JP2019133742A - Sealing body and non-aqueous electrolyte secondary battery using the same - Google Patents

Abstract

To provide a sealing body for a power storage device that is capable of discharging gas at an appropriate speed only from a gas discharge valve without causing breakage at a portion other than a gas discharge valve when the internal pressure of the device is increased.SOLUTION: A sealing body 13 which is an example of the embodiment includes a metal plate 14 and closes the opening of an outer can 12. The sealing body 13 includes a gas discharge valve 20 that is integrally formed with the metal plate 14 and opens when the internal pressure of a device rises to a predetermined pressure, and a reinforcing portion 22 provided around the gas discharge valve 20 and having a heat capacity of twice or more per unit area than a base portion P which is another portion of the metal plate 14 excluding the gas discharge valve 20.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a sealing body and a nonaqueous electrolyte secondary battery using the same.

  A power storage device such as a non-aqueous electrolyte secondary battery includes, for example, an outer can that contains an electrode body and a non-aqueous electrolyte, and a sealing body that closes an opening of the outer can. Many sealing bodies are provided with a gas discharge valve that opens when the internal pressure of the power storage device rises to a predetermined pressure. For example, Patent Document 1 discloses a sealing body for a power storage device including a gas discharge valve welded to a mounting hole. Patent Document 1 describes that an aluminum-based metal layer is provided around the inner surface of the mounting hole and the gas discharge valve.

JP 2014-135140 A

  By the way, with the increase in energy density of power storage devices, the amount of heat generated when an abnormality such as an internal short circuit occurs increases, and the amount of gas discharged increases. For this reason, in a power storage device having a conventional sealing body, it is assumed that the sealing body breaks around the gas discharge valve and gas is discharged from a portion other than the valve. In this case, the target gas discharge speed cannot be maintained, and there is a risk of ignition. On the other hand, weight reduction of the sealing body and reduction of material cost are also important issues.

  A sealing body according to the present disclosure is a sealing body for a power storage device that is made of a metal plate and closes an opening of an outer can, and is formed integrally with the metal plate, and the internal pressure of the device rises to a predetermined pressure. A gas exhaust valve that opens and a reinforcing portion that is provided around the gas exhaust valve and has a heat capacity that is twice or more per unit area than a base that is the other part of the metal plate excluding the gas exhaust valve.

  A nonaqueous electrolyte secondary battery according to the present disclosure includes an outer can, the sealing body that closes the opening of the outer can, an electrode body that is accommodated in the outer can, and a nonaqueous electrolyte.

  According to the sealing body according to the present disclosure, when the internal pressure of the apparatus is increased, the portion other than the gas discharge valve is not broken, and the gas can be discharged from the gas discharge valve only at an appropriate speed.

It is a perspective view which shows the external appearance of the nonaqueous electrolyte secondary battery which is an example of embodiment. It is a top view of the gas exhaust valve of the sealing body which is an example of embodiment, and its vicinity. FIG. 3 is a sectional view taken along line AA in FIG. 2. It is a figure which shows the sealing body which is another example of embodiment. It is a figure which shows the sealing body which is another example of embodiment. It is a figure which shows the sealing body which is another example of embodiment.

  As described above, it is necessary to prevent the sealing body from being broken at portions other than the gas discharge valve. The gas discharge valve discharges gas when high temperature gas is generated due to an internal short circuit and the internal pressure of the device rises. However, if a large amount of high temperature gas is generated, the surroundings of the gas discharge valve are melted, for example. There is a possibility that the sealing body breaks at other portions. The breakage of the portion other than the gas discharge valve occurs starting from the edge of the valve, and the breakage point spreads at a stretch. In addition, the designed gas discharge rate cannot be maintained, which may lead to ignition.

  As a result of intensive studies to prevent breakage of portions other than the gas discharge valve while reducing the weight and reducing the material cost, the present inventors have determined that the unit area is larger than the other portion (base) around the gas discharge valve. It has been found that by providing a reinforcing portion having a heat capacity of twice or more per hit, the gas can be discharged at an appropriate rate only from the gas discharge valve without breaking at portions other than the gas discharge valve. For example, when reinforcing the periphery of the gas valve with the same material as the base portion, a thick portion having a thickness exceeding twice the thickness of the base portion may be provided around the gas discharge valve. According to such a sealing body, breakage does not occur in portions other than the gas discharge valve, and gas can be discharged at an appropriate speed only from the gas discharge valve.

