JP2000113908A - Non-aqueous electrolyte secondary battery - Google Patents
Non-aqueous electrolyte secondary batteryInfo
- Publication number
- JP2000113908A JP2000113908A JP10286989A JP28698998A JP2000113908A JP 2000113908 A JP2000113908 A JP 2000113908A JP 10286989 A JP10286989 A JP 10286989A JP 28698998 A JP28698998 A JP 28698998A JP 2000113908 A JP2000113908 A JP 2000113908A
- Authority
- JP
- Japan
- Prior art keywords
- carbon material
- lithium
- negative electrode
- secondary battery
- active material
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Classifications
-
- 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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Landscapes
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、リチウムのドープ
・脱ドープ現象を利用した非水電解液二次電池に関し、
特に過放電による電池特性変化の小さい非水電解液二次
電池に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery utilizing the doping and undoping of lithium.
In particular, the present invention relates to a non-aqueous electrolyte secondary battery having a small change in battery characteristics due to overdischarge.
【０００２】[0002]
【従来の技術】リチウムをドープ・脱ドープ可能な活物
質を利用した非水電解液二次電池、いわゆるリチウムイ
オン二次電池は、高エネルギー密度であることから、パ
ソコン、携帯電話等の情報関連機器、通信機器の分野で
は実用化され広く普及するに至っている。そして、これ
らの機器は、電池の浪費を防止するためあるいは過放電
を防止するためにオートパワーオフ回路等の回路が接続
され、これらの回路によって二次電池の放電を制御する
ことが一般的に行われている。2. Description of the Related Art A non-aqueous electrolyte secondary battery using an active material capable of doping and undoping lithium, a so-called lithium ion secondary battery has a high energy density, and is therefore used in information-related applications such as personal computers and mobile phones. In the field of equipment and communication equipment, it has been practically used and has become widely used. In general, these devices are connected to a circuit such as an auto power-off circuit to prevent waste of the battery or to prevent overdischarge, and the discharge of the secondary battery is generally controlled by these circuits. Is being done.
【０００３】リチウムイオン二次電池は、通常、電池電
圧（正極と負極との端子間電圧を意味する。以下、本明
細書において「電池電圧」とは、特に断りのない限りこ
の端子間電圧をいう）が約４．５Ｖ〜約３Ｖの間で充放
電が行われるように制御される。ところが、上述のオー
トパワーオフ回路等に接続されている場合、機器自体の
機能は停止しているが、オートパワーオフ回路等の回路
負荷で放電が進行し、二次電池は過放電の状態となる。[0003] A lithium ion secondary battery generally means a battery voltage (a voltage between terminals of a positive electrode and a negative electrode. Hereinafter, in this specification, a "battery voltage" refers to a voltage between terminals unless otherwise specified. Is controlled between about 4.5V and about 3V. However, when connected to the above-described auto power-off circuit or the like, the function of the device itself is stopped, but discharge proceeds with a circuit load such as the auto power-off circuit, and the secondary battery is in an overdischarged state. Become.
【０００４】リチウムイオン二次電池の場合、適正な放
電終止電圧である３Ｖ程度の電池電圧においては、負極
の電位は１Ｖ程度（金属リチウムの電極電位を０Ｖとし
た場合における電位を意味する。以下、本明細書におい
て「電位」とは、特に断りのない限り、金属リチウムの
電極電位を基準とする。）となる。ところが、過放電の
状態に至った場合は、負極である炭素材料の中からさら
にリチウムが脱ドープし、負極電位がさらに上昇して、
遂には電池電圧が０Ｖとなってしまう。In the case of a lithium ion secondary battery, at a battery voltage of about 3 V, which is an appropriate end-of-discharge voltage, the potential of the negative electrode is about 1 V (meaning the potential when the electrode potential of metallic lithium is 0 V. In the present specification, the term “potential” is based on the electrode potential of lithium metal unless otherwise specified.) However, in the case of an overdischarged state, lithium is further undoped from the carbon material as the negative electrode, and the negative electrode potential further increases.
Finally, the battery voltage becomes 0V.
【０００５】従来のリチウムイオン二次電池では、一旦
過放電が行われた場合、負極の炭素材料中から可逆的に
ドープ・脱ドープ可能なリチウムがほとんど脱ドープし
た状態となっていた。このような状態に負極が曝された
場合、負極を構成する銅箔集電体の電解液中への溶解が
可能となり、その後に再充電を行っても、一旦溶出した
銅イオンは、負極表面等に析出し、電極反応を低下させ
ていた。このことから、従来のリチウムイオン二次電池
は、過放電後再充電を行った場合でも、電池容量があま
り回復しないという問題を抱えていた。[0005] In a conventional lithium ion secondary battery, once overdischarged, lithium which can be reversibly doped and undoped from the carbon material of the negative electrode is almost undoped. When the negative electrode is exposed to such a state, the copper foil current collector constituting the negative electrode can be dissolved in the electrolytic solution, and even after recharging, the copper ions once eluted remain on the negative electrode surface. Etc., thereby reducing the electrode reaction. For this reason, the conventional lithium ion secondary battery has a problem that the battery capacity does not recover much even when recharging is performed after overdischarge.
【０００６】この問題を解決するために、現状では、特
開平５−１４４４７２号公報に示すように、炭素材料を
負極活物質とする負極に、予め金属リチウム箔を貼り付
けておき、リチウムイオン二次電池が過放電の状態に陥
った場合でも、金属リチウムと炭素材料との間に存在す
る電位差でもって、金属リチウムから活物質たる炭素材
料中にリチウムをドープさせ、負極電位の上昇を防止す
るるという手段等が検討されている。In order to solve this problem, at present, as shown in JP-A-5-144472, a metal lithium foil is previously attached to a negative electrode using a carbon material as a negative electrode active material, and a lithium ion Even when the secondary battery falls into an overdischarged state, the potential difference existing between the metal lithium and the carbon material causes the lithium to be doped into the carbon material as the active material from the metal lithium, thereby preventing a rise in the negative electrode potential. The means of doing so are being studied.
