JP2004139961A - Battery manufacturing method and battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a battery which maintains a desired thickness and has excellent battery characteristics and which is superior in mass production nature with low cost and simplicity. <P>SOLUTION: The manufacturing method comprises a process of preliminary charging the uncharged battery in which a power generation element comprising a positive electrode, a negative electrode, a separator, and a non-aqueous electrolytic solution is housed in an outer package member, a process of pressurizing the battery of preliminary charging by a high pressure gas, and a process of finally charging the battery after pressurization. <P>COPYRIGHT: (C)2004,JPO

Description

【００９２】
前記表１から明らかなように予備充電、ガス加圧、さらに本充電の処理を施した実施例１の二次電池は、予備充電後にガス加圧を行わずに大気圧下で充電した比較例１の二次電池、予備充電および予備充電後のガス加圧を行わずに大気圧下で充電した比較例２の二次電池に比べ、本充電後の厚さが薄く、放電容量が大きいことが分かる。
【００９３】
また、充放電サイクルを繰り返した後も、予備充電、ガス加圧、さらに本充電の処理を施した実施例１の二次電池は、予備充電後にガス加圧を行わずに大気圧下で充電した比較例１の二次電池、予備充電および予備充電後のガス加圧を行わずに大気圧下で充電した比較例２の二次電池に比べ、厚さが薄く、放電容量維持率が高いことが分かる。
【００９４】
（実施例２）
実施例１と同様の帯状の正極、帯状の負極、セパレータ、電解液を用意した。つづいて、前記帯状の正極と帯状の負極を、厚さ２０μｍ、気孔率５０％、透気度３００秒／１００ｃｃのポリエチレン製微多孔膜からなるセパレータを介して、正極／セパレータ／負極／セパレータの順序に積層し、断面が扁平状の巻芯で渦巻き状に捲回し、さらに油圧式プレスで加熱圧縮し、成形して扁平状電極体（電極群）を作製した。
【００９５】
次いで、前記電極体をアルミニウム合金Ａ３００３のアルミニウム板をプレス成形により得た肉厚が２０μｍのアルミニウム缶に挿入した。つづいて、中心付近に負極端子がハーメティックシールされ、かつ電解液の注液孔が開口されたアルミニウム製蓋体を用意し、この負極端子に前記アルミニウム缶内の電極体の負極に取り付けた外部リードを接続した後、前記蓋体を前記アルミニウム缶の開口部に溶接して封止した。ひきつづき、減圧下で組成が実施例１と同様なエチレンカーボネート／メチルエチルカーボネート／ＬｉＰＦ_６＝３４．９／５３．１／１２（質量比）の混合液にトリオクチルフォスフェート（ＴＯＰ）を０．５重量％加えた電解液を前記蓋体の注液孔を通して注入することにより未初充電の角形非水電解液二次電池を組み立てた。
【００９６】
次いで、前記二次電池を２０℃の大気圧の乾燥空気中にて０．５Ｃ（３１０ｍＡ）で２時間予備充電を行なった。この予備充電で発生したガスの一部は、前記蓋体の注液孔を通して外部に排出された。この後、前記蓋体の注液孔を封じた。
【００９７】
次いで、前記予備充電を終了した前記二次電池を加圧容器に入れた後、室温にて圧縮された乾燥空気を送り込み、前記アルミニウム缶を介してゲージ圧で０．９ＭＰａにて１５時間加圧した。このとき、前記予備充電で発生したガスは電解液に溶け込まれると同時に、アルミニウム缶と電極体の間、および電極体の正負極の間に生じた微小な隙間が押し潰された。最後に、２０℃において０．２Ｃ（１２４ｍＡ）、４．２Ｖの条件で６時間本充電を行うことにより定格外寸法が厚さ外装部材のみアルミニウム缶を用いて前述した図６に示す構造の厚さ４．４ｍｍ、幅３０ｍｍ、高さ４８ｍｍで、０．２Ｃ放電容量が６２０ｍＡｈの角型非水電解液二次電池を製造した。
【００９８】
（実施例３）
アルミニウム缶内に電極体を挿入し、このアルミニウム缶の開口部にアルミニウム製蓋体を溶接し、減圧下で組成が実施例１と同様な電解液を前記蓋体の注液孔を通して注入し、この注液孔を封じた後、０．５Ｃ（３１０ｍＡ）で２時間予備充電を行なった以外、実施例２と同様な方法により定格外寸法が厚さ４．４ｍｍ、幅３０ｍｍ、高さ４８ｍｍで、容量が６２０ｍＡｈ（０．２Ｃ）の角形非水電解液二次電池を製造した。
【００９９】
（比較例３）
予備充電および予備充電後のガス加圧を行わずに、２０℃、０．２Ｃ（１２４ｍＡ）、４．２Ｖの条件で６時間本充電を行った以外、実施例２と同様な方法により定格外寸法が厚さ４．４ｍｍ、幅３０ｍｍ、高さ４８ｍｍで、容量が６２０ｍＡｈ（０．２Ｃ）の角形非水電解液二次電池を製造した。
【０１００】
（比較例４）
予備充電および予備充電後のガス加圧を行わずに、２０℃、０．２Ｃ（１２４ｍＡ）、４．２Ｖの条件で６時間本充電を行い、さらに本充電を終了した二次電池を加圧容器に入れた後、室温にて圧縮された乾燥空気を送り込み、前記アルミニウム缶を介してゲージ圧で０．９ＭＰａにて１５時間加圧した以外、実施例２と同様な方法により厚さ４．４ｍｍ、幅３０ｍｍ、高さ４８ｍｍで、容量が６２０ｍＡｈ（０．２Ｃ）の角形非水電解液二次電池を製造した。
【０１０１】
＜電池性能試験＞
得られた実施例２、３および比較例３、４の角形非水電解液二次電池について、本充電後の厚さおよび０．２Ｃ放電容量を測定した。また、初充電後の各二次電池について２０℃で１．０Ｃ／１．０Ｃの条件で充放電（充電条件；６２０ｍＡ、４．２Ｖ、３時間、放電条件；６２０ｍＡ、３．０Ｖカットオフ）した際の５００サイクル後の厚さ、放電容量および放電容量維持率を測定した。これらの結果を表２に示す。
【０１０２】
【表２】

【０１０３】
前記表２から明らかなように予備充電、ガス加圧、さらに本充電の処理を施した実施例２の二次電池は、予備充電および予備充電後のガス加圧を行わずに大気圧下で充電した比較例３の二次電池に比べ、本充電後の厚さが薄く、放電容量が大きいことが分かる。
【０１０４】
注液後に封口した状態で予備充電、ガス加圧、さらに本充電の処理を施した実施例３の電池は、注液孔を開放した状態で予備充電し、その後注液孔を封じ、ガス加圧し、本充電処理を施した実施例２の二次電池に比べやや厚さが厚くなり、放電容量が小さいが、定格を満足するものであった。
【０１０５】
本充電後にガス加圧した比較例４の二次電池は、本充電前に加圧した実施例２の二次電池に比べ厚さが厚くなってしまうことが分かる。
【０１０６】
また、充放電サイクルを繰り返した後も、予備充電、ガス加圧、さらに本充電の処理を施した実施例２、３の二次電池は、予備充電および予備充電後のガス加圧を行なわないで大気圧下で充電した比較例３および本充電後ガス加圧した比較例４の二次電池に比べて、厚さが薄く、放電容量維持率が高いことが分かる。
【０１０７】
なお、前述した実施例では予備充電を密封した状態で行なったが、工程が煩雑になるものの、予備充電を開放状態で行ない、その後の高圧力の気体による加圧工程で密封状態にしてもよい。
【０１０８】
（実施例４）
＜正極の作製＞
まず、リチウムコバルト酸化物（ＬｉＣｏＯ_２）粉末９０重量％に、アセチレンブラック５重量％と、ポリフッ化ビニリデン（ＰＶｄＦ）５重量％のジメチルフォルムアミド（ＤＭＦ）溶液とを加えて混合し、スラリーを調製した。このスラリーを厚さ１５μｍのアルミニウム箔からなる集電体の両面に塗布した後、乾燥し、プレスすることにより、正極層が集電体の両面に担持された構造の正極を作製した。なお、正極層の厚さは、片面当り６０μｍであった。
【０１０９】
＜負極の作製＞
炭素質材料として３０００℃で熱処理したメソフェーズピッチ系炭素繊維（粉末Ｘ線回折により求められる（００２）面の面間隔（ｄ_００２）が０．３３６ｎｍ）の粉末を９５重量％と、ポリフッ化ビニリデン（ＰＶｄＦ）５重量％のジメチルフォルムアミド（ＤＭＦ）溶液とを混合し、スラリーを調製した。このスラリーを厚さ１２μｍの銅箔からなる集電体の両面に塗布し、乾燥し、プレスすることにより、負極層が集電体に担持された構造の負極を作製した。なお、負極層の厚さは、片面当り５５μｍであった。
【０１１０】
なお、前記炭素繊維の（００２）面の面間隔ｄ_００２は粉末Ｘ線回折スペクトルから半値幅中点法によりそれぞれ求めた。この際、ローレンツ散乱等の散乱補正は行わなかった。
【０１１１】
＜セパレータ＞
厚さ２０μｍ、気孔率５０％、透気度３００秒／１００ｃｃのポリエチレン製微多孔膜からなるセパレータを用意した。
【０１１２】
＜非水電解液の調製＞
エチレンカーボネート（ＥＣ）／メチルエチルカーボネート（ＭＥＣ）／六フッ化リン酸リチウム（ＬｉＰＦ_６）＝３４．９／５３．１／１２（重量比）の混合液にビニレンカーボネート（ＶＣ）を０．５重量％加えた非水電解液を調製した。
【０１１３】
＜電極群の作製＞
前記正極の集電体に帯状アルミニウム箔（厚さ１００μｍ）からなる正極リードを超音波溶接し、前記負極の集電体に帯状ニッケル箔（厚さ１００μｍ）からなる負極リードを超音波溶接した後、前記正極及び前記負極をその間に前記セパレータを介して渦巻き状に捲回した後、扁平状に成形し、さらに油圧式プレスで加熱圧縮し、成形して扁平状電極体（電極群）を作製した。
【０１１４】
この電極体を肉厚が０．２５ｍｍのアルミニウム製の外装缶に挿入し、この外装缶の上端開口部に注液孔が開口された蓋体をレーザシーム溶接して前記電極体を密封した。
【０１１５】
次いで、前記外装缶内の電極群に８５℃で真空乾燥を１２時間施すことにより電極群および外装缶に含まれる水分を除去した。つづいて、前記組成の非水電解液を前記蓋体の注液孔を通して前記外装缶内の電極群に定量注液した後、注液孔を上向きにして不活性ガス中で０．５Ｃ（３１０ｍＡ）、３．７Ｖで２時間予備充電を行った。ここで、充電時に前記外装缶内に生成する反応ガスは前記蓋体の注液孔から外部に排出された。その後、例えばアルミニウム製の矩形板からなる封止部材を前記注液孔周囲の前記蓋体に対して例えば超音波溶接により接合し、前記注液孔を気密封止した。
【０１１６】
