CN1173057C - Hydrogen-bearing mixed rare-earth alloy as electrodes of secondary nickel-metal oxide battery - Google Patents

Abstract

The present invention discloses a novel hydrogen-storing electrode alloy in a mixed rare earth system for nickel-metal hydride (Ni-MH) secondary batteries. The novel hydrogen-storing electrode alloy comprises the component of Ml<1-y>My(NiCoN)x, wherein Ml represents mixed rare earth, the total rare-earth elements account for at least 90 wt%, La accounts for at least 30 wt%, Ce accounts for no more than 70 wt%, 0.01<=y<=0.8, 2.0<=x<=4.0, M is one, two or more than two kinds of Mg, Ca, Be, Sr and Ba, N is one, two or more than two kinds of Mn, Fe, Mo, Co, Al, Si, Ga, S, Sc, Ti, V, Cr, Cu, Zn, Zr, Nb, Ru, Rh, Cd, W, Hf, Ta, B, P, Ge, As, Se, In and Sn. The nickel-hydride battery prepared from the novel hydrogen-storing electrode alloy has the advantage that the activate property, the initial capacity, the high-power discharge performance and other technical performance indexes of the nickel-hydride battery are considerably superior to those of a nickel-hydride battery prepared from the existing traditional commercial AB5 alloy in a rare earth system.

Description

Nickle-metal hydride secondary battery mixed rare-earth alloys for hydrogen-bearing electrode

Technical field

The present invention relates to secondary cell, relate in particular to the mixed rare-earth alloys for hydrogen-bearing electrode that nickel-metal hydrides (Ni-MH) secondary cell is used.

Background technology

Since LaNi is found in Dutch Philips laboratory in 1970 ₅Reversible hydrogen storage property since, hydrogen-storage alloy has obtained widespread use in the accumulating of hydrogen, the purification of hydrogen and the fields such as separation of isotopes of compression, heat pump and refrigeration, hydrogen-burning automobile, nickle-metal hydride secondary battery, fuel cell and hydrogen.Especially on nickle-metal hydride secondary battery, become the focus of lot of domestic and foreign scholar's research owing to advantages such as it have the capacity height, has extended cycle life, memory-less effect, anti-over-charging are crossed the strong and non-environmental-pollution of exoergic power.

The cell reaction of nickel-metal hydrides (Ni-MH) secondary cell can be expressed as:

Anodal reaction:

Negative reaction:

Total reaction:

More than the reaction of expression charging to the right in all formulas, to the left representation exoelectrical reaction.As seen in the charge and discharge process of battery, the quantity of alkaline electrolyte does not change, i.e. additive decrementation electrolytic solution not.

From at present, the hydrogen-storage alloy in the research mainly contains AB ₅Type rare earth-based alloy, AB ₂Type Zr (Ti) is that Laves phase alloy, AB type TiFe are alloy, A ₂Type B Mg-Ni is base types such as alloy and V based solid solution type alloy.Wherein, with LaNi ₅AB for prototype ₅Solid type rare earth-based alloy is owing to can be under room temperature and normal pressure reversibly inhale in the mode of gas-reaction or electrochemical reaction and put hydrogen, and and have advantage such as easily-activated, that suction hydrogen discharge reaction speed is fast and extremely pay attention to, develop also the fastest.But because rare earth based AB ₅The capacity of type alloy lower (about 320mAh/g), this has just impelled people to remove the higher hydrogen-storing alloy as electrode of research and development capacity.

AB ₂The type alloy was once once causing people's attention, and it has higher electrochemical discharge capacity and long cycle life, but its large current discharging capability and initial stage activation performance are poor, and cost is higher, so be difficult to practicability.Magnuminium is owing to adopt the comparatively cheap elements of price such as magnesium, nickel as starting material, therefore cost is quite low, and Magnuminium has very high initial electrochemical discharge capacity and good activation performance, but the corrosion of this alloy in alkaline electrolyte is quite serious, caused the rapid decline of capacity, also can't practicability within the short-term.Vanadium radical sosoloid alloy is the same with Magnuminium, also has higher initial electrochemical discharge capacity, but because the precipitation of vanadium in alkaline electrolyte is very serious, also can cause the rapid decline of capacity, and not possess practical value because the price comparison of vanadium is expensive.

