-GDC composite electrode shows excellent activity for oxygen reduction reaction but mediocre activity for hydrogen oxidation reaction. With MCO-GDC as the cathode, the Ni-YSZ (Y₂O₃ stabilized ZrO₂) anode supported asymmetrical cell demonstrates a peak power density of 665 mW cm⁻² at 800 °C. The above results suggest MCO-GDC is a promising candidate cathode material for solid oxide fuel cells.     

The effect of ceria content in nickel–ceria composite anode catalysts on the discharge performance for solid oxide fuel cells

Optimum ceria content in nickel–ceria composite anode catalyst from the point of discharge performance is discussed. The ohmic loss increased when the ceria content was higher than 30 mol%. Even though the electrical conductivity of the anode decreased with increasing ceria content in the anode catalyst in association with decreasing nickel content, the ohmic loss was kept low until the ceria content was ≤30 mol% because the semiconducting ceria compensated for the decreased current path owing to the decreasing nickel content. The lowest activation loss was observed when the ceria content in the nickel anode catalyst was 30 mol% and the maximum activation loss was obtained for ceria content of 2 mol%. Ceria content in nickel anode influenced microstructure of the anode matrix. When the CeO₂ content was 2 mol%, sintering of anode catalyst was evident and the porosity of anode matrix was almost 57% - highest in this study. Whereas sintering of anode catalyst was not evident and the porosity of anode matrix was 46% when the ceria content in the nickel anode catalyst was 30 mol%. Activation loss was strongly influenced by microstructure of anode matrix, and highest activation loss when the CeO₂ content was 2 mol% was owing to the inappropriate microstructure for electrochemical reaction: sintering of the anode catalyst and excessive porosity of the anode.     

A novel doped CeO2–LaFeO3 composite oxide as both anode and cathode for solid oxide fuel cells

A novel composite oxide Ce(Mn,Fe)O₂-La(Sr)Fe(Mn)O₃ (CFM-LSFM) was synthesized and evaluated as both anode and cathode materials for solid oxide fuel cells. The cell with CFM-LSFM electrodes was fabricated by tape-casting and screen printing technique. The power-generating performance of this cell was comparable to that of the cell with Ni-SSZ anode and LSM-SSZ cathode. During the 120 h long-term test in hydrogen at 800 °C, the performance increased by 8.6% from 256 to 278 mW cm⁻². This was attributed to the decrease of polarization resistance and ohmic resistance during the test. The XRD results showed the presence of Fe, MnO and some unknown second phases after heat-treating the electrode materials in H₂ which may be beneficial to the anode electrochemical process. The gradual decrease of polarization resistance as increasing the current density possibly resulted from the increasing content of water in the anode.     

Metal-organic frameworks derived spinel NiCo2O4/graphene nanosheets composite as a bi-functional cathode for high energy density Li–O2 battery applications

Electrode materials having a combined heterostructure morphology can boost the electrochemical performance of energy conversion and storage applications. In this paper, we prepared three-dimensional (3D) porous NiCo₂O₄ dodecahedron nanosheets (NCO) from a metal–organic framework template (ZIF-67) and incorporated them with two-dimensional (2D) multilayer graphene nanosheets (GNS) through a simple and rapid ultrasonication process. The combination of these 3D/2D nanostructures created effective interfaces between the NCO and GNS components that enhanced the intrinsic electronic properties and increased the number of active catalytic sites on the NCO@GNS surfaces. Accordingly, the NCO@GNS electrocatalyst displayed superior kinetics for both the oxygen reduction and evolution reactions in both aqueous and non-aqueous electrolytes and could be fabricated into an air-cathode for Li–O₂ battery applications. The NCO@GNS air-cathode delivered a specific storage capacity (7201 mA h g^?1) higher than those of the NCO and commercial carbon black electrodes. We tested the durability of the Li–O₂ battery featuring the NCO@GNS cathode in a new PAT-cell configuration; it exhibited long-term cyclability for 200 cycles with a limited capacity of 500 mA h g^?1 at a current density of 100 mA g^?1. This cathode design featuring meso- and micropores shortened the pathways for Li⁺ ion diffusion and ensured rapid electron and oxygen transfer, thereby increasing the lifetime of its corresponding Li–O₂ battery.     

Core–shell tin-multi walled carbon nanotube composite anodes for lithium ion batteries

Carbon nanotube papers were produced from Multi wall carbon nanotubes (MWCNTs). Tin deposition was conducted via RF magnetron sputtering technique on the MWCNT papers to produce tin-MWCNT composite anodes. The effect of different sputtering power on the electrochemical performance of anodes was investigated. Galvanostatic charge/discharge technique was employed to determine the cyclic performance of the anode electrodes. Results showed that improvement on cyclic performance of tin anodes was achieved with novel composite tin-MWCNT composite anode structures.