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This study examined the effect of aging at 850 °C on the precipitation of secondary phases and the resultant erosion-corrosion behavior of 25% Cr duplex stainless steels (DSS). An aging time of 30 min, which led to a ratio of reactivation current to activation current (ir/ia × 100) of ˜1% in a DL-EPR test and a current density of ˜0.8 mA cm−2 at 9 m s−1 in a jet impingement test, is regarded as a boundary aging condition for erosion-corrosion. Further, the current density response of ˜0.8 mA cm−2 can be considered a criterion for the surface depassivation resulting from erosion-corrosion.

The solid-state Li–O2 battery is considered an ideal candidate for high-performance energy storage because of its high safety, due to use of non-flammable and non-volatile electrolytes, and high specific energy, as it uses Li metal and O2 gas as active materials. We present an original solid-state Li–O2 cell composed of a Li metal anode, a flexible polymer interlayer, a perovskite-structured Al-doped Li–La–Ti–O (A-LLTO) solid electrolyte, and an integrated cathode in which a porous A-LLTO solid electrolyte frame was covered with a carbon layer and CoO nanoparticles as the catalyst for the cyclic oxygen evolution and reduction reactions. The designed solid-state cell operated safely in pure O2 atmosphere at temperatures from 25 °C to 100 °C and delivered the first discharge capacity from 796 mA h gC+CoO−1 to 4035 mA h gC+CoO−1, respectively, at a current density of 0.05 mA cm−2. Notably, at 50 °C, the cell was maintained for 132 cycles under a limited capacity mode of 500 mA h gC+CoO−1 at a high current density of 0.3 mA cm−2, demonstrating the first step of success towards realizing Li batteries with high energy and cyclability, as well as safety.

Lithium metal has attracted much attention as an anode material for high-performance batteries owing to its high specific capacity and electrode potential. However, the Li metal electrode could suffer from the dendritic growth of Li during the cell operation due to the high reactivity of Li with organic electrolytes. To address this issue, we propose the use of thiourea as an electrolyte additive for Li metal-based batteries. The thiourea additive in LiTFSI/TEGDME electrolyte allowed the formation of a stable and uniform solid electrolyte interface layer on the Li electrode, thereby aiding the suppression of dendritic growth of Li and further electrolyte decomposition. Accordingly, a Li symmetric cell containing the thiourea additive exhibited six-times longer cycle life than a cell without the additive. Further, the electrolyte additive was also successfully employed in a Li-O2 cell to improve its cyclability.

Here, we propose a simple method for direct synthesis of a Si@SiC composite derived from a SiO2@C precursor via a Mg thermal reduction method as an anode material for Li-ion batteries. Owing to the extremely high exothermic reaction between SiO2 and Mg, along with the presence of carbon, SiC can be spontaneously produced with the formation of Si. The synthesized Si@SiC was composed of well-mixed SiC and Si nanocrystallites. The SiC content of the Si@SiC was adjusted by tuning the carbon content of the precursor. Among the resultant Si@SiC materials, the Si@SiC-0.5 sample, which was produced from a precursor containing 4.37 wt % of carbon, exhibits excellent electrochemical characteristics, such as a high first discharge capacity of 1642 mAh g–1 and 53.9% capacity retention following 200 cycles at a rate of 0.1C. Even at a high rate of 10C, a high reversible capacity of 454 mAh g–1 was obtained. Surprisingly, at a fixed discharge rate of C/20, the Si@SiC-0.5 electrode delivered a high capacity of 989 mAh g...

An aluminium-doped lithium lanthanum titanate (A-LLTO) solid electrolyte was prepared using a simple citrate-gel method, and this was followed by a pelletization and the conventional sintering process. When the sintering time was varied at 1350°C for the synthesis of the A-LLTO, the A-LLTO ceramic that was sintered at 1350°C for 6 h exhibited the highest ionic conductivity of 3.17 × 10−4 S cm−1 at 25°C. In addition, the stability and durability of the synthesized A-LLTO ceramic was tested through a one-month aqueous-solution immersion for which the pH values were varied between 0 and 14. The stability of the A-LLTO is the highest in the alkaline environment; furthermore, for its use in the aqueous-electrolyte environment, a protected lithium electrode (PLE) structure was made by combining the lithium (Li) metal, a lithium phosphorous oxynitride (LiPON) interlayer, and the A-LLTO, whereby the LiPON interlayer prevented a direct reaction between the Li metal and the A-LLTO. The Li-LiCoO2 and Li-O2 cells comprising the PLE exhibited a superior electrochemical performance when they were used in the alkaline 1 M LiNO3-electrolyte environment. After 100 cycles of the charge-discharge at the 1C rate, the aqueous Li-LiCoO2 cells maintained 59.3% of the initial capacity with a coulombic efficiency of 98.3%. In addition, the aqueous Li-O2 cell operated stably for 40 cycles under the limited capacity mode of 0.5 mAh cm−2. The outstanding performance of the Li-metal-based cells originates from the A-LLTO solid electrolyte, due to the latter’s high stability, ionic conductivity, and an effective suppression effect regarding the dendritic growth of the Li.

We demonstrate the synthesis of nano Ge/C composite using a facile and cost-effective electrochemical deposition method, and its application as an anode material in Li-ion batteries. Nano Ge/C composite is electrodeposited directly on Cu foil in ethylene glycol containing GeCl 4 and carbon black. The Ge particles with an average size of ∼20 nm are uniformly covered with carbon. Compared with the pure Ge electrode, the Ge/C electrode exhibits a higher first reversible capacity of 1224 mA g −1 , and maintains a capacity of 1095 mAh g −1 at 0.1C over 50 cycles. Even at the high rate of 2C, the capacity of the Ge/C electrode is still high at 972 mAh g −1 . The presence of carbon black and pores in the Ge/C electrode improves the conductivity of the electrode, and mitigates the stress inside the electrode by supplying buffer volume, leading to the enhanced electrochemical characteristics of the electrode. Further, the full Li-ion cell composed of Ge/C anode and LiCoO 2 cathode exhibits good cyclability, rate capability, and coulombic efficiency.

