BATTERY MODULE FOR A BATTERY PACK OF AN ELECTRIC VEHICLE
The improved collective rail arrangement in lithium ion battery modules addresses thermal energy management challenges by evenly distributing heat across the module, enhancing performance and safety by minimizing temperature variations between cells.
Patent Information
- Application Number
- DE102018102074
- Authority / Receiving Office
- DE · DE
- Patent Type
- Patents
- Current Assignee / Owner
- Priority Date
- 2017-02-01
- Filing Date
- 2018-01-30
- Publication Date
- 2025-03-13
- Estimated Expiration
- 2038-01-30
AI Technical Summary
Existing lithium ion battery packs for electric vehicles face challenges in managing thermal energy efficiently, leading to performance limitations and safety concerns due to temperature variations between cells and inadequate heat dissipation from long collective rails.
A novel collective rail arrangement for lithium ion battery modules, where the first and second outer collective rails are configured to generate canceling electromagnetic fields, and the inner collective rails are thermally connected to cell caps and cooling fins to distribute heat evenly across the module.
The improved collective rail arrangement effectively distributes thermal energy across the battery module, minimizing temperature differences between cells and enhancing overall battery performance and safety by ensuring optimal temperature management.
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Abstract
Description
TECHNICAL FIELD
[0001] The present invention relates to lithium-ion batteries for electric vehicles, and more particularly to a battery module for a battery pack having an improved bus bar arrangement with improved thermal energy management. BACKGROUND
[0002] Hybrid electric vehicles (HEVs) and fully electric vehicles (EVs) are emerging as promising solutions for sustainable transportation systems in the near future. The harmful environmental impacts of conventional internal combustion engines (ICEs) and certain economic problems associated with petroleum-based fuels are the primary reasons for the development of electric powertrains.
[0003] While EVs rely entirely on power from an electrochemical storage system (e.g., batteries), in HEVs, a combination of engine power and battery system power provides propulsion in the hybrid powertrain. Equipping a vehicle with a regeneration system enables battery recharging by capturing kinetic energy during braking. Furthermore, a small ICE in EVs can be used as a generator to recharge the batteries and extend the driver's driving range.
[0004] Hybrid and fully electric vehicles must overcome many hurdles to address concerns about safety and efficiency. Despite technological advances in battery technology, large-scale application of batteries with high energy and power density has not yet reached their full potential. These shortcomings are attributed to the fact that the charging capacity, power delivery characteristics, and calendar life of batteries are highly dependent on their temperature. It has been proven repeatedly that excessive heating of batteries during operation (charging and discharging) leads to unstable reactions, which can subsequently lead to serious safety problems such as fires and explosions. Exposure of batteries to subzero temperatures significantly reduces their power delivery.Accordingly, a battery thermal management system (BTMS) is a must for all medium or large-scale battery packs to maintain their temperature within an optimal range, regardless of the load on the battery pack.
[0005] Lithium-ion (Li-ion) batteries have become the predominant battery technology due to several compelling features, such as high power and energy densities, long cycle life, excellent storage capacities, and recharging properties without memory effect. Prismatic Li-ion cells, also known as pouch cells, are well-known in the art and are preferred in automotive electrification due to their negligible container (pouch) weight, relatively low manufacturing costs, and flexibility in design.
[0006] Lithium-based batteries are room-temperature batteries, meaning their ideal operating temperature is approximately 25°C. Nevertheless, they can operate in a range between -20°C and 60°C, although their capacity drops sharply at temperatures below 0°C, and they become vulnerable to serious thermal hazards at temperatures above 50°C. Accordingly, thermal management of lithium-ion batteries is critical to promoting their safety and performance.
[0007] In general, the complexity of a BTMS increases with the size of a battery system. Significant temperature variations can occur between individual cells as the battery system size increases. If one cell has a higher temperature than the others, it will also have a different electrical performance, leading to a performance imbalance of the entire battery pack. To promote peak performance, the temperature differential between the cells in the battery pack should be minimized; meanwhile, the entire battery pack must be maintained within a desired temperature range.
