JP3454574B2 - Manufacturing method of alkaline secondary battery - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline secondary battery provided with a positive electrode containing a metal oxide and a negative electrode containing a hydrogen storage alloy, and more particularly, to a method for manufacturing a negative electrode hydrogen storage alloy. The present invention relates to an improved alkaline secondary battery. 2. Description of the Related Art A nickel-hydrogen secondary battery, which is an example of an alkaline secondary battery, is wound spirally with a separator interposed between a positive electrode containing nickel hydroxide and a negative electrode containing a hydrogen storage alloy. It has a structure in which the turned electrode group is housed in a container together with the alkaline electrolyte. The nickel-hydrogen secondary battery has a higher capacity and a higher energy density than a nickel-cadmium secondary battery using a cadmium negative electrode instead of the hydrogen storage alloy negative electrode. The charge characteristics and discharge characteristics of the negative electrode of the nickel-metal hydride secondary battery are determined by the hydrogen storage and release characteristics of the hydrogen storage alloy. For this reason, the hydrogen storage alloy is diversified to improve the hydrogen storage and release characteristics. Examples of the multiplexed hydrogen storage alloy include those in which the Ni component of a LaNi ₅ -based alloy is replaced with Co, Al, Mn, Fe, Cu, or the like, or the La component of the LaNi ₅ -based alloy in which La
It is known that the metal is replaced with a misch metal which is a mixture of lanthanum elements such as e, Pr, Nd, and Sm. A secondary battery provided with a negative electrode containing the above-mentioned hydrogen storage alloy is hermetically sealed by a Neumann system in which oxygen gas generated from the positive electrode during overcharge is absorbed by the negative electrode. However, since the oxygen gas absorption reaction is an exothermic reaction in such a secondary battery, the temperature of the secondary battery increases when overcharge occurs. Since the hydrogen storage amount of the hydrogen storage alloy of the negative electrode decreases with increasing temperature,
Hydrogen not stored in the hydrogen storage alloy of the negative electrode due to the charge reaction exists as free hydrogen in the battery. As a result, the internal pressure of the secondary battery rises, so that the cycle life is shortened. The hydrogen gas pressure in the battery during storage of the secondary battery is an equilibrium pressure (hereinafter referred to as a plateau pressure) required for the hydrogen storage alloy of the negative electrode to store and release a sufficient amount of hydrogen. ). Therefore, when the secondary battery is stored at a high temperature, the plateau pressure of the hydrogen storage alloy of the negative electrode increases, and the hydrogen gas pressure in the battery increases accordingly.
The increased hydrogen gas is Ni, which is a charge product of the positive electrode.
Since the OOH is reduced and the discharge reaction proceeds, the secondary battery has a problem that the self-discharge characteristic during high-temperature storage is deteriorated. Further, in a secondary battery provided with a negative electrode containing a hydrogen storage alloy having the above-described composition, the negative electrode is pulverized as the charge / discharge cycle proceeds, and the negative electrode is corroded.
There was a problem that the cycle life was shortened. Also,
Since the degree of pulverization with the progress of the charge / discharge cycle of the negative electrode differs for each hydrogen storage alloy lot, there is a problem that the cycle life of the secondary battery varies. The difference in the degree of progress of the pulverization is considered to be due to the influence of impurities in the hydrogen storage alloy, variations in alloy homogeneity due to variations in alloy manufacturing conditions, and the like, but is not clear at this stage. SUMMARY OF THE INVENTION The present invention has been made to solve the conventional problems, has excellent hydrogen storage and release characteristics, and suppresses pulverization accompanying progress of a charge / discharge cycle. It is an object of the present invention to provide an alkaline secondary battery provided with a negative electrode containing the hydrogen storage alloy. [0008] According to the present invention, there is provided an alkaline secondary battery according to the present invention.
