JP4291915B2

JP4291915B2 - Inside-out cylindrical battery

Info

Publication number: JP4291915B2
Application number: JP12432499A
Authority: JP
Inventors: 行由村上; 友之永井; 廣彦太田; 千洋村田
Original assignee: FDK Corp
Current assignee: FDK Corp
Priority date: 1999-04-30
Filing date: 1999-04-30
Publication date: 2009-07-08
Anticipated expiration: 2019-04-30
Also published as: JP2000315495A

Description

【０００１】
【発明の属する技術分野】
この発明はインサイドアウト形リチウム電池に関し、とくに、放電特性を向上させるための集電構造の改良に関する。
【０００２】
【従来の技術】
従来の代表的なインサイドアウト構造の円筒形リチウム電池は、放電反応に寄与する面積が小さいため大きい電流が必要な用途には適さなかった。そこで反応面積を増大させるために通常とは逆の電極配置、つまりボリュームが小さくて薄いリチウム負極をボリュームが大きくて厚い正極合剤の外側に配置する図４のような構造が考え出された。図４において、有底円筒形に形成された負極缶１は、円筒形電池ケースの主体となるとともに負極端子を兼ねる。この負極缶１の内周面には長方形の金属リチウム板を巻いて中空円筒形に成形されたリチウム負極２が密着配置されている。このリチウム負極２の中空部内面側にポリプロピレン不織布などで有底中空円筒形に形成されたセパレータ３が密着配置されている。このセパレータ３の内周面に密着して、リング状に加圧成形された中空円筒形の正極合剤４（電解二酸化マンガン＋黒鉛＋結着剤）が積層配置されている。この正極合剤４の内周面には正極合剤４とほぼ等しい高さの中空円筒形に成形されたステンレス製の集電体５が圧入されており、この圧接部分が集電に寄与することになる。この集電体５と正極合剤４からなる集電構造の斜視図を図５に示す。
この集電体５の先端は板状の封口板６の内面にスポット溶接されており、その封口板６は皿状の正極端子板７とその外周部で接している。これにより正極合剤４は正極端子板７と電気的に接続されている。有機溶媒からなる非水電解液８が負極缶１内部に充填された状態で、封口板６および正極端子板７がリング状の封口ガスケット９を介して負極缶１の開口部にカシメ付け固定され、電池が密閉されている。
【０００３】
【発明が解決しようとする課題】
図４に示したリチウム電池においては、厚みのある正極合剤４を内側に配しているので、正極合剤４の内周面の面積は非常に小さくなる。正極側の集電は、この小面積の部分に集電体５が接することで行われるが、正極合剤４の電気伝導度はあまり良くないので、基本的に集電効率は悪い構造だと言える。このままではいくら反応面積を増やしたといっても、集電効率が低いため、大電流を取り出すことはできない。そこで正極側の集電効率を向上させるために、正極合剤４と集電体５との間に生じる接触抵抗を可能な限り小さくする必要がある。とくに低温環境下では電池の内部抵抗が極めて大きくなるため、接触抵抗による放電効率の低下は極力避けたい。しかし、従来の構造では集電のために利用できる部分が集電体５の外周面に限られているため、十分な接触面積を確保できず、接触抵抗を大幅に低減することは難しかった。
【０００４】
また、集電体５の圧入作業を容易にするため集電体５の外径は正極合剤４の外径よりやや小さくする必要があることから、集電体５と正極合剤４との密着性は良くなく、両者間の接触抵抗は大きくなりがちだった。
【０００５】
さらに、集電体５の内側にはその動きを規制するものがないので、電池が消費されて正極合剤４が肥大化すると、集電体５が中心方向に押圧され、この集電体５と正極合剤４との接触圧力にムラが生じてしまう。このため、全体としての接触抵抗が増大してしまい、高い集電効率が得られなくなっていた。
【０００６】
この発明は前述の問題に鑑みてなされたもので、集電構造を改良することによって電気損失を低減し、低温・高負荷の条件下でも良好な放電特性を維持できるリチウム電池を提供することを目的とする。
【０００７】
【課題を解決するための手段】
