LARGE FORMAT ELECTROCHEMICAL ENERGY STORAGE DEVICE HOUSING AND MODULE
An assembly includes non-load bearing housings, each housing including several cavities. Each cavity includes a stack of freely stacked electrochemical storage cells in the housings. Each electrochemical storage cell includes an anode electrode, a cathode electrode, and a separator located between the anode electrode and the cathode electrode. The assembly is configured such that pressure applied to the assembly is born by the freely stacked electrochemical storage cells.
The present invention is directed to aqueous batteries and hybrid energy storage devices, and in particular to housings for such devices.
BACKGROUNDSmall renewable energy harvesting and power generation technologies (such as solar arrays, wind turbines, micro sterling engines, and solid oxide fuel cells) are proliferating, and there is a commensurate strong need for intermediate size secondary (rechargeable) energy storage capability. Batteries for these stationary applications typically store between 1 and 50 kWh of energy (depending on the application) and have historically been based on the lead-acid (Pb acid) chemistry. Banks of deep-cycle lead-acid cells are assembled at points of distributed power generation and are known to last 1 to 10 years depending on the typical duty cycle. While these cells function well enough to support this application, there are a number of problems associated with their use, including: heavy use of environmentally unclean lead and acids (it is estimated that the Pb-acid technology is responsible for the release of over 100,000 tons of Pb into the environment each year in the US alone), significant degradation of performance if held at intermediate state of charge or routinely cycled to deep levels of discharge, a need for routine servicing to maintain performance, and the implementation of a requisite recycling program. There is a strong desire to replace the Pb-acid chemistry as used by the automotive industry. Unfortunately the economics of alternative battery chemistries has made this a very unappealing option to date.
Despite all of the recent advances in battery technologies, there are still no low-cost, clean alternates to the Pb-acid chemistry. This is due in large part to the fact that Pb-acid batteries are remarkably inexpensive compared to other chemistries ($200/kWh), and there is currently a focus on developing higher-energy systems for transportation applications (which are inherently significantly more expensive than Pb-acid batteries).
SUMMARYAn embodiment relates to an assembly including a plurality of non-load bearing housings, each housing including a plurality of cavities. Each cavity includes a stack of freely stacked electrochemical storage cells in the housings. Each electrochemical storage cell includes an anode electrode, a cathode electrode and a separator located between the anode electrode and the cathode electrode. The assembly is configured such that pressure applied to the assembly is born by the freely stacked electrochemical storage cells.
Another embodiment relates to a method of making an assembly including a plurality of non-load bearing housings. Each housing includes a plurality of cavities. The method includes freely stacking anode electrodes, cathode electrodes and separators between the anode electrodes and the cathode electrodes in the plurality of cavities. The assembly is configured such that pressure applied to the assembly is born by the freely stacked electrochemical storage cells.
Embodiments of the invention are drawn to electrochemical energy storage devices and systems, such as primary and secondary batteries and asymmetric/hybrid energy storage systems described below. While secondary hybrid aqueous energy storage devices described below are preferred embodiments of the invention, the invention is also applicable to any suitable electrochemical energy storage systems, such as aqueous and non-aqueous electrolyte containing batteries (e.g., having anodes and cathodes which intercalate ions from the electrolyte, including Li-ion batteries, etc.) or electrolytic capacitors (also known as supercapacitors and ultracapacitors, e.g., having capacitor or pseudocapacitor anode and cathode electrodes that store charge through a reversible nonfaradaic reaction of cations on the surface of the electrode (double-layer) and/or pseudocapacitance rather than by intercalating alkali ions).
Hybrid electrochemical energy storage devices and systems of embodiments of the present invention include a double-layer capacitor or pseudocapacitor electrode (e.g., anode) coupled with an active electrode (e.g., cathode). Such devices are also known as asymmetric electrochemical energy storage devices. In these systems, the capacitor or pseudocapacitor electrode stores charge through a reversible nonfaradaic reaction of alkali cations on the surface of the electrode (double-layer) and/or pseudocapacitance, while the active electrode undergoes a reversible faradaic reaction in a transition metal oxide that intercalates and deintercalates alkali cations similar to that of a battery, such as those described in U.S. patent application Ser. No. 13/043,787 filed on Mar. 9, 2011 and incorporated herein by reference in its entirety.
