JP3913385B2

JP3913385B2 - Secondary battery

Info

Publication number: JP3913385B2
Application number: JP00538699A
Authority: JP
Inventors: 広一佐藤; 一成大北; 義人近野; 育郎米津; 晃治西尾
Original assignee: Sanyo Electric Co Ltd
Current assignee: Sanyo Electric Co Ltd
Priority date: 1998-09-29
Filing date: 1999-01-12
Publication date: 2007-05-09
Anticipated expiration: 2019-01-12
Also published as: JP2000173676A

Description

【０００１】
【発明の属する技術分野】
本発明は、二次電池に関し、特に充放電時の電池内圧測定の精度の向上を可能とする二次電池に関する。
【０００２】
【従来の技術】
近年、小型、軽量であるにもかかわらず、電池電圧が高く、高エネルギー密度のリチウムイオン二次電池が注目を集めているが、高エネルギー密度であるが故に電池特性に注意を払う必要がある。特に充電に伴って電池内部に発生するガスにより電池内圧が大きく変化するため、この電池内圧の変化を精度良く測定し、充電を制御する必要がある。この電池内圧を測定するためには、電池外装缶に圧力センサを取り付ける方法や特開平５−１５２００３号公報のように、充電に伴って各素電池の内部に発生するガスによる電池内圧の変化を検出するためのひずみゲージを各素電池の電池ケースに取り付ける方法が採られていた。
【０００３】
【発明が解決しようとする課題】
しかしながら、電池の外装缶に圧力センサを取り付ける方法では、電池自身の重量を増加させ、大型化になるという問題点があり、また電池缶にひずみゲージを取り付けて電池内圧を測定するという方法では、電池外装缶が樹脂製の場合は弾性力があるので、電池内圧をひずみゲージにより測定することができるが、金属製の電池外装缶の場合、電池缶の厚みを薄くしないと測定の精度を低下させ、缶の厚みを薄くすると逆に測定精度は向上するが、電池缶の耐圧強度は減少するという問題点があった。
【０００４】
【課題を解決するための手段】
本発明は、上述のような問題点に鑑みてなされたものであり、正極板、負極板、セパレータ及び電解液からなる発電要素を収納した電池外装缶と、外装缶を封口する蓋とよりなる二次電池であって、外装缶の外側面に凹凸部を形成し、少なくとも凹部の一部に電池内圧の上昇による前記電池外装缶の体積変化を検出する検出手段を取り付けている。また、本発明は電池外装缶の凸部（Ａ）と凹部（Ｂ）の厚みの比（Ａ／Ｂ）を１．５〜３としている。
【０００５】
【発明の実施の形態】
以下、本発明に係る二次電池の実施例を図面を参照しながら詳細に説明する。図１は本発明二次電池の素電池の斜視図を示したものであり、例えばリチウム二次電池が使用される。このリチウム二次電池からなる素電池は、正極板と負極板がセパレータを介して重ねあわせられて巻回されてなる渦巻状の発電要素が、円筒型のアルミニウムなどの金属製電池外装缶１内に収納されている。この外装缶１は、その側面を凸部２と凹部３に形成し、図２の断面図に示すように内周部４の発電要素が接する部分は平滑状に形成させ、外周部５に凸部２と凹部３として形成している。尚、図２は本発明に使用する素電池の断面図である。
【０００６】
また、この電池外装缶１は蓋６にて封口されている。
【０００７】
そして、この凹凸状に形成された外装缶１の凹部３の少なくとも一部には、電池の内圧の上昇による外装缶１の体積変化を検出する検出手段となる歪みセンサ７を取り付けている。この歪みセンサ７からの信号は制御回路（図示せず）に入り、制御回路内で圧力値を判断している。
【０００８】
この上記したリチウム二次電池の素電池の複数個を電気的に直列に接続し容器８に収納することで、図３に示すように組電池を構成する。図３は本発明の二次電池８本の配置状態を示す組電池の斜視図である。
【０００９】
本発明による電池缶Ａとして、缶直径６５ｍｍ、長さ３００ｍｍのアルミニウム部材を使用して、その側面に凹凸部２、３を有する電池外装缶１を形成する。
【００１０】
ここで、凸部２（Ａ）の肉厚は２ｍｍ、凹部３（Ｂ）の肉厚は０．８ｍｍであり、外装缶１における厚みの比（Ａ／Ｂ）を２．５とし、この凹部３に歪みセンサ７を取り付けている。
【００１１】
従来法による電池缶Ｂとして、缶直径６５ｍｍ、長さ３００ｍｍ、缶の肉厚２ｍｍのアルミニウム部材を使用して、その側面が平滑な電池外装缶１を形成した。そして、この缶表面の平滑部に歪みセンサ７を装着している。
【００１２】
また、従来法による電池缶Ｃとして、缶直径６５ｍｍ、長さ３００ｍｍ、缶の肉厚０．８ｍｍのアルミニウム部材を使用して、その側面が平滑な電池外装缶１を形成した。そして、この缶表面の平滑部に歪みセンサ７を装着している。
【００１３】
以上の３種類の電池缶を用いて組電池を各々作成し、電池外装缶の耐圧試験を行い、缶内部の圧力を測定した。
【００１４】
耐圧試験は、水圧試験装置を用いて、加圧範囲：０〜３０ｋｇ／ｃｍ²で行った。その測定結果を表１に示す。
【００１５】
【表１】

