Patent Application
20130143110
1. Technical Field
The subject matter disclosed herein relates to an enclosure for an energy storage cell.
2. Discussion of Art
Energy storage cells may have challenges with leakage and manufacturability. Multiple welded seams may increase the number of discontinuities in the packaging, which may result in inefficient thermal management or increased electrical resistance limiting the efficiency of the cell. Multiple welded seams may also adversely affect the manufacturability of energy storage cells having an electrochemical cell under vacuum within the cell housing.
It may be desirable to have an enclosure for an energy storage cell that differs from those that are currently available.
Presently disclosed is a terminal apparatus. In an embodiment, the terminal apparatus includes a terminal body having a peripheral edge extending substantially around a perimeter of the terminal body such that the terminal body is configured to be secured to a cell housing to retain an electrochemical cell in the cell housing; a terminal connector extending from the peripheral edge forming a first terminal for an energy storage cell; a sealable vacuum port extending through the terminal body; and an aperture in the terminal body configured to receive a second terminal of the energy storage cell.
Also disclosed is a method of manufacturing an energy storage cell. In embodiments, the method includes the steps of securing a terminal body to a cell housing containing an electrochemical cell; evacuating the energy storage cell through a vacuum port of the terminal body; and sealing the vacuum port to maintain a partial pressure within the energy storage cell.
An energy storage cell is also disclosed. In embodiments, the energy storage cell includes an rechargeable electrochemical cell and a cell housing, wherein the electrochemical cell is disposed within the cell housing. The energy storage cell also includes a terminal apparatus secured to the cell housing to retain the electrochemical cell, wherein the terminal apparatus includes a monolithic terminal body with a peripheral edge extending substantially around a perimeter of the terminal body wherein the peripheral edge is secured to the cell housing to provide a seal; a terminal connector extending from the peripheral edge forming a first terminal for the energy storage cell; a sealable vacuum port extending through the terminal body; and an aperture in the terminal body configured to receive a second terminal of the energy storage cell; and wherein the electrochemical cell is secured to the terminal body to provide a seal such that the energy storage cell is configured to be evacuated through the sealable vacuum port and configured to maintain a partial pressure when the sealable vacuum port is sealed.
Reference is made to the accompanying drawings in which particular embodiments and further benefits of the invention are illustrated as described in more detail in the description below, in which:
The subject matter disclosed herein relates to an enclosure for an energy storage cell and more particularly to a terminal apparatus for an energy storage cell. Referring to
In an embodiment, a terminal apparatus for an energy storage cell includes a terminal body with a peripheral edge extending around a perimeter of the terminal body such that the terminal body is configured to be secured to a cell housing to retain an electrochemical cell in the cell housing. The terminal body also includes a terminal connector extending from the peripheral edge forming a first terminal for an energy storage cell, a sealable vacuum port extending through the terminal body, and an aperture in the terminal body configured to receive a second terminal of the energy storage cell.
In some embodiments, the energy storage cell (having a terminal apparatus as described herein) can have dimensions of about 37 mm×27 mm×240 mm, any of which dimensions may vary by up to +/−50%, in accordance with various embodiments. In other embodiments, the dimensions of the energy storage cell may vary as desired to support the electrochemical cell for a given application. In embodiments, the chemistry of a cell is of the sodium-metal-halide type, in which NaCl and Ni are converted to Na and NiCl2 during battery charging. The energy capacity of a cell can range from about 30 amp*hours to about 250 amp*hours.
Referring now to
The terminal apparatus 10 also includes a terminal connector 16 extending from the peripheral edge 14 of the terminal body 12. The terminal connector 16 forms a first terminal for an energy storage cell, and provides an electrical connection point for the energy storage cell. In an embodiment, the terminal connector 16 includes a first tab 22 and a second tab 24 each extending from a first portion 26 of the peripheral edge 14. The terminal 10 also includes an aperture 20 in the terminal body 12 configured to receive a second terminal of the energy storage cell.
The first tab 22 and second tab 24 may be used either individually or in combination as the first terminal of the energy storage cell. A terminal apparatus 10 having a first terminal including two tabs may facilitate manufacturing of the terminal. In one embodiment, a plurality of energy storage cells may be electrically connected in parallel, where the first and second tabs of an energy storage cell are each electrically connected to the first terminal connectors of different energy storage cells. In another embodiment, the first and second tabs of the energy storage cell may be connected to the second terminal of another energy storage cell for those applications in which energy storage cells are electrically connected in series. As illustrated, the first tab 22 and second tab 24 extend from the peripheral edge 14 and are bent inward towards the aperture 20 of the terminal body 12. As shown in
In an embodiment, the first portion 26 of the peripheral edge 14 corresponds to one of the four sides of the substantially rectangular terminal body 12. In other embodiments, the first portion of the peripheral edge may correspond to less than one side, such as one-half of one side of the peripheral edge. In yet other embodiments, the first portion of the peripheral edge may correspond to that portion of the peripheral edge from which the terminal connector extends. In embodiments where the terminal has a circular configuration, the first portion of the peripheral edge may be a portion, such as one-quarter or one-eighth of the circumference of the terminal defined by the peripheral edge. In various embodiments, the first terminal and second terminal of the energy storage cell may correspond to either the positive or negative terminal of the energy storage cell depending upon the configuration of the cell.
