WO2025072580A1

WO2025072580A1 - Activatable vent assembly and closed container including the same

Info

Publication number: WO2025072580A1
Application number: PCT/US2024/048744
Authority: WO
Inventors: Kelly HILLEN; Jacob HERSH; Austin CROUSE; Daniel KEGLMEIER
Original assignee: WL Gore and Associates GmbH; WL Gore and Associates Inc
Current assignee: WL Gore and Associates GmbH; WL Gore and Associates Inc
Priority date: 2023-09-29
Filing date: 2024-09-27
Publication date: 2025-04-03
Anticipated expiration: 2026-03-29

Abstract

There are herein provided vent assemblies (1) for use in a closed container, the vent assembly comprising a membrane (2), and a barrier (4), the barrier being fixed on a first side of the membrane, the membrane extending around the barrier to form a pocket such that the first side of the membrane forms the interior surface of the pocket and a second side of the membrane forms the exterior surface of the pocket, the barrier being configured to fail when a threshold is exceeded. Closed container containing the vent assemblies are also provided.

Description

Activatable Vent Assembly and Closed Container Including the Same

Field

The present disclosure is directed to activatable vents and vent assemblies, and closed containers comprising the same.

Background

Closed containers are used widely to retain fluids in a controlled environment. These containers are often sealed from the exterior of the closed container to ensure that the fluid retained within the closed container is not contaminated from exterior particulates, or fluids, which may interact negatively with the retained fluid by chemical reaction or otherwise.

However, some liquids retained within the closed container may produce a gas through decomposition reactions over time or otherwise. As gas is produced, the pressure within the closed container increases and if it is allowed to increase beyond a certain threshold for a given closed container, could cause the closed container to fail or burst.

Accordingly, in some closed containers vents are provided to allow excess gases to escape the closed container to attempt to prevent failure of the closed container. These vents are also often required to prevent the ingress of at least some gases and liquids, such as water vapor or liquid water, for example. Therefore, the selection of materials for use in such vents has to be carefully tailored for a given application and often inherently limits the rate of gas flow through the vent in order to retain the necessary selectivity.

For example, lithium-ion batteries are often provided in a housing such as a prismatic can or a pouch that retain an electrolyte and that must be isolated from oxygen and water in order to retain the integrity of the electrolyte and electrodes. However, during normal operation of a lithium ion battery, gases may be produced through either electrolyte decomposition or other unwanted side reactions that may occur during operation of the battery.

If the rate of gas production is greater than the ability of the vent to allow to escape, or if no vent is present, the battery can swell, and, if this is allowed to continue, can fail or cause malfunction of the device within which it is installed.

Accordingly, there remains a need for improved vent assemblies for use in closed containers. Summary

According to a first aspect there is provided a vent assembly for use in a closed container, the vent assembly comprising a membrane, and a barrier, the barrier being fixed on a first side of the membrane, the membrane extending around the barrier to form a pocket such that the first side of the membrane forms the interior surface of the pocket and a second side of the membrane forms the exterior surface of the pocket, the barrier being configured to prevent the passage of fluid through the pocket, wherein the barrier is configured to fail when a threshold is exceeded and the membrane is configured not to fail when the threshold is exceeded such that gas may pass through the membrane past the failed barrier.

During use when installed across an aperture formed within the housing wall of a closed container the vent assembly may substantially prevent the egress of gas and liquid from within the closed container to the exterior of the closed container through the aperture and the ingress of gas, liquid and particulates from the exterior of the closed container into the interior of the closed container through the aperture. When the threshold is exceeded, the vent assembly may allow the egress of gas from within the closed container to the exterior of the closed container through the membrane of the vent assembly and the aperture. Accordingly, the gas transmission rate through the pocket may be increased when the threshold is exceeded.

Therefore, the vent assembly may be in a closed configuration before the threshold is exceeded, in which fluid and particulates are substantially prevented from passing through the vent assembly, and the vent assembly may be in an open configuration after the threshold is exceeded in which gas may pass through the vent assembly. Accordingly, the gas transmission rate through the vent assembly may be increased when the vent assembly transitions from the closed configuration to the open configuration.

Accordingly, the vent assembly is “turned off” before the threshold is exceeded and is only “turned on” or activated when the threshold is exceeded.

As used herein, the term “barrier” refers to a feature that substantially blocks or prevents passage of fluid past or through it in the vent assembly. Typically, the barrier substantially blocks or prevents passage of fluid past or through it in the pocket to the membrane. Accordingly, when the barrier fails fluid is no longer blocked and can flow past, or through the barrier to the membrane within the pocket. For the avoidance of doubt, the phase “the membrane is configured not to fail” as used herein refers to the membrane not breaking or detaching from a closed container wall when installed within a closed container when the threshold is exceeded.

Typically, the pocket comprises an open end and an opposed closed end.

The pocket may be formed by the membrane folding around the barrier. The pocket may be formed by folding the membrane and barrier over themselves. The pocket may comprise a first interior surface on a first side of the pocket and an opposed second interior surface on a second side of the pocket. The barrier may be fixed to the first interior surface and the opposed second interior surface of the pocket. Accordingly, the barrier may seal the pocket and prevent fluid contacting at least a majority of the first side of the membrane within the pocket.

In some embodiments, the pocket may at least partially open when the threshold is exceeded to thereby cause the barrier to fail. The pocket may at least partially open when the open ends of the pocket are pulled away from one another. For example, when the vent assembly is installed within a closed container, the second side of the membrane may be fixed to opposed interior surfaces of the closed container such that when the opposed interior surfaces move apart the pocket may be at least partially opened. The opposed interior surfaces may move apart when the internal pressure within the closed container increases, for example.

The ends of the membrane at the open end of the pocket may move apart when the pocket is at least partially opened. Movement of the ends of the membrane at the open end of the pocket apart from each other may apply a force to the barrier such that the barrier fails.

The barrier may at least partially detach from the first side of the membrane when the threshold is exceeded. The barrier may detach from the first side of the membrane when the threshold is exceeded. The barrier may detach from one side of the first surface of the membrane within the pocket when the threshold is exceeded. Movement of the ends of the membrane at the open end of the pocket apart from each other may apply a force to the barrier such that the barrier fails when that force is sufficient to detach the barrier from at least a portion of the first side of the membrane. The barrier may detach from the first interior surface of the pocket and remain fixed on the opposed second interior surface when the threshold is exceeded. A passage may be formed between the first interior surface and the barrier when the threshold is exceeded. Fluid may be able to flow along the passage to contact a greater surface area of the membrane. The barrier may be adhered to the membrane with an adhesive. The adhesive may fail when the threshold is exceeded to thereby detach the barrier from the membrane such that the barrier fails.

The barrier may be laminated to the membrane. The barrier may delaminate from the membrane when the threshold is exceeded to thereby detach the barrier from the membrane such that the barrier fails.

The barrier may be configured to break when the threshold is exceeded. The barrier may break into a first barrier portion and a second barrier portion when the threshold is exceeded and a barrier space may be formed between the first barrier portion and the second barrier portion. Movement of the ends of the membrane at the open end of the pocket apart from each other may apply a force to the barrier such that the barrier fails when that force is sufficient to break the barrier into a first barrier portion and a second barrier portion. The first barrier portion and the second barrier portion may be moved away from each other when the threshold is exceeded. Fluid may be able to flow along the passage to contact a greater surface area of the membrane.

The barrier may comprise a fault element that is configured to break when the threshold is exceeded. The fault element may be positioned between the first barrier portion and the second barrier portion such that when the barrier breaks at the fault element, the first barrier portion and the second barrier portion are separated at the fault element.

The fault element may be a formation within the barrier portion that is weaker than the rest of the barrier. The fault element may be a portion of the barrier that is thinner than the rest of the barrier. The fault element may be a scored line on the barrier that is configured to be the weak point of the barrier. The fault element may be a portion of the barrier that has a lower tensile or z-strength than the rest of the barrier.

In some embodiments the barrier may extend across at least 30% of the surface area of the first side of the membrane in the pocket. The barrier may extend across at least 40% of the surface area of the first side of the membrane in the pocket. The barrier may extend across at least 50% of the surface area of the first side of the membrane in the pocket. The barrier may extend across at least 60% of the surface area of the first side of the membrane in the pocket. The barrier may extend across at least 70% of the surface area of the first side of the membrane in the pocket. The barrier may extend across at least 75% of the surface area of the first side of the membrane in the pocket. The barrier may extend across at least 80% of the surface area of the first side of the membrane in the pocket.

It will be understood that in embodiments where the barrier extends across at least 50% of the surface area of the first side of the membrane in the pocket, for example, the barrier will extend across at least 25% of the first interior surface of the pocket and at least 25% of the second interior surface of the pocket.

