Alkaline secondary battery, nickel-hydrogen secondary battery, and manufacturing method thereof

Abstract

The object of this invention is to suppress capacity reduction caused by the addition of ytterbium compounds in alkaline secondary batteries and their manufacturing methods. The alkaline secondary battery of this invention comprises a positive electrode, a negative electrode, and an alkaline electrolyte, wherein the positive electrode contains 3.0% by weight or more of a ytterbium compound relative to the nickel hydroxide, the nickel hydroxide contains dissolved Mn, and the electrolyte volume is 1.5 mL / Ah or more relative to the positive electrode capacity. The alkaline secondary battery of this invention has a positive electrode containing 3.0% by weight or more of a ytterbium compound relative to the nickel hydroxide, a negative electrode containing Mn, and an electrolyte volume of 1.5 mL / Ah or more relative to the positive electrode capacity.

Description

Technical Field

[0001] This invention relates to alkaline secondary batteries, nickel-metal hydride secondary batteries, and methods for manufacturing them. Background Technology

[0002] Alkaline secondary batteries have been used for various purposes, and in order to ensure long-term reliability and reduce the frequency of battery replacement, their lifespan is required to be longer.

[0003] Alkaline secondary batteries have been used in a variety of applications. For example, in industrial applications, they are used as backup power and automotive power sources. These industrial applications require operation over a wide temperature range, from high to low.

[0004] Typically, charge acceptability decreases when charging secondary batteries with aqueous electrolytes at high temperatures. Therefore, charge acceptability has been improved by adding compounds of yttrium (Y), ytterbium (Yb), and erbium (Er) to the positive electrode.

[0005] Yttrium compounds, ytterbium compounds, and erbium compounds can inhibit the corrosion of hydrogen storage alloys. Patent documents 1, 2, and 3 demonstrate that adding these compounds to the positive and negative electrodes extends battery life.

[0006] As a method to achieve a longer battery life, adding Mn into the battery is also known. Patent documents 4 and 5 propose that by containing Mn, the electrolyte retention performance of the separator is improved, electrolyte consumption is suppressed, and the battery life is increased.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 5-28992 (see paragraphs

[0011] and

[0025] )

[0010] Patent Document 2: Japanese Patent Application Publication No. 6-215765 (see paragraph

[0007] )

[0011] Patent Document 3: Japanese Patent Application Publication No. 9-92279 (see paragraph

[0016] )

[0012] Patent Document 4: Japanese Patent Application Publication No. 2005-142146 (see paragraph

[0019] )

[0013] Patent Document 5: Japanese Patent Application Publication No. 2002-42861 (see paragraph

[0040] ) Summary of the Invention

[0014] The problem the invention aims to solve

[0015] The inventors have conducted in-depth research on extending the lifespan of alkaline secondary batteries and found that if an excessive amount of ytterbium compounds are added to an alkaline secondary battery, the capacity of the positive electrode active material decreases and increases when used under high-temperature conditions.

[0016] Even if electrode corrosion can be suppressed by adding ytterbium compounds, the lifespan improvement effect of ytterbium compounds will be offset due to the reduced capacity.

[0017] The present invention was made in view of the following circumstances, and its object is to provide alkaline secondary batteries, nickel-metal hydride secondary batteries, and methods for manufacturing the same, which are capable of suppressing capacity reduction caused by the addition of ytterbium compounds.

[0018] Methods for solving problems

[0019] To address the aforementioned issues, the alkaline secondary battery, nickel-metal hydride secondary battery, and their manufacturing methods of the present invention are provided in the following manner.

[0020] The first aspect of the present invention is an alkaline secondary battery comprising:

[0021] A cathode using nickel hydroxide as the active material,

[0022] Negative electrode, and

[0023] alkaline electrolyte,

[0024] Compared to the aforementioned nickel hydroxide, the aforementioned positive electrode contains 3.0% by weight or more of a ytterbium compound.

[0025] The above nickel hydroxide contains Mn dissolved in it.

[0026] The amount of alkaline electrolyte relative to the positive electrode capacity is 1.5 mL / Ah or more.

[0027] The second aspect of the present invention is an alkaline secondary battery according to the first aspect described above, wherein the active material of the negative electrode is a hydrogen storage alloy, or zinc and zinc oxide.

[0028] The third aspect of the present invention is an alkaline secondary battery according to the first aspect described above, wherein the active material of the negative electrode is a hydrogen storage alloy that does not contain Mn.

