WO2014119095A1

WO2014119095A1 - Secondary battery

Info

Publication number: WO2014119095A1
Application number: PCT/JP2013/081315
Authority: WO
Inventors: 将史村岡; 宏志岡本; 西村　直人; 功浅子; 大谷　拓也
Original assignee: シャープ株式会社
Priority date: 2013-02-04
Filing date: 2013-11-20
Publication date: 2014-08-07

Abstract

Provided is a secondary battery equipped with a current interrupting mechanism, the size of which can be made to be small without being affected by the characteristics of an electrolyte. In the battery (100), a positive electrode collector plate (41) for electrically connecting an electrode and a battery cell (6) is provided along a thermal expansion agent housing chamber (51) for housing a thermal expansion agent (7) that expands at a temperature lower than the boiling point of an electrolyte (L). The deformation of the thermal expansion agent housing chamber (51) brings the positive electrode collector plate (41) into an electrical disconnection state.

Description

Secondary battery

The present invention relates to a secondary battery such as a non-aqueous electrolyte secondary battery.

In recent years, nonaqueous electrolyte secondary batteries such as lithium ion secondary batteries are frequently used as secondary batteries. In this type of secondary battery, charge energy is applied beyond the battery capacity of the battery (overcharge), or a current larger than a predetermined value flows due to misuse or the like, whereby the temperature in the battery rises. In general, a battery using an organic electrolyte causes thermal runaway as the temperature in the battery rises, and gas is generated due to decomposition of the electrolyte and active material, resulting in an increase in battery internal pressure.

When the internal pressure of the battery becomes excessive, the battery may swell or rupture. Therefore, it is common to provide a mechanism for releasing the pressure when a predetermined pressure is exceeded (hereinafter, such a mechanism will be called a safety valve).

Here, the gas generated by the decomposition of the electrolytic solution and the active material is generally a combustible gas because the electrolytic solution vapor is also mixed. Therefore, it is preferable to provide a current interrupt mechanism that physically cuts the electrical path before the safety valve is cleaved and the gas is discharged outside the battery.

Examples of batteries provided with a current interruption mechanism include the batteries disclosed in Patent Document 1 and Patent Document 2 listed below.

The configuration described in Patent Document 1 discloses a current interrupting mechanism that includes a deformed metal plate that is processed to be curved in an arch shape, and a connecting metal that is formed by welding the local portions of the deformed metal plate and electrically connecting them. is doing. When the internal pressure of the battery cell becomes higher than the set pressure, the current interrupting mechanism is deformed so as to separate the welding point and interrupts the current.

Patent Document 2 discloses an explosion-proof sealed battery. Specifically, a lead-blocking stripper is attached to an explosion-proof valve that deforms in the internal pressure direction as the internal pressure increases, and when the specified internal pressure is reached, the lead plate peels off from the explosion-proof valve or / and leads The plate breaks to interrupt the current.

Japanese Patent Publication “Japanese Patent Laid-Open No. 2000-000000 (Released on 00:00:00)” Japanese Patent Publication “Japanese Patent Laid-Open No. 2-112151 (published on April 24, 1990)”

However, the above-described conventional technology is configured to operate the current interrupting mechanism by interrupting the current by the decomposition / evaporation of the electrolyte, that is, the increase in the internal pressure of the battery caused by the thermal expansion of the electrolyte. For this reason, a large-sized battery requires a large-sized current interrupting mechanism, and the configuration becomes large. In addition, the current interruption mechanism needs to be designed according to the characteristics of thermal expansion of the electrolytic solution, and the degree of design freedom is small.

The present invention has been made in view of the above-described problems, and the object thereof is a secondary equipped with a current interrupting mechanism that can be reduced in size without being affected by the characteristics of the electrolytic solution. To provide a battery.

In order to solve the above-described problems, a secondary battery according to one embodiment of the present invention is independent of a battery case that houses an electrolytic solution and a battery cell, and a region where the electrolytic solution is present inside the battery case. A thermal expansion agent that is formed at a temperature lower than the boiling point of the electrolyte solution and is accommodated therein, and is provided in the battery case and a thermal expansion agent storage chamber that is deformed by thermal expansion of the thermal expansion agent. The first electrode, which is a positive electrode or a negative electrode, is electrically connected to the battery cell, provided along the thermal expansion agent storage chamber, and the thermal expansion agent storage chamber is deformed, thereby causing an electrical disconnection. And a conductive member that is in a state.

According to one aspect of the present invention, the current interruption mechanism is operated by a thermal expansion agent that expands the volume at a temperature lower than the boiling point of the electrolytic solution, which is different from the electrolytic solution. Therefore, there is an effect that the current interrupting mechanism can be reduced in size without being affected by the characteristics of the electrolytic solution.

It is a figure which shows the structure of the secondary battery which concerns on one Embodiment of this invention. 1A is a plan view showing a secondary battery according to an embodiment of the present invention, and FIG. 1B is a longitudinal sectional view of the secondary battery shown in FIG. It is a longitudinal cross-sectional view which expands and shows the structure between the 2nd positive electrode terminal shown in (b) of FIG. 1, and a negative electrode terminal. It is a figure explaining what kind of case each is used about the 1st electrode terminal and 2nd electrode terminal of the battery of FIG. FIG. 3A is an explanatory diagram showing a normal charging / discharging state of the secondary battery shown in FIG. 1A, and FIG. 3B is a diagram illustrating the state shown in FIG. It is explanatory drawing which shows the discharge state at the time of the emergency in a secondary battery. It is a figure which shows the structure of the secondary battery which concerns on other embodiment of this invention. 4A is a plan view showing a secondary battery according to another embodiment of the present invention, and FIG. 4B is a longitudinal sectional view of the secondary battery shown in FIG. FIG. 5 is a detailed view of the battery shown in FIG. 4, in which the electrode current collector plate includes a first electrode current collector plate electrically connected to the first electrode terminal and a second electrode electrically connected to the second electrode terminal. It is a figure which shows that a current collector plate is connected by the welding part, and the 1st electrode current collector plate is provided with the notch part. It is a figure which shows the structure of the secondary battery which concerns on other embodiment of this invention. 6A is a plan view showing a secondary battery according to still another embodiment of the present invention, and FIG. 6B is a longitudinal sectional view of the secondary battery shown in FIG. 6A. . FIG. 7 is a detailed view of the battery shown in FIG. 6, wherein the positive electrode current collector plate includes a first positive electrode current collector plate and a second positive electrode current collector plate, a fitting concave portion of the first positive electrode current collector plate, and a second positive electrode current collector. It shows that it is connected by fitting the fitting convex part of the electric plate. It is a figure which shows the structure of the secondary battery which concerns on other embodiment of this invention. 8A is a plan view showing a secondary battery according to still another embodiment of the present invention, and FIG. 8B is a longitudinal sectional view of the secondary battery shown in FIG. 8A. . It is a figure which shows the structure of the secondary battery which concerns on other embodiment of this invention. 9A is a plan view showing a secondary battery according to still another embodiment of the present invention, and FIG. 9B is a longitudinal sectional view of the secondary battery shown in FIG. 9A. . It is a figure which shows the structure of the secondary battery which concerns on other embodiment of this invention. 10A is a plan view showing a secondary battery according to another embodiment of the present invention, and FIG. 10B is a longitudinal sectional view of the secondary battery shown in FIG. Examples 1 to 5 which are secondary batteries having the same structure as the battery shown in FIG. 1 and different from the battery shown in FIG. 1 only in the materials used for the electrolyte and / or the thermal expansion agent, and comparative examples thereof It is a figure which shows the installation position of the thermocouple used when performing the overcharge test about. It is a graph which shows the relationship between overcharge time, battery temperature, and battery voltage at the time of performing overcharge at 1 C about the battery which does not have an electric current interruption mechanism. It is a graph which shows the relationship between the overcharge time and battery temperature at the time of performing overcharge at 2C about the battery which does not have an electric current interruption mechanism as compared with the case where overcharge is performed at 1C. FIG. 14 is a table format showing the relationship between the overcharge time and the battery temperature shown in FIGS. 12 and 13 in an organized manner. The battery shown in FIG. 1 and the embodiment having the same structure as the battery shown in FIG. 1 and different from the battery shown in FIG. 1 only in the material used for the electrolyte and / or the thermal expansion agent. FIG. 5 is a table format showing the results of overcharge tests for 1 to 5 and comparative examples. As an example of a solvent that can be used as a thermal expansion agent for a secondary battery according to an embodiment of the present invention and expands at a temperature lower than the boiling point of an electrolyte, a fluorine-based flame-retardant low-boiling solvent manufactured by 3M, It is a figure of the tabular form which arranges and shows a boiling point. It is a figure of the tabular form which arranges and shows an example of a chemical foaming material which can be used as a thermal expansion agent of a rechargeable battery concerning one embodiment of the present invention, and its gas generation temperature. It is sectional drawing at the time of cut | disconnecting about the battery of FIG. 1 in a surface parallel to a battery cover.

The embodiment of the present invention will be described in detail with reference to FIGS. The size of each battery will be described later in detail, but the unit is “millimeter (mm)”.

It should be noted that the structure common to each embodiment will be described before the description of each embodiment.

A secondary battery according to an embodiment of the present invention includes a battery case 1, a battery lid 2, a safety valve 21, a packing 5, a positive current collector 41, a first positive terminal 31, a negative current collector 43, a negative terminal 33, The battery cell 6 and the electrolyte L are provided.

The battery lid 2 is provided so as to close the mouth of the battery case 1. The safety valve 21 is designed to be cleaved at a predetermined pressure or higher.

The positive electrode current collector 41 is disposed on the battery lid 2 via the insulating packing 5, and the first positive electrode terminal 31 is electrically connected to the positive electrode current collector 41.

Similarly to the positive electrode current collector plate 41, the negative electrode current collector plate 43 is also arranged on the battery lid 2 via the insulating packing 5, and the negative electrode terminal 33 is electrically connected to the negative electrode current collector plate 43. .

The plurality of battery cells 6 are electrically connected to the positive electrode current collector plate 41 and the negative electrode current collector plate 43.

In a space 51 surrounded by the packing 5, the battery lid 2, and the positive electrode current collector 41, a thermal expansion agent 7 that expands at a temperature lower than the boiling point of the electrolytic solution L is accommodated.

The emergency current cutting mechanism electrically connects the space 51 containing the thermal expansion agent 7, the first positive electrode terminal 31 and the battery cell 6, and the positive electrode collector provided along the space 51. The battery case 1 is built into the battery case 1.

