CN102683653A - Compound hydrogen storing alloy and nickel-hydrogen storage battery - Google Patents

Abstract

The invention provides a composite hydrogen storage alloy with high discharge capacity and high-efficiency discharge performance and a nickel-hydrogen storage battery using the composite hydrogen storage alloy. The composite hydrogen storage alloy contains a hydrogen storage alloy having an I phase and a hydrogen storage alloy having an AB ₃ type crystal phase.

Description

Composite hydrogen storage alloy and nickel-hydrogen accumulator

Technical field

The present invention relates to a kind of nickel-hydrogen accumulator that has the composite hydrogen storage alloy of high discharge capacity and efficient discharge performance and use this composite hydrogen storage alloy.

Background technology

Hydrogen-storage alloy can be safely and storage of hydrogen easily, is the material of expectation as clean energy resource, and get most of the attention as the new storage of energy and transition material.

At present, as hydrogen-storage alloy, has CaCu to containing ₅The AB of type structure ₅Type, have the AB type of CsCI type structure, AB with cubic system C15 or hexagonal crystal system C14 structure ₂The hydrogen-storage alloy of crystalline phases such as type is just at its electrochemical properties of broad research.

On the other hand, known have have 5 pairs of symmetry axis, accurate crystalline phase (I phase) that positive 20 body structures, the alloy that is made up of transition metal such as Ti, Zr, Ni have the Icosahedral type, its high hydrogen storage capacity get most of the attention (non-patent literature 1).

Many-sides such as the adaptation field of this hydrogen-storage alloy spreads all over that the storage of hydrogen is carried, the catalyst in the separation of the separation and purification of the conversion of the storage conveying of heat, heat-mechanical energy, hydrogen, hydrogen isotope, nickel-hydrogen accumulator, synthetic chemistry, temperature sensor; Wherein, Use hydrogen-storage alloy to have advantages such as small-sized, lightweight, high output as the nickel-hydrogen accumulator of its negative electrode active material; Therefore, demand enlarges.

As the negative electrode active material of nickel-hydrogen accumulator, use at present the AB as the main composition element with rare earth element and Ni ₅Type alloy, but present employed AB ₅The discharge capacity of type alloy has reached LaNi ₅Theoretical capacity about 85%, can not expect than this higher capacity.

[prior art document]

[non-patent literature]

[non-patent literature 1] Appl.Phys.Lett.69 (1996) 2998-3000

Summary of the invention

Therefore, the present invention is in view of above-mentioned present situation, has the composite hydrogen storage alloy of high discharge capacity and efficient discharge performance and uses the nickel-hydrogen accumulator of this composite hydrogen storage alloy to develop in order to provide a kind of.

The result that the inventor concentrates on studies finds to have AB through in the hydrogen-storage alloy with the I phase that possesses excellent hydrogen storage performance, mixing ₃The hydrogen-storage alloy of the crystalline phase of type forms composite alloy, can realize that hydrogen emits the raising of ability, has finally accomplished the present invention.

That is, composite hydrogen storage alloy of the present invention is characterised in that, contains the hydrogen-storage alloy with I phase and has AB ₃The hydrogen-storage alloy of the crystalline phase of type.

In composite hydrogen storage alloy of the present invention, the preferred said AB that has ₃The content of the hydrogen-storage alloy of the crystalline phase of type is 10～30 weight % in composite hydrogen storage alloy.

The hydrogen-storage alloy of the said I of having phase preferably is to constitute element at least with Ti, wherein, serves as to constitute element with Ti, V and Ni at least more preferably.

As the purposes of composite hydrogen storage alloy of the present invention, there is not special qualification, can suitably be used as the negative electrode active material of nickel-hydrogen accumulator.Like this, the nickel-hydrogen accumulator that possesses the negative pole that contains composite hydrogen storage alloy of the present invention also is one of the present invention.

According to the present invention, has AB through in hydrogen-storage alloy, mixing with the I phase that possesses excellent hydrogen storage performance ₃The hydrogen-storage alloy of the crystalline phase of type forms composite alloy, can seek the raising that hydrogen is emitted ability.And the composite hydrogen storage alloy that hydrogen storage performance through will having both this excellence and hydrogen are emitted ability can obtain the battery of discharge capacity height and efficient discharge excellent performance as the negative electrode active material of nickel-hydrogen accumulator.

Description of drawings

Fig. 1 is expression AB ₃Type alloy (a), Ti _1.4V _0.6The figure of the XRD figure case of Ni alloy (b) and their composite alloy (c).

