Patent Application
20220200082
The present disclosure relates to space fillers for use in electrochemical cell packs.
Thermal management systems for electrochemical cell packs are described in, for example, U.S. Pat. App. Pub. 2017/0279172, U.S. Pat. No. 8,852,772, U.S. Pat. App. Pub. 2017/0279172, DE Pat. App. 102015005529, and DE Pat. App. 102013213550.
In some embodiments, an electrochemical cell pack is provided. The electrochemical cell pack includes a housing having an interior space; a plurality of electrochemical cells disposed within the interior space; a thermal management fluid disposed within the interior space such that the electrochemical cell is in thermal communication with the thermal management fluid; and one or more space fillers disposed with the interior volume and in direct contact with the thermal management fluid. The space fillers have a density that is less than the density of the thermal management fluid.
In some embodiments, an electrochemical cell pack is provided. The electrochemical cell pack includes a housing having an interior space; a plurality of electrochemical cells disposed within the interior space; a thermal management fluid disposed within the interior space such that the electrochemical cell is in thermal communication with the thermal management fluid; and one or more space fillers disposed with the interior volume and in direct contact with the thermal management fluid. The volume occupied by the space fillers within the interior space, cumulatively, is at least 20% of the volume occupied by the thermal management fluid within the interior space.
The above summary of the present disclosure is not intended to describe each embodiment of the present disclosure. The details of one or more embodiments of the disclosure are also set forth in the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and from the claims.
Electrochemical cells (e.g., lithium-ion batteries) are in widespread use worldwide in a vast array of electronic and electric devices ranging from hybrid and electric vehicles to power tools, portable computers, and mobile devices.
Thermal management systems for packs of electrochemical cells (e.g., lithium-ion battery packs) are often required to maximize the cycle life of the cells and for safety. These types of thermal management systems function to control/maintain the temperature of the cells within the pack. High temperatures can increase the capacity fade rate and impedance of the cells while decreasing their lifespan.
While generally safe and reliable energy storage devices, electrochemical cells are subject to catastrophic failure known as thermal runaway under certain conditions. Thermal runaway is a series of internal exothermic reactions that are triggered by heat. The creation of excessive heat can be from electrical over-charge, thermal over-heat, or from an internal electrical short. Internal shorts are typically caused by manufacturing defects or impurities, dendritic lithium formation, or mechanical damage.
Effective thermal management of electrochemical cells, or packs of electrochemical cells, can assist in the prevention of catastrophic, thermal runaway events while also providing necessary ongoing thermal management for the efficient normal operation of the packs. Such thermal management can be achieved for example by dielectric fluids, using a system designed for single phase or two-phase immersion or direct contact thermal management. In either scenario, thermal management fluids are placed in thermal communication with the electrochemical cells to maintain, increase, or decrease the temperature of the electrochemical cells (i.e., heat may be transferred to or from the electrochemical cells via the fluid).
To sufficiently protect against the potential harmful effects of thermal runaway propagation, significant quantities of thermal management fluid are required to be contained within the electrochemical cell packs. However, most industries where fluid immersion thermal management may be employed are driven, at least in part, by weight reduction and cost down considerations. In this regard, in known immersion thermal management systems, the amount of fluid that may be necessary to adequately mitigate against thermal runaway events, may result in pack weights or pack costs that are unacceptably high. Consequently, systems, articles, and methods for minimizing the amount of thermal management fluid (and thus the weight and cost of the electrochemical cell pack) needed to properly manage the temperature of electrical cell packs and sufficiently protect against the potential harmful effects of thermal runaway propagation are desirable.
Generally, the present disclosure is directed to electrochemical cell packs that include low cost, light weight space fillers disposed therein such that an amount of thermal management fluid within the electrochemical cell packs may be reduced or minimized. Benefits and characteristics of the space fillers of the present disclosure may include:
As used herein, “catenated heteroatom” means an atom other than carbon (for example, oxygen, nitrogen, or sulfur) that is bonded to at least two carbon atoms in a carbon chain (linear or branched or within a ring) so as to form a carbon-heteroatom-carbon linkage.
As used herein, “fluoro-” (for example, in reference to a group or moiety, such as in the case of “fluoroalkylene” or “fluoroalkyl” or “fluorocarbon”) or “fluorinated” means (i) partially fluorinated such that there is at least one carbon-bonded hydrogen atom, or (ii) perfluorinated.
