CN105039815B

CN105039815B - Preparation method of Mg-Li solid solution hydrogen storage material

Info

Publication number: CN105039815B
Application number: CN201510227212.8A
Authority: CN
Inventors: 蓝志强; 郭进; 谢政专; 彭雯琦; 李柳杰
Original assignee: Guangxi University
Current assignee: Guangxi University
Priority date: 2015-08-20
Filing date: 2015-08-20
Publication date: 2017-03-22
Anticipated expiration: 2035-08-20
Also published as: CN105039815A

Abstract

The invention discloses a preparation method of an Mg-Li solid solution hydrogen storage material. The preparation method comprises the steps of uniformly mixing magnesium powder, lithium hydride powder and silicon powder, pressing the mixture to form circular sheets, annealing the round sheets, crushing the annealed sample, and preparing the Mg-Li solid solution hydrogen storage material through a mechanical-alloying method. The invention is advantaged in that the composite in which Mg:Li:Si=90:(10-x):x is prepared through firstly annealing and then mechanical ball milling for 50 h, wherein the X=0,2,4,6. When the X=4 and the X=6, the alloy is high in hydrogen storage capacity, and the alloy is low in dehydrogenation activation energy, thereby providing a strong foundation for researching the solid solution hydrogen storage materials in future.

Description

A kind of preparation method of Mg-Li solid solution hydrogen storages material

Technical field

The invention belongs to hydrogen storage material technical field, specifically a kind of preparation method of Mg-Li solid solution hydrogen storages material, the party Method is prepared a kind of with the Mg-Li solid solution hydrogen storage materials for being easier to activate, reversible hydrogen storage capacity is high, dehydrogenation activation energy is low.

Background technology：

Mg and Li are light-weight metal element, and their theoretical hydrogen storage capability is respectively 7.76wt% and 12.5wt%, is Very the high-energy-density hydrogen storage material with development prospect, excessively active yet with Mg and Li elements, is combined with hydrogen atom Relatively stable hydride is formed, causes their practical application to be restricted.In MgH₂In LiH, hydrogen atom is mainly occupied In interstitial site between metallic atom, therefore, the number of interstitial site directly affects the hydrogen storage content of metal hydride.Mg and Li's is compounded in the hydrogen storage property that can to a certain degree improve Mg-Li systems, but the thermodynamics of Mg-Li system composite hydrogen storage materials according to It is so relatively stable, be the comprehensive hydrogen storage property for improving Mg-Li systems, third element or more multielement is mixed in Mg-Li systems It is expected to solve the above problems.The requirement of practical application is reached for ensureing Mg-Li system hydrogen storage capabilities simultaneously, Mg-Li system systems It is standby to can yet be regarded as a kind of effective method into solid-solution material, because the lattice types of solid solution are remained in that and solvent lattice Type is consistent, and the occupied position in solid solution of hydrogen atom is not reduced.Therefore Mg- is prepared as matrix using Mg or Li Li system solid-solution materials, can guarantee that the hydrogen storage capability of composite to a great extent.Si has both as a kind of special elementses The characteristics of inorganic material and organic material, Mg, Li and Si ternary lightweight element it is compound, be expected to solve Mg-Li system hydrogen storages Material Thermodynamics stability is high, the characteristics of be not easily decomposed and inhale hydrogen desorption kineticses poor performance.

The content of the invention

It is an object of the invention to provide a kind of preparation method of Mg-Li solid solution hydrogen storages material.

The technical scheme that the present invention solves above-mentioned technical problem is as follows：

A kind of processing step of the preparation method of Mg-Li solid solution hydrogen storages material is as follows：

1. according to Mg:Li:Si=90:(10-X):The atomic ratio of X is pressed into round sheet sample after uniformly mixing, secondly Round sheet sample is placed in vacuum annealing furnace, is protected using argon, anneal under the conditions of temperature is for 500 DEG C 2h, Ran Houzai Round sheet sample broke, composite powder is obtained；The X=0,2,4,6.

2., under argon protection, using planetary ball mill, it is 40 by ratio of grinding media to material:1, with 300 revs/min of rotating speed to step 1) Composite powder carry out mechanical ball milling.

