WO2023108215A1

WO2023108215A1 - Porous interlayer

Info

Publication number: WO2023108215A1
Application number: PCT/AU2022/051507
Authority: WO
Inventors: Ehsan GHASEMIESTAHBANATI; Declan Mcnamara; Areeb SHEHZAD; Mahdokht SHAIBANI; Mainak MAJUMDER; Matthew Hill
Original assignee: Monash University
Priority date: 2021-12-14
Filing date: 2022-12-14
Publication date: 2023-06-22

Abstract

The present disclosure generally relates to an interlayer for an electrochemical cell. The present disclosure also relates to porous interlayers comprising a carbon material and porous particles, and to a process for preparing the interlayers. The present disclosure also relates to energy storage devices comprising the interlayers and to use of the interlayers in energy storage devices, in particular lithium-sulfur (Li-S) batteries or vanadium redox flow batteries (VRFBs).

Description

POROUS INTERLAYER

FIELD

BACKGROUND

The reduction of sulfur in Li-S batteries involves a complex multistep reaction and the products of these reactions, so-called “higher order polysulfides”, are highly soluble in the electrolyte. The liberation of these species from the sulfur cathode to the electrolyte and their migration through the separator to the lithium anode and back again is mainly responsible for the low durability of Li-S batteries. The competition between the reactions induced by the charge/discharge current and by the side reactions originating from diffusion of high order poly sulfides between anode and cathode can be considered as a type of serious self-discharge, which results in permanent loss of electrode active material, degradation of discharge capacity and low Coulombic efficiency. A number of strategies have been employed to mitigate the liberation of polysulfides in the electrolyte, including (1) confmement/trapping approaches by incorporating functional host materials into a composite sulfur cathode; (2) electrolyte modification approaches by changing the composition and/or concentration of the electrolyte, or by using additives; and (3) multifunctional membrane separators and/or interlayers with permselectivity/localizing abilities.

Among these three main strategies, producing composite cathodes by immobilising sulfur particles within various host materials has been the most widely used, while the utilisation of permselective membrane separators has received very little attention. Providing a physical barrier between the two electrodes to prevent electrical short circuit while enabling ionic transport, the separator, is a critical component in liquid electrolyte batteries. Typically, the separators are not involved in the battery reactions; however, their structural properties can play a major role in determining a range of important performance metrics such as energy and power characteristics. Due to the ionic nature of the polysulfides and their narrow size distribution, adding a permselective membrane and/or interlayer to the configuration of a Li-S battery may retard the migration of these negatively-charged sub-nanometre size poly sulfide species. To this end, several ion-sieving membrane designs based on the negative charge of various functional groups and/or a narrow distribution of subnanometre pores have been examined as polysulfide-blocking layers in the configuration of Li-S batteries, amongst them, Nafion, graphene oxide (GO), and microporous polymer membrane have received the most attention. While Nafion and GO membranes provide a strong ionic shield for the polysulfide species, they impose too great a restriction on Li ion movement due to their tortuous pore structure, which, in turn, lowers the high current response of the battery.

Vanadium crossover hinders widespread commercial adoption of Vanadium Redox Flow Batteries (VRFBs). In VRFBs, two redox couples (Vanadium ions) are dissolved as negative and positive electrolytes, which are separately stored in two external tanks and continuously pumped into the redox reaction centre. Unlike a conventional flow battery setup, there is no gap between the membrane and electrodes in a zero-gap cell architecture which results in lower ohmic resistance. In addition, in this architecture the flow field channel distributes electrolyte on to the porous electrodes in a uniform manner to minimize pressure drop and concentration polarization which are common issues of conventional architectures. The membrane/interlayer, which is usually located at the centre of each cell stack, separates half-cell electrolytes. More importantly, the membrane selectively transfers protons over vanadium, thereby maintaining neutrality of the electrolytes while preventing vanadium crossover between the half-cells. Holding such a key role, the membrane has been the subject of research in the field, aiming at more cost-effective, reliable, and longer-lasting energy storage systems for grid-scale applications.

In general, there are three types of membranes with the intended principal function as a VRFB separator. Anion exchange membranes (AEMs) to repel vanadium, cation exchange membranes (CEMs) to conduct protons, and porous membranes to sieve the ions. Nation® (manufactured by DuPont) as a perfluorinated cation exchange membrane formed by incorporating perfluorovinyl ether groups terminated with hydrophilic sulfonate groups onto a hydrophobic PTFE backbone, has been widely used as a separator in VRFBs due to its high proton conductivity and chemical stability in acids. However, Nafion still has shortcomings such as fast crossover of Vanadium ions (low proton/Vanadium selectivity), proton conductance deterioration at low humidity or high temperature, and high cost limiting this promising battery technology from widespread commercialization. Efforts to modify Nafion have been particularly focused on tailoring the surface structure and chemistry of this membrane, for example by applying a perm-selective barrier layer on Nafion. To this end, materials such as graphene oxide (GO), conductive polymers, and polyelectrolytes have demonstrated some success in enhancing the ion selectivity when coated on Nafion. Another widely used approach is to introduce inorganic particles into the Nafion to prevent its swelling in the aqueous medium and the resultant formation of interconnected channels of hydrophilic clusters, which in turn leads to the unwanted migration of Vanadium ions. To this end, materials such as TiCh, CNT, and M0S2 have assisted with preventing the swelling when used as fillers in Nafion. While modified Nafion membranes have been contemplated, it imposes too great a restriction on V ion movement due to its tortuous pore structure, which, in turn, lowers the high current response of the flow battery. Polymeric microporous membranes have also been investigated as porous membranes to sieve the ions, i.e. separation of the redox-active ions by pore size exclusion. Polymers such as polyacrylonitrile (PAN), polysulfone (PSF), and polyvinylidene fluoride (PVDF) membranes have shown sized based separation of vanadium and proton ions. However, they suffer from low proton conductivity.

Membranes in redox flow systems operate at lower temperature, but are required to be highly selective to avoid cross-over of species between anode and cathode compartments.

Therefore, there is a need to provide new and alternative permselective membranes and/or interlayers that can retard the crossover of higher order polysulphide species while enabling the free transport of Li ions over extended cycles. There is also a need to provide new and alternative permselective membranes and/or interlayers that can selectively transfer protons over vanadium, thereby maintaining neutrality of the electrolytes while reducing or preventing vanadium crossover between the half-cells.

SUMMARY

The present disclosure provides porous interlayers comprising a carbon material and a plurality of porous particles. The present disclosure also provides interlayers that may be capable of controlling the transport of ions, in particular lithium ions or vanadium ions, and their application to electrochemistry.

In one aspect, there is provided an interlayer for an electrochemical cell comprising a carbon material and a plurality of porous aromatic framework particles, wherein the porous aromatic framework particles are sulfonated porous aromatic framework particles (SPAF).

In another aspect, there is provided an interlayer consisting of a carbon material, a plurality of porous aromatic framework (PAF) particles, wherein the porous aromatic framework particles are sulfonated porous aromatic framework particles (SPAF), optionally one or more binders, optionally one or more polymers, and optionally one or more additives.

In another aspect, there is provided an interlayer consisting of a plurality of porous aromatic framework (PAF) particles, wherein the porous aromatic framework particles are sulfonated porous aromatic framework particles (SPAF), optionally one or more binders, optionally one or more polymers, and optionally one or more additives.

In another aspect, there is provided an electrochemical cell comprising: a negative electrode; a positive electrode; at least one electrolyte; an interlayer as defined herein; and an optional separator.

In another aspect, there is provided an electrochemical cell comprising: an anode; a cathode; at least one electrolyte comprising one or more electrolyte solvents; an interlayer; and an optional separator, wherein the interlayer comprises a carbon material, a plurality of sulfonated porous aromatic framework (PAF) particles and one or more polymers according to any embodiments or examples thereof as described herein. In yet another aspect, there is provided an electrochemical cell comprising: an anode; a cathode; at least one electrolyte comprising one or more electrolyte solvents; an interlayer; and an optional separator, wherein the interlayer is at least partially coated on the anode and comprises a plurality of sulfonated porous aromatic framework (PAF) particles and one or more polymers according to any embodiments or examples thereof as described herein.

Alternatively, in another aspect, there is provided an electrochemical cell comprising: a negative and positive electrode; at least one electrolyte; an interlayer; and an optional separator, wherein the at least one electrolyte comprises an anolyte and a catholyte, and the interlayer comprises a plurality of sulfonated porous aromatic framework (PAF) particles and one or more polymers according to any embodiments or examples thereof as described herein.

In another aspect, there is provided a method for improving cycling stability of a battery having an anode comprising lithium metal and a cathode comprising elemental sulfur, at least one electrolyte, and an interlayer, wherein the interlayer is defined by any one of the embodiments or examples as described herein.

In another aspect, there is provided a method for improving cycling stability of a battery having an anode comprising lithium metal and a cathode comprising elemental sulfur, at least one electrolyte, and an interlayer, wherein the interlayer is at least partially coated on the anode and comprises a plurality of sulfonated porous aromatic framework (PAF) particles and one or more polymers according to any embodiments or examples thereof as described herein.

Alternatively, in another aspect, there is provided a method for improving cycling stability of a redox flow battery having a negative and positive electrode; an anolyte; a catholyte; and an interlayer, wherein the interlayer comprises a plurality of sulfonated porous aromatic framework (PAF) particles and one or more polymers according to any embodiments or examples thereof as described herein.

In another aspect, there is provided a use of an interlayer, as defined by any one of the embodiments or examples as described herein, as an interlayer in an electrochemical cell. The electrochemical cell may be an energy storage device, for example a batery, preferably a secondary batery. The batery may be a lithium-sulfur batery or a vanadium redox flow batery.

In another aspect, there is provided a process for preparing an interlayer for an electrochemical cell, comprising the steps of: (i) providing a carbon material and porous aromatic framework particles in a solvent system for a predetermined time to produce a solution thereof, wherein the porous aromatic framework particles are sulfonated porous aromatic framework particles (SPAF); and (ii) casting a film of the solution onto a substrate to provide a wet interlayer supported on the substrate. The process may further comprise the steps of: (a) preparing porous aromatic framework particles in a solvent system; (b) converting the porous aromatic framework particles to sulfonated porous aromatic framework particles in a solvent system; (i) providing a carbon material and sulfonated porous aromatic framework particles in a solvent system for a predetermined time to produce a solution; and (ii) casting a film of the solution onto a substrate to provide a wet interlayer supported on the substrate.

In another aspect, there is provided a process for preparing an interlayer for an electrochemical cell, comprising the steps of: (i) providing sulfonated porous aromatic framework particles in a solvent system for a predetermined time to produce a solution thereof; and (ii) casting a film of the solution onto a substrate to provide a wet interlayer supported on the substrate. The process may further comprise the steps of: (a) preparing porous aromatic framework particles in a solvent system; (b) converting the porous aromatic framework particles to sulfonated porous aromatic framework particles in a solvent system; (i) providing sulfonated porous aromatic framework particles in a solvent system for a predetermined time to produce a solution; and (ii) casting a film of the solution onto a substrate to provide a wet interlayer supported on the substrate.

In another aspect there is provided a process for assembling an electrochemical cell, whereby the process comprises the following steps: preparing an interlayer as defined by the process according to any embodiments or examples thereof as described herein, wherein the interlayer comprises a carbon material and a plurality of porous particles, wherein the porous particles are porous aromatic framework for example, sulfonated porous aromatic framework (SPAF) particles, , according to any embodiments or examples thereof as described herein; and assembling the interlayer into an electrochemical cell.

In another aspect, there is provided a process for assembling an electrochemical cell, whereby the process comprises the following steps: preparing an interlayer as defined by the process according to any embodiments or examples thereof as described herein, wherein the interlayer comprises a plurality of sulfonated porous aromatic framework (PAF) particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives according to any embodiments or examples thereof as described herein; and assembling the interlayer into an electrochemical cell.

In an embodiment, the interlayer of the above method or use can be provided by an interlayer according to any aspects, embodiments or examples thereof as described herein.

Any embodiment herein shall be taken to apply mutatis mutandis to any other embodiment unless specifically stated otherwise.

The present disclosure is not to be limited in scope by the specific embodiments described herein, which are intended for the purpose of exemplification only. Functionally-equivalent products, compositions and methods are clearly within the scope of the disclosure, as described herein.

Throughout this specification, unless specifically stated otherwise or the context requires otherwise, reference to a single step, composition of matter, group of steps or group of compositions of matter shall be taken to encompass one and a plurality (i.e. one or more) of those steps, compositions of matter, groups of steps or groups of compositions of matter.

BRIEF DESCRIPTION OF DRAWINGS

Preferred embodiments of the present disclosure will be further described and illustrated, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a structural model of a porous aromatic framework. Figure 2 is a structural model of a sulfonated porous aromatic framework.

Figure 3 is a graph showing characterization of the porous structure of a porous aromatic framework (PAF-1) particle: (a) shows N2 adsorption isotherm at 77K, and (b) shows pore-size distribution of PAF-1 based on DFT calculations from the related isotherm.

Figure 4 is a graph showing characterization of the porous structure of sulfonated porous aromatic framework (SPAF): (a) shows N2 adsorption isotherm at 77K, and (b) shows pore-size distribution and surface area of SPAF.

Figure 5 is a graph showing (a) characteristic wavelengths of poly sulfide species Li2Se and its absorption by sulfonated porous aromatic framework (SPAF), and (b) normalized polysulfide absorption vs logarithmic time plot for Li2Se transport through sulfonated aromatic framework (SPAF), black pearl (BP) and sulfonated black pearl (SBP).

Figure 6 is a graph showing ¹³C MAS onepulse NMR spectrum of PAF-1, SPAF, SPAF-M and SPAF-L, for quantitative analysis.

Figure 7 is a schematic of hybrid ionic/conductive interlayer incorporating sulfonated porous aromatic framework (SPAF), providing fast lithium diffusion while suppressing polysulfide shuttling. SEM image of a) PAF particles after functionalization (SPAF), b) top surface and c) cross section of the hybrid interlayer, which showed a uniform distribution of materials and formation of a ~ 10 pm thick layer on top of the glass fiber (GF), d-f) Elemental mapping of the hybrid interlayer that confirmed the presence and homogenous distribution of SPAF and BP.