[0029] The fourth aspect of the present invention is an alkaline secondary battery according to the first aspect described above, wherein, relative to the nickel hydroxide, the positive electrode contains 5.0% by weight or less of a ytterbium compound, and the amount of the alkaline electrolyte is 3.0 mL / Ah or less relative to the capacity of the positive electrode.

[0030] The fifth aspect of the present invention is a nickel-metal hydride secondary battery comprising: a positive electrode with nickel hydroxide as the active material, a negative electrode with a hydrogen storage alloy as the active material, and an alkaline electrolyte, wherein the positive electrode contains 3.0% by weight or more of a ytterbium compound relative to the nickel hydroxide, the negative electrode contains Mn, and the amount of alkaline electrolyte is 1.5 mL / Ah or more relative to the capacity of the positive electrode.

[0031] The sixth aspect of the present invention is a nickel-metal hydride secondary battery according to the fifth aspect described above, wherein the hydrogen storage alloy does not contain Mn.

[0032] The seventh aspect of the present invention is a nickel-metal hydride secondary battery according to the fifth aspect described above, wherein, relative to the nickel hydroxide, the positive electrode contains 5.0% by weight or less of a ytterbium compound, and the amount of the alkaline electrolyte is 3.0 mL / Ah or less relative to the capacity of the positive electrode.

[0033] The eighth aspect of the present invention is a method for manufacturing an alkaline secondary battery, the alkaline secondary battery comprising a positive electrode, a negative electrode and an alkaline electrolyte, wherein the method comprises: adding 3.0% by weight or more of a ytterbium compound relative to the nickel hydroxide in which Mn is dissolved, preparing a positive electrode slurry, coating or filling the positive electrode slurry onto a conductive core material to prepare the positive electrode, and injecting the alkaline electrolyte in such a way that the amount of alkaline electrolyte relative to the capacity of the positive electrode is 1.5 mL / Ah or more.

[0034] The ninth aspect of the present invention is a method for manufacturing an alkaline secondary battery according to the eighth aspect described above, wherein a hydrogen storage alloy, or zinc and zinc oxide are used in the active material of the negative electrode.

[0035] The tenth aspect of the present invention is a method for manufacturing an alkaline secondary battery according to the eighth aspect described above, wherein a hydrogen storage alloy that does not contain Mn is used in the active material of the negative electrode.

[0036] The eleventh aspect of the present invention is a method for manufacturing an alkaline secondary battery according to the eighth aspect described above, wherein, in the preparation of the positive electrode slurry, the amount of ytterbium compound added relative to the nickel hydroxide in which Mn is dissolved is 5.0% by weight or less, and the alkaline electrolyte is injected in such a way that the amount of alkaline electrolyte is 3.0 mL / Ah or less relative to the positive electrode capacity.

[0037] The 12th aspect of the present invention is a method for manufacturing a nickel-metal hydride secondary battery, the nickel-metal hydride secondary battery comprising a positive electrode with nickel hydroxide as the active material, a negative electrode with a hydrogen storage alloy as the active material, and an alkaline electrolyte. The method comprises: adding 3.0% by weight or more of a ytterbium compound relative to the nickel hydroxide to prepare a positive electrode slurry; filling the positive electrode slurry into a conductive core material, drying and rolling to prepare the positive electrode; adding Mn or a Mn compound to the hydrogen storage alloy to prepare a negative electrode slurry; coating the negative electrode slurry onto a conductive core material, drying and rolling to prepare the negative electrode; and injecting the alkaline electrolyte in such a manner that the amount of alkaline electrolyte relative to the positive electrode capacity is 1.5 mL / Ah or more.

[0038] The 13th aspect of the present invention is a method for manufacturing a nickel-metal hydride secondary battery according to the 12th aspect described above, wherein the hydrogen storage alloy does not contain Mn.

[0039] The 14th aspect of the present invention is a method for manufacturing a nickel-metal hydride secondary battery according to the 12th aspect described above, wherein, in the preparation of the positive electrode slurry, the amount of ytterbium compound added relative to the nickel hydroxide is 5.0% by weight or less, and the alkaline electrolyte is injected in such a way that the amount of alkaline electrolyte is 3.0 mL / Ah or less relative to the positive electrode capacity.

