Patent Application
20220102816
The present application claims priority from Japanese Patent Application No. 2020-156930 filed on Sep. 18, 2020, which is incorporated by reference herein in its entirety.
The present invention relates to secondary batteries.
CN 110518174 A discloses a structure in which a plurality of electrode assemblies connected in series are enclosed in a battery case.
JP 2019-204799 A discloses a secondary battery in which two flat wound electrode assembles are housed in a square exterior package. In the secondary battery disclosed in the publication, each of the winding axes of the wound electrode assemblies is arranged in a direction perpendicular to a sealing plate. The positive electrode tab portion and the negative electrode tab portion of each of the wound electrode assemblies are positioned on the sealing plate side. The positive electrode tab portions of the two wound electrode assemblies are connected to a positive electrode current collector inside the exterior package. The negative electrode tab portions of the two wound electrode assemblies are connected to a negative electrode current collector inside the exterior package. The positive electrode tab portions and the positive electrode current collectors of the two wound electrode assemblies are welded by resistance welding. The negative electrode tab portions and the negative electrode current collectors of the two wound electrode assemblies are welded by resistance welding.
More specifically, as disclosed in
The present inventors have conducted a research on a technique of enclosing a plurality of electrode assemblies within a battery case and a technique of increasing the capacity of a secondary battery by connecting a plurality of electrode assemblies enclosed in a battery case to each other in parallel. According to JP2019-204799 A, the two wound electrode assemblies are connected in parallel to each other by the positive electrode current collector and the negative electrode current collector attached to the battery case. However, when a further larger number of electrode assemblies needs to be housed in a battery case, the structure disclosed in JP 2019-204799 A cannot be employed without any modification.
A secondary battery disclosed in the present disclosure includes a battery case and a plurality of electrode assemblies housed in the battery case. Each of the electrode assemblies includes a stacked structure in which a positive electrode sheet and a negative electrode sheet are stacked with a separator interposed therebetween. The positive electrode sheet includes a first positive electrode tab protruding from a stacked region in which the positive electrode sheet and the negative electrode sheet are stacked with the separator, and a second positive electrode tab protruding from the stacked region a position different from where the first positive electrode tab protrudes. The negative electrode sheet includes a first negative electrode tab protruding from the stacked region at a position different from where first positive electrode tab and the second positive electrode tab protrude, and a second negative electrode tab protruding from a position different from where the first positive electrode tab, the second positive electrode tab, and the first negative electrode tab protrude. The plurality of electrode assemblies are arranged in the battery case in a predetermined orderly arrangement. Positive electrode sheets of adjacent two of the electrode assemblies are electrically connected to each other by joining one of the first and second positive electrode tabs of the adjacent two of the electrode assemblies to another one. In addition, negative electrode sheets of the adjacent two of the electrode assemblies are electrically connected to each other by joining one of the first and second negative electrode tabs of the adjacent two of the electrode assemblies to another one.
In such a secondary battery as described above, a plurality of electrode assemblies are housed in the battery case. This serves to obtain a higher capacity. Moreover, adjacent ones of the plurality of electrode assemblies housed in the battery case are connected in parallel to each other by electrically connecting one of the positive electrode tabs to another one and also electrically connecting one of the negative electrode tabs to another one As a result, it is easy to obtain the voltage of the plurality of electrode assemblies housed in the battery case.
The positive electrode sheet and the negative electrode sheet may include a rectangular region in which the positive electrode sheet and the negative electrode sheet are stacked with the separator interposed therebetween. The first positive electrode tab may be disposed at one side edge of the rectangular region. The first negative electrode tab may be disposed at a position of the one side edge of the rectangular region that does not interfere with the first positive electrode tab. The second positive electrode tab may be disposed at the opposite side edge of the rectangular region. The second negative electrode tab may be disposed at a position of the opposite side edge of the rectangular region that does not interfere with the second positive electrode tab.
The first positive electrode tab may be disposed closer to a first end along the one side edge of the rectangular region. The second positive electrode tab may be disposed closer to a second end that is opposite the first end at which the first positive electrode tab is disposed, along the opposite side edge of the rectangular region. The first negative electrode tab may be disposed closer to the second end along the one side edge of the rectangular region. The second negative electrode tab may be disposed closer to the first end along the opposite side edge of the rectangular region. The plurality of electrode assemblies may be arranged in alternate orientations.
