CN102618754A - Preparation method of AB3-AB5 composite alloy - Google Patents

Abstract

The invention discloses a preparation method of an AB3-AB5 composite alloy. The preparation method comprises the following steps of: preparing an AB3 type La0.78Mg0.22Ni2.67Mn0.11Al0.11Co0.52 matrix alloy and an AB5 type MlNi3.5Co0.6Mn0.4Al0.5 alloy serving as a modifier through a vacuum induction smelting method respectively; mechanically crushing two alloy ingots and then ball-milling at the rotation speed of 250-300 rpm for 60-90 minutes; sieving 200-mesh to 300-mesh granular powder for preparing the composite alloy; and uniformly mixing the two prepared alloys according to the composition proportion in percentage by weight: 50-99.5 percent of La0.78Mg0.22Ni2.67Mn0.11Al0.11Co0.52 and 0.5-50 percent of MlNi3.5Co0.6Mn0.4Al0.5 and then ball-milling at the ratio of grinding media to material of 20:1 and the rotation speed of 200-300 rpm for 30-60 minutes to obtain the composite alloy. According to the preparation method, the AB3 type hydrogen storage alloy serving as a negative material of a power Ni/MH battery is compositely modified, so that an alloy electrode with high discharge capacity, good cyclic stability and superior dynamic performance is obtained.

Description

A kind of AB 3-AB 5The preparation method of composite alloy

Technical field

The present invention relates to metallurgical chemistry and electrochemical research field, particularly AB ₅The type alloy is to AB ₃Type La _0.78Mg _0.22Ni _2.67Mn _0.11Al _0.11Co _0.52Hydrogen storage alloy carries out composite modified method.

Background technology

Present commercial Ni/MH battery can not satisfy the demand of power supplys such as high-energy-density, powerful requirement, especially electric bicycle, electromobile and hybrid electric vehicle.Therefore develop more heavy body, better cyclical stability, more high-power and over-all properties ideal Ni/MH battery is the important directions of current research.So far, as novel high capacity hydrogen storage alloy electrode material, AB ₃(R is rare earth or Y to type R-Mg-Ni alloy, Ca) has been carried out big quantity research.The R-Mg-Ni alloy under the temperature of gentleness, have high relatively loading capacity (360～410mAh/g), than commercial AB ₅The mixed rare earths-based alloy of type improves about 30～40%.Yet; Because this type alloy surface forms surface film oxide easily, the velocity of diffusion of electro catalytic activity, electroconductibility, exchange current density and the hydrogen on surface etc. are all lower, and the capacity attenuation of electrode is very fast; High-rate discharge ability is poor, and their practical application is restricted.So far, to AB ₃The research that the type alloy property improves mainly concentrates on element and replaces, and the research of relevant formation composite alloy aspect is few.Adopt the good AB of cycle performance ₅The type alloy is to AB ₃Type La _0.78Mg _0.22Ni _2.67Mn _0.11Al _0.11Co _0.52Hydrogen storage alloy carries out the rarely seen report of composite modified research.

Summary of the invention

The purpose of this invention is to provide a kind of excellent AB of cyclical stability that utilizes ₅The type alloy is as properties-correcting agent, with AB ₃The type alloy prepares La through ball milling _0.78Mg _0.22Ni _2.67Mn _0.11Al _0.11Co _0.52-x wt%MlNi _3.5Co _0.6Mn _0.4Al _0.5The method of (x=0.5～50) composite alloy is to improve AB ₃The cycle performance of type hydrogen storage alloy electrode.

Concrete steps are:

(1) prepares AB respectively through vacuum induction melting method ₃Type La _0.78Mg _0.22Ni _2.67Mn _0.11Al _0.11Co _0.52Precursor alloy and as the AB of properties-correcting agent ₅Type MlNi _3.5Co _0.6Mn _0.4Al _0.5Alloy, two kinds of alloy pigs be respectively after the mechanical disintegration, and with 250～300 rev/mins of ball millings of rotating speed 60～90 minutes, screening was 200～300 purpose particle powders; Said Ml is a mishmetal, and the weight percent of composition is: 37.7%La, 38.9%Ce, 6.3%Pr and 17.1%Nd;

(2) AB that step (1) is made ₃Type and AB ₅The type alloy is according to weight percent: La _0.78Mg _0.22Ni _2.67Mn _0.11Al _0.11Co _0.52Be 50～99.5% and MlNi _3.5Co _0.6Mn _0.4Al _0.5Be to carry out ball milling again after 0.5～50% proportion of composing mixes, ball-to-powder weight ratio is 20: 1,200～300 rev/mins of rotating speeds, and the ball milling time is 30～60 minutes, obtains composite alloy.

The present invention uses AB to the Ni/MH cell negative electrode material with applications well prospect ₃Type hydrogen storage alloy carries out composite modified, has obtained to have the hydrogen-bearing alloy electrode of good circulation stability and excellent dynamic performance.