[0040] The effects of the invention

[0041] According to the present invention, in a design where the amount of electrolyte in the battery is up to 1.5 mL / Ah or more relative to the positive electrode capacity and the positive electrode contains 3.0 wt% or more of a ytterbium compound, by dissolving Mn in the nickel hydroxide as the positive electrode active material or by containing Mn in the negative electrode, the post-charge voltage during high-temperature storage can be suppressed.

[0042] In addition, by adding Mn to suppress the structural changes of the positive electrode active material after high-temperature storage, it is possible to manufacture an alkaline secondary battery in which the capacity reduction after high-temperature storage is suppressed.

[0043] According to the present invention, by adding Mn, a battery design that achieves a balance between the lifespan improvement effect resulting from the suppression of positive electrode degradation can be obtained. Detailed Implementation

[0044] The alkaline secondary battery of the present invention comprises a positive electrode, a negative electrode, and an alkaline electrolyte, wherein nickel hydroxide is used as the active material. The alkaline secondary battery includes: a nickel-metal hydride secondary battery in which a hydrogen storage alloy is used as the active material of the negative electrode, and a nickel-zinc secondary battery in which zinc and zinc oxide are used as the active material of the negative electrode.

[0045] The following description uses a nickel-metal hydride secondary battery as an example to illustrate one embodiment of the alkaline secondary battery and its manufacturing method of the present invention.

[0046] [First Embodiment] (Ni-MH Secondary Battery)

[0047] The nickel-metal hydride secondary battery in this embodiment is a non-sintered type.

[0048] The nickel-metal hydride secondary battery of this embodiment is designed such that the amount of electrolyte in the battery is 1.5 mL / Ah or more relative to the positive electrode capacity, preferably 1.5 mL / Ah or more and 3.0 mL / Ah or less, and more preferably 1.8 mL / Ah or more and 3.0 mL / Ah or less.

[0049] The nickel-metal hydride secondary battery of this embodiment includes a positive electrode, a negative electrode, and an alkaline electrolyte.

[0050] The positive electrode contains nickel hydroxide as the active material. Mn is dissolved in the nickel hydroxide. Mn is dissolved in the nickel hydroxide at a concentration of 0.3% to 2.0% by weight, preferably 0.5% to 1.0% by weight, relative to the nickel hydroxide.

[0051] For the positive electrode, relative to nickel hydroxide, it contains 3.0% by weight or more, preferably 3.0% by weight or more and 5.0% by weight or less of a ytterbium compound. Examples of ytterbium compounds that can be used are Yb₂O₃, YbF₃, etc.

[0052] The ytterbium compound content recorded here is substantially equal to the amount of ytterbium compound added relative to nickel hydroxide during the fabrication of the cathode, and errors arising during the fabrication process are permissible.

[0053] The negative electrode contains a hydrogen storage alloy that does not contain Mn as the active material. An example of a Mn-free hydrogen storage alloy is La. 0.76 Zr 0.01 Mg 0.24 Ni 3.30 Al 0.10 Etc. Hydrogen storage alloys that do not contain Mn are preferably superlattice alloys with a structure in which AB2 and AB5 structures are regularly stacked.

[0054] Alkaline electrolytes are typically solutions obtained by dissolving alkali metal hydroxides such as KOH, NaOH, and LiOH in water.

[0055] (Manufacturing method of nickel-metal hydride secondary batteries)

[0056] In the manufacturing method of the nickel-metal hydride secondary battery of this embodiment, a positive electrode slurry and a negative electrode slurry are prepared, and positive electrode plates and negative electrode plates are prepared using these slurries. The prepared positive electrode plates and negative electrode plates are wound up with a separator, inserted into the battery case, electrolyte is injected into the battery case, and then sealed and assembled.

[0057] The amount of alkaline electrolyte injected is set to be 1.5 mL / Ah or more relative to the positive electrode capacity, preferably 1.5 mL / Ah or more and 3.0 mL / Ah or less.

[0058] The positive electrode slurry is prepared by mixing a mixture of active material and additives with a solvent. The active material is prepared by solid-dissolving a given amount of Mn in a core mainly composed of nickel hydroxide. Ytterbium compounds are used as additives. The amount of ytterbium compound added relative to nickel hydroxide is 3.0% by weight or more, preferably 3.0% by weight or more and 5.0% by weight or less.

[0059] Positive electrode plates are manufactured by filling or coating a positive electrode slurry onto a plate-shaped conductive core material, followed by drying / rolling. Conductive core materials can be, for example, foamed nickel substrates or nickel felt substrates.