More specifically, the secondary battery according to the embodiment of the present invention includes a space 51 sandwiched between at least one of the positive electrode current collector plate 41 and the negative electrode current collector plate 43 and the battery lid 2. A thermal expansion agent 7 that expands at a temperature lower than the boiling point of the electrolytic solution L is provided. As the thermal expansion agent 7, an organic solvent having a lower boiling point than the electrolytic solution L or an organic chemical foaming material that thermally decomposes at a temperature lower than the boiling point of the electrolytic solution L can be used. Therefore, the secondary battery according to one embodiment of the present invention uses the pressure at which the thermal expansion agent 7 expands during overcharging to make use of the positive electrode current collector 41, the first positive electrode terminal 31, and / or the negative electrode collector. The electric plate 43 and the negative electrode terminal 33 are electrically disconnected.

That is, in the secondary battery according to the embodiment of the present invention, the thermal expansion agent 7 that expands at a temperature lower than the boiling point of the electrolytic solution L is accommodated therein, and the space portion that is deformed by the thermal expansion of the thermal expansion agent 7 is contained. 51 (thermal expansion agent storage chamber).

The first positive electrode terminal 31 (first electrode which is a positive electrode or a negative electrode) and the battery cell 6 are electrically connected to each other, and the positive electrode current collector plate 41 (conductive member) provided along the space 51 is heated. When the expansion agent 7 is thermally expanded and the space 51 is deformed, an electrically disconnected state is obtained.

Here, the deformation of the space 51 (thermal expansion agent accommodation chamber) includes a case where the space 51 is destroyed by the thermal expansion of the thermal expansion agent 7 accommodated in the space 51.

Further, the configuration in which the positive electrode current collector plate 41 (conductive member) is provided along the space 51 includes a case where the positive electrode current collector 41 constitutes a part of a wall surrounding the space 51, for example.

In the secondary battery according to the embodiment of the present invention, the current interruption mechanism is operated by the thermal expansion agent 7 that expands the volume at a temperature lower than the boiling point of the electrolytic solution L, which is different from the electrolytic solution L. That is, the secondary battery according to the embodiment of the present invention accommodates the thermal expansion agent 7 during overcharge or short circuit by the thermal expansion agent 7 that expands the volume at a temperature lower than the boiling point of the electrolyte L. The space 51 is deformed, and the electrical connection between the first positive electrode terminal 31 and the battery cell 6 is cut. Therefore, the current interruption mechanism for preventing accidents due to overcharging and short-circuiting can be reduced in size without being affected by the characteristics of the electrolytic solution L.

[Embodiment 1]
FIG. 1 is a diagram showing a structure of a battery 100 according to an embodiment of the present invention. FIG. 1A is a plan view showing the positional relationship among the space 51 in which the thermal expansion agent 7 is sealed, the first positive electrode terminal 31, and the second positive electrode terminal 32 in the battery 100. FIG. 1B is a cross-sectional view showing that the thermal expansion agent 7 is sealed in a space 51 in which an opening provided in the packing 5 is sandwiched between the battery lid 2 and the positive electrode current collector 41. is there.

FIG. 18 is a cross-sectional view of the battery 100 of FIG. 1 taken along a plane parallel to the battery lid 2.

FIG. 2 shows a thermal expansion agent 7 sealed in a space 51 in which an opening provided in the packing 5 is sandwiched between the battery lid 2 and the positive current collector 41 in the battery 100, and the positive current collector 41. FIG. 4 is a diagram showing details of a positional relationship between a thin portion 41 a and a cut portion 41 b provided in the first positive electrode terminal 31.

FIG. 3 is a diagram illustrating what case each of the first positive electrode terminal 31 and the second positive electrode terminal 32 of the battery 100 is used. 3A shows that the battery 100 is charged and discharged using the first positive electrode terminal 31 in a normal case. FIG. 3B shows that when the first positive electrode terminal 31 is electrically disconnected from the battery cell 6 in the battery case 1 due to overcharge or the like, the battery 100 is discharged using the second positive electrode terminal 32. Indicates what to do.

In the battery 100, the positive electrode current collector plate 41 (conductive member) has a thin portion 41a (low strength portion) having relatively low strength, and the space portion 51 (thermal expansion agent accommodation chamber) is deformed to deform the thin portion. 41a breaks, and the positive electrode current collector plate 41 is electrically disconnected.

(Structure details)
As shown in FIGS. 1 and 2, in the battery 100, the positive electrode current collector plate 41 is fixed to the battery lid 2 via the packing 5 using the first positive electrode terminal 31 and the second positive electrode terminal 32. A safety valve 21 is provided at the center of the battery lid 2.

The packing 5 ensures electrical insulation between the battery lid 2 and the positive electrode current collector plate 41 and electrical insulation between the battery lid 2 and the negative electrode current collector plate 43.

An opening provided in the packing 5 is sandwiched between the battery lid 2 and the positive electrode current collector 41 (conductive member), thereby forming a space 51 (thermal expansion agent accommodation chamber). That is, in the battery 100, the positive electrode current collecting plate 41 constitutes a part of a wall surrounding the space 51.

The space 51 contains the thermal expansion agent 7 that expands the volume at a temperature lower than the boiling point of the electrolyte L, and the space 51 has sufficient airtightness to prevent the thermal expansion agent 7 from leaking. Have.

As shown in FIG. 1B, the positive electrode current collector plate 41 is bent at a substantially right angle when viewed from the side, and extends toward the bottom of the battery case 1. Further, in a part of the positive electrode current collector plate 41 extending in parallel with the battery lid 2, a slit is formed between the first positive electrode terminal 31 and the second positive electrode terminal 32, that is, a thin portion 41 a (low strength portion). ) Is provided.

That is, the positive electrode current collector plate 41 has a surface parallel to the battery cover 2 and a surface perpendicular to the battery cover 2, and the surface parallel to the battery cover 2 of the positive electrode current collector plate 41 is the first positive electrode. The terminal 31 and the second positive terminal 32 are electrically connected and electrically insulated from the battery lid 2 by the packing 5. The electrical connection point between the surface of the positive current collector plate 41 parallel to the battery lid 2 and the first positive electrode terminal 31, and the electrical connection between the surface of the positive current collector plate 41 parallel to the battery lid 2 and the second positive electrode terminal 32. Between the connection points, the surface parallel to the battery lid 2 of the positive electrode current collector plate 41 includes a thin portion 41a and a cut portion 41b.

The thin portion 41 a is thinner than the other portions of the positive electrode current collector plate 41. Therefore, the positive electrode current collector plate 41 is easily broken when it receives a force perpendicular to the surface around the thin portion 41a.

The cut portion 41 b is a portion where a cut is provided in the thickness direction of the positive current collector plate 41, and is easier to bend than the other portions of the positive current collector plate 41. That is, when the positive electrode current collecting plate 41 receives a force perpendicular to the surface around the notch 41b, it is easily bent along the notch 41b. In addition, the position of the cut portion 41 b is preferably far from the space portion 51. This is because the force to bend by the lever principle is larger when the position is far from the position where the vertical force is received.

The negative electrode current collector plate 43 is fixed to the battery lid 2 via the packing 5 by the negative electrode terminal 33. The negative electrode current collector plate 43 has the same shape as the positive electrode current collector plate 41, and the negative electrode terminal 33 has the same shape as the first positive electrode terminal 31.

For convenience, an integrated body of the battery lid 2, the positive current collector 41 and the negative current collector 43 is referred to as a lid plate assembly.

As shown in FIG. 18, the battery cell 6 is formed by laminating a plurality of positive electrodes, separators, and negative electrodes. The positive electrode and the negative electrode include an electrode coating part and an electrode foil for current collection, and are welded to the positive electrode current collector plate 41 and the negative electrode current collector plate 43, so that a part of the electrode foil is stretched. The current collector foil is electrically connected to the positive electrode current collector plate 41 and the negative electrode current collector plate 43.

(Size and material)
Next, an example of the size and material of the battery 100 will be described.

The battery case 1 has a substantially rectangular parallelepiped shape with one side opened, the length of the side corresponding to the long side of the opening is 259.5 mm, the length of the side corresponding to the short side of the opening is 50 mm, and the battery cover The length of the side perpendicular to 2 is 170 mm, and the material is an Al1050 metal plate having a thickness of 2 mm. Accordingly, the inner dimension of the battery case 1 is 255.5 mm (long side) × 46 mm (short side).

The battery cover 2 uses a metal plate made of Al1050 of 255.9 mm (long side) × 46.4 mm (short side) × 3 mm (thickness).

The safety valve 21 provided at the center of the battery lid 2 is a thin part having a diameter of 20 mm. The cleavage pressure of the safety valve 21 is designed to be 1.0 MPa.

For the first positive terminal 31 and the second positive terminal 32, a columnar aluminum material (made of Al1050) having a diameter of 10 mm × 30 mm (height from the upper surface of the battery lid 2) is used.

The negative electrode terminal 33 is made of a cylindrical copper material having a diameter of 10 mm × 30 mm (height from the upper surface of the battery lid 2).

The packing 5 is a laminate of PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) resin, PPS (polyphenylene sulfide) resin, and PFA resin in this order. The PFA resin has a thickness of 2 mm and the PPS resin has a thickness of 2 mm, and each has the same shape. PPS resin is excellent in mechanical strength, chemical resistance, and heat resistance. The packing 5 has a hole penetrating in the thickness direction in order to provide the space 51. Since the size of the hole is 20 mm long × 20 mm wide and the thickness of the packing is 6 mm, the volume of the space 51 is 2400 mm ³ .

As the positive electrode current collecting plate 41, an aluminum member (made of Al1050) having a thickness of 1 mm is used. The length in the vertical direction when viewed from the side surface of the positive electrode current collector plate 41, that is, the length of the surface perpendicular to the battery lid 2 of the positive electrode current collector plate 41 is 155 mm.

The thickness of the portion other than the thin portion 41a of the positive current collector 41 is 1 mm, whereas the thickness of the thin portion 41a is 0.5 mm, and unnecessary portions are scraped off within a range where the resistance value does not increase. It has a structure.

As the negative electrode current collector plate 43, a copper member having a thickness of 1 mm is used.

As described above, the battery cell 6 is formed by laminating a plurality of positive electrodes, separators, and negative electrodes. The thickness of the positive electrode was 230 μm, and 100 positive electrodes were used. The thickness of the negative electrode was 180 μm, and 101 negative electrode plates were used. As a separator, 200 polyethylene films having a thickness of 25 μm were used. The size of the battery cell 6 is 250 mm × 147.5 mm × 46 mm, and is inserted into the battery case 1.