Fig. 2 is the Ti that expression utilizes transmission electron microscope (TEM) to observe _1.4V _0.6The bright field image of Ni alloy (a), 5 times electron diffraction pattern (b) and the figure of common electron diffraction pattern (c).

Fig. 3 comprises Ti _1.4V _0.6The negative pole of Ni alloy with comprise Ti _1.4V _0.6Ni alloy and AB ₃The cycle-index of the negative pole of the composite alloy of type alloy and the coordinate diagram of the correlation between the discharge capacity.

Fig. 4 is that expression comprises Ti _1.4V _0.6The negative pole of Ni alloy with comprise Ti _1.4V _0.6Ni alloy and AB ₃The coordinate diagram of the spectrum of the electrochemical impedance of the negative pole of the composite alloy of type alloy in 50%DOD.

Fig. 5 is the figure of expression corresponding to the equivalent circuit of the spectrum of electrochemical impedance shown in Figure 4.

Fig. 6 is that expression comprises Ti _1.4V _0.6The negative pole of Ni alloy with comprise Ti _1.4V _0.6Ni alloy and AB ₃The negative pole of the composite alloy of type alloy, anode current is with respect to the coordinate diagram of single logarithmic curve of current time response.

Embodiment

Below, the present invention is detailed.

Composite hydrogen storage alloy of the present invention contains the hydrogen-storage alloy with I phase and has AB ₃The hydrogen-storage alloy of the crystalline phase of type.At this, I is meant the accurate crystalline phase of Icosahedral type, AB mutually ₃The crystalline phase of type is meant to have with AB ₃The crystalline phase of the composition of expression.Need to prove that A representes to be selected from least a kind of element (hydrogen storage metal) in the group that is made up of rare earth element and Mg, B representes to be selected from least a kind of element (hydrogen is emitted metal) in the group that is made up of transition elements beyond the rare earth element and Al.

As above-mentioned hydrogen-storage alloy, for example can enumerate: Ti with I phase _1.4V _0.6Ni, Ti _1.6V _0.4Ni, Ti _1.7V _0.3Ni, Ti _1.8V _0.2Ni, Ti _1.9V _0.1Ni, Ti ₄₅Zr ₃₀Ni ₁₃Pd ₇, Ti ₄₅Zr ₃₀Ni ₂₅Y, Ti ₄₅Zr ₃₅Ni ₁₇Cu ₃, Ti ₄₅Zr ₃₈Ni ₁₇, Ti ₅₉Ni ₃₄V ₇Deng titanium alloy; Mg ₂₅Y ₁₁Zn ₆₄In magnesium is alloy; Al ₆₃Cu ₂₅Fe ₁₂, Al ₇₀Cu ₂₀Fe ₁₀, Al ₈₆Mn ₁₄, Al _56.1Cu _10.2Li _33.7, Al _85.7V1 _4.3, Al _78.4Mn _10.6Ru ₄, Al _80.4Mn _19.6, Al ₇₈Re ₂₂, Al ₆Aluminum series alloys such as Mn; Sc _16.2Cu _12.3Zn _71.5Deng scandium is alloy; Zn ₅₉Mg ₃₁Ho ₁₀Deng Zn based alloy etc.These alloys are the alloy of the accurate crystalline phase with Icosahedral type, can use separately, and also two or more kinds may be used.In these alloys, be the titanium alloy of main composition element with Ti, consider preferred the use from its excellent hydrogen storage performance aspect, more preferably Ti content is the above titanium alloy of 45at%.

As above-mentioned titanium alloy; Because excellent in stability; Therefore, being widely used with Ti, Zr and Ni serves as that the TiZrNi that constitutes element is an alloy, is that alloy is the alloy phase ratio with TiZrNi but TiZrNi is at least a portion of the Zr of alloy by the TiVNi that V has replaced; Dynamic effect (activity) is higher, and hydrogen is emitted more excellence of ability.In addition because V is more cheap than Zr, therefore, with TiZrNi be the alloy phase ratio, TiVNi is that alloy also is favourable aspect cost.This serve as to constitute in the titanium alloy of element at least with Ti, V and Ni, preferred use for example has general formula Ti _xV _yThe alloy of the composition of Ni (1.4≤x≤1.9,0.1≤y≤0.6, x+y=2) expression.

