JP4383781B2 - Battery manufacturing method - Google Patents

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／ＬｉＰＦ₆＝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（ＬｉＣｏＯ₂）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（ｄ₀₀₂）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ｄ₀₀₂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（ＬｉＰＦ₆）＝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]
BACKGROUND OF THE INVENTION
The present invention relates to a battery manufacturing method and a battery in which a power generation element is sealed inside an exterior member.
[0002]
[Prior art]
With the advancement of electronic devices such as mobile phones and personal computers, batteries used in these devices have been constantly required to be smaller, lighter, larger in capacity, higher in performance, and lower in cost. For this reason, in the battery, the electrode material such as the positive electrode active material or the negative electrode active material is changed to a material 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 such as changing the material of the metal can from iron to aluminum and using a bag-like exterior film made of a laminated film with an aluminum foil interposed between resin films by replacing the exterior member with a metal can It was.
[0003]
However, these improvements, on the other hand, increase the amount of gas generated at the time of initial charging, reduce the free space inside the battery, increase the internal pressure, twist the electrode, and the exterior member is made of aluminum or laminated film. Due to the fact that the low-elasticity material was replaced and it was easily deformed, there was a problem that the battery swelled during the initial charge and the desired thickness could not be maintained.
[0004]
In order to solve such a problem, for example, Patent Document 1 discloses a method for manufacturing a prismatic sealed battery that performs initial charge and discharge while pressing the wide surface of a metal can inward from the left and right sides. .
[0005]
Patent Document 2 discloses a method for manufacturing a prismatic non-aqueous electrolyte secondary battery that is pressed from the outside until after the first charge.
[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 rectangular non-battery described in Patent Documents 1 and 2, the apparatus is complicated and inferior in mass productivity, and because it is pressed with a press, the electrode plate is easily damaged, and characteristic deterioration is likely to occur. There was a problem such as.
[0009]
The present invention provides a battery manufacturing method and a battery that are inexpensive, simple, and excellent in mass productivity while maintaining a desired thickness.
[0010]
[Means for Solving the Problems]
  The battery manufacturing method according to the present invention includes:Preparing a metal outer can attached with a lid having a liquid injection hole;
  Assembling an uncharged battery having a power generation element by housing a positive electrode, a negative electrode, and a separator in the outer can and injecting a non-aqueous electrolyte into the outer can through the injection hole;
  Precharging the uncharged battery under a voltage condition of 3.6 to 3.9 V with the liquid injection hole opened and the liquid injection hole facing upward;
  Hermetically sealing and injecting the liquid injection hole of the precharged battery; and
  AboveSealed battery0.1 to 15 MPa in gauge pressurePressurizing with high-pressure gas;
  A step of fully charging the pressurized battery;
It is characterized by including.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
In the following, a method for manufacturing a thin battery (for example, a thin non-aqueous electrolyte secondary battery) using a bag-shaped outer film made of a laminated film in which a metal sheet and a resin film are overlaid is used as the outer member of the present invention. Will be described with reference to FIG.
[0014]
(First step)
First, a positive electrode active material layer including an active material and a binder is supported on, for example, both surfaces of a current collector, and a negative electrode active material layer including a separator, an active material and a binder is supported on, for example, both surfaces of a current collector. The negative electrode and the separator are spirally wound to produce a substantially cylindrical object. In this winding, external leads are connected to the positive and negative electrodes, for example, by welding.
[0015]
Next, the positive electrode in which the positive electrode active material layer 1 containing the active material and the binder shown in FIGS. 1 and 2 is supported on both surfaces of the current collector 2 by heating and pressing the obtained cylindrical electrode object. 3, a flat electrode body (electrode group) 8 having a negative electrode 7 having separators 4 and a negative electrode active material layer 5 containing an active material and a binder carried on both sides of a current collector 6 is prepared. External leads 9, 10 connected to the positive and negative electrodes 3, 7 extend outward from the same side surface of the electrode body 8.
[0016]
The heating and pressing is preferably 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]
(Second step)
A film material for a bi-fold cup type exterior material having a dimension slightly longer than the long side of the electrode body and having a length that is, for example, twice the short side is prepared, as shown in FIG. 3 and FIG. The flat electrode body 8 is housed in a cup 12 formed by drawing the outer film material 11 so that the side opposite to the external leads 9 and 10 is located at the bent portion of the material. The outer film material 11 is constituted by 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 stored, the adhesive insulating film 16 is placed between the upper and lower surfaces of the external lead 9 of the positive electrode and the heat-fusible resin film (sealant film) 13 of the outer film material 11 and the negative electrode. The external lead 10 is interposed between the upper and lower surfaces of the external lead 10 and the sealant film 13 of the outer film material 11. Here, at least a portion (not shown) of the outer film material 11, the adhesive insulating film 16, the positive external lead 9 and the negative external lead 10 to be heat-sealed in a later process (not shown). First, plasma irradiation treatment is performed. Thereafter, the sealant film is sealed (sealed) by heat-sealing the sealant films at the left end portion of the outer film material 11 corresponding to the long side of the electrode body 8 to form a seal portion 17c. Further, the sealant films 13, the sealant film 13 / adhesive insulating film 16 / adhesive insulating film 16 / the sealant film 13, and adhesion at the end of the material 11 corresponding to the extending side of the external leads 9 and 10 The sealing portion 17b is formed by thermally fusing the conductive insulating film 16 and the external leads 9 and 10 together.
