WO2001069700A1

WO2001069700A1 - Hydrogen absorbing alloy and negative electrode for nickel-metal hydride secondary cell

Info

Publication number: WO2001069700A1
Application number: PCT/JP2001/001719
Authority: WO
Inventors: Yuji Tanibuchi; Yasushi Asahi; Toshimi Tokui; Kiyofumi Takamaru
Original assignee: Santoku Corporation
Priority date: 2000-03-15
Filing date: 2001-03-06
Publication date: 2001-09-20
Also published as: JP2001266864A

Abstract

A hydrogen absorbing alloy having a chemical composition represented by the formula (1): AxR1-x(MyNi1-y)n wherein A represents Y, Gd, Tb, Dy or a mixture thereof, R represents La, Ce, Pr, Nd or a mixture thereof, M represents Co, Al, Mn, Fe, Cu, Zr, Ti, Mo, W, B or a mixture thereof, x, y and n are each a number independently satisfying 0.01 ≤ x ≤ 0.1, 0.01 ≤ y ≤ 0.5, or 4.9 ≤ n ≤ 5.4, and exhibits a Hv of 900 kg/mm2 or more; and a nickel-metal hydride secondary cell using the alloy. The hydrogen absorbing alloy is excellent in strength and, when used as the material of a negative electrode of a nickel-metal hydride secondary cell, exhibits suppressed pulverization, high corrosion resistance and high capacity.

Description

Negative electrode for hydrogen storage alloy and nickel hydrogen secondary battery

Technical field

The present invention relates to a hydrogen storage alloy which has excellent corrosion resistance and can be used for a negative electrode material of a nickel hydrogen secondary battery to improve the battery life, and a nickel hydrogen secondary battery using the alloy. For negative electrodes.

Background art

As the negative electrode alloys of the nickel-hydrogen secondary battery which is currently produced, Mm- N i- C o-A l- Mn -based AB ₅ alloys are mainly used. This alloy has a feature that it has a large hydrogen storage capacity compared to other alloys, and has a hydrogen absorption and release pressure at room temperature of 1 to 5 atm, making it easy to use. And then force, rare earth twelve Tsu Kell-based alloy of a conventional AB ₅ type structure, the alloy contains the expansion and shrinkage crack by hydrogen absorption and release, there is a drawback of deteriorating the battery characteristics micronized. In recent years, high-capacity electrodes have been desired, and in order to increase the electric capacity, the transition metal is composed of 4.5 to 5 transition metals in comparison with the rare-earth element 1 in atomic ratio. Alloys with increased La content in rare earth metals and Mn content in transition metals have been developed. However, there is a problem in that, as the electric capacity increases, pulverization and deterioration of corrosion resistance occur, and the battery life characteristics decrease.

Regarding the improvement of the battery life, a method of increasing the amount of Co is disclosed in Japanese Patent Application Laid-Open No. Hei 6-215765, in which at least one additive of an indium and a lithium compound is coated on the negative electrode surface, or A method of adding the compound to the inside of the negative electrode has been proposed. Further, Japanese Patent Publication No. 2713881 proposes that rare earths contain yttrium as an alloying element. Japanese Patent Application Laid-Open No. H10-255529 proposes a hydrogen storage alloy excellent in initial activity, low-temperature characteristics, and high-rate discharge characteristics and containing 100 ppm or less of alkaline earth metal as an impurity. Those having a Vickers hardness of 600 kg mm ² or more have been proposed.

By the way, the secondary battery negative electrode alloy has higher corrosion resistance during use and longer battery life as the hardness of the alloy is higher. Therefore, such alloys are being developed, but no alloys with a Vickers hardness of 900 kg Zinni ² or more have been obtained. Disclosure of the invention

An object of the present invention is to provide a hydrogen storage alloy which has excellent alloy strength, suppresses fine powdering when used as a negative electrode material of a nickel-metal hydride secondary battery, and exhibits high corrosion resistance and high capacity. To provide a negative electrode for a nickel-metal hydride secondary battery.

