Patent Application
20210159478
This invention relates generally to cells for energy storage devices. More particularly, the present invention relates to electrodes having a continuous tab, a secondary battery that utilizes electrodes having continuous tabs, and a method of producing the same.
With initial reference to
As shown in
Each of the insulating discs 122 has a central opening 134 that, when the electrode assembly 106 is inserted into the can 124, is aligned with a corresponding central hollow 136 formed in the electrode assembly. In other cases, discs 122 might include openings that allow tabs to exit in the center of the wound electrode assembly 106. Electrode tab 112 is bent towards the central opening 134 of the bottom insulating disc 122. A welding rod may then be inserted through the aligned central openings 134 of the insulating discs and central hollow 136 of the electrode assembly 106 to weld electrode tab 112 to the bottom end 128 of the can 124. Alternatively, a laser welder may be directed through the same aligned openings 134 and central hollow 136 to form the weld. Alternatively, electrode tab 112 may be welded to the bottom end 128 of can 124 by externally contacting the bottom end of the can with the welder. In this way, can 124 has the same polarity as electrode 102 and may serve as an electrode terminal. Electrode tab 110 may then be welded to cap 144, the can 124 is filled with an electrolyte, is crimped over the cap to complete the manufacturing process.
One of the problems of welding electrode tab 112 via aligned openings 134 and central hollow 136 in the manner discussed above is that the procedure is very delicate and requires a very high degree of accuracy. Additionally, laser welders suitable for the welding process are expensive. If the welding process is not carried out perfectly, the electrode assembly 106, including the electrodes 100, 102 or separator 104, might be damaged during the process, which could cause the resulting battery to experience an electrical short or a degradation of battery life. A problem of welding electrode tab 112 through the bottom end 128 of the can 124 is that the electrode tab 112 may be easily damaged. To weld the electrode tab 112 to the bottom end 128, a large amount of heat must be provided to heat the can 124. The can 124 is typically much thicker than the electrode tab 112. For this reason, unless extreme care is taken in heating the can 124, the heat can quickly damage the thinner electrode tab 112.
A boxed portion of the electrode 100, including electrode tab 110, shown in
Attempts have been made to address the internal resistance problem by reducing the coating weight of the electrodes 100, 102 and also by increasing the number of electrode tabs 110, 112, such that the distances that electrons 138 travel along the electrode is minimized. Reducing the coating weight of the electrodes 100, 102 reduces the energy density of the cell and increases the power density. As the coat weight is reduced the electrodes become thinner and longer. Longer electrodes require more tabs to be placed, which increases the manufacturing cost and complexity. Also, the larger height of the tab and tape creates a height discontinuity in the electrode compared to the smaller height of the thinner coating of the electrode surrounding the tab and tape. More particularly, the tab and tape added to the electrode results in an area of the electrode that has a thicker cross section than the surrounding electrode that, when wound in a jelly roll (i.e., electrode assembly 106), does not bend like the surrounding electrodes. This results in a jelly roll that is not perfectly round after the winding process and can result in areas of high pressure within the electrode during cycling (expansion and contraction). In addition, the tab placement is limited by performance and safety issues that arise from the need to have anode coating located opposite to cathode coating. When the anode coating is not located opposite the cathode coating, ions in the electrolyte might become plated to the electrode material rather than intercalated into the electrode material. This plating process can lead to dendrite formation that can short circuit the battery causing failure. This phenomenon limits the use of center-placed tabs in the anode (i.e., tabs located in the center of the electrode). Next, placing tabs towards the center of the electrode typically creates a larger discontinuity in the electrode or winding. Lastly, increasing the number of tabs also adds complexity to the manufacturing process. For example, the electrode tabs 110, 112 must be carefully located on the electrodes 100, 102 and aligned, which requires that the winding be carefully carried out. Additionally, creating multiple non-coated portions 108 is more difficult than creating just a single non-coated section.
What is needed, therefore, is a cell design that minimizes the distance that current must travel along the electrode to reach an electrode tab mounted to the electrode. Furthermore, a cell design and a manufacturing process that simplifies the attachment of electrode tabs to electrodes, that reduces the complexity of processing electrodes, and that reduces the risk of damage to electrode tabs and electrodes during the manufacturing process are needed.
The use of the terms “a”, “an”, “the” and similar terms in the context of describing embodiments of the invention are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising”, “having”, “including” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The terms “substantially”, “generally” and other words of degree are relative modifiers intended to indicate permissible variation from the characteristic so modified. The use of such terms in describing a physical or functional characteristic of the invention is not intended to limit such characteristic to the absolute value which the term modifies, but rather to provide an approximation of the value of such physical or functional characteristic.
