FIELD OF INVENTION

[0001] This invention relates to redox-active layers as well as electrodes and thin-film charge-storage devices comprising the same, which combine a high charge content and fast power delivery as a result of modifications of the geometry and/or composition of the redox-active layer, in addition, the present invention relates to a method of maximizing charge content and power delivery of a charge storage device.

BACKGROUND OF THE INVENTION

[0002] In the recent years, there has been a high interest in the development of charge- storage devices which ideal!y exhibit both the high energy density associated with batteries and high power density, which is typically attributed to supercapacitors.

[0003] Supercapacitors rely on the adsorption of electrically charged ions at the interfaces between the electrode materials and the electrolyte (i.e. the formation of electrical double layers). They display very fast discharge behaviour (i.e. high power delivery), in combination with relatively low charge content.

[0004] On the other hand, batteries rely on electrochemical reactions of the anode and cathode materials to generate electric current. They are characterised by higher charge contents than supercapacitors, in combination with much lower current delivery.

[0005] In comparison to many inorganic redox materials, semiconducting n- and p-type polymers give rise to relatively low charge densities. This disadvantage is due to the fact that the electron and hole transporting monomers in these polymers only account for a fraction of the overall volume as they comprise large portions of electrochemically inert features such as solubilising sidechains. Removing these sidechains increases the charge density at the cost of the materials becoming insoluble, which severely limits their processability.

[0006] In comparison to inorganic materials, such as those disclosed in CN 103426649 B and CN 102522218 B, an advantage of using polymers as active redox materials is the fact that as predominantly amorphous materials, polymers can be optimised to display high ion content and relatively high ionic mobility in the bulk, in particular when polar and/or ionic sidechains are included into the polymer chain. [0007] In addition to the molecular structure of the active redox material, the thickness of the anode and cathode materials is an important factor. Obviously, the charge content increases with the thickness of the anode and cathode materials. On the other hand, when conjugated polymers are discharged, their electrical conductivity is greatly reduced. Accordingly, it is difficult to simultaneously maximise charge content and power delivery, since thick layers of (insoluble) materials with high charge density are likely to result in high ionic resistivity, and therefore low current delivery, whereas thin layers of polymer materials with high ion content and high ion mobility in the bulk result in low ionic and electrical resistivity, and therefore high current/power delivery, but low charge content.

[0008] In this context, it is also important to note that for many applications, the power requirements can vary largely as a function of time. For example, in sensor systems the power consumption can be very high during short time intervals, with intermittent periods of low power consumption. For this kind of applications, it would be desirable to provide a battery/supercapacitor that combines high charge content (i.e. energy content) with the ability to provide high power (i.e. high discharge currents) during short periods of time.

[0009] US 2015/0162139 A1 proposes a multilayer electrode structure comprising different concentrations of redox-active material to improve the capacity performance of a supercapacitor. However, the problem of simultaneously achieving a high charge content and high discharge currents during short time periods is not mentioned.

[00 0] Therefore, it remains desirable to provide charge storage devices which may be manufactured easily and simultaneously enable maximized charge content and power delivery. Moreover, it would be desirable to provide a simple method which allows a fine- tuning between these battery and supercapacitor characteristics. SUMMARY OF THE INVENTION

[0011] The present invention solves these objects with the subject matter of the claims as defined herein. The advantages of the present invention will be further explained in detail in the section below and further advantages will become apparent to the skilled artisan upon consideration of the invention disclosure.

[0012] In general, the present invention relates to a single layer for use in a charge storage device, wherein the single layer comprises a redox-active polymer and multiple sections having different charge densities per unit volume. This aspect may be alternately expressed as the single layer comprising a redox-active polymer and multiple sections (or regions or areas) having different charge densities (or capacities) per unit area. In preferred embodiments, said difference between the charge densities is established: a) through different layer thicknesses of the sections; and/or b) by configuring the single layer as a composite comprising high charge density particles dispersed in a matrix comprising or consisting of the redox-active polymer, wherein the high charge density particles consist of a redox-active materia! different from the redox-active polymer and have a higher specific charge capacity per unit mass than the material constituting the matrix.

