JP2004014300A - Nonaqueous electrolyte battery and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte battery having excellent high-temperature storage characteristics by suppressing a deterioration of battery characteristics even if stored in the high temperature and to provide a method for manufacturing the same. <P>SOLUTION: The nonaqueous electrolyte battery can dope lithium/dedope the lithium, has a positive electrode 2 having a positive active material containing a lithium carbonate, a negative electrode 3 having a negative active material which can dope and dedope the lithium, and a solid electrolyte 4 having a nonaqueous solvent added with a carbamate or the like and an electrolyte salt. Thus, a decomposition of the solid electrolyte 4 by heat is suppressed by the lithium carbonate contained in the positive active material and a gas generation by heating is suppressed by the carbamate or the like added to the solid electrolyte 4. Accordingly, the deterioration of the battery characteristics due to storage in high temperatures is suppressed. <P>COPYRIGHT: (C)2004,JPO

Description

【００１２】
これにより、この非水電解質電池では、正極活物質に含有された炭酸リチウム及び非水溶媒に添加されたカーバメート類が高温保存時の非水電解質の分解やガス発生を抑えることから、高温保存により電池特性が劣化してしまうことを抑制させる。
【００１３】
また、本発明に係る非水電解質電池の製造方法は、リチウムのドープ／脱ドープが可能な正極活物質を有する正極と、リチウムのドープ／脱ドープが可能な負極活物質を有する負極と、非水溶媒と電解質塩とを含有する非水電解質とを備える非水電解質電池の製造方法であって、正極活物質に炭酸リチウムを含有させると共に、非水溶媒に一般式（１）で示されるカーバメート類を添加させることを特徴としている。
【００１４】
【化４】

【００１５】
この、非水電解質電池の製造方法では、炭酸リチウムが含有している正極活物質を有する正極と、非水溶媒にカーバメート類を添加させた非水電解質とを用いた非水電解質電池が得られる。したがって、この非水電解質電池の製造方法では、正極活物質に含有されている炭酸リチウムや非水電解質の非水溶媒に添加されたカーバメート類により高温保存時の非水電解質の分解やガス発生が抑えられることから、高温保存による電池特性の劣化が抑制された非水電解質電池が得られる。
【００１６】
【発明の実施の形態】
以下、本発明を適用した非水電解質電池について説明する。この非水電解質電池としてリチウムイオン二次電池（以下、電池と記す。）の一構成例を図１に示す。この電池１は、長尺状に形成された正極２と、長尺状に形成された負極３と、高分子マトリックスに電解質塩と共に非水溶媒も含浸させたゲル状電解質といった固体電解質４とを備えている。そして、この電池１は、正極２及び負極３の主面上に固体電解質４を形成し、正極２と負極３とを固体電解質４を介して積層させた状態で捲回することで発電要素となる電池素子５を構成し、この電池素子５を外装材６に封入させた構造となっている。
【００１７】
正極２は、正極活物質と結着剤とを含有する正極合剤塗液を長尺状の正極集電体７上に塗布、乾燥、加圧することにより、正極集電体７上に正極合剤層８が圧縮形成された構造となっている。正極２には、正極端子９が正極集電体７の所定の位置に、正極集電体７の幅方向に突出するように接続されている。この正極端子９には、例えばアルミニウムからなる短冊状金属片等を用いる。
【００１８】
正極活物質には、ＴｉＳ_２、ＭｏＳ_２、ＮｂＳｅ_２、Ｖ_２Ｏ_５等の金属硫化物あるいは酸化物を使用することができる。また、ＬｉＭ_ｘＯ_２（式中ＭはＣｏ、Ｎｉ、Ｍｎ、Ｆｅ、Ａｌ、Ｖ、Ｔｉ等による一種以上の遷移金属を表し、ｘは電池の充放電状態によって異なり、通常０．０５以上、１．１０以下である。）を主体とするリチウム複合酸化物等を使用することができる。このリチウム複合酸化物を構成する遷移金属Ｍとしては、Ｃｏ、Ｎｉ、Ｍｎ等が好ましい。このようなリチウム複合酸化物の具体例としては、ＬｉＣｏＯ_２、ＬｉＮｉＯ_２、ＬｉＮｉ_ｙＣｏ_１−ｙＯ_２（式中、０＜ｙ＜１である。）、ＬｉＭｎ_２Ｏ_４等を挙げることができる。
【００１９】
そして、正極活物質には、炭酸リチウムが含有されている。これにより、電池１では、高温状態に保存された際に、炭酸リチウムが固体電解質４中の電解質塩等が例えば熱により分解されてしまうことを抑えることから、高温保存による電池特性の劣化が抑制される。
【００２０】
また、正極２では、正極活物質に対し、炭酸リチウムの含有量が０．０５重量％以上、０．２重量％以下の範囲にされている。例えば、正極活物質に対し、炭酸リチウムの含有量が０．０５重量％より少ない場合、電池１では、高温保存中に固体電解質４中の電解質塩等が分解されてしまうことを抑制させることが困難になる。一方、正極活物質に対し、炭酸リチウムの含有量が０．２重量％より多い場合、電池１では、高温保存中に多すぎる炭酸リチウムが分解されて電池素子５内に二酸化炭素ガスを発生させてしまうことから、正極２と負極３との間に二酸化炭素ガスが貯留して電池抵抗を向上させてしまう。したがって、正極２では、正極活物質に対し、炭酸リチウムの含有量を０．０５重量％以上、０．２重量％以下の範囲にすることにより、高温時に固体電解質４が分解されてしまうことを適切に抑制させることが可能となる。
【００２１】
炭酸リチウムを正極活物質に含有させる方法としては、例えば正極活物質としてＬｉＣｏＯ_２を得る場合、出発原料である炭酸リチウムと炭酸コバルトとを混合し、この混合物を焼成することで正極活物質に炭酸リチウムを含有させる。すなわち、この場合、炭酸リチウムと炭酸コバルトとを混合する際の混合比率を調整することで炭酸リチウムの含有量が制御された正極活物質が得られることになる。
【００２２】
正極２では、正極合剤層８の結着剤として、非水電解質電池の正極合剤に用いられる例えばポリフッ化ビニリデンやスチレンブタジエンゴム等といった結着剤を用いることができる他に、正極合剤層８に例えば導電材として炭素質材料等を添加したり、公知の添加剤等を添加したりすることができる。また、正極２では、正極集電体９として例えばアルミニウム等からなる箔状金属や網状金属等が用いられる。
【００２３】
負極３は、負極活物質と結着剤とを含有する負極合剤塗液を長尺状の負極集電体１０上に塗布、乾燥、加圧することにより、負極集電体１０上に負極合剤層１１が圧縮形成された構造となっている。負極３には、負極端子１２が負極集電体１０の所定の位置に、負極集電体１０の幅方向に突出するように接続されている。この負極端子１２には、例えば銅やニッケル等からなる短冊状金属片等を用いる。
【００２４】
負極活物質には、リチウム、リチウム合金、又はリチウムをドープ／脱ドープできる炭素材料が用いられる。リチウムをドープ／脱ドープできる炭素材料としては、例えば２０００℃以下の比較的低い温度で焼成して得られる低結晶性炭素材料、結晶化しやすい原材料を３０００℃付近の高温で焼成した人造黒鉛等の高結晶性炭素材料等を使用することができる。具体的には、難黒鉛化炭素、熱分解炭素類、コークス類、黒鉛類、ガラス状炭素繊維、有機高分子化合物焼成体、炭素繊維、活性炭、カーボンブラック類等の炭素質材料を使用することができる。コークス類には、ピッチコークス、ニードルコークス、石油コークス等がある。また、有機高分子化合物焼成体とは、フェノール樹脂、フラン樹脂等を適当な温度で焼成し、炭素化したものである。上述した炭素質材料のほか、リチウムをドープ／脱ドープできる材料としては、例えばポリアセチレン、ポリピロール等の高分子や、酸化鉄、酸化ルテニウム、酸化モリブデン、酸化タングステン、酸化チタン、酸化錫等の酸化物や、これら酸化物の酸素を窒素に置き換えた窒化物等を使用することもできる。
【００２５】
負極３では、負極合剤層１１の結着剤として、非水電解質電池の負極合剤に用いられる例えばポリフッ化ビニリデンやスチレンブタジエンゴム等といった結着剤を用いることができる他に、負極合剤層１１に例えば公知の添加剤等を添加したりすることができる。また、負極３では、負極集電体１０として例えば銅等からなる箔状金属や網状金属等が用いられる。
【００２６】
固体電解質４は、高分子マトリックスといった有機高分子に、非水溶媒と電解質塩からなる非水電解液を含浸させたゲル状電解質を用いる。
【００２７】
高分子マトリックスとしては、非水電解液を吸収してゲル化するものであれば種々の高分子が利用できる。具体的には、例えばポリ（ビニリデンフルオロライド）やポリ（ビニリデンフルオロライド−ｃｏ−ヘキサフルオロプロピレン）等のフッ素系高分子、ポリ（エチレンオキサイド）やこれの架橋体等のエーテル系高分子、ポリ（アクリロニトリル）等が挙げられ、これらのうちの何れか一種又は複数種を混合して用いる。
【００２８】
非水溶媒としては、比較的誘電率が高い溶媒を用いる。具体的には、例えば炭酸プロピレン、炭酸エチレン等の環状炭酸エステル類や、炭酸ジエチル、炭酸ジメチル等の鎖状炭酸エステル類、これら炭酸エステル類の水素をハロゲンに置換させた溶媒、プロピオン酸メチルや酪酸メチル等のカルボン酸エステル類、２−メチルテトラヒドロフランやジメトキシエタン等のエーテル類、γ−ブチルラクトン等のブチルラクトン類、γ−ヴァレロラクトン等のヴァレロラクトン類、スルホラン類等が挙げられる。そして、これら非水溶媒のうちの一種又は複数種を混合して用いる。
【００２９】
電解質塩としては、非水電解質電池の非水電解液に用いられる電解質塩を使用することができる。具体的には、例えばＬｉＰＦ_６、ＬｉＢＦ_４、ＬｉＡｓＦ_６、ＬｉＣｌＯ_４、ＬｉＢ（Ｃ_６Ｈ_５）_４、ＣＨ_３ＳＯ_３Ｌｉ、ＣＦ_３ＳＯ_３Ｌｉ、ＬｉＮ（ＳＯ_２ＣＦ_３）_２、ＬｉＮ（ＳＯ_２Ｃ_２Ｆ_５）_２、ＬｉＣ（ＳＯ_２ＣＦ_３）_３、ＬｉＡｌＣｌ_４、ＬｉＳｉＦ_６、ＬｉＣｌ、ＬｉＢｒ等の電解質塩が挙げられる。そして、これらのうちの一種又は複数種を混合して用いる。特に、電解質塩としては、酸化安定性の点で優れているＬｉＰＦ_６、ＬｉＢＦ_４を用いる。なお、電解質塩の非水溶媒に対する濃度は特に限定されないが、０．４モル／リットル以上、１．５モル／リットル以下の範囲にすることにより、非水電解液のイオン伝導度を高くすることができる。
【００３０】
そして、固体電解質４において、非水溶媒には、カーバメート類が添加されている。具体的には、カーバメート類として例えば化学式（２）に示すエチルＮ，Ｎ−ジメチルカーバメート（以下、ＥＭＣＡと記す。）、化学式（３）に示すメチルＮ，Ｎ−ジエチルカーバメート（以下、ＭＥＣＡと記す。）、化学式（４）に示すメチルＮ，Ｎ−ジメチルカーバメート（以下、ＭＭＣＡと記す。）等が挙げられ、これらのうちの一種以上が非水溶媒に添加されている。
【００３１】
【化５】

