JP2001266812A - Nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a big-sized and flat nonaqueous secondary battery with high safety. SOLUTION: The flat nonaqueous secondary battery, composed of a cathode, an anode, a separator and nonaqueous electrolyte including lithium salt, sealed in a case, has a pressure releasing structure 72 operating with low pressure at the marginal area 71 of flat surface part, and a thin wall thickness part 82 restraining the deformation caused by expansion at the outer side of the marginal area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a non-aqueous secondary battery, and more particularly to a non-aqueous secondary battery for a power storage system.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of effective use of energy for resource saving and global environmental problems, a home-use decentralized power storage system for late-night power storage and power storage for photovoltaic power generation has been developed. Power storage systems are attracting attention. For example, JP-A-6-86463 discloses that
As a system capable of supplying energy to an energy consumer under optimum conditions, a total system combining electricity supplied from a power plant, gas cogeneration, a fuel cell, a storage battery, and the like has been proposed. A secondary battery used in such a power storage system has an energy capacity of 10
Unlike small secondary batteries for portable devices of Wh or less, large batteries having large capacities are required. For this reason, in the above-described power storage system, a plurality of secondary batteries are stacked in series, and usually used as a battery pack having a voltage of, for example, 50 to 400 V. In most cases, a lead battery is used.

On the other hand, in the field of small rechargeable batteries for portable equipment, nickel-metal hydride batteries and lithium rechargeable batteries have been developed as new types of batteries in order to meet the needs of small size and high capacity, and volume energy of 180 Wh / l or more has been developed. Batteries having a density are commercially available. In particular, lithium-ion batteries
It has the potential of a volume energy density exceeding 350 Wh / l, and its reliability, such as safety and cycle characteristics, is superior to a lithium secondary battery using lithium metal as a negative electrode. Prolonged.

[0004] In response to this, in the field of large-sized batteries for power storage systems, lithium-ion batteries have been targeted as candidates for high-energy density batteries, and lithium battery power storage technology research associations (LIBES) and others have been vigorously developing them. Have been.

The energy capacity of these large lithium ion batteries is about 100 Wh to 400 Wh, and the volume energy density is 200 to 300 Wh / l, which is at the level of a small secondary battery for portable equipment. Its shape is
Diameter 50mm-70mm, length 250mm-450mm
And a rectangular prism having a thickness of 35 mm to 50 mm or an oblong prism or the like are typical.

[0006] As for the thin lithium secondary battery, for example, a film battery (for example, Japanese Patent Application Laid-Open Nos. Hei 5-159575 and Hei 7-15975) in which a thin film having a thickness of 1 mm or less in which metal and plastic are laminated is accommodated in a thin exterior. -5
No. 7788), a small rectangular battery having a thickness of about 2 mm to 15 mm (JP-A-8-195204, JP-A-8-195204).
138727, JP-A-9-213286, etc.) are known. The purpose of these lithium secondary batteries is to respond to the miniaturization and thinning of portable devices. For example, an area of about JIS A4 size with a thickness of several mm that can be stored on the bottom surface of a portable personal computer. Japanese Patent Application Laid-Open No. 5-28310 discloses a thin battery.
No. 5), since the energy capacity is 10 Wh or less, the capacity is too small for a secondary battery for a power storage system.

[0007]

In the case of a flat battery, as the thickness of the battery is reduced for the purpose of improving heat dissipation, the front and back area of the battery increases. In addition, in order to maintain a high energy density, the tendency is particularly strong when a flat lithium battery (energy capacity of 30 Wh or more) used in a power storage system is prototyped, for example, a 100 Wh class battery. In the case of a lithium ion battery having a thickness of 6 mm, the size of the front and back surfaces of the battery is 600 c.
m ² (one side), very large.

In general, in a small lithium ion battery for a portable device, when a malfunction occurs due to a failure of the device or an abuse of a user causes an overcharge or an external short circuit,
When the inside of the battery is heated and the electrolytic solution is decomposed or evaporated, gas is generated inside. Therefore, in order to prevent an accident due to an increase in internal pressure, for example, Japanese Patent Application Laid-Open No. 6-36
High operating pressure range 1-2M as described in 752
A safety valve designed for Pa is provided on the lid and bottom of the container.

However, when the above-mentioned general safety mechanism is provided for a large battery having a large front and back surface of the battery and a small container thickness, the small battery may be used in an abnormal situation in which gas is generated inside the battery and the internal pressure rises. Even at low pressures that do not matter, the container, especially its front and back, easily swells,
There has been a problem in that the safety mechanism has not been fully operated, and has fallen into a dangerous state that may cause ignition or explosion.

An object of the present invention is to provide a highly safe, flat non-aqueous secondary battery capable of reliably preventing an accident such as ignition or explosion in the event of an abnormality in order to solve the above problems.

A further object of the present invention is to provide a highly safe non-aqueous secondary battery having a large capacity of 30 Wh or more and a volume energy density of 180 Wh / l or more and excellent in heat radiation characteristics.

