Filter cartridge for extracting lithium from brine, filter cartridge assembly and apparatus

Abstract

The present invention provides a filter cartridge (1) for extracting lithium from lithium-containing brine, a filter cartridge assembly comprising a cartridge container (80) which contains such a filter cartridge (1), and an apparatus comprising a plurality of such filter cartridge assemblies (1, 80). The filter cartridge (1) at least comprises a capture electrode (47) for capturing lithium ions from the brine, a capture electrode current collector (48) for imparting a negative charge to the capture electrode, a counter electrode (51), and a counter electrode current collector (52) for imparting a positive charge to the counter electrode. Each of the capture electrode, the capture electrode current collector, the counter electrode and the counter electrode current collector comprises a brine-permeable sheet. The sheets are each in the form of a long strip, so that each sheet has an opposing pair of long edges and an opposing pair of short edges. The sheets are stacked in layers forming a stack (67) which is wound into a spiral cylinder, so that the opposing pairs of long edges of all the sheets form opposite ends of the cylinder, allowing the lithium-containing brine to flow radially through the cylinder. At least one of the capture electrode current collector and the counter electrode current collector are provided with a respective plurality of electrical contacts along a respective one of the opposing pair of long edges of the respective current collector, and the plurality of electrical contacts are electrically connected to each other and to a common electrical current connector. The apparatus comprises a plurality of the filter cartridge assemblies (1, 80) arranged in series and / or parallel with each other and sharing a common electrical supply.

Description

[0001] The present invention relates to a filter cartridge for extracting lithium from lithium-containing brine according to claim 1, a filter cartridge assembly according to claim 9, which comprises a cartridge container and such a filter cartridge, and an apparatus comprising a plurality of such filter cartridge assemblies according to claim 11.Background of the Invention

[0002] Prior art WO 2023 / 067101 A, also in the name of the present applicant, describes a method and electrochemical filter cell for extracting lithium from lithium-containing brine. This prior art document describes several different embodiments of the electrochemical filter cell disclosed therein, all of which are designed to produce a concentrated solution of lithium chloride from lithium-containing brine, rather than lithium metal, which is instead produced by subsequent processes applied to the concentrated solution of lithium chloride. In some of the embodiments described therein, a spiral electrochemical filter element employs a stack of different sheets of electrode material, each on the order of several tens of microns to several millimeters thick, which are stacked on top of each other and spirally wound around a mandrel in the form of a cylinder, which is contained within a housing and perfused with the brine. In each case, an electrical circuit is established to supply an electrical current to the electrochemical filter element via a pair of electrical contacts of opposite polarity on an exterior of the housing. However, the distribution of lithium ions captured by the electrochemical filter element is found to depend on the respective locations of these electrical contacts, and in some cases, the current pathway between the pair of electrical contacts comes into contact with the flow of brine at locations inside the filter cell other than within the filter element itself.Object of the Invention

[0003] An object of the present invention, therefore, is to provide an improved filter cartridge for extracting lithium from lithium-containing brine, a filter cartridge assembly comprising a cartridge container and such a filter cartridge, and an apparatus comprising a plurality of such filter cartridge assemblies.Description of the Invention

[0004] Accordingly, in a first aspect, the present invention provides a filter cartridge for capturing lithium from lithium-containing brine. The filter cartridge at least comprises a capture electrode for capturing lithium ions from the brine, a capture electrode current collector for imparting a negative charge to the capture electrode, a counter electrode, and a counter electrode current collector for imparting a positive charge to the counter electrode. Each of the capture electrode, the capture electrode current collector, the counter electrode and the counter electrode current collector comprises a brine-permeable sheet. The sheets are each in the form of a long strip, so that each sheet has an opposing pair of long edges and an opposing pair of short edges. The sheets are stacked in layers forming a stack which is wound into a spiral cylinder, so that the opposing pairs of long edges of all the sheets form opposite ends of the cylinder, allowing the lithium-containing brine to flow radially through the cylinder. At least one of the capture electrode current collector and the counter electrode current collector are provided with a respective plurality of electrical contacts along a respective one of the opposing pair of long edges of the respective current collector, and the plurality of electrical contacts are electrically connected to each other and to a common electrical current connector.

[0005] This arrangement has the advantage that the electrical charge imparted by the capture electrode current collector and / or the counter electrode current collector is distributed throughout the respective one of the capture electrode and the counter electrode, so that the uptake of lithium ions by the capture electrode is also distributed along the length of the capture electrode, even though the capture electrode is in the form of a long strip. This ensures a more even distribution of the lithium ions throughout the spiral cylinder in comparison to a situation in which an electrical current is supplied to the capture electrode and the counter electrode by only a single electrical contact at a single location, which would instead tend to produce a gradient of electrical potential along the length of the respective one of the capture electrode and the counter electrode. This in turn increases the amount of lithium the filter cartridge can recover from the brine before it becomes fully loaded with lithium an avoids a concentration of lithium uptake in proximity to the location of only a single electrical contact.

[0006] In some embodiments, the capture electrode current collector may be provided with a first plurality of electrical contacts along a first one of the opposing pair of long edges of the capture electrode current collector, and the counter electrode current collector may be provided with a second plurality of electrical contacts along a second one of the opposing pair of long edges of the counter electrode current collector, which are opposite to the first plurality of electrical contacts. This arrangement has the advantage that the distribution of electrical current across the capture electrode then mirrors the distribution of electrical current across the counter electrode, making the distribution of lithium ions captured by the capture electrode more even as well.

[0007] In some embodiments, a separation, s, between adjacent ones of the respective plurality of electrical contacts along the respective long edge of the respective current collector may be non-uniform and arranged such that when the stack is wound into a spiral cylinder, the respective plurality of electrical contacts are aligned with each other along a radius of the cylinder. This arrangement has the advantage that the common electrical current connector to which the plurality of electrical contacts are connected may then be rectilinear, which simplifies manufacture.

[0008] In some embodiments, a current density per unit area of the stack supplied by each one of the electrical contacts may be not greater than 1 A cm -2< . This has the advantage that since the current density is determined by the number of electrons flowing per second per unit area of the stack, the density of lithium ions captured by the capture electrode is controlled to have the same density per second per unit area, which prevents the capture electrode from becoming overloaded with lithium in local areas.

[0009] In some embodiments, at least one of the capture electrode current collector and the counter electrode current collector may be wider along the short edge thereof than the capture electrode or the counter electrode, respectively, is along the short edge thereof, and the respective one of the capture electrode current collector and the counter electrode current collector may comprises a strip of electrically insulating sealant located inside and spaced apart from an exposed long edge thereof. This arrangement has the advantage that it prevents the capture electrode or the counter electrode, respectively, from coming into direct electrical contact with any of the plurality of electrical contacts and provides an electrically insulated space between the common electrical current connector and the sheet stack.

[0010] In some embodiments, the opposite ends of the cylinder may each be provided with a respective end seal sealing against the flow of brine therethrough, and through which end seal the electrical contacts protrude. This arrangement has the advantage that the end seal prevents the flow of brine laterally out of the stack whilst still allowing an electrical circuit to be established with the sheet stack via the opposite ends of the cylinder.

[0011] In such embodiments, the filter cartridge may further comprise a respective endcap enclosing the electrical contacts between the respective end seal and the respective endcap within a part of the filter cartridge, which, during use of the cartridge, is not perfused by brine. This arrangement has the advantage that the electrical contacts and the common electrical current connector may then be protected against corrosion by the brine.

[0012] In such embodiments, the common electrical current connector may be in electrical contact with a current connector located on an exterior surface of the respective endcap. This has the advantage that it permits an electrical circuit to be established with the sheet stack from outside the filter cartridge without the electrical current pathway being exposed to the brine.

[0013] In a second aspect, the present invention also provides a filter cartridge assembly comprising a filter cartridge and a cartridge container for containing the filter cartridge therein. The filter cartridge is constructed such that the electrical contacts are enclosed within a part of the filter cartridge, which, during use of the cartridge, is not perfused by brine, and the common electrical current connector is in electrical contact with a current connector located on an end face of the cartridge. The cartridge container comprises a first mating assembly for electrical connection with the capture electrode current connector of the filter cartridge, a second mating assembly for electrical connection with the counter electrode current connector of the filter cartridge, a capture electrode current connector on an exterior of the cartridge container in electrical connection with the first mating assembly, a counter electrode current connector on the exterior of the cartridge container in electrical connection with the second mating assembly, an inlet for supplying lithium-containing brine to the stack of the filter cartridge contained therein, and an outlet for lithium-depleted brine from the stack of the filter cartridge. Such an assembly has the advantage that it allows the cartridge container to be permanently connected to a supply of lithium-containing brine and to a supply of electrical power and for the filter cartridge to be perfused with brine without the electrical contacts being exposed to the brine. On the other hand, it also allows the filter cartridge it contains to be removed and / or replaced, for example when loaded with lithium.