A composite gel polymer electrolyte (CGPE) based on poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) polymer that includes Al-doped Li0.33La0.56TiO3 (A-LLTO) particles covered with a modified SiO2 (m-SiO2) layer was fabricated through a simple solution-casting method followed by activation in a liquid electrolyte. The obtained CGPE possessed high ionic conductivity, a large electrochemical stability window, and interfacial stability-all superior to that of the pure gel polymer electrolyte (GPE). In addition, under a highly polarized condition, the CGPE effectively suppressed the growth of Li dendrites due to the improved hardness of the GPE by the addition of inorganic A-LLTO/m-SiO2 particles. Accordingly, the Li-ion polymer and Li-O2 cells employing the CGPE exhibited remarkably improved cyclability compared to cells without CGPE. In particular, the CGPE as a protection layer for the Li metal electrode in a Li-O2 cell was effective in blocking the contamination of the Li electrode by oxygen gas or impurities diffused from the cathode side while suppressing the Li dendrites.

In this study, a self-encapsulated Sb–C nanocomposite as an anode material for sodium-ion batteries (SIBs) was successfully synthesised using an SbCl3–citrate complex precursor, followed by a drying and calcination process under an inert N2 atmosphere. When the molar ratio of SbCl3 to citric acid was varied from 1 : 1 to 1 : 4, the Sb–C nanocomposite with a molar ratio of 1 : 3 (Sb–C3) exhibited the highest specific surface area (265.97 m2 g−1) and pore volume (0.158 cm3 g−1). Furthermore, the Sb–C3 electrode showed a high reversible capacity of 559 mA h g−1 at a rate of C/10 and maintained a high reversible capacity of 430 mA h g−1 even after 195 cycles at a rate of 1C. The Sb–C3 electrode exhibited an excellent rate capability of 603, 445, and 357 mA h g−1 at the rates of C/20, 5C, and 10C, respectively. Furthermore, a full cell composed of an Sb–C3 anode and a Na3V2(PO4)3 cathode exhibited good specific capacity and cyclability, making the Sb–C composite a promising anode material for high-performance SIBs.

Lithium (Li) metal can be degraded by factors such as irregular Li stripping, Li dendritic growth, and the growth of a solid electrolyte interphase (SEI) layer, finally leading to the performance deterioration of Li–air batteries. In particular, the operation of the Li–air battery in ambient air remains a considerable challenge due to the possible occurrence of parasitic reactions on Li metal with moisture and other contaminants diffusing from the outside air. In this work, a protected Li electrode (PLE) composed of Li metal covered with a bilayer lithium phosphorous oxynitride (LiPON)/aluminium substituted lithium lanthanum titanate (A-LLTO) solid electrolyte was suggested. The mechanism for the degradation of Li electrodes with and without the LiPON/A-LLTO protection layer was compared using the Li symmetric cell and Li–air cell by investigating the electrochemical performance of cells and the growth of Li dendrites. The Li symmetric cell employing the LiPON/A-LLTO exhibited superior cyclability to the cell without the solid electrolyte due to the effective suppression of Li dendritic growth. Further, the aprotic Li–air cell employing the PLE showed outstanding electrochemical performance when operated in pure oxygen and even in an air atmosphere: a long life span of 128 cycles in oxygen atmosphere and 20 cycles in air atmosphere under the limited capacity mode of 1000 mA h g−1. The obtained excellent performance of the Li–air cell employing the PLE is attributed to the effective suppression of the Li dendrite growth and electrolyte decomposition with the presence of LiPON/A-LLTO. In addition, dense LiPON/A-LLTO completely protected the Li metal electrode from the penetration of oxygen, moisture, and other contaminants which can degrade the Li metal electrode.

Germanium oxide (GeO2), which possesses great potential as a high-capacity anode material for lithium ion batteries, has suffered from its poor capacity retention and rate capability due to significant volume changes during lithiation and delithiation. In this study, we introduce a simple synthetic route for producing nanosized GeO2 anchored on a nitrogen-doped carbon matrix (GeO2/N–C) via the sol–gel method followed by a calcination process in an inert argon atmosphere. The GeO2/N–C showed superior electrochemical performance over pure GeO2; almost 91.8% capacity retention of 905 mA h g−1 was shown after 200 cycles at the rate of C/2. Interestingly, even at a high rate of 20C, a specific capacity of 412 mA h g−1 was retained. This unique anode performance of GeO2/N–C is derived from the effective combination of nano-size GeO2 and its uniform distribution in a nitrogen-doped carbon matrix. Herein, the nitrogen doped-carbon matrix not only strengthens the structure but also promotes the lithium diffusion in the GeO2/C–N material. Further, the adaptability of GeO2/N–C as an anode in a full cell configuration in combination with the LiCoO2 cathode was demonstrated by exhibiting high specific capacity and good cyclability.

We investigated the effects of adding Sn and Si to Al alloys on the corrosion of the alloys and the generation of hydrogen from an alkaline solution using the alloys. With increasing Sn content of up to 20 wt% in the Al-Sn alloy, the volume fraction of the Sn phase as a cathodic site at grain boundaries increased, and consequently, the hydrogen generation rate from an alkaline solution by the alloy also increased. In addition, the quenched Al-Sn alloys had smaller grain sizes compared to the furnace-cooled alloys, and accordingly, exhibited a slightly higher hydrogen generation rate. A galvanic cell was formed between the Al grain and the Sn phase of the grain boundary, and accordingly, intergranular type corrosion was observed on the Al-Sn alloys. Compared with the Al-Sn alloys, a more uniform type corrosion was observed on the Al-Si alloys because the nobler Si was uniformly distributed in the eutectic region formed between the primary Al grains. The hydrogen generation rate increased with an increasing Si content up to 10 wt% and was greater for the furnace-cooled samples than that for the quenched samples due to the more clearly formed eutectic structure.