[0018]
In the plasma surface treatment, if a surface with very high energy (high activity) plasma ionized by separating into positive ions and electrons is irradiated onto a surface contaminated material, the dirt adhering to the material surface and the plasma particles are combined. Dirt is removed and the surface is cleaned. In addition, the chemical bond on the surface of the substance is changed, and a hydrophilic group such as an OH group that is easily compatible with the liquid is generated to facilitate adhesion. In addition, the plasma particles decompose the molecular layer with low activity on the surface, and an oxide layer with high activity appears on the surface to improve the wettability. Further, the plasma particles can create atomic level irregularities on the surface. For this reason, when the plasma irradiation treatment is performed on the surface of the resin or metal, the wettability of the surface of the workpiece is improved and the contact angle with water is lowered. As a result, the adhesion between the metal and the resin subjected to the plasma surface treatment and between the resin and the resin is improved.
[0019]
In the plasma surface treatment, a commercial plasma irradiator (for example, a product name manufactured by Keyence Corporation; ST-7000) is separated from the sample by 5 mm to 50 mm in the air and generated for several seconds (for example, 1 to 3 seconds). If the plasma is irradiated, the above-described effects can be obtained.
[0020]
(Third step)
A non-aqueous electrolyte is injected through the unsealed portion (right end portion) of the outer film material 11 and the surface of the unsealed portion near the right end portion of the electrode body 8 is subjected to plasma irradiation treatment in advance. The sealant films 13 are heat-sealed. Thereafter, the uncoated thin non-aqueous electrolyte secondary battery 19 in which the flat electrode body 8 is sealed with the bag-shaped exterior film 18 shown in FIG. Make it.
[0021]
In the step, it is preferable that the inside of the bag-shaped outer film material is sealed in a state where it has been degassed in advance. Specifically, 1) A method in which an electrode body is housed in a bag-shaped exterior film material, the exterior film material is degassed under reduced pressure, and then a nonaqueous electrolyte is injected and sealed as it is. 2) The electrode body In addition, after storing the nonaqueous electrolytic solution in a bag-shaped exterior film material in an air atmosphere, a method of degassing under reduced pressure and sealing can be employed.
[0022]
(4th process)
The secondary battery is housed in a pressure vessel (not shown) and subjected to pressurization to impregnate the non-aqueous electrolyte into the flat electrode body in the secondary battery, whereby the uncharged thin non-aqueous electrolyte 2 The next battery is manufactured.
[0023]
For the pressurizing process, a method of supplying a pressurizing medium into the pressure vessel can be employed. As this pressurizing medium, for example, any one of carbon dioxide, nitrogen, dry air, and argon can be used. Moreover, water can be used as the pressurizing medium. However, from the viewpoint of preventing moisture from entering the bag-shaped outer layer film, it is preferable to use a gas, particularly a gas not containing moisture, as the pressurizing medium. When carbon dioxide is used as the gas, carbon dioxide penetrates into the bag-shaped outer film by pressurization to form a more stable solid electrolyte interface (SEI). This is effective because an effect such as improvement can be expected.
[0024]
In the pressurizing treatment using the pressure vessel, it is preferable to increase the pressure because the impregnation rate of the non-aqueous electrolyte into the electrode body can be increased in proportion to the differential pressure. However, it is necessary to increase the thickness of the pressure vessel or strengthen structural reinforcement as the applied pressure increases. For this reason, it is preferable that the applied pressure is 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, only the electrode body portion impregnated in the initial charging step (preliminary charging and main charging) described later is charged. For this reason, compared to a so-called fully impregnated state where the entire space including the space between the electrodes is completely impregnated with the non-aqueous electrolyte, the charged portion is substantially at a high rate, and the discharge capacity is small. Thus, various characteristics of the battery including cycle characteristics are deteriorated. In addition, the variation in the impregnation state increases the variation in discharge capacity and other characteristics. Therefore, it is necessary to fully impregnate the battery when it is 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 much larger than the relative permittivity of the gap, so that the non-aqueous electrolyte is impregnated in the gap of the electrode group and replaced with the non-aqueous electrolyte. This is based on the fact that the capacitance between the electrodes of the electrode group increases by an order of magnitude. Similarly, since the impedance of the non-aqueous electrolyte is significantly lower than the impedance of the gap, the non-aqueous electrolyte is impregnated into the gap of the electrode group and replaced with the non-aqueous electrolyte, so that the gap between the electrodes of the electrode group is reduced. This is based on an order of magnitude drop in impedance.
[0027]
The determination of the fully impregnated state of the battery is specifically performed by detecting the electrostatic capacity and / or impedance of the battery and determining whether or not the value of the predetermined electrostatic capacity and / or impedance has been reached through experiments. 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 has reached a value corresponding to full impregnation, it is determined as full impregnation.
[0028]
(5th process)
After the secondary battery is taken out 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 manufacture a thin non-aqueous electrolyte secondary battery that has been initially charged.
[0029]
Here, the “preliminary charging” means that charging is performed at a voltage at which the active material of the positive and negative electrodes does not substantially expand and 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 preliminary 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 in an open state or a sealed state. However, the secondary battery is sealed when pressurized with a high-pressure gas.
[0030]
The “main charge” means that the active material of the positive and negative electrodes is charged at a voltage higher than the preliminary charge and the positive and negative electrode active materials are sufficiently charged to cause expansion of the electrode group. To 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 these gases are preferably dried. In addition, by using a dry gas, moisture permeates into the exterior member and prevents degradation of battery performance due to reaction with an electrolyte in the electrolyte, for example, lithium hexafluorophosphate to generate hydrofluoric acid. Is possible. By using carbon dioxide gas, nitrogen gas, or inert gas as gas, oxygen penetrates into the exterior member and prevents oxidation of electrolyte, positive electrode, negative electrode, separator, current collector, etc. Can be prevented.