[0008] Multiple battery cells, especially lithium-ion (Li-ion) batteries, are widely used due to their high energy density, high specific energy, long cycle life, and lightweight design. Generally, a lithium-ion battery consisting of multiple battery cells includes a battery case and a set of cells grouped within the battery case as battery modules. Each of these battery cells includes a positive electrode with a positive lead and a negative electrode with a negative lead. In construction, these positive and negative leads are connected in series, parallel, or in combination to meet various voltage and energy requirements at the battery level.
[0009] Typically, a battery includes a busbar, which is a metallic conductor with low impedance and high current carrying capacity that connects electrodes in the required arrangement. The busbar is generally used as a conductor to distribute electrical current to multiple locations in the battery, and the busbar is generally used to connect the electrodes to each battery cell where the busbar connects the cells in series, connecting the positive terminal of one battery cell to a negative terminal of another battery cell. The busbar is generally welded to each electrode terminal. Alternatively, the busbar may be connected to the electrode terminals by mechanical fasteners.Accordingly, the busbars are used to carry significant electrical currents between cells over relatively short distances.
[0010] An example of a traditional state-of-the-art busbar arrangement for a lithium-ion battery pack is shown in the Fig. 1A and Fig. 1B. As is known in the art, the main purpose of busbars is electrical transmission. However, since the length of the busbar can be relatively long (as in the Fig. 1A and Fig. 1B), however, the temperature of the bus bar may rise as electricity flows through the bus bar. Accordingly, although not necessary, heat 174 may be transferred through cell components due to the conduction of electrical currents between the battery cells from the central region 114 of each bus bar 112 (where heat accumulates between the cells) toward the end regions 116 of each bus bar 112, where the bus bar 112 is coupled to a cooling fin (not shown). The end regions 116 of each bus bar may be attached to each cell tab (electrode) so that heat may be transferred from the cell cap 164 to the cell tab and then to the cell and a heat-dissipating cooling fin. It should be understood that cable 120 may provide a connection between the battery pack and the vehicle.
[0011] However, due to the rather long Z-shaped busbars, relatively high temperatures are generated while current flows through the busbars 112. Furthermore, due to the rather long distance between the center of the Z-shaped busbars and the cooling fins, it is difficult to transfer the heat 174 from the busbars 112 to the cooling fins.
[0012] Accordingly, there is no need for an improved busbar arrangement for a lithium-ion vehicle battery that better manages thermal energy. SUMMARY
[0013] According to the invention, a battery module is presented which is characterized by the features of claim 1.
[0014] Alternatively, the first inner bus bar is connected to the second inner bus bar via an end-connecting bus bar. It is understood that the first and second outer bus bars are operatively configured to generate mutually canceling electromagnetic fields. Each of the first and second outer bus bars, as well as each of the first and second inner bus bars, defines a proximal end and a distal end, with each distal end attached to a cell cap. The proximal end of the first outer bus bar is configured to be attached to a first outer connecting bus bar. The proximal end of the second outer bus bar is configured to be attached to a second outer connecting bus bar to couple the module to another module.The module further includes a plurality of battery cells having a cooling fin disposed between each battery cell in the plurality of battery cells, each battery cell further including a cell tab and a corresponding cell cap. The first and second outer bus bars, the first and second inner bus bars, the corresponding cell cap, the cell tab, the battery cell, and the cooling fin are thermally connected to each other.
[0015] The thermal energy generated by the busbars in the flexible module is evenly distributed throughout the module because the first and second busbars are operatively configured to thermally balance each other on each lateral side of the module.
