EP3172785A1 - Alliages d'hydrures métalliques bcc du type phase de laves et leur activation pour applications électrochimiques - Google Patents

Alliages d'hydrures métalliques bcc du type phase de laves et leur activation pour applications électrochimiques

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Publication number
EP3172785A1
EP3172785A1 EP15825302.1A EP15825302A EP3172785A1 EP 3172785 A1 EP3172785 A1 EP 3172785A1 EP 15825302 A EP15825302 A EP 15825302A EP 3172785 A1 EP3172785 A1 EP 3172785A1
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EP
European Patent Office
Prior art keywords
alloy
optionally
phase
bcc
metal hydride
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP15825302.1A
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German (de)
English (en)
Other versions
EP3172785A4 (fr
Inventor
Kwo-Hsiung Young
Taihei Ouchi
Baoquan Huang
Diana Wong
Lixin Wang
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Ovonic Battery Co Inc
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Ovonic Battery Co Inc
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Filing date
Publication date
Priority claimed from US14/340,913 external-priority patent/US9768445B2/en
Priority claimed from US14/340,959 external-priority patent/US20160024620A1/en
Application filed by Ovonic Battery Co Inc filed Critical Ovonic Battery Co Inc
Publication of EP3172785A1 publication Critical patent/EP3172785A1/fr
Publication of EP3172785A4 publication Critical patent/EP3172785A4/fr
Withdrawn legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C14/00—Alloys based on titanium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C27/00—Alloys based on rhenium or a refractory metal not mentioned in groups C22C14/00 or C22C16/00
    • C22C27/02—Alloys based on vanadium, niobium, or tantalum
    • C22C27/025—Alloys based on vanadium, niobium, or tantalum alloys based on vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C30/00—Alloys containing less than 50% by weight of each constituent
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/383—Hydrogen absorbing alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/03—Alloys based on nickel or cobalt based on nickel
    • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/34—Gastight accumulators
    • H01M10/345—Gastight metal hydride accumulators
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/32—Hydrogen storage

Definitions

  • This invention relates to alloy materials and methods for their fabrication.
  • the invention relates to metal hydride alloy materials that are capable of absorbing and desorbing hydrogen.
  • Activated metal hydride alloys with a Laves phase-related body centered cubic (BCC) structure are provided that have unique electrochemical properties including high capacity for use in electrochemical applications.
  • Certain metal hydride (MH) alloy materials are capable of absorbing and desorbing hydrogen. These materials can be used as hydrogen storage media, and/or as electrode materials for fuel cells and metal hydride batteries including nickel/metal hydride (Ni/MH) and metal hydride/air battery systems.
  • Ni/MH nickel/metal hydride
  • metal hydride/air battery systems due to limited gravimetric energy density ( ⁇ 110 Wh kg -1 ), current Ni/MH batteries lose market share in portable electronic devices and the battery- powered electrical vehicle markets to the lighter Li-ion technology. As such, the next generation of Ni/MH batteries is geared toward improving two main targets: raising the energy density and lowering cost.
  • the electrodes are typically separated by a non-woven, felted, nylon or polypropylene separator.
  • the electrolyte is usually an alkaline aqueous electrolyte, for example, 20 to 45 weight percent potassium hydroxide.
  • AB X type materials are disclosed, for example, in U.S. Patent 5,536,591 and U.S. Patent 6,210,498. Such materials may include, but are not limited to, modified LaNis type (AB5) as well as the Laves-phase based active materials (AB2). These materials reversibly form hydrides in order to store hydrogen.
  • Such materials utilize a generic Ti— Zr— i composition, where at least Ti, Zr, and Ni are present with at least one or more modifiers from the group of Cr, Mn, Co, V, and Al.
  • the materials are multiphase materials, which may contain, but are not limited to, one or more Laves phase crystal structures and other non-Laves secondary phase.
  • Current AB5 alloys have -320 mAh g "1 capacity and Laves-phase based AB2 has a capacity up to 440 mAh g _1 such that these are the most promising alloy alternatives with a good balance among high-rate dischargeability (HRD), cycle life, charge retention, activation, self discharge, and applicable temperature range.
