The effects of low-Co AB_5 type hydrogen storage alloys prepared by quenchingand annealing on the performances of MH-Ni batteries were investigated, and the characteristics ofthe low-Co AB_5 type hydrogen storage allo...The effects of low-Co AB_5 type hydrogen storage alloys prepared by quenchingand annealing on the performances of MH-Ni batteries were investigated, and the characteristics ofthe low-Co AB_5 type hydrogen storage alloys were compared with those of the high-Co AB_5 typehydrogen storage alloy as well. The results showed that the faster the cooling of the low-Cohydrogen storage alloy is, the better homogeneity of the chemical composition for the alloy and thelonger cycle life of the battery are, but the electrochemical discharge capacity and high-ratedischarge ability are reduced. The high-rate discharge ability and charge retention of MH-Nibatteries for the conventional as-cast annealed low-Co hydrogen storage alloy were superior to thosefor the rapidly quenched low-Co hydrogen storage alloy and the high-Co hydrogen storage alloy, buta little inferior in the cycle life.展开更多
In order to investigate the effect of substituting La with Pr on structural and hydrogen storage properties of La-Mg-Ni system (AB3.5-type) hydrogen storage alloys, a series of La0.65-xPrxNd0.12Mg0.23Ni3.4Al0.1(x=0...In order to investigate the effect of substituting La with Pr on structural and hydrogen storage properties of La-Mg-Ni system (AB3.5-type) hydrogen storage alloys, a series of La0.65-xPrxNd0.12Mg0.23Ni3.4Al0.1(x=0, 0.10, 0.15, 0.2) hydrogen storage alloys were prepared. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) analyses revealed that two alloys (x=0.0 and 0.10) were composed of (La,Mg)2(Ni,Al)7 phase, La(Ni,A1)5 phase and (La,Mg)Ni2 phase, while other alloys (x=0.15 and 0.20) consisted of (La,Mg)2(Ni,A1)7 phase, La(Ni,A1)5 phase, (La,Mg)Ni2 phase and (La,Mg)(Ni,A1)3 phase. All alloys showed, however, only one pressure plateau in P-C isotherms. The Pr/La ratio in alloy composition influenced hydrogen storage capacity and kinetics properties. Electrochemical studies showed that the discharge capacity decreased from 360 mAh/g (x=-0.00) to 335 mAh/g (x=-0.20) as x increased. But the high-rate dischargeability (HRD) of alloy electrodes increased from 26% (x=0.00) to 56% (x=-0.20) at a discharge current density of Id=1800 mA/g. Anode polarization measurements were done to further understand the electrochemical kinetics properties after Pr substitution.展开更多
The effect of heat-treatment process on the properties of Mm0.8Mg0.2(NiCoAlMn)3.5 hydrogen storage alloy was discussed . The electrochemical properties such as cycling stability, activation property, and the plateau v...The effect of heat-treatment process on the properties of Mm0.8Mg0.2(NiCoAlMn)3.5 hydrogen storage alloy was discussed . The electrochemical properties such as cycling stability, activation property, and the plateau voltage of the alloy which was heat-treated in various temperatures and times had different changes during the cycle process, the optimum heat-treatment conditions of this alloy were determined by this work.展开更多
The structure and electrochemical properties of the La0.7Mg0.3Ni3.4-xMn0.1Cox (x=01.05) hydrogen storage alloys were investigated. The crystal structure and the lattice parameters of the alloys were analyzed by X-ra...The structure and electrochemical properties of the La0.7Mg0.3Ni3.4-xMn0.1Cox (x=01.05) hydrogen storage alloys were investigated. The crystal structure and the lattice parameters of the alloys were analyzed by X-ray diffractometry and Rietveld method. Electrochemical properties of the alloys including p—c—t curves, discharge capacity, discharge capacity retention were studied. The results show that (La, Mg)Ni3 and LaNi5 are the main phases of all the alloys. The plateau pressure for hydrogen absorption/desorption decreases and the hydrogen storage capacity firstly increases and subsequently decreases with increasing Co content. The values of the maximum discharge capacity of the alloy electrodes remain in range of 395.3403.1mA·h/g in spite of the change of Co content. The cycling stability of the alloy electrodes is greatly improved with increasing Co content, which is attributed to the suppression of the cell volume expansion during hydriding, leading the pulverization of the alloy particles lowered and the oxidation/corrosion of the active elements reduced.展开更多
