JP2005025991A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery having high energy density and capable of preventing the generation of expansion when it is left in the high-temperature condition. <P>SOLUTION: In this nonaqueous electrolyte secondary battery including a negative electrode provided with a negative mix layer and a negative electrode collector, the negative mix layer contains a negative electrode active material and a binder, and the negative electrode active material contains a material, which contains Si and O, and a carbon material. Atomic ratio x of O in relation to Si in the material, which contains si and O, satisfies an expression 0<x<2, and the binder contains SBR, and adhesion strength between the negative electrode mix layer and the negative electrode collector is 75 N/m or more. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００８３】
［電池評価試験］
実施例１〜３および比較例１〜３の電池にについて、つぎのようにして、電池膨れ、高率放電性能、高温放置時の電池膨れを測定した。
【００８４】
各電池の電池厚みｔ１（ｍｍ）を測定した後、２５℃の恒温槽内で充放電試験をおこなった。この試験においては、３５ｍＡで４．２Ｖに達するまでの定電流およびそれに続く４．２Ｖにおける２時間の定電圧での充電と、１４０ｍＡで２．７Ｖまでの定電流での放電とを行った。この時の放電容量をＣ１とする。つづいて、３５ｍＡで４．２Ｖに達するまでの定電流およびそれに続く４．２Ｖにおける２時間の定電圧での充電と、１４００ｍＡで２．７Ｖまでの定電流での放電とを行った。この時の放電容量をＣ２とする。ここで、高率放電性能をつぎの式から算出した。高率放電性能（％）＝Ｃ２／Ｃ１×１００
ポータブルコンピュータや電動工具などの用途に使用するためには、高率放電時に高容量を示さなければならない。したがって、高率放電性能は７０％以上であることが好ましい。
【００８５】
さらに、この電池を用いて、３５ｍＡで４．２Ｖに達するまでの定電流およびそれに続く４．２Ｖにおける２時間の定電圧での充電を行った。この電池を１００℃の恒温槽内に３時間放置後、再び電池厚みｔ２（ｍｍ）を測定した。ここで、高温放置時の電池膨れをつぎの式から算出した。電池膨れ（ｍｍ）＝ｔ２（ｍｍ）−ｔ１（ｍｍ）
電池膨れが１．５０ｍｍを超えるものをポータブルコンピュータや電動工具などの用途に用いることは、電池パックが壊れる危険性があるので不適である。したがって、電池膨れは１．５０ｍｍ以下でなくてはならない。充放電を繰り返すことによって電池が若干膨れるものと予想されるため、電池膨れが１．４０ｍｍ以下であることが望ましい。
【００８６】
また、負極製造に必要な時間を比較した。実施例１の電池Ａ１に用いた負極製造に要した時間を１００とし、その他の電池に用いた負極製造に要した時間を相対的に表示した。
【００８７】
実施例１〜３および比較例１〜３の電池についての測定結果を表２にまとめた。
【００８８】
【表２】

【００８９】
表２からつぎのようなことが明らかとなった。比較例１、実施例１〜３の比較により、負極合剤層中のＳＢＲの種類を適宜選択することにより、負極合剤層中のＳＢＲの組成にかかわらず、密着強度を７５Ｎ／ｍ以上とすることができ、電池の膨れを１．５０ｍｍ以下にし、放電容量Ｃ１や高率放電性能に優れた電池が得られた。ただし、負極の結着材としてＳＢＲ（ｓ２）を用いた実施例２および３では、ＳＢＲ（ｓ２）の分散性がＳＢＲ（ｓ１）よりも劣るため、均一な合剤ペーストを作製するためには長時間必要であることが示された。
【００９０】
なお、比較例２の電池は負極合剤層中の結着材の占める割合が大きいため、また、比較例３の電池は、負極活物質がＳｉＯ（ａ１）を含まないため、いずれも初期の放電容量Ｃ１がかなり小さくなった。
【００９１】
以上のように、本願の請求項１の条件を満たす負極を用いることにより、初期の放電容量Ｃ１が大きく、電池膨れが１．５０ｍｍ以下で、高率放電性能に優れた電池が得られることが示された。
【００９２】
［実施例４〜１０］
負極合剤層中における負極活物質の含有率を９７．０〜８６．０質量％およびＳＢＲの含有率を０．５〜１２．０質量％としたこと以外は実施例１と同様にして、実施例４〜１０の電池（Ａ４）〜（Ａ１０）を製作した。
【００９３】
［実施例１１］
負極活物質および結着材としてのＳＢＲ（ｓ１）を所定量秤取して、これらをＮＭＰに分散させてペーストを得て、このペーストを厚さ１５μｍの銅箔の片面に塗布して１５０℃で乾燥したのちに、もう一方の面にも同様の塗布および乾燥をおこない、両面に負極合剤層を備えた銅箔を得たこと以外は実施例１と同様にして、実施例１１の電池（Ａ１１）を製作した。なお、この負極合剤層には、負極活物質が９８．０質量％およびＳＢＲ（ｓ１）が２．０質量％含まれるようにした。
【００９４】
実施例１、４〜１１および比較例１の電池の内容を表３に示す。
【００９５】
【表３】

【００９６】
［実施例１２〜１４、比較例４］
結着材としてのＳＢＲ（ｓ１）の代わりに、前述のＳＢＲ（ｓ２）、ラテックスの粒径が１４０ｎｍでガラス転移点が−１５℃でであるＳＢＲ（ｓ３）、ラテックスの粒径が１４０ｎｍでガラス転移点が−５℃でであるＳＢＲ（ｓ４）を用いたこと以外は実施例４と同様にして実施例１２〜１４の電池（Ａ１２）〜（Ａ１４）を製作した。
【００９７】
また、結着材としてのＳＢＲ（ｓ１）の代わりに、ラテックスの粒径が８０ｎｍでガラス転移点が−１５℃であるＳＢＲ（ｓ５）を用いたこと以外は実施例４と同様にして比較例４の電池（Ｒ４）を製作した。実施例４、１２〜１４の電池（Ａ４）、（Ａ１２）〜（Ａ１４）、および比較例４の電池（Ｒ４）の内容を表４に示す。
【００９８】
【表４】

【００９９】
これらの電池についての測定結果を表５および表６に示した。
【０１００】
【表５】

【０１０１】
【表６】

【０１０２】
ここで、表３および６から得られる負極合剤層中におけるＳＢＲの含有率と電池膨れとの関係を図１に、負極合剤層中におけるＳＢＲの含有率と高率放電性能との関係を図２に、それぞれ示す。また、表４および６から得られる負極合剤質層と負極集電体との密着強度と電池膨れとの関係を図３に示す。
【０１０３】
図１〜図３から、高温放置時に膨れが１．５０ｍｍ以下と小さく、かつ、高率放電性能が７０％以上と優れる電池を得るためには、負極合剤層中におけるＳＢＲの含有率が０．５〜１０．０質量％であって、かつ、負極合剤層−負極集電体間の密着強度が７５Ｎ／ｍ以上である必要があることが示された。
【０１０４】
［実施例１５］
熱処理を行っていないＳｉＯ粉末（ａ０）（ＳｉＯ_ｘにおいて、ｘ＝１のもの）を用いたこと以外は実施例４と同様にして、実施例１５の電池（Ｂ１）を得た。
【０１０５】
［実施例１６〜２０］
ＳｉＯの熱処理温度を８３０℃〜１０５０℃として、ＳｉＯ粉末（ａ２）〜（ａ６）を得た。これらを負極活物質に用いたこと以外は実施例４と同様にして、実施例１６〜２０の電池（Ｂ２）〜（Ｂ６）を得た。なお、ＳｉＯ粉末（ａ２）〜（ａ６）は、いずれも、ＳｉＯ_ｘと記した場合にｘ＝１となるのものである。
【０１０６】
電池（Ａ４）および（Ｂ１）〜（Ｂ６）の内容を表７に示す。なお、表７において、「Ｓｉ（１１１）の半値幅」の単位は「°（２θ、Ｃｕｋα）」とした。
【０１０７】
【表７】

【０１０８】
実施例１５〜２０の電池（Ｂ１）〜（Ｂ６）を用いて、実施例４の電池（Ａ４）と同じ条件で、電池膨れおよび高率放電性能を測定した。その結果を表８に示す。
【０１０９】
【表８】

【０１１０】
半値幅と電池膨れとの関係を図４に示す。これより、半値幅が３．０以下の場合に、電池膨れが１．４０ｍｍ以下と小さくなることが明らかである。したがって、本発明の非水電解質二次電池に用いるＳｉＯ粉末の半値幅は３．０以下であることが好ましい。
【０１１１】
［実施例２１〜２５］
負極活物質として、１．０〜５０．０質量％のＳｉＯ粉末（ａ１）と、９９．０〜５０．０質量％の材料（ｊ１）との混合物を用いたこと以外は実施例４と同様にして、実施例２１〜２５の電池（Ｃ１）〜（Ｃ５）を得た。電池（Ａ４）および（Ｃ１）〜（Ｃ５）の内容を表９にまとめた。
【０１１２】
【表９】

【０１１３】
実施例２１〜２５の電池（Ｃ１）〜（Ｃ５）を用いて、実施例４の電池（Ａ４）と同じ条件で、電池膨れおよび高率放電性能を測定した。その結果を表１０に示す。
【０１１４】
【表１０】

【０１１５】
これより、負極活物質の質量に対するＳｉＯ粉末の質量の割合が３．０〜１０．０％である場合に、電池膨れが１．４０ｍｍ以下と小さく、高率放電性能が８０％以上と高いことが明らかである。したがって、負極活物質の質量に対するＳｉＯ粉末の質量の割合は３．０〜１０．０％であることが好ましい。
【０１１６】
［実施例２６］
材料（ｊ１）の代わりに、５０質量％のメソカーボンマイクロビーズ（ＭＣＭＢ）と５０質量％の天然黒鉛との混合物を用いたこと以外は実施例４と同様にして、実施例２６の電池（Ｄ１）を得た。
【０１１７】
［実施例２７］
材料（ｊ１）の代わりに、天然黒鉛のみを用いたこと以外は実施例４と同様にして、実施例２７の電池（Ｄ２）を得た。
【０１１８】
［実施例２８］
材料（ｊ１）の代わりに、５０質量％の天然黒鉛と５０質量％の人造黒鉛との混合物を用いたこと以外は実施例４と同様にして、実施例２８の電池（Ｄ３）を得た。電池（Ａ４）および（Ｄ１）〜（Ｄ３）の内容を表１１にまとめた。
【０１１９】
【表１１】

【０１２０】
実施例２６〜２８の電池（Ｄ１）〜（Ｄ３）を用いて、実施例４の電池（Ａ４）と同じ条件で、電池膨れおよび高率放電性能を測定した。その結果を表１２に示す。
【０１２１】
【表１２】

