JP3617628B2

JP3617628B2 - Anode container for sodium-sulfur battery

Info

Publication number: JP3617628B2
Application number: JP2001134458A
Authority: JP
Inventors: 孝志安藤; 洋浦上
Original assignee: NGK Insulators Ltd
Current assignee: NGK Insulators Ltd
Priority date: 2001-05-01
Filing date: 2001-05-01
Publication date: 2005-02-09
Anticipated expiration: 2021-05-01
Also published as: JP2002329525A

Description

【０００１】
【発明の属する技術分野】
本発明は、ナトリウム−硫黄電池において、陽極活物質を含浸した陽極用導電材を収容するために用いられる陽極容器に関する。
【０００２】
【従来の技術】
ナトリウム−硫黄電池は、一方に陰極活物質である溶融金属ナトリウム、他方には陽極活物質である溶融硫黄を配し、両者をナトリウムイオンに対して選択的な透過性を有するβ−アルミナ固体電解質で隔離し、３００〜３６０℃程度の温度で作動させる高温二次電池である。
【０００３】
このようなナトリウム−硫黄電池の構造は、例えば図８に示すように、陽極活物質である溶融硫黄Ｓが含浸されたグラファイトマット等の陽極用導電材１２を収容する有底円筒状の陽極容器１と、陰極活物質である溶融金属ナトリウムＮａを収容するカートリッジ（ナトリウム保護管）６と、このカートリッジ６を内部に収容し、ナトリウムイオンＮａ^＋を選択的に透過させる機能を有する有底円筒状の固体電解質管５と、カートリッジ６と固体電解質管５の間の間隙部に、そのカートリッジ６及び固体電解質管５からそれぞれ所定の間隔をおいて配設された有底円筒状の隔壁管１１からなる。
【０００４】
固体電解質管５はその開口端にガラス接合されたα−アルミナ製の絶縁リング４及び陽極筒状金具３を介して陽極容器１と結合されている。また、絶縁リング４の上端面には陰極金具８が熱圧接合され、この陰極金具８に陰極蓋９が溶接固定されている。陽極容器１の外周上部と陰極蓋９の上面には、それぞれ陽極側端子２と陰極側端子１０が設けられている。カートリッジ６の上部空間には、窒素ガスやアルゴンガス等の不活性ガスＧが所定の圧力で封入され、この不活性ガスＧによりカートリッジ６内のナトリウムＮａがカートリッジ６底部に設けられた小孔７から流出する方向へ加圧されている。
【０００５】
このような構造を有するナトリウム−硫黄電池において、放電時にはカートリッジ６の小孔７から供給されるナトリウムＮａが、隔壁管１１とカートリッジ６との間隙内で上方に移動した後、隔壁管１１の上端を乗り越えて、隔壁管１１と固体電解質管５との間隙内で下方に移動し、更に、固体電解質管５をナトリウムイオンＮａ^＋となって透過して、陽極容器１内の硫黄Ｓ及び外部回路を通ってきた電子と反応し多硫化ナトリウムを生成する。充電時には放電とは逆にナトリウムＮａ及び硫黄Ｓの生成反応が起こる。
【０００６】
ナトリウム−硫黄電池用の陽極容器１は、アルミニウムやアルミニウム合金等の金属材料を円筒状に形成し、下端開口部に底蓋を嵌合するとともに、上端近傍部に、容器の熱変化に伴う膨張・収縮を吸収緩和するための径方向に屈曲するくびれ部１３を形成することにより構成される。また、陽極容器１は、腐食性の活物質に対する耐食性を高めるため、容器本体の内周面に、クロム−鉄合金粉末等をプラズマ溶射して耐腐食性の高い金属からなる耐食皮膜が形成される。
【０００７】
