JP2007095570A - Lithium secondary battery and negative electrode used in that battery - Google Patents

Lithium secondary battery and negative electrode used in that battery Download PDF

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JP2007095570A
JP2007095570A JP2005285282A JP2005285282A JP2007095570A JP 2007095570 A JP2007095570 A JP 2007095570A JP 2005285282 A JP2005285282 A JP 2005285282A JP 2005285282 A JP2005285282 A JP 2005285282A JP 2007095570 A JP2007095570 A JP 2007095570A
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negative electrode
active material
battery
secondary battery
lithium secondary
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Katsuichiro Sawa
勝一郎 澤
Kazuyuki Sato
和之 佐藤
Taizo Sunano
泰三 砂野
Maruo Jinno
丸男 神野
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Sanyo Electric Co Ltd
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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
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium secondary battery capable of improving by leaps and bounds cycle characteristics by suppressing cut-off of the conductive network in a negative electrode by improving an active material layer of the negative electrode, even if the negative electrode active material is separated from the negative electrode current collector. <P>SOLUTION: The lithium ion secondary battery comprises a negative electrode 2 including a negative electrode active material, a conductive agent, and a binder, a positive electrode 1 including a transition metal compound oxide as a positive electrode active material, and a non-aqueous electrolyte. As the negative electrode active material, an alloy containing Sn having a charging capacity of 1200 mAh/g or less is used, and as the conductive agent, carbon material having a particle size of primary particle of 100 nm or less is used. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、リチウム二次電池及びその電池に用いる負極に関するものである。   The present invention relates to a lithium secondary battery and a negative electrode used for the battery.

近年、携帯電話、ノートパソコン、ＰＤＡ等の移動情報端末の小型・軽量化が急速に進展しており、その駆動電源としての電池にはさらなる高容量化が要求されている。充放電に伴い、リチウムイオンが正、負極間を移動することにより充放電を行うリチウム二次電池は、高いエネルギー密度を有し、高容量であるので、上記のような移動情報端末の駆動電源として広く利用されている。今後、これらの移動情報端末の更なる小型化、高機能化により、電源であるリチウム二次電池への負荷が大きくなっていくことが予想され、リチウム二次電池の高エネルギー密度化への要求は非常に高いものになると考えられる。   In recent years, mobile information terminals such as mobile phones, notebook personal computers, and PDAs have been rapidly reduced in size and weight, and batteries as drive power sources are required to have higher capacities. A lithium secondary battery that performs charging / discharging by moving lithium ions between the positive and negative electrodes along with charging / discharging has a high energy density and high capacity. As widely used. In the future, with further miniaturization and higher functionality of these mobile information terminals, it is expected that the load on the lithium secondary battery as a power source will increase, and there is a demand for higher energy density of the lithium secondary battery. Will be very expensive.

ここで、電池の高エネルギー密度化には、活物質として、より大きなエネルギー密度を有する材料を用いることが有効な手段であり、リチウム二次電池の負極材料として、黒鉛を用いたものが実用化されている。しかしながら、黒鉛の理論容量は３７２ｍＡｈ／ｇであって、電池の高エネルギー密度化を十分に達成するには不十分であることから、黒鉛よりも理論容量が大きいリチウム金属を負極材料に用いることが考えられる。このように、リチウム二次電池の負極材料としてリチウム金属を用いると、高い充放電容量を得ることができるが、充電の際にリチウム金属が負極上にデンドライト状に析出するため、電池の内部短絡が生じ易いという問題を有していた。   Here, to increase the energy density of the battery, it is an effective means to use a material having a larger energy density as the active material, and the use of graphite as a negative electrode material for the lithium secondary battery has been put into practical use. Has been. However, the theoretical capacity of graphite is 372 mAh / g, which is insufficient to sufficiently achieve the high energy density of the battery. Therefore, it is necessary to use lithium metal having a theoretical capacity larger than that of graphite as the negative electrode material. Conceivable. As described above, when lithium metal is used as the negative electrode material of the lithium secondary battery, a high charge / discharge capacity can be obtained. However, since lithium metal is deposited in a dendrite shape on the negative electrode during charging, the battery is short-circuited internally. Has a problem that it is easy to occur.

そこで、最近のリチウム二次電池においては、デンドライトを抑制でき、且つ、高いエネルギー密度を有する負極活物質として、リチウムとの合金化反応によってリチウムを吸蔵するアルミニウム、錫、ケイ素が提案され、検討されている。
しかしながら、リチウム二次電池の負極活物質としてリチウムと合金化する材料を用いた場合、充放電時に負極活物質が膨張、収縮して、急激に体積変化する。このため、充放電サイクルの進行に伴い、負極活物質が微粉化し、負極集電体からの剥離を生じるという課題を有していた。 Therefore, in recent lithium secondary batteries, aluminum, tin, and silicon that occlude lithium by an alloying reaction with lithium have been proposed and studied as negative electrode active materials that can suppress dendrite and have a high energy density. ing.
However, when a material alloyed with lithium is used as the negative electrode active material of the lithium secondary battery, the negative electrode active material expands and contracts during charge and discharge, and the volume changes rapidly. For this reason, with the progress of the charge / discharge cycle, the negative electrode active material was pulverized and had a problem of causing peeling from the negative electrode current collector.

このようなことを考慮して、Ｓｎ合金、結着剤及び希釈溶媒を含むスラリーを負極集電体表面に塗工、乾燥した後、リチウム化合物の形成能の低い金属を電解めっきすることにより、負極集電体から負極活物質が剥離するのを抑制する方法が提案されている（下記特許文献１参照）。   In consideration of the above, by applying a slurry containing Sn alloy, a binder and a diluting solvent to the surface of the negative electrode current collector and drying, by electroplating a metal having a low lithium compound forming ability, A method for suppressing the separation of the negative electrode active material from the negative electrode current collector has been proposed (see Patent Document 1 below).

また、ケイ素および/珪素合金を含む活物質粒子と、銅などの導電性金属粉末との混合物とを集電体上に配置した後、不活性雰囲気化で焼結することによって融着効果を発揮させ、負極集電体と負極活物質との密着性を向上させて、負極活物質の剥離を抑制する方法が提案されている（下記特許文献２参照）。   In addition, a mixture of active material particles containing silicon and / or a silicon alloy and a conductive metal powder such as copper is placed on a current collector and then sintered in an inert atmosphere to achieve a fusion effect. Thus, a method has been proposed in which the adhesion between the negative electrode current collector and the negative electrode active material is improved to prevent peeling of the negative electrode active material (see Patent Document 2 below).

特開２００４−２４１３２９号公報JP 2004-241329 A

特開２００２−２６０６３７号公報Japanese Patent Laid-Open No. 2002-260637

しかしながら、上述した膨張、収縮の大きい活物質を用いた場合には、上記従来の発明を用いても、負極集電体から負極活物質が剥離するのを完全に抑制することが難く、しかも、一旦このような剥離が生じた場合には、負極内での導電性のネットワークが切断されてしまうため、サイクル特性が大きく低下するという課題を有していた。   However, when the active material having a large expansion and contraction is used, it is difficult to completely prevent the negative electrode active material from peeling from the negative electrode current collector, even if the above-described conventional invention is used. Once such delamination occurs, the conductive network in the negative electrode is cut, so that there is a problem that the cycle characteristics are greatly deteriorated.

したがって、本発明は、負極の活物質層を改良することにより、例え、負極集電体から負極活物質が剥離した場合であっても、負極内での導電性のネットワークが切断するのを抑制することにより、サイクル特性を飛躍的に向上させることができるリチウム二次電池を提供することを目的とする。   Therefore, the present invention suppresses the disconnection of the conductive network in the negative electrode by improving the active material layer of the negative electrode, for example, even when the negative electrode active material is separated from the negative electrode current collector. Accordingly, an object of the present invention is to provide a lithium secondary battery capable of dramatically improving cycle characteristics.