【０００７】[0007]
【発明が解決しようとする課題】ところが、金属リチウ
ムは化学的に非常に活性な物質であるため、負極に金属
リチウム箔を貼り付けるといった手段を採用しようとす
る場合、電池の製造過程、金属リチウム箔の保存過程に
おいて、充分な管理を行い、危険のない作業環境を作り
出す必要がある。また、貼り付け箇所に関しても、安全
性を考慮に入れて決定する必要があり、さらには、貼り
付け箇所および貼り付け量によっては、意図した効果を
得られなかったり、過放電特性と安全性が両立しない場
合があり得るものとなっていた。However, since metallic lithium is a chemically very active substance, when using means such as attaching metallic lithium foil to the negative electrode, the production process of the metallic lithium is difficult. In the process of storing the foil, it is necessary to take sufficient care to create a work environment free from danger. In addition, it is necessary to determine the location to be pasted in consideration of safety.Furthermore, depending on the location and amount of pasting, the intended effect cannot be obtained, or the overdischarge characteristics and safety may not be obtained. It could be incompatible.
【０００８】本発明は、上記実状に鑑みてなされたもの
であり、負極活物質として用いる炭素材料を適正なもの
とすることにより、過放電の状態にあっても、負極活物
質たる炭素材料中に可逆的にドープ・脱ドープ可能なリ
チウムを残存させ、簡便かつ安全な手段によって、過放
電後の電池特性変化の小さい非水電解液二次電池を提供
することを目的とする。[0008] The present invention has been made in view of the above-mentioned circumstances, and by making the carbon material used as the negative electrode active material appropriate, the carbon material used as the negative electrode active material can be used even in an overdischarged state. It is an object of the present invention to provide a non-aqueous electrolyte secondary battery in which a change in battery characteristics after overdischarge is small by a simple and safe means in which reversibly doped / undoped lithium remains.
【０００９】[0009]
【課題を解決するための手段】本発明の非水電解液二次
電池は、リチウムをドープ・脱ドープ可能な炭素材料を
負極活物質とする負極と、リチウム遷移金属複合酸化物
を正極活物質とする正極と、リチウム塩を有機溶媒に溶
解させた非水電解液とを有する非水電解液二次電池であ
って、前記炭素材料は、金属リチウムの電極電位を０Ｖ
とした場合における０．５Ｖの電位から１．０Ｖの電位
までの間で、単位重量当たり２０ｍＡｈ／ｇ以上の可逆
的充放電が可能な高残存容量炭素材を含んでなることを
特徴とする。According to the present invention, there is provided a non-aqueous electrolyte secondary battery comprising a negative electrode having a carbon material capable of doping and dedoping lithium as a negative electrode active material, and a lithium transition metal composite oxide comprising a positive electrode active material. A non-aqueous electrolyte secondary battery having a positive electrode and a non-aqueous electrolyte in which a lithium salt is dissolved in an organic solvent, wherein the carbon material has an electrode potential of metallic lithium of 0V.
And a high residual capacity carbon material capable of reversible charge / discharge of 20 mAh / g or more per unit weight between a potential of 0.5 V and a potential of 1.0 V in the above case.
【００１０】上述したように、いわゆるリチウムイオン
二次電池では、通常、電池電圧が約３Ｖで放電が終了す
るように制御される。この電池電圧約３Ｖは、炭素材料
を用いた負極の電位が、金属リチウムの電極電位を０Ｖ
とした場合における約１Ｖの電位となったときに相当す
る。したがって、上記「高残存容量炭素材」とは、１．
０Ｖ以上の高い電位においても可逆的に放電なリチウム
を残存させることができる特性をもつ炭素材料を意味す
る。As described above, a so-called lithium ion secondary battery is usually controlled so that the discharge is completed when the battery voltage is about 3 V. When the battery voltage is about 3 V, the potential of the negative electrode using a carbon material is 0 V
It corresponds to a potential of about 1 V in the case of. Therefore, the above-mentioned “high residual capacity carbon material” means:
It means a carbon material having the property of allowing reversibly discharged lithium to remain even at a high potential of 0 V or more.
【００１１】すなわち、本発明の非水電解液二次電池
は、この高残存容量炭素材を負極活物質構成材料として
用いることによって、１Ｖの負極電位、つまり電池の通
常の終止電圧となった場合であっても、負極内に可逆的
にドープ・脱ドープ可能なリチウムを残存させ、過放電
後の容量劣化を防止するものである。高残存容量炭素材
は、その特性から、１．０Ｖの近傍の電位においても大
きな容量の可逆的充放電が可能である。そこで１．０Ｖ
の電位における残存容量に代え、０．５Ｖの電位から
１．０Ｖの電位までの間で可逆的充放電が可能な容量を
もって高残存容量炭素材であるか否かを判断した。そし
て、本発明の非水電解液二次電池の負極活物質を構成す
る高残存容量炭素材は、０．５Ｖの電位から１．０Ｖの
電位までの間で、単位重量当たり２０ｍＡｈ／ｇ以上の
可逆的充放電が可能な炭素材料とした。That is, the non-aqueous electrolyte secondary battery of the present invention uses the high residual capacity carbon material as a negative electrode active material constituent material to achieve a negative electrode potential of 1 V, that is, a normal end voltage of the battery. Even in this case, lithium capable of being reversibly doped and undoped remains in the negative electrode to prevent capacity deterioration after overdischarge. Due to its characteristics, the high residual capacity carbon material can reversibly charge and discharge a large capacity even at a potential near 1.0 V. So 1.0V
Was determined as a high residual capacity carbon material having a capacity capable of reversible charging and discharging between a potential of 0.5 V and a potential of 1.0 V instead of the residual capacity at the potential of. The high remaining capacity carbon material constituting the negative electrode active material of the nonaqueous electrolyte secondary battery of the present invention has a potential of 20 mAh / g or more per unit weight between a potential of 0.5 V and a potential of 1.0 V. A carbon material capable of reversible charge and discharge was used.