Method for producing a next cell, the production of alkaline secondary battery provided with a separator interposed, the alkaline electrolyte between a positive electrode including a metal oxide, a negative electrode, the positive electrode and the negative electrode
A method, formula _{LmNi w Co x Mn y Al z} ( however
And Lm is at least selected from rare earth elements including La.
And the total value of the atomic ratios w, x, y, and z is
5.1 ≦ w + x + y + z ≦ 5.4)
And the equilibrium pressure of the composition isotherm at 80 ° C. is 3 atm.
H / M (atomic ratio between hydrogen and rare earth hydrogen storage alloy)
0.5 or more, and at 5 to 30 ° C., 5 to 10 atm
BET method when hydrogenated and pulverized once under hydrogen pressure
Rare earth system with specific surface area of 0.04 to 0.11 m ² / g
Selecting a hydrogen storage alloy, and the rare earth hydrogen storage
Producing a negative electrode containing an alloy.
It is assumed that. [0009] The atomic ratio H / M of hydrogen and the rare earth-based hydrogen storage alloy of 0.5 or more means that at least 0.5 atoms of hydrogen are stored per metal element constituting the rare-earth-based hydrogen storage alloy. Means The rare earth-based hydrogen storage alloy does not store hydrogen in an amount equivalent to one atom or more per one metal element constituting the alloy. Hereinafter, the alkaline secondary battery of the present invention will be described with reference to the nickel-metal hydride secondary battery shown in FIG. The hydrogen storage alloy negative electrode 1 is spirally wound with a separator 3 made of synthetic resin fiber interposed between the negative electrode 1 and the nickel positive electrode 2.
It is stored in a cylindrical container 4 of AA size. The negative electrode 1 is arranged at the outermost periphery of the prepared electrode group and is in electrical contact with the container 4. The alkaline electrolyte is contained in the container 4. A circular sealing plate 6 having a hole 5 in the center is arranged at the upper opening of the container 4.
The ring-shaped insulating gasket 7 is disposed between the peripheral edge of the sealing plate 6 and the inner surface of the upper opening of the container 4, and is formed by caulking to reduce the diameter of the upper opening inward.
The sealing plate 6 is hermetically fixed. The lower surface of the flange portion of the positive electrode terminal 8 having a flange portion is welded to the sealing plate 6 via a ring-shaped spacer 9. Positive electrode lead 10
Has one end connected to the positive electrode 2 and the other end connected to the positive electrode terminal 8. The negative electrode 1 has a general formula of LmNi _w Co _x M
_ny Al _z (where Lm is at least one selected from rare earth elements including La, and the atomic ratio w, x,
The sum of y and z is represented by 5.1 ≦ w + x + y + z ≦ 5.4, and the equilibrium pressure at 80 ° C.-composition isotherm (hereinafter referred to as PCT line; PCT line is Pressur)
When the equilibrium pressure of the e-composition isotherm is 3 atm, the atomic ratio H / M between hydrogen and the rare earth-based hydrogen storage alloy is 0.5 or more, and 5 to 30
Specific surface area by BET method when hydrogenated and pulverized once under a hydrogen pressure of 5 to 10 atm at 0.040 to 0.11
Rare earth hydrogen storage alloys containing 0 m ² / g are included. The negative electrode 1 is manufactured by the following method. The rare earth-based hydrogen storage alloy is pulverized by mechanical pulverization or hydrogenation pulverization. Subsequently, a paste is prepared by adding a polymer binder and a conductive material powder to the powder and kneading the mixture in the presence of water. Subsequently, the paste is applied to a conductive substrate, dried, and then rolled to produce the negative electrode 1. The rare earth element containing La in the rare earth hydrogen storage alloy is, for example, La, Ce, Pr, Nd.
And the like. The atomic ratio w, x, y, z of the rare earth hydrogen storage alloy is 3.1 ≦ w ≦ 4.