The electrolytic solution L of the battery 100 was prepared by mixing 1 mol concentration of lithium hexafluorophosphate (LiPF) in a solvent obtained by mixing ethylene carbonate (EC, Ethylene Carbonate) and diethyl carbonate (DEC, Diethyl Carbonate) at a volume ratio of 3: 7. ₆ ) is dissolved. The boiling point of ethylene carbonate is 248 ° C, and the boiling point of diethyl carbonate is 126 ° C. However, the electrolytic solution L is not limited to this, and an electrolytic solution that can be generally used for a secondary battery can be used as the electrolytic solution L.

As the thermal expansion agent 7, absorbent cotton containing 3M Novec ^™ 7200 is used. The component of Novec ^™ 7200 is hydrofluoroether, the boiling point is 76 ° C., which is lower than the boiling point of the electrolyte L. However, although details will be described later, the material of the thermal expansion agent 7 is not limited to this, and an organic solvent having a boiling point lower than that of the electrolytic solution L or an organic system that is thermally decomposed at a temperature lower than the boiling point of the electrolytic solution L. Chemical foam can be used.

(Production method)
After an assembly of the lid plate assembly and the battery cell 6 is inserted into the battery case 1, the battery lid 2 and the battery case 1 are welded and electrolyzed from a liquid injection port (not shown) provided in the battery lid 2. Liquid L was injected. Thereafter, chemical charging was performed, and the generated gas was degassed. After degassing, the liquid inlet was welded to the battery lid 2.

Next, as shown in FIG. 1 and FIG. 2, the thermal expansion agent 7 is disposed in the space 51 provided between the positive electrode current collector 41 and the battery lid 2 to seal the space 51. The cap 22 was covered and welded to the battery lid 2.

(Characteristics of battery 100, etc.)
As shown in FIG. 2, in the battery 100, when the temperature in the battery 100 rises due to overcharging or the like, the thermal expansion agent 7 held in the space 51 evaporates or decomposes to expand, and the contacts are electrically disconnected. That is, the electrical connection between the battery cell 6 and the first positive electrode terminal 31 is cut.

Specifically, the thin-walled portion 41a (low-strength portion) and each of the positions corresponding to two opposing sides of the surface forming the space portion 51 in which the thermal expansion agent 7 is sealed of the positive electrode current collector plate 41 are provided. In addition, a notch 41b is provided. When the temperature in the battery 100 rises due to overcharge or the like, the thermal expansion agent 7 held in the space 51 is thermally expanded, the space 51 is deformed, and the positive electrode current collector 41 is broken at the thin wall portion 41a. It bends outward with respect to the space 51 at the insertion portion 41b. Thereby, an electrical disconnection state between the battery cell 6 and the first positive electrode terminal 31 is formed.

Whereas the safety valve 21 is operated by an increase in the internal pressure of the battery due to the vaporized electrolyte L, the current interruption mechanism of the battery 100 is such that the thermal expansion agent 7 is thermally expanded at a temperature lower than the boiling point of the electrolyte L and the space 51 is formed. By deforming, an electrical disconnection state between the battery cell 6 and the first positive electrode terminal 31 is formed.

Therefore, since the current cutoff mechanism of the battery 100 is based on an operating pressure different from that of the safety valve 21, it does not affect the operation of the safety valve for which absolute reliability is required or adversely affected.

In addition, the conventional current interrupting mechanisms described in, for example, Patent Document 1 and Patent Document 2 described above are part of an electrical path for charging and discharging so that the current interrupting mechanism operates at a battery internal pressure lower than the battery internal pressure at which the safety valve operates. In addition, it is configured to include a contact that is released (welded) at a low battery internal pressure. That is, conventionally, it has been necessary to design the operating pressure of the current interruption mechanism with the peel strength of the (welding) contact. Therefore, since the current interruption mechanism must be operated at a pressure lower than that of the safety valve, the contact strength should not be too strong. However, it is difficult to “obtain the contact weakly and uniformly” regardless of the welding method. This necessitates a precise inspection of the weld contacts, which hinders cost reduction of the secondary battery.

In contrast, the operating pressure of the current interruption mechanism of the battery 100 is determined by the internal pressure of the space 51. Since the internal pressure of the space 51 can be designed separately from the operating pressure of the safety valve, it is not necessary to be “weak and uniform” as severely as in the past. That is, even when the contact point (low-strength part) in the current interrupting mechanism is not uniform in strength, the operating pressure of the current interrupting mechanism (internal pressure of the space 51) is set high, so that the electric A disconnection state can be formed. For this reason, the conventional precise inspection is unnecessary, and the cost can be reduced. Moreover, since the operating pressure can be set higher than the conventional pressure for the above reason, the contact in the current interruption mechanism can be strengthened.

In other words, in the case of a current interrupting mechanism that operates with an increase in the internal pressure of the battery and operates at an operating pressure lower than the operating pressure of the safety valve, a thin metal plate that deforms at a low pressure or a welded portion that peels at a low pressure Must be used as a contact for the current interrupt mechanism. However, in the current interrupt mechanism that operates by the internal pressure of the thermal expansion agent storage chamber, which is different from the internal pressure of the battery, it is not necessary to use a metal thin plate that deforms at a low pressure and a welded portion that peels at a low pressure. Instead, for example, a metal plate having a relatively large thickness or a welded portion having a relatively large welding area and a high physical strength and an electrically low resistance can be used as a contact of the current interrupting mechanism. Become. For this reason, the electrical resistance of the contact is low and resistant to vibration.

The structure of the battery 100 is simple and space-saving, and since the number of parts related to the current interruption mechanism is small, the manufacturing cost is lower than that of a secondary battery equipped with a conventional current interruption mechanism. Since only a small amount of the thermal expansion agent 7 is required, the material cost is low.

Further, since the battery 100 has a configuration in which the positive electrode current collecting plate 41 is broken when overcharged, the electrical connection between the battery cell 6 and the first positive electrode terminal 31 is reconnected by temperature change, pressure change, vibration, or the like. There is nothing and high reliability.

(About battery temperature rise due to overcharge)
FIG. 12 to FIG. 14 are diagrams showing the relationship between overcharge and increase in battery temperature in relation to lithium ion secondary batteries (for example, Non-Patent Document 1).

FIG. 12 is a graph showing the relationship between the overcharge time, the battery temperature, and the battery voltage when overcharge is performed at 1 C for a secondary battery that does not have a current interruption mechanism.

FIG. 13 shows the relationship between the overcharge time and the battery temperature when overcharged at 2C for the same secondary battery as shown in FIG. It is a graph shown in contrast with the case. Note that 1C is a current value at which charging is completed in just one hour after a battery having a nominal capacity is charged with a constant current. That is, in FIG. 13, the dotted line indicated as temperature (2C) indicates the battery temperature of the secondary battery charged with a current value twice that indicated by the dotted line indicated as temperature (1C), the overcharge time, Shows the relationship.

FIG. 14 is a tabular diagram showing the relationship between the overcharge time and the battery temperature shown in FIGS. 12 and 13 in an organized manner. In charging at 1C, from stage A (transfer to lithium ions / lithium deposition), through stage B / C (stage after oxidative decomposition of electrolyte L by overcharged cathode), stage D / E (thermal runaway) It takes a relatively long time to reach the stage one step before. On the other hand, in charging at 2C, the time from the I stage (transfer to lithium ions / lithium deposition) to the IV stage (the stage just before the thermal runaway) is extremely short compared to the case of 1C. .

Here, when charging at the rated rate (1C), the current increases as the battery capacity increases. Since the calorific value is proportional to the square of the current (Q = RI ² , where Q is the calorific value and R is the internal resistance of the battery), the temperature of the electrolyte rises rapidly. That is, for example, when charging a large-capacity secondary battery having a battery capacity of 10 Ah or more and less than 1000 Ah, a large current flows through the secondary battery, so that the battery temperature rapidly rises due to overcharging or the like. Therefore, in the large capacity secondary battery, the reliable operation of the current interruption mechanism is required more strongly than the small capacity secondary battery.

Further, as shown in FIG. 14, in the battery showing the increase in battery temperature during overcharge in FIGS. 12 and 13, the oxidative decomposition of the electrolyte L by the overcharged positive electrode accelerates from 60 ° C. This temperature of 60 ° C. is lower than the boiling point of the electrolytic solution. Therefore, when the battery temperature exceeds 60 ° C. and becomes abnormally overheated, the battery operates reliably regardless of whether the internal pressure of the battery is increased, that is, whether the electrolyte is boiling. A current interruption mechanism is desirable. That is, a current interrupt mechanism that operates reliably at a constant battery temperature without being affected by characteristics such as the boiling point of the electrolytic solution is desirable.

In particular, for example, in a large-capacity secondary battery having a battery capacity of 10 Ah or more and less than 1000 Ah, the battery temperature rises due to overcharging or the like, and the battery temperature is a predetermined temperature lower than the boiling point of the electrolyte (FIG. 14). In this example, when the temperature exceeds 60 ° C.), the battery temperature tends to jump rapidly. Therefore, the current interruption mechanism provided in the large-capacity secondary battery is desirably a current interruption mechanism that operates reliably at a constant battery temperature without being affected by the characteristics of the electrolyte solution, and more desirably if the current interruption mechanism can be reduced in size.

It should be noted that, for example, a large-capacity second battery used for a solar power generation system (including home-use stationary), a camper and a ship sub-battery, an electric senior car, an electric motorcycle, an electric reel, an electric car for children, an electric forklift, an acoustic device, a mobile radio, etc. As secondary batteries, secondary batteries having a battery capacity of 10 Ah or more and less than 1000 Ah are often serially paralleled to obtain a predetermined system battery capacity. In addition, large-capacity secondary batteries used as standby batteries in UPS (uninterruptible power supply), disaster prevention / crime prevention systems, emergency lighting equipment, emergency call system equipment, fire fighting equipment, etc., have a battery capacity of 10 Ah or more and 1000 Ah. In many cases, less than the number of secondary batteries are serially paralleled to obtain a predetermined system battery capacity. Further, the same applies to large-capacity secondary batteries used in EVs (electric vehicles) such as automobiles and buses.

Furthermore, when the battery capacity per one battery (single cell) is less than 10 Ah, the number of single cells in parallel at the time of module production increases, workability is reduced, and cell fastening costs are increased, which is not preferable. When the unit cell capacity is 1000 Ah or more, a system such as a NaS battery or a redox flow battery is advantageous in terms of cost and the like, which is not preferable.

The current interrupt mechanism according to one embodiment of the present invention can be suitably used in the large-capacity secondary battery used in the above example. A secondary battery having a battery capacity of less than 10 Ah has a smaller amount of heat generation than a secondary battery having a battery capacity of 10 Ah or more. Therefore, a secondary battery having a battery capacity of less than 10 Ah has a larger room for suppressing thermal runaway by devising a material such as a separator as compared with a secondary battery having a battery capacity of 10 Ah or more.