[0016] The present invention and its specific features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] These and other features and advantages of the present invention will become apparent from the following detailed description, best mode, claims, and accompanying drawings: Fig. Figure 1A is an isometric view of a traditional bus bar assembly on a lithium-ion battery for a vehicle. Fig. Figure 1B is a top view of a traditional bus bar assembly on a lithium-ion battery for a vehicle. Fig. 2 is an isometric view of a bus bar assembly according to various embodiments of the present invention, wherein the bus bar assembly is implemented on a lithium-ion battery for a vehicle. Fig. 3 is a plan view of a bus bar assembly according to various embodiments of the present invention, wherein the bus bar assembly is implemented on a lithium-ion battery for a vehicle. Fig. 4 is a partial cross-sectional view of an outer bus bar, the cells, the cell caps, the cell tongue of the battery of Fig. 2 along lines 4-4.
[0018] Like reference numbers refer to like parts throughout the description of the several views of the drawings. DETAILED DESCRIPTION
[0019] With reference to Fig. 2 and Fig. 3, the present invention provides a lithium-ion battery 10 for an electric vehicle in which the bus bar assembly better manages thermal energy throughout the vehicle. As shown in Fig. 2, a lithium-ion battery 10 for an electric vehicle is shown. Fig. 2 includes four battery modules 70. A plurality of bus bars are provided that connect one battery module 70 to another battery module 70. A pair of outer bus bars 12, 36 are arranged on the lateral sides of each battery module 70. The first outer bus bar 12 (shown as a positive terminal 97) is arranged on the first lateral side 66 of the battery module 70, while a second outer bus bar 36 (shown as a negative terminal 99) is arranged on the second lateral side 68 of the battery module, as shown in Fig. 3. The first and second outer bus bars 12, 36 (positive terminal 97 and negative terminal 99) are attached to the corresponding first and second outer connecting bus bars 44, 46, which are generally arranged between each module - first and second modules 84, 82. The first and second outer bus bars 44, 46 are configured to connect the first and second outer bus bars 12, 36 (positive terminal 97 and negative terminal 99) of one module to the oppositely charged terminals (negative terminal 99 and positive terminal 97) of an adjacent module 70.
[0020] Consequently, the first outer busbar 12, in an example from Fig. 3, a proximal end 60 and a distal end 62, wherein the proximal end 60 is attached to a first outer connecting bus bar 44, while the distal end 62 is attached to a cell cap 64 (or a cell component) located near the first lateral side 66 of the first module. The second outer bus bar 36 also includes a proximal end 60 and a distal end 62, wherein the proximal end 60 is attached to a second outer connecting bus bar 46, while the distal end 62 of the second outer bus bar 36 is attached to a cell cap 64 (or a cell component) located near the second lateral side 68 of the first module 70, 84. The proximal end 60 of the first outer bus bar 12 may, but need not, be attached to the first outer connecting bus bar 44 via a mechanical fastener 63.The proximal end 60 of the first outer bus bar 12 may also be welded to the first outer connecting bus bar 44. It should be understood that the distal end 62 of the first outer bus bar 12 may be connected to a cell cap 64 located as shown in FIG. Fig. 4, located near the first lateral side 66, may be welded, but need not be welded. The heat 74 from the first outer connecting busbar 44 and the first outer busbar 12 may then be transferred to the cell cap 64, the cell tab 92, the cell 94, and the cooling fins 22 adjacent to each cell 94.
[0021] The proximal end 60 of the second outer bus bar may, but need not, be similarly attached to the second outer connecting bus bar 46 via a mechanical fastener 63. The proximal end 60 of the second outer bus bar 36 may also be welded to the second outer connecting bus bar 46. It is understood that the distal end 62 of the second outer bus bar 36 may be attached to a cell cap 64 located near the second lateral side, as shown in Fig. 4, may be welded, but need not be welded. Similarly, heat 74 from the second outer bus bar 36 may then be transferred from the second outer bus bar 36 to the cell cap 64, the cell tab 92, the cell 94, and then to the cooling fins 22 adjacent each cell 94.