上記目的を達成するために、本発明のうち請求項１記載の発明は、負極活物質、導電剤、及び結着剤を含む負極と、正極活物質として遷移金属複合酸化物を含む正極と、非水電解質と、を備えたリチウムイオン二次電池であって、上記負極活物質として、理論充電容量が１２００ｍＡｈ／ｇ以下のＳｎを含む合金を用いると共に、上記導電剤として、一次粒子の粒径が１００ｎｍ以下の炭素材料を用いたことを特徴とする。   In order to achieve the above object, the invention according to claim 1 of the present invention includes a negative electrode including a negative electrode active material, a conductive agent, and a binder, a positive electrode including a transition metal composite oxide as a positive electrode active material, A lithium ion secondary battery comprising a non-aqueous electrolyte, wherein an alloy containing Sn having a theoretical charge capacity of 1200 mAh / g or less is used as the negative electrode active material, and the particle size of primary particles is used as the conductive agent. Is a carbon material having a thickness of 100 nm or less.

上記構成であれば、負極集電体と負極合剤層とが剥離した場合であっても、電池の構成圧だけで負極集電体と負極合剤層との間で集電可能な導電ネットワークを構築し、内部抵抗の上昇によるサイクル特性の低下を抑制することができる。これは、以下に示す理由による。
即ち、負極集電体と負極合剤層とが剥離した場合であっても、電池の構成圧だけで負極集電体と負極合剤層との間で集電可能な導電ネットワークを構築するためには、負極合剤層内に導電剤を配置することが必要である。 If it is the said structure, even if it is a case where a negative electrode collector and a negative mix layer peel, the electrically conductive network which can collect current between a negative electrode collector and a negative mix layer only with the structural pressure of a battery Thus, it is possible to suppress a decrease in cycle characteristics due to an increase in internal resistance. This is due to the following reason.
That is, in order to construct a conductive network capable of collecting current between the negative electrode current collector and the negative electrode mixture layer only with the constituent pressure of the battery even when the negative electrode current collector and the negative electrode mixture layer are separated. It is necessary to dispose a conductive agent in the negative electrode mixture layer.

しかしながら、負極合剤層内に導電剤を配置したとしても、負極活物質自体の導電性が悪いと、負極内に導電ネットワークを形成するのが困難である。そこで、上記構成の如く、負極活物質としてＳｎを含む合金を用いれば、当該合金はＳｉと比べて導電率が１０４倍程度大きいので（即ち、抵抗率が１０４倍程度小さいので）、負極活物質自体の導電性を向上させ、負極内に導電ネットワークを形成することができる。 However, even if a conductive agent is disposed in the negative electrode mixture layer, it is difficult to form a conductive network in the negative electrode if the negative electrode active material itself has poor conductivity. Therefore, when an alloy containing Sn is used as the negative electrode active material as in the above configuration, the alloy has a conductivity about 10 4 times larger than that of Si (that is, the resistivity is about 10 4 times smaller). The conductivity of the active material itself can be improved, and a conductive network can be formed in the negative electrode.

また、負極合剤層内に導電剤を配置し、且つ、負極活物質としてＳｎを含む合金を用いたとしても、導電剤の一次粒子の粒径が余り大きいと、比表面積が小さくなって、負極内に導電ネットワークを形成するのが困難である。そこで、上記構成の如く、導電剤の一次粒子の粒径を１００ｎｍ以下に規制すれば、導電剤の比表面積が大きくなって、Ｓｎを含む合金の表面に導電剤が均一に存在することになるので、導電剤としての効果が十分に発揮されて、負極内に優れた導電ネットワークを形成することができる。   Further, even if a conductive agent is arranged in the negative electrode mixture layer and an alloy containing Sn is used as the negative electrode active material, if the primary particle size of the conductive agent is too large, the specific surface area becomes small, It is difficult to form a conductive network in the negative electrode. Therefore, if the particle size of the primary particles of the conductive agent is regulated to 100 nm or less as in the above configuration, the specific surface area of the conductive agent is increased, and the conductive agent is uniformly present on the surface of the alloy containing Sn. Therefore, the effect as a conductive agent is sufficiently exhibited, and an excellent conductive network can be formed in the negative electrode.

加えて、負極合剤層内に一次粒子の粒径が１００ｎｍ以下の導電剤を配置し、且つ、負極活物質としてＳｎを含む合金を用いたとしても、合金活物質の膨張量が大きいと、充放電のたびに生じる膨張、収縮で導電ネットワークを破壊することがある。ここで、負極活物質としてＳｎを含む合金を用いる場合には、基本的に、理論充電容量と負極活物質の膨張量とは比例関係にある。そこで、理論充電容量を１２００ｍＡｈ／ｇ以下に規制すれば、充放電のたびに生じる膨張、収縮が規定量以下となるので、導電ネットワークを破壊するのを抑制することができる。   In addition, even if a conductive agent having a primary particle size of 100 nm or less is disposed in the negative electrode mixture layer and an alloy containing Sn is used as the negative electrode active material, the expansion amount of the alloy active material is large, The conductive network may be destroyed by the expansion and contraction that occurs at each charge and discharge. Here, when an alloy containing Sn is used as the negative electrode active material, the theoretical charge capacity and the expansion amount of the negative electrode active material are basically in a proportional relationship. Therefore, if the theoretical charge capacity is regulated to 1200 mAh / g or less, the expansion and contraction that occurs each time charging / discharging is less than the specified amount, so that it is possible to suppress the destruction of the conductive network.

このようにして、負極集電体から負極活物質が剥離した場合であっても、負極内での導電性のネットワークが切断するのを抑制することができるので、内部抵抗の上昇によるサイクル特性の低下を抑制することができる。   In this way, even when the negative electrode active material is peeled off from the negative electrode current collector, it is possible to suppress the disconnection of the conductive network in the negative electrode. The decrease can be suppressed.

尚、本明細書において、平均粒径とはメディアン径（Ｄ５０）をいうものとする。また、理論充電容量とは、負極活物質にＬｉを吸蔵させたときに、Ｌｉに対して電位が１ｍＶに低下するまでの単位質量当たりの容量をいう。   In addition, in this specification, an average particle diameter shall mean a median diameter (D50). The theoretical charge capacity refers to the capacity per unit mass until the potential is reduced to 1 mV with respect to Li when Li is occluded in the negative electrode active material.

更に、Ｓｎを含む合金としては、Ｓｎと他の１種以上の元素との固溶体、Ｓｎと他の１種以上の元素との金属間化合物、Ｓｎと他の１種以上の元素との共晶合金などが挙げられる。合金の作製方法としては、アーク溶解法、液体急冷法、メカニカルアロイング法、スパッタリング法、化学気相成長法、焼成法などが挙げられる。特に、上記液体急冷法としては、単ロール急冷法、双ロール急冷法、及びガスアトマイズ法、水アトマイズ法、ディスクアトマイズ法などの各種アトマイズ法が挙げられる。   Further, the alloy containing Sn includes a solid solution of Sn and one or more other elements, an intermetallic compound of Sn and one or more other elements, and a eutectic of Sn and one or more other elements. An alloy etc. are mentioned. Examples of the method for producing the alloy include an arc melting method, a liquid quenching method, a mechanical alloying method, a sputtering method, a chemical vapor deposition method, and a firing method. In particular, examples of the liquid quenching method include a single roll quenching method, a twin roll quenching method, and various atomizing methods such as a gas atomizing method, a water atomizing method, and a disk atomizing method.

加えて、本発明における導電剤の量は、負極合剤層の総質量に対して、０．１〜２０質量％、特に１〜１０質量％であることが好ましい。なぜなら、導電剤の量が余り少ないと、導電剤の添加効果を発揮することができない一方、導電剤の量が余り多いと、負極活物質の量が減少して電池の容量が低下すると共に、負極作製時にスラリーがゲル化するため、負極を円滑に作製することができないからである。   In addition, the amount of the conductive agent in the present invention is preferably 0.1 to 20% by mass, particularly 1 to 10% by mass with respect to the total mass of the negative electrode mixture layer. Because, if the amount of the conductive agent is too small, the addition effect of the conductive agent cannot be exhibited, while if the amount of the conductive agent is too large, the amount of the negative electrode active material is reduced and the capacity of the battery is reduced. This is because the slurry gels during the production of the negative electrode, and thus the negative electrode cannot be produced smoothly.