  The metal plate constituting the sealing body is preferably thinned in consideration of weight reduction, material cost reduction, and the like. For this reason, the thickness of the base portion of the metal plate is reduced to such an extent that the metal plate breaks when the internal pressure rises when the thickness around the gas discharge valve is set to the thickness. In the sealing body according to the present disclosure, the base is thinned, and only the periphery of the gas discharge valve is locally thickened to prevent breakage in parts other than the valve while reducing the weight and reducing the material cost. Yes. The inventors of the present invention have found that breakage of portions other than the gas discharge valve can be efficiently prevented by setting the heat capacity per unit area of the reinforcing portion to be twice or more the heat capacity per unit area of the base. In addition, when the heat capacity of the reinforcement part is less than twice the heat capacity of the base part, the probability that breakage occurs around the valve is greatly increased. Alternatively, it is necessary to increase the overall thickness of the sealing body, leading to an increase in weight and cost.

  By the way, in the case of nonaqueous electrolyte secondary batteries, such as a lithium ion battery, the gas generated at the time of thermal runaway is generally 700 ° C. or higher. In addition, an appropriate gas discharge time (discharge speed) from the viewpoint of preventing ignition is generally 1 to 30 seconds. That is, the periphery of the gas discharge valve is required not to break even when exposed to a gas of 700 ° C. or higher for 1 to 30 seconds. As a result of studies by the present inventors, it has been found that the preferable thickness of the reinforcing portion is approximately 2 mm to 10 mm, although it varies somewhat depending on the composition of the metal plate, the width of the reinforcing portion, and the like. The thickness of the base is, for example, 1 mm to 5 mm, and can be less than ½ of the thickness of the reinforcing portion.

  Hereinafter, an example of an embodiment will be described in detail with reference to the drawings. The drawings referred to in the description of the embodiments are schematically described, and specific dimensions and the like of each component should be determined in consideration of the following description. In addition, in the present specification, “substantially to” is intended to include those that are recognized as being substantially constant as well as being completely constant when described as being substantially constant.

  Below, the nonaqueous electrolyte secondary battery 10 provided with the rectangular metal case (battery case 11) comprised by the exterior can 12 and the sealing body 13 is illustrated as an electrical storage apparatus, but an electrical storage apparatus is limited to a battery. Alternatively, a capacitor may be used. The battery case may have a shape other than a square. In the description of the embodiment, the direction in which the external terminals provided on the sealing body are arranged is `` lateral direction '', the direction along the thickness direction of the sealing body is `` vertical direction '', and the direction orthogonal to the lateral direction and the vertical direction is `` "Vertical direction".

  FIG. 1 is a perspective view showing an appearance of a nonaqueous electrolyte secondary battery 10 which is an example of an embodiment. As illustrated in FIG. 1, the nonaqueous electrolyte secondary battery 10 includes a battery case 11 including an outer can 12 and a sealing body 13 that closes an opening of the outer can 12. The nonaqueous electrolyte secondary battery 10 is a prismatic battery including a battery case 11 that is a rectangular metal case, and is preferably a lithium ion battery. The type of the nonaqueous electrolyte secondary battery 10 is not particularly limited, but will be described below as a lithium ion battery.

  The outer can 12 contains an electrode body and a non-aqueous electrolyte. The electrode body includes a positive electrode, a negative electrode, and a separator, and has a structure in which leads are drawn from the positive electrode and the negative electrode. The electrode body may be either a laminated type or a wound type. The non-aqueous electrolyte is composed of a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent. Examples of the non-aqueous solvent include cyclic carbonates, chain carbonates, carboxylic esters, and halogen-substituted products obtained by substituting these hydrogen atoms with halogen atoms such as fluorine atoms.