[0013] Accordingly, the battery and supercapacitor characteristics can be tailored via the area ratio of thin vs. thick portions of redox films, and/or via the volume density and the size distribution of high charge density particles dispersed in composites with the solution- processable conjugated polymers. Moreover, these redox-active layers may be manufactured easily by solution deposition techniques.

[0014] The charge storage device may be intended for and capable of supplying current to an electrical load.

[0015] In another embodiment, the present invention provides an electrode assembly and a charge storage device comprising said single layer.

[0016] In a further embodiment, the present invention provides a method of maximizing charge content and power delivery of a charge storage device, wherein the method comprises: depositing a single layer comprising a redox-active polymer and multiple sections having different charge densities per unit volume, preferably by: a) structuring the single layer to provide sections with different layer thicknesses; and/or b) dispersing high charge density particles in a matrix comprising or consisting of the redox-active polymer before deposition of the single layer, wherein the high charge density particles consist of a redox-active material different from the redox-active polymer and have a higher specific charge capacity than the material constituting the matrix.

[0017] Preferred embodiments of the present invention and other aspects are described in the following description and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1a shows a side-sectional view of an exemplary electrode assembly using the single layer in accordance with the second embodiment during discharge.

[0019] FIG. 1 b shows a side-sectional view of the exemplary electrode assembly using the single layer in accordance with the second embodiment during re-charging.

[0020] FIG. 2a shows a side-sectional view of an exemplary electrode assembly using the single layer in accordance with the third embodiment during discharge.

[0021] FIG. 2b shows a side-sectional view of the exemplary electrode assembly using the single layer in accordance with the third embodiment during re-charging. [0022] FIG. 3a shows a side-sectional view of an exemplary electrode assembly using the single layer in accordance with the fourth embodiment during discharge.

[0023] FIG. 3b shows a side-sectional view of the exemplary electrode assembly using the single layer in accordance with the fourth embodiment during re-charging.

[0024] FIG. 4 illustrates the side-sectional view of an electrode assembly comprising different exemplary geometrica! forms.

[0025] FIG. 5 shows an exemplary configuration of a charge-storage device.

DETAILED DESCRIPTION OF THE INVENTION

[0026] For a more complete understanding of the present invention, reference is now made to the following description of the illustrative embodiments thereof: Redox Layer

[0027] In a first embodiment, the present invention relates to a single layer for use in a charge storage device, wherein the single layer comprises a redox-active polymer and multiple sections having different charge densities per unit volume.

[0028] The term "single layer" is meant to exclude the presence of other continuous layers or layers formed by a concentration gradient of materials along the thickness direction of the layer.

[0029] The expression "charge density per unit volume" refers to the charge density in the material constituting the single layer relative to a unit volume. If the single layer has a structured/patterned surface with multiple thicknesses, the charge density per unit volume is calculated based on the assumption of a layer having two flat surfaces and the maximum thickness (as illustrated by the dashed line in Fig. 1 a).

[0030] The term "redox-active polymer" refers to a polymer which is capable of reversibly transitioning between at least two oxidation states wherein the transition between states occurs through oxidation (i.e. electron loss) and reduction (i.e. electron gain) processes.

[0031] As it will be understood, the specific redox-active polymer is not particularly limited and may be suitably chosen by the skilled artisan from materials known in the art.

[0032] In a preferred embodiment, the redox-active polymer is a p-doped or n-doped polymer rendered conductive by doping of p-type or n-type conjugated organic polymers, respectively.

[0033] Suitable p-type conjugated organic polymers may be based on known electron donating conjugated organic polymers. In a preferred embodiment, the p-type conjugated organic polymer is a homopolymer or a co-polymer including alternating, random or block copolymers. As exemplary p-type conjugated organic polymers, polymers selected from conjugated hydrocarbon or heterocyclic polymers may be mentioned. As examples, in-chain conjugated polymers or co-polymers comprising as monomer units one or more selected from the group consisting of acene, aniline, azulene, benzofuran, fluorene, furan, indenofluorene, indole, phenylene, pyrazoline, pyrene, pyridazine, pyridine, diarylaikylamine, triarylamine, phenylene vinylene, 3-substituted thiophene, 3,4- bisubstituted thiophene, selenophene, 3-substituted selenophene, 3,4-bisubstituted selenophene, bisthiophene, terthiophene, bisselenophene, terselenophene, thieno[2,3- b]thiophene, thieno[3,2-b]thiophene, benzothiophene, benzo[1 ,2-b:4,5-b']dithiophene, isothianaphthene, monosubstituted pyrrole, 3,4-bisubstituted pyrrole, 1 ,3,4-oxadiazo!es, isothianaphthene, and derivatives thereof may be mentioned. Preferred examples of such p-type polymers are in-chain conjugated homopolymers or co-polymers of monomers selected from at least one, more preferably at least two of the group of fluorenyi derivatives, phenylene derivatives, aniline derivatives, dialkylarylamines, diarylalkylamtnes, diarylamines, triarylamines and heteroaromatic hydrocarbons.