The content of the I phase in the hydrogen-storage alloy of the above-mentioned I of having phase preferably is 30～70 volume % in this hydrogen-storage alloy.When the content of I phase was lower than 30 volume %, hydrogen storage amount was abundant sometimes, and on the other hand, when the content of I phase surpassed 70 volume %, hydrogen was emitted ability sometimes.

As above-mentioned manufacturing approach with hydrogen-storage alloy of I phase; Do not have special qualification, for example can enumerate: the method that spin processes, gas atomization (gas atmys method) etc. carry out quenching with the alloy of molten condition in single roller melt spinning method, two roller melt spinning method, centrifugal spray method, REP method, the rotation liquid; Solid reaction processes such as mechanical alloy (machinery fusion) method; The methods that sputtering method etc. are formed by gas phase etc. are used these methods through suitable selection, can make the hydrogen-storage alloy of the above-mentioned I of having phase.

As having above-mentioned AB ₃The hydrogen-storage alloy of the crystalline phase of type, not special the qualification can be enumerated for example with AB _3.0～AB _3.8The hydrogen-storage alloy represented of composition, as this hydrogen-storage alloy, can enumerate and for example have general formula La _aMg _bM _1-a-bNi _cM2 _d(in the formula; Be 0.3≤a≤0.65,0.15≤b≤0.3,2.5≤c≤3.8,3≤c+d≤3.8; M1 representes to be selected from least a kind of element in the group that is made up of the rare earth element beyond the La, and M2 representes to be selected from least a kind of element in the group that is made up of transition elements except that rare earth element and Ni and Al.) alloy of composition of expression.

As alloy, can enumerate for example La with composition that above-mentioned general formula representes _aNd _bMg _1-a-bNi _cAl _3-c(0.60≤a≤0.65,0.10≤b≤0.12,2.5≤c＜3), La _aNd _bMg _1-a-bNi _2.85Co _cSi _dAl1-c-d (0.50≤a≤0.52,0.25≤b≤0.30,0.60≤c≤0.70,0≤d≤0.10), La _aNd _bY _cMg _1-a-b-cNi _dCo _eSi _fAl _gFor example La more specifically can be enumerated in (0.30≤a≤0.40,0.10≤b≤0.20,0.1≤c≤0.20,2.5≤d≤2.7,0.30≤e≤0.40,0≤f≤0.10,0≤g≤0.10) etc. _0.65Nd _0.12Mg _0.23Ni _2.9Al _0.1, La _0.52Nd _0.30Mg _0.18Ni _2.85Co _0.70Si _0.10Al _0.15, La _0.4Nd _0.2Y _0.2Mg _0.2Ni _2.7Co _0.4Si _0.1Al _0.1Deng.These alloys can use separately, also can be also with more than 2 kinds.

Examples of the having AB ₃ -type crystal phase method for producing a hydrogen-absorbing alloy is not particularly limited, and include, for example: Induction floating dissolution method (floating-induced dissolution method), sintering , quench solidification method, etc., by appropriately selecting the use of these methods can be manufactured with the AB ₃ -type crystal phase hydrogen storage alloys.

Composite hydrogen storage alloy of the present invention is in the hydrogen-storage alloy with I phase, to add to have AB ₃The hydrogen-storage alloy of the crystalline phase of type, and these alloys are carried out composite alloying, thus, in the composite alloy of gained, AB ₃The crystalline phase of type promotes moving of atom shape hydrogen, and its result can make the hydrogen ability of emitting improve.Therefore, contain hydrogen-storage alloy and have AB with I phase ₃The composite hydrogen storage alloy of the present invention of the hydrogen-storage alloy of the crystalline phase of type is compared with having I hydrogen-storage alloy mutually separately, and discharge capacity is bigger, and the efficient discharge performance is more excellent.

In the present invention, as the hydrogen-storage alloy with I phase with have an AB ₃The mixing ratio of the hydrogen-storage alloy of the crystalline phase of type is preferably to have AB in the composite hydrogen storage alloy of gained ₃The content of the hydrogen-storage alloy of the crystalline phase of type is the mode of 10～30 weight %, in the hydrogen-storage alloy with I phase, adds to have AB ₃The hydrogen-storage alloy of the crystalline phase of type, and they are mixed.Above-mentioned have an AB ₃When the content of the hydrogen-storage alloy of the crystalline phase of type was lower than 10 weight %, it is insufficient that hydrogen is emitted ability sometimes, on the other hand, even have AB ₃The content of the hydrogen-storage alloy of the crystalline phase of type surpasses 30 weight %, also can't obtain the effect of improving than its better discharge capacity, and like this, the content with hydrogen-storage alloy of I phase reduces, and therefore, hydrogen storage performance is insufficient sometimes.

