JP2004319353A - Solid electrolyte and fuel cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new solid electrolyte with little fuel crossover and capable of attaining a high output, and to provide a direct type fuel cell or the like with high performance using the same. <P>SOLUTION: The solid electrolyte is composed of fine particles having at least an ionic group on the surface, and advantageously, the fine particles are made of an organic polymer as a main component. As preferable ion groups, a sulfonic group, sulfate acid group, phosphonic acid group, phosphate group, carboxylic acid group or the like are recommended. The solid electrolyte is suitably used for the direct type fuel cell or the like using 1C to 3C alcohol, dimethyl ether, or aqueous solution thereof, as an electrolyte film. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４７】
【化２】

【００４８】
【化３】

【００４９】
【化４】

【００５０】
（ここで、Ｚは芳香環を含む有機基、ｎは繰返しの数である。）
本発明の固体電解質は、上記の微粒子とバインダーとで主として構成される。微粒子の混合量が少なすぎるとＭＣＯの低減および高いイオン伝導性が期待できない。より好ましい微粒子の混合量は、体積分率で３０〜８０％が好ましい。求められるＭＣＯ、イオン伝導、膜強度、あるいはポリマー種により適宜選択されるべきものである。
【００５１】
本発明の固体電解質の製造において、基材ポリマーと微粒子の混合方法としては、微粒子を基材ポリマーに溶融あるいは溶液状態で分散させる方法、あるいは微粒子前駆体を基材ポリマーに溶融あるいは溶液状態で混合した後に微粒子単体とする方法などが挙げられるが、特に限定されない。
【００５２】
本発明の固体電解質の形状は、用途に応じた形状に成形して用いることができる。例えば、本発明の固体電解質を膜状に成形して電解質膜とし、これを燃料電池に用いることができる。
【００５３】
本発明の固体電解質は膜状に成形し、電解質膜とすることで、燃料電池に好適に使用できる。成膜方法としては、通常の溶媒キャスト法、押し出し成形法、加熱プレス法などが適用可能である。
【００５４】
次に、本発明の電解質膜を用いた燃料電池について説明する。本発明の電解質膜は、電極基材と電極触媒層とから構成される電極と組み合わせて膜電極複合体として燃料電池に用いられる。
【００５５】
本発明の電解質膜が適用される燃料電池における電極触媒層は、特に限定されることなく公知のものを利用することが可能である。電極触媒層とは、電極反応を促進する電子伝導やプロトン伝導に寄与する物質を含む層である。また、燃料が液体や気体の場合には、その液体や気体が透過しやすい構造を有していることが好ましく、電極反応に伴う副生成物質の排出も促す構造であることが好ましい。燃料電池の燃料としては、水素などの気体、アルコールなどの液体が挙げられ、これらは１種または２種以上の混合物でもよい。特に、反応効率や電池全体のシステム簡素化の観点から、炭素数１〜３のアルコール、ジメチルエーテルおよびこれらの水溶液が好適に使用される。また、電極触媒層に含まれる触媒としては公知の触媒を用いることができ、特に限定されるものではないが、白金、パラジウム、ルテニウム、イリジウムおよび金などの貴金属触媒が好ましく用いられる。また、これらの貴金属触媒の合金や混合物などのように、２種以上の元素が含まれていても構わない。
【００５６】
電極触媒層に含まれる電子伝導体（導電材）としては、特に限定されるものではないが、電子伝導性や化学的な安定性の点から、炭素材料や無機導電材料が好ましく用いられる。なかでも、非晶質または結晶質の炭素材が挙げられる。例えば、チャネルブラック、サーマルブラック、ファーネスブラックおよびアセチレンブラックなどのカーボンブラックが電子伝導性と比表面積の大きさから好ましく用いられる。ファーネスブラックとしては、キャボット社製バルカンＸＣ−７２、バルカンＰ、ブラックパールズ８８０、ブラックパールズ１１００、ブラックパールズ１３００、ブラックパールズ２０００、リーガル４００（いずれも商品名）、ケッチェンブラック・インターナショナル社製ケッチェンブラックＥＣおよびＥＣ６００ＪＤ（いずれも商品名）、三菱化学社製＃３１５０および＃３２５０（いずれも商品名）などが挙げられ、アセチレンブラックとしては、電気化学工業社製デンカブラックなどが挙げられる。
【００５７】
また、カーボンブラックのほか、天然の黒鉛、ピッチ、コークス、ポリアクリロニトリル、フェノール樹脂およびフラン樹脂などの有機化合物から得られる人工黒鉛や炭素なども使用することができる。これらの炭素材の形態としては特に限定されず、不定形粒子状のほか繊維状、鱗片状、チューブ状、円錐状およびメガホン状のものも用いることができる。また、これら炭素材を後処理加工した炭素材も用いることが可能である。また、電子伝導体は、触媒粒子と均一に分散していることが電極性能の点で好ましいものである。このため、触媒粒子と電子伝導体は予め塗液として良く分散しておくことが好ましい。さらに、電極触媒層として、触媒と電子伝導体とが一体化した触媒担持カーボン等を用いることも好ましい実施態様である。この触媒担持カーボンを用いることにより、触媒の利用効率が向上し、電池性能の向上および低コスト化に寄与できる。ここで、電極触媒層に触媒担持カーボンを用いた場合においても、電子伝導性をさらに高めるために導電剤を添加することも可能である。このような導電剤としては、上述のカーボンブラックが好ましく用いられる。
【００５８】
上記、触媒と電子伝導体類は通常粉体であるので、これらを固めるためにプロトン伝導性を有する物質を使用する。電極触媒層に用いられるプロトン伝導体としては、一般的に、種々の有機、無機材料が公知であるが、燃料電池に用いる場合には、プロトン伝導性を向上するスルホン酸基、スルホンイミド基、硫酸基、ホスホン酸基、リン酸基およびカルボン酸基などのイオン性基を有するポリマが好ましく用いられる。なかでも、イオン性基の安定性の観点から、フルオロアルキルエーテル側鎖とフルオロアルキル主鎖とから構成されるプロトン交換基を有するポリマが好ましく用いられる。例えば、デュポン社製のナフィオン（登録商標）、旭化成社製のアシプレックス（登録商標）、旭硝子社製フレミオン（登録商標）などが好ましく用いられる。これらのプロトン交換ポリマーは、溶液または分散液の状態で電極触媒層中に設ける。この際に、ポリマーを溶解あるいは分散化する溶媒は特に限定されるものではないが、プロトン交換ポリマの溶解性の点から極性溶媒が好ましい。
【００５９】
プロトン伝導体は、電極触媒層を作製する際に電極触媒粒子と電子伝導体とを主たる構成物質とする塗液に予め添加し、均一に分散した状態で塗布することが電極性能の点から好ましいものであるが、電極触媒層を塗布した後にプロトン伝導体を塗布してもかまわない。ここで、電極触媒層にプロトン伝導体を塗布する方法としては、スプレーコート、刷毛塗り、ディップコート、ダイコート、カーテンコートおよびフローコートなどが挙げられ、特に限定されるものではない。電極触媒層に含まれるプロトン伝導体の量としては、要求される電極特性や用いられるプロトン伝導体の伝導度などに応じて適宜決められるべきものであり、特に限定されるものではないが、重量比で１〜８０％の範囲が好ましく、５〜５０％の範囲がさらに好ましい。プロトン伝導体は、少な過ぎる場合はプロトン伝導性が低く、多過ぎる場合はガス透過性を阻害する点で、いずれも電極性能を低下させることがある。
【００６０】
電極触媒層には、上記の触媒、電子伝導体およびプロトン伝導体の他に、種々の物質を含んでいてもかまわない。特に、電極触媒層中に含まれる物質の結着性を高めるために、上述のプロトン交換樹脂以外のポリマーを含んでもよい。このようなポリマーとしては、フッ素原子を含むポリマーが挙げられ、特に限定されるものではないが、例えば、ポリフッ化ビニル、ポリフッ化ビニリデン、ポリヘキサフルオロプロピレン、ポリテトラフルオロエチレンおよびポリパーフルオロアルキルビニルエーテルなど、あるいはこれらの共重合体、これらのポリマーを構成するモノマ単位とエチレンやスチレンなどの他のモノマーとの共重合体、さらには、ブレンドなども用いることができる。これらポリマーの電極触媒層中の含有量としては、重量比で５〜４０％の範囲が好ましい。ポリマー含有量が多すぎる場合、電子およびイオン抵抗が増大し電極性能が低下する傾向がある。
【００６１】