  A lithium-containing composite oxide is used as the positive electrode active material. As an example of a suitable composite oxide, a Ni-Co-Mn-based or Ni-Co-Al-based lithium-containing composite oxide can be given. The negative electrode active material is not particularly limited as long as it can reversibly occlude and release lithium ions. For example, carbon materials such as natural graphite and artificial graphite, metals such as Si and Sn, alloys that form an alloy with lithium, alloys, A composite oxide or the like can be used.

  The energy density of the nonaqueous electrolyte secondary battery 10 is, for example, 160 Wh / kg to 270 Wh / kg. It is particularly preferable that the sealing body 13 provided with a reinforcing portion 22 (see FIG. 2 and the like) described later is applied to a power storage device having an energy density of 200 Wh / kg or more.

  The outer can 12 is a bottomed rectangular cylindrical metal container having an open upper end. The outer can 12 has a flat shape that is longer in the horizontal and vertical directions than in the vertical direction, but the shape of the outer can is not particularly limited. The metal material constituting the outer can 12 is, for example, a metal material mainly composed of aluminum.

  The sealing body 13 is a member for closing the opening of the outer can 12 and sealing the internal space of the battery case 11, and includes a metal plate 14. The metal plate 14 constituting the sealing body 13 has a shape corresponding to the opening of the outer can 12, and has a substantially rectangular shape that is longer in the horizontal direction than in the vertical direction in the example shown in FIG. 1. The sealing body 13 is attached to the outer can 12 by, for example, welding the peripheral portion of the metal plate 14 to the outer can 12.

  It is preferable that the metal plate 14 is comprised from the metal material which has aluminum as a main component from viewpoints, such as weight reduction. The metal material is, for example, aluminum or an aluminum alloy, and the aluminum content is 90% by weight or more. Below, the metal plate 14 is demonstrated as what is comprised from the metal material which has aluminum as a main component.

  The sealing body 13 is provided with a positive external terminal 15, a negative external terminal 16, a liquid injection part 17, and a gas discharge valve 20. In the example shown in FIG. 1, a positive electrode external terminal 15 is provided at one end portion in the horizontal direction of the sealing body 13, and a negative electrode external terminal 16 is provided at the other end portion in the horizontal direction. For example, through holes are respectively formed at both lateral ends of the metal plate 14, and the positive electrode external terminal 15 and the negative electrode external terminal 16 are electrically insulated from the metal plate 14 through an insulating gasket. It is attached to the through hole. Each external terminal is connected to a lead drawn out from the electrode body directly or via another current collecting member. In addition, it is good also as a form which provides only the negative electrode external terminal as an external terminal in the sealing body 13, and uses the armored can 12 as a positive electrode external terminal.

  The gas discharge valve 20 is preferably formed at the lateral center of the sealing body 13 so as to enable smooth gas discharge. The gas discharge valve 20 is formed, for example, at a substantially equidistant position from the positive external terminal 15 and the negative external terminal 16. The liquid injection part 17 is formed between the negative electrode external terminal 16 and the gas discharge valve 20. The liquid injection part 17 is generally composed of a liquid injection hole for injecting an electrolytic solution and a sealing plug for closing the liquid injection hole.

  Hereinafter, the gas discharge valve 20 and the reinforcing portion 22 will be described in detail with reference to FIGS. 2 and 3. 2 is a plan view showing the gas discharge valve 20 of the sealing body 13 and the vicinity thereof, and FIG. 3 is a sectional view taken along line AA in FIG.

  As illustrated in FIGS. 2 and 3, the sealing body 13 includes a gas exhaust valve 20 and a reinforcing portion 22 provided around the gas exhaust valve 20. The gas discharge valve 20 is formed integrally with the metal plate 14 by a processing means such as coining, and opens when the internal pressure of the nonaqueous electrolyte secondary battery 10 rises to a predetermined pressure. By processing the metal plate 14 constituting the sealing body 13 and integrally forming the gas discharge valve 20, it is not necessary to attach a valve, for example, by welding, and the sealing performance and reliability of the sealing body 13 are improved.