As used herein, “perfluoro-” (for example, in reference to a group or moiety, such as in the case of “perfluoroalkylene” or “perfluoroalkyl” or “perfluorocarbon”) or “perfluorinated” means completely fluorinated such that, except as may be otherwise indicated, there are no carbon-bonded hydrogen atoms replaceable with fluorine.
As used herein, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended embodiments, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
As used herein, the recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.8, 4, and 5).
Unless otherwise indicated, all numbers expressing quantities or ingredients, measurement of properties and so forth used in the specification and embodiments are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached listing of embodiments can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings of the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claimed embodiments, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
In some embodiments, the present disclosure relates to an electrochemical cell pack that contains one or more space fillers. Generally, the electrochemical cell packs may include a housing defining an interior volume that contains a plurality of electrochemical cells. A thermal management fluid may be disposed within the interior volume of the housing such that the fluid is in thermal communication with one or more (up to all) of the electrochemical cells. Thermal communication may be achieved via direct contact immersion, or indirect thermal contact. In embodiments in which direct contact immersion is employed, the thermal management fluid may surround and directly contact any portion (up to totally surround and directly contact) one or more (up to all) of the electrochemical cells. In some embodiments, the electrochemical cells may be rechargeable batteries (e.g., rechargeable lithium-ion batteries). In some embodiments, the space fillers may be in direct contact with the thermal management fluid (e.g., the space fillers may be at least partially immersed (up to totally immersed) in the thermal management fluid)). In some embodiments, the space fillers may have a density that is less than the density of the thermal management fluid. In some embodiments, the space fillers may have a density that is equal to or more than the thermal management fluid. For purposes of the present application, it is to be appreciated that electrochemical cells (e.g., batteries) are not to be considered space fillers.
Referring now to
In some embodiments, although not shown, the modules 25 (and/or the electrochemical cells) may be electrically connected to each other using any electrical conductor, such as busbars, wires, cables, or the like. The battery modules may be electrically coupled in a series configuration, a parallel configuration, or some combination of parallel and series configurations, as desired for the particular application.
In some embodiments, each of the modules 25 may include a casing 30 that defines an interior volume of the modules 25 and contains a plurality of electrochemical cells 35. As shown in
In some embodiments, the casing 30 may be formed in any conventional fashion and of any conventional materials that allow for an interior volume of the module 25 to contain hold/maintain a thermal management fluid. In some embodiments, the casing 30 may entirely encase the electrochemical cells 35 such that the casing 30 forms a continuous casing surrounding the entirety of the electrochemical cells. Alternatively, the casing 30 may encase only a portion of the electrochemical cells 35 (e.g., one or more sides of the casing 30 may be at least partially open. In some embodiments, the interior volume of the modules 25 may be in fluid communication with the interior volume 20 of the housing 15. For example, one or more openings in an upper end of the casing 30 may permit fluid to be transferred from the interior volume of the modules 25 to the interior volume 20 of the housing 15 (i.e., the interior volume 20 may service as an overflow for fluid that is contained within the modules 25). Alternatively, or additionally, the casing 30 may include one or more inlets/outlets for permitting flow of fluid between the interior volume of the modules 25 and the interior volume 20 of the housing 15.
In some embodiments, a thermal management fluid F may be disposed within the interior volume 20 of the housing, the interior volume of the modules 25, or both. For example, in some embodiments, a thermal management fluid F may be disposed within the interior volume of one or more of the modules 25 such that substantially the entire volume (e.g., at least 80%, at least 90%, at least 95%, or at least 99%) of the interior volume of the modules 25 that is not occupied by electrochemical cells 35 (or any other solid components within the module 25) is occupied by the thermal management fluid F.
For purposes of illustration, in
Referring now to
Referring still to
As previously discussed, the concepts of the present disclosure can be employed with respect to electrochemical cell packs having electrochemical cells of any type. In this regard,
In some embodiments, as best described with respect to
In any of the above-described embodiments, and as shown in
Referring now to
In some embodiments, although not shown, the electrochemical cells with the pack 300 may be electrically connected to each other using any electrical conductor, such as busbars, wires, cables, or the like. The cells may be electrically coupled in a series configuration, a parallel configuration, or some combination of parallel and series configurations, as desired for the particular application.