Figure 8 is a graph that shows (a) long-term cycling performance of Li-S batteries with SPAF-BP and BP interlayers at 0.2 °C rate over 500 cycles, b) rate capacity of the SPAF-BP and BP batteries, and c) capacity retention of SPAF-BP battery with higher sulfur loading at 0. 1 C rate providing high areal capacity of 7.3 mAh cm'².

Figure 9 is a graph showing (a) lithium ion transference number for SPAF-BP and SBP using current time (i-t) curve data obtained from potentiostatic polarization process; (b) electrochemical impedance spectra of Li-S batteries a) before and b) after cycling using SBP and SPAF-BP interlayers; CV profiles with SPAF-BP (c) and SBP (d) at different scan rates to calculate lithium-ion diffusion coefficient.

Figure 10 is a series of Electron Dispersive X-ray (EDX) images displaying the composition of the coated layer on uncycled lithium foil where (a) shows the backscattered electron image of the cross-section, (b) shows the EDX mapping of silicon in the cross-section of the coating matrix, and (c) shows the EDX mapping of carbon in the cross-section of the coating matrix.

Figure 11 is a series of SEM images showing the thickness of the coated layer, and the strong adhesion between the lithium foil and the coated layer, (a) and (b) show a cross section of the foil and flexible layer that may be tuned between >1 pm and 10 pm thick, (c) shows a cross section of the homogeneous layer, (d) and (e) show the homogeneous surface of the coated layer on lithium.

Figure 12 is a series of SEM images displaying the presence and dispersion of SPAF in the coated matrix on lithium foil, (a) shows the backscattered electron image of the cross-section, (b) shows the Electron Dispersive X-ray mapping of sulfur in the coating matrix, and (c) shows an overlay of the BSE and EDX mapping to correlate the particulates in the matrix with high sulfur content SPAF.

Figure 13 is a graph showing cycling data for the 5 % SPAF 95% PTMSP coated lithium foil’s cycling performance at 0.1C and 0.5C for 50 cycles each.

Figure 14 presents two lithium anodes on steel current collectors that have been removed from cells after cycling. Figures 14a) and 14d) are composite SEM images. Figure 14b) is an enlarged backscatter SEM image. Figures 14c) and 14e) are false contrast images of Figures 14a) and 14d). The contrast is used to indicate differences in morphology /phase. Figures 14a), 14b), and 14c) are of the control cell after 275 cycles. Figures 14d), and 14e) are of the PTMSP@Li cell after 275 cycles. Figures 14c) and 14d) illustrate the substantial morphological differences between the control cell and PTMSP@Li. The control cell has a large area in the centre of the anode where high surface area morphologies can be observed (see Fig 14b) referred to as mossy Li). The lithium in these areas consists of high aspect ratio growths, and random three-dimensional appendages with high surface area-volume ratios. By contrast, the PTMSP@Li anode and current collector displays lower surface area-volume ratios, and presents flatter, smoother, and more even growths. As described above, higher SA/V growths contribute to capacity fading. The higher density of plating sites in PTMSP@Li is attributed to PTMSP’s intrinsic nanoporosity. The cycling performance for each cell can be seen below in Figure 15. The current collector of the control cell has several areas where no lithium is observed, at the edge and in the centre. The lack of lithium may be due to dead lithium formation and float-off, as illustrated in the Figure 16. The PTMSP@Li anode by contrast has substantially more Li present on its surface after extended cycling (see also Figure 17). It is believed that the PTMSP coating functions as a lithium scaffold during morphology evolution, anchoring Li and ensuring coherent, electronically conductive growths form. This unique morphology reduces the volume of dead lithium formed during cycling, improving capacity retention.

Figure 15 is graph showing cycling performance of lithium anodes coated with PSMSP compared to a control after over 250 cycles.

Figure 16 is a schematic of capacity fading mechanism and Li scaffolding.

Figure 17 is a schematic showing substantially more Li present on the surface of a current collector after extended cycling

Figure 18 is a graph showing permeability and selectivity of PAN, Nafion212, PTMSP/PAF-l-SOsH/PAN (CCMS), and PTMSP/PAN membranes, which revealed suppression of vanadium crossover and improved proton transfer through the CCMS membrane.

Figure 19 is a graph showing self-discharge/OCV decay rates of the interlayer (PTMSP/PAF-l-SOsH/PAN) and Nafion212 membrane showing nearly four-fold improvement.

Figure 20 is a graph showing capacity retention comparison at constant current density of 60 mA cm'² resulted in 45 % improvement compared to Nafion.

DETAILED DESCRIPTION

The present disclosure describes the following various non-limiting examples, which relate to investigations undertaken to identify alternative and improved interlayer compositions, and to any methods of making and use thereof. General Definitions and Terms

In the following description, reference is made to the accompanying drawings which form a part hereof, and which is shown, by way of illustration, several embodiments. It is understood that other embodiments may be utilised and structural changes may be made without departing from the scope of the present disclosure.

With regards to the definitions provided herein, unless stated otherwise, or implicit from context, the defined terms and phrases include the provided meanings. In addition, unless explicitly stated otherwise, or apparent from context, the terms and phrases below do not exclude the meaning that the term or phrase has acquired by a person skilled in the relevant art. The definitions are provided to aid in describing particular embodiments, and are not intended to limit the claimed invention, because the scope of the invention is limited only by the claims. Furthermore, unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular.

All publications discussed and/or referenced herein are incorporated herein in their entirety.

Throughout this disclosure, unless specifically stated otherwise or the context requires otherwise, reference to a single step, composition of matter, group of steps or group of compositions of matter shall be taken to encompass one and a plurality (i.e., one or more) of those steps, compositions of matter, groups of steps or groups of compositions of matter. Thus, as used herein, the singular forms “a”, “an” and “the” include plural aspects unless the context clearly dictates otherwise. For example, reference to “a” includes a single as well as two or more; reference to “an” includes a single as well as two or more; reference to “the” includes a single as well as two or more and so forth.

Those skilled in the art will appreciate that the disclosure herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the disclosure includes all such variations and modifications. The disclosure also includes all of the examples, steps, features, methods, compositions, coatings, processes, and coated substrates, referred to or indicated in this specification, individually or collectively, and any and all combinations or any two or more of said steps or features.

The term “and/or”, e.g., “X and/or Y” shall be understood to mean either “X and Y” or “X or Y” and shall be taken to provide explicit support for both meanings or for either meaning.

Unless otherwise indicated, the terms “first,” “second,” etc. are used herein merely as labels, and are not intended to impose ordinal, positional, or hierarchical requirements on the items to which these terms refer. Moreover, reference to a “second” item does not require or preclude the existence of lower-numbered item (e.g., a “first” item) and/or a higher-numbered item (e.g., a “third” item).

As used herein, the phrase “at least one of’, when used with a list of items, means different combinations of one or more of the listed items may be used and only one of the items in the list may be needed. The item may be a particular object, thing, or category. In other words, “at least one of’ means any combination of items or number of items may be used from the list, but not all of the items in the list may be required. For example, “at least one of item A, item B, and item C” may mean item A; item A and item B; item B; item A, item B, and item C; or item B and item C. In some cases, “at least one of item A, item B, and item C” may mean, for example and without limitation, two of item A, one of item B, and ten of item C; four of item B and seven of item C; or some other suitable combination.

It is to be appreciated that certain features that are, for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any subcombination.

Throughout the present specification, various aspects and components of the invention can be presented in a range format. The range format is included for convenience and should not be interpreted as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical values within that range, unless specifically indicated. For example, description of a range such as from 1 to 5 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 5, from 3 to 5 etc., as well as individual and partial numbers within the recited range, for example, 1, 2, 3, 4, 5, 5.5 and 6, unless where integers are required or implicit from context. This applies regardless of the breadth of the disclosed range. Where specific values are required, these will be indicated in the specification.

Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Throughout this specification, the term “consisting essentially of’ is intended to exclude elements which would materially affect the properties of the claimed composition.

The terms “comprising”, “comprise” and “comprises” herein are intended to be optionally substitutable with the terms “consisting essentially of’, “consist essentially of’, “consists essentially of’, “consisting of’, “consist of’ and “consists of’, respectively, in every instance.

Herein the term “about” encompasses a 10% tolerance in any value or values connected to the term.

Herein the term “weight %” may be abbreviated to as “wt%”.

Herein the term “microporous” may be a particle having pores with an average size of less than about 2 nm (micropores).

Herein the term “mesoporous” may be a particle having pores with an average size in the range of about 2-50 nm (mesopores).

Herein the term “macroporous” may be a particle having pores with an average size of at least about 50 nm (macropores).

Interlayer Composition

The present disclosure is directed to providing improvements in permselective membranes and/or interlayers for an electrochemical cell. The present disclosure covers various research and development directed to identifying materials that can act as a filler and avoids physical aging to provide an interlayer for an electrochemical cell that has excellent stability and capable of controlling the transport of ions, in particular lithium or vanadium ions. It will be appreciated that an interlayer may be defined as any electrically conductive material that can be placed in between an anode and cathode and may serve as a conductive extension of the electrode. Herein, the inventors have found that the interlayer as described herein may exhibit ionic transport and selectivity between molecular species.

The inventors have surprisingly found that the interlayer, at least according to some examples as described herein, can retard the crossover of higher order polysulphide species while enabling the free transport of lithium ions over extended cycles (e.g. in a Li-S battery). The inventors have also surprisingly found that the interlayer can selectively transfer protons over vanadium, thereby maintaining neutrality of the electrolytes while reducing or preventing vanadium crossover between the half-cells, wherein the interlayer comprises a plurality of porous aromatic framework (PAF) particles and one or more polymers as defined herein (e.g. in a VRFB).

It has also been found that the interlayer for an electrochemical cell, at least according to some examples as described herein, may provide one or more further advantages such as:

(a) long term cyclic stability of lithium sulfur (Li-S) cells or vanadium redox flow cells;

(b) high Li-ion transport or H⁺ migration; and/or

(c) high rate capability.

The interlayer as described herein may comprise a carbon material and a plurality of porous particles, wherein the porous particles are porous aromatic framework (PAF), for example, sulfonated porous aromatic framework (SPAF), particles. In other embodiments, the interlayer as described herein may comprise a plurality of porous particles, wherein the porous particles are porous aromatic framework (PAF), for example, sulfonated porous aromatic framework (SPAF), particles. In some embodiments or examples, the interlayer may comprise a high surface area activated carbon and a plurality of porous particles, wherein the porous particles are porous aromatic framework (PAF), for example, sulfonated porous aromatic framework (SPAF), particles.

The interlayer as described herein may consist of a carbon material, a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives. Alternatively, the interlayer as described herein may consist of a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives.

In some embodiments or examples, the sulfur content of the interlayer may be less than about 75 wt.% based on the total weight of the interlayer. It will be appreciated that further advantages may be shown when the sulfur content of the interlayer remains below 75 wt.%. The sulfur content may be less than about 75 wt.%, 50 wt.%, 25 wt.%, 15 wt.%, 10 wt.%, or 5 wt.%. The sulfur content may be at least about 1 wt.%, 5 wt.%, 10 wt.%, 15 wt.%, 25 wt.%, 50 wt.% or 75 wt.%. The sulfur content of the interlayer may be in a range provided by any two of these upper and/or lower amounts.

In some embodiments or examples, the thickness of the interlayer may be substantially uniform and in the range of about 1 pm to about 50 pm. The thickness (pm) of the interlayer may be less than about 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, or 1. The thickness (pm) of the interlayer may be at least about 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50. The thickness of the interlayer may be in a range provided by any two of these upper and/or lower amounts.

In some embodiments or examples, the interlayer may be supported on a substrate. In some embodiments or examples, the interlayer may be a coating or film on a substrate. The substrate may be selected from the group comprising a glass fibre support substrate, polymer support, or an electrode substrate. The substrate may be selected from the group comprising an electrode (e.g. anode and/or cathode), glass fibre, polyacrylonitrile (PAN), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), CELGARD 2400 and CELGARD 2500, polyvinylidene fluoride (PVdF), polyamides (Nylons), polyurethanes, polycarbonates, polyesters, polyetheretherketones (PEEK), polyethersulfones (PES), polyimides (PI), polyamideimides, polyethers, polyoxymethylene (e.g., acetal), polybutylene terephthalate, polyethylenenaphthenate, polybutene, polyolefin copolymers, acrylonitrile -butadiene styrene copolymers (ABS), polystyrene copolymers, polymethylmethacrylate (PMMA), polyvinyl chloride (PVC), polysiloxane polymers (such as polydimethylsiloxane (PDMS)), polybenzimidazole (PBI), polybenzoxazole (PBO), polyphenylenes (e.g., PARMAX™ (Mississippi Polymer Technologies, Inc., Bay Saint Louis, Miss.)), polyarylene ether ketones, polyperfluorocyclobutanes, polytetrafluoroethylene (PTFE), polyvinylidene fluoride copolymers and terpolymers, polyvinylidene chloride, polyvinylfluoride, liquid crystalline polymers (e.g., VECTRAN™ (Hoechst AG, Germany) and ZENITE® (DuPont, Wilmington, Del.)), polyaramides, polyphenylene oxide, and/or combinations thereof. For example, the interlayer, comprising or consisting of a carbon material, a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives, may be supported on a glass fibre support substrate (e.g. in a Li-S battery interlayer). In another example, the interlayer, comprising or consisting of a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives, may be supported on a polymer support substrate, such as a PAN support (e.g. in a VRFB interlayer). In still another example, the interlayer, comprising or consisting of a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives, may be supported on an electrode substrate, such as lithium foil (e.g. in a Li- S battery wherein the interlayer is coated on the anode). In some embodiments or examples, the thickness of the support substrate may in the range of about 10 pm to about 100 pm. The thickness (pm) of the support substrate may be less than about 100, 90, 80, 70, 60, 50, 40, 30, 20, or 10. The thickness (pm) of the support substrate may be at least about 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100. The thickness of the support substrate may be in a range provided by any two of these upper and/or lower amounts. In some embodiments or examples, the interlayer may have a pore size distribution in the range of about 0.5 nm to about 30 nm. The pore size distribution (nm) may be less than about 30, 25, 20, 15, 10, 5, 1, or 0.5. The pore size distribution (nm) may be at least about 0.5, 1, 5, 10, 15, 20, 25 or 30. The pore size distribution on the interlayer may be in a range provided by any two of these upper and/or lower amounts.