[0014] In some embodiments, therefore, the cartridge container may be adapted and arranged such that the filter cartridge can be removed from within the cartridge container when loaded with lithium and replaced with a like filter cartridge containing less lithium. For example, the cartridge container may comprise a removable end cap. Such an arrangement has the advantage that operation of the cartridge assembly may then be only briefly suspended whilst the filter cartridges are exchanged.

[0015] In a third aspect, the present invention provides an apparatus comprising a plurality of filter cartridge assemblies according to the second aspect of the invention, wherein the filter cartridge assemblies are arranged in series with each other and share a common electrical supply. This has the advantage that the percentage amount of lithium recovered from brine flowing through the series of cartridge assemblies is increased as it passes through successive ones of the filter cartridges in the series in comparison to passing through just a single one of the filter cartridges. Moreover, if at least one of the cartridge containers is adapted and arranged to allow the filter cartridge therein to be removed when loaded with lithium and replaced with a like one containing less lithium, this allows operation of the apparatus to be only briefly interrupted whilst the filter cartridges are exchanged.

[0016] In some embodiments, the plurality of filter cartridge assemblies may be arranged in parallel with each other, as well as or instead of being arranged in series with each other, and may share a common electrical supply. This has the advantage that a plurality of filter cartridge assemblies working in parallel with each other increases the total volume of lithium-containing brine which may be processed by them per unit time. Moreover, if at least one of the cartridge containers is adapted and arranged to allow the filter cartridge therein to be removed when loaded with lithium and replaced with a like one containing less lithium, this allows the apparatus to continue operation with a reduced flow rate whilst the filter cartridges are exchanged.Brief Description of the Drawings

[0017] Further features and advantages of the present invention will become apparent from the following detailed description, which is given by way of example and in association with the accompanying drawings, in which: Fig. 1 is a schematic edge-on view of an embodiment of a stack of sheets of electrode materials; Fig. 2 is a schematic diagram of microscopic lithium-binding particles in a capture electrode sheet; Fig. 3 is a perspective view of a stack of sheets of electrode materials rolled into a spiral and mounted on a mandrel within a housing; Fig. 4 is a schematic diagram of an embodiment of an electrical circuit; Fig. 5 a schematic cross-sectional view of part of a first embodiment of a filter cartridge; Fig. 6 a schematic cross-sectional view of part of a second embodiment of a filter cartridge mounted in a cartridge container; Fig. 7A is a schematic longitudinal sectional view of part of a stack of sheets of electrode materials rolled into a spiral; Fig. 7B is a schematic end-on view of the assembly of Fig. 7A; Fig. 7C is a schematic end-on view of the assembly of Fig. 7B with an end seal mounted thereon; Fig. 8A is a schematic longitudinal sectional view of the assembly of Fig. 7C with an electrode current collector mounted thereon; Fig. 8B is a schematic longitudinal sectional view of the assembly of Fig. 8A with a cartridge housing counter endcap mounted thereon; Fig. 8C is a schematic close-up longitudinal sectional view of part of the assembly of Fig. 8B; Fig. 9A is a schematic exterior view of an embodiment of a filter cartridge; Fig. 9B is a schematic view of the filter cartridge of Fig. 9A mounted in a cartridge container; Fig. 10A is a schematic diagram of demounting a filter cartridge as in Fig. 9A from the cartridge container thereof for replacement; Fig. 10B is a schematic diagram of replacing the filter cartridge demounted from the cartridge container in Fig. 10A with a replacement filter cartridge; Figs. 11A to 11C are schematic diagrams showing successive processes in preparing an electrode for connection to an electrode current collector; Fig. 12A is a schematic end-on view of a first embodiment of an electrode current collector; Fig. 12B is a schematic end-on view of a second embodiment of an electrode current collector; Fig. 13A is a schematic diagram of an embodiment of a plurality of filter cartridges connected in series; Fig. 13B is a schematic diagram of an embodiment of a plurality of filter cartridges connected in series and in parallel; Fig. 14A is a photo of a first embodiment of a battery of filter cartridges connected in series and in parallel; and Fig. 14B is a photo of a second embodiment of a battery of filter cartridges connected in series and in parallel. Detailed Description

[0018] Fig. 1 schematically shows an embodiment of a stack 67 of sheets of electrode materials. In this embodiment, the stack 67 comprises the following sheets of material stacked in order: a. Capture electrode sheet 47 b. Capture electrode current collector sheet 48 c. Capture electrode sheet 47 d. Flow spacer sheet 49 e. Counter electrode sheet 51 f. Counter electrode current collector sheet 52 g. Counter electrode sheet 51 h. Flow spacer sheet 49

[0019] Each of these sheets is of millimeter or sub-millimeter thickness, so that Fig. 1 is greatly enlarged in scale. In other possible embodiments, one or both of the flow spacer sheets 49 may be omitted from the sheet stack 67 shown in Fig. 1. The capture electrode sheets 47 comprise a porous material permeable to brine, with high internal surface area and good electrical conductivity, such as silver mesh, or carbon or titanium felt, which is impregnated with a lithium-binding compound, such as lithium manganese oxide (LMO), sodium manganese oxide (Na 0.44 MnO 2 ) or a Prussian Blue analogue, and a suitable binder, for example. The counter electrode sheets 51 comprise a material also permeable to brine and with good electrical conductivity, such as silver mesh, or carbon or titanium felt, which may optionally also be porous and impregnated with a chlorine-binding compound, such as polypyrrole, and a suitable binder, for example. If any are present, the flow spacer sheet(s) 49 comprise an electrically insulating material permeable to brine, including plastic meshes, such as PTFE mesh, for example. The current collector sheets 48, 52 comprise a material permeable to brine with good electrical conductivity, such as steel, aluminum, copper, and nickel meshes.

[0020] The broad arrows in Fig. 1 indicate one possible direction of flow of brine through the stack 67 of sheets of electrode materials from A to B, although in use, the direction of flow indicated in Fig. 1 may also be reversed from B to A. Fig. 2 schematically shows a plurality of microscopic lithium-binding particles 100 with which the capture electrode sheets 47 are impregnated. When brine flows through the capture electrode sheets 47, lithium ions 101 are intercalated into the lithium-binding particles 100 with a time constant on the order of less than a second. Lithium ions do not accumulate between the lithium-binding particles 100 in the manner indicated in Fig. 2 by the dashed box 102, so that the resistance to flow of brine through the capture electrode sheets 47 is not increased thereby.

[0021] As shown in Fig. 3, the stack 67 of sheets is wound in a spiral onto a mandrel 53, both of which are contained within a concentric housing 10. Although the sheets of the stack 67 are of millimeter or sub-millimeter thickness, they are also very long, so that once wound, the resulting spiral cylinder has many layers. When brine is flowing through the stack 67 of sheets in the direction indicated in Fig. 1, brine flows from a flow channel 77 inside the housing 10 through the stack 67 of sheets towards the central axis of the mandrel 53. The latter is provided throughout with flow holes, not visible in Fig. 3, so that the brine may emerge from the center of the mandrel 53 in the direction indicated in Fig. 3 by the broad arrow B. The total pressure drop across the stack 67 of sheets once wound into a cylinder is generally less than about 2 bar, and a flow rate of more than about 200 liters of brine per m 2< per bar per hour may be achieved. Returning to Fig. 1, after having been wound into a spiral, each end of the stack 67 of sheets of electrode materials is sealed by a respective end seal 72, 74 to prevent lateral outflow of brine from stack 67. In the prior art, electrical contacts were made to the current collector sheets 48, 52 by respective current collector tabs 55a, 55b, in the manner shown in Fig. 3. However, according to the present invention, the current collector sheets 48, 52 are instead each provided with respective electrical contacts which protrude through respective ones of the end seals 72, 74 as schematically shown in Fig. 1 and as will be described further below.

