FIELD OF INVENTION

[0001] This invention relates to charge storage devices having both high charge capacity and high voltage output for high discharge currents, wherein the devices comprise an electroactive layer prepared from a blend comprising an electroactive polymer, a conductive carbon material, and an ionic liquid, wherein the electroactive polymer is selected from any of a fluorene-based polymer, a polymeric Schiff base, a polytriarylamine, or a conjugated polymer comprising one or more pendant polar side chains. In addition, the invention relates to a method of manufacturing electroactive layers and charge storage devices, as well as the use of aforementioned electroactive polymers in both the n-type electroactive layer and the p-type electroactive layer of a charge storage device. BACKGROUND OF THE INVENTION

[0002] It has been demonstrated that doped p- and n-type semiconducting polymers may simultaneously display good electronic and ionic conductivities, which then enables their use as redox-active materials in charge storage devices (see e.g. US 4,442,187 A) that may simultaneously exhibit varying degrees of battery and supercapacitor properties, depending on factors such as the density of electron or hole acceptor units, and the mobility of electronic charges and ions within the polymer layers.

[0003] Recent years have seen a considerable interest in the development of polymer- based electrodes which simultaneously offer high charge storage capacity and high peak power output, and which may be manufactured in a simple and inexpensive manner.

[0004] For example, in Y. Sun et al., Chem. Commun. 2016, 52, 3000-3002, conjugated Schiff base polymer networks have been proposed as promising negative electrode materials which may potentially enable the provision of full polymeric secondary batteries with favorably high cell voltages (i.e. intrinsic battery voltages of 2.0 V or higher).

[0005] However, when increasing the thickness of the layers of electroactive materials in order to achieve higher charge capacities, a decrease of the measured voltage output for high discharge currents and a lowered utilisation level of the theoretical maximum charge storage capacity are typically observed.

[0006] It is known that adding conductive carbon to the active redox materials can improve the electronic conductivity of the resulting electrodes. Also, US 2007/0139862 A1 discloses that blending a carbon material with conductive polymers selected from polypyrroles, poiythiophenes, polyquinones and polymers prepared by polymerisation of amino-group containing aromatic compounds may improve the repetition stability of the doping-dedoping reaction of the conductive polymers. However, the problem of providing a charge storage device with improved charge capacity and high voltage output for high discharge currents is not addressed therein.

[0007] Recently, fluorene-based conjugated polymers such as the homopolymer poly(9,9'-dioctylfluorene) (PFO), or copolymers with benzothiadiazole (e.g. poly(9,9- dioctylfluorene-a/f-benzothiadiazole (F8BT)) or triarylamines (e.g. F8PFB or F8TFB) have gained increased attention due to their efficient emission performance in optical applications (see e.g. J.-C. Denis, Phys. Chem. Chem. Phys. 2016, 18, 21937-21948). By using a combination of a fluorene triarylamine co-poiymer (e.g. F8TFB) with a fluorene benzothiadiazole co-polymer (e.g. F8BT) as positive and negative electrode materials, intrinsic battery voltages of 2.0 V and above may potentially be achieved. However, although fluorene-based conjugated polymers have been demonstrated to exhibit electrochemical activity when provided as ultra-thin (<50 nm) films on glassy carbon, batteries comprising thicker films (100-500 nm) of F8BT as negative electrode material do not show the expected electrochemical activity.

[0008] These problems may be addressed by altering the morphology or the physical constitution of the active layer. For example, US 6,096,453 B1 discloses electrochemical energy storage devices, wherein the active polymer layer is modified by combining an organic conjugated compound and an ionically conductive polymer, in order to form a bi- continuous interpenetrating network. However, the preparation of such devices is elaborate, as it requires a careful selection of additives and extensive analysis and control of the phase distribution. Accordingly, it remains desirable to provide charge storage devices which may be manufactured in a simpler manner.

[0009] In view of the above, it remains desirable to provide thin-film charge storage devices which may be manufactured easily and provide for excellent battery capacity and favourably high peak discharge power, as this problem has not been satisfactorily addressed by the prior art.

SUMMARY OF THE INVENTION

[0010] The present invention solves these objectives 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. [0011] In general, the present invention relates to a charge storage device comprising an electroactive layer prepared from a blend comprising an electroactive polymer, a conductive carbon material, and an ionic liquid, wherein the electroactive polymer is selected from any of: a) a fluorene-based polymer, b) a polymeric Schiff base, c) a polytriarylamine, or d) a conjugated polymer comprising one or more pendant polar side chains. By using the specific blend of materials, devices which exhibit excellent charge capacity and high voltages for high discharge currents may be manufactured easily. In addition, the charge capacity utilisation within the electroactive layer may be retained even when increasing the layer thickness.

[0012] In another aspect, the present invention relates to a charge storage device, comprising an n-type electroactive layer, a p-type electroactive layer and a separator between the electroactive layers, wherein both the n-type and the p-type electroactive layers are prepared from a blend comprising an electroactive polymer, a carbon material, and an ionic liquid, and wherein the electroactive polymer is independently selected from any of: a) a fluorene-based polymer, b) a polymeric Schiff base, c) a polytriarylamine, or d) a conjugated polymer comprising one or more pendant polar side chains. In such embodiments, the voltage output at a given discharge current of the resulting charge storage device may be further improved. Taking further into account that the n- and p-type material layers may be processed in the same manner, the fabrication may be further simplified, thereby reducing processing costs.

[0013] Further aspects of the present invention include methods of manufacturing electroactive layers and charge storage devices, comprising the steps of mixing an electroactive polymer with at least a conductive carbon material and an ionic liquid to prepare a blend, and depositing the blend by a solution deposition or a coating process to form an electroactive layer; wherein the electroactive polymer is selected from any of: a) a fluorene-based polymer, b) a polymeric Schiff base, c) a polytriarylamine, or d) a conjugated polymer comprising one or more pendant polar side chains.

[0014] In addition, the present invention relates to the use of a single electroactive polymer in both the n-type electroactive layer and the p-type electroactive layer of a charge storage device, wherein the electroactive polymer is selected from any of: a) a fluorene-based polymer, b) a polymeric Schiff base, c) a polytriarylamine, or d) a conjugated polymer comprising one or more pendant polar side chains.

