JP4843848B2 - Non-aqueous electrolyte secondary battery - Google Patents
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- JP4843848B2 JP4843848B2 JP2001013594A JP2001013594A JP4843848B2 JP 4843848 B2 JP4843848 B2 JP 4843848B2 JP 2001013594 A JP2001013594 A JP 2001013594A JP 2001013594 A JP2001013594 A JP 2001013594A JP 4843848 B2 JP4843848 B2 JP 4843848B2
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Description
【０００１】
【発明の属する技術分野】
本発明は、高い安全性を有する非水電解液二次電池に関する。
【０００２】
【従来の技術】
近年、ビデオカメラや携帯型電話機等のコードレス電子機器の発達はめざましいものがある。これらの民生用機器の電源としては電池電圧が高く、高エネルギー密度を有したリチウム二次電池等の非水電解質二次電池が注目されており実用化されてきている。さらに現在、環境問題等の観点からは自動車の分野でも電気自動車やハイブリッド自動車等のクリーンエネルギーを利用する自動車の開発がなされている。この様な車載用の電源としても非水電解質二次電池が注目されており、さらなる高性能化（高エネルギー密度化、高出力化等）や低コスト化が検討されてきている。上記電池の正極活物質としては４Ｖ程度の電池電圧を示すＬｉＣｏＯ2、ＬｉＮｉＯ2、ＬｉＭｎ2Ｏ4などのリチウム−金属複合酸化物が、負極活物質としてはリチウム金属やリチウムイオンを可逆的に吸蔵しうる炭素材料等が、また電解液としては４Ｖ程度の電池電圧で使用できる有機系の電解液がそれぞれ使用または検討されている。
【０００３】
非水電解質二次電池の高エネルギー密度化、高出力化等の高性能化を図る際には、安全性の確保が重要な問題である。たとえばリチウム二次電池では、化学的活性の高いリチウム、可燃性の高い電解液、充電状態での熱安定性の低い酸化物正極活物質を用いているので電池の取扱いについては細心の注意が必要となる。特に高性能のリチウム電池を市場に出す場合は、誤使用に基づく危険に対する充分な安全対策を施すことが必要となる。たとえば、電池の短絡、過充電、高温下（８０℃以上）での放置等の誤使用による電池の破損等の不都合が挙げられる。誤使用に基づく不都合（熱暴走）の原因としては電池材料間の化学反応が過熱により促進されることが挙げられる。その対策として、ＰＴＣ素子の使用、融点の低いポリプロピレン、ポリエチレンをセパレ−タに用いた電池内部温度上昇に伴うセパレ−タのシャットダウン効果による過電流のカット、内部圧力上昇によって作動する電流遮断機構が安全手段として考案されている。
【０００４】
【発明が解決しようとする課題】
このように従来から多くの安全手段が開発されているが、さらなる安全性向上のためには多種類の安全手段を開発し併用することが望まれる。
【０００５】
したがって本発明は、従来と異なる手段で安全性を確保した非水電解液二次電池を提供することを解決すべき課題とする。
【０００６】
【課題を解決するための手段】
従来の安全確保の手段としては上述のように熱に応答して作動するものが多く、過充電などにより電池に異常が発生した際に、その安全手段が作動するまで長時間を要する。
【０００７】
ここで非水電解質二次電池が熱により安全性が低下する原因を考察する。高温下に放置した場合に熱暴走に至る主な原因としては、充電状態の正極活物質の高温下での不安定さを発見した。つまり、高温下では正極活物質（一般的に非水電解質二次電池の正極活物質にはリチウム−金属複合酸化物が用いられる。）に含まれる酸素が脱離し、その活性な酸素と電解液等との反応により連鎖的に発熱していくと考えられる。したがってその対策として高温下においても酸素の脱離が少ない正極活物質を用いれば電池を高温下に放置しても熱暴走が起こらないことに想到しそのような正極活物質として、Ｌｉを含有するオリビン構造のリン酸化合物含有正極活物質を見出した。これは、リンと酸素との結合力が強いために、高温下においても安定な状態で存在できるものと考えられる。
【０００８】