Ti-based AB2-type hydrogen storage alloys are a group of promising materials, which will probably replace the prevalent rare earth-based AB5-type alloys and be adopted as the main cathode materials of nickel-metal hyd...Ti-based AB2-type hydrogen storage alloys are a group of promising materials, which will probably replace the prevalent rare earth-based AB5-type alloys and be adopted as the main cathode materials of nickel-metal hydride (Ni-MH) batteries in the near future. Alloying in side B is a major way to improve the performance of Ti-based AB2-type alloys. Based on recent studies, the effects of alloying elements in side B upon the performance of Ti-based AB2-type hydrogen storage alloys are systematically reviewed here. These performances are divided into two categories, namely PCI characteristics, including hydrogen storage capacity (HSC), plateau pressure (PP), pressure hysteresis (PH) and pressure plateau sloping (PPS), and electrochemical properties, including discharge capacity (DC), activation property (AP), cycling stability (CS) and high-rate dischargeability (HRD). Furthermore, the existing problems in these investigations and some suggestions for future research are proposed.展开更多
Oxygen evolution causes a high inner pressure during charge and overcharge for MH/Ni battery, and an inappropriate eliminating way of the oxygen in the battery results in accumulation of heat. This is the main obstacl...Oxygen evolution causes a high inner pressure during charge and overcharge for MH/Ni battery, and an inappropriate eliminating way of the oxygen in the battery results in accumulation of heat. This is the main obstacle to develop and apply high capability and high power battery. How to reduce the ratio of the chemical catalysis rate to the electric catalysis rate in MH/Ni battery is considered as an urgent question. Iron phthalocyanine(FePc) was chosen as an electrochemical catalyst. The batteries were prepared by adding iron phthalocyanine with different dosages. The inner pressure, the capacity attenuation, the discharge voltage and capacity at high current of these three batteries were compared. The battery with 1 mg FePc in the negative electrode exhibits a good performance.展开更多
In order to improve the electrochemical kinetic performances of La-Mg-Ni-based alloy,complex surface modification of Ni with excellent catalytic activity and conducting polymer polypyrrole(PPy)was performed via electr...In order to improve the electrochemical kinetic performances of La-Mg-Ni-based alloy,complex surface modification of Ni with excellent catalytic activity and conducting polymer polypyrrole(PPy)was performed via electroless plating method.FESEM images revealed that the complex Ni-PPy treatment resulted in more micropores at the alloy surface,with Ni particles and cotton fiber-shape PPy microspheres attached.Both the larger surface area induced by the micropore and the higher catalytic activity and conductivity on account of the dispersed Ni particles/PPy microspheres promoted the electrode reaction,thereby increasing the discharge capacity of the modified alloy electrode.Electrochemical impedance spectroscopy(EIS)and linear polarization results showed that the Ni-PPy treatment decreased the charge-transfer resistance and increased the exchange current density greatly,far more than the single-component Ni or PPy treatment.Consequently,a notable improvement in high rate dischargeability(HRD)was observed,and at a high discharge current density of 1800 mA/g,the HRD of the modified electrode increased by 10.4%compared with that of the bare electrode.展开更多