【００３２】
【化６】

【００３３】
【化７】

【００３４】
これにより、電池１では、高温状態に保存された際に、カーバメート類が例えば固体電解質４が熱で分解されてしまうことや正極２が固体電解質４と反応してガスを発生させてしまうこと等を抑えることが可能となる。
【００３５】
また、固体電解質４では、例えばカーバメート類としてＥＭＣＡ及び／又はＭＥＣＡを添加させた場合、ＥＭＣＡ及び／又はＭＥＣＡ全体の添加量が非水電解液の非水溶媒に対して０．１重量％以上、５重量％以下の範囲にされている。例えば、非水溶媒に対してＥＭＣＡ及び／又はＭＥＣＡ全体の添加量が０．１重量％より少ない場合、電池１では、高温保存時にカーバメート類による作用効果が得ることが困難であり、固体電解質４の分解やガス発生等が起こってしまう。一方、非水溶媒に対してＥＭＣＡ及び／又はＭＥＣＡ全体の添加量が５重量％より多い場合、電池１では、カーバメート類が過剰量なことから電池特性が劣化してしまう。
【００３６】
したがって、正極２では、カーバメート類としてＥＭＣＡ及び／又はＭＥＣＡを添加させた場合、非水電解液の非水溶媒に対するカーバメート類の添加量を０．１重量％以上、５重量％以下の範囲にすることにより、高温状態に保存された際の固体電解質４の分解やガス発生を抑えると共に、過剰に添加されたカーバメート類による電池特性の劣化を抑えることが可能となる。
【００３７】
また、固体電解質４では、例えばカーバメート類としてＭＭＣＡを添加させた場合、ＭＭＣＡの添加量が非水電解液の非水溶媒に対して０．３重量％以上、５重量％以下の範囲にされている。例えば、非水溶媒に対してＭＭＣＡの添加量が０．３重量％より少ない場合、電池１では、高温保存時にＭＭＣＡによる作用効果が得ることが困難となる。一方、非水溶媒に対してＭＭＣＡの添加量が５重量％より多い場合、電池１では、ＭＭＣＡが過剰量なことから電池特性が劣化してしまう。
【００３８】
したがって、正極２では、カーバメート類としてＭＭＣＡを添加させた場合、非水電解液の非水溶媒に対するＭＭＣＡの添加量を０．３重量％以上、５重量％以下の範囲にすることにより、高温状態に保存された際の固体電解質４の分解やガス発生を抑えると共に、過剰に添加されたＭＭＣＡによる電池特性の劣化を抑えることが可能となる。
【００３９】
外装材６は、例えば絶縁層や金属層等が二層以上に積層されて、ラミネート加工等により貼り合わされており、電池内面が絶縁層となるようにされている。絶縁層としては、正極端子９及び負極端子１２に対して接着性を示すものであれば材料は特に限定されないが、ポリエチレン、ポリプロピレン、変性ポリエチレン、変性ポリプロピレン及びこれらの共重合体等、ポリオレフィン樹脂からなるものが透過性を低くできて気密に優れることから用いられる。金属層としては、例えば箔状、板状等に成形されているアルミニウム、ステンレス、ニッケル、鉄等が用いられる。また、外装材６においては、電池１の外周層なる層に例えばナイロン等からなる絶縁層を用いることにより、破れや突き刺し等に対する強度を向上させることができる。
【００４０】
そして、以上のような構成の電池１は、次のようにして製造される。先ず、正極２を作製する。正極２を作製する際は、上述した炭酸リチウムが所定量含有された正極活物質と導電材と結着剤とを含有する正極合剤塗液を調製し、この正極合剤塗液を例えばアルミニウム箔等からなる正極集電体７上に均一に塗布、乾燥することで正極合剤層８を形成し、所定の寸法に裁断する。次に、正極集電体７の所定の位置に正極端子９を例えば超音波溶接や、スポット溶接等により接続する。このようにして、長尺状の正極２が作製される。
【００４１】
次に、負極３を作製する。負極３を作製する際は、上述した負極活物質と結着剤とを含有する負極合剤塗液を調製し、この負極合剤塗液を例えば銅箔等からなる負極集電体１０上に均一に塗布、乾燥することで負極合剤層１１を形成し、所定の寸法に裁断する。次に、負極集電体１０の所定の位置に負極端子１２を例えば超音波溶接や、スポット溶接等により接続する。このようにして、長尺状の負極３が作製される。
【００４２】
次に、以上のように作製された正極３の正極合剤層８の主面及び負極３の負極合剤層１１の主面に固体電解質４をそれぞれ層状に形成する。固体電解質４を形成する際は、上述した非水溶媒に電解質塩を溶解させることで非水電解液を調製する。このとき、非水電解液においては、非水溶媒にカーバメート類を所定量添加させる。
【００４３】
次に、この非水電解液と、上述したマトリックス高分子と、必要に応じて希釈溶剤としての非水溶媒とを混合撹拌してゾル状態の電解質溶液を作製し、この電解質溶液を性極合剤層８の主面及び負極合剤層１１の主面にそれぞれ塗布することで、正極２及び負極３の主面上にゲル状電解質からなる電解質膜を形成する。なお、希釈溶剤を用いた場合は、非水溶媒を揮発させてゲル状電解質を形成する。このようにして正極２上及び負極３上に固体電解質４をそれぞれ形成させる。
【００４４】
次に、図２に示すように、以上のように固体電解質４が主面上に形成された正極２及び負極３を固体電解質４が対向するように積層し、電極の長尺方向に扁平捲回して電池素子５を作製する。この際には、電池素子５の一方端面から正極端子９及び負極端子１２が突出するようにさせる。
【００４５】
次に、図３に示すように、この電池素子５に備わる正極端子９と負極端子１２とを外部に導出しつつ、外装材６の内部に収納する。このとき、電池素子５は、正極端子９及び負極端子１２と、外装材６との間に接着性を示すプロピレン等からなす樹脂片１３をあてがうようにして、外装材６に収納させる。これにより、電池１では、正極端子９及び負極端子１２と外装材６における金属層とが短絡することや、気密性が低下すること等が防止される。
【００４６】
次に、図４に示すように、電池素子５を内部に収納した外装材６の周縁部を例えばヒートシール等で張り合わせることにより、電池素子５が外装材６に封入される。このようにして電池１が製造される。
【００４７】
以上のように製造された電池１では、正極活物質に含有された炭酸リチウムにより、高温保存時に起こる固体電解質４の分解、特に電解質塩の分解が抑えられる。また、この電池１では、非水溶媒に添加されたカーバメート類により、高温保存時に起こる非水電解質の分解やガス発生が抑えられる。
【００４８】
したがって、この電池１では、正極活物質に炭酸リチウムを含有添加しつつ、固体電解質４の非水溶媒にカーバメート類を添加させることにより、高温保存時に起こる固体電解質４の分解や、固体電解質４の分解に伴うガスの発生等を適切に抑えることから高温保存による電池特性の劣化が抑制される。
【００４９】
本発明を適用した非水電解質電池は、外装材に金属製容器を用いた例えば円筒形、角型、コイン型、ボタン型等その形状については特に限定されることはなく、また、薄型、大型等の種々の大きさにすることも可能である。また、本発明を適用した非水電解質電池においては、上述した実施の形態で電池１の電池素子５は捲回されているが、このことに限定されることはなく、例えば負極と正極との間にセパレータを介して積層して捲回させた構成や、長尺状の負極と正極とをセパレータを介した状態で葛折り、いわゆる蛇腹状に折り畳んだ構成等の電池素子を用いた場合でも適用可能である。
【００５０】
【実施例】
以下、本発明を適用した非水電解質電池としてゲル状電解質と用いたリチウムイオン二次電池を実際に作製したサンプルについて説明する。
【００５１】
〈サンプル１〉
サンプル１となるリチウムイオン二次電池を製造するのに、先ず、正極活物質を合成した。正極活物質を得るためには、出発原料として炭酸リチウムと炭酸コバルトとをそれぞれ所定量づつ混合した混合物を９００℃の空気中で約５時間焼成し、粉砕することにより平均粒径が８μｍのＬｉＣｏＯ_２が得られた。このとき、得られたＬｉＣｏＯ_２は、中和滴定法により炭酸リチウムの含有量を測定したところ０．０５重量％であった。
【００５２】
次に、得られたＬｉＣｏＯ２を９１重量部と、導電材として鱗片状黒鉛を６重量部と、結着剤としてポリフッ化ビニリデン（以下、ＰＶｄＦと記す。）を３重量部と、溶剤としてＮ−メチル−２−ピロリドン（以下、ＮＭＰと記す。）とを加えて、プラネタリーミキサーによって混練して分散を行い、正極合剤塗液を作製した。次に、塗工装置としてダイコータを用いて正極集電体となる厚み２０μｍの帯状アルミニウム箔の両面に均一に塗布して、１００℃、減圧状態で２４時間乾燥させた後に、ロールプレス機で圧縮成形し、幅１１８ｍｍ、長さ６４０ｍｍに裁断した。以上のようにして長尺状の正極を作製した。
【００５３】
次に、負極を作製した。負極を作製する際は、負極活物質として（００２）面の面間隔が０．３３７ｎｍ、（００２）面のＣ軸結晶子厚みが５０ｎｍ、ピクノメータ法による真密度が２．２３ｇ／ｃｃ、ＢＥＴ法による比表面積が１．６ｍ^２／ｇ、平均粒径が３３μｍ、嵩密度が０．９８ｇ／ｃｍ^３の黒鉛を９０重量％と、結着剤としてＰＶｄＦを１０重量％と、溶剤にＮＭＰとを加えて、プラネタリーミキサーによって混練して分散を行い、負極合剤塗液を作製した。次に、この負極合剤塗液を塗工装置としてダイコータを用いて負極集電体となる厚み１０μｍの帯状銅箔の両面に均一にそれぞれ塗布して、１２０℃、減圧状態で２４時間乾燥させた後に、ロールプレス機で圧縮成形し、幅１２０ｍｍ、長さ８００ｍｍに裁断した。以上のようにして長尺状の負極を作製した。
【００５４】
次に、以上のように作製された正極及び負極の両主面にゲル状電解質を電解質層として形成した。ゲル状電解質からなる電解質層を形成する際は、エチレンカーボネート（以下、ＥＣと記す。）を３９．６重量％と、プロピレンカーボネート（以下、ＰＣと記す。）を５９．４重量％と、カーバメート類としてエチルＮ，Ｎ−ジメチルカーバメート（以下、ＥＭＣＡと記す。）を１重量％とを混合させた非水溶媒に溶媒重量に対してＬｉＰＦ_６を０．８ｍｏｌ／ｋｇ溶解させた非水電解液を調製した。
【００５５】
次に、この非水電解液と、ヘキサフルオロプロピレンを７％の割合で共重合されたＰＶｄＦと、ジメチルカーボネートとを混合撹拌してゾル状態のゲル状電解質溶液を作製した。次に、このゲル状電解質溶液を正極及び負極の両主面上にそれぞれ塗布し、ジメチルカーボネートを揮発させた。このようにして正極及び負極の両主面上にゲル状電解質からなる電解質層を形成させた。
【００５６】
次に、以上のように電解質層が主面上に形成された正極及び負極をゲル状電解質が対向するように貼り合わせ、正極の長尺方向に扁平捲回して電池素子を作製した。この際には、正極の任意の位置にアルミニウムからなる短冊状の正極端子を取り付け、負極の任意の位置にニッケルからなる短冊状の負極端子を取り付けた。
【００５７】
次に、この電池素子に備わる正極端子と負極端子とを外部に導出しつつ、厚み５０μｍのアルミニウム箔が厚み３０μｍのポリオレフィンフィルムで挟んだ三層構造の外装材の内部に収納した。このとき、電池素子は、正極端子及び負極端子と外装材との間に接着性を示すプロピレン樹脂片をあてがうようにして、外装材に収納された。これにより、電池素子は、正極端子と負極端子とが外装材のアルミニウム箔と介して短絡することや、気密性が劣化すること等が防止される。次に、電池素子を内部に収納した外装材の周縁部を張り合わせることにより、電池素子を外装材に封入した。以上のようにして、サンプル１のリチウムイオン二次電池を製造した。なお、以下の説明では、便宜上、リチウムイオン二次電池のことを単に電池と称する。
【００５８】
〈サンプル２〉
サンプル２では、正極及び負極の両主面上に、ＥＣを４０重量％と、ＰＣを５９．９重量％と、ＥＭＣＡを０．１重量％とを混合させた非水溶媒に溶媒重量に対してＬｉＰＦ_６を０．８ｍｏｌ／ｋｇ溶解させた非水電解液を用いたゲル状電解質を電解質層として形成させたこと以外は、サンプル１と同様にして電池を製造した。
【００５９】
〈サンプル３〉
サンプル３では、正極及び負極の両主面上に、ＥＣを３８重量％と、ＰＣを５７重量％と、ＥＭＣＡを５重量％とを混合させた非水溶媒に溶媒重量に対してＬｉＰＦ_６を０．８ｍｏｌ／ｋｇ溶解させた非水電解液を用いたゲル状電解質を電解質層として形成させたこと以外は、サンプル１と同様にして電池を製造した。
【００６０】
〈サンプル４〉
サンプル４では、正極活物質として、炭酸リチウムと炭酸コバルトとの混合比を調整することで炭酸リチウムが０．２重量％含有されたＬｉＣｏＯ_２を合成し、このＬｉＣｏＯ_２を用いたこと以外は、サンプル２と同様にして電池を製造した。
【００６１】
〈サンプル５〉
サンプル５では、正極活物質として、炭酸リチウムと炭酸コバルトとの混合比を調整することで炭酸リチウムが０．２重量％含有されたＬｉＣｏＯ_２を合成し、このＬｉＣｏＯ_２を用いたこと以外は、サンプル３と同様にして電池を製造した。
【００６２】
〈サンプル６〉
サンプル６では、正極及び負極の両主面上に、ＥＣを４０重量％と、ＰＣを６０重量％とを混合させた非水溶媒に溶媒重量に対してＬｉＰＦ_６を０．８ｍｏｌ／ｋｇ溶解させ、カーバメート類を添加させていない非水電解液を用いたゲル状電解質を電解質層として形成させたこと以外は、サンプル１と同様にして電池を製造した。
【００６３】
〈サンプル７〉
サンプル７では、正極及び負極の両主面上に、ＥＣを３７．６重量％と、ＰＣを５６．４重量％と、ＥＭＣＡを６重量％とを混合させた非水溶媒に溶媒重量に対してＬｉＰＦ_６を０．８ｍｏｌ／ｋｇ溶解させた非水電解液を用いたゲル状電解質を電解質層として形成させたこと以外は、サンプル１と同様にして電池を製造した。
【００６４】
〈サンプル８〉
サンプル８では、正極活物質として、炭酸リチウムと炭酸コバルトとの混合比を調整することで炭酸リチウムが添加されていないＬｉＣｏＯ_２を合成し、このＬｉＣｏＯ_２を用いたこと以外は、サンプル２と同様にして電池を製造した。
【００６５】
〈サンプル９〉
サンプル９では、正極活物質として、炭酸リチウムと炭酸コバルトとの混合比を調整することで炭酸リチウムが添加されていないＬｉＣｏＯ_２を合成し、このＬｉＣｏＯ_２を用いたこと以外は、サンプル３と同様にして電池を製造した。
【００６６】
〈サンプル１０〉
サンプル１０では、正極活物質として、炭酸リチウムと炭酸コバルトとの混合比を調整することで炭酸リチウムが０．２５重量％含有されたＬｉＣｏＯ_２を合成し、このＬｉＣｏＯ_２を用いたこと以外は、サンプル２と同様にして電池を製造した。
【００６７】
〈サンプル１１〉
サンプル１１では、正極活物質として、炭酸リチウムと炭酸コバルトとの混合比を調整することで炭酸リチウムが０．２５重量％含有されたＬｉＣｏＯ_２を合成し、このＬｉＣｏＯ_２を用いたこと以外は、サンプル３と同様にして電池を製造した。
【００６８】
次に、以上のように作製したサンプル１〜サンプル１１の電池について、高温保存後のサイクル特性、具体的には高温保存後に２５０サイクル充放電した際の放電容量維持率を測定した。
【００６９】
以下、各サンプルにおける、高温保存した電池における２５０サイクル後の放電容量維持率の評価結果を表１に示す。
【００７０】
【表１】

