JP4161400B2 - Non-aqueous electrolyte lithium secondary battery and manufacturing method thereof - Google Patents

Description

【０１４９】
負極集電体（Ｃｕ箔）は、孔がないものより孔があるものの方が電位ムラが小さく好ましい。リチウムイオンは、負極集電体の孔を通り、負極の表面と裏面の間を自由に移動できるので、電位ムラが小さくなる。
【０１５０】
サンプルＮｏ．１及び２は、Ｌｉ片巾が４ｍｍであり、Ｌｉ片チップが１０ｍｍであるので、Ｌｉ箔が負極合剤層の表面の４０％（＝４ｍｍ／１０ｍｍ）を被覆している。サンプルＮｏ．３及び４は、Ｌｉ片巾が８ｍｍであり、Ｌｉ片チップが２０ｍｍであるので、Ｌｉ箔が負極合剤層の表面の４０％（＝８ｍｍ／２０ｍｍ）を被覆している。サンプルＮｏ．５及び６は、Ｌｉ片巾が８ｍｍであり、Ｌｉ片チップが１０ｍｍであるので、Ｌｉ箔が負極合剤層の８０％（＝８ｍｍ／１０ｍｍ）を被覆している。同様に、サンプルＮｏ．７及び８は、Ｌｉ箔が負極合剤層の８０％（１６ｍｍ／２０ｍｍ）を被覆し、サンプルＮｏ．９〜１２は、Ｌｉ箔が負極合剤層の１００％を被覆している。Ｌｉ箔が負極合剤層の８０％以上を被覆しているものが、電位ムラが小さく、量産適性に優れている。
【０１５１】
Ｌｉ箔の厚みは、サンプルＮｏ．１〜８が４５μｍであり、サンプルＮｏ．９〜１２が３６μｍである。Ｌｉ箔の厚み変動率は、サンプルＮｏ．１〜１０が１５％であり、サンプルＮｏ．１１が５％であり、サンプルＮｏ．１２が２５％である。Ｌｉ箔の厚みが６０μｍ以下、かつ厚み変動率が平均厚みに対して２０％以下であるものが、好ましい。さらに、Ｌｉ箔の厚みが１０〜４０μｍ、かつ厚み変動率が１０％以下のものが、より好ましい。
【０１５２】
Ｌｉ箔は、負極の両面に貼るよりも、片面に貼る方が量産適性に優れ、好ましい。
【０１５３】
（実施例２）
〔表２〕に示すサンプルＮｏ．１〜８の８個の電池について上記の電位ムラ測定を行うと共に、負極をスリットする工程において発生する屑の量の度合いを調べた。サンプルＮｏ．１〜８は、負極集電体（Ｃｕ箔）の孔の開口率及び孔の大きさが異なる。負極の片面の表面には、３６μｍ厚のＬｉ箔を全面に貼り付けた。
【０１５４】
【表２】

【０１５５】
負極集電体（Ｃｕ箔）の孔の開口率が０．１％以上、１０％以下であり、孔の大きさが１×１０^-7ｃｍ² 以上、１×１０^-2ｃｍ² のものが、電位ムラが小さく、スリット工程時の屑の発生が少ないので好ましい。
【０１５６】
（実施例３）
以下のサンプルＮｏ．１〜４の４個の電池を作成した。各電池の負極集電体（Ｃｕ箔）は孔を有し、その孔の開口率は５％であり、孔の大きさは０．００１ｃｍ² である。負極の片面には、原則として３６μｍ厚のＬｉ箔を全面に貼った。全ての電池は、巻回群の最外周がセパレータで覆われている。
【０１５７】
サンプルＮｏ．１：負極は、表裏面とも同じ長さの負極合剤を塗設した。巻回した時に最外周は正極合剤層よりもさらに外側に負極合剤層があり、かつ最内周は正極合剤層よりもさらに内側に負極合剤層があるように巻いた。Ｌｉ箔は、負極の外面のみに全面貼りした。
【０１５８】
サンプルＮｏ．２：サンプルＮｏ．１と同様に作った。ただし、図２に示すように、負極の最外周は内側にのみ負極合剤層を塗設し、負極の最内周は、外側にのみ負極合剤層を塗設し、かつその部分にはＬｉ箔の貼り付け量を半分にした。すなわち、その部分には負極集電体上に４ｍｍ巾のＬｉ片を８ｍｍピッチで貼り付けた。
【０１５９】
サンプルＮｏ．３：負極は、表裏面とも同じ長さの負極合剤を塗設した。巻回した時に最外周は負極合剤層よりもさらに外側に正極合剤層があり、かつ最内周は負極合剤層よりもさらに内側に正極合剤層があるように巻いた。正極のその最外周部分は、内面にのみ正極合剤層を塗設し、かつ正極の最内周部分は外面のみに正極合剤層を塗設した。Ｌｉ箔は、負極の外面にのみ負極合剤層の全長に渡り全面貼りした。
【０１６０】
サンプルＮｏ．４：サンプルＮｏ．３と同様に作成した。ただし、Ｌｉ箔は負極の内面にのみ全面貼りした。
【０１６１】
〔表３〕に示す活性化前のエージング条件により、サンプルＮｏ．１〜４をエージング処理（前処理、活性活処理、後処理を含む）し、負極内にリチウムを拡散させた。〔表３〕に、その時に、Ｌｉ箔が溶解せずに残った程度及びサイクル寿命を調べた結果を示す。サイクル寿命は、５００サイクルの充放電後の容量維持率を表す。
【０１６２】
【表３】

【０１６３】
サンプルＮｏ．１よりもサンプルＮｏ．２の方がサイクル寿命が長い。サンプルＮｏ．１は、最外周の負極両面に負極合剤層が設けられている。その外側面の負極合剤層は、正極が対向していないので、その部分で無駄なエネルギが放出され、サイクル寿命が短くなる。サンプルＮｏ．２は、正極が対向しない負極の部分には負極合剤層を設けないので、充放電の効率が高くなり、サイクル寿命が長くなる。その部分では、負極集電体の片面にのみ負極合剤層が設けられているので、両面に負極合剤層が設けられている部分に比べ、Ｌｉ箔の量は半分でよい。負極集電体上のＬｉ箔は、集電体の孔を通り、逆側の面の負極合剤層に拡散する。
【０１６４】
サンプルＮｏ．３及び４を同条件でエージングした場合、サンプルＮｏ．３よりもサンプルＮｏ．４の方がＬｉ箔の溶解残りが小さく、サイクル寿命が長い。すなわち、Ｌｉ箔は、電極（好ましくは負極）の外面に貼るのが好ましい。
【０１６５】
サンプルＮｏ．３において、活性化前のエージング条件は、５０℃１４日よりも５０℃７日の方がサイクル寿命が長い。活性化前のエージング条件は、２０℃以上、６０℃以下の温度、１日以上１０日以下の時間が好ましい。
【０１６６】
【発明の効果】
本発明によれば、有孔集電体の両面に合剤層を設けることにより、正極又は負極を形成する。有孔集電体の孔を通って、両面の合剤層の間をリチウムイオンが移動することができるので、電位ムラが小さく、電池の性能が向上する。
【０１６７】
また、有孔集電体を有する負極又は正極の少なくとも片面の表面にリチウム金属箔を圧着することにより、リチウムは集電体の孔を通って集電体の両面の合剤層に拡散可能である。必ずしも、負極又は正極の両面にリチウム金属箔を圧着する必要はない。リチウム合剤層に拡散させることにより、合剤層が活性化する。
【図面の簡単な説明】
【図１】巻回前の巻回電極群の断面図である。
【図２】巻回電極群の上面図である。
【図３】円筒型電池の断面図である。
【符号の説明】
１ 電池缶
２ 負極
３ 正極
４ セパレータ
５ 下部絶縁板
６ 上部絶縁板
７ ガスケット
８ 正極リード
９ 防爆弁体
１０ 電流遮断スイッチ
１０ａ 第一導通体
１０ｂ 第二導通体
１０ｃ 絶縁リング
１１ ＰＴＣリング
１３ 端子キャップ
１５ 溶接プレート
１６ 絶縁カバー
２０ 巻芯
２１、２２ セパレータ
２３ 正極集電体
２４ 正極リード
２６ 負極集電体
２７ 負極合剤
３０ 絶縁性材料
３５ 正極シート
３６ 負極シート
５３ リチウム箔
５４ａ、５４ｂ 孔
６０ｎ 負極
６０ｐ 正極
６１ｎ 負極集電体
６１ｐ 正極集電体
６２ｎ 内側面の負極合剤
６２ｐ 内側面の正極合剤
６３ｎ 外側面の負極合剤
６３ｐ 外側面の正極合剤[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a nonaqueous electrolyte lithium secondary battery having a high discharge capacity and easy to manufacture.
[0002]
[Prior art]
Lithium secondary batteries that use lithium and lithium alloys as the negative electrode active material have the advantage that the negative electrode has a high capacity density, but there are safety issues due to the deposition of metallic lithium (dendritic generation) and the cycle life is reduced due to this. Is a practical obstacle. In order to improve this, various carbonaceous materials and metal oxide materials have been developed as materials for reversibly intercalating (inserting and releasing) lithium into the negative electrode in the ionic state, and also reversibly inserting and releasing lithium ions. A so-called rocking chair type lithium ion secondary battery has been developed by combining a lithium-containing oxide capable of being used with a positive electrode active material, and is currently mass-produced as a general-purpose 4V class secondary battery.
[0003]
However, it is known that carbonaceous materials and metal oxide materials used for the negative electrode have irreversibility that the entire amount of inserted lithium is not released. For this reason, development of a material with low irreversibility, synthesis | combination of the material which inserted a small amount of lithium previously, etc. are tried. In addition, International Publication No. WO96 / 27910 describes using an electrode in which a thin film of metallic lithium is pasted on an electrode mixture in a strip shape. However, with this method, the load on the process of cutting or pasting the lithium foil into strips is large, and the lithium is in contact with the electrolyte and dissolves in the part where the lithium is pasted and the part where it is not pasted. There are problems such as variations in the distribution of lithium ions occluded in the electrode material.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for producing a non-aqueous electrolyte lithium secondary battery that is suitable for production and solves the above-described problems. Another object of the present invention is to provide a high capacity non-aqueous electrolyte lithium secondary battery excellent in discharge capacity.
[0005]
  In the non-aqueous electrolyte lithium secondary battery including a positive electrode and a negative electrode each having a mixture layer on both sides of the current collector, and a non-aqueous electrolyte, the above-described problems are solved.ButA perforated current collector having one or more holes communicating with the front and back surfaces thereof, and on the perforated current collectorNegativeOf the mixture layerOne side outside the winding groupLithium metal foil is crimped on the surfaceAnd the size of one hole of the perforated current collector is 1 × 10 ^-7 cm ² 1 × 10 ^-2 cm ² IsThis has been solved by a non-aqueous electrolyte lithium secondary battery.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Although the preferable form of this invention is enumerated below, this invention is not limited to these.