The first positive electrode tab may be disposed closer to a first end along the one side edge of the rectangular region. The second positive electrode tab may be disposed closer to the first end along the opposite side edge of the rectangular region. The first negative electrode tab may be disposed closer to a second end that is opposite the first end at which the first positive electrode tab is disposed, along the one side edge of the rectangular region. The second negative electrode tab may be disposed closer to the second end along the opposite side edge of the rectangular region.
Each of the plurality of electrode assemblies may include positive electrode sheets and negative electrode sheets each being formed in a predetermined shape, the positive electrode sheets and negative electrode sheets being alternately stacked with separators each interposed between one of the positive electrode sheets and one of the negative electrode sheets. Each of the plurality of electrode assemblies may be a wound electrode assembly in which a strip-shaped positive electrode sheet and a strip-shaped negative electrode sheet are stacked with their longitudinal axes being aligned in a uniform orientation and are wound around a winding axis extending along a lateral axis.
The plurality of electrode assemblies may be arranged in a row along a longitudinal axis of the battery case with respective stacking axes of the positive electrode sheet and the negative electrode sheet being aligned in a uniform orientation, and may be electrically connected in parallel to each other in the battery case. An embodiment of the secondary battery may further include a positive electrode terminal attached to one of the plurality of electrode assemblies that is located at one end of the plurality of electrode assemblies arranged in a row, and a negative electrode terminal attached to another one of the plurality of electrode assemblies that is located at the other end.
The battery case may include a substantially rectangular bottom surface portion, a pair of wider surface portions extending upwardly from respective longer sides of the bottom surface portion, a pair of narrower surface portions extending upwardly from respective shorter sides of the bottom surface portion, and a top surface portion disposed opposite the bottom surface portion. Each of the shorter sides may have a length corresponding a thickness of the electrode assembly along a stacking axis of the positive electrode sheet and the negative electrode sheet. Each of the longer sides may have a length corresponding to a total length of the plurality of electrode assemblies that are arranged in a row with the stacking axes being parallel to each other.
The battery case may be a prismatic case in which at least two plate members are combined and the combined plate members are joined to each other.
The adjacent two of the plurality of electrode assemblies may be electrically connected in parallel to each other, and the adjacent two of the plurality of electrode assemblies may further include a joining part joining the adjacent two of electrode assemblies and being bent so that the stacked regions of the two adjacent electrode assemblies are stacked on each other in the battery case. The battery case may be a prismatic case in which at least two plate members are joined to each other. The battery case may be a laminate film case covering the plurality of electrode assemblies.
Hereinbelow, embodiments of a secondary battery according to the present disclosure are described. Throughout the drawings, identical reference characters and descriptions are used to designate like elements or features as appropriate. It should be noted that dimensional relationships in the drawings do not necessarily reflect actual dimensional relationships.
In the present description, the term “battery” is intended to mean any electricity storage device in general that is capable of providing electric energy therefrom, which is intended to include primary batteries and secondary batteries. The term “secondary battery” refers to a repeatedly rechargeable electrical storage device in general. The term “secondary battery” is meant to include what is called a storage battery such as a lithium secondary battery, a nickel-metal hydride battery, and a nickel-cadmium storage battery. Herein, a lithium-ion secondary battery, one type of secondary battery, is used to describe an example of the secondary battery according to the present disclosure in detail. However, the secondary battery according to the present disclosure is not limited to the embodiments described herein unless specifically stated otherwise.
The battery case h is a housing that houses the plurality of electrode assemblies 12, as illustrated in
The bottom surface portion 11a is in a substantially rectangular shape. In this embodiment, in the battery case 11, the plurality of electrode assemblies 12 are arranged in a row in a uniform orientation, as illustrated in
The wider surface portion 11b extends upward from one longer side of the bottom surface portion 11a. The wider surface portion 11c extends upward from the other side of the bottom surface portion 11a. The narrower surface portion 11d extends upward from one shorter side of the bottom surface portion 11a. The narrower surface portion 11e extends upward from the other shorter side of the bottom surface portion 11a. The top surface portion 11f is disposed opposite the bottom surface portion 11a. The top surface portion 11f closes the opening formed by the upper sides of the pair of wider surface portions 11b and 11c and the pair of the narrower surface portions 11d and 11e. The details of the battery case 11 will be further described later.