On the contrary, when the battery capacity is 1000 Ah or more, the calorific value is extremely large, so that deterioration of materials such as electrodes becomes severe. Therefore, in a secondary battery having a battery capacity of 1000 Ah or more, a cooling mechanism for suppressing an increase in battery temperature is essential and the size is increased. Therefore, a current interruption mechanism for suppressing thermal runaway is reduced in size and reduced in size. The demand for cost reduction is low.

The secondary battery according to one embodiment of the present invention is preferably used in the above example, that is, the secondary battery according to one embodiment of the present invention desirably has a battery capacity of 10 Ah or more and less than 1000 Ah. That is, not only the secondary battery according to Embodiment 1 but also the secondary batteries according to other embodiments described below, the battery capacity is desirably 10 Ah or more and less than 1000 Ah.

Next, an overcharge test was performed on a secondary battery having the same structure as that of the battery 100 and at least one of the material of the electrolyte L and the thermal expansion agent 7 different from that of the battery 100. Details of the test results will be described below.

(Overcharge test)
For the secondary battery according to one embodiment of the present invention, an overcharge test was performed in order to confirm the difference between the conventional secondary battery having a current interruption mechanism and the secondary battery not having a current interruption mechanism. . Details will be described below.

FIG. 11 shows an overcharge for Examples 1 to 5 and Comparative Examples 1 to 3 which are secondary batteries having the same structure as the battery 100 and differing only in the materials used for the electrolyte L and / or the thermal expansion agent 7. It is a figure which shows the installation position of the thermocouple used when the test was done. The thermocouple was fixed to the outside of the battery case using aluminum tape. The safety valve 21 of the battery 100 was designed to be cleaved at 1.0 MPa, and the current interruption mechanisms of Comparative Example 1 and Comparative Example 2 were designed to work at 0.5 MPa. Details of the batteries of Examples 1 to 4 and Comparative Examples 1 to 4 will be described later.

FIG. 15 is a tabular diagram showing the results of overcharge tests for Examples 1 to 4 and Comparative Examples 1 to 4.

First, the overcharge test method will be explained.

First, the batteries according to Examples 1 to 4 and Comparative Examples 1 to 4 having a nominal capacity of 120 Ah are charged at a constant current of 40 A until the battery voltage becomes 3.6 V, and then the current becomes 4 A at a constant voltage of 3.6 V. Until fully charged.

Next, charging was performed at a constant current of 120 A for 90 minutes, and the battery voltage, current, and temperature in the battery case at that time were measured.

The power source used was four parallel stabilized DC power sources PWR1600L made by Kikusui Electronics. The current measurement was performed using a clamp meter DCM400AD manufactured by Sanwa Denki Keiki. For voltage and temperature measurement, a data logger midi LOGGER GL820 made by Graphtec was used. The test was performed at room temperature.

FIG. 15 is a table showing the results of the overcharge test performed by the above method.

In FIG. 15, Example 1 is a secondary battery having the same structure as the battery 100. The electrolytic solution L of Example 1 was prepared by mixing 1 mol of lithium hexafluorophosphate (EC) with a solvent obtained by mixing ethylene carbonate (EC, Ethylene Carbonate) and diethyl carbonate (DEC, Diethyl Carbonate) at a volume ratio of 3: 7. LiPF ₆ ) is dissolved. Further, in the space 51 of Example 1, as a thermal expansion agent 7 that thermally expands at a temperature lower than the boiling point of the electrolyte L, Novec ^™ 7300 (a typical chemical formula is C ₂ F ₅ CF) that is a low boiling point solvent. Absorbent cotton containing 400 mg of (OCH ₃ ) C ₃ F ₇ (molecular weight 350 g / mol) is housed.

Note that ethylene carbonate has a boiling point of 248 ° C. and diethyl carbonate has a boiling point of 126 ° C., whereas Novec ^™ 7300 has a boiling point of 98 ° C., and Novec ^™ 7300 has a boiling point lower than that of the electrolyte L.

When the pressure value is calculated for Example 1, since the volume of the space 51 is 2400 mm ³ , the pressure of the space 51 rises to 1.5 MPa when all of the thermal expansion agent 7 evaporates (Comparative Example 1 and Comparative Example). Higher than the operating pressure of current interruption of 2). The current interruption is activated by this pressure, and the vapor of the thermal expansion agent 7 diffuses into the battery case 1. In Example 1, since the distance between the liquid surface of the electrolyte L and the lower surface of the battery lid 2 was about 20 mm, the volume of the space inside the battery case 1 was about 2.4 × 10 ⁵ mm ³ (255 0.5 mm (long side) × 46 mm (short side) × 20 mm (depth), and the volume of the current interrupting part is ignored. Therefore, in Example 1, even if the thermal expansion agent 7 is all evaporated and diffused into the battery case 1, the internal pressure of the battery case 1 increases only by 0.015 MPa. That is, in Example 1, it can be said that the thermal expansion agent 7 hardly affects 1.0 MPa that the safety valve 21 opens.

In Example 1, after charging started at a constant current of 120 A, when the battery voltage was 5.1 V and the battery case temperature was 81 ° C. in 13 minutes, the current value was 0 A, and the load was not applied to the battery. Thereafter, the battery did not deform, rupture or ignite.

After the test was completed, the voltages of the negative electrode terminal 31 and the second positive electrode terminal 32 were confirmed. Since the voltage was still high and dangerous, it was conducted and discharged through a wiring having resistance. After that, when the battery 100 was disassembled, it was confirmed that the thin portion 41a was broken and the current interruption mechanism was operated. From this, it is considered that the thermal expansion agent 7 reached a boiling point of 98 ° C. 13 minutes after the start of charging, and the current interruption mechanism worked. Although the temperature indicated by the thermocouple was 81 ° C., the temperature of the space 51 was considered to have reached around 98 ° C., and a temperature difference was observed between the temperature indicated by the thermocouple and the temperature in the space 51.

In Example 2, as in Example 1, an electrolytic solution L in which 1 molar concentration of LiPF ₆ was dissolved in a solvent in which EC and DEC were mixed at a volume ratio of 3: 7 was used, and Novec ^™ 7200 was included. Absorbent cotton is used as the thermal expansion agent 7. That is, Example 2 is the battery 100 described so far.

The difference between Example 2 and Example 1 is that, as thermal expansion agent 7, instead of Novec ^™ 7300, Novec ^™ 7200 (typical chemical formula is C ₄ F ₉ OC ₂ H ₅ , molecular weight is 264 g / mol). It is only used. That is, absorbent cotton containing 400 mg of Novec ^™ 7200 as in Example 1 is used as the thermal expansion agent 7. Novec ^™ 7200 has a boiling point of 76 ° C., which is lower than the boiling point of the electrolyte L as in Example 1.

When the pressure value is calculated for Example 2, the volume of the space 51 is 2400 mm ³ , and thus when the thermal expansion agent 7 is completely evaporated, the pressure of the space 51 rises to 1.8 MPa (similar to Example 1). Higher than the operating pressure of current interruption in Comparative Example 1 and Comparative Example 2). The current interruption is activated by this pressure, and the vapor of the thermal expansion agent 7 diffuses into the battery case 1. In Example 2, since the distance between the liquid level of the electrolytic solution L and the lower surface of the battery lid 2 was about 20 mm, the volume of the space inside the battery case 1 was about 2.4 × 10 ⁵ mm ³ (255 0.5 mm (long side) × 46 mm (short side) × 20 mm (depth), and the volume of the current interrupting part is ignored. Therefore, in Example 2, even if all of the thermal expansion agent 7 evaporates and diffuses into the battery case 1, the internal pressure of the battery case 1 increases only by 0.019 MPa. That is, in Example 2, it can be said that the thermal expansion agent 7 hardly affects 1.0 MPa that the safety valve 21 opens.

In Example 2, after charging started at a constant current of 120 A, the current value became 0 A when the battery voltage was 5.1 V and the battery case temperature was 66 ° C. in 12 minutes and 30 seconds, and the load was not applied to the battery. . Thereafter, the battery did not deform, rupture or ignite.

After the test was completed, the voltages of the negative electrode terminal 31 and the second positive electrode terminal 32 were confirmed. Since the voltage was still high and dangerous, it was conducted and discharged through a wiring having resistance. Thereafter, when the battery 100 was disassembled, it was confirmed that the thin portion 41a was broken and the current interrupting mechanism worked. It is considered that the thermal expansion agent 7 reached a boiling point of 76 ° C. at 12 minutes and 30 seconds after the start of charging, and the current interruption mechanism worked. Compared with Example 1, by using a low-boiling-point thermal expansion agent, the time during which current interruption occurred could be accelerated, and the temperature rise could be suppressed to a low level.

In Example 3, as in Example 1, an electrolytic solution L in which 1 molar concentration of LiPF ₆ was dissolved in a solvent in which EC and DEC were mixed at a volume ratio of 3: 7 was used. It is a secondary battery having the same structure as the battery 100 using the medicinal azo polymerization initiator V-60. The difference between Example 3 and Example 1 is that V-60 is used as the thermal expansion agent 7 instead of Novec ^™ 7300. V-60 expands at a temperature lower than the boiling point of the electrolyte L (half-life is 65 ° C.).

In Example 3, after charging started at a constant current of 120 A, the current value became 0 A when the battery voltage was 5.1 V and the battery case temperature was 72 ° C. in 12 minutes and 50 seconds, and the load was not applied to the battery. . Thereafter, the battery did not deform, rupture or ignite.

After the test was completed, the voltages of the negative electrode terminal 31 and the second positive electrode terminal 32 were confirmed. Since the voltage was still high and dangerous, it was conducted and discharged through a wiring having resistance. After that, when the battery 100 was disassembled, it was confirmed that the thin portion 41a was broken and the current interruption mechanism was operated. It is considered that the thermal expansion agent 7 reached a decomposition temperature of 88 ° C. in 13 minutes after the start of charging, and the current interruption mechanism worked. Compared to Example 1, by using a solid material that expands at a low temperature, it was possible to speed up the time when current interruption occurred, and to suppress a rise in temperature.

In Example 4, an electrolytic solution L in which 1 mol of LiPF ₆ was dissolved in a solvent in which EC and dimethyl carbonate (DMC) were mixed at a volume ratio of 3: 7 was used, and Novec was used as a thermal expansion agent 7. Absorbent cotton containing ^TM 7200 is used. Example 4 is a secondary battery having the same structure as the battery 100. The difference between Example 4 and Example 1 is that DMC is used instead of DEC as the solvent of the electrolytic solution L, and Novec ^™ 7200 is used instead of Novec ^™ 7300 as the thermal expansion agent 7. It is a point to use. In addition, since the boiling point of dimethyl carbonate is 90.3 ° C., the boiling point of Novec ^™ 7200 is 76 ° C., the Novec ^™ 7200 has a boiling point lower than that of the electrolyte L.

