Effect of electrolyte concentration on low-temperature electrochemical properties of LaNi_5 alloy electrodes at 233 K

The effect of KOH electrolyte concentration on low-temperature electrochemical properties of LaNi5 alloy electrodes at 233 K was studied. The results indicated that the electrolyte concentration had great influence on discharge capacity and discharge voltage plateau of LaNi5 alloy electrode at 233 K, and the highest discharge capacity and discharge voltage plateau were both obtained at 6 mol/L KOH. When the KOH electrolyte concentration changed from 5 to 9 mol/L at 233 K, the high rate discharge ability （HRD） had the same change tendency as the diffusion coefficient, but the exchange current density did not change significantly, which implied that hydrogen diffusion was the control step at low temperature 233 K for discharge process of LaNi5 alloy electrode.

Microstructure and electrochemical properties of low-temperature hydrogen storage alloy used in Ni/MH batteries

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.

Unveiling the tailorable electrochemical properties of zeolitic imidazolate framework-derived Ni-doped LiCoO_(2) for lithium-ion batteries in half/full cells

As a prevailing cathode material of lithium-ion batteries(LIBs),LiCoO_(2)(LCO)still encounters the tricky problems of structural collapse,whose morphological engineering and cation doping are crucial for surmounting the mechanical strains and alleviating phase degradation upon cycling.Hereinafter,we propose a strategy using a zeolitic imidazolate framework(ZIF)as the self-sacrificing template to directionally prepare a series of LiNi_(0.1)Co_(0.9)O_(2)(LNCO)with tailorable electrochemical properties.The rational selection of sintering temperature imparts the superiority of the resultant products in lithium storage,during which the sample prepared at 700℃(LNCO-700)outperforms its counterparts in cyclability(156.8 mA h g^(-1)at 1 C for 200 cycles in half cells,1 C=275 mA g^(-1))and rate capability due to the expedited ion/electron transport and the strengthen mechanical robustness.The feasibility of proper Ni doping is also divulged by half/full cell tests and theoretical study,during which LNCO-700(167 mA h g^(-1)at 1 C for 100 cycles in full cells)surpasses LCO-700 in battery performance due to the mitigated phase deterioration,stabilized layered structu re,ameliorated electro nic co nductivity,a nd exalted lithium sto rage activity.This work systematically unveils tailorable electrochemical behaviors of LNCO to better direct their practical application.

Effects of anode slime removing by Fe^(2+)dissolution method on electrochemical properties of Pb−0.6%Ag anode and zinc electrowinning

Fe^(2+)dissolution method and manual method were used to remove the anode slime and their effects on properties of cast Pb−0.6wt.%Ag anode and zinc electrowinning were compared.The results reveal that the Fe^(2+)dissolution method can avoid mechanical damage to the oxide film layer on the anode surface,which cannot be achieved by traditional manual method.This can lower the anode corrosion rate by 57.14%,thus reducing Pb contamination in electrolyte and zinc products.Meanwhile,compared with manual method,Fe^(2+)dissolution method can significantly improve the electrocatalytic activity of the anode and lower the initial power consumption of zinc electrowinning to 2720 kW·h/t after removing anode slime.

Electrochemical properties of magnesium alloy anodes discharged in seawater

Magnesium alloys can be developed as anode materials for seawater activated batteries. The electrochemical properties of AZ31, AP65 and Mg-3%Ga-2%Hg alloy anodes discharged in seawater were studied. The potentiodynamic polarization shows that the Mg-3%Ga-2%Hg alloy provides more negative corrosion potentials than AZ31 or AP65 alloy. The galvanostatic discharge results show that the Mg-3%Ga-2%Hg alloy exhibits good electrochemical properties as anodes in seawater. And the EIS studies reveal that the magnesium alloy anode/seawater interfacial process is determined by an activation controlled reaction. The Mg3Hg and Mg21Ga5Hg3 phases in Mg-3%Ga-2%Hg alloy improve its electrochemical properties better than the Mg17（Al,Zn）12 phase in AZ31 and Mg（Pb） solid solution phase in AP65 alloys.

