JP7236031B2 - sealed battery - Google Patents

Description

The present invention relates to sealed batteries.

A sealed battery in which an electrode body and an electrolyte are housed in a case is known. A sealed battery may generate gas in the case. If the generated gas increases the internal pressure of the case, the case may be deformed or damaged. Furthermore, in sealed batteries, multiple types of gases may be generated in the case. Therefore, it is desirable to suppress the rise in the internal pressure of the case by discharging each of the plurality of types of gas to the outside of the case. For example, in a sealed battery disclosed in Patent Document 1, an electrode assembly and an electrolytic solution are accommodated in a case. The case is provided with electrode terminals that are connected to an external device. The electrode terminal includes a collector member and a sealing member. The sealing member is made of gas permeable resin. A gas conversion catalyst is disposed within the case. The gas conversion catalyst converts an impermeable gas, which is difficult to permeate the gas-permeable resin, into a permeable gas, which is easy to permeate the gas-permeable resin, among the gases generated in the case.

JP 2018-152164 A

In the conventional sealed battery described above, it is difficult to improve the energy density because a space is required in the case for arranging the gas conversion catalyst. Also, there is the cost of using a gas conversion catalyst. Therefore, regardless of the presence or absence of a gas conversion catalyst, it is desirable to discharge each of the multiple types of gases generated within the case to the outside of the case.

A typical object of the present invention is to provide a sealed battery capable of appropriately discharging each of a plurality of types of gases generated within the case to the outside of the case.

In order to achieve such an object, a sealed battery of one embodiment disclosed herein is formed of a case containing an electrode assembly and an electrolyte, and a gas-permeable polymer material. a plurality of sealing portions for sealing gaps, wherein the plurality of sealing portions includes a first sealing portion and a second sealing portion; the first sealing portion includes a second sealing portion; The second sealing portion is formed of a material having a higher permeability to one gas than the material of the second sealing portion, and the second sealing portion has a permeability to a second gas different from that of the first gas. characterized by being made of a material higher than the material of Here, both the first gas and the second gas are types of gas that can be generated inside the case of the sealed battery.

In such a sealed battery, the first sealing portion allows the first gas to pass through more than the second sealing portion, and the second sealing portion allows the second gas different from the first gas to pass through the first sealing portion. permeate more than As a result, regardless of the presence or absence of the gas conversion catalyst, each of the multiple types of gas generated within the case can be appropriately discharged outside the case.

1 is a longitudinal sectional view showing the configuration of a sealed battery 1; FIG. 2 is a vertical cross-sectional view of the vicinity of the positive electrode internal terminal of the sealed battery 1 shown in FIG. 1. FIG. 4 is a graph showing measurement results of case internal pressure in the first test example. 7 is a graph showing measurement results of case internal pressure in the second test example.

One typical embodiment of the present disclosure will be described in detail below with reference to the drawings. Matters other than those specifically referred to in this specification that are necessary for implementation can be grasped as design matters for those skilled in the art based on the prior art in the relevant field. The present invention can be implemented based on the contents disclosed in this specification and common general technical knowledge in the field. In the drawings below, members and portions having the same function are denoted by the same reference numerals. Also, the dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect the actual dimensional relationships.

As used herein, the term “battery” is a general term for power storage devices from which electrical energy can be extracted, and is a concept that includes primary batteries and secondary batteries. "Secondary battery" generally refers to an electricity storage device that can be repeatedly charged and discharged, and includes so-called storage batteries (ie, chemical batteries ) such as lithium ion secondary batteries, nickel-hydrogen batteries, and nickel-cadmium batteries. Hereinafter, the sealed battery according to the present disclosure will be described in detail by taking a lithium ion secondary battery as an example. However, the sealed battery according to the present disclosure is not intended to be limited to those described in the following embodiments.