【００１２】ちなみに、炭素材料の単位重量あたりの
０．５Ｖの電位から１．０Ｖの電位までの間で可逆的充
放電が可能な容量は、目的とする炭素材料と金属リチウ
ムとを対向させて電気化学セルを構成し、この炭素材料
にリチウムをまったくドープさせていない状態から電位
が０．５Ｖとなる状態まで０．１ｍＡ／ｃｍ2の定電流
で充電し、次いで電位０．５Ｖの状態から電位１．０Ｖ
となるまで０．１ｍＡ／ｃｍ2の定電流で放電させて放
電容量を求め、この放電容量を炭素材料の重量で除した
値もって定義するものとする。なお、充電とは、炭素材
料にリチウムをドープさせることを意味し、放電とは、
炭素材料からリチウムを脱ドープさせることを意味す
る。Incidentally, the capacity at which reversible charging / discharging can be performed between a potential of 0.5 V and a potential of 1.0 V per unit weight of the carbon material depends on whether the target carbon material and metallic lithium are opposed to each other. An electrochemical cell was constructed and charged with a constant current of 0.1 mA / cm 2 from a state in which lithium was not doped into the carbon material to a state in which the potential became 0.5 V, and then from a state in which the potential was 0.5 V. Potential 1.0V
The discharge capacity is determined by discharging at a constant current of 0.1 mA / cm 2 until the value becomes, and the discharge capacity is defined by a value obtained by dividing the discharge capacity by the weight of the carbon material. Note that charging means doping a carbon material with lithium, and discharging means
This means that lithium is dedoped from the carbon material.
【００１３】[0013]
【発明の実施の形態】本発明の非水電解液二次電池は、
リチウムをドープ・脱ドープ可能な炭素材料を負極活物
質とする負極と、リチウム遷移金属複合酸化物を正極活
物質とする正極と、リチウム塩を有機溶媒に溶解させた
非水電解液とを主要構成要素として構成される。BEST MODE FOR CARRYING OUT THE INVENTION The non-aqueous electrolyte secondary battery of the present invention
A negative electrode using a carbon material capable of doping and undoping lithium as a negative electrode active material, a positive electrode using a lithium transition metal composite oxide as a positive electrode active material, and a non-aqueous electrolyte in which a lithium salt is dissolved in an organic solvent are mainly used. It is configured as a component.
【００１４】本発明の非水電解液二次電池の特徴をなす
負極活物質となるリチウムをドープ・脱ドープ可能な炭
素材料は、上記高残存容量炭素材のみから構成すること
もでき、また、この高残存容量炭素材と一般的に用いら
れるリチウムをドープ・脱ドープ可能な炭素材とを混合
して構成することもできる。高残存容量炭素材は、例え
ば、メソフェーズピッチをアルゴン雰囲気化において、
１０００〜１５００℃で、熱処理することによって製造
することができる。高温で熱処理すれば黒鉛化が進行し
すぎ、上述した０．５Ｖの電位から１．０Ｖの電位まで
の間で可逆的充放電が可能な容量が小さくなるなるた
め、比較的低温で熱処理するのが望ましい。The carbon material capable of being doped with and dedoped with lithium as the negative electrode active material, which is a feature of the nonaqueous electrolyte secondary battery of the present invention, can be composed of only the above-mentioned high residual capacity carbon material. The high residual capacity carbon material may be mixed with a commonly used lithium-doped / dedopable carbon material. High residual capacity carbon material, for example, in the atmosphere of argon mesophase pitch,
It can be manufactured by heat treatment at 1000 to 1500 ° C. If the heat treatment is performed at a high temperature, the graphitization proceeds excessively, and the capacity at which reversible charging and discharging can be performed between the potential of 0.5 V and the potential of 1.0 V described above decreases. Is desirable.
【００１５】高残存容量炭素材と混合して用いることの
できる炭素材には、天然黒鉛、人造黒鉛、熱分解炭素、
ピッチコークス、ニードルコークス、石油コークス、フ
ェノール樹脂・フラン樹脂等の有機化合物焼成体、炭素
繊維等種々のものが挙げられる。これらのもののうち１
種のもの、あるいは２種以上を混合したものを上記高残
存容量炭素材と混合して負極活物質とすることができ
る。Carbon materials that can be used in combination with the high residual capacity carbon material include natural graphite, artificial graphite, pyrolytic carbon,
Various types such as pitch coke, needle coke, petroleum coke, fired organic compounds such as phenolic resin and furan resin, and carbon fiber are exemplified. One of these
A negative electrode active material can be obtained by mixing one or a mixture of two or more with the high residual capacity carbon material.
【００１６】負極は、上記負極活物質に、結着剤を混合
し、適当な溶剤を加えてペースト状にした負極合材を、
銅箔製等の集電体の表面に塗布乾燥し、必要に応じて電
極密度を高めるべく圧縮して形成することができる。結
着剤は、活物質粒子を繋ぎ止める役割を果たすものでポ
リテトラフルオロエチレン、ポリフッ化ビニリデン、フ
ッ素ゴム等の含フッ素樹脂、ポリプロピレン、ポリエチ
レン等の熱可塑性樹脂を用いることができる。これら活
物質、導電材、結着剤を分散させる溶剤としては、Ｎ−
メチル−２−ピロリドン等の有機溶剤を用いることがで
きる。The negative electrode is obtained by mixing a binder with the negative electrode active material, adding an appropriate solvent, and forming a paste into a paste.
It can be formed by coating and drying on the surface of a current collector made of copper foil or the like, and compressing as necessary to increase the electrode density. The binder plays a role of binding the active material particles, and may be a fluororesin such as polytetrafluoroethylene, polyvinylidene fluoride, or fluororubber, or a thermoplastic resin such as polypropylene or polyethylene. As a solvent for dispersing these active material, conductive material and binder, N-
An organic solvent such as methyl-2-pyrrolidone can be used.