前述の目的を達成するため、この発明は、有底円筒形の負極缶と、この負極缶の内周面に密着配置された中空円筒形のリチウム負極と、このリチウム負極の内周面に密着配置されたセパレータと、このセパレータの内周面に密着配置された中空円筒形の外側正極合剤と、この外側正極合剤の内周面に密着配置されてかつ上部の正極端子板に電気的に接続する中空円筒形の集電体と、この集電体の内周面に密着配置されてかつ前記集電体に設けられた複数の空孔を介して前記外側正極合剤と電気的に接続する中空円筒形の内側正極合剤と、前記負極缶の開口端部の内周に嵌め込まれた封口ガスケットと、この封口ガスケットの内周に嵌め込まれて前記負極缶を密閉する前記正極端子板とを備えたことを特徴とするインサイドアウト構造の円筒形電池とした。
【０００８】
【発明の実施の形態】
この発明の一実施例のリチウム電池を図１に示す。正極合剤１０ａ、１０ｂおよび集電体１１に特徴を有する他は、図４に示した従来のものと基本的に同じである。以下、その正極合剤１０ａ、１０ｂおよび集電体１１について説明する。
【０００９】
図１に示すように、正極合剤は外側の正極合剤１０ａと内側の正極合剤１０ｂとに分割して形成され、中空円筒形に加圧成形された外側の正極合剤１０ａの内周面には、これとほぼ等しい高さの中空円筒形に成形されたステンレス等の金属性の集電体１１が圧入されている。この集電体１１において実際に集電に寄与する円筒部分には空孔１１ａが２５〜６５％の空孔率で設けられている。さらに集電体１１の内周面には、前記正極合剤１０ａの内径よりもやや小さい外径を有する中空円筒形に加圧成形された内側の正極合剤１０ｂが圧入されている。この正極合剤１０ｂは、前記空孔１１ａを通じて外側の正極合剤１０ａと電気的に接続している。以上述べた正極合剤１０ａ、１０ｂおよび集電体１１からなる集電構造の斜視図を図２に示す。
【００１０】
この実施例では、電気的に接続された正極合剤１０ａと１０ｂとの間に集電体１１を介在させることにより、集電体１１の外周面だけでなく集電体１１の内周面からも集電に寄与させることができる。このため集電面積が飛躍的に増加する。また、正極合剤１０ｂによって集電体１１が正極合剤１０ａの内周面に強い圧力で押し付けられるため、集電体１１と正極合剤１０ａ、１０ｂとの密着状態が良好となる。これらのことから集電部分の接触抵抗が大幅に低減され、集電効率が向上する。
【００１１】
図１に示したこの発明のリチウム電池と図４に示した従来のリチウム電池の低温・高負荷の条件下での放電特性を比較するため、これらの閉路電圧測定（−２０℃、２０〜１００ｍＡ、５０ｍSec）を行った。その測定結果を図３に示す。１００ｍＡの負荷における閉路電圧は従来に比べて約１６％改善されている。
【００１２】
【発明の効果】
以上説明したように、この発明によるインサイドアウト構造の円筒形リチウム電池にあっては、複数の空孔を有する中空円筒形の集電体を外側正極合剤の内周面に密着配置するとともに集電体の内側に中空円筒形の正極合剤を圧入するようにしたことで、集電体の外周面のみでなく内周面からの集電も可能になる。また、内側の正極合剤が集電体を外側の正極合剤に強い圧力で押しつけるため、集電体と正極合剤との密着性が良好となる。これらにより、集電部分の接触抵抗が大幅に低減されて集電効率が向上し、低温・高負荷の条件下でも良好な放電特性を維持できる。
【図面の簡単な説明】
【図１】この発明の一実施例に関わるリチウム電池を示している。（ａ）は側面からの一部破断面図であり、（ｂ）は開口端側からのＡ−Ａ’断面図である。
【図２】図１の集電部分の概略を示す斜視図である。
【図３】この発明の一実施例に関わるリチウム電池（図１）および従来のリチウム電池（図４）について行った閉路電圧測定の測定結果である。
【図４】従来のリチウム電池を示している。（ａ）は側面からの一部破断面図であり、（ｂ）は開口端側からのＡ−Ａ’断面図である。
【図５】図４の集電部分の概略を示す斜視図である。
【符号の説明】
１負極缶
２リチウム負極
３セパレータ
４正極合剤
５集電体
６封口板
７正極端子
８非水電解液
９封口ガスケット
１０ａ正極合剤
１０ｂ正極合剤
１１集電体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inside-out type lithium battery, and more particularly, to an improvement in a current collecting structure for improving discharge characteristics.