【０１２２】
電池（Ａ４）および（Ｄ１）〜（Ｄ３）は、いずれも、電池膨れが１．４０ｍｍ以下と小さく、高率放電性能が８０％以上と高かった。これより、材料（ｊ１）として用いる黒鉛は単一の種類のものを用いてもよいし、複数の種類のものを任意の割合で混合して用いてもよいことが明らかである。
【０１２３】
［実施例２９］
ＳｉＯ粉末（ａ１）を０．５ｍｏｌ／ｄｍ^−３のフッ化水素酸中に中に浸漬してＳｉＯ_２相の一部を溶解させることによって、ＳｉＯ_０．８を得た。これをＳｉＯ粉末（ａ１）の代わりに用いたこと以外は実施例４と同様にして、実施例２９の電池（Ｅ１）を得た。
【０１２４】
［実施例３０］
ＳｉＯ粉末（ａ１）を０．８ｍｏｌ／ｄｍ^−３のフッ化水素酸中に中に浸漬してＳｉＯ_２相の一部を溶解させることによって、ＳｉＯ_０．５を得た。これをＳｉＯ粉末（ａ１）の代わりに用いたこと以外は実施例４と同様にして、実施例３０の電池（Ｅ２）を得た。電池（Ｅ１）および（Ｅ２）の内容を表１３に示す。
【０１２５】
【表１３】

【０１２６】
実施例２９および３０の電池（Ｅ１）および（Ｅ２）を用いて、実施例４の電池（Ａ４）と同じ条件で、電池膨れおよび高率放電性能を測定した。その結果を表１４に示す。
【０１２７】
【表１４】

【０１２８】
電池（Ａ４）、（Ｅ１）および（Ｅ２）は、いずれも、電池膨れが１．４０ｍｍ以下と小さく、高率放電性能が８０％以上と高かった。したがって、ＳｉとＯとを含む物質（Ａ）におけるＳｉに対するＯの原子比ｘは、０＜ｘ＜２の任意の値をとることができる。
【０１２９】
［実施例３１］
ＳｉＯ粉末（ａ１）をホウ酸水溶液に浸漬したのちに８００℃で焼成することで、ＳｉＯ_１．０３Ｂ_０．０２を得た。これをＳｉＯ粉末（ａ１）の代わりに用いたこと以外は実施例４と同様にして、実施例３１の電池（Ｆ１）を得た。
【０１３０】
［実施例３２］
ＳｉＯ粉末（ａ１）を［Ｃｕ（ＮＨ_３）_４］^２＋を含む水溶液に浸漬したのちに８００℃で焼成することで、ＳｉＯ_１．０１Ｃｕ_０．０１を得た。これをＳｉＯ粉末（ａ１）の代わりに用いたこと以外は実施例４と同様にして、実施例３２の電池（Ｆ２）を得た。電池（Ｆ１）および（Ｆ２）の内容を表１５に示す。
【０１３１】
【表１５】

【０１３２】
実施例３１および３２の電池（Ｆ１）および（Ｆ２）を用いて、実施例４の電池（Ａ４）と同じ条件で、電池膨れおよび高率放電性能を測定した。その結果を表１６に示す。
【０１３３】
【表１６】

【０１３４】
電池（Ｆ１）および（Ｆ２）は、いずれも、電池膨れが１．４０ｍｍ以下と小さく、高率放電性能が８０％以上と高かった。したがって、ＳｉとＯとを含む物質（Ａ）には、任意量の非金属元素や金属元素を添加することができることが明らかである。
【０１３５】
［実施例３３〜３６］
９５〜７０質量％のＳｉＯ粉末（ａ１）と、５〜３０質量％のＭＣＭＢとを秤取して、これらをメカノフュージョン法（ホソカワミクロン製ＡＭＳ−Ｌａｂを使用）により機械的に複合化させて材料（ｍ１）を得た。材料（ｍ１）をＳｉＯ粉末（ａ１）の代わりに用いたこと以外は実施例４と同様にして、実施例３３〜３６の電池（Ｇ１）〜（Ｇ４）を得た。なお、材料（ｍ１）のＳＥＭ観察の結果から、１個のＭＣＭＢの粒子上に複数のＳｉＯ粒子が担持されていることがわかった。
【０１３６】
［実施例３７］
８０質量％のＳｉＯ粉末（ａ１）と、２０質量％の天然黒鉛とを秤取して、これらをメカノフュージョン法（ホソカワミクロン製ＡＭＳ−Ｌａｂを使用）により機械的に複合化させて材料（ｍ２）を得た。これをＳｉＯ粉末（ａ１）の代わりに用いたこと以外は実施例４と同様にして、実施例３７の電池（Ｇ５）を得た。なお、材料（ｍ２）のＳＥＭ観察の結果から、複数の天然黒鉛の粒子と複数のＳｉＯ粒子とが複合化されていることがわかった。電池（Ｇ１）〜（Ｇ５）の内容を表１７に示す。
【０１３７】
【表１７】

【０１３８】
実施例３３〜３７の電池（Ｇ１）〜（Ｇ５）を用いて、実施例４の電池（Ａ４）と同じ条件で、電池膨れおよび高率放電性能を測定した。その結果を表１８に示す。
【０１３９】
【表１８】

【０１４０】
電池（Ｇ１）〜（Ｇ５）は、いずれも、電池膨れが１．４０ｍｍ以下と小さく、高率放電性能が８０％以上と高く、加えて、電池（Ａ４）より優れていた。したがって、ＳｉとＯとを含む物質（Ａ）は、炭素材料と複合化されることが好ましい。
【０１４１】
［実施例３８〜４２］
ＳｉＯ粉末と炭素材料（ｂ１）との合計質量に対して炭素材料（ｂ１）の質量が１〜３０％となるように、ＳｉＯ粉末の表面に炭素材料（ｂ１）を化学気相蒸着（ＣＶＤ）することによって、材料（ｃ１）〜（ｃ５）を得た。なお、上記ＣＶＤは、メタンを炭素源に用いて、Ａｒ雰囲気下で１０００℃の条件でおこなった。
【０１４２】
ＳｉＯ粉末（ａ１）の代わりに材料（ｃ１）〜（ｃ５）を用いたこと、および、２０質量％の材料（ｃ１）〜（ｃ５）と８０質量％の材料（ｊ１）とを混合して負極活物質としたこと以外は実施例４と同様にして、実施例３８〜４２の電池（Ｈ１）〜（Ｈ５）を製作した。電池（Ｈ１）〜（Ｈ５）の内容を表１９に示す。
【０１４３】
【表１９】

【０１４４】
実施例３７〜４１の電池（Ｈ１）〜（Ｈ５）を用いて、実施例４の電池（Ａ４）と同じ条件で、電池膨れおよび高率放電性能を測定した。その結果を表２０に示す。
【０１４５】
【表２０】

【０１４６】
電池（Ｈ１）〜（Ｈ５）は、いずれも、電池膨れが１．４０ｍｍ以下と小さく、高率放電性能が８０％以上と高かった。したがって、ＳｉとＯとを含む物質（Ａ）に炭素材料をＣＶＤした材料を負極活物質に適用することが好ましいことが明らかになった。
【０１４７】
［実施例４３］
ＳｉＯ粉末と炭素材料（ｂ２）との合計質量に対して炭素材料（ｂ２）の質量が５％となるように、ＳｉＯ粉末の表面に炭素材料（ｂ２）をプラズマＣＶＤすることによって、材料（ｃ６）を得た。なお、上記ＣＶＤは、トルエンを炭素源に用いて、Ａｒ雰囲気下で１０００℃の条件でおこなった。材料（ｃ１）の代わりに材料（ｃ６）を用いたこと以外は実施例３９と同様にして、実施例４３の電池（Ｈ６）を製作した。
【０１４８】
［実施例４４］
ＳｉＯ粉末と炭素材料（ｂ３）との合計質量に対して炭素材料（ｂ３）の質量が５％となるように、ＳｉＯ粉末の表面に炭素材料（ｂ３）を化学気相蒸着（ＣＶＤ）することによって、材料（ｃ７）を得た。なお、上記ＣＶＤは、ベンゼンを炭素源に用いて、Ａｒ雰囲気下で１０００℃の条件でおこなった。材料（ｃ１）の代わりに材料（ｃ７）を用いたこと以外は実施例３９と同様にして、実施例４４の電池（Ｈ７）を製作した。
【０１４９】
［実施例４５］
ＳｉＯ粉末と炭素材料（ｂ４）との合計質量に対して炭素材料（ｂ４）の質量が５％となるように、ＳｉＯ粉末の表面に炭素材料（ｂ４）をプラズマＣＶＤすることによって、材料（ｃ８）を得た。なお、上記ＣＶＤは、アセチレンを炭素源に用いて、Ａｒ雰囲気下で１０００℃の条件でおこなった。材料（ｃ１）の代わりに材料（ｃ８）を用いたこと以外は実施例３９と同様にして、実施例４５の電池（Ｈ８）を製作した。
【０１５０】
実施例４３〜４５の電池（Ｈ６）〜（Ｈ８）を用いて、実施例４の電池（Ａ４）と同じ条件で、電池膨れおよび高率放電性能を測定した。その結果を表２１に示す。
【０１５１】
【表２１】

【０１５２】
電池（Ｈ２）および（Ｈ６）〜（Ｈ８）は、いずれも、電池膨れが１．４０ｍｍ以下と小さく、高率放電性能が８０％以上と高かった。したがって、ＳｉとＯとを含む物質（Ａ）に炭素材料をＣＶＤした材料を負極活物質に適用する場合には、炭素源として何を用いてもよいことが明らかである。
【０１５３】
［実施例４６〜４９］
負極活物質として、１．０〜２０．０質量％の材料（ｃ４）と、９９．０〜８０．０質量％の材料（ｊ１）との混合物を用いたこと以外は実施例４１と同様にして、実施例４６〜４９の電池（Ｉ１）〜（Ｉ４）を得た。電池（Ｈ４）および（Ｉ１）〜（Ｉ４）の内容を表２２に示す。
【０１５４】
【表２２】

【０１５５】
実施例４６〜４９の電池（Ｉ１）〜（Ｉ４）を用いて、実施例４の電池（Ａ４）と同じ条件で、電池膨れおよび高率放電性能を測定した。その結果を表２３に示す。
【０１５６】
【表２３】