請求項２記載の発明は請求項１記載の発明において、前記炭素材料は無定形炭素であることを特徴とする。
炭素材料として無定形炭素を用いれば、無定形炭素は嵩高で比表面積が非常に大きいということから、請求項１記載の効果を一層発揮できる。 The invention according to claim 2 is the invention according to claim 1, wherein the carbon material is amorphous carbon.
If amorphous carbon is used as the carbon material, the amorphous carbon is bulky and has a very large specific surface area. Therefore, the effect of claim 1 can be further exhibited.

請求項３記載の発明は請求項２記載の発明において、前記無定形炭素がアセチレンブラック又はケッチェンブラックであることを特徴とする。
無定形炭素としては上記アセチレンブラック等が例示されるが、これに限定するものではなく、コークス等であっても良い。 The invention described in claim 3 is the invention described in claim 2, characterized in that the amorphous carbon is acetylene black or ketjen black.
The amorphous carbon is exemplified by the above acetylene black, but is not limited thereto, and may be coke or the like.

請求項４記載の発明は請求項１〜３記載の発明において、前記結着剤がポリフッ化ビニリデンであることを特徴とする。
上述の如く、負極活物質として膨張、収縮が大きい合金を使用する場合において、結着剤の機械的強度や密着性が高すぎると、負極活物質の膨張、収縮により負極集電体に大きな応力が加わって、負極集電体に皺が生じることがあり、その結果、サイクル特性の低下や、極板厚み増加などが発生する。そこで、負極の結着剤として一般的に用いられているフッ素樹脂やポリイミド樹脂のうちで、負極集電体にかける負担が少なく適度な密着性を有するポリフッ化ビニリデンを用いることで、負極集電体に大きな応力が加わることによる皺の発生を抑制できるので、サイクル特性の低下や、極板厚み増加を抑えることができる。 According to a fourth aspect of the present invention, in the first to third aspects of the present invention, the binder is polyvinylidene fluoride.
As described above, when an alloy having large expansion and contraction is used as the negative electrode active material, if the mechanical strength and adhesion of the binder is too high, a large stress is applied to the negative electrode current collector due to the expansion and contraction of the negative electrode active material. May cause wrinkles in the negative electrode current collector, resulting in a decrease in cycle characteristics and an increase in electrode plate thickness. Therefore, among the fluororesins and polyimide resins generally used as the binder for the negative electrode, the negative electrode current collector can be obtained by using polyvinylidene fluoride which has a small burden on the negative electrode current collector and has appropriate adhesion. Since generation | occurrence | production of the wrinkles by big stress being added to a body can be suppressed, the fall of cycling characteristics and the electrode plate thickness increase can be suppressed.

ここで、本発明において、負極結着剤の量は、負極合剤層の総質量の５％以上５０％以下、負極結着剤の占める体積が負極合剤層の総体積の５％以上５０％以下であることが好ましい。これは、負極結着剤量が合剤層の総質量の５％未満、負極結着剤の占める体積が合剤層の総体積の５％未満である場合には、負極活物質粒子に対して負極結着剤量が少な過ぎるために負極結着剤による電極内の密着性が不十分となる一方、負極結着剤量が負極合剤層の総質量の５０％を超えたり、負極結着剤の占める体積が負極合剤層の総体積の５０％を超えたりすると、電極内の抵抗が増加するため、初期の充電が困難になるからである。尚、上記負極合剤層の総体積とは、負極合剤層内に含まれる負極活物質や負極結着剤などの材料それぞれの体積を総和したものであり、負極合剤層内に空隙が存在する場合にはこの空隙が占める体積を含まないものとする。   Here, in the present invention, the amount of the negative electrode binder is 5% to 50% of the total mass of the negative electrode mixture layer, and the volume occupied by the negative electrode binder is 5% to 50% of the total volume of the negative electrode mixture layer. % Or less is preferable. When the amount of the negative electrode binder is less than 5% of the total mass of the mixture layer and the volume occupied by the negative electrode binder is less than 5% of the total volume of the mixture layer, As a result, the amount of the negative electrode binder is too small, resulting in insufficient adhesion within the electrode due to the negative electrode binder, while the amount of the negative electrode binder exceeds 50% of the total mass of the negative electrode mixture layer, or This is because if the volume occupied by the adhesive exceeds 50% of the total volume of the negative electrode mixture layer, the resistance in the electrode increases, so that initial charging becomes difficult. The total volume of the negative electrode mixture layer is the sum of the volumes of materials such as the negative electrode active material and the negative electrode binder contained in the negative electrode mixture layer, and there are voids in the negative electrode mixture layer. If present, it does not include the volume occupied by this void.

請求項５記載の発明は請求項１〜４記載の発明において、前記正負両極とこれら正負両極間に配置されたセパレータとを含む電極体の断面形状が略円形状を成すことを特徴とする。
上記構成の如く、電極体の断面形状が略円形状を成す、即ち、円筒型の電池に本発明を適用すると、当該電池においては極板の構成圧が大きく、しかも電極体全体に均一に構成圧が加わるので、導電ネットワークが効果的に維持され、サイクル特性の更なる向上を図ることができる。 According to a fifth aspect of the present invention, in the first to fourth aspects of the invention, an electrode body including the positive and negative electrodes and a separator disposed between the positive and negative electrodes has a substantially circular shape.
As in the above configuration, the cross-sectional shape of the electrode body is substantially circular, that is, when the present invention is applied to a cylindrical battery, the constituent pressure of the electrode plate is large in the battery, and the entire electrode body is configured uniformly. Since the pressure is applied, the conductive network is effectively maintained, and the cycle characteristics can be further improved.

また、上記目的を達成するために、本発明のうち請求項６記載の発明は、負極活物質、導電剤、及び結着剤を含むリチウムイオン二次電池用負極であって、上記負極活物質として、理論充電容量が１２００ｍＡｈ／ｇ以下のＳｎを含む合金を用いると共に、上記導電剤として、一次粒子の粒径が１００ｎｍ以下の炭素材料を用いたことを特徴とする。
上記構成であれば、請求項１記載の発明と同様の作用効果を奏する。 In order to achieve the above object, the invention according to claim 6 of the present invention is a negative electrode for a lithium ion secondary battery including a negative electrode active material, a conductive agent, and a binder, and the negative electrode active material As described above, an alloy containing Sn having a theoretical charge capacity of 1200 mAh / g or less is used, and a carbon material having a primary particle size of 100 nm or less is used as the conductive agent.
If it is the said structure, there exists an effect similar to the invention of Claim 1.

請求項７記載の発明は請求項６記載の発明において、前記炭素材料は無定形炭素であることを特徴とする。
上記構成であれば、請求項２記載の発明と同様の作用効果を奏する。 A seventh aspect of the invention is characterized in that, in the sixth aspect of the invention, the carbon material is amorphous carbon.
If it is the said structure, there exists an effect similar to the invention of Claim 2.

請求項８記載の発明は請求項７記載の発明において、前記無定形炭素がアセチレンブラック又はケッチェンブラックであることを特徴とする。
上記構成であれば、請求項３記載の発明と同様の作用効果を奏する。 The invention according to claim 8 is the invention according to claim 7, wherein the amorphous carbon is acetylene black or ketjen black.
If it is the said structure, there exists an effect similar to the invention of Claim 3.

請求項９記載の発明は請求項６〜８記載の発明において、前記結着剤がポリフッ化ビニリデンであることを特徴とする。
上記構成であれば、請求項４記載の発明と同様の作用効果を奏する。 A ninth aspect of the invention is characterized in that, in the sixth to eighth aspects of the invention, the binder is polyvinylidene fluoride.
If it is the said structure, there exists an effect similar to the invention of Claim 4.