In Example 4, after charging started at a constant current of 120 A, the current value became 0 A when the battery voltage reached 4.8 V and the battery case temperature 68 ° C. in 12 minutes and 20 seconds, and the load was not applied to the battery. . Thereafter, the battery did not deform, rupture or ignite.

After the test was completed, the voltages of the negative electrode terminal 31 and the second positive electrode terminal 32 were confirmed. Since the voltage was still high and dangerous, it was conducted and discharged through a wiring having resistance. After that, when the battery 100 was disassembled, it was confirmed that the thin portion 41a was broken and the current interruption mechanism was operated. It is considered that the thermal expansion agent 7 reached a boiling point of 76 ° C. at 12 minutes and 20 seconds after the start of charging, and the current interruption mechanism worked. In Example 4, an electrolyte solution having a lower boiling point than that of Example 1 was used, but it was confirmed that current interruption occurred by using a thermal expansion agent having a lower boiling point than that of the electrolyte solution.

Comparative Example 1 is a secondary battery provided with a current blocking mechanism having the same physical structure as the current blocking mechanism described in Patent Document 1, and a solvent in which EC and DEC are mixed at a volume ratio of 3: 7, An electrolytic solution in which 1 mol concentration of LiPF ₆ is dissolved is used.

In Comparative Example 1, after charging was started at a constant current of 120 A, the current value became 0 A when the battery voltage was 5.1 V and the battery case temperature was 105 ° C. in 13 minutes and 40 seconds, and the current interruption mechanism worked. The battery did not rupture or ignite. The internal pressure of the battery case increased due to the evaporation and oxidative decomposition of the electrolyte, and it was considered that the current interruption worked because it reached 0.5 MPa.

However, the maximum temperature reached was markedly higher than in Examples 1 to 4, and the battery case was swollen and deformed by the internal pressure. The time until the current interruption worked was also slow.

Comparative Example 2 is a secondary battery provided with a current interruption mechanism having the same physical structure as the current interruption mechanism described in Patent Document 2. In Comparative Example 2, as in Comparative Example 1, an electrolytic solution in which 1 molar concentration of LiPF ₆ was dissolved in a solvent in which EC and DEC were mixed at a volume ratio of 3: 7 was used.

In Comparative Example 2, after charging started at a constant current of 120 A, the current value became 0 A when the battery voltage reached 4.9 V and the battery case temperature 98 ° C. in 13 minutes and 30 seconds, and the current interruption mechanism worked. The battery did not rupture or ignite. The internal pressure of the battery case increased due to the evaporation and oxidative decomposition of the electrolyte, and it was considered that the current interruption worked because it reached 0.5 MPa.

In Comparative Example 1 and Comparative Example 2, the battery was not ruptured or ignited due to overcharging. However, Comparative Example 1 and Comparative Example 2 were compared with Examples 1 to 5 when the current interruption mechanism was operated. Case temperature is high.

Comparative Example 3 is a secondary battery that includes only a safety valve and does not include a current interruption mechanism. Like Comparative Example 1, EC and DEC were mixed at a volume ratio of 3: 7 in a solvent having a molar ratio of 1 molar. An electrolytic solution L in which LiPF ₆ is dissolved is used.

In Comparative Example 3, after starting charging at a constant current of 120 A, the safety valve opened at 23 minutes after the battery voltage was 5.9 V and the battery case temperature was 150 ° C., and white smoke was ejected. The current remained at 120A. After 35 minutes, the battery voltage was 0 V, the maximum battery case temperature was 300 ° C., and the current remained at 120 A. Thereafter, the battery did not burst or ignite for 55 minutes, but the battery case temperature was 200 ° C.

Comparative Example 4 uses an electrolytic solution L in which 1 mol of LiPF ₆ is dissolved in a solvent in which EC and dimethyl carbonate (DMC) are mixed at a volume ratio of 3: 7, and Novec as a thermal expansion agent 7. It is used cotton wool moistened with ^TM 7300. The structure of Comparative Example 4 is the same as that of the battery 100. The difference between Comparative Example 4 and Example 1 is that DMC is used as the solvent of the electrolytic solution L instead of DEC. Since the boiling point of DMC is 90.3 ° C., the boiling point of Novec ^™ 7300 is 98 ° C., so that the thermal expansion agent 7 does not expand unless the temperature is higher than the boiling point of the electrolytic solution L.

In Comparative Example 4, after starting charging at a constant current of 120 A, the safety valve opened at 23 minutes after the battery voltage was 5.9 V and the battery case temperature was 150 ° C., and white smoke was ejected. The current remained at 120A. After 35 minutes, the battery voltage was 0 V, the maximum battery case temperature was 300 ° C., and the current remained at 120 A. Thereafter, the battery did not burst or ignite for 55 minutes, but the battery case temperature was 200 ° C.

As can be seen from the above experimental results, it was confirmed that the battery 100 has a lower temperature of the battery case in which the current interruption mechanism operates than the secondary battery having the conventional current interruption mechanism.

(Second positive terminal)
The battery 100 includes a second positive electrode terminal connected to the positive electrode current collector plate 41 at a portion closer to the battery cell 6 than the thin-walled portion 41a (electrically disconnected portion) of the positive electrode current collector plate 41 (conductive member). 32 (second electrode terminal).

Note that, in the battery 100, the position where the second positive electrode terminal 32 is connected to the positive electrode current collector plate 41 is the portion closer to the battery cell 6 than the thin portion 41a. In the secondary battery, the position where the second electrode terminal is provided is not limited to this.

The secondary battery according to one embodiment of the present invention only needs to include the second electrode terminal that is connected to the conductive member at a portion closer to the battery cell 6 than the portion of the conductive member that is electrically disconnected.

For example, the

batteries

101 and 102, which are secondary batteries according to one embodiment of the present invention described later, have battery cells 6 rather than the welding portion 8 or the fitting portion (the fitting concave portion 451d and the fitting convex portion 452c) of the conductive member. In the side part, the 2nd electrode terminal connected with the electrically-conductive member is provided.

The battery 100 can be forcibly discharged using the second positive electrode terminal 32 even after the operation of the current interruption mechanism. That is, the positive electrode current collector plate 41 provided along the space 51 (thermal expansion agent storage chamber) in which the thermal expansion agent 7 is stored breaks when the space 51 is deformed by the thermal expansion of the thermal expansion agent 7. Then, the 1st positive electrode terminal 31 (1st electrode which is a positive electrode or a negative electrode) and the battery cell 6 will be in a disconnection state electrically. However, even after the first positive electrode terminal 31 and the battery cell 6 are in an electrically disconnected state, the positive electrode current collector plate is closer to the battery cell 6 than the fractured portion (thinned portion 41a) of the positive electrode current collector plate 41. The battery 100 can be forcibly discharged using the second positive terminal 32 connected to the terminal 41.

The battery 100 can be safely collected because the battery cell 6 can be discharged by the second positive electrode terminal 32 even after the operation of the current interrupting mechanism. Therefore, providing the second positive electrode terminal 32 leads to a reduction in the battery manufacturing cost in terms of the total from manufacturing to recovery after the accident.

Moreover, since the positive electrode current collector plate 41 has a broken portion (thin wall portion 41a) having a relatively low strength, the electrical resistance of this portion is relatively high. This is not limited to the current interrupting mechanism of the present invention, and the same applies to a conventional current interrupting mechanism having a breakage point. A large electrical resistance means that a voltage loss occurs when a current is passed. That is, accurately measuring the voltage of the battery cell 6 causes a voltage shift as described above. It suggests that it is difficult. In other words, the battery is generally charged before shipment. At that time, for example, when charging is performed by connecting a voltmeter and an ammeter between the first positive terminal 31 and the negative terminal 33, the current interrupting mechanism Pick up electrical resistance. As a result, the voltmeter does not indicate the net voltage of the battery cell 6 and there is a possibility that the desired voltage cannot be charged. Note that the larger the battery, the larger the current flows at the rated rate (1C), so the voltage deviation becomes larger.

However, in the battery cell 100 of the present invention, the above fear can be solved. For example, when charging by connecting an ammeter between the first positive terminal 31 and the negative terminal 33 and connecting a voltmeter between the second positive terminal 32 and the negative terminal 33 in charging before shipping, The voltmeter shows the net voltage of the battery cell 6 without picking up the electrical resistance. This is because the second positive terminal 32 is located closer to the battery cell 6 than the current interrupt mechanism. Therefore, it is possible to charge to a desired voltage, and from this, the second positive electrode terminal 32 is suitable as a voltage measurement terminal.

Furthermore, when impedance measurement is performed between the first positive electrode terminal and the negative electrode terminal 33 before shipment, only the all-over impedance of the battery 100 can be measured. However, by providing the second positive terminal 32, the impedance between the second positive terminal 32 and the negative terminal 33 and the electrical resistance between the second positive terminal and the first positive terminal can be measured. That is, the impedance of the battery cell 6 and the electric resistance of the current interrupt mechanism can be distinguished. For this reason, the battery 100 is easy to extract the electrical problem before shipment by providing the 2nd positive electrode terminal 32. FIG.

[Embodiment 2]
A battery 101 according to another embodiment of the present invention will be described below with reference to FIGS. 4 and 5. For convenience of explanation, members having the same functions as those described in the embodiment are given the same reference numerals, and descriptions thereof are omitted.

FIG. 4 is a diagram showing the structure of the battery 101. FIG. 4A is a plan view showing the positional relationship among the space 51 in which the thermal expansion agent 7 is sealed, the first positive terminal 31, and the second positive terminal 32 in the battery 101. FIG. 4B is a cross-sectional view showing that the thermal expansion agent 7 is sealed in a space 51 in which an opening provided in the packing 5 is sandwiched between the battery lid 2 and the positive electrode current collector plate 44. is there.

FIG. 5 is a detailed view of the battery shown in FIG. 4, and the positive current collector 44 constituting a part of the wall surrounding the space 51 enclosing the thermal expansion agent 7 is the first positive current collector 441. The second positive electrode current collector plate 442 is connected by the welded portion 8.

Note that the battery cell 6 is not shown because it is the same as the battery 100.

The battery 101 has a positive current collector plate 44 (conductive member) in which a first positive current collector plate 441 (first conductive member) and a second positive current collector plate 442 (second conductive member) are connected by welding. The positive electrode current collector plate 44 (conductive member) is disconnected from the welded portion 8 (welded portion).