As illustrated in
In this embodiment, a region 12a in which a positive electrode sheet 31 and a negative electrode sheet 32 are stacked with a separator 33 is in a substantially rectangular shape. In the region in which the positive electrode sheet 31 and the negative electrode sheet 32 are stacked with the separator 33 interposed therebetween (i.e., the stacked region 12a), the positive electrode active material layer 31b is formed on both sides of the positive electrode sheet 31. The positive electrode sheet 31 further includes a first positive electrode tab 31a1 and a second positive electrode tab 31a2. The first positive electrode tab 31a1 and the second positive electrode tab 31a2 are portions of the positive electrode current collector foil 31a that protrude from the rectangular region in which the positive electrode sheet 31 and the negative electrode sheet 32 are stacked with the separator 33 interposed therebetween (i.e., the stacked region 12a). In this embodiment, the first positive electrode tab 31a1 and the second positive electrode tab 31a2 are disposed at diagonally opposite corners of the rectangular region in which the positive electrode sheet 31 and the negative electrode sheet 32 are stacked with the separator 33 interposed therebetween.
As illustrated in
In this embodiment, in the region in which the positive electrode sheet 31 and the negative electrode sheet 32 are stacked with the separator 33 interposed therebetween (i.e., the stacked region 12a), the negative electrode active material layer 32b is formed on both sides of the negative electrode sheet 32. The negative electrode active material layer 32b is formed with a width that is slightly wider than the positive electrode active material layer 31b so that the negative electrode active material layer 32b can cover the positive electrode active material layer 31b of the positive electrode sheet 31. The negative electrode sheet 32 further includes a first negative electrode tab 32a1 and a second negative electrode tab 32a2. The first negative electrode tab 32a1 and the second negative electrode tab 32a2 are portions of the negative electrode current collector foil 32a that protrude from the rectangular region in which the positive electrode sheet 31 and the negative electrode sheet 32 are stacked with the separator 33 interposed therebetween (i.e., the stacked region 12a). In this embodiment, the first negative electrode tab 32a1 and the second negative electrode tab 32a2 are disposed at diagonally opposite corners of the rectangular region in which the positive electrode sheet 31 and the negative electrode sheet 32 are stacked with the separator 33 interposed therebetween.
The separator 33 may be formed of, for example, an electrolyte-permeable porous resin sheet provided with required heat resistance. The separator 33 is formed in a rectangular shape that is slightly larger than the negative electrode active material layer 32b so that the separator 33 can cover the negative electrode active material layer 32b of the negative electrode sheet 32. Various embodiments of the separator 33 have been proposed, and the separator 33 is not limited to a particular type of separator. The negative electrode active material layer 32b of the negative electrode sheet 32 may cover the positive electrode active material layer 31b of the positive electrode sheet 31 with the separator 33 interposed therebetween. The separator 33 may further cover the positive electrode active material layer 31b of the positive electrode sheet 31 and the negative electrode active material layer 32b of the negative electrode sheet 32.
As illustrated in
As illustrated in
The strip-shaped positive electrode current collector foil 31a and a positive electrode mixture containing a positive electrode active material are prepared in the step of forming the positive electrode active material layer 31b. The strip-shaped positive electrode current collector foil 31a is provided with a region in which the positive electrode active material layer 31b is to be formed, at its laterally central portion. In the region in which the positive electrode active material layer 31b is to be formed, a positive electrode mixture is coated at a predetermined weight per unit area on the positive electrode current collector foil 31a using a die-coater 41, as illustrated in
Thereafter, as illustrated in
Although not shown in the drawings, negative electrode sheets 32 are also manufactured in a similar method to the method of manufacturing the positive electrode sheets 31. Specifically, after the negative electrode active material layer 32b has been formed on a strip-shaped negative electrode current collector foil 32a, negative electrode sheets 32 are cut out into predetermined shapes, including first negative electrode tabs 32a1 and second negative electrode tabs 32a2. In addition, rectangular-shaped separators 33 each having a shape corresponding to the positive electrode sheet 31 and the negative electrode sheet 32 are prepared, as illustrated in
As shown in
Herein, the stacked electrode assembly 12, in which positive electrode sheets 31 and negative electrode sheets 32 are alternately stacked in a predetermined order with separators 33 interposed therebetween, has been illustrated as an example. The electrode assembly 12 is not limited to being a stacked electrode assembly, but may be what is called a wound electrode assembly.