【００７１】
なお、各サンプルでは、高温保存した後のサイクル特性を以下のように評価した。先ず、初回充放電として、各サンプルに対して２３℃雰囲気中、電流０．２Ｃ、上限電圧４．２Ｖ、充電時間１０時間の定電流定電圧充電を行った後に、２３℃雰囲気中、０．５Ｃの電流値で３Ｖまでの定電流放電を行った。次に、各サンプルに対して２３℃雰囲気中、電流０．５Ｃ、上限電圧４．２Ｖ、充電時間５時間の定電流定電圧充電を行った後に、６０℃雰囲気中に３０日間保存し、高温保存後に、２３℃雰囲気中、１Ｃの電流値で３Ｖまでの定電流放電を行った。次に、各サンプルに対し、２３℃雰囲気中、電流１Ｃ、上限電圧４．２Ｖ、充電時間３時間の定電流定電圧充電、２３℃雰囲気中、１Ｃの電流値で３Ｖまでの定電流放電といった充放電条件で充放電を２５０回繰り返し行った。そして、高温保存後のサイクル特性は、以上のようにして充放電を繰り返し行った際の３サイクル目の放電容量に対する２５０サイクル目の放電容量の比率である。
【００７２】
表１に示す評価結果から、ゲル状電解質中の非水溶媒に対してＥＭＣＡが０．１重量％以上、５重量％以下の範囲で添加されたサンプル１〜サンプル５では、ゲル状電解質中の非水溶媒に対してＥＭＣＡが添加されていないサンプル６に比べて、高温保存後のサイクル特性が良好であることがわかる。
【００７３】
サンプル６では、ゲル状電解質中の非水溶媒にＥＭＣＡが添加されていないことから、高温保存中の熱によりゲル状電解質の分解や正極からのガス発生を抑制することが困難となり、高温保存後の電池特性を劣化させてしまう。
【００７４】
また、表１に示す評価結果から、ゲル状電解質中の非水溶媒に対してＥＭＣＡが０．１重量％以上、５重量％以下の範囲で添加されたサンプル１〜サンプル５では、ゲル状電解質中の非水溶媒に対してＥＭＣＡが６重量％添加されたサンプル７に比べて、高温保存後のサイクル特性が良好であることがわかる。
【００７５】
サンプル７では、ゲル状電解質中の非水溶媒に対するＥＭＣＡの添加量が多過ぎることから、高温保存中に余剰なＥＭＣＡが電池特性を劣化させてしまう。
【００７６】
これに対し、サンプル１〜サンプル５では、ゲル状電解質中の非水溶媒に対し、カーバメート類としてＥＭＣＡが０．１重量％以上、５重量％以下の範囲で添加されており、非水溶媒に対するカーバメート類の添加量が適切なことから、高温保存中に起こるゲル状電解質の分解、ガスの発生等を抑えて高温保存後のサイクル特性の劣化が抑制される。
【００７７】
以上のことから、ゲル状電解質中の非水溶媒に対してカーバメート類としてＥＭＣＡを０．１重量％以上、５重量％以下の範囲で添加させることは、高温保存後のサイクル特性が優れた電池を製造する上で大変有効である。
【００７８】
表１に示す評価結果から、正極活物質に対して炭酸リチウムが０．０５重量％以上、０．２重量％以下の範囲で含有されたサンプル１〜サンプル５では、正極活物質に炭酸リチウムが添加されていないサンプル８、サンプル９に比べて、高温保存後のサイクル特性が良好であることがわかる。
【００７９】
サンプル８及びサンプル９では、正極活物質に炭酸リチウムを含有していないことから、高温保存時にゲル状電解質の電解質塩であるＬｉＰＦ_６が分解してフッ酸（ＨＦ）が発生し、このＨＦが電池素子やゲル状電解質等を劣化させてしまう。
【００８０】
また、表１に示す評価結果から、正極活物質に対して炭酸リチウムが０．０５重量％以上、０．２重量％以下の範囲で含有されたサンプル１〜サンプル５では、正極活物質に炭酸リチウムを０．２５重量％含有しているサンプル１０、サンプル１１に比べて、高温保存後のサイクル特性が良好であることがわかる。
【００８１】
サンプル１０及びサンプル１１では、正極活物質に対する炭酸リチウムの含有量が多過ぎることから、高温保存中に余剰な炭酸リチウムが分解されて電池素子内に例えば二酸化炭素等のガスが発生し、このガスが正極と負極との間で貯留して電池抵抗が高くなり電池特性が劣化する。
【００８２】
一方、サンプル１〜サンプル５では、正極活物質に対して炭酸リチウムを０．０５重量％以上、０．２重量％以下の範囲で含有しており、正極活物質に対する炭酸リチウムの添加量が適切なことから、高温保存中に起こるＨＦの発生、ガスの発生等を抑えて高温保存後のサイクル特性の劣化が抑制される。
【００８３】
以上のことから、正極活物質に対して炭酸リチウムを０．０５重量％以上、０．２重量％以下の範囲で含有していることは、高温保存後のサイクル特性が優れた電池を製造する上で大変有効である。
【００８４】
次に、上述したサンプル１とは、ゲル状電解質に添加されるカーバメート類をＥＭＣＡからメチルＮ，Ｎ−ジエチルカーバメート（以下、ＭＥＣＡと記す。）に変えて製造したサンプル１２〜サンプル１５の電池について説明する。
【００８５】
〈サンプル１２〉
サンプル１２では、正極及び負極の両主面上に、ＥＣを３８．８重量％と、ＰＣを５８．２重量％と、ＭＥＣＡを３重量％とを混合させた非水溶媒に溶媒重量に対してＬｉＰＦ_６を０．８ｍｏｌ／ｋｇ溶解させた非水電解液を用いたゲル状電解質を電解質層として形成させたこと以外は、サンプル１と同様にして電池を製造した。
【００８６】
〈サンプル１３〉
サンプル１３では、正極及び負極の両主面上に、ＥＣを４０重量％と、ＰＣを５９．９重量％と、ＭＥＣＡを０．１重量％とを混合させた非水溶媒に溶媒重量に対してＬｉＰＦ_６を０．８ｍｏｌ／ｋｇ溶解させた非水電解液を用いたゲル状電解質を電解質層として形成させたこと以外は、サンプル１と同様にして電池を製造した。
【００８７】
〈サンプル１４〉
サンプル１４では、正極及び負極の両主面上に、ＥＣを３８重量％と、ＰＣを５７重量％と、ＭＥＣＡを５重量％とを混合させた非水溶媒に溶媒重量に対してＬｉＰＦ_６を０．８ｍｏｌ／ｋｇ溶解させた非水電解液を用いたゲル状電解質を電解質層として形成させたこと以外は、サンプル１と同様にして電池を製造した。
【００８８】
〈サンプル１５〉
サンプル１５では、正極及び負極の両主面上に、ＥＣを３７．６重量％と、ＰＣを５６．４重量％と、ＭＥＣＡを６重量％とを混合させた非水溶媒に溶媒重量に対してＬｉＰＦ_６を０．８ｍｏｌ／ｋｇ溶解させた非水電解液を用いたゲル状電解質を電解質層として形成させたこと以外は、サンプル１と同様にして電池を製造した。
【００８９】
次に、以上のように作製したサンプル１２〜サンプル１５、及び上述したサンプル６の電池について、高温保存後のサイクル特性、具体的には高温保存後に２５０サイクル充放電した際の放電容量維持率を測定した。
【００９０】
以下、各サンプルにおける、高温保存した電池における２５０サイクル後の放電容量維持率の評価結果を表２に示す。
【００９１】
【表２】