[0007]
(1) In a non-aqueous electrolyte lithium secondary battery that includes a positive electrode and a negative electrode each having a mixture layer on both sides of the current collector and a non-aqueous electrolyte, at least one of the current collectors of the positive electrode and the negative electrode has its front and back surfaces It is a perforated current collector having one or a plurality of holes communicating with each other, and a lithium metal foil is pressure-bonded to at least one surface of a mixture layer on both sides of the perforated current collector A non-aqueous electrolyte lithium secondary battery.
[0008]
(2) The nonaqueous electrolyte lithium secondary battery according to item 1, wherein the aperture ratio of the holes of the perforated current collector is 0.1% or more and 10% or less.
[0009]
(3) The size of one hole of the perforated current collector is 1 × 10^-7cm² 1 × 10^-2cm² Item 3. The nonaqueous electrolyte lithium secondary battery according to Item 1 or 2, wherein:
[0010]
(4) The nonaqueous electrolyte lithium secondary battery according to any one of (1) to (3), wherein the hole of the perforated current collector is a through hole.
[0011]
(5) The nonaqueous electrolyte lithium secondary battery according to any one of items 1 to 4, wherein the lithium metal foil is pressure-bonded on one side of the mixture layer on the perforated current collector .
[0012]
(6) The pressed lithium metal foil covers 80% or more of the surface of the mixture layer on the surface where the pressed lithium metal foil is present. Non-aqueous electrolyte lithium secondary battery.
[0013]
(7) The nonaqueous electrolyte lithium secondary battery according to any one of Items 1 to 6, wherein the thickness of the lithium metal foil is 60 μm or less and the thickness variation rate is 20% or less with respect to the average thickness. .
[0014]
(8) The nonaqueous electrolyte lithium secondary battery according to any one of Items 1 to 7, wherein the electrode to which the lithium metal foil is pressure-bonded is a negative electrode.
[0015]
(9) The mixture application amount of the negative electrode portion having the opposite positive electrode on only one side is a times the mixture application amount of the negative electrode portion having the opposite positive electrode on both surfaces (where 0.3 <a <0.7), The non-aqueous electrolyte lithium secondary battery according to Item 8, wherein the pressure-bonding amount of the lithium is 0.8 × a to 1.1 × a times.
[0016]
(10) The nonaqueous electrolyte lithium secondary battery according to any one of (1) to (9), wherein the negative electrode includes a composite oxide containing at least one kind of tin.
[0017]
(11) A non-aqueous electrolyte comprising a wound electrode group formed by laminating and winding the electrode according to any one of Items 1 to 10 and a separator, and then inserting the wound electrode group into a battery can. A method for producing a lithium secondary battery.
[0018]
(12) The method for producing a non-aqueous electrolyte lithium secondary battery according to item 11, wherein in the wound electrode group, the lithium metal foil is pressure-bonded on the outer surface of the negative electrode.
[0019]
(13) The electrode having the mixture layer on the innermost circumference and the outermost circumference of the wound electrode group is a negative electrode, and the negative electrode in the innermost circumference and the outermost circumference portion has the mixture layer only on one side. Item 13. The method for producing a nonaqueous electrolyte lithium secondary battery according to Item 11 or 12.
[0020]
(14) The steps 11 to 13 are characterized in that, after the wound electrode group is inserted into the battery can, the steps from injection of the electrolyte into the battery can until the battery can is crimped and sealed are performed at 20 ° C. or less. The manufacturing method of the nonaqueous electrolyte lithium secondary battery in any one of.
[0021]
(15) The wound electrode group is inserted into a battery can, an electrolyte is injected into the battery can, the battery can is crimped and sealed, and then aged before activation. Of manufacturing a non-aqueous electrolyte lithium secondary battery.
[0022]
(16) The method for producing a nonaqueous electrolyte lithium secondary battery according to item 15, wherein the aging before activation is performed at a temperature of 20 ° C. or more and 60 ° C. or less for 1 day or more and 10 days or less.
[0023]
Hereinafter, the present invention will be described in detail.
The battery according to the present embodiment has a positive electrode, a negative electrode, and a separator formed by applying an electrode mixture on both surfaces of a current collector, which will be described in detail below. The rotated electrode group is inserted into a battery can, and an electrolyte is injected into the battery can, then sealed, and appropriately aged to produce. The form of the battery may be any of a so-called square shape, cylindrical shape, and sheet shape.
[0024]
FIG. 1 is a side view of an electrode group before winding.
The core 20 has a diameter of, for example, 3.5 mm, and is sandwiched so that the vicinity of one end of the two sheet-like insulating separators 21 and 22 is folded. The positive electrode current collector 23 has a thin positive electrode mixture layer 44a applied to the upper surface (inner peripheral surface) and a thick positive electrode mixture layer 44b applied to the lower surface (outer peripheral surface). The positive electrode mixture is not applied. The positive electrode lead 24 is bonded to a portion on the positive electrode current collector 23 where the positive electrode mixture is not applied. In the negative electrode current collector 26, a thin negative electrode mixture layer 27a is applied to the upper surface, and a thick negative electrode mixture layer 27b is applied to the lower surface, and the negative electrode mixture is not applied to both surfaces near the tip CT. The positive electrode mixture layer 44a is displaced from the positive electrode mixture layer 44b by a length L1 outside the winding (right side in the figure), and the negative electrode mixture layer 27a is a length L1 outside the winding from the negative electrode mixture layer 44b. It is only shifted.
[0025]
The positive electrode current collector 23 and the negative electrode current collector 26 have a large number of holes 54a and 54b, respectively. In the lithium secondary battery, lithium ions can freely move between the negative electrode mixture 27 a on the upper surface and the negative electrode mixture 27 b on the lower surface through the holes 54 b of the negative electrode current collector 26. Similarly, in the positive electrode 35, lithium ions can move between the positive electrode mixture 44a and 44b through the hole 54a. By providing the holes 54a and 54b in the current collectors 23 and 26, lithium ions can pass through the current collectors 23 and 26, so that the potential unevenness of the positive electrode 35 and the negative electrode 36 is reduced, and the performance of the battery is improved. The current collector holes 54a and 54b may be one or plural, but many are preferable.
[0026]
In order to activate the negative electrode mixture 27a, 27b, it is necessary to preliminarily insert Li into the negative electrode mixture 27a, 27b. Therefore, the Li foil 53 is attached to the surface of the negative electrode mixture on the lower surface (outer peripheral surface). Thereafter, the electrode is wound around the winding core 20 to create a wound electrode group, the wound electrode group is inserted into the battery can, the electrolyte is injected into the electrode can, the battery can is sealed, and then aged. . By this aging treatment, the Li foil 53 diffuses into the mixture 27b on the lower surface, and further passes through the holes 54b of the current collector and diffuses into the negative electrode mixture 27a on the upper surface.
[0027]
When there is no hole in the current collector 26, the Li foil 53 diffuses only in the negative electrode mixture 27b on the lower surface, and the Li foil does not diffuse in the negative electrode mixture 27a on the upper surface. In that case, it is necessary to provide Li foil not only on the negative electrode mixture 27b on the lower surface but also on the negative electrode mixture 27a on the upper surface.
[0028]
Even when the current collector 26 has holes 54b, Li foil may be provided on the negative electrode mixtures 27a and 27b on both sides. However, for mass production, it is more costly and work to provide Li foil only on one side. It is advantageous in terms of time. The Li foil may be provided on one of the surfaces of the negative electrode mixture 27a and 27b. However, it is preferable to provide the negative electrode mixture 27b on the outer peripheral surface because the Li foil is easily melted during aging as compared with the case of providing the negative electrode mixture 27a on the inner peripheral surface.
[0029]
The Li foil may be provided on the surface of the positive electrode mixture.
As a material for the current collector, the positive electrode is preferably aluminum, stainless steel, nickel, titanium, or an alloy thereof, and the negative electrode is preferably copper, stainless steel, nickel, titanium, or an alloy thereof. It is particularly preferable to use an aluminum foil for the positive electrode and a copper foil for the negative electrode.
[0030]
The shape of the current collector may be a perforated foil or an expanded metal, or a foamed metal, a porous foamed metal, or about 1 to 20 μm described in JP-A-59-18578, 61-74268, etc. It may be a metal fiber sheet made of metal fiber or a wire mesh.
[0031]
The aperture of the perforated current collector has an opening ratio of preferably 0.1% to 10%, particularly preferably 1% to 10%. The hole size of the perforated current collector is 1 × 10^-7cm² 1 × 10^-2cm² The following is preferred: 3 × 10^-6cm² 2 × 10^-3cm² The following are particularly preferred:
[0032]
It is necessary that the holes communicate with the front and back surfaces of the current collector so that lithium ions can permeate (pass). The communicating hole means a hole through which lithium ions can pass, and includes not only a straight through hole but also a hole connected in a maze shape. Particularly preferred is the case where the holes penetrate the current collector so that lithium ions can pass through the current collector in a short time.
[0033]
The positive electrode current collector 23 is wound between the core 20 and the separator 21. The negative electrode current collector 26 is wound between the two separators 21 and 22. A part 51 of the positive electrode current collector 23 is a part of the positive electrode current collector 23 where the tip CT of the negative electrode current collector 26 faces with the separator 21 in between. In the portion 51, the positive electrode lead 24 is bonded to the surface of the positive electrode current collector 23 on the core 20 side. That is, the portion of the positive electrode current collector 23 where the positive electrode lead 24 is bonded faces the end portion of the tip CT of the negative electrode current collector 26 with the separator 21 in between.
[0034]
When the positive electrode lead 24 is joined to the positive electrode current collector 23, burrs are generated, and the separator 21 facing the positive electrode lead 24 may be damaged. For example, the thickness of the separator 21 is 1 to 20 μm, and the thickness of the positive electrode current collector 23 is 2 to 15 μm. If the separator 21 is damaged at that portion, the positive electrode current collector 23 and the negative electrode current collector 26 are short-circuited. In order to avoid such a short circuit, the following measures are taken.
[0035]
A part 52 of the negative electrode current collector 26 is a peripheral portion of the tip CT of the negative electrode sheet 36 facing the portion of the positive electrode current collector 23 to which the positive electrode lead 24 is bonded with the separator 21 interposed therebetween. The surface (surface) of the portion 52 is covered with the insulating material 30. You may coat | cover an insulating material so that the surface and back surface of the peripheral part of the said CT may be covered. The insulating material 30 is preferably provided on the exposed portion of the negative electrode current collector 26, but the negative electrode mixture may be provided up to the tip CT of the negative electrode current collector 26 and the insulating material may be provided on the negative electrode mixture. In order to cover with an insulating material, a resin may be applied or an insulating tape may be attached. The insulating material is preferably an adhesive insulating tape.
[0036]
If the negative electrode current collector 26 is covered with the insulating material 30, even if the burr of the positive electrode lead 24 penetrates the separator 21, it is protected by the insulating material 30. Since the contact between the burr of the positive electrode lead 24 and the negative electrode current collector 26 can be avoided, a short circuit between the positive electrode 35 and the negative electrode 36 can be prevented. Further, even if creases occur in the negative electrode current collector 26 during winding, the ole portion is protected by the insulating material, so that an internal short circuit can be prevented.
