Patent Application
20240021885
Embodiments of the present invention relate to a bipolar storage battery.
In recent years, the number of power generation facilities using natural energy such as sunlight and wind power has been increasing. In such a power generation facility, an amount of power generation cannot be controlled. Thus, a power load is leveled using a storage battery. That is, when the amount of power generation is larger than consumption, a difference is charged into the storage battery, and when the amount of power generation is smaller than consumption, a difference is discharged from the storage battery. As the above-described storage battery, a lead-acid battery is frequently used for economic efficiency, safety, and the like.
In such a lead-acid battery, a substrate (also called a bipolar plate) made of resin is provided inside a frame (also called a rim) made of resin having a picture frame shape, for example, and a positive lead layer and a negative lead layer are disposed on one surface and an other surface of the substrate. A positive active material layer is adjacent to the positive lead layer. A negative active material layer is adjacent to the negative lead layer. In addition, a glass mat (also called an electrolytic layer) containing an electrolytic solution is disposed inside a spacer made of resin having a picture frame shape. A plurality of the frames and a plurality of the spacers are alternately stacked and assembled.
Furthermore, the positive lead layer and the negative lead layer are directly joined in a plurality of perforations formed in the substrate. That is, the lead-acid battery is a bipolar lead-acid battery in which a plurality of the substrates each having the perforations (also called communication holes) that allow the one surface side and the other surface side to communicate with each other and a plurality of cell members are alternately stacked. Each of the cell members includes a positive pole in which the positive active material layer is provided on the positive lead layer, a negative pole in which the negative active material layer is provided on the negative lead layer, and the electrolytic layer interposed between the positive pole and the negative pole. The positive lead layer of one cell member and the negative lead layer of another cell member enter the inside of the perforations of the substrate to be joined together. Thereby, the cell members are connected in series.
Here, to join the frame and the spacer together, for example, welding using ultrasonic waves is performed as described in JP Patent Application No. 6571091 B2. In addition, the bipolar storage battery is configured by being accommodated in an exterior case so that no stress is applied to a joined portion from the outside.
To keep hermeticity and mechanical strength with such a configuration, however, the number of components constituting the bipolar storage battery may increase because it is necessary to use other components to reinforce the strength in joining in some cases, for example. On the other hand, if the number of components is reduced blindly, a problem may occur, such as leakage of an electrolytic solution to the outside of the battery due to insufficient mechanical strength against external stress.
An object of the present invention is to provide a bipolar storage battery that can prevent outward leakage of an electrolytic solution and reduction of mechanical strength by strongly joining plates each holding a cell member, thereby ensuring hermeticity of the inside of a cell and the mechanical strength, and also making the bipolar storage battery compact while reducing the number of components.
A bipolar storage battery according to an embodiment of the present invention includes an internal frame unit including a bipolar plate in which a positive pole is provided on one surface and a negative pole is provided on an other surface, and an internal rim provided in an outer edge of the bipolar plate. The bipolar storage battery also includes an end frame unit including an end plate constituting a cell in conjunction with the bipolar plate facing the end plate, and an end rim provided in an outer edge of the end plate. A plurality of the internal frame units are stacked, and the end frame unit is provided in each of opposite ends along a direction in which the internal frame units are stacked. Adjacent internal rims of the internal rims are welded to each other, and one of the internal rims and the end rim adjacent to each other are welded to each other. A ratio of a value of a width of the internal rim or the end rim to a value indicating a depth of welding between the rims is between 2.7 times and 16.0 times, inclusive.
According to implementations of the present invention, because the plates each holding a cell member can be strongly joined together, it is possible to provide the bipolar storage battery that can prevent outward leakage of an electrolytic solution and reduction of mechanical strength, thereby ensuring hermeticity of the inside of a cell and the mechanical strength, and also making the bipolar storage battery compact while reducing the number of components.
Specifically, when the internal frame unit and the end frame unit are welded and stacked, the ratio of the value of a width L1 of the internal rim or the end rim to the value indicating the depth of welding is between 2.7 times and 16.0 times, inclusive. By performing joining at such a ratio, the internal frame unit and the end frame unit are strongly joined together. Therefore, it is possible to prevent the outward leakage of the electrolytic solution and the reduction of the mechanical strength to ensure the hermeticity of the inside of the cell and the mechanical strength.
In addition, because the hermeticity and mechanical strength of the bipolar storage battery can be ensured by using only required constituent elements for constituting the bipolar storage battery, it is possible to make the bipolar storage battery compact while reducing the number of components.