[0012]

SUMMARY OF THE INVENTION The object of the present invention is to provide a flat battery container having a positive electrode, a negative electrode, a separator and a non-aqueous electrolyte containing a lithium salt, having an energy capacity of 30 Wh or more and a volume energy density of at least 30 Wh. Is 180
A non-aqueous secondary battery having an operating pressure of 5 kPa or more and less than 500 kPa at Wh / l or more, wherein the non-aqueous secondary battery is disposed on a wide flat portion of the flat battery container and has a distance from the outer periphery of the container to the center of gravity of the wide flat portion. A thin portion which includes at least a portion thereof in a range close to the outer periphery within 60% and which is broken by the operating pressure, and a wide plane defined by two straight lines passing through the center of gravity of the wide flat portion and both ends of the thin portion. A non-aqueous secondary battery, comprising : a deformation preventing portion formed so that at least a part thereof is included in a region including the thin portion and outside the thin portion in the inside. good Ri is achieved.

It is preferable that at least a part of the deformation preventing portion is formed in a region near an outer periphery within 30% of a distance from the outer periphery of the container to the center of gravity of the wide plane within the region.

It is preferable that the thin portion is formed by at least one linear or curved groove.

[0015] The deformation preventing portion is preferably formed by thinning a part of the battery container, and is preferably formed by at least one linear or curved groove.

The deformation preventing portion may be formed by a linear or curved rib provided on the battery container.

The battery container has a polygonal flat shape,
The groove forming the thin portion is disposed so as to intersect a virtual straight line connecting the center of gravity and the corner of the polygon, and an intersection angle between a tangent or a straight line of a curve formed by the groove and a perpendicular to the virtual straight line Is preferably set within a range of ± 60 degrees.

The tangent line or the straight groove of the curved groove constituting the deformation preventing portion is ± 20 with respect to the outer peripheral line of the flat plane.
It is preferable that they are provided so as to form an angle within degrees.

The deformation preventing portions are arranged to face each other with the virtual straight line interposed therebetween, and the deformation preventing portions arranged to face each other are spaced apart from each other, and each of the deformation preventing portions is also spaced from the thin portion. Is preferred.

Preferably, the shape of the wide plane of the battery container is rectangular.

It is preferable that the non-aqueous secondary battery has a flat shape with a thickness of less than 12 mm.

The thickness of the battery container is 0.2 mm or more and 1
mm or less.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A non-aqueous secondary battery according to one embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a flat rectangle (note type) according to an embodiment of the present invention.
FIG. 2 is a plan view and a side view of the non-aqueous secondary battery for a power storage system of FIG. 1, and FIG. 2 is a side view showing a configuration of an electrode laminate housed inside the battery shown in FIG.

As shown in FIGS. 1 and 2, the non-aqueous secondary battery according to the present embodiment has a battery case (battery container) including an upper lid 1 and a bottom container 2, and is housed in the battery case. And an electrode stack including a plurality of positive electrodes 101a, negative electrodes 101b and 101c, and a separator 104. In the case of a flat nonaqueous secondary battery as in this embodiment, the positive electrode 101a and the negative electrode 101b (or the negative electrode 101c disposed on both outer sides of the stacked body) are provided with, for example, a separator 104 as shown in FIG. However, the present invention is not particularly limited to this arrangement, and the number of layers and the like can be variously changed according to required capacity and the like.

The positive electrode current collector 105a of each positive electrode 101a is:
Each of the negative electrodes 101 is electrically connected to the positive electrode terminal 3.
The negative electrode current collectors 105b of b and 101c are electrically connected to the negative electrode terminal 4. The positive terminal 3 and the negative terminal 4 are
It is attached in a state insulated from the battery case, that is, the top cover 1. The upper lid 1 and the bottom container 2 are welded by melting the upper lid all around at a point A shown in the enlarged view in FIG. An electrolyte injection port 5 is opened in the upper lid 1.
After the injection of the electrolytic solution, the film is sealed by heat fusion using a thermoplastic film 6 having a low moisture permeability represented by an aluminum-modified polypropylene laminated film and an aluminum-modified polyethylene laminated film.

In the closing step, it is preferable that the pressure inside the battery is lower than the atmospheric pressure. Preferably 650 torr
r or less, more preferably 550 torr or less. This pressure is determined in consideration of the separator used, the type of electrolyte, the material and thickness of the battery can, and the shape of the battery. When the internal pressure is equal to or higher than the atmospheric pressure, the battery becomes larger than the designed thickness or the thickness variation becomes large, which causes the internal resistance and the capacity of the battery to vary.

The shape of the non-aqueous secondary battery shown in FIGS. 1 and 2 is, for example, 300 mm in length × 210 mm in width × 6 mm in thickness, and LiMn ₂ O ₄ , negative electrode 101 b,
In the case of a lithium secondary battery using a carbon material for 01c, for example, it can be used for a power storage system.

The positive electrode active material used for the positive electrode 101a is not particularly limited as long as it is a lithium-based positive electrode material. A lithium composite cobalt oxide, a lithium composite nickel oxide, a lithium composite manganese oxide, or a mixture thereof is used. Further, a system in which one or more different metal elements are added to these composite oxides can be used, and a battery with high voltage and high capacity can be obtained, which is preferable. When importance is placed on safety, a manganese oxide having a high thermal decomposition temperature is preferable. Examples of the manganese oxide include a lithium composite manganese oxide represented by LiMn ₂ O ₄ , a system in which one or more different metal elements are added to these composite oxides, and an excess of lithium, oxygen, etc. in excess of the stoichiometric ratio. LiMn
₂ O ₄ .

