CN1174507C - Thin-film electrode for nickel-metal hydride battery and preparation method thereof - Google Patents

Abstract

_{[ _ _ 1-y]} B _[y] ; the protective film is Pd, Pt, Ag, Au, Co or their binary or multi-element alloys; the preparation method is to prefabricate the alloy target by induction melting or powder metallurgy at first, and then use physical vapor phase The deposition method forms a base film on the substrate, and covers a protective film on the surface of the base film. The thin film can be used in the negative electrode of nickel-metal hydride batteries. The characteristics of this kind of hydrogen storage thin film electrode are: the film grain is small (about 50nm), has a large specific surface area, so the film is highly sensitive to hydrogen and has good kinetic performance; the film can be used as the negative electrode of the nickel-hydrogen battery to save the traditional battery. The space occupied by foamed nickel improves the energy density of the nickel-metal hydride battery.

Description

Thin-film electrode for nickel-metal hydride battery and preparation method thereof

(1) Technical field

The invention relates to the technical field of physical vapor deposition synthesis thin film materials, in particular to a thin film electrode for a nickel-hydrogen battery and a preparation method thereof.

(2) Background technology

At present, the global annual output of Ni-MH batteries has reached more than one billion, but the specific energy density and high-rate discharge capacity of Ni-MH batteries still need to be improved. To this end, the development of nickel metal hydride battery anode materials is a key technology. Among the currently researched hydrogen storage electrode alloys for nickel-hydrogen batteries, Mg-based alloys have excellent prospects. Among them, the theoretical electrochemical capacity of Mg ₂ Ni reaches 1000mAh/g, which is much higher than other hydrogen storage alloys, and the price is much higher than that of other hydrogen storage alloys. Much lower than other alloy systems. Therefore, the development of Mg-based alloys has very attractive prospects. However, the hydrogen absorption/release kinetics of Mg-based hydrogen storage alloys is poor, and the chemical properties of Mg are very active, and it is easy to react with the electrolyte, resulting in performance attenuation. Therefore, improving the adsorption/release kinetics and electrode performance of Mg-based alloys has always been an issue of concern. The main methods currently used, such as element substitution, acid, alkali, fluorine liquid surface modification treatment and surface coating, compounding with other hydrogen storage alloys, mechanical alloying methods, and the formation of nanocrystalline and amorphous structures in Mg-based alloys, etc. method. These methods have improved the electrode performance of Mg-Ni alloys to a certain extent, but the results are still unsatisfactory. For example, the discharge capacity of the amorphous alloy electrode decays quickly, and the cycle life is only dozens of times. Therefore, further improving the stability of Mg-based alloy electrodes, that is, the cycle life, has become the key to the development of Mg-Ni alloy electrode materials. Not only that, the current films prepared by co-sputtering or co-deposition of magnesium targets and nickel targets are difficult to control the composition, have poor repeatability, and are not suitable for mass production.

(3) Contents of the invention

The present invention aims to solve the deficiencies in the above-mentioned prior art, and provides a thin-film electrode for a nickel-metal hydride battery and a preparation method thereof. Good, suitable for mass production.

A thin film electrode for a nickel-metal hydride battery according to the present invention is characterized in that it consists of a base film covered with a protective film, the main components of the base film are magnesium and nickel, and the chemical composition is Mg _[px] A _[x] Ni _[1-y] B _[y] , A is Al, Mn, Sn, Ca, Li, B, La, Ce, Nd, Pr, Y, misch, B is Cu, Ti, Co, Fe, Cr, Zr , V, Nb, Mo, W, where 1.0≤p≤2.5, 0≤x≤1.5, 0≤y≤0.8; the protective film is palladium (Pd), platinum (Pt), silver (Ag), gold (Au) , cobalt (Co) or palladium (Pd), platinum (Pt), silver (Ag), gold (Au), cobalt (Co) binary or multiple alloys.

In order to better realize the present invention, the thickness of the base film can be 1-200 μm, and the thickness of the protective film can be 2-1000 nm.

The preparation method of a thin-film electrode for a nickel-hydrogen battery according to the present invention is characterized in that, firstly, an alloy target is prefabricated by induction melting or powder metallurgy, and then a matrix film is made on a substrate by a physical vapor deposition method, and finally a physical The vapor deposition method covers a protective film on the surface of the base film.

