Papers by Keyword: Hydrogen Storage Alloy

Abstract: In this article the results of the negative electrode performance produced by La_0.7Mg_0.3Al_0.3Mn_0.4Co_0.5Ni_3.8 as-cast alloy adding 1 to 10% of carbon nanotube (CNT) or reduced graphene oxide (rGO) were investigated as Ni-MH batteries. The as cast alloy were investigated with X-ray diffraction (XRD) and scanning electron microscopy (SEM). The CNT and rGO were characterized by high resolution SEM-FEG. The discharge capacity obtained during the electrochemical characterization showed that in the addition of 1% rGO the discharge capacity was 332 mAh and 1% CNT 364 mAh , being that the rGO batteries maintaining better cyclic stability during the electrochemical test.

Abstract: La_0.70Mg_0.30Ni_2.45Co_0.75Al_0.30 alloys were synthesized by milling and blending of the La_0.70Ni_2.45Co_0.75Al_0.30 pre-alloy prepared by melting and elemental Mg, followed by annealing. The effects of milling time on the microstructures and electrochemical properties of the La_0.70Mg_0.30Ni_2.45Co_0.75Al_0.30 hydrogen storage alloys were investigated. The structure, microstructure and electrochemical properties of the alloys were investigated by XRD, SEM and electrochemical measurements. The results showed that a noticeable (La,Mg)₂Ni₇ phase can be observed in the alloy milled for 2 h. Moreover, the distribution of the Mg element in the alloy milled for 15 h presents some aggregation phenomena. The La_0.70Mg_0.30Ni_2.45Co_0.75Al_0.30 alloy milled for 2 h exhibits the best maximum discharge capacity (313.5 mAh/g) and discharge potential characteristic. The cyclic stability of the as-cast La_0.70Ni_2.45Co_0.75Al_0.30 alloy is better than that of the milled La_0.70Mg_0.30Ni_2.45Co_0.75Al_0.30 alloy.

Abstract: The effects of annealing on the microstructures and electrochemical characteristics of a La_0.7Mg_0.3Al_0.3Mn₀.₄Co₀.₅Ni_3.8 hydrogen storage alloy have been studied. The heat treatment by vacuum annealing was carried out at 700 °C, 800 °C, 900 °C and 1000 °C. The microstructure and phase composition of the alloy have been investigated using inductively coupled plasma - atomic emission spectrometry (ICP-AES), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction analysis (XRD). The battery anode was prepared using a mixture of the pulverized alloy with carbon black and polytetrafluoroethylene as a binder.

Abstract: The effects of effects of additional elements on hydrogen storage properties and crystal structures for vanadium alloys and their hydrides were investigated in order to obtain high hydrogen capacity. With increasing Cr content in V-xCr binary alloys, fully hydrogen content of the alloys slightly decreased until less than 9 at.%Cr. A clear distinction of the PC isotherm curves between the 15 at.%Cr alloy and the other alloys is observed. V alloys with an excessive Cr addition would come not to form gamma hydride (dihydride). This led the drastic decrement of the hydrogen content in the alloys. Meanwhile, the Cr addition in V alloys was effective to low hydrogen concentration in unstabilizing the beta hydride phases. In addition, it was found that the addition of X elements in V-Cr alloys (X=Al. Mo, Ti, W) was effective to expand the gamma-phase forming range of Cr amounts. As the results, high reversible hydrogen-capacity, 2.68mass% H was obtained in a V-18Cr-2Ti-0.5Al alloy.

Abstract: The phase structure and electrochemical properties of La4MgNi17M2(M=Ni,Co,Mn) alloys were investigated in detail. The XRD analysis revealed that the main phases in the alloys are LaNi5 and La4MgNi19 phases (Ce5Co19+Pr5Co19 structure). When the Ni element in the alloy was substituted by Mn or Co, the abundant of La4MgNi19 phase increased, and especially in the La4MgNi17Mn2 alloy, that increased to 70.7%. The electrochemical measurement showed that the activation of La4MgNi17M2(M=Ni,Co,Mn) alloy electrodes were improved, and it only needed 1-2 cycles.what’s more, with the elements substitution for Ni ,the maximum discharge capacity gradually increased to 386.10 mA·h/g (Co) and 375.18 mA·h/g (Mn), but high-rate dischargeability (HRD) decreased somewhat (Co, HRD900=86.2%). It is found that the HRD was mainly controlled by the electrocatalytic activity on the alloy electrode surface, and the decline of cyclic stability was due to the appearance of A5B19 type phase with larger hydrogen storage capacity, which lead to bigger volume expansion or intercrystalline stress, then easier pulverization during charging/discharging. In addition, the cyclic stability (S100) was improved with Co substitution, and worsened with Mn substitution, because Mn element was easily corroded and Co improved the ability of Corrosion resistance.