[0022] Fig. 4 schematically shows an embodiment of an electrical circuit established between the capture electrode sheets 47 and the counter electrode sheets 51 via their respective current collector sheets 48, 52. According to the invention, a plurality of electrical contacts, which are represented in Fig. 4 by black circles, are provided at multiple locations along the edges of each respective one of the current collector sheets 48, 52, so that the separation, s, between adjacent electrical contacts along one of the sheets 48, 52 is generally less than about 1 m. Although the electrical contacts may be placed at regular intervals, for convenience, they may also be placed at irregular intervals in the manner shown in Fig. 4, so that the separation, s, is variable. This is so that when the sheets are wound into a spiral, as described above, the electrical contacts may be arranged in a manner which enables their mutual connection. In Fig. 4, the area of the sheets designated by reference numeral 103 represents the area per electrical contact. The electrical contacts are located so that the current density is generally not greater than about 1 A cm -2< . The potential difference, V, across the sheets is generally less than about 1.2 V. The electrical contacts and the rest of the circuit may comprise copper conductors of a conventional type.

[0023] Fig. 5 schematically shows part of a first embodiment of a filter cartridge 1. As may be seen in Fig. 5, multiple layers of the sheet stack 67 are wound onto a mandrel 53 within a cartridge housing 10, although for ease of representation, the multiple layers of the stack 67 of sheets of the resulting spiral cylinder are shown greatly magnified, so that what, in fact, are many layers are represented in Fig. 5 by just three. A plurality of flow spacers 90 permits a flow of brine entering the filter cartridge 1 via an inlet located at A to flow through the sheet stack 67 and exit via an outlet located at B, as indicated in Fig. 5 by the broad arrows, although as mentioned previously, in use, the direction of flow may also be reversed. Parts of the filter cartridge 1 perfused by brine as a result are represented in Fig. 5 by stippling. Grey circles represent the locations of seals and black circles represent possible locations for attaching electrical contacts, as in Fig. 4. The plurality of capture electrode current collector sheets 48a, 48b, 48c, ... 48x and the plurality of counter electrode current collector sheets 52a, 52b, 52c, ... 52x may each be respectively connected to respective common current connectors of opposite polarity exterior to the filter cartridge 1, for example.

[0024] Fig. 6 schematically shows part of a second embodiment of a filter cartridge 1 mounted inside a cartridge container 80, only part of which is also shown in Fig. 6. The diagrammatic conventions used in Fig. 6 to represent the locations of seals and electrical contacts, and parts of the filter cartridge 1 perfused by brine, are the same as in Fig. 5 and like components are represented by the same reference numerals. However, as may be seen by comparing Fig. 6 with Fig. 5, the filter cartridge 1 in this second embodiment comprises respective endcaps 3, 12, so that the locations of the electrical contacts are enclosed between the respective endcaps 3, 12 and the respective end seals 72, 74 of the sheet stack 67, within parts of the filter cartridge 1 which as a result, are not perfused by brine. The electrical contacts to the capture electrode current collector sheets 48 are mutually connected to each other and to a capture electrode current connector 25 of the filter cartridge 1. Similarly, the electrical contacts to the counter electrode current collector sheets 52 are mutually connected to each other and to a counter electrode current connector 26 of the filter cartridge 1. The capture electrode current connector 25 mates with a corresponding mating assembly 82 of the cartridge container 80, and similarly, the counter electrode current connector 26 mates with a corresponding mating assembly 83 of the cartridge container 80, so that an electrical circuit may be established through the sheet stack 67 from outside the cartridge container 80.

[0025] How these parts of the filter cartridge 1 in the embodiment of Fig. 6 are assembled will now be described with reference to Figs. 7A to 8C, wherein electrical contacts are again represented by black circles. Fig. 7A therefore schematically shows a longitudinal section through part of the sheet stack 67 rolled into a spiral cylinder, with electrical contacts established to one of the capture electrode current collector 48 or the counter electrode current collector 52, depending on which of these is selected for connection on a respective end of the spiral cylinder. Fig. 7B shows an end-on view of the same spiral cylinder with the electrical contacts established to one of the capture electrode current collector 48 or the counter electrode current collector 52. A respective end seal 72, 74 is then mounted on the end of the spiral cylinder with the electrical contacts protruding therethrough, as shown in Fig. 7C. Taking the end of the spiral cylinder with electrical contacts to the counter electrode current collector 52 as an example, these electrical contacts are mutually connected to each other and to a common current connector 59, as shown in Fig. 8A. Fig. 8A therefore schematically shows a longitudinal section through part of the sheet stack 67 rolled into a spiral with an end seal 74 and a common current connector 59 mounted thereon. Thereafter, the common current connector 59 is inserted into a receiving portion of the counter electrode current connector 26 located on the endcap 12 of the filter cartridge 1, as shown in Fig. 8B. Fig. 8C provides a close-up view of part of the same. A similar procedure is used to connect the capture electrode current collector 48 to the capture electrode current connector 25 on the opposite end of the filter cartridge 1.

[0026] Fig. 9A provides an exterior view of the filter cartridge 1, which has a generally cylindrical form with endcaps 3, 12 and the capture electrode current connector 25 and the counter electrode current connector 26 located on opposite ones of the endcaps 3, 12 as a result. In this embodiment, the outlet 13 of the filter cartridge 1, which has male profile, is located on the same end of the filter cartridge 1 as the counter electrode current connector 26, and an inlet, which has a female profile and which is therefore not visible in Fig. 9A, is located on the same end of the filter cartridge 1 as the capture electrode current connector 25. In other possible embodiments, however, depending on the direction of flow of brine through the filter cartridge 1, the locations of the inlet and outlet may be reversed, and the profiles of the inlet and outlet may also be varied independently of that.

[0027] Fig. 9B schematically shows the embodiment of the filter cartridge 1 of Fig. 9A mounted in a cartridge container 80. The cartridge container 80 generally has the form of a hollow cylinder open at one end, the open end of which may be sealed by an endcap 81. When mounted in the cartridge container 80, the capture electrode current connector 25 mates with the corresponding mating assembly 82 of the cartridge container 80, and the counter electrode current connector 26 mates with the corresponding mating assembly 83 of the cartridge container 80, as described above. These mating assemblies 82, 83 are in turn respectively connected electrically to corresponding current connectors 85, 86 mounted on an exterior of the cartridge container 80, so that an electrical circuit may be established through the filter cartridge 1 from outside the cartridge container 80. The outlet 13 of the filter cartridge 1 protrudes through a hole in the closed end of the cartridge container 80 and the endcap 81 of the cartridge container 80 comprises an inlet 2, which allows brine to flow into the cartridge container 80 and therefore into the female inlet of the filter cartridge 1.

[0028] Once a filter cartridge 1 has become loaded with lithium ions, it may be demounted from the cartridge container 80 and replaced with a new, similar filter cartridge 1' using the procedure shown in Figs. 10A and 10B. Firstly, the endcap 81 of the cartridge container 80 is removed. The filter cartridge 1 loaded with lithium ions is then withdrawn from the cartridge container 80 in the direction indicated by the arrows labelled C in Fig. 10A, before the new filter cartridge 1' in inserted into the same cartridge container 80 in the direction indicated by the arrows labelled D in Fig. 10B and the endcap 81 is replaced in the manner indicated by the arrow labelled E in Fig. 10B.

[0029] How the electrical contacts to respective ones of the capture electrode 47 and counter electrode 51 are made will now be described with reference to Figs. 11A to 12C. Fig. 11A therefore schematically shows either the capture electrode 47 and the capture electrode current collector 48 or the counter electrode 51 and the counter electrode current collector 52, which are arranged such that the respective current collector sheet 48, 52 extends beyond the edge of the respective electrode sheet 47, 51. The respective current collector 48, 52 is then immersed in a dip 104, so that a layer of insulating sealant 104a is formed on the respective current collector 48, 52, as shown in Fig. 11B. The same is then immersed to a lesser depth in an etch bath 105 to reveal a portion of the respective current collector 48, 52 again, but also to leave a portion of unetched insulating sealant 104b thereon, as shown in Fig. 11C. Thus a respective end seal 72, 74 may be provided to the sheet stack 67, leaving a portion of the respective current collector 48, 52 protruding beyond the respective end seal 72, 74 for establishment of an electrical contact thereto.