[0060] The negative electrode slurry can be prepared by mixing hydrogen storage alloy powder that does not contain Mn, Mn or a Mn compound, and a solvent. The amount of Mn or a Mn compound added is 0.5 parts by weight or more and 3.0 parts by weight or less, preferably 1 part by weight, relative to 100 parts by weight of the Mn-free hydrogen storage alloy. Mn or the Mn compound can be mixed with the hydrogen storage alloy powder in the form of a compound with a given amount of carbon, a binder, and a solvent.

[0061] The negative electrode plate is manufactured by coating a negative electrode slurry onto a plate-shaped conductive core material, followed by drying / rolling. Conductive core materials can be selected from, for example, nickel stamping metal or lath metal.

[0062] [Second Implementation]

[0063] The configuration of the positive and negative electrodes in this embodiment differs from that in the first embodiment. Otherwise, it is the same as the first embodiment.

[0064] The positive electrode contains nickel hydroxide as the active material. Mn is not dissolved in nickel hydroxide.

[0065] The cathode contains, relative to nickel hydroxide, 3.0% by weight or more, preferably 3.0% by weight or more and 5.0% by weight or less of a ytterbium compound. The ytterbium compound is, for example, Yb₂O₃.

[0066] The ytterbium compound content recorded here is substantially equal to the amount of ytterbium compound added relative to nickel hydroxide during the fabrication of the cathode, and errors arising during the fabrication process are permissible.

[0067] The positive electrode slurry is prepared by mixing a mixture of an active material, primarily composed of nickel hydroxide, and additives with a solvent. Ytterbium compounds are used as additives. The amount of ytterbium compound added is the same as in the first embodiment.

[0068] The negative electrode contains a hydrogen storage alloy that does not contain Mn as the active material. The hydrogen storage alloy that does not contain Mn is the same as in the first embodiment.

[0069] The negative electrode contains Mn. The Mn content is 0.5 parts by weight or more and 3.0 parts by weight or less, preferably 1 part by weight, relative to 100 parts by weight of hydrogen storage alloy that does not contain Mn.

[0070] The negative electrode slurry is prepared by mixing Mn-free hydrogen storage alloy powder with Mn or a Mn compound and a solvent. The amount of Mn or a Mn compound added is 0.5 parts by weight or more and 3.0 parts by weight or less, preferably 1 part by weight, relative to 100 parts by weight of the Mn-free hydrogen storage alloy. The Mn or Mn compound is mixed with the hydrogen storage alloy powder after being kneaded with a given amount of carbon, a binder, and a solvent.

[0071] The positive and negative electrode plates are manufactured in the same manner as in the first embodiment.

[0072] Next, the basis for setting the nickel-metal hydride secondary battery and its manufacturing method described in the first and second embodiments above will be explained.

[0073] Nickel-metal hydride secondary batteries containing Mn dissolved in the active material of the positive electrode (Example A), nickel-metal hydride secondary batteries containing Mn in the negative electrode (Example B), and nickel-metal hydride secondary batteries containing no Mn in either the positive or negative electrode (Comparison: Examples C and D) were subjected to high-temperature intermittent charging tests.

[0074] [Manufacturing of Experimental Example A]

[0075] (positive electrode)

[0076] 0.5% by weight of Mn was dissolved in a core mainly composed of nickel hydroxide. A film layer of cobalt hydroxide was formed on the surface of the nickel hydroxide containing dissolved Mn.

[0077] Nickel hydroxide with a film layer was treated with hot alkali in air to obtain spherical particles of cobalt hydroxide with a valence of 3.2 on the surface, which could be used as positive electrode active material.

[0078] The positive electrode active material and additives were mixed at a ratio of 100:0~4 (parts by weight), and 0.2 parts by weight of a binder formed from a hydrophilic resin were added and mixed to obtain a mixture. Ytterbium oxide was used in the additives.

[0079] 30 parts by weight of water were added to the obtained mixture and kneaded to produce the positive electrode slurry.

[0080] The positive electrode slurry was filled into a foamed nickel matrix and then dried / rolled to produce a positive electrode plate.

[0081] (negative electrode)

[0082] A mixture was obtained by adding 1 part by weight of yttrium oxide to 1 part by weight of carbon, and further mixing in 0.3 parts by weight of a binder formed from a hydrophilic resin and 40 parts by weight of water.