An overall configuration of a sealed battery 1 according to the present disclosure will be described with reference to FIG. A sealed battery 1 illustrated in FIG. 1 is a lithium ion secondary battery, and includes a case 2, an electrode body 3, and an electrolytic solution 35 that is an example of an electrolyte. The case 2 accommodates the electrode assembly 3 and the electrolytic solution 35 in a hermetically sealed state. The shape of the case 2 in this embodiment is a flat square. The case 2 includes a box-shaped main body 21 having an opening at one end and a plate-like lid member 22 that closes the opening of the main body 21 . The main body 21 and the lid member 22 are integrated by welding or the like. As the material of the case 2, for example, a metal material such as aluminum which is lightweight and has good thermal conductivity can be used. As an example, the electrode body 3 in the present embodiment uses a wound electrode body in which a long positive electrode body, a negative electrode body, and a separator are superimposed and wound. A non-aqueous electrolyte containing a lithium salt is used as the electrolyte 35 in this embodiment.

The shape of the lid member 22 in the case 2 is a rectangular plate. A pair of electrode terminal members 4 (a positive electrode terminal member 4A and a negative electrode terminal member 4B) are provided at both ends of the lid member 22 in the longitudinal direction (horizontal direction in FIG. 1). Specifically, a positive electrode terminal member 4A is provided at one longitudinal end (left end in FIG. 1) of the lid member 22, and a negative electrode terminal member 4B is provided at the other longitudinal end (right end in FIG. 1). It is

The positive terminal member 4A includes a positive connecting terminal 5A, a positive external terminal 6A, a positive internal terminal 7A, and a positive collector terminal 8A. The positive electrode connection terminal 5A is arranged outside the case 2 and serves as an external connection terminal on the positive electrode side. The positive external terminal 6A is arranged outside the case 2 and connected to the positive connecting terminal 5A and the positive internal terminal 7A. The positive electrode internal terminal 7A is arranged inside the case 2 and connected to the positive electrode external terminal 6A through a through hole 23A (see FIG. 2) provided in the case 2 . The positive collector terminal 8A is connected inside the case 2 to the positive electrode 3A of the electrode body 3 and the positive electrode internal terminal 7A.

The negative terminal member 4B includes a negative connecting terminal 5B, a negative external terminal 6B, a negative internal terminal 7B, and a negative collector terminal 8B. The negative connection terminal 5B is arranged outside the case 2 and serves as an external connection terminal on the negative electrode side. The negative external terminal 6B is arranged outside the case 2 and connected to the negative connecting terminal 5B and the negative internal terminal 7B. The negative internal terminal 7B is arranged inside the case 2 and connected to the negative external terminal 6B through a through hole provided in the case 2 . The negative collector terminal 8B is connected to the negative electrode 3B of the electrode body 3 and the negative electrode internal terminal 7B inside the case 2 . Each member constituting the positive electrode terminal member 4A and the negative electrode terminal member 4B is appropriately formed of a metal or the like having high conductivity.

The configuration of the electrode terminal member 4 in the vicinity of the positive internal terminal 7A and the negative internal terminal 7B in the sealed battery 1 will be described with reference to FIG. The structures of the positive electrode internal terminal 7A and the negative electrode internal terminal 7B in this embodiment are formed in a substantially symmetrical structure with the center in the longitudinal direction of the sealed battery 1 as the center. Therefore, the configuration near the positive internal terminal 7A will be described in detail below, and the detailed description of the configuration near the negative internal terminal 7B will be omitted.

The positive electrode external terminal 6A, the lid member 22 of the case 2, and the sealing portion 9 are provided in the vicinity of the positive electrode internal terminal 7A. The external shape of the positive electrode external terminal 6A is a stepped shape formed by bending a plate-like member (see FIG. 1). A through hole 62A through which the positive electrode internal terminal 7A is inserted is formed in the positive electrode external terminal 6A.

