Battery system having improved end separator and electric vehicle including the same
By using deformable end insulators in the battery system, including plate elements and metal foam or honeycomb structures, the problem of unstable pressure in traditional battery systems is solved, ensuring constant pressure and stable performance of the battery during its life.
Patent Information
- Application Number
- CN202411779358.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-04-10
- Filing Date
- 2024-12-05
- Publication Date
- 2025-10-17
AI Technical Summary
The cell stack frames of conventional battery systems are susceptible to length or positioning deviations, which cause large variations in the forces applied to the cell stack, affecting performance and making it difficult to maintain constant pressure conditions during the battery's life.
Deformable end spacers are used, including parallel plate elements and metal foam or metal honeycomb structures, to compensate for production tolerances and aging-induced expansion by compression deformation between the unit stack and the end plates, ensuring constant pressure application.
This ensures constant pressure conditions during the battery life, compensating for production tolerances and expansion forces, and ensuring reliable and safe operation of the battery system.
Smart Images
Figure CN120810169A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] Aspects of embodiments of the present disclosure relate to battery systems with improved end spacers. BACKGROUND
[0002] Recently, vehicles for transportation of goods and people using electric power as a power source have been developed. Such electric vehicles are automobiles propelled permanently or temporarily by electric motors using energy stored in rechargeable batteries. Electric vehicles can be powered by batteries only (so-called battery electric vehicles or BEVs), or can include a combination of electric motors and, for example, a conventional internal combustion engine (so-called plug-in hybrid electric vehicles or PHEVs). BEVs and PHEVs use rechargeable batteries designed to provide electric power for a sustained period of time.
[0003] Generally, a rechargeable (or secondary) battery cell includes an electrode assembly comprising a positive electrode, a negative electrode, and a separator interposed between the electrodes. A solid or liquid electrolyte allows ions to move during charging and discharging of the battery cell. The electrode assembly is positioned (or arranged) in a case, and electrode terminals located on the outside of the case establish an electrically conductive connection with the electrodes. The case can have, for example, a cylindrical or rectangular shape.
[0004] A battery module is generally formed of a plurality of battery cells connected together in series or in parallel. For example, a battery module is formed by interconnecting the electrode terminals of a plurality of battery cells to provide a high-power rechargeable battery, the number and configuration of the battery cells depending on the amount of electricity required.
[0005] A battery module can be constructed in a block design or a modular design. In the block design, each battery cell is incorporated into a common current collector structure and a common battery management system, and its unit is arranged in an outer case. In the modular design, a plurality of battery cells are connected together to form a sub-module, and several sub-modules are connected together to form a battery module. In automotive applications, a battery system generally includes a plurality of battery modules connected together in series to provide the required voltage.
[0006] A battery pack is a group of any number (usually the same) of battery modules or individual battery cells. The battery modules or individual battery cells can be constructed in series, in parallel, or in a mixture of both series and parallel to provide the required voltage, capacity, and / or power density. The components of a battery pack include individual battery modules and interconnects that provide electrical conductivity between the battery modules.
[0007] The battery cells of the battery pack can be formed into a cell stack by stacking the battery cells on top of each other or arranging the battery cells in a row. Adjacent battery cells in the cell stack can be pulled apart (or spaced apart) from each other by cell spacers. The cell stack can be placed inside a cell stack frame that bounds the battery cells from the outside. Pressure (e.g., a predetermined pressure) is exerted on the battery cells by the cell stack frame to compensate for possible production tolerances and swelling of the battery cells, thereby ensuring optimal performance of the battery cells during their lifetime.