In some embodiments or example, the interlayer may have a pore dimension in the range of about 0.1 nm and 10 nm. The pore dimension (nm) may be less than 10, 8, 6, 4, 2, 1.8, 1.6, 1.4, 1.2, 1, 0.5, or 0.1. The pore dimension (nm) may be at least 0.1, 0.5, 1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.2, 2.4, 2.5, 5, 7, 9, or 10. The pore dimension may be in a range provided by any two of these upper and/or lower amounts. The inventors have found that the pore dimension may provide further advantages for ion-selective transport. It has been found that the interlayer formed using the carbon material and the porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles provides a particularly effective interlayer for use in Li-S batteries or vanadium redox flow batteries capable of providing a barrier to polysulfide species or vanadium ions, respectively. It has also been found that the interlayer formed using the porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles provides a particularly effective interlayer for use as anode coatings in Li-S batteries or an interlayer located in between the anolyte and catholyte in VRFBs capable of providing a barrier to poly sulfide species or vanadium ions, respectively.

In some embodiments or examples, the interlayer may be a battery interlayer, flow cell interlayer, or a fuel cell interlayer. For example, the interlayer may be a lithium sulfur battery interlayer. For example, the interlayer may be a vanadium redox flow battery interlayer (VRFB).

Carbon material

The interlayer as described herein may comprise or consist one or more carbon material(s). In some embodiments or examples, the carbon material is a carbon-based material. In an embodiment or example, the carbon-based material may have a high surface area. In an embodiment or example, the carbon-based material may be selected from the group comprising a high surface area activated carbon, a highly conductive expandable graphite, a carbon nanotube, a carbon nanofiber, graphene, or a conductive polymer. The carbon material may be selected from the group comprising graphene, graphite, carbon nanotubes, carbon nanofiber, conductive polymer, or combinations thereof. For example, the carbon material may be a high surface area activated carbon.

In some embodiments or examples, the ratio of carbon material to porous aromatic framework (PAF) particles or sulfonated porous aromatic framework (SPAF) particles may be about 10:90, 15:85, 20:80, 25:75, 30:70, 40:60, 50:50, 60:40, 70:30. 80:20, or 90: 10. The ratio of carbon material to PAF particles or SPAF particles may be about 15:85. The ratio of carbon material to PAF particles or SPAF particles may be about 20:80. The ratio of carbon material to PAF particles or SPAF particles may be about 25:75. The ratio of carbon material to PAF particles or SPAF particles may be about 30:70. The ratio of carbon material to PAF particles or SPAF particles may be about 40:60. The ratio of carbon material to PAF particles or SPAF particles may be about 50:50.

Porous aromatic framework (PAF)

The interlayer as described herein may comprise or consist porous aromatic framework (PAF) particles. It will be appreciated that a “porous” particle in the context of the present disclosure is a self-supporting particle having voids in the form of channels and/or holes surrounded by continuous matter, wherein the channels and/or the holes can be interconnected thus providing a continuous path for fluid molecules to flow throughout the particle. The overall system of interconnected channels and/or holes constitutes the particle's porosity. By the porous particles being “self-supporting” is meant that the particles substantially maintain their shape and size when used according to the present disclosure. The porous particles may therefore generally be solid porous particles. A desirable characteristic of the porous particles is their capability to adsorb on their surface (which includes their internal porous surface) certain fluid species in a selective, differential and reversible manner. That is, certain fluid species can have a tendency to get adsorbed on the porous surface stronger than other fluid species. This may create a differential diffusivity of fluid molecules through the particle's porosity depending on the nature of the fluid species.

In some embodiments or examples, the PAF particles may have a median pore diameter of less than about 100 pm. The PAF particles may have a median pore diameter (pm) of less than about 100, 80, 60, 40, 20, 10, 8, 6, 4, 2, 1, 0.8, 0.6, 0.4, 0.2 or 0.1. The PAF particles may have a median pore diameter (pm) of at least about 0.1, 0.2, 0.4, 0.6, 0.8, 1, 2, 4, 6, 8, 10, 20, 40, 60, 80 or 100. The PAF particles may have a median pore diameter of about 0.1 pm to about 10 pm. The median pore diameter of the PAF particles may be in a range provided by any two of these upper and/or lower amounts.

In some embodiments or examples, the PAF particles may comprise a combination of micropores, mesopores and macropores.

In some embodiments or examples, the PAF particles may have a pore volume in the range of from about 20 to about 90% of the total volume of the porous particle. The PAF particles may have a pore volume in the range of from about 30 to about 80% of the total volume of the porous particle. The PAF particles may have a pore volume in the range of from about 50 to about 80% of the total volume of the porous particle. The PAF particles may have a pore volume (%) of at least about 10, 20, 30, 40, 50, 60, 70, 80, or 90. The PAF particles may have a pore volume (%) of less than about 90, 80, 70, 60, 50, 40, 30, 20, or 10. The pore volume of the PAF particles may be in a range provided by any two of these upper and/or lower amounts.

It will be appreciated that PAF is a type of porous organic framework characterized by a rigid aromatic open-framework structure constructed by covalent bonds (Ben et al., 2009, Angew. Chem., Infl Ed. 48:9457; Ren et al., 2010, Chem. Commun. 46:291; Peng et al., 201 1, Dalton Trans. 40:2720; Ben et al., 201 1, Energy Environ. Sci. 4:3991; Ben et al., J. Mater. Chem. 21 : 18208; Ren et al., J. Mater. Chem. 21: 10348; Yuan et al., 20 1, J. Mater. Chem. 2 1: 13498; Zhao et al., 201 1, Chem. Commun. 47:6389; Ben & Qiu, 2012, CrystEngComm, DOI: 10.1039/c2ce25409c). PAFs show high surface areas and excellent physicochemical stability, generally with long range orders and, to a certain extent, an amorphous nature. In some embodiments or examples, the PAF particles may be selected from PAF-1 (PAF-302), PAF-3, PAF-4, PAF-11 (PAF-304), PAF-301, PAF-303, SOsLi- PAF, JUC-Z1, JUC-Z2, PPN-4, PPN-5, PPN-6-SO3H, PPN-6-SO3H, a salt thereof, or any mixtures thereof. PAFs useful within the interlayer as described herein may be obtained from commercial sources or prepared according to methods known to those skilled in the art (Ben & Qiu, 2012, CrystEngComm, D01: 10.1039/c2ce25409c).

In some embodiments or examples, the PAF particles may be provided with one or more functional groups selected from -NHR, -N(R)2, -NH, -NO, -NH(aryl), halides, aryl, aralkyl, alkenyl, alkynyl, pyridyl, bipyridyl, terpyridyl, anilino, -O(alkyl), cycloalkyl, cycloalkenyl, cycloalkynyl, sulfonamide, hydroxyl, cyano, -(CO)R, - (SO2)R, -(CO₂)R, -SH, -S(alkyl), -SO3H, -SO3R, -SO³ M⁺, -COOH, -COO M⁺, -PO3H, -PO3H'M⁺, -PO3²'M⁺, -CO₂H, silyl derivatives, borane derivatives, ferrocenes and other metallocenes, where M is a metal atom, and R is Ci-ioalkyl.

In some embodiments or examples, the PAF particles may be PAF-1.

The inventors have found that the fabrication of a functionalized interlayer, comprising or consisting of a carbon material, a plurality of porous aromatic framework (PAF) particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives, have shown advantageously outstanding Li ion conductivity / polysulfide retention with structural stability over long-term cycling. The inventors have unexpectedly found that the interlayer, comprising or consisting of a carbon material, a plurality of porous aromatic framework (PAF) particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives, can retard the crossover of the higher order poly sulphide species while enabling the free transport of Li ions over extended cycles. In particular, the inventors found that further functionalising the porous aromatic framework (PAF) particles with sulfonation can further advantageously enhance the performance of a Li-S battery system using a control passage for Li-ions.

The inventors have also found that the fabrication of a functionalized interlayer, comprising or consisting of a plurality of porous aromatic framework (PAF) particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives, have shown advantageously outstanding Li ion conductivity / polysulfide retention with structural stability over long-term cycling. The inventors have unexpectedly found that the interlayer, comprising or consisting of a carbon material, a plurality of porous aromatic framework (PAF) particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives, can retard the crossover of the higher order poly sulphide species while enabling the free transport of Li ions over extended cycles. In particular, the inventors found that further functionalising the porous aromatic framework (PAF) particles with sulfonation can further advantageously enhance the performance of a Li-S battery system using a control passage for Li-ions.

The inventors have also found that the fabrication of a functionalized interlayer, comprising or consisting of a plurality of porous aromatic framework (PAF) particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives, have shown advantageously outstanding improvement in capacity retention with structural stability over long-term cycling. The inventors have unexpectedly found that the interlayer, comprising or consisting of a carbon material, a plurality of porous aromatic framework (PAF) particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives, can selectively transfer protons over vanadium, thereby maintaining neutrality of the electrolytes while reducing or preventing vanadium crossover between the half cells. In particular, the inventors found that further functionalising the porous aromatic framework (PAF) particles with sulfonation can further advantageously alleviated interlayer resistivity and assisted proton migration through hydrophilic domains created by its negatively charged sulfonic acid groups. Even further advantageously reducing or preventing separator degradation and hence loss of battery capacity after cycling through the suppression of physical aging.

In some embodiments or examples, the PAF particles may be sulfonated PAF (SPAF). In one example, the PAF particles may be SPAF-1. In some embodiments or examples, the PAF particles, for example PAF-1 particles, may be functionalized with at least one of the functional groups listed above. The PAF-1 particles may comprise sulfur groups of sulfonic acids. For example, PAF-1 particles may be functionalized with -SOsH groups. In some embodiments or examples, the sulfur content of the SPAF may be less than about 50 wt.% based on the total weight of SPAF. It will be appreciated that further advantages may be shown when the sulfur content of SPAF remains below 50 wt.%. The sulfur content may be less than about 45 wt.%, 40 wt.%, 30 wt.%, 35 wt.%, 30 wt.%, 25 wt.%, 20 wt.%, 15 wt.%, 10 wt.%, or 5 wt.%. The sulfur content may be at least about 1 wt.%, 5 wt.%, 10 wt.%, 15 wt.%, 25 wt.%, 40 wt.% or 50 wt.%. The sulfur content of SPAF may be in a range provided by any two of these upper and/or lower values, for example between about 1 wt.% and 35 wt.%, 5 wt.% and 25 wt.%, or 10 wt.% and 20 wt.%.

The inventors have found that the interlayers may comprise PAF for example, sulfonated porous aromatic framework (SPAF), particles that are capable of holding an adequate amount of electrolyte and also providing pores that are smaller than the particle size of the electrode constituents that may be present in the electrolyte. It will be appreciated that this property may provide a further advantage such that the particles which peel off the electrodes are restricted from crossing through the interlayer to the other side of the battery (e.g. in Li-S batteries any poly sulphides formed at the cathode during discharge are restricted from contact with the anode). This may ultimately allow better passage for the Li-ions to cross through the interlayer and maintain the cyclic stability of an electrochemical cell, for example a Li-S battery. It will also be appreciated that this property may also provide a further advantage such that the pore size distribution is sufficiently small to inhibit the free travel of the hydrated vanadium ions (e.g. in vanadium redox flow batteries (VRFBs)).

In some embodiments or examples, PAF-1 for example, sulfonated porous aromatic framework (SPAF), may have an average pore size in the range of from about 0.2 to about 10 nm, from about 0.2 to about 7 nm, from about 0.2 to about 5 nm, from about 0.5 to about 5 nm, from about 0.5 to about 4 nm, from about 0.5 to about 3 nm, from about 0.5 to about 2 nm, or from about 1 to about 2 nm. The average pore size (nm) may be less than about 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.8, 0.6, 0.4, 0.2 or 0.1. The average pore size (nm) may be at least about 0.1, 0.2, 0.4, 0.6, 0.8, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10. The average pore size of the PAF for example, sulfonated porous aromatic framework (SPAF), particles may be in a range provided by any two of these upper and/or lower amounts.

In some embodiments or examples, PAF-1 for example, sulfonated porous aromatic framework (SPAF), particles may have an average size of between about 20 nm to about 100 pm, between about 20 nm and 50 pm, between about 20 nm and 10 pm, between about 20 nm and 5 pm, between about 20 nm and 1 pm, between about 20 nm and 800 nm, between about 20 nm and 500 nm, or between about 20 nm and 100 nm. The average size of the PAF-1 particles may be less than about 100 pm, 80 pm, 60 pm, 40 pm, 20 pm, 10 pm, 5 pm, 2 pm, 1 pm, 800 nm, 600, nm, 400 nm, 200 nm, 100 nm, 80 nm, 60 nm, 40 nm, 20nm or 10 nm. The average size of the PAF-1 particles may be at least about 10 nm, 20 nm, 40 nm, 60 nm, 80 nm, 100 nm, 200 nm, 400 nm, 600 nm, 800 nm, 1 pm, 2 pm, 5 pm, 10 pm or 20 pm. The average size of the PAF for example, sulfonated porous aromatic framework (SPAF), particles may be in a range provided by any two of these upper and/or lower amounts.