以上の知見に基づいて以下の発明を行った。すなわち、本発明の非水電解液二次電池は、リチウムイオンを吸蔵乃至は放出できる正極活物質をもつ正極と、リチウムイオンを吸蔵乃至は放出できる負極とを有する非水電解液二次電池において、前記正極活物質は、層状構造のＬｉＭｎＯ ２ と層状構造のＬｉＭｎ ０．９ Ｃｒ ０．１ Ｏ ２ とから選ばれる少なくとも１種であるリチウム−金属複合酸化物含有活物質と、Ｌｉを含有するオリビン構造のリン酸化合物のうちの１種以上であるリン酸化合物含有活物質とをもち、該正極活物質は、該リン酸化合物含有活物質を、高温下で発生する酸素の量が電池の熱暴走を引き起こさない割合含有することを特徴とする。
【００１０】
また、前記リン酸化合物含有活物質は、コスト低減の目的から鉄を含有することが好ましい。その場合に前記リン酸化合物含有活物質は、一般式ＬｉＭｘＦｅ１−ｘＰＯ４（Ｍ：鉄以外の一種以上の金属元素、０≦ｘ≦０．５）で表されることがエネルギー密度向上の観点から好ましい。
さらに、前記リン酸化合物含有活物質は、前記正極活物質全体に対して質量比で２５／８５以上含まれるのが好ましい。
【００１１】
【発明の実施の形態】
以下に本発明の非水電解液二次電池をリチウム二次電池に適用した実施形態に基づいて説明する。なお、本発明は、以下の実施形態により限定されるものではない。
【００１２】
本実施形態のリチウム二次電池は、正極と負極と電解液とその他必要に応じた要素とからなる。本実施形態のリチウム二次電池は、その形状には特に制限を受けず、コイン型、円筒型、角型等、種々の形状の電池として使用できる。本実施形態では、円筒型のリチウム二次電池に基づいて説明を行う。
【００１３】
本実施形態のリチウム二次電池は、正極および負極をシート形状として両者をセパレータを介して積層し渦巻き型に多数回巻回した巻回体を空隙を満たす電解液とともに所定の円筒状のケース内に収納したものである。正極と正極端子部とについて、そして負極と負極端子部とについては、それぞれ電気的に接合されている。
【００１４】
正極は、リチウムイオンを充電時には放出し且つ放電時には吸蔵することができる正極活物質をもつ。正極活物質は、層状構造またはスピネル構造のリチウム−金属複合酸化物のうちの１種以上であるリチウム−金属複合酸化物含有活物質と、Ｌｉを含有するオリビン構造のリン酸化合物のうちの１種以上であるリン酸化合物含有活物質とをもつ。
【００１５】
リチウム−金属複合酸化物含有活物質としては、たとえば、Ｌｉ(1-Y)ＮｉＯ2、Ｌｉ(1-Y)ＭｎＯ2、Ｌｉ(1-Y)Ｍｎ2Ｏ4、Ｌｉ(1-Y)ＣｏＯ2、Ｌｉ(1-Y)ＦｅＯ2等や、各々にＬｉ、Ａｌ、そしてＣｒ等の遷移金属を添加または置換した材料等である。この例示におけるＹは０〜１の数を示す。なお、これらのリチウム−金属複合酸化物を正極活物質として用いる場合には単独で用いるばかりでなくこれらを複数種類混合して用いることもできる。このなかでもリチウム−金属複合酸化物含有活物質としては、層状構造またはスピネル構造のリチウムマンガン含有複合酸化物、リチウムニッケル含有複合酸化物およびリチウムコバルト含有複合酸化物のうちの１種以上であることが好ましい。コスト低減の観点からはリチウム−金属複合酸化物含有活物質は、層状構造またはスピネル構造のリチウムマンガン含有複合酸化物およびリチウムニッケル含有複合酸化物おうちの１種以上であることがさらに好ましい。
【００１６】
リン酸化合物含有正極活物質としては、鉄を含有することが好ましい。その場合のリン酸化合物含有正極活物質は、一般式ＬｉＭxＦｅ1-xＰＯ4（Ｍ：鉄以外の一種以上の金属元素、０≦ｘ≦０．５）で表される化合物が例示できる。ここでＭで表される金属元素としてはＣｏ、Ｎｉ、Ｍｎ、Ｍｇ、Ｃａ、Ｓｃ、Ｔｉ、Ｖ、Ｃｒ、Ｃｕ、Ｚｎ、Ｇａ、Ａｌ、Ｌｉ等が例示でき、そのなかでもＣｏ、Ｎｉ、Ｍｎが高エネルギー密度の理由から好ましい。このリン酸化合物含有正極活物質はリンと酸素との結合が強く高温下においても活性な酸素の発生が抑制できる。したがって、好ましいリン酸化合物含有正極活物質の含有割合としては高温下（電池の安定性を要求される最高の温度）で発生する酸素の量が電池の熱暴走を引き起こさない最低限の割合以上である。たとえば、１１０℃において安定なリチウム二次電池を必要とする場合には全体の正極活物質に対して２５／８５以上リン酸化合物含有正極活物質を含有させることで安定性の高い電池を得ることができる。正極活物質にリン酸化合物含有正極活物質を含有させることの副次的な効果としてコバルト等の高価な元素の含有量を低下できコストを低下できる。
【００１７】
正極は前述の正極活物質を結着材、導電材等の公知の添加材と混合した後に金属箔等からなる集電体上に塗布され正極合材層が形成される。
【００１８】