【００１７】また、これらの材料に代えて、負極結着剤
としてメチルセルロース、カルボキシメチルセルロース
等のグループから選ばれる１種又は２種以上のセルロー
スエーテル系物質とスチレンブタジエンゴムラテック
ス、カルボキシ変性スチレンブタジエンゴムラテックス
等の合成ゴム系ラテックス型接着剤との複合バインダを
用い、溶剤として水を用いることもできる。Instead of these materials, one or more cellulose ether-based substances selected from the group consisting of methylcellulose, carboxymethylcellulose and the like, and a styrene-butadiene rubber latex and a carboxy-modified styrene-butadiene rubber latex are used as a negative electrode binder. It is also possible to use a composite binder with a synthetic rubber-based latex-type adhesive such as, for example, and use water as a solvent.
【００１８】正極は、リチウム遷移金属複合酸化物から
なる正極活物質に導電材および結着剤を混合し、適当な
溶剤を加えてペースト状の正極合材としたものを、アル
ミニウム箔製等の集電体表面に塗布乾燥し、必要に応じ
て電極密度を高めるべく圧縮して形成することができ
る。正極活物質となるリチウム遷移金属複合酸化物に
は、４Ｖ級の電池が構成できるものとして、ＬｉＣｏＯ
2、ＬｉＮｉＯ2、ＬｉＭｎＯ2、ＬｉＭｎ2Ｏ4等のリチ
ウム複合酸化物粉状体を用いることができる。この中で
も層状岩塩構造のＬｉＣｏＯ2は、原料コストが高いも
のの、合成および取り扱いが容易であり、サイクル特性
等の良好な電池を構成できる正極活物質となる。これに
対し、層状岩塩構造のＬｉＭｎＯ2およびスピネル構造
のＬｉＭｎ2Ｏ4は、原料コストが安く、大量の活物質を
使用する用途、例えば電気自動車用電源として用いる二
次電池の場合等に、有利なものとなる。The positive electrode is obtained by mixing a conductive material and a binder with a positive electrode active material composed of a lithium transition metal composite oxide and adding an appropriate solvent to form a paste-like positive electrode mixture. It can be formed by coating and drying on the surface of the current collector and, if necessary, compressing it to increase the electrode density. As a lithium transition metal composite oxide serving as a positive electrode active material, LiCoO 2 can be used to form a 4V-class battery.
2 , a lithium composite oxide powder such as LiNiO 2 , LiMnO 2 , and LiMn 2 O 4 can be used. Among them, LiCoO 2 having a layered rock salt structure has a high raw material cost, but is easy to synthesize and handle, and is a positive electrode active material that can constitute a battery having good cycle characteristics and the like. On the other hand, LiMnO 2 having a layered rock salt structure and LiMn 2 O 4 having a spinel structure have low raw material costs and are advantageous in applications using a large amount of active materials, for example, in the case of a secondary battery used as a power source for an electric vehicle. It becomes something.
【００１９】導電材は、正極の電気伝導性を確保するた
めのものであり、カーボンブラック、アセチレンブラッ
ク、黒鉛等の炭素物質粉状体の１種又は２種以上を混合
したものを用いることができる。負極の場合と同様、結
着剤には、ポリフッ化ビニリデン等の含フッ素樹脂等を
用いることができ、また、これら活物質、導電材、結着
剤を分散させる溶剤としては、Ｎ−メチル−２−ピロリ
ドン等の有機溶剤を用いることができる。The conductive material is for ensuring the electrical conductivity of the positive electrode, and may be a mixture of one or more powdered carbon materials such as carbon black, acetylene black and graphite. it can. As in the case of the negative electrode, a fluorine-containing resin such as polyvinylidene fluoride can be used as the binder, and N-methyl- as a solvent for dispersing the active material, the conductive material, and the binder is used. An organic solvent such as 2-pyrrolidone can be used.
【００２０】非水電解液二次電池を形成する場合、上記
正極と負極とを分離し電解液を保持する目的で、正極と
負極との間にセパレータを挟装させる。このセパレータ
には、ポリエチレン、ポリプロピレン等の薄い微多孔膜
を用いることができる。非水電解液は、電解質としての
リチウム塩を有機溶媒に溶解させたものである。リチウ
ム塩は有機溶媒に溶解することによって解離し、リチウ
ムイオンとなって電解液中に存在する。使用できるリチ
ウム塩としては、ＬｉＢＦ4、ＬｉＰＦ6、ＬｉＣｌ
Ｏ4、ＬｉＣＦ3ＳＯ3、ＬｉＡｓＦ6、ＬｉＮ（ＣＦ3Ｓ
Ｏ2）2、ＬｉＮ（Ｃ2Ｆ5ＳＯ2）2等が挙げられる。これ
らのリチウム塩は、それぞれ単独で用いてもよく、ま
た、これらのもののうち２種以上のものを併用すること
もできる。When a non-aqueous electrolyte secondary battery is formed, a separator is interposed between the positive electrode and the negative electrode for the purpose of separating the positive electrode and the negative electrode and holding the electrolytic solution. As this separator, a thin microporous film such as polyethylene or polypropylene can be used. The non-aqueous electrolyte is obtained by dissolving a lithium salt as an electrolyte in an organic solvent. The lithium salt is dissociated by dissolving in an organic solvent, and is present in the electrolyte as lithium ions. Examples of usable lithium salts include LiBF 4 , LiPF 6 and LiCl
O 4 , LiCF 3 SO 3 , LiAsF 6 , LiN (CF 3 S
O 2 ) 2 and LiN (C 2 F 5 SO 2 ) 2 . Each of these lithium salts may be used alone, or two or more of these lithium salts may be used in combination.
