WO2025068387A1

WO2025068387A1 - Electrochemical cell and vent assembly

Info

Publication number: WO2025068387A1
Application number: PCT/EP2024/077098
Authority: WO
Inventors: Joachim GEGG; John Allen; Mark GOODRICH
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: 2023-09-26
Filing date: 2024-09-26
Publication date: 2025-04-03
Anticipated expiration: 2026-03-26

Abstract

An electrochemical cell is described comprising an electrode layer having an electrode layer thickness, wherein the electrode layer comprises an electrode material and an electrolyte material; and a vent assembly comprising a gas-permeable material. The vent assembly is arranged adjacent to the electrode layer thickness, such that, in use, the vent assembly contains the electrolyte within the electrode layer, and permits a gas formed within the electrode layer to be vented from the electrode layer.

Description

Electrochemical Cell and Vent Assembly

Field

The present disclosure is directed to an electrochemical cell comprising a vent assembly, specifically a vent assembly for permitting gas permeation from an electrode layer within the electrochemical cell.

Background

The performance and safety of lithium-ion batteries critically depend on the electrolyte, which acts as a medium for ion transport between the cathode and anode.

The performance of the electrolyte is influenced by several key properties, including its ionic conductivity, viscosity, electrochemical stability, and compatibility with electrode materials. High ionic conductivity is essential for efficient ion transport, leading to improved battery performance. Viscosity affects the flowability and ease of electrode/electrolyte penetration, impacting battery power and energy density. Electrochemical stability ensures that the electrolyte remains stable during the charging and discharging processes, preventing side reactions and degradation. Compatibility with electrode materials is also crucial to avoid unwanted chemical reactions and enhance battery lifespan.

Recent advancements in electrolyte research aim to address the limitations and improve the overall performance of high-performance batteries, such as lithium-ion batteries. For example, novel electrolyte additives, including lithium salts with improved stability and new solvents with enhanced safety characteristics, are being explored. Solid-state electrolytes, which offer the potential for higher energy density (for example, by providing a lithium metal anode) and improved safety, are also gaining attention. Furthermore, efforts are being made to develop electrolytes that enable high-voltage operation, allowing for increased energy storage capacity.

Electrolyte solvent decomposition and solid-electrolyte interface (SEI) instability can lead to gas formation. The gaseous species typically include carbon monoxide, carbon dioxide, and ethylene. Gas generation is readily evident during the battery formation process step in manufacturing but can also occur during the battery use lifetime. This leads to safety and cell performance issues including electrode degradation, diminished shelf life, reduced cycle lifetime, electrolyte displacement, and increased cell impedance.

For example, in solid-state lithium-ion batteries, gas generation during the formation process is typically a result of the initial activation and conditioning of the battery. The formation process typically involves initial charging and discharging cycles to prepare the solid-state battery for optimal performance. During this process, gas generation can occur due to several factors including electrode-electrolyte interfaces not being fully optimized/imperfect leading to localized reactions at these interfaces; impurities and defects in the electrolyte and electrode materials leading to localized reactions; and electrolyte decomposition. Factors such as high temperature, overvoltage, or improper composition of the solid electrolyte can contribute to electrolyte decomposition and gas formation. Gas generation during the formation process is highly undesirable as it can lead to the formation of gas pockets, delamination or degradation of the solid-state battery structure. Therefore, efforts are made to optimize the formation process to minimize gas generation and ensure the long-term stability and performance of solid-state batteries.

During use, gas-generation typically occurs due to various factors such as overcharging, overdischarging, or internal faults. During overcharging, excess lithium ions can lead to the decomposition of the electrolyte, resulting in the production of gas. For example, overcharging usually results in oxygen being released from the cathode which then reacts with the electrolyte to form carbon dioxide and carbon monoxide. Similarly, over-discharging can cause the lithium ions to be driven into the negative electrode, leading to the decomposition of the electrolyte and gas generation. These factors can also lead to increased impedance within the battery.

An increase in impedance can occur due to several reasons, including the formation of a solidelectrolyte interface (SEI) layer on the electrodes, electrode degradation, or the growth of dendrites. Gas generation can contribute to an increase in impedance by affecting the integrity of the battery's components. The gas bubbles created can block the movement of ions and electrons, reducing the battery's performance and increasing its internal resistance.

Gas generation and accumulation can affect the battery's performance and lifespan. The formation of gas bubbles can create internal pressure gradients and hinder the movement of ions within the battery, reducing its efficiency and capacity. Additionally, gas evolution can contribute to the loss of active materials from the electrodes, leading to a decrease in the battery's overall performance over time. The accumulation of gas within the battery can lead to several issues. First, it can increase the internal pressure, potentially causing the battery to swell or even rupture in extreme cases. This poses safety concerns, as it can result in the release of hazardous substances or cause fires or explosions.

Sealing batteries to protect them from external gas and moisture can also result in accumulation of internal gases. Electrolyte migration is a concern in cells with a need to isolate the electrolyte (specifically, the catholyte and/or anolyte). For example, dual-electrolyte batteries contain two unique electrolytes optimized separately for application at the anode and cathode interfaces. Preventing cross-contamination of the two electrolytes is required in order to provide for effective operation of the battery. Solid state or semi-solid state batteries may only contain a catholyte. These catholytes could be solid, or gel-based, or contain a small amount of liquid to improve properties. The isolation of this catholyte is critical to prevent reactivity with the Li metal anode.

Accordingly, there remains a need for new solutions to the problem of preventing gas accumulation within electrochemical cells whilst also preventing electrolyte migration within the cell.

Summary

According to a first aspect, there is provided an electrochemical cell comprising: an electrode layer having an electrode layer thickness, wherein the electrode layer comprises an electrode material and an electrolyte material; and a vent assembly comprising a gas-permeable material, wherein the vent assembly is arranged adjacent to the electrode layer thickness, such that, in use, the vent assembly contains the electrolyte material within the electrode layer, and permits a gas formed within the electrode layer to be vented from the electrode layer.

The present invention provides for an electrochemical cell with a vent assembly which can, in use, both contain the electrolyte within an electrode layer whilst allowing gas to be vented from the electrode layer. The arrangement of the vent assembly therefore prevents migration of the electrolyte from the electrode layer, avoiding cross contamination with other electrochemical cell components, whilst also mitigating against the possibility of gas accumulation within the electrode layer. Electrochemical cells of the present disclosure may therefore have improved life span and performances compared to existing electrochemical cell arrangements.

Use of the electrochemical cell may encompass formation of the electrochemical cell. For example, activation of the electrochemical cell and conditioning of the electrochemical cell. Use of the electrochemical cell may also encompass use of the cell under the usual interpretation of the word use, for example including but not limited to the use of the electrochemical cell in an intended purpose such as to provide electrical power and any associated charging or discharging of the cell. The electrode layer may comprise two electrode surfaces extending in an x-y plane and an electrode perimeter surface extending in the z-direction between the electrode surfaces. The electrode perimeter surface may define the electrode layer thickness. The electrode material and electrolyte material together may form the electrode layer surfaces and the electrode layer thickness. The electrode layer surfaces may comprise theoretical surfaces which can be used in this instance to describe the arrangement of the electrode layer comprising electrolyte material and electrode materials.

For example, the electrode layer may comprise an electrode material mixed with electrolyte material. The electrode material may comprise at least one of: discrete electrode material particles, or a network of electrode material particles, or films or layers of solid electrolyte materials. The electrolyte may comprise a liquid electrolyte, a solid electrolyte or a gel-based electrolyte. For example, the electrode layer may comprise electrode material particles suspended in liquid electrolyte. The electrode layer may comprise a three-dimensional network of electrode particles and electrolyte particles, wherein the electrolyte may comprise a liquid, gel or solid material. The electrode particles and electrolyte particles may be dispersed throughout the electrode layer, wherein the electrolyte may comprise a liquid, gel or solid material.

The electrode material may be a cathode material. The electrode material may be chosen from at least one of the following: Lithium Nickel Manganese Cobalt Oxide (“NMC”), Lithium Nickel Cobalt Aluminum Oxide (“NCA”), Lithium Manganese Oxide (“LMO”), Lithium Iron Phosphate (“LFP”), Lithium Cobalt Oxide (“LCO”), Lithium Vanadium Oxide, or any combination thereof.