【００１６】
表１から明らかなように、電池缶Ａでは、歪みセンサの値は、低圧から高圧の範囲の全般において圧力センサの値とほぼ同じ値を示し、精度良く測定できている。
【００１７】
次に電池缶Ｂでは、高圧になるに従い、歪みセンサの値は圧力値に近い値になるが、低圧になるに従い、歪みセンサの値の精度は低下していることがわかる。
【００１８】
また、電池缶Ｃでは、外装缶１が肉厚０．８ｍｍと薄いため、低圧時には歪みセンサの値と圧力センサの値とが一致しているが、圧力が２０ｋｇ／ｃｍ²の時点で外装缶が塑性変形を起こし、大きく膨れ上がり測定不可能となった。
【００１９】
以上のように、外装缶に凹部３を形成し、この凹部３に歪みセンサ７を装着した本発明に係る電池缶Ａに依れば、内部圧力の変化を精度良く測定することが出来る。
【００２０】
次に、電池缶Ａの凸部２（Ａ）と凹部３（Ｂ）の厚みの比（Ａ／Ｂ）を変化させて電池外装缶１の耐圧試験を行い、そのときの缶内部の圧力を歪みセンサ７にて測定した。この凸部２（Ａ）の肉厚は２ｍｍとした。
【００２１】
耐圧試験は、水圧試験装置を用いて、加圧範囲：０〜３０ｋｇ／ｃｍ²で行った。その結果を表２に示す。
【００２２】
【表２】

【００２３】
表２から明らかなように、凸部２（Ａ）と凹部３（Ｂ）との厚みの比（Ａ／Ｂ）が１．５より小さくなると、低圧時の圧力センサの指示値と歪みセンサによる測定値の誤差が非常に大きくなる。
【００２４】
また、厚みの比（Ａ／Ｂ）が３．０より大きくなると、耐圧基準値が２０Ｋｇ／ｃｍ²であるにも拘わらず、缶自身の耐圧の値が２０Ｋｇ／ｃｍ²以下になってしまう。
【００２５】
従って、厚みの比（Ａ／Ｂ）として１．５〜３．０の値を用いることが好ましい。
【００２６】
次に、電池缶Ａと電池缶Ｂを用いて円筒型リチウムイオン電池を作製した。各々を組電池Ａ、組電池Ｃとする。これらの電池において、２５℃中０．１２５Ｃで４．１Ｖまで充電した後、２５℃において１Ｃで２．７Ｖまで放電した。そのときの電池缶表面温度を測定した。その結果を表３に示す。
【００２７】
【表３】