Referring now to
In some embodiments, the peripheral edge 14 of the terminal body 12 is welded to a cell housing to secure the terminal apparatus to the cell housing. The peripheral edge 14 may provide a weldable edge configured to mate with the cell housing. In some embodiments, the terminal apparatus 10 is secured to the cell housing by a mechanical connection. In one embodiment, the terminal body 12 extends outward from the aperture 20 and is bent approximately 90 degrees to form a weldable edge extending around the perimeter of the terminal. In other embodiments, the peripheral edge may include a portion extending radially from the terminal body or extending downward from the terminal body. In yet other embodiments, the peripheral edge may include a stepped portion configured to seat on a corresponding step in the cell housing.
In embodiments, the terminal apparatus 10 is electrically conductive and conducts current from the electrochemical cell through the terminal connector 16. The electrical resistance of the terminal apparatus thus affects the available power output of the energy storage cell. The electrical resistance of the terminal apparatus 10 may be determined by the conductivity or resistivity of the material selected for the terminal as well as the thickness of the material of the terminal body 12 including terminal connector 16. The thickness of the terminal body 12 adjacent the aperture is indicated by dimension A in
Referring now to
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In some embodiments, the peripheral edge 84 is welded to the cell housing 72 around the cell housing rim 76. In embodiments, the peripheral edge 84 provides a weldable edge and the terminal apparatus is welded to the cell housing by a weld process suitable to the materials selected for the terminal apparatus and the cell housing. The weld seam between the terminal and the cell housing may be a continuous weld or, alternatively, the weld seam may be two or more discrete welds. In various embodiments, the weld seam is created by a laser weld process, a resistance weld process, an electron beam weld process, a plasma arc weld process, a tungsten inert gas weld process, a wire weld process, a solder weld process, or any other appropriate welding technique. Additionally, the connection between the terminal and the cell housing may be any suitable weld joint geometry, such as butt joint, lap joint, corner joint, edge joint, or T-joint. The peripheral edge of the terminal apparatus may thus be understood as including the portion of the terminal which is secured to the cell housing. In some embodiments, the terminal apparatus may be further secured to cell walls of the cell housing by welding or mechanical connections.
In one embodiment, the second terminal 78 of the electrochemical cell 80 is a positive terminal of the energy storage cell 70. The negative terminal of the electrochemical cell may be conductively coupled to the cell housing 72, which is conductively coupled to the terminal body 82 and the terminal connector 86. In this manner, the terminal connector 86 serves as the negative terminal of the energy storage cell 70. In an embodiment, the second terminal 78 of the electrochemical cell 80 is secured to the terminal body 82 prior to assembly into the cell housing 72. In some embodiments, the electrochemical cell 80 is electrically isolated from the terminal body 82 by an insulator to maintain electrical isolation between the positive terminal and the negative terminal of the energy storage cell 70. In yet other embodiments, the terminal connector 86 is the positive terminal while the second terminal 78 is the negative terminal of the energy storage cell depending on the configuration of the electrochemical cell 80.
In an embodiment, a method of manufacturing an energy storage cell 70 includes securing a terminal body 12 to a cell housing 72 containing an electrochemical cell 80. The method also includes evacuating the energy storage cell 70 through a sealable vacuum port of the terminal body 12, and sealing the vacuum port to maintain a partial pressure within the energy storage cell. As used herein, a partial pressure refers to the reduced pressure achieved by evacuating an enclosure using reasonable commercial methods. In one embodiment, a partial pressure is a vacuum, such as a total vacuum that is free of all atmosphere. In another embodiment, a partial pressure is a nominal residual atmosphere remaining after evacuation of the energy storage cell. As such, a vacuum may be defined as a pressure less than a predetermined threshold, such as no more than 25 millibars, no more than 5 millibars, or no more than 1 millibar. The predetermined threshold may be selected based upon the methods and equipment used to evacuate the energy storage cell.
In yet another embodiment, the method of manufacturing an energy storage cell includes adding an inert gas into the energy storage cell through the vacuum port to achieve the partial pressure within the energy storage cell. In embodiments, the inert gas may be helium or argon. The inert gas may be a noble gas or may be a non-reactive gas formed of two or more elements. In one embodiment, the inert gas is added after the energy storage cell is evacuated. The energy storage cell may be placed in a vacuum chamber and the vacuum chamber evacuated to achieve a vacuum within the energy storage cell. The inert gas may be added to the vacuum chamber, such as through a bleed valve, until the desired partial pressure is achieved within the chamber. With the sealable vacuum port open, the inert gas also enters the energy storage cell. In one embodiment, the inert gas is added such that the partial pressure within the energy storage cell is no greater than 500 millibars. In another embodiment, the inert gas is added until the partial pressure within the energy storage cell is no less than 10 millibars and no more than 300 millibars. In another embodiment, the energy storage cell may be placed in a vacuum chamber. The vacuum chamber may be evacuated while the inert gas is provided to the chamber. The rate of addition of the inert gas and the rate of evacuation of the chamber may be controlled to provide the desired partial pressure within the vacuum chamber and within the energy storage cell. In some embodiments, once the partial pressure is established within the energy storage cell, the sealable vacuum port is sealed such that the energy storage cell maintains the partial pressure within the energy storage cell.
