Battery module without welding

Abstract

The present invention relates to a weld-free battery module or battery pack in which battery cells and bus bars are electrically connected using pogo pins instead of welding them. The present invention relates to a battery module including a plurality of cylindrical battery cells, a module case accommodating the plurality of cylindrical battery cells, a cover coupled to at least one of open sides of the module case, a bus bar coupled to the cover, and a pogo pin interposed for electrical connection between each of the plurality of cylindrical battery cells and the bus bar.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0126767, filed on October 5, 2022, and all the contents disclosed in the Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a battery module without welding, and more particularly, to a battery module or battery pack without welding that electrically connects between battery cells and busbars without welding.

Background Art

[0003] The lithium secondary battery is classified into a cylindrical secondary battery and a prismatic secondary battery in which an electrode assembly is built in a cylindrical or prismatic metal can according to the shape of the battery case, and a pouch-type secondary battery in which an electrode assembly is built in a pouch-shaped case of an aluminum laminate sheet. Among them, the cylindrical secondary battery has the advantages of relatively large capacity and structural stability.

[0004] Battery modules and / or battery packs in which a plurality of battery cells are electrically connected as high-capacity and high-output energy sources are widely used. Since safety issues in electric energy sources have been continuously raised, the use ratio of highly safe cylindrical battery cells is gradually increasing.

[0005] In order to manufacture a battery module and / or a battery pack, a process of electrically connecting a plurality of cylindrical battery cells is required. For example, the positive and negative terminals of the cylindrical battery cell can be connected by wire bonding or directly welded to the busbar.

[0006] FIG. 1 is an exploded perspective view showing an example of a conventional battery module, FIG. 2 is another exploded perspective view showing an example of a conventional battery module, and FIG. 3 is a vertical cross-sectional view taken along line A-A of FIG. 2, showing a form (a) in which busbars are combined and a modified example (b) thereof.

[0007] Referring to Figures 1 to 3, the conventional battery modules 1000 and 2000 consist of multiple cylindrical battery cells 1010 and 2010 arranged within module cases 1100 and 2100. In Figure 3a), busbars 2020 are provided at the upper and lower electrode terminals of the cylindrical battery cell 2010 seated in module case 2100, and are electrically connected via welding spots 2030. Figure 3 is a cross-sectional view, and the busbars 2020 may be arranged in series or parallel connections across the upper or lower surfaces of multiple cylindrical battery cells 2010, or on the upper or lower surface of a single cylindrical battery cell 2010.

[0008] Figure 3b) is a plan view, not a cross-sectional view, and is an example of wire bonding. Wire 2040 electrically connects the upper electrode terminal of the cylindrical battery cell 2010 to the busbar 2020.

[0009] During wire bonding and busbar welding, 1) weak welds can occur, resulting in a weak physical bond that is easily broken by vibrations and other shocks. 2) Current wire bonding and busbar welding processes are performed after cylindrical battery cells have been fully assembled and placed into battery modules and / or battery packs, making it difficult to improve efficiency in terms of space and time. 3) Wire bonding and busbar welding require welding for all electrical connections, resulting in a large workload, a high probability of defects, and complex manufacturing equipment. Despite these drawbacks, wire bonding and busbar welding are still used because they are the only methods that can provide strong, stable bonds over long periods in environments with vibrations and shocks.

[0010] The root cause of many of these problems lies in the fact that electrical connections are made by welding, specifically wire bonding and busbar welding. There is a need to provide a means to electrically connect battery cells within battery modules and / or battery packs in a long-term, stable, and strong manner without welding.

[0011] Patent Document 1 discloses a battery module and a battery pack including the same for improving connectivity and cooling efficiency. The battery module of Patent Document 1 includes a plurality of cylindrical battery cells, each having electrode terminals formed on its upper and lower parts; a module housing having a plurality of hollow structures for housing the cylindrical battery cells in an insertion manner; a current collector plate mounted on the outer surface of the module housing, with a plurality of weld holes formed therein so that the electrode terminals of the cylindrical battery cells are exposed to the outside; bus bars contacting the electrode terminals and the current collector plate, respectively, to electrically connect the electrode terminals and the current collector plate; and a heat conductive pad positioned outside the current collector plate, with contact protrusions extending in the direction in which the electrode terminals are located so as to contact the contact connection portion between the electrode terminals and the bus bars.