次いで、予備充電を終了した前記二次電池を、加圧容器に入れた後、室温にて圧縮された乾燥空気を送り込み、前記蓋体付外装缶を０．５ＭＰａ（ゲージ圧）で２４時間ガス加圧を行なった。これにより、予備充電で発生したガスを電解液に溶け込ますと同時に、外装缶と電極群の間、および電極群の正負極、セパレータの間に生じた微小な隙間を押し潰した。最後に、２０℃において、０．２Ｃ（１２４ｍＡ）、４．２Ｖの条件で１０時間本充電を行うことにより定格外寸法が厚さ４．４ｍｍ、幅３０ｍｍ、高さ４８ｍｍで、容量が６２０ｍＡｈ（０．２Ｃ）の角形非水電解液二次電池を製造した。
【０１１７】
（実施例５）
予備充電後のガス加圧を５ＭＰａ（ゲージ圧）で１２時間行なった以外、実施例４と同様な方法により角型非水電解液二次電池を製造した。
【０１１８】
（実施例６）
予備充電後のガス加圧を１０ＭＰａ（ゲージ圧）で４時間行なった以外、実施例４と同様な方法により角型非水電解液二次電池を製造した。
【０１１９】
（実施例７）
予備充電後のガス加圧を１５ＭＰａ（ゲージ圧）で１時間行なった以外、実施例４と同様な方法により角型非水電解液二次電池を製造した。
【０１２０】
（比較例５）
予備充電後にガス加圧を行わない以外、実施例４と同様な方法により角型非水電解液二次電池を製造した。
【０１２１】
＜電池性能試験＞
得られた実施例４〜７、比較例１の角型非水電解液二次電池について、本充電後の厚さおよび０．２Ｃ放電容量を測定した。また、本充電後の各二次電池について２０℃で１．０Ｃ／１．０Ｃの条件で充放電（充電条件；６２０ｍＡ、４．２Ｖ、３時間、放電条件；６２０ｍＡ、３．０Ｖカットオフ）した際の５００サイクル後の放電容量維持率（初期放電容量に対する維持率）を測定した。それらの結果を下記表３に示す。
【０１２２】
【表３】

【０１２３】
表３から明らかなように予備充電後にガス加圧した後本充電処理した実施例４〜７の二次電池は、予備充電後のガス加圧を行なわないで充電した比較例５の二次電池に比べ、本充電後の厚さが薄く、放電容量が大きいことがわかる。
【０１２４】
また、２０℃で１Ｃ／１Ｃの充放電サイクルを５００サイクル繰り返した後も、厚さが薄く、放電容量維持率が高いことがわかる。
【０１２５】
【発明の効果】
以上詳述したように、本発明によれば予備充電後にガス加圧し、さらに本充電処理することにより、厚さが薄く、初期及び充放電サイクルの繰返し後の放電容量が大きい電池の製造方法および電池を提供することができる。
【図面の簡単な説明】
【図１】本発明の薄形非水電解液二次電池の製造工程を示す斜視図。
【図２】図１のＩＩ−ＩＩ線に沿う断面図。
【図３】本発明の薄形非水電解液二次電池の製造工程を示す斜視図。
【図４】図３のＶＩ−ＶＩ線に沿う断面図。
【図５】本発明の薄形非水電解液二次電池の製造工程を示す斜視図。
【図６】本発明の外装部材にアルミニウム製の外装缶を用いた角形非水電解液二次電池を示す部分切欠斜視図。
【符号の説明】
３、２６…正極、４、２５…セパレータ、７、２４…負極、８、２３…電極体、９、１０…外部リード、１１…外装フィルム用素材、１２…カップ、１６…接着性絶縁フィルム、１７ａ、１７ｂ、１７ｃ…シール部、１８…外装フィルム、２１…アルミニウム製の外装缶、２８…蓋体、２９…注液孔、３０…封止部材、３１…負極端子。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a battery in which a power generation element is sealed inside an exterior member, and a battery.
[0002]
[Prior art]
With advances in electronic devices such as mobile phones and personal computers, batteries used in these devices have been constantly required to be smaller, lighter, have higher capacity, have higher performance, and have lower costs. For this reason, in the battery, the electrode material such as the positive electrode active material and the negative electrode active material is changed to one having a higher energy density, the separator is made thinner, the thickness of the battery outer can is reduced, or the outer member is used. Improvements have been made such as changing the material of the metal can from iron to aluminum, and further changing the exterior member to a metal can and using a bag-shaped exterior film consisting of a laminated film with aluminum foil interposed between resin films. Was.
[0003]
However, conversely, due to these improvements, the amount of gas generated during initial charging increased, and the free space inside the battery decreased, so that the internal pressure increased, the electrodes were twisted, and the exterior member was made of aluminum or a laminated film. Due to the low-elasticity material being replaced, the battery swells at the time of initial charging due to the fact that the battery is easily deformed, and a problem that the desired thickness cannot be maintained.
[0004]
In order to solve such a problem, for example, Patent Literature 1 discloses a method of manufacturing a sealed rectangular battery in which initial charging and discharging are performed while pressing a wide surface of a metal can inward from both left and right sides. .
[0005]
Further, Patent Document 2 discloses a method of manufacturing a rectangular nonaqueous electrolyte secondary battery in which pressing is performed from the outside until after initial charging.
[0006]
[Patent Document 1]
JP-A-8-293320
[0007]
[Patent Document 2]
JP-A-11-339853
[0008]
[Problems to be solved by the invention]
However, in any of the methods for manufacturing a prismatic non-battery described in Patent Documents 1 and 2, the apparatus becomes complicated, mass production is inferior, and the plate is pressed by a press, so that the electrode plate is easily damaged and characteristics are easily deteriorated. And so on.
[0009]
An object of the present invention is to provide a method and a battery for manufacturing a battery which is inexpensive, simple, and has excellent mass productivity while maintaining a desired thickness and having excellent battery characteristics.
[0010]
[Means for Solving the Problems]
The method for manufacturing a battery according to the present invention includes a step of precharging an uncharged battery containing a power generation element having a positive electrode, a negative electrode, a separator and a nonaqueous electrolyte in an exterior member,
Pressurizing the precharged sealed battery with a high-pressure gas;
A step of fully charging the pressurized battery; and
It is characterized by including.
[0011]
The battery according to the present invention is characterized in that an uncharged battery containing a power generating element having a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte in an exterior member is pressurized with a high-pressure gas after preliminary charging, and further fully charged. It is a feature.