In some embodiments, the pack 300 may further include a plurality of space fillers 340 configured as hollow, elongated members having an open top and bottom end, the hollow portions defining cavities 345 that are sized and shaped to accommodate the size and shape of the electrochemical cells and extend the length of the space filler 340. For example, as shown, the space fillers 340 may be formed as having elongated cylindrical cavities, each of the cylindrical cavities sized and shaped to accommodate the size and shape of cylindrical electrochemical cells. Similar to the embodiments of
While generally conforming to the size and shape of the electrochemical cells (the cells fit within the cavity with minimal gap), in some embodiments, the cavities 345 may be sized and shaped relative to the electrochemical cells such that the thermal management fluid may be passed between a sidewall 350 of the cavity and an outer surface of the electrochemical cells. In such embodiments, if centered within the cavity 345, an outer surface of the electrochemical cell (around the entire perimeter of the cell) may be spaced from the sidewall 350 a distance of between 0.01 mm and 10 mm, between 0.01 mm and 4 mm, between 0.1 mm and 1 mm, or between 0.25 mm and 0.5 mm, along the length of the cavity 345.
As with previous embodiments, a thermal management fluid (not depicted) may be disposed within the interior volume 320 of the housing 315. For example, in some embodiments, a thermal management fluid may be disposed within the interior volume 320 such that substantially the entire volume (e.g., at least 80%, at least 90%, at least 95%, or at least 99%) of the interior volume 320 that is not occupied by electrochemical cells or the space fillers 340 (or any other solid components within the interior volume 320) is occupied by the thermal management fluid. As with previous embodiments, given the presence of the space fillers, direct contact of the thermal management fluid with the surface of the electrochemical cells may be achieved while also minimizing the total volume of thermal management fluid with the pack 300.
As with previous embodiments, the number, size, shape, and location of the space fillers 340 depicted in
In some embodiments, the space fillers of the present disclosure may include a filler material and, optionally, a membrane the at least partially (and up to completely) encases the filler material.
In some embodiments, filler materials may include any material having a density (mass per unit volume) that is less than the density of the thermal management fluid F and/or is available at a lower cost than that thermal management fluid. In some embodiments, the filler materials may have a density that is greater than the density of the thermal management fluid. Examples of suitable filler materials include compressible gases (e.g, air), polymeric materials (such as nylon, polycarbonate, polyethylene, polyurethane, polystyrene, or combinations thereof), phase change materials such as paraffin wax for absorbing heat at constant temperature, or combinations thereof. Any of the polymeric materials may be present as polymeric open or closed cell foams. The filler materials may be selected such that they are nonflammable or of low flammability and may carry a UL-94 certification of HB, 5VB, 5VA, V-2, V-1 or V-0. The filler materials may be selected such that they have high electrical resistivity (e.g., greater than 1×104 Ohm-cm). In some embodiments, the filler materials may exhibit compressibility as to allow for cell expansion and provide cushioning, with a Young's Modulus of no more than 3000 MPa (e.g. high density polymers), no more than 50 MPa (e.g. rubber), no more than 15 MPa (e.g. high density foam) or no more than 1 MPa (e.g. low density foam). In some embodiments, compressible gases may be present in the filler material in an amount of at least 50 volume %, at least 90 volume %, at least 95 volume %, or at least 99 vol. %, based on the total volume of the filler material. In some embodiments, polymers may be present in the filler material in an amount of at least 50 wt. %, at least 90 wt. %, at least 95 wt. %, or at least 99 wt. %, based on the total weight of the filler material.
In some embodiments, thermal conductivity of the filler materials may be enhanced by inclusion of one or more thermally conductive filler materials. For example, in embodiments in which the filler material includes a polymeric material, such polymeric material may have dispersed throughout its body one or more thermally conductive inorganic filler materials such as ceramics such as oxides, hydroxides, oxyhydroxides, silicates, borides, carbides, or nitrides.
In some embodiments, the membranes for the space fillers may include any materials that are compatible with the thermal management fluid (e.g., do not degrade in the presence of the fluid and do not cause degradation of the thermal management fluid) and are impermeable relative to the thermal management fluid, air, or both. Examples of suitable materials for the membrane may include polymers or metalized polymers. Particular examples include aluminized polymers, polypropylene foils, PET foils, or PTFE foils. In embodiments in which no membrane is employed, the filler material may include materials that are compatible with the thermal management fluid (e.g., do not degrade in the presence of the fluid, e.g. dissolution of containing plasticizer, and do not cause degradation of the thermal management fluid).