[0034] Suitable n-type conjugated organic polymers may be based on known electron accepting conjugated organic polymers. Preferably, the n-type conjugated organic polymer is a homopolymer or co-poiymer including alternating, random or block copolymers. As exemplary n-type conjugated organic polymers, in-chain conjugated polymers or copolymers of monomers selected from the group of fluorenyi derivatives, heteroaromatic hydrocarbons (such as e.g. benzothiadiazoles and its derivatives, triazine derivatives (e.g. 1 ,3,5-triazine derivatives), azafluorene derivatives, or quinoxalines), conjugated aromatic hydrocarbons (e.g. arenes, acenes), carbonyl-based monomers (such as fluorenone derivatives), and derivatives may be mentioned.

[0035] The dopants are likewise not particularly limited as long as they capable of inducing the formation of charge carriers in the conjugated organic polymers. A number of suitable p-type dopants is disclosed in US 2016/0013392 A1 , for example. Preferably, the p-type dopant is selected from the group of electron acceptors. As examples thereof, TCNQ (tetracyanoquinodimethane), halogenated tetracyanoquinodimethane (including e.g. tetrafluorotetracyanoquinodimethane (F4TCNQ)), 1 ,1 -dicyanovinylene, 1 ,1 ,2- tricyanovinyiene, benzoquinone, pentatluorophenol, dicyanotluorenone, cyano- fluoroalkylsulfonyl-fluorenone, pyridine, pyrazine, triazine, tetrazine, pyridopyrazine, benzothiadiazole, heterocyclic thiadiazole, porphyrin, phthalocyanine, and boron atom- containing compounds may be mentioned. N-type dopants may be selected from electron donors or reducing agents. As examples thereof, imidazol derivatives (e. g. dihydro-1 H- benzoimidazoI-2-yI (N-DBI)), metal acetylacetonate complexes (e.g. Co(acac) ₃ , Fe(acac)3, n(acac) ₃ ) and inorganic reducing agents (e.g. SnC ) may be mentioned.

[0036] Other exemplary redox-active polymers include redox-active species based on homo- or co-polymers comprising monomeric units on the basis of quinolines, anthraquinones, metal complex polymers, and derivatives or combinations thereof.

[0037] The redox-active polymers may generally comprise solubilizing groups which facilitate the solution processability of the layer composition. While not being limited thereto, alkyl (e.g. C2-C3o-alkyl), haloalkyl (e.g. C2-C3o-haloalkyl), aryl (e.g. Ce-Cso aryl), haioaryl (e.g. Ce-Cao haloaryi), alkoxy (e.g. C-1-C30 a!koxy), poly- or oligoether groups (e.g. poly(oxyaikylene), olio(oxyalkylene)) and combinations thereof may be mentioned as exemplary solubilizing groups.

[0038] The single layer may consist of the redox-active polymer. In addition, the single layer may comprise further additives, such as e.g. plasticizers, surfactants, cross-linking agents or low-molecular weight compounds.

[0039] By use of the above-described single layer, electrochemical charge storage devices that combine the high charge content of batteries with the capability to deliver high power during short intervals which is typical for supercapacitors may be realized.

[0040] In the following, preferred embodiments of establishing the difference between the charge densities (per unit volume) in the sections will be discussed below. It will be understood that these embodiments may be employed separately or may be suitably combined.

Structured Redox Layer

[0041] In a second embodiment, the organic material single layer exhibits sections with different layer thicknesses.

[0042] While not being limited thereto, it may be preferable that the sections are arranged parallel to the surface of the single layer. In another preferred embodiment, the sections having different layer thicknesses may be arranged as a multiplicity of alternating sections.