【００２８】
表３より明らかなように、放電容量を７０Ａｈとしたとき、組電池Ａの温度は組電池Ｂよりも低温となるが、これは外装缶１が凹凸部２、３を有しているために、外装缶１の表面積が実質的に増加し、電池における放熱性が向上したものと思われる。
【００２９】
さらに、この２種類の電池に対して、上述の条件で充放電サイクルを３００サイクル行った。その結果を図４に示す。図４は充放電サイクル数と組電池Ａ、Ｂの電池容量との関係を示すサイクル特性図である。
【００３０】
この図４から明らかなように、組電池Ａは組電池Ｂに比べてサイクル数が増加しても電池容量の低下が少ない。
【００３１】
また、その時の容量の変化を確認した。その結果を表４に示す。
【００３２】
【表４】

【００３３】
表４より明らかなように、組電池Ｂに比べ、組電池Ａは３００サイクル後の容量の維持率が０．０６即ち、６％向上している。これは、組電池Ａの外装缶が凹凸部を有する結果、外装缶の表面積が大きくなり放熱性が高まることにより、放電時の電池の温度上昇が小さくなり、電極の劣化が小さくなったためと思われる。
【００３４】
【発明の効果】
本発明によれば、正極板、負極板、セパレータ及び電解液からなる発電要素を収納した電池外装缶と、外装缶を封口する蓋とよりなる二次電池であって、外装缶の外側面に、凸部（Ａ）と凹部（Ｂ）の厚みの比（Ａ／Ｂ）が１．５〜３である凹凸部を形成し、少なくとも凹部の一部に電池内圧の上昇による電池外装缶の体積変化を検出する検出手段を取り付けたので、外装缶の耐圧強度を損ねることなく、電池内圧を精度良く検出することができる。
【００３５】
更に、凹凸部を形成することにより外装缶の表面積が増加するので、電池の放熱性を向上させることができ、電池の温度上昇に伴う電池特性の劣化を抑制することができる。
【図面の簡単な説明】
【図１】本発明による二次電池の素電池を示した斜視図である。
【図２】本発明に係る素電池の断面図である。
【図３】本発明による二次電池の組電池を示した斜視図である。
【図４】本発明による二次電池のサイクルに伴う電池容量の変化を示したサイクル特性図である。
【符号の説明】
１外装缶
２凸部
３凹部
４内周部
５外周部
６蓋
７歪みセンサ
８容器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a secondary battery, and more particularly to a secondary battery capable of improving the accuracy of battery internal pressure measurement during charging and discharging.
[0002]
[Prior art]
In recent years, despite the small size and light weight, lithium-ion secondary batteries with high battery voltage and high energy density have attracted attention. However, due to the high energy density, it is necessary to pay attention to battery characteristics. . In particular, since the internal pressure of the battery greatly changes due to the gas generated inside the battery as the battery is charged, it is necessary to accurately measure the change in the internal battery pressure and control the charging. In order to measure the internal pressure of the battery, the method of attaching a pressure sensor to the battery outer can or the change in the internal pressure of the battery due to the gas generated inside each unit cell as charged as disclosed in JP-A-5-152003. A method of attaching a strain gauge for detection to a battery case of each unit cell has been adopted.
[0003]
[Problems to be solved by the invention]
However, in the method of attaching the pressure sensor to the battery outer can, there is a problem that the weight of the battery itself is increased and the size is increased, and the method of measuring the internal pressure of the battery by attaching a strain gauge to the battery can, If the battery outer can is made of resin, there is elasticity, so the internal pressure of the battery can be measured with a strain gauge. However, in the case of a metal battery outer can, the measurement accuracy decreases unless the thickness of the battery can is reduced. In contrast, when the can thickness is reduced, the measurement accuracy is improved, but the pressure resistance of the battery can is reduced.
[0004]
[Means for Solving the Problems]
The present invention has been made in view of the above-described problems, and includes a battery outer can that contains a power generation element including a positive electrode plate, a negative electrode plate, a separator, and an electrolyte, and a lid that seals the outer can. In the secondary battery, a concavo-convex portion is formed on the outer surface of the outer can, and at least a part of the concave portion is provided with detection means for detecting a change in the volume of the battery outer can due to an increase in battery internal pressure. Moreover, this invention sets the ratio (A / B) of the thickness (A / B) of the convex part (A) and concave part (B) of a battery exterior can to 1.5-3.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the secondary battery according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of a unit cell of the secondary battery of the present invention, for example, a lithium secondary battery is used. The unit cell composed of the lithium secondary battery has a spiral power generation element in which a positive electrode plate and a negative electrode plate are overlapped and wound via a separator inside a metal battery outer can 1 such as cylindrical aluminum. It is stored in. The outer can 1 is formed with a convex portion 2 and a concave portion 3 on its side surfaces, and the portion of the inner peripheral portion 4 that is in contact with the power generation element as shown in the cross-sectional view of FIG. The part 2 and the recessed part 3 are formed. FIG. 2 is a cross-sectional view of the unit cell used in the present invention.
[0006]
The battery outer can 1 is sealed with a lid 6.
[0007]
And the distortion sensor 7 used as the detection means which detects the volume change of the outer can 1 by the raise of the internal pressure of a battery is attached to at least one part of the recessed part 3 of the outer can 1 formed in this uneven | corrugated shape. The signal from the strain sensor 7 enters a control circuit (not shown), and the pressure value is determined in the control circuit.
[0008]
A plurality of the above-described lithium secondary battery cells are electrically connected in series and housed in a container 8 to form an assembled battery as shown in FIG. FIG. 3 is a perspective view of an assembled battery showing an arrangement state of eight secondary batteries of the present invention.
[0009]
As the battery can A according to the present invention, an aluminum member having a can diameter of 65 mm and a length of 300 mm is used to form the battery outer can 1 having the concavo-