In an alternative embodiment, the electrochemical energy storage device comprises a battery in which both the anode electrode and the cathode electrode are made of materials that intercalate ions. For example, the battery may be a sodium or lithium ion based battery which includes a graphite anode and a metal oxide containing cathode, such as a layered oxide, e.g., lithium cobalt oxide, or a polyanion, e.g., lithium iron phosphate, or a spinel, e.g., manganese oxide, for example a doped or undoped cubic spine λ-MnO2-type material that intercalates lithium or sodium ions, or a NaMn9O18 tunnel structured orthorhombic material. In another alternative embodiment, the anode electrode is made of a mixture of materials, one of which intercalates ions (e.g., sodium or lithium) in a faradaic reaction and the other one of which is a capacitive electrode material which stores charge through the reversible nonfaradaic reaction of alkali metal cations on a surface of the anode electrode or the pseudocapacitive electrode material which undergoes a partial charge transfer surface interaction with alkali metal cations on a surface of the anode electrode. An example of such a mixed anode material is a mixture of “faradaic” graphite and “nonfaradaic” active amorphous or polycrystalline carbon.
Embodiments include configurations of and packaging for a manufacturable large-scale electrochemical energy storage device. Specifically, there is a need to develop a new way of containing the electrochemical energy storage device cells that is both economically feasible and high performing. Embodiments include the individual building block unit housing comprising outer walls and an integral base wall formed to include cavities separated by partitions which are preferably integral with the outer walls and base wall and a lid which may separable from the housing or attached to the housing e.g., by a hinge or the like. Individual building block unit housings include a 4-cavity configuration, each cavity containing an electrochemical energy storage device connected in series or parallel in a square “2 by 2” format. Alternative units may have more or less cavities and may be arranged in other configurations, such as 1 by 2, 1 by 3, 1 by 4, 2 by 3, 2 by 4, 3 by 4, etc. Embodiments also include a module, which is a stack of these units stacked on top of each other. The housings and lids may be made of a polymer, such as polypropylene.
Design considerations for the embodiments discussed below include the electrochemistry and electrode materials. In an embodiment, the electrodes (anode, cathode or both anode and cathode) are made from free standing pressed pellets. In an embodiment, electrochemical energy storage device is made by stacking the pellets into the housing in the proper order (e.g., current collector, cathode, separator, anode, current collector, anode, separator, cathode, and repeat). Each of the cavities in the electrochemical energy storage device may have many cells like this connected in parallel to make, for example, a 0 to 2.5 V electrochemical energy storage device. In an embodiment, each stack may then be connected in series. For a four cavity device, the device may be a 0 to 10 V system.
The housing lids may be hot plate sealed to the housing after assembly. The lid to housing interface may also be laser-sealed, sealed with adhesives, or sealed using a compression force and some type of polymeric gasketing. In an embodiment, the housing has a single pressure relief valve. Preferably, the cavities have small airways connecting them such that any excess gas that evolves anywhere in the electrochemical energy storage device can be released by the pressure relief valve. The electrical connections between stacks disposed in individual cavities of unit may be described as “jumpers” and they are formed by either directly spot welding current collection tabs together, or via a metal pass-through between the cavities. Typically, the jumpers are metal, such as stainless steel, although Al, and/or Al/stainless clad structures may also be used. Other conductive materials may also be used.