  In the present embodiment, an annular recess 21 is formed in the metal plate 14, and a portion surrounded by the recess 21 becomes the gas discharge valve 20. In the central portion in the horizontal direction of the gas discharge valve 20, a linear recess 21 is formed that extends in the vertical direction and has both ends connected to an annular recess 21 in order to facilitate opening of the valve when the internal pressure increases. The concave portion 21 is an inscription formed on the outer surface of the sealing body 13 (the surface facing the outside of the battery case 11), and the portion where the concave portion 21 is formed is a thin-walled portion having a smaller thickness than the other portions. When rising, the metal plate 14 is broken at the thin portion, and the gas discharge valve 20 is opened. Instead of forming the recess 21 or forming the recess 21, the thickness of the metal plate 14 may be reduced throughout the gas discharge valve 20.

The gas discharge valve 20 has a rounded rectangular shape that is long in the lateral direction. If there is an angled portion at the edge of the gas exhaust valve 20, a portion located around the gas exhaust valve 20 from the portion is easily broken, and therefore, an angular portion may not be formed at the edge of the gas exhaust valve 20. preferable. The size of the gas discharge valve 20 is determined based on the amount of gas discharged when an abnormality such as an internal short circuit occurs, for example, and is set to a size that allows the gas to be discharged at an appropriate speed at which ignition does not occur. In the case of a lithium ion battery having an energy density of 200 Wh / kg, for example, from the viewpoint of securing the strength of the gas discharge valve 20, the width of the sealing body 13 is Lw, and the length of the gas discharge valve 20 in the vertical direction (length in the short direction). the when the _{L 2, L 2 / Lw =} 1 / 2~1 / 4 is preferred. From the viewpoint of the gas exhaust efficiency, when the lateral length of the gas discharge valve 20 (longitudinal length) was _{L 1, L 2 / L 1} = 1 / 2~1 / 4 is preferred.

The reinforcing portion 22 surrounds the gas exhaust valve 20 and is provided around the entire valve, and reinforces a portion of the sealing body 13 located around the gas exhaust valve 20. The reinforcing portion 22 is a portion having a heat capacity twice or more per unit area than the base portion P which is the other portion of the metal plate 14 excluding the gas discharge valve 20, and has a thickness exceeding twice the thickness of the base portion P, for example. Have For example, the thickness T ₁₄ × 2 in the thickness T _22> base P of the reinforcing portion 22, the heat capacity when compared by the heat capacity × 2 heat capacity ≧ base P of the reinforcing portion 22 in the same area, width of the sealing member 13 It is possible to efficiently prevent breakage of portions other than the gas discharge valve 20 without causing a significant increase in weight and cost.

The thickness T ₁₄ of the base portion P is a gas exhaust valve 20 and the portion other than the reinforcing portion 22 of the sealing member 13 is, for example, 1 mm to 5 mm, preferably 1.5 mm to 3 mm. Metal plate 14 constituting the sealing member 13, since it is preferable to thin from the viewpoint of weight reduction, the thickness T ₁₄ of the base portion P, as described above, when the surrounding gas discharge valve 20 and its thickness The thickness is reduced to such an extent that the metal plate 14 is broken when the internal pressure increases. When the thickness T _{14 of the} base portion P is such a thickness, if the thickness T ₂₂ of the reinforcing portion ₂₂ ≦ the thickness T ₁₄ × 2 of the base portion P, the probability of breakage around the gas discharge valve 20 is large. To rise. The thickness T ₂₂ of the reinforcing portion 22 is, for example, 2 mm to 10 mm, preferably 3 mm to 6 mm.

  The reinforcing portion 22 is a thick portion formed by locally increasing the thickness of the metal plate 14 around the gas discharge valve 20. That is, the gas discharge valve 20, the reinforcement portion 22, and the base portion P are integrally formed by processing one metal plate 14. In the present embodiment, the metal plate 14 bulges outside the battery case 11 around the gas discharge valve 20. That is, the outer surface of the sealing body 13 (the surface facing the outside of the battery case 11) rises around the gas discharge valve 20, and a thick wall portion is formed along the edge of the gas discharge valve 20.

