JP3588933B2 - Hydrogen storage alloy electrode for alkaline storage batteries - Google Patents
Hydrogen storage alloy electrode for alkaline storage batteries Download PDFInfo
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- JP3588933B2 JP3588933B2 JP24049696A JP24049696A JP3588933B2 JP 3588933 B2 JP3588933 B2 JP 3588933B2 JP 24049696 A JP24049696 A JP 24049696A JP 24049696 A JP24049696 A JP 24049696A JP 3588933 B2 JP3588933 B2 JP 3588933B2
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- Prior art keywords
- hydrogen storage
- storage alloy
- battery
- calcium carbonate
- hydrogen
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Description
【0001】
【発明の属する技術分野】
本発明はアルカリ蓄電池用水素吸蔵合金電極に関するものである。
【0002】
【従来の技術】
水素吸蔵合金電極を負極として用いるニッケル−水素蓄電池等のアルカリ蓄電池は、エネルギー密度が高く、環境汚染が少ないため、近年、特に注目されている。一般に水素吸蔵合金電極は、次のようにして製造する。まず、ランタンを主成分としたMm(メッシュメタル)・Ni合金等に各種の金属を添加したものを加熱溶解させたものを粉砕して水素吸蔵合金粉末を作る。次にこの水素吸蔵合金粉末とバインダとを混練して、ペーストを作り、このペーストをパンチングメタル等の集電体に充填する。そして、これを乾燥、プレスして完成する。なお、水素は電池の充電することにより水素吸蔵合金に吸蔵させる。
【0003】
【発明が解決しようとする課題】
しかしながら、水素吸蔵合金電極を負極として用いるアルカリ蓄電池は、過放電した後に通常の充放電を行うと過放電を行う前の放電容量を得ることができないという問題があった。例えば、水酸化ニッケルを主成分とした正極と組合わせたニッケル−水素蓄電池では、約−1.0Vまで過放電すると過放電を行う前の放電容量を得ることができない。これは、約−1.0Vまで過放電すると正極と負極とが転極して、水素吸蔵合金電極から酸素ガスが発生するからである。このように酸素ガスが発生すると水素吸蔵合金が酸化し、劣化する。その結果、水素吸蔵合金の水素吸蔵特性が低下して、放電容量が回復しなくなる(過放電を行う前の放電容量を得ることができない)。このように水素吸蔵合金電極においては、特に過放電後の放電容量の回復が困難であった。
【0004】
本発明の目的は、過放電を行っても、水素吸蔵合金電極上の酸素ガスの発生を抑制して放電容量を回復できるアルカリ蓄電池用水素吸蔵合金電極を提供することにある。
【0005】
【課題を解決するための手段】
本発明は、水素吸蔵合金を含有する活物質層を有するアルカリ蓄電池用水素吸蔵合金電極を対象にして、活物質層に、炭酸カルシウム(CaCO3 )を含有させる。炭酸カルシウムを添加させると、水素吸蔵合金電極は酸素発生電位がより貴な電位になる。そこで、本発明のように、活物質層に炭酸カルシウムを含有させると、過放電を行っても、酸素ガスの発生を抑制できる。その結果、水素吸蔵合金の酸化を抑制でき、水素吸蔵合金の水素吸蔵特性の低下を抑制できる。また、炭酸カルシウムはアルカリ溶液中でも安定している。
【0006】
炭酸カルシウムの含有量は、水素吸蔵合金に対して0.1〜3.0重量%とするのが好ましい。炭酸カルシウムの含有量が水素吸蔵合金に対して0.1重量%以上になると過放電前の放電容量に対する過放電後の放電容量の割合(回復容量割合)が高くなる。また、炭酸カルシウムの含有量が水素吸蔵合金粉末に対して3.0重量%を超えると電池の低温での温度特性(低温/常温の放電容量比)が低下して電池特性が低下する。
【0007】
【発明の実施の形態】
試験に用いた各アルカリ蓄電池用水素吸蔵合金電極を次のようにして製造した。まず、ランタンを主体としたMm(メッシュメタル)・Ni合金(MmNi5 :Mm=La55Ce30Pr3 Nd12)に所定量のCo、Al、Mnを添加したものをアーク溶解で加熱溶解した後、これを冷却した。そして、これをボールミルを用いて平均径100μm程度の粉末に機械粉砕して水素吸蔵合金粉末(MmNi3.5 Co0.7 Al0.3 Mn0.5 粉末)を得た。次に水素吸蔵合金粉末と、該水素吸蔵合金粉末に対して0.5重量%のニッケル粉末と、該水素吸蔵合金粉末に対してそれぞれ0.1重量%、0.5重量%、1.0重量%、2.0重量%、3.0重量%、4.0重量%、5.0重量%の炭酸カルシウム(CaCO3 )粉末と、該水素吸蔵合金粉末に対して1.0重量%のエチレン−酢酸ビニル共重合体とメチルセルロースとの混合物からなるバインダとを混練して粘度20,000mPa・sの複数のペーストを作った。次に各ペーストを厚み約0.1mmのパンチングメタルからなる集電体の両面にドクターブレード法により塗着してから乾燥、プレスを行い厚み約0.35mmの水素吸蔵合金極板を構成する水素吸蔵合金電極を得た。また炭酸カルシウム粉末を添加せずその他は、上記と同じ方法で比較例の水素吸蔵合金極板も得た。