Manufacturing approach as composite hydrogen storage alloy of the present invention; Not special the qualification; Can make composite hydrogen storage alloy of the present invention through following method; That is, for example will using hydrogen-storage alloy with I phase that single roller melt spinning method etc. processes and usability to swim with the mode of the composition that becomes regulation respectively, dissolution method etc. processes has AB ₃The hydrogen-storage alloy of the crystalline phase of type is mechanically pulverized respectively and carry out micropowderization, mixes with the mixing ratio of regulation then, the mixture of gained is carried out mechanical alloying handle.

Need to prove, composite hydrogen storage alloy of the present invention and as the hydrogen-storage alloy with I phase of its raw material with have AB ₃The accurate crystalline phase in the hydrogen-storage alloy of the crystalline phase of type or the existence of crystalline phase for example can use X-ray diffraction method (XRD) or transmission electron microscope (TEM) to confirm.

As the purposes of composite hydrogen storage alloy of the present invention, not special the qualification can be applied to use the various uses as representative such as jar with the fuel that nickel-hydrogen accumulator, fuel cell, hydrogen vehicle use, and wherein, is preferred for the negative electrode active material of nickel-hydrogen accumulator.Like this, the nickel-hydrogen accumulator that possesses the negative pole that contains composite hydrogen storage alloy of the present invention also is one of the present invention.

Nickel-hydrogen accumulator of the present invention for example contains the negative pole of composite hydrogen storage alloy of the present invention as negative electrode active material except that possessing, and possesses also that to contain with the nickel hydroxide be positive pole (nickel electrode), separator and the alkaline electrolyte etc. of the positive active material of main component.

Above-mentioned negative pole is combined with composite hydrogen storage alloy of the present invention as negative electrode active material.Composite hydrogen storage alloy of the present invention for example is matched with in the negative pole with the composite hydrogen storage alloy form of powder of powdered.

The average grain diameter of above-mentioned composite hydrogen storage alloy powder is preferably 20～100 μ m, more preferably 40～70 μ m.When average grain diameter was lower than 20 μ m, the activation of alloy was insufficient, and on the other hand, when average grain diameter surpassed 100 μ m, productivity ratio was low sometimes.Above-mentioned composite hydrogen storage alloy powder waits and obtains through for example in the presence of inert gas, composite hydrogen storage alloy of the present invention being carried out mechanical disintegration.

Except that above-mentioned composite hydrogen storage alloy powder, above-mentioned negative pole can also contain conductive agent, adhesive (tackifier) etc.

As above-mentioned conductive agent, for example can enumerate: carbon series conductive agent such as native graphite (flaky graphite, flaky graphite, amorphous graphite etc.), Delanium, carbon black, acetylene black, Ketjen black, carbon whisker, carbon fiber, vapor deposition carbon; The metal that is made up of the powder of metals such as nickel, cobalt, copper or fiber etc. is a conductive agent; Yittrium oxide etc.These conductive agents can use separately, also can be also with more than 2 kinds.

Above-mentioned relatively composite hydrogen storage alloy powder 100 mass parts of the use level of above-mentioned conductive agent are preferably 0.1～10 mass parts, more preferably 0.2～5 mass parts.When the use level of above-mentioned conductive agent is lower than 0.1 mass parts, be difficult to obtain sufficient conductivity, on the other hand, when the use level of above-mentioned conductive agent surpassed 10 mass parts, the raising effect of discharge capacity was insufficient sometimes.

As above-mentioned adhesive, for example can enumerate: polyolefin-based resins such as polytetrafluoroethylene (PTFE), polyethylene or polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated epdm, styrene butadiene ribber (SBR), contain fluorubber, polyvinyl alcohol, methylcellulose, carboxymethyl cellulose, xanthans etc.These adhesives can use separately, also can be also with more than 2 kinds.

The use level of above-mentioned adhesive is preferably 0.1～0.5 mass parts, more preferably 0.1～0.3 mass parts with respect to above-mentioned composite hydrogen storage alloy powder 100 mass parts.When the use level of above-mentioned adhesive is lower than 0.1 mass parts, be difficult to obtain sufficient tackifying, on the other hand, when the use level of above-mentioned adhesive surpasses 0.5 mass parts, the poor performance of electrode sometimes.