Rare earth compositions, La, Ce and Pr in Mm(NiCoMnAl)(5) hydrogen storage alloy, were arranged by uniform design method. The discharge performances and kinetics parameters including capacity, exchange current density...Rare earth compositions, La, Ce and Pr in Mm(NiCoMnAl)(5) hydrogen storage alloy, were arranged by uniform design method. The discharge performances and kinetics parameters including capacity, exchange current density, symmetry factor and hydrogen diffusion coefficient of the alloy at -40degreesC, were tested in standard tri-electrode cell. And linear regression method was used to analyze the effect of rare earth compositions on the performances of hydrogen storage alloys. The results show that the capacities of the alloys are positively correlative to the square of Ce content at -40degreesC and under both 0.4 and 0.2C rate. The kinetics parameters and hydrogen diffusion coefficient indicate that the low-temperature performances of the alloys are mainly controlled by hydrogen diffusion process, and the surface electrochemical reaction affects the low-temperature performances to a certain extent. The low-temperature discharge capacities of the battery were also tested. The results show excellent low-temperature performances. The battery delivers 69.6% of its room-temperature capacity at -40degreesC and 0.2C rate, 77.7% at -40degreesC and 0.4C rate, 59.1% at -45degreesC and 0.2C rate.展开更多
AB5 hydrogen storage alloys La0.54Ce0.28Pr0.18Ni4-xCo0.6Mn0.35Alx(x=0.1,0.2,0.3) were prepared by arc melting method under an Ar atmosphere. The results show that the contents of Ni and Al have obvious influences on t...AB5 hydrogen storage alloys La0.54Ce0.28Pr0.18Ni4-xCo0.6Mn0.35Alx(x=0.1,0.2,0.3) were prepared by arc melting method under an Ar atmosphere. The results show that the contents of Ni and Al have obvious influences on the microstructure and electrochemical properties of the alloys. Both the lattice parameters and the cell volumes decrease with decreasing x value. Moreover,the discharge capacity at different temperatures,the high rate discharge property,and the cycling life of the alloy electrode are also in close relationship with the x value. When x value increases from 0.1 to 0.3,the discharge capacities with a discharge current density of 60 mA/g slightly decreases at 25 ℃,but evidently deteriorates at -40 ℃,the high-rate property gravely decreases,and the cycle life of the alloy electrode is improved in some extent. Therefore,it is meaningful to control Al content for the AB5 hydrogen storage alloys used in Ni/MH batteries.展开更多
The influences of deeply overdischarge on the negative electrode alloy of Ni/MH battery were studied. After overdischarge, La(OH) 3 and Al(OH) 3 are found to form in the negative electrode through XRD analysis. The ...The influences of deeply overdischarge on the negative electrode alloy of Ni/MH battery were studied. After overdischarge, La(OH) 3 and Al(OH) 3 are found to form in the negative electrode through XRD analysis. The hydrogen storage alloy powder from spent Ni/MH batteries was recovered by chemical and melting method according to degradation mechanism. The structure of recovered alloy was measured by XRD. The experimental results demonstrate that the alloy structure is CaCu 5 type. The constant current charge/discharge test was carried out to the original alloy and the recovered alloy. It is found that their discharge capacities are almost the same, but the discharge potential of the recovered alloy is higher than that of the original alloy. The results of cyclic lifetime test demonstrate that the capacity degradation of the recovered alloy is slower than that of the original one.展开更多
Phase structure and electrochemical characteristics of Co-free La0.7Ce0.3(Ni3.65Cu0.75Mn0.35Al0.15(Fe0.43B0.57)0.10)x (0.90≤x≤1.10) alloys were investigated. When x was 0.90, the alloy was composed of LaNi5, L...Phase structure and electrochemical characteristics of Co-free La0.7Ce0.3(Ni3.65Cu0.75Mn0.35Al0.15(Fe0.43B0.57)0.10)x (0.90≤x≤1.10) alloys were investigated. When x was 0.90, the alloy was composed of LaNi5, La3Ni13B2 and Ce2Ni7 phases. The Ce2Ni7 phase disappeared, and the abundant of La3Ni13B2 phase decreased when x increased to 0.95. When x was 1.00 or higher the alloys consisted of LaNi5 phase. The lattice parameter a and the cell volume V of the LaNi5 phase decreased, and the c/a ratio of the LaNi5 phase increased with x value increasing. Maximum discharge capacity of the alloy electrodes first increased and then decreased with x value increasing from 0.90 to 1.10, and the highest value was obtained when x was 1.00. High-rate dischargeability at the discharge current density of 1200 mA/g increased from 50.7% (x= 0.90) to 64.1% (x=1.10). Both the charge-transfer reaction at the electrode/electrolyte interface and the hydrogen diffusion in the alloy were responsible for the high-rate dischargeability. Cycling capacity retention rate at 100^th cycle ($10o) gradually increased from 77.3% (x= 0.90) to 84.6% (x= 1.10), which resulted from the increase in Ni content and the c/a ratio of the LaNi5 phase with x value increasing.展开更多