[0037]
The positive electrode sheet 35 and the negative electrode sheet 36 are wound by a winding machine with the separators 21 and 22 interposed therebetween. Since the electrode sheet is gradually thickened in three stages, it is easy to wind and an electrode winding group with high roundness can be created. Furthermore, since the electrode mixture 44a or 27a on the upper surface is thinner than the electrode mixture 44b or 27b on the lower surface of the electrode sheet, it is easy to wind and a winding group with high roundness can be created. Thereby, the electrode sheet is cut at the time of winding, or a winding group with low roundness is created, and the inconvenience that the winding group cannot be inserted into the battery can can be prevented.
[0038]
In the electrode having a perforated current collector, a lithium metal foil is preferably pressure-bonded to at least one side of a mixture layer formed on both surfaces of the perforated current collector. The coating amount of the lithium metal foil on the mixture layer is preferably 80% or more of the surface of the mixture layer on the side (surface) where the pressed lithium metal is present. The thickness of the covering lithium metal foil is preferably 60 μm or less and the thickness variation rate is 20% or less with respect to the average thickness. Particularly preferred is a lithium metal foil having a thickness of 10 to 40 μm and a thickness fluctuation rate of 10% or less.
[0039]
The electrode to which the lithium metal foil is pressure bonded is preferably a negative electrode. When the electrode group is a wound electrode group, the surface to which the lithium metal foil is crimped is preferably the outer surface of the negative electrode. When the outermost peripheral electrode of the laminated electrode group or the wound electrode group is a negative electrode, the outer peripheral side mixture layer of this negative electrode does not have an opposing positive electrode, so the amount of lithium metal foil to be crimped to the outer peripheral layer is adjusted. It is preferable to do. When the amount of the mixture applied to the negative electrode portion having the opposite positive electrode only on one side is a times the amount of the mixture applied to the negative electrode portion having the opposite positive electrode on both sides, the pressure bonding amount of the lithium is 0.8 × a times to 1.1 × a times, where a satisfies the relationship of 0.3 <a <0.7. More preferable a is 0.4 <a <0.6.
[0040]
FIG. 2 shows a wound electrode group in which an electrode having a mixture on the outermost periphery and innermost periphery is a negative electrode. The positive electrode 60p has a positive electrode mixture 62p on the inner surface of the current collector 61p and a positive electrode mixture 63p on the outer peripheral surface. The negative electrode 60n has a negative electrode mixture 62n on the inner surface of the current collector 61n, and a negative electrode mixture 63n on the outer surface, except for the outermost periphery and the innermost periphery. In this wound electrode group, the outermost periphery is the negative electrode 60n and the innermost periphery is also the negative electrode 60n.
[0041]
In the outermost negative electrode 60n, the positive electrode 60p is opposed to the inner side, but the positive electrode 60p is not opposed to the outer side. In the outermost negative electrode current collector 61n, the negative electrode mixture 62n is provided only on the inner surface facing the positive electrode 60p, and the negative electrode mixture is not provided on the outer surface where the positive electrode 60p is not opposed. Even in the outermost negative electrode 60n, if a negative electrode mixture is provided on both sides of the current collector 61n, the negative electrode mixture on the outer surface is not opposed to the positive electrode 60p, and wasteful energy is released therefrom. The cycle life of the battery will be shortened. As shown in FIG. 2, in the outermost negative electrode 60n, by providing the negative electrode mixture 62n only on the inner surface, the charge / discharge efficiency can be improved and the cycle life can be extended.
[0042]
In the innermost negative electrode 60n, the mixture layer of the positive electrode 60p is opposed to the outer side (electrode group side), but the mixture layer of the positive electrode 60p is not opposed to the inner side (center cavity side). In the innermost negative electrode 60n, the negative electrode mixture 63n is provided only on the outer surface where the mixture layer of the positive electrode 60p faces, and the negative electrode mixture is not provided on the inner surface where the mixture layer of the positive electrode 60p does not face. For the same reason as described above, the cycle life of the battery can be extended.
[0043]
As described above, in order to preliminarily insert lithium into the negative electrode mixture, it is preferable to press-bond lithium foil to the outer surface of the negative electrode. The innermost and outermost negative electrode parts PA have a negative electrode mixture only on one side, and the other negative electrode part (the negative electrode part in the central part) PB has a negative electrode mixture on both sides. The amount of the negative electrode mixture in the innermost and outermost negative electrode portion PA is about ½ of the amount of the negative electrode mixture in the negative electrode portion PB in the center. The amount of the lithium foil to be pressure-bonded is preferably proportional to the amount of the negative electrode mixture. Therefore, it is preferable that the amount of the lithium foil to be crimped to the innermost and outermost negative electrode portions PA is about ½ of the amount of the lithium foil to be crimped to the central negative electrode portion PB. For example, a lithium foil having a predetermined thickness is pressure-bonded to the entire negative electrode portion PB at the center, and lithium foils having the same thickness are selectively disposed on the innermost and outermost negative electrode portions PA (for example, dotted). Or a foil having a thickness of about ½ may be applied.
[0044]
In the outermost negative electrode portion, a lithium foil is pressure-bonded onto the current collector 61n. Since the current collector 61n has holes, lithium diffuses into the negative electrode mixture 62n on the inner surface through the holes due to the aging treatment. Similarly, in the negative electrode portion PB in the central portion, lithium first diffuses into the negative electrode mixture 63n on the outer surface, and then diffuses into the negative electrode mixture 62n on the inner surface through the holes of the current collector 61n.
[0045]
When the innermost and outermost electrodes of the wound electrode group are positive electrodes, the innermost and outermost positive electrodes preferably have a mixture layer only on one side.
[0046]
The thickness of the lithium foil to be bonded to the negative electrode can be determined by the amount of lithium inserted into the negative electrode. When lithium is used as the counter electrode, the negative electrode can be inserted up to 0.01 V. However, in this embodiment, lithium is partially inserted to compensate for the irreversible capacity of the negative electrode material. And a method in which the negative electrode is inserted up to 0.3 V when lithium is used as a counter electrode is used.
[0047]
The lithium metal foil preferably has a purity of 90% by weight or more, particularly preferably 98% by weight or more. As the overlapping pattern of lithium on the negative electrode sheet, it is preferable to superimpose on the entire surface of the sheet, but since lithium preliminarily inserted into the negative electrode material gradually diffuses into the negative electrode material by aging, it is not a full sheet, but a stripe, frame shape Any of the disk-like partial overlaps may be used. The term “overlay” as used herein means that the lithium metal foil is pressure-bonded directly on the negative electrode mixture layer or on a sheet having an auxiliary layer described below.
[0048]
The handling atmosphere such as cutting and sticking of the metal foil mainly composed of lithium is preferably a dry air or argon gas atmosphere having a dew point of −30 ° C. or lower and −80 ° C. or higher. In the case of dry air, a dew point of −40 ° C. or lower and −80 ° C. or higher is more preferable. Carbon dioxide gas may be used in combination during handling. Particularly in the case of an argon gas atmosphere, it is preferable to use carbon dioxide in combination.
[0049]
FIG. 3 is a cross-sectional view of a cylinder type battery. The battery shape can be applied to both cylinders and corners. A cylindrical battery can be manufactured by making the winding core into a cylinder shape, and a rectangular battery can be manufactured by making the winding core into a square shape. The battery is formed by inserting the positive electrode sheet 3 and the negative electrode sheet 2 wound together with the separator 4 into the battery can 1, electrically connecting the battery can 1 and the negative electrode sheet 2, and injecting and sealing the electrolyte. The terminal cap 13 also serves as a positive electrode terminal and is fitted into the upper opening of the battery can 1 via the gasket 7. The positive electrode sheet 3 is electrically connected to the terminal cap 13 via a positive electrode lead 8, a welding plate 15, an explosion-proof valve body 9, a current cutoff switch 10, and a positive temperature coefficient resistance (hereinafter referred to as PTC) ring 11.
[0050]
In the sealing body, the terminal cap 13, the PTC ring 11, the current cutoff switch 10, and the explosion-proof valve body 9 are stacked in order from the top, and are fitted and supported by the gasket 7. The terminal cap 13 is a surface exposed portion of the battery, and the explosion-proof valve body 9 is inside the battery. The insulating cover 16 covers the upper surface of the explosion-proof valve body 9. The current cutoff switch 10 includes a first conductive body 10a, a second conductive body 10b, and an insulating ring 10c.
[0051]
The electrode group is obtained by winding the positive electrode sheet 3 and the negative electrode sheet 2 with the separator 4 interposed therebetween. The upper insulating plate 6 is disposed between the electrode group and the explosion-proof valve body 9. The upper insulating plate 6 insulates the electrode group and the sealing body, and insulates the electrode group and the battery can 1. A lower insulating plate 5 is disposed between the electrode group and the battery can 1 to insulate the electrode group from the battery can 1.
[0052]
The PTC ring 11 has a function of cutting off current by increasing resistance when the temperature inside the battery rises. The current cutoff switch 10 is a laminated structure of a first conducting body 10a, an insulating ring 10c, and a second conducting body 10b. The first conducting body 10a is disposed on the explosion-proof valve body 9 side and has a through hole. The conductive body 10b is arranged on the PTC ring 11 side, that is, the terminal cap 13 side, and has a structure having a through hole. The first conductor 10a and the second conductor 10b are electrically connected at the center, and have a thin portion around the connection portion of the first conductor 10a. The explosion-proof valve body 9 can be deformed to the side opposite to the electrode group side when the internal pressure is increased, and may be anything that can push up the central connection portion of the first conductive body 10a. When the internal pressure rises due to an abnormal reaction in the battery, the explosion-proof valve body 9 is deformed to break the connecting portion between the first conducting body 10a and the second conducting body 10b of the current cutoff switch 10 to cut off the current. If it increases, the thin part of the explosion-proof valve body 9 is destroyed and the pressure is released. At this time, since the current cut-off switch 10 is arranged on the side opposite to the electrode group side of the explosion-proof valve body 9, even if a spark occurs in the cut-off portion, the battery is prevented from rupture due to ignition of the electrolyte vapor. Is done.
[0053]
The positive electrode (or negative electrode) can be prepared by coating and molding a positive electrode mixture (or negative electrode mixture) on a current collector. The positive electrode mixture (or negative electrode mixture) includes a positive electrode active material (or negative electrode material), a conductive agent, a binder, a dispersant, a filler, an ionic conductive agent, a pressure enhancer, and various additives. it can. These electrodes may be disk-shaped or plate-shaped, but are preferably in the form of a flexible sheet.
[0054]
The material used for an electrode mixture is demonstrated below.
The positive electrode active material is preferably a lithium-containing transition metal oxide. The lithium-containing transition metal oxide is an oxide mainly containing at least one transition metal element selected from Ti, V, Cr, Mn, Fe, Co, Ni, Mo, and W and lithium, This is a compound having a transition metal molar ratio of 0.3 to 2.2.
[0055]
More preferably, the oxide mainly contains at least one transition metal element selected from V, Cr, Mn, Fe, Co, and Ni and lithium, and the molar ratio of lithium to transition metal is 0.3 to 0.3. It is the compound of 2.2. In addition, Al, Ga, In, Ge, Sn, Pb, Sb, Bi, Si, P, B, or the like may be contained within a range of less than 30 mole percent with respect to the transition metal present mainly.