（その他、電池の主要構成に関する事項）
（１）本発明のリチウム二次電池における負極活物質粒子の平均粒子径は、特に限定されないが、１００μｍ以下であることが好ましく、更に好ましくは５０μｍ以下、最も好ましくは１５μｍ以下である。これは、粒径の小さい活物質粒子を用いた場合、充放電でのリチウムの吸蔵、放出に伴う活物質粒子の体積の膨張、収縮の絶対量が小さくなるため、充放電時の電極内での活物質粒子間の歪みの絶対量も小さくなる。このため、負極結着剤の破壊が生じ難くなり、電極内の集電性の低下を抑制することができる結果、優れた充放電サイクル特性を得ることができるからである。 (Other matters concerning the main components of the battery)
(1) The average particle diameter of the negative electrode active material particles in the lithium secondary battery of the present invention is not particularly limited, but is preferably 100 μm or less, more preferably 50 μm or less, and most preferably 15 μm or less. This is because when an active material particle having a small particle size is used, the absolute amount of volume expansion and contraction of the active material particle due to insertion and extraction of lithium during charging and discharging is reduced. The absolute amount of distortion between the active material particles is also reduced. For this reason, it is difficult to cause destruction of the negative electrode binder, and it is possible to obtain excellent charge / discharge cycle characteristics as a result of suppressing the decrease in the current collecting ability in the electrode.

（２）本発明のリチウム二次電池における負極活物質粒子の粒度分布は、できる限り狭いことが好ましい。これは、幅広い粒度分布である場合、粒径が大きく異なる負極活物質粒子間において、リチウムの収蔵、放出に伴う体積の膨張、収縮の絶対量に大きな差が存在することになるため、負極合剤層内で歪みが生じる。このため、結着剤の破壊が生じて、電極内の集電性が低下することにより、充放電サイクル特性が低下するからである。 (2) The particle size distribution of the negative electrode active material particles in the lithium secondary battery of the present invention is preferably as narrow as possible. This is because, in the case of a wide particle size distribution, there is a large difference in the absolute amount of volume expansion and contraction associated with lithium storage and release between negative electrode active material particles having greatly different particle sizes. Distortion occurs in the agent layer. For this reason, it is because the destruction of the binder occurs and the current collecting property in the electrode is lowered, so that the charge / discharge cycle characteristics are lowered.

（３）本発明に用いる負極集電体としては、例えば、銅、ニッケル、鉄、チタン、コバルト等の金属またはこれらの組み合わせからなる合金のものを挙げることができる。特に，銅元素を含む金属箔が好ましく，更に好ましくは，銅箔または銅合金箔が挙げられる。 (3) Examples of the negative electrode current collector used in the present invention include metals such as copper, nickel, iron, titanium, cobalt, and alloys made of combinations thereof. In particular, a metal foil containing a copper element is preferable, and a copper foil or a copper alloy foil is more preferable.

（４）本発明のリチウム二次電池の正極活物質としては、ＬｉＣｏＯ２、ＬｉＮｉＯ２、ＬｉＭｎ２Ｏ４、ＬｉＭｎＯ２、ＬｉＣｏ０．５Ｎｉ０．５Ｏ２、ＬｉＮｉ０．７Ｃｏ０．２Ｍｎ０．１Ｏ２などのリチウム含有遷移金属酸化物や、ＭｎＯ２などのリチウムを含有していない金属酸化物が例示される。また、この他にも、リチウムを電気化学的に挿入，脱離する物質であれば，制限なく用いることができる。 (4) As the positive electrode active material of the lithium secondary battery of the present invention, LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , LiMnO 2 , LiCo 0.5 Ni 0.5 O 2 , LiNi 0.7 Co 0.2 Examples include lithium-containing transition metal oxides such as Mn 0.1 O 2 and metal oxides such as MnO 2 that do not contain lithium. In addition, any substance that electrochemically inserts and desorbs lithium can be used without limitation.

（５）本発明に用いる非水電解質の溶媒は、特に限定されるものではないが、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などの環状カーボネートや、ジメチルカーボネート、メチルエチルカーボネート、ジエチルカーボネートなどの鎖状カーボネートや、酢酸メチル、酢酸エチル、酢酸プロピル、プロピオン酸メチル、プロピオン酸エチル、γ−ブチロラクトンなどのエステル類や、１，２−ジメトキシエタン、１，２−ジエトキシエタン、テトラヒドロフラン、１，２−ジオキサン、２−メチルテトラヒドロフランなどのエーテル類や、アセトニトリル等のニトリル類や、ジメチルホルムアミド等のアミド類などを用いることができ、これらを単独又は複数組み合わせて使用することができる。特に環状カーボネートと鎖状カーボネートとの混合溶媒を好ましく用いることができる。 (5) The solvent of the nonaqueous electrolyte used in the present invention is not particularly limited, but cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, etc. Chain carbonates, esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1 , 2-dioxane, ethers such as 2-methyltetrahydrofuran, nitriles such as acetonitrile, amides such as dimethylformamide, etc. can be used alone or in combination. It can be. In particular, a mixed solvent of a cyclic carbonate and a chain carbonate can be preferably used.

（６）本発明に用いる非水電解質の溶質としては、特に限定されるものではないが、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＡｓＦ６などの化学式ＬｉＸＦｙ（式中、ＸはＰ、Ａｓ、Ｓｂ、Ｂ、Ｂｉ、Ａｌ、Ｇａ、又はＩｎであり、ＸがＰ、Ａｓ又はＳｂのときｙは６であり、ＸがＢ、Ｂｉ、Ａｌ、Ｇａ、又はＩｎのときｙは４である）で表されるものや、ＬｉＣＦ３ＳＯ３、ＬｉＮ(ＣＦ３ＳＯ２)２、ＬｉＮ(Ｃ２Ｆ５ＳＯ２)２、ＬｉＮ(ＣＦ３ＳＯ２)（Ｃ４Ｆ９ＳＯ２）、ＬｉＣ(ＣＦ３ＳＯ２)３、ＬｉＣ(Ｃ２Ｆ５ＳＯ２)３、ＬｉＣｌＯ４、Ｌｉ２Ｂ１０Ｃｌ１０、Ｌｉ２Ｂ１２Ｃｌ１２などのリチウム化合物を用いることができる。これらの中でも、特にＬｉＰＦ６を好ましく用いることができる。 (6) The solute of the nonaqueous electrolyte used in the present invention is not particularly limited, but is a chemical formula LiXF y such as LiPF 6 , LiBF 4 , LiAsF 6 (wherein X is P, As, Sb, B) , Bi, Al, Ga, or In, and when X is P, As, or Sb, y is 6, and when X is B, Bi, Al, Ga, or In, y is 4. And LiCF 3 SO 3 , LiN (CF 3 SO 2 ) 2 , LiN (C 2 F 5 SO 2 ) 2 , LiN (CF 3 SO 2 ) (C 4 F 9 SO 2 ), LiC (CF 3 SO Lithium compounds such as 2 ) 3 , LiC (C 2 F 5 SO 2 ) 3 , LiClO 4 , Li 2 B 10 Cl 10 , Li 2 B 12 Cl 12 can be used. Among these, LiPF 6 can be particularly preferably used.

（７）本発明に用いる非水電解質としては、ポリエチレンオキシド、ポリアクリロニトリルなどのポリマー電解質に電解液を含浸したゲル状ポリマー電解質や、ＬｉＩ、Ｌｉ３Ｎなどの無機固体電解質が挙げられる。本発明における非水電解質は、リチウムイオン導電性を発現させる溶質としてのリチウム化合物と、これを溶解、保持する溶媒が電池の充放電時あるいは保存時に分解しない限り、制約なく用いることができる。 (7) Examples of the nonaqueous electrolyte used in the present invention include gel polymer electrolytes in which a polymer electrolyte such as polyethylene oxide and polyacrylonitrile is impregnated with an electrolytic solution, and inorganic solid electrolytes such as LiI and Li 3 N. The non-aqueous electrolyte in the present invention can be used without limitation as long as the lithium compound as a solute that develops lithium ion conductivity and the solvent that dissolves and retains the lithium compound do not decompose during charge / discharge or storage of the battery.