【０１５７】
電池（Ｈ４）および（Ｉ１）〜（Ｉ４）は、いずれも、電池膨れが１．４０ｍｍ以下と小さく、高率放電性能が８０％以上と高かった。また、負極活物質中の材料（ｃ４）の質量比率が２０％以下であるとき、電池膨れが１．００ｍｍ以下ときわめて小さくなる。したがって、ＳｉとＯとを含む物質（Ａ）に炭素材料をＣＶＤした材料を負極活物質に適用する場合には、負極活物質中の材料（ｃ４）の質量比率が２０％以下であることが好ましい。
【０１５８】
［実施例５０〜５６、比較例６］
負極合剤層中における負極活物質の含有率を９８．５〜８６．０質量％およびＳＢＲの含有率を０．５〜１２．０質量％に変更したこと以外は、実施例４１と同様にして実施例５０〜５６の電池（Ｊ１）〜（Ｊ６）を製作した。
【０１５９】
また、負極合剤層中における負極活物質の含有率を９７．７質量％およびＳＢＲの含有率を０．３質量％としたこと以外は、実施例４１と同様にして比較例６の電池（Ｒ６）を製作した。
【０１６０】
実施例４１および５０〜５６、ならびに、比較例６の電池の内容を表２４に示す。
【０１６１】
【表２４】

【０１６２】
実施例５０〜５６の電池（Ｊ１）〜（Ｊ６）を用いて、実施例４の電池（Ａ４）と同じ条件で、電池膨れおよび高率放電性能を測定した。その結果を表２５に示す。
【０１６３】
【表２５】

【０１６４】
負極合剤層中におけるＳＢＲの含有率と電池膨れとの関係を図５に示す。負極合剤層中におけるＳＢＲの含有率と高率放電性能との関係を図６に示す。負極合剤層−負極集電体間の密着強度と電池膨れとの関係を図７に示す。
【０１６５】
図５〜図７から、高温放置時に膨れが１．５０ｍｍ以下と小さく、かつ、高率放電性能が７０％以上と優れる電池を得るためには、負極活物質に、ＳｉとＯとを含む物質（Ａ）に炭素材料をＣＶＤした材料を適用した場合であっても、さらに負極合剤層中におけるＳＢＲの含有率が０．５質量％〜１０．０質量％であって、かつ、負極合剤層と負極集電体との密着強度が７５Ｎ／ｍ以上であることが好ましい。
【０１６６】
［実施例５７］
ＳｉＯ粉末と天然黒鉛とを３０：５５の質量比で秤取して、これらをボールミル法（フリッチュ製遊星型ＭＯＮＯミルＰ−６を使用）により機械的に複合化させて材料（ｇ１）を得た。
【０１６７】
この材料（ｇ１）と炭素材料（ｈ１）との合計質量に対して炭素材料（ｈ１）の質量が１５％となるように、材料（ｇ１）の表面に炭素材料（ｈ１）をＣＶＤすることによって、材料（ｉ１）を得た。なお、上記ＣＶＤは、トルエンを炭素源に用いて、Ａｒ雰囲気下で１０００℃の条件でおこなった。材料（ｃ１）の代わりに材料（ｉ１）を用いたこと以外は実施例３８と同様にして、実施例５７の電池（Ｋ１）を製作した。
［実施例５８〜６１］
材料（ｇ１）を製造するときに秤取するＳｉＯ粉末と天然黒鉛との質量比、および、材料（ｉ１）を製造するときにＣＶＤする炭素材料（ｈ１）の質量を変更したこと以外は、実施例５５と同様にして実施例５８〜６１の電池（Ｋ２）〜（Ｋ５）を製作した。電池（Ｋ１）〜（Ｋ５）の内容を表２６に示す。
【０１６８】
【表２６】

【０１６９】
実施例５７〜６１の電池（Ｋ１）〜（Ｋ５）を用いて、実施例４の電池（Ａ４）と同じ条件で、電池膨れおよび高率放電性能を測定した。その結果を表２７に示す。
【０１７０】
【表２７】

【０１７１】
電池（Ｋ１）〜（Ｋ５）は、いずれも、電池膨れが１．４０ｍｍ以下と小さく、高率放電性能が８０％以上と高かった。物質（Ａ）と炭素材料（Ｆ）とが混合したものを物質（Ｇ）とし、その物質（Ｇ）の表面のすくなくとも一部を炭素材料（Ｈ）によって被覆したものを物質（Ｉ）とすると、電池（Ｋ１）〜（Ｋ５）の結果から、この物質（Ｉ）を負極活物質に適用することが好ましいことが明らかになった。
【０１７２】
［実施例６２〜６６］
負極活物質として、１．０〜２０．０質量％の材料（ｇ１）と、９９．０〜８０．０質量％の材料（ｊ１）との混合物を用いたこと以外は実施例５７と同様にして、実施例６２〜６６の電池（Ｌ１）〜（Ｌ５）を得た。電池（Ｋ１）および（Ｌ１）〜（Ｌ５）の内容を表２８にまとめた。
【０１７３】
【表２８】

【０１７４】
実施例６２〜６６の電池（Ｌ１）〜（Ｌ５）を用いて、実施例４の電池（Ａ４）と同じ条件で、電池膨れおよび高率放電性能を測定した。その結果を表２９に示す。
【０１７５】
【表２９】