In the battery 101, the positive electrode current collector plate 44 includes a first positive electrode current collector plate 441 electrically connected to the first positive electrode terminal 31 and a second positive electrode current collector plate electrically connected to the second positive electrode terminal 32. 442 is welded at the welded portion 8. That is, the 1st positive electrode current collecting plate 441 and the 2nd positive electrode current collecting plate 442 are mutually connected by the welding part 8, and are electrically connected.

Unlike the battery 100 including the positive electrode current collector plate 41 that is a single metal plate, the battery 101 is broken by the thermal expansion agent 7 being thermally expanded and the space 51 (thermal expansion agent accommodation chamber) being deformed. The positive current collector 44 is composed of two metal plates, a first positive current collector 441 and a second positive current collector 442.

In the battery 101, the first positive electrode current collector plate 441 and the second positive electrode current collector plate 442 are connected by the welding portion 8, but the electrical connection between the first positive electrode current collector plate 441 and the second positive electrode current collector plate 442 is performed. The method for forming a general connection is not limited to this. For example, the first positive electrode current collector plate 441 and the second positive electrode current collector plate 442 may be connected by laser welding, resistance welding, or ultrasonic welding of a thin aluminum plate.

That is, the battery 101 has a structure in which the first positive electrode current collector plate 441 and the second positive electrode current collector plate 442 which are two metal plates are connected by the welded portion 8, and the first positive electrode current collector plate 441 and the first positive electrode current collector plate 441 are connected to the first positive electrode current collector plate 441. The two positive electrode current collector plates 442 are separated, and an electrical disconnection state between the first positive electrode terminal 31 and the battery cell 6 is formed.

On the other hand, the battery 100 is configured such that the thin-walled portion 41 a provided on the positive electrode current collector plate 44 that is a single metal plate is broken by the thermal expansion of the thermal expansion agent 7. In the battery 100, since the thin portion 41a is provided at the break portion, the strength is determined by the thickness of the thin portion 41a and material properties such as the Young's modulus of the material.

On the other hand, the battery 101 utilizes the low physical strength of the weld 8. That is, when the thermal expansion agent 7 is thermally expanded and the space 51 (thermal expansion agent storage chamber) is deformed, the welded portion 8 is detached, and the first positive current collector plate 441 and the second positive current collector plate 442 are separated. Then, the first positive electrode terminal 31 and the battery cell 6 are electrically disconnected. For example, when laser welding or the like is used, the physical strength of the welded portion 8 can be easily adjusted by at least one of the welding output and the welding time. The battery 101 and the battery 100 have different strength adjustment methods.

However, since the battery 101 electrically connects the first positive electrode current collector plate 441 and the second positive electrode current collector plate 442 with the welded portion 8 or the like, the battery 101 has a slightly higher electrical resistance than the battery 100, and is resistant to vibration. weak.

In addition, the battery 101 requires an additional process in manufacturing, for example, ultrasonic welding or resistance welding, and the member cost is increased in that there are two current collecting plates. That is, the positive current collector 44 of the battery 101 includes two metal plates, the first positive current collector 441 and the second positive current collector 442, and thus the positive current collector of the battery 100 made of one metal plate. Compared with the plate 41, the member cost is high.

As shown in FIGS. 4 and 5, the battery 101 has a positive current collector plate 44, more precisely, in the portion closer to the battery cell 6 than the welded portion 8 of the positive current collector plate 44 (conductive member). A second positive electrode terminal 32 (second electrode terminal) connected to the two positive electrode current collector plate 442 may be provided. Since the details of the second positive electrode terminal 32 have already been described in the battery 100, a description thereof is omitted here.

In addition, the battery 101 includes a cut portion 441b in the first positive electrode current collector plate 441. When the thermal expansion agent 7 is thermally expanded and the space portion 51 is deformed, the first positive electrode current collector plate 441 is cut by the cut portion 441b. However, it is easy to bend outward with respect to the space 51.

[Embodiment 3]
A battery 102 according to still another embodiment of the present invention will be described below with reference to FIGS. For convenience of explanation, members having the same functions as those described in the embodiment are given the same reference numerals, and descriptions thereof are omitted.

FIG. 6 is a diagram showing the structure of the battery 102. FIG. 6A is a plan view showing a positional relationship among the space 51 in which the thermal expansion agent 7 is sealed, the first positive terminal 31, and the second positive terminal 32 in the battery 102. FIG. 6B is a cross-sectional view showing that the thermal expansion agent 7 is sealed in a space 51 in which an opening provided in the packing 5 is sandwiched between the battery lid 2 and the positive electrode current collector plate 45. is there.

FIG. 7 is a detailed view of the battery shown in FIG. 6. The positive electrode current collector plate 45 includes a first positive electrode current collector plate 451 and a second positive electrode current collector plate 452, and a fitting recess 451 d and a fitting protrusion. 452c is connected by fitting.

The battery 102 has a positive current collector 45 (conductive member) in which a first positive current collector 451 (first conductive member) and a second positive current collector 452 (second conductive member) are fitted, The positive electrode current collector plate 45 is disconnected when the fitting portion is disengaged.

In the battery 102, the positive current collector 45 includes a first positive current collector 451 that is electrically connected to the first positive terminal 31 and a second positive current collector that is electrically connected to the second positive terminal 32. 452. Each of the first positive current collector plate 451 and the second positive current collector plate 452 has a fitting recess 451d (fitting portion) and a fitting projection 452c (fitting portion). The first positive electrode current collector plate 451 and the second positive electrode current collector plate 452 are electrically connected by fitting the fitting concave portion 451d and the fitting convex portion 452c.

The first positive electrode current collector plate 451 and the second positive electrode current collector plate 452 of the battery 102 have a larger contact area and electric resistance than the first positive electrode current collector plate 441 and the second positive electrode current collector plate 442 of the battery 101. small. In addition, the battery 102 is stronger than the battery 101 in terms of vibration strength.

However, the battery 102 requires the additional process of forming the fitting concave portion 451d and the fitting convex portion 452c and fitting them together, and the member cost is increased in that two current collecting plates are used.

As shown in FIGS. 6 and 7, the battery 102 is located in a portion closer to the battery cell 6 than the fitting portion (the fitting concave portion 451 d and the fitting convex portion 452 c) of the positive electrode current collector plate 45 (conductive member). The positive electrode current collector plate 45, more precisely, the second positive electrode current collector plate 452 may be provided with a second positive electrode terminal 32 (second electrode terminal). Since the details of the second positive electrode terminal 32 have already been described in the battery 100, a description thereof is omitted here.

In addition, the battery 102 includes a cut portion 451b in the first positive electrode current collector plate 451. When the thermal expansion agent 7 is thermally expanded and the space 51 is deformed, the first positive electrode current collector plate 451 is cut by the cut portion 451b. However, it is easy to bend outward with respect to the space 51.

[Embodiment 4]
A battery 103 according to still another embodiment of the present invention will be described below with reference to FIG. For convenience of explanation, members having the same functions as those described in the embodiment are given the same reference numerals, and descriptions thereof are omitted.

FIG. 8 is a diagram showing the structure of the battery 103. FIG. 8A shows the positional relationship between the space 51 in which the inner bag 71 enclosing the thermal expansion agent 7 is stored, the first positive terminal 31, and the second positive terminal 32 in the battery 103. FIG. FIG. 8B shows an inner bag 71 in which an opening provided in the packing 5 is sandwiched between the battery lid 2 and the positive electrode current collector plate 41 and in which the thermal expansion agent 7 is enclosed. It is sectional drawing which shows having done.

In the battery 103, the thermal expansion agent 7 is placed in an inner bag 71 and stored in a space 51 (thermal expansion agent storage chamber).

The difference between the battery 103 and the battery 100 is that the thermal expansion agent 7 directly stored in the space 51 in the battery 100 is stored in the space 51 after being put in the inner bag 71 in the battery 103. Is a point.

The inner bag 71 is like a capsule used for an automobile airbag or a medicine, and the thermal expansion agent 7 swells and breaks the positive electrode current collector plate 44 while remaining in the inner bag 71. Cut off current. Alternatively, the thermal expansion agent 7 may break the inner bag 71 and expand to increase the pressure in the space 51, thereby interrupting the current.

As a material of the inner bag 71, nylon 66, which is also used for a bag material of an airbag, or a polyamide fiber, a metal such as aluminum that can be formed into a thin thickness (in order to reinforce at least one of hermeticity and chemical resistance, These bag materials may further contain an inner bag), and examples thereof include cellulose and gelatin used as capsule materials.

The battery 103 is more reliable as a battery because the inner bag 71 has a lower possibility of leakage of the thermal expansion agent 7 than the battery 100. That is, the battery 103 can prevent the thermal expansion agent 7 from leaking with higher accuracy by providing the inner bag 71 with the sealing required for the space 51. As the leakage of the thermal expansion agent 7, leakage due to vibration and impact is considered in addition to leakage due to aging and the like, but by placing the thermal expansion agent 7 in the inner bag 71, it is more effective against vibration and impact. Leakage of the thermal expansion agent 7 can be prevented, and the reliability as a battery is improved.

However, the battery 103 requires the inner bag 71 as an additional part, and a process of encapsulating the thermal expansion agent 7 in the inner bag 71 is necessary. Therefore, the manufacturing cost of the battery 103 is higher than the manufacturing cost of the battery 100.

In addition, the battery 103 takes time for the heat of the battery cell 6 to be transmitted to the thermal expansion agent 7 due to the presence of the inner bag 71, and there is a possibility that the response of current interruption is delayed as compared with the batteries 100 to 102. If the thickness of the inner bag 71 is made sufficiently thin or a material having high thermal conductivity is selected, there is almost no influence.

[Embodiment 5]
A battery 104 according to still another embodiment of the present invention will be described below with reference to FIG. For convenience of explanation, members having the same functions as those described in the embodiment are given the same reference numerals, and descriptions thereof are omitted.

FIG. 9 is a diagram showing the structure of the battery 104. FIG. 9A is a plan view showing the positional relationship among the space 51 including the holding chamber 52 in which the thermal expansion agent 7 is sealed, the first positive electrode terminal 31, and the second positive electrode terminal 32 in the battery 104. FIG. In FIG. 9B, a space 51 in which an opening provided in the packing 5 is sandwiched between the battery lid 2 and the positive electrode current collector 41 includes a holding chamber 52 in which the thermal expansion agent 7 is enclosed. FIG.

The battery 104 has a holding chamber 52 in the space 51 (thermal expansion agent storage chamber), and the thermal expansion agent 7 is stored in the holding chamber 52.

The difference between the battery 104 and the battery 100 is that the thermal expansion agent 7 directly accommodated in the space 51 in the battery 100 is put in the holding chamber 52 provided in the space 51 in the battery 104. It is a point.