[0043] The advantageous effects of a structure having sections with different layer thicknesses will be explained with reference to Figures 1 a and 1 b. Fig. 1 a shows the cross- section of a single layer (12) formed on a substrate layer/charge collector layer (1 1 ), wherein the single layer (12) has a structured surface with alternating sections A having a relatively high thickness†A (i.e. a relatively high charge density per unit volume) and sections B having a relatively low thickness te (i.e. a relatively low charge density per unit volume). The thick areas (sections A) ensure high charge content, whereas the thin areas (sections B) ensure high power delivery (during a short amount of time), so that during discharge, sections B will be preferably discharged in the redox film (Fig. 1 a). During time intervals with low power consumption, the thin sections B are then re-charged by redox equilibration with the thick sections A (Fig. 1 b). Hence, the organic material single layer combines a high discharge current during short time intervals with the ability of storing large charge quantities.

[0044] The ratio of the thicknesses and the width and/or area of the different sections may be appropriately selected depending on the purpose of the charge storage device (i.e. power delivery and charge storage characteristics) and the desired structural or mechanical strength of the resulting single layer. For example, if the charge storage device is to be used in applications which require high power delivery during especially short periods and relatively long intermittent periods with low power consumption, a relatively low layer thickness for section B may be preferable. Accordingly, the battery and supercapacitor characteristics may be fine-tuned via the ratio of the thin portion area to thick portion area and/or via the differences in layer thickness.

[0045] It may be preferable that the sections comprise one or more sections A and one or more sections B, wherein the layer thickness te of section B is between 2% and 90% of the maximum layer thickness ΪΑ of section A, further preferably between 3% and 80%, especialiy preferably between 5% and 40%. Such a ratio ensures that the effect of the present invention is attained to a favourable degree. In a further preferred embodiment, te is in a range of from 10 nm to 500 pm, preferably in a range of from 20 to 300 nm and/or ΪΑ is in a range of from 50 nm to 800 pm, preferably in a range of from 100 nm to 1 pm. It is to be noted that, in general, section B is defined as the section, wherein the layer thickness is 90% or less of the maximum layer thickness†A of section A, thereby setting a boundary between sections A and B.

[0046] in a preferred embodiment, sections A and B may form a grating structure, in another preferred embodiment, section A may be pillar-shaped (including, but not limited to rectangular, cylindrical, triangular, conical and/or star-shaped pillar forms). As is illustrated in Fig. 4, the cross-section of the organic single layer is not limited to rectangular patterns, but may also comprise pyramid/cone shapes (a), rounded rectangular forms (b), hemispherical shapes (c), flat cone (e) and convex flat cone shapes (f), for example. Also, sections B do not necessarily exhibit a flat cross-section, but may also be rounded (d). In the latter case, the minimum thickness is referred to as layer thickness te (see Fig. 4).

[0047] In a preferred embodiment, patterned surfaces comprising the sections A and B are formed by micro- or nanoembossing. Examples thereof include hot embossing techniques (see e.g. L. Peng et a!., Journal of Micromechanics and Microengineering 2013, 24(1 ); . Worgull, "Hot Embossing: Theory and Technology of Microreplication", William Andrew, 2009, Elsevier), ultrasonic embossing techniques, and combinations thereof. In order to combine the provision of high discharge currents during short periods of time with a high level of charge content, the anode and cathode layers can be structured to comprise areas that enable fast discharge (i.e. high power delivery), and areas that can store large quantities of charge.

Composite Redox Layers

[0048] in a third embodiment, the present invention relates to a single layer for use in a charge storage device, wherein the single layer comprises a redox-active polymer and multiple sections having different charge densities per unit volume, wherein the differences in charge density is established by configuring the single layer as a composite comprising high charge density particles dispersed in a matrix comprising or consisting of the redox- active polymer, wherein the high charge density particles consist of a redox-active material different from the redox-active polymer and have a higher volume-specific charge density than the material constituting the matrix. Accordingly, the composite combines a polymer with low charge density (but high ionic mobility) with particies of an insoluble material that has high charge density.

[0049] Thereby, similar to the approach of surface structuring, areas which enable fast discharge and high power delivery are generated next to areas enabling high charge capacity.