【００９２】
なお、サンプル１２〜サンプル１５、及びサンプル６では、上述したサンプル１〜サンプル１１と同様の方法で高温保存した後のサイクル特性を評価した。
【００９３】
表２に示す評価結果から、ゲル状電解質中の非水溶媒に対してＭＥＣＡが０．１重量％以上、５重量％以下の範囲で添加されたサンプル１２〜サンプル１４では、ゲル状電解質中の非水溶媒に対してＭＥＣＡが添加されていないサンプル６に比べて、高温保存後のサイクル特性が良好であることがわかる。
【００９４】
サンプル６では、上述したように、ゲル状電解質中の非水溶媒にカーバメート類としてＭＥＣＡが添加されていないことから、高温保存中の熱によりゲル状電解質の分解や正極からのガス発生を抑制することが困難となり、高温保存後の電池特性を劣化させる。
【００９５】
また、表２に示す評価結果から、ゲル状電解質中の非水溶媒に対してＭＥＣＡが０．１重量％以上、５重量％以下の範囲で添加されたサンプル１２〜サンプル１４では、ゲル状電解質中の非水溶媒に対してＭＥＣＡが６重量％添加されたサンプル１５に比べて、高温保存後のサイクル特性が良好であることがわかる。
【００９６】
サンプル１５では、上述したサンプル７と同様に、ゲル状電解質中の非水溶媒に対し、カーバメート類としてＭＥＣＡの添加量が多過ぎることから、高温保存中に余剰なＭＥＣＡが電池特性を劣化させる。
【００９７】
これに対し、サンプル１２〜サンプル１４では、上述したサンプル１〜サンプル５と同様に、ゲル状電解質中の非水溶媒に対し、カーバメート類としてＭＥＣＡが０．１重量％以上、５重量％以下の範囲で添加されており、非水溶媒に対するカーバメート類の添加量が適切なことから、高温保存中に起こるゲル状電解質の分解、ガスの発生等を抑えて高温保存後のサイクル特性の劣化が抑制される。
【００９８】
以上のことから、ゲル状電解質中の非水溶媒に対してカーバメート類としてＭＥＣＡを０．１重量％以上、５重量％以下の範囲で添加させることは、高温保存後のサイクル特性が優れた電池を製造する上で大変有効である。
【００９９】
次に、上述したサンプル１とは、ゲル状電解質に添加されるカーバメート類をＥＭＣＡからメチルＮ，Ｎ−ジメチルカーバメート（以下、ＭＭＣＡと記す。）に変えて製造したサンプル１６〜サンプル２０の電池について説明する。
【０１００】
〈サンプル１６〉
サンプル１６では、正極及び負極の両主面上に、ＥＣを３９．６重量％と、ＰＣを５９．４重量％と、ＭＭＣＡを１重量％とを混合させた非水溶媒に溶媒重量に対してＬｉＰＦ_６を０．８ｍｏｌ／ｋｇ溶解させた非水電解液を用いたゲル状電解質を電解質層として形成させたこと以外は、サンプル１と同様にして電池を製造した。
【０１０１】
〈サンプル１７〉
サンプル１７では、正極及び負極の両主面上に、ＥＣを３９．９重量％と、ＰＣを５９．８重量％と、ＭＥＣＡを０．３重量％とを混合させた非水溶媒に溶媒重量に対してＬｉＰＦ_６を０．８ｍｏｌ／ｋｇ溶解させた非水電解液を用いたゲル状電解質を電解質層として形成させたこと以外は、サンプル１と同様にして電池を製造した。
【０１０２】
〈サンプル１８〉
サンプル１８では、正極及び負極の両主面上に、ＥＣを３８重量％と、ＰＣを５７重量％と、ＭＥＣＡを５重量％とを混合させた非水溶媒に溶媒重量に対してＬｉＰＦ_６を０．８ｍｏｌ／ｋｇ溶解させた非水電解液を用いたゲル状電解質を電解質層として形成させたこと以外は、サンプル１と同様にして電池を製造した。
【０１０３】
〈サンプル１９〉
サンプル１９では、正極及び負極の両主面上に、ＥＣを３９．９重量％と、ＰＣを５９．９重量％と、ＭＥＣＡを０．２重量％とを混合させた非水溶媒に溶媒重量に対してＬｉＰＦ_６を０．８ｍｏｌ／ｋｇ溶解させた非水電解液を用いたゲル状電解質を電解質層として形成させたこと以外は、サンプル１と同様にして電池を製造した。
【０１０４】
〈サンプル２０〉
サンプル２０では、正極及び負極の両主面上に、ＥＣを３７．６重量％と、ＰＣを５６．４重量％と、ＭＥＣＡを６重量％とを混合させた非水溶媒に溶媒重量に対してＬｉＰＦ_６を０．８ｍｏｌ／ｋｇ溶解させた非水電解液を用いたゲル状電解質を電解質層として形成させたこと以外は、サンプル１と同様にして電池を製造した。
【０１０５】
次に、以上のように作製したサンプル１６〜サンプル２０の電池について、高温保存後のサイクル特性、具体的には高温保存後に２５０サイクル充放電した際の放電容量維持率を測定した。
【０１０６】
以下、各サンプルにおける、高温保存した電池における２５０サイクル後の放電容量維持率の評価結果を表３に示す。
【０１０７】
【表３】

【０１０８】
なお、サンプル１６〜サンプル２０では、上述したサンプル１〜サンプル１１と同様の方法で高温保存した後のサイクル特性を評価した。
【０１０９】
表３に示す評価結果から、ゲル状電解質中の非水溶媒に対してＭＭＣＡが０．３重量％以上、５重量％以下の範囲で添加されたサンプル１６〜サンプル１８では、ゲル状電解質中の非水溶媒に対してＭＭＣＡが０．２重量％添加されたサンプル１９に比べて、高温保存後のサイクル特性が良好であることがわかる。
【０１１０】
サンプル１９では、ゲル状電解質中の非水溶媒に対し、カーバメート類としてＭＭＣＡの添加量が少な過ぎることから、高温保存中の熱によりゲル状電解質の分解や正極からのガス発生を抑制することが困難となり、高温保存後の電池特性を劣化させる。
【０１１１】
また、表３に示す評価結果から、ゲル状電解質中の非水溶媒に対してＭＭＣＡが０．３重量％以上、５重量％以下の範囲で添加されたサンプル１６〜サンプル１８では、ゲル状電解質中の非水溶媒に対してＭＭＣＡが６重量％添加されたサンプル２０に比べて、高温保存後のサイクル特性が良好であることがわかる。
【０１１２】
サンプル２０では、上述したサンプル７及びサンプル１５と同様に、ゲル状電解質中の非水溶媒に対し、カーバメート類としてＭＭＣＡの添加量が多過ぎることから、高温保存中に余剰なＭＭＣＡが電池特性を劣化させる。
【０１１３】
これに対し、サンプル１６〜サンプル１８では、ゲル状電解質中の非水溶媒に対し、カーバメート類としてＭＭＣＡが０．３重量％以上、５重量％以下の範囲で添加されており、非水溶媒に対するカーバメート類の添加量が適切なことから、高温保存中に起こるゲル状電解質の分解、ガスの発生等を抑えて高温保存後のサイクル特性の劣化が抑制される。
【０１１４】
以上のことから、ゲル状電解質中の非水溶媒に対してカーバメート類としてＭＭＣＡを０．３重量％以上、５重量％以下の範囲で添加させることは、高温保存後のサイクル特性が優れた電池を製造する上で大変有効である。
【０１１５】
【発明の効果】
以上の説明から明らかなように、本発明によれば、正極活物質に炭酸リチウムを含有しつつ、非水電解質の非水溶媒にカーバメート類を添加させることにより、高温保存中に起こる非水電解質の分解、ガスの発生を抑えることから、高温保存による電池特性の劣化が抑制された高温保存特性に優れた非水電解質電池が得られる。
【図面の簡単な説明】
【図１】本発明に係るリチウムイオン二次電池の内部構造を示しており、（ａ）は一部を透視している透視平面図、（ｂ）は概略断面図である。
【図２】同リチウムイオン二次電池の製造工程を説明するための図であり、電池素子を示す概略斜視図である。
【図３】同リチウムイオン二次電池の製造工程を説明するための図であり、電池素子を外装材に収納させる状態を示す概略斜視図である。
【図４】同リチウムイオン二次電池の製造工程を説明するための図であり、完成したリチウムイオン二次電池を示す概略斜視図である。
【符号の説明】
１　リチウムイオン二次電池、２　正極、３　負極、４　固体電解質、５　電池素子、６　外装材、７　正極集電体、８　正極合剤層、９　正極端子、１０負極集電体、１１　負極合剤層、１２　負極端子、１３　樹脂片[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a non-aqueous electrolyte battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte, having significantly improved battery characteristics, and a method for manufacturing the same.
[0002]
[Prior art]
2. Description of the Related Art In recent years, development of lightweight, high-energy-density secondary batteries as power supplies for portable electronic devices such as notebook-type portable computers, mobile phones, and camera-integrated VTRs (video tape recorders) has been promoted. A secondary battery having a high energy density has a higher energy density than, for example, a lead battery or a nickel cadmium battery, and the charge / discharge reaction of the battery is performed by moving lithium ions between a positive electrode and a negative electrode. Lithium ion secondary batteries are known.
[0003]
The lithium ion secondary battery uses a non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent, unlike the above-described lead battery and nickel cadmium battery. For this reason, in this lithium ion secondary battery, it is necessary to use a metal container having high airtightness for preventing the leakage of the nonaqueous electrolyte solution as the exterior material. When such an exterior material is used, it is difficult for the lithium ion secondary battery to be formed into a thin shape such as a sheet type or a card type or to have flexibility.
[0004]
As means for solving such a problem, for example, a battery using a solid electrolyte made of an inorganic or organic substance, a gel electrolyte containing a polymer substance, or the like has been proposed. Specifically, for example, a solid electrolyte battery using a polymer solid electrolyte having a polymer material and an electrolyte salt, a gel electrolyte in which a matrix polymer holds a nonaqueous electrolyte, and the like have been proposed.
[0005]
Since the solid electrolyte battery has a solid or gel electrolyte, liquid leakage can be prevented and the thickness of the electrolyte can be controlled. Further, in this solid electrolyte battery, since the electrolyte has adhesiveness to the electrode, the contact between the electrolyte and the electrode and the interval between the positive electrode and the negative electrode can be improved. For this reason, in this solid electrolyte battery, for example, it is not necessary to use a metal container in order to prevent the electrolyte from leaking and press the electrodes in the thickness direction. be able to. Specifically, in a solid electrolyte battery, a moisture-proof laminated film made of, for example, a heat-fusible polymer film and a metal foil is used as a film-like exterior material.
[0006]
Thereby, in the solid electrolyte battery, it is possible to increase the airtightness by sealing the moisture-proof laminate film with a hot seal or the like, and to reduce the overall thickness. Further, in this solid electrolyte battery, the moisture-proof laminate film is lighter and cheaper than the metal container, so that the weight and cost can be reduced.
[0007]
[Problems to be solved by the invention]
However, since a lithium ion secondary battery is used as a power source of a portable electronic device as described above, for example, in the case of a notebook type portable computer or the like, the temperature is generated by heat generated by a CPU (central processing unit) or the like. In some cases, battery characteristics such as cycle characteristics are deteriorated. In addition, the portable electronic device may be exposed to a high temperature state where the ambient temperature becomes about 100 ° C. when the portable electronic device is left in a car or the like in summer. In this case, especially for solid electrolyte batteries, a thin moisture-proof laminate film is used for the exterior material, which is easily affected by the ambient temperature. Will deteriorate.
[0008]
Therefore, the present invention has been proposed in view of such conventional circumstances, and a non-aqueous electrolyte battery excellent in high-temperature storage characteristics in which deterioration of battery characteristics has been suppressed even when stored at high temperatures, and a method for manufacturing the same. It is intended to provide.
[0009]
[Means for Solving the Problems]
To achieve this object, the present inventors have conducted intensive studies and found that lithium carbonate was contained in the positive electrode active material, and carbamates were added to the non-aqueous solvent of the non-aqueous electrolyte, thereby allowing high-temperature storage. It has been found that it is possible to suppress later deterioration of battery characteristics.
[0010]
That is, the non-aqueous electrolyte battery according to the present invention includes a positive electrode having a positive electrode active material capable of doping / dedoping lithium, and a negative electrode active material capable of doping / dedoping lithium. And a non-aqueous electrolyte containing a non-aqueous solvent to which a carbamate represented by the general formula (1) is added and an electrolyte salt.
[0011]
Embedded image