An aspect of the embodiments below is that the electrode stacks disposed inside respective individual cavities of the housings are placed in mating contact with each other by an externally applied pressure or compression force tending to compress the stacks. Absent this pressure, the electronic integrity of individual stacks of the electrochemical energy storage device may suffer and performance may be sub-standard. In particular the pressure or compression force applied to each stack places adjacent stack elements in mating contact thereby decreasing the gap between adjacent elements which tends to increase ion exchange between the anodes, the cathodes and the electrolyte present in the gap between them, as well as to increase current flow from the anodes and cathode to the adjacent current collectors. In an embodiment, the electrochemical energy storage device units (i.e., housings containing the storage device stacks) include a hole in their center to provide for a tie bar that can go through a plurality of the units stacked together in an assembly and attach to two opposing rigid plates with one positioned at a top of the units stacked together and the other positioned at a bottom of the units stacked together to thereby apply a compression force to the stacked together units when the tie bar is placed into a condition of tension. Moreover, the pressure plates are configured to transfer the tension force applied to the tie bar directly to the electrode stack. Optionally, a semi-rigid body may used to provide “spring force” on the top of the electrochemical energy storage device stack such that there is some room for electrode stack breathing during use. These stacks of electrochemical energy storage devices can then be connected in series or parallel as needed. Also, in an embodiment, stacks of electrochemical energy storage devices can be fitted onto pallet structures with integrated electronic controls and power lines to form modules. These modules can then be stacked integrated into larger systems. To allow for the facile translation of pressure from outside the case to the electrode stack, a completely flexible battery lid may be used.
Embodiments may include one or more of the following features as well as other features as described above and illustrated in the attached figures:
-
- 1) a single tie rod through the middle of the electrochemical energy storage device stack housing used to keep a stacks together,
- 2) the electrochemical energy storage device units (i.e., housings) are designed such that the electrode stacks inside them bear the load of the pressure imparted on the stack by the tie rod,
- 3) a mildly elastic member may be used as a “spring force” to maintain long term positive pressure on the stacks,
- 4) the housings may be assembled onto pallets with integrated electronic controls and power lines,
- 5) inside the electrochemical energy storage device housing, there may be single pressure relief valve and the electrochemical energy storage devices in the cavities may then be connected in series or parallel,
- 6) There may be an open gas pathway between the cavities, and
- 7) The electrochemical energy storage device cavities may be filled with a gelled liquid electrolyte (or gelled water) as a source of moisture for the electrode stacks that will not “slosh” around and affect performance.
Preferably, each cavity 104 includes a stack 110 of electrochemical cells 111. Each electrochemical cell 111 includes an anode 112, a cathode 114 and a separator 116 located between the anode 112 and the cathode 114. In further embodiments a hybrid or asymmetric electrochemical cell 111 may include a second anode and a second cathode separated by a second separator. The electrochemical cells 111 may be electrically connected in series or prismatically in the stack 110 of electrochemical cells 111. In a prismatic configuration, the electrochemical cells 111 in the stack 110 are connected in parallel as illustrated in
Each electrochemical cell 111 further includes two current collectors 130, 132 provided to collect the current generated by the electrochemical cells 111. The current collectors 130, 132 may be made of any suitable electrically conducting material, such as carbon (e.g. graphite) or metal. In a prismatic stack 110, described for example in U.S. patent application Ser. No. 13/043,787 and illustrated in
A third electrochemical cell 111 is located adjacent to the second (anode) side of the first electrochemical cell 111 in the prismatic stack 110. The anode electrode 112 of the first electrochemical cell 111 electrically contacts a first anode current collector 132 and the anode electrode 112 of the third electrochemical cell 111 also electrically contacts the first anode current collector 132. Stacking can continue in this manner. The resulting prismatic stack 110 therefore may include a plurality of electrochemical cells 111 that are stacked in pairs, front-to-front and back-to-back, alternating adjacent anode electrodes 112 and adjacent cathode electrodes 114.
Preferably, the anodes 112, cathodes 114, separators 116 and current collectors 130, 132 are freely stacked and are not laminated to each other in the cavities 104. That is, no adhesives or binders are located between the individual components (anodes 112, cathodes 114, separators 116 and current collectors 130, 132) in the stacks 110 as are typically found in conventional laminated electrochemical cells. Instead, one embodiment of the present invention applies a longitudinal pressure force to a plurality of freely stacked electrochemical cells that forces adjacent cell elements into mating contact to improve the electrochemical reaction between the anodes and cathodes and the electrolyte that fills the cavities as well as to improve electrical contact between the current collectors corresponding anodes and cathodes to increase current flow to the current collectors.