[0015] Preferred embodiments of the charge storage device and the methods and uses according to the present invention and other aspects of the present invention are described in the following description and the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 shows a side-sectional view of an exemplary thin-film charge storage device;

[0017] FIG. 2 shows the manual blade coating schematic used in the preparation of the exemplary charge storage devices;

[0018] FIG. 3 is a graph showing the discharge curves of battery devices according to the present invention in comparison with prior art devices;

[0019] FIG. 4 is a graph showing the discharge curves of different battery devices according to the present invention; and

[0020] FIG. 5 is a graph showing the discharge curves of different battery devices according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0021] For a more complete understanding of the present invention, reference is now made to the following description of the illustrative embodiments thereof:

[0022] Generally speaking, the present invention relates to a charge storage device comprising an electroactive layer prepared from a blend comprising an electroactive polymer, a conductive carbon material, and an ionic liquid, wherein the electroactive polymer is selected from any of: a) a fluorene-based polymer, b) a polymeric Schiff base, c) a polytriarylamine, or d) a conjugated polymer comprising one or more pendant polar side chains. Electroactive Layer

[0023] The term "electroactive polymer", as used herein, denotes a polymer which exhibits variable physical and/or chemical properties resulting from an electrochemical reaction within the polymer upon application of an external electrical potential when in contact with an electrolyte, and must be thus distinguished from electrochemically inert materials or insulating materials, such as the electrolytes or the porous separator layer supports.

[0024] The electroactive polymer classes a), b), c) and d) are not mutually exclusive. For example, where a fluorene-based polymer a), a polymeric Schiff base b) or a polytriarylamine c) is conjugated and comprises one or more pendant polar side chains, then these polymers a), b) and c), may also fail into class d) and thus also be described as conjugated polymers comprising one or more pendant polar side chains. Where a fluorene-based polymer a), a polymeric Schiff base b) or a conjugated polymer comprising one or more pendant polar side chains d) comprises a triarylamine group, then these polymers a) b) and d) may also fall into class c) and thus also be described as polytriarylamines. Where a fluorene-based polymer a), a polytriarylamine c), a conjugated polymer comprising one or more pendant polar side chains d) comprises a Schiff base, then these polymers a) c) and d) may also fall into class b) and thus also be described as polymeric Schiff bases. Where a polymeric Schiff base b), a polytriarylamine c) or a conjugated polymer comprising one or more pendant polar side chains d) comprises a fiourene group, then these polymers b), c) and d) may also fall into class a) and thus also be described as fluorene-based polymers.

[0025] The ionic liquid for use in the charge storage device of the present invention is not particularly limited and may be suitably selected by the skilled artisan. As examples thereof, ionic compounds 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. Any one of these cations may be combined with any anion selected from, for example, tetrafluoroborate, hexafluorophosphate, bis(fluorosulfonyf)imide or dicyanamide. Other preferred examples include bis(trifluoromethane)sulfonimide (TFSI)-based ionic liquids such as e.g. 1 -ethyf-3- methyl imidazolium bis(trifluoromethane)suIfonimide (EMl-TFSI), triethyfmethoxyethyl phosphonium bis(trifluoromethane)sulfonimide (TEMEP-TFSI), triethyl sulfonium bis(trifluoromethane)sulfonimide (TES-TFSI) or 1-butyl-1-methylpyrrolidinium bis(trifluoromethane)sulfonimide (BMP-TSFI), the latter being particularly preferable. In other preferred embodiments, N-propyl-N-methylpyrroIidinium bis(fluorosu!fonyl)imide (PMP-FSI) is used as the ionic liquid. It has been surprisingly found that - in comparison to embodiments, wherein ionic liquid ingresses from the separator material into the electroactive polymer layer after device manufacture - adding ionic liquid to the fluorene- based or Schiff base electroactive polymer before or during the preparation of the electroactive layer not only improves the internal ionic conductivity of the electroactive layer, but thereby also enables an increased output voltage (nominal voltage) of the charge storage device.

[0026] The conductive carbon material may be selected from one or more of the group consisting of carbon black, carbon fiber, graphite, carbon nanotube and the like, for example. Preferably, the BET specific surface area of the conductive carbon material is in the range of 10 m ² /g to 3000 m ² /g. By adding a conductive carbon material to the formulation for depositing the electroactive polymer, the electroactive material utilization (ratio of measured capacity to theoretical capacity) in the charge storage device is remarkably improved, which leads to a higher charge capacity, and also a further increase of the output voltage of the device (the latter is not a direct consequence of the increase in materials utilization).

[0027] Hence, by blending the conductive carbon material and the ionic liquid with the electroactive polymer, charge storage devices with favourably high charge capacities and discharge voltages may be provided in a simple manner. Also, compared to conventional charge storage devices, the thickness of the electroactive layer(s) may be substantially increased to further improve the charge capacity, without requiring additional modification of the morphology of the active material layer, and without imparting the voltage output and the level of utilization of the theoretical charge capacity.

[0028] In preferred embodiments from the viewpoint of optimized charge capacity and voltage output the weight ratio of electroactive polymer and the conductive carbon material in the blend is in the range of from 1:0.01 to 1:10, further preferably from 1:0.1 to 1:1.2, and/or the weight ratio of electroactive polymer and the ionic liquid in the blend is in the range of from 1 :0.01 to 1 : 1 , preferably from 1 :0.05 to 1 :0.5.

[0029] The thickness of the electroactive layer is not particularly limited and may be suitably selected by the skilled artisan depending on the desired charge capacity and mechanical stability. Typically, the electroactive layer has a thickness in the range of 0.05 to 500 μηη, preferably 0.15 to 400 μιτι.

[0030] The blend may comprise an additional polymeric binder (e.g. fluorinated polymers (incl. PTFE, PVDF), carboxymethylcellulose-based binders (CMC and its alkali metal salts) in a content of less than 5% by weight. From an environmental viewpoint, it is preferable that the blend does not comprise polymeric binders selected from fluorinated polymers, as their processing often requires the use of toxic organic solvents. In some embodiments, it may be preferable that the blend does not comprise an additional polymeric binder at all.