[0008] Conventional battery systems typically include a cell stack frame with a rigid linear or progressively elastic pressure characteristic, whose end plates (in some cases) exert pressure onto the cell stack via end spacers. Such rigid frames can be susceptible to length or positioning deviations, as small displacements can cause a large (or sharp) increase or decrease in the force exerted on the cell stack, which in turn can degrade the performance of the cell stack. Therefore, to mitigate this, very precise production tolerances must be met, or other expensive and complex ways of adjusting the cell stack pre-tension via positioning end plates during assembly must be implemented. Such end plates can not ensure the right amount of pressure exerted onto the cell stack during the entire lifetime of the cell stack. SUMMARY
[0009] The present disclosure is defined by the appended claims and their equivalents. The following description is limited thereby. Any disclosure that is outside the scope of the claims and their equivalents is intended for illustrative and comparative purposes.
[0010] Embodiments of the present application provide a battery system with an improved cell stack frame that ensures the right pressure conditions for the battery cells to perform optimally during their entire lifetime of use.
[0011] According to embodiments of the present disclosure, a battery system comprises a cell stack comprising a plurality of battery cells arranged, a cell stack frame housing the cell stack and comprising an end plate exerting pressure onto the cell stack, and a deformable end spacer arranged between the cell stack and the end plate. The deformable end spacer is compressed by the pressure exerted via the end plate and comprises parallel plate elements and a metal foam and / or a metal honeycomb structure arranged between the plate elements. The plate elements have a different material composition than the metal foam and / or the metal honeycomb structure, the metal foam is an aluminum foam and / or the metal honeycomb structure is an aluminum honeycomb structure, and the plate elements are steel plate elements.
[0012] According to another embodiment of the present disclosure, the end spacer has a thickness that can be substantially the same as the thickness of one of the battery cells under nominal compression.
[0013] According to another embodiment of the disclosure, the metal foam has a porosity in a range of about 80% to about 90% (e.g., about 85%).
[0014] Another embodiment of the disclosure relates to an electric vehicle comprising a battery system as described above.
[0015] Further aspects and features of the disclosure can be gleaned from the claims and / or the following description. BRIEF DESCRIPTION OF DRAWINGS
[0016] Aspects and features of the disclosure will become apparent to those of ordinary skill in the art by reference to the following detailed description of embodiments of the disclosure in conjunction with the accompanying drawings.
[0017] Figure 1 is a schematic top view of a battery system according to an embodiment.
[0018] Figure 2 is Figure 1 is a schematic side view of an end spacer of the battery system shown in
[0019] Figure 3A , Figure 3B and Figure 3C are three schematic top views of battery systems having different cell stack lengths.
[0020] Figure 4 is a graph showing force versus elongation length (e.g., displacement) ratio for a battery system according to an embodiment. DETAILED DESCRIPTION
[0021] Reference will now be made in detail embodiments, examples of which are illustrated in the accompanying drawings. Aspects and features of embodiments and methods for realizing the same will be described with reference to the accompanying drawings. However, the disclosure can be embodied in various different forms, and should not be construed as being limited to the embodiments shown herein. Rather, these embodiments are provided as examples so that the disclosure will be thorough and complete, and will fully convey the aspects and features of the disclosure to those skilled in the art.
[0022] Therefore, processes, elements, and techniques that are not considered necessary for a person of ordinary skill in the art to fully understand the aspects and features of the disclosure can not be described or only be briefly described.
[0023] It will be understood that when an element or layer is referred to as being "on" another element or layer, "connected to" or "coupled to" another element or layer, it can be directly on, directly connected to, or directly coupled to the other element or layer or one or more intervening elements or layers can also be present. In contrast, when an element or layer is referred to as being "directly on," "directly connected to," or "directly coupled to" another element or layer, there are no intervening elements or layers present. For example, when a first element is described as being "coupled" or "connected" to a second element, the first element can be directly coupled or directly connected to the second element or the first element can be indirectly coupled or indirectly connected to the second element via one or more intervening elements.
[0024] In the drawings, the size of various elements, layers, etc. can be exaggerated for clarity. Like reference numbers signify like elements. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. In addition, use of "may" when describing embodiments of the present disclosure relates to "one or more embodiments of the present disclosure." When expressions such as "at least one of," and "any one of" precede a list of two or more items, the expression relates to any single one of the listed items and to all possible combinations of any two or more of the listed items. For example, the expression "at least one of a, b, and c" means a, b, c, a and b, a and c, b and c, and a, b, and c. As used herein, the term "use" and variations thereof can be considered synonymous with the term "utilize" and variations thereof, respectively.