Another embodiment is illustrated in
In an aspect of this embodiment, the separator 116 includes flanges 116A around the periphery of the separator 116. The flanges 116A define one or more cavities that are configured to receive the anode/cathode electrode pieces 112, 114. In another aspect, the electrochemical storage cells 111 include a plurality of flexible, electrically conductive contacts (e.g., tabs) 118 operatively connected to the plurality of cathode and anode current collectors 130, 132. The flexible, electrically conductive contacts 118 may be affixed to one side of the cathode and anode current collectors 130, 132. In this embodiment, electrical connection to the stacks 110 of electrochemical storage cells 111 in adjacent cavities 104 in the housing 102 may be made by draping the flexible, electrically conductive contacts 118 over the walls 105 between adjacent cavities 104 and connecting the stacks 110. The stacks 110 in adjacent cavities 104 may be electrically connected in series, in parallel or combination thereof as desired. In the embodiment illustrated in
In an embodiment, the stack 110 of electrochemical storage cells 111 is prismatically stacked. A plurality of electrically conductive contacts (e.g., tabs) 118 operatively connected to the plurality of cathode and anode current collectors 130, 132. As in the previous embodiments, the electrically conductive contacts 118 may be affixed to one side of the cathode and anode current collectors 130, 132 as shown in
In an embodiment, the electrically conductive contacts 118 of alternate cells 111 in the stack 110 of cells 111 are affixed to each other, such as by welding or brazing. That is, the electrically conductive contacts 118 connected to successive cathode electrodes 114/cathode current collectors 130 are connected to each other while the electrically conductive contacts 118 connected to successive anode electrodes 112/anode current collectors 132 are connected to each other. In this manner, the electrochemical cells 111 in the stack 110 can be electrically connected in parallel.
In an alternative embodiment shown in
The electrochemical device 100 also includes a liquid or gel electrolyte (not shown) in the cavities 104 which substantially fills the cavity to immerse each electrochemical cell in electrolyte. The housing 102 of the electrochemical device 100 is preferably hermitically sealed with a lid 106 to prevent the loss of electrolyte from the electrochemical device 100 and a common gas volume is provided above each cavity between the top of each cavity and the lid to allow outgassing from all of the cavities to collect in the gas volume. In an embodiment, the lid 106 includes a hole 160 in the center which is aligned with a corresponding hole 161 that extends through the housing 102 for receiving the tie rod 206 there through. The lid 106 may also include lid cavities 107 which are recessed to ensure that a bottom surface of each cavity 107 contacts the top surface of the electrode stack in the corresponding cavity in order to transfer a pressure or compression force from pressure plates 202 through each unit in an assembly 200 when the units are stacked in an assembly, as shown in
As illustrated in
In a method of making the electrochemical device 100, the lid 106 is sealed onto the housing 102 after the solid components (e.g. the anode electrodes 112, cathode electrodes 114, separators 116, anode current collectors 132 and cathode current collectors 130) are stacked in the housing 102. Then, the device 100 is evacuated via the electrolyte ports 162 to remove any undesired gases. After evacuation, the cavities 104 of the electrochemical device 100 are partially filled with electrolyte, leaving a gas space or volume above the electrolyte in the cavities 104.
As illustrated in
The pass through connectors 140/terminals 133 are located within the housing 102 and therefore protected by the housing 102. That is, the housing 102 provides a “shroud” 143 surrounding the vertically oriented pass through connectors 140/terminals 133 which protect the pass through connectors 140/terminals 133 and the underlying electrochemical devices 100 during handling of the assembly 200. In contrast, the use of horizontal, i.e. protruding, terminals may risk puncture with adjacent electrochemical cells 100 during handling of the assembly 200. In an embodiment, the pass through connector 140 is held in place with a push retainer 142. To protect the housing 102 and further secure the push retainer 142, a washer 144, such as a flat washer or lock washer, may be provided on one side of the housing 102, and a seal 146, such as a silicone rubber seal, may be provided on the other side of the housing 102.