【0008】
次に各極板の特性を調べるために密閉形ニッケル−水素蓄電池からなるアルカリ蓄電池を作った。最初に正極板を次のようにして作った。まず水酸化ニッケル粉末と、該水酸化ニッケル粉末に対して0.45重量%のカルボキシメチルセルロースからなる結着剤とを混練してペーストを作った。次にこのペーストを発泡ニッケルからなる集電体に充填してから乾燥、プレス、裁断を行って容量1300mAhの正極板を作った。次に各負極板(水素吸蔵合金極板)をナイロン製の不織布からなるセパレータを介して正極板とそれぞれ巻回して極板群を作った。次に各極板群を円筒形電池容器に挿入後、極板群に濃度31重量%の水酸化カリウム水溶液からなる電解液を注液して公称容量1300mAhの正極容量規制の密閉形ニッケル−水素蓄電池を作った。そして、各電池に公知の活性化処理を施し後、電池周囲温度20℃において、0.1CmAの電流で16時間充電し、0.2CmAの電流で電池電圧が1.0Vになるまで放電する充放電を数回繰り返した。この充電により、水素吸蔵合金極板に水素が吸蔵される。そして、次に実験1及び2を行った。
【0009】
(実験1)
電池周囲温度20℃において、各電池を0.2CmAの電流で−1.0Vになるまで過放電した。そして、過放電後に0.1CmAの電流で16時間充電してから0.2CmAの電流で1.0Vになるまで放電した。これにより過放電前の放電容量に対する過放電後の放電容量の割合(回復容量割合)を求めて、水素吸蔵合金粉末に対する炭酸カルシウム量と回復容量割合との関係を調べた。表1はその測定結果を示している。
【0010】
【表1】
本表より炭酸カルシウムが僅かに含まれるだけで回復容量割合が大きくなり、水素吸蔵合金粉末に対して0.1重量%以上含まれると回復容量割合はほぼ一定になるのが分る。
【0011】
(実験2)
本実験では、水素吸蔵合金粉末に対する炭酸カルシウム量と電池の低温での温度特性との関係を調べた。まず、電池周囲温度−10℃において、各電池を0.1CmAの電流で16時間充電してから0.2CmAの電流で1.0Vになるまで放電して放電容量を測定した。また電池周囲温度20℃においても、各電池を0.1CmAの電流で16時間充電してから0.2CmAの電流で1.0Vになるまで放電して放電容量を測定した。そして、20℃における放電容量に対する−10℃における放電容量の割合(−10℃/20℃の放電容量比)を算出して水素吸蔵合金粉末に対する炭酸カルシウム量と−10℃/20℃の放電容量比との関係を調べた。表1にその測定結果を示す。
【0012】
本表より水素吸蔵合金粉末に対する炭酸カルシウム量が3.0重量%を超えると−10℃/20℃の放電容量比が低下して電池特性が低下するのが分る。
【0013】
以上、実験1及び2より炭酸カルシウムの含有量は、水素吸蔵合金に対して0.1〜3.0重量%とするのが好ましいのが分る。
【0014】
【発明の効果】
炭酸カルシウムは酸素過電圧を上昇させる作用を有しているため、本発明のように、活物質層に炭酸カルシウムを含有させると過放電を行っても、酸素ガスの発生を抑制できる。そのため、水素吸蔵合金の酸化を抑制できて、水素吸蔵合金の水素吸蔵特性の低下を抑制できる。その結果、電池を過放電しても放電容量を回復することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hydrogen storage alloy electrode for an alkaline storage battery.
[0002]
[Prior art]
Alkaline storage batteries such as nickel-hydrogen storage batteries using a hydrogen storage alloy electrode as a negative electrode have attracted particular attention in recent years because of their high energy density and low environmental pollution. Generally, a hydrogen storage alloy electrode is manufactured as follows. First, a hydrogen storage alloy powder is produced by pulverizing a material obtained by heating and dissolving various metals added to an Mm (mesh metal) / Ni alloy or the like containing lanthanum as a main component. Next, the hydrogen storage alloy powder and the binder are kneaded to prepare a paste, and the paste is filled into a current collector such as a punching metal. Then, it is dried and pressed to complete. Note that hydrogen is stored in the hydrogen storage alloy by charging the battery.