Microstructure and electrochemical characteristics of La0.7Ce0.3Ni3.75Mn0.35Al0.15Cu0.75-x(V0.81Fe0.19)x hydrogen storage alloys were investigated. XRD indicated that La0.7Ce0.3Ni3.75Mn0.35Al0.15Cu0.75-x(V0.81Fe0.1...Microstructure and electrochemical characteristics of La0.7Ce0.3Ni3.75Mn0.35Al0.15Cu0.75-x(V0.81Fe0.19)x hydrogen storage alloys were investigated. XRD indicated that La0.7Ce0.3Ni3.75Mn0.35Al0.15Cu0.75-x(V0.81Fe0.19)x alloys consisted of a single phase with CaCus-type structure, and the lattice parameter a and cell volume V increased with increasing x value. The maximum discharge capacity first increased from 319.0 (x=0) to 324.0 mAh/g (x=0.05), and then decreased to 307.0 mAh/g (x=0.20). The high-rate dischargeability at the discharge current density of 1200 mA/g first increased from 52.1% (x=0) to 59.1% (x=0.15), and then decreased to 55.4% (x=0.20). The hydrogen diffusion in the bulky alloy was responsible for the high-rate dischargeability. Cycling stability first increased with increasing x from 0 to 0.10 and then de- creased when x increased to 0.20, which was resulted fi'om the synthesized effect of the improvement of the pulverization resistance and the decrease of corrosion resistance.展开更多
The effect of chemical plating with Ni Co P alloy on the properties of MH electrodes is investigated. The results show that the efficiency of storage alloy and the activation of MH electrode have been improved by intr...The effect of chemical plating with Ni Co P alloy on the properties of MH electrodes is investigated. The results show that the efficiency of storage alloy and the activation of MH electrode have been improved by introducing 1.74% cobalt in the Ni Co P alloy coating. The initial discharge capacity is 208 mAh/g. The maximum discharge capacity gets to 298.5 mAh/g. At the same time the cycle life of MH electrodes is improved. The discharge capacity of MH electrodes coated with Ni Co P is 88% of the maximum discharge capacity after 300 cycles. Whereas the discharge capacity of bare alloy electrodes retains 62% of the maximum capacity after 300 cycles. An increment of discharge capacity is mainly due to the superposition of the oxidation current of Co as well as improved efficiency of microcurrent collection. The effect of Ni Co P alloy coating by electroless plating on the kinetic properties of hydride electrode has been systematically investigated by electrochemical techniques. The results indicate that the kinetic properties of MH electrodes, including exchange current density, limiting current density, have been improved markedly. This improvement of kinetic properties leads to the decrease of the overpotential of anodic and cathodic polarization.展开更多
Effects of iron phthalocyanine (FePc) on the inner pressure of MH/Ni batteries dur-ing charging were examined. Experimental results show that the battery with appropriate quantity of FePc displays a much lower inner p...Effects of iron phthalocyanine (FePc) on the inner pressure of MH/Ni batteries dur-ing charging were examined. Experimental results show that the battery with appropriate quantity of FePc displays a much lower inner pressure under charging and overcharging than the battery without FePc, especially the battery with 1 mg FePc exhibits the slowest increasing speed of inner pressure and the best charging efficiency and overchargeability.展开更多
On the basis of typical high Co MI(Lanthanum rich mischmetal) based hydrogen storage alloy, a series oflow Co or Co free alloys have been prepared by means of partial or full replacement of Co by a combination of othe...On the basis of typical high Co MI(Lanthanum rich mischmetal) based hydrogen storage alloy, a series oflow Co or Co free alloys have been prepared by means of partial or full replacement of Co by a combination of other elements. The microstructures, p c T (pressure concentration temperature) characteristics and electrochemical propertiesunder different charge discharge conditions of the alloys have been investigated. Compared with the high Co alloy, thelow Co or Co free alloys have the lower hydrogen equilibrium pressure and discharge capacity, but have the nearly samehigh rate and high temperature discharge capability, and better charge discharge cycling stability. The reason is revealedby SEM, XPS and XRD results. \[展开更多