As above-mentioned positive pole, can enumerate for example being combined with in the nickel hydroxide composite oxides that mix zinc hydroxide or cobalt hydroxide and form as the electrode of positive active material etc. as the nickel hydroxide of main component.As these nickel hydroxide composite oxides, the preferred use carried out homodisperse material through coprecipitation.

Except that above-mentioned nickel hydroxide composite oxides, above-mentioned positive pole preferably contains and is useful on the additive that improves electrode performance.As above-mentioned additive, for example can enumerate: conductive modified agent such as cobalt hydroxide, cobalt oxide, in addition, can utilize oxygen or oxygen-containing gas, K ₂S ₂O ₈, hypochlorous acid etc., will on above-mentioned nickel hydroxide composite oxides, apply cobalt hydroxide or the part of above-mentioned nickel hydroxide composite oxides will be carried out oxidation.

As above-mentioned additive, the material that also can use compound or the Ca compound etc. of rare earth elements such as containing Y, Yb that oxygen overvoltage is improved.Therefore rare earth element such as Y, Yb, also can expect to suppress the effect of the corrosion of negative electrode active material because one of which is partly dissolved, is disposed at negative terminal surface.

Above-mentioned positive pole and above-mentioned negative pole are same, can also contain above-mentioned conductive agent, adhesive etc.

This positive pole and negative pole can be made through following method; Promptly; In each active material, add above-mentioned conductive agent, adhesive etc. as required; And they are mixing with organic solvents such as water or alcohol or toluene, the slurry coating of gained is carried out roll forming etc. in the conductivity supporter and after making its drying.

As above-mentioned conductivity supporter, can enumerate steel plate for example, on steel plate, implement the plating of metal materials such as nickel and plated steel sheet of forming etc.As the shape of above-mentioned conductivity supporter, for example can enumerate: the formed body of foaming body, group of fibers, implemented concavo-convex processing 3 the dimension base materials; 2 dimension base materials such as punch retainer (punch plate).In these conductivity supporters, as the conductivity supporter of positive pole usefulness, preferably to be material to the corrosion resistance of alkali and the excellent nickel of oxidative resistance, to be the foaming body that porous structure constitutes by the excellent structure of current collection property.On the other hand, as the conductivity supporter that negative pole is used, preferably on the iron foil of cheapness and excellent electric conductivity, implemented the punch retainer of nickel plating.

The thickness of above-mentioned conductivity supporter is preferably 30～100 μ m, more preferably 40～70 μ m.When the thickness of above-mentioned conductivity supporter is lower than 30 μ m, produce rate variance sometimes, on the other hand, when the thickness of above-mentioned conductivity supporter surpassed 100 μ m, discharge capacity was insufficient sometimes.

When above-mentioned conductivity supporter was porous material, its internal diameter was preferably 0.8～2 μ m, more preferably 1～1.5 μ m.When internal diameter is lower than 0.8 μ m, produce rate variance sometimes, on the other hand, when internal diameter surpassed 2 μ m, the maintenance performance of hydrogen-storage alloy was insufficient sometimes.

As the method that above-mentioned conductivity supporter is applied each electrode slurry, can enumerate methods such as the roller coat, silk screen coating, scraper coating, spin coating, the rod that have for example used coating roll etc. are coated with.

As above-mentioned separator, for example can enumerate with polyolefin-based resins such as polyethylene or polypropylene, propylene, polyamide etc. is perforated membrane or nonwoven fabrics of material etc.

The order of above-mentioned separator is paid (weight per unit area) and is preferably 40～100g/m ²Order is paid and is lower than 40g/m ²The time, be short-circuited sometimes or the reduction of self-discharge performance, on the other hand, order is paid above 100g/m ²The time, the ratio of the separator that per unit volume is shared increases, and therefore, battery capacity is tended to descend.In addition, the venting quality of above-mentioned separator is preferably 1～50cm/sec.When venting quality was lower than 1cm/sec, inner pressure of battery was too high sometimes, on the other hand, when venting quality surpasses 50cm/sec, was short-circuited sometimes or the reduction of self-discharge performance.And the average fiber of above-mentioned separator directly is preferably 1～20 μ m.When average fiber directly was lower than 1 μ m, the intensity of separator reduced sometimes, and the defect rate in the battery installation procedure increases, and on the other hand, when it surpasses 20 μ m, caused the reduction of average fiber footpath short circuit or self-discharge performance sometimes.