In the battery 104, it is preferable that the holding chamber 52 is formed in the packing 5 or the positive electrode current collector plate 41 (conductive member), and the holding chamber 52 is formed using this recess.

By providing a holding chamber 52 in the space 51 of the battery 100 and accommodating the thermal expansion agent 7 in the holding chamber 52, when the thermal expansion agent 7 is liquid, there is a risk of leakage due to leaching or the like. Compared to the battery 100, the number is further reduced. That is, since the thermal expansion agent 7 is accommodated in a double-structured room called the holding chamber 52 provided in the space 51, the thermal expansion agent 7 is directly enclosed in the space 51. Compared with the battery 100, the thermal expansion agent 7 can be accommodated more safely. That is, the reliability as a battery is improved.

However, the battery 104 can leak the thermal expansion agent 7 due to vibration and impact as compared with the battery 103 in which the inner bag 71 containing the thermal expansion agent 7 is accommodated in the space 51 (thermal expansion agent accommodation chamber). High nature.

Since the battery 104 needs to form the holding chamber 52, the manufacturing cost of the battery 104 is higher than the manufacturing cost of the battery 100.

In addition, the battery 104 takes time for the heat of the battery cell 6 to be transmitted to the thermal expansion agent 7 by the amount of the holding chamber 52, and the current interruption response may be delayed as compared with the batteries 100 to 102. If the members constituting the holding chamber 52 are made thin, there is almost no influence.

[Embodiment 6]
A battery 105 according to another embodiment of the present invention will be described below with reference to FIG. For convenience of explanation, members having the same functions as those described in the embodiment are given the same reference numerals, and descriptions thereof are omitted.

FIG. 10 is a diagram showing the structure of the battery 105. FIG. 10A shows the positional relationship among the space 51 in which the thermal expansion agent 7 is sealed, the first positive terminal 31, and the second positive terminal 32 in the battery 105, and the second positive terminal 32. It is a top view which shows that the electrically conductive material 34 is connected to. FIG. 10B is a cross-sectional view showing that the conductive material 34 is connected to the second positive terminal 32. The battery 105 shown in FIG. 10B and the battery 100 shown in FIG. 1 are the same except that the conductive material 34 is connected to the second positive terminal 32.

The battery 105 includes a second positive electrode terminal connected to the positive electrode current collector plate 41 in a portion closer to the battery cell 6 than the thin portion 41a (electrically disconnected portion) of the positive electrode current collector plate 41 (conductive member). 32 (second electrode terminal). In the battery 105, the conductive material 34 is connected to the second positive terminal 32.

Since the battery 105 has a structure in which the conductive material 34 electrically connected to the second positive electrode terminal 32 is extended outward, the second positive electrode terminal 32 can be used as an inspection terminal for voltage measurement. it can.

Since the first positive electrode terminal 31 is for energization, when the battery cells 6 are serialized, the first positive electrode terminal 31 is generally covered with an insulating member for the purpose of spark / conduction measures. However, since the second positive terminal 32 is not for energization, it is not necessary to cover it with an insulating member.

As shown in FIG. 10, by making the conductive material 34 electrically connected to the second positive terminal 32 extend outside the battery, even when there is a control circuit or the like above the battery 105 in FIG. The second positive terminal 32 can be used for voltage inspection or the like. Therefore, the workability can be remarkably improved before discharge, maintenance, and emergency discharge.

That is, the battery 105 is suitable for using the second positive terminal 32 for a voltage inspection before shipment or maintenance. In addition, it is easy to access for emergency discharge and workability can be improved.

(Points to remember)
In the batteries 100 to 105, conductive members that are provided along the space 51 (thermal expansion agent storage chamber) that stores the thermal expansion agent 7 and are electrically disconnected when the space 51 is deformed are as follows: A positive electrode current collector plate is used.

However, for the secondary battery according to the embodiment of the present invention, it is not essential to use the positive electrode current collector plate as the conductive member. For example, the negative electrode current collector plate is used as the space 51 (heat You may provide along an expansion | swelling agent storage chamber.

In the batteries 100 to 105, the positive electrode current collector plate (conductive member) forms a part of the wall surrounding the space 51 (thermal expansion agent storage chamber), but the secondary battery according to one embodiment of the present invention is used. For the battery, it is not essential that the conductive member forms part of the wall surrounding the space 51.

For example, the space 51 (thermal expansion agent storage chamber) is formed of a thin film that is thin and stretchable and can transmit heat from the battery cell 6 to the thermal expansion agent 7, and the conductive member is formed along the film. It may be provided.

Furthermore, in the batteries 100 to 105, the conductive member (positive electrode current collector plate) is broken by the thermal expansion of the thermal expansion agent 7, that is, the space 51 (thermal expansion agent accommodation chamber) is destroyed. However, it is not essential for the secondary battery according to one embodiment of the present invention that the space 51 containing the thermal expansion agent 7 is destroyed by the thermal expansion of the thermal expansion agent 7. In the secondary battery according to one embodiment of the present invention, the space 51 containing the thermal expansion agent 7 is deformed by the thermal expansion of the thermal expansion agent 7, and the first positive electrode terminal 31 (the first positive electrode or the negative electrode is the first The electrode) and the battery cell 6 may be electrically disconnected.

Although the absorbent cotton containing 3M Novec ^™ 7200 was used as the thermal expansion agent 7, it is not limited to this, and any solvent that expands at a temperature lower than the boiling point of the electrolytic solution L may be used. As an example of the solvent that expands at a temperature lower than the boiling point of the electrolytic solution L, a fluorine-based flame-retardant low-boiling solvent manufactured by 3M shown in FIG. Since the fluorine-based flame retardant low boiling point solvent manufactured by 3M is flame retardant, has high chemical stability, and has a choice of boiling point, the thermal expansion agent 7 used in the secondary battery according to one embodiment of the present invention Is preferred. The thermal expansion agent 7 may be mixed with an azeotropic mixture such as IPA (isopropyl alcohol) to adjust the boiling point. Furthermore, as the thermal expansion agent 7, a chemical foaming material that thermally decomposes at a temperature lower than the boiling point of the electrolytic solution L may be used instead of the low boiling point solvent. An example is V-60 manufactured by Wako Pure Chemical Industries, which generates N ₂ gas at 65 ° C. FIG. 17 is a table format in which the relationship between an example of a chemical foaming material that can be used as the thermal expansion agent 7 and its gas generation temperature is arranged.

In addition, the space 51 (thermal member) of the positive electrode current collector 41 (conductive member) that is provided along the space 51 (thermal expansion agent storage chamber) and is electrically disconnected when the space 51 is deformed. The area of the portion along the inflating agent storage chamber is desirably 1 cm ² or more.

Furthermore, the size of the secondary battery according to one embodiment of the present invention is desirably 0.16 L or more.

[Summary]
The secondary battery according to the first aspect of the present invention is formed independently of the battery case 1 containing the electrolytic solution L and the battery cell 6 and the region where the electrolytic solution L exists inside the battery case 1. A thermal expansion agent 7 that expands at a temperature lower than the boiling point of the electrolytic solution L is accommodated therein, and a thermal expansion agent accommodating chamber (space 51) that deforms due to thermal expansion of the thermal expansion agent 7 is provided in the battery case 1. The first electrode (first positive electrode terminal 31), which is a positive electrode or a negative electrode, and the battery cell 6 are electrically connected to each other, provided along the thermal expansion agent storage chamber, and the thermal expansion agent storage chamber And a conductive member (positive electrode current collector plate 41) that is electrically disconnected by being deformed.

Here, the deformation of the thermal expansion agent accommodation chamber includes a case where the thermal expansion agent accommodation chamber is destroyed by the thermal expansion of the thermal expansion agent 7 accommodated in the thermal expansion agent accommodation chamber.

Further, in the configuration in which the conductive member is provided along the thermal expansion agent accommodation chamber, the conductive member may constitute a part of the wall surrounding the thermal expansion agent accommodation chamber, for example, the floor surface of the thermal expansion agent accommodation chamber. included.

According to the above configuration, the current interruption mechanism is operated by the thermal expansion agent 7 that expands the volume at a temperature lower than the boiling point of the electrolytic solution L, which is different from the electrolytic solution L. Therefore, the current interrupting mechanism can be reduced in size without being affected by the characteristics of the electrolytic solution L.

Furthermore, especially in the case of a large-sized large-capacity secondary battery, since the value of the current handled is large, a loss due to electrical resistance always occurs even during normal charge / discharge. Loss due to electrical resistance reduces energy efficiency and is accompanied by wasteful heat generation.

When the temperature rises, the electrolytic solution L decomposes or boils, the internal pressure of the battery increases, and the current interruption mechanism that cuts the contact point requires a thin pressure-sensitive part, so that the electrical resistance tends to increase.

On the other hand, since the current interruption mechanism of the secondary battery according to the embodiment of the present invention is operated by the thermal expansion agent 7 instead of the electrolytic solution L, depending on the characteristics of the thermal expansion of the electrolytic solution L. There is no need to make a new design and the degree of freedom in design is great.

Therefore, as shown in the batteries 100 to 105, for example, as a conductive member, a sheet having a large area and sufficient thickness and electrically low resistance is used, and the volume is expanded at a temperature lower than the boiling point of the electrolyte L. It is possible to design a current interruption mechanism that is operated by the thermal expansion agent 7 to be caused. That is, the current interruption mechanism of the secondary battery according to the embodiment of the present invention can be electrically low resistance.

Further, in the case of a current interruption mechanism that operates by decomposition / evaporation (thermal expansion) of the electrolytic solution L, if the operating pressure is specified, a battery that uses the decomposed / evaporated electrolytic solution L is used in a method that guarantees the operating pressure. The overall pressure in the case becomes a problem. Therefore, in a secondary battery having a current interruption mechanism that operates by decomposition / evaporation (thermal expansion) of the electrolyte L, a test for confirming the operating pressure is not a simple destructive test using only the current interruption mechanism. It is enough. On the other hand, since the secondary battery according to the embodiment of the present invention operates with the thermal expansion agent 7 instead of the electrolyte L, the method of guaranteeing reliability is inexpensive.

Furthermore, in the case of a current interruption mechanism that uses the swelling of the battery case, the operating pressure of the safety valve changes due to the operation of the current interruption mechanism. In addition, it is necessary to consider an expansion when assembling the module, and the influence of the safety mechanism is not completed inside the battery case.

On the other hand, the current interruption mechanism of the secondary battery according to the embodiment of the present invention does not use the swelling of the battery case, and even if the current interruption mechanism operates, the operation of the safety valve is unstable. And does not affect the outside of the battery case.