8, 0.2 ≦ x ≦ 0.8, 0.2 ≦ y ≦ 0.8, 0.2
It is desirable to satisfy ≦ z ≦ 0.8. The total value of the atomic ratio of the rare earth-based hydrogen storage alloy is limited to the above range for the following reason. When the total value of the atomic ratios is less than 5.1, the cycle life of the secondary battery including the negative electrode including the alloy decreases. On the other hand, when the total value of the atomic ratios exceeds 5.4, the hydrogen storage capacity of the alloy decreases, and the negative electrode containing the alloy is corroded. PC of 80 ° C. of the rare earth hydrogen storage alloy
The T line is JIS H7 defined by Japanese Industrial Standards.
It can be measured by the 201 method. When the atomic ratio H / M of hydrogen and the rare earth-based hydrogen storage alloy, which is an index of the hydrogen storage amount when the equilibrium pressure of the PCT line is 3 atm, exceeds 0.5, the hydrogen storage amount of the alloy at high temperature decreases. I do. The specific surface area by the BET method when the rare earth-based hydrogen storage alloy is hydrogenated and pulverized under the aforementioned conditions is limited to the above range for the following reason. When the specific surface area is less than 0.040 m ² / g, the secondary battery provided with the negative electrode containing the alloy is activated by crushing the alloy by the first charge. Since the reaction area is small, the discharge capacity and discharge voltage of the secondary battery at the beginning of the charge / discharge cycle are reduced.
If the specific surface area exceeds 0.110 m ² / g, the negative electrode containing the alloy is pulverized as the charge / discharge cycle progresses, so that the cycle life of the secondary battery including the negative electrode decreases. Examples of the conductive material powder include carbon black and graphite. Examples of the polymer binder include sodium polyacrylate, polytetrafluoroethylene (PTFE), carboxymethyl cellulose and its salt (CMC). Examples of the conductive substrate include those having a two-dimensional structure such as punched metal, expanded metal, and wire mesh, and those having a three-dimensional structure such as foamed metal and reticulated sintered metal fibers. The positive electrode 2 is prepared by adding a conductive material to nickel hydroxide powder as an active material, kneading the mixture with a polymer binder and water to prepare a paste, filling the paste into a conductive substrate, and drying the paste. After that, it is manufactured by molding. Examples of the conductive material include cobalt compounds such as cobalt oxide and cobalt hydroxide. Examples of the polymer binder include those similar to the negative electrode 1. Examples of the conductive substrate include a porous substrate having a three-dimensional structure such as a nickel fiber sintered body, a felt-like porous nickel body, and a sponge-like porous nickel body. Examples of the separator 3 include a nonwoven fabric made of a polyamide fiber and a nonwoven fabric made of a polyolefin fiber such as polyethylene and polypropylene provided with a hydrophilic functional group. As the alkaline electrolyte, for example, a mixed solution of potassium hydroxide, sodium hydroxide and lithium hydroxide, a mixed solution of potassium hydroxide and lithium hydroxide and the like can be used. According to the alkaline secondary battery of the present invention, when the equilibrium pressure of the PCT wire at 80 ° C. is 3 atm, the atomic ratio H / M of hydrogen and the rare-earth hydrogen storage alloy is 0.5 or more. By providing the negative electrode including the rare earth-based hydrogen storage alloy, the hydrogen storage alloy of the negative electrode can maintain a high hydrogen storage amount in a high temperature region from room temperature, so that the secondary battery including the negative electrode is overcharged. Free hydrogen can be prevented from being generated in the battery when the temperature rises. Therefore, an increase in the internal pressure of the secondary battery can be suppressed, and the cycle life can be improved. Further, the negative electrode has the specific composition and the H
Since the hydrogen storage alloy whose / M is specified in the above range has a low plateau pressure at a high temperature, an increase in the hydrogen gas pressure in the battery when the secondary battery is stored at a high temperature can be suppressed. As a result, a reduction reaction of NiOOH, which is a charge product of the positive electrode, with the hydrogen gas, that is, a self-discharge reaction can be suppressed. The rare earth-based hydrogen storage alloy has the specific composition described above, and has a specific surface area of 0.040-0.
