JP7038285B2

JP7038285B2 - Magnesium air battery

Info

Publication number: JP7038285B2
Application number: JP2018009478A
Authority: JP
Inventors: 始男小島; 剛安田; 和紀清水; 昭中川; 智明石黒; 栄治本保; 龍則角田; 耕児高田
Original assignee: Toyama Prefecture; Sankyo Tateyama Inc
Current assignee: Toyama Prefecture; Sankyo Tateyama Inc
Priority date: 2017-01-27
Filing date: 2018-01-24
Publication date: 2022-03-18
Anticipated expiration: 2038-01-24
Also published as: JP2018125283A

Description

特許法第３０条第２項適用富山県工業技術センター研究報告Ｎｏ．３０２０１６第１１５頁にて公開Application of Article 30, Paragraph 2 of the Patent Law Toyama Prefectural Industrial Technology Center Research Report No. 30 2016 Published on page 115

本発明は、マグネシウム空気電池に関する。 The present invention relates to a magnesium-air battery.

従来より、負極にマグネシウム又はマグネシウム合金を用い、正極に空気中の酸素を用いるマグネシウム空気電池が知られている。マグネシウム空気電池は、電解液が強い酸性であると負極で自己放電が起こり、電解液が強いアルカリ性であると、電気を通さない反応生成物（水酸化マグネシウム）が生成され、負極表面がこの反応生成物で覆われると電池反応が停止する。そのため、理論上発電できる放電容量の半分程度の電力しか取り出せない問題があった。
特許文献１には、マグネシウム空気電池の電解液中にリン酸化合物、硫化物、アミノカルボン酸系塩、ホスホン酸系塩、グルコン酸塩のうち少なくとも２種類以上配合することが記載されている。この場合、電解液に複数のものを含有させる必要があり、それら含有物の管理が大変であった。 Conventionally, a magnesium-air battery using magnesium or a magnesium alloy for the negative electrode and oxygen in the air for the positive electrode has been known. In a magnesium-air battery, self-discharge occurs at the negative electrode when the electrolytic solution is strongly acidic, and when the electrolytic solution is strongly alkaline, a reaction product (magnesium hydroxide) that does not conduct electricity is generated, and the negative electrode surface reacts with this reaction. Battery reaction ceases when covered with product. Therefore, there is a problem that only about half of the discharge capacity that can be generated theoretically can be taken out.
Patent Document 1 describes that at least two or more of a phosphoric acid compound, a sulfide, an aminocarboxylic acid salt, a phosphonic acid salt, and a gluconate salt are blended in an electrolytic solution of a magnesium air cell. In this case, it was necessary to contain a plurality of substances in the electrolytic solution, and it was difficult to manage those contained substances.

特開２０１５－８２４９７号公報Japanese Unexamined Patent Publication No. 2015-82497

本発明は以上に述べた実情に鑑み、電解液中の含有物の管理が容易で、且つ効率の良いマグネシウム空気電池の提供を目的とする。 In view of the above-mentioned circumstances, it is an object of the present invention to provide a magnesium-air battery in which the contents in the electrolytic solution can be easily managed and efficiently.

上記の課題を達成するために請求項１記載の発明によるマグネシウム空気電池は、正極と負極と電解液とを備え、正極は、空気を通し且つ導電性を有するものであり、負極は、マグネシウム又はマグネシウム合金からなり、電解液は、塩化ナトリウム水溶液にリン酸を所定濃度含有し、ｐＨが初期状態で４．０～１１．２であることを特徴とする。なお、電解液は、リン酸の化合物を含有するものでもよく、リン酸基を有し、電解液中でリン酸イオンを生じさせるものであればよい。 In order to achieve the above problems, the magnesium pneumatic battery according to the invention according to claim 1 includes a positive electrode, a negative electrode, and an electrolytic solution, the positive electrode is one that allows air to pass through and has conductivity, and the negative electrode is magnesium or The electrolytic solution is made of a magnesium alloy, contains a predetermined concentration of phosphoric acid in an aqueous sodium chloride solution, and has a pH of 4.0 to 11.2 in the initial state . The electrolytic solution may contain a compound of phosphoric acid , and may have a phosphoric acid group and generate phosphoric acid ions in the electrolytic solution.