Above-mentioned separator is preferably implemented hydrophilicity-imparting treatment to its fiber surface.As this hydrophilicity-imparting treatment, for example can enumerate: sulfonation processing, corona treatment, fluorine gas processing, Cement Composite Treated by Plasma etc.Wherein, fiber surface is implemented the separator of oversulfonate processing because absorption causes the NO of the moving phenomenon of shuttle ₃ ^-, NO ₂ ^-, NH ₃ ^-Deng impurity or high from the ability of the stripping element of negative pole, therefore, it is high and preferred that self discharge suppresses effect.

As above-mentioned alkaline electrolyte, can enumerate alkaline aqueous solutions such as for example containing potassium hydroxide, NaOH, lithium hydroxide.Above-mentioned alkaline electrolyte can use separately, also can be also with more than 2 kinds.

With regard to the concentration of above-mentioned alkaline electrolyte, the total of ion concentration is preferably below the 9.0mol/L, more preferably 5.0～8.0mol/L.

In order to improve the oxygen overvoltage in the positive pole, the corrosion resistance that improves negative pole, raising self discharge, in above-mentioned alkaline electrolyte, can add various additives.As this additive, for example can enumerate: oxide such as yttrium, ytterbium, erbium, calcium, zinc or hydroxide etc.These additives can use separately, also can be also with more than 2 kinds.

When nickel-hydrogen accumulator of the present invention is opening nickel-hydrogen accumulator; This battery can be through for example inserting negative pole anodal across separator; And make the fixing state of electrode inject alkaline electrolyte down with the mode of the pressure that these electrodes applied regulation, opening shape battery is installed is again made.

On the other hand, when nickel-hydrogen accumulator of the present invention was closed nickel-hydrogen storage battery, this battery can seal with housing material and make through before or after lamination positive pole, separator and negative pole, injecting alkaline electrolyte again.In addition, in the closed nickel-hydrogen storage battery that forms across generating important document that spacer layer is pressed into by anodal and negative pole of reeling, preferably before or after the above-mentioned generating important document of reeling with the alkaline electrolyte fluid injection in the important document that generates electricity.As the injection process of alkaline electrolyte, not special the qualification can also can be used for example vacuum infiltration method, pressure impregnation method, centrifugal method of impregnation etc. in fluid injection under the normal pressure.In addition, as the housing material of closed nickel-hydrogen storage battery, can the enumerate plating for example iron of metal materials such as iron, nickel, stainless steel, the material that constitutes by polyolefin-based resins etc.

Form as above-mentioned closed nickel-hydrogen storage battery; Not special the qualification, for example can enumerate: Coin-shaped battery, coin shape battery, square battery, platypelloid type battery etc. have positive pole, negative pole and single or multiple lift separator battery or have the cylindrical battery etc. of positive pole, negative pole and the separator of roller shape.

[embodiment]

Below, enumerate embodiment the present invention is described in further detail, but the present invention has more than and is defined in these embodiment.

< test method >

Under argon atmospher, use single roller melt spinning method to prepare the Ti of wide 2.5mm * thick 35 μ m _1.4V _0.6The shoestring of Ni alloy.This moment, the circular velocity of copper wheel was 34m/s.Has La _0.65Nd _0.12Mg _0.23Ni _2.9Al _0.1The AB of composition ₃Should the swim dissolution method preparation of type alloy usability under argon atmospher.With Ti _1.4V _0.6Ni alloy and AB ₃The sample of type alloy carries out mechanical disintegration, forms thin powder to 200～400 meshes, utilizes the Ti of high-energy ball mill to 80 weight % _1.4V _0.6The AB of Ni alloy and 20 weight % ₃The mechanical alloying that the mixture of powders of type alloy carried out 30 minutes is handled.The X-ray diffraction method (XRD) that utilizes mutually of the shoestring of the composite alloy that is prepared into is studied, and micro-structure utilizes transmission electron microscope (TEM) to study.