  • HRD high-rate dischargeability
  • Rare earth (RE) magnesium-based AB3- or A2B7-types of MH alloys are promising candidates to replace the currently used AB5 MH alloys as negative electrodes in Ni/MH batteries due in part to their higher capacities. While most of the RE-Mg-Ni MH alloys were based on La-only as the rare earth metal, some Nd-only A2B7 (AB3) alloys have recently been reported. In these materials, the AB3.5 stoichiometry is considered to provide the best overall balance among storage capacity, activation, HRD, charge retention, and cycle stability.
  • PCT pressure-concentration-temperature
  • AB X materials include the Laves phase-related body centered cubic (BCC) materials that are a family of MH alloys with a two-phase microstructure including a BCC phase and a Laves phase historically present as C14 as an example. These materials are based on a theoretical electrochemical capacity of 938 mAh g _1 for Ti-V-Cr alloy with full BCC structure that unfortunately has very poor electrochemical properties. As such, Laves phase with similar chemical make-up is added to the BCC material. These Laves phase-related BCC materials exhibit high density of the phase boundaries that allow the combination of higher hydrogen storage capacity of BCC and good hydrogen absorption kinetics and relatively high surface catalytic activity of the C14 phase.
  • BCC body centered cubic
  • the alloy materials as described have improved capacities relative to prior alloys of similar composition as well as significantly improved cycle life at the high capacity. While some prior materials are capable of high capacity, this capacity decreases rapidly in 1 -5 cycles. Improvements in cycle life in Laves phase-related BCC metal hydrides historically reduce capacity.
  • the Laves phase-related BCC metal hydride alloys as provided herein solve the issue of reduced capacity and demonstrate greatly improved capacity over many more cycles by tailoring the ratio of Ti to Cr in the systems.
  • a Laves phase-related BCC metal hydride is provided that includes the composition of Formula I:
  • w+x+y+z 1, 0.1 ⁇ w ⁇ 0.6, 0.1 ⁇ x ⁇ 0.6, 0.01 ⁇ y ⁇ 0.6
  • M is selected from the group consisting of B, Al, Si, Sn and transition metals, the metal hydride alloy having a capacity in excess of 350 mAh/g at cycle 10.
  • Some aspects have a capacity of 400 mAh/g or greater, optionally 420 mAh/g or greater, at cycle 10.
  • An alloy optionally includes less than 24% C14 phase.
  • the alloy is predominantly a combination of BCC phase and Laves phase, said BCC phase in abundance of greater than 5% and less than 95%, said Laves phase in abundance of greater than 5% and less than 95%.
  • the alloy includes a BCC phase crystallite size of less than 400 angstroms, optionally less than 200 angstroms.
  • the B/A ratio is 1.20 the 1.31, optionally 1.20 to 1.30.
  • the ratio x/y is from 1 to 3.
  • x is a value in excess of 0 and 12 or less
  • M is a combination of Mn, Fe, Co, Ni, and Al.
  • the alloy of Formula II optionally has x of 2, 4, 6, 8, 10 or 12.
  • alloys provided and their equivalents represent superior materials for use in an anode of a cell or battery system.
  • M is selected from the group consisting of B, Al, Si, Sn and transition metals, where the process includes: subjecting the laves phase-related BCC metal hydride alloy to an atmosphere comprising hydrogen at a
  • the step of cooling is at a maximum activation temperature of 300 degrees Celsius or less.
  • the atmosphere is at a hydrogenation pressure that is optionally 1.4 megapascals or greater, optionally 6 megapascals or greater.
  • the processes produce an activated metal hydride alloy optionally having a capacity of 300 mAh/g or greater, optionally 350 mAh/g or greater, optionally 400 mAh/g or greater, optionally 450 mAh/g or greater.
  • the activated metal hydride alloy has less than 24% C14 phase.
  • the activated metal hydride alloy is predominantly a combination of BCC phase and Laves phase, the BCC phase in abundance of greater than 5% and less than 95%, the Laves phase in abundance of greater than 5% and less than 95%.
  • the activated metal hydride alloy includes a BCC phase crystallite size of less than 400 angstroms.
  • the Laves phase-related BCC metal hydride alloy is optionally of Formula II: Tio. 4 +x/6Zro.6-x/6Mno. 44 Nii.oAlo.o 2 Coo.o9(VCro.3Feo.o63)x ( ⁇ ) where x is 0.7 to 2.8.