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Note that the embodiment described below illustrates an example of the present invention. Various changes or improvements can be added to the present embodiment, and a mode to which such changes or improvements are added can also be included in the present invention. This embodiment and modifications thereof are included in the scope and gist of the invention and are included in the scope of the invention described in the claims and its equivalents. Note that, hereinafter, a lead-acid battery will be described as an example from among various storage batteries.
A bipolar lead-acid battery according to an embodiment of the present invention will be described with reference to
The bipolar lead-acid battery 1 illustrated in
A plurality of the internal frame units 11 is stacked between the first end frame unit 12 and the second end frame unit 13 to form the bipolar lead-acid battery 1 having, for example, a substantially rectangular parallelepiped shape. The number of internal frame units 11 to be stacked is set such that the storage capacity of the bipolar lead-acid battery 1 has a desired numerical value.
In addition, a negative terminal 107 is fixed to the first end frame unit 12, and a negative pole 110 and the negative terminal 107 fixed to the first end frame unit 12 are electrically connected. On the other hand, a positive terminal 108 is fixed to the second end frame unit 13, and a positive pole 120 and the positive terminal 108 fixed to the second end frame unit 13 are electrically connected.
Each of the internal frame units 11 includes a substrate (hereinafter, such a substrate is appropriately referred to as a bipolar plate 111) having a rectangular planar shape in which a positive pole 120 is provided on one surface and a negative pole 110 is provided on an other surface, and includes an internal rim 112 having, for example, a quadrangular frame shape (picture frame shape) provided in an outer edge of the bipolar plate 111.
The bipolar plate 111 of each of the internal frame units 11 is arranged between cell members 130 adjacent in a stacking direction (vertical direction in
The bipolar plate 111 is integrated with the inside of each of the internal rims 112. In addition, the bipolar plate 111 is positioned in the middle of the internal rim 112 in a thickness direction (vertical direction in
The internal frame unit 11 is formed of a thermoplastic resin (e.g., polyethylene, polypropylene, polystyrene, polyvinyl chloride, polymethyl methacrylate (acrylic resin), acrylonitrile-butadiene-styrene copolymer (ABS), polyamide (nylon), or polycarbonate). These thermoplastic resins are excellent in moldability and in sulfuric acid resistance. Hence, for example, even when an electrolytic solution contacts the bipolar plate 111, decomposition, deterioration, corrosion, and the like hardly occur in the bipolar plate 111.
The bipolar plate 111 is provided with a communication hole (not illustrated) that allows the one surface and the other surface to communicate with each other. A positive lead layer 101 and a negative lead layer 102 are joined via the inside of the communication hole so that they are electrically connected to each other. Thus, conduction between the positive pole 120 and the negative pole 110 is achieved.
The positive pole 120 includes the positive lead layer 101 made of lead or a lead alloy and arranged on the one surface of the bipolar plate 111, and a positive active material layer 103 arranged on the positive lead layer 101. This positive lead layer 101 is bonded to the one surface of the bipolar plate 111 by an adhesive layer (not illustrated) such as an adhesive provided between the one surface of the bipolar plate 111 and the positive lead layer 101. Accordingly, the adhesive layer, the positive lead layer 101, and the positive active material layer 103 are stacked in this order on the one surface (in the drawings such as
The negative pole 110 includes the negative lead layer 102 made of lead or a lead alloy and arranged on the other surface (in the drawings such as
The first end frame unit 12 includes a first end plate 121 having a rectangular planar shape, and a first end rim 122 having, for example, a quadrangular frame shape (picture frame shape) provided in an outer edge of the first end plate 121. The first end plate 121 is integrated with the inside of the first end rim 122. The first end frame unit 12 is also made of a thermoplastic resin having sulfuric acid resistance.
The first end frame unit 12 surrounds a side surface and the negative pole 110 side of the cell member 130 at one end side (lower end side in
The first end plate 121 is arranged in parallel with the bipolar plate 111 of the internal frame unit 11. The first end rim 122 is arranged to be in contact with the internal rim 112 of the internal frame unit 11 positioned adjacent thereto. That is, the first end rim 122 includes a joining surface 122a facing the internal rim 112 of the internal frame unit 11 in the stacking direction (vertical direction in
The first end plate 121 has a larger thickness than the thickness of the bipolar plate 111. The first end rim 122 has a larger thickness than the thickness of the first end plate 121. The first end plate 121 is positioned at one end (lower end in
A negative lead layer 102 is provided on an other surface of the first end plate 121. A negative active material layer 104 is provided on the negative lead layer 102 on the first end plate 121. Between the negative active material layer 104 on the first end plate 121 and the positive active material layer 103 of the bipolar plate 111 facing the negative active material layer 104, an electrolytic layer 105 is provided that is made of a glass fiber mat or the like impregnated with an electrolytic solution such as sulfuric acid.