請求項２記載の発明によるマグネシウム空気電池は、正極と負極と電解液とを備え、正極は、空気を通し且つ導電性を有するものであり、負極は、マグネシウム又はマグネシウム合金からなり、電解液は、塩化ナトリウム水溶液にリン酸二水素カリウムを所定濃度含有し、ｐＨが初期状態で４．３～１０．１であることを特徴とする。The magnesium air battery according to the invention according to claim 2 includes a positive electrode, a negative electrode, and an electrolytic solution, the positive electrode allows air to pass through and has conductivity, the negative electrode is made of magnesium or a magnesium alloy, and the electrolytic solution is. The aqueous sodium chloride solution contains potassium dihydrogen phosphate at a predetermined concentration, and the pH is 4.3 to 10.1 in the initial state.

請求項３記載の発明によるマグネシウム空気電池は、正極と負極と電解液とを備え、正極は、空気を通し且つ導電性を有するものであり、負極は、マグネシウム又はマグネシウム合金からなり、電解液は、塩化ナトリウム水溶液にリン酸とカリウムを所定濃度含有し、ｐＨが初期状態で３．２～１１．７であることを特徴とする。なお、電解液は、リン酸とカリウムの化合物を含有するものでもよく、リン酸を含有するものの場合でいえば、リン酸基を有し、電解液中でリン酸イオンを生じさせるものであればよい。The magnesium air battery according to the invention according to claim 3 includes a positive electrode, a negative electrode, and an electrolytic solution, the positive electrode allows air to pass through and has conductivity, the negative electrode is made of magnesium or a magnesium alloy, and the electrolytic solution is. , The sodium chloride aqueous solution contains phosphoric acid and potassium at predetermined concentrations, and the pH is 3.2 to 11.7 in the initial state. The electrolytic solution may contain a compound of phosphoric acid and potassium, and in the case of a solution containing phosphoric acid, it may have a phosphoric acid group and generate phosphoric acid ions in the electrolytic solution. Just do it.

請求項４記載の発明によるマグネシウム空気電池は、正極と負極と電解液とを備え、正極は、空気を通し且つ導電性を有するものであり、負極は、マグネシウム又はマグネシウム合金からなり、電解液は、塩化ナトリウム水溶液にカリウムとホウ酸を所定濃度含有し、ｐＨが初期状態で４．２～８．０であることを特徴とする。なお、電解液は、カリウムとホウ酸の化合物を含有するものであってもよい。The magnesium air battery according to the invention of claim 4 includes a positive electrode, a negative electrode, and an electrolytic solution, the positive electrode allows air to pass through and has conductivity, the negative electrode is made of magnesium or a magnesium alloy, and the electrolytic solution is. , The sodium chloride aqueous solution contains potassium and boric acid at predetermined concentrations, and the pH is 4.2 to 8.0 in the initial state. The electrolytic solution may contain a compound of potassium and boric acid.

請求項１記載の発明によるマグネシウム空気電池は、電解液が塩化ナトリウム水溶液にリン酸を所定濃度含有し、ｐＨが初期状態で４．０～１１．２であることにより、放電容量のロスを防ぎ、効率良く電力を取り出すことができる。また電解液は、塩化ナトリウム水溶液にリン酸だけを含有させたものでよいため、含有物の管理が容易である。 The magnesium-air battery according to the invention according to claim 1 prevents loss of discharge capacity because the electrolytic solution contains phosphoric acid in a sodium chloride aqueous solution at a predetermined concentration and the pH is 4.0 to 11.2 in the initial state. , Power can be taken out efficiently. Further, since the electrolytic solution may be a sodium chloride aqueous solution containing only phosphoric acid , it is easy to manage the contents.

請求項２記載の発明によるマグネシウム空気電池は、電解液が塩化ナトリウム水溶液にリン酸二水素カリウムを所定濃度含有し、ｐＨが初期状態で４．３～１０．１であることにより、放電容量のロスを防ぎ、効率良く電力を取り出すことができる。また電解液は、塩化ナトリウム水溶液にリン酸二水素カリウムを含有させるだけでよく、しかもリン酸二水素カリウムは粉末状のため、保管や電解液に溶かす際の取扱いが容易である。The magnesium-air battery according to the invention according to claim 2 has a discharge capacity because the electrolytic solution contains potassium dihydrogen phosphate in a sodium chloride aqueous solution at a predetermined concentration and the pH is 4.3 to 10.1 in the initial state. It is possible to prevent loss and efficiently extract power. Further, the electrolytic solution only needs to contain potassium dihydrogen phosphate in an aqueous solution of sodium chloride, and since potassium dihydrogen phosphate is in the form of powder, it is easy to store and handle when dissolving in the electrolytic solution.