[0083] 100 parts by weight of hydrogen storage alloy powder were added to the resulting mixture and kneaded to prepare the negative electrode slurry. The hydrogen storage alloy powder used here has a composition of La. 0.76 Zr 0.01 Mg 0.24 Ni 3.30 Al 0.10 It has a superlattice structure and a particle size (MV) of 35 μm.

[0084] The negative electrode slurry was coated onto a stamped metal core and then dried / rolled to produce a negative electrode plate.

[0085] (Ni-MH secondary battery)

[0086] The positive and negative electrode plates prepared above are sandwiched together and rolled up, inserted into the battery case, and electrolyte is injected into the battery case in such a way that the electrolyte volume is 1.4 mL / Ah, 1.5 mL / Ah or 1.9 mL / Ah relative to the positive electrode capacity. After that, the case is sealed and assembled into a battery.

[0087] The aging process (from assembly to activation) was carried out for 12 hours at a temperature below 40°C.

[0088] As an activation treatment, a 1000mAh nickel-metal hydride secondary battery with AA size (14.0Φ×49.5mm) was fabricated by performing 5 charge-discharge cycles. The charge-discharge cycle consisted of charging at a charging current of 100mA for 16 hours and discharging at a discharging current of 200mA until the battery voltage reached 1.0V as one cycle.

[0089] [Manufacturing of Experimental Example B]

[0090] (positive electrode)

[0091] A coating layer made of cobalt hydroxide was formed on the surface of the core, which is mainly composed of nickel hydroxide.

[0092] Nickel hydroxide with a coating layer was treated with hot alkali in air to obtain spherical particles with cobalt hydroxide on the surface becoming 3.2 valence, which could be used as positive electrode active material.

[0093] The positive electrode active material and additives were mixed at a ratio of 100:0~4 (parts by weight), and 0.2 parts by weight of a binder formed from a hydrophilic resin were added and mixed to obtain a mixture. Ytterbium oxide was used in the additives.

[0094] 30 parts by weight of water were added to the obtained mixture and kneaded to produce the positive electrode slurry.

[0095] The positive electrode slurry was filled into a foamed nickel matrix and then dried / rolled to produce a positive electrode plate.

[0096] (negative electrode)

[0097] A mixture was obtained by adding 1 part by weight of manganese oxide (Mn2O3) relative to 1 part by weight of carbon, and further mixing it with 0.3 parts by weight of a binder formed from a hydrophilic resin and 40 parts by weight of water.

[0098] 100 parts by weight of hydrogen storage alloy powder were added to the resulting mixture and kneaded to obtain the negative electrode slurry. The hydrogen storage alloy powder used here has a composition of La. 0.76 Zr 0.01 Mg 0.24 Ni 3.30 Al 0.10 It has a superlattice structure and a particle size (MV) of 35 μm.

[0099] The negative electrode slurry was coated onto a stamped metal core and then dried / rolled to produce a negative electrode plate.

[0100] (Ni-MH secondary battery)

[0101] The positive and negative electrode plates prepared above are sandwiched together and rolled up, inserted into the battery case, and electrolyte is injected into the battery case in such a way that the electrolyte volume is 1.4 mL / Ah, 1.5 mL / Ah or 1.9 mL / Ah relative to the positive electrode capacity. After that, the case is sealed and assembled into a battery.

[0102] The aging process (from assembly to activation) was carried out for 12 hours at a temperature below 40°C.

[0103] As an activation treatment, a 1000mAh nickel-metal hydride secondary battery with AA size (14.0Φ×49.5mm) was fabricated by performing 5 charge-discharge cycles. The charge-discharge cycle consisted of charging at a charging current of 100mA for 16 hours and discharging at a discharging current of 200mA until the battery voltage reached 1.0V as one cycle.

[0104] [Manufacturing of Experimental Example C]

[0105] (positive electrode)

[0106] The positive electrode active material and positive electrode plate were prepared following the same steps as in Experimental Example B.

[0107] (negative electrode)

[0108] The negative electrode active material and negative electrode plate were prepared following the same steps as in Experimental Example A.

[0109] (Ni-MH secondary battery)

[0110] The battery was assembled using the same steps as in Experimental Example A, and then subjected to aging and activation treatments to produce a nickel-metal hydride secondary battery.

[0111] [Manufacturing of Experimental Example D]

[0112] (positive electrode)

[0113] The positive electrode active material and positive electrode plate were prepared following the same procedures as in Test Example B. In this comparative example, yttrium oxide was used instead of ytterbium oxide as an additive. The additive was mixed in at 2 or 4 parts by weight relative to 100 parts by weight of the positive electrode active material.