Terms concerning attachments, coupling, joinder and the like, such as “attached”, “connected” and “interconnected”, “coupled”, and the like are only used to aid the reader's understanding of the present disclosure, and may not create limitations, particularly as to the position, orientation, or use of the elements disclosed herein. These terms may refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both moveable and rigid attachments or relationships, unless otherwise specified herein or clearly indicated as having a different relationship by context. Therefore, these references, if any, are to be construed broadly. Moreover, such references may not necessarily infer that two elements are directly connected to each other. For example, the term “operatively connected” is such an attachment, coupling or connection that allows the pertinent structures to operate as intended by virtue of that relationship.
The use of any and all examples or exemplary language (e.g., “such as” and “preferably”) herein is intended merely to better illuminate the invention and the preferred embodiments thereof, and not to place a limitation on the scope of the invention. Nothing in the specification should be construed as indicating any element as essential to the practice of the invention unless so stated with specificity. Various embodiments disclosed herein are to be taken in the illustrative and explanatory sense and should in no way be construed as limiting of the present disclosure.
Numerical terms, such as, but not limited to, “first”, “second”, “one”, “another”, or other ordinary and/or numerical terms, should also be taken only as identifiers, to assist the reader's understanding of the various elements, embodiments, variations and/or modifications of the present disclosure, and may not create any limitations, particularly as to the order, or preference, of any element, embodiment, variation and/or modification relative to, or over, another element, embodiment, variation and/or modification unless otherwise indicated herein or clearly contradicted by context.
It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed in certain cases, as is useful in accordance with a particular application.
The above and other needs are met by an electrode assembly having a first elongate substrate having a top end, a bottom end, a width between the top end and the bottom end, a first end, a second end and a length L1 between the first end and the second end. A first active material composite coats at least a first side of the first substrate. A first electrode tab is formed by an uncoated portion of the first substrate, which uncoated portion extends continuously between the first end and the second end of the first substrate and is located at the top end of the first electrode. The assembly further includes a second elongate substrate having a top end, a bottom end, a width between the top end and the bottom end, a first end, a second end and a length L2 between the first end and the second end. A second active material composite coats at least a first side of the second substrate. A second electrode tab is formed by an uncoated portion of the second substrate, which uncoated portion extends continuously between the first end and the second end of the second substrate and is located at the bottom end of the second electrode. Lastly, an electrically-insulative separator is located between the first substrate and the second substrate. The first substrate and second substrate are stacked together with their respective top ends and bottom ends aligned. The separator is located between the first and second substrates. Finally, the first and second substrates and the separate are rolled about a central axis to form a jelly roll. In certain embodiments, an uncoated offset portion is located at one of the first end or second end of the first substrate. Preferably, the offset portion extends continuously between the top end and the bottom end of the first substrate. The length L2 is shorter than the length L1 such that, when the jelly roll is formed, the offset portion forms an outermost layer of the jelly roll and completely encircles the jelly roll.
According to certain preferred embodiments, a battery assembly is formed using the electrode assembly described above. The battery assembly includes a can that includes a top and a bottom and that also includes a first electrical contact and a second electrical contact. An electrolyte is located in the can. The electrode assembly is inserted into the can and one of the electrode tabs is welded to the first electrical contact and the other electrode tab is welded to the second electrical contact. The electrolyte and electrode assembly are then sealed within the can. In some cases, a lollipop-shaped electrical bridge having a circular portion is welded to one of the electrode tabs at an end of the jelly roll. A flexible ribbon portion extending away from the circular portion is then welded to one of the electrical contacts for electrically connecting the electrode tab to the electrical contact. The lollipop-shaped electrical bridge may include a central hollow that is configured to align with a central hollow in the jelly roll when the electrical bridge is welded to the electrode tab. In some cases, the lollipop-shaped electrical bridge includes a flexible ribbon portion extending away from the circular portion that is welded to one of the electrical contacts, such that the electrode tab is indirectly welded to the electrical contact. In some cases, electrical bridges are located at opposite ends of the jelly roll and each electrical bridge has a first portion that is welded to an electrode tab and a second portion that is welded to an electrical contact of the can, such that the electrode tabs are indirectly welded to the electrical contacts.
In certain embodiments, electrode assembly may include a first crushed portion located at the top end of rolled electrodes, where the jelly roll has been crushed. The assembly also includes an uncrushed portion of the jelly roll located adjacent the crushed end. An electrically-conductive bridge having a circular portion may be welded to the top end of the electrode assembly. In certain embodiments, the electrode assembly may include a second crushed portion located at the bottom end of rolled electrodes, where the jelly roll has been crushed. In some cases, the top and the bottom end of the electrode assembly have the same diameter. In certain embodiments, electrically-conductive bridges that each have a circular portion are welded to each of the top end and bottom ends of the electrode assembly.