燃料電池の電極基材は特に限定されることなく公知のものを用いることが可能であり、電気抵抗が低く、集（給）電を行えるものであれば用いることができる。また、前記電極触媒層を集電体兼用で使用する場合は、特に電極基材を用いなくてもよい。電極基材の構成材としては、例えば、炭素質や導電性無機物質が挙げられ、例えば、ポリアクリロニトリルからの焼成体、ピッチからの焼成体、黒鉛および膨張黒鉛などの炭素材、ステンレススチール、モリブデンおよびチタンなどが例示される。これらの、形態は特に限定されず、例えば、繊維状あるいは粒子状で用いられるが、燃料透過性の点から炭素繊維などの繊維状導電性物質（導電性繊維）が好ましい。導電性繊維を用いた電極基材としては、織布あるいは不織布いずれの構造も使用可能である。例えば、東レ（株）製カーボンペーパーＴＧＰシリーズおよびＳＯシリーズ（いずれも商品名）、Ｅ−ＴＥＫ社製カーボンクロスなどが用いられる。織布としては、平織、斜文織、朱子織、紋織および綴織など、特に限定されることなく用いられる。また、不織布としては、抄紙法、ニードルパンチ法、スパンボンド法、ウォータージェットパンチ法およびメルトブロー法によるものなど特に限定されることなく用いられる。また、編物であっても構わない。
【００６２】
これらの布帛において、特に炭素繊維を用いた場合、耐炎化紡績糸を用いた平織物を炭化あるいは黒鉛化した織布、耐炎化糸をニードルパンチ法やウォータージェットパンチ法などによる不織布加工した後に炭化あるいは黒鉛化した不織布、および耐炎化糸あるいは炭化糸あるいは黒鉛化糸を用いた抄紙法によるマット不織布などが好ましく用いられる。特に、薄く強度のある布帛が得られる点から不織布を用いるのが好ましい。
【００６３】
電極基材に炭素繊維からなる導電性繊維を用いた場合、炭素繊維としては、ポリアクリロニトリル系炭素繊維、フェノール系炭素繊維、ピッチ系炭素繊維およびレーヨン系炭素繊維などが挙げられる。
【００６４】
燃料電池に用いられる電極基材に、水の滞留によるガス拡散・透過性の低下を防ぐために行う撥水処理、水の排出路を形成するための部分的撥水、親水処理や、抵抗を下げるために行われる炭素粉末の添加等を行うこともできる。また、燃料電池においては、電極基材と電極触媒層の間に、少なくとも無機導電性物質と疎水性ポリマを含む導電性中間層を設けることが好ましい。特に、電極基材が空隙率の大きい炭素繊維織物や不織布である場合、導電性中間層を設けることで、電極触媒層が電極基材にしみ込むことによる性能低下を抑えることができる。
【００６５】
本発明の電解質膜、電極触媒層あるいは電極触媒層と電極基材を用いて膜電極複合体とする際の作製方法は特に限定されるものではなく、公知の方法（例えば、電気化学，１９８５， ５３， ２６９．記載の化学メッキ法、Ｊ． Ｅｌｅｃｔｒｏｃｈｅｍ． Ｓｏｃ．： Ｅｌｅｃｔｒｏｃｈｅｍｉｃａｌ Ｓｃｉｅｎｃｅ ａｎｄ Ｔｅｃｈｎｏｌｏｇｙ， １９８８， １３５（９）， ２２０９． 記載のガス拡散電極の熱プレス接合法など）を適用することが可能である。
【００６６】
本発明の電解質膜は、種々の用途に適用可能である。例えば、イオン交換膜として水浄化装置、燃料電池、水電解装置およびクロロアルカリ電解装置等の各種電気化学装置が挙げられるが、中でも燃料電池がもっとも好ましい。燃料電池のなかでも固体高分子型燃料電池に好適であり、さらに炭素数１〜３のアルコール、ジメチルエーテルおよびこれらの水溶液を燃料とする直接型燃料電池にはより好適であり、メタノールを燃料とする直接メタノール型燃料電池に最も好適である。
【００６７】
さらに、本発明の燃料電池の用途としては、特に限定されないが、移動体の電力供給源が好ましいものである。特に、携帯電話、パソコン、ＰＤＡ（ｐｅｒｓｏｎａｌ ｄｉｇｉｔａｌ ａｓｓｉｓｔａｎｔ）などの携帯機器、掃除機等の家電、乗用車、バス、トラックなどの自動車や船舶、鉄道などの移動体の電力供給源として好ましく用いられる。
【００６８】
【実施例】
以下、実施例により本発明の固体電解質についてさらに詳しく説明するが、本発明はこれらに限定されるものではない。なお、各物性の測定条件は次のとおりである。
（１）粒径および数平均粒径の測定
走査型電子顕微鏡（ＳＥＭ）により撮影した写真から任意に選んだ１００個の粒子について個々の粒子の粒径（円相当平均径）を測定し、その数平均として算出した。
（２）電解質膜のプロトン伝導度測定法
電解質膜を２５℃の純水に２４時間浸漬した後、２５℃、相対湿度５０〜８０％の雰囲気中に取り出し、定電位交流インピーダンス法で抵抗を測定して求めた。Ｓｏｌａｒｔｒｏｎ製電気化学測定システム（Ｓｏｌａｒｔｒｏｎ１２８７ Ｅｌｅｃｔｒｏｃｈｅｍｉｃａｌ ＩｎｔｅｒｆａｃｅおよびＳｏｌａｒｔｒｏｎ １２５５Ｂ Ｆｒｅｑｕｅｎｃｙ Ｒｅｓｐｏｎｓｅ Ａｎａｌｙｚｅｒ）を使用した。サンプルをφ２ｍｍおよびφ１０ｍｍの２枚の円形電極（ステンレス製）間に加重１ｋｇをかけて挟持した（有効電極面積０．０３１４ｃｍ^２）。サンプルと電極の界面には、ポリ（２−アクリルアミド−２−メチルプロパンスルホン酸）の１５％水溶液を塗布した。２５℃において、定電位インピーダンス測定を行い、膜厚方向のイオン伝導度を求めた。交流振幅は５０ｍＶとした。
（３）電解質膜のメタノール透過量測定法
電解質膜を２５℃の純水に２４時間浸漬した後、取り出して、図１に示すように、アクリル樹脂製Ｈ型セル間に電解質膜を挟み、一方のセルには純水（６０ｍＬ）を入れ、他方のセルには１Ｍメタノール水溶液（６０ｍＬ）を入れた。セルの容量は各８０ｍＬであった。また、セル間の開口部は直径１．５ｃｍの円形であり有効膜面積は１．７７ｃｍ^２であった。２０℃において両方のセルを撹拌した。１時間、２時間および３時間経過時点で純水中に溶出したメタノール量を島津製作所製ガスクロマトグラフィ（ＧＣ−２０１０）（商品名）で測定し定量した。グラフの傾きから単位時間、単位面積あたりのメタノール透過量を求めた。
【００６９】
（実施例１）
（１）スルホン化スチレン−ジビニルベンゼン微粒子の合成
還流冷却管、撹拌装置および窒素ガス導入管を備えた３００ｍＬ四ツ口フラスコに、スチレン（４．５ｇ）およびジビニルベンゼン（０．５ｇ）を入れた。フラスコに窒素ガスを導入し撹拌しながら、日本油脂製ノニオン系界面活性剤”ノニオンＨＳ−２１０”（商品名）水溶液（９３．５ｇ）および過硫酸カリウム水溶液（２ｇ）を滴下した。反応の進行にともない、スチレン−ジビニルベンゼン微粒子が生成した。該スチレン−ジビニルベンゼン微粒子を遠心分離により固液分離した後、クロロスルホン酸の１，２−ジクロロエタン溶液中で撹拌した。反応終了後、透析チューブを用いて十分に洗浄を行い、目的のスルホン化スチレン−ジビニルベンゼンを得た。該スルホン化スチレン−ジビニルベンゼンの数平均粒径を測定したところ５００ｎｍであった。該スルホン化スチレン−ジビニルベンゼンの硫黄濃度をＳＴＥＭ−ＥＤＸ法で分析したところ、微粒子表面および内部に硫黄原子が存在することが確認され、微粒子表面および内部にスルホン酸基が存在することが分かった。微粒子表面と内部の硫黄濃度比、すなわちスルホン酸基濃度比は１：１で変わらなかった。
（２）スルホン化ポリフェニレンオキシドの合成
室温、窒素雰囲気下で三菱エンジニアリングプラスチック社製ポリフェニレンオキシド（ＹＰＸ−１００Ｌ）（商品名）（１００ｇ）をクロロホルム（１０００ｇ）に溶解させた後、撹拌しながらクロロスルホン酸（３４ｍＬ）をゆっくり滴下した。滴下終了後室温で３０分間撹拌を続けた。析出したポリマーを濾別後、ミルで粉砕し、水で十分に洗浄後、真空乾燥し、目的のスルホン化ポリフェニレンオキシドを得た（イオン交換当量：３．０ｍｅｑ）。得られたスルホン化ポリフェニレンオキシドをＮ，Ｎ−ジメチルアセトアミド（ＤＭＡｃ）に溶解し、１５重量％溶液とした。
（３）固体電解質膜の作製
前記（１）のスルホン化スチレン−ジビニルベンゼン微粒子０．２ｇおよび前記（２）のスルホン化ポリフェニレンオキシドＤＭＡｃ溶液４．５ｇを混合した。この液をガラス板上にキャストし、１００℃、３時間加熱して固体電解質膜を作製した。膜厚は１００μｍであった。
（４）固体電解質膜の性能評価
前記（３）で得られた膜のメタノール透過量とイオン伝導度を評価した。この膜のメタノール透過量は７．０μｍｏｌ／ｃｍ^２・ｍｉｎ、イオン伝導度は８．０Ｓ／ｃｍ^２であった。
【００７０】
（実施例２）
スルホン化ポリフェニレンオキシドＤＭＡｃ溶液の代わりに、市販の２０％Ｎａｆｉｏｎ溶液（デュポン社製登録商標）を用いたこと以外は、実施例１と同様にして固体電解質を作製した。この電解質膜の性能を実施例１と同様に評価したところ、メタノール透過量は７．３μｍｏｌ／ｃｍ^２／ｍｉｎ、イオン伝導度は７．５Ｓ／ｃｍ^２であった。
【００７１】
（比較例１）
実施例２において、市販の２０％Ｎａｆｉｏｎ溶液（デュポン社製登録商標）のみを用い、実施例１と同様にして固体電解質膜を得た。この電解質膜のメタノール透過量は８．０μｍｏｌ／ｃｍ^２／ｍｉｎ、イオン伝導度は６．７Ｓ／ｃｍ^２であり、有機微粒子を加えた実施例１よりも性能が悪かった。
【００７２】
（実施例３）
スルホン化ポリフェニレンオキシドＤＭＡｃ溶液の代わりに、ポリフェニレンオキシドのクロロホルム溶液を用いたこと以外は、実施例１と同様にして固体電解質膜を作製した。この電解質膜の性能を実施例１と同様に評価したところ、メタノール透過量は５．０μｍｏｌ／ｃｍ^２／ｍｉｎ、イオン伝導度は４．０Ｓ／ｃｍ^２であった。
【００７３】
（比較例２）