[0114] (negative electrode)

[0115] The negative electrode active material and negative electrode plate were prepared following the same steps as in Experimental Example A.

[0116] (Ni-MH secondary battery)

[0117] The battery was assembled using the same steps as in Experimental Example A, and then subjected to aging and activation treatments to produce a nickel-metal hydride secondary battery.

[0118] [High-Temperature Intermittent Charging Test]

[0119] After the activated nickel-metal hydride secondary batteries of the above test examples A to D were placed in an environment of 90°C for 4 days, they were fully charged at room temperature at 0.2C (100 minutes + dT / dt control) and then the operation of placing them in an environment of 90°C for 4 days was repeated again.

[0120] After each charge, one unit was removed and subjected to AC resistance (1kHz AC) and 2W discharge at room temperature (23±3℃) to confirm its lifespan. The results are shown in Tables 1-4.

[0121] It should be noted that the nickel-metal hydride secondary batteries in Test Examples A to D were designed based on the positive electrode capacity. The positive electrode capacity can be understood as directly equivalent to the overall capacity of the battery. Therefore, the "amount of electrolyte relative to the positive electrode capacity" is expressed as the volume of electrolyte injected (mL) / battery capacity (Ah).

[0122] In this test, lifetime was determined based on two criteria: internal resistance limitation and capacity limitation. Tables 1-4 indicate which criterion was used to determine lifetime. An internal resistance limitation was defined as a charge at room temperature followed by an AC resistance (1kHz) of 50mΩ or higher. A capacity limitation was defined as an internal resistance of 50mΩ or less, and a 2W discharge time at room temperature after storage that was 40% less than the initial value.

[0123] Table 1 shows the experimental results of test examples C-1 to C-21 (with Yb2O3 added to the positive electrode) where neither the positive nor negative electrode contains Mn.

[0124]

[0125] Each group of test examples C-1 to C-7, C-8 to C-14, and C-15 to C-21 had different amounts of electrolyte relative to the positive electrode capacity. Each comparative example within a group had a different amount of Yb2O3 added.

[0126] According to Table 1, the battery life was improved by adding Yb₂O₃ to the positive electrode. Furthermore, a comparative example with the same amount of Yb₂O₃ was compared among groups with different amounts of electrolyte relative to the positive electrode capacity. The results showed that the battery life improved with increasing electrolyte amount relative to the positive electrode capacity.

[0127] Comparisons within each group showed that in the groups with lower electrolyte levels (Examples C-15~21), the battery life also increased with the addition of Yb₂O₃. This can be attributed to the suppression of alloy corrosion through the addition of Yb₂O₃.

[0128] On the other hand, in the groups with a large amount of electrolyte relative to the positive electrode capacity (test examples C-1 to C-7 and test examples C-8 to C-14), although the lifetime was extended with the amount of Yb2O3 added until the amount of Yb2O3 added reached 3% by weight, no effect on the extension of lifetime was confirmed even if the amount of Yb2O3 was further increased (see test examples C-1 to C-4 and test examples C-8 to C-11).

[0129] The lifetime mode of test examples C-1~C-4 and test examples C-8~C-11 is capacity-limited. Therefore, it can be concluded that by placing the positive electrode containing more ytterbium in a high-temperature environment, the structure of the positive electrode active material changes, and the active material cannot be charged and discharged smoothly.

[0130] Among additives that can be added to the positive electrode, ytterbium compounds are particularly effective in increasing the oxygen evolution potential as a side reaction, and the voltage after charging can remain at a high level even when stored at high temperatures. Therefore, degradation caused by structural changes in the positive electrode active material is more likely to occur, leading to a decrease in capacity.

[0131] According to the results of test examples C-15 to 21, the corrosion inhibition effect of ytterbium compounds is particularly large when the content is above 3.0% by weight. However, according to the results of test examples C-1 to C-4 and test examples C-8 to C-11, it can be confirmed that by increasing the amount of ytterbium compound added, there is a tendency to increase the capacity reduction caused by structural changes in the positive electrode active material.

[0132] Table 2 shows the experimental results of test examples D-1 to D-9 (with Y2O3 added to the positive electrode) where neither the positive nor negative electrode contained Mn.