The electrode material may be an anode material. The electrode material can be chosen from at least one of the following: Silicon, Graphite, Silicon-Graphite composites, Lithium, Lithium alloys (including Lithium-silicon or Lithium-tin) Lithium Titanate (“LTO”), a Tin-Cobalt alloy, or any combination thereof.

The electrolyte material may comprise a polymer, ceramic, glass or any combination thereof and may be in at least one of liquid form, gel form or solid form. The electrolyte material may comprise an organic liquid, solid or gel electrolyte material.

The electrolyte material may comprise an electrolytic solution comprising at least one solvent and at least one electrolytic salt. The solvent may be selected from at least one of the following ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC), or combinations thereof. The electrolyte salt may be a lithium salt selected from at least one of the following: lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), or a combination thereof. The electrolyte material may comprise an ionic liquid electrolyte. Ionic liquid electrolytes are salts with low melting points, for example below 100°C and they can often have unique properties such as high thermal stability, low volatility, and good ionic conductivity.

The electrolyte material may comprise a polymer electrolyte material. A polymer electrolyte material may comprise a solid or gel-like material comprising a polymer matrix. The polymer matrix may comprise, for example, at least one of: polyethylene oxide, or polyacrylonitrile gel, poly (vinylidene fluoride-co-hexafluoropropylene), or any combination thereof. The polymer matrix may comprise an electrolyte salt, such as a lithium salt. The lithium salt may be selected from at least one of the following: lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), or a combination thereof. In some examples, the polymer matrix may further comprise a plasticizer. The use of a polymer electrolyte may offer advantages including improved safety, enhanced stability, and the potential for flexible battery designs. The polymer electrolyte may comprise a polymeric ionic liquid-based gel electrolyte. The use of a polymer electrolyte comprising a polymeric ionic liquid-based gel electrolyte may combine advantages of both polymer and ionic liquid electrolytes, offering improved conductivity and thermal stability.

The electrolyte material may comprise a solid-state electrolyte material. Solid-state electrolytes materials comprise solid materials that conduct lithium ions. Solid-state electrolyte materials may have improved safety and have the potential to enable high-energy-density batteries. The solid-state electrolyte materials may include at least one of: lithium ceramics such as lithium phosphorous oxynitride (LiPON), lithium garnets (e.g., Li7La3Zr2O12 or LLZO) or sulfides (e.g., Li10GeP2S12 or LGPS), and solid polymer electrolytes comprising a polymer matrix with added lithium salts.

The vent assembly may comprise an electrode contact surface. The electrode contact surface may also be termed an electrolyte contact surface. The electrode contact surface may be a portion of the vent assembly which is adjacent to the electrode layer. As used herein, adjacent may encompass the electrode contact surface being adjacent to the electrode layer and in direct physical contact with the electrode layer. The term adjacent may encompass the electrode contact surface being adjacent to but not in direct physical contact with the electrode assembly. The vent assembly may be arranged relative to the electrode layer in the x-y plane such that the electrode contact surface is adjacent to at least a portion the electrode layer. For example, the vent assembly may comprise an electrode contact surface configured to be positioned adjacent to at least a portion of one side of the electrode layer. The vent assembly may be arranged relative to the electrode layer in the x-y plane such that the electrode contact surface surrounds at least a portion of the electrode perimeter surface. The vent assembly may be arranged relative to the electrode layer in the x-y plane such that the electrode contact surface surrounds the electrode perimeter surface. The vent assembly being arranged to surround the electrode perimeter surface may permit the vent assembly to contain the electrolyte within the electrode layer, for example within the x-y plane. This arrangement may also permit any gas formed within the electrode layer to be vented via the electrode perimeter surface through the vent assembly. The electrode contact surface may comprise a height in the z-direction which corresponds to the electrode layer thickness.

The vent assembly may be configured to accommodate for changes in the electrode layer thickness. For example, the vent assembly may be configured to accommodate for compression and/or expansion of the electrode layer thickness during manufacture of the electrochemical cell. Additionally, or alternatively, the vent assembly may be configured to accommodate for compression and/or expansion of the electrode layer thickness during use of the electrochemical cell. The gas-permeable material may be elastic such that the vent assembly comprising the gas-permeable material is able to expand and contract in order to accommodate for changes in the electrode layer thickness.

The vent assembly may comprise a gas-permeable and liquid-impermeable material. The vent assembly may comprise at least a portion of material which is gas-permeable and liquid impermeable. The gas-permeability and liquid-impermeability requirements of the vent assembly may be dependent upon the electrode and electrolyte material.

The liquid-impermeability requirements may be dependent on the state of the electrolyte, for example if the electrolyte material is a solid, gel or liquid. The liquid-impermeability requirements may be dependent upon the viscosity of the electrolyte material, for example when the electrolyte material is a liquid or gel electrolyte material. The vent assembly material may have sufficient liquid-impermeability to contain the electrolyte within the electrode layer.

The gas-permeability requirement of the vent assembly material may be dependent upon the electrode material and electrolyte material. The gas-permeability requirements may be dependent upon the gas-generation of the electrochemical cell. For example, the vent assembly material should be sufficiently gas-permeable to allow for venting of gas formed during an activation and conditioning process of the electrochemical cell. The term gas- permeable material is intended to encompass a material which permits a flow of a gas through the material via permeation (for example, under Darcy’s law) and/or by diffusion (for example, under Fick’s law).

The vent assembly may comprise at least one of a porous fabric, a porous tape, a fabric or foam. The vent assembly may comprise a polymer material. The vent assembly may comprise an expanded material. The vent assembly may comprise an expanded polymer material. The vent assembly may comprise a densified material. The vent assembly may comprise a densified polymer material. The gas-permeable material may be a porous material. As used herein, the term “porous” is meant to denote a structure comprising a plurality of pores (i.e. , voids) within a solid matrix. The plurality of pores define a total pore volume of the porous material. At least some of the pores may be inter-connected and form passageways through the material. The solid matrix refers to the solid portion of the porous material excluding its pore volume. The porous material may be a microporous material. As used herein, the term “microporous” refers to material that comprises pores that are not visible to the naked eye. The gas-permeable material may comprise at least one of a porous fabric, a porous tape, or porous foam. The gas-permeable material may comprise a polymer material. The gas- permeable material may comprise an expanded material. The gas-permeable material may comprise an expanded polymer material. The gas-permeable material may comprise a densified material. The gas-permeable material may comprise a densified polymer material.

The vent assembly may comprise a gas-permeable material selected from the group: polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), polyvinylidene fluoride (PVDF), polyethylene (PE), polyetherketoneketone (PEKK), polyether ether ketone (PEEK), poly(tetramethyl-p-silphenylenesiloxane) (PTMPS), polydimethylsiloxane (PDMS), polyparaxylylene (PPX), polyamide 6, polyurethane, thermoplastic polyurethane, polypropylene, polyimide, or polyacrylonitrile (PAN) or combinations thereof.

Where the vent assembly comprises a gas-permeable material which comprises an expanded material, the expanded material may be selected from the group: expanded PTFE (ePTFE), expanded FEP (eFEP), expanded PVDF (ePVDF), expanded polyethylene (ePE), expanded PEKK (ePEKK), expanded PEEK (ePEEK), expanded PTMPS (ePTMPS), expanded polydimethylsiloxane (ePDMS), expanded PPX (ePPX), expanded polyamide 6, expanded polyurethane, expanded thermoplastic polyurethane, expanded polypropylene, expanded polyimide, or expanded polyacrylonitrile (PAN) or combinations thereof. The vent assembly may comprise gas-permeable material which is resistant to deformation through a thickness of the vent assembly. The thickness of the vent assembly may be measured in a z-direction which corresponds to the electrode layer thickness. For example, the gas-permeable material may be crush resistant. For example, the gas-permeable material may comprise high strength ePTFE according to US Patent Number 4,598,011 , the contents of which are incorporated by reference herein, The vent assembly comprising a gas- permeable material which is resistant to deformation through a thickness of the vent assembly may ensure that gas-permeability is maintained during manufacture, formation and other uses of the electrochemical cell.