The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, by appropriately selecting cooling conditions, heat treatment conditions, and the like with respect to a molten alloy having a specific composition, a Vickers hardness of 900 kgZmm ^The present inventors have found that ^two or more hydrogen storage alloys can be obtained and that such an alloy can be used as a negative electrode material of a nickel hydrogen secondary battery to obtain a nickel hydrogen secondary battery that exhibits excellent performance. Was completed. That is, according to the present invention, there is provided a hydrogen storage alloy having a composition represented by the formula (1) and a Vickers hardness of 90 Ok gZmm ² or more.

Α _Χ Ι ^ — _x (M _y N i _{y y} ) n

(Wherein, A is Y, Gd, Tb, Dy or a mixture thereof, R is La, Ce, Pr, Nd or a mixture thereof, M is Co, A1, Mn, Fe, Cu, Z r, T i, Mo, W, B or a mixed element thereof, x, y and n are 0.011≤x≤0.1, 0.011y≤0.5, 4. 9≤n≤5.4)

Further, according to the present invention, there is provided a negative electrode for a nickel-metal hydride secondary battery including the hydrogen storage alloy and a conductive material.

Further, according to the present invention, there is provided use of the hydrogen storage alloy for manufacturing a negative electrode for a nickel-metal hydride secondary battery.

Preferred embodiments of the invention

Hereinafter, the present invention will be described in more detail.

The hydrogen storage alloy of the present invention has a composition represented by the above formula (1), and has a Vickers hardness (hereinafter, referred to as Hv) of 900 kg / mm ² or more, preferably 900 to 1500 kgZmm ² , particularly preferably. is of 900~1200 k gZmm ² alloy.

In the formula (1), A is Y (ittrium), Gd (gadmium), Tb (terbium), Dy (dysprosium) or a mixture thereof, and R is La (lantern), Ce (cellium), P τ ( (Praseodymium), Nd (neodymium) or a mixture thereof, M is Co (cobalt), A1 (anorenium), Mn (manganese), Fe (iron), Cu (copper), Zr (zirconium), Tr i Tan), Mo (molybdenum), W (tandasten), B (boron) or a mixture thereof. xy and n are each such that X is 0.011 ^ x ^ 0.1, preferably 0.03≤x≤0.08, more preferably 0.03≤x≤0.05 y force 0.011≤ y ≤ 0.5 n is 4.9 ≤ n ≤ 5.4.

If X is less than 0.01, the mechanical strength and corrosion resistance of the obtained alloy will be reduced, and the battery life will be significantly reduced when used as a negative electrode material for a secondary battery. When X exceeds 0.1, no improvement in mechanical strength and corrosion resistance of the obtained alloy is observed. If n is outside the above range, the second phase will precipitate and the corrosion resistance will be significantly reduced.

The composition of the hydrogen storage alloy of the present invention is not particularly limited as long as the above formula is satisfied, and the following composition is preferably used.

_{_{... La 0 3 5 Ce}} 0 4 0. 03 Nd 0 Y o 5. (Ni 3 75 Co 0. 60 -. ^ -.. 0 3 0 Mn 0 45) 5 1

_{_{. La 3 8 Ce 0, 4}} 0. 03 Nd 0 05 (i 3 9 o ^ 0 0 t 50 -. ^ -.. 0 3 0 n 0 50) 5, 2

_{_{_{La 0. 4 2 Ce 0 <}}} 40 r 0. 02 Nd 0. 1 1 Y x 0. 05 (i 4. 20

3 ₀ n ₀ .50) 5 * 40

_{_{_{La 0. 3 0 Ce 0,}}} 45 x A 0. 04 Nd Q. Y o 3 (Ni 3. 55C00. 75- ^ 0. 3 0 Mn 0. 40) 5

_{_{... La 0 3 0 Ce}} 0 45 0. 04 Nd 0 1 8 Y 1 0. o 3 (i 3 90 Co o, 50 -. ^ -.. 0 3 0 n 0 50) 5 · 2

3 ₀ Mn _0. 40 5

_{_{_{0. 28 Pr 0. 05 Nd 0}}} . 19 Y 1 0. 0 _{_{_{immediately. 65 Co 0. 6 5 A1}}} 0. 3 on 0. 40) 5ヽ

_{^{_{La 0 .4 e Ce c Pr 0}}} . 02 Nd 0. 09 Y 0. 1 o (i 3. 55 Co 0. 7 5 AI 0. 40) 5ヽ_{_{_{La n ¾n Ce f Pr 0.}}} 04 Nd 0. 3 0 ^Mn 0. 40) 5 ヽ