[0012]
In the method for producing a battery according to the present invention, the exterior member is a metal exterior can attached with a lid having a liquid injection hole, and the preliminary charging is performed by passing the nonaqueous electrolyte through the liquid injection hole. It is preferable that the liquid injection hole is opened after the liquid is injected into the outer can, and that the liquid injection hole is directed upward at a voltage of 3.6 to 3.9 V.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a method of manufacturing a thin battery (for example, a thin nonaqueous electrolyte secondary battery) using a bag-shaped exterior film made of a laminated film in which a metal sheet and a resin film are laminated as an exterior member according to the present invention will be described. This will be described with reference to FIG.
[0014]
(First step)
First, the positive electrode active material layer containing the active material and the binder was supported on both sides of the current collector, for example, the positive electrode, the separator, the negative electrode active material layer containing the active material and the binder was supported on both sides of the current collector, for example The negative electrode and the separator are spirally wound to produce a substantially cylindrical object. At the time of this winding, external leads are connected to the positive and negative electrodes by, for example, welding.
[0015]
Next, the obtained cylindrical electrode product is heated and pressed to form a positive electrode in which the positive electrode active material layer 1 containing the active material and the binder shown in FIGS. A flat electrode body (electrode group) 8 having 3, a separator 4, and a negative electrode 7 in which a negative electrode active material layer 5 containing an active material and a binder is supported on both surfaces of a current collector 6 is produced. External leads 9 and 10 connected to the positive and negative electrodes 3 and 7, respectively, extend outside from the same side surface of the electrode body 8.
[0016]
The heat-press molding is desirably performed at a temperature of 60 to 100 ° C, more preferably 80 to 95 ° C, and a pressure of 1 to 3 MPa, more preferably 1.2 to 2.2 MPa.
[0017]
(2nd process)
A two-fold cup-type exterior material film material having a dimension slightly longer than the long side of the electrode body and having a length, for example, twice as long as the short side is prepared, and as shown in FIGS. The flat electrode body 8 is housed in a cup 12 formed by drawing of the exterior film material 11 such that the side surface opposite to the external leads 9 and 10 is located at a bent portion of the material. The exterior film material 11 is composed of a laminated film in which a sealant film 13, an aluminum or aluminum alloy sheet 14, and a rigid resin film 15 are laminated in this order from the inner surface side where the electrode body 8 is located. When the electrode body 8 is housed, the adhesive insulating film 16 is placed between the upper and lower surfaces of the external leads 9 of the positive electrode and the heat-fusible resin film (sealant film) 13 of the exterior film material 11 and the negative electrode. It is interposed between the upper and lower surfaces of the external lead 10 and the sealant film 13 of the exterior film material 11. Here, at least portions (not shown) of the exterior film material 11, the adhesive insulating film 16, the positive external lead 9 and the negative external lead 10 which are heat-sealed in a later process are not shown. The plasma irradiation treatment is performed in advance. Thereafter, at the left end of the exterior film material 11 corresponding to the long side of the electrode body 8, the sealant films are sealed by heat-sealing the sealant films together to form a seal portion 17c. Further, at the end of the material 11 corresponding to the extension side of the external leads 9 and 10, the sealant films 13 are bonded to each other, the sealant film 13 / the adhesive insulating film 16 / the adhesive insulating film 16 / the sealant film 13 are bonded. The sealing portion 17b is formed by thermally fusing the conductive insulating film 16 and the external leads 9 and 10 to each other.
[0018]
In the plasma surface treatment, when extremely high-energy (high-activity) plasma, which has been separated into positive ions and electrons and ionized, is applied to a substance having a dirty surface, the dirt attached to the material surface and the plasma particles are combined. To remove dirt and clean the surface. In addition, the chemical bond on the surface of the substance changes, and a hydrophilic group such as an OH group that is easily compatible with the liquid is generated, so that the substance is easily bonded. In addition, the plasma particles decompose the low-activity molecular layer on the surface, and a highly active oxide layer appears on the surface to improve wettability. Furthermore, the surface of the plasma particles has irregularities at the atomic level. Therefore, when the surface of the resin or metal is subjected to the plasma irradiation treatment, the wettability of the surface of the object to be treated is improved, and the contact angle with water is reduced. As a result, the adhesive force between the metal subjected to the plasma surface treatment and the resin and between the resin and the resin is improved.
[0019]
In the plasma surface treatment, a commercially available plasma irradiator (for example, trade name: ST-7000, manufactured by Keyence Corp.) is used for several seconds (for example, 1 to 3 seconds) at a distance of 5 mm to 50 mm from the sample in air. By irradiating the plasma, the above-described effects can be obtained.
[0020]
(3rd step)
A non-aqueous electrolyte is injected through the unsealed portion (right end) of the exterior film material 11, and a portion of the surface of the unsealed portion near the right end of the electrode body 8 whose surface has been subjected to plasma irradiation processing in advance. The sealant films 13 are heat-sealed. Thereafter, the extra non-aqueous non-aqueous electrolyte secondary battery 19 in which the flat electrode body 8 is sealed with the bag-shaped external film 18 shown in FIG. Make it.
[0021]
In the above step, it is preferable to seal the inside of the bag-shaped exterior film material in a state where the inside of the bag is degassed under reduced pressure in advance. Specifically, 1) a method in which the electrode body is housed in a bag-shaped exterior film material, and the exterior film material is degassed under reduced pressure, and then a non-aqueous electrolyte is injected and sealed as it is. 2) The electrode body After the non-aqueous electrolyte is stored in a bag-like material for an exterior film in an air atmosphere, the air is degassed under reduced pressure and sealed.
[0022]
(4th process)
The secondary battery is housed in a pressure vessel (not shown), and the flat non-aqueous electrolyte is impregnated into the flat electrode body in the secondary battery by performing a pressure treatment. The next battery is manufactured.
[0023]
The pressurizing process may employ a method of supplying a pressurized medium into a pressure vessel. As this pressurized medium, for example, any one of carbon dioxide, nitrogen, dry air, and argon can be used. Further, water can be used as the pressurizing medium. However, it is preferable to use a gas as the pressurizing medium, particularly a gas containing no water, from the viewpoint of preventing moisture from entering the inside of the bag-shaped outer layer film. When carbon dioxide gas is used as the gas, the carbon dioxide gas penetrates into the bag-shaped exterior film by pressurization to form a more stable solid electrolyte interface (SEI), and the cycle characteristics of the non-aqueous electrolyte are reduced. This is effective because effects such as improvement can be expected.
[0024]
In the pressure treatment using the pressure vessel, it is preferable to increase the pressing force because the impregnation rate of the nonaqueous electrolyte into the electrode body can be increased in proportion to the pressure difference. However, it is necessary to increase the thickness of the pressure vessel and strengthen the structural reinforcement with the increase in the pressing force. For this reason, it is preferable that the applied pressure be 0.3 to 1.0 MPa as a gauge pressure.
[0025]
If the impregnation of the non-aqueous electrolyte into the electrode body is incomplete, charging is performed only at the impregnated electrode body part in an initial charging step (preliminary charging and main charging) described later. Therefore, compared to the so-called fully impregnated state in which the entire space including the space between the electrodes is completely impregnated with the non-aqueous electrolyte, the charged portion is made at a substantially higher rate, and the discharge capacity is small. Thus, various characteristics of the battery including the cycle characteristics are deteriorated. In addition, variations in the impregnation state result in large variations in discharge capacity and other characteristics. Therefore, the battery must be fully impregnated when initially charged.
[0026]
Here, by measuring the capacitance and / or impedance between the positive and negative electrodes of the battery, the impregnation state of the electrolytic solution can be determined nondestructively. This is because the relative permittivity of the non-aqueous electrolyte is orders of magnitude greater than the relative permittivity of the voids, so that the non-aqueous electrolyte is impregnated into the pores of the electrode group and replaced with the non-aqueous electrolyte, It is based on an order of magnitude increase in the capacitance between the electrodes of the electrode group. Similarly, the impedance of the non-aqueous electrolyte is significantly lower than the impedance of the gap, so that the non-aqueous electrolyte is impregnated into the gaps of the electrode group and replaced with the non-aqueous electrolyte, so that the gap between the electrodes of the electrode group is reduced. Is significantly lower.
[0027]
Specifically, the determination of the fully impregnated state of the battery can be performed by detecting the capacitance and / or impedance of the battery and determining whether or not the capacitance and / or impedance set in advance by experiment is reached. it can. In the production line, the capacitance and / or impedance between the positive and negative electrodes of the battery is measured, and when this value reaches a value corresponding to full impregnation, it is determined that the battery is fully impregnated.
[0028]
(Fifth step)
After taking out the secondary battery from a pressure vessel (not shown), preliminary charging is performed. Subsequently, the precharged sealed secondary battery is housed in a pressure vessel (not shown) and pressurized with a high-pressure gas. At this time, most of the gas generated during the preliminary charging is dissolved in the electrolyte. Next, the secondary battery is fully charged to produce a thin nonaqueous electrolyte secondary battery that has been subjected to an initial charging process.