[0002]
[Prior art]
A conventional typical cylindrical lithium battery with an inside-out structure is not suitable for applications requiring a large current because of its small area contributing to the discharge reaction. Therefore, in order to increase the reaction area, a reverse electrode arrangement, that is, a structure as shown in FIG. 4 was devised, in which a thin lithium anode with a small volume is arranged outside a thick positive electrode mixture with a large volume. In FIG. 4, the negative electrode can 1 formed in a bottomed cylindrical shape serves as a main body of a cylindrical battery case and also serves as a negative electrode terminal. A lithium negative electrode 2 formed into a hollow cylindrical shape by winding a rectangular metal lithium plate is closely disposed on the inner peripheral surface of the negative electrode can 1. A separator 3 formed into a hollow cylindrical shape with a bottom made of polypropylene nonwoven fabric or the like is disposed in close contact with the inner surface side of the hollow portion of the lithium negative electrode 2. A hollow cylindrical positive electrode mixture 4 (electrolytic manganese dioxide + graphite + binder) that is pressure-formed in a ring shape is laminated and disposed in close contact with the inner peripheral surface of the separator 3. A stainless steel current collector 5 formed into a hollow cylindrical shape having a height substantially equal to that of the positive electrode mixture 4 is press-fitted into the inner peripheral surface of the positive electrode mixture 4, and this press contact portion contributes to the current collection. It will be. FIG. 5 shows a perspective view of a current collecting structure composed of the current collector 5 and the positive electrode mixture 4.
The front end of the current collector 5 is spot welded to the inner surface of the plate-like sealing plate 6, and the sealing plate 6 is in contact with the plate-like positive electrode terminal plate 7 at the outer periphery thereof. Thus, the positive electrode mixture 4 is electrically connected to the positive electrode terminal plate 7. The sealing plate 6 and the positive electrode terminal plate 7 are caulked and fixed to the opening of the negative electrode can 1 via the ring-shaped sealing gasket 9 in a state where the non-aqueous electrolyte solution 8 made of an organic solvent is filled in the negative electrode can 1. The battery is sealed.
[0003]
[Problems to be solved by the invention]
In the lithium battery shown in FIG. 4, since the thick positive electrode mixture 4 is arranged inside, the area of the inner peripheral surface of the positive electrode mixture 4 becomes very small. Current collection on the positive electrode side is performed by the current collector 5 coming into contact with this small area portion. However, since the electric conductivity of the positive electrode mixture 4 is not so good, the current collection efficiency is basically poor. I can say that. Even if the reaction area is increased as it is, a large current cannot be taken out because the current collection efficiency is low. Therefore, in order to improve the current collection efficiency on the positive electrode side, it is necessary to reduce the contact resistance generated between the positive electrode mixture 4 and the current collector 5 as much as possible. In particular, the internal resistance of the battery becomes extremely large in a low temperature environment, so we want to avoid as much as possible the decrease in discharge efficiency due to contact resistance. However, since the portion that can be used for current collection is limited to the outer peripheral surface of the current collector 5 in the conventional structure, a sufficient contact area cannot be secured, and it has been difficult to significantly reduce the contact resistance.