By using a material having a power of 110 m ² / g, it is possible to suppress the pulverization of the negative electrode containing the rare earth-based hydrogen storage alloy as the charge / discharge cycle proceeds. As a result, corrosion of the negative electrode can be suppressed, so that the charge / discharge cycle life of a secondary battery including the negative electrode can be further improved. Embodiments of the present invention will be described below in detail with reference to the drawings. Examples 1 to 4 First, a misch metal (Lm) mainly containing lanthanum, cerium, neodymium, and praseodymium, and nickel, cobalt, aluminum, and manganese were mixed at an atomic ratio shown in Table 1 below, and these were mixed in an argon gas atmosphere. A rare earth hydrogen storage alloy was prepared by melting in a high frequency melting furnace. This alloy is placed in an argon gas atmosphere for 10 minutes.
Heat treatment was performed at 00 ° C. for 10 hours. The obtained alloy was heated at 10 ° C. and 10 atm.
Was hydrogenated and pulverized once under hydrogen pressure, and the specific surface area was measured by the BET method. A rare earth-based hydrogen storage alloy having a specific surface area shown in Table 1 below was selected. Next, these alloys were mechanically pulverized to obtain a rare earth hydrogen storage alloy powder having a particle size of 74 μm. The PCT characteristics at 80 ° C. of each of the obtained alloy powders were measured by JIS H
The atomic ratio H / M of hydrogen and the rare earth hydrogen storage alloy at an equilibrium pressure of 3 atm was determined by the method of 7201. Eight kinds of rare earth hydrogen storage alloys in which the H / M is the value shown in Table 2 below Powder was selected. Subsequently, the plateau pressure at 80 ° C. was determined for each of the selected alloy powders, and the results are shown in Table 2 below. Next, 1.5 parts by weight of polytetrafluoroethylene, 0.5 parts by weight of sodium polyacrylate, and 0.12 parts by weight of carboxymethyl cellulose were added to 100 parts by weight of the rare earth hydrogen storage alloy powder as a polymer binder.
5 parts by weight, 1 part by weight of carbon black as a conductive material powder and 50 parts by weight of water were further added, and these were kneaded to prepare a paste. After applying the paste to a punched metal as a conductive substrate, drying, pressing,
By cutting, eight kinds of negative electrodes were produced. To a mixed powder comprising 90 parts by weight of nickel hydroxide powder and 10 parts by weight of cobalt oxide powder, 3 parts by weight of carboxymethyl cellulose and 5 parts by weight of polytetrafluoroethylene were added to the nickel hydroxide powder. Further, a paste was prepared by adding 45 parts by weight of pure water thereto and kneading them. After filling this paste into a sintered fiber substrate, the paste was further applied to both surfaces thereof, dried, and rolled by a roller press to produce a paste-type nickel positive electrode. Next, a separator made of a polypropylene nonwoven fabric provided with a hydrophilic functional group was interposed between each of the negative electrode and the positive electrode, and spirally wound to form an electrode group. These electrode groups were housed in a container together with an alkaline electrolyte mainly composed of potassium hydroxide to assemble an AA-size nickel-metal hydride secondary battery having a structure shown in FIG. 1 and a capacity of 1200 mAh. The obtained secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 3 were charged at a current of 1.2 A for 90 minutes, and then discharged at a current of 1.2 A to a final voltage of 1.0 V. A discharge cycle test was performed, and the battery capacity was 8 at the beginning of the cycle.
The number of cycles required to reduce to 0% was measured, and the results are also shown in Table 2 below. The battery capacities of the secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 3 were charged at a current of 360 mA for 5 hours and then discharged at a current of 1.2 A to a final voltage of 1.0 V. (Initial capacity) was measured. Next, 360
After charging at a current of mA for 5 hours, the battery was stored at a high temperature of 45 ° C. for 30 days. After that, a cut-off voltage of 1.0 with a current of 1.2 A is applied.