In some embodiments or examples, the PAF-1 for example, sulfonated porous aromatic framework (SPAF), particles may have a measured BET surface area (measured from N2 adsorption isotherms at 87K) of from about 100 to about 10000 m²/g, from about 100 to about 9000 m²/g, from about 100 to about 8000 m²/g, from about 100 to about 7000 m²/g, from about 300 to about 5000 m²/g, from about 400 to about 4000 m²/g, from about 500 to about 4000 m²/g, from about 600 to about 3800 m²/g, from about 750 to 3000 m²/g, from about 1000 to 2500 m²/g, or from about 1000 to 2000 m²/g. The measured BET surface area (m²/g) of the PAF-1 for example, sulfonated porous aromatic framework (SPAF), particles may be less than about 10000, 9000, 8000, 7000, 6000, 5000, 4000, 3000, 2000, 1000, 900, 800, 700, 600, 500, 400, 300, 200 or 100. The measured BET surface area (m²/g) of the PAF-1 for example, sulfonated porous aromatic framework (SPAF), particles may be at least 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000 or 10000. The measured BET surface area (m²/g) of the PAF-1 for example, sulfonated porous aromatic framework (SPAF), particles may be in a range provided by any two of these upper and/or lower amounts. Polymer

The interlayer as described herein may further comprise or consist a polymer. It will be appreciated that a polymer's free volume is defined as the difference between the specific polymer volume in its glassy or rubbery state and the occupied volume associated with the material in its crystalline configuration extrapolated to zero Kelvin. The fractional free volume is the ratio between that difference and the polymer volume in its glassy or rubbery state at the given temperature. The fractional free volume can therefore be expressed in vol. % or volumetric fraction. The fractional free volume is therefore a measure of the residual “voids” that remain between the polymeric chains when these are inter-locked in their 3D arrangements. On the other hand, the firee- volume distribution relates to how the free volume is arranged spatially within the polymer, by way of interconnected porosity and channels. It is the free volume distribution that is of interest in understanding the mechanisms underlying the separation of fluid mixtures, since its configuration will dictate which molecules filters through the polymer and which molecules may remain adsorbed on the surface of the free volume pockets. While two polymers may have the same total free volume, they may have vastly differing transport properties based upon a different free volume distribution. Ideally, separation membranes should exhibit both high flux and high selectivity. In some embodiments or examples, the polymers may be characterized by fractional free volume values ranging from about 0. 1 to about 0.5.

In some embodiments or examples, the polymer may have a fractional free volume of at least about 0.1.

It will be appreciated that previously Nafion and GO membranes have shown to provide a strong ionic shield for the polysulfides, however they impose too great a restriction on Li ion movement due to their tortuous pore structure, which, in turn, lowers the high current response of the battery. Glassy polymers on the other hand, have been found to provide further advantages and may allow an abundance of uniformly distributed micropores. It will also be appreciated that Nafion as a perfluorinated cation exchange membrane formed by incorporating perfluorovinyl ether groups terminated with hydrophilic sulfonate groups onto a hydrophobic PTFE backbone, has been widely used as a separator in VRFBs due to its high proton conductivity and chemical stability in acids. However, Nation still has shortcomings such as fast crossover of vanadium ions (low proton/vanadium selectivity), proton conductance deterioration at low humidity or high temperature, and high cost limiting this promising battery technology from widespread commercialization. Amongst these drawbacks, the continuous diffusion/migration of vanadium ions between the half-cells is primarily responsible for concentration and electrolyte imbalance, which result in rapid capacity fading of the vanadium flow system.

Glassy polymers, on the other hand, can enhance the interlayer performance. Glassy polymers are a class of polymers known for their rigidity, i.e. changing to a rubbery state only upon sufficient heating to transition them through their glass transition temperature.

In some embodiments or examples, the polymer may be selected from polymers of intrinsic microporosity (PIMs), thermally rearranged (TR) polymers, hyperbranched polymers, substituted polyacetylenes, and combinations thereof.

In some embodiments or example, the polymer may be a substituted polyacetylene selected from poly(l -trimethylsilyl)- 1 -propyne), poly (l-(dimethyl-n- propylsilyl)- 1 -propyne), poly( 1 -(dimethyl -n-butylsilyl)- 1 -propyne), poly( 1 -phenyl- 1 - propyne)poly 1 (diphenylacetylene), poly (1 -butylacetylene), poly(l -phenyl -2 -p- trimethylsilylphenyl-acetylene), poly(l-phenyl-2-/l-hydroxyphenyl-acetylene), copolymers thereof, and combinations thereof. The polymer may be provided with one or more functional groups selected from -NHR, -N(R)2, -NH, -NO, -NH(aryl), halides, aryl, aralkyl, alkenyl, alkynyl, pyridyl, bipyridyl, terpyridyl, anilino, -O(alkyl), cycloalkyl, cycloalkenyl, cycloalkynyl, sulfonamide, hydroxyl, cyano, -(CO)R, - (SO₂)R, -(CO₂)R, -SH, -S(alkyl), -SOsH, -SO₃ M⁺, -COOH, -C00 M⁺, -PO₃H, -PO3H- M⁺, -PO3²'M⁺, -CO₂H, silyl derivatives, borane derivatives, ferrocenes and other metallocenes, where M is a metal atom, and R is C1-10 alkyl.

In some embodiments or examples, the polymer may be poly(l-trimethylsilyl- 1 -propyne) (PTMSP).

Poly(l -trimethylsilyl- 1 -propyne) (PTMSP) has a very high fractional free volume for a glassy polymer, borne largely from the inefficient packing of its bulky side-chains. Further advantages may be provided utilising the rigidity of glassy polymers such that they may provide the interlayer with well-defined pores that may be capable of differentiating between similarly sized molecules, such as partially reduced poly sulfide species or hydrated vanadium ions.

Binder

The interlayer as disclosed herein may further comprise one or more binders. Binders may include gum arabic in H2O, carboxymethyl cellulose (CMC)Zcitric acid in FbO/A./V’ dimethylformamide, CMC/Styrene-Butadiene Rubber (SBR) in ethanol/H2O,olytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), poly(l- trimethylsilyl-1 -propyne) (PTMSP), gum binders such as gum arabic, xanthan gum, and guar gum, natural cellulose based binders, polysaccharides such as sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium alginate, polyacrylates, aliphatic polymers such as Polyvinyl butyral, aromatic polymers such as styrene-butadiene rubber. In an embodiment or example, the binder may be a gum binder selected from the group comprising gum arabic, xanthan gum, guar gum, or combinations thereof. In another embodiment or example, the binder may be a polysaccharide selected from the group comprising sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium alginate, or combinations thereof.

In some embodiments or examples, the binder, by volume, may be present in the interlayer composition in a range of about 1 to 40%. The binder, by volume, may be present in the interlayer composition in an amount of less than about 40%, 30%, 20% 15%, 10%, 5% or 2%. The binder, by volume, may be present in the interlayer composition in an amount of at least about 1%, 2%, 5%, 10%, 15%, 20%, or 30%. The binder, by volume, may be present in the interlayer composition in a range provided by any two of these upper and/or lower amounts.

Additives

The interlayer as disclosed herein may further comprise one or more additives. In some embodiments or examples, the interlayer may further comprise a hypercrosslinked polymer. It will be appreciated that hypercrosslinked polymers (HCPs) are a class of nanoporous organic network that can be synthesized using Friedel-Crafts chemistry to generate extensive cross-linking within existing polymers, lightly cross-linked networks, or small molecules. The resulting polymers consist of aromatic rings joined together through multiple methylene bridges. In some embodiments or examples, the hypercrosslinked polymer is p-DCX. It will be appreciated that p-DCX may be generated using Friedel-Crafts polymerization of a,a’- dichloro-p-xylene. It will also be appreciated that Friedel-Crafts chemistry may be used to generate a large number of HCPs using a diverse range of different aromatic building blocks, which may also be post-synthetically modified (e.g. aminated to generate NH2-7-DCX). In some embodiments or examples, p-DCX may have a surface area of 1400 m²g^-1.

In some embodiments or examples, the additive may be present in an amount (by weight % of total formulation) between about 1% and 40%, about 2% and 20%, or about 5% and 15%. The additive may be present in an amount (by weight % of total formulation) of less than about 40, 35, 30, 25, 20, 15, 10, 8, 6, 4, 2, or 1. The additive may be present in an amount (by weight % of total formulation) of at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 30, or 40. The additive (by weight % of total formulation) may be present in the interlayer composition in a range provided by any two of these upper and/or lower amounts.

Electrochemical cell

The present disclosure is directed to providing improvements in permselective membranes and/or interlayers for an electrochemical cell. In some embodiments or examples, the present disclosure is directed to an interlayer for an electrochemical cell comprising an interlayer at least according to some examples as described herein.

In some embodiments or examples, an electrochemical cell may comprise: a negative electrode, a positive electrode, at least one electrolyte, an interlayer, and an optional separator, wherein the interlayer comprises a carbon material, a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles and one or more polymers as defined herein. For example, the electrochemical cell may comprise: an anode; a cathode; at least one electrolyte comprising one or more electrolyte solvents; an interlayer comprising a carbon material, a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles and one or more polymers as defined herein; and an optional separator. In one example, the electrochemical cell may comprise: an anode; a cathode; at least one electrolyte comprising one or more electrolyte solvents; an interlayer comprising or consisting of a carbon material, a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives; and an optional separator. In some embodiments or examples, the interlayer may be located between the anode and the cathode. In alternative embodiments or examples, the interlayer may be at least partially coated on the anode. The interlayer may be provided as a partial coating or a complete layer on the anode. The interlayer may be provided on one or both sides or surfaces of the anode. For example, the interlayer may be deposited on the anode by solution casting, dip coating, spray coating or spin coating. It will be appreciated that other coating methods may be applicable such as brush coating, painting, slurry spraying, spray pyrolysis, sputtering, chemical or physical vapour deposition techniques, electroplating, screen printing, or tape casting. In one example, the coating may be deposited on the anode by solution casting.

In some embodiments or examples, the negative electrode may be an anode comprising lithium metal and the positive electrode may be a cathode comprising elemental sulfur (e.g. in a Li-S cell). The cathode may be a composite sulfur cathode. For example, the composite sulfur cathode may be a sulfur-microporous carbon nanocomposite.

In some alternate embodiments or examples, an electrochemical cell may comprise: a negative and positive electrode; at least one electrolyte; an interlayer; and an optional separator, wherein the at least one electrolyte comprises an anolyte and a catholyte, and wherein the interlayer comprises a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles and one or more polymers as defined herein. In one example, the electrochemical cell may comprise: a negative and positive electrode; at least one electrolyte; an interlayer; and an optional separator, wherein the at least one electrolyte comprises an anolyte and a catholyte, wherein the interlayer may comprise or consist of a carbon material, a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additive. In some embodiments or examples, the interlayer may be located between the anolyte and catholyte. The negative and positive electrode in the electrochemical cell (e.g. a vanadium redox flow cell) may each independently be carbon based. For example, the negative and positive electrode may each independently be selected from the group comprising carbon felt, carbon paper, carbon cloth, graphite felt, carbon nanotubes, or a combination thereof. In some embodiments or example, the positive and negative electrode may each be selected from the same material. For example, the negative and positive electrode may each be graphite felt.

In some embodiments or examples, the electrolytes may be selected from nonaqueous solutions of lithium salts (e.g. in Li-S cells). The lithium salts may be selected from the group comprising lithium bis(trifluoromethane sulfone)imide, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium bis(trifluorosulfonylimide), lithium trifluoromethanesulfonate, lithium fluoroalkylsulfonimides, lithium fluoroarylsulfonimides, lithium bis(oxalate borate), lithium tris(trifhioromethylsulfonylimide)methide, lithium tetrafluoroborate, lithium perchlorate, lithium tetrachloroaluminate, lithium chloride, or combinations thereof. For example, the electrolyte may comprise lithium bis(trifluoromethane sulfone)imide.

In some embodiments or examples, the lithium salt may be dissolved in an organic solvent. The lithium salt may be dissolved in an organic solvent selected from ethers, esters, carbonates, and acetals. In one example, the solvent may be selected from dimethoxyethane, diglyme, triglyme, tetraglyme, ethylene carbonate, propylene carbonate, dimethyl carbonate, tetrahydrofuran, and dioxolane. In some embodiments or examples, the lithium salt may be dissolved in an organic solvent selected from the group comprising ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, methylpropyl carbonate, butylmethyl carbonate, ethylpropyl carbonate, dipropyl carbonate, cyclopentanone, sulfolane, dimethyl sulfoxide, 3-methyl-l,3-oxazolidine-2-one, y-butyrolactone, 1,2- diethoxymethane, tetrahydrofuran, 2 -methyltetrahydrofuran, 1,3 -dioxolane, 1,2- dimethoxy ethane, methyl acetate, ethyl acetate, nitromethane, 1,3-propane sultone, y- valerolactone, methyl isobutyryl acetate, 2-methoxyethyl acetate, 2-ethoxyethyl acetate, diethyl oxalate, or an ionic liquid, or combinations thereof. In some embodiments or examples, the lithium salt may be dissolved in an organic solvent selected from the group comprising 1,3-dioxolane, dimethoxyethane, or a combination thereof.

In some embodiments or examples, the lithium salt may be dissolved in one or more organic solvents listed above, wherein the one or more organic solvents are present in a volume to volume ratio ranging from 10 to 1 to 1 to 10. The volume to volume ratio may be 10 to 1. The volume to volume ratio may be 9 to 1. The volume to volume ratio may be 8 to 1. The volume to volume ratio may be 7 to 1. The volume to volume ratio may be 6 to 1. The volume to volume ratio may be 5 to 1. The volume to volume ratio may be 4 to 1. The volume to volume ratio may be 2 to 1. The volume to volume ratio may be 2 to 1. The volume to volume ratio may be 1 to 1. The volume to volume ratio may be 1 to 2. The volume to volume ratio may be 1 to 2. The volume to volume ratio may be 1 to 3. The volume to volume ratio may be 1 to 4. The volume to volume ratio may be 1 to 5. The volume to volume ratio may be 1 to 6. The volume to volume ratio may be 1 to 7. The volume to volume ratio may be 1 to 8. The volume to volume ratio may be 1 to 9. The volume to volume ratio may be 1 to 10. For example, the lithium salt may be dissolved in 1,3-dioxolane and dimethoxy ethane at a ratio of 1 to 1 v/v.