[0012] Although Patent Document 1 takes expandability into consideration, it still includes multiple welds, and therefore fails to solve the fundamental problems of the conventional method.

[0013] Patent Document 2 discloses a battery pack including a plurality of electrically connected cylindrical battery cells. In Patent Document 2, the battery cells are arranged in a module case including a housing having an inner surface shape corresponding to the outer surface shape of the battery cells, with the electrode terminals of the same electrodes facing in the same direction, and each electrode terminal is electrically connected to a connecting plate via a connecting member, the connecting member includes a safety device for blocking the flow of excessive current, and the connecting member further includes an elastic member.

[0014] Patent Document 2 includes a first connecting member 131 in the shape of a bent plate, which is commonly seen in remote controls that use cylindrical batteries. Although Patent Document 2 aims to provide a fuse via the first connecting member, it does not disclose a welding configuration. Even assuming that welding is not used, the connecting plates 121 and 122 that support the first connecting member are made of plate-shaped metal and are unlikely to provide sufficient strength and vibration resistance. Furthermore, there is the problem that the plate-shaped first connecting member 131 must ultimately be welded to the connecting plates 121 and 122 using additional means.

[0015] Patent Document 3 discloses a probe card and an inspection method. The probe card 100 of Patent Document 3 includes a planar secondary battery 10 which includes a planar electrode 22 and is positioned such that the planar electrode 22 faces the workpiece 50, and an electrical coupling body 30 which is positioned between the workpiece 50 and the secondary battery 10. The secondary battery 10 includes a structure which allows wiring to be drawn out at any position on the planar electrode 22. The electrical coupling body 30 includes a plurality of contact portions 31 which protrude toward the facing pads 51, and electrically connects the plurality of pads 51 and the planar electrode 22 via the plurality of contact portions 31 interposed between them.

[0016] In Patent Document 3, the electrical coupling body may include pogo pins configured to contact planar electrodes. In Patent Document 3, the pogo pins are merely configured to make electrical contact, and there is no description or implication of using them in battery modules and / or battery packs.

[0017] Conventional technologies do not offer solutions to the fundamental problems in battery modules / battery packs today, namely wire bonding and busbar welding, which are electrical connection welding processes. [Prior art documents] [Patent Documents]

[0018] [Patent Document 1] Korean Published Patent Publication No. 10-2019-0083533 [Patent Document 2] Korean Published Patent No. 10-2019-0042990 [Patent Document 3] Korean Published Patent Publication No. 10-2019-0029662 [Overview of the project] [Problems that the invention aims to solve]

[0019] The present invention aims to solve the aforementioned problems and, as one objective, provides a battery module and / or battery pack without welding that: 1) eliminates the problem of weakened electrical bonding due to weak welding; 2) efficiently performs electrical connection of battery cells in a battery module / battery pack; and 3) maintains stable and strong electrical connection for a long period of time in environments such as vibration and shock. [Means for solving the problem]

[0020] To achieve the above objectives, the present invention provides a battery module comprising: a plurality of cylindrical battery cells; a module case housing the plurality of cylindrical battery cells; a cover coupled to at least one of the open surfaces of the module case; a metal plate coupled to the cover; and a conductive member interposed for electrical connection between each of the plurality of cylindrical battery cells and the metal plate, wherein the conductive member comprises: a hollow cylindrical body; an elastic body provided inside the body; and a pin inserted inside the body, supported by the elastic body, and protruding only to the outside of the body to a certain length.

[0021] The energizing member may be a pogo pin. The energizing member may be either a single-sided pogo pin, in which the pin is provided on only one side of the body, or a double-sided pogo pin, in which the pin is provided on both sides of the body.

[0022] At least one or more of a thread, a hook, a locking projection, and a donut-shaped protrusion may be provided on the outer surface of the body.

[0023] The energizing member is coupled through the cover, and the method of coupling through the cover may be at least one or more of the following 1) to 5).

[0024] 1) interference fit, 2) hook coupling, 3) screwing, 4) fusion bonding, 5) coupling by the methods of 1) to 4) of the coupling portion integrally injection-molded with the energizing member and the cover.

[0025] The cover and the metal plate may be coupled by at least one or more of heat fusion bonding and interference fit.