Germanium (Ge) possesses a great potential as a high-capacity anode material for lithium ion batteries but suffers from its poor capacity retention and rate capability due to significant volume expansion by lithiation. Here, a facile synthetic route is introduced for producing nanometer-sized Ge crystallites interconnected by carbon (GEC) via thermal decomposition of a Ge-citrate complex followed by a calcination process in an inert atmosphere. The GEC electrode shows outstanding electrochemical performance, i.e., an almost 98.8% capacity retention of 1232 mAh g−1, even after 1000 cycles at the rate of C/2. Importantly, a high discharge capacity of 880 mAh g−1 is maintained at the very high rate of 10 C. The excellent anode performance of GEC stems from both effective buffering of carbon anchored to the Ge nanocrystals and the high open porosity of the GEC aggregated powder with an average pore diameter of 32 nm. Furthermore, the interfacial layer formed between Ge and carbon plays an essential role in prolonging the cycle life. The GEC electrode can be successfully employed as an anode for next generation lithium ion batteries.

The present investigation evaluates the effect of milling the hydriding combustion synthesized (HCSed) MgNiC composite with NbF5 catalyst. X-ray analysis revealed that h-Mg-(1 0 1) peak positions of the ball-milled samples shifted by an amount that varied with the milling time. Morphologically, among the SPEX ball-milled samples the samples with the NbF5 catalyst showed slightly delayed refinement/agglomeration with milling time which was attributed to lubricating-behavior of NbF5 during milling. The final products from both (planetary and SPEX) ball mills showed insignificant agglomeration. A general trend of decreasing surface area with increasing milling time was observed. The HCSed sample manually mixed with catalyst showed the largest surface area of 23.78 m2/g. The presence of the catalyst and different interfaces, such as Mg–Nb, Mg–Ni and Mg–CNTs, in the samples played a crucial role in decreasing the thermal constraints for dehydrogenation. Analysis of hydrogenation kinetics revealed that the catalyst added samples requires activation and can be easily activated. By relating the hydrogenation kinetic data with the JMAK model, the value of the reaction order, n, was found to be close to 1 for all the samples, suggesting a possible diffusional phase transition. The lowest activation energy observed in synthesized sample for hydrogenation was 64.9 kJ/mol.

In the present study, a nanocrystalline GeO 2 /C core shell was synthesized by a cost-effective and simple citric-gel method for various parameters, and the effects of these parameters on the microstructural and electrochemical properties of the GeO 2 /C core shell were investigated. Thermo-gravimetric-analysis showed that the combustion of gel-complexes occurred in the temperature range from 178 to 247 °C. Among the samples pre-heated at 150 °C, the sample pre-heated for 4 h had the highest surface area (11.12 m 2 g −1 ; particle size ∼ 30 nm). TEM analysis revealed that the citric-gel synthesized GeO 2 was encapsulated with carbon. This carbon encapsulation acted as a critical buffer layer against capacity degradation in the fabricated electrodes. The optimized sample showed a specific capacity of 738 mA h g −1 and maintained its reversibility after 50 cycles at a capacity of 697 mA h g −1 . The electrode containing the optimized sample showed a reversible capacity of 530 mA h g −1 at 1 C rate

To fulfill the high power and high energy density demands for Li-ion batteries (LIBs) new anode materials need to be explored to replace conventional graphite. Herein, we report the urea assisted facile co-precipitation synthesis of spinel NiCo2O4 and its application as an anode material for LIBs. The synthesized NiCo2O4 exhibited an urchin-like microstructure and polycrystalline and mesoporous nature. In addition, the mesoporous NiCo2O4 electrode exhibited an initial discharge capacity of 1095 mA h g(-1) and maintained a reversible capacity of 1000 mA h g(-1) for 400 cycles at 0.5 C-rate. The reversible capacity of NiCo2O4 could still be maintained at 718 mA h g(-1), even at 10 C. The mesoporous NiCo2O4 exhibits great potential as an anode material for LIBs with the advantages of unique performance and facile preparation.

Point relaxations for the pressure–composition isotherms were analyzed as a solid-state diffusion problem of hydrogen solutes from the gas phase provided in a limited amount by a pulse-like supply. For the large differential hydrogen storage, typical in the PCI plateau region, represented by small effective volume ratio λ parameter in the diffusion equation, the relaxation occurs much faster than in the galvanostatic or potentiostatic relaxations for the same chemical diffusivity values. The analysis was successfully applied to Mg/MgH2 system and the apparent chemical diffusivity and the hydrogen self-diffusivity were evaluated as a function of the state of hydrogen storage, in an analogous manner to the well-known electrochemical titration techniques. The increase in the apparent chemical diffusivity and hydrogen self-diffusivity in the plateau region with the increasing state of storage can be consistently explained by the lower hydrogen self-diffusivity in MgH2 than in Mg solid solution. The hydrogen s...

In this paper, we investigated the hydrogen storage and electrochemical characteristics of the bcc type Ti 0.32 Cr 0.43− x − y V 0.25 Fe x Mn y ( x = 0, 0.03, 0.055; y = 0, 0.03, 0.055, 0.080) alloys and their composites with the AB 5 type MmNi 3.99 Al 0.29 Mn 0.3 Co 0.6 (Mm: misch-metal) alloy. The maximum hydrogen capacities of the bcc alloys were proportional to the lattice parameters of the alloys. The increased substitution of Fe/Mn for Cr in the bcc alloys increased the plateau pressure in the respective pressure–composition isotherms. In particular, the plateau pressure was more sensitive to Fe substitution than Mn substitution. Electrochemically, the Ti 0.32 Cr 0.345 V 0.25 Fe 0.03 Mn 0.055 composite alloy electrode showed the optimum discharge capacity and cyclability because it had the beneficial effects of both Fe and Mn substitutions. Furthermore, among the other composite alloy electrodes, the Ti 0.32 Cr 0.345 V 0.25 Fe 0.03 Mn 0.055 composite alloy electrode showed the smallest charge transfer resistance, which allowed its easy activation and, higher rate capability.