In order to better realize the present invention, the main components of the alloy target can be magnesium and nickel, the chemical composition is Mg _[px] A _[x] Ni _[1-y] B _[y] , A is Al, Mn, Sn, Ca , Li, B, La, Ce, Nd, Pr, Y, mixed rare earth, B is Cu, Ti, Co, Fe, Cr, Zr, V, Nb, Mo, W, where 1.0≤p≤2.5, 0≤x ≤2.5, 0≤y≤0.8; the substrate can be metal, semiconductor, insulator; the physical vapor deposition method can be sputtering, electron beam evaporation or laser evaporation and other methods.

The principle of the present invention: studies have shown that amorphous alloys have good corrosion resistance, and the surface structure and composition of the alloy have an important impact on the cycle performance of the electrode. It is relatively difficult to treat the surface of the conventionally used hydrogen storage alloy powder. It is easier to cover a protective film on the surface of the hydrogen storage alloy thin film material. Therefore, the present invention prepares amorphous and/or nanocrystalline thin films by physical vapor deposition, and covers palladium (Pd), platinum (Pt) on the surface of the alloy thin film material. ) and other alloy protective films. The invention uses an alloy target during physical vapor deposition, which overcomes the disadvantage of uneven composition, and can directly prepare a film with a _Mg2Ni structure with good repeatability, and the size and composition of the alloy target can be flexibly controlled, and is suitable for industrial production. The thin-film electrodes for nickel-hydrogen batteries react with hydrogen during charging to form metal hydrides to store hydrogen, and the metal hydrides are dehydrogenated and reduced during discharge. The working principle and working environment of thin-film electrodes for nickel-metal hydride batteries require the thin film to have good cycle characteristics and oxidation resistance. The invention covers the surface of the alloy thin film with a protective film through which hydrogen gas can pass freely but not hydrogen element, so as to prevent the hydrogen storage thin film from reacting with harmful gas or electrolyte to reduce the cycle characteristics and capacity of the nickel-metal hydride battery. Nickel is a paramagnetic element. During the vapor deposition process, especially the magnetron sputtering process, the distribution of magnetic force lines is changed, which seriously affects the sputtering speed and the uniformity of the structure and composition of the film. After alloying, the nickel element forms a solid solution or an intermetallic compound, and the paramagnetism disappears. At the same time, in the process of preparing the alloy target, the composition is pre-controlled and homogenized, so the alloy target is more conducive to physical vapor deposition. process.

Compared with the prior art, the present invention has the following advantages and beneficial effects: this alloy thin film is made up of amorphous and nanocrystalline, and the thin film crystal grain is fine (about 50nm), and the response speed to hydrogen is fast, and dynamic performance is good, avoids The harm of the heavy metal powder in the conventional production process is eliminated, and the preparation method is an environmentally friendly method for producing the negative electrode of the nickel-hydrogen battery; the thin film as the negative electrode of the nickel-hydrogen battery can save the space occupied by the foam nickel in the traditional battery, and improves the efficiency of the nickel-hydrogen battery. Energy Density. The alloy thin film prepared by the invention is easy to carry out surface modification, avoids the environmental pollution brought by the powder modification process, and can conveniently adjust the composition and structure of the thin film surface. The thickness of the alloy film prepared by the invention can be controlled arbitrarily, the composition is uniformly distributed, the repeatability is good, the specific capacity is high (900mAh/g), and the cycle life is long, which overcomes the difficulty in controlling the film composition, poor repeatability and specific capacity in the existing film preparation methods. Low (228mAh/g) disadvantage.

(4) Specific implementation methods

Below in conjunction with embodiment, the present invention will be further described:

Embodiment one

The block 45wt% magnesium and 55%wt nickel are smelted into alloy castings by induction melting method. After high temperature annealing, they are processed into target materials by wire cutting method. They are deposited on silicon wafers by laser evaporation with a film thickness of 1 μm and replaced with Pt target, a 20nm Pt layer was vapor-deposited on this film.

Embodiment two

The block 45wt% magnesium and 55%wt nickel are smelted into alloy castings by induction melting method. After high temperature annealing, they are processed into target materials by wire cutting method. They are sputtered on the glass sheet by magnetron sputtering with a film thickness of 3 μm and replaced with Pd target, a 50nm Pd layer was vapor-deposited on this film.

