JP2006338992A - Square lithium ion battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a square lithium ion battery in which swelling of a battery due to expansion of an electrode substance at charging and repeating of charge and discharge is suppressed and which is highly reliable. <P>SOLUTION: The square lithium ion battery houses in a battery can 1 a battery element of flat shape in which a positive electrode and a negative electrode are laminated and wound around through a separator. The plate thickness at the central part 3 of the side face of the battery can in parallel with the flat face of the battery element is made thinner than that of the end 2 of the side face of the battery can. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a battery structure, and relates to a thin rectangular lithium ion battery.

  Various types of batteries are used as power sources for small electronic devices, and small and large-capacity sealed batteries are used as power sources for mobile phones and digital cameras, and non-aqueous electrolytes such as lithium ion batteries are used. A sealed battery is used. As the electronic equipment becomes thinner, a rectangular battery suitable for a thin equipment is excellent in space efficiency and is widely used.

  FIG. 5 is a diagram for explaining an example of a conventional prismatic lithium ion battery, and is a cross-sectional view of the central part of the battery. Fig.5 (a) is sectional drawing before repeating charging / discharging, and FIG.5 (b) is sectional drawing after repeating charging / discharging. The battery shown in FIG. 5 houses a battery element 4 formed by laminating and winding a positive electrode and a negative electrode on a battery can 1 made of aluminum or an alloy thereof via a separator.

  A battery using a wound-type electrode according to the prior art is known as a battery with high volumetric efficiency, but the capacity of a thin and square lithium ion battery is the amount of active material of the positive and negative electrodes constituting the battery element 4 Depends on. The capacity of the active material applied to the positive electrode and the negative electrode current collector can be increased by increasing the coating thickness. However, when the coating thickness is increased, the expansion and contraction of the active material layer due to charge / discharge repeatedly occur. Therefore, the battery can 1 has a problem that, as shown in FIG. 5 (b), the battery element 4 having the active material layer is deformed without being able to prevent the battery element 4 from being swollen, and it is difficult to attach the battery can to a battery using device. .

  In order to prevent the deformation of the battery can due to the swelling of the battery element, Patent Document 1, Patent Document 2, Patent Document 3 and the like describe a prismatic battery in which a recess is provided on the side surface of the can.

JP 2002-245975 A JP 2001-155893 A JP 2001-57179 A

  In a square battery containing a wound and laminated battery element according to the prior art, the battery element expands by repeated charge and discharge. If the thickness of the battery can plate is reduced in order to increase the volume inside the can in anticipation of the swelling of the battery elements, the corners gradually become brittle during deep drawing, making it difficult to mold the battery can. In addition, when a concave portion is provided on the side surface of the battery can to suppress deformation of the can, it is necessary to reduce the thickness of the battery element that can be stored in the can by the amount of the concave portion, and the space cannot be used as the battery element portion. This is not preferable in terms of increasing the capacity. In this situation, an object of the present invention is to provide a prismatic lithium ion battery with high reliability and high capacity against expansion of battery elements due to repeated charge and discharge.

  In order to solve the above problems, a prismatic lithium ion battery according to the present invention is a prismatic lithium ion battery in which a flat battery element in which a positive electrode and a negative electrode are stacked and wound via a separator is housed in a battery can. The central plate thickness of the side surface of the battery can parallel to the flat surface of the battery element is thinner than the end plate thickness, and the cross-sectional shape of the battery can perpendicular to the central axis of the winding of the battery element is the plate thickness near the four corners. On the other hand, the thickness of the central part of the long side of the outer shape is thin. The battery can may be formed by drawing from a deformed material whose center plate thickness is thinner than the end plate thickness. The battery can may be formed by molding an aluminum alloy plate with a convex portion at the center of the side surface.

  According to the prismatic lithium ion battery of the present invention, it is possible to prevent the battery can from being deformed by absorbing the expansion of the battery element at a thin plate pressure portion at the center of the can even when charging and discharging are repeated. . In addition, since the inner volume of the can increases, the amount of injection of the electrolyte can be increased, and the injection of the electrolyte is facilitated. For example, the rectangular shape is highly reliable and easy to manufacture. A lithium ion battery can be provided.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view showing a battery can used in the prismatic lithium ion battery of the present invention, and FIG. 2 is an explanatory view of an example of the prismatic lithium ion battery of the present invention, and is a cross-sectional view of the central portion of the battery. . 2A is a cross-sectional view before repeated charging and discharging, and FIG. 2B is a cross-sectional view after repeatedly charging and discharging.

  The battery element 4 is produced by laminating a positive electrode and a negative electrode through a separator and winding them flat, and then pressing them further to make them flat. The battery element 4 is housed in a battery can whose plate thickness at the central portion 3 on the side is thinner than the plate thickness at the end portion 2, and an electrolyte is injected from the liquid injection port of the lid that seals the opening of the battery can. Type lithium ion battery.

  In the rectangular lithium ion battery of the present invention, the part of the battery element 4 that contacts the battery can holds the battery element 4 at the end 2 of the side face of the battery can as shown in FIG. In addition, a gap is formed between the central portion of the battery element 4 and the central portion 3 on the side surface of the can. The central portion of the flat surface of the battery element 4 expands the most due to repeated charge and discharge. In this case, as shown in FIG. 2B, the end of the battery element 4 hardly expands, so that the side surface of the battery can There is no change in the structure held at the end 2.