[0030] Figs. 12A and 12B schematically show two different possible embodiments of how electrical contacts may be established to an electrode current collector. As described above in relation to Fig. 4, the plurality of electrical contacts to a respective one of the current collectors 48, 52 are each located at different distances along the edge of the current collector sheet 48, 52, so that when the sheet stack 67 is rolled up into a spiral cylinder, the electrical contacts are aligned with each other along a radius of the cylinder. In other words, as the circumference of the cylinder increases as it is wound on to the mandrel 53, the separation, s, between adjacent ones of the electrical connections increases to compensate for the increasing size of the circumference. This therefore allows a single, rectilinear common current connector 59 to be electrically connected to all of the electrical contacts at once. Fig. 12A shows an embodiment in which the electrical contacts are positioned along a single radius of the spiral cylinder. Fig. 12B shows an alternative embodiment in which the electrical contacts are positioned along a diameter of the spiral cylinder, connected by a common current connector 59 comprising two rectilinear portions connected to each other by an arcuate portion so as not to obstruct the outflow of brine from the center of the spirally wound sheet stack 67.

[0031] Fig. 13A schematically shows an embodiment of an apparatus 110 comprising a plurality of cartridge containers 80a, 80b, 80c of the type shown in Figs. 9B to 10B connected in series with each other. Each of the cartridge containers 80a, 80b, 80c contain a respective filter cartridge 1 of the type shown in Fig. 9A. The outlets 13a, 13b of respective ones of the cartridge containers 80a, 80b are connected in fluid communication with respective ones of the inlets 2b, 2c, so that brine may flow from A to B through the plurality of cartridge containers 80a, 80b, 80c in the manner indicated by the broad arrows in Fig. 13A. The capture electrode current connectors 85a, 85b, 85c of respective ones of the cartridge containers 80a, 80b, 80c are electrically connected to a negative voltage rail 112 and the corresponding counter electrode current connectors 86a, 86b, 86c are electrically connected to a positive voltage rail 111 as shown. Thus the percentage amount of lithium recovered from the brine flowing from A to B may be increased as it passes through successive ones of the filter cartridges 1.

[0032] Fig. 13B schematically shows an embodiment of an apparatus 113 comprising a plurality of cartridge containers 80a, 80b, ... 80i; 80j, 80k, ... 80r; 80s, 80t, ... 80z of the type shown in Figs. 9B to 10B connected in series and in parallel with each other via pipework 114. As in Fig. 13 A, each of the cartridge containers of Fig. 13B also contains a respective filter cartridge 1 of the type shown in Fig. 9A. The plurality of cartridge containers shown in Fig. 13B are supplied with brine by a pump P. If, for example, the pump P can deliver 50 bars of pressure, then the total pressure drop across the plurality of filter cartridges 1 contained within the cartridge containers in this embodiment should not exceed 50 bars either, due to the pipe and sealing requirements of the filter cartridges 1 and of the connecting pipework 114. This in turn determines the number of filter cartridges 1 which can be connected in series and in parallel. Whereas connecting a plurality of filter cartridges 1 in series with each other, as in Fig. 13A, increases the percentage amount of lithium which can be recovered from brine flowing through successive ones of the filter cartridges in series, connecting a plurality of filter cartridges 1 in parallel with each other, as in Fig. 13B, instead increases the volume of brine which may be processed by them per unit time. Although not shown in Fig. 13B for clarity of illustration, the plurality of cartridge containers of Fig. 13B are also electrically connected to a power supply in a similar manner to that described above in relation to Fig. 13A.

[0033] Figs. 14A and 14B are photos of desalination plants, which give some idea of how an apparatus comprising a plurality of filter cartridges 1 may be connected in series and in parallel with each other in practice, as described above in relation to Fig. 13B, although the construction of each module of the desalination plants differs considerably in several respects from each filter cartridge assembly in the apparatus of the invention.

[0034] In summary, therefore, the present invention provides a filter cartridge for extracting lithium from lithium-containing brine, a filter cartridge assembly comprising a cartridge container which contains such a filter cartridge, and an apparatus comprising a plurality of such filter cartridge assemblies. The filter cartridge at least comprises a capture electrode for capturing lithium ions from the brine, a capture electrode current collector for imparting a negative charge to the capture electrode, a counter electrode, and a counter electrode current collector for imparting a positive charge to the counter electrode. Each of the capture electrode, the capture electrode current collector, the counter electrode and the counter electrode current collector comprises a brine-permeable sheet. The sheets are each in the form of a long strip, so that each sheet has an opposing pair of long edges and an opposing pair of short edges. The sheets are stacked in layers forming a stack which is wound into a spiral cylinder, so that the opposing pairs of long edges of all the sheets form opposite ends of the cylinder, allowing the lithium-containing brine to flow radially through the cylinder. At least one of the capture electrode current collector and the counter electrode current collector are provided with a respective plurality of electrical contacts along a respective one of the opposing pair of long edges of the respective current collector, and the plurality of electrical contacts are electrically connected to each other and to a common electrical current connector. The apparatus comprises a plurality of the filter cartridge assemblies arranged in series and / or parallel with each other and sharing a common electrical supply.List of Reference Numerals

[0035] 85Capture electrode current connector of cartridge container1Filter cartridge2Inlet of cartridge housing86Counter electrode current connector of cartridge container3Cartridge housing endcap10Cartridge housing90Flow spacers12Cartridge housing counter endcap100Lithium-binding particles of capture electrode13Outlet of filter cartridge25Capture electrode current connector of filter cartridge101Lithium ion102Accumulation of lithium ions26Counter electrode current connector of filter cartridge103Electrode area per contact104Dip47Capture electrode104aLayer of insulating sealant48Capture electrode current collector104bUnetched insulating sealant49Flow spacer105Etch51Counter electrode110Series of filter cartridges52Counter electrode current collector111Positive voltage rail53Mandrel112Negative voltage rail55Current collector tabs113Apparatus with filter cartridges arranged in series and in parallel59Current connector67Stack of electrode sheet materials114Pipework72End seal of stackPPump74Counter end seal of stack77Flow channel80Cartridge container81Cartridge container endcap82Mating assembly of cartridge container for capture electrode current connector of filter cartridge83Mating assembly of cartridge container for counter electrode current connector of filter cartridge

Examples

Embodiment Construction

[0018]Fig. 1 schematically shows an embodiment of a stack 67 of sheets of electrode materials. In this embodiment, the stack 67 comprises the following sheets of material stacked in order:

a. Capture electrode sheet 47 b. Capture electrode current collector sheet 48 c. Capture electrode sheet 47 d. Flow spacer sheet 49 e. Counter electrode sheet 51 f. Counter electrode current collector sheet 52 g. Counter electrode sheet 51 h. Flow spacer sheet 49

[0019]Each of these sheets is of millimeter or sub-millimeter thickness, so that Fig. 1 is greatly enlarged in scale. In other possible embodiments, one or both of the flow spacer sheets 49 may be omitted from the sheet stack 67 shown in Fig. 1. The capture electrode sheets 47 comprise a porous material permeable to brine, with high internal surface area and good electrical conductivity, such as silver mesh, or carbon or titanium felt, which is impregnated with a lithium-binding compound, such as lithium manganese oxide (LMO), sodium mang...

[0001] The present invention relates to a filter cartridge for extracting lithium from lithium-containing brine according to claim 1, a filter cartridge assembly according to claim 9, which comprises a cartridge container and such a filter cartridge, and an apparatus comprising a plurality of such filter cartridge assemblies according to claim 11.Background of the Invention

[0002] Prior art WO 2023 / 067101 A, also in the name of the present applicant, describes a method and electrochemical filter cell for extracting lithium from lithium-containing brine. This prior art document describes several different embodiments of the electrochemical filter cell disclosed therein, all of which are designed to produce a concentrated solution of lithium chloride from lithium-containing brine, rather than lithium metal, which is instead produced by subsequent processes applied to the concentrated solution of lithium chloride. In some of the embodiments described therein, a spiral electrochemical filter element employs a stack of different sheets of electrode material, each on the order of several tens of microns to several millimeters thick, which are stacked on top of each other and spirally wound around a mandrel in the form of a cylinder, which is contained within a housing and perfused with the brine. In each case, an electrical circuit is established to supply an electrical current to the electrochemical filter element via a pair of electrical contacts of opposite polarity on an exterior of the housing. However, the distribution of lithium ions captured by the electrochemical filter element is found to depend on the respective locations of these electrical contacts, and in some cases, the current pathway between the pair of electrical contacts comes into contact with the flow of brine at locations inside the filter cell other than within the filter element itself.Object of the Invention

[0003] An object of the present invention, therefore, is to provide an improved filter cartridge for extracting lithium from lithium-containing brine, a filter cartridge assembly comprising a cartridge container and such a filter cartridge, and an apparatus comprising a plurality of such filter cartridge assemblies.Description of the Invention

[0004] Accordingly, in a first aspect, the present invention provides a filter cartridge for capturing lithium from lithium-containing brine. The filter cartridge at least comprises a capture electrode for capturing lithium ions from the brine, a capture electrode current collector for imparting a negative charge to the capture electrode, a counter electrode, and a counter electrode current collector for imparting a positive charge to the counter electrode. Each of the capture electrode, the capture electrode current collector, the counter electrode and the counter electrode current collector comprises a brine-permeable sheet. The sheets are each in the form of a long strip, so that each sheet has an opposing pair of long edges and an opposing pair of short edges. The sheets are stacked in layers forming a stack which is wound into a spiral cylinder, so that the opposing pairs of long edges of all the sheets form opposite ends of the cylinder, allowing the lithium-containing brine to flow radially through the cylinder. At least one of the capture electrode current collector and the counter electrode current collector are provided with a respective plurality of electrical contacts along a respective one of the opposing pair of long edges of the respective current collector, and the plurality of electrical contacts are electrically connected to each other and to a common electrical current connector.