[0029]
Here, the "preliminary charge" means that the active material of the positive and negative electrodes does not substantially expand, and is charged at a voltage at which gas generation accompanying the charging reaction between the positive and negative electrodes is substantially completed. Specifically, in the case of a non-aqueous electrolyte secondary battery, the pre-charging is performed at 3.7 V, for example, at a rate of 0.5 C for 2 hours. The secondary battery to be precharged may be open or sealed. However, the secondary battery is sealed when pressurized by a high-pressure gas.
[0030]
The term "main charge" means that the active material of the positive and negative electrodes is charged at a voltage higher than that of the preliminary charge and a sufficient charge reaction between the positive and negative electrodes causes the electrode group to expand. I do. Specifically, in the case of a non-aqueous electrolyte secondary battery, the main charging is performed at 4.2 V, for example, at a rate of 0.2 C for 6 hours.
[0031]
As the gas, for example, air, nitrogen gas, carbon dioxide gas or inert gas can be used, and it is preferable that these gases are dried. In addition, by using a dry gas, it is possible to prevent a decrease in battery performance due to moisture penetrating into the exterior member and reacting with an electrolyte in the electrolytic solution, for example, lithium hexafluorophosphate to generate hydrofluoric acid. Becomes possible. The use of carbon dioxide, nitrogen, and inert gas as gases prevents oxygen from penetrating into the exterior member and oxidizing the electrolyte, positive electrode, negative electrode, separator, current collector, etc., and lowering battery performance. Can be prevented.
[0032]
The pressure of the gas is preferably 0.1 to 15 MPa as a gauge pressure. When the pressure of the gas is less than 0.1 MPa in gauge pressure, expansion due to the gas generated during the pre-charging is sufficiently suppressed, and it may be difficult to quickly dissolve the generated gas in the electrolyte. . On the other hand, if the pressure applied by the gas exceeds 15 MPa in gauge pressure, it is necessary to increase the wall thickness of the container wall in order to increase the pressure resistance of the pressure container, or the operability becomes poor.
[0033]
Next, the positive electrode 3, the separator 4, the negative electrode 7, the non-aqueous electrolyte, the external leads 9, 10, the outer film material 11, and the adhesive insulating film 16 will be described.
[0034]
1) Positive electrode 3
The positive electrode 3 has, for example, a structure in which a positive electrode active material layer 1 containing an active material and a binder is supported on both surfaces of a current collector 2. Note that the positive electrode may have a structure in which a positive electrode active material layer is supported on one surface of a current collector.
[0035]
Examples of the current collector include aluminum.
[0036]
As the active material, a lithium composite oxide having a high energy density is preferable. Specifically, LiCoO ₂ , LiNiO ₂ , Li _x Ni _y Co _1-y O ₂ (However, x and y differ depending on the state of charge of the battery, and are usually 0 <x <1, 0.7 <y <1.0), Li _x Co _y Sn _z O ₂ (However, x, y, and z represent the numbers of 0.05 ≦ x ≦ 1.10, 0.85 ≦ y ≦ 1.00, and 0.001 ≦ z ≦ 0.10, respectively). Lithium composite oxide is obtained by mixing and grinding lithium carbonate, nitrate, oxide or hydroxide and carbonate, nitrate, oxide or hydroxide such as cobalt, manganese or nickel with a predetermined composition, It can be obtained by firing at a temperature of 600 to 1000 ° C. in an atmosphere. Among them, Li _x Co _y Sn _z O ₂ (However, x, y, and z represent the numbers of 0.05 ≦ x ≦ 1.10, 0.85 ≦ y ≦ 1.00, and 0.001 ≦ z ≦ 0.10, respectively). As a result, the particle size of the lithium-containing compound becomes small and uniform, so that a battery having excellent cycle characteristics can be obtained. The reason for setting 0.001 ≦ z ≦ 0.10 is that if z is less than 0.001, it is difficult to sufficiently control the particle size. On the other hand, when z exceeds 0.1, the capacity is reduced.
[0037]
As the binder, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR) and the like can be used.
[0038]
The positive electrode active material layer is allowed to contain a conductive agent such as acetylene black, carbon black, and graphite.
[0039]
2) Separator 4
The separator 4 is made of, for example, a microporous membrane made of polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, or a woven or nonwoven fabric having fibers of these materials.
[0040]
3) Negative electrode 7
The negative electrode 7 has a structure in which a negative electrode active material layer 5 containing an active material and a binder is supported on both surfaces of a current collector 6. Note that the negative electrode may have a structure in which a negative electrode active material layer is supported on one surface of a current collector.
[0041]
Examples of the current collector include a copper or nickel plate or mesh.
[0042]
The active material may be any material capable of doping / dedoping lithium. Examples of the active material include graphites, cokes (petroleum coke, pitch coke, needle coke, etc.), pyrolytic carbons, and fired products of organic polymer compounds (phenols). Resin or the like fired and carbonized at an appropriate temperature) or metallic lithium, polyacetylene, polypyrrole, or the like.
[0043]
The binder preferably contains, for example, a binder such as polytetrafluoroethylene, polyvinylidene fluoride, ethylene-propylene-diene copolymer, styrene-butadiene rubber, and carboxymethyl cellulose.
[0044]
4) Non-aqueous electrolyte
This non-aqueous electrolyte has a composition in which an electrolyte is dissolved in a non-aqueous solvent.
[0045]
As the electrolyte, for example, lithium perchlorate (LiClO ₄ ), Lithium tetrafluoroborate (LiBF ₄ ), Lithium hexafluorophosphate (LiPF ₆ ), Lithium hexafluoroarsenate (LiAsF) ₆ ), Lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), Lithium (bis) trifluoromethanesulfonimide [LiN (CF ₃ SO ₂ ) ₂ ], Lithium bis [5-fluoro-2orato-1-benzene-sulfonato (2-)] borate and the like can be used.
[0046]
Examples of the non-aqueous solvent include γ-butyrolactone, ethylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,3-dioxolan, methylsulfolane, Acetonitrile, propyl nitrile, anisole, acetate, propionate and the like can be used, and two or more kinds may be used in combination. It is preferable to add a surfactant such as trioctyl phosphate (TOP), di-n-butyl carbonate (DNBC) or the like to the non-aqueous solvent. The addition of such a surfactant makes it possible to improve the wettability of the non-aqueous electrolyte with respect to the separator.
[0047]
It is preferable that the concentration of the electrolyte in the non-aqueous solvent is 0.5 mol / L or more.
[0048]
In particular, as the non-aqueous electrolyte, lithium tetrafluoroborate (LiBF) is used in a non-aqueous solvent of ethylene carbonate (EC) and γ-butyrolactone (γ-BL). ₄ When a solution in which the electrolyte is dissolved is used, it is difficult to evaporate even when the degree of vacuum is increased at reduced pressure, and there is little bubbling, so that a battery can be easily manufactured. In this case, EC has a higher viscosity than γ-BL, and has a smaller capacity at low temperatures. For this reason, there is a possibility that the lower the temperature, the more the EC. Conversely, the more γ-BL, the better the low-temperature characteristics. Further, γ-BL easily reacts with the negative electrode carbon at a high temperature, and the capacity decrease at a high temperature becomes large. Therefore, the mixing ratio of EC / γ-BL is preferably set to 2/1 to 1/5 (volume ratio). The LiBF ₄ Is preferably 0.75 to 2 mol / L with respect to the total amount of the solvent. When the content is less than 0.75 mol / L, it becomes difficult to obtain a battery having a desired large capacity. On the other hand, if it exceeds 2 mol / L, cycle deterioration of the battery is likely to occur, and the nonaqueous electrolyte may be expensive.
[0049]
In addition to the electrolytic solution, a polymer gel electrolyte impregnated with the electrolytic solution or an all-solid polymer solid electrolyte containing no solvent may be used.
[0050]
The polymer used as the polymer gel electrolyte is not particularly limited, and examples thereof include polyacrylonitrile resin, polyethylene oxide resin, polyether resin, polyester resin, polyacrylate resin, and fluorine resin. Can be
[0051]
5) External leads 9, 10
The material of the external lead connected to the positive electrode is, for example, aluminum, and the material of the external lead connected to the negative electrode is, for example, nickel, copper, or the like. Here, aluminum and copper are easily corroded by the electrolytic solution, and nickel is not easily corroded. Therefore, it is preferable to use nickel as the external lead material. It elutes. High purity ferritic steel such as titanium or stainless steel (29Cr-4Mo-2Ni) does not elute in the electrolytic solution, but these metals are not suitable because the impedance of the battery becomes high. Therefore, aluminum or an aluminum alloy must be used. Further, it is preferable to use nickel as the negative electrode lead terminal material for the above-mentioned reason. Nickel is less likely to be corroded by the electrolytic solution, and thus it is possible to use a negative electrode-side external lead that is not subjected to surface treatment with a chemical solution. Of course, it is possible to manufacture a more reliable battery by treating the negative electrode side external lead with a chemical solution. Since nickel has a high impedance, the terminal is liable to be melted due to abnormal heat generation due to resistance loss when an external short circuit occurs. In this case, a copper band whose surface is plated with nickel may be used.