  • the Laves phase-related BCC metal hydride alloy is optionally of Formula III:
  • FIG. 1A illustrates alloy phase distribution as observed in an SEM image of a hydrogen storage alloy of P8
  • FIG. IB illustrates alloy phase distribution as observed in an SEM image of a hydrogen storage alloy of P9
  • FIG. 1C illustrates alloy phase distribution as observed in an SEM image of a hydrogen storage alloy of P10
  • FIG. ID illustrates alloy phase distribution as observed in an SEM image of a hydrogen storage alloy of PI 1;
  • FIG. IE illustrates alloy phase distribution as observed in an SEM image of a hydrogen storage alloy of PI 2;
  • FIG. IF illustrates alloy phase distribution as observed in an SEM image of a hydrogen storage alloy of P13
  • FIG. 1G illustrates alloy phase distribution as observed in an SEM image of a hydrogen storage alloy of P 14;
  • FIG. 2A illustrates the major constituent elements and the metal ratio in the C14 phase as a function of Ti-content in the alloy design;
  • FIG. 2B illustrates the major constituent elements and the metal ratio in the BCC phase as a function of Ti-content in the alloy design
  • FIG. 3 A illustrates the microstructure of hydrogen storage alloys activated to provide improved electrochemical properties and illustrating two predominant phases, C14 and BCC;
  • FIG. 3B illustrates the FWHM of the BCC (110) peak from control and hydrogen storage alloys activated to provide improved electrochemical properties and demonstrating the reduced crystallite size of the alloys activated by exemplary processes as described herein;
  • FIG. 4 illustrates a schematic of the C14 unit cell of the various alloys composed of alternating A2B and B3 layers stacked along the c axis while larger A-atoms occupy 4 -sites and smaller B-atoms occupy 2a-sites (on the A2B layer) and 6 z-sites (on the B3 layer);
  • FIG. 5 illustrates the FWHM of the BCC (110) peak from control and hydrogen storage alloys activated to provide improved electrochemical properties and demonstrating the reduced crystallite size of the alloys activated by exemplary processes as described herein;
  • FIG. 6 illustrates gaseous phase hydrogen storage characteristics of various alloy materials formed by exemplary processes as described herein;
  • FIG. 7A illustrates gaseous phase hydrogen storage characteristics of various alloy materials
  • FIG. 7B illustrates gaseous phase hydrogen storage characteristics of various alloy materials
  • FIG. 8A illustrates the half-cell discharge capacity measured at 4 mA/g of the first 13 cycles
  • FIG. 8B illustrates and high-rate dischargeability (HRD) in the first 13 cycles
  • FIG. 9 illustrates hydrogen storage capacities converted from gaseous phase hydrogen storage and as measured electrochemically as functions of alloy number
  • FIG. 10 illustrates diffusion coefficient and C14-phase crystallite size as functions of alloy number where the trends indicate that hydrogen diffuses easier within an alloy with smaller C14-phase crystallites.
  • a Laves-phase related BCC metal hydride alloy of the composition of Formula I is provided.
  • w+x+y+z 1, 0.1 ⁇ w ⁇ 0.6, 0.1 ⁇ x ⁇ 0.6, 0.01 ⁇ y ⁇ 0.6 and M is selected from the group consisting of B, Al, Si, Sn and one or more transition metals.
  • the alloy is activated by particular processes to promote formation of increased BCC phase and limit AB2 phase in the resulting materials.
  • the result is an activated metal hydride alloy having improved electrochemical properties including a capacity at or in excess of 200 mAh/g, optionally 350 mAh/g or greater at cycle 10.
  • x is a value in excess of 0 and 12 or less, and M is a combination of Mn, Fe, Co, Ni, and Al.
  • x is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, or any value between greater than 0 and 12 or less, including non-whole numbers.
  • x is 2, 4, 6, 8, 10, or 12.
  • x is 2 or 4.
  • a Laves-phase related BCC metal hydride alloy is of the composition of Tio. 4 +x/6Zro.6-x/6Mno. 44 Nii.oAlo.o 2 Coo.o9(VCro.3Feo.o63)x (HI) where x is 0.7 to 2.8.