  On the other hand, the battery can side surface central portion 3 corresponding to the expanded portion has a structure in which the plate thickness of the can is smaller than that of the end portion and enters the gap formed inside the can. It will be absorbed by the thin part of the central part 3.

  The central part of the side surface of the battery can does not have to be a flat surface, and may be a curved surface according to the shape of the battery element when it is expanded, a flat surface with a step, or a combination thereof. The length from the end surface of the thick portion of the end portion of the battery can side surface portion is determined by the shape of the battery element as long as it holds at least the flat portion of the battery element before repeated charging and discharging.

  The battery can 1 is produced by deep-drawing an aluminum alloy deformed material in which the thickness of the central portion 7 shown in the perspective view illustrating the deformed material in FIG. The plate thickness of 3 is thinner than the plate thickness of the end portion 2. By using a deformed material as the manufacturing material of the can, there is an advantage that the ironing of the thickness of the central portion of the side surface is unnecessary and the number of processes can be shortened. Further, the battery can has several steps using a male die 9 having a convex portion at the center of the side surface of the aluminum alloy flat plate shown in the perspective view of FIG. 4 and a female die 10 having a substantially rectangular parallelepiped shape inside the die. It may be manufactured by transfer molding. There is an advantage that processing can be performed by transfer molding even from a flat plate material without using a specially shaped profile material.

  A positive electrode and a negative electrode are made of a microporous polypropylene film on a battery can made of an aluminum plate (A3003) having an outer dimension of 48 mm in length, 30 mm in width, 4 mm in thickness, 0.2 mm in side edge plate thickness, and 0.15 mm in side wall center plate thickness. A battery element having a length of 44 mm, a width of 29 mm, and a thickness of 3.5 mm produced by being wound in a spiral shape is accommodated, and a lid is fitted into a can and laser welded. An electrolytic solution was injected from an injection port provided in the lid to produce a square lithium ion battery. Charging / discharging cycle test of the obtained battery, that is, charging current 680 mA, charging end voltage 4.2 V, holding for 2.5 hours, discharging current 680 mA, discharging end voltage 3.0 V, after 20 cycles, As a result of measuring the thickness of the battery can, the average value of 10 pieces was 4.75 mm.

(Comparative example)
A square lithium ion battery was fabricated and charged in the same manner as in Example 1 except that a battery can made of an aluminum plate (A3003) having an outer dimension of 48 mm in length, 30 mm in width, 4 mm in thickness, and 0.2 mm in thickness was used. As a result of conducting a discharge cycle test and measuring the thickness of the battery can, the average value of 10 pieces was 4.78 mm.

  An aluminum plate (A3003) consisting of an aluminum plate (A3003) with a center width of 20 mm, a plate thickness of 0.15 mm, an end width of 50 mm, and a plate thickness of 0.2 mm is provided with a convex portion having a width of 20 mm and a height of 0.05 mm at the center of the side surface. A battery can was formed by molding with the provided mold, and the outer dimensions were 48 mm in length, 30 mm in width, 4 mm in thickness, 0.2 mm in side edge plate thickness, and 0.15 mm in thickness at the side center plate.

An aluminum flat plate (A3003) made of an aluminum alloy (A3003) is molded with a mold having a convex part with a width of 20 mm and a height of 0.05 mm at the center of the side surface and is molded with an outer dimension of 48 mm in length and 30 mm in width. A battery can having a thickness of 4 mm, a side surface end plate thickness of 0.2 mm, and a side surface center plate thickness of 0.15 mm was produced.

  In the prismatic lithium ion battery of the present invention, since the central plate thickness of the side surface of the battery can parallel to the flat surface of the battery element is smaller than the end plate thickness, the thickness of the battery can changes even when charging and discharging are repeated. Is small and reliable.

The perspective view of the battery can of the square-shaped lithium ion battery of this invention. FIG. 2A is a cross-sectional view of the prismatic lithium ion battery of the present invention, and FIG. FIG. 2B is a cross-sectional view after repeated charge and discharge. The perspective view explaining the deformed material used for the square lithium ion battery of this invention. The perspective view of the metal mold | die and flat plate which are used for the square-shaped lithium ion battery of this invention. FIG. 5A is a cross-sectional view of a conventional prismatic lithium ion battery, FIG. 5A is a cross-sectional view before repeated charge / discharge, and FIG. 5B is a cross-sectional view after repeated charge / discharge.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery can 2 (Battery can side surface) End part 3 (Battery can side surface) Center part 4 Battery element 5 Deformed material 6 (Deformed material) End part 7 (Deformed material) Center part 8 Flat plate material 9 Male mold 10 Female mold

Claims (3)

  In a rectangular lithium ion battery in which a flat battery element in which a positive electrode and a negative electrode are stacked and wound via a separator is housed in a battery can, the thickness of the central portion of the side surface of the battery can parallel to the flat surface of the battery element The cross-sectional shape of the battery can perpendicular to the central axis of the battery element winding is thinner than the end plate thickness, and the thickness of the central portion of the long side of the outer shape is thinner than the plate thickness near the four corners. A featured prismatic lithium-ion battery.   2. The prismatic lithium ion battery according to claim 1, wherein the battery can comprises a battery can formed by drawing from a deformed material having a center plate thickness smaller than an end plate thickness.   2. The prismatic lithium ion battery according to claim 1, wherein the battery can is made of a battery can formed by using a mold in which an aluminum alloy plate is provided with a convex portion at the center of the side surface.

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