BATTERY PACK SYSTEM WITH FUNCTIONS TO PREVENT THERMAL ROLLOUT

Abstract

Battery pack system (1), comprising: a stack of battery cells (2), each battery cell (2) having a first end (21), a second end (22) opposite the first end (21) and side edges (23) extending from the first end (21) to the second end (22), and wherein at least one of the side edges (23) of each battery cell (2) is arranged adjacent to at least one side edge (23) of another of the battery cells (2); a thermochemical material (4) that undergoes an endothermic reaction at temperatures above 50 °C; and wherein the thermochemical material (4) is located: (a) inside the stack of battery cells (2) and outside of battery cells (2) or (b) adjacent to the stack of battery cells (2) or (c) both; characterized by the fact that the battery pack system (1) further comprises: a storage container (10) for thermochemical material (4) and one or more valves (9) that can release the thermochemical material (4) upon reaching a predetermined threshold, wherein the predetermined threshold is a temperature, pressure, or chemical composition of gases escaping from the cells; and a one-way valve (12) between the reservoir (10) and a cooling system (15) with a coolant (34), wherein the one-way valve (12) opens to discharge coolant (34) into the reservoir (10) after the opening of one or more valves (9).

Description

INTRODUCTION

[0001] The present invention relates to a battery pack system according to the preamble of claim 1, as is known essentially from DE 10 2020 124 376 A1.

[0002] Further state of the art can also be found in the documents CN 1 10 523 025 A, EP 3 975 317 A1 and DE 10 2010 004 110 A1.

[0003] Battery modules can contain a variety of rechargeable battery cells (often called secondary batteries). Rechargeable battery cells are useful in a wide range of modern technical applications, such as electronic devices, e-bikes, hybrid vehicles, electric cars, and more. Battery modules can sometimes experience thermal runaway when the heat generated by a source (e.g., a battery cell) exceeds the module's ability to dissipate that heat to the environment. This can lead to an unfavorable temperature rise within the battery module. Thermal runaway can occur, for example, if the battery is short-circuited or damaged.

[0004] The phenomenon of thermal runaway in a battery cell of the battery module can trigger corresponding adverse thermal events in neighboring battery cells.

[0005] Accordingly, it is desirable to provide a containment system that prevents the spread or propagation of a thermal runaway or rapidly suppresses a thermal runaway. SUMMARY

[0006] According to the invention, a battery pack system is presented that is characterized by the features of claim 1. Each battery cell has a first end, a second end facing away from the first end, and side edges extending from the first end to the second end. At least one of the side edges of each battery cell abuts at least one side edge of another battery cell. The battery pack system contains a thermochemical material located within the stack of cells and / or outside the battery cells and / or adjacent to the stack. The thermochemical material undergoes an endothermic reaction at temperatures above 50 °C. The thermochemical material is located (a) within the stack of battery cells and outside the battery cells, or (b) adjacent to the stack of battery cells.

[0007] Furthermore, the battery system may have one or more of the following features. The battery cells are pouch cells or prismatic cells. The thermochemical material is located between the lateral edges of adjacent battery cells, possibly within a matrix material such as a foam. The battery pack system has a gap formed by the first end and an inner surface of a frame. An inner surface of the frame contains the thermochemical material. The stack is divided into two or more containment zones, each zone having a plurality of battery cells, a gap between the top end of these cells and the reservoir, and a thermally actuated valve associated with the reservoir to release the thermochemical material into the zone. The two or more containment zones are separated from each other by a thermal runaway suppression element.The gap is in fluid communication with a region containing the thermochemical material. The thermochemical material comprises a hydrated salt such as one or more of the following: NaAl(SO4)2·10H2O, Na2B4O7·10H2O, Na2P2O7·10H2O, Al(NO3)2·9H2O, Ba(OH)2·8H2O, Mg(NO3)2·6H2O, KAl(SO4)2Al(NO3)2·12H2O, MgCl2·6H2O, and MgSO4·7H2O. The battery pack system also includes a cooling element.

[0008] The above features and advantages, as well as further features and advantages of the invention, are readily apparent from the following detailed description in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Further features, advantages and details are listed only as examples in the following detailed description, which refers to the drawings in which the following applies: Fig. Figure 1 is a schematic cross-sectional view of an exemplary battery pack system with thermochemical material; Fig. Figure 2 is a schematic cross-sectional view of an exemplary battery pack system with a reservoir containing thermochemical material; and Fig. Figures 3a - 3d are schematic views showing exemplary arrangements of battery cells in a pack with venting to areas containing thermochemical material. DETAILED DESCRIPTION

[0010] The following description is merely exemplary. It should be understood that in the drawings, corresponding reference numbers denote identical or corresponding parts and features.

[0011] The present invention solves the problem of thermal runaway in a battery pack system by introducing a thermochemical material into the battery pack system at specific locations.