[0026] The metal plate and the energizing member may be coupled after the module case in a state of accommodating the plurality of cylindrical battery cells and the cover are coupled.

[0027] The module case is composed of an upper case and a lower case, and the upper case and the lower case may be detachably coupled.

[0028] The inside of the battery module may be filled with a phase change material (PCM: Phase Change Material).

[0029] In addition, the present invention can also be provided in a form in which various combinations of the means for solving the above problems are made.

Advantages of the Invention

[0030] As described above, the weld-free battery module according to the present invention connects cylindrical battery cells and metal busbars using pogo pins, which are separate conductive members. By using the weld-free battery module according to the present invention, 1) the problem of weakened electrical coupling due to weak welding is eliminated, 2) electrical coupling of battery cells is efficiently implemented in the battery module / battery pack, and 3) stable and strong battery coupling can be achieved over a long period of time in environments such as vibration and shock. In addition, there is the advantage that the pogo pins, which are conductive members, can be easily replaced in the event of a malfunction. [Brief explanation of the drawing]

[0031] [Figure 1] This is an exploded perspective view of an example of a conventional battery module. [Figure 2] This is a disassembled perspective view of another example of a conventional battery module. [Figure 3] Figure 2 shows a vertical cross-sectional view along line AA, illustrating the configuration with the busbars connected (a) and a modified example thereof (b). [Figure 4] This is a cross-sectional view of a battery module according to one embodiment of the present invention. [Figure 5] This figure shows various modifications of the pogopin according to the present invention. [Figure 6] This figure shows various modified examples of how the pogo pins are connected to the cover in the battery module according to the present invention. [Figure 7] This figure shows various modified examples of how the pogo pins are connected to the cover in the battery module according to the present invention. [Figure 8] This figure shows another variation of the battery module according to the present invention, in which the pogo pins are connected to the cover. [Modes for carrying out the invention]

[0032] Hereinafter, embodiments that allow a person with ordinary skill in the art to carry out the present invention will be described in detail based on the attached drawings. However, in describing the operating principle of a preferred embodiment of the present invention in detail, if it is determined that a specific description of a related known function or configuration may unnecessarily obscure the gist of the present invention, such detailed description will be omitted.

[0033] Furthermore, the same reference numerals shall be used throughout the drawings for parts that have similar functions and operations. Throughout the specification, when it is said that one part is connected to another part, this includes not only direct connections but also indirect connections through other elements in between. Also, when it is said that a component is included, unless otherwise stated, it does not mean that other components are excluded, but rather that other components may be included.

[0034] Furthermore, explanations that limit or add to the constituent elements are applicable to all inventions unless otherwise specified, and are not limited to a particular invention.

[0035] Furthermore, unless otherwise specified, the singular form used throughout the description of this invention and the claims also includes the plural form.

[0036] Furthermore, throughout the description and claims of this invention, "or" includes "and" unless otherwise specified. Therefore, "including A or B" means three cases: including A, including B, or including both A and B.

[0037] Figure 4 is a cross-sectional view of a battery module according to one embodiment of the present invention, Figure 5 shows various modifications of the pogo pin according to the present invention, Figures 6 and 7 show various modifications of the form in which the pogo pin is connected to the cover in the battery module according to the present invention, and Figure 8 shows another modification of the form in which the pogo pin is connected to the cover in the battery module according to the present invention. The present invention will be described in detail with reference to Figures 4 to 8, along with the examples.

[0038] The present invention includes a plurality of cylindrical battery cells 3010, a module case 3100 housing the plurality of cylindrical battery cells 3010, a cover 3200 coupled to the upper and lower surfaces of the module case 3100, a metal plate bus bar 3020 coupled to the cover 3200, and a pogo pin 3500, an energizing member, interposed for electrical connection between each of the plurality of cylindrical battery cells 3010 and the bus bar 3020.

[0039] The aforementioned top and bottom surfaces refer to their relative positions when the module case is positioned vertically, and refer to the open side of the module case and the other side corresponding to the opposite side of that side. If the module case is open on only one side, the cover may be placed only on that open side. If the module case is open on both sides, the cover may be placed on both open sides, but if electrical connections are required on only one side, the pogo pins may be placed only on the cover of the side where the electrical connections are required.