負極は、リチウムイオンを充電時には吸蔵し、かつ放電時には放出する負極活物質を用いることができれば、その材料構成で特に限定されるものではなく、公知の材料・構成のものを用いることができる。たとえば、リチウム金属、グラファイト又は非晶質炭素等の炭素材料等である。そのなかでも特に炭素材料を用いることが好ましい。炭素材料は比表面積が比較的大きくでき、リチウムの吸蔵、放出速度が速いため大電流での充放電特性、出力・回生密度に対して良好となる。特に、出力・回生密度のバランスを考慮すると、充放電に伴ない電圧変化の比較的大きい炭素材料を使用することが好ましい。また、このような炭素材料を負極活物質に用いることで、より高い充放電効率と良好なサイクル特性とが得られる。
【００１９】
このように負極活物質として炭素材料を用いた場合には、これに必要に応じて導電材および結着材を混合して得られた負極合材が集電体に塗布されてなるものを用いることが好ましい。
【００２０】
電解液は、有機溶媒に支持塩を溶解させたものである。
【００２１】
有機溶媒は、通常リチウム二次電池の電解液の用いられる有機溶媒であれば特に限定されるものではなく、例えば、カーボネート類、ハロゲン化炭化水素、エーテル類、ケトン類、ニトリル類、ラクトン類、オキソラン化合物等を用いることができる。特に、プロピレンカーボネート、エチレンカーボネート、１，２−ジメトキシエタン、ジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネート等及びそれらの混合溶媒が適当である。
【００２２】
例に挙げたこれらの有機溶媒のうち、特に、カーボネート類、エーテル類からなる群より選ばれた一種以上の非水溶媒を用いることにより、支持塩の溶解性、誘電率および粘度において優れ、電池の充放電効率も高いので、好ましい。
【００２３】
支持塩は、その種類が特に限定されるものではないが、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＣｌＯ4およびＬｉＡｓＦ6から選ばれる無機塩、該無機塩の誘導体、ＬｉＳＯ3ＣＦ3、ＬｉＣ（ＳＯ3ＣＦ3）2、ＬｉＮ（ＳＯ3ＣＦ3）2、ＬｉＮ（ＳＯ2Ｃ2Ｆ5）2およびＬｉＮ（ＳＯ2ＣＦ3）（ＳＯ2Ｃ4Ｆ9）から選ばれる有機塩、並びにその有機塩の誘導体の少なくとも１種であることが好ましい。
【００２４】
これらの支持塩の使用により、電池性能をさらに優れたものとすることができ、かつその電池性能を室温以外の温度域においてもさらに高く維持することができる。支持塩の濃度についても特に限定されるものではなく、用途に応じ、支持塩および有機溶媒の種類を考慮して適切に選択することが好ましい。
【００２５】
セパレータは、正極および負極を電気的に絶縁し、電解液を保持する役割を果たすものである。たとえば、多孔性合成樹脂膜、特にポリオレフィン系高分子（ポリエチレン、ポリプロピレン）の多孔膜を用いればよい。なおセパレータは、正極と負極との絶縁を担保するため、正極および負極よりもさらに大きいものとするのが好ましい。
【００２６】
ケースは、特に限定されるものではなく、公知の材料、形態で作成することができる。
【００２７】
ガスケットは、ケースと正負の両端子部の間の電気的な絶縁と、ケース内の密閉性とを担保するものである。たとえば、電解液にたいして、化学的、電気的に安定であるポリプロピレンのような高分子等から構成できる。
【００２８】
【実施例】
（リチウム二次電池の作製）
〔正極〕
表１に示す各試験例の構成で、リチウム−金属複合酸化物含有正極活物質としてのリチウム−金属複合酸化物と、リン酸化合物含有正極活物質としてのオリビン構造のＬｉ含有リン酸化合物と、導電材としてのグラファイトと、結着材としてのＰＶＤＦとを溶剤としてのＮ−メチル−２−ピロリドン中に混合してペーストを作製した。このペーストをＡｌ箔集電体上の両面に所定の質量、膜厚で塗布し、乾燥の後に、所定の膜厚に加圧成形した。この電極を幅５．４ｃｍ、長さ８６ｃｍにカットし、電流取り出し用のリードタブ溶接部として長さ方向に２．５ｃｍ分の電極合材を掻き取った。この電極の有効反応面積は５．４ｃｍ×８３．５ｃｍ×２＝９０１．８ｃｍ2である。なお、本明細書および表に記載の「％」はすべて質量百分率を示す。
【００２９】
〔負極〕
メソフェーズ系カーボンを９０％、バインダーのＰＶＤＦを１０％の配合でＮ−メチル−２−ピロリドン中に混合してペーストを作製した。このペーストをＣｕ箔集電体上の両面に所定の質量、膜厚で塗布し、乾燥の後に、所定の膜厚に加圧成形した。この電極を幅５．６ｃｍ、長さ９０．５ｃｍにカットし、電流取り出し用のリードタブ溶接部として長さ方向に０．５ｃｍ分の電極合材を掻き取った。この電極の有効反応面積は５．６ｃｍ×９０ｃｍ×２＝１００８ｃｍ2である。
【００３０】
〔非水電解液〕