[0012] According to exemplary aspects and as in Fig. 1, Fig. 2 and Fig. As shown in Figure 3, the battery pack system 1 disclosed herein can comprise battery cells 2 in a stacked configuration. The battery cells 2 can be, for example, pouch cells or prismatic cells. The cells can be stacked such that their maximum dimension is perpendicular to a frame section 7 and / or to a lower section 3, as shown in Figure 3. Fig. Figure 1 shows that each cell can have a first end 21, a second end 22, and side edges 23 extending from the first end 21 to the second end 22. Adjacent battery cells 2 can touch at their outer edges 23. The cells can be stacked such that the side edges are parallel to the horizontal (see, for example, Figure 1). Fig. 3d) or in a structure where the side edges run parallel to the vertical (see Fig. 3a and Fig. 3b).

[0013] As in Fig. As shown in Figure 1, the battery pack system 1 can comprise a frame section 7. The frame section 7 can form a structure and / or contain the cells. The frame section 7 can be made of plastic, composite, or metal plates, or similar materials. The frame section 7 can have an inner surface 8. A gap 6 can be formed between the inner surface 8 and the first ends 21 of the battery cells 2. The gap 6 can be in fluid contact with a gas distributor 13 (e.g., to allow gas flow). As shown, for example, in Fig. 3b, Fig. 3c, Fig. As shown in Figure 3d, this gas distributor 13 can comprise an end section 31 of the battery pack system 1. The gas distributor 13 can be located in or adjacent to the frame section 7. Note that in an alternative embodiment (not shown in the figures), there is no gap between the frame section 7 and the first end 21 of the battery cells 2. The inner surface 8, the gas distributor 13, and / or the end section 31 can contain the thermochemical material 4. The thermochemical material can, for example, be provided in or on the inner surface 8 (e.g., as a layer on the surface, applied to certain areas of the surface, or embedded in the surface) or in or on the end section 31.The thermochemical material can be provided on a solid, porous or lattice-like structure (not shown) that is inserted into one or more sections of the gap 6, the gas distributor 13 or the end section 31.

[0014] The battery pack system 1 can include a lower section 3. This lower section 3 can serve as a holder for the battery cells. In an exemplary aspect shown in Fig. As shown in Figure 2, the lower section 3 can include a cooling element, such as a cooling plate 32. Coolant 34 from a cooling system 15 can flow through such a cooling plate 32.

[0015] The battery pack system 1 can contain an element 5 for suppressing the propagation of thermal runaway. As in the Fig. 1 and Fig. As shown in Figure 2, the thermal runaway suppression element 5 can extend from the lower section 3 to the frame section 7. Alternatively, the thermal runaway suppression element can extend only to the first end 21 of the battery cells 2. If a solid, continuous thermal runaway suppression element extends to the frame section 7, openings 25 can be added to allow gases to be vented to a gas distributor 13 with an end section 31 (as shown in Figure 2). Fig. 3b, Fig. 3c, Fig. (shown in 3D) or to facilitate removal from the battery pack system. Fig. 3c is a cross-sectional view of Fig. 3b.

[0016] A containment zone 11 to prevent thermal runaway can be defined as a plurality of battery cells 2 located between two thermal runaway suppression elements 5 or between a thermal runaway suppression element 5 and the end of the battery pack 1. The thermal runaway suppression element 5 may include a heat-insulating layer. The thermal runaway suppression element 5 may include a thermally conductive component extending to the gap 6, the frame 7, and / or the lower section 3 to dissipate heat from the battery cells 2.If the thermal runaway suppression element 5 comprises both a thermally conductive component and a thermally insulating layer, the thermally conductive component can be located between the thermally insulating layer and the battery cells 2. The thermal runaway suppression element 5 could, for example, comprise a thermally insulating layer, a heat pipe, or a vapor column between two metal layers (e.g., metal foil). Optionally, one or more compression layers 38 can also be included in or adjacent to the thermal runaway suppression element 5 or elsewhere in the battery pack (as shown in the figures). Fig. 1 and Fig. (2 shown). The heat-insulating layer could, for example, also serve as a compression layer. The element 5 for suppressing the propagation of thermal runaway can optionally further comprise the thermochemical material 4, which is distributed in or on a surface of the element 5 for suppressing the propagation of thermal runaway.

[0017] The battery pack system 1 can include layers 38 between the side edges of two adjacent battery cells 2, between a battery cell 2 and the suppression layer 5, and / or between a battery cell 2 and the outer end frame of the battery pack system. The layers 38 can be compression layers. They can, for example, comprise a foamed material such as microcellular polyurethane. Alternatively, or in addition to serving as compression layers, the layers 38 can comprise the thermochemical material 4. For example, the thermochemical material 4 can be distributed within the foam of the compression layer 38.