A series of hydrogen storage Co-free AB3-type alloys were directly synthesized with vacuum mid-frequency melting method,within which Ni of La0.7Mg0.3Ni3 alloy was substituted by Fe,B and(FeB) alloy,respectively.Alloys...A series of hydrogen storage Co-free AB3-type alloys were directly synthesized with vacuum mid-frequency melting method,within which Ni of La0.7Mg0.3Ni3 alloy was substituted by Fe,B and(FeB) alloy,respectively.Alloys were characterized by XRD,EDS and SEM to investigate the effects of B and Fe substitution for Ni on material structure.The content of LaMg2Ni9 phase within La0.7Mg0.3Ni3 alloy reaches 37.9% and that of La0.7Mg0.3Ni2.9(FeB)0.1 alloys reduces to 23.58%.Among all samples,ground particles with different shapes correspond to different phases.The major substitution occurs in LaMg2Ni9 phase.Electrochemical tests indicate that substituted alloys have different electrochemical performance,which is affected by phase structures of alloy.The discharge capacity of La0.7Mg0.3Ni3 alloy reaches 337.3 mA·h/g,but La0.7Mg0.3Ni2.9(FeB)0.1 alloy gets better high rate discharge(HRD) performance at the discharge rate of 500 mA/g with a high HRD value of 73.19%.展开更多
文摘The effects of low-Co AB_5 type hydrogen storage alloys prepared by quenchingand annealing on the performances of MH-Ni batteries were investigated, and the characteristics ofthe low-Co AB_5 type hydrogen storage alloys were compared with those of the high-Co AB_5 typehydrogen storage alloy as well. The results showed that the faster the cooling of the low-Cohydrogen storage alloy is, the better homogeneity of the chemical composition for the alloy and thelonger cycle life of the battery are, but the electrochemical discharge capacity and high-ratedischarge ability are reduced. The high-rate discharge ability and charge retention of MH-Nibatteries for the conventional as-cast annealed low-Co hydrogen storage alloy were superior to thosefor the rapidly quenched low-Co hydrogen storage alloy and the high-Co hydrogen storage alloy, buta little inferior in the cycle life.
基金supported by the Key Projects in International Science and Technology Cooperation from Ministry of Science and Technology of the PRC (2006DFB52550, 2007DFA51020)the National Natural Science Foundation of China (20363001)
文摘In order to investigate the effect of substituting La with Pr on structural and hydrogen storage properties of La-Mg-Ni system (AB3.5-type) hydrogen storage alloys, a series of La0.65-xPrxNd0.12Mg0.23Ni3.4Al0.1(x=0, 0.10, 0.15, 0.2) hydrogen storage alloys were prepared. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) analyses revealed that two alloys (x=0.0 and 0.10) were composed of (La,Mg)2(Ni,Al)7 phase, La(Ni,A1)5 phase and (La,Mg)Ni2 phase, while other alloys (x=0.15 and 0.20) consisted of (La,Mg)2(Ni,A1)7 phase, La(Ni,A1)5 phase, (La,Mg)Ni2 phase and (La,Mg)(Ni,A1)3 phase. All alloys showed, however, only one pressure plateau in P-C isotherms. The Pr/La ratio in alloy composition influenced hydrogen storage capacity and kinetics properties. Electrochemical studies showed that the discharge capacity decreased from 360 mAh/g (x=-0.00) to 335 mAh/g (x=-0.20) as x increased. But the high-rate dischargeability (HRD) of alloy electrodes increased from 26% (x=0.00) to 56% (x=-0.20) at a discharge current density of Id=1800 mA/g. Anode polarization measurements were done to further understand the electrochemical kinetics properties after Pr substitution.
文摘The effect of heat-treatment process on the properties of Mm0.8Mg0.2(NiCoAlMn)3.5 hydrogen storage alloy was discussed . The electrochemical properties such as cycling stability, activation property, and the plateau voltage of the alloy which was heat-treated in various temperatures and times had different changes during the cycle process, the optimum heat-treatment conditions of this alloy were determined by this work.