図６及び図７は従来の陽極容器の部分断面図であり、耐食皮膜１４は、図６のように、くびれ部１３を含めて陽極容器１の内周面全体を被覆するように形成されるか、図７のように、耐食皮膜１４の上端が、くびれ部１３の下側の屈曲が開始するくびれ最下端部１３ａより上方に位置するように形成されるのが一般的であった。
【０００８】
【発明が解決しようとする課題】
しかしながら、前記図６のように、くびれ部１３の内周面全体にクロム−鉄合金のような硬質の耐食皮膜１４が形成されていると、当該耐食皮膜１４によりくびれ部１３の変形が規制されて、陽極容器１の膨張・収縮を十分に吸収緩和できず、耐食皮膜１４にクラックが発生しやすいという問題があった。
【０００９】
また、陽極容器１の内周面は、耐食皮膜１４との密着性を向上させる目的で、耐食皮膜１４の溶射に先立って、ブラスト処理（粗面化処理）が施されるが、このように粗面化された陽極容器１の内周面は、活性化されるとともに多流化ナトリウムとの濡れ性が良くなっている。このため、クロム−鉄合金のような多流化ナトリウムとの濡れ性が非常に良い耐食皮膜１４の上端が、前記図７のようにくびれ最下端部１３ａより上方に位置するように形成されていると、多硫化ナトリウムが短期間でくびれ部１３まで浸み上がって、粗面化されたくびれ部１３内周面の凹部に残存し、化学的な局部腐食を進行させるという問題もあった。
【００１０】
本発明は、このような従来の事情に鑑みてなされたものであり、その目的とするところは、くびれ部が熱変化による陽極容器の膨張・収縮を十分に吸収緩和できるとともに、くびれ部の腐食が進行しにくく寿命が向上したナトリウム−硫黄電池用陽極容器を提供することにある。
【００１１】
【課題を解決するための手段】
本発明によれば、金属材料よりなる有底円筒状の容器の上端近傍部位に径方向に屈曲するくびれ部を備えるとともに、容器の内周面に耐腐食性の高い金属からなる耐食皮膜が形成されたナトリウム−硫黄電池用陽極容器であって、前記耐食皮膜の上端が、陽極容器に収容される陽極活物質を含浸した陽極用導電材の上端面より上方で、前記くびれ部の下側の屈曲が開始するくびれ最下端部より下方に位置するとともに、前記くびれ部の下側の屈曲が開始するくびれ最下端部から陽極容器上端までの内周面が、粗面化処理を施されておらず、その表面の算術平均粗さＲａが１．０μｍ以下であることを特徴とするナトリウム−硫黄電池用陽極容器、が提供される。
【００１２】
【発明の実施の形態】
図１は、本発明の実施形態の一例を示す部分断面図である。陽極容器１の内周面に形成された耐食皮膜１４の上端は、陽極容器１に収容される陽極活物質を含浸したグラファイトマット等の陽極用導電材１２の上端面よりも上方に位置し、これにより、腐食しやすいアルミニウムやアルミニウム合金からなる陽極容器１が、陽極用導電材１２と直接接触するのを防止する。
【００１３】
そしてまた、耐食皮膜１４の上端は、くびれ部１３の下側の屈曲が開始するくびれ最下端部１３ａより下方、すなわちくびれ部１３の下の直管部に位置するので、従来のように耐食皮膜１４の上端がくびれ最下端部１３ａより上方まで達している場合に比して、多硫化ナトリウムがくびれ部１３まで浸み上がりにくく、多硫化ナトリウムによるくびれ部１３の腐食が著しく減少する。
【００１４】
更に、陽極容器１のくびれ最下端部１３ａより上方の部分の内周面は、耐食皮膜形成のための溶射が必要ないので、溶射時間の短縮及び溶射材料の使用量の削減が可能になる。
【００１５】
本発明においては、くびれ部１３の下側の屈曲が開始するくびれ最下端部１３ａから陽極容器１の上端までの内周面が、粗面化処理を施されておらず、その表面の算術平均粗さＲａが１．０μｍ以下であり、０．３〜０．６μｍであるとより好ましい。なお、本発明における「算術平均粗さＲａ」とは、ＪＩＳＢ０６０１−１９９４に定義される値である。
【００１６】