[0005] This arrangement has the advantage that the electrical charge imparted by the capture electrode current collector and / or the counter electrode current collector is distributed throughout the respective one of the capture electrode and the counter electrode, so that the uptake of lithium ions by the capture electrode is also distributed along the length of the capture electrode, even though the capture electrode is in the form of a long strip. This ensures a more even distribution of the lithium ions throughout the spiral cylinder in comparison to a situation in which an electrical current is supplied to the capture electrode and the counter electrode by only a single electrical contact at a single location, which would instead tend to produce a gradient of electrical potential along the length of the respective one of the capture electrode and the counter electrode. This in turn increases the amount of lithium the filter cartridge can recover from the brine before it becomes fully loaded with lithium an avoids a concentration of lithium uptake in proximity to the location of only a single electrical contact.

[0006] In some embodiments, the capture electrode current collector may be provided with a first plurality of electrical contacts along a first one of the opposing pair of long edges of the capture electrode current collector, and the counter electrode current collector may be provided with a second plurality of electrical contacts along a second one of the opposing pair of long edges of the counter electrode current collector, which are opposite to the first plurality of electrical contacts. This arrangement has the advantage that the distribution of electrical current across the capture electrode then mirrors the distribution of electrical current across the counter electrode, making the distribution of lithium ions captured by the capture electrode more even as well.

[0007] In some embodiments, a separation, s, between adjacent ones of the respective plurality of electrical contacts along the respective long edge of the respective current collector may be non-uniform and arranged such that when the stack is wound into a spiral cylinder, the respective plurality of electrical contacts are aligned with each other along a radius of the cylinder. This arrangement has the advantage that the common electrical current connector to which the plurality of electrical contacts are connected may then be rectilinear, which simplifies manufacture.

[0008] In some embodiments, a current density per unit area of the stack supplied by each one of the electrical contacts may be not greater than 1 A cm -2< . This has the advantage that since the current density is determined by the number of electrons flowing per second per unit area of the stack, the density of lithium ions captured by the capture electrode is controlled to have the same density per second per unit area, which prevents the capture electrode from becoming overloaded with lithium in local areas.

[0009] In some embodiments, at least one of the capture electrode current collector and the counter electrode current collector may be wider along the short edge thereof than the capture electrode or the counter electrode, respectively, is along the short edge thereof, and the respective one of the capture electrode current collector and the counter electrode current collector may comprises a strip of electrically insulating sealant located inside and spaced apart from an exposed long edge thereof. This arrangement has the advantage that it prevents the capture electrode or the counter electrode, respectively, from coming into direct electrical contact with any of the plurality of electrical contacts and provides an electrically insulated space between the common electrical current connector and the sheet stack.

[0010] In some embodiments, the opposite ends of the cylinder may each be provided with a respective end seal sealing against the flow of brine therethrough, and through which end seal the electrical contacts protrude. This arrangement has the advantage that the end seal prevents the flow of brine laterally out of the stack whilst still allowing an electrical circuit to be established with the sheet stack via the opposite ends of the cylinder.

[0011] In such embodiments, the filter cartridge may further comprise a respective endcap enclosing the electrical contacts between the respective end seal and the respective endcap within a part of the filter cartridge, which, during use of the cartridge, is not perfused by brine. This arrangement has the advantage that the electrical contacts and the common electrical current connector may then be protected against corrosion by the brine.

[0012] In such embodiments, the common electrical current connector may be in electrical contact with a current connector located on an exterior surface of the respective endcap. This has the advantage that it permits an electrical circuit to be established with the sheet stack from outside the filter cartridge without the electrical current pathway being exposed to the brine.

[0013] In a second aspect, the present invention also provides a filter cartridge assembly comprising a filter cartridge and a cartridge container for containing the filter cartridge therein. The filter cartridge is constructed such that the electrical contacts are enclosed within a part of the filter cartridge, which, during use of the cartridge, is not perfused by brine, and the common electrical current connector is in electrical contact with a current connector located on an end face of the cartridge. The cartridge container comprises a first mating assembly for electrical connection with the capture electrode current connector of the filter cartridge, a second mating assembly for electrical connection with the counter electrode current connector of the filter cartridge, a capture electrode current connector on an exterior of the cartridge container in electrical connection with the first mating assembly, a counter electrode current connector on the exterior of the cartridge container in electrical connection with the second mating assembly, an inlet for supplying lithium-containing brine to the stack of the filter cartridge contained therein, and an outlet for lithium-depleted brine from the stack of the filter cartridge. Such an assembly has the advantage that it allows the cartridge container to be permanently connected to a supply of lithium-containing brine and to a supply of electrical power and for the filter cartridge to be perfused with brine without the electrical contacts being exposed to the brine. On the other hand, it also allows the filter cartridge it contains to be removed and / or replaced, for example when loaded with lithium.

[0014] In some embodiments, therefore, the cartridge container may be adapted and arranged such that the filter cartridge can be removed from within the cartridge container when loaded with lithium and replaced with a like filter cartridge containing less lithium. For example, the cartridge container may comprise a removable end cap. Such an arrangement has the advantage that operation of the cartridge assembly may then be only briefly suspended whilst the filter cartridges are exchanged.

[0015] In a third aspect, the present invention provides an apparatus comprising a plurality of filter cartridge assemblies according to the second aspect of the invention, wherein the filter cartridge assemblies are arranged in series with each other and share a common electrical supply. This has the advantage that the percentage amount of lithium recovered from brine flowing through the series of cartridge assemblies is increased as it passes through successive ones of the filter cartridges in the series in comparison to passing through just a single one of the filter cartridges. Moreover, if at least one of the cartridge containers is adapted and arranged to allow the filter cartridge therein to be removed when loaded with lithium and replaced with a like one containing less lithium, this allows operation of the apparatus to be only briefly interrupted whilst the filter cartridges are exchanged.

[0016] In some embodiments, the plurality of filter cartridge assemblies may be arranged in parallel with each other, as well as or instead of being arranged in series with each other, and may share a common electrical supply. This has the advantage that a plurality of filter cartridge assemblies working in parallel with each other increases the total volume of lithium-containing brine which may be processed by them per unit time. Moreover, if at least one of the cartridge containers is adapted and arranged to allow the filter cartridge therein to be removed when loaded with lithium and replaced with a like one containing less lithium, this allows the apparatus to continue operation with a reduced flow rate whilst the filter cartridges are exchanged.Brief Description of the Drawings