_{_{_{La, Ce (Pr 0. 04}}} Nd 0,

_{_{3 0 Mn 0. 40) 5}} , La, Ce (Pr 0. 04 Nd 0. I 7 Dy 0. 03 (Ni 3. 5 5 Co 0. 75 0, 30 Mn 0 • 40) 5, La 0. 3 _{_{_{, Ce (Pr 0. o 4}}} Nd 0. i 7 Dy 0. 05 (Ni 3. 40) 5,

_{La 0. 30 Ce o. Pr 0} . 04 Nd 0 .1 7 T x b u o. 05 (Ni 3.

40) 5 The hydrogen-absorbing alloy of the present invention, when producing a secondary battery using the alloy as a negative electrode material for a nickel-metal hydride secondary battery, has a constant temperature of 1.0 mAcm- ^{2 at} a constant temperature of 25 ° C. It is preferable that the oxidation rate ((oxygen value after 200 cycles) Z (initial oxygen value)) after repeating charge / discharge for 200 cycles by electric current is 10.0% or less. When the hydrogen storage alloy of the present invention is used for the production of a negative electrode for a nickel-hydrogen secondary battery, the average particle size is usually 60 m or less, preferably 10 to 50 im. The method for producing the hydrogen storage alloy of the present invention is not particularly limited as long as an alloy having the composition represented by the above formula (1) and having an Hv of 900 kg / mm ² or more can be obtained. Not done. For example, it can be obtained by appropriately selecting conditions from the conditions shown below with reference to the conditions of the examples described later. At this time, the important point is the value of X in the composition represented by the above formula (1). In short, the composition in which R is replaced with A is important, and the hydrogen storage alloy of the present invention can be obtained by adopting this composition and appropriately selecting cooling conditions and the like.

As the production conditions, for example, the molten alloy having the above composition is supplied to a single-roll cooling device or the like via a tundish, and a supercooling degree of 50 to 500 ° C and a cooling rate of 100 to L0000 ° C / sec are particularly preferable. Is solidified uniformly to a thickness of about 0.1 to 0.5 mm under cooling conditions of SOOO lOOOOtTC / sec. Next, the obtained alloy ribbon is subjected to a vacuum or an inert atmosphere at 600 to 1100. C, preferably 800-150. C, more preferably 850-1000. In C, 0.:! It can be obtained by appropriately selecting each condition such as a heat treatment method for up to 12 hours, preferably 1 to 8 hours, more preferably 4 to 6 hours.

At this time, if the cooling rate is less than 100 ° C / sec, improvement in the strength and corrosion resistance of the obtained alloy cannot be expected.

In order to make the hydrogen storage alloy of the present invention into an alloy powder for use in, for example, manufacturing a negative electrode of a nickel-metal hydride secondary battery, the hydrogen storage alloy is ground to a desired particle size by a pole mill, a disc mill, a hammer mill, or the like. It can be done by doing. This pulverization can be performed in an inert atmosphere, a hydrogen atmosphere, a vacuum, or the like.

A negative electrode for a nickel-metal hydride secondary battery of the present invention includes the hydrogen storage alloy and a conductive material. Preferably, it is not particularly limited as long as it contains the hydrogen storage alloy powder of the present invention having the above preferred particle size and a conductive material, and can be produced using a binder or the like according to a conventional method.

The negative electrode for a nickel-metal hydride secondary battery of the present invention has an oxidation rate ((2 0 0 0) after repeating charging and discharging 200 cycles at a constant temperature of 25 ° C. and a constant current of 1.0 mA′cm− ² . Those having an oxygen value after cycle (initial oxygen value) of 10.0% or less are preferred. Since the hydrogen storage alloy of the present invention has a specific composition and excellent Hv, it has excellent alloy strength, and when used as a negative electrode material of a nickel-metal hydride secondary battery, pulverization is suppressed and high It shows insect resistance and high capacity.