The vent assembly may comprise a gas-flow direction which defines a direction of travel of gas through the vent assembly. The vent assembly may be arranged such that the gas-flow direction is orthogonal to the electrode layer thickness. This arrangement may allow for gasflow through the vent assembly in the direction needed to ensure sufficient venting from the electrode material. In some examples, the flow of gas through the vent assembly may be in plane with the electrode layer in the x-y plane. In some examples, the flow of gas through the vent assembly may be orthogonal to the electrode layer in the x-y plane. The vent assembly may be gas-permeable and liquid impermeable at least at the electrode contact surface and extending across the width of the vent assembly in the x-y plane at the electrode contact surface. The vent assembly may be gas-permeable and liquid-impermeable across the full width of the vent assembly material in the x-y plane.

The vent assembly may be formed of a gas-permeable material. As such, the vent assembly may be gas-permeable at substantially all of the electrode contact surface and through the corresponding portion of the vent assembly. The vent assembly may comprise a frame. The vent assembly may be formed from component parts which are joined, in use, to form a vent assembly frame. The component parts may comprise the same or different materials. The frame may comprise a unitary structure. The frame may comprise a frame component having a first configuration and a second configuration, wherein in the second configuration, the frame component may be arranged adjacent to the electrode layer thickness. The frame component may comprise at least one notch or indentation, wherein the at least one notch or indentation may facilitate reconfiguration of the frame component from the first configuration to the second configuration. The first configuration may be a substantially linear arrangement. The vent assembly may comprise a layer of gas-permeable material which, in use, is wrapped around or positioned adjacent to the electrode layer perimeter surface. The vent assembly may comprise an aperture having a volume, wherein the volume is configured to contain a portion of the electrode layer. The electrode contact surface of the vent assembly may define the perimeter of the volume.

The electrochemical cell may further comprise a current collector. The current collector may be configured to collect charge from the electrode layer. The current collector may be a cathode current collector. The current collector may be an anode current collector. The current collector may be arranged in a parallel layer which is adjacent to the electrode layer. The current collector may be in physical contact with the electrode layer with the electrode layer. The electrochemical cell may comprise a cathode current collector and an anode current collector.

Where the current collector is a cathode current collector, the current collector may comprise at least one of the following materials: copper, aluminium, nickel, titanium, stainless steel, graphite, other carbon-based materials such as carbon nanotubes, or any combination thereof.

Where the current collector is an anode current collector, the current collector may comprise at least one of the following materials: copper, aluminium, platinum, lithium, graphite, other carbon-based materials such as carbon nanotubes, or any combination thereof.

The electrochemical cell may further comprise an electrochemical separator. The electrochemical separator may comprise any material suitable to permit the selective transport of ions through the electrochemical separator. The electrochemical separator may be positioned adjacent to the electrode layer. The electrochemical separator may be arranged in a parallel layer adjacent to the electrode layer. The electrochemical separator may be in physical contact with the electrode layer.

The electrochemical separator may also comprise an electrolyte material. The electrolyte material may the same or different to the electrolyte material in the electrode layer.

The electrochemical separator may comprise at least one material chosen from a polyolefin such as polypropylene and/or polyethylene, polyethylene oxide, at least one of tetrafluoroethylene (TFE) polymer or copolymer, at least one homopolymer of vinylidene fluoride, at least one hexafluoropropylene (HFP)-vinylidene fluoride copolymer, or any combination thereof. The electrochemical separator may comprise a polymer and/ or a ceramic material. The ceramic material may comprise, for example alumina (AL2O3), lithium aluminium titanium phosphate (LATP), or lithium lanthanum zirconate (LLZO). The electrochemical separator may comprise a ceramic coated separator. For example, a separator comprising a ceramic coating on the surface of a polyolefin-based separator. The ceramic coating helps improve the thermal stability and safety of the battery. The ceramic materials used for the coating may include, for example, aluminum oxide (AI2O3) with polyvinylidene fluoride (PVDF) as a binder The electrochemical separator may comprise a composite electrochemical separator, for example a composite blend of a polymer material with ceramic particles or fibers. The electrochemical separator may comprise a non-woven electrochemical separator. Non-woven electrochemical separators may comprise, for example, porous materials such as polyesters or cellulose fibers.

The vent assembly may be sealed relative to at least one of the current collector or electrochemical separator. Sealing the vent assembly relative to at least one other component of the electrochemical cell may further facilitate containment of the electrolyte within the electrode layer and direct gas into the gas-flow direction for venting through the vent assembly. The vent assembly being sealed relative to the at least one of the current collector or electrochemical separator may comprise the vent assembly being sealed using at least one of pressure, bonding, welding, adhesives, or any other appropriate method or apparatus to provide for sealing engagement between the vent assembly and at least one of the current collector or electrochemical separator. The vent assembly may be sealed relative to at least one of the current collector or electrochemical separator such that the vent assembly may be configured to accommodate for changes in the electrode layer thickness. For example, where sealing is achieved using an adhesive, the adhesive may have elastic properties such that the vent assembly may be able to move relative to the electrode layer.

The vent assembly may comprise at least one treated surface configured to promote adhesion between an adhesive and the gas-permeable material of the vent assembly. Examples of surface treatments include, but are not limited to, corona or plasma surface treatments or similar which are configured to alter the surface properties of a material, such as surface energy, and thereby improve adhesion of, for example, adhesives. Another example surface treatment may be irradiation-induced surface grafting, wherein the surface energy of the vent assembly is modified by chemically bonding of other polymer materials to the surface.

The electrochemical cell may be configured to retain the gas formed within the electrode layer. The vent assembly may be configured to act as reservoir for the gas vented from the electrode layer. The vent assembly may comprise the porous gas-permeable material, and the vent assembly may be configuredsuch that some or all of the total pore volume of the gas- permeable material may be a void space. As used herein, a void space is intended to encompass at least some or substantially all of the total pore volume of the gas-permeable material being empty of gases or liquids, Typically, prior to use, the total pore volume of the gas-permeable material may be occupied by, for example, air. The electrochemical cell may comprise an outer layer such as a housing, a pouch or a coating which may be arranged to allow for gas vented from the electrode layer to be retained within the vent assembly. For example, the outer layer may comprise a non-gas permeable material. The outer layer may comprise a vacuum pouch, and the electrochemical cell may be placed under a vacuum. For example, the electrochemical cell can be placed under a vacuum and as such, most or all of the air or residual gas from forming the cell may be removed from the pore volume of the gas- permeable material. During use of the electrochemical cell, the gas generated from the electrode layer may enter and reside in the void space of the gas-permeable material.

The electrochemical cell may comprise a sorbent, wherein the sorbent is provided to absorb the gas vented from the electrode layer. The vent assembly may comprise the sorbent. The sorbent chemistries will be dependent upon the gas vented from the electrode layer. For example, a suitable sorbent for the absorption of CO2 may be polyethylenimine functionalized silica. The provision of a sorbent may act to prevent the vent assembly from expansion due to, for example, gas accumulation from the electrode layer during use and/or manufacture of the electrochemical device. The gas-permeable material may comprise the sorbent. For example, the gas-permeable material may be a porous tape or film which may comprise a sorbent material.

The electrochemical cell may further comprise an anode. In some examples, the anode may be formed during use of the electrochemical cell such as in a solid-state or semi-solid state lithium battery. The anode may comprise a lithium anode. The anode may comprise at least one of the following: Silicon, Graphite, Silicon-Graphite composites, Lithium, Lithium alloys (including Lithium-silicon or Lithium-tin), Lithium Titanate (“LTO”), Lithium Iron Phosphate, a Tin-Cobalt alloy, or any combination thereof.