[0004]
Further, since the outer diameter of the current collector 5 needs to be slightly smaller than the outer diameter of the positive electrode mixture 4 in order to facilitate the press-fitting work of the current collector 5, the current collector 5 and the positive electrode mixture 4 The adhesion was not good, and the contact resistance between the two tended to increase.
[0005]
Furthermore, since there is nothing that restricts the movement inside the current collector 5, when the battery is consumed and the positive electrode mixture 4 is enlarged, the current collector 5 is pressed in the center direction, and this current collector 5. And unevenness in the contact pressure between the positive electrode mixture 4 and the positive electrode mixture 4. For this reason, the contact resistance as a whole increases, and high current collection efficiency cannot be obtained.
[0006]
The present invention has been made in view of the above-described problems. It is an object of the present invention to provide a lithium battery capable of reducing electrical loss by improving the current collecting structure and maintaining good discharge characteristics even under conditions of low temperature and high load. Objective.
[0007]
[Means for Solving the Problems]
In order to achieve the above-described object, the present invention provides a bottomed cylindrical negative electrode can, a hollow cylindrical lithium negative electrode arranged in close contact with the inner peripheral surface of the negative electrode can, and an inner peripheral surface of the lithium negative electrode. A separator, a hollow cylindrical outer positive electrode mixture disposed in close contact with the inner peripheral surface of the separator, and an electric contact with the upper positive terminal plate disposed in close contact with the inner peripheral surface of the outer positive electrode mixture. A hollow cylindrical current collector connected to the current collector and electrically connected to the outer positive electrode mixture through a plurality of holes provided in close contact with the inner peripheral surface of the current collector and provided in the current collector A hollow cylindrical inner positive electrode mixture to be connected, a sealing gasket fitted in the inner periphery of the opening end of the negative electrode can, and the positive terminal plate fitted in the inner periphery of the sealing gasket to seal the negative electrode can Inside-out cylindrical shape characterized by comprising It was a pond.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a lithium battery according to an embodiment of the present invention. Except for the characteristics of the positive electrode mixture 10a, 10b and the current collector 11, it is basically the same as the conventional one shown in FIG. Hereinafter, the positive electrode mixtures 10a and 10b and the current collector 11 will be described.
[0009]
As shown in FIG. 1, the positive electrode mixture is divided into an outer positive electrode mixture 10a and an inner positive electrode mixture 10b, and the inner periphery of the outer positive electrode mixture 10a formed into a hollow cylinder by pressure. A metallic current collector 11 such as stainless steel formed into a hollow cylindrical shape having a height substantially equal to this is press-fitted into the surface. In the current collector 11, a cylindrical portion that actually contributes to current collection is provided with holes 11a with a porosity of 25 to 65%. Further, an inner positive electrode mixture 10b that is press-molded into a hollow cylindrical shape having an outer diameter slightly smaller than the inner diameter of the positive electrode mixture 10a is press-fitted into the inner peripheral surface of the current collector 11. The positive electrode mixture 10b is electrically connected to the outer positive electrode mixture 10a through the holes 11a. FIG. 2 shows a perspective view of the current collecting structure composed of the positive electrode mixture 10a, 10b and the current collector 11 described above.
[0010]
In this embodiment, by interposing the current collector 11 between the positive electrode mixtures 10a and 10b that are electrically connected, not only the outer peripheral surface of the current collector 11 but also the inner peripheral surface of the current collector 11 is used. Can also contribute to current collection. For this reason, the current collection area increases dramatically. Moreover, since the current collector 11 is pressed against the inner peripheral surface of the positive electrode mixture 10a by the positive electrode mixture 10b with a strong pressure, the close contact state between the current collector 11 and the positive electrode mixtures 10a and 10b is improved. For these reasons, the contact resistance of the current collecting portion is greatly reduced, and the current collecting efficiency is improved.