The barrier may extend across 100% of the surface area of the first side of the membrane. The barrier may extend across less than 100% of the surface area of the first side of the membrane such that at least a portion of the surface of the first side of the membrane is not covered by the barrier. The barrier may extend across less than 90% of the surface area of the first side of the membrane. The barrier may extend across less than 80% of the surface area of the first side of the membrane. The barrier may extend across less than 70% of the surface area of the first side of the membrane.

The barrier may extend across from 20% to 100% of the surface area of the first side of the membrane. The barrier may extend across from 30% to 100% of the surface area of the first side of the membrane. The barrier may extend across from 40% to 100% of the surface area of the first side of the membrane. The barrier may extend across from 50% to 100% of the surface area of the first side of the membrane. The barrier may extend across from 60% to 100% of the surface area of the first side of the membrane. The barrier may extend across from 70% to 100% of the surface area of the first side of the membrane. The barrier may extend across from 75% to 100% of the surface area of the first side of the membrane. The barrier may extend across from 20% to 95% of the surface area of the first side of the membrane. The barrier may extend across from 20% to 90% of the surface area of the first side of the membrane. The barrier may extend across from 20% to 80% of the surface area of the first side of the membrane. The barrier may extend across from 20% to 70% of the surface area of the first side of the membrane. The barrier may extend across from 20% to 60% of the surface area of the first side of the membrane.

In embodiments where the barrier extends across less than 100% of the surface area of the first side of the membrane, the barrier may be provided at the open end of the pocket. Accordingly, there may be a space between the barrier and the closed end of the pocket. The barrier may be provided at the closed end of the pocket. Accordingly, there may be a space between the barrier and the open end of the pocket. The barrier may be provided between the open end and the closed end of the pocket. Accordingly, there may be a space between the barrier and the open end of the pocket and a space between the barrier and the closed end of the pocket.

The pocket may have a length from the open end of the pocket to the closed end of the pocket. The barrier may be configured to substantially prevent the flow of fluid along the length of the pocket from the open end to the closed end.

The barrier may comprise a gas impermeable material. Accordingly, the barrier may prevent or substantially prevent the flow of gas along the length of the pocket from the open end of the pocket to the closed end of the pocket. The barrier may comprise a liquid impermeable material. Accordingly the barrier may prevent or substantially prevent the flow of liquid along the length of the pocket from the open end of the pocket to the closed end of the pocket. The barrier may prevent or substantially prevent the flow of liquid along the length of the pocket from the closed end of the pocket to the open end of the pocket. The barrier may comprise a material that is both gas impermeable and liquid impermeable and may prevent or substantially prevent the flow of fluid along the length of the pocket from the open end of the pocket to the closed end of the pocket.

The barrier may comprise a gas permeable material and may have an extent along the length of the pocket that presents a diffusion pathway for gas through the barrier along the length of the pocket that is sufficient to substantially prevent the passage of gas through the pocket from the open end to the closed end. Accordingly, the diffusion pathway may be sufficiently long and narrow to effectively prevent the passage of gas through the pocket from the open end to the closed end. The diffusion pathway may be sufficiently long and narrow to effectively prevent the passage of gas through the pocket from the closed end to the open end. The diffusion pathway for gas through the barrier along the length of the pocket may be at least 0.5 mm. The diffusion pathway for gas through the barrier along the length of the pocket may be at least 1 mm. The diffusion pathway for gas through the barrier along the length of the pocket may be at least 1.5 mm. The diffusion pathway for gas through the barrier along the length of the pocket may be at least 2 mm.

The material of the barrier and the thickness of the barrier may be chosen to ensure that the flow of gas along the length of the pocket from the open end to the closed end is substantially prevented by the barrier before the threshold is exceeded. For example, the extent that the barrier extends along the length of the pocket may be greater for a barrier comprising a gas permeable material than for a barrier comprising a substantially gas impermeable material to ensure that the diffusion pathway through the barrier of the gas permeable material is sufficient to substantially prevent the flow of gas along the length of the pocket from the open end to the closed end. The extent that the barrier extends along the length of the pocket may be greater for a barrier comprising a gas permeable material than for a barrier comprising a substantially gas impermeable material to ensure that the diffusion pathway through the barrier of the gas permeable material is sufficient to substantially prevent the flow of gas along the length of the pocket from the closed end to the open end.

The barrier may comprise a material selected from the group: an adhesive, a laminate, a sealant, a material with low tensile strength, a material with low z-strength, or a degradable material.

In embodiments where the barrier comprises a laminate, the laminate may comprise at least one binding layer and at least one break layer. The at least one binding layer may comprise a material configured to form a strong bond between the barrier and the first surface of the membrane. The at least one break layer may be configured to form a weak bond between the barrier and the first surface of the membrane. The weak bond may be configured to break when the threshold is exceeded. The laminate may comprise at least a first binding layer, a second binding layer and at least one break layer. The at least one break layer may be positioned between the first binding layer and the second binding layer. The at least one break layer may be configured to form a weak bond between the first binding layer and the second binding layer. The weak bond between the first binding layer or the second binding layer and the at least one break layer may be configured to break when the threshold is exceeded.

The barrier may comprise a material selected from the group: thermoset adhesive, acrylic based adhesive, epoxy, urethane-based adhesive, rubber adhesive, silicone-based adhesive, metal foils including aluminium foil, laminated metal foils, fluorinated ethylene propylene (FEP), ethylene fluorinated ethylene propylene (EFEP), PTFE and co-polymers of tetrafluoroethylene (TFE), polyethylene (PE), polypropylene (PP), polybutene-1 , polyolefin blends, or combinations or co-polymers thereof.

The barrier may comprise a material selected from the group: FEP, PE, PP, polybutene-1 , polyolefin blends, combinations and co-polymers thereof.

The barrier may have a thickness from the first interior surface of the pocket to the opposed second interior surface of less than 250 pm. The barrier may have a thickness from the first interior surface of the pocket to the opposed second interior surface of less than 200 pm. The barrier may have a thickness from the first interior surface of the pocket to the opposed second interior surface of less than 150 m. The barrier may have a thickness from the first interior surface of the pocket to the opposed second interior surface of less than 100 pm. The barrier may have a thickness from the first interior surface of the pocket to the opposed second interior surface of less than 90 pm. The barrier may have a thickness from the first interior surface of the pocket to the opposed second interior surface of less than 80 pm. The barrier may have a thickness from the first interior surface of the pocket to the opposed second interior surface of less than 70 pm. The barrier may have a thickness from the first interior surface of the pocket to the opposed second interior surface of less than 60 pm. The barrier may have a thickness from the first interior surface of the pocket to the opposed second interior surface of less than 50 pm. The barrier may have a thickness from the first interior surface of the pocket to the opposed second interior surface of less than 40 pm.

The barrier may have a thickness from the first interior surface of the pocket to the opposed second interior surface of from 5 to 250 pm. The barrier may have a thickness of from 10 to 250 pm. The barrier may have a thickness of from 20 to 250 pm. The barrier may have a thickness of from 30 to 250 pm. The barrier may have a thickness of from 40 to 250 pm. The barrier may have a thickness of from 5 to 200 pm. The barrier may have a thickness of from 5 to 150 pm. The barrier may have a thickness of from 5 to 100 pm. The barrier may have a thickness of from 5 to 90 pm. The barrier may have a thickness of from 5 to 80 pm. The barrier may have a thickness of from 5 to 70 pm. The barrier may have a thickness of from 5 to 60 pm. The barrier may have a thickness of from 5 to 50 pm. The barrier may have a thickness of from 5 to 40 pm.

The membrane may comprise a non-porous material. The membrane may comprise a non- porous material that is configured to allow gas transfer through the membrane via a solution diffusion mechanism, for example.

The membrane may comprise a porous material. The membrane may be sufficiently porous to allow the flow of gas through the membrane. Accordingly, the membrane may be configured to allow gas flow through the membrane.

The membrane may be configured to allow the flow of gas through the membrane. The membrane may be configured to allow diffusion of gas through the membrane. The membrane may comprise pores that allow gas to diffuse through the membrane. The pores may be sized such that they allow gas to diffuse through the membrane but are sufficiently small to prevent a flow of gas through the membrane. The membrane may be structured such that the gas must take an indirect route through the membrane. The membrane may be impermeable to liquid. Accordingly, the membrane may allow the passage of gas through the membrane and not allow the passage of liquid through the membrane.

The membrane may comprise a fluoropolymer. The fluoropolymer may comprise a fluoropolymer selected from the group: polytetrafluoroethylene (PTFE), perfluoroalkoxy alkane (PFA), polyvinylfluoride (PVF), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), or polyethylenetetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), ethylene fluorinated ethylene propylene (EFEP), or co-polymers or combinations thereof.