[0017] Further features and advantages of the present invention will become apparent from the following detailed description, which is given by way of example and in association with the accompanying drawings, in which: Fig. 1 is a schematic edge-on view of an embodiment of a stack of sheets of electrode materials; Fig. 2 is a schematic diagram of microscopic lithium-binding particles in a capture electrode sheet; Fig. 3 is a perspective view of a stack of sheets of electrode materials rolled into a spiral and mounted on a mandrel within a housing; Fig. 4 is a schematic diagram of an embodiment of an electrical circuit; Fig. 5 a schematic cross-sectional view of part of a first embodiment of a filter cartridge; Fig. 6 a schematic cross-sectional view of part of a second embodiment of a filter cartridge mounted in a cartridge container; Fig. 7A is a schematic longitudinal sectional view of part of a stack of sheets of electrode materials rolled into a spiral; Fig. 7B is a schematic end-on view of the assembly of Fig. 7A; Fig. 7C is a schematic end-on view of the assembly of Fig. 7B with an end seal mounted thereon; Fig. 8A is a schematic longitudinal sectional view of the assembly of Fig. 7C with an electrode current collector mounted thereon; Fig. 8B is a schematic longitudinal sectional view of the assembly of Fig. 8A with a cartridge housing counter endcap mounted thereon; Fig. 8C is a schematic close-up longitudinal sectional view of part of the assembly of Fig. 8B; Fig. 9A is a schematic exterior view of an embodiment of a filter cartridge; Fig. 9B is a schematic view of the filter cartridge of Fig. 9A mounted in a cartridge container; Fig. 10A is a schematic diagram of demounting a filter cartridge as in Fig. 9A from the cartridge container thereof for replacement; Fig. 10B is a schematic diagram of replacing the filter cartridge demounted from the cartridge container in Fig. 10A with a replacement filter cartridge; Figs. 11A to 11C are schematic diagrams showing successive processes in preparing an electrode for connection to an electrode current collector; Fig. 12A is a schematic end-on view of a first embodiment of an electrode current collector; Fig. 12B is a schematic end-on view of a second embodiment of an electrode current collector; Fig. 13A is a schematic diagram of an embodiment of a plurality of filter cartridges connected in series; Fig. 13B is a schematic diagram of an embodiment of a plurality of filter cartridges connected in series and in parallel; Fig. 14A is a photo of a first embodiment of a battery of filter cartridges connected in series and in parallel; and Fig. 14B is a photo of a second embodiment of a battery of filter cartridges connected in series and in parallel. Detailed Description

[0018] Fig. 1 schematically shows an embodiment of a stack 67 of sheets of electrode materials. In this embodiment, the stack 67 comprises the following sheets of material stacked in order: a. Capture electrode sheet 47 b. Capture electrode current collector sheet 48 c. Capture electrode sheet 47 d. Flow spacer sheet 49 e. Counter electrode sheet 51 f. Counter electrode current collector sheet 52 g. Counter electrode sheet 51 h. Flow spacer sheet 49

[0019] Each of these sheets is of millimeter or sub-millimeter thickness, so that Fig. 1 is greatly enlarged in scale. In other possible embodiments, one or both of the flow spacer sheets 49 may be omitted from the sheet stack 67 shown in Fig. 1. The capture electrode sheets 47 comprise a porous material permeable to brine, with high internal surface area and good electrical conductivity, such as silver mesh, or carbon or titanium felt, which is impregnated with a lithium-binding compound, such as lithium manganese oxide (LMO), sodium manganese oxide (Na 0.44 MnO 2 ) or a Prussian Blue analogue, and a suitable binder, for example. The counter electrode sheets 51 comprise a material also permeable to brine and with good electrical conductivity, such as silver mesh, or carbon or titanium felt, which may optionally also be porous and impregnated with a chlorine-binding compound, such as polypyrrole, and a suitable binder, for example. If any are present, the flow spacer sheet(s) 49 comprise an electrically insulating material permeable to brine, including plastic meshes, such as PTFE mesh, for example. The current collector sheets 48, 52 comprise a material permeable to brine with good electrical conductivity, such as steel, aluminum, copper, and nickel meshes.

[0020] The broad arrows in Fig. 1 indicate one possible direction of flow of brine through the stack 67 of sheets of electrode materials from A to B, although in use, the direction of flow indicated in Fig. 1 may also be reversed from B to A. Fig. 2 schematically shows a plurality of microscopic lithium-binding particles 100 with which the capture electrode sheets 47 are impregnated. When brine flows through the capture electrode sheets 47, lithium ions 101 are intercalated into the lithium-binding particles 100 with a time constant on the order of less than a second. Lithium ions do not accumulate between the lithium-binding particles 100 in the manner indicated in Fig. 2 by the dashed box 102, so that the resistance to flow of brine through the capture electrode sheets 47 is not increased thereby.

[0021] As shown in Fig. 3, the stack 67 of sheets is wound in a spiral onto a mandrel 53, both of which are contained within a concentric housing 10. Although the sheets of the stack 67 are of millimeter or sub-millimeter thickness, they are also very long, so that once wound, the resulting spiral cylinder has many layers. When brine is flowing through the stack 67 of sheets in the direction indicated in Fig. 1, brine flows from a flow channel 77 inside the housing 10 through the stack 67 of sheets towards the central axis of the mandrel 53. The latter is provided throughout with flow holes, not visible in Fig. 3, so that the brine may emerge from the center of the mandrel 53 in the direction indicated in Fig. 3 by the broad arrow B. The total pressure drop across the stack 67 of sheets once wound into a cylinder is generally less than about 2 bar, and a flow rate of more than about 200 liters of brine per m 2< per bar per hour may be achieved. Returning to Fig. 1, after having been wound into a spiral, each end of the stack 67 of sheets of electrode materials is sealed by a respective end seal 72, 74 to prevent lateral outflow of brine from stack 67. In the prior art, electrical contacts were made to the current collector sheets 48, 52 by respective current collector tabs 55a, 55b, in the manner shown in Fig. 3. However, according to the present invention, the current collector sheets 48, 52 are instead each provided with respective electrical contacts which protrude through respective ones of the end seals 72, 74 as schematically shown in Fig. 1 and as will be described further below.

[0022] Fig. 4 schematically shows an embodiment of an electrical circuit established between the capture electrode sheets 47 and the counter electrode sheets 51 via their respective current collector sheets 48, 52. According to the invention, a plurality of electrical contacts, which are represented in Fig. 4 by black circles, are provided at multiple locations along the edges of each respective one of the current collector sheets 48, 52, so that the separation, s, between adjacent electrical contacts along one of the sheets 48, 52 is generally less than about 1 m. Although the electrical contacts may be placed at regular intervals, for convenience, they may also be placed at irregular intervals in the manner shown in Fig. 4, so that the separation, s, is variable. This is so that when the sheets are wound into a spiral, as described above, the electrical contacts may be arranged in a manner which enables their mutual connection. In Fig. 4, the area of the sheets designated by reference numeral 103 represents the area per electrical contact. The electrical contacts are located so that the current density is generally not greater than about 1 A cm -2< . The potential difference, V, across the sheets is generally less than about 1.2 V. The electrical contacts and the rest of the circuit may comprise copper conductors of a conventional type.

[0023] Fig. 5 schematically shows part of a first embodiment of a filter cartridge 1. As may be seen in Fig. 5, multiple layers of the sheet stack 67 are wound onto a mandrel 53 within a cartridge housing 10, although for ease of representation, the multiple layers of the stack 67 of sheets of the resulting spiral cylinder are shown greatly magnified, so that what, in fact, are many layers are represented in Fig. 5 by just three. A plurality of flow spacers 90 permits a flow of brine entering the filter cartridge 1 via an inlet located at A to flow through the sheet stack 67 and exit via an outlet located at B, as indicated in Fig. 5 by the broad arrows, although as mentioned previously, in use, the direction of flow may also be reversed. Parts of the filter cartridge 1 perfused by brine as a result are represented in Fig. 5 by stippling. Grey circles represent the locations of seals and black circles represent possible locations for attaching electrical contacts, as in Fig. 4. The plurality of capture electrode current collector sheets 48a, 48b, 48c, ... 48x and the plurality of counter electrode current collector sheets 52a, 52b, 52c, ... 52x may each be respectively connected to respective common current connectors of opposite polarity exterior to the filter cartridge 1, for example.

[0024] Fig. 6 schematically shows part of a second embodiment of a filter cartridge 1 mounted inside a cartridge container 80, only part of which is also shown in Fig. 6. The diagrammatic conventions used in Fig. 6 to represent the locations of seals and electrical contacts, and parts of the filter cartridge 1 perfused by brine, are the same as in Fig. 5 and like components are represented by the same reference numerals. However, as may be seen by comparing Fig. 6 with Fig. 5, the filter cartridge 1 in this second embodiment comprises respective endcaps 3, 12, so that the locations of the electrical contacts are enclosed between the respective endcaps 3, 12 and the respective end seals 72, 74 of the sheet stack 67, within parts of the filter cartridge 1 which as a result, are not perfused by brine. The electrical contacts to the capture electrode current collector sheets 48 are mutually connected to each other and to a capture electrode current connector 25 of the filter cartridge 1. Similarly, the electrical contacts to the counter electrode current collector sheets 52 are mutually connected to each other and to a counter electrode current connector 26 of the filter cartridge 1. The capture electrode current connector 25 mates with a corresponding mating assembly 82 of the cartridge container 80, and similarly, the counter electrode current connector 26 mates with a corresponding mating assembly 83 of the cartridge container 80, so that an electrical circuit may be established through the sheet stack 67 from outside the cartridge container 80.