The negative electrode active material used for the negative electrodes 101b and 101c is not particularly limited as long as it is a lithium-based negative electrode material. A material capable of doping and undoping lithium can be used for safety and cycle life. This is preferable because the reliability of the device improves. As a material capable of doping and undoping lithium, a graphite-based material, a carbon-based material, a tin oxide-based material, which is used as a negative electrode material of a known lithium ion battery,
Examples thereof include metal oxides such as silicon oxides, and conductive polymers typified by polyacene-based organic semiconductors. In particular, from the viewpoint of safety, a polyacene-based substance that generates a small amount of heat at about 150 ° C. or a material containing the same is desirable.

Although the structure of the separator 104 is not particularly limited, a single-layer or multi-layer separator can be used, and at least one sheet is preferably made of a nonwoven fabric, thereby improving cycle characteristics. Separator 1
04 is not particularly limited, for example, polyethylene, polyolefin such as polypropylene,
Polyamide, kraft paper, glass and the like can be mentioned, and polyethylene and polypropylene are preferred from the viewpoint of cost, water content and the like. When polyethylene or polypropylene is used as the separator 104, the basis weight of the separator is preferably 5 g / m ² or more and 30 g / m ² or less, more preferably 5 g / m ² or more and 20 g / m ² or less. More preferably, it is 8 g / m ² or more and 20 g / m ² or less. If the basis weight of the separator exceeds 30 g / m ² , the separator becomes too thick or the porosity decreases, and the internal resistance of the battery increases.
If it is less than / m ² , it is not preferable because practical strength cannot be obtained.

As the electrolyte of the non-aqueous secondary battery of the present embodiment, a known non-aqueous electrolyte containing a lithium salt can be used, which is appropriately determined according to the conditions of use such as a positive electrode material, a negative electrode material, and a charging voltage. , More specifically LiPF ₆ ,
LiBF ₄ , LiClO _{4 and} other lithium salts are converted to organic solvents such as propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, dimethoxyethane, γ-butyl lactone, methyl acetate, methyl formate, or a mixed solvent of two or more of these. Examples thereof include those dissolved in a solvent. Further, the concentration of the electrolytic solution is not particularly limited, but is generally practically 0.5 mol / l to 2 mol / l. Naturally, the electrolytic solution has a water content of 100 ppm or less. Preferably, it is used. In addition, the non-aqueous electrolyte used in this specification means a concept including a non-aqueous electrolyte and an organic electrolyte, and also a concept including a gel or solid electrolyte.

The non-aqueous secondary battery configured as described above can be used for home power storage systems (nighttime power storage, cogeneration, solar power generation, etc.), power storage systems for electric vehicles, etc. It can have capacity and high energy density. In this case, the energy capacity is preferably 30 Wh or more, more preferably 50 Wh or more, and the energy density is preferably 180 Wh /
1 or more, more preferably 200 Wh / l. When the energy capacity is less than 30 Wh or when the volume energy density is less than 180 Wh / l, the capacity is small for use in a power storage system, and it is necessary to increase the number of series-parallel batteries in order to obtain a sufficient system capacity. In addition, it is not preferable for a power storage system because a compact design is difficult.

By the way, in general, a large lithium secondary battery (energy capacity of 30 Wh or more) for a power storage system can obtain a high energy density, but its battery design is an extension of a small battery for a portable device. Alternatively, the battery has a cylindrical shape, a square shape, or the like having a thickness three times or more that of a small battery for a portable device. In this case, heat easily accumulates inside the battery due to Joule heat generated by the internal resistance of the battery during charge / discharge or internal heat generated by the battery due to a change in entropy of the active material due to the entrance and exit of lithium ions. For this reason, the difference between the temperature inside the battery and the temperature near the battery surface is large, and the internal resistance differs accordingly. As a result, the charge amount and the voltage are likely to vary. Also, since a plurality of batteries of this type are used as assembled batteries, the heat storage easiness varies depending on the installation position of the batteries in the system, causing variations among the batteries, and accurate control of the entire assembled battery. It becomes difficult. Furthermore, the battery temperature rises due to insufficient heat radiation during high-rate charging and discharging, etc., and the battery is put in an unfavorable state. Problems such as induction of reliability and, in particular, safety remain.

The flat non-aqueous secondary battery of the present embodiment has a large heat radiation area and is advantageous for heat radiation, so that the above-mentioned problems can be solved. That is, the non-aqueous secondary battery of the present embodiment has a flat shape,
Its thickness is preferably less than 12 mm, more preferably less than 10 mm, even more preferably less than 8 mm. The lower limit of the thickness is practically 2 mm or more in consideration of the filling rate of the electrode and the battery size (the smaller the thickness, the larger the area for obtaining the same capacity). Battery thickness is 12
mm or more, it becomes difficult to sufficiently radiate the heat generated inside the battery to the outside, or the temperature difference between the inside of the battery and the vicinity of the battery surface increases, resulting in a difference in internal resistance.
Variations in the amount of charge and voltage in the battery increase. Although the specific thickness is appropriately determined according to the battery capacity and the energy density, it is preferable to design the thickness so as to obtain the expected heat radiation characteristics.