Embodiment Three

Melt blocky 55%wt magnesium and 45wt% nickel into alloy castings by induction melting method, after high temperature annealing, process them into targets by wire cutting method, and sputter on 2.5mm thick nickel sheet by magnetron sputtering, the film thickness is 20μm , replace the Pd target, and vapor-deposit a 100nm Pd layer on the film.

Embodiment Four

55%wt magnesium and 45wt% nickel powder were sintered at 650°C for 20 hours by powder metallurgy method, and after high temperature annealing, they were processed into target material by wire cutting method, and deposited on a 0.5mm thick nickel sheet by electron beam evaporation, with a film thickness of 50 μm, replace it with a Pt target, and evaporate a 200nm Pt layer on this film.

Embodiment five

The bulk 53%wt magnesium, 42wt% nickel and 5wt% aluminum are smelted into alloy castings by induction melting method, after high temperature annealing, processed into targets by wire cutting method, and sputtered on 0.5mm thick aluminum sheet by magnetron sputtering, The thickness of the film was 40 μm, and a Pd target was replaced, and a Pd layer of 300 nm was vapor-deposited on the film.

Embodiment six

The bulk 53%wt magnesium, 42wt% nickel and 5wt% aluminum were smelted into alloy castings by induction melting method, and after high temperature annealing, they were processed into targets by wire cutting method, and were sputtered on a 1.5mm thick nickel sheet by magnetron sputtering, The thickness of the film is 80 μm, and a Pd target is replaced, and a Pd layer of 200 nm is vapor-deposited on the film.

Embodiment seven

The bulk 50%wt magnesium, 41wt% nickel, 3wt% aluminum, and 6%wt copper were smelted into alloy castings by induction melting method. On a nickel sheet with a thickness of mm, the film thickness is 50 μm, and a Pd target is replaced, and a 500 nm Pd layer is evaporated on this film.

Embodiment eight

The block 50%wt magnesium, 41wt% nickel, 3wt% aluminum, and 6%wt copper were smelted into alloy castings by induction melting method. On an aluminum sheet with a thickness of mm, the film thickness is 100 μm, and a Pd target is replaced, and a 500 nm Pd layer is evaporated on this film.

Embodiment nine

The block 50%wt magnesium, 41wt% nickel, 3wt% aluminum, and 6%wt copper were smelted into alloy castings by induction melting method. On a nickel sheet with a thickness of 40 μm, the film thickness is 40 μm, and a Pd target is replaced, and a 200 nm Pd layer is evaporated on this film.

Embodiment ten

The bulk 50%wt magnesium, 41wt% nickel, 3wt% aluminum, and 6%wt copper were smelted into alloy castings by induction smelting, and after high temperature annealing, they were processed into targets by wire cutting, and evaporated by laser beam at 1.5 On a nickel sheet with a thickness of 40 μm, the film thickness is 40 μm, and a Pd target is replaced, and a 200 nm Pd layer is evaporated on this film.

Embodiment Eleven

The block 30wt% magnesium and 70%wt nickel are smelted into alloy castings by induction melting method. After high temperature annealing, they are processed into target materials by wire cutting method. They are deposited on silicon wafers by laser evaporation with a film thickness of 200μm and replaced with Au target, and a 800nm Au layer was vapor-deposited on this film.

Embodiment 12

Melt blocky 30wt% magnesium and 70%wt nickel into alloy castings by induction melting method, after high temperature annealing, process them into targets by wire cutting method, and sputter on the glass sheet by magnetron sputtering, the film thickness is 3μm, replace with Au target, a 50nm Au layer was vapor-deposited on this film.

Embodiment Thirteen

The blocky 55%wt magnesium and 45wt% nickel were smelted into alloy castings by induction melting method. After high-temperature annealing, they were processed into target materials by wire cutting method and sputtered on a 2.5mm thick silicon wafer by magnetron sputtering. The film thickness is 200 μm, replace with a Pd target, and vapor-deposit a 5nm Pd layer on this film.

Embodiment Fourteen

55%wt magnesium and 45wt% nickel powder were sintered at 650°C for 20 hours by powder metallurgy method, and after high temperature annealing, they were processed into targets by wire cutting method, and deposited on a glass sheet with a thickness of 0.5mm by electron beam evaporation, with a film thickness of 5 μm, replace it with a Pt target, and vapor-deposit a 5nm Pt layer on this film.