The assembly 200, as illustrated in
As discussed above, the components of the electrochemical cells 111 are freely stacked. However, the inventors have discovered that the electrochemical devices 100 are more robust when the stacks 110 of electrochemical cells 111 are under pressure. Therefore, as discussed in more detail below, assemblies 200 of electrochemical devices 100 are configured such that the stacks 110 of electrochemical cells 111 are assembled such that the cells 111 are under pressure. Preferably, the stacks 110 bear most or all (e.g. at least 90%, such as 90-100%, e.g. 95-99%) of the compressive loading. That is, it is preferable that the housings 102 and the lids 106 bear little or no compressive loading (e.g. 0-10%, such as 1-5%). That is, the housing 102 and the lid 106 are made of a flexible material (e.g. plastic, such as polypropylene) that bends or otherwise plastically deforms under a pressure/load applied by the pressure plates and the weight of the electrochemical device units stacked one above another.
One or more elastic elements 208 may be provided between the pressure plates 202 and the electrochemical devices 100 in the assembly 200. Elastic elements 208 (see
A binding member 206 (such as the tie rod illustrated in
In the embodiment illustrated in
The assemblies 200 in the module may be connected together either in series or in parallel, depending on the desired use of the module 300. The series/parallel connections may be located in either the module lid assembly 306 or the pallet assembly 302. If the series/parallel connections are provided in the module lid assembly 306, then the module 300 can be easily reconfigured by simply replacing a first module lid assembly 306 with one connection configuration with a second module lid assembly 306 having a different connection configuration. In one example, as illustrated in
Although the foregoing refers to particular preferred embodiments, it will be understood that the invention is not so limited. It will occur to those of ordinary skill in the art that various modifications may be made to the disclosed embodiments and that such modifications are intended to be within the scope of the invention. All of the publications, patent applications and patents cited herein are incorporated herein by reference in their entirety.
Claims
1. An electrochemical device comprising:
- a housing comprising bottom surfaces and interior and exterior walls extending from the bottom surfaces, so as to at least partially define cavities in the housing;
- a liquid or gel electrolyte disposed in the cavities;
- stacks of electrochemical storage cells, each stack freely standing in one of the cavities and immersed in the electrolyte, each cell comprising: an anode; a cathode; and a separator disposed between the anode and the cathode; and
- a lid disposed on the housing and configured to seal the stacks in the housing,
- wherein the housing and lid comprise a flexible material and are configured to compress the stacks when the bottom surfaces and the lid are pressed toward one another.
2. The electrochemical device of claim 1, further comprising:
- electrical busses that electrically connect the cells of each stack in parallel; and
- electrical contacts that extend over the interior walls and electrically connect the stacks in series.
3. The electrochemical device of claim 2, further comprising first and second electrical connectors integrated with one of the exterior walls, the first electrical connector configured to receive a positive voltage from one of the stacks, and the second electrical connector configured to receive a negative voltage from a different one of the stacks.
4. The electrochemical device of claim 1, wherein the lid comprising recessed lid cavities respectively configured to contact an upper surface of each stack.
5. The electrochemical device of claim 4, wherein the lid cavities are configured to receive bottom surfaces of cavities of an adjacent electrochemical device, so as to interlock with the adjacent electrochemical device, and wherein non-recessed portions of the lid are configured to be inserted between the cavities of the adjacent electrochemical device.
6. The electrochemical device of claim 1, wherein the lid comprises:
- electrolyte ports configured to receive electrolyte added to the housing; and
- caps configured to seal the respective electrolyte ports.
7. The electrochemical device of claim 1, wherein the interior walls comprise through holes fluidly connecting adjacent cavities.