[0056]
More preferred lithium-containing transition metal oxides are Li_xCoO₂ , Li_xNiO₂ , Li_xMnO₂ , Li_xCo_aNi_1-aO₂ , Li_xCo_bV_1-bO_z, Li_xCo_bFe_1-bO₂ , Li_xMn₂ O_Four , Li_xMn_cCo_2-cO_Four , Li_xMn_cNi_2-cO_Four , Li_xMn_cV_2-cO_Four , Li_xMn_cFe_2-cO_Four (Where x = 0.02 to 1.2, a = 0.1 to 0.9, b = 0.8 to 0.98, c = 1.6 to 1.96, z = 2.1-2. .3).
[0057]
The most preferred lithium-containing transition metal oxide is Li_xCoO₂ , Li_xNiO₂ , Li_xMnO₂ , Li_xCo_aNi_1-aO₂ , Li_xMn₂ O_Four , Li_xCo_bV_1-bO_z(X = 0.02 to 1.2, a = 0.1 to 0.9, b = 0.9 to 0.98, z = 2.01 to 2.3). In addition, the value of x is a value before the start of charging / discharging, and increases / decreases by charging / discharging.
[0058]
The positive electrode active material can be synthesized by a method in which a lithium compound and a transition metal compound are mixed and fired, or by a solution reaction, and the firing method is particularly preferable.
[0059]
Details for firing are described in paragraph 35 of JP-A-6-60,867, JP-A-7-14,579, and the like, and these methods can be used. The positive electrode active material obtained by firing may be used after being washed with water, an acidic aqueous solution, an alkaline aqueous solution, or an organic solvent.
[0060]
Furthermore, as a method of chemically inserting lithium ions into the transition metal oxide, a method of synthesis by reacting lithium metal, a lithium alloy or butyl lithium with a transition metal oxide may be used.
[0061]
Although the average particle size of a positive electrode active material is not specifically limited, 0.1-50 micrometers is preferable. The volume of particles of 0.5 to 30 μm is preferably 95% or more. More preferably, the volume occupied by a particle group having a particle size of 3 μm or less is 18% or less of the total volume, and the volume occupied by a particle group of 15 μm or more and 25 μm or less is 18% or less of the total volume. Although it does not specifically limit as a specific surface area, it is 0.01-50m in BET method²/ G is preferred, especially 0.2 m² / G-1m² / G is preferred. The pH of the supernatant when 5 g of the positive electrode active material is dissolved in 100 ml of distilled water is preferably 7 or more and 12 or less.
[0062]
When the positive electrode active material is obtained by firing, the firing temperature is preferably 500 to 1500 ° C, more preferably 700 to 1200 ° C, and particularly preferably 750 to 1000 ° C. The firing time is preferably 4 to 30 hours, more preferably 6 to 20 hours, and particularly preferably 6 to 15 hours.
[0063]
The negative electrode material may be any compound that can occlude and release lithium ions. Examples of such negative electrode materials include metallic lithium, lithium alloys, carbonaceous compounds, inorganic oxides, inorganic chalcogen compounds, metal complexes, and organic polymer compounds. These may be used alone or in combination. Among these negative electrode materials, carbonaceous materials, metal or metalloid oxides, and chalcogens are preferable.
[0064]
One of the negative electrode materials is a carbonaceous material capable of occluding and releasing lithium. The carbonaceous material is a material substantially made of carbon. Examples thereof include carbonaceous materials obtained by baking various synthetic resins such as artificial pitches such as petroleum pitch, natural graphite, and vapor-grown graphite, and PAN-based resins and furfuryl alcohol resins. Further, various carbon fibers such as PAN-based carbon fiber, cellulose-based carbon fiber, pitch-based carbon fiber, vapor-grown carbon fiber, dehydrated PVA-based carbon fiber, lignin carbon fiber, glassy carbon fiber, activated carbon fiber, and mesophase Examples thereof include microspheres, graphite whiskers, and flat graphite.
[0065]
These carbonaceous materials can be divided into non-graphitizable carbon materials and graphite-based carbon materials depending on the degree of graphitization. Further, the carbonaceous material preferably has the surface spacing, density, and crystallite size described in JP-A-62-122066, JP-A-2-66856, and JP-A-3-245473.
[0066]
The carbonaceous material does not need to be a single material, and a mixture of natural graphite and artificial graphite described in JP-A-5-290844, graphite having a coating layer described in JP-A-6-84516, or the like is used. You can also.
[0067]
Another negative electrode material, an oxide or chalcogen compound of a metal or metalloid element, is a compound composed of periodic groups 13, 14, and 15 atoms and oxygen or chalcogen group atoms.
[0068]
As the negative electrode material, an amorphous chalcogen compound or an amorphous oxide mainly containing three or more kinds of atoms selected from Group 1, 2, 13, 14, and 15 atoms of the periodic table is particularly preferably used. The term “amorphous” as used herein refers to an X-ray diffraction method using CuKα rays, which has a broad scattering band having an apex from 20 ° to 40 ° as a 2θ value, and has a crystalline diffraction line. Also good.
[0069]
Preferably, the strongest intensity of the crystalline diffraction lines seen at 2θ values of 40 ° or more and 70 ° or less is 500 of diffraction line intensities at the apexes of broad scattering bands seen at 20 ° or more and 40 ° or less of 2θ values. It is preferably not more than twice, more preferably not more than 100 times, particularly preferably not more than 5 times, and most preferably not having a crystalline diffraction line.
[0070]
The above chalcogen compound and oxide are composite chalcogen compounds mainly composed of two or more elements of B, Al, Ga, In, Tl, Si, Ge, Sn, Pb, P, As, Sb, and Bi, A composite oxide is more preferable. Particularly preferred are complex chalcogen compounds or oxides mainly composed of two or more elements of B, Al, Si, Ge, Sn, and P. These composite chalcogen compounds and composite oxides mainly contain at least one element selected from elements of Groups 1 to 2 of the periodic table in order to modify the amorphous structure.
[0071]
Among the above negative electrode materials, an amorphous composite oxide mainly composed of Sn is preferable, and is represented by the following general formula (1).
[0072]
General formula (1) SnM^Three _cM^Four _dO_t
Where M^Three Is at least one of Al, B, P, Si, Ge, and M^Four Represents at least one of group 1 element and group 2 element in the periodic table, c is a number of 0.2 or more and 2 or less, d is a number of 0.01 or more and 1 or less, and 0.2 <c + d <2, t represents a number from 1 to 6.
[0073]
As the amorphous composite oxide, either a firing method or a solution method can be adopted, but the firing method is more preferable. In the firing method, it is preferable to obtain an amorphous composite oxide by thoroughly mixing oxides or compounds of the elements described in the general formula (1) and then firing.
[0074]
As firing conditions, the temperature rise rate is preferably 5 ° C. or more and 200 ° C. or less per minute, the firing temperature is preferably 500 ° C. or more and 1500 ° C. or less, and the firing time is 1 hour. It is preferable that it is 100 hours or less. In addition, the cooling rate is 2 ° C. or more per minute and 10⁷ It is preferable that it is below ℃.
[0075]
The rate of temperature increase in this specification is the average rate of temperature rise from “50% of the firing temperature (indicated in ° C.)” to “80% of temperature in the displayed (° C.)”. Is the average rate of temperature drop from reaching “80% of the firing temperature (indicated in degrees Celsius)” to “50% of firing temperature (indicated in degrees Celsius)”.
[0076]
The temperature drop may be cooled in a firing furnace or taken out of the firing furnace and may be cooled, for example, in water. In addition, a super rapid cooling method such as a gun method, a Hammer-Anvil method, a slap method, a gas atomization method, a plasma spray method, a centrifugal quenching method, or a melt drag method described on page 217 of ceramics processing (Gihodo Publishing 1987) can also be used. Moreover, you may cool using the single roller method and the double roller method of New Glass Handbook (Maruzen 1991) p.172. In the case of a material that melts during firing, the fired product may be continuously taken out while supplying raw materials during firing. In the case of a material that melts during firing, it is preferable to stir the melt.
[0077]
The firing gas atmosphere is preferably an atmosphere having an oxygen content of 5% by volume or less, and more preferably an inert gas atmosphere. Examples of the inert gas include nitrogen, argon, helium, krypton, and xenon. The most preferred inert gas is pure argon.
[0078]
The average particle size of the compound of the negative electrode material is preferably 0.1 to 60 μm. More specifically, it is preferable that the average particle diameter is 0.7 to 25 μm, and 60% or more of the total volume is 0.5 to 30 μm. The volume occupied by the particle group having a particle size of 1 μm or less of the negative electrode material is preferably 30% or less of the total volume, and the volume occupied by the particle group having a particle size of 20 μm or more is preferably 25% or less of the total volume. Needless to say, the particle size of the material used does not exceed the thickness of the mixture on one side of the negative electrode.
[0079]
To obtain a predetermined particle size, a well-known pulverizer or classifier is used. For example, a mortar, a ball mill, a sand mill, a vibrating ball mill, a satellite ball mill, a planetary ball mill, a swirling air flow type jet mill, a sieve, or the like is used. When pulverizing, wet pulverization in the presence of water or an organic solvent such as methanol can be performed as necessary. In order to obtain a desired particle size, classification is preferably performed. The classification method is not particularly limited, and a sieve, an air classifier, or the like can be used as necessary. Classification can be used both dry and wet. The average particle diameter is a median diameter of primary particles, and is measured by a laser diffraction type particle size distribution measuring apparatus.
[0080]
The specific surface area of the negative electrode material is 0.1 to 5 m as measured by the BET specific surface area measurement method.²/ G is preferable.
[0081]
Examples of the negative electrode material are shown below, but are not limited thereto.