The fluoropolymer may comprise a fluoropolymer selected from the group: PTFE, PFA and FEP.

The membrane may comprise a non-fluoropolymer. The non-fluoropolymer may comprise a non-fluoropolymer selected from the group: polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and poly(tetramethyl-p-silphenylenesiloxane) (PTMPS) or co-polymers or combinations thereof.

The membrane may comprise a polymer selected from the group: polytetrafluoroethylene (PTFE), perfluoroalkoxy alkane (PFA), polyvinylfluoride (PVF), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), or polyethylenetetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), ethylene fluorinated ethylene propylene (EFEP), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and poly(tetramethyl-p- silphenylenesiloxane) (PTMPS) or co-polymers or combinations thereof.

The membrane may comprise an expanded polymer. The expanded polymer may be selected from the group consisting of expanded PE (ePE), expanded PP (ePP), expanded PET (ePET), or an expanded fluoropolymer such as expanded PTFE (ePTFE) or expanded FEP (eFEP).

An expanded polymer may have an increased porosity when compared to the corresponding non-expanded polymer.

The membrane may comprise a dense polymer. The dense polymer may be selected from the group consisting of dense PE, dense PP, dense PET, or dense fluoropolymer such as dense PTFE, dense PCTFE, dense ETFE, dense PFA or dense FEP. As used herein, the term “dense polymer” refers to a polymer material that is substantially non-porous. Accordingly, the dense polymer may have a non-measurable airflow using the test method described herein.

The membrane may comprise a densified expanded polymer. The densified expanded polymer may be selected from the group consisting of densified ePE, densified ePP, densified ePET, or densified expanded fluoropolymer such as densified ePTFE or densified eFEP.

The term “densified expanded polymer” as used herein refers to an expanded polymer that has been densified after the material has been expanded.

A densified expanded polymer may have the microstructure of an expanded polymer and a lower porosity than the expanded polymer. For example, the densified expanded polymer may have the node and fibril structure of the expanded porosity but have a reduced porosity.

In some embodiments the membrane may comprise a laminate. The laminate may comprise an open layer. The open layer may comprise an expanded material. The open layer may comprise a porous material. The laminate may comprise a plurality of open layers. The laminate may comprise a dense layer. The dense layer may comprise a non-porous material. The laminate may comprise a plurality of dense layers.

The laminate may comprise an open layer and a dense layer. The open layer may be more porous than the dense layer. Accordingly, the gas permeability of the membrane may be determined by the dense layer.

The first surface of the membrane may comprise the dense layer. The second surface of membrane may comprise the open layer. The open layer may be configured to fix the vent assembly to opposed interior surfaces of a closed container. The open layer may be configured to fix the vent assembly to opposed sides of an aperture within the housing wall of a closed container.

In a second aspect there is provided a closed container comprising the vent assembly of the first aspect.

The closed container may be a battery. The closed container may be a chemical container.

The closed container may be food container. The closed container may comprise a housing wall defining an aperture.

The housing wall may be a flexible housing wall. The flexible housing wall may comprise a polymer material. The flexible housing wall may comprise polypropylene (PP), polyamide (PA) including nylon, or polybutylene terephthalate (PBT), polyethylene (PE), or polyethylene terephthalate (PET). The housing wall may comprise a metallic material. The housing wall may comprise aluminium. The housing wall may comprise aluminium foil, for example.

The housing wall may comprise a laminate material. The laminate material may comprise at least one polymer layer. The laminate material may comprise at least one metallic layer. The laminate material may comprise at least one polymer layer and at least one metallic layer. The laminate material may comprise a first polymer layer, a metallic layer and a second polymer layer. The metallic layer may be located between the first polymer layer and the second polymer layer.

The closed container may be a pouch.

In embodiments where the closed container is a battery, the battery may comprise a pouch cell. The battery may comprise a prismatic or cylindrical can. The closed container may be configured to retain battery fluid or electrolyte that allows the transfer of ions from a first electrode to a second electrode through the battery fluid. Accordingly, the closed container may retain at least two electrodes and at least two electrical contacts that are configured to connect the at least two electrodes to an external electrical circuit. The housing wall may be configured to be substantially impervious to the fluid that is retained within the closed container. For example, the battery pouch may be a lithium (Li) ion pouch cell.

In embodiments where the closed container is a pouch cell, the aperture may be formed in a seam of the pouch cell. The aperture may be formed in a seam that is typically sealed by heat to close the battery pouch. For example, the seam may be a side seal, or a terrace seal.

The housing wall may be a rigid housing wall. The rigid housing wall may comprise a rigid polymer material. The rigid housing wall may comprise a thermoplastic material. The rigid housing wall may comprise a reinforced thermoplastic material. For example, the rigid housing wall may comprise a thermoplastic material such as polypropylene (PP), polyethylene (PE), polybutylene terephthalate (PBT), or polyethylene terephthalate (PET) reinforced with a fiber such as glass fiber or similar. The rigid housing may comprise a rigid metallic material. The rigid housing wall may comprise aluminium, steel, stainless steel, copper, brass, bronze, tin or lead, for example.

The threshold may be a pressure threshold. When the pressure threshold is exceeded the housing wall may flex or bend such that the open end of the pocket is opened and the barrier fails to thereby allow gas to flow through the membrane of the vent assembly and aperture to the exterior of the closed container.

The closed container may be configured to transition from a first configuration to a second configuration when the threshold is exceeded. In the first configuration the vent assembly may substantially prevent the flow of fluid through the vent assembly to the exterior of the closed container. In the second configuration the barrier has failed to thereby allow gas to flow from the interior of the closed container to the exterior of the closed container through the vent assembly and the aperture in the housing wall.

Typically, the threshold may be a pressure threshold. The closed container may be configured to transition from the first configuration to the second configuration when the pressure within the closed container is greater than the pressure threshold.

The pressure threshold may be dependent on the material of the housing wall of the closed container. For example, the pressure threshold may be a higher pressure for a housing wall comprising a rigid material than the pressure threshold for a housing wall comprising a flexible material. In embodiments where the closed container is a battery, the pressure threshold may be a higher pressure for a battery comprising a prismatic or cylindrical can than the pressure threshold for a battery comprising a pouch cell, for example.

The pressure threshold may be at least 0.01 bar. The pressure threshold may be at least 0.05 bar. The pressure threshold may be at least 0.1 bar. The pressure threshold may be at least 0.2 bar. The pressure threshold may be at least 0.3 bar. The pressure threshold may be at least 0.4 bar. The pressure threshold may be at least 0.5 bar.

The pressure threshold may be from 0.01 to 6 bar. The pressure threshold may be from 0.01 to 5 bar. The pressure threshold may be from 0.01 to 4 bar. The pressure threshold may be from 0.01 to 3 bar. The pressure threshold may be from 0.01 to 2 bar. The pressure threshold may be from 0.01 to 1.5 bar. The pressure threshold may be from 0.01 to 1 bar. The pressure threshold may be from 0.01 to 0.5 bar. The pressure threshold may be from 0.01 to 0.1 bar. The pressure threshold may be from 0.05 to 6 bar. The pressure threshold may be from 0.1 to 6 bar. The pressure threshold may be from 0.2 to 6 bar. The pressure threshold may be from 0.3 to 6 bar. The pressure threshold may be from 0.4 to 6 bar. The pressure threshold may be from 0.5 to 6 bar.

In embodiments where the closed container is a battery, the threshold may be an electrical measurement from the battery such as voltage, current, or resistance.

According to a third aspect there is provided a closed container comprising a housing wall defining an aperture, and a vent assembly occluding the aperture, the vent assembly comprising a membrane and a barrier, the barrier being fixed on a first side of the membrane, the membrane extending around the barrier to form a pocket such that the first side of the membrane forms the interior surface of the pocket and a second side of the membrane forms the exterior surface of the pocket, a pathway is defined between the interior of the closed container and the exterior of the closed container through the pocket and aperture, wherein the closed container is configured to move between a first configuration where the barrier prevents passage of fluid along the pathway to the exterior of the closed container and a second configuration where the pocket is at least partially opened and the barrier does not prevent passage of fluid along the pathway to the exterior of the closed container, wherein the closed container is configured to transition from the first configuration to the second configuration when a threshold is exceeded, wherein the barrier is configured to fail when the threshold is exceeded and the membrane is configured not to fail when the threshold is exceeded to thereby allow gas to flow through the membrane when the closed container is in the second configuration.