本発明によれば、エネルギー密度の向上を図りつつ、充放電を繰り返すことにより、例え、負極活物質が剥離した場合であっても、構成圧のみで負極活物質の集電性が確保されるので、サイクル特性を飛躍的に向上させることができるという優れた効果を奏する。   According to the present invention, by repeating charging and discharging while improving the energy density, even if the negative electrode active material is peeled off, the current collecting property of the negative electrode active material is ensured only by the constituent pressure. As a result, the cycle characteristics can be remarkably improved.

以下、本発明をさらに詳細に説明するが、本発明は以下の最良の形態に何ら限定されるものではなく、その要旨を変更しない範囲において適宜変更して実施することが可能なものである。   Hereinafter, the present invention will be described in more detail. However, the present invention is not limited to the following best modes, and can be appropriately modified and implemented without departing from the scope of the present invention.

〔負極の作製〕
活物質としての平均粒径〔メディアン径（Ｄ５０）〕が５μｍのＳｎＣｏ（ＳｎとＣｏとの質量比が、７３．１：２２．１）と、導電剤としてのアセチレンブラックとを質量比で９５：５となるように秤量した後に両者を混合し、この混合物を９５質量部と、結着剤としてのポリフッ化ビニリデンを５質量部含む８質量％のＮ―メチルピロリドン溶液とを混合して負極合剤スラリーを得た。次に、この負極合剤スラリーを、負極集電体である電解銅箔（厚み１０μｍ）の片面に塗布し、乾燥した後、これを圧延した。最後に、得られたものを３０×３０ｍｍに切り抜いた後、集電タブとなるニッケル金属片を負極集電体の端部に取り付けることにより、負極を作製した。 (Production of negative electrode)
95 mass ratio of SnCo (mass ratio of Sn and Co: 73.1: 22.1) having an average particle size [median diameter (D50)] of 5 μm as an active material and acetylene black as a conductive agent is 95 A mixture of 95 parts by mass with this mixture and 8% by mass of an N-methylpyrrolidone solution containing 5 parts by mass of polyvinylidene fluoride as a binder A mixture slurry was obtained. Next, this negative electrode mixture slurry was applied to one side of an electrolytic copper foil (thickness 10 μm) as a negative electrode current collector, dried, and then rolled. Finally, the obtained product was cut out to 30 × 30 mm, and then a nickel metal piece serving as a current collecting tab was attached to the end of the negative electrode current collector to produce a negative electrode.

〔正極の作製〕
先ず、出発原料としてＬｉ２ＣＯ３とＣｏＣＯ３とを用い、Ｌｉ：Ｃｏの原子比が１：１となるように両者を秤量して乳鉢で混合した後、これを直径１７ｍｍの金型でプレスして加圧成形し、更に、空気雰囲気中にて８００℃で２４時間焼成することにより、ＬｉＣｏＯ２で表されるリチウムコバルト複合酸化物（リチウム遷移金属複合酸化物）の焼成体を得た。次に、この焼成体を乳鉢で粉砕し、平均粒径約２０μｍに調製した。 [Production of positive electrode]
First, Li 2 CO 3 and CoCO 3 were used as starting materials, both were weighed so that the atomic ratio of Li: Co was 1: 1, mixed in a mortar, and then pressed with a mold having a diameter of 17 mm. Then, it was pressure-molded, and further fired at 800 ° C. for 24 hours in an air atmosphere to obtain a fired body of lithium cobalt composite oxide (lithium transition metal composite oxide) represented by LiCoO 2 . Next, this fired body was pulverized in a mortar to prepare an average particle size of about 20 μm.

次いで、正極活物質としての上記ＬｉＣｏＯ２粉末と、正極導電剤としての炭素材料粉末と、正極結着剤としてのポリフッ化ビニリデンとを、分散媒としてのＮ−メチル−２−ピロリドンに加えた後、これらを混練することにより、正極合剤スラリーを作製した。尚、ＬｉＣｏＯ２粉末と炭素材料粉末とポリフッ化ビニリデンとの質量比は９４：３：３とした。 Next, after adding the LiCoO 2 powder as the positive electrode active material, the carbon material powder as the positive electrode conductive agent, and polyvinylidene fluoride as the positive electrode binder to N-methyl-2-pyrrolidone as the dispersion medium These were kneaded to prepare a positive electrode mixture slurry. The mass ratio of LiCoO 2 powder, carbon material powder, and polyvinylidene fluoride was 94: 3: 3.

この後、この正極合剤スラリーを、正極集電体であるアルミニウム箔の片面に塗布し、乾燥した後、これを圧延した。最後に、得られたものを２０×２０ｍｍに切り抜いた後、集電タブとなるアルミニウム金属片を正極集電体の端部に取り付けることにより、正極を作製した。   Thereafter, this positive electrode mixture slurry was applied to one surface of an aluminum foil as a positive electrode current collector, dried, and then rolled. Finally, the obtained product was cut out to 20 × 20 mm, and an aluminum metal piece serving as a current collecting tab was attached to the end of the positive electrode current collector to produce a positive electrode.

〔非水電解液の調製〕
先ず、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３：７で混合した混合溶媒に対し、ＬｉＰＦ６を１モル／リットルの割合で溶解させて非水電解液を調製した。 (Preparation of non-aqueous electrolyte)
First, LiPF 6 was dissolved at a ratio of 1 mol / liter to a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 3: 7 to prepare a non-aqueous electrolyte.

〔電池の作製〕
上記正極と上記負極との間に、ポリエチレン多孔質体から成るセパレータを挟み込んで電極体を作製した後、この電極体と非水電解液とを常温、常圧のアルゴン雰囲気下でアルミニウムラミネートからなる外装体内に挿入、注液してリチウム二次電池を作製した。
[Production of battery]
An electrode body is prepared by sandwiching a separator made of a polyethylene porous body between the positive electrode and the negative electrode, and then the electrode body and the non-aqueous electrolyte are made of an aluminum laminate in an argon atmosphere at normal temperature and normal pressure. The lithium secondary battery was produced by inserting and injecting the liquid into the exterior body.

ここで、上記リチウム二次電池の具体的な構造は、図１及び図２に示すように、正極１と負極２とセパレータ３とから成る電極体が、周縁同士がヒートシールされた閉口部７を備えるアルミラミネート外装体６の収納空間内に配置されている構造であり、また、正極集電タブ４と負極集電タブ５とが外方に突出配置されて、二次電池としての充電及び放電が可能な構造となっている。   Here, as shown in FIGS. 1 and 2, the specific structure of the lithium secondary battery is as follows. An electrode body composed of a positive electrode 1, a negative electrode 2, and a separator 3 has a closed portion 7 in which the peripheral edges are heat-sealed. The positive electrode current collection tab 4 and the negative electrode current collection tab 5 are projected outside and are arranged in the storage space of the aluminum laminate exterior body 6 comprising: It has a structure capable of discharging.

〔第１実施例〕
（実施例１）
実施例１としては、前記最良の形態で示した電池を用いた。
このようにして作製した電池を、以下、本発明電池Ａ１と称する。 [First embodiment]
Example 1
As Example 1, the battery shown in the best mode was used.
The battery thus produced is hereinafter referred to as the present invention battery A1.

（実施例２）
導電剤としてケッチェンブラック〔メディアン径（Ｄ５０）：１００ｎｍ〕を用いた以外は、実施例１と同様にして電池を作製した。
このようにして作製した電池を、以下、本発明電池Ａ２と称する。 (Example 2)
A battery was fabricated in the same manner as in Example 1 except that ketjen black (median diameter (D50): 100 nm) was used as the conductive agent.
The battery thus produced is hereinafter referred to as the present invention battery A2.