In an embodiment, an energy storage cell having a partial pressure of inert gas is leak tested using an inert gas detector. The energy storage cell may be placed into a vacuum chamber, which is then evacuated. If the energy storage cell is not sealed, inert gas leaking from the energy storage may be detected. In one embodiment, the energy storage cell is provided with a partial pressure of helium and a helium leak tester is utilized to identify leaks from the energy storage cell. In this manner, manufacturing defects may be identified and the energy storage cells repaired prior to incorporation into an energy storage device. This may improve the quality of the energy storage cells and their reliability in various applications, including rechargeable batteries.
In one embodiment, the electrochemical cell 80 is installed into the cell housing 72 and the terminal body 82 is secured to the cell housing without evacuating the energy storage cell. In an embodiment, the method of manufacturing an energy storage cell includes welding the peripheral edge 84 of the terminal body 82 to the cell housing 72 as discussed above. Welding the terminal body 82 to the cell housing 72 may be facilitated by performing this step in a non-vacuum environment where traditional welding techniques may be economically employed. For example, welding in a vacuum environment may require more frequent interruptions in production to clean or maintain the welding equipment. By assembling the electrochemical cell, cell housing, and terminal apparatus in a non-vacuum environment, the amount of welding required to be formed in a vacuum environment is reduced. In addition, the electrochemical cell 80 may be secured to the perimeter 98 of the aperture of the terminal body 82 prior to evacuating the energy storage cell. An insulator may be provided between the electrochemical cell and the terminal body to maintain electrical isolation between the positive and negative terminals of the energy storage device. In some embodiments, a partial pressure of an inert gas is provided within the energy storage cell and an inert gas leak detector is used to ensure a sealed connection between the terminal apparatus, the cell housing, and the electrochemical cell.
In some embodiments, after the terminal apparatus is secured to the cell housing, the energy storage cell may be evacuated by placing one or more energy storage cells in a vacuum chamber or other device capable of being evacuated. During the evacuation process, the atmosphere within the cell housing may be drawn out through the sealable vacuum port 88 until the interior of the cell housing 72 is sufficiently evacuated to provide a partial pressure as previously described. In an embodiment, when the energy storage cell is evacuated and the desired partial pressure established, the sealable vacuum port 88 is sealed by laser welding. Once the sealable vacuum port 88 is sealed, the energy storage cell maintains the partial pressure within the cell housing. The welding occurring under partial pressure, such as under vacuum, is thus limited to sealing the vacuum port. In some embodiments, the welding under partial pressure may have a duration of less than 50 milliseconds per energy storage cell providing a reduction in the total welding occurring under partial pressure and a corresponding increase in the number of energy storage cells that may be produced before maintenance of the welding equipment is required.
Another embodiment relates to a terminal body for a terminal apparatus. The terminal body comprises a terminal body member and a terminal connector. The terminal body member comprises a planar intermediate portion (generally indicated as 12 in
In embodiments, the intermediate portion defines a major plane (the plane coincident with the surface of 12 in
In the specification and claims, reference will be made to a number of terms that have the following meanings. The singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise. Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term such as “about” is not to be limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Similarly, “free” may be used in combination with a term, and may include an insubstantial number, or trace amounts, while still being considered free of the modified term. Moreover, unless specifically stated otherwise, any use of the terms “first,” “second,” etc., do not denote any order or importance, but rather the terms “first,” “second,” etc., are used to distinguish one element from another.
As used herein, the terms “may” and “may be” indicate a possibility of an occurrence within a set of circumstances; a possession of a specified property, characteristic or function; and/or qualify another verb by expressing one or more of an ability, capability, or possibility associated with the qualified verb. Accordingly, usage of “may” and “may be” indicates that a modified term is apparently appropriate, capable, or suitable for an indicated capacity, function, or usage, while taking into account that in some circumstances the modified term may sometimes not be appropriate, capable, or suitable. For example, in some circumstances an event or capacity can be expected, while in other circumstances the event or capacity cannot occur—this distinction is captured by the terms “may” and “may be.” The terms “generator” and “alternator” are used interchangeably herein (however, it is recognized that one term or the other may be more appropriate depending on the application). The term “instructions” as used herein with respect to a controller or processor may refer to computer executable instructions.
This written description uses examples to disclose the invention, including the best mode, and also to enable one of ordinary skill in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to one of ordinary skill in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not different from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