通常、陽極容器は、引き抜き加工によって円筒状に形成されるが、引き抜き加工後の加工面は、その算術平均粗さＲａが１．０μｍ以下の平滑な表面状態となっている場合が多いので、引き抜き加工後にブラスト処理等の粗面化処理を施さなければ、前記のような表面粗さが満たされる。
【００１７】
図３はくびれ最下端部から陽極容器１の上端までの内周面に粗面化処理（ブラスト処理）が施されている場合における、くびれ部１３の腐食状態を示す概要図である。陽極容器は、通常、アルミニウム又はアルミニウム合金から構成されており、これらの材質にブラスト処理を施すと、その表面に凹凸が形成されるとともに著しく活性化して、多硫化ナトリウムとの濡れ性が向上する。そして、このような状態となったくびれ部の内周面に多硫化ナトリウムが浸み上がってくると、その多硫化ナトリウムが凹部に残存して科学的な局部腐食が生じ、短期間の内にかなりの深さまで腐食が進行する。
【００１８】
これに対し、くびれ最下端部から陽極容器１の上端までの内周面が、粗面化処理を施されておらず、その表面の算術平均粗さＲａが１．０μｍ以下である場合には、図２のように、くびれ部１３の内周面全体が、均一な平滑面となっているため、浸み上がってきた多硫化ナトリウムが内周面上に残存しにくく、図に示すような位置に極浅い腐食が生じる程度で、局部的な腐食は発生しにくい。更に、当該範囲に粗面化処理を施さない場合には、陽極容器内周面全体に粗面化処理を施す場合に比して処理時間が短縮するので、電池の製造費用が低減される。
【００１９】
また、本発明においては、耐食皮膜１４の上端部分が、上方に向かって漸次肉薄になるように形成されていることが好ましい。図５のように、耐食皮膜１４の厚みが、その上端までほぼ一定である場合には、耐食皮膜１４の上端と陽極容器１との接触部分に溶射時の残留応力が作用して、耐食皮膜１４の剥離が生じたり、当該接触部分に異種金属の接触による深い腐食が発生しやすい。
【００２０】
これに対し、図４のように耐食皮膜１４の上端部分が漸次肉薄になるよう肉厚に勾配を持たせると、溶射時の残留応力が軽減されて、耐食皮膜１４の剥離が生じにくくなるとともに、異種金属の接触による腐食も極浅い腐食に抑えられる。
【００２１】
【実施例】
以下、本発明を実施例に基づいて更に詳細に説明するが、本発明はこれらの実施例に限定されるものではない。
【００２２】
（試験Ｎｏ．１）
長さ４９０ｍｍ、外径８０ｍｍ、厚み２．３ｍｍのアルミニウム合金からなる容器を引き抜き加工により形成し、その上端近傍部位に径方向に屈曲するくびれ部を設けた。次いで、くびれ部の下側の屈曲が開始するくびれ最下端部から陽極容器上端までの範囲を除く容器内周面に、ブラスト処理を施して粗面化した後、容器の内周面にクロム−鉄合金（クロム含有量が７２質量％）を溶射し、図１に示すように、その上端が、陽極容器１に収容される陽極用導電材１２の上端面より上方で、くびれ最下端部１３ａより下方に位置するような、厚さ６０μｍの耐食皮膜１４を形成した。なお、当該耐食性皮膜１４の上端部分には、上方に向かって漸次肉薄になるように、皮膜の肉厚に勾配を持たせた。
【００２３】
こうして得られた陽極容器を使用して図８に示すような構造のナトリウム−硫黄電池を５本作製し、運転時の最高温度を３６０℃として５年間の試験運転を行い、２年運転後と５年運転後とにおける陽極容器くびれ部の腐食状態（腐食発生数、最大腐食深さ）を光学顕微鏡で観察した。その結果を表１に示す。
【００２４】
（試験Ｎｏ．２）
長さ４９０ｍｍ、外径８０ｍｍ、厚み２．３ｍｍのアルミニウム合金からなる容器を引き抜き加工により形成し、その上端近傍部位に径方向に屈曲するくびれ部を設けた。次いで、容器の内周面全体にブラスト処理を施して粗面化した後、クロム−鉄合金（クロム含有量が７２質量％）を溶射し、図７に示すように、その上端が、くびれ最下端部１３ａより上方に位置するような、厚さ６０μｍの耐食皮膜１４を形成した。こうして得られた陽極容器を使用して図８に示すような構造のナトリウム−硫黄電池を５本作製し、前記試験Ｎｏ．１と同様に試験運転及び観察を行った。その結果を表１に示す。