請求項３記載の発明によるマグネシウム空気電池は、電解液が塩化ナトリウム水溶液にリン酸とカリウムを所定濃度含有し、ｐＨが初期状態で３．２～１１．７であることにより、放電容量のロスを防ぎ、効率良く電力を取り出すことができる。The magnesium-air battery according to the invention according to claim 3 has a loss of discharge capacity because the electrolytic solution contains a predetermined concentration of phosphoric acid and potassium in an aqueous sodium chloride solution and the pH is 3.2 to 11.7 in the initial state. Can be prevented and power can be taken out efficiently.

請求項４記載の発明によるマグネシウム空気電池は、電解液が塩化ナトリウム水溶液にカリウムとホウ酸を所定濃度含有し、ｐＨが初期状態で４．２～８．０であることにより、放電容量のロスを防ぎ、効率良く電力を取り出すことができる。The magnesium-air battery according to the invention according to claim 4 has a loss of discharge capacity because the electrolytic solution contains a predetermined concentration of potassium and boric acid in an aqueous sodium chloride solution and the pH is 4.2 to 8.0 in the initial state. Can be prevented and power can be taken out efficiently.

本発明に係るマグネシウム空気電池について行った実験の結果をまとめた表（実施例）である。It is a table (example) summarizing the result of the experiment which performed on the magnesium-air battery which concerns on this invention. 本発明に係るマグネシウム空気電池について行った実験の結果をまとめた表（比較例）である。It is a table (comparative example) summarizing the results of the experiment performed on the magnesium-air battery according to the present invention. 電解液にリン酸を含有する場合のｐＨと放電容量の関係を示すグラフである。It is a graph which shows the relationship between pH and discharge capacity when phosphoric acid is contained in an electrolytic solution. 電解液にリン酸二水素カリウムを含有する場合のｐＨと放電容量の関係を示すグラフである。It is a graph which shows the relationship between pH and discharge capacity when potassium dihydrogen phosphate is contained in an electrolytic solution. 電解液にリン酸＋塩化カリウム、ホウ酸＋塩化カリウムを含有する場合のｐＨと放電容量の関係を示すグラフである。It is a graph which shows the relationship between pH and discharge capacity when phosphoric acid + potassium chloride and boric acid + potassium chloride are contained in an electrolytic solution. 本発明の一実施形態に係るマグネシウム空気電池を模式的に示す図である。It is a figure which shows typically the magnesium-air battery which concerns on one Embodiment of this invention.

以下、本発明の実施の形態を図面に基づいて説明する。図５は、本発明に係るマグネシウム空気電池の一実施形態を示している。本マグネシウム空気電池は、電解液３を収納する容器４と、電解液３に浸漬して設けた正極１と負極２を備える。
正極１は、いわゆる空気極であって、空気を通し且つ導電性を有するものとしてある。正極１は、例えばポーラス構造を有するカーボン繊維を用いることができる。正極１は、電解液３を収納する容器４の側壁に沿って設けてあり、容器４の側壁に設けた開口より容器４の外の空気と接している。
負極２は、マグネシウム又はマグネシウム合金からなる。マグネシウム合金としては、種々のものを用いることができるが、例えば汎用マグネシウム合金であるＡＺ３１や、Ｃａを添加して難燃性を持たせたＡＭＸ６０１を用いることができる。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 5 shows an embodiment of a magnesium-air battery according to the present invention. The magnesium-air battery includes a container 4 for storing the electrolytic solution 3, and a positive electrode 1 and a negative electrode 2 provided by immersing the electrolytic solution 3 in the container 4.
The positive electrode 1 is a so-called air electrode, which allows air to pass through and has conductivity. For the positive electrode 1, for example, carbon fiber having a porous structure can be used. The positive electrode 1 is provided along the side wall of the container 4 for storing the electrolytic solution 3, and is in contact with the air outside the container 4 through the opening provided in the side wall of the container 4.
The negative electrode 2 is made of magnesium or a magnesium alloy. Various magnesium alloys can be used. For example, AZ31, which is a general-purpose magnesium alloy, and AMX601, which is made flame-retardant by adding Ca, can be used.

電解液３は、塩化ナトリウム水溶液にリン酸又はカリウム又はホウ酸を所定濃度含有し、ｐＨを４～１１としてある。なお、電解液３のｐＨは、初期状態で４～１１であればよい。塩化ナトリウム水溶液は、水に塩を溶かしたものでもよいが、海水を用いることもできる。 The electrolytic solution 3 contains a predetermined concentration of phosphoric acid, potassium or boric acid in an aqueous sodium chloride solution, and has a pH of 4 to 11. The pH of the electrolytic solution 3 may be 4 to 11 in the initial state. The sodium chloride aqueous solution may be one in which a salt is dissolved in water, but seawater may also be used.