[0025] It will be understood that, although the terms first, second, third, etc. can be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.
[0026] For ease of description, spatially relative terms, such as "under", "below", "lower", "over", "upper" and the like, can be used herein for describing an element's or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device is inverted in the figures, elements described as "below" or "under" other elements or features would then be oriented "above" the other elements or features. Thus, the term "below" can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
[0027] The terminology used herein is for the purpose of describing embodiments of the present disclosure and is not intended to be limiting of the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises", "comprising", "includes" and / or "including", when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.
[0028] In view of the entire disclosure, those of ordinary skill in the art will appreciate that individual suitable features of various embodiments of the present disclosure can be combined, in part or whole, with each other, and can be technically interlocked and operated in various suitable ways, and unless otherwise stated or implied, individual embodiments can be implemented independently of each other or in combination with each other in any suitable manner.
[0029] As used herein, the terms "substantially", "approximately", and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values that would be recognized by those of ordinary skill in the art. Moreover, if the term "substantially" is used in combination with a feature that can be expressed using a numerical value, the term "substantially" indicates a range of + / - 5% of the value centered on that value.
[0030] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this present disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and / or the
[0031] According to embodiments of the present disclosure, a battery system comprises a plurality of battery cells, e.g. prismatic battery cells or pouch-type battery cells. The battery cells are arranged to form a cell stack, e.g. by stacking the battery cells on top of each other or by arranging the battery cells in rows. Cell spacers can be provided between adjacent or neighboring battery cells. Thus, adjacent battery cells of the cell stack can be pulled apart (or spaced apart) from each other via the cell spacers. The cell stack can form one or more battery packs.
[0032] The cell stack is arranged inside a cell stack frame. The cell stack frame comprises at least one end plate that exerts pressure onto the cell stack. The cell stack frame can comprise two end plates and two side walls connecting the end plates, and one or both end plates can exert pressure onto the cell stack. Thus, the cell stack arranged inside the cell stack frame can be bounded from four sides by the end plates and the side walls. The cell stack frame can further comprise a top cover and a bottom cover, such that the cell stack can be bounded from all six sides. The end plates can be fixed to the side walls (and / or the top cover and the bottom cover), e.g. by riveting or screwing. The end plates can be rigid, e.g. non-deformable. The cell stack frame can bound the cell stack from the outside, i.e. from the external environment of the cell stack. The end plates can form the outer boundary of the cell stack frame. Further, the other end plate and / or the side walls can form the outer boundary of the cell stack frame. In other words, the cell stack frame (e.g. the two end plates and the two side walls) can bound the inner space of the cell stack frame from the external environment, and the cell stack is arranged in the inner space.
[0033] A deformable end spacer is arranged between the cell stack and the end plate. Thus, the deformable end spacer is arranged inside the inner space bounded by the cell stack frame. The end plate in the mounted position exerts pressure onto the cell stack via the deformable end spacer, thereby compressing the deformable end spacer, e.g. deforming it. The end plate can exert pressure onto the cell stack via the deformable end spacer while being supported or fixed to other parts of the cell stack frame, e.g. to the side walls. Thus, the cell stack frame provides a pre-tension of the cell stack. In embodiments, the cell stack frame comprises two end plates at opposite ends of the cell stack frame, and such deformable end spacers are provided on both ends of the cell stack (e.g. at the opposite ends) between the respective end of the cell stack and the respective end plate. The deformable end spacer can have a shape corresponding to the shape of the inner space of the cell stack frame that accommodates the cell stack, such as a rectangular shape.