The width d2 of the negative electrode active material layer 32b is wider than the width d1 of the positive electrode active material layer 31b. The width d3 of the separators 33A is wider than the width d2 of the negative electrode active material layer 32b. The first positive electrode tab 31a1 and the second positive electrode tab 31a2 as well as the first negative electrode tab 32a1 and the second negative electrode tab 32a2 have a required length so that they can protrude from the separators 33A. As illustrated in
In this state, the positive electrode sheet 31, the negative electrode sheet 32, and the separators 33A are stacked in the following order, positive electrode sheet 31, separator 33A, negative electrode sheet 32, and separator 33A so that the negative electrode sheet 32 is disposed outward of the positive electrode sheet 31 and a separator 33A is disposed further outward of the negative electrode sheet 32 at the outermost circumference. Then, the positive electrode sheet 31, the negative electrode sheet 32, and the separators 33A are wound in such a manner that the positive electrode sheet 31 is disposed inward of the negative electrode sheet 32. Note that the wound electrode assembly 12A is shaped in a substantially rectangular flat shape in which the positive electrode sheet 31 and the negative electrode sheet 32 are wound. When the wound electrode assembly 12A is shaped in a flat shape, the first positive electrode tab 31a1, the second positive electrode tab 31a2, the first negative electrode tab 32a1, and the second negative electrode tab 32a2 are located at substantially the same positions. As thus described, each of the plurality of electrode assemblies 12 may be a wound electrode assembly in which the strip-shaped positive electrode sheet 31A and the strip-shaped negative electrode sheet 32A are stacked with their longitudinal axes being aligned in a uniform orientation and are wound around the winding axis extending along the lateral axis.
It should be noted that, in the case of the wound electrode assembly 12A, the first positive electrode tab 31a1, the second positive electrode tab 31a2, the first negative electrode tab 32a1, and the second negative electrode tab 32a2 may be provided at predetermined positions in the strip-shaped positive electrode sheet 31A and the strip-shaped negative electrode sheet 32A so that the first positive electrode tab 31a1, the second positive electrode tab 31a2, the first negative electrode tab 32a1, and the second negative electrode tab 32a2 can be stacked at substantially the same position when the wound electrode assembly 12A is shaped into a flat shape. That is, the strip-shaped positive electrode sheet 31A and the strip-shaped negative electrode sheet 32A that are shown in
To be precise, for example, the pitch between bend lines b1 is narrower toward the inside and wider toward the outside along the circumferential direction. The pitch between the bend lines b1 can be obtained in advance by calculation. The positions and shapes of the first positive electrode tabs 31a1 and the second positive electrode tabs 31a2 that are formed in the strip-shaped positive electrode sheet 31A may be adjusted in advance according to the pitch between the bend lines b1. The positions and shapes of the first negative electrode tabs 32a1 and the second negative electrode tab 32a2 that are formed in the strip-shaped negative electrode sheet 32A may also be adjusted in advance according to the pitch between the bend lines b1. In
Although not shown in the drawings, the electrode assembly 12 may be composed of what is called an all-solid-state battery. In the case of all-solid-state battery, the separator 33 may be replaced with a solid electrolyte layer. Unless specifically stated otherwise, the term “separator” is meant to include a solid electrolyte layer. When the electrode assembly 12 is composed of an all-solid-state battery, the electrode assembly 12 may be provided with a stacked structure in which the positive electrode sheet 31 and the negative electrode sheet 32 are stacked with a solid electrolyte layer, serving as a separator, interposed therebetween. Various structures of the electrode assembly 12 that constitutes an all-solid-state battery have been proposed, which may be employed as appropriate, and the structure of the electrode assembly 12 is not limited to any particular structure.