Typically, the membrane has a rate at which gas may flow through the membrane. In some embodiments, the rate at which gas is generated within the closed container may exceed the rate at which gas may flow through the membrane. The closed container may be configured to transition to a third configuration where the membrane fails such that there is no obstruction in the pathway. Accordingly, rapid pressure equalisation may occur when the closed container transitions to the third configuration. The closed container may be configured to transition from the second configuration to the third configuration when a second threshold is exceeded. Accordingly, the closed container may be configured to transition from the first configuration to the second configuration when a first threshold is exceeded and the closed container may be configured to transition from the second configuration to the third configuration when the second threshold is exceeded.

Typically, the second threshold is greater than the first threshold. The closed container may be a battery. The closed container may be a chemical container.

The closed container may be food container.

The housing wall may be a flexible housing wall. The flexible housing wall may comprise a polymer material. The flexible housing wall may comprise polypropylene (PP), polyamide (PA), or polybutylene terephthalate (PBT), polyethylene (PE), or polyethylene terephthalate (PET). The housing wall may comprise a metallic material. The housing wall may comprise aluminium. The housing wall may comprise aluminium foil, for example.

The closed container may be a pouch.

In embodiments where the closed container is a battery, the battery may comprise a pouch cell. The battery may comprise a prismatic or cylindrical can. The closed container may be configured to retain battery fluid such as electrolyte that allows the transfer of ions from a first electrode to a second electrode through the battery fluid. Accordingly, the closed container may retain at least two electrodes and at least two electrical contacts that are configured to connect the at least two electrodes to an external electrical circuit. The housing wall may be configured to be substantially impervious to the fluid that is retained within the closed container. For example, the battery pouch may be a lithium (Li) ion pouch cell.

The housing wall may be a rigid housing wall. The rigid housing wall may comprise a rigid polymer material. The rigid housing wall may comprise a thermoplastic material. The rigid housing wall may comprise a reinforced thermoplastic material. For example, the rigid housing wall may comprise a thermoplastic material such as polypropylene (PP), polyethylene (PE), polybutylene terephthalate (PBT), or polyethylene terephthalate (PET) reinforced with a fiber such as glass fiber or similar. The rigid housing may comprise a rigid metallic material. The rigid housing wall may comprise aluminium, steel, stainless steel, copper, brass, bronze, tin or lead, for example. The threshold may be a pressure threshold. When the pressure threshold is exceeded the housing wall may flex or bend such that the open end of the pocket is opened and the barrier fails to thereby allow gas to flow along the pathway through the membrane of the vent assembly and aperture to the exterior of the closed container.

The second threshold may be a second pressure threshold. When the second pressure threshold is exceeded the housing wall may flex or bend such that the membrane fails to thereby allow gas to flow along the pathway of the vent assembly and aperture to the exterior of the closed container. Alternatively, when the second pressure threshold is exceeded, the membrane may fail without bending or flexing of the housing wall. Typically, the second pressure threshold is a greater pressure than the pressure threshold.

The closed container may be configured to transition from the first configuration to the second configuration when the pressure within the closed container is greater than the pressure threshold.

The pressure threshold may be from 0.01 to 6 bar. The pressure threshold may be from 0.01 to 5 bar. The pressure threshold may be from 0.01 to 4 bar. The pressure threshold may be from 0.01 to 3 bar. The pressure threshold may be from 0.01 to 2 bar. The pressure threshold may be from 0.01 to 1.5 bar. The pressure threshold may be from 0.01 to 1 bar. The pressure threshold may be from 0.01 to 0.5 bar. The pressure threshold may be from 0.01 to 0.1 bar. The pressure threshold may be from 0.05 to 6 bar. The pressure threshold may be from 0.1 to 6 bar. The pressure threshold may be from 0.2 to 6 bar. The pressure threshold may be from 0.3 to 6 bar. The pressure threshold may be from 0.4 to 6 bar. The pressure threshold may be from 0.5 to 6 bar. In embodiments where the closed container is a battery, the threshold may be an electrical measurement from the battery such as voltage, current, or resistance.

Typically, the pocket comprises an open end and an opposed closed end.

The second side of the membrane may be fixed to opposed interior surfaces of the housing wall of the closed container. The second side of the membrane may be fixed across the aperture of the closed container. The second side of the membrane may be fixed to the housing wall around the aperture of the closed container. The second side of the membrane may be fixed to the housing wall adjacent to the aperture of the closed container. The second side of the membrane may be fixed to the housing wall such that the closed end of the pocket is proximate to the aperture and the open end of the pocket is facing into the interior of the closed container away from the aperture.

In some embodiments, the pocket may at least partially open when the threshold is exceeded to thereby cause the barrier to fail. The pocket may at least partially open when the open ends of the pocket are pulled away from one another.

Movement of the opposed interior surfaces of the housing wall away from one another may at least partially open the pocket. The opposed interior surfaces may move apart when the internal pressure within the closed container increases, for example. The ends of the membrane at the open end of the pocket may move apart when the pocket is at least partially opened.

The barrier may at least partially detach from the first side of the membrane when the threshold is exceeded. The barrier may detach from the first side of the membrane when the threshold is exceeded. Movement of the ends of the membrane at the open end of the pocket apart from each other may apply a force to the barrier such that the barrier fails when that force is sufficient to detach the barrier from at least a portion of the first side of the membrane. The barrier may detach from one side of the first surface of the membrane within the pocket when the threshold is exceeded. The barrier may detach from the first interior surface of the pocket and remain fixed on the opposed second interior surface when the threshold is exceeded. A passage may be formed between the first interior surface and the barrier when the threshold is exceeded. Fluid may be able to flow along the passage to contact a greater surface area of the membrane.

The barrier may be adhered to the membrane with an adhesive. The adhesive may fail when the threshold is exceeded to thereby detach the barrier from the membrane such that the barrier fails.

The fault element may be a formation within the barrier portion that is weaker than the rest of the barrier. The fault element may be a portion of the barrier that is thinner than the rest of the barrier. The fault element may be a scored line on the barrier that is configured to be the weak point of the barrier. The fault element may be a portion of the barrier that has a lower tensile or z-strength than the rest of the barrier. In some embodiments the barrier may extend across at least 30% of the surface area of the first side of the membrane in the pocket. The barrier may extend across at least 40% of the surface area of the first side of the membrane in the pocket. The barrier may extend across at least 50% of the surface area of the first side of the membrane in the pocket. The barrier may extend across at least 60% of the surface area of the first side of the membrane in the pocket. The barrier may extend across at least 70% of the surface area of the first side of the membrane in the pocket. The barrier may extend across at least 75% of the surface area of the first side of the membrane in the pocket. The barrier may extend across at least 80% of the surface area of the first side of the membrane in the pocket.

The barrier may extend across from 20% to 100% of the surface area of the first side of the membrane. The barrier may extend across from 30% to 100% of the surface area of the first side of the membrane. The barrier may extend across from 40% to 100% of the surface area of the first side of the membrane. The barrier may extend across from 50% to 100% of the surface area of the first side of the membrane. The barrier may extend across from 60% to 100% of the surface area of the first side of the membrane. The barrier may extend across from 70% to 100% of the surface area of the first side of the membrane. The barrier may extend across from 75% to 100% of the surface area of the first side of the membrane. The barrier may extend across from 20% to 95% of the surface area of the first side of the membrane. The barrier may extend across from 20% to 90% of the surface area of the first side of the membrane. The barrier may extend across from 20% to 80% of the surface area of the first side of the membrane. The barrier may extend across from 20% to 70% of the surface area of the first side of the membrane. The barrier may extend across from 20% to 60% of the surface area of the first side of the membrane. In embodiments where the barrier extends across less than 100% of the surface area of the first side of the membrane, the barrier may be provided at the open end of the pocket. Accordingly, there may be a space between the barrier and the closed end of the pocket. The barrier may be provided at the closed end of the pocket. Accordingly, there may be a space between the barrier and the open end of the pocket. The barrier may be provided between the open end and the closed end of the pocket. Accordingly, there may be a space between the barrier and the open end of the pocket and a space between the barrier and the closed end of the pocket.

The barrier may comprise a gas impermeable material. Accordingly, the barrier may prevent or substantially prevent the flow of gas along the length of the pocket from the open end of the pocket to the closed end of the pocket. The barrier may comprise a liquid impermeable material. Accordingly, the barrier may prevent or substantially prevent the flow of liquid along the length of the pocket from the open end of the pocket to the closed end of the pocket. The barrier may comprise a material that is both gas impermeable and liquid impermeable and may prevent or substantially prevent the flow of fluid along the length of the pocket from the open end of the pocket to the closed end of the pocket.