Embodiment

Embodiment 1:

(1) prepares AB through vacuum induction melting method ₃Type La _0.78Mg _0.22Ni _2.67Mn _0.11Al _0.11Co _0.52Precursor alloy and as the AB of properties-correcting agent ₅Type MlNi _3.5Co _0.6Mn _0.4Al _0.5(Ml is a mishmetal, and the weight percent of composition is: 37.7%La, 38.9%Ce, 6.3%Pr and 17.1%Nd), above-mentioned two kinds of alloy pigs be respectively after the mechanical disintegration, with 250 rev/mins of ball millings of rotating speed 60 minutes, sieves 300 purpose particle powders;

(2) two kinds of alloys that step (1) made are according to La _0.78Mg _0.22Ni _2.67Mn _0.11Al _0.11Co _0.52Be 90% and MlNi _3.5Co _0.6Mn _0.4Al _0.5Be that 10% weight percent mixes, carry out ball milling and obtain composite alloy that ball-to-powder weight ratio is 20: 1,300 rev/mins of rotating speeds, the ball milling time is 30 minutes;

(3) preparation of electrode negative plate: the powdered alloy that step (2) is made; Adding carbonyl nickel powder by weight 1: 2 mixes; On desk-top tabletting machine, with the pressure of 20MPa powder compression being become diameter is the small pieces of 10mm; With two nickel foam electrode slice is coated then, adopt 30MPa pressure to compress and be prepared into negative plate, calculate the real content of alloy powder sample.

Embodiment 2:

In the step (2), the alloy composition ratio changes weight percent La into _0.78Mg _0.22Ni _2.67Mn _0.11Al _0.11Co _0.52Be 80% and MlNi _3.5Co _0.6Mn _0.4Al _0.5Be 20%, all the other are with embodiment 1.

Utilize above-mentioned technology, carry out composite modified alloy.Measure phase structure, cyclical stability and the dynamic performance of alloy respectively with x-ray diffractometer, LAND 5.3B battery test system and PARSTAT 2273 electrochemical workstations, the result is following:

1) AB ₅The type alloy is by hexahedral CaCu ₅The LaNi of type ₅Phase composite, AB ₃Type alloy La _0.78Mg _0.22Ni _2.67Mn _0.11Al _0.11Co _0.52By LaNi ₅Phase and La ₂Ni ₇Phase composite is when adding AB ₅Behind the type alloy, do not change the principal phase crystalline structure of precursor alloy, composite alloy is main still to be LaNi mutually ₅Phase and La ₂Ni ₇Phase.

2) alloy electrode has good activation performance, all activation fully in 3 circulations.After ball milling was compound, along with the increase of x value, the electrode maximum discharge capacity was reduced to 356mAh/g (x=30) from 371mAh/g (x=0).

3) add AB ₅Alloy can improve the cyclical stability of electrode.After 50 circulations, the circulation volume conservation rate of electrode is increased to 76.5% (x=20) from 55.4%, is reduced to 73.3% (x=30), i.e. AB then ₃Alloy and AB ₅After the alloy ball milling was compound, the cycle performance of electrode improved.

4) the high-rate discharge capacity HRD of electrode ₆₀₀, exchange current density, limit current density and Wasserstoffatoms spread coefficient increase afterwards earlier and reduce.In the electrode of being studied, the x=20 electrode has best comprehensive electrochemical.

La of the present invention _0.78Mg _0.22Ni _2.67Mn _0.11Al _0.11Co _0.52-x wt%MlNi _3.5Co _0.6Mn _0.4Al _0.5(x=0.5～50) composite alloy prepares through the mechanical ball milling method.Ball milling does not change the structure of precursor alloy, and composite alloy is by LaNi ₅Phase and La ₂Ni ₇Phase composite.All electrodes have excellent activation performance, can in 3 circulations, reach maximum discharge capacity.Result of study confirms, AB ₅The type alloy not only can improve AB as surface-modifying agent ₃Type La _0.78Mg _0.22Ni _2.67Mn _0.11Al _0.11Co _0.52The cyclical stability of alloy electrode can also improve the kinetic property of electrode.

Claims (1)

1. the preparation method of a composite alloy is characterized in that concrete steps are:

(1) prepares AB respectively through vacuum induction melting method ₃Type La _0.78Mg _0.22Ni _2.67Mn _0.11Al _0.11Co _0.52Precursor alloy and as the AB of properties-correcting agent ₅Type MlNi _3.5Co _0.6Mn _0.4Al _0.5Alloy, two kinds of alloy pigs be respectively after the mechanical disintegration, and with 250～300 rev/mins of ball millings of rotating speed 60～90 minutes, screening was 200～300 purpose particle powders; Said Ml is a mishmetal, and the weight percent of composition is: 37.7%La, 38.9%Ce, 6.3%Pr and 17.1%Nd;

(2) AB that step (1) is made ₃Type and AB ₅The type alloy is according to weight percent: La _0.78Mg _0.22Ni _2.67Mn _0.11Al _0.11Co _0.52Be 50～99.5% and MlNi _3.5Co _0.6Mn _0.4Al _0.5Be to carry out ball milling again after 0.5～50% proportion of composing mixes, ball-to-powder weight ratio is 20: 1,200～300 rev/mins of rotating speeds, and the ball milling time is 30～60 minutes, obtains composite alloy.