Related Applications

[0001] This application claims priority from U.S. Provisional Application No. 63/033,548, filed June 2, 2020, the disclosure of which is incorporated by reference in its entirety.

Background

[0002] In some known bipolar batteries, solder joints are used to join lead sheets on opposite sides of the bipole frame. The solder joint is formed in the bipole frame’s through-hole. However, an inadequate fill of the solder joint within the bipole frame can cause two potential defects: 1) high electrical resistance; and 2) electrolyte communication between adjacent half cells.

Summary

[0003] Some embodiments of the present invention are directed to a bipole frame assembly for a bipolar battery, the bipole frame assembly including: a bipole frame including first and second opposite surfaces and a plurality of solder through holes; a negative bipole lead sheet on the first surface of the bipole frame; a positive bipole lead sheet on the second surface of the bipole frame; and a plurality of solder joints with one at each of the plurality of solder through holes. Each solder joint may include a central portion that fills the solder through hole, a first outer portion on the first surface of the bipole frame and between the bipole frame and the negative bipole lead sheet, and a second outer portion on the second surface of the bipole frame and between the bipole frame and the positive bipole lead sheet.

[0004] In some embodiments, a diameter of the first outer portion and a diameter of the second outer portion are each greater than a diameter of the solder through hole. The diameter of the first outer portion and the diameter of the second outer portion may each be at least 1.5 times greater than the diameter of the solder through hole.

[0005] In some embodiments, the first outer portion is convex relative to the first surface of the bipole frame, and the second outer portion is convex relative to the second surface of the bipole frame. [0006] Some other embodiments of the present invention are directed to a method of assembling a bipole frame assembly for a bipolar battery, the method including: providing a bipole frame including first and second opposite surfaces and a plurality of solder through holes; placing the bipole frame on a first bipole lead sheet with the first surface of the bipole frame on the first bipole lead sheet; dispensing solder paste into each of the plurality of solder through holes; placing a second bipole lead sheet on the second surface of the bipole frame; and refl owing the solder paste such that a solder joint is at each solder through hole with a central portion of the solder joint completely filling the solder through hole, with a first outer portion of the solder joint on the first surface of the bipole frame, and with a second outer portion on the second surface of the bipole frame.

[0007] In some embodiments, dispensing the solder paste includes dispensing a greater amount of solder paste than is needed to fill the solder through hole.

[0008] In some embodiments, the reflowing step is carried out using an upper heat platen and a lower heat platen with the bipole frame assembly between the upper heat platen and the lower heat platen. The upper heat platen and lower heat platen may be configured to locally heat the bipole frame assembly at the solder joints. The upper heat platen and the lower heat platen may each include a concave recess such that the first outer portion of the reflowed solder joint is convex relative to the first surface of the bipole frame and the second outer portion of the reflowed solder joint is convex relative to the second surface of the bipole frame.

[0009] Some other embodiments of the present invention are directed to a bipolar battery including: a positive end frame; a negative end frame; and a plurality of bipole frame assemblies between the positive end frame and the negative end frame. Each bipolar battery assembly includes: a bipole frame including first and second opposite surfaces and a plurality of solder through holes; a negative bipole lead sheet on the first surface of the bipole frame; a positive bipole lead sheet on the second surface of the bipole frame; and a plurality of solder joints with one at each of the plurality of solder through holes. Each solder joint may include a central portion that fills the solder through hole, a first outer portion on the first surface of the bipole frame and between the bipole frame and the negative bipole lead sheet, and a second outer portion on the second surface of the bipole frame and between the bipole frame and the positive bipole lead sheet. [0010] Further features, advantages and details of the present invention will be appreciated by those of ordinary skill in the art from a reading of the figures and the detailed description of the preferred embodiments that follow, such description being merely illustrative of the present invention.

Brief Description of the Drawings

[0011] Figure 1 is a perspective view of a bipolar battery according to some embodiments of the present invention.

[0012] Figure 2 is another perspective view of the bipolar battery of Figure 1.

[0013] Figure 3 is a schematic sectional view of the bipolar battery of Figure 1.

[0014] Figure 4 is a sectional view of the bipolar battery of Figure 1.

[0015] Figure 5 is a perspective view of a bipole frame according to some embodiments of the present invention.

[0016] Figure 6 is another perspective view of the bipole frame of Figure 5.

[0017] Figure 7 is a plan view of a bipole frame assembly according to some embodiments of the present invention.

[0018] Figure 8 is an opposite plan view of the bipole frame assembly of Figure 7.

[0019] Figure 9 is an enlarged fragmentary sectional view of the bipole frame and a solder joint of the bipole frame assembly of Figure 7.