[0031] In a preferred embodiment of the present invention, the fluorene-based polymer a) comprises at least one repeat unit according to the General Formula (G-1):

[0032] In General Formula (G-1), R1 to R8 are independently selected from hydrogen, optionally substituted C _1-20 -alkyl, optionally substituted C _1-20 -alkyl ether, optionally substituted C _1-20 -carboxyl, optionally substituted C _1-20 -carbonyl, optionally substituted C _1-20 - ester, optionally substituted C _6-18 -aryl, optionally substituted C _6-18 -heteroaryl groups, and polar groups, and wherein Z1 and Z2 are independently selected from a single bond, an optionally substituted C _1-20 -alky!ene, optionally substituted C _1-20 -oxyalkylene, optionally substituted C _6-18 -arylene, or an optionally substituted C _6-18 -heteroarylene group. In another preferred embodiment, the fluorene-based polymer comprises two or more repeat units according to the General Formula (G-1), which may be identical or different.

[0033] In one preferred embodiment, Zi and Z2 may be independently selected from a single bond, an optionally substituted C _1-12 -alkylene, optionally substituted C _1-12 - oxyalkylene, optionally substituted C _6-12 -arylene, or an optionally substituted C _6-12 - heteroarylene group. More preferably, Zi and Z ₂ are independently selected from a single bond, a C _1-12 -alkyiene, and a C _6-12 -arylene group, and further preferably represent optionally substituted phenyiene group, wherein at least one of the residues R1 and R2 preferably represent a polar group and are preferably located in m- or p-position relative to the fluorene scaffold. In a further preferred embodiment, at least two of Ri to R ₈ represent a polar side group, which will be further explained below.

[0034] The polymeric Schiff base b) is generally characterized in that it comprises the functionality "-HC=N-" within its repeat unit.

[0035] Preferably, the polymeric Schiff base comprises a repeat unit according to the following General Formula (G2):

Herein, Yi represents an optionally substituted conjugated unsaturated hydrocarbon group, preferably an optionally substituted aromatic hydrocarbon group, such as an optionally substituted C _6-18 -aryl group, for example. Yi may comprise a polar side chain as a substituent.

[0036] In other preferred embodiments, the polymeric Schiff base comprises a repeat unit according to the following formula (P9):

Optionally, the repeat unit of formula P9 is unsubstituted or one or more H atoms is replaced with a C _1-20 alkyl group or a C _6-18 aryl group. A C _6-18 aryl group may be unsubstituted or substituted with one or more substituents, optionally one or more C _1-12 alkyl groups.

[0037] Other preferred examples of polymeric Schiff bases are hyperbranched Schiff base polymers comprising a repeat unit according to the following General Formula (G3)

[0038] Herein, Z3 to Z5 and Y3 to Y3 are independently selected from optionally substituted conjugated unsaturated hydrocarbon groups, preferably from optionally substituted aromatic hydrocarbon groups, such as optionally substituted C _6-18 -aryl groups, for example. Z3 to Zs and Y3 to Y5 may likewise comprise polar side chains as substituents.

[0039] The inventors have surprisingly found that combining a polymeric Schiff base with an organic ionic liquid electrolyte improves the specific capacity of the charge storage device at high rates compared with combining the Schiff base with an inorganic alkali- metal (e.g. a lithium salt or sodium salt) electrolyte.

[0040] The polytriarylamine c) is a polymer comprising or consisting of optionally substituted triarylamine repeat units, preferably optionally substituted triphenylamine repeat units, wherein optional substituents may include C _1-20 -alkyl, C _1-20 -alkyl ether, C _1-20 - carboxyl, C _1-20 -carbonyl, C _1-20 -ester, C _6-18 -aryl, C _6-18 -heteroaryl groups, and polar groups.

[0041] The polymer d) is generally an electroactive polymer having one or more repeat units, wherein at least one of the repeat units comprises one or more polar side chains, preferably one or more pendant oligo- or polyether groups. The at least one repeat unit having one or more pendant oligo- or polyether groups as substituent(s) is not particularly limited and may be preferably selected from at least one of the group of fluorenyl derivatives, conjugated aromatic hydrocarbons, acenaphtene, carbonyl-based monomers, phenylene, aniline, dialkylarylamines, diarylalkylamines, diarylamines, triarylamines, naphthalene, acenaphtene, phenanthrene, naphthalene diimide, perylene diimide, phtalimide, thieno pyrrole dione, heteroaromatic hydrocarbons, and derivatives thereof; wherein the heteroaromatic hydrocarbons are preferably selected from pyridines, quinolines, thiophenes, dithienes, benzothiophenes, benzothiadiazoles, benzotriazoles, carbazoles, and derivatives thereof.

[0042] The electroactive polymer may consist of repeat units selected from one or more fluorenyl derivatives, of repeat units selected from one or more Schiff base derivatives, of substituted or unsubstituted triarylamine repeat units, or a repeat unit comprising one or more pendant polar side chains.

[0043] In general, it may be preferable to combine any of a fluorene-based repeat unit, a Schiff base repeat unit, a substituted or unsubstituted triarylamine repeat unit, or a repeat unit comprising one or more pendant polar side chains, with at least a second repeat unit to form the electroactive polymer. In a generally preferred embodiment, the second repeat unit may be selected from at least one of the group of fluorenyl derivatives, conjugated aromatic hydrocarbons (e.g. napthalene, phenanthrene, and derivatives thereof), acenaphtene, carbonyl-based monomers, phenylene, anilines (including N-substituted anilines, for example), dialkylarylamines, diarylalkylamines, diarylamines (including N- substituted diarylamines, for example), triarylamines, naphthalene, acenaphtene, phenanthrene, naphthalene diimide, perylene diimide, phtalimide, thieno pyrrole dione, heteroaromatic hydrocarbons (e.g. pyridines, quinolines, thiophenes, dithienes, benzothiophenes, benzothiadiazoles, benzotriazoles, carbazoles, and their derivatives), and derivatives thereof. Further preferably, the heteroaromatic hydrocarbons are selected from pyridines, quinolines, thiophenes, dithienes, benzothiophenes, benzothiadiazoles, benzotriazoles, carbazoles, and derivatives thereof. Especially preferably, the at least one repeat unit is selected from at least one of the group of fluorene, dialkylarylamines, diarylalkylamines, diarylamines, triarylamines, benzothiadiazole, carbazoles and derivatives thereof.