【００２５】
【表１】

【００２６】
表１に示す試験運転後の観察結果より、くびれ最下端部から陽極容器上端までの範囲については内周面に粗面化処理を施さず、耐食性皮膜の上端がくびれ最下端部より下方に位置するようにした試験Ｎｏ．１の陽極容器は、容器の内周全面に粗面化処理を施し、耐食性皮膜の上端がくびれ最下端部より上方に位置するようにした試験Ｎｏ．２の陽極容器に比して、くびれ部が腐食しにくいことが確認された。
【００２７】
（試験Ｎｏ．３）
前記試験Ｎｏ．１と同様にして作製した陽極容器を使用して図８に示すような構造のナトリウム−硫黄電池を５本作製し、運転時の最高温度を３４０℃として５年間の試験運転を行い、２年運転後と５年運転後とにおける陽極容器くびれ部の腐食状態（腐食発生数、最大腐食深さ）を光学顕微鏡で観察した。その結果を表２に示す。
【００２８】
（試験Ｎｏ．４）
容器の内周面全体にブラスト処理を施して粗面化した以外は、前記試験Ｎｏ．１と同様にして作製した陽極容器を使用して図８に示すような構造のナトリウム−硫黄電池を５本作製し、前記試験Ｎｏ．３と同様に試験運転及び観察を行った。その結果を表２に示す。
【００２９】
【表２】

【００３０】
表２に示す試験運転後の観察結果より、くびれ最下端部から陽極容器上端までの範囲については内周面に粗面化処理を施さなかった試験Ｎｏ．３の陽極容器は、容器の内周全面に粗面化処理を施した試験Ｎｏ．４の陽極容器に比して、くびれ部が腐食しにくいことが確認された。
【００３１】
【発明の効果】
以上説明したように、本発明のナトリウム−硫黄電池用陽極容器は、くびれ部が陽極容器の熱変化による膨張・収縮を十分に吸収緩和できるだけの変形の自由度を有するとともに、従来の陽極容器に比して、多硫化ナトリウムの浸み上がりによるくびれ部の腐食が著しく低減されるので、電池の耐久性と信頼性が向上し、長期に渡って安定して使用できる。また、溶射時間や粗面化処理時間の短縮、溶射材料使用量の削減が可能となり、電池製造費用の低減を図ることができる。
【図面の簡単な説明】
【図１】本発明の実施形態の一例を示す部分断面図である。
【図２】くびれ最下端部から陽極容器の上端までの内周面に粗面化処理が施されておらず、その表面の算術平均粗さＲａが１．０μｍ以下である場合における、くびれ部の腐食状態を示す概要図である。
【図３】くびれ最下端部から陽極容器の上端までの内周面に粗面化処理が施されている場合における、くびれ部の腐食状態を示す概要図である。
【図４】耐食皮膜の上端部分が漸次肉薄になるよう肉厚に勾配を持たせた場合における、陽極容器の腐食状態を示す概要図である。
【図５】耐食皮膜の厚みが、その上端までほぼ一定である場合における、陽極容器の腐食状態を示す概要図である。
【図６】従来のナトリウム−硫黄電池用陽極容器を示す部分断面図である。
【図７】従来のナトリウム−硫黄電池用陽極容器を示す部分断面図である。
【図８】ナトリウム−硫黄電池の構造の一例を示す断面図である。
【符号の説明】
１…陽極容器、２…陽極側端子、３…陽極筒状金具、４…絶縁リング、５…固体電解質管、６…カートリッジ、７…小孔、８…陰極金具、９…陰極蓋、１０…陰極側端子、１１…隔壁管、１２…陽極用導電材、１３…くびれ部、１３ａ…くびれ最下端部、１４…耐食皮膜。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an anode container used for accommodating a conductive material for an anode impregnated with an anode active material in a sodium-sulfur battery.
