Venting of prismatic battery cells

Abstract

A battery cell includes a cell stack. The cell unit stack comprises A anode electrodes; c cathode electrodes; and S diaphragms, wherein A, C and S are integers greater than one. An enclosure for accommodating a stack of battery cells includes: a can defining a first opening and a second opening at both ends of the can; a cap portion joined to the first opening of the can body by a first brazing filler material disposed between the cap portion and the can body and having a first melting temperature; and a bottom joined to the second opening of the can body.

Description

Technical Field

[0001] The present invention relates to battery cells, and more particularly, to venting of prismatic battery cells. Background Art

[0002] The information provided in this section is intended to generally introduce the background of the invention. The work of the presently named inventors, to the extent it is described in this section and insofar as it may not qualify as prior art at the time of filing, is neither explicitly nor implicitly admitted to be prior art against the present invention.

[0003] An electric vehicle (EV), such as a battery electric vehicle (BEV), a hybrid vehicle, and / or a fuel cell vehicle, includes one or more motors and a battery system, which includes one or more battery cells, battery modules, and / or battery packs. A power control system is used to control the charging and / or discharging of the battery system during charging and / or driving. Summary of the invention

[0004] A battery cell includes a battery cell stack. The battery cell stack includes A anode electrodes; C cathode electrodes; and S separators, wherein A, C, and S are integers greater than one. A housing for accommodating the battery cell stack includes: a can body, defining a first opening and a second opening at both ends of the can body; a cover portion, joined to the first opening of the can body by a first brazing filler material, the first brazing filler material being disposed between the cover portion and the can body and having a first melting temperature; and a bottom portion, joined to the second opening of the can body.

[0005] In some examples, the bottom portion is attached to the second opening of the can body by a second brazing filler material disposed between the cover portion and the can body and having a second melting temperature.

[0006] In some examples, the first braze filler material and the second braze filler material are the same.

[0007] In some examples, the first laser brazing filler material and the second laser brazing filler material are different, and the second laser brazing filler material has a second melting temperature different than the first melting temperature.

[0008] In some examples, at least one of the cover and the base includes a pressure-based vent cap.

[0009] In some examples, the can, lid, and / or bottom are made of the same material.

[0010] In some examples, the can, cover, and / or bottom are made of one or more materials selected from the group consisting of steel, stainless steel, and aluminum.

[0011] In some examples, the can body is made of a first metal material, and at least one of the cover and / or the bottom is made of a second metal material different from the first metal material.

[0012] In some examples, the first metal material includes steel and the second metal material includes at least one of aluminum and an aluminum alloy.

[0013] In some examples, the first brazing filler material is selected from the group consisting of an alloy of tin, zinc and aluminum, a eutectic of aluminum and silicon, an alloy of copper, silver and phosphorus, a eutectic of copper and silver, an alloy of copper, magnesium and nickel, and an alloy of nickel, chromium and iron.

[0014] A battery cell includes a battery cell stack. The battery cell stack includes A anode electrodes; C cathode electrodes; and S separators, wherein A, C, and S are integers greater than one. A housing for a prismatic battery cell is configured to accommodate the battery cell stack and includes: a can body, defining a first opening and a second opening at both ends of the can body; a cover portion, coupled to the first opening of the can body; and a bottom portion, coupled to the second opening of the can body. At least one of the cover portion and the bottom portion is crimped to the can body.

[0015] In some examples, the bottom is crimped to the second opening of the can body.

[0016] In some examples, the cover includes a pressure-based vent cap.

[0017] In some examples, the can, lid, and / or bottom are made of the same material.

[0018] In some examples, the can, lid, and / or bottom are made of a material selected from the group consisting of steel, stainless steel, and aluminum.

[0019] In some examples, the can body is made of a first metal material, and at least one of the cover and / or the bottom is made of a second metal material different from the first metal material.

[0020] In some examples, the first metallic material includes steel and the second metallic material includes aluminum.

[0021] In some examples, the lid and bottom are crimped to the can body.