実施例３において、ポリフェニレンオキシドのクロロホルム溶液のみを用い、実施例１と同様にして固体電解質膜を得た。この電解質膜のメタノール透過量は５．０μｍｏｌ／ｃｍ^２／ｍｉｎ、イオン伝導度は０Ｓ／ｃｍ^２であり、有機微粒子を加えた実施例２よりも性能が悪かった。
【００７４】
（実施例４）
（１）スルホン化スチレン−ジビニルベンゼン微粒子の合成
還流冷却管、撹拌装置および窒素ガス導入管を備えた３００ｍＬ四ツ口フラスコに、スチレン（３．２ｇ）およびジビニルベンゼン（１．８ｇ）を入れた。フラスコに窒素ガスを導入し撹拌しながら、日本油脂製ノニオン系界面活性剤”ノニオンＨＳ−２１０”（商品名）水溶液（９３．５ｇ）および過硫酸カリウム水溶液（２ｇ）を滴下した。反応の進行にともない、スチレン−ジビニルベンゼン微粒子が生成した。該スチレン−ジビニルベンゼン微粒子を遠心分離により固液分離した後、濃硫酸中で加熱撹拌した。反応終了後、多量のメタノールで精製し、目的のスルホン化スチレン−ジビニルベンゼンを得た。該スルホン化スチレン−ジビニルベンゼンの数平均粒径を測定したところ４８０ｎｍであった。該スルホン化スチレン−ジビニルベンゼンの硫黄濃度をＳＴＥＭ−ＥＤＸ法で分析したところ、微粒子表面と内部の硫黄濃度比すなわち、スルホン酸基濃度比は５：１であった。
（２）固体電解質膜の性能評価
実施例１のスルホン化スチレン−ジビニルベンゼン微粒子の代わりに、前記（１）のスルホン化スチレン−ジビニルベンゼン微粒子を用い、実施例１と同様にして固体電解質膜を作製した。この電解質膜の性能を実施例１と同様に評価したところ、メタノール透過量は５．７μｍｏｌ／ｃｍ^２／ｍｉｎ、イオン伝導度は８．０Ｓ／ｃｍ^２であり、実施例１よりも性能が良かった。
【００７５】
（実施例５）
スルホン化ポリフェニレンオキシドＤＭＡｃ溶液の代わりに、市販の２０％Ｎａｆｉｏｎ溶液（デュポン社製登録商標）を用いたこと以外は、実施例４と同様にして固体電解質膜を作製した。この電解質膜の性能を実施例１と同様に評価したところ、メタノール透過量は６．９μｍｏｌ／ｃｍ^２／ｍｉｎ、イオン伝導度は７．５Ｓ／ｃｍ^２であった。
【００７６】
（実施例６）
（１）スルホン化フェニルマレイミド−スチレン−ジビニルベンゼン微粒子の合成
還流冷却管、撹拌装置および窒素ガス導入管を備えた３００ｍＬ四ツ口フラスコに、スチレン（３．０ｇ）、ジビニルベンゼン（０．５ｇ）およびフェニルマレイミド（１．５ｇ）を入れた。フラスコに窒素ガスを導入し撹拌しながら、日本油脂製ノニオン系界面活性剤”ノニオンＨＳ−２１０”（商品名）水溶液（９３．５ｇ）および過硫酸カリウム水溶液（２ｇ）を滴下した。反応の進行にともない、フェニルマレイミド−スチレン−ジビニルベンゼン微粒子が生成した。該フェニルマレイミド−スチレン−ジビニルベンゼン微粒子を遠心分離により固液分離した後、濃硫酸中で撹拌した。反応終了後、多量のメタノールで精製し、目的のスルホン化フェニルマレイミド−スチレン−ジビニルベンゼンを得た。該スルホン化フェニルマレイミド−スチレン−ジビニルベンゼンの数平均粒径を測定したところ５５０ｎｍであった。該スルホン化フェニルマレイミド−スチレン−ジビニルベンゼンの硫黄濃度をＳＴＥＭ−ＥＤＸ法で分析したところ、微粒子表面と内部の硫黄濃度比すなわちスルホン酸基濃度比は９：１であった。
（２）固体電解質膜の性能評価
実施例１のスルホン化スチレン−ジビニルベンゼン微粒子の代わりに、前記（１）のスルホン化フェニルマレイミド−スチレン−ジビニルベンゼン微粒子を用い、実施例１と同様にして固体電解質膜を作製した。この電解質膜の性能を実施例１と同様に評価したところ、メタノール透過量は５．５μｍｏｌ／ｃｍ^２／ｍｉｎ、イオン伝導度は８．０Ｓ／ｃｍ^２であり、実施例１よりも性能が良かった。
【００７７】
（実施例７）
スルホン化ポリフェニレンオキシドＤＭＡｃ溶液の代わりに市販の２０％Ｎａｆｉｏｎ溶液（デュポン社製登録商標）を用いたこと以外は、実施例６と同様にして固体電解質膜を作製した。この電解質膜の性能を実施例１と同様に評価したところ、メタノール透過量は６．９μｍｏｌ／ｃｍ^２／ｍｉｎ、イオン伝導度は７．５Ｓ／ｃｍ^２であった。
【００７８】
（実施例８）
スルホン化ポリフェニレンオキシドＤＭＡｃ溶液の代わりにポリビニリデンフルオライドのＤＭＡｃ溶液を用いる他は、実施例６と同様にして固体電解質を作製した。この膜の性能を実施例１と同様に評価したところ、メタノール透過量は０．９μｍｏｌ／ｃｍ^２／ｍｉｎ、イオン伝導度は１．０Ｓ／ｃｍ^２であった。
【００７９】
（実施例９）
（１）有機シランの加水分解
クロロスルホニルフェニルエチルトリクロロシラン５ｇに０．０１Ｎ塩酸水溶液を添加し、室温にて３０分間撹拌し、加水分解物を得た。該加水分解物をＮ，Ｎ−ジメチルアセトアミド（ＤＭＡｃ）に溶解し、１５重量％溶液とした。
（２）シリカ微粒子の表面処理
撹拌装置および窒素ガス導入管を備えた３００ｍＬ四ツ口フラスコに球状シリカ（３．０ｇ）、メタノール（９０ｇ）を入れ、撹拌しながら前記（１）の加水分解物のＤＭＡｃ溶液（２．０ｇ）を滴下した。室温にて１時間撹拌し、シリカ微粒子を表面処理した。該表面処理シリカ微粒子の数平均粒径を測定したところ４５０ｎｍであった。該表面処理シリカ微粒子の硫黄濃度をＳＴＥＭ−ＥＤＸ法で分析したところ、微粒子表面からのみ硫黄原子の存在が確認された。
（３）固体電解質膜の性能評価
スチレン−ジビニルベンゼン微粒子の代わりに前記（２）の表面処理シリカ微粒子を用いたこと以外は、実施例１０と同様にして固体電解質膜を作製した。この電解質膜の性能を実施例１と同様に評価したところ、メタノール透過量は６．８μｍｏｌ／ｃｍ^２／ｍｉｎ、イオン伝導度は７．０Ｓ／ｃｍ^２であった。
【００８０】
（実施例１０）
（１）バインダーの調整
東レダウコーニングシリコーン社製γ−グリシドキシプロピルトリメトキシシラン５ｇに０．０１Ｎ塩酸水溶液を添加し、室温にて３０分間攪拌し、加水分解物を得た。該γ−グリシドキシプロピルトリメトキシシランの加水分解物をＮ，Ｎ−ジメチルアセトアミド（ＤＭＡｃ）に溶解したものとポリビニルアルコールを混合した。
（２）固体電解質膜の性能評価
スルホン化ポリフェニレンオキシドＤＭＡｃ溶液の代わりに前記（１）のポリビニルアルコールおよびγ−グリシドキシプロピルトリメトキシシラン加水分解物のＤＭＡｃ溶液を用いる他は実施例６と同様にして固体電解質を作製した。この膜の性能を実施例１と同様に評価したところ、メタノール透過量は１．５μｍｏｌ／ｃｍ^２／ｍｉｎ、イオン伝導度は１．２Ｓ／ｃｍ^２であった。
【００８１】
（実施例１１）
（１）スチレン−ジビニルベンゼン微粒子の合成
還流冷却管、撹拌装置および窒素ガス導入管を備えた３００ｍＬ四ツ口フラスコに、スチレン（４．５ｇ）およびジビニルベンゼン（０．５ｇ）を入れた。フラスコに窒素ガスを導入し撹拌しながら、日本油脂製ノニオン系界面活性剤”ノニオンＨＳ−２１０”（商品名）水溶液（９３．５ｇ）および過硫酸カリウム水溶液（２ｇ）を滴下した。反応の進行にともない、目的のスチレン−ジビニルベンゼン微粒子が生成した。該スチレン−ジビニルベンゼンの数平均粒径を測定したところ５０ｎｍであった。
（２）固体電解質膜の作製
前記（１）のスチレン−ジビニルベンゼン微粒子０．２ｇとポリビニリデンフルオライドのＤＭＡｃ溶液４．５ｇを混合した。この液をガラス板上にキャストし、１００℃、３時間加熱して固体電解質膜を作製した。この膜をクロロスルホン酸の１，２−ジクロロエタン溶液中に浸漬させた後、十分洗浄した。
（３）固体電解質膜の性能評価
前記（２）で得られた電解質膜の性能を実施例１と同様に評価したところ、メタノール透過量は１．５μｍｏｌ／ｃｍ^２・ｍｉｎ、イオン伝導度は２．２Ｓ／ｃｍ^２であった。
【００８２】
（実施例１２）
（１）フェニルマレイミド−スチレン−ジビニルベンゼン微粒子の合成
還流冷却管、撹拌装置および窒素ガス導入管を備えた３００ｍＬ四ツ口フラスコに、スチレン（３．０ｇ）、ジビニルベンゼン（０．５ｇ）およびフェニルマレイミド（１．５ｇ）を入れた。フラスコに窒素ガスを導入し撹拌しながら、日本油脂製ノニオン系界面活性剤”ノニオンＨＳ−２１０”（商品名）水溶液（９３．５ｇ）および過硫酸カリウム水溶液（２ｇ）を滴下した。反応の進行にともない、目的のフェニルマレイミド−スチレン−ジビニルベンゼン微粒子が生成した。該フェニルマレイミド−スチレン−ジビニルベンゼン微粒子の数平均粒径を測定したところ８０ｎｍであった。
（２）固体電解質膜の性能評価
スチレン−ジビニルベンゼン微粒子の代わりに前記（１）のフェニルマレイミド−スチレン−ジビニルベンゼン微粒子を用いたこと以外は、実施例１０と同様にして固体電解質膜を作製した。この電解質膜の性能を実施例１と同様に評価したところ、メタノール透過量は１．４μｍｏｌ／ｃｍ^２／ｍｉｎ、イオン伝導度は２．０Ｓ／ｃｍ^２であった。
【００８３】
【発明の効果】
本発明によれば、燃料クロスオーバーを抑制し、イオン伝導性が高く、高出力を達成できる新規な固体電解質が得られる。この固体電解質を用いることにより、高性能な直接型燃料電池を得ることができ、その実用性は高い。
【図面の簡単な説明】
【図１】図１は、本発明の固体電解質のメタノール透過量を分析する際に用いられるセルの模式図を示す側面図である。
【符号の説明】[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a solid electrolyte and a fuel cell using the same.