convex portions

2 and 3 on its side surface.
[0010]
Here, the thickness of the convex portion 2 (A) is 2 mm, the thickness of the concave portion 3 (B) is 0.8 mm, and the thickness ratio (A / B) in the outer can 1 is 2.5. A strain sensor 7 is attached to 3.
[0011]
As the battery can B according to the conventional method, an aluminum member having a can diameter of 65 mm, a length of 300 mm, and a can thickness of 2 mm was used to form a battery outer can 1 having a smooth side surface. The strain sensor 7 is attached to the smooth portion of the can surface.
[0012]
Moreover, as the battery can C according to the conventional method, an aluminum member having a can diameter of 65 mm, a length of 300 mm, and a can thickness of 0.8 mm was used, and the battery outer can 1 having a smooth side surface was formed. The strain sensor 7 is attached to the smooth portion of the can surface.
[0013]
An assembled battery was prepared using each of the above three types of battery cans, a pressure resistance test was performed on the battery outer can, and the pressure inside the can was measured.
[0014]
The pressure resistance test was performed using a water pressure test apparatus at a pressure range of 0 to 30 kg / cm ² . The measurement results are shown in Table 1.
[0015]
[Table 1]

[0016]
As is clear from Table 1, in the battery can A, the value of the strain sensor shows almost the same value as the value of the pressure sensor in the entire range from low pressure to high pressure, and can be measured with high accuracy.
[0017]
Next, in the battery can B, as the pressure increases, the value of the strain sensor becomes closer to the pressure value, but as the pressure decreases, the accuracy of the value of the strain sensor decreases.
[0018]
Further, in the battery can C, since the outer can 1 is as thin as 0.8 mm, the value of the strain sensor and the value of the pressure sensor coincide with each other at low pressure, but when the pressure is 20 kg / cm ² , the outer can Caused plastic deformation and swollen greatly, making it impossible to measure.
[0019]
As described above, according to the battery can A according to the present invention in which the recess 3 is formed in the outer can and the strain sensor 7 is attached to the recess 3, a change in internal pressure can be measured with high accuracy.
[0020]
Next, the pressure resistance test of the battery outer can 1 was performed by changing the thickness ratio (A / B) of the convex portion 2 (A) and the concave portion 3 (B) of the battery can A, and the pressure inside the can at that time was changed. Measurement was performed with a strain sensor 7. The thickness of the convex portion 2 (A) was 2 mm.
[0021]
The pressure resistance test was performed using a water pressure test apparatus at a pressure range of 0 to 30 kg / cm ² . The results are shown in Table 2.
[0022]
[Table 2]