In some embodiments, two or more pieces of the membrane may be coupled or joined to at least partially encase the filler material (e.g., form a pouch that at least partially encases the filler material). For example, top and bottoms sections of a membrane may be brought together and sealed about one or more edges to form a pouch or pocket for encasing the filler material. In some embodiments, the membrane (or one or more pieces of membrane that, collectively (or when joined), make up the total membrane) may be formed of a single layer of material or a plurality of material layers (e.g., multi-layer film).
In some embodiments, the space fillers of the present disclosure may be characterized as sealed, compressible gas filled pouches. In such embodiments, the space filler may include or consist essentially of a compressible gas and the membrane may fully encase the space filler such that the compressible gas is retained within a pouch formed by the membrane (e.g., via a seal disposed about the perimeter of the membrane). In such embodiments, the compressible gas may occupy at least 95%, at least 99%, or 100% of the total volume of the pouch.
In some embodiments, the volume occupied by the space fillers within the interior volume of electrochemical cell pack housing, cumulatively, may be at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 100%, at least 110%, at least 150%, at least 200%, or at least 300% of the volume occupied by the thermal management fluid within the interior volume of electrochemical cell pack housing. In some embodiments, the thermal management fluid may be present in the interior volume of electrochemical cell pack housing such that there is between 0.02 and 2 liters/kW-h, 0.02 and 1 liters/kW-h, or between 0.02 and 0.5 liters/kW-h, based on the total (cumulative) energy of the electrochemical cells present in the electrochemical cell pack.
As previously discussed, the space fillers of the present disclosure may have a density that is less than the density of the thermal management fluid in which they are disposed. Therefore, in some embodiments, to prevent movement of the space fillers within the pack (e.g., via buoyancy forces), the space fillers may be held in position using any suitable coupling mechanism. Suitable coupling mechanisms may include adhesives, fasteners, or structural elements within the interior volume that serve to maintain the position of the space fillers within the interior volume.
In some embodiments, the thermal management fluids may include or consist essentially of halogenated compounds, oils (e.g., mineral oils, synthetic oils, or silicone oils), or combinations thereof. In some embodiments, the halogenated compounds may include fluorinated compounds, chlorinated compounds, brominated compounds, or combinations thereof. In some embodiments, the halogenated compounds may include or consist essentially of fluorinated compounds. In some embodiments, the thermal management fluids may have an electrical conductivity (at 25 degrees Celsius) of less than about 1e-5 S/cm, less than about 1e-6 S/cm, less than 1e-7 S/cm, or less than about 1e-10 S/cm. In some embodiments, the thermal management fluids may have a dielectric constant that is less than about 25, less than about 15, or less than about 10, as measured in accordance with ASTM D150 at room temperature. In some embodiments, the thermal management fluids may have any one of, any combination of, or all of the following additional properties: sufficiently low melting point (e.g., <−40 degrees C. or −35 degrees C.) and high boiling point (e.g., >80 degrees C. for single phase heat transfer), high thermal conductivity (e.g., >0.05 W/m-K), high specific heat capacity (e.g., >800 J/kg-K), low viscosity (e.g., <2 cSt at room temperature), and non-flammability (e.g., no closed cup flashpoint) or low flammability (e.g., flash point >100 F). In some embodiments, fluorinated compounds having such properties may include or consist of any one or combination of fluoroethers, fluorocarbons, fluoroketones, fluorosulfones, and fluoroolefins. In some embodiments fluorinated compounds having such properties may include or consist of partially fluorinated compounds, perfluorinated compounds, or a combination thereof. In some embodiments, the thermal management fluid may include fluorinated compounds in an amount of at least 20%, at least 50 wt. %, at least 75 wt. %, at least 90 wt. %, at least 95 wt. %, or at least 99 wt. %, based on the total weight of the thermal management fluid.
In some embodiments, the thermal management fluids of the present disclosure may be relatively chemically unreactive, thermally stable, and non-toxic. The working fluids may have a low environmental impact. In this regard, the working fluids of the present disclosure may have a zero, or near zero, ozone depletion potential (ODP) and a global warming potential (GWP, 100 yr ITH) of less than 500, 300, 200, 100 or less than 10.
In some embodiments, the electrochemical cell packs of the present disclosure may be may be configured to store and supply electrical power to any electrical system, such as in a Battery Electric Vehicle (BEV), a Plug-in Hybrid Electric Vehicle (PHEV), a hybrid electric vehicle (HEV), an Uninterruptible Power Supply (UPS) system, a residential electrical system, an industrial electrical system, a stationary energy storage system, or the like.