Abstract: The influence of substitution Co for Ni on the phase structure and electrochemical properties of La4MgNi19 phase composition alloys have been investigated systematically.The structure analyses show that the alloys are mainly composed of multiphase,such as CaCu5 phase ,Pr5Co19 phase and Ce5Co19 phase.The electrochemical measurement showed that alloy electrodes could be activated in 2-3 cycles, with increasing of x value, the maximum discharge capacity gradually increased from 345.7 mA·h/g (x = 0.0) to 382.8 mA·h/g (x = 2.0), cyclic stability increased a little ,but high-rate dischargeability (HRD) decreased somewhat. It is found that the HRD was mainly controlled by the electrocatalytic activity on the alloy electrode surface,and the improvement of cyclic stability was due to the increase of CaCu5 phase and Ce5Co19 phase . CaCu5 phase increased with increasing Co content. Ce5Co19 phase has a small corrosion rate in the electrochemical cycle.

Abstract: In order to analysis the properties of hydrogen storage alloy, hydrogen storage properties, the test principle of pressure-composition-temperature (PCT) was analyzed in detailed, the new type PCT test system was designed on the base of the state equation of ideal gas. The PCT test system is composed of five parts: air supply system, vacuum system, response system, data acquisition system and electric control system. The PCT test system can be carried out in four channel linkage experiments. The hydrogen storage performance experiments of LaNi5 hydrogen storage alloy were carried out by using this system. Hydrogen absorption curve was gained by two kinds of modeling methods. Results show that: the test system can test the hydrogen absorption curve smoothly, efficiently and accurately. The design of this system is reasonable and the test result is reliable.

Abstract: Microstructuresand electrochemical properties of La0.73Ce0.27Ni3.25+xMn0.35Al0.15Cu0.75Fe0.25 alloys are investigated. XRD results indicate that all alloys are identified with LaNi5 phase with CaCu5 type hexagonal structure, and lattice parameter a, c and cell volume V decrease with increasing x value. Maximum discharge capacity first increases from 286.4 mAh/g (x = 0) to 313.2 mAh/g (x = 0.25), and then decreases to 308.9 mAh/g (x = 0.75). High-rate dischargeability of the alloy electrodes increases when x increases from 0 to 0.75. HRD1200 increases with the increase in the I0 and D, and shows a linear relationship with the I0 and D.

Abstract: This study developed a heating mechanism applicable to hydrogen storage tank, in order to enhance the stability and durability of proton exchange membrane fuel cell (PEMFC). This study discussed two heating modes. The first mode was using heating wire to wind the hydrogen storage tank body. Heating wires were used to wind the upper, middle and lower parts of the hydrogen storage tank and the whole tank respectively for discussion. The second heating mode was to use the PEMFC cathode waste heat to heat the hydrogen storage tank body. This study discussed the variations of hydrogen release rate and tank body temperature with the hydrogen release time in different heating mechanisms. The research results can serve as reference for system design in various applications.

Abstract: Microstructures and electrochemical characteristics of La_0.7Ce_0.3Ni_3.83Mn_0.43Co_0.25-x Al_0.26Cu_0.48(Fe_0.43B_0.57)_x hydrogen storage alloys have been investigated. XRD results indicate that La_0.7Ce_0.3Ni_3.83Mn_0.43Co_0.25-xAl_0.26Cu_0.48 alloy is single LiNi₅ phase, and the alloys containing Fe_0.43B_0.57 are composed of LaNi₅ matrix phase and La₃Ni₁₃B₂ secondary phase, and the abundance of the secondary phase gradually increases with increasing Fe_0.43B_0.57 content. Maximum discharge capacity of the alloy electrodes monotonically decreases from 311.2 mAh/g (x = 0) to 289.6 mAh/g (x = 0.20). High-rate dischargeability at the discharge current density of 1200 mA/g first increases from 53.1% (x = 0) to 64.0% (x = 0.15), and then decreases to 56.5% (x = 0.20).