[0032]
The pressure applied by the gas is preferably 0.1 to 15 MPa as a gauge pressure. If the pressure applied by the gas is less than 0.1 MPa in terms of gauge pressure, expansion due to the gas generated during the preliminary charging is sufficiently suppressed, and it may be difficult to quickly dissolve the generated gas in the electrolyte. . On the other hand, when the pressure applied by the gas exceeds 15 MPa in gauge pressure, it is necessary to increase the thickness of the wall of the container in order to increase the pressure resistance of the pressure container, or the operability may be deteriorated.
[0033]
Next, the positive electrode 3, the separator 4, the negative electrode 7, the nonaqueous electrolyte, the external leads 9 and 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 a structure in which, for example, 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, LiCoO₂, LiNiO₂, Li_xNi_yCo_1-yO₂(However, x and y differ depending on the state of charge of the battery, and usually 0 <x <1, 0.7 <y <1.0), Li_xCo_ySn_zO₂(However, x, y, and z represent numbers of 0.05 ≦ x ≦ 1.10, 0.85 ≦ y ≦ 1.00, and 0.001 ≦ z ≦ 0.10, respectively). Lithium composite oxide is a mixture of lithium carbonate, nitrate, oxide or hydroxide and carbonate, nitrate, oxide or hydroxide of cobalt, manganese, nickel, etc. with a predetermined composition, It can be obtained by firing at a temperature of 600 to 1000 ° C. in an atmosphere. Among them, Li_xCo_ySn_zO₂(Where x, y, and z represent numbers of 0.05 ≦ x ≦ 1.10, 0.85 ≦ y ≦ 1.00, and 0.001 ≦ z ≦ 0.10, respectively). Since the particle size of the lithium-containing compound is small and uniform, the battery having excellent cycle characteristics can be obtained. The reason for setting 0.001 ≦ z ≦ 0.10 is that when 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 becomes small.
[0037]
As the binder, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), or 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, an ethylene-propylene copolymer, an ethylene-butene copolymer, or a woven fabric or a 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 copper and nickel plates or meshes.
[0042]
The active material may be any material that can dope and dedope lithium, such as graphites, cokes (petroleum coke, pitch coke, needle coke, etc.), pyrolytic carbons, and fired bodies of organic polymer compounds (phenols). Resin or the like is calcined and carbonized at an appropriate temperature), or lithium metal, 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, or carboxymethylcellulose.
[0044]
4) Non-aqueous electrolyte
This nonaqueous electrolytic solution has a composition in which an electrolyte is dissolved in a nonaqueous solvent.
[0045]
Examples of the electrolyte include lithium perchlorate (LiClO)._Four), Lithium tetrafluoroborate (LiBF)_Four), Lithium hexafluorophosphate (LiPF)₆), Lithium hexafluoroarsenate (LiAsF)₆), Lithium trifluoromethanesulfonate (LiCF)_ThreeSO_Three), Lithium (bis) trifluoromethanesulfonimide [LiN (CF_ThreeSO₂)₂], Lithium bis [5-fluoro-2-olato-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-dioxolane, methylsulfolane, Acetonitrile, propyl nitrile, anisole, acetate ester, propionate ester and the like can be used, and two or more kinds may be mixed and used. 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. By adding such a surfactant, it becomes possible to improve the wettability of the non-aqueous electrolyte with respect to the separator.
[0047]
The concentration of the electrolyte in the non-aqueous solvent is preferably 0.5 mol / L or more.
[0048]
In particular, as the non-aqueous electrolyte, lithium tetrafluoroborate (LiBF) is used as a non-aqueous solvent of ethylene carbonate (EC) and γ-butyrolactone (γ-BL)._FourWhen the solution in which the electrolyte is dissolved is used, it is difficult to evaporate even when the degree of vacuum is increased at the time of depressurization, and there is little foaming. Therefore, the battery can be easily manufactured. In this case, EC has a higher viscosity than γ-BL, and its capacity decreases at low temperatures. For this reason, there exists a possibility that a low temperature characteristic may deteriorate, so that there are many ECs. 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. For this reason, it is preferable that the blending ratio of EC / γ-BL is 2/1 to 1/5 (volume ratio). LiBF_FourIs preferably 0.75 to 2 mol / L based on the total amount of the solvent. When it 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 non-aqueous 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. It is done.
[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 or copper. Here, since aluminum and copper are easily corroded by the electrolytic solution and nickel is difficult to corrode, it is preferable to use nickel as the external lead material. However, if copper or nickel is used as the positive external lead material, Elutes. Titanium or stainless steel high-purity ferritic steel (29Cr-4Mo-2Ni) does not elute into the electrolyte, but these metals are not suitable because they increase the battery impedance. Therefore, aluminum or an aluminum alloy must be used. Moreover, it is preferable to use nickel as a negative electrode lead terminal material for the said reason. Nickel is unlikely to be corroded by an electrolytic solution, so it is possible to use a negative electrode-side external lead that is not subjected to a surface treatment with a chemical solution. Of course, it is possible to manufacture a more reliable battery by subjecting the negative electrode-side external lead to surface treatment with a chemical solution. Since nickel has a high impedance, it generates heat abnormally due to a resistance loss when an external short circuit occurs, and the terminal is likely to melt. In this case, a copper strip having a nickel plating on the surface may be used.