New-type hydrogen-storing RE electrode alloy has higher electrochemical discharge capacity.Kohno has studied La ₅Mg ₂Ni ₂₃The electrochemical discharge capacity of type hydrogen-storing alloy as electrode electrode can reach 400mAh/g, has surmounted rare earth based AB greatly ₅The loading capacity of type hydrogen-storing alloy as electrode electrode.And its alloy electrode has good cyclical stability, good high magnification characteristic and advantage such as activation capacity and low price and has demonstrated powerful application prospect in electrolytic solution.Therefore, we have reason to believe that in the near future New-type hydrogen-storing RE electrode alloy will replace traditional AB ₅Type hydrogen-storing alloy as electrode and being applied among the production of Ni-MH secondary cell.

Summary of the invention

Purpose of the present invention just is to have proposed a kind of nickle-metal hydride secondary battery mixed rare-earth alloys for hydrogen-bearing electrode.

Its composition is: Ml _1-yM _y(NiCoN) _x, Ml is a mishmetal, and wherein the rare earth element total content is not less than 90 (weight) %, and La content is not less than 30 (weight) %, and Ce content is not higher than 70 (weight) %, 0.01≤y≤0.8; 2.0≤x≤4.0; One or both compositions among M=Mg, the Ca, one or both among N=Mn, Fe, Mo, Co, Al, Si, Ga, S, Ti, V, Cr, Cu, Zn, Zr, B, the Sn or two or more composition.

Designed nickel-metal hydrides (Ni-MH) secondary battery negative pole of the method that adopts the present invention the to propose comprehensive electrochemical of New-type hydrogen-storing RE electrode alloy electrode, comprise that loading capacity and high magnification characteristic etc. and pure rare earth alloy electrode relatively significantly do not descend, cyclical stability increases.Charge and discharge under the condition at little electric current, its performance has substantially exceeded business-like AB ₅Hydrogen-storing alloy as electrode.Its cost is cheaper in addition, therefore in the near future, will replace existing traditional AB ₅Hydrogen-storing alloy as electrode and become the nickle-metal hydride secondary battery negative pole hydrogen-storing alloy as electrode of a new generation, its cost performance will substantially exceed lithium-ion secondary cell, thus the market competitiveness of raising nickel-metal hydrides (Ni-MH) secondary cell.

Description of drawings

Fig. 1 is according to the Ml of New-type hydrogen-storing RE electrode alloy described in the embodiment _0.7Mg _0.3(NiCoAl) _3.3The loading capacity of electrode and the relation curve between the cycle index;

Fig. 2 is according to Ml described in pure La New-type hydrogen-storing RE electrode alloy and the embodiment described in the comparative example 1 _0.7Mg _0.3(NiCoAl) _3.3Relation curve between alloy loading capacity and the cycle index;

Fig. 3 is according to the AB of commercialization rare earth based described in the comparative example 2 ₅Ml described in hydrogen-storing alloy as electrode electrode and the embodiment _0.7Mg _0.3(NiCoAl) _3.3Relation curve between alloy loading capacity and the cycle index.

Embodiment

Nickel-metal hydrides (Ni-MH) secondary battery negative pole New-type hydrogen-storing RE electrode alloy Ml _0.7Mg _0.3(NiCoN) _3.3Alloy adopts vacuum magnetic suspension stove or arc melting preparation.