[0050] The single layer according to the third embodiment may consist of the redox-active polymer and the high charge density particles. Alternatively, the single layer may comprise further additives, such as e.g. plasticizers, surfactants, cross-linking agents or low- molecular weight compounds.

[0051] An example illustrating the effect of this embodiment is shown in Figures 2a and 2b. Fig. 2a shows the cross-section of a single layer (22) formed on an optional substrate/charge collector layer (21), wherein the single layer (22) comprises alternating sections having different relative volume concentrations of high charge density particles (23). The areas with relatively high concentration of high charge density particies ensure high charge content, whereas areas with a reiatively low (or zero) concentration of high charge density particles ensure a high power delivery during a short amount of time, so that during discharge the latter areas will be preferably discharged in the redox film (Fig. 2a). During time intervals with low power consumption, these sections may then be re-charged by redox equilibration with the areas having a reiatively high concentration of high charge density particles (Fig. 2b). Hence, the organic material single layer combines a high discharge current during short time intervals with the ability of storing large charge quantities. [0052] The material used for the high charge density particles is not particularly limited as long as it is redox-active and exhibits a higher specific charge capacity than the redox-active polymer used in the matrix. The specific charge capacity may be determined by methods commonly used in the art, such as by integration of anodic or cathodic waves in cyclic voltammograms or by integration of current transients in response to a potential step from a fully oxidized to a fully reduced state.

[0053] In a preferred embodiment, the high charge density particles consist of a p-doped or n-doped polymer as specified above, with the exception that it contains less soiubilizing groups or preferably no soiubilizing groups at all. In the material used for high charge density particles, soiubilizing side-chains do not need to be present and the high charge density particles will typically represent insoluble redox components for which the redox-active polymer acts as an electronically and ionicaily conductive binder. By using the redox-active poiymer as a matrix in which insoluble high charge density particles are dispersed, solution processability is enabled.

[0054] In general, when using a n-doped poiymer as matrix material, it is preferable to use a material for the high charge density particles which exhibits a redox potential equal to or lower (more negative) than the redox potential of the n-doped polymer. On the other hand, when using a p-doped polymer as matrix material, it is preferable to use a material for the high charge density particles which exhibits a redox potential equal to or higher (more positive) than the redox potential of the p-doped polymer. Further preferably, the maximum difference between the redox potentials of the doped polymer and the materia! constituting the high charge density particles is 0.3 V or less, such as 0.2 V or less, for example.

[0055] The particle size distribution of the high charge density particles may be selected in accordance to the purpose of the final device and depending on the thickness of the single layer. Typically, the average particle size may be in the range of from 1 nm to 100 pm.

[0056] In this third embodiment, the battery and supercapacitor characteristics may be fine- tuned via the volume density and/or the size distribution of the high charge density particles in the composite.

Structured Redox Layers Comprising Composites

[0057] In a fourth embodiment, the two above-described concepts of establishing the difference between the charge densities (per unit volume) within the sections are combined in a single organic redox layer which enables the provision of charge storage devices with particularly favourable charge content and power delivery and advantageously allows improved fine-tuning between battery and supercapacitor characteristics. [0058] An example of such a configuration is shown in Figures 3a and 3b. In particular, Fig. 3a shows the cross-section of a single layer (32) formed on an optional substrate/charge collector layer (31), wherein the single layer (32) has a structured surface with alternating sections A having a relatively high thickness†A (i.e. a relatively high charge density per unit volume) and sections B having a relatively low thickness (i.e. a relatively low charge density per unit volume), which may be defined in accordance to the second embodiment. In addition, as described in the third embodiment, the single layer is configured as a composite comprising high charge density particles (33) dispersed in a matrix comprising or consisting of the redox-active polymer, wherein the high charge density particles (33) consist of a redox-active material different from the redox-active poiymer and have a higher volume-specific charge density than the material constituting the matrix.

[0059] It is to be understood that Figures 3a and 3b, which do not show high charge density particles in section B, are illustrative only and that the fourth embodiment is not limited to such a configuration.

[0060] In a preferred embodiment, a volume concentration CA of the high charge density particles in section A is higher than a volume concentration CB of the high charge density particles in section B.