[0022] It should be understood that the first and second outer connecting bus bars 36, 46 are operatively configured to connect the first module 70, 84 to the second module 70, 82 such that electricity may be transferred from the first module 84 to the second module 82. With reference to the first outer connecting bus bar 44, the first outer connecting bus bar 44 may be operatively configured to electrically connect the positive terminal 97 (first outer bus bar 12) on the positive side 96 of the first module 84 to the negative terminal 99 (first outer bus bar 12) on the negative side 98 of the second module 82. Furthermore, the corresponding outer bus bar 12 (negative terminal 99 of the second module 82) is, as can be seen, disposed proximally to the first lateral side 66 of the adjacent (second) battery module 70, 82.The corresponding outer bus bar 12 of the adjacent (second) battery module 70, 82 may also be referred to as a first outer bus bar 12, since this bus bar 12, as shown in . Fig. 2, is arranged proximally to the first lateral side 66 of the second battery module 70, 82.
[0023] With reference to the second outer connecting bus bar 46, the second outer connecting bus bar 46 may be operatively configured to connect the negative terminal 99 on the negative side 98 of the first module 84 to the positive terminal 97 on the positive side 98 of the second module 82. As can be seen, the second outer connecting bus bar 46 couples the second outer bus bar 36 to a corresponding outer bus bar 36 of an adjacent (second) battery module 70, 82, wherein the corresponding outer bus bar 36 (negative terminal 99 of the first module 84) is disposed proximally to the second lateral side 68 of the adjacent (second) battery module 70, 82. The corresponding outer bus bar 36 (positive terminal 97) of the adjacent (second) battery module 70, 82 may also be referred to as a second outer bus bar 36, since this bus bar 36, as in Fig. 2, is arranged proximally to the second lateral side 68 of the second battery module 70, 82.
[0024] It is understood that the first and second outer bus bars 12, 36 of the first module are arranged near the second end 32 of the first module. At the first end 30 of the first module, the first and second inner bus bars 20, 24 are arranged, as shown in Fig. 2 and Fig. 3, disposed near the central region 90 of the first module. Each of the first and second inner bus bars 20, 24 includes a distal end 62 that is attached to a cell cap 64 or the like via a weld or mechanical fastener 63. It will be appreciated that heat 74 may be transferred from each of the first and second inner bus bars 20, 24 to a corresponding cell cap 64, then to a corresponding cell tab 92, to the cell 94, and then to a cooling fin 22. The first and second bus bars may be interconnected via an inner interconnecting bus bar 56. The inner interconnecting bus bar 56 is configured to electrically connect a positive terminal 97 (first inner bus bar 20) on the positive side 96 of the first module 84 to the negative terminal 99 (second inner bus bar 24) on the negative side 98 of the first module 84.
[0025] As in Fig. 2 and Fig. 3, the second module 82 also includes first and second inner busbars 20, 24, which are also arranged at a second end 32 of the second module 82 - the second end 32 of each module 70 (e.g., the second module 82) is located opposite the first end 30 of the same module (e.g., the second module 82). However, as shown in the Fig. 2 and Fig. 3, are similarly disposed in the central region 90 of the second module 82. Each of the first and second inner bus bars 20, 24 includes a distal end 62 attached to a cell cap 64 or the like via a weld or mechanical fastener 63. It will be appreciated that heat 74 may be transferred from each of the first and second inner bus bars 20, 24 to a corresponding cell cap 64 and then to a corresponding cell tab 92, to the cell 94, and then to a cooling fin 22. Each of the first and second inner bus bars 20, 24 of the second module 82 may include a proximal end, with each proximal end attached to a corresponding inner bus bar via a mechanical fastener(s) or a weld, or the like.Accordingly, the proximal end of the first inner bus bar in the second module 82 is attached to a first inner connecting bus bar 51, while the proximal end of the second inner bus bar 24 in the second module 82 is attached to a second inner connecting bus bar 50. The first connecting bus bar 51 of the second module 82 is configured to connect a negative terminal 99 (first inner bus bar 20) on the negative side 98 of the second module 82 to the positive terminal 97 (first inner bus bar 20) on the positive side 96 of the third module 86. Similarly, the second inner connecting bus bar 50 of the second module 82 is configured to connect a positive terminal 97 (second inner bus bar 24) on the positive side 98 of the second module 82 to the negative terminal 99 (second inner bus bar 24) on the negative side 98 of the third module 86.