[0022] In some examples, the cover is crimped to the can body and the bottom is brazed to the can body.

[0023] In some examples, the cover is brazed to the can body and the bottom is crimped to the can body.

[0024] Other application areas of the present invention will become apparent from the detailed description, claims and drawings.The detailed description and specific examples are for illustrative purposes only and are not intended to limit the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be more fully understood through the detailed description and accompanying drawings, in which:

[0026] Figure 1 is a cross-sectional side view of an example of a battery cell according to the present invention, the battery cell including a cathode electrode, an anode electrode, and a separator disposed in a battery cell housing;

[0027] Figure 2A is a perspective view of an example of a prismatic battery cell according to the present invention;

[0028] Figure 2B is a perspective view of an example of a prismatic battery cell having a pressure-based vent cap according to the present invention;

[0029] Figure 3 is a graph showing an example of temperature and pressure of a prismatic battery cell during a thermal runaway event.

[0030] Figure 4 is a perspective view of an example of a prismatic battery cell having a pressure-based vent cap during a thermal runaway event;

[0031] Figure 5A and Figure 5B is a perspective view of an example of a prismatic battery cell according to the present invention including a brazed or crimped cover and / or bottom that provides temperature or pressure based venting;

[0032] Fig. 6A and Figure 6B is a perspective view of an example of a prismatic battery cell including a laser brazed or crimped cover (with a pressure-based vent cap) and / or bottom that provides temperature or pressure-based venting according to the present invention; and

[0033] Figure 7 Examples of temperatures as a function of time during a thermal runaway event and the melting temperatures of various laser brazing filler materials according to the present invention are shown.

[0034] Among the drawings, reference numerals may be repeated to identify similar and / or identical elements. DETAILED DESCRIPTION

[0035] Although prismatic battery cells according to the present invention are illustrated in the context of an electric vehicle, prismatic battery cells may be used in stationary applications and / or other applications.

[0036] During a thermal runaway event, a series of exothermic reactions occur within the battery cell, resulting in a large amount of gas release, a rapid increase in pressure within the battery cell, and an increase in the temperature of the battery cell. During a thermal runaway event, the exhaust gases should be released from the battery cell through one or more designated exit paths. In existing prismatic battery cells, when the pressure within the battery cell is greater than a predetermined pressure, a pressure-based vent opens a small area on the cover. All gases and combustion materials need to be exhausted through this vent area.

[0037] A large amount of energy is retained in the battery cell for a longer time, which allows the exothermic reaction to continue. In other words, during a thermal runaway event, the pressure on the cover activates the vent (such as Figure 2B The venting strategy described herein is modified to provide a larger venting area to release the gas so that the tank face is not punctured.

[0038] The present invention relates to a prismatic battery cell including a cover and / or bottom that is joined to a can body using one or more brazing filler materials. In some examples, laser brazing is used. During thermal runaway, as the battery temperature rises, the brazing material will melt at a predetermined temperature, separate the cover / bottom from the can body, and provide a discharge path for the gas. Alternatively, a mechanical double seam (crimping) can be used to connect the cover and bottom to the can. The crimping will fail at a predetermined pressure level to allow the cover / bottom to separate from the can body, thereby releasing hot gases through the can end. In some examples, laser brazing is used instead of traditional laser welding. One or more brazing filler materials have a melting temperature corresponding to one or more desired temperatures for discharging hot gases from the can body during a thermal runaway event. In some examples, the cover and / or bottom are attached to the can body using the same brazing filler material so that the cover and / or bottom are separated from the can body and the gas is discharged at the same temperature.

[0039] In other examples, the cover and / or bottom are attached to the can body using different brazing filler materials so that the cover and / or bottom exhaust hot gases at different temperatures. The brazing filler material has a lower melting temperature than the material used to make the can body.

[0040] In some examples, the cover and / or bottom spans the entire top opening and bottom opening of the housing can. In some examples, the cover may also include a pressure-based vent (e.g., a vent cap or vent valve) that releases exhaust gas at a predetermined pressure (through an opening with a relatively small area).