The perimeter surface of the electrode layer may define an outer perimeter in the x-y plane of the electrode layer. The electrochemical separator may comprise a surface with an outer perimeter in the x-y plane corresponding to the outer perimeter of the electrode layer. The current collector may comprise a surface with an outer perimeter in the x-y plane corresponding to the outer perimeter of the electrode layer. The vent assembly may comprise a thickness which corresponds to the electrode layer thickness. The vent assembly may be sealed at adjoining edges between the vent assembly and at least one of the electrochemical separator or current collector. The electrochemical separator may comprise a perimeter surface which extends in the z- direction relative to an electrochemical separator surface in the x-y plane. The current collector may comprise a perimeter surface which extends in the z-direction relative to a current collector surface in the x-y plane. The vent assembly may comprise a thickness which is greater than the electrode layer thickness. When the vent assembly thickness is greater than the electrode layer thickness, the vent assembly electrode contact surface may extend to be adjacent the perimeter surface of the current collector, or the perimeter surface of the electrochemical separator. The vent assembly may be sealed between the electrode contact surface and the adjacent perimeter surfaces of at least one of the electrochemical separator or current collector. This arrangement may facilitate ease of manufacturing of the electrochemical cell. For example, by providing a surface external to the components of the electrochemical cell which may be define a boundary for the electrochemical cell, containing the components within the boundary.

The electrochemical separator may comprise a surface having a portion which extends beyond the outer perimeter of the electrode layer in the x-y plane. The current collector may comprise a surface having a portion which extends beyond the outer perimeter of the electrode layer in the x-y plane. The electrochemical cell may comprise the electrochemical separator and the current collector, and the electrode layer may be positioned therebetween. The vent assembly may be sandwiched between the portions of the electrochemical separator and the current collector which extend beyond the outer perimeter of the electrode layer in the x-y plane. The vent assembly may be in physical contact with at least one of the portions of the electrochemical separator and the current collector which extend beyond the outer perimeter of the electrode layer in the x-y plane. This arrangement may facilitate ease of manufacturing of the electrochemical cell whilst also permitting the electrolyte to be contained within the electrode layer during use of the cell.

The vent assembly may be configured to surround a surface of the current collector in the x-y plane. For example, the vent assembly may further comprise a surface extending in the x-y plane which can be arranged adjacent to an external surface of the current collector in the x- y plane. The vent assembly in this arrangement may therefore function as a barrier between adjacent cells, where a plurality of electrochemical cells are present, or the vent assembly may function as barrier between adjacent current collector portions, for example, if the electrochemical cell comprises a rolled configuration. The vent assembly being configured to surround a surface of the current collector in the x-y plane may also facilitate ease of manufacturing of the cell by containing the electrode layer relative to the current collector during formation of the electrochemical cell. The electrochemical cell may comprise a plurality of electrochemical cell components comprising a cathode current collector, the electrode layer wherein the electrode material comprises a cathode material and an electrolyte material, an electrochemical separator, an anode and an anode current collector, wherein each of these electrochemical cell components are arranged in a stacked configuration. The vent assembly being arranged at least adjacent to the electrode layer thickness.

The electrochemical cell may be a battery. The electrochemical cell may be a secondary battery. The electrochemical cell may be a solid-state or semi-solid state battery.

The electrochemical cell may comprise a plurality of electrochemical cells. Each of the plurality of electrochemical cells may comprise an electrode layer having an electrode material and an electrolyte material. The electrochemical cell may therefore comprise a plurality of electrode layers. The electrochemical cell may comprise a plurality of vent assemblies, and wherein each of the plurality of vent assemblies may be arranged adjacent to an electrode layer. The plurality of electrode layers may have a total electrode layer thickness. The vent assembly may be arranged adjacent to the total electrode layer thickness. The vent assembly contact surface may comprise a height in the z-direction which is at least equal to the total electrode layer thickness. The vent assembly may be arranged adjacent to the total electrode layer thickness such that the vent assembly contains the electrolyte material within each of the plurality of electrode layers, and permits a gas formed within each of the electrode layers to be vented from the electrode layer.

The electrochemical cell may further comprise a casing arranged to house the electrode layer and the vent assembly, and the current collector(s) and electrochemical separator (when present). The casing may comprise a casing volume within which the electrode layer and vent assembly may be housed. The casing may be arranged to contain the vent assembly such that a gas generated in the electrode layer is vented through the vent assembly into the volume of the casing. The electrochemical cell may be arranged such that the vent assembly forms part of the casing. In this arrangement, a gas generated in the electrode layer may be vented through the vent assembly to an environment external to the casing volume.

According to a second aspect, there is provided a vent assembly for use in an electrochemical cell comprising an electrode layer having an electrode layer thickness, and wherein the electrode layer comprises an electrode material and an electrolyte material; wherein the vent assembly comprises a gas-permeable vent material which is arranged, in use, to contain the electrolyte within the electrode layer and permit a gas formed within the electrode layer to be vented from the electrode layer.

The vent assembly may comprise the vent assembly as set out in the first aspect.

According to a third aspect, there is provided a cathode assembly for use in a solid-state or semi-solid state battery, wherein the cathode assembly comprises a cathode layer having a cathode material and a catholyte, and a vent assembly arranged to surround at least a portion of the cathode layer, and the vent assembly being configured, in use, to contain the catholyte within the portion of the cathode layer, and permit a gas formed within the cathode layer to be vented from the cathode layer.

The vent assembly may comprise the vent assembly as set out in the first aspect. The cathode layer may comprise the features of the electrode layer as set out in the first aspect. The cathode material may comprise the features of the electrode material as set out in the first aspect. The catholyte may comprise the features of the electrolyte material as set out in the first aspect.

According to a fourth aspect, there is provided a method of making an electrochemical cell according to the first aspect. The method may comprise providing an electrode layer comprising an electrode material and an electrolyte material, providing a vent assembly comprising a gas-permeable material, and arranging the venting assembly to be adjacent to the electrode layer thickness such that the vent assembly may contain the electrolyte material within the electrode layer and permit a gas formed within the electrode layer to be vented from the electrode layer.

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 : An exploded view of a schematic electrochemical cell comprising an example vent assembly according to the present disclosure;

Figure 2: A perspective view of the schematic electrochemical cell shown in Figure 1 ;

Figure 3: A cross-sectional view of the schematic electrochemical cell of Figure 1 ;

Figure 4: An end view of the schematic electrochemical cell of Figure 1 ;

Figure 5A: An exploded view of an example vent assembly prior to construction according to the present disclosure; Figure 5B: A perspective view of the vent assembly of Figure 5A, constructed;

Figure 5C: An exploded view of an example vent assembly prior to construction;

Figure 5D: A perspective view of the vent assembly of Figure 5C, constructed;

Figure 6: An exploded view of a schematic electrochemical cell comprising an example vent assembly according to the present disclosure;

Figure 7: A perspective view of the schematic electrochemical cell shown in Figure 6;

Figure 8: A cross-sectional view of the schematic electrochemical cell of Figure 6;

Figure 9: An end view of the schematic electrochemical cell of Figure 6;

Figure 10: An exploded view of a schematic electrochemical cell comprising an example vent assembly according to the present disclosure;

Figure 11: A perspective view of the schematic electrochemical cell shown in Figure 10;

Figure 12: A cross-sectional view of the schematic electrochemical cell of Figure 10;

Figure 13a: A perspective view of an example vent assembly according to the present disclosure prior to positioning in an electrochemical cell;

Figure 13b: A perspective view of the vent assembly of Figure 13a, configured for positioning in electrochemical cell;

Figure 13c: An exploded view of a schematic electrochemical cell according to the present disclosure comprising the vent assembly of Figures 13a and 13b;

Figure 13d: A perspective view of the schematic electrochemical cell of Figure 13c;

Figure 14: A schematic perspective view of an electrochemical cell having a jelly roll configuration and comprising an example vent assembly according to the present disclosure; Figure 15: A cross-sectional view of the electrochemical cell shown in Figure 14 in an unrolled configuration;

Figure 16: A schematic perspective view of an electrochemical cell having a jelly roll configuration and comprising another example vent assembly according to the present disclosure;

Figure 17: A cross-sectional view of the electrochemical cell shown in Figure 16 in an unrolled configuration;

Figure 18: A schematic cross-sectional view of an electrochemical cell having a vent assembly according to the present disclosure, further comprising an external casing for the cell;

Figure 19: A schematic cross-sectional view of an electrochemical cell having a vent assembly according to the present disclosure, wherein the vent assembly forms part of an external casing for the cell;

Figure 20: A schematic of a battery comprising a plurality of electrochemical cells in a stacked configuration and a plurality of vent assemblies according to the present disclosure; and Figure 21 : A schematic of a battery comprising a plurality of electrochemical cells in a stacked configuration and a vent assembly according to the present disclosure. Figure 22: A cross-sectional view of a schematic electrochemical cell according to the present disclosure.