The electrolyte may comprise an additive selected from one or more alkali metal salts of LiPF₆ LiBF₄, LiAsFe, LiSbFe, LiCIC , LiAICk, LiGaCh, LiC(SO2CF₃)3, LiN(SO₂CF₃)2, LiSCN, LiSO2CF₂CF3, LiCeFsSOs, LiO₂CCF3, LiSOsF, LiB(C₆H₅)4, LiCF3SC>3, LiNOs, and mixtures thereof. Electrolyte additives can further improve certain characteristics of the cell. For example, the electrolyte (e.g. lithium bis(trifluoromethane sulfone)imide) may comprise an additive (e.g. LiNOs) dissolved in an organic solvent (e.g. 1: 1 v/v ratio 1,3-dioxolane and dimethoxy ethane).

In some embodiments or examples, the electrochemical cell may have two divided electrolyte reservoirs (e.g. half-cells). The two electrolyte reservoirs are halfcells each comprising the catholyte and the anolyte. In some embodiments or examples, the catholyte and anolyte may be separated by an interlayer. In some embodiments, the catholyte and anolyte may be selected from vanadium-based compounds. It will be appreciated that the electrolyte in the anolyte half-cell comprises of V³⁺ and V²⁺ ions, while the electrolyte in the catholyte half-cell comprises VO²⁺ (V⁴⁺) and VC>2⁺ (V⁵⁺) ions. In some embodiments or examples, the electrolytes can be prepared by several processes, including for example, electrolytically dissolving a vanadium-based compound in an acid, wherein the acid may be selected from the group comprising sulfuric acid (H2SO4), hydrochloric acid (HC1), sulfuric acid/hydrochloric acid (H2SO4/HCI), sodium sulfate (Na2SC>4), potassium sulfate (K2SO4), phosphoric acid (H3PO4), sodium phosphate (NaiPO ). potassium phosphate (K3PO4), nitric acid (HNO3), sodium nitrate (NaNOi). potassium nitrate (KNO3), or combinations thereof. For example, the catholyte and the anolyte may be selected from the group comprising vanadyl sulfate (VOSO4), vanadium trioxide (V2O3), vanadium pentoxide (V2O5), or combinations thereof. In a particular example, the catholyte and analyte may be prepared from a starting vanadium based electrolyte comprising vanadyl sulfate (VOSO4) in sulfuric acid (H2SO4).

In some embodiments or examples, the volume ratio of anolyte to catholyte may be present in a volume to volume ratio ranging from 10 to 1 to 1 to 10. The volume to volume ratio may be 10 to 1, 9 to 1, 8 to 1, 7 to 1, 6 to 1, 5 to 1, 4 to 1, 2 to 1, 1 to 1, 1 to 2, 1 to 3, 1 to 4, 1 to 5, 1 to 6, 1 to 7, 1 to 8, 1 to 9, or 1 to 10. For example, the volume ratio of anolyte to catholyte may be 1 to 2. It will be appreciated that the 1 :2 volume of the anolyte to catholyte is due to the 1:2 electron transfer that occurs in the redox reaction.

In some embodiments or examples, the electrochemical cell may be an energy storage device. The energy storage device may be a battery. For example, the battery may be a secondary battery. In one particular example, the battery may be a lithiumsulfur battery (Li-S battery). In another particular example, the battery may be a vanadium redox flow battery (VRFB). Interlayer for Lithium-Sulfur Battery

In some embodiments or examples, the present disclosure also provides a method for improving cycling stability of a battery having an anode comprising lithium metal and a cathode comprising elemental sulfur, at least one electrolyte, and an interlayer comprising or consisting of a carbon material, a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives, wherein the interlayer may be provide between the anode and the cathode. In some other embodiments or examples, the present disclosure also provides a method for improving cycling stability of a battery having an anode comprising lithium metal and a cathode comprising elemental sulfur, at least one electrolyte, and an interlayer comprising or consisting of a carbon material, a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives, wherein the interlayer is provided as at least a partial coating on the anode. It has been found that the interlayer comprising the carbon material and porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles provides a particularly effective interlayer for use in a battery (e.g. Li-S battery) capable of maintaining a long-term capacity retention. In some embodiments or examples, the battery may have a discharge capacity of at least about 800 mAh/g for at least 100 cycles of the battery. In some embodiments or examples, the specific capacity (mAh/g) may be at least about 800, 1000, 1200, 1400, 1600, 1800, 2000, 2200, 2400, 2600, 2800, or 3000. In some embodiments or examples, the specific capacity (mAh/g) may be less than about 4200, 4000, 3800, 3600, 3400, 3200, 3000, 2800, 2600, 2400, 2200, 2000, 1800, 1600, 1400, 1200, 1000, or 800. The specific capacity (mAh/g) may be in a range provided by any two of these upper and/or lower values. In some embodiments or examples, the number of cycles may be at least 80, 100, 120, 140, 160, 180, 200, 220, 240, 260, 280, 300, 320, 340, 360, 380, 400, 420, 440, 460, 480 or 500.

The long-term cyclic performance of an electrochemical cell (e.g. Li-S battery) comprising the interlayer may be tested for low and high loaded sulfur cathodes ranging 3.4 to 9 mg cm’² sulfur (i.e. about 70 % of the cathode mass). The initial discharge capacity of the interlayer comprising carbon material and porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, according to at least some embodiments or examples as described herein, can be at least about (in mAhg'¹) 1100, 1200, 1300, 1400, 1500, or 1600. At least according to some embodiments or examples, this discharge capacity may be retained after cycles of 100, 200, 300, 400, or 500.

It will be appreciated that galvanostatic charge-discharge cycling experiments may typically be used to evaluate the performance metrics of a battery: capacity, rate capability, Coulomb ic efficiency, and capacity retention upon cycling. The chargedischarge (V-t) profile which can be plotted as potential vs. depth of discharge (charge) can be used to obtain information similar to that extracted from cyclic voltammetry (CV). A capacity test may be used to obtain real capacity of a battery and typically used for tracking the health and real capacity of a battery as well as estimating battery life.

In some embodiments or examples, the present disclosure is also directed to a use of the interlayer comprises a carbon material, a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives in an electrochemical cell. In some other embodiments or examples, the present disclosure is also directed to a use of an interlayer as coating on an anode in an electrochemical cell, wherein the interlayer is at least provided as a partial coating on the anode, and wherein the interlayer comprises a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives. For example, the electrochemical cell may be an energy storage device, such as a battery, preferably a secondary battery. More particularly, the battery may be a lithium sulfur battery.

In some embodiments or examples, the present disclosure is also directed to an interlayer, which may comprise or consist of a carbon material, a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives, wherein the interlayer may be a battery interlayer or a fuel cell interlayer. In an example the interlayer may be a fuel cell. In another example, the interlayer may be a battery interlayer. More particularly, a lithium sulfur battery interlayer.

The inventors have found that the interlayer, which may comprise or consist of a carbon material, a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives, significantly reduces the polysulphide shuttle effect, and therefore provides improved performance of Li-S batteries. The interlayer, which may comprise or consist of a carbon material, a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives, provides a shield for the polysulfides, and further advantages providing improved lithium diffusion by enabling the flow of Li ions, which, in turn, improves the high current response and performance of the battery. For example, electrochemical cells comprising the interlayer, which may comprise or consist of a carbon material, a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives, allows polysulfide species to be adsorbed/trapped within the interlayer, providing an improved average Coulombic efficiency (CE) of at least about 95, 96, 97, or 98% over at least 300 cycles, indicating effective suppression of poly sulfide shuttling. In another example, the interlayer, comprising or consisting of a carbon material, a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives, provides improved performance of Li-S batteries showing cyclic stability after at least 400 cycles at 0.2C. Interlayer for a Vanadium Redox Flow Battery

In some embodiments or examples, the present disclosure also provides a method for improving cycling stability of a redox flow battery having a negative and positive electrode; an anolyte; a catholyte; and an interlayer, wherein the interlayer may comprise or consist of a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives. It has been found that the interlayer comprising the porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles provides a particularly effective interlayer for use in a redox flow battery (e.g. VRFB) capable of maintaining a long-term capacity retention.

Battery performance may be examined by cycling tests (i.e. charging and discharging) conducted with the potentiostat at constant current densities. The cut-off voltage may be set at 1.7 and 0.8 V in order to avoid electrode and flow channel plate corrosion and the effective membrane-electrode-assembly area may be 5 cm². It will be appreciated that the performance of a redox flow battery (e.g. VRFB) may be evaluated with coulombic efficiency (CE), voltage efficiency (VE), and energy efficiency (EE).

In some embodiments or examples, the battery may have a discharge capacity of at least about 800 mAh/g for at least 100 cycles of the battery. In some embodiments or examples, the specific capacity (mAh/g) may be at least about 800, 1000, 1200, 1400, 1600, 1800, 2000, 2200, 2400, 2600, 2800, or 3000. In some embodiments or examples, the specific capacity (mAh/g) may be less than about 4200, 4000, 3800, 3600, 3400, 3200, 3000, 2800, 2600, 2400, 2200, 2000, 1800, 1600, 1400, 1200, 1000, or 800. The specific capacity (mAh/g) may be in a range provided by any two of these upper and/or lower values. In some embodiments or examples, the number of cycles may be at least 80, 100, 120, 140, 160, 180, 200, 220, 240, 260, 280, 300, 320, 340, 360, 380, 400, 420, 440, 460, 480 or 500.

The initial discharge capacity of the interlayer comprising porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, according to at least some embodiments or examples as described herein, can be at least about (in mAhg’¹) 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1800, or 2000. At least according to some embodiments or examples, this discharge capacity may be retained after cycles of 50, 100, 200, 300, 400, or 500.

It will be appreciated that charge-discharge cycling experiments may typically be used to evaluate the performance metrics of a battery: capacity, rate capability, Coulombic efficiency, and capacity retention upon cycling. The charge-discharge (V-t) profile which can be plotted as potential vs. depth of discharge (charge) can be used to obtain information similar to that extracted from cyclic voltammetry (CV). A capacity test may be used to obtain real capacity of a battery and typically used for tracking the health and real capacity of a battery as well as estimating battery life.

In some embodiments or examples, the present disclosure is also directed to a use of the interlayer in an electrochemical cell. In one embodiment or example, the present disclosure is also directed to a use of an interlayer in an electrochemical cell, wherein the interlayer comprises a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives. For example, the electrochemical cell may be an energy storage device, such as a redox flow battery. More particularly, the battery may be a vanadium redox flow battery.

In some embodiments or examples, the present disclosure is also directed to an interlayer, comprising or consisting of a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives, wherein the interlayer may be a battery interlayer, flow cell (e.g. redox flow cell), or a fuel cell interlayer. In an example the interlayer may be a flow cell. In another example, the interlayer may be a battery interlayer. More particularly, a vanadium redox flow battery interlayer.

The inventors have found that the interlayer, which may comprise or consist of a plurality of porous aromatic framework (PAF) particles for example, sulfonated porous aromatic framework (SPAF), optionally one or more binders, optionally one or more polymers, and optionally one or more additives, can address vanadium crossover, and therefore provides improved performance and stability in VRFBs. The interlayer, which may comprise or consist of a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives, may also provide further advantages such as reducing and/or preventing separator degradation, and therefore loss of battery capacity after cycling through the suppression of physical aging. For example, electrochemical redox flow cells comprising the interlayer, which may comprise or consist of a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives, allows blocking of hydrated vanadium ions by the hydrophobic microporous structure of the interlayer, providing an improved average Coulombic efficiency (CE) of at least about 94, 96, or 98%, indicating reduced vanadium penetration. In an example, the interlayer, which may comprise or consist of a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives, also provides improved energy efficiency (EE) of at least about 80, 84, 86, or 88% of the cell. In another example, the interlayer, which may comprise or consist of a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives, provides improved capacity retention after at least 100 cycles (85 %), compared to the cell configured with the commercial Nafion membrane (58 %).

Preparation Process

In some embodiments or examples, the present disclosure is directed to a process for preparing an interlayer for an electrochemical cell. The process may be for preparing an interlayer according to any embodiments or examples as described herein. It will be appreciated that the interlayer prepared by the process may comprise a carbon material and a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles. It will also be appreciated that the interlayer prepared by the process may consist of a carbon material, a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, optionally one or more additives, and optionally a solvent. The carbon material, PAF particles for example, sulfonated porous aromatic framework (SPAF), one or more optional binder, one or more optional polymer, one or more optional additives, and one or more optional solvents may be selected from any one or more of the embodiments or examples as described herein. It will also be appreciated that the interlayer prepared by the process may consist of a plurality of porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles, optionally one or more binders, optionally one or more polymers, optionally one or more additives, and optionally a solvent. The PAF for example, SPAF, particles, one or more optional binder, one or more optional polymer, one or more optional additives, and one or more optional solvents may be selected from any one or more of the embodiments or examples as described herein.

In some embodiments or examples, a process for preparing of an interlayer for an electrochemical cell, may comprise the steps of: (i) providing a carbon material and porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles in a solvent system for a predetermined time to produce a solution thereof; and (ii) casting a film of the solution onto a substrate to provide a wet interlayer supported on the substrate. In some other embodiments or examples, a process for preparing of an interlayer for an electrochemical cell, may comprise the steps of: (i) providing a porous aromatic framework (PAF) for example, sulfonated porous aromatic framework (SPAF), particles in a solvent system for a predetermined time to produce a solution thereof; and (ii) casting a film of the solution onto a substrate to provide a wet interlayer supported on the substrate.

In some embodiments or examples, the process may further comprise the steps of: (a) preparing porous aromatic framework particles in a solvent system; (b) converting the porous aromatic framework particles to sulfonated porous aromatic framework particles in a solvent system; (i) providing a carbon material and sulfonated porous aromatic framework particles in a solvent system for a predetermined time to produce a solution; and (ii) casting a film of the solution onto a substrate to provide a wet interlayer supported on the substrate. In some other embodiments or examples, the process may further comprise the steps of: (a) preparing porous aromatic framework particles in a solvent system; (b) converting the porous aromatic framework particles to sulfonated porous aromatic framework particles in a solvent system; (i) providing a sulfonated porous aromatic framework particles in a solvent system for a predetermined time to produce a solution; and (ii) casting a fdm of the solution onto a substrate to provide a wet interlayer supported on the substrate.