[0041] In some examples, the cover and bottom can be made of the same material or a different material as that used for the can body to provide other controlled failure stages. For example, the cover and / or bottom can be made of aluminum or an aluminum alloy, and the can body can be made of a steel alloy. The cover and / or bottom are attached to the can body using one or more brazing filler materials. The cover can optionally include a pressure-based vent. During a thermal runaway event, the pressure-based vent will open as the pressure inside the battery cell increases. Then, if the temperature of the battery cell continues to rise, the brazing filler material melts to separate the cover and / or bottom from the can body (creating other larger venting areas). Then, the cover will melt. The last part to melt will be the main body.

[0042] In other examples, the cover and / or bottom are attached to the can body using crimping (rather than brazing filler material and laser brazing). The cover and / or bottom can be made of the same or different material as the can body. For example, the can body can be made of steel. The cover and / or bottom can be made of aluminum and crimped to the can body. The cover can optionally include a pressure-based vent. During a thermal runaway event, the pressure-based vent will open as the pressure in the battery cell increases. If the pressure in the battery cell continues to increase, the crimping at the cover and / or bottom will not cause the cover and / or bottom to separate from the can body. Then, if the temperature continues to rise, the cover and the main body melt.

[0043] The prismatic battery cell according to the present invention can be designed to release venting at a specified temperature and through a specified path (e.g., through the top opening and the bottom opening at the same temperature, through the top opening and then through the bottom opening, or through the bottom opening and then through the top opening). When the cover and / or bottom rupture due to increased temperature (brazing) or increased pressure (crimping), the cover and / or bottom separate from the can and open a much larger venting area than a pressure-based vent cap on the cover.

[0044] Reference now Figure 1 , the battery cell 10 includes C cathode electrodes 20, A anode electrodes 40, and S separators 32, which are arranged in a predetermined order in the battery stack 12 located in the housing 50. The C cathode electrodes 20-1, 20-2, ..., and 20-C (where C is an integer greater than one) include a cathode active layer 24 disposed on one side or both sides of a cathode current collector 26. The A anode electrodes 40-1, 40-2, ..., and 40-A (where A is an integer greater than one) include an anode active layer 42 disposed on one side or both sides of an anode current collector 46.

[0045] In some examples, the anode active layer 42 and / or the cathode active layer 24 are freestanding electrodes disposed adjacent to (or attached to) the current collector. In some instances, the anode active layer 42 and / or the cathode active layer 24 include a coating comprising one or more active materials, one or more conductive fillers / additives, and / or one or more adhesive materials. In some examples, the battery cell and / or the electrode are manufactured by applying a slurry to coat the current collector in a roll-to-roll manufacturing process. In some examples, the cathode current collector 26 and / or the anode current collector 46 include a foil layer. In some examples, the current collector is made of one or more materials selected from the group consisting of copper, stainless steel, brass, bronze, zinc, aluminum, and alloys thereof.

[0046] Reference now Figure 2A and Figure 2B , the prismatic battery cell 58 includes a housing 60. In some examples, the housing 60 has a rectangular cross-section in the x-axis, y-axis, and z-axis planes. The housing 60 includes a can 61, which includes a side 80 and a side 82 that define a top opening 63 and a bottom opening 65. As will be further described below, a cover 84 and a bottom 86 are laser brazed or crimped to the can 61 to close the top opening 63 and the bottom opening 65, respectively. The prismatic battery cell 58 includes an external terminal 62 and an external terminal 64 that pass through the cover 84. A stack 12 of C cathode electrodes 20, A anode electrodes 40, and S separators 32 is disposed in the housing 60.

[0047] The external terminal 62 and the external terminal 64 are connected to the external terminals of the A anode electrodes 40 and the C cathode electrodes 20, respectively. Figure 2A In the embodiment, the cover 84 does not include a pressure-based vent. Figure 2B In the embodiment, the cover 84 includes a pressure-based vent cap 66, which opens to a vent area that is significantly smaller than the vent area of ​​the top opening 63 and / or the bottom opening 65. The pressure-based vent cap 66 is configured to release vent when the pressure within the housing 60 is greater than a predetermined pressure.