The second end frame unit 13 includes a second end plate 131 having a rectangular planar shape, and a second end rim 132 having, for example, a quadrangular frame shape (picture frame shape) provided in an outer edge of the second end plate 131. The second end plate 131 is integrated with the inside of the second end rim 132. The second end frame unit 13 is also made of a thermoplastic resin having sulfuric acid resistance.
The second end frame unit 13 surrounds a side surface and the positive pole 120 side of the cell member 130 at an other end side (upper end side in
The second end plate 131 is arranged in parallel with the bipolar plate 111 of the internal frame unit 11. The second end rim 132 is arranged to be in contact with the internal rim 112 of the internal frame unit 11 positioned adjacent thereto. That is, the second end rim 132 includes a joining surface 132a facing the internal rim 112 of the internal frame unit 11 in the stacking direction (vertical direction in
The second end plate 131 has a larger thickness than the thickness of the bipolar plate 111. The second end rim 132 has a larger thickness than the thickness of the second end plate 131. The second end plate 131 is positioned at an other end (upper end in
A positive lead layer 101 is provided on one surface of the second end plate 131. A positive active material layer 103 is provided on the positive lead layer 101 on the second end plate 131. Between the positive active material layer 103 on the second end plate 131 and the negative active material layer 104 of the bipolar plate 111 facing the positive active material layer 103, an electrolytic layer 105 as described is provided.
In the bipolar lead-acid battery 1 having such a configuration, as described above, the bipolar plate 111, the positive lead layer 101, the positive active material layer 103, the negative lead layer 102, and the negative active material layer 104 constitute a bipolar electrode 140. The bipolar electrode 140 is an electrode having both positive and negative pole functions in one electrode. The bipolar lead-acid battery 1 of the embodiment of the present invention has a battery configuration in which the plurality of cell members 130 each formed by interposing the electrolytic layer 105 between the positive pole 120 and the negative pole 110 are alternately stacked and assembled to connect the cell members 130 in series.
The above-described cell members 130 are arranged to be stacked at intervals in the stacking direction (vertical direction in
The cell members 130 adjacent in the stacking direction are electrically connected in series. Therefore, the bipolar plate 111 interposed between the cell members 130 adjacent in the stacking direction includes the above-described communication hole for electrically connecting the positive lead layer 101 and the negative lead layer 102.
In addition, the joining surfaces 112a of the internal rims 112 of the internal frame units 11 adjacent to each other, the joining surface 122a of the first end rim 122 of the first end frame unit 12 and the joining surface 112a of the internal rim 112 of the internal frame unit 11 adjacent thereto, and the joining surface 132a of the second end rim 132 of the second end frame unit 13 and the joining surface 112a of the internal rim 112 of the internal frame unit 11 adjacent thereto are welded and joined to each other.
Here, for example, various welding methods such as vibration welding, ultrasonic welding, and hot plate welding can be adopted as a method of welding. Among the welding methods, vibration welding is performed by vibrating surfaces to be joined while pressurizing the surfaces at the time of joining. Vibration welding has a fast cycle of welding and good reproducibility. Therefore, vibration welding is more preferably used.
Here,
Specifically, during the vibration welding that is performed to join together the joining surfaces 112a of the internal rims 112 of the internal frame units 11 adjacent to each other, one of the joining surfaces 112a is pressed against the other joining surface 112a and vibrated to generate frictional heat, so that the one joining surface 112a and the other joining surface 112a are melted and joined together. Furthermore, in the present embodiment, a value of a depth of welding in the vibration welding is set such that the following relationship is established between the depth of welding and a width of each of the internal rims 112.
Here, the depth of welding will be described with reference to
From this state, while both the upper member and the lower member are being pressurized in a vertical direction, the member(s) is(are) vibrated. Note that the member(s) to be vibrated may be the upper member, the lower member, or both the upper member and the lower member. As indicated by an arrow in
In this manner, joining surfaces of the upper member and the lower member melt to be joined together. Therefore, as illustrated in
That is, a ratio of a value L1 of a width of each of the internal rims 112 or the first end rim 122 and the second end rim 132 (hereinafter, when the first end rim 122 and the second end rim 132 are collectively referred to, the rims are referred to as “end rims”) to the value w indicating the depth of welding between the adjacent rims is set to be between 2.7 times and 16.0 times, inclusive.