[0052]
Examples of surface treatment methods for aluminum and aluminum alloys 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. Anodization at 20V in an aqueous chromic acid solution of (4) surface treatment by immersion in 140 g / L of caustic soda, (5) 60-70 aqueous solution of sodium chromate / sulfuric acid / water at a mass ratio of 3/30/100 For example, surface treatment by dipping at a temperature of ° C. By the surface treatment with these chemical solutions, an oxide film made of porous alumina having a hole shape and having many protrusions having a height of several nanometers to several thousand nanometers is formed on the aluminum and aluminum alloy surfaces.
[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 resin film 15 having rigidity are laminated in this order.
[0054]
The sealant film seals the power generation 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]
The sealant film is preferably an unstretched film that does not dissolve or swell in the non-aqueous electrolyte. For example, polyolefin polymer such as unstretched polypropylene (PP), 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), may be used polymethylpentene (PMP) and the like. In particular, a resin film obtained by graft polymerization of 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 beneficial.
[0056]
The aluminum or aluminum alloy sheet acts as a barrier to prevent permeation of non-aqueous electrolyte and 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 resin having rigidity, for example, a biaxially stretched polyolefin polymer such as polyethylene (PE) or polypropylene (PP), a film of polyethylene terephthalate (PET), polyamide (PA), or the like can be used.
[0059]
7) Adhesive insulating film 16
As this adhesive insulating film, it is preferable to use a film that has the same characteristics and formability as the sealant film and has excellent adhesion to the metal that is the positive and negative external leads. Specifically, a polymer obtained by graft polymerization of an acid anhydride such as maleic anhydride to the base polymer made of the resin used for the sealant film described above 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 highly reliable sealing structure in which the periphery of the positive and negative external lead portions is uniform can be obtained.
[0061]
The present invention is not limited to the manufacture of the thin battery shown in FIG. 5 described above, but can also manufacture a square battery (for example, a square nonaqueous electrolyte secondary battery) having the structure shown in FIG. 6 described below. it can.
[0062]
That is, in FIG. 6, the outer can 21 made of a metal and made of, for example, aluminum serves as a positive electrode terminal, and the 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 a structure in which an active material layer is formed on both sides of a negative electrode 24 and a separator 25 having a structure in which an active material layer is formed on both surfaces of a current collector such as a copper plate and an aluminum plate, for example. The positive electrode 26 is wound in a spiral shape so that the positive electrode 26 is located on the outermost periphery, and then press-molded into a flat shape.
[0063]
A spacer 27 made of, for example, synthetic resin having a lead extraction hole (not shown) near the center is disposed on the electrode group 23 in the outer can 21. The lid 28 made of a metal such as aluminum is airtightly 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 body 28, an extraction hole for the negative electrode terminal is opened, and a liquid injection hole 29 is opened at a location separated from the extraction hole. For example, the sealing member 30 made of a rectangular plate made of aluminum, for example, injects the non-aqueous electrolyte through the liquid injection hole 29 of the cover body 28, with respect to the cover body 28 around the liquid injection hole 29. Joined by ultrasonic welding, the liquid injection hole 29 is hermetically sealed.
[0064]
The negative electrode terminal 31 is hermetically sealed in the hole of the lid body 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 the 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 accommodated, and a non-aqueous electrolyte is covered. In addition to the method of injecting and containing the liquid through the injection hole 29 of the body 28, sealing it with a sealing member, precharging it, pressurizing it with a high-pressure gas, and further performing the main charging, the precharging is performed as follows. It is preferable to carry out under conditions.
[0066]
That is, the electrode group 23 is accommodated in the outer can 21, and the non-aqueous electrolyte is injected and stored through the injection hole 29 of the lid 28, and then 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 liquid injection hole 29 is hermetically sealed with the sealing member 30, the sealed battery is pressurized with a high-pressure gas, and the pressurized battery is fully charged.
[0067]
The potential for precharging is preferably 3.6 V to 3.9 V, and is performed at a rate of 0.5 C for 2 hours, for example. When the precharge potential is less than 3.6 V, hydrogen gas is generated in the main charge, and the outer can may be swollen. If the precharge potential exceeds 3.9 V, the hydrogen gas generation rate in the precharge increases, and the outer can may swell in the precharge. Although it is conceivable to suppress the expansion of the outer can by lowering the rate by increasing the preliminary charging potential, the charging time becomes longer, and accordingly, the battery opening time at the time of preliminary charging (injection port (Opening time) becomes longer. As a result, the non-aqueous electrolyte in the outer can volatilizes and the electrolyte composition 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 example, for the same reason as described above. For example, the pressure is 0.5 MPa (gauge pressure) for 24 hours.
[0069]
The gas has the same reason as described above, that is, dry air is used because of the relationship with the non-aqueous electrolyte, or nitrogen gas or inert gas is used because the relationship between the electrode group and the non-aqueous electrolyte is prevented. It is preferable to do.
[0070]
As described above, according to the present invention, an initial charging battery (secondary battery) is precharged, and the precharged sealed battery is subjected to gas pressurization and then the main charging is performed. Can suppress swelling due to gas generation and expansion of the active material of the positive and negative electrodes, and can prevent separation of the positive electrode and the negative electrode, so that the charge and discharge capacity is not reduced, and it falls within the required dimensions after the completion of the initial charge, For example, the thickness of a thin battery can be reduced.