【０１７６】
これより、材料（ｇ１）と材料（ｊ１）との合計質量に対する材料（ｇ１）の質量の割合が５〜３０％である場合に、電池膨れが１．００ｍｍ以下と小さく、高率放電性能が９０％以上と非常に高いことがわかった。したがって、材料（ｇ１）と材料（ｊ１）との合計質量に対する材料（ｇ１）の質量の割合は５〜３０％であることが好ましいことが明らかである。
【０１７７】
［実施例６７］
負極集電体として、厚さ１５μｍの電解銅箔の代わりに、厚さ１５μｍの圧延銅箔を用いたこと以外は実施例４と同様にして、実施例６７の電池（Ｍ）を作製した。電池（Ｍ）に用いた負極では、負極合剤層−集電体間の密着強度は９８Ｎ／ｍであった。
【０１７８】
この電池（Ｍ）を用いて、実施例４の電池（Ａ４）と同じ条件で、電池膨れおよび高率放電性能を測定した。その結果、電池膨れは１．３３ｍｍであり、高率放電性能は８１％と良好であった。したがって、負極集電体として用いる金属箔としては、電解銅箔や圧延銅箔のいずれを用いた場合でも、優れた特性が得られることがわかった。
【０１７９】
【発明の効果】
本発明の非水電解質二次電池は、負極合剤層および負極集電体を備えた負極を備えており、前記負極合剤層が負極活物質および結着材を含み、前記負極活物質がＳｉとＯとを含む物質と炭素材料とを含み、前記ＳｉとＯとを含む物質におけるＳｉに対するＯの原子比ｘが０＜ｘ＜２を満たし、前記結着材がＳＢＲを含有し、前記負極合剤層と負極集電体との密着強度を７５Ｎ／ｍ以上とすることによって、珪素酸化物を含む負極を備えた非水電解質二次電池の高温放置時に生じる電池膨れを大幅に抑制し、加えて、常温における高率放電性能を従来から公知の電池と比較して同等以上とすることができた。さらに、前記負極合剤層中における結着材の含有率を０．５〜１０．０質量％とすることにより、より高温放置時の膨れを抑制することができた。したがって、本発明の工業的価値はきわめて大である。
【図面の簡単な説明】
【図１】負極活物質にＳｉＯ粉末（ａ１）と材料（ｊ１）との混合物を用いた場合の、負極合剤層中におけるＳＢＲの含有率と電池膨れとの関係を示す図。
【図２】負極活物質にＳｉＯ粉末（ａ１）と材料（ｊ１）との混合物を用いた場合の、負極合剤層中におけるＳＢＲの含有率と高率放電性能との関係を示す図。
【図３】負極活物質にＳｉＯ粉末（ａ１）と材料（ｊ１）との混合物を用いた場合の、密着強度と電池膨れとの関係を示す図。
【図４】半値幅と電池膨れの関係を示す図。
【図５】負極活物質に材料（ｃ４）と材料（ｊ１）との混合物を用いた場合の、負極合剤層中におけるＳＢＲの含有率と電池膨れとの関係を示す図。
【図６】負極活物質にＳｉＯ粉末（ｃ４）と材料（ｊ１）との混合物を用いた場合の、負極合剤層中におけるＳＢＲの含有率と高率放電性能との関係を示す図。
【図７】負極活物質にＳｉＯ粉末（ｃ４）と材料（ｊ１）との混合物を用いた場合の、密着強度と電池膨れとの関係を示す図。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to suppression of battery swelling that occurs when a nonaqueous electrolyte secondary battery including a negative electrode containing silicon oxide is left at a high temperature.
[0002]
[Prior art]
Lithium secondary batteries using graphite carbon material as the negative electrode active material and lithium transition metal oxide as the positive electrode active material each had higher energy density than other secondary batteries. It has been used for applications. In recent years, since the weight reduction and miniaturization thereof are progressing rapidly, there is an urgent need to improve the energy density of the secondary battery incorporated therein. Currently, in a commercially available lithium secondary battery, the reversible capacity of the negative electrode is very close to its theoretical capacity. Therefore, it is very difficult to continuously improve the energy density by improving the utilization rate of the negative electrode.
[0003]
Therefore, it is necessary to develop a new negative electrode active material having a capacity higher than that of the graphitic carbon material. Currently, for example, oxides such as silicon oxide, tin oxide, copper oxide, and cobalt oxide, lithium alloys, lithium transition metal nitrides, and the like have been proposed as novel negative electrode active materials. Among them, silicon oxide is particularly expected because it has a particularly high capacity.
[0004]
As reported in Patent Document 1, it seems that a battery to which a negative electrode using a mixture of silicon oxide and lithium transition metal nitride is applied is practical because it has high Coulomb efficiency. However, since this battery swells particularly when left at high temperatures, it is difficult to apply it to applications such as portable computers and electric tools where an increase in battery temperature is predicted, and it has not been put into practical use until now.
[0005]
Patent Document 2 discloses a technique in which LixSiOy (0 ≦ x, 0 <y <2) is used as a negative electrode active material of a non-aqueous secondary battery and styrene butadiene rubber is used as a binder. Also, SiO and SiO₂A technique using a negative electrode active material coated with a carbonaceous material and using styrene butadiene rubber as a binder is disclosed in Patent Document 3, but there is no description about adhesion strength.
[0006]
On the other hand, Patent Document 4 discloses the relationship between the roughness and the adhesion strength with a current collector when a carbon material is used as the negative electrode active material of the non-aqueous secondary battery and a copper foil is used as the current collector. However, although a method for measuring adhesion strength is disclosed in Patent Document 5, none of these uses styrene butadiene rubber as a binder.
[0007]
[Patent Document 1]
Special Table 2000-164207
[Patent Document 2]
JP-A-10-270088
[Patent Document 3]
JP 2000-090916 A
[Patent Document 4]
Japanese Patent Laid-Open No. 06-260168
[Patent Document 5]
JP 2000-294247 A
[0008]
[Problems to be solved by the invention]
As described above, a battery provided with a silicon oxide on the negative electrode has a problem that it greatly swells when left at a high temperature. The present invention solves the above-mentioned problems that impede the practical application of this battery by systematic experiments. An object of the present invention is to provide a high energy density non-aqueous electrolyte secondary battery that does not swell when left at high temperatures.
[0009]
[Means for Solving the Problems]
The invention according to claim 1 is a nonaqueous electrolyte secondary battery including a negative electrode including a negative electrode mixture layer and a negative electrode current collector, wherein the negative electrode mixture layer includes a negative electrode active material and a binder, and the negative electrode The active material contains a substance containing Si and O and a carbon material, the atomic ratio x of O to Si in the substance containing Si and O satisfies 0 <x <2, and the binder contains SBR. The adhesion strength between the negative electrode mixture layer and the negative electrode current collector is 75 N / m or more.
[0010]
According to the first aspect of the present invention, it is possible to obtain a high energy density non-aqueous electrolyte secondary battery that does not swell when left at high temperatures.
[0011]
According to a second aspect of the present invention, in the nonaqueous electrolyte secondary battery according to the first aspect, the content of the binder in the negative electrode mixture layer is 0.5 to 10.0% by mass.
[0012]
According to the second aspect of the present invention, it is possible to suppress swelling when left at a higher temperature.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a material containing Si and O as a negative electrode active material (hereinafter, this material is referred to as “substance (A)”, where 0 <x <2 when this material is represented by SiOx). And a carbon material, and a non-aqueous electrolyte secondary battery including a negative electrode using a styrene butadiene copolymer (hereinafter abbreviated as “SBR”) as a binder, a negative electrode mixture layer and a negative electrode current collector, By specifying the adhesion strength, the swelling of the nonaqueous electrolyte secondary battery when left at high temperature is suppressed.
[0014]
Furthermore, by setting the content of SBR in the negative electrode mixture layer within a specific range, swelling at higher temperatures is suppressed.
[0015]
When the nonaqueous electrolyte secondary battery provided with the negative electrode containing the substance A and the carbon material as active materials is compared with the battery provided with the negative electrode containing the graphitic carbon material used in the conventional lithium ion secondary battery Although high capacity can be expected, on the other hand, there is a problem that large battery swelling occurs when left at high temperatures. For this reason, it is very difficult to apply to applications where an increase in battery temperature is foreseen. Therefore, suppressing the swelling of the battery when it is left at high temperature is one of the biggest problems.
[0016]
In order to solve this problem, the inventor used SBR as a binder used for the negative electrode, and manufactured batteries with different contents and adhesion strengths between the negative electrode mixture layer and the negative electrode current collector. In addition, we systematically analyzed the effect on battery swelling when left at high temperature. As a result, there is an extremely large dependency between the content of SBR in the negative electrode active material phase and the adhesion strength between the negative electrode mixture layer and the negative electrode current collector and the swelling of the battery equipped with the negative electrode when left at high temperature. I found out.
[0017]
Then, when the influence on the swelling of the battery at high temperature was closely examined, when the adhesion strength between the negative electrode mixture layer and the negative electrode current collector was 75 N / m or more, the nonaqueous electrolyte secondary battery was left at high temperature. It was found that the swelling of the water becomes smaller. Furthermore, it has been found that when the SBR content in the negative electrode mixture layer is 0.5 to 10.0% by mass, the swelling of the nonaqueous electrolyte secondary battery when left at high temperature is significantly reduced.
[0018]
In the nonaqueous electrolyte secondary battery of the present invention, the substance (A) containing Si and O, which is one of the negative electrode active materials, has a composition of SiO._xIt is represented by (0 <x <2), and may be composed of a single phase or a plurality of phases.
[0019]
Since the simple substance of Si (in the case of x = 0) has a large expansion / contraction due to charging / discharging, it is pulverized when the charging / discharging cycle is repeated, resulting in a large capacity deterioration. In addition, SiO₂In the case of x = 2, since it is almost inert electrochemically, charging and discharging cannot be performed. Therefore, it is necessary to satisfy 0 <x <2.
[0020]
SiO_xIs composed of a plurality of phases, Si phase and SiO_yIt is preferable to include both phases (1 <y ≦ 2), and this negative electrode active material Cukα₁Among the peaks observed in the X-ray diffraction pattern by the line, at least one of the half-value widths of the Si (111) plane having the strongest diffraction intensity or the Si (220) plane having the second highest diffraction intensity is 3 °. The following is more preferable.
[0021]
The Si (hkl) plane of the X-ray diffraction pattern described here is JCPDS No. Although it is the one described in 271402, strictly speaking, the peaks appear at 2θ (Cukα) = 28 ° ± 2 ° and 47 ± 2 °, respectively. Here, the reason for using at least one of the Si (111) plane and the Si (220) plane is that the peak of the Si (111) plane overlaps the peak of 2θ (Cukα) = 26 ° of graphite, and the half-width cannot be obtained. Because there are things.
[0022]
Further, the structure of the substance (A) may be crystalline or amorphous, but is more preferably amorphous.
[0023]
In the battery of the present invention, the negative electrode active material must contain a substance (A) containing Si and O and a carbon material. The reason is that when the negative electrode active material contains only the former, the substance (A) has a very low electron conductivity and cannot be charged / discharged. When the negative electrode active material contains only the latter, the energy density is higher than in the prior art. This is because it is extremely difficult to obtain a battery continuously.
[0024]
In the battery of the present invention, the substance (A) containing Si and O, which is one of the negative electrode active materials, contains, as additive elements, nonmetallic elements such as B, P, S, and F, and In, Pb, Zn, and Cu. Any amount of a metal element such as Ni can be included.
[0025]
In the battery of the present invention, the carbon material that is one of the negative electrode active materials may be a single material or a simple mixture or a composite of a plurality of materials.
[0026]
In the battery of the present invention, a mixture of the substance (A) and the carbon material may be used as the negative electrode active material, or a composite of these may be used, but the latter is preferred. When a mixture of the substance (A) and the carbon material is used for the negative electrode active material, the ratio of the mass of the substance (A) to the total mass of the substance (A) and the carbon material is preferably 1 to 20%. More preferably, it is 10%.
[0027]
In the battery of the present invention, when a composite of the substance (A) and the carbon material is used as the negative electrode active material, any form of the composite may be used. (A) Substance (C) whose surface is at least partially coated with carbon material (B), substance (E) on which substance (A) is supported on carbon material (D), substance (A) and carbon material And a substance (I) in which at least a part of the surface of the substance (G) mixed with (F) is coated with the carbon material (H). When the negative electrode active material contains the substance (I), the carbon material (F) and the carbon material (H) may be the same or different. Among these, it is particularly preferable that the negative electrode active material contains the substance (C) or the substance (I).
[0028]
Any composite method may be used. As a specific example, a substance (A) and a carbon material (B) precursor such as pitch are mixed and fired at a high temperature. A method for obtaining a substance (C) by crushing, a method for obtaining a substance (C) by mechanically binding the substance (A) and the carbon material (B) by powder treatment, and a chemical on the substance (A). A method of obtaining the substance (C) by supporting the carbon material (B) by a vapor deposition (CVD) method or the like, and a substance (G) by combining the substance (A) and the carbon material (F) by a granular treatment or the like. And the like, and a method of obtaining the substance (I) by supporting the carbon material (H) by a CVD method or the like.
[0029]
When compounding is performed by the CVD method, any type of CVD may be used, and examples thereof include thermal CVD and plasma CVD. Further, any carbon source may be used for CVD, and examples thereof include toluene, benzene, xylene, methane, acetylene, and the like. Among these composite methods, it is particularly preferable to use the CVD method because the carbon material can be uniformly coated.
[0030]
In the battery of the present invention, when the substance (C) is contained in the negative electrode active material, the ratio of the mass of the carbon material (B) to the mass of the substance (C) is preferably 1 to 30%, and 10 to 20 % Is more preferable. The reason why this ratio is preferably 1 to 30% is that if it is less than 1%, the conductivity of the substance (C) cannot be secured, so the cycle performance is extremely low, and if it exceeds 30%, a large discharge capacity can be obtained. Because it disappears.
[0031]
Moreover, it is preferable that the number average particle diameter (henceforth only described as a number average particle diameter) calculated | required by the laser diffraction method of a substance (C) is 0.1-20 micrometers. When the number average particle size is smaller than this value, it is difficult to handle at the time of producing the negative electrode, so that problems such as a significant decrease in yield occur. Further, when the number average particle size is larger than this value, it becomes difficult to consolidate the negative electrode plate, resulting in problems such as failure to obtain a high energy density battery.
[0032]
The substance (C) is preferably used by mixing with the carbon material (J). In that case, the ratio of the mass of the substance (C) to the total mass of the substance (C) and the carbon material (J) is preferably 1 to 30%, and more preferably 5 to 10%.
[0033]
The carbon material (J) may be any material, and examples thereof include natural graphite, artificial graphite, acetylene black, ketjen black, and vapor grown carbon fiber. The carbon material (J) may be a single material or a mixture of two or more carbon materials.
[0034]
Moreover, what kind of shape of what is used for carbon material (J) may be used, for example, spherical shape, such as mesocarbon microbead, fibrous shape, such as mesocarbon fiber, scale shape, lump shape, etc. can be used suitably. At this time, from the viewpoint of ensuring the conductivity of the negative electrode, it is preferable that scaly graphite having a number average particle diameter of 5 to 25 μm is included as the carbon material (J).
[0035]
The carbon material (J) preferably includes mesocarbon microbeads and mesocarbon fibers. At this time, it is more preferable that the B element is contained in the mesocarbon microbead or the mesocarbon fiber.
[0036]
In the battery of the present invention, when the substance (I) is contained in the negative electrode active material, the mass ratio of the substance (A) to the mass of the substance (I) is preferably 20 to 70%. The carbon material (F) used for the substance (I) may be any material. For example, natural graphite, artificial graphite, acetylene black, ketjen black, vapor grown carbon fiber, coke, pyrolytic carbon Activated carbon or the like can be used. The shape may be any shape, and for example, a spherical shape, a fiber shape, a scale shape, a lump shape, or the like can be used as appropriate.
[0037]
Among these, from the viewpoint of ensuring conductivity in the negative electrode active material during charge and discharge, it is preferably a flaky graphite having a number average particle diameter of 5 to 25 μm. The mass ratio of the substance (F) to the mass of the substance (I) is preferably 15 to 65%.
[0038]
Further, the carbon material (H) may be any material from a high crystalline material to a low crystalline material, but a low crystalline material is preferable since cracks of the negative electrode active material are unlikely to occur during charging and discharging.
[0039]
The number average particle diameter of the substance (H) is preferably 1 to 30 μm. When the number average particle size is smaller than this value, it is difficult to handle at the time of production, and thus problems such as a significant decrease in yield occur. Further, when the number average particle size is larger than this value, it becomes difficult to consolidate the negative electrode plate, resulting in problems such as failure to obtain a high energy density battery.
[0040]
The ratio of the mass of the carbon material (H) to the mass of the substance (I) is preferably 1 to 30%, and more preferably 5 to 20%. The reason why this ratio is preferably 1 to 30% is that if it is less than 1%, the conductivity of the substance (H) cannot be ensured, so the cycle performance is extremely low, and if it exceeds 30%, a large discharge capacity can be obtained. Because it disappears.
[0041]
The substance (I) is preferably used by mixing with the carbon material (J). In that case, the ratio of the mass of the substance (I) to the total mass of the substance (I) and the carbon material (J) is preferably 1 to 50%, and more preferably 5 to 30%.
[0042]
The carbon material (J) may be any material, and examples thereof include natural graphite, artificial graphite, acetylene black, ketjen black, and vapor grown carbon fiber. The carbon material (J) may be a single material or a mixture of two or more carbon materials.
[0043]
Moreover, what kind of shape of what is used for carbon material (J) may be used, for example, spherical shape, such as mesocarbon microbead, fibrous shape, such as mesocarbon fiber, scale shape, lump shape, etc. can be used suitably. At this time, from the viewpoint of ensuring the conductivity of the negative electrode, it is preferable that scaly graphite having a number average particle diameter of 5 to 25 μm is included as the carbon material (J).
[0044]
The carbon material (J) preferably includes mesocarbon microbeads and mesocarbon fibers. At this time, it is more preferable that the B element is contained in the mesocarbon microbead or the mesocarbon fiber.
[0045]
In the battery of the present invention, the negative electrode mixture layer must contain SBR as a binder. This is because the amount of addition to the negative electrode can be remarkably reduced as compared with the case where a fluorine-based resin such as PVdF is used as the binder, and the safety of the battery is greatly improved.
[0046]
The negative electrode mixture layer is obtained by removing the current collector from the negative electrode, and includes a negative electrode active material, a conductive material such as a carbon material, a binder such as SBR or polyvinylidene fluoride (PVdF), and carboxymethyl cellulose ( CMC) means a combination of all binders.
[0047]
The content of SBR in the negative electrode mixture layer is preferably 0.5 to 10.0% by mass, and particularly preferably 0.8 to 3.2% by mass. When this content is less than 0.5% by mass, there is a problem in manufacturing that the negative electrode mixture layer is remarkably easily peeled off from the negative electrode current collector, and a problem that the battery swells when left at high temperature is extremely large. . Moreover, when this content rate exceeds 10.0 mass%, since the internal resistance of a battery increases, it is unpreferable.
[0048]
SBR used as a binder is CMC, PVdF, carboxy-modified polyvinylidene fluoride, polyethylene, polypropylene, polytetrafluoroethylene, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer fluoride. It can be used by mixing with vinylidene chloride-chlorotrifluoroethylene copolymer or the like.
[0049]
In the battery of the present invention, the SBR content in the negative electrode mixture layer and the adhesion strength between the negative electrode mixture layer and the negative electrode current collector have a large dependency, but the SBR latex particle size, glass transition point, etc. In the case where the SBR content is the same, the adhesion strength value is greatly different even when the SBR content is the same, and the battery swelling when left at high temperature is remarkably changed.
[0050]
In the battery of the present invention, the adhesion strength between the negative electrode mixture layer and the negative electrode current collector must be 75 N / m or more, and preferably 90 N / m or more.
[0051]
However, the adhesion strength described here is measured as follows. First, the negative electrode was cut into a 10 cm × 4 cm rectangle, and then the entire surface of one side was adhered to the sample table with double-sided tape. Next, a tape was cut into a width of 18 mm and a length of 15 cm, and a length of 5 cm from one end of the tape was attached to the center of the negative electrode. A string was attached to the other end of the tape and tied to a spring-loaded hook. In the direction in which the tape bends at 170 to 180 °, the spring alone is pulled at a speed of 300 mm / min, and the tensile load (N / m) when the negative electrode mixture layer starts to peel from the negative electrode current collector is determined as the adhesion strength. Defined.
[0052]
Here, an adhesive tape having an adhesive strength of 294 [N / m] and a width of 18 mm, as defined in JIS Z1522, was used.
[0053]
The adhesion strength between the negative electrode mixture layer and the negative electrode current collector varies depending on the surface roughness of the copper foil used for the current collector. However, there are four types of definition of the surface roughness of the copper foil, for example, in JIS B 0601-2001, and it is difficult to quantify the surface roughness. Therefore, in the present invention, as the copper foil that is the current collector, regardless of the surface roughness of the copper foil, regardless of the surface roughness of the copper foil, the negative electrode mixture layer and the negative electrode current collector are used. When the adhesion strength is 75 N / m or more, excellent high temperature storage characteristics are exhibited.
[0054]
A solvent or a solution can be used when mixing the negative electrode active material and the binder. The solvent or solution may be non-aqueous or aqueous as long as it can disperse or dissolve the binder. When using a non-aqueous system, for example, N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N-dimethylaminopropylamine, ethylene oxide, Tetrahydrofuran or the like can be used.
[0055]
On the other hand, when an aqueous type is used, an aqueous solution to which water, a dispersant, a thickener, or the like is added can be used. As the negative electrode current collector, iron, copper, stainless steel, nickel, or the like can be used. The shape may be any shape, and examples thereof include a planar body, a foamed body, a sintered porous body, an expanded lattice, and those in which holes having an arbitrary shape are formed.
[0056]
In the nonaqueous electrolyte secondary battery of the present invention, either a nonaqueous liquid electrolyte or a solid electrolyte may be used as the nonaqueous electrolyte.
[0057]
When a non-aqueous liquid electrolyte is used, as its solvent, ethylene carbonate, propylene carbonate, butylene carbonate, trifluoropropylene carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide, 1,2-dimethoxyethane 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyl-1,3-dioxolane, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, A polar solvent such as dipropyl carbonate and methylpropyl carbonate or a mixed solvent optionally containing them can be used.
[0058]
In addition, as a solute of the non-aqueous liquid electrolyte, LiPF₆, LiBF₄, LiAsF₆LiClO₄, LiSCN, LiI, LiCl, LiBr, LiCF₃CO₂, LiCF₃SO₃, LiC₄F₉SO₃, LiN (SO₂CF₃)₂, LiN (SO₂CF₂CF₃)₂, LiN (SO₂CF₃) (SO₂CF₂CF₂CF₂CF₃), LiCF₄(CF₃)₂, LiCF₅(CF₃), LiN (COCF₃)₂And LiN (COCF₂CF₃)₂Lithium salts such as and mixtures containing these optionally can be used. Moreover, you may contain additives, such as a propane sultone, in nonaqueous electrolyte solution.
[0059]
When a solid electrolyte is used, for example, an inorganic solid electrolyte such as a Li-containing chalcogenide, Li⁺A single ion conductor made of a polymer containing a polymer, a polymer electrolyte containing a lithium salt in the polymer, and the like can be used. The polymer electrolyte may be one in which a lithium salt is contained in the polymer by wetting or swelling the non-aqueous liquid electrolyte into the polymer, or only the lithium salt is dissolved in the polymer. May be.
[0060]
The lithium salt contained in the polymer electrolyte is LiPF.₆, LiBF₄, LiAsF₆LiClO₄, LiSCN, LiI, LiCl, LiBr, LiCF₃CO₂, LiCF₃SO₃, LiC₄F₉SO₃, LiN (SO₂CF₃)₂, LiN (SO₂CF₂CF₃)₂, LiN (SO₂CF₃) (SO₂CF₂CF₂CF₂CF₃), LiCF₄(CF₃)₂, LiCF₅(CF₃), LiN (COCF₃)₂And LiN (COCF₂CF₃)₂Lithium salts such as and mixtures containing these optionally can be used. Furthermore, when a solid electrolyte is used, a plurality of electrolytes may be included in the battery. For example, different electrolytes can be used for the positive electrode and the negative electrode, respectively.
[0061]
The polymer used for the polymer electrolyte is preferably a polymer that exhibits good ionic conductivity when wetted or swollen by a non-aqueous liquid electrolyte. For example, polyethers such as polyethylene oxide (PEO) and polypropylene oxide (PPO), Vinylidene chloride (PVdF), polyvinyl chloride (PVC), polyacrylonitrile (PAN), polyvinylidene chloride, polymethyl methacrylate, polymethyl acrylate, polyvinyl alcohol, polyacrylonitrile, polymethacrylonitrile, polyvinyl acetate, polyvinyl pyrrolidone, polyethyleneimine Polybutadiene, polystyrene, polyisoprene, or derivatives thereof can be used alone or in combination. In addition, a polymer obtained by copolymerizing each monomer constituting the polymer, for example, vinylidene fluoride / hexafluoropropylene copolymer (P (VdF / HFP)), styrene butadiene rubber, or the like may be used.
[0062]
The reason for using these polymer electrolytes is that Li⁺This is because the ionic conductivity and mobility of the battery increase, so that the polarization of the battery can be reduced. The polymer electrolyte is preferably one that can change its shape. This is because the negative electrode active material can follow the volume expansion and contraction due to charge / discharge, so that the electronic conductivity and ionic conductivity of the negative electrode can be maintained well.
[0063]
In the nonaqueous electrolyte secondary battery of the present invention, the negative electrode may contain a polymer electrolyte. The polymer electrolyte preferably exhibits lithium ion conductivity and binding properties. This is because the negative electrode has good binding properties between the active material and the active material and between the active material and the polymer electrolyte, and the negative electrode's electronic and ionic conduction performance after repeated charge and discharge. This is because it can be maintained well. In particular, the polymer electrolyte is preferably porous. This is because the ionic conductivity of the polymer electrolyte is further improved by holding the electrolytic solution in the pores.
[0064]
In the nonaqueous electrolyte secondary battery of the present invention, the positive electrode active material may be any material as long as it absorbs and releases Li, and various materials can be appropriately used. For example, lithium transition metal composite oxide Li_xMO_2-δ(Wherein M represents Co, Ni or Mn, 0.4 ≦ x ≦ 1.2, 0 ≦ δ ≦ 0.5), a part of M of this lithium transition metal composite oxide is Al, Mn, One substituted with at least one metal element selected from Fe, Ni, Co, Cr, Ti, Zn, one obtained by adding a nonmetallic element such as P or B to this lithium transition metal composite oxide, MnO₂, FeO₂, V₂O₅, V₆O₁₃TiO₂TiS₂, NiOOH, FeOOH, FeS and the like. Moreover, you may mix and use the said various active materials arbitrarily.
[0065]
In particular, lithium nickel composite oxide Li_xNi_pM¹ _qM² _rO_2-δ(However, M¹, M²Represents at least one element selected from Al, Mn, Fe, Ni, Co, Cr, Ti, Zn, 0.4 ≦ x ≦ 1.2, 0.8 ≦ p + q + r ≦ 1.2, 0 ≦ δ ≦ 0.5) or a lithium nickel composite oxide to which a nonmetallic element such as B or P is added, a lithium cobalt composite oxide, or a lithium cobalt nickel composite oxide is preferably used.
[0066]
As the positive electrode active material, MnO₂, FeO₂, V₂O₅, V₆O₁₃TiO₂TiS₂In the case of using a material that does not contain Li, such as NiOOH, FeOOH, or FeS, a battery may be manufactured using a material in which Li is chemically occluded in the positive electrode or the negative electrode. For example, the positive electrode or negative electrode and metallic lithium⁺And a method of applying a material in contact with a non-aqueous electrolyte containing metal, a method of attaching metal Li on the surface of a positive electrode or a negative electrode, and the like.
[0067]
Any binder may be used for the positive electrode, and a known binder can be used as appropriate. For example, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene , Fluorinated polyvinylidene fluoride, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, acrylonitrile-butadiene rubber, fluororubber, polyvinyl acetate, polymethyl methacrylate, polyethylene, nitrocellulose, or derivatives thereof, These can be used alone or in admixture of two or more.
[0068]
Moreover, as a separator of the nonaqueous electrolyte secondary battery of the present invention, a woven fabric, a non-woven fabric, a synthetic resin microporous membrane or the like can be used, and a synthetic resin microporous membrane is particularly preferable. Examples of the material include nylon, cellulose acetate, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, and polyolefins such as polypropylene, polyethylene, and polybutene. Of these, polyolefin microporous membranes such as polyethylene, polypropylene microporous membranes, and microporous membranes composed of these are preferred in terms of thickness, membrane strength, membrane resistance, and the like.
[0069]
In addition, the shape of the battery is not particularly limited, and the present invention is applicable to non-aqueous electrolyte secondary batteries having various shapes such as a square, an ellipse, a coin, a button, a sheet, a cylinder, and a long cylinder. Applicable to batteries.
[0070]
【Example】
Hereinafter, the present invention will be described using preferred embodiments, but the scope of the present invention is not limited thereto.
[0071]
[Example 1]
SiO powder (SiO_xIn which x = 1) is heat-treated at 1000 ° C. for 6 hours to obtain Si and SiO.₂SiO powder (a1) containing both phases was obtained. As a result of X-ray diffraction measurement of this SiO powder (a1), peaks attributable to the Si (111) plane and the Si (220) plane at 2θ (Cukα) = 28.4 ° and 47.3 °, respectively. It was observed. The full width at half maximum of both peaks was 1.7 °. (Hereinafter, the full width at half maximum of the peak attributed to the Si (111) plane is simply referred to as “half width”).
A material (j1) was prepared by mixing in advance at a ratio of mesocarbon microbeads (MCMB): natural graphite: artificial graphite = 40: 40: 20 (mass ratio), and SiO powder (a1) 5.0 mass%. And 95.0% by mass of material (j1) were mixed to make a negative electrode active material.
[0072]
As the binder, SBR (s1) and carboxymethyl cellulose (CMC) having a latex particle size of 190 nm and a glass transition point of −15 ° C. were used. A predetermined amount of the negative electrode active material, SBR (s1), and CMC was weighed and dispersed in ion-exchanged water to obtain a negative electrode mixture paste. This negative electrode mixture paste was applied on one side of an electrolytic copper foil having a thickness of 15 μm and dried at 150 ° C., and then the other side was coated and dried in the same manner, and a negative electrode mixture layer was provided on both sides. A copper foil was obtained. Further, this was compression molded by a roll press to obtain a negative electrode.
[0073]
In addition, it was made for the content rate of SBR (s1) in a negative mix layer to be 0.5 mass%, and the content rate of CMC to be 2.0 mass%. In this negative electrode, the adhesion strength between the negative electrode mixture layer and the negative electrode current collector was 76 N / m.
[0074]
Next, 90% by mass of lithium cobaltate, 5% by mass of acetylene black, and 5% by mass of polyvinylidene fluoride (PVdF) were dispersed in N-methyl-2-pyrrolidone (NMP) to prepare a paste. This paste was applied to an aluminum foil having a thickness of 20 μm at 2.5 mg · cm.^{− 2}Then, the NMP was evaporated by applying the positive electrode active material contained in the battery so that the amount of the positive electrode active material was 5.3 g, and then drying at 150 ° C. The above operation was performed on both sides of the aluminum foil, and both sides were compression molded with a roll press. Thus, the positive electrode provided with the positive mix layer on both surfaces was manufactured.
[0075]
After winding a positive electrode and a negative electrode so that a polyethylene separator, which is a continuous porous body having a thickness of 20 μm and a porosity of 40%, is positioned between both electrodes, this is 48 mm in height, 30 mm in width, and 5.2 mm in thickness. Inserted into a container. Further, a non-aqueous liquid electrolyte was injected into the container and then sealed to prepare a battery (A1) having a rated capacity of 700 mAh. The non-aqueous liquid electrolyte is composed of 1 mol / l LiPF in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1: 1.₆Is dissolved.
[0076]
[Example 2]
Instead of SBR (s1), SBR (s2) having a latex particle size of 250 nm and a glass transition point of −15 ° C. was used as the binder, and the content of SBR (s2) in the negative electrode mixture layer was determined. A battery (A2) of Example 2 was made in the same manner as Example 1 except that the content was 0.3% by mass.
[0077]
[Example 3]
As in Example 1, except that SBR (s2) was used instead of SBR (s1) as the binder, and the content of SBR (s2) in the negative electrode mixture layer was 0.5 mass%. Thus, a battery (A3) of Example 3 was produced.
[0078]
[Comparative Example 1]
A battery (R1) of Comparative Example 1 was produced in the same manner as in Example 1, except that the content of SBR (s1) in the negative electrode mixture layer was 0.3% by mass.
[0079]
[Comparative Example 2]
As a binder, PVdF was used in place of SBR (s1), and the content of PVdF in the negative electrode mixture layer was 0.5 mass%, in the same manner as in Example 1, except for Comparative Example 2. A battery (R2) was produced.
[0080]
[Comparative Example 3]
A battery (R3) of Comparative Example 3 was produced in the same manner as in Example 1 except that the negative electrode active material was 100% by mass of the material (j1) not containing the SiO powder (a1).
[0081]
About the negative electrode used for the battery of Examples 1-3 and Comparative Examples 1-3, the adhesive strength of a negative mix layer and a negative electrode electrical power collector was measured by the above-mentioned method. The contents of these batteries are summarized in Table 1. The unit of “composition” in Table 1 is “mass%”.
[0082]
[Table 1]