[0002]
[Prior art]
A sodium-sulfur battery is a β-alumina solid electrolyte that has molten metal sodium as a cathode active material on one side and molten sulfur as an anode active material on the other side, and both of them are selectively permeable to sodium ions. It is a high temperature secondary battery that is isolated at a temperature of 300 to 360 ° C.
[0003]
The structure of such a sodium-sulfur battery is, for example, as shown in FIG. 8, a bottomed cylindrical anode container that accommodates an anode conductive material 12 such as a graphite mat impregnated with molten sulfur S as an anode active material. 1 and a cartridge (sodium protective tube) 6 containing a molten metal sodium Na as a cathode active material, and a bottomed cylindrical shape having a function of accommodating this cartridge 6 inside and selectively transmitting sodium ions Na ⁺ From the solid electrolyte pipe 5 and a gap between the cartridge 6 and the solid electrolyte pipe 5 and a cylindrical tube 11 having a bottomed cylindrical shape disposed at a predetermined distance from the cartridge 6 and the solid electrolyte pipe 5. Become.
[0004]
The solid electrolyte tube 5 is connected to the anode container 1 through an α-alumina insulating ring 4 and an anode cylindrical fitting 3 which are glass-bonded to the opening end. A cathode fitting 8 is hot-pressure bonded to the upper end surface of the insulating ring 4, and a cathode lid 9 is welded and fixed to the cathode fitting 8. An anode-side terminal 2 and a cathode-side terminal 10 are provided on the outer periphery of the anode container 1 and the upper surface of the cathode lid 9, respectively. An inert gas G such as nitrogen gas or argon gas is sealed in the upper space of the cartridge 6 at a predetermined pressure, and sodium Na in the cartridge 6 is provided at the bottom of the cartridge 6 by the inert gas G. Pressurized in the direction of flowing out of the air.
[0005]
In the sodium-sulfur battery having such a structure, the sodium Na supplied from the small hole 7 of the cartridge 6 at the time of discharging moves upward in the gap between the partition tube 11 and the cartridge 6, and then the upper end of the partition tube 11. Is moved downward in the gap between the partition wall tube 11 and the solid electrolyte tube 5, and further passes through the solid electrolyte tube 5 as sodium ion Na ⁺ so as to pass through the sulfur S and the external circuit in the anode container 1. It reacts with the electrons passing through it to produce sodium polysulfide. When charging, contrary to discharging, sodium Na and sulfur S are generated.
[0006]
An anode container 1 for a sodium-sulfur battery is formed of a metal material such as aluminum or aluminum alloy in a cylindrical shape, and a bottom cover is fitted to a lower end opening, and expansion in the vicinity of the upper end due to a heat change of the container. -It is comprised by forming the constriction part 13 bent in the radial direction for absorbing and relaxing shrinkage. Moreover, in order to improve the corrosion resistance with respect to the corrosive active material, the anode container 1 is formed with a corrosion-resistant film made of a metal having high corrosion resistance by plasma spraying chromium-iron alloy powder or the like on the inner peripheral surface of the container body. The
[0007]
6 and 7 are partial sectional views of a conventional anode container, and the corrosion-resistant coating 14 is formed so as to cover the entire inner peripheral surface of the anode container 1 including the constricted portion 13 as shown in FIG. However, as shown in FIG. 7, the upper end of the corrosion-resistant film 14 is generally formed so as to be positioned above the lowermost end 13 a of the constriction at which the lower side of the constriction 13 starts to bend.
[0008]
[Problems to be solved by the invention]
However, as shown in FIG. 6, when a hard corrosion-resistant film 14 such as a chromium-iron alloy is formed on the entire inner peripheral surface of the constricted part 13, deformation of the constricted part 13 is restricted by the corrosion-resistant film 14. Thus, the expansion and contraction of the anode container 1 cannot be sufficiently absorbed and relaxed, and there is a problem that cracks are likely to occur in the corrosion-resistant film 14.