[0071]
That is, during the preliminary charging, a decomposition reaction such as hydrogen, methane, ethylene, or carbon monoxide is generated due to a charging reaction that occurs between the electrolyte and the positive and negative electrodes, and the internal pressure of the exterior member (for example, the packaging material) is increased. The laminated film constituting the material is spread out, and in particular, the thickness of the central portion of the battery is increased. In some cases, the packaging material holding the electrode group is separated from the electrode group, and therefore, 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 active material of the positive and negative electrodes 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 electrodeposited to form a thin metal lithium layer. As a result, the battery becomes thick or the charge / discharge capacity decreases.
[0072]
In view of the above, the present invention provides the above-described decomposition gas which is generated in the preliminary charging and retained between the electrode plates by pressurizing the sealed battery with a high-pressure gas after the preliminary charging and before the main charging. Is dissolved in the electrolyte solution in the exterior member (for example, the packaging material) (Henry's law) and can be returned to the shape before precharging without swelling by pressing the electrode group through the packaging material. Can be prevented from being separated from the electrode group or 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 space 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 during the main charging, the electrode is twisted, the finished thickness of the battery is increased, or in the case of a non-aqueous electrolyte secondary battery, a metal is interposed between the electrode plates. Since it is possible to prevent lithium from being electrodeposited, a battery having a set thin dimension can be manufactured without causing a decrease in charge / discharge capacity.
[0073]
In particular, by making the pressure applied by the gas 0.1 to 15 MPa as a gauge pressure, the effect of dissolving the gas generated in the preliminary charging in the electrolytic 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]
In addition, it is possible to manufacture a battery in which an increase in battery thickness and a decrease in discharge capacity when a charge / discharge cycle is repeated are suppressed. This is because active sites for the electrolyte such as positive and negative electrodes disappear due to the above-described preliminary charging and initial charging, and gas is hardly generated during subsequent charging and discharging.
[0075]
Furthermore, according to the present invention, in order to suppress the swelling of the secondary battery as in the prior art, after exhausting the gas generated during charging to the outside, a charging method (hereinafter referred to as open charging) for sealing the exterior member, Steps such as a method of charging an uncharged battery fixed with a mold or a jig (hereinafter referred to as press charging) are not required.
[0076]
In the open charging, a countermeasure is required for the electrolyte to overflow with the gas. The press charging requires a complicated process such as mounting / removal of a mold or a jig. In addition, since the press charging is forcibly pressurized, there is a high risk of damaging the battery.
[0077]
Since the precharging, 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 causing contamination and corrosion. In addition, since the pressurization is performed with gas, the risk of damaging the battery can be reduced compared to 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 precharge is performed after the non-aqueous electrolyte is injected into the exterior can through the liquid injection hole. By carrying out under the voltage condition of 3.6 to 3.9 V with the liquid injection hole opened and the liquid injection hole facing upward, the swelling of the metal outer can can be effectively suppressed. .
[0079]
In other words, since hydrogen, methane, ethylene, carbon monoxide, and other gases are generated during the initial charge, charging is performed in a sealed state, that is, in the state of an outer can with a lid attached and its injection hole sealed. If done, the internal pressure of the outer can increases, the outer can expands, the thickness of the outer can increases, and the finished thickness of the battery becomes thicker. In some cases, the positive and negative electrodes of the electrode group are separated from each other due to gas generation and expansion of the outer can, so that the electrode is twisted due to the expansion of the active material of the positive and negative electrodes due to repeated charging cycles, or the lithium ion secondary In the battery, metallic lithium is deposited between the electrode plates, and the deterioration of the discharge capacity of the battery is accelerated.
[0080]
Therefore, paying attention that the peak of gas generation is around 3.6 to 3.9 V, the battery is opened at that voltage and precharged to release the generated gas upward. Therefore, the outer can can be prevented from being swollen, and the thickness of the outer can and thus 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 positive electrode active material_0.98Sn_0.02O₂89 parts by weight, 6 parts by weight of graphite (KS6 manufactured by Lonza) as the conductive filler, 3 parts by weight of polyvinylidene fluoride (trade name manufactured by Kureha Chemical Co., Ltd .; # 1100) as the binder, 25 parts by weight of N-methylpyrrolidone as a solvent In addition to the above, the mixture was stirred uniformly and then dispersed using a bead mill to prepare a positive electrode slurry. The apparent viscosity of this slurry was 7500 mPa · s. Subsequently, this positive electrode slurry is uniformly applied to both sides of a 20 μm-thick strip-shaped aluminum foil as a current collector, the solvent is dried, and further press-molded with a roll press, and then cut into a predetermined size. Thus, a belt-like 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 current collector of the positive electrode by welding.
[0083]
<Production 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. 50 parts by weight of a fibrous carbon material was added to this dispersion and shear dispersed in the same manner. Further, 2.4 parts by weight of styrene butadiene rubber latex was further added and mixed and stirred to prepare a negative electrode slurry. The apparent viscosity of this slurry was 4500 mPa · s. Subsequently, the negative electrode slurry is uniformly applied to both sides of a 10 μm thick strip-shaped copper foil as a current collector, the solvent is dried, and further press-molded with a roll press, and then cut into a predetermined size. Thus, 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 negative electrode current collector by welding.