The barrier may comprise a gas permeable material and may have an extent along the length of the pocket that presents a diffusion pathway for gas through the barrier along the length of the pocket that is sufficient to substantially prevent the passage of gas through the pocket from the open end to the closed end. Accordingly, the diffusion pathway may be sufficiently long and narrow to effectively prevent the passage of gas through the pocket from the open end to the closed end. The diffusion pathway may be sufficiently long and narrow to effectively prevent the passage of gas through the pocket from the closed end to the open end. The diffusion pathway for gas through the barrier along the length of the pocket may be at least 0.5 mm. The diffusion pathway for gas through the barrier along the length of the pocket may be at least 1 mm. The diffusion pathway for gas through the barrier along the length of the pocket may be at least 1.5 mm. The diffusion pathway for gas through the barrier along the length of the pocket may be at least 2 mm. The material of the barrier and the thickness of the barrier may be chosen to ensure that the flow of gas along the length of the pocket from the open end to the closed end is substantially prevented by the barrier before the threshold is exceeded. For example, the extent that barrier extends along the length of the pocket may be greater for a barrier comprising a gas permeable material than for a barrier comprising a substantially gas impermeable material to ensure that the diffusion pathway through the barrier of the gas permeable material is sufficient to substantially prevent the flow of gas along the length of the pocket from the open end to the closed end. The extent that the barrier extends along the length of the pocket may be greater for a barrier comprising a gas permeable material than for a barrier comprising a substantially gas impermeable material to ensure that the diffusion pathway through the barrier of the gas permeable material is sufficient to substantially prevent the flow of gas along the length of the pocket from the closed end to the open end.

The barrier may comprise a material selected from the group: thermoset adhesive, acrylic based adhesive, epoxy, urethane-based adhesive, rubber adhesive, silicone-based adhesive, metal foils including aluminium foil, laminated metal foils, fluorinated ethylene propylene (FEP), ethylene fluorinated ethylene propylene (EFEP), PTFE and co-polymers of tetrafluoroethylene (TFE), polyethylene (PE), polypropylene (PP), polybutene-1 , polyolefin blends, or combinations or co-polymers thereof. The barrier may comprise a material selected from the group: FEP, PE, PP, polybutene-1 , polyolefin blends, combinations and co-polymers thereof.

The barrier may have a thickness from the first interior surface of the pocket to the opposed second interior surface of less than 250 pm. The barrier may have a thickness from the first interior surface of the pocket to the opposed second interior surface of less than 200 pm. The barrier may have a thickness from the first interior surface of the pocket to the opposed second interior surface of less than 150 pm. The barrier may have a thickness from the first interior surface of the pocket to the opposed second interior surface of less than 100 pm. The barrier may have a thickness from the first interior surface of the pocket to the opposed second interior surface of less than 90 pm. The barrier may have a thickness from the first interior surface of the pocket to the opposed second interior surface of less than 80 pm. The barrier may have a thickness from the first interior surface of the pocket to the opposed second interior surface of less than 70 pm. The barrier may have a thickness from the first interior surface of the pocket to the opposed second interior surface of less than 60 pm. The barrier may have a thickness from the first interior surface of the pocket to the opposed second interior surface of less than 50 pm. The barrier may have a thickness from the first interior surface of the pocket to the opposed second interior surface of less than 40 pm.

The membrane may comprise a porous material. The membrane may be sufficiently porous to allow the flow of gas through the membrane. Accordingly, the membrane may be configured to allow gas flow through the membrane. The membrane may be configured to allow diffusion of gas through the membrane. The membrane may comprise pores that allow gas to diffuse through the membrane. The pores may be sized such that they allow gas to diffuse through the membrane but are sufficiently small to prevent a flow of gas through the membrane. The membrane may be structured such that the gas must take an indirect route through the membrane.

The membrane may be impermeable to liquid. The membrane may be substantially impermeable to liquid. Accordingly, the membrane may allow the passage of gas through the membrane and not allow the passage of liquid through the membrane.

The membrane may comprise an expanded polymer. The expanded polymer may be selected from the group consisting of expanded PE (ePE), expanded PP (ePP), expanded PET (ePET), or an expanded fluoropolymer such as expanded PTFE (ePTFE) or expanded FEP (eFEP). An expanded polymer may have an increased porosity when compared to the corresponding non-expanded polymer.

The membrane may comprise a dense polymer. The dense polymer may be selected from the group consisting of dense PE, dense PP, dense PET, or dense fluoropolymer such as dense PTFE, dense PCTFE, dense ETFE, dense PFA or dense FEP.

As used herein, the term “dense polymer” refers to a polymer material that is substantially non-porous. Accordingly, the dense polymer may have a non-measureable airflow using the test method described herein.

A densified expanded polymer may have the microstructure of an expanded polymer and a lower porosity than the expanded polymer. For example, the densified expanded polymer may have the node and fibril structure of the expanded polymer but have a reduced porosity.

The first surface of the membrane may comprise the dense layer. The second surface of membrane may comprise the open layer. The open layer may fix the vent assembly to opposed interior surfaces of housing wall of the closed container. The open layer may fix the vent assembly to opposed sides of the aperture within the housing wall of the closed container. A dense layer may fix the vent assembly to opposed interior surfaces of housing wall of the closed container. The dense layer may fix the vent assembly to opposed sides of the aperture within the housing wall of the closed container.

In a fourth aspect there is provided a method of making a vent assembly according to the first aspect, the method comprising the steps: providing membrane and a barrier; positioning the barrier on a first side of the membrane; heating the barrier and membrane to form a laminate; and forming a pocket such that the barrier is provided on the inside of the pocket and a second side of the membrane forms the outside of the pocket, wherein the vent assembly comprises the pocket.

The step of heating to form the laminate may be carried out before the step of forming the pocket.

The step of heating to form the laminate may be carried out after the step of forming the pocket.

The threshold at which the barrier fails may be tailored to a given application by adjusting the temperature at which the barrier and membrane are heated in the heating step.

In some embodiments, heating the barrier and the membrane to form a laminate at a higher temperature may raise the threshold. Heating the barrier and the membrane to form the laminate at a lower temperature may lower the threshold.

For the avoidance of doubt, features of the vent assembly of the first aspect are features of the vent assemblies of the second, third and fourth aspects.

Brief Description of the Figures

Embodiments of the present invention will now be described, by way of non-limiting example, with reference to the accompanying drawings.

Figure 1 : A schematic side view of a laminate that is then folded to form the pocket of a vent assembly according to an embodiment;

Figure 2: A schematic side view of a vent assembly of an embodiment before and after failure of the barrier; Figure 3: A schematic side view of a battery pouch cell comprising a vent assembly according to an embodiment;

Figure 4: A schematic side view of a laminate that is then folded to form the pocket of a vent assembly according to an embodiment;

Figure 5: A schematic side view of a vent assembly of an embodiment installed within a battery pouch cell before and after failure of the barrier;

Figure 6: A schematic side view of a laminate that is then folded to form the pocket of a vent assembly according to an embodiment;

Figure 7: A schematic top view of a battery pouch cell including a vent assembly of an embodiment;

Figure 8: A schematic side view of a vent assembly according to an embodiment;

Figure 9: A schematic side view of a vent assembly according to an embodiment;

Figure 10: A schematic side view of a vent assembly according to an embodiment before and after the barrier fails; and

Figure 11 : A schematic side view of a representative vent assembly installed within a closed container moving from a first configuration to a second configuration.

Detailed Description

While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention.

To facilitate the understanding of this invention, a number of terms are defined below. Terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention. Terms such as “a”, “an” and “the” are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terminology herein is used to describe specific embodiments of the invention, but their usage does not delimit the invention, except as outlined in the claims.

Test Methods

T-Peel Strength Test Method

The t-peel strength test method was carried out on an IMASS SP-2100 Peel Tester using the T-peel fixturing and 22 N load cell. A sample was created by laminating or adhering two materials together and then prepared for testing by cutting 10 mm wide strips. The sample strips are loaded into the tester by clamping one material into the first clamp and the second material in the laminate into the second clamp. The material was manually brought to a taught position and then the test was started. The equipment pulls the two materials apart at a rate of 1 mm/second for a total length of 14 mm. The data collection starts after a 4 second delay and the load was averaged for a total of 10 seconds. This average load was used to compare the sample’s peel strength.

Opening Pressure Test Method

The following system was used to measure the opening pressure of vent assemblies outfitted in mock battery pouches. The mock battery pouches were built to represent a standard 645464 battery by utilizing a 5.6 mm thick by 52.7 mm wide by 59.6 mm long acrylic block as the mock jelly roll. This acrylic block also includes a tapped hole to accept a quick connect air fitting. Battery pouch material was sealed around the acrylic block. During the pouch construction a vent assembly was installed. Utilizing the tapped hole, the quick connect air fitting was attached through the pouch material and into the acrylic block. With the mock battery pouch in a box to constrain its available head space to 10% of its total thickness, compressed air was slowly flowed into the mock battery pouch. A pressure regulator and pressure gauge were used to slowly increase the pressure until the vent assembly moved into the open state (from the first configuration to the second configuration) and this pressure value was recorded for comparison to different configurations.