[0026] It is understood that the first and second modules 84, 82 form a first pair 26 of modules and the third and fourth modules 86, 80 form a second pair 28 of modules, the first pair and second pair 26, 28 being electrically coupled to one another via a first inner connecting busbar 51 and a second inner connecting busbar 50. The first and second modules 84, 82 in the first pair 26 are electrically coupled to one another via the first and second outer busbars 12, 36. The third and fourth modules 86, 80 in the second pair 28 are also electrically coupled to one another via the first and second outer busbars 12, 36.
[0027] As in Fig. 2 and Fig. 3, the third module 86 also includes the first and second inner busbars 20, 24, which are also arranged on a first end 30 of the third module 86 - the second end 32 of each module is opposite the first end 30 of each module. The first and second inner busbars 20, 24 are, as shown in the Fig. 2 and Fig. 3, are similarly disposed near the central region 90 of the third module 86. Each of the first or second inner bus bars 20, 24 similarly includes a distal end 62 attached to a cell cap 64 via a weld or mechanical fastener 63 or the like. It should be understood that heat 74 may also be transferred from each of the first and second inner bus bars 20, 24 to a corresponding cell cap 64 and then to a corresponding cell tab 92, to the cell 94, and then to a cooling fin 22. Each of the first and second inner bus bars 20, 24 of the third module 86 may each include a proximal end, with each proximal end attached to a corresponding inner connecting bus bar via a mechanical fastener(s) or a weld or the like.Accordingly, the first inner busbar 20 of the third module 86 is attached to the first inner connecting busbar 51, such that the first inner busbar 20 of the third module 86 is electrically coupled to the first inner busbar 20 of the second module 82. The second inner busbar 24 (negative terminal 99) of the third module 86 is attached to the second inner connecting busbar 48, 50, such that the second inner busbar 24 (negative terminal 99) of the third module 86 is electrically coupled to the second inner busbar 24 (positive terminal 97) of the second module 82 via a second inner connecting busbar 48, 50, thereby enabling electrical connection between the negative and positive terminals of the second and third modules 82, 86, or between the first module pair 26 and the second module pair 28.The first and second inner connecting busbars 51, 50 may each also be referred to as an inner connecting busbar 48.
[0028] It will be appreciated that the first and second outer connecting bus bars 36, 46 between the third and fourth modules 86, 86 are operatively configured to electrically connect the third module 86 to the fourth module 86 such that electricity can be transferred from the third module 86 to the fourth module 86. With respect to the first outer connecting bus bar 44, the first outer connecting bus bar 44 can be operatively configured to connect the positive terminal 97 (first outer bus bar 12 of the third module 86) on the positive side 96 of the third module 86 to the negative terminal 99 (first outer bus bar 12) on the negative side 98 of the fourth module 86.Additionally, the first outer connecting bus bar 44 is operatively configured to couple the first outer bus bar 12 (positive terminal 97 of the third module 86) to a corresponding outer bus bar 12 (negative terminal 99) of an adjacent (fourth) battery module 86, wherein each first outer bus bar 12 is proximally disposed near the first lateral side 66 of each battery module 86, 86.
[0029] With respect to the second outer connecting bus bar 46, the second outer connecting bus bar 46 may be operatively configured to connect the negative terminal 99 (second outer bus bar 36) on the negative side 98 of the third module 86 to the positive terminal 97 (second outer bus bar 26) on the positive side 96 of the fourth module 86. As can be seen, the second outer connecting bus bar 46 couples the second outer bus bar 36 (negative terminal 99) of the third module 86 to a corresponding outer bus bar 36 (positive terminal 97) of an adjacent (fourth) battery module 86, wherein each of the aforementioned outer bus bars 36 is disposed proximate the second lateral side 68 of the adjacent (fourth) battery module 86.The corresponding outer busbar 36 of the adjacent (fourth) battery module 86 may also be referred to as a second outer busbar 36, since this busbar 36, as in . Fig. 2, is arranged near the second lateral side 68 of the fourth battery module 86. It is understood that the first and second busbars 12, 36 of the fourth module 86 are arranged near the second end 32 of the fourth module 86.