[0034] The deformable end insulator comprises two parallel plate elements and one or more metal foams and / or metal honeycomb structures. For example, the deformable end insulator comprises metal foam, metal honeycomb structure or metal foam and metal honeycomb structure. For example, the first layer of the deformable end insulator may comprise or may consist of metal foam and the second layer of the deformable end insulator may comprise or may consist of metal honeycomb structure. Metal foam is a material or structure composed of solid metal having pores that form most of the volume and are filled with gas. The metal foam may have an open-pore structure in which the pores may be interconnected or a closed-pore structure in which the pores may be closed / sealed. The metal foam and the metal honeycomb structure may exhibit deformation properties that make them suitable for use as end insulators as described below.
[0035] Due to the metal foam / metal honeycomb structure, the deformable end spacers are configured to deform elastically under lower compressive stresses and plastically under higher compressive stresses. The metal foam and metal honeycomb structures can exhibit appropriate deformation characteristics to ensure that the pressure acting on the cell stack (i.e., the compressive stress acting on the cell stack) remains substantially constant over the life of the cell stack. Therefore, compared to conventional battery systems that may exhibit rigid linear or progressive elastic pressure characteristics, the deformable end spacers enable battery systems according to embodiments of the present disclosure to exhibit constant deformation characteristics within a relevant pre-tension range. For example, due to the deformable end spacers, the end plates can apply a constant compressive stress to the cell stack within a relevant pre-tension range for prismatic or pouch-type battery cells. Unavoidable tolerances of the cell stack components and the cell stack frame can be compensated for by the inherent deformability of the deformable end spacers, which can eliminate the need for additional shimming or other adjustment work during cell stacking. Furthermore, any expansion of the battery cells in the cell stack (possibly due to aging, for example) can also be compensated. Furthermore, loads that may occur during an accident can be compensated. Due to these tolerances and expansion, the lengths of the cell stacks can vary. However, due to the deformable end spacers, the end plates can apply substantially the same pressure to the cell stack regardless of the length of the cell stack. As a result, the cell stack can be maintained within an optimal pressure range for peak performance, ensuring reliable and safe operation throughout its lifecycle, until the end of its life. Overall, therefore, because the deformable end spacers are configured to maintain a substantially constant pressure, the battery system is configured to compensate for production tolerances of the battery cells and expansion forces / displacements of the battery cells over the life of the battery system.
[0036] The metal foam can be an aluminum (Al) foam. The metal honeycomb structure can be an aluminum (Al) honeycomb structure. Thus, the metal foam and / or the metal honeycomb structure comprises or can consist of aluminum. The metal foam can be a metal alloy foam, e.g., the metal foam can be made of a metal alloy. The metal alloy can comprise aluminum. The metal foam can be a composite metal foam made of a combination of hollow metal spheres and a metal matrix surrounding the spheres. Aluminum can be suitable because of its light weight.
[0037] In some embodiments, the end spacer comprises two parallel plate elements, and the metal foam and / or the metal honeycomb structure is disposed between the plate elements. For example, the metal foam and / or the metal honeycomb structure is sandwiched between the two plate elements. The first plate element can face the end plate, and the second plate element can face the monobloc stack. The plate elements can have the same material composition as the metal foam and / or the metal honeycomb structure, e.g., the plate elements can comprise or consist of aluminum. The plate elements can be rigid, e.g., not deformable. The plate elements can provide suitable contact surfaces for the end plate and the monobloc stack. For example, the plate elements can contact the end plate and the monobloc stack with a large area, such that the force / pressure applied by the end plate is transmitted uniformly. For example, the force / pressure applied by the end plate can be transmitted uniformly from the end plate to the first plate element, from the first plate element to the metal foam and / or the metal honeycomb structure, from there to the second plate element, and finally from the second plate element to the monobloc stack. Regardless, the metal foam and / or the metal honeycomb structure can exhibit their intended deformation characteristics.
[0038] The plate elements have a different material composition than the metal foam and / or the metal honeycomb structure. For example, the plate elements can be steel plate elements, while the metal foam and / or the metal honeycomb structure can comprise or be made of aluminum. The plate elements having a different material composition than the metal foam and / or the metal honeycomb structure can provide a more stable structure while maintaining the intended deformation characteristics.