[0025] How these parts of the filter cartridge 1 in the embodiment of Fig. 6 are assembled will now be described with reference to Figs. 7A to 8C, wherein electrical contacts are again represented by black circles. Fig. 7A therefore schematically shows a longitudinal section through part of the sheet stack 67 rolled into a spiral cylinder, with electrical contacts established to one of the capture electrode current collector 48 or the counter electrode current collector 52, depending on which of these is selected for connection on a respective end of the spiral cylinder. Fig. 7B shows an end-on view of the same spiral cylinder with the electrical contacts established to one of the capture electrode current collector 48 or the counter electrode current collector 52. A respective end seal 72, 74 is then mounted on the end of the spiral cylinder with the electrical contacts protruding therethrough, as shown in Fig. 7C. Taking the end of the spiral cylinder with electrical contacts to the counter electrode current collector 52 as an example, these electrical contacts are mutually connected to each other and to a common current connector 59, as shown in Fig. 8A. Fig. 8A therefore schematically shows a longitudinal section through part of the sheet stack 67 rolled into a spiral with an end seal 74 and a common current connector 59 mounted thereon. Thereafter, the common current connector 59 is inserted into a receiving portion of the counter electrode current connector 26 located on the endcap 12 of the filter cartridge 1, as shown in Fig. 8B. Fig. 8C provides a close-up view of part of the same. A similar procedure is used to connect the capture electrode current collector 48 to the capture electrode current connector 25 on the opposite end of the filter cartridge 1.

[0026] Fig. 9A provides an exterior view of the filter cartridge 1, which has a generally cylindrical form with endcaps 3, 12 and the capture electrode current connector 25 and the counter electrode current connector 26 located on opposite ones of the endcaps 3, 12 as a result. In this embodiment, the outlet 13 of the filter cartridge 1, which has male profile, is located on the same end of the filter cartridge 1 as the counter electrode current connector 26, and an inlet, which has a female profile and which is therefore not visible in Fig. 9A, is located on the same end of the filter cartridge 1 as the capture electrode current connector 25. In other possible embodiments, however, depending on the direction of flow of brine through the filter cartridge 1, the locations of the inlet and outlet may be reversed, and the profiles of the inlet and outlet may also be varied independently of that.

[0027] Fig. 9B schematically shows the embodiment of the filter cartridge 1 of Fig. 9A mounted in a cartridge container 80. The cartridge container 80 generally has the form of a hollow cylinder open at one end, the open end of which may be sealed by an endcap 81. When mounted in the cartridge container 80, the capture electrode current connector 25 mates with the corresponding mating assembly 82 of the cartridge container 80, and the counter electrode current connector 26 mates with the corresponding mating assembly 83 of the cartridge container 80, as described above. These mating assemblies 82, 83 are in turn respectively connected electrically to corresponding current connectors 85, 86 mounted on an exterior of the cartridge container 80, so that an electrical circuit may be established through the filter cartridge 1 from outside the cartridge container 80. The outlet 13 of the filter cartridge 1 protrudes through a hole in the closed end of the cartridge container 80 and the endcap 81 of the cartridge container 80 comprises an inlet 2, which allows brine to flow into the cartridge container 80 and therefore into the female inlet of the filter cartridge 1.

[0028] Once a filter cartridge 1 has become loaded with lithium ions, it may be demounted from the cartridge container 80 and replaced with a new, similar filter cartridge 1' using the procedure shown in Figs. 10A and 10B. Firstly, the endcap 81 of the cartridge container 80 is removed. The filter cartridge 1 loaded with lithium ions is then withdrawn from the cartridge container 80 in the direction indicated by the arrows labelled C in Fig. 10A, before the new filter cartridge 1' in inserted into the same cartridge container 80 in the direction indicated by the arrows labelled D in Fig. 10B and the endcap 81 is replaced in the manner indicated by the arrow labelled E in Fig. 10B.

[0029] How the electrical contacts to respective ones of the capture electrode 47 and counter electrode 51 are made will now be described with reference to Figs. 11A to 12C. Fig. 11A therefore schematically shows either the capture electrode 47 and the capture electrode current collector 48 or the counter electrode 51 and the counter electrode current collector 52, which are arranged such that the respective current collector sheet 48, 52 extends beyond the edge of the respective electrode sheet 47, 51. The respective current collector 48, 52 is then immersed in a dip 104, so that a layer of insulating sealant 104a is formed on the respective current collector 48, 52, as shown in Fig. 11B. The same is then immersed to a lesser depth in an etch bath 105 to reveal a portion of the respective current collector 48, 52 again, but also to leave a portion of unetched insulating sealant 104b thereon, as shown in Fig. 11C. Thus a respective end seal 72, 74 may be provided to the sheet stack 67, leaving a portion of the respective current collector 48, 52 protruding beyond the respective end seal 72, 74 for establishment of an electrical contact thereto.

[0030] Figs. 12A and 12B schematically show two different possible embodiments of how electrical contacts may be established to an electrode current collector. As described above in relation to Fig. 4, the plurality of electrical contacts to a respective one of the current collectors 48, 52 are each located at different distances along the edge of the current collector sheet 48, 52, so that when the sheet stack 67 is rolled up into a spiral cylinder, the electrical contacts are aligned with each other along a radius of the cylinder. In other words, as the circumference of the cylinder increases as it is wound on to the mandrel 53, the separation, s, between adjacent ones of the electrical connections increases to compensate for the increasing size of the circumference. This therefore allows a single, rectilinear common current connector 59 to be electrically connected to all of the electrical contacts at once. Fig. 12A shows an embodiment in which the electrical contacts are positioned along a single radius of the spiral cylinder. Fig. 12B shows an alternative embodiment in which the electrical contacts are positioned along a diameter of the spiral cylinder, connected by a common current connector 59 comprising two rectilinear portions connected to each other by an arcuate portion so as not to obstruct the outflow of brine from the center of the spirally wound sheet stack 67.

[0031] Fig. 13A schematically shows an embodiment of an apparatus 110 comprising a plurality of cartridge containers 80a, 80b, 80c of the type shown in Figs. 9B to 10B connected in series with each other. Each of the cartridge containers 80a, 80b, 80c contain a respective filter cartridge 1 of the type shown in Fig. 9A. The outlets 13a, 13b of respective ones of the cartridge containers 80a, 80b are connected in fluid communication with respective ones of the inlets 2b, 2c, so that brine may flow from A to B through the plurality of cartridge containers 80a, 80b, 80c in the manner indicated by the broad arrows in Fig. 13A. The capture electrode current connectors 85a, 85b, 85c of respective ones of the cartridge containers 80a, 80b, 80c are electrically connected to a negative voltage rail 112 and the corresponding counter electrode current connectors 86a, 86b, 86c are electrically connected to a positive voltage rail 111 as shown. Thus the percentage amount of lithium recovered from the brine flowing from A to B may be increased as it passes through successive ones of the filter cartridges 1.

[0032] Fig. 13B schematically shows an embodiment of an apparatus 113 comprising a plurality of cartridge containers 80a, 80b, ... 80i; 80j, 80k, ... 80r; 80s, 80t, ... 80z of the type shown in Figs. 9B to 10B connected in series and in parallel with each other via pipework 114. As in Fig. 13 A, each of the cartridge containers of Fig. 13B also contains a respective filter cartridge 1 of the type shown in Fig. 9A. The plurality of cartridge containers shown in Fig. 13B are supplied with brine by a pump P. If, for example, the pump P can deliver 50 bars of pressure, then the total pressure drop across the plurality of filter cartridges 1 contained within the cartridge containers in this embodiment should not exceed 50 bars either, due to the pipe and sealing requirements of the filter cartridges 1 and of the connecting pipework 114. This in turn determines the number of filter cartridges 1 which can be connected in series and in parallel. Whereas connecting a plurality of filter cartridges 1 in series with each other, as in Fig. 13A, increases the percentage amount of lithium which can be recovered from brine flowing through successive ones of the filter cartridges in series, connecting a plurality of filter cartridges 1 in parallel with each other, as in Fig. 13B, instead increases the volume of brine which may be processed by them per unit time. Although not shown in Fig. 13B for clarity of illustration, the plurality of cartridge containers of Fig. 13B are also electrically connected to a power supply in a similar manner to that described above in relation to Fig. 13A.