In another embodiment or example, the process may further comprise a step (iii) solidifying the wet interlayer supported on the substrate by solvent evaporation.

In some embodiments or examples, the process may further comprise step (i)(a) addition of a polymer.

In some embodiments or examples, the solvent may be an organic solvent selected from aromatics, halogenated aromatics, halogenated aliphatic hydrocarbons, aliphatic hydrocarbons, glycols, ethers, glycol ethers, esters, alcohols, ketones, or combinations thereof. In some embodiments or examples, the solvent may be present in an amount (by weight % of total formulation) between about 35 and 99, between about 50% and 90%, or between about 35% and 60%. In an embodiment or example, the solvent may be selected for solvent casting of the interlayer. The solvent may be a low boiling point organic solvent, or a mixture of one or more of such solvents. In some embodiments or examples, the solvent may be selected from the group comprising methanol, ethanol, n-propanol, isopropanol, tetrahydrofuran, methylene chloride, chloroform, diethyl ether, room temperature ionic liquids, ethylene glycol, glycerol, formamide, N-methylformamide, dimethylformamide, N-methylsydnone, an aqueous solution thereof, or any mixtures thereof. For example, the solvent may be ethanol. For example, the solvent may be chloroform.

In some embodiments or examples, the ratio of carbon material to porous aromatic framework (PAF) particles or sulfonated porous aromatic framework (SPAF) particles may be about 80:20 to 50:50. For example, the ratio of carbon material to PAF particles or SPAF particles may be about 70:30.

In some embodiments or examples, the viscosity of the casting solution may be in a range between about 10 mPas and 10,000 mPas. The viscosity (mPas) may be less than about 10,000, 8000, 6000, 4000, 2000, 1000, 800, 600, 400, 200, 100, 50, or 10. The viscosity may be at least about 10, 20, 40, 60, 80, 100, 300, 500, 700, 900, 1000, 3000, 5000, 7000, 9000 or 10,000. The viscosity (mPas) of the casting solution may be in a range provided by any two of these upper and/or lower amounts.

In some embodiments or example, the thickness of the dry interlayer may be in a range between about 1 pm to about 50 pm. The thickness (pm) of the dry interlayer may be less than about 50, 45, 40, 35, 30, 25, 20, 15, 10, 8, 6, 4, 2, or 1. The thickness (pm) of the dry interlayer may be at least about 1, 2, 4, 6, 8, 10, 15, 20, 25, 30, 35, 40, 45, or 50. The thickness (pm) of the dry interlayer may be in a range provided by any two of these upper and/or lower values.

In some embodiments or examples, the wet interlayer may be maintained at a temperature of between about 50 °C and about 100 °C in step (i)(a) for about 30 minutes to about 48 hours. The wet interlayer may be maintained at a temperature (°C) of less than about 100, 90, 80, 70, 60, or 50. The wet interlayer may be maintained at a temperature (°C) of at least about 50, 60, 70, 80, 90, or 100. The wet interlayer may be maintained at a temperature (°C) in a range provided by any two of these upper and/or lower values. The wet interlayer may be maintained at a temperature as described herein for less than about 48 hours, 30 hours, 20 hours, 10 hours, 5 hours, 1 hour, or 30 minutes. The wet interlayer may be maintained at a temperature as described herein for at least about 30 minutes, 1 hour, 5 hours, 10 hours, 20 hours, 30 hours, or 48 hours. The wet interlayer may be maintained at a temperature as described herein for a time in a range provided by any two of these upper and/or lower values.

In some embodiments or examples, the casting solution can be made homogeneous to provide further advantages/improvements.

In some embodiments or examples, the present disclosure is directed to a process for assembling an electrochemical cell, whereby the process may comprise the steps of: preparing an interlayer as defined by the process at least according to any one of the examples described herein, wherein the interlayer may comprise a carbon material and a plurality of porous particles, wherein the porous particles are porous aromatic framework for example, sulfonated porous aromatic framework (SPAF), particles, at least according to any one of the examples described herein; and assembling the interlayer into an electrochemical cell. In some other embodiments or examples, the present disclosure is directed to a process for assembling an electrochemical cell, whereby the process may comprise the steps of: preparing an interlayer as defined by the process at least according to any one of the examples described herein, wherein the interlayer may comprise a plurality of porous particles, wherein the porous particles are porous aromatic framework for example, sulfonated porous aromatic framework (SPAF), particles, at least according to any one of the examples described herein; and assembling the interlayer into an electrochemical cell.

Upon formation of the casting solution, some or all of the solvent may be removed (e.g., by natural evaporation or under vacuum) to generate a solid or viscous casting solution. The casting solution may be formed or moulded in any desired shape, such as an interlayer.

In some embodiments or examples, the casting solution may also be deposited on a support substrate (e.g. glass fibre and/or Celgard, PAN support, or an electrode material (e.g. the anode and/or the cathode of an electrochemical cell)) to generate a supported interlayer. It will be appreciated that a supported interlayer is the combination of the support substrate and the interlayer, also referred to as an interlayer supported on a substrate. Support substrates of varying pore size may be used within the present disclosure, generating supported interlayers of distinct porosity. For example, the support substrate may be, but not limited to, glass fibre, polypropylene type membrane, polyethylene type membrane, ceramic, alumina, or combinations thereof. In some embodiments or examples, the interlayer composition is localized on the surface of the support substrate and may not penetrate the support substrate. In other embodiments or examples, the interlayer composition may penetrate at least a fraction of the thickness of the support substrate. In yet another embodiment or example, the interlayer composition may be present throughout the thickness of the support substrate, so that the thickness of the supported interlayer may be taken as the thickness of the support substrate itself.

During preparation of a supported interlayer, the interlayer composition may be applied to only a portion of the surface of the support substrate. In some embodiments or examples, the portion (%) may be less than about 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, or 5. The interlayer composition may be retained within the support substrate by mechanical interlocking of the interlayer composition with the support substrate. In some embodiments or examples, the interlayer composition may be applied by solvent casting on the support substrate. In other embodiments or examples, the interlayer composition may be applied a multitude of times to the support substrate, in order to obtain the desired interlayer thickness.

In some embodiments or examples, the interlayer composition may be attached to the support substrate. In other embodiments or examples, the interlayer composition may form a layer on the surface of the support substrate. In yet another embodiment or example, the thickness (pm) of the layer may be less than about 10, 5, 2, 1, or 0.5.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

EXAMPLES

The present disclosure is further described by the following examples. It is to be understood that the following description is for the purpose of describing particular examples only and is not intended to be limiting with respect to the above description.

Example 1 Synthesis of porous aromatic frameworks (PAFs)

Example la

A 250 ml flask was evacuated and charged with 2,2’ -bipyridyl (1.13g, 7.25 mmol). 120 mL of anhydrous dimethyl formamide (DMF) was added followed by bis( 1,5 -cyclooctadiene) nickel (0) (Ni(COD)2, 2g, 7.25 mmol), and 1,5 -cyclooctadiene (COD, 0.9 mL, 7.25 mmol). The resulting purple solution was stirred at 80°C for 1 hour before the addition of tetrakis(4-bromophenyl) methane (1g, 1.6 mmol). The mixture was stirred at 80°C under inert, e.g. argon, atmosphere overnight. Then, the mixture was cooled to room temperature and 6 mol/L HC1 solution (20 mL) was added, the resulting mixture was stirred for another 6 hours to provide a green solution with an off-white precipitate. The precipitate was collected, then washed with chloroform (6 x 30 mL), tetahydrofuran (THF) (6 x 30 mL), and H2O (6 x 10 mL), respectively, and dried in vacuum to produce PAF as off-white powder (1g). Structural model of PAF-1

Example 2 Synthesis of sulphonated porous aromatic frameworks (SPAFs) Example 2a

To an ice-bath-cooled mixture of PAF (100 mg) in dichloromethane (10 mL), chlorosulfonic acid (1.0 mL, 15 mmol) was added dropwise. The resulting mixture was stirred at room temperature for three days. Then, the mixture was poured into ice, the solid was collected, washed with water substantially, and dried to produce PAF-SOsH (SPAF) as blue powder (125 mg). Figure 2 shows a structural model of SPAF.

Example 2b

To an ice-bath-cooled mixture of PAF (0.2187 mg) in sulphuric acid (2 mL), methanol (2 mL) was added dropwise. The resulting mixture was stirred at room temperature for three days. Then, the mixture was poured into ice, the solid was collected, washed with water substantially, and dried to produce PAF-SMe as white powder (0.5 mg).

Example 3 Surface area characterization of PAF

Surface area and pore textural characteristics of the PAF was obtained from the N2 adsorption isotherms for pressures up to 1 bar measured by a volumetric method using a Micromeritics ASAP 2420 instrument at 77 K (liquid nitrogen bath). Samples were evacuated and activated at 200 °C under dynamic vacuum at 10^-6 Torr for 12 h to remove any residual solvent and measure the sample mass precisely. Gas adsorption measurements were performed using ultrahigh- purity nitrogen. Brunauer-Emmett- Teller surface area and pore size distribution data were calculated from the N2 adsorption isotherms based on the density functional theory model in the software provided within the Micromeritics ASAP 2420 instrument and shown in Figure 3 for PAF-1 and Figure 4 for SPAF-1. Example 4 Ex-situ polysulfide absorption testing

Ex situ adsorption of polysulfide, e.g. Li2Se, with sulfonated porous aromatic framework (SPAF), carbon material, e.g. sulfonated black Pearl (SBP) and black pearl (BP), was undertaken at 1 SPAF, 1.5 BP; 1.5 SBP / Li2Se mass ratio, respectively, and known mass was added into a known volume of Li2Se solution (concentration, 0.4 mg mL"¹) in mixed dimethoxy ethane-dioxolane (DME-DOL) solvent (volume ratio, 1: 1). The supernatant solution was monitored with UV-vis spectroscopy. UV-vis spectroscopy was used to monitor the supernatant solution after a prescribed time to monitor the adsorption. To verify the capability of SPAF in adsorbing/trapping polysulfide, the interactions with a representative polysulfide species, Li2Se, was studied by investigating polysulfide adsorption on the porous SPAF. Two parallel experiments with BP and SBP were also conducted for the purpose of comparison. Figure 5(b) shows the colour change of the polysulfide solutions upon exposure to the corresponding materials for 5 min, 1 hr, 6 hr, and 20 hr, respectively, relative to the reddish brown blank Li2Se solution. It can be noted that the solution exposed to SPAF shows a remarkable change in colour throughout the whole adsorption period after 20 hours. However, a very slight darkening in colour after 20 hr is noticed in case of BP, which is reasoned to the sedimentation of suspended tiny carbon particles over longstanding. On the contrary, the colour of the other solution exposed to the SBP gradually lightens with the increase of the adsorption time, with a minimum change observed even after 6 hours. The solution exposed to SPAF has become completely colourless, indicating the advantageously effective adsorption of the polysulfide species.

Figure 5(a) compares the UV-vis spectra of the three solutions exposed to the corresponding materials after exposure for various times. The solution exposed to SPAF after 5 minutes and 20 hours shows a significant decrease in the intensity of spectra as the blank solution with the strong absorbance within 360-500 nm, verifying the complete adsorption of the polysulfide on SPAF. On the contrary, less reductions in the UV-vis absorbance are observed with the solutions exposed to BP and SBP, even shortly after 20 hours of exposure. The reduction becomes increasingly pronounced with the increase of exposure time in case of SPAF. After exposure for 20 hours, the residual polysulfide becomes marginal according to the insignificant UV-vis absorbance. Meanwhile, according to the reductions in peak intensity of the UV-vis absorbance, advantageously the rate of poly sulfide adsorption by the SPAF is unexpectedly efficient within the first hour. The described adsorption experiment indicates the strong interactions between SPAF and polysulfides.

Example 5 Quantitative analysis of PAF, SPAF and various fractions thereof

¹³C cross-polarisation (CP) and direct excitation (DE) magic angle spinning (MAS) NMR spectra were acquired on a Bruker Avance III spectrometer at a magnetic field strength of 11.7 T and with continuous wave ^JH decoupling applied during signal acquisition. A Bruker 4 mm HX MAS probe was used with samples finely ground into powders, packed into 4 mm zirconia MAS rotors and spun at 10 kHz. For the CP spectra, the contact time used was 1 ms and the recycle delay was set to 1 s. For the DE spectra the recycle delay was set to 10 s to ensure quantitative signals. The number of scans varied between 1000 and 5500 depending on the sample.

Example 6 Interlayer fabrication

A vacuum filtration method was used to fabricate the interlayer as defined by the present disclosure, for example, the interlayer may comprise a sulfonated porous aromatic framework (SPAF) and carbon material, such as black pearl (BP). The interlayer was casted onto a glass fibre (GF) substrate. SPAF (20 mg) and BP (60 mg) was added to 10 ml of ethanol and stirred for 24 hours. After stirring for 24 hours, ultrasonication was performed for a further two hours to achieve a homogeneous solution. The resulting solution was casted using vacuum filtration method onto glass fibre and interlayer was dried in a vacuum oven for 6 hours at 80 °C in order to evaporate ethanol from the substrate.

High building block structure of as synthesized SPAF advantageously allow for highly stable SPAF in any non-aqueous environment and easily processable into ultrathin interlayers with a vacuum filtration technique. In order to compare the electrochemical performance, SBP interlayer with similar thickness was also fabricated. The schematic illustration of the interaction mechanism of-SOsH and PAF with Li- ions is shown in Figure 7 (a). After exfoliation, scanning electron microscope (SEM) confirms the morphology of SPAF and BP mixture to a highly dispersed interlayer onto GF as shown in Figure 7 (d-f). The elemental EDX mapping analysis was used to confirm the homogeneous distribution of sulfur and carbon on interlayer. This homogeneity of sulfur in PAF may allow the uniform retention of negatively charged species during cycling and allows for uniform distribution of current in the cell, assisting with retarding the dendrite formation on Li anode. Cross-sectional image Figure 7 (c) of the hybrid interlayer, which showed a uniform distribution of materials and formation of a ~ 10 pm thick layer on top of the glass fiber (GF). The interconnected network of SPAF particles may allow the electrolyte and Li ions transfer faster which in return enhance the ionic conductive property of the separator. These highly ordered SPAF particles with the addition of BP can provide uniform porosity and unhindered ionic flow. Hence, delivers uniform current density.