[0002]
[Prior art]
A fuel cell is a power generation device that emits little, has high energy efficiency, and has a low burden on the environment. For this reason, they have been spotlighted again in recent years as global environmental protection has increased. Compared with the conventional large-scale power generation facilities, the power generation apparatus is expected to be a relatively small-scale distributed power generation facility and a power generation apparatus for mobile objects such as automobiles and ships in the future. In addition, it is attracting attention as a power source for small mobile devices and portable devices, and is expected to be mounted on mobile phones and personal computers instead of secondary batteries such as nickel-metal hydride batteries and lithium ion batteries.
[0003]
In polymer electrolyte fuel cells, in addition to conventional polymer electrolyte fuel cells that use hydrogen gas as fuel, direct fuel cells that directly supply fuel, such as alcohol or dimethyl ether, without reforming them into hydrogen are also attracting attention. Have been. Although the direct fuel cell has a lower output than conventional polymer electrolyte fuel cells, it uses a liquid fuel and does not use a reformer, resulting in a higher energy density and the use time of a portable device per charge. There is an advantage that it takes a long time. Among direct fuel cells, a direct methanol fuel cell using methanol as a fuel has a high output at around room temperature, and is particularly attracting attention as a promising alternative to a secondary battery.
[0004]
In a fuel cell, an anode and a cathode, in which a reaction responsible for power generation occurs, and an electrolyte membrane serving as a proton conductor between the anode and the cathode, usually constitute a membrane electrode assembly, and the membrane electrode assembly is sandwiched between separators. The cell is configured as a unit. Here, the electrode is composed of an electrode base material (also referred to as a gas diffusion electrode or a current collector) for promoting gas diffusion and collecting (supplying) electricity, and an electrode catalyst layer which actually serves as an electrochemical reaction field. ing. For example, at the anode electrode of a polymer electrolyte fuel cell, a fuel such as hydrogen gas reacts in the catalyst layer of the anode electrode to generate protons and electrons, the electrons conduct to the electrode base material, and the protons conduct to the electrolyte membrane. I do. Therefore, the anode electrode is required to have good gas diffusivity, electron conductivity, and proton conductivity. On the other hand, in the cathode electrode, an oxidizing gas such as oxygen or air in the catalyst layer of the cathode electrode reacts with protons conducted from the electrolyte membrane and electrons conducted from the electrode base material to generate water. Therefore, in the cathode electrode, it is necessary to efficiently discharge generated water in addition to gas diffusivity, electron conductivity, and proton conductivity.
[0005]
Although high proton conductivity is required for an electrolyte membrane for a polymer electrolyte fuel cell, fuel permeation suppression is also required for an electrolyte membrane for a direct fuel cell. Fuel permeation through the electrolyte membrane is also referred to as fuel crossover or chemical short, and causes a problem that cell output and energy efficiency are reduced.
[0006]
Heretofore, for example, Nafion (a registered trademark of DuPont), which is a super-strong acid group-containing fluorine-based polymer compound, has been used in an electrolyte membrane of a polymer electrolyte fuel cell. However, Nafion has a problem that a fuel crossover of methanol or the like is large because water in the membrane forms a cluster structure. Therefore, in order to put these electrolyte membranes to practical use, an electrolyte having a high proton conductivity comparable to that of Nafion and suppressing fuel crossover has been desired from the market.
[0007]
In the improvement of a conventional perfluoro-based electrolyte, fuel crossover is reduced and proton conductivity is improved by filling an inorganic proton conductor in an electrolyte membrane (see Patent Document 1). Separately, an electrolyte membrane composed of an organic polymer and an inorganic proton conductor has been proposed (see Patent Literature 2 and Patent Literature 3).
[0008]
[Patent Document 1]
JP-A-2000-516014
[0009]
[Patent Document 2]
JP 2001-102071 A
[0010]
[Patent Document 3]
JP-A-2002-015742
[0011]
[Problems to be solved by the invention]
However, in these conventional techniques, high proton conductivity and fuel crossover suppression cannot be completely realized, and when high proton conductivity is maintained, fuel crossover suppression is not sufficient. When the crossover suppression is sufficient, there is a problem that the proton conductivity is small.
[0012]
An object of the present invention is to provide a solid electrolyte having a high proton conductivity comparable to that of Nafion and suppressing fuel crossover. Still another object of the present invention is to provide a fuel cell using the solid electrolyte, and particularly to provide a direct fuel cell using an alcohol having 1 to 3 carbon atoms, dimethyl ether or an aqueous solution thereof as a fuel. Things.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has the following configuration. That is, the solid electrolyte of the present invention is characterized by containing fine particles having an ionic group on at least the surface, and includes the following preferred embodiments.
(1) The ionic group is at least one or more selected from sulfonic acid groups, sulfonimide groups, sulfate groups, phosphonic acid groups, phosphoric acid groups, and carboxylic acid groups.
(2) The ionic group is a sulfonic acid group or a sulfonimide group.
(3) The ionic group concentration ratio between the surface and the inside of the fine particles is 3: 1 or more.
(4) The fine particles are mainly composed of an organic polymer.
(5) Fine particles having at least primary particles having a number average particle diameter of 1 μm or less.
[0014]
Further, a fuel cell of the present invention is constituted by using the above-mentioned solid electrolyte.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the solid electrolyte of the present invention will be described.
[0016]
The solid electrolyte of the present invention is characterized by containing fine particles having an ionic group on at least the surface. Here, the fine particles having an ionic group are those in which an ionic group is chemically bonded to the surface of the fine particles. High ionic conductivity can be obtained by introducing an ionic group. Further, when the solid electrolyte of the present invention is used as an electrolyte membrane, by including fine particles in the electrolyte membrane, swelling by alcohol, dimethyl ether or a mixture thereof and water is suppressed, and fuel crossover is reduced, This has the effect of suppressing a decrease in the strength of the film.
[0017]
The fine particles contained in the solid electrolyte of the present invention may be either an organic compound or an inorganic compound, but need to have an ionic group. When it does not have an ionic group, it becomes difficult to obtain high ionic conductivity.
[0018]
Specific examples of the ionic group are not particularly limited as long as they are atomic groups having a negative charge, but a functional group having a proton exchange ability is preferable. As such a functional group, a sulfonic acid group, a sulfonimide group, a sulfate group, a phosphonic acid group, a phosphoric acid group, and a carboxylic acid group are preferably used. Here, the sulfonic acid group is -SO ₂ (OH), the sulfonimide group is -SO ₂ -NH-SO ₂ -R (R represents an arbitrary substituent), and the sulfate group is -OSO ₂ (OH), the phosphonic acid group is -PO (OH) ₂ , The phosphate group is -OPO (OH) ₂ , A carboxylic acid group means —CO (OH), and salts thereof. Among these, it is more preferable to have at least a sulfonic acid group, a sulfonimide group, and / or a sulfate group from the viewpoint of high proton conductivity, and to have at least a sulfonic acid group or a sulfonimide group from the viewpoint of hydrolysis resistance. Is most preferred. These ionic groups can be contained in the solid electrolyte in two or more types.
[0019]
The structure of the fine particles contained in the solid electrolyte of the present invention preferably has as few ionic groups inside the fine particles as possible from the viewpoint of reducing MCO. The ionic group concentration ratio (surface: inside) between the surface and the inside of the fine particles is preferably 3: 1 or more, more preferably 5: 1 or more, and most preferably 10: 1 or more. Use of such fine particles makes it possible to achieve both high ion conductivity and low MCO. Here, the surface of the fine particles refers to a layer within 5% of the primary particle radius from the outside, and the inside is defined as within 5% of the center of the primary particle radius.
[0020]
In the present invention, in order to calculate the ratio of the ionic group concentration between the surface of the fine particles and the inside thereof, for example, the STEM-EDX method (Scanning Transmission Electron Microscope-Energy Dispersion X-ray Spectroscopy; energy-dispersive X-ray spectroscopy) A composition analysis method combining the methods) can be used. In the STEM-EDX method, the atomic ratio of the constituent elements of the sample can be measured, and the ionic group concentration ratio can be calculated from the atomic ratio.
[0021]
The fine particles contained in the solid electrolyte of the present invention preferably have a number average particle diameter of primary particles of 1 μm or less. When the number average particle size is larger than 1 μm, it is difficult to disperse the polymer in the binder well, and as a result, a high-quality solid polymer solid electrolyte cannot be obtained. The number average particle size of the primary particles is more preferably 500 nm or less, and most preferably 2 to 100 nm. Regarding the method of calculating the number average particle diameter, the particle diameter (equivalent circle diameter) of each particle is measured from a photograph of a cross section of the electrolyte taken with a scanning electron microscope (SEM), and the number average is obtained. If the measurement is easy, a transmission electron microscope (TEM) can be used.
[0022]
The fine particles contained in the solid electrolyte of the present invention may be composed of any of an organic compound and an inorganic compound, but fine particles mainly composed of an organic polymer as the organic compound are preferable.
[0023]
Specific examples of the inorganic compound include sulfated zirconia, silica having an ionic group, alumina, and titania, but are not particularly limited.
[0024]
Examples of the organic polymer include polymers that do not dissolve or swell in alcohol, dimethyl ether, or the like. Specific examples of the organic polymer include polystyrene, polyvinylidene fluoride, polytetrafluoroethylene, polysulfone, polyphenylene sulfide, polyphenylene sulfide sulfone, polyether sulfone, polyphenylene oxide, and polyimide.
[0025]
As the organic polymer, a copolymer obtained by polymerization of a monomer may be used. Here, the monomer is a substance capable of undergoing a polymerization reaction, which is a main component of a component constituting fine particles to be finally produced, and is not particularly limited as long as polymerization is possible. Specific examples of the monomer include styrene monomers such as styrene, methylstyrene, ethylstyrene, chlorostyrene, styrenesulfonic acid, and t-butoxystyrene, methyl (meth) acrylate, ethyl (meth) acrylate, and (meth) acryl. 2-ethylhexyl acid, lauryl (meth) acrylate, glycidyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, hydroxyethyl (meth) acrylate, diethylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, butanediol (Meth) acrylic ester monomers such as mono (meth) acrylate, unsaturated carboxylic monomers such as (meth) acrylic acid and maleic acid, and alkyls such as methyl vinyl ether and ethyl vinyl ether Vinyl ether monomers, vinyl ester monomers such as vinyl acetate and vinyl butyrate, (meth) acrylamide monomers such as (meth) acrylamide, N-methyl (meth) acrylamide and N-ethyl (meth) acrylamide, and (meth) acrylonitrile Of the nitrile-based monomer. These polyfunctional monomers may be used alone or as a mixture of two or more. Further, among the above monomers, styrene, methyl acrylate and methyl methacrylate are particularly preferably used.