電解液３は、ｐＨを４～１１に調整するためのｐＨ調整剤を含有することができる。ｐＨ調整剤としては、例えばＮａＯＨ、ＮＨ_３を用いることができる。電解液３にリン酸等を含有させたことで、そのままではｐＨが４未満となる場合でも、ｐＨ調整剤を用いることでｐＨを４～１１に調整できる。 The electrolytic solution 3 can contain a pH adjusting agent for adjusting the pH to 4 to 11. As the pH adjuster, for example, NaOH or NH ₃ can be used. By containing phosphoric acid or the like in the electrolytic solution 3, the pH can be adjusted to 4 to 11 by using a pH adjuster even if the pH is less than 4 as it is.

図１－１，１－２の表に示すように、負極合金種、電解液組成、初期ｐＨを変化させ、放電容量への影響を調べた。放電容量の測定は、３０ｍＡ／ｃｍ^２で定電流放電させ、負極２が完全に溶解、または電圧１０ｍＶ以下で終了した。反応面積は、正極１が１．０ｃｍ^２、負極２が１．５ｃｍ^２、正極と負極の間隔は一定とした。電解液３の量は、４０ｍｌとした。放電容量の測定は、恒温恒湿機内で２５℃の環境で行った。
電解液が塩化ナトリウム水溶液単体の場合の放電容量１４９０ｍＡｈ／ｇ（比較例２参照）に対して３％ｕｐの１５３５ｍＡｈ／ｇを基準とし、放電容量がそれより大きいものを効果有りとした。
実施例１－１～１－２４は、負極にＡＺ３１を用い、電解液として塩化ナトリウム水溶液にリン酸を添加したものであり、放電容量が基準値を超えるものである。比較例１－１～１－１５はその比較例であって、電解液として塩化ナトリウム水溶液にリン酸を添加し、放電容量が基準値を超えなかったものである。
実施例２－１～２－８は、負極にＡＺ３１又はＡＭＸ６０１を用い、電解液として塩化ナトリウム水溶液にリン酸二水素カリウムを添加したものであり、放電容量が基準値を超えるものである。比較例２－１～２－４はその比較例であって、電解液として塩化ナトリウム水溶液にリン酸二水素カリウムを添加し、放電容量が基準値を超えなかったものである。
実施例３－１～３－４は、負極にＡＺ３１を用い、電解液として塩化ナトリウム水溶液にリン酸と塩化カリウムを添加したものであり、放電容量が基準値を超えるものである。比較例３－１はその比較例であって、電解液として塩化ナトリウム水溶液にリン酸と塩化カリウムを添加し、放電容量が基準値を超えなかったものである。
実施例４－１～４－２は、負極にＡＺ３１を用い、電解液として塩化ナトリウム水溶液にホウ酸と塩化カリウムを添加したものであり、放電容量が基準値を超えるものである。比較例４－１～４－２はその比較例であって、電解液として塩化ナトリウム水溶液にホウ酸と塩化カリウムを添加し、放電容量が基準値を超えなかったものである。
比較例１～６は、負極２にＡＺ３１又はＡＭＸ６０１を用い、電解液３を単なる塩化ナトリウム水溶液（リン酸、カリウム、ホウ酸の何れも含有しないもの）としたものである。 As shown in the tables of FIGS. 1-1, 1-2, the negative electrode alloy type, the electrolytic solution composition, and the initial pH were changed, and the influence on the discharge capacity was investigated. The measurement of the discharge capacity was completed by constant current discharge at 30 mA / cm ² and the negative electrode 2 was completely melted or the voltage was 10 mV or less. The reaction area was 1.0 cm ² for the positive electrode 1, 1.5 cm ² for the negative electrode 2, and the distance between the positive electrode and the negative electrode was constant. The amount of the electrolytic solution 3 was 40 ml. The discharge capacity was measured in a constant temperature and humidity chamber at 25 ° C.
When the electrolytic solution was a sodium chloride aqueous solution alone, the discharge capacity was 1490 mAh / g (see Comparative Example 2), and the discharge capacity was 1535 mAh / g, which was 3% up, and the one having a larger discharge capacity was considered to be effective.
In Examples 1-1 to 1-24, AZ31 is used as the negative electrode, and phosphoric acid is added to the sodium chloride aqueous solution as the electrolytic solution, and the discharge capacity exceeds the reference value. Comparative Examples 1-1 to 1-15 are Comparative Examples in which phosphoric acid was added to an aqueous sodium chloride solution as an electrolytic solution, and the discharge capacity did not exceed the reference value.
In Examples 2-1 to 2-8, AZ31 or AMX601 was used as the negative electrode, and potassium dihydrogen phosphate was added to the sodium chloride aqueous solution as the electrolytic solution, and the discharge capacity exceeded the reference value. Comparative Examples 2-1 to 2-4 are comparative examples in which potassium dihydrogen phosphate was added to an aqueous sodium chloride solution as an electrolytic solution, and the discharge capacity did not exceed the reference value.
In Examples 3-1 to 3-4, AZ31 is used as the negative electrode, and phosphoric acid and potassium chloride are added to the sodium chloride aqueous solution as the electrolytic solution, and the discharge capacity exceeds the reference value. Comparative Example 3-1 is a comparative example in which phosphoric acid and potassium chloride were added to an aqueous sodium chloride solution as an electrolytic solution, and the discharge capacity did not exceed the reference value.
In Examples 4-1 to 4-2, AZ31 is used as the negative electrode, boric acid and potassium chloride are added to the sodium chloride aqueous solution as the electrolytic solution, and the discharge capacity exceeds the reference value. Comparative Examples 4-1 to 4-2 are the comparative examples in which boric acid and potassium chloride were added to an aqueous sodium chloride solution as an electrolytic solution, and the discharge capacity did not exceed the reference value.
In Comparative Examples 1 to 6, AZ31 or AMX601 was used for the negative electrode 2, and the electrolytic solution 3 was simply an aqueous sodium chloride solution (which does not contain any of phosphoric acid, potassium, and boric acid).