[0012]
Thereby, in this non-aqueous electrolyte battery, lithium carbonate contained in the positive electrode active material and carbamates added to the non-aqueous solvent suppress decomposition and gas generation of the non-aqueous electrolyte during high-temperature storage. Deterioration of battery characteristics is suppressed.
[0013]
In addition, the method for manufacturing a nonaqueous electrolyte battery according to the present invention includes a positive electrode having a positive electrode active material capable of doping / dedoping lithium, a negative electrode having a negative electrode active material capable of doping / dedoping lithium, A method for producing a non-aqueous electrolyte battery comprising a non-aqueous electrolyte containing an aqueous solvent and an electrolyte salt, wherein lithium carbonate is contained in a positive electrode active material, and the carbamate represented by the general formula (1) is contained in the non-aqueous solvent. Is added.
[0014]
Embedded image

[0015]
In this method of manufacturing a nonaqueous electrolyte battery, a nonaqueous electrolyte battery using a positive electrode having a positive electrode active material containing lithium carbonate and a nonaqueous electrolyte obtained by adding carbamates to a nonaqueous solvent is obtained. . Therefore, in this method for producing a non-aqueous electrolyte battery, decomposition and gas generation of the non-aqueous electrolyte during high-temperature storage are caused by lithium carbonate contained in the positive electrode active material and carbamates added to the non-aqueous solvent of the non-aqueous electrolyte. As a result, a non-aqueous electrolyte battery in which deterioration of battery characteristics due to high-temperature storage is suppressed can be obtained.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a non-aqueous electrolyte battery to which the present invention is applied will be described. FIG. 1 shows a configuration example of a lithium ion secondary battery (hereinafter, referred to as a battery) as the nonaqueous electrolyte battery. The battery 1 includes a long positive electrode 2, a long negative electrode 3, and a solid electrolyte 4 such as a gel electrolyte in which a polymer matrix is impregnated with a non-aqueous solvent together with an electrolyte salt. Have. The battery 1 has a solid electrolyte 4 formed on the main surfaces of the positive electrode 2 and the negative electrode 3, and is wound with the positive electrode 2 and the negative electrode 3 laminated with the solid electrolyte 4 interposed therebetween, thereby forming a power generating element. And the battery element 5 is sealed in an exterior material 6.
[0017]
The positive electrode 2 is coated with a positive electrode mixture coating liquid containing a positive electrode active material and a binder on a long positive electrode current collector 7, dried, and pressurized to form a positive electrode mixture on the positive electrode current collector 7. The agent layer 8 has a structure formed by compression. A positive electrode terminal 9 is connected to the positive electrode 2 at a predetermined position on the positive electrode current collector 7 so as to protrude in the width direction of the positive electrode current collector 7. For the positive electrode terminal 9, for example, a strip-shaped metal piece made of aluminum is used.
[0018]
Metal sulfides or oxides such as TiS ₂ , MoS ₂ , NbSe ₂ , and V ₂ O ₅ can be used as the positive electrode active material. LiM _x O ₂ (where M represents one or more transition metals such as Co, Ni, Mn, Fe, Al, V, and Ti; x varies depending on the charge / discharge state of the battery; 1.10 or less.) Can be used. As the transition metal M constituting the lithium composite oxide, Co, Ni, Mn, or the like is preferable. Specific examples of such a lithium composite oxide include LiCoO ₂ , LiNiO ₂ , LiNi _y Co _1-y O ₂ (where 0 <y <1), and LiMn ₂ O ₄ . it can.
[0019]
The positive electrode active material contains lithium carbonate. Thereby, in the battery 1, when stored in a high temperature state, lithium carbonate suppresses decomposition of the electrolyte salt or the like in the solid electrolyte 4 due to, for example, heat, and thus deterioration of battery characteristics due to high temperature storage is suppressed. Is done.
[0020]
In the positive electrode 2, the content of lithium carbonate is in the range of 0.05% by weight or more and 0.2% by weight or less based on the positive electrode active material. For example, when the content of lithium carbonate is less than 0.05% by weight with respect to the positive electrode active material, in the battery 1, it is possible to suppress decomposition of the electrolyte salt and the like in the solid electrolyte 4 during high-temperature storage. It becomes difficult. On the other hand, when the content of lithium carbonate with respect to the positive electrode active material is more than 0.2% by weight, in the battery 1, too much lithium carbonate is decomposed during high-temperature storage to generate carbon dioxide gas in the battery element 5. Therefore, carbon dioxide gas is stored between the positive electrode 2 and the negative electrode 3 to improve the battery resistance. Therefore, in the positive electrode 2, by setting the content of lithium carbonate in the range of 0.05% by weight or more and 0.2% by weight or less with respect to the positive electrode active material, the solid electrolyte 4 is decomposed at a high temperature. It becomes possible to suppress appropriately.
[0021]
As a method for incorporating lithium carbonate into the positive electrode active material, for example, when LiCoO ₂ is obtained as the positive electrode active material, lithium carbonate and cobalt carbonate, which are the starting materials, are mixed, and the mixture is calcined to give the positive electrode active material a carbonate. Contains lithium. That is, in this case, by adjusting the mixing ratio when mixing lithium carbonate and cobalt carbonate, a positive electrode active material in which the content of lithium carbonate is controlled can be obtained.
[0022]
In the positive electrode 2, as a binder of the positive electrode mixture layer 8, for example, a binder such as polyvinylidene fluoride or styrene-butadiene rubber used for the positive electrode mixture of a nonaqueous electrolyte battery can be used. For example, a carbonaceous material or the like as a conductive material, or a known additive or the like can be added to the layer 8. Further, in the positive electrode 2, for example, a foil-like metal or a net-like metal made of aluminum or the like is used as the positive electrode current collector 9.
[0023]
The negative electrode 3 is formed by applying a negative electrode mixture coating liquid containing a negative electrode active material and a binder on a long negative electrode current collector 10, drying, and pressing the negative electrode mixture coating liquid. The agent layer 11 has a structure formed by compression. A negative electrode terminal 12 is connected to the negative electrode 3 at a predetermined position on the negative electrode current collector 10 so as to protrude in the width direction of the negative electrode current collector 10. For the negative electrode terminal 12, a strip-shaped metal piece made of, for example, copper or nickel is used.
[0024]
As the negative electrode active material, lithium, a lithium alloy, or a carbon material capable of doping / dedoping lithium is used. Examples of carbon materials that can be doped / dedoped with lithium include low-crystalline carbon materials obtained by firing at a relatively low temperature of 2000 ° C. or less, and artificial graphites obtained by firing raw materials that easily crystallize at a high temperature of around 3000 ° C. A highly crystalline carbon material or the like can be used. Specifically, use of carbonaceous materials such as non-graphitizable carbon, pyrolytic carbons, cokes, graphites, glassy carbon fibers, organic polymer compound fired bodies, carbon fibers, activated carbon, and carbon blacks Can be. The cokes include pitch coke, needle coke, petroleum coke, and the like. The organic polymer compound fired body is obtained by firing a phenol resin, a furan resin, or the like at an appropriate temperature and carbonizing the same. In addition to the carbonaceous materials described above, materials that can be doped / dedoped with lithium include polymers such as polyacetylene and polypyrrole, and oxides such as iron oxide, ruthenium oxide, molybdenum oxide, tungsten oxide, titanium oxide, and tin oxide. Alternatively, a nitride obtained by replacing oxygen of these oxides with nitrogen can be used.
[0025]
In the negative electrode 3, as a binder for the negative electrode mixture layer 11, for example, a binder such as polyvinylidene fluoride or styrene butadiene rubber used for a negative electrode mixture of a nonaqueous electrolyte battery can be used. For example, a known additive or the like can be added to the layer 11. Further, in the negative electrode 3, a foil-like metal or a net-like metal made of, for example, copper is used as the negative electrode current collector 10.
[0026]
As the solid electrolyte 4, a gel electrolyte in which an organic polymer such as a polymer matrix is impregnated with a non-aqueous electrolyte containing a non-aqueous solvent and an electrolyte salt is used.
[0027]
Various polymers can be used as the polymer matrix as long as it absorbs the non-aqueous electrolyte and gels. Specifically, for example, fluorine-based polymers such as poly (vinylidene fluoride) and poly (vinylidene fluoride-co-hexafluoropropylene), ether-based polymers such as poly (ethylene oxide) and cross-linked products thereof, (Acrylonitrile) and the like, and any one of these or a mixture of a plurality of them may be used.
[0028]
As the non-aqueous solvent, a solvent having a relatively high dielectric constant is used. Specifically, for example, cyclic carbonates such as propylene carbonate and ethylene carbonate, chain carbonates such as diethyl carbonate and dimethyl carbonate, solvents in which hydrogen of these carbonates is substituted with halogen, methyl propionate and the like. Examples thereof include carboxylic esters such as methyl butyrate, ethers such as 2-methyltetrahydrofuran and dimethoxyethane, butyl lactones such as γ-butyl lactone, valerolactones such as γ-valerolactone, and sulfolane. Then, one or more of these non-aqueous solvents are mixed and used.
[0029]
As the electrolyte salt, an electrolyte salt used for a non-aqueous electrolyte of a non-aqueous electrolyte battery can be used. Specifically, for example, LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiN (SO ₂ CF ₃ ) ₂ , LiN ( _{SO 2 C 2 F 5) 2} , LiC (SO 2 CF 3) 3, LiAlCl 4, LiSiF 6, LiCl, and electrolytic salt such as LiBr. Then, one or more of these are mixed and used. In particular, LiPF ₆ and LiBF ₄ , which are excellent in oxidation stability, are used as the electrolyte salt. The concentration of the electrolyte salt with respect to the non-aqueous solvent is not particularly limited. However, by setting the concentration in a range of 0.4 mol / L or more and 1.5 mol / L or less, the ionic conductivity of the non-aqueous electrolyte is increased. Can be.
[0030]
In the solid electrolyte 4, carbamates are added to the non-aqueous solvent. Specifically, as carbamates, for example, ethyl N, N-dimethylcarbamate (hereinafter, referred to as EMCA) represented by chemical formula (2), and methyl N, N-diethylcarbamate (hereinafter, referred to as MECA) represented by chemical formula (3) ), Methyl N, N-dimethyl carbamate (hereinafter referred to as MMCA) shown in chemical formula (4), and one or more of these are added to the non-aqueous solvent.
[0031]
Embedded image