Example 7 Electrochemical measurements

The electrolyte was 1.0 M LiTFSI/0. 1 M LiNOs in a mixed solvent of 1,3- dioxolane (DOI) and 1,2-dimethoxyethane (DME) (1: 1, v/v). In cells with SPAF-BP and SBP as interlayers, 30 pl of electrolyte was used to wet the interlayers, and in cells with the SPAF-BP and SBP interlayers, and additionally a commercial separator, e.g. celgard, 20 pL of electrolyte was applied on the commercial separator. The thickness of commercially available separator was 25 pm while optimized thickness of the fabricated SPAF-BP and SBP interlayers, as defined here, were in the range of 10-12 pm. Cells were assembled in an argon-filled glovebox and galvanostatically discharged and charged using a Solartron 1470 cell test galvanostat at room temperature. All the basic electrochemical performance experiments were performed including long term charge/discharge of Li-S cell, rate capability and electrochemical impedance spectroscopy using Solartron 1470 cell test galvanostat.

Example 7a Electrochemical performance of fabricated interlayers

In order to determine that the cells comprising the fabricated interlayers are capable of retaining the poly sulfides on the cathode side of the electrochemical cell, e.g. battery, and that the influence of SPAF-BP on the overall lithium ion transport rate, cycling behaviour was monitored. All the basic electrochemical performance experiments were performed including long term charge/discharge of Li-S cell, rate capability and electrochemical impedance spectroscopy (EIS). Long term cyclic performance of Li-S cell was tested at low and high loaded cathodes ranging 3.5-6 mg cm'² S, and results are highlighted in figure 8 (a) to (c). In comparison to the BP interlayer with maximum discharge capacity of 1010 mAhg'¹, the initial discharge capacity of the SPAF-BP incorporated interlayer was found to be 1596 mAhg'¹ and 1217 mAhg'¹ at 3.40 and 6 mg/cm² respectively. Meanwhile, the average CE of the cells assembled using SPAF-BP was 99.5 % over 500, and 100 cycles each advantageously indicating effective suppression of polysulfide shuttling. Capacity of SPAF-BP interlayer starts at theoretical scale and retain discharge capacity of >1000 mAh/g even after 500 cycles while SBP shows steady, continuous, capacity loss with cycling (Figure 8(a)). SPAF-BP interlayer demonstrates remarkable long-term capacity retention at higher loading of cathodes in Figure 8(b) 3.5 mg and Figure 8(c) 6 mg.

Table 1 below shows the effect of interlayer compositions on the electrochemical performance of a Li-S coin cell.

Table 1 Effect of interlayer compositions

It is notable that thickness and fraction of organic additive incorporated with BP plays a very critical role in its electrochemical performance and highly conductive and ultra-thin membranes could allow uniform distribution of current in the cell. For SBP, the resulting trend is consistent and shows the localization of poly sulfide near the cathode. It is important to understand the transport mechanism of positively charged species before introducing any sulfonic groups in Li based batteries. Li-ion conductivity for SPAF-BP interlayer using EIS and the measurements was carried out after the interlayer was fully adsorbed with the electrolyte and reached equilibrium. The electrolyte saturated interlayer was sandwiched between two stainless steel electrodes in coin type cells, and Li⁺ conductivity was calculated according to the following equation. o = l/ (Rb A) eq (1) where o stood for Li⁺ conductivity, 1 represented the thickness of the interlater, A was the area of the stainless-steel electrode, and Rb referred to the bulk resistance. For comparison, EIS of SBP was also performed and recorded EIS curves for both interlayers exhibit a single semicircle in high frequency region, whereas the bulk resistance (Rb) of SPAF-BP was found to be comparatively lower than SBP.

Detailed transference numbers were obtained for lithium ions (TLE). SPAF-BP and SBP interlayers sandwiched between two lithium electrodes, and a constant potential of 10 mV applied. Consequently, a current-time (i-t) curve is obtained (Figure 9 (a)) using Bruce-Vincent method, in which the Ti.r is estimated from the ratio of steady state current to initial current as mentioned in eq (2) where: Io is the initial current and Iss is the steady state current.

TL; = Iss /Io eq (2)

During this process, the anion current vanished in the steady state, and thus the cation transference number can be determined. Significant improvement from 0.54 (SBP) to 0.70 (SPAF-BP) was observed by incorporating the SPAF interlayer into this system. Unexpectedly, the SPAF interlayer was advantageously very efficient and capable of ultra-fast flow of cations indicating its excellent lithium ion transport property as demonstrated in Table 2. It has been advantageously found that the interlayer, as defined herein, is capable of not only enforcing sieving of cations but also unexpectedly provides the ability to tune the pores from 14 A to 5 A by the implementation of guest molecules. It has been found that a large reduction in pore size may further reject the polysulfide species on the cathode side of the cell, and the interlayer comprising porous aromatic framework (PAF) combined with sulfonation make Li-S batteries highly effective and efficient.

Table 2 Lithium-ion diffusivity measurements for various materials

Example 7b Lithium ion diffusivity measurements

The effect of interlayers on lithium ion diffusion was determined using cyclic voltammetry (CV) and NMR experimental study. The unexpected ultrafast lithium ion movement within Li-S battery system was found by first quantitatively measuring the Li ion diffusion coefficients (D ) for SPAF-BP and SBP by cyclic voltammetry (CV) and a series of cyclic voltammograms (CVs) with different scan rates (0.1-0.3 mVs'¹) and calculated by Randle s-Sevick equation as given below.

Ip = 2.69 x 10⁵ n^{1 5} ADLi ⁰⁵CLi V⁰⁵ eq (3)

As shown in Figure 9(c) and (d), the cathodic peaks at 1.8-2.0 V and 2.3-2.4 V are respectively labelled as C and B, while the anodic peak at around 2.4-2.5 V as A. Di.i- is calculated based on the slope of the linear plot of the peak current (I_P) versus the square root of the scan rate (V° ⁵) and the results are summarized in Table 3. It is important to note that different peaks obtained at different voltages has different effect on overall lithium ion diffusivity rate. For instance, formation of polysulfides at peak B of higher voltage starts to occur resulting in lowering the lithium ion diffusion for any interlayer. However, even at peak C of lower voltage (6.67 x 10"⁸) is higher than SBP (2.95 x 10'⁸). In fact, at this voltage peak, Li2S2 and Li2S starts to participate at the cathode surface and hinder the lithium ion diffusion. Due to highly ordered structure of PAF and functionalization on each aromatic ring, it can reject various redox species and helps in facile movement of lithium ions.

Table 3 Summary of various Li-ion transport parameters for SPAF-BP and SBP interlayers

To validate results from electrochemical measurements, a set of Li⁺ diffusion experiments using NMR were performed in a series ranging from commercially available materials such as Nafion to porous materials such as PAF and the results are summarized in Table 1. The lithium diffusion measurements were carried out using ⁷Li pulsed field gradient and samples were packed into 4 mm zirconia MAS rotors which were then put inside 5 mm NMR tubes. Sample temperature was controlled using a dry air gas flow, BCU II cooling unit and probe heating element with around 20 minutes of thermal equilibration time before each experiment. A stimulated echo pulse sequence was used with a diffusion time of 25 ms, gradient pulses with duration 2 ms and gradient strengths varied from 0 to around 3000 G/cm.⁴⁴ The resulting decay in ⁷Li signal intensity was fitted to the Stejskal -Tanner equation within the Bruker Topspin software as mentioned below.

I=Io exp (-DY²g²5²(A- 5/3)) (eq 4)

The largest Li+ diffusion coefficient in DOL:DME (7.98 x 10'¹¹ m² s^{- 1}) accounts for SPAF-BP in DOL:DME during the discharge as shown in Table 1 while SBP (3.83 x 10"¹¹ m² s^{- 1}) has shown only half of the diffusivity as compared to SPAF- BP. The most sluggish Li⁺ diffusion was in Nafion (1.15 x 10“ ¹² m² s“ ¹) suggesting an ultra-thin membrane required for cationic crossover. Li⁺ diffusion coefficient is generally accepted to describe diffusion behaviour, but the Li⁺ conductivity can also be calculated under external electrical potential. The relationship between ionic conduction and the diffusion coefficient can be described by the Nemst-Einstein equation as given below.

D= RTo/Z²F²Ci (eq 5)

Using the above equation, Li-ion conductivity of SPAF-BP was almost double comparing to SBP confirming the consistency of results obtained from electrochemistry calculations.

Example 7c Diffusion Measurement

Lithium diffusion measurements were carried out using ⁷Li pulsed field gradient (PFG) NMR on a Bruker Avance III spectrometer with a field strength of 7.05 T and a Bruker Diff50 Z-gradient probe. Samples were packed into 4 mm zirconia MAS rotors which were then put inside 5 mm NMR tubes. Sample temperature was controlled using a dry air gas flow, BCU II cooling unit and probe heating element with around 20 minutes of thermal equilibration time before each experiment. A stimulated echo pulse sequence was used with a diffusion time of 25 ms, gradient pulses with duration 2 ms and gradient strengths varied from 0 to around 3000 G/cm. The resulting decay in ⁷Li signal intensity was fitted to the Stejskal -Tanner equation within the Bruker Topspin software.

Example 8 Interlayer fabrication for anode coating

A solution casting method was used to fabricate the coated lithium as defined by the present disclosure, for example, the coating may comprise a sulfonated porous aromatic framework (SPAF), and polymer of intrinsic microporosity, such as poly(l- trimethylsilyl-1 -propyne) (PTMSP). The solution was casted onto a lithium foil electrode substrate. SPAF (5 mg) and PTMSP (95 mg) was added to 5 ml of chloroform and stirred for 24 hours. The resulting solution was cast using a drawdown rod onto lithium foil and the coating was dried in using convective currents of argon gas in order to evaporate chloroform from the substrate. High building block structure of as synthesized SPAF advantageously allow for highly stable SPAF in any non-aqueous environment and easily processable into ultrathin coatings with a solution casting technique. In order to compare the electrochemical performance, uncoated lithium electrodes were also fabricated. After drying, scanning electron microscope (SEM) confirms the morphology of SPAF and PTMSP mixture to a highly dispersed homogeneous coating onto lithium foil as shown in Figure 10 (a). The elemental EDX mapping analysis was used to confirm the homogeneous distribution of sulfur and PTMSP on lithium foil (as shown in Fig. 10 (b) and 10 (c), respectively). This homogeneity of sulfur in PAF may allow the uniform blocking of negatively charged species during cycling and allows for uniform distribution of current in the cell, assisting with retarding the dendrite formation on Li anode. Rejection of corrosive polysulfides by lithium selective SPAF channels during cycling may improve long term cycling stability. Cross-sectional image Figure 11 (a)- (d) of coated lithium anode further confirms that the coating is composed of homogeneous SPAF-PTMSP matrix with thickness of around 5 pm. The interconnected network of SPAF particles (Figure 12(c)) may allow the electrolyte and Li ions transfer faster which in return enhance the ionic conductive property of the coating. These highly ordered SPAF particles with the addition of PTMSP can provide uniform porosity and unhindered ionic flow. Hence, delivers uniform current density.

Example 9 Characterisation of Coated Lithium Electrode via Electrochemical Cycling

The electrolyte was 1.0 M LiTFSI/0. 1 M LiNOs in a mixed solvent of 1,3- dioxolane (DOI) and 1,2-dimethoxyethane (DME) (1: 1, v/v). In galvanic cells with SPAF-PTMSP coated lithium anodes cells were assembled in an argon-filled glovebox and galvanostatically discharged and charged using a BioLogic BCS-128 galvanostat at room temperature. All the basic electrochemical performance experiments were performed including long term charge/discharge of Li-S cell and rate capability were performed with a BioLogic BCS-128 and BT-Lab software. Symmetrical lithium metal batteries were tested using a BioLogic VSP-128 and EC-Lab software. The solution was composed of 95mg of PTMSP and 5mg SPAF dissolved in 5ml chloroform. The coating was performed using a wire-wound rod (RDS 10) and a wet thickness of 25um. The cell contains a composite sulfur cathode with 70wt% sulfur, 20wt% conductive carbon and 10% CMC binder. The cathode is 2cm² and contains 5 ,4mg of sulfur. The cell also contained a carbon-coated glass fiber interlayer, a polymer Celgard separator, and 160pl of electrolyte. The electrolyte was composed of 0.75 M L ¹ LiNOs, 0.25 M L ¹ LiTFSI as salts and 1: 1 DOL:DME.

The cell displays an average efficiency of 99.7% at 0.1°C and 99.2% at 0.5°C as shown in Figure 13.

Example 10 Additional functionality of Coated Lithium Electrode

It was observed that within Li-S cells, anodes coated with PTMSP (PTMSP@Li) experience substantially less metallic Li loss during extended cycling when compared to a control cell. This translates to improved cycling performance, specifically improved capacity retention in a coin cell over 250 cycles. The morphological distribution of the observed lithium in both samples was also distinct. It is believed that the PTMSP acts as a structural scaffold during volume expansion, as well as an ion-redistributor during plating and stripping.

Figure 14 presents two lithium anodes on steel current collectors that have been removed from cells after cycling. Figures 14a) and 14d) are composite SEM images. Figure 14b) is an enlarged backscatter SEM image. Figures 14c) and 14e) are false contrast images of Figures 14a) and 14d). The contrast is used to indicate differences in morphology /phase. Figures 14a), 14b), and 14c) are of the control cell after 275 cycles. Figures 14d), and 14e) are of the PTMSP@Li cell after 275 cycles. Figures 14c) and 14d) illustrate the substantial morphological differences between the control cell and PTMSP@Li. The control cell has a large area in the centre of the anode where high surface area morphologies can be observed (see Fig 14b) referred to as mossy Li). The lithium in these areas consists of high aspect ratio growths, and random three-dimensional appendages with high surface area-volume ratios. By contrast, the PTMSP@Li anode and current collector displays lower surface area-volume ratios, and presents flatter, smoother, and more even growths. As described above, higher SA/V growths contribute to capacity fading. The higher density of plating sites in PTMSP@Li is attributed to PTMSP’s intrinsic nanoporosity. The cycling performance for each cell can be seen below in Figure 15.