[0040] The metal plate limited by this invention is a metal plate-shaped busbar used in battery modules and battery packs.

[0041] Multiple cylindrical battery cells 3010 are arranged in a configuration in which electrode assemblies are housed in a cylindrical battery case made of a metal can. In Figures 4 and 8, the longitudinal central axes of the cylindrical battery cases are arranged parallel to each other within the module case 3100, and covers 3200 are placed on the top and bottom surfaces of the module case 3100. Covers 3200 may be used as a means for a separate partition wall 3210 to interrupt the electrical connection between busbars 3020. The partition wall 3210 may also be used as a means for fixing the inserted busbars 3020.

[0042] The conductive member is a pogo pin. The pogo pin 3500 includes a hollow cylindrical body 3510, an elastic body 3520 provided inside the body 3510, and a pin 3530 inserted inside the body 3510, supported by the elastic body 3520, and protruding to the outside of the body by a certain length. The pogo pin 3500 may be one of a single-sided pogo pin (Figure 5 a), b), c), d)) in which the pin 3530 is provided only on one side of the body 3510, or a double-sided pogo pin (Figure 5 e), f), g), h)) in which the pin 3530 is provided on both sides of the body 3510.

[0043] In the case of a single-sided pogo pin 3500, a single elastic spring is provided. A single elastic spring may also be provided in the case of a double-sided pogo pin. All of the pogo pins 3500 shown as examples in this invention have one spring.

[0044] The pogo pin 3500 facilitates smooth movement by providing a metal ball 3540 between the elastic body 3520 and the pin 3530. Of the pogo pins 3500 shown in Figure 5, single-sided pogo pins (a), b), c), d)) have a ball 3540 or, without a ball, the pin 3530 is seated on the elastic body 3520 via a pin support 3532. Double-sided pogo pins (e), f), g), h)) are shown as examples of having a ball 3540 or having only one, but two balls 3540 can support two pins 3530, and the drawings show various modifications and are not limited to the drawings.

[0045] Although not shown in the drawing, the pogo pins may be high-current pogo pins depending on the capacity of the battery module used. High-current pogo pins have materials such as the body, elastic material, and pin that are suitable for high temperatures and high currents, or they are made thicker.

[0046] The outer surface of the body 3510 of the pogo pin 3500 may be provided with at least one of the following: screw threads (Figure 5d), hooks (Figure 5h), locking projections (Figure 5c), and donut-shaped protrusions (Figures 5a), b), c), and e). If screw threads (Figure 5d) are provided, the pogo pin 3500 is a single-sided pogo pin, and a screw head 3518 may be provided on the other side of the pin 3530 relative to the body 3510, into which a cross-shaped, L-shaped, or hexagonal wrench for screw fastening can be inserted. A groove for a L-shaped screwdriver is formed in Figure 5d).

[0047] The pogo pin 3500 is joined by passing through the cover 3200. The method of joining by passing through the cover 3200 can be at least one of the following 1) to 5).

[0048] 1) Interference fit. In this case, a through hole is provided in the cover 3200, and the size of the pogo pin 3500 is set to be larger than the through hole, so that they are joined by an interference fit. Figure 6 may show the left and right sides of the pogo pin body differently to illustrate various joining methods. In Figure 6a), the left side corresponds to the interference fit. The surface of the through hole or pogo pin may be treated for friction or its shape may be deformable.

[0049] Referring to Figure 6e), the through-hole is formed to have a step. The pogo pin 3500 protrudes to the outside of the cover 3200 through the fully through portion of the through-hole, and the protruding portion 3512 of the pogo pin engages with the step provided around the fully through portion. The groove formed by the step provided around the fully through portion can be joined by an additional groove cover by interference fit, fusion, adhesive, and adhesive.

[0050] 2) Hook connection. This involves connecting the pogo pin 3500 and the cover 3200 with hooks provided on at least one of them. The right side of Figure 6a) and Figure 6b) correspond to the hook connection. Hook connections are usually connected in only one direction. Therefore, it is preferable to fasten the pogo pin 3500 in a direction that penetrates the cover 3200.