エチレンカーボネートとジメチルカーボネートとの体積比３：７の混合溶媒に、ＬｉＰＦ6 を１ｍｏｌ／Ｌの濃度で溶解させて電解液を調製した。
【００３１】
〔電池の組み立て〕
上記の正極、負極及び電解液を使用して、１８６５０サイズの電池を組み立てた。なお、セパレ−タにはポリエチレン製の微多孔膜を使用した。
【００３２】
（リチウム二次電池の安全性評価）
〔高温放置評価〕
４．２Ｖの満充電の状態（室温にて充電を１．１ｍＡ／ｃｍ2 の一定電流で４．２Ｖまでおこない、その後、４．２Ｖの定電圧で合計４時間行った）で、１１０℃の恒温層にて１日放置し、観察・評価した。評価方法は、電池に異常がない場合には○と、熱暴走のみが生じた場合には△と、熱暴走と電池の破損とが併せて生じた場合には×とそれぞれ評価した。
【００３３】
（リチウム二次電池の特性評価結果）
安全性評価の結果を表１に併せて示す。
【００３４】
表１から明らかなように、リン酸化合物含有正極活物質を含有させた試験例２、４、６、８、１０、１２ではすべて熱暴走等の不都合が生じなかった。また、リン酸化合物含有正極活物質を含有させる割合は正極活物質全体に対して２５／８５程度で充分熱暴走を抑制する効果が得られた。
【００３５】
したがって、本発明の正極を用いることにより、安全性の高い非水電解液二次電池が得られることが解った。
【００３６】
【表１】
【発明の効果】
本発明で得られる非水電解液二次電池は、正極活物質として少なくともＬｉを含有するオリビン構造のリン酸化合物含有正極活物質をもつことから、高温下に電池が放置された場合においても熱暴走に至らない非水電解液二次電池を提供することが可能となる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a nonaqueous electrolyte secondary battery having high safety.
[0002]
[Prior art]
In recent years, the development of cordless electronic devices such as video cameras and mobile phones has been remarkable. As a power source for these consumer devices, a nonaqueous electrolyte secondary battery such as a lithium secondary battery having a high battery voltage and a high energy density has attracted attention and has been put into practical use. Furthermore, from the viewpoint of environmental problems and the like, automobiles using clean energy such as electric cars and hybrid cars are also being developed in the field of automobiles. Non-aqueous electrolyte secondary batteries are also attracting attention as such on-vehicle power sources, and further improvements in performance (higher energy density, higher output, etc.) and lower costs have been studied. Lithium-metal composite oxides such as LiCoO 2 , LiNiO 2 , and LiMn 2 O 4 exhibiting a battery voltage of about 4 V are used as the positive electrode active material of the battery, and lithium metal and lithium ions are reversibly occluded as the negative electrode active material. Carbon materials that can be used, and organic electrolytes that can be used at a battery voltage of about 4 V have been used or studied.