[0020] Figure 10 is a perspective view of the solder joint of Figure 10.

[0021] Figure 11 is a schematic sectional view of equipment used for the solder reflow process according to some embodiments of the present invention.

Detailed Description

[0022] The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which illustrative embodiments of the invention are shown. In the drawings, the relative sizes of regions or features may be exaggerated for clarity. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. [0023] It will be understood that when an element is referred to as being "coupled" or "connected" to another element, it can be directly coupled or connected to the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly coupled" or "directly connected" to another element, there are no intervening elements present. Like numbers refer to like elements throughout. As used herein the term "and/or" includes any and all combinations of one or more of the associated listed items.

[0024] In addition, spatially relative terms, such as "under," "below," "lower," "over," "upper" and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is inverted, elements described as "under" or "beneath" other elements or features would then be oriented "over" the other elements or features. Thus, the exemplary term "under" can encompass both an orientation of over and under. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0025] Well-known functions or constructions may not be described in detail for brevity and/or clarity.

[0026] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes" and/or "including," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

[0027] It is noted that any one or more aspects or features described with respect to one embodiment may be incorporated in a different embodiment although not specifically described relative thereto. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination. Applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to be able to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner. These and other objects and/or aspects of the present invention are explained in detail in the specification set forth below.

[0028] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0029] A bipolar battery 10 according to some embodiments is shown in Figures 1-4. The battery 10 includes a positive end frame or plate 12, a negative end frame or plate 14, and a central outer casing 16. The positive end frame 12, the negative end frame 14, and the central outer casing 16 may be referred to herein as the battery casing 18.

[0030] A positive terminal 17 may be at the positive end frame 12 and a negative terminal 19 may be at the negative end frame 14.

[0031] Figure 3 is a simplified schematic of the bipolar battery 10 with some features omitted including the battery casing. The battery 10 includes a stack S of plates, frames, and/or material layers. Starting at the left side of the drawing, the battery includes the positive end frame 12, a positive end frame lead foil or sheet 20, positive active material (PAM) 22, a separator 24, negative active material (NAM) 26, a negative bipole lead foil or sheet 28, and a bipole frame 30. The next cell or module includes a positive bipole lead foil or sheet 32, the PAM 22, the separator 24, the NAM 26, and the negative bipole lead foil or sheet 28. This same sequence is continued in the stack S until, at the right side of the drawing, there is a negative end frame lead foil or sheet 34 and the negative end frame 14.

[0032] Referring to Figures 1 and 4, one or more stabilization channels 36 extend through the stack S. The channels 36 may be defined by aligned holes or apertures defined in the positive end frame 12, the positive end frame lead sheet 20, the negative end frame 14, the negative end frame lead sheet 34, the bipole frames 30, the negative bipole lead sheets 28, and/or the positive bipole lead sheets 32.

[0033] A stabilization member 38 may be received in each of the stabilization channels 36. The stabilization members 38 may be a fastener such as a bolt, post, or rod. The stabilization member 38 may be an elongated polymer member that is injected into the channels 36. The stabilization members 38 may provide mechanical stability and strength for the stack S.

[0034] Although eight channels 36 and corresponding stabilization members 38 are illustrated, it is contemplated that a lesser or greater number of channels and corresponding stabilization members may be used.

[0035] An electrolyte channel or manifold 40 extends at least partially through the stack S. The electrolyte channel 40 may be defined by aligned holes or apertures defined in the positive end frame lead sheet 20, the negative end frame lead sheet 34, the bipole frames 30, the negative bipole lead sheets 28, and/or the positive bipole lead sheets 32. An electrolyte fill port 42 in fluid communication with the electrolyte channel 40 may be on the positive end frame 12. In other embodiments, the fill port 42 may be positioned differently (e.g., on the negative end frame 14).

[0036] Each separator 24 may include an electrolyte storage reservoir. The channel 40 may supply electrolyte to each electrolyte storage reservoir.

[0037] Figures 5 and 6 are perspective views of the bipole frame 30. The bipole frame 30 includes a body 44 having first and second opposite primary sides or surfaces 46, 48. The body 44 of the bipole frame 30 may be formed of a polymer such as ABS.

[0038] One or more bosses 50A extend outwardly from the first surface 46. One or more bosses 50B extends outwardly from the second surface 48. The bosses 50A, 50B surround stabilization through holes 52 that partially define the stabilization channels 36 described above. [0039] A boss 54A extends outwardly from the first surface 46. A boss 54B extends outwardly from the second surface 48. The bosses 54A, 54B surround an electrolyte through hole 56 that partially defines the electrolyte fill channel 40 described above.