[0023]
As is clear from Table 2, when the thickness ratio (A / B) between the convex portion 2 (A) and the concave portion 3 (B) is smaller than 1.5, it depends on the indication value of the pressure sensor at the low pressure and the strain sensor. The measurement error is very large.
[0024]
Further, when the thickness ratio (A / B) is larger than 3.0, the pressure resistance value of the can itself becomes 20 Kg / cm ² or less even though the pressure resistance reference value is 20 Kg / cm ² .
[0025]
Therefore, it is preferable to use a value of 1.5 to 3.0 as the thickness ratio (A / B).
[0026]
Next, using the battery can A and the battery can B, a cylindrical lithium ion battery was produced. Let each be an assembled battery A and an assembled battery C. In these batteries, the battery was charged to 0.1 V at 0.125 C in 25 ° C. and then discharged to 2.7 V at 1 C at 25 ° C. The battery can surface temperature at that time was measured. The results are shown in Table 3.
[0027]
[Table 3]

[0028]
As is apparent from Table 3, when the discharge capacity is 70 Ah, the temperature of the assembled battery A is lower than that of the assembled battery B. This is because the outer can 1 has the

uneven portions

2 and 3. It seems that the surface area of the outer can 1 is substantially increased, and the heat dissipation in the battery is improved.
[0029]
Furthermore, 300 cycles of charge / discharge cycles were performed on these two types of batteries under the above-described conditions. The result is shown in FIG. FIG. 4 is a cycle characteristic diagram showing the relationship between the number of charge / discharge cycles and the battery capacities of the assembled batteries A and B.
[0030]
As apparent from FIG. 4, the assembled battery A has a smaller decrease in battery capacity than the assembled battery B even if the number of cycles is increased.
[0031]
Also, the change in capacity at that time was confirmed. The results are shown in Table 4.
[0032]
[Table 4]

[0033]
As is clear from Table 4, the battery pack A has a capacity retention rate of 0.06, that is, 6% higher than that of the battery pack B after 300 cycles. This is probably because the battery case of the assembled battery A has uneven portions, and as a result, the surface area of the battery can increases and the heat dissipation increases, so that the temperature rise of the battery during discharge is reduced and the deterioration of the electrode is reduced. It is.
[0034]
【The invention's effect】
According to the present invention, there is provided a secondary battery comprising a battery outer can containing a power generation element composed of a positive electrode plate, a negative electrode plate, a separator, and an electrolyte, and a lid for sealing the outer can. The volume of the battery outer can is formed by forming a concavo-convex portion having a thickness ratio (A / B) of 1.5 to 3 between the convex portion (A) and the concave portion (B) and increasing the internal pressure of the battery at least in a part of the concave portion. Since the detecting means for detecting the change is attached, the battery internal pressure can be detected with high accuracy without impairing the pressure resistance of the outer can.
[0035]
Furthermore, since the surface area of the outer can is increased by forming the concavo-convex portion, the heat dissipation of the battery can be improved, and the deterioration of the battery characteristics accompanying the temperature rise of the battery can be suppressed.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a unit cell of a secondary battery according to the present invention.
FIG. 2 is a cross-sectional view of a unit cell according to the present invention.
FIG. 3 is a perspective view showing an assembled battery of a secondary battery according to the present invention.
FIG. 4 is a cycle characteristic diagram showing a change in battery capacity with a cycle of a secondary battery according to the present invention.
[Explanation of symbols]
1 exterior can 2 convex part 3 concave part 4 inner peripheral part 5 outer peripheral part 6 lid 7 strain sensor 8 container

Claims

A battery outer can containing a power generation element composed of a positive electrode plate, a negative electrode plate, a separator and an electrolyte, and a secondary battery comprising a lid for sealing the outer can,
On the outer surface of the outer can , an uneven portion having a thickness ratio (A / B) of the convex portion (A) to the concave portion (B) of 1.5 to 3 is formed, and at least a part of the concave portion has a battery internal pressure. A secondary battery comprising a detecting means for detecting a change in volume of the battery outer can due to ascending.