As illustrated in
More specifically, in this embodiment, the first positive electrode tab 31a1 and the second positive electrode tab 31a2 are disposed at diagonally opposite each other and the first negative electrode tab 32a1 and the second negative electrode tab 32a2 are also disposed diagonally opposite each other in the electrode assembly 12. Specifically, in this embodiment, the first positive electrode tab 31a1 is disposed closer to a first end along the one side edge 12a1 of the rectangular region 12a. The second positive electrode tab 31a2 is disposed closer to a second end that is opposite the first end at which the first positive electrode tab 31a1 is disposed, along the opposite side edge 12a2 of the rectangular region 12a. The first negative electrode tab 32a1 is disposed closer to the second end along the one side edge 12a1 of the rectangular region 12a. The second negative electrode tab 32a2 is disposed closer to the first end along the opposite side edge 12a2 of the rectangular region 12a.
Thus, the first positive electrode tab 31a1 and the second positive electrode tab 31a2 are disposed diagonally opposite each other while the first negative electrode tab 32a1 and the second negative electrode tab 32a2 are disposed diagonally opposite each other in each of the plurality of electrode assemblies 12. Therefore, it is easy to arrange the plurality of electrode assemblies 12 in a row and electrically connect the plurality of electrode assemblies 12 in parallel to each other. In addition, because the first positive electrode tab 31a1 and the second positive electrode tab 31a2 are disposed diagonally opposite each other and the first negative electrode tab 32a1 and the second negative electrode tab 32a2 are disposed diagonally opposite each other in each one of the electrode assemblies 12, the shortest path connecting the first positive electrode tab 31a1 and the second positive electrode tab 31a2 of the positive electrode sheet 31 intersects the shortest path connecting the first negative electrode tab 32a1 and the second negative electrode tab 32a2 of the negative electrode sheet 32 in a plan view viewed in a stacking direction. This reduces uneven reaction between the positive electrode sheet 31 and the negative electrode sheet 32. Accordingly, it is possible to reduce the resistance to the battery reaction between the positive electrode sheet 31 and the negative electrode sheet 32.
The joining of the positive electrode tabs to each other and the negative electrode tabs to each other may be achieved by, for example, solid phase bonding. The use of solid phase bonding may reduce the electrical resistance between the positive electrode tabs and between the negative electrode tabs at the joined portions. For solid phase bonding, it is possible to employ, for example, ultrasonic welding. In ultrasonic welding, the positive electrode tabs, or the negative electrode tabs, are stacked on each other and sandwiched by a horn and an anvil, and the horn is vibrated. Thereby, the stacked positive electrode tabs or the stacked negative electrode tabs are heated and softened without being fused while being kept in a solid phase (solid state), and the stacked positive electrode tabs or the stacked negative electrode tabs are further pressed to undergo plastic deformation, whereby the stacked positive electrode tabs or the stacked negative electrode tabs are joined to each other. Other than ultrasonic welding, various techniques of solid phase bonding may be employed, including cold pressure welding, hot pressure welding, and friction pressure welding. When a joining technique of solid phase bonding is employed, the positive electrode tabs and the negative electrode tabs may be welded together with an electrically lower resistance value. The techniques of joining the positive electrode tabs to each other and joining the negative electrode tabs to each other is not limited to those illustrated herein, and various other techniques may be employed. For example, the joining of the positive electrode tabs to each other and the negative electrode tabs to each other may be effected by welding, unless specifically stated otherwise.
In the embodiment shown in
In this embodiment, the battery case 11 includes a frame 51 and plates 52 to 54. Each of the frame 51 and the plates 52 to 54 may be composed of, for example, a metal member composed of aluminum or an aluminum alloy. The frame 51 has such a shape corresponding to the bottom surface portion 11a and the pair of wider surface portions 11b and 11c of the battery case 11. The frame 51 may be formed by, for example, bending a plate-shaped material that are cutout into a predetermined shape. The plate 52 has a shape corresponding to the narrower surface portion 11d. The plate 53 has a shape corresponding to the narrower surface portion 11e. The plate 54 has a shape corresponding to the top surface portion 11f.