[0084]
Next, the positive electrode / separator / negative electrode / separator order is formed by separating the belt-like positive electrode and the belt-like 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 wound in a spiral shape with a flat core in cross section, further heated and compressed with a hydraulic press, and formed into 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 adhesive. Was prepared and cup-molded by heating and pressing from the maleated polypropylene film side of this material using a molding punch and a molding die. The maleated polypropylene film has a melting point of 138 ° C. Subsequently, this was cut into strips, and the short side of the cup of the exterior film material was bent 180 ° with a molding machine so that the maleated polypropylene film face was opposed to the inside. Next, of the surfaces of the sealant films on both sides facing inside the exterior material, non-cup-molded parts (parts other than the cup-formed part) that will be heat-fused in the subsequent process and plasma on the opposite parts Irradiation treatment was performed. Next, the flat electrode body was vacuum-heated and dried at 60 ° C. to remove moisture so as to be 300 ppm or less, and then the heat-sealed portions of the positive electrode side and negative electrode side external lead surfaces were subjected to plasma irradiation treatment. Then, the external lead of the positive and negative electrodes was housed in the cup of the outer film material so as to protrude outside the outer film material, and the 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 with a press head heated to 210 ° C. for several seconds, and the maleated polypropylene films were bonded together to form a seal portion. Further, in the state where the external lead of the exterior film material is extended, an adhesive insulating film in which at least a surface facing the external lead is plasma-irradiated in advance is interposed between the external lead and the exterior film. , Pressurizing for 5 seconds with a press head heated to 210 ° C, and bonding the positive and negative external leads and adhesive insulating film, adhesive insulating film and maleated polypropylene film, and maleated polypropylene film together to form a seal part did. These heat sealing orders may be performed simultaneously or first.
[0086]
Next, the non-aqueous electrolyte was injected and impregnated under a vacuum of 1 torr or less through the open long side portion of the outer film material. As this non-aqueous electrolyte, ethylene carbonate / methyl ethyl carbonate / LiPF₆= 34.9 / 53.1 / 12 (mass ratio) mixed liquid with 0.5% by weight of trioctyl phosphate (TOP) was used. After that, the unsealed part is pressed for 5 seconds by a press head (not shown) heated to 210 ° C., and the maleated polypropylene films of the parts subjected to plasma irradiation treatment are bonded together to form a sealed part. Then, an extra exterior film material part was cut and removed to produce a thin nonaqueous electrolyte secondary battery in an uncharged state. Subsequently, the secondary battery was placed in an autoclave that was a pressure vessel, and the secondary battery was pressurized at a gauge pressure of 0.5 MPa for 10 minutes by supplying dry air into the pressure vessel.
[0087]
Next, preliminary charging was performed at 0.5 C (375 mA) for 2 hours in the atmosphere at 20 ° C. Subsequently, after the secondary battery, which has been precharged, is placed in a pressurized container, dry air compressed at room temperature is fed into the secondary battery, and applied at 0.9 MPa (gauge pressure) for 5 hours through the exterior film. Pressed. As a result, the gas generated in the preliminary charging was dissolved in the electrolytic solution, and at the same time, a minute gap generated between the exterior film and the electrode body, the positive and negative electrodes, and the separator was crushed. Finally, by performing main charging for 8 hours under the conditions of 0.2 C (150 mA) and 4.2 V at 20 ° C., the non-rated dimensions are 3.8 mm in thickness, 35 mm in width, 62 mm in height, and the capacity is 750 mAh (0 .2C) thin non-aqueous electrolyte secondary battery 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 the preliminary charging was not performed.
[0089]
(Comparative Example 2)
The same method as in Example 1 except that the main charge is performed for 8 hours under the condition of 4.2 V at 0.5 C (375 mA) in the atmosphere of 20 ° C. without performing the precharge and the gas pressurization after the precharge. Thus, a thin nonaqueous electrolyte secondary battery was manufactured.
[0090]
<Battery performance test>
For the thin non-aqueous electrolyte secondary batteries of Example 1 and Comparative Examples 1 and 2 obtained, the thickness and 0.2C discharge capacity after the main charge (initial charge) were measured. In addition, each secondary battery after the initial charge is charged and discharged at 20 ° C. under the condition of 1.0 C / 1.0 C (charge condition: 650 mA, 4.2 V, 3 hours, discharge condition: 650 mA, 3.0 V cutoff) The thickness, discharge capacity, and discharge capacity retention ratio (maintenance ratio relative to the initial discharge capacity) after 500 cycles were measured. These results are shown in Table 1.
[0091]
[Table 1]

[0092]
As is clear from Table 1, the secondary battery of Example 1 that had been subjected to preliminary charging, gas pressurization, and main charging was a comparative example in which charging was performed at atmospheric pressure without performing gas pressurization after preliminary charging. Compared to the secondary battery of No. 1 and the secondary battery of Comparative Example 2 charged under atmospheric pressure without pre-charging and gas pressurization after the pre-charging, the thickness after the main charging is small and the discharge capacity is large. I understand.
[0093]
In addition, even after repeating the charge / discharge cycle, the secondary battery of Example 1 that had undergone preliminary charging, gas pressurization, and further main charge was charged at atmospheric pressure without performing gas pressurization after the precharge. Compared to the secondary battery of Comparative Example 1 and the secondary battery of Comparative Example 2 charged under atmospheric pressure without performing precharging and gas pressurization after precharging, the thickness is thin and the discharge capacity retention rate is high. I understand that.