  • a Laves-phase related BCC metal hydride alloy includes a capacity well in excess of 200 mAh/g, optionally 220 mAh/g, 240 mAh/g, 260 mAh/g, 280 mAh/g, 300 mAh/g, 310 mAh/g, 320 mAh/g, 330 mAh/g, 340 mAh/g, 350 mAh/g, 360 mAh/g, 370 mAh/g, 380 mAh/g, 390 mAh/g, 400 mAh/g, 410 mAh/g, 420 mAh/g, 430 mAh/g, 440 mAh/g, 450 mAh/g, or more.
  • a metal hydride alloy includes a capacity between 200 and 450 mAh/g.
  • an activated metal hydride alloy includes a capacity between 200 and 450 mAh/g.
  • a metal hydride alloy includes a capacity between 300 and 450 mAh/g.
  • an activated metal hydride alloy includes a capacity between 300 and 380 mAh/g.
  • a metal hydride alloy includes a capacity between 350 and 450 mAh/g.
  • a metal hydride alloy includes a capacity between 400 and 450 mAh/g.
  • a metal hydride alloy includes a capacity between 400 and 420 mAh/g.
  • any of the foregoing capacities are optionally present at 2 or more cycles, optionally 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or more cycles.
  • a metal hydride alloy has a capacity at or in excess of 350 mAh/g at cycle 10, optionally at or in excess of 400 mAh/g at cycle 10, optionally at or in excess of 420 mAh/g at cycle 10.
  • a metal hydride alloy optionally is predominantly formed of BCC phase and Laves phase structure. Without being limited to one particular theory, it is believed that the predominance of the structure being in the BCC phase and Laves phase increases a synergistic effect produced by the presence of the two phases.
  • the metal hydride alloy optionally produced by the processes as disclosed herein, optionally has BCC phase in abundance of greater than 5% and less than 95%, a Laves phase in abundance of greater than 5% and less than 95% with the combination of BCC phase and Laves phase being in excess of 50% of the material structure.
  • the BCC phase is at or between 10% and 95%, 20% and 95%, 30% and 95%, 40% and 95%, 50% and 95%, 60% and 95%, 70% and 95%, or 80% and 95%, optionally also in any such instance with a Laves phase in excess of 5%.
  • the Laves phase is at or between 10% and 95%, 20% and 95%, 30% and 95%, 40% and 95%, 50% and 95%, 60% and 95%, 70% and 95%, or 80% and 95%, optionally also in any such instance with a BCC phase in excess of 5%.
  • composition has a C14 Laves phase that is less than 30%, optionally less than 25%, optionally less than 24%, optionally less than 20%, optionally less than 15%, optionally less than 14%, optionally, less than 13%, optionally less than 12%.
  • the hydrogen storage alloy is provided with a crystallite size of the BCC phase that is sufficiently small to allow a large inter-granular region and a higher synergetic connection between storage and catalytic phase to promote the electrochemical properties.
  • the alloys as provided have a BCC crystallite size of 400 A or less, optionally 390 A or less, optionally 380 A or less, optionally 370 A or less, optionally 360 A or less, optionally 350 A or less, optionally 340 A or less, optionally 330 A or less, optionally 320 A or less, optionally 310 A or less, optionally 300 A or less, optionally 290 A or less, optionally 280 A or less, optionally 270 A or less, optionally 260 A or less, optionally 250 A or less, optionally 240 A or less, optionally 230 A or less, optionally 220 A or less, optionally 210 A or less, optionally 200 A or less, optionally 19 A or less, optionally 180 A or less, optionally 170 A or less, optionally
  • the crystallite size of the BCC phase is from 200 A to 300 A.
  • the crystallite size of the BCC phase is from 120 A to 300 A.
  • the crystallite size of the BCC phase is from 120 A to 200 A.
  • the crystallite size of the BCC phase is from 120 A to 160 A.
  • the crystallite size of the BCC phase is from 140 A to 160 A.
  • a process includes subjecting the Laves phase-related BCC metal hydride alloy to an atmosphere including hydrogen at a hydrogenation pressure and simultaneously cooling the alloy to produce an activated metal hydride alloy having the desired capacity, optionally 200 mAh/g or more at cycle 10.