[0003]
Ensuring safety is an important issue when improving the performance of non-aqueous electrolyte secondary batteries such as higher energy density and higher output. For example, lithium secondary batteries use lithium with high chemical activity, highly flammable electrolytes, and oxide positive electrode active materials with low thermal stability in the charged state, so careful handling of the batteries is necessary. It becomes. In particular, when a high-performance lithium battery is put on the market, it is necessary to take sufficient safety measures against danger due to misuse. For example, there are inconveniences such as battery shortage, overcharge, battery damage due to misuse such as leaving under high temperature (80 ° C. or higher). A cause of inconvenience (thermal runaway) due to misuse is that a chemical reaction between battery materials is promoted by overheating. Countermeasures include the use of a PTC element, a low melting point polypropylene, polyethylene using a separator as a separator to prevent overcurrent due to the separator's shutdown effect due to the rise in the battery's internal temperature, and a current cutoff mechanism that operates when the internal pressure rises. It is designed as a safety measure.
[0004]
[Problems to be solved by the invention]
Thus, many safety means have been developed in the past, but it is desired to develop and use various kinds of safety means in order to further improve safety.
[0005]
Accordingly, the present invention aims to solve is to provide a nonaqueous electrolyte secondary battery ensuring safety in unconventional means.
[0006]
[Means for Solving the Problems]
Many conventional means for ensuring safety operate in response to heat as described above, and when an abnormality occurs in the battery due to overcharging or the like, it takes a long time for the safety means to operate.
[0007]
Here, the reason why the safety of the nonaqueous electrolyte secondary battery is lowered by heat will be considered. The main cause of thermal runaway when left at high temperature was found to be instability of the charged positive electrode active material at high temperature. That is, oxygen contained in the positive electrode active material (generally, a lithium-metal composite oxide is used as the positive electrode active material of a nonaqueous electrolyte secondary battery) is desorbed at high temperatures, and the active oxygen and the electrolyte It is thought that the reaction generates heat in a chain. Therefore, as a countermeasure, if a positive electrode active material with little desorption of oxygen even at high temperature is used, it is conceived that thermal runaway does not occur even if the battery is left at high temperature, and Li is contained as such a positive electrode active material. A phosphoric acid compound-containing positive electrode active material having an olivine structure has been found. This is considered to be able to exist in a stable state even at high temperatures because of the strong binding force between phosphorus and oxygen.
[0008]
Based on the above knowledge, the following invention was performed. That is, the non-aqueous electrolyte secondary battery of the present invention is a non-aqueous electrolyte secondary battery having a positive electrode having a positive electrode active material capable of occluding or releasing lithium ions and a negative electrode capable of occluding or releasing lithium ions. the positive electrode active material, lithium is at least one selected from LiMn 0.9 Cr 0.1 O 2 Metropolitan of LiMnO 2 and the layered structure of the layered structure - and metal composite oxide containing active material, containing Li A phosphoric acid compound-containing active material that is at least one of phosphoric acid compounds having an olivine structure, and the positive electrode active material is obtained by converting the phosphoric acid compound-containing active material into an amount of oxygen generated at a high temperature. It is characterized by containing a proportion that does not cause thermal runaway.
[0010]
Moreover, it is preferable that the said phosphoric acid compound containing active material contains iron from the objective of cost reduction. In this case, the phosphoric acid compound-containing active material is represented by the general formula LiM x Fe 1-x PO 4 (M: one or more metal elements other than iron, 0 ≦ x ≦ 0.5). It is preferable from the viewpoint of improvement.
Further, the phosphoric acid compound-containing active material is preferably contained in a mass ratio of 25/85 or more with respect to the whole positive electrode active material .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Will be explained based on embodiments of the non-aqueous electrolyte secondary battery is applied to a lithium secondary battery of the present invention are described below. In addition, this invention is not limited by the following embodiment.
[0012]
The lithium secondary battery according to this embodiment includes a positive electrode, a negative electrode, an electrolytic solution, and other elements as required. The lithium secondary battery of the present embodiment is not particularly limited in its shape, and can be used as a battery having various shapes such as a coin shape, a cylindrical shape, and a square shape. In the present embodiment, description will be made based on a cylindrical lithium secondary battery.
[0013]
The lithium secondary battery according to the present embodiment has a positive electrode and a negative electrode in the form of a sheet, and both are stacked via a separator and wound in a spiral shape. It is what was stored in. The positive electrode and the positive electrode terminal portion, and the negative electrode and the negative electrode terminal portion are electrically joined to each other.
[0014]
The positive electrode has a positive electrode active material capable of releasing lithium ions during charging and occluding during discharging. The positive electrode active material is one of a lithium-metal composite oxide-containing active material that is one or more of lithium-metal composite oxides having a layered structure or a spinel structure, and one of phosphoric compounds having an olivine structure containing Li. It has a phosphoric acid compound-containing active material that is more than a seed.