The thickness T ₂₂ of the reinforcing portion 22 is preferably set to be more than twice and less than 5 times the thickness T ₁₄ of the base portion P. If the reinforcing portion 22 is bulged to the outside of the battery case 11, an excessively large thickness T _22, since the outer shape of the battery is increased, undesirably. On the other hand, if the reinforcing portion 22 is bulged to the inside of the battery case 11, an excessively large thickness T _22, since the reinforcing portion 22 may interfere with the current collector member such as the electrode body or a lead, which is not preferable. The thickness T ₂₂ of the reinforcing portion 22 is more preferably more than twice as large as the thickness T ₁₄ of the base portion P and 4.5 times or less, and particularly preferably 2.5 times or more and 4 times or less. If the thickness T ₂₂ is set within this range, the surroundings of the gas discharge valve 20 can be efficiently reinforced without causing the above-described problems.

  The reinforcing portion 22 is locally provided around the gas discharge valve 20. When the reinforcing portion 22 is provided outside the battery case 11, it is preferable to form the reinforcing portion 22 so that it does not protrude from the peripheral edge of the outer can 12. Further, when the reinforcing portion 22 is provided inside the battery case 11, it is not provided in a portion that interferes with the outer can 12. The reinforcing portion 22 is provided in a portion spaced a predetermined length from the end of the metal plate 14 so as not to hinder the welding of the outer can 12 and the sealing body 13.

The width W of the reinforcing portion 22 is not particularly limited as long as it does not protrude from the peripheral edge of the outer can 12 or does not interfere with the outer can 12, but in order to reinforce the periphery of the gas exhaust valve 20, the gas exhaust valve It is preferably substantially constant over the entire circumference of 20. Further, it is preferable that the thickness T ₂₂ of the reinforcing portion 22 is substantially constant over the entire periphery of the gas discharge valve 20. That is, the reinforcing portion 22 is preferably formed with a substantially constant thickness and a substantially constant width over the entire circumference of the gas discharge valve 20.

  As described above, according to the nonaqueous electrolyte secondary battery 10 provided with the sealing body 13, when high-temperature gas is generated due to an internal short circuit or the like and the internal pressure is increased, the gas discharge valve 20 alone is used at an appropriate speed. Gas can be discharged. The breakage of the portion other than the gas discharge valve 20 of the sealing body 13 is likely to occur from the edge of the gas discharge valve 20, but by providing a bank-shaped reinforcing portion 22 surrounding the valve, the weight of the sealing body 13 and the material cost are reduced. It is possible to efficiently prevent breakage of parts other than the valve while achieving reduction of the above. And by using the sealing body 13, the nonaqueous electrolyte secondary battery 10 with high energy density and high safety | security can be provided.

  It should be noted that the design of the above-described embodiment can be changed as appropriate without departing from the object of the present disclosure. For example, the shape of the gas discharge valve is not limited to a rounded rectangular shape that is long in the lateral direction, and may be an elliptical shape, a perfect circular shape, or the like. And the reinforcement part is formed according to the shape of a gas exhaust valve.

4-6 is a figure which shows sealing body 13A, 13B, 13C which is another example of embodiment. Each reinforcing portion of the sealing member 13A, 13B, @ 13 C, similar to the reinforcing portion 22 preferably has a 2-fold excess 5-fold less than the thickness of the thickness T ₁₄ of the base portion P. Further, each reinforcing portion is preferably formed with a substantially constant thickness and a substantially constant width over the entire circumference of the gas discharge valve 20.

The reinforcing portion 23 of the sealing body 13A illustrated in FIG. 4 is different from the sealing body 13 in that it bulges not only outside the battery case 11 but also inside. That is, the inner surface and the outer surface of the sealing body 13A (metal plate 14A) swell around the gas discharge valve 20, and a bank-shaped thick portion along the edge of the gas discharge valve 20 is formed on both surfaces of the sealing body 13A. . In this case, it is possible to increase the total thickness T ₂₃ of the reinforcing portion 23 while suppressing the degree of swelling with respect to the inside and the outside of the battery case 11.