The negative electrode for a nickel-hydrogen secondary battery of the present invention uses the above-mentioned hydrogen storage alloy, so that the battery life of the nickel-hydrogen secondary battery can be improved.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1

As starting materials, yttrium metal, lanthanum metal, cerium metal, praseodymium metal and neodymium metal manufactured by Santoku Metal Industry Co., Ltd. (currently Santoku Co., Ltd., same hereafter), rare earth composition of La 25 vol. 5 0 volume ^_0/0, P r 5 volume%及Pi 3 2 0 volume%, and Santoku metal industry Co., Ltd. Mm (misch metal), and Dondo 9 9.9% of N i, purity 99.9% of A1, Mn and Co were blended so as to have the composition shown in Table 1, and were subjected to high frequency melting in an argon gas atmosphere to prepare a molten alloy. Subsequently, the obtained molten alloy was subjected to subcooling of 150 ° C. and a cooling rate of 200 to 500 ° C. for 0 seconds using a single roll forming apparatus equipped with a tundish. Strip alloys of 1-0.3 mm were produced. The obtained alloy was heat-treated at 950 ° C. for 6 hours in an argon gas atmosphere. Next, the obtained heat-treated alloy was mirror-polished, and the Hv of the alloy was measured using a micro hardness tester (manufactured by Akashi Seisakusho Co., Ltd.). Table 1 shows the results.

Examples 2 to: L5, Comparative Examples 1 to 3

A hydrogen storage alloy was prepared in the same manner as in Example 1 except that the raw material composition was changed as shown in Table 1, and Δν was measured. Table 1 shows the results.

Comparative Example 4

In Example 1, the molten alloy was cooled by a single-roll forming apparatus by pouring into a water-cooled copper mold to obtain a 20-mm-thick alloy ingot, and heat-treated and pulverized as in Example 1. A hydrogen storage alloy was prepared and Hv was measured. Table 1 shows the results. Alloy composition (^ child ratio) AB x

L a C e P r N d γ G d D y T b N i C o A l Mn X

Example 1 0.30 0.44 0.04 0.17 0.05 3.55 0.75 0.30 0.40 5.00 Single roll 990 Example 2 0.30 0.44 0.04 0. 17 0.05 3.40 0.80 0.30 0.40 4.90 Single roll 990 Example 3 0.35 0.42 0.03 0.15 0.05 3.75 0.60 0.30 0 45 5.10 980 Example 4 0.38 0.40 0.03 0.14 0.05 3.90 0.50 0.30 0.50 5.20 Single roll 976 Example 5 0.42 0.40 0.02 0.11 0.05 4.20 0.40 0.30 0.50 5.40 Single roll 956 Example 6 0.30 0.45 0.04 0.18 0.03 3. 55 0.75 0.30 0.40 5.00 Single roll 9 ^ 0 Example 7 0 30 0.45 0.04 0.18 0 03 0 50 0 50 5.20 Single roll 932 Example 8 0.28 0.47 0.05 0.19 0.01 3.55 0.75 0.30 0.40 5.00 Single roll 912 Example 9 0.28 0.47 0.05 0.19 0.01 3. 65 0.65 0.30 0.40 5.00 Single roll 900 Example 10 0.46 0.33 0.02 0.09 0.01 3.55 0.75 0.30 0.40 5.00 Single Roll 1000 Example 11 0.30 0.44 0.04 0.17 0.03 3.55 0.7.5 5 0.30 0.40 5.00 Single Roll 940 Example 12 0.30 0.44 0. 04 0.17 0. 05 3.55 0.75 0.30 0.40 5.00 Single roll 978 Example 13 0.30 0.44 0.04 0.17 0.03 3.55 0.75 0.30 0.405 00 Single Roll 942 Example 14 0.30 0.44 0.04 0.17 0.05 3.55 0.75 0.30 0.40 5.00 Single Roll 980 Example 15 0.30 0.34 0.04 0.17 0.05 3.55 0.75 0.30 0.40 5.00 Single roll 985 Comparative example 1 0.32 0.46 0.04 0.18 3.55 0.75 0. 30 0.40 5.00 Single roll 850 Comparative example 2 0.41 0.42 0.03 0.14 3.90 0.50 0.30 0.50 5.20 Single roll 813 Comparative example 3 0.48 0 30 0.02 0.05 0.15 3.55 0.75 0.30 0.40 5.00 Single roll 855 Comparative example 4 0.30 0.44 0.04 0.17 0.05 3.55 0.75 0.30 0.40 5.00 840