Phase structure and electrochemical properties of La_(1.7+x)Mg_(1.3-x)(NiCoMn)_(9.3)(x=0-0.4) hydrogen storage alloys

The phase structure and electrochemical properties of La1.7＋xMg1.3-x（NiCoMn）9.3（x=0-0.4） alloys were investigated. The XRD analysis reveals that the alloys consist of LaNi5 phase and other phases, such as LaMg2Ni9 phase （PuNi3 structure） and La4MgNi19 phases （Ce5Co19＋Pr5Co19 structure, namely A5B19 type）. With the increase of the x value, the LaMg2Ni9 phase fades away and La4MgNi19 phases appear, while the abundance of LaNi5 phase firstly increases and then decreases. At the same time, the cell volume of LaNi5 phase and LaMg2Ni9 phase decreases. The electrochemical measurement shows that alloy electrodes could be activated in 4-5 cycles, and with the increase of the x value, the maximum discharge capacity gradually increases from 330.9 mA-h/g （x=0） to 366.8 mA-h/g （x=0.4）, but the high-rate dischargeability （HRD） and cyclic stability （S） decrease somewhat （x=0.4, HRD600=82.32%, S100=73.8%）. It is found that the HRD is mainly controlled by the electrocatalytic activity on the alloy electrode surface, and the decline of cyclic stability is due to the appearance of A5B19 type phase with larger hydrogen storage capacity, which leads to larger volume expansion and more intercrystalline stress and then easier pulverization during charging/discharging.

Phase structure and electrochemical properties of La_(0.7)Ce_(0.3)Ni_(3.75)Mn_(0.35)Al_(0.15)Cu_(0.75-x)Fe_x hydrogen storage alloys

La0.7Ce0.3Ni3.75Mn0.35Al0.15Cu0.75-xFex （x=0-0.20） hydrogen storage alloys were synthesized by induction melting and subsequent annealing treatment, and phase structure and electrochemical characteristics were investigated. All alloys consist of a single LaNi5 phase with CaCu5 structure, and the lattice constant a and the cell volume （V） of the LaNi5 phase increase with increasing x value. The maximum discharge capacity gradually decreases from 319.0 mA？h/g （x=0） to 291.9 mA？h/g （x=0.20） with the increase in x value. The high-rate dischargeability at the discharge current density of 1200 mA/g decreases monotonically from 53.1% （x=0） to 44.2% （x=0.20）. The cycling stability increases with increasing x from 0 to 0.20, which is mainly ascribed to the improvement of the pulverization resistance.

Influence of heat treatment on electrochemical properties of Ti_(1.4)V_(0.6)Ni alloy electrode containing icosahedral quasicrystalline phase

The structures and electrochemical properties of the Ti1.4V0.6Ni ribbon before and after heat treatment are investigated systematically. The structure of the sample is characterized by X-ray powder diffraction analysis. Electrochemical properties including the discharge capacity, the cyclic stability and the high-rate discharge ability are tested. X-ray powder diffraction analysis shows that after heat treatment at 590 °C for 30 min, all samples mainly consist of the icosahedral quasicrystal phase (I-phase), Ti2Ni phase (FCC), V-based solid solution phase (BCC) and C14 Laves phase (hexagonal). Electrochemical measurements show that the maximum discharge capacity of the alloy electrode after heat treatment is 330.9 mA?h/g under the conditions that the discharge current density is 30 mA/g and the temperature is 30 °C. The result indicates that the cyclic stability and the high-rate discharge ability are all improved. In addition, the electrochemical kinetics of the alloy electrode is also studied by electrochemical impedance spectroscopy (EIS) and hydrogen diffusion coefficient (D).