Moisture Vapor Transmission Rate (MVTR)

MVTR was measured according to the standard test method ASTM F1249-13. Instrument (any is acceptable):

2. Mocon PERMATRAN-W 3/34 G GTR Tec GTR-30XAGR

Moisture (gaseous H2O) permeability was measured where a sample material divides a chamber into a high humidity section and a low humidity section where a dry gas is flowed across the sample material. Moisture that passes through the material to the low humidity section is measured by relative humidity detection (Mocon) or gas chromatography (GTR Tec).

Gas Transmission Rate (GTR)

GTR was measured according to the standard test method ASTM D1434-82 or ASTM F2476.

Instrument (any is acceptable): 1. Labthink VAC-V2

2. GTR Tec GTR-30XAGR

3. GTR Tec GTR-11MJGG

4. Mocon Permatran-C 4/41

Gas (CO2, N2, O2) permeability was measured using a gas detector at 40°C. A sample material is placed in an evaluation cell to cover an aperture. For Labthink and GTR Tec instruments, gas is supplied into the evaluation cell to create a pressure differential. Gas that passes through the material to the low pressure section is measured by pressure sensor (Labthink) or gas chromatography (GTR Tec). For Mocon instrument, gas is supplied into the evaluation cell to create a concentration gradient with measurement under isobaric conditions. Gas that passes through the material to the low concentration section is measured by gas sensor.

Method of calculating CO2/H2O selectivity

The CO2 to H2O selectivity of a sample material was calculated by converting the CO2 gas transmission rate (GTR, units of cm³/(m² x 24h x atm)) of the sample material and moisture vapor transmission rate (MVTR, units of g/(m² x day)) of the sample material into respective permeability coefficients (CO2: units of cm³/(cm² x s x cmHg), moisture: units of g/(cm² x s x cmHg)) and the selectivity is calculated as the CO2 permeability coefficient divided by the moisture permeability coefficient. This method may be used to calculate selectivity between other gases such as CO2/O2 or CO2/N2, for example.

Airflow

The ATEQ airflow test measures laminar volumetric flow rates of air through membrane samples. Each membrane sample was clamped between two plates in a manner that seals an area of 2.99 cm² across the flow pathway. An ATEQ® (ATEQ Corp., Livonia, Ml) Premier D Compact Flow Tester was used to measure airflow rate (L/hr) through each membrane sample by challenging it with a differential air pressure of 1.2 kPa (12 mbar) through the membrane. The instrument was operated with calibrated 30 and 150 L flow tubes for making airflow measurements within the ranges of 0.5 to 30 L/hr and 3.8 to 150 L/hr, respectively.

It will be appreciated that the schematic representations of the vent assemblies shown in the Figures are not to scale and are for illustrative purposes only.

Example 1

With reference to Figures 1 to 3 there is provided a vent assembly 1 comprising a membrane

2 and a barrier 4. The membrane 2 had a thickness of 27 pm and comprises an expanded polytetrafluoroethylene (PTFE) layer 8 (acting as an open layer) and a dense PTFE layer 10 (acting as a dense layer) as described in WO 2022/224012 to W. L. Gore & Associates, Inc. which is incorporated by reference herein in its entirety. The expanded PTFE layer 8 is adhered to the dense PTFE layer 10 by a thin layer 12 of fluorinated ethylene propylene (FEP). The barrier 4 comprises FEP with a thickness of 25 pm, (FEP 100A obtained from DuPont Fluoroproducts, DE, US).

The membrane 2 had the following properties. CO2 and H2O permeability were measured at 40°C, and it was found that CO2 GTR is 24500 cm³/m²/day/atm, and MVTR is 2.4 g/m²/day. The calculated CO2/H2O selectivity is 744 cm³/g, which is high among polymer films and ideal for the application in battery pouch cells, since it maximizes CO2 release while minimizing ingress of water vapor. Airflow was also measured according to the method above and it was zero. This confirms the membrane is nonporous and suitable for the application in battery pouch cells because it can contain electrolyte within the cell.

The barrier 4 is overlayed onto the dense PTFE layer 10 of the membrane 2 and folded to form a pocket 14. The barrier 4 was then laminated to the dense PTFE layer 10 of the membrane 2 using a hot press at 255°C for 15 seconds. The pocket 14 has an open end 16 and a closed end 18. The membrane 2 extended beyond the barrier 4 at the open end 16 of the pocket 14 and the barrier 4 extended across approximately 50% of the interior surface of the membrane.

With reference to Figure 7, the vent assembly 1 was integrated into the seam 20 of a battery pouch cell 22 such that the expanded PTFE layer 8 of the membrane 2 was bonded to the cell wall 24 of the battery pouch cell 22 using an impulse sealer. The cell wall 24 (acting as a housing wall) was a polypropylene/aluminium/nylon laminate with a thickness of 88 pm (obtained from Dai Nippon Printing (D-EL35H(3)A)) with the polypropylene on the interior of the cell wall. The jelly roll of the battery pouch cell 22 was replaced with a mock jelly roll 26 comprising an acrylic sheet. An aperture 28 is defined by the cell wall 24 and the vent assembly 1 occludes the aperture 28.

For the avoidance of doubt, a “jelly roll” is an electrode assembly comprised of an anode current collector, an anode, a separator, a cathode, and a cathode current collector, which are wound around a flat or round mandrel, depending on the required configuration. Jelly rolls are often used in battery applications to maximize the available charge density for the battery in a compact format. According to the test method described above, the internal pressure within the battery pouch cell 22 was increased until the barrier 4 of the vent assembly 1 failed. The barrier 4 delaminated from the membrane 2 when the barrier failed. As a result, a space 26 is formed between the membrane 2 and the barrier 4 to thereby allow the gas to pass through the membrane 2 along the pathway 28. The pressure at which the barrier 4 failed and the seam was observed to open was recorded.

In addition, the T peel strength of the barrier/membrane bond was measured using the test methods described above and recorded.

Examples 2-5

Examples 2-5 were prepared as described above for Example 1 with a different lamination temperature and the barrier fail pressure was recorded.

Table 1 below shows that as the lamination temperature used to form the pocket of the vent assembly increases the measured T peel strength as measured using the methods described above and barrier fail pressure also increases. The barriers formed in Examples 1-3 were found to not have been effectively formed resulting in a negligible change in gas permeability before and after “barrier failure”.

Table 1 : Lamination temperatures of Examples 1-5 and their T peel strengths and Barrier fail pressures.

Example 6

With reference to Figures 4-5, a vent assembly 50 comprises a membrane 52 and a barrier layer 54 (acting as a barrier). The membrane 52 comprises a 1.5 mil (38 pm) polypropylene film (obtained from LILINE). The barrier layer 54 comprises a 2 mil (50 pm) low density polyethylene (LDPE) film (obtained from RELOC ZIPPIT). A first side of the membrane 52 was laminated to a first edge of a cell wall 66 of a battery pouch cell 64 using an impulse sealer at 200°C for 10 seconds. The cell wall 66 (acting as a housing wall) was a polypropylene/aluminium/nylon laminate 88 pm thick (obtained from Dai Nippon Printing (D-EL35H(3)A)) with the polypropylene on the interior of the cell wall. A second side of the membrane 52 was laminated to a second edge of the cell wall 66 using an impulse sealer at 200°C for 10 seconds. The membrane 52 and the cell wall 64 were then folded over the barrier layer 54 such that the membrane 52 and barrier layer 54 form a pocket 58. The membrane 52 and barrier layer 54 were laminated together using an impulse sealer at 130°C for 10 seconds. The membrane 52 extended beyond the barrier layer 54 at the open end 60 of the pocket 58 and the barrier layer 54 extended across approximately 50% of the interior surface of the membrane 52. A mock jelly roll 68 comprising an acrylic sheet was used in place of a jelly roll in the battery pouch cell 64. An aperture 70 is defined by the cell wall 66 around the vent assembly 50 and the vent assembly 50 occludes the aperture 70.

According to the test method described above, the internal pressure within the battery pouch cell 64 was increased until the barrier layer 54 of the vent assembly 50 failed. When the barrier layer 54 failed it delaminated from the membrane 52 and a space 72 was formed between the barrier layer 54 and the membrane 52 (see Figure 5) to allow gas to pass through the membrane (see the arrow 74 in Figure 5). The pressure at which the barrier layer 54 failed and the seam was observed to open was recorded.

The barrier layer 54 delaminated from the membrane at an internal pressure of 0.15 bar.