文摘The structure and electrochemical properties of the La0.7Mg0.3Ni3.4-xMn0.1Cox (x=01.05) hydrogen storage alloys were investigated. The crystal structure and the lattice parameters of the alloys were analyzed by X-ray diffractometry and Rietveld method. Electrochemical properties of the alloys including p—c—t curves, discharge capacity, discharge capacity retention were studied. The results show that (La, Mg)Ni3 and LaNi5 are the main phases of all the alloys. The plateau pressure for hydrogen absorption/desorption decreases and the hydrogen storage capacity firstly increases and subsequently decreases with increasing Co content. The values of the maximum discharge capacity of the alloy electrodes remain in range of 395.3403.1mA·h/g in spite of the change of Co content. The cycling stability of the alloy electrodes is greatly improved with increasing Co content, which is attributed to the suppression of the cell volume expansion during hydriding, leading the pulverization of the alloy particles lowered and the oxidation/corrosion of the active elements reduced.
文摘Ti-based AB2-type hydrogen storage alloys are a group of promising materials, which will probably replace the prevalent rare earth-based AB5-type alloys and be adopted as the main cathode materials of nickel-metal hydride (Ni-MH) batteries in the near future. Alloying in side B is a major way to improve the performance of Ti-based AB2-type alloys. Based on recent studies, the effects of alloying elements in side B upon the performance of Ti-based AB2-type hydrogen storage alloys are systematically reviewed here. These performances are divided into two categories, namely PCI characteristics, including hydrogen storage capacity (HSC), plateau pressure (PP), pressure hysteresis (PH) and pressure plateau sloping (PPS), and electrochemical properties, including discharge capacity (DC), activation property (AP), cycling stability (CS) and high-rate dischargeability (HRD). Furthermore, the existing problems in these investigations and some suggestions for future research are proposed.
文摘Oxygen evolution causes a high inner pressure during charge and overcharge for MH/Ni battery, and an inappropriate eliminating way of the oxygen in the battery results in accumulation of heat. This is the main obstacle to develop and apply high capability and high power battery. How to reduce the ratio of the chemical catalysis rate to the electric catalysis rate in MH/Ni battery is considered as an urgent question. Iron phthalocyanine(FePc) was chosen as an electrochemical catalyst. The batteries were prepared by adding iron phthalocyanine with different dosages. The inner pressure, the capacity attenuation, the discharge voltage and capacity at high current of these three batteries were compared. The battery with 1 mg FePc in the negative electrode exhibits a good performance.
基金Supported by the National Natural Science Foundation of China(Nos.51571173,51701175,51771164).
文摘In order to improve the electrochemical kinetic performances of La-Mg-Ni-based alloy,complex surface modification of Ni with excellent catalytic activity and conducting polymer polypyrrole(PPy)was performed via electroless plating method.FESEM images revealed that the complex Ni-PPy treatment resulted in more micropores at the alloy surface,with Ni particles and cotton fiber-shape PPy microspheres attached.Both the larger surface area induced by the micropore and the higher catalytic activity and conductivity on account of the dispersed Ni particles/PPy microspheres promoted the electrode reaction,thereby increasing the discharge capacity of the modified alloy electrode.Electrochemical impedance spectroscopy(EIS)and linear polarization results showed that the Ni-PPy treatment decreased the charge-transfer resistance and increased the exchange current density greatly,far more than the single-component Ni or PPy treatment.Consequently,a notable improvement in high rate dischargeability(HRD)was observed,and at a high discharge current density of 1800 mA/g,the HRD of the modified electrode increased by 10.4%compared with that of the bare electrode.
文摘Rare earth compositions, La, Ce and Pr in Mm(NiCoMnAl)(5) hydrogen storage alloy, were arranged by uniform design method. The discharge performances and kinetics parameters including capacity, exchange current density, symmetry factor and hydrogen diffusion coefficient of the alloy at -40degreesC, were tested in standard tri-electrode cell. And linear regression method was used to analyze the effect of rare earth compositions on the performances of hydrogen storage alloys. The results show that the capacities of the alloys are positively correlative to the square of Ce content at -40degreesC and under both 0.4 and 0.2C rate. The kinetics parameters and hydrogen diffusion coefficient indicate that the low-temperature performances of the alloys are mainly controlled by hydrogen diffusion process, and the surface electrochemical reaction affects the low-temperature performances to a certain extent. The low-temperature discharge capacities of the battery were also tested. The results show excellent low-temperature performances. The battery delivers 69.6% of its room-temperature capacity at -40degreesC and 0.2C rate, 77.7% at -40degreesC and 0.4C rate, 59.1% at -45degreesC and 0.2C rate.