図２に示すように、リン酸を添加した場合（実施例１－１～１－２４、比較例１－１～１－１５）のｐＨと放電容量をグラフ上にプロットし、リン酸の濃度毎に近似曲線（二次曲線）を引き、濃度毎の近似曲線と基準放電容量（＝１５３５ｍＡｈ／ｇ）との交点より、リン酸の濃度毎の「効果有り」となるｐＨの範囲を求めた。同図より、リン酸の濃度が０．０５ｍｏｌ／ＬのときはｐＨが３．０～１２．２、リン酸の濃度が０．２０ｍｏｌ／ＬのときはｐＨが４．０～１２．９、リン酸の濃度が０．２５ｍｏｌ／ＬのときはｐＨが３．３～１１．２、リン酸の濃度が０．３０ｍｏｌ／ＬのときはｐＨが４．０～１１．７、リン酸の濃度が０．３５ｍｏｌ／ＬのときはｐＨが３．８～１１．８で、放電容量を向上する効果がある。したがって、上記の濃度毎のｐＨの範囲の重複する範囲であるｐＨ４．０～１１．２であれば、リン酸の濃度が０．０５～０．３５ｍｏｌ／Ｌの何れの濃度であっても、放電容量を向上する効果がある。 As shown in FIG. 2, the pH and discharge capacity when phosphoric acid was added (Examples 1-1 to 1-24, Comparative Examples 1-1 to 1-15) were plotted on a graph, and the concentration of phosphoric acid was plotted. An approximate curve (quadratic curve) was drawn for each concentration, and the range of pH that was "effective" for each concentration of phosphoric acid was obtained from the intersection of the approximate curve for each concentration and the reference discharge capacity (= 1535 mAh / g). .. From the figure, when the concentration of phosphoric acid is 0.05 mol / L, the pH is 3.0 to 12.2, and when the concentration of phosphoric acid is 0.20 mol / L, the pH is 4.0 to 12.9. When the concentration of phosphoric acid is 0.25 mol / L, the pH is 3.3 to 11.2, when the concentration of phosphoric acid is 0.30 mol / L, the pH is 4.0 to 11.7, and the concentration of phosphoric acid. When the pH is 0.35 mol / L, the pH is 3.8 to 11.8, which has the effect of improving the discharge capacity. Therefore, if the pH is 4.0 to 11.2, which is an overlapping range of the pH ranges for each concentration, the concentration of phosphoric acid may be any concentration of 0.05 to 0.35 mol / L. It has the effect of improving the discharge capacity.