[0026]
Further, a polyfunctional monomer can be used as a crosslinking agent to introduce a crosslinked structure into the copolymer. The polyfunctional monomer is not particularly limited as long as it has two or more copolymerizable unsaturated functional groups in the molecule. Specific examples of the polyfunctional monomer include aromatic polyfunctional monomers such as o-divinylbenzene, m-divinylbenzene, p-divinylbenzene, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, and triethylene glycol. Di (meth) acrylate, glycerol (di / tri) (meth) acrylate, trimethylolpropane (di / tri) (meth) acrylate, dihydric alcohol such as pentaerythritol (di / tri / tetra) (meth) acrylate -, Tri-, tetra- (meth) acrylate compounds, (meth) acrylates such as polyethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and methoxypolyethylene glycol mono (meth) acrylate Products, di (meth) allyl phthalate, di (meth) allyl (meth) acrylamide, (meth) allyl compounds such as tri (meth) allyl cyanurate, vinyl (meth) acrylate, allyl (meth) acrylate, etc. Ester compounds, diallyl compounds such as diethylene glycol bisallyl carbonate and diallyl phthalate, and diene compounds such as butadiene, hexadiene and pentadiene. These polyfunctional monomers may be used alone or as a mixture of two or more. Also, among the polyfunctional monomers, aromatic polyfunctional monomers are preferable, and divinylbenzenes are particularly preferable, from the viewpoint of polymerizability with a styrene-based monomer and miniaturization of the particle diameter. Divinylbenzene may be mixed with various isomers.
[0027]
The method for producing the fine particles contained in the solid electrolyte of the present invention is not particularly limited, and a generally known method can be used.
[0028]
In the case of inorganic fine particles, they can be produced by hydrolyzing and condensing a metal alkoxide. The metal alkoxide used is not particularly limited as long as it is a metal compound containing a hydrolyzable group, such as Si, Al, Ti, or Zr, which can be hydrolyzed to form a condensation compound. For example, alkoxysilanes such as tetraethoxysilane, tetramethoxysilane, tetraisopropoxysilane, tetra-n-propoxysilane, tetra-n-butoxysilane, alkoxyaluminums such as aluminum triethoxide and aluminum tri-n-propoxide, tetra Examples thereof include alkoxy titaniums such as ethoxy titanium and tetraisopropoxy titanium. In the production, it is preferable that water necessary for hydrolysis of the metal alkoxide coexist, and it is also preferable to add a catalyst for promoting the hydrolysis and condensation reaction. The contents of the water and the catalyst are experimentally determined depending on the type of the metal compound and the particle diameter and shape of the target particles. Examples of the catalyst include inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid, organic acids such as formic acid, acetic acid, propionic acid, oxalic acid, sulfonic acid, and acetic anhydride, ammonia, monomethylamine, dimethylamine, monoethylamine, diethylamine, and ethylenediamine. And the like. Further, in the production of inorganic fine particles, if the mixture is left standing without stirring at all, a lump-shaped product tends to be generated and the particle diameter tends to increase, so that stirring is preferable. The stirring speed can be experimentally determined by the scale of the reaction vessel, the shape of the stirring blade, the stirring method, and the like. For solid-liquid separation of the obtained fine particles, generally known methods such as filtration, centrifugation, and evaporation can be used.
[0029]
As a method of introducing an ionic group to the surface of the inorganic fine particles, a method of treating the particle surface with a surface treating agent to introduce an ionic group can be mentioned. For example, the surface treatment may be performed by reacting a hydroxyl group present on the surface of inorganic fine particles such as silica or titania with an organic compound having a functional group and an ionic group capable of reacting with the hydroxyl group. Further, a chemical surface treatment can be performed from an organometallic compound having a functional group and a compound capable of reacting with the functional group. Examples of the surface treatment agent include a silane coupling agent.
[0030]
In the case of organic fine particles, the monomer may be mixed in a homogeneous solution such as an organic solvent and polymerized, or may be polymerized in a heterogeneous system consisting of a monomer-containing phase and an aqueous phase. At this time, the monomer phase may be a single monomer or an appropriate solvent may be added for the purpose of controlling the reaction rate. Further, a catalyst such as a polymerization initiator and other additives may be contained.
[0031]
There is no particular limitation on the solvent used, and water, methanol, ethanol, isopropyl alcohol, n-propyl alcohol, acetone, methyl ethyl ketone, methyl isobutyl ketone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, benzene, toluene and N-methyl- 2-pyrrolidone and the like. These may be used alone or in combination. In the case of producing a heterogeneous system, there is no particular limitation as long as it does not completely dissolve the polymerizable monomer, but an aqueous solvent is preferably used.
[0032]
As the polymerization initiator used for the polymerization, generally known ones can be used, and examples thereof include various peroxide compounds, azo compounds, peroxides, and cerium ammonium salts. Specific examples include 2,2'-azobisisobutyronitrile, 1,1'-azobis (cyclohexane-1-carbonitrile), and 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile). ), 2,2'-azobis (2-cyclopropylpropionitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2-methylbutyronitrile), Azonitrile compounds such as-[(1-cyano-1-methylethyl) azo] formamide, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, and 2,2'-azobis (2-methyl-N- Azoamidine compounds such as phenylpropionamidine) dibasic acid salt and 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dibasic acid Cyclic azoamidine compounds such as salts, azoamide compounds such as 2,2′-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, 2,2′-azobis Alkylazo compounds such as (2,4,4-trimethylpentane), peroxides such as potassium persulfate, ammonium persulfate, hydrogen peroxide and benzoyl peroxide; cerium ammonium such as ceric ammonium sulfate and ceric ammonium nitrate And the like. The polymerization conditions and the polymerization initiator concentration can be experimentally determined as appropriate depending on the type of the monomer and the polymerization initiator used.
[0033]
In the case of producing fine particles in a heterogeneous system, it is preferable to emulsify the particles with an emulsifier or the like in order to reduce the particle size and achieve monodispersion of the particle size distribution. The emulsifier can be arbitrarily selected from anionic, cationic, nonionic and amphoteric surfactants.
[0034]
Examples of anionic surfactants include fatty acid soaps such as fatty acid soda soap, fatty acid potash soap, soap stearate, alkyl sulfate Na salt, alkyl ether sulfate Na salt, alkyl sulfate triethanolamine salt, and alkyl sulfate. Alkyl sulfates such as ether sulfate triethanolamine salt; alkyl alcohol sulfate Na salts such as lauryl alcohol sulfate Na salt and macaw alcohol sulfate Na salt; sodium dodecylbenzenesulfonate; sodium n-dodecylbenzenesulfonate; Methyl taurate such as sodium dodecylbenzenesulfonate, sodium alkyl (tallow) methyl taurate, sodium oleoyl methyl taurate, and sodium lauryl methyl taurate; Moniumu salts, perfluoroalkyl carboxylic acid potassium salt and fluorine-based, dioctyl sulfosuccinate Na, oleoyl sarcosine and lauroyl sarcosinate, and the like.
[0035]
Examples of the cationic surfactant include amine salts such as octadecylamine acetate, tetradecylamine acetate, and alkylamine hydrochloride, octadecyltrimethylammonium chloride, dodecyltrimethylammonium chloride, and alkyl (hardened tallow, coconut, etc.) trimethylammonium chloride. , Such as methyl, hexadecyltrimethylammonium chloride, quaternary salts of alkylimidazoline, benzyl such as alkyl (coconut) dimethylbenzylammonium chloride, tetradecyldimethylbenzylammonium chloride, octadecyldimethylbenzylammonium chloride, oxyethylene dodecylamine, polyoxy Ethylene dodecylamine, polyoxyethylene octadecylamine, polyoxyethylene alkyl (tallow, yam Etc.) amines, alkylamine type such as polyoxyethylene alkyl (tallow) propylene diamine, 1-hydroxyethyl-2-alkyl (tallow) imidazoline quaternary salt, alkyl (coco) isoquinolinium bromide, polymer amine and perm And fluoroalkyl quaternary ammonium iodides.
[0036]
Examples of nonionic surfactants include ether types such as polyoxyethylene oleyl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, loxyethylene lauryl ether, and polyoxyethylene tridecyl ether, and polyoxyethylene nonylphenol ether. , Alkyl phenol type such as polyoxyethylene octyl phenol ether, ester type such as polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene monooleate, polyethylene glycol tallow fatty acid ester, sorbitan monolaurate, sorbitan Monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, sorbitan trioleate, etc. Sorbitan ester ether type such as rubitan ester type, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, oxyethylene oxypropylene block polymer, polyoxyethylene distearate, glycerol Monostearate and perfluoroalkylpolyoxyethylene ethanol are exemplified.
[0037]
Examples of the amphoteric surfactant include alkyl betaines such as lauryl betaine and stearyl betaine, sodium alkylamino fatty acids, and alkylamine oxides.
[0038]
In the case of producing fine particles in a heterogeneous system, if the particles are allowed to stand without stirring at all, a bulk polymerization product tends to be easily generated at the interface. Conversely, if the stirring is too early, the reaction proceeds rapidly, and the particle size distribution tends to be widened. The stirring speed can be experimentally determined by the scale of the reaction vessel, the shape of the stirring blade, the stirring method, and the like. For solid-liquid separation of the obtained fine particles, generally known methods such as filtration, centrifugation, and evaporation can be used.
[0039]
The fine particles constituting the solid electrolyte of the present invention are fine particles having an ionic group on the surface by introducing an ionic group into the above-mentioned organic compound or inorganic compound.
[0040]
Examples of the method of introducing a sulfonic acid group as an ionic group into the organic fine particles include: reacting the organic polymer with a sulfonating agent such as chlorosulfonic acid in a solvent such as chloroform, or reacting in a concentrated sulfuric acid or fuming sulfuric acid. By doing so, a sulfone group can be introduced. The sulfonating agent is not particularly limited as long as it sulfonates the organic polymer. When the organic polymer is sulfonated by this method, the degree of sulfonation can be easily controlled by the amount of the sulfonating agent used, the reaction temperature and the reaction time.
[0041]
In order to produce fine particles having a core-shell structure having different sulfonic acid group concentrations on the surface and inside of the fine particles, for example, a method of reacting in concentrated sulfuric acid or a method of diluting chlorosulfonic acid with a mixed solvent and reacting is preferable.