This ratio is one of the conditions to be set when the vibration welding is performed. If this ratio is outside of the above range, it is difficult to obtain sufficient welding strength.
The above ratio is a value that can be derived by performing a tensile test and calculating a tensile strength retention rate from unwelded breaking strength. Specifically, after samples for performing the tensile test were prepared, each sample was pulled using a tensile testing machine so that a strain rate obtained by dividing a tensile rate by a gauge length was 0.285 mi−1, and the strength was obtained by calculating a cross-sectional area from a tensile breaking force. The ratio of the value L1 of the width of each of the internal rims 112 or the end rims to the value w indicating the depth of welding between the adjacent rims described above is a value where the retention rate is equal to or higher than 80%.
A specific example is shown in Table 1 below. In Table 1, the left column shows the ratio of the value L1 of the rim width to the value w indicating the depth of welding, that is, the rim width (L1)/the depth of welding (w). On the other hand, the right column shows the tensile strength retention rate (%) corresponding to each of the above ratios.
According to Table 1, the ratio of the value of the rim width to the value w indicating the depth of welding where the tensile strength retention rate (%) exceeds 80% is between 2.7 times and 16.0 times, inclusive. In addition,
In addition, here, the ratio of the value L1 of the width of each of the internal rims or the end rims to the value w indicating the depth of welding is between 2.7 times and 16.0 times, inclusive, but it is particularly preferable that the depth of welding be set such that the ratio is between 2.7 times and 8.0 times, inclusive.
This ratio is applied not only to the case of welding joining between the internal rims 112 of the internal frame units 11, but also to the case of welding joining between the internal rim 112 and the first end rim 122 constituting the first end frame unit 12, and to the case of welding joining between the internal rim 112 and the second end rim 132 constituting the second end frame unit 13.
In addition, for the value L1 of the width of each of the internal rims 112 or the end rims, a relationship with the thickness of the bipolar plate 111 can be further taken into consideration. Here, the thickness of the bipolar plate 111 is a value indicated by reference character L2 in
Table 2 below shows a relationship between such a ratio of the value L1 of the width of the internal rim 112 to the value L2 indicating the thickness of the bipolar plate 111, and the tensile strength retention rate (%).
In Table 2, the left column shows the ratio of the value L1 of the width of the internal rim 112 to the value L2 indicating the thickness of the bipolar plate 111, that is, L1/L2. On the other hand, the right column shows the tensile strength retention rate (%) corresponding to each of the above ratios. As shown in Table 2, the tensile strength retention rate (%) has a value exceeding 80% when the above ratio is between 2.0 times and 3.5 times, inclusive.
Table 2 is represented as a graph in
It is not preferable that the above ratio is higher than 3.5 times because the strength is easily reduced, and it is not preferable that the above ratio is lower than 2.0 times because it is difficult to dissipate heat. On the other hand, when the above ratio is between 2.0 times and 3.5 times, inclusive, it is possible to achieve weight reduction and size reduction while reducing a decrease in strength and a decrease in heat dissipation, thereby providing a bipolar storage battery having high energy density, which is very preferable.
Here, because the value L1 of the rim width is described using
Although the rim width has various lengths, the rim width can be preferably selected from a range of, for example, 2.0 mm to 10.0 mm, inclusive.
As described above, it is possible to strongly join together the plates each holding the cell member by joining the rims at the above-described ratio and by setting the width of the rim and the thickness of the bipolar plate to satisfy the above-described ratio when the joining is performed. By strongly joining the plates together, it is possible to prevent outward leakage of the electrolytic solution and reduction of mechanical strength to ensure hermeticity of the inside of the cell and the mechanical strength.
In addition, because the hermeticity and mechanical strength of the bipolar storage battery can be ensured by using only required constituent elements for constituting the bipolar storage battery, it is possible to make the bipolar storage battery compact while reducing the number of components.
In addition, the bipolar lead-acid battery has been described as an example. However, when the aforementioned descriptive content applies to other storage batteries in which other metals (for example, aluminum, copper, or nickel), alloys, or conductive resins are used instead of lead for a current collector, such application is naturally not excluded.
The following is a list of reference signs used in this specification and in the drawings.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-020218 | Feb 2021 | JP | national |
CROSS-REFERENCE TO RELATED APPLICATION(S) This application is a continuation of PCT Application No. PCT/JP2021/047000, filed Dec. 20, 2021, the disclosure of which is incorporated herein in its entirety by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2021/047000 | Dec 2021 | US |
| Child | 18362893 | US |