（比較例１）
導電剤として黒鉛粉末〔メディアン径（Ｄ５０）：３００ｎｍ〕を用いた以外は、実施例１と同様にして電池を作製した。
このようにして作製した電池を、以下、比較電池Ｚ１と称する。 (Comparative Example 1)
A battery was fabricated in the same manner as in Example 1 except that graphite powder (median diameter (D50): 300 nm) was used as the conductive agent.
The battery thus manufactured is hereinafter referred to as a comparative battery Z1.

（比較例２）
導電剤として黒鉛粉末〔メディアン径（Ｄ５０）：５μｍ〕を用い、且つ、負極活物質と黒鉛粉末との割合を質量比で８０：２０としたこと以外は、実施例１と同様にして電池を作製した。
このようにして作製した電池を、以下、比較電池Ｚ２と称する。 (Comparative Example 2)
A battery was fabricated in the same manner as in Example 1 except that graphite powder (median diameter (D50): 5 μm) was used as the conductive agent, and the ratio of the negative electrode active material to the graphite powder was 80:20 by mass ratio. Produced.
The battery thus produced is hereinafter referred to as a comparative battery Z2.

（比較例３）
導電剤として黒鉛粉末〔メディアン径（Ｄ５０）：２０μｍ〕を用い、且つ、負極活物質と黒鉛粉末との割合を質量比で８０：２０としたこと以外は、実施例１と同様にして電池を作製した。
このようにして作製した電池を、以下、比較電池Ｚ３と称する。 (Comparative Example 3)
A battery was prepared in the same manner as in Example 1 except that graphite powder [median diameter (D50): 20 μm] was used as the conductive agent and the ratio of the negative electrode active material and the graphite powder was 80:20 by mass ratio. Produced.
The battery thus produced is hereinafter referred to as comparative battery Z3.

（実験）
本発明電池Ａ１、Ａ２と比較電池Ｚ１〜Ｚ３との、初期効率（１サイクル目充放電効率）とサイクル特性とについて調べたので、その結果を表１に示す。尚、初期効率は下記数１により算出し、また、充放電条件は下述の通りである。また、サイクル特性試験においては、１サイクル目の放電容量の７０％に達したときにサイクル寿命とし、更に、表１においては、各電池のサイクル寿命は、電池Ａ１のサイクル寿命を１００とした指数で表している。 (Experiment)
Table 1 shows the results of the initial efficiency (first cycle charge / discharge efficiency) and cycle characteristics of the present invention batteries A1 and A2 and the comparative batteries Z1 to Z3. The initial efficiency is calculated by the following formula 1, and the charge / discharge conditions are as described below. In the cycle characteristic test, the cycle life is defined as 70% of the discharge capacity of the first cycle. Further, in Table 1, the cycle life of each battery is an index with the cycle life of the battery A1 as 100. It is represented by

［充放電条件］
・充電条件
１４ｍＡの電流で、電池電圧が４．２Ｖまで定電流充電を行なった後、電池電圧を４．２Ｖに保持しつつ、電流値が０．７ｍＡになるまで充電するという条件。
・放電条件
１４ｍＡの電流で、電池電圧が２．７５Ｖまで定電流放電を行なうという条件。
尚、充放電を行なう際の温度は２５℃である。 [Charging / discharging conditions]
-Charging conditions The condition of charging at a current of 14 mA and carrying out constant current charging to a battery voltage of 4.2 V, and then charging until the current value reaches 0.7 mA while holding the battery voltage at 4.2 V.
-Discharge condition The condition that constant current discharge is performed up to a battery voltage of 2.75 V at a current of 14 mA.
In addition, the temperature at the time of charging / discharging is 25 degreeC.

上記表１から明らかなように、導電剤の平均粒径が１００ｎｍ以下の本発明電池Ａ１、Ａ２は、導電剤の平均粒径が１００ｎｍを超える比較電池Ｚ１〜Ｚ３と比べて、初期効率を低下させることなく、サイクル特性が格段に向上していることが認められる。   As apparent from Table 1 above, the batteries A1 and A2 of the present invention having an average particle diameter of the conductive agent of 100 nm or less have a lower initial efficiency than the comparative batteries Z1 to Z3 in which the average particle diameter of the conductive agent exceeds 100 nm. It can be seen that the cycle characteristics are remarkably improved without causing them.

これは、本発明電池Ａ１、Ａ２の如く、導電剤の一次粒子の粒径を１００ｎｍ以下に規制すれば、導電剤の比表面積が大きくなって、Ｓｎ合金の表面に導電剤が均一に存在し、導電剤としての効果が十分に発揮されることになるので、例え、負極活物質が剥離した場合であっても、優れた導電ネットワークを維持することができる。これに対して、比較電池Ｚ１〜Ｚ３の如く、導電剤の一次粒子の粒径が１００ｎｍを超えていると、導電剤の比表面積が小さくなって、Ｓｎ合金の表面に導電剤が均一に存在しないので、負極活物質が剥離した場合には、優れた導電ネットワークを維持することができなくなるという理由によるものと考えられる。   This is because, as in the case of the present invention batteries A1 and A2, if the particle size of the primary particles of the conductive agent is regulated to 100 nm or less, the specific surface area of the conductive agent increases, and the conductive agent is uniformly present on the surface of the Sn alloy. Since the effect as the conductive agent is sufficiently exhibited, an excellent conductive network can be maintained even when the negative electrode active material is peeled off. On the other hand, when the particle size of the primary particles of the conductive agent exceeds 100 nm as in the comparative batteries Z1 to Z3, the specific surface area of the conductive agent is reduced and the conductive agent is uniformly present on the surface of the Sn alloy. Therefore, it is considered that when the negative electrode active material is peeled off, an excellent conductive network cannot be maintained.

〔第２実施例〕
（実施例１）
負極活物質として、平均粒径５μｍのＳｎＣｏＣ（質量比、Ｓｎ：Ｃｏ：Ｃ＝４２：３０：２８）を用いた以外は、第１実施例の実施例１と同様にして電池を作製した。
このようにして作製した電池を、以下、本発明電池Ｂ１と称する。 [Second Embodiment]
Example 1
A battery was fabricated in the same manner as in Example 1 of the first example, except that SnCoC (mass ratio, Sn: Co: C = 42: 30: 28) having an average particle diameter of 5 μm was used as the negative electrode active material.
The battery thus produced is hereinafter referred to as the present invention battery B1.

（実施例２）
負極活物質として、平均粒径５μｍのＳｉＳｎＣｕＣ（質量比、Ｓｉ：Ｓｎ：Ｃｕ：Ｃ＝２０：５２．５：１７．５：１０）を用いた以外は、第１実施例の実施例１と同様にして電池を作製した。
このようにして作製した電池を、以下、本発明電池Ｂ２と称する。 (Example 2)
Example 1 of the first example was used except that SiSnCuC (mass ratio, Si: Sn: Cu: C = 20: 52.5: 17.5: 10) having an average particle diameter of 5 μm was used as the negative electrode active material. A battery was produced in the same manner.
The battery thus produced is hereinafter referred to as the present invention battery B2.

（実施例３）
負極活物質として、平均粒径５μｍのＳｉＳｎＣｕＣＦｅ（質量比、Ｓｉ：Ｓｎ：Ｃｕ：Ｃ：Ｆｅ＝３２．２：３４．１：１０．６：１２．８：４．７）を用いた以外は、第１実施例の実施例１と同様にして電池を作製した。
このようにして作製した電池を、以下、比較電池Ｙと称する。 (Example 3)
Except that SiSnCuCFe (mass ratio, Si: Sn: Cu: C: Fe = 32.2: 34.1: 10.6: 12.8: 4.7) having an average particle diameter of 5 μm was used as the negative electrode active material. A battery was fabricated in the same manner as in Example 1 of the first example.
The battery thus produced is hereinafter referred to as comparative battery Y.