図３に示すように、リン酸二水素カリウムを添加した場合（実施例２－１～２－８、比較例２－１～２－４）のｐＨと放電容量をグラフ上にプロットし、リン酸二水素カリウムの濃度毎に近似曲線を引き、濃度毎の近似曲線と基準放電容量との交点より、リン酸二水素カリウムの濃度毎の「効果有り」となるｐＨの範囲を求めた。同図より、リン酸二水素カリウムの濃度が０．２０ｍｏｌ／ＬのときはｐＨが３．０～１０．１、リン酸二水素カリウムの濃度が０．３０ｍｏｌ／ＬのときはｐＨが４．３～１１．２で、放電容量を向上する効果がある。したがって、上記の濃度毎のｐＨの範囲の重複する範囲であるｐＨ４．３～１０．１であれば、リン酸二水素カリウムの濃度が０．２０～０．３０ｍｏｌ／Ｌの何れの濃度であっても、放電容量を向上する効果がある。 As shown in FIG. 3, the pH and discharge capacity when potassium dihydrogen phosphate was added (Examples 2-1 to 2-8, Comparative Examples 2-1 to 2-4) were plotted on a graph and phosphorus was added. An approximate curve was drawn for each concentration of potassium dihydrogen acid, and the pH range that was "effective" for each concentration of potassium dihydrogen phosphate was obtained from the intersection of the approximate curve for each concentration and the reference discharge capacity. From the figure, when the concentration of potassium dihydrogen phosphate is 0.20 mol / L, the pH is 3.0 to 10.1, and when the concentration of potassium dihydrogen phosphate is 0.30 mol / L, the pH is 4. From 3 to 11.2, there is an effect of improving the discharge capacity. Therefore, if the pH is 4.3 to 10.1, which is an overlapping range of the pH ranges for each concentration, the concentration of potassium dihydrogen phosphate is any concentration of 0.20 to 0.30 mol / L. However, it has the effect of improving the discharge capacity.

図４に示すように、リン酸と塩化カリウムを添加した場合（実施例３－１～３－４、比較例３－１）、ホウ酸と塩化カリウムを添加した場合（実施例４－１～４－２、比較例４－１）のｐＨと放電容量をグラフ上にプロットし、添加剤の濃度毎に近似曲を引き、濃度毎の近似曲線と基準放電容量との交点より、添加剤の濃度毎の「効果有り」となるｐＨの範囲を求めた。同図より、リン酸と塩化カリウムの濃度が０．２０ｍｏｌ／Ｌで、ｐＨが３．２～１１．７のとき、ホウ酸と塩化カリウムの濃度が０．２０ｍｏｌ／Ｌで、ｐＨが４．２～８．０のときに、放電容量を向上する効果がある。 As shown in FIG. 4, when phosphoric acid and potassium chloride were added (Examples 3-1 to 3-4, Comparative Example 3-1), and when boric acid and potassium chloride were added (Examples 4-1 to 4-1). 4-2, Plot the pH and discharge capacity of Comparative Example 4-1) on the graph, draw an approximate curve for each concentration of the additive, and use the intersection of the approximate curve for each concentration and the reference discharge capacity to determine the additive. The pH range that was "effective" for each concentration was determined. From the figure, when the concentration of phosphoric acid and potassium chloride is 0.20 mol / L and the pH is 3.2 to 11.7, the concentration of boric acid and potassium chloride is 0.20 mol / L and the pH is 4. When it is 2 to 8.0, it has the effect of improving the discharge capacity.

以上の結果より、添加剤の種類と濃度毎に「効果有り」となるｐＨの範囲をまとめると、下記の表１に示すとおりである。

Based on the above results, the pH range that is "effective" for each type and concentration of additive is summarized in Table 1 below.

塩化ナトリウム単体の場合（比較例１～６）には、負極をＡＭＸ６０１としたものの方がＡＺ３１のものよりも放電容量が大きいが、本願発明の実施例では負極がＡＺ３１の場合とＡＭＸ６０１の場合とで放電容量にあまり違いはなかった。また、ｐＨ調整剤をＮａＯＨとした場合とＮＨ_３とした場合で、放電容量の増加量に大差はなかった。
初期ｐＨを３～５に調整した実施例１－４，１－５，１－１２，１－１７，２－１，２－２，２－３，３－１，４－１は、放電実験後もｐＨが酸性領域に維持され、電解液３が白濁しない。 In the case of sodium chloride alone (Comparative Examples 1 to 6), the case where the negative electrode is AMX601 has a larger discharge capacity than that of AZ31, but in the embodiment of the present invention, the case where the negative electrode is AZ31 and the case where the negative electrode is AMX601. There was not much difference in the discharge capacity. In addition, there was no significant difference in the amount of increase in discharge capacity between the case where the pH adjuster was NaOH and the case where _NH3 was used.
Examples 1-4, 1-5, 1-12, 1-17, 2-1, 2-2, 2-3, 3-1, 4-1 in which the initial pH was adjusted to 3 to 5 are discharge experiments. After that, the pH is maintained in the acidic region, and the electrolytic solution 3 does not become cloudy.