[0009]
In addition, the inner peripheral surface of the anode container 1 is subjected to a blast treatment (roughening treatment) prior to thermal spraying of the corrosion resistant coating 14 for the purpose of improving the adhesion with the corrosion resistant coating 14. The roughened inner surface of the anode container 1 is activated and has good wettability with multi-flow sodium. For this reason, the upper end of the corrosion-resistant film 14 having very good wettability with multi-flow sodium such as chromium-iron alloy is formed so as to be located above the lowermost end portion 13a as shown in FIG. If so, sodium polysulfide soaks up to the constricted portion 13 in a short period of time and remains in the concave portion of the inner peripheral surface of the roughened constricted portion 13 to cause chemical local corrosion.
[0010]
The present invention has been made in view of such conventional circumstances, and the object of the present invention is that the constricted portion can sufficiently absorb and mitigate expansion / contraction of the anode container due to thermal change, and the constricted portion is corroded. It is an object of the present invention to provide an anode container for a sodium-sulfur battery that is difficult to progress and has an improved life.
[0011]
[Means for Solving the Problems]
According to the present invention, a constricted portion that is bent in the radial direction is provided in the vicinity of the upper end of a bottomed cylindrical container made of a metal material, and a corrosion-resistant film made of a highly corrosion-resistant metal is formed on the inner peripheral surface of the container. An anode container for a sodium-sulfur battery, wherein the upper end of the corrosion-resistant film is above the upper end surface of the anode conductive material impregnated with the anode active material accommodated in the anode container and below the constricted portion. The inner peripheral surface from the lowermost part of the constriction where the lower part of the constriction starts to the upper end of the anode container is subjected to a roughening treatment, and is positioned below the lowermost part of the constriction where the constriction starts. In addition , there is provided an anode container for a sodium-sulfur battery , wherein the surface has an arithmetic average roughness Ra of 1.0 μm or less .
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a partial cross-sectional view showing an example of an embodiment of the present invention. The upper end of the corrosion-resistant film 14 formed on the inner peripheral surface of the anode container 1 is located above the upper end face of the anode conductive material 12 such as graphite mat impregnated with the anode active material accommodated in the anode container 1, This prevents the anode container 1 made of corrosive aluminum or aluminum alloy from coming into direct contact with the anode conductive material 12.
[0013]
Further, the upper end of the corrosion-resistant film 14 is located below the lowermost end 13a of the constriction at which the lower part of the constricted part 13 begins to bend, that is, at the straight pipe part below the constricted part 13, so Compared with the case where the upper end of 14 is constricted and reaches above the lowermost end 13a, sodium polysulfide is less likely to soak into the constricted portion 13, and corrosion of the constricted portion 13 due to sodium polysulfide is significantly reduced.
[0014]
Furthermore, since the inner peripheral surface of the portion above the constricted lowermost end portion 13a of the anode container 1 does not require spraying for forming a corrosion-resistant coating, it is possible to shorten the spraying time and to reduce the amount of sprayed material used.
[0015]
In the present invention, the inner peripheral surface from the constricted lowermost end portion 13a where the constricted portion 13 starts to be bent to the upper end of the anode container 1 is not roughened, and the arithmetic average of the surface thereof is not applied. roughness Ra Ri der less 1.0 .mu.m, more preferably a 0.3 to 0.6 .mu.m. The “arithmetic mean roughness Ra” in the present invention is a value defined in JIS B 0601-1994.
[0016]
Usually, the anode container is formed into a cylindrical shape by drawing, but the processed surface after drawing is often in a smooth surface state with an arithmetic average roughness Ra of 1.0 μm or less. If a roughening process such as blasting is not performed after the drawing process, the surface roughness as described above is satisfied.
[0017]
FIG. 3 is a schematic diagram showing the corrosion state of the constricted portion 13 when the inner surface from the lowest end portion of the constriction to the upper end of the anode container 1 is subjected to a roughening treatment (blasting treatment). The anode container is usually made of aluminum or an aluminum alloy, and when these materials are subjected to blasting, irregularities are formed on the surface thereof and remarkably activated to improve wettability with sodium polysulfide. . And when sodium polysulfide soaks into the inner peripheral surface of the constricted part that has been in such a state, the sodium polysulfide remains in the concave portion, causing scientific local corrosion, and within a short period of time. Corrosion proceeds to a considerable depth.