Embodiment

According to New-type hydrogen-storing RE electrode alloy Ml _0.7Mg _0.3(NiCoN) _3.3Design mix, adopt vacuum magnetic suspension stove melting preparation.The alloy of institute's melting comprises: Ml _0.7Mg _0.3(NiCo) _x, Ml _0.7Mg _0.3(NiCoMn) _x, Ml _0.7Mg _0.3(NiCoAl) _3.3, Ml _0.7Mg _0.3(NiCoFe) _x, Ml _0.7Mg _0.3(NiCoMnAl) _x, Ml _0.7Mg _0.3(NiCoMo) _x, Ml _0.7Mg _0.3(NiCoS) _x, Ml _0.7Mg _0.3(NiCoSi) _x, Ml _0.7Mg _0.3(NiCoGa) _xWherein, x=3.3, Ml are mishmetal, and wherein the rare earth element total content is not less than 90wt%, and La content is not less than 30wt%, and Ce content is not higher than 70wt%, and the purity of alloy constituent element Mg, Mn, Ni, Fe, Mo, Co, Al, Si, Ga, S is all more than 90%.Respectively get alloy part then and carry out the test of electrochemistry cycle life.This test is to carry out in an open type three-electrode system, and it comprises a working electrode (being hydrogen-occlussion alloy electrode), a sintering Ni (OH) ₂/ NiOOH supporting electrode and a Hg/HgO reference electrode.Electrolytic solution adopts the 6N KOH aqueous solution, and probe temperature remains on 303K.All test electrodes all are to form by uniform mixing 100mg hydrogen-storing alloy as electrode powder (300 order) and 400mg carbonyl nickel powder and the electrode slice that is pressed into diameter 10mm, thickness 1mm under the pressure of 20Mpa.Electrode adopts the current charges of 100mA/g, the current discharge of 60mA/g, and wherein the duration of charging is 5 hours, the discharge stopping potential is-0.6V (with respect to the Hg/HgO reference electrode).

Comparative example 1

The Ml of selected part pure rare earth element melting _0.7Mg _0.3(NiCoAl) _3.3Hydrogen-storing alloy as electrode carries out the test of electrochemistry cycle life to it.The system and the condition of test are all identical with embodiment.

Comparative example 2

The business-like rare earth based AB that selected part three general companies produce ₅Hydrogen-storing alloy as electrode carries out the test of electrochemistry cycle life to it.The system and the condition of test are all identical with embodiment.

As can be seen from Figure 1, mixed rare-earth alloys for hydrogen-bearing electrode Ml _0.7Mg _0.3(NiCoAl) _3.3Activation performance fine, in 2 circulations, just can activate fully, its high discharge capacity can reach 386mAh/g, loading capacity also can keep 85% after 250 circulations.

As can be seen from Figure 2, after the process mixed rare-earth elements substituted, the loading capacity and the cycle life of alloy electrode did not all decrease drastically.

As can be seen from Figure 3, under the same condition that discharges and recharges, mixed rare-earth alloys for hydrogen-bearing electrode Ml _0.7Mg _0.3(NiCoAl) _3.3Comprehensive electrochemical obviously be better than business-like rare earth based AB ₅Hydrogen-storing alloy as electrode, its high discharge capacity is than business-like rare earth based AB ₅The peak capacity of hydrogen-storing alloy as electrode exceeds nearly 70mAh/g, and increase rate is about 23%, and cyclical stability is also not second to business-like rare earth based AB ₅Hydrogen-storing alloy as electrode.

Claims (1)

1. a nickle-metal hydride secondary battery mixed rare-earth alloys for hydrogen-bearing electrode is characterized in that its composition is: Ml _1-yM _y(NiCoN) _x, Ml is a mishmetal, and wherein the rare earth element total content is not less than 90 (weight) %, and La content is not less than 30 (weight) %, and Ce content is not higher than 70 (weight) %, 0.01≤y≤0.8; 2.0≤x≤4.0; One or both compositions among M=Mg, the Ca, one or both among N=Mn, Fe, Mo, Co, Al, Si, Ga, S, Ti, V, Cr, Cu, Zn, Zr, B, the Sn or two or more composition.

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