[0048] When the prismatic battery cell uses laser brazing to attach the cover 84 and the bottom 86 to the can 61, the cover 84 and the bottom 86 open in response to the temperature rising above the melting temperature of the brazing filler material to provide a primary vent or an auxiliary vent with a large surface area. When the prismatic battery cell uses crimping to attach the cover 84 and the bottom 86 to the can 61, the cover 84 and the bottom 86 open in response to the pressure in the battery cell increasing to above a predetermined pressure (greater than the release pressure of the vent cap 66).

[0049] Reference now Figure 3 and Figure 4, shows an example of the temperature and pressure of a battery cell (without venting as described herein) during a thermal runaway event. During a thermal runaway event, an exothermic reaction produces gas inside the battery, thereby increasing the pressure inside the battery. As the pressure 96 of the exhaust gas increases, the temperature 98 also increases at a first rate. When the pressure-based vent bursts, the temperature soars and may reach over 1000°C. The increased temperature of the exhaust gas and the burning electrode, electrolyte, and / or separator materials may cause the temperature of the battery cell surface to reach 700°C to 800°C.

[0050] The pressure-based exhaust port releases part of the exhaust pressure. However, the exhaust area is smaller and the ejection of exhaust and / or burning materials is restricted. After the exhaust cap bursts, the temperature of the exhaust gas increases rapidly. Figure 4 In the present invention, ion particles 90 can be generated by hot gases and / or burning electrodes, electrolytes and / or separator materials. Ionic particles 90 can cause arc discharge with adjacent conductive structures.

[0051] When the can 61 is made of aluminum, the sides 80 and 82 of the can 61 melt at the local hot spots 94. The opening in the can 61 releases combustion gases and / or burns electrodes, electrolytes, and / or separator materials laterally in the direction of the adjacent battery cells. The increased heating of the adjacent battery cells may cause heating and / or thermal runaway (e.g., thermal runaway propagation (TRP)) to occur in the adjacent battery cells. When the can 61 is made of steel, the can 61 softens and / or ruptures due to the heat and pressure of the exhaust gases and / or the burning electrodes, electrolytes, and / or separator materials.

[0052] like Figure 4 As shown, the opening provided by the pressure-based vent cap 66 has a relatively small area that may be blocked by the injected burning electrode, electrolyte and / or separator material. Because the vent area is limited, the energy release of the battery cell is slower, the exothermic reaction continues, and a higher pressure and / or temperature may be reached.

[0053] As will be further described below, a prismatic battery cell according to the present invention provides one or more vents during thermal runaway. Each vent provides a larger vent area to allow for a higher mass loss of the battery cell in a shorter time during a thermal runaway event. When the lid and bottom are separated from the can body in a controlled manner by melting the brazed can / lid joint, one or more large openings are formed. When the vent bursts and forms one or more large openings, the energy of the battery cell is released rapidly, and the remaining energy in the battery cell drops more quickly to a lower energy level that can be extracted by the battery cooling system.

[0054] Reference now FIG. 5A to FIG. 6B, show examples of prismatic battery cells 158 and 200 having a cover and / or bottom that vents in response to the temperature and / or pressure of the battery cell, respectively. Figure 5A and Figure 5B In the embodiment of the present invention, the prismatic battery cell 158 includes a housing 160. In some examples, the housing 160 has a rectangular cross-section in the x-axis, y-axis, and z-axis planes, but cylindrical, elliptical, polygonal, and / or other cross-sectional shapes may also be used. The housing 160 includes a can 161, which includes a side 180 and a side 182 (e.g., a rectangular cube with open ends). The cover 184 and the bottom 186 are attached to the can 161 using laser brazing filler material and / or crimping to close the first opening 163 and / or the second opening 165 of the can 161. The prismatic battery cell 158 includes an external terminal 162 and an external terminal 164.