[0018] As in Fig. As shown in Figure 2, the frame section 7 forms a reservoir 10 for the thermochemical material 4 and forms the upper boundary of the gap 6. (Again, the gap 6 is optional.) The reservoir 10 can hold the thermochemical material 4. The reservoir can be under increased pressure (e.g., at least 300 or at least 400 kilopascals gauge pressure (kPag) up to 1500 or up to 1200 kPag), which can facilitate emptying the reservoir when a valve 9 is opened. In this case, the thermochemical material can be in the form of free (i.e., not adhering to or embedded in another layer) small particles (e.g., powder) that can flow through the valves. The use of small particles, such as powder, can maximize the surface area and thus improve heat absorption. In an alternative embodiment, a gas distributor could be arranged next to (e.g., above) the reservoir 10.

[0019] When a thermal event occurs in a cell 36 (overheating cell) and a threshold value of a property (e.g., temperature, pressure, chemical composition) is reached, one or more valves 9 open, as shown in Fig. 2, and release the thermochemical material onto the battery cells 2 and / or into the gap 6. The valves 9 can comprise a material that closes an opening and melts or deforms at a specific temperature (e.g., at a temperature above the normal operating temperature of the battery assembly, such as above 50, above 55, or above 60 °C up to 100 °C), thereby releasing thermochemical material. The valves 9 can, for example, comprise wax pellets enclosed in pins or a wax-actuated valve similar to current thermostats used to control the flow of internal combustion engines. In another example, the valves 9 can comprise a bimetallic strip that bends out of the path of the opening when heated. Alternatively, the valves 9 can also be actuated by the pressure released during thermal runaway.Another alternative is to actuate the valves when gases are released from the cell module by detecting chemical components indicative of thermal runaway. In this latter variant, a control unit can be used to actuate the valve.

[0020] A one-way valve 12 is connected to the cooling system 15. The cooling system contains a coolant 34, for example, a dielectric heat transfer fluid. During thermal runaway, a valve 9 closest to the overheating cell 36 opens, and the pressure in the reservoir releases the thermochemical material 4 into this containment zone 11 to prevent the propagation of thermal runaway toward the overheating cell 36. This reduces the pressure in the reservoir 10 to near atmospheric pressure (e.g., less than 10 kPag or 0.1–0.2 kPag), causing the pressure in the cooling system 15 to open the one-way valve 12. The coolant 34 can then flow into the reservoir 10, dissolve the remaining thermochemical material 4, and also flow through the open valve 9 toward the overheating cell 36.This can further help to control thermal runaway due to the absorption of heat by the electrochemical material and the heat of vaporization of the coolant in containment zone 11.

[0021] As soon as the temperature drops, if the valve 9 is actively controlled and responds to the current conditions (like a thermostatic valve) and not to the maximum conditions (like a wax plug), it can be closed and prevent further coolant leakage to allow a minimum level of further cooling of the rest of the battery pack system 1.

[0022] The thermochemical material 4 reacts endothermically and absorbs energy, thereby preventing the energy available for the propagation of thermal runaway to adjacent cells or modules. The thermochemical material 4 can be located on or in a layer between or adjacent to the battery cells (e.g., layer 38 or element 5 for thermal runaway suppression), on the surfaces of a gap 6 adjacent to the battery cells (e.g., surface 8), on a mesh or sieve structure in a gap region, in a gas distributor 13 or in an end region 31, in a reservoir 10, or in a combination of two or more of these locations. The thermochemical material 4 can be a material suitable for deployment at these locations.

[0023] A strongly endothermic reaction is more effective at preventing thermal runaway by absorbing the energy that would otherwise trigger further events. The thermochemical material 4 should not react at normal operating temperatures of the battery pack system. Therefore, the thermochemical material 4 preferably has a reaction initiation temperature of at least 50, 60, or 70 °C, but is thermally stable below these temperatures. However, if the temperature at which the endothermic reaction begins is too high, the battery pack system 1 may be damaged too severely before the thermochemical material 4 can prevent thermal runaway. Thus, the thermochemical material preferably has a reaction initiation temperature of no more than approximately 120, 105, 100, or 90 °C.

[0024] The desired reaction initiation temperature can vary depending on the placement of the thermochemical material 4. For example, a thermochemical material 4 placed only in the end regions of the battery pack system may, if desired, have a lower reaction initiation temperature because it is further away from the thermal event. Likewise, a thermochemical material 4 located immediately adjacent to it (e.g., between the edges of battery cells) may, if desired, have a higher reaction initiation temperature. Similarly, a thermochemical material 4 placed on a porous matrix directly exposed to the exhaust gases of the thermal runaway may require a higher reaction temperature to be effective due to the temperature of these combustion products.