The shape of the non-aqueous secondary battery of the present embodiment is, for example, that the flat front and back surfaces are square, circular,
Various shapes such as an oval shape can be used. In the case of a square shape, the shape is generally a rectangle, but it can also be a polygon such as a triangle or a hexagon. Further, it may be a cylindrical shape such as a thin-walled cylinder. In the case of a cylindrical shape, the thickness of the cylinder is the thickness referred to here. Further, from the viewpoint of ease of production, the flat front and back surfaces of the battery are preferably rectangular, and a notebook-type shape as shown in FIG. 1 is preferable.

The material used for the top lid 1 and the bottom container 2 serving as the battery case is appropriately selected depending on the use and shape of the battery, and is not particularly limited.
Aluminum and the like are common and practical. Also,
The thickness of the battery case is also appropriately determined depending on the use and shape of the battery or the material of the battery case, and is not particularly limited. Preferably, the thickness of the portion of 80% or more of the battery surface area (the thickness of the portion having the largest area constituting the battery case) is 0.2 mm or more. When the thickness is less than 0.2 mm, the strength required for battery production cannot be obtained, which is not desirable.
m or more. Further, it is desirable that the thickness of the portion is 1 mm or less. When the thickness exceeds 1 mm, the force for pressing down the electrode surface increases, but it is not desirable because the internal volume of the battery is reduced and a sufficient capacity cannot be obtained, or the weight increases, which is not desirable. Preferably it is 0.7 mm or less.

As described above, the thickness of the non-aqueous secondary battery is set to 1
By designing it to be less than 2 mm, for example,
When the battery has a large capacity of 0 Wh or more and a high energy density of 180 Wh / l, the battery temperature rise is small even during high-rate charging and discharging, and excellent heat radiation characteristics can be obtained. Therefore, heat storage of the battery due to internal heat generation is reduced, and as a result, thermal runaway of the battery can be suppressed, and a non-aqueous secondary battery excellent in reliability and safety can be provided.

Next, a safety mechanism provided in the non-aqueous secondary battery of the present invention configured as described above will be described in detail. The safety mechanism has a thin portion formed in the battery container, and the thin portion acts as a safety valve that is broken when an internal pressure exceeding a certain level is generated in the battery container. The lower limit of the operating pressure of this safety valve (the difference between the increased pressure inside the battery and the atmospheric pressure) is preferably 5 kPa or more, more preferably 20 kPa or more.
kPa or more, the upper limit is preferably less than 500 kPa, more preferably less than 120 kPa, particularly preferably 80 kPa.
It is less than Pa. The operating pressure is appropriately designed depending on the shape and thickness of the battery, the material of the battery container, the capacity of the battery, the type of separator used, the type of electrolyte, and the like. It is not preferable because it may be done. If the operating pressure is equal to or higher than the above upper limit, there is a danger that even in an abnormal situation where gas is generated inside the battery, the safety valve does not operate and easily expands and deforms, causing ignition or explosion. In the present invention, the number of safety valves may be at least one or more, and in particular, two or more safety valves may be provided.

The place where the safety valve is arranged is shown in FIG.
It is preferable that the battery case is disposed in a wide flat portion of the battery container having a flat shape as shown by a hatched region 51 in (a), and is provided so as to include at least a part thereof within a predetermined distance from the outer periphery of the wide flat surface. The range near the outer periphery is preferably within 60% of the distance from the outer periphery of the container to the center of gravity of the wide plane portion, more preferably within 40%. When the battery has a large flat surface and a small container thickness, the container swells and is inexpensive as described above. Although the degree depends on the shape and thickness of the battery used and the material of the battery container, distortion accompanying the bulging of the container occurs particularly in a range close to the outer periphery within 60% of the distance from the outer periphery to the center of gravity of the wide flat portion. easy.
This distortion tends to be greater in a range closer to the outer periphery within 40% of the distance from the outer periphery to the center of gravity. This means that the force for deforming the container wall is largely acting in the above range. In addition, it can be said that the stress acting on the entire container wall as the internal pressure rises propagates in this range and acts intensively. Therefore, if a safety valve is provided in these ranges, even if the internal pressure of the container is low, a concentrated large stress acts on the portion where the safety valve is provided, and the device can be reliably operated. Conversely, if a safety valve is provided only in the range from the center of gravity to the above range, the range will tend to be lifted as it is without much deformation when the container is inflated, and the deformation curvature will be small and almost flat. , The force to operate the safety valve is hard to act.

In the case where the shape of the wide plane portion of the battery container is a polygon such as a rectangle or the like, if it is provided near the corner, the distortion will concentrate there, so that the distortion can be used effectively and reliable operation can be achieved. It is preferable for obtaining. In addition, since the safety valve is operated by utilizing the distortion due to the concentration of the internal pressure of the battery container, in a normal state where the container is not swelled by the internal gas and there is no abnormal situation, carelessness may be caused by some external pressure. No opening occurs.