[0052]
Examples of the surface treatment method of aluminum and aluminum alloy include (1) anodization at 15 V in a 100 g / L phosphoric acid aqueous solution, (2) anodization at 15 V in a 100 g / L sulfuric acid aqueous solution, and (3) 75 g / L. (4) Surface treatment by immersion in 140 g / L of caustic soda water, (5) An aqueous solution of sodium chromate / sulfuric acid / water of 3/30/100 in a mass ratio of 60 to 70% Surface treatment by immersion at a temperature of ° C. As a result of the surface treatment using these chemicals, an oxide film of porous alumina having a large number of protrusions having a height of about several nm to several thousand nm is formed on the surface of aluminum and an aluminum alloy.
[0053]
6) Material 11 for exterior film
The exterior film material 11 is composed of a laminated film in which a sealant film 13, an aluminum or aluminum alloy sheet 14, and a rigid resin film 15 are laminated in this order.
[0054]
The sealant film seals the power generating element inside the material by thermocompression bonding between the sealant films, between the sealant film and the external leads, or between the sealant film and the adhesive insulating film.
[0055]
As the sealant film, a non-stretched film that does not dissolve or swell in a non-aqueous electrolyte is preferable. For example, unstretched polypropylene (PP), polyolefin-based polymer such as linear low density polyethylene (LLDPE), ethylene / vinyl acetate (EVA) copolymer, ionomer (IO), polyamide (PA), nylon (Ny) , Polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyvinyl alcohol (PVA), ethylene vinyl alcohol (EVOH), polycarbonate (PC), polystyrene (PS ), Polyacrylonitrile (PAN), ethylene / acrylic acid copolymer (EAA), ethylene / methacrylic acid copolymer (EMAA), ethylene / methyl acrylate copolymer (EMA), ethylene / methyl methacrylate copolymer EMMA), ethylene-ethyl acrylate copolymer (EEA), it may be used polymethylpentene (PMP) and the like. In particular, a resin film obtained by graft-polymerizing an acid anhydride such as maleic anhydride with these resins as a base polymer is suitable not only when an adhesive insulating film is not used, but also for increasing the adhesion to a metal. It is informative.
[0056]
The aluminum or aluminum alloy sheet functions as a barrier for preventing the permeation of the non-aqueous electrolyte or gas.
[0057]
The rigid resin film (surface material) has a function of protecting the aluminum or aluminum alloy sheet and maintaining the mechanical structural characteristics of the battery.
[0058]
As the rigid resin, for example, films such as biaxially stretched polyolefin-based polymers such as polyethylene (PE) and polypropylene (PP), polyethylene terephthalate (PET), and polyamide (PA) can be used.
[0059]
7) Adhesive insulating film 16
As the adhesive insulating film, it is preferable to use a film having the same properties and moldability as the sealant film and having excellent adhesion to the metal as the positive and negative external leads. Specifically, a product obtained by graft-polymerizing an acid anhydride such as maleic anhydride to a base polymer made of the resin used for the above-mentioned sealant film can be used. The adhesive insulating film is not essential for the structure of the battery, and may not be used as necessary.
[0060]
The adhesive insulating film may be the same system as or different from the sealant film. If the adhesive insulating film and the sealant film are made of the same composition, a uniform and highly reliable sealing structure around the positive and negative electrode side external leads can be obtained.
[0061]
The present invention is not limited to the manufacture of the thin battery shown in FIG. 5 described above, but may also manufacture a square battery (for example, a square nonaqueous electrolyte secondary battery) having a structure shown in FIG. 6 described below. it can.
[0062]
That is, in FIG. 6, an outer can 21 made of a metal and having a bottomed rectangular cylindrical shape and made of, for example, aluminum also serves as, for example, a positive electrode terminal, and an insulating film 22 is disposed on the inner surface of the bottom. The electrode body (electrode group) 23 is housed in the outer can 1. The electrode group 23 has, for example, a structure in which an active material layer is formed on both sides of a current collector such as a copper plate, a separator 25, and an active material layer formed on both sides of a current collector such as an aluminum plate. The positive electrode 26 is spirally wound so that the positive electrode 26 is located at the outermost periphery, and then press-formed into a flat shape.
[0063]
A spacer 27 made of, for example, synthetic resin and having a lead extraction hole (not shown) near the center is arranged on the electrode group 23 in the outer can 21. The lid 28 made of a metal such as aluminum is hermetically joined to the upper end opening of the outer can 21 by, for example, laser welding. In the vicinity of the center of the lid 28, an extraction hole for the negative electrode terminal is opened, and a liquid injection hole 29 is opened at a position separated from the extraction hole. For example, after the sealing member 30 made of an aluminum rectangular plate is injected with the non-aqueous electrolyte through the injection hole 29 of the lid 28, the sealing member 30 around the injection hole 29 is It is joined by ultrasonic welding, and hermetically seals the injection hole 29.
[0064]
The negative electrode terminal 31 is hermetically sealed in a hole of the lid 28 via an insulating material (not shown) made of glass or resin. An external lead 32 attached to the negative electrode 24 of the electrode group 23 is connected to a lower end surface of the negative electrode terminal 31.
[0065]
When such an exterior member is an exterior can (for example, an aluminum or aluminum alloy exterior can) 21 to which a lid 28 having a liquid injection hole 29 is attached, the electrode group 23 is housed, and the nonaqueous electrolyte is further covered with a lid. The liquid is injected through the injection hole 29 of the body 28, stored, sealed with a sealing member, pre-charged, pressurized with high-pressure gas, and further fully charged. It is preferable to carry out under conditions.
[0066]
That is, after the electrode group 23 is housed in the outer can 21 and the nonaqueous electrolyte is injected and stored through the injection hole 29 of the lid 28, the injection hole 29 is opened. Precharge is performed under a voltage condition of 3.6 to 3.9 V with 29 facing upward. After the preliminary charging, the injection hole 29 is hermetically sealed with a sealing member 30, the sealed battery is pressurized with a high-pressure gas, and the pressurized battery is fully charged.
[0067]
The potential of the pre-charging is preferably 3.6 V to 3.9 V, for example, at a rate of 0.5 C for 2 hours. If the pre-charge potential is less than 3.6 V, hydrogen gas may be generated during the main charge, and the outer case may swell. If the pre-charge potential exceeds 3.9 V, the rate of hydrogen gas generation in pre-charge increases, and the outer can may swell during pre-charge. In addition, it is conceivable to suppress the swelling of the outer can by increasing the pre-charging potential and lowering the rate. However, the charging time is prolonged, and accordingly, the battery opening time during pre-charging (i.e. Opening time) becomes longer. As a result, the non-aqueous electrolyte in the outer can volatilizes, and the composition of the electrolyte changes, which adversely affects battery characteristics.
[0068]
The pressure applied by the gas is preferably 0.1 MPa to 15 MPa, more preferably 0.5 MPa to 15 MPa for the same reason as described above, and is performed at, for example, 0.5 MPa (gauge pressure) for 24 hours.
[0069]
The gas is used for the same reason as described above, that is, using dry air in relation to the non-aqueous electrolyte, or using nitrogen gas and an inert gas in order to prevent oxidation of the electrode group and the non-aqueous electrolyte. Is preferred.
[0070]
As described above, according to the present invention, the uncharged battery (secondary battery) is precharged, and the precharged hermetically sealed battery is gas-pressurized and then fully charged, whereby the first charge is performed. Gas generation and expansion of the active material of the positive and negative electrodes due to expansion can be suppressed, and separation of the positive electrode and the negative electrode can be prevented. For example, the thickness of a thin battery can be reduced.
[0071]
That is, at the time of preliminary charging, a decomposition reaction such as hydrogen, methane, ethylene, or carbon monoxide is generated by a charging reaction occurring between the electrolyte and the positive and negative electrodes, and the internal pressure of the exterior member (for example, the packaging material) increases. The laminated film constituting the material is pushed out, and the thickness of the central part of the battery is increased, particularly. In some cases, the packaging material holding down the electrode group is separated from the electrode group, and thus the positive and negative electrodes are separated. Further, the decomposition gas stays between the electrode plates of the electrode group. When the main charge is performed in such a state, the electrodes are twisted due to the expansion of the positive and negative electrode active materials accompanying the main charge, and the finished thickness of the battery is increased. In the case of a non-aqueous electrolyte secondary battery, since charging is performed in a local overload state, lithium ions are deposited to form a thin metal lithium layer. As a result, the battery becomes thicker or the charge / discharge ability is reduced.