Structure and electrochemical performance of delafossite AgFeO_(2)nanoparticles for supercapacitor electrodes

Delafossite AgFeO_(2)nanoparticles with a mixture of 2H and 3R phases were successfully fabricated by using a simple co-precipitation method.The resulting precursor was calcined at temperatures of 100,200,300,400,and 500℃to obtain the delafossite AgFe0_(2)phase.The morphology and microstructure of the prepared AgFeO_(2)samples were characterized by using field emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM),N_(2) adsorption/desorption,X-ray absorption spectroscopy(XAS),and Xray photoelectron spectroscopy(XPS)techniques.A three-electrode system was employed to investigate the electrochemical properties of the delafossite AgFeO_(2)nanoparticles in a 3 M KOH electrolyte.The delafossite AgFeO_(2)nanoparticles calcined at 100℃(AFO100)exhibited the highest surface area of 28.02 m^(2)·g^(-1)and outstanding electrochemical performance with specific capacitances of 229.71 F·g^(-1)at a current density of 1 A·g^(-1)and 358.32 F·g^(-1)at a scan rate of 2 mV·s^(-1).This sample also demonstrated the capacitance retention of 82.99% after 1000 charge/discharge cycles,along with superior specific power and specific energy values of 797.46 W·kg^(-1)and 72.74Wh·kg^(-1),respectively.These findings indicate that delafossite AgFeO_(2)has great potential as an electrode material for supercapacitor applications.

Effects of annealing treatment on the microstructure and electrochemical properties of low-Co hydrogen storage alloys containing Cu and Fe

The effects of annealing treatment on the microstructure and electrochemical properties of low-Co LaNi 3.55 Mn 0.35 Co 0.20 Al 0.20 Cu 0.75 Fe 0.10 hydrogen storage alloys were investigated. X-ray diffraction （XRD） analysis indicated that annealing treatment remarkably reduced the lattice strain and defects, and increased the unit-cell volume. The optical microscope analysis showed that the as-cast alloy had a crass dendrite microstructure with noticeable composition segregation, which gradually disappeared with increasing annealing temperature, and the micro-structure changed to an equiaxed structure after annealing the alloy at 1233 K. The electrochemical tests indicated that the annealed alloys demonstrated much better cycling stability compared with the as-cast one. The capacity retention at the 100th cycle increased from 90.0% （as-cast） to 94.7% （1273 K）. The annealing treatment also improved the discharge capacity. However, the high rate dischargeability （HRD） value of the annealed alloy slightly dropped, which was believed to be ascribed to the decreased exchange current density and the hydrogen diffusion coefficient in alloy bulk.

Heat treatment effect on electrochemical properties of spinel Li_4Ti_5O_(12)

Anode material Li4Ti5O12 was prepared at 800℃ by a solid-state reaction, followed by heat-treatment at 600℃ for different times （0, 2, 8, and 12 h）. The effects of heat-treatment time on the particle morphology, rate-capability, and electrode kinetic process of the Li4Ti5O12 electrode, and on the lithium ion diffusion coefficient inside the Li4Ti5O12 electrode were investigated. Proper heat treatment could smoothen the particle surface of Li4Ti5O12 particles and increase the rate-capability of the electrode. Overlong heat treatment might cause particle aggregation and hence result in a poor electrode kinetic process. A sample with 8 h of heat treatment showed the best rate-capability and the lowest electrode reaction resistance. Heat treatment for 2-8 h does not significantly change the lithium ion diffusion coefficient inside the Li4Ti5O12 electrode, whereas, 12-h treatment results in a lower lithium ion diffusion coefficient.

Carbon-coated manganese dioxide nanoparticles and their enhanced electrochemical properties for zinc-ion battery applications

In this study, we report the cost-effective and simple synthesis of carbon-coated α-MnOnanoparticles(α-MnO@C) for use as cathodes of aqueous zinc-ion batteries(ZIBs) for the first time. α-MnO@C was prepared via a gel formation, using maleic acid(CHO) as the carbon source, followed by annealing at low temperature of 270 °C. A uniform carbon network among the α-MnOnanoparticles was observed by transmission electron microscopy. When tested in a zinc cell, the α-MnO@C exhibited a high initial discharge capacity of 272 m Ah/g under 66 m A/g current density compared to 213 m Ah/g, at the same current density, displayed by the pristine sample. Further, α-MnO@C demonstrated superior cycleability compared to the pristine samples. This study may pave the way for the utilizing carbon-coated MnOelectrodes for aqueous ZIB applications and thereby contribute to realizing high performance eco-friendly batteries.