[0003]
[Problems to be solved by the invention]
However, an alkaline storage battery using a hydrogen storage alloy electrode as a negative electrode has a problem in that when normal charge and discharge are performed after overdischarge, a discharge capacity before overdischarge cannot be obtained. For example, in a nickel-hydrogen storage battery combined with a positive electrode mainly composed of nickel hydroxide, if overdischarged to about -1.0 V, the discharge capacity before overdischarge cannot be obtained. This is because, when overdischarged to about -1.0 V, the positive electrode and the negative electrode are inverted, and oxygen gas is generated from the hydrogen storage alloy electrode. When oxygen gas is generated in this way, the hydrogen storage alloy is oxidized and deteriorated. As a result, the hydrogen storage properties of the hydrogen storage alloy decrease, and the discharge capacity does not recover (the discharge capacity before overdischarge cannot be obtained). As described above, in the hydrogen storage alloy electrode, it was particularly difficult to recover the discharge capacity after overdischarge.
[0004]
An object of the present invention is to provide a hydrogen storage alloy electrode for an alkaline storage battery that can suppress the generation of oxygen gas on the hydrogen storage alloy electrode and recover the discharge capacity even when overdischarge is performed.
[0005]
[Means for Solving the Problems]
The present invention is directed to a hydrogen storage alloy electrode for an alkaline storage battery having an active material layer containing a hydrogen storage alloy, wherein the active material layer contains calcium carbonate (CaCO 3 ). When calcium carbonate is added, the hydrogen storage alloy electrode has a more noble oxygen generation potential. Therefore, when calcium carbonate is contained in the active material layer as in the present invention, generation of oxygen gas can be suppressed even when overdischarge is performed. As a result, the oxidation of the hydrogen storage alloy can be suppressed, and a decrease in the hydrogen storage characteristics of the hydrogen storage alloy can be suppressed. Calcium carbonate is stable even in an alkaline solution.
[0006]
The content of calcium carbonate is preferably set to 0.1 to 3.0% by weight based on the hydrogen storage alloy. When the content of calcium carbonate is 0.1% by weight or more with respect to the hydrogen storage alloy, the ratio of the discharge capacity after overdischarge to the discharge capacity before overdischarge (recovery capacity ratio) increases. On the other hand, when the content of calcium carbonate exceeds 3.0% by weight with respect to the hydrogen-absorbing alloy powder, the temperature characteristics of the battery at a low temperature (low-temperature / normal temperature discharge capacity ratio) are reduced, and the battery characteristics are reduced.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
The hydrogen storage alloy electrodes for each alkaline storage battery used in the test were manufactured as follows. First, Mm mainly composed of lanthanum (mesh metal) · Ni alloy: the (MmNi 5 Mm = La 55 Ce 30 Pr 3 Nd 12) a predetermined amount of Co, Al, a material obtained by adding Mn was heated and dissolved in an arc melting Later, it was cooled. This was mechanically pulverized into a powder having an average diameter of about 100 μm using a ball mill to obtain a hydrogen storage alloy powder (MmNi 3.5 Co 0.7 Al 0.3 Mn 0.5 powder). Next, a hydrogen storage alloy powder, 0.5% by weight nickel powder with respect to the hydrogen storage alloy powder, and 0.1% by weight, 0.5% by weight, and 1.0% by weight with respect to the hydrogen storage alloy powder, respectively. %, 2.0% by weight, 3.0% by weight, 4.0% by weight, 5.0% by weight of calcium carbonate (CaCO 3 ) powder and 1.0% by weight based on the hydrogen storage alloy powder. A plurality of pastes having a viscosity of 20,000 mPa · s were prepared by kneading a binder composed of a mixture of an ethylene-vinyl acetate copolymer and methyl cellulose. Next, each paste is applied to both sides of a current collector made of punching metal having a thickness of about 0.1 mm by a doctor blade method, and then dried and pressed to form a hydrogen absorbing alloy plate having a thickness of about 0.35 mm. An occlusion alloy electrode was obtained. A hydrogen-absorbing alloy electrode plate of a comparative example was also obtained in the same manner as described above except that the calcium carbonate powder was not added.