Magnesium may be the most promising solid-state hydrogen storage material owing to its high storage capacity (7.6 wt%) and highest volumetric density (2 times of liquid H2). On the other hand, suffers from its sluggish absorption/desorption characteristics. In the present study, the simple/cost-effective hydriding combustion synthesis (HCS) was used to prepare highly-active Mg-based-samples. The preparative parameters of HCS were varied, and its effects on the micro-structural and hydrogen storage properties were determined. The results and its analysis showed that the simple HCS process possesses a multifaceted dependence on a range of experimental factors and affect the final product. The estimated dependence enabled us to explain the combined effect of individual experimental factors on the prepared samples. The Mg–Ni–C sample prepared at 610 °C with 6%wt-nano-Ni and 4 wt%-multi-walled-CNTs as reactants, resulted in sample with a surface area as high as 19.01 m2/g and a desorption capacity of 5.77 wt%, highlighting the promising characteristics of HCS to prepare highly-active Mg-based-materials.

This study examined the hydrogen storage and electrochemical characteristics of bcc type Ti 0.32 Cr 0.43 − x V 0.25 Fe x ( x = 0–0.08) alloys and their ball-milled composites with AB 5 type LmNi 41 Al 0.25 Mn 0.3 Co 0.65 alloy. With increasing Fe content in the bcc alloy, the hydrogen storage capacity decreased and the plateau pressure increased due to the decreased lattice volume. In addition, the plateau pressure of the bcc alloys decreased with decrease in its temperature. The discharge capacity of the composite alloys of bcc and AB 5 alloy decreased with increasing Fe content in the bcc alloy at 25 °C, attributed to the increased plateau pressure. On the other hand, at low temperatures, the discharge capacity of the Fe-doped composite alloys was higher than that of the un-doped alloy due to the catalytic effect of Fe. In addition, with increasing discharge rate, the Fe-doped composite alloys with improved surface catalytic activity showed better discharge capacity.

This study employed a fast, simple and cost-effective hydriding combustion synthesis (HCS) to prepare nano/submicron Mg based alloys, which are the most promising solid state hydrogen storage materials owing to their high storage capacity (7.6 wt.%) and highest volumetric density. The microstructural and absorption/desorption kinetic properties of the prepared MgH 2 samples were characterized and compared with commercially available MgH 2 powders. The detailed BET analysis of the HCS prepared samples showed a higher surface area than that of commercial MgH 2 , which resulted in better absorption/desorption kinetics. The HCS-prepared MgH 2 powder absorbed 6.2 wt.% H 2 with a rate of 0.31 wt.%/min, whereas it desorbed at a rate of 0.98 wt.%/min. These results highlight the superiority of the HCS method to prepare MgH 2 powders over conventional ingot-metallurgy.

Electrode degradation can affect the lifetime and safety of Ni-MH secondary batteries. This study examined the factors responsible for the degradation of metal hydride (MH) electrodes. The charge-discharge characteristics and cycle life of an MmNi3.9Co0.6Mn0.3Al0.2 (Mm: misch metal) type MH electrode were examined in a cell with a KOH electrolyte. After the charge-discharge cycles, the surface morphology of the electrodes was analyzed to monitor the extent of degradation. Electrochemical impedance spectroscopy provided information on the conductivity of the electrode. X-ray photon spectroscopy (XPS) was used to quantify the degradation of the electrode in terms of its composition. The MH electrodes degraded with cycling. This phenomenon was more prominent at higher C-rates and temperatures. The electrode degradation was attributed to the loss of active material from the current collector by the repeated absorption and desorption of hydrogen and the formation of an Al2O3 oxide layer on the electrode surface with cycling. In addition, the effects of the addition of Co nano and Y2O3 powder on the degradation of the MmNi3.9Co0.6Mn0.3Al0.2 electrode were examined. The addition of the Y2O3 and Co nano powder significantly improved the performance of the MH electrode by increasing the cycle life and initial activation rate.

The discharge capacities of lanthanum-rich mischmetal (LM)-Ni3.9Co0.6Mn0.3Al0.2 alloy electrodes are significantly degraded by an increase in the C rate. Nevertheless, the discharge capacity of alloy electrodes pretreated with KOH/NaBH4 is maintained higher than that of raw alloy electrodes, with the difference in discharge capacities between the raw and pretreated alloy electrodes more prominent at higher C rates. The charge retention of the electrodes decreases with increasing rest time. In particular, the charge retention of the pretreated alloy electrode is lower than that of the raw alloy electrode due to the higher self-discharge rate. The overvoltage for hydrogen evolution of the pretreated alloy electrode is superior to that of the raw alloy electrode, particularly at higher temperatures. This phenomenon indicates that the charge efficiency of the electrode was significantly improved by the surface pretreatment, resulting from its high surface catalytic activity. Repeated charge-discharge increases the inner pressure of the battery. Nevertheless, due to its higher charge efficiency and faster recombination rate, the inner pressure of the battery made using the pretreated alloy electrode is much smaller than that of the battery made using a raw alloy electrode.

To increase the hydrogen storage capacity and the plateau pressure of the Ti 0.32 Cr 0.43 V 0.25 alloy, a fraction of the Cr was replaced with Mn or a combination of Mn and Fe. When Mn was used alone, the effective hydrogen storage capacity increased to about 2.5 wt% though the plateau pressure showed no significant change. When Fe was added with Mn, however, both the effective hydrogen storage capacity and the plateau pressure increased. The BCC (body centered cubic) lattice parameter of the alloy decreased linearly with the Fe content, but it was not affected by Mn alone. The effective hydrogen storage capacity of the Ti 0.32 Cr 0.32 V 0.25 Fe 0.03 Mn 0.08 alloy was about 2.5 wt%, higher than 2.35 wt% in the original alloy. The estimated usable hydrogen stored in the Ti 0.32 Cr 0.32 V 0.25 Fe 0.03 Mn 0.08 alloy was 2.71 wt% in the temperature and pressure range of 293–353 K and 5–0.002 MPa, respectively.