Example 7

With reference to Figure 6 a vent pocket 100 (acting as a vent assembly) comprised a membrane 102 and a barrier 104. The membrane 102 had a thickness of 27 pm and comprises an expanded polytetrafluoroethylene (PTFE) layer 108 (acting as an open layer) and a dense PTFE layer 110 (acting as a dense layer) as described in WO 2022/224012 to W. L. Gore & Associates, Inc. which is incorporated by reference herein in its entirety. The expanded PTFE layer 108 is adhered to the dense PTFE layer 110 by a thin layer 112 of fluorinated ethylene propylene (FEP). The barrier 104 comprises an acrylic adhesive having a thickness of 30 pm (tesa 4983, obtained from Tesa).

A first side of the membrane 102 was laminated to a first edge of a cell wall (not shown) of a battery pouch cell (not shown) using an impulse sealer at 200°C for 10 seconds. The cell wall (acting as a housing wall) was a polypropylene/aluminium/nylon laminate 88 pm thick (obtained from Dai Nippon Printing (D-EL35H(3)A)) with the polypropylene on the interior of the cell wall. A second side of the membrane 102 was laminated to a second edge of the cell wall using an impulse sealer at 200°C for 10 seconds. The membrane 102 and the cell wall were then folded over the barrier 104 such that the membrane 102 and barrier 104 form the vent pocket 100. The membrane 102 and barrier 104 were then laminated together using a roller at room temperature to form a laminate. The membrane 102 extended beyond the barrier 104 at the open end 114 of the vent pocket 100 and the barrier extended across approximately 50% of the interior surface of the membrane.

A mock jelly roll comprising an acrylic sheet was used to replace the jelly roll of the battery pouch cell.

According to the test method described above, the internal pressure within the battery pouch cell was increased until the barrier 104 of the vent pouch 100 failed. The pressure at which the barrier 104 failed was recorded.

The barrier 104 delaminated from the membrane 102 at an internal pressure of 0.07 bar.

Examples 8-12

The vent assembly comprises a membrane and a barrier layer, identified in the table below. The membrane was folded around the barrier and laminated together using the Lamination Temperature indicated in the table. The vent assembly was integrated into the seam of a battery pouch cell using a hot press. The cell wall (acting as a housing wall) was a polypropylene/aluminium/nylon laminate 88 pm thick (obtained from Dai Nippon Printing (D- EL35H(3)A)) with the polypropylene on the interior of the cell wall. The jelly roll of the battery pouch cell was replaced with a mock jelly roll comprising an acrylic sheet. An aperture is defined by the cell wall and the vent assembly occludes the aperture.

The CO2 GTR was measured according to the test methods described above and recorded as Closed Vent Assembly CO2 GTR.

According to the test method described above, the internal pressure within the battery pouch cell was increased until the barrier of the vent assembly failed. The barrier delaminated from the membrane when the barrier failed. As a result a space is formed between the membrane and the barrier to thereby allow the gas to pass through the membrane along the pathway. The pressure at which the barrier failed and the seam was observed to open was recorded. Then, the CO2 GTR was measured again according to the test methods described above and recorded as Open Vent Assembly CO2 GTR. The increase in permeability after the barrier has failed is also recorded, which is calculated by the ratio of Open/Closed CO2 GTR.

Table 2: Examples 8-12 showing failure pressures and permeability changes between the closed and open vent.

³ PTFE/FEP laminate has a thickness of 16 pm. It comprises an expanded polytetrafluoroethylene (PTFE) layer (acting as an open layer) and a dense PTFE layer (acting as a dense layer) as described in WO 2022/224012 to W. L. Gore & Associates, Inc. which is incorporated by reference herein in its entirety. The expanded PTFE layer is adhered to the dense PTFE layer by a thin layer of fluorinated ethylene propylene (FEP). When the vent assembly is integrated in the pouch cell, the expanded PTFE layer is bonded to the inner PP layer of the pouch wall. ^b Cast polypropylene (PP) has a thickness of 50 pm, CP440AB obtained from Copol International, Nova Scotia. ^c Fluorinated ethylene propylene (FEP) has a thickness of 25 pm, FEP 100A obtained from DuPont Fluoroproducts, DE. ^d Ethylene fluorinated ethylene propylene (EFEP) has a thickness of 25 pm, Neoflon RP-5000 obtained from Daikin Industries. ^e Polychlorotrifluoroethylene (PCTFE) has a thickness of 25 pm, Neoflon M-300P obtained from Daikin Industries. ^f Polymethylpentene (PMP) has a thickness of 25 pm, TPX DX845 obtained from Mitsui Chemicals.

Example 8 is a comparative example to show that when the lamination temperature is not sufficiently high for a specific vent assembly, the barrier properties are not good. Accordingly, the CO2 GTR is the same for both configurations, before and after the barrier has failed.

Example 9 shows that when the lamination temperature is increased to 270°C, the thermoplastic barrier FEP becomes sufficiently flowable to conform to the dense PTFE membrane and form a stable bond. Accordingly, the CO2 GTR is very low in the first configuration before the barrier has failed.

Examples 10 and 11 are vent assemblies with alternative barrier films that are appropriate for this application. Because PCTFE and EFEP have lower melting points, the laminate can be made at a lower temperature of 240°C and still form a stable bond.

Example 12 uses a different membrane and different barrier, while still achieving similar CO2 GTR.

Therefore, it is clearly shown that the vent assemblies of the examples all successfully seal the battery pouch cell as in each case the battery pouch cell was inflated to increase the internal pressure successfully. In addition, the barrier of each assembly failed at a pressure threshold to thereby allow gas to escape the battery pouch cell and thereby allow the battery pouch cell to deflate.

The ability of the vent assemblies to be activated at a specific threshold internal pressure by failure of the barrier ensures that before the internal pressure is problematic (i.e. it is below the threshold pressure) the battery pouch cell is sealed and does not allow fluid or particulates into or out of the battery pouch cell. Such an arrangement ensures that the introduction of contaminants such as water, oxygen or nitrogen is minimized to prevent adverse reactions of the electrolyte or electrodes or additives that are typically retained within a battery pouch. If gas is produced in the battery pouch cell due to electrolyte decomposition or unwanted side reactions, the pressure is not allowed to exceed the threshold pressure as the barrier of the vent assembly will fail at that pressure, thereby breaking the seal in the vent assembly and allowing the gas to escape.

Accordingly, catastrophic pressure build up is prevented and so reduces the risk of or prevents failure of the battery pouch cell wall itself or damage to surrounding components within the device within which the battery pouch cell is installed.

Membranes comprising materials with good CO2 to H2O selectivity can allow the vent assembly to continue to prevent the ingress of water whilst allowing gases to escape the battery pouch cell after the barrier has failed.

Alternatively, membranes with large permeability, such as membranes with higher porosity, for example, can be used to provide maximum gas flow out of the battery pouch cell after failure of the barrier to prevent failure of the battery pouch cell. Such vent assemblies could be used as fail-safe vents and after the activation of such vent assemblies the battery pouch cell would be no longer used.

Alternative positionings of the barrier within the pocket are shown in Figures 8 and 9 and are illustrated using the general construction of the vent assembly as described above for Example 1 . These alternative positionings of the barrier 4 may be incorporated into any of Examples 1-12 and would be expected to work in a similar way.

In another example and referring to Figure 10, a vent pocket 150 (acting as a vent assembly) comprising a membrane 152 and a barrier 154. The membrane 152 comprises an expanded polytetrafluoroethylene (PTFE) layer 158 (acting as an open layer) and a dense PTFE layer 160 (acting as a dense layer) as described in WO 2022/224012 to W. L. Gore & Associates, Inc. which is incorporated by reference herein in its entirety. The expanded PTFE layer 158 is adhered to the dense PTFE layer 160 by a thin layer 162 of fluorinated ethylene propylene (FEP). The barrier 154 comprises ePTFE membrane imbibed with FEP.

The membrane 152 was folded over the barrier 154 to form the vent pocket 150 such that the barrier contacted the dense PTFE layer 160 of the membrane 152. The barrier 154 was then laminated to the dense PTFE layer 160 of the membrane using a hot press at 280°C for 15 seconds. The expanded PTFE layer 158 of the membrane 152 was on the exterior surface of the vent pocket 150. The vent pocket 150 has an open end 164 and a closed end 166. The membrane 152 extended beyond the barrier 154 at the open end 164 of the vent pocket 150 and the barrier extended across approximately 50% of the interior surface of the membrane .

The barrier 154 is configured to break when the ends of the membrane 168, 170 adjacent the open end 164 of the vent pocket 150 are pulled away from one another. The barrier 154 breaks into a first barrier portion 172 and a second barrier portion 174 and a space 176 (acting as a barrier space) is formed between the first barrier portion 172 and the second barrier portion 174.