The battery case 11 includes shorter sides having a length corresponding to the thickness of the electrode assembly 12, and longer sides having a length corresponding to the total length of the plurality of electrode assemblies 12 that are arranged in a row. It is difficult to form such an oblong battery case 11 by a drawing process. In this embodiment, the battery case 11 is formed by combining the four plate members 51 to 54 and joining the edges of the combined four plate members 51 to 54. In this case, a drawing process is not required. Therefore, this embodiment can employ a large-sized oblong battery case 11. Thus, the battery case 11 may be a prismatic case in which at least two plate members are combined and the edges of the at least two combined plate members are joined to each other. The at least two plate members may have boundaries that are defined in units of surfaces, such as the bottom surface portion 11a, the pair of wider surface portions 11b, 11c, the pair of narrower surface portions 11d, 11e, and the top surface portion 11f. The edges of the combined plate members may be joined to each other. There are no specific limitations on the number of the plate members and how the boundaries are to be defined.
As illustrated in
The plurality of electrode assemblies 12 are housed in the frame 51 in a state in which the plates 52 and 53 are attached to the opposite ends. Although not shown in the drawings, an insulating film may be interposed between the plurality of electrode assemblies 12 and the battery case 11. The plates 52 and 53 are fitted to opposite sides of the frame 51. The plate 54, which corresponds to the top surface portion 11f, is fitted to the opening in the top of the frame 51. The frame 51 and the plates 52 to 54 may be fitted together without space and welded along the edges of the frame 51, for example. Herein, the frame 51 and the plates 52 to 54 may be welded by seam welding. The seam welding may be carried out by, for example, laser welding. In addition, the battery case 11 may be provided with a filling port, a safety vent, and the like, as needed.
Thus, the secondary battery 10 disclosed in the present disclosure includes the battery case 11 and the plurality of electrode assemblies 12 housed in the battery case 11, for example, as illustrated in
In such a secondary battery 10 as described above, the plurality of electrode assemblies 12 are housed in the battery case 11. Therefore, it is possible to achieve a higher capacity of the secondary battery 10 by increasing the number of the electrode assemblies 12 that are housed in the battery case 11. Moreover, in adjacent ones of the plurality of electrode assemblies 12 housed in the battery case 11, the positive electrode tabs are electrically connected to each other and the negative electrode tabs are electrically connected to each other. This allows the adjacent ones of the plurality of electrode assemblies 12 to be connected in parallel to each other. The plurality of electrode assemblies 12 housed in the battery case 11 are charged and discharged through the positive electrode terminal 61, which is disposed at one end, and the negative electrode terminal 62, which is disposed at the other end. In this case, because the plurality of electrode assemblies 12 housed in the battery case 11 are connected in parallel to each other, each of the electrode assemblies 12 is brought to the same voltage. In other words, the voltage applied to each of the electrode assemblies 12 inside the battery case 11 is not directly measured. However, the voltage applied to each of the electrode assemblies 12 housed in the battery case 11 is equal to the voltage between the positive electrode terminal 61 and the negative electrode terminal 62, which can be measured from outside the battery case 11 (even if there is a difference in a strict sense, the voltage difference is negligibly small). Therefore, it is possible to obtain the voltage across each of the electrode assemblies 12 within the battery case 11. It is possible to prevent such an event that only one of the plurality of electrode assemblies 12 housed inside the battery case 11 has an abnormally higher voltage than those of the other electrode assemblies 12.