[0032]
Embedded image

[0033]
Embedded image

[0034]
Thereby, in the battery 1, when stored in a high temperature state, the carbamates are decomposed by, for example, the solid electrolyte 4 due to heat, and the positive electrode 2 reacts with the solid electrolyte 4 to generate gas. Can be suppressed.
[0035]
Further, in the solid electrolyte 4, for example, when EMCA and / or MECA are added as carbamates, the total amount of EMCA and / or MECA added is 0.1% by weight or more based on the nonaqueous solvent of the nonaqueous electrolytic solution. It is in the range of 5% by weight or less. For example, when the addition amount of the whole EMCA and / or MECA to the non-aqueous solvent is less than 0.1% by weight, it is difficult for the battery 1 to obtain the effect of the carbamates at the time of high-temperature storage, and the solid electrolyte 4 Decomposition and gas generation occur. On the other hand, when the addition amount of the whole EMCA and / or MECA to the non-aqueous solvent is more than 5% by weight, in the battery 1, the battery characteristics are deteriorated due to the excessive amount of carbamates.
[0036]
Therefore, in the positive electrode 2, when EMCA and / or MECA are added as carbamates, the amount of the carbamates added to the non-aqueous solvent of the non-aqueous electrolyte is in the range of 0.1% by weight or more and 5% by weight or less. This makes it possible to suppress decomposition and gas generation of the solid electrolyte 4 when stored in a high-temperature state, and to suppress deterioration of battery characteristics due to excessively added carbamates.
[0037]
Further, in the solid electrolyte 4, for example, when MMCA is added as a carbamate, the amount of MMCA added is in the range of 0.3% by weight or more and 5% by weight or less with respect to the non-aqueous solvent of the non-aqueous electrolyte. I have. For example, when the amount of MMCA added is less than 0.3% by weight with respect to the non-aqueous solvent, it is difficult for the battery 1 to obtain the effect of MMCA during high-temperature storage. On the other hand, when the amount of MMCA added is more than 5% by weight with respect to the non-aqueous solvent, the battery 1 in the battery 1 has an excessive amount of MMCA, so that the battery characteristics deteriorate.
[0038]
Therefore, in the positive electrode 2, when MMCA is added as a carbamate, the addition amount of MMCA with respect to the non-aqueous solvent of the non-aqueous electrolyte is in the range of 0.3% by weight or more and 5% by weight or less, so In addition to suppressing the decomposition of the solid electrolyte 4 and the generation of gas when stored, the deterioration of the battery characteristics due to the excessively added MMCA can be suppressed.
[0039]
The exterior material 6 is formed by laminating, for example, two or more insulating layers and metal layers and bonding them together by laminating or the like, so that the inner surface of the battery becomes an insulating layer. As the insulating layer, the material is not particularly limited as long as it shows adhesiveness to the positive electrode terminal 9 and the negative electrode terminal 12, but is not limited to polyolefin resin such as polyethylene, polypropylene, modified polyethylene, modified polypropylene and a copolymer thereof. Are used because they can have low permeability and are airtight. As the metal layer, for example, aluminum, stainless steel, nickel, iron, or the like formed into a foil shape, a plate shape, or the like is used. Further, in the exterior material 6, by using an insulating layer made of, for example, nylon or the like as a layer serving as the outer peripheral layer of the battery 1, it is possible to improve the strength against breakage or piercing.
[0040]
The battery 1 configured as described above is manufactured as follows. First, the positive electrode 2 is manufactured. When producing the positive electrode 2, a positive electrode mixture coating solution containing a positive electrode active material containing a predetermined amount of lithium carbonate, a conductive material and a binder is prepared, and the positive electrode mixture coating solution is made of, for example, aluminum. The positive electrode mixture layer 8 is formed by uniformly applying and drying the positive electrode current collector 7 made of a foil or the like, and cut into predetermined dimensions. Next, the positive electrode terminal 9 is connected to a predetermined position of the positive electrode current collector 7 by, for example, ultrasonic welding or spot welding. Thus, the long positive electrode 2 is manufactured.
[0041]
Next, the negative electrode 3 is manufactured. When producing the negative electrode 3, a negative electrode mixture coating solution containing the above-described negative electrode active material and the binder is prepared, and the negative electrode mixture coating solution is placed on the negative electrode current collector 10 made of, for example, a copper foil. The negative electrode mixture layer 11 is formed by uniformly applying and drying, and cut into predetermined dimensions. Next, the negative electrode terminal 12 is connected to a predetermined position of the negative electrode current collector 10 by, for example, ultrasonic welding or spot welding. Thus, the long negative electrode 3 is manufactured.
[0042]
Next, the solid electrolyte 4 is formed in layers on the main surface of the positive electrode mixture layer 8 of the positive electrode 3 and the main surface of the negative electrode mixture layer 11 of the negative electrode 3 manufactured as described above. When the solid electrolyte 4 is formed, a non-aqueous electrolyte is prepared by dissolving an electrolyte salt in the above-described non-aqueous solvent. At this time, in the non-aqueous electrolyte, a predetermined amount of carbamates is added to the non-aqueous solvent.
[0043]
Next, this non-aqueous electrolyte, the above-described matrix polymer, and a non-aqueous solvent as a diluting solvent are mixed and stirred as necessary to prepare an electrolyte solution in a sol state, An electrolyte membrane made of a gel electrolyte is formed on the main surfaces of the positive electrode 2 and the negative electrode 3 by coating the main surface of the agent layer 8 and the main surface of the negative electrode mixture layer 11, respectively. When a diluting solvent is used, the gel electrolyte is formed by volatilizing the non-aqueous solvent. Thus, the solid electrolytes 4 are formed on the positive electrode 2 and the negative electrode 3, respectively.
[0044]
Next, as shown in FIG. 2, the positive electrode 2 and the negative electrode 3 each having the solid electrolyte 4 formed on the main surface as described above are laminated so that the solid electrolytes 4 face each other, and are flat-wound in the longitudinal direction of the electrodes. Then, the battery element 5 is manufactured. At this time, the positive electrode terminal 9 and the negative electrode terminal 12 are made to protrude from one end surface of the battery element 5.
[0045]
Next, as shown in FIG. 3, the positive electrode terminal 9 and the negative electrode terminal 12 provided in the battery element 5 are housed inside the exterior material 6 while being led out. At this time, the battery element 5 is housed in the exterior material 6 such that a resin piece 13 made of propylene or the like having adhesiveness is applied between the positive electrode terminal 9 and the negative electrode terminal 12 and the exterior material 6. As a result, in the battery 1, a short circuit between the positive electrode terminal 9 and the negative electrode terminal 12 and the metal layer of the exterior material 6, a reduction in airtightness, and the like are prevented.
[0046]
Next, as shown in FIG. 4, the battery element 5 is sealed in the exterior material 6 by bonding the peripheral edge of the exterior material 6 in which the battery element 5 is housed by, for example, heat sealing or the like. Thus, the battery 1 is manufactured.
[0047]
In the battery 1 manufactured as described above, the decomposition of the solid electrolyte 4, which occurs during high-temperature storage, particularly the decomposition of the electrolyte salt, is suppressed by the lithium carbonate contained in the positive electrode active material. In the battery 1, the carbamates added to the non-aqueous solvent can suppress decomposition of the non-aqueous electrolyte and gas generation that occur during high-temperature storage.
[0048]
Therefore, in this battery 1, by adding carbamates to the nonaqueous solvent of the solid electrolyte 4 while adding lithium carbonate to the positive electrode active material, decomposition of the solid electrolyte 4 that occurs during high-temperature storage, Since the generation of gas accompanying the decomposition is appropriately suppressed, deterioration of battery characteristics due to high-temperature storage is suppressed.
[0049]
The nonaqueous electrolyte battery to which the present invention is applied is not particularly limited in its shape such as a cylindrical shape, a square shape, a coin shape, and a button shape using a metal container as an exterior material, and is thin and large. And so on. In the nonaqueous electrolyte battery to which the present invention is applied, the battery element 5 of the battery 1 is wound in the above-described embodiment. However, the present invention is not limited to this. Even when using a battery element such as a configuration in which a separator and a long negative electrode and a positive electrode are laminated with a separator interposed therebetween, and a configuration in which a long negative electrode and a positive electrode are folded in a so-called bellows shape, with a separator interposed therebetween, are used. Applicable.
[0050]
【Example】
Hereinafter, a sample in which a lithium ion secondary battery using a gel electrolyte as a nonaqueous electrolyte battery to which the present invention is applied will be described.
[0051]
<Sample 1>
First, a positive electrode active material was synthesized to manufacture a lithium ion secondary battery serving as Sample 1. In order to obtain a positive electrode active material, a mixture obtained by mixing predetermined amounts of lithium carbonate and cobalt carbonate as starting materials is fired in air at 900 ° C. for about 5 hours and pulverized to obtain LiCoO 2 having an average particle diameter of 8 μm. ₂ was obtained. At this time, when the content of lithium carbonate in the obtained LiCoO ₂ was measured by a neutralization titration method, it was 0.05% by weight.
[0052]
Next, 91 parts by weight of the obtained LiCoO2, 6 parts by weight of flake graphite as a conductive material, 3 parts by weight of polyvinylidene fluoride (hereinafter referred to as PVdF) as a binder, and N- as a solvent. Methyl-2-pyrrolidone (hereinafter referred to as NMP) was added, and the mixture was kneaded and dispersed by a planetary mixer to prepare a positive electrode mixture coating liquid. Next, using a die coater as a coating device, the both surfaces of a 20 μm-thick strip-shaped aluminum foil serving as a positive electrode current collector are uniformly applied, dried at 100 ° C. under reduced pressure for 24 hours, and then compressed by a roll press. It was molded and cut into a width of 118 mm and a length of 640 mm. As described above, a long cathode was produced.
[0053]
Next, a negative electrode was manufactured. When a negative electrode is produced, the (002) plane spacing is 0.337 nm, the (002) plane C-axis crystallite thickness is 50 nm, the true density by a pycnometer method is 2.23 g / cc, and the BET method is used. 90% by weight of graphite having a specific surface area of 1.6 m ² / g, an average particle size of 33 μm, and a bulk density of 0.98 g / cm ³ , 10% by weight of PVdF as a binder, and NMP as a solvent. In addition, the mixture was kneaded and dispersed by a planetary mixer to prepare a negative electrode mixture coating liquid. Next, this negative electrode mixture coating liquid was uniformly applied to both surfaces of a 10 μm-thick strip-shaped copper foil serving as a negative electrode current collector using a die coater as a coating device, and dried at 120 ° C. under reduced pressure for 24 hours. After that, it was compression-molded by a roll press machine and cut into a width of 120 mm and a length of 800 mm. A long negative electrode was produced as described above.
[0054]
Next, a gel electrolyte was formed as an electrolyte layer on both main surfaces of the positive electrode and the negative electrode manufactured as described above. When forming an electrolyte layer comprising a gel electrolyte, 39.6% by weight of ethylene carbonate (hereinafter, referred to as EC), 59.4% by weight of propylene carbonate (hereinafter, referred to as PC), and carbamate Non-aqueous electrolyte obtained by dissolving 0.8 mol / kg of LiPF ₆ in a non-aqueous solvent mixed with 1% by weight of ethyl N, N-dimethylcarbamate (hereinafter referred to as EMCA) as a solvent. Was prepared.
[0055]
Next, this non-aqueous electrolyte, PVdF obtained by copolymerizing hexafluoropropylene at a ratio of 7%, and dimethyl carbonate were mixed and stirred to prepare a sol-state gel electrolyte solution. Next, this gel electrolyte solution was applied on both main surfaces of the positive electrode and the negative electrode, respectively, and dimethyl carbonate was volatilized. Thus, an electrolyte layer composed of a gel electrolyte was formed on both the main surfaces of the positive electrode and the negative electrode.
[0056]
Next, the positive electrode and the negative electrode each having the electrolyte layer formed on the main surface as described above were attached to each other so that the gel electrolyte was opposed to each other, and were flat-wound in the longitudinal direction of the positive electrode to produce a battery element. At this time, a strip-shaped positive electrode terminal made of aluminum was attached to an arbitrary position of the positive electrode, and a strip-shaped negative electrode terminal made of nickel was attached to an arbitrary position of the negative electrode.
[0057]
Next, a positive electrode terminal and a negative electrode terminal provided in the battery element were led out to the outside, and housed inside a three-layer structure exterior material in which a 50-μm-thick aluminum foil was sandwiched by a 30-μm-thick polyolefin film. At this time, the battery element was housed in the exterior material such that a propylene resin piece having adhesiveness was applied between the positive electrode terminal and the negative electrode terminal and the exterior material. This prevents the battery element from being short-circuited between the positive electrode terminal and the negative electrode terminal via the aluminum foil of the exterior material, from deteriorating the airtightness, and the like. Next, the battery element was sealed in the exterior material by laminating the peripheral portion of the exterior material in which the battery element was housed. As described above, the lithium ion secondary battery of Sample 1 was manufactured. In the following description, a lithium ion secondary battery is simply referred to as a battery for convenience.
[0058]
<Sample 2>
In sample 2, a non-aqueous solvent in which 40% by weight of EC, 59.9% by weight of PC, and 0.1% by weight of EMCA were mixed on both main surfaces of the positive electrode and the negative electrode with respect to the solvent weight. A battery was manufactured in the same manner as in Sample 1, except that a gel electrolyte using a nonaqueous electrolyte in which 0.8 mol / kg of LiPF ₆ was dissolved was formed as an electrolyte layer.
[0059]
<Sample 3>
In sample 3, LiPF ₆ was added to a non-aqueous solvent obtained by mixing 38% by weight of EC, 57% by weight of PC, and 5% by weight of EMCA on both main surfaces of the positive electrode and the negative electrode with respect to the solvent weight. A battery was manufactured in the same manner as in Sample 1, except that a gel electrolyte using a nonaqueous electrolyte in which 0.8 mol / kg was dissolved was formed as an electrolyte layer.
[0060]
<Sample 4>
In sample 4, LiCoO ₂ containing 0.2% by weight of lithium carbonate was synthesized by adjusting the mixing ratio of lithium carbonate and cobalt carbonate as the positive electrode active material, and this LiCoO ₂ was used. A battery was manufactured in the same manner as in Sample 2.
[0061]
<Sample 5>
In Sample 5, LiCoO ₂ containing 0.2% by weight of lithium carbonate was synthesized by adjusting the mixing ratio of lithium carbonate and cobalt carbonate as the positive electrode active material, and this LiCoO ₂ was used. A battery was manufactured in the same manner as in Sample 3.
[0062]
<Sample 6>
In Sample 6, 0.8 mol / kg of LiPF ₆ was dissolved in a nonaqueous solvent in which 40% by weight of EC and 60% by weight of PC were mixed on both main surfaces of the positive electrode and the negative electrode with respect to the solvent weight. A battery was manufactured in the same manner as in Sample 1, except that a gel electrolyte using a non-aqueous electrolyte solution to which no carbamates were added was formed as an electrolyte layer.
[0063]
<Sample 7>
In Sample 7, a non-aqueous solvent obtained by mixing 37.6% by weight of EC, 56.4% by weight of PC, and 6% by weight of EMCA was placed on both main surfaces of the positive electrode and the negative electrode with respect to the solvent weight. A battery was manufactured in the same manner as in Sample 1, except that a gel electrolyte using a nonaqueous electrolyte in which 0.8 mol / kg of LiPF ₆ was dissolved was formed as an electrolyte layer.
[0064]
<Sample 8>
In sample 8, as the positive electrode active material, LiCoO ₂ to which lithium carbonate was not added was synthesized by adjusting the mixing ratio of lithium carbonate and cobalt carbonate, and the same as sample 2 except that this LiCoO ₂ was used. To manufacture a battery.
[0065]
<Sample 9>
In sample 9, LiCoO ₂ to which lithium carbonate was not added was synthesized by adjusting the mixing ratio of lithium carbonate and cobalt carbonate as the positive electrode active material, and the same as sample 3 except that this LiCoO ₂ was used. To manufacture a battery.
[0066]
<Sample 10>
In Sample 10, LiCoO ₂ containing 0.25% by weight of lithium carbonate was synthesized as a positive electrode active material by adjusting the mixing ratio of lithium carbonate and cobalt carbonate, and this LiCoO ₂ was used. A battery was manufactured in the same manner as in Sample 2.
[0067]
<Sample 11>
In Sample 11, LiCoO ₂ containing 0.25% by weight of lithium carbonate was synthesized as the positive electrode active material by adjusting the mixing ratio of lithium carbonate and cobalt carbonate, and this LiCoO ₂ was used. A battery was manufactured in the same manner as in Sample 3.
[0068]
Next, with respect to the batteries of Samples 1 to 11 manufactured as described above, the cycle characteristics after high-temperature storage, specifically, the discharge capacity retention ratio when charging and discharging for 250 cycles after high-temperature storage were measured.
[0069]
Table 1 below shows the evaluation results of the discharge capacity retention rate after 250 cycles in the battery stored at a high temperature in each sample.
[0070]
[Table 1]