[0133]

[0134] Each group of test examples D-1 to D-3, D-4 to D-6, and D-7 to D-9 had a different amount of electrolyte relative to the positive electrode capacity. Each comparative example within a group had a different amount of Y2O3 added.

[0135] According to Table 2, the battery life was improved by adding Y₂O₃ to the positive electrode and by increasing the amount of electrolyte relative to the positive electrode capacity. However, Table 2 did not show an increase in battery life with increasing Y₂O₃ addition.

[0136] Table 3 shows the experimental results of test examples A-1 to A-21 in which 0.5% Mn was dissolved in the positive electrode active material.

[0137]

[0138] Each group of Test Examples A-1 to A-7, Test Examples A-8 to A-14, and Test Examples A-15 to A-21 had different amounts of electrolyte relative to the positive electrode capacity. Each comparative example within a group had a different amount of Yb2O3 added.

[0139] The "lifetime difference with test example C" in Table 3 is the value obtained by subtracting the lifetimes of test examples C-1 to C-21 in Table 1 from the lifetimes of test examples A-1 to A-21.

[0140] According to Table 3, even when Mn is dissolved in the positive electrode active material, the battery life is improved as Yb2O3 is added and the amount of electrolyte relative to the positive electrode capacity increases, just like in Test Example C where Mn is not dissolved.

[0141] According to Table 3, in test examples A-1 to A-4 and test examples A-8 to A-11 where the electrolyte volume relative to the positive electrode capacity is 1.5 mL / Ah or more and the amount of Yb2O3 added to the positive electrode is designed to be 3.0% by weight or more, the lifespan can be improved compared with test examples C-1 to C-4 and test examples C-8 to C-11 in Table 1.

[0142] Furthermore, comparing test examples A-1 to A-4 and test examples A-8 to A-11, the results showed that even when the amount of Yb2O3 added was 3.0% by weight or more, an increase in lifespan was confirmed to accompany the increase in the amount added.

[0143] According to Table 3, the lifetime mode of test examples A-1 to A-4 and test examples A-8 to A-11, which are designed with an electrolyte volume of 1.5 mL / Ah or more relative to the positive electrode capacity, is internal resistance limited.

[0144] These results indicate that by dissolving Mn in the positive electrode active material, the capacity reduction of the positive electrode active material caused by the addition of more Yb2O3 can be suppressed.

[0145] On the other hand, in test examples A-15 to A-18 where the electrolyte volume was designed to be 1.4 mL / Ah relative to the positive electrode capacity, no improvement in lifespan was confirmed compared to test examples C-15 to C-18 in Table 1 where 3.0% by weight or more of Yb2O3 was added to the positive electrode.

[0146] This indicates that in designs with an electrolyte volume of less than 1.5 mL / Ah relative to the positive electrode capacity, the lifespan improvement effect resulting from solid-dissolved Mn in the positive electrode active material cannot be obtained.

[0147] Table 4 shows the experimental results of test examples B-1 to B-2 in which 1.0% by weight of Mn2O3 was added to the negative electrode slurry.

[0148]

[0149] The amount of Yb2O3 added to the negative electrode slurry differed between Experimental Example B-1 and Experimental Example B-2.

[0150] According to Table 4, it was confirmed that even when Mn compounds were added to the negative electrode slurry, the same effect of inhibiting electrode degradation and improving lifespan was achieved as when Mn was dissolved in the positive electrode active material.

[0151] Based on the results of Test Example A and Test Example B, in a design where the amount of electrolyte in the battery is 1.5 ml / Ah or more relative to the positive electrode capacity and the positive electrode contains 3.0% by weight or more of ytterbium compounds, by solid-dissolving Mn in the positive electrode active material or by including Mn in the negative electrode, a nickel-metal hydride secondary battery that can suppress capacity reduction during high-temperature storage and voltage reduction after charging can be manufactured.

[0152] In automotive applications where high-temperature environments are required, alloys without Co are preferred, considering the reduced self-discharge characteristics after placement. For automotive applications, where both extended lifespan and low-temperature discharge characteristics are required, superlattice alloys with regularly stacked AB2 and AB5 structures are preferred as Mn-free alloys. These alloys are less prone to micronization during alloy degradation and exhibit high reactivity after activation.

[0153] Furthermore, in alkaline secondary batteries, for nickel-zinc secondary batteries that use zinc as the active material in the negative electrode, the presence of Mn in the negative electrode is often undesirable in terms of storage characteristics, so it is preferable to use a structure in which Mn is dissolved in the positive electrode.