  • the alloys are hydrogenated by a process that includes an active cooling step. Without being limited one particular theory, controlling the temperature of the material during hydriding promotes excess
  • AB2 phase structure from forming in the alloy during activation. Temperature control is achieved by cooling the reaction vessel such as with a water jacketed system or bath, or by other methods known in the art. Optionally, the reaction temperature of the alloy does not exceed 300 °C.
  • the temperature of the alloy is maintained during hydrogenation between room temperature and optionally 300 °C, optionally 295 °C, optionally 290 °C, optionally 285 °C, optionally 280 °C, optionally 275 °C, optionally 270 °C, optionally 260 °C, optionally 250 °C, optionally 240 °C, optionally 230 °C, optionally 220 °C, optionally 210 °C, optionally 200 °C, optionally 190 °C, optionally 180 °C, optionally 170 °C, optionally 160 °C, optionally 150 °C, optionally 140 °C, optionally 130 °C, optionally 120 °C, optionally 110 °C, optionally 100 °C, optionally 90 °C, optionally 80 °C, optionally 70 °C, optionally 60 °C, optionally 50 °C, optionally 40 °C, optionally 30 °C.
  • optionally 300 °C optionally
  • Increasing hydrogen pressure was also discovered to be useful to promote formation of increased amounts of BCC phase in the resulting activated hydrogen storage alloy.
  • a some aspects hydrogenating the Laves phase-related BCC metal hydride alloy is performed at a hydrogenation pressure of 1.4 MPa or greater, optionally 1.5 MPa or greater, optionally 1.8 MPa or greater, optionally 2 MPa or greater, optionally 3 MPa or greater, optionally 4 MPa or greater, optionally 5 MPa or greater, optionally 6 MPa or greater.
  • the Laves phase-related BCC metal hydride alloy is hydrogenated using both a hydrogenation pressure in excess of 1.4 MPa and controlling the temperature to 300 °C or less.
  • an alloy is optionally activating with a hydrogenation pressure of between 1.4 MPa to 6 MPa, or greater, with cooling to prevent the alloy from exceeding 300 °C, optionally 295 °C, optionally 290 °C, optionally 285 °C, optionally 280 °C, optionally 275 °C, optionally 270 °C, optionally 260 °C, optionally 250 °C, optionally 240 °C, optionally 230 °C, optionally 220 °C, optionally 210 °C, optionally 200 °C, optionally 190 °C, optionally 180 °C, optionally 170 °C, optionally 160 °C, optionally 150 °C, optionally 140 °C, optionally 130 °C, optionally 120 °C, optional
  • MPa optionally 1.9 MPa, optionally 2 MPa, optionally 2.1 MPa, optionally 2.2 MPa, optionally
  • MPa optionally 2.4 MPa, optionally 2.5 MPa, optionally 2.6 MPa, optionally 2.7 MPa, optionally 2.8 MPa, optionally 2.9 MPa, optionally 3 MPa, optionally 3.1 MPa, optionally 3.2 MPa, optionally 3.3 MPa, optionally 3.4 MPa, optionally 3.5 MPa, optionally 3.6 MPa, optionally 3.7 MPa, optionally 3.8 MPa, optionally 3.9 MPa, optionally 4 MPa, optionally 4.1 MPa, optionally 4.2 MPa, optionally 4.3 MPa, optionally 4.4 MPa, optionally 4.5 MPa, optionally 4.6 MPa, optionally 4.7 MPa, optionally 4.8 MPa, optionally 4.9 MPa, optionally 5 MPa, optionally 5.1 MPa, optionally 5.2 MPa, optionally 5.3 MPa, optionally 5.4 MPa, optionally 5.5 MPa, optionally 5.6 MPa, optionally 5.7 MPa, optionally 5.8 MPa, optionally 5.9 MPa.
  • the resulting activated hydrogen storage alloy produced by the provided processes possesses capacities that nearly double and often more than double those of compositionally similar materials produced in traditional manners.
  • a series of metal hydride alloys of Formula I or II were prepared and hydrided by various conditions in connection with an experimental series illustrating the principles of the present invention.
  • the raw materials were arc melted under conditions of continuous argon flow using a non-consumable tungsten electrode and a water cooled copper tray.
  • the residual oxygen concentration in the system was reduced by subjecting a piece of sacrificial titanium to several melt-cool cycles. Study ingots where then subjected to several re-melt cycles with turning over to ensure uniformity in chemical composition.