Effects of acetic acid on microstructure and electrochemical properties of nano cerium oxide films coated on AA7020-T6 aluminum alloy

Nano cerium oxide films were applied on AA7020-T6 aluminum alloy and the effects of acetic acid concentration on the microstructure and electrochemical properties of the coated samples were investigated by using scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and potentiodynamic polarization methods. It has been found that by increasing the acetic acid/CeCl3·7H2O molar ratio, high uniform and crack-free films with well-developed grains were obtained and grain sizes of the films decreased. Elimination of cracks and decreasing grain size of the nano cerium oxide films caused corrosion resistance to increase.

Hydrothermal Synthesis,Crystal Structure and Electrochemical Properties of Complex Cu(α-Furacrylic acid)_2(phen)

The title complex （C26H18CuN206, Mr= 517.96） has been synthesized by the reaction of α-furanacrylic acid with 1,10-phenanthroline （phen） in the solvent mixture of water and methanol. Crystal data： monoclinic, space group C2/c with a = 2.2927（4）, b = 1.01248（18）, c = 1.05061（18） nm, β = 111.188（3）°, V= 2.274（7） nm^3, Dc = 1.513 g/cm^3, Z = 4, F（000） = 1060,μ = 1.007mm^-1, R = 0.0320 and ωR = 0.0781. The crystal structural analysis shows that the copper atom is coordinated with four oxygen atoms from two α-furacrylic acids and two nitrogen atoms from 1,10-phenanthroline, giving a distorted octahedral coordination geometry. The result of electrochemical analysis shows that the electron transfer in the electrode reaction is quasi-reversible.

Effects of Cr content on electrochemical properties of melt-spun Al_(75-x)Si_(25)Cr_x alloy anodes for lithium-ion batteries

Melt-spun Al75-xSi25Crx （x=2, 4, 7, 10, mole fraction, %） alloys were investigated as anode materials for lithium-ion batteries. The as-quenched ribbons consist of nano-grains and metallic glass. The electrochemical measurements reveal that an activation behavior is exhibited in the anodes. The specific capacity of the A173Si25Cr2 anodes can reach a maximum of 1119 mA.h/g and maintain at 586 mA·hg after 30 cycles. A more stable cycle performance is shown and a capacity loss is only 24% over 30 cycles for Al71Si25Cr4. The intermetallic compounds with Li cannot be detected in the lithiated anodes. After the ribbons were annealed, the specific capacities become much lower due to the formation of inert Al13SiaCr4, and an A1Li phase can be tested in the lithiated anodes. The Cr dissolved in the non-equilibrium alloys causes low lithiation activity and strong structure stability, which could be the main reason of the activation and a restriction of structure evolution.

Synthesis, Crystal Structure and Electrochemical Properties of a One-dimensional Chain Coordination Polymer [Cu(phen)(2,4,6-TMBA)_2(H_2O)]_n

A one-dimensional chain coordination polymer [Cu（phen）（2,4,6-TMBA）2（H2O）]n has been synthesized by reacting 2,4,6-trimethyl-benzoic acid, 1,10-phenanthroline and Cu（Ⅱ） perchlorate and its structure was characterized. Crystal data for this complex： tetragonal, space group I41, a = 2.0293（3）, b = 2.0293（3）, c = 1.3758（2） nm, α =β= γ = 90°, V= 5.6657（13） nm3, Dc= 1.379 g/cm3, Z = 8, μ（MoKa） = 0.815 mm-1, Mr = 588.14, F（000） = 2456, S = 1.047, R = 0.0459 and wR = 0.1053. The crystal structure shows that two neighboring Cu（Ⅱ） ions are linked together by one bridging-chelating 2,4,6-trimethyl-benzoic group, forming a one-dimensional chain structure. Each Cu（Ⅱ） ion is coordinated with two nitrogen atoms from one 1,10-phenanthroline molecule, three oxygen atoms from three 2,4,6-trimethyl-benzoic acid molecules and one oxygen atom from one water molecule, giving a six-coordinate distorted octahedral coordination geometry. The cyclic voltammetry behavior of the complex was also investigated.