【００２１】リチウム塩を溶解させる有機溶媒には、非
プロトン性の有機溶媒を用いる。例えば、環状カーボネ
ート、鎖状カーボネート、環状エステル、環状エーテル
あるいは鎖状エーテルの１種または２種以上からなる混
合溶媒を用いることができる。環状カーボネートの例示
としてはエチレンカーボネート、プロピレンカーボネー
ト、ブチレンカーボネート、ビニレンカーボネート等
が、鎖状カーボネートの例示としてはジメチルカーボネ
ート、ジエチルカーボネート、メチルエチルカーボネー
ト等が、環状エステルの例示としてはガンマブチルラク
トン、ガンマバレルラクトン等が、環状エーテルの例示
としてはテトラヒドロフラン、２−メチルテトラヒドロ
フラン等が、鎖状エーテルの例示としてはジメトキシエ
タン、エチレングリコールジメチルエーテル等がそれぞ
れ挙げられる。An aprotic organic solvent is used as the organic solvent for dissolving the lithium salt. For example, a mixed solvent composed of one or more of cyclic carbonate, chain carbonate, cyclic ester, cyclic ether or chain ether can be used. Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate.Examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.Examples of the cyclic ester include gamma butyl lactone and gamma. Examples of barrel lactone include cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran, and examples of chain ether include dimethoxyethane and ethylene glycol dimethyl ether.
【００２２】以上のもので構成される本発明の非水電解
液二次電池であるが、その形状は円筒型、積層型等、種
々のものとすることができる。いずれの形状を採る場合
であっても、正極および負極にセパレータを挟装させ電
極体とし、正極集電体および負極集電体から外部に通ず
る正極端子および負極端子までの間を集電用リード等を
用いて接続し、この電極体に非水電解液を含浸させ、電
池ケースに密閉して電池を完成させることができる。The non-aqueous electrolyte secondary battery of the present invention composed of the above-mentioned components can have various shapes such as a cylindrical type and a laminated type. Regardless of the shape used, a separator is sandwiched between the positive electrode and the negative electrode to form an electrode body, and a current collecting lead extends from the positive electrode current collector and the negative electrode current collector to the positive electrode terminal and the negative electrode terminal that lead to the outside. The electrode body is impregnated with a non-aqueous electrolyte and sealed in a battery case to complete the battery.
【００２３】[0023]
【実施例】〈炭素材Ａ〉メソフェーズピッチをアルゴン
雰囲気下において２８００℃の温度で熱処理をして球状
黒鉛を作製し、これを炭素材Ａとした。この炭素材Ａ９
５重量部に結着剤としてポリフッ化ビニリデン（ＰＶＤ
Ｆ）５重量部を混合し、溶剤としてＮ−メチル−２−ピ
ロリドン（ＮＭＰ）を添加し、ペースト状の合材を調製
した。この合材を銅箔集電体の表面に塗工して、炭素材
Ａを活物質とした電極を作製した。この電極と対極とな
る金属リチウムとの間にポリプロピレン製多孔性フィル
ムのセパレータを介して電気化学セルを構成させた。そ
して、０．１ｍＡ／ｃｍ2の定電流で電位が０Ｖとなる
まで炭素材Ａに充電し、その後０．１ｍＡ／ｃｍ2の定
電流で電位が１．０Ｖとなるまで炭素材Ａから放電させ
た。この時の充放電曲線を図１に示す。EXAMPLES <Carbon material A> A mesophase pitch was heat-treated at a temperature of 2800 ° C. in an argon atmosphere to produce spherical graphite, which was used as carbon material A. This carbon material A9
5 parts by weight of polyvinylidene fluoride (PVD) as a binder
F) 5 parts by weight were mixed, and N-methyl-2-pyrrolidone (NMP) was added as a solvent to prepare a paste-like mixture. This mixture was applied to the surface of a copper foil current collector to produce an electrode using carbon material A as an active material. An electrochemical cell was formed between the electrode and lithium metal as a counter electrode via a polypropylene porous film separator. Then, charges to the carbon material A at a constant current of 0.1 mA / cm 2 until the potential becomes 0V, is discharged from the carbon material A in the subsequent 0.1 mA / cm 2 constant current until the potential becomes 1.0V Was. FIG. 1 shows a charge / discharge curve at this time.
【００２４】図１が示すように、炭素材Ａの単位重量当
たりの充電容量は２９０ｍＡｈ／ｇであり、放電容量は
２６５ｍＡｈ／ｇであった。したがって電位１Ｖにおい
ては、２５ｍＡｈ／ｇの容量が残存していることが判
る。また、この炭素材Ａは、０．５Ｖ以上の電位では、
ごくわずかな容量の充放電しか可能でないことも判る。
上記と同じ要領で、０．１ｍＡ／ｃｍ2の定電流で電位
が０．５Ｖとなるまで炭素材Ａに充電し、その後０．１
ｍＡ／ｃｍ2の定電流で電位が１．０Ｖとなるまで炭素
材Ａから放電させた。この場合の充電容量は６ｍＡｈ／
ｇであり、放電容量は３ｍＡｈ／ｇであった。したがっ
て、炭素材Ａは、上述した高残存容量炭素材にはなり得
ないものであることが確認できた。As shown in FIG. 1, the charge capacity per unit weight of the carbon material A was 290 mAh / g, and the discharge capacity was 265 mAh / g. Therefore, it can be seen that at a potential of 1 V, a capacity of 25 mAh / g remains. Further, this carbon material A has a potential of 0.5 V or more.
It can also be seen that only a very small amount of charge / discharge is possible.
In the same manner as described above, the carbon material A is charged at a constant current of 0.1 mA / cm 2 until the potential becomes 0.5 V, and thereafter, the carbon material A is charged at 0.1 mA / cm 2.
The carbon material A was discharged at a constant current of mA / cm 2 until the potential reached 1.0 V. The charging capacity in this case is 6 mAh /
g, and the discharge capacity was 3 mAh / g. Therefore, it was confirmed that the carbon material A could not be the high residual capacity carbon material described above.
