BATTERY CELL CONSTRUCTION WITH A RESEALABLE OVERPRESSURE VALVE

Abstract

A battery cell comprises a cell casing and an electrode stack arranged within the cell casing. The electrode stack includes a pair of flags that connect to a pair of terminals on the cell casing. A vent is provided in the cell casing, and a pressure relief valve is also provided in the cell casing, the pressure relief valve having a lower overpressure than the vent.

Description

INITIATIONThe present disclosure relates to a battery cell structure having a resealable pressure relief valve.Early detection of cell venting, such as thermal events, is useful for the control of lithium ion batteries for electric vehicles. It has been observed that prior to a thermal event, gases (H2, etc.) are generated in the cell before the thermal event can be detected. It has also been observed that gas buildup due to cycles during the life of a battery cell can lead to capacity degradation.The document DE 10 2022 112 088 A1 discloses a battery cell according to the preamble of claim 1. the documents DE 10 2016 112 664 A1, DE 10 2020 209 759 A1 and DE 10 2022 205 365 A1 disclose related battery cells.SUMMARYAccording to an aspect of the present disclosure, a battery cell includes a cell case and an electrode stack disposed within the cell case. The electrode stack includes a pair of tabs that communicate with a pair of terminals on the cell housing. A vent is provided in the cell housing and a relief valve is provided in the cell housing, the relief valve having a lower relief pressure than the vent.In another aspect, the vent is at a first end of the cell housing and the relief valve is at a second end of the cell housing opposite the first end.According to a further aspect, both the venting opening and the overpressure valve are located at one end of the cell housing.According to a further aspect, the pressure relief valve is integrated into the venting opening.In another aspect, the relief valve includes a valve element biased by a spring to a closed position.In another aspect, the cell case includes a membrane liner.According to a further aspect, the overpressure valve has an overpressure of 50-300 kPa.According to a further aspect, the venting opening has a burst pressure of at least 800 kPa.The battery cell according to the present disclosure aims to release gas from the cells by the incorporation of a resealable valve to allow earlier detection of cell heating by pack sensors (H2sensor) and to improve cell performance retention by gas removal (>90% CO2). The resealable pressure relief valve may be any one-way valve having a particular opening pressure (i.e., 50-300 kPa gauge), such as a check valve or a pressure relief valve. The valve could contain a gas permeable membrane to prevent electrolyte losses. In prismatic or cylindrical cells, the pressure relief valve opens at a lower pressure than the cell vent. In pouch cells, the pressure relief valve opens at a lower pressure than the pressure at which the pouch would burst.Further areas of applicability of the present disclosure will become apparent from the detailed description, claims and drawings. The detailed description and specific examples are provided for illustrative purposes only.BRIEF DESCRIPTION OF THE DRAWINGSThe present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: FIG. 1 is a schematic view of a battery cell having a vent and a relief valve according to an embodiment of the present invention not according to the present invention; FIG. 2 is a schematic view of a battery cell having a vent and a relief valve according to an embodiment of the present invention not according to the present invention; FIG. 3 is a schematic view of a battery cell having a vent and a relief valve according to an embodiment of the present invention; FIG. 4 is a schematic view of a battery cell having a vent and a relief valve according to an embodiment of the present invention not according to the present invention; FIG. 5 is a schematic view of a battery cell having a vent and a relief valve according to an embodiment of the present invention not according to the present invention; and FIG. 6 is a schematic view of a battery cell having a vent and a temperature / pressure sensor according to an embodiment of the present invention not according to the present invention.In the drawings, reference numerals may be reused to identify similar and / or identical elements.DETAILED DESCRIPTIONThe present disclosure relates to a battery cell construction that includes a resealable valve, such as a check valve or a pressure relief valve, for allowing gas generated in the cell to escape into the package housing at a particular pressure that is lower than the conventional cell vent opening or burst pressure of the pouch. This allows the cell to exhaust gas