[0025] The thermochemical material 4 can be, for example, a hydrated salt, hydrated zeolites, or metal hydroxides. Hydrated salts can be effective due to their high heat storage capacity.

[0026] For example, hydrated salts with dehydration temperatures above 50, 55, or 60 °C can be used. At the same time, the dehydration temperature of an example hydrated salt can be, for example, less than 105, 100, or 90 °C. Salts with a large heat change during dehydration (ΔH) dehydration ) can allow for greater energy absorption per unit mass. ΔH dehydration For example, it can be at least 150, at least 175 or at least 200 kilojoules / kilogram.

[0027] Non-bonding examples of hydrated salts are NaAl(SO4)2·10H2O, Na2B4O7·10H2O, Na2P2O7·10H2O, Al(NO3)2·9H2O, Ba(OH)2·8H2O, Mg(NO3)2·6H2O, KAl(SO4)2Al(NO3)2·12H2O, MgCl2·6H2O and MgSO4·7H2O.

[0028] The thermochemical material 4 is preferably non-reactive with other components of the battery pack system that are exposed to it. For example, a thermochemical material 4 with a substantially neutral pH (e.g., pH 6–8) can be used. The thermochemical material 4 can be non-conductive or only slightly conductive. Since, according to the invention, the reservoir 10 is used and the coolant 34 is combined with the thermochemical material 4, the thermochemical material 4 should not significantly increase the conductivity of the coolant. Furthermore, it is desirable that the thermochemical material 4 does not decompose into compounds more toxic than the electrolyte and other battery constituents during a thermal event, and that it contains only a small amount of oxygen to limit additional oxidation interactions during a thermal runaway.

[0029] The battery pack system 1 can include features beyond the housing, physical structure, thermal runaway prevention functions, and the cells themselves. These include a thermal management and cooling system for normal operation to maintain the battery cells within their ideal temperature range and dissipate excess heat; electric buses to connect the cells in parallel and series to meet the voltage and current requirements of a vehicle; voltage management systems to maintain the overall capacity of the pack by balancing voltage and capacity between parallel cell groups; and a battery disconnect unit that enables control of the charging and discharging of the battery system as well as the electrical connections to the drive, charging, and other vehicle subsystems. As described in the Fig. 3a - 3d representation, the following can be found in the Fig. 1 and Fig. The two battery packs shown are arranged in a 14-unit assembly, either vertically ( Fig. 3b and Fig. 3c) or horizontal ( Fig. 3D alignment can be combined.

Claims

[1] Battery pack system (1), comprising: a stack of battery cells (2), each battery cell (2) having a first end (21), a second end (22) opposite the first end (21) and side edges (23) extending from the first end (21) to the second end (22), and wherein at least one of the side edges (23) of each battery cell (2) is arranged adjacent to at least one side edge (23) of another of the battery cells (2); a thermochemical material (4) that undergoes an endothermic reaction at temperatures above 50 °C; and wherein the thermochemical material (4) is located: (a) inside the stack of battery cells (2) and outside of battery cells (2) or (b) adjacent to the stack of battery cells (2) or (c) both; characterized by , that the battery pack system (1) further comprises: a storage container (10) for thermochemical material (4) and one or more valves (9) that can release the thermochemical material (4) upon reaching a predetermined threshold, wherein the predetermined threshold is a temperature, pressure, or chemical composition of gases escaping from the cells; and a one-way valve (12) between the reservoir (10) and a cooling system (15) with a coolant (34), wherein the one-way valve (12) opens to discharge coolant (34) into the reservoir (10) after the opening of one or more valves (9). [2] Battery pack system (1) according to claim 1, wherein the battery cells (2) are pouch cells or prismatic cells. [3] Battery pack system (1) according to claim 1, wherein the stack comprises one or more layers (38) located between side edges (23) of adjacent battery cells (2), wherein the one or more layers (38) comprise the thermochemical material (4). [4] Battery pack system (1) according to claim 1, further comprising a gap (6) formed by the first end (21) and an inner surface of a frame (7), wherein the inner surface of the frame (7) comprises the thermochemical material (4), the gap (6) is in fluid communication with a region comprising the thermochemical material (4), or both. [5] Battery pack system (1) according to claim 1, wherein the stack is divided into two or more containment zones (11), each containment zone (11) comprising a plurality of battery cells (2), a gap (6) between the first end (21) of the cells (2) and the reservoir (10), and a thermally actuated valve (9) in conjunction with the reservoir (10) to release the thermochemical material (4) into the containment zone (11), wherein the two or more containment zones (11) are separated from each other by an element for suppressing the propagation of thermal runaway. [6] Battery pack system (1) according to claim 1, wherein the thermochemical material (4) comprises a hydrated salt. [7] Battery pack system (1) according to claim 1, further comprising a cooling element (32).

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