The current collector of the control cell has several areas where no lithium is observed, at the edge and in the centre. The lack of lithium may be due to dead lithium formation and float-off, as illustrated in the Figure 16. The PTMSP@Li anode by contrast has substantially more Li present on its surface after extended cycling (see also Figure 17). It is believed that the PTMSP coating functions as a lithium scaffold during morphology evolution, anchoring Li and ensuring coherent, electronically conductive growths form. This unique morphology reduces the volume of dead lithium formed during cycling, improving capacity retention.

Example 11 Interlayer fabrication for a redox flow battery

The filler particles (PAF-l-SOsH) were dispersed well into chloroform as solvent by stirring for 6 h followed by 15 min sonication in order to have a uniform and homogenous solution without any agglomeration. After that, 15 wt.% of the polymer (PTMSP) was added to the solution and stirred for another 6 h to make a dilute polymer solution. In this way, the filler surface is coated by the dilute polymer solution to reduce the stress and have a perfect adhesion at the filler/polymer interface. Finally, the rest of the polymer (85 wt.%) was added to the solution and stirred at ambient temperature for 24 h to get a homogenous polymer solution (3 wt.% PTMSP in chloroform incorporating 10 wt.% polymer based PAF-l-SOsH). The thin-film composite mixed matrix membranes were cast by a wire rod coating method. In this method, the prepared polymer solution is placed in front of the rod and the rod is moved across in line with the substrate. The polymer solution then goes through the very narrow space/grooves of the rod and gets coated on top of the PAN support. Finally, the CCMS membranes (PTMSP/PAF-l-SOsH/PAN) were dried in a vacuum oven at ambient temperature under vacuum for one day. Example 12a Permeation performance of interlayer in a redox flow cell

The single zero-gap cell hardware including a separator equipped with pairs of peristaltic pumps (BT300-2J Longer Precision Pump Co, Ltd.) and electrolyte reservoirs (10 mb), was connected to a Solartron 1470E multi-channel potentiostat to run the flow battery with a flow rate of 30 ml/min at room temperature. As a pre- treatment, the interlayers were protonated by soaking in 3M sulfuric acid overnight. To enhance activity and hydrophilicity of the electrodes, battery felts were thermally treated in air at 400 °C overnight. The starting electrolyte was synthesized with 1.5 M vanadyl sulfate in 3 M sulfuric acid due to the balance between vanadium reaction and infiltration. Then, a 1:2 volume of the starting electrolyte was used as anolyte and catholyte respectively due to the 1:2 electron transfer that occurs in the redox reaction. The excess of the positive electrolyte was removed after making the electrolyte by a typical pre-charging protocol. Both reservoirs were continuously purged with inlet/outlet N2 needles from the first to the last step of the experiments. Battery performance was examined by cycling tests (i.e. charging and discharging) conducted with the potentiostat at constant current densities. The cut-off voltage was set at 1.7 and 0.8 V in order to avoid electrode and flow channel plate corrosion. The effective membrane-electrode-assembly area was 5cm². The performance was evaluated with coulombic efficiency (CE), voltage efficiency (VE), and energy efficiency (EE) calculated by the following equations:

EE = CE X VE (eq 8)

Figure 18 compares the vanadium permeability of PTMSP/PAF-l-SOsH membrane with the control membranes, including PAN, Nafion (N212), and PTMSP using the diffusion cell. As hypothesized, the CCMS (PTMSP/PAF-l-SOsH) membrane exhibited nearly zero vanadium permeability, significantly lower than that of Nafion, which is due to the blocking of hydrated Vanadium ions by the hydrophobic microporous structure of the membrane. This behaviour should result in lower capacity decay. It is also observed that the membrane H⁺/V⁴⁺ selectivity improved by a factor of nearly two after incorporating PAF-l-SOsH into the PTMSP matrix.

Example 12b Battery performance

Single performance of the interlayer (PTMSP/PAF-l-SOsH) was measured as a new VRFB separator by charging and discharging the battery under constant current densities. In any battery system, regardless of the chemistry, the self-discharge behaviour must be minimised as it has a direct bearing on battery “shelf life,” as well as contributing to electrical inefficiency. Nonetheless, this big challenge has not been sufficiently examined, with scant reports in the area. The self-discharge performance of our membrane at the cell level is studied and compared with Nafion through measurement of open-circuit voltage (OCV) started at 50 % state of charge (SOC) and stopped at OCV of 0.8 V. As can be seen from Figure 19, the CCMS configured cell excels at maintaining the remaining discharge capacity over considerably longer periods of time. The improved self-discharge behaviour is attributed to the low vanadium permeability of the interlayer, in agreement with the permeation test described in Example 12a above.

Example 12c Stability of the interlayer

The operational and electrochemical stability of the membrane were also examined by long-term cycling at 300 mA or 60 mA cm’². Figure 20 showed that the cell configured with PTMSP/PAF-I-SO3H membrane demonstrated a significant improvement in capacity retention after 100 cycles (85 %) compared to the cell configured with the commercial Nafion membrane (58 %). Although it is difficult to make a comparison due to different material compositions, current densities, and cell assemblies, our novel concept showed comparable performance to the state of the art literature while providing competitive retention and charge efficiency. This improvement may be attributed to higher electrolyte utilization due to the large volume of narrow micropores in the PTMSP matrix, which retains the vanadium ions within the half cells, assisted by the PAF-l-SOsH fillers that enhances the proton mobility in the cell. These anti-aging additives may also prevent the glassy membrane from the commonly observed mechanical degradation as a result of the collapse of free volume.

Claims

59 CLAIMS:

1. An interlayer for an electrochemical cell comprising a carbon material and porous aromatic framework particles, wherein the porous aromatic framework particles are sulfonated porous aromatic framework particles (SPAF).

2. The interlayer of claim 1, wherein the carbon material is selected from the group comprising graphene, graphite, carbon nanotubes, carbon nanofiber, conductive polymer, or combinations thereof.

3. The interlayer of claim 1 or claim 2, wherein the ratio of carbon material to porous aromatic framework particles is about 80:20 to 50:50.

4. The interlayer of any one of the preceding claims, wherein the porous aromatic framework particles are selected from a rigid aromatic open-framework structure constructed by covalent bonds.

5. The interlayer of any one of the preceding claims, wherein the porous aromatic framework particles have a median pore diameter of less than about 100 pm.

6. The interlayer of any one of the preceding claims, wherein the porous aromatic framework particles have a median pore diameter of about 0. 1 nm to about 10 nm.

7. The interlayer of any one of the preceding claims, wherein the porous aromatic framework particles comprise a combination of micropores, mesopores and macropores.

8. The interlayer of any one of the preceding claims, wherein the porous aromatic framework particles have a pore volume in the range of from about 20 to about 90% of the total volume of the porous particle, preferably about 30 to about 80%, or more preferably from about 50 to about 80%. 60

9. The interlayer of any one of the preceding claims, wherein the sulfonated porous aromatic framework particles are SPAF-1 particles.

10. The interlayer of any one of the preceding claims, wherein the sulfur content of the interlayer is less than about 75 wt.% based on the total weight of the interlayer.

11. The interlayer of any one of the preceding claims, wherein the interlayer composition further comprises a polymer.

12. The interlayer of claim 11, wherein the polymer has a fractional free volume of at least 0.1.

13. The interlayer of claim 11 or claim 12, wherein the polymer is poly(l- trimethylsilyl-1 -propyne) (PTMSP).

14. The interlayer of any one of the preceding claims, wherein the interlayer further comprises a binder.

15. The interlayer of any one of the preceding claims, wherein the interlayer further comprises a hypercrosslinked polymer.

16. The interlayer of any one of the preceding claims, wherein the interlayer is a coating or fdm on a substrate.

17. The interlayer of claim 16, wherein a support substrate is selected from the group comprising a glass fibre support substrate, polymer support, or an electrode substrate.

18. The interlayer of any one of the preceding claims, wherein (a) the thickness of the interlayer is uniform and in the range of about 1 pm to about 50 pm and/or (b) has a pore size distribution in the range of about 0.5 nm to about 30 nm. 61

19. The interlayer of any one of the preceding claims, wherein the interlayer is a battery interlayer, redox flow battery interlayer, or a fuel cell interlayer.

20. The interlayer of any one of the preceding claims, wherein the interlayer is a lithium-sulfur battery interlayer or a vanadium redox flow battery interlayer.

21. An electrochemical cell comprising: a negative electrode; a positive electrode; an electrolyte; an interlayer as defined by any one of claims 1 to 20; and an optional separator.

22. The electrochemical cell of claim 21, wherein the interlayer is located between the anode and the cathode or is at least partially coated on the anode or the cathode, or both.

23. The electrochemical cell of claim 21 or claim 22, wherein the electrochemical cell is an energy storage device.

24. The electrochemical cell of claim 23, wherein the energy storage device is a battery, preferably a secondary battery.

25. The electrochemical cell of claim 24, wherein the battery is a lithium sulfur battery.

26. The electrochemical cell of any one of claims 21 to 25, wherein the negative electrode is an anode comprising lithium metal and the positive electrode is a cathode comprising elemental sulfur.

27. The electrochemical cell of any one of claims 21 to 26, wherein the positive electrode is a cathode and is a composite sulfur cathode. 62

28. The electrochemical cell of any one of claims 21 to 27, wherein the electrolytes are selected from non-aqueous solutions of lithium salts.

29. The electrochemical cell of claim 28, wherein the electrolyte comprises an anolyte and a catholyte.

30. The electrochemical cell of claim 29, wherein the interlayer is located between the anolyte and catholyte.

31. The electrochemical cell of claims 29 or 30, wherein the positive and negative electrode in the electrochemical cell are each independently carbon based.

32. The electrochemical cell of any one of claims 29 to 31, wherein the catholyte and the anolyte are selected from vanadium-based compounds.

33. The electrochemical cell of any one of claims 29 to 32, wherein the electrolyte is prepared by electrolytically dissolving a vanadium-based compound in an acid, wherein the acid is selected from the group comprising sulfuric acid (H2SO4), hydrochloric acid (HC1), sulfuric acid/hydrochloric acid (H2SO4/HCI), sodium sulfate (Na2SC>4), potassium sulfate (K2SO4), phosphoric acid (H3PO4), sodium phosphate (NaiPO ). potassium phosphate (K3PO4), nitric acid (HNO3), sodium nitrate (NaNOi). potassium nitrate (KNO3), or combinations thereof.

34. The electrochemical cell of any one of claims 29 to 33, wherein the electrochemical cell is a redox flow battery.

35. The electrochemical cell of claim 34, wherein the redox flow battery is a vanadium redox flow battery.

36. A method for improving cycling stability of a battery having an anode comprising lithium metal and a cathode comprising elemental sulfur, at least one 63 electrolyte, and an interlayer, wherein the interlayer is defined by any one of claims 1 to 20.

37. Use of an interlayer as defined by any one of claims 1 to 20 in an electrochemical cell.

38. Use of an interlayer as a coating on an anode in an electrochemical cell, wherein the interlayer is at least provided as a partial coating on the anode, and wherein the interlayer comprises a plurality of porous aromatic framework (PAF) particles, optionally one or more binders, optionally one or more polymers, and optionally one or more additives as defined by any one of claims 1 to 20.

39. The use of claim 37 or 38, wherein the electrochemical cell is a battery.

40. The use of claim 39, where in the battery is a lithium sulfur battery.

41. A process for preparing of an interlayer for an electrochemical cell, comprising the steps of:

(i) providing a carbon material and porous aromatic framework particles in a solvent system, wherein the porous aromatic framework particles are sulfonated porous aromatic framework particles (SPAF), for a predetermined time to produce a solution thereof; and

(ii) casting a film of the solution onto a substrate to provide a wet interlayer supported on the substrate.

42. The process of claim 41, further comprising the steps of:

(a) preparing porous aromatic framework particles in a solvent system;

(b) converting the porous aromatic framework particles to sulfonated porous aromatic framework particles in a solvent system;

(i) providing a carbon material and sulfonated porous aromatic framework particles in a solvent system for a predetermined time to produce a solution; and (ii) casting a film of the solution onto a substrate to provide a wet interlayer supported on the substrate.

43. The process of claim 41 or claim 42, wherein the process further comprises step (iii) solidifying the wet interlayer supported on the substrate by solvent evaporation.

44. The process of any one of claims 41 to 43, wherein the process further comprises step (i)(a) addition of a polymer.

45. The process of any one of claims 41 to 44, wherein the solvent is an organic solvent selected from aromatics, halogenated aromatics, halogenated aliphatic hydrocarbons, aliphatic hydrocarbons, glycols, ethers, glycol ethers, esters, alcohols, ketones, or combinations thereof.

46. The process of any one of claims 41 to 45, wherein the ratio of carbon material to sulfonated porous aromatic framework particles (SPAF) is about 80:20 to 50:50.

47. The process of any one of claims 41 to 46, wherein the thickness of the dry interlayer is in a range between about 1 pm to about 50 pm.

48. The process of any one of claims 41 to 47, wherein the wet interlayer is maintained at a temperature of between about 50 °C and about 100 °C in step (i)(a) for about 30 minutes to about 48 hours.

49. An interlayer for an electrochemical cell comprising a carbon material and a plurality of porous particles, wherein the porous particles are sulfonated porous aromatic framework particles (SPAF), prepared by the process as defined in any one of claims 41 to 48.

50. A process for assembling an electrochemical cell, whereby the process comprises the following steps: preparing an interlayer as defined by the process in any one of claims 41 to 48, wherein the interlayer comprises a carbon material and a plurality of porous particles, wherein the porous particles are porous aromatic framework particles, as defined in any one of claims 1 to 20; and assembling the interlayer into an electrochemical cell.

51. The process of claim 50, wherein the interlayer is located between an anode and a cathode of the electrochemical cell as defined in claim 21.