[0094]
(Example 2)
A belt-like positive electrode, a belt-like negative electrode, a separator, and an electrolytic solution similar to those in Example 1 were prepared. Next, the positive electrode / separator / negative electrode / separator is connected to the belt-like positive electrode and the belt-like negative electrode through a separator made of a microporous polyethylene film having a thickness of 20 μm, a porosity of 50%, and an air permeability of 300 seconds / 100 cc. Laminated in order, wound in a spiral shape with a winding core having a flat cross section, further heated and compressed with a hydraulic press, and formed into 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 body in which the negative electrode terminal was hermetically sealed in the vicinity of the center and an injection hole for electrolyte was opened was prepared, and the 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, ethylene carbonate / methyl ethyl carbonate / LiPF having the same composition as in Example 1 under reduced pressure.₆= 34.9 / 53.1 / 12 (mass ratio) mixed solution containing 0.5% by weight of trioctyl phosphate (TOP) is injected through the injection hole of the lid body, and this is unprecedented. A rechargeable prismatic nonaqueous 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. under atmospheric pressure. Part of the gas generated by this 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]
Next, after putting the secondary battery that has been precharged into a pressurized container, dry air compressed at room temperature is sent in and pressurized through the aluminum can at 0.9 MPa with a gauge pressure of 15 MPa for 15 hours. did. At this time, the gas generated by the preliminary charging was dissolved in the electrolytic solution, and at the same time, 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, by carrying out the main charging at 20 ° C. for 6 hours under the condition of 0.2 C (124 mA) and 4.2 V, the thickness of the structure shown in FIG. A prismatic nonaqueous electrolyte secondary battery having a thickness of 4.4 mm, a width of 30 mm, a height of 48 mm, and a 0.2C discharge capacity of 620 mAh was manufactured.
[0098]
(Example 3)
An electrode body is inserted into the aluminum can, an aluminum lid is welded to the opening of the aluminum can, and an electrolytic solution having the same composition as in Example 1 is injected under reduced pressure through the injection hole of the lid, After sealing this injection hole, the non-rated dimensions were 4.4 mm in thickness, 30 mm in width and 48 mm in height by the same method as in Example 2 except that preliminary charging was performed at 0.5 C (310 mA) for 2 hours. A rectangular nonaqueous 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, it was not rated by the same method as in Example 2 except that the main charging was performed for 6 hours at 20 ° C., 0.2 C (124 mA), 4.2 V. A rectangular non-aqueous electrolyte secondary battery having a thickness of 4.4 mm, a width of 30 mm, a height of 48 mm, and a capacity of 620 mAh (0.2 C) was manufactured.
[0100]
(Comparative Example 4)
Without pre-charging and gas pressurization after pre-charging, the main battery is charged for 6 hours under the conditions of 20 ° C, 0.2C (124mA), 4.2V, and the secondary battery that has completed the main charging is pressurized. After putting in the container, dry air compressed at room temperature was fed, and the thickness was changed by the same method as in Example 2 except that the pressure was 0.9 MPa at 0.9 MPa through the aluminum can. A square nonaqueous electrolyte secondary battery having a capacity of 4 mm, a width of 30 mm, a height of 48 mm, and a capacity of 620 mAh (0.2 C) was produced.
[0101]
<Battery performance test>
For the obtained prismatic nonaqueous electrolyte secondary batteries of Examples 2 and 3 and Comparative Examples 3 and 4, the thickness and the 0.2 C discharge capacity after the main charging were measured. In addition, each secondary battery after the initial charge is 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 cutoff) The thickness, discharge capacity, and discharge capacity retention rate after 500 cycles were measured. These results are shown in Table 2.
[0102]
[Table 2]

[0103]
As can be seen from Table 2, the secondary battery of Example 2 that had undergone preliminary charging, gas pressurization, and further main charge processing was under atmospheric pressure without performing precharge and gas pressurization after precharge. Compared to the charged secondary battery of Comparative Example 3, it can be seen that the thickness after the main charging is thin and the discharge capacity is large.
[0104]
The battery of Example 3 that had been precharged, gas pressurized, and further charged in a sealed state after injection was precharged with the injection hole open, and then the injection hole was sealed and the gas added. The secondary battery of Example 2 subjected to this charging process was slightly thicker and the discharge capacity was small, but the rating was satisfied.
[0105]
It can be seen that the secondary battery of Comparative Example 4 that was pressurized after the main charging was thicker than the secondary battery of Example 2 that was pressurized before the main charging.
[0106]
In addition, the secondary batteries of Examples 2 and 3 that have undergone preliminary charging, gas pressurization, and further main charge after repeated charge / discharge cycles do not perform precharge and gas pressurization after the precharge. It can be seen that the thickness is smaller and the discharge capacity retention rate is higher than the secondary batteries of Comparative Example 3 charged under atmospheric pressure and Comparative Example 4 charged with gas after the main charging.
[0107]
In the above-described embodiment, the preliminary charging is performed in a sealed state. However, although the process becomes complicated, the preliminary charging may be performed in an open state, and the sealing may be performed in a subsequent pressurizing process using a high-pressure gas. .
[0108]
(Example 4)
<Preparation of positive electrode>
First, lithium cobalt oxide (LiCoO₂) To 90% by weight of powder, 5% by weight of acetylene black and 5% by weight of polyvinylidene fluoride (PVdF) in dimethylformamide (DMF) were added and mixed to prepare a slurry. The slurry was applied to both surfaces of a current collector made of an aluminum foil having a thickness of 15 μm, then dried and pressed to produce a positive electrode having a structure in which the positive electrode layer was supported on both surfaces of the current collector. The thickness of the positive electrode layer was 60 μm per side.
[0109]
<Production of negative electrode>
Mesophase pitch carbon fiber heat treated at 3000 ° C. as a carbonaceous material ((002) plane spacing (d determined by powder X-ray diffraction) (d₀₀₂) 0.336 nm) was mixed with 95% by weight of a powder and 5% by weight of a polyvinylidene fluoride (PVdF) dimethylformamide (DMF) solution 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 prepare a negative electrode having a structure in which the negative electrode layer was supported on the current collector. The thickness of the negative electrode layer was 55 μm per side.