[0015]
Examples of the lithium-metal composite oxide-containing active material include Li (1-Y) NiO 2 , Li (1-Y) MnO 2 , Li (1-Y) Mn 2 O 4 , Li (1-Y) CoO. 2 , Li (1-Y) FeO 2, etc., and materials obtained by adding or substituting transition metals such as Li, Al, and Cr to each. Y in this example represents a number from 0 to 1. When these lithium-metal composite oxides are used as the positive electrode active material, they can be used alone or in combination. Among these, the lithium-metal composite oxide-containing active material is at least one of a layered structure or spinel structure lithium manganese-containing composite oxide, lithium nickel-containing composite oxide, and lithium cobalt-containing composite oxide. Is preferred. From the viewpoint of cost reduction, the lithium-metal composite oxide-containing active material is more preferably at least one of a lithium manganese-containing composite oxide and a lithium nickel-containing composite oxide having a layered structure or a spinel structure.
[0016]
The phosphoric acid compound-containing positive electrode active material preferably contains iron. The phosphoric acid compound-containing positive electrode active material in that case can be exemplified by a compound represented by the general formula LiM x Fe 1-x PO 4 (M: one or more metal elements other than iron, 0 ≦ x ≦ 0.5). . Examples of the metal element represented by M include Co, Ni, Mn, Mg, Ca, Sc, Ti, V, Cr, Cu, Zn, Ga, Al, Li, and the like. Among them, Co, Ni, Mn is preferred because of its high energy density. This phosphoric acid compound-containing positive electrode active material has a strong bond between phosphorus and oxygen and can suppress the generation of active oxygen even at high temperatures. Accordingly, the preferable content ratio of the phosphoric acid compound-containing positive electrode active material is such that the amount of oxygen generated at a high temperature (the highest temperature required for battery stability) is not less than the minimum ratio that does not cause thermal runaway of the battery. is there. For example, when a lithium secondary battery stable at 110 ° C. is required, a highly stable battery can be obtained by including a phosphoric acid compound-containing positive electrode active material of 25/85 or more with respect to the entire positive electrode active material. Can do. As a secondary effect of including the phosphoric acid compound-containing positive electrode active material in the positive electrode active material, the content of expensive elements such as cobalt can be reduced, and the cost can be reduced.
[0017]
The positive electrode is mixed with a known additive such as a binder or a conductive material after the positive electrode active material is mixed, and then applied onto a current collector made of a metal foil or the like to form a positive electrode mixture layer.
[0018]
The negative electrode is not particularly limited in its material configuration as long as it can use a negative electrode active material that occludes lithium ions during charging and discharges during discharge, and can use materials of known materials and configurations. For example, a carbon material such as lithium metal, graphite, or amorphous carbon. Among these, it is particularly preferable to use a carbon material. The carbon material can have a relatively large specific surface area, and the lithium occlusion and release speed is fast, so that it is favorable for charge / discharge characteristics, output and regeneration density at a large current. In particular, in consideration of the balance between output and regenerative density, it is preferable to use a carbon material having a relatively large voltage change accompanying charging / discharging. Further, by using such a carbon material for the negative electrode active material, higher charge / discharge efficiency and better cycle characteristics can be obtained.
[0019]
Thus, when a carbon material is used as the negative electrode active material, a material obtained by coating a current collector with a negative electrode mixture obtained by mixing a conductive material and a binder as necessary is used. It is preferable.
[0020]
The electrolytic solution is obtained by dissolving a supporting salt in an organic solvent.
[0021]
The organic solvent is not particularly limited as long as it is an organic solvent that is usually used for an electrolyte solution of a lithium secondary battery. For example, carbonates, halogenated hydrocarbons, ethers, ketones, nitriles, lactones, An oxolane compound or the like can be used. In particular, propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and the like, and mixed solvents thereof are suitable.
[0022]
Among these organic solvents mentioned in the examples, in particular, by using one or more non-aqueous solvents selected from the group consisting of carbonates and ethers, the solubility of the supporting salt, the dielectric constant and the viscosity are excellent, and the battery The charge / discharge efficiency is also preferable.
[0023]
The kind of the supporting salt is not particularly limited, but an inorganic salt selected from LiPF 6 , LiBF 4 , LiClO 4 and LiAsF 6 , a derivative of the inorganic salt, LiSO 3 CF 3 , LiC (SO 3 CF 3 ) 2 , LiN (SO 3 CF 3 ) 2 , LiN (SO 2 C 2 F 5 ) 2 and LiN (SO 2 CF 3 ) (SO 2 C 4 F 9 ), and derivatives of the organic salts It is preferable that it is at least 1 type of these.