Finally, the present disclosure provides a battery cell manufacturing method that includes the steps of providing an electrode assembly having: a first elongate substrate having a top end, a bottom end, a width between the top end and the bottom end, a first end, a second end and a length L1 between the first end and the second end; a first active material composite coating at least a first side of the first substrate; a first electrode tab formed by an uncoated portion of the first substrate extending continuously between the first end and the second end of the first substrate and disposed at the top end of the first electrode; a second elongate substrate having a top end, a bottom end, a width between the top end and the bottom end, a first end, a second end and a length L2 between the first end and the second end; a second active material composite coating at least a first side of the second substrate; a second electrode tab formed by an uncoated portion of the second substrate extending continuously between the first end and the second end of the second substrate and disposed at the bottom end of the second electrode; and an electrically-insulative separator. The method further includes the step of placing the separator between the first substrate and the second substrate such that the first substrate and second substrate are stacked together with their respective top ends and bottom ends aligned and with the separator located between the first and second substrates. Finally, the method provides rolling the stacked first substrate, separator, and second substrate about a central axis to form a jelly roll.
Certain embodiments of the method include crushing a top portion of the jelly roll to provide a first crushed portion. In some cases, the method includes providing a first electrically-conductive bridge having a first portion and a second flexible ribbon portion extending away from the first portion. A can having a first electrical contact is provided. Then, the method includes welding the first portion of a first electrically-conductive bridge to the top surface of the first crushed portion of the jelly roll. Similarly, the method includes welding the flexible ribbon portion of a first electrically-conductive bridge to the first electrical contact of the can.
In certain embodiments of the invention, the disclosed method includes the steps of crushing a bottom portion of the jelly roll to provide a second crushed portion, wherein a bottom surface of the second crushed portion has a third diameter centered on the central axis that is smaller than the second diameter. In certain embodiments, that method includes providing a first electrically-conductive bridge, a second electrically-conductive bridge, and a can having a first electrical contact and a second electrical contact. Then, indirectly welding the top surface of the first crushed portion to the first electrical contact via the first bridge and indirectly welding the bottom surface of the second crushed portion to the second electrical contact via the first bridge. In some cases, the first bridge includes a first portion that is welded to the top surface of the first crushed portion and a second flexible ribbon portion extending away from the first portion of the first bridge that is welded to the first electrical contact. Lastly, in some cases, the method may include providing a can having a first electrical contact and a second electrical contact. Then, inserting the jelly roll into the can, welding the first and second electrode tabs to the first and second electrical contacts, respectively, providing an electrolyte within the can, and sealing the jelly roll and electrolyte within the can.
Further advantages of the invention are apparent by reference to the detailed description when considered in conjunction with the figures, which are not to scale so as to more clearly show the details, wherein like reference numerals represent like elements throughout the several views, and wherein:
With reference to
Each of the electrodes 200, 202 is preferably formed by coating one or both sides of a substrate (i.e., collector plate or current collector) with an electrically-conductive active material composite, including either a positive electrode active material composite having a first electrical conductivity, which may comprise one or more of lithium, manganese, iron, nickel, cobalt, etc., or negative electrode active material composite having a second electrical conductivity, which may comprise one or more of graphite, silicon, hard carbon, etc. Combinations of these and other materials known to persons of skill in the art could be used to coat the collector plates to form electrodes 200, 202. Each of the active material composites is typically comprised of a particulate electrode active material, a conductive material, and a binder. The active material composite may also include a plasticizer in a solvent, which is removed during the electrode formation process. The collector plates are typically a metal foil, mesh, etc., typically made of aluminum or copper. The coatings may be deposited on to the electrodes by any means known to persons skilled in the art. These methods include, but are not limited to, mechanical deposition, electromechanical deposition, electrochemical deposition, or any combination of processes known to persons skilled in the art.
In order for an electrode cell to function properly and/or optimally, cathode material should ideally face corresponding anode material across a separator 204 along the entire length of the cathode. If the electrodes 200, 202 are exactly the same length, there is a chance that a portion of one of the electrodes (the outer electrode in the jelly roll, the anode) might extend beyond the other electrode (the inner electrode of the jelly roll, the cathode) once they are wound together. As such, in preferred embodiments, one of the electrodes 200, 202 is slightly longer than the other electrode such that, when the electrodes are wound together, the longer electrode (i.e., electrode 200) provides the final wind and is located on the outside of the jelly roll. In the illustrated embodiment, electrode 200 has an overall length L1 and electrode 202 has an overall length L2. Length L1 is longer than length L2 by length L3. Preferably, length L3 of electrode 200 is sized to extend beyond the end of electrode 202 when the two electrodes are wound together.