以上に述べたように本マグネシウム空気電池は、電解液３が塩化ナトリウム水溶液にリン酸又はカリウム又はホウ酸を所定濃度含有し、ｐＨが４～１１であることにより、放電容量のロスを防ぎ、効率良く電力を取り出すことができる。これは、電解液中に含まれるリン酸又はカリウム又はホウ酸により、ｐＨを弱酸性から弱アルカリ性の間に調整しつつ、負極２表面に保護膜を形成させて負極２の溶解を抑えられるためと推察される。電解液３のｐＨが強酸性であると、負極２で自己放電が顕著に起こり、自己放電が起こると、放電量が低下する。一方、強アルカリ性であると、負極２の反応性が低下し、出力が出ない。また、ｐＨが高いと反応生成物が発生し、反応生成物は電気を通さない性質のため、負極２の表面がこれに覆われると電池反応が停止する。そこで本マグネシウム空気電池は、自己放電を抑制すると共に、負極２の反応性の低下と、反応生成物が多く発生して電池反応が阻害されるのを防止するため、電解液３のｐＨを４～１１としている。
図２～４より明らかなように、何れの添加剤の種類・濃度の場合でも、ｐＨが６～８の中性域のときに放電容量が最も大きくなる。特に、電解液３にリン酸又はリン酸二水素カリウムを０．２～０．３ｍｏｌ／ｌ含有し、ｐＨを６～８の中性域としたときに、放電容量を向上する効果が高い。本マグネシウム空気電池は、電解液３が塩化ナトリウム水溶液にリン酸又はカリウム又はホウ酸の何れか一つだけを含有させたものでもよいため、含有物の管理が容易である。
電解液３にリン酸を含有する場合と、リン酸二水素カリウムを含有する場合とでは、リン酸が液体であるのに対して、リン酸二水素カリウムは粉末状のため、保管や電解液に溶かす際の取扱いが容易である。例えば、容器４に食塩とリン酸二水素カリウムを入れておき、電気が必要なときに容器に水を入れて発電するといった使い方が可能になる。
さらに本マグネシウム空気電池は、電解液３にｐＨを４～１１に調整するためのｐＨ調整剤を含有することで、電解液３のｐＨを４～１１に調整できる。
電解液３のｐＨが初期状態で５．０以下であると、電池反応が終了した時点で電解液３が透明なまま保持される。このことは、反応を阻害する生成物が少ないことを意味し、よって電池反応が長時間持続することが期待できる。また、電解液３が白濁しないことで、電解液３を繰り返し使用できる、回収が容易といった効果が期待できる。
本マグネシウム空気電池は、電解液３に塩化ナトリウム水溶液を用いるため、水を入れない状態で保管し、必要なときに水又は海水と、リン酸又はカリウム又はホウ酸を入れるだけで発電ができ、屋台用、レジャー用電源、災害時用の電源として好適である。
本マグネシウム空気電池は、使用後に負極２を新しいものに交換するだけで、繰り返し電池として使用することができる。 As described above, in the present magnesium-air battery, the electrolytic solution 3 contains phosphoric acid, potassium or boric acid at a predetermined concentration in the sodium chloride aqueous solution, and the pH is 4 to 11 to prevent loss of discharge capacity. Power can be taken out efficiently. This is because the phosphoric acid, potassium, or boric acid contained in the electrolytic solution adjusts the pH between weakly acidic and weakly alkaline, and forms a protective film on the surface of the negative electrode 2 to suppress the dissolution of the negative electrode 2. It is inferred that. When the pH of the electrolytic solution 3 is strongly acidic, self-discharge occurs remarkably at the negative electrode 2, and when self-discharge occurs, the amount of discharge decreases. On the other hand, if it is strongly alkaline, the reactivity of the negative electrode 2 is lowered and no output is output. Further, when the pH is high, a reaction product is generated, and the reaction product does not conduct electricity. Therefore, when the surface of the negative electrode 2 is covered with the reaction product, the battery reaction is stopped. Therefore, in this magnesium-air battery, the pH of the electrolytic solution 3 is set to 4 in order to suppress self-discharge, reduce the reactivity of the negative electrode 2, and prevent a large amount of reaction products from being generated to inhibit the battery reaction. It is set to ~ 11.
As is clear from FIGS. 2 to 4, the discharge capacity becomes the largest when the pH is in the neutral range of 6 to 8, regardless of the type and concentration of the additive. In particular, when the electrolytic solution 3 contains 0.2 to 0.3 mol / l of phosphoric acid or potassium dihydrogen phosphate and the pH is in the neutral range of 6 to 8, the effect of improving the discharge capacity is high. In this magnesium-air battery, since the electrolytic solution 3 may contain only one of phosphoric acid, potassium and boric acid in an aqueous solution of sodium chloride, it is easy to manage the contents.
When the electrolytic solution 3 contains phosphoric acid and when it contains potassium dihydrogen phosphate, the phosphoric acid is a liquid, whereas the potassium dihydrogen phosphate is in the form of a powder, so that it can be stored or used as an electrolytic solution. Easy to handle when dissolving in phosphoric acid. For example, it is possible to put salt and potassium dihydrogen phosphate in the container 4 and put water in the container when electricity is needed to generate electricity.
Further, in this magnesium-air battery, the pH of the electrolytic solution 3 can be adjusted to 4 to 11 by containing a pH adjusting agent for adjusting the pH to 4 to 11 in the electrolytic solution 3.
When the pH of the electrolytic solution 3 is 5.0 or less in the initial state, the electrolytic solution 3 is kept transparent when the battery reaction is completed. This means that there are few products that inhibit the reaction, and therefore the battery reaction can be expected to last for a long time. Further, since the electrolytic solution 3 does not become cloudy, the effects that the electrolytic solution 3 can be used repeatedly and recovery can be expected can be expected.
Since this magnesium-air battery uses an aqueous solution of sodium chloride as the electrolyte 3, it can be stored without water, and power can be generated simply by adding water or seawater and phosphoric acid, potassium, or boric acid when necessary. It is suitable as a power source for stalls, leisure, and disasters.
This magnesium-air battery can be used repeatedly as a battery by simply replacing the negative electrode 2 with a new one after use.