Further, as shown in FIG. 4, the thin portion is defined by two straight lines m and n passing through the center of gravity of the wide flat portion and both ends of the thin portion (64). And a deformation preventing portion (6) formed so as to include at least a part thereof in a region outside the thin portion in a region including
5), and the deformation preventing portion is arranged on a wide flat portion of the flat battery container as shown by a hatched region 52 in FIG. 3B, and extends from the outer periphery of the container to the center of gravity of the wide flat surface. When a deformation preventing portion formed by at least one thin wall different from the thin wall portion including at least a part thereof is formed in a range close to the outer periphery within 30% of the distance, the internal pressure increases, and the battery container becomes When the central portion expands so as to be lifted, there is an effect of suppressing deformation on the outer peripheral side. The larger the difference between the degree of deformation distortion on the expanding part and the outer peripheral side,
This is more preferable because the opening area of the safety valve can be widened and the internal heat storage can be quickly released to the outside in the event of an abnormality. This suppression effect is even greater in a range closer to the outer periphery within 20% of the distance from the outer periphery to the center of gravity. The deformation preventing portion can be formed by the same thin portion as the thin portion, or can be formed by providing a rib.

As a safety valve having a thin portion, a method of mounting a rupture disk component formed by cold-pressing a thin metal foil, a method of thinning a part of a container to make it weaker, and the like can be adopted. Preferably, the thin portion is
At least one straight or curved groove formed on the container wide flat surface side. This groove can be formed, for example, by kerf processing.

The arrangement of the linear grooves will be described with reference to FIG.
The battery container shown in FIG. 4 has a rectangular wide surface, and the tangent line 64a of the linear groove 64 or the curved groove 64 is arranged so as to cross the virtual straight line 61 connecting the center of gravity (center) G and the corner of the rectangle. It is preferable that a tangent to a straight line or a curve formed by the groove is provided at an angle within ± 60 degrees with respect to a perpendicular to the virtual straight line. This is because the distortion in the wide flat area that occurs when the container expands is caused by the virtual straight line 6.
This is because it is large in the direction crossing 1. Therefore, by setting the corner 62 in the above range, the groove can be formed along the direction in which large distortion occurs, and as a result, a safety valve that can be easily broken and opened with a low internal pressure of the container can be obtained. If the angle 62 formed by the groove is less than 30 degrees, the container will be lifted up without causing large distortion when it expands, and it will be difficult to operate reliably at low pressure. When the wide plane of the container is rectangular as in this example, the virtual straight line connecting the center of gravity and the corner is, of course, a diagonal. In addition, even if the container wide plane portion is a polygon other than a rectangle, the tangent of the linear groove or the curved groove is disposed so as to cross a virtual straight line connecting the center of gravity (center) and the corner of the polygon. tangential eggplant straight or curved in serial grooves, by being provided at an angle of within ± 60 degrees with respect to normal of the virtual straight line, the same effect as the above can be obtained.

As described above, by forming the groove of the safety valve within the above-mentioned angle range on the wide plane portion side, it is possible to prevent the battery contents from scattering around when the valve is opened. The groove of the safety valve can be opened in the range of the predetermined pressure which is predetermined by the design of the shape and the thickness of the thin portion. Also,
By providing the safety valve on the side of the container wide flat surface side, it is possible to have a large opening area and quickly extract internal gas. Further, it is more preferable in that the cost can be reduced as compared with a rupture disk which requires a protective cover and requires a large capital investment.

Preferably, the deformation preventing portion for suppressing at least one distortion different from the thin portion is at least one linear or curved groove on the flat side of the container. Furthermore, it is more preferable that the tangent of the one linear groove or the curved groove having the effect of suppressing distortion is provided so as to form an angle within ± 20 degrees with respect to the outer peripheral line of the flat plane. . This is because if the angle of the container is more than 20 degrees with respect to the outer peripheral line, when the container is swollen, there is no effect of suppressing the swollenness, the container is lifted as it is, and the opening area cannot be increased. The arrangement of the linear grooves for suppressing the distortion will be described with reference to FIG. The battery container shown in FIG. 4 has a rectangular wide surface, and a tangent 65 of the linear groove 65 or the curved groove 65.
a is at a position along the outer periphery on the corner side of the safety valve,
A tangent to a straight line or a curve formed by the groove is provided so as to form an angle within ± 20 degrees with respect to a parallel line with the outer peripheral line.

The method of manufacturing the safety valve is not particularly limited.
In the case of the above-described kerf processing method, kerf processing of a thin portion can be performed by a method such as etching or pressing while leaving a predetermined thickness in an arbitrary shape. FIG. 5 shows various examples in which a grooved safety valve and a groove for suppressing distortion are combined. By providing a large thin-walled grooving portion 72 near the periphery of the surface of the upper lid 1 and near the corner 71 and providing a grooving portion 82 along the outer peripheral line on the outer peripheral side, a safety valve having low pressure and a large opening area Become. 72a in the figure is linear,
72b is an arc shape, 72c is a shape leaving only a part of a circle, 7
2d is an X-marked groove type safety valve.

[0047]

The present invention will be described more specifically below with reference to examples of the present invention. (Example 1) (1) As shown in FIG.
A thin plate made of US304 was drawn down to a depth of 5 mm, and the top cover 1 of the battery was also made of a thin plate made of SUS304 having a thickness of 0.5 mm. Battery external dimensions are 210 mm on the short side and 30 mm on the long side.
0 mm, which is approximately equivalent to JIS A4 size. The upper lid has a positive electrode terminal made of aluminum and a negative electrode terminal 3 made of copper,
4 (6 mmφ, M3 thread cutting) was attached. The positive and negative terminals 3 and 4 were insulated from the upper lid 1 by a polypropylene gasket. The upper lid 1 was arranged without inserting the electrode laminate into the bottom container 2, and the corner A of FIG. 1 was laser-welded over the entire circumference to produce an assembly having only the battery outer package.