【００２５】〈炭素材Ｂ〉メソフェーズピッチをアルゴ
ン雰囲気下において１２００℃の温度で熱処理をして球
状黒鉛を作製し、これを炭素材Ｂとした。炭素材Ａの場
合と同様の方法で、この炭素材Ｂを活物質とする電極を
作製し、電気化学セルを構成させた。そして、炭素材Ａ
の場合と同様、０．１ｍＡ／ｃｍ2の定電流で電位が０
Ｖとなるまで炭素材Ｂに充電し、その後０．１ｍＡ／ｃ
ｍ2の定電流で電位が１．０Ｖとなるまで炭素材Ｂから
放電させた。この時の充放電曲線を図２に示す。<Carbon Material B> The mesophase pitch was heat-treated at 1200 ° C. in an argon atmosphere to produce spherical graphite, which was used as carbon material B. An electrode using the carbon material B as an active material was produced in the same manner as in the case of the carbon material A, and an electrochemical cell was formed. And carbon material A
As in the case of the above, the potential is 0 at a constant current of 0.1 mA / cm 2.
Charge to carbon material B until it reaches V, then 0.1 mA / c
The carbon material B was discharged at a constant current of m 2 until the potential reached 1.0 V. The charge / discharge curve at this time is shown in FIG.
【００２６】図２が示すように、炭素材Ｂの単位重量当
たりの充電容量は２００ｍＡｈ／ｇであり、放電容量は
１０５ｍＡｈ／ｇであった。充電容量、放電容量ともに
炭素材Ａと比べて小さいものとなっているが、炭素材Ｂ
は、電位１Ｖにおいて９５ｍＡｈ／ｇの容量が残存して
おり、１Ｖ以上の電位において可逆的に充放電可能な容
量は、炭素材Ａに比較してはるかに大きいことが判る。As shown in FIG. 2, the charging capacity per unit weight of the carbon material B was 200 mAh / g, and the discharging capacity was 105 mAh / g. Both the charge capacity and the discharge capacity are smaller than the carbon material A, but the carbon material B
Shows that a capacity of 95 mAh / g remains at a potential of 1 V, and that the capacity capable of reversibly charging and discharging at a potential of 1 V or more is much larger than that of carbon material A.
【００２７】炭素材Ａと同様、０．１ｍＡ／ｃｍ2の定
電流で電位が０．５Ｖとなるまで炭素材Ｂに充電し、そ
の後０．１ｍＡ／ｃｍ2の定電流で電位が１．０Ｖとな
るまで炭素材Ｂから放電させた。この場合の充電容量は
４８ｍＡｈ／ｇであり、放電容量は２３ｍＡｈ／ｇであ
った。したがって、この炭素材Ｂは、上述した高残存容
量炭素材に該当するものとなっていることが確認でき
た。[0027] As with the carbon material A, 0.1 mA / potential at a constant current of cm 2 is charged to the carbon material B until 0.5V, then the potential at a constant current of 0.1 mA / cm 2 is 1.0V Was discharged from the carbon material B until the following condition was reached. The charge capacity in this case was 48 mAh / g, and the discharge capacity was 23 mAh / g. Therefore, it was confirmed that this carbon material B corresponds to the above-mentioned high residual capacity carbon material.
【００２８】〈非水電解液二次電池の作製〉上記炭素材
Ａおよび炭素材Ｂを用いて、非水電解液二次電池を作製
した。まず、炭素材Ａと、高残存容量炭素材である炭素
材Ｂとを重量比７：３の割合で混合し負極活物質となる
炭素材料を調製した。この炭素材料９５重量部に、結着
剤としてＰＶＤＦ５重量部混合し、適量のＮＭＰを添加
してペースト状の負極合材を調製した。この負極合材
を、厚さ１５μｍの銅箔製集電体の両面に片面あたり８
０μｍの厚さで塗工してシート状の負極を作製した。<Preparation of Non-Aqueous Electrolyte Secondary Battery> A non-aqueous electrolyte secondary battery was prepared using the carbon materials A and B described above. First, carbon material A and carbon material B, which is a carbon material having a high residual capacity, were mixed at a weight ratio of 7: 3 to prepare a carbon material to be a negative electrode active material. 95 parts by weight of this carbon material was mixed with 5 parts by weight of PVDF as a binder, and an appropriate amount of NMP was added to prepare a paste-like negative electrode mixture. This negative electrode mixture was applied to both sides of a 15 μm thick copper foil current collector in an amount of 8
A sheet-shaped negative electrode was prepared by coating with a thickness of 0 μm.
【００２９】正極は、Ｌｉ2ＣＯ3とＣｏ3Ｏ4とを混合し
て大気中で９００℃の温度で焼成することにより得たＬ
ｉＣｏＯ2を正極活物質に用いた。このＬｉＣｏＯ2９０
重量部に、導電材としてグラファイト５重量部と、結着
剤としてＰＶＤＦ５重量部とを混合し、適量のＮＭＰを
添加してペースト状の正極合材を調製した。この正極合
材を、負極の場合と同様、厚さ２０μｍのアルミニウム
箔製集電体の両面に片面あたり１００μｍの厚さで塗工
してシート状の正極を作製した。The positive electrode was obtained by mixing Li 2 CO 3 and Co 3 O 4 and firing the mixture at a temperature of 900 ° C. in the air.
iCoO 2 was used as the positive electrode active material. This LiCoO 2 90
5 parts by weight of graphite as a conductive material and 5 parts by weight of PVDF as a binder were added to the parts by weight, and an appropriate amount of NMP was added to prepare a paste-like positive electrode mixture. This positive electrode mixture was coated on both surfaces of a 20-μm-thick aluminum foil current collector at a thickness of 100 μm per side, similarly to the case of the negative electrode, to produce a sheet-like positive electrode.
【００３０】上記正極および負極を、厚さ３０μｍのポ
リプロピレン製多孔性フィルムのセパレータを介して捲
回し、ロール状の電極体を形成させた。この電極体を１
８６５０型円筒電池ケースに組付け、電池を完成させ
た。なお、非水電解液には、エチレンカーボネートとジ
エチルカーボネートとを体積比１：１に混合した混合溶
媒にＬｉＰＦ6を１Ｍの濃度で溶解させたものを用い
た。このように作製した電池を実施例の二次電池とし
た。The positive electrode and the negative electrode were wound through a 30-μm-thick polypropylene porous film separator to form a roll-shaped electrode body. This electrode body is
The battery was completed by assembling it into an 8650 type cylindrical battery case. The non-aqueous electrolyte used was one in which LiPF 6 was dissolved at a concentration of 1 M in a mixed solvent obtained by mixing ethylene carbonate and diethyl carbonate at a volume ratio of 1: 1. The battery manufactured in this manner was used as the secondary battery of the example.