Figure 23: A schematic of the electrochemical cell according to the present disclosure having a vacuum pouch.

Figure 24: A schematic view of the arrangement shown in Figure 23 after a vacuum is applied.

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.

Figures 1 to 4 show a schematic electrochemical cell 10 comprising a vent assembly 20 according to the present disclosure. The electrochemical cell 10 comprises a cathode current collector 12, an anode current collector 14 and a cathode layer 18 arranged therebetween. An electrochemical separator 16 is also provided adjacent to the cathode layer 18 and the anode current collector 14. The electrochemical cell 10 is a solid-state or semi-solid state battery wherein the cathode layer 18 comprises a cathode material and an electrolyte (or catholyte) material. The cathode material is dispersed with electrolyte material which may mainly be in the form of a gel or solid. In use, ions produced within the cathode layer 18 are transported beyond the electrochemical separator 16 to form an anode adjacent the electrochemical separator 16 and anode current collector 14. It will be appreciated that the cathode layer 18 may in some examples also include liquid based electrolyte materials. It will also be appreciated that in some examples, the electrochemical cell may comprise a permanent anode, i.e. an anode which is always present within the cell.

The vent assembly 20 comprises a housing in the form of a frame 22 of gas-permeable, liquid- impermeable material. The frame 22 is a unitary structure formed from a single component of the gas-permeable, liquid impermeable material and comprises an aperture 23 defining a volume 24 which, in use, is configured to contain a portion of the cathode layer 18.

As shown in Figure 1 , the cathode layer 18 is sandwiched between the cathode current collector 12 and the electrochemical separator 16, and has an exposed perimeter surface 19 therebetween which extends around the perimeter of the cathode layer 18 and defines a thickness (or height) 18a of the cathode layer 18 (see, Figure 3).

The constructed electrochemical cell 10 is shown in Figure 2, with a cross-section between A-A’ shown in Figure 3. The vent assembly 20 in combination with the cathode current collector 12 and electrochemical separator 16 form an enclosed volume encapsulating the cathode layer 18 therein. The vent assembly 20 functions with at least one other component of the electrochemical cell 10 (in this example, the cathode current collector 12 and the electrochemical separator 16) to support and contain the electrolyte material within the cathode layer 18 whilst permitting gas-permeation from the electrolyte 18 via the vent assembly 20.

In this example, the vent assembly frame 22 comprises two major surfaces 22a, 22b which lie in an x-y plane, and a perimeter surface 22c therebetween which defines a thickness (or height) 22d (in the z-direction) of the frame 22. The aperture 23 extends through the thickness 22d of the frame 22 to define an internal electrolyte contact surface 26 which is sized to correspond to the exposed perimeter surface 19 of the cathode layer 18. The electrolyte contact surface 26 can also be termed an electrode contact surface. That is to say, the dimensions (i.e., the surface area) of the electrolyte contact surface 26 correspond to the dimensions (i.e., the surface area) of the exposed surface 19 of the cathode layer 18. As shown in Figure 3, the thickness 22d of the frame 22 corresponds to the height of the electrolyte contact surface 26, and to the thickness 18a of the cathode layer 18. The vent assembly 20 is therefore configured such that the volume 24 of the aperture 23 permits the vent assembly 20 to surround the cathode layer 18 at the perimeter surface 19 of the cathode layer 18..

It will be appreciated that in some embodiments, that the thickness 18a of the cathode layer 18 may be defined by the spacing between the cathode current collector 12 and electrochemical separator 16.

The vent assembly frame 22 may be formed from any suitable gas-permeable and liquid impermeable material. Such materials typically comprise a gas-flow direction which defines the direction of flow of gas through the material. The frame 22, in this example, is formed from an expanded polymer material having a porous structure through which gas can permeate. The expanded polymer material is porous with at least some of the pores being interconnected as passageways for gas through the material. The direction of gas-permeation through the frame 22 is shown by arrows 28 in Figure 3. The frame 22 is therefore arranged around the cathode layer 18 such that the direction of gas-permeation 28 through the vent assembly 20 is orthogonal to the thickness 18a of the cathode layer 18. The gas-permeable direction 28 is therefore also orthogonal to the height of the electrolyte contact surface 26. The gas- permeable direction 28 of the vent assembly 20 is also considered to be in-plane (in the x-y plane) with the cathode assembly 18. The frame 22 may be constructed by, for example, die cutting of a gas-permeable material having the desired thickness to form the aperture 23 within the material. Although an expanded polymer is described, it will be appreciated that any suitable gas-permeable material may be used depending on the permeability requirements of the electrochemical cell.

In some applications, the gas-permeable material can accommodate for changes in the electrode layer thickness. For example, the electrode layer may expand or contract during manufacture of the electrochemical cell, or during use of the electrochemical cell. The gas- permeable material can be elastic such that the vent assembly comprising the gas-permeable material is able to expand and contract in order to accommodate for changes in the electrode layer thickness. It can also be desirable for the gas-permeable material to be resistant to deformation through the thickness of the vent assembly to ensure that gas-permeability is maintained during manufacture and use of the electrochemical cell.

The vent assembly 20 is positioned to be adjacent to the cathode current collector 12 outer perimeter edge and the electrochemical separator 16 outer perimeter edge. The vent assembly 20 can be sealed to the cathode current collector 12 and the electrochemical separator 16 at the adjoining edges 30 of the vent assembly with the cathode current collector 12 and electrochemical separator 16, respectively. The cathode layer 18 is therefore sealed between the vent assembly 20, the cathode current collector 12 and the electrochemical separator 16 such that electrolyte with the cathode layer 18 is contained within the cathode layer 18, and gas formed in the cathode layer 18 can permeate through the vent assembly in the gas-flow direction 28. The vent assembly 20 can be sealed to the cathode current collector 12 and the electrochemical separator 16 at the adjoining edges using any suitable means or apparatus, including but not limited to the use of pressure, the use of bonding or adhesives, the use of welding, such as ultrasonic welding. Where sealing is achieved using an adhesive, the adhesive may have elastic properties such that the vent assembly is able to move relative to the electrode layer such that the vent assembly can accommodate for changes in the electrode layer thickness.

The vent assembly 20 can in some applications be provided with a surface treatment configured to promote adhesion between an adhesive and the gas-permeable material of the vent assembly 20. For example, the vent assembly 20 can include at least one treated surface configured to promote adhesion between an adhesive and the gas-permeable material of the vent assembly 20. Examples of surface treatments include, but are not limited to, corona or plasma surface treatments, or irradiation-induced surface grafting, or similar which are configured to alter the surface properties of a material, such as surface energy, and thereby improve adhesion of, for example, adhesives. Another example surface treatment may be irradiation-induced surface grafting, wherein the surface energy of the vent assembly is modified by chemically bonding of other polymer materials to the surface.

Figure 4 shows an end view of the constructed electrochemical cell 10. In this example, the vent assembly frame 22 is sized such that the cathode layer 18 nests inside the aperture 23 volume 24. The major surfaces 22a, 22b of the frame 22 are considered to lie in an x-y plane, and comprise a length 21. The cathode layer 18 also comprises two major surfaces in the same x-y plane, comprising a length 13. The length 21 of the major surfaces 22a, 22b of the frame 22 is greater than the length 13 of the cathode layer 18. The same can be said about the width of the frame 22 and width of the cathode layer 18. The vent assembly 20 therefore extends beyond the outer perimeter limit of the cathode layer 18 in the x-y plane.

Figures 5A and 5B show an alternative vent assembly 40 which comprises a frame 42 which is constructed from a plurality of frame components 42a-42d. The frame components 42a-42d each comprise a gas-permeable and liquid impermeable material having a mitred edge 45. The components 42a-42d can be joined 30 at the mitred edges 45 to form a frame 42 having an aperture 43 with an electrolyte contact surface 46, and defining a volume to contain a portion of a cathode layer as described above in relation to Figures 1 to 4. The mitred edges 45 can be joined using any suitable means, for example using adhesives, welding, or overlapping the edges and joining by compression and welding or using adhesives.