3., in mechanical milling process, sample was processed under argon protection at interval of 5 hours, it is to avoid composite powder Viscous tank.

4. sample is gathered after ball milling 50h, finally carry out XRD, PCT and DTA/TG test.

Above-mentioned annealed mechanical ball milling again is after 50 hours, Mg₉₀Li₆Si₄And Mg₉₀Li₄Si₆Alloy is at a lower temperature Can inhale and put hydrogen, and their dehydrogenation activation energy is relatively low.

Above-mentioned Mg-Li solid solution hydrogen storage materials are prepared into fuel cell, are mainly used in Hydrogen Energy storage system.

Advantages of the present invention：Mg prepared by the annealed 50h of mechanical ball milling again:Li:Si=90:(10-X):X composites, Wherein：X=0,2,4,6, in X=4 alloys corresponding with X=6 have higher hydrogen storage capability, and their dehydrogenation activation energy compared with Low, solid foundation is established in the research of solid solution hydrogen storage material after being.

Description of the drawings

Fig. 1 Mg₉₀Li_10-xSi_x(X=0,2,4,6) XRD figure of composite.

Fig. 2 Mg₉₀Li_10-xSi_x(X=0,2,4,6) XRD figure after composite hydrogenation.

Fig. 3 Mg₉₀Li_10-xSi_x(X=0,2,4,6) XRD figure after composite dehydrogenation.

Fig. 4 Mg₉₀Li_10-xSi_x(X=0,2,4,6) composite is in 325 DEG C of P-C-T curves.

Fig. 5 Mg₉₀Li_10-xSi_x(X=0,2,4,6) the alternating temperature Hydrogen desorption isotherms of composite.

Fig. 6 Mg₉₀Li_10-xSi_x(X=0,2,4,6) the Kissinger curves of composite.

Specific embodiment

With reference to embodiment, the invention will be further described.

Embodiment 1

The processing step of the preparation method of Mg-Li solid solution hydrogen storage materials is as follows：

By Mg:Li=90:10 atomic ratio has configured sample, is pressed into radius using powder compressing machine and is after mix homogeneously The round sheet of 1.6cm, is placed in vacuum annealing furnace, and anneal under argon protection 2h, then the circular piece of annealing gained Shape sample broke, is 40 by ratio of grinding media to material:1, rotating speed be 300 revs/min in the case of carry out mechanical ball milling, at interval of 5 hours during ball milling Alloy powder is processed under argon protection, after ball milling 50h, gather sample, finally carry out XRD, PCT and DTA/TG survey Examination.

Embodiment 2

By Mg:Li:Si=90:8:2 atomic ratio has configured sample, is pressed into half using powder compressing machine after mix homogeneously Footpath is the round sheet of 1.6cm, is placed in vacuum annealing furnace, and anneal under argon protection 2h, then the circle of annealing gained Shape sheet sample is crushed, and is 40 by ratio of grinding media to material:1, rotating speed be 300 revs/min in the case of carry out mechanical ball milling, at interval of 5 during ball milling Hour is processed to alloy powder under argon protection, gathers sample, finally carry out XRD, PCT and DTA/ after ball milling 50h TG is tested.

Embodiment 3

By Mg:Li:Si=90:6:4 atomic ratio has configured sample, is pressed into half using powder compressing machine after mix homogeneously Footpath is the round sheet of 1.6cm, is placed in vacuum annealing furnace, and anneal under argon protection 2h, then the circle of annealing gained Shape sheet sample is crushed, and is 40 by ratio of grinding media to material:1, rotating speed be 300 revs/min in the case of carry out mechanical ball milling, at interval of 5 during ball milling Hour is processed to alloy powder under argon protection, gathers sample, finally carry out XRD, PCT and DTA/ after ball milling 50h TG is tested.