The powder and the carbonyl nickel powder of the composite alloy that is prepared into are mixed with weight ratio at 1: 5, make negative pole.The mixture of powders of gained is applied the pressure of 15MPa, be compressed into the small-sized particle of diameter 10mm and thickness 1.5mm.For electrochemical gaging, in the KOH of 6M electrolyte with Ni (OH) ₂/ NiOOH electrode as reference electrode and active electrode, is made half-cell with Hg/HgO with doing electrode.Electrochemical test uses automatic constant current charge electric discharge device (DC-5) to carry out with 303K.Negative pole charged 6 hours with 60mA/g, was discharged to final voltage with 30mA/g again to be-0.6V (to Hg/HgO).Whenever once discharge and recharge, ended 5 minutes.Use Solalto (ソ ラ Le ト Application) 1287 potentiostats/galvanostat and the Solalto 1255B frequency response analyzer that has carried the Z-PLOT software that windows uses, carry out electrochemical impedance beam split (EIS) with the discharge (DOD) of 50% degree of depth and analyze.In this test,, select the constant voltage electric discharge in order to estimate the effect of hydrogen diffusion in the electrode of regulation.After open loop was proceeded full charging in 30 minutes, use M352 corrosion software, utilize EG&G PARC model 273 potentiostats/galvanostat, test was discharged 3600 seconds with the potential step of electrode with+500mV.

< result >

(1) phase structure

Fig. 1 is expression AB ₃Type alloy, Ti _1.4V _0.6The figure of the XRD figure case of Ni alloy and these composite alloys.AB ₃The type alloy is shown in Fig. 1 (a), observes this alloy mainly by having PuNi ₃(La, Mg) Ni of the surperficial body crystal structure (spatial group R 3m) of type ₃Mutually with have CaCu ₅The LaNi of the hexagonal system structure (spatial group P6/mmm) of system ₅Constitute mutually.Corresponding to Ti _1.4V _0.6The diffraction maximum of Fig. 1 of Ni alloy (b) is represented I phase, Ti ₂The centroid cubic lattice structure of Ni type (FCC) mutually with body-centered cubic lattic structure (BCC) solid solution mutually.With Ti _1.4V _0.6Ni alloy and AB ₃The mixture of type alloy utilizes ball mill to pulverize back (Fig. 1 (c)), and the anisotropy of lattice enlarges, result, (La, Mg) Ni ₃Phase and LaNi ₅The diffraction maximum of phase obviously broadens.

Fig. 2 (a) is the bright field image of the typical growth form of expression and the existence of I fritter mutually.About the point group symmetry of I phase and crystalline BCC mutually, shown in Fig. 2 (b) and Fig. 2 (c), observe 5 times and common electron diffraction pattern (001) of expectation respectively.Though do not observe Ni corresponding to (La, Mg) ₃Phase, LaNi ₅Reach Ti mutually ₂The electron diffraction pattern of Ni type FCC phase, still, XRD result (Fig. 1) obviously is presented at the existence that these phases are arranged in the composite alloy sample.Other crystalline phase that under various conditions, is formed by liquid also can be deposited in the zones of different of sample usually like this, therefore, this phenomenon can take place.

(2) discharge capacity and stability

Fig. 3 is that expression comprises Ti _1.4V _0.6The negative pole of Ni alloy, comprise Ti _1.4V _0.6Ni alloy and AB ₃The cycle-index of the negative pole of the composite alloy of type alloy and the coordinate diagram of the correlation between the discharge capacity.Discharge capacity is because of AB ₃The interpolation of type alloy and significantly improving.Do not adding AB ₃During the type alloy, discharge capacity reaches the peak of 272.7mAh/g in circulation for the second time, has the AB of higher hydrogen storage property (340mAh/g) through adding ₃Type alloy discharge capacity increases, and is adding AB ₃Behind the type alloy 20 weight %, in circulation for the first time, reach the peak of 294.7mAh/g.It is illustrated in the composite hydrogen storage alloy electrode, at AB ₃Type alloy and Ti _1.4V _0.6There is synergy between the Ni alloy.But, even add AB ₃Type alloy 30 weight % do not see the effect of improving of discharge capacity that it is above yet.

(3) efficient discharge performance and dynamic characteristic

Table 1 expression comprises Ti _1.4V _0.6The negative pole of Ni alloy (a) and comprise Ti _1.4V _0.6Ni alloy and AB ₃The efficient discharge performance (HRD) of the negative pole of the complex of type alloy (b).

[table 1]

Electrode	30(mA/g)	60(mA/g)	90(mA/g)	120(mA/g)	180(mA/g)	240(mA/g)	HRD(C 240/C 30)
								a	276.3	248.3	245.9	244.6	230.9	205.1	74.2％
b	294.7	272.4	266.3	262.1	240.9	229.6	77.9％

Result by shown in the table 1 learns, and comprises Ti _1.4V _0.6The electrode of Ni alloy (a) is compared, and comprises Ti _1.4V _0.6Ni alloy and AB ₃The electrode of the complex of type alloy (b) has more excellent efficient discharge performance.At present known is that the HRD of metal hydride (MH) electrode mainly receives the electric charge mobile response of the generation at the electrode/electrolyte interface and the influence of the hydrogen diffusion velocity in the electrode.