In some embodiments, during operation or use of the electrochemical cell packs, the thermal management fluid may be circulated (e.g., via a pump) within or to/from the interior volume of the housing. For example, the thermal management fluid may be provided to the housing though pipes or hoses and may flow around or between the modules or electrochemical cells before periodically or continuously being routed to a radiator or heat exchanger. In some embodiments, after flow through the radiator or heat exchanger, the thermal management fluid may be once again routed to the electrochemical cells. Alternatively, the thermal management fluid may not be circulated within or to/from the housing.
Objects and advantages of this disclosure are further illustrated by the following comparative and illustrative examples. Unless otherwise noted, all parts, percentages, ratios, etc. in the examples and the rest of the specification are by weight, and all components used in the examples were obtained, or are available, from general suppliers such as, for example, Sigma-Aldrich Corp., Saint Louis, Mo., US or Thermo-Fisher Scientific, Waltham, Mass., US. The following abbreviations are used herein: Amps=amperes; Ahr=ampere-hours; in =inches; mm=millimeters; cm=centimeters; ml=milliliters, L=liters, sec=seconds min=minutes, hr=hours, V=volts, ° C.=degrees Celsius, g=grams.
Ten cylindrical format electrochemical cells, each having a diameter of 21 mm and a length of 70 mm, were assembled into a 2S5P battery pack configuration as shown in
The battery pack was placed into a glass vessel of square cross-section with internal dimensions 14 cm×14 cm×18.5 cm. For the comparative, 1000 ml of NOVEC 7300 fluid (1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-(trifluoromethyl)-pentane, available from 3M Company, Saint Paul, Minn., US) was placed in the vessel with the battery pack. No space fillers were added to the vessel. The height of the fluid from the bottom of the vessel on the outside was measured to be 8 cm. A schematic of the test vessel is shown in
To dissipate heat transferred to the working fluid during testing, cold water was flowed through a cooling tube, made from a 40 cm length of ⅛ inch (0.32 cm) outer diameter copper tube, and bent so that a 24 cm long U-shaped section was immersed in the fluid above the battery pack. The water flow rate was determined by recording the time required to collect 1000 ml of water in a graduated cylinder using a calibrated stop watch (Thermo-Fisher Scientific, Waltham, Mass., US). An average of two flow rate measurements were taken, as shown in Table 2.
The battery pack was then cycled (charged and discharged) 4 times from 5 Volts to 8.4 Volts at a constant current charge of 30 Amps and constant current discharge of 50 Amps. Voltage and temperature were logged during the cycling procedure.
Materials used to prepare the space fillers for Example 1 are provided in Table 3. Three exemplary space fillers were made by inserting 3 sheets of 14 cm×18 cm×0.635 cm polyurethane foam sheet into 7.5 mil thick metallized bags, cutting the bags to size, and heat sealing the bags.
The battery pack and the three space fillers were placed into the same glass vessel used for Comparative Example CE1. NOVEC 7300 fluid was then added to the glass vessel to a height of 8 cm and the volume of fluid was recorded as 500 ml. A schematic of the test vessel setup is shown in
To dissipate heat transferred to the working fluid during testing, cold water was flowed through a cooling tube, made from a 40 cm length of ⅛ inch (0.32 cm) outer diameter copper tube, and bent so that a 24 cm long U-shaped section was immersed in the fluid above the battery pack. The water flow rate was the same as for the Comparative Example. The battery pack was cycled (charged and discharged) using the same test protocol as the Comparative Example.
Average pack temperatures (average from the three thermocouples T1, T2, T3) and voltages for Example 1 and the Comparative Example are shown in
The weight of the fluid used in Comparative Example and the fluid and space filler (foam only) used in Example 1 were calculated using the densities provided in Table 6 and the measured volumes of NOVEC 7300 fluid. The volume of the foam was taken as the volume of fluid it displaced. Final weight comparisons are shown in Table 7, showing a reduction in fluid weight of approximately 42% for the pack with space filler versus the pack without.
Various modifications and alterations to this disclosure will become apparent to those skilled in the art without departing from the scope and spirit of this disclosure. It should be understood that this disclosure is not intended to be unduly limited by the illustrative embodiments and examples set forth herein and that such examples and embodiments are presented by way of example only with the scope of the disclosure intended to be limited only by the claims set forth herein as follows. All references cited in this disclosure are herein incorporated by reference in their entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2020/054480 | 5/12/2020 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62898985 | Sep 2019 | US | |
| 62848626 | May 2019 | US |