[0008]
Next, an alkaline storage battery composed of a sealed nickel-hydrogen storage battery was manufactured to examine the characteristics of each electrode plate. First, a positive electrode plate was made as follows. First, a paste was prepared by kneading a nickel hydroxide powder and a binder made of carboxymethyl cellulose at 0.45% by weight based on the nickel hydroxide powder. Next, this paste was filled in a current collector made of foamed nickel, and then dried, pressed, and cut to produce a positive electrode plate having a capacity of 1300 mAh. Next, each negative electrode plate (hydrogen storage alloy electrode plate) was wound around a positive electrode plate via a separator made of a nonwoven fabric made of nylon to form an electrode plate group. Next, after inserting each electrode group into a cylindrical battery container, an electrolyte composed of an aqueous solution of potassium hydroxide having a concentration of 31% by weight is injected into the electrode group to form a sealed nickel-hydrogen having a nominal capacity of 1300 mAh and a positive electrode capacity regulated. I made a storage battery. After performing a known activation process on each battery, the battery is charged at a current of 0.1 CmA for 16 hours at a battery ambient temperature of 20 ° C., and discharged at a current of 0.2 CmA until the battery voltage reaches 1.0 V. The discharge was repeated several times. By this charging, hydrogen is stored in the hydrogen storage alloy electrode plate. Then, experiments 1 and 2 were performed.
[0009]
(Experiment 1)
At a battery ambient temperature of 20 ° C., each battery was overdischarged at a current of 0.2 CmA until it reached −1.0 V. After the overdischarge, the battery was charged with a current of 0.1 CmA for 16 hours and then discharged with a current of 0.2 CmA until the voltage reached 1.0 V. Thus, the ratio of the discharge capacity after overdischarge to the discharge capacity before overdischarge (recovery capacity ratio) was obtained, and the relationship between the amount of calcium carbonate and the recovery capacity ratio with respect to the hydrogen storage alloy powder was examined. Table 1 shows the measurement results.
[0010]
[Table 1]
From this table, it can be seen that the recovery capacity ratio is increased when calcium carbonate is slightly contained, and the recovery capacity ratio becomes substantially constant when the content is 0.1% by weight or more based on the hydrogen storage alloy powder.
[0011]
(Experiment 2)
In this experiment, the relationship between the amount of calcium carbonate with respect to the hydrogen storage alloy powder and the temperature characteristics of the battery at a low temperature was examined. First, at a battery ambient temperature of −10 ° C., each battery was charged with a current of 0.1 CmA for 16 hours, and then discharged with a current of 0.2 CmA until the voltage reached 1.0 V, and the discharge capacity was measured. At a battery ambient temperature of 20 ° C., each battery was charged at a current of 0.1 CmA for 16 hours and then discharged at a current of 0.2 CmA until the voltage reached 1.0 V, and the discharge capacity was measured. Then, the ratio of the discharge capacity at −10 ° C. to the discharge capacity at 20 ° C. (ratio of the discharge capacity at −10 ° C./20° C.) is calculated, and the amount of calcium carbonate relative to the hydrogen storage alloy powder and the discharge capacity at −10 ° C./20° C. The relationship with the ratio was examined. Table 1 shows the measurement results.
[0012]
From this table, it can be seen that when the amount of calcium carbonate with respect to the hydrogen storage alloy powder exceeds 3.0% by weight, the discharge capacity ratio of −10 ° C./20° C. decreases and battery characteristics deteriorate.
[0013]
As described above, it can be seen from Experiments 1 and 2 that the content of calcium carbonate is preferably set to 0.1 to 3.0% by weight based on the hydrogen storage alloy.
[0014]
【The invention's effect】
Since calcium carbonate has an effect of increasing oxygen overvoltage, generation of oxygen gas can be suppressed even when overdischarge is performed by adding calcium carbonate to the active material layer as in the present invention. Therefore, the oxidation of the hydrogen storage alloy can be suppressed, and a decrease in the hydrogen storage characteristics of the hydrogen storage alloy can be suppressed. As a result, the discharge capacity can be recovered even when the battery is over-discharged.
Claims (2)
前記活物質層には、炭酸カルシウムが含有されていることを特徴とするアルカリ蓄電池用水素吸蔵合金電極。In a hydrogen storage alloy electrode for an alkaline storage battery having an active material layer containing a hydrogen storage alloy,
A hydrogen storage alloy electrode for an alkaline storage battery, wherein the active material layer contains calcium carbonate.
Priority Applications (1)
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JP24049696A JP3588933B2 (en) | 1996-09-11 | 1996-09-11 | Hydrogen storage alloy electrode for alkaline storage batteries |
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JP24049696A JP3588933B2 (en) | 1996-09-11 | 1996-09-11 | Hydrogen storage alloy electrode for alkaline storage batteries |
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JP3588933B2 true JP3588933B2 (en) | 2004-11-17 |
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DE10337970B4 (en) * | 2003-08-19 | 2009-04-23 | Gkss-Forschungszentrum Geesthacht Gmbh | Metal-containing, hydrogen storage material and process for its preparation |
JP2009170287A (en) * | 2008-01-17 | 2009-07-30 | Mitsubishi Chemicals Corp | Electrode for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery using the same |
JP6112822B2 (en) * | 2012-10-30 | 2017-04-12 | Fdk株式会社 | Nickel metal hydride secondary battery |
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