(2) Etching a straight groove having a shape of the groove 72a in FIG. 5, a width of 0.5 mm, a depth of 0.04 mm, and a length of 60 mm in the corner portion (corner portion 71 in FIG. 5) of the upper lid 1 A safety valve formed by processing. This groove connects the inside by 10 mm from both sides of the corner,
The straight groove is formed so as to cross a straight line connecting the center of gravity and the corner of the rectangular upper lid, and the straight groove forms an angle of 10 degrees toward the corner on the short side with respect to the perpendicular of the straight line (diagonal). It is provided so as to make it easier. In addition, a corner portion of the upper cover 1 (FIG. 5)
5 is formed as a groove 82 in FIG. 5 on the outer peripheral side of the corner portion 71), the width is 0.5 mm, the depth is 0.03 mm, and the length is 20 mm
Two linear grooves having the following dimensions were formed by etching to form grooves for suppressing distortion. This groove is 8mm from the corner
It is a linear groove formed in parallel on both sides from the inside into which each is inserted.

(3) When the internal pressure of the battery was increased using the injection port 5 and the opening test of the safety valve was performed on the assembly having only the battery outer body obtained as described above, the pressure was 40 kPa.
It operates quickly at low pressure and the battery thickness after expansion is 18mm
Stayed at. The width of the opening was as large as 2 mm.
In addition, a similar assembly having only the battery exterior body was produced without forming the groove for suppressing the distortion, and the internal pressure of the battery was increased using the liquid inlet 5, and the opening test of the safety valve was performed. The battery was quickly operated at a low pressure of 40 kPa, and the thickness of the battery after expansion was 18 mm. However, the width of the opening is 0.
5 mm.

(Example 2) An assembly having only a battery exterior body was manufactured in the same manner as in Example 1 except for the safety valve structure of (2) of Example 1. At the corner of the battery cover 1, the position and shape of the groove 72b at the corner 71 of FIG.
5mm, depth 0.04mm, 50mm from both sides
An arcuate kerf having a radius of 40 mm and an inner angle of 90 degrees and protruding toward the corner with an inner point at the center was etched to produce a safety valve. When the internal pressure of the battery was increased using the injection port 5 and an opening test of the safety valve was performed on the assembly having only the battery outer body obtained as described above, the battery was quickly operated at a low pressure of 50 kPa, and the battery was expanded. The thickness also stayed at 22 mm. The width of the opening was 1.5 mm.

(Example 3) The safety valve structure of Example 1 (2) and a groove for suppressing distortion were formed in the corner portion of the battery upper lid 1, and an actual battery was assembled as follows.

(1) 100 parts by weight of LiCo 2 O 4, 8 parts by weight of acetylene black, and 3 parts by weight of polyvinylidene fluoride (PVDF) were mixed with N-methylpyrrolidone (NM)
P) to obtain a positive electrode mixture slurry. The slurry was applied to both sides of a 20 μm-thick aluminum foil serving as a current collector, dried, and then pressed to obtain a positive electrode. FIG.
Is an explanatory diagram of an electrode. In this embodiment, the positive electrode 101a
Has an application area (W1 × W2) of 262.5 × 192 mm 2, and is applied to both surfaces of a 20 μm current collector 105 a with a thickness of 103 μm. As a result, the electrode thickness t is 226 μm. Further, on the short side of the electrode, there is an ear portion where the electrode is not applied, and a hole of φ3 is formed.

(2) Graphitized mesocarbon microbeads (MCMB, manufactured by Osaka Gas Chemicals, product number 6-28) 10
0 parts by weight and 10 parts by weight of PVDF were mixed with 90 parts by weight of NMP to obtain a negative electrode mixture slurry. The slurry was applied on both sides of a 14 μm-thick copper foil serving as a current collector, dried, and then pressed to obtain a negative electrode. This will be described with reference to FIG. The application area (W1 × W2) of the negative electrode 101b or 101c is 267 ×
195 mm2, 108 μm on both sides of 18 μm current collector 105 b
It is applied with a thickness of μm. As a result, the electrode thickness t is 234 μm. Further, on the short side of the electrode, there is an ear portion where the electrode is not applied, and a hole of φ3 is formed. Further, a single-sided electrode having a thickness of 126 μm was formed in the same manner except that the coating was performed on only one side.
The single-sided electrode is disposed outside in the electrode laminate of item (3) (101c in FIG. 2).

(3) Eight positive electrodes obtained in the above (1),
As shown in FIG. 2, a separator 104a (polypropylene non-woven fabric: Nippon Kogyo Paper Industries,
MP1050, basis weight 10g / m2) and separator 104b (polyethylene microporous membrane; Asahi Kasei Corporation HIPORE6022, basis weight 13.3g / m2)
2) (indicated as 104 in FIG. 2), and alternately laminated to form an electrode laminate. The separator 104b was arranged on the positive electrode side. Further, for insulation from the container, a separator 104b was arranged further outside the negative electrode plate 101c outside the laminate.