[0051] 3) Threading. Referring to Figure 6c) and Figure 5d), the cover 3200 is provided with a through hole, and the pogo pin 3500 is joined by having threads 3514 on the body 3510 of the pogo pin 3500. When threads 3514 are provided, the pogo pin 3500 is a single-sided pogo pin, and a screw head 3518 may be provided on the other side of the pin 3530 relative to the body 3510, into which cross-shaped, straight-end, hexagonal ranges, etc., can be inserted for screw fastening.

[0052] Referring to Figure 4, the pogo pin 3500 is connected to the cover 3200, and then the bus bar 3020 is connected to its upper surface. In the case of screw connections, the pogo pin 3500 can be connected to the cover 3200 in the same manner, and then the bus bar 3020 can be connected to its upper surface. Referring to Figure 8, in the case of screw connections, it is also possible to connect or seat the bus bar 3020 to the cover 3200 first, and then simultaneously fix the cover 3200 and the bus bar 3020 by screwing in the pogo pin 3500. In this case, if a problem occurs with the pogo pin 3500 later, it is possible to easily replace the pogo pin 3500 externally.

[0053] The threading is standard, and after screwing, there is a step at the end, allowing connection in less than one turn of the screw. Although not shown in the drawings, an example of this is the spike connection used in golf shoes in recent years.

[0054] 4) Fusion bonding. Referring to Figure 6d), this method involves providing through holes in the cover 3200, inserting pogo pins 3500 into the through holes, and then fusing the cover 3200 together. Fusion bonding can be substituted with bonding by melting the cover or by using an adhesive or tack.

[0055] 5) Joining the pogo pin 3500 and the joint 3600 (left side of Figure 7), which is injection-molded integrally with the pogo pin 3500, and the cover using methods 1) to 4). Figure 7 shows a configuration in which the joint 3600 is provided on the pogo pin 3500. This is a method of joining the pogo pin 3500, which is provided with such a joint 3600, using methods 1) to 4) above.

[0056] When injection-molded as a single unit, the outer surface of the pogo pin body can be equipped with a donut-shaped protrusion (left side of the pogo pin body in the left side of Figure 7), a hook, or indentations (right side of the pogo pin body in the left side of Figure 7) to increase the strength of the injection molding. The joint 3600 is strongly bonded to the pogo pin 3500 by injection molding, and the larger joint 3600 is bonded to the cover 3200, thus further strengthening the bonding force of the pogo pin to the cover.

[0057] Another method of joining the joints without injection molding is shown in the pogo pin on the right side of Figure 7. The joint 3600 has a through portion, and a stepped portion is provided around the through portion. The pogo pin 3500 protrudes outward through the through portion, and the protruding portion of the pogo pin engages with the stepped portion provided around the through portion. The groove created by the stepped portion can be joined by an additional joint cover 3610 by interference fit, fusion, adhesive, or bonding.

[0058] Referring to Figures 4 and 8, the cover 3200 and the busbar 3020 can be joined by at least one of the following: heat fusion and interference fit.

[0059] Busbars and pogo pins can be attached after the module case and cover, which house multiple cylindrical battery cells, are joined. Alternatively, busbars and pogo pins can be attached before or after the module case and cover, which house multiple cylindrical battery cells, are joined.

[0060] Specifically, i) a method in which the module case and cover are assembled, the pogo pins are connected to the cover, and the busbar is connected on top of that.

[0061] ii) A method of joining or positioning the busbar on the cover with the module case and cover assembled, and then using pogo pins to jointly connect the busbar and cover. This method is shown in Figure 8.

[0062] iii) A method of connecting the pogo pins to the cover, then connecting the busbar on top of that, and finally connecting the cover with all of these connected to it to the module case.

[0063] iv) One possible method is to attach or position the busbars on the cover, then use pogo pins to securely attach the busbars and cover together, and finally attach the combined cover to the module case.

[0064] Although not shown in the drawings, the module case consists of an upper case and a lower case, and the upper case and the lower case are detachably connected.

[0065] On the other hand, the inside of the battery module is filled with a phase change material (PCM), which is injected in a liquid state and can change into an insulating solid inside the module case. The phase change material can fill the spaces formed between multiple cylindrical battery cells.

[0066] The cylindrical battery cell 3010 is composed of a lithium secondary battery. This lithium secondary battery has the characteristic of generating heat and increasing in temperature even during normal charging and discharging processes. Since an increase in the internal temperature of the battery module can cause problems such as a decrease in the function of the battery module, the temperature increase of the battery module can be suppressed by filling the inside of the module case 3100 with a phase change material (PCM).