[0061] In another preferred embodiment, the volume concentration c _B of the high charge density particles in section B is less than 70%, more preferably less than 50%, further preferably less than 30% of the volume concentration c _A of the high charge density particles in section A. In one embodiment, section B does not comprise high charge density particles.

Electrode Assembly & Charge Storage Device

[0062] A fifth embodiment of the present invention is directed to an electrode assembly comprising the single layer described in the first to fourth embodiments.

[0063] Preferably, the electrode assembly consists of the single layer according to the first to fourth embodiments and either a current collector layer or a substrate layer.

[0064] Suitable materials for current collector layers include material that is selected from the group consisting of porous graphite, porous, highly doped inorganic semiconductor, highly doped conjugated polymer, carbon nanotubes or carbon particles dispersed in a non- conjugated polymer matrix, aluminum, silver, platinum, gold, palladium, tungsten, indium, zinc, copper, nickel, iron, stainless steel, lead, lead oxide, tin oxide, indium tin oxide, graphite, doped silicon, doped germanium, doped gallium arsenide, doped polyaniline, doped poiypyrrole, doped polythiophene, and their derivatives, with indium tin oxide being particularly preferred. [0065] Alternatively, the redox layers may comprise conductive particles (such as graphene, carbon nanotubes or carbon particles, for example) that are dispersed in the redox polymer layer at a concentration higher than a percolation threshold concentration in order for the redox layers themselves to perform as current collectors. In this case, a electrode assembly may comprise a substrate layer which provides mechanical support. The substrate layer material is not particularly limited and may be selected by the skilled artisan depending on the desired rigidity or flexibility, for example. For instance, polymeric material may be employed as substrate layer material.

[0066] In a sixth embodiment, the present invention relates to a charge storage device comprising the electrode assembly in accordance to the fifth embodiment.

[0067] in a preferred embodiment, the charge storage device of the present invention is a thin-film charge storage device and/or a battery and/or a battery/supercapacitor hybrid.

More preferably, the charge storage device of the present invention is a polymer battery.

[0068] While not being limited thereto, an exemplary configuration of a charge storage device is shown in Fig. 5, the device comprising a first redox layer (2), a second redox layer

(4) and a separator (3) between the redox layers, wherein the single layer according to any of the first to fourth embodiments constitutes at least one of the first and redox layers (2) and (4). The charge storage device is for supplying current to an electrical load.

[0069] Typically, as in the configuration of Fig. 5, the charge storage device comprises layers (1) and (5) at the side of the polymer layers opposed to the separator which may be independently current collector layers or substrate layers.

[0070] The material for the separator layer (3) is not particularly limited and may be made of known materials that are chemically and electrochemically unreactive with respect to the charges and to the electrode polymer materials in their neutral and charged states.

[0071] Typically, the separator contacts the n-type and p-type electroactive polymer layers (2) and (4) such that the transport of ions is facilitated. As suitable materials, porous polymeric materials (e.g. polyethylene, polypropylene, polyester, teflon or cellulose-based polymers), ion-conductive po!ymer membranes (e.g. Nafion™), (electronically nonconductive) gel electrolytes (e.g. polymers, copolymers and oligomers having monomer units selected from the group consisting of substituted or unsubstituted vinylidene fluoride, urethane, ethylene oxide, propylene oxide, acrylonitrile, methyimethacry!ate, aikylacrylate, acrylamide, vinyl acetate, vinylpyrrolidinone, tetraethylene glycol diacrylate, phosphazene and dimethylsiloxane), cellulose-based gel electrolytes or cellulose-based membranes (e.g. filter paper) may be mentioned, with the proviso that the materials are resistant towards dissolution by the electrolyte, which may be appropriately achieved by methods known to the skiiled artisan (e.g. by suitable selection of materials or by cross-tinking in case of polymers).

[0072] The separator layer thickness may likewise be appropriately selected by the skilled artisan depending on the purpose. Typically, the separator thickness is between 5 pm and 100 pm.