[0044] In a polymer consisting of two repeat units, the ratio of the two repeat units (with respect to the number of units) is preferably between 90:10 and 10:90, more preferably between 80:20 to 20:80, especially preferably between 30:70 to 70:30. [0045] In principle, the electroactive polymer may be a p-type, an n-type semiconductive polymer, or act both as a p-type and an n-type semiconductive polymer. Accordingly, the charge storage device preferably comprises an n-type electroactive layer, a p-type electroactive layer and a separator between the electroactive layers.

[0046] If performing as a p-type semiconductive polymer, the electroactive polymer may be selected from known electron donating conjugated organic polymers, provided that it comprises at least one repeating unit selected from a fluorene derivative or a Schiff base. Preferably, the p-type conjugated organic polymer has a HOMO level between -4.5 and - 6.5 eV, more preferably between -4.8 and -6 eV. While deeper HOMO levels may result in a higher battery voltage, the reactivity of the polymer increases, which is accompanied by a lower stability.

[0047] In a preferred embodiment, the p-type conjugated organic polymer is a homopolymer or a co-polymer including alternating, random or block copolymers, each of which at least contain a fluorene derivative, a Schiff base, a substituted or unsubstituted triarylamine or a repeat unit comprising one or more pendant polar side chains as a monomer unit. As exemplary p-type conjugated organic polymers, polymers selected from conjugated hydrocarbon or heterocyclic polymers comprising a fluorene derivative, a Schiff base, a substituted or unsubstituted triarylamine or a repeat unit comprising one or more pendant polar side chains as a repeat unit may be mentioned. As examples, in- chain conjugated polymers or co-polymers comprising as monomer units a fluorene derivative, a Schiff base, a substituted or unsubstituted triarylamine and/or a repeat unit comprising one or more pendant polar side chains, in combination with one or more selected from the group consisting of acene, aniline, azulene, benzofuran, furan, indenofluorene, indole, phenylene, pyrazoline, pyrene, pyridazine, pyridine, diarylalkylamine, 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 ^-b^.S-b'jdithiophene, isothianaphthene, monosubstituted pyrrole, 3,4-bisubstituted pyrrole, 1 ,3,4-oxadiazoles, isothianaphthene, and derivatives thereof, may be mentioned. Preferred examples of such p-type polymers are in-chain conjugated homopolymers or co-polymers comprising as monomer units a fluorene derivative, a Schiff base, a substituted or unsubstituted triarylamine or a repeat unit comprising one or more pendant polar side chains, in combination with monomers selected from at least one of the group of phenylene derivatives, aniline derivatives, dialkylarylamines, diarylalkylamines, diarylamines, triarylamines and heteroaromatic hydrocarbons. As preferred examples of the latter amine-based monomers, compounds in accordance to the following General Formulae (G-4) and (G-5) may be mentioned:

[0048] In the above General Formulae (G-4) and (G-5), Re to R17 are independently selected from hydrogen, optionally substituted C _1-20 -alkyl, optionally substituted C _1-20 -aikyl ether, optionally substituted C _1-20 -carboxyl, optionally substituted C _1-20 -carbonyl, optionally substituted C _1-20 -ester, optionally substituted C _6-18 -aryl, optionally substituted C _6-18 - heteroaryl groups, and oligo- or polyether groups having at least two a!koxy repeat units. Index n is greater than or equal to 1 and preferably 1 or 2. ¾ is selected from a single bond, an optionally substituted C _1-20 -alkylene, optionally substituted O-aroxyalkylene, optionally substituted C _6-18 -arylene, or an optionally substituted Cwe-heteroaryiene group. In preferred embodiments, Rg to R17 are independently selected from hydrogen, optionally substituted C _1-12 -alkyl, optionally substituted C _1-12 -alkyl ether, optionally substituted C _1-12 - carboxyl, optionally substituted C _1-12 -carbonyl, optionally substituted C _1-12 -ester, optionally substituted C _6-12 -aryl, optionally substituted C _6-12 -heteroaryl groups, and oligo- or polyether groups having at least two alkoxy repeat units. Index n is greater than or equal to 1 and preferably 1 or 2. Further preferably, Z6 is selected from a single bond, an optionally substituted C _1-12 -alkylene, optionally substituted C _1-12 -oxyalkylene, optionally substituted C _6-12 -arylene, or an optionally substituted C _6-12 -heteroarylene group. In one embodiment, Z ₆ is an optionally substituted phenylene group. [0049] In further preferred embodiments, ¾ is an arylene having a C _1-12 -ester group, Re is an optionally substituted C _1-12 -alkyl ether and R10 to R17 are hydrogen.

[0050] If performing as an n-type semiconductive polymer, the electroactive polymer may be selected from known electron accepting conjugated organic polymers, provided that it comprises at least one repeating unit selected from a fluorene derivative, a Schiff base, a substituted or unsubstituted triarylamine or a repeat unit comprising one or more pendant polar side chains. Preferably, the n-type conjugated organic polymer has a LUMO level between -4.5 and -1.5 eV, more preferably between -3.5 and -2.0 eV. While shallower LUMO levels may result in a higher battery voltage, the reactivity of the polymer increases, which is accompanied by a lower stability.