[0083]
[Battery evaluation test]
The batteries of Examples 1 to 3 and Comparative Examples 1 to 3 were measured for battery swelling, high rate discharge performance, and battery swelling when left at high temperature as follows.
[0084]
After measuring the battery thickness t1 (mm) of each battery, a charge / discharge test was performed in a thermostatic chamber at 25 ° C. In this test, a constant current to reach 4.2 V at 35 mA, followed by charging at a constant voltage of 4.2 V for 2 hours, and discharging at a constant current of up to 2.7 V at 140 mA were performed. The discharge capacity at this time is C1. Subsequently, a constant current until reaching 4.2 V at 35 mA, followed by charging at a constant voltage of 2 hours at 4.2 V, and discharging at a constant current of up to 2.7 V at 1400 mA were performed. The discharge capacity at this time is C2. Here, the high rate discharge performance was calculated from the following equation. High rate discharge performance (%) = C2 / C1 × 100
In order to be used in applications such as portable computers and power tools, high capacity must be exhibited during high rate discharge. Therefore, the high rate discharge performance is preferably 70% or more.
[0085]
Further, using this battery, a constant current until reaching 4.2 V at 35 mA and subsequent charging at a constant voltage of 4.2 V for 2 hours were performed. The battery was left in a constant temperature bath at 100 ° C. for 3 hours, and then the battery thickness t2 (mm) was measured again. Here, the swelling of the battery when left at high temperature was calculated from the following equation. Battery swelling (mm) = t2 (mm) -t1 (mm)
It is unsuitable to use a battery with a battery swelling exceeding 1.50 mm for applications such as portable computers and electric tools because the battery pack may be broken. Therefore, the battery bulge must be 1.50 mm or less. Since the battery is expected to swell slightly due to repeated charge and discharge, the battery swell is preferably 1.40 mm or less.
[0086]
Moreover, the time required for negative electrode manufacture was compared. The time required for manufacturing the negative electrode used for the battery A1 of Example 1 was set as 100, and the time required for manufacturing the negative electrode used for other batteries was relatively displayed.
[0087]
The measurement results for the batteries of Examples 1 to 3 and Comparative Examples 1 to 3 are summarized in Table 2.
[0088]
[Table 2]