[0039] According to embodiments, the end spacer has a thickness (e.g., along the extension of the stacking axis) that is substantially the same as the thickness of one of the battery cells under nominal compression. Nominal compression can refer to, for example, the compression value or range applied by the end plate to the monobloc stack during nominal operation, e.g., before any aging-related expansion of the battery cells. Adapting the thickness of the end spacer to the thickness of the battery cells can ensure the intended deformation characteristics. For example, a thicker battery cell can increase in thickness much more than a thinner battery cell due to aging-related expansion. Thus, a thicker end spacer can be provided to support a thicker battery cell, and a thinner end spacer can be provided to support a thinner battery cell.
[0040] According to embodiments, the metal foam has a porosity in the range of about 80% to about 90% (e.g., about 85%). Such a porosity range or value can be suitable to provide the intended deformation characteristics.
[0041] The present disclosure also relates to an electric vehicle comprising a battery system as described herein.
[0042] According to embodiments of the present disclosure, a method for assembling a battery system as described herein can be provided. Therein, in a first embodiment, the cell stack frame can be provided with end plates placed in their fixed / mounted position and deformable end spacers provided adjacent to the end plates. For example, the end plates can be brought into the fixed / mounted position and fixed to the side walls of the cell stack frame. Subsequently, the cell stack can be compressed and then inserted in its pre-compressed state into the cell stack frame with the end plates already in their fixed / mounted position. The cell stack can then be released and can expand until it contacts the deformable end spacers, such that the end plates exert a pressure to the cell stack via the deformable end spacers. In a second embodiment, a cell stack frame can be provided which does not have end plates placed in their fixed / mounted position. The cell stack can be inserted into the cell stack frame without pre-compression. Subsequently, deformable end spacers can be placed next to the cell stack and then the end plates can be placed in their fixed / mounted position, thereby compressing the cell stack, i.e. exerting a pressure to the cell stack via the deformable end spacers.
[0043] Figure 1 is a schematic top view of a battery system 100 according to embodiments. The battery system 100 comprises a plurality of battery cells 12 arranged to form a cell stack 10 and a cell stack frame 20 housing the cell stack 10. The battery cells 12 are stacked (or arranged) along a stacking axis A.
[0044] The cell stack frame 20 comprises two end plates 22, 23 and two side walls 24, 25 connecting the end plates 22, 23. For example, as shown in Figure 1 the end plates 22, 23 and the side walls 24, 25 bound the cell stack 10 from four sides. The cell stack frame 20 can also comprise a top cover and a bottom cover to completely enclose the cell stack 10. The end plates 22, 23 can be fixed to the opposite side walls 24, 25 via, for example, screws or rivets.
[0045] The deformable end spacers 30 are placed between the end plates 22 and the cell stack 10. The deformable end spacers 30 have a rectangular shape corresponding to the shape of the interior space of the cell stack frame 20 housing the cell stack 10.
[0046] Due to production tolerances of the battery cells 12 and any cell separators (if present) arranged between the battery cells 12, the lengths of the cell stacks 10 can vary. For example, not all cell stacks 10 produced during production will have the same length. Furthermore, the battery cells 12 of the cell stacks 10 will expand due to aging, thus expanding along the axis A and thus increasing the length of the cell stack 10. The cell stack frame 20 according to embodiments of the present disclosure can compensate for these varying lengths of the cell stacks 10 due to the deformable end separators 30.
[0047] Referring to Figure 2 The deformable end separators 30 comprise two parallel plate elements 32 and a metal foam 34 arranged between the plate elements 32.