To the knowledge of the present inventors, there is a possibility that a potential difference may arise in the electrolyte solution around the electrode assemblies, for example, when the plurality of electrode assemblies 12 housed in the battery case 11 are connected in series to each other. This may lead to an undesirable event such that a short circuit occurs between the electrode assemblies 12 through the electrolyte solution. For this reason, the present inventors believe that it is necessary to separate the electrolyte solution for each one of the electrode assemblies 12. However, when the plurality of electrode assemblies 12 housed in the battery case 11 are connected in parallel to each other as illustrated in
Moreover, in order to obtain a higher capacity for the secondary battery 10, it is necessary to increase the capacity of each electrode assembly 12 that is incorporated therein. When the size of each electrode assembly 12 is increased, the inside of the electrode assembly 12 may not be impregnated sufficiently with the electrolyte solution, for example. In contrast, in the embodiment shown in
In the embodiment shown in
In this embodiment, the two adjacent electrode assemblies 12 are housed in the battery case 70 by being bent and folded at the joining part 12b, so that the stacked regions 12a, in which the positive electrode sheet and the negative electrode sheet are stacked, are stacked on each other. In this case, the aspect ratio of the battery case 70 is made smaller. Moreover, because a plurality of electrode assemblies are housed in the battery case 70, a higher capacity is obtained. Furthermore, the plurality of electrode assemblies 12 housed in the battery case 70 are electrically connected in parallel to each other. For this reason, the voltage applied to each of the electrode assemblies 12 inside the battery case 70 is not directly measured. However, the voltage across each of the electrode assemblies 12 is equal to the voltage between the positive electrode terminal 61 and the negative electrode terminal 62, which can be measured outside the battery case 70. Therefore, it is possible to obtain the voltage across each of the electrode assemblies 12 within the battery case 70. In addition, as illustrated in
The battery case 70 is a prismatic case. The battery case 70 includes a substantially rectangular bottom surface portion 70a, a pair of wider side surface portions 70b and 70c each extending upwardly from a longer side of the bottom surface portion 70a, and a pair of narrower side surface portions 70d and 70e each extending upwardly from a shorter side of the bottom surface portion 70a, and a top surface portion 70f disposed opposite the bottom surface portion 70a. A prismatic case that can accommodate a plurality of electrode assemblies 12 is inevitably large in size, so it is difficult to produce such a prismatic case by a drawing process. In this embodiment, the battery case 70 includes at least two plate members that are joined to each other. The combined plate members may be joined by, for example, fitting the edges together. In this case, a drawing process is not required, and therefore, the size of the battery case 70 can be increased. As a result, it is possible to employ a prismatic case even when the battery case needs to accommodate a large component such that a plurality of electrode assemblies 12 are stacked, as illustrated in
In this embodiment, the battery case 70 is formed by combining six plate members, which respectively correspond to the substantially rectangular bottom surface portion 70a, the pair of wider side surfaces 70b, 70c, the pair of wider side surfaces 70d, 70e, and the top surface portion 70f, and welding the edges of the combined plate members with no gaps therebetween. For welding, it is possible to employ, for example, laser seam welding. Note that the structure of the battery case 70 is not limited to such an embodiment. The battery case 70 composed of a prismatic case in a substantially rectangular parallelepiped shape may include surfaces respectively corresponding to the substantially rectangular bottom surface portion 70a, the pair of wider side surfaces 70b, 70c, the pair of wider side surfaces 70d, 70e, and the top surface portion 70f. The battery case 70 may include at least two plate members to form the surfaces that respectively correspond to the substantially rectangular bottom surface portion 70a, the pair of wider side surfaces 70b, 70c, the pair of wider side surfaces 70d, 70e, and the top surface portion 70f, the at least two plate members may be combined in a rectangular parallelepiped shape, and the edges of the combined plate members may be joined together. This makes it possible to produce a large-sized prismatic case without use of a deep drawing process. Various techniques may be employed to constitute the surfaces that respectively correspond to the substantially rectangular bottom surface portion 70a, the pair of wider side surfaces 70b, 70c, the pair of wider side surfaces 70d, 70e, and the top surface portion 70f, with use of at least two plate members. The technique of how the battery case 70 may be fabricated is not limited to a particular technique, unless specifically stated otherwise.
In this embodiment, as illustrated in
In this embodiment, the positive electrode tab 31a1 at one end of the tree electrode assemblies 12 and the negative electrode tab 32a2 at the other end may be disposed closer to an end near the top surface portion 70f and housed in the battery case 70. A positive electrode terminal 81 and a negative electrode terminal 82 are attached to a lid 72 that forms the top surface portion 70f. The positive electrode terminal 81 and the negative electrode terminal 82 may be insulated from the lid 72, and also provided with hermeticity, by a gasket or the like. The positive electrode terminal 81 is joined to the positive electrode tab 31a1 of one of the plurality of electrode assemblies 12 that is disposed atone end. The negative electrode terminal 82 is joined to the negative electrode tab 32a2 of another one of the plurality of electrode assemblies 12 that is disposed at the other end.