【００３１】実施例の二次電池と比較するために、高残
存容量炭素材を負極活物質に含まない二次電池を作製
し、比較例の二次電池とした。比較例の二次電池は、負
極活物質となる炭素材料に上記炭素材Ａのみを用いて作
製したものである。負極活物質となる炭素材料を除い
て、実施例の二次電池と同様の構成とした。 〈過放電後の容量変化の評価〉まず、実施例および比較
例の二次電池に対して、コンディショニングのため、環
境温度２０℃において、０．２ｍＡ／ｃｍ2の定電流で
上限電圧４．１Ｖまで充電を行い、０．２ｍＡ／ｃｍ2
の定電流で下限電圧３．０Ｖまで放電を行った。次い
で、環境温度２０℃において、１ｍＡ／ｃｍ2の定電流
で上限電圧４．１Ｖまで充電を行い、１ｍＡ／ｃｍ2の
定電流で下限電圧３．０Ｖまで放電を行う充放電サイク
ルを５サイクルまで実施した。そして５サイクル目の放
電容量を基準容量とした。For comparison with the secondary battery of the example, a secondary battery containing no high residual capacity carbon material in the negative electrode active material was produced, and was used as a secondary battery of the comparative example. The secondary battery of the comparative example was manufactured using only the carbon material A as the carbon material serving as the negative electrode active material. Except for a carbon material serving as a negative electrode active material, the configuration was the same as that of the secondary battery of the example. <Evaluation of change in capacity after overdischarge> First, the upper limit voltage of the secondary batteries of Examples and Comparative Examples was 4.1 V at a constant current of 0.2 mA / cm 2 at an ambient temperature of 20 ° C. for conditioning. Charge to 0.2 mA / cm 2
Was discharged to a lower limit voltage of 3.0 V at a constant current of. Then, at ambient temperature 20 ° C., was charged at a constant current of 1 mA / cm 2 until the upper limit voltage 4.1 V, the charging and discharging cycle to discharge at a constant current of 1 mA / cm 2 until the lower limit voltage 3.0V to 5 cycles Carried out. The discharge capacity at the fifth cycle was set as the reference capacity.
【００３２】基準容量測定後、放電状態にある実施例お
よび比較例の二次電池に対し、１ｋΩの抵抗を接続し、
定抵抗放電を１周間継続実施した。その後、基準容量測
定と同一条件で再び５サイクルの充放電を実施し、５サ
イクル目の放電容量を測定し、これを過放電後容量とし
た。過放電後の容量維持率（過放電後容量／基準容量）
を下記表１に示す。After the reference capacity measurement, a 1 kΩ resistor was connected to the secondary batteries of the embodiment and the comparative example in a discharged state.
The constant resistance discharge was continuously performed for one round. Thereafter, charge and discharge were repeated for 5 cycles under the same conditions as in the measurement of the reference capacity, and the discharge capacity at the 5th cycle was measured. Capacity retention rate after overdischarge (capacity after overdischarge / reference capacity)
Are shown in Table 1 below.
【００３３】[0033]
【表１】 上記表１から明らかなように、高残存容量炭素材を負極
活物質となる炭素材料に含む実施例の非水電解二次電池
は、過放電後においても大きな容量を維持しており、過
放電によっても特性変化の小さい二次電池であることが
確認できた。[Table 1] As is clear from the above Table 1, the nonaqueous electrolytic secondary battery of the embodiment including the high residual capacity carbon material in the carbon material serving as the negative electrode active material maintains a large capacity even after overdischarge. Thus, it was confirmed that the secondary battery had a small characteristic change.
【００３４】〈高温保存特性の評価〉過放電によっても
高い容量維持率を示す二次電池は、高温保存特性にも優
れているとの予見の下、実施例および比較例の二次電池
にて対して高温保存特性の評価を行った。まず、コンデ
ィショニングを行い、次いで５サイクルの充放電を行
い、基準容量を測定した。この方法については上記と同
様の条件にて行った。基準容量測定後、環境温度２０℃
において、１ｍＡ／ｃｍ2の定電流で上限電圧４．１Ｖ
まで充電を行い、満充電の状態で６０℃の恒温槽に１ヶ
月間保存した。保存後、環境温度２０℃で、１ｍＡ／ｃ
ｍ2の定電流で下限電圧３．０Ｖまで放電を行い、放電
容量を測定し、この放電容量を残存容量とした。その
後、基準容量測定と同一条件で再び５サイクルの充放電
を実施し、５サイクル目の放電容量を測定し、これを高
温保存後容量とした。高温保存後の容量残存率（残存容
量／基準容量）および高温保存後の容量維持率（高温保
存後容量／基準容量）を下記表２に示す。<Evaluation of High-Temperature Storage Characteristics> The secondary batteries of Examples and Comparative Examples were premised on that secondary batteries exhibiting a high capacity retention ratio even by overdischarging had excellent high-temperature storage characteristics. On the other hand, high-temperature storage characteristics were evaluated. First, conditioning was performed, followed by charging and discharging for 5 cycles, and the reference capacity was measured. This method was performed under the same conditions as described above. After measuring the reference capacity, the ambient temperature is 20 ° C
At a constant current of 1 mA / cm 2 and an upper limit voltage of 4.1 V
The battery was fully charged and stored in a thermostat at 60 ° C. for one month. After storage, at an ambient temperature of 20 ° C, 1 mA / c
Discharge was performed to a lower limit voltage of 3.0 V at a constant current of m 2 , the discharge capacity was measured, and this discharge capacity was defined as the remaining capacity. After that, charge and discharge were performed again for 5 cycles under the same conditions as in the measurement of the reference capacity, and the discharge capacity at the 5th cycle was measured. Table 2 below shows the remaining capacity ratio (remaining capacity / reference capacity) after high-temperature storage and the capacity retention rate (high-temperature storage capacity / reference capacity) after high-temperature storage.