SnAl_0.4B_0.5P_0.5K_0.1O_3.65, SnAl_0.4B_0.5P_0.5Na_0.2O_3.7, SnAl_0.4B_0.3P_0.5Rb_0.2O_3.4, SnAl_0.4B_0.5P_0.5Cs_0.1O_3.65, SnAl_0.4B_0.5P_0.5K_0.1Ge_0.05O_3.85, SnAl_0.4B_0.5P_0.5K_0.1Mg_0.1Ge_0.02O_3.83,SnAl_0.4B_0.4P_0.4O_3.2, SnAl_0.3B_0.5P_0.2O_2.7, SnAl_0.3B_0.5P_0.2O_2.7, SnAl_0.4B_0.5P_0.3Ba_0.08Mg_0.08O_3.26, SnAl_0.4B_0.4P_0.4Ba_0.08O_3.28, SnAl_0.4B_0.5P_0.5O_3.6, SnAl_0.4B_0.5P_0.5Mg_0.1O_3.7,
[0082]
SnAl_0.5B_0.4P_0.5Mg_0.1F_0.2O_3.65, SnB_0.5P_0.5Li_0.1Mg_0.1F_0.2O_3.05, SnB_0.5P_0.5K_0.1Mg_0.1F_0.2O_3.05, SnB_0.5P_0.5K_0.05Mg_0.05F_0.1O_3.03, SnB_0.5P_0.5K_0.05Mg_0.1F_0.2O_3.03, SnAl_0.4B_0.5P_0.5Cs_0.1Mg_0.1F_0.2O_3.65, SnB_0.5P_0.5Cs_0.05Mg_0.05F_0.1O_3.03, SnB_0.5P_0.5Mg_0.1F_0.1O_3.05, SnB_0.5P_0.5Mg_0.1F_0.2O_Three , SnB_0.5P_0.5Mg_0.1F_0.06O_3.07, SnB_0.5P_0.5Mg_0.1F_0.14O_3.03, SnPBa_0.08O_3.58, SnPK_0.1O_3.55, SnPK_0.05Mg_0.05O_3.58, SnPCs_0.1O_3.55, SnPBa_0.08F_0.08O_3.54, SnPK_0.1Mg_0.1F_0.2O_3.55, SnPK_0.05Mg_0.05F_0.1O_3.53, SnPCs_0.1Mg_0.1F_0.2O_3.55, SnPCs_0.05Mg_0.05F_0.1O_3.53, Sn_1.1Al_0.4B_0.2P_0.6Ba_0.08F_0.08O_3.54, Sn_1.1Al_0.4B_0.2P_0.6Li_0.1K_0.1Ba_0.1F_0.1O_3.65, Sn_1.1Al_0.4B_0.4P_0.4Ba_0.08O_3.34,
[0083]
Sn_1.1Al_0.4PCs_0.05O_4.23, Sn_1.1Al_0.4PK_0.05O_4.23, Sn_1.2Al_0.5B_0.3P_0.4Cs_0.2O_3.5, Sn_1.2Al_0.4B_0.2P_0.6Ba_0.08O_3.68, Sn_1.2Al_0.4B_0.2P_0.6Ba_0.08F_0.08O_3.64, Sn_1.2Al_0.4B_0.2P_0.6Mg_0.04Ba_0.04O_3.68, Sn_1.2Al_0.4B_0.3P_0.5Ba_0.08O_3.58, Sn_1.3Al_0.3B_0.3P_0.4Na_0.2O_3.3 , Sn_1.3Al_0.2B_0.4P_0.4Ca_0.2O_3.4, Sn_1.3Al_0.4B_0.4P_0.4Ba_0.2O_3.6, Sn_1.4Al_0.4PK_0.2O_4.6, Sn_1.4Al_0.2Ba_0.1PK_0.2O_4.45, Sn_1.4Al_0.2Ba_0.2PK_0.2O_4.6, Sn_1.4Al_0.4Ba_0.2PK_0.2Ba_0.1F_0.2O_4.9, Sn_1.4Al_0.4PK_0.3O_4.65, Sn_1.5Al_0.2PK_0.2O_4.4, Sn_1.5Al_0.4PK_0.1O_4.65, Sn_1.5Al_0.4PCs_0.05O_4.63, Sn_1.5Al_0.4PCs_0.05Mg_0.1F_0.2O_4.63,
[0084]
SnSi_0.5Al_0.1B_0.2P_0.1Ca_0.4O_3.1, SnSi_0.4Al_0.2B_0.4O_2.7, SnSi_0.5Al_0.2B_0.1P_0.1Mg_0.1O_2.8, SnSi_0.6Al_0.2B_0.2O_2.8, SnSi_0.5Al_0.3B_0.4P_0.2O_3.55, SnSi_0.5Al_0.3B_0.4P_0.5O_4.30, SnSi_0.6Al_0.1B_0.1P_0.3O_3.25, SnSi_0.6Al_0.1B_0.1P_0.1Ba_0.2O_2.95. SnSi_0.6Al_0.1B_0.1P_0.1Ca_0.2O_2.95, SnSi_0.6Al_0.4B_0.2Mg_0.1O_3.2, SnSi_0.6Al_0.1B_0.3P_0.1O_3.05, SnSi_0.6Al_0.2Mg_0.2O_2.7, SnSi_0.6Al_0.2Ca_0.2O_2.7, SnSi_0.6Al_0.2P_0.2O_Three , SnSi_0.6B_0.2P_0.2O_Three , SnSi_0.8Al_0.2O_2.9, SnSi_0.8Al_0.3B_0.2P_0.2O_3.85, SnSi_0.8B_0.2O_2.9, SnSi_0.8Ba_0.2O_2.8, SnSi_0.8Mg_0.2O_2.8, SnSi_0.8Ca_0.2O_2.8, SnSi_0.8P_0.2O_3.1,
[0085]
Sn_0.9Mn_0.3B_0.4P_0.4Ca_0.1Rb_0.1O_2.95, Sn_0.9Fe_0.3B_0.4P_0.4Ca_0.1Rb_0.1O_2.95, Sn_0.8Pb_0.2Ca_0.1P_0.9O_3.35, Sn_0.3Ge_0.7Ba_0.1P_0.9 O_3.35, Sn_0.9Mn_0.1Mg_0.1P_0.9O_3.35, Sn_0.2Mn_0.8Mg_0.1P_0.9O_3.35, Sn_0.7Pb_0.3Ca_0.1P_0.9O_3.35, Sn_0.2Ge_0.8Ba_0.1P_0.9O_3.35, SnSi_0.8B_0.2O_2.9, SnSi_0.7B_0.3O_2.85, SnSi_0.7B_0.3Al_0.1O_3.0, SnSi_0.5B_0.3Al_0.1Mg_0.1O_2.7, Sn_0.8Si_0.6B_0.2Al_0.1Li_0.1O_2.5, Sn_0.8Si_0.6B_0.2Al_0.1Cs_0.1O_2.65, Sn_0.8Si_0.7B_0.1P_0.1Al_0.1O_2.75, Sn_0.8Si_0.5B_0.3P_0.2Al_0.1O_2.9, Sn_0.8Si_0.7B_0.1P_0.1Al_0.1Li_0.05O_2.78, Sn_0.8Si_0.5B_0.3P_0.1Al_0.1Li_0.1O_2.7, Sn_0.8Si_0.5B_0.3P_0.2Al_0.1Cs_0.1O_2.95, Sn_0.8Si_0.7P_0.3O_2.95, Sn_0.8Si_0.7P_0.3Al_0.1O_3.1, SnSi_0.5B_0.3Zr_0.1O_2.65, Sn_0.8Si_0.6P_0.2Zr_0.1O_2.7, Sn_0.8Si_0.6B_0.2P_0.1Zr_0.1O_2.75
[0086]
The chemical formula of the compound obtained by firing can be calculated from the weight difference between the powders before and after firing as an inductively coupled plasma (ICP) emission spectroscopic analysis method as a measurement method.
[0087]
The conductive agent used for the electrode mixture may be anything as long as it is an electron conductive material that does not cause a chemical change in the constructed battery. Specific examples include natural graphite such as scaly graphite, scaly graphite, earthy graphite, high-temperature fired bodies such as petroleum coke, coal coke, celluloses, saccharides and mesophase pitch, and graphite such as artificial graphite such as vapor-grown graphite. , Carbon blacks such as acetylene black, furnace black, ketjen black, channel black, lamp black, thermal black, etc., carbon materials such as asphalt pitch, coal tar, activated carbon, mesofuse pitch, polyacene, conductivity of metal fibers, etc. Examples thereof include fibers, metal powders such as copper, nickel, aluminum and silver, conductive whiskers such as zinc oxide and potassium titanate, and conductive metal oxides such as titanium oxide. It is preferable to use a graphite plate having an aspect ratio of 5 or more. Among these, graphite and carbon black are preferable, and the size of the particles is preferably 0.01 μm or more and 20 μm or less, and more preferably 0.02 μm or more and 10 μm or less. These may be used alone or in combination of two or more. When using together, it is preferable to use together carbon blacks, such as acetylene black, and a 1-15 micrometers graphite particle.
[0088]
The amount of the conductive agent added to the electrode mixture layer is preferably 1 to 50% by weight, particularly 2 to 30% by weight, based on the negative electrode material or the positive electrode active material. In the case of carbon black or graphite, the content is particularly preferably 3 to 20% by weight.
[0089]
A binder is used to hold the electrode mixture. Examples of the binder include polysaccharides, thermoplastic resins, and polymers having rubber elasticity. Preferred binders include starch, carboxymethyl cellulose, cellulose, diacetyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, sodium alginate, polyacrylic acid, polyacrylic acid Na, polyvinyl phenol, polyvinyl methyl ether, polyvinyl alcohol, polyvinyl pyrrolidone. Water-soluble polymers such as polyacrylamide, polyhydroxy (meth) acrylate, styrene-maleic acid copolymer, polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene furo Ride-tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene, polypropylene, ethylene-propylene (Meth) acrylic acid ester copolymers containing (meth) acrylic acid esters such as ethylene-diene terpolymer (EPDM), sulfonated EPDM, polyvinyl acetal resin, methyl methacrylate, 2-ethylhexyl acrylate, (meth) acrylic Acid ester-acrylonitrile copolymer, polyvinyl ester copolymer containing vinyl ester such as vinyl acetate, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, polybutadiene, neoprene rubber, fluoro rubber, polyethylene oxide, polyester polyurethane Resin, polyether polyurethane resin, polycarbonate polyurethane resin, polyester resin, phenol resin, epoxy resin emulsion (latex) or suspension It can be cited.
[0090]
In particular, polyacrylate ester latex, carboxymethyl cellulose, polytetrafluoroethylene, and polyvinylidene fluoride are exemplified. These binders are preferably those in which fine powder is dispersed in water, more preferably those having an average particle size in the dispersion of 0.01 to 5 μm, and 0.05 to 1 μm. It is particularly preferable to use one.
[0091]
These binders can be used alone or in combination. When the amount of the binder added is small, the holding power and cohesion of the electrode mixture is weak. If the amount is too large, the electrode volume increases and the capacity per electrode unit volume or unit weight decreases. For this reason, the addition amount of the binder is preferably 1 to 30% by weight, and particularly preferably 2 to 10% by weight.
[0092]
Any filler can be used as long as it is a fibrous material that does not cause a chemical change in the constructed battery. Usually, olefin polymers such as polypropylene and polyethylene, fibers such as glass and carbon are used. Although the addition amount of a filler is not specifically limited, 0 to 30 weight% is preferable.
[0093]
As the ionic conductive agent, those known as inorganic and organic solid electrolytes can be used, and details are described in the section of the electrolytic solution.
[0094]
A pressure enhancer is a compound that increases the internal pressure of a battery, and carbonates such as lithium carbonate are typical examples.
[0095]
Next, the configuration of the positive and negative electrodes will be described. The positive and negative electrodes are preferably in a form in which an electrode mixture is applied to both sides of the current collector. In this case, the number of layers per side may be one or may be composed of two or more layers. When the number of layers per side is 2 or more, the positive electrode active material (or negative electrode material) -containing layer may be 2 or more. A more preferable configuration is a case where the layer is composed of a layer containing a positive electrode active material (or negative electrode material) and a layer not containing a positive electrode active material (or negative electrode material).