(4) The battery bottom container 2 (see FIG. 1)
A SUS304 thin plate of 0.5 mm was drawn to a depth of 5 mm. Also, the top cover 1 of the battery is made of SUS of 0.5 mm thickness.
It was made of 304 thin plate. An aluminum positive electrode terminal and a copper negative electrode terminal 3 and 4 (6 mmφ, M3 threaded) were attached to the upper lid. The positive and negative terminals 3, 4
It is insulated from the upper lid 1 by a polypropylene gasket.

(5) The holes of the respective positive electrode lugs of the electrode laminate prepared in the above item (3) are inserted into the positive electrode terminal 3 and the holes of the respective negative electrode ears 1 are inserted into the negative electrode terminal 4, and are respectively bolted with aluminum and copper. Connected. The electrode laminate was fixed with an insulating tape, and the corner A of FIG. 1 was laser-welded over the entire circumference. Then, fill the electrolyte injection hole 5
(6 mmφ), a solution in which LiPF6 was dissolved at a concentration of 1 mol / l into a solvent in which ethylene carbonate and diethyl carbonate were mixed at a weight ratio of 1: 1 was injected as an electrolytic solution. This battery was punched out to 12mmφ and had a thickness of 0.08m
The electrolyte injection hole 5 was sealed by heat-sealing an aluminum foil-modified polypropylene laminated film having a thickness of 300 m under a reduced pressure of 300 torr. (6) The battery obtained as described above is charged up to 4.1 V with a current of 5 A, and thereafter, a constant current constant voltage charge of applying a constant voltage of 4.1 V is performed for 12 hours, followed by a low current of 5 A Discharge to 2.5 V at a discharge capacity of 23.5
Ah, and the energy capacity was 85 Wh. After confirming the capacity, the battery was charged again in the same manner as described above, and the battery was brought to a charged state.
Next, in order to confirm safety, an overcharge test at a constant current charge of 10 A was conducted by the Battery Association of Japan Guideline SBA G1101.
It went according to. When the battery was overcharged for about 70%, the battery container started to expand due to gas generation inside the battery,
It was found that the safety valve 72a at 71 in FIG. 5 was opened widely, steam was quickly released, and even though the battery was a large-capacity type battery, it did not generate heat or ignite or the like, and was highly safe. The thickness of the battery after expansion was 18 mm.

Comparative Example 1 A battery was manufactured in the same manner as in Example 3 except for the safety valve structure used in Example 3. A groove 72a in a corner 71 of FIG.
A linear groove having a position and shape as described above, a width of 1 mm, a depth of 0.048 mm, and a length of 60 mm was formed by etching. This groove is formed so as to connect 10 mm inside from both sides of the corner portion and to cross a virtual straight line (diagonal line) connecting the center of gravity and the corner portion of the rectangular upper lid, and the straight groove is perpendicular to the straight line. On the other hand, a safety valve having an operating pressure of 1 kPa was provided so as to form an angle of 10 degrees toward the corner on the short side. However, in the laser welding process, a part of the safety valve had already been damaged and opened when the attached jig such as a heat sink was detached. It was expected that if the operating pressure was too low, it would open easily during normal use.

Comparative Example 2 A battery was manufactured in the same manner as in Example 3 except for the safety valve structure used in Example 3. A groove 72a in a corner 71 of FIG.
Like position and shape, width 0.8mm depth 0.046m
A linear groove having an m length of 60 mm was formed by etching. This groove is formed so as to connect 10 mm inside from both sides of the corner portion and to cross a virtual straight line (diagonal line) connecting the center of gravity and the corner portion of the rectangular upper lid, and the straight groove is perpendicular to the straight line. 10 on the short side toward the corner
A safety valve provided at an angle of degree and having an operating pressure of 2 kPa was formed. However, in the injection step, it was found that when the electrolytic solution was injected by returning the pressure from the reduced pressure to the normal pressure, the liquid leaked from a part of the safety valve and opened. If the operating pressure is too low, it is expected that the opening will easily occur even in a general manufacturing process.

(Comparative Example 3) An assembly having only the battery exterior body was manufactured in the same manner as in Example 1 except for the safety valve structure of (2) of Example 1. As shown in FIG. 6 , the width is 0.5 mm, the depth is 0.4 mm, and the short side is 5 mm as shown on the upper side surface 81 of the bottom container 2.
A cross-sealed safety valve 82 having a long side of 40 mm was produced. When the internal pressure of the battery was increased using the liquid inlet 5 and an opening test of the safety valve was performed on the assembly having only the battery outer body obtained as described above, the safety valve did not operate at a low pressure and the pressure was 500 kPa.
At the time of reaching, a large portion was expanded to a thickness of 120 mm, and a part of the weld was suddenly opened due to deformation distortion. A very dangerous situation was expected if the battery contents were included.

[0060]

As is apparent from the above, according to the present invention, a flat battery, particularly a flat battery having a large capacity and a high volume energy density, has a safety mechanism which is opened by a low internal pressure rise, A highly safe non-aqueous secondary battery can be provided.

[Brief description of the drawings]

FIG. 1 is a plan view (top) and a side view (bottom) of a non-aqueous secondary battery for a power storage system according to an embodiment of the present invention.