[0073] The electrolyte for use in the charge storage device is not particularly limited and may be suitably selected by the skilled artisan depending on the chosen separator and electroactive materials. As examples thereof, electrolyte salts dissolved in appropriate solvents as commonly used in the art or ionic liquids that are typically liquid below 100 °C may be mentioned, the latter including, but not being limited to ammonium-, imidazolium-, phosphonium-, pyridinium-, pyrrolidinium-, and sulfonium-based ionic liquids. Other preferred examples include bis(trifluoromethane)sulfonimide (TFSI)-based ionic liquids such as e.g. 1 -ethyl-3-methy! imidazolium bis(trifluoromethane)sulfonimide (EMI-TFSI), triethylmethoxyethyl phosphonium bis(trifluoromethane)sulfonimide (TEMEP-TFSI), triethyl sulfonium bis(trtfluoromethane)sulfonimide (TES-TFSI) or 1 -butyl-1 -methylpyrrolidinium bis(trifluoromethane}sulfonimide (BMP-TSFI), the latter being particularly preferable.

[0074] It is to be understood that the charge storage device according to the present invention may also comprise additional layers not shown in Fig. 5, such as one or more encapsulation layers, for example.

Methods of Preparation and Tuning of Batterv/Supercapacitor Characteristics

[0075] The methods for the preparation of the single layer and the electrode assembly according to the first to fifth embodiments are not particularly limited.

[0076] In a preferred embodiment, the single layer according to the second embodiment of the present invention is prepared by depositing the composition comprising the redox-active polymer from solution and by subsequent micro- or nanoembossing of the deposited composition in order to provide the sections having different layer thicknesses. Examples of micro- or nanoembossing techniques include hot embossing, ultrasonic embossing, and combinations thereof.

[0077] The single layer according to the third embodiment is preferably prepared by dispersing high charge density particles in a matrix comprising or consisting of the redox- active polymer before deposition of the single layer from solution.

[0078] For the preparation of the single layer of the fourth embodiment, both methods may be suitably combined. Moreover, for the preparation of the electrode assembly according to the fifth embodiment, the single layer composition may be deposited from solution directly onto the current collector layer or the substrate layer. [0079] The solution deposition technique includes but is not limited to coating or printing or microdispensing methods like for example spin coating, spray coating, web printing, brush coating, dip coating, slot-die printing, ink jet printing, letter-press printing, screen printing, doctor blade coating, roller printing, offset lithography printing, flexographic printing, or pad printing. Preferably, the solution deposition method is a blade coating or screen printing method,

[0080] Accordingly, the redox single layers of the present invention as weil as the electrode assembly may be fabricated in a simple and straightforward manner, particularly when compared to the preparation of redox-active multilayers or redox-active layers which may not be processed by solution deposition.

[0081] While for the preparation of the single layer and the electrode assembly the above-defined methods are preferable, the charge storage device of the present invention as a whole may be manufactured by methods commonly known in the art.

[0082] In another embodiment, the present invention relates to a method of maximizing charge content and power delivery of a charge storage device. The method comprises: depositing a single layer comprising a redox-active polymer and multiple sections having different charge densities per unit volume, preferably by: a) structuring the single layer to provide sections with different layer thicknesses; and/or b) dispersing high charge density particles in a matrix comprising or consisting of the redox-active polymer before deposition of the single layer, wherein the high charge density particles consist of a redox-active material different from the redox-active polymer and have a higher specific charge capacity than the material constituting the matrix.

[0083] As a result, single layers in accordance to the first to sixth embodiments may be obtained which enable the provision of charge storage devices with rapid current delivery and improved charge storage.

[0084] Single layers in accordance with the third to sixth embodiments may also exhibit charge capacities for continuous discharge which are improved as compared to an equivalently thick layer of redox-active polymer which does not include high charge density particles. This may arise as a result of increasing the average charge capacity of the single layer by including the dispersed high charge density particles.

[0085] It will be appreciated that the method of the present invention may employ any of the preferred features specified above with respect to the description of the single layers, and that the preferred features may be combined in any combination, except for combinations where at least some of the features are mutually exclusive.

[0086] Once given the above disclosure, many other features, modifications, and improvements will become apparent to the skilled artisan. REFERENCE NUMERALS

11 , 21 , 31 , 41 : current collector layer/substrate layer 12, 22, 32, 42: redox layer

23, 33: high charge density particles

1 : cathode current collector layer/substrate layer 2: cathode side redox layer

3: separator

4: anode side redox layer

5: anode current collector layer/substrate layer