[0030] In a similar manner to the first module, the fourth module 80 also has a first and second inner busbar 20, 24 arranged near the first end 30. At the first end 30 of the fourth module 86, as shown in the Fig. 2 and Fig.3, the first and second inner bus bars 20, 24 are disposed near the central region 90 of the fourth module 86. Each of the first and second inner bus bars 20, 24 includes a distal end 62 that is attached to a cell cap 64 or the like via a weld or mechanical fastener 63. It will be appreciated that heat 74 may be transferred from each of the first and second inner bus bars 20, 24 to a corresponding cell cap 64, then to a corresponding cell tab 92, to the cell 94, and then to a cooling fin 22. The first and second bus bars 20, 24 of the fourth module 86 may then be connected to each other via an inner connecting bus bar 56.The inner connecting bus bar 56 is configured to electrically connect a positive side 96 (via a positive terminal 97 for the second inner bus bar 24) of the fourth module to the negative side 98 (via the negative terminal 99 or the first inner bus bar 20) of the fourth module 86 to thereby close the electrical loop between the positive and negative sides of each module 70.
Claims
[1] Battery module for a battery pack, the battery module comprising: a first module (84) having a central region (90), a first lateral side (66), a second lateral side (68), a first end (30), and a second end (32) opposite the first end (30); a second module (82) at the first end (30) of the first module (84) and a third module (86) at the second end (32) of the first module (84); a first positive terminal (97) of the first module (84) in the form of a first outer bus bar (12) near the first lateral side (66) of the first module (84); a first negative terminal (99) of the first module (84) in the form of a second outer bus bar (36) disposed proximate the second lateral side (68) of the first module (84), wherein the first outer bus bar (12) is coupled to a first outer connecting bus bar (44) and wherein the second outer bus bar (36) couples to a second outer connecting bus bar (46); and a first inner bus bar (20) and a second inner bus bar (24) disposed proximate the central region (90), the first and second inner bus bars (20, 24) each having a proximal end (60) and a distal end (62), the proximal end (60) being attached to a corresponding cell tab (92) of the first module (84); wherein the first inner busbar (20) is electrically coupled to the second module (82) via a first inner connecting busbar (51) and wherein the second inner busbar (24) is electrically coupled to the second module (82) via a second inner connecting busbar (50); and wherein the third module (86) is electrically connected to the first module (84) via the first outer connecting busbar (44) and via the second outer connecting busbar (46). [2] The battery module of claim 1, wherein the first and second outer bus bars (12, 36) are operatively configured to generate mutually canceling electromagnetic fields. [3] The battery module of claim 2, wherein the first and second inner bus bars (20, 24) are operatively configured to generate mutually canceling electromagnetic fields. [4] The battery module of claim 3, wherein each of the first and second outer bus bars (12, 36) and each of the first and second inner bus bars (20, 24) defines a proximal end (60) and a distal end (62), each of the distal ends (62) being attached to a cell cap (64). [5] The battery module of claim 4, wherein the proximal end (60) of the first outer bus bar (12) is configured to be disposed on the first outer connecting bus bar (44) and the proximal end (60) of the second outer bus bar (36) is configured to be attached to the second outer connecting bus bar (46). [6] The battery module of claim 5, wherein the first module (84) further comprises a plurality of battery cells (94) having a cooling fin (22) disposed between each battery cell (94) in the plurality of battery cells (94), each battery cell (94) further including a cell tab (92) and a corresponding cell cap (64). [7] The battery module of claim 6, wherein the first and second outer bus bars (12, 36), the first and second inner bus bars (20, 24), the corresponding cell cap (64), the cell tab (92), the battery cell (94), and the cooling fin (22) are thermally connected to each other. [8] The battery module of claim 7, wherein the first and second outer bus bars (20, 24) are operatively configured to thermally balance each other.
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