[0042]
Alternatively, the ionic groups can be introduced by mixing fine particles and a binder, forming the mixture into a film by a solution casting method or the like, and then immersing the mixture in chlorosulfonic acid or the like.
[0043]
Similarly, other ionic groups other than the sulfonic acid group can be introduced by a conventionally known method. For example, a sulfonimide group can be introduced by a method of reacting a sulfonic acid group with a sulfonamide group. As described above, the ionic groups can be concentrated on the surface of the fine particles in the fine particle film using the core-shell type particles.
[0044]
The shape of the fine particles constituting the solid electrolyte of the present invention is preferably spherical from the viewpoint of improving the packing density, but is not particularly limited, such as flaky, granular, granulated, amorphous, porous, and hollow. . Further, functional fine particles having a smaller particle diameter may be attached to the surface of the fine particles, or functional fine particles having a surface modified by chemically bonding a desired functional substance to the fine particle surface may be used.
[0045]
In the solid electrolyte of the present invention, it is also a preferred embodiment to mix the ionic group-containing fine particles with a binder. As such a binder, organic and inorganic polymers can be widely used. For example, polystyrene, polyphenylene sulfide sulfone represented by the following formula (1), polyphenylene sulfide represented by the following formula (2), polyphosphazene represented by the following formula (3), polyimide represented by the following formula (4), and Polysulfone (PSF), polyphenylene oxide (PPO), polyetherketone (PEK), polyetheretherketone (PEEK), polybenzimidazole (PBI) and polyethersulfone (PES) and their sulfonated products, represented by Nafion Perfluoro-based electrolyte, polyvinyl alcohol, partially saponified polyvinyl acetate, partially saponified ethylene-vinyl acetate copolymer, hydroxyethyl (meth) acrylate (co) polymer, cellulose, hydroxypropylcellulose, chitin, Chitosan, carrageenan, polysaccharide polymers such as dextran, polyvinylidene fluoride, polysiloxanes, organopolysiloxanes, alumina, titania are preferred examples. Two or more of these binders can be used in combination.
[0046]
Embedded image

[0047]
Embedded image

[0048]
Embedded image

[0049]
Embedded image

[0050]
(Here, Z is an organic group containing an aromatic ring, and n is the number of repetitions.)
The solid electrolyte of the present invention is mainly composed of the fine particles and the binder. If the mixing amount of the fine particles is too small, reduction of MCO and high ion conductivity cannot be expected. A more preferable mixing amount of the fine particles is 30 to 80% by volume fraction. It should be appropriately selected according to the required MCO, ionic conduction, membrane strength, or polymer type.
[0051]
In the production of the solid electrolyte of the present invention, as a method of mixing the base polymer and the fine particles, a method of melting the fine particles in the base polymer or dispersing them in a solution state, or a method of mixing the fine particle precursor in the base polymer in a melt or solution state After that, a method of using the fine particles alone is exemplified, but is not particularly limited.
[0052]
The shape of the solid electrolyte of the present invention can be used after being shaped into a shape according to the application. For example, the solid electrolyte of the present invention is formed into a membrane to form an electrolyte membrane, which can be used for a fuel cell.
[0053]
The solid electrolyte of the present invention can be suitably used for a fuel cell by being formed into a membrane to form an electrolyte membrane. As a film forming method, a normal solvent casting method, an extrusion molding method, a hot press method, or the like can be applied.
[0054]
Next, a fuel cell using the electrolyte membrane of the present invention will be described. The electrolyte membrane of the present invention is used in a fuel cell as a membrane electrode assembly in combination with an electrode composed of an electrode substrate and an electrode catalyst layer.
[0055]
As the electrode catalyst layer in the fuel cell to which the electrolyte membrane of the present invention is applied, a known one can be used without any particular limitation. The electrode catalyst layer is a layer containing a substance that contributes to electron conduction and proton conduction that promote an electrode reaction. Further, when the fuel is a liquid or gas, it is preferable that the structure has a structure through which the liquid or gas easily permeates, and it is preferable that the structure promotes discharge of by-products accompanying the electrode reaction. Examples of the fuel for the fuel cell include a gas such as hydrogen and a liquid such as alcohol, and these may be one kind or a mixture of two or more kinds. In particular, alcohols having 1 to 3 carbon atoms, dimethyl ether, and aqueous solutions thereof are preferably used from the viewpoint of reaction efficiency and simplification of the entire battery system. A known catalyst can be used as the catalyst contained in the electrode catalyst layer, and is not particularly limited, but a noble metal catalyst such as platinum, palladium, ruthenium, iridium, and gold is preferably used. Further, two or more elements may be contained, such as alloys and mixtures of these noble metal catalysts.
[0056]
The electron conductor (conductive material) contained in the electrode catalyst layer is not particularly limited, but a carbon material or an inorganic conductive material is preferably used from the viewpoint of electron conductivity and chemical stability. Especially, an amorphous or crystalline carbon material is mentioned. For example, carbon blacks such as channel black, thermal black, furnace black and acetylene black are preferably used from the viewpoint of electron conductivity and specific surface area. Furnace black includes Vulcan XC-72, Vulcan P, Black Pearls 880, Black Pearls 1100, Black Pearls 1300, Black Pearls 2000, Regal 400 (all trade names) manufactured by Cabot Corporation, Ketjen manufactured by Ketjen Black International Examples include Black EC and EC600JD (all are trade names), # 3150 and # 3250 (all are trade names) manufactured by Mitsubishi Chemical Corporation, and acetylene black includes Denka Black manufactured by Denki Kagaku Kogyo KK.
[0057]
In addition to carbon black, artificial graphite and carbon obtained from organic compounds such as natural graphite, pitch, coke, polyacrylonitrile, phenol resin and furan resin can also be used. The form of these carbon materials is not particularly limited, and fibrous, scale-like, tube-like, conical-like, and megaphone-like ones can be used in addition to amorphous particles. It is also possible to use carbon materials obtained by post-processing these carbon materials. Further, it is preferable that the electron conductor is uniformly dispersed with the catalyst particles from the viewpoint of electrode performance. For this reason, it is preferable that the catalyst particles and the electron conductor are well dispersed in advance as a coating liquid. Further, it is also a preferred embodiment to use, as the electrode catalyst layer, a catalyst-supporting carbon or the like in which a catalyst and an electron conductor are integrated. By using the catalyst-supporting carbon, the utilization efficiency of the catalyst is improved, which can contribute to improvement in battery performance and cost reduction. Here, even when the catalyst-supporting carbon is used for the electrode catalyst layer, it is possible to add a conductive agent in order to further increase the electron conductivity. As such a conductive agent, the above-described carbon black is preferably used.
[0058]
Since the catalyst and the electron conductor are usually powders, a substance having proton conductivity is used to solidify them. As the proton conductor used for the electrode catalyst layer, generally, various organic and inorganic materials are known, but when used for a fuel cell, a sulfonic acid group that improves proton conductivity, a sulfonimide group, A polymer having an ionic group such as a sulfate group, a phosphonic acid group, a phosphoric acid group and a carboxylic acid group is preferably used. Among them, from the viewpoint of the stability of the ionic group, a polymer having a proton exchange group composed of a fluoroalkyl ether side chain and a fluoroalkyl main chain is preferably used. For example, Nafion (registered trademark) manufactured by DuPont, Aciplex (registered trademark) manufactured by Asahi Kasei Corporation, Flemion (registered trademark) manufactured by Asahi Glass Co., Ltd. are preferably used. These proton exchange polymers are provided in the electrode catalyst layer in the form of a solution or a dispersion. At this time, the solvent for dissolving or dispersing the polymer is not particularly limited, but a polar solvent is preferable from the viewpoint of the solubility of the proton exchange polymer.
[0059]
The proton conductor is preferably added in advance to a coating liquid containing the electrode catalyst particles and the electron conductor as main constituents when preparing the electrode catalyst layer, and applied in a uniformly dispersed state from the viewpoint of electrode performance. However, the proton conductor may be applied after the application of the electrode catalyst layer. Here, the method for applying the proton conductor to the electrode catalyst layer includes spray coating, brush coating, dip coating, die coating, curtain coating, and flow coating, and is not particularly limited. The amount of the proton conductor contained in the electrode catalyst layer should be appropriately determined according to the required electrode characteristics and the conductivity of the proton conductor used, and is not particularly limited, but is not particularly limited. The ratio is preferably in the range of 1 to 80%, more preferably 5 to 50%. When the proton conductor is too small, the proton conductivity is low, and when the proton conductor is too large, the gas permeability is impaired.
[0060]
The electrode catalyst layer may contain various substances in addition to the above-mentioned catalyst, electron conductor and proton conductor. In particular, a polymer other than the above-described proton exchange resin may be included in order to enhance the binding property of a substance contained in the electrode catalyst layer. Examples of such a polymer include a polymer containing a fluorine atom, and are not particularly limited. For example, polyvinyl fluoride, polyvinylidene fluoride, polyhexafluoropropylene, polytetrafluoroethylene, and polyperfluoroalkylvinyl ether Or a copolymer of these, a copolymer of a monomer unit constituting these polymers with another monomer such as ethylene or styrene, or a blend. The content of these polymers in the electrode catalyst layer is preferably in the range of 5 to 40% by weight. If the polymer content is too large, the electron and ionic resistances tend to increase and the electrode performance tends to decrease.
[0061]
The electrode substrate of the fuel cell is not particularly limited, and a known material can be used. Any material having a low electric resistance and capable of collecting (supplying) power can be used. Further, when the electrode catalyst layer is used also as a current collector, it is not particularly necessary to use an electrode substrate. Examples of the constituent material of the electrode substrate include, for example, carbonaceous materials and conductive inorganic substances, for example, fired bodies from polyacrylonitrile, fired bodies from pitch, carbon materials such as graphite and expanded graphite, stainless steel, molybdenum And titanium. The form of these is not particularly limited, and is used, for example, in a fibrous or particulate form, but a fibrous conductive substance (conductive fiber) such as carbon fiber is preferable from the viewpoint of fuel permeability. As an electrode substrate using conductive fibers, any structure of a woven fabric or a nonwoven fabric can be used. For example, carbon paper TGP series and SO series (both trade names) manufactured by Toray Industries Inc., carbon cloth manufactured by E-TEK, and the like are used. As the woven fabric, plain weave, oblique weave, satin weave, crest weave, stitch weave and the like can be used without particular limitation. In addition, as the nonwoven fabric, a papermaking method, a needle punch method, a spun bond method, a water jet punch method, a melt blow method, and the like are used without any particular limitation. Also, it may be a knitted fabric.