The sealing portion 9 is made of a polymer material having gas permeability, and seals a gap from the inside of the case 2 to the outside. The sealing portion 9 of this embodiment includes an insulating portion 91 and a sealing portion 92 . The insulating portion 91 is arranged between the positive electrode external terminal 6</b>A and the lid member 22 . The insulating portion 91 is made of an insulating material. A through hole 911 through which the positive electrode internal terminal 7A is inserted is formed in the insulating portion 91 . The case 2 (in this embodiment, the lid member 22 of the case 2) is provided with a through hole 23A through which the positive electrode internal terminal 7A is inserted.

The positive electrode internal terminal 7A includes a large diameter portion 71A, a rivet 75A, and a crimped portion 76A. The large diameter portion 71A is formed in a substantially plate shape (substantially disk shape in this embodiment). The rivet 75A is columnar (columnar in this embodiment) and extends vertically (upward in FIG. 2) from the plate surface of the large-diameter portion 71A. The diameter of the rivet 75A is smaller than the diameter of the large diameter portion 71A. The rivet 75A is inserted through the through hole 23A provided in the case 2 from the inside (lower side in FIG. 2) to the outside (upper side in FIG. 2). The crimped portion 76A is formed by crimping the tip portion (upper end portion in FIG. 2) of the rivet 75A from the outside.

A seal portion 92 is sandwiched between the positive electrode internal terminal 7A and the inner surface 25A of the case 2 (the lid member 22 in this embodiment). The seal portion 92 is made of a material having elasticity, insulation, and electrolyte resistance. The sealing portion 92 is compressed between the positive electrode internal terminal 7A and the inner surface 25A of the case 2 to seal between them. Moreover, the sealing portion 92 insulates between the positive electrode internal terminal 7A and the case 2 . The seal portion 92 includes a substantially flat plate-shaped base portion in which a through hole is formed, and a cylindrical portion that protrudes outward from the case 2 from the peripheral portion of the through hole. The tubular portion of the seal portion 92 is fitted into the through hole 23A provided in the lid member 22 .

In the sealed battery 1 according to this embodiment, the sealing portion 9 (the insulating portion 91 and the sealing portion 92) is made of gas permeable resin. The gas-permeable resin can be appropriately selected according to the type of gas that is mainly generated within the case 2 during charging and discharging. The sealed battery 1 is provided with a plurality of sealing portions including a first sealing portion and a second sealing portion. For example, in the present embodiment, the sealed battery 1 is provided with a first sealing portion and a second sealing portion. Specifically, a sealing portion 9 is provided in the vicinity of the positive electrode internal terminal 7A as a first sealing portion. The second sealing portion is provided near the negative electrode internal terminal 7B. The second sealing portion is made of a polymeric material, like the sealing portion 9 (first sealing portion). In this embodiment, the second sealing portion includes an insulating portion and a sealing portion, like the sealing portion 9 (first sealing portion). The second sealing portion may have a shape different from that of the sealing portion 9 (first sealing portion).

The first sealing portion is made of a material having a higher permeability to the first gas than the material of the second sealing portion. The second sealing portion is formed of a material having a higher permeability to the second gas, which is different from the first gas, than the material of the first sealing portion. Therefore, in the sealing portion 9 (first sealing portion) provided near the positive electrode internal terminal 7A and the sealing portion (second sealing portion) provided near the negative electrode internal terminal 7B, the first gas and the permeability of the second gas are different. For example, the first gas and the second gas may be multiple types of gases that may be generated within the case 2 (for example, carbon dioxide (CO ₂ ), carbon monoxide (CO), methane (CH ₄ ), ethane (C ₂ H ₆ ), etc.).