[0018]
On the other hand, when the inner peripheral surface from the bottom end of the constriction to the upper end of the anode container 1 is not subjected to roughening treatment, and the arithmetic average roughness Ra of the surface is 1.0 μm or less, 2, since the entire inner peripheral surface of the constricted portion 13 is a uniform smooth surface, the sodium polysulfide that has soaked up hardly remains on the inner peripheral surface, as shown in the figure. Local corrosion is unlikely to occur to the extent that extremely shallow corrosion occurs at the location. Further, when the surface roughening treatment is not performed in this range, the processing time is shortened compared to the case where the entire surface of the inner surface of the anode container is subjected to the surface roughening treatment, so that the manufacturing cost of the battery is reduced.
[0019]
Moreover, in this invention, it is preferable that the upper end part of the corrosion-resistant film 14 is formed so that it may become thin gradually toward upper direction. As shown in FIG. 5, when the thickness of the corrosion-resistant coating 14 is substantially constant up to its upper end, the residual stress at the time of thermal spraying acts on the contact portion between the upper end of the corrosion-resistant coating 14 and the anode container 1, and the corrosion-resistant coating 14 14 is likely to be peeled off or deep corrosion due to contact of different metals is likely to occur at the contact portion.
[0020]
On the other hand, if the thickness is given a gradient so that the upper end portion of the corrosion-resistant coating 14 gradually becomes thinner as shown in FIG. 4, the residual stress during thermal spraying is reduced, and the corrosion-resistant coating 14 is less likely to be peeled off. Corrosion caused by contact with different metals can be suppressed to extremely shallow corrosion.
[0021]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.
[0022]
(Test No. 1)
A container made of an aluminum alloy having a length of 490 mm, an outer diameter of 80 mm, and a thickness of 2.3 mm was formed by drawing, and a constricted portion bent in the radial direction was provided in the vicinity of the upper end. Next, the inner peripheral surface of the container excluding the range from the lowermost end of the constriction where the lower side of the constriction starts to the upper end of the anode container is roughened by blasting, and then the chromium- An iron alloy (chromium content is 72 mass%) is sprayed, and as shown in FIG. 1, the upper end of the iron alloy is above the upper end surface of the anode conductive material 12 accommodated in the anode container 1, and the lowermost end 13 a is constricted. A corrosion-resistant film 14 having a thickness of 60 μm was formed so as to be positioned further downward. The upper end portion of the corrosion-resistant film 14 was provided with a gradient in the thickness of the film so that it gradually became thinner upward.
[0023]
Using the anode container thus obtained, five sodium-sulfur batteries having a structure as shown in FIG. 8 were produced, and the test was conducted for 5 years at a maximum temperature of 360 ° C. during operation. The corrosion state (the number of corrosion occurrences and the maximum corrosion depth) of the constricted portion of the anode container after 5 years of operation was observed with an optical microscope. The results are shown in Table 1.
[0024]
(Test No. 2)
A container made of an aluminum alloy having a length of 490 mm, an outer diameter of 80 mm, and a thickness of 2.3 mm was formed by drawing, and a constricted portion bent in the radial direction was provided in the vicinity of the upper end. Next, after blasting the entire inner peripheral surface of the container to roughen it, a chromium-iron alloy (chromium content is 72 mass%) is sprayed, and as shown in FIG. A corrosion-resistant film 14 having a thickness of 60 μm was formed so as to be positioned above the lower end portion 13a. Using the thus obtained anode container, five sodium-sulfur batteries having the structure as shown in FIG. The test operation and observation were performed in the same manner as in 1. The results are shown in Table 1.
[0025]
[Table 1]

[0026]
From the observation results after the test operation shown in Table 1, the inner peripheral surface is not roughened in the range from the lowermost end of the constriction to the upper end of the anode container, and the upper end of the corrosion-resistant film is positioned below the lowermost constriction. Test no. No. 1 was subjected to a roughening treatment on the entire inner periphery of the container, and the upper end of the corrosion-resistant film was constricted so that it was positioned above the lowest end. It was confirmed that the constricted part is less likely to corrode than the anode container of No. 2.