In this embodiment, the positive electrode terminal 81 is joined to the positive electrode tab 31a1 (see
Thus, each of the electrode assemblies 12 is provided with two positive electrode tabs disposed at diagonally opposite corners and two negative electrode tabs disposed at diagonally opposite corners that are different from those at which the two positive electrode tabs are disposed, and two adjacent electrode assemblies 12 of an odd number of electrode assemblies 12 are electrically connected in parallel to each other. Although an embodiment in which three electrode assemblies 12 are connected together is described as an example herein, it is also possible that a similar configuration may be employed when an odd number, such as 5 or 7, of electrode assemblies 12 are connected together. In such cases, the positive electrode tab 31a1 of one of the plurality of electrode assemblies 12 at one end and the negative electrode tab 32a2 of another one of the electrode assemblies 12 at the other end are disposed closer to one side surface of the prismatic case. As a result, the positive electrode tab 31a1 of one of the plurality of electrode assemblies 12, which are connected in parallel, at one end and the negative electrode tab 32a2 of another one of the electrode assemblies 12 at the other end may be connected easily to the positive electrode terminal and the negative electrode terminal that are provided on the one side surface of the prismatic case. In other words, it is possible to simplify the terminal structure of the positive electrode terminal and the negative electrode terminal provided on one side surface of the prismatic case.
In this embodiment, as illustrated in
In the four electrode assemblies 12, the joining part 12b that joins two adjacent electrode assemblies 12 is bent so that the stacked regions 12a of the two adjacent electrode assemblies 12, in which the positive electrode sheet and the negative electrode sheet are stacked, are stacked on each other. In this case, the positive electrode tab and the negative electrode tab of the electrode assemblies 12 located at both ends among the four electrode assemblies 12 are disposed on the same side surface, as illustrated in
Herein, a prismatic case is shown as an example of the battery case that houses a plurality of electrode assemblies 12. However, the battery case is not limited to such an embodiment. Although not shown in the drawings, the battery case may be, for example, a laminate film battery case that covers the plurality of electrode assemblies 12. The laminate film battery case may be composed of, for example, a laminate film in which a substrate sheet made of aluminum is covered with an insulating resin. Various types of laminate films used for the laminate film battery case have been proposed for use in secondary batteries, and the laminate film is not limited to a particular type.
For example, when a laminate film battery case is used, the shapes of the battery case and the joined part of the laminate film battery case and the electrode assemblies 12 are not strictly fixed. The joined part between the laminate film battery case and the electrode assembly 12 has a certain extent of range of motion. For example, when the electrode assemblies need to be pressed in order to increase the energy density, the joined part between the laminate film battery case and the electrode assemblies 12 may change the location because of the pressing. As a result, it may be possible to alleviate the load acting on the joined part of the electrode assemblies 12, which results from, for example, handling in the manufacturing process, such as work of mounting the battery in a vehicle, as well as acceleration and deceleration, vibrations, and the like that affect the battery when the vehicle is traveling. Moreover, depending on the structure of the electrode assembly, a laminate film battery case may be employed for the battery case when appropriate, such as when a higher pressure needs to be applied to the electrode assembly.
As illustrated in
Thus, various modifications are possible in various respects, such as the number and arrangement of the electrode assemblies housed in the battery case, the positions of the terminals provided on the battery case, and so forth.
Various embodiments of the secondary battery have been described hereinabove according the present disclosure. Unless specifically stated otherwise, the embodiments of the secondary battery described herein do not limit the scope of the present invention. It should be noted that various other modifications and alterations may be possible in the embodiments of the battery disclosed herein. In addition, the features, structures, or steps described herein may be omitted as appropriate, or may be combined in any suitable combinations, unless specifically stated otherwise.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-156930 | Sep 2020 | JP | national |