For the above examples, it will be appreciated that the provision of a membrane that comprises a material that has good gas permeability (validated by using the test methods provided above) but is liquid impermeable allows the closed container of each example to continue operation after the barrier has failed as the membrane will prevent any liquid retained within the closed container escaping whilst continuing to allow gas generated within the closed container to escape.

Furthermore, if the membrane comprises a material with good selectivity between carbon dioxide and water (as validated using the test methods described above) gas such as carbon dioxide generated within the closed container can escape through the membrane whilst the ingress of water vapour into the closed container through the membrane will be minimized.

With reference to Figure 11 , for the avoidance of doubt, a schematic general representation of a vent assembly 200 installed within a closed container 202 is shown in a closed configuration 204 where there is slack in the membrane 210 and an open configuration 206. A fixed portion 208 of the membrane 210 of the vent assembly 200 is fixed to the interior surface of the wall 212 of the closed container 202 and a free portion 214 of the membrane 210 is not fixed. When the closed container 204 moves from the first configuration to the second configuration the walls 212 of the closed container 204 move apart from one another such that the vent assembly 200 moves to the open configuration 206 within which the fixed portion 208 of the membrane 210 remains fixed and the free portion 214 of the membrane 210 opens up to allow the membrane 210 to adopt the open configuration 206 and induces the barrier 216 to fail.

While there has been hereinbefore described approved embodiments of the present invention, it will be readily apparent that many and various changes and modifications in form, design, structure and arrangement of parts may be made for other embodiments without departing from the invention and it will be understood that all such changes and modifications are contemplated as embodiments as a part of the present invention as defined in the appended claims.

Claims

1. A vent assembly for use in a closed container, the vent assembly comprising a membrane and a barrier, the barrier being fixed on a first side of the membrane, the membrane extending around the barrier to form a pocket such that the first side of the membrane forms the interior surface of the pocket and a second side of the membrane forms the exterior surface of the pocket, the barrier being configured to prevent the passage of fluid through the pocket, wherein the barrier is configured to fail when a threshold is exceeded and the membrane is configured not to fail when the threshold is exceeded such that gas may pass through the membrane past the failed barrier.

2. The vent assembly of claim 1 , wherein when the threshold is exceeded the pocket at least partially opens to thereby cause the barrier to fail.

3. The vent assembly of claim 1 or claim 2, wherein exceeding the threshold causes the barrier to at least partially detach from the first side of the membrane.

4. The vent assembly of claim 1 or claim 2, wherein exceeding the threshold causes the barrier to break.

5. The vent assembly of any preceding claim, wherein the barrier extends across at least 50% of the surface area of the first side of the membrane in the pocket.

6. The vent assembly of claim 5, wherein the barrier extends across at least 75% of the surface area of the first side of the membrane in the pocket.

7. The vent assembly of any preceding claim, wherein a diffusion pathway through the barrier along a length of the pocket is at least 0.5 mm.

8. The vent assembly of any preceding claim, wherein the barrier comprises a material selected from the group: thermoset adhesive, acrylic based adhesive, epoxy, urethane-based adhesive, rubber adhesive, silicone-based adhesive, metal foils including aluminium foil, laminated metal foils, fluorinated ethylene propylene (FEP), ethylene fluorinated ethylene propylene (EFEP), PTFE and co-polymers of tetrafluoroethylene (TFE), polyethylene (PE), polypropylene (PP), polybutene-1 , polyolefin blends, or combinations or co-polymers thereof.

9. The vent assembly of any preceding claim, wherein the barrier has a thickness of less than 250 pm.

10. The vent assembly of any preceding claim, wherein the barrier has a thickness of from 5 to 250 pm.

11. The vent assembly of any preceding claim, wherein the membrane comprises a polymer selected from the group: polytetrafluoroethylene (PTFE), perfluoroalkoxy alkane (PFA), polyvinylfluoride (PVF), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), or polyethylenetetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), ethylene fluorinated ethylene propylene (EFEP), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and poly(tetramethyl-p-silphenylenesiloxane) (PTMPS) or co-polymers or combinations thereof.

12. The vent assembly of any preceding claim, wherein the membrane comprises a laminate, the laminate comprising an open layer and a dense layer.

13. The vent assembly of claim 12, wherein the first surface of the membrane comprises the dense layer and the second surface of membrane comprises the open layer.

14. A closed container comprising the vent assembly of any of preceding claim.

15. The closed container of claim 14, wherein the closed container is a battery.

16. The closed container of claim 15, wherein the battery comprises a pouch cell.

17. A closed container comprising a housing wall defining an aperture, and a vent assembly occluding the aperture, the vent assembly comprising a membrane, and a barrier, the barrier being fixed on a first side of the membrane, the membrane extending around the barrier to form a pocket such that the first side of the membrane forms the interior surface of the pocket and a second side of the membrane forms the exterior surface of the pocket, a pathway is defined between the interior of the closed container and the exterior of the closed container through the pocket and the aperture, wherein the closed container is configured to move between a first configuration where the barrier prevents passage of fluid along the pathway to the exterior of the closed container and a second configuration where the pocket is at least partially opened and the barrier does not prevent passage of fluid along the pathway to the exterior of the closed container, wherein the closed container is configured to transition from the first configuration to the second configuration when a threshold is exceeded, wherein the barrier is configured to fail when the threshold is exceeded and the membrane is configured not to fail when the threshold is exceeded to thereby allow gas to flow through the membrane when the closed container is in the second configuration.

18. The closed container of to claim 17, wherein the closed container is a battery.

19. The closed container of claim 18, wherein the battery comprises a pouch cell.

20. The closed container of any of claim 17 to claim 19, wherein the threshold is a pressure threshold and the closed container transitions from the first configuration to the second configuration when the pressure within the closed container is greater than the pressure threshold.

21 . The closed container of claim 20, wherein the pressure threshold is at least 0.01 bar.

22. The closed container of any of claim 17 to claim 21 , wherein the second surface of the membrane is connected to two opposing walls of the housing wall or two opposing portions of the housing wall.

23. The closed container of any of claim 17 to claim 22, wherein the pocket is configured to open or at least partially open when the threshold is exceeded.

24. The closed container of any of claim 17 to claim 23, wherein exceeding the threshold causes the barrier to fail by detaching from the first side of the membrane.

25. The closed container of any of claim 17 or claim 23, wherein exceeding the threshold causes the barrier to fail by breaking.

26. The closed container of any of claim 17 to claim 25, wherein the membrane comprises a polymer selected from the group: polytetrafluoroethylene (PTFE), perfluoroalkoxy alkane (PFA), polyvinylfluoride (PVF), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), or polyethylenetetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), ethylene fluorinated ethylene propylene (EFEP), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and poly(tetramethyl-p-silphenylenesiloxane) (PTMPS) or co-polymers or combinations thereof.

27. The closed container of any of claim 17 to claim 26, wherein the membrane comprises a laminate, the laminate comprising an open layer and a dense layer.

28. The closed container of claim 27, wherein the first surface of the membrane comprises the dense layer and the second surface of membrane comprises the open layer.

29. The closed container of any of claim 17 to claim 28, wherein the barrier extends across at least 50% of the surface area of the first side of the membrane in the pocket.

30. The closed container of claim 29, wherein the barrier extends across at least 75% of the surface area of the first side of the membrane in the pocket.

31. The closed container of any of claim 17 to claim 30, wherein a diffusion pathway through the barrier along a length of the pocket is at least 0.5 mm in length.

32. The closed container of any of claim 17 to claim 31 , wherein the barrier comprises a material selected from the group: thermoset adhesive, acrylic based adhesive, epoxy, urethane-based adhesive, rubber adhesive, silicone-based adhesive, metal foils including aluminium foil, laminated metal foils, fluorinated ethylene propylene (FEP), ethylene fluorinated ethylene propylene (EFEP), PTFE and co-polymers of tetrafluoroethylene (TFE), polyethylene (PE), polypropylene (PP), polybutene-1, polyolefin blends, or combinations or co-polymers thereof.

33. A method of making a vent assembly according to any of claim 1 to claim 13, the method comprising the steps: providing membrane and a barrier; positioning the barrier on a first side of the membrane; heating the barrier and membrane to form a laminate; and forming a pocket such that the barrier is provided on the inside of the pocket and a second side of the membrane forms the outside of the pocket, wherein the vent assembly comprises the pocket.

34. The method of claim 33, wherein the step of heating to form the laminate is carried out before the step of forming the pocket.

35. The method of claim 33, wherein the step of heating to form the laminate is carried out after the step of forming the pocket.

36. The method of any of claim 33 to 35, wherein the threshold at which the barrier fails is tailored to a given application by adjusting the temperature at which the barrier and membrane are heated in the heating step.