[0071]
In each sample, the cycle characteristics after storage at a high temperature were evaluated as follows. First, as the first charge / discharge, each sample was subjected to constant-current constant-voltage charging at a current of 0.2 C, an upper limit voltage of 4.2 V, and a charging time of 10 hours in a 23 ° C. atmosphere. A constant current discharge up to 3 V was performed at a current value of 5 C. Next, each sample was subjected to constant-current constant-voltage charging in a 23 ° C. atmosphere at a current of 0.5 C, an upper limit voltage of 4.2 V, and a charging time of 5 hours, and then stored in a 60 ° C. atmosphere for 30 days. After storage, constant current discharge was performed in a 23 ° C. atmosphere at a current value of 1 C up to 3 V. Next, for each sample, a constant current constant voltage charge of 1 C, an upper limit voltage of 4.2 V, a charging time of 3 hours in a 23 ° C. atmosphere, and a constant current discharge of 3 C at a current value of 1 C in a 23 ° C. atmosphere was performed. The charge / discharge was repeated 250 times under the charge / discharge conditions. The cycle characteristics after high-temperature storage are the ratio of the discharge capacity at the 250th cycle to the discharge capacity at the third cycle when charge and discharge are repeatedly performed as described above.
[0072]
From the evaluation results shown in Table 1, from Sample 1 to Sample 5 in which EMCA was added in a range of 0.1% by weight or more and 5% by weight or less with respect to the nonaqueous solvent in the gel electrolyte, It can be seen that the cycle characteristics after high-temperature storage are better than Sample 6 in which EMCA was not added to the non-aqueous solvent.
[0073]
In sample 6, since EMCA was not added to the nonaqueous solvent in the gel electrolyte, it was difficult to suppress decomposition of the gel electrolyte and gas generation from the positive electrode due to heat during high-temperature storage. Battery characteristics of the battery.
[0074]
Also, from the evaluation results shown in Table 1, the samples 1 to 5 in which EMCA was added in a range of 0.1% by weight or more and 5% by weight or less with respect to the non-aqueous solvent in the gel electrolyte showed that the gel electrolyte It can be seen that the cycle characteristics after high-temperature storage are better than Sample 7 in which EMCA was added at 6% by weight to the nonaqueous solvent in the sample.
[0075]
In Sample 7, since the amount of EMCA added to the non-aqueous solvent in the gel electrolyte is too large, the excess EMCA deteriorates battery characteristics during high-temperature storage.
[0076]
On the other hand, in samples 1 to 5, EMCA was added as a carbamate in a range of 0.1% by weight or more and 5% by weight or less with respect to the non-aqueous solvent in the gel electrolyte. Since the addition amount of the carbamates is appropriate, decomposition of the gel electrolyte and gas generation that occur during high-temperature storage are suppressed, and deterioration of cycle characteristics after high-temperature storage is suppressed.
[0077]
As described above, adding EMCA as a carbamate in a range of 0.1% by weight or more and 5% by weight or less as a carbamate to a non-aqueous solvent in a gel electrolyte is a battery having excellent cycle characteristics after high-temperature storage. It is very effective in manufacturing.
[0078]
From the evaluation results shown in Table 1, in Samples 1 to 5 in which lithium carbonate was contained in a range of 0.05% by weight or more and 0.2% by weight or less based on the positive electrode active material, lithium carbonate was contained in the positive electrode active material. It can be seen that the cycle characteristics after high-temperature storage are better than those of Samples 8 and 9, which were not added.
[0079]
In Samples 8 and 9, since the positive electrode active material does not contain lithium carbonate, LiPF ₆ which is an electrolyte salt of the gel electrolyte is decomposed during high-temperature storage to generate hydrofluoric acid (HF). It degrades the battery element, the gel electrolyte, and the like.
[0080]
Also, from the evaluation results shown in Table 1, in Samples 1 to 5 in which lithium carbonate was contained in a range of 0.05% by weight or more and 0.2% by weight or less with respect to the positive electrode active material, carbonic acid was added to the positive electrode active material. It can be seen that the cycle characteristics after high-temperature storage are better than those of Samples 10 and 11 containing 0.25% by weight of lithium.
[0081]
In Samples 10 and 11, since the content of lithium carbonate with respect to the positive electrode active material was too large, excess lithium carbonate was decomposed during high-temperature storage, and a gas such as carbon dioxide was generated in the battery element. Is stored between the positive electrode and the negative electrode, so that the battery resistance increases and the battery characteristics deteriorate.
[0082]
On the other hand, Samples 1 to 5 contain lithium carbonate in a range of 0.05% by weight or more and 0.2% by weight or less based on the positive electrode active material, and the amount of lithium carbonate added to the positive electrode active material is appropriate. Therefore, generation of HF and gas generated during high-temperature storage is suppressed, and deterioration of cycle characteristics after high-temperature storage is suppressed.
[0083]
From the above, the fact that lithium carbonate is contained in the range of 0.05% by weight or more and 0.2% by weight or less based on the positive electrode active material produces a battery having excellent cycle characteristics after high-temperature storage. Very effective above.
[0084]
Next, the above-mentioned sample 1 refers to batteries of samples 12 to 15 manufactured by changing carbamates added to the gel electrolyte from EMCA to methyl N, N-diethyl carbamate (hereinafter referred to as MECA). explain.
[0085]
<Sample 12>
In sample 12, a non-aqueous solvent obtained by mixing 38.8% by weight of EC, 58.2% by weight of PC, and 3% by weight of MECA was mixed on both main surfaces of the positive electrode and the negative electrode with respect to the solvent weight. A battery was manufactured in the same manner as in Sample 1, except that a gel electrolyte using a nonaqueous electrolyte in which 0.8 mol / kg of LiPF ₆ was dissolved was formed as an electrolyte layer.
[0086]
<Sample 13>
In Sample 13, a non-aqueous solvent in which 40% by weight of EC, 59.9% by weight of PC, and 0.1% by weight of MECA were mixed on both main surfaces of the positive electrode and the negative electrode with respect to the solvent weight. A battery was manufactured in the same manner as in Sample 1, except that a gel electrolyte using a nonaqueous electrolyte in which 0.8 mol / kg of LiPF ₆ was dissolved was formed as an electrolyte layer.
[0087]
<Sample 14>
In sample 14, LiPF ₆ was added to the non-aqueous solvent obtained by mixing 38% by weight of EC, 57% by weight of PC, and 5% by weight of MECA on both main surfaces of the positive electrode and the negative electrode with respect to the solvent weight. A battery was manufactured in the same manner as in Sample 1, except that a gel electrolyte using a nonaqueous electrolyte in which 0.8 mol / kg was dissolved was formed as an electrolyte layer.
[0088]
<Sample 15>
In sample 15, a non-aqueous solvent obtained by mixing 37.6% by weight of EC, 56.4% by weight of PC, and 6% by weight of MECA was mixed on both main surfaces of the positive electrode and the negative electrode with respect to the solvent weight. A battery was manufactured in the same manner as in Sample 1, except that a gel electrolyte using a nonaqueous electrolyte in which 0.8 mol / kg of LiPF ₆ was dissolved was formed as an electrolyte layer.
[0089]
Next, with respect to the batteries of Samples 12 to 15 and Sample 6 prepared as described above, the cycle characteristics after high-temperature storage, specifically, the discharge capacity retention rate when charging and discharging for 250 cycles after high-temperature storage were determined. It was measured.
[0090]
Table 2 shows the evaluation results of the discharge capacity retention rate after 250 cycles in the battery stored at high temperature in each sample.
[0091]
[Table 2]