[0051] Preferably, the n-type conjugated organic polymer is a homopolymer or co-polymer including alternating, random or block copolymers, each of which at least contain a fluorene derivative, a Schiff base, a substituted or unsubstituted triarylamine or a repeat unit comprising one or more pendant polar side chains as a monomer unit. As exemplary n-type conjugated organic polymers, in-chain conjugated polymers or co-polymers comprising as monomer units a fluorene derivative, a Schiff base, a substituted or unsubstituted triarylamine and/or a repeat unit comprising one or more pendant polar side chains, in combination with repeat units selected from the group of fluorenyl derivatives (if used in combination monomers other than fluorene 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 thereof may be mentioned. A specifically preferred n-type conjugated organic polymer is a conjugated Schiff base homopolymer in accordance to the above description. As preferred examples of benzothiadiazoles, compounds according to General Formula (G-6) may be mentioned:

[0052] In General Formula (G-6), R ₁₈ and R ₁₉ are independently selected from hydrogen, optionally substituted C _1-20 -alkyl, optionally substituted C _1-20 -alkyl ether, optionally substituted C _1-20 -carboxyl, optionally substituted C _1-20 -carbonyl, optionally substituted C _1-20 ester, optionally substituted C _6-18 -aryl, optionally substituted C _6-18 -heteroaryl groups, and oligo- or polyether groups having at least two alkoxy repeat units. In a preferred embodiment, R ₁₈ and R ₁₉ are independently selected from hydrogen, optionally substituted C _1-12 -alkyl, optionally substituted C _1-12 -alkyl ether, optionally substituted C _1-12 -carboxyl, optionally substituted C _1-12 -carbonyl, optionally substituted C _1-12 -ester, optionally substituted C _6-12 -aryl, optionally substituted C _6-12 -heteroaryl groups, and oligo- or polyether groups having at least two alkoxy repeat units.

[0053] In case the above-defined residues R1 to R19, Z1 to Z6, and Y1 to Y ₅ in General Formulae (G-1) to (G-6) comprise substituents, it is preferred that the substituents are independently selected from any of the group of halogens, C _1-12 -alkyl groups, C4-8- cycloalkyl groups, C _1-12 -alkoxy groups, C _1-12 -ester groups, amino groups, amido groups, silyl groups, cyano groups or C _1-12 alkenyl groups.

[0054] In general, it is preferred that the eiectroactive polymer comprises a polar side chain in at least one of its repeating units. Advantageously, such pendant polar side chains help diffusion of mobile ions from an ionic liquid into the active material consisting of a polymer film and hence enable excellent battery performance.

[0055] As an especially preferred example of a polar side chain which may be used in polymer d) or as a substituent in any of the repeating units described above (such as the repeat units according to structures (G1) to (G6), for example), an oligo- or polyether group having at least two alkoxy repeat units may be mentioned. Specifically preferably, at least two of R1 to R8, more preferably at least Ri and R2 represent an oligo- or polyether group having at least two alkoxy repeat units, which may be identical or different. The oligoether group, as defined herein, denotes a residue comprising between 2 and 10 oxyalky!ene units, each of which may be the same or different, while a polyether group, as defined herein, denotes a residue comprising more than 10 oxyalkylene units, each of which may be the same or different. In a preferred embodiment, the oxyalkylene unit comprised in the oligo- or polyether group is an oxyethylene unit.

[0056] More preferably, the oligo- or polyether group is represented by one of the following General Formulae (G-7) or (G-8):

wherein Z7 is selected from a single bond, oxygen, a C _1-20 -alky!ene group, or a C _1-20 - oxyalkylene group; wherein R20 is selected from hydrogen, a hydroxy group, a C _1-20 -alkyf group, a C _1-20 -ester group, or a C _1-20 -alkoxy group; and wherein n is at least 2, preferably between 2 and 20, preferably between 2 and 10, more preferably between 2 and 5, especially preferably 3. In a further preferred embodiment, in the oligo- or polyether group represented by one of the following General Formulae (G-7) or (G-8) Z7 is selected from a single bond or oxygen, and/or Rg is selected from hydrogen, a methyl group or an ethyl group.

[0057] It will be understood that if the n-type semiconductive polymer is selected from any of: a) a fluorene-based polymer, b) a polymeric Schiff base, c) a polytriarylamine, or d) a conjugated polymer comprising one or more pendant polar side chains, the corresponding p-type semiconductive material is not limited to the above materials and may be suitably chosen from any conventional p-type semiconductive materials known in the art, and vice versa.

[0058] The electroactive polymer as used in the present invention may generally also comprise cross-linking units, i.e. functional groups which enable to bond the polymer chains, which may be appropriately chosen by the skilled artisan.

[0059] In a preferred embodiment, however, the charge storage device according to the present invention comprises an n-type electroactive layer, a p-type electroactive layer and a separator between the electroactive layers, wherein both the n-type and the p-type electroactive layers are prepared from a blend comprising an electroactive polymer, a carbon material, and an ionic liquid, wherein the electroactive polymer is independently selected from any of: a) a fluorene-based polymer, b) a polymeric Schiff base, c) a polytriarylamine, or d) a conjugated polymer comprising one or more pendant polar side chains. [0060] In a second embodiment, the present invention relates to a charge storage device comprising an n-type electroactive layer, a p-type electroactive layer and a separator between the electroactive layers, wherein each of the electroactive layers are prepared from a blend comprising an electroactive polymer, a conductive carbon material, and an ionic liquid, wherein the electroactive polymer is independently selected from any of: a) a fluorene-based polymer, b) a polymeric Schiff base, c) a polytriarylamine, or d) a conjugated polymer comprising one or more pendant polar side chains, and wherein the electroactive polymers used in the n-type electroactive layer and the p-type electroactive layer of the charge storage device are identical. Preferably, the blends used for the preparation of the n-type electroactive layer and the p-type electroactive layers are also identical. By using the same polymers (or blend) for the preparation of both electroactive layers, the fabrication process is additionally simplified and the processing costs are further reduced.

[0061] Preferably, the electroactive polymer used in the second embodiment is an electroactive polymer in accordance with the description of the first embodiment, which acts both as a p-type and an n-type semiconductive polymer. For this purpose, it may be preferred that the electroactive polymer has a HOMO level between -4.5 and -6.5 eV and a LUMO level between -4.5 and -1.5 eV. Further preferably, the band gap (i.e. the difference between HOMO and LUMO levels) is at least 1.8 eV, further preferably at least 2.0 eV. In general, HOMO and LUMO levels may be measured by square wave voltammetry, as will be further outlined beiow.