Claims

1. An alkaline secondary battery, comprising: Using nickel hydroxide as the active material in the positive electrode, Negative electrode, and alkaline electrolyte, The positive electrode contains 3.0% by weight or more of a ytterbium compound relative to the nickel hydroxide. The nickel hydroxide contains Mn dissolved in it. The amount of alkaline electrolyte relative to the positive electrode capacity is 1.5 mL / Ah or more.

2. The alkaline secondary battery according to claim 1, wherein, The active material of the negative electrode is a hydrogen storage alloy, or zinc and zinc oxide.

3. The alkaline secondary battery according to claim 1, wherein, The active material of the negative electrode is a hydrogen storage alloy that does not contain Mn.

4. The alkaline secondary battery according to claim 1, wherein, The positive electrode contains less than 5.0% by weight of a ytterbium compound relative to the nickel hydroxide. The amount of alkaline electrolyte is less than 3.0 mL / Ah relative to the positive electrode capacity.

5. A nickel-metal hydride secondary battery, comprising: Using nickel hydroxide as the active material in the positive electrode, Anode with hydrogen storage alloy as active material, and alkaline electrolyte, The positive electrode contains 3.0% by weight or more of a ytterbium compound relative to the nickel hydroxide. The negative electrode contains Mn. The amount of alkaline electrolyte relative to the positive electrode capacity is 1.5 mL / Ah or more.

6. The nickel-metal hydride secondary battery according to claim 5, wherein, The hydrogen storage alloy does not contain Mn.

7. The alkaline secondary battery according to claim 5, wherein, The positive electrode contains less than 5.0% by weight of a ytterbium compound relative to the nickel hydroxide. The amount of alkaline electrolyte is less than 3.0 mL / Ah relative to the positive electrode capacity.

8. A method for manufacturing an alkaline secondary battery, the alkaline secondary battery comprising a positive electrode using nickel hydroxide as the active material, a negative electrode, and an alkaline electrolyte, the method comprising: A positive electrode slurry is prepared by adding 3.0% by weight or more of a ytterbium compound relative to the nickel hydroxide containing Mn in solid solution. This positive electrode slurry is then coated or filled onto a conductive core material to fabricate the positive electrode. The alkaline electrolyte is injected in such a manner that the amount of alkaline electrolyte relative to the positive electrode capacity is 1.5 mL / Ah or more.

9. The method for manufacturing an alkaline secondary battery according to claim 8, wherein, The active material of the negative electrode uses a hydrogen storage alloy, or zinc and zinc oxide.

10. The method for manufacturing an alkaline secondary battery according to claim 8, wherein, The active material of the negative electrode uses a hydrogen storage alloy that does not contain Mn.

11. The method for manufacturing an alkaline secondary battery according to claim 8, wherein, In the preparation of the positive electrode slurry, the amount of ytterbium compound added relative to the nickel hydroxide containing dissolved Mn is 5.0% by weight or less. The alkaline electrolyte is injected in such a manner that the amount of alkaline electrolyte is less than 3.0 mL / Ah relative to the capacity of the positive electrode.

12. A method for manufacturing a nickel-metal hydride secondary battery, the nickel-metal hydride secondary battery comprising a positive electrode with nickel hydroxide as the active material, a negative electrode with a hydrogen storage alloy as the active material, and an alkaline electrolyte, the method comprising: A positive electrode slurry is prepared by adding at least 3.0% by weight of a ytterbium compound relative to the nickel hydroxide, filling the positive electrode slurry into a conductive core material, and then drying and rolling it to produce the positive electrode. Mn or a Mn compound is added to the hydrogen storage alloy to prepare a negative electrode slurry. The negative electrode slurry is then coated onto a conductive core material, dried, and rolled to produce the negative electrode. The alkaline electrolyte is injected in such a manner that the amount of alkaline electrolyte relative to the positive electrode capacity is 1.5 mL / Ah or more.

13. The method for manufacturing a nickel-metal hydride secondary battery according to claim 12, wherein, The hydrogen storage alloy does not contain Mn.

14. The method for manufacturing a nickel-metal hydride secondary battery according to claim 12, wherein, In the preparation of the positive electrode slurry, the amount of ytterbium compound added relative to the nickel hydroxide is 5.0% by weight or less. The alkaline electrolyte is injected in such a manner that the amount of alkaline electrolyte is less than 3.0 mL / Ah relative to the capacity of the positive electrode.

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