[0072]
For this reason, the present invention provides a method for pressurizing a sealed battery with a high-pressure gas after the pre-charging and before the main charging, so that the decomposition gas generated in the pre-charging and retained between the electrode plates. Can be dissolved in an electrolytic solution in an exterior member (for example, a packaging material) (Henry's law), and can be returned to a shape before swelling without swelling due to pressing of an electrode group through the packaging material. Can be prevented from being separated from the electrode group and between the positive and negative electrode plates. That is, the inner surface of the exterior member can be in close contact with the outer surface of the electrode group, and the electrode plates can be in close contact with each other. In addition, since the distance between the positive and negative electrode plates can be reduced, the occurrence of electrodeposition of the metallic lithium can be prevented. As a result, even if the active material of the positive and negative electrodes expands in this charging, the electrodes are twisted, the finished thickness of the battery becomes thicker, or in the case of a non-aqueous electrolyte secondary battery, Since deposition of lithium can be prevented, a battery having a set thin dimension can be manufactured without lowering the charge / discharge capability.
[0073]
In particular, by setting the pressure of the gas to a gauge pressure of 0.1 to 15 MPa, the effect of dissolving the gas generated in the preliminary charging into the electrolyte solution in the exterior member (for example, the packaging material) and the preliminary charging without swelling The effect of returning to the previous shape can be more reliably exhibited.
[0074]
Further, it is possible to manufacture a battery in which an increase in the thickness of the battery and a decrease in the discharge capacity when the charge / discharge cycle is repeated are suppressed. This is because the active points for the electrolyte such as the positive electrode and the negative electrode disappear by the initial charge by the preliminary charge and the main charge described above, and almost no gas is generated during the subsequent charge and discharge.
[0075]
Furthermore, according to the present invention, in order to suppress the swelling of the secondary battery as in the prior art, a gas generated at the time of charging is exhausted to the outside, and then a charging method for sealing the exterior member (hereinafter referred to as open charging), A process such as a method of charging an uncharged battery in a fixed state with a mold or a jig (hereinafter, referred to as press charging) becomes unnecessary.
[0076]
In the open charging, a countermeasure is necessary because the electrolyte overflows with the gas. The press charging requires complicated steps such as mounting and removing a mold and a jig. Further, in the press charging, since the pressure is forcibly applied, there is a high risk of damaging the battery.
[0077]
Since the pre-charging, gas pressurization, and main charging processes are performed after the exterior member is sealed as in the present invention, it is possible to prevent the electrolyte from overflowing and the occurrence of contamination and corrosion. In addition, since the pressurization is performed with gas, the risk of damaging the battery can be reduced as compared with the press charging.
[0078]
Further, particularly when the exterior member is a metal exterior can attached with a lid having a liquid injection hole, the preliminary charging is performed after the non-aqueous electrolyte is injected into the exterior can through the liquid injection hole. The swelling of the metal outer can can be effectively suppressed by performing the operation under a voltage condition of 3.6 to 3.9 V with the liquid injection hole opened and the liquid injection hole facing upward. .
[0079]
In other words, during the initial charge, hydrogen, methane, ethylene, carbon monoxide and other gases are generated, so charging is performed in a sealed state, that is, in a state of an outer can with a lid attached and its injection hole sealed. When this is done, the internal pressure of the outer can increases, the outer can swells, the thickness of the outer can increases, and the finished thickness of the battery increases. In some cases, the positive electrode and the negative electrode of the electrode group are separated from each other due to gas generation and swelling of the outer can.Therefore, by repeating the charging cycle, the electrodes are twisted due to expansion of the active material of the positive and negative electrodes, and lithium ion secondary In a battery, metallic lithium is deposited between the electrode plates, thereby accelerating deterioration of the discharge capacity of the battery.
[0080]
Therefore, focusing on the peak of gas generation near 3.6 to 3.9 V, the battery is opened at that voltage and pre-charged to release the generated gas upward. Since it is possible to escape through the injected liquid injection hole, swelling of the outer can can be suppressed, and the thickness of the outer can and, consequently, the finished thickness of the battery can be kept within the design dimensions.
[0081]
【Example】
Hereinafter, preferred embodiments will be described in detail.
[0082]
(Example 1)
<Preparation of positive electrode>
LiCo with an average particle size of 3 μm as a positive electrode active material _0.98 Sn _0.02 O ₂ 89 parts by weight, 6 parts by weight of graphite (KS6 manufactured by Lonza), 3 parts by weight of polyvinylidene fluoride (trade name: # 1100 manufactured by Kureha Chemical Co.) as a conductive filler, 25 parts by weight of N-methylpyrrolidone as a solvent , And after uniform shear stirring, the mixture was dispersed using a bead mill to prepare a positive electrode slurry. The apparent viscosity of this slurry was 7,500 mPa · s. Subsequently, this positive electrode slurry is uniformly applied to both sides of a 20 μm-thick strip-shaped aluminum foil serving as a current collector, the solvent is dried, and further subjected to pressure molding by a roll press machine, and then cut into a predetermined size. Thus, a belt-shaped positive electrode was produced. Thereafter, an aluminum external lead having a thickness of 0.1 mm, a width of 5 mm, and a length of 50 mm was attached to one end of the positive electrode current collector by welding.
[0083]
<Preparation of negative electrode>
50 parts by weight of flaky graphite was dispersed in 1.5 parts by weight of carboxymethyl cellulose to prepare a carbon master batch paint. To this dispersion was added 50 parts by weight of a fibrous carbon material, and the mixture was similarly shear-dispersed. Further, 2.4 parts by weight of a styrene-butadiene rubber latex was added, and the mixture was uniformly mixed and stirred to prepare an anode slurry. The apparent viscosity of this slurry was 4500 mPa · s. Subsequently, this negative electrode slurry is uniformly applied to both sides of a 10 μm-thick strip-shaped copper foil serving as a current collector, the solvent is dried, and the resultant is further pressed and formed by a roll press, and then cut into a predetermined size. In this way, a strip-shaped negative electrode was produced. Thereafter, a nickel external lead having a thickness of 0.1 mm, a width of 5 mm, and a length of 50 mm was attached to one end of the current collector of the negative electrode by welding.
[0084]
Next, the order of the positive electrode / separator / negative electrode / separator was established by interposing the strip-shaped positive electrode and the strip-shaped negative electrode through a separator made of a polyethylene microporous film having a thickness of 25 μm, a porosity of 50%, and an air permeability of 300 seconds / 100 cc. , And spirally wound with a core having a flat cross section, and further heated and compressed by a hydraulic press to form a flat electrode body (electrode group).
[0085]
Next, an exterior film material in which a stretched nylon film having a thickness of 25 μm, an aluminum foil having a thickness of 40 μm, and a maleated polypropylene film (sealant film) having a thickness of 70 μm are laminated and bonded in this order via a urethane-based adhesive. Was prepared and heated and pressed from the maleated polypropylene film side of the material using a forming punch and a forming die to form a cup. The melting point of the maleated polypropylene film is 138 ° C. Subsequently, this was cut into a strip shape, and the short side of the cup of the material for the exterior film was bent 180 ° by a molding machine so that the maleated polypropylene film faces inside on the inside. Subsequently, of the sealant film surfaces on both sides facing each other inside the exterior material, plasma is applied to a non-cup-formed portion (a portion other than the cup-formed portion) and a portion to be heated and fused in a later step and the opposed portion. Irradiation treatment was performed. Next, the flat electrode body was vacuum-heated and dried at 60 ° C. to remove water to 300 ppm or less, and then a plasma irradiation treatment was performed on the heat-sealed portions of the external lead surfaces on the positive electrode side and the negative electrode side. Then, the external leads of the positive and negative electrodes were housed in a cup of the exterior film material so as to protrude outside the exterior film material, and a flat material portion was bent so as to overlap the electrode group. In this state, the long side of the exterior film material was pressed for several seconds by a press head heated to 210 ° C. to bond the maleated polypropylene films together to form a seal portion. Further, in a state where the external leads of the exterior film material are extended, an adhesive insulating film that has been subjected to plasma irradiation treatment on at least the surface facing the external leads is inserted between the external leads and the exterior film. Pressed for 5 seconds with a press head heated to 210 ° C. to bond the external leads of the positive and negative electrodes to the adhesive insulating film, the adhesive insulating film to the maleated polypropylene film, and the maleated polypropylene film to form a seal portion. did. These heat sealing sequences may be performed simultaneously or one of them may be performed first.
[0086]
Next, a nonaqueous electrolyte was injected and impregnated under a vacuum of 1 torr or less through the open long side portion of the exterior film material. As the non-aqueous electrolyte, ethylene carbonate / methyl ethyl carbonate / LiPF ₆ = 34.9 / 53.11 / 12 (mass ratio) to which 0.5% by weight of trioctyl phosphate (TOP) was added. Thereafter, the unsealed portion is pressurized by a press head (not shown) heated to 210 ° C. for 5 seconds, and the maleated polypropylene films in the portions which have been subjected to the plasma irradiation treatment are bonded to each other to form a sealed portion. Then, the extra non-aqueous electrolyte secondary battery in an uninitialized state was manufactured by cutting and removing an extra exterior film material portion. Subsequently, the secondary battery was placed in an autoclave as a pressure vessel, and dry air was supplied into the pressure vessel to pressurize the secondary battery at a gauge pressure of 0.5 MPa for 10 minutes.