[0062] The repeat units used for polymers acting both as p- and n-type polymer may be suitably selected by the skilled artisan from the repeat units described above in conjunction with the first embodiment depending on the HOMO and LUMO properties of the resulting polymer by methods known in the art (e.g., computational calculation and/or voltammetric analysis after synthesis).

[0063] As a specifically preferred electroactive polymer for the use in the second embodiment, a fluorene-based polymer comprising two different repeat units according to General Formula (G-1), more preferably a combination of a repeat unit according to (G-1) comprising one or more polar groups (according to the above description) and a repeat unit according to (G-1) without polar groups, may be mentioned.

[0064] In a third embodiment, the present invention also relates to the use of a single electroactive polymer in both the n-type electroactive layer and the p-type electroactive layer of a charge storage device, wherein the electroactive polymer is selected from any of: a) a fluorene-based polymer, b) a polymeric Schiff base, c) a polytriarylamine, or d) a conjugated polymer comprising one or more pendant polar side chains. [0065] Preferred constitutions of the electroactive polymer to be used in the second and third embodiments are described in the context of the first embodiment.

Charge Storage Device

[0066] While not being limited thereto, an exemplary configuration of a charge storage device is shown in Fig. 1, the device comprising an n-type electroactive layer (2), a p-type electroactive layer (4) and a separator (3) between the electroactive layers, wherein the the electroactive polymer selected from any of: a) a fluorene-based polymer, b) a polymeric Schiff base, c) a polytriarylamine, or d) a conjugated polymer comprising one or more pendant polar side chains is comprised in one or both of the n-type electroactive layer (2) and the p-type electroactive layer (2).

[0067] As mentioned above, the thickness of each of the n-type and p-type electroactive layers containing the electroactive polymer(s) may be chosen appropriately depending on the required purpose. For example, layers with relatively low thicknesses may be preferable for applications where high power delivery during a short period of time intervals is required, whereas relatively thick layers may be preferable for uses requiring higher charge contents.

[0068] Typically, as in the configuration of Fig. 1, the charge storage device may comprise current collector layers (1) and (5) at the side of the electroactive layers opposed to the separator. Suitable materials for current collector layers include materia! 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 polypyrrole, doped polythiophene, and their derivatives, with indium tin oxide being particularly preferred.

[0069] While the electroactive layer(s) may consist of the composite prepared from the blend comprising the electroactive polymer described in the first embodiment, the conductive carbon material, and the ionic liquid, the electroactive layer(s) may comprise further materials that are conventionally used in the preparation of polymeric films for charge storage devices. For example, the electroactive polymer layers may be combined with one or more layers that may be polymeric or non-polymeric and/or comprise material embedded into the respective polymer films (e.g. a conductive material for electrode connection etc.). Also, instead of using separate current collector layers (1) and (5), conductive particles (such as carbon nanotubes or carbon particles, for example) may be dispersed in the polymer layers (2) and (4) at a concentration higher than a percolation threshold concentration in order for the polymer layers to perform as current collectors. In addition to the above, a substrate layer may be provided adjacent to the electroactive polymer layers, e.g. as a mechanical support. In addition, the electroactive layer(s) may comprise further additives, such as e.g. plasticizers, surfactants, cross-linking agents or low-molecular weight compounds.

[0070] The material for the separator layer (3) is not particularly limited and may be made of known materials that are chemically and electrochemicaily 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 tons is facilitated. As suitable materials, porous polymeric materials (e.g. polyethylene, polypropylene, polyester, teflon or cellulose-based polymers), ion-conductive polymer 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, methylmethacrylate, alkylacrylate, 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 skilled artisan (e.g. by suitable selection of materials or by cross-linking in case of polymers).

[0072] The separator layer thickness may likewise be appropriately selected by the skilled artisan depending on the purpose. While not being limited thereto, the separator thickness is typically between 5 pm and 100 pm.

[0073] 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. Methods of manufacture

[0074] In a fourth embodiment, the present invention relates to a method of manufacturing an electroactive layer for a charge storage device, comprising the steps of: mixing an electroactive polymer with at least a conductive carbon material and an ionic liquid to prepare a blend, and depositing the blend by a solution deposition or a coating process to form an electroactive layer; wherein the electroactive polymer is selected from any of: a) a fluorene-based polymer, b) a polymeric SchifF base, c) a polytriarylamine, or d) a conjugated polymer comprising one or more pendant polar side chains.

[0075] In a fifth embodiment, the present invention relates to a method of manufacturing a charge storage device according to the first and second embodiments, comprising: mixing an electroactive polymer with at least a conductive carbon material and an ionic liquid to prepare a blend, and depositing the blend by a solution deposition or coating process to form an electroactive layer; wherein the electroactive polymer is selected from any of: a) a fluorene-based polymer, b) a polymeric Schiff base, c) a polytriarylamine, or d) a conjugated polymer comprising one or more pendant polar side chains. Preferably, the method specifically comprises the steps of: mixing an electroactive polymer with at least a conductive carbon material and an ionic liquid to prepare a blend, and depositing the blend by a solution deposition or coating process on a current collector or substrate layer to form a first electroactive layer, providing a separator layer on and preferably in contact with the first electroactive layer; and providing a second electroactive layer on the separator layer surface opposed to the first electroactive layer.

[0076] With respect to the nature of each of the constituents of the electroactive layer, reference is being made to the first embodiment described above.

[0077] Preferably, the methods according to the fourth and fifth embodiments further comprise the steps of: forming the electroactive polymer by polymerisation; mixing the electroactive polymer with an organic solvent; and subsequently adding conductive carbon material and ionic liquid to the mixture to prepare the blend. Compared to conventional techniques, wherein electroactive materials are formed by electrochemical deposition from the monomers, the deposition from a solution comprising the polymer is easier to perform and offers improved controllability of the layer morphology.