By using the sealing portion, a gas discharge path P is formed in the sealing portion. A predetermined gas inside the case 2 is discharged to the outside of the case 2 through the gas discharge path P. The gas permeation rate in the sealed portion can be calculated, for example, based on the following formula. The "gas permeability coefficient" in the following formula can be calculated based on the differential pressure method based on JIS K7126.
Permeation rate = gas permeability coefficient x pressure difference x (cross-sectional area of sealing member/length of gas discharge path)
Thus, in the sealed battery 1, the first sealing portion allows the first gas to permeate and is discharged to the outside of the case 2, and the second sealing portion allows the second gas different from the first gas. is permeated and discharged to the outside of the case 2. Thereby, the sealed battery 1 can appropriately discharge each of the plurality of types of gases generated within the case 2 to the outside of the case regardless of the presence or absence of the gas conversion catalyst.

For example, in a lithium-ion secondary battery, CO ₂ is mainly generated due to the SEI film formation reaction during charging and discharging. In addition, CO may be generated during charging and discharging. In this case, the first sealing portion is made of a material having a higher _CO2 permeability than the material of the second sealing portion, and the second sealing portion is made of a material having a higher CO2 permeability than the first sealing portion. It may be made of a material higher than the Examples of resins that preferably permeate CO ₂ gas include polyolefin resins such as polyethylene and polypropylene, and fluorine resins such as perfluoroalkoxyalkane (PFA) and polytetrafluoroethylene (PTFE). The first sealing portion may be formed from any one of these resin materials. A second sealing portion may be formed.

Next, test results using the first test example and the second test example will be described with reference to FIGS. 3 and 4. FIG. In the first test example, two types of sealing portions, a first sealing portion and a second sealing portion, were used. Specifically, the electrode terminal member was produced by using the first sealing portion for one of the sealing portion near the positive electrode internal terminal and the sealing portion near the negative electrode internal terminal, and using the second sealing portion for the other. The prepared electrode terminal member was attached to an empty case in which no electrode body and electrolytic solution were contained to prepare a test pack. The case of the test pack was connected to a gas supply device, and two kinds of gases (first gas and second gas) were introduced into the case from the gas supply device at predetermined flow rates. Here, the inflow velocity of the second gas was set to 0.8 times the inflow velocity of the first gas. Regarding the first sealing portion, the permeability of the first gas was five times the permeability of the second gas. Regarding the second sealing portion, the transmittance of the second gas was five times the transmittance of the first gas.

In the second test example, one type of sealing portion similar to the first sealing portion was used. In Test Example 2, an electrode terminal member was produced using the first sealing portion as one of the sealing portion near the positive electrode internal terminal and the sealing portion near the negative electrode internal terminal. As in the first test example, the prepared electrode terminal member was attached to an empty case to prepare a test pack. Also in the test pack of the second test example, two kinds of gases (first gas and second gas) were introduced into the case in the same manner as in the first test example.

As described above, gas was introduced into the test pack of the first test example and the test pack of the second test example, and the internal pressure increase rate of the case was examined by measuring the case internal pressure of each test pack. FIG. 3 shows the internal pressure increase rate of the case internal pressure in the first test example, and FIG. 4 shows the measurement result of the internal pressure increase rate of the case internal pressure in the second test example.

In FIG. 3, N1 indicates the internal pressure of the entire gas introduced into the test pack when the test pack is sealed without using a sealing portion. On the other hand, N2 indicates the internal pressure of the test pack in the first test example. In the first test example, the internal pressure initially increased during the introduction of the two types of gases, but the internal pressure gradually decreased.

In FIG. 4, N1 indicates the internal pressure of the entire gas introduced into the test pack when the test pack is sealed without using a sealing portion, as in FIG. On the other hand, N3 indicates the internal pressure of the test pack in the second test example. In the second test example, the internal pressure gradually decreased after the internal pressure increased while the two types of gases were being introduced. However, in the second test example, the decrease speed of the internal pressure was slower than in the first test example.

From the measurement results of the internal pressure increase rates for the first test example and the second test example, the test pack of the first test example showed a faster decrease speed of the internal pressure than the test pack of the second test example. As a result, it was confirmed that the test pack of the first test example was able to discharge the gas inside the case to the outside of the case more appropriately than the test pack of the second test example. From this, it is considered that in the test pack of the first test example, both of the two types of gases inside the case could be appropriately discharged to the outside of the case.