[0087]
Next, preliminary charging was performed for 2 hours at 0.5 C (375 mA) in the air at 20 ° C. Subsequently, the precharged secondary battery is placed in a pressurized container, and then compressed dry air is sent in at room temperature, and is applied at 0.9 MPa (gauge pressure) for 5 hours through the exterior film. Pressed. As a result, the gas generated during the pre-charging was dissolved in the electrolytic solution, and at the same time, minute gaps formed between the exterior film and the electrode body, the positive and negative electrodes, and the separator were crushed. Lastly, the main battery was charged at 20 ° C. under the conditions of 0.2 C (150 mA) and 4.2 V for 8 hours, whereby the non-rated dimensions were 3.8 mm in thickness, 35 mm in width, 62 mm in height, and 750 mAh (0 in 0). .2C) was manufactured.
[0088]
(Comparative Example 1)
A thin non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that gas pressurization after pre-charging was not performed.
[0089]
(Comparative Example 2)
A method similar to that of Example 1 except that the main charge is performed in the atmosphere of 20 ° C. at 0.5 C (375 mA) at 4.2 V for 8 hours without performing the precharge and gas pressurization after the precharge. Produced a thin non-aqueous electrolyte secondary battery.
[0090]
<Battery performance test>
With respect to the obtained thin nonaqueous electrolyte secondary batteries of Example 1 and Comparative Examples 1 and 2, the thickness and the 0.2 C discharge capacity after full charge (initial charge) were measured. In addition, each secondary battery after the initial charge was charged and discharged at 20 ° C. under the conditions of 1.0 C / 1.0 C (charge condition: 650 mA, 4.2 V, 3 hours, discharge condition: 650 mA, 3.0 V cut-off). The thickness, discharge capacity, and discharge capacity retention rate (retention rate with respect to the initial discharge capacity) after 500 cycles were measured. Table 1 shows the results.
[0091]
[Table 1]

[0092]
As is clear from Table 1, the secondary battery of Example 1 subjected to the pre-charging, gas pressurizing, and main-charging processes was charged under atmospheric pressure without gas pressurizing after the pre-charging. The thickness after full charge and the discharge capacity of the secondary battery of Comparative Example 2 are smaller than those of the secondary battery of Comparative Example 2 which was charged under atmospheric pressure without performing precharge and gas pressurization after precharge. I understand.
[0093]
Further, even after repeating the charge / discharge cycle, the secondary battery of Example 1 subjected to the precharge, gas pressurization, and main charge treatments was charged at atmospheric pressure without gas pressurization after the precharge. The secondary battery of Comparative Example 1 was thinner and had a higher discharge capacity retention ratio than the secondary battery of Comparative Example 2 which was charged under atmospheric pressure without performing precharge and gas pressurization after precharge. You can see that.
[0094]
(Example 2)
A strip-shaped positive electrode, a strip-shaped negative electrode, a separator, and an electrolytic solution similar to those in Example 1 were prepared. Subsequently, the strip-shaped positive electrode and the strip-shaped negative electrode were separated through a separator made of a polyethylene microporous film having a thickness of 20 μm, a porosity of 50%, and an air permeability of 300 seconds / 100 cc, and then forming a positive electrode / separator / negative electrode / separator. The layers were laminated in this order, spirally wound with a core having a flat cross section, heated and compressed by a hydraulic press, and molded to produce a flat electrode body (electrode group).
[0095]
Next, the electrode body was inserted into an aluminum can having a thickness of 20 μm obtained by press-molding an aluminum plate of aluminum alloy A3003. Subsequently, an aluminum lid was prepared in which the negative electrode terminal was hermetically sealed near the center and the electrolyte injection hole was opened, and this negative electrode terminal was attached to the negative electrode of the electrode body in the aluminum can. After connecting the external lead, the lid was welded to the opening of the aluminum can and sealed. Subsequently, the composition of ethylene carbonate / methyl ethyl carbonate / LiPF was the same as that of Example 1 under reduced pressure. ₆ = 34.9 / 53.12 / 12 (mass ratio) and an electrolyte solution obtained by adding 0.5% by weight of trioctyl phosphate (TOP) to the mixed solution is injected through the injection hole of the lid. A charged rectangular non-aqueous electrolyte secondary battery was assembled.
[0096]
Next, the secondary battery was precharged for 2 hours at 0.5 C (310 mA) in dry air at 20 ° C. and atmospheric pressure. A part of the gas generated by the preliminary charging was discharged to the outside through the liquid injection hole of the lid. Thereafter, the injection hole of the lid was sealed.
[0097]
Then, after putting the secondary battery after the pre-charging into a pressurized container, compressed air at room temperature is fed into the container and pressurized at 0.9 MPa at a gauge pressure through the aluminum can for 15 hours. did. At this time, the gas generated during the preliminary charging was dissolved in the electrolytic solution, and at the same time, the minute gaps generated between the aluminum can and the electrode body and between the positive and negative electrodes of the electrode body were crushed. Finally, the main battery is charged at 20 ° C. under the conditions of 0.2 C (124 mA) and 4.2 V for 6 hours, so that the dimensions outside the rating are thick. The thickness of the structure shown in FIG. A square nonaqueous electrolyte secondary battery having a length of 4.4 mm, a width of 30 mm, and a height of 48 mm and a 0.2 C discharge capacity of 620 mAh was manufactured.
[0098]
(Example 3)
The electrode body was inserted into the aluminum can, an aluminum lid was welded to the opening of the aluminum can, and an electrolyte having the same composition as in Example 1 was injected under reduced pressure through the injection hole of the lid, After closing the injection hole, non-rated dimensions were 4.4 mm in thickness, 30 mm in width, and 48 mm in height in the same manner as in Example 2 except that precharging was performed at 0.5 C (310 mA) for 2 hours. A rectangular non-aqueous electrolyte secondary battery having a capacity of 620 mAh (0.2 C) was manufactured.
[0099]
(Comparative Example 3)
Except for pre-charging and gas pressurization after pre-charging, the main battery was charged for 6 hours under conditions of 20 ° C., 0.2 C (124 mA) and 4.2 V for 6 hours. A rectangular non-aqueous electrolyte secondary battery having dimensions of thickness 4.4 mm, width 30 mm, height 48 mm, and capacity of 620 mAh (0.2 C) was manufactured.
[0100]
(Comparative Example 4)
Without performing pre-charging and gas pressurization after pre-charging, main charging is performed for 6 hours under the conditions of 20 ° C., 0.2 C (124 mA) and 4.2 V, and then the secondary battery that has been fully charged is pressurized. After being placed in a container, dry air compressed at room temperature was fed into the container, and pressure was applied at a gauge pressure of 0.9 MPa through the aluminum can for 15 hours, except that the thickness was 4. A square non-aqueous electrolyte secondary battery having a capacity of 620 mAh (0.2 C) having a size of 4 mm, a width of 30 mm and a height of 48 mm was manufactured.
[0101]
<Battery performance test>
With respect to the obtained square nonaqueous electrolyte secondary batteries of Examples 2 and 3 and Comparative Examples 3 and 4, the thickness after the main charge and the 0.2 C discharge capacity were measured. In addition, each secondary battery after the initial charge is charged and discharged at 20 ° C. under the conditions of 1.0 C / 1.0 C (charge condition: 620 mA, 4.2 V, 3 hours, discharge condition: 620 mA, 3.0 V cut off). The thickness, discharge capacity and discharge capacity retention after 500 cycles were measured. Table 2 shows the results.
[0102]
[Table 2]

[0103]
As is clear from Table 2, the secondary battery of Example 2 which was subjected to the pre-charging, gas pressurizing, and main-charging treatments was subjected to the atmospheric pressure without performing the pre-charging and the gas pressurizing after the pre-charging. It can be seen that, compared to the charged secondary battery of Comparative Example 3, the thickness after the main charge is smaller and the discharge capacity is larger.
[0104]
The battery of Example 3 which had been subjected to precharging, gas pressurization, and main charging in the sealed state after the injection was precharged with the injection hole opened, and then the injection hole was sealed and gas injection was performed. The secondary battery of Example 2 was slightly thicker and had a smaller discharge capacity than the secondary battery of Example 2 in which the charging was performed and the main charging process was performed, but satisfied the rating.
[0105]
It can be seen that the secondary battery of Comparative Example 4 which was gas-pressurized after the main charge was thicker than the secondary battery of Example 2 which was pressurized before the main charge.