We optimized the composition of additives for the anode in a Ni-MH battery using the response surface method (RSM) to improve the electrode discharge capacities. When the amount of additives was small, the discharge characteristics of the electrode were degraded by charge-discharge cycling due to the low binding strength among the alloy powders and the resultant separation of the powder from the electrode surface. In contrast, the addition of a large amount of the additives increased the electrical impedance of the electrode. Through a response optimization process, we found an optimum composition range of additives to exhibit the greatest discharge capacity of the electrode.

This study examined the effects of surface modifications of the LMNi3.9Co0.6Mn0.3Al0.2 (LM; Lanthanum rich misch metal) alloy in KOH solutions, both with and without NaBH4, on its electrode characteristics in a nickel–metal–hydride (Ni–MH) secondary battery at low and ambient temperatures. The activation behavior, discharge capacity, rate capability, and electrochemical catalytic activity of the alloy were significantly improved by surface treatment with a KOH/NaBH4 solution. This phenomenon is attributable to the alkaline treatment's removal of the oxide film and corrosion products on the surface of the alloy that can hinder surface activation, as well as its formation of a nickel- and cobalt-rich layer that exhibits high catalytic activity on the surface.

Hydrogen storage alloys based on LmNi4.2Co0.2Mn0.3Al0.3 were fabricated to study the equilibrium hydrogen pressure and electrochemical performance. The surface morphology and structure of the alloys were analyzed by SEM and XRD, and then the hydrogenation behaviors of all alloys were evaluated by PCT and electrochemical half-cell. We studied the hydrogenation behavior of the Lm-based alloy with changes in composition elements such as Mn, Al, and Co and investigated the optimal design for Lm-based alloy in a sealed battery system. As a result of studying the hydrogenation characterization of alloys with the substitution elements, hydrogen storage alloys such as LmNi3.75Co0.15Mn0.5Al0.3 and LmNi3.5Co0.5Mn0.5Al0.5 were obtained to correspond with the characteristics of a sealed battery with a higher capacity, long life cycle, lower internal pressure, and lower battery cost. The capacity preservation rate of LmNi3.5Co0.5Mn0.5Al0.5 was greatly improved to 92.7% (255 mAh/g) at 60 cycles, indicating a low equilibrium hydrogen pressure of 0.03 atm in PCT devices.

This study examines the effects of the addition of Mn and LmNi 4.1 Al 0.25 Mn 0.3 Co 0.65 (Lm: lanthanum-rich mischmetal) alloy on the electrochemical characteristics of body centered cubic (BCC) type Ti 0.32 Cr 0.43− x Mn x V 0.25 ( x = 0–0.08) alloys as negative electrode (anode) materials for nickel–metal-hydride (Ni-MH) batteries. The activation behaviour and discharge capacity of the BCC alloys are improved significantly by ball-milling with LmNi 4.1 Al 0.25 Mn 0.3 Co 0.65 alloy because this AB 5 alloy acts as a path for hydrogen on the surface of the BCC alloy. Among the Mn-substituted alloys, a Ti 0.32 Cr 0.38 Mn 0.05 V 0.25 alloy ball-milled with the AB 5 alloy yields the greatest discharge capacity of 340 mAh g −1 . In addition, compared with the alloy without Mn, the Mn-substituted alloys exhibit a lower plateau pressure for hydrogen, a better hydrogen-storage capacity in the pressure–composition isotherms and faster surface activation.

The effects of boron addition on the hydrogen absorption–desorption properties of the Ti 0.32 Cr 0.43 V 0.25 alloy were studied. Boron was added either directly or indirectly through a mother alloy Ti 0.75 B 0.25 . Direct boron addition caused the decrease in the titanium content of the BCC matrix through formation of Ti–B phases, resulting in the decrease in the lattice constant. Conversely, mother alloy addition increased the titanium content and the lattice constant of the matrix, for it contained enough titanium to contribute to the matrix even after forming the second phase TiB. Such lattice constant changes caused by boron addition resulted in drastic changes in hydrogen plateau pressure and great decrease in effective hydrogen storage capacity.

Li[Cr x Li (1− x )/3 Mn 2(1− x )/3 ]O 2 with x = 0, 0.05, 0.1 and 0.328 were synthesized by a solution method with subsequent quenching. The structures were investigated by X-ray diffraction (XRD), Rietveld refinement, electron diffraction and HRTEM. Li[Cr x Li (1− x )/3 Mn 2(1− x )/3 ]O 2 ( x = 0 and 0.05) and annealed Li[Li 1/3 Mn 2/3 ]O 2 were indexed based on the monoclinic structure, while Li 1.2 Cr 0.4 Mn 0.4 O 2 was shown to be that of a nanocomposite. Li[Cr 0.1 Li 0.29 Mn 0.602 ]O 2 material formed based on the stoichiometry in between Li[Li 1/3 Mn 2/3 ]O 2 and Li[Cr 0.328 Li 0.22 Mn 0.436 ]O 2 showed both sides features of the monoclinic and hexagonal structures in a nanocomposite structure and provided the lack of a developed anodic peak between 4.6 and 4.9 V, a good reversible capacity of around 250 mAh/g in a discharge voltage range between 2.8 and 3.5 V.