The technology disclosed in the above embodiment is merely an example. Therefore, it is also possible to modify the techniques exemplified in the above embodiments. For example, in the above embodiment, the first sealing portion (sealing portion 9) is provided near the positive electrode internal terminal 7A, and the second sealing portion is provided near the negative electrode internal terminal 7B. However, the arrangement positions of the first sealing portion and the second sealing portion are not limited as long as each of the first sealing portion and the second sealing portion seals the gap communicating from the inside of the case 2 to the outside. For example, at least one of the first sealing portion and the second sealing portion may be arranged at a position other than the vicinity of the electrode internal terminals (the positive electrode internal terminal 7A and the negative electrode internal terminal 7B). For example, the case 2 may be provided with an injection port for supplying the electrolytic solution to the inside of the case 2, and at least one of the first sealing portion and the second sealing portion may be arranged in the injection port. For example, when the sealing portion is arranged at a position other than the vicinity of the electrode internal terminals (the positive electrode internal terminal 7A and the negative electrode internal terminal 7B), the sealing portion may be formed of a polymer material having gas permeability. , and may not have properties such as insulating properties.

In the above embodiment, the first sealing portion and the second sealing portion are arranged at separated positions. However, the first sealing portion and the second sealing portion may be arranged adjacent to each other. In the above-described embodiment, an example in which the sealed battery 1 is provided with two sealing portions, the first sealing portion and the second sealing portion, is shown. However, the sealed battery 1 may be provided with three or more sealing portions.

1 sealed battery 2 case 3 electrode body 9 sealing part

Claims (1)

an electrode body having a positive electrode and a negative electrode;
an electrolyte;
a case having a plurality of through holes and containing the electrode body and the electrolyte;
a positive electrode internal terminal having a large-diameter portion electrically connected to the positive electrode inside the case and a cylindrical rivet inserted through the through hole, a portion of which is exposed to the outside of the case;
a positive electrode external terminal disposed outside the case and connected to the positive electrode internal terminal;
a negative electrode internal terminal having a large-diameter portion electrically connected to the negative electrode inside the case and a cylindrical rivet inserted through the through hole, a portion of which is exposed outside the case;
a negative electrode external terminal disposed outside the case and connected to the negative electrode internal terminal;
a plurality of sealing portions each formed of a polymer material having gas permeability and sealing the plurality of through-holes ;
A sealed battery comprising
The plurality of sealing portions includes a first sealing portion that seals the through hole through which the positive electrode internal terminal is inserted, and a second sealing portion that seals the through hole through which the negative electrode internal terminal is inserted. and contains
The first sealing portion is
An insulating portion for insulating the outer surface of the case from the positive electrode external terminal, a base portion for insulating the inner surface of the case from the large diameter portion of the positive electrode internal terminal, and the through hole through which the positive electrode internal terminal is inserted. a seal portion having a cylindrical portion that is fitted to insulate the case and the rivet of the positive electrode internal terminal;
made of a material having a higher permeability to the first gas than the material of the second sealing portion,
configured to permeate the first gas and discharge it to the outside of the case,
The second sealing portion is
An insulating portion for insulating the outer surface of the case from the negative electrode external terminal, a base portion for insulating the inner surface of the case from the large diameter portion of the negative electrode internal terminal, and the through hole through which the negative electrode internal terminal is inserted. a seal portion having a cylindrical portion that is fitted to insulate the case and the rivet of the negative electrode internal terminal;
made of a material having a higher permeability to a second gas different from the first gas than the material of the first sealing part,
configured to permeate the second gas and discharge it to the outside of the case,
The sealed battery, wherein the first gas and the second gas are both types of gases that can be generated inside the case of the sealed battery.

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