基金Project (2001AA322050) supported by the National Hi-tech Research and Development Program of China
文摘AB5 hydrogen storage alloys La0.54Ce0.28Pr0.18Ni4-xCo0.6Mn0.35Alx(x=0.1,0.2,0.3) were prepared by arc melting method under an Ar atmosphere. The results show that the contents of Ni and Al have obvious influences on the microstructure and electrochemical properties of the alloys. Both the lattice parameters and the cell volumes decrease with decreasing x value. Moreover,the discharge capacity at different temperatures,the high rate discharge property,and the cycling life of the alloy electrode are also in close relationship with the x value. When x value increases from 0.1 to 0.3,the discharge capacities with a discharge current density of 60 mA/g slightly decreases at 25 ℃,but evidently deteriorates at -40 ℃,the high-rate property gravely decreases,and the cycle life of the alloy electrode is improved in some extent. Therefore,it is meaningful to control Al content for the AB5 hydrogen storage alloys used in Ni/MH batteries.
文摘The influences of deeply overdischarge on the negative electrode alloy of Ni/MH battery were studied. After overdischarge, La(OH) 3 and Al(OH) 3 are found to form in the negative electrode through XRD analysis. The hydrogen storage alloy powder from spent Ni/MH batteries was recovered by chemical and melting method according to degradation mechanism. The structure of recovered alloy was measured by XRD. The experimental results demonstrate that the alloy structure is CaCu 5 type. The constant current charge/discharge test was carried out to the original alloy and the recovered alloy. It is found that their discharge capacities are almost the same, but the discharge potential of the recovered alloy is higher than that of the original alloy. The results of cyclic lifetime test demonstrate that the capacity degradation of the recovered alloy is slower than that of the original one.
基金Project supported by National Natural Science Foundation of China (51001043)Program for New Century Excellent Talents in University (NCET2011)+3 种基金China Postdoctoral Science Special Foundation (201104390, 20100470990)Program for Innovative Research Team (in Science and Technology) in the University of Henan Province (2012IRTSTHN007)Baotou Science and Technology Project (2011J1003)and the Doctoral Foundation of Henan Polytechnic University (B2010-13)
文摘Phase structure and electrochemical characteristics of Co-free La0.7Ce0.3(Ni3.65Cu0.75Mn0.35Al0.15(Fe0.43B0.57)0.10)x (0.90≤x≤1.10) alloys were investigated. When x was 0.90, the alloy was composed of LaNi5, La3Ni13B2 and Ce2Ni7 phases. The Ce2Ni7 phase disappeared, and the abundant of La3Ni13B2 phase decreased when x increased to 0.95. When x was 1.00 or higher the alloys consisted of LaNi5 phase. The lattice parameter a and the cell volume V of the LaNi5 phase decreased, and the c/a ratio of the LaNi5 phase increased with x value increasing. Maximum discharge capacity of the alloy electrodes first increased and then decreased with x value increasing from 0.90 to 1.10, and the highest value was obtained when x was 1.00. High-rate dischargeability at the discharge current density of 1200 mA/g increased from 50.7% (x= 0.90) to 64.1% (x=1.10). Both the charge-transfer reaction at the electrode/electrolyte interface and the hydrogen diffusion in the alloy were responsible for the high-rate dischargeability. Cycling capacity retention rate at 100^th cycle ($10o) gradually increased from 77.3% (x= 0.90) to 84.6% (x= 1.10), which resulted from the increase in Ni content and the c/a ratio of the LaNi5 phase with x value increasing.