[0110]
In addition, the surface interval d of the (002) plane of the carbon fiber.₀₀₂Were 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 film 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) A non-aqueous electrolyte was prepared by adding 0.5% by weight of vinylene carbonate (VC).
[0113]
<Production of electrode group>
After the positive electrode lead made of a strip-shaped aluminum foil (thickness 100 μm) is ultrasonically welded to the positive electrode current collector, and the negative electrode lead made of a strip-shaped nickel foil (thickness 100 μm) is ultrasonically welded to the negative electrode current collector The positive electrode and the negative electrode are spirally wound through the separator therebetween, then formed into a flat shape, further heated and compressed with a hydraulic press, and formed into a flat electrode body (electrode group). did.
[0114]
This electrode body was inserted into an aluminum outer can having a thickness of 0.25 mm, and a lid body 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 vacuum dried at 85 ° C. for 12 hours to remove moisture contained in the electrode group and the outer can. Subsequently, after quantitatively injecting the non-aqueous electrolyte having the above composition into the electrode group in the outer can through the injection hole of the lid, 0.5C (310 mA in an inert gas with the injection hole facing upward. ) Precharging was performed at 3.7V for 2 hours. Here, the reaction gas generated in the outer can at the time of charging was discharged to the outside from the injection hole of the lid. Thereafter, a sealing member made of, for example, an aluminum rectangular plate was joined to the lid around the liquid injection hole by, for example, ultrasonic welding, and the liquid injection hole was hermetically sealed.
[0116]
Next, after the secondary battery that has been precharged is placed in a pressurized container, dry air compressed at room temperature is fed in, and the outer can with lid is gasped at 0.5 MPa (gauge pressure) for 24 hours. Pressurization was performed. As a result, the gas generated in the preliminary charging was dissolved in the electrolytic solution, and at the same time, the minute gaps generated 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, by performing main charging at 20 ° C. for 10 hours under the conditions of 0.2 C (124 mA) and 4.2 V, the non-rated dimensions are 4.4 mm thick, 30 mm wide, 48 mm high, and the capacity is 620 mAh ( 0.2 C) square nonaqueous electrolyte secondary battery was manufactured.
[0117]
(Example 5)
A prismatic non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 4 except that gas pressurization after precharging was performed at 5 MPa (gauge pressure) for 12 hours.
[0118]
(Example 6)
A prismatic non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 4 except that gas pressurization after precharging was performed at 10 MPa (gauge pressure) for 4 hours.
[0119]
(Example 7)
A prismatic non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 4 except that gas pressurization after precharging was performed at 15 MPa (gauge pressure) for 1 hour.
[0120]
(Comparative Example 5)
A square nonaqueous electrolyte secondary battery was produced in the same manner as in Example 4 except that gas pressurization was not performed after the preliminary charging.
[0121]
<Battery performance test>
For the obtained square nonaqueous electrolyte secondary batteries of Examples 4 to 7 and Comparative Example 1, the thickness and 0.2C discharge capacity after main charging were measured. Moreover, about each secondary battery after this charge, it is charging / discharging on the conditions of 1.0C / 1.0C at 20 degreeC (charging conditions; 620mA, 4.2V, 3 hours, discharge conditions; 620mA, 3.0V cutoff) The discharge capacity maintenance rate after 500 cycles (maintenance 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 that were charged after gas pressure after preliminary charging and then subjected to main charging were the secondary batteries of Comparative Example 5 that were charged without performing gas pressure after preliminary charging. It can be seen that the thickness after the main charge is small and the discharge capacity is large.
[0124]
Moreover, it turns out that thickness is thin and the discharge capacity maintenance factor is high even after repeating 1C / 1C charge / discharge cycles at 20 ° C. for 500 cycles.
[0125]
【The invention's effect】
As described above in detail, according to the present invention, a method for manufacturing a battery having a small thickness and a large discharge capacity after repeated initial and charge / discharge cycles by applying gas pressure after preliminary charging and further performing main charging treatment and 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.
2 is a cross-sectional view taken along line II-II in FIG.
FIG. 3 is a perspective view showing a manufacturing process of the thin nonaqueous electrolyte secondary battery of the present invention.
4 is a cross-sectional view taken along line VI-VI in FIG.
FIG. 5 is a perspective view showing a manufacturing process of the thin non-aqueous electrolyte secondary battery of the present invention.
FIG. 6 is a partially cutaway perspective view showing a rectangular non-aqueous electrolyte secondary battery using an aluminum outer can as the outer member of the present invention.
[Explanation of symbols]
DESCRIPTION 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 films, 12 ... Cup, 16 ... Adhesive insulating film, 17a, 17b, 17c ... sealing portion, 18 ... exterior film, 21 ... aluminum exterior can, 28 ... lid, 29 ... injection hole, 30 ... sealing member, 31 ... negative electrode terminal.

Claims (2)

Preparing a metal outer can attached with a lid having a liquid injection hole;
Assembling an uncharged battery having a power generation element by housing a positive electrode, a negative electrode, and a separator in the outer can and injecting a non-aqueous electrolyte into the outer can through the injection hole;
Precharging the uncharged battery under a voltage condition of 3.6 to 3.9 V with the liquid injection hole opened and the liquid injection hole facing upward;
Hermetically sealing and injecting the liquid injection hole of the precharged battery; and
A step of pressurizing by the high pressure gas in 0.1~15MPa battery gauge pressure of the sealed,
And a step of fully charging the pressurized battery. The battery manufacturing method according to claim 1, wherein the gas is dry air, nitrogen, or an inert gas.

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