[0024]
By using these supporting salts, the battery performance can be further improved, and the battery performance can be maintained even higher in a temperature range other than room temperature. The concentration of the supporting salt is not particularly limited, and it is preferable to appropriately select the supporting salt and the organic solvent in consideration of the use.
[0025]
The separator plays a role of electrically insulating the positive electrode and the negative electrode and holding the electrolytic solution. For example, a porous synthetic resin film, particularly a polyolefin polymer (polyethylene, polypropylene) porous film may be used. Note that the separator is preferably larger than the positive electrode and the negative electrode in order to ensure insulation between the positive electrode and the negative electrode.
[0026]
The case is not particularly limited and can be made of a known material and form.
[0027]
The gasket secures electrical insulation between the case and both the positive and negative terminal portions and airtightness in the case. For example, it can be composed of a polymer such as polypropylene that is chemically and electrically stable to the electrolyte.
[0028]
【Example】
(Production of lithium secondary battery)
[Positive electrode]
In the configuration of each test example shown in Table 1, a lithium-metal composite oxide as a lithium-metal composite oxide-containing positive electrode active material, an Li-containing phosphate compound with an olivine structure as a phosphoric acid compound-containing positive electrode active material, A paste was prepared by mixing graphite as a conductive material and PVDF as a binder in N-methyl-2-pyrrolidone as a solvent. This paste was applied to both surfaces of the Al foil current collector with a predetermined mass and film thickness, and after drying, pressure-molded to a predetermined film thickness. This electrode was cut into a width of 5.4 cm and a length of 86 cm, and 2.5 cm of the electrode mixture was scraped off in the length direction as a lead tab weld for extracting current. The effective reaction area of this electrode is 5.4 cm × 83.5 cm × 2 = 901.8 cm 2 . In addition, "%" described in this specification and a table | surface all shows a mass percentage.
[0029]
[Negative electrode]
A paste was prepared by mixing 90% mesophase carbon and 10% PVDF binder in N-methyl-2-pyrrolidone. This paste was applied to both surfaces of the Cu foil current collector with a predetermined mass and film thickness, and after drying, pressure-molded to a predetermined film thickness. This electrode was cut into a width of 5.6 cm and a length of 90.5 cm, and 0.5 cm of the electrode mixture was scraped off in the length direction as a lead tab weld for extracting current. Effective reaction area of the electrode is 5.6cm × 90cm × 2 = 1008cm 2 .
[0030]
[Non-aqueous electrolyte]
An electrolyte solution was prepared by dissolving LiPF 6 at a concentration of 1 mol / L in a mixed solvent of ethylene carbonate and dimethyl carbonate in a volume ratio of 3: 7.
[0031]
[Assembling the battery]
A battery of 18650 size was assembled using the above positive electrode, negative electrode and electrolyte. Note that a polyethylene microporous film was used as the separator.
[0032]
(Safety evaluation of lithium secondary battery)
[High temperature neglect evaluation]
In a fully charged state of 4.2 V (charging at room temperature to 4.2 V with a constant current of 1.1 mA / cm 2 , and then at a constant voltage of 4.2 V for a total of 4 hours), 110 ° C. The samples were left for 1 day in a thermostatic layer and observed and evaluated. The evaluation method was evaluated as ◯ when there was no abnormality in the battery, △ when only thermal runaway occurred, and x when thermal runaway and battery damage occurred together.
[0033]
(Characteristic evaluation results of lithium secondary battery)
The results of safety evaluation are also shown in Table 1.
[0034]
As is apparent from Table 1, in Test Examples 2, 4, 6, 8, 10, and 12 containing the phosphoric acid compound-containing positive electrode active material, inconvenience such as thermal runaway did not occur. Moreover, the ratio which contains a phosphoric acid compound containing positive electrode active material is about 25/85 with respect to the whole positive electrode active material, and the effect which suppresses thermal runaway sufficiently was acquired.
[0035]
Therefore, it was found that a highly safe non-aqueous electrolyte secondary battery can be obtained by using the positive electrode of the present invention.
[0036]
[Table 1]
【The invention's effect】
Non-aqueous electrolyte secondary battery obtained by the present invention, the heat even if because of its phosphate compound-containing positive electrode active material having an olivine structure containing at least Li, the battery under high temperature was left as a positive electrode active material it is possible to provide a nonaqueous electrolyte secondary battery does not reach runaway.