Embodiment 4

By Mg:Li:Si=90:4:6 atomic ratio has configured sample, is pressed into half using powder compressing machine after mix homogeneously Footpath is the round sheet of 1.6cm, is placed in vacuum annealing furnace, and anneal under argon protection 2h, then the circle of annealing gained Shape sheet sample is crushed, and is 40 by ratio of grinding media to material:1, rotating speed be 300 revs/min in the case of carry out mechanical ball milling, at interval of 5 during ball milling Hour is processed to alloy powder under argon protection, gathers sample, finally carry out XRD, PCT and DTA/ after ball milling 50h TG is tested.

As shown in Figures 1 to 3, sample anneal at a temperature of 773K 2h again mechanical ball milling after 50 hours, composite mainly contains There are Mg phases, Li or LiH to be solidly soluted into completely in Mg matrixes, form Mg-Li system solid solution, in addition to X=0, Mg₉₀Li_10-xSi_x(X=2,4,6) also there is Mg in composite₂Si phases, and Mg₂Si phases do not occur in front and back change in putting for composite Change.As shown in figure 4, at a temperature of 325 DEG C, Mg₉₀Li_10-xSi_x(X=0,2,4,6) composite hydrogen-sucking amount is respectively 6.87wt.%, 6.69wt%, 5.78wt% and 5.28wt%, as the hydrogen storage capability that Si contents increase composite declines, but The addition of Si effectively can reduce inhaling hydrogen platform pressure；In the case of hydrogen pressure is put for 0.06atm, due in the corresponding composite woods of X=2 In material, Si contents are too low, Mg₂Si catalytic action is not obvious, causes the corresponding composites of X=2 and the corresponding composite woods of x=0 Material is the same, can not discharge hydrogen at a temperature of 325 DEG C, but after the value of X increases to 4 or 6, in Mg₂The catalytic action of Si Under, composite can discharge hydrogen at a temperature of 325 DEG C.As shown in figure 5, at ambient pressure, 390 DEG C are progressively increased to from room temperature When, Mg₉₀Li_10-xSi_x(X=0,2,4,6) composite amount of dehydrogenation be followed successively by 4.39wt.%, 4.51wt.%, 4.57wt.% and 5.38wt.%, the amount of dehydrogenation of material gradually increase with the increase of Si contents, and initial dehydrogenated temperature is decreased obviously, especially As X=6, under normal pressure, 370 DEG C from before addition Si of the initial dehydrogenated temperature of composite have decreased to 340 DEG C or so, initially Desorption temperature have dropped 30 DEG C than the composite for being not added with Si.As shown in fig. 6, Mg₉₀Li_10-xSi_x(X=0,2,4,6) it is combined The apparent activation energy of material be followed successively by 179.5,163.6,155.2 and the addition of 128.3Kj/mol, Si advantageously reduce Mg-Li The apparent activation energy of solid solution composite material, especially the apparent activation energy ratio of X=6 correspondences composite are not added with reducing during Si 51.2kJ/mol.

Claims

1. a kind of preparation method of Mg-Li solid solution hydrogen storages material, it is characterised in that the processing step of the method is as follows：

1) it is first according to Mg:Li:Si=90:(10-X):The atomic ratio of X is pressed into round sheet sample after uniformly mixing, secondly Round sheet sample is placed in vacuum annealing furnace, is protected using argon, anneal under the conditions of temperature is for 500 DEG C 2h, Ran Houzai Round sheet sample broke, composite powder is obtained；The X=0,2,4,6；

2) under argon protection, using planetary ball mill, it is 40 by ratio of grinding media to material:1, with 300 revs/min of rotating speed to step 1) answer Condensation material powder carries out mechanical ball milling；

3) in mechanical milling process, sample was processed under argon protection at interval of 5 hours, it is to avoid composite powder glues Tank；

4) sample is gathered after ball milling 50h, finally carry out XRD, PCT and DTA/TG test.

2. the preparation method of the Mg-Li solid solution hydrogen storage materials as described in claims 1, it is characterised in that described annealed Mechanical ball milling is after 50 hours again, Mg₉₀Li₆Si₄And Mg₉₀Li₄Si₆Alloy can be inhaled at a lower temperature and put hydrogen, and theirs is de- Hydrogen activation energy is relatively low.