[0096]
The layer that does not contain the positive electrode active material (or negative electrode material) includes a protective layer for protecting the layer containing the positive electrode active material (or negative electrode material) and a layer containing the divided positive electrode active material (or negative electrode material). And an undercoat layer between the positive electrode active material (or negative electrode material) -containing layer and the current collector. These are collectively referred to as an auxiliary layer in this specification.
[0097]
The protective layer is preferably on both the positive and negative electrodes or on the positive and negative electrodes. In the negative electrode, when lithium is inserted into the negative electrode material in the battery, the negative electrode preferably has a protective layer. The protective layer is composed of at least one layer, and may be composed of a plurality of layers of the same type or different types. Moreover, the form which has a protective layer only in the single side | surface of the mixture layers of both surfaces of a collector may be sufficient. These protective layers are composed of water-insoluble particles and a binder. The binder used when forming the above-mentioned electrode mixture can be used as the binder. As the water-insoluble particles, various conductive particles and organic and inorganic particles having substantially no conductivity can be used. The solubility of water-insoluble particles in water is 100 ppm or less, preferably insoluble.
[0098]
The proportion of particles contained in the protective layer is preferably 2.5% by weight or more and 96% by weight or less, more preferably 5% by weight or more and 95% by weight or less, and particularly preferably 10% by weight or more and 93% by weight or less.
[0099]
Examples of water-insoluble conductive particles include carbon particles such as metals, metal oxides, metal fibers, carbon fibers, carbon black, and graphite. Among these water-insoluble conductive particles, those having low reactivity with alkali metals, particularly lithium, are preferable, and metal powders and carbon particles are more preferable. The electrical resistivity at 20 ° C. of the elements constituting the particles is 5 × 10⁹ Ω · m or less is preferable.
[0100]
The metal powder is preferably a metal having low reactivity with lithium, that is, a metal that is difficult to form a lithium alloy. Specifically, copper, nickel, iron, chromium, molybdenum, titanium, tungsten, and tantalum are preferable. The shape of these metal powders may be any of acicular, columnar, plate-like, and massive, and the maximum diameter is preferably 0.02 μm or more and 20 μm or less, more preferably 0.1 μm or more and 10 μm or less. These metal powders are preferably those whose surfaces are not excessively oxidized, and when oxidized, heat treatment is preferably performed in a reducing atmosphere.
[0101]
As the carbon particles, a known carbon material used as a conductive material used in combination when the electrode active material is not conductive can be used. Specifically, a conductive agent used for making an electrode mixture is used.
[0102]
Examples of the water-insoluble particles having substantially no conductivity include fine powder of Teflon, SiC, aluminum nitride, alumina, zirconia, magnesia, mullite, forsterite, and steatite. These particles may be used in combination with conductive particles, and are preferably used in an amount of 0.01 to 10 times that of the conductive particles.
[0103]
The positive (negative) electrode sheet can be prepared by applying a positive (negative) electrode mixture onto a current collector, drying, and compressing.
[0104]
The mixture is prepared by mixing a positive electrode active material (or negative electrode material) and a conductive agent, adding a binder (suspension or emulsion of resin powder) and a dispersion medium, kneading and mixing, It can be carried out by dispersing with a mixer / disperser such as a mixer, homogenizer, dissolver, planetary mixer, paint shaker or sand mill. As the dispersion medium, water or an organic solvent is used, but water is preferable. In addition, additives such as a filler, an ionic conductive agent, and a pressure enhancer may be added as appropriate. The pH of the dispersion is preferably 5 to 10 for the negative electrode and 7 to 12 for the positive electrode.
[0105]
Application can be performed by various methods, for example, reverse roll method, direct roll method, blade method, knife method, extrusion method, slide method, curtain method, gravure method, bar method, dip method and squeeze method. I can list them. A method using an extrusion die and a method using a slide coater are particularly preferred. The application is preferably performed at a speed of 0.1 to 100 m / min. Under the present circumstances, the surface state of a favorable coating layer can be obtained by selecting the said application | coating method according to the liquid physical property of a mixture paste, and drying property. When the electrode layer is a plurality of layers, it is preferable to apply the plurality of layers at the same time from the viewpoint of uniform electrode production, production cost, and the like. The thickness, length and width of the coating layer are determined by the size of the battery. The thickness of a typical coating layer is 10 to 1000 μm in a compressed state after drying.
[0106]
The electrode sheet after application is dried and dehydrated by the action of hot air, vacuum, infrared rays, far infrared rays, electron beams and low-humidity air. These methods can be used alone or in combination. The drying temperature is preferably in the range of 80 to 350 ° C, particularly preferably in the range of 100 to 260 ° C. The water content after drying is preferably 2000 ppm or less, and more preferably 500 ppm or less.
[0107]
For the compression of the electrode sheet, a generally employed pressing method can be used, but a die pressing method and a calendar pressing method are particularly preferable. The press pressure is not particularly limited, but is 10 kg / cm.²~ 3t / cm²Is preferred. The press speed of the calendar press method is preferably 0.1 to 50 m / min. The pressing temperature is preferably room temperature to 200 ° C.
[0108]
The separator has only to have a high ion permeability, a predetermined mechanical strength, and an insulating thin film. The material is olefin polymer, fluorine polymer, cellulose polymer, polyimide, nylon, glass fiber, alumina fiber. And non-woven fabric, woven fabric, and microporous film are used as forms. In particular, the material is preferably polypropylene, polyethylene, a mixture of polypropylene and polyethylene, a mixture of polypropylene and Teflon, or a mixture of polyethylene and Teflon, and the form is preferably a microporous film. In particular, a microporous film having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm is preferable. These microporous films may be a single film or a composite film composed of two or more layers having different properties such as the shape, density, and material of the micropores. For example, the composite film which bonded the polyethylene film and the polypropylene film can be mentioned.
[0109]
The electrolytic solution is generally composed of a supporting salt and a solvent. Lithium salt is mainly used as the supporting salt in the lithium secondary battery.
[0110]
Examples of the lithium salt include LiClO._Four , LiBF_Four , LiPF₆ , LiCF_Three CO₂ , LiAsF₆ , LiSbF₆ , LiB_TenCl_Ten, LiOSO₂ C_nF_{2n + 1}(N is a positive integer of 6 or less), LiN (SO₂ C_nF_{2n + 1}) (SO₂ C_mF_{2m + 1}) (Wherein m and n are each a positive integer of 6 or less), LiN (SO₂ C_pF_{2p + 1}) (SO₂ C_qF_{2q + 1}) (SO₂ C_rF_{2r + 1}) (Wherein p, q, and r are each a positive integer of 6 or less), lower aliphatic lithium carboxylate, LiAlCl_Four Li salts such as LiCl, LiBr, LiI, chloroborane lithium and lithium tetraphenylborate can be raised, and these can be used alone or in combination. Above all, LiBF_Four And / or LiPF₆ What melt | dissolved is preferable.
[0111]
The concentration of the supporting salt is not particularly limited, but is preferably 0.2 to 3 mol per liter of the electrolytic solution.
[0112]
Examples of the solvent include propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, methyl formate, methyl acetate, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, dioxane, acetonitrile, nitromethane, ethyl monoglyme, phosphate triester, trimethoxymethane, dioxolane derivative, sulfolane, 3-methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran List aprotic organic solvents such as derivatives, ethyl ether, and 1,3-propane sultone. Can be, mixed and used alone or in combination. Among these, carbonate-based solvents are preferable, and it is particularly preferable to use a mixture of a cyclic carbonate and an acyclic carbonate. As the cyclic carbonate, ethylene carbonate and propylene carbonate are preferable. Moreover, as an acyclic carbonate, diethyl carbonate, dimethyl carbonate, and methyl ethyl carbonate are preferable.
[0113]
As an electrolytic solution, LiCF is added to an electrolytic solution in which ethylene carbonate, propylene carbonate, 1,2-dimethoxyethane, dimethyl carbonate or diethyl carbonate is appropriately mixed._Three SO_Three LiClO_Four , LiBF_Four And / or LiPF₆ An electrolytic solution containing is preferable. In particular, in a mixed solvent of at least one of propylene carbonate or ethylene carbonate and at least one of dimethyl carbonate or diethyl carbonate, LiCF_Three SO_Three LiClO_Four Or LiBF_Four At least one salt selected from the group consisting of LiPF and LiPF₆ An electrolytic solution containing is preferable. The amount of the electrolyte added to the battery is not particularly limited, and can be used depending on the amount of the positive electrode material or the negative electrode material or the size of the battery.
[0114]
In addition to the electrolytic solution, the following solid electrolyte can be used in combination.
The solid electrolyte is classified into an inorganic solid electrolyte and an organic solid electrolyte.
[0115]
Well-known inorganic solid electrolytes include Li nitrides, halides, oxyacid salts, and the like. Among them, Li_Three N, LiI, Li_Five NI₂ , Li_Three N-LiI-LiOH, Li_Four SiO_Four , Li_Four SiO_Four -LiI-LiOH, xLi_Three PO_Four -(1-x) Li_Four SiO_Four , Li₂ SiS_Three In addition, phosphorus sulfide compounds are effective.
[0116]
In the organic solid electrolyte, a polyethylene oxide derivative or a polymer containing the derivative, a polypropylene oxide derivative or a polymer containing the derivative, a polymer containing an ion dissociation group, a mixture of a polymer containing an ion dissociation group and the above aprotic electrolyte, phosphoric acid A polymer matrix material containing an ester polymer and an aprotic polar solvent is effective. Furthermore, there is a method of adding polyacrylonitrile to the electrolytic solution. A method of using an inorganic and organic solid electrolyte in combination is also known.
[0117]
Further, other compounds may be added to the electrolyte for the purpose of improving discharge and charge / discharge characteristics. For example, pyridine, pyrroline, pyrrole, triphenylamine, phenylcarbazole, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric triamide, nitrobenzene derivative, sulfur, quinoneimine dye, N-substituted oxazolidinone and N , N′-substituted imidazolidinone, ethylene glycol dialkyl ether, quaternary ammonium salt, polyethylene glycol, pyrrole, 2-methoxyethanol, AlCl_Three, Conductive polymer electrode active material monomers, triethylene phosphoramide, trialkylphosphine, morpholine, aryl compounds having a carbonyl group, crown ethers such as 12-crown-4, hexamethylphosphoric triamide and 4-alkyl Examples thereof include morpholine, bicyclic tertiary amine, oil, quaternary phosphonium salt, tertiary sulfonium salt and the like. Particularly preferred is a case where triphenylamine and phenylcarbazole are used alone or in combination.
[0118]
In order to make the electrolyte nonflammable, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride chloride can be contained in the electrolyte. In addition, carbon dioxide gas can be included in the electrolyte in order to make it suitable for high-temperature storage.
[0119]
It is desirable that the electrolytic solution contains as little water and free acid as possible. For this reason, the raw material of the electrolytic solution is preferably one that has been sufficiently dehydrated and purified. The electrolyte solution is preferably adjusted in dry air or an inert gas with a dew point of minus 30 ° C. or less. The amount of water and free acid content in the electrolyte is 0.1 to 500 ppm, more preferably 0.2 to 100 ppm.