Claims (4)
前記正極活物質は、層状構造のＬｉＭｎＯ ２ と層状構造のＬｉＭｎ ０．９ Ｃｒ ０．１ Ｏ ２ とから選ばれる少なくとも１種であるリチウム−金属複合酸化物含有活物質と、Ｌｉを含有するオリビン構造のリン酸化合物のうちの１種以上であるリン酸化合物含有活物質とをもち、
該正極活物質は、該リン酸化合物含有活物質を、高温下で発生する酸素の量が電池の熱暴走を引き起こさない割合含有することを特徴とする非水電解液二次電池。In a non-aqueous electrolyte secondary battery having a positive electrode having a positive electrode active material capable of occluding or releasing lithium ions and a negative electrode capable of occluding or releasing lithium ions,
The positive electrode active material, lithium is at least one selected from LiMn 0.9 Cr 0.1 O 2 Metropolitan of LiMnO 2 and the layered structure of the layered structure - and metal composite oxide containing active material, olivine containing Li Having a phosphoric acid compound-containing active material that is one or more of the phosphoric acid compounds of the structure,
The non-aqueous electrolyte secondary battery, wherein the positive electrode active material contains the phosphate compound-containing active material in such a proportion that the amount of oxygen generated at a high temperature does not cause thermal runaway of the battery.
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| CA2455540C (en) * | 2002-12-19 | 2012-08-28 | Valence Technology, Inc. | Electrode active material and method of making the same |
| JP4252331B2 (en) * | 2003-02-24 | 2009-04-08 | 住友大阪セメント株式会社 | Method for producing positive electrode active material for lithium ion battery |
| FR2864349B1 (en) * | 2003-12-23 | 2014-08-15 | Cit Alcatel | ELECTROCHEMICALLY ACTIVE MATERIAL FOR LITHIUM RECHARGEABLE ELECTROCHEMICAL ELECTROCHEMICAL GENERATOR POSITIVE ELECTRODE |
| FR2873497B1 (en) * | 2004-07-23 | 2014-03-28 | Accumulateurs Fixes | LITHIUM ELECTROCHEMICAL ACCUMULATOR OPERATING AT HIGH TEMPERATURE |
| JP4959145B2 (en) | 2005-03-30 | 2012-06-20 | 日本碍子株式会社 | Positive electrode for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery |
| JP2007207490A (en) * | 2006-01-31 | 2007-08-16 | Sanyo Electric Co Ltd | Lithium secondary battery |
| JP4240078B2 (en) | 2006-07-19 | 2009-03-18 | トヨタ自動車株式会社 | Lithium secondary battery |
| JP5250948B2 (en) * | 2006-07-28 | 2013-07-31 | 株式会社Ｇｓユアサ | Nonaqueous electrolyte secondary battery |
| JP5100143B2 (en) * | 2007-02-05 | 2012-12-19 | 三洋電機株式会社 | Battery unit |
| JP5036348B2 (en) * | 2007-02-27 | 2012-09-26 | 三洋電機株式会社 | Method for producing positive electrode active material for non-aqueous electrolyte secondary battery |
| JP5381024B2 (en) | 2008-11-06 | 2014-01-08 | 株式会社Ｇｓユアサ | Positive electrode for lithium secondary battery and lithium secondary battery |
| JP5159681B2 (en) | 2009-03-25 | 2013-03-06 | 株式会社東芝 | Non-aqueous electrolyte battery |
| JP5081886B2 (en) * | 2009-10-13 | 2012-11-28 | トヨタ自動車株式会社 | Non-aqueous electrolyte type lithium ion secondary battery |
| JP5656012B2 (en) * | 2009-11-27 | 2015-01-21 | 戸田工業株式会社 | Positive electrode active material powder for non-aqueous electrolyte secondary battery, method for producing the same, and non-aqueous electrolyte secondary battery |
| WO2012060349A1 (en) * | 2010-11-02 | 2012-05-10 | 株式会社 村田製作所 | All-solid-state battery |
| KR101560862B1 (en) * | 2012-08-02 | 2015-10-15 | 주식회사 엘지화학 | Positive-electrode active material with improved output property, and lithium secondary battery comprising the same |
| KR101551523B1 (en) * | 2012-08-02 | 2015-09-08 | 주식회사 엘지화학 | Positive-electrode active material with improved output and safety, and lithium secondary battery including the same |
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| JP2002075368A (en) * | 2000-09-05 | 2002-03-15 | Sony Corp | Positive electrode active material, nonaqueous electrolyte battery, and their manufacturing method |
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