  • the as-cast compositions are in excellent agreement with the composition as designed.
  • the previous series of alloys showed unevenness in Cr content, and this has been improved by increasing the power during arc melting.
  • the measured B/A ratio of this series of alloys (P8-P14) varies from 2.61 to 5.36, and the range is similar to the previous series (P1-P8) from Young et al., Int. J. Hydrogen Energy, http://dx.doi.Org/10.1016/j.ijhydene.2014.01.134 (article in press).
  • Table 2 Summary of EDS results. All compositions are in atomic percent. Compositions of C14 and BCC phase are in italic and bold, respectively.
  • the alloys of P8-P 14 are subjected to various activation conditions by varying either the maximum temperature of the alloy during activation through cooling the system, by altering the hydrogen pressure, or both. Four activation processes are depicted in Table 3.
  • the cla ratio increases, stabilizes, and decreases as the Ti-content increases.
  • the anisotropic growth of the C14 unit cell arises from the partial replacement of B-site Cr (metallic radius in AB2 intermetallic alloy of 1.423 A) with the relatively larger A-site Ti (radius of 1.614 A).
  • Lattice constant a in BCC phase increases from 2.9683 to 3.0165 A as the V-content in the alloy increases.
  • Table 4 also illustrates the crystallite sizes of each phase in the P8-P14 alloys. As the Ti-content in the alloy increases, the abundance of the C14 phase increases from 11.0 to 56.4 wt.% and drops slightly to 52.5 wt.% in alloy P14. The BCC phase shows the reverse trend dropping from 89.0% to 47.5% from P8 to P 14. At the same time, the C14 crystallite size first increases and then decreases, while the BCC crystallite size decreases monotonically.
  • FIG. 4 illustrates the FWHM of the BCC peak (110) for sample P8 as it is varied between the control and the samples hydrogenated by the methods of Examples 1-3.
  • the calculated crystallite sizes of the BCC phase are presented in Table 5.
  • Table 5 Crystallite sizes of the BCC (110) phase.
  • Each of the exemplary hydrogenated materials show crystallite sizes of the BCC phase of less than 300 A.
  • the hysteresis of the PCT isotherm is defined as In (PJPd), where P a and Pd are the absorption and desorption equilibrium pressures at the mid-point of desorption isotherm, respectively.
  • the hysteresis can be used to predict the pulverization rate of the alloy during cycling. Alloys with larger hysteresis have higher pulverization rates during hydriding/dehydriding cycles. From the hysteresis, a large increase in cycle stability is expected by activating according to the processes of Examples 1 -3. Particularly, by cooling the ingot during activation so that the maximum temperature does not exceed 300°C, the hysteresis decreases significantly.
  • Table 7 Summary of gaseous phase and thermodynamic properties. Desorption pressure, hysteresis, and thermodynamic properties are calculated at 1.3 wt.% for P8-P 10 and 1.5 wt.% for P 1 1 -P 14.
  • each alloy was measured in a flooded-cell configuration against a partially pre-charged Ni(OH)2 positive electrode.
  • each ingot was first ground and then passed through a 200-mesh sieve. The sieved powder was then compacted onto an expanded nickel metal substrate by a 10-ton press to form a test electrode (about 1 cm 2 in area and 0.2 mm thick) without using any binder. This allowed improved measurement of the activation behavior.
  • Discharge capacities of the resulting small- sized electrodes were measured in a flooded cell configuration using a partially pre-charged Ni(OH)2 pasted electrode as the positive electrode and a 6M KOH solution as the electrolyte.
  • Each sample electrode was charged at a constant current density of 50 mA/g for 10 h and then discharged at a current density of 50 mA/g followed by two pulls at 12 and 4 mA/g.
  • the full capacities (4 mA/g) from the first 13 cycles are plotted in Fig. 8A to study the activation and cycling behavior of these alloys.
  • the activation of the alloys becomes easier with the decrease in BCC phase abundance and the Cr-content due to the corrosion resistance of BCC phase compared to C14 phase and the corrosion resistance of Cr against KOH. Reduction in the corrosion resistance helps activation; however, it also reduces cycle stability.