（実験）
本発明電池Ｂ１、Ｂ２及び比較電池Ｙにおける、初期効率とサイクル特性とについて調べたので、その結果を表２に示す。尚、表２においては、前記本発明電池Ａ１の結果についても示している。また、実験条件、実験内容及び表の標記方法については、前記第１実施例の実験と同様であり、更に、表２においては、各電池の負極における理論充電容量についても記載している。 (Experiment)
The initial efficiency and cycle characteristics of the present invention batteries B1 and B2 and the comparative battery Y were examined, and the results are shown in Table 2. In Table 2, the results of the battery A1 of the present invention are also shown. In addition, the experimental conditions, the experimental contents, and the table marking method are the same as those in the experiment of the first embodiment, and Table 2 also describes the theoretical charge capacity at the negative electrode of each battery.

上記表２から明らかなように、Ｓｎ合金の理論充電容量が１２００ｍＡｈ／ｇ以下の本発明電池Ａ１、Ｂ１、Ｂ２は、Ｓｎ合金の理論充電容量が１２００ｍＡｈ／ｇを超える比較電池Ｙと比べて、初期効率を低下させることなく、サイクル特性が格段に向上していることが認められる。   As apparent from Table 2 above, the present invention batteries A1, B1 and B2 having a theoretical charge capacity of Sn alloy of 1200 mAh / g or less are compared with the comparative battery Y in which the theoretical charge capacity of Sn alloy exceeds 1200 mAh / g. It can be seen that the cycle characteristics are significantly improved without lowering the initial efficiency.

これは、本発明電池Ａ１、Ｂ１、Ｂ２の如く、Ｓｎ合金の理論充電容量を１２００ｍＡｈ／ｇ以下に規制すれば、極板の膨張、収縮が小さくなるので、充放電を繰り返し行ったとしても、形成された導電ネットワークが破壊され難い。これに対して、比較電池Ｙの如く、Ｓｎ合金の理論充電容量が１２００ｍＡｈ／ｇを超えていれば、極板の膨張、収縮が大きくなるので、充放電を繰り返し行ったときに、形成された導電ネットワークが破壊され易いという理由によるものと考えられる。   This is because, if the theoretical charge capacity of the Sn alloy is regulated to 1200 mAh / g or less as in the present invention batteries A1, B1, B2, the expansion and contraction of the electrode plate are reduced, so even if charging and discharging are repeated, The formed conductive network is difficult to be destroyed. On the other hand, when the theoretical charging capacity of the Sn alloy exceeds 1200 mAh / g as in the comparative battery Y, the electrode plate expands and contracts, so that it is formed when charging and discharging are repeated. This is probably because the conductive network is easily destroyed.

尚、上記本発明電池Ａ１の負極を用いて、極板の膨張率と理論充電容量との関係を調べたので、その結果を図３及び表３に示す。図３及び表３から明らかなように、極板の膨張率と理論充電容量とは略比例関係にあるので、上記の如く理論充電容量を規制することにより、極板の膨張率が一義的に決定されるということが確認できる。   In addition, since the relationship between the expansion coefficient of the electrode plate and the theoretical charge capacity was examined using the negative electrode of the battery A1 of the present invention, the results are shown in FIG. As apparent from FIG. 3 and Table 3, since the expansion rate of the electrode plate and the theoretical charging capacity are in a substantially proportional relationship, the expansion rate of the electrode plate is uniquely determined by regulating the theoretical charging capacity as described above. It can be confirmed that it is determined.

〔第３実施例〕
（実施例）
結着剤としてのポリイミド用いた以外は、第１実施例の実施例１と同様にして電池を作製した。
このようにして作製した電池を、以下、本発明電池Ｃと称する。 [Third embodiment]
(Example)
A battery was produced in the same manner as in Example 1 of the first example except that polyimide was used as the binder.
The battery thus produced is hereinafter referred to as the present invention battery C.

（実験）
本発明電池Ｃにおける、初期効率とサイクル特性と下記数２で算出した極板膨張率とについて調べたので、その結果を表４に示す。尚、表４においては、前記本発明電池Ａ１の結果についても示している。また、実験条件、実験内容及び表の標記方法については、前記第１実施例の実験と同様である。 (Experiment)
Table 4 shows the results obtained by examining the initial efficiency, the cycle characteristics, and the electrode plate expansion coefficient calculated by the following formula 2 in the battery C of the present invention. Table 4 also shows the results of the battery A1 of the present invention. The experimental conditions, the experimental contents, and the table marking method are the same as in the experiment of the first embodiment.

上記表４から明らかなように、負極の結着剤としてポリフッ化ビニリデンを用いた本発明電池Ａ１は、負極の結着剤としてポリイミドを用いた本発明電池Ｃと比べて、初期効率とサイクル特性とは略同等であるが、極板膨張率が格段に小さくなっていることが認められる。   As is clear from Table 4 above, the present battery A1 using polyvinylidene fluoride as the binder for the negative electrode has an initial efficiency and cycle characteristics as compared with the present battery C using polyimide as the binder for the negative electrode. It is recognized that the electrode plate expansion coefficient is remarkably small.

これは、本発明電池Ａ１の如く、結着剤としてポリフッ化ビニリデンを用いると、当該結着剤は密着性が適度であるため、負極合剤層内での密着性を確保しつつ負極集電体に負荷がかかり過ぎるのを抑制できるのに対して、本発明電池Ｃの如く、結着剤としてポリイミドを用いると、負極集電体と負極合剤層の密着性が強すぎるため、負極集電体にかかる応力が大きくなって、皺が生じる結果、極板厚みが増加したものと考えられる。
尚、本発明電池Ａ１の如く極板厚みの増加を抑制することができれば、電池内部で短絡を抑えることができ、且つ、電池の体積エネルギー密度を向上させることができる。 This is because, when polyvinylidene fluoride is used as a binder as in the present invention battery A1, the binder has an appropriate adhesion, so that the negative electrode current collector is secured while ensuring the adhesion in the negative electrode mixture layer. While it is possible to suppress overloading of the body, when the polyimide is used as the binder as in the present invention battery C, the adhesion between the negative electrode current collector and the negative electrode mixture layer is too strong. It is considered that the electrode plate thickness increased as a result of the occurrence of wrinkles due to an increase in stress applied to the electric body.
If an increase in the electrode plate thickness can be suppressed as in the case of the present invention battery A1, a short circuit can be suppressed inside the battery, and the volume energy density of the battery can be improved.

〔第４実施例〕
（実施例１）
負極を４００×５２ｍｍに、正極を３４０×５０ｍｍに、それぞれ切り出し、且つ、これら正負両極をセパレータを介して、φ１．５ｍｍの巻き芯で円筒型に巻き取りそれを円筒型の外装体内に挿入した以外は、第１実施例の実施例１と同様にして電池を作製した。
このようにして作製した電池を、以下、本発明電池Ｄ１と称する。 [Fourth embodiment]
Example 1
The negative electrode was cut to 400 × 52 mm and the positive electrode was cut to 340 × 50 mm, and both the positive and negative electrodes were wound into a cylindrical shape with a φ1.5 mm core through a separator and inserted into a cylindrical outer package. A battery was fabricated in the same manner as in Example 1 of the first example except for the above.
The battery thus produced is hereinafter referred to as the present invention battery D1.

（実施例２）
φ２０ｍｍの巻き芯で円筒型に巻き取った電極体をプレスして、断面略楕円形状とし、これをアルミラミネートフィルムから成る外装体内に挿入した以外は、上記実施例１と同様にして電池を作製した。
このようにして作製した電池を、以下、本発明電池Ｄ２と称する。 (Example 2)
A battery was fabricated in the same manner as in Example 1 except that the electrode body wound into a cylindrical shape with a φ20 mm winding core was pressed into a substantially oval cross section and inserted into an exterior body made of an aluminum laminate film. did.
The battery thus produced is hereinafter referred to as the present invention battery D2.