This study examined the effects of ball-milling with an AB 5 type LmNi 4.1 Al 0.25 Mn 0.3 Co 0.65 (Lm: Lanthanum rich mischmetal) alloy on the electrode characteristics of a BCC type Ti 0.32 Cr 0.43 V 0.25 alloy in order to determine its potential as an anode material for Ni–MH batteries. A mixture of the BCC type Ti 0.32 Cr 0.43 V 0.25 alloy powder and various concentrations of the AB 5 type LmNi 4.1 Al 0.25 Mn 0.3 Co 0.65 alloy powder was ball-milled for various ball-milling times. The discharge capacity of the electrode made from the Ti 0.32 Cr 0.43 V 0.25 alloy ball-milled with the LmNi 4.1 Al 0.25 Mn 0.3 Co 0.65 alloy was superior to the electrode made from the Ti 0.32 Cr 0.43 V 0.25 alloy alone. The highest discharge capacity of 310 mAh g - 1 was obtained when 20 wt% LmNi 4.1 Al 0.25 Mn 0.3 Co 0.65 alloy was added to the Ti 0.32 Cr 0.43 V 0.25 alloy and ball-milled for 20 min.

A study was made on how desorption temperature affected the usable hydrogen of the Ti0.32Cr0.43V0.25 alloy. The temperature was varied from 303 to 423 K, and the pressure from 5 to 0.002 MPa. The usable hydrogen of the alloy was 2.63 wt% when absorbed and desorbed at 303 and 423 K, respectively. The heat of hydride formation of the alloy was approximately - 38 kJ / mol H 2 . The effects of substituting Fe for Cr on the hydrogen storage property of the Ti0.32Cr0.43V0.25 alloy have also been studied. The purpose of the substitution was twofold: to raise the desorption plateau pressure of the alloy to 0.1 MPa or higher and to examine the possibility of using cheaper ferrovanadium. The logarithmic desorption plateau pressure increased linearly with the decrease of the lattice volume. When the Fe content was 8 at%, the desorption plateau pressure increased to several atmospheres without decrease in the effective hydrogen storage capacity of the alloy. This result suggested the possibility of using ferrovanadium as a substitute for the expensive pure vanadium.

This work reports the effect of doping aluminium in the Li[Li(1/3-x/3)Crx-0.05M0.05Mn(2/3- 2x/3)]O2 (x= 0.2; M= Al), layered cathode material. The cathode material was prepared by citric acid assisted sol-gel process. The sample is characterized by TG/DTA, XRD and FESEM measurements. The Al- doped cathode has delivered an initial discharge capacity of 250 mAh/g with a current density of 0.12 mA/cm2.

Ti 0.32 Cr 0.43 V 0.25 alloy specimens were heat treated, and its various hydrogen storage properties were measured at 303 K to examine its potential as a hydrogen storage material. The heat treatment improved not only the total and the effective hydrogen storage capacities, but also the plateau flatness. The heat of hydride formation was approximately −36 kJ/mol H 2 . The effective hydrogen storage capacity remained at approximately 2 wt% after 1000 cycles of pressure swing cyclic tests. The hydrogen storage capacity could be recovered almost to the initial state by reactivating the alloy. The hydrogen absorption rate increased with the repetition of cycling for the first several cycles and remained almost constant afterward. At the 504th cycle, more than 98% of the hydrogen was absorbed within the first 2 min. X-ray diffraction (XRD) patterns showed that the crystal structure of the alloy became more amorphous as the number of cycles increased.

A study concerned with controlling particle morphology and size of CsH 2 PO 4 was conducted by modifying the precipitation method and varying the types of adding solvents to aqueous solutions of Cs 2 CO 3 and H 3 PO 4 . Polyols of ethylene glycol were mixed with methanol and added into the solution. The obtained samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Conductivity of CsH 2 PO 4 powders studied in this work is around ∼10 −5 to 10 −4 S cm −1 and differ with their morphologies. The participation of different types of polyols in the precipitation kinetics and the resulting morphologies of the particles obtained were investigated. The scheme considers methanol as a primary precipitation agent, while the polyols are assumed to play a role in controlling morphologies.

The Li[Li (1/3-x/3) Cr x Mn (2/3-2x/3) ]O 2 (0.15 ≤x≤0.3) cathode materials were synthesized by sol-gel process using aqueous solutions of metal acetates and citric acid as the chelating agent. The precipitate of metal citrate was dried in a vacuum oven for 10 h at 100 °C. After drying, the gel precursor was calcined at 300 °C for about 10 h. The resulted powder was ground and heated at 900 °C. The structural characterization was carried out by fitting the XRD data with Rietveld program. The samples exhibited a well defined layered structure and the unit cell parameters linearly increased with increasing chromium contents in Li[Li (1/3-x/3) Cr x Mn (2/3-2x/3) ]O 2 Surface morphology was determined by SEM and HRTEM and it is found that the cathode material consisted of highly ordered single crystalline particles with layered-hexagonal structure. Test cells were assembled and cycled in the voltage range of 2.0-4.9 V with a current density of 7.947 mA/g. Electrode with (x= 0.2) delivered a high reversible capacity of around 280 mA h/g in cycling.

A series of Li[Cr x Li (1− x )/3 Mn 2(1− x )/3 ]O 2 (0.15 ≤ x ≤ 0.3) cathode materials was prepared by citric acid-assisted, sol–gel process. Sub-micron sized particles were obtained and the X-ray diffraction (XRD) results showed that the crystal structure was similar to layered lithium transition metal oxides (R-3m space group). The electrochemical performance of the cathodes was evaluated over the voltage range 2.0–4.9 V at a current density of 7.947 mA g −1 . The Li 1.27 Cr 0.2 Mn 0.53 O 2 electrode delivered a high reversible capacity of up to 280 mAh g −1 during cycling. Li[Cr x Li (1− x )/3 Mn 2(1− x )/3 ]O 2 yielded a promising cathode material.