  • cap cap 4 4 th cycle circuit cycle to reach coefficient current
  • Half-cell HRD values of each alloy defined as the ratio of discharge capacity measured at 50 mA/g to that measured at 4 mA/g, are measured at the stabilized 4 th cycle and listed in Table 8. Except for P10, HRDs of all alloys are stabilized within 4 cycles. As the Ti- content in the alloy increases, HRD decreases rapidly. The increase in the catalytic C14 phase abundance does not help the HRD performance. Comparing the HRD of P8* and P8, we find that the electrochemical HRD in P8* is higher despite the lower hydrogen pressure used during activation and its lower reversibility in the gaseous phase (FIG. 7A). We can attribute this observation to the different phases in the alloys.
  • the two pressure plateaus observed in the PCT curves can be associated with two different phases.
  • the first phase with lower plateau pressure (from 0.3 to 1.0 wt.% in FIG. 7A) has better rate capability than the second phase (from 1.0 to 1.6 wt.% in FIG. 7A).
  • C14 phase is believed to be more catalytic than BCC phase. Therefore, we assign the phase with lower plateau pressure to the C14 phase and the phase with higher plateau pressure to the BCC phase.
  • the increasing range of the first plateau is consistent with the increase in C14 phase abundance
  • the decreasing range of the second plateau is consistent with the decrease in BCC phase abundance derived in the XRD analysis (Table 4).
  • Patents, publications, and applications mentioned in the specification are indicative of the levels of those skilled in the art to which the invention pertains. These patents, publications, and applications are incorporated herein by reference to the same extent as if each individual patent, publication, or application was specifically and individually incorporated herein by reference.

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  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

Les alliages d'hydrures métalliques BCC du type phase de Laves ont historiquement des capacités électrochimiques limitées. La présente invention concerne de nouveau exemples de ces alliages utiles comme matériaux actifs d'électrode. L'invention concerne également des procédés d'activation de ces alliages. Les alliages comprennent une composition définie par la formule I : TiwVxCryMz (I) dans laquelle w + x + y + z = 1, 0,1 < w < 0,6, 0,1 < x < 0,6, 0,01 < y < 0,6, et M est choisi dans le groupe comprenant B, Al, Si, Sn et un ou plusieurs métaux de transition qui permettent d'obtenir des capacités de décharge de 350 mAh/g ou plus pour des cycles de 10 ou plus.
EP15825302.1A 2014-07-25 2015-07-17 Alliages d'hydrures métalliques bcc du type phase de laves et leur activation pour applications électrochimiques Withdrawn EP3172785A4 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US14/340,913 US9768445B2 (en) 2014-07-25 2014-07-25 Activation of laves phase-related BCC metal hydride alloys for electrochemical applications
US14/340,959 US20160024620A1 (en) 2014-07-25 2014-07-25 Laves phase-related bcc metal hydride alloys for electrochemical applications
PCT/US2015/040892 WO2016014356A1 (fr) 2014-07-25 2015-07-17 Alliages d'hydrures métalliques bcc du type phase de laves et leur activation pour applications électrochimiques

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EP3172785A1 true EP3172785A1 (fr) 2017-05-31
EP3172785A4 EP3172785A4 (fr) 2018-02-28

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JP2018070931A (ja) * 2016-10-27 2018-05-10 トヨタ自動車株式会社 負極材料および電池

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JP3533766B2 (ja) * 1995-07-14 2004-05-31 松下電器産業株式会社 水素吸蔵合金電極およびその製造法
JP3528502B2 (ja) * 1997-03-04 2004-05-17 トヨタ自動車株式会社 初期活性と反応速度に優れた水素吸蔵合金
JPH11106859A (ja) * 1997-10-01 1999-04-20 Toyota Motor Corp プラトー平坦性に優れた水素吸蔵合金
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US7108757B2 (en) * 2003-08-08 2006-09-19 Ovonic Hydrogen Systems Llc Hydrogen storage alloys providing for the reversible storage of hydrogen at low temperatures
US20140193722A1 (en) * 2013-01-07 2014-07-10 Ovonic Battery Company, Inc. Metal hydride alloy with improved low-temperature performance

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KR20170036018A (ko) 2017-03-31
WO2016014356A1 (fr) 2016-01-28
CN106575749A (zh) 2017-04-19
JP2017528596A (ja) 2017-09-28
EP3172785A4 (fr) 2018-02-28

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