[0106]
Further, even after repeating the charge / discharge cycle, the secondary batteries of Examples 2 and 3 which have been subjected to the precharge, gas pressurization, and main charge processes do not perform the precharge and gas pressurization after the precharge. It can be seen that the thickness is smaller and the discharge capacity retention ratio is higher than the secondary batteries of Comparative Example 3 charged under atmospheric pressure and Comparative Example 4 gas-pressurized after main charging.
[0107]
In the above-described embodiment, the pre-charging is performed in a sealed state. However, although the process is complicated, the pre-charging may be performed in an open state, and then the pre-charging may be performed in a sealed state by a high-pressure gas pressurizing step. .
[0108]
(Example 4)
<Preparation of positive electrode>
First, lithium cobalt oxide (LiCoO ₂ ) A slurry was prepared by adding 90% by weight of powder, 5% by weight of acetylene black and a solution of 5% by weight of polyvinylidene fluoride (PVdF) in dimethylformamide (DMF) and mixing. This slurry was applied to both surfaces of a current collector made of an aluminum foil having a thickness of 15 μm, dried, and pressed to produce a positive electrode having a structure in which a positive electrode layer was supported on both surfaces of the current collector. In addition, the thickness of the positive electrode layer was 60 μm per side.
[0109]
<Preparation of negative electrode>
Mesophase pitch-based carbon fiber heat-treated at 3000 ° C. as a carbonaceous material (plane spacing (d) determined by powder X-ray diffraction (d) ₀₀₂ ) Was mixed with 95% by weight of a powder of 0.336 nm) and a solution of 5% by weight of polyvinylidene fluoride (PVdF) in dimethylformamide (DMF) to prepare a slurry. This slurry was applied to both sides of a current collector made of a copper foil having a thickness of 12 μm, dried, and pressed to produce a negative electrode having a structure in which a negative electrode layer was supported on the current collector. The thickness of the negative electrode layer was 55 μm per one side.
[0110]
The spacing d of the (002) plane of the carbon fiber ₀₀₂ Was determined from the powder X-ray diffraction spectrum by the half-width half-point method. At this time, scattering correction such as Lorentz scattering was not performed.
[0111]
<Separator>
A separator made of a polyethylene microporous membrane having a thickness of 20 μm, a porosity of 50%, and an air permeability of 300 seconds / 100 cc was prepared.
[0112]
<Preparation of non-aqueous electrolyte>
Ethylene carbonate (EC) / methyl ethyl carbonate (MEC) / lithium hexafluorophosphate (LiPF ₆ ) = 34.9 / 53.1 / 12 (weight ratio) to prepare a non-aqueous electrolyte in which 0.5% by weight of vinylene carbonate (VC) was added.
[0113]
<Preparation of electrode group>
The positive electrode current collector of the positive electrode is ultrasonically welded to a positive electrode lead made of a band-shaped aluminum foil (thickness: 100 μm), and the negative electrode current collector is ultrasonically welded to a negative electrode lead made of a band-shaped nickel foil (thickness: 100 μm). Then, the positive electrode and the negative electrode are spirally wound therebetween with the separator interposed therebetween, formed into a flat shape, and further heated and compressed by a hydraulic press to form a flat electrode body (electrode group). did.
[0114]
The electrode body was inserted into an aluminum outer can having a wall thickness of 0.25 mm, and a lid having a liquid injection hole opened at the upper end opening of the outer can was laser seam-welded to seal the electrode body.
[0115]
Next, the electrode group in the outer can was subjected to vacuum drying at 85 ° C. for 12 hours to remove water contained in the electrode group and the outer can. Subsequently, after a fixed amount of the non-aqueous electrolyte having the above composition was injected into the electrode group in the outer can through the injection hole of the lid, the injection hole was turned upward to 0.5 C (310 mA) in an inert gas. ) Preliminary charge was performed at 3.7 V for 2 hours. Here, the reaction gas generated in the outer can at the time of charging was discharged to the outside through the liquid injection hole of the lid. Thereafter, a sealing member made of, for example, a rectangular plate made of aluminum was joined to the lid around the injection hole by, for example, ultrasonic welding, and the injection hole was hermetically sealed.
[0116]
Next, after putting the secondary battery, which has been preliminarily charged, into a pressurized container, compressed dry air is sent at room temperature, and the outer can with lid is subjected to gassing at 0.5 MPa (gauge pressure) for 24 hours. Pressure was applied. As a result, the gas generated during the pre-charging was dissolved in the electrolytic solution, and at the same time, minute gaps formed between the outer can and the electrode group, and between the positive and negative electrodes of the electrode group and the separator were crushed. Finally, at 20 ° C., the battery was fully charged for 10 hours under the conditions of 0.2 C (124 mA) and 4.2 V, and the dimensions outside the rating were 4.4 mm in thickness, 30 mm in width, 48 mm in height, and the capacity was 620 mAh ( 0.2C) was manufactured.
[0117]
(Example 5)
A prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 4, except that the gas pressurization after the preliminary charge was performed at 5 MPa (gauge pressure) for 12 hours.
[0118]
(Example 6)
A prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 4, except that the gas pressurization after the preliminary charge was performed at 10 MPa (gauge pressure) for 4 hours.
[0119]
(Example 7)
A prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 4, except that the gas pressurization after the preliminary charge was performed at 15 MPa (gauge pressure) for 1 hour.
[0120]
(Comparative Example 5)
A prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 4, except that gas pressurization was not performed after the preliminary charge.
[0121]
<Battery performance test>
With respect to the obtained square nonaqueous electrolyte secondary batteries of Examples 4 to 7 and Comparative Example 1, the thickness after the main charge and the 0.2 C discharge capacity were measured. In addition, each secondary battery after the main charge was charged and discharged at 20 ° C. under the condition of 1.0 C / 1.0 C (charge condition: 620 mA, 4.2 V, 3 hours, discharge condition: 620 mA, 3.0 V cut off). The discharge capacity retention rate after 500 cycles (retention rate with respect to the initial discharge capacity) was measured. The results are shown in Table 3 below.
[0122]
[Table 3]

[0123]
As is clear from Table 3, the secondary batteries of Examples 4 to 7 which were subjected to the main charge treatment after gas pressurization after the preliminary charge were charged without performing gas pressurization after the preliminary charge of Comparative Example 5 It can be seen that the thickness after the main charge is smaller and the discharge capacity is larger as compared to
[0124]
In addition, even after 500 charge / discharge cycles of 1C / 1C at 20 ° C. were repeated, the thickness was small and the discharge capacity retention ratio was high.
[0125]
【The invention's effect】
As described in detail above, according to the present invention, a method for manufacturing a battery having a small thickness, a large initial discharge capacity and a large discharge capacity after repeated charge and discharge cycles, A battery can be provided.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a manufacturing process of a thin nonaqueous electrolyte secondary battery of the present invention.
FIG. 2 is a sectional view taken along the line II-II in FIG.
FIG. 3 is a perspective view showing a manufacturing process of the thin non-aqueous electrolyte secondary battery of the present invention.
FIG. 4 is a sectional view taken along the line VI-VI in FIG. 3;
FIG. 5 is a perspective view showing a manufacturing process of the thin nonaqueous electrolyte secondary battery of the present invention.
FIG. 6 is a partially cutaway perspective view showing a prismatic non-aqueous electrolyte secondary battery using an aluminum outer can for the outer member of the present invention.
[Explanation of symbols]
3, 26 ... positive electrode, 4, 25 ... separator, 7, 24 ... negative electrode, 8, 23 ... electrode body, 9, 10 ... external lead, 11 ... material for exterior film, 12 ... cup, 16 ... adhesive insulating film, 17a, 17b, 17c: sealing part, 18: exterior film, 21: aluminum exterior can, 28: lid, 29: liquid injection hole, 30: sealing member, 31: negative electrode terminal.

Claims (7)

A step of pre-charging an uncharged battery containing a power generation element having a positive electrode, a negative electrode, a separator and a non-aqueous electrolyte in an exterior member,
Pressurizing the precharged sealed battery with a high-pressure gas;
And a step of fully charging the pressurized battery. The method for manufacturing a battery according to claim 1, wherein the exterior member is made of a laminated film in which an aluminum foil is interposed between resin films. The method according to claim 1, wherein the exterior member is made of a metal can. 4. The method according to claim 1, wherein the gas is dry air, nitrogen, or an inert gas. The method for manufacturing a battery according to any one of claims 1 to 4, wherein the pressure for pressurizing the battery is 0.1 to 15 MPa in gauge pressure. A battery characterized in that an uncharged battery containing a power generation element having a positive electrode, a negative electrode, a separator and a non-aqueous electrolyte in an exterior member is pressurized by high-pressure gas after preliminary charging, and further fully charged. The exterior member is a metal exterior can attached with a lid having a liquid injection hole, and the preliminary charging is performed after the non-aqueous electrolyte is injected into the external can through the liquid injection hole. 2. The method for producing a battery according to claim 1, wherein the liquid injection hole is opened at a voltage condition of 3.6 to 3.9 V with the liquid injection hole facing upward.

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