[0055] The battery stack 12 including C cathode electrodes 20, A anode electrodes 40 and S separators 32 is disposed in a housing 160. External terminals 162 and 164 are connected to external tabs of the electrodes. Figure 5A and Figure 5B In FIG. 1 , the cover portion 184 does not include a vent cap.

[0056] exist Fig. 6A and Figure 6B In the embodiment of the present invention, the cover 184 of the prismatic battery cell 200 includes a vent cap 166. The vent cap 166 is configured to release when the pressure within the housing 160 is greater than a predetermined pressure. In some examples, the surface area occupied by the vent cap 166 is less than 25% of the cover 184.

[0057] In some examples, the lid and / or bottom are joined to the tank body using a laser brazing filler material having one or more melting temperatures corresponding to the desired temperature to vent the lid and / or bottom of the tank body during a thermal runaway event. The melting temperature of the laser brazing filler material is lower than the melting temperature of the material used to make the tank body and lid / bottom.

[0058] In some examples, the cover and / or bottom are attached to the tank using the same brazing filler material so that the cover and / or bottom are separated from the tank at the same temperature to allow hot gases to be discharged from the battery cell. In some examples, different brazing filler materials are used to attach the cover and / or bottom to the tank so that the cover and / or bottom are separated at different temperatures. In some examples, the cover may also include a pressure-based vent that is released at a predetermined pressure. Using different brazing filler materials can control the ejection direction of hot gases and / or ion particles during thermal runaway.

[0059] In some examples, the cover and bottom can be made of the same material or a different material than that used for the tank body to provide additional venting control measures. For example, the cover and / or bottom can be made of aluminum or an aluminum alloy, while the tank body can be made of steel. The cover and / or bottom are attached to the tank body using one or more brazing filler materials. The cover can include a pressure-based vent. During a thermal runaway event, the pressure-based vent opens as pressure increases. Then, if the temperature continues to rise, the laser brazed filler material melts to separate the cover and / or bottom from the tank body. Then, if the temperature continues to rise, the cover and bottom melt. The last part of the tank to melt is the main body.

[0060] In some examples, the cover and / or bottom can be attached to the can using a crimp. The crimp allows the cover and / or bottom to be released from the can at a predetermined pressure within the battery cell. The cover and / or bottom can be made of the same or different material as the can to provide additional venting measures.

[0061] For example, the can body may be made of steel and the cover and / or bottom may be made of aluminum crimped to the steel can body. The cover may include a pressure-based vent. During a thermal runaway event, the pressure-based vent opens in response to an increase in exhaust pressure in the battery cell. If the pressure in the battery cell continues to increase, one or both of the crimps fail and the cover and / or bottom separate from the can body. If the temperature continues to rise, the cover and / or body melt (e.g., before the can body melts).

[0062] Reference now Figure 7 , illustrates an example of temperature as a function of time during a thermal runaway event. At 310, the battery cell voltage is shown. At 314, the battery surface temperature is shown. At 318, the exhaust gas pressure is shown. At 322, the reactor gas temperature is shown. At 326, the first exhaust event occurs. At 328, the maximum battery case temperature is reached.

[0063] Different types of brazing materials can be selected to provide exhaust at one or more predetermined temperatures. For example, the melting temperature of pure tin (Sn) is 232°C. For example, the melting temperature of an alloy of zinc (Zn) and aluminum (Al) is 470°C. For example, the melting temperature of the eutectic of Al and silicon (Si) is 570°C. For example, the melting temperature of an alloy of copper (Cu), silver (Ag) and phosphorus (P) is 666°C. For example, the melting temperature of the eutectic of Cu and Ag is 780°C. Additional brazing materials with higher melting temperatures can be used, such as alloys of copper, magnesium and nickel (e.g., Cu-40Mn-10Ni) or alloys of nickel, chromium and iron (e.g., Ni-7Cr-4-3Fe), which have higher melting temperatures of 900°C and 1000°C, respectively.