[0078] Electroactive polymers a), c) and d) may be synthesized by methods known in the art, typically by derivatizing the monomers to introduce polymerization-enabling leaving groups (which may include but are not limited to halogens (e.g. bromine), tosylate, mesylate, triflate, or boronic ester groups) and polymerizing the monomers, e.g. via Suzuki or Yamamoto polymerization (in analogy to WO 00/53656 A1, US 5,777,070 B1, WO 2015/147340 A1 , US 5,900,327 B1 , WO 2012/095629 A1 , for example).

[0079] The method of synthesizing the polymeric Schiff base b) is likewise not particularly limited. As an example, polycondensation reactions may be mentioned, including but not limited to polycondensation reactions between aldehydes and amines (such as di- or trialdehyde derivatives, therephthalaldehydes or its derivatives, and di- or triamines, for example, as disclosed in Y. Sun et al.; Chem. Commun. 2016, 52, 3000-3002 and E. Castillo-Martinez et al., Angew. Chem. Int. Ed. 2014, 53, 1-6). [0080] The solution deposition or coating process is not particularly limited and may be followed by a heating treatment in order to further enhance the densification and uniformity of the electroactive layer. The method of deposition may include thermal deposition, vacuum deposition, laser deposition, screen printing, printing, imprinting, spin coating, dipping, inkjetting, roll coating, flow coating, blade coating, drop casting, spray coating, and/or roll printing, for example.

[0081] In general, it will be appreciated that the preferred features specified above with respect to the first to fifth embodiments may be combined in any combination, except for combinations where at least some of the features are mutually exclusive.

[EXAMPLES

[0082] Charge storage devices having a device architecture in accordance to Fig. 1 with the following configuration have been manufactured:

[0083]

TABLE 1: Exemplary battery device architecture

[0084] As conductive carbon material, Super P ^® Carbon Black (commercially available from Imerys (TIMCAL)) has been used, while BMP-TFSI {1-Butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide) has been used as ionic liquid.

[0085] Eight different electroactive polymers have been prepared from diester or dibromide derivatives of the following structures (M1) to (M9):

[0086] A further electroactive polymer formed by polymerisation of monomers (M11) was prepared:

[0087] The HOMO/LUMO levels of the polymers have been determined via square wave voltammetry using a CHI660D Electrochemical workstation with software (IJ Cambria Scientific Ltd)), a CHI 104 3mm glassy carbon disk working electrode (IJ Cambria Scientific Ltd)); a platinum wire auxiliary electrode; an Ag/AgCI reference electrode (Havard Apparatus Ltd); acetonitrile as eel) solution solvent (Hi-dry anhydrous grade- ROMIL); toluene as sample preparation solvent (Hi-dry anhydrous grade); ferrocene as reference standard (FLUKA); and tetrabutylammoniumhexafluorophosphate (FLUKA) as cell solution salt. For sample preparation, the polymer was spun as thin film (-20 nm) onto the working electrode and the dopant material was measured as a dilute solution (0.3 w%) in toluene. The measurement cell contained the electrolyte, a glassy carbon working electrode onto which the sample was coated as a thin film, a platinum counter electrode, and a Ag/AgCI reference glass electrode. Ferrocene was added into the ceil at the end of the experiment as reference material (LUMO (ferrocene) = -4.8eV). An overview of the polymer constitution, their HOMO/LUMO properties and their theoretical capacity is given in Table 2 below.

[0088]

TABLE 2: Electroactive polymer composition and properties

*P9 was synthesized from 4-terephthalaldehyde (M10) and p-phenylenediamine (M11) via a polycondensation reaction as reported in E. Castillo-Martinez et al., Angew. Chem. Int. Ed. 2014, 53, 1. Example 1

[0089] For the preparation of a blend for the n-type electroactive layer, 20 mg Polymer P1 and 16 mg Super P were mixed in a pestle and mortar with 0.5 ml of odichlorobenzene (o-DCB) until a smooth paste has been obtained. Then, BMP-TFSI was added as a 5 wt% solution in o-DCB (4 mg, 80 pL), and mixed with the polymer: carbon-paste for 1 minute in order to prepare a blend, wherein the relative ratio (by weight) polymer : carbon material : ionic liquid was 1.0 : 0.8 : 0.2. For the preparation of a composite blend for the p-type electroactive layer the same procedure was repeated, with the exception that polymer P2 was used instead of P1.

[0090] In accordance with the manual doctor blade coating schematic illustrated by Fig. 2, two one-inch ITO (150 nm) or evaporated aluminum (200 nm) slides were pressed together side by side and 2 layers of transparent 3M tape (2 x 50 pm thick) were put on each side to define a 3 cm ² area (2.5 x 1.2 cm). The electroactive layer blends were spread separately (left/right portions in Fig. 2) on one side of the ITO or Al substrate and a scalpel blade was used to spread the material evenly over the area. The tapes were peeled off and the electroactive layers were dried on a hotplate at 100 °C for 10 minutes. The loading (mg/cm ² ) was determined by weighing the plate before and after deposition of the film.

[0091] The composite electrodes on ITO or Al were dehydrated at 150 °C for 20 minutes on a hotplate in the glovebox, before assembly. Thereafter, fitter paper (vacuum oven dried) soaked in ionic liquid (BMP-TFSI) was applied between the composite electrodes as a separator and metal clips were used to provide a firm contact in the sandwiched assembly.

[0092] For device testing, the clips were removed and the device (active area: 3 cm ² ) was placed into a sealed glass container and connected to a potentiostat (CHI660D Electrochemical workstation with software (IJ Cambria Scientific Ltd)). Charge-discharge sequences were performed 150 times and the mid-point voltage and area capacity was calculated for each cycle. Galvanostatic charging was performed at 0.5 rnA/cm ² , followed by a 30 s potentiostatic hold at 3V and galvanostatic discharge at 0.5 mA/cm ² .

Example 2

[0093] For Example 2, the procedure of Example 1 was repeated, with the exception that polymers P3 and P2 were used as n- and p-type electroactive polymers, respectively. Here, galvanostatic charging was performed at 0.2 mA/cm ² , followed by a 90 s potentiostatic hold at 3.3V and galvanostatic discharge at 0.2 mA/cm ² . Example 3

[0094] For Example 3, the procedure of Example 1 was repeated, with the exception that polymer P4 was used both as n- and p-type electroactive polymer and the relative ratio (by weight) polymer : carbon material : ionic liquid was 1.0 : 0.8 : 0.4. Galvanostatic charging was performed at 0.5 mA/cm ² , followed by a 30 s potentiostatic hold at 3.8V and galvanostatic discharge at 0.5 mA/cm ² .