本発明は以上に述べた実施形態に限定されない。負極には、ＡＺ３１とＡＭＸ６０１に限らず、あらゆるマグネシウム合金を用いることができる。正極は、導電性材料で空気を通すように形成してあればよく、材質は適宜変更することができ、例えば活性炭や銅を用いることもできる。正極及び負極の形状、配置は、任意である。電解液に含有させるリン酸又はカリウム又はホウ酸は、化合物の状態で含有するものであってもよく、リン酸二水素カリウム、塩化カリウムの他、種々の化合物を用いることができる。ｐＨ調整剤は、必ずしも使用しなくてもよい。 The present invention is not limited to the embodiments described above. As the negative electrode, not only AZ31 and AMX601 but also any magnesium alloy can be used. The positive electrode may be formed of a conductive material so as to allow air to pass through, and the material can be appropriately changed. For example, activated carbon or copper can be used. The shape and arrangement of the positive electrode and the negative electrode are arbitrary. The phosphoric acid, potassium or boric acid contained in the electrolytic solution may be contained in the form of a compound, and various compounds may be used in addition to potassium dihydrogen phosphate and potassium chloride. The pH regulator does not necessarily have to be used.

１正極
２負極
３電解液 1 Positive electrode 2 Negative electrode 3 Electrolyte

Claims

It is provided with a positive electrode, a negative electrode and an electrolytic solution, the positive electrode is one that allows air to pass through and has conductivity, the negative electrode is made of magnesium or a magnesium alloy, and the electrolytic solution contains a predetermined concentration of phosphoric acid in a sodium chloride aqueous solution. , A magnesium air battery characterized in that the pH is 4.0 to 11.2 in the initial state .

It is provided with a positive electrode, a negative electrode and an electrolytic solution, the positive electrode is one that allows air to pass through and has conductivity, the negative electrode is made of magnesium or a magnesium alloy, and the electrolytic solution is a sodium chloride aqueous solution containing potassium dihydrogen phosphate. A magnesium air cell containing a concentration and having a pH of 4.3 to 10.1 in the initial state .

It is provided with a positive electrode, a negative electrode and an electrolytic solution, the positive electrode is one that allows air to pass through and has conductivity, the negative electrode is made of magnesium or a magnesium alloy, and the electrolytic solution is a sodium chloride aqueous solution containing phosphoric acid and potassium. A magnesium air cell containing a concentration and having a pH of 3.2 to 11.7 in the initial state .

It is provided with a positive electrode, a negative electrode and an electrolytic solution, the positive electrode is one that allows air to pass through and has conductivity, the negative electrode is made of magnesium or a magnesium alloy, and the electrolytic solution is a sodium chloride aqueous solution containing potassium and boric acid. A magnesium air cell containing a concentration and having a pH of 4.2 to 8.0 in the initial state .