[0067] Phase-change materials can absorb a certain amount of heat while undergoing a phase change from solid to liquid, thereby maintaining a constant temperature. Conversely, when undergoing a phase change from liquid to solid, the phase-change material releases stored latent heat, allowing it to maintain a constant temperature. Phase-change materials have the property of maintaining a constant temperature by absorbing ambient heat above a set temperature to keep the temperature low, and then releasing stored heat to raise the temperature when it falls below the set temperature.

[0068] In this invention, the phase change material is injected into the module case in a liquid state, so that the space formed between the cylindrical battery cells can be filled with the phase change material. When the liquid phase change material undergoes a phase change to a solid inside the module case, it exhibits an insulating function, so even if one of the cylindrical battery cells ignites, it has the effect of preventing the spread of flames.

[0069] If the phase change material is in a liquid state, a problem may arise where it leaks out of the module case. Therefore, to prevent the phase change material from leaking out, it is preferable to inject it after attaching a cover to the module case.

[0070] A person with ordinary skill in the art to which this invention belongs will be able to make various applications and modifications within the scope of this invention based on the above content. [Explanation of Symbols]

[0071] 1000, 2000, 3000 battery modules 1010, 2010, 3010 cylindrical battery cells 2020, 3020 Bus Bar 2030 Welding Spot 2040 wire 1100, 2100, 3100 Module Cases 3200 cover 3210 Bulkhead 3500 Pogopin 3510 Torso 3512 Protrusion 3514 Screw thread 3516 Hook 3518 Screw head 3520 Elastic body 3530 pins 3532 Pin support section 3540 balls 3600 Joint 3610 Joint lid

Claims

1. Multiple cylindrical battery cells, A module case housing the aforementioned plurality of cylindrical battery cells, A cover that is coupled to at least one of the open surfaces of the module case, A metal plate attached to the cover, A conductive member interposed for electrical connection between each of the plurality of cylindrical battery cells and the metal plate, Includes, The aforementioned energizing member is A hollow cylindrical body, An elastic body provided inside the aforementioned body, A pin is inserted inside the body, supported by the elastic body, and protrudes only to the outside of the body up to a certain length. Includes, A battery module in which the cover and the metal plate are joined by at least one of heat fusion and interference fit.

2. A plurality of cylindrical battery cells, A module case housing the aforementioned plurality of cylindrical battery cells, A cover that is coupled to at least one of the open surfaces of the module case, A metal plate attached to the cover, A conductive member interposed for electrical connection between each of the plurality of cylindrical battery cells and the metal plate, Includes, The aforementioned energizing member is A hollow cylindrical body, An elastic body provided inside the aforementioned body, A pin is inserted inside the body, supported by the elastic body, and protrudes only to the outside of the body up to a certain length. Includes, A battery module in which the current-carrying member is screwed into the cover and the metal plate, thereby fixing the cover and the metal plate to each other.

3. The battery module according to claim 1, wherein the current-carrying member is one of a single-sided pogo pin, in which the pin is provided only on one side of the body, and a double-sided pogo pin, in which the pin is provided on both sides of the body.

4. The battery module according to claim 1 or 3, wherein the outer surface of the body is provided with at least one of the following: screw threads, hooks, locking projections, and donut-shaped protrusions.

5. The battery module according to claim 1 or 2, wherein the current-carrying member is connected through the cover.

6. The battery module according to claim 5, wherein the method of connection through the cover is at least one of the following 1) to 5). 1) Tightening, 2) Hook connection, 3) Screwing, 4) Fusion, 5) The coupling portion and the cover, which are injection-molded integrally with the current-carrying member, are joined by the methods described in 1) to 4).

7. The battery module according to claim 1, wherein the cover and the metal plate are joined by at least one of heat fusion and interference fit.

8. The battery module according to claim 1 or 2, wherein the metal plate and the conductive member are joined after the module case containing the plurality of cylindrical battery cells and the cover are joined together.

9. The aforementioned module case consists of an upper case and a lower case. The battery module according to claim 1 or 2, wherein the upper case and the lower case are detachably connected.

10. The battery module according to claim 1 or 2, wherein the inside of the battery module is filled with a phase change material (PCM).

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