Examples 4 to 7

[0095] For Examples 4 to 7, the procedure of Example 1 was repeated, with the appropriate polymer as listed in Table 3 but Galvanostatic charging was performed at 1 mA/cm ² , followed by a 60 s potentiostatic hold at 3V and galvanostatic discharge at 1 mA/cm ² .

Example 8

[0096] for Example 8, the procedure of Example 1 was repeated, with the exception that polymer P9 was used as n- type electroactive polymer with soluble PVDF binder dissolved in DMSO and the relative ratio (by weight) was polymer : carbon material : PVDF 1.0 : 0.8 : 0.2. Galvanostatic charging was performed at 1 mA/cm ² , followed by a 60 s potentiostatic hold at 3V and galvanostatic discharge at 1 mA/cm ² .

Comparative Example 1

[0097] For Comparative Example 1, the procedure of Example 1 was repeated, with the exception that the electroactive layers were formed without using conductive carbon and ionic liquid.

Comparative Example 2

[0098] For Comparative Example 2, the procedure of Example 1 was repeated, with the exception that the electroactive layers were formed without using ionic liquid.

Comparative Example 3

[0099] For Comparative Example 3, the procedure of Example 1 was repeated, with the exception that the electroactive layers were formed without using conductive carbon.

[00100] The measurement results are shown in Figures 3, 4 and 5 as well as in Table 3. [00101] A comparison between Example 1 and Comparative Examples 2 and 3 shows that the use of a blend comprising the electroactive polymer, the conductive carbon and the ionic liquid results in an improved material utilisation and higher capacity, when compared to devices, wherein conductive carbon or ionic liquid is not used. Comparative Example 1 , wherein both conductive carbon and ionic liquid have been omitted does not show any battery behaviour at all (no capacity). Moreover, although the calculated discharge voltages (determined by the energy difference between the HOMO and LUMO levels in the p-type and n-type polymers P2 and P1 , respectively) is identical in Examples 1 and Comparative Examples 1 to 3 (i.e. 2.19 V), Example 1 achieves a significantly increased discharge voltage compared to the comparative devices (see also Fig. 3).

£00102] Example 2 shows that by replacing Polymer P1 with Polymer P3, which is a polyfluorene having a shallower LUMO than the benzothiadiazole-containing electron acceptor, an intrinsic battery voltage of around 2.73 V is achieved (calculated discharge voltage: 2.74 V).

[00103] While the theoretically expected voltage for an all-polyfluorene battery according to Example 3 having polymer P4 as n-type and p-type material is 3.36 V, the measured discharge voltage was 3.23 V while the charge capacity of around 21 to 23 mAh/g is similar to that of Examples 1 to 2. Thus, in comparison to Example 1, the material combination in Example 3 results in a nominal voltage increase of 1.18 V and an energy density increase of 50% (67 mWh/g in Example 3 vs. 45 mWh/g in Example 1, respectively). Energy density is calculated by multiplying charge density by voltage.

[00104] The use of a blend comprising the electroactive polymer, the conductive carbon and the ionic liquid is further exemplified in Examples 4 to 7 with the combination of benzothiadiazole-containing n-type polymers with triary!amine containing p-type polymers resulting in a nominal voltage of around 2V. High specific capacities of 58 and 57 mAh/g were measured for polar-side chain n-type polymers P5 (Example 4) and P6 (Example 5) respectively when combined with an excess cathode (P2) when compared with Example 1 where the theoretical capacity of both electrodes are similar. Apolar-side chain n-type polymers P7 may be combined with P2 (Example 6) and P8 (polar polytriarylamine p-type polymer, Example 7) and achieve suitable material utilization of 79 and 60% respectively.

[00105] The specific capacity of P8 is improved by 56% in Example 7 when compared with P2 in Example 6.

[00106] Examples 8 shows that Schiff base polymer P9 can be used as an alternative to benzothiadiazole polymers (P1, P5, P6, P7) and achieve high specific capacity of 69 mAh/g at a similar discharge profile of 1.95V when compare to example 1. £00107] In a further example, the effect of the choice of electrolyte on the specific capacity at different rates of a charge storage device was investigated.

Example 9

[00108] For Example 9, the procedure of Example 8 was repeated, with the exception that polymers P9 and P2 were used as n- and p-type electroactive polymers, respectively, the ionic liquid was 1-butyl-1-methylpyrrolidiniuum (BMP-TFSI. Here, galvanostatic charge and discharge (equal charge and discharge current) was performed at two current densities 0.2 and 1 mA/cm ² (1000 and 5000 mA/g relative to P9) with a 60 s potentiostatic hold at 3V. The specific capacity of the charge storage device described in Example 9 was measured at specific current densities of 1000 and 5000 mA/g. The results are shown in Table 4. The specific capacities may be compared to a charge storage device ("Literature Example") described by Armand et al. in Angew. Chem. Int. Ed., 2014, 53, 5341 , which use alkali-metal based electrolytes only.

TABLE 4: Battery characteristics as a function of electrolyte and rate

[00109] The results show that the specific capacity of the device according to Example 9 at a current density of 1000 mA/g is very close to the specific capacity of the literature device at a current density of 260 mA/g. A further five-fold increase in current density to 5000 mA/g only results in a 30% drop in specific capacity to 67 mAh/g. This shows that the ionic liquid used in Example 9 has a positive effect on the specific capacity of the charge storage device at high rate, an advantage for high power applications.

[00110] Once given the above disclosure, many other features, modifications, and improvements will become apparent to the skilled artisan. REFERENCE NUMERALS

1 : first current collector layer

2: n-type electroactive layer

3: separator

4: p-type electroactive layer

5: second current collector layer

10a/10b: transparent adhesive tapes (double-layer)

11 a/10b: ITO current collector plates