[0092]
In addition, in the samples 12 to 15 and the sample 6, the cycle characteristics after high-temperature storage were evaluated in the same manner as the samples 1 to 11 described above.
[0093]
From the evaluation results shown in Table 2, in Samples 12 to 14 in which MECA was added in a range of 0.1% by weight or more and 5% by weight or less with respect to the nonaqueous solvent in the gelled electrolyte, It can be seen that the cycle characteristics after high-temperature storage are better than Sample 6 in which MECA was not added to the non-aqueous solvent.
[0094]
In sample 6, as described above, since MECA was not added as a carbamate to the nonaqueous solvent in the gel electrolyte, decomposition of the gel electrolyte and gas generation from the positive electrode were suppressed by heat during high-temperature storage. And the battery characteristics after storage at high temperatures are degraded.
[0095]
In addition, from the evaluation results shown in Table 2, the samples 12 to 14 in which MECA was added in a range of 0.1% by weight or more and 5% by weight or less with respect to the nonaqueous solvent in the gel electrolyte showed that the gel electrolyte It can be seen that the cycle characteristics after high-temperature storage are better than that of Sample 15 in which 6% by weight of MECA was added to the nonaqueous solvent therein.
[0096]
In sample 15, as in sample 7, the amount of MECA added as a carbamate to the non-aqueous solvent in the gel electrolyte is too large, so that excess MECA degrades battery characteristics during high-temperature storage.
[0097]
On the other hand, in Samples 12 to 14, similarly to Samples 1 to 5, MECA as carbamates in an amount of 0.1% by weight or more and 5% by weight or less with respect to the nonaqueous solvent in the gel electrolyte was used. The amount of carbamates added to the non-aqueous solvent is appropriate, so the decomposition of gel electrolyte and gas generation during high-temperature storage are suppressed, and the deterioration of cycle characteristics after high-temperature storage is suppressed. Is done.
[0098]
From the above, adding MECA as a carbamate in a range of 0.1% by weight or more and 5% by weight or less as a carbamate to a non-aqueous solvent in a gel electrolyte is a battery having excellent cycle characteristics after high-temperature storage. It is very effective in manufacturing.
[0099]
Next, the above-mentioned sample 1 refers to batteries of samples 16 to 20 manufactured by changing the carbamates added to the gel electrolyte from EMCA to methyl N, N-dimethylcarbamate (hereinafter referred to as MMCA). explain.
[0100]
<Sample 16>
In sample 16, a non-aqueous solvent obtained by mixing 39.6% by weight of EC, 59.4% by weight of PC, and 1% by weight of MMCA was added on both main surfaces of the positive electrode and the negative electrode to the solvent weight. A battery was manufactured in the same manner as in Sample 1, except that a gel electrolyte using a nonaqueous electrolyte in which 0.8 mol / kg of LiPF ₆ was dissolved was formed as an electrolyte layer.
[0101]
<Sample 17>
In sample 17, the solvent weight was added to a non-aqueous solvent obtained by mixing 39.9% by weight of EC, 59.8% by weight of PC, and 0.3% by weight of MECA on both main surfaces of the positive electrode and the negative electrode. A battery was manufactured in the same manner as in Sample 1, except that a gel electrolyte using a nonaqueous electrolyte in which 0.8 mol / kg of LiPF ₆ was dissolved was used as an electrolyte layer.
[0102]
<Sample 18>
In sample 18, LiPF ₆ was added to a non-aqueous solvent obtained by mixing 38% by weight of EC, 57% by weight of PC, and 5% by weight of MECA on both main surfaces of the positive electrode and the negative electrode with respect to the solvent weight. A battery was manufactured in the same manner as in Sample 1, except that a gel electrolyte using a nonaqueous electrolyte in which 0.8 mol / kg was dissolved was formed as an electrolyte layer.
[0103]
<Sample 19>
In sample 19, the solvent weight was mixed with a non-aqueous solvent obtained by mixing 39.9% by weight of EC, 59.9% by weight of PC, and 0.2% by weight of MECA on both main surfaces of the positive electrode and the negative electrode. A battery was manufactured in the same manner as in Sample 1, except that a gel electrolyte using a nonaqueous electrolyte in which 0.8 mol / kg of LiPF ₆ was dissolved was used as an electrolyte layer.
[0104]
<Sample 20>
In sample 20, a non-aqueous solvent obtained by mixing 37.6% by weight of EC, 56.4% by weight of PC, and 6% by weight of MECA was mixed on both main surfaces of the positive electrode and the negative electrode with respect to the solvent weight. A battery was manufactured in the same manner as in Sample 1, except that a gel electrolyte using a nonaqueous electrolyte in which 0.8 mol / kg of LiPF ₆ was dissolved was formed as an electrolyte layer.
[0105]
Next, with respect to the batteries of Samples 16 to 20 prepared as described above, the cycle characteristics after high-temperature storage, specifically, the discharge capacity retention rate when charging and discharging for 250 cycles after high-temperature storage were measured.
[0106]
Table 3 shows the evaluation results of the discharge capacity retention rate after 250 cycles of the battery stored at high temperature in each sample.
[0107]
[Table 3]

[0108]
In addition, in Samples 16 to 20, the cycle characteristics after high-temperature storage were evaluated in the same manner as in Samples 1 to 11 described above.
[0109]
From the evaluation results shown in Table 3, from Samples 16 to 18 in which MMCA was added in a range of 0.3% by weight or more and 5% by weight or less with respect to the nonaqueous solvent in the gelled electrolyte, It can be seen that the cycle characteristics after high-temperature storage are better than Sample 19 in which MMCA was added at 0.2% by weight to the non-aqueous solvent.
[0110]
In sample 19, the amount of MMCA added as a carbamate to the non-aqueous solvent in the gel electrolyte was too small, so that the heat during storage at high temperature prevented decomposition of the gel electrolyte and gas generation from the positive electrode. It becomes difficult and deteriorates battery characteristics after high-temperature storage.
[0111]
In addition, from the evaluation results shown in Table 3, it was found that in Samples 16 to 18 in which MMCA was added in a range of 0.3% by weight or more and 5% by weight or less with respect to the nonaqueous solvent in the gel electrolyte, the gel electrolyte It can be seen that the cycle characteristics after high-temperature storage are better than Sample 20 in which MMCA was added at 6% by weight to the nonaqueous solvent in the sample.
[0112]
In Sample 20, as in Samples 7 and 15 described above, the amount of MMCA added as a carbamate to the non-aqueous solvent in the gel electrolyte was too large, so that excess MMCA reduced the battery characteristics during high-temperature storage. Deteriorate.
[0113]
In contrast, in Samples 16 to 18, MMCA as a carbamate was added in a range of 0.3% by weight or more and 5% by weight or less with respect to the non-aqueous solvent in the gel electrolyte. Since the addition amount of the carbamates is appropriate, decomposition of the gel electrolyte and gas generation that occur during high-temperature storage are suppressed, and deterioration of cycle characteristics after high-temperature storage is suppressed.
[0114]
From the above, adding MMCA as a carbamate in a range of 0.3% by weight or more and 5% by weight or less as a carbamate to a non-aqueous solvent in a gel electrolyte is a battery having excellent cycle characteristics after high-temperature storage. It is very effective in manufacturing.
[0115]
【The invention's effect】
As is apparent from the above description, according to the present invention, while containing lithium carbonate in the positive electrode active material, by adding carbamates to the non-aqueous solvent of the non-aqueous electrolyte, the non-aqueous electrolyte occurring during high-temperature storage Therefore, a non-aqueous electrolyte battery excellent in high-temperature storage characteristics in which deterioration of battery characteristics due to high-temperature storage is suppressed can be obtained.
[Brief description of the drawings]
FIGS. 1A and 1B show an internal structure of a lithium ion secondary battery according to the present invention, wherein FIG. 1A is a perspective plan view partially see-through, and FIG. 1B is a schematic sectional view.
FIG. 2 is a diagram for explaining a manufacturing process of the lithium ion secondary battery, and is a schematic perspective view showing a battery element.
FIG. 3 is a diagram for explaining a manufacturing process of the lithium ion secondary battery, and is a schematic perspective view showing a state where the battery element is housed in an exterior material.
FIG. 4 is a diagram for explaining a manufacturing process of the lithium ion secondary battery, and is a schematic perspective view showing a completed lithium ion secondary battery.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 lithium ion secondary battery, 2 positive electrode, 3 negative electrode, 4 solid electrolyte, 5 battery element, 6 exterior material, 7 positive electrode current collector, 8 positive electrode mixture layer, 9 positive electrode terminal, 10 negative electrode current collector, 11 negative electrode Agent layer, 12 negative electrode terminal, 13 resin piece

Claims (10)

A positive electrode having a positive electrode active material capable of doping / dedoping lithium and containing lithium carbonate;
A negative electrode having a negative electrode active material capable of doping / dedoping lithium;
A non-aqueous electrolyte battery comprising a non-aqueous electrolyte containing a non-aqueous solvent to which a carbamate represented by the general formula (1) is added and an electrolyte salt.

The nonaqueous electrolyte battery according to claim 1, wherein the content of the lithium carbonate is in a range of 0.05% by weight or more and 0.2% by weight or less based on the positive electrode active material. 2. The non-aqueous electrolyte according to claim 1, wherein at least one of ethyl N, N-dimethyl carbamate, methyl N, N-diethyl carbamate, methyl N, N-dimethyl carbamate is added as the carbamate. Non-aqueous electrolyte battery. When the carbamates added to the non-aqueous electrolyte are ethyl N, N-dimethyl carbamate and / or methyl N, N-diethyl carbamate, the entirety of ethyl N, N-dimethyl carbamate and / or methyl N, N-diethyl carbamate 4. The non-aqueous electrolyte battery according to claim 3, wherein the amount of addition is in the range of 0.1% by weight or more and 5% by weight or less based on the non-aqueous solvent. The carbamates added to the non-aqueous electrolyte are methyl N, N-dimethyl carbamate, and the amount of methyl N, N-dimethyl carbamate is 0.3% by weight or more and 5% by weight based on the non-aqueous solvent. 4. The non-aqueous electrolyte battery according to claim 3, wherein the content is not more than%. A positive electrode having a positive electrode active material capable of doping / dedoping lithium, a negative electrode having a negative electrode active material capable of doping / dedoping lithium, and a nonaqueous electrolyte containing a nonaqueous solvent and an electrolyte salt are provided. In a method for manufacturing a non-aqueous electrolyte battery,
A method for producing a nonaqueous electrolyte battery, comprising adding lithium carbonate to the positive electrode active material and adding a carbamate represented by the general formula (1) to the nonaqueous solvent.

7. The nonaqueous electrolyte battery according to claim 6, wherein the positive electrode active material contains the lithium carbonate in a range of 0.05% by weight or more and 0.2% by weight or less based on the positive electrode active material. Production method. The non-aqueous electrolyte, wherein at least one of ethyl N, N-dimethyl carbamate, methyl N, N-diethyl carbamate, methyl N, N-dimethyl carbamate is added as the carbamate. 7. The method for producing a nonaqueous electrolyte battery according to item 6. When the carbamates added to the non-aqueous electrolyte are ethyl N, N-dimethyl carbamate and / or methyl N, N-diethyl carbamate, the entirety of ethyl N, N-dimethyl carbamate and / or methyl N, N-diethyl carbamate 9. The method for producing a nonaqueous electrolyte battery according to claim 8, wherein the amount of addition is in the range of 0.1% by weight or more and 5% by weight or less based on the nonaqueous solvent. The carbamate added to the non-aqueous electrolyte is methyl N, N-dimethyl carbamate, and the amount of methyl N, N-dimethyl carbamate added is 0.3% by weight or more and 5% by weight based on the non-aqueous solvent. The method for producing a nonaqueous electrolyte battery according to claim 8, wherein the range is set as follows.

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