[0040] A plurality of solder through holes 58 extend through the body 44. As described in more detail below, solder is dispensed in the solder through holes 58 to form a joint for lead sheets on each of the first and second surfaces 46, 48.

[0041] Figures 7 and 8 are plan views of the bipole frame assembly 60. The bipole frame assembly 60 includes the bipole frame 30, the negative bipole lead sheet 28 on the first surface 46, and the positive bipole lead sheet 32 on the second surface 48. A solder joint 62 is in each of the solder through holes 58 between the negative bipole lead sheet 28 and the positive bipole lead sheet 32. The solder joint 62 will be described in more detail below. [0042] An example process for assembling the bipole frame assembly 60 will now be described. The negative bipole lead sheet 28 may be placed onto a solder paste dispense station fixture. The bipole frame 30 may be placed on top of the negative bipole lead sheet 28. Solder paste may be dispensed onto the bipole frame (e.g., into the solder through holes 58). The positive bipole lead sheet 32 may be placed on top of the bipole frame 30. The assembly may be moved to a solder paste reflow station and the solder paste may be reflowed.

[0043] Some known bipolar batteries include bipole frame assemblies that tend to have an inadequate fill of the solder joint within the bipole frame. For example, the bipole frame solder through holes may be under filled due to solder wi eking away from the joint under the lead sheets. This may be caused by using an excessive heating time. The under fill of the solder joint within the bipole frame may result in high electrical resistance and/or electrolyte communication between adjacent half cells.

[0044] According to embodiments of the present invention, the solder joint is manufactured by filling the bipole frame’s solder through holes with solder paste and to include additional solder paste on each side of the bipole frame to join the mating lead sheets to the solder within the through hole.

[0045] The solder paste may contain a no clean flux as well as a solder alloy compatible with lead acid battery electrochemistry. The density of the solder paste may be less than that of the reflowed solder paste.

[0046] The solder joint 62 is shown in greater detail in Figures 9 and 10. The solder joint 62 includes a central portion 64 and first and second outer portions 66, 68 (also referred to herein as first and second rivet heads). The central portion 64 may fill (e.g., completely fill) the solder through hole 58. The first outer portion 66 is on the first surface 46 of the bipole frame 30 and between the bipole frame 30 and the negative bipole lead sheet 28 (Figure 7). The second outer portion 68 is on the second surface 48 of the bipole frame 30 and between the bipole frame 30 and the positive bipole lead sheet 32 (Figure 8}.

[0047] The solder through hole 58 has a diameter or width Dl, the central portion 64 has a diameter or width D2, the first outer portion 66 has a diameter or width D3, and the second outer portion 68 has a diameter or width D4. The diameter Dl of the solder through hole 58 and the diameter D2 of the central portion 64 may be equal. The diameter D3 of the first outer portion 66 and the diameter D4 of the second outer portion 68 may be equal or substantially equal. The diameter D3 of the first outer portion 66 and the diameter D4 of the second outer portion 68 may be at least 1.5 times greater than the diameter D1 of the solder through hole 58 and the diameter D2 of the central portion 64.

[0048] The first outer portion 66 may have an outer surface 70 that is convex relative to the first surface 46 of the bipole frame 30. Similarly, the second outer portion 68 may have an outer surface 72 that is convex relative to the second surface 48 of the bipole frame 30.

[0049] Figure 11 is a simplified illustration of equipment that may be used during the solder reflow process. The equipment 100 includes an upper heat platen 102 and a lower heat platen 104. The heat platens 102, 104 may be “waffle type” that apply heat only at the solder rather than the entire bipole frame. Although only one each is shown, the upper heat platen 102 includes a plurality of first recesses 106 and the lower heat platen 104 includes a plurality of second recesses 108 that are aligned with the plurality of first recesses 106. The bipole frame assembly 60 is received between the upper heat platen 102 and the lower hear platen 104 with each area of solder paste received between an aligned pair of the recesses 106, 108. The recesses 106, 108 may be concave and help manage the geometry of the solder joint 62 as described above.

[0050] Embodiments of the present invention may provide an improved solder joint that reduces electrical resistance through the bipole frame between adjacent half cells in a bipolar battery. The improved joint may also reduce the risk of gaps forming between the solder joint and the plastic through hole which would allow chemical communication between adjacent half cells.

[0051] The rivet head design may ensure that there is adequate reflowed solder within the joint to completely fill out the solder barrel. In addition, the rivet head may increase the strength of the joint by decreasing the stress concentration around the solder joint’s perimeter.

[0052] The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although a few exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the claims. The invention is defined by the following claims, with equivalents of the claims to be included therein.