[0089]
From Table 2, the following became clear. By comparing the comparative example 1 and the examples 1 to 3 with the appropriate selection of the type of SBR in the negative electrode mixture layer, the adhesion strength is 75 N / m or more regardless of the composition of the SBR in the negative electrode mixture layer. As a result, the swelling of the battery was 1.50 mm or less, and a battery excellent in discharge capacity C1 and high rate discharge performance was obtained. However, in Examples 2 and 3 using SBR (s2) as the binder for the negative electrode, the dispersibility of SBR (s2) is inferior to that of SBR (s1). It was shown to be necessary for a long time.
[0090]
In addition, since the battery of Comparative Example 2 has a large proportion of the binder in the negative electrode mixture layer, and the battery of Comparative Example 3 does not contain SiO (a1), both of the batteries are initial. The discharge capacity C1 has become considerably small.
[0091]
As described above, by using the negative electrode satisfying the condition of claim 1 of the present application, it is possible to obtain a battery having a high initial discharge capacity C1, a battery swelling of 1.50 mm or less, and excellent high-rate discharge performance. Indicated.
[0092]
[Examples 4 to 10]
In the same manner as in Example 1, except that the content of the negative electrode active material in the negative electrode mixture layer was 97.0 to 86.0 mass% and the content of SBR was 0.5 to 12.0 mass%, Batteries (A4) to (A10) of Examples 4 to 10 were produced.
[0093]
[Example 11]
A predetermined amount of SBR (s1) as a negative electrode active material and a binder is weighed and dispersed in NMP to obtain a paste. This paste is applied to one side of a 15 μm thick copper foil at 150 ° C. The battery of Example 11 was made in the same manner as in Example 1 except that the same application and drying were performed on the other surface after drying, and a copper foil provided with a negative electrode mixture layer on both sides was obtained. (A11) was manufactured. The negative electrode mixture layer contained 98.0% by mass of the negative electrode active material and 2.0% by mass of SBR (s1).
[0094]
The contents of the batteries of Examples 1, 4 to 11 and Comparative Example 1 are shown in Table 3.
[0095]
[Table 3]