[0048] As shown in Figure 3A , Figure 3B and Figure 3C , the deformable end separators 30 deform to varying degrees depending on the cell stack length. In Figure 3A , the cell stack 10 has a first length LI, in Figure 3B , the cell stack 10 has a second length L2, and in Figure 3C , the cell stack 10 has a third length L3. The second length L2 can be the minimum length, the third length L3 is the maximum length, and the first length LI is the nominal length, such that L3 > LI > L2. For a cell stack 10 having the minimum length L2, the deformable end separators 30 deform only slightly (see, e.g., Figure 3B ). For a cell stack 10 having the maximum length L3, the deformable end separators 30 deform severely (or substantially) (see, e.g., Figure 3C ). For a cell stack 10 having the nominal length LI, the deformable end separators 30 deform moderately (see, e.g., Figure 3A ). Due to the deformable end separators 30, the end plate 22 can apply substantially the same pressure to the cell stack 10 regardless of the length of the cell stack 10. Thus, the battery system 100 having the deformable end separators 30 can be configured to ensure the correct pressure conditions for the battery cells 12 to operate optimally throughout their entire service life.
[0049] In contrast to conventional battery systems, which can exhibit a rigid linear or progressive elastic pressure behavior, the battery system according to embodiments of the present disclosure has an elastic deformation behavior at lower compression forces and a plastic deformation behavior at higher compression forces due to the deformable end separators 30. As shown in Figure 4 , for prismatic or pouch cells, the plastic deformation behavior has a smooth force-displacement-inclination in the relevant pre-tension range.
[0050] Figure 4 is a graph showing the force F versus elongation length (e.g., displacement) S ratio for a deformable end spacer 30 comprising metal foam. As shown, the applied force F increases linearly with elongation length S (may also be, stack length L) in a first portion at lower forces (e.g., the deformable end spacer 30 undergoes elastic deformation), and remains constant in a second portion at higher forces (e.g., the deformable end spacer 30 undergoes plastic deformation). The force (may also be, pressure) applied by the end plate 22 is regulated by the deformable end spacer 30 such that for Figure 3A , Figure 3B and Figure 3C different monobloc stack lengths shown in FIGS. 1-3, the force remains within the ideal monobloc stack pre-tension window or range.
[0051] Thus, due to the deformable end spacer 30, the end plate 22 can apply a constant compressive stress to the monobloc stack 10 and is therefore configured to compensate for the production tolerances of the battery monoblocs as well as the swelling force / displacement of the battery monoblocs during the service life of the battery system. The end plate 22 and deformable end spacer 30 are designed such that the minimum-maximum monobloc stack tolerance is in the flat plateau region of the force / deflection curve as shown in FIG. 4. The flat plateau can be formed by plastic deformation of the metal foam until air is almost completely squeezed out of the foam. The foam then becomes increasingly stiffer such that the force increases with deformation. Thus, the monobloc stack 10 can be kept within the optimal pressure range for peak performance, ensuring reliable and safe operation throughout its entire life cycle until end of life. Figure 4
[0052] Some reference numerals 10: monobloc stack 12: battery monobloc 20: monobloc stack frame 22: end plate 23: end plate 24: side wall 25: side wall 30: deformable end spacer 32: plate element 34: metal foam 100: battery system A: axis.
Claims
1. A battery system, comprising: a cell stack comprising a plurality of battery cells arranged; as well as a cell stack frame accommodating the cell stack, the cell stack frame including end plates for applying pressure to the cell stack; as well as a deformable end insulator disposed between the cell stack and the end plates, the deformable end insulator being compressed by pressure applied via the end plates, the deformable end insulator comprising: parallel plate elements; and a metal foam and / or metal honeycomb structure disposed between the plate elements, wherein the plate element and the metal foam and / or the metal honeycomb structure have different material compositions, wherein the metal foam is aluminum foam and / or the metal honeycomb structure is an aluminum honeycomb structure, and Wherein, the plate element is a steel plate element.
2. The battery system according to claim 1, wherein: Under nominal compression, the deformable end spacer has a thickness that is the same as a thickness of a battery cell in the plurality of battery cells.
3. The battery system according to claim 1, wherein: The metal foam has a porosity in the range of 80% to 90%.
4. The battery system according to claim 3, wherein: The metal foam had a porosity of 85%. 5 . An electric vehicle comprising the battery system according to claim 1 .