[0011]
In order to compare the discharge characteristics of the lithium battery of the present invention shown in FIG. 1 and the conventional lithium battery shown in FIG. 4 under conditions of low temperature and high load, these closed circuit voltage measurements (−20 ° C., 20 to 100 mA) are used. , 50 mSec). The measurement results are shown in FIG. The closed circuit voltage at a load of 100 mA is improved by about 16% compared to the conventional case.
[0012]
【The invention's effect】
As described above, in the cylindrical lithium battery having an inside-out structure according to the present invention, the hollow cylindrical current collector having a plurality of holes is disposed in close contact with the inner peripheral surface of the outer positive electrode mixture. By press-fitting the hollow cylindrical positive electrode mixture inside the current collector, current collection from the inner peripheral surface as well as the outer peripheral surface of the current collector becomes possible. Further, since the inner positive electrode mixture presses the current collector against the outer positive electrode mixture with a strong pressure, the adhesion between the current collector and the positive electrode mixture is improved. As a result, the contact resistance of the current collecting portion is greatly reduced, the current collecting efficiency is improved, and good discharge characteristics can be maintained even under conditions of low temperature and high load.
[Brief description of the drawings]
FIG. 1 shows a lithium battery according to an embodiment of the present invention. (A) is a partially broken sectional view from the side, and (b) is an AA ′ sectional view from the opening end side.
FIG. 2 is a perspective view showing an outline of a current collecting portion in FIG. 1;
FIG. 3 is a measurement result of a closed circuit voltage measurement performed on a lithium battery (FIG. 1) and a conventional lithium battery (FIG. 4) according to an embodiment of the present invention.
FIG. 4 shows a conventional lithium battery. (A) is a partially broken sectional view from the side, and (b) is an AA ′ sectional view from the opening end side.
5 is a perspective view showing an outline of a current collecting portion in FIG. 4; FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Negative electrode can 2 Lithium negative electrode 3 Separator 4 Positive electrode mixture 5 Current collector 6 Sealing plate 7 Positive electrode terminal 8 Nonaqueous electrolyte 9 Sealing gasket 10a Positive electrode mixture 10b Positive electrode mixture 11 Current collector

Claims

有底円筒形の負極缶と、この負極缶の内周面に密着配置された中空円筒形のリチウム負極と、このリチウム負極の内周面に密着配置されたセパレータと、このセパレータの内周面に密着配置された中空円筒形の外側正極合剤と、この外側正極合剤の内周面に密着配置されてかつ上部の正極端子板に電気的に接続する中空円筒形の集電体と、この集電体の内周面に密着配置されてかつ前記集電体に設けられた複数の空孔を介して前記外側正極合剤と電気的に接続する中空円筒形の内側正極合剤と、前記負極缶の開口端部の内周に嵌め込まれた封口ガスケットと、この封口ガスケットの内周に嵌め込まれて前記負極缶を密閉する前記正極端子板とを備えたことを特徴とするインサイドアウト構造の円筒形電池。Bottomed cylindrical negative electrode can, hollow cylindrical lithium negative electrode placed in close contact with the inner peripheral surface of the negative electrode can, separator placed in close contact with the inner peripheral surface of the lithium negative electrode, and inner peripheral surface of the separator A hollow cylindrical outer positive electrode mixture disposed in close contact with, and a hollow cylindrical current collector disposed in close contact with the inner peripheral surface of the outer positive electrode mixture and electrically connected to the upper positive electrode terminal plate; A hollow cylindrical inner positive electrode mixture that is disposed in close contact with the inner peripheral surface of the current collector and is electrically connected to the outer positive electrode mixture through a plurality of holes provided in the current collector, An inside-out structure comprising: a sealing gasket fitted to the inner periphery of the opening end of the negative electrode can; and the positive electrode terminal plate fitted to the inner periphery of the sealing gasket to seal the negative electrode can Cylindrical battery.