基金Project supported by National Natural Science Foundation of China(51001043)China Postdoctoral Science Special Foundation(201104390,20100470990)+2 种基金Program for Innovative Research Team(in Science and Technology)in the University of Henan Province(2012IRTSTHN007)Baotou Science and Technology Project(2011J1003)the Doctoral Foundation of Henan Polytechnic University(B2010-13)
文摘Microstructure and electrochemical characteristics of La0.7Ce0.3Ni3.75Mn0.35Al0.15Cu0.75-x(V0.81Fe0.19)x hydrogen storage alloys were investigated. XRD indicated that La0.7Ce0.3Ni3.75Mn0.35Al0.15Cu0.75-x(V0.81Fe0.19)x alloys consisted of a single phase with CaCus-type structure, and the lattice parameter a and cell volume V increased with increasing x value. The maximum discharge capacity first increased from 319.0 (x=0) to 324.0 mAh/g (x=0.05), and then decreased to 307.0 mAh/g (x=0.20). The high-rate dischargeability at the discharge current density of 1200 mA/g first increased from 52.1% (x=0) to 59.1% (x=0.15), and then decreased to 55.4% (x=0.20). The hydrogen diffusion in the bulky alloy was responsible for the high-rate dischargeability. Cycling stability first increased with increasing x from 0 to 0.10 and then de- creased when x increased to 0.20, which was resulted fi'om the synthesized effect of the improvement of the pulverization resistance and the decrease of corrosion resistance.
文摘The effect of chemical plating with Ni Co P alloy on the properties of MH electrodes is investigated. The results show that the efficiency of storage alloy and the activation of MH electrode have been improved by introducing 1.74% cobalt in the Ni Co P alloy coating. The initial discharge capacity is 208 mAh/g. The maximum discharge capacity gets to 298.5 mAh/g. At the same time the cycle life of MH electrodes is improved. The discharge capacity of MH electrodes coated with Ni Co P is 88% of the maximum discharge capacity after 300 cycles. Whereas the discharge capacity of bare alloy electrodes retains 62% of the maximum capacity after 300 cycles. An increment of discharge capacity is mainly due to the superposition of the oxidation current of Co as well as improved efficiency of microcurrent collection. The effect of Ni Co P alloy coating by electroless plating on the kinetic properties of hydride electrode has been systematically investigated by electrochemical techniques. The results indicate that the kinetic properties of MH electrodes, including exchange current density, limiting current density, have been improved markedly. This improvement of kinetic properties leads to the decrease of the overpotential of anodic and cathodic polarization.
文摘Effects of iron phthalocyanine (FePc) on the inner pressure of MH/Ni batteries dur-ing charging were examined. Experimental results show that the battery with appropriate quantity of FePc displays a much lower inner pressure under charging and overcharging than the battery without FePc, especially the battery with 1 mg FePc exhibits the slowest increasing speed of inner pressure and the best charging efficiency and overchargeability.
文摘On the basis of typical high Co MI(Lanthanum rich mischmetal) based hydrogen storage alloy, a series oflow Co or Co free alloys have been prepared by means of partial or full replacement of Co by a combination of other elements. The microstructures, p c T (pressure concentration temperature) characteristics and electrochemical propertiesunder different charge discharge conditions of the alloys have been investigated. Compared with the high Co alloy, thelow Co or Co free alloys have the lower hydrogen equilibrium pressure and discharge capacity, but have the nearly samehigh rate and high temperature discharge capability, and better charge discharge cycling stability. The reason is revealedby SEM, XPS and XRD results. \[
基金Project(2007AA11A104) supported by the High-tech Research and Development Program of ChinaProject(2009CB220100) supported by the National Basic Research Program of China
文摘A series of hydrogen storage Co-free AB3-type alloys were directly synthesized with vacuum mid-frequency melting method,within which Ni of La0.7Mg0.3Ni3 alloy was substituted by Fe,B and(FeB) alloy,respectively.Alloys were characterized by XRD,EDS and SEM to investigate the effects of B and Fe substitution for Ni on material structure.The content of LaMg2Ni9 phase within La0.7Mg0.3Ni3 alloy reaches 37.9% and that of La0.7Mg0.3Ni2.9(FeB)0.1 alloys reduces to 23.58%.Among all samples,ground particles with different shapes correspond to different phases.The major substitution occurs in LaMg2Ni9 phase.Electrochemical tests indicate that substituted alloys have different electrochemical performance,which is affected by phase structures of alloy.The discharge capacity of La0.7Mg0.3Ni3 alloy reaches 337.3 mA·h/g,but La0.7Mg0.3Ni2.9(FeB)0.1 alloy gets better high rate discharge(HRD) performance at the discharge rate of 500 mA/g with a high HRD value of 73.19%.