8. The electrochemical device of claim 1, wherein the housing comprises molded plastic.
9. The electrochemical device of claim 1, wherein the housing comprises molded polypropylene.
10. The electrochemical device of claim 1, further comprising:
- aligned central holes located in the housing and the lid and configured to receive a tie rod that extends through the assembly between the chambers;
- an upper pressure plate configured to apply pressure to the lid;
- a lower pressure plate configured to apply pressure to the bottom surfaces; and
- a binding member attached to the upper and lower pressure plates and extending through the aligned holes of the housing and the lid, the binding member configured to compress the upper and lower pressure plates, such that the stacks are compressed by the lid and the bottom wall.
11. The electrochemical device of claim 1, wherein:
- the stacks comprise anode and cathode current collectors disposed between adjacent cells; and
- the cells in each stack are arranged such that the cathode current collectors electrically connect the cathode electrodes of adjacent cells, and the anode current collectors electrically connect the anodes of adjacent cells.
12. The electrochemical device of claim 11, further comprising:
- first electrical busses that electrically connect the anode current collectors of respective stacks; and
- second electrical busses that electrically connect the cathode current collectors of respective stacks.
13. The electrochemical device of claim 1, wherein the lid comprises a pressure relief valve configured to relieve excess gas pressure inside the housing.
14. An electrochemical device comprising:
- a housing;
- stacks of electrochemical storage cells located in the housing;
- electrical busses that electrically connect the cells of each stack in parallel;
- electrical contacts that electrically connect the stacks in series;
- a first electrical connector extending outside the housing and connected to a positive output of one of the stacks; and
- a second electrical connector extending outside the housing and connected to a negative output of a different one of the stacks.
15. The electrochemical device of claim 14, wherein:
- the housing comprises bottom surfaces and interior and exterior walls extending from the bottom surfaces, so as to at least partially define cavities in the housing which contain a liquid or gel electrolyte;
- a lid is disposed on the housing to seal the stacks in the housing; and
- the electrical contacts extend over the interior walls to electrically connect the stacks in series;
- each stack freely stands immersed in the electrolyte in a respective one of the cavities; and
- each cell comprises an anode, a cathode, and a separator disposed between the anode and the cathode.
16. The electrochemical device of claim 15, wherein the cells comprise hybrid devices.
17. The electrochemical device of claim 15, wherein the cells comprise battery cells in which the anode electrodes and the cathode electrodes intercalate ions.
18. A method of assembling an electrochemical device comprising:
- providing a flexible housing comprising bottom surfaces and interior and exterior walls extending from the bottom surfaces, so as to at least partially define cavities in the housing;
- providing a liquid or gel electrolyte in the cavities;
- providing stacks of free standing electrochemical storage cells immersed in the electrolyte in the respective cavities, each cell comprising an anode, a cathode, and a separator disposed between the anode and the cathode;
- providing a flexible lid on the housing to seal the stacks in the housing; and
- pressing the bottom surfaces and the lid toward one another to compress the free standing stacks.
19. The method of claim 18, further comprising:
- electrically connecting the cells of each stack in parallel using electrical buses;
- electrically connecting the stacks in series using electrical contacts that extend over the interior walls;
- connecting a positive output of one of the stacks to a first electrical connector which extends outside the housing; and
- connecting a negative output of another one of the stacks to a second electrical connector which extends outside the housing.
20. The method of claim 19, further comprising:
- stacking a second housing containing a plurality of additional stacks of free standing electrochemical storage cells on the lid; and
- connecting the first or the second electrical connector to an electrical connector extending outside the second housing.
Type: Application
Filed: Apr 6, 2016
Publication Date: Jul 28, 2016
Inventors: Jay Whitacre (Pittsburgh, PA), David Blackwood (Pittsburgh, PA), Eric Weber (Pittsburgh, PA), Wenzhou Yang (Pittsburgh, PA), Eric Sheen (Pittsburgh, PA), William Campbell (Pittsburgh, PA), Don Humphreys (Pittsburgh, PA), Edward Lynch-Bell (Pittsburgh, PA)
Application Number: 15/091,764