[0033] Figs. 14A and 14B are photos of desalination plants, which give some idea of how an apparatus comprising a plurality of filter cartridges 1 may be connected in series and in parallel with each other in practice, as described above in relation to Fig. 13B, although the construction of each module of the desalination plants differs considerably in several respects from each filter cartridge assembly in the apparatus of the invention.

[0034] In summary, therefore, the present invention provides a filter cartridge for extracting lithium from lithium-containing brine, a filter cartridge assembly comprising a cartridge container which contains such a filter cartridge, and an apparatus comprising a plurality of such filter cartridge assemblies. The filter cartridge at least comprises a capture electrode for capturing lithium ions from the brine, a capture electrode current collector for imparting a negative charge to the capture electrode, a counter electrode, and a counter electrode current collector for imparting a positive charge to the counter electrode. Each of the capture electrode, the capture electrode current collector, the counter electrode and the counter electrode current collector comprises a brine-permeable sheet. The sheets are each in the form of a long strip, so that each sheet has an opposing pair of long edges and an opposing pair of short edges. The sheets are stacked in layers forming a stack which is wound into a spiral cylinder, so that the opposing pairs of long edges of all the sheets form opposite ends of the cylinder, allowing the lithium-containing brine to flow radially through the cylinder. At least one of the capture electrode current collector and the counter electrode current collector are provided with a respective plurality of electrical contacts along a respective one of the opposing pair of long edges of the respective current collector, and the plurality of electrical contacts are electrically connected to each other and to a common electrical current connector. The apparatus comprises a plurality of the filter cartridge assemblies arranged in series and / or parallel with each other and sharing a common electrical supply.List of Reference Numerals

[0035] 85Capture electrode current connector of cartridge container1Filter cartridge2Inlet of cartridge housing86Counter electrode current connector of cartridge container3Cartridge housing endcap10Cartridge housing90Flow spacers12Cartridge housing counter endcap100Lithium-binding particles of capture electrode13Outlet of filter cartridge25Capture electrode current connector of filter cartridge101Lithium ion102Accumulation of lithium ions26Counter electrode current connector of filter cartridge103Electrode area per contact104Dip47Capture electrode104aLayer of insulating sealant48Capture electrode current collector104bUnetched insulating sealant49Flow spacer105Etch51Counter electrode110Series of filter cartridges52Counter electrode current collector111Positive voltage rail53Mandrel112Negative voltage rail55Current collector tabs113Apparatus with filter cartridges arranged in series and in parallel59Current connector67Stack of electrode sheet materials114Pipework72End seal of stackPPump74Counter end seal of stack77Flow channel80Cartridge container81Cartridge container endcap82Mating assembly of cartridge container for capture electrode current connector of filter cartridge83Mating assembly of cartridge container for counter electrode current connector of filter cartridge

Examples

Embodiment Construction

[0018]Fig. 1 schematically shows an embodiment of a stack 67 of sheets of electrode materials. In this embodiment, the stack 67 comprises the following sheets of material stacked in order:

a. Capture electrode sheet 47 b. Capture electrode current collector sheet 48 c. Capture electrode sheet 47 d. Flow spacer sheet 49 e. Counter electrode sheet 51 f. Counter electrode current collector sheet 52 g. Counter electrode sheet 51 h. Flow spacer sheet 49

[0019]Each of these sheets is of millimeter or sub-millimeter thickness, so that Fig. 1 is greatly enlarged in scale. In other possible embodiments, one or both of the flow spacer sheets 49 may be omitted from the sheet stack 67 shown in Fig. 1. The capture electrode sheets 47 comprise a porous material permeable to brine, with high internal surface area and good electrical conductivity, such as silver mesh, or carbon or titanium felt, which is impregnated with a lithium-binding compound, such as lithium manganese oxide (LMO), sodium mang...

Claims

1. A filter cartridge (1) for extracting lithium from lithium-containing brine, at least comprising: a capture electrode (47) for capturing lithium ions from the brine; a capture electrode current collector (48) for imparting a negative charge to the capture electrode (47); a counter electrode (51); and a counter electrode current collector (52) for imparting a positive charge to the counter electrode (51); wherein: each of the capture electrode (47), the capture electrode current collector (48), the counter electrode (51) and the counter electrode current collector (52) comprises a brine-permeable sheet, each sheet having an opposing pair of long edges and an opposing pair of short edges and being stacked in layers forming a stack (67) wound into a spiral cylinder, such that the opposing pairs of long edges of all the sheets form opposite ends of the cylinder allowing the lithium-containing brine to flow radially therethrough; at least one of the capture electrode current collector (48) and the counter electrode current collector (52) are provided with a respective plurality of electrical contacts along a respective one of the opposing pair of long edges of the respective current collector (48, 52); and the plurality of electrical contacts are electrically connected to each other and to a common electrical current connector (59).

2. A filter cartridge (1) according to claim 1, wherein the capture electrode current collector (48) is provided with a first plurality of electrical contacts along a first one of the opposing pair of long edges of the capture electrode current collector (48), and the counter electrode current collector (52) is provided with a second plurality of electrical contacts along a second one of the opposing pair of long edges of the counter electrode current collector (52), which are opposite to the first plurality of electrical contacts.

3. A filter cartridge (1) according to claim 1 or claim 2, wherein a separation (s) between adjacent ones of the respective plurality of electrical contacts along the respective long edge of the respective current collector (48, 52) is non-uniform and is arranged such that when the stack (67) is wound into a spiral cylinder, the respective plurality of electrical contacts are aligned with each other along a radius of the cylinder.

4. A filter cartridge (1) according to any one of the preceding claims, wherein a current density per unit area of the stack (67) supplied by each one of the electrical contacts is not greater than 1 A cm-2.

5. A filter cartridge (1) according to any one of the preceding claims, wherein at least one of the capture electrode current collector (48) and the counter electrode current collector (52) is wider along the short edge thereof than the capture electrode (47) or the counter electrode (51), respectively, is along the short edge thereof, and the respective one of the capture electrode current collector (48) and the counter electrode current collector (52) comprises a strip of electrically insulating sealant (104b) located inside and spaced apart from an exposed long edge thereof.

6. A filter cartridge (1) according to any one of the preceding claims, wherein the opposite ends of the cylinder are each provided with a respective end seal (72, 74) sealing against the flow of brine therethrough, and through which end seal (72, 74) the electrical contacts protrude.

7. A filter cartridge (1) according to claim 6, further comprising a respective endcap (3, 12) enclosing the electrical contacts between the respective end seal (72, 74) and the respective endcap (3, 12) within a part of the filter cartridge (1), which, during use of the cartridge, is not perfused by brine.

8. A filter cartridge (1) according to claim 7, wherein the common electrical current connector (59) is in electrical contact with a current connector (25, 26) on an exterior surface of the respective endcap (3, 12).

9. A filter cartridge assembly comprising a filter cartridge (1) according to claim 8 and a cartridge container (80) for containing the filter cartridge (1) therein, wherein the cartridge container (80) comprises: a first mating assembly (82) for electrical connection with the capture electrode current connector (25) of the filter cartridge (1); a second mating assembly (83) for electrical connection with the counter electrode current connector (26) of the filter cartridge (1); a capture electrode current connector (85) on an exterior of the cartridge container (80) in electrical connection with the first mating assembly (82); a counter electrode current connector (86) on the exterior of the cartridge container (80) in electrical connection with the second mating assembly (82); an inlet (2) for supplying lithium-containing brine to the stack (67) of the filter cartridge (1) therein; and an outlet (13) for lithium-depleted brine from the stack (67) of the filter cartridge (1).

10. A filter cartridge assembly according to claim 9, wherein the cartridge container (80) is adapted and arranged to allow the filter cartridge (1) to be removed from within the cartridge container (80) when loaded with lithium and replaced with a like filter cartridge (1') containing less lithium.

11. An apparatus (110) comprising a plurality of filter cartridge assemblies according to claim 9 or claim 10 arranged in series with each other and sharing a common electrical supply.

12. An apparatus (113) comprising a plurality of filter cartridge assemblies according to any one of claims 9 to 11 arranged in parallel with each other and sharing a common electrical supply.

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