Effect of modified elastomeric binders on the electrochemical properties of silicon anodes for lithium-ion batteries

Silicon has been investigated intensively as a promising anode material for rechargeable lithium-ion batteries. The choice of a binder is very important to solve the problem of the large capacity fade observed along cycling. The effect of modified elastomeric binders on the electrochemical performance of crystalline nano-silicon powders was studied. Compared with the conventional binder （polyvinylidene fluoride （PVDF））, Si electrodes using the elastomeric styrene butadiene rubber （SBR） and sodium carboxymethyl cellulose （SCMC） com- bined binder show an improved cycling performance. The reversible capacity of the Si electrode with the SCMC/SBR binder is as high as 2221 mA.h/g for 30 cycles in a voltage window between 0.005 and 2 V. The structure changes from SEM images of the silicon electrodes with different binders were used to explore the property improvement.

Effect of Ni,Fe and Fe-Ni alloy catalysts on the synthesis of metal contained carbon nano-onions and studies of their electrochemical hydrogen storage properties

Three types of carbon nano-onions（CNOs） including Ni@CNOs.Fe3C@CNOs and Fe0.64Ni0.36@CNOs nanoparticles have been synthesized by catalytic decomposition of methane at 850 ℃ using nickel,iron and iron-nickel alloy catalysts.Comparative and systematic studies have been carried out on the morphology,structural characteristics and graphitic crystallinity of these CNOs products.Furthermore,the electrochemical hydrogen storage properties of three types of CNOs have been investigated.Measurements show that the Ni@CNOs have the highest discharge capacity of 387.2 mAh/g,coiTesponding to a hydrogen storage of 1.42%.This comparison study shows the advantages of each catalyst in the growth of CNOs.enabling the controllable synthesis and tuning the properties of CNOs by mediating different metals and their alloy for using in the fuel cell system.

Preparation and electrochemical properties of carbon-coated LiFePO_4 hollow nanofibers

Carbon-coated LiFePO_4 hollow nanofibers as cathode materials for Li-ion batteries were obtained by coaxial electrospinning. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller specific surface area analysis, galvanostatic charge–discharge, and electrochemical impedance spectroscopy（EIS） were employed to investigate the crystalline structure, morphology, and electrochemical performance of the as-prepared hollow nanofibers. The results indicate that the carbon-coated LiFePO_4 hollow nanofibers have good long-term cycling performance and good rate capability： at a current density of 0.2C（1.0C = 170 mA ·g^-1） in the voltage range of 2.5–4.2 V, the cathode materials achieve an initial discharge specific capacity of 153.16 mA h·g^-1 with a first charge–discharge coulombic efficiency of more than 97%, as well as a high capacity retention of 99% after 10 cycles; moreover, the materials can retain a specific capacity of 135.68 mA h·g^-1, even at 2C.

Effects of Strip Casting and Annealing on Electrochemical Properties of LPCNi_(3.55)Co_(0.75)Mn_(0.4)Al_(0.3) Hydrogen Storage Alloys

The effect of thickness (1 similar to 10 mm) of the ingots on the electrochemical properties of as-cast and annealed strip cast LPCNi3.55Co0.75Mn0.4Al0.3 hydrogen storage alloys was investigated. It is found that the 0.2 C discharge capacity of as-cast LPCNi3.55Co0.75Mn0.4Al0.3 alloy increases with the increase of the thickness of the ingots. As-east alloy with the thickness of 10 mm shows better activation property, higher 1C discharge capacity and better cyclic stability than others. It is mainly contributed to its larger unit cell volume and less internal stress. Annealed LPCNi3.55Co0.75Mn0.4Al0.3 alloy with the thickness of 3 mm shows much better comprehensive electrochemical properties than as-east one; The cyclic. stability of the alloy with the thickness of 6 mm and the activation properties of the alloys with the thickness of 3 similar to 6 mm are improved after annealing. It is mainly owing to the great release of internal stress and the decrease of the segregation of Mn in the alloys.