during operation. The gas moves only in a direction from the higher pressure inside the cell to the lower pressure outside the cell, thus preventing moisture from entering the cell. A gas permeable membrane may be incorporated into the valve to prevent electrolyte losses. The gas may then be detected by the package housing sensors and corrective action taken.Referring now to FIG. 1, a prismatic battery cell 10 according to a non-inventive embodiment of the present invention is disclosed. The prismatic battery cell 10 comprises a cell housing 12 which can be lined with a membrane 14. The cell housing may comprise a container, a pouch, a prismatic box-shaped housing or other known cell housing. An electrode stack 16 is disposed within the cell housing and a thermal gap that can be filled with an insulating filler, adhesive tape, or foam 18. The electrode stack 16 includes a pair of tabs 20 that are in communication with a pair of terminals 22. A bottom of the cell case 12 includes a vent hole 24. a top of the cell case 12 includes a relief valve 26. the relief valve 26 has a certain opening pressure that is below the burst pressure of the vent hole 24, and the relief valve 26 is resealable after the relief valve 26 is opened. The opening pressure of the relief valve 26 may be set to a pressure (i.e., 50-300 kPa relief) to optimize thermal release detection and cell performance. As is known in the art, the cell vent 24 is designed to open upon thermal runaway. As a non-limiting example, the vent 24 may have a burst pressure of 800 kPa. The vent 24 may comprise a notched, notched, or otherwise weakened aluminum sheet designed to burst at the designed burst pressure.Referring now to FIG. 2, a prismatic battery cell 110 according to a non-inventive embodiment of the present invention is disclosed. The prismatic battery cell 110 comprises a cell housing 12 which may be lined with a membrane 14. An electrode stack 16 is disposed within the cell container and a thermal gap that may be filled with one of a filler, tape, or foam 18. The electrode stack 16 includes a pair of tabs 20 that are in communication with a pair of terminals 22. An upper surface of the cell case 12 includes a vent opening 24. an upper surface of the cell case 12 also includes a relief valve 26. the relief valve 26 has a certain opening pressure that is below the burst pressure of the vent opening 24, and the relief valve 26 is resealable after the relief valve 26 is opened. The opening pressure of the relief valve 26 may be set to a pressure (i.e., 50-300 kPa relief) to optimize thermal release detection and cell performance. As is known in the art, the cell vent 24 is designed to open upon thermal runaway.Referring now to FIG. 3, a prismatic battery cell 210 according to an embodiment of the present invention is disclosed. The prismatic battery cell 210 comprises a cell housing 12 which may be lined with a membrane 14. An electrode stack 16 is disposed within the cell container and a thermal gap that may be filled with one of a filler, tape, or foam 18. The electrode stack 16 includes a pair of tabs 20 that are in communication with a pair of terminals 22. An upper side of the cell housing 12 includes a vent opening 24. a relief valve 26 is integrated into the vent opening 24. The pressure relief valve 26 has a certain opening pressure which is below the burst pressure of the vent opening 24, and the pressure relief valve 26 is resealable after the pressure relief valve 26 is opened. The opening pressure of the relief valve 26 may be set to a pressure (i.e., 50-300 kPa relief) to optimize thermal release detection and cell performance. As is known in the art, the cell vent 24 is designed to open upon thermal runaway.Referring now to FIG. 4, a prismatic battery cell 310 according to a non-inventive embodiment of the present invention is disclosed. The prismatic battery cell 310 comprises a cell housing 12 which may be lined with a membrane 14. An electrode stack 16 is disposed within the cell housing and a thermal gap that may be filled with one of a filler, adhesive tape, or foam 18. The electrode stack 16 includes a pair of tabs 20 that are in communication with a pair of terminals 22. A bottom of the cell housing 12 includes a vent opening 24. The relief valve 126 has a certain opening pressure that is below the burst pressure of the vent port 24, and the relief valve 126 is resealable after the relief valve 126 is opened. The relief valve 126 may take various forms including, but not limited to, a reed valve, a ball check valve, a plunger check valve, and a poppet valve. By way of limiting example, the pressure relief valve 126 may include a valve body 100 having an inlet nozzle 102 communicating with an outlet passage 128 of the cell container 12, and the valve body 100 includes an outlet