[0062]
In these fabrics, particularly when carbon fibers are used, a woven fabric obtained by carbonizing or graphitizing a plain woven fabric using oxidized spun yarn, and carbonizing oxidized yarn after processing the nonwoven fabric by a needle punch method, a water jet punch method, or the like. Alternatively, a graphitized nonwoven fabric, a matted nonwoven fabric formed by a papermaking method using flame-resistant yarn, carbonized yarn, or graphitized yarn are preferably used. In particular, it is preferable to use a nonwoven fabric because a thin and strong fabric can be obtained.
[0063]
When a conductive fiber made of carbon fiber is used for the electrode substrate, examples of the carbon fiber include polyacrylonitrile-based carbon fiber, phenol-based carbon fiber, pitch-based carbon fiber, rayon-based carbon fiber, and the like.
[0064]
Water repellency treatment to prevent gas diffusion and permeability decrease due to water stagnation, partial water repellency for forming a water discharge path, hydrophilic treatment, and lowering resistance to electrode base materials used in fuel cells For example, the addition of carbon powder or the like can be performed. Further, in the fuel cell, it is preferable to provide a conductive intermediate layer containing at least an inorganic conductive substance and a hydrophobic polymer between the electrode substrate and the electrode catalyst layer. In particular, when the electrode substrate is a carbon fiber woven fabric or nonwoven fabric having a large porosity, the provision of the conductive intermediate layer can suppress the performance deterioration due to the electrode catalyst layer penetrating into the electrode substrate.
[0065]
The method for producing the membrane electrode assembly using the electrolyte membrane, the electrode catalyst layer, or the electrode catalyst layer and the electrode substrate of the present invention is not particularly limited, and a known method (for example, Electrochemistry, 1985, 53, 269. J. Electrochem. Soc .: Electrochemical Science and Technology, 1988, 135 (9), 2209.). is there.
[0066]
The electrolyte membrane of the present invention is applicable to various uses. For example, examples of the ion exchange membrane include various electrochemical devices such as a water purification device, a fuel cell, a water electrolysis device, and a chloroalkali electrolysis device. Among them, the fuel cell is most preferable. Among the fuel cells, it is suitable for a polymer electrolyte fuel cell, and further suitable for a direct fuel cell using an alcohol having 1 to 3 carbon atoms, dimethyl ether and an aqueous solution thereof as a fuel, and using methanol as a fuel. Most suitable for direct methanol fuel cells.
[0067]
Further, the use of the fuel cell of the present invention is not particularly limited, but a power supply source for a moving body is preferable. In particular, it is preferably used as a power supply source for mobile devices such as mobile phones, personal computers, PDAs (personal digital assistants), home appliances such as vacuum cleaners, automobiles such as cars, buses and trucks, and mobile bodies such as ships and railways.
[0068]
【Example】
Hereinafter, the solid electrolyte of the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. In addition, the measurement conditions of each physical property are as follows.
(1) Measurement of particle size and number average particle size
With respect to 100 particles arbitrarily selected from a photograph taken by a scanning electron microscope (SEM), the particle size (equivalent average diameter of a circle) of each particle was measured and calculated as a number average.
(2) Method for measuring proton conductivity of electrolyte membrane
After immersing the electrolyte membrane in pure water at 25 ° C. for 24 hours, it was taken out in an atmosphere at 25 ° C. and a relative humidity of 50 to 80%, and the resistance was measured by a constant potential AC impedance method. An electrochemical measurement system manufactured by Solartron (Solartron 1287 Electrochemical Interface and Solartron 1255B Frequency Response Analyzer) was used. The sample was sandwiched by applying a load of 1 kg between two circular electrodes (made of stainless steel) of φ2 mm and φ10 mm (effective electrode area: 0.0314 cm) ² ). A 15% aqueous solution of poly (2-acrylamido-2-methylpropanesulfonic acid) was applied to the interface between the sample and the electrode. At 25 ° C., constant potential impedance measurement was performed to determine the ion conductivity in the film thickness direction. The AC amplitude was 50 mV.
(3) Method for measuring methanol permeation through electrolyte membrane
After the electrolyte membrane was immersed in pure water at 25 ° C. for 24 hours, it was taken out and, as shown in FIG. 1, the electrolyte membrane was sandwiched between acrylic resin H-type cells, and pure water (60 mL) was placed in one of the cells. The other cell was charged with a 1M aqueous methanol solution (60 mL). The cell capacity was 80 mL each. The opening between the cells is a circle having a diameter of 1.5 cm, and the effective film area is 1.77 cm. ² Met. Both cells were stirred at 20 ° C. The amount of methanol eluted in pure water after 1 hour, 2 hours and 3 hours was measured and quantified by gas chromatography (GC-2010) (trade name) manufactured by Shimadzu Corporation. The permeation amount of methanol per unit time and unit area was determined from the slope of the graph.
[0069]
(Example 1)
(1) Synthesis of sulfonated styrene-divinylbenzene fine particles
Styrene (4.5 g) and divinylbenzene (0.5 g) were placed in a 300 mL four-necked flask equipped with a reflux condenser, a stirrer, and a nitrogen gas inlet tube. While introducing nitrogen gas into the flask and stirring, an aqueous solution (93.5 g) of a nonionic surfactant “Nonion HS-210” (trade name) and an aqueous solution of potassium persulfate (2 g) were added dropwise while the mixture was stirred. As the reaction proceeded, styrene-divinylbenzene fine particles were generated. After the styrene-divinylbenzene fine particles were separated into solid and liquid by centrifugation, the mixture was stirred in a 1,2-dichloroethane solution of chlorosulfonic acid. After the completion of the reaction, the resultant was sufficiently washed using a dialysis tube to obtain a target sulfonated styrene-divinylbenzene. The number average particle diameter of the sulfonated styrene-divinylbenzene was 500 nm when measured. When the sulfur concentration of the sulfonated styrene-divinylbenzene was analyzed by the STEM-EDX method, it was confirmed that a sulfur atom was present on the surface and inside of the fine particles, and it was found that a sulfonic acid group was present on the surface and inside of the fine particles. . The sulfur concentration ratio between the surface of the fine particles and the inside, that is, the sulfonic acid group concentration ratio was 1: 1 and did not change.
(2) Synthesis of sulfonated polyphenylene oxide
After dissolving polyphenylene oxide (YPX-100L) (trade name) (100 g) (manufactured by Mitsubishi Engineering-Plastics Co., Ltd.) (100 g) in chloroform (1000 g) at room temperature under a nitrogen atmosphere, chlorosulfonic acid (34 mL) was slowly added dropwise with stirring. After completion of the dropwise addition, stirring was continued at room temperature for 30 minutes. The precipitated polymer was separated by filtration, pulverized with a mill, sufficiently washed with water, and dried under vacuum to obtain a target sulfonated polyphenylene oxide (ion exchange equivalent: 3.0 meq). The obtained sulfonated polyphenylene oxide was dissolved in N, N-dimethylacetamide (DMAc) to obtain a 15% by weight solution.
(3) Preparation of solid electrolyte membrane
0.2 g of the sulfonated styrene-divinylbenzene fine particles (1) and 4.5 g of the sulfonated polyphenylene oxide DMAc solution (2) were mixed. This liquid was cast on a glass plate and heated at 100 ° C. for 3 hours to produce a solid electrolyte membrane. The film thickness was 100 μm.
(4) Performance evaluation of solid electrolyte membrane
The methanol permeation amount and ionic conductivity of the membrane obtained in the above (3) were evaluated. The methanol permeation amount of this membrane is 7.0 μmol / cm. ² -Min, ion conductivity is 8.0 S / cm ² Met.
[0070]
(Example 2)
A solid electrolyte was prepared in the same manner as in Example 1 except that a commercially available 20% Nafion solution (registered trademark of DuPont) was used instead of the sulfonated polyphenylene oxide DMAc solution. When the performance of this electrolyte membrane was evaluated in the same manner as in Example 1, the permeation amount of methanol was 7.3 μmol / cm. ² / Min, ionic conductivity 7.5 S / cm ² Met.
[0071]
(Comparative Example 1)
In Example 2, a solid electrolyte membrane was obtained in the same manner as in Example 1 using only a commercially available 20% Nafion solution (registered trademark, manufactured by DuPont). The methanol permeation amount of this electrolyte membrane was 8.0 μmol / cm. ² / Min, ionic conductivity is 6.7 S / cm ² And the performance was worse than that of Example 1 in which organic fine particles were added.
[0072]
(Example 3)
A solid electrolyte membrane was prepared in the same manner as in Example 1 except that a chloroform solution of polyphenylene oxide was used instead of the sulfonated polyphenylene oxide DMAc solution. When the performance of this electrolyte membrane was evaluated in the same manner as in Example 1, the methanol permeation amount was 5.0 μmol / cm. ² / Min, ion conductivity is 4.0 S / cm ² Met.
[0073]
(Comparative Example 2)
In Example 3, a solid electrolyte membrane was obtained in the same manner as in Example 1 except that only a chloroform solution of polyphenylene oxide was used. The methanol permeation amount of this electrolyte membrane was 5.0 μmol / cm. ² / Min, ion conductivity is 0 S / cm ² And the performance was worse than that of Example 2 to which organic fine particles were added.
[0074]
(Example 4)
(1) Synthesis of sulfonated styrene-divinylbenzene fine particles
Styrene (3.2 g) and divinylbenzene (1.8 g) were placed in a 300 mL four-necked flask equipped with a reflux condenser, a stirrer, and a nitrogen gas inlet tube. While introducing nitrogen gas into the flask and stirring, an aqueous solution (93.5 g) of a nonionic surfactant “Nonion HS-210” (trade name) and an aqueous solution of potassium persulfate (2 g) were added dropwise while the mixture was stirred. As the reaction proceeded, styrene-divinylbenzene fine particles were generated. After the styrene-divinylbenzene fine particles were separated into solid and liquid by centrifugation, they were heated and stirred in concentrated sulfuric acid. After the completion of the reaction, purification was carried out with a large amount of methanol to obtain the target sulfonated styrene-divinylbenzene. The number average particle diameter of the sulfonated styrene-divinylbenzene was 480 nm when measured. When the sulfur concentration of the sulfonated styrene-divinylbenzene was analyzed by the STEM-EDX method, the sulfur concentration ratio between the surface of the fine particles and the inside of the fine particles, that is, the sulfonic acid group concentration ratio was 5: 1.