  The reinforcing portion 25 of the sealing body 13B illustrated in FIG. 5 is different from the sealing bodies 13 and 13A in that the reinforcing plate 24 is formed around the gas discharge valve 20. In the example shown in FIG. 5, the reinforcing plate 24 is fixed to the outer surface of the metal plate 14B. However, the reinforcing plate 24 may be fixed to the inner surface of the metal plate 14B, or may be fixed to both surfaces of the metal plate 14B. . The reinforcing plate 24 has a substantially rectangular shape in plan view, and is superimposed on the metal plate 14B constituting the sealing body 13B to increase the thickness of the sealing body 13B around the gas discharge valve 20, that is, to form the reinforcing portion 25. . In the sealing body 13 </ b> B, the thickness of the reinforcing portion 25 can be adjusted by changing the thickness of the reinforcing plate 24.

  An opening 26 that penetrates in the thickness direction is formed in the reinforcing plate 24 with substantially the same shape and dimensions as the gas discharge valve 20. And the reinforcement board 24 is arrange | positioned at the metal plate 14B so that the opening part 26 may overlap with the gas exhaust valve 20 in an up-down direction. The reinforcing plate 24 is fixed to the metal plate 14B, for example, by welding, brazing, or using an adhesive. The reinforcing plate 24 may be made of the same metal material as the metal plate 14B, but is preferably made of a metal material or ceramic having a melting point higher than that of the metal plate 14B (the same applies to the reinforcing plate 27 described later). Suitable examples include copper, stainless steel (SUS), and alumina. By using a material having a larger heat capacity than the metal plate 14B, the thickness of the reinforcing plate 24 can be reduced.

  The reinforcing part 28 of the sealing body 13C illustrated in FIG. 6 is common to the sealing body 13B in that the reinforcing plate 27 is fixed around the gas exhaust valve 20. On the other hand, the reinforcing plate 27 differs from the sealing body 13B in that it has a plurality of through holes 29. A total of four through holes 29 are formed near each of the four corners of the reinforcing plate 27. Further, the metal plate 14C has a pin 30 protruding outward. Four pins 30 are formed around the gas discharge valve 20. In the sealing body 13C, the pin 30 is press-fitted into the through hole 29, whereby the reinforcing plate 27 is fixed to the metal plate 14C. Note that the shape, number, arrangement, and the like of the through holes 29 and the pins 30 are not particularly limited as long as the reinforcing plate 27 can be stably fixed to the metal plate 14C.

  DESCRIPTION OF SYMBOLS 10 Nonaqueous electrolyte secondary battery, 11 Battery case, 12 Exterior can, 13 Sealing body, 14 Metal plate, 15 Positive electrode external terminal, 16 Negative electrode external terminal, 17 Injection part, 20 Gas discharge valve, 21 Recessed part, 22, 23 , 25, 28 Reinforcement part, 24, 27 Reinforcement plate, 26 Opening part, 29 Through hole, 30 pin, P base

Claims (8)

It is composed of a metal plate, and is a sealing body for a power storage device that closes an opening of an outer can,
A gas discharge valve that is formed integrally with the metal plate and opens when the internal pressure of the device rises to a predetermined pressure;
A reinforcing portion provided around the gas discharge valve and having a heat capacity of twice or more per unit area than a base portion which is another portion of the metal plate excluding the gas discharge valve;
Sealing body with   The sealing member according to claim 1, wherein the reinforcing portion is formed by increasing the thickness of the metal plate around the gas discharge valve.   The sealing body according to claim 1, wherein the reinforcing portion is formed by fixing a reinforcing plate around the gas discharge valve.   The thickness of the said reinforcement part is a sealing body of any one of Claims 1-3 which is 2 times more than the thickness of the said base, and less than 5 times.   The sealing body according to claim 4, wherein the thickness of the base portion is 1 mm to 5 mm, and the thickness of the reinforcing portion is 2 mm to 10 mm.   The said metal plate is a sealing body of any one of Claims 1-5 comprised from the metal material which has aluminum as a main component.   The said reinforcement part is a sealing body of any one of Claims 1-6 formed in the substantially constant thickness and the substantially constant width | variety over the perimeter of the said gas exhaust valve. The outer can,
The sealing body according to any one of claims 1 to 7, which closes the opening of the outer can.
An electrode body and a non-aqueous electrolyte housed in the outer can,
A non-aqueous electrolyte secondary battery.

Images