opening 104. A hood 106 is attached to the valve body 100 with a seal 108 therebetween. A cap 110 may be attached to the hood 106. A seat retainer 112 supports a valve member 114 against the inlet nozzle 102 and is biased to a closed position by a spring 116. A pressure adjustment screw 118 is carried by the hood 106 within the cap 109 and can be adjusted to adjust the spring force on the seat holder 112. The opening pressure of the relief valve 126 may be set to a pressure (i.e., 50-300 kPa relief) to optimize thermal release detection and cell performance. As is known in the art, the cell vent 24 is designed to open upon thermal runaway. Referring to FIG. 5, a hose 120 may connect the pressure relief valve 126 to the outlet passage 128 of the cell housing 12 to provide flexibility in packaging the pressure relief valve 126.Referring now to FIG. 6, a prismatic battery cell 410 according to a non-inventive embodiment of the present invention is disclosed. The prismatic battery cell 410 comprises a cell housing 12 which may be lined with a membrane 14. An electrode stack 16 is disposed within the cell container and a thermal gap that may be filled with one of a filler, tape, or foam 18. The electrode stack 16 includes a pair of tabs 20 that are in communication with a pair of terminals 22. A bottom of the cell housing 12 includes a vent opening 24. a top of the cell housing 12 includes at least one of a temperature / pressure sensor 50. the temperature / pressure sensor 50 measures at least one of a temperature and / or a pressure of the battery cell. The temperature / pressure sensor 50 may be connected to a battery controller 52, which may be used to deactivate the battery cell 410 in response to a temperature and / or pressure exceeding a predetermined level indicative of a precursor to a thermal event. As is known in the art, the cell vent 24 is designed to open upon thermal runaway.The present disclosure provides a novel cell design that includes a one-way flow resealable valve (i.e., a check valve or a relief valve) and a certain opening pressure that is lower than the venting pressure of the cell to allow gas to escape from a cell while the cell continues to operate, thereby preventing performance degradation due to gas buildup in the cell. The relief valve 26 also allows gas generated when the cell / TR is heated to escape into the package housing, so that this can be detected earlier than in a conventional vent or when a bag is burst. The valve could also be used to exhaust gases generated during formation. The gas permeable membrane may be incorporated into the valve to prevent electrolyte losses.The present disclosure may be applied to any cell format / construction / chemistry, with or without a cell vent to allow prior venting of gas from the cells, to prevent degradation due to gas buildup in the cells, and to allow prior detection of thermal runaway or cell heating.Spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.) are described with various terms including "connected," "engaged," "coupled," "adjacent," "next," "top-on," "over," "under," and "arranged.". Unless a relationship between first and second elements is expressly described as "direct" in the foregoing disclosure, this relationship may be a direct relationship in which no other intervening elements are present between the first and second elements, but also an indirect relationship in which one or more intervening elements are present (either spatially or functionally) between the first and second elements. As used herein, the term "A, B, and / or C" should be construed as being logical (A ORed with B ORed with C) using a non-exclusive logical OR operation and should not be understood as "at least one of A, at least one of B, and at least one of C.".

Claims

A battery cell (210) comprising: a cell case (12); an electrode stack (16) disposed within the cell case (12), the electrode stack (16) comprising a pair of tabs (20) communicating with a pair of terminals (22) on the cell case (12); wherein a vent opening (24) is provided in the cell case (12); and wherein a relief valve (26) is provided in the cell case (12), the relief valve (26) having a lower relief pressure than the vent opening (24), characterized in that the relief valve (26) is integrated into the vent opening (24).The battery cell (210) of claim 1, wherein both the vent (24) and the relief valve (26) are located at an end of the cell housing (12).The battery cell (210) of claim 1, further comprising a membrane (14) lining the cell case (12).The battery cell (210) of claim 1, wherein the relief valve (26) has a discharge pressure between 50 and 300 kPa relief.The battery cell (210) of claim 1, wherein the vent (24) has a burst pressure of at least 800 kPa.

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