The battery capacity at the time of discharging to V was measured, and the remaining capacity ratio (based on the initial capacity) was determined from the obtained battery capacity. The results are also shown in Table 2 below. [Table 1] [Table 2] As is apparent from Table 1 and Table 2, the composition is represented by Formula LmNi _w Co _x Mn _y Al _z described above, and the equilibrium pressure at 80 ° C. is hydrogen and the rare earth-based hydrogen storage alloy when the 3atm The atomic ratio H / M is 0.5 or more, and the specific surface area by the BET method when hydrogenated and pulverized once at 10 ° C. under a hydrogen pressure of 10 atm is 0.040 to 0.11.
The secondary batteries of Examples 1 to 4 each provided with a negative electrode containing a rare earth-based hydrogen storage alloy of 0 m ² / g,
It can be seen that the plateau pressure at 0 ° C. is as low as 1.78 to 2.80 atm, the cycle life is as long as 300 to 470, and the residual capacity ratio at high temperature storage is as large as 35 to 45 or more. On the other hand, the above H / M is 0.77, but the rare earth hydrogen whose composition is represented by the formula LmNi _4.0 Co _0.4 Mn _0.3 Al _0.3 and whose specific surface area is 0.130 m ² / g. The secondary battery of Comparative Example 1 including the negative electrode containing the storage alloy has a low plateau pressure of 1.24 atm and a high residual capacity ratio of 50 at high temperature storage, but has a very short cycle life of 150. . The composition is represented by the same general formula as in Examples 1 to 4, and the specific surface area is 0.040 m ² / g, but the H / M is 0.48.
The secondary battery of Comparative Example 2 provided with a negative electrode containing a rare earth-based hydrogen storage alloy having a high plateau pressure of 3.20 atm, a low residual capacity ratio at high temperature storage of 20 and a short cycle life of 230. You can see that. On the other hand, when the composition is represented by the formula LmN
i _4.35 Co _0.4 Mn _0.3 Al _0.3
/ M is 0.38 and the specific surface area is 0.038 m ²
The secondary battery of Comparative Example 3 provided with a negative electrode containing a rare earth-based hydrogen storage alloy having a plateau pressure of 4.60 atm / g
And the remaining capacity ratio at high temperature storage is as extremely low as 10,
It can be seen that the cycle life is as short as 180. As described in detail above, according to the alkaline secondary battery of the present invention, it has a high hydrogen storage capacity in a range from room temperature to a high temperature, has a low plateau pressure at a high temperature, and further has a high charge / discharge rate. A negative electrode containing a rare earth-based hydrogen storage alloy in which pulverization accompanying the progress of a cycle is suppressed is provided, and remarkable effects such as improvement in cycle life and self-discharge characteristics during high-temperature storage can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing a nickel-metal hydride secondary battery as an example of an alkaline secondary battery according to the present invention. [Description of Signs] 1 ... negative electrode, 2 ... positive electrode, 3 ... separator, 4 ... bottomed cylindrical container.

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01M 4/38

Claims (1)

(57) Claims 1. An alkaline battery comprising a positive electrode containing a metal oxide, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an alkaline electrolyte. Secondary battery manufacturing method
Te, formula _{LmNi w Co x Mn y Al z} ( where, Lm is the La
Comprising at least one selected from rare earth elements,
And the sum of the atomic ratios w, x, y, z is 5.1 ≦ w + x +
y + z ≦ 5.4) and equilibrium at 80 ° C.
H / M (hydrogen) when the equilibrium pressure of the pressure-composition isotherm is 3 atm
And the atomic ratio of the rare earth hydrogen storage alloy) is 0.5 or more.
At 5-30 ° C. under 5-10 atm hydrogen pressure
The specific surface area by the BET method when hydrogenated and ground once is 0.
Rare earth hydrogen storage alloys with a capacity of 0.4 to 0.11 m ² / g
Selecting, and preparing a negative electrode containing the rare earth-based hydrogen storage alloy
A method for producing an alkaline secondary battery, comprising:
Law.