Figures 5C and 5D show an alternative vent assembly 50 which comprises a frame 52 which is constructed from a plurality of frame components 52a-52d. The frame components 52a-52d each comprise a gas-permeable and liquid impermeable material having a straight edge 55. The components 52a-52d can be joined 30 at the straight edges 55 to form frame 52 having an aperture 53 with an electrolyte contact surface 56, and defining a volume to contain a portion of a cathode layer as described above in relation to Figures 1 to 4. The straight edges 55 can be joined using any suitable means, for example using adhesives, welding, or overlapping the edges and joining by compression and welding, or using adhesives.

In some examples, the frame components 42a-42d, 52a-52d could be comprised of different materials. For example, one frame component can be comprised of the gas-permeable and liquid impermeable material, or at least a portion of one frame component can be comprised of the gas-permeable and liquid impermeable material to provide for gas venting from the electrode layer through the x-y plane at the position of that frame component. The other frame components can be comprised of, for example, a liquid impermeable material.

Figures 6 to 9 show a schematic electrochemical cell 100 comprising another example vent assembly 120 according to the present disclosure. The vent assembly 120 can be the same as the vent assembly 20, 40 or 50 described previously. The constructed electrochemical cell 100 is shown in Figures 7-9, with Figure 8 showing the cross-sectional view through line B-B’ in Figure 7. The electrochemical cell 100 comprises a cathode current collector 112, an anode current collector 114 and a cathode layer 118 arranged therebetween. An electrochemical separator 116 is also provided adjacent to the cathode layer 118 and the anode current collector 114.

In this example, the vent assembly 120 is sized such that the vent assembly comprises an aperture 123 having a volume 124 which permits the vent assembly 120 to surround the cathode layer 118 at the exposed surface 119 of the cathode layer 118. The aperture 123 extends through the thickness 122d of the vent assembly to define an internal electrolyte contact surface 126 which is sized to correspond to the exposed perimeter surface 119 of the cathode layer 118.

The cathode current collector 112 and the electrochemical separator 116 extend in the x-y plane beyond the outer perimeter limit of the cathode layer 118 in the x-y plane. The vent assembly 120 is configured to be sandwiched between the extended portions 112a, 116a of the cathode current collector 112 and the electrochemical separator 116, respectively. In some examples, the vent assembly 120 may be configured to correspond to the outer dimensions of the cathode and/or separator and/or cathode. The vent assembly 120 is sealed 130 to the cathode current collector 112 and electrochemical separator 116, for example between the adjacent surfaces at the extended portions 112a, 116a forming a sealed volume which encapsulates the cathode layer 118. The electrolyte within the cathode layer 118 is therefore contained within the cathode layer 118, and gas generated within the cathode layer 118 can be vented through the vent assembly 120. In this example, the vent assembly 120 extends further than the outer perimeter limits of the cathode current collector 112 and the electrochemical separator 116, however, it will be appreciated that the vent assembly 120 could be dimensioned to be within or match the outer perimeter limits of the cathode current collector 112 and the electrochemical separator 116. Such an arrangement may facilitate ease of manufacturing as the vent assembly may contain the cathode layer relative to the cathode current collector 112 during the construction of the layers of the electrochemical cell 100.

The vent assembly 120 can be sealed to the cathode current collector 112 and the electrochemical separator 116 between the adjacent surfaces at the extended portions 112a, 116a using any suitable means or apparatus, including but not limited to the use of pressure, the use of bonding or adhesives, the use of welding, such as ultrasonic welding.

Similarly to the previous example, the vent assembly 120 is arranged such that the gaspermeation direction 128 of gas flow through the vent assembly 120 is orthogonal to the thickness (or height) 118a of the cathode layer 118 and the height 122d of the vent assembly 120, as shown in Figure 8.

Figures 10 to 12 show a schematic electrochemical cell 200 comprising another example vent assembly 220 according to the present disclosure. Figure 11 shows the constructed electrochemical cell 200 and Figure 12 provides a cross-sectional view through line C-C’ in Figure 11. The electrochemical cell 200 comprises a cathode current collector 212, an anode current collector 214 and a cathode layer 218 arranged therebetween. An electrochemical separator 216 is also provided adjacent to the cathode layer 218 and the anode current collector 214.

In this example, the vent assembly 220 comprises a layer 222 of gas-permeable, liquid impermeable material which is configured to be positioned around the outer perimeter of the cathode layer 218 and joined at the adjoining edges 223 of the layer 222. The layer 222 comprises an electrolyte contact surface 226 extending around an inside perimeter of the layer 222, and defining a volume 224 for enclosing a portion of the cathode layer 218 around the exposed surface 219 of the cathode layer 218.

Additionally, as shown in Figure 12, the vent assembly 220 comprises a height 222d which is greater than the thickness (or height) 218a of the electrolyte 218. As such, the layer 222 also surrounds at least a portion of an external surface of the cathode current collector 212, and the electrochemical separator 216. The vent assembly 220 is sealed 230 to the adjoining external surfaces of the cathode current collector 212 and the electrochemical separator 216, respectively. The vent assembly 220 can be sealed to the cathode current collector 212 and the electrochemical separator 216 using any suitable means or apparatus, including but not limited to the use of pressure, the use of bonding or adhesives, the use of welding, such as ultrasonic welding.

In some examples, the vent assembly 220 may comprise a height in the z-direction which corresponds to the total height of the cathode current collector, the cathode layer, the electrochemical separator, and the anode current collector.

The vent assembly 220 is arranged such that the gas-permeation direction 228 of gas flow through the vent assembly 220 is orthogonal to the thickness (or height) 218a of the electrolyte 218 and the height 222d of the vent assembly 220, as shown in Figure 12.

Figures 13a to 13d show a schematic electrochemical cell 250 comprising another example vent assembly 270 according to the present disclosure.

In this example, the vent assembly 270 comprises a frame component 272 comprising gas- permeable, liquid impermeable material which is configured to be positioned around the outer perimeter of the cathode layer 268 and joined at the adjoining edges 273 of the frame component 272. The frame component 272 comprises a first configuration shown in Figure 13a which may be substantially linear. The adjoining edges 273 can joined using any suitable means, for example using adhesives, welding, or overlapping the edges and joining by compression and welding or using adhesives. The adjoining edges 273 may be joined prior to positioning in the electrochemical cell (for example, as shown in Figure 13b), or may be joined in-situ (for example, by orientating the frame component 272 around the portion of the cathode layer 268, and then joining the adjoining edges 273).

The frame component 272 comprises an electrolyte contact surface 276 which in a second configuration of the frame component 272 can extend around an inside perimeter of the frame component 272, and defines a volume 274 for enclosing a portion of the cathode layer 268 around the exposed surface 269 of the cathode layer 268. To facilitate positioning of the frame component 272, notches 275 are provided on the frame component 272 which permit the frame component 272 to be orientated (for example, bent) into the second configuration which allows for the vent assembly 270 to be placed around the portion of the cathode layer 268. In this example, three notches 275 are provided and the frame component 272 is bent to form a generally cuboidal shape as shown in Figure 13b. It will be appreciated that any number of notches 275 may be provided to allow the frame component 272 to be orientated (e.g. bent) into a required shape. This arrangement allows for increased flexibility for the vent assembly 270 to be used with a variety of shapes and dimensions of the electrochemical cell. Additionally, the method of forming the vent assembly 270 from a frame component 272 with notches 275 allows for increased efficiencies in manufacturing, such as increased material utilization compared to, for example, die cutting a desired shape from a portion of material.

An exploded view of the electrochemical cell 250 and vent assembly 270 is shown in Figure 13c. The electrochemical cell 250 is shown assembled in Figure 13d. Similarly to electrochemical cell 100, electrochemical cell 250 comprises a cathode current collector 262 and an electrochemical separator 266 which extend in the x-y plane beyond the outer perimeter limit of the cathode layer 268 in the x-y plane. The vent assembly 270 is configured to be sandwiched between the extended portions 262a, 266a of the cathode current collector 262 and the electrochemical separator 266, respectively. An anode current collector 264 is positioned adjacent to the electrochemical separator 266. In some examples, the vent assembly 270 may be configured to correspond to the outer dimensions of the cathode and/or separator and/or cathode (for example, similar to the arrangement shown in Figures 10-12), or configured to be positioned adjacent to the cathode current collector outer perimeter edge and the electrochemical separator outer perimeter edge (for example, similar to the arrangement shown in Figures 1 to 4).