[0064] It will be appreciated that other variations of the above features may be used. For example, the laser brazed top or bottom of the can may be combined with a curled edge of the bottom or top of the can, respectively.

[0065] The foregoing description is essentially merely illustrative and is in no way intended to limit the present invention, its application or use. The broad teachings of the present invention can be implemented in many forms. Therefore, although the present invention includes specific examples, the true scope of the present invention should not be so limited, because other modifications will become apparent after studying the drawings, descriptions and appended claims. It should be understood that one or more steps within a method can be performed in different orders (or simultaneously) without changing the principles of the present invention. In addition, although each embodiment is described as having certain features above, any one or more of those features described with respect to any embodiment of the present invention can be implemented in the features of any other embodiment and / or combined with the features of any other embodiment, even if the combination is not clearly described. In other words, the described embodiments are not mutually exclusive, and the arrangement of one or more embodiments to each other is still within the scope of the present invention.

[0066] Spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including "connected," "engaged," "coupled," "adjacent," "next to," "on," "above," "below," and "disposed." Unless explicitly described as "directly," when describing a relationship between a first element and a second element in the above disclosure, the relationship may be a direct relationship, in which no other intermediate elements exist between the first element and the second element, but may also be an indirect relationship, in which one or more intermediate elements (spatially or functionally) exist between the first element and the second element. As used herein, at least one of A, B, and C should be interpreted to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be interpreted to mean "at least one of A, at least one of B, and at least one of C."

[0067] In the drawings, the direction of arrows (as indicated by the arrows) generally demonstrates the flow of information (e.g., data or instructions) of interest to the illustration. For example, when hardware A and component B exchange multiple types of information, but the information transmitted from component A to component B is relevant to the illustration, the arrow may be directed from component A to component B. This unidirectional arrow does not mean that no other information is transmitted from component B to component A. In addition, for information sent from component A to component B, component B may send a request or a receipt confirmation to component A for the information.

Claims

1. A battery cell, comprising: A battery cell stack, the battery cell stack comprising: A anode electrode; C cathode electrodes; and S diaphragms, where A, C, and S are integers greater than one; and A housing for accommodating a battery cell stack, comprising: a tank body, defining a first opening and a second opening at two ends of the tank body; a cover portion joined to the first opening of the can body through a first brazing filler material, the first brazing filler material being disposed between the cover portion and the can body and having a first melting temperature; and A bottom portion is coupled to the second opening of the can body.

2. The battery cell according to claim 1, wherein: The bottom portion is attached to the second opening of the can body by a second brazing filler material, which is disposed between the cover portion and the can body and has a second melting temperature.

3. The battery cell according to claim 2, wherein: The first brazing filler material and the second brazing filler material are the same.

4. The battery cell according to claim 2, wherein: The first brazing filler material and the second brazing filler material are different, and the second brazing filler material has a second melting temperature different from the first melting temperature.

5. The battery cell according to claim 1, wherein: At least one of the cover and the base includes a pressure-based vent cap.

6. The battery cell according to claim 1, wherein: The tank body, the cover and / or the bottom are made of the same material.

7. The battery cell according to claim 6, wherein: The tank body, the cover and / or the bottom are made of one or more materials selected from the group consisting of steel, stainless steel and aluminum.

8. The battery cell according to claim 1, wherein: The can body is made of a first metal material, and at least one of the cover and / or the bottom is made of a second metal material different from the first metal material.

9. The battery cell according to claim 8, wherein: The first metal material includes steel, and the second metal material includes at least one of aluminum and an aluminum alloy.

10. The battery cell according to claim 1, wherein: The first brazing filler material is selected from the group consisting of an alloy of tin, zinc and aluminum, a eutectic of aluminum and silicon, an alloy of copper, silver and phosphorus, a eutectic of copper and silver, an alloy of copper, magnesium and nickel, and an alloy of nickel, chromium and iron.

Images