【００３５】[0035]
【表２】 上記表２から明らかなように、高残存容量炭素材を負極
活物質となる炭素材料に含む実施例の非水電解二次電池
は、高温保存後の容量残存率および高温保存後の容量維
持率においても高い値を示し、高温保存によっても特性
変化の小さい二次電池であることが確認できた。[Table 2] As is clear from Table 2 above, the non-aqueous electrolytic secondary batteries of the examples including the high residual capacity carbon material in the carbon material serving as the negative electrode active material have a capacity retention rate after high-temperature storage and a capacity retention rate after high-temperature storage. , A high value was obtained, and it was confirmed that the secondary battery had a small characteristic change even when stored at high temperature.
【００３６】[0036]
【発明の効果】本発明の非水電解液二次電池は、負極活
物質となる炭素材料に、１．０Ｖ以上の高い負極電位に
おいても可逆的に放電なリチウムを残存させることがで
きる特性をもつ高残存容量炭素材を含んでなるように構
成したものである。このような構成としたことにより、
本発明の非水電解液二次電池は、電池電圧３Ｖを下回る
過放電状態となった後でも、再充電によって高い容量を
維持できる非水電解液となる。さらにまた、本発明の二
次電池は、高温保存特性にも優れた二次電池となる。The non-aqueous electrolyte secondary battery according to the present invention has a characteristic that a reversibly dischargeable lithium can be left in a carbon material as a negative electrode active material even at a high negative electrode potential of 1.0 V or more. It is configured to include a high residual capacity carbon material. With this configuration,
The non-aqueous electrolyte secondary battery of the present invention is a non-aqueous electrolyte capable of maintaining a high capacity by recharging even after an overdischarged state where the battery voltage is lower than 3 V. Furthermore, the secondary battery of the present invention is a secondary battery having excellent high-temperature storage characteristics.
【図面の簡単な説明】[Brief description of the drawings]
【図１】 高残存容量炭素材とならない炭素材料の充放
電曲線を示す。FIG. 1 shows a charge / discharge curve of a carbon material that does not become a high residual capacity carbon material.
【図２】 高残存容量炭素材となる炭素材料の充放電曲
線を示す。FIG. 2 shows a charge / discharge curve of a carbon material to be a high residual capacity carbon material.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 佐伯 徹 愛知県愛知郡長久手町大字長湫字横道41番 地の１株式会社豊田中央研究所内 Ｆターム(参考） 5H029 AJ02 AJ05 AK03 AL06 AM05 AM07 HJ18 HJ19 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tohru Saeki 41-Cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture F-term in Toyota Central Research Laboratory Co., Ltd. 5H029 AJ02 AJ05 AK03 AL06 AM05 AM07 HJ18 HJ19
Claims (1)
材料を負極活物質とする負極と、リチウム遷移金属複合
酸化物を正極活物質とする正極と、リチウム塩を有機溶
媒に溶解させた非水電解液とを有する非水電解液二次電
池であって、 前記炭素材料は、金属リチウムの電極電位を０Ｖとした
場合における０．５Ｖの電位から１．０Ｖの電位までの
間で、単位重量当たり２０ｍＡｈ／ｇ以上の可逆的充放
電が可能な高残存容量炭素材を含んでなることを特徴と
する非水電解液二次電池。1. A negative electrode using a carbon material capable of doping / dedoping lithium as a negative electrode active material, a positive electrode using a lithium transition metal composite oxide as a positive electrode active material, and a non-aqueous solution prepared by dissolving a lithium salt in an organic solvent. A non-aqueous electrolyte secondary battery having an electrolyte solution, wherein the carbon material has a unit weight between 0.5 V and 1.0 V when the electrode potential of metallic lithium is 0 V. A non-aqueous electrolyte secondary battery comprising a high residual capacity carbon material capable of reversible charge / discharge of 20 mAh / g or more per unit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10286989A JP2000113908A (en) | 1998-10-08 | 1998-10-08 | Non-aqueous electrolyte secondary battery |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10286989A JP2000113908A (en) | 1998-10-08 | 1998-10-08 | Non-aqueous electrolyte secondary battery |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2000113908A true JP2000113908A (en) | 2000-04-21 |
Family
ID=17711585
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10286989A Pending JP2000113908A (en) | 1998-10-08 | 1998-10-08 | Non-aqueous electrolyte secondary battery |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2000113908A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2003081697A1 (en) * | 2002-03-22 | 2003-10-02 | Lg Chem, Ltd. | Lithium secondary battery comprising overdischarge-preventing agent |
| US7695867B2 (en) | 2002-03-22 | 2010-04-13 | Lg Chem, Ltd. | Method for regulating terminal voltage of cathode during overdischarge and cathode active material for lithium secondary battery |
| US8835055B2 (en) | 2002-03-22 | 2014-09-16 | Lg Chem, Ltd. | Cathode active material for lithium secondary battery |
-
1998
- 1998-10-08 JP JP10286989A patent/JP2000113908A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2003081697A1 (en) * | 2002-03-22 | 2003-10-02 | Lg Chem, Ltd. | Lithium secondary battery comprising overdischarge-preventing agent |
| US7282300B2 (en) | 2002-03-22 | 2007-10-16 | Lg Chem, Ltd. | Lithium secondary battery comprising overdischarge-preventing agent |
| US7695867B2 (en) | 2002-03-22 | 2010-04-13 | Lg Chem, Ltd. | Method for regulating terminal voltage of cathode during overdischarge and cathode active material for lithium secondary battery |
| US8835055B2 (en) | 2002-03-22 | 2014-09-16 | Lg Chem, Ltd. | Cathode active material for lithium secondary battery |
| US9023525B2 (en) | 2002-03-22 | 2015-05-05 | Lg Chem, Ltd. | Cathode active material for lithium secondary battery |
| US9236610B2 (en) | 2002-03-22 | 2016-01-12 | Lg Chem, Ltd. | Cathode active material for lithium secondary battery |
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