The type of current interruption mechanism that uses bimetal to change the bending method due to the difference in thermal expansion coefficient and cut the contact point may return to the energized state again when the temperature drops after the current interruption mechanism is activated. Lack. In the case of a current interruption mechanism that uses metal displacement due to the pressure of the decomposed / evaporated electrolyte L, it cannot be said that there is no risk of re-conduction, and a mechanism for preventing re-conduction is required, leading to higher costs.

On the other hand, the secondary battery according to one embodiment of the present invention is a positive electrode or a negative electrode, for example, as shown in batteries 100 to 105, by deforming the thermal expansion agent storage chamber and breaking the conductive member. The first electrode (first positive terminal 31) and the battery cell 6 are in an electrically disconnected state. Therefore, the secondary battery according to the embodiment of the present invention is not likely to be re-conducted when the pressure of the decomposed / evaporated electrolyte L changes after the current interruption mechanism is activated.

Further, in the case of a current interruption mechanism that utilizes the change in the internal pressure of the battery due to the decomposition / evaporation (thermal expansion) of the electrolytic solution L, when the pressure of the decomposed / evaporated electrolytic solution L rises at once, It is thought that it becomes very severe to separate the pressure and the operating pressure of the safety valve.

In addition, this type of current interruption mechanism generally requires a thin pressure-sensitive part, and there is a case where the operating pressure of the current interruption mechanism and the operation pressure of the safety valve compete with each other.

On the other hand, in the secondary battery according to the embodiment of the present invention, the thermal expansion agent 7 which expands at a temperature lower than the boiling point of the electrolytic solution L, which is different from the electrolytic solution L, has a battery temperature due to overcharge or the like. Since the current interrupting mechanism operates by expanding when it rises, the operating pressure of the current interrupting mechanism does not compete with the operating pressure of the safety valve. That is, a sufficient margin can be provided between the timing at which the current interrupt mechanism operates and the timing at which the safety valve operates.

A current interrupting mechanism using an element (for example, a PTC thermistor) whose electric resistance increases as the temperature in the battery rises has a limited operating temperature or requires a large element area to interrupt a large current. Yes, not suitable for space saving and cost reduction.

On the other hand, in the secondary battery according to the embodiment of the present invention, the current interruption mechanism can be reduced in size without being affected by the characteristics of the electrolytic solution L.

Furthermore, in the secondary battery according to the second aspect of the present invention, the conductive member (positive electrode current collector 41) has a low strength portion (thin portion 41a) having a relatively low strength, and a thermal expansion agent accommodating chamber. The low-strength portion may be electrically disconnected by deforming the (space portion 51).

According to said structure, since it can manufacture only by providing the thermal expansion agent 7 as an additional component and providing the thin part 41a in the positive electrode current collecting plate 41 with which the conventional secondary battery was equipped, The manufacturing process of a secondary battery provided with a blocking mechanism can be simplified.

Furthermore, the secondary battery according to the third aspect of the present invention has a battery capacity of 10 Ah or more and less than 1000 Ah.

Here, for example, large capacity used in solar power generation systems (including home-use stationary), campers and marine sub-batteries, electric senior cars, electric motorcycles, electric reels, children's electric cars, electric forklifts, acoustic equipment, mobile radio, etc. As secondary batteries, secondary batteries having a battery capacity of 10 Ah or more and less than 1000 Ah are often serially paralleled to obtain a predetermined system battery capacity. Large capacity secondary batteries used as standby batteries in UPS (uninterruptible power supply), disaster prevention / crime prevention systems, emergency lighting equipment, emergency call system equipment, fire fighting equipment, etc. also have a battery capacity of 10 Ah or more, 1000 Ah. In many cases, less than the number of secondary batteries are serially paralleled to obtain a predetermined system battery capacity. The same applies to large-capacity secondary batteries used in EVs such as automobiles and buses. The secondary battery according to one embodiment of the present invention is suitably used for the above example.

A large-capacity secondary battery having a battery capacity of 10 Ah or more and less than 1000 Ah as used in the above example has a large flowing current even when charged at a rated rate. Since the calorific value is proportional to the square of the current (Q = RI ² , Q is the calorific value, R is the internal resistance of the battery), the electrolyte of the large-capacity secondary battery is a secondary battery with a small capacity. Compared to the case, the temperature rises more rapidly. In general, even when the secondary battery is at a temperature lower than the boiling point of the electrolyte, when the battery temperature rises to a temperature at which the self-heating reaction of the electrolyte begins, the oxidative decomposition reaction of the electrolyte proceeds and the battery temperature further rises. There is a tendency to end up.

Therefore, the current interrupting mechanism operates reliably at a predetermined battery temperature such as a temperature at which the self-heating reaction of the electrolyte starts without being affected by the characteristics of the electrolyte, particularly in a large capacity secondary battery. It is desirable that the current interruption mechanism can be miniaturized.

A secondary battery with a battery capacity of less than 10 Ah has a smaller amount of heat generation than a secondary battery with a battery capacity of 10 Ah or more. Therefore, a secondary battery having a battery capacity of less than 10 Ah has a larger room for suppressing thermal runaway by devising a material such as a separator as compared with a secondary battery having a battery capacity of 10 Ah or more.

According to the above configuration, for a secondary battery having a battery capacity of 10 Ah or more and less than 1000 Ah, the current interruption mechanism can be made small and low-cost without being affected by the characteristics of the electrolytic solution.

Furthermore, in the secondary battery according to the third aspect of the present invention, the conductive member (positive electrode current collector plate 44) includes a first conductive member (first positive electrode current collector plate 441) and a second conductive member (second positive electrode). Current collector plate 442) is connected by welding, and the conductive member is disconnected from the welded portion (welded portion 8).

According to said structure, a 1st electrically-conductive member and a 2nd electrically-conductive member isolate | separate more easily by the thermal expansion of a thermal expansion agent, and the electric disconnection of the 1st electrode which is a positive electrode or a negative electrode, and the battery cell 6 is carried out. A state is formed. That is, it is possible to provide a secondary battery in which the current interruption mechanism operates with higher accuracy.

Furthermore, in the secondary battery according to the fourth aspect of the present invention, the conductive member (positive current collector 45) includes a first conductive member (first positive current collector 451) and a second conductive member (second positive electrode). Current collector plate 452) is fitted, and the conductive member is disconnected from the fitting portion when the fitting portion is disengaged.

According to said structure, a 1st electroconductive member and a 2nd electroconductive member isolate | separate more easily by the thermal expansion of a thermal expansion agent, and the electric disconnection of the 1st electrode which is a positive electrode or a negative electrode, and the battery cell 6 is carried out. A state is formed.

Furthermore, since the first conductive member and the second conductive member are connected with a sufficient area, it is possible to provide a secondary battery including a current interruption mechanism with an electrically low resistance.

Furthermore, in the secondary battery according to the fifth aspect of the present invention, the thermal expansion agent 7 may be contained in the inner bag 71 and accommodated in the thermal expansion agent accommodation chamber (space 51).

According to the above configuration, the possibility of leakage of the thermal expansion agent 7 becomes lower, so that the reliability as a battery is higher.

Furthermore, the secondary battery according to the sixth aspect of the present invention has a holding chamber 52 in the thermal expansion agent storage chamber (space 51), and the thermal expansion agent 7 is stored in the holding chamber 52. Also good.

According to the above configuration, the thermal expansion agent can be accommodated more safely by accommodating the thermal expansion agent in the double-structured room. It is even better if the holding chamber is highly airtight.

Furthermore, the secondary battery according to the seventh aspect of the present invention is connected to the conductive member in a portion closer to the battery cell 6 than a portion in which the conductive member (positive electrode current collector plate 45) is electrically disconnected. The second electrode terminal (second positive electrode terminal 32) may be provided.

According to the above configuration, even after the operation of the current interrupting mechanism, that is, the thermal expansion agent 7 thermally expands to form the thermal expansion agent storage chamber (space portion 51), and the conductive provided along the thermal expansion agent storage chamber. Even after the member is electrically disconnected, the battery cell 6 can be forcibly discharged using the second electrode terminal (second positive terminal 32).

The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention. Furthermore, a new technical feature can be formed by combining the technical means disclosed in each embodiment.

The present invention realizes a battery in which an electrode current collector plate breaks due to heat generation of the battery that occurs during overcharging or short-circuiting and cuts off the current. Therefore, the present invention can be widely used for batteries in general, and in particular, a secondary battery. Can be suitably used.

DESCRIPTION OF SYMBOLS 1 Battery case 2 Battery cover 5 Packing 6 Battery cell 7 Thermal expansion agent 8 Welding part (welding part)
21 Safety valve 22 Cap 31 1st positive electrode terminal (1st electrode which is a positive electrode or a negative electrode)
32 Second positive terminal (second electrode terminal)
33 Negative electrode terminal 34 Conductive material 41 Positive electrode current collector plate (conductive member)
41a Thin part (low strength part)
41b Notch part 43 Negative electrode current collecting plate 44 Positive electrode current collecting plate (conductive member)
441 First positive electrode current collector (first conductive member)
441b Cut portion 442 Second positive electrode current collector plate (second conductive member)
45 Positive current collector (conductive member)
451 First positive current collector (first conductive member)
451b Notch 451d Fitting recess (fitting part)
452 Second positive electrode current collector (second conductive member)
452c Fitting convex part (fitting part)
51 Space (thermal expansion agent storage chamber)
52 Holding chamber 71 Inner bag 100 to 105 Battery L Electrolyte

Claims

A battery case containing the electrolyte and battery cells;
A thermal expansion agent that is formed independently of the region where the electrolytic solution is present in the battery case and expands at a temperature lower than the boiling point of the electrolytic solution is contained therein, and the thermal expansion of the thermal expansion agent A deformable thermal expansion agent storage chamber;
The battery cell is electrically connected to a first electrode, which is a positive electrode or a negative electrode, provided in the battery case, provided along the thermal expansion agent storage chamber, and the thermal expansion agent storage chamber is deformed. A conductive member that is electrically disconnected; and
A secondary battery comprising:
2. The conductive member according to claim 1, wherein the conductive member has a low-strength portion having a relatively low strength, and the low-strength portion is electrically disconnected when the thermal expansion agent storage chamber is deformed. The secondary battery as described.
The secondary battery according to claim 1, wherein the thermal expansion agent is contained in an inner bag and is accommodated in the thermal expansion agent accommodation chamber.
There is a holding chamber in the thermal expansion agent storage chamber,
The secondary battery according to claim 1, wherein the thermal expansion agent is accommodated in the holding chamber.
5. The device according to claim 1, further comprising a second electrode terminal connected to the conductive member at a portion closer to the battery cell than a portion of the conductive member that is electrically disconnected. The secondary battery according to item 1.