Embodiment 15

The blocky 53%wt magnesium, 42wt% and 5wt% aluminum were smelted into alloy castings by induction melting method, and after high temperature annealing, they were processed into targets by wire cutting method, and were sputtered on 0.5mm thick palladium sheet by magnetron sputtering, thin film The thickness is 2 μm, and a Pd target is replaced, and a 2 nm Pd layer is vapor-deposited on this film.

Embodiment sixteen

The blocky 53%wt magnesium, 42wt% and 5wt% aluminum were smelted into alloy castings by induction melting method, and after high temperature annealing, they were processed into targets by wire cutting method, and were sputtered on a 1.5mm thick nickel sheet by magnetron sputtering, thin film The thickness is 100 μm, and an Ag target is replaced, and a 400 nm Ag layer is vapor-deposited on this thin film.

Embodiment 17

The bulk 50%wt magnesium, 41wt% nickel, 3wt% aluminum, and 6%wt copper were smelted into alloy castings by induction melting method. On a nickel sheet with a thickness of mm, the thickness of the film is 150 μm, and an Ag target is replaced, and a 300 nm Ag layer is vapor-deposited on this film.

Embodiment eighteen

The block 50%wt magnesium, 41wt% nickel, 3wt% aluminum, and 6%wt copper were smelted into alloy castings by induction melting method. On an aluminum sheet with a thickness of mm, the film thickness is 100 μm, and an Ag target is replaced, and a 1000 nm Ag layer is vapor-deposited on this film.

Embodiment nineteen

The block 50%wt magnesium, 41wt% nickel, 3wt% aluminum, and 6%wt copper were smelted into alloy castings by induction melting method. On a nickel sheet with a thickness of mm, the film thickness is 200 μm, and an Ag target is replaced, and a 1000 nm Ag layer is vapor-deposited on this film.

Embodiment 20

The bulk 50%wt magnesium, 41wt% nickel, 3wt% aluminum, and 6%wt copper were smelted into alloy castings by induction smelting, and after high temperature annealing, they were processed into targets by wire cutting, and evaporated by laser beam at 1.5 On a copper sheet with a thickness of mm, the film thickness is 150 μm, and an Au target is replaced, and a 100 nm Au layer is vapor-deposited on this film.

Claims (7)

1. a film electrode for a nickel-hydrogen battery is characterized in that it is made up of a base film outer covering protective film, and the main components of the base film are magnesium and nickel, and the chemical composition is Mg _[px] A _[x] Ni _{[1- y]} B _[y] , A is Al, Mn, Y, mixed rare earth, B is Cu, Zr, V, where 1.0≤p≤2.5, 0≤x≤1.5, 0≤y≤0.8; the protective film is Pd, Pt, Ag, Au or binary or multi-element alloys of Pd, Pt, Ag, Au. 2. A thin-film electrode for a nickel-metal hydride battery according to claim 1, wherein the thickness of the base film is 1-200 μm. 3. A thin-film electrode for a nickel-metal hydride battery according to claim 1, characterized in that the thickness of the protective film is 2-1000 nm. 4. A preparation method for thin-film electrodes for nickel-hydrogen batteries is characterized in that, at first prefabricated alloy targets by induction melting or powder metallurgy, then make matrix films on substrates by physical vapor deposition, and finally use physical vapor deposition A protective film is covered on the surface of the base film. 5. the preparation method of a kind of film electrode for nickel-hydrogen battery according to claim 4 is characterized in that, the main component of alloy target is magnesium and nickel, and chemical composition is Mg _[px] A _[x] Ni _{[1- y]} B _[y] , A is Al, Mn, Y, misch, B is Cu, Zr, V, where 1.0≤p≤2.5, 0≤x≤2.5, 0≤y≤0.8. 6. the preparation method of a kind of film electrode for nickel-hydrogen battery according to claim 4 is characterized in that, substrate comprises metal, semiconductor, insulator. 7. The preparation method of a thin-film electrode for a nickel-hydrogen battery according to claim 4, wherein the physical vapor deposition method comprises sputtering, electron beam evaporation or laser evaporation.