[0120]
The entire amount of the electrolytic solution may be injected once, but it is preferable to inject it in two or more times. When injecting in two or more times, each solution may have the same composition but a different composition (for example, a non-aqueous solvent or a non-aqueous solvent having a higher viscosity than the solvent after injecting a solution in which a lithium salt is dissolved in the non-aqueous solvent). Or a solution in which a lithium salt is dissolved in a solvent or a non-aqueous solvent may be injected). In order to shorten the time for injecting the electrolyte, etc., the battery can may be decompressed, or centrifugal force or ultrasonic waves may be applied to the battery can.
[0121]
Battery can and battery cover are made of nickel-plated steel plate, stainless steel plate (SUS304, SUS304L, SUS304N, SUS316, SUS316L, SUS430, SUS444, etc.), nickel-plated stainless steel plate (same as above), aluminum or an alloy thereof Nickel, titanium, and copper, and the shapes are a perfect circular cylinder, an elliptical cylinder, a square cylinder, and a rectangular cylinder. In particular, when the outer can also serves as the negative electrode terminal, a stainless steel plate and a nickel-plated steel plate are preferable, and when the outer can also serves as the positive electrode terminal, a stainless steel plate, aluminum, or an alloy thereof is preferable. The shape of the battery can may be any of buttons, coins, sheets, cylinders, and corners.
[0122]
A safety valve can be used for the sealing plate as a countermeasure against an increase in the internal pressure of the battery can. In addition, a method of cutting a member such as a battery can or a gasket can be used. In addition, various conventionally known safety elements (for example, fuses, bimetals, PTC elements, etc. as overcurrent prevention elements) may be provided.
[0123]
For the lead plate, a metal having electrical conductivity (for example, iron, nickel, titanium, chromium, molybdenum, copper, aluminum, or the like) or an alloy thereof can be used. As a welding method for the battery lid, battery can, electrode sheet, and lead plate, a known method (eg, direct current or alternating current electric welding, laser welding, ultrasonic welding) can be used. As the sealing agent for sealing, a conventionally known compound or mixture such as asphalt can be used.
[0124]
The gasket is made of an olefin-based polymer, a fluorine-based polymer, a cellulose-based polymer, a polyimide, or a polyamide, and is preferably an olefin-based polymer, particularly a propylene-based polymer, from the viewpoint of organic solvent resistance and low moisture permeability. Furthermore, a block copolymer of propylene and ethylene is preferable.
[0125]
The battery is aged before activation after the electrode group is inserted into the battery can, the electrolyte is injected, the battery can is crimped and sealed. It is preferable to perform the process from injection of the electrolyte to caulking and sealing the battery can at 20 ° C. or lower.
[0126]
The battery assembled as described above is preferably subjected to an aging treatment. The aging treatment includes pre-treatment, activation treatment, post-treatment, and the like, whereby a battery with high charge / discharge capacity and excellent cycleability can be produced. The pretreatment is a treatment for homogenizing the distribution of lithium in the electrode. For example, control of lithium dissolution, temperature control to make the lithium distribution uniform, oscillation and / or rotation treatment, optional charging / discharging A combination is made. The aging before activation is preferably performed at a temperature of 20 ° C. or more and 60 ° C. or less for 1 day or more and 10 days or less. The activation process is a process for inserting lithium into the negative electrode of the battery body, and 50 to 120% (for example, lithium insertion amount at the time of actual use charging of the battery (for example, terminal voltage 4.0 V to 4.2 V) (for example, The terminal voltage is preferably 3.5V to 4.4V). The post-processing is processing for sufficient activation processing, and includes storage processing for uniform battery reaction and charge / discharge processing for determination, which can be arbitrarily combined.
[0127]
The battery is covered with an exterior material as necessary. Examples of the exterior material include a heat-shrinkable tube, an adhesive tape, a metal film, paper, cloth, paint, and a plastic case. Further, at least a part of the exterior may be provided with a portion that changes color by heat so that the heat history during use can be known.
[0128]
A plurality of batteries are assembled in series and / or in parallel as required, and stored in a battery pack. In addition to safety elements such as positive temperature coefficient resistors, temperature fuses, fuses and / or current interrupting elements, the battery pack also requires safety circuits (monitoring the voltage, temperature, current, etc. of each battery and / or the entire battery pack) In this case, a circuit having a function of interrupting current may be provided. In addition to the positive and negative terminals of the entire assembled battery, the battery pack should be provided with the positive and negative terminals of each battery, the entire assembled battery, the temperature detection terminal of each battery, the current detection terminal of the entire assembled battery, etc. as external terminals. You can also. The battery pack may incorporate a voltage conversion circuit (such as a DC-DC converter). The connection of each battery may be fixed by welding a lead plate, or may be fixed so that it can be easily attached and detached with a socket or the like. Further, the battery pack may be provided with display functions such as the remaining battery capacity, the presence / absence of charging, and the number of uses.
[0129]
Batteries are used in various devices. In particular, video movies, portable video decks with built-in monitors, movie cameras with built-in monitors, digital cameras, compact cameras, single-lens reflex cameras, film with lenses, notebook computers, notebook-type word processors, electronic notebooks, mobile phones, cordless phones, whiskers, It is preferably used for electric tools, electric mixers, automobiles and the like.
[0130]
【Example】
Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to the examples unless it exceeds the gist of the invention.
[0131]
[Creation of positive electrode mixture paste]
A mixture of lithium carbonate and tricobalt tetroxide in a molar ratio of 3: 2 was placed in an alumina crucible, heated to 750 ° C. at a heating rate of 2 ° C. per minute in air, and calcined for 4 hours. The temperature was raised to 900 ° C. at a temperature rising rate of 2 ° C. per minute, calcined at that temperature for 8 hours, pulverized, and LiCoO as the positive electrode active material₂Was generated. LiCoO₂Has a conductivity of 0.6 mS / m, a pH of 10.1, and a specific surface area by a nitrogen adsorption method of 0.42 m when 50 g of a powder having a center particle size of 5 μm is dispersed in 100 ml of water.²/ G. LiCoO₂200 g of acetylene black and 7 g of acetylene black were mixed with a homogenizer, 90 g of carboxymethyl cellulose aqueous solution having a concentration of 2% by weight was added and kneaded and mixed, and 70 g of water, 2-ethylhexyl acrylate and acrylic acid were mixed. 6 g of an aqueous dispersion of acrylonitrile copolymer (solid concentration 50% by weight) was added and stirred and mixed with a homogenizer to prepare a positive electrode mixture paste.
[0132]
[Create negative electrode mixture paste]
SnSi as negative electrode active material_0.5B_0.3P_0.2Cs_0.05Al_0.2O_3.28200 g and a conductive agent (artificial graphite) 40 g are mixed with a homogenizer, and further 100 g of water and 100 g of water are added and kneaded and mixed with 100 g of polyvinylidene fluoride and 100 g of 2% by weight carboxymethylcellulose aqueous solution as a binder. A negative electrode mixture paste was prepared.
[0133]
[Create negative electrode protective layer paste]
85 g of alumina and 9 g of artificial graphite were added to 300 g of an aqueous carboxymethyl cellulose solution having a concentration of 2% by weight and kneaded and prepared.
[0134]
[Creation of positive and negative electrode sheets]
The positive electrode mixture paste prepared above was applied on both sides of a porous aluminum foil current collector having a thickness of 20 μm with a blade coater to a coating amount of about 240 g / m in terms of positive electrode active material per side.²After being applied and dried, it was compression molded by a roller press so that the thickness of the compressed sheet was 170 μm. Then, it cut | judged to the predetermined | prescribed magnitude | size and created the strip | belt-shaped positive electrode sheet. Furthermore, it heated with the far-infrared heater in the dry box (dew point: -50 degrees C or less dry air), fully dehydrated and dried at the electrode temperature of about 210 degrees C, and produced the positive electrode sheet.
[0135]
Similarly, a negative electrode mixture paste and a negative electrode protective layer paste were applied to both surfaces of an 18 μm copper foil current collector. At this time, the negative electrode mixture paste was applied to the current collector side so that the negative electrode protective layer paste was the uppermost layer. The coating amount in terms of negative electrode material per side is about 80 g / m²The solid content of the protective layer is 15 g / m²Thus, a negative electrode sheet having a thickness of 110 μm after compression with a roller press was prepared.
[0136]
Lithium metal (purity 99.8%) foil was affixed on both sides of this negative electrode sheet or on one side as needed.
[0137]
[Electrolyte preparation]
In an argon atmosphere, 65.3 g of diethyl carbonate was placed in a 200 cc narrow-necked polypropylene container, and 22.2 g of ethylene carbonate was dissolved little by little while taking care not to exceed a liquid temperature of 30 ° C. Next, 0.4 g of LiBF_Four, 12.1 g LiPF₆The solution was dissolved in a small amount in the polypropylene container in order, taking care that the liquid temperature did not exceed 30 ° C. The obtained electrolyte was a colorless and transparent liquid with a specific gravity of 1.135. Moisture was 18 ppm (measured with a trade name MKC-210, Karl Fischer moisture measuring device, manufactured by Kyoto Electronics), free acid content was 24 ppm (measured by neutralization titration with 0.1 N NaOH aqueous solution using bromthymol blue as an indicator) )Met.
[0138]
[Create cylinder battery]
A cylinder battery as shown in FIG. 3 was produced. A positive electrode sheet 3, a microporous polyethylene film separator (manufactured by Ube Industries, EF4500) 4, a negative electrode sheet 2 and a separator 4 were laminated in this order, and this was wound in a spiral shape. The wound body is housed in an iron-bottomed cylindrical battery can 1 having a nickel plating which also serves as a negative electrode terminal, and then the electrolyte is poured into the battery can, and the battery lid 13 having the positive terminal is attached to the gasket 7. The cylindrical battery was made by caulking.
[0139]
The potential unevenness of the non-aqueous electrolyte lithium secondary battery produced through the above steps was measured by the following method.
[0140]
[Measurement method of potential unevenness]
(1) Charge the battery to be measured to 4.1V.
[0141]
(2) Disassemble the measurement battery and separate the positive electrode sheet and the negative electrode sheet.
[0142]
(3) Set the intelligent recorder manufactured by Toa Denpa Kogyo Co., Ltd. to voltage measurement mode, set the range to 0-0.5V for negative electrode measurement, and set the range to 4.0-4.5V for positive electrode measurement, and connect the lead wire to one terminal. Connect to the lead part of the negative electrode sheet.
[0143]
(4) Connect the lead wire to the other terminal, attach a worm clip to the tip, and attach a small piece of metallic lithium to the tip.
[0144]
(5) The electrode sheet is stretched flat and placed on an insulating material such as polyethylene, and a separator is placed thereon so that the electrode sheet is completely covered.
[0145]
(6) Drip the electrolyte over the separator with a dropper about 3cc and spread it evenly.
[0146]
(7) Start the recorder, scan the metal lithium piece on the separator in the direction (longitudinal direction, width direction) to be measured at a speed of about 1 mm / sec, and measure the potential.