(2) Performance evaluation of solid electrolyte membrane
A solid electrolyte membrane was produced in the same manner as in Example 1 except that the sulfonated styrene-divinylbenzene fine particles of (1) were used instead of the sulfonated styrene-divinylbenzene fine particles of Example 1. When the performance of this electrolyte membrane was evaluated in the same manner as in Example 1, the permeation amount of methanol was 5.7 μmol / cm. ² / Min, ionic conductivity 8.0S / cm ² And the performance was better than that of Example 1.
[0075]
(Example 5)
A solid electrolyte membrane was prepared in the same manner as in Example 4, except that a commercially available 20% Nafion solution (registered trademark of DuPont) was used instead of the sulfonated polyphenylene oxide DMAc solution. When the performance of this electrolyte membrane was evaluated in the same manner as in Example 1, the methanol permeation amount was 6.9 μmol / cm. ² / Min, ionic conductivity 7.5 S / cm ² Met.
[0076]
(Example 6)
(1) Synthesis of sulfonated phenylmaleimide-styrene-divinylbenzene fine particles
Styrene (3.0 g), divinylbenzene (0.5 g) and phenylmaleimide (1.5 g) were placed in a 300 mL four-necked flask equipped with a reflux condenser, a stirrer, and a nitrogen gas inlet tube. While introducing nitrogen gas into the flask and stirring, an aqueous solution (93.5 g) of a nonionic surfactant “Nonion HS-210” (trade name) and an aqueous solution of potassium persulfate (2 g) were added dropwise while the mixture was stirred. As the reaction proceeded, fine particles of phenylmaleimide-styrene-divinylbenzene were formed. The phenylmaleimide-styrene-divinylbenzene fine particles were separated into solid and liquid by centrifugation, and then stirred in concentrated sulfuric acid. After the completion of the reaction, purification was carried out with a large amount of methanol to obtain the desired sulfonated phenylmaleimide-styrene-divinylbenzene. The number average particle size of the sulfonated phenylmaleimide-styrene-divinylbenzene was measured and found to be 550 nm. When the sulfur concentration of the sulfonated phenylmaleimide-styrene-divinylbenzene was analyzed by the STEM-EDX method, the ratio of the sulfur concentration on the surface of the fine particles to the inside, that is, the sulfonic acid group concentration ratio was 9: 1.
(2) Performance evaluation of solid electrolyte membrane
A solid electrolyte membrane was prepared in the same manner as in Example 1, except that the sulfonated phenylmaleimide-styrene-divinylbenzene fine particles (1) were used instead of the sulfonated styrene-divinylbenzene fine particles of Example 1. When the performance of this electrolyte membrane was evaluated in the same manner as in Example 1, the methanol permeation amount was 5.5 μmol / cm. ² / Min, ionic conductivity 8.0S / cm ² And the performance was better than that of Example 1.
[0077]
(Example 7)
A solid electrolyte membrane was prepared in the same manner as in Example 6, except that a commercially available 20% Nafion solution (registered trademark of DuPont) was used instead of the sulfonated polyphenylene oxide DMAc solution. When the performance of this electrolyte membrane was evaluated in the same manner as in Example 1, the methanol permeation amount was 6.9 μmol / cm. ² / Min, ionic conductivity 7.5 S / cm ² Met.
[0078]
(Example 8)
A solid electrolyte was produced in the same manner as in Example 6, except that a DMAc solution of polyvinylidene fluoride was used instead of the sulfonated polyphenylene oxide DMAc solution. When the performance of this membrane was evaluated in the same manner as in Example 1, the methanol permeation amount was 0.9 μmol / cm. ² / Min, ion conductivity is 1.0 S / cm ² Met.
[0079]
(Example 9)
(1) Hydrolysis of organic silane
An aqueous solution of 0.01 N hydrochloric acid was added to 5 g of chlorosulfonylphenylethyltrichlorosilane, and the mixture was stirred at room temperature for 30 minutes to obtain a hydrolyzate. The hydrolyzate was dissolved in N, N-dimethylacetamide (DMAc) to obtain a 15% by weight solution.
(2) Surface treatment of silica fine particles
A spherical silica (3.0 g) and methanol (90 g) were charged into a 300 mL four-necked flask equipped with a stirrer and a nitrogen gas inlet tube, and a DMAc solution (2.0 g) of the hydrolyzate of the above (1) was added with stirring. Was dropped. The mixture was stirred at room temperature for 1 hour to surface-treat the silica fine particles. The number average particle diameter of the surface-treated silica fine particles was measured and found to be 450 nm. When the sulfur concentration of the surface-treated silica fine particles was analyzed by the STEM-EDX method, the presence of sulfur atoms was confirmed only from the surface of the fine particles.
(3) Performance evaluation of solid electrolyte membrane
A solid electrolyte membrane was prepared in the same manner as in Example 10, except that the surface-treated silica fine particles of (2) were used instead of the styrene-divinylbenzene fine particles. When the performance of this electrolyte membrane was evaluated in the same manner as in Example 1, the methanol permeation amount was 6.8 μmol / cm. ² / Min, ion conductivity is 7.0 S / cm ² Met.
[0080]
(Example 10)
(1) Adjustment of binder
To 5 g of γ-glycidoxypropyltrimethoxysilane manufactured by Toray Dow Corning Silicone Co., was added a 0.01N aqueous hydrochloric acid solution, and the mixture was stirred at room temperature for 30 minutes to obtain a hydrolyzate. A solution in which the hydrolyzate of the γ-glycidoxypropyltrimethoxysilane was dissolved in N, N-dimethylacetamide (DMAc) was mixed with polyvinyl alcohol.
(2) Performance evaluation of solid electrolyte membrane
A solid electrolyte was prepared in the same manner as in Example 6 except that the DMAc solution of the polyvinyl alcohol and the γ-glycidoxypropyltrimethoxysilane hydrolyzate of the above (1) was used instead of the sulfonated polyphenylene oxide DMAc solution. When the performance of this membrane was evaluated in the same manner as in Example 1, the methanol permeation amount was 1.5 μmol / cm. ² / Min, ionic conductivity 1.2S / cm ² Met.
[0081]
(Example 11)
(1) Synthesis of styrene-divinylbenzene fine particles
Styrene (4.5 g) and divinylbenzene (0.5 g) were placed in a 300 mL four-necked flask equipped with a reflux condenser, a stirrer, and a nitrogen gas inlet tube. While introducing nitrogen gas into the flask and stirring, an aqueous solution (93.5 g) of a nonionic surfactant “Nonion HS-210” (trade name) and an aqueous solution of potassium persulfate (2 g) were added dropwise while the mixture was stirred. As the reaction progressed, desired styrene-divinylbenzene fine particles were formed. It was 50 nm when the number average particle diameter of this styrene-divinylbenzene was measured.
(2) Preparation of solid electrolyte membrane
0.2 g of the styrene-divinylbenzene fine particles of the above (1) and 4.5 g of a polyvinylidene fluoride DMAc solution were mixed. This liquid was cast on a glass plate and heated at 100 ° C. for 3 hours to produce a solid electrolyte membrane. The membrane was immersed in a solution of chlorosulfonic acid in 1,2-dichloroethane, and then sufficiently washed.
(3) Performance evaluation of solid electrolyte membrane
When the performance of the electrolyte membrane obtained in the above (2) was evaluated in the same manner as in Example 1, the permeation amount of methanol was 1.5 μmol / cm. ² -Min, ion conductivity is 2.2 S / cm ² Met.
[0082]
(Example 12)
(1) Synthesis of fine particles of phenylmaleimide-styrene-divinylbenzene
Styrene (3.0 g), divinylbenzene (0.5 g) and phenylmaleimide (1.5 g) were placed in a 300 mL four-necked flask equipped with a reflux condenser, a stirrer, and a nitrogen gas inlet tube. While introducing nitrogen gas into the flask and stirring, an aqueous solution (93.5 g) of a nonionic surfactant “Nonion HS-210” (trade name) and an aqueous solution of potassium persulfate (2 g) were added dropwise while the mixture was stirred. As the reaction proceeded, desired phenylmaleimide-styrene-divinylbenzene fine particles were formed. The number average particle diameter of the phenylmaleimide-styrene-divinylbenzene fine particles was measured and found to be 80 nm.
(2) Performance evaluation of solid electrolyte membrane
A solid electrolyte membrane was prepared in the same manner as in Example 10, except that the phenylmaleimide-styrene-divinylbenzene fine particles (1) were used instead of the styrene-divinylbenzene fine particles. When the performance of this electrolyte membrane was evaluated in the same manner as in Example 1, the methanol permeation amount was 1.4 μmol / cm. ² / Min, ion conductivity is 2.0 S / cm ² Met.
[0083]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the novel solid electrolyte which suppresses fuel crossover, has high ion conductivity, and can achieve high output is obtained. By using this solid electrolyte, a high-performance direct fuel cell can be obtained, and its practicality is high.
[Brief description of the drawings]
FIG. 1 is a side view showing a schematic diagram of a cell used when analyzing the methanol permeation amount of a solid electrolyte of the present invention.
[Explanation of symbols]

Claims (10)

A solid electrolyte comprising fine particles having an ionic group on at least the surface. 2. The solid according to claim 1, wherein the ionic group is at least one or more selected from a sulfonic acid group, a sulfonimide group, a sulfate group, a phosphonic acid group, a phosphoric acid group and a carboxylic acid group. Electrolytes. 2. The solid electrolyte according to claim 1, wherein the ionic group is a sulfonic acid group or a sulfonimide group. The solid electrolyte according to any one of claims 1 to 3, wherein the ionic group concentration ratio (surface: inside) between the surface and the inside of the fine particles is 3: 1 or more. The solid electrolyte according to any one of claims 1 to 4, wherein the fine particles are fine particles containing an organic polymer as a main component. The solid electrolyte according to any one of claims 1 to 5, further comprising fine particles having a number average particle diameter of at least primary particles of 1 µm or less. An electrolyte membrane comprising the solid electrolyte according to claim 1. A fuel cell using the electrolyte according to claim 7. 9. The fuel cell according to claim 8, wherein the fuel cell is a direct fuel cell using an alcohol having 1 to 3 carbon atoms, dimethyl ether, or a mixture thereof with water. A mobile power source using the fuel cell according to claim 8.

Images