FIG. 2 is a side view showing a configuration of an electrode laminate housed inside the battery shown in FIG.

FIGS. 3A and 3B are explanatory views showing the arrangement areas of (a) a thin portion and (b) a deformation preventing portion which are components of the present invention.

FIG. 4 is an explanatory view showing an arrangement angle of a kerf processing type safety valve of the present invention and grooves for suppressing distortion.

FIG. 5 is an explanatory view of a safety valve and a groove for suppressing distortion used in the embodiment of the non-aqueous secondary battery of the present invention.

6A and 6B are explanatory views of a safety valve used for a non-aqueous secondary battery as a comparative example, where FIG. 6A is a plan view, FIG.
(C) is an enlarged view of a side surface, and (d) is a sectional view taken along line EE of (c).

[Description of Signs] 1 Top lid 2 Bottom container 3 Positive electrode terminal 4 Negative terminal 5 Injection port 6 Sealing film 51 Safety valve arrangement range 61 Virtual straight line (diagonal line) 62 Example of linear grooved safety valve 63 Diagonal and linear grooved safety valve Narrow 71 sandwiched by the above 71 Upper lid corner 72a, 72b, 72c, 72d Safety valve 81 Bottom container upper side surface 82 Safety valve 101a Positive electrode (both sides) 101b Negative electrode (both sides) 101c Negative electrode (one side) 104, 104a, 104b Separator 105a Positive electrode collection Electric body 105b Negative electrode current collector

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Shizukuni Yada 4-1-2 Hirano-cho, Chuo-ku, Osaka-shi, Osaka Prefecture Inside Kansai New Technology Research Institute Co., Ltd. (72) Haruo Kikuta, Hirano-cho, Chuo-ku, Osaka-shi, Osaka 4-chome 1-2-2 Osaka Gas Co., Ltd. F-term (reference) 5H011 AA10 AA13 CC06 DD13 FF02 JJ04 KK01 KK02 5H012 AA03 BB01 DD05 EE04 FF01 5H029 AJ01 AJ12 AK03 AL06 AM03 AM04 AM05 AM07 BJ04 HJ14 DJ01

Claims (13)

[Claims] 1. A sealed, flat battery container comprising a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte containing a lithium salt, having an energy capacity of 30 Wh or more, a volume energy density of 180 Wh / l or more, and an operating pressure of 5 kPa or more. A non-aqueous secondary battery having a pressure of less than 500 kPa, wherein the non-aqueous secondary battery is disposed on a wide flat portion of the flat battery container, and is at least in a range close to the outer periphery within 60% of a distance from the outer periphery of the container to the center of gravity of the wide flat portion. A region including the thin portion, the thin portion including a part thereof and breaking by the operating pressure, and the inside of the wide plane divided by two straight lines passing through the center of gravity of the wide flat portion and both ends of the thin portion. A non-aqueous secondary battery comprising: a deformation preventing portion formed so as to include at least a part thereof in a range outside the thin portion. 2. The deformation preventing portion is formed so as to be at least partially included in a region near the outer periphery within 30% of a distance from the outer periphery of the container to the center of gravity of the wide plane within the region. The non-aqueous secondary battery according to claim 1, wherein 3. The non-aqueous secondary battery according to claim 1, wherein the thin portion is formed by at least one linear or curved groove. 4. The non-aqueous secondary battery according to claim 1, wherein the deformation preventing portion is formed by thinning a part of a battery container. 5. The non-aqueous secondary battery according to claim 4, wherein the deformation preventing portion is formed by at least one linear or curved groove. 6. The non-aqueous secondary battery according to claim 1, wherein the deformation preventing portion is formed by a linear or curved rib provided on the battery container. . 7. The battery container has a polygonal flat shape, and a groove constituting the thin portion is disposed so as to cross an imaginary straight line connecting a center of gravity and a corner of the polygon. The non-aqueous secondary battery according to any one of claims 1 to 6, wherein an intersection angle between a tangent or a straight line of the curved line and a perpendicular of the virtual straight line is set within a range of ± 60 degrees. . 8. A tangent line or a straight groove of the curved groove constituting the deformation preventing portion is provided so as to form an angle within ± 20 degrees with respect to an outer peripheral line in the area in the wide plane portion. The non-aqueous secondary battery according to claim 5, wherein: 9. A tangent or a straight rib of the curved rib constituting the deformation preventing portion is provided so as to form an angle within ± 20 degrees with an outer peripheral line in the area in the wide plane portion. The non-aqueous secondary battery according to claim 6 , wherein: 10. The deformation preventing portions are arranged opposite to each other with the virtual straight line interposed therebetween, and the opposed deformation preventing portions are spaced apart from each other, and each of the deformation preventing portions is also spaced from the thin portion. The non-aqueous secondary battery according to claim 7, which is arranged. 11. The non-aqueous secondary battery according to claim 1, wherein the shape of the wide plane of the battery container is rectangular. 12. The non-aqueous secondary battery has a thickness of 12 m.
m is a flat shape less than m.
2. The non-aqueous secondary battery according to any one of 1. 13. The non-aqueous secondary battery according to claim 1, wherein the thickness of the battery container is 0.2 mm or more and 1 mm or less.