[0096]
[Examples 12 to 14, Comparative Example 4]
Instead of SBR (s1) as a binder, SBR (s2) described above, SBR (s3) having a latex particle size of 140 nm and a glass transition point of −15 ° C., latex having a particle size of 140 nm and glass Batteries (A12) to (A14) of Examples 12 to 14 were produced in the same manner as in Example 4 except that SBR (s4) having a transition point of −5 ° C. was used.
[0097]
Further, instead of SBR (s1) as a binder, a comparative example was made in the same manner as in Example 4 except that SBR (s5) having a latex particle size of 80 nm and a glass transition point of −15 ° C. was used. 4 batteries (R4) were produced. Table 4 shows the contents of the batteries (A4), (A12) to (A14) of Example 4, and 12 to 14 and the battery (R4) of Comparative Example 4.
[0098]
[Table 4]

[0099]
The measurement results for these batteries are shown in Tables 5 and 6.
[0100]
[Table 5]

[0101]
[Table 6]

[0102]
Here, the relationship between the SBR content and the battery swelling in the negative electrode mixture layer obtained from Tables 3 and 6 is shown in FIG. 1, and the relationship between the SBR content in the negative electrode mixture layer and the high rate discharge performance is shown in FIG. Each is shown in FIG. FIG. 3 shows the relationship between the adhesion strength between the negative electrode mixture layer obtained from Tables 4 and 6 and the negative electrode current collector and the battery swelling.
[0103]
From FIG. 1 to FIG. 3, in order to obtain a battery having a low swelling of 1.50 mm or less when left at high temperature and an excellent high-rate discharge performance of 70% or more, the SBR content in the negative electrode mixture layer is 0. It was 0.5-10.0 mass%, and it was shown that the adhesive strength between a negative mix layer and a negative electrode collector needs to be 75 N / m or more.
[0104]
[Example 15]
Non-heat treated SiO powder (a0) (SiO_xThe battery (B1) of Example 15 was obtained in the same manner as in Example 4 except that x = 1) was used.
[0105]
[Examples 16 to 20]
SiO powders (a2) to (a6) were obtained by setting the heat treatment temperature of SiO to 830 ° C to 1050 ° C. Batteries (B2) to (B6) of Examples 16 to 20 were obtained in the same manner as Example 4 except that these were used for the negative electrode active material. The SiO powders (a2) to (a6) are all made of SiO._xWhere x = 1.
[0106]
Table 7 shows the contents of the batteries (A4) and (B1) to (B6). In Table 7, the unit of “half width of Si (111)” is “° (2θ, Cukα)”.
[0107]
[Table 7]

[0108]
Using the batteries (B1) to (B6) of Examples 15 to 20, battery swell and high rate discharge performance were measured under the same conditions as the battery (A4) of Example 4. The results are shown in Table 8.
[0109]
[Table 8]

[0110]
FIG. 4 shows the relationship between the full width at half maximum and battery swelling. From this, it is clear that the battery swelling is as small as 1.40 mm or less when the half-value width is 3.0 or less. Therefore, it is preferable that the half width of the SiO powder used for the nonaqueous electrolyte secondary battery of the present invention is 3.0 or less.
[0111]
[Examples 21 to 25]
As Example 4, except that a mixture of 1.0 to 50.0% by mass of SiO powder (a1) and 99.0 to 50.0% by mass of material (j1) was used as the negative electrode active material. Thus, the batteries (C1) to (C5) of Examples 21 to 25 were obtained. The contents of the batteries (A4) and (C1) to (C5) are summarized in Table 9.
[0112]
[Table 9]

[0113]
Using the batteries (C1) to (C5) of Examples 21 to 25, battery swelling and high rate discharge performance were measured under the same conditions as the battery (A4) of Example 4. The results are shown in Table 10.
[0114]
[Table 10]

[0115]
From this, when the ratio of the mass of the SiO powder to the mass of the negative electrode active material is 3.0 to 10.0%, the battery swelling is as small as 1.40 mm or less and the high rate discharge performance is as high as 80% or more. Is clear. Therefore, the ratio of the mass of the SiO powder to the mass of the negative electrode active material is preferably 3.0 to 10.0%.
[0116]
[Example 26]
The battery of Example 26 (D1) was prepared in the same manner as in Example 4 except that a mixture of 50% by mass of mesocarbon microbeads (MCMB) and 50% by mass of natural graphite was used instead of the material (j1). )
[0117]
[Example 27]
A battery (D2) of Example 27 was obtained in the same manner as in Example 4 except that only natural graphite was used instead of the material (j1).
[0118]
[Example 28]
A battery (D3) of Example 28 was obtained in the same manner as in Example 4 except that a mixture of 50% by mass of natural graphite and 50% by mass of artificial graphite was used instead of the material (j1). The contents of the batteries (A4) and (D1) to (D3) are summarized in Table 11.
[0119]
[Table 11]

[0120]
Using the batteries (D1) to (D3) of Examples 26 to 28, battery swelling and high rate discharge performance were measured under the same conditions as the battery (A4) of Example 4. The results are shown in Table 12.
[0121]
[Table 12]

[0122]
In each of the batteries (A4) and (D1) to (D3), the battery swelling was as small as 1.40 mm or less, and the high rate discharge performance was as high as 80% or more. From this, it is clear that the graphite used as the material (j1) may be a single type, or a plurality of types may be mixed at an arbitrary ratio.
[0123]
[Example 29]
SiO powder (a1) 0.5 mol / dm^-3Soaked in hydrofluoric acid in SiO₂By dissolving a part of the phase, SiO_0.8Got. A battery (E1) of Example 29 was obtained in the same manner as in Example 4 except that this was used instead of the SiO powder (a1).
[0124]
[Example 30]
SiO powder (a1) 0.8 mol / dm^-3Soaked in hydrofluoric acid in SiO₂By dissolving a part of the phase, SiO_0.5Got. A battery (E2) of Example 30 was obtained in the same manner as in Example 4 except that this was used instead of the SiO powder (a1). Table 13 shows the contents of the batteries (E1) and (E2).
[0125]
[Table 13]

[0126]
Using the batteries (E1) and (E2) of Examples 29 and 30, battery swell and high rate discharge performance were measured under the same conditions as the battery (A4) of Example 4. The results are shown in Table 14.
[0127]
[Table 14]

[0128]
The batteries (A4), (E1), and (E2) all had a battery bulge as small as 1.40 mm or less and a high rate discharge performance as high as 80% or more. Therefore, the atomic ratio x of O to Si in the substance (A) containing Si and O can take an arbitrary value of 0 <x <2.
[0129]
[Example 31]
After immersing the SiO powder (a1) in an aqueous boric acid solution and firing at 800 ° C., SiO_1.03B_0.02Got. A battery (F1) of Example 31 was obtained in the same manner as in Example 4 except that this was used instead of the SiO powder (a1).
[0130]
[Example 32]
SiO powder (a1) [Cu (NH₃)₄]²⁺After being immersed in the aqueous solution containing_1.01Cu_0.01Got. A battery (F2) of Example 32 was obtained in the same manner as in Example 4 except that this was used instead of the SiO powder (a1). Table 15 shows the contents of the batteries (F1) and (F2).
[0131]
[Table 15]

[0132]
Using the batteries (F1) and (F2) of Examples 31 and 32, battery swelling and high rate discharge performance were measured under the same conditions as the battery (A4) of Example 4. The results are shown in Table 16.
[0133]
[Table 16]

[0134]
In each of the batteries (F1) and (F2), the battery swelling was as small as 1.40 mm or less, and the high rate discharge performance was as high as 80% or more. Therefore, it is clear that an arbitrary amount of a nonmetallic element or a metallic element can be added to the substance (A) containing Si and O.
[0135]
[Examples 33 to 36]
95 to 70% by mass of SiO powder (a1) and 5 to 30% by mass of MCMB are weighed and mechanically combined by a mechano-fusion method (using AMS-Lab manufactured by Hosokawa Micron). (M1) was obtained. Batteries (G1) to (G4) of Examples 33 to 36 were obtained in the same manner as in Example 4 except that the material (m1) was used instead of the SiO powder (a1). From the result of SEM observation of the material (m1), it was found that a plurality of SiO particles were supported on one MCMB particle.
[0136]
[Example 37]
80% by mass of SiO powder (a1) and 20% by mass of natural graphite were weighed and mechanically combined by the mechano-fusion method (using AMS-Lab manufactured by Hosokawa Micron). Got. A battery (G5) of Example 37 was obtained in the same manner as in Example 4 except that this was used instead of the SiO powder (a1). From the result of SEM observation of the material (m2), it was found that a plurality of natural graphite particles and a plurality of SiO particles were combined. Table 17 shows the contents of the batteries (G1) to (G5).
[0137]
[Table 17]

[0138]
Using the batteries (G1) to (G5) of Examples 33 to 37, battery swelling and high rate discharge performance were measured under the same conditions as the battery (A4) of Example 4. The results are shown in Table 18.
[0139]
[Table 18]

[0140]
In each of the batteries (G1) to (G5), the battery swelling was as small as 1.40 mm or less, the high rate discharge performance was as high as 80% or more, and in addition, the batteries (A4) were superior. Therefore, the substance (A) containing Si and O is preferably compounded with the carbon material.
[0141]
[Examples 38 to 42]
Chemical vapor deposition (CVD) of the carbon material (b1) on the surface of the SiO powder so that the mass of the carbon material (b1) is 1 to 30% with respect to the total mass of the SiO powder and the carbon material (b1). Thus, materials (c1) to (c5) were obtained. The CVD was performed under conditions of 1000 ° C. in an Ar atmosphere using methane as a carbon source.
[0142]
The materials (c1) to (c5) were used instead of the SiO powder (a1), and 20% by mass of the materials (c1) to (c5) and 80% by mass of the material (j1) were mixed to form a negative electrode Batteries (H1) to (H5) of Examples 38 to 42 were produced in the same manner as Example 4 except that the active material was used. Table 19 shows the contents of the batteries (H1) to (H5).
[0143]
[Table 19]

[0144]
Using the batteries (H1) to (H5) of Examples 37 to 41, battery swelling and high rate discharge performance were measured under the same conditions as the battery (A4) of Example 4. The results are shown in Table 20.
[0145]
[Table 20]