The hydrogen absorption–desorption characteristics of Ti (0.22 + X ) Cr (0.28 + 1.5 X ) V (0.5 − 2.5 X ) ( X = 0, 0.04, 0.08, 0.10, 0.12) bcc alloys have been investigated at 303 K. The compositions of alloys were chosen for alloys to have equal lattice parameters of about 3.03 A by a linear combination of each element. The alloys of about 20 g each were arc-melted into button shaped ingots under argon atmosphere and re-melted five times to improve their homogeneities. The XRD analysis showed that all of the samples prepared had bcc single phases and their lattice parameters were nearly the same regardless of their chemical compositions. The P C isotherms of the alloys revealed that the hydrogen storage capacities of the alloys exceeded 3 mass% owing to the control of the lattice parameters and only the second plateau was reversible at room temperature. A reversible structural transition from fcc to bcc occurred with dehydrogenation of the second plateau. Some hydrogen remained unreleased even at a considerable low pressure corresponds to the bcc hydride and needed thermal activation energy for desorption. The hydrogen absorption rate of the Ti 0.32 Cr 0.43 V 0.25 alloy was considerably fast and more than 95% of the hydrogen was absorbed within the first 10 min.

Commercial La–Ni–Al–Co–Mn–V hydrogen storage alloys have been investigated to examine the effect of non-stoichiometry on the microstructure and electrochemical properties. It is found that for the stoichiometric ‘B’-rich compound, single phase with CaCu 5 -type exists. However, for B-poor compounds, there is principally a CaCu 5 -type phase with a small amount of V-rich type phase and the amount of V-rich phase reduces with vanadium. With the increase of V y ⩽0.1 content, hydrogen storage capacity is enhanced, whereas when y =0.2–0.3 it is decreased. The discharge capacity and cyclability are increased considerably by addition of vanadium in the range 0.02–0.1 with a maximum value at about 0.02%. The decrease of capacity for high V content was also correlated with the amount of V-rich phase. The V-rich phase is consisted of La 0.1 Ni 2.6 Al 0.2 Co 2.0 Mn 0.6 V 1.3 . The improvement of kinetics is due to the catalytic effect, grain boundary diffusion effect or more pronounced alloy pulverization upon cycling. This can be explained because the improvement of capacity for alloys with low V content is due to better kinetics. These alloys have been subjected to analysis by EDS, SEM and XRD. In order to determine the hydrogen storage capacity, the pressure composition isotherms (PCT curves) have been used. The metal hydride electrodes were characterized by galvanostatic cycling test.

AB 5 -type intermetallic compounds were prepared by arc-melting in an argon atmosphere. The composition of a stoichiometric compound ( LMNi 3.6 Al 0.4 Co 0.7 Mn 0.3 ) M y ( LM = La - rich mischmetal , M=Ti, Zr; y=0.0, 0.02, 0.05, 0.1, 0.2, 0.3 ) with a hexagonal CaCu 5 structure was varied by stoichiometric and nonstoichiometric addition of Ti or Zr. The alloy surface was analyzed by energy-dispersive spectroscopy and scanning electron microscopy and the crystal structure was characterized by X-ray diffraction. To determine hydrogen storage capacity, the pressure composition isotherms (PCT curves) were utilized. Metal hydride electrode was characterized by galvanostatic cycling test. It was found that the addition of Ti ( y =0.05) or Zr ( y =0.02) improves the activation, discharge capacity and cycle life property. But, the alloy with Ti addition ( y ⩾0.2), containing a Zr addition ( y ⩾0.2), is found to have bad discharge capacity and cycle life. The kinetic properties are additionally increased by the formation of a Ti- or Zr-rich second phase. The improvement in discharge capacity caused by increasing the Ti or Zr content (0.1⩾ y ) in the alloy is attributed to active sites for the electrochemical reaction. Also, they seem to be strongly related with the shapes and amounts of the second phases.

AB 5 -type intermetallic compounds were prepared by arc-melting in argon atmosphere. The composition of a stoichiometric compound LaNi 3.6 Al 0.4 Co 0.7 Mn 0.3 with a hexagonal CaCu 5 structure was varied by stoichiometric and nonstoichiometric addition of Ti. With the increase of the Ti y ⩽0.05 content in LaNi 3.6 Al 0.4 Co 0.7 Mn 0.3 Ti y , the hydrogen storage capacity is enhanced, whereas when y =0.1–0.3, it is decreased. The discharge capacity and cyclability are increased considerably by addition of titanium in the range of 0.02–0.1 with a maximum value at about 0.1%. The highest maximum capacity is achieved for a nonstoichiometric addition of 0.05% Ti. The kinetic properties are also additionally improved by the formation of a titanium-rich second phase. This can explain the improvement of the capacity for alloys with low Ti content. The decrease in capacity for high Ti content was also correlated with the amount of the Ti-rich phase. Therefore, the improvement of kinetics are due to the catalytic effect, grain boundary diffusion effect or more pronounced alloy pulverization upon cycling. This study has been aimed to improve the electrode properties of a series of multicomponent LaNi 3.6 Al 0.4 Co 0.7 Mn 0.3 Ti y ( y =0.0, 0.02, 0.05, 0.1, 0.2, 0.3) alloys which have mutual complementary properties. All the prepared alloys have been subjected to analyses by EDS, SEM and XRD. In order to determine the hydrogen storage capacity, the pressure composition isotherms ( P – C – T curves) have been used. The metal hydride electrodes were characterized by galvanostatic cycling test.

In this study, a novel method has been proposed for synthesizing amorphous GeO2/C composites. The amorphous GeO2/C composite without carbon black as an electrode for Li-ion batteries exhibited a high specific capacity of 914 mA h g(-1) at the rate of C/2 and enhanced rate capability. The amorphous GeO2/C electrode exhibited excellent electrochemical stability with a 95.3% charge capacity retention after 400 charge-discharge cycles, even at a high current charge-discharge of C/2. Furthermore, a full cell employing the GeO2/C anode and the LiCoO2 cathode displayed outstanding cycling performance. The superior performance of the GeO2/C electrode enables the amorphous GeO2/C to be a potential anode material for secondary Li-ion batteries.