With further reference to
The total length of the electrodes 200, 202 that may be used is limited by the inside diameter of the can used in the assembly. By leaving a portion of one of the electrodes uncoated (i.e., portion 209), the diameter of the electrode assembly is slightly reduced when compared to the diameter of an electrode assembly formed with electrodes having their entire length coated. Then, by reducing the diameter of the electrode assembly 206, the overall electrode length can be increased, which results in a higher capacity at the cell level. Next, battery materials having performance losses associated with their activation (i.e., first cycle loss) and their use (i.e., capacity fade). By providing a bare or uncoated section on one of the electrodes 200, 202, certain of those losses (i.e., losses that would have occurred at the uncoated portion) may be reduced or possibly even eliminated entirely. Lastly, leaving a portion of the anode uncoated can result in an increased anode yield than a fully-coated anode electrode. For example, in the production of electrode assembly 206, the uncoated portion is created by not coating a certain percentage of the electrode foil. In the illustrate case, the uncoated end is approximately 3-5% of the total anode area. It is anticipated that the uncoated area would result in an approximately 3-5% higher electrode yield compared to a fully-coated anode electrode. Uncoated strip portions 208 function as electrically-conductive electrode tabs 210, 212. Preferably, in forming electrode assembly 206, electrodes 200, 202 are oriented such that one electrode tab 210 is located on one end 214 of one of the electrodes, and the other electrode tab 212 is located on an opposing end 216 of the other electrode. As such, in those preferred cases, no tabs extend above the top end 214 or below the bottom end 216 of the electrodes 200, 202 in transverse direction 218. Electrode tabs 210, 212 preferably extend continuously from end 240 to opposing end 242, in direction 220, on each of the electrodes 200, 202. Direction 220 is parallel with the direction that the electrodes 200, 202 are rolled to form the electrode assembly 206, and direction 218 is preferably orthogonal to direction 220 and is also orthogonal to the direction that the electrodes are rolled to form electrode assembly. In other embodiments, only one electrode is provided with a continuous electrode tab. In those cases, the other electrode may be provided with one or more conventional electrode tabs, such as tab 110 (shown in
As shown in
With reference to
With further reference to
Referring to
Bridges 250, 252 connect the electrode assembly 206 to a can 224 (first electrical contact) and corresponding cap 244 (second electrical contact), which are both illustrated in
Next, it important to prevent the cap 244, bridge 250, and electrode tab 210, which all have one polarity, from contacting the can 224, bridge 252, or electrode tab 212, which all have a different polarity. Contact between any two components with different polarities could create a short circuit and degrade the life of the cell. For that reason, as shown in
Referring again to
The entire battery assembly 262, which preferably includes electrode assembly 206 as well as bridges 250, 252 welded to the electrode assembly, gasket 264, and cap 244, is inserted into can 224 via a top opening 226. As shown in
After assembly 262 is inserted into the can 224, bridge 250 is positioned near top opening 226 and bridge 252 is positioned near bottom 228. In this illustrated embodiment, bottom 228 is integrally formed with the can 224 and cap 244 is a separate component that covers opening 226. However, in other embodiments, the bottom 228 may be removable from the can 224 and used to cover a lower opening (not shown) in the can and cap 244 may be integrally formed with the can. In still further embodiments, both ends may be removable from the can 224.
In the illustrated embodiment, since the central hollow 258 was aligned with central hollow 236 when welding bridge 250 to end 214, as described above, a welding rod or laser welder may be directed down through the aligned openings to weld bridge 252 to the bottom 228 of the can 224. Alternatively, resistance or laser welding may be used to weld bridge 252 to the bottom 228 of the can 224 through the bottom of the can. In this way, can 224 has the same polarity as electrode 212 and may serve as an electrode terminal. In preferred embodiments, bridge 252 has a thickness that is approximately equal to the wall thickness of can 224 and that is thicker than conventional electrode tabs, such as electrode tab 112 (shown in
The table shown in
Although this description contains many specifics, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments thereof, as well as the best mode contemplated by the inventor of carrying out the invention. The invention, as described herein, is susceptible to various modifications and adaptations as would be appreciated by those having ordinary skill in the art to which the invention relates.
This application claims the benefit of U.S. Provisional Patent Application No. 62/938,524, filed on Nov. 21, 2019, and entitled SECONDARY BATTERY WITH ELECTRODE HAVING CONTINUOUS TAB, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62938524 | Nov 2019 | US |