[0147]
Example 1
Sample No. shown in [Table 1] The twelve batteries 1 to 12 were subjected to the above-described potential unevenness measurement and examined for mass production suitability, and the results are shown in [Table 1].
[0148]
[Table 1]

[0149]
A negative electrode current collector (Cu foil) having a hole is more preferable than a non-hole having a small potential unevenness. Lithium ions can freely move between the front and back surfaces of the negative electrode through the holes of the negative electrode current collector, so that the potential unevenness is reduced.
[0150]
Sample No. In 1 and 2, since the Li piece width is 4 mm and the Li piece chip is 10 mm, the Li foil covers 40% (= 4 mm / 10 mm) of the surface of the negative electrode mixture layer. Sample No. In Nos. 3 and 4, since the Li piece width is 8 mm and the Li piece chip is 20 mm, the Li foil covers 40% (= 8 mm / 20 mm) of the surface of the negative electrode mixture layer. Sample No. In Nos. 5 and 6, since the Li piece width is 8 mm and the Li piece chip is 10 mm, the Li foil covers 80% (= 8 mm / 10 mm) of the negative electrode mixture layer. Similarly, sample no. In Nos. 7 and 8, the Li foil covered 80% (16 mm / 20 mm) of the negative electrode mixture layer. In Nos. 9 to 12, the Li foil covers 100% of the negative electrode mixture layer. A Li foil covering 80% or more of the negative electrode mixture layer has small potential unevenness and excellent mass production suitability.
[0151]
The thickness of the Li foil is the same as that of sample no. 1-8 are 45 micrometers, sample No. 9-12 is 36 micrometers. The thickness fluctuation rate of the Li foil is the sample No. 1 to 10 is 15%. 11 is 5%, and sample no. 12 is 25%. It is preferable that the thickness of the Li foil is 60 μm or less and the thickness variation rate is 20% or less with respect to the average thickness. Furthermore, it is more preferable that the Li foil has a thickness of 10 to 40 μm and a thickness variation rate of 10% or less.
[0152]
The Li foil is more preferable for mass production than being applied to both sides of the negative electrode.
[0153]
(Example 2)
Sample No. shown in [Table 2] The above-described potential unevenness measurement was performed on eight batteries 1 to 8, and the degree of waste generated in the process of slitting the negative electrode was examined. Sample No. 1-8 differ in the aperture ratio and the hole size of the holes of the negative electrode current collector (Cu foil). On one surface of the negative electrode, a 36 μm thick Li foil was attached to the entire surface.
[0154]
[Table 2]

[0155]
The aperture ratio of the holes of the negative electrode current collector (Cu foil) is 0.1% or more and 10% or less, and the size of the holes is 1 × 10^-7cm²1 × 10^-2cm²Is preferable because the potential unevenness is small and the generation of dust during the slitting process is small.
[0156]
(Example 3)
Sample No. below Four batteries 1 to 4 were prepared. The negative electrode current collector (Cu foil) of each battery has holes, the opening ratio of the holes is 5%, and the hole size is 0.001 cm.²It is. In principle, a 36 μm-thick Li foil was applied to the entire surface of one side of the negative electrode. In all the batteries, the outermost periphery of the winding group is covered with a separator.
[0157]
Sample No. 1: For the negative electrode, a negative electrode mixture having the same length was applied to both the front and back surfaces. When wound, the outermost periphery was wound such that the negative electrode mixture layer was further outside than the positive electrode mixture layer, and the innermost periphery was wound so that the negative electrode mixture layer was further inside than the positive electrode mixture layer. The Li foil was stuck on the entire outer surface of the negative electrode only.
[0158]
Sample No. 2: Sample No. Made in the same way as 1. However, as shown in FIG. 2, the outermost periphery of the negative electrode is coated with a negative electrode mixture layer only on the inner side, and the innermost periphery of the negative electrode is coated with a negative electrode mixture layer only on the outer side, The amount of Li foil applied was halved. That is, 4 mm wide Li pieces were attached to the negative electrode current collector at an 8 mm pitch.
[0159]
Sample No. 3: The negative electrode was coated with a negative electrode mixture having the same length on both the front and back surfaces. When wound, the outermost periphery was wound such that the positive electrode mixture layer was further outside than the negative electrode mixture layer, and the innermost periphery was wound so that the positive electrode mixture layer was further inside than the negative electrode mixture layer. The outermost peripheral portion of the positive electrode was coated with a positive electrode mixture layer only on the inner surface, and the innermost peripheral portion of the positive electrode was coated with a positive electrode mixture layer only on the outer surface. The Li foil was affixed over the entire length of the negative electrode mixture layer only on the outer surface of the negative electrode.
[0160]
Sample No. 4: Sample No. Created in the same way as 3. However, the Li foil was stuck on the entire inner surface of the negative electrode only.
[0161]
According to the aging conditions before activation shown in [Table 3], sample no. 1 to 4 were subjected to aging treatment (including pretreatment, active activation treatment and post-treatment), and lithium was diffused into the negative electrode. [Table 3] shows the results of examining the extent to which the Li foil remained undissolved at that time and the cycle life. The cycle life represents a capacity retention rate after 500 cycles of charge / discharge.
[0162]
[Table 3]

[0163]
Sample No. Sample no. 2 has a longer cycle life. Sample No. 1 is provided with a negative electrode mixture layer on both surfaces of the outermost negative electrode. Since the negative electrode mixture layer on the outer surface does not face the positive electrode, useless energy is released at that portion, and the cycle life is shortened. Sample No. In No. 2, since the negative electrode mixture layer is not provided in the negative electrode portion where the positive electrode is not opposed, the charge / discharge efficiency is increased and the cycle life is increased. In that portion, since the negative electrode mixture layer is provided only on one side of the negative electrode current collector, the amount of Li foil may be half that of the portion in which the negative electrode mixture layer is provided on both sides. The Li foil on the negative electrode current collector passes through the holes of the current collector and diffuses into the negative electrode mixture layer on the opposite side.
[0164]
Sample No. When aging 3 and 4 under the same conditions, sample no. Sample No. 3 No. 4 has a smaller dissolution residue of the Li foil and a longer cycle life. That is, the Li foil is preferably attached to the outer surface of the electrode (preferably the negative electrode).
[0165]
Sample No. 3, the cycle life is longer at 7 days at 50 ° C. than 14 days at 50 ° C. as the aging condition before activation. The aging conditions before activation are preferably a temperature of 20 ° C. or more and 60 ° C. or less and a time of 1 day or more and 10 days or less.
[0166]
【The invention's effect】
According to this invention, a positive electrode or a negative electrode is formed by providing a mixture layer on both surfaces of a perforated current collector. Since lithium ions can move between the mixture layers on both sides through the holes of the perforated current collector, the potential unevenness is small and the performance of the battery is improved.
[0167]
In addition, by pressing a lithium metal foil on the surface of at least one surface of a negative electrode or positive electrode having a perforated current collector, lithium can diffuse into the mixture layer on both surfaces of the current collector through the holes of the current collector. is there. It is not always necessary to press the lithium metal foil on both sides of the negative electrode or the positive electrode. The mixture layer is activated by diffusing into the lithium mixture layer.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a wound electrode group before winding.
FIG. 2 is a top view of a wound electrode group.
FIG. 3 is a cross-sectional view of a cylindrical battery.
[Explanation of symbols]
1 Battery can
2 Negative electrode
3 Positive electrode
4 Separator
5 Lower insulation plate
6 Upper insulation plate
7 Gasket
8 Positive lead
9 Explosion-proof valve body
10 Current cut-off switch
10a First conductor
10b Second conductor
10c Insulation ring
11 PTC ring
13 Terminal cap
15 Welding plate
16 Insulation cover
20 core
21, 22 Separator
23 Positive current collector
24 Positive lead
26 Negative electrode current collector
27 Negative electrode mix
30 Insulating material
35 Positive electrode sheet
36 Negative electrode sheet
53 Lithium foil
54a, 54b hole
60n negative electrode
60p positive electrode
61n negative electrode current collector
61p positive electrode current collector
62n Negative electrode mixture on the inner surface
62p Positive electrode mixture on the inner surface
63n Negative electrode mixture on outer surface
63p Positive electrode mixture on the outer surface

Claims (12)

Each in a non-aqueous electrolyte lithium secondary battery comprising a positive electrode and a negative electrode and a nonaqueous electrolyte having a mixture layer on both sides of the current collector, one or more current collector of the positive electrode and the negative electrode communicates the front and back surfaces A lithium metal foil is bonded to the surface of the outer surface of the wound group of the negative electrode mixture layer on the perforated current collector, and the perforated current collector A nonaqueous electrolyte lithium secondary battery, wherein the size of one hole of the body is 1 × 10 ⁻⁷ cm ² or more and 1 × 10 ⁻² cm ² or less .   2. The nonaqueous electrolyte lithium secondary battery according to claim 1, wherein the aperture ratio of the holes of the perforated current collector is 0.1% or more and 10% or less.   3. The nonaqueous electrolyte lithium secondary according to claim 1, wherein the pressed lithium metal foil covers 80% or more of the surface of the mixture layer on the surface where the pressed lithium metal foil is present. battery.   4. The nonaqueous electrolyte lithium secondary battery according to claim 1, wherein the lithium metal foil has a thickness of 60 μm or less and a thickness variation rate of 20% or less with respect to the average thickness.   The mixture coating amount of the negative electrode portion having the opposing positive electrode only on one side is a times the mixture coating amount of the negative electrode portion having the opposing positive electrode on both sides (where 0.3 <a <0. The non-aqueous electrolyte lithium secondary battery according to any one of claims 1 to 4, wherein the pressure bonding amount of lithium is 0.8 x a to 1.1 x a times.   The non-aqueous electrolyte lithium secondary battery according to claim 1, wherein the negative electrode includes a composite oxide containing at least one kind of tin.   A wound electrode group is formed by laminating and winding the electrode according to any one of claims 1 to 6 and a separator, and then the wound electrode group is inserted into a battery can. A method for manufacturing a secondary battery.   8. The method for producing a non-aqueous electrolyte lithium secondary battery according to claim 7, wherein in the wound electrode group, the lithium metal foil is crimped to the outer surface of the negative electrode.   The electrode having a mixture layer on the innermost circumference and the outermost circumference of the wound electrode group is a negative electrode, and the negative electrode in the innermost circumference and the outermost circumference part has the mixture layer only on one side. Item 9. The method for producing a nonaqueous electrolyte lithium secondary battery according to Item 7 or 8.   10. The method according to claim 7, wherein the steps from the injection of the electrolyte into the battery can and the caulking of the battery can after being inserted into the battery can are performed at 20 ° C. or less. A method for producing a nonaqueous electrolyte lithium secondary battery according to claim 1.   The non-winding electrode according to any one of claims 7 to 10, wherein the wound electrode group is inserted into a battery can, an electrolyte is injected into the battery can, the battery can is crimped and sealed, and then aged before activation. A method for producing a water electrolyte lithium secondary battery.   12. The method for producing a non-aqueous electrolyte lithium secondary battery according to claim 11, wherein the aging before activation is performed at a temperature of 20 ° C. or more and 60 ° C. or less for 1 day or more and 10 days or less.

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