The vent assembly 270 is sealed to the cathode current collector 262 and electrochemical separator 266, for example between the adjacent surfaces at the extended portions 262a, 266a forming a sealed volume which encapsulates the cathode layer 268. The electrolyte within the cathode layer 268 is therefore contained within the cathode layer 268, and gas generated within the cathode layer 268 can be vented through the vent assembly 270. The vent assembly 270 is sealed to the cathode current collector 262 and electrochemical separator 266 using any suitable means or apparatus, including but not limited to the use of pressure, the use of bonding or adhesives, the use of welding, such as ultrasonic welding.

Figures 14 and 15 show a schematic electrochemical cell 300 comprising another example vent assembly 320 according to the present disclosure. The electrochemical cell 300 is configured to have a rolled configuration 340. Figure 14 therefore shows a schematic of cell 300 in a partially rolled configuration, and Figure 15 shows an end view in an unrolled configuration. Vent assembly 320 is a layer of gas-permeable, liquid impermeable material arranged to encapsulate cathode layer 318, and the cathode current collector 312 and is sealed 330 to the electrochemical separator 316 which is adjacent to the cathode layer 318. The electrochemical separator 316 extends beyond the outer perimeter of the cathode layer 318 providing an extension surface 316a upon to which the vent assembly 320 may be sealed. The vent assembly 320 can be sealed to the electrochemical separator 316 using any suitable means or apparatus, including but not limited to the use of pressure, the use of bonding or adhesives, the use of welding, such as ultrasonic welding. The vent assembly 320 therefore functions with the electrochemical separator 316 to form an enclosed volume surrounding the cathode layer 318 and the cathode current collector 312, containing the electrolyte material within the cathode layer 318 whilst permitting gas formed in the cathode layer 318 to be released from the cathode layer 318 via the vent assembly 320. The vent assembly 320 is arranged such that the gas-permeable direction 328 is orthogonal to a thickness 318a of the cathode layer 318.

In a rolled configuration, the vent assembly 320 can also form a barrier between the cathode current collector 312 and anode current collector 314 when in the rolled configuration. The vent assembly 320 being configured to surround an outer surface of the cathode current collector 312 may also have advantages for simplifying the manufacturing process of the electrochemical cell 300.

Figures 16 and 17 show a schematic electrochemical cell 400 comprising another example vent assembly 420. The electrochemical cell 400 is configured to have a rolled configuration 440. Figure 16 therefore shows a schematic of cell 400 in a partially rolled configuration, and Figure 17 shows an end view in an unrolled configuration.

Vent assembly 420 comprises two strips of gas-permeable, liquid-impermeable material arranged adjacent to the cathode layer 418 such that the vent assembly 420 extends along two sides 419a, 419b of the perimeter surface 419 of the cathode layer 418. In some examples, only one of the strips of the vent assembly 420 is gas-permeable. In the rolled configuration, the third and fourth sides of the perimeter surface 419 (one of which 419c is shown in Figure 17) of the cathode layer 418 are encapsulated by a second electrochemical separator 417 (or insulating material layer).

In this example, the cathode current collector 412 and electrochemical separator 416 extend beyond the outer perimeter of the cathode layer 418. An anode current collector 414 is arranged adjacent to the electrochemical separator 416. The vent assembly 420 can be sandwiched and sealed 430 between the adjacent surfaces of the vent assembly 420 and the portions of the cathode current collector 412 and electrochemical separator 416 which extend beyond the outer perimeter of the cathode layer 418. The vent assembly 420 can be sealed to the electrochemical separator 416 and cathode current collector 412 using any suitable means or apparatus, including but not limited to the use of pressure, the use of bonding or adhesives, the use of welding, such as ultrasonic welding. The vent assembly 420 is arranged such that the gas-permeable direction 428 is orthogonal to a thickness 418a of the cathode layer 418.

Each of the electrochemical cells 10, 100, 200, 250, 300, 400 described above may be further provided with an external casing, as shown in Figures 18 and 19. In these figures, electrochemical cell 10 is shown, however, it will be appreciated that the concepts are equally applicable to electrochemical cells 100, 200, 250, 300 and 400.

Figure 18 shows an electrochemical cell 500 comprising the electrochemical cell 10 and an external casing 560 which houses all of the components of the electrochemical cell 10. Therefore, gas formed within the cathode layer 18 of the electrochemical cell 10 may be vented through the vent assembly 20 into the casing 560. The casing 560 may be provided with a further vent assembly to allow for venting of gases to the environment external to the cell 500, if desired.

Figure 19 shows an alternative electrochemical cell 600 with an external casing 660. An external perimeter surface 22e of the vent assembly 20 forms part of the external casing 660 housing the electrochemical cell 10, therein. As such, gas formed within the cathode layer 18 of the electrochemical cell 10 is vented through the vent assembly 20 to the environment external to the casing 660.

The electrochemical cells 10, 100, 200, and 250 can be stacked to form a battery comprising a plurality of electrochemical cells. A schematic of a battery 700 comprising plurality of electrochemical cells is shown in Figure 20. For simplicity, only the cathode layer 718 of each cell is shown, however it will be appreciated that the other components of the cells outlined above in respect of electrochemical cells 10, 100 and 200 will also be present. In this example, the cathode layers 718 are stacked and a plurality of vent assemblies 720 are provided. Each vent assembly 720 is arranged adjacent to a cathode layer 718, and is sealed to at least one other cell component (for example, the cathode current collector and electrochemical separator as described for electrochemical cell 10) to contain the electrolyte material within cathode layer 718 and permit the flow of gas from the cathode layer 718 to within the battery housing 760. The battery 700 may comprise a vent 762 within the battery housing 760 to allow for venting of gas from the battery housing 760. The vent assemblies 720 could alternatively or additionally form part of the battery housing 760 to allow for direct venting to the external environment.

An alternative battery 800 comprising a plurality of electrochemical cells is shown in Figure 21. For simplicity only the cathode layer 818 of each cell is shown, however it will be appreciated that the other components of the cells outlined above in respect of electrochemical cells 10, 100, 200 and 250 will also be present. In the example, a single vent assembly 820 is provided and comprises thickness 822d which corresponds to at least a total thickness 818a of cathode layers 818 in their stacked arrangement. The total thickness 818a of the cathode layers 818 in their stacked configuration will also encompass the thickness of any intermediate electrochemical cell components between the cathode layers 818. The vent assembly 820 is arranged adjacent to a cathode layers 818, and is sealed to at least one other cell component (for example, the cathode current collector and electrochemical separator as described for electrochemical cell 10) to contain the electrolyte material within each of the cathode layers 818 and permit the flow of gas from each of the cathode layer 818 to within the battery housing 860. The battery 800 may comprise a vent 862 within the battery housing 860 to allow for venting of gas from the battery housing 860. The vent assembly 820 could alternatively or additionally form part of the battery housing 860 to allow for direct venting to the external environment.

Figure 22 depicts a cross-sectional view of an electrochemical cell 900 which includes a cathode current collector 912, an anode current collector 914 and a cathode layer 918 arranged therebetween. An electrochemical separator 916 is also provided adjacent to the cathode layer 918 and the anode current collector 914. The vent assembly 920 is sized such that the vent assembly 920 comprises an aperture having a volume which permits the vent assembly 120 to surround the cathode layer 918 at the exposed surface 919 of the cathode layer 918. The aperture extends through the thickness of the vent assembly 920 to define an internal electrode contact surface 926 which is sized to correspond to the exposed perimeter surface 919 of the cathode layer 918. As shown in Figure 22, a gap 925 is present between the exposed perimeter surface 919 and the electrode contact surface 926. The provision a gap 925 between the cathode layer 918 and the vent assembly 920 may allow space for the cathode layer 918 to expand and contract during manufacture and use of the electrochemical cell 900. The gap 925 between the cathode layer 918 and the vent assembly also may allow for space for the vent assembly to expand laterally, for example, if an external pressure is applied to the electrochemical cell 900 during operation or during assembly of the electrochemical cell 900.