The discharge capacities of pellet- and paste-type AB 5 alloy electrodes were investigated. The LmNi 3.6 Al 0.4 Co 0.7 Mn 0.3 alloy was chosen and the alloy powder was coated with various amounts of copper by the electroless plating method. The pellet-type electrodes were fabricated by cold pressing the copper-coated alloy powder into disks of 10 mm diameter without any binding material and the paste-type electrodes were prepared by pasting the bare or the copper-coated alloy powders onto the foamed nickel with some organic binders. The discharge capacities of the electrodes were measured through half cell tests. The experimental results showed that for the pellet-type electrodes, as the amount of copper coat increased the discharge capacity per weight of electrode decreased whereas that per weight of alloy increased. For the paste-type electrodes the copper coated alloy powder showed a much higher discharge capacity than the bare alloy powder. However, the increase of the copper coat over a certain amount did not increase the discharge capacity per weight of alloy while decreasing that per weight of electrode. Considering the discharge capacity and mechanical endurance, the most promising electrode was the paste-type electrode with 2.5 wt.% Cu-coated alloy powder and no carbon black.

We have investigated the structural transitions of Ti 1.0 Mn 0.9 V 1.1 H X (D X ) and Ti 1.0 Cr 1.5 V 1.7 H X (D X ) upon hydrogenation at 293 K and discussed the effect of hydrogen isotope on their crystal structures. The various hydride samples used for X-ray diffraction (XRD) investigation were obtained after measurement of the P–C isotherms by taking them out of the reactor. The crystal structures, phase abundance and lattice parameters of the hydrides were determined by the Rietveld method using XRD data. Because the hydrides of the alloy Ti 1.0 Mn 0.9 V 1.1 revealed complex peak profiles, we double-checked the structures through transmission electron microscope (TEM) investigations. The results of the TEM observation agreed well with those of XRD data. The crystal structures of corresponding isotope hydrides, the phase abundance and the lattice parameters do not depend on the kind of hydrogen isotope, but only on the hydrogen content. That is, if the corresponding isotope hydrides have the same hydrogen contents, they have also the same crystal structures, although they show a large difference between the equilibrium pressures in their P–C isotherms. At the experimental temperature, the Ti 1.0 Mn 0.9 V 1.1 alloy and Ti 1.0 Cr 1.5 V 1.7 alloy revealed different structural transition processes upon hydrogenation although the crystal structures of these two alloys are both body centered cubic (BCC). The structural transitions of the alloys Ti 1.0 Mn 0.9 V 1.1 and Ti 1.0 Cr 1.5 V 1.7 can be summarized by BCC ( a =3.0183(1) A)→body centered tetragonal (BCT) ( a =2.874(3) A, c =3.89(1) A)→face centered cubic (FCC) ( a =4.311(8) A) in alloy Ti 1.0 Mn 0.9 V 1.1 and BCC ( a =3.0212(9) A)→FCC ( a =4.261(4) A) in alloy Ti 1.0 Cr 1.5 V 1.7 . The Ti-rich phases with NiTi 2 structure and α-Ti with hexagonal close packed (HCP) structure absorbed hydrogen at relatively low hydrogen pressures and the phase abundance remained almost constant. From this fact, it can be deduced that it is desirable to decrease their amount as far as possible in order to increase the effective hydrogen storage capacities of the alloys.

This study introduces the hydrogen heat treatment of hydrogen absorbing materials and its applicability for practical use. This treatment is somewhat different from normal heat treatment because of the interaction between metal atoms and hydrogen. Since hydrogen can be removed very fast by pumping it out the hydrogen-induced new lattice phase which can not be obtained without hydrogen can be preserved in a meta-stable state. A thermodynamic interpretation of the hydrogen heat treatment established previously was reformulated for graphical and analytical methods and applied to Pd-Pt-H and Pd-Ag-H alloy systems and a fair correlation between the calculation and experimental results was shown. The feasibility of applying the thermodynamic interpretation to intermetallic compounds-hydrogen systems was also discussed.

The crystal structures, the lattice parameters and the characteristics of hydrogen storage at 303 K have been investigated in ternary alloys of the Ti–Cr–V system. All of these alloys, in the range of this study, have shown a BCC structure. The hydrogen storage capacities and the effective hydrogen storage capacities of the alloys were strongly dependent on the composition ratio of Ti/Cr, showing their maximum values at a Ti/Cr ratio of about 0.75. It was also found that the lattice parameters of the alloys increased linearly with increasing Ti/Cr ratio. The differences in affinities to hydrogen and the atomic radius of each element could explain the Ti/Cr ratio dependence of the lattice parameter and hydrogen storage capacity of the alloys.

(LM)Ni 4.49 Co 0.1 Mn 0.205 Al 0.205 hydrogen storage alloy powder was coated with 25 wt.% Cu by electroless plating in an acidic bath, compacted into disk-type electrodes at room temperature and the disks were finally coated with nickel by electroplating or sputtering. The characteristics of the metal hydride electrodes were examined through electrochemical measurements, scanning electron microscopy and mechanical testing. The nickel coating, when its amount was less than 2.5 wt.%, has improved the properties of electrodes, especially the cycle life and mechanical endurance. The effects were more significant when the nickel coating was done after one charge-discharge cycle or by sputtering. The mechanical strength of the electrodes increased on nickel coating but was not sufficient to prevent the alloy powder from falling off from electrode during cycling in the open half-cell.

(LM)Ni4.49Co0.1Mn0.205Al0.205 (LM, lanthanum-rich mischmetal) hydrogen storage alloy powder was coated by 25 wt.% electroless copper plating in an acidic bath, mixed with organosilicon and compacted into disk-type electrodes at room temperature. The characteristics of the metal hydride electrodes were examined through electrochemical measurements in a half-cell. As the amount of organosilicon increased, the initial discharge capacity of the electrode became lower and the activation rate at high current density was slower. For extended cycling, however, the electrodes with organosilicon were superior in terms of high rate discharge capacity, useful range of temperature and cycle life to the silicon-free electrode, though the charge retention was not improved. It is suggested from the results that organosilicon can be usefully applied as a binder in the preparation of metal hydride electrodes.