[0146]
In all of the batteries (H1) to (H5), the battery swelling was as small as 1.40 mm or less, and the high rate discharge performance was as high as 80% or more. Therefore, it became clear that it is preferable to apply a material obtained by CVD of a carbon material to the substance (A) containing Si and O as the negative electrode active material.
[0147]
[Example 43]
By subjecting the carbon material (b2) to plasma CVD on the surface of the SiO powder such that the mass of the carbon material (b2) is 5% with respect to the total mass of the SiO powder and the carbon material (b2), the material (c6 ) The CVD was performed under conditions of 1000 ° C. in an Ar atmosphere using toluene as a carbon source. A battery (H6) of Example 43 was produced in the same manner as in Example 39 except that the material (c6) was used instead of the material (c1).
[0148]
[Example 44]
Chemical vapor deposition (CVD) of the carbon material (b3) on the surface of the SiO powder so that the mass of the carbon material (b3) is 5% with respect to the total mass of the SiO powder and the carbon material (b3). Gave material (c7). The CVD was performed under conditions of 1000 ° C. in an Ar atmosphere using benzene as a carbon source. A battery (H7) of Example 44 was made in the same manner as Example 39 except that the material (c7) was used instead of the material (c1).
[0149]
[Example 45]
By subjecting the carbon material (b4) to plasma CVD on the surface of the SiO powder such that the mass of the carbon material (b4) is 5% with respect to the total mass of the SiO powder and the carbon material (b4), the material (c8 ) The CVD was performed under the condition of 1000 ° C. in an Ar atmosphere using acetylene as a carbon source. A battery (H8) of Example 45 was produced in the same manner as in Example 39 except that the material (c8) was used instead of the material (c1).
[0150]
Using the batteries (H6) to (H8) of Examples 43 to 45, battery swelling and high rate discharge performance were measured under the same conditions as the battery (A4) of Example 4. The results are shown in Table 21.
[0151]
[Table 21]

[0152]
In each of the batteries (H2) and (H6) to (H8), the battery swelling was as small as 1.40 mm or less and the high rate discharge performance was as high as 80% or more. Therefore, when a material obtained by CVD of a carbon material to the substance (A) containing Si and O is applied to the negative electrode active material, it is clear that any carbon source may be used.
[0153]
[Examples 46 to 49]
Except having used the mixture of 1.0-20.0 mass% material (c4) and 99.0-80.0 mass% material (j1) as a negative electrode active material, it is the same as that of Example 41. Thus, batteries (I1) to (I4) of Examples 46 to 49 were obtained. Table 22 shows the contents of the batteries (H4) and (I1) to (I4).
[0154]
[Table 22]

[0155]
Using the batteries (I1) to (I4) of Examples 46 to 49, battery swelling and high rate discharge performance were measured under the same conditions as the battery (A4) of Example 4. The results are shown in Table 23.
[0156]
[Table 23]

[0157]
In each of the batteries (H4) and (I1) to (I4), the battery swelling was as small as 1.40 mm or less, and the high rate discharge performance was as high as 80% or more. Further, when the mass ratio of the material (c4) in the negative electrode active material is 20% or less, the battery swelling is extremely small as 1.00 mm or less. Therefore, when a material obtained by CVD of a carbon material to the substance (A) containing Si and O is applied to the negative electrode active material, the mass ratio of the material (c4) in the negative electrode active material may be 20% or less. preferable.
[0158]
[Examples 50 to 56, Comparative Example 6]
Except having changed the content rate of the negative electrode active material in a negative electrode mixture layer into 98.5-86.0 mass%, and changing the content rate of SBR into 0.5-12.0 mass%, it carried out similarly to Example 41, and. Thus, batteries (J1) to (J6) of Examples 50 to 56 were manufactured.
[0159]
Further, the battery of Comparative Example 6 was prepared in the same manner as in Example 41 except that the content of the negative electrode active material in the negative electrode mixture layer was 97.7% by mass and the content of SBR was 0.3% by mass. R6) was produced.
[0160]
Table 24 shows the contents of the batteries of Examples 41 and 50 to 56 and Comparative Example 6.
[0161]
[Table 24]

[0162]
Using the batteries (J1) to (J6) of Examples 50 to 56, battery swelling and high rate discharge performance were measured under the same conditions as the battery (A4) of Example 4. The results are shown in Table 25.
[0163]
[Table 25]

[0164]
FIG. 5 shows the relationship between the SBR content in the negative electrode mixture layer and battery swelling. FIG. 6 shows the relationship between the SBR content in the negative electrode mixture layer and the high rate discharge performance. FIG. 7 shows the relationship between the adhesion strength between the negative electrode mixture layer and the negative electrode current collector and battery swelling.
[0165]
From FIG. 5 to FIG. 7, in order to obtain a battery having a small swelling of 1.50 mm or less when left at high temperature and an excellent high rate discharge performance of 70% or more, a material containing Si and O in the negative electrode active material Even when a material obtained by CVD of a carbon material is applied to (A), the content of SBR in the negative electrode mixture layer is 0.5 mass% to 10.0 mass%, and the negative electrode composite The adhesion strength between the agent layer and the negative electrode current collector is preferably 75 N / m or more.
[0166]
[Example 57]
SiO powder and natural graphite are weighed at a mass ratio of 30:55, and these are mechanically combined by a ball mill method (using a planetary MONO mill P-6 manufactured by Fritsch) to obtain a material (g1). It was.
[0167]
By CVD of the carbon material (h1) on the surface of the material (g1) so that the mass of the carbon material (h1) is 15% with respect to the total mass of the material (g1) and the carbon material (h1). Material (i1) was obtained. The CVD was performed under conditions of 1000 ° C. in an Ar atmosphere using toluene as a carbon source. A battery (K1) of Example 57 was made in the same manner as Example 38 except that the material (i1) was used instead of the material (c1).
[Examples 58 to 61]
Except that the mass ratio of the SiO powder and natural graphite weighed when producing the material (g1) and the mass of the carbon material (h1) to be CVDed when producing the material (i1) were changed. In the same manner as in Example 55, batteries (K2) to (K5) of Examples 58 to 61 were manufactured. Table 26 shows the contents of the batteries (K1) to (K5).
[0168]
[Table 26]

[0169]
Using the batteries (K1) to (K5) of Examples 57 to 61, battery swelling and high rate discharge performance were measured under the same conditions as the battery (A4) of Example 4. The results are shown in Table 27.
[0170]
[Table 27]

[0171]
In all of the batteries (K1) to (K5), the battery swelling was as small as 1.40 mm or less, and the high rate discharge performance was as high as 80% or more. A mixture of the substance (A) and the carbon material (F) is defined as a substance (G), and at least a part of the surface of the substance (G) is covered with the carbon material (H) as a substance (I). From the results of the batteries (K1) to (K5), it was revealed that the substance (I) is preferably applied to the negative electrode active material.
[0172]
[Examples 62 to 66]
Example 57 was used except that a mixture of 1.0 to 20.0% by mass of material (g1) and 99.0 to 80.0% by mass of material (j1) was used as the negative electrode active material. Thus, batteries (L1) to (L5) of Examples 62 to 66 were obtained. The contents of the batteries (K1) and (L1) to (L5) are summarized in Table 28.
[0173]
[Table 28]

[0174]
Using the batteries (L1) to (L5) of Examples 62 to 66, battery swelling and high rate discharge performance were measured under the same conditions as the battery (A4) of Example 4. The results are shown in Table 29.
[0175]
[Table 29]

[0176]
From this, when the ratio of the mass of the material (g1) to the total mass of the material (g1) and the material (j1) is 5 to 30%, the battery swelling is as small as 1.00 mm or less, and the high rate discharge performance is high. It was found to be very high at 90% or more. Therefore, it is clear that the ratio of the mass of the material (g1) to the total mass of the material (g1) and the material (j1) is preferably 5 to 30%.
[0177]
[Example 67]
A battery (M) of Example 67 was made in the same manner as Example 4 except that a rolled copper foil having a thickness of 15 μm was used instead of the electrolytic copper foil having a thickness of 15 μm as the negative electrode current collector. In the negative electrode used for the battery (M), the adhesion strength between the negative electrode mixture layer and the current collector was 98 N / m.
[0178]
Using this battery (M), battery swelling and high rate discharge performance were measured under the same conditions as the battery (A4) of Example 4. As a result, the battery swelling was 1.33 mm, and the high rate discharge performance was as good as 81%. Therefore, it has been found that excellent characteristics can be obtained regardless of whether an electrolytic copper foil or a rolled copper foil is used as the metal foil used as the negative electrode current collector.
[0179]
【The invention's effect】
The nonaqueous electrolyte secondary battery of the present invention includes a negative electrode including a negative electrode mixture layer and a negative electrode current collector, the negative electrode mixture layer includes a negative electrode active material and a binder, and the negative electrode active material includes A substance containing Si and O and a carbon material, wherein an atomic ratio x of O to Si in the substance containing Si and O satisfies 0 <x <2, and the binder contains SBR; By setting the adhesion strength between the negative electrode mixture layer and the negative electrode current collector to 75 N / m or more, battery swelling that occurs when a nonaqueous electrolyte secondary battery including a negative electrode containing silicon oxide is left at high temperature is greatly suppressed. In addition, the high rate discharge performance at room temperature could be equal to or higher than that of conventionally known batteries. Furthermore, by setting the content of the binder in the negative electrode mixture layer to 0.5 to 10.0% by mass, it was possible to suppress swelling when left at a higher temperature. Therefore, the industrial value of the present invention is extremely great.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the SBR content in a negative electrode mixture layer and battery swelling when a mixture of SiO powder (a1) and material (j1) is used as a negative electrode active material.
FIG. 2 is a diagram showing the relationship between the SBR content in the negative electrode mixture layer and the high rate discharge performance when a mixture of SiO powder (a1) and material (j1) is used as the negative electrode active material.
FIG. 3 is a graph showing the relationship between adhesion strength and battery swelling when a mixture of SiO powder (a1) and material (j1) is used as the negative electrode active material.
FIG. 4 is a diagram showing a relationship between a half-value width and battery swelling.
FIG. 5 is a graph showing the relationship between the SBR content in the negative electrode mixture layer and battery swelling when a mixture of the material (c4) and the material (j1) is used as the negative electrode active material.
FIG. 6 is a diagram showing the relationship between the SBR content in the negative electrode mixture layer and the high rate discharge performance when a mixture of SiO powder (c4) and material (j1) is used as the negative electrode active material.
FIG. 7 is a diagram showing the relationship between adhesion strength and battery swelling when a mixture of SiO powder (c4) and material (j1) is used as the negative electrode active material.

Claims (2)

In a non-aqueous electrolyte secondary battery including a negative electrode including a negative electrode mixture layer and a negative electrode current collector, the negative electrode mixture layer includes a negative electrode active material and a binder, and the negative electrode active material includes Si and O. And a carbon material, wherein the atomic ratio x of O to Si in the substance containing Si and O satisfies 0 <x <2, the binder contains SBR, and the negative electrode mixture layer A nonaqueous electrolyte secondary battery, wherein the adhesion strength between the electrode and the negative electrode current collector is 75 N / m or more. The nonaqueous electrolyte secondary battery according to claim 1, wherein the content of the binder in the negative electrode mixture layer is 0.5 to 10.0% by mass.

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