Example 16

The alloy prepared in Example 1 was pulverized with a hammer mill, and the alloy powder (10 g), copper powder (1 g) as a conductive agent, and FEP (tetrafluoroethylene / tetrafluoropropylene copolymer) powder 0.3 were used. g was mixed to produce a 20 mm diameter pellet electrode. The obtained electrode was immersed in a 6N KOH solution, a battery was constructed using a mercury oxide reference electrode, and the electrode characteristics were measured using a potentiogalvanostat (manufactured by Hokuto Denko). The measurement was conducted at a constant temperature of 25 ° C. and at a constant current of 60 mA / g for 200 cycles of charge / discharge. Further, the oxygen value of the pellet electrode before and after the 200 cycles was measured using a HORIBA oxygen analyzer. Further, the particle size distribution of the alloy powder in the pellet electrode after 200 cycles was measured by Nikkiso Microtrack. Table 2 shows the results. The acid rate in Table 2 was determined by the following equation: oxidation rate = (oxygen value after 200 cycles) / (initial oxygen value).

Examples 17 to 21 and Comparative Examples 5 to 6

In Example 16, in place of the alloy prepared in Example 1, the alloy prepared in Example 2 (Example 17), the alloy prepared in Example 4 (Example 18), and the alloy prepared in Example 6 were used. The prepared alloy (Example 19), the alloy prepared in Example 7 (^ Example 20), the alloy prepared in Example 8 (Example 21), the alloy prepared in Comparative Example 1 (Comparative Example 5), the alloy prepared in Comparative Example 2 (Comparative Example 6), or the alloy prepared in Comparative Example 4 (Comparative Example 7), a pellet electrode was prepared in the same manner, and various measurements were performed. . Table 2 shows the results.

Table 2 Battery capacity (mAh / g) Capacity decrease rate Oxygen value (P m) Oxidation rate (%)

5 cycles 200 cycles (200 cycles initial 200 cycles 难 initial 200 cycles) Example 16 310 285 91. 9 670 5200 7.8 50 45 Example 17 320 293 91. 6 690 4800 7.0 50 43 Example 18 305 282 92.5 610 4600 7.5 50 44 Example 19 310 280 90.3 590 5400 9.2 50 44 Example 20 300 275 91.7 640 5200 8.1 50 41 Example 21 315 285 90.5 620 4900 7.95 50 Comparative example 5 315 185 58.7 740 9500 12.8 50 21 Comparative example 6 310 160 51.6 755 12000 15.9 50 15 Comparative example 7 310 240 77.4 720 8300 11.5 50 19

Claims

Claims 1) A hydrogen storage alloy having a composition represented by the formula (1) and a Pickers hardness of 900 kg / mm 2 or more. AxR1--x (MyN i or y) n… hi)

(In the formula (1), A is Y, Gd, Tb, Dy or a mixture thereof, R is La, Ce, Pr, Nd or a mixture thereof, M is Co, Al, Mn, Fe , Cu, Zr, Ti, Mo, W, B or a mixed element thereof, x, y, and n are respectively 0.011≤x≤0.1, 0.011≤y≤0.5, 4. 9≤n≤5.4.)

2) The hydrogen storage alloy according to claim 1, wherein X in the formula (1) is 0.03≤x≤0.08.

3) The hydrogen storage alloy according to claim 1, which is in the form of a powder having an average particle size of 60 m or less.

4) A negative electrode for a nickel-hydrogen secondary battery comprising a hydrogen storage alloy having a composition represented by the formula (1) and a Vickers hardness of 900 kg / mm ² or more, and a conductive material.

5) the hydrogen storage alloy, negative electrode according to claim 4, wherein an average particle size of ₆₀ μ πι following powder.

6) Oxidation rate ((oxygen value after 200 cycles) no (initial oxygen) after repeating charge / discharge cycles for 200 cycles at a constant temperature of 25 ° C and a constant current of 6 OmAZg when a secondary battery was fabricated. Alloy powder for a negative electrode of a nickel hydride secondary battery, the value of which is below 10.0%.

7) Use of a hydrogen storage alloy having a composition represented by the formula (1) and a Vickers hardness of 900 kg / mm ² or more for manufacturing a negative electrode for a nickel-hydrogen secondary battery.