（実験）
上記本発明電池Ｄ１、Ｄ２における、サイクル特性について調べたので、その結果を表５に示す。尚、充放電条件は下記の通りであり、表５においては、前記本発明電池Ａ１の結果についても示している。また、１サイクル目の放電容量の７０％に達したときのサイクル数をサイクル寿命とした。 (Experiment)
Since the cycle characteristics of the present invention batteries D1 and D2 were examined, the results are shown in Table 5. The charging / discharging conditions are as follows. Table 5 also shows the results of the battery A1 of the present invention. Further, the cycle number when the discharge capacity reached 70% of the first cycle was defined as the cycle life.

［充放電条件］
・充電条件
９００ｍＡの電流で、電池電圧が４．２Ｖまで定電流充電を行なった後、電池電圧を４．２Ｖに保持しつつ、電流値が１６０ｍＡになるまで充電するという条件。
・放電条件
１６０ｍＡの電流で、電池電圧が２．５Ｖまで定電流放電を行なうという条件。
尚、充放電を行なう際の温度は２５℃である。 [Charging / discharging conditions]
-Charging conditions The condition of charging at a current of 900 mA and carrying out constant-current charging to a battery voltage of 4.2 V, and then charging until the current value reaches 160 mA while holding the battery voltage at 4.2 V.
-Discharge condition The condition that constant current discharge is performed up to a battery voltage of 2.5 V at a current of 160 mA.
In addition, the temperature at the time of charging / discharging is 25 degreeC.

上記表５から明らかなように、円筒型の本発明電池Ｄ１は、単層平面型の本発明電池Ａ１及び薄型の本発明電池Ｄ２と比べて、サイクル特性が格段に向上していることが認められる。   As is clear from Table 5 above, it is recognized that the cycle type battery battery D1 has significantly improved cycle characteristics as compared with the single layer planar battery A1 and the thin battery B2. It is done.

これは、本発明電池Ｄ１においては、電極体全体に均一に構成圧がかかるので、充放電を繰り返しても導電ネットワークが効果的に維持されるのに対して、本発明電池Ａ１及び本発明電池Ｄ２においては、電極体全体に均一に構成圧がかからないため、充放電を繰り返した場合に、導電ネットワークの効果維持に関して若干劣るという理由によるものと考えられる。   In the present invention battery D1, since the constituent pressure is uniformly applied to the entire electrode body, the conductive network is effectively maintained even after repeated charging and discharging, whereas the present invention battery A1 and the present invention battery. In D2, since the component pressure is not uniformly applied to the entire electrode body, it is considered that the charge network is somewhat inferior in maintaining the effect of the conductive network when charging and discharging are repeated.

本発明は、例えば携帯電話、ノートパソコン、ＰＤＡ等の移動情報端末の駆動電源のみならず、電気自動車やハイブリッド自動車の車載用電源等の大型電池に適用することもできる。   The present invention can be applied not only to a driving power source of a mobile information terminal such as a mobile phone, a notebook computer, and a PDA, but also to a large battery such as an in-vehicle power source of an electric vehicle or a hybrid vehicle.

本発明にかかるリチウム二次電池の正面図である。It is a front view of the lithium secondary battery concerning this invention. 図１のＡ−Ａ線矢視断面図（充電前）である。It is AA arrow sectional drawing (before charge) of FIG. 極板の膨張率と理論充電容量との関係を示すグラフである。It is a graph which shows the relationship between the expansion coefficient of an electrode plate, and theoretical charge capacity.

符号の説明Explanation of symbols

１：正極
２：負極
３：セパレータ ６：アルミラミネート外装体 1: Positive electrode 2: Negative electrode 3: Separator 6: Aluminum laminate outer package

Claims (9)

負極活物質、導電剤、及び結着剤を含む負極と、正極活物質として遷移金属複合酸化物を含む正極と、非水電解質と、を備えたリチウムイオン二次電池であって、
上記負極活物質として、理論充電容量が１２００ｍＡｈ／ｇ以下のＳｎを含む合金を用いると共に、上記導電剤として、一次粒子の粒径が１００ｎｍ以下の炭素材料を用いたことを特徴とするリチウム二次電池。 A lithium ion secondary battery comprising a negative electrode including a negative electrode active material, a conductive agent, and a binder, a positive electrode including a transition metal composite oxide as a positive electrode active material, and a non-aqueous electrolyte,
Lithium secondary characterized in that an alloy containing Sn having a theoretical charge capacity of 1200 mAh / g or less is used as the negative electrode active material, and a carbon material having a primary particle size of 100 nm or less is used as the conductive agent. battery. 前記炭素材料は無定形炭素である、請求項１記載のリチウム二次電池。   The lithium secondary battery according to claim 1, wherein the carbon material is amorphous carbon. 前記無定形炭素がアセチレンブラック又はケッチェンブラックである、請求項２記載のリチウム二次電池。   The lithium secondary battery according to claim 2, wherein the amorphous carbon is acetylene black or ketjen black. 前記結着剤がポリフッ化ビニリデンである、請求項１〜３記載のリチウム二次電池。   The lithium secondary battery according to claim 1, wherein the binder is polyvinylidene fluoride. 前記正負両極とこれら正負両極間に配置されたセパレータとを含む電極体の断面形状が略円形状を成す、請求項１〜４記載のリチウム二次電池。   5. The lithium secondary battery according to claim 1, wherein a cross-sectional shape of an electrode body including the positive and negative electrodes and a separator disposed between the positive and negative electrodes is substantially circular. 負極活物質、導電剤、及び結着剤を含むリチウムイオン二次電池用負極であって、
上記負極活物質として、理論充電容量が１２００ｍＡｈ／ｇ以下のＳｎを含む合金を用いると共に、上記導電剤として、一次粒子の粒径が１００ｎｍ以下の炭素材料を用いたことを特徴とするリチウム二次電池用負極。 A negative electrode for a lithium ion secondary battery comprising a negative electrode active material, a conductive agent, and a binder,
Lithium secondary characterized in that an alloy containing Sn having a theoretical charge capacity of 1200 mAh / g or less is used as the negative electrode active material, and a carbon material having a primary particle size of 100 nm or less is used as the conductive agent. Battery negative electrode. 前記炭素材料は無定形炭素である、請求項６記載のリチウム二次電池用負極。   The negative electrode for a lithium secondary battery according to claim 6, wherein the carbon material is amorphous carbon. 前記無定形炭素がアセチレンブラック又はケッチェンブラックである、請求項７記載のリチウム二次電池用負極。   The negative electrode for a lithium secondary battery according to claim 7, wherein the amorphous carbon is acetylene black or ketjen black. 前記結着剤がポリフッ化ビニリデンである、請求項６〜８記載のリチウム二次電池用負極。   The negative electrode for a lithium secondary battery according to claim 6, wherein the binder is polyvinylidene fluoride.
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011014409A (en) * 2009-07-02 2011-01-20 Nippon Zeon Co Ltd Method of manufacturing electrode for lithium ion secondary battery, and composite particle
JP2012094490A (en) * 2010-09-30 2012-05-17 Daido Steel Co Ltd Lithium secondary battery anode active material and lithium secondary battery anode
KR20130035930A (en) * 2011-09-30 2013-04-09 다이도 스틸 코오퍼레이션 리미티드 Nagative electrode active material for lithium ion battery, and negative electrode for lithium ion battery using the same
JP5416128B2 (en) * 2008-10-31 2014-02-12 日立マクセル株式会社 Non-aqueous secondary battery

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5416128B2 (en) * 2008-10-31 2014-02-12 日立マクセル株式会社 Non-aqueous secondary battery
JP2011014409A (en) * 2009-07-02 2011-01-20 Nippon Zeon Co Ltd Method of manufacturing electrode for lithium ion secondary battery, and composite particle
JP2012094490A (en) * 2010-09-30 2012-05-17 Daido Steel Co Ltd Lithium secondary battery anode active material and lithium secondary battery anode
KR20130035930A (en) * 2011-09-30 2013-04-09 다이도 스틸 코오퍼레이션 리미티드 Nagative electrode active material for lithium ion battery, and negative electrode for lithium ion battery using the same

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