[0027]
(Test No. 3)
The test No. Five sodium-sulfur batteries having the structure shown in FIG. 8 were produced using the anode container produced in the same manner as in No. 1, and the test was conducted for 5 years at a maximum temperature of 340 ° C. for 2 years. The corrosion state (the number of corrosion occurrences and the maximum corrosion depth) of the constricted portion of the anode container after operation and after 5 years of operation was observed with an optical microscope. The results are shown in Table 2.
[0028]
(Test No. 4)
Except that the entire inner peripheral surface of the container was roughened by blasting, the test no. Five sodium-sulfur batteries having a structure as shown in FIG. The test operation and observation were performed in the same manner as in 3. The results are shown in Table 2.
[0029]
[Table 2]

[0030]
From the observation results after the test operation shown in Table 2, in the range from the lowest end of the constriction to the upper end of the anode container, test No. in which the inner peripheral surface was not roughened. The anode container of No. 3 has a test No. 1 in which the entire inner peripheral surface of the container is roughened. It was confirmed that the constricted portion was less likely to corrode than the anode container of No. 4.
[0031]
【The invention's effect】
As described above, the anode container for a sodium-sulfur battery of the present invention has a degree of freedom of deformation in which the constricted portion can sufficiently absorb and mitigate expansion and contraction due to the heat change of the anode container, and the conventional anode container. In contrast, since the corrosion of the constricted part due to the soaking of sodium polysulfide is remarkably reduced, the durability and reliability of the battery are improved, and the battery can be used stably over a long period of time. In addition, the spraying time and the surface roughening treatment time can be shortened and the amount of sprayed material used can be reduced, and the battery manufacturing cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view showing an example of an embodiment of the present invention.
FIG. 2 shows a constricted portion when the inner peripheral surface from the lowest end of the constriction to the upper end of the anode container is not roughened and the arithmetic average roughness Ra of the surface is 1.0 μm or less. It is a schematic diagram which shows the corrosion state of.
FIG. 3 is a schematic view showing a corrosion state of the constricted portion when a roughening treatment is performed on the inner peripheral surface from the lowermost end portion of the constricted portion to the upper end of the anode container.
FIG. 4 is a schematic diagram showing the corrosion state of the anode container when the thickness is given a gradient so that the upper end portion of the corrosion-resistant film gradually becomes thinner.
FIG. 5 is a schematic diagram showing the corrosion state of the anode container when the thickness of the corrosion-resistant film is substantially constant up to its upper end.
FIG. 6 is a partial cross-sectional view showing a conventional anode container for a sodium-sulfur battery.
FIG. 7 is a partial sectional view showing a conventional anode container for a sodium-sulfur battery.
FIG. 8 is a cross-sectional view showing an example of the structure of a sodium-sulfur battery.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Anode container, 2 ... Anode side terminal, 3 ... Anode cylindrical metal fitting, 4 ... Insulation ring, 5 ... Solid electrolyte pipe, 6 ... Cartridge, 7 ... Small hole, 8 ... Cathode metal fitting, 9 ... Cathode lid, 10 ... Cathode side terminal, 11 ... partition wall tube, 12 ... conductive material for anode, 13 ... constricted portion, 13a ... lowermost end portion of constricted portion, 14 ... corrosion-resistant film.

Claims

A sodium-sulfur battery having a constricted portion that is bent in the radial direction in a portion near the upper end of a bottomed cylindrical container made of a metal material, and a corrosion-resistant film made of a highly corrosion-resistant metal is formed on the inner peripheral surface of the container An anode container,
The upper end of the corrosion-resistant film is located above the upper end surface of the anode conductive material impregnated with the anode active material accommodated in the anode container and below the lowermost end of the constriction where the lower side of the constricted portion starts to bend. At the same time, the inner peripheral surface from the lowermost end of the constriction where the lower part of the constriction starts to bend to the upper end of the anode container is not roughened, and the arithmetic average roughness Ra of the surface is 1. An anode container for a sodium-sulfur battery, characterized by being 0 μm or less .

The sodium-sulfur battery anode container according to claim 1, wherein an upper end portion of the corrosion-resistant film is formed so as to gradually become thinner upward.