Comprise Ti in order to estimate _1.4V _0.6Ni alloy and AB ₃The electrode of the complex of type alloy with comprise Ti _1.4V _0.6The electrochemical reaction rates of the electrode of Ni alloy, the spectrum of mensuration electrochemical impedance and potential step.Fig. 4 representes the spectrum of the electrochemical impedance of the bipolar electrode sample among the 50%DOD.Can know that any one EIS curve constitutes by 2 circular arcs of convergence straight line.

According to the analytical model (with reference to J.Alloys.Compd.202 (1993) 183-197) by propositions such as Li Shan, the bigger arc representation in medium frequency zone moves resistance with respect to the electric charge of the electrochemical reaction on surface, at this, and R ₁Be bath resistance, R ₂And C ₁Respectively as contact resistance between collector body and the alloying pellet and hand capacity.Contact resistance between the alloy powder in the alloying pellet and hand capacity are used R respectively ₃And C ₂Expression.Rct and C ₃Represent that respectively electric charge moves resistance and electric double layer capacitance.Wo is a Wo Baige resistance.Based on equivalent electric circuit shown in Figure 5, utilize fit procedure Z-VIEW to obtain electric charge and move resistance R ct.

According to result of calculation, the Rct of alloy electrode is increased to 0.218 Ω (a) from 0.148 Ω (b).As everyone knows, electric charge moves resistance and exchange current density and confirms by eelctro-catalyst is active.Add AB ₃Ti behind the type alloy _1.4V _0.6The electrode Rct of Ni alloy reduces.But the enlightenment that provides is, the result that electrochemical impedance is measured is different with the result of HRD, and surface charge moves and is not rate determining step.

The hydrogen diffusion coefficient of block type electrode utilizes potential step method to obtain.Fig. 6 representes that anode current can obviously be divided into by spectrum with respect to single logarithmic curve of current time response and applies 3 time zones after the overvoltage.According to the model (with reference to J.Electrochem.Soc.142 (1995) 2695-2699) of Zheng etc., the hydrogen diffusion coefficient in the block type electrode that uses for the diffusion velocity of confirming hydrogen can be calculated by the slope corresponding to the linearity region of describing of following formula.

[formula 1]

$\mathrm{Logi}=\log \left(\frac{6\mathrm{FD}(\mathrm{Co}-\mathrm{Cs})}{{\mathrm{da}}^2}\right)-\frac{{\mathrm{\&pi;}}^2\mathrm{Dt}}{2.303a^2}$

In the formula, D is hydrogen diffusion coefficient (cm ²/ s), a is the radius (cm) of spherical particle, I is diffusion current density (A/g), C ₀Initial hydrogen concentration (mol/cm for block type electrode ³), Cs is the hydrogen concentration (mol/cm on alloy particle surface ³), d is the density (g/cm of storage hydrogen material ³), t is discharge time.Utilize formula (1) to calculate the hydrogen diffusion coefficient D in the block type electrode of assumed average particle diameter when being 15 μ m, be shown in table 2.

[table 2]

By the result shown in the table 2, the D value is Ti _1.4V _0.6Ni+AB ₃(b)＞Ti _1.4V _0.6The order of Ni (a), the sequence consensus high with discharge capability.This enlightenment of giving us is that diffusion technology is superior when the electrochemical reaction of control.As stated, think AB ₃The type alloy promotes moving of atom shape hydrogen, is effective to the raising of electrochemical reaction speed.

Claims (5)

1. A composite hydrogen storage alloy, characterized in that, A hydrogen storage alloy having a phase I and a hydrogen storage alloy having a crystalline phase of type AB ₃ are contained. 2. The composite hydrogen storage alloy according to claim 1, wherein, It contains 10 to 30% by weight of the hydrogen storage alloy having the AB ₃ type crystal phase. 3. The composite hydrogen storage alloy according to claim 1 or 2, wherein, The hydrogen storage alloy having phase I contains at least Ti as a constituent element. 4. The composite hydrogen storage alloy as claimed in claim 1, 2 or 3, wherein, The hydrogen storage alloy having phase I contains at least Ti, V and Ni as constituent elements. 5. A nickel-metal hydride storage battery having a negative electrode containing the composite hydrogen storage alloy according to claim 1, 2, 3 or 4.

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