In another example of the present disclosure, the vent assemblies described herein can be placed under a vacuum in order to form a porous gas-permeable material having a total pore volume that is a void space. The vent assembly can therefore act as a reservoir for gas formed and vented from the electrode layer. The vent assemblies of the present disclosure comprise a porous gas-permeable material having a plurality of interconnected pores that allow for gas to flow through the gas-permeable material and which define a total pore volume of the gas-permeable material. Prior to the use of the electrochemical cell, the total pore volume of the gas-permeable material will typically be filled with air. As exemplified in Figures 23-24, electrochemical cell 100 can be placed within a vacuum pouch 950. During use of the electrochemical cell 100, a vacuum is applied to vacuum pouch 950 containing electrochemical cell 100 and substantially all air which may have been residing within the total pore volume of the gas-permeable material of the vent assembly 120 is removed (Figure 24). As such, any gas produced within the cathode layer of the electrochemical cell 100 is vented to the gas-permeable material of the vent assembly 120, and this gas resides in the pore volume of the gas-permeable material. The vacuum pouch 950 will remain relatively tight around the electrochemical cell 100. The vent assembly 120 therefore acts a reservoir for the gas produced by the cathode layer. Use of the electrochemical cell 100 is also intended to encompass formation of the electrochemical cell 100. For example, the activation of the electrochemical cell 100 and conditioning of the electrochemical cell 100. Use of the electrochemical cell 100 is also intended to encompass use of the cell under the usual interpretation of the word use, for example including but not limited to the use of the electrochemical cell 100 in an intended purpose such as to provide electrical power and any associated charging or discharging of the cell. Although, electrochemical call 100 is shown in this example, it will be appreciated that this concept is applicable to all of the electrochemical cells of the present disclosure.

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. An electrochemical cell comprising: an electrode layer having an electrode layer thickness, wherein the electrode layer comprises an electrode material and an electrolyte material; and a vent assembly comprising a gas-permeable material, wherein the vent assembly is arranged adjacent to the electrode layer thickness, such that, in use, the vent assembly contains the electrolyte material within the electrode layer, and permits a gas formed within the electrode layer to be vented from the electrode layer.

2. The electrochemical cell of claim 1 , wherein: the electrode layer comprises two electrode surfaces extending in an x-y plane, and an electrode perimeter surface extending in the z direction between the electrode surfaces, and wherein the electrode perimeter surface defines the electrode layer thickness; and the vent assembly comprises an electrode contact surface; wherein the vent assembly is arranged relative to the electrode layer in the x-y plane such that the electrode contact surface surrounds at least a portion of the electrode perimeter surface.

3. The electrochemical cell of claim 1 or 2, wherein the vent assembly comprises a gas- permeable and liquid impermeable material.

4. The electrochemical cell of any of claims 1 to 3, wherein the vent assembly comprises at least one of a porous membrane, a porous tape, a fabric, or a foam material.

5. The electrochemical cell of any of claims 1 to 4, wherein the gas permeable material comprises a material selected from the group: polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), polyvinylidene fluoride (PVDF), polyethylene (PE), polyetherketoneketone (PEKK), polyether ether ketone (PEEK), poly(tetramethyl-p-silphenylenesiloxane) (PTMPS), polydimethylsiloxane (PDMS), polyparaxylylene (PPX), polyamide 6, polyurethane, thermoplastic polyurethane, polypropylene, polyimide, or polyacrylonitrile (PAN) or combinations thereof.

6. The electrochemical cell of any one of claims 1 to 4, wherein the gas-permeable material comprises a material selected from the group: expanded PTFE (ePTFE), expanded FEP (eFEP), expanded PVDF (ePVDF), expanded polyethylene (ePE), expanded PEKK (ePEKK), expanded PEEK (ePEEK), expanded PTMPS (ePTMPS), expanded polydimethylsiloxane (ePDMS), expanded PPX (ePPX), expanded polyamide 6, expanded polyurethane, expanded thermoplastic polyurethane, expanded polypropylene, expanded polyimide, or expanded polyacrylonitrile (PAN) or combinations thereof.

7. The electrochemical cell of any one of the preceding claims, wherein the gas- permeable material is elastic such that the vent assembly comprising the gas- permeable material is able to expand and contract in order to accommodate for changes in the electrode layer thickness.

8. The electrochemical cell of any one of claims 1 to 7, wherein the vent assembly comprises a gas-flow direction which defines a direction of travel of gas through the vent assembly, and wherein the vent assembly is arranged such that the gas-flow direction is orthogonal to the electrode layer thickness.

9. The electrochemical cell of any one of the preceding claims, wherein the electrode material comprises a cathode material.

10. The electrochemical cell of any one of the preceding claims, wherein the electrolyte material comprises at least one of a solid electrolyte material, a gel based electrolyte material, or a liquid electrolyte material.

11. The electrochemical cell of any one of the preceding claims, further comprising a current collector and an electrochemical separator, and wherein, the vent assembly is sealed relative to at least one of the current collector or the electrochemical separator.

12. The electrochemical cell of claim 11 , wherein the current collector and electrochemical separator comprise surfaces having portions which extend beyond an outer perimeter of the electrode layer in the x-y plane, and wherein the vent assembly is sandwiched between the portions which extend beyond the outer perimeter of the electrode layer.

13. The electrochemical cell of any one of the preceding claims, wherein the vent assembly comprises a thickness which corresponds to the electrode layer thickness.

14. The electrochemical cell of claim 11 , wherein the vent assembly comprises a thickness which is greater than the electrode thickness, such that the vent assembly electrode contact surface is adjacent to at least one of a perimeter surface of the current collector or a perimeter surface of the electrochemical separator.

15. The electrochemical cell of claim 13 or 14, wherein the gas-permeable material is resistant to deformation through the thickness of the vent assembly.

16. The electrochemical cell of any of one of the preceding claims, wherein the vent assembly may comprise at least one treated surface configured to promote adhesion between an adhesive and the gas-permeable material of the vent assembly

17. The electrochemical cell of any preceding claim, wherein the gas-permeable material is a porous gas-permeable material having a plurality of pores defining a total pore volume and the vent assembly is configured such that some or all of a total pore volume is a void space; and wherein the vent assembly acts as a reservoir for the gas formed from the electrode layer.

18. The electrochemical cell of any one of the preceding claims, wherein the gas- permeable material further comprises a sorbent.

19. The electrochemical cell of any one of the preceding claims, wherein the electrochemical cell is a solid-state battery or semi-solid state battery.

20. The electrochemical cell of any one of the preceding claims, wherein the electrochemical cell comprises a plurality of electrode layers, wherein each of the plurality of electrode layers comprises an electrode material and an electrolyte material; and a plurality of vent assemblies, wherein each of the plurality of vent assemblies is arranged adjacent to one of the plurality of electrode layers.

21 . The electrochemical cell of any one of claims 1 to 19, wherein the electrochemical cell comprises a plurality of electrode layers wherein each of the plurality of electrode layers comprises an electrode material and an electrolyte material; and the plurality of electrode layers comprise a total electrode layer thickness; and wherein the vent assembly is arranged adjacent to the total electrode layer thickness such that the vent assembly contains the electrolyte material within each of the plurality of electrode layers, and permits a gas formed within each of the electrode layers to be vented from the electrode layers.

22. A vent assembly for use with an electrochemical cell, wherein the electrochemical cell comprises an electrode layer having a thickness, and wherein the electrode layer comprises an electrode material and an electrolyte material; wherein the vent assembly comprises a gas-permeable vent material which is arranged, in use, to contain the electrolyte within the electrode layer and permit a gas formed within the electrode layer to be vented from the electrode layer.

23. A cathode assembly for use in a solid-state or semi-solid state battery, wherein the cathode assembly comprises a cathode layer having a cathode material and a catholyte, and a vent assembly arranged to encapsulate at least a portion of the cathode layer, the vent assembly being